Carbon coated SnO2 particles stabilized in the elastic network of carbon nanofibers and its improved electrochemical properties

Three dimensional networks, herein carbon coated SnO2 micron-sized particles are fixed in carbon nanofibers (CNF/SnO2@C), is fabricated and synthesized by using hydrothermal method and carbonization. The weight ratio of SnO2 reaches to 50% of CNF/SnO2@C, meanwhile, CNF/SnO2@C remains its flexibility. CNF/SnO2@C film is directly used as a binder-free anode for lithium ion batteries without conductive additive and polymer binder. The discharge capacities of CNF/SnO2@C are 1286 mAh g(-1) at 0.05 A g(-1) and 397 mAh g(-1) at 1 A g(-1), respectively. The buffering effect of CNFs is studied by using ex-situ SEM in the cycled electrodes operated at various lithiation states. The particles size of SnO2@C sample increase to 4 mu m after 20 charge/discharge cycles, and a serious aggregation of particles occurs in the cycled SnO2@C electrode which is in coincidence with its rapidly faded capacity. The particles of CNF/SnO2@C sample also present the increased size from the original size of 2 mu m to the lithiated size of 4 mu m but they are still fixed in CNFs network without any aggregation. The improved specific capacity, cyclic stability and rate performance of CNF/SnO2@C are attributed to the structural synergy of CNFs and SnO2 particles, because CNFs as flexible substrate provides excellent conductive channel improving the rate capability and effective network buffering the volume change to promote the cyclic performance.