Ruocun Wang1,2,Mark Anayee1,2,Muhammad Nihal Naseer3,Teng Zhang1,2,Yuan Zhang1,2,Mikhail Shekhirev1,2,Kateryna Shevchuk1,2,Yong-Jie Hu2,Yury Gogotsi1,2
A.J. Drexel Nanomaterials Institute1,Drexel University2,University of Picardie Jules Verne3
Ruocun Wang1,2,Mark Anayee1,2,Muhammad Nihal Naseer3,Teng Zhang1,2,Yuan Zhang1,2,Mikhail Shekhirev1,2,Kateryna Shevchuk1,2,Yong-Jie Hu2,Yury Gogotsi1,2
A.J. Drexel Nanomaterials Institute1,Drexel University2,University of Picardie Jules Verne3
Pseudocapacitors have the potential to achieve high energy and high power density simultaneously, a holy grail for electrochemical energy storage. However, one obstacle facing pseudocapacitors is their shorter lifetime than commercial supercapacitors using the double-layer charge storage mechanism. In MXene-based pseudocapacitors, this concern is pronounced particularly at high temperatures due to the limited stability of the active material in aqueous solutions. This work shows that Ti<sub>3</sub>C<sub>2</sub>T<i><sub>x</sub></i> MXene thin-film electrodes in 5 M H<sub>2</sub>SO<sub>4</sub> possess excellent rate capabilities from -50 °C to 70 °C but also a sufficient lifetime at 70 °C using a float test holding at -0.9 V vs. Hg/Hg<sub>2</sub>SO<sub>4</sub>. Post-mortem characterization using X-ray photoelectron spectroscopy and Raman spectroscopy showed negligible signs of oxidation in the bulk of the film. This work suggests sufficient stability of Ti<sub>3</sub>C<sub>2</sub>T<i><sub>x</sub></i> MXene as a negative electrode in protic aqueous electrolytes across a wide temperature range rooted in thermodynamics, making it promising for pseudocapacitor energy storage.