A type of battery that could eventually store twice as much energy as a conventional one could be about to move beyond niche applications to wearable devices, phones, and even electric cars.

Solid-state batteries, as they’re called, have been available for a while and are used in some wireless sensors, but they have been too expensive to use elsewhere. Applied Materials, one of the world’s biggest equipment suppliers for the semiconductor and display industries, says it can make these batteries much cheaper. This could clear the way for slimmer, longer-lasting smart watches as well as electric cars with a range similar to gas-powered ones.

In solid-state batteries the liquid electrolytes normally used in conventional lithium-ion batteries are replaced with solid ones, which makes it possible to replace conventional electrodes with lithium metal ones that hold far more energy. Doing away with the liquid electrolyte, which is flammable, can also improve the safety of batteries, which leads to cost and size savings, particularly in electric vehicles, by reducing the need for complex cooling systems (see “TR10: Solid-State Batteries”).

The manufacturing tools shipped so far by Applied Materials, which perform extremely high-precision deposition of materials over large areas, will be used initially for prototyping and demonstrations of solid-state batteries.

Making high-quality electrode and electrolyte materials over large areas has been one of the challenges to making the solid-state batteries economically.  The batteries are made by successively depositing electrical contacts, electrodes, and the solid electrolyte that separates them, in much the way that the many layers of a display are deposited. If the solid electrolyte has gaps it can lead to short circuits. Applied Materials says it can overcome this as well as other manufacturing challenges.

“The thing that’s holding [solid-state batteries] back is materials processing and the cost,” says Andy Chu, head of product marketing for energy storage solutions at Applied Materials. “We’re addressing these problems. That will allow you to take this to high volume.”

Applied Materials says customers are using its equipment to make batteries, but it won’t disclose who those customers are. The company says, however, that one of the first commercial applications of its equipment will likely be making batteries for wearable devices, such as smart watches, where size is a serious limitation.

Solid-state batteries can also easily be made in different shapes because you don’t have to worry about containing a liquid electrolyte, making them easier to pack inside a watch, for example. Thin solid-state batteries could even be incorporated into a flexible watch band.

Applied Materials hasn’t disclosed how much solid-state batteries made using its technology would cost, how much energy they would store, or how quickly they could be recharged. One perennial challenge with solid-state batteries has been that the solid electrolyte, which isn’t as conductive as liquid ones, tends to limit power output. Applied Materials says it is working on ways to improve that conductivity by doping the solid electrolyte, much as you would dope semiconductor materials for chips. The company is also working on ways to deposit the energy-storing materials faster, to enable thick layers that store large amounts of energy.