Regulation of Ion Transport Behavior in Layer-by-Layer Assembled Polymer/MXene Heterostructure Anodes for Metal-Free Aqueous Zinc Ion Batteries

Abstract

Recently, the development of Zn-host materials in metal-free aqueous Zinc ion batteries (AZIBs) has emerged as an effective strategy to address the challenges of uncontrollable dendrite growth and severe corrosion in Zn anodes. Herein, the layer-by-layer assembly conjugated polyimide nanocomposite (PTN-MXene) through in situ polymerization is proposed to realize high energy density and stability metal-free AZIBs. Specifically, the unique layered structure and abundant redox centers of conjugated diketone-based polyimide (PTN), combined with its high structural compatibility with MXene, enable the formation of a layer-by-layer assembled 2D/2D heterostructure. This design ensures sufficient contact and expands the interlayer spacing of MXene, facilitating faster electron/ion transport kinetics and providing better access to redox centers. Importantly, the regulation of ion transport behavior from H⁺ or Zn²⁺ to H⁺/Zn²⁺ coinsertion in PTN-MXene is achieved and verified by different characterization techniques. Thus, PTN-MXene anode exhibits high specific capacity (283.4 mAh g⁻¹ at 0.1 A g⁻¹), excellent rate performance and outstanding cycling performance. As a proof-of-concept, the full batteries fabricated by Prussian blue analogs cathode and PTN-MXene anode deliver a high energy density of 72.4 Wh kg⁻¹ and exceptional cycling stability over 2000 cycles.