Solid State Battery are any battery technology that uses solid electrodes and solid electrolyte. This offers potential improvements in energy density and safety, but has very significant challenges with cycling, manufacturing and durability of the solid sandwich.
Billy Wu gives a great introduction to Solid State Batteries in this YouTube video:
These 10 topics give a reasonable overview of solid-state batteries in terms of what is less transparent in the publicity and hype of solid state. To be clear, we need solid state batteries, but we need to put claims in context and be wary of missing information.
Packaging is critical because it links to many of the other 9 points in the things you need to know about SSBs. The pressure system remains the biggest unknown. It is rarely talked about, and it has not been proven at scale. High pressures are required by most SSBs to overcome interfacial resistance. This problem is exasperated by the need to accommodate volume changes and further complicated for semi-solid / hybrid cells because liquid can disperse unevenly under pressure.
An all-solid-state battery would revolutionise the electric vehicles of the future. The successful implementation of an alkali metal negative electrode and the replacement of the flammable organic liquid electrolytes, currently used in Li-ion batteries, with a solid would increase the range of the battery and address the safety concerns. Current efforts to commercialise such batteries worldwide are failing and will continue to fail until we understand the fundamental processes taking place in these devices.