<p>The sluggish Li<sup>+</sup> migration kinetics and unstable electrode/electrolyte interface severely hinder the commercial application of high-performance lithium metal batteries (LMBs). Herein, an artificial protective layer is constructed using zwitterionic covalent organic framework (Z-COF) simultaneously containing sulfonate and ethidium groups, aiming to facilitate rapid, uniform Li<sup>+</sup> transport and stabilize anode interface. The sulfonate groups with high lithiophilicity provide abundant hopping sites for fast Li<sup>+</sup> diffusion. The ethidium cations immobilize TFSI<sup>−</sup> and solvent molecules by ion–dipole interactions, which accelerate the dissociation of LiTFSI and Li<sup>+</sup> desolvation. Moreover, the monodispersed zwitterionic units coupling with ordered micropore structures in Z-COF create exclusive Li<sup>+</sup> migration channels, modulate homogeneous space charge distribution, kinetically facilitating uniform Li<sup>+</sup> deposition. Experiments and theoretical calculations indicate that C–F and S–N bonds of TFSI<sup>−</sup> exhibit enhanced cleavage susceptibility driven by electrostatic attraction, realizing a LiF/Li<sub>3</sub>N-rich electrolyte/electrode interface. The designed Z-COF protection layer enables Li|Li symmetrical cells stable cycling over 6300&#xa0;h at 2&#xa0;mA cm<sup>−2</sup>/2&#xa0;mAh cm<sup>−2</sup>. The Z-COF@Li|LiFePO<sub>4</sub> (LFP) full cells deliver high-capacity retention of 85.2% after 1000 cycles at 8 C. The assembled Z-COF@Li|LFP pouch cells demonstrate a lifespan of more than 240 cycles. This work provides fresh insights into the practical application of zwitterionic COF in next-generation LMBs.</p><p></p>

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Regulating Li+ Transport and Interfacial Stability with Zwitterionic COF Protective Layer Towards High-Performance Lithium Metal Batteries

  • Liya Rong,
  • Yifeng Han,
  • Chi Zhang,
  • Hongling Yao,
  • Zhaojun He,
  • Xianbao Wang,
  • Zaiping Guo,
  • Tao Mei

摘要

The sluggish Li+ migration kinetics and unstable electrode/electrolyte interface severely hinder the commercial application of high-performance lithium metal batteries (LMBs). Herein, an artificial protective layer is constructed using zwitterionic covalent organic framework (Z-COF) simultaneously containing sulfonate and ethidium groups, aiming to facilitate rapid, uniform Li+ transport and stabilize anode interface. The sulfonate groups with high lithiophilicity provide abundant hopping sites for fast Li+ diffusion. The ethidium cations immobilize TFSI and solvent molecules by ion–dipole interactions, which accelerate the dissociation of LiTFSI and Li+ desolvation. Moreover, the monodispersed zwitterionic units coupling with ordered micropore structures in Z-COF create exclusive Li+ migration channels, modulate homogeneous space charge distribution, kinetically facilitating uniform Li+ deposition. Experiments and theoretical calculations indicate that C–F and S–N bonds of TFSI exhibit enhanced cleavage susceptibility driven by electrostatic attraction, realizing a LiF/Li3N-rich electrolyte/electrode interface. The designed Z-COF protection layer enables Li|Li symmetrical cells stable cycling over 6300 h at 2 mA cm−2/2 mAh cm−2. The Z-COF@Li|LiFePO4 (LFP) full cells deliver high-capacity retention of 85.2% after 1000 cycles at 8 C. The assembled Z-COF@Li|LFP pouch cells demonstrate a lifespan of more than 240 cycles. This work provides fresh insights into the practical application of zwitterionic COF in next-generation LMBs.