Maximizing the Energy Density of LNMO‖Graphite Cells by Mitigating First Cycle Losses Associated With Solid Electrolyte Interphase Formation

This study investigates the use of lithium oxalate (LO) as a pre‐lithiation additive in LNMO‖Graphite pouch cells. The electrochemical utilization of LO is optimized by particle downsizing and the addition of high surface carbon additives such as ketjen black. By this combination, the mitigation of the kinetic barrier of LO decomposition is demonstrated. LNMO cathodes blended with 5 wt% LO exhibit superior cycling performance and improved reversible capacity compared to reference LNMO‖Graphite cells. The addition of 5 wt% LO showed an increase in material level energy density by ~30% after 200 cycles. The use of ketjen black with its high surface area and porous structure improves the salt efficiency but also exacerbating side reactions at high voltage. Postmortem cross‐sectional images of the electrodes showed an increase in measured porosity as well as an increase in the electrode thickness. The continuous cycling of the 4 V manganese redox region of LNMO resulted in an increase in transition metal dissolution due to the excess cyclable lithium provided through the pre‐lithiation. This issue was minimized by cycling the electrodes in a narrower voltage range from 4.2 to 4.8 V, thereby improving the long‐term cycling stability while retaining the energy density benefits.