Tuning the electrochemical performance of graphite electrodes in lithium-ion batteries: Thermodynamics versus kinetics

Abstract

Improving the energy density of lithium-ion batteries is a goal pursued in state-of-the-art batteries, and the use of thick electrodes is one of the most direct and effective methods. However, thick electrodes are often accompanied by severe deterioration in electrochemical performance. Graphite is a widely used anode material and great efforts are made from kinetic parameters to improve the performance of thick electrodes, while the thermodynamic effects are ignored for a long time. Herein, this work focuses on elucidating the thermodynamic effects on electrode processes and revealing regulatory effects of the equilibrium potential on reaction. Kinetics can cause electrodes to react nonuniformly, while thermodynamics can rectify electrodes reacting nonuniformly, leading to fluctuations in the reaction rate. The competitive relationship between kinetics and thermodynamics is explored in detail. The results demonstrate that the electrode process is still dominated by thermodynamics at high rates for thin graphite electrodes, while thick graphite electrodes quickly tend to be dominated by kinetics as the rate increases. Finally, a favorable performance enhancement can be obtained by optimizing the thermodynamic properties of graphite. This work illustrates that the alleviation of kinetic constraints is limited, providing a completely new guideline for future electrode design of lithium-ion batteries.