Walnut core-like hollow carbon micro/nanospheres supported SnOx@C composite for high performance lithium-ion battery anode.

Herein, to cope with the volume variation problem of SnO₂ anodes for lithium-ion batteries, individual walnut core-like hollow carbon micro/nanospheres (WCSs) have been prepared to be used as a supporting skeleton to form WCSs@SnO_x@C composite. In WCSs@SnO_x@C the SnO_x (SnO₂ with relatively small amounts of SnO) nanoparticles are well sandwiched between inner WCSs supporting skeleton and outmost glucose derived carbon anchoring coating. It is suggested that the characteristic composite construction has three key contributions to the electrochemical performance of WCSs@SnO_x@C composite: firstly, with structural characteristics such as network filled cavities and porous shells, the WCSs has stronger stress tolerance, and therefore can be better able to withstand structural deformation of SnO_x nanoparticles; secondly, the outmost glucose derived carbon, as an anchoring coating, can not only prevent SnO_x nanoparticles from aggregating but also pulverization; finally, the ultrafine SnO_x nanoparticles have low absolute volume change and shortened ions and electrons transfer distances, and therefore possess improved electrochemical performance. As a result, with the combined effect of WCSs, ultrafine SnO_x nanoparticles and outmost carbon coating, the as-constructed WCSs@SnO_x@C exhibits outstanding electrochemical performances such as high capacity (853 mAh g^-1 at 200 mA g^-1 after 400 cycles) and ultra-long lifespan (417 mAh g^-1 at 1000 mA g^-1 after even 1000 cycles).