Ti₃C₂ has been considered as a potential material for lithium-ion storage because of its abundant surface terminals, excellent metal-like conductivity, and modifiable layered structure. However, the Li⁺ diffusion rate in interlayer is limited by the small interlayer spacing determined by the van der Waals forces. Herein, the dehydration condensation reaction between amino-functionalized Ti₃C₂ (Ti₃C₂-NH₂) and maleic acid (MA) molecules was utilized to enlarge the interlayer spacing of Ti₃C₂. The MA molecules were successfully welded into interlayers of Ti₃C₂ by HN–C═O bonds (namely, chemical welding) and MA chemical welded Ti₃C₂ (MA-Ti₃C₂) with self-adaption layered structure were obtained. The MA molecules can contribute double effects to the layered structure of Ti₃C₂, and they act as chains to remit the volume change during Li⁺ insertion and serve as pillars to enhance the structure stability during Li⁺ extraction. The MA-Ti₃C₂ exhibits an interlayer spacing of 1.28 nm, a fast Li⁺ diffusion rate (1.4 × 10^–8 to 5.8 × 10^–7 cm² s^–1), and improved Li⁺ storage performance. The MA-Ti₃C₂//AC lithium-ion capacitor (LIC) demonstrates an excellent energy density of 102.5 Wh kg^–1 at 200 W kg^–1 and cycle stability with 76.3% at 1.0 A g^–1 after 1000 cycles. This novel chemical welding delivers an effective perspective for modifying the layered structure, enhancing the structure stability, and achieving fast Li⁺ diffusion and high-rate capability of two-dimension materials.

中文翻译：

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二酸分子焊接实现自适应层状结构 Ti3C2 MXene 实现快速稳定的锂离子存储

Ti ₃ C ₂因其丰富的表面末端、优异的类金属导电性和可改性的层状结构而被认为是一种潜在的锂离子存储材料。然而，层间的 Li ⁺扩散速率受到范德华力决定的小层间距的限制。在此，利用氨基官能化的Ti ₃ C ₂ (Ti ₃ C ₂ -NH ₂ )与马来酸(MA)分子之间的脱水缩合反应来扩大Ti ₃ C ₂的层间距。MA 分子成功焊接到 Ti ₃夹层中c ^ ₂由HN-C = O键（即，化学焊接）和MA化学焊接的Ti ₃ Ç ₂（MA-的Ti ₃ Ç ₂）与自适应分层结构中获得。MA分子对Ti ₃ C ₂的层状结构具有双重作用，它们作为链减轻Li ⁺插入过程中的体积变化，并作为支柱增强Li ⁺提取过程中的结构稳定性。MA-Ti ₃ C ₂的层间距为 1.28 nm，Li ⁺扩散速率快（1.4 × 10 ^–8至 5.8 × 10 ^–7 cm² s ^–1 )，并提高了 Li ⁺存储性能。MA-Ti ₃ C ₂ //AC 锂离子电容器 (LIC)在 200 W kg ^{–1 下}具有 102.5 Wh kg ^–1的出色能量密度，并且在 1000 次循环后在 1.0 A g ^{–1 下}具有 76.3% 的循环稳定性。这种新型化学焊接为改变层状结构、增强结构稳定性以及实现二维材料的快速 Li ⁺扩散和高倍率能力提供了有效的视角。