Sb-doped SnO2/graphene-CNT aerogels for high performance Li-ion and Na-ion battery anodes

SnO2 has been extensively explored as a potential anode material for both Li-ion (LIBs) and Na-ion batteries (SIBs). It possesses however an extremely poor electrical conductivity, making it difficult to be used as the standalone electrode. Herein, Sb-doped SnO2 (ATO) nanoparticles are in situ grown on N-doped graphene-CNT aerogels (N-GCAs) based on a facile hydrothermal self-assembly route for the first time. The ATO/N-GCA composite presents a highly porous structure along with an electrical conductivity enhanced by over two orders of magnitude through the in situ Sb doping. The composite electrode delivers an outstanding rate capability of 659 mA h g(-1) at 10 A g(-1) with capacity retention of 73% after 1000 cycles at 1 A g(-1) in LIBs. The same electrode also maintains 74% of its capacity after 500 cycles in SIBs, confirming a promising anode for both rechargeable batteries. We reveal distinct reaction kinetics and phase transition behaviors of ATO electrodes in different rechargeable batteries. The lithiation of ATO ensues consecutive conversion and alloying reactions while only the conversion reaction takes place during sodiation. Furthermore, the diffusion coefficient of Na+ ion in ATO is nine orders of magnitude lower than that of Li+ ions. The enhanced electrical conductivity of SnO2 by Sb doping dominates the capacity enhancements in LIBs whereas the mesoporous structure of hybrid aerogel plays a more important role in enhancing the Na+ ion storage performance. These new findings may offer insights into the relatively poor performance of SIBs and will help proper structural design of high performance bi-functional anodes for alkali metal ion batteries.