[en] The unique composite of Ni@NiO core/shell structure and active carbon (AC) had been synthesized through a two-step method. The Ni"2"+ was first reduced to Ni on the surface of AC supporter. Then the NiO shell was obtained after the following oxidized treatment. The transmission electron microscopy (TEM) observed that Ni@NiO particles with thin shell were sporadically dispersed on AC surface without vast reaggregation. And the electrochemical impedance spectroscopy (EIS) showed that Ni@NiO_c_o_r_e_-_s_h_e_l_l/AC composite had higher electrical conductivity. Thus, the outside thin NiO shell would expose more electroactive surface and shorten the ionic diffusion distance. While the Ni core could accelerate the electronic transport due to its low contact resistance. When employed as supercapacitor electrodes, Ni@NiO_c_o_r_e_-_s_h_e_l_l/AC composite exhibited a high specific capacitance of ca. 700 F g"−"1 at 0.5 A g"−"1 and remained above 90% of the initial capacity after 1000 cycles at 1 A g"−"1. The high specific capacitance and long cycle life of the hybrid structure made it alternative for energy storage systems

[en] Highlights: • Hair was directly carbonized by environmental and energy-saving methods. • Hair was utilized to prepare nitrogen-doped carbon materials for supercapacitor. • A new approache for preparing nitrogen-rich active carbon from biomass waste of hair-like precursor. • Hair-based carbon having a non-crystalline layered structure and excellent capacitive performance. -- Abstract: Hair, a high-nitrogen energetic material, is utilized as a precursor for nitrogen-doped porous carbon. The preparation procedures for obtaining carbon from hair are very simple, namely, reductant or deionized water activation process followed by hair carbonization under argon atmosphere at 800 °C for 2 h. The samples are characterized through scanning electron microscopy, transmission electron microscopy, X-ray diffraction, nitrogen adsorption, and X-ray photoelectron microscopy. The carbon samples are tested as electrode materials in supercapacitors in a three-electrode system. The carbon (soaked in deionized water at 80 °C) presents relatively low specific surface areas (441.34 m² g⁻¹) and shows higher capacitance (154.5 F g⁻¹) compared with nitrogen-free commercial activated carbons (134.5 F g⁻¹) at 5 A g⁻¹. The capacitance remains at 130.5 F g⁻¹ even when the current load is increased to 15 A g⁻¹. The capacitance loss is only 5% in 6 M KOH after 10,000 charge and discharge cycles at 5 A g⁻¹. It is the unique microstructure after activation processing and electroactive nitrogen functionalities that enable the carbon obtained through a simple, ecological, and economical process to be utilized as a potential electrode material for electrical double-layer capacitors

[en] A one-pot sol-gel method was modified through delaying gel curing by compositing Li₃V₂(PO₄)₃ with carbon. As a result, mesoporous carbon film inlaid with Li₃V₂(PO₄)₃ nanoclusters (named as LVP-C) was prepared to serve as cathode for the “non-consumable electrolyte type” and “internal serial hybrid type” Lithium-ion hybrid supercapacitor (LIHS). The LVP-C17 composite exhibited a considerably high initial discharge capacity of 128 mAh g⁻¹ at 0.2C-rate, which was extremely close to the theoretical specific capacity. The BET specific surface area of the LVP-C17 composite is as high as 53.65 m² g⁻¹ and the Barret-Joyner-Halenda (BJH) pore-size-distribution curve displays that the pore sizes of the composite are mainly below 10 nm. The Raman test of the LVP-C17 composite mainly exhibits the graphitized carbon (SP² hybridization) and a smaller R value (0.86), from which it can be inferred that the electronic conductivity of the composite is improved. The LIHS was designed by using LVP-C17 as cathode and active carbon (AC) as anode (LVP-C17//AC LIHS), which exhibited a higher energy density of 24 Wh kg⁻¹ at a power density 405 W kg⁻¹, with 77% specific capacitance retention after 1000 cycles in a wider voltage range of 0–2.7 V. Furthermore, even at higher power density of 2.03 kW kg⁻¹, the energy density provided by the device can still retain 12.4 Wh kg⁻¹. The device combines the electrochemical performance advantages of lithium-ion batteries (LIBs) with supercapacitors (SCs) and is comparable to the energy density and power density of currently commercially available Ni/MH batteries.

[en] Highlights: • Characteristics of energy loss for CVT hydraulic system are studied. • Influence of speed ratio rate of change on energy loss is obtained. • DVSRCS-G considering energy loss of CVT hydraulic system is proposed. -- Abstract: By using the continuously variable transmission (CVT) to change the speed ratio continuously, the power resource components can operate in the high efficiency region for plug-in hybrid electric vehicle (PHEV) equipped with CVT, which improves the driving efficiency of powertrain. However, the frequent change of CVT speed ratio causes large energy loss of CVT hydraulic system and reduces the energy economy of PHEV. In view of this issue, the characteristic of energy loss for CVT hydraulic system is studied and the influence of speed ratio rate of change on energy loss of hydraulic system is obtained. Then, the simulation based on the continuously variable speed ratio control strategy (CVSRCS) is carried out and the results indicate that there is large energy loss of the CVT hydraulic system due to the frequent change of CVT speed ratio, which influences energy economy of the vehicle. Moreover, excessive driving jerk is generated, which significantly affects ride comfort of the vehicle. In order to reduce the adverse impact of frequent changes of CVT speed ratio on energy economy and ride comfort, a discretely variable speed ratio control strategy (DVSRCS) is proposed and discrete speed ratio is optimized by genetic algorithm. A comparative simulation for PHEV’s performance by adopting the CVSRCS and the proposed discretely variable speed ratio control strategy is carried out under a comprehensive driving cycle. The results of this study demonstrate that the proposed control strategy can not only significantly reduce the energy loss of CVT hydraulic system and enhance the energy economy, but also improve ride comfort.