Jiang Minxia, Li Minxi, Cui Chang, Wang Jie, Cheng Yang, Wang Yixin, Zhang Xing, Qin Jinwen, Cao Minhua
Key Laboratory of Cluster Science, Ministry of Education of China, Beijing Key Laboratory of Photoelectronic/Electrophotonic Conversion Materials, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, P. R. China.
China Academy of Aerospace Science and Innovation, No. 2, Taihe Third Street, Yizhuang Zone, Daxing District, Beijing 100176, P. R. China.
ACS Nano. 2024 Mar 12;18(10):7532-7545. doi: 10.1021/acsnano.3c12329. Epub 2024 Feb 27.
TiCT MXene often suffers from poor lithium storage behaviors due to its electrochemically unfavorable OH terminations. Herein, we propose molecular-level interfacial chemistry regulation of TiCT MXene with phytic acid (PA) to directly activate its OH terminations. Through constructing hydrogen bonds (H-bonds) between oxygen atoms of PA and OH terminations on TiCT surface, interfacial charge distribution of TiCT has been effectively regulated, thereby enabling sufficient ion-storage sites and expediting ion transport kinetics for high-performance energy storage. The results show that Li ions preferably bind to H-bond acceptors (oxygen atoms from PA), and the flexibility of H-bonds therefore renders their interactions with adsorbed Li ions chemically "tunable", thus alleviating undesirable localized geometric changes of the OH terminations. Meanwhile the H-bond-induced microscopic dipoles can act as directional Li-ion pumps to expedite ion diffusion kinetics with lower energy barrier. As a result, the as-designed TiCT/PA achieves a 2.4-fold capacity enhancement compared with pristine TiCT (even beyond theoretical capacity), superior long-term cyclability (220.0 mAh g after 2000 cycles at 2.0 A g), and broad temperature adaptability (-20 to 50 °C). This work offers a promising interface engineering strategy to regulate microenvironments of inherent terminations for breaking through the energy storage performance of MXenes.
由于其在电化学方面不利的羟基端基，TiCT MXene常常具有较差的锂存储性能。在此，我们提出用植酸（PA）对TiCT MXene进行分子水平的界面化学调控，以直接激活其羟基端基。通过在PA的氧原子与TiCT表面的羟基端基之间构建氢键（H键），TiCT的界面电荷分布得到了有效调控，从而实现了充足的离子存储位点，并加快了离子传输动力学，以实现高性能储能。结果表明，锂离子优先与氢键受体（来自PA的氧原子）结合，因此氢键的灵活性使其与吸附的锂离子之间的相互作用在化学上具有“可调性”，从而减轻了羟基端基不良的局部几何变化。同时，氢键诱导的微观偶极子可作为定向锂离子泵，以较低的能垒加快离子扩散动力学。结果，所设计的TiCT/PA与原始TiCT相比容量提高了2.4倍（甚至超过理论容量），具有优异的长期循环稳定性（在2.0 A g下循环2000次后为220.0 mAh g），以及宽泛的温度适应性（-20至50°C）。这项工作提供了一种很有前景的界面工程策略，用于调控固有端基的微环境，以突破MXenes的储能性能。
