• Energy Research

Abstract The ageing of 75 commercial Li-ion secondary batteries with LiNiMnCoO 2 | hard carbon chemistry was studied up to 4 years. The nominal capacity was 17.5 Ah. The batteries were cycled at different current rates and between different states of charge. Shelf studies were carried out at different temperatures and at different states of charge. The ageing temperature varied from 18-55 °C. The specific ohmic resistance was obtained as a function of state of health, ageing temperature, and ageing time. We found that the cell tolerated less cycles at higher temperatures. The loss of capacity also increased for storage at higher temperatures, in a predictable manner. We observed that the state of charge at the moment of storage was very important for the loss of discharge capacity. Thermal conductivities of pristine and aged electrodes were measured in the presence and absence of electrolyte solvent and under different compaction pressures. The thermal conductivity was found to range from 0.14–0.41 WK −1 m −1 for dry electrode active material and from 0.52–0.73 WK −1 m −1 for electrolyte solvent-soaked electrode active material. The thermal conductivity of the electrode materials did not change significantly with ageing, but a strong correlation was seen between remaining battery capacity and increasing ohmic resistance. To assess the impact of these changes, the measured results were used in a one-dimensional model to compute the battery internal temperature. Temperature profiles were computed as a function of discharging rate (2C - 10C) and ageing time (0 - 4 years). The model showed that the internal temperature can raise by a factor about 2.5 during ageing from the pristine state of health at 100 % to 58 % capacity.

Abstract The ageing of 75 commercial Li-ion secondary batteries with LiNiMnCoO 2 | hard carbon chemistry was studied up to 4 years. The nominal capacity was 17.5 Ah. The batteries were cycled at different current rates and between different states of charge. Shelf studies were carried out at different temperatures and at different states of charge. The ageing temperature varied from 18-55 °C. The specific ohmic resistance was obtained as a function of state of health, ageing temperature, and ageing time. We found that the cell tolerated less cycles at higher temperatures. The loss of capacity also increased for storage at higher temperatures, in a predictable manner. We observed that the state of charge at the moment of storage was very important for the loss of discharge capacity. Thermal conductivities of pristine and aged electrodes were measured in the presence and absence of electrolyte solvent and under different compaction pressures. The thermal conductivity was found to range from 0.14–0.41 WK −1 m −1 for dry electrode active material and from 0.52–0.73 WK −1 m −1 for electrolyte solvent-soaked electrode active material. The thermal conductivity of the electrode materials did not change significantly with ageing, but a strong correlation was seen between remaining battery capacity and increasing ohmic resistance. To assess the impact of these changes, the measured results were used in a one-dimensional model to compute the battery internal temperature. Temperature profiles were computed as a function of discharging rate (2C - 10C) and ageing time (0 - 4 years). The model showed that the internal temperature can raise by a factor about 2.5 during ageing from the pristine state of health at 100 % to 58 % capacity.

Palladium is a vital commodity in the industry. To guarantee a stable supply in the future, it is imperative to adopt more effective recycling practices. In this proof-of-concept study, we explore the potential of electrodialysis to enhance the palladium concentration in a residual solution of palladium recycling, thus promoting higher recovery rates. Experiments were conducted using an industrial hydrochloric acid solution containing around 1000 mg/L of palladium, with a pH below 1. Two sets of membranes, Selemion AMVN/CMVN and Fujifilm Type 12 AEM/CEM, were tested at two current levels. The Fujifilm membranes, which are designed for low permeability of water, show promising results, recovering around 40% of palladium within a two-hour timeframe. The Selemion membranes were inefficient due to excessive water transport. All membranes accumulated palladium in their structures. Anion-exchange membranes showed higher palladium accumulation at lower currents, while cation-exchange membranes exhibited increased palladium accumulation at higher currents. Owing to the low concentration of palladium and the presence of abundant competing ions, the current efficiency remained below 2%. Our findings indicate a strong potential for augmenting the palladium stage in industrial draw solutions through electrodialysis, emphasizing the importance of membrane properties and process parameters to ensure a viable process. Beyond the prominent criteria of high permselectivity and low resistance, minimizing the permeability of water within IEMs remains a key challenge to mitigating the efficiency loss associated with uncontrolled mixing of the electrolyte solution.

Palladium is a vital commodity in the industry. To guarantee a stable supply in the future, it is imperative to adopt more effective recycling practices. In this proof-of-concept study, we explore the potential of electrodialysis to enhance the palladium concentration in a residual solution of palladium recycling, thus promoting higher recovery rates. Experiments were conducted using an industrial hydrochloric acid solution containing around 1000 mg/L of palladium, with a pH below 1. Two sets of membranes, Selemion AMVN/CMVN and Fujifilm Type 12 AEM/CEM, were tested at two current levels. The Fujifilm membranes, which are designed for low permeability of water, show promising results, recovering around 40% of palladium within a two-hour timeframe. The Selemion membranes were inefficient due to excessive water transport. All membranes accumulated palladium in their structures. Anion-exchange membranes showed higher palladium accumulation at lower currents, while cation-exchange membranes exhibited increased palladium accumulation at higher currents. Owing to the low concentration of palladium and the presence of abundant competing ions, the current efficiency remained below 2%. Our findings indicate a strong potential for augmenting the palladium stage in industrial draw solutions through electrodialysis, emphasizing the importance of membrane properties and process parameters to ensure a viable process. Beyond the prominent criteria of high permselectivity and low resistance, minimizing the permeability of water within IEMs remains a key challenge to mitigating the efficiency loss associated with uncontrolled mixing of the electrolyte solution.

The reverse electrodialysis heat engine (REDHE) is a promising salinity gradient energy technology, capable of producing hydrogen with an input of waste heat at temperatures below 100 °C. A salinity gradient drives water electrolysis in the reverse electrodialysis (RED) cell, and spent solutions are regenerated using waste heat in a precipitation or evaporation unit. This work presents a non-equilibrium thermodynamics model for the RED cell, and the hydrogen production is investigated for KCl/water solutions. The results show that the evaporation concept requires 40 times less waste heat and produces three times more hydrogen than the precipitation concept. With commercial evaporation technology, a system efficiency of 2% is obtained, with a hydrogen production rate of 0.38 gH2 m−2h−1 and a waste heat requirement of 1.7 kWh gH2−1. The water transference coefficient and the salt diffusion coefficient are identified as membrane properties with a large negative impact on hydrogen production and system efficiency. Each unit of the water transference coefficient in the range tw=[0–10] causes a −7 mV decrease in unit cell electric potential, and a −0.3% decrease in system efficiency. Increasing the membrane salt diffusion coefficient from 10−12 to 10−11 leads to the system efficiency decreasing from 2% to 0.6%.

The reverse electrodialysis heat engine (REDHE) is a promising salinity gradient energy technology, capable of producing hydrogen with an input of waste heat at temperatures below 100 °C. A salinity gradient drives water electrolysis in the reverse electrodialysis (RED) cell, and spent solutions are regenerated using waste heat in a precipitation or evaporation unit. This work presents a non-equilibrium thermodynamics model for the RED cell, and the hydrogen production is investigated for KCl/water solutions. The results show that the evaporation concept requires 40 times less waste heat and produces three times more hydrogen than the precipitation concept. With commercial evaporation technology, a system efficiency of 2% is obtained, with a hydrogen production rate of 0.38 gH2 m−2h−1 and a waste heat requirement of 1.7 kWh gH2−1. The water transference coefficient and the salt diffusion coefficient are identified as membrane properties with a large negative impact on hydrogen production and system efficiency. Each unit of the water transference coefficient in the range tw=[0–10] causes a −7 mV decrease in unit cell electric potential, and a −0.3% decrease in system efficiency. Increasing the membrane salt diffusion coefficient from 10−12 to 10−11 leads to the system efficiency decreasing from 2% to 0.6%.

Abstract Water electrolyzers that use a membrane electrolyte between the electrodes are a promising technology towards mass production of renewable hydrogen. High power setups produce a lot of heat which has to be transported through the cell, making heat management essential. Knowing thermal conductivity values of the employed materials is crucial when modeling the temperature distribution inside an electrolyzer. The thermal conductivity was measured for different titanium-based porous transport layers (PTL) and a partially methylated Hexamethyl-p-Terphenyl Polybenzimidazolium (HMT-PMBI-Cl- membrane. The four titanium-based sintered transport layers materials have thermal conductivities between 1.0 and 2.5 ± 0.2 WK−1m−1 at 10 bar compaction pressure. The HMT-PMBI-Cl- membrane has a thermal conductivity of 0.19 ± 0.04 WK−1m−1 at 0% relative humidity at 10 bar compaction pressure and 0.21 ± 0.03 WK−1m−1 at 100% relative humidity ( λ = 12 water molecules per ion exchange site at room temperature) at 10 bar compaction pressure. Combining the determined thermal conductivity values with data from the literature, 2D thermal models of a proton exchange membrane water electrolyzer (PEMWE) and an anion exchange membrane water electrolyzer (AEMWE) were built to evaluate the temperature distribution in the through-plane direction. A temperature difference of 7–17 K was shown to arise between the center of the membrane electrode assembly and bipolar plates for the PEMWE and more than 18 K for the AEMWE.

Abstract Water electrolyzers that use a membrane electrolyte between the electrodes are a promising technology towards mass production of renewable hydrogen. High power setups produce a lot of heat which has to be transported through the cell, making heat management essential. Knowing thermal conductivity values of the employed materials is crucial when modeling the temperature distribution inside an electrolyzer. The thermal conductivity was measured for different titanium-based porous transport layers (PTL) and a partially methylated Hexamethyl-p-Terphenyl Polybenzimidazolium (HMT-PMBI-Cl- membrane. The four titanium-based sintered transport layers materials have thermal conductivities between 1.0 and 2.5 ± 0.2 WK−1m−1 at 10 bar compaction pressure. The HMT-PMBI-Cl- membrane has a thermal conductivity of 0.19 ± 0.04 WK−1m−1 at 0% relative humidity at 10 bar compaction pressure and 0.21 ± 0.03 WK−1m−1 at 100% relative humidity ( λ = 12 water molecules per ion exchange site at room temperature) at 10 bar compaction pressure. Combining the determined thermal conductivity values with data from the literature, 2D thermal models of a proton exchange membrane water electrolyzer (PEMWE) and an anion exchange membrane water electrolyzer (AEMWE) were built to evaluate the temperature distribution in the through-plane direction. A temperature difference of 7–17 K was shown to arise between the center of the membrane electrode assembly and bipolar plates for the PEMWE and more than 18 K for the AEMWE.