Characterisation of a Nickel-iron Battolyser, an Integrated Battery and Electrolyser

Abstract

Electricity systems require energy storage on all time scales to accommodate the variations in output of solar and wind power when those sources of electricity constitute most, or all, of the generation on the system. This paper builds on recent research into nickel-iron battery-electrolysers or “battolysers” as both short-term and long-term energy storage. For short-term cycling as a battery, the internal resistances and time constants have been measured, including the component values of resistors and capacitors in equivalent circuits. The dependence of these values on state-of-charge and temperature have also been measured. The results confirm that a nickel-iron cell can hold 25% more than its nominal charge. However, this increased capacity disappears at temperatures of 60°C and may be dissipated quickly by self-discharge. When operating as an electrolyser for long-term energy storage, the experiments have established the importance of a separation gap between each electrode and the membrane for gas evolution and established the optimum size of this gap as approximately 1.25 mm. The nickel-iron cell has acceptable performance as an electrolyser for Power-to-X energy conversion but its large internal resistance limits voltage efficiency to 75% at 5-h charge and discharge rate, with or without a bubble separation membrane.

Iron anode‐based aqueous electrochemical energy storage devices: Recent advances and future perspectives

“…[ 123 ] The incorporation of a H 2 storage or delayed generation strategy, and a novel control style for energy‐storage cells would allow for current control/distribution at distinct electrode regions with specific purposes. [ 124 ] This device configuration may be quite useful and applicable when the electricity is cheap and rich at overnight time slots; a fraction of electricity turns into H 2 resources, while the other can be stored into grid‐scale power stations for electricity compensation/peak‐power supply.…”

Modeling the Performance of an Integrated Battery and Electrolyzer System

“…However, there is also an accumulation of gaseous products in the gap that results in a reduction of hydroxide concentration close to the electrode surface. 8 Given the simplification of bubble transport in the model, the optimization results do not consider the products bubbling out. Consequently, a constant gap thickness of 3 mm on each side of the membrane was chosen for the sake of comparison.…”

“…8,9 However, because of their cost, limited cycling rate, self-discharge, and low specific energy storage capacity (energy stored per unit mass), large-scale, longer-term storage options are required alongside battery capacity. 7,8 An alternative solution for long-term energy storage is the production of fuels using renewable energy. Hydrogen is an example of such a fuel that can either be burned in a gasfired internal combustion engine and gas turbine or electrochemically converted in a fuel cell to generate electricity.…”

“…The advantages of using hydrogen as an energy carrier include it being a carbon-free fuel with a high mass specific energy density. 8,10,11 In addition to being a fuel, hydrogen is also used as feedstock in the chemical industry, as well as in the refining industry, food industry, metallurgical industry, and electronics industry. 12 An integrated battery and electrolyzer device, known as the battolyser, has recently been developed.…”

Neutron Diffraction Study of a Sintered Iron Electrode In Operando

“…When such batteries are overcharged, they electrolyze the water in the electrolyte to form hydrogen and oxygen. In a battolyser, , the hydrogen is collected, combining the storage and conversion function in one device. Replacing the positive nickel electrode with a reversible oxygen electrode creates the iron–air battery.…”