New vehicle sales figures for June will be released this week as the Senate works on pulling federal tax credits for electric cars and a surprise proposal to raise the tax on new wind and solar projects.

It makes for a shaky time for makers of EVs, but last week a company called QuantumScape — backed by Volkswagen — announced what it says is a major breakthrough in solid-state battery production.

Solid-state battery technology is seen as something of a holy grail for the EV industry and the potential advance has investors excited.

Batteries need electrolytes to move ions between two electrodes, and, in current EV batteries, those electrolytes are liquid or gel.

“The material that is used as that electrolyte contains oxygen, and it's combustible,” said Sam Abuelsamid, vice president of market research at automotive market research firm Telemetry.

Even though EVs ignite less often than gas cars, he added that the fires are harder to put out. Solid-state batteries significantly reduce that risk. They’re also more energy-dense.

“You can have double the capacity, double the range,” Abuelsamid said.

Sounds pretty great, right? So … why haven’t we switched?

Solid electrolytes present some manufacturing challenges, according to Arumugam Manthiram, an engineering professor at UT Austin.

“The solid electrolytes are all ceramic. They are very brittle; they are not flexible. They can crack,” he said.

Building large ceramic pieces that are thin, flat and uniform is tough at scale.

But Quantumscape said it’s improved its process to make these ceramic parts and plans to start selling solid-state batteries to companies like Volkswagen by next year.