Improving the Performance of LiNi_0.925Co_0.065Mn_0.01O₂ via Ti⁴⁺& Nb⁵⁺ Co-Modifications

Ni-rich layer-structured materials are some of the most promising cathodes owing to their attractive reversible capacity and cost-effectiveness. When the Ni content is increased to 90% and higher, mechanical deterioration becomes serious and leads to accelerated cyclic degradation, since removable Li⁺ is ∼0.85, accompanied by large lattice variation during operation. Here, we investigate the influences of Ti⁴⁺ bulky substitution, Nb⁵⁺ surface treatment, and their coutilization on the behavior of LiNi_0.925Co_0.065Mn_0.01O₂ (NCM92). In contrast to the limited positive effects of monousage, the coutilization of Ti⁴⁺ and Nb⁵⁺ obviously suppresses particles' pulverization, relying on their synergistic effects of the shape of lattice variation and the protection of a tough shell layer. As a result, Ti & Nb-LiNi_0.925Co_0.065Mn_0.01O₂ (TiNb-NCM92) presents the best capacity retention, as high as 90.2% after 300 cycles, much higher than NCM92 (49.0%), Ti-NCM92 (76.3%), and Nb-NCM92 (72.4%). Our approaches demonstrate that the serious mechanical challenges of ultrahigh nickel cathodes could be alleviated by various remedies coutilized together.