Metallic Lithium Anodes and Fast-Charging investigated by pulse EPR

Today, we face the ongoing process of Li-ion battery implementation in our everyday lives. Especially for electric vehicles, capacity and fast-charging need to be optimized for broad user acceptance. Strategies are the use of metallic lithium instead of state-of-the art graphite anodes and various chemical alterations to enable high currents. However, both points still suffer from a severe safety risk due to the formation of lithium microstructures upon cycling, which ultimately cause internal short circuits. The effect of counter-measures necessitates a suitable real-time detection technique.

Here, we introduce pulse Electron Paramagnetic Resonance (EPR) as an ideal tool for online detection of these microstructures. The obtained sampling timescale in the millisecond regime is surpassing other in-operando/in-situ techniques by at least one order of magnitude. In our study, we use pulse EPR to identify the dynamics of lithium microstructure. Specifically, the morphological evolution of freshly deposited microstructures after a current pulse was monitored. Electron spin relaxation times, which are accessible with pulse EPR, indicate this process to be a fusing or sintering process driven by lithium surface diffusion. The awareness of these processes will aid the understanding and optimization of metallic lithium anodes.

Szczuka, C., Ackermann, J., Schleker, P.P.M. et al. Transient morphology of lithium anodes in batteries monitored by in operando pulse electron paramagnetic resonance. Commun Mater 2, 20 (2021).

Published: 24 February 2021