Mechanochemical Reduction and Doping of Cobalt (II,III) Oxide (Co3O4) by Lithium Metal: A Facile Route to LixCoyO Materials

The reduction and doping of transition-metal oxides (MOx) are essential processes in battery materials manufacturing, heterogeneous catalysis and metallurgy. However, due to the stability and inertness of MOx, their reduction and doping are energetically demanding, requiring high temperature and/or a strong electro-potential. In this work, by introducing lithium metal as both a reductant and Li-ion source, we report the facile (10‒15 minutes at room temperature) reduction and doping of cobalt (II,III) oxide (Co3O4) under mechanochemical conditions, to produce lithium-doped cobalt oxides (LixCoyO) and cobalt metal. Reactions at different stoichiometric ratios are studied in one-pot and stepwise manners. Our combined experimental‒computational analysis reveals the strongly exothermic profile of these reactions and proves that higher lithium contents in LixCoyO materials are achievable by conducting the reaction in a stepwise manner. This work provides a facile route for the reduction of Co3O4 and its Li doping to producing LixCoyO and LiCoO2 battery cathode materials, which can only currently be made under energy- and carbon-intensive conditions (high temperatures for several hours).