Stanford’s EV battery magic: 20-min high-current 1st charge means 50% more life

Researchers at Stanford Linear Accelerator Center (SLAC) have uncovered a surprising method to boost battery performance.

A recent study revealed that charging batteries at unusually high currents for the first time can extend their lifespan by 50 percent and reduce the initial charging time from 10 hours to just 20 minutes.

With the aid of scientific machine learning, the researchers were able to identify precise modifications to the battery electrodes that are responsible for the increased performance and lifespan.

According to the team led by SLAC professor Will Chueh, these findings will be extremely helpful to battery producers who want to enhance their output and optimize their workflows.

Critical first charge

The initial charge of a lithium-ion battery is more significant than it may seem. It establishes the battery’s performance and lifespan thereafter, namely the number of cycles of charging and discharging it can withstand before degrading.

The team constructed pouch cells, in which the positive and negative electrodes are encircled by an electrolyte solution in which lithium ions are free to travel, in order to better understand what occurs during the battery’s first cycling.

Lithium ions move into the negative electrode of a battery during charging to be stored. When the battery becomes low, the electrons exit the cell and move to the positive electrode, where they start to flow again. This process powers everything from electric vehicles to the electrical grid.

According to researchers, a fresh battery’s positive electrode is 100 percent lithium-filled. However, a portion of the lithium is deactivated with each charge/discharge cycle. Reducing those losses increases the battery’s operational life.

Strangely enough, one strategy to reduce the overall loss of lithium is to purposefully lose a significant portion of the initial lithium supply during the battery’s first charge. It’s comparable to making a tiny investment that will eventually pay off handsomely.

“Formation is the final step in the manufacturing process, so if it fails, all the value and effort invested in the battery up to that point are wasted,” said Xiao Cui, the lead researcher for the battery informatics team in Chueh’s lab, in a statement .

Efficient charging strategy

Manufacturers typically charge new batteries at low currents during the first cycle, aiming to create the strongest solid electrolyte interface (SEI layer).

However, there is a drawback: charging at low currents takes longer, costs more money, and may not always produce the best results. It was, therefore, encouraging news when recent research revealed that faster charging at greater currents does not impair battery performance.

However, scientists desired to learn more. Numerous elements contribute to the creation of SEI during the initial charge, of which the charging current is just one. It’s a daunting endeavor to test every potential combination of them in the lab and determine which one performed best.

To address the issue, the research team employed scientific machine learning to pinpoint the key factors for optimal battery performance. Surprisingly, they found that just two variables—charging temperature and current—were crucial.

Their experiments revealed that charging at higher currents dramatically extended battery lifespan by 50 percent. Although this approach deactivated about 30 percent of lithium upfront, compared to 9 percent with traditional methods, it had a beneficial effect.

Cui says the process is similar to removing some water from a full bucket before carrying it, which reduces spillage. Similarly, deactivating more lithium ions during the initial charge creates additional headroom in the positive electrode, enabling it to cycle more efficiently. This adjustment enhances the overall performance and longevity of the battery.

“This understanding is crucial for finding the best balance between battery performance and manufacturing efficiency,” said Cui.

The details of the team’s research were published in the journal Joule .