Multi-Functional Gradient Fibrous Membranes Aiming at High Performance for Both Lithium-Sulfur and Zinc-Air Batteries

Lithium-sulfur batteries have been considered one of the most promising energy storage batteries in the future of flexible and wearable electronics. However, the shuttling of polysulfides, low sulfur utilization, and bad cycle stability restricted the widespread application of lithium-sulfur batteries. Currently, gradient materials with multiple functions can solve those defects simultaneously and can be applied to various parts of batteries. Herein, an electrospinningtriple-gradient Co-N-C/PVDF/PAN fibrous membrane was prepared and applied to lithium-sulfur batteries. The Co-N-C fibrous membrane provided efficient active sites, excellent electrode conductivity, and boosted polysulfide confinement. At the same time, the PVDF/PAN membrane enhances electron transfer and lithium-ion diffusion. As a result, the integrated S@Co-N-C/PVDF/PAN/Li battery delivered a high initial capacity of 1124.1 mA h g(-1). Even under high sulfur loading (6 mg cm(-2)), this flexible Li-S battery still exhibits high areal capacity (846.9 mA h cm(-2)) without apparent capacity attenuation and security issues. Meanwhile, the gradient fibrous membranes can be used in zinc-air batteries, and the same double-gradient Co-N-C/PVDF membranes were also used as a binder-free air cathode with bifunctional catalytic activity and a facile hydrophobic and aerophile membrane, delivering remarkable cycling stability and small voltage gap in aqueous ZABs. The well-tunable structures and materials of the gradient strategy would bring inspiration for excellent performance in flexible and wearable energy storage devices.