The nanochain structure is the black material on the copper electrode of this coin cell. Photo: Purdue University image/Kayla Wiles.
The nanochain structure is the black material on the copper electrode of this coin cell. Photo: Purdue University image/Kayla Wiles.

How long the battery of your phone or computer lasts depends on how many lithium ions can be stored in the battery's negative electrode material. If the battery runs out of these ions, it can't generate an electrical current to run a device and ultimately fails. But materials with a high lithium ion storage capacity are either too heavy or the wrong shape to replace graphite, the electrode material used in today's batteries.

Now, scientists at Purdue University have revealed a potential way to restructure these materials into a new electrode design that could increase a battery's lifespan, make it more stable and shorten its charging time. The study, reported in a paper in ACS Applied Nano Materials, created a net-like structure, called a ‘nanochain’, of antimony, a metalloid known to enhance lithium-ion charge capacity in batteries.

The researchers compared the nanochain electrodes with graphite electrodes, finding that when coin cell batteries with the nanochain electrode were charged for just 30 minutes, they achieved double the lithium-ion capacity over 100 charge-discharge cycles.

Some types of commercial batteries already use carbon-metal composites similar to antimony-metal negative electrodes, but the composite tends to expand by up to three times as it takes in lithium ions, causing it to become a safety hazard as the battery charges.

"You want to accommodate that type of expansion in your smartphone batteries. That way you're not carrying around something unsafe," said Vilas Pol, a Purdue associate professor of chemical engineering.

By applying two different chemical compounds – a reducing agent and a nucleating agent – the Purdue scientists connected the tiny antimony particles into a nanochain shape that would accommodate the required expansion. The particular reducing agent the team used, ammonia borane, is responsible for creating the empty spaces – the pores inside the nanochain – that accommodate expansion and suppress electrode failure.

The team applied ammonia borane to several different compounds of antimony, finding that only antimony chloride produced the desired nanochain structure. "Our procedure to make the nanoparticles consistently provides the chain structures," said Veeraraghavan Ramachandran, a professor of organic chemistry at Purdue.

The nanochain also keeps lithium-ion capacity stable for at least 100 charging-discharging cycles. "There's essentially no change from cycle 1 to cycle 100, so we have no reason to think that cycle 102 won't be the same," Pol said.

Henry Hamann, a chemistry graduate student at Purdue, synthesized the antimony nanochain structure, while Jassiel Rodriguez, a Purdue chemical engineering postdoctoral candidate, tested the electrochemical battery performance.

The electrode design has the potential to be scalable for larger batteries, the researchers say, and they next plan to test the design in pouch cell batteries.

This story is adapted from material from Purdue University, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.