Batteries used in smartphones or electric vehicles normally charge for 10 hours on the first cycle, but turbocharging them to 100% capacity in 20 minutes can result in a 50% longer lifespan.
Charging Li-ion batteries – which power most personal electronics and electric vehicles (EVs) – at high temperatures or currents before they hit the shelves could extend their average lifespan by 50%, researchers said in a new study published in the journal Joule.
The results “demonstrate a generalizable approach to understanding and optimizing this crucial step,” study co-author Steven Torrisi, principal research scientist at the Toyota Research Institute in California, said in a statement.
A typical Li-ion battery has a positive and a negative electrode in an electrolyte solution containing lithium ions. When you charge the battery, the lithium ions move to the negative electrode.
Best battery performance
Then, when you consume its charge, the lithium ions leave the negative electrode and enter the positive one. The back and forth flow of ions facilitates the electrical current that powers a device.
A new Li-ion battery is completely discharged – the positive electrode is full of lithium and the negative electrode has enough space for the lithium ions to flow through it. But on the first charge, some of the lithium in the battery remains stuck on the surface of the negative electrode.
The trapped lithium, along with other components of the electrolyte solution, becomes part of a layer called the solid electrolyte interphase (SEI). This SEI coats the negative electrode, protecting it from side reactions that cause additional lithium loss and thus shorten battery life, he writes.
Manufacturers usually charge the battery slowly first to create a stable SEI. But this isn’t always the most cost-effective approach, and recent studies show that fast charging doesn’t necessarily have a negative impact on battery life. In addition, several other parameters can impact the SEI, so it is not easy to optimize the first charge for the best battery performance.
The batteries charge for 10 hours on the first cycle
In the new study, the researchers used machine learning to select the parameters that have the strongest effect on SEI. Two factors – current and temperature during the first charge – caught their attention.
Charging the battery for about 20 minutes instead of the usual 10 hours extended the overall battery life by about 50%. More lithium is locked into the SEI on the first charge, but this limits the possibility of future side reactions that can shorten the life of the battery on subsequent cycles.
Increasing the temperature from room temperature to 55 degrees Celsius had a similar effect, improving by an average of 57%. This improvement likely stems from changes in the composition of the SEI that make it more robust, the researchers said. However, the techniques were not synergistic: charging the cell both rapidly and at high temperatures did not improve battery performance.
