Rational design of continuous gradient composite films for high-performance zinc-ion batteries

Abstract

• Continuous gradient composite films was firstly fabricated by one-step electrospinning strategy. • The gradient compositional distributions can be accurately controlled. • The strategy is universal and can be feasible for a variety of functional materials. • Many different components can be simultaneously introduced into one gradient film with independently adjustable gradient distribution and orientation. • The VO-based gradient composite films displayed ultrahigh capacity and superior rate capability as cathodes of aqueous ZIBs. Gradient materials are attracting extensive attention since the gradient compositional distributions endow them with excellent environmental adaptability in specific working conditions. However, the universal and accurately controllable synthesis of continuous gradient materials remains a challenge. Here, a universal strategy is developed to fabricate continuous gradient composite films (GCFs) with different components and gradient distributions by combining the dynamic concentration-regulation method and electrospinning technique. The gradient compositional distributions can be accurately regulated in such GCFs. Furthermore, a variety of functional materials can be also introduced into the continuous gradient composite films, respectively or simultaneously with controllable gradient orientation. As a proof of concept, the GCFs with VO nanoparticles were fabricated and used as the cathodes of aqueous zinc ion batteries. The matching of gradient compositional distribution and electron/ion transport within the electrodes would contribute to the ultrahigh capacity as well as superior rate capability. The universality and ease of this strategy would make it a promising route to design continuous GCFs with desired components and gradient distributions for various potential applications in many fields.