Solid-state electrolyte

A solid-state electrolyte (SSE) is a solid ionic conductor and electron-insulating material and it is the characteristic component of the solid-state battery. It is useful for applications in electrical energy storage in substitution of the liquid electrolytes found in particular in the lithium-ion battery.^[1][2] Their main advantages are their absolute safety, no issues of leakages of toxic organic solvents, low flammability, non-volatility, mechanical and thermal stability, easy processability, low self-discharge, higher achievable power density and cyclability.^[3] This makes possible, for example, the use of a lithium metal anode in a practical device, without the intrinsic limitations of a liquid electrolyte thanks to the property of lithium dendrite suppression in the presence of a solid-state electrolyte membrane. The use of a high-capacity and low reduction potential anode, like lithium with a specific capacity of 3860 mAh g⁻¹ and a reduction potential of -3.04 V vs standard hydrogen electrode, in substitution of the traditional low capacity graphite, which exhibits a theoretical capacity of 372 mAh g⁻¹ in its fully lithiated state of LiC₆,^[4] is the first step in the realization of a lighter, thinner and cheaper rechargeable battery.^[5] This allows for gravimetric and volumetric energy densities high enough to achieve 500 miles per single charge in an electric vehicle.^[6] Despite these promising advantages, there are still many limitations that are hindering the transition of SSEs from academic research to large-scale production, mainly the poor ionic conductivity compared to that of liquid counterparts. However, many car OEMs (Toyota, BMW, Honda, Hyundai) expect to integrate these systems into viable devices and to commercialize solid-state battery-based electric vehicles by 2025.^[7][8]