Sodium-ion batteries (SIBs) are emerging as power sources for large-scale storage owing to their abundant and inexpensive sodium (Na) source, but their limited energy density hinders their commercialization. High-capacity anode materials, such as antimony (Sb), which are potential energy boosters for SIBs, suffer from battery degradation owing to large-volume-changes and structural instability. The rational design of bulk Sb-based anodes to enhance the initial reversibility and electrode density inevitably requires atomic- and microscale-considered internal/external buffering or passivation layers. However, unsuitable buffer engineering causes electrode degradation and lowers energy density. Herein, the rationally designed intermetallic inner and outer oxide buffers for bulk Sb anodes are reported. The two chemistries in the synthesis process provide an atomic-scale aluminum (Al) buffer within the dense microparticles and an external mechanically stabilizing dual oxide layer. The prepared nonporous bulk Sb anode maintained excellent reversible capacity at a high current density and Na-ion full battery evaluations with Na3V2(PO4)3 (NVP) showing negligible capacity decay over 100 cycles. The demonstrated buffer designs for commercially favorable micro-sized Sb and intermetallic AlSb shed light on the stabilization of high-capacity or large-volume-change electrode materials for various metal-ion rechargeable batteries.
Keywords: antimony anode; buffer engineering; bulk; energy-dense; intermetallic; micro-size; sodium-ion battery.