Electrospun graphene@SnO2 nanofibers as anode materials with excellent electrochemical performance for lithium-ion batteries

Tin dioxide (SnO2) is one of the most promising anode materials for lithium-ion batteries (LIBs) due to its high theoretical specific capacity, suitable working potential and eco-friendliness. However, the low conductivity and excessive capacity attenuation resulting from serious volume expansion during alloying reactions greatly limit its application. Doping the substance with high conductivity into SnO2 is regarded as an effective way to improve its electrochemical performance. In this work, the graphene@SnO2 (G@SnO2) nanofibers with the threedimensional network structure were successfully fabricated via electrospinning and subsequent heat treatment. The effect of the doped graphene content on electrochemical performance of G@SnO2 nanofibers as anode materials for LIBs was investigated in details, based on which the optimum doping content was confirmed (0.070 wt% graphene in the composite). The G@SnO2 anode with 0.070 wt% graphene exhibited the best rating capability. A rate of 46.9 % was retained with the current density drastically increased from 0.1 A g- 1 to 2 A g- 1 and a high retained rate of 70.4 % was obtained when the current density was recovered to the initial value (the value of pure SnO2 anode was 11.1 % and 66.3 %, respectively). This improvement should result from more active sites provided by graphene with the large specific surface area, which greatly accelerate electrochemical reactions. Besides that, graphene with the high conductivity also promotes the charge transfer. The anode also demonstrated the excellent cycling stability owing to the high specific discharge capacity of 349.7 mA h g- 1 still reserved after 100 cycles at the current density of 0.1 A g- 1 (the value of pure SnO2 electrode was only 67.8 mA h g- 1). The change should be attributed to the flexible structural characteristic of graphene, which effectively alleviates the volume expansion of anode materials during the cycling. This work confirms that introducing suitable content of graphene into SnO2 is conducive to the improvement in electrochemical performance. Moreover, electrospinning is capable of realizing continuous production and suitable for large-scale preparation of nanofiber materials, which provides a possible strategy to meet the substantial demand for anode materials in next-generation LIBs.