Correlating the Peukert's Constant with Phase Composition of Electrode Materials in Fast Lithiation Processes

The electrochemical performance of energy storage devices decreasing with the increase of charging/discharging rates is described as the Peukert's effect. To minimize this effect, the reduction of the Peukert's constant towards the ideal value of 1.0 is needed. Herein, for the first time, we reveal a correlation between the Peukert's constant and the phase composition of electrode materials in lithium-ion batteries (LIBs). As a proof-of-concept, a parabola-like correlation is observed in the anatase/TiO2(B) electrode with a significant reduction in the Peukert's constant from 2.15 to 1.20, when the content of anatase phase increases from 0% to 22%. This corresponds to a capacity enhancement of about three times from 42.2 to 131.5 mAh g-1 at a current density of 12.0 A g-1. The boosted charge-transfer kinetics in the composite electrode, relative to that of the single component electrode, is the cause for the reduction in the Peukert's constant. Theoretical calculations well support the cooperative effect of maximizing both electronic conductivity and Li-ion diffusivity in the composite electrode. Our present findings provide a new way for reducing the Peukert's constant in LIBs via manipulating the materials composition, which constitutes a generalized solution towards the improved rate-performance in electrochemical reactions.