The formation of the solid electrolyte interphase (SEI) is critical to stabilization of lithium metal electrodes.^1,2 When the electrodes contact electrolyte, a thin solid layer is immediately deposited on the surface. Ideally, this layer should be electronically insulating, while conducting Li-ions, and only a few nanometers thick to ensure that lithium can diffuse to the electrode surface without the reduction of any electrolyte components.² Unfortunately, much research has shown that even after initial formation, the SEI layer continues to grow, and eventually leads to cell failure by limiting the ability of lithium to diffuse to the electrode surface.^3,4 In order make electrodes practical for use in lithium metal batteries, the growth of the SEI needs to be well controlled and limited in thickness.

Previous work has shown that the use of high surface area porous metal anodes can prevent dendrite formation, another key barrier to commercialization of lithium metal batteries.⁵ However, as the number of cycles increases and the SEI layer on the electrode grows too thick, the pore network fills and lithium diffusion is limited, and plating subsequently reverts to unwanted dendritic growth.

In this work, a method for improving the cycling stability of these porous foam electrodes by controlling the SEI is examined. Accordingly, the work focuses on the utilization of novel surface additives to achieve this goal. The approach has shown to greatly increase the number of achievable cycles. The engineered systems already show ~99% efficiency over 100 cycles, far better than the 70 cycles at ~95% efficiency previously obtained using unmodified foams. By controlling the initial SEI formation and limiting its thickness, saturation of the pore network can be inhibited, thus extending the stable cycling window.

Acknowledgements: The authors acknowledge the financial support of DOE grant DE-EE 0007797, Edward R. Weidlein Chair Professorship funds, and the Center for Complex Engineered Multifunctional Materials (CCEMM).

References

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2. Peled, S. Menkin, J. Electrochem. Soc., 164 (7), A1703-1719 (2017).
3. Zheng, S. W. Lee, Z. Liang, H. Lee, K. Yan, H. Yao, H. Wang, W. Li, S. Chu, and Y. Cui, Nature Nanotech. 9, 618-623 (2014)
4. Vetter et al., Journal of Power Sources 147, 269–281 (2005)
5. A. Day, P. Jampani, P. M. Shanthi, B. Gattu, P. N. Kumta. ECS 232, National Harbor Maryland (2017).