Solid Electrolytes for Stable Electrodeposition in Li Metal Anode-based Batteries

High energy density batteries require a functioning Li metal anode to realize their full capacity. However, Li deposition on Li metal anode leads to the growth of dendrites which are a grave safety concern. Solid electrolytes present a new opportunity for attacking this problem of unstable electrodeposition. It is known that Li/solid polymer electrolyte system can be stabilized if the polymer electrolyte has a sufficiently high shear modulus [1]. In this work, we show that the condition on shear modulus for stable electrodeposition depends on the relative density of the metal ion in the electrolyte and electrode, for both, isotropic and anisotropic mechanical properties at the interface. An anisotropic linear stability analysis is useful since Li metal has a high elastic anisotropy. We illustrate two different regimes of stability, the pressure-driven stability and density-driven stability through a two-parameter stability diagram [2]. Our results show that a soft solid electrolyte can suppress the growth of dendrites when the metal ion is more densely packed in the electrolyte than in the metallic form.

References
[1] C. Monroe and J. Newman, J. Electrochem. Soc. 152, A396 (2005).
[2] Z. Ahmad and V. Viswanathan, Phys. Rev. Lett. 119, 056003 (2017).