Low‐Temperature High‐Areal‐Capacity Rechargeable Potassium‐Metal Batteries

Abstract High mass loading and high areal capacity are key metrics for commercial batteries, which are usually limited by the large charge‐transfer impedance in thick electrodes. This can be kinetically deteriorated under low temperatures, and the realization of high‐areal‐capacity batteries in cold climates remains challenging. Herein, a low‐temperature high‐areal‐capacity rechargeable potassium–tellurium (K–Te) battery is successfully fabricated by knocking down the kinetic barriers in the cathode and pairing it with stable anode. Specifically, the in situ electrochemical self‐reconstruction of amorphous Cu 1.4 Te in a thick electrode is realized simply by coating micro‐sized Te on the Cu collector, significantly improving its ionic conductivity. Meanwhile, the optimized electrolyte enables fast ion transportation and a stable K‐metal anode at a large current density and areal capacity. Consequently, this K–Te battery achieves a high areal capacity of 1.25 mAh cm −2 at −40 °C, which greatly exceeds those of most reported works. This work highlights the significance of electrode design and electrolyte engineering for high areal capacity at low temperatures, and represents a critical step toward practical applications of low‐temperature batteries.