Study On The Preparation Of Porous Silicon Oxide/Carbon Anode Materials And The Performance For Lithium Storage

As anode materials for lithium-ion batteries,the silicon-based materials have the advantages such as high specific capacity,low lithium insertion potential,readily available raw materials,and environmental friendliness.Nevertheless,their poor conductivity and huge volume change during cycling lead to poor cycling and rate performance.To overcome these issues,we designed and prepared porous SiOC composites by using amphiphilic triblock copolymers?i.e.,P123 or F127?as template agents and some precursors as the carbon or silicon sources.The materials possess the following merits:the porous structure can accommodate the volume change during cycling and help to form stable solid electrolyte interphase?SEI?film,thus avoiding the pulverization of the electrode materials and the detachment of the active materials.Meanwhile,these pore channels also offer short pathway for lithium ion transport.In addition,integrating carbon components into the composites helps to improve the conductivity and retard the agglomeration of active nanoparticles.The main research contents and results are as follows:1.Reduced graphene oxide-encapsulated porous SiOx?P-SiOx/rGO?have been prepared by partial aluminothermic-reduction of GO-encapsulated porous SiO₂,which was first synthesized by using P123 as template agent,tetraethyl orthosilicate as silicon source,and GO as carbon carrier.The composite shows highly porous structure with a specific surface area of 240 m² g^-1 and a pore volume of 0.38 cm³ g^-1.As an anode material for lithium-ion batteries,the materials exhibit high initial Coulombic efficiency of 68%,excellent cycling stability(⁵75 mAh g^-1 after 200 cycles at 0.1 A g^-1),and good rate capability(126 mAh g^-1 at a high current density of 10.0 A g^-1).The decent lithium storage properties of the P-SiOx/rGO composite should be attributed to developed porosity and three-dimensional interconnected conductive networks formed by graphene.2.The silsesquioxanes?RSiO1.5?n are a type oxygen-deficient species in respect to SiO₂.Considering that,we have prepared nitrogen-doped ordered porous SiOC composites by using octaaminophenyl sesquisiloxane?OAPS?as both carbon and silicon sources,oligomeric phenolic resin?Resol?as a curing agent,and block copolymer F127 as a template agent.The influence of OAPS/Resol ratio,pyrolysis atmosphere and temperature on the structure and electrochemical performance was investigated in detail.Nitrogen doping is beneficial for enhancing the conductivity of carbon skeleton,and highly ordered mesostructure enables fast transport for lithium ions.The optimal material has a specific surface area of 217 m² g^-1 and a pore volume of 0.17 cm³ g^-1,which was prepared by employing OAPS/Resol ratio of 95:5,reducing pyrolysis atmosphere,and pyrolysis temperature of 900°C.As an anode material for lithium-ion batteries,the materials exhibit first Coulombic efficiency of 61%.Impressively,the material enables ultralong cycle life.It retains a reversible capacity of 438 mAh g^-1 after 585 cycles at a low current density of 0.1 A g^-1 and the test runs for nearly 7 months.At a high current density of 10.0 A g^-1,the reversible specific capacity is still 92 mAh g^-1.