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Electrochemical properties and structural and thermal stability of LiNi0.65Co0.13Mn0.22O2 (FCG65), LiNi0.75Co0.08Mn0.17O2 (TSFCG75), and LiNi0.85Co0.05Mn0.10O2 (TSFCG85) with concentration gradients of Ni and Mn were evaluated to comprehensively demonstrate the effectiveness of compositional gradation for a wide range of Ni-rich LiNixCoyMn1–x–yO2 (NCM) cathodes. The discharge capacities of FCG65, TSFCG75, and TSFCG85 were 194.2, 206.8, and 222.2 mAh g–1, respectively with capacity retention of over 90% after 100 cycles. The high capacities and enhanced cycling stability relative to those of conventional Ni-rich NCM cathodes were attributed to the compositional partitioning, strong crystallographic texture, and unique particle morphology. In addition, the highly correlated particle orientation helped to reduce the anisotropic internal strain induced by Li removal/extraction from the Ni-rich NCM cathodes. The accelerated aging test (storing the delithiated cathodes in an electrolyte at elevated temperature) reconfirmed the superior stability of the TSFCG85 cathode compared to the commercial LiNi0.82Co0.14Al0.04O2 cathode, which exhibited fast structural degradation. Thus, NCM cathodes with concentration gradients represent a viable solution that simultaneously addresses the specific energy density, cycling and chemical stability, and safety issues of Ni-enriched NCM cathodes for general electromobility.
Yoon et al. (Wed,) studied this question.