Enovix Corporation, the developer of 3D Silicon Lithium-ion batteries (earlier post), announced BrakeFlow technology, an intra-cell system that significantly increases tolerance against thermal runaway from internal shorts, without compromising high energy density.

Enovix’ 3D cell architecture vertically stacks high-capacity silicon anodes, cathodes, and separators in an inherently flat structure. Unlike the horizontally wound structure of a conventional lithium-ion cell, 3D architecture allows for an integrated stainless-steel constraint to apply stack pressure and maintain silicon particle connection for uniform discharge. The result is both a significant increase in energy density and high cycle life.

This 3D cell architecture enables multiple parallel cell-to-busbar connections. This, in turn, uniquely enables BrakeFlow—which includes a resistor with a set value—at the busbar junction.

Under normal operation, each electrode carries a small current which results in negligible energy loss. In the event of an internal short, BrakeFlow regulates current flux from other areas of the battery to the short, thus limiting the short area from overheating and inhibiting thermal runaway

When we founded Enovix in 2007, our approach to improving cell performance was unique from other advanced battery technology companies. Solving a big problem differently than others is inherently challenging and creates unique issues. At the same time, it avoids problems others face and enables new opportunities others can’t exploit or even imagine. Today’s announcement is a momentous day for Enovix. It’s a great example of how taking a different approach can lead to game-changing technology.

—Harrold Rust, Co-Founder, President and CEO of Enovix

We believe our battery architecture is one of the most significant advancements in Li-ion battery design in decades. Not only does our architecture enable a 100 percent active silicon anode, which notably increases energy density, but also enables us to launch new innovations like BrakeFlow, which by design, reduces the temperature rise at a short location, adding exceptional tolerance against thermal runaway.

—Ashok Lahiri, Co-Founder and CTO of Enovix

Unlike conventional “jellyroll” Li-ion cell architecture, where energy density and safety can be in conflict, the Enovix 3D cell architecture incorporates multiple intra-cell features to improve electrical, physical and environmental abuse tolerance over conventional wound Li-ion cells. In addition to BrakeFlow, the Enovix cell architecture:

• Provides better Lithium Plating Protection over graphite anode cells due to a 100% active silicon anode (140mV higher lithiation potential);

• Enables hotspot reduction and heat dissipation due to excellent thermal conductivity (nearly 5X cell thermal conductivity compared to similar pouch cells);

• Includes enhanced protection from physical abuse, including crush, pinch and nail penetration due to its mechanical internal constraint system; and

• Is designed to limit movement of the anode, cathode and separator due to internal “pinning,” which is a known source of internal shorting in conventional Li-ion batteries.

BrakeFlow technology will become part of the company’s automatic tooling and production set at its Fremont factory, Fab-1. The company anticipates BrakeFlow will be available in its battery cells in 2023.