E-Cars: How Lithium Batteries Last Longer

Status: 11:19 am| Reading time: 2 minutes

HA three-minute charge break when fast-charging lithium-ion batteries can help batteries maintain a high charge capacity for longer. This was reported by scientists from Great Britain and the USA after a detailed examination of physical processes in the specialized journal “Nature CommunicationsThey also discovered that the size and shape of the graphite particles in the negative electrode affects 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.

Lu and his colleagues worked out what was happening at the pole using a special form of microscopy and a computer model. “Using a 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 melts back out when fast charging is interrupted for a short time.

When do you stop charging?

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 milliampere-hours per square centimeter, the optimal pause time is at 45 percent charge (charge time: 1 hour), 30 percent charge (charge time: 30 minutes), or 20 percent percent (charging time: 30 min. : 20 min).

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 rapid charging capability, range, and safety of lithium-ion vehicle batteries are the major issues affecting the wider adoption of electric vehicles,” they wrote.