Amprius's Silicon Nanowire Batteries Seek Faster Manufacturing Processes For Lower Price

Nowadays, batteries are hardly meeting the normal consumer’s demand regarding their capacity and lifetime. Complaints about laptops whose charge lasts too little, or about electric cars not being able to charge as quick and last as long as gasoline are frequent. Amprius, a US-based company, addresses these issues and develops a battery that they say it can hold double the charge of regular lithium ion batteries.

Amprius’s approach is based on research performed by Stanford University’s Yi Cui. In 2007, he discovered that he could replace a battery’s carbon cathode with nanostructured silicon films, and that these can store twice the energy that carbon electrodes, otherwise used in today’s batteries, can. Devices using them could run 40 percent longer.

Silicon had been previously proposed for use as battery cathode, but it had one issue: it cracked. Cui’s silicon nanowires, on the other hand, didn’t have this problem. Lithium coming from the battery’s anode has to be stored completely in the cathode during charge. While the battery discharges, the reverse phenomenon happens, giving birth to a flow of electrons through the circuit (payload). Though, because the silicon nanowire approach didn’t have enough mechanical endurance, the Amprius researchers reinforced the nanowires with metal cores, just like the steel struts reinforce concrete in buildings.

Now, three years after the first theoretical and practical birth time of silicon nanowire batteries, Amprius is thinking of manufacturing processes that are suitable for mass production. Kang Sun, CEO, says: “We are in a hurry, because electrification is moving forward faster than anyone thought,” he says. Sun, the former president of Chinese solar manufacturer JA Solar, notes that there are already about 80 electric-vehicle makers in China. “We have to be fast,” he says. The company expects to disclose some automaker partnerships in the next few months.

The company’s researchers now study how to develop roll-to-roll manufacturing processes for their silicon nanowire batteries, similar to those used in carbon-based cathodes, for making their technology as cheap as possible. However, the increased energy storage will compensate the eventual high price.

The technical side also has issues to be solved, for the batteries to be a serious contender for use in electric cars. For the moment, they have only been tested and lasted at their full capacity for about 250 charge/discharge cycles. The electric vehicle industry demands that a battery should be able to last for at least 3,000 cycles (11 years, if we count one charge a day), says Ryan Kottenstette, the company’s director of business development.

As we see from above, even one of the most involved companies in the battery industry says it’s a matter of short time until we will replace gasoline cars with electrics, not to mention the latest trend of every car manufacturer in the world. The disputed dream of electrification is not so far away, after all…

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