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Key takeaways
- A new Department of Energy center at UCLA is working to improve sodium batteries to where lithium batteries are now — within the next 10 years.
- Currently existing sodium ion batteries charge slowly and their use life is shorter than that of lithium ion batteries.
- Because sodium is a larger cation than lithium, it faces more resistance as it moves through the material between the cathode and anode.
Lithium ion batteries are the state of the art for energy storage, but much of the world's lithium supplies lie outside the United States, making its use costly and subject to geopolitical constraints. Now, a new Department of Energy center at UCLA, the Center for Strain Optimization for Renewable Energy, or STORE center, aims to improve batteries made from an alternative element that is one of the world's most abundant: sodium.
Sodium ion batteries exist, but not in useful forms for most consumers. The batteries charge slowly, and their use life is shorter than that of lithium ion batteries. Lithium is preferred for batteries because it's the smallest cation, or positively charged ion, that is not chemically reactive. This quality enables it to move into and out of the battery's cathode and anode without bumping into too many other atoms. The free movement of ions enable lithium ion batteries to charge quickly and with relatively few atoms pushed out of place, giving them a long use life.
Meanwhile, sodium is the next smallest cation but is much larger, meaning it faces more resistance as it moves through the material between the cathode and anode. The resistance deforms the arrangement of atoms in the material, making the battery charge slowly and giving it a shorter use life.
"We're setting out to make sodium ion batteries a marketable commodity. Our goal is to get sodium batteries to where lithium is now within the next 10 years," said center director Sarah Tolbert, a UCLA distinguished professor of chemistry. "We are doing this by developing materials that have big spaces in them so sodium can move without forcing other atoms to rearrange, by engineering layers that resist rearrangement by sodium, and by making materials that are malleable and able to flex to accommodate volume change."
Another big challenge is to ensure that all the other elements in the battery are also low cost. That requires moving away from traditional battery materials like nickel and cobalt, and instead focusing on low-cost elements such as iron, manganese, titanium, sulfur and phosphorous.
"The exciting challenge of this project is to solve fundamental materials problems in a practical space. When you can do that, it baecomes possible to both advance science and have a positive impact on society," Tolbert said.
The STORE Center will receive $4.5 million over the next three years from the Department of Energy's new Energy Earthshots program, which is investing $264 million to accelerate clean energy technologies within the next 10 years. The program recalls the wholesale mobilization of scientific and engineering talent called for by President John F. Kennedy in 1962, dubbed the Moonshot program, that put humans on the moon within the decade.
UCLA chemistry professor Xiangfeng Duan, materials science professor Bruce Dunn and chemical engineering professor Yuzhang Li also play key roles in the center. Collaborators include scientists from UCSB, the University of Southern California, Caltech and the Stanford Linear Accelerator Center.
