Novel synthesis and characterisation of Mn-Co-Fe nanocomposites and lamellar oxides for supercapacitors

Ce travail visait à développer de nouveaux matériaux d'électrode pour les supercondensateurs, qui, dans le contexte actuel d'expansion des énergies renouvelables, sont des dispositifs incontournables capables de stocker/délivrer de l'énergie à forte puissance. Des stratégies d'ingéniérie et de synthèse de matériaux originales (exfoliation/réempilement de feuillets, nanostructuration en milieu liquide ionique ou échange ionique) ont été mises en oeuvre : i) Exfoliation/réempilement d’oxyhydroxydes de cobalt et de manganèse où l’impact de la morphologie a été étudié. C’est en combinant des voiles d’oxydes de manganèse de type birnessite avec des nanoplaquettes d’oxyhydroxyde de cobalt que les meilleures performances sont obtenues, notamment grâce un mélange très intime entre les nanoobjets et une surface spécifique supérieure aux composés initiaux. Le composite Mn-Co démontre un effet de synergie en atteignant une capacité supérieure à la capacité théorique calculée sur la base des capacités des 2 matériaux initiaux et également supérieure à celle du composé initial au manganèse, ii) Nanostructuration d’oxyhydroxydes de cobalt en milieu liquide ionique de type imidazolium bromure où l’influence de la chaine alcane du liquide ionique a été étudiée. De plus, le liquide ionique vient, non seulement nanostructurer, mais également fonctionnaliser l’oxyhydroxyde de cobalt, donnant naissance à un matériau hydride. C’est avec la chaine alcane la plus longue à 10 carbones que les meilleures performances sont atteintes avec 42 mAh.g-1, iii) Matériaux de type birnessite à feuillets mixte manganèse-fer, où le fer a été intégré à la birnessite par synthèse céramique et par échange ionique. En combinant plusieurs spectroscopies, le fer a ainsi été localisé exclusivement au sein du feuillet de manganèse dans les matériaux préparés par voie céramique, et à la fois dans le feuillet et entre les feuillets de manganèse dans les matériaux obtenus par échange ionique. Ainsi par voie céramique, les ratios élevés en fer améliorent significativement la capacité en atteignant plus de 35 mAh.g-1 avec 15% de fer contre 25 mAh.g-1 pour la birnessite sans fer. La voie échange conduit à une capacité 10 fois supérieure à celle de la birnessite de départ, mais la capacité s’effondre au cours des cycles.This thesis was aiming at developing new electrode materials for supercapacitors, which, in the current context of the renewable energies, are major devices capable of storing / delivering energy at high power. Original material engineering strategies and synthesis have been set up (exfoliation / restacking of lamellar materials, nanostructuration in ionic liquid or ionic exchange) : i) Exfoliation/restacking of cobalt and manganese oxyhydroxides with different morphologies were investigated to define the best morphologies for the composite. By combining manganese veals with cobalt oxyhydroxide nanoplatelets, the best performance is achieved, thanks to a very intimate mixture between nanoobjects and a specific surface larger than those of the initial compounds. The Mn-Co composite demonstrates a synergistic effect since it reaches a capacity higher than the theoretical capacity calculated on the basis of those of the initial materials, and especially higher than that of the starting manganese material, ii) Nanostructuration of cobalt oxyhydroxides has been investigated in imidazolium bromide ionic liquid medium with different alkyl chains. In addition to nanostructuring, the ionic liquid functionalizes cobalt oxyhydroxide, giving rise to a new hydrid material, which reaches a capacity of 42 mAh.g-1 with le longest alkyl chain of 10 carbons, iii) Birnessite-type materials with mixed manganese-iron slabs, where iron has been incorporated into birnessite by ceramic synthesis and ionic exchange. By combining several spectroscopies, iron is shown to be located within the MnO2 slabs in the materials prepared by ceramic synthesis, and both in the MnO2 slabs and between those layers for the materials prepared by ion exchange synthesis. By ceramic synthesis, the highest iron ratios significantly improve the capacity by reaching more than 35 mAh.g-1 against 25 mAh.g-1 for the starting birnessite with 15% of iron. The exchange route leads to a capacity that is multiplied by more than 10 times compared to the starting birnessite phase, but the capacity drops upon cycling

Synthèses innovantes et caractérisation de nanocomposites et d’oxydes lamellaires à base de Mn-Co-Fe pour supercondensateurs

This thesis was aiming at developing new electrode materials for supercapacitors, which, in the current context of the renewable energies, are major devices capable of storing / delivering energy at high power. Original material engineering strategies and synthesis have been set up (exfoliation / restacking of lamellar materials, nanostructuration in ionic liquid or ionic exchange) : i) Exfoliation/restacking of cobalt and manganese oxyhydroxides with different morphologies were investigated to define the best morphologies for the composite. By combining manganese veals with cobalt oxyhydroxide nanoplatelets, the best performance is achieved, thanks to a very intimate mixture between nanoobjects and a specific surface larger than those of the initial compounds. The Mn-Co composite demonstrates a synergistic effect since it reaches a capacity higher than the theoretical capacity calculated on the basis of those of the initial materials, and especially higher than that of the starting manganese material, ii) Nanostructuration of cobalt oxyhydroxides has been investigated in imidazolium bromide ionic liquid medium with different alkyl chains. In addition to nanostructuring, the ionic liquid functionalizes cobalt oxyhydroxide, giving rise to a new hydrid material, which reaches a capacity of 42 mAh.g-1 with le longest alkyl chain of 10 carbons, iii) Birnessite-type materials with mixed manganese-iron slabs, where iron has been incorporated into birnessite by ceramic synthesis and ionic exchange. By combining several spectroscopies, iron is shown to be located within the MnO2 slabs in the materials prepared by ceramic synthesis, and both in the MnO2 slabs and between those layers for the materials prepared by ion exchange synthesis. By ceramic synthesis, the highest iron ratios significantly improve the capacity by reaching more than 35 mAh.g-1 against 25 mAh.g-1 for the starting birnessite with 15% of iron. The exchange route leads to a capacity that is multiplied by more than 10 times compared to the starting birnessite phase, but the capacity drops upon cycling.Ce travail visait à développer de nouveaux matériaux d'électrode pour les supercondensateurs, qui, dans le contexte actuel d'expansion des énergies renouvelables, sont des dispositifs incontournables capables de stocker/délivrer de l'énergie à forte puissance. Des stratégies d'ingéniérie et de synthèse de matériaux originales (exfoliation/réempilement de feuillets, nanostructuration en milieu liquide ionique ou échange ionique) ont été mises en oeuvre : i) Exfoliation/réempilement d’oxyhydroxydes de cobalt et de manganèse où l’impact de la morphologie a été étudié. C’est en combinant des voiles d’oxydes de manganèse de type birnessite avec des nanoplaquettes d’oxyhydroxyde de cobalt que les meilleures performances sont obtenues, notamment grâce un mélange très intime entre les nanoobjets et une surface spécifique supérieure aux composés initiaux. Le composite Mn-Co démontre un effet de synergie en atteignant une capacité supérieure à la capacité théorique calculée sur la base des capacités des 2 matériaux initiaux et également supérieure à celle du composé initial au manganèse, ii) Nanostructuration d’oxyhydroxydes de cobalt en milieu liquide ionique de type imidazolium bromure où l’influence de la chaine alcane du liquide ionique a été étudiée. De plus, le liquide ionique vient, non seulement nanostructurer, mais également fonctionnaliser l’oxyhydroxyde de cobalt, donnant naissance à un matériau hydride. C’est avec la chaine alcane la plus longue à 10 carbones que les meilleures performances sont atteintes avec 42 mAh.g-1, iii) Matériaux de type birnessite à feuillets mixte manganèse-fer, où le fer a été intégré à la birnessite par synthèse céramique et par échange ionique. En combinant plusieurs spectroscopies, le fer a ainsi été localisé exclusivement au sein du feuillet de manganèse dans les matériaux préparés par voie céramique, et à la fois dans le feuillet et entre les feuillets de manganèse dans les matériaux obtenus par échange ionique. Ainsi par voie céramique, les ratios élevés en fer améliorent significativement la capacité en atteignant plus de 35 mAh.g-1 avec 15% de fer contre 25 mAh.g-1 pour la birnessite sans fer. La voie échange conduit à une capacité 10 fois supérieure à celle de la birnessite de départ, mais la capacité s’effondre au cours des cycles

Novel synthesis and characterisation of Mn-Co-Fe nanocomposites and lamellar oxides for supercapacitors

Ce travail visait à développer de nouveaux matériaux d'électrode pour les supercondensateurs, qui, dans le contexte actuel d'expansion des énergies renouvelables, sont des dispositifs incontournables capables de stocker/délivrer de l'énergie à forte puissance. Des stratégies d'ingéniérie et de synthèse de matériaux originales (exfoliation/réempilement de feuillets, nanostructuration en milieu liquide ionique ou échange ionique) ont été mises en oeuvre : i) Exfoliation/réempilement d’oxyhydroxydes de cobalt et de manganèse où l’impact de la morphologie a été étudié. C’est en combinant des voiles d’oxydes de manganèse de type birnessite avec des nanoplaquettes d’oxyhydroxyde de cobalt que les meilleures performances sont obtenues, notamment grâce un mélange très intime entre les nanoobjets et une surface spécifique supérieure aux composés initiaux. Le composite Mn-Co démontre un effet de synergie en atteignant une capacité supérieure à la capacité théorique calculée sur la base des capacités des 2 matériaux initiaux et également supérieure à celle du composé initial au manganèse, ii) Nanostructuration d’oxyhydroxydes de cobalt en milieu liquide ionique de type imidazolium bromure où l’influence de la chaine alcane du liquide ionique a été étudiée. De plus, le liquide ionique vient, non seulement nanostructurer, mais également fonctionnaliser l’oxyhydroxyde de cobalt, donnant naissance à un matériau hydride. C’est avec la chaine alcane la plus longue à 10 carbones que les meilleures performances sont atteintes avec 42 mAh.g-1, iii) Matériaux de type birnessite à feuillets mixte manganèse-fer, où le fer a été intégré à la birnessite par synthèse céramique et par échange ionique. En combinant plusieurs spectroscopies, le fer a ainsi été localisé exclusivement au sein du feuillet de manganèse dans les matériaux préparés par voie céramique, et à la fois dans le feuillet et entre les feuillets de manganèse dans les matériaux obtenus par échange ionique. Ainsi par voie céramique, les ratios élevés en fer améliorent significativement la capacité en atteignant plus de 35 mAh.g-1 avec 15% de fer contre 25 mAh.g-1 pour la birnessite sans fer. La voie échange conduit à une capacité 10 fois supérieure à celle de la birnessite de départ, mais la capacité s’effondre au cours des cycles.This thesis was aiming at developing new electrode materials for supercapacitors, which, in the current context of the renewable energies, are major devices capable of storing / delivering energy at high power. Original material engineering strategies and synthesis have been set up (exfoliation / restacking of lamellar materials, nanostructuration in ionic liquid or ionic exchange) : i) Exfoliation/restacking of cobalt and manganese oxyhydroxides with different morphologies were investigated to define the best morphologies for the composite. By combining manganese veals with cobalt oxyhydroxide nanoplatelets, the best performance is achieved, thanks to a very intimate mixture between nanoobjects and a specific surface larger than those of the initial compounds. The Mn-Co composite demonstrates a synergistic effect since it reaches a capacity higher than the theoretical capacity calculated on the basis of those of the initial materials, and especially higher than that of the starting manganese material, ii) Nanostructuration of cobalt oxyhydroxides has been investigated in imidazolium bromide ionic liquid medium with different alkyl chains. In addition to nanostructuring, the ionic liquid functionalizes cobalt oxyhydroxide, giving rise to a new hydrid material, which reaches a capacity of 42 mAh.g-1 with le longest alkyl chain of 10 carbons, iii) Birnessite-type materials with mixed manganese-iron slabs, where iron has been incorporated into birnessite by ceramic synthesis and ionic exchange. By combining several spectroscopies, iron is shown to be located within the MnO2 slabs in the materials prepared by ceramic synthesis, and both in the MnO2 slabs and between those layers for the materials prepared by ion exchange synthesis. By ceramic synthesis, the highest iron ratios significantly improve the capacity by reaching more than 35 mAh.g-1 against 25 mAh.g-1 for the starting birnessite with 15% of iron. The exchange route leads to a capacity that is multiplied by more than 10 times compared to the starting birnessite phase, but the capacity drops upon cycling

Stabilization and improvement of energy storage performance of high mass loading cobalt hydroxide electrode by surface functionalization

Nano-oxides and hydroxides generate great interest as promising positive electrode materials for the development of high energy density supercapacitors. However, their usually limited ionic and electronic conductivities significantly decrease their energy storage performances when increasing the electrode's mass loading. Here, we report on a sonochemical approach to functionalize the surface of Co(OH)2 nanomaterials by EmimBF4 ionic liquid that greatly improves the stability and the electrochemical performances of high mass loading electrodes (13 mg cm−2). This surface functionalization boosts the transport properties and strongly enhances the capacity as well as the capacity retention at higher current densities compared to basic Co(OH)2 (e.g. 113.5 C g−1 vs 59.2 C g−1 at 1 A g−1). Additionally, the protective layer formed by the ionic liquid stabilizes the electrode material upon cycling in KOH aqueous electrolyte and protects the material from oxidation upon open-air storage.Laboratory of excellency for electrochemical energy storag

Relating the electrochemical behavior of Birnessite to the morphology and specific surface: interest of studying the surface reactivity

International audienceThis article focuses on understanding the link between the morphologies and specific surfaces of well-known birnessites with electrochemical performance by studying the surface reactivity of each material. Our study is especially dedicated to show the impact of the material’s surface on the faradaic and pseudocapacitive mechanisms involved in the energy storage of the supercapacitors. For this purpose, a multiscale study was carried out on three birnessites, nonprotonated (Na-MnO2, K-MnO2 and HT-MnO2) and protonated (HNa-MnO2, HK-MnO2 and HHT-MnO2), to ensure the investigation of the surface reactivity on birnessites for each step of the nanocomposite conception based on birnessite. Scanning electron microscopy (SEM) was used to characterize the morphology of the materials. Coupling X-ray photoemission spectroscopy (XPS) and SO2 gas probe adsorption are especially devoted to determine the nature of active sites and the electronic structure of the material’s surface. Thus, we provide evidence that the surface properties, such as specific surface area and surface active sites, are linked to the electrochemical mechanism (faradaic or pseudocapacitive) of storage depending on the scan rate. We show that the site concentration determined by XPS can be directly linked to the contribution of the pseudocapacitive mechanism observed at low and moderate scan rates. As the capacitive mechanism is discriminated at a high scan rate, its contribution is related to the Brunauer–Emmett–Teller (BET) surface. The largest specific surface is obtained for HK-MnO2 with its eroded veils (85 m2/g). Redox reactivity was evaluated from XPS quantification comparing the S/M values, i.e., atom % of S/atom % of Mn. HT-MnO2, its protonated derivative HHT-MnO2, and Na-MnO2 exhibit the largest redox reactivity, with, respectively, S/M values of 0.49, 0.46, and 0.31, according to their smooth platelet morphology. Except for the high temperature birnessite, the change of morphology after protonation decreases the concentration of redox active sites while the BET surface increases. This work shows that HK-MnO2 presents the best performance, 46.6 F/g at 100 mV/s, to be used as an electrode material in supercapacitor storage systems

Incorporation of Fe3+ into MnO2 birnessite for enhanced energy storage: Impact on the structure and the charge storage mechanisms

Birnessite δ-MnO2, with its low cost, high theoretical capacity, and stable cycling performance in aqueous electrolytes, holds promise as an electrode material for high-power and cost-effective electrochemical energy storage devices. To address its poor electronic conductivity, we incorporated environmentally friendly iron into birnessite and conducted a comprehensive study on its influence on crystal structure, electrochemical reaction mechanisms, and energy storage performance. In this study, a series of birnessite samples with varying iron content (δ-Mn1-xFexO2 with 0 ≤ x ≤ 0.20) were synthesized using solid-state reactions, resulting in well-crystallized particles with micrometric platelet morphology. Through X-ray absorption and Mössbauer spectroscopies, we clearly demonstrated that Fe replaces Mn in the metal oxide layer, while X-ray diffraction revealed that iron content significantly affects interlayer site symmetry and the resulting polytype. The sample with the lowest iron content (δ-Mn0.96Fe0.04O2) exhibits a monoclinic birnessite structure with an O-type interlayer site, while increasing iron content leads to hexagonal symmetry with P-type interlayer sites. Electrochemical investigations indicated that these P-type sites facilitate the diffusion of partially hydrated alkaline ions and exhibit superior rate capabilities compared to the O-type phase. Furthermore, operando XAS revealed that Fe is electrochemically inactive and that the charge storage in birnessite-type phases in a 0.5M K2SO4 electrolyte primarily relies on the redox reaction of Mn. Finally, we determined that P-type δ-Mn0.87Fe0.13O2 achieved the best compromise between enhancing electrical conductivity and maintaining a maximum content of electrochemically active Mn cations

Surface reactivity and surface characterization of the layered β(III)-CoOOH material: an experimental and computational study

In this article, we focused on the comprehension of the surface reactivity of layered β(III)-cobalt oxyhydroxide, β(III)-CoOOH, by implementing a multiscale study associating both experimental, surface characterization by X-ray photoemission spectroscopy (XPS) and scanning electron microscopy and first-principles calculations. The surface reactivity and the chemical properties of the surface are key factors in the charge-storage mechanism, and β(III)-CoOOH presents interesting characteristics to be used as pseudo-capacitive electrode materials in supercapacitors thanks to its large surface specific area (∼100 m2/gs) and its high electronic conductivity (10–3 to 1 S cm–1). The surface reactivity (basic and redox character) of the synthesized compounds, which consists in aggregates of particles with 60–100 nm length, has been explored from the adsorption of SO2 molecules followed by XPS analyses. A kinetic study of the reactivity allowed us to identify three steps in the adsorption mechanism of our β(III)-CoOOH samples. The coupling of XPS and computational results allows us to establish a link between the surface reactivity in the identified domains, the formation of sulfate and sulfite species, and the cobalt Co3+ and Co4+ species of the active sites along with the underlying electronic processes

Controlled nanostructuration of cobalt oxyhydroxide electrode material for hybrid supercapacitors

International audienceNanostructuration is one of the most promising strategies to develop performant electrode materials for energy storage devices, such as hybrid supercapacitors. In this work, we studied the influence of precipitation medium and the use of a series of 1-alkyl-3-methylimidazolium bromide ionic liquids for the nanostructuration of β(III) cobalt oxyhydroxides. Then, the effect of the nanostructuration and the impact of the different ionic liquids used during synthesis were investigated in terms of energy storage performances. First, we demonstrated that forward precipitation, in a cobalt-rich medium, leads to smaller particles with higher specific surface areas (SSA) and an enhanced mesoporosity. Introduction of ionic liquids (ILs) in the precipitation medium further strongly increased the specific surface area and the mesoporosity to achieve well-nanostructured materials with a very high SSA of 265 m2/g and porosity of 0.43 cm3/g. Additionally, we showed that ILs used as surfactant and template also functionalize the nanomaterial surface, leading to a beneficial synergy between the highly ionic conductive IL and the cobalt oxyhydroxide, which lowers the resistance charge transfer and improves the specific capacity. The nature of the ionic liquid had an important influence on the final electrochemical properties and the best performances were reached with the ionic liquid containing the longest alkyl chain

Incorporation of Fe3+ into MnO2 birnessite for enhanced energy storage: Impact on the structure and the charge storage mechanisms

Birnessite δ-MnO2, with its low cost, high theoretical capacity, and stable cycling performance in aqueous electrolytes, holds promise as an electrode material for high-power and cost-effective electrochemical energy storage devices. To address its poor electronic conductivity, we incorporated environmentally friendly iron into birnessite and conducted a comprehensive study on its influence on crystal structure, electrochemical reaction mechanisms, and energy storage performance. In this study, a series of birnessite samples with varying iron content (δ-Mn1-xFexO2 with 0 ≤ x ≤ 0.20) were synthesized using solid-state reactions, resulting in well-crystallized particles with micrometric platelet morphology. Through X-ray absorption and Mössbauer spectroscopies, we clearly demonstrated that Fe replaces Mn in the metal oxide layer, while X-ray diffraction revealed that iron content significantly affects interlayer site symmetry and the resulting polytype. The sample with the lowest iron content (δ-Mn0.96Fe0.04O2) exhibits a monoclinic birnessite structure with an O-type interlayer site, while increasing iron content leads to hexagonal symmetry with P-type interlayer sites. Electrochemical investigations indicated that these P-type sites facilitate the diffusion of partially hydrated alkaline ions and exhibit superior rate capabilities compared to the O-type phase. Furthermore, operando XAS revealed that Fe is electrochemically inactive and that the charge storage in birnessite-type phases in a 0.5M K2SO4 electrolyte primarily relies on the redox reaction of Mn. Finally, we determined that P-type δ-Mn0.87Fe0.13O2 achieved the best compromise between enhancing electrical conductivity and maintaining a maximum content of electrochemically active Mn cations

Kraft black liquor as a carbonaceous source for the generation of porous monolithic materials and applications toward hydrogen adsorption and ultrastable supercapacitors

High internal phase emulsions (HIPEs) have templated self-standing porous carbonaceous materials (carboHIPEs) while employing Kraft Black Liquor, a paper milling industry byproduct, as a carbon precursor source. As such, the starting emulsion has been prepared through a laboratory-made homogenizer, while native materials have been characterized at various length scales either with Raman spectrometry, X-ray diffraction (XRD), mercury intrusion porosimetry, and nitrogen absorption. After thermal carbonization, specific surface areas ranging from ∼600 m2 g–1 to 1500 m2 g–1 have been reached while maintaining a monolithic character. Despite a poor graphitization yield, the carbonaceous materials offer good electronic transport properties, reaching 31 S m–1. When tested toward energy storage applications, the native unwashed materials revealed a hydrogen storage of 0.07 wt % at 40 bar and room temperature (RT), while hydrogen retention is reaching 0.37 wt % at 40 bar and RT for the washed sample. When employed as supercapacitor electrodes, these carbonaceous foams are able to deliver high capacities of ∼140 F/g at 1 A/g, thereby matching the ones obtained from a commercial carbon reference, while additionally providing a restored remnant capacity of 120 F/g at 2 A/g over 5000 cycle numbers