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Aluminium ion batteries are considered to be a promising development for large-scale energy storage and conversion applications. In this research, a nanosphere-rod-like Co3O4 has been synthesized after the hydrothermal reaction and the subsequent heat treatment process, which is used for the cathode materials of aluminium ion batteries. The working mechanisms of the Co3O4 are deeply investigated. It is found that the electrochemical deposition and dissolution of aluminum occurs on the surface of pure aluminium anode, and the Al3+ cations are intercalated and de-intercalated in the cathode materials during the discharge and charge processes. The battery exhibits a high discharge specific capacity of 490 mAh g−1 at the first cycle, with the current density of 50 mA g−1. Furthermore, the discharge capacity still maintains a high level of 122.1 mAh g−1 after 100 cycles at the current density of 200 mA g−1, indicating a good cycle performance. Therefore, the nanosphere-rod-like Co3O4 as the cathode for aluminium ion batteries has a promising potential.

In Al-C batteries, graphite and aluminum are used as positive electrode and negative electrode in room temperature ionic liquid AlCl3/1-ethyl-3-methylimidazolium chloride ([EMIm]Cl), respectively. Due to that the electrochemical energy storage is performed by the anions and cations in the electrolyte, the electrochemical properties and pseudocapacitance characteristics of Al-C batteries at different temperatures are systematically analyzed. At 1 mV s−1, the ratio of pseudocapacitance are 36.9%, 19.8% and 15.2% at 20 °C, 40 °C and 60 °C, respectively. In addition, the diffusion coefficient of polyaluminium anions improved with the increase of temperature. This interesting phenomenon can be attributed to the fact that high temperature accelerates the diffusion and transmission of polyaluminium anions in the electrolyte and takes full advantages of electrode materials. This will increase the discharge capacity, accelerate the transport of ions and electrons and show more dominant traditional battery characteristics. However, too high temperature may accelerate the corrosion effect of electrolyte to aluminum metal, so expanded graphite shows excellent cycling performance in Al-C batteries at 40 °C. This work plays a guiding role in the development of aluminum secondary batteries.

Solid solution cathode material 0.5Li2MnO3·0.5LiNi1/3Co1/3Mn1/3O2 has been synthesized by a co-precipitation method and a mild acid was adopted to give rise to the H+/Li+ exchange reaction. The inductively coupled plasma-atomic emission spectrometry (ICP-AES) and atomic absorption spectroscopy (AAS) data show that the H+/Li+ exchange reaction actually occurs and the chemical composition is H0.06Li1.15Ni0.13Co0.14Mn0.55O2.03 after the material was treated. The X-ray powder diffraction patterns indicates that the structure doesn't change through the H+/Li+ exchange reaction and remains the hexagonal α-NaFeO2 layered structure with space group of R-3m. The field-emission scanning electron microscope (SEM) and transmission electron microscope (TEM) images show that there are traces of erosion on the surface of the H+/Li+ exchanged sample. The initial charge–discharge curve measured at 0.05C (12.5 mA g−1) demonstrates that the H+/Li+ exchanged electrode delivers a capacity of up to 314.0 mAh g−1 and coulombic increased initial efficiency. Cycle voltammetry (CV) measurement confirms this is attributed to the improvement of the reduction catalytic activity of oxygen released during the initial charging. The processed electrode also displays improved rate performance.

Birnessite-type MnO2 (Bir-MnO2) nanospheres have been successfully synthesized by the microwave–hydrothermal (M–H) method at 75 °C for 30 min under low pressure. The properties and electrochemical performance of the as-prepared MnO2 are analyzed and evaluated by the field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) measurements and electrochemical tests. The Bir-MnO2 appears mesoporous nanosphere structure with 70–90 nm in diameter, and it exhibits a large specific surface (SS) of 213.6 m2 g−1 by the results of FE-SEM, XRD and BET. The electrochemical test results show that the specific capacitance (SC) is 210 F g−1 at 200 mA g−1 in 1.0 M Na2SO4 electrolyte, and the SC retention and coulombic efficiency are over 96% and 98% respectively after 300 cycles at 1.6 A g−1. Compared with the conventional syntheses of MnO2, the performance of the Bir-MnO2 nanospheres synthesized by M–H method is significantly improved.

Asymmetric electrochemical capacitor was categorized into two types: a battery-type electrode|capacitor-type electrode capacitor and a capacitor-type electrode|capacitor-type electrode capacitor. When designing asymmetric electrochemical capacitor, the influences of both current density and the electrode's potential window were taken into account. This article analyzed how the mass ratio between two electrodes influenced the electrochemical performances of asymmetric electrochemical capacitor. The formulas describing capacitor performance parameters (work voltage, specific capacitance, energy density and power density) were derived and applied to two types of asymmetric electrochemical capacitors. Therefore, the concrete relationships between mass ratio of electrodes and capacitor parameters were obtained. The influence of current density on mass ratio was investigated with organic LiMn 2 O 4 /AC system and others.

To aim at reducing the platinum loading and increasing the utilization of platinum in PEMFC electrode, a new pulse electrodeposition technique for preparing proton exchange membrane fuel cell (PEMFC) electrodes has been developed in this paper. This method combines coating Pt seeds on the C-Nafion substrate and introducing polyethylene glycol (PEG) into the deposition solution. SEM images of the samples show that Pt seeds and PEG take an important role in the morphology of the Pt deposit. The surface area and average particle size of Pt were determined by charge integration under the hydrogen desorption peaks of cyclic voltammetry. The electrocatalytic activities of these electrodes towards oxygen reduction reaction (ORR) were investigated by using rotating disc electrode (RDE). The Pt catalyst which was prepared by Pt seeds and PEG, its active surface area and electrocatalytic activity towards ORR were improved remarkably. And the optimized electrode displayed higher catalytic activity than a conventional electrode made from commercial Pt/C catalyst. The possible reasons for the effects of Pt seeds and PEG on the higher catalytic activity of prepared Pt catalysts have been preliminarily discussed.

As a potential electrolyte for lithium-ion batteries, a porous polymer electrolyte membrane based on poly(vinylidenefluoride-hexafluoropropylene) (PVDF-HFP) was prepared by a phase inversion method. The casting solution, effects of the solvent and non-solvent and addition of micron scale TiO 2 particles were investigated. The membranes were characterized by SEM, XRD, AC impedance, and charge/discharge tests. By using acetone as the solvent and water as the non-solvent, the prepared membranes showed good ability to absorb and retain the lithium ion containing electrolyte. Addition of micron TiO 2 particles to the polymer electrolyte was found to enhance the tensile strength, electrolyte uptake, ion conductivity and the electrolyte/electrode interfacial stability of the membrane.

Surface structure and electrochemical behavior of surface-fluorinated petroleum coke samples (original petroleum coke and those heat-treated at 1860, 2300 and 2800 °C, abbreviated to original PC, PC1860, PC2300 and PC2800, respectively) have been investigated. Surface fluorination of petroleum cokes by elemental fluorine reduced surface oxygen. Surface areas of fluorinated petroleum cokes were nearly the same as those of non-fluorinated ones or only slightly increased by fluorination except original PC fluorinated at 300 °C. Total meso-pore volumes of fluorinated samples showed the same trend. The charge capacity of non-fluorinated petroleum coke was increased by heat-treatment at 2300 and 2800 °C. However, the first coulombic efficiency was the highest, 90–89% in PC1860, decreasing to 72–70 and 65–64% for PC2300 and PC2800, respectively. It is noted that first coulombic efficiencies were increased by 12–18% for PC2300 and PC2800 fluorinated at 300 °C.