Researchers at the University of California, Riverside’s Bourns College of Engineering have developed a novel paper-like material for lithium-ion batteries. It has the potential to boost by several times the specific energy, or amount of energy that can be delivered per unit weight of the battery.
This paper-like material is composed of sponge-like silicon nanofibers more than 100 times thinner than human hair. It could be used in batteries for electric vehicles and personal electronics.
The nanofibers were produced using a technique known as electrospinning, whereby 20,000 to 40,000 volts are applied between a rotating drum and a nozzle, which emits a solution composed mainly of tetraethyl orthosilicate (TEOS), a chemical compound frequently used in the semiconductor industry. The nanofibers are then exposed to magnesium vapor to produce the sponge-like silicon fiber structure.
Silicon is widely considered as the successor to graphite-based anodes for Li-ion batteries given its highest theoretical capacity among known materials of 3579 mAh g−1, which corresponds to an ambient temperature formation of Li15Si4.
Researchers report the first synthesis of a binderless free-standing Si nanofiber (SiNF) paper with a Si weight percent in excess of 80% for application as Li-ion battery anodes, which forgoes the need for inactive polymer binders or metallic current collectors.
(a) Schematic representation of the electrospinning process and subsequent reduction process. Digital photographs of (b) as-spun SiO2 NF paper, (c) etched SiNF paper, and (d) C-coated SiNF paper as used in the Li-ion half-cell configuration.