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New Graphite Nanowire Batteries By Amprius, Having More Energy Than Tesla Model 3 Cells

Amprius claims it has created a lithium battery with a silicon nanowire anode that contains 73% more energy than the cells of the Tesla Model 3, with 37% less volume.
Tesla Model 3, Courtesy of Tesla Inc.

California based company Amprius just announced it has already been able to manufacture the first batch of what it claims are the lithium battery cells with the “highest energy density available today”. The use of its own silicon nanowire anode technology resulted in cells capable of storing 73% more energy than Tesla Model 3 cells and occupying 37% less volume.

Tesla Model 3, Courtesy of Tesla Inc.

Amprius has resorted to a "weighty argument" to visualize its new state-of-the-art battery cells: compare them with those in the best-selling - and probably best-known worldwide - electric car, the Tesla Model 3. As published by Enpower, and referring to the first “battery day” held by Tesla back in September 2020, the Model 3 battery cells have an energy density of around 260 Wh/kg and 730 Wh/l.

The new Amprius cells represent a significant advance in this field, both in terms of specific energy and energy density, since they claim they are capable of reaching 450 Wh/kg and 1,150 Wh/l. According to the company, these are the cells it has just delivered, in an unspecified number, to "an aerospace industry leader," giving it bragging rights for offering "the highest energy density cells available in the industry" as of today.

This impressive performance is due to its silicon nanowire anode technology, as per their explanation: when a lithium-ion battery is charged, an electron is removed from each lithium atom on the cathode by moving to the anode through external wiring, since electrons cannot pass through the electrolyte or the separator that is placed between the electrodes. Its negative charge draws positively charged lithium ions through the electrolyte and separator, where each finds an electron and embeds itself in a lattice at the anode, that is usually made of graphite.

Tesla Charger, courtesy of Tesla Inc.

Amprius has replaced that graphite network-lattice with silicon nanowires. Silicon can store about 10 times more lithium than graphite, but it tends to swell and crack, drastically reducing cell life. But when the silicon is transformed into porous nanowires, arranged like a kind of forest of longer wires with shorter wires in between, the silicon is able to tolerate the swelling and can better resist cracking. This extends the useful life of the cell to such an extent that silicon anodes can become a competitive technology.

Silicon nanowires are rooted directly into the anode substrate, so the conductivity (and thus the power it can deliver) is high. Lifespan is "excellent" and "continually improving" according to the company, though Amprius doesn't specify a number of charge/discharge cycles or degradation over time. Another advantage they mention is the fact that this is the only part of the battery that is different from conventional lithium batteries, so the rest can be produced using existing manufacturing methods, components and processes.

Energy density and specific energy are just two metrics to judge a battery capacity. Other parameters such as thermal performance, safety, charge and discharge rates, life cycle and of course the cost of production play an important role in the industrialization and commercialization of battery technology. The fact that Amprius's first customer is in the advanced aerospace and satellite manufacturing field suggests that, at least for now, they won't be very competitive on price; as is, on the contrary, the case with Tesla and the current Model 3 cells (not to mention upcoming 4680 cells).

Tesla Model 3, courtesy of Tesla Inc.Amprius is selecting the location where it will begin building a mass production facility for these cells, with the aim of generating economies of scale that hopefully will make this technology relevant – and competitive - in the electric vehicle market.

You can check more details directly from the source, on this link.

All images courtesy of Tesla Inc.

Nico Caballero is the VP of Finance of Cogency Power, specializing in solar energy. He also holds a Diploma in Electric Cars from Delft University of Technology in the Netherlands, and enjoys doing research about Tesla and EV batteries. He can be reached at @NicoTorqueNews on Twitter. Nico covers Tesla and electric vehicle latest happenings at Torque News.

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