All-solid-state rechargeable lithium-ion batteries have attracted much interest because they have features partic- ularly favorable for large-scale application. The replacement of an organic liquid electrolyte with a non-flammable and more reliable inorganic solid electrolyte (SE) simplifies the battery design and improves safety and durability of the system[3]. However, the mechanical behavior of such electrodes will be considerably different than their liquid electrolyte counterparts. Direct stacking of solid-state cells enables the achievement of high operating voltages in a reduced volume. Furthermore, all-solid-state batteries allow the use of large-capacity electrode materials, for instance sulfur positive electrode paired with a lithium metal negative electrode, which are difficult to employ in conventional liquid electrolyte batteries.

A key development to the success of all-solid-state batteries is a SE with high Li+ ion conductivity at room temperature[4, 5, 6]. In recent years, several solid electrolytes having level of conductivity comparable to organic liquid electrolytes have been discovered and tested with many active materials. The durability of a cohering solid- solid interface between electrode and electrolyte is likely to be important practical consideration. Notwithstanding the several techniques investigated to increase the contact area at the interface[7], interface cohesion and its effects on the rate capability and the overall performance throughout the expected life cycles needs to be maintained.

The present research focuses on the development of a nonlinear continuum model able to account for the com- bined effects of Li diffusion and for the consequent volumetric expansion of the hosting material. The electrode and electrolyte are modeled as idealized as elastic materials, with elastic properties varying with lithium concentration.

The complexity and the multi-physical nature of the problem requires numerical modeling strategies and poses several challenges. To address this, we have established a computational framework based on large deformation theory and in a thermodynamically consistent fashion. This is implemented in an in-house, object oriented C++ numerical code that incorporates three-dimensional finite element calculations. The numerical analysis allows for delamination at the interface between electrode particles and solid electrolyte. Crack formation and propagation is predicted by means of a cohesive zone model extended to include decreased Li flux across interfaces due to their loss of mechanical integrity.

Our simulations indicate trends of mechanical reliability of all-solid state batteries realized with some of the most promising solid electrolyte materials (e.g. Li2S-P2S5 [1], LIPON [4], garnet SE [8]); our calculations are based on the mechanical properties available in literature.

When physical values for the solid electrolyte’s mechanical behavior are not available, our calculations indicate trends of how mechanical reliability correlates with the battery design and operating conditions (i.e., charging rate).