Reviving and upgrading storage-degraded nickel-rich cathodes via solid-state electrolyte coating

Abstract

Large-scale production of nickel-rich cathodes inevitably results in severe storage degradation (forming surface lithium impurities and the NiO rock-salt phase) under humid air conditions that preclude their direct use in the battery manufacturing industry. Herein, we propose a facile remediation strategy for storage-degraded LiNi_0.9Co_0.05Mn_0.05O₂ cathodes via a wet-chemistry-assisted Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (LLZTO) coating approach followed by calcination under an O₂ atmosphere. During calcination, surface lithium impurities are consumed, Ni²⁺ is re-oxidized to Ni³⁺, and Li/Ni disorder is reduced, thereby regenerating the ordered layered structure of the cathode. Meanwhile, the uniformly formed LLZTO coating serves as a fast Li⁺ conductor and a protective barrier against electrolyte corrosion, suppressing interfacial side reactions and accelerating lithium-ion transport. The repaired cathode not only recovers its performance but even outperforms the pristine cathode. At 200 mA g⁻¹, the capacity retention of the repaired cathode is 94.9% after 100 cycles, compared with 84.4% for the pristine cathode. The capacity at 4C rate also increases by 18.38%. Post-cycling characterization studies confirm a stable layered structure, thinner cathode–electrolyte interphase, lower impedance, and no obvious microcracks after the remediation strategy. This work provides a practical solution for reutilization of storage-degraded nickel-rich cathodes, contributing to cost reduction and resource sustainability in battery production.