Polyaniline-hybridized quantum-confined 1D lepidocrocite titania for ultra-high-energy supercapacitors.

Abstract

High-energy capacitors have garnered significant interest due to their dual ability to store energy and deliver high power, influenced by the properties of their electrode materials. Herein, we report a unique composite structure created through in situ polymerization of polyaniline (PANI) in the presence of one-dimensional lepidocrocite (1DL) titania nanofilaments (NFs). The hierarchical 1DL NF structures allow direct and fast ion transport, enhancing both capacity and stability when combined with PANI. The resultant composite (PANI : 1DLs in a 2 : 1 wt ratio) exhibits a specific capacity of 377 mA h g-1 at 0.5 Ag-1, with high mass loading (∼5 mg cm-2). The composite's performance in a symmetric cell configuration demonstrates a specific energy of 154 Wh kg-1 at 0.5 A g-1, which is the highest specific energy among other reported TiO2-based supercapacitor electrodes over a wide voltage window of 3.5 V. A peak specific power of 17 kW kg-1 was measured while maintaining a specific energy of 31Wh kg-1. After 10 000 charge-discharge cycles, the cell retained ∼56% of its initial capacity with 94% coulombic efficiency. To enhance cell stability and reduce self-discharge, an asymmetric arrangement with activated carbon improved voltage retention, resulting in a 29.7% open-circuit potential retention after 24 h and 80% capacitance retention after post-cycling. The synthesis method is inexpensive, sustainable, and potentially scalable, highlighting the potential for high-energy supercapacitors.

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