Solvent Co-intercalation into Few-layered Ti<sub>3</sub>C<sub>2</sub>T<i><sub><i>x</i></sub></i> MXenes in Lithium Ion Batteries Induced by Acidic or Basic Post-treatment.
basic_science · Level V
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- Record sourced from PubMed, PMID 33522794.
- Also identified by DOI 10.1021/acsnano.0c10153.
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Abstract
MXenes, as an emerging class of 2D materials, display distinctive physical and chemical properties, which are highly suitable for high-power battery applications, such as lithium ion batteries (LIBs). Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> (T<sub><i>x</i></sub> = O, OH, F, Cl) is one of the most investigated MXenes to this day; however, most scientific research studies only focus on the design of multilayered or monolayer MXenes. Here, we present a comprehensive study on the synthesis of few-layered Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> materials and their use in LIB cells, in particular for high-rate applications. The synthesized Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> MXenes are characterized <i>via</i> complementary XRD, Raman spectroscopy, XPS, EDX, SEM, TGA, and nitrogen adsorption techniques to clarify the structural and chemical changes, especially regarding the surface groups and intercalated cations/water molecules. The structural changes are correlated with respect to the acidic and basic post-treatment of Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub>. Furthermore, the detected alterations are put into an electrochemical perspective <i>via</i> galvanostatic and potentiostatic investigations to study the pseudocapacitive behavior of few-layered Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub>, exhibiting a stable capacity of 155 mAh g<sup>-1</sup> for 1000 cycles at 5 A g<sup>-1</sup>. The acidic treatment of Ti<sub>3</sub>C<sub>2</sub>T<i><sub><i>x</i></sub></i> synthesized <i>via</i> the <i>in situ</i> formation of HF through LiF/HCl is able to increase the initial capacity in comparison to the pristine or basic treatment. To gain further insights into the structural changes occurring during (de)lithiation, <i>in situ</i> XRD is applied for LIB cells in a voltage range from 0.01 to 3 V to give fundamental mechanistic insights into the structural changes occurring during the first cycles. Thereby, the increased initial capacity observed for acidic-treated MXenes can be explained by the reduced co-intercalation of solvent molecules.