Conducting Diblock Copolymers as Multifunctional Binders for Lithium-Ion Batteries & Surface-Agnostic Highly Stretchable and Bendable Conductive MXene Multilayers
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A conductive block copolymer binder P3HT-b-PEO was studied to form a flexible, tough, carbon-free hybrid battery cathode. Only 5 wt. % polymer was required to triple the flexibility of V₂O₅, and electrodes comprised of 10 wt. % polymer had unusually high toughness (293 kJ/m3) and specific energy (530 Wh/kg), both higher than reduced graphene oxide paper electrodes. Addition of P3HT-b-PEO increased lithium-ion diffusion, eliminated cracking during cycling, and enhanced cyclability relative to V₂O₅ alone. We compared the P3HT-b-PEO block copolymer binders with P3HT, PEO, and a P3HT/PEO homopolymer blend in carbon-free V₂O₅. The electrode with P3HT-b-PEO binder showed the highest capacity of 190 mAh/g at a 0.1 C-rate after over 200 cycles, a 2.5-fold improvement of that of pure V₂O₅, whereas P3HT, PEO, and the blend exhibited capacities of 139, 130, and 70 mAh/g. The unique architecture of P3HT-b-PEO, wherein P3HT and PEO blocks are covalently bonded, improved the uniform distribution of the conductive binders within the V₂O₅ structure, whereas the analogous P3HT/PEO blend suffers from phase separation. We presented the strong effects of regioregularity and molecular weight of the P3HT block in P3HT-b-PEO on molecular conformation and electrochemical properties by comparing four different P3HT-b-PEOs of varying P3HT regioregularity (86-97%) and molecular weight (8-19 kDa) while the PEO block was kept the same (7 kDa) to isolate the influence of the P3HT block. Our data show that, as increasing regioregularity, the capacity of P3HT-b-PEO significantly increase and, as increasing molecular weight, the redox potential decreases. The underlying reasons for this finding are revealed by the characterizations of P3HT backbone conformation and chain packing. Also, we studied highly stretchable conductive titanium carbide (MXene) multilayer coatings that can undergo extreme deformation while maintaining their electrical conductivity. The conductive and conformal MXene multilayer coatings that can undergo large-scale mechanical deformation while maintaining a conductivity as high as 2,000 S/m. MXene multilayers were successfully prepared onto flexible polymer sheet, stretchable poly(dimethylsiloxane), nylon fiber, and glass. The coating showed a recoverable resistance response to bending (up to 2.5 mm bending radius) and stretching (up to 40% tensile strain).
An, Hyosung (2018). Conducting Diblock Copolymers as Multifunctional Binders for Lithium-Ion Batteries & Surface-Agnostic Highly Stretchable and Bendable Conductive MXene Multilayers. Doctoral dissertation, Texas A & M University. Available electronically from