How they differ from lithium-ion
In a lithium-ion cell, lithium ions move through a liquid electrolyte between the anode and cathode. In a solid-state cell, that liquid is replaced by a solid, such as a ceramic, a sulfide or a polymer. A solid electrolyte may allow a lithium-metal anode, which can store more energy in the same space.
The promise
Developers are aiming for more range from the same weight, faster charging, and a cell that is less likely to catch fire if it is damaged. Because the electrolyte is not a flammable liquid, the safety case is stronger, though no battery is risk-free.
The hard parts
Keeping a good contact between solid layers as the cell charges and discharges, stopping thin metal spikes called dendrites from growing, and making cells cheaply at scale are difficult. Pilot lines and early products exist, but how soon solid-state cells become mainstream, and at what cost, is still uncertain.
Where it is used
- Electric vehicles (expected) More range or faster charging from the same weight.
- Consumer devices (expected) Slimmer cells with a stronger safety case.
- Home and grid storage (expected) Where safety matters most, if the cost comes down.
Solid-state compared with lithium-ion
Lithium-ion cells use a liquid electrolyte and are mature, cheap and made at enormous scale. Solid-state cells swap in a solid electrolyte, aiming for more energy per kilogram and less fire risk.
Today lithium-ion has the cost and supply-chain advantage, and solid-state has to prove it can be made reliably at scale. Other chemistries, such as lithium iron phosphate, also keep improving, so the race is not one-sided.
Key terms
- Electrolyte
- The material that carries ions between a battery’s electrodes.
- Energy density
- How much energy a battery stores for its weight or size.
- Dendrite
- A thin metal spike that can grow inside a cell and cause a short circuit.
- Anode and cathode
- The two electrodes between which the ions move.
Common questions
Are solid-state batteries safer?
- They are expected to be less flammable than liquid-electrolyte cells, but real-world safety has to be proven for each design.
When will solid-state batteries be in cars?
- Several makers have announced pilot or limited production in the second half of this decade, and timelines have slipped before. Treat dates as targets.
What about grid storage?
- The same safety benefit applies, but cost matters more for storage, so cheaper chemistries are likely to compete for a long time.
Sources and further reading
Independent pages we checked while writing this guide. They are not Reinnder products, and Reinnder is not affiliated with them.
Reinnder’s angle
How Reinnder looks at solid-state batteries
Reinnder Energy is the planned home for storage work, and Reinnder Labs lists solid-state chemistries as a research interest.
This guide explains the technology in general terms. It is not advice, and it does not describe a Reinnder product on sale.