Cobalt and Nickel Free Disorder Rock Salt Cathodes – Recent Developments

Abstract

Disordered Li-excess rock salt (DRX) cathodes are a promising class of high capacity (and voltage) cathodes for next-generation Li-ion batteries. Compared to conventional Li-ion cathodes which are generally restricted to Co/Ni-based compositions with specific cation ordering, DRX materials have a wide compositional design space based on earth abundant metals such as Mn, Ti, Mo, Al, Zr, V, and Nb. Furthermore, Li-rich oxyfluoride DRX cathodes have demonstrated specific energies up to 1,000 Wh/kg which exceeds that of state-of-the-art layered LiNixMnyCo1-x-yO2 (NMC) cathodes (~700 Wh/kg). Despite such scientific advancements, widespread adoption of DRX cathodes has been hindered by several technical challenges. First, most of the high fluorine content DRX compositions are synthesized using mechano-chemical synthesis that has inherent limitation in scalability and maintaining a uniform particle-size and morphology. Further, DRX compositions have about 3-4 order lower electronic conductivity compared to layered cathodes requiring a high carbon loading in the electrode (up to 25%) compromising energy density. The focus of this talk will be on developing alternate synthesis method for Li-Mn rich DRX compositions. Specifically solid-state and sol-gel synthesis methods to produce DRX cathodes with the nominal composition Li1.2Mn0.4+xTi0.4-xO2-xFx (x = 0-0.3). Detailed advanced characterization (i.e., neutron total scattering and electron microscopy) and modelling efforts (i.e., Reverse Monte Carlo simulations) to understand how SRO impacts cathode performance will be presented. Different choice of precursors based on thermodynamic and kinetic consideration that minimizes formation of LiF impurity phases will be proposed.AcknowledgmentThis work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Vehicle Technologies Office, under the Applied Battery Materials Program, of the U.S. Department of Energy under Contract No. DE-AC05-00OR22725