Li2O:Li-Mn-O Disordered Rock-Salt Nanocomposites as Cathode Prelithiation Additives for High-Energy Density Li-Ion Batteries

The irreversible loss of lithium from the cathode material during the first cycles of rechargeable Li-ion batteries notably reduces the overall cell capacity. Here, a new family of sacrificial cathode additives based on Li2O:Li2/3Mn1/3O5/6 composites synthesized by mechanochemical alloying is reported. These nanocomposites display record (but irreversible) capacities within the Li-Mn-O systems studied, of up to 1157 mAh g(-1), which represents an increase of over 300% of the originally reported capacity in Li2/3Mn1/3O5/6 disordered rock salts. Such a high irreversible capacity is achieved by the reaction between Li2O and Li2/3Mn1/3O5/6 during the first charge, where electrochemically active Li2O acts as a Li+ donor. A 13% increase of the LiFePO4 and LiCoO2 first charge gravimetric capacities is demonstrated by the addition of only 2 wt% of the nanosized composite in the cathode mixture. This result shows the great potential of these newly discovered sacrificial additives to counteract initial losses of Li+ ions and improve battery performance.