Bio-Based Poly(hydroxy urethane)s for Efficient Organic High-Power Energy Storage

International audience; Fast, low-cost and efficient energy storage technologies are urgently needed to balance the intermittence of sustainable energy sources. High-power capacitors using organic polymers offer a green and scalable answer. They require dielectrics with high permittivity ($\epsilon _r$) and breakdown strength ($E_B$), which bio-based poly(hydroxy urethane)s (PHUs) can provide. PHUs combine high concentrations of hydroxyl and carbamate groups, thus enhancing their $\epsilon _r$, and a highly tuneable glass transition ($T_g$), which dictates the regions of low dielectric losses. By reacting erythritol dicarbonate with bio-based diamines, fully bio-based PHUs were synthesised with $T_g$ ~ 50 °C, $\epsilon _r$ > 8, $E_B$ > 400 MV•m$^{-1}$ and low losses (tan δ < 0.03). This results in energy storage performance comparable with the flagship petrochemical materials (discharge energy density, $U_e$ > 6 J•cm$^{-3}$) combined with a remarkably high discharge efficiency, with η = 85% at $E_B$ and up to 91% at 0.5 $E_B$. These bio-based PHUs thus represent a highly promising route to green and sustainable energy-storage.