Enabling fast-charging capability of high-voltage solid-state lithium metal batteries by in-situ composite of COF into polymer electrolyte

Nowadays, low ionic conductivity, narrow electrochemical window of solid polymer electrolytes (SPEs) and the uneven deposition of Li + at the interface restrict the practical application of the assembled solid lithium metal batteries for fast charging-discharging(>5C). To address this issue, a new in-situ composite strategy is developed by constructing of B-containing COF and a modified lithium alginate electrospinning membrane. Beneficial from the synergy of the strong polar groups in the polymer chains and the B atoms in the COF backbone to promote the dissociation of lithium salts, the SPE exhibits high room-temperature ionic conductivity (0.879 mS cm⁻¹) and Li⁺ transference number (0.51). Through the interactions between the polymers and COF, the electrolyte achieves high strength (1.07GPa) and wide electrochemical window (5.39 V). More importantly, combining the suppleness of the SPE and the strong lithophilicity of COF realizes the controlled deposition of Li⁺, the improved interface stability of devices is proved by Cryo-TEM and TOF-SIMS. As a result, the assembled Li/Li cells exhibit 10500 h stable cycling under 50 mA cm⁻², far better than currently reported work. Meanwhile, the assembled NCM811/Li solid cells realize excellent performance at 10C. Our research provides a strong impetus for the practical implementation of solid-state lithium batteries with high-voltage cathode.