Regulating the surface termination of a confined space to achieve ultrafast ion transport remains an ongoing challenge. Two-dimensional (2D) MXenes possess adjustable structures and interlayer spacing, which provide an ideal platform for in-depth investigation of ion transport in 2D confined space; however, the strong interaction of the negatively charged terminations in MXenes hinders the transport of intercalated cations. In this work, we proposed a strategy that precisely regulates the surface modification of Ti₃C₂T_x MXene with the weak polarity of boron atoms (SCB-MXene) via the distinct effect of supercritical CO₂. This not only could effectively substitute −OH termination in MXene but also can prevent the loss of −O active sites, and then, both ultrafast ion transport and high volumetric capacitance can be achieved simultaneously. Ideally, a volumetric capacitance up to 742.7 C cm^–3 at 1000 mV s^–1 for the SCB-MXene film as pseudocapacitive materials that provides an energy density of 66.3 Wh L^–1 even at an ultrahigh power density of 132.5 kW L^–1 is obtained, which is a prominent record of energy density and power density reported up to now. Subsequently, it can be used in large-scale energy storage and conversion devices.

中文翻译：

---

在 2D 受限 MXene 中实现超快离子传输以提高电化学性能：硼原子取代的 −OH 终止


调节狭窄空间的表面终端以实现超快离子传输仍然是一个持续的挑战。二维 （2D） MXene 具有可调节的结构和层间间距，为深入研究 2D 受限空间中的离子传输提供了理想的平台;然而，MXenes 中带负电荷的末端的强相互作用阻碍了插层阳离子的传输。在这项工作中，我们提出了一种策略，通过超临界 CO₂ 的独特效应精确调节具有硼原子弱极性 （SCB-MXene） 的 Ti₃C₂T_x MXene 的表面改性。这不仅可以有效地替代 MXene 中的 −OH 终止，还可以防止 −O 活性位点的损失，然后可以同时实现超快离子传输和高体积电容。理想情况下，作为伪电容材料的 SCB-MXene 薄膜在 1000 mV s^–1 时体积电容高达 742.7 C cm^–3，即使在 132.5 kW L^–1 的超高功率密度下也能提供 66.3 Wh L^–1 的能量密度，这是迄今为止报道的能量密度和功率密度的突出记录。随后，它可以用于大型储能和转换设备。