Silicon "sandwiches" make for lightweight, high-capacity batteries
The pursuit of better batteries means the exploration of alternative materials, and one that scientists see a lot of promise in is silicon. A team at Clemson University has come up with a new design that overcomes some of the problems with incorporating this material into lithium-ion batteries, enabling them to demonstrate a lightweight and multipurpose device that could be used to power satellites and spacesuits.
Scientists have been investigating the potential of silicon in lithium-ion batteries for a long time, and with good reason. Using the material for the anode component instead of the graphite used today could increase the storage capacity of these devices by as much as 10 times, but there are a few kinks to iron out first.
Silicon doesn’t exhibit the same durability as graphite in these scenarios, tending to expand, contract and break apart into small pieces as the battery is charged and discharged. This causes the deterioration of the anode and failure of the battery, but we have seen a number of potential solutions to this over the years, including fashioning the silicon into sponge-like nanofibers or tiny nanospheres before integrating them into the device.
The new research out of Clemson University looks to shore up the dependability of silicon with the help of carbon nanotube sheets called Buckypaper, which we’ve also seen used in the development of next-generation heat shields for aircraft. These sheets were paired with tiny, nanosized silicon particles in what the team says is an arrangement much like a deck of cards, with the silicon particles sandwiched in between each layer.
“The freestanding sheets of carbon nanotubes keep the silicon nanoparticles electrically connected with each other,” says Shailendra Chiluwal, first author on the study. “These nanotubes form a quasi-three-dimensional structure, hold silicon nanoparticles together even after 500 cycles, and mitigate electrical resistance arising from the breaking of nanoparticles.”
The beauty of this approach, according to the team, is that even if the charging and discharging of the battery causes the silicon particles to break apart, they remain locked inside the sandwich and able to perform their function. This means that, theoretically, this functioning but experimental battery has a much higher capacity, which means the energy can be stored in much lighter cells, reducing the overall weight of the device.
As a bonus, the use of the nanotubes creates a buffer mechanism that enables the batteries to be charged at four times the speed of current iterations, according to the scientists. These lightweight, fast-charging batteries with high capacity could find a multitude of uses, including electric vehicles, but space is an area where the team sees real potential, with part of the funding for the project coming from NASA.
“Most satellites mainly get their power from the Sun,” says study author Ramakrishna Podila. “But the satellites have to be able to store energy for when they are in the Earth’s shadow. We have to make the batteries as light as possible, because the more the satellite weighs, the more its mission costs.”
Other possibilities include power systems for spacesuits and Mars rovers, the researchers say. They are now working with industry partners with a view to taking this technology out of the lab and into the real world.
The research was published in the journal Applied Materials and Interfaces.
Source: Clemson University
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