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Engineered polycrystalline electrodes are critical to the cycling stability and safety of lithium-ion batteries, yet it is challenging to construct high-quality coatings at both the primary-and secondaryparticle levels. Here, we present a room-temperature synthesis route to achieve full surface coverage of secondary particles and facile infusion into grain boundaries, thus offering a complete "coatingplus-infusion" strategy. Cobalt boride metallic glass is successfully applied to Ni-rich layered cathode LiNi 0.8 Co 0.1 Mn 0.1 O 2 . It dramatically improves the rate capability and cycling stability, including under high-discharge-rate and elevated-temperature conditions and in pouch full cells.The superior performance originates from simultaneous suppression of microstructural degradation of intergranular cracking and side reactions with electrolyte. Atomistic simulations identified the critical role of strong selective interfacial bonding, which offers not only a large chemical driving force to ensure uniform reactive wetting and facile infusion but also lowered the surface/interface 2 oxygen activity, contributing to the exceptional mechanical and electrochemical stabilities of the infused electrode.

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Spinel LiMn2O4, whose electrochemical activity was first reported by Prof. John B. Goodenough's group at Oxford in 1983, is an important cathode material for lithium‐ion batteries that has attracted continuous academic and industrial interest. It is cheap and environmentally friendly, and has excellent rate performance with 3D Li+ diffusion channels. However, it suffers from severe degradation, especially under extreme voltages and during high‐temperature operation. Here, the current understanding and future trends of the spinel cathode and its derivatives with cubic lattice symmetry (LiNi0.5Mn1.5O4 that shows high‐voltage stability, and Li‐rich spinels that show reversible hybrid anion‐ and cation‐redox activities) are discussed. Special attention is given to the degradation mechanisms and further development of spinel cathodes, as well as concepts of utilizing the cubic spinel structure to stabilize high‐capacity layered cathodes and as robust framework for high‐rate electrodes. “Good spinel” surface phases like LiNi0.5Mn1.5O4 are distinguished from “bad spinel” surface phases like Mn3O4.

The development of Li‐excess disordered‐rocksalt (DRX) cathodes for Li‐ion batteries and interpretation through the framework of percolation theory of Li diffusion have steered researchers to consider “Li‐excess” (x > 1.1 in LixTM2−xO2; TM = transition metal) as being critical to achieving high performance. It is shown that this is not necessary for Mn‐rich DRX‐cathodes demonstrated by Li1.05Mn0.90Nb0.05O2 and Li1.20Mn0.60Nb0.20O2, which both deliver high capacity (>250 mAh g−1) regardless of their Li‐excess level. By contextualizing this finding within the broader space of DRX chemistries and confirming with first‐principles calculations, it is revealed that the percolation effect is not crucial at the nanoparticle scale. Instead, Li‐excess is necessary to lower the charging voltage (through the formation of condensed oxygen species upon oxygen oxidation) of certain DRX cathodes, which otherwise would experience difficulties in charging due to their very high TM‐redox potential. The findings reveal the dual roles of Li‐excess – modifying the cathode voltage in addition to promoting Li diffusion through percolation – that must be simultaneously considered to determine the criticality of Li‐excess for high‐capacity DRX cathodes.