A well-controlled cracks and gliding-free single-crystal Ni-rich cathode for long-cycle-life lithium-ion batteries

Single-crystalline (SC) high energy nickel (Ni)-rich cathodes play a key role as a potential cathode material in lithium-ion batteries (LIBs) to address the challenges in a hierarchical structure of their secondary particles by decreasing phase boundaries and materials surfaces. The SC LiNi_0.78Mn_0.12Co_0.1O₂ (SC-NMC78) cathode with primary particles of several micron-sized particles are developed and thoroughly investigated in this study, demonstrating superior cycling performance, along with significantly enhanced structural reliability after long-term cycling. The improved SC-NMC78 has an octahedral SC morphology with a modest grain size, which reduces the lithium-ion diffusion route and enhances structural stability. The SC-NMC78 offers a high discharge capacity of 175 and 155 mAh g⁻¹ at 0.2 and 1 C, respectively, and better capacity retention of 132 mAh g⁻¹ after 200 cycles at 1 C as a cathode in LIBs. The cycled SC-NMC78 particles exhibited no lattice gliding and micro-cracks, demonstrating that the SC shape may substantially reduce anisotropic micro-strain. This efficient, repeatable, and customizable method for producing SC Ni-rich cathodes without any additives should accelerate their commercialization. The density functional theory also proved that the low global hardness of Ni²⁺ in SC-NMC78 and optimized content of Ni/Li exchange were well-consistent with the experimental findings.