Toray Industries has created a non-porous separator for lithium-ion batteries, that could dramatically increase capacity by enhancing safety of lithium metal anode batteries, notably in wearable electronic devices, drones, and electric vehicles.

The lithium-ion battery market continues to expand, underscoring the need to lift the capacity and energy density of lithium-ion batteries. This situation has focused attention on lithium metal anode because of their high theoretical capacity and low redox potential.
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.

Batteries with lithium metal anode have greater capacity, therefore safety requirements become more serious than conventional ones, necessitating higher heat resistance and thermal stability of separators.
Toray tackled this challenge by utilizing the high heat resistance aramid polymer  molecular design technology that it amassed over the years to control the gaps between molecular chains and the affinity to lithium ions.
It thereby created a highly ion-conductive polymer with outstanding heat resistance. The company was able to suppress dendrite formation in lithium metal anode batteries while keeping ion conductivity by employing this polymer as a non-porous separator comprising a pore-free layer onto a microporous separator.
Toray showes that a battery with such a separator suppressed short circuits attributable to dendrites and maintained more than 80% of its capacity after 100 charge/discharge cycles. It will accelerate research and development to swiftly establish technologies with lithium metal anodes batteries so it can drive ultra-high capacity and safety for tomorrow’s lithium-ion batteries.