Alkaline electrolysis using a zero gap configuration combines the efficiency of PEM with the cost efficiency of alkaline.

Virtually all types of electrodes used in lithium-ion batteries expand and contract during cycling, which poses an engineering and design challenge. Information provided by X-ray diffraction (XRD) about alterations in the crystal structure of active materials may be insufficient to inform these engineering tasks. This is because it is unclear how these evolutions of the crystal structure translate into the measurable thickness changes at the electrode or cell level. In this study we investigate the thickness changes of electrodes during cycling using a dilatometry setup and compare them to XRD-measured crystal structure changes from scientific literature. Both the reliability of the dilation measurement and the electrochemical performance of the dilatometry setup are thoroughly validated and significantly exceed those of related studies that have been published in recent years. Various laboratory-made graphites as well as LiNi1/3Co1/3Mn1/3O2 (NMC111), LiNi0.6Co0.2Mn0.2O2 (NMC622), LiNi0.8Co0.1Mn0.1O2 (NMC811) and LiNi0.8Co0.15Al0.05O2 (NCA) electrodes and the positive electrode from a Kokam SLPB356495 pouch cell are investigated. The results show that electrode expansion does not necessarily correlate with the unit cell volume changes of its active materials in any meaningful way and thus only by measuring the expansion of the full electrode can we fully understand and predict its behavior during cycling.

The efficiency of an alkaline electrolysis cell depends strongly on its internal cell resistance, which becomes the dominant efficiency driver at high current densities. This paper uses Electrochemical Impedance Spectroscopy to decouple the ohmic resistance from the cell voltage, and, for the first time, quantify the reduction in cell resistance achieved by employing a zero gap cell configuration when compared to the conventional approach. A 30 % reduction in ohmic resistance is demonstrated for the zero gap cell when compared to a more conventional design with a 2 mm electrode gap (in 1 M NaOH and at standard conditions). The effect on the ohmic resistance of operating parameters, including current density and temperature, is quantified; the zero gap cell outperforms the standard cell at all current densities, particularly above 500 mA•cm −2. Furthermore, the effect of electrode morphology on the ohmic resistance is investigated, showing that high surface area foam electrodes permit a lower ohmic resistance than the coarser mesh electrodes. These results show that zero gap cell design will allow both low cost and highly efficient alkaline electrolysis, which will become the key technology for short term and inter-seasonal energy storage and accelerate the transition towards a decarbonised society.