Researchers at the Department of Energy’s Oak Ridge National Laboratory have developed a new method to produce a key component of lithium-ion batteries. The result is a more affordable battery from a faster, less expensive process that uses less toxic material.
Lithium-ion batteries – used in products from appliances to mobile phones, as well as in most electric vehicles – are made up of a cathode and an anode with an electrolyte in between. Ions move from the anode to the cathode through the electrolyte in a reaction that converts chemical energy into electrical energy.
The drive towards decarbonisation and the demand for electric cars have increased the focus on the sustainable production of energy-dense cathodes. However, traditional processing presents challenges.
The first obstacle is a reliance on cobalt, a rare metal mined and refined abroad. This reliance on foreign sources poses risks to American manufacturing supply chains and transportation infrastructure.
The availability of cobalt is not the only complication. The balance of other common metals in cathodes can also make the manufacturing process longer and more dangerous. For example, the high concentration of nickel has led to the widespread use of a chemical mixing method for the production of cathodes that require large amounts of ammonia for corrosive reactions. The use of toxic chemicals increases costs, increases health and environmental problems, and wastes a large amount of water to reduce acidity.
ORNL researchers report in the Journal of Power Sources that they have developed a cleaner, cheaper, more efficient method for making a new class of cobalt-free high-capacity cathode material. Instead of continuously stirring cathode materials with chemicals in a reactor, their hydrothermal synthesis approach crystallizes the cathode with metals dissolved in ethanol. Ethanol is safer to store and handle than ammonia, and can then be distilled and reused.
“This novel process offers the key advantage of moving the cathode industry to cleaner, more cost-competitive production, while placing less burden on our environment,” said ORNL’s Ilias Belharouak, the project’s principal investigator. .
The hydrothermal synthesis method is also much faster, said ORNL principal investigator Rachid Essehli. The time required to make particles and prepare them for the next cathode batch drops from several days to 12 hours.
Also, the material produced has more uniform, round and narrow particles that are ideal for a cathode, Essehli said. Although the ORNL team has previously identified other cobalt-free combinations that work, the material developed for this study was better at maintaining stability throughout the battery’s charge cycle.
Because its properties are similar to those of today’s cobalt-based cathodes, the new material can be seamlessly integrated into existing battery manufacturing processes. A patent is pending on the technology, which is ready to be scaled up for commercial production by industry, Essehli said. “This cathode material can give more energy and lower the cost of electric car batteries,” he said.
The research was funded by the Office of Energy Efficiency and Renewable Energy of the DOE’s Office of Vehicle Technologies. He used resources from ORNL’s Center for Nanophase Materials Science and the Advanced Photon Source at Argonne National Laboratory. Both are facilities for users of the DOE Office of Science.
Materials provided by DOE/Oak Ridge National Laboratory. Note: Content may be edited for style and length.
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