In the recent years, lithium-ion batteries have prevailed and dominated as the primary power sources for mobile electronic applications. Equally, their use in electric resources of transportation and other high-level applications is hindered to some certain extent. As a result, innovative fabrication of lithium-ion batteries based on best performing cathode materials should be developed as electrochemical performances of batteries depends largely on the electrode materials. Elemental doping and coating of cathode materials as a way of upgrading Li-ion batteries have gained interest and have modified most of the commonly used cathode materials. This has resulted in enhanced penetration of Li-ions, ionic mobility, electric conductivity and cyclability, with lesser capacity fading compared to traditional parent materials. The current paper reviews the role and effect of metal oxides as coatings for improvement of cathode materials in Li-ion batteries. For layered cathode materials, a clear evaluation of how metal oxide coatings sweep of metal ion dissolution, phase transitions and hydrofluoric acid attacks is detailed. Whereas the effective ways in which metal oxides suppress metal ion dissolution and capacity fading related to spinel cathode materials are explained. Lastly, challenges faced by olivine-type cathode materials, namely; low electronic conductivity and diffusion coefficient of Li+ ion, are discussed and recent findings on how metal oxide coatings could curb such limitations are outlined.

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Hydrolysis of MgH2 has a high theoretical hydrogen yield (15.2%) and is very attractive for onsite hydrogen production. However, the low solubility of Mg(OH)2 causes sluggish kinetics and incomplete utilization of MgH2. In this paper, we solve this problem by using organic acids (acetic, citric and oxalic) and nanoscale graphene-like carbon. The organic acid solution significantly increases the yield and rate of H2 generation due to its acidic nature. The hydrogen yield approaches 100% with a fast hydrolysis rate when the molar ratio Acid/MgH2 exceeds 0.9, 2.0 and 2.7 for the citric, oxalic and acetic acid, respectively. In doing so, pH of the reaction solutions after hydrolysis corresponds to 4.53, 2.11 and 4.28, accordingly, testifying about buffer nature of the solutions “citric acid / magnesium citrate” and “acetic acid / magnesium acetate”. The addition of graphene-like material (GLM) also significantly increases the yield and rate of H2 generation due to the decrease of particle size and increase of defects in the material, as well as due to stabilising the MgH2 nanoparticles and preventing their agglomeration. Additionally, GLM encapsulates the MgH2 particles thus suppressing the formation of MgO and, in turn, promoting achievement of the maximum hydrogen yield. In addition, this work presents layout and operation features of the developed apparatus for the controlled generation of pressurised hydrogen using hydrolysis of Mg or MgH2 in acidic solutions, as well as its testing results for the hydrolysis of Mg and MgH2 in the solution of citric acid.

Hydrolysis of light metals and hydrides can potentially be used for the generation of hydrogen on-board fuel cell vehicles, or, alternatively, for refilling their fuel tanks with H2 generated and pressurised without compressor on site, at near-ambient conditions. Implementation of this approach requires solution of several problems, including the possibility of controlling H2 release and avoiding thermal runaway. We have solved this problem by developing the apparatus for the controlled generation of pressurised H2 using hydrolysis of Mg or MgH2 in organic acid solutions. The development is based on the results of experimental studies of MgH2 hydrolysis in dilute aqueous solutions of acetic, citric, and oxalic acids. It was shown that the hydrogen yield approaches 100% with a fast hydrolysis rate when the molar ratio acid/MgH2 exceeds 0.9, 2.0, and 2.7 for the citric, oxalic, and acetic acids, respectively. In doing so, the pH of the reaction solutions after hydrolysis corresponds to 4.53, 2.11, and 4.28, accordingly, testifying to the buffer nature of the solutions “citric acid/magnesium citrate” and “acetic acid/magnesium acetate”. We also overview testing results of the developed apparatus where the process rate is effectively controlled by the control of the acid concentration in the hydrolysis reactor.