Interfacial Engineering of Li[Ni_0.84Co_0.10Mn_0.06]O₂ Cathodes for Safer Lithium-Ion Batteries

The structural instability and poor thermal stability of Ni-rich ternary cathode materials with high nickel content (x_Ni > 0.80) at high state of charge or highly delithiated state are major concerns in their application. Here, a finely tunable nanosized Li-Al-P-O layer on Li[Ni_0.84Co_0.10Mn_0.06]O₂ (NCM84) particles is proposed to suppress the "trigger" effects of highly oxidizing atomic oxygen and corresponding electrolyte oxidation processes. It shows that the thermal power of delithiated cathodes with electrolytes is suppressed in half by construction of a gradient Al³⁺ inner layer combined with a nanosized Li-Al-P-O layer (<10 nm) on NCM84 particles. The accelerating rate calorimeter analysis of the NCM/graphite full cells demonstrates that the heat generation of lithium-aluminum-phosphate (LAPO)-modified cathodes is markedly reduced without leading to thermal runaway. Our results disclose that the nanosized LAPO layer effectively inhibits the atomic oxygen "escaping" from the interfacial area, thus promoting it to form oxygen molecules and fast phase transition, then releasing as oxygen molecules rather than atomic oxygen species, and thereafter results in distinctive decomposition of the electrolytes and related thermal stabilities. This work provides a promising strategic guideline for atomic layer deposition-modified cathode materials in high energy density lithium-ion batteries with high thermal stability.