| Mar 12, 2022 |
High-voltage aqueous MXene planar micro-supercapacitors
(Nanowerk News) A research group led by Prof. WU Zhongshuai from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS), in collaboration with Prof. CHENG Huiming from the Institute of Metal Research of CAS, developed high-voltage aqueous MXene planar micro-supercapacitors (MSCs) with wide temperature range based on water-in-LiCl (WIL) salt electrolyte.
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This study was published in National Science Review ("Kinetic regulation of MXene with water-in-LiCl electrolyte for high-voltage micro-supercapacitors").
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MXenes, a family of 2D transition metal carbides and nitrides with over 30 species, are emerging as high-performance electrode materials. However, MXene electrode is easily oxidized at high anodic potential in aqueous electrolytes, and its operating voltage is normally limited by the electrochemical thermodynamic stability window of water.
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In addition, aqueous electrolytes freeze easily at sub-zero temperatures, leading to a sharp decline in ionic conductivity. While, at high temperatures, the structure of aqueous electrolytes is so unstable that it is difficult to retain internal water molecules because of volatility.
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| Characteristics of water-in-LiCl electrolytes and flexibility and integration characterization of MXene-MSC-3.2. (Image: ZHU Yuanyuan and ZHENG Shuanghao)
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"We developed a low-cost and environment-friendly WIL salt electrolyte to regulate reaction kinetics of MXene (Ti3C2Tx) electrode and electrolyte, which not only broadened the operation voltage of MXene-MSCs by inhibiting oxidation at high potential, but also increased the temperature range owing to a low freezing point," said Prof. WU.
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The as-fabricated symmetric planar aqueous MXene-MSCs with the above-mentioned electrolyte achieved an operating voltage of up to 1.6 V, and energy density of up to 31.7 mWh cm-3 at room temperature.
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The low freezing point (-57 °C) of WIL gel electrolyte also enabled MXene-MSCs to operate stably in a wide temperature range (-40 °C to 60 °C). The scalability and flexibility of MXene-MSCs made it easily for them to be integrated into wearable microelectronics.
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