Nanocomposite Cathode Research Articles

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.

Degradation Mitigation of Infiltrated Solid Oxide Fuel Cell Cathodes Via Atomic Layer Deposited Zirconia Overcoats

To reduce Solid Oxide Fuel Cell (SOFC) cathode operating temperatures, solution infiltration has been used to fabricate Nano-Composite Cathodes (NCCs) comprised of nano-sized mixed ionic electronic conducting oxygen exchange catalysts on sintered, micro-porous, ion-conducting scaffolds.1,2 In these cathodes, degradation due to nano-particle coarsening and/or Sr segregation are a major concern.3 Recent studies have suggested that conformal zirconia overcoats several nm thick produced via Atomic Laser Deposition (ALD) can improve the long-term stability of SOFC cathodes. 4 Since, the low ~200oC ALD deposition temperatures do not coarsen the nanoparticle networks in infiltrated cathodes,5 here ZrO2 ALD overcoats of various thickness were deposited onto high=performance 12 vol% La0.6Sr0.4Co0.8Fe0.2O3-x (LSCF) - Gd0.2Ce0.8O2 (GDC) NCCs. Symmetrical cathodes were produced on both sides of dense, ~500 micron thick (Y2O3)0.08(ZrO2)0.92 electrolytes using previously described procedures.1 Then, porous La0.6Sr0.4MnO3 and gold grids were printed on both sides as current collecting layers, and 400oC-700oC Electrochemical Impedance Spectroscopy (EIS) measurements were performed with a push-contact setup to determine the NCC polarization resistance (Rp) from the EIS Nyquist plot x-intercepts. Transmission Electron Microscopy (TEM) and X-ray Photoelectron Spectroscopy (XPS) were also conducted on NCCs as function of overcoat thickness and degradation time at 650oC. Figure 1 shows that ZrO2 ALD overcoats 1-10 nm in thickness did not significantly alter the 400-700oC LSCF-GDC NCC Rp. However, as shown in the 1000-hour, 650oC, open circuit Rp degradation tests of Figure 2, increased zirconia overcoat thickness resulted in increased performance stability (at least up to 5 nm of ZrO2). Specifically, the degradation dropped from ~31.6 %/khrs for uncoated LSCF-GDC NCCs, to ~28 %/khrs, ~18 %/khrs, and ~11.7 %/khrs with 1, 2, and 5 nm of ZrO2 overcoat, respectively. TEM analysis showed that the ZrO2 overcoat maintained a constant, conformal, target thickness after 1000 hours at 650oC. XPS analyses on 1000-hour, 650oC aged cells showed that zirconia overcoats decreased the Sr/(La+Sr+Co+Fe) ratio at the surface, providing a possible explanation for the reduced degradation rates of LSCF-GDC NCCs containing ZrO2 ALD overcoats. Figure 1

Dual-Phase Nanocomposite Cathode Materials for Low-Temperature Protonic Ceramic Fuel Cells

Due to the relative low activation energy, protonic ceramic fuel cells (PCFCs) have attracted increasing attention in recent years because of the efficient low-temperature (LT, 300-600oC) operation. However, the insufficient LT activity of cathode materials for oxygen reduction reaction (ORR) is still one of the significant challenges to achieve excellent performance. It has been recognized that the triple conductivity (electron, oxygen ion, and proton) are prerequisite properties for a high-performance PCFC cathode. Many strategies on material selection have already been done to meet this requirement. BaCo0.4Fe0.4Zr0.1Y0.1O3-δ (BCFZY0.1) was reported as a single-phase triple conducting oxide cathode material which provides improvement of cell performance. However, the pure phase in return limits the further adjustment of the triple conductivities. The composite structures comprised proton conducting oxide and mixed ionic and electronic conducting can also introduce triple conductivity for cathode materials. Unfortunately, traditional fabrication methods for these composites are limited by mechanical mixing with two or more components, which significantly restricted contact sites/areas of different components and further obstacle ORR performance. Thus, the nanocomposite cathodes are demanded with high phase connection and flexible phase adjustment. Herein, the modified Pechini method was utilized to synthesize nanocomposite materials comprised of a mixed ionic and electronic conducting cubic perovskite phase and a protonic conducting orthorhombic perovskite phase from a nominal composition of BaCe0.4Fe0.4Co0.2O3-δ (BCFC). This one-pot method not only increased the density of the activated sites/areas for ORR by decreasing grain sizes for each phase but also provided excellent thermodynamic stability because the solid-state reaction thermodynamic equilibrium has arrived during synthesis. BCFC was confirmed to be a new promising nanocomposite cathode material for LT-PCFCs.

Chemically Synthesised ϒ-MnO2, and β-MnO2/Single Wall Carbon Nanotube Composites As a Promising High Capacity Cathode Materials for Lithium-Ion Batteries

This work reports the ϒ-MnO2, and β-MnO2 single wall carbon nanotube (SWCNT) nanocomposite cathode material synthesised successfully by chemical method for lithium-ion batteries. The electrochemical properties galvanostatic charge-discharge, cycle ability, rate performance and cyclic voltammetry were greatly enhanced by using the (SWCNT) composite cathode as a comparison to the pristine ϒ-MnO2, and β-MnO2. As a consequence, the modified (SWCNT) composite cathode material exhibits superior initial discharge capacity 255 mAh g-1 at 0.1C with coulombic efficiency of 99.22% and 118 mAh g-1 at 1C with a capacity retention (coulombic efficiency) of 95.5% (99.9%) after 100 cycles in the potential window of 2.0-4.5V (vs Li/Li+). In comparison pristine β-MnO2 exhibit only 169 mAh g-1 at 0.1C, corresponding to lower initial coulombic efficiency of 97% and 73 mAh g-1 at 1C with capacity retention (coulombic efficiency) of 71.4% (92%) after 100 cycles. The significant improvement in the de-/lithiation kinetic can be accredited to the enhancement in apparent lithium ion diffusion coefficient and electronic conductivity making it more applicable in high power commercialization.

High-Energy Lithium/SeS2 Batteries with Hierarchical Nanocomposite Cathode and Ionic Liquid-Based Electrolytes

Selenium disulfide (SeS2)-based composites have received much attention as a promising cathode material for high-energy lithium metal batteries due to their higher theoretical capacity (1342 mAh g−1) than that (675 mAh g−1) of selenium and a less significant shuttle effect than that of sulfur.[1] However, the biggest challenges faced by Li/SeS2 batteries are (1) the development of high-performance cathodes that can maintain the functional interface during cycling and (2) the identification of suitable electrolytes that can allow good cyclability without the degradation of lithium metal anodes. It has been reported that an ionic liquid, N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, i.e. Py14TFSI, can be used as co-solvent in ether-based electrolytes to form high-quality protection layer on lithium metal.[2] In this study, an effective strategy for developing high-performance Li/SeS2 batteries is introduced via a synergistic enhancement comprising the effective cathode design and the lithium anode protection in Py14TFSI containing electrolytes. We found that the hierarchical SeS2@carbon nanocomposites, confirmed by X-ray nano-computed tomography, facilitated Li-ion transportation and enhanced the electrochemical utilization of SeS2, enabling the improved rate capability of Li/SeS2 battery. Furthermore, the systematic studies on the morphological change as well as the electrochemical stability of lithium anode indicate that Py14TFSI-LiNO3­-containing electrolytes could effectively suppress the shuttle effect and protect lithium metal by forming a stable and LiF-dominated solid-electrolyte-interphase layer, leading to much improved Coulombic efficiency and cyclability of Li/SeS2 batteries. These results underscore a synergistic approach toward the development of high-energy Li/SeS2 batteries with long cycle life. [1] a) A. Abouimrane, D. Dambournet, K. W. Chapman, P. J. Chupas, W. Weng, K. Amine, J. Am. Chem. Soc. 2012, 134, 4505-4508; b) Y. Cui, A. Abouimrane, J. Lu, T. Bolin, Y. Ren, W. Weng, C. Sun, V. A. Maroni, S. M. Heald, K. Amine, J. Am. Chem. Soc. 2013, 135, 8047-8056. [2] J. Zheng, M. Gu, H. Chen, P. Meduri, M. H. Engelhard, J.-G. Zhang, J. Liu, J. Xiao, Journal of Materials Chemistry A 2013, 1, 8464. Figure 1

Binary superlattice ceramic membrane-coated soft carbon/hard carbon microspheres for high energy mixed-ion batteries

The assembly of two different materials into a composite with binary superlattices can provide a most efficient and inexpensive path to the synthesis of electrode materials with high energy density. Here, Li9Fe3P8O29/Na2HPO4 binary superlattice ceramic membrane-coated mesoporous soft carbon/hard carbon microspheres (BSLCM-MSC/HCMs) are synthesized via a hydrothermal carbonization method using acyl nucleoside triphosphate disodium salt (Na2ATP) as a multifunctional template. Here Na2ATP is not only a phosphorus source, a sodium source and a nucleating agent for the rapid synthesis of BSLCM, but also is a carbon source which is easily transformed into MSC/HCMs after being heat-treated in a N2 atmosphere. This special structure design brings a remarkable synergic effect for both Li+/Na+ mixed-ion storage and transfer kinetics. As a new nanocomposite cathode for mixed-ion batteries (MIBs), the BSLCM-MSC/HCMs display a self-enhancement of discharge capacity via electrolyte penetration in the core-shell mesoporous microspheres. Importantly, the discharge specific energy of a MIB assembled with the BSLCM-MSC/HCMs-2 cathode is up to 400 W h kg−1 at a high current rate of 10C, which outperforms all lithium-ion batteries and sodium-ion batteries reported so far. The findings in this study may benefit to the development of high energy mixed-ion batteries.

CuCl2-Based Cathode Material with Incombustible Inorganic Liquid Electrolyte Towards Room-Temperature Na Rechargeable Battery

Na rechargeable batteries have gained much attention as an alternative power sources of Li rechargeable batteries. Nevertheless, further advance on Na rechargeable batteries is necessary, to compete in rechargeable battery market because of their low energy density and reliability. Here, we demonstrate a new type of room temperature Na rechargeable battery which employs CuCl2/C nanocomposite cathode material and SO2-based inorganic liquid electrolyte. A high discharge capacity of 200 mAh g−1 corresponding to theoretical energy density of 580 Wh kg−1 is achieved, and also a high round-trip energy efficiency (>96%) and excellent cycle-life over 1000 cycles, which has never been obtained in conventional organic electrolyte system. The remarkable electrochemical performance is mainly attributed to the use of the non-flammable SO2-based electrolyte, which guarantees a reversible conversion reaction between CuCl2 and CuCl with NaCl. Further, detailed reaction mechanism of the new battery system will be discussed in the presentation.

Realizing an Asymmetric Supercapacitor Employing Carbon Nanotubes Anchored to Mn3O4 Cathode and Fe3O4 Anode

A facile route to anchor pseudocapacitive materials on multi-walled Carbon Nanotubes (CNTs) to realize high-performance electrode materials for Asymmetric Supercapacitors (ASCs) is reported. The anchoring process is developed subsequent to direct decomposition of metal-hexacyanoferrate complex on the CNT surface. Transmission electron microscopy (TEM) analysis reveals that the nanoparticles (NPs) are discretely attached over CNT surface without forming a uniform layer, thus making nearly entire NP surface available for electrochemical reactions. Accordingly, CNT-Mn3O4 nanocomposite cathode shows significantly improved capacitive performance as compared to pristine CNT electrode, validating the efficacy of designing the composite electrode. With CNT-Fe3O4 nanocomposite as paired anode, the hybrid ASC delivers a specific capacitance of 135.2 F/g at a scan rate of 10 mV/s within a potential window of 0-1.8V in the aqueous electrolyte and retains almost 100% of its initial capacitance after 15000 cycles. The serially connected ASCs can power commercial LEDs and mobile phones reflecting their potential in next-generation storage applications.

Selenium Nanocomposite Cathode with Long Cycle Life for Rechargeable Lithium‐Selenium Batteries

AbstractSelenium (Se) is a potential cathode material for high energy density rechargeable lithium batteries. In this study, a binder‐free Se‐carbon nanotube (CNT) composite electrode has been prepared by a facile chemical method. At initial state, Se is present in the form of branched nanowires with a diameter of <150 nm and a length of 1–2 μm, interwoven with CNTs. After discharge and re‐charge, the Se nanowires are converted to nanoparticles embedded in the CNT network. This synthesis method provides a path for fabricating the Se cathodes with controllable mass loading and thickness. By studying the composite electrodes with different Se loading and thickness, we found that the electrode thickness has a critical impact on the distribution of Se during repeated cycling. Promising cycling performance was achieved in thin electrodes with high Se loading. The composite electrode with 23 μm thickness and 60 % Se loading shows a high initial capacity of 537 mAh g−1 and stable cycling performance with a capacity of 401 mAh g−1 after 500 cycles at 1 C rate. This study reports a synthesis strategy to obtain Se/CNT composite cathode with long cycle life for rechargeable Li−Se batteries.

Chemical Origins of Electrochemical Overpotential in Surface‐Conversion Nanocomposite Cathodes

AbstractA new branch of promising nanocomposite cathode materials for rechargeable batteries based on non‐intercalation materials has been recently discovered. However, all the nanocomposite cathodes reported thus far suffer from a large overpotential in the first charge, which hinders the activation and lowers the energy efficiency. Here, a series of model nanocomposites consisting of MnO and various metal fluorides (LiF, NaF, KF, RbF, CsF, MgF2, CaF2, and AlF3) to identify the key parameters affecting the activation and overpotential in the first charge are evaluated. It is demonstrated that the F 1s binding energy of the metal fluorides is a plausible indicator of the overpotential in the first charge as well as the subsequent reversible discharge capacity. The stability of the cation in the electrolyte and its solvation nature are also shown to affect the overall activation process. Finally, it is proposed that appropriate tuning of the binding energy of metal fluorides (e.g., by forming solid solutions such as LiCsF2) is a feasible approach to reduce the overpotential and increase the reversible capacity. The findings broaden the current understanding of surface‐conversion nanocomposite chemistries, thus providing guidelines for the design of nanomixture cathode materials for rechargeable batteries.

Combination of air-dispersion cathode with sacrificial iron anode generating Fe2+Fe3+2O4 nanostructures to degrade paracetamol under ultrasonic irradiation

In the present study, ultrasound (US) was coupled with an electrochemical process (ECP) consisting of a novel cathode of carbon cloth (CC)-carbon black (CB) as the nano-composite air-dispersion cathode (NADC) for the degradation of paracetamol (APAP) in an aquatic medium. The NADC favored in situ production of H2O2 by the cathodic reduction. The implementation of iron sacrificial anode instead of dimensionally stable anodes resulted in the generation of Fe2+Fe3+2O4 nanostructures in the solution. The Fe2+Fe3+2O4 nanostructures were activated by means of both US and H2O2 to produce more OH in the aqueous solution. In addition, the utilization of US caused the conversion of H2O2 to OH irrespective of free oxidizing radicals generated through cavitation phenomenon. The hybrid method based on coupling US and NADC-ECP in the presence of Fe2+Fe3+2O4 nanostructures proved synergism (39.8%) allowing to effective decomposition of APAP. The pulse mode of US enhanced the degradation efficiency of APAP as compared to the sweep and normal modes. The intermediates of the degradation route were identified using GC–MS analysis as well as mineralization efficiency. The toxicity assay was also performed based on the inhibition test using activated sludge of a biological wastewater treatment plant.

Three-Dimensionally Reinforced Freestanding Cathode for High-Energy Room-Temperature Sodium-Sulfur Batteries.

Room-temperature sodium-sulfur (RT Na-S) battery cathodes suffer from poor conductivity, rapid dissolution of intermediate products, and potentially destructive volume change during cycling. The optimal way to minimize these problems could be a construction of a nanocomposite cathode scaffold combining different components selected for their particular functions. Here, we have combined the excellent electronic conductivity of reduced graphene oxide, polysulfide adsorption ability of the ultrafine manganese oxide nanocrystals, rapid ion/electron dissemination efficiency of nanosized sulfur, and outstanding mechanical stiffness and good electrical conductivity of Na alginate/polyaniline hybrid binder in a single electrode heterostructure. At 0.2 A g-1, an RT Na-S battery containing the freestanding cathode delivers an initial specific cap acity of 631 mA h g-1. By delivering a nominal discharge voltage of 1.81 V, our Na-S batteries bestow a high specific energy of 737 W h kg-1 at the 2nd cycle and 660 W h kg-1 was retained after 50 cycles. The effect of the amount of electrolyte additive is also well demonstrated in this study. The electrode fabrication process provides a new approach to tailor the design and preparation of effective cathodes for the room-temperature sodium-sulfur batteries.

Tailored sonochemical synthesis of V2O5|graphene nanoplatelets composites and its enhanced Li-ion insertion properties

Ultrasound-assisted surface modification of graphene nanoplatelets (GNPs) has made possible for in situ growth of V2O5 nanoparticles; homogeneously decorating inter-connected two-dimensional GNPs. The as-fabricated One-Step V2O5|GNPs nanocomposite exhibited enhanced electronic conductivity and facilitates higher Li+ ion insertion/ extraction kinetics, attained the high capacity of 297 mA h g−1 (10 mA g−1) corresponding to ∼2 Li+ ion insertion/ extraction. Consequently, the sonochemically tailored One-Step V2O5|GNPs nanocomposite delivered the specific capacity of 248 mA h g−1 at 50 mA g−1 with 83% capacity retention and 98.4% coulombic efficiency for the cycling studies. In addition, the rate capability studies were extended to One-Step V2O5|GNPs cathode at different current density from 10 to 200 mA g-1. On the other hand, the Two-Step (sonochemical synthesis of 200 nm V2O5 particles followed by its deposition on GNPs) V2O5|GNPs composite cathode yielded less specific capacity of 225 mA h g−1 (10 mA g-1) than the One-Step V2O5|GNPs nanocomposite cathode.

LiCoO2/Li7La3Zr2O12 nanocomposite cathodes synthesized via self-assembled block copolymer templates and used in all-solid-state lithium batteries

Nanocomposite cathodes comprising an active cathode material (LiCoO2) and a solid lithium electrolyte (Li7La3Zr2O12) were synthesized by using a self-assembled polystyrene‑b‑poly(4‑vinylpyridine) block copolymer template containing precursors of the active cathode material and solid electrolyte. Calcination at 1023 K was used to remove the block copolymer template and crystallize the active cathode material and solid electrolyte. The molecular weight of the block copolymer template was controlled to optimize the structure of the nanocomposite cathode and maximize capacity. When the nanocomposite cathode that was obtained by using the block copolymer template with the highest molecular weight was used in an all-solid-state lithium battery, the obtained discharge capacity per electrode (98.2 mAh/g) was substantially higher than literature values for other cathodes used in all-solid-state lithium batteries. We conclude that increasing the molecular weight of the block copolymer template allowed for greater dispersion of the precursors and binding of the well-dispersed nanoparticles of active cathode material and solid lithium electrolyte, which promoted the formation of fine conducting paths and an electrochemically effective interface between the active cathode material and solid lithium electrolyte.

Attaining a high energy density of 106 Wh kg−1 for aqueous supercapacitor based on VS4/rGO/CoS2@Co electrode

Improving the energy density has been being a challenge for supercapacitors, and the efficient approach is to choose active materials (composites) based on the potential window (chemical stability) and theoretical specific capacitance of both matched electrodes, which usually own unique nano-sized and porous (hierarchical) structure. Herein, hierarchical VS4/rGO/CoS2@Co (VRCS@Co) nanocomposite cathode and rGO/Co9S8@Co (RCS@Co) anode with nanosheet arrays were both in-situ synthesized on Co foam through a simple one-step hydrothermal process in the presence of graphene oxide (GO). VRCS@Co cathode exhibited a high capacitance of 274.3 mAh g−1 (1353 F g−1) at 0.625 A g−1 and an excellent cyclic life of 89.6% retention at 20,000th cycles, while RCS@Co anode delivered a superior capacitance of 619.5 mAh g−1 (2230 F g−1) at 0.714 A g−1 and a good cyclability of 93.3% retention at 2000th cycles. An asymmetric supercapacitor (ASC) assembled by using VRCS@Co cathode and RCS@Co anode revealed an ultrahigh energy density of 106 Wh kg−1 along with a power density of 2.67 kW kg−1.

Ultrahigh‐Capacity and Fire‐Resistant LiFePO4‐Based Composite Cathodes for Advanced Lithium‐Ion Batteries

AbstractThe growing demand for advanced energy storage devices with high energy density and high safety has continuously driven the technical upgrades of cell architectures as well as electroactive materials. Designing thick electrodes with more electroactive materials is a promising strategy to improve the energy density of lithium‐ion batteries (LIBs) without alternating the underlying chemistry. However, the progress toward thick, high areal capacity electrodes is severely limited by the sluggish electronic/ionic transport and easy deformability of conventional electrodes. A self‐supported ultrahigh‐capacity and fire‐resistant LiFePO4 (UCFR‐LFP)‐based nanocomposite cathode is demonstrated here. Benefiting from the structural and chemical uniqueness, the UCFR‐LFP electrodes demonstrate exceptional improvements in electrochemical performance and mass loading of active materials, and thermal stability. Notably, an ultrathick UCFR‐LFP electrode (1.35 mm) with remarkably high mass loading of active materials (108 mg cm−2) and areal capacity (16.4 mAh cm−2) is successfully achieved. Moreover, the 1D inorganic binder‐like ultralong hydroxyapatite nanowires (HAP NWs) enable the UCFR‐LFP electrode with excellent thermal stability (structural integrity up to 1000 °C and electrochemical activity up to 750 °C), fire‐resistance, and wide‐temperature operability. Such a unique UCFR‐LFP electrode offers a promising solution for next‐generation LIBs with high energy density, high safety, and wide operating‐temperature window.

Highly accelerated oxygen reduction reaction kinetics in colloidal-processing-derived nanostructured lanthanum strontium cobalt ferrite/gadolinium-doped ceria composite cathode for intermediate-temperature solid oxide fuel cells

Fully nanostructured La0.6Sr0.4Co0.2Fe0.8O3-δ/Gd0.2Ce0.8O1.9 [lanthanum strontium cobalt ferrite (LSCF)/gadolinium-doped ceria (GDC)] composite cathode is successfully demonstrated with conventional powder processing using nanocomposite particles, grown via a colloidal-processing-based bottom-up approach, as starting material. The cathode/electrolyte interface adheres well at a relatively low temperature of 900 °C because of the promoted surface diffusion of constituent elements by the higher surface energy of the nano-sized particles. By contrast, successful fabrication of a nanostructured porous cathode composed of uniformly distributing LSCF and GDC grains with a diameter of 50–70 nm strongly supports the prevented grain growth and pore closure by the co-existing hetero-phases in the composite particles acting as bulk diffusion barrier of each other's constituents during sintering. The nanocomposite cathode exhibits quite low area-specific polarization resistances for oxygen reduction reaction (ORR) of 0.127, 0.054, 0.032, 0.015 and 0.009 Ω cm2 at 600, 650, 700, 750 and 800 °C, respectively. These are significantly lower than those reported in the literature. The highly accelerated ORR kinetics contribute directly to the very high power densities of the anode-supported cells of 0.40, 0.77, 1.40, 2.32, and 3.29 W cm−2 at 600, 650, 700, 750, and 800 °C, respectively, with a cell voltage at 0.7 V.

Encapsulation of LiFePO4Nanoparticles into 3D Interpenetrating Ordered Mesoporous Carbon as a High-Performance Cathode for Lithium-Ion Batteries Exceeding Theoretical Capacity

A nanocomposite cathode based on LiFePO4 (LF) nanoparticles embedded 3D cubic ordered mesoporous carbon CMK-8 for lithium-ion batteries is synthesized by a facile impregnation method followed by further modification with carbon coating. The effects of variation of carbon contents on electrochemical performances of cathodes are investigated. The highly crystalline nanophase of LiFePO4 particles is confirmed by X-ray diffraction and TEM analysis. Nitrogen adsorption–desorption isotherms reveal persistence mesoporosity after encapsulation of LiFePO4 nanoparticles. The graphitic phase in LF/C@CMK-8-X (X = amount of CMK-8) nanocomposites is detected by analyzing the Raman spectra of the matrix carbon due to CMK-8 and the coated carbon (C). The electrochemical properties of the LF/C@CMK-8-X nanocomposites are evaluated with cyclic voltammetry, impedance spectroscopy, and charge–discharge cycling. The excellent rate capability with a discharge capacity value of 184.8 mA h g–1 is obtained for LF/C@CMK-8-0.5 nanoc...

Carbon/Sulfur Composites Stabilized with Nano-TiNi for High-Performance Li–S Battery Cathodes

In this work we proposed a novel strategy to prepare high-performance Li–S battery cathodes by nano-TiNi synergistically stabilizing C/S composites, whereby the TiNi/C/S hybrid composites were synthesized by infusing S gas into carbon black (CB) and nano-TiNi composites in vacuum. After several initial conditioning charge/discharge cycles, this unique TiNi/C/S hybrid nanocomposite cathode shows a high capacity (300 mAh/g based on total and 960 mAh/g based on S) with Coulombic efficiency of near 100% at 100 mA/g for around 300 cycles without obvious capacity decay. Due to its high electronic/ionic conductivity, the TiNi/C/S nanocomposite can retain an overall capacity of 150 mAh/g (480 mAh/g based on S) even at a higher current density of 10.0 A/g, demonstrating the outstanding rate capability. The exceptional performance of TiNi/C/S cathode can be ascribed to (i) the strong interactions between nano-TiNi and S to form metal disulfide clusters, (ii) the CB percolating throughout the composite to prevent na...

Enhancing the triiodide reduction activity of a perovskite-based electrocatalyst for dye-sensitized solar cells through exsolved silver nanoparticles

A silver/perovskite nanocomposite cathode is designed by an exsolution strategy for dye-sensitized solar cells, showing a superior efficiency to Pt.