Isothermal Microcalorimetry Evaluation of In Situ Prelithiation in Lithium-ion Batteries

Abstract

Prelithiation promises higher energy density and better cycle performance by providing additional lithium into a Li-ion battery and is therefore gaining increasing attention in industry. However, to achieve extra lithium introduction, additional processes or species need to be introduced, leading to potentially new parasitic reactions. In this work, in operando isothermal microcalorimetry is used to evaluate both the prelithiation process and the associated parasitic reactions. We show with the case of cathode prelithiation using Li 2 O 2 as the prelithiation additive, that while the prelithiation event completed on the first charge, an elevated heat signal extended beyond the first cycle, indicating continued presence of additional parasitic reactions even after the major prelithiation event. The heat signals from such additional parasitic reactions decreased over cycling. After three cycles, similar heat signals from parasitic events were observed for the prelithiation cells and the control cells, indicating stabilization and possibility of no long-term side effects from prelithiation. This first demonstration of in operando isothermal microcalorimetry method for prelithiation application provides valuable insights into heat production in prelithiation cells and offers a first look into prelithiation-associated parasitic reactions and their evolution.