Silicon-tin anode to improve lithium-ion batteries

US researchers have created a silicon-tin nanocomposite anode that will improve the charge capacity and stability of lithium-ion batteries. The batteries, which can be charged and discharged more times before they reach the end of their useful lives, could be used in everything from handheld electronic devices to electric vehicles.

Lithium-ion batteries are composed of three main parts: an anode, a cathode and a lithium salt dissolved in an organic solvent. While graphite is the material of choice for most anodes, its performance is a limiting factor in making better batteries and expanding their applications. Both silicon and tin have been investigated as novel high-performance alternatives for graphite anodes.

Now, researchers from the University of California, Riverside (UCR) have shown that combining silicon and tin into a single composite leads to dramatic improvements in battery performance. Writing in the journal Scientific Reports, the study authors explain how they “developed a structure in which the tin nanoparticles are segregated at the interface between the silicon-containing active layer and the solid electrolyte interface”.

“The synergistic effects between these two materials lead to batteries that exceed the performance of each of the two components alone — an improvement that is a result of the high electrical conductivity and good energy storage capacity of tin,” said project leader Lorenzo Mangolini. “This can be achieved with the addition of even minor amounts of tin; as small as 2% by weight.”

Mangolini noted that the use of tin, rather than another conductive material such as carbon black, circumvents the low conductivity of silicon without decreasing energy storage. So in addition to tripling the charge capacity offered by graphite, the silicon-tin nanocomposite is extremely stable over many charge-discharge cycles, essentially extending its useful life. These features, coupled with a simple manufacturing process, could help the expansion of lithium-ion batteries for use in next-generation vehicles.

“Lithium-ion batteries are growing in popularity for electric vehicles and aerospace applications, but there is a clear need to alleviate range anxiety — the fear that a vehicle won’t have enough charge to reach its destination — before we will see large-scale adoption,” said Mangolini. “Any technology that can help is welcome, as long as it is simple and scalable, and our technology meets both those criteria.”

Image caption: The silicon-tin nanocomposite developed at UCR viewed by high-angle angular dark field imaging. The larger green particles are silicon and the smaller red particles are tin. Image credit: UC Riverside.