2D Layered MnO2 with an Ultralarge Interlayer Spacing for Aqueous Zinc Ion Batteries

Delta MnO2 (δ-MnO2) is a promising cathode material for aqueous zinc ion batteries. However, the electrochemical performance of a δ-MnO2 cathode is severely limited by sluggish reaction kinetics, low electronic conductivity, and inferior structural stability. In this study, we propose a simple and general approach for the preintercalation of large-sized organic cations between the layers of δ-MnO2. Our method is based on layer-by-layer electrostatic assembly of colloidal building blocks consisting of MnO2 nanosheets and various organic cations. The preintercalation results in unprecedented expansion of the interlayer spacing to more than 1.0 nm, thereby significantly enhancing the kinetics of ionic diffusion. These introduced cations act as supportive pillars and contribute to the modulation of the electronic structure of δ-MnO2, ultimately enhancing its structural stability and electronic conductivity. Electrochemical evaluations demonstrate superior performance in terms of capacity, rate capability, and cycling stability compared with that of a pristine δ-MnO2 cathode. The findings provide valuable insights into the design of high-performance cathode materials with improved ion diffusion kinetics and superior energy storage capabilities.