Study On Improvement In Lithium/sodium-ion Storage Properties Of Antimony Oxides-based Composites By Transition Metal Doping

Facing the urgent need to address the severe global energy situation,there is growing attention to the development and utilization of renewable energy storage systems and clean energy.Among the various existing energy storage systems,lithium-ion batteries（LIBs）and sodium-ion batteries（SIBs）remain the most popular secondary energy storage systems.However,the limited theoretical capacity of graphite(～372 mAh g^-1),which is the traditional anode material for LIBs,has rendered it unsuitable for high specific capacity applications.Moreover,the weak interaction between graphite and sodium ions hinders the effective embedding of sodium,thereby making it essential to search for the next generation of high-performance anode materials for LIBs.Similarly,the commercialization of SIBs will necessitate the discovery of low-cost,high-theoretical capacity anode materials.Antimony oxides（Sb_xO_y）,such as Sb₂O₃,Sb₂O₄,and Sb₂O₅,have gained a lot of attention due to their high theoretical specific capacity and appropriate lithium/sodium storage potential.Nevertheless,their low intrinsic conductivity,slow reaction kinetics during lithium/sodium storage,incomplete reversibility of the conversion reaction,and the large volume effect pose significant challenges to these materials,leading to poor cyclic stability and lower first coulomb efficiency（ICE）（<50%）.To overcome these hurdles,this thesis adopts solvothermal method combined with low-temperature heat treatment,using graphene oxide（GO）with good mechanical stability and large specific surface area as a carbon matrix,and chooses different transition metal salts to composite with antimony sources（Sb₂O₃）to form a nanostructure of transition metal composite antimony oxides.The study aims to explore the ways of improving the electrochemical lithium/sodium storage performance of these materials,this thesis focuses on the details of the specific research contents and results described below.1.Co-Sb₂O₅/rGO composites were synthesized by solvothermal method.The structure of nanomaterials was characterized by XRD,SEM,TEM,XPS,and other methods.The composition,morphology,microstructure,and elemental morphology of nanomaterials were analyzed.And the lithium/sodium storage properties were studied.After optimizing the preparation conditions,the optimal composite material was obtained.When used in LIBs,the ICE was 57%at a current density of 200 mA g^-1,the reversible capacity remained at 1036 mAh g^-1 after 200 cycles,and after 800 cycles at a current density of 1 A g^-1,still maintaining a reversible specific capacity of 450 mAh g^-1.At the same time,when used as an anode electrode for SIBs,it also has good theoretical specific capacity,cycle stability,and rate performance.Due to the doping of Co,the conductivity of the composite material is effectively improved and the particle size was reduced.The addition of SA solution effectively reduces particle aggregation and alleviates the volume effect.2.FeSbO₄-Sb₂O₄/rGO（FSG）nanostructures were synthesized by solvothermal method using reduced graphene oxide（rGO）as a carbon base.The results showed that FeSbO₄-Sb₂O₄ nanoparticles were uniformly fixed on rGO sheets,and after low-temperature treatment,FeSbO₄-Sb₂O₄/rGO-200（FSG-200）nanomaterials were obtained.When FSG-200 composite material was used for LIBs,the ICE at 200 mA g^-1 current density was 67%,and the capacity retention rate was 98%after 200 cycles.When used for the anode electrode of SIBs,the capacity retention rate reaches 82%after 200 cycles,and the reversible specific capacity remained at 204 mAh g^-1 after 1000 cycles at 500 mA g^-1 current density.The excellent lithium/sodium storage performance benefits from the small grain size of FeSbO₄-Sb₂O₄ nanoparticles,which can effectively alleviate the volume effect of the Li⁺/Na⁺insertion/removal process.Reducing graphene oxide sheets as a carbon matrix improved electrical conductivity.Simultaneously,the internal electric field generated between FeSbO₄ and Sb₂O₄ promoted electron transport and ion diffusion,and the formation of the reaction intermediate Fe is conducive to reducing the energy barrier for the conversion of Li₂O and Sb to Sb O_x,promoting the reversible progress of the conversion reaction,the electrochemical lithium/sodium storage performance of the composites were effectively improved.