Toray Industries non-porous separators could increase the capacity of li-ion batteries and enhance the safety of the batteries in wearable electronic devices and electronic vehicles, Electronics Weekly reported.

As the lithium battery market continues to expand there is a need to lift their capacity and energy density. Lithium metal anode batteries with their high theoretical capacity and low redox potential is now getting attention. “This anode has not seen practical use, however, as lithium dendrites form on lithium metal surfaces during charging, penetrating separators and causing short circuits that deteriorate safety. Lithium dendrites form along the pores of microporous film. Eliminating separator pores can stop such growth, but the downside is greatly reduced lithium-ion permeability. It is essential to suppress dendrites while maintaining ion conductivity,” EW noted.

Higher heat resistance and thermal stability of separators is needed as batteries with lithium metal anode have greater capacity, and higher safety requirements. Toray addressed this challenge by using high heat resistance aramid polymer  molecular design technology that it has employed over the years to control the gaps between molecular chains and the affinity to lithium ions.

By using a highly ion-conductive polymer with outstanding heat resistance Toray found it could suppress dendrite formation in lithium metal anode batteries and kept ion conductivity with “this polymer as a non-porous separator comprising a pore-free layer onto a microporous separator”.

The separator suppresses short circuits attributable to dendrites and maintains more than 80% of its capacity after 100 charge/discharge cycles. Research into ultra-high capacity and safety for tomorrow’s lithium-ion batteries is still needed, but the battery demand pushes that needle.