Sodium batteries are set to become an important component of energy systems, providing much of lithium’s power without the high price and environmental costs.
US researchers have made a solid-state, anode-free sodium battery, which promises higher levels of safety and lower costs than traditional batteries.
“Although there have been previous sodium, solid-state, and anode-free batteries, no one has been able to successfully combine these three ideas until now,” says Grayson Deysher, a PhD candidate at the University of California – San Diego, and first author of a paper published in Nature Energy.
The battery can be charged and discharged for 400 cycles without degrading.
Deysher has filed a patent application for the battery, along with senior author Professor Ying Shirley Meng from the University of Chicago.
Batteries typically contain an anode, which supplies electrons, and a cathode, which accepts them. The flow of electrons from anode to cathode, through a circuit, creates electricity. Batteries also need current collectors, which connect the anode and cathode with outer circuits, and electrolytes, which allow charged particles to flow through the interior of the battery.
It’s possible to make a battery without an anode, by storing charged particles directly on a current collector. This theoretically makes a battery that’s cheaper and more energy dense, since it contains fewer materials, but in reality it’s tricky to pull off.
“In any anode-free battery there needs to be good contact between the electrolyte and the current collector,” says Deysher.
“This is typically very easy when using a liquid electrolyte, as the liquid can flow everywhere and wet every surface. A solid electrolyte cannot do this.”
Unfortunately, anode-free batteries with liquid electrolytes tend to be very short lived, because the liquid reacts with other components of the battery and solidifies.
This team dodged the problem by using a current collector made from aluminium powder, which could flow around a solid electrolyte while the battery was being assembled.
This produced a stable, solid-state sodium battery, without the anode.
“Sodium solid-state batteries are usually seen as a far-off-in-the-future technology, but we hope that this paper can invigorate more push into the sodium area by demonstrating that it can indeed work well, even better than the lithium version in some cases,” says Deysher.
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