Rechargeable Li/Cl2 Battery Down to −80 °C

Abstract Low temperature rechargeable batteries are important to life in cold climates, polar/deep‐sea expeditions, and space explorations. Here, this work reports 3.5–4 V rechargeable lithium/chlorine (Li/Cl 2 ) batteries operating down to −80 °C, employing Li metal negative electrode, a novel carbon dioxide (CO 2 ) activated porous carbon (KJCO 2 ) as the positive electrode, and a high ionic conductivity (≈5–20 mS cm −1 from −80 °C to room‐temperature) electrolyte comprised of aluminum chloride (AlCl 3 ), lithium chloride (LiCl), and lithium bis(fluorosulfonyl)imide (LiFSI) in low‐melting‐point (−104.5 °C) thionyl chloride (SOCl 2 ). Between room‐temperature and −80 °C, the Li/Cl 2 battery delivers up to ≈29 100–4500 mAh g −1 first discharge capacity (based on carbon mass) and a 1200–5000 mAh g −1 reversible capacity over up to 130 charge–discharge cycles. Mass spectrometry and X‐ray photoelectron spectroscopy probe Cl 2 trapped in the porous carbon upon LiCl electro‐oxidation during charging. At −80 °C, Cl 2 /SCl 2 /S 2 Cl 2 generated by electro‐oxidation in the charging step are trapped in porous KJCO 2 carbon, allowing for reversible reduction to afford a high discharge voltage plateau near ≈4 V with up to ≈1000 mAh g −1 capacity for SCl 2 /S 2 Cl 2 reduction and up to ≈4000 mAh g −1 capacity at ≈3.1 V plateau for Cl 2 reduction.