Preparation And Properties Of Potassium Ion Batteries Cathode Materials Based On Layered MnO₂

With the wide application of lithium-ion batteries in portable electronic devices,energy storage equipment and other fields,the demand for lithium is increasing rapidly year by year.However,global reserves of lithium are very limited and unevenly distributed,which causes the rapid rise in the price of raw materials,seriously restricting the rapid development of low-cost,high-performance energy storage devices in China.Potassium with abundant reserves and low cost attracts more and more researchers to turn their attention to potassium ion batteries because of its similar physical and chemical properties to lithium and lower redox potential compared with sodium.Manganese dioxide is rich in minerals,low in cost and numerous in synthetic methods.The layered MnO₂ layer has larger spacing,which can be used for potassium ions with larger ionic radius to embed and exfoliate between the layers.The selection of low cost layered manganese dioxide as the cathode material of the potassium ion battery can solve the urgent problem of the lack of suitable cathode material（Effective insertion and removal of potassium ions）.The main contents of this thesis include the following aspects:（1）The energy storage mechanism and composition of potassium ion batteries are reviewed in detail in this paper.The positive and negative materials of the potassium ion battery were summarized,the classification and storage mechanism of the electrode materials were briefly analyzed and introduced,and the research prospect and research ideas of this paper were put forward.At the same time,the experimental drugs and experimental equipment involved in the experiment were summarized,and the experimental methods and testing methods used in the paper were expounded in detail.（2）In this paper,a homogeneous MnO₂ nanosheet arrays was prepared on carbon fiber by hydrothermal method,and then the interlayer potassium ion content was regulated on the basis of no obvious change of the original structure by further hydrothermal reaction.The further hydrothermal conditions were 0 h,2 h,5 h and 10 h at 205℃,respectively,and S0,S1,S2 and S3 with different potassium contents were obtained.The electrochemical performance of the cathode material for potassium ion battery was tested.The results showed that the electrochemical performance of S2 was the best.Under the current density of 100 mA g^-1,the high reversible capacity of 134 mAh g^-1 is shown,and the capacity remains at 93%after 100cycles,reflecting the good cycle performance.In this paper,a method to regulate the concentration of potassium ion in MnO₂ layer and the electrochemical performance of different potassium ion content samples can be used to guide the application of other layered materials to the research of potassium ion batteries.