Mechanically robust solid electrolyte interphase via in situ adhesion of organic-inorganic bilayers for energy-dense...

The poor mechanical stability of solid electrolyte interphase (SEI) critically compromises the cycle life of practical lithium (Li) metal batteries, as repeated volume changes induce continuous SEI fracture and regeneration. Here, we propose a robust organic layer, in situ formed from 3‑glycidoxypropyltrimethoxysilane (GPTS) and anchored onto an inorganic underlayer, to enhance interfacial adhesion between the organic and inorganic layer, thereby improving the mechanical stability of the SEI. The epoxy groups of GPTS can polymerize in situ to form a robust organic layer, while the methoxysilane groups facilitate the anchoring of the organic layer onto the inorganic layer through chemical reactions. The elastic modulus of the formed bilayer SEI is much enhanced, thereby effectively mitigating its cracking and reconstruction during cycles. Li metal coin cells with GPTS-derived SEI deliver capacity retention of 80% after 290 cycles under practical conditions, which is 1.6 times higher than that of the coin cells with base SEI. A 5.5 Ah Li metal pouch cell with GPTS-derived SEI achieves a high energy density of 503 Wh kg^-1 and maintains stable cycling for 107 cycles. This work presents a rational strategy for engineering the SEI nanostructure to enhance mechanical stability, thereby promoting the stability of Li metal anodes.