Nanostructured Cathode Research Articles

Radially Inwardly Aligned Hierarchical Porous Carbon for Ultra-Long-Life Lithium-Sulfur Batteries.

Rational design of hollow micro- and/or nano-structured cathodes as sulfur hosts has potential for high-performance lithium-sulfur batteries. However, their further commercial application is hindered because infusing sulfur into hollow hosts is hard to control and the interactions between high loading sulfur and electrolyte are poor. Herein, we designed hierarchical porous hollow carbon nanospheres with radially inwardly aligned supporting ribs to mitigate these problems. Such a structure could aid the sulfur infusion and maximize sulfur utilization owing to the well-ordered pore channels. This highly organized internal carbon skeleton can also enhance the electronic conductivity. The hollow carbon nanospheres with further nitrogen-doping as the sulfur host material exhibit good capacity and excellent cycling performance (0.044 % capacity degradation per each cycle for 1000 cycles).

Binder-Free V2O5 Cathode for High Energy Density Rechargeable Aluminum-Ion Batteries.

Nowadays, research on electrochemical storage systems moves into the direction of post-lithium-ion batteries, such as aluminum-ion batteries, and the exploration of suitable materials for such batteries. Vanadium pentoxide (V2O5) is one of the most promising host materials for the intercalation of multivalent ions. Here, we report on the fabrication of a binder-free and self-supporting V2O5 micrometer-thick paper-like electrode material and its use as the cathode for rechargeable aluminum-ion batteries. The electrical conductivity of the cathode was significantly improved by a novel in-situ and self-limiting copper migration approach into the V2O5 structure. This process takes advantage of the dissolution of Cu by the ionic liquid-based electrolyte, as well as the presence of two different accommodation sites in the nanostructured V2O5 available for aluminum-ions and the migrated Cu. Furthermore, the advanced nanostructured cathode delivered a specific discharge capacity of up to ~170 mAh g−1 and the reversible intercalation of Al3+ for more than 500 cycles with a high Coulomb efficiency reaching nearly 100%. The binder-free concept results in an energy density of 74 Wh kg−1, which shows improved energy density in comparison to the so far published V2O5-based cathodes. Our results provide valuable insights for the future design and development of novel binder-free and self-supporting electrodes for rechargeable multivalent metal-ion batteries associating a high energy density, cycling stability, safety and low cost.

The application of hollow micro-/nanostructured cathodes for sodium-ion batteries

This work will open a new view for the design of hollow micro-/nanostructures used as cathodes for sodium-ion batteries, enclosing the superiority of this unique structure to enhance the electrochemical performance.

AUTOELECTRONIC CATHODES BASED ON ARRAYS OF NIOBIUM-OXIDE COLUMNAR NANOSTRUCTURES FOR FIELD EMISSION DISPLAYS

The article discusses the prospects of creating controlled field-effect cathodes based on arrays of columnar oxide niobium nanostructures for field emission displays. Geometrical models of field-emission cathodes and vacuum elements have been developed and investigated. The distribution of the electric field in the vacuum device at various distances between the cathode and the anode, the applied voltages between them, the shape and microgeometry of the cathodes were obtained. The optimal geometric parameters of nanostructured autoelectronic cathodes and matrices of these were calculated based on the simulation. The technological route has been developed for the production of autoelectronic cathode matrices based on arrays of niobium-oxide columnar nanostructures formed by electrochemical anodization of Al/Nb thin-film system. The samples of controlled arrays of autoelectronic cathodes were fabricated and the current-voltage characteristics with interelectrode gap of 2, 5 and 10 μm in various electric modes with change in the electric field strength from 3 to 85 V/μm were studied. At 2 μm gap between the anode and cathode, the emission occurs at minimum threshold voltages, but it is characterized by limited current values. The increasing in the interelectrode gap allows rising the emission currents, however, the threshold voltages increase. In the pulsed mode, the large emission currents are achieved. The threshold voltage of autoelectronic cathode matrices with interelectrode gap of 5 μm was 9.16 V, the maximum currents reached 350 μA at voltage of 22.5 V. In the pulsed mode, the emission arose at 11.06 V, the maximum current reached 1500 μA at 40 V.

Compositional Engineering of a La1-xBaxCoO3-δ-(1-a) BaZr0.9Y0.1O2.95 (a = 0.6, 0.7, 0.8 and x = 0.5, 0.6, 0.7) Nanocomposite Cathodes for Protonic Ceramic Fuel Cells.

Compositionally engineered a La1-xBaxCoO3-δ-(1-a) BaZr0.9Y0.1O2.95 (a = 0.6, 0.7, 0.8 and x = 0.5, 0.6, 0.7) (LBZ) nanocomposite cathodes were prepared by oxidation driven in situ exsolution of a single-phase material deposited on a BaZr0.9Y0.1O2.95 electrolyte. The processing procedure of the cathode was optimized by reducing the number of thermal treatments as the single-phase precursor was deposited directly on the electrolyte. The exsolution and firing of the cathodes occurred in one step. The electrochemical performance of symmetrical cells with the compositionally engineered cathodes was investigated by impedance spectroscopy in controlled atmospheres. The optimized materials processing gave web-like nanostructured cathodes with superior electrochemical performance for all compositions. The area specific resistances obtained were all below 12 Ω·cm2 at 400 °C and below 0.59 Ω·cm2 at 600 °C in 3% moist synthetic air. The resistances of the nominal 0.6 La0.5Ba0.5CoO3-δ-0.4 BaZr0.9Y0.1O2.95 and 0.8 La0.5Ba0.5CoO3-δ-0.2 BaZr0.9Y0.1O2.95 composite cathodes were among the lowest reported for protonic ceramic fuel cells cathodes in symmetrical cell configuration with ASR equal to 4.04 and 4.84 Ω·cm2 at 400 °C, and 0.21 and 0.27 Ω·cm2 at 600 °C, respectively.

Synthesis and research of layered CoS/graphene nanoflakes as sulfur cathode for high-energy lithium sulfur batteries

In this work, CoS nanoflakes were directly grown on graphene followed by sulfur storing by annealing sulfur/carbon disulfide and CoS nanoflakes at 155 °C for 10 h in N2. The microstructural and morphologies of the CoS/graphene nanoflake composites (CoS/G) were investigated by X-ray diffraction/photoelectron spectroscopy and electron microscopy. Benefiting from the strong chemical binds between CoS and lithium polysulfide species, and good electrical conductivity of graphene, the nanostructured sulfur cathode displays high sulfur utilization, promising rate capability and cycling stability compared to pristine sulfur cathode. The discharge capacity of the 100th cycle is maintained at 675.7 mA h g−1 at 0.5C.

A Molecular‐Cage Strategy Enabling Efficient Chemisorption–Electrocatalytic Interface in Nanostructured Li2S Cathode for Li Metal‐Free Rechargeable Cells with High Energy

AbstractUsing high‐capacity and metallic Li‐free lithium sulfide (Li2S) cathodes offers an alternative solution to address serious safety risks and performance decay caused by uncontrolled dendrite hazards of Li metal anodes in next‐generation Li metal batteries. Practical applications of such a cathode, however, still suffer from low redox activity, unaffordable cost, and poor processability of infusible and moisture‐sensitive Li2S. Herein, these difficulties are addressed by developing a molecular cage–engaged strategy that enables low‐cost production and interfacial engineering of Li2S cathodes for rechargeable Li2S//Si cells. An efficient chemisorption–electrocatalytic interface is built in extremely nanostructured Li2S cathodes by harnessing the confinement/separation effect of metal–organic molecular cages on ionic clusters of air‐stable, soluble, and low‐cost Li salt and their chemical transformation. It effectively boosts the redox activity toward Li2S activation/dissociation and polysulfide chemisorption–conversion in Li‐S batteries, leading to low activation voltage barrier, stable cycle life of 1000 cycles, ultrafast current rate up to 8 C, and high areal capacities of Li2S cathodes with high mass loading. Encouragingly, this highly active Li2S cathode can be applied for constructing truly workable Li2S//Si cells with a high specific energy of 673 Wh kg−1 and stable performance for 200 cycles at high rates against hollow nanostructured Si anode.

Understanding the Effect of Polymer Surface Layers on Magnesium Insertion in PEDOT/MnO2 Coaxial Nanowires

Rechargeable magnesium batteries are a possible alternative technology to lithium-ion batteries. However, there are challenges associated with all parts of magnesium battery systems – anode, cathode, and electrolyte. Regarding cathodes, the divalent Mg ion has slow insertion kinetics in many common metal oxide materials due to strong electrostatic interactions with the host ionic lattice. These materials are desirable due to their high voltage and thus the potential to contribute to a high energy density battery, therefore strategies to aid Mg2+ insertion in metal oxides are an important research focus. Two strategies to improve Mg2+ insertion include utilizing nanostructured cathode materials as well as introducing water, either in the electrolyte or crystal water within the metal oxide structure. Previous work demonstrated that manganese dioxide (MnO2) nanowires deposited via anodic electrodeposition effectively intercalated Mg ions when water was present in a ratio of 6:1 (H2O:Mg2+) in Mg(ClO4)2/propylene carbonate electrolyte (1). Without water in the electrolyte to solvate the Mg2+ and shield the charge, Mg2+ does not insert into the MnO2. Further, an investigation of the charge storage mechanism for this process determined that a conversion reaction on the MnO2 surface in addition to Mg insertion into the bulk both were dependent on the presence of water (2). Following this work, there were two additional characteristics of interest regarding MnO2 cathodes cycled in water-containing organic electrolyte: manganese dissolution and electronic conductivity. A previously published one-step co-electrodeposition process of MnO2 and poly(3,4-ethylenedioxythiophene)(PEDOT) provided a tunable structure to test both effects (3). With the PEDOT surface layer, there are two possible advantages: first is confining the MnO2 layer to minimize Mn dissolution, and second is addition of the more electronically conductive PEDOT layer for fast electron transport along the comparatively resistive MnO2 material. Here, coaxial PEDOT/MnO2 nanowires served as a test structure to investigate how a PEDOT surface layer affected Mg ion insertion into the MnO2 at the core and to develop additional understanding of the properties of MnO2 and how structural alterations could influence the electrochemical reactions. By altering the voltage of electrodeposition, the thickness of the PEDOT layer was varied. Cyclic voltammetry and galvanostatic charge/discharge tests were done to evaluate the Mg insertion capabilities, power performance, and cyclability of coaxial nanowires with PEDOT thicknesses ranging from 10-90 nm. Transmission electron microscopy and scanning electron microscopy were used to monitor structural properties and changes. Inductively coupled plasma atomic emission spectroscopy (ICP-AES) was used to monitor changes in manganese content. This work will address how PEDOT thickness influences the ability of Mg2+ to insert into MnO2, how it affects Mn dissolution, and how the increased electronic conductivity of PEDOT impacts performance when cycling at higher current densities. These results could help inform better design of future cathode materials for rechargeable Mg battery systems. 1. J. Song, M. Noked, E. Gillette, J. Duay, G. Rubloff and S. B. Lee, Physical Chemistry Chemical Physics, 17, 5256 (2015).2. E. Sahadeo, J. Song, K. Gaskell, N. Kim, G. Rubloff and S. B. Lee, Physical Chemistry Chemical Physics, 20, 2517 (2018).3. R. Liu and S. B. Lee, Journal of the American Chemical Society, 130, 2942 (2008).

Study of Higher Discharge Capacity, Phase Transition, and Relative Structural Stability in Li2FeSiO4 Cathode upon Lithium Extraction Using an Experimental and Theoretical Approach and Full Cell Prototype Study

We have revisited the study of the nanostructured lithium iron silicate-based cathode for a safe lithium-ion battery and to understand the reaction mechanism from the first cycle to the second cycl...

Electrochemical investigation of cubic structured Fe-doped-SrCoO3 nano-structured cathode for SOFC synthesized via sol-gel route

Renewable alternative energy sources are required due to rapidly depletion of fossil fuels in the current scenario. Low temperature-solid oxide fuel cell (LT-SOFC) is one of the best alternative energy conversion devices. The commercialization of LT-SOFC requires a highly efficient, oxygen permeable, good electro-chemically performing cathode. The Sr0.3Co0.6Fe0.1 oxide (SCF) composite cathode was prepared by environmentally friendly sol-gel method. The crystal structure of prepared material was analyzed by x-ray Diffractometry, while structural characteristics were studied by Fourier Transform Infrared Spectroscopy. The particle size was calculated by Scherer’s formula and found to be 36 nm. The results were also confirmed by SEM images. The prepared material showed porous coral reef like surface morphology in recorded scanning electron micrograph (SEM). The activation energy was calculated by Arrhenius curve that is 0.3 eV and highest electronic conductivity measured and calculated was 4.201 Scm−1. SCF oxide cathode was tested for potential LT-SOFC between the range of 450 °C–650 °C temperature. The maximum current density and power density obtained at 650 °C was 887 mAcm−2 and 110 mWcm−2 respectively.

Core-shell nanostructured organic redox polymer cathodes with superior performance

Core-shell nanoparticles stabilized by a cationic surfactant are prepared from the poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl methacrylate) redox polymer. The nanoparticles are further self-assembled with negatively charged reduced graphene oxide nanosheets and negatively charged multi-walled carbon nanotubes. This results in the formation of a free-standing cathode with a layered nanostructure and a high content of redox polymer that exhibits 100% utilization of the active substance with a measured capacity as high as 105 mAh/g based on the whole weight of the electrode.

A high-performance lithium-ion capacitor with carbonized NiCo2O4 anode and vertically-aligned carbon nanoflakes cathode

Lithium ion capacitors (LICs) are energy storage devices integrating the complementary features of both supercapacitors and lithium ion batteries to simultaneously reach high energy and power densities. One of the major challenges in LIC technology is the kinetic imbalance between the faradaic insertion anode and capacitive cathode. Therefore, the design of electrode materials is crucial to enhance the rate performance of anode and the capacitance of the cathode in LIC devices. In this work, novel LICs were demonstrated with nanostructured cathode and anode. A vertically-aligned carbon nanoflakes (VACNFs) cathode provided high electrochemically active surface area and excellent conductivity, while a metal organic framework (MOF) derived carbonized nickel cobalt oxide (cNiCo2O4) anode ensured fast conversion reactions and remarkable cyclability. Electrochemical characterization of individual electrode confirmed that both electrodes exhibited good electron and ion transport capability. The LICs were fabricated with optimized electrode active materials loading to deliver high energy densities at desired charge/discharge rates. The devices exhibited energy density up to 136.9 W h/kg (at 200 W/kg). At higher power density of 40 kW/kg, under which a full charge-discharge can be finished within 4 s, the LICs could still deliver an energy density of 26.44 W h/kg. The devices also showed a good cycle stability (≈90% capacitance retention after 9000 cycles, under current density of 4 A/g) within the voltage range of 1–4.2 V.

Concept and electrochemical mechanism of an Al metal anode ‒ organic cathode battery

Aluminum (Al) batteries are fundamentally a promising future post-Li battery technology. The recently demonstrated concept of an Al-graphite battery represents some significant progress for the technology, but the cell energy density is still very modest and limited by the quantity of the AlCl3 based electrolyte, as it relies on AlCl4‒ intercalation. For further progress, cathode materials capable of an electrochemical reaction with Al positively charged species are needed. Here such a concept of an Al metal anode ‒ organic cathode battery based on anthraquinone (AQ) electrochemistry with a discharge voltage of 1.1 V is demonstrated. Further improvement of both the cell capacity retention and rate capability is achieved by nano-structured and polymerized cathodes. The intricate electrochemical mechanism is proven to be that the anthraquinone groups undergo reduction of their carbonyl bonds during discharge and become coordinated by AlCl2+ species. Altogether the Al metal anode – AQ cathode cell has almost the double energy density of the state-of-the-art Al-graphite battery.

Surface Modifications of Nano-Structured Cathodes to Enhance Durability of Intermediate Temperature Solid Oxide Fuel Cells

The bulk-to-surface Sr-segregation can seriously compromise the stability of oxygen electrocatalysis in Sr-doped perovskite oxides such as La1-xSrxCoO3-δ and La1-xSrxCo1-yFeyO3-δ and limit their practical applications as cathode materials in solid oxide fuel cells. This work aims to acquire fundamental knowledge of Sr-segregation process under practical conditions in solid oxide fuel cells and develop suppression method to ensure the long-term stability through surface modifications. In this work, the pristine and ZrO2 atomic layer deposition (ALD) modified La0.6Sr0.4CoO3- d (LSCo) epitaxial films were used as the model systems to investigate how the temperature, time and surface coating affect the surface concentration of Sr via in situ synchrotron-based ambient pressure XPS. This information was also correlated with their electrochemical performances characterized by electrochemical impedance spectroscopy. We also report a Sr-segregation-free SrCo0.9Ta0.1O3-δ (SCT) multifunctional coating on a benchmark cathode LSCF as a means of enhancing ORR activity and durability against Cr-poison.

Facile fabrication of nanostructured NiMo cathode for high-performance proton exchange membrane water electrolyzer

Clean hydrogen production via water electrolyzer connected with renewable energies is an essential technology for a sustainable energy in future. To realize the system, development of high-performance electrode remains a challenge. In this study, simple cathodic electrodepositions allow for the facile fabrication of a nanostructured non-noble metal cathode. Under optimized deposition condition, the NiMo catalyst supported by Cu foam exhibits overpotential of 68.7mV at −10mA/cm2 for hydrogen evolution reaction in acidic medium. The proton exchange membrane water electrolyzer employing the cathode demonstrates a remarkable current density of ˜2.0A/cm2 at 2.0V, which is the highest performance among state-of-the-art non-noble cathodes reported to date. The results presented herein indicate a promising cost-effective cathode for practical applications.

New Tetraazapentacene-Based Redox-Active Material As a Promising High-Capacity Organic Cathode for Potassium Batteries

Following the Paris agreement signed in 2015 to address the problem of global climate change, many countries are aiming to decrease CO2 emissions particularly by using renewable sources of energy, e.g. solar, wind, geothermal, etc. However, any massive implementation of renewables requires cheap and efficient solutions for bulk energy storage. There are limited examples of application of lithium-ion batteries (LIBs) for peak shaving in electric grids and for storage of the energy produced by solar plants. The main obstacle for implementation of LIBs on a large scale is related to their high cost dictated by both low abundance of lithium resources and use of expensive nanostructured inorganic cathode materials. It should be emphasized that the total amount of lithium available on the planet is insufficient even for replacing all cars currently used in the world with electric vehicles while leaving unsatisfied all other demands for energy storage. Therefore, it is imperative to develop alternative post-lithium battery technologies. Potassium-ion batteries (KIBs) have recently attracted a particular attention since there are abundant resources of potassium in both Earth’s crust and oceans, which make this element almost an order of magnitude cheaper than lithium. Moreover, KIBs usually show higher discharge voltages in comparison with lithium-ion and, especially, sodium-ion batteries thus featuring a potential for reaching high energy densities [1]. However, the current progress in the development of KIBs is strongly limited by scarce number of suitable inorganic cathodes, which can deliver decent capacities and charge-discharge cycling stabilities. Organic redox-active materials represent a promising alternative since they are based on abundant elements, can be cheap and environment friendly [2]. In this work we present a new organic cathode for metal-ion batteries based on octahydroxytetraazapentacene (OHTAP) possessing a theoretical capacity of ~ 520 mAh g-1. To evaluate the K-ion storage properties of OHTAP, we assembled K//OHTAP cells using either the tape or the spray coating of the slurry (OHTAP+Super-P+PVDF in NMP) on Al or Al/C current collectors. A 1 M potassium bis(trifluoromethane sulfonyl) imide (KTFSI) solution in dimethoxyethane and dioxolane mixture (DOL : DME = 1:1 v/v) was used as the electrolyte. The fabricated cells delivered stabilized capacities of >220 mAh g-1 after 10 cycles, which are among the best values reported so far for both organic and inorganic cathode materials in potassium-ion batteries. The obtained results pave a way to the development of a new family of organic cathodes for advanced potassium-ion batteries.

Copper sulfide nanoparticles as high-performance cathode materials for Mg-ion batteries

Rechargeable magnesium batteries are appealing as safe, low-cost systems with high-energy-density storage that employ predominantly dendrite-free magnesium metal as the anode. While significant progress has been achieved with magnesium electrolytes in recent years, the further development of Mg-ion batteries, however, is inherently limited by the lack of suitable cathode materials, mainly due to the slow diffusion of high-charge-density Mg-ions in the intercalation-type host structures and kinetic limitations of conversion-type cathodes that often causes poor cyclic stability. Nanostructuring the cathode materials offers an effective means of mitigating these challenges, due to the reduced diffusion length and higher surface areas. In this context, we present the highly reversible insertion of Mg-ions into nanostructured conversion-type CuS cathode, delivering high capacities of 300 mAh g−1 at room temperature and high cyclic stability over 200 cycles at a current density of 0.1 A g−1 with a high coulombic efficiency of 99.9%. These materials clearly outperform bulk CuS, which is electrochemically active only at an elevated temperature of 50 °C. Our results not only point to the important role of nanomaterials in the enhancement of the kinetics of conversion reactions but also suggest that nanostructuring should be used as an integral tool in the exploration of new cathodes for multivalent, i.e., (Mg, Ca, Al)-ion batteries.

Nano-fabrication of a high-performance LaNiO3 cathode for solid oxide fuel cells using an electrochemical route

The cost-effective fabrication of nanostructured cathodes for solid oxide fuel cells (SOFCs) that catalyze the oxygen reduction reaction effectively is a milestone to be achieved. Infiltration being the conventional method for the fabrication of nanostructured SOFC cathodes requires many infiltration and calcination cycles due to the low catalyst loading per infiltration cycle. Chemically assisted electrodeposition (CAED), a new means of fabricating nanostructured SOFC cathodes in a single loading step, provides the advantage of the simultaneous deposition of multiple cations while using dilute aqueous solutions of readily available salts. In this study, CAED is demonstrated by fabricating a cobalt-free LaNiO3/GDC composite cathode. The LaNiO3/GDC composite cathode prepared by CAED exhibits superior electrochemical properties compared to LaNiO3/GDC composite cathodes fabricated by sintering or self-assembly (a recently introduced low-temperature SOFC cathode fabrication method) approaches. An anode-supported SOFC with a LaNiO3/GDC composite cathode fabricated by CAED shows a high power density of 974 mW cm−2 at an intermediate operating temperature of 750 °C. Low-temperature nano-fabrication by CAED, producing a cathode with a high surface area while avoiding the formation of insulating phases, is believed to play an important role in achieving better SOFC performance.

MXene based self-assembled cathode and antifouling separator for high-rate and dendrite-inhibited Li–S battery

We demonstrate a novel strategy to enhance sulfur loading and rate performance for Li–S battery by synchronously coupling a nanostructured cathode with an antifouling separator via a facile electrostatic self-assembly approach. The assembly of two dimensional (2D) MXene and positively charged 1D CNT-Polyethyleneimine was observed to controllably address the key issues of sluggish ionic transport, and produce an integrate cathode with dynamic crosslinking network. Moreover, an antifouling separator is proposed by this strategy for the first time, which features well-organized inter-lamellar porosity, dual polarity and high conductivity. The antifouling separator is found to play a pivotal role in: 1) low-order polysulfide activation, 2) high rate cyclability, and 3) Li dendrites inhibition. Our integrated design realizes a long-term capacity of 980 mAh g−1 at 5 mA cm−2 over 500 cycles (sulfur loading: 2.6 mg cm−2). Furthermore, a flexible self-assembled cathode with high loading (5.8 mg cm−2) and superb mechanical strength (13 MPa), demonstrates an appealing areal capacity of 7.1 mAh cm−2 and rate performance at nearly 10 mA cm−2.

Insights into the Effects of Electrolyte Composition on the Performance and Stability of FeF2 Conversion‐Type Cathodes

AbstractAs an alternative to commercial Ni‐ and Co‐based intercalation‐type cathode materials, conversion‐type metal fluoride (MFx) cathodes are attracting more interest due to their promises to increase cell‐level energy density when coupled with lithium (Li) or silicon (Si)‐based anodes. Among metal fluorides, iron fluorides (FeF2 and FeF3) are regarded as some of the most promising candidates due to their high capacity, moderately high potential and the very low cost of Fe. In this study, the impacts of electrolyte composition on the performance and stability of nanostructured FeF2 cathodes are systematically investigated. Dramatic impacts of Li salt composition, Li salt concentration, solvent composition, and cycling potential range on the cathode's most critical performance parameters—stability, capacity, rate, and voltage hysteresis are discovered. In contrast to previous beliefs, it is observed that even if the Fe2+ cation dissolution could be avoided, the dissolution of F− anions may still negatively affect cathode performance. Formation of the more favorable cathode solid electrolyte interface (CEI) is found to minimize both processes.