Synthesis Of LiFePO₄ And Its Electrochemical Properties

LiFePO4 (LFP) is regarded as a promising cathode material for next-generation lithium-ion battery (LIB), owning to its high theoretical capacity (170 mAh g-1), suitable voltage plateau (3.4 V), low cost, environmental compatibility, ideal thermal stability, etc. However, large-scale application of LFP is limited due to low electronic conductivity and Li+ diffusion coefficient of solid phase, low tap density and poor rate capability. The main contents in the present work are as follows:(1) LFP microspheres with different particle sizes and structures were fabricated by using a hydrothermal process. Theses microspheres were composed of nanoparticles and used as the cathode materials for LIBs. It exhibited an attractive rate capability with initial discharge capacities of 168,152,144,130, and 115 mAh g"1 at 0.1,1,2,5 and 10 C, respectively. This material with a large number of pores allows permeation of electrolyte sufficiently, and also provides a huge electrochemically available surface for enhancing the rate capability of Li+ intercalation. On the other hand, LFP microsphere composed of nanoparticles could offer a short distance for Li+ transport and electrolyte diffusion in the electrode material, resulting in the electrochemical properties were enhanced.(2) LFP nanoplates with the exposed facets of (010) and (100) were successfully synthesized via a solvothermal route. It was found that LFP nanoplates with crystal orientations along the ac facet and be facet exhibited different electrochemical performances. The impedances of LFP nanoplates with an exposed facet (010) were less than that with an exposed facet (100).(3) Using an ionic liquid solvothermal method, hierarchically structured LFP constructed from nanostructured platelets with an exposed (010) facets mainly was successfully synthesized, and a tentative mechanism for the formation of hierarchical structures was proposed. The cathode made of hierarchical LFP coated with a thin carbon layer exhibited excellent high-rate discharge capability and cycling stability.