Abstract
Ti3C2Tx-based aerogels have attracted widespread attention for three-dimensional porous structures, which are promising to realize high-rate energy storage. However, disordered Ti3C2Tx aerogels with highly tortuous porosity fabricated by conventional unidirectional freeze-casting substantially increase ion diffusion lengths and hinder electrolyte ions transport. Herein we demonstrate a new bidirectional ice-templated approach to synthesize porous ordered Ti3C2Tx aerogel with straight and aligned channels, straight and short ion diffusion pathways, leading to better ion accessibility. The aligned Ti3C2Tx aerogel exhibits the high specific capacitance of 345 F g−1 at 20 mV s−1 and rate capability of 52.2% from 10 to 5000 mV s−1. The specific capacitance is insensitive of mass loadings even at 10 mg cm−2 and an excellent power density of 137.3 mW cm–2 is obtained in symmetric supercapacitors. The electrochemical properties of Ti3C2Tx aerogel supercapacitors at sub-zero (to −30 °C) temperatures are reported for the first time. The aligned Ti3C2Tx aerogel delivers temperature-independent rate performance and high capacitance retention (73% at 50 mV s−1 from 25 to −30 °C) due to the unique structure with metallic conductivity.
Highlights
Published: 6 February 2022MXenes, a burgeoning family of two-dimensional nanomaterials, have attracted widespread interest for outstanding electrochemical properties [1]
Cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) and electrochemical impedance spectroscopy (EIS) measurements were conducted through the electrochemical workstation (PGSTAT302N, Metrohm Autolab B.V., Switzerland)
Ti3C2Tx films are attributed to the sufficient ion-accessible redox sites, short ion diffusion pathways and unobstructed ion transport
Summary
MXenes, a burgeoning family of two-dimensional nanomaterials, have attracted widespread interest for outstanding electrochemical properties [1]. It is crucial to develop an effective assembly and fabrication technique for Ti3 C2 Tx aerogels to optimize ion transport and diffusion kinetics without sacrificing its inherent metallic conductivity, thereby improving the overall electrochemical performance. A 3D porous ordered Ti3 C2 Tx architecture (i.e., aligned Ti3 C2 Tx aerogel) is rationally devised via a simple bidirectional ice-templated strategy without any other additives Such architecture can effectively shorten ion diffusion pathways, accelerate ion transport, and provide more electrochemically active sites, thereby improving the rate performance, power density, and low-temperature stability of the supercapacitor. Benefiting from fast ion diffusion kinetics in the 3D ordered conductive architecture, the aligned Ti3 C2 Tx aerogel exhibits temperature-independent rate performance 63.6% from 10 to 1000 mV s−1 at 25 ◦ C and −30 ◦ C, respectively) and high capacitance retention of 73% at 50 mV s−1 within the range of operating temperatures from 25 to −30 ◦ C
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