A homologous series of ionic liquids (IL) with 1-alkyl-3-methylimidazolium cations of different l... more A homologous series of ionic liquids (IL) with 1-alkyl-3-methylimidazolium cations of different lengths of alkyl chain was used to study the effect of cation size on the capacitive response of two carbons with a tailored pore size distribution. The results reveal a clear ion-sieving effect in pure ILs, while the effect is heavily mitigated for the same salts used in solution, most likely due to somewhat stronger geometrical flexibility of dissolved ions. For the electrode material showing the ion-sieving effect in solution, the gravimetric capacitance values are higher than in pure ILs. The dissimilarity of capacitance values between pure and dissolved ILs with ion-sieving carbons highlights their respective advantages and disadvantages in terms of energy density: whereas pure ILs can potentially provide a larger working voltage window, the corresponding dissolved salts can access smaller pores, mostly contributing to higher capacitance values.
The integration of capacitive and faradaic energy storage mechanism in the form of hybrid materia... more The integration of capacitive and faradaic energy storage mechanism in the form of hybrid materials, electrodes and devices aims at increasing energy and power densities for the next generation of electrochemical energy storage devices.
The development of a novel hybrid symmetric micro-supercapacitor based on poly(3,4-ethylenedioxyt... more The development of a novel hybrid symmetric micro-supercapacitor based on poly(3,4-ethylenedioxythiophene) coated silicon nanowires using an ionic liquid PYR13TFSI as an electrolyte has been demonstrated.
This work presents a systematic evaluation of the effect of dissimilar charging / discharging tem... more This work presents a systematic evaluation of the effect of dissimilar charging / discharging temperatures on the long-term performance of lithium iron phosphate / graphite based cells by using multi-factor analysis of variance. Specifically, the degradation of prototype pouch cells is presented in a range of charging and discharging temperatures from -20 °C to +30 °C, counting a total of 10 temperature combinations. In this manner, not only the effect of charging and discharging temperatures was analyzed, but also the correlations between them.
Fitting of the data showed a quadratic relationship of degradation rate with charging temperature, a linear relationship with discharging temperature and a correlation between charging and discharging temperature. Cycling at the charge/discharge temperatures (+30 °C, -5 °C) produced the highest degradation rate, whereas cycling in the range from -20 °C to +15 °C, in various charge/discharge temperature combinations, created almost no degradation. It was also found that when Tc≅15 °C the degradation rate is independent of Td. When Tc < +15 °C, the higher degradation occurs at higher Td and at Tc > +15 °C lower degradation occurs at higher Td.
This study aims at analyzing the response of Li-ion cells and at identifying the hazards and gove... more This study aims at analyzing the response of Li-ion cells and at identifying the hazards and governing phenomena from hard to soft external short circuit conditions. 10 Ah pouch cells and 4.5 mAh coin cells were short circuited while synchronized current, potential and temperature signals, audio, IR and visual video recordings were registered. The anode, cathode and separator harvested from the cells were characterized by Scanning Electron Microscopy, micro X-ray Computed Tomography and 3D-profilometry.
The complex short circuit behavior obtained can be described by 3 regions: In the first region 274C-rate is observed which is mainly governed by the cell's double and diffusion layer discharge. In the second region, the current drops significantly to 50–60C-rate where mass transport becomes the current limiting factor. The maximum temperature (77–121 °C) is reached and cell rupture, venting and electrolyte leakage may occur. In the final, third region the current decline continues due to the decaying electromotive force. The normalized external/internal resistance ratio is found to be the main influential factor on current and hazards rather than the external resistance or the capacity of the cell. The implications on the relevance and fitness-for-purpose of external short circuit test in standards are outlined.
The present work reports the use and application of a novel protic ionic liquid (triethylammonium... more The present work reports the use and application of a novel protic ionic liquid (triethylammonium bis(trifluoromethylsulfonyl)imide; NEt3H TFSI) as an electrolyte for symmetric planar micro-supercapacitors based on silicon nanowire electrodes. The excellent performance of the device has been successfully demonstrated using cyclic voltammetry, galvanostatic charge-discharge cycles and electrochemical impedance spectroscopy. The electrochemical characterization of this system exhibits a wide operative voltage of 4 V as well as an outstanding long cycling stability after millions of galvanostatic cycles at a high current density of 2 mA cm−2. In addition, the electrochemical double layer micro-supercapacitor was able to deliver a high power density of 4 mW cm−2 in a very short time pulses (a few ms). Our results could be of interest to develop prospective on-chip micro-supercapacitors using protic ionic liquids as electrolytes with high performance in terms of power and energy densities
In this paper, phosphomolybdic acid H3PMo12O40 (PMo12) was anchored to four synthetic micro-mesop... more In this paper, phosphomolybdic acid H3PMo12O40 (PMo12) was anchored to four synthetic micro-mesoporous carbons and a commercial one to analyse the relationship between the porous texture of the support, the PMo12 adsorption and the performance of the resulting hybrid materials as electrodes in supercapacitors. The uptake of PMo12 on carbon supports follows a clear correlation with the micropore volume, which implies that PMo12 is mainly adsorbed in microporosity as a consequence of a greater confinement in this kind of pores instead of mesopores. Transmission electron microscopy indicates that the PMo12 adsorbed is homogeneously dispersed in the carbon texture. Finally, the addition of PMo12 to the original carbon electrodes provided capacitances up to 293 F per gram of electrode, substantially larger than the 206–240 F g−1 of the unmodified activated carbon. This result represented an increase of up to 35% in terms of gravimetric energy density and 160% in terms of volumetric energy density, after PMo12 integration into the carbon matrix.
The hybrid approach allows for a reinforcing combination of properties of dissimilar components i... more The hybrid approach allows for a reinforcing combination of properties of dissimilar components in synergic combinations. From hybrid materials to hybrid devices the approach offers opportunities to tackle much needed improvements in the performance of energy storage devices. This paper reviews
the different approaches and scales of hybrids, materials, electrodes and devices striving to advance
along the diagonal of Ragone plots, providing enhanced energy and power densities by combining
battery and supercapacitor materials and storage mechanisms. Furthermore, some theoretical aspects
are considered regarding the possible hybrid combinations and tactics for the fabrication of optimized
final devices. All of it aiming at enhancing the electrochemical performance of energy storage systems
Stable anchoring of polyoxometalate H3PMo12O40 onto in-situ Reduced Graphene Oxide leads to a hyb... more Stable anchoring of polyoxometalate H3PMo12O40 onto in-situ Reduced Graphene Oxide leads to a hybrid electrode with combined capacitive (GO) and faradaic (H3PMo12O40) charge storage mechanisms featuring increased capacitance, energy density and extended cyclability.
The development of a novel hybrid symmetric micro-ultracapacitor based on poly(3,4-ethylenedioxyt... more The development of a novel hybrid symmetric micro-ultracapacitor based on poly(3,4-ethylenedioxythiophene) coated silicon nanowires using an ionic liquid (N-methyl-N-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide) as an electrolyte has been demonstrated. The hybrid supercapacitor device was able to deliver a specific energy of 10 Wh kg-1 and a maximal power density of 85 kW kg-1 at a cell voltage of 1.5 V. The hybrid device exhibited long lifetime and an outstanding electrochemical stability retaining 80 % of the initial capacitance after thousands of galvanostatic charge-discharge cycles at a high current density of 1 mA cm-2. The improvement of the capacitive properties compared with the bare SiNWs was attributed to the pseudo-capacitive behavior induced by the conducting polymer coating.
This work describes the development and performance of a symmetric micro-supercapacitor made of n... more This work describes the development and performance of a symmetric micro-supercapacitor made of nanostructured electrodes based on silicon nanowires (SiNWs) deposited using chemical vapor deposition (CVD) on silicon substrates. The performance of the SiNWs micro-supercapacitor employing an aprotic ionic liquid (N-methyl-N-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide) (PYR13TFSI) as an electrolyte was able to deliver a maximal power density of 182 mW cm−2 and a specific energy of 190 μJ cm−2 operating at a wide cell voltage of 4 V with a quasi-ideal capacitive behavior. The lifetime of the device exhibited a remarkable electrochemical stability retaining 75% of the initial capacitance after several million galvanostatic charge–discharge cycles at a high current density of 1 mA cm−2. Furthermore, a coulombic efficiency of approximately 99% was obtained after galvanostatic cycling test without structural degradation on the morphology of SiNWs.
The hybrid approach allows for a reinforcing combination of properties of dissimilar components i... more The hybrid approach allows for a reinforcing combination of properties of dissimilar components in synergic combinations. From hybrid materials to hybrid nanocomposite electrodes the approach offers opportunities to tackle much needed improvements in the performance of energy storage devices. This paper presents different types of hybrid materials with emphasis on those synthesized and studied in our laboratory and reviews the different approaches and scales of hybrids, materials, electrodes and finally presents recent efforts to develop hybrid battery-supercapacitor devices
The hybrid approach allows for a reinforcing combination of properties of dissimilar components i... more The hybrid approach allows for a reinforcing combination of properties of dissimilar components in synergic combinations. From hybrid materials to hybrid nanocomposite electrodes the approach offers opportunities to tackle much needed improvements in the performance of energy storage devices. This paper presents different types of hybrid materials with emphasis on those synthesized and studied in our laboratory and reviews the different approaches and scales of hybrids, materials, electrodes and finally presents recent efforts to develop hybrid battery-supercapacitor devices.
A homologous series of ionic liquids (IL) with 1-alkyl-3-methylimidazolium cations of different l... more A homologous series of ionic liquids (IL) with 1-alkyl-3-methylimidazolium cations of different lengths of alkyl chain was used to study the effect of cation size on the capacitive response of two carbons with a tailored pore size distribution. The results reveal a clear ion-sieving effect in pure ILs, while the effect is heavily mitigated for the same salts used in solution, most likely due to somewhat stronger geometrical flexibility of dissolved ions. For the electrode material showing the ion-sieving effect in solution, the gravimetric capacitance values are higher than in pure ILs. The dissimilarity of capacitance values between pure and dissolved ILs with ion-sieving carbons highlights their respective advantages and disadvantages in terms of energy density: whereas pure ILs can potentially provide a larger working voltage window, the corresponding dissolved salts can access smaller pores, mostly contributing to higher capacitance values.
The integration of capacitive and faradaic energy storage mechanism in the form of hybrid materia... more The integration of capacitive and faradaic energy storage mechanism in the form of hybrid materials, electrodes and devices aims at increasing energy and power densities for the next generation of electrochemical energy storage devices.
The development of a novel hybrid symmetric micro-supercapacitor based on poly(3,4-ethylenedioxyt... more The development of a novel hybrid symmetric micro-supercapacitor based on poly(3,4-ethylenedioxythiophene) coated silicon nanowires using an ionic liquid PYR13TFSI as an electrolyte has been demonstrated.
This work presents a systematic evaluation of the effect of dissimilar charging / discharging tem... more This work presents a systematic evaluation of the effect of dissimilar charging / discharging temperatures on the long-term performance of lithium iron phosphate / graphite based cells by using multi-factor analysis of variance. Specifically, the degradation of prototype pouch cells is presented in a range of charging and discharging temperatures from -20 °C to +30 °C, counting a total of 10 temperature combinations. In this manner, not only the effect of charging and discharging temperatures was analyzed, but also the correlations between them.
Fitting of the data showed a quadratic relationship of degradation rate with charging temperature, a linear relationship with discharging temperature and a correlation between charging and discharging temperature. Cycling at the charge/discharge temperatures (+30 °C, -5 °C) produced the highest degradation rate, whereas cycling in the range from -20 °C to +15 °C, in various charge/discharge temperature combinations, created almost no degradation. It was also found that when Tc≅15 °C the degradation rate is independent of Td. When Tc < +15 °C, the higher degradation occurs at higher Td and at Tc > +15 °C lower degradation occurs at higher Td.
This study aims at analyzing the response of Li-ion cells and at identifying the hazards and gove... more This study aims at analyzing the response of Li-ion cells and at identifying the hazards and governing phenomena from hard to soft external short circuit conditions. 10 Ah pouch cells and 4.5 mAh coin cells were short circuited while synchronized current, potential and temperature signals, audio, IR and visual video recordings were registered. The anode, cathode and separator harvested from the cells were characterized by Scanning Electron Microscopy, micro X-ray Computed Tomography and 3D-profilometry.
The complex short circuit behavior obtained can be described by 3 regions: In the first region 274C-rate is observed which is mainly governed by the cell's double and diffusion layer discharge. In the second region, the current drops significantly to 50–60C-rate where mass transport becomes the current limiting factor. The maximum temperature (77–121 °C) is reached and cell rupture, venting and electrolyte leakage may occur. In the final, third region the current decline continues due to the decaying electromotive force. The normalized external/internal resistance ratio is found to be the main influential factor on current and hazards rather than the external resistance or the capacity of the cell. The implications on the relevance and fitness-for-purpose of external short circuit test in standards are outlined.
The present work reports the use and application of a novel protic ionic liquid (triethylammonium... more The present work reports the use and application of a novel protic ionic liquid (triethylammonium bis(trifluoromethylsulfonyl)imide; NEt3H TFSI) as an electrolyte for symmetric planar micro-supercapacitors based on silicon nanowire electrodes. The excellent performance of the device has been successfully demonstrated using cyclic voltammetry, galvanostatic charge-discharge cycles and electrochemical impedance spectroscopy. The electrochemical characterization of this system exhibits a wide operative voltage of 4 V as well as an outstanding long cycling stability after millions of galvanostatic cycles at a high current density of 2 mA cm−2. In addition, the electrochemical double layer micro-supercapacitor was able to deliver a high power density of 4 mW cm−2 in a very short time pulses (a few ms). Our results could be of interest to develop prospective on-chip micro-supercapacitors using protic ionic liquids as electrolytes with high performance in terms of power and energy densities
In this paper, phosphomolybdic acid H3PMo12O40 (PMo12) was anchored to four synthetic micro-mesop... more In this paper, phosphomolybdic acid H3PMo12O40 (PMo12) was anchored to four synthetic micro-mesoporous carbons and a commercial one to analyse the relationship between the porous texture of the support, the PMo12 adsorption and the performance of the resulting hybrid materials as electrodes in supercapacitors. The uptake of PMo12 on carbon supports follows a clear correlation with the micropore volume, which implies that PMo12 is mainly adsorbed in microporosity as a consequence of a greater confinement in this kind of pores instead of mesopores. Transmission electron microscopy indicates that the PMo12 adsorbed is homogeneously dispersed in the carbon texture. Finally, the addition of PMo12 to the original carbon electrodes provided capacitances up to 293 F per gram of electrode, substantially larger than the 206–240 F g−1 of the unmodified activated carbon. This result represented an increase of up to 35% in terms of gravimetric energy density and 160% in terms of volumetric energy density, after PMo12 integration into the carbon matrix.
The hybrid approach allows for a reinforcing combination of properties of dissimilar components i... more The hybrid approach allows for a reinforcing combination of properties of dissimilar components in synergic combinations. From hybrid materials to hybrid devices the approach offers opportunities to tackle much needed improvements in the performance of energy storage devices. This paper reviews
the different approaches and scales of hybrids, materials, electrodes and devices striving to advance
along the diagonal of Ragone plots, providing enhanced energy and power densities by combining
battery and supercapacitor materials and storage mechanisms. Furthermore, some theoretical aspects
are considered regarding the possible hybrid combinations and tactics for the fabrication of optimized
final devices. All of it aiming at enhancing the electrochemical performance of energy storage systems
Stable anchoring of polyoxometalate H3PMo12O40 onto in-situ Reduced Graphene Oxide leads to a hyb... more Stable anchoring of polyoxometalate H3PMo12O40 onto in-situ Reduced Graphene Oxide leads to a hybrid electrode with combined capacitive (GO) and faradaic (H3PMo12O40) charge storage mechanisms featuring increased capacitance, energy density and extended cyclability.
The development of a novel hybrid symmetric micro-ultracapacitor based on poly(3,4-ethylenedioxyt... more The development of a novel hybrid symmetric micro-ultracapacitor based on poly(3,4-ethylenedioxythiophene) coated silicon nanowires using an ionic liquid (N-methyl-N-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide) as an electrolyte has been demonstrated. The hybrid supercapacitor device was able to deliver a specific energy of 10 Wh kg-1 and a maximal power density of 85 kW kg-1 at a cell voltage of 1.5 V. The hybrid device exhibited long lifetime and an outstanding electrochemical stability retaining 80 % of the initial capacitance after thousands of galvanostatic charge-discharge cycles at a high current density of 1 mA cm-2. The improvement of the capacitive properties compared with the bare SiNWs was attributed to the pseudo-capacitive behavior induced by the conducting polymer coating.
This work describes the development and performance of a symmetric micro-supercapacitor made of n... more This work describes the development and performance of a symmetric micro-supercapacitor made of nanostructured electrodes based on silicon nanowires (SiNWs) deposited using chemical vapor deposition (CVD) on silicon substrates. The performance of the SiNWs micro-supercapacitor employing an aprotic ionic liquid (N-methyl-N-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide) (PYR13TFSI) as an electrolyte was able to deliver a maximal power density of 182 mW cm−2 and a specific energy of 190 μJ cm−2 operating at a wide cell voltage of 4 V with a quasi-ideal capacitive behavior. The lifetime of the device exhibited a remarkable electrochemical stability retaining 75% of the initial capacitance after several million galvanostatic charge–discharge cycles at a high current density of 1 mA cm−2. Furthermore, a coulombic efficiency of approximately 99% was obtained after galvanostatic cycling test without structural degradation on the morphology of SiNWs.
The hybrid approach allows for a reinforcing combination of properties of dissimilar components i... more The hybrid approach allows for a reinforcing combination of properties of dissimilar components in synergic combinations. From hybrid materials to hybrid nanocomposite electrodes the approach offers opportunities to tackle much needed improvements in the performance of energy storage devices. This paper presents different types of hybrid materials with emphasis on those synthesized and studied in our laboratory and reviews the different approaches and scales of hybrids, materials, electrodes and finally presents recent efforts to develop hybrid battery-supercapacitor devices
The hybrid approach allows for a reinforcing combination of properties of dissimilar components i... more The hybrid approach allows for a reinforcing combination of properties of dissimilar components in synergic combinations. From hybrid materials to hybrid nanocomposite electrodes the approach offers opportunities to tackle much needed improvements in the performance of energy storage devices. This paper presents different types of hybrid materials with emphasis on those synthesized and studied in our laboratory and reviews the different approaches and scales of hybrids, materials, electrodes and finally presents recent efforts to develop hybrid battery-supercapacitor devices.
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Papers by Vanesa Ruiz
Fitting of the data showed a quadratic relationship of degradation rate with charging temperature, a linear relationship with discharging temperature and a correlation between charging and discharging temperature. Cycling at the charge/discharge temperatures (+30 °C, -5 °C) produced the highest degradation rate, whereas cycling in the range from -20 °C to +15 °C, in various charge/discharge temperature combinations, created almost no degradation. It was also found that when Tc≅15 °C the degradation rate is independent of Td. When Tc < +15 °C, the higher degradation occurs at higher Td and at Tc > +15 °C lower degradation occurs at higher Td.
The complex short circuit behavior obtained can be described by 3 regions: In the first region 274C-rate is observed which is mainly governed by the cell's double and diffusion layer discharge. In the second region, the current drops significantly to 50–60C-rate where mass transport becomes the current limiting factor. The maximum temperature (77–121 °C) is reached and cell rupture, venting and electrolyte leakage may occur. In the final, third region the current decline continues due to the decaying electromotive force. The normalized external/internal resistance ratio is found to be the main influential factor on current and hazards rather than the external resistance or the capacity of the cell. The implications on the relevance and fitness-for-purpose of external short circuit test in standards are outlined.
the different approaches and scales of hybrids, materials, electrodes and devices striving to advance
along the diagonal of Ragone plots, providing enhanced energy and power densities by combining
battery and supercapacitor materials and storage mechanisms. Furthermore, some theoretical aspects
are considered regarding the possible hybrid combinations and tactics for the fabrication of optimized
final devices. All of it aiming at enhancing the electrochemical performance of energy storage systems
Fitting of the data showed a quadratic relationship of degradation rate with charging temperature, a linear relationship with discharging temperature and a correlation between charging and discharging temperature. Cycling at the charge/discharge temperatures (+30 °C, -5 °C) produced the highest degradation rate, whereas cycling in the range from -20 °C to +15 °C, in various charge/discharge temperature combinations, created almost no degradation. It was also found that when Tc≅15 °C the degradation rate is independent of Td. When Tc < +15 °C, the higher degradation occurs at higher Td and at Tc > +15 °C lower degradation occurs at higher Td.
The complex short circuit behavior obtained can be described by 3 regions: In the first region 274C-rate is observed which is mainly governed by the cell's double and diffusion layer discharge. In the second region, the current drops significantly to 50–60C-rate where mass transport becomes the current limiting factor. The maximum temperature (77–121 °C) is reached and cell rupture, venting and electrolyte leakage may occur. In the final, third region the current decline continues due to the decaying electromotive force. The normalized external/internal resistance ratio is found to be the main influential factor on current and hazards rather than the external resistance or the capacity of the cell. The implications on the relevance and fitness-for-purpose of external short circuit test in standards are outlined.
the different approaches and scales of hybrids, materials, electrodes and devices striving to advance
along the diagonal of Ragone plots, providing enhanced energy and power densities by combining
battery and supercapacitor materials and storage mechanisms. Furthermore, some theoretical aspects
are considered regarding the possible hybrid combinations and tactics for the fabrication of optimized
final devices. All of it aiming at enhancing the electrochemical performance of energy storage systems