Performance improvement of electrochemical capacitors through the integration of advanced materials and the cell configuration assessment

209 p.The electrochemical capacitors or supercapacitors are envisioned as potential next-generation energy storage systems because of their excellent storage capacity, power density, and long-term durability. However, all these advantages are overshadowed by their poor energy density. Thus, this thesis aims to achieve a high-energy supercapacitor device without compromising its power performance to make them more commercially viable for many applications. The research work is associated with the improvement of the supercapacitors in different device configurations, such as EDL, asymmetric, and hybrid LIC systems by integration of advanced material and cell design. The results obtained from the studies of different supercapacitor systems demonstrate that the variation in electrode mass, cell voltage, and electrolyte has a huge impact on the overall electrochemical performance, stability, life expectancy, and safety of the device. Therefore, careful optimization of cell design and advancement in electrode materials retains the high importance driving factors of the supercapacitors for the development of future energy storage technology

Performance improvement of electrochemical capacitors through the integration of advanced materials and the cell configuration assessment

209 p.The electrochemical capacitors or supercapacitors are envisioned as potential next-generation energy storage systems because of their excellent storage capacity, power density, and long-term durability. However, all these advantages are overshadowed by their poor energy density. Thus, this thesis aims to achieve a high-energy supercapacitor device without compromising its power performance to make them more commercially viable for many applications. The research work is associated with the improvement of the supercapacitors in different device configurations, such as EDL, asymmetric, and hybrid LIC systems by integration of advanced material and cell design. The results obtained from the studies of different supercapacitor systems demonstrate that the variation in electrode mass, cell voltage, and electrolyte has a huge impact on the overall electrochemical performance, stability, life expectancy, and safety of the device. Therefore, careful optimization of cell design and advancement in electrode materials retains the high importance driving factors of the supercapacitors for the development of future energy storage technology

Fabrication of high-performance dual carbon Li-ion hybrid capacitor: mass balancing approach to improve the energy-power density and cycle life

Most lithium-ion capacitor (LIC) devices include graphite or non-porous hard carbon as negative electrode often failing when demanding high energy at high power densities. Herein, we introduce a new LIC formed by the assembly of polymer derived hollow carbon spheres (HCS) and a superactivated carbon (AC), as negative and positive electrodes, respectively. The hollow microstructure of HCS and the ultra large specific surface area of AC maximize lithium insertion/diffusion and ions adsorption in each of the electrodes, leading to individual remarkable capacity values and rate performances. To optimize the performance of the LIC not only in terms of energy and power densities but also from a stability point of view, a rigorous mass balance study is also performed. Optimized LIC, using a 2:1 negative to positive electrode mass ratio, shows very good reversibility within the operative voltage region of 1.5-4.2V and it is able to deliver a specific cell capacity of 28mAh(-1) even at a high current density of 10Ag(-1). This leads to an energy density of 68Wh kg(-1) at an extreme power density of 30kWkg(-1). Moreover, this LIC device shows an outstanding cyclability, retaining more than 92% of the initial capacity after 35,000 charge-discharge cycles.Spanish Ministry of Economy and Competiveness (MINECO/FEDER) (RTI2018-096199-B-I00) and the Basque Government (Elkartek 2018) are acknowledge for the financial support of this work. We also thank Maria Echeverria and Maria Jauregui for the acquisition of the TEM images and the XRD patterns, respectively

Nitrogen and phosphorus co-doped cubic ordered mesoporous carbon as a supercapacitor electrode material with extraordinary cyclic stability

Heteroatoms and porosity both have different, but definite effects on the electrochemical capacitance of carbon materials. These effects are studied in detail by using cubic ordered mesoporous carbons (OMCs) co-doped with N and P. 3-Dimensional (3D) mesoporous silica, KIT-6, with bicontinuous cubic Ia3d symmetry is utilized as a hard template to synthesize the cubic OMCs. Interestingly, although the porosity parameters e.g. surface area and pore volume do not change much with N doping, a significant increase of these values is observed upon P doping. Moreover, the P content does not affect the N doping characteristics on co-doping of both N and P. When tested as a supercapacitor electrode, the N-OMC, despite its much lower porosity parameters, exhibits a similar specific capacitance to that of the P-OMC. The high specific capacitance of N-OMC arises mainly from the pseudocapacitive effect of doped N species, whereas high porosity parameters are the main reason for the specific capacitance shown by P-OMC. The synergistic contribution of both effects enables the NP co-doped OMC to show the highest specific capacitance of 210 F g-1 at 1.0 A g-1. Moreover, excellent retention of specific capacitance with more than 90% of initial capacitance is observed for NP-OMC at a high current density of 10 A g-1 and also for 3000 charge-discharge cycles. This is mainly because of high-surface area hierarchical porous structures with uniform and ordered mesopores in the cubic OMC, which facilitate the unrestricted movement of electrolyte ions to access the active surfaces, as well as the excellent synergistic effect of co-doping of N and P. This is also supported by electrochemical impedance spectroscopic analysis, which shows negligible mass transfer resistance and internal cell resistance. Overall, the synthesized cubic OMC materials are found to be highly promising as electrodes for supercapacitors and other energy-related applications. © The Royal Society of Chemistry 2015.

Publisher Correction: Fabrication of high-performance dual carbon Li-ion hybrid capacitor: mass balancing approach to improve the energy-power density and cycle life

Correction to: Scientific Reports https://doi.org/10.1038/s41598-020-67216-x, published online 02 July 2020Peer reviewe

Publisher Correction: Fabrication of high-performance dual carbon Li-ion hybrid capacitor: mass balancing approach to improve the energy-power density and cycle life

Correction to: Scientific Reports https://doi.org/10.1038/s41598-020-67216-x, published online 02 July 2020Peer reviewe

Graphene Nanoplatelets with Selectively Functionalized Edges as Electrode Material for Electrochemical Energy Storage

In recent years, graphene-based materials have been in the forefront as electrode material for electrochemical energy generation and storage. Despite this prevalent interest, synthesis procedures have not attained three important efficiency requirements, that is, cost, energy, and eco-friendliness. In this regard, in the present work, graphene nanoplatelets with selectively functionalized edges (XGnPs) are prepared through a simple, eco-friendly and efficient method, which involves ball milling of graphite in the presence of hydrogen (H-2), bromine (Br-2), and iodine (I-2). The resultant HGnP, BrGnP, and IGnP reveal significant exfoliation of graphite layers, as evidenced by high BET surface area of 414, 595, and 772 m(2) g(-1), respectively, in addition to incorporation of H, Br, and I along with other oxygen-containing functional groups at the graphitic edges. The BrGnP and IGnP are also found to contain 4.12 and 2.20 at % of Br and I, respectively in the graphene framework. When tested as supercapacitor electrode, all XGnPs show excellent electrochemical performance in terms of specific capacitance and durability at high current density and long-term operation. Among XGnPs, IGnP delivers superior performance of 172 F g(-1) at 1 A g(-1) compared with 150 F g(-1) for BrGnP and 75 F g(-1) for HGnP because the large surface area and high surface functionality in the IGnP give rise to the outstanding capacitive performance. Moreover, all XGnPs show excellent retention of capacitance at high current density of 10 A g(-1) and for long-term operation up to 1000 charge-discharge cyclesclose10

Nitrogen-Doped Porous Carbons from Ionic Liquids@MOF: Remarkable Adsorbents for Both Aqueous and Nonaqueous Media

Porous carbons were prepared from a metal–organic framework (MOF, named ZIF-8), with or without modification, via high-temperature pyrolysis. Porous carbons with high nitrogen content were obtained from the calcination of MOF after introducing an ionic liquid (IL) (IL@MOF) via the ship-in-bottle method. The MOF-derived carbons (MDCs) and IL@MOF-derived carbons (IMDCs) were characterized using various techniques and used for liquid-phase adsorptions in both water and hydrocarbon to understand the possible applications in purification of water and fuel, respectively. Adsorptive performances for the removal of organic contaminants, atrazine (ATZ), diuron, and diclofenac, were remarkably enhanced with the modification/conversion of MOFs to MDC and IMDC. For example, in the case of ATZ adsorption, the maximum adsorption capacity of IMDC (<i>Q</i>₀ = 208 m²/g) was much higher than that of activated carbon (AC, <i>Q</i>₀ = 60 m²/g) and MDC (<i>Q</i>₀ = 168 m²/g) and was found to be the highest among the reported results so far. The results of adsorptive denitrogenation and desulfurization of fuel were similar to that of water purification. The IMDCs are very useful in the adsorptions since these new carbons showed remarkable performances in both the aqueous and nonaqueous phases. These results are very meaningful because hydrophobic and hydrophilic adsorbents are usually required for the adsorptions in the water and fuel phases, respectively. Moreover, a plausible mechanism, H-bonding, was also suggested to explain the remarkable performance of the IMDCs in the adsorptions. Therefore, the IMDCs derived from IL@MOF might have various applications, especially in adsorptions, based on high porosity, mesoporosity, doped nitrogen, and functional groups