Beyond lithium: how sodium-ion batteries could change the world
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Beyond lithium: how sodium-ion batteries could change the world
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Sodium-ion batteries being produced in Luoyang, China. Credit: Zhang Yixi/VCG via Getty
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The lithium-ion battery is the beating heart of the modern world. It powers eight billion mobile phones, hundreds of millions of laptops and rapidly growing fleets of electric cars and energy-storage banks. But there’s a new contender breaking into the battery market.<br>Batteries based on sodium promise to be cheaper, safer and much more environmentally friendly than lithium-ion cells. And this year could mark the start of the sodium era.<br>In April, Chinese firm CATL — the world’s largest battery producer — announced that it will start mass-producing sodium-ion batteries before the end of 2026. CATL, which is headquartered in Ningde, added that it had signed deals to sell the batteries both to a car manufacturer and to a provider of energy-storage stations for electricity grids.<br>Sodium-ion batteries were first developed in the 1980s, around the same time as lithium-ion ones. But early prototypes had some major shortcomings: they couldn’t hold as much energy as lithium-ion batteries, and they weren’t as durable, quickly losing their ability to recharge. For decades, therefore, research focused on lithium-ion technology. But interest and investment in sodium-ion batteries has ramped up in the past half-decade. Companies in China have already introduced motorcycles and small cars powered by sodium batteries, and have developed sodium-battery manufacturing facilities. CATL’s mass production promises to substantially increase the technology’s spread. Another Chinese firm, Shenzhen-based BYD, which is the biggest electric-car maker by global sales, is also investing heavily in sodium-ion batteries, analysts report.<br>Sodium-ion batteries made by CATL in China are used in electric cars (left) and energy-storage banks for electricity grids (right).Credit: CATL<br>What has surprised many observers is how rapidly companies claim to have improved on sodium-ion’s flaws. Auke Hoekstra, an energy analyst at Eindhoven University of Technology in the Netherlands, says he has been taken aback by the pace of advancement. “I honestly did not expect it to go that fast — and I am usually the guy who is seen as an optimist,” he says.<br>Hoekstra is known for his bullish predictions about renewable energy, which have often been correct. Now he is bullish on sodium-ion. Although other analysts and researchers are unsure how strongly the technology can compete with lithium-ion devices, he sees it as an innovation that will enable the price of batteries to keep falling, thus speeding up the electrification of the world’s economy. “For the future of energy, this really would be a game-changer,” he says.<br>Battery prices: decline and fall<br>The expectation that sodium-ion technology will cut battery prices rests mainly on the fact that its raw materials are cheaper and more abundant than those of lithium-ion batteries.<br>The prices of battery cells have already fallen by more than 90% since 2010 (see ‘Falling prices of lithium-ion batteries’). Most of this reduction is a result of improvements in the efficiency of industrial processes, as well as increases in battery production volumes. This means that the raw materials in the cells make up a larger share of the total cost than they did previously.<br>Source: Adapted from Our World in Data/BloombergNEF<br>For lithium-ion batteries, those raw materials include not only lithium — typically stored as ions in a graphite and copper electrode (the anode) — but also the components of the other electrode, the cathode, that draw lithium ions across when a battery discharges.<br>To boost energy capacities, materials scientists and engineers have developed cells that use the heavy-metal elements nickel, manganese and cobalt (NMC) to form ‘layered oxide’ microscopic crystals that hold lithium in the cathode. Because lithium ions can be packed so tightly and strongly in these crystals, commercial NMC cells have reached record capacities of more than 300 watt-hours of energy per kilogram (Wh kg−1) — enabling some high-end electric cars to cover more than 800 kilometres before they need to recharge.<br>However, some of these cathode elements are pricey and scarce, meaning that the trend of falling NMC prices is showing signs of levelling off. But in the past five years or so, many car producers, especially...