General Motors is the latest automaker reported to be working on solid-state lithium batteries, thanks to a $2 million grant from Uncle Sam.

The money is part of a larger grant to develop more fuel-efficient powertrains, CNET reported. The company is expected to use the rest of the money to develop a lighter-weight, more efficient engine for medium duty trucks, perhaps to replace the company's 6.2-liter V-8.

Solid-state lithium batteries replace the flammable liquid organic solvents such as ethylene carbonate as an electrolyte in conventional lithium batteries with a solid, ceramic electrolyte that isn't flammable. That allows engineers to cram more lithium atoms into the battery to give it more energy without increasing volatility, which could lead to lighter, batteries for electric cars with longer ranges.

VW Battery Packs

So far, complex manufacturing challenges, cost, and power output have held the batteries back.

Other automakers, including Volkswagen, Toyota, Honda, Nissan, and startup automaker Fisker are also racing to develop solid state batteries for electric cars.

GM is also working with Honda in a joint venture to develop future electric-car and fuel-cell technologies, including batteries.

Nio ES6 battery

John Goodenough, an engineering professor at the University of Texas, who co-invented the modern lithium-ion battery, announced a breakthrough in solid-state lithium batteries in 2017, but with long automotive development lead times, it has not yet seen the light of day.

Not all automakers or battery companies are optimistic about the prospects for solid-state batteries. Panasonic, Tesla's battery partner, has said it doesn't expect solid-state lithium batteries to be commercially viable for another 10 years, and Tesla recently bought ultracapacitor producer Maxwell Technologies. Tesla CEO Elon Musk has said ultracapacitors have more promise for electric cars than lithium-ion batteries.