Reducing the Charge Carrier Transport Barrier in Functionally Layer-Graded Electrodes

Lithium-ion batteries (LIBs) are primary energy storage devices to power consumer electronics and electric vehicles, but their capacity is dramatically decreased at ultrahigh charging/discharging rates. This mainly originates from a high Li-ion/electron transport barrier within a traditional electrode, resulting in reaction polarization issues. To address this limitation, a functionally layer-graded electrode was designed and fabricated to decrease the charge carrier transport barrier within the electrode. As a proof-of-concept, functionally layer-graded electrodes composing of TiO2 (B) and reduced graphene oxide (RGO) exhibit a remarkable capacity of 128 mAh g-1 at a high charging/discharging rate of 20 C (6.7 A g-1 ), which is much higher than that of a traditionally homogeneous electrode (74 mAh g-1 ) with the same composition. This is evidenced by the improvement of effective Li ion diffusivity as well as electronic conductivity in the functionally layer-graded electrodes.