Flexible fibre-shaped fuel cells with gel-mediated internal pressure encapsulation.

The development of flexible fuel cells has been hindered by the rigid components and stringent requirements for pressure encapsulation and fuel sealing. Here we report an adaptive internal pressure encapsulation strategy that leverages the dynamic swelling behaviour of woven cotton fibres enclosed in a gel matrix in methanol. This strategy achieves simultaneous interfacial self-reinforcement and pressure modulation, enabling the fabrication of fibre-shaped direct methanol fuel cells. These flexible fuel cells operate across a broad temperature range, from -22 °C to 70 °C, showcasing cuttability, water resistance and fast refuelling capabilities, with full refuelling being achieved within 1 min. Furthermore, the fuel cells maintain consistent discharge performance, even after enduring 2,000 continuous flexing cycles. With an energy density of 161.36 Wh kg-1, these fibre-shaped direct methanol fuel cells surpass the energy densities of typical fibre-based power systems. This technology mitigates many of the technical challenges related to the lightweight and flexible application of fuel cells or fuel cell stacks for powering high-energy flexible devices.