Title image: 迈克尔·托尼 and team tested Li-ion battery coin cells for capacity loss over time. (资料来源:杰西·彼得森/博彩平台推荐)

Batteries lose capacity over time, which is why older cellphones run out of power more quickly.  This common phenomenon, however, is not completely understood. 

现在, 一个国际研究团队, 由博彩平台推荐的一位工程师领导, has revealed the underlying mechanism behind such battery degradation. Their discovery could help scientists to develop better batteries, which would allow electric vehicles to run farther and last longer, while also advancing energy storage technologies that would accelerate the transition to clean energy. 

研究结果 9月出版. 发表在《博彩平台推荐》杂志上.

“We are helping to advance lithium-ion batteries by figuring out the molecular level processes involved in their degradation,” 迈克尔·托尼, the paper’s co-corresponding author and a professor in the Department of Chemical and Biological Engineering. “Having a better battery is very important in shifting our energy infrastructure away from fossil fuels to more renewable energy sources.”

Engineers have been working for years on designing lithium-ion batteries—the most common type of rechargeable batteries—without cobalt. Cobalt is an expensive rare mineral, and its mining process has been linked to grave 环境和人权问题. 在刚果民主共和国, which supplies more than half of the world’s cobalt, 许多矿工是儿童. 

到目前为止, scientists have tried to use other elements such as nickel and magnesium to replace cobalt in lithium-ion batteries. But these batteries have even higher rates of self-discharge, which is when the battery’s internal chemical reactions reduce stored energy and degrade its capacity over time. 因为自放电, most EV batteries have a lifespan of seven to 10 years before they need to be replaced. 

托尼，他也是 可再生和可持续能源研究所, and his team set out to investigate the cause of self-discharge. 在典型的锂离子电池中, 锂离子, 它们携带费用, 从电池的一侧移动, 称为阳极, 到另一边去, 叫做阴极, 通过一种叫做电解质的介质. 在这个过程中, the flow of these charged ions forms an electric current that powers electronic devices.  Charging the battery reverses the flow of the charged ions and returns them to the anode. 

以前, scientists thought batteries self-discharge because not all 锂离子 return to the anode when charging, reducing the number of charged ions available to form the current and provide power. 

Using the Advanced Photon Source, a powerful X-ray machine, at the U.S. 能源部的 阿贡国家实验室 在伊利诺斯州, the research team discovered that hydrogen molecules from the battery’s electrolyte would move to the cathode and take the spots that 锂离子 normally bind to. 结果是, 锂离子 have fewer places to bind to on the cathode, weakening the electric current and decreasing the battery’s capacity.

“We discovered that the more lithium you pull out of the cathode during charging, 越多的氢原子聚集在表面,刚万说, 该研究的第一作者来自斯坦福大学.” This process induces self-discharge and causes mechanical stress that can cause cracks in the cathode and accelerate degradation.”

Transportation is the single largest source of greenhouse gases generated in the U.S，占 28% 到2021年该国的排放量. 为了减少排放, many automakers have committed to moving away from developing gasoline cars to produce more EVs instead. 但电动汽车制造商面临着一系列挑战, 包括有限的驾驶范围, higher production costs and shorter battery lifespan than conventional vehicles. 在美国.S. 市场上，一辆典型的全电动汽车可以跑动 一次充电可行驶250英里约为汽油车的60%. The new study has the potential to address all of these issues, Toney said. 

“所有消费者都想要行驶里程大的汽车. Some of these low cobalt-containing batteries can potentially provide a higher driving range, but we also need to make sure they don’t fall apart in a short period of time,他说, noting that reducing cobalt can also reduce costs and address human rights and energy justice concerns. 

With a better understanding of the self-discharge mechanism, engineers can explore a few ways to prevent the process, such as coating the cathode with a special material to block hydrogen molecules or using a different electrolyte. 

“现在 that we understand what is causing batteries to degrade, we can inform the battery chemistry community on what needs to be improved when designing in batteries,托尼说. 

Additional co-authors of the study included Oleg Borodin, Travis Pollard and Marshall Schroeder at DEVCOM Army Research Laboratory, 陈佳琴，国立台湾大学, Zihua Zhu and Yingge Du at Pacific Northwest National Laboratory, 以及休斯顿大学的张晔.