Researchers at the Department of Energy’s Oak Ridge National Laboratory have developed a new method for producing a key component of lithium-ion batteries. The result is a more affordable battery from a faster, less wasteful process that uses less toxic material.
Lithium-ion batteries — used in products from appliances to cell phones, as well as in most electric vehicles — are made of a cathode and an anode with an electrolyte in between. Ions move from anode to cathode through the electrolyte in a reaction that converts chemical energy into electrical energy.
The move 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 the dependence on cobalt, a rare metal mined and refined abroad. This reliance on foreign sources poses risks to American manufacturing supply chains and transportation infrastructure.
Cobalt availability 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, a high concentration of nickel has led to the widespread use of a chemical mixing method for cathode production that requires large quantities of ammonia for corrosive reactions. The use of toxic chemicals increases costs, increases health and environmental concerns, and wastes large amounts of water to reduce acidity.
ORNL researchers report in the Journal of Energy Sources that they have developed a cleaner, cheaper and more efficient method to make a new class of cobalt-free high-capacity cathode material. Instead of constantly mixing cathode materials with chemicals in a reactor, their hydrothermal synthesis approach crystallizes the cathode using metals dissolved in ethanol. Ethanol is safer to store and handle than ammonia, and can then be distilled and reused.
“This new 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 principal investigator for the project.
The hydrothermal synthesis method is also much faster, said ORNL lead researcher Rachid Essehli. The time required to make particles and prepare them for the next batch of cathode drops from a few days to 12 hours.
In addition, the material produced has more uniform, round and tightly packed particles that are ideal for a cathode, Essehli said. Although the ORNL team previously identified other cobalt-free combinations that work, the material developed through this study was better at maintaining stability during 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 deliver more energy and reduce the cost of electric car batteries,” he said.
The research was funded by the DOE Office of Energy Efficiency and Renewable Energy’s Office of Vehicle Technologies. Use resources of ORNL’s Center for Nanophase Materials Sciences and the Advanced Photon Source at Argonne National Laboratory. Both are DOE Office of Science user facilities.
Materials provided by DOE/Oak Ridge National Laboratory. Note: Content may be edited for style and length.
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