1D Lithium-Ion Transport in a LiMn₂O₄ Nanowire Cathode during Charge-Discharge Cycles

Understanding the mechanism of Li-ion transport is essential to the development of fast-charging Li-ion batteries. This study uses operando electron energy loss spectroscopy (EELS) to visualize the 1D movement of Li ions inside a LiMn₂O₄ nanowire cathode with one end immersed in an ionic liquid electrolyte during charge-discharge cycles. A series of maps is obtained quantifying the Li distribution near the interface between the nanowire cathode and electrolyte, which shows that changes in the Li concentration near the interface lag behind changes in the cell current. During delithiation, the Li concentration in the nanowire cathode decreases at locations away from the interface. Based on these observations, a model is developed that explains lithium-ion transport in 1D cathodes as drifting according to the electrochemical potential gradient rather than through simple diffusion.