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/Cl₂) batteries operating down to −80 °C, employing Li metal negative electrode, a novel carbon dioxide (CO₂) activated porous carbon (KJCO₂) 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 (AlCl₃), lithium chloride (LiCl), and lithium bis(fluorosulfonyl)imide (LiFSI) in low‐melting‐point (−104.5 °C) thionyl chloride (SOCl₂). Between room‐temperature and −80 °C, the Li/Cl₂ 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 Cl₂ trapped in the porous carbon upon LiCl electro‐oxidation during charging. At −80 °C, Cl₂/SCl₂/S₂Cl₂ generated by electro‐oxidation in the charging step are trapped in porous KJCO₂ carbon, allowing for reversible reduction to afford a high discharge voltage plateau near ≈4 V with up to ≈1000 mAh g⁻¹ capacity for SCl₂/S₂Cl₂ reduction and up to ≈4000 mAh g⁻¹ capacity at ≈3.1 V plateau for Cl₂ reduction.