Researchers at Stanford University’s National Accelerator Laboratory (SLAC), USA, have developed a new method that promises to recover rechargeable lithium-ion batteries, increasing their life and performance for use in electric cars and electronic devices.
They figured out how to revitalize the lithium accumulated in small inactive islands that remain isolated from the electrodes. So-called “dead lithium” is formed during the charge and discharge cycles of a power cell, decreasing its storage capacity over time.
“We saw that we could make this inactive lithium crawl like a worm towards one of the electrodes until it reconnected, reversing the wear process. This approach reduced battery degradation and increased battery life by nearly 30%,” explains materials science professor Yi Cui, lead author of the study.
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dead lithium
Conventional batteries—used in electric vehicles and portable electronic equipment—use positively charged lithium ions that move between electrodes. Over time, some of this metallic lithium becomes inactive, forming isolated islands that can no longer communicate efficiently with the electrodes.
With this new technique, scientists have shown that it is possible to mobilize and reconnect this dead lithium, extending the life of storage cells and making it possible to manufacture batteries that can be charged much faster, without degrading their energy capacity.
“We always thought of isolated lithium as a bad thing, as it causes batteries to deteriorate and even catch fire. “adds Professor Cui.
crawling to the electrode
To prove this theory, the scientists used an optical cell made from a lithium-nickel-manganese-cobalt oxide cathode, a lithium anode and an isolated island in the middle of the device. With this test battery, they were able to monitor what was happening inside the cell in real time.
By observing the behavior of the battery, they realized that the insulated lithium island was not dead and that it responded to stimuli inside the power cell. During the loading process, the island moved slowly towards the cathode and then “crawled” in the opposite direction when unloading.
“It’s like a very slow worm that advances its head and pulls its tail to move nanometer by nanometer. In this case, the lithium moves around by dissolving at one end and depositing material at the other end. If we can keep it moving, it will end up touching the anode and re-establish the electrical connection, reusing the lithium that was previously lost”, concludes Professor Yi Cui.
