Architecture Of MXenes Based Anode Materials And The Investigation Of Energy Storage Mechanism

With the development of mobile consumer electronics,electric and hybrid vehicles,home power storage equipment and large-scale power supply facilities,the demand for storage of electric energy continues to increase.Lithium ion battery as an important representative of secondary energy storage,the development of a new generation of anode materials with high capacity,ideal charge/discharge voltage platform,excellent safety and low cost is the core issue of lithium ion battery research.In this dissertation,with the consideration of the electrochemical reaction mechanism, the electron transfer and ion transport were selected as the parameters of the anodes.Depend on the ability of fast electronic and ionic transport of MXenes,the nanosized Co Fe₂O₄ particles and silica particles were employed to construct hybrid anodes with the three-dimensional structure.The details are as follows:1.As a prerequisite of the investigation,Ti₃C₂T_x-MXene was prepared via selectively etching Al in the MAX phase ceramic material Ti₃Al C₂ by using HCl and LiF.And a flexible and free-standing Ti₃C₂T_x-MXene film was fabricated by vacuum auxiliary suction filtration technology.Monodisperse Co Fe₂O₄ nanoparticles were obtained by high-temperature thermal decomposition of organic alkoxide.Structure and morphology characterizations were conducted in detail.The preparation principle of the two materials and the energy storage mechanism of lithium ion batteries were summarized.2.A flexible and integrated film electrode with three-dimensional porous structure of Ti₃C₂T_x-MXene and Co Fe₂O₄ nanoparticles composites was constructed by two-step vacuum filtration technology.The introduction of Ti₃C₂T_x-MXene builds a channel for electron/ion transport,which not only effectively improves the specific capacity and magnification,but also optimizes the structural stability of Co Fe₂O₄ nanoparticles in the cycle.This architecture exhibits promising electrochemical performance with a reversible capacity of 676 m Ah g^-1 and stable cycling behaviour for 940 cycles.3.The introducing of Ti₃C₂T_x-MXene as a carrier for Si nanoparticles,a composite film electrode was constructed by suction filtration.Ti₃C₂T_x-MXene provides fast ion/electron transport for composite electrodes,and which can also store charge by synergistic Si alloying reaction with Ti₃C₂T_x-MXene intercalation reaction mechanism.In addition,the introduction of Ti₃C₂T_x-MXene can reduce the charge accumulation in the electrode and inhibit the volume expansion of Si,thereby increasing the electrode depth of Si and the electrochemical cycle capability.This architecture exhibits a gravitational specific capacity of～557.7 m Ah g^-1 after 500 cycles(the c-discharge current density is～100 m A g^-1)and an excellent cycling stability were obtained.In this paper,Ti₃C₂T_x-MXene was introduced to construct Ti₃C₂T_x-MXene&Co Fe₂O₄integrated electrode and Ti₃C₂T_x-MXene&Si hybrid electrode.The introduction of Ti₃C₂T_x-MXene not only optimizes the electrochemical performance of the electrodes by improving their electron transfer/ion transport capabilities,but also improves the mechanical properties of the electrodes so that they can resist electrode damage during charge-discharge cycles.