Research On High Performance Of SnO₂ Based Lithium Ion Battery Anode

As a kind of clean energy storage device,lithium ion battery(LIB)is widely used in military,aviation,aerospace and other fields.In recent years,with the rapid development of electronic equipment and electric vehicles,the requirements for high energy and long life of LIBs are also rising.At present,the research on the energy improvement of the cathode electrode material has reached a certain limit.In order to further increase the volume energy and mass energy of the battery,therefore,the anode electrode material bears more expectations.Compared with the graphite specific capacity(372 mAh/g)of the commercial anode material,the specific capacity of the SnO2 anode material(1491 mAh/g)is larger,the resource storage is rich,and its deintercalation/intercalation operating potential is about 0.6 V,so that it is not easy to cause lithium precipitation.However,SnO2 electrical conductivity is not that good.The electrochemical performance of the material is greatly limited during high current charge and discharge,which does not meet the increasing needs of modern society.Moreover,during the charge and discharge process,SnO2 electrodes face large volume expansion(>260%),which in turn causes the active material SnO2 to agglomerate,smash,and even fall off the current collector,causing battery failure.At the same time,SnO2 material faces a large loss of irreversible specific capacity.In this article,we try to solve the issues of large irreversible specific capacity,poor electrical conductivity,and large volume expansion of SnO2 based anode materials.Carbon materials are used to modify SnO2 based anode materials,and the synergies between the materials are combined to play important roles.The advantages of the material,suppress its shortcomings,and obtain SnO2 based composite materials with good comprehensive electrochemical performance.Through in-depth research and exploration of composite materials,we have reached the following conclusions:1.With water-soluble pitch as the carbon source,spray drying method was used to obtain amorphous carbon-coated SnO2(SnO2@C).Spray drying can obtain composite materials with hollow structure.This structure is benefit to reduce the volume of the active material.Besides,the methode is simple and convenient to operate.The presence of amorphous carbon also improves the conductivity of the composite.The prepared SnO2@C showed good electrochemical performance.At the current density of 100 mA/g,the SnO2@C electrode first coulomb efficiency reached 65%.After 80 cycles of charge and discharge,the capacity was kept at 446 mAh/g.With the current density of 1200 mA/g,137.25 mAh/g specific capacity can be stabilized.When the current density is restored to 100 mA/g,the specific capacity can be recovered to 396 mAh/g.2%Based on SnO2@C,a flexible electrode is prepared to replace the traditional copper foil current collector.By combining it with paper fibers and carbon nanotubes,the self-supporting anode pole piece is prepared by a simple process of vacuum filtration to achieve the unity of a current collector and an active material.The free-standing anode avoid the risk of the active material falling from the copper foil.At the same time,the structure constructed by the carbon nanotubes can realize the separation of the active material and prevent the charge and discharge process.The agglomeration of the nanoparticles and volume expansion of the active material was buffered during this process.The prepared SnO2@C/MWCNTs independent electrode has good mechanical properties and can be flexibly applied to various electrical equipment.This electrode has excellent electrochemical performance.After 80 cycles of charge and discharge,its specific discharge capacity was maintained at 716 mAh/g.With a large rate of 1600 mA/g current density,the specific discharge capacity was maintained at 260 mAh/g.After charging and discharging at different rates,the specific capacity of the electrode can be restored to 700 mAh/g,showing very good resistance to current shock.3.LiF is added to the SnO2@C/MWCNTs composite material to supplement the LiF required in the SEI film formation process.At the same time,as the main component of the SEI film,it can enhance the stability of the SEI film and improve the coulomb efficiency and the capacity retention rate of the electrode.Therefore,adding LiF to SnO2 based material can obtain the electrode material with excellent electrochemical performance.After 200 cycles of this anode material,the specific capacity was maintained at 483 mAh/g,and the capacity retention rate reached 70.1%.The specific capacity was maintained at 274 mAh/g at 2400 mA/g.