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Ni-rich layered cathodes have been regarded as one of the high-priority materials, but their commercial application was limited by the highly active surfaces, poor thermal stability, and irreversible phase transition. Furthermore, when they are stored in moist air, the particles can easily form an impurity layer of Li2CO3/LiOH. This inert substance hinders the transmission of lithium ions and electrons, leading to electrochemical performance deterioration. Herein, we report a simple method, namely, metaphosphate repair, which can successfully restore the degraded LiNi0.8Co0.1Mn0.1O2(NCM811) cathode materials and form an in situ multifunctional hybrid repaired layer of Li3PO4-YPO4-Y(PO3)3on the secondary particle. The repaired NCM811 delivers a discharge capacity of 171.7 mAh g–1after 100 cycles, which is much higher than those of pristine (147.6 mAh g–1) and stored degraded (116.2 mAh g–1) samples. Moreover, the restored sample could deliver a capacity retention of 92.3% after 100 cycles at 1C along with a better initial Coulombic efficiency (CE) of 88.4%. This study provides a facile strategy to revive degraded Ni-rich cathode materials and other similar layered oxide cathodes for advanced batteries.

Single-crystalline LiNi0.6Co0.2Mn0.2O2cathodes have received great attention due to their high discharge capacity and better electrochemical performance. However, the single-crystal materials are suffering from severe lattice distortion and electrode/electrolyte interface side reactions when cycling at high voltage. Herein, a unique single-crystal LiNi0.6Co0.2Mn0.2O2with Al and Zr doping in the bulk and a self-formed coating layer of Li2ZrO3in the surface has been constructed by a facile strategy. The optimized cathode material exhibits excellent structural stability and cycling performance at room/elevated temperatures after long-term cycling. Specifically, even after 100 cycles (1C, 3.0–4.4 V) at 50 °C, the capacity retention for the Al and Zr co-doped sample reaches 92.1%, which is much higher than those of the single Al-doped (85.4%), single Zr-doped (87.1%), and bare samples (76.3%). The characterization results and first-principles calculations reveal that the excellent electrochemical properties are attributed to the stable structure and interface, in which the Al and Zr co-doping hinders cation mixing and suppresses detrimental phase transformations to reduce internal stress and mitigate microcracks, and the coating layer of Li2ZrO3can protect the surface and suppress interfacial parasitic reactions. Overall, this work provides important insights into how to simultaneously build a stable bulk structure and interface for the single-crystal NCM cathode via a facile preparation process.