Research On Modification Of Silicon-based Hollow Sphere Lithium-ion Battery Negative Electrode Material

With the development of global technology and economy,the consumption of energy is gradually increasing.Traditional non-renewable energy resources are limited,so renewable,sustainable and clean energy sources are needed to be developed to replace non-renewable energy sources.With the advantages of high energy density,good cycling performance,long service life and no enviromental pollution,lithium-ion batteries are widely used in many fields.SiO₂has attracted much attention due to its high theoretical specific capacity and abundant resources,and has become a hot research topic for lithium-ion battery anode materials.However,SiO₂anode materials have low electrical conductivity and undergo huge volume changes during the lithiation/delithiation process,which can lead to lower first Coulomb efficiency and poor electrochemical performance,hindering the application of SiO₂anode materials in Li-ion batteries.In order to reduce a series of effects caused by these problems,SiO₂anode materials are modified from the perspective of dimensional design and material compounding to improve the performance of SiO₂anode materials in the paper.The main study contents and findings are as follows:（1）Hollow porous silica spheres（HP-SiO₂）anode electrode materials were firstly prepared by cationic surfactant-assisted selective etching method.HP-SiO₂with different shell thickness was prepared by controlling the concentration of cetyltrimethylammonium bromide（CTAB）,etching temperature and etching time during the synthesis process.The shell thickness of 22 nm was achieved when the CTAB concentration was 3 mg m L^-1,and then HP-SiO₂@Cu O composites were prepared based on this HP-SiO₂.The test results showed that HP-SiO₂@Cu O exhibited excellent cycling stability with a discharge specific capacity of up to 545.7m Ah g^-1after 1000 cycles at a current density of 1 A g^-1,and Cu O improved the overall cycling performance of the material.Subsequently,HP-SiO₂@Cu O@graphene（HP-SiO₂@Cu O@G）composites were prepared,and HP-SiO₂@Cu O@G could achieve a discharge specific capacity of 752 m Ah g^-1after 180cycles at a current density of 0.1 A g^-1,showing excellent cycling performance.Finally,the HP-SiO₂@carbon（HP-SiO₂@C）composites were prepared by wrapping carbon of the HP-SiO₂material with a shell layer thickness of 22 nm using glucose as the carbon source,and the composites were tested.The HP-SiO₂@C composites showed excellent cycling performance with a reversible capacity of 658.2 m Ah g^-1after 500 cycles at a current density of 1 A g^-1.The test results showed that the carbon layer improved the electrical conductivity of the material during the charging and discharging process,and at the same time,it was acted as a buffer layer to mitigate the volume change of the silica anode material.（2）In order to investigate the improvement of hollow silica sphere（SiO₂）performance by inner and outer double-layer carbon cladding,carbon@SiO₂@carbon（C@SiO₂@C）hollow sphere composites with inner and outer double-layer carbon cladding were prepared using zinc oxide（Zn O）as the template,tetraethyl silicate（TEOS）as the silica source and glucose as the carbon source.C@SiO₂@C composites still exhibited a high reversible capacity of 629.9 m Ah g^-1at a current density of 1 A g^-1and after 400 cycles.The test results show that the inner and outer double-layer carbon cladding layer improves the electrical conductivity of the material,while the inner and outer double-layer carbon cladding layer can further alleviate the volume expansion of the SiO₂negative electrode material during the charge and discharge process,while the hollow structure of SiO₂provides a buffer space for the huge volume expansion.