Suppressing the Structure Deterioration of Ni-Rich LiNiCoMnO through Atom-Scale Interfacial Integration of Self-Forming Hierarchical Spinel Layer with Ni Gradient Concentration.

Ni-rich layered cathodes have attracted great interest due to the high specific capacity, but they suffer from the layered structure deterioration and the resultant poor cyclability and inferior storage performance. Herein, we propose a novel facile strategy to in situ generate an integrated hierarchical spinel layer on the surface of layered LiNiCoMnO (SC-LNCMO) through a pH modulation induced gradient change of Mn ions valence in the precursor. The self-forming hierarchical spinel layer through this strategy is tightly integrated into the layered phase by atom-scale interfacial junctions, and a Ni gradient concentration from the outer to inner has also formed, which strengthens the interface bonding, reduces the surface layer-host phase mismatch, alleviates the Li/Ni mixing, and substantially enhances the structure stability of LiNiCoMnO during charge-discharge cycles. These contribute to the large improvement of the cycling stability, rate capability, and low-temperature performances. More importantly, the long-term storage stability of SC-LNCMO has also been significantly improved due to the effective suppression of the integrated spinel layer on the reduction of Ni to Ni, cations migration and Li/Ni exchange, and LiCO formation. This study not only offers a facile novel strategy to create tightly integrated spinel-layered high-performance cathode materials but also presents some new insights into the structure deterioration and the stabilization mechanism of Ni-rich layered cathode materials during charge/discharge cycles or long-term storage.