Rechargeable lithium-ion batteries are basically everywhere, powering everything from smartphones to notebooks, earbuds to gaming devices, and so much more.
But while the convenience of this ubiquitous (and Nobel Prize-winning) battery chemistry has radically changed the way we use and charge portable technology, lithium-ion is far from perfect.
The performance of lithium-ion batteries degrades over time, and sometimes flaws in the battery cells can lead to overheating and dangerous fire hazards – with companies sometimes having to issue urgent recalls for products that can explode without warning.
And as anybody who owns a smartphone, tablet, or laptop can attest, charging up lithium-ion batteries can be a slow and time-consuming process. On that front, scientists have some good news to report.
Researchers in Russia have developed a new type of battery technology that they say can charge approximately 10 times faster than existing lithium-ion batteries – a speed-up that could offer huge time-saving advantages if it got rolled out in everyday devices.
“A battery manufactured using our polymer will charge in seconds – about 10 times faster than a traditional lithium-ion battery,” says electrochemistry researcher Oleg Levin from St Petersburg University. “This has already been demonstrated through a series of experiments.”
The key to the new batteries is a kind of nitroxyl-based redox polymer, a material that can undergo reversible oxidation (loss of electrons) and reduction (gain of electrons) when it discharges and charges.
In this case, the redox polymer used is a synthesized form of NiSalen (nickel-salen), a metal-containing metallopolymer, in which chains of nickel and salen atoms act as molecular wires to boost electron conductivity, which is a limitation of nitroxyl-based polymer batteries.
“In nitroxyl‐based polymers the only charge‐transport pathway is electron hopping between adjacent redox centers, which is fast on the microscopic scale,” the researchers explain in their study.
“Despite this, the macroscopic electron conductivity of nitroxyl‐based material appears to be very low.”
In testing, the researchers explored a number of different polymer types, but the NiSalen chemistry was the only device that turned out to be stable and efficient, thanks to the way the nickel and salen structures worked as a conductive backbone. The structures simultaneously acted as a charge collector for nitroxyl pendants while also supporting the redox capacity of the substance.
The device also works well in low temperatures, which isn’t something that can be said for temperature-sensitive lithium-ion batteries. Not that the speedy NiSalen is necessarily perfect in all areas just yet, however.
“At this stage, it is still lagging behind in terms of capacity – 30 to 40 percent lower than in lithium-ion batteries,” Levin says.
“We are currently working to improve this indicator while maintaining the charge-discharge rate.”
Theoretically, nitroxyl‐based polymers should ultimately offer good capacitive potential, so it may just be a matter of time before the team figures out how to tweak the battery so that it offers good charging headroom in addition to attractive conductivity.
Here’s hoping, because in addition to the charging gains, there are other significant advantages this kind of battery could also deliver.
“It is safe to use – there is nothing that may pose a combustion hazard, unlike the cobalt-based batteries [including lithium-ion batteries] that are widespread today,” Levin says.
“It also contains significantly less metals that can cause environmental harm. Nickel is present in our polymer in a small amount, but there is much less of it than in lithium-ion batteries.”
The findings are reported in Batteries and Supercaps.