Dynamic interplay between phase transformation instabilities and reaction heterogeneities in particulate intercalation electrodes

Lithium-ion batteries rely on particulate porous electrodes to realize high performance, especially fast-charging capabilities. To minimize the particle-wise reaction heterogeneities, a deeper understanding of these electrodes at mesoscale, i.e., hundreds of particles, is necessary. Here, we report that the seemingly random reaction heterogeneities are actually controlled by the interplay between non-equilibrium material thermodynamics and electrochemical kinetics. Our operando experiments reveal that, under constant current, autonomous dynamic loops exist that control the intra- and inter-particle phase-transformation dynamics that determine the true local current density. The combined theoretical and experimental analyses reveal that unlike other phase-transforming electrodes, not all phase-separation processes in graphite electrodes can be suppressed by high currents. Our results highlight the necessity to examine the concentration-dependent exchange current density for intercalation electrodes undergoing phase-transformation processes. Incorporating non-equilibrium thermodynamics into classical electrochemical models and electro-analytical techniques will ensure self-consistent understandings of practical electrodes toward precision design.

Automated summary

Lithium-ion batteries rely on particulate porous electrodes to achieve high performance. This study reveals that the seemingly random reaction heterogeneities in these electrodes are actually controlled by the interplay between non-equilibrium material thermodynamics and electrochemical kinetics. Operando experiments show the existence of autonomous dynamic loops that control the phase-transformation dynamics within and between particles, determining the true local current density.