Countless researchers are working to create more energy dense and scalable lithium-ion batteries as the market demands powerful electronic devices and electric vehicles. A team from the University of California, Riverside (UC Riverside) has developed a paper-like silicon material that could help create more efficient batteries by replacing graphite, which is typically used in anodes.
Silicon has almost ten times the electrical charge that graphite has per weight, but its dramatic volume expansion degrades a battery. The UC Riverside team’s material addresses this problem and allows a battery to be used for hundreds of cycles without suffering extensive degradation. The new sponge-like material is made of silicon nanofibers that are 100 times thinner than human hair. It has potential for improving specific energy—the amount of energy that can be delivered per unit weight of battery.
The new material also solves a longstanding problem of scalability with binderless electrodes. The team was able to produce several grams of silicon nanofibers at a time, which is huge compared to conventional techniques which produce micrograms. They produced the nanofiber material using a technique called electrospinning. The process starts with 20,000-40,000 volts of power being applied between a rotating drum and a nozzle emitting a solution made up of tetraethyl orthosilicate, a chemical compound frequently used in the semiconductor industry. Then the nanofibers are exposed to magnesium vapor to produce the sponge-like structure.
The details of the project are described in Nature Scientific Reports, in a paper authored by husband and wife duo Mihri and Cengiz Ozkan and six of their graduate students. Looking ahead, the UC Riverside researchers will work on potential electric vehicle applications using the silicon nanofibers in a larger-scale pouch cell format lithium-ion battery.