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Open Access Research Article Issue
Stoichiometric Ti3C2Tx Coating for Inhibiting Dendrite Growth in Anode-Free Lithium Metal Batteries
Energy & Environmental Materials 2024, 7(4): e12686
Published: 15 October 2023
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Lithium metal batteries (LMBs) and anode-free LMBs (AFLMBs) present a solution to the need for batteries with a significantly superior theoretical energy density. However, their adoption is hindered by low Coulombic efficiency (CE) and rapid capacity fading, primarily due to the formation of unstable solid electrolyte interphase (SEI) layer and Li dendrite growth as a result of uneven Li plating. Here, we report on the use of a stoichiometric Ti3C2Tx (S-Ti3C2Tx) MXene coating on the copper current collector to enhance the cyclic stability of an anode-free lithium metal battery. The S-Ti3C2Tx coating provides abundant nucleation sites, thereby lowering the overpotential for Li nucleation, and promoting uniform Li plating. Additionally, the fluorine (−F) termination of S-Ti3C2Tx participates in the SEI formation, producing a LiF-rich SEI layer, vital for stabilizing the SEI and improving cycle life. Batteries equipped with S-Ti3C2Tx@Cu current collectors displayed reduced Li consumption during stable SEI formation, resulting in a significant decrease in capacity loss. AFLMBs with S-Ti3C2Tx@Cu current collectors achieved a high initial capacity density of 4.2 mAh cm−2, 70.9% capacity retention after 50 cycles, and an average CE of 98.19% in 100 cycles. This innovative application of MXenes in the energy field offers a promising strategy to enhance the performance of AFLMBs and could potentially accelerate their commercial adoption.

Open Access Research Article Issue
Free-Standing α-MoO3/Ti3C2 MXene Hybrid Electrode in Water-in-Salt Electrolytes
Energy & Environmental Materials 2023, 6(4)
Published: 29 August 2022
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While transition-metal oxides such as α-MoO3 provide high capacity, their use is limited by modest electronic conductivity and electrochemical instability in aqueous electrolytes. Two-dimensional (2D) MXenes, offer metallic conductivity, but their capacitance is limited in aqueous electrolytes. Insertion of partially solvated cations into Ti3C2 MXene from lithium-based water-in-salt (WIS) electrolytes enables charge storage at positive potentials, allowing a wider potential window and higher capacitance. Herein, we demonstrate that α-MoO3/Ti3C2 hybrids combine the high capacity of α-MoO3 and conductivity of Ti3C2 in WIS (19.8 m LiCl) electrolyte in a wide 1.8 V voltage window. Cyclic voltammograms reveal multiple redox peaks from α-MoO3 in addition to the well-separated peaks of Ti3C2 in the hybrid electrode. This leads to a higher specific charge and a higher rate capability compared to a carbon and binder containing α-MoO3 electrode. These results demonstrate that the addition of MXene to less conductive oxides eliminates the need for conductive carbon additives and binders, leads to a larger amount of charge stored, and increases redox capacity at higher rates. In addition, MXene encapsulated α-MoO3 showed improved electrochemical stability, which was attributed to the suppressed dissolution of α-MoO3. The work suggests that oxide/MXene hybrids are promising for energy storage.

Research Article Issue
An aqueous 2.1 V pseudocapacitor with MXene and V-MnO2 electrodes
Nano Research 2022, 15(1): 535-541
Published: 26 May 2021
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MXenes have shown record-breaking redox capacitance in aqueous electrolytes, but in a limited voltage window due to oxidation under anodic potential and hydrogen evolution under high cathodic potential. Coupling Ti3C2Tx MXene negative electrode with RuO2 or carbon-based positive electrodes expanded the voltage window in sulfuric acid electrolyte to about 1.5 V. Here, we present an asymmetric pseudocapacitor using abundant and eco-friendly vanadium doped MnO2 as the positive and Ti3C2Tx MXene as the negative electrode in a neutral 1 M Li2SO4 electrolyte. This all-pseudocapacitive asymmetric device not only uses a safer electrolyte and is a much less expensive counter-electrode than RuO2, but also can operate within a 2.1 V voltage window, leading to a maximum energy density of 46 Wh/kg. This study also demonstrates the possibility of using MXene electrodes to expand the working voltage window of traditional redox-capable materials.

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