Interphase Building of Organic–Inorganic Hybrid Polymer Solid Electrolyte with Uniform Intermolecular Li+ Path for Stable Lithium Metal Batteries

Lithium (Li) metal has been generally noticed as the most prospective anode for next-generation batteries attributed to its outstanding theoretical capacity and low electrochemical potential. Nevertheless, the unstable solid-electrolyte interphase (SEI) and uncontrollable dendrite growth cause poor reversibility and fetter the practical application of Li metal anodes. Herein, a new organic–inorganic hybrid polymer artificial SEI (POSS-LiBMAB) layer with uniform lithium-ion paths at a molecular level is designed to stabilize Li metal anodes. The SEI layer is constructed by the thiol–ene “click chemistry” reaction between inorganic polyhedral oligomeric silsesquioxane containing eight-mercaptopropyl (POSS-SH) with lithium bis (allylmalonato) borate (LiBMAB) on Li foil. What is more, the POSS-LiBMAB film can be cross-linked and self-reinforced via intermolecular S  C bonds. Benefiting from its flexible polymeric covalent structure and noble inorganic Si 8 O 16 -type cubes, the organic–inorganic hybrid polymer layer is flexible and effectively tolerates the volume change of Li metal anodes during plating/stripping cycles. In addition, this layer shows loose and uniformly distributed electrostatic interaction between Li + and charge delocalized sp 3 boron–oxygen anions, which aids to form a uniform intermolecular Li + path regulating the homogeneous distribution of Li + flux on Li anodes. Finally, the designed POSS–LiBMAB layer has high ionic conductivity and lithium-ion transference number, which can effectively promote Li + diffusion and guide Li deposition beneath the SEI layer. Therefore, with the protection of the POSS-LiBMAB layer, the Li metal anode exhibits stable cycling at 5 mA cm −2 for more than 1000 h, and the LFP//Li full cells also present outstanding cycling stability.