Fibre-reinforced multifunctional composite solid electrolytes for structural batteries

Multifunctional energy storage devices are being pursued in a quest for more reliable battery systems for use in electric vehicles. However, the full realization of these batteries rests on the fabrication of solid electrolytes with high mechanical integrity and good processibility. In the present work, high modulus polyether ether ketone (PEEK) fibres are embedded inside a Li+-ion conducting poly(ethylene) oxide matrix. The macromolecular backbone of PEO provides lithium ion transport pathways while the robust rigidity of PEEK fibres enhances mechanical strength. The Young's modulus of the composite solid polymer electrolyte (CSPE) was increased by more than two orders of magnitude (from 0.9 MPa to up to 900 MPa) in the presence of the mechanical fillers. The ionic conductivity of 3.3 x 10-4 S/cm at 60 degrees C enabled successful cycling of Lithium metal batteries based on these CSPEs with high capacity retention of more than 96% over 200 cycles at 0.1 C. This prototypical system provides a straightforward approach to effectively decouple the mechanical properties from the ionic conduc-tivity which will facilitate the development of mechanically strong highly conducting electrolytes for the next generation of batteries.