Few-layer bismuth selenide cathode for low-temperature quasi-solid-state aqueous zinc metal batteries

The performances of rechargeable batteries are strongly affected by the operating environmental temperature. In particular, low temperatures (e.g., ≤0 °C) are detrimental to efficient cell cycling. To circumvent this issue, we propose a few-layer Bi₂Se₃ (a topological insulator) as cathode material for Zn metal batteries. When the few-layer Bi₂Se₃ is used in combination with an anti-freeze hydrogel electrolyte, the capacity delivered by the cell at −20 °C and 1 A g⁻¹ is 1.3 larger than the capacity at 25 °C for the same specific current. Also, at 0 °C the Zn | |few-layer Bi₂Se₃ cell shows capacity retention of 94.6% after 2000 cycles at 1 A g⁻¹. This behaviour is related to the fact that the Zn-ion uptake in the few-layer Bi₂Se₃ is higher at low temperatures, e.g., almost four Zn²⁺ at 25 °C and six Zn²⁺ at −20 °C. We demonstrate that the unusual performance improvements at low temperatures are only achievable with the few-layer Bi₂Se₃ rather than bulk Bi₂Se₃. We also show that the favourable low-temperature conductivity and ion diffusion capability of few-layer Bi₂Se₃ are linked with the presence of topological surface states and weaker lattice vibrations, respectively.