Surface engineering of Li3V2(PO4)3-based cathode materials with enhanced performance for lithium-ion batteries working in a wide temperature range

Abstract

Operating at extreme temperatures is the biggest challenge for lithium-ion batteries (LIBs) in practical applications, as both the capacity and cycling stability of LIBs are largely decreased due to the sluggish reaction kinetics of the cathodes. Therefore, developing suitable cathode materials is the key point to tackling this challenge. Lithium vanadium phosphate [Li3V2(PO4)3, LVP] is a promising cathode with good features of a high working voltage, high intrinsic ionic diffusion coefficiency, and stable olivine structure in a wide temperature range, although it is perplexed by the low electronic conductivity. To tackle this issue, a series of nitrogen-doped carbon network (NC) coated LVP composites were synthesized using a hydrothermal-assisted sol-gel method. Among them, the LVP@NC-0.8 sample exhibited a remarkable tolerance at a high charging cutoff voltage of 4.8 V in a wide temperature range. Full cells of LVP@NC-0.8||graphite exhibited superior performance at different current rates. Moreover, the reaction mechanism of the LVP@NC-0.8 electrode was proved by in-situ X-ray diffraction technique, demonstrating that temperature was a critical factor that contributed to the sluggish phase transformation with high voltage hysteresis at low temperature and severe crystal structure distortion at high temperature. Theoretical calculations further demonstrated the superiority of the NC for high electronic conductivity and reduced lithium transportation barriers. The enhanced electrochemical performances of LVP-based cathode materials have provided the possible application of LIBs in a wide temperature range.