MXenes are rising star materials for electrochemical energy storage, but their low potential window severely constrains their high-energy-density potential. When subjected to a high potential window, MXenes undergo an irreversible oxidative failure. However, the mechanisms behind this failure are not well understood. Here, we disclose a previously unreported ion-accumulation mechanism that limits the high operating potential of MXenes. Under excessive polarization at high potential, the representative MXene, Ti3C2Tx, shows oxidation behavior but a reversible electrochemical response. Spectroscopic analyses and electrochemical kinetic field simulations disclose the conformational state variation, ion flux distribution, and vertical displacement behavior of MXene electrodes, confirming that electrolyte ions predominantly accumulate at the edges of overly thick stacked MXenes, with only a limited number shuttling freely into the interior. To address this potential-limiting ion-accumulation mechanism, we develop a transferring–engraving method to build free ion-shuttling ultrathin MXenes that guarantees a 100% increase in the potential window and a high volumetric energy density of 45.7 mWh cm–3.

Yanting Xie

Haitao Zhang

Yuanxiao Qu

Xinglin Jiang

Junfeng Huang

Xiong Zhang

Yuyu Gao

Liang Tang

Qiang Lv

Xingxing Jiao

Weiqing Yang

Zhengyou He

ACS Energy Letters

ACS ENERGY LETTERS 发表的论文报告了能源研究各个方面的新科学进展。下面列出了与能量捕获、转换和存储相关的主题。能源材料、光捕获组件能量转换过程（催化和光催化）太阳能燃料（制氢、减少二氧化碳）无机、有机和混合光伏光合作用和生物燃料燃料电池、蓄电池和超级电容器等离子、OLED 和光显示系统串联器件、压电和热电过程

ACS Energy Letters publishes papers reporting new scientific advancements in various aspects of energy research. The topics covered include energy capture, conversion, and storage, such as energy materials, light-harvesting components, energy conversion processes (catalysis and photocatalysis), solar fuels (hydrogen production, carbon dioxide reduction), inorganic, organic, and hybrid photovoltaics, photosynthesis and biofuels, fuel cells, batteries, and supercapacitors, plasma, OLEDs and optical display systems, tandem devices, piezoelectric and thermoelectric processes.

《ACS Energy Letters》发表关于能源研究各个方面的新科学进展的论文。主要涵盖以下主题：能量捕获、转换和存储，包括能源材料、光捕获组件、能量转换过程（催化和光催化）、太阳能燃料（制氢、减少二氧化碳）、无机、有机和混合光伏、光合作用和生物燃料、燃料电池、蓄电池和超级电容器、等离子体、OLED和光显示系统、串联器件、压电和热电过程等。

Category	Quartile
材料科学	1
材料科学, 物理化学	1
材料科学, 电化学	1
材料科学, 能源与燃料	1
材料科学, 材料科学综合	1
材料科学, 纳米科技	1

Unraveling the Ion-Accumulation-Induced Potential Limitations of MXene-Based Supercapacitors

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Journal Info

Category	Quartile
NANOSCIENCE & NANOTECHNOLOGY	1