Molecular-Level Interfacial Chemistry Regulation of MXene Enables Energy Storage beyond Theoretical Limit.
basic_science · Level V
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- Record sourced from PubMed, PMID 38412072.
- Also identified by DOI 10.1021/acsnano.3c12329.
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Abstract
Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> MXene often suffers from poor lithium storage behaviors due to its electrochemically unfavorable OH terminations. Herein, we propose molecular-level interfacial chemistry regulation of Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> 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 Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> surface, interfacial charge distribution of Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> 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 Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub>/PA achieves a 2.4-fold capacity enhancement compared with pristine Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> (even beyond theoretical capacity), superior long-term cyclability (220.0 mAh g<sup>-1</sup> after 2000 cycles at 2.0 A g<sup>-1</sup>), 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.