Abstract
In recent years, as the popularity rate of consumer electronic product increases, the demand of secondary energy storage device increases. Among them, lithium ion battery(LIB) which possessed outstanding energy density and cycle life has gotten much attention. For the commercial anode materials of LIB, lithium titanate(LTO)metal oxide anode has shown 300 times the cycle life of carbon materials and higher charge/discharge rate, making it stand out from the market. In recent research, vanadium pentoxide(V2O5) has revealed the same lithium storage mechanism as LTO and has the higher amount of lithium intercalation than LTO, it’s more suitable for anode material. Moreover, amorphous V2O5 gets more reversible specific capacity than crystalline state. In this thesis, we directly deposited amorphous V2O5 on porous nickel foam current collector by hydrothermal process. The LIB test demonstrates that after 50 cycles, the reversible specific capacity can reach 884 mAh/g and the retention can be maintained at 94.21% under low current density 0.5C. However, when the current density increases to 1C level, the retention decreases merely to 77.74% after 50 cycles. By taking differential capacity curves into comparison, we find the effect of charge/discharge rate that affects the low-voltage specific capacity. In contrast, the degradation of retention mainly takes place at high-voltage peak. On the other hand, when amorphous V2O5 combined with reduced graphene oxide(rGO), it promotes the retention to 82% at a rate of 1C. Besides, through AC impedance analysis, the RC time constant model has been utilized to simulate the electrochemical reaction of equivalent circuit. Based on the result of time constant, the key point of charging/discharging stability is caused by the charge transfer resistance Rct between amorphous V2O5 and nickel foam interface.