Nanocomposite Cathode Research Articles

LiNi0.5Mn0.3Co0.2O2/Au nanocomposite thin film cathode with enhanced electrochemical properties

Li(NixMnyCo1−x−y)O2 (NMC) is considered as one of the most promising cathode materials for Li-ion batteries. Highly textured LiNi0.5Mn0.3Co0.2O2 (NMC532) thin films with well dispersed Au nanoparticles (~ 5 nm in average diameter) were deposited by pulsed laser deposition. Microstructure studies reveal the epitaxial nature of the Au nanoparticles and NMC matrix, and their lattice matching relationships. The Au nanoparticles are uniformly distributed and form faceted interfaces with NMC matrix. NMC with 2 at.% Au shows the highest volumetric capacity, best initial columbic efficiency, highest cycling performance, best rate capability and highest capacity retention among all the samples, due to alteration of chemical environment of transition metal while keeping high crystallinity. Moreover, the electrochemical impedance spectroscopy data shows that the incorporation of the Au nanoparticles also reduces charge transfer resistance compared to the pure NMC. The results suggest that appropriate Au nanoparticle incorporation enhances the volumetric capacity and promotes the charge transfer process, and thus could lead to enhanced battery performance.

Enhancement of microbial fuel cell performance by introducing a nano-composite cathode catalyst

Iron aminoantipyrine (Fe-AAPyr), graphene nanosheets (GNSs) derived catalysts and their physical mixture Fe-AAPyr-GNS were synthesized and investigated as cathode catalysts for oxygen reduction reaction (ORR) with the activated carbon (AC) as a baseline. Fe-AAPyr catalyst was prepared by Sacrificial Support Method (SSM) with silica as a template and aminoantipyrine (AAPyr) as the organic precursor. 3D-GNS was prepared using modified Hummers method technique. The Oxygen Reduction Reaction (ORR) activity of these catalysts at different loadings was investigated by using rotating ring disk (RRDE) electrode setup in the neutral electrolyte. The performance of the catalysts integrated into air-breathing cathode was also investigated. The co-presence of GNS (2 mg cm−2) and Fe-AAPyr (2 mg cm−2) catalyst within the air-breathing cathode resulted in the higher power generation recorded in MFC of 235 ± 1 μW cm−2. Fe-AAPyr catalyst itself showed high performance (217 ± 1 μW cm−2), higher compared to GNS (150 ± 5 μW cm−2) while AC generated power of roughly 104 μW cm−2.

(Pr0.9La0.1)2(Ni0.74Cu0.21Nb0.05)O4+δ-Ce0.9Gd0.1O2−δ (GDC) as an active and CO2-tolerant nano-composite cathode for intermediate temperature solid oxide fuel cells

Nano composite of Ruddlesden-Popper electrocatalyst-oxygen ionic conductor, (Pr0.9La0.1)2(Ni0.74Cu0.21Nb0.05)O4+δ (PLNCN)-Ce0.9Gd0.1O2−δ (GDC), is developed as composite cathode for intermediate temperature solid oxide fuel cells (IT-SOFCs) via a infiltration way. The electrochemical behavior of PLNCN-GDC nanostructured electrode is assessed with respect to infiltration loading and oxygen partial pressure. The optimized PLNCN loading can improve charge transfer dynamics for electrochemical oxygen reduction reaction, thus promoting cathode performance. Importantly, the encouraging results of single cell highlight high activity and good CO2 tolerance of PLNCN-GDC nanostructured cathode.

Enhanced cathode performance of a rGO-V2O5 nanocomposite catalyst for microbial fuel cell applications.

A reduced graphene oxide-V2O5 nanocomposite was synthesized by a low temperature surfactant free hydrothermal method and its MFC performance was assessed. The structural properties of the synthesized nanocomposite were studied by X-ray diffraction. Field emission scanning electron microscopy of the nanocomposite revealed a wrinkled paper-like structure of rGO and a nanobelt-like structure of V2O5. This study estimated the viability of the graphene-based nanocomposite rGO-V2O5 as a novel cathode catalyst in single chamber air-cathode MFCs. A series of MFCs with different catalyst loadings were produced. The electrochemical behavior of the MFCs was calculated by cyclic voltammetry. The MFCs with the rGO-V2O5 nanocomposite cathode exhibited superior maximum power densities (83%) to those with the pure V2O5 cathodes. The rGO-V2O5 with a double-loaded nanocomposite catalyst achieved an enhanced power density of 1668 ± 11 mW m-2 and an OCP of 698 ± 4 mV, which was 83% of that estimated for the Pt/C 2004 ± 15 mW m-2 nanocomposite cathode. The significant increase in power density suggests that the reduced graphene oxide-V2O5 nanocomposite is a promising material for MFC applications. The CV result showed good agreement with the MFC result. The prepared rGO-V2O5 nanocomposite cathode, particularly with a double loading catalyst, is promising as a sustainable low-cost green material for stable power generation and long-term operation of MFCs.

Li2S/carbon nanocomposite strips from a low-temperature conversion of Li2SO4 as high-performance lithium–sulfur cathodes

A Li2S/carbon nanocomposite strip cathode derived from Li2SO4/poly(vinyl alcohol) nanocomposite strips at a record low temperature shows an excellent electrochemical performance.

Urea Assisted Combustion Synthesis of LiFePO4/C Nano composite Cathode Material for Lithium Ion Battery Storage System

In this present work, we demonstrated economical way to synthesize nano crystalline LiFePO4Olivine structured LiFePO4/C nanocomposite using urea as fuel and sucrose as carbon source were calculated using the total oxidizing and reducing valencies of the components which provide as numerical coefficients for stoichiometric balance so that the equivalent ratio is unity followed by heat treatment at 600 °C for 6 - 10 h, under Ar (90%) and H2 (10%) gas atmosphere.The resultant products are characterized by XRD to know the phase formation and for estimation of the crystallite size. The XRD patterns were collected in steps of 0.02° over the range of 10° ≤2θ ≤80° at room temperature with a constant counting time of 0.1 s per step, From XRD all the powders showing the nano sized crystallite sizes in the range of 40-45nm. The morphologies of the powders were investigated by a scanning electron microscopy (SEM) all samples indicate the agglomeration of powder with highly porous nature in all the samples. The synthesized olivine powders were subjected to thermogravimetric / differential scanning calorimetry (TG-DSC) as the reference material in the temperature range of 25–1000°C with a heating rate of 10°C/min in air and nitrogen atmosphere. Raman spectra were obtained with 514.5 nm Ar-Ion laser radiation at a laser power of 150 mW in the range of 100- 2000cm-1 for a total of 10 scans to increase the signal-to-noise ratio and with 4 cm-1 spectral resolutionwerestudied.

Synthesis, characterization and electrochemical performance of Nb doped LiFePO4/C cathodes

We synthesized Nb-doped LiFePO4 /C nano composite cathode materials by mechanochemical activation followed by a single step calcination. The starting chemicals of Li2 CO3 , FeC2 O4 .2H2O, NH4 H2 .PO4 and C6 H8 O7 as lithium, iron, phosphate, and carbon sources are mixed in a high energy ball mill 250 rpm, 5h and calcined at 650 °C and 10 hours. The resultant materials are structurally XRD, SEM, TEM and electrochemically characterized and high purity LiFePO4 with high electrochemical performance is obtained. Voltage vs. specific capacity, discharge capacity vs. cycle number in manufactured battery is presented. An initial specific discharge capacity of 153 mAhg−1 and a specific discharge capacity of 128.4 mAhg−1 after the 8th charge/discharge cycling at 1C is recorded.

Synthesis of metal oxide nanocomposites from self-assembled block copolymer templates as cathode materials for all-solid-state lithium batteries

Self-assembled structures are useful for fabrication of nanostructures as a sustainable process with minimum energy consumption. Alternately stacked layers on a nanometre scale are produced by adsorption process denoted as layer by layer process, however, shape is limited in layers and chemical composition is also limited. Superlattice structures are produced by sputtering or self-assembly process using nanoparticles. But the construction of three-dimensional ordered inorganic nanocomposite structures remains a great challenge. All-solid-state lithium batteries (LiBs) are attracting much attention as innovative devices for upsized safety secondary batteries with high energy density. However, bulk-type all-solid-state LiBs face a number of hurdles, particularly the construction of an electrochemically favourable interface between the solid Li electrolytes and the active materials. In this study, we synthesised inorganic nanocomposite cathode materials by using self-assembled block copolymers (BCPs) as templates; this nanocomposite was composed of Li0.5La0.5TiO3 (LLT) as the electrolyte and LiCoO2 (LCO) as the cathode active material. Several LCO/LLT ratios were examined with the goal of producing a nanocomposite for use in all-solid-state LiBs. This nanostructured material, with the electrochemically favourable interface between electrode and electrolyte, resulted in a high capacity even at a high LCO content. The process we used to prepare the nanocomposite is expected to be versatile for producing other highly functional devices, such as quantum dot solar cells, thermoelectrics, and solid oxide fuel cells.

Highly efficient La0.8Sr0.2MnO3-δ - Ce0.9Gd0.1O1.95 nanocomposite cathodes for solid oxide fuel cells

La0.8Sr0.2MnO3-δ-Ce0.9Gd0.1O1.95 (LSM-CGO) nanostructured cathodes are successfully prepared in a single process by a chemical spray-pyrolysis deposition method. The cathode is composed of nanometric particles of approximately 15nm of diameter, providing high triple-phase boundary sites for the oxygen reduction reactions. A low polarization resistance of 0.046Ωcm2 is obtained at 700°C, which is comparable to the most efficient cobaltite-based perovskite cathodes. A NiO-YSZ anode supported fuel cell with the nanostructured cathode generates a power output of 1.4Wcm−2 at 800°C, significantly higher than 0.75Wcm−2 for a cell with conventional LSM-CGO cathode. The results suggest that this is a promising strategy to achieve high efficiency electrodes for Solid Oxide Fuel Cells in a single preparation step, simplifying notably the fabrication process compared to traditional methods.

LiFe0.5Mn0.5PO4/C prepared using a novel colloidal route as a cathode material for lithium batteries

A new colloidal route for the preparation of LiFe0.5Mn0.5PO4/C nanocomposite cathode material for lithium batteries is revealed. The method uses lithium dihydrogen phosphate (LiH2PO4), ferrous chloride (FeCl2) and manganese chloride(MnCl2) in stoichiometric amounts with N-methylimidazole (NMI) as the solvent and carbon source. The coating process is performed at 650 °C for 3 h under vacuum. Elemental analysis shows a carbon content of 3.71 wt%, rendering the material to exhibit excellent electronic conductivity (9.29 × 10−2 S cm−1 at room temperature) and a significant increase in rate capability. Scanning electron and high-resolution transmission electron microscopy (SEM/HRTEM) images exhibited particles of uniform size (around 40–60 nm) that are covered by a 3–6 nm thick carbon layer. At a C/20 discharge rate and between 2.2 and 4.2 V vs. Li+/Li, the cell delivers a high capacity (140 mAh g−1) at the first cycle. The electrode stability was studied at C/10 rate, with only a small decrease (3.9%) of discharge capacity over 100 cycles, which suggests that the new synthesis method for carbon-coated LiFe0.5Mn0.5PO4/C material is very promising.

Evaluation of numerical characteristics of the current load distribution on the surface of multi-tip field emitters

The uniformity of the emission sites distribution over the surface of the multi-tip field emitter is one of the main factors affecting its electrical characteristics. Increase of the uniformity leads to increase of the thermal stability and allowable current limit. The paper describes an experimental setup and a method for monitoring uniformity of the emission sites based on analysis of a field emission site images registered on the phosphor screen of a computerized field-emission projector. The analysis includes estimation of the statistical distributions of the sites by radius, by angle and by intensity, as well as the distribution of the current load over the emitter surface. The technique was tested with the perspective nanocomposite cathode MWCNT / polystyrene.

Metal-Organic Frameworks Derived Nanocomposites of Mixed-Valent MnOx Nanoparticles In-Situ Grown on Ultrathin Carbon Sheets for High-Performance Supercapacitors and Lithium-Ion Batteries

Manganese oxide and carbon hybrid materials have attracted intensive research attention as advanced electrode materials for energy storage. Herein, starting form metal-organic frameworks (MOFs), the nanocomposites of mixed-valent manganese oxide nanoparticles in-situ grown on ultrathin carbon sheets (MnOx-CSs nanocomposites) have been synthesized via a simple method. Benefiting from the unique structural merits, the nanocomposite obtained at 600°C (MnOx-CSs-600) exhibits excellent performance for both supercapacitors (SCs) and lithium-ion batteries (LIBs). A high specific capacitance of 220Fg−1 is achieved at the current density of 1Ag−1. An asymmetric supercapacitor (ASC) based on the MnOx-CSs-600 nanocomposite cathode and activated carbon anode exhibits a high energy density of 27.5Whkg−1 at the power density of 225Wkg−1. Moreover, the MnOx-CSs-600 nanocomposite displays a high reversible capacity of 1217.7mAhg−1 at 200mAg−1 after 160 cycles as an anode material for LIBs. Remarkably, the discharge capacity is still as high as 612.1mAhg−1 even at high current density of 2000mAg−1, indicating good rate capability. This synthetic strategy is quite simple, cost-effective and environmental friendly, which is highly promising for scaled-up production.

LSCF-CGO nanocomposite cathodes deposited in a single step by spray-pyrolysis

La0.6Sr0.4Co0.2Fe0.8O3-δ-Ce0.9Gd0.1O1.95 (LSCF-CGO) nanostructured cathodes with different LSCF-content are prepared in a single step by spray-pyrolysis deposition, simplifying notably the fabrication process compared to the traditional methods. The phase formation, structure, microstructure and electrochemical properties of the cathodes are investigated as a function of the CGO-content and the temperature by using X-ray diffraction, electron microscopy and impedance spectroscopy. The addition of CGO to LSCF limits the grain growth, giving rise to fine particles of approximately 30nm of diameter after sintering at 800°C. A small particle size of 50nm is retained even after sintering at 1000°C. However, the polarization resistance, determined by impedance spectroscopy, is not significantly improved with the CGO-addition. The performance of these nanocomposite electrodes, investigated in NiOCGO anode-supported cells, shows an improved power density of 0.9Wcm−2 at 650°C, compared to 0.56Wcm−2 for a conventional screen-printed cathode.

Morphological and Electrical Stability Studies of Pt/Yttria-Stabilized Zirconia Nanocomposite Thin Film Cathodes for Microfabricated Solid Oxide Fuel Cells

Abstract Microfabricated solid oxide fuel cells (mSOFCs) have recently gained attention as a promising technology for portable power applications. At present, porous Pt is the most common cathode being investigated for mSOFCs, which has poor bulk ionic conductivity and suffers from instability due to Ostwald ripening. Nanocomposite materials based on Pt/Yttria-Stabilized Zirconia (YSZ) are a promising alternative approach for high performance mSOFCs because of their potential for providing mixed ionic-electronic conduction, improving adhesion to the YSZ electrolyte, and improving oxygen diffusion characteristics over a pure Pt material. The objective of this research was to systematically explore the processing of the nanocomposite thin films to achieve stable morphological and electrical properties for use as a mSOFC cathode. A percolation theory model was utilized to guide the processing of the Pt/YSZ composition, ensuring a networked connection of ionic- and electronic-conduction through the electrode. The Pt/YSZ nanocomposite cathodes were deposited by co-sputtering. It was observed that the Ar deposition pressure played a key role in stabilizing the morphology of the film to higher temperatures, up of 600°C. Analyses of the Pt/YSZ composite microstructure and composition by TEM confirmed an interconnected network of Pt and YSZ thereby suggesting that it is a viable candidate as a high performance and stable cathode material for mSOFCs.

High-Performance All-Inorganic Solid-State Sodium-Sulfur Battery

All-inorganic solid-state sodium-sulfur batteries (ASSBs) are promising technology for stationary energy storage due to their high safety, high energy and abundant resources of both sodium and sulfur. However, current ASSB shows poor cycling and rate performances mainly due to the huge electrode/electrolyte interfacial resistance arising from the insufficient triple-phase contact among sulfur active material, ionic conductive solid electrolyte, and electronic conductive carbon. Herein, we present an innovative approach to address the interfacial problem by using Na3PS4-Na2S-C (carbon) nanocomposite as the cathode for ASSBs. Highly ionic conductive Na3PS4 contained in the nanocomposite can function as both solid electrolyte and active material (catholyte) after mixing with electronic conductive carbon, leading to an intrinsic superior electrode/electrolyte interfacial contact because only a two-phase contact is required for the charge transfer reaction. Introducing nano-sized Na2S into the nanocomposite cathode can effectively improve the capacity. The homogeneous distribution of nano-sized Na2S, Na3PS4 and carbon in the nanocomposite cathode could ensure a high mixed (ionic and electronic) conductivity and a sufficient interfacial contact. The Na3PS4-nanosized Na2S-carbon nanocomposite cathode delivered a high initial discharge capacity of 869.2 mAh g-1 at 50 mA g-1 with great cycling and rate capabilities at 60 oC, representing the best performance of ASSBs reported to date, and therefore constituting a significant step towards high-performance ASSBs for practical applications. Reference: J. Yue, F. Han, X. Fan, X. Zhu, Z. Ma, J. Yang and C. Wang, "High-Performance All-Inorganic Solid-State Sodium-Sulfur Battery", submitted.

Large‐Scale Syntheses of Zinc Sulfide⋅(Diethylenetriamine)0.5 Hybrids as Precursors for Sulfur Nanocomposite Cathodes

AbstractNanostructured metal sulfide–amine hybrid materials have attracted attention because of their unique properties and versatility as precursors for functional inorganic nanomaterials. However, large‐scale synthesis of metal sulfide–amine hybrid nanomaterials is limited by hydrothermal and solvothermal preparative reaction conditions; consequently, incorporation of such materials into functional nanomaterials is hindered. An amine molecule‐assisted refluxing method was used to synthesize highly uniform zinc sulfide⋅(diethylenetriamine)0.5 (ZnS⋅(DETA)0.5) hybrid nanosheets and nanobelts in a large scale. The obtained ZnS⋅(DETA)0.5 hybrid nanomaterials can be used as efficient precursors to fabricate functional ZnS nanomaterials and carbon encapsulated sulfur (S@C) nanocomposite cathodes for Li–S batteries.

Large-Scale Syntheses of Zinc Sulfide⋅(Diethylenetriamine)0.5 Hybrids as Precursors for Sulfur Nanocomposite Cathodes.

Nanostructured metal sulfide-amine hybrid materials have attracted attention because of their unique properties and versatility as precursors for functional inorganic nanomaterials. However, large-scale synthesis of metal sulfide-amine hybrid nanomaterials is limited by hydrothermal and solvothermal preparative reaction conditions; consequently, incorporation of such materials into functional nanomaterials is hindered. An amine molecule-assisted refluxing method was used to synthesize highly uniform zinc sulfide⋅(diethylenetriamine)0.5 (ZnS⋅(DETA)0.5 ) hybrid nanosheets and nanobelts in a large scale. The obtained ZnS⋅(DETA)0.5 hybrid nanomaterials can be used as efficient precursors to fabricate functional ZnS nanomaterials and carbon encapsulated sulfur (S@C) nanocomposite cathodes for Li-S batteries.

High-Performance All-Inorganic Solid-State Sodium-Sulfur Battery.

All-inorganic solid-state sodium-sulfur batteries (ASSBs) are promising technology for stationary energy storage due to their high safety, high energy, and abundant resources of both sodium and sulfur. However, current ASSB shows poor cycling and rate performances mainly due to the huge electrode/electrolyte interfacial resistance arising from the insufficient triple-phase contact among sulfur active material, ionic conductive solid electrolyte, and electronic conductive carbon. Herein, we report an innovative approach to address the interfacial problem using a Na3PS4-Na2S-C (carbon) nanocomposite as the cathode for ASSBs. Highly ionic conductive Na3PS4 contained in the nanocomposite can function as both solid electrolyte and active material (catholyte) after mixing with electronic conductive carbon, leading to an intrinsic superior electrode/electrolyte interfacial contact because only a two-phase contact is required for the charge transfer reaction. Introducing nanosized Na2S into the nanocomposite cathode can effectively improve the capacity. The homogeneous distribution of nanosized Na2S, Na3PS4, and carbon in the nanocomposite cathode could ensure a high mixed (ionic and electronic) conductivity and a sufficient interfacial contact. The Na3PS4-nanosized Na2S-carbon nanocomposite cathode delivered a high initial discharge capacity of 869.2 mAh g-1 at 50 mA g-1 with great cycling and rate capabilities at 60 °C, representing the best performance of ASSBs reported to date and therefore constituting a significant step toward high-performance ASSBs for practical applications.

Performance of a Nano-CNC Machined 220-GHz Traveling Wave Tube Amplifier

We report on hot test measurements of a wide-bandwidth, 220-GHz sheet beam traveling wave tube amplifier developed under the Defense advanced research projects agency (DARPA) HiFIVE program. Nano-computer numerical control (CNC) milling techniques were employed for the precision fabrication of double vane, half-period staggered interaction structures achieving submicrometer tolerances and nanoscale surface roughness. A multilayer diffusion bonding technique was implemented to complete the structure demonstrating wide bandwidth (>50 GHz) with an insertion loss of about −5 dB achieved during transmission measurements of the circuit. The sheet beam electron gun utilized nanocomposite scandate tungsten cathodes that provided over 438-A/cm2 current density in the 12.5:1 ratio sheet beam. An InP HBT-based monolithic microwave integrated circuit preamplifier was employed for TWT gain measurements in the stable amplifier operation region. In the wide-bandwidth operation mode (for gun voltage of 20.9 kV), a gain of over 24 dB was measured over the frequency range of 207–221 GHz. In the high-gain operation mode (for gun voltage of 21.8 kV), over 30 dB of gain was measured over the frequency range of 197–202 GHz. High-power tests were conducted employing an extended interaction klystron.

Controllable embedding of sulfur in high surface area nitrogen doped three dimensional reduced graphene oxide by solution drop impregnation method for high performance lithium-sulfur batteries

Abstract High capacity lithium-sulfur batteries with stable cycle performance and sulfur loadings greater than 70 wt% are regarded as promising candidates for energy storage devices. However, it has been challenged to achieving practical application of sulfur cathode because of low loading of active sulfur and poor cycle performance. Herein, we design novel nanocomposite cathode materials consist of sulfur (80 wt%) embedded within nitrogen doped three-dimensional reduced graphene oxide (N-3D-rGO) by controllable sulfur-impregnation method. Nitrogen doping helps increase the surface area by ten times from pristine graphene, and pore volume by seven times. These structural features allow the cathode to hold more sulfur. It also adsorbs polysulfides and prevents their detachment from the host materials; thereby achieving stable cycle performance. The solution drop sulfur-impregnation method provides uniform distribution of nano-sulfur in controlled manner. The material delivers a high initial discharge capacity of 1042 mAhg−1 and 916 mAhg−1 with excellent capacity retention of 94.8% and 81.9% at 0.2 C and 0.5 C respectively after 100 cycles. Thus, the combination of solution drop and nitrogen doping opens a new chapter for resolving capacity fading as well as long cycling problems and creates a new strategy to increase sulfur loading in controlled mechanism.