Much greater effective surface area. In a battery with a liquid electrolyte, the interfacial layer between the electrode and the electrolyte is fractal in shap

Much greater effective surface area. In a battery with a liquid electrolyte, the interfacial layer between the electrode and the electrolyte is fractal in shape, created by a carefully engineered chemical reaction between the electolyte and the electrode to maximize the surface area. You can't really do that with any solid battery chemistry we are currently studying. I think the issue is overblown. Most users who need high power also benefit from high energy, and you can always run more batteries in parallel.