Lithium-sulfur (Li-S) battery is a promising electrochemical energy storage system that has high theoretical energy density of 2600 Wh·kg^-1, which is 3 to 5 times that of Li-ion batteries. It has attracted more and more attentions in recent years. Great efforts have been made to improve the stability of electrode structure, the utilization efficiency of sulfur in the cathode and the enhancement of cycle life of the battery. In this paper, the recent progress of the lithium-sulfur battery is reviewed from four aspects: modification of sulfur-based composite cathode material, electrolytes, protection of lithium anode and design of lithium-sulfur cell configurations. The main factors on the specific capacity and cycle stability of the lithium-sulfur battery are analyzed. The prospects and development trends on lithium-sulfur battery are also discussed.

Contents
1 Introduction
2 Lithium sulfur battery system
3 Cathode materials of lithium sulfur battery
3.1 Metal sulfides
3.2 Organic sulfides
3.3 Sulfur /metallic oxide composite materials
3.4 Sulfur / carbon composite materials
3.5 Sulfur / polymer composite materials
3.6 Other cathode materials
4 Electrolytes
4.1 Organic liquid electrolytes
4.2 All solid sate electrolytes
4.3 Gel polymer electrolyte
4.4 Ionic liquids
5 Lithium anode protection
5.1 Coating method
5.2 Electrolyte additive
5.3 Lithium alloy
5.4 Pre-passivation of lithium
6 Li-S cell configuration
7 Conclusion and outlook