Boosting Ni‐Rich Cathode Stability Through Grain Boundary Strengthening and Phase Transition Degradation Suppression

Abstract Nickel‐rich layered cathodes are promising for high‐energy‐density lithium‐ion batteries but suffer from rapid capacity fading, primarily due to intergranular cracking and structural degradation during the H2‐H3 phase transition, especially under high voltage. To address these challenges, a novel Ta 5+ /Ti 4+ co‐doping strategy has been introduced that simultaneously stabilizes grain boundaries and enhances the mechanical strength of the cathode. The dopants effectively mitigate intergranular cracking and form a pre‐cation‐mixing layer, stabilizing the layered structure during deep delithiation and preventing structural collapse. Moreover, this co‐doping approach also improves the reversibility of the H2‐H3 phase transition and reduces lattice distortions, thereby enhancing cycling stability. As a result, the co‐doped cathode exhibits excellent capacity retention of 96.66% after 150 cycles at 1 C in liquid electrolyte. In solid‐state batteries, it demonstrates superior interfacial compatibility with significantly reduced side reactions with the solid electrolyte, achieving a high initial capacity of 181.4 mAh g −1 and retaining 89.3% of its capacity after 100 cycles. This marks a significant improvement over the pristine cathode. These results highlight the effectiveness of Ta 5+ /Ti 4+ co‐doping as a pratical strategy for developing high‐performance nickel‐rich cathodes for next‐generation lithium‐ion batteries.