Understanding key limiting factors for the development of all-solid-state-batteries

The All-Solid-State-Battery (ASSB) is projected to offer higher energy density and enhanced safety compared to the current commercial Li-ion battery. In this study, we have used a simple model to evaluate the effect of different cell components on the battery's overall performance. We critically examine the promised 100% increase (vs. a standard Li-ion battery) in the overall energy density of an ASSB— a claim often made in both the literature and industry. Through a survey of cell parameters possible with current technology, we were able to evaluate optimum parameters that can be expected in future ASSBs. Herein, we identify three critical parameters required to reach the promised energy density: (1) minimize the thickness of the solid electrolyte to less than 20 μm; (2) modify the cathode formulation to minimize the amount of catholyte and optimize the electrode thickness; and (3) minimize the N/P ratio by developing cells that are anode-free or utilize ultrathin lithium anodes. In conclusion, we believe that the often-cited 100% improvement in energy density for ASSBs is overly optimistic. Instead, a 30% improvement is a more reasonable target for the near future.