University of California, Irvine researchers have invented nanowire-based battery material that can be recharged hundreds of thousands of times, moving us closer to a battery that would never require replacement. The breakthrough work could lead to commercial batteries with greatly lengthened lifespans for computers, smartphones, appliances, cars and spacecraft.
Scientists have long sought to use nanowires in batteries. Thousands of times thinner than a human hair, they're highly conductive and feature a large surface area for the storage and transfer of electrons. However, these filaments are extremely fragile and don't hold up well to repeated discharging and recharging, or cycling. In a typical lithium-ion battery, they expand and grow brittle, which leads to cracking.
UCI researchers have solved this problem by coating a gold nanowire in a manganese dioxide shell and encasing the assembly in an electrolyte made of a Plexiglas-like gel. The combination is reliable and resistant to failure.
The study leader, UCI doctoral candidate Mya Le Thai, cycled the testing electrode up to 200,000 times over three months without detecting any loss of capacity or power and without fracturing any nanowires. The findings were published today in the American Chemical Society's Energy Letters.
Hard work combined with serendipity paid off in this case, according to senior author Reginald Penner.
"Mya was playing around, and she coated this whole thing with a very thin gel layer and started to cycle it," said Penner, chair of UCI's chemistry department. "She discovered that just by using this gel, she could cycle it hundreds of thousands of times without losing any capacity."
"That was crazy," he added, "because these things typically die in dramatic fashion after 5,000 or 6,000 or 7,000 cycles at most."
The researchers think the goo plasticizes the metal oxide in the battery and gives it flexibility, preventing cracking.
"The coated electrode holds its shape much better, making it a more reliable option," Thai said. "This research proves that a nanowire-based battery electrode can have a long lifetime and that we can make these kinds of batteries a reality."
ABSTRACT: We demonstrate reversible cycle stability for up to 200 000 cycles with 94−96% average Coulombic
efficiency for symmetrical δ-MnO2 nanowire capacitors operating across a 1.2 V voltage window in a poly(methyl
methacrylate) (PMMA) gel electrolyte. The nanowires investigated here have a Au@δ-MnO2 core@shell architecture in
which a central gold nanowire current collector is surrounded by an electrodeposited layer of δ-MnO2 that has a thickness
of between 143 and 300 nm. Identical capacitors operating in the absence of PMMA (propylene carbonate (PC), 1.0 M
LiClO4) show dramatically reduced cycle stabilities ranging from 2000 to 8000 cycles. In the liquid PC electrolyte, the δ-
MnO2 shell fractures, delaminates, and separates from the gold nanowire current collector. These deleterious processes are
not observed in the PMMA electrolyte.
JI_Joe84 wrote:Sweet but I see they need gold and magnesium to make it. Not the most plentiful of materials there. Hhmmm better keep looking
Gold is actually not *that* uncommon, it's just that people tend to think of it more as a precious metal and only as an industrial resource second. Dunno about magnesium. If you want to talk rarity, lithium is more of a pain in the ass.
Magnesium is plentiful and cheap. They make engine blocks and structural frames out of it, and it costs slightly more than aluminum.
It is completely unrelated to Manganese, atomic symbol Mn... which is also plentiful and cheap and costs slightly more than aluminum, but would make a lousy engine block. Manganese is the element described in the paper.
It would depend on just how much gold we are talking about. The stuff on connectors is actually very thin gold, there just enough to prevent corrosion and other stuff.
Credo!
Chat with me on Skype if you want to talk about writing, ideas or if you want a test-reader! PM for address.
Lithium Ion still has a long way to evolve, and Sodium-Ion is unlikely to match it. Its not really competing technology, sodium batteries main point is to be cheaper then lithium but better then lead acid batteries, while nanowire batteries and many other technologies are trying to make us batteries outright far superior to the best conventionally arranged lithium-ion cells. Nanowires are aimed at laptop batteries more or less, while sodium would be useful for a car starter battery or grid energy storage.
"This cult of special forces is as sensible as to form a Royal Corps of Tree Climbers and say that no soldier who does not wear its green hat with a bunch of oak leaves stuck in it should be expected to climb a tree"
— Field Marshal William Slim 1956
