High precision coulometry studies of single-phase layered compositions in the Li-Mn-Ni-O system

Positive electrode materials which do not react with electrolyte at high potentials (≥ 4.6 V vs. Li/Li⁺) are essential for developing Li-ion batteries with high energy densities and long cycle lives. Reactions with electrolyte can be detected using precise measurements of coulombic efficiency (CE) and charge end point capacity slippage. Three single-phase layered compositions in the Li-Mn-Ni- O system, Li[Li_0.16Ni _0.12Mn_0.65-0.07]O₂, Li[Li_0.12Ni _0.32Mn_0.56]O₂, and Li[Li_0.09Ni _0.46Mn_0.45]O₂ were studied by high precision coulometry at upper potential limits of 4.6 V and 4.8 V. When cycled to 4.6 V, Li[Li_0.16Ni_0.12Mn_0.65-0.07]O₂ had a reversible capacity of 225 mAh g^-1 after 50 cycles, and maintained a substantially higher CE and a lower charge end point capacity slippage per cycle than Li[Li_0.12Ni_0.32Mn_0.56]O₂, Li[Li_0.09Ni_0.46Mn_0.45]O₂, and industry standard Li[Ni_1/3Mn_1/3Co_1/3]O ₂ (cycled to only 4.2 V). Overall, these results highlight the inherent "inertness" of Li[Li_0.16Ni_0.12Mn _0.65-0.07]O₂ and its suitability as a thin protective shell in a core-shell particle configuration.