Toward Extremely Fast Charging through Boosting Intercalative Redox Pseudocapacitance: A SbCrSe₃ Anode for Large and Fast Sodium Storage

Alloying-type metals with high theoretical capacity are promising anode materials for sodium ion batteries, but suffer from large volume expansion and sluggish reaction kinetics. Dispersing alloying-type metal into a buffer matrix with interfacial anionic covalent bonding is an effective method to solve the above issues. Here, this bifunctional structural unit is designed by incorporating high-capacity Sb metal into a rigid Cr-Se framework for fast-charging applications. The high-capacity and high-rate sodium storage can be synergistically realized in the bifunctional Sb-Cr-Se system, where the rigid Cr-Se framework endows the SbCrSe3 anodes with superior structural stability and improved intercalative redox pseudocapacitance. Moreover, the volume expansion of Sb during discharge can be buffered by the Cr-Se chain-like matrix. The novel SbCrSe3 anode delivers a high charge capacity of 472 mAh g(-1) at a current density of 0.4 C and retains approximate to 100% capacity at 60 C over 10 000 cycles. Further in situ and ex situ characterization reveal the multistep reaction mechanism, and the breakage and formation of reversible Sb-Se bonds during (dis)charge. The proposed bifunctional structural unit that combines alloying type anodes and intercalative anodes is expected to pave a new road for the development of high capacity and high rate anode materials.