LAUSR

DOI: 10.1002/aenm.201902788 The direct contact of anode materials and lithium metal[3,4] is a common prelithiation strategy for improving the Coulombic efficiency of the battery, although this is not exempt from several disadvantages mostly related to the use of Li metal in battery manufacture (i.e., incompatibility with ambient environments, common solvents, binders, and thermal processing). These practical challenges, are partly overcome in Stabilized Lithium Metal Powder[5,6] SLMP, where lithium metal is suspended in hydrocarbon solvents providing stability in dry air. Interestingly, SLMP has been used as a fully lithiated anode in batteries utilizing nonlithiated V6O13 or LiV3O8 cathodes.[7] More recently, the also dry air stable LixSi–Li2O core–shell nanoparticles[8] have proven an excellent prelithiation reagent and are potentially compatible with current industrial battery fabrication methods. As an alternative route to the arduous prelithiation of anodes demanding more reactive lithium sources leading to unstable reaction products and low battery potentials,[3] several prelithiation additives of cathode materials have been studied. Sacrificial salts[9] (e.g., azides,[10] oxocarbones, dicarboxylic acids, or hydrazides) contain oxidizable anions that lose electrons during the first charge, forming Li+ donors and gaseous species (e.g., CO, CO2, or N2) amounting to ≈70% of the salt 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.