The Preparation Of Ti₃C₂T_x Mxene Composite For Sodium-ion Batteries

Lithium-ion batteries have been widely used in people's production and life due to their high energy density,high operating voltage and fast charge and discharge rates.However,the development of lithium-ion batteries has been hampered by the dilemma of limited reserves and unequal distribution of lithium resources.Fortunately,sodium is abundant in the earth's crust,the raw materials are cheap,and sodium has electrochemical energy storage properties similar to lithium.However,the low energy density and slow charge-discharge rate of Na-ion batteries limit their applications.Therefore,it is necessary to explore new electrode materials and develop next-generation Na-ion batteries.In this paper,based on the electrostatic self-assembly strategy,Ti₃C₂T_xMXene/r GO(MX-G)aerogels were prepared as anode materials for sodium-ion batteries,and Na₃V₂(PO₄)₂F₃@C(NVPF@C)composites were prepared by sol-gel method.The material is used as a cathode material for sodium-ion batteries,and the two are paired to assemble a sodium-ion full battery.The main research contents and main results obtained are as follows:(1)Negatively charged Ti₃C₂T_x MXene materials were prepared by an optimized minimum strength layer exfoliation method,and GO nanosheets were modified with polydiallyldimethylammonium chloride to obtain positively charged r GO.Nanosheets.Ti₃C₂T_x MXenes were combined with r GO nanosheets based on electrostatic self-assembly strategy,and then MX-G aerogels were obtained by freeze-drying.Experimental tests show that the MX-G aerogel has a large specific surface area and a porous microstructure,and the Ti₃C₂T_x MXene and r GO nanosheets are arranged in an orderly manner.The effects of different r GO mass fractions on the electrochemical properties of MX-G aerogels as anodes for sodium-ion batteries were comparatively studied.(2)NVPF@C composites were synthesized by the sol-gel method,and it was found that the synthesized materials had small size and high purity,and the carbon coating layer was uniform.Electrochemical tests show that NVPF@C has high specific discharge capacity and good cycling stability as a cathode material for Na-ion batteries.(3)A sodium-ion full battery was assembled with the MX-G aerogel electrode as the negative electrode and the NVPF@C composite electrode as the positive electrode.The influence of the change of the mass ratio of positive and negative active materials on the electrochemical performance of the whole battery was studied and analyzed,and the optimal mass ratio of positive and negative active materials was determined.Experimental tests show that the assembled Na-ion full battery has high specific capacity and excellent cycling and rate characteristics.