Study On Potassium Ion Storage Properties Of SbVO₄ And BiVO₄

Potassium-ion batteries have attracted much attention due to their high resource abundance,low cost and high theoretical specific capacity.However,the carbon-based anodes used in most potassium-ion batteries have become one of the biggest obstacles in their development and application due to their low specific capacity,easily damaged material structure,and poor reversibility.The alloy-type anode material has excellent electrical conductivity and cycle reversibility,and can form a potassium alloy when combined with potassium ions,has a high theoretical specific capacity.In addition,conversion-type anode materials also have good theoretical specific capacity,but due to poor conductivity,voltage hysteresis and excessive polarization often occur.In this paper,alloying elements are combined with conversion matrixes（such as vanadates）in order to promote each other:（1）In Chapter 3,an attempt is made to combine the alloying element Sb with a conversion matrix such as vanadate to form a SbVO₄ anode material by a simple hydrothermal method.The charge-discharge cycle proves that the finally obtained Sb VO₄ anode material has the characteristics of high capacity and long life.The potassium ion storage mechanism of Sb VO₄ anode material was studied by in-situ X-ray diffraction,X-ray photoelectron spectroscopy and other means,and it was confirmed that it underwent electrochemical reconstruction during the first discharge process,and then Sb and K₃VO₄ Each reacts with potassium ions,which just shows that the alloy-type reaction and the transformation-type reaction can promote each other to maintain stability.It provides a reference for designing different types of composite reactions to realize high-performance（2）In Chapter 4,we designed to combine the alloying element Biwith a vanadate matrix to obtain a Polypodiodes chinensis-like BiVO₄ anode by a one-step hydrothermal method.The charge-discharge test found the high rate characteristics of BiVO₄ anode material.In-situ XRD proves that the BiVO₄ electrode material realizes potassium ion storage through the combination of Biand vanadate ions VO₄^3-replacement with potassium ions,which is a new potassium storage mechanism and delays the original Bisingle potassium storage.The potassium ion storage can be stabilized even with high current charge and discharge.