Fluorinating All Interfaces Enables Super‐Stable Solid‐State Lithium Batteries by In Situ Conversion of Detrimental Surface Li2CO3

Li-stuffed battery materials intrinsically have surface impurities, typically Li2CO3, which introduce severe kinetic barriers and electrochemical decay for a cycling battery. For energy-dense solid-state lithium batteries (SSLBs), mitigating detrimental Li2CO3 from both cathode and electrolyte materials is required, while the direct removal approaches hardly avoid Li2CO3 regeneration. Here, a decarbonization-fluorination strategy to construct ultrastable LiF-rich interphases throughout the SSLBs by in situ reacting Li2CO3 with LiPF6 at 60 °C is reported. The fluorination of all interfaces effectively suppresses parasitic reactions while substantially reducing the interface resistance, producing a dendrite-free Li anode with an impressive cycling stability of up to 7000 h. Particularly, transition metal dissolution associated with gas evolution in the cathodes is remarkably reduced, leading to notable improvements in battery rate capability and cyclability at a high voltage of 4.5 V. This all-in-one approach propels the development of SSLBs by overcoming the limitations associated with surface impurities and interfacial challenges.