MXene is a rising star of two-dimensional (2D) materials for energy relative applications, however, the traditional synthesis of MXene etched by hazard HF acid or LiF+HCl mixed solution is highly dangerous with the risk of splashing or pouring liquid solutions. In this work, we developed a water-free ionothermal synthesis of 2D Ti₃C₂ MXene via etching pristine Ti₃AlC₂ MAX in low-cost choline chloride and oxalic acid based deep eutectic solvents (DES) with the presence of NH₄F, thus it was highly safe and convenient to operate solid precursor and product materials at room temperature. Benefited from the low vapor pressure and solvating properties of DES, the prepared Ti₃C₂ (denoted as DES-Ti₃C₂) possessed a high purity up to 98% compared with 95% for HF etched Ti₃C₂ (denoted as HF-Ti₃C₂). Notably, an expanded interlayer spacing of 1.35 nm could be achieved due to the intercalation of choline cations in DES-Ti₃C₂, larger than that of HF-Ti₃C₂ (0.98 nm). As a result, the DES-Ti₃C₂ anodes exhibited enhanced lithium storage performance, such as high reversible capacity of 208 mAh g⁻¹ at 0.5 A g⁻¹, and long cycle life over 400 times, outperforming most reported pure MXene anodes. The ionothermal synthesis of MXene developed here may pave a new way to safely prepare other MXene for various energy relating applications.

MXene是用于能源相关应用的二维（2D）材料的后起之秀，但是，由危险的HF酸或LiF + HCl混合溶液腐蚀的MXene的传统合成方法非常危险，有喷溅或倾倒液体溶液的危险。在这项工作中，我们通过在低成本的氯化胆碱和草酸基深共熔溶剂（DES）中，在存在NH ₄ F的情况下蚀刻原始的Ti ₃ AlC ₂ MAX ，开发了无水电热合成2D Ti ₃ C ₂ MXene的方法。因此，在室温下操作固体前驱物和产品材料是高度安全和方便的。得益于DES的低蒸气压和溶剂化性能，制备的Ti ₃ C₂（表示为DES-Ti ₃ C ₂）具有高达98％的高纯度，而HF蚀刻的Ti ₃ C ₂（表示为HF-Ti ₃ C ₂）为95％。值得注意的是，由于胆碱阳离子在DES-Ti ₃ C _2中的嵌入比HF-Ti ₃ C ₂（0.98 nm）大，因此可以实现1.35 nm的扩展层间距。结果，DES-Ti ₃ C ₂阳极表现出增强的锂存储性能，例如在0.5 A g ^-1时具有208 mAh g ^-1的高可逆容量。，循环寿命超过400倍，胜过大多数报道的纯MXene阳极。此处开发的MXene的离子热合成可能为安全地制备用于各种能源相关应用的其他MXene铺平了新途径。