Suppression of CO₂ induced lithium anode corrosion by fluorinated functional group in quasi-solid polymer electrolyte enabling long-cycle and high-safety Li-CO₂ batteries

Given high theoretical energy density and environmental-friendly CO₂ fixation ability, rechargeable Li-CO₂ battery is explored as a promising energy storage device. However, its cycling stability and safety are challenged by the continuous pulverization of Li anode and the leakage of liquid electrolytes (LEs). Herein, a quasi-solid polymer electrolyte (QSPE) with -CF₃ functional groups was designed and in-situ fabricated for Li-CO₂ battery. The solidification of electrolyte avoids the leakage of LEs and effectively inhibits the diffusion of the acid CO₂ and cathode by-products to etch Li anode. Besides, the introduction of -CF₃ can construct a fish scale-like LiF-rich solid electrolyte interface on Li anode, which induces the uniform and dense deposition of Li to inhibit the deeper Li from being further etched. The QSPE also exhibits high ion conductivity (1.98×10⁻³ S cm⁻¹ at 25 °C), enhanced Li⁺ transport number (0.47), and superb stability (>5.27 V vs. Li/Li⁺). Consequently, the Li-CO₂ battery with QSPE delivers effectively suppressed pulverization of Li anode, extraordinary cyclic stability over 295 cycles (1250 h) at 50 μA cm⁻², and lower overpotential (1.05 V) compared to the cells with LE. Moreover, the as-prepared QSPE also demonstrates excellent application potential in other Li metal batteries and flexible electronic devices.