Lithium Ion Battery Technology
Lithium ion batteries have been iteratively improved on over the last 25 years. However, promising new chemistries that would further improve gains in energy and power density have proved impractical due to safety concerns or performance degradation. For example, sulfur based cathodes allow for much higher energy density, but they degrade over time. A silicon anode would also allow for a much higher energy density, but silicon expands when charged which causes cracking and breakdown of anode. Our approach consists of leveraging proprietary advances in carbon nanotubes and semi-conductor manufacturing techniques to enable the use of next generation lithium ion battery chemistries such as the silicon/sulfur-based batteries previously mentioned.
We use a vertically organized array of carbon nanotubes (VACNTs) coated with active material instead of a matrix of carbon additive and binder mixed in with conventional active materials. This provides a larger surface area of active materials, reliable electrical conductivity and better electrolyte access. In addition, the strength and porosity of the carbon nanotubes can accommodate the volume change of silicon during cycling, preventing cracking and breaking down of the anode. The dense growth and regular tight packing of carbon nanotubes also allow polysulfides to be retained during cycling and significantly improve the cycle life of the sulfur-based cathode. By creating a 3D zig-zag pattern of VACNTs, the anode and cathode can be integrated. This 3D “interleaved” architecture is designed so that the distance between the anode and the cathode is minimized, allowing for maximum power at very high energy density.