  Low temperature rechargeable batteries are important to life in cold
climates, polar/deep-sea expeditions and space explorations. Here, we report ~
3.5 - 4 V rechargeable lithium/chlorine (Li/Cl2) batteries operating down to
-80 {\deg}C, employing Li metal negative electrode, a novel CO2 activated
porous carbon (KJCO2) as the positive electrode, and a high ionic conductivity
(~ 5 to 20 mS cm-1 from -80 {\deg}C to 25 {\deg}C) electrolyte comprised of 1 M
aluminum chloride (AlCl3), 0.95 M lithium chloride (LiCl), and 0.05 M lithium
bis(fluorosulfonyl)imide (LiFSI) in low melting point (-104.5 {\deg}C) thionyl
chloride (SOCl2). Between room-temperature and -80 {\deg}C, the Li/Cl2 battery
delivered up to ~ 30,000 - 4,500 mAh g-1 first discharge capacity and a 1,200 -
5,000 mAh g-1 reversible capacity (discharge voltages in ~ 3.5 to 3.1 V) over
up to 130 charge-discharge cycles. Mass spectrometry and X-ray photoelectron
spectroscopy (XPS) probed Cl2 trapped in the porous carbon upon LiCl
electro-oxidation during charging. At lower temperature down to -80 {\deg}C,
SCl2/S2Cl2 and Cl2 generated by electro-oxidation in the charging step were
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. Towards practical use, we made CR2032 Li/Cl2 battery cells
to drive digital watches at -40 {\deg}C and light emitting diode at -80
{\deg}C, opening Li/Cl2 secondary batteries for ultra-cold conditions.
