Coupling W₁₈O₄₉/Ti₃C₂T_x MXene Pseudocapacitive Electrodes with Redox Electrolytes to Construct High‐Performance Asymmetric Supercapacitors

Abstract

A pseudocapacitive electrode with a large surface area is critical for the construction of a high‐performance supercapacitor. A 3D and interconnected network composed of W18O49 nanoflowers and Ti3C2Tx MXene nanosheets is thus synthesized using an electrostatic attraction strategy. This composite effectively prevents the restacking of Ti3C2Tx MXene nanosheets and meanwhile sufficiently exposes electrochemically active sites of W18O49 nanoflowers. Namely, this self‐assembled composite owns abundant oxygen vacancies from W18O49 nanoflowers and enough active sites from Ti3C2Tx MXene nanosheets. As a pseudocapacitive electrode, it shows a big specific capacitance, superior rate capability and good cycle stability. A quasi‐solid‐state asymmetric supercapacitor (ASC) is then fabricated using this pseudocapacitive anode and the cathode of activated carbon coupled with a redox electrolyte of FeBr3. This ASC displays a cell voltage of 1.8 V, a capacitance of 101 F g−1 at a current density of 1 A g−1, a maximum energy density of 45.4 Wh kg−1 at a power density of 900 W kg−1, and a maximum power density of 18 000 W kg−1 at an energy density of 10.8 Wh kg−1. The proposed strategies are promising to synthesize different pseudocapacitive electrodes as well as to fabricate high‐performance supercapacitor devices.

In Situ Synthesis of Mo and Ti-Dual Oxide-Incorporated Mo2Ti2C3Tx MXene Electrode Using a Lewis Acid-Assisted Method for Pseudocapacitors

“…The CV curves of (Mo, Ti)­O x -Mo 2 Ti 2 C 3 T x -700 at various scan rates, ranging from 10 to 200 mV s –1 (Figure b), displayed symmetric oxidation and reduction peaks, indicating the excellent reversibility of the composite MXene electrode. The potential of the redox peaks slightly shifted with the increase in scan rates, which can be attributed to the slightly reduced conductivity resulting from the electrode–electrolyte interfaces. , …”

“…The potential of the redox peaks slightly shifted with the increase in scan rates, which can be attributed to the slightly reduced conductivity resulting from the electrode−electrolyte interfaces. 30,31 For galvanostatic charge−discharge (GCD) measurements, a slightly narrowed potential window ending at 0.5 V was chosen due to observation of a plateau beyond 0.5 V. As depicted in Figure 3c, the (GCD) curves at 5 mA cm −2 for the electrodes show the distinct pseudocapacitive characteristic of a substantial voltage plateau. The (Mo, Ti)O x -Mo 2 Ti 2 C 3 T x -700 exhibits the longest plateau region during the charge transfer reaction, indicating a higher capacity compared to that of (Mo, Ti)O x -Mo 2 Ti 2 C 3 T x -750 and Mo 2 Ti 2 C 3 T x .…”

Construction of Binder‐Free, Self‐Supported, Hetero‐Core–Shell Honeycomb Structured CuCo2O4@Ni0.5Co0.5(OH)2 with Abundant Mesopores and High Conductivity for High‐Performance Energy Storage

“…Figure 4h illustrates that N 2 adsorption–desorption curves that display a typical IV isotherm, signifying the existence of porous structure in the samples. [ 72 ] Upon computation of the data, the S BET values of CCO/NF and CCO@N 0.5 C 0.5 OH/NF are determined to be 8.39 and 23.07 m 2 g −1 , respectively. The larger specific surface area of composite CCO@N 0.5 C 0.5 OH/NF provides a greater quantity of active sites for carriers, which is conducive to enhancing the energy storage performance of the electrode material, in electrochemical reaction.…”

MXene-Based Micro-Supercapacitors: Ink Rheology, Microelectrode Design and Integrated System

“…To achieve high capacitance while maintaining a high voltage window, pseudocapacitive materials such as metal oxides/sulfides/hydroxides and conductive polymers may be a more ideal choice for constructing asymmetric devices. ,,− Xu et al proposed a simple, cost-effective, and scalable two-step screen printing process to fabricate a flexible coplanar asymmetric microhybrid device (MHD), with Ti 3 C 2 T x serving as the negative electrode and Co-Al-LDH (layered double hydroxides) serving as the positive electrode . This screen-printed asymmetric MHD exhibited a wide voltage window (1.45 V), excellent cycling stability (92% capacitance retention after 10,000 cycles), improved energy density (10.80 μWh cm –2 ), and good mechanical flexibility (Figure c).…”