Stable bismuth-antimony alloy cathode with a conversion-dissolution/deposition mechanism for high-performance zinc batteries

Although a large number of intercalation cathode materials for aqueous Zn batteries have been reported, limited intercalation capacity precludes achieving a higher energy density. Here we develop a high-performance aqueous Zn battery based on BiSb alloy (Bi_0.5Sb_0.5) using a high-concentrated strong-basic polyelectrolyte. We demonstrate that a conversion-dissolution/deposition electrochemical mechanism (BiSb ↔ Bi + SbO₂⁻ ↔ Bi + SbO₃⁻ ↔ Bi₂O₃) through in situ X-ray diffraction (XRD), Raman, and ex-situ X-ray photoelectron spectrometry (XPS) characterizations with the help of density functional theory calculations. The BiSb cathode delivers large capacity of 512 mAh g⁻¹ at 0.3 Ag⁻¹ and superior rate capability of 90 mAh g⁻¹ even at 20 Ag⁻¹, and long-term cyclability with capacity retentions of 184 mAh g⁻¹ after 600 cycles at 0.5 Ag⁻¹ and 130 mAh g⁻¹ after 1300 cycles at 1 Ag⁻¹. Remarkably, even at temperatures as low as −10 and −20 °C, capacities of 210 and 197 mAh g⁻¹ are reserved at 1 Ag⁻¹, respectively. Moreover, the prepared pouch Zn//BiSb battery delivers a high energy density of 303 Wh kg⁻¹_BiSb at 0.3 Ag⁻¹. When coupled with a high concentration polyelectrolyte, the Zn/BiSb battery exhibits an excellent performance over a wide temperature range (−40 to 40 °C). Our research reveals the metal cathode is promising for Zn batteries to achieve a high performance with the unique mechanism and alloys can be an effective approach to stabilize metal electrodes for cycling.