Synthesis And Electrochemical Performance Of Tin Oxide-Based Anodes For Lithiun-Ion Batteries

Currently,lithium-ion batteries(LIBs)are one of the major energy storage devices.Apart from their widespread usage in consumer electronics,they are also expected to service large-scale electrical equipment,which is stimulating the development of low-cost electrode materials with high energy density.Tin-based materials are prospective electrodes owing to their high theoretical capacity.However,the use of tin-based anodes is confronted with a major drawback that is the drastic volumetric change during repeated charge/discharge process,which results in severe electrode pulverization and finally rapid deterioration in capacity.SnO2 is taken as the research subject in this work.Two strategies are applied to improve the cycle performance of SnO2 anode in this work,involving preparing carbon/Sn-Mo oxide composite and elemental doping.Firstly,a facile solvothermal strategy was employed to prepare carbon/Sn-Mo oxide composite(C/SnOx/MoOy).Best electrochemical performance is achieved by C/SnOx/MoOy anode with a Sn:Mo ratio of about 1:1,indicating a mutual buffering relationship between tin and molybdenum oxide due to the different working voltage towards to lithium.In addition,carbon phase contributes greatly to the enhanced electrochemical conductivity,structural integrity and pseudocapacitance contribution of the electrode.When used as LIBs anode,the as-prepared C/SnOx/MoOy demonstrates excellent cycle stability:after 500 cycles,high reversible capacity of 836.6 mA h g-1,734.0 mA h g-1 and 605.3 mA h g-1 could be remained at the current density of 0.5 A g-1,1.0 A g-1 and 2.0 A g-1,respectively.Secondly,cation doping was applied with Na2MoO4 as raw material to enhance the cycling stability of SnO2.Experimental results demonstrate that Mo-doped could reduce the size of the particles and the charge transfer resistance of the electrode,which leads to enhanced structural stability and cyclic stability.In addition,Mo-doping is demonstrated to improve the reversibility of the SnO2 conversion reaction,resulting in higher capacity.However,Mo-doped SnO2 delivers rapid capacity decline and low initial coulomb efficiency when used as LIBs anode.The Mo-doped SnO2 was then uniformly dispersed in carbon nanofibers and reduced in-situ to prepare a free-standing anode via electrospinning and carbonization method(SnMoCNF).When used directly as an anode in LIBs(without a polymeric binder or conductive agent,as well as a current collector),the nanofiber membrane anode delivers enhanced cycling performance and initial coulombic efficiency.Finally,solvothermal method was applied to prepare the P-doped SnOx/C composite with red phosphorus as phosphorus source and PVP as carbon source.Experimental results demonstrate that carbon materials could effectively improve the cycle stability performance of the electrode,and meanwhile phosphorus doping could increase the electrode capacity by improving the reversibility of the tin oxide conversion reaction.Thus,the as-prepared P-doped SnOx/C demonstrates excellent cycle stability.