Accepted Manuscripts

Aniruddha M. Dive and Dr. Soumik Banerjee
J. Electrochem. En. Conv. Stor.   doi: 10.1115/1.4037582
Ionic liquids are considered promising electrolytes for developing electric double-layer capacitors with high energy density. To identify optimal operating conditions, we performed molecular dynamics simulations of N-methyl-N-propyl pyrrolidinium bis(trifluoromethanesulfonyl)imide (mppy+ T¬¬FSI-) ionic liquid confined in the interstices of vertically aligned carbon nanostructures mimicking the electrode structure. We modelled various surface charge densities as well as varied the distance between nanotubes in the array. Our results indicate that high-density ion storage occurs within the non-interacting double-layer region formed in the nano-confined domain between charged nanotubes. We determined the specific arrangement of these ions relative to the nanotube surface and related the layered configuration to the molecular structure of the ions. The pitch distance of the nanotube array that enables optimal mppy+ T¬¬FSI- storage and enhanced capacitance is determined to be 16 Å.
Kyle Brinkman
J. Electrochem. En. Conv. Stor.   doi: 10.1115/1.4037583
A perspective on emergent phase formation is presented using an interdisciplinary approach gained by working at the "interface" between diverse application areas including solid oxide fuel cells and ionic membrane systems, solid state lithium batteries, and ceramics for nuclear waste immobilization. The grain boundary interfacial characteristics of model single-phase materials in these application areas including i) CeO2, ii) Li7La3Zr2O12 (LLZO) and iii) hollandite of the form BaxCsyGa2x+yTi8-2x-yO16 are discussed as well as the potential for emergent phase formation in composite systems. The potential physical properties resulting from emergent phase structure and distribution are discussed, including an overview of existing 3D imaging techniques recently used for characterization. Finally, an approach for thermodynamic characterization of emergent phases based on melt solution calorimetry is outlined which may be used to predict the energy landscape including phase formation and stability of complex multi-phase systems.
TOPICS: Stability, Radioactive wastes, Composite materials, Ceramics, Calorimetry, Grain boundaries, Solid oxide fuel cells, Lithium, Membranes, Imaging
Haitao Yang, Chuanlin Fan and Q. S. Zhu
J. Electrochem. En. Conv. Stor.   doi: 10.1115/1.4037532
In the present paper, a composite electrode material was developed for vanadium redox flow batteries (VRFBs). Activated charcoal particles were evenly immobilized on the graphite felt (GF) via a sucrose pyrolysis process for the first time. The in site formed pyrolytic carbon is used as the binder, because it is essentially carbon material as well as GF and activated charcoal, which has a natural tendency to realize good adhesion and low contact resistance. The activated charcoal decorated GF electrode (abbreviated as the composite electrode) possesses larger surface area (13.8 m2 g-1), more than two times as GF (6.3 m2 g-1). The composite electrode was demonstrated to lower polarization and increase the reversibility towards the VO2+/VO2+ redox couple according to the cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements. The charge-discharge cycling test was conducted with a single VRFB cell. The results indicate that the cell with composite electrode presents higher charge-discharge capacity, larger electrolyte utilization efficiency and higher energy conversion efficiency (79.1%) compared with that using GF electrode. The increasing electrochemical performances of composite electrodes are mainly ascribed to the high electrochemical activity of activated charcoal particles and increasing superficial area.
TOPICS: Flow (Dynamics), Activated carbon, Electrodes, Graphite, Batteries, Composite materials, Particulate matter, Electrochemical impedance spectroscopy, Carbon, Pyrolysis, Contact resistance, Electrolytes, Energy conversion, Polarization (Electricity), Polarization (Light), Binders (Materials), Polarization (Waves), Adhesion
Gert Berckmans, Joris Jaguemont, Ahmadou Samba, Noshin Omar, Omar Hegazy, Jan Ronsmans, Mahdi Soltani, Yousef Firouz, Peter Van den Bossche and Joeri Van Mierlo
J. Electrochem. En. Conv. Stor.   doi: 10.1115/1.4037491
The large push for more environmental energy-storage solutions for the automotive industry by different actors has led to the usage of lithium-ion capacitors combining the features of both lithium-ion batteries and electric-double layer capacitors. In this paper, the thermal behaviour of two types of advanced lithium-ion capacitors have been thoroughly studied and analysed by developing a 3D thermal model in COMSOL Multiphysics®. Such an extensive and accurate thermal 3D has not been fully addressed in literature, which is a key building block for designing battery packs with an adequate thermal management. After an extensive measurement campaign, the high accuracy of the developed model in this paper is proven for both types of lithium-ion capacitors, the 3300F and the 2300F one. An error between the simulation and measurements is maximum 2 Degrees Celsius. This 3D model has been developed to gain insight in the thermal behaviour of lithium-ion capacitors which is necessary to develop a thermal management system which can ensure the safe operation of lithium-ion capacitors when used in modules or packs.
TOPICS: Lithium, Capacitors, Thermal management, Three-dimensional models, Batteries, Lithium-ion batteries, Blocks (Building materials), Simulation, Automotive industry, Design, Energy storage, Errors
Review Article  
Ruijie Ye, Dirk Henkensmeier, Sang Jun Yoon, Zhifeng Huang, Dong Kyu Kim, Zhenjun Chang, Sangwon Kim and Ruiyong Chen
J. Electrochem. En. Conv. Stor.   doi: 10.1115/1.4037248
The utilization of intermittent renewable energy sources needs low-cost, reliable energy storage systems in the future. Among various electrochemical energy storage systems, redox flow batteries (RFBs) are promising with merits of independent energy storage and power generation capability, localization flexibility, high efficiency, low scaling-up cost, and excellent long charge/discharge cycle life. RFBs typically use metal ions as reacting species. The most exploited types are all-vanadium RFBs (VRFBs). Here, we discuss the core components for the VRFBs, including the development and application of different types of membranes, electrode materials, and stack system. In addition, we introduce the recent progress in the discovery of novel electrolytes, such as redox active organic compounds, polymers and organic/inorganic suspensions. Versatile structures, tunable properties, and abundant resources of organic-based electrolytes make them suitable for cost-effective stationary applications. With the active species in solid form, suspension electrolytes are expected to provide enhanced volumetric energy density.
TOPICS: Flow (Dynamics), Energy storage, Electrolytes, Membranes, Organic compounds, Renewable energy sources, Ions, Metals, Electrodes, Energy generation, Polymers, Cycles, Density
Expert View  
Matthias Klingele, Riko Moroni, Severin Vierrath and Simon Thiele
J. Electrochem. En. Conv. Stor.   doi: 10.1115/1.4037244
The microstructure of a fuel cell electrode largely determines the performance of the whole fuel cell system. In this regard, tomographic imaging is a valuable tool for the understanding and control of the electrode morphology. The distribution of pore- and feature-sizes within fuel cell electrodes covers several orders of magnitude, ranging from millimeters in the gas diffusion layer down to few nanometers in the catalyst layer. This obligates the application of various tomographic methods for imaging every aspect of a fuel cell. This perspective evaluates the capabilities, limits and challenges of each of these methods. Further it highlights and suggests efforts towards the integration of multiple tomographic methods into single multiscale datasets, a venture which aims at large scale, and morphologically fully resolved fuel cell reconstructions.
TOPICS: Fuel cells, Electrodes, Imaging, Gas diffusion layers, Catalysts

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