Synergistic surface restructuring and cation mixing via ultrafast Joule heating enhancing ultrahigh-nickel cathodes for advanced lithium-ion batteries

The implementation of ultrahigh-Ni cathodes in high-energy lithium-ion batteries (LIBs) is constrained by significant structural and interfacial degradation during cycling. In this study, doping-induced surface restructuring in ultrahigh-nickel cathode materials is rapidly facilitated through an ultrafast Joule heating method. Density functional theory (DFT) calculations, synchrotron X-ray absorption spectroscopy (XAS), and single-particle force test confirmed the establishment of a stable crystal framework and lattice oxygen, which mitigated H2-H3 phase transitions and improved structural reversibility. Additionally, the Sc doping process exhibits a pinning effect on the grain boundaries, as shown by scanning transmission electron microscopy (STEM), enhancing Li⁺ diffusion kinetics and decreasing mechanical strain during cycling. The in situ development of a cation-mixing layer at grain boundaries also creates a robust cathode/electrolyte interphase, effectively reducing interfacial parasitic reactions and transition metal dissolution, as validated by STEM and time-of-flight secondary ion mass spectrometry (TOF-SIMS). These synergistic modifications reduce particle cracking and surface/interface degradation, leading to enhanced rate capability, structural integrity, and thermal stability. Consequently, the optimized Sc-modified ultrahigh-Ni cathode (Sc-1) exhibits 93.99% capacity retention after 100 cycles at 1 C (25 °C) and 87.06% capacity retention after 100 cycles at 1 C (50 °C), indicating excellent cycling and thermal stability. By presenting a one-step multifunctional modification approach, this research delivers an extensive analysis of the mechanisms governing the structure, microstructure, and interface properties of nickel-rich layered cathode materials (NCMs). These results underscore the potential of ultrahigh-Ni cathodes as viable candidates for advanced lithium-ion batteries (LIBs) in next-generation electric vehicles (EVs).