In some peoples’ opinion, electric cars won’t become truly viable until their batteries offer a lot more driving range, and can be recharged much more quickly than is currently possible. Well, those people may soon be getting their wish. Scientists at the University of Southern California have developed a new type of lithium-ion battery, that they claim holds three times as much energy as a conventional li-ion, and can be recharged in just ten minutes.
The battery was developed by a team led by Prof. Chongwu Zhou. Its secret is that it utilizes anodes made from porous silicon nanoparticles – anodes are the electrodes through which electrical current flows into a battery. Ordinarily, anodes in li-ion batteries are made from graphite.
Because silicon is relatively inexpensive and highly conductive, its use as an alternative anode material has been explored for some time now. Some of the previous efforts have involved constructing anodes made of layered silicon plates. Unfortunately, as those anodes swelled and shrunk during the charge/discharge process, the plates separated and the anodes ceased functioning.
Last year, however, Zhou had success using silicon nanowires. Only a few microns long and less than 100 nanometers in diameter, those wires were able to withstand the constant expansions and contractions. Additionally, their porous structure gave them a large surface area, which allowed lithium ions to travel through them much more quickly than would be possible with graphite. What’s more, they lasted for up to 2,000 recharging cycles, as compared graphite’s average of 500.
The nanowires had a downside, though: they’re not practical to manufacture on a commercial scale. Therefore, Zhou’s team proceeded to take commercially-available tiny silicon spheres (the nanoparticles), dope them with boron, and then etch pores into them, similar to those found on the nanowires. Anodes made from those particles offer charging performance on par with the nanowires, and can be made in any size – that in turn means that the silicon nanoparticle anodes could be used in any size of battery, usable in any type of device. We've inquired as to whether the ten-minute charging time refers to one specific size of battery, and are still waiting to hear back from USC.
Unfortunately, there still is one more “however.” The new anodes currently only last for about 200 recharge cycles. That said, Zhou is hoping that further developments will substantially increase that number. His team is also looking into new cathode materials, with the hope of developing batteries that discharge current as efficiently as the new anodes allow them to receive it.
He believes that such batteries should be commercially available within two to three years.
A paper on the research was recently published in the journal Nano Research.