What Are Solid-State Batteries?

Solid-state batteries use a solid electrolyte to facilitate the flow of an electrical charge between the positively charged end (the cathode) and the negatively charged end (the anode). Recent developments have generated significant OEM interest in solid-state batteries because they have the potential to address some of the biggest challenges electric vehicles (EVs) face, including driving range and battery life span.

In 2021, Nissan announced plans to go into production on vehicles with proprietary solid-state battery technology by the end of the decade and claimed that the new batteries will charge 66 percent faster than traditional batteries. Combined with battery management programs and high-voltage components, solid-state batteries could potentially charge in as little as 10 minutes. Long charging times contribute to the range anxiety that consumers cite as the primary reason for their reluctance to purchase an EV.

Also contributing to range anxiety are limitations on the amount of energy that batteries can store. The single greatest strength of gasoline is that it has very high energy density, packing 47.5 megajoules of energy into every kilogram. That is about 100 times the energy density of lithium-ion batteries. EVs have become more efficient than gas-power vehicles when it comes to converting energy into motion, but engineers are also looking at ways to increase the energy density of batteries. Solid-state batteries could be a solution, thanks to the high energy density of lithium metal.

In partnership with Panasonic, Toyota announced a $13.6 billion investment in a variety of battery technologies in 2021, including developments in a solid-state option, potentially doubling the range of its EVs without increasing the size of their battery packs. For example, Toyota’s bZ4X SUV could extend its range from 250 miles to approximately 500 miles ­— exceeding the average for vehicles with internal combustion engines.

Extended battery life

One of the biggest challenges in developing viable solid-state batteries is creating a stable separator to prevent physical contact between the anode and the cathode. However, new breakthroughs could eliminate this hurdle. Volkswagen has increased its investment in battery developer QuantumScape, a company that promises to extend EV battery life span with a proprietary ceramic separator material. Studies estimate that the average EV battery pack’s life span is around 200,000 miles, but QuantumScape’s tests in single-layer cells have shown a retention rate of 90 percent charging capacity after 1,000 charge/discharge cycles — the equivalent of driving more than 300,000 miles in an EV with a 300-mile range.

Meanwhile, Solid Power, the battery producer backed by BMW and Ford, recently demonstrated the durability of solid-state batteries. When fully charged cells were punctured, the solid-state batteries tested had slightly elevated temperatures but no flames or venting of materials. Other test scenarios, including overcharging and short-circuiting, also did not reveal any safety issues.

Future-proof vehicle architecture

At Aptiv, we do not build batteries, but we design the solutions that enable OEMs to get the most from each generation of batteries — from charging inlets with active and passive cooling to optimized high-voltage technologies, including busbars and aluminum cables. And every Aptiv high-voltage connector is engineered to handle up to 1,000V, far exceeding the industry standard.

Aptiv is constructing a dedicated laboratory to test emerging battery technologies and is developing algorithms to enable fast charging and ensure the best performance from current-day battery chemistries. As new battery developments become mainstream, OEMs need a partner that understands how batteries interact with the larger electrical/electronic architecture of the vehicle.