Dr. Ionel Stefan

CTO, Amprius Technologies


Dr. Ionel Stefan is Amprius’ Chief Technology Officer. He joined Amprius in its very early days in 2009 as a Senior Scientist, initially to lead electrochemistry for silicon nanowire anode-based lithium-ion batteries. Dr. Stefan now leads Amprius' development of silicon nanowire electrochemistry, cell technology --including material design, cell design and engineering -- and product development. At Amprius, he has served as Principal Investigator on multiple projects, including NASA, Army, DOE and USABC-funded research and development efforts.

Dr. Ionel Stefan received his Ph.D in Chemistry from Case Western Reserve University(2002) with research activities focused on the development of new materials and devices for energy production and storage. He was a Postdoctoral Fellow at Lawrence Berkeley National Laboratory, developing high temperature solid oxide fuel cells. Later, at Nanosys, he became familiar with silicon nanowire materials and developed methanol fuel cells with catalysts supported on nanowire electrodes. At Nanosys, Ionel began developing silicon anodes for lithium-ionbatteries. At Amprius since 2009, he leads development of materials and electrochemistry for silicon anode-based cells and products.


High Energy Density Lithium-Ion Cells with Silicon Nanowire AnodeTechnology

Amprius is continually improving its cell designs with silicon nanowire anode that have enabled lithium-ion batteries with energy density and specific energy performance that exceed current state of the art graphite cells by 30-80%,depending on cell size and form factor. Amprius products have shown tha tsilicon anode-based batteries can reach 1,300 Wh/L and 500 Wh/Kg while maintaining a cycle life compatible with aerospace, military and other high-end applications. Moreover, the open nanowire structure enables cells to function at high rates of charge and discharge without overheating, achieving 1500 W/kg power density in cells with over 400 Wh/kg specific energy density. Recent cell design optimization has substantially improved resilience to thermal runaway conditions, such as internal short circuit and nail penetration.


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