Electrodeposited binder-free Sb/NiSb anode of sodium-ion batteries with excellent cycle stability and rate capability and new insights into its reaction mechanism by operando XRD analysis

Antimony has attracted a substantial amount of attention and has been proven to be the most promising anode material for sodium-ion batteries (SIBs) due to its suitable sodium insertion plateaus and high theoretical storage capacity. However, the dramatic volume expansion (up to 390%) during sodiation/desodiation results in severe structural deterioration and rapid capacity decay. As a consequence, antimony anodes exhibit poor cycling stability. Herein, we report a binder-free Sb/NiSb alloy prepared by a controllable electrodeposition process. The inactive nickel provided both good conductivity and structural reinforcement to reduce the large volume expansion/contraction, which endowed the Sb/NiSb anode with excellent cycle stability (521 mAh∙g−1 upon 100 cycles) and rate performance (above 400 mAh∙g−1 at 2000 mA∙g−1) that were superior to those of the bare Sb anode. The excellent Na storage performance of the Sb/NiSb anode was attributed to the synergistic effect of its cauliflower-like structure and the alloying effect of the Sb/NiSb. The operando XRD results indicated that the reaction mechanism resembled that of analogous transition metal antimonides. In addition, a stable solid electrolyte interface (SEI) was observed with operando XRD and HR-TEM of the Sb/NiSb anode. The cost-effective preparation of Sb/NiSb composite anodes and their excellent electrochemical properties offer the potential to prepare a broad spectrum of binder-free metallic alloys (e.g., Bi and Sn) as high-performance anode materials for SIBs.