Look to silicon nanotubes for really long lasting batteries

How many of us have gone through numerous batteries for our laptops, because over time aging batteries start to lose their ability to charge? Yep, me too. Well, Stanford’s materials scientist Yi Cui, who founded startup Amprius, is working on a lithium ion battery that could last for 6,000 charge and discharge cycles without degrading below 85 percent, according to some of Cui’s latest research (hat tip IEEE). For comparison, a lithium ion battery in your Mac laptop goes for about 1,000 charge and discharge cycles before it starts to only be able to hold 80 percent of the charge.

Cui’s latest breakthrough is to use silicon nanotubes coated with silicon oxide shells for the anode part of the battery. A battery is made up of an anode on one side and a cathode on the other, with an electrolyte in between. For a lithium ion battery, lithium ions travel from the anode to the cathode through the electrolyte, creating a chemical reaction that allows electrons to be harvested along the way.

The silicon oxide coating stops the silicon nanotube from expanding, keeping it away from the electrolyte, and enabling the battery to have more cycles. Most anodes are made of graphite, but silicon has a much higher capacity to store a charge. However, silicon anodes tend to break down or have a small cycle life because of that expansion characteristic. Stanford’s SLAC group explains how this works in more detail.

The IEEE points out that this jump in cycle life probably isn’t such a breakthrough for the electric car industry, as other types of batteries can lead to tens of thousands of cycles for the future of next-generation electric car batteries.

Amprius is a Valley startup that has been developing technology that can shrink the anode roughly fourfold from today’s carbon-based anode material technology, CEO Kang Sun told us a couple years ago in an interview. That could allow a fourfold increase in energy density if concurrent improvements in cathode technology can keep up, which is an uncertain prospect, to be sure. Last year Amprius raised a $25 million Series B investment to help it move toward its first commercial product, likely for the consumer electronics market. The round was led by Kleiner Perkins, Chinese firms IPV Capital and Qian Neng Fund, and Google’s (s goog) former CEO Eric Schmidt, VantagePoint Venture Partners, Trident Capital and Stanford University.