Solid-state battery technology is emerging as a lighter, potentially safer alternative to lithium-ion batteries currently powering electric vehicles. While Li-ion power sources have made strides in terms of cost and power density and driving range, solid-state alternatives promoted at this week’s Web Summit promise to offer improved performance and greater safety.
For instance, EV battery developer Solid Power touted its solid-state approach as a way to boost performance, cut emissions and improve the reliability of EV powertrains. Douglas Campbell, founder and CEO, claimed Solid Power has developed a solid-state battery alternative with improved energy density compared to Li-ion. The design replaces liquid electrolyte with a sulfur-based, solid ion-conducting chemistry. It can also be manufactured on the same production lines used for Li-ion production
A “lithium-ion battery typically needs to be kept to about 30 to 35 degrees Celsius,” Campbell said during a presentation. Heat “will degrade the life of that battery.” Hence, EV makers integrate cooling schemes into battery packs.
That approach “is a major cost driver,” Campbell added. “A good rule of thumb is that the cost of that pack cooling represents about 10 percent of the overall cost of an EV battery, which is not trivial.”
The company’s other selling point is safety. Campbell stressed that Li-ion batteries can be extremely dangerous when subject to abuse. “There’s no shortage of videos on YouTube where you can see batteries going into a thermal runaway when subjected to abuse. The issue there is, when you subject a lithium-ion battery to an abuse condition, like a penetration, you’re essentially shorting the cell. You’re physically touching the cathode and anode. And so, what it wants to do is immediately release all of that energy that generates heat and essentially ignites the liquid electrolyte.”
As with solid-state batteries, the flammable liquid electrolyte in a conventional Li-ion battery is replaced with a proprietary sulfide solid electrolyte. Proponents say that makes solid-state batteries more stable and therefore safer across a broad temperature range.
Additionally, solid-state technology can provide up to a 75-percent increase in energy density compared to rechargeable batteries, enabling a cheaper, more energy-dense battery pack design compatible with current manufacturing processes.
“As in lithium-ion [manufacturing], we have materials enter into the facility in powder form,” Campbell said. Active materials as well as electrolytes in powdered form are then processed into large batches of slurry, then incorporated in a stack cell architecture.
“What we don’t need is a formation process that represents about 30 to 35 percent of the [capital expenditure] associated with the typical gigafactory,” a reference to huge facilities like Tesla’s where Li-ion batteries are manufactured.
Solid Power, Louisville, Colo, is currently producing 2 amp-hour (Ah) cells with energy density of 320 watt-hour/kg, scaling up to 500 Wh/kg in cell capacity at as much as 100 Ah.
The battery manufacturer’s third-generation cell design could eliminate costly metals like nickel and cobalt, providing a 90-percent decline in the cost of the cathode—”far and away from the most expensive component in lithium-ion batteries today,” Campbell noted.