Solid-State for Homes? | Tech Brief

What is a solid-state battery?

A conventional lithium-ion battery has a positive electrode, a negative electrode and an electrolyte that allows lithium ions to move as the battery charges and discharges. In many current batteries, the electrolyte contains a flammable liquid solvent.

A solid-state battery replaces some or all of that liquid with a solid material. Possible materials include ceramic, sulfide, polymer or combinations of these. Solid-state is not one single battery recipe, and some products described as solid-state are semi-solid and still contain liquid.

Why electric vehicle makers are interested

Energy density is the main attraction for electric vehicles. Because a car must carry its battery, reducing the weight and volume needed for a given amount of energy can improve efficiency. Alternatively, manufacturers could use the same-sized pack to provide more range, or maintain range with a smaller and lighter pack that leaves more space in the vehicle.

Some designs can also use lithium metal instead of the conventional graphite anode. This is one reason they may achieve considerably higher energy density. Faster charging and improved safety are also commonly associated with the technology. Toyota has targeted a 10 to 80 per cent charge in 10 minutes or less, although this remains a development target.

The engineering and safety challenges

Replacing flammable liquid may remove one source of fire risk, but a solid-state battery is not indestructible or impossible to burn. The cell still stores substantial energy, its electrodes can react, and lithium can form dendrites. Damage can still create heat and failure.

A major challenge is maintaining contact between solid materials. Batteries expand and contract during cycling, which can create gaps and cracks that reduce performance over time. Some designs may require pressure to maintain contact, careful temperature control and extremely thin layers manufactured without defects.

Producing an impressive laboratory cell is different from manufacturing millions of cells cheaply and consistently, while also providing long warranties. Durability, production yield, scale and cost are key reasons the technology has remained a future possibility for years.

Where development stands in 2026

Mercedes-Benz began road testing a solid-state EQS in 2025 and then drove it 1,205 kilometres without charging. Mercedes said the prototype held 25 per cent more usable energy than a comparable production battery, but it remained a development vehicle.

BMW has tested a solid-state power cell in an i7, while Stellantis began road testing a Factorial-powered development vehicle in June 2026. Toyota is targeting an all-solid-state EV around 2027 to 2028, and Samsung SDI is targeting full-scale production in late 2027. These are development and production targets, not guarantees of affordable Australian vehicles being available at those times. In 2026, a normal production EV with a true all-solid-state battery cannot be bought.

What about home batteries?

The case for solid-state is less direct in home energy storage. A home battery does not need to carry itself down a motorway, so extra weight matters much less than installed price, cycle life, warranty, power output and safety certifications.

Solid-state technology could make a home battery smaller and reduce the use of flammable liquid. That may be useful where space is limited or safety requirements are demanding. However, higher energy density is less valuable on a wall than in a car. Lithium iron phosphate, or LFP, remains the dominant chemistry for stationary storage, exceeding 90 per cent of global installations in 2025 according to the IEA. A solid-state home battery would need to compete with mature LFP systems on price, lifespan and reliability.