Mechanical Reinforcement of Layered Oxide Cathodes for Continuous High-Power Rate Delivery throughout Cycling

Demand for high-energy-density cathodes with high power and stable cycling is increasing. Ni-rich layered cathodes, notably Li[Ni_0.9Co_0.05Mn_0.05]O₂ (NCM90), satisfy this requirement but suffer capacity loss driven by anisotropic volume expansion and deleterious phase transitions that cause structural instability under high current densities. Here, a core-shell gradient plus shell (CSGPS90) architecture integrates a Ni-rich core for high capacity and a Mn-rich shell for stability with a gradient and elongated nanorod microstructure in between to better facilitate Li⁺ transport. Owing to the higher particle hardness and enhanced mechanical integrity of CSGPS90, the CSGPS90 achieves 89.0% capacity retention rate versus 61.9% for NCM90 under regular 0.8 C/1 C cycling conditions after 1000 cycles. Under the variable 4N3F (four normal (0.5 C), three fast (2 or 3 C)) cycling protocol, the CSGPS90 consistently delivered high-power rates, with a capacity retention rate of 83.0%, compared to the 33.9% of NCM90 after 1000 cycles. Post-mortem analyses reveal extensive Li⁺ trapping along microcracks and NiO-like rock-salt phase formation in the charged NCM90, whereas CSGPS90 maintains uniform Li⁺ extraction. Our findings provide evidence that structural durability contributes to improved Li⁺ kinetics and highlight the importance of microstructural gradient engineering to reinforce mechanical stability and continued power delivery stability for large battery applications requiring high power.