Preparation And Electrochemical Properties Of Silicon-based Composite Anode Materials

Green energy batteries have been widely used in all aspects of human production and life,from mobile phones and laptops in daily life to energy storage and conversion power stations that maintain operation in production.Green energy batteries are inseparable from lithium-ion secondary batteries have become the center of development in recent years due to the rich content of lithium in the earth's crust and the low cost.As the anode materials are an important part of the lithium secondary battery that determines the battery capacity,stability,safety,and service life,the development of anode materials with high specific capacity and high energy density is the key to the current research and development of lithium ion battery materials.The theoretical specific capacity of the silicon-based anode materials can reach 4200 mAh/g,but its huge volume expansion has limited its large-scale commercial applications.In this paper,carbon nanotubes and MXene,two-dimensional sheet materials,are introduced into silicon elemental materials,and the silicon-based composite material MXene/CNTs/Si is constructed as lithium battery anodes.While suppressing the volume expansion of silicon,the electrochemical properties of the silicon-based anode materials are improved.In this paper discussed the composition of lithium-ion battery materials when pure silicon nanoparticles were used as the negative electrodes,calculated and simulated the volume change of the silicon unit cell structure to Li+insertion.The study found that the volume expansion of pure silicon negative electrodes are obvious when lithium is inserted.And it composed of nano silicon particles with smaller particle size,sodium carboxymethyl cellulose as binder,and LiPF6 electrolyte containing 5%fluoroethylene carbonate,lithium-ion batteries have smaller internal resistances,better cycle stabilities and rate performances.The selection of battery materials composition optimizes to a certain extent the volume expansion and capacity loss of pure silicon anodes during charge and discharge.On the basis of the above research,the different ratios and different synthesis methods of silicon element and carbon nanotubes were discussed.The silicon-carbon nanotube composites prepared by the best ratio and the best synthesis method has excellent cycle performance and high rate performance,and the electrochemical performance of the pure silicon anode materials are significantly improved.Carbon nanotubes wrap and intersperse silicon nanoparticles,which effectively reduces the volume expansion and poor conductivity of pure silicon anodes.Through a series of progressive experiments,the synthesis method and optimal ratio of silicon carbon nanotubes composite materials were combined with MXene by ultrasonic and vacuum filtration methods,and the "sandwich" type MXene/CNTs/Si were successfully prepared,which are film flexible composite materials.The three-dimensional layered structure is conducive to limiting the volume expansion of silicon,and also provides a channel for shortening the transmission path of lithium ions.The materials can be directly used as the anode electrodes of lithium-ion batteries,which improves the utilization rate of the active materials of the electrode materials and makes the silicon-based carbon nanotubes MXene composite materials have more excellent electrochemical properties.