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Synthesis of Ni-Rich Layered-Oxide Nanomaterials with Enhanced Li-Ion Diffusion Pathways as High-Rate Cathodes for Li-Ion Batteries  

As one of the most promising cathode materials for Li-ion batteries, Ni-rich layered transition-metal-mixed oxide LiNixCoyMn1-x-yO2 (NCM, x>0.5) has drawn intense attention in the search for high energy density, low cost, and reduced Co content materials. However, Ni-rich NCM cathodes are still suffering from several drawbacks, where cation disorder and volume expansion during Li-ion (de)intercalation are mainly responsible for the inadequate storage capacity and moderate cycling stability of Ni-rich NCM cathodes. Further improvement and optimization are therefore necessary to realize their full potential as the next-generation cathode in Li-ion batteries. Several strategies have been employed to overcome these problems, such as cation doping, surface coating, and structure modification. Among them, architecture control is crucial for promoting Li-ion transport inside the electrode particles and this can improve the electrode performance without compromising the energy density of NCM cathode materials.

Herein, we designed and successfully synthesized Ni-rich LiNi0.6Co0.2Mn0.2O2 nanomaterials with a unique nanobrick morphology. This structure presented a large exposed ratio of high energy {010} facets, where two-dimension Li-ion diffusion pathways are created in the NCM materials. A facile hydrothermal method combined with surfactant assistance was used for the synthesis. The highly exposed {010} facets accordingly resulted in favorable Li-ion diffusion coefficients. Consequently, the nanostructured electrode materials demonstrated an enhanced rate capability, higher cycling stability, and fast charging characteristics. In addition, ordered structural orientation in micro-particles displayed crack-free surfaces even after long-term cycling due to the moderate inner-grain stress induced by volume expansion.