IEEE Spectrum recently published an article, “How to Build a Safer, More Energy-Dense Lithium-ion Battery,” authored by Ashok Lahiri, Nirav Shah, and Cam Dales of Enovix. It describes how our patented 3D cell architecture and silicon wafer production produces a lithium-ion battery with increased energy density and improved safety.

I’ll be serializing key parts of the article over the next few posts. Following is the first excerpt from the IEEE Spectrum article regarding the genesis of our company and our patented 3D cell architecture.

Microelectromechanical systems (MEMS) fabricated in three dimensions with photolithography, provided the model for the research that one of us (Lahiri) and two other cofounders of our company began in 2007. We already had experience in developing such MEMS designs—initially for use in high-density disk-drive read-write heads, then for testing semiconductor wafers.

That collaboration resulted in the founding of Enovix Corp. (originally called microAzure Corp.) and the initial funding of the company by several Silicon Valley venture capital firms. The company’s first goal was to conduct proof-of-concept research on a lithium-ion rechargeable battery that used silicon in place of the usual graphite for the anode. By 2012, the company was producing cells that had had a much higher energy density than conventional Li-ion cells of comparable size. Enovix then began to develop a low-cost high-volume production system, with the help of strategic investors Cypress Semiconductor, Intel Capital, and Qualcomm Ventures.

Cypress Semiconductor had previously helped its SunPower subsidiary produce high-performance solar cells at a much lower cost and at a higher volume than could be done by other companies with their complex, multistep processes. Since 2014, Enovix has been developing and refining methods to construct its battery, based on SunPower’s production techniques. We expect to begin scaling up production for commercialization later this year.

The Enovix battery uses a three-dimensional cell architecture in which the electrodes are etched into a silicon wafer and the plated metal current collectors that are much thinner than the foil used in conventional cells. By interlacing a cathode, an anode and a separator on the 1-millimeter thick wafer, it significantly reduces wasted space. In our battery, a full 75 percent of the volume is dedicated to storing energy. This alone increases capacity by about 25 percent over conventional cells. Similarly, the weight goes down proportionally for a battery of a given capacity, although typically volume is the more critical constraint in mobile devices.

 

Densely Packed: The 3D cell architecture orients and interlaces a cathode, 100 percent silicon anode, and ceramic separator in a thin (1 millimeter) flat plane, which significantly improves energy density and safety.

Illustration: Jean-Luc Fortier

The next excerpt will describe how our 3D cell architecture enables use of a 100% silicon anode.