China Nonferrous Metallurgy

K_xV₂O₅ with excellent electrochemical properties can be used as an excellent cathode material for aqueous zinc-ion batteries, and its controllable synthesisis especially important.In this study,the effects of the molar ratio of oxalic acid (C₂H₂O₄·₂H₂O) to vanadium pentoxide (V₂O₅) on the structure, morphology and electrochemical properties of potassium vanadate (K_0.486V₂O₅) cathodes were investigated. The controllable preparation of K_0.486V₂O₅ was achieved.The results show that when the molar ratio of C₂H₂O₄·₂H₂O/V₂O₅ is about 5∶2, potassium vanadate has higher crystallinityandmore regularnanorod-likemorphology. The distinct pseudocapacitive effect endows it with excellent rate performance and outstanding kinetic characteristics, showing high capacity and good cycling stability. At current densities of 0.1,0.2,0.5, 1,2,5 and 10A·g^-1, the discharge specific capacities are 395.3,366.9,323.4,283.5,247.7,181.8 and 127.3mAh·g^-1, respectively. At a high current density of 5A·g^-1, it still delivers a reversible capacity of 196.5mAh·g^-1 after 2000 cycles with an ultrahigh capacity retention rate of 127.9%.The energy storage process of K_0.486V₂O₅ is controlled by ion diffusion process and surface capacitance behavior. With the increase of the scanning rate, the storage of Zn²⁺ is mainly controlled by the capacitive behavior. The significant pseudocapacitance effect is the key factor to obtaining excellent rate performance and eminentkinetic behavior.