Earth-Abundant Mn-Rich Li-Ion Cathode Materials with High Energy Density

With the energy storage industry scaling to multiple terawatt hours of annual production, current reliance on Co and Ni can lead to increase in cost and supply chain burden due to their low abundance. Over the last decade, Li-excess disordered rocksalt materials (DRX) have demonstrated high energy density and capacity with Mn as redox couple, which enable high performance Earth-abundant cathode materials and make them a promising crystal structure for Mn-based cathode materials. Our work demonstrates how the mobility of Mn cations can be used to obtain a unique nanosized microstructure in large-particle-sized DRX with enhanced electrochemical properties. By combining atomic-resolution scanning transmission electron microscopy, four-dimensional scanning electron nanodiffraction, and in situ X-ray diffraction, we show that when a partially delithiated Mn-rich DRX is slightly heated, it forms partially ordered spinel domains of 3-7 nm in size, which impinge on each other at antiphase boundaries. The short coherence length of these domains removes the detrimental two-phase lithiation reaction present near 3 V in a regular spinel and turns it into a solid solution. This nanodomain structure enables good rate performance and delivers 200 mAh/g discharge capacity and 645 Wh/kg energy density in a partially disordered material with an average primary particle size of ∼5 μm.