Revitalizing interphase in all-solid-state Li metal batteries by electrophile reduction

All-solid-state lithium metal batteries promise high levels of safety and energy density, but their practical realization is limited by low Li reversibility, limited cell loading and demand for high-temperature and high-pressure operation, stemming from solid-state electrolyte (SSE) low-voltage reduction and high-voltage decomposition, and from lithium dendrite growth. Here we concurrently address these challenges by reporting that a family of reductive electrophiles gain electrons and cations from metal–nucleophile materials (here a Li sulfide SSE) upon contact to undergo electrochemical reduction and form interphase layers (named solid reductive-electrophile interphase) on material surfaces. The solid reductive-electrophile interphase is electron blocking and lithiophobic, prevents SSE reduction, suppresses Li dendrites and supports high-voltage cathodes. Consequently, a reductive-electrophile-treated SSE exhibits high critical capacity and Li reversibility at the anode, and enables Li(1% Mg)/SSE/LiNi0.8Co0.15Al0.05O2 all-solid-state lithium metal batteries to achieve a high coulombic efficiency (>99.9%), long cycle life (~10,000 h) and high loading (>7 mAh cm−2) at 30 °C and 2.5 MPa. This concept also extends to cathodes of other materials (for example, metal oxides), boosting the high-nickel cathode’s cycle life and expanding the operational voltage up to 4.5 V. Such solid reductive-electrophile interphase tailoring of material surfaces holds promise to accelerate all-solid-state lithium metal battery commercialization and offer solutions for a wide range of materials. Solid-state electrolyte reduction and Li dendrite growth limit the stability of all-solid-state Li metal batteries. Here the authors show that reductive electrophiles gain electrons and metal cations from metal–nucleophile materials on contact, allowing the electrochemical formation of a dense, electron-blocking film that improves the stability of both the anode and high-voltage cathode.