A few weeks ago, Murali Ramasubramanian, Enovix co-founder and vice president of research and development, delivered the first public technical presentation of our 3D Silicon™ Lithium-ion Battery at the 2019 International Battery Seminar & Exhibit. Since then, we’ve had requests for copies of the presentation. While I can’t send everyone a copy, I can provide you with an overview of the presentation.
In the news release announcing the presentation, Murali said, “To date, small amounts of silicon have been added to predominantly graphite anodes in conventional lithium-ion battery architecture, but this has increased energy density only about 5%. Through innovative 3D cell architecture, Enovix has developed a lithium-ion battery that enables a high-capacity silicon anode to increase energy density by 30% to 80%, depending on cell size, while achieving a cycle life over 500.” Murali opened his presentation with the following slide.
Murali described key features of the Enovix 3D Silicon Lithium-ion Cells tested: a lithium-cobalt-oxide (LCO) cathode, a silicon anode, and standard electrolyte. The smart-watch size cells (26 mm x 20 mm x 3.4 mm) had a typical core energy density of 960 Wh/l with a capacity of 260 mAh and a packaged energy density of 530 Wh/l.
The graph at the bottom left shows cycle life performance of cells with these typical specifications. The graph shows that the cells achieved a median cycle life of about 600 to 20% fade or 80% capacity. The graph on the right shows the 1C charge (to 4.35 V) and 1C discharge (to 2.7 V) profile of a typical cell under test. Additional analysis confirmed that the present cell capacity fade is due to cathode impedance rise, not anode failure. Therefore, cell enhancements should resolve cathode impedance rise and enable greater than 1,000 cycle life in future generation cells.
In the next posts we’ll examine how our 3D Silicon Lithium-ion Cells have achieved a combination of increased energy density and high cycle life.