Integrated structure design and synthesis of a pitaya-like SnO 2 /N-doped carbon composite for high-rate lithium storage capability.

Tin dioxide (SnO 2 ) with a high theoretical capacity of 1494 mA h g -1 has great potential to break through the capacity limitation of the conventional graphite anode (372 mA h g -1 ) in lithium-ion batteries. However, its practical application still faces several obstacles such as high volumetric expansion and poor electrical conductivity. To solve these problems, innovative design and synthesis of SnO 2 -based nanocomposite structures are necessary. Herein, we demonstrate an integrated design of a hierarchical pitaya-like P-SnO 2 /C@NC core-shell nanostructure which includes the core of SnO 2 nanoparticles (∼4-12 nm) uniformly embedded in the porous carbon sphere and the shell of a continuous nitrogen-doped carbon (NC) layer. Specifically, during repetitive lithiation and delithiation processes, the ultrasmall SnO 2 nanoparticles reduce the internal stress greatly, the porous carbon matrix provides buffer space for a large volume change, and the N-doped carbon shell further guarantees the whole structure unit sufficient electrical conductivity and structural stability. Consequently, the resultant battery exhibits a reversible capacity of 936.8 mA h g -1 after 100 cycles at 100 mA g -1 and even an average capacity of 460.0 mA h g -1 at a high current density of 3.2 A g -1 . The excellent electrochemical performance of pitaya-like SnO 2 /C@NC proves the efficacy of this structure design and thus provides significant reference for the construction of other electrode materials in rechargeable alkali metal ion batteries.