Breaking the voltage hysteresis of conversion electrodes for high energy batteries

Abstract Large voltage hysteresis on the conversion electrode between charging and discharging leads to unacceptable energy loss, which severely bottlenecks their application in batteries. Herein, we clarify that the voltage hysteresis stems from the phase difference in the electrochemical interface in between the conversion and reconversion. An unique interface inducing-stabilizing regulation is proposed to achieve “voltage hysteresis free” conversion electrode for the first time, through inducing and stabilizing a Cu(I) phase-dominated electrochemical interface and therefore paving a thermodynamically reversible reaction pathway. An unprecedented energy efficiency of 95.5% and an extremely high energy density of 1515 Wh kgcathode-1 are achieved in the lithium battery configuration based on a CuF2 cathode. This work not only advance the understanding of conversion electrochemistry but also unlock the potential of conversion electrodes toward high energy batteries.