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 SC bonds. Benefiting from its flexible polymeric covalent structure and noble inorganic Si8 O16 -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 sp3 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.
Keywords: Silsesquioxane; artificial solid electrolyte interphase; lithium metal batteries; organic-inorganic hybrid; single-ion conducting polymer.
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