The search for a better EV battery
Battery makers are tweaking — or altogether revamping — the chemistry and mechanics of batteries in an attempt to get a new generation of devices from the lab to the market.
Why it matters: The adoption of electric vehicles, the promise of renewable energy and the bottom line of dozens of companies may hinge on new, solid-state batteries that are meant to be lighter, faster and more powerful.
- But breakthroughs are needed in materials science and mass manufacturing to turn today's devices into the game changers battery makers are betting on.
How it works: Cell phones and electric vehicles are powered today by lithium-ion batteries that have an anode and a cathode, with a separator between them, and a liquid electrolyte. The current default anode is made of graphite.
- The electrodes are made of materials that can store and release lithium ions that have an electrical charge.
- A liquid electrolyte carries the ions back and forth between the electrodes as the battery supplies current or is being charged.
Solid-state batteries try to get more energy from highly reactive lithium metal anodes by using a solid electrolyte. They have some key advantages.
- The main two: the capacity to store more energy and to charge faster than conventional batteries with graphite anodes.
- They're also likely to be safer because they don't contain flammable solvents used in liquid electrolytes. Instead, the electrolyte is made of ceramic or other materials.
Zoom in: There's an inherent tradeoff in batteries between how fast power can flow in and out of the device, and the amount of energy it can store.
- The thicker the anodes and electrodes in a battery, the more lithium ions it can hold and the more energy it can store. But that also means the ions have to travel farther and wiggle their way through more material —which is harder and takes longer — when the battery charges and discharges.
- The tradeoff is apparent in electric cars that strike a balance between their range and their charge time.
- The impact: Batteries with more energy density can give battery makers a choice they don't have with conventional lithium-ion batteries. They can keep roughly the same battery size with a greater range, or shrink the battery and drop the cost.
What's happening: The name of the game then is creating energy-dense batteries — typically with lithium metal anodes, but not necessarily — that can push the limits of cost and distance. Solid-state electrolytes are one path.
- One approach, taken by battery startup QuantumScape as well as researchers at Pacific Northwest National Laboratory and other institutions, is to omit the anode altogether.
- Anode-less batteries require less manufacturing equipment, which potentially lowers the cost of producing them.
- "It really is a big simplification to the manufacturing process that we're hoping to lean into," says Tim Holme, co-founder and CTO of QuantumScape. Their approach is to manufacture the battery anode-free, then it forms from lithium on the battery's first charge.
- The design also gets around using graphite — a common anode material — that is sourced largely from China, which recently said it would be imposing export controls on the material.
Yes, but: Solid-state batteries have some issues scientists are still trying to address.
- A major problem is the ceramics used as solid electrolytes in many batteries are brittle and can crack due to mechanical stress. Those cracks open as the battery charges.
- Microscopic lithium metal formations can grow from the lithium anode into those tiny cracks in the solid electrolyte and short-circuit the battery.
- Battery makers are testing a variety of solutions to block or prevent dendrites — from coatings to innovative designs. QuantumScape's battery packaging tries to minimize the stress — and resulting cracks — from the lithium expanding and contracting by 15% as the battery cycles. The battery also contains a ceramic solid-state separator that aims to resist dendrites forming.
Another hurdle is the cost of producing solid-state batteries. The raw materials for solid-state batteries, including lithium, are expensive, and the precision and quality control needed to produce them drive the cost up even further.
- Toyota recently said it cleared a major hurdle in its manufacturing process.
What to watch: "Solid-state batteries may be inevitable, but it will take a long time for them to be in mainstream [electric vehicles]," Halle Cheeseman, a program director at ARPA-E, said last year.
- But conventional batteries have a lot of momentum in the market, which is further fueled by innovations that are improving them.
- The market for batteries will be "enormous" and "mind-boggling," Holme says, adding there will likely be large markets for "all sorts of batteries, solid-state batteries, lithium-ion batteries and a lot of other kinds of batteries as well."
Editor's note: This story has been updated with more details about QuantumScape's battery packaging and design.