Ion expressways directed by vertically aligned TiO₂ nanotubes in quasi-solid electrolyte for flexible zinc-ion batteries

Flexible zinc-ion batteries are promising power sources for wearable devices, but are hindered by zinc dendrite growth and limited cycle life, due to limited ionic transport and poor mechanical strength of electrolyte. This work presents a quasi-solid polymer gel (PG) electrolyte incorporating vertically aligned TiO₂ nanotubes (PATG) in a crosslinked polyvinyl alcohol matrix. PATG exhibited a compressive Young’s modulus of 56.7 MPa (vs. 21.9 MPa for PG), and especially much higher Zn²⁺ conductivity of 0.26 mS·cm^–1 than that of PG (0.056 mS∙cm^–1) and PPTG (0.074 mS·cm^–1) and larger Zn²⁺ transference number of 0.71 than those of PPTG film (0.61) and PG film (0.43). PATG electrolyte exhibited stable cycling performance over 3000 hours with low polarization and effectively suppressed zinc dendrite growth. In full batteries, Zn|PATG|α-MnO₂ delivered an initial capacity of 301.2 mAh·g^–1 at 0.1 C and 212.9 mAh·g^–1 at 0.5 C. Moreover, the flexible Zn|PATG|α-MnO₂ can work at different bending states and power electronic devices well. This work underscores that the directed ion-transport strategy is feasible and promising for safe, flexible, and durable zinc-ion batteries.