High-Rate Rechargeable Li/SOCl₂ Batteries Enabled by Cobalt Phthalocyanine Cathodic Catalysts

Rechargeable lithium/thionyl chloride (Li/SOCl₂) batteries are considered promising alternatives to lithium-ion batteries because of their ultrahigh energy density and wide operating temperature range. However, current rechargeable Li/SOCl₂ batteries exhibit unsatisfactory rate performance that originates from the poor reversibility of SOCl₂ and is dominated by the difficulty in oxidizing the discharge product lithium chloride (LiCl). In response to this issue, cobalt phthalocyanine (CoPc) is employed as a cathode catalyst to boost the oxidation kinetics of LiCl products and thus improve the reversibility of SOCl₂ in rechargeable Li/SOCl₂ batteries. The CoPc catalyst in the Li/SOCl₂ batteries is found to not only promote the discharge reduction of SOCl₂ but also remarkably accelerate the reversible charge transformation of LiCl products by lowering the chloride ions oxidation barrier. The CoPc-catalyzed Li/SOCl₂ batteries deliver a high specific capacity of 800 mAh g^-1 at a current density of 500 mA g^-1, with a stable voltage plateau of 3.5 V over 200 cycles. Even at the ultrahigh current density of 5 mA cm^-2, these batteries can still provide a reversible capacity of 1 mAh cm^-2 over 250 cycles, demonstrating excellent rate performance.