Ceramics R&D Key to Solid-State Battery Future

 

Ceramic solid-state batteries offer the promise of faster recharging, greater energy storage, better thermal stability and longer life. Using sodium-ion instead of lithium-ion could add more benefits and solve some of the environmental and supply chain problems associated with lithium.

Toyota shares surged in the second half of 2023 after the car gigant announced a breakthrough in solid-state batteries development. Toyota claimed their new technology would more than double the range of current electric vehicles (EVs) on 10 minutes charging time. Vehicles powered by the batteries should become availabe by 2027.

Other car manufacturers, including Hyundai, Honda, Nissan, BMW, Ford, GM and Volkswagen, are also working towards solid-state batteries. Startups, including Factorial, QuantumScape, Blue Solutions and Ion Storage systems, have joined the race. There are still many hurdles in finding the right combination of chemicals, materials and manufacturing processes to produce solid-state batteries reliably, at scale and within cost.

Lithium-ion batteries in EVs are structurally similar to the ones in laptops and mobile phones. They are comprised of four components; a cathode or positive electrode, an anode or negative electrode, a separator between the anode and cathode and an electrolyte serving as a medium for ions to carry the charge between the cathode and anode. In common lithium-ion batteries the electrolyte is a liquid solution.

Liquid electrolyte solution is extremely flammable and reactive with oxygen, requiring many safety measures to prevent traditional batteries from spontaneously combusting. A solid-state battery only has a solid separator between the anode and cathode, doing double duties as the electrolyte. The separator is a solid piece of ceramic or hybrid ceramic-polymer material allowing the direct flow of ions.

Elimination of the liquid electrolyte makes solid-state batteries less likely to catch fire. With a high melting point due to their strong covalent bonds, ceramics give solid electrolytes high thermal stability. Ceramics also help prevent dendrites from growing as happens in liquid electrolytes, reducing the chance of an internal short. But ceramics are brittle. The process of charging and discharging can cause volume changes in the electrode material, requiring a relatively thick separator to prevent cracks and contact loss.

One way to remedy these downsides is to use ceramic-polymer hybrid materials. Polymers have a lower melting point and reintroduce some fire risks, but ceramic-polymer hybrid allow for thinner separators and creating lightweight batteries with high energy densities and better thermal properties. Solid-state lithium-ion batteries would provide more capacity in a smaller package, allowing vehicles to travel further with less charging and, for example, finally making electric trucks competitive with traditional internal combustion trucks.

However some of the solid-state research efforts are now focusing on sodium-ion (Na-ion) as an alternative to lithium-ion. Unlike lithium, sodium-ion raw materials are naturally abundant and less environmentally disruptive to extract. Sodium-ion is still similar enough to the already mature lithium-ion technology to make fabrication on existing production lines feasible, although supply chains for sodium-ion raw materials and processing are not yet as well-developed as for lithium-ion.

Sodium-ion batteries have lower energy density, typically operate at a lower voltage and have a shorter cycle life before capacity significantly degrades. They are apparently already good enough for mass production in China, where they have been used in electric scooters and are moving into the next-generation cheaper EVs. The latest sodium-ion batteries are approaching the energy density of lithium iron phosphate (LFP) cells currently used in cheaper EVs.

‘We need to start talking about sodium-ion batteries,’ says Alevtina Smirnova, Director of the NSF Industry-University Cooperative Research Center for Solid State Electric Power Storage (CEPS). ‘I am very concerned that here in the United States, sodium-ion is just not on the radar. I can tell you, in ten years we will stop talking about lithium. The lithium reserves are only sufficient for 100 years, max, and it is not eco-friendly.’

 

The role of ceramics in the solid-state battery race will be discussed at the Ceramics Expo conference, April 30 to May 1 in Novi, Michigan.