Abstract
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.
Highlights
The performances of rechargeable batteries are strongly affected by the operating environmental temperature
The transmission electron microscopy (TEM) analysis of P-Bi2Se3 presented in Supplementary Fig. 4a indicates irregular granules ranging in size from 200 nm to 1 μm
The high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) image of E-Bi2Se3 recorded along the [010] zone axis (Fig. 1e) is a magnified view from the A region of Supplementary Fig. 5a, where 1 QL is well assigned to the layered structure
Summary
The performances of rechargeable batteries are strongly affected by the operating environmental temperature. Fading electrochemical performance at low temperatures can be mitigated by introducing electrolyte additives[6], coating surfaces with some material that is highly electronically conductive[7,8], and heteroatom doping[9,10], but the attenuation is inevitable, and to date the highest retention of 86% at −25 °C for a sodium ion cell is achieved by Goodenough’s group using an organic electrolyte[5] This progress is valuable, for a cell required to operate over a long period in a cold climate, performance degradation remains unavoidable[5]. Bi2Se3, a topological insulator with a 0.3-eV nontrivial bulk gap and superficial single Dirac cone, is formed by periodic layers composed of five atomic planes (Se-Bi-Se-Bi-Se; namely, a quintuple layer denoted QL) connected through van der Waals forces; numerous unoccupied tetrahedral and octahedral exist between the Se atomic planes and result in the material’s potential as an intercalating cathode in batteries[14,15]
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