Preparation And Electrochemical Properties Of P Phase Manganese Based Oxide Cathode Materials For Potassium-ion Batteries

P-type layered Mn-based materials could be considered as a kind of promoting materials for potassium-ion storage as a result of their high theoretical capacities,low cost and environmentally friendly.However,the larger oxygen–oxygen distance leads to a less effective screening of the K⁺–K⁺repulsion,creating large effective ordering interactions and low content of potassium in the materials.As a result,multiple phase transitions lead to rapid capacity decay and low potassium content leads to low initial capacity.All of these will lead to poor electrochemical performance.Research on potassium ion batteries is at a bottleneck.At present,there is no specific way to solve this problem.We try to use the doping method to improve the capacity and multiplier performance of the material.The main contents are summarized as follows:1.Copper doped P2-K_0.35Mn_0.89Cu_0.11O₂·0.37H₂O was successfully prepared by a high-temperature solid-phase method with K_xMnO2 as the modified original material.We found that the copper doping can change the thickness of the TMO₂ layer and the KO₂layer,thus affecting the content of potassium ions and water between layers.Phase characterization and electrochemical tests showed that copper doping thickened the KO₂layer,which was conducive to the absorption of more potassium ions,and the material showed an additional capacity of 30 m Ahg^-1.The appropriate crystal water content provided the support function to the structure without affecting the potassium ion transport.After 150 cycles of the doped material,the capacity retention rate was 50%.The results show that doping has a positive effect on the concentration of potassium ions in the electrode and copper doped potassium manganate electrode has a potential application prospect.2.Representative P3-K_0.51Mn_0.73Co_0.27O₂ micron electrode material was successfully synthesized by a sol-gel method.The optimum temperature of the synthesis of cobalt-doped K_xMnO₂ was studied by regulating the reaction temperature.The structural evolution during charging and discharging was as revealed through a series of electrochemical tests and structural characterization.By analyzing the change of the shape of the charge-discharge curve in the process of charging and discharging,the change of the reaction electric pair in the process of cycling is studied.Utilizing ex-situ XRD test in the process of charging and discharging,we obtained the variation of cell parameters and the generation of the superstructure in the process of charging and discharging which is helpful to understand the application prospect of the elements doped with the cathode materials of lithium-ion and sodium-ion batteries in the new potassium-ion batteries.The initial discharge capacity of P3-K_0.51Mn_0.73Co_0.27O₂ micron crystal in the current density of25 mAh g^-1 is 98 mAh g^-1,after 150 cycles,the discharge capacity of 76 mAh g^-1 and capacity retention rate of 77.6%are obtained,showing the potential application prospects of this cathode in potassium ion batteries.