The sandwiched buffer zone enables porous SnO2@C micro-/nanospheres to toward high-performance lithium-ion battery anodes

Abstract

With high theoretical specific capacity and relatively safe working potential, SnO2 has drawn widespread attention as a promising candidate of advanced anode for next generation lithium-ion batteries. However, the practical application of SnO2 anode in lithium-ion batteries is severely blocked by some shortcomings such as the inferior rate capability, fast capacity decay and low initial coulombic efficiency during charge/discharge process. Gratifyingly, there are many works which have demonstrated that the SnO2 anode achieves extra improvement in lithium storage performance after being reduced to nanoscale and embedded into porous carbon matrixes. Herein, porous SnO2@C micro-/nanospheres with a sandwiched buffer zone resulted from unevenly radial distribution of pores in carbon micro-/nanospheres are prepared for the first time. These SnO2@C micro-/nanospheres consist of small SnO2 nanoparticles embedded within porous carbon micro-/nanospheres with a sandwiched buffer zone. The results of this study indicate that the sandwiched buffer zone of carbon micro-/nanospheres and the confinement effect of nanopores on small SnO2 nanoparticles synergistically contribute to outstanding structural stability and excellent electrochemical performance of thus porous SnO2@C micro-/nanospheres. Besides, it is found that the lithium storage performance of the SnO2@C micro-/nanospheres can be tuned by adjusting the SnO2 contents. As a result, the as-prepared SnO2@C micro-/nanospheres with an optimalizing SnO2 content exhibit the best performance, delivering a high capacity of 955 mAh g−1 at 200 mA g−1 after 250 cycles as well as a high capacity of 836 mAh g−1 at even 1000 mA g−1 after 350 cycles.