Nano-silicon And Ti₃C₂ Composite Material And Its Lithium-ion Battery Anode Performance

With the concept of sustainable development and green environmental protection,today,people pay more attention to the use of clean energy.Unlike traditional energy,electric energy is not only related to all aspects of our lives,but also plays an important role in gradually replacing non-renewable energy sources such as coal and oil.As a device for storing and transforming electric energy,lithium-ion batteries have been received more and more attention from researchers.Therefore,the development of lithium-ion batteries with high energy density and long cycle life will become a hot research direction.As we all know,lithium-ion batteries are mainly composed of a cathode,an electrolyte,a separator,and an anode.In the current research on lithium-ion batteries,the anode material graphite has been commercialized,but at the same time,researchers have also found that silicon(Si)is used as an anode material.It can reach a theoretical capacity of 4200 m Ah/g,and other forms of silicon-based materials also have a certain capacity for storing lithium,such as metallic silicon and silicon oxide.In this paper,the two-dimensional MXene Ti₃C₂ obtained by etching is used as the reaction substrate,and different silicon sources such as ethyl silicate and inorganic small molecule silicon tetrachloride are used as the silicon source to explore its application in the two-dimensional MXene Ti₃C₂,in order to research on the reaction mechanism of interlayer fixation and various aspects of performance as an anode material for lithium-ion batteries.The results are as follows:(1)Use 40%HF to etch the MAX phase material to obtain two-dimensional MXene Ti₃C₂,wash it repeatedly until the p H is about 6,centrifuge to obtain the precipitate,dry it,and then wash using alkaline to obtain the sample which is rich-OH functional groups on the surface.Ti₃C₂ is inspected by infrared spectroscopy(IR),X-ray diffraction(XRD),etc.,and the changes of surface functional groups are also analyzed.(2)The ethyl silicate using as the silicon source is in-situ synthesized to perform a compound with the two-dimensional MXene Ti₃C₂.Using the abundant functional groups on the surface of the two-dimensional MXene Ti₃C₂ to react with ethyl silicate,the silicon-based material is fixed between the interlayers of the two-dimensional material,and the resulting intermediate product Ti₃C₂/Si O₂ is reduced to obtain the final target Ti₃C₂/Si,and characterization,such as Raman spectrum(Raman),scanning electron microscope(SEM),X-ray photoelectron spectroscopy(XPS),etc.;electrochemical testing,such as constant current charge and discharge test,cyclic voltammetry.The results show that the capacity of Ti₃C₂/Si is about 690 m Ah/g at a current density of 0.2 A/g.(3)Using the small molecule Si Cl₄ as the silicon source is in-situ synthesized with two-dimensional MXene Ti₃C₂.Physical and electrochemical detection is performed and the results show that small molecules can enter the various layers of Ti₃C₂ more easily and uniformly.At the same time,the original structure is not destroyed.The electrochemical performance shows that the obtained composite material has a higher capacity.At a current density of 0.2 A/g,the first coulombic efficiency is about 90%,and the capacity remains about 855 m Ah/g after 100 cycles.It is proved that the small molecule Si Cl₄ can interact in the two-dimensional Ti₃C₂ in the negative electrode of the lithium ion battery,and has good reversibility and stability.