Vertically Aligned Micropillar Arrays Coated with a Conductive Polymer for Advanced Pseudocapacitance Energy Storage

Fluoridation of D-A Ambipolar Polymers to Accelerate Ion Migration toward High-Performance Symmetric Dual-Ion Energy Storage Devices

Dual-ion electrochemical energy storage devices have attracted much attention due to their cost effectiveness and high operating voltage. Electrochemical properties such as the specific capacity of dual-ion energy storage devices are closely related to ion migration. However, the ion migration of dual-ion energy storage devices is slow, especially the cation migration, resulting in limited discharge capacity and poor rate performance. In this study, fluorinated and nonfluorinated ambipolar conductive polymers were prepared as electrode materials. The effects of fluorination on aggregation and solvent were studied as well as its role in improving ion migration. The results show that fluorination can increase the force of fluorination on the solvent, reduce the level of binding of the solvent to the ion, and regulate the aggregation state. Compared with the unfluorinated polymer of PEPOPE, the ion migration and electrochemical kinetics of PEPFEP were significantly improved, and the PEPFPE (71 F/cm3) has a higher negative specific capacity than PEPOPE (24 F/cm3) at a current density of 5 A/cm3.

Ultra-Stable High-Capacity Polythiophene Derivative for Wide-Potential-Window Supercapacitors

Conducting polymer (CP)-based supercapacitors show great promise for applications in the field of wearable and portable electronics. However, these supercapacitors face persistent challenges, notably low energy density and inadequate stability. In this study, we introduce a polythiophene derivative, designated as poly(EPE), synthesized via the electrochemical polymerization of 8-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepine (EPE). The resulting poly(EPE) polymer exhibits an exemplary 3D porous network-like structure, significantly enhancing its capacitance performance. When employed as the electrode material, the symmetric supercapacitor demonstrates an exceptionally high specific capacitance of 1342 F g-1 at a current density of 4.0 A g-1, along with impressive energy and power densities of 119.3 W h kg-1 and 38.83 kW kg-1, respectively. These capacitance values surpass those of previously reported pristine CP-based supercapacitors. Notably, the supercapacitor showcases outstanding stability, maintaining a retention rate of 92.5% even after 50,000 charge-discharge cycles. These findings underscore the substantial potential of poly(EPE) as an electrode material for the advancement of the supercapacitor technology.

Li Salt Assisted Highly Flexible Carbonaceous Ni3N@polyimide Electrode for an Efficient Asymmetric Supercapacitor

This work used a highly flexible, sustainable polyimide tape as a substrate to deposit ductile-natured carbonaceous Ni3N (C/Ni3N@polyimide) material for supercapacitor application. C/Ni3N was prepared using a co-sputtering technique, and this method also provided better adhesion of the electrode material over the substrate, which is helpful in improving bending performance. The ductile behavior of the sputter-grown electrode and the high flexibility of the polyimide tape provide ultimate flexibility to the C/Ni3N@polyimide-based supercapacitor. To achieve optimum electrochemical performance, a series of electrochemical tests were done in the presence of various electrolytes. Further, a flexible asymmetric supercapacitor (NC-FSC) (C/Ni3N//carbon@polyimide) was assembled by using C/Ni3N as a cathode and a carbon thin film as an anode, separated by a GF/C-glass microfiber soaked in optimized 1 M Li2SO4 aqueous electrolyte. The NC-FSC offers a capacitance of 324 mF cm-2 with a high areal energy density of 115.26 μWh cm-2 and a power density of 811 μW cm-2, with ideal bending performance.

Three dimensional high-performance micro-supercapacitors with switchable high power density and high energy density

In the field of microscale energy storage, the fabrication of micro-supercapacitors (MSCs) with high power density and high energy density has always been a focus of research. In this work, laser-induced porous graphene and chemically deposited manganese dioxide nanoparticles are used as electrode materials, and a switchable MSC with two energy storage principles is obtained by designing symmetric interdigitated and square electrode structures. The aim is to overcome the preparation challenge of supercapacitors with high energy density and high power density by switching between two modes. In this MSC, the energy density of the high energy density mode (5.89 μW h cm-2) is 3.36 times that of the high power density mode (1.75 μW h cm-2), while the power density of the high power density mode (43.06 μW cm-2) is 1.44 times that of the high energy density mode (29.96 μW cm-2). In addition, under the drive of five serially connected MSCs, 27 LED lights can be continuously lit for 5 minutes. Therefore, this work provides a facile and novel method for the development of MSCs with high power density and high energy density, suggesting a great practical application value in the development of MSCs.

Self-assembled micropillar arrays via near-field electrospinning

Self-assembly in near-field electrospinning is reported for the first time in this paper, which realized the conversion from two-dimensional planar printing to three-dimensional (3D) structures. Repeatedly stacked fibres formed a micropillar array structure (MPAS) with intervals on the deposition paths by adding carbonyl iron powder particles to a polyethylene oxide (PEO) solution. The growth process of the self-assembled MPAS is documented, and the mechanism of the self-assembled MPAS is proposed. In addition, the effects of substrate speed and injection speed on self-assembly were investigated. Electric field distribution simulations show that the electric field strength around the MPAS is enhanced by nearly ten times so that the micropillar can attract the jet for further deposition. Self-assembly can obtain MPASs with arbitrary paths on different substrates, and the interval of the MPAS can be controlled by using bulging substrates. Furthermore, a self-assembled MPAS has been successfully used to prepare mold cavities, which can be used to prepare MPASs of other materials. Due to their small feature size, large surface area and structural periodicity, micropillar arrays will have promising applications, such as hydrophobicity of surfaces and electrochemical detection. Self-assembly in near-field electrospinning can significantly reduce the preparation cost of an MPAS and provide new processes and ideas.

Rare Earth Doping Engineering Tailoring Advanced Oxygen-Vacancy Co3 O4 with Tunable Structures for High-Efficiency Energy Storage

Co₃ O₄  with high theoretical capacitance is a promising electrode material for high-end energy applications, yet the unexcited bulk electrochemical activity, low conductivity, and poor kinetics of Co₃ O₄  lead to unsatisfactory charge storage capacity. For boosting its energy storage capability, rare earth (RE)-doped Co₃ O₄  nanostructures with abundant oxygen vacancies are constructed by simple, economical, and universal chemical precipitation. By changing different types of RE (RE = La, Yb, Y, Ce, Er, Ho, Nd, Eu) as dopants, the RE-doped Co₃ O₄  nanostructures can be well transformed from large nanosheets to coiled tiny nanosheets and finally to ultrafine nanoparticles, meanwhile, their specific surface area, pore distribution, the ratio of Co²⁺ /Co³⁺ , oxygen vacancy content, crystalline phase, microstrain parameter, and the capacitance performance are regularly affected. Notably, Eu-doped Co₃ O₄  nanoparticles with good cycle stability show a maximum specific capacitance of 1021.3 F g^-1 (90.78 mAh g^-1 ) at 2 A g^-1 , higher than 388 F g^-1 (34.49 mAh g^-1 ) of pristine Co₃ O₄  nanosheets. The assembling asymmetric supercapacitor delivers a high energy density of 48.23 Wh kg^-1  at high power density of 1.2 kW kg^-1 . These findings denote the significance and great potential of RE-doped Co₃ O₄  in the development of high-efficiency energy storage.

Effect of Surface Treatment on Performance and Internal Stacking Mode of Electrohydrodynamic Printed Graphene and Its Microsupercapacitor

Microelectronic devices are developing rapidly in portability, wearability, and implantability. This puts forward an urgent requirement for the delicate deposition process of materials. Electrohydrodynamic printing has attracted academic and industrial attention in preparing ultrahigh-density microelectronic devices as a new noncontact, direct graphic, and low-loss thin film deposition process. In this work, a printed graphene with narrow line width is realized by combining the electrohydrodynamic printing and surface treatment. The line width of printed graphene on the hydrophobic treatment surface reduced from 80 to 28 μm. The resistivity decreased from 0.949 to 0.263 Ω·mm. Unexpectedly, hydrophobic treatment can effectively induce random stacking of electrohydrodynamic printed graphene, which avoids parallel stacking and agglomeration of graphene sheets. The performance of printed graphene is thus effectively improved. After optimization, a graphene planar supercapacitor with a printed line width of 28 μm is successfully obtained. Its capacitance can reach 5.39 mF/cm² at 50 mV/s, which is twice higher than that of the untreated devices. The device maintains 84.7% capacitance after 5000 cycles. This work provides a reference for preparing microelectronic devices by ultrahigh precision printing and a new direction for optimizing two-dimensional material properties through stacking adjustment.

Integratable photodetectors based on photopolymerized conductive polymer via femtosecond laser direct writing

Conductive polymers have attracted a great deal of attention due to their remarkable electrical conductivity. However, the low solubility and inability to meet the limit for the flexible patterning fabrication ability of conductive polymers hinders their applications in miniaturized and integrated electronic devices. Here, femtosecond laser direct writing (FsLDW) is employed to achieve the in situ fabrication of polypyrrole (PPy) with flexibility. Notably, high-precision flexible patterning with a minimum feature size of 5.2 µm and spatial control over the polymerization of PPy is achieved. Moreover, PPy microwires are constructed into a photodetector that exhibits a responsivity of 644 A/W at 0.1-V bias under ultraviolet (UV) irradiation. Ultimately, an image sensor is fabricated by integrating multiple photodetectors, demonstrating the application potential of FsLDW technology for developing miniaturized and integrated electronic devices based on conductive polymers.