The lithium-ion (Li-ion) battery that we curse under our breath every time we find ourselves needing to charge our smart phones may become less a target of our wrath in the near future.
Researchers at Purdue University have developed a new material made from tin-oxide nanoparticles that could reduce the charge time for a Li-ion battery from hours down to minutes.
In research published in the journal Advanced Energy Materials, the Purdue researchers developed an anode that used tin-oxide nanoparticles in place of graphite to nearly double the theoretical charging capacity of graphite, which is now limited to 372 milliamp hours per gram (mAh/g).
The researchers demonstrated that the resulting tin-oxide nanoparticle anode could be charged in 30 minutes and still have a capacity of 430 mAh/g, which is higher than the theoretical maximum of a graphite anode that has been charged for 10 hours.
Perhaps the most attractive aspect of the material is that the researchers claim that it is fairly straightforward to produce the “ordered network” of interconnected tin oxide nanoparticles for the anode,so commercial manufacturing could be relatively easy. The process involves simply adding a tin alkoxide precursor into boiling water and then following that with heating the nanoparticle to 400 degrees Celsius.
"We are not using any sophisticated chemistry here," said Vilas Pol, an associate professor of chemical engineering at Purdue University, in a press release. "This is very straightforward rapid 'cooking' of a metal-organic precursor in boiling water. The precursor compound is a solid tin alkoxide – a material analogous to cost-efficient and broadly available titanium alkoxides.”
It is the heat treatment to 400 degrees Celsius that leads the nanoparticles to self assemble into a network structure that contains pores allowing the material to expand and contract during charge-discharge cycles.
"These spaces are very important for this architecture," said Purdue postdoctoral research associate, Vinodkumar Etacheri, in the press release. "Without the proper pore size, and interconnection between individual tin oxide nanoparticles, the battery fails."
For years, researchers have been trying to replace the graphite on anodes with nanostructured silicon, after it was determined that silicon without special treatment would begin to crack and break after a few charge-discharge cycles despite it increasing the capacity by a factor of ten. The nanostructured silicon improved the ability of the material to withstand the expanding and contracting, but it never really reached the ability of graphite.
The researchers report that the new tin-oxide nanoparticle network was tested through 100 charge-discharge cycles. If they can increase the tests to over 6000 cycles, a point at which nanostructured silicon was able to maintain 85 percent of its original capacity, then we may see this new approach take on more interest in the research community than nanostructured silicon. It certainly seems to be easier to produce.
Dexter Johnson is a contributing editor at IEEE Spectrum, with a focus on nanotechnology.