Preparation And Lithium Storage Performance Of Metal Oxides/Mxene Composites

The development of new technologies,such as electric vehicles,pushes up the demand of high-performance lithium ion batteries(LIBs),as well as excellent anode materials.Metal oxides are rich in resources and have a large specific capacity,making them competitive candidates for LIB anode materials.However,poor conductivity and large volume expansion make them difficult for practical applications.MXene is a new type of graphene-like two-dimensional material with high conductivity,toughness,mechanical strength and excellent hydrophilicity.Here,by combining MXene with metal oxides and taking advantage of their synergy effect,this thesis designs flexible integrated metal oxide/MXene electrodes and improves the electrochemical performance.1.Flower-like NiO and MXene solutions are mixed and filtered to prepare flower-NiO/MXenes composite electrode.MXene plays a multifunctional role in the electrode,including as a binder,a flexible backbone,and a conductive additive,which helps to improve the conductivity of the over-all electrode and accommodate the volume expansion of metal oxides during the repeated charge/discharge process.NiO are encapsulated between the MXene layers and can avoid the restacking of MXene nanosheets.Thus NiO/MXene-70%shows stable cycle performance with a specific capacity of 917 mAh g-1 after 30 cycles at 100 mA g-1 and a specific capacity of 410 mAh g-1 at 2 A g-1.Compared with pure nickel oxide,the performance has been significantly improved.2.Two-dimensional NiO and MXene are combined to construct NiO/MXene flexible composite electrodes with 2D-2D structure,and explore the influence of different mass ratios of MXene(20%,30%and 40%)on the structure and performance of the composite electrodes.2D-2D structure can optimize the electrical contact between NiO and MXene and improve the rate performance of the composite electrode.When the content of MXenes is 30%,the electrochemical performance is optimal.The specific capacity can reach 952 mAh g-1 after 50 cycles at a current density of 100 mA g-1,and 579 mAh g-1 at a current density of 2 A g-1.3.Flexible integrated composite electrodes and Bi2MoO6/MXene/CNT were prepared through vacuum filtration.MXene is used to improve the electrode conductivity and buffer the volume expansion of Bi2MoO6 during cycles,and Bi2MoO6 is used to avoid the restacking of MXene.Bi2MoO6/MXene-80%exhibits a specific capacity of 557 mAh g-1 after 100 cycles at 100 mA g-1,and the specific capacity still maintains 278 mAh g-1 at 2 A g-1.Adding CNT into the electrodes can further expand the layer spacing of MXene,construct a three-dimensional conductive network,and optimize the ion and electron transport.BMC-1%electrode keeps a specific capacity of 646 mAh g-1 after 100 cycles,and the specific capacity is 295 mAh g-1 at 2 A g-1.