The very first charge of a lithium-ion battery is more important than most people realize.
This initial charge determines how well the battery will perform over time and how many times it can be charged and discharged before it starts to wear out.
In a groundbreaking study published in Joule, researchers at the SLAC-Stanford Battery Center found that charging batteries for the first time using a much higher current than usual can significantly boost their performance.
This approach increased the average battery lifespan by 50% and reduced the initial charging time from 10 hours to just 20 minutes.
What’s even more exciting is that the researchers used scientific machine learning to understand the specific changes happening inside the battery that lead to this improvement.
These insights are invaluable for battery manufacturers who want to make better products faster and more efficiently.
The study was led by Professor Will Chueh and his team at SLAC and Stanford University, in collaboration with researchers from the Toyota Research Institute, MIT, and the University of Washington.
This research is part of SLAC’s broader efforts to develop sustainable energy technologies through innovative science and strong industry partnerships.
“This research is a perfect example of how we’re using advanced science to solve real-world problems in battery manufacturing,” Chueh said.
“We’re working closely with industry to make critical technologies more affordable and efficient.”
The findings have significant implications for the manufacturing of lithium-ion batteries, which are used in everything from electric vehicles to the power grid. The study could also impact other technologies that rely on these types of batteries.
Steven Torrisi, a senior research scientist at the Toyota Research Institute, expressed excitement about the study’s results. “Battery manufacturing is incredibly complex and time-consuming,” he said.
“It takes a lot of effort to optimize the process, but this study shows a promising approach to understanding and improving that crucial first charge. What we’ve learned here could be applied to new processes, equipment, and even different types of batteries in the future.”
To understand why the first charge is so important, the researchers built test batteries where the positive and negative electrodes are surrounded by a liquid electrolyte, allowing lithium ions to move freely.
During charging, these ions flow into the negative electrode, and when discharging, they flow back to the positive electrode, creating a flow of electrons that powers devices like electric cars.
The positive electrode of a new battery is fully loaded with lithium. But each time the battery is charged and discharged, some lithium is lost, which shortens the battery’s life.
Surprisingly, the researchers found that intentionally losing a significant amount of lithium during the first charge can actually make the battery last longer. This lost lithium forms a protective layer called the solid electrolyte interphase (SEI) on the negative electrode.
Xiao Cui, who leads the battery informatics team in Chueh’s lab, explained that the SEI layer is crucial because it protects the negative electrode from side reactions that could speed up the battery’s degradation.
This process, known as the “formation charge,” is the final step in manufacturing a battery, and if it fails, the entire battery could be worthless.
Typically, manufacturers give new batteries their first charge at low currents, thinking it will create the strongest SEI layer. However, this method is slow, costly, and doesn’t always yield the best results.
Recent studies suggested that faster charging with higher currents might not harm the battery, but the researchers wanted to investigate further.
Using scientific machine learning, they identified that only two factors—temperature and charging current—were crucial for achieving the best results. Experiments confirmed that charging at high currents greatly improved the battery’s lifespan, even though it deactivated a higher percentage of lithium up front.
Cui compared this to scooping water out of a full bucket before carrying it. The extra space in the bucket prevents spills, just as deactivating more lithium creates headspace in the battery, allowing it to perform better in the long run.
“We didn’t just want to find the best way to charge a battery,” Chueh said. “We wanted to understand why it works. This understanding is essential for balancing battery performance with manufacturing efficiency.”
This discovery could pave the way for more efficient and longer-lasting batteries, benefiting everything from electric vehicles to renewable energy storage systems.
