Last week was a busy one for two of our leading scientists-technologists. On Monday, October 10, Michael Armstrong, Enovix Fellow, spoke at the 242nd Electrochemical Society Meeting in Atlanta, Georgia. Two days later, on Wednesday, October 12, Ashok Lahiri, Enovix Co-Founder and CTO, spoke at the 12th Annual Battery Safety Summit in Tysons Corner, Virginia.
Michael presented an overview of Enovix battery architecture, “Designing High Energy Density Batteries for Abuse Tolerance.” It described how our 3D architecture uniquely enables BrakeFlow™ technology — an intra-cell system that significantly improves tolerance against thermal runaway from an internal short circuit without compromising high energy density.
Ashok’s presentation, “Enovix 100% Active Silicon Anode Battery,” describes how Enovix has overcome the challenges of a 100% active silicon anode — such as volume expansion, formation lithium loss, and break-up of silicon during cycling — to produce a high-energy lithium-ion (Li-ion) battery that retains high cycle life. He also described how BrakeFlow is a safety feature that complements the increased energy of our 100% active silicon anode.
With conventional Li-ion wound cell architecture, energy density and safety can be in conflict. Battery designers have found that when they try to improve energy density they compromise safety, and vice versa. This balancing act has meant the progress on each front has been slow and fraught with problems. Enovix 3D cell architecture upends the conventional paradigm and enables both a step-change increase in energy density and an unprecedented level of abuse tolerance to reduce the risks of an internal short circuit leading to thermal runaway.
Both Mike and Ashok presented how our 3D cell architecture incorporates multiple parallel cell-to-busbar connections, as illustrated above. The enables implementation of BrakeFlow — a system with a resistor of set value at the busbar junction. Under normal operation, each electrode carries a small current that results in negligible energy loss. In the event of an internal short circuit, BrakeFlow regulates current flux from other areas of the cell to the short, which limits overheating in the shorted area and inhibits thermal runaway.
As a result, BrakeFlow:
· limits the peak current of the short to prevent instantaneous ignition
· reduces the current of the short to reduce overall temperature rise
· improves heat transfer from the cell core to the package surface, which conducts electrical heat, due to the short, away from the source location to the pouch surface
· subdivides the cell into small capacity zones that can be regulated during a short
· allows the cell to completely discharge and remain in a discharged state
Nail penetration is a common method used to induce an internal short circuit in a Li-ion cell. Both presentations described and demonstrated the stringent requirements of our nail-penetration tests.
Learn more about how BrakeFlow works, and view a video of our nail-penetration test here.