All-solid-state lithium metal batteries based on non-flammable inorganic ceramic electrolytes hold promise for achieving both high energy density and safety. However, inadequate physical contact and chemical incompatibility at the Li/electrolyte interface can provoke interfacial thermal runaway far exceeding those in liquid-electrolyte batteries. Here, we employ in situ high-resolution thermal imaging to monitor thermal runaway at the Li|LATP interface in real time. Results show that after the initial contact reaction at 320 °C, the interface enters a stochastic stress-release stage, during which LATP cracks nucleate and localized hot spots form at the cracks, with the representative hot-spot region showing a temperature-rise rate of ~9.5 °C s^-1 before violent ignition. Transitioning to violent ignition and combustion, the heating rate surges beyond 1943.8 °C s^-1 and interfacial temperature exceeds 1500 °C, causing catastrophic thermal breakdown. In situ imaging coupled with ex situ characterization delineates a safety failure pathway wherein interfacial failure generates hot spots that drive localized thermal runaway. Guided by this, we design a dual-passivation LiI|a-Si heterogeneous interlayer that substantially suppresses interfacial heat and oxygen- containing species releasing reactions, eliminating hot spots initiation and thermal runaway at their source. The all-solid-state lithium metal symmetric batteries with this interlayer demonstrate stable cycling at 150 °C. This work paves the way for developing safe and high-energy all-solid-state batteries.

Lithium–carbon dioxide (Li–CO₂) batteries have attracted considerable attention due to their high theoretical energy densities and potential for capturing and converting CO₂ toward net-zero carbon dioxide emissions. However, the reversible cycling capability of Li–CO₂ batteries is greatly limited by the sluggish kinetics of the CO₂ evolution reaction (CO₂ER), which leads to excessive charge voltages exceeding 4.0 V, thus significantly hindering the practical advancement of the battery technology. Herein, we report dual-active-site AuRu catalysts supported on TiO₂ nanorod arrays, grown on carbon nanofiber, where TiO₂ layers effectively prevent carbon corrosion and the electronic synergy of the dual active site design comprising Au and Ru can lower the reaction energy barriers of the CO₂ reduction reaction (CO₂RR) and CO₂ER. Calculation results reveal that this synergy gives rise to complementary catalytic roles: Au facilitates CO₂ activation, whereas Ru promotes Li₂CO₃ breakdown, collectively enhancing the overall reaction kinetics. Consequently, Li–CO₂ batteries employing AuRu/TiO₂ cathode deliver an ultralong cycle life exceeding 1100 cycles (~ 2200 h), low charge voltages (2.9–3.1 V), high energy efficiency (~ 77.9%), and excellent stability at elevated temperatures. This work establishes a generalizable catalyst-support strategy for long lifespan metal–CO₂ batteries, offering a promising route toward high-performance carbon neutral energy storage devices.