Laser-based surface modification of high energy graphite anodes for lithium-ion batteries to improve the wettability and rate capability

Summary:

Many battery applications require both, a high energy and a high power density. Reflecting electric vehicles, that represents a high driving range with a fast charging option. To increase the energy density of lithium-ion batteries, it is common practice to reduce passive material of the battery by producing electrodes with high active material layer thickness and high compaction[1]. However, such thick and compact electrodes exhibit a poor rate capability and impede the wetting with liquid electrolyte[2,3]. 3D laser structuring such as trenching or perforation with a deep ablation of the active material layer is a promising approach to partially overcome the rate performance issues of high energy electrodes[4–6] as well as to improve the wettability[7]. However, ablation of the active material leads to a noticeable loss of capacity. Bolsinger et al. and Enderle et al. reported a “2D”-laser-based surface modification of NCM-based cathodes that enables selective ablation of the surface near binder-additive compound – which in turn reduces the Li-ion transport resistance and enhances the rate capability of the cathodes[8,9].

In this study, this “2D”-process is applied to graphite anodes. To do so, we did an extensive study on adjusting the laser parameters accordingly. As a result, we will show that it is possible to increase the anodes surface roughness without significantly ablating the active material. The surface-near microstructural changes, evaluated by microscopic analysis and white light interferometry are shown and correlated with the electrolyte wetting which can be improved significantly. Additionally, we will present a rate capability test comparing differently modified and pristine anodes indicating that the kinetics of the electrodes benefits at the same time.

References
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