Physics-based modeling on how mechanics influences lithium plating and stripping in a porous lithium metal electrode

Physics-based electrochemical models with porous electrode theory are proven to aid in understanding lithium-ion battery performance. Here, we adapt porous electrode theory for a porous lithium metal electrode constructed with solid electrolyte particles and open pores. We find that with only the core set of porous electrode equations (including ohm's law in the electronic and ionic phases, a kinetics equation, and charge conservation), the current distribution will be static and there is no mechanism present to fill the electrode. Inspired by pore-network models, we propose a dual-one-dimensional (“dual-1D”) porous electrode model that incorporates pressure-driven lithium metal flux (using Darcy's law) that directly accounts for lithium transport that could enable pore filling, along with lithium pressure – equilibrium potential coupling. The proposed model employs linear elasticity to relate pore filling and pore pressure. For stripping, formulating the current density as a function of pore lithium content is important for the reaction distribution to move to electrode regions in which lithium remains. Our simulation results show that pressure-driven lithium metal flow is needed for porous lithium metal electrodes to achieve full usage of the pores while avoiding pressures that could lead to fracture. The current study also analyzes how the transient current distribution during lithium plating is affected by the relative magnitude of electronic and ionic conductivity, thereby quantifying the influence of the lithium metal on the effective electronic conductivity of the porous electrode. • Dual-1D model predicts lithium plating/stripping in porous Li metal electrode. • Captures pressure modified thermodynamics and pressure driven transport • Darcy's law is used for Li transport through the thickness of the porous electrode. • Effective electronic vs ionic conductivity influences Li deposition patterns.