Is Sodium the new Lithium?

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Chemistry  |  News from Science

Is sodium the new lithium?

Lithium-ion batteries are everywhere—in earbuds, phones, cars, and even massive facilities that store renewable energy. But lithium itself is relatively scarce, expensive, and available from just a few countries. Now, a decades-old technology may be rising as a challenger: batteries that use abundant and cheap sodium rather than lithium.

Like lithium batteries, those based on sodium work by passing positively charged metal ions between a pair of electrodes. During charging, electrons are fed to the negatively charged anode, attracting metal ions to flow through the electrolyte from the positively charged cathode. During discharge, electrons are drawn out of the battery, causing the ions to travel back from anode to cathode.

Because sodium ions are larger than lithium ions, fewer of them can squeeze into the anode to store charge, which means larger cells are needed to hold the same amount of power. Sodium batteries have struggled to reach even half the storage capacity of the best lithium batteries. But new anodes and cathodes are showing signs of promise. For example, by adding tin to their carbon-based anodes, the San Diego-based startup UNIGRID has developed sodium-ion batteries that hold 170 Wh/kg. Although this remains less than the 200 Wh/kg of a low-end lithium battery, “it looks very exciting,” says sodium-ion battery expert Yan Yao.

Still, many experts remain cautious in suggesting that sodium-ion batteries are ready to go head-to-head with lithium. An analysis recently concluded that to be fully competitive with low-cost lithium-ion batteries, researchers will need several breakthroughs, including eliminating all the expensive materials sodium batteries currently require.