CO₂ Nanoenrichment and Nanoconfinement in Cage of Imine Covalent Organic Frameworks for High‐Performance CO₂ Cathodes in Li‐CO₂ Batteries

The Li‐CO 2 battery is an emerging green energy technology coupling CO 2 capture and conversion. The main drawback of present Li‐CO 2 batteries is serious polarization and poor cycling caused by random deposition of lithium ions and big insulated Li 2 CO 3 formation on the cathode during discharge. Herein, covalent organic frameworks (COF) are identified as the porous catalyst in the cathode of Li‐CO 2 batteries for the first time. Graphene@COF is fabricated, graphene with thin and uniform imine COF loading, to enrich and confine CO 2 in the nanospaces of micropores. The discharge voltage is raised by higher local CO 2 concentration, which is predicted by the Nernst equation and realized by CO 2 nanoenrichment. Moreover, uniform lithium ion deposition directed by the graphene@COF nanoconfined CO 2 can produce smaller Li 2 CO 3 particles, leading to easier Li 2 CO 3 decomposition and thus lower charge voltage. The graphene@COF cathode with 47.5% carbon content achieves a discharge capacity of 27833 mAh g −1 at 75 mA g −1 , while retaining a low charge potential of 3.5 V at 0.5 A g −1 for 56 cycles.