Lithium-ion batteries can increase the charging capacity of electric vehicles when fast charging is paused.
A three-minute charging break when fast-charging lithium-ion batteries can help batteries maintain high charge capacity for longer. This was stated by scientists from Great Britain and the USA after a detailed study of physical processes in the journal “Nature Communications”. They also discovered that the size and shape of the graphite particles in the negative electrode affected the deposition of metallic lithium on and in the electrode.
When charging a lithium-ion battery, lithium ions are deposited between the graphite layers of the negative electrode. However, lithium mineral deposits can also form on the electrode, and this becomes more frequent the faster the battery is charged. As a result, fewer lithium ions are available as charge carriers.
The electrode porosity decreases and with it the embedding interface. Branches, called dendrites, can form, which can lead to an internal short circuit, write the group led by Xuequn Lu of Queen Mary University of London. Therefore, such deposits should be avoided to ensure a long battery life.
“Using an innovative 3D battery model, we can understand when and where lithium deposition begins and how fast it grows,” Lu said in a statement from his university. Their experiments showed that precipitation cannot be completely avoided. But they also found that most sediment dissolves back in if fast charging is stopped for a short time.
Pleasant loading break
The researchers determined that for an electrode with a capacity of 2 milliamps per square centimeter and a charging time of 20 minutes at a 45 percent charge level, a three-minute charging break should be taken. For an electrode with a capacity of three milliamperes per square centimeter, the optimal pause time is at 45 percent charge level (charge time: 1 hour), 30 percent charge (charge time: 30 minutes), or 20 percent charge level (charge time: 1 hour). 30 minutes) Time: 20 minutes).
The research team also discovered that mineral deposits occur mainly on smaller graphite particles and on the corners and edges of larger particles. Therefore, the researchers consider it important to improve the shape of the graphite particles in the negative electrode of the lithium-ion battery.
Lu and his team see their research as an important contribution to the future development of electric vehicles. “The ability to quickly charge and the range and safety of lithium-ion batteries for cars are the main issues affecting the wider adoption of electric vehicles,” they wrote.