Unraveling and Suppression of Multi‐Directional Planar Slipping and Microcracking in Single‐Crystal Co‐Free, Ni‐Rich Cathodes

High-capacity Co-free Ni-rich layered oxides are promising cathode materials for lithium-based batteries, but they suffer from chemo-electro-mechanical instabilities. While single-crystal morphologies reduce these issues, slipping, and microcracking persist during extended cycling, and the degradation mechanisms remain inadequately understood. Herein, we report on multi-directional planar slipping and microcracking along the (003) and (100) planes in a single-crystal LiNi_0.75Mn_0.25O₂ (LNM) cathode. According to the Darken-Gurry theory and formation energy in LNM, magnesium (Mg²⁺) has been selected as the best pillaring element to strengthen the structural integrity and improve cycling stability. Notably, Li_0.99Mg_0.01Ni_0.75Mn_0.25O₂ (LMNM) achieves a capacity retention of 91% after 1000 cycles at 4.3 V operation against graphite by alleviating instability issues. We systematically unravel the pillaring effect, for the first time, from the quantum scale to the lattice level and from the microscale to the macroscopic level of the cathode particles, providing an in-depth understanding of chemo-electro-mechanical degradation.