Surface Of Current Collectors Research Articles

Unveiling Cu Nanoparticles Formed During Li Deposition in Anode-Free Batteries.

Developing high-energy-density Li metal batteries is essential for sustainable progress, necessitating in-depth studies of complex battery reactions. The presence of metallic Cu impurities detrimentally impacts battery performance, leading to issues such as self-discharging and internal soft short-circuit. Nevertheless, their formation mechanism and structural characteristics have not been revealed clearly. Here the formation of single-crystalline Cu nanoparticles during the Li deposition process in anode-free cells was identified by transmission electron microscopy. Through investigation of the chemical state of Cu before and after Li deposition, the formation of Cu NPs was attributed to the reduction of the oxide layers formed on the surface of Cu current collectors. Additionally, it was observed that Cu nanoparticles can be formed inside of deposited Li metal. This work reveals the formation pathway and microstructural characteristics of Cu nanoparticles appearing during Li deposition, underscoring the importance of nanoscale investigations into the underlying battery reactions.

Plasma Surface Treatment of Cu Current Collectors for Improving the Electrochemical Performance of Si Anodes.

The practical utilization of Si electrodes is hindered by their substantial volume expansion during alloying and dealloying processes, which causes mechanical damage and separation from Cu current collectors. To alleviate the problem of Si composite detachment from Cu current collectors, the surface of the Cu current collectors is modified using atmospheric oxygen plasma. Plasma treatment improves the wetting ability of the Cu current collectors and, consequently, the coating quality of the Si electrodes. The uniform distribution of the Si electrode components reduces the sheet resistance and improves the adhesion properties of the Si electrodes containing surface-modified Cu current collectors. As a result, the volume expansion of Si during alloying and dealloying is reduced; this results in an excellent rate capability of 1584 mA h g-1 at a current density of 3.6 A g-1 (135% that of bare Cu) and excellent cycle performance of 1545 mA h g-1 after 300 cycles (Si electrodes with bare Cu exhibit 930 mA h g-1). Therefore, the developed plasma treatment method for Cu current collectors is expected to be an economical and efficient approach for improving the Li-ion battery performance.

Spider Silk-Inspired Binder Design for Flexible Lithium-Ion Battery with High Durability.

The development of flexible lithium-ion batteries (LIBs) imposes demands on energy density and high mechanical durability simultaneously. Due to the limited deformability of electrodes, as well as the flat and smooth surface of the metal current collectors, stable/durable/reliable contact between electrode materials and the current collectors remains a challenge, in particular, for electrodes with high loading mass and heavily deformed batteries. Binders play an essential role in binding particles of electrode materials and adhering them to current collectors. Herein, inspired by spider silk, a binder for flexible LIBs is developed, which equips a cross-linked supramolecular poly(urethane-urea) to the polyacrylic acid. The binder imparts super high elastic restorability originating from the meticulously engineered hydrogen-bonding segments as well as extraordinary adhesion. The developed binder provides excellent flexibility and intact electrode morphologies without disintegration even when the electrode is largely deformed, enabling a stable cycling and voltage output even when the batteries are put under tough dynamic deformation tests. The flexible LIBs exhibit a high energy density of 420WhL-1 , which is remarkably higher than reported numbers. The unique binder design is greatly promising and offers a valuable material solution for LIBs with high-loading mass and flexible designs.

Homogeneous Li deposition guided by ultra-thin lithiophilic layer for highly stable anode-free batteries

Li-metal batteries (LMBs) are intensively studied to keep up with the growing demand for sustainable and high-capacity energy storage devices. However, the practical implementation of LMBs is still challenging owing to the catastrophic side effects associated with the growth of dendritic Li and inferior Coulombic efficiency. To enhance the long-term electrochemical stability and high-rate performance of LMBs, it is crucial to control the morphology of Li deposition over the current collectors. Herein, we propose surface-modified current collectors to investigate how a lithiatable layer affects the morphology of Li deposition and thus contributes to the stable electrochemical performance of LMBs at high current densities. The lithiatable layer improves the electrolyte wetting ability, which efficiently diminishes the interfacial resistance between electrode and electrolyte. Moreover, the lithiatable layer induces homogeneous Li nucleation, consequently leading to the uniform Li deposition over the surface of current collectors. Due to these synergistic effects, the anode-free cells with surface-modified current collectors have achieved excellent cycle stability in comparison to that with conventional Cu current collector.

Nanostructured coatings based on titanium for electrodes of electrochemical devices with proton exchange membrane

During the operation of electrochemical devices with a proton-exchange membrane under the action of oxygen, the electrode is gradually destroyed and degraded from the anode side. It is possible to increase the performance and service life of electrodes of electrochemical devices by applying Ti-based protective coatings to the surface of current collectors. In this work, nanostructured films of the compositions Ti, TiO𝑥, TiN𝑦, TiO𝑥N𝑦 were obtained by magnetron sputtering of a titanium target under various conditions. The structure and composition of the samples were studied by scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction phase analysis. The effect of various modes and conditions of magnetron sputtering on the composition and structure of titanium coatings has been established. The service life of an electrode coated with the TiN𝑦 composition in the electrolyzer mode is 2 times higher than the service life of an anode without a coating under similar conditions with comparable efficiency

Biologically Assisted One-Step Synthesis of Electrode Materials for Li-Ion Batteries

Mn(II)-oxidizing organisms promote the biomineralization of manganese oxides with specific textures, under ambient conditions. Controlling the phases formed and their texture on a larger scale may offer environmentally relevant routes to manganese oxide synthesis, with potential technological applications, for example, for energy storage. In the present study, we sought to use biofilms to promote the formation of electroactive minerals and to control the texture of these biominerals down to the electrode scale (i.e., cm scale). We used the bacterium Pseudomonas putida strain MnB1 which can produce manganese oxide in a biofilm. We characterized the biofilm-mineral assembly using a combination of electron microscopy, synchrotron-based X-ray absorption spectroscopy, X-ray diffraction, thermogravimetric analysis and electron paramagnetic resonance spectroscopy. Under optimized conditions of biofilm growth on the surface of current collectors, mineralogical characterizations revealed the formation of several minerals including a slightly crystalline MnOx birnessite. Electrochemical measurements in a half-cell against Li(0) revealed the electrochemical signature of the Mn4+/Mn3+ redox couple indicating the electroactivity of the biomineralized biofilm without any post-synthesis chemical, physical or thermal treatment. These results provide a better understanding of the properties of biomineralized biofilms and their possible use in designing new routes for one-pot electrode synthesis.

Lithium-Ion Battery Anodes Based on Silicon Nitride Nanoparticles as Active Material and Vertically Aligned Carbon Nanotubes as Electrically Conductive Scaffolding

As part of lithium-ion battery research, especially in the field of electromobility, the improvement in battery capacity and rate capability is increasingly important to, e.g., be able to travel further and charge faster. Silicon in the form of nanoparticles as anode active material is therefore heavily investigated due to its high gravimetric capacity and tolerance against pulverization. However, the low electrical conductivity of silicon nanoparticle-coated layers, as a consequence of numerous point contacts between particles with and without a native oxide shell, has a negative impact on the silicon anode’s rate capability. To achieve silicon anodes with a high rate performance, vertically aligned carbon nanotubes with their intrinsically beneficial electrical properties, grown via chemical vapor deposition on copper foil and structured by solvent spray treatment, are used as an electrically conductive scaffolding in conjunction with silicon nanoparticles. The aim of this approach is to expand the two-dimensional surface of copper current collectors. Compared to conventional anodes, the carbon nanotube concept offers a higher proportion of active material in good electrical contact with the current collector and hence superior performance at higher C-rates. In our case, instead of using pure silicon nanoparticles, silicon-rich silicon nitride nanoparticles are integrated into this carbon nanotube structure by ultrasonic spray coating due to their superior cycling stability. As proof of principle, the first cycling results of half-cells with the silicon nitride/carbon nanotube composite anode structure are discussed, which show a capacity retention of 52% at a current of 10C. This corresponds to an improvement of 20% over a copper/silicon nanoparticle reference anode without vertically aligned carbon nanotubes.

Lithium-Ion Battery Anodes Based on Silicon Nanoparticles and Vertically Aligned Carbon Nanotubes

A new concept for silicon-based anodes with potentially high rate capabilities is investigated. Vertically-aligned carbon nanotubes (CNT-forests/VACNTs) grown via chemical vapor deposition act as electrically conductive scaffolding with the aim to expand the two-dimensional surface of Cu current collectors (fig. 1 a) & b)). Silicon nanoparticles (Si-NP), integrated into this CNT-structure, are used as active material due to their high Li storage capability and their high tolerance against pulverization. Compared to conventional anodes, this concept offers a higher proportion of active material in direct electrical contact with the current collector and hence, possibly better performance at higher C-rates. Figure 1 b) illustrates the basic anode concept pursued by this contribution.As grown VACNTs are densely packed and therefore, leave no space for a coating with Si-NPs beyond the topmost surface (Fig. 1 a) & c)). In order to be able to benefit from the CNT’s advantages, such as an enlarged electrode surface area, two methods for structuring VACNTs were developed: UV-Laser and solvent treatment. These process steps induce a CNT density dependent “CNT-bunching” which yields a compacted structure with gaps that can be used for the infiltration of Si-NPs (Fig. 1 b) & d)). The Si-NP coating is investigated in dependence of different slurry coating methods. The experiments are evaluated using a SEM study in the interest of finding the most suitable approach for a homogeneous coating of the entire three-dimensional CNT-surface. In order to enhance the CNT/Si-NP adhesion, as well as to increase the active material’s electrical conductivity, UV-laser experiments were performed and evaluated with the aim to sinter the Si-NPs and thereby reduce the number of NP grain boundaries, which typically negatively influence the electronic transport and thereby the C-rate.These anodes are evaluated for their battery suitability, using electrochemical cycling tests in a half cell setup with Lithium as counter electrode in a potential range between 10 mV and 1 V. The VACNT anodes have allowed for a capacity of 1030 mAh/g after 300 cycles with an initial discharge capacity of 2638 mAh/g and an average Coulombic efficiency of 99.59 % (cycle 4 to 300) at a rate of C/2. First results on tests with high C-rates of up to 10C will be discussed for the purpose of proving the superiority of our anode concept in terms of rate capability. Figure 1

Hierarchically Micro/Nanostructured Current Collectors Induced by Ultrafast Femtosecond Laser Strategy for High‐Performance Lithium‐ion Batteries

Commercial Cu and Al current collectors for lithium‐ion batteries (LIBs) possess high electrical conductivity, suitable chemical and electrochemical stability. However, the relatively flat surface of traditional current collectors causes weak bonding strength and poor electrochemical contact between current collectors and electrode materials, resulting in potential detachment of active materials and rapid capacity degradation during extended cycling. Here, we report an ultrafast femtosecond laser strategy to manufacture hierarchical micro/nanostructures on commercial Al and Cu foils as current collectors for high‐performance LIBs. The hierarchically micro/nanostructured current collectors (HMNCCs) with high surface area and roughness offer strong adhesion to active materials, fast electronic delivery of entire electrodes, significantly improving reversible capacities and cyclic stability of HMNCCs based LIBs. Consequently, LiNi0.5Co0.2Mn0.3O2 (NCM523) cathode with Al HMNCC generated a high reversible capacity after 200 cycles (25% higher than that of cathode with Al CC). Besides, graphite anode with Cu HMNCC also maintained prominent reversible capacity even after 600 cycles. Moreover, the full cell assembled by graphite anode with Cu HMNCC and NCM523 cathode with Al HMNCC achieved high reversible capacity and remarkable cycling stability under industrial‐grade mass loading. This study provides promising candidate for achieving high‐performance LIBs current collectors.

Effects of a nanometrically formed lithiophilic silver@copper current collector on the electrochemical nucleation and growth behaviors of lithium metal anodes

Herein, we study the effects of a nanometrically uniform array of Ag nanoparticles (AgNPs) on the electrochemical nucleation and electrodeposition behavior of Li metal anodes (LMAs). The AgNP array is grown directly on the surface of commercial planar Cu current collectors (CCs) using a thermal evaporation system by limiting the growth of Ag thin films to an island stage. When the film is grown to an evaporation thickness of 3 nm, AgNPs with an average diameter of 11.4 nm are uniformly formed on the surface of Cu CCs. On the electrochemical nucleation of Li, the uniformly distributed AgNPs effectively provide nucleation sites for Li deposition and hence increase the nuclei density and spatial uniformity and decrease the size of the nuclei and nucleation overpotential. As a result, a dendrite-free, dense and pebble-like morphology of Li deposits is formed, and a high Coulombic efficiency (CE) of 98.5% is obtained during 100 cycles of the repeated electrodeposition and stripping of Li at a current density of 0.5 mA cm−2 for 1 mAh cm−2. In contrast, the cycle life of pristine Cu is limited to the 83rd cycle in the same testing environment.

(Invited) Influence of Current Collector on the Long-Term Performance of Electrochemical Capacitors

Electrochemical capacitors store the energy by the formation of the electrical double-layer at the electrode/electrolyte interface. These devices are characterized by high power density, short charge/discharge time and excellent cycling stability. The main goal of supercapacitor development nowadays is to increase their energy density and mentioned cycling stability. The former parameter could be improved by increasing the capacitance or operating voltage of the system, while the second by preserving current collectors from electrochemical corrosion phenomena. The increase of capacitance could be realized by the so-called pseudocapacitance effect, which can originate from the quick faradaic reactions at the electrode/electrolyte interface. These reactions can be induced by the appropriate modification of electrode in order to enforce the pseudocapacitive effect [1-4]. Electrochemical capacitors are composed of two electrodes separated by a separator and soaked in the electrolyte solution. Electrode material (mainly activated carbon) is coated on the surface of the current collectors made either of metals or stainless steel. In such a case, current collectors are exposed to corrosive electrolytes and can be subjected to corrosion processes [5-7]. There are several methods that are utilized to protect metals and steel from the harmful effects of electrochemical corrosion. One of them is the utilization of ionic liquids (ILs), which are added to an aggressive aqueous environment [8]. They act as corrosion inhibitors. This form of protection is being discussed in the scientific literature from about 20 years. A majority of articles describes the ability of this class of compounds to provide anti-corrosive protection for metal and steel. For these materials, an inhibitive influence on corrosion processes has been documented for dozens of ILs, vastly diversified in their chemical structure. A list of almost 90 investigated substances can be found in the literature [8]. Ionic liquids (ILs) are organic compounds which exhibit ionic structure and melting points below 100 degrees of Celsius. Due to their numerous advantageous properties, from some decades ILs stay in the scope of intense scientific interest, what results in the extensive research on possible ways to utilize them industrially. It covers various fields of IL application, for example as a solvent, an electrolyte, a catalyst, as a pharmaceutical or as corrosion inhibitors.In this work, the influence of ionic liquids additives on the performance of electrochemical capacitors is presented. Strictly, ionic liquids have been added to aqueous 1 M Na2SO4 electrolyte to inhibit corrosion processes on the surface of 316L stainless steel current collectors, which also influence the performance of electrochemical capacitors. Ionic liquids compounds were based on a common 2,5-dihydroxybenzenesulfonic anion. Electrochemical measurements were performed for a 2,5-dihydroxybenzenesulfonic acid, introduced to the electrolyte solution in 4 different concentrations ranging from 0,001% to 1%. Analogous tests were also conducted for 0,1% addition of 6 chosen ILs. All of ILs used in the research were composed of 2,5-dihydroxybenzenesulfonic anion and alkyldimethylammonium cation. The alkyl substituent of this cation varied, including n-ethyl, n-butyl, n-hexyl, cyclohexyl, n-octyl and n-decyl groups. The performed analysis proved an inhibitive effect of investigated compounds on the corrosion processes. The highest effectivities were observed for the ILs with bulkier alkyl substituent (i.e. containing cyclohexyl, n-octyl and n-decyl groups). On the basis of potentiodynamic polarization tests, a mixed corrosion inhibition mechanism was identified, with a predominant influence on the anodic process. Moreover, particular ionic liquids with the best anti-corrosive properties were used as additives to the electrolyte solution in electrochemical capacitors at a concentration of 0.1%. The results of electrochemical tests indicate a significant effect of the addition of ionic liquids on the working parameters of the electrochemical capacitors systems.This work was financially supported by the National Science Centre of Poland granted on the basis of the decision number 2018/31/B/ST8/01619 and by European Research Council (ERC) within ERC-StG-2017 project (grant agreement No. 759603) under the European Union’s Horizon 2020 research and innovation programme. References 1) F. Béguin, V. Presser, A. Balducci, E. Frackowiak, Adv. Mater., 26, 2219 (2014).2) T. Brousse, D. Bélanger, J.W. Long, J. Electrochem. Soc., 162, A5185 (2015).3) M. Graś, Ł. Kolanowski, J. Wojciechowski, G. Lota, Electrochem. Commun., 68, 28 (2018).4) K. Fic, G. Lota, M. Meller, E. Frackowiak, Energy & Environmental Science, 5, 842 5 (2012).5) J. Wojciechowski, Ł. Kolanowski, A. Bund, G. Lota, J. Power Sources 368, 18 (2017).6) E. McCafferty, Introduction to Corrosion Science, Springer, New York (2010).7) R.W. Revie, H.H. Uhlig, Corrosion and Corrosion Control, fourth ed., John Wiley & Sons, New Jersey (2008).8) C. Verma, E.E. Ebenso, M.A. Quraishi, J. Mol. Liq., 233, 403 (2017).

Effect of Thermally Evaporated Silver Nanoparticles on the Surface Morphology and Stability of Electrodeposited Lithium Metal Anode

Due to the extra-high capacity (3860 mAhg-1) and the lowest electrochemcial equilibrium potential (-3.040 VSHE), lithium metal has been considered as a promising candidate for high-energy lithium ion battery anode [1]. However, the undesired dendrite growth results in detrimental effects in the cell performance, such as cell short-circuit, low coulombic efficiency, and dead lithium, which have hampered widespread exploits of lithium metal-based batteries. Therefore, in recent year, numerous strategies to prevent or mitigate the problematic dendrite growth, including protective layers on Li metal surface, solid electrolytes, artificial solid electrolyte interphase (SEI) layer and so forth has been reported. Among them, one of the effective methods is to provide heterogeneous lithiophilic nucleation sites on the surface of current collectors as first suggested by Yan et al., [2]. They found that heterogeneous metal seeds, which have solubility of lithium in binary phase diagram, could induce selective deposition of lithium on its surface. Recently, Hou et al., reported lithiophilic Ag nanoparticles as nucleation sites by using electroless deposition for stable electrodeposition of lithium [3]. However, from a heterogeneous nucleation point of view, the morphology of electrodeposited lithium metal will be strongly affected by uniformity of nucleation seed layers, in other words, the more uniform distribution of nucleation seeds, the more stable morphology of lithium. In this study, we introduce a thermal evaporation method to deposit Ag nanoparticles as well-distributed nucleation sites. The Ag seeds with various evaporation thicknesses (1, 3 and 5 nm) were deposited on the commercial copper foils (thickness ≈ 25 um) to study the effect of evaporation thickness on the morphology of electrodeposited lithium metal. To electrodeposit lithium on Ag-seeded Cu foil and investigate the electrochemical properties of deposited Li metal electrodes, CR 2032-type coin cells were assembled in an Ar-filled glove box (CE: Li strip, WE: Ag-seeded Cu foil, and Celgard separator). We used 1M lithium bis(trifluoromethane)sulfonamide (LiTFSI) dissolved in 1,3-dioxolane/1,2-dimethoxyethane (DOL/DME, 1:1 by volume) as electrolyte without any additives. Figure 1 shows SEM surface morphologies of a pristine copper foil and Ag-seeded Cu foils with different evaporation thicknesses of Ag. After evaporation of Ag 1 nm on the pristine Cu foil (Fig. 1-(a)), it is showed that nano-sized Ag particles uniformly distributed on the surface of Cu foil (Fig. 1-(b)). In addition, from Fig. 1-(b) to Fig. 1-(d) it is clearly confirmed that the sizes of Ag particles increased with increasing evaporation thicknesses. Figure 2 shows the morphologies of electrodeposited lithium on Ag-seeded layers with different evaporation thickness. Figure 2-(a) shows SEM image of lithium metal deposited on a pristine Cu foil, which has well-known dendritic structure. In case of electrodeposited lithium on the Ag 1 nm-seeded Cu foil (Fig. 2-(b)), it also shows dendrites on its surface although heterogeneous nucleation sites are provided. However, the morphology of lithium on the Ag-3nm seeded Cu foil has distinct differences in shape and size of lithium deposits (Fig. 2-(c)). The width size of lithium deposits was smaller than those of Ag 1 nm-seeded Cu foil and pristine Cu foil, and they have interlacing vine-like structure. Further increased evaporation thickness of Ag nucleation layer to 5 nm leads to large morphological changes of electrodeposited lithium metal (Fig. 2-(d)). It shows highly dense structure with less pore and flat surface, meaning that dendrite-free lithium film was deposited. In summary, we used thermally evaporated Ag nanoparticles as heterogeneous nucleation sites to electroplate uniform lithium metal. From the results, it was concluded that through a facile thermal evaporation controllable and well-distributed heterogeneous nucleation metal seeds can be formed on the commercial Cu current collectors, leading to a dendrite-free deposition of lithium.

Capacity Fade Analysis of Silicon Anodes with a Polydopamine-Treated Copper Foil: A Multiphysics-Based Model Approach

Treating the surface of current collectors with polydopamine has proven to be a means of resolving the issues related to delamination of silicon composite electrodes (1, 2). This is manifested in the improvement in the electrochemical performance owing to the enhanced adhesion between the silicon composite electrode and current collectors. However, the mechanisms underlying this enhancement is not well understood. In this study, a porous composite-electrode physics-based model is used to analyze the cycle performance of silicon-based anode half-cells with bare and PD-treated copper current collectors via a parameter estimation technique. Based on the estimation of the parameters that change with cycling, the various mechanisms associated with the capacity fade in the bare and PD-treated copper current collector are investigated. A quantitative analysis of the aging mechanism of silicon-based anodes in terms of Li ions loss is performed and discussed for the two cell configurations. The percentage contribution of the various identified mechanisms are estimated for the cells with the bare and PD-treated copper current collector. D. Song, D. Jung, I. Cho, M. H. Ryou and Y. M. Lee, Advanced Materials Interfaces, 3, 1600270 (2016).W. A. Appiah, J. Park, S. Byun, I. Cho, A. Mozer, M.-H. Ryou and Y. M. Lee, Journal of Power Sources (2018). Figure 1. Schematic diagram of electrode design and cycle performance of cells with bare and PD-treated copper current collector. Figure 1

Hierarchical‐dimensional Material: A Co(OH)2 Superstructure with Hybrid Dimensions for Enhanced Water Oxidation

AbstractHerein, we propose the concept of hierarchical‐dimensional materials (HDMs), which are 3D superstructures built by low‐dimensional single‐crystalline substructures. HDMs combine the low‐ and high‐dimensional features and are a new class of promising functional materials toward electrochemical reactions. We reported a hierarchical‐dimensional cobalt hydroxide nanosheet assembly for electrocatalytic water oxidation. The assembling is 1D‐oriented, the substructures are 2D nanosheets, and 3D voids are created in the material. The as‐prepared material achieved superior electrocatalytic activity than isolated substructures. The better performance is associated with the improved mass transport, which is demonstrated by the analysis of kinetic‐controlled currents. This protocol can also be applied in preparing efficient catalysts on the surface of industrial current collectors. The proposed concept of HDMs might open a new area of functional materials in heterogeneous electrocatalysis.

Surface engineering of commercial Ni foams for stable Li metal anodes

The short life span of lithium metal anodes (LMAs) due to dendrite growth and low coulombic efficiency (CE) has been regarded as the bottleneck in developing next-generation high-energy-density lithium metal based secondary batteries. Employing three-dimensional (3D) current collectors is one approach to reduce the effective current density and delay dendrite growth. Commercial Ni foam, in spite of its high electronic conductivity and 3D topology, has not been considered for this application due to its low specific surface area and lithiophobic nature. In this study, we develop a surface engineering strategy to uniformly coat lithiophilic AuLi3 particles on Ni foam skeletons through lithiation of electrodeposited gold nanoparticles. In comparison with the bare Ni foam, the AuLi3@Ni foam is more lithiophilic, significantly lowering the nucleation energy barrier and enhancing the uniformity for Li deposition. Such a structure results in effective suppression of Li dendrite growth in the void space of the foam. As a result, the AuLi3@Ni foam current collector based LMAs can run for 740 h without cell failure in a symmetric cell. Furthermore, the Li-AuLi3@Ni foam|LiFePO4 full cell shows an excellent capacity retention of 43.8% with a high CE of 99.2% at 1C for 500 cycles. This work further illustrates the critical importance of surface lithiophilicity in guiding lithium cycling and suggests engineering the skeleton surface of commercial metal foam current collectors is important to improve 3D structured LMAs.

Uniform Li deposition by regulating the initial nucleation barrierviaa simple liquid-metal coating for a dendrite-free Li–metal anode

Dendrite-free Li deposition is achieved by coating a thin liquid-metal layer on the surface of lithiophobic current collectors.

Performance investigation and effect of temperature on a passive μDMFC with stainless steel mesh

In this paper, we provide a novel type of micro-direct methanol fuel cell (μDMFC) fabricated with two stainless steel plates as metal current collectors. In order to improve cell performance, two sheets of stainless steel mesh (SSM) are added between the membrane electrode assembly (MEA) and current collectors. To avoid electrochemical corrosion, titanium nitride (TiN) layers with thickness of 500 nm are deposited onto the surface of current collectors and stainless steel mesh. The results show that the embedded stainless steel mesh can remarkably reduce the interior impedance of the μDMFC. Moreover, compared with μDMFC without SSM, the novel cell exhibits a more outstanding performance, yielding a maximum power density of 54.4 mW cm−2 at 80 °C.

Oxide film formation and diffusion processes in near-surface layers of current collectors in solid oxide fuel cells

A method is developed for modifying the surface of current collectors in solid-oxide fuel cells (SOFC) prepared from ferrite stainless steel (Crofer22APU). Diffusion of the protective coating material into the Crofer22APU bulk and reverse diffusion of steel components into the coating are studied. The cross-sectional microstructure and composition are studied by the electron-microscopic technique. The elemental composition of the junction between the current collector and the lanthanum-strontium manganite cathode is studied depending on the time of service-life tests in the SOFC working mode (50–6000 h). The formation of the Cr2O3 oxide islet structure on the current collector surface at the steel/coating interface is observed. It is shown that the mutual diffusion of coating components (Ni) and Crofer22APU steel together with the redox reaction at the interface prevent the chromium diffusion to the surface and protect the steel current collector from oxidation.

Prospects of Carbon Based Micro-Fluid Electrolyte for the Vanadium Redox Flow Battery (VRB)

The effects of carbon black particle dispersed in the electrolyte and used in a modified VRB which was traditionally used of carbon felt as electrode has been removed were studied. The adding of the carbon black particle reduced both activation overpotential and ohmic overpotential especially at low OCV. The functional group on the surface of the carbon black particle helps to increase the rate of reaction which results in the reduction of activation overpotential. When the electrolyte with the carbon black particle dispersed flows into the cell, it is possible that some of carbon particles settle on the surface of current collectors and this effectively increases the surface area of current collectors. Hence, it reduces the ohmic overpotential.

Ferritic Cathodes Degradation by Potassium/Chromium Poisoning and Air Humidification

AbstractDegradation mechanisms inherent to ferritic LSF‐SDC and LSCF‐GDC cathodes are studied by post‐mortem analysis of cells which suffered the most significant performance deterioration in a set of 18 500 h tests carried out under a specific experimental design. Three cathode processing parameters (composition, thickness, and sintering temperature) were combined with five operation conditions (chromium presence, current density, operating temperature, air flow, and humidification) through this design of experiments based in a L18 Taguchi matrix. In the case of cells exposed to chromium vapors from Crofer 22 APU pieces, those cells which exhibited K2Cr2O7 deposition in the cathode/GDC barrier interface underwent the most aggressive ASR degradation. Similar deposits were also observed on the surface of LSC current collectors. Two cells exposed to highly humidified air (20%) exhibited cathode delamination and GDC barrier deterioration by crack propagation though no foreign elements diffusion to the interface could be detected.