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Carbon-Based Materials for Modification of Polyolefin Separators to Improve the Performance of Lithium-Sulfur Batteries

Xinye Liu , Zhichao Liang , Shanxing Wang , Yuanfu Deng , Guohua Chen

Progress in Chemistry ›› 2021, Vol. 33 ›› Issue (9) : 1665 -1678.

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Progress in Chemistry ›› 2021, Vol. 33 ›› Issue (9) : 1665-1678 DOI: 10.7536/PC201215
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Carbon-Based Materials for Modification of Polyolefin Separators to Improve the Performance of Lithium-Sulfur Batteries
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Abstract

Owing to their great theoretical energy density (2600 Wh·kg-1), lithium-sulfur (Li-S) batteries are one of the most promising candidates of the next generation energy storage devices. Moreover, the high theoretical specific capacity (1675 mAh·g-1), good eco-friendliness, abundant natural resource and low cost of cathode sulfur are also good for the cheap cost and low environmental pollution of Li-S batteries. However, the practical applications of Li-S batteries are severely impeded by several key challenges, such as the low practical specific capacities, low coulomb efficiencies and fast capacity decay, which resulting from the poor electronic conductivity of sulfur and final products Li2S2/Li2S, the shuttle effects of lithium polysulfides and the growth of lithium dendrite during the electrochemical cycling. It is noted that the modification of the polyolefin separators is one of the effective methods to obviously improve the performances of Li-S batteries. In particular, various carbons and their composites are widely used materials for separator modification because of their unique properties, also, many advancements have been achieved. Herein, the research progresses of the various carbons and their composites for separator modification are reviewed, which will provide guidance for the future research on improving the performance of Li-S batteries by separator modification method.

Contents

1 Introduction

2 Carbon materials for separator modification

3 Carbon-based composite materials for separator modification

4 Conclusion and outlook

Graphical abstract

Keywords

lithium-sulfur batteries / separator modification / electrochemical performance improvement / shuttle effect / catalysis

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Xinye Liu, Zhichao Liang, Shanxing Wang, Yuanfu Deng, Guohua Chen. Carbon-Based Materials for Modification of Polyolefin Separators to Improve the Performance of Lithium-Sulfur Batteries. Progress in Chemistry, 2021, 33(9): 1665-1678 DOI:10.7536/PC201215

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1 Introduction

Lithium-ion batteries (LIBs) with lithium cobalt oxide (LiCoO2) cathode and/or carbon anode have been widely used in various fields, such as mobile phones, notebook computers and electric vehicles, since the introduction of LIBs by SONY in 1991[1]. However, due to the limitation of the specific capacity of cathode materials, it is difficult to improve the specific energy of LIBs, which is difficult to meet people's needs. It is imperative to develop new electrochemical energy storage devices with high specific energy. Sulfur has high theoretical specific capacity and abundant reserves. Lithium-sulfur (Li-S) battery, which uses sulfur as the positive electrode and lithium as the negative electrode, has 2600 Wh·kg-1 theoretical energy density and is considered to be one of the most promising lithium secondary battery systems[2].
Although the energy density of Li-S battery is as high as 2600 Wh·kg-1, it has great development value and application potential. However, the Li-S battery has some disadvantages such as fast capacity fading, low coulombic efficiency and short battery life during charge-discharge cycles, which make it a long way from practical commercial application[3,4]. In order to realize the commercial application of Li-S batteries, the following main problems must be overcome: (1) Shuttle effect: During the discharge process of Li-S batteries, elemental sulfur and lithium ions gradually react to form an intermediate product, long-chain lithium polysulfide.These long-chain lithium polysulfides can dissolve in the electrolyte, diffuse to the negative electrode under the action of concentration gradient and electric field, pass through the diaphragm to the surface of lithium, and react with lithium to form Li2S2 or Li2S. In the charging process, the Li2S2 or the Li2S is oxidized to generate long-chain polysulfides, and the generated polysulfides migrate to a lithium cathode under the action of a concentration gradient to react with lithium and are reduced into short-chain lithium polysulfide,The short-chain lithium polysulfide migrates to the positive electrode through the diaphragm under the action of electric field force and is oxidized into long-chain lithium polysulfide, and the phenomenon that the long-chain and short-chain polysulfides continuously transform and migrate between the positive electrode and the negative electrode is called shuttle effect. As shown in fig. 1[5,6].
The shuttle effect is one of the main reasons for the capacity fading and the low coulombic efficiency of Li-S batteries. First, the final product of the polysulfide is an insoluble insulating substance, Li2S2/Li2S, which coats the surface of the lithium metal and blocks the migration of electrons and Li+. In addition, the shuttle effect also directly leads to the low utilization of sulfur in the active material, the self-discharge of the battery and the low coulombic efficiency of the battery. (2) Volumetric effect during electrochemical cycling: The positive electrode undergoes a solid-liquid-solid phase transition during the transition from S to Li2S. During repeated charging and discharging, the electrode undergoes a huge volume change, which even causes the active material to fall off from the conductive substrate, affecting the cycle life and coulombic efficiency of the battery. (3) Low utilization rate of active materials: The conductivity of elemental sulfur and its discharge products (Li2S2 or Li2S) is low, and the internal resistance of the battery is large, which makes the reaction kinetics of the battery slow, resulting in insufficient effective utilization rate of active materials. (4) The stability of lithium anode: the stability of the solid electrolyte (SEI) film on the surface of lithium metal is insufficient, and it is easy to have side reactions with the electrolyte. In addition, the formation of lithium dendrites formed in the reaction process will also seriously threaten the safety of the battery[7].
At present, there are several ways to improve the performance of Li-S batteries: (1) to modify the sulfur cathode: to find a suitable material to form a composite cathode with sulfur to increase the conductivity and adapt to the volume change during charge and discharge, and to suppress the shuttle effect by various methods[8⇓~10]; And (2) modification of that electrolyte, namely reconstruct the electrolyte by adding different auxiliary agent into the electrolyte, inhibiting the dissolution of lithium polysulfide in the electrolyte and reducing the occurrence of a shuttle effect[11,12]. (3) protection of the lithium negative electrode: a layer of protective film is constructed on the metal lithium negative electrode by adopting an in-situ/external in-situ method to slow down the formation of lithium dendrites and promote the formation of a stable solid electrolyte (SEI) film on the surface of the lithium negative electrode[13,14]. (4) membrane modification: coating/modifying the surface of the membrane by using different materials to reduce/prevent the migration of lithium polysulfide to the cathode so as to improve the performance of the Li-S battery,Modification of the separator can also improve the electrochemical reaction environment on the surface of the positive and negative electrodes, which plays a positive role in improving the utilization of active materials, inhibiting the growth of lithium dendrites and improving the cycle performance of batteries[15]. Among them, great progress has been made in the research of separator modification. Materials with different characteristics are used to modify the separator of Li-S battery, which greatly improves the electrochemical performance of Li-S battery. Carbon materials have been widely used in the modification of Li-S battery separators because of their unique properties and rich varieties. The research progress of carbon materials and their composites in the modification of Li-S battery separators was reviewed in this paper.The structural design of various carbon materials and their composites and the mechanism of improving the performance of Li-S batteries were systematically summarized, and the electrochemical performance of different modified layers used in Li-S batteries was compared, which was expected to provide reference for the related research on improving the performance of Li-S batteries through membrane modification.

2 Carbon material modified diaphragm

Carbon materials have excellent electrical conductivity and low price, so they are the main choice for membrane modification materials in early research. Carbon materials as separator modification materials have many advantages: (1) carbon materials have abundant pore structure, which can provide abundant sites for the adsorption of lithium polysulfide, thus blocking its migration to the negative electrode and inhibiting the shuttle effect; (2) the carbon material has higher electronic and ionic conductivity, which is favorable for forming a second current collector on the diaphragm and accelerating the electron transfer in the conversion process of the lithium polysulfide on the modified layer; (3) The density of carbon materials is low, and the use of carbon materials for separator modification usually does not bring about a large increase in the mass of inactive materials, which has little impact on the mass energy density of Li-S batteries.
Due to the above advantages, the carbon material modified separator used for the Li-S battery greatly improves the utilization rate of the active material sulfur, thereby improving the electrochemical performance of the Li-S battery. In order to better compare the performance of carbon material-modified separators in improving the performance of Li-S batteries, Table 1 lists the electrochemical properties of several typical carbon material-modified separators, including conductive carbon, graphene, biomass-derived carbon and heteroatom-doped carbon. Initially, commercial conductive carbon attracted the attention of researchers. Common conductive carbon materials include carbon paper, Super P (SP), Ketjen black (KB), carbon nanotubes (CNTs) and acetylene black (CB)[16⇓⇓~19]. These materials have high electron transmission rate, which can accelerate the electron transmission in the conversion reaction of high-order lithium polysulfide, thus accelerating the conversion of lithium polysulfide. Meanwhile, the porous structure of the material is beneficial to containing lithium polysulfide so as to reduce the loss of active substances, and the preparation process is simple and the raw materials are cheap, so that the material has wide application prospect. Therefore, the specific capacity and cycle stability of Li-S batteries can be greatly improved by using the separator modified with conductive carbon materials. For example, in 2012, Manthiram's team innovatively used activated carbon paper as an intermediate layer to capture soluble lithium polysulfide, as shown in Figure 2 (a)[20].
By comparing the specific surface area of the intermediate layer before and after cycling, they not only confirmed that carbon paper could adsorb lithium polysulfide through pores to reduce its shuttle effect, but also confirmed that carbon paper could be used as a second current collector to improve the utilization of sulfur. This work has opened up research on the use of carbon materials to modify separators. In 2014, Chung et al. Coated SP on one side of a commercial separator and assembled a Li-S battery using the modified separator for related research[21]. By analyzing the SEM results of the separator before and after cycling, it was confirmed that the modified separator reduced the charge transfer resistance of the battery and reduced the migration of polysulfide to the negative electrode, which greatly improved the electrical performance of the battery.The modified separator as the second current collector improved the utilization efficiency of the active material, i.e. The initial reversible specific capacity of the 60 wt% sulfur positive electrode was as high as 1400 mAh·g-1, and the capacity decay rate per cycle was only 0.2% within 200 charge-discharge cycles.
Although a single commercial carbon material has achieved some results in modifying the separator to improve the performance of Li-S batteries, it is difficult to improve the electrical performance of batteries by modifying a single commercial carbon material due to the limited pore structure or conductivity. Therefore, researchers have turned their attention to the composite carbon material modified separator. Through the combination of various carbon materials, the modified layer can have a richer pore structure and a more complete conductive network.
Zhao Di mixed KB and Super P with porous structure and coated them on the surface of commercial separator (in which Super P was used as a conductive agent to improve the conductivity of the separator as a second current collector, while porous KB provided abundant sites for the adsorption of polysulfides), and studied the effects of KB and Super P modified coatings on the cycle performance and rate performance of batteries[22]. The results show that the membrane modified by 10 μm thick coating has good ionic conductivity and high specific surface area. Under the same conditions, the cycle performance of the Li-S battery assembled with the modified separator was significantly improved.
In addition to the common commercial carbon materials mentioned above, graphene has also attracted wide attention of researchers because of its unique two-dimensional structure. In theory, the lamellar structure of graphene is more conducive to physically blocking the migration of polysulfides. In addition, its excellent flexibility and mechanical strength can better adapt to the volume change during charging and discharging. Graphene coated sulfur nanoparticles with core-shell structure were synthesized by one-pot method in our group. Benefiting from the high conductivity of graphene, suitable particle size of sulfur particles and unique core-shell structure, the material showed high specific capacity and cycle stability for the cathode of Li-S battery[23]. Similarly, graphene is often used to modify membranes[24,25]. Cheng's research team prepared a graphene-modified separator by a simple suction filtration method, and then directly coated the cathode slurry on the surface of graphene to obtain an electrode with an integrated sulfur cathode and separator, as shown in Figure 2 (B)[26]. The results show that the graphene coating acts as a physical barrier to effectively prevent the diffusion of polysulfides to the anode, and the new electrode structure effectively reduces the interface resistance through the direct contact between the anode sulfur and graphene. Therefore, the initial discharge specific capacity of the assembled Li-S battery was as high as 1278 mAh·g-1 at the current density of 0.3 A·g-1, and the specific capacity was still as high as 1150 mAh·g-1 after 50 cycles at the same current density, which indicated that the graphene modified separator had a good inhibition effect on the shuttle effect and effectively improved the utilization of active material.
The pore structure and surface properties of graphene materials obtained by different synthesis methods are very different, and then they also show different properties as membrane modification materials. For example, Zhai et al. First prepared a porous MgO/C material by CVD reaction using magnesium oxide as a template, then removed the magnesium oxide template to obtain a complete large area of graphene, and then coated it on the PP membrane, as shown in Figure 2 (C)[27]. The graphene prepared by the process has high conductivity, high specific surface area and moderate pore diameter, and is beneficial to the transmission of electrons and lithium ions. The authors used the graphene modified commercial separator to assemble Li-S batteries for testing, and the results showed that the specific capacity and cycle performance of Li-S batteries were greatly improved by using the modified separator.
Compared with graphene, graphene oxide (GO) has more active oxygen-containing functional groups, such as epoxy, hydroxyl and carboxyl, which can enhance the wettability of electrolyte to the separator and help to improve the ionic conductivity[28,29]. In addition, there are polar interactions and electrostatic repulsion between these functional groups and polysulfides, which are beneficial to inhibit the shuttle effect of polysulfides, so GO is also often used as membrane modification materials[30,31]. However, the amount and type of functional groups on the surface of the material will affect the conductivity of the material itself and its interaction with polysulfides[32,33]. The results show that with the increase of oxidation time, the content of oxygen atoms on the surface of graphene increases (the increase of oxygen-containing functional groups on the surface), and the surface functional groups gradually change from hydroxyl groups to epoxy groups[30]. In addition, with the further oxidation of graphene, its conductivity decreases, so the oxidation degree of graphene or the reduction degree of graphene oxide will also have a great impact on the performance of Li-S batteries. Zhu et al. Selected two kinds of graphene oxides with similar specific surface areas but different reduction degrees (the types and numbers of oxygen-containing groups on their surfaces and the conductivity of materials are different).The effects of graphene oxide with different reduction degrees on the electrochemical performance of Li-S batteries were investigated, and the results showed that the reduced graphene with appropriate number of oxygen-containing functional groups and high conductivity had faster reaction kinetics.The initial discharge capacity of the Li-S battery assembled by the modified separator and the sulfur positive electrode (the sulfur content in the positive electrode is 70%) in the electrolyte without lithium nitrate reaches 1419 mAh·g-1, and after 40 cycles at a current density of 0.2 C, the specific discharge capacity still reaches 853 mAh·g-1[34].
Although conventional carbon materials can be used to modify the separator and improve the performance of Li-S batteries, the discharge reversible specific capacity and cycle performance of the corresponding Li-S batteries are not ideal. One of the important reasons is that conventional carbon, as a non-polar (weakly polar) material, has limited interaction with polysulfides. Subsequently, theoretical calculations showed that heteroatom-doped carbon materials could improve their "fixing" effect on polysulfides through strong polar interactions between heteroatoms and polysulfides[35]. Therefore, researchers have introduced heteroatoms (such as N, S, etc.) Or nano-metals (such as Co, Fe, etc.) On carbon materials as polar centers to improve the interaction between carbon-based materials and polar polysulfides[36]. Doped carbon materials are widely used as sulfur host materials. In our research group, N-doped carbon spheres were synthesized by using dopamine spheres as precursors, and the specific capacity of sulfur cathode was improved by using their high conductivity, porous characteristics and the polar effect of N and polysulfide[37]. In the field of Li-S battery separator modification, researchers have also synthesized a series of doped carbon materials for separator modification and achieved good results, including N-doped porous carbon, N-doped hollow porous carbon, nitrogen-doped nanowires, O-doped carbon, N-S co-doped carbon and so on[35,38][39][40][41][42]. In addition to introducing heteroatoms into porous carbon, similar N-doping techniques have also been applied to graphene materials[43].
In 2018, Pei et al. Synthesized a hollow nitrogen-doped carbon using GO@SiO2 as a template, as shown in Figure 2 (e)[44]. Firstly, a silicon dioxide template is coated with graphite oxide with a two-dimensional structure to obtain a GO@SiO2, then a layer of polybenzoxazine (PB) and a SiO2 coating layer are sequentially introduced on the surface of the GO@SiO2 to obtain a GO@SiO2@PB/SiO2 precursor, and finally the precursor is carbonized at high temperature and the SiO2 is etched by HF to obtain the G @ PC nanosheet. The nitrogen-doped carbon nanosheet with the hollow structure has a large specific surface area and abundant micropores, and meanwhile, doped N atoms in the material can adsorb lithium polysulfide through chemical interaction, so that the effects of fixing the lithium polysulfide and reducing the shuttle effect of the lithium polysulfide are achieved. The G @ PC material was modified on the commercial PP membrane by suction filtration, and a modified layer composed of two-dimensional nanosheets was obtained on the PP membrane. When the thickness and mass density of the modified layer were only 0. 9 μm and 0.075 mg·cm-2 respectively, good results were obtained. The initial specific capacity of the battery assembled with the G @ PC/PP separator was as high as 1257 mAh·g-1 at a current density of 0.2 C when the areal density of the positive electrode was as high as 3.5 mg·cm-2. At the same time, the reversible discharge capacity of the battery was still up to 754 mAh·g-1 after 500 cycles at a current density of 1 C (the capacity retention rate was up to 88.6%, and the decay rate per cycle was only 0.023%), and the coulombic efficiency of the battery was above 99% during the whole cycle.
Biomass carbon materials are obtained by calcining and carbonizing biomass as a precursor at high temperatures. They are widely used in Li-S batteries because of their rich porous structure and heteroatom doping[45]. Biomass carbon has a wide range of sources, different biomass has different structure and composition, and a variety of carbon materials with different characteristics can be obtained by calcination. For example, cellulose is a common biomass with a wide range of sources and low cost, and porous carbon biomass materials with abundant hydroxyl groups can be obtained by calcining it with an activator at high temperature.For example, some biomass materials have a unique three-dimensional network structure, which forms a three-dimensional cross-linked conductive framework after high temperature carbonization, and this three-dimensional conductive structure is conducive to improving the electronic conductivity of materials[46,47][48,49]. In addition, as mentioned above, heteroatom doping of carbon materials can effectively improve the polarity of materials, and the complex composition of biomass provides rich impurity elements for doping, for example, sponge gourd contains rich S and O elements, so S-doped carbon materials can be obtained after high temperature carbonization, thus improving the polarity of carbon materials[50]. In a word, biomass carbon materials have abundant sources and unique structures, and the synthesized biomass carbon materials are simple to prepare, low in cost and have good application prospects, so a large number of studies have been devoted to the use of biomass carbon materials in the modification of separators for Li-S batteries.
By changing the ratio of activator to nitrogen source, a porous carbon material with ultra-high nitrogen doping content (about 12. 2 atom%) was obtained by carbonizing bagasse at high temperature, which was used as a sulfur-carrying matrix for the positive electrode of Li-S battery to greatly improve the specific capacity of the positive electrode[51]. Furthermore, we confirmed that the porous carbon can effectively adsorb polysulfides as a membrane modification material[52]. The results show that the thickness of the modified layer of the separator has a great influence on the electrochemical performance of Li-S battery. With the increase of the thickness of the modified layer, the adsorption of polysulfides on the separator increases, but the increase of the thickness increases the diffusion path of lithium ions, resulting in the decrease of the number of Li+ transfers. Therefore, it is very important to design the appropriate thickness of the modified layer to modify the separator to improve the overall performance of Li-S batteries.
The porous carbon synthesized by Huang et al. From crab shells has a large specific surface area and abundant N-doped atoms (Fig. 2 (f)), and is used to modify the diaphragm[53]. The abundant N atoms of the material effectively improve the interaction between the modified layer material and the polysulfide, the mesoporous structure is also beneficial to the infiltration of electrolyte to the separator and the migration of Li+, and the high conductivity enables the modified layer to be used as a second current collector to promote the reuse of active substances. Therefore, the battery assembled by the separator modified by the nitrogen-doped carbon material and the S/C composite positive electrode (the sulfur content of the positive electrode is 63%, and the surface density is 1.5~2 mg·cm-2) has good electrochemical performance, and the reversible specific discharge capacity of the battery still reaches 971.3 mAh·g-1 after 100 cycles at a current density of 0.1 C.
The data in Table 1 shows that various carbon materials have their own advantages and disadvantages as Li-S battery separator modification materials. Although conductive carbon materials are easy to synthesize and have high conductivity and porosity, their single structure and fixed morphology limit their wider application. Graphene and graphene oxide have unique two-dimensional structures, which are conducive to reducing the thickness of the modification layer and will not bring serious burden to the energy density of the battery. However, these carbon materials have weak polarity and very limited binding effect on lithium polysulfide, so the cycle performance is not ideal. The heteroatom-doped carbon material greatly improves the polarity of the material and better inhibits the shuttle effect of polysulfides, and especially when the N-doped carbon material G @ PC with a two-dimensional structure is used for modifying the separator, a light thin modified layer is obtained, and good rate capability and cycle stability are achieved under high sulfur loading. Biomass-derived carbon materials have abundant porous structure and heteroatom doping, which can better inhibit the shuttle effect and improve the electrochemical performance of Li-S batteries. They have wide sources and simple synthesis, so they have broad commercial application prospects.
Carbon materials as membrane modification materials also have some shortcomings, for example, most carbon materials are non-polar, and the interaction with lithium polysulfide is relatively weak, although the polarity of materials can be effectively enhanced by introducing polar centers (N, O and S).However, at present, the doping amount of carbon materials is generally not high, and the interaction between doped carbon materials and polysulfides is still weak compared with other materials with strong polarity (metal oxides, metal sulfides, etc.). In addition, the density of carbon materials is usually low, resulting in a thicker modification layer, which has a partial impact on the volumetric energy density of Li-S batteries. Finally, most carbon materials are inefficient in catalyzing the conversion of polysulfides, making it difficult to substantially accelerate the conversion of polysulfides. Therefore, the construction of carbon-based composite modified separator is a feasible means to further improve the performance of Li-S battery.

3 Carbon-based composite material modified diaphragm

As mentioned above, carbon materials have been widely used in Li-S battery separator modification, but the defects of carbon materials limit their application, so carbon-based composites composed of other substances are a promising separator modification material. For example, inorganic compounds usually have high polarity, so they have strong interactions with polysulfides, which can effectively fix polysulfides in the positive region. In addition, some inorganic compounds can catalyze the conversion of lithium polysulfide. As mentioned above, the slow redox reaction kinetics of Li-S batteries during charge and discharge brings about a serious shuttle effect, which leads to the loss of active materials.Therefore, adding a material with a catalytic function to the separator modification layer can promote the conversion of high-order lithium polysulfide to low-order lithium polysulfide and lithium sulfide in time, thereby reducing the loss of active materials and improving the utilization rate of the sulfur cathode. However, the conductivity of these inorganic compounds is generally poor and the specific surface area is small, so the conductivity and the specific surface area of the material are improved by adding conductive carbon and compounding with the inorganic compounds,By utilize that synergistic effect of physical adsorption, chemical adsorption and catalytic conversion, the diffusion of polysulfide to the negative electrode is effectively inhibited, the utilization rate of active material is improved, and the performance of the Li-S battery is further improved.
At present, composite materials have been widely used as sulfur carriers in the positive electrode of Li-S batteries. Previously, our group successfully synthesized WS2/C and MoS2/g-C3N4 composite materials with high polarity and high specific surface area, and used them in the positive electrode of Li-S batteries, and achieved good electrochemical performance[54][55]. In the field of membrane modification, composite materials are also widely used. This paper mainly introduces the application of several materials in membrane modification, such as metal compound/carbon, metal atom/carbon, and polymer/carbon composite materials. Metal compound/carbon composites can be divided into metal compound/conductive carbon (conductive carbon black, CNTs and CNFs, etc.), metal compound/rGO and metal compound/porous carbon according to the type of carbon.
Initially, inorganic compound particles such as TiO 2, Al2, O 3, MoP 2 and MoS 2 were uniformly coated on the substrate of conductive carbon nanotubes to obtain metal compound/conductive carbon composites for membrane modification[56,57][58][59][60]. For example, Xu et al. Simply coated a layer of Al2O3 and a layer of conductive carbon nanotubes (CNT) on the same side of a commercial separator to obtain a three-layer separator (CNT/Al2O3/PP).CNTs as the conductor and the second current collector effectively improve the kinetics of the redox reaction, while the high specific surface area and porous structure of CNTs provide abundant sites for capturing lithium polysulfide in the electrolyte, thus hindering the shuttle effect[58]. The addition of the Al2O3 coating increases the hydrophilicity of the separator, reduces the charge transfer resistance of the battery, and can prevent the battery from being short-circuited due to the shedding of conductive carbon nanotubes. Based on these advantages, the Li-S battery composed of the sulfur cathode with 42 wt% sulfur loading and the modified separator showed the best electrochemical performance.
Although the performance of the separator can be effectively improved by simply physically mixing carbon materials with inorganic materials or directly coating a layer of inorganic compounds on the surface of carbon, this method of directly adding conductive carbon also has drawbacks. For example, the distribution of carbon and inorganic materials in the obtained composite material is not uniform, and the inorganic material particles will aggregate to form some non-conductive areas, which can not make the modified layer form a complete conductive network and is not conducive to the transfer of electrons in the material[61]. Therefore, functional groups are introduced on the surface of conductive carbon such as CNTs and carbon fiber (CNF) by acidification or encapsulation, and then the interaction between the rich functional groups on the surface of carbon materials and metal ions is utilized.It is also a common method to react under hydrothermal conditions or directly calcine at high temperature to obtain inorganic substances grown in situ on carbon materials, to achieve uniform distribution of metal ions on the surface of carbon materials, and to construct composite modified diaphragms.
Recently, composite materials such as Co(OH)2@CNF/KB,mTiO2-CNTs,CNFO@CNT,C-PDA@TiO2@CNF and Co/mSiO2-NCNTs have been synthesized and successfully used as separator modification materials for Li-S batteries[62][63][64][65][66]. Li et al. prepared a novel polysulfide barrier layer (mTiO2-CNTs) composed of mesoporous TiO2 and CNTs, in which the mesoporous TiO2 particles in the composite were connected in series by linear CNTs (fig. 3 (a))[63]. Because the TiO2 has a strong ability to absorb polysulfide and the interlaced CNTs form a good conductive network, the material can be used as a membrane modification material to well limit polysulfide and the blocked polysulfide can be well reused. At the same time, the interconnected framework formed by the one-dimensional structure of the material can increase the stability of the separator modification layer and better adapt to the volume change of the battery during charging and discharging. Based on these advantages, the Li-S battery assembled with the modified separator and the "S/SP" composite cathode (sulfur content of 65 wt%) showed high initial specific capacity (0.2 C,1323 mAh·g-1) and cycle performance, and the capacity decay rate was only 0. 07% per cycle after 500 cycles at 0. 5 C current density. It is worth noting that the amount of the separator modification layer is very low (only 0.06 mg·cm-2), so that this weight does not have a significant negative effect on the energy density of the battery as a whole.
In our research group, CNF was used as a template to prepare TiO2@SiO2@CNF composites by a two-step hydrolysis method, and then a layer of polydopamine was coated on the surface of the composites. After high temperature carbonization, the SiO2 in the calcined product was removed by sodium hydroxide solution, and finally C-PDA@TiO2@CNF(CTC) composites with hollow structure were obtained[75]. Because the C-PDA and CNF in the composite material have high conductivity, and the TiO2 has strong polarity, the CNF and the TiO2 are interlaced to form a conductive network, and the hollow structure of the material provides a large space for containing polysulfide, and also provides a plurality of active sites for polar TiO2 to adsorb polysulfide. Therefore, the membrane modified by the material can effectively inhibit the shuttle effect of the polysulfide and accelerate the charge transfer capability. The Li-S battery assembled with the modified separator and "S/KB" composite cathode (sulfur content in the cathode material is 72.7 wt%, sulfur surface density is about 1.8 mg·cm-2) shows good cycle stability, and the capacity loss rate per cycle is only 0.06% after 500 cycles at a current density of 2 C.
In addition, GO, which has high conductivity and abundant negatively charged functional groups, also often provides a carrier for metal compounds, uniformly adsorbs metal cations through the electrostatic effect of functional groups, and further obtains a "metal compound/rGO" composite material uniformly distributed on the reduced GO through a solvothermal reaction. At present, many inorganic and graphene composites have been used to modify the separator of Li-S batteries, such as metal oxides (MnO2, SnO2, TiO2 and ZnO), sulfides ( MoS 2), nitrides (TiO2-TiN, boron nitride) and carbides (TiC)[67][28][69][70][71,72][73][74][75]. The obtained composite material has chemical adsorption effect and high conductivity, and can greatly improve the specific capacity of the Li-S battery when being used as a diaphragm modification material[76]. For example, Tan et al. prepared rGO@MoS2 composite material by hydrothermal method, and realized that molybdenum sulfide particles were uniformly embedded on the surface of reduced GO, and then the composite material was deposited on the PP diaphragm by suction filtration to modify the diaphragm[71]. Among them, rGO forms a good conductive network and a physical barrier for polysulfides (Fig. 3 (B)), and molybdenum sulfide not only improves the polarity of the material and enhances the interaction with polysulfides, but also has been shown to catalyze the conversion of polysulfids to the end product lithium sulfide.The reaction kinetics of the battery is improved, and meanwhile, because lithium ions are embedded in the molybdenum sulfide, the modified diaphragm has high Li+ conductivity, so that the Li-S battery has high utilization rate of active materials, excellent rate performance and stable cycle performance[72]. The Li-S battery composed of the modified separator and the sulfur cathode (sulfur content 70%, surface density 1.8~2.0 mg·cm-2) has an initial discharge specific capacity of 1184 mAh·g-1 at 0. 1 C rate, and still has a specific capacity of 615 mAh·g-1 when the current density is increased to 2 C.
With the in-depth study of Li-S battery, researchers gradually realize that the areal density of S cathode in Li-S battery is far from meeting the needs of commercialization. Therefore, more and more attention has been paid to the performance of the positive electrode with high sulfur loading. Zhou et al. Synthesized a TiO2-TiN heterostructure combining highly polar TiO2 and highly conductive TiN on graphene, and realized the smooth capture-diffusion-conversion of lithium polysulfide on the separator[73]. In the composite material, the strong interaction between the TiO2 and the polysulfide is favorable for blocking the polysulfide in the positive electrode part through chemisorption, the catalytic effect of TiN on the polysulfide conversion reaction accelerates the conversion of the captured polysulfide to the final product Li2S, and the graphene is favorable for the rapid transfer of electrons in the electrochemical reaction (fig. 3 (C)). The membrane was successfully modified by suction filtration, and the results showed that the shuttle effect of polysulfide was well inhibited even at high sulfur loading, and the electrochemical performance of the assembled Li-S battery was greatly improved. When the sulfur loading in the sulfur positive electrode reached the 4.3 mg·cm-2, the battery still had 67% capacity retention after 2000 cycles at 1 C.
In addition to the shuttle effect, the growth of lithium dendrites caused by lithium anode in Li-S batteries also poses a serious threat to the safety of Li-S batteries. Lithiophilic atoms such as N and O in the material can reduce the local concentration of lithium ions and make lithium ions deposit uniformly, thus inhibiting the formation of lithium dendrites[77]. Therefore, it is a promising solution to improve the performance of Li-S batteries by modifying the separator to inhibit the shuttle effect and the growth of lithium dendrites. Recently, metal compounds/graphene composites, such as MQD @ NG and Nb2O5-rGO, have been synthesized and used to modify Li-S battery separators[78][79].
Yu et al. synthesized Mo2C N-doped graphene embedded with quantum dots by high temperature calcination, and the specific synthesis path is shown in Figure 3 (d)[78]. The theoretical calculation confirms that there is a high binding energy between the Mo2C@NG and lithium ions, and the Mo2C quantum dots are uniformly fixed on the ultra-thin graphene nanosheets, forming a rich electrolyte diffusion path, which is conducive to the uniform transport of Li+ and the uniform deposition of Li. Therefore, the Mo2C@NG layer can not only inhibit the shuttle of lithium polysulfide through the polar effect, but also effectively inhibit the formation of lithium dendrite, which greatly improves the safety performance of Li-S batteries. Under the current density of 7.5 mA·cm-2, the lithium symmetric battery assembled by the Mo2C@NG can maintain stable voltage polarization within 1600 H. The Li-S battery assembled with the Mo2C@NG modified separator and the S/C composite cathode (S content in the material is 80%) has a capacity of 1230 mAh·g-1 at a current density of 0.2 C. After 400 cycles at 2 C, the capacity decay rate of the battery is only 0.045% per cycle.
In addition to the use of functional groups on the surface of carbon materials to adsorb inorganic ions to obtain uniformly distributed composites, inspired by the preparation of carbon materials by high temperature calcination, metal compounds/porous carbon composites can also be prepared by decomposing some precursors at high temperature. In this synthesis method, the preparation of nanocomposites using metal-organic frameworks (MOFs) as templates has attracted much attention. In the nanocomposites prepared by using MOFs as templates, the functional nanoparticles can be uniformly dispersed in the conductive carbon materials, and lithium-friendly atoms such as N and O can be introduced into the porous carbon, thereby promoting the uniform deposition of the Li+ and inhibiting the formation of lithium dendrites. Therefore, this kind of composite materials show excellent electrochemical properties in the fields of electrocatalysis and batteries[80]. Such composites have many advantages: (1) the composites usually maintain the specific morphology of MOFs precursors (such as nanosheets, nanospheres, cubes, etc.); (2) the metal and metal compound nanoparticles in the composites can be uniformly dispersed in the conductive carbon materials; (3) Since the ligands of many MOFs contain N atoms, porous nitrogen-doped carbon-based materials can be obtained in high temperature processing. At present, many composite materials, such as N-Ti3C2/C,Co/NCNS/CNT, MnO/C and Co3O4/PI/LLZO, have been prepared by calcining MOFs precursors or MOFs-based composite materials. These composite materials are also widely used in Li-S batteries as positive sulfur carrier matrix or separator modification materials[81][82][83][84].
For example, Jiang et al. prepared a new type of 2D composite material (N-Ti3C2/C) of N-doped MXene nanosheets and porous carbon by heat treating the MXene/MOF(Ti3C2/ZIF-67) composite material, and the specific synthesis scheme is shown in Figure 4 (a)[81]. Because the 2D structure has abundant mesopores and macropores and is beneficial to exposing more Lewis acid sites on the surface for chemisorbing polysulfide, simultaneously,N-doped MXene greatly improves the interaction between the material and polysulfide, so the membrane modified by the material significantly inhibits the shuttle effect of polysulfide and greatly improves the reaction kinetics of the active material. At the same time, as mentioned above, the presence of the lipophilic N atoms and the carbon material with a high specific surface area is beneficial to the sufficient wetting of the electrolyte and the reduction of the local concentration of the Li+, so that the Li+ is uniformly deposited on the negative electrode, thereby inhibiting the formation of lithium dendrites. Based on this, the electrochemical performance of the Li-S battery assembled with the modified separator and the "S/CNT" composite cathode (the sulfur content in the cathode material is 64 wt%, and the areal density is 3.4 mg·cm-2) is significantly improved. At the current density of 0. 5 C, the specific capacity of the battery remained 716 mAh·g-1 after 500 cycles, and the average decay rate per cycle was only 0. 07%.
Since Qiao et al. Synthesized Pt monatomic catalyst in 2011, the monoatomic catalyst with uniform dispersion has high catalytic performance and high catalyst utilization rate.However, due to the high surface energy, monoatoms tend to aggregate together to form nanoparticles, so it is very important to find a suitable monoatomic support for its catalytic performance[85][86]. In recent years, in the field of Li-S batteries, the research of carbon materials loaded with metal atoms as separator modification or sulfur-carrying matrix has been developed rapidly. For example, in 2019, Du et al. Synthesized Co-N/G and used it as the cathode of Li-S battery, and confirmed that the existence of bond enables Co monoatom to be stably dispersed on graphene. Therefore, N and O-doped carbon materials are considered to be a good monoatom carrier because they can form M-N4(M-O4) with transition metal M[87]. Subsequently, various metal monatomic/carbon composites were used as cathode materials for Li-S batteries[88,89]. In the field of Li-S membrane modification, metal monoatom/doped carbon composites have also attracted the attention of researchers, and Ni @ NG, B/2D MOF-Co and Fe1/NG have been synthesized and used for membrane modification[90][91][92].
Zhang et al. prepared Ni @ NG by high temperature pyrolysis, and the specific synthesis method is shown in Figure 4 (B)[90]. Ni atoms are confined in the N-doped graphene matrix by the g-C3N4 as a template. In addition, the cross-linked layered graphene forms a good conductive network. The results of high-angle annular dark-field scanning electron microscopy and X-ray near-edge absorption fine structure spectroscopy prove that the monatomic Ni is stabilized on the graphene by forming a Ni-N4structure with the N atom on the graphene. Due to the high catalytic activity of Ni mono atom and the polarity of N-doped graphene, Ni @ NG has also achieved good results in the modification of Li-S battery separators. The Li-S battery assembled with the modified separator and the Li2S6 solution as the active material (the sulfur areal density in the positive electrode is 1.5 mg·cm-2) still has a high specific capacity of 612 mAh·g-1 at a current density of 10 C. After 500 cycles at 10 C, the capacity retention rate is as high as 70%, and the decay rate per cycle is only 0.06%.
In addition to the composite materials constructed by carbon and inorganic compounds, polymer/carbon composite materials prepared by combining carbon-based materials with high specific surface area and high conductivity with other materials are also widely used as membrane modification materials. The application of polymer materials in membrane modification is limited by the few types of conductive polymers, so the composites formed by polymer materials and carbon-based materials greatly improve the conductivity of materials, thus promoting the application of polymer-based composites in membrane modification. For example, MPC-PEG, GO/Nafion, PANINF/MWCNT, PSS-CNT, PVDF-PEO/CB, rGO-PVDF and g-C3N4/GS have been successfully prepared and widely used as separators for Li-S batteries[93][94][95][96][97][98][99].
PVDF has good wettability, ideal chemical and mechanical stability and excellent heat resistance, and is often used as an adhesive for electrode preparation. PVDF membrane modification is not only low cost, but also can improve the safety of battery at high temperature. However, the conductivity of PVDF membrane is poor. Therefore, the research of PVDF membrane modification with high conductivity carbon-based materials to further improve the performance of battery has attracted much attention. For example, Zhu et al. prepared a new bifunctional rGO-PVDF membrane using a simple electrospinning technique and used it for the first time in the separator modification of Li-S batteries (Fig. 4 (C))[98]. The results showed that the porous PVDF nanofiber framework in the modified membrane provided good thermal stability and maintained the structural integrity of the membrane.The conductive rGO-PVDF layer can adsorb polysulfides through the porous structure of graphene and improve the wettability of electrolyte to the diaphragm, thereby effectively promoting the rapid transfer of Li+ on the diaphragm, and the conductivity of rGO can promote the transmission of electrons.Therefore, the Li-S battery assembled with the modified separator and the "S/CB" composite positive electrode (the sulfur content of the positive electrode part is 70 wt%, and the areal density is about 1.1 mg·cm-2) shows high specific capacity and good cycle performance. At a current density of 0.2 C, the specific discharge capacity of the first cycle is as high as 1322 mAg·h-1, and after 100 cycles, the specific capacity remains at 646 mAg·h-1.
Graphite phase carbon nitride (g-C3N4) is a kind of layered material with very high nitrogen content (about 56%), which is obtained by condensation polymerization of urea and melamine at high temperature. The shuttle effect of polysulfides can be inhibited by the mechanism of interaction between their abundant N atoms and polysulfides. However, the nearly insulating nature of g-C3N4 limits its application in batteries, and it is necessary to combine it with carbon materials for separator modification. Qu et al. Synthesized 2D graphene and g-C3N4 to obtain g-C3N4/GS composite materials through a simple ultrasonic and stirring synthesis route (Fig. 4 (d))[99]. Graphene in the material forms a conductive network to accelerate charge transfer and Li+ diffusion, while g-C3N4 traps polysulfides through strong interactions with polysulfides to inhibit their shuttle effect. The Li-S battery assembled by the separator modified by the composite material and the "S/KB" composite positive electrode (the sulfur content in the positive electrode material is 45 wt%, and the surface density is 0.9~1.1 mg·cm-2) has good cycle stability, and after 1000 cycles at a current density of 1 C, the specific capacity of the battery still maintains 612.4 mAh·g-1.
It can be seen from Table 2 that different materials have their own advantages and disadvantages when they are compounded and used as membrane modification materials. The composite materials of metal compounds and various carbon materials integrate the catalysis of metal compounds and the adsorption of carbon materials.The shuttle effect of polysulfides is synergistically inhibited, and some composite materials are also proved to have the function of inhibiting the growth of lithium dendrites.However, the utilization of metal compounds with catalytic activity in these materials is usually low, so metal oxide/carbon composites with high catalytic activity and catalyst utilization are promising composites, and good results have been achieved in the modification of Li-S battery separators. Polymer/carbon materials have good mechanical properties, abundant functional groups, high lithium ion conductivity of polymers and high conductivity and porous characteristics of carbon materials, which greatly improve the performance of Li-S batteries when used for separator modification. However, compared with other carbon-based composites, their cycle performance needs to be further improved.

4 Conclusions and outlook

As a new type of secondary battery with high theoretical specific capacity, high energy density, low cost, good safety and environmental friendliness, Li-S battery meets the requirements of new energy vehicles, aerospace and power grid industries for high-performance batteries, and has good prospects for practical development and application. In order to solve the problems of performance degradation and low coulombic efficiency in the cycling process of Li-S battery, it is an effective and necessary strategy to modify the separator with appropriate materials. In this paper, the research progress in the modification of Li-S battery separators is reviewed from two aspects: the introduction of carbon materials and the modification of carbon-based composites. The results show that there are several strategies to modify the separator of Li-S battery: (1) to improve the utilization of active material by inhibiting the shuttle effect through physical adsorption, chemical adsorption, electrostatic effect and catalytic conversion; (2) the lyophilicity of the diaphragm to the electrolyte is enhanced, and the ionic conductivity of the Li+ is improved; And (3) optimizing the chemical environment of the lithium anode, stabilizing the solid electrolyte SEI film and inhibiting the growth of lithium dendrite. These strategies have made great progress in improving the electrochemical performance, cycle stability and coulombic efficiency of Li-S batteries, laying a solid foundation for the full commercialization of Li-S batteries.
Although great progress has been made in the modification of Li-S battery separators, several important problems need to be solved in the commercialization of Li-S batteries: (1) The commercial Li-S battery separator modification materials need to meet the characteristics of simple preparation, wide raw material sources and low cost.Therefore, although many complex synthesis methods and expensive materials can effectively improve the electrochemical performance of Li-S batteries, they are not suitable for large-scale industrial production. (2) For most of the modified separators, the current research is still limited to the study of low sulfur loading (1~2 mg·cm-2), however, the areal energy density of commercial Li-S batteries needs to reach at least 4 mAh·cm-2, and most of the sulfur loading in the current laboratory is far from meeting this requirement, so it is necessary to further strengthen the research on improving the performance of modified separators in high sulfur loading positive electrode; (3) The thickness and quality of the modified layer usually affect the volumetric energy density and the mass energy density of the Li-S battery, and generally, the increase of the thickness can accommodate more polysulfides,However, it also leads to the decrease of the volume and mass energy density of the battery, so under the condition of meeting the high performance in the battery with high sulfur loading, the modification layer should also meet the requirements of lighter mass and thinner thickness. (4) In Li-S batteries, the formation of lithium dendrite is a serious threat to the safety of Li-S batteries, but there are few real solutions to this problem.Coating a modification layer on the side of the separator facing the negative electrode is expected to inhibit the formation of lithium dendrites or help form a more stable SEI film, so the research on the modification of the separator should also focus on the modification layer on the side facing the negative electrode. (5) The mechanical stability of the modified layer in the cycling process is also a concern. During the charging and discharging process, the modified layer will also undergo a huge volume change, which may cause the modified layer to fall off from the PP separator, fall into the electrolyte or adhere to the positive electrode, thus bringing about changes in interface resistance; (6) Although there have been many studies on catalysts promoting the conversion of polysulfides, the mechanism of the conversion process of Li-S batteries is not very clear at present, and the explanation of the catalytic mechanism lacks reliable theoretical support, which needs further in-depth study; (7) The thermal effect in the process of battery charging and discharging will bring potential safety hazards to the battery, so the thermal stability of the separator modification material within a certain temperature also needs to be considered. In a word, although Li-S battery has great development potential and great progress has been made in improving the performance of Li-S battery by modifying the separator of Li-S battery, on the road of commercialization, it is still necessary to balance the difficulty of obtaining modified materials, the price and the improvement of the comprehensive performance of the battery.

References

Publishing order | Descend order by publishing year | Descend order by cited within
[1]

Ma Z, Wang F F, Dou M, Yao Q N, Wu F, Kan E J. Appl. Surf. Sci., 2019, 495: 143534.
[2]

Chung S H, Manthiram A. Adv. Mater., 2019, 31(27): 1901125.
[3]

Shao Q J, Wu Z S, Chen J. Energy Storage Mater., 2019, 22: 284.
[4]

Cha E, Patel M, Bhoyate S, Prasad V, Choi W. Nanoscale Horiz., 2020, 5(5): 808.
[5]

Wang D W, Zeng Q C, Zhou G M, Yin L C, Li F, Cheng H M, Gentle I R, Lu G Q M. J. Mater. Chem. A, 2013, 1(33): 9382.
[6]

Busche M R, Adelhelm P, Sommer H, Schneider H, Leitner K, Janek J. J. Power Sources, 2014, 259: 289.
[7]

Hu Y X, Zhu X B, Wang L Z. ChemSusChem, 2020, 13(6): 1366.
[8]

Ji X L, Lee K T, Nazar L F. Nat. Mater., 2009, 8(6): 500.
[9]

Wu Q P, Zhou X J, Xu J, Cao F H, Li C L. J. Energy Chem., 2019, 38: 94.
[10]

Yuan Z, Peng H J, Hou T Z, Huang J Q, Chen C M, Wang D W, Cheng X B, Wei F, Zhang Q. Nano Lett., 2016, 16(1): 519.
[11]

Liang X, Wen Z Y, Liu Y, Wu M F, Jin J, Zhang H, Wu X W. J. Power Sources, 2011, 196(22): 9839.
[12]

Wang L N, Liu J Y, Yuan S Y, Wang Y G, Xia Y Y. Energy Environ. Sci., 2016, 9(1): 224.
[13]

Ma L B, Chen R P, Hu Y, Zhang W J, Zhu G Y, Zhao P Y, Chen T, Wang C X, Yan W, Wang Y R, Wang L, Tie Z X, Liu J, Jin Z. Energy Storage Mater., 2018, 14: 258.
[14]

Yang H J, Guo C, Naveed A, Lei J Y, Yang J, Nuli Y N, Wang J L. Energy Storage Mater., 2018, 14: 199.
[15]

Deng N P, Liu Y, Li Q X, Yan J, Lei W W, Wang G, Wang L Y, Liang Y Y, Kang W M, Cheng B W. Energy Storage Mater., 2019, 23: 314.
[16]

Xin S, Gu L, Zhao N H, Yin Y X, Zhou L J, Guo Y G, Wan L J. J. Am. Chem. Soc., 2012, 134(45): 18510.
[17]

Zhang Z, Lai Y, Zhang Z, Li J. Solid State Ionics, 2015, 278:166.
[18]

Zhao D, Qian X Y, Jin L N, Yang X L, Wang S W, Shen X Q, Yao S S, Rao D W, Zhou Y Y, Xi X M. RSC Adv., 2016, 6(17): 13680.
[19]

Feng J N, Qin X J, Ma Z P, Yang J, Yang W, Shao G J. Electrochimica Acta, 2016, 190: 426.
[20]

Su Y S, Manthiram A. Nat. Commun., 2012, 3: 1166.
[21]

Chung S H, Manthiram A. Adv. Funct. Mater., 2014, 24(33): 5299.
[22]

Zhao D. Master's Dissertation of Jiangsu University, 2017.
[23]

(赵迪. 江苏大学硕士论文, 2017.).
[24]

Xu H, Deng Y F, Shi Z C, Qian Y X, Meng Y Z, Chen G H. J. Mater. Chem. A, 2013, 1(47): 15142.
[25]

Zhou G M, Pei S F, Li L, Wang D W, Wang S G, Huang K, Yin L C, Li F, Cheng H M. Adv. Mater., 2014, 26(4): 625.
[26]

Du Z Z, Guo C K, Wang L J, Hu A J, Jin S, Zhang T M, Jin H C, Qi Z K, Xin S, Kong X H, Guo Y G, Ji H X, Wan L J. ACS Appl. Mater. Interfaces, 2017, 9(50): 43696.
[27]

Zhou G M, Li L, Wang D W, Shan X Y, Pei S F, Li F, Cheng H M. Adv. Mater., 2015, 27(4): 641.
[28]

Zhai P Y, Peng H J, Cheng X B, Zhu L, Huang J Q, Zhu W C, Zhang Q. Energy Storage Mater., 2017, 7: 56.
[29]

Ji L W, Rao M M, Zheng H M, Zhang L, Li Y C, Duan W H, Guo J H, Cairns E J, Zhang Y G. J. Am. Chem. Soc., 2011, 133(46): 18522.
[30]

Song M K, Zhang Y G, Cairns E J. Nano Lett., 2013, 13(12): 5891.
[31]

Zeng Q R, Leng X, Wu K H, Gentle I R, Wang D W. Carbon, 2015, 93: 611.
[32]

Du X Y, Zhang X L, Guo J L, Zhao S P, Zhang F X. J. Alloy. Compd., 2017, 714: 311.
[33]

Shaibani M, Akbari A, Sheath P, Easton C D, Banerjee P C, Konstas K, Fakhfouri A, Barghamadi M, Musameh M M, Best A S, Rüther T, Mahon P J, Hill M R, Hollenkamp A F, Majumder M. ACS Nano, 2016, 10(8): 7768.
[34]

Zhuang T Z, Huang J Q, Peng H J, He L Y, Cheng X B, Chen C M, Zhang Q. Small, 2016, 12(3): 381.
[35]

Zhu P, Zang J, Zhu J D, Lu Y, Chen C, Jiang M J, Yan C Y, Dirican M, Selvan R K, Kim D, Zhang X W. Carbon, 2018, 126: 594.
[36]

Balach J, Jaumann T, Klose M, Oswald S, Eckert J, Giebeler L. J. Power Sources, 2016, 303: 317.
[37]

Pang Q, Liang X, Kwok C Y, Nazar L F. Nat. Energy, 2016, 1(9): 16132.
[38]

Xu H, Deng Y F, Zhao Z X, Xu H J, Qin X S, Chen G H. Chem. Commun., 2014, 50(72): 10468.
[39]

Zhou X Y, Liao Q C, Bai T, Yang J. J. Electroanal. Chem., 2017, 791: 167.
[40]

Zhang Z A, Wang G C, Lai Y Q, Li J, Zhang Z Y, Chen W. J. Power Sources, 2015, 300: 157.
[41]

Zhou X Y, Liao Q C, Tang J J, Bai T, Chen F, Yang J. J. Electroanal. Chem., 2016, 768: 55.
[42]

Zhang L L, Wan F, Wang X Y, Cao H M, Dai X, Niu Z Q, Wang Y J, Chen J. ACS Appl. Mater. Interfaces, 2018, 10(6): 5594.
[43]

Yuan X Q, Wu L S, He X L, Zeinu K, Huang L, Zhu X L, Hou H J, Liu B C, Hu J P, Yang J K. Chem. Eng. J., 2017, 320: 178.
[44]

Han P, Manthiram A. J. Power Sources, 2017, 369: 87.
[45]

Pei F, Lin L L, Fu A, Mo S G, Ou D H, Fang X L, Zheng N F. Joule, 2018, 2(2): 323.
[46]

Yuan H D, Liu T F, Liu Y J, Nai J W, Wang Y, Zhang W K, Tao X Y. Chem. Sci., 2019, 10(32): 7484.
[47]

Li S Q, Ren G F, Hoque M N F, Dong Z H, Warzywoda J, Fan Z Y. Appl. Surf. Sci., 2017, 396: 637.
[48]

Liu T, Sun S M, Song W, Sun X L, Niu Q H, Liu H, Ohsaka T, Wu J F. J. Mater. Chem. A, 2018, 6(46): 23486.
[49]

Huang Y, Zheng M B, Lin Z X, Zhao B, Zhang S T, Yang J Z, Zhu C L, Zhang H, Sun D P, Shi Y. J. Mater. Chem. A, 2015, 3(20): 10910.
[50]

Li S Q, Mou T, Ren G F, Warzywoda J, Wei Z D, Wang B, Fan Z Y. J. Mater. Chem. A, 2017, 5(4): 1650.
[51]

Yang J, Chen F, Li C, Bai T, Long B, Zhou X Y. J. Mater. Chem. A, 2016, 4(37): 14324.
[52]

Wang S X, Zou K X, Qian Y X, Deng Y F, Zhang L, Chen G H. Carbon, 2019, 144: 745.
[53]

Wang S X, Liu X Y, Zou K X, Deng Y F, Chen G H. J. Electroanal. Chem., 2020, 858: 113797.
[54]

Shao H Y, Ai F, Wang W K, Zhang H, Wang A B, Feng W, Huang Y Q. J. Mater. Chem. A, 2017, 5(37): 19892.
[55]

Majumder S, Shao M H, Deng Y F, Chen G H. J. Electrochem. Soc., 2019, 166(3): A5386.
[56]

Majumder S, Shao M H, Deng Y F, Chen G H. J. Power Sources, 2019, 431: 93.
[57]

Yang L Q, Li G C, Jiang X, Zhang T R, Lin H B, Lee J Y. J. Mater. Chem. A, 2017, 5(24): 12506.
[58]

Xu G Y, Yuan J R, Tao X Y, Ding B, Dou H, Yan X H, Xiao Y, Zhang X G. Nano Res., 2015, 8(9): 3066.
[59]

Xu Q, Hu G C, Bi H L, Xiang H F. Ionics, 2015, 21(4): 981.
[60]

Luo Y F, Luo N N, Kong W B, Wu H C, Wang K, Fan S S, Duan W H, Wang J P. Small, 2018, 14(8): 1702853.
[61]

Yan L J, Luo N N, Kong W B, Luo S, Wu H C, Jiang K L, Li Q Q, Fan S S, Duan W H, Wang J P. J. Power Sources, 2018, 389: 169.
[62]

Xiang M W, Wu H, Liu H, Huang J, Zheng Y F, Yang L, Jing P, Zhang Y, Dou S X, Liu H K. Adv. Funct. Mater., 2017, 27(37):1702573.
[63]

Yang Y B, Zhang L T, Xu H, Qin X S, Deng Y F, Chen G H. ACS Sustainable Chem. Eng., 2018, 6(12): 17099.
[64]

Li N, Chen Z X, Chen F, Hu G J, Wang S G, Sun Z H, Sun X D, Li F. Carbon, 2019, 143: 523.
[65]

Liu T, Sun S M, Hao J L, Song W, Niu Q H, Sun X L, Wu Y, Song D P, Wu J F. ACS Appl. Mater. Interfaces, 2019, 11(17): 15607.
[66]

Yang Y B, Xu H, Wang S X, Deng Y F, Qin X Y, Qin X S, Chen G H. Electrochimica Acta, 2019, 297: 641.
[67]

Fang D, Wang Y, Liu X, Yu J, Qian C, Chen S, Wang X, Zhang S. ACS Nano, 2019, 13:1563.
[68]

Sun W, Ou X G, Yue X Y, Yang Y X, Wang Z H, Rooney D, Sun K N. Electrochimica Acta, 2016, 207: 198.
[69]

Hu N N, Lv X, Dai Y, Fan L L, Xiong D B, Li X F. ACS Appl. Mater. Interfaces, 2018, 10(22): 18665.
[70]

Xiao Z B, Yang Z, Wang L, Nie H G, Zhong M E, Lai Q Q, Xu X J, Zhang L J, Huang S M. Adv. Mater., 2015, 27(18): 2891.
[71]

Yi R W, Liu C G, Zhao Y C, Hardwick L J, Li Y Q, Geng X W, Zhang Q, Yang L, Zhao C Z. Electrochimica Acta, 2019, 299: 479.
[72]

Tan L, Li X H, Wang Z X, Guo H J, Wang J X. ACS Appl. Mater. Interfaces, 2018, 10(4): 3707.
[73]

He J R, Hartmann G, Lee M, Hwang G S, Chen Y F, Manthiram A. Energy Environ. Sci., 2019, 12(1): 344.
[74]

Zhou T H, Lv W, Li J, Zhou G M, Zhao Y, Fan S X, Liu B L, Li B H, Kang F Y, Yang Q H. Energy Environ. Sci., 2017, 10(7): 1694.
[75]

Fan Y, Yang Z, Hua W X, Liu D, Tao T, Rahman M M, Lei W W, Huang S M, Chen Y. Adv. Energy Mater., 2017, 7(13): 1602380.
[76]

Zhou T H, Zhao Y, Zhou G M, Lv W, Sun P J, Kang F Y, Li B H, Yang Q H. Nano Energy, 2017, 39: 291.
[77]

Babu G, Masurkar N, Al Salem H, Arava L M R. J. Am. Chem. Soc., 2017, 139(1): 171.
[78]

Wei Y H, Wang Y C, Zhang X M, Wang B Y, Wang Q, Wu N T, Zhang Y, Wu H. ACS Appl. Mater. Interfaces, 2020, 12(31): 35058.
[79]

Yu B, Chen D J, Wang Z G, Qi F, Zhang X J, Wang X Q, Hu Y, Wang B, Zhang W L, Chen Y F, He J R, He W D. Chem. Eng. J., 2020, 399: 125837.
[80]

Ma Q Y, Hu M F, Yuan Y, Pan Y K, Chen M Q, Zhang Y Y, Long D H. J. Colloid Interface Sci., 2020, 566: 11.
[81]

Du M, Li Q, Zhao Y, Liu C S, Pang H. Coord. Chem. Rev., 2020, 416: 213341.
[82]

Jiang G Y, Zheng N, Chen X, Ding G Y, Li Y H, Sun F G, Li Y S. Chem. Eng. J., 2019, 373: 1309.
[83]

Song C L, Li G H, Yang Y, Hong X J, Huang S, Zheng Q F, Si L P, Zhang M, Cai Y P. Chem. Eng. J., 2020, 381: 122701.
[84]

Skoda D, Kazda T, Munster L, Hanulikova B, Styskalik A, Eloy P, Debecker D P, Vyroubal P, Simonikova L, Kuritka I. J. Mater. Sci., 2019, 54(22): 14102.
[85]

Zhou, Li, Fang, Zhao, Wang, Zhang, Zhou,. Nanomaterials, 2019, 9(11): 1574.
[86]

Qiao B T, Wang A Q, Yang X F, Allard L F, Jiang Z, Cui Y T, Liu J Y, Li J, Zhang T. Nat. Chem., 2011, 3(8): 634.
[87]

Li Z, Ji S F, Liu Y W, Cao X, Tian S B, Chen Y J, Niu Z Q, Li Y D. Chem. Rev., 2020, 120(2): 623.
[88]

Du Z Z, Chen X J, Hu W, Chuang C H, Xie S, Hu A J, Yan W S, Kong X H, Wu X J, Ji H X, Wan L J. J. Am. Chem. Soc., 2019, 141(9): 3977.
[89]

Li Y J, Wu J B, Zhang B, Wang W, Zhang G Q, Seh Z W, Zhang N, Sun J, Huang L, Jiang J J, Zhou J, Sun Y M. Energy Storage Mater., 2020, 30: 250.
[90]

Shi H D, Ren X M, Lu J M, Dong C, Liu J, Yang Q H, Chen J, Wu Z S. Adv. Energy Mater., 2020, 10(39): 2002271.
[91]

Zhang L L, Liu D B, Muhammad Z, Wan F, Xie W, Wang Y J, Song L, Niu Z Q, Chen J. Adv. Mater., 2019, 31(40): 1903955.
[92]

Li Y J, Lin S Y, Wang D D, Gao T T, Song J W, Zhou P, Xu Z K, Yang Z H, Xiao N, Guo S J. Adv. Mater., 2020, 32(8): 1906722.
[93]

Zhang K, Chen Z X, Ning R Q, Xi S B, Tang W, Du Y H, Liu C B, Ren Z Y, Chi X, Bai M H, Shen C, Li X, Wang X W, Zhao X X, Leng K, Pennycook S J, Li H P, Xu H, Loh K P, Xie K Y. ACS Appl. Mater. Interfaces, 2019, 11(28): 25147.
[94]

Chung S H, Manthiram A. Adv. Mater., 2014, 26(43): 7352.
[95]

Zhuang T Z, Huang J Q, Peng H J, He L Y, Cheng X B, Chen C M, Zhang Q. Small, 2016, 12(3): 381.
[96]

Chang C H, Chung S H, Manthiram A. J. Mater. Chem. A, 2015, 3(37): 18829.
[97]

Wang A X, Xu G Y, Ding B, Chang Z, Wang Y, Dou H, Zhang X G. ChemElectroChem, 2017, 4(2): 362.
[98]

Fu X W, Wang Y, Scudiero L, Zhong W H. Energy Storage Mater., 2018, 15: 447.
[99]

Zhu P, Zhu J D, Zang J, Chen C, Lu Y, Jiang M J, Yan C Y, Dirican M, Kalai Selvan R, Zhang X W. J. Mater. Chem. A, 2017, 5(29): 15096.
[100]

Qu L, Liu P, Yi Y K, Wang T, Yang P, Tian X L, Li M T, Yang B L, Dai S. ChemSusChem, 2019, 12(1): 213.

Funding

NSFC-RGC Joint Research Scheme(21661162002)

NSFC-RGC Joint Research Scheme(N_HKUST601/16)

Guangdong Key R&D Program of China(2019B090908001)

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