(693g) Highly Flexible Self-Assembled V2O5 Cathodes Enabled By Conducting Diblock Copolymers

Structural energy storage materials combining load-bearing mechanical properties and high energy storage performance are desired for applications in wearable devices or flexible displays. Vanadium pentoxide (V₂O₅) is a promising cathode material for possible use in flexible battery electrodes, but it remains limited by low Li⁺ diffusion coefficient and electronic conductivity, severe volumetric changes upon cycling, and limited mechanical flexibility. Here, we demonstrate a route to address these challenges by blending a diblock copolymer bearing electron- and ion-conducting blocks, poly(3-hexylthiophene)-block-poly(ethyleneoxide) (P3HT-b-PEO), with V₂O₅ to form a mechanically flexible, electro-mechanically stable hybrid electrode. V₂O₅ layers were arranged parallel in brick-and-mortar-like fashion held together by the P3HT-b-PEO binder. . This unique structure significantly enhances mechanical flexibility, toughness and cyclability without sacrificing capacity. Properties are probed as a function of composition using dynamic mechanical analysis, impedance spectroscopy, cyclic voltammetry, and galvanostatic cycling. It is found that optimum composition exists, where too little polymer results in brittle inflexible electrodes and too much polymer reduces the electrochemical activity. Only 5 wt % polymer is required to triple the flexibility (normal strain) of V₂O₅, and electrodes comprised of 10 wt % polymer have unusually high toughness (293 kJ/m³) and specific energy (530 Wh/kg), both higher than reduced graphene oxide paper electrodes. Electrodes with commercial binder poly(vinylidene difluoride) shows no remarkable improvement. These results demonstrate a new approach for the development of structural energy storage materials.