A multifunctional natural clay mineral additive for stabilizing Ni-rich layered oxide cathodes

Layered Ni-rich lithium transition metal oxides exhibit high specific capacities and broad application potential in various advanced energy storage systems. However, even trace amounts of water in the electrolyte can trigger irreversible phase transitions and detrimental interfacial reactions, such as transition metal ions (TMs) dissolution and HF-induced corrosion, ultimately leading to premature battery failure. Herein, natural clay mineral halloysite (7 Å HNT) acts as a multifunctional additive and is applied in the LiNi_0.6Mn_0.2Co_0.2O₂ (NCM622) electrode to improve its cycling stability. The external Si–O–Si surface and internal Al–OH lumen of HNT can effectively scavenge H₂O/HF and suppress TMs dissolution, thereby preventing cathode microstructural degradation and mitigating crosstalk side reactions. Additionally, the negatively charged outer surface of HNT promotes the accumulation of Li⁺ near the electrode interface, which helps to alleviate concentration polarization and enhance interfacial lithium-ion transport, thereby improving the rate capability. As a result, the assembled HNT-LiNi_0.6Mn_0.2Co_0.2O₂//Li (HNT-NCM) cell displays a high capacity retention of 86.6% after 500 cycles at 2 C. Even at 55 °C, the HNT-NCM//Li cell retains 79.5% of its original capacity after 150 cycles, exhibiting a 22.1% enhancement in capacity retention compared to the pristine NCM//Li cell. In this work, a straightforward yet efficient approach for constructing a protective barrier to mitigate the hazards of H₂O, TMs, and HF in modern battery systems is proposed.