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

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 Ta⁵⁺/Ti⁴⁺ 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 Ta⁵⁺/Ti⁴⁺ co-doping as a pratical strategy for developing high-performance nickel-rich cathodes for next-generation lithium-ion batteries.