The liquid state method has the advantages of fast heat and mass transfer, controlled particle size and shape of materials, so it is widely used in the preparation of various types of materials. In this paper, the process, principle and research progress of co-precipitation method, solvothermal method and sol-gel method for the synthesis of lithium iron phosphate are compared and summarized:the basic requirement of liquid phase synthesis is nano particle size, high specific surface area and carbon coating,which can solve the problem of low electron conductivity and slow lithium ion diffusion rate, accordingly improve the rate performance of materials. The co-precipitation method has advantage in synthesizing the densely packed spherical morphology materials to obtain high tap density and improve the energy density of materials. Solvothermal method is beneficial to synthesize large (010) surface materials, shorten the distance of lithium ion diffusion, and improve the rate performance of the material. Sol-gel can achieve molecular level mixing, which is favorable for the preparation of homogeneous and in situ carbon coated materials. Scientists introduce materials of high electronic conductivity and ionic conductivity to improve conductivity of LiFePO₄. Compared with the solid phase method, to investigate a fast, facile process, low cost and easily-industrialized method, and to promote the development and progress of liquid state method in principle and technology is the research direction.

Contents
1 Introduction
2 Synthesis of lithium iron phosphate by co-precipitation method
2.1 Syntheses of nano material
2.2 The reaction mechanism
2.3 Improving tap density of the material
2.4 Introduce high conductivity materials
3 Synthesis of lithium iron phosphate by solvothermal method
3.1 Syntheses of the material of large (010) surface
3.2 Syntheses of the material with nano particle size and high specific surface area
3.3 Introduce high conductivity materials
3.4 The reaction mechanism
4 Synthesis of lithium iron phosphate by sol-gel method
4.1 The chelant
4.2 Introduce high conductivity materials
4.3 Amphiphilic surfactant
5 Conclusion