Transient morphology of lithium anodes in batteries monitored by in operando pulse electron paramagnetic resonance

Conrad Szczuka,Josef Granwehr,Rüdiger-A Eichel,P Philipp M Schleker,Jörg Ackermann,Peter Jakes

doi:10.1038/s43246-021-00126-1

Abstract

Enhancing lithium-ion battery technology in terms of specific capacity and charging time is key for the advancement of the electrification of transportation. Particularly for fast charging, inhomogeneous deposition of metallic lithium, for example on commercial graphite or metallic lithium anodes, leads to cell degradation and safety issues. To understand the underlying mechanisms and develop counter-measures, non-invasive online detection techniques providing satisfactory time resolution are crucial. Here, we demonstrate in operando pulse electron paramagnetic resonance to observe transient processes during pulsed fast charging in cells with metallic lithium anodes. Sampling timescales of 100 ms enable real-time monitoring of the formation and evolution of porous lithium during and after charging pulses. It was observed that the generated morphology continued to evolve after the end of a charging pulse, whereby surface features were fusing with a time constant that was slower than their formation.

Highlights

Enhancing lithium-ion battery technology in terms of specific capacity and charging time is key for the advancement of the electrification of transportation
High current density (CD) result in a large number of deposition nucleation sites, facilitating smooth lithium plating[8,9] but may cause needle-like dendrites, which are responsible for rapid cell degradation and short-circuiting
To compare all nine cells, these positions are identical regarding the areal charge, corresponding to identical amounts of deposited lithium. These three regions vary in duration for each cell since by using a higher pulse CD yet identical charging protocol, the respective areal charge is reached at different times

Summary

Introduction

Enhancing lithium-ion battery technology in terms of specific capacity and charging time is key for the advancement of the electrification of transportation. Depending on the cell chemistry, cycle age, and charging protocol, microstructures of different morphologies are found; whiskers, moss, and dendrites are discriminated when using liquid carbonate-based electrolytes[7]. Their appearances can be strongly affected by the applied current density (CD). High CDs result in a large number of deposition nucleation sites, facilitating smooth lithium plating[8,9] but may cause needle-like dendrites, which are responsible for rapid cell degradation and short-circuiting. Post-testing revealed smoothed structures upon using large CDs of 10–15 mA cm−2, which induce extensive surface diffusion through high local temperatures

Methods

Results

Conclusion