The Missing Piece: The Structure of the Ti3C2Tx MXene and Its Behavior as Negative Electrode in Sodium Ion Batteries

Ferrara, Chiara; Gentile, Antonio; Marchionna, Stefano; Quinzeni, Irene; Fracchia, Martina; Ghigna, Paolo; Pollastri, Simone; Ritter, C.; Vanacore, Giovanni Maria; Ruffο, Riccardo

doi:10.1021/acs.nanolett.1c02809

Cited by 35 publications

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“…The lamellae have an average thickness of 150–200 nm for all the samples and different degree of surface roughness. This final aspect could be associated with the presence of impurities or with partial molten materials, in particular amorphous and nanometric TiO 2‐x F 2x particles formed following the exothermic reaction between hydrofluoric acid and aluminum and already observed for similar compositions [14,36,41] . The considered etching methods thus allow to obtain different morphology as the NaF/HCl solution leads to the formation of a compact MXene structure while the use of NH 4 HF 2 solution allows for the formation of open 2D system.…”

Section: Resultsmentioning

confidence: 99%

“…The etching procedure also affects the degree of disorder of the layered materials; this can be inferred from the blurring of several reflections of the (10 l) class in the 30°-50°angular range, as widely discussed previously by our group. [36] Considering the 002 reflection, the broadening is also associated to the thicknesses of the coherent crystalline domains inside the lamellae along the c axis. The simple application of the Scherrer formula leads to thicknesses and estimation of particles size that are reported in Table 2.…”

Section: Resultsmentioning

confidence: 99%

“…x F 2x particles formed following the exothermic reaction between hydrofluoric acid and aluminum and already observed for similar compositions. [14,36,41] The considered etching methods thus allow to obtain different morphology as the NaF/HCl solution leads to the formation of a compact MXene structure while the use of NH 4 HF 2 solution allows for the formation of open 2D system. The obtained MXenes have been characterized also in terms of chemical composition; the elemental composition from CHNS analysis is reported in Table 3.…”

Section: Chemelectrochemmentioning

confidence: 99%

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Critical Analysis of MXene Production with In‐Situ HF Forming Agents for Sustainable Manufacturing

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MXenes are an emerging class of materials considered for many applications, such as sensors, catalysis, energy storage devices. The main obstacle towards their massive implementation is the synthesis requiring the direct use of HF as etching agent. The development of alternative synthetic routes exploiting in-situ forming HF agents is the main strategies to overcome this limitation. In this study four different etching methods based on the use of NH 4 HF 2 , NaFÀ HCl, HBF 4 , and NaBF 4 À HCl are compared to produce Ti 3 C 2 T x from Ti 3 AlC 2 towards the application of MXenes in sodium ion batteries. Three of such etching methods have already been reported while one is here presented for the first time. The structural analysis of the obtained products is based on X-ray diffraction (XRD), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX), and X-ray photoelectron spectroscopy (XPS) analysis. All the materials have been tested in half-cell configuration vs. Na; the charge/discharge profiles and the C-rate tests are discussed and related to specific structural features. Overall, the results reveal that the MXene obtained using the HBF 4 etching agent under mild conditions is comparable both in structure and functional properties to the benchmark material, i. e., the MXene produced using HF at 5 % concentration. Indeed, the MXene synthetized with the HBF 4 presents the lowest mean voltage and potential hysteresis and shows the highest first cycle efficiency (69.7 %), overcoming the performance of the MXene produced with 5 % HF (67 %). This study proves the possibility to produce MXene with a more sustainable route.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Chemelectrochemmentioning

confidence: 99%

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Critical Analysis of MXene Production with In‐Situ HF Forming Agents for Sustainable Manufacturing

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“…Moreover, different etching conditions lead to variations in stacking structure. For example, fitting of X-ray and neutron diffraction measurements reveals a considerable increase in out-of-plane layer stacking disorder and in-plane layer sliding disorder for Ti 3 C 2 T x etched with 30 wt % HF compared to 5 wt % . Overall, multiple characterization techniques are needed together to confirm that MXenes have been “fully-etched,” which is a tedious process that can be replaced by in situ monitoring of the etching progress.…”

Section: Discussionmentioning

confidence: 99%

“…For example, fitting of X-ray and neutron diffraction measurements reveals a considerable increase in out-of-plane layer stacking disorder and in-plane layer sliding disorder for Ti 3 C 2 T x etched with 30 wt % HF compared to 5 wt %. 22 Overall, multiple characterization techniques are needed together to confirm that MXenes have been "fully-etched," which is a tedious process that can be replaced by in situ monitoring of the etching progress. Finally, in region IV, nonselective etching may occur where Ti and C atoms are attacked, leading to other gaseous species like CH 4 and CF 4 in addition to H 2 .…”

Section: Gas Collection Setup For Measuring Reactionmentioning

confidence: 99%

Kinetics of Ti₃AlC₂ Etching for Ti₃C₂T_x MXene Synthesis

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The family of two-dimensional (2D) carbides and nitrides called MXenes has grown to encompass numerous structures and compositions. MXenes have been explored in a variety of applications such as energy storage, wireless communication, optoelectronics, and medicine because of their high electrical conductivity, redox-active surfaces, plasmonic behavior, and other attractive properties. Knowledge of the process kinetics is of fundamental importance for synthesis and property control of MXenes. Prediction of the optimal processing time as a function of various parameters will also facilitate scaling wet chemical synthesis of MXenes for industrial use. Herein, we performed a systematic study of the kinetics of the MAX phase precursor etching reaction for topochemical MXene synthesis by collecting and tracking the evolution of the byproduct H2 gas. For the Ti3AlC2 MAX to Ti3C2T x MXene conversion, we investigated the influence of critical parameters, such as etchant composition, concentration, temperature, and MAX particle size, on the etching kinetics and developed an empirical predictive model to determine the optimal synthesis conditions given any input parameters. We tested a set of 12 kinetics models as well as a model-free fitting method and found the best agreement with the experimental results from three models and the model-free method (R 2 > 0.990). The measured apparent activation energies ranged from 54.2 to 55.7 kJ/mol. Overall, our results suggest NH4HF2 as the most efficient etchant, such that the etching time required to produce Ti3C2T x can be reduced to a few hours. We also demonstrated the importance of separating MAX powders based on particle size into narrow fractions. Finally, we discuss how this method can be improved and applied to study yet-to-be synthesized MXenes and how the MAX/MXene transformation can serve as a platform to model reactions under confinement.

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Functional MXene‐Based Materials for Next‐Generation Rechargeable Batteries

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fuels), such as excessively high temperatures, heavy downpours, severe floods, and droughts. As a response to the climate change, a global coalition for carbon neutrality is committed to be built by 2050 to maintain the sustainability of the global development. An imminent transition of the energy structure from traditional fossil fuels to the renewable energy sources, such as wind, solar, and tide is of great urgency. Due to the intermittent nature of these resources, energy-storage devices, especially the electrochemical energy-storage technologies, are of great significance in ensuring the stability and quality of the energy output. Lithium-ion batteries (LIBs) have been dominating the energy-storage market since its first commercialization in the 1990s. [1] They are currently widely applied in consumable electronics, electric vehicles, and grid-scale energy storage. [2] Yet more concerns have been raised regarding the scarcity and price of the lithium resources in recent years. Therefore, alternative battery technologies based on other metal ions beyond Li ions have been extensively explored. [3] However, finding suitable electrode materials for these batteries to achieve comparative performance to the LIBs remains a challenging task since the charge-carrier metal ions possess much larger ionic radius and stronger interaction with the host materials owing to their multivalent nature. MXenesare seen as an exceptional candidate to reshape the future of energy with their viable surface chemistry, ultrathin 2D structure, and excellent electronic conductivity. The extensive research efforts bring about rapid expansion of the MXene families with enriched functionalities, which significantly boost performance of the existing energy-storage devices. In this review, the strategies that are developed to functionalize the MXene-based materials, including tailoring their microstructure by ions/molecules/polymers-initiated interaction or self-assembly, surface/interface engineering with dopants or functional groups, constructing heterostructures from MXenes with various materials, and transforming them into a series of derivatives inheriting the merits of the MXene precursors are highlighted. Their applications in emerging battery technologies are demonstrated and discussed. With delicate functionalization and structural engineering, MXene-based electrode materials exhibit improved specific capacity and rate capability, and their presence further suppresses and even eliminates dendrite formation on the metal anodes, which lengthens the lifespan of the rechargeable batteries. Meanwhile, MXenes serve as additives for electrolytes, separators, and current collectors. Finally, some future directions worth of exploration to address the remaining challenging issues of MXene-based materials and achieve the nextgeneration high-power and low-cost rechargeable batteries are proposed.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adma.202204988.

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The Missing Piece: The Structure of the Ti₃C₂T_x MXene and Its Behavior as Negative Electrode in Sodium Ion Batteries

Cited by 35 publications

References 49 publications

Critical Analysis of MXene Production with In‐Situ HF Forming Agents for Sustainable Manufacturing

Critical Analysis of MXene Production with In‐Situ HF Forming Agents for Sustainable Manufacturing

Kinetics of Ti₃AlC₂ Etching for Ti₃C₂T_x MXene Synthesis

Functional MXene‐Based Materials for Next‐Generation Rechargeable Batteries

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The Missing Piece: The Structure of the Ti3C2Tx MXene and Its Behavior as Negative Electrode in Sodium Ion Batteries

Cited by 35 publications

References 49 publications

Critical Analysis of MXene Production with In‐Situ HF Forming Agents for Sustainable Manufacturing

Critical Analysis of MXene Production with In‐Situ HF Forming Agents for Sustainable Manufacturing

Kinetics of Ti3AlC2 Etching for Ti3C2Tx MXene Synthesis

Functional MXene‐Based Materials for Next‐Generation Rechargeable Batteries

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Product

Resources

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The Missing Piece: The Structure of the Ti₃C₂T_x MXene and Its Behavior as Negative Electrode in Sodium Ion Batteries

Kinetics of Ti₃AlC₂ Etching for Ti₃C₂T_x MXene Synthesis