Solid Power Releases Safety and Performance Data for its High-Content Silicon Cell

Solid Power’s battery is a silicon all-solid-state battery that is supposed to be used to power and store energy for electric vehicles. The data in the report show that the cell meets the key requirements to operate in the automotive industry.

The key requirements for a battery to be standardized in the automotive industry are the capability to pack high energy, high retention rate at a high cycle life target, quick charging, temperature tolerance at low and high temperatures, and promising early performance.

 

Key Requirements achieved by Solid Power High-Content Silicon cells. Image courtesy of Solid Power.

 

Performance Data

The performance data released by Solid Power show extraordinary characteristics in different aspects and tests performed.

The tests show a long cycle life where it achieved more than 1000 cycles at room temperature and the same statistics when operating at 45 degrees celsius. At both tests, the battery was also able to preserve a high capacity retention rate above 80% after 1000 cycles at a C/5 rate.

 

A graph from Solid Power shows the capacity retention/Cycles for their High-Silicon battery. Image courtesy of Solid Power.

 

The report also contains testing the battery at high specific energy approximately 350 Wh/kg stack level at 45 degrees Celsius temperature. The capacity retention rates reached 80% after 750 cycles.

Fast Charging is becoming a requirement for EV batteries. The tests showed that the High-Silicon Cell could stand up to 650 cycles with a C/2 rating at nearly room temperature conditions.

Also, low-temperature tests were performed. The cells were subjected to a C/10 charge/discharge rate. The results are shown in the figure below.

 “As Solid Power gears up to enter the automotive qualification phase, we are laser focused on optimizing cell design in order to meet or exceed all of our customer’s requirements,” said Josh Buettner-Garrett, Chief Technology Officer at Solid Power. “We are now working to replicate these initial results in a larger format, production-line produced cells.”

 

A graph from Solid Power showing cell voltage/Capacity test at low temperatures. Image courtesy of Solid Power.

 

Safety Data

First of all, to overcome the flammability problem of conventional lithium-ion batteries, Solid Power replaced liquid and gel electrolytes with a sulfide-based electrolyte.

Then a non-profit research and development organization performed different abuse tests on Solid Power’s 2 ampere-hours high-content silicon battery that satisfied the standards set by the Society of Automotive Engineers.

The tests performed are the nail penetration test, overcharge test, and external short circuit test. The nail penetration test included puncturing fully charged cells with a conductive nail at room temperature. During the test, the highest reading of the cell temperature was 27 degrees celsius. Here is a link for a video of the penetration test.

 The overcharge test included charging the battery to a 200% state of charge with a C/1 charging rate. The cells were tested under compression and without compression. The highest recording of temperature was 35 degrees celsius for uncompressed cells and 69 degrees celsius for the compressed cells.

The cells then were fully charged and subjected to short-circuit. The cells didn’t show any hazards such as flame, venting, or loss of material during the test.

“The automotive industry has seen very recent examples of lithium-ion battery safety concerns, resulting in danger to vehicle occupants and expensive electric vehicle recalls,” said Doug Campbell, CEO, and co-founder of Solid Power. “Our all-solid-state cells could reduce the risk of EV fires and lead to significant battery pack cost reductions by removing the flammable liquid and gel electrolyte.”

Solid Power is looking forward to changing flammable lithium-ion batteries to safer and more powerful cells.

 

Featured image used courtesy of Solid Power