Nanocellulose-reinforced nanofiber composite poly(aryl ether ketone) polymer electrolyte for advanced lithium batteries

Solid polymer batteries (SPEs) are highly desirable for energy storage because of the urgent need for higher energy density and safer lithium ion batteries (LIBs). In this work, the single-ion lithium salt PAEK₅₀-LiCPSI was synthesized by grafting 3-chloropropanesulfonyl trifluoromethanesulimide lithium (LiCPSI) onto poly(aryl ether ketone)₅₀ (PAEK₅₀). Nanocellulose (NCC), PAEK₅₀-LiCPSI, and poly(vinylidene fluoride) (PVDF-HFP) were compounded to obtain NCC reinforced high-performance nanofiber composite polymer electrolytes (NCC/PAEK/PVDF) through electrospinning, which presented tensile strength of 15.35 MPa, ionic conductivity of 1.13 × 10^-4 S cm^-1, and Li⁺ transfer number as high as 0.80 at 25 °C. The assembled LIBs with NCC/PAEK/PVDF illustrated an initial discharge specific capacity of 155.2 mAh g^-1 at 0.2C, and the capacity retention rate was close to 93 % after cycling 700 cycles at 25 °C. Furthermore, its initial specific discharge capacity at -20 °C was 103.4 mAh g^-1, and can cycle over 300 cycles. The NCC with sulfonic acid group reinforced the mechanical performance, promoted the dissociation of Li⁺, and synergized with PAEK₅₀-LiCPSI and PVDF-HFP to form a 3D nanofiber ionic bridge network through hydrogen bond, which promoted the more stable and faster Li⁺ transportation. This work suggested that the NCC/PAEK/PVDF can be a good choice of solid polymer electrolytes (SPE) for the next generation of LIBs, even working at low-temperatures.