Search

Traditional synthetic routes for transition metal sulfides typically involve solution and thermal-based processes to exploit their favorable pseudo-capacitive properties. However, there is a practical need to develop alternative processes to fabricate metal sulfide electrodes because of the time-consuming processes (>12 h), additional heat-treatment to active reactants, relatively high post-heat-treatment temperature (200–400 °C) and non-scalable nature of existing synthetic routes. Herein, utilizing a solution-based sulfur precursor, one-dimensional single-crystalline Cu2S nanostructures have been successfully prepared via a solution-based direct synthesis process within 10 min at room temperature without the need for thermal treatment steps. The fabricated electrode exhibits a capacitance of 750 mF cm−2 at a current density of 2 mA cm−2. Moreover, the rate capacitance is maintained at about 82.3% as the current density is increased to 40 mA cm−2, and the capacity retains 90.5% of the initial value after 20 000 cycles. Importantly, as this method involves a solution-based formulation it is compatible with roll-to-roll processes, which is promising for mass and scalable production of the electrodes. The synthetic method ensures a facile and efficient approach to fabricating scalable one-dimensional single crystalline Cu2S nanostructures, highlighting the uniqueness of the solution-based sulfur activation method.

Chemical doping is one of the most effective methods to tune the electrochemical properties of graphene. We report a simple and relatively low-temperature process for the fabrication of boron doped graphene by using a spin-on dopant (SOD) method. SOD-treated graphene was successfully doped with boron atoms at a temperature lower than 600 °C. The fabricated boron doped graphene exhibits a specific capacitance of 4 mF cm−2, as well as a high-rate performance of 91.9% at 200 mV s−1 as an electrode material for pseudocapacitors. It also shows excellent oxygen reduction activity and durability with a current retention of 91.4% and methanol-tolerance properties. These features are beneficial for catalyst applications in the oxygen reduction reaction due to well-engineered boron sites with high electrical conductivity and many active sites for electrochemical reactions.

Spinel metal cobaltites (MCo2O4) composed of different transition metals and their corresponding oxides are a significant class of materials for capacitive energy storage due to their novel-redox nature which enables faradaic kinetics of electrodes with high energy storage ability. It is also still important to investigate and adjust the logical selection of transition metal atoms in M sites of spinel metal cobaltites in order to positively affect their overall storage behavior. Herein, we report a strategy to design novel spinel metal cobaltite nanostructures with multiple transition metal heteroatoms so as to achieve optimized capacitive performance. We develop a Zn–Ni–Co2O4 electrode with hetero-transition metals (ZNCH) to simultaneously achieve a large capacitance, high conductivity, favorable ion diffusion, and stable structural integrity. The proposed combined atomic configuration of the electrode materials exhibits excellent energy storage characteristics with a capacitance of 5.58 F cm−2 (1390.1 F g−1) and a good energy density of 36.73 W h kg−1, as well as a charge–discharge retention stability of 87.7% at a current density of 10 mA cm−2 after 3000 cycles. Through the combined utilization of multiple transition metal heteroatoms, the synergistic integration of different electrochemical properties, such as high energy storage performance, and structural stability can be directly realized.

To achieve the further development of supercapacitors (SCs), which have intensively received attention as a next-generation energy storage system, the rational design of active electrode materials with electrochemically more favorable structure is one of the most important factors to improve the SC performance with high specific energy and power density. We propose and successfully grow copper sulfide (CuS) nanowires (NWs) as a chalcogenide-based electrode material directly on a Cu mesh current collector using the combination of a facile liquid-solid chemical oxidation process and an anion exchange reaction. We found that the as-prepared CuS NWs have well-arrayed structures with nanosized crystal grains, a high aspect ratio and density, as well as a good mechanical and electrical contact to the Cu mesh. The obtained CuS NW based electrodes, with additional binder- and conductive material-free, exhibit a much higher areal capacitance of 378.0 mF/cm2 and excellent cyclability of an approximately 90.2 percentage retention during 2000 charge/discharge cycles due to their unique structural, electrical, and electrochemical properties. Furthermore, for practical SC applications, an asymmetric supercapacitor is fabricated using active carbon as an anode and CuS NWs as a cathode, and exhibits the good capacitance retention of 91% during 2000 charge/discharge processes and the excellent volumetric energy density of 1.11 mW h/cm3 compared to other reported pseudo-capacitive SCs., 18 pages, 4 figures

Metal-oxide-based anode materials in energy storage devices continue to be of considerable interest for both fundamental science and potential technological applications because of their diverse functionalities, high theoretical capacity, cost-effectiveness, and non-polluting nature. However, despite these favourable features for various power source applications, important challenges associated with insertion-induced structural degradation remain, leading to capacity fading, and must be addressed to move towards the practical use of high-capacity metal oxide anodes. Here, we report the successful synthesis of novel hierarchical carbon-encapsulated manganese oxide architectures with hollow-tube structures and unique porous walls via a simple microwave process coupled with a hydrothermal method. This approach provides beneficial synergistic effects in terms of structural stability, electrochemical active surface areas, and electrical and ionic pathways. The carbon-encapsulated porous hollow manganese oxide nanotubes exhibit excellent electrochemical characteristics with large reversible specific capacity and excellent cycling stability (875 mA h g−1 capacity retention up to 100 cycles) as well as outstanding high-rate performance (729 mA h g−1 at 700 mA g−1), which is the highest value thus far reported for manganese-oxide-based anode materials.

We demonstrate the impressive performance of sparsely studied nickel titanate anode materials for Li-ion batteries (LIBs). The nickel titanate anode delivers a high reversible discharge capacity of 435 mA h g−1 at a current density of 35 mA g−1, high-rate performance and excellent cycling retention of 96% with a long-term cycling stability at 1500 mA g−1 over 300 cycles. The coulombic efficiency is obtained as high as 98%. This superior nickel titanate electrode material could be used as a safe, low-cost, long cycle life anode material for next-generation LIBs with a high power capability.

Correction for ‘Electrochemical and electrocatalytic reaction characteristics of boron-incorporated graphene via a simple spin-on dopant process’ by A-Rang Jang et al., J. Mater. Chem. A, 2018, DOI: 10.1039/c7ta09517a.