Preparation of N-doped graphite oxide for supercapacitors by NH3 cold plasma

In this work, N-doped graphite oxide (GO-P) was prepared by cold plasma treatment of GO using a mixture of NH3 and Ar as the working gas. When the ratios of NH3:Ar were 1:2, 1:3, and 1:4, the specific capacitances of the GO-P(NH3:Ar1:2), GO-P(NH3:Ar1:3), and GO-P(NH3:Ar1:4) were 124.5, 187.7, and 134.6 Fg−1, respectively, which were 4.7, 7.1, and 5.1 times that of GO at the current density of 1 Ag−1. The capacitance retention of the GO-P(NH3:Ar1:3) was 80% when it was cycled 1000 times. The characterization results showed that the NH3 cold plasma could effectively produce N-doped GO and generate more active defects. The N/C ratio and the contents of pyridinic nitrogen and graphitic nitrogen of the GO-P(NH3:Ar1:3) were the highest. These were conducive to providing pseudocapacitance and reducing the internal resistance of the electrode. In addition, the ID/IG of the GO-P(NH3:Ar=1:3) (1.088) was also the highest, indicating the highest number of defects. The results of discharge parameters measurement and in situ optical emission spectroscopy diagnosis of NH3 plasma showed that the discharge is the strongest when the ratio of NH3:Ar was 1:3, thereby the generated nitrogen active species can effectively promote N-doping. The N-doping and abundant defects were the keys to the excellent electrochemical performance of the GO-P(NH3:Ar1:3). NH3 cold plasma is a simple and rapid method to prepare N-doped GO and regulate the N-doping to prepare high-performance supercapacitors.

A scalable, ecofriendly, and cost-effective lithium metal protection layer from a Post-it note

A low-cost, ecofriendly, and scalable paper-derived protective layer is designed to achieve excellent electrochemical performance.

Recent Progress on the Applications of Carbonaceous and Metal-Organic Framework Nanomaterials for Supercapacitors

Supercapacitors (SCs) have been widely investigated in the realm of energy resulting from their superior long lifespan and remarkable power density. However, their practical usage is limited because of the high effective resistance and relatively low energy density. Electrode material is crucial for determining the performance of SCs, so the innovation and development of advanced electrode materials is particularly important. Metal-organic frameworks (MOFs) and carbonaceous materials, including MOF-derived carbons and carbon nanotubes (CNTs), are befitting as electrode active materials for SCs on the strength of the unique features of high porosity, tunable structures, and easy formation of composites with other compounds. Hence, great efforts were devoted on the synthesis strategies and structural modifications of electrodes to enhance the performance of SCs. In this review, the recent innovations in the realm of SCs, including the application of pristine and derivatives of MOFs as SC electrode materials, were extensively studied. Furthermore, the functions and electrochemical performance of various MOFs and their derivatives (e.g., MOF-derived carbons) were analyzed accordingly. Lastly, the innovations and application of CNTs as SC electrode active materials are systematically summarized. This review highlights the electrochemical performance of some advanced MOF- and carbon-based materials, and the critical factors for SC electrode active materials to achieve excellent electrochemical performance in the application of energy storage systems.

Recent advances and future perspectives for aqueous zinc-ion capacitors

The ion hybrid capacitor is expected to combine the high specific energy of battery-type materials and the superior specific power of capacitor-type materials, being considered as a promising energy storage technique. Particularly, the aqueous zinc-ion capacitors (ZIC) possessing merits of high safety, cost-efficiency and eco-friendliness, have been widely explored with various electrode materials and electrolytes to obtain excellent electrochemical performance. In this review, we first summarized the research progress on enhancing the specific capacitance of capacitor-type materials and reviewed the research on improving the cycling capability of battery-type materials under high current densities. Then, we looked back on the effects of electrolyte engineering on the electrochemical performance of ZIC. Finally, the research challenges and development directions of ZIC have been proposed. This review provides a guidance for the design and construction of the high-performance ZIC.

Co3O4 Nanoneedle Array Grown on Carbon Fiber Paper for Air Cathodes towards Flexible and Rechargeable Zn–Air Batteries

An economical and efficient method is developed for preparing flexible cathodes. In this work, a dense mesoporous Co3O4 layer was first hydrothermally grown in situ on the surface of chopped carbon fibers (CFs), and then carbon fiber paper (Co3O4/CP) was prepared by a wet papermaking process as a flexible zinc-air battery (ZAB). The high-performance air cathode utilizes the high specific surface area of a single chopped carbon fiber, which is conducive to the deposition and adhesion of the Co3O4 layer. Through the wet papermaking process, Co3O4/CP has ultra-thin, high mechanical stability and excellent electrical conductivity. In addition, the assembled ZAB exhibits relatively excellent electrochemical performance, with a continuous cycle of more than 180 times at a current density of 2 mA·cm−2. The zinc-air battery can maintain a close fit and work stably and efficiently even under high bending conditions. This process of combining single carbon fibers to prepare ultra-thin, high-density, high-conductivity carbon fiber paper through a papermaking process has huge application potential in the field of flexible wearables.

A Strategic Approach to Use Upcycled Si Nanomaterials for Stable Operation of Lithium-Ion Batteries

Silicon, as a promising next-generation anode material, has drawn special attention from industries due to its high theoretical capacity (around 3600 mAh g−1) in comparison with conventional electrodes, e.g., graphite. However, the fast capacity fading resulted by a large volume change hinders the pragmatic use of Si anodes for lithium ion batteries. In this work, we propose an efficient strategy to improve the cyclability of upcycled Si nanomaterials through a simple battery operation protocol. When the utilization degree of Si electrodes was decreased, the electrode deformation was significantly alleviated. This directly led to an excellent electrochemical performance over 100 cycles. In addition, the average charge (delithation) voltage was shifted to a lower voltage, when the utilization degree of electrodes was controlled. These results demonstrated that our strategic approach would be an effective way to enhance the electrochemical performance of Si anodes and improve the cost-effectiveness of scaling-up the decent nanostructured Si material.

MnCo2O4/g-C3N4 composite material preparation and its capacitance performance

MnCo2O4/g-C3N4 composite material was synthesized by the hydrothermal method, compared with MnCo2O4 without g-C3N4, it has excellent electrochemical performance. The composite material can reach a specific capacitance of 350 Fg[Formula: see text] at 1 Ag[Formula: see text]. The capacity retention rate is 96% after 1000 cycles at the rate of 2 Ag[Formula: see text]. Experiments show that g-C3N4 can effectively disperse and improve the conductivity of urchin-like MnCo2O4, and the composite of sufficient g-C3N4 can give full play to the performance of urchin-like MnCo2O4, provide faster electronic transport channels, effectively improve the ion migration rate, and make urchin-like MnCo2O4 increase the rate performance under high charge and discharge rates.