High Magnification K-birnessite Cathode For Potassium-ion Battery:preparation Technology And Potassium Storage Performance Research

The research on the new type of secondary battery with low cost and fast charge and discharge is of great significance to the development and application of energy storage systems today.Birnessite is a very competitive battery anode material because of its low raw material price and special layered structure.In this paper,P2 short rod-shaped birnessite was prepared by high-temperature calcination and solvothermal method was used to prepare P3 flower-shaped birnessite,and the flower-shaped birnessite was modified by ion doping method.Potassium storage properties of manganese ore materials were studied.Using potassium permanganate as raw material,mixed solution of ethanol and deionized water as solvent,MnOOH nanoneedles were prepared by hydrothermal method;MnOOH nanoneedles are precursors and potassium carbonate is used as a raw material.A series of short rod-shaped potassium-type sodium bimanganese ore materials were prepared by high-temperature calcination by changing the K/Mn ratio(K0.314Mn0.98O2·0.5H2O)·The sample prepared under the conditions of 850? and K/Mn=1 has best crystallinity.The potassium ion half-cell assembled as a positive electrode material was discharged at the first cycle at 20mA g-1 current density The specific capacity can reach 166 mAh g-1 Comparing the sodium bimanganese ore prepared by the traditional manganese source precursor,it is confirmed that the nanoneedle precursor has obviously optimized and improved the product structure and performance.Directly synthesize P3-type flower globular birnessite material by solvothermal method,and successfully apply it to the positive electrode of potassium ion battery.Regulating the potassium content in the product and particle size only changes the K/Mn ratio of the reactants.The effects of K content,sample microstructure on electrochemical performance were studied in detail.K0.26MnO2·0.33H2O prepared at K/Mn=6 for potassium ion half-cells can provide a first-cycle discharge specific capacity of 131 mAh g-1 at a current density of 500 mA g-1;At the high current density of 10000 mA g-1,the electrode can provide a specific capacity of 57 mAh g-1,and can circulate 5,000 cycles steadily(A charge and discharge process can be completed within 2min).Furthermore,In-situ XRD analysis showed that the layer structure changed reversibly during the charging and discharging process,which made potassium ions reversible deintercalation,thus ensuring the stability of the battery charging and discharging process.Prepared P3 type flower globular birnessite modified by magnesium ion doping.When Mg/Mn=0.1,the potassium ion half-cell assembled from the prepared sample can provide a specific discharge capacity of 87 mAh g-1 at the current density of 1000 mA g-1.After 100 cycles,there are still 55%Retention rate,Coulomb efficiency is always maintained above 95%,with the best cycle stability and rate performance.