Reducing the Initial Capacity Loss in High-Nickel Cathodes with a Higher Upper Cut-off Voltage Formation Cycle Protocol

LiNiO2-based layered oxides are regarded as promising cathode candidates for high-energy-density lithium-ion batteries. However, the large initial capacity loss (ICL) and severe electrode–electrolyte interfacial reactions significantly compromise the discharge capacity and cycle life of high-Ni cathodes. Here, we present a systemic investigation of the ICL in high-Ni cathodes by controlling the upper cutoff voltage (UCV) and dopants. It is demonstrated that the elevated ICL due to an incomplete M–H1 phase transition during discharge can be reduced via an activation step to H2–H3 phase transition at high voltages. It is shown that performing formation cycles of LiNiO2 cells with a high UCV of 4.4 V offers significantly improved discharge capacity with minimal capacity retention penalty on cycling under a low UCV of 4.1 V. Furthermore, it is found that doping with Co reduces ICL, while other dopants, such as Mn, Al, and Mg, lead to an increase in ICL.