A 2D layered semiconducting (LCu3I3)n coordination polymer for energy storage through dual ion intercalation

Abstract

For an exclusive exploration of renewable energies, it is imperative to have efficient energy storage devices to ensure an uninterrupted energy supply, which mandates the development of new electrode materials with better energy storage performance. This work presents a facile synthesis of a layered two-dimensional semiconducting copper(I) iodide coordination polymer (CuI-CP), using CuI and 1,3,5-trithiane linker, which has been investigated as a cathode material for energy storage applications. The coordination polymer has a hitherto unknown continuous Cu(I) iodide sheet-like structure having a Cu₃I₃ hexagon repeating unit decorated with the ligand. Electron microscopy suggests the nano-crystalline hexagonal plate morphology of the material. The unique 2D layered structure of semiconducting CuI-CP, originating from the stacking of a redox-active framework, encouraged us to investigate its applicability as an electrode material in electrochemical energy storage devices. The material demonstrates supercapattery behavior, achieving a specific capacity of 498 Cg⁻¹ at 1 Ag⁻¹. Additionally, the symmetric device fabricated with CuI-CP offers high energy and power densities (^maxE_d = 77 W h kg⁻¹ and ^maxP_d = 3.08 kW kg⁻¹) and maintains excellent cycling stability of 94% over 10 000 cycles. The high efficiency is attributed to the semiconducting nature and facile ion diffusion via the 2D layered structure of the material having redox-active Cu centers. The present work demonstrates the first report of integrating a Cu(I) iodide coordination polymer as an electrode material for energy storage devices.