Direct Laser Writing of Transparent Polyimide Film for Supercapacitor

Inkjet-printed flexible V2CTx film electrodes with excellent photoelectric properties and high capacities for energy storage device

Energy storage devices are progressively advancing in the light-weight, flexible, and wearable direction. Ti3C2Tx flexible film electrodes fabricated via a non-contact, cost-effective, high-efficiency, and large-scale inkjet printing technology were capable of satisfying these demands in our previous report. However, other MXenes that can be employed in flexible energy storage devices remain undiscovered. Herein, flexible V2CTx film electrodes (with the low formula weight vs Ti3C2Tx film electrodes) with both high capacities and excellent photoelectric properties were first fabricated. The area capacitances of V2CTx film electrodes reached 531.3-5787.0 μF⋅cm-2 at 5 mV⋅s-1, corresponding to the figure of merits (FoMs) of 0.07-0.15. Noteworthy, V2CTx film electrode exhibited excellent cyclic stability with the capacitance retention of 83 % after 7,000 consecutive charge-discharge cycles. Furthermore, flexible all solid-state symmetric V2CTx supercapacitor was assembled with the area capacitance of 23.4 μF⋅cm-2 at 5 mV⋅s-1. Inkjet printing technology reaches the combination of excellent photoelectric properties and high capacities of flexible V2CTx film electrodes, which provides a new strategy for manufacturing MXene film electrodes, broadening the application prospect of flexible energy storage devices.

Laser Direct Writing of MnO2/Carbonized Carboxymethylcellulose-Based Composite as High-Performance Electrodes for Supercapacitors

Manganese dioxide and its derivatives are widely used as promising electrode materials for supercapacitors. To achieve the environmentally friendly, simple, and effective material synthesis requirements, the laser direct writing method is utilized to pyrolyze the MnCO₃/carboxymethylcellulose (CMC) precursors to MnO₂/carbonized CMC (LP-MnO₂/CCMC) in a one-step and mask-free way successfully. Here, CMC is utilized as the combustion-supporting agent to promote the conversion of MnCO₃ into MnO₂. The selected materials have the following advantages: (1) MnCO₃ is soluble and can be converted into MnO₂ with the promotion of a combustion-supporting agent. (2) CMC is an eco-friendly and soluble carbonaceous material, which is widely used as the precursor and combustion-supporting agent; (3) the redundant part of the MnCO₃/CMC precursor can be removed by deionized water, which is simple and convenient. The different mass ratios of MnCO₃ and CMC-induced LP-MnO₂/CCMC(R1) and LP-MnO₂/CCMC(R1/5) composites are investigated in the electrochemical performance toward electrodes, respectively. The LP-MnO₂/CCMC(R1/5)-based electrode showed the high specific capacitance of 74.2 F/g (at the current density of 0.1 A/g) and good electrical durability for 1000 times charging-discharging cycles. Simultaneously, the sandwich-like supercapacitor which was assembled by LP-MnO₂/CCMC(R1/5) electrodes presents the maximum specific capacitance of 49.7 F/g at the current density of 0.1 A/g. Moreover, the LP-MnO₂/CCMC(R1/5)-based energy supply system is used to light a light-emitting diode, which demonstrates the great potential of LP-MnO₂/CCMC(R1/5)-based supercapacitors for power devices.

Copper electrode preparation by a selective laser reduction of copper oxide on lignin fiber membranes and its application as a photodetector

The performance of electrodes is a key factor affecting the development of smart fabrics. The preparation of common fabric flexible electrodes has defects such as high cost, complicated preparation, and complex patterning that limit the development of fabric-based metal electrodes. Therefore, this paper presented a simple fabrication method for preparing Cu electrodes using selective laser reduction of CuO nanoparticles. By optimizing laser processing power, scanning speed, and focusing degree), we prepared a Cu circuit with an electrical resistivity of ∼ 5.53 µΩ.m. Based on the photothermoelectric properties of Cu electrodes, a white light photodetector is developed. The detectivity of the photodetector reaches ∼2.14 mA/W at a power density of 10.01 mW/cm². This method is instructive for preparing metal electrodes or conductive lines on the surface of fabrics, and provides specific techniques for manufacturing wearable photodetectors.

Inkjet Printing Transparent and Conductive MXene (Ti3C2Tx) Films: A Strategy for Flexible Energy Storage Devices

MXene is a generic name for a large family of two-dimensional transition metal carbides or nitrides, which show great promise in the field of transparent supercapacitors. However, the manufacturing of supercapacitor electrodes with a high charge storage capacity and desirable transmittance is a challenging task. Herein, a low-cost, large-scale, and rapid preparation of flexible and transparent MXene films via inkjet printing is reported. The MXene films realized the sheet resistance (R_s) of 1.66 ± 0.16 MΩ sq^-1 to 1.47 ± 0.1 kΩ sq^-1 at the transmissivity of 87-24% (λ = 550 nm), respectively, corresponding to the figure of merit (the ratio of electronic to optical conductivity, σ_DC/σ_OP) of ∼0.0012 to 0.13. Furthermore, the potential of inkjet-printed transparent MXene films in transparent supercapacitors was assessed by electrochemical characterization. The MXene film, with a transmittance of 24%, exhibited a superior areal capacitance of 887.5 μF cm^-2 and retained 85% of the initial capacitance after 10,000 charge/discharge cycles at the scan rate of 10 mV s^-1. Interestingly, the areal capacitance (192 μF cm^-2) of an assembled symmetric MXene transparent supercapacitor, with a high transmittance of 73%, still surpasses the performance of previously reported graphene and single-walled carbon nanotube (SWCNT)-based transparent electrodes. The convenient manufacturing and superior electrochemical performance of inkjet-printed flexible and transparent MXene films widen the application horizon of this strategy for flexible energy storage devices.