Free‐Standing α‐MoO₃/Ti₃C₂ MXene Hybrid Electrode in Water‐in‐Salt Electrolytes

Abstract

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.

Cation-Driven Assembly of Bilayered Vanadium Oxide and Graphene Oxide Nanoflakes to Form Two-Dimensional Heterostructure Electrodes for Li-Ion Batteries

“…A similar phenomenon for BVO was observed in the case of oxide/carbon heterointerfaces created via carbonization of chemically preintercalated dopamine molecules and nanocomposites with graphene and carbon nanotubes . It is possible that the rGO in these materials stabilizes the electrodes by inhibiting the dissolution of LVO in electrolytes, an occurrence observed in previous studies. − In the case of the 2D LVO/rGO heterostructures prepared in this work, the stabilization effect could be attributed to both the formation of bonds between the LVO and rGO surfaces via the Li + ions incorporated between the layers as well as encapsulation of the oxide nanoflakes by rGO nanoflakes preventing active dissolution of LVO in the electrolyte, similar to reported MoO 3 /MXene composite electrodes . This encapsulation could also explain why the capacity of the LVO/rGO-35 wt % electrode initially increases.…”

“…53−55 In the case of the 2D LVO/rGO heterostructures prepared in this work, the stabilization effect could be attributed to both the formation of bonds between the LVO and rGO surfaces via the Li + ions incorporated between the layers as well as encapsulation of the oxide nanoflakes by rGO nanoflakes preventing active dissolution of LVO in the electrolyte, similar to reported MoO 3 /MXene composite electrodes. 56 This encapsulation could also explain why the capacity of the LVO/rGO-35 wt % electrode initially increases. The increased rGO content may initially block electrolyte access to the LVO component, and electrochemical cycling could activate this material by opening diffusion pathways.…”

Heterostructures of MXenes and transition metal oxides for supercapacitors: an overview

“…The electrochemical performance shows multiple redox peaks in a water-in-salt electrolyte (19.8 m LiCl), and a wide operating potential of 1.8 V ( vs. Ag wire). 116 Zheng et al prepared Mn 3 O 4 (+ve electrode)/Ti 3 C 2 T z (−ve electrode) with high mass loading (10 mg cm −2 ) and low self-discharge rates in a 14 M LiCl electrolyte, respectively. Subsequent ASC devices showed ultrahigh energy and power density with excellent rate capability and a wide operating potential window of 1.5 V due to the usage of WIS electrolytes.…”

Covalent Organic Frameworks (COFs)/MXenes Heterostructures for Electrochemical Energy Storage

“…For example, graphene shows high conductivity, but its energy density is limited due to EDLC behavior. Similarly, oxides show high capacity but due to their poor electronic conductivity, their rate performance is very poor and often shows poor cyclability due to dissolution . Hence designing a heterostructure of materials with complement properties is a viable approach to maximize the energy storage performance.…”

“…Similarly, oxides show high capacity but due to their poor electronic conductivity, their rate performance is very poor and often shows poor cyclability due to dissolution. 18 Hence designing a heterostructure of materials with complement properties is a viable approach to maximize the energy storage performance. Recently, MXenes have gained wide attention in the energy storage owing to their metallic conductivity and redox-active surfaces, however, a narrow operational voltage limits their capacity and energy density.…”