Lithium-ion batteries are excellent for electric vehicles because of their weight and relatively high energy storage capacities. However, they have a problem; as they age, lithium-ion batteries lose capacity, and the amount of energy they can store reduces. But now, a group of Stanford University researchers has been able to reverse the process.
These researchers boosted an old battery’s range according to their report published in Nature.
The loss of capacity comes due to lithium that separates from the electrodes. The Stanford group was able to make the ‘dead’ lithium move toward one of the electrodes and reconnect. Once reconnected, the lithium can then resuming helping the battery to hold a charge.
The lithium moved after lithium metal was added at one end and dissolved at the other end, and a short, high-current discharging step was added just after charging the battery. This process slowed the battery degradation down and increased its useful life by about 30 percent.
Professor Yi Cui had theorized that free-standing lithium could be moved physically by supplying a voltage to the battery’s cathode and anode, inspiring the research. His speculation has now been confirmed.
The researchers set up an optical cell with a lithium-nickel-manganese-cobalt-oxide cathode and a lithium anode, with an island of lithium between them. While tracking the content of the battery in real-time as it worked, the team realized that the isolated lithium was not dead and could react to the battery operation.
The researchers carried out their test on other batteries to confirm the finding. They also did some computer simulations.
Fang Liu, a member of the research group, said:
“We found that we can move the detached lithium toward the anode during discharging, and these motions are faster under higher currents. So we added a fast, high-current discharging step right after the battery charges, which moved the isolated lithium far enough to reconnect it with the anode. This reactivates the lithium so it can participate in the life of the battery. Our findings also have wide implications for the design and development of more robust lithium-metal batteries.”
With breakthroughs like this, electric vehicle batteries could be ‘repaired’ and made to last longer, thereby helping prevent environmental pollution.
Renewable Brief 