



Heat the battery to minimize the formation of lithium plates

Charged at a temperature of 20 ° C, lithium plates gradually appear on the electrodes. But the higher the charging temperature, the less the plates develop. At 60 ° C, no plaque is formed. Credits: Wang et al. 2019

High temperature charge: optimized performance

In recent years, electric cars have become popular, to the point of today investing a certain share of the automotive market. If they are more and more common, their charging time still repels many potential users. To remedy this, a team of engineers from Penn State University has developed a new battery that can charge in just 10 minutes, thanks to a rapid heating process, increasing the rate of ion transport.The key to making electric cars more commercially attractive is the development of batteries that can reach 80% charge (or a range of about 300km) in 10 minutes, explains Chao-Yang Wang of Penn State University . But this requires that batteries quickly absorb 400 kilowatts, which is not possible with those currently available on the market.When the batteries are charged quickly - the phase in which the lithium ions move from the positive electrode to the negative electrode - the lithium tends to form on the surface of the electrode deposits in the form of plates, likely to reduce the life of the battery.Wang and his colleagues thought they could minimize this problem by first heating the battery to a temperature too high to allow the formation of lithium plates. To test this, they took a commercially available industrial battery and inserted micron nickel sheets into a stack of electrode layers.This structure allows the electrode to heat in less than 30 seconds, thereby creating the conditions for ions to move rapidly in the negative electrode without causing plaque formation on its surface. They then tested cell function when charged at 40 ° C, 49 ° C or 60 ° C and compared their performance to that of a control battery charging at 20 ° C.They found that at 20 ° C, the battery could maintain a fast charge for only 60 cycles before lithium plating caused problems that significantly reduced performance. In contrast, heating the electrode to 60 ° C allowed the battery to recharge for 2500 cycles without forming lithium plating. This equates to 14 years of use or approximately 750,000 kilometers. The results were published in Joule magazine .This calls into question the old idea that lithium batteries should not be charged at high temperatures because they would degrade. Instead, the results suggest that the benefits of a brief, high-temperature surge greatly outweigh the disadvantages, Wang explains.