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Graphene and Silicon 'Sawdust' Could Make Better Batteries

Category: Science & Technology
Posted: 08:01AM

Batteries are an integral part of many modern technologies, especially those that use lithium ions for storing energy. Typically these batteries use a graphite anode but for some time researchers have been trying to build silicon anodes, which offer greater energy storage, but they have significant resiliency problems. Now researchers at SLAC National Accelerator Laboratory and Stanford University have found a way to make viable silicon anodes with the help of graphene.

Batteries work by moving ions between the anode and the cathode, and charging involves the ions entering the anode. A silicon anode in a lithium-ion battery could hold ten times the energy of a graphite anode, but silicon swells when it absorbs the ions, and this swelling can cause it to break and the battery to fail. To One way to address this issue is to work with silicon particles so small that the swelling does not matter, but previous attempts tended to be inefficient. This new design though works a bit differently as it places the silicon particles inside of graphene cages. Graphene is an atom-thick sheet of carbon that is very strong, flexible, and conductive, and it actually improves the conductivity of the silicon particles. To create the cages, the researchers start with the silicon particles and coat them with a layer of nickel. The nickel then acts as a catalyst to grow the graphene on top of, and the nickel can then be etched away to leave the particle plenty of room to swell without damage.

Just as important as the viability of a silicon anode is that the silicon particles can be micrometers in width, which are much easier and cheaper to produce than smaller nanostructures. In fact, silicon particles microns in width are a waste product to the milling of silicon for computer chips, like sawdust is for cutting wood.

Source: SLAC National Accelerator Laboratory

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