Electrochemical Performances And Mechanism Explorations For Ti₃C₂ MXenes As Anode Materials For Rechargeable Batteries

High performace rechargeable batteries are urgently desired by the high power viechles,especially electric cars.Sodium-ion battery possesses abundant resource,low price and superior theoretical reversible capacity,attracting extensive interests.Anode material is a key part for battery.Therefore,it is necessary to develop anode materials with high power density and energy density,long lifespan under high rates and wide operating temperature window.MXenes can be promising anode materials for SIBs due to graphene-like structure,high conductivity and metallic and superior sodium storage performance.Therefore,sulfur-decorated and sodium intercalated Ti₃C₂ MXenes are designed and synthesized by ball-ming method and solution soaking method.Corresponding structure,fuctional group construction,morphology and related electrochemical storage mechanism are conducted by X-ray Diffraction,Fourier Transform Infrared Spectrometer,Raman,X-ray Photoelectron Spectroscopy,Scanning Electron Microscope,Transmission Electron Microscope,Cyclic Voltammetry,Electrochemical Impedance Spectroscopy,Galvanostatic cycling and ex-situ test.Kinetic parameters are calculated to research dynamical behavior.?1?Ball-mining method was chosed as pre-processing method by comparing the electrochemical performance of obtained Ti₃C₂?BM-Ti₃C₂ and NBM-Ti₃C₂?for lithium-ion batteries at amibent temperature or high temperature.?2?Sulfur-decorated Ti₃C₂ MXenes are synthesized via solution soaking method with electrostatic attraction and oxgen conjunction.More sodium-storage situations derived from sulfur groups and more rapid sodium diffusion paths have appeared in two-dimensional sodium-pillared and sulfur-decorated MXenes interlayers,contributing to excellent electrochemical performance.As an anode material for sodium-ion battery,sulfur-decorated Ti₃C₂ MXene renders an impressive reversible capacity of 135 mAh g^-1 at a high current density of 2 A g^-1 after 1000 cycles,with a low average capacity loss of 0.033%per cycle and a superior rate capability of 136.6 mAh g^-1 at 5 A g^-1.?2?Cyclic Voltammetry and Electrochemical Impedance Spectroscopy tests are used to explore the storage mechanism of two-dimensional sulfur-decorated Ti₃C₂ MXenes.Kinetic are calculated and the changes during charge/diachrage process are also determined by ex-situ test.We find that sulfur-decorated Ti₃C₂ MXenes possess self-enhanced kinetic and hybrid energy storage mechanisms,i.e.,intercalation pseudocapacitance and surface-controlled pseudocapacitance.These attributes enable sulfur-decorated Ti₃C₂ MXene to be a promising long-term and high-rate anode material for sodium-ion battery.