Difunctional MOF for dendrite-free all-solid-state lithium metal batteries by synergistic effect of hydrogen bond and electrostatic interaction

The interphase formed between solid polymer electrolyte (SPE) and highly reductive lithium metal largely determines the overall performance of the battery. Although various types of nanoparticles have been continuously employed as fillers to achieve a stable interphase for long cycling performance, the irregular growth of lithium dendrites cannot be completely suppressed due to uneven lithium deposition. Herein, a new type of zwitter-ion modified metal-organic framework (NH3+·SO3-@ZIFs) is prepared as a modifier for PEO-LiTFSI. Due to the unique ionic structure of NH3+·SO3-@ZIFs, the formed electrostatic interaction could inhibit the movement of TFSI-, enhance the ion migration number. More importantly, TOF-SIMS effectively confirms the formation of Li+-conductive LiF-rich SEI due to the catalytic effect of NH3+·SO3-@ZIFs, which could homogenize the lithium flux, inhibit the growth of Li dendrite. Results show that the PEO-NH3+·SO3-@ZIFs exhibits high ion migration number (tLi+ = 0.78). The Li/Li symmetric cells equipped NH3+·SO3-@ZIFs SPE can be stably operated for more than 4600 h at 60 °C while the full cell with LiFePO4 cathode also enables long-term stability over 1200 cycles with capacity stabilizing at around 103 mAh g−1, demonstrating the great potential of this kind of SPEs for preparing high-performance LMBs.