Lithium-rich layered oxides with the capability to realize extraordinary capacity through anodic redox as well as classical cationic redox have spurred extensive attention. However, the oxygen-involving process inevitably leads to instability of the oxygen framework and ultimately lattice oxygen release from the surface, which incurs capacity decline, voltage fading, and poor kinetics. Herein, it is identified that this predicament can be diminished by constructing a spinel Li Mn O coating, which is inherently stable in the lattice framework to prevent oxygen release of the lithium-rich layered oxides at the deep delithiated state. The controlled KMnO oxidation strategy ensures uniform and integrated encapsulation of Li Mn O with structural compatibility to the layered core. With this layer suppressing oxygen release, the related phase transformation and catalytic side reaction that preferentially start from the surface are consequently hindered, as evidenced by detailed structural evolution during Li extraction/insertion. The heterostructure cathode exhibits highly competitive energy-storage properties including capacity retention of 83.1% after 300 cycles at 0.2 C, good voltage stability, and favorable kinetics. These results highlight the essentiality of oxygen framework stability and effectiveness of this spinel Li Mn O coating strategy in stabilizing the surface of lithium-rich layered oxides against lattice oxygen escaping for designing high-performance cathode materials for high-energy-density lithium-ion batteries.

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Li + -conductive ceramic oxide electrolytes, such as garnetstructured Li 7 La 3 Zr 2 O 12, have been considered as promising candidates for realizing the next-generation solid-state Li-metal batteries with high energy density. Practically, the ceramic pellets sintered at elevated temperatures are often provided with high stiffness yet low fracture toughness, making them too brittle for the manufacture of thin-film electrolytes and straininvolved operation of solid-state batteries. The ceramic powder, though provided with ductility, does not yield satisfactorily high Li + conductivity due to poor ion conduction at the boundaries of ceramic particles. Here we show, with solid-state nuclear magnetic resonance, that a uniform conjugated polymer nanocoating formed on the surface of ceramic oxide particles builds pathways for Li + conduction between adjacent particles in the unsintered ceramics. A tapecasted thin-film electrolyte (thickness: <10 μm), prepared from the polymer-coated ceramic particles, exhibits sufficient ionic conductivity, a high Li + transference number, and a broad electrochemical window to enable stable cycling of symmetric Li/Li cells and all-solid-state rechargeable Li-metal cells.

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