Exceptional layered cathode stability at 4.8 V via supersaturated high-valence cation design

Abstract

High-energy-density lithium-ion batteries for extreme conditions require cathodes that remain stable under harsh operation, including ultrahigh cutoff voltage and extreme temperatures. For Ni-rich layered cathodes, raising the charge voltage from 4.3 V to 4.8 V (versus Li+/Li) increases the energy density, yet this sacrifices cycling stability and remains challenging. Here we report a dopant-pairing method that achieves highly enriched Ti4+ (~9-nm surface layer) in LiNi0.8Co0.1Mn0.1O2 facilitated by Na+, enabling significantly enhanced high-voltage cyclability. Such high surface Ti4+ concentrations are unattainable without pairing Na+, representing a form of supersaturation within the layered cathode matrix. The enhanced stability is linked to improved structural integrity and reduced cathode–electrolyte side reactions (for example, O2 and CO2 evolution). In addition, ion transport is better preserved even after prolonged cycling at 4.8 V. This work highlights the power of supersaturated high-valence d0 cation Mz+ (z ≥ 4) in modifying the cathode–electrolyte interactions and degradation pathway. Ni-rich layered cathodes promise higher energy density at high voltages, but suffer from poor cycling stability. This study improves stability by introducing a supersaturated high-valence cation surface layer that stabilizes the structure and suppresses side reactions for durable cycling at 4.8 V.