Preparation And Properties Of Lithium Battery Anode Material SiSn/C

With the progress of society,lithium-ion batteries with graphite as the anode electrode have become difficult to meet people’s requirements.Therefore,it is urgent to develop anode electrode materials with high specific capacity.As the anode material with the highest theoretical specific capacity,Si shows great application potential.However,as a semiconductor material,the conductivity of Si is difficult to meet the requirements for anode materials,and the huge volume effect in the process of lithium intercalation also seriously restricts the development of Si anodes.In this paper,a carbon material(NPC)with a three-dimensional porous structure was prepared by high-pressure carbonization,and the SiSn/NPC composite anode material was prepared by using its internal pore structure as a micro-site for the synthesis of Si and Sn.On the one hand,the porous structure weakens the adverse effects caused by the volume effect of the Si anode.On the other hand,the porous structure also provides a large number of ion channels for lithium ions to enter the material;and Sn,as an active metal with high electrical conductivity,can improve the material system.overall electrical conductivity.(1)Using glucose and Si powder as raw materials,a Si/C composite anode material was prepared by hydrothermal method and high temperature carbonization method.The research shows that the reversible capacity of the 80-Si/C(the mass of carbon in the material is 80 mg)after 50 cycles at a current density of 0.2 A/g is about twice that of the Si anode,and the carbon material has good electrical conductivity.The electrochemical performance of Si/C anode was improved to a certain extent.(2)Using micron silicon powder,glucose(C6H12O6)and phthalimide as raw materials,Si/C,Si/GO and Si/NPC composite anode materials were prepared through carbonization,composite and structural design.The test results showed that,the Si/NPC composite exhibits the best electrochemical performance,with a reversible capacity of651.75 m Ah/g after 50 charge-discharge cycles.The rich three-dimensional porous structure and huge specific surface area of NPC provide abundant active sites for the material system and can form a porous carbon coating,which improves the electrical conductivity of the material system and prevents the direct contact between the electrolyte and the active material.,reducing the massive deactivation of active materials during SEI film formation.(3)A SiSn/NPC composite anode material was prepared on the basis of Si/NPC composite material,and the optimal preparation process of the composite material was explored.The study shows that the initial capacity of the SiSn/NP-20 anode material prepared at 800 °C is 3157.6 m Ah/g,and it still maintains a reversible capacity of 1652.1m Ah/g after 50 charge-discharge cycles,showing excellent cycle performance.and rate performance.Sn nanoparticles and Si nanoparticles form an inter-embedded structure,which can inhibit the agglomeration between the same nanoparticles and maintain their original nanometer size,thereby improving the cycle performance of the material.Sn has good electrical conductivity,and Sn embedded in the pore structure of NPC will form a good ohmic contact with NPC,thereby improving the overall electrical conductivity of the material system.