Aqueous asymmetric pseudocapacitor featuring high areal energy and power using conjugated polyelectrolytes and Ti3C2Tx MXene
Benjamin Rui Peng Yip, Chaofan Chen, Yan Jiang, David Ohayon, Guillermo C. Bazan, Xuehang Wang
Abstract
Despite the development of various pseudocapacitive materials, full-cell pseudocapacitors have yet to surpass the power density of conventional electric double layer capacitors, primarily due to the lack of high-rate positive pseudocapacitive materials. This work reports a solid-state conjugated polyelectrolyte that achieves high-rate charge storage as a positive electrode, facilitated by a co-ion desorption mechanism. The conjugated polyelectrolyte retains 70% of its capacitance at 100 A g−1 with a mass loading of 2.8 mg cm−2 and exhibits a long cycling life of 100,000 cycles in a Swagelok cell configuration. Increasing the electrode thickness fourfold has minimal impact on ion diffusivity and accessibility, yielding a high areal capacitance of 915 mF cm−2. When paired with a high-rate negative pseudocapacitive electrode Ti3C2Tx, the device leverages the redox-active potentials of both materials, achieving a device voltage of 1.5 V and supports operation rates up to 10 V s−1 or 50 A g−1. This configuration enables the pseudocapacitor to deliver an areal power of 160 mW cm−2, while significantly increasing the areal energy (up to 71 μWh cm−2). The high areal performance, combined with the additive-free and water-based fabrication process, makes pseudocapacitors promising for on-chip and wearable energy storage applications. Pseudocapacitors are emerging as alternatives to conventional supercapacitors. Here, authors showed an uncommon charge storage mechanism in a high-rate conjugated polyelectrolyte and demonstrated practical pouch and solid-state pseudocapacitor devices with competitive energy up to 71 μWh cm−2 and power performance up to 160 mW cm−2.