Studies On The Influence Of Doping And Hybrid On The Electrochemical Properties Of Tin Oxide Anode Materials

Lithium-ion batteries（LIBs）have been widely studied due to their advantages of long cycle life,wide operating temperature range and high specific capacity.As one of the key components for lithium-ion batteries,anode have been a focus in this field.Currently,graphite is the main anode electrode material for commercial LIBs,but the theoretical capacity of graphite is only 372 mAh/g,which is difficult to be widely used in the fields with high energy density requirements such as electric vehicles and large energy storage systems.Due to its high specific capacity（782 mAh/g）and good safety performance,low price and abundant resources,tin dioxide is expected to be the next-generation of commercial anode material.However,there are serious volume effects in the charging and discharging process of tin oxide materials,resulting in agglomeration and pulverization of active material in the insertion/exaction process of lithium,thus leading to the poor cycling performance and rate performance.In this paper,the electrochemical properties of tin dioxide were improved by doping and hybridizing with graphene.The experimental results show that this method can effectively buffer the volume change of the active material,improve the coulomb efficiency,specific capacity,ion/electron transport and cycle life of the tin oxide material.The corresponding researches are as follows:（1）Si-doped SnO₂/graphene composites were prepared by wet chemical method,and the electrochemical properties of Si-doped SnO₂/graphene composites with different proportions were compared.The experimental results showed that Si-doped SnO₂/graphene composites had the best electrochemical performance when the precursor ratio（molar ratio）was 15%,and the discharge capacity of Si-doped SnO₂/graphene was 1110.9 mAh/g after 100 cycle at the current density of 0.1 A/g.Under current density of 0.2,0.5 and 1 A/g,Si-doped SnO₂/graphene electrodes has a high reversible discharge capacity of 999,864 and 697 mAh/g,respectively.The improved cyclic performance could be attributed to the synergistic effect of silicon doping and grapheme,which significantly enhances the electron migration and lithium-ion diffusion in electrode materials.（2）Co-doped SnO₂/graphene composites were prepared by wet chemical method,and the electrochemical properties of materials composites with different proportions were investigated.The results showed that the materials composite with molar ratio of 15%had the best electrochemical performance.When the current density was 0.1 A/g,the discharge capacity of materials was 1157.4 mAh/g after 90 cycles.The doping of cobalt into SnO₂ can significantly reduce the grain size of SnO₂,but does not change the crystal structure of SnO₂,which has a great impact on its conductivity and electrochemical properties.The particle size of the doped sample is greatly reduced,and the electronic conductivity is enhanced.Thus,the cycling performance of Co-doped SnO₂/grapheme composites were improved.（3）B₂O₃ was added to SnO₂/graphene composites,and the electrochemical properties of SnO₂/graphene composites with different amounts of boron oxide were studied.The experimental results showed that B₂O₃-doped SnO₂/graphene composites had the best electrochemical performance when the additive amount was 5 wt%,and the discharge capacity of B₂O₃-doped SnO₂/graphene was 1084.7 mAh/g after 200 cycles at the current density of 0.1 A/g.Under the current density of 0.2,0.5 and 1 A/g,the B₂O₃-doped SnO₂/graphene electrodes have a high reversible discharge capacity of 994.2,908.2,788.2 mAh/g,respectively.The addition of B₂O₃ can suppress the aggregation of nanoparticles and enhance the electronic conductivity of composites.Therefor,the composite electodes show excellent lithium storage capability.