Research On Preparation And Pre-Lithiation And Electrochemical Performance Of Carbon-Coated Tin Oxide Anode Material

Tin-based anode material is regarded as a promising anode material due to high specific capacity,abundant resources and low cost.However,large volume variation of tin-based material during lithiation/delithiation leads to pulverization and shedding of active materials and repeated formation of SEI films,causing its rapid capacity decay.At the same time,the low initial Coulombic efficiency of tin-based materials severely hinders the practical application of tin-based materials.Therefore,improving the cycling stability and initial Coulombic efficiency of tin-based materials is the key to promoting the large-scale applications of tin-based materials.In this paper,the low-cost stannous chloride was used as raw material to prepare carbon-coated tin oxide(Sn O_x@C)by a simple method of condensation polymerization of phenolic resin-pyrolysis.The results showed that the adjustiment of heat treatment temperature could effectively control the phase composition of Sn O_x@C to improve its the electrochemical performance.When the heat treatment temperature was 450?,Sn O_x@C was made up of Sn O and a small amount of Sn,showing the best cycle stability.By adjusting the adding amount of resorcinol and formaldehyde,the thickness of carbon coating of Sn O_x@C can be controlled.A proper carbon layer thickness can effectively alleviate the volume change and promote the formation of stable SEI film.The optimal 80-Sn O_x@C prepared by this method delivered a high capacity of 804.1 m Ah g^-1 after 300 cycles with the capacity retention of 94.1%.80-Sn O_x@C also showed excellent rate performance of 642.2 m Ah g^-1 at 5 A g^-1.In this paper,we used two methods of electrochemical prelithiation and chemical prelithiation to compensate the irreversible capacity of Sn O_x@C.At first,the electrochemical prelithiation of Sn O_x@C was carried out in a battery-like form by using the lithium metal as the anode.With the increase of the electrochemical pre-lithiation time,the initial coulombic efficiency of Li-Sn O_x@C gradually increased,and the initial coulombic efficiency of Sn O_x@C can be increased to more than 100%with 7 h of electrochemical lithiation.The full cell assembled by electrochemical pre-lithiated Sn O_x@C anode and Li Fe PO₄ cathode delivered a high capacity of 105.1 m Ah g^-1 after 80 cycles at 2 C.In addition,the Sn O_x@C electrode was immersed in 1 M Li-4,4'-dimethyl BP/DME solution for chemical-prelithiation.The degree of prelithiation gradually increases with the increasing time of chemical-prlithiation.The initial coulombic efficiency of Sn O_x@C reached 224.86%after 20minutes of chemical-prelithiation.The full cell assembled by chemical pre-lithiated Sn O_x@C anode and Li Fe PO₄ cathode delivered a reversible capacity of 107.7 m Ah g^-1 at 2 C with the capacity retention of 91.06%after 80 cycles.