COF‐based single Li⁺ solid electrolyte accelerates the ion diffusion and restrains dendrite growth in quasi‐solid‐state organic batteries

Abstract

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.

The application of covalent organic frameworks in Lithium-Sulfur batteries: A mini review for current research progress

“…The composite PTDCOF had a capacity contribution of 1,644.3 mAh g −1 at 0.1 A g −1 with good rate and cycling performance. (Zhou et al, 2021;Zhao et al, 2021;Yang et al, 2022;Xu et al, 2021;Zhu et al, 2021;Sun et al, 2022;Zhao et al, 2022).…”

“…At present, some modified COFs have been developed as solid electrolytes for LIBs. For example, Zhao et al (2022) constructed a lithium carboxylate COFs (LiOOC-COF3) (Figure 2G) with ordered one-dimensional channels. The single Li-ion conductor of LiOOC-COF3 exhibits an excellent ionic conductivity of 1.36 × 10 −5 S cm −1 and a high mobility number of 0.91 at room temperature (Zhao et al, 2022), where the LIBs shows good cycling performance, high capacity output and no lithium dendrites.…”

“…For example, Zhao et al (2022) constructed a lithium carboxylate COFs (LiOOC-COF3) (Figure 2G) with ordered one-dimensional channels. The single Li-ion conductor of LiOOC-COF3 exhibits an excellent ionic conductivity of 1.36 × 10 −5 S cm −1 and a high mobility number of 0.91 at room temperature (Zhao et al, 2022), where the LIBs shows good cycling performance, high capacity output and no lithium dendrites. Therefore, the applicable potential of COF-related solid-state electrolyte in Li-S batteries can be expected in the future to construct ordered ion transport channels and guarantee the longevity and safety.…”

“…FIGURE 2Summary of schematic diagram of the COFs in anode, separator and solid electrolytes materials (A-G)(Zhou et al, 2021;Zhao et al, 2021;Yang et al, 2022;Xu et al, 2021;Zhu et al, 2021;Sun et al, 2022;Zhao et al, 2022).…”

Understanding a Single-Li-Ion COF Conductor for Being Dendrite Free in a Li-Organic Battery

“…Moreover, the polarization of concentration difference can be addressed because there are no randomly removable anion and solvent in SLCs. Notably, the multiple species of freely mobile anion and solvent molecule inevitably trigger ununiform Li + deposition and dendrite formation on the Li metal surface [6][7][8][9]. Consequently, designing and constructing advanced SLCs without anion and solvent are urgently needed.…”