• Volkswagen-backed QuantumScape is building a solid-state lithium metal battery for electric vehicles that it says will be safer and better than the cells on the market today.
• In extensive testing, QuantumScape found that its batteries should allow a car to charge to 80% of its full capacity in about 15 minutes.
• QuantumScape's board includes ex-Tesla CTO JB Straubel and SolarCity CFO Brad Buss, along side Volkswagen execs, Juergen Leohold and Frank Blome, among others.

Newly public QuantumScape is on a mission to build a better battery that helps make electric vehicles affordable, charge faster and safer. On Tuesday, the company revealed testing results for its solid-state lithium metal batteries.

QuantumScape's batteries should allow drivers to charge their electric cars to 80% of their full capacity within just fifteen minutes, the company said. The batteries should last around 12 years in normal use in a vehicle with a 300-mile range or better. It also expects its batteries to perform well even in sub-zero temperatures.

QuantumScape went public via SPAC in late November. Prior to going public, it raised $380 million from Volkswagen and additional funding from tech investors including Bill Gates, Breakthrough Energy Ventures, Khosla Ventures and KPCB.

Volkswagen's Juergen Leohold and Frank Blome sit on QuantumScape's board, and the German auto titans have also committed to invest more funds to manufacture batteries in a joint venture with QuantumScape. The automakers aim to use the company's solid-state batteries in vehicles by 2025.

QuantumScape may give Volkswagen, which makes electric vehicles like the Porsche Taycan and the increasingly popular VW ID.3 and ID.4, a big competitive edge in battery electric vehicles. But that didn't stop Tesla's former CTO and co-founder JB Straubel, or former Tesla director and SolarCity CFO Brad Buss from joining the QuantumScape board.

QuantumScape CEO Jagdeep Singh, who founded the company in 2010 with fellow Stanford scientists Fritz Prinz and Tim Holme, believes the electric battery share of the overall vehicle market will eventually grow beyond the approximate 2% where it stands today to represent a majority of vehicles on the road.

A transition to transportation that runs on electricity from renewable energy won't happen, Singh said, until batteries are on par with or better than the internal combustion engine.

"Today's batteries are not competitive. They don't have the energy density to get the range that's needed. They don't have the power to get the fast charge," Singh explained. "Today's best batteries take about an hour to charge where it's obviously easy to re-fuel a gas car in 5 or 10 minutes."

Electric vehicle batteries are expensive to manufacture and don't last as long as the life of a car. They use flammable electrolytes that can burn under what Singh called "abuse conditions." "You want a non-oxidizable set of materials to achieve safety," the CEO said.

The solution QuantumScape has developed is a solid-state battery that's about the size of a pack of cards.

A typical battery cell used in an electric car today is like a metal cylinder that has an anode on one side, cathode on the other, and a conductive liquid electrolyte that flows through a porous separator layer in between. The separator can be made of plastic or another organic material. This three-layer design allows lithium ions to dissolve and move from the anode, when you charge the battery, back down to the cathode when you discharge it.

QuantumScape's design requires less volume to hold the same energy. Its solid-state lithium metal batteries have two main layers, including a cathode and a solid-state ceramic separator, but no manufactured anode. As the battery charges, the lithium leaves the cathode, travels through the ceramic separator, and deposits between the separator and an electrical contact where it forms an anode of metallic lithium within the battery.

QuantumScape isn't alone in its quest to build a better battery. Ultimately, the company will compete with stalwart battery manufacturers like CATL and BYD in China, Panasonic, LG, Samsung and others that manufacture lithium ion battery cells. It will also compete against Tesla, which has designed and started producing some of its own cells, and other companies building solid-state batteries, like Solid Power and Toyota.

-- CNBC's Mike Wayland contributed reporting.