Victor Roev - Academia.edu (original) (raw)

Papers by Victor Roev

Research paper thumbnail of Multifunctional hybrid polymer nanocomposites for automotive‐battery packaging

Journal of Applied Polymer Science, 2020

Global sales of new electric vehicles (EV) already passed a million units last year. Lithium-ion ... more Global sales of new electric vehicles (EV) already passed a million units last year. Lithium-ion battery packs are composed of cells and assembly of modules. Nevertheless, the development of light-weighted with high oxygen and moisture barrierability remains one of the untouched issues in battery technology. This study aimed to fabricate multifunctional hybrid nanocomposites for barrier films for Liion battery packs on electric vehicles applications. The synthesized carbon supported MgO nanoparticles (hereafter referred to as CSMO) were dispersed in high density polyethylene (HDPE) polymer to satisfy several requirements for EV battery packs. The loading amount of MgO was achieved up to 22 wt % of carbon, and the size distribution was in the range of 50 to 100 nm. The hybrid nanocomposites were characterized by water-vapor transmission rate (WVTR), various spectroscopic methods, thermo-gravimetric analysis and elemental analysis. Mechanical properties were also tested. The extremely low WVTR value of CSMO/HDPE composites below 0.5 mgm −2 day −1 is the lowest value among any other gas barrier films reported in the literature. Suitable mechanical properties were also achieved. The newly proposed multifunctional hybrid nanocomposites would be very promising for barrier films on automotive packaging applications.

Research paper thumbnail of Geometric Optimization of Li-O2 Battery Cathodes with Pore Structure By Meso-Scale Modeling and Simulation Pursuing Practical Systems

ECS Meeting Abstracts, 2015

Research paper thumbnail of Degradation of Platinum-based Catalyst Supported on Carbon in High Temperature Proton Exchange Membrane Fuel Cells

ECS Meeting Abstracts, 2009

not Available.

Research paper thumbnail of Lyophobized Ordered Mesoporous Silica Additives for Li-O2Battery Cathode

Journal of Electrochemical Science and Technology, 2014

The surface of an ordered mesoporous silica (OMS) was functionalized using 1H,1H,2H,2H-perfluoroo... more The surface of an ordered mesoporous silica (OMS) was functionalized using 1H,1H,2H,2H-perfluorooctyltrimethoxysilane at 20 o C and 60 o C. It was shown that only elevated temperature allows lyophobic properties on the walls of OMS, eventually preventing pore flooding with nonaqueous electrolytes. The functionalized OMSs (OMS-F) were characterized with various techniques: wettability test, N 2 sorption measurement, high-resolution transmission electron microscopy (HR-TEM). Cathodes of 10 mg/cm 2 loading were prepared with a commercial Pt/C catalyst and polyvinylidene fluoride (PVDF, 2.5 wt.%) binder using a typical doctor blade method on a commercial gas diffusion layer (GDL) in the presence or in the absence of OMS-F additives. Subsequent discharge-charge curves were taken in a 1M LiTFSI-TEGDME electrolyte at 60 o C in pure oxygen atmosphere. It was found that the discharge capacity was significantly affected by OMS-F: 5 wt.% of additive extended discharge capacity by a factor 1.5. On the other hand, a similar OMS material but synthesized at 20 o C did not show lyophobic properties and deteriorated cathode capacity.

Research paper thumbnail of Numerical predictions and experimental verification of Li-O2 battery capacity limits for cathodes with spherical conductors and solid electrolytes

Journal of Power Sources, 2016

Abstract The capacity limits, local formation of Li 2 O 2 , passivation of active surfaces, and d... more Abstract The capacity limits, local formation of Li 2 O 2 , passivation of active surfaces, and depletion of oxygen by mass transport characteristics in a composite cathode are modeled, numerically simulated, and experimentally evaluated for non-aqueous Li-O 2 batteries employing composites of a solid polymer electrolyte and carbon particles as the cathode, Li metal as the anode, and an ion conductive oxide membrane as the separator. Although the theoretical maximum specific energy of the Li-O 2 battery is known to be 3458 Wh kg −1 cathode , our simulation predicts a maximum specific energy of 1840 Wh kg −1 cathode with an optimized weight ratio of all essential components as well as cathode thickness. A specific energy of 1713 Wh kg −1 cathode is experimentally demonstrated in a cell with a composite cathode of poly(ethylene oxide) electrolyte and Printex carbon nanoparticles with 48% carbon volume and 30 μm thickness. The model also predicts that the incorporation of voids in the cathode can significantly improve the specific energy.

Research paper thumbnail of Porous carbonaceous composite material, positive electrode and lithium air battery including porous carbonaceous composite material, and method of preparing the same

Research paper thumbnail of Lithium air battery

Research paper thumbnail of Positive Electrode for Lithium Air Battery, Method of Preparing the Positive Electrode, and Lithium Air Battery Including the Positive Electrode

Research paper thumbnail of Effect of porosity on electrochemical properties of carbon materials as cathode for lithium-oxygen battery

Journal of Power Sources, 2013

Abstract Porosity effect of carbon materials on the electrochemical performances as cathode mater... more Abstract Porosity effect of carbon materials on the electrochemical performances as cathode materials in non-aqueous Li-oxygen cells has been investigated. A carbon aerogel material is chosen to represent mesoporosity and a couple of activated carbon materials are selected to represent microporosity. Carbon aerogel shows at least ten times higher discharge capacity (4155 mAh g −1 ) than activated carbons. It is found that as much as 61% of pore volume of carbon aerogel is filled with discharge products (Li 2 O 2 ) while less than 18% of pore volume is occupied with Li 2 O 2 at the end of discharge in activated carbons, indicating that mesopore is more effective than micropore. In another experiments, the electrolyte impregnated electrode shows a capacitor-like discharge behavior, meaning it is necessary to have some open pore for the oxygen supply even though they are micropores.

Research paper thumbnail of High-energy and durable lithium metal batteries using garnet-type solid electrolytes with tailored lithium-metal compatibility

Nature Communications

Lithium metal batteries using solid electrolytes are considered to be the next-generation lithium... more Lithium metal batteries using solid electrolytes are considered to be the next-generation lithium batteries due to their enhanced energy density and safety. However, interfacial instabilities between Li-metal and solid electrolytes limit their implementation in practical batteries. Herein, Li-metal batteries using tailored garnet-type Li7-xLa3-aZr2-bO12 (LLZO) solid electrolytes is reported, which shows remarkable stability and energy density, meeting the lifespan requirements of commercial applications. We demonstrate that the compatibility between LLZO and lithium metal is crucial for long-term stability, which is accomplished by bulk dopant regulating and dopant-specific interfacial treatment using protonation/etching. An all-solid-state with 5 mAh cm−2 cathode delivers a cumulative capacity of over 4000 mAh cm−2 at 3 mA cm−2, which to the best of our knowledge, is the highest cycling parameter reported for Li-metal batteries with LLZOs. These findings are expected to promote the...

Research paper thumbnail of Elektrolyt für lithium-luft-batterie und lithium-luft-batterie diese umfassend

Research paper thumbnail of Synthesis and characterization of nanostructured PtCo-CeOx/C for oxygen reduction reaction

Highly dispersed PtCo–CeO x couples of fine Pt 3 Co alloy particles with adjacent CeO x are synth... more Highly dispersed PtCo–CeO x couples of fine Pt 3 Co alloy particles with adjacent CeO x are synthesized on a carbon support using the modified colloid method. The average sizes of Pt 3 Co and CeO x particles are approximately 1.7 and 4 nm, respectively. According to XPS studies, the CeO x particle consists of a CeO 2 phase crystal for the core and a Ce 2 O 3 phase for the shell. The CeO x -containing electrocatalysts of PtCo–CeO x and Pt–CeO x show improved electrochemical performances for the oxygen reduction reaction compared with PtCo and Pt electrocatalysts without CeO x in both ring-disc electrode and cell tests. It seems that the unsaturated Ce 2 O 3 phase of the CeO x surface causes the facile adsorption and desorption of oxygen, leading to an enhanced oxygen supply to the PtCo alloy.

Research paper thumbnail of Ethylene oxide–based polymer electrolytes with fluoroalkyl moieties for stable lithium metal batteries

Ionics, 2020

Persistent and productive cultivars of limpograss (Hemarthriu altissima (Poir.) Stapf et C.E. Hub... more Persistent and productive cultivars of limpograss (Hemarthriu altissima (Poir.) Stapf et C.E. Hubb.) are required if the species is to be useful in Northland cattle systems. A study was undertaken to investigate plant morphological traits, adaptation and persistence of 8 accessions. A series of abandoned research sites was revisited to determine long-term persistence and adaptation. Trials were established at 4 new sites throughout the northern North Island to assess morphological variation and plant survival. There was considerable variation in morphological traits assessed and plant survival, allowing scope for future selection. Bigalta used in earlier research trials had largely failed to persist under normal pasture management practices. Future work should use the cultivar Floralta.

Research paper thumbnail of Electrocatalyst for Fuel Cell, Method of Preparing the Same and Fuel Cell Including an Electrode Having the Electrocatalyst

Research paper thumbnail of Supported catalyst, method for preparing the same, cathode electrode comprising the same, and fuel cell comprising the cathode electrode

Research paper thumbnail of Enhanced electrochemical stability of quasi-solid-state electrolyte containing SiO2 nanoparticles for Li-O2 battery applications

ACS applied materials & interfaces, Jan 23, 2015

A stable electrolyte is required for the open-packing environment of a Li-O2 battery system. Here... more A stable electrolyte is required for the open-packing environment of a Li-O2 battery system. Herein, a gelled quasi-solid-state electrolyte using SiO2 nanoparticles was designed to provide solidified electrolyte having the high discharge capacity and long cyclability. We successfully achieved an organic-inorganic hybrid matrix with a gelled structure, having high ionic conductivity to enhance discharge capacity. In particular, the improved electrochemical stability of the gelled cathode led to long-term cyclability. The organic-inorganic hybrid matrix with the gelled structure plays a beneficial role on the promotion of the ionic conductivity and long-term cyclability, and diminishes electrolyte evaporation. Both experimental and theoretical findings suggest that preferential binding between the amorphous SiO2 and the polyethylene glycol dimethyl ether (PEGDME) solvent leads to the solidified gelled electrolyte and improved electrochemical stability during cycling, keeping the stabl...

Research paper thumbnail of Supported catalyst for fuel cell, method of preparing the same, electrode for fuel cell including the supported catalyst, and fuel cell including the electrode

Research paper thumbnail of Electrode catalyst for fuel cell, method of manufacturing the same, and fuel cell using the Electrode catalyst

Research paper thumbnail of An Aggregate Cluster-Dispersed Electrolyte Guides the Uniform Nucleation and Growth of Lithium at Lithium Metal Anodes

Research paper thumbnail of Synthesis and characterization of nanostructured PtCo-CeO x /C for oxygen reduction reaction

Journal of Power Sources, 2008

Highly dispersed PtCo–CeOx couples of fine Pt3Co alloy particles with adjacent CeOx are synthesiz... more Highly dispersed PtCo–CeOx couples of fine Pt3Co alloy particles with adjacent CeOx are synthesized on a carbon support using the modified colloid method. The average sizes of Pt3Co and CeOx particles are approximately 1.7 and 4nm, respectively. According to XPS studies, the CeOx particle consists of a CeO2 phase crystal for the core and a Ce2O3 phase for the shell.

Research paper thumbnail of Multifunctional hybrid polymer nanocomposites for automotive‐battery packaging

Journal of Applied Polymer Science, 2020

Global sales of new electric vehicles (EV) already passed a million units last year. Lithium-ion ... more Global sales of new electric vehicles (EV) already passed a million units last year. Lithium-ion battery packs are composed of cells and assembly of modules. Nevertheless, the development of light-weighted with high oxygen and moisture barrierability remains one of the untouched issues in battery technology. This study aimed to fabricate multifunctional hybrid nanocomposites for barrier films for Liion battery packs on electric vehicles applications. The synthesized carbon supported MgO nanoparticles (hereafter referred to as CSMO) were dispersed in high density polyethylene (HDPE) polymer to satisfy several requirements for EV battery packs. The loading amount of MgO was achieved up to 22 wt % of carbon, and the size distribution was in the range of 50 to 100 nm. The hybrid nanocomposites were characterized by water-vapor transmission rate (WVTR), various spectroscopic methods, thermo-gravimetric analysis and elemental analysis. Mechanical properties were also tested. The extremely low WVTR value of CSMO/HDPE composites below 0.5 mgm −2 day −1 is the lowest value among any other gas barrier films reported in the literature. Suitable mechanical properties were also achieved. The newly proposed multifunctional hybrid nanocomposites would be very promising for barrier films on automotive packaging applications.

Research paper thumbnail of Geometric Optimization of Li-O2 Battery Cathodes with Pore Structure By Meso-Scale Modeling and Simulation Pursuing Practical Systems

ECS Meeting Abstracts, 2015

Research paper thumbnail of Degradation of Platinum-based Catalyst Supported on Carbon in High Temperature Proton Exchange Membrane Fuel Cells

ECS Meeting Abstracts, 2009

not Available.

Research paper thumbnail of Lyophobized Ordered Mesoporous Silica Additives for Li-O2Battery Cathode

Journal of Electrochemical Science and Technology, 2014

The surface of an ordered mesoporous silica (OMS) was functionalized using 1H,1H,2H,2H-perfluoroo... more The surface of an ordered mesoporous silica (OMS) was functionalized using 1H,1H,2H,2H-perfluorooctyltrimethoxysilane at 20 o C and 60 o C. It was shown that only elevated temperature allows lyophobic properties on the walls of OMS, eventually preventing pore flooding with nonaqueous electrolytes. The functionalized OMSs (OMS-F) were characterized with various techniques: wettability test, N 2 sorption measurement, high-resolution transmission electron microscopy (HR-TEM). Cathodes of 10 mg/cm 2 loading were prepared with a commercial Pt/C catalyst and polyvinylidene fluoride (PVDF, 2.5 wt.%) binder using a typical doctor blade method on a commercial gas diffusion layer (GDL) in the presence or in the absence of OMS-F additives. Subsequent discharge-charge curves were taken in a 1M LiTFSI-TEGDME electrolyte at 60 o C in pure oxygen atmosphere. It was found that the discharge capacity was significantly affected by OMS-F: 5 wt.% of additive extended discharge capacity by a factor 1.5. On the other hand, a similar OMS material but synthesized at 20 o C did not show lyophobic properties and deteriorated cathode capacity.

Research paper thumbnail of Numerical predictions and experimental verification of Li-O2 battery capacity limits for cathodes with spherical conductors and solid electrolytes

Journal of Power Sources, 2016

Abstract The capacity limits, local formation of Li 2 O 2 , passivation of active surfaces, and d... more Abstract The capacity limits, local formation of Li 2 O 2 , passivation of active surfaces, and depletion of oxygen by mass transport characteristics in a composite cathode are modeled, numerically simulated, and experimentally evaluated for non-aqueous Li-O 2 batteries employing composites of a solid polymer electrolyte and carbon particles as the cathode, Li metal as the anode, and an ion conductive oxide membrane as the separator. Although the theoretical maximum specific energy of the Li-O 2 battery is known to be 3458 Wh kg −1 cathode , our simulation predicts a maximum specific energy of 1840 Wh kg −1 cathode with an optimized weight ratio of all essential components as well as cathode thickness. A specific energy of 1713 Wh kg −1 cathode is experimentally demonstrated in a cell with a composite cathode of poly(ethylene oxide) electrolyte and Printex carbon nanoparticles with 48% carbon volume and 30 μm thickness. The model also predicts that the incorporation of voids in the cathode can significantly improve the specific energy.

Research paper thumbnail of Porous carbonaceous composite material, positive electrode and lithium air battery including porous carbonaceous composite material, and method of preparing the same

Research paper thumbnail of Lithium air battery

Research paper thumbnail of Positive Electrode for Lithium Air Battery, Method of Preparing the Positive Electrode, and Lithium Air Battery Including the Positive Electrode

Research paper thumbnail of Effect of porosity on electrochemical properties of carbon materials as cathode for lithium-oxygen battery

Journal of Power Sources, 2013

Abstract Porosity effect of carbon materials on the electrochemical performances as cathode mater... more Abstract Porosity effect of carbon materials on the electrochemical performances as cathode materials in non-aqueous Li-oxygen cells has been investigated. A carbon aerogel material is chosen to represent mesoporosity and a couple of activated carbon materials are selected to represent microporosity. Carbon aerogel shows at least ten times higher discharge capacity (4155 mAh g −1 ) than activated carbons. It is found that as much as 61% of pore volume of carbon aerogel is filled with discharge products (Li 2 O 2 ) while less than 18% of pore volume is occupied with Li 2 O 2 at the end of discharge in activated carbons, indicating that mesopore is more effective than micropore. In another experiments, the electrolyte impregnated electrode shows a capacitor-like discharge behavior, meaning it is necessary to have some open pore for the oxygen supply even though they are micropores.

Research paper thumbnail of High-energy and durable lithium metal batteries using garnet-type solid electrolytes with tailored lithium-metal compatibility

Nature Communications

Lithium metal batteries using solid electrolytes are considered to be the next-generation lithium... more Lithium metal batteries using solid electrolytes are considered to be the next-generation lithium batteries due to their enhanced energy density and safety. However, interfacial instabilities between Li-metal and solid electrolytes limit their implementation in practical batteries. Herein, Li-metal batteries using tailored garnet-type Li7-xLa3-aZr2-bO12 (LLZO) solid electrolytes is reported, which shows remarkable stability and energy density, meeting the lifespan requirements of commercial applications. We demonstrate that the compatibility between LLZO and lithium metal is crucial for long-term stability, which is accomplished by bulk dopant regulating and dopant-specific interfacial treatment using protonation/etching. An all-solid-state with 5 mAh cm−2 cathode delivers a cumulative capacity of over 4000 mAh cm−2 at 3 mA cm−2, which to the best of our knowledge, is the highest cycling parameter reported for Li-metal batteries with LLZOs. These findings are expected to promote the...

Research paper thumbnail of Elektrolyt für lithium-luft-batterie und lithium-luft-batterie diese umfassend

Research paper thumbnail of Synthesis and characterization of nanostructured PtCo-CeOx/C for oxygen reduction reaction

Highly dispersed PtCo–CeO x couples of fine Pt 3 Co alloy particles with adjacent CeO x are synth... more Highly dispersed PtCo–CeO x couples of fine Pt 3 Co alloy particles with adjacent CeO x are synthesized on a carbon support using the modified colloid method. The average sizes of Pt 3 Co and CeO x particles are approximately 1.7 and 4 nm, respectively. According to XPS studies, the CeO x particle consists of a CeO 2 phase crystal for the core and a Ce 2 O 3 phase for the shell. The CeO x -containing electrocatalysts of PtCo–CeO x and Pt–CeO x show improved electrochemical performances for the oxygen reduction reaction compared with PtCo and Pt electrocatalysts without CeO x in both ring-disc electrode and cell tests. It seems that the unsaturated Ce 2 O 3 phase of the CeO x surface causes the facile adsorption and desorption of oxygen, leading to an enhanced oxygen supply to the PtCo alloy.

Research paper thumbnail of Ethylene oxide–based polymer electrolytes with fluoroalkyl moieties for stable lithium metal batteries

Ionics, 2020

Persistent and productive cultivars of limpograss (Hemarthriu altissima (Poir.) Stapf et C.E. Hub... more Persistent and productive cultivars of limpograss (Hemarthriu altissima (Poir.) Stapf et C.E. Hubb.) are required if the species is to be useful in Northland cattle systems. A study was undertaken to investigate plant morphological traits, adaptation and persistence of 8 accessions. A series of abandoned research sites was revisited to determine long-term persistence and adaptation. Trials were established at 4 new sites throughout the northern North Island to assess morphological variation and plant survival. There was considerable variation in morphological traits assessed and plant survival, allowing scope for future selection. Bigalta used in earlier research trials had largely failed to persist under normal pasture management practices. Future work should use the cultivar Floralta.

Research paper thumbnail of Electrocatalyst for Fuel Cell, Method of Preparing the Same and Fuel Cell Including an Electrode Having the Electrocatalyst

Research paper thumbnail of Supported catalyst, method for preparing the same, cathode electrode comprising the same, and fuel cell comprising the cathode electrode

Research paper thumbnail of Enhanced electrochemical stability of quasi-solid-state electrolyte containing SiO2 nanoparticles for Li-O2 battery applications

ACS applied materials & interfaces, Jan 23, 2015

A stable electrolyte is required for the open-packing environment of a Li-O2 battery system. Here... more A stable electrolyte is required for the open-packing environment of a Li-O2 battery system. Herein, a gelled quasi-solid-state electrolyte using SiO2 nanoparticles was designed to provide solidified electrolyte having the high discharge capacity and long cyclability. We successfully achieved an organic-inorganic hybrid matrix with a gelled structure, having high ionic conductivity to enhance discharge capacity. In particular, the improved electrochemical stability of the gelled cathode led to long-term cyclability. The organic-inorganic hybrid matrix with the gelled structure plays a beneficial role on the promotion of the ionic conductivity and long-term cyclability, and diminishes electrolyte evaporation. Both experimental and theoretical findings suggest that preferential binding between the amorphous SiO2 and the polyethylene glycol dimethyl ether (PEGDME) solvent leads to the solidified gelled electrolyte and improved electrochemical stability during cycling, keeping the stabl...

Research paper thumbnail of Supported catalyst for fuel cell, method of preparing the same, electrode for fuel cell including the supported catalyst, and fuel cell including the electrode

Research paper thumbnail of Electrode catalyst for fuel cell, method of manufacturing the same, and fuel cell using the Electrode catalyst

Research paper thumbnail of An Aggregate Cluster-Dispersed Electrolyte Guides the Uniform Nucleation and Growth of Lithium at Lithium Metal Anodes

Research paper thumbnail of Synthesis and characterization of nanostructured PtCo-CeO x /C for oxygen reduction reaction

Journal of Power Sources, 2008

Highly dispersed PtCo–CeOx couples of fine Pt3Co alloy particles with adjacent CeOx are synthesiz... more Highly dispersed PtCo–CeOx couples of fine Pt3Co alloy particles with adjacent CeOx are synthesized on a carbon support using the modified colloid method. The average sizes of Pt3Co and CeOx particles are approximately 1.7 and 4nm, respectively. According to XPS studies, the CeOx particle consists of a CeO2 phase crystal for the core and a Ce2O3 phase for the shell.