Controlled SnO₂ Crystallinity Effectively Dominating Sodium Storage Performance

The exploration of sodium ion batteries (SIBs) is a profound challenge due to the rich sodium abundance and limited supply of lithium on earth. Here, amorphous SnO 2 /graphene aerogel (a‐SnO 2 /GA) nanocomposites have been successfully synthesized via a hydrothermal method for use as anode materials in SIBs. The designed annealing process produces crystalline SnO 2 /graphene aerogel (c‐SnO 2 /GA) nanocomposites. For the first time, the significant effects of SnO 2 crystallinity on sodium storage performance are studied in detail. Notably, a‐SnO 2 /GA is more effective than c‐SnO 2 /GA in overcoming electrode degradation from large volume changes associated with charge–discharge processes. Surprisingly, the amorphous SnO 2 delivers a high specific capacity of 380.2 mAh g −1 after 100 cycles at a current density of 50 mA g −1 , which is almost three times as much as for crystalline SnO 2 (138.6 mAh g −1 ). The impressive electrochemical performance of amorphous SnO 2 can be attributed to the intrinsic isotropic nature, the enhanced Na + diffusion coefficient, and the strong interaction between amorphous SnO 2 and GA. In addition, amorphous SnO 2 particles with the smaller size better function to relieve the volume expansion/shrinkage. This study provides a significant research direction aiming to increase the electrochemical performance of the anode materials used in SIBs.