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Papers by Anetta Platek-Mielczarek
ACS Applied Materials & Interfaces, Jan 8, 2021
chlorides with Pluronic F127 were used as a soft-salt template for tuning the textural and struct... more chlorides with Pluronic F127 were used as a soft-salt template for tuning the textural and structural properties of carbon. Highly conductive metal hydroxide solutions, where the cations are the same as those in the salt template, have been used as electrolytes. By increasing the size of the cation in the template, the textural properties of carbon, such as the specific surface area, micropore volume, and pore size, were remarkably enhanced. It directly translates to an increase in the specific capacitance of the electrode material. For a constant current charge/ discharge at 0.1 A g −1 , the electrode composed of LiCl-T and operating with 1 mol L −1 LiOH demonstrates the capacitance of 124 F g −1 , whereas CsCl-T with the same electrolyte has a capacitance of 216 F g −1. Moreover, the materials show the highest capacitance retention (up to 75%) vs. the current regime applied when the cation used during synthesis matches the cation present in the electrolyte (i.e., LiCl-T with LiOH). Interestingly, capacitance normalized by specific surface area has been found to be the highest when LiOH solution is applied as an electrolyte. Thus, for this metric, the size of ions seems to be a crucial parameter. The importance of mesoporosity is highlighted as well by using materials with a similar fraction of micropores and with or without mesopores. Briefly, the presence of mesopore fraction proved to be essential for improved capacity retention (69% vs. 30%). Besides textural properties, the graphitization degree impacts the electrochemical performance as well. It increases among the samples, in accordance with cation-π binding energy, e.g., LiCl-T is the most "graphitic-like" material and CsCl-T is the most disordered. Thus, the more graphitic-like materials demonstrate higher rate capability and cycle stability.
ACS Applied Materials & Interfaces, May 4, 2023
Energy and Environmental Science, 2021
This paper reports on the ion fluxes at the interfaces of various porous carbon electrodes/aqueou... more This paper reports on the ion fluxes at the interfaces of various porous carbon electrodes/aqueous solutions of alkali metal cations (Na + , K + and Rb +) and iodide anions, monitored by an electrochemical quartz crystal microbalance (EQCM). Different electrode material compositions as well as various electrolyte concentrations have also been considered. By tracking the ions during electrochemical polarization, we aimed to identify the reasons for the fading capacitor performance that occurs during long-term operation. The mass change profile suggests that hydroxide anions are responsible for counterbalancing the charge stored on the negative electrode. Furthermore, we found that iodidebased species are physically adsorbed on the carbon surface immediately after the electrodes come into contact with the electrolyte, regardless of the textural properties of the activated carbon used or electrode composition. Apart from the qualitative description, the mass change profiles allow the sequence of pore occupation to be determined. Additionally, the solvation numbers for alkali metals (Na + , K + and Rb +) and hydroxide-based species have been determined. It is claimed that the solvation number is strongly affected by the electrolyte composition. Apparently, the concentration of water molecules available in the electrolyte cannot be neglected. The outcome of this research has fundamental and application context. Broader context Providing a reasonable response to the ever-growing demand from society for devices to store increasingly more energy in the same or a smaller volume, to be available as fast as possible, is a stimulating challenge for researchers in the energy storage field. Thus, to date, various types of materials, electrolytes and technological concepts have been proposed in order to cover all application niches. Stretching the limits of energy storage materials is currently realized at the nanoscale, and a deep understanding of these processes seems to be a crucial step towards the further development of energy storage devices. Our report elucidates the behavior of iodide-based species as the redox-active components of the electrolytic solution in electrochemical capacitors. It has been assumed that the peculiar performance of iodides seriously impacts the lifetime of devices that exploit the pseudocapacitive effect of the iodide-based redox couple. We confirmed that iodide anions demonstrate a specific affinity for the activated carbon surface; furthermore, it appears that they do not actively contribute to the ion flux on the positive electrode and tend to be instantly adsorbed on the carbon surface, as indicated by in situ EQCM measurements. Solvent-ion interactions, ion mixing, and the transport of ions confined in the pores have been considered.
Journal of Power Sources, Sep 1, 2021
Alternate floating remarkably prolongs the capacitor lifetime. •Electrolyte concentration is a ke... more Alternate floating remarkably prolongs the capacitor lifetime. •Electrolyte concentration is a key factor of aging rate. •Alternate floating ages both electrodes to the same extend. •Almost 2-fold lifespan improvement achieved for 0.2 mol L − 1 LiNO 3 .
Journal of Power Sources, Sep 1, 2022
The point of zero charge (PZC) is crucial for investigating molecular level charging mechanisms i... more The point of zero charge (PZC) is crucial for investigating molecular level charging mechanisms in energy storage systems, as demonstrated in electrochemical capacitors. Three electrochemical techniques were studied: cyclic voltammetry (CV), staircase potentio electrochemical impedance spectroscopy (SPEIS) and step potential electrochemical spectroscopy (SPECS) for two activated carbons (ACs) with 0.1 mol L− 1 aqueous solutions of LiNO3, Li2SO4, and KI. The porous AC charging process in aqueous electrolytes is a complex phenomenon; the ion mixing zone covered a wide potential region. Inadequate PZC determination could lead to obscure data evaluation, which could further provide a misguided mechanism description at the molecular level. In the aqueous solutions studied, the adsorption of specific ions and active participation of all ionic species in the electrical double-layer formation were considered. The SPECS technique was determined to be the most beneficial for the PZC determina...
Journal of Power Sources, 2021
Alternate floating remarkably prolongs the capacitor lifetime. •Electrolyte concentration is a ke... more Alternate floating remarkably prolongs the capacitor lifetime. •Electrolyte concentration is a key factor of aging rate. •Alternate floating ages both electrodes to the same extend. •Almost 2-fold lifespan improvement achieved for 0.2 mol L − 1 LiNO 3 .
chlorides with Pluronic F127 were used as a soft-salt template for tuning the textural and struct... more chlorides with Pluronic F127 were used as a soft-salt template for tuning the textural and structural properties of carbon. Highly conductive metal hydroxide solutions, where the cations are the same as those in the salt template, have been used as electrolytes. By increasing the size of the cation in the template, the textural properties of carbon, such as the specific surface area, micropore volume, and pore size, were remarkably enhanced. It directly translates to an increase in the specific capacitance of the electrode material. For a constant current charge/ discharge at 0.1 A g −1 , the electrode composed of LiCl-T and operating with 1 mol L −1 LiOH demonstrates the capacitance of 124 F g −1 , whereas CsCl-T with the same electrolyte has a capacitance of 216 F g −1. Moreover, the materials show the highest capacitance retention (up to 75%) vs. the current regime applied when the cation used during synthesis matches the cation present in the electrolyte (i.e., LiCl-T with LiOH). Interestingly, capacitance normalized by specific surface area has been found to be the highest when LiOH solution is applied as an electrolyte. Thus, for this metric, the size of ions seems to be a crucial parameter. The importance of mesoporosity is highlighted as well by using materials with a similar fraction of micropores and with or without mesopores. Briefly, the presence of mesopore fraction proved to be essential for improved capacity retention (69% vs. 30%). Besides textural properties, the graphitization degree impacts the electrochemical performance as well. It increases among the samples, in accordance with cation-π binding energy, e.g., LiCl-T is the most "graphitic-like" material and CsCl-T is the most disordered. Thus, the more graphitic-like materials demonstrate higher rate capability and cycle stability.
Energy & Environmental Science, 2021
This paper reports on the ion fluxes at the interfaces of various porous carbon electrodes/aqueou... more This paper reports on the ion fluxes at the interfaces of various porous carbon electrodes/aqueous solutions of alkali metal cations (Na+, K+ and Rb+) and iodide anions, monitored by an electrochemical quartz crystal microbalance (EQCM).
ACS Applied Materials & Interfaces, Jan 8, 2021
chlorides with Pluronic F127 were used as a soft-salt template for tuning the textural and struct... more chlorides with Pluronic F127 were used as a soft-salt template for tuning the textural and structural properties of carbon. Highly conductive metal hydroxide solutions, where the cations are the same as those in the salt template, have been used as electrolytes. By increasing the size of the cation in the template, the textural properties of carbon, such as the specific surface area, micropore volume, and pore size, were remarkably enhanced. It directly translates to an increase in the specific capacitance of the electrode material. For a constant current charge/ discharge at 0.1 A g −1 , the electrode composed of LiCl-T and operating with 1 mol L −1 LiOH demonstrates the capacitance of 124 F g −1 , whereas CsCl-T with the same electrolyte has a capacitance of 216 F g −1. Moreover, the materials show the highest capacitance retention (up to 75%) vs. the current regime applied when the cation used during synthesis matches the cation present in the electrolyte (i.e., LiCl-T with LiOH). Interestingly, capacitance normalized by specific surface area has been found to be the highest when LiOH solution is applied as an electrolyte. Thus, for this metric, the size of ions seems to be a crucial parameter. The importance of mesoporosity is highlighted as well by using materials with a similar fraction of micropores and with or without mesopores. Briefly, the presence of mesopore fraction proved to be essential for improved capacity retention (69% vs. 30%). Besides textural properties, the graphitization degree impacts the electrochemical performance as well. It increases among the samples, in accordance with cation-π binding energy, e.g., LiCl-T is the most "graphitic-like" material and CsCl-T is the most disordered. Thus, the more graphitic-like materials demonstrate higher rate capability and cycle stability.
ACS Applied Materials & Interfaces, May 4, 2023
Energy and Environmental Science, 2021
This paper reports on the ion fluxes at the interfaces of various porous carbon electrodes/aqueou... more This paper reports on the ion fluxes at the interfaces of various porous carbon electrodes/aqueous solutions of alkali metal cations (Na + , K + and Rb +) and iodide anions, monitored by an electrochemical quartz crystal microbalance (EQCM). Different electrode material compositions as well as various electrolyte concentrations have also been considered. By tracking the ions during electrochemical polarization, we aimed to identify the reasons for the fading capacitor performance that occurs during long-term operation. The mass change profile suggests that hydroxide anions are responsible for counterbalancing the charge stored on the negative electrode. Furthermore, we found that iodidebased species are physically adsorbed on the carbon surface immediately after the electrodes come into contact with the electrolyte, regardless of the textural properties of the activated carbon used or electrode composition. Apart from the qualitative description, the mass change profiles allow the sequence of pore occupation to be determined. Additionally, the solvation numbers for alkali metals (Na + , K + and Rb +) and hydroxide-based species have been determined. It is claimed that the solvation number is strongly affected by the electrolyte composition. Apparently, the concentration of water molecules available in the electrolyte cannot be neglected. The outcome of this research has fundamental and application context. Broader context Providing a reasonable response to the ever-growing demand from society for devices to store increasingly more energy in the same or a smaller volume, to be available as fast as possible, is a stimulating challenge for researchers in the energy storage field. Thus, to date, various types of materials, electrolytes and technological concepts have been proposed in order to cover all application niches. Stretching the limits of energy storage materials is currently realized at the nanoscale, and a deep understanding of these processes seems to be a crucial step towards the further development of energy storage devices. Our report elucidates the behavior of iodide-based species as the redox-active components of the electrolytic solution in electrochemical capacitors. It has been assumed that the peculiar performance of iodides seriously impacts the lifetime of devices that exploit the pseudocapacitive effect of the iodide-based redox couple. We confirmed that iodide anions demonstrate a specific affinity for the activated carbon surface; furthermore, it appears that they do not actively contribute to the ion flux on the positive electrode and tend to be instantly adsorbed on the carbon surface, as indicated by in situ EQCM measurements. Solvent-ion interactions, ion mixing, and the transport of ions confined in the pores have been considered.
Journal of Power Sources, Sep 1, 2021
Alternate floating remarkably prolongs the capacitor lifetime. •Electrolyte concentration is a ke... more Alternate floating remarkably prolongs the capacitor lifetime. •Electrolyte concentration is a key factor of aging rate. •Alternate floating ages both electrodes to the same extend. •Almost 2-fold lifespan improvement achieved for 0.2 mol L − 1 LiNO 3 .
Journal of Power Sources, Sep 1, 2022
The point of zero charge (PZC) is crucial for investigating molecular level charging mechanisms i... more The point of zero charge (PZC) is crucial for investigating molecular level charging mechanisms in energy storage systems, as demonstrated in electrochemical capacitors. Three electrochemical techniques were studied: cyclic voltammetry (CV), staircase potentio electrochemical impedance spectroscopy (SPEIS) and step potential electrochemical spectroscopy (SPECS) for two activated carbons (ACs) with 0.1 mol L− 1 aqueous solutions of LiNO3, Li2SO4, and KI. The porous AC charging process in aqueous electrolytes is a complex phenomenon; the ion mixing zone covered a wide potential region. Inadequate PZC determination could lead to obscure data evaluation, which could further provide a misguided mechanism description at the molecular level. In the aqueous solutions studied, the adsorption of specific ions and active participation of all ionic species in the electrical double-layer formation were considered. The SPECS technique was determined to be the most beneficial for the PZC determina...
Journal of Power Sources, 2021
Alternate floating remarkably prolongs the capacitor lifetime. •Electrolyte concentration is a ke... more Alternate floating remarkably prolongs the capacitor lifetime. •Electrolyte concentration is a key factor of aging rate. •Alternate floating ages both electrodes to the same extend. •Almost 2-fold lifespan improvement achieved for 0.2 mol L − 1 LiNO 3 .
chlorides with Pluronic F127 were used as a soft-salt template for tuning the textural and struct... more chlorides with Pluronic F127 were used as a soft-salt template for tuning the textural and structural properties of carbon. Highly conductive metal hydroxide solutions, where the cations are the same as those in the salt template, have been used as electrolytes. By increasing the size of the cation in the template, the textural properties of carbon, such as the specific surface area, micropore volume, and pore size, were remarkably enhanced. It directly translates to an increase in the specific capacitance of the electrode material. For a constant current charge/ discharge at 0.1 A g −1 , the electrode composed of LiCl-T and operating with 1 mol L −1 LiOH demonstrates the capacitance of 124 F g −1 , whereas CsCl-T with the same electrolyte has a capacitance of 216 F g −1. Moreover, the materials show the highest capacitance retention (up to 75%) vs. the current regime applied when the cation used during synthesis matches the cation present in the electrolyte (i.e., LiCl-T with LiOH). Interestingly, capacitance normalized by specific surface area has been found to be the highest when LiOH solution is applied as an electrolyte. Thus, for this metric, the size of ions seems to be a crucial parameter. The importance of mesoporosity is highlighted as well by using materials with a similar fraction of micropores and with or without mesopores. Briefly, the presence of mesopore fraction proved to be essential for improved capacity retention (69% vs. 30%). Besides textural properties, the graphitization degree impacts the electrochemical performance as well. It increases among the samples, in accordance with cation-π binding energy, e.g., LiCl-T is the most "graphitic-like" material and CsCl-T is the most disordered. Thus, the more graphitic-like materials demonstrate higher rate capability and cycle stability.
Energy & Environmental Science, 2021
This paper reports on the ion fluxes at the interfaces of various porous carbon electrodes/aqueou... more This paper reports on the ion fluxes at the interfaces of various porous carbon electrodes/aqueous solutions of alkali metal cations (Na+, K+ and Rb+) and iodide anions, monitored by an electrochemical quartz crystal microbalance (EQCM).