Cobalt-free battery promises higher energy density, cheaper cost
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Lithium-ion batteries that do not feature cobalt, a rare element with a high cost and a history of poor human rights issues in the extraction process, have been developed by researchers at the University of Texas.
Mines in the Congo currently produce around 60 per cent of the world’s cobalt supply but have been associated with child labour and poor working conditions.
Global supplies of the metal are also expected to become critical by 2050, which will make the production of batteries using current technology very expensive.
But while past attempts to develop cobalt-free batteries have produced products that cannot match the expected performance standards, the researchers believe they can now eliminate the element from production and even achieve a boost in performance.
The key lies in a new class of cathodes - the electrode in a battery where all the cobalt typically resides – which is anchored by high nickel content. The cathode in their study is 89 per cent nickel with manganese and aluminium making up the other key elements.
More nickel in a battery means it can store more energy. That increased energy density can lead to longer battery life for a phone or greater range for an electric vehicle with each charge.
Typically, increased energy density leads to trade-offs, such as a shorter cycle life—the number of times a battery can be charged and discharged before it loses efficiency and can no longer be fully charged.
Eliminating cobalt usually slows down the kinetic response of a battery and leads to lower rate capability – how quickly the cathode can be charged or discharged. However, the researchers said they’ve overcome the short cycle life and poor rate capability problems through finding an optimal combination of metals and ensuring an even distribution of their ions.
Cathodes can make up roughly half of the materials costs for the entire battery, with cobalt being the priciest element. At a price of approximately $28,500 per ton, it is more expensive than nickel, manganese and aluminium combined, and it makes up 10 to 30 per cent of most lithium-ion battery cathodes.
“Cobalt is the least abundant and most expensive component in battery cathodes,” said researcher Arumugam Manthiram. “And we are completely eliminating it.”
During synthesis of their new battery, the team were able to ensure the ions of the various metals remained evenly distributed across the crystal structure in the cathode.
When these ions bunch up, performance degrades, and that problem has plagued previous cobalt-free, high-energy batteries. By keeping the ions evenly distributed, the researchers were able to avoid performance loss.
“Our goal is to use only abundant and affordable metals to replace cobalt while maintaining the performance and safety and to leverage industrial synthesis processes that are immediately scalable,” said researcher Wangda Li.
Last month, a team demonstrated a sodium-ion battery that can store as much energy as commonplace lithium-ion batteries at a much-reduced environmental cost.
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