A solid‐state electrolyte (SSE), which is a solid ionic conductor and electron‐insulating material, is known to play a crucial role in adapting a lithium metal anode to a high‐capacity cathode in a solid‐state battery. Among the various SSEs, the single Li‐ion conductor has advantages in terms of enhancing the ion conductivity, eliminating interfacial side reactions, and broadening the electrochemical window. Covalent organic frameworks (COFs) are optimal platforms for achieving single Li‐ion conduction behavior because of well‐ordered one‐dimensional channels and precise chemical modification features. Herein, we study in depth three types of Li‐carboxylate COFs (denoted LiOOC‐COFn, n = 1, 2, and 3) as single Li‐ion conducting SSEs. Benefiting from well‐ordered directional ion channels, the single Li‐ion conductor LiOOC‐COF3 shows an exceptional ion conductivity of 1.36 × 10−5 S cm−1 at room temperature and a high transference number of 0.91. Moreover, it shows excellent electrochemical performance with long‐term cycling, high‐capacity output, and no dendrites in the quasi‐solid‐state organic battery, with the organic small molecule cyclohexanehexone (C6O6) as the cathode and the Li metal as the anode, and enables effectively avoiding dissolution of the organic electrode by the liquid electrolyte.

Covalent organic frameworks (COFs) show considerable attention and potential value in energy storage and conversion. However, design and preparation novel dual-active-center modified COFs for high-performance Li storage and accelerating Li diffusion are still challengeable. In this work, we synthesize dual-active-group of C N and C O decorated COF (denoted as Tp-Ta-COF) as the anode material for lithium-ion batteries (LIBs). Benefiting from the dual-active-site, the Li + diffusion kinetics on the Tp-Ta-COF are improved and Tp-Ta-COF electrode delivers high reversible capacity of 413 mAh g À1 under current density with 200 mA g À1 . Moreover, 18 Li + can be embed in Tp-Ta-COF with C N and C O containers. The mechanism between Li + and active-site is deeply deduced and studied by multiple in situ techniques and density functional theory (DFT) theoretical calculation, suggesting interactions of Li + and active-group are highly reversible procedures. Consequently, we expect this work could create a universal strategy for construction high-performance Li storage COF-based materials.

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The growth of disordered lithium dendrite and the notorious reaction between Li and electrolyte hamper the practical application of Li metal batteries (LMBs). Herein, an artificial solid electrolyte interphase (ASEI) constructed by a nitro‐functionalized covalent organic framework (NO2‐COF) is designed to regulate Li+ deposition and stable Li anodes. Strong electron‐withdrawing nitro groups can gather the surrounding electrons of connected monomer by the donor‐acceptor (D‐A) effect, thus regulating the electron structure of the covalent organic framework (COF) and constructing a specific cation‐oriented channel. The uniform Li+ deposition and inhibition of Li dendrites are achieved under such a high‐selective Li+ transportation channel and regulated surface electric charge. In addition, the nitro can also be reduced to NO2− and further react with Li to produce high ionic‐conductivity Li3N and LiNxOy during the charging/discharging, which contributes to the migration of Li+. As a result, NO2‐COF‐modified symmetrical batteries realize an ultra‐long cycling life of more than 6000 h under a current density of 5 mA cm−2 compared to bare Li and TpBD‐COF/Li (without nitro). The full cells coupled with LiFePO4 stably cycle 1000 times with a capacity retention of 91%. Hence, effectively optimizing electron structure by the donor‐acceptor (D‐A) effect  provides a better platform to elevate the performance of LMB.

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