A New Free-Standing Aqueous Zinc-Ion Capacitor Based on MnO2–CNTs Cathode and MXene Anode

Abstract

HIGHLIGHTS • A new zinc-ion capacitor (ZIC) was realized by assembling the free-standing manganese dioxide-carbon nanotubes (MnO 2-CNTs) battery-type cathode and MXene (Ti 3 C 2 T x) capacitor-type anode in an aqueous electrolyte. • The large specific capacitance of the MXene anode avoids the mismatch in capacitance between the cathode and anode of the ZIC. • The superior performance of the proposed ZIC makes it a promising candidate for the next-generation energy storage devices. ABSTRACT Restricted by their energy storage mechanism, current energy storage devices have certain drawbacks, such as low power density for batteries and low energy density for supercapacitors. Fortunately, the nearest ion capacitors, such as lithium-ion and sodium-ion capacitors containing battery-type and capacitor-type electrodes, may allow achieving both high energy and power densities. For the inspiration, a new zinc-ion capacitor (ZIC) has been designed and realized by assembling the free-standing manganese dioxide-carbon nanotubes (MnO 2-CNTs) battery-type cathode and MXene (Ti 3 C 2 T x) capacitortype anode in an aqueous electrolyte. The ZIC can avoid the insecurity issues that frequently occurred in lithium-ion and sodium-ion capacitors in organic electrolytes. As expected, the ZIC in an aqueous liquid electrolyte exhibits excellent electrochemical performance (based on the total weight of cathode and anode), such as a high specific capacitance of 115.1 F g −1 (1 mV s −1), high energy density of 98.6 Wh kg −1 (77.5 W kg −1), high power density of 2480.6 W kg −1 (29.7 Wh kg −1), and high capacitance retention of ~ 83.6% of its initial capacitance (15,000 cycles). Even in an aqueous gel electrolyte, the ZIC also exhibits excellent performance. This work provides an essential strategy for designing next-generation high-performance energy storage devices.

Low-Temperature Growing Anatase TiO2/SnO2 Multi-dimensional Heterojunctions at MXene Conductive Network for High-Efficient Perovskite Solar Cells

“…The 2D materials and their tailored products, such as black phosphorene and 0D graphene quantum dot (QD), have been employed as dopants to modify the SnO 2 ETLs in PSCs on the electrical conductivity, energy-level properties, and reducing the surface defects and surface electron traps [24,25]. As a new group of 2D materials, the MXene is constructed of M N+1 X N T X structure, where the M represents an early transition metal such as Ti, and the X representing C and/or N element, and the T X meaning the terminal functional groups [26]. With its excellent metallic electrical conductivity, hydrophilic surface, and pseudocapacitance properties, the MXene has been explored as electrode materials for solar cells [27][28][29], zinc-ion capacitors [26,30], supercapacitors [31], or sensors [32].…”

“…As a new group of 2D materials, the MXene is constructed of M N+1 X N T X structure, where the M represents an early transition metal such as Ti, and the X representing C and/or N element, and the T X meaning the terminal functional groups [26]. With its excellent metallic electrical conductivity, hydrophilic surface, and pseudocapacitance properties, the MXene has been explored as electrode materials for solar cells [27][28][29], zinc-ion capacitors [26,30], supercapacitors [31], or sensors [32]. In PSC application, it has also been reported that the PCE can be enhanced on the basis of the improved functional layers with MXene dopant.…”

A New Route to Enhance the Packing Density of Buckypaper for Superior Piezoresistive Sensor Characteristics

“…The discovery of carbon nanotubes (CNTs) by Iijima [1] led to extensive research for the utilization of these unique structures with extraordinary properties in the field of electrical storage devices [2,3], digital electronics devices [4,5], structure health monitoring (SHM) sensors [6,7] and concrete reinforcement applications [8,9], etc. Both theoretically and experimentally, it is proved that CNTs inherit excellent physical properties having an electrical conductivity of 3 × 10 6 S/m [10,11], the thermal conductivity of 2000-3500 W/m•K [12,13], the mechanical strength of 100 GPa [14], the Young's modulus of 1 TPa [15,16] and the piezoresistive gauge factor (GF) of 2900 [17,18].…”

Highly Flexible and Self‐Healable Zinc‐Ion Hybrid Supercapacitors Based on MWCNTs‐RGO Fibers

“…The GCD curves maintain the shape of the isosceles triangle, further indicating the excellent electrochemical performance of the MWCNTs‐RGO hybrid fibers. [ 41 ] The specific capacitance calculated by CV results of the MWCNTs‐RGO hybrid fibers are shown in Figure 3f. When the scan rates increased from 1 to 100 mV s −1 , the specific capacitance decreased from 134.1 to 38.0 F cm −3 .…”