Local State-of-Charge Mapping of Lithium-Ion Battery Electrodes

Current lithium-ion battery technology is gearing towards meeting the robust demand of power and energy requirements for all-electric transportation without compromising on the safety, performance, and cycle life. The state-of-charge (SOC) of a Li-ion cell can be a macroscopic indicator of the state-of-health of the battery. The microscopic origin of the SOC relates to the local lithium content in individual electrode particles and the effective ability of Li-ions to transport or shuttle between the redox couples through the cell geometric boundaries. Herein, micrometer-resolved Raman mapping of a transition-metal-based oxide positive electrode, Li(1-x)(Ni(y)Co(z)Al(1-y-z))O(2), maintained at different SOCs, is shown. An attempt has been made to link the underlying changes to the composition and structural integrity at the individual particle level. Furthermore, an SOC distribution at macroscopic length scale of the electrodes is presented.