Functional Polymer Derived Hybrid Materials As High Performance Anode Of Lithium-Ion Batteries

Excessive reliance on fossil fuels creates many environmental problems,so the development of clean energy has become an important research direction.Lithium-ion batteries(LIBs)are highly efficient,easy to charge,and low in cost,and have been commercialized in many industries.However,as a power battery,it needs to further increase the energy density,improve and enhance the capacity of the positive/negative material,coordinate the matching of the electrode with the electrolyte,and develop a new high-performance anode material.In this paper,polymer-converted carbon-rich silicon oxide(SiO_x/C),cobalt-rich carbon-doped silica(Co-SiO_x/C),zinc-containing is designed and prepared by using functional polymer-converted hybrid materials or ceramic materials as the entry point.Silicon carbon(Zn-SiO_x/C)and nitrogen-sulfur double-doped silicon-boron carbon-nitrogen ceramic composite nanographene sheets(SiBCN/NSGs)are used as basic materials for lithium ion battery anode materials mainly includes:In the first part,a simple carbon-rich silicon oxide(SiO_x/C)anode material preparation method was proposed.Poly(dimethylsilylene)diacetylene(PDSDA)was used as precursor to prepare carbon by high temperature pyrolysis.Silicon-rich polymer-derived ceramics,excellent in electrochemical performance of SiO_x/C prepared by pyrolysis at 800°C,achieves883 mAh g^-1 capacity retention after 500 cycles at 400 mA g^-1 current density,and the coulombic efficiency is greater than 99%.The high specific capacity is mainly attributed to the continuous SiO_x/C network structure in the material which limits the volume expansion of SiO_x and provides a stable electrolyte interface.In the second part,in order to improve the performance of the lithium ion battery,Co-SiO_x/C is obtained by pyrolyzing a complex of octacarbonylcobalt and PDSDA.The Co-SiO_x/C anode material has good cycle performance and maintains a capacity of 905 mAh g^-1after 100 cycles at 100 mA g^-1,and the capacity retention rate is 81.9%.The structure of Co-SiO_x/C remains intact after several cycles of charge and discharge,providing structural guarantee for efficient and stable electrochemical performance.In the third part,the Zn-SiO_x/C anode material was prepared by PDSDA precursor-loaded ZIF-8 pyrolysis.The material has a porous structure and a large surface area.The presence of zinc changes the electron cloud distribution of Siand C atoms,increases the active site of the electrode material,and contributes to the diffusion and electron transport of lithium ions.The Zn-SiO_x/C material exhibits excellent electrochemical performance with a specific capacity of940 mAh g^-1 after 80 cycles at 100 mA g^-1 current density.In the fourth part,N and S were mixed into the polyborosilazane precursor by ball milling method,and the nitrogen-sulfur double-doped silicon-boron carbon-nitrogen ceramic composite nanographene sheets(SiBCN/NSGs)were prepared by pyrolysis.Inserting double-doped N and S in SiBCN expands the interlayer spacing of carbon,which enhances the lithiation activity of the carbon layer,and the ability of the active material to load lithium is significantly improved,accelerating ion transport performance.SiBCN/NSGs exhibited a reversible specific capacity of 785 mAh g^-1 after 800 charge and discharge cycles at a high current density of 450 mA g^-1.