In Situ Polymerization‐Driven Exfoliation of COFs: A Universal Strategy Toward High‐Performance Polymer Organic Cathodes

ABSTRACT Although covalent organic frameworks (COFs) are promising organic cathodes for lithium‐ion batteries, their compact layered bulk structure limits ion/electron transport, which results in low active site utilization and poor rate capability. Here, we present an in situ composite strategy: polymerizing electroactive monomers within COF pores. Bulk COFs are converted into few‐layer nanosheets with polymer penetrating COFs (COF@Polymer) by taking advantage of polymerization stress and polymer‐COF interactions to reduce interlayer bonding. Compared to traditional exfoliation, this method delivers a higher yield, wider applicability, and better nanosheet quality. The COF@Polymer cathodes exhibit triple advantages: the nanosheet morphology enhances active site accessibility and shortens mass transfer distances; the penetrated polymers establish efficient and additional carrier transport pathways; and polymer‐COF interactions boost structural stability. Thus, COF@Polymer cathodes perform better than pristine COFs, conventionally exfoliated nanosheets, and COF‐carbon composites in terms of active site utilization (95% for DACOF@FS‐5, 98% for BTCOF@FS‐20 and 92% for PTCOF@FS‐10), rate performance (∼ 70% capacity retention at 10 A g −1 comparing to the capacity at 0.2 A g −1 for BTCOF@FS‐20 and PTCOF@FS‐10), cycle stability, energy density, and power density (30.5 kW kg −1 with an energy density up to 336 Wh kg −1 for BTCOF@FS‐20).