Electrochemical Performance Of Cathode Research Articles

A comparative study on the production of Ni1/3Co1/3Mn1/3C2O4 cathode precursor material for lithium-ion batteries using batch and slug-flow reactors

The intermittent nature of the renewable energy sources drifts research interest towards various electrochemical energy storage devices, such as the lithium ion battery, which offers consistent power supply. The manufacturing cost and electrochemical performance of a battery pack largely depends on the quality of the cathode material, which further depends on the production method and its parameters. However, the traditional stirred tank-based co-precipitation manufacturing process for precursors of lithium nickel manganese cobalt oxide (NCM111) cathode suffers from inhomogeneity in the reaction environment, which leads to non-uniform morphology and particle size distribution (PSD). In this work, slug-flow-based manufacturing platform, which offers a homogeneous reaction environment, is used for the continuous production of NCM111 oxalate precursors. One of the novel features of this work is the comparative study between the quality of batch and slug-flow-derived products. The slug-flow-derived product is found to be better in terms of having bigger particle size, narrower PSD and higher tap density. The study on the single and dual-element precipitation in similar conditions to understand the co-precipitation behavior in the slug-flow manufacturing platform is also a unique feature of this work. Furthermore, the effect of NH4OH concentration and residence time (RT) on the electrochemical performance of cathode were also studied and it is found that the cathode precursors synthesized at a NH4OH concentration of 0.08 M and a RT of 2 minutes followed by lithiation shows a better electrochemical performance of 128 mAh g−1 at 0.1 C with cycling stability of more than 80% both at 0.5 C and 1 C.

Comparative Analysis of LiCo0.6Sr0.4O2 Cathode Electrochemical Performance in Oxide- and Proton-Conducting Intermediate-Temperature Solid Fuel Oxide Cells

Solid fuel oxide cells (SOFCs) are made up of three main parts: anode, electrolyte, and cathode. The main challenge in SOFCs is their high operating temperature, which can reach 1000 °C and lead to cell degradation issues. To address this, the utilization of lithium-based materials is suggested for the cathode component, facilitating intermediate-temperature SOFC operation within the temperature range of 500 to 800 °C. Previous studies have demonstrated the potential of producing high-quality lithium-based cathode ink using a triple-roll mill (TRM). By employing the fabrication parameters recommended in these studies, the lithium-based cathode (LCSO) was tested in different working environments, specifically the oxide-conducting SOFC and proton-conducting SOFC. The LCSO inks were screen-printed on SDC for oxide-conducting SOFC and BCZY for proton-conducting SOFC electrolyte before the analysis. Electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) are used to characterize the electrochemical performance and morphology of the LCSO cathode. Based on the results, the LCSO cathode is found to respond well in oxide-conducting SOFC environment with an area-specific resistance (ASR) value of 0.75 ohms-cm2 compared to proton-conducting SOFC which shows an ASR value higher by 11.45 ohms-cm2.

Mechanism insights into salt tolerance strengthened by CoCe encapsulated N-doped CNTs cathode in microbial fuel cell

To address the challenges of bioanode deactivation and instability of cathode catalysts in the treatment of high-salt organic wastewater using microbial fuel cells (MFCs), a series of CoCe catalysts encapsulated within nitrogen-doped carbon nanotubes (CoCe@NCNTs) was synthesized using a one-pot calcination method. Among the synthesized catalysts, CoCe0.5@NCNTs demonstrated outstanding and stable electrochemical performance in a high-salt environment with 600 mM NaCl, achieving a power density of 144.29 mW m−2, which was 2.7 times higher than that of Co@NCNTs. Notably, the characterization of the catalyst revealed that the addition of Ce element enhanced the stability of the Co crystal structure, mitigated Co leaching, and facilitated the retention of a higher valence state of the Co species after the reaction under high salt conditions. Specifically, the Co3+/(Co2+ + Co3+) ratio in CoCe0.5@NCNTs was 2.82 times larger than that of Co@NCNTs, signifying the favorable influence of the mutual electron conversion between the bimetallic Ce and Co on the performance and stability of catalyst in a high-salt environment. Furthermore, the study assessed the removal efficiency of norfloxacin (NOR), NAD+/NADH ratios, and microbial diversity in conjunction with the stability of cathode electrochemical performance, demonstrating the interconnection between cathode and anode. By considering the practical challenges in treating high-salinity wastewater and the principles of bioelectrochemistry, this paper proposes a mechanism for enhancing anode performance through cathode linkage, thereby providing a novel strategy for MFCs to treat high-salinity organic wastewater treatment.

What Affects More the NMC811 Cathode Powders: Lithium Excess, Washing or Aging?

Lithium Nickel Manganese Cobalt Oxides with R-3m space group have gained significant attention in recent years due to their high energy density, high power capability, and long cycle life. There are several synthesis methods to obtain NMC active powders, like solid-state or sol-gel, but co-precipitation synthesis is a widely used method for preparing NMC cathode materials for lithium-ion batteries, offering advantages in terms of control over particle size, morphology, and homogeneity (Xie et al., 2016).The main difficulty of synthesizing Ni-rich materials is the minimization of the degree of Li/Ni cation mixing, which refers to the interchange of the nickel and lithium ions in the 3a/3b sites of the crystal lattice. Perfect NMC materials have a hexagonal layered structure of α-NaFeO2-type, where Li and transition metal atoms form alternating layers between oxygen layers. To minimize phenomenon of cation mixing an excess of lithium source prior to sintering is required (Arai et al., 1995).However, unreacted lithium remain on the surface of NMC after the synthesis in the form of Li2O and it turns into LiOH and Li2CO3 as impurities if stored in ambient conditions. Those residual lithium compounds (RLC) on NMC811 surface can have significant impacts on the cathode's morphology, crystal structure, surface chemistry and, thus, electrochemical performance. Despite it was previously shown that Ni-rich materials have poor charge-discharge capacity retention, related to the electrolyte oxidization at the positive electrode surface (Jung et al., 2017) and/or structural changes of the material, such as large c-axis shrinkage, at high potentials (Teichert et al., 2020), many efforts are made to synthesize Ni-rich NMC for battery applications.Our research explores the impact of lithium excess on the physicochemical properties of NMC811. We compared self-made fresh samples with commercially available NMC811 in terms of structural parameters, morphology and electrochemical performance at high C-rates before and after lithium surplus was washed. Lithium removing procedure was applied to mitigate issues with RLC during battery operation, such as electrolyte degradation and gassing (Hartmann et al., 2022). However, over-washing can change physical properties of NMC811, including surface reconstruction as a consequence of the leaching of active transition metal ions and lithium from the cathode. Therefore, it is important to carefully optimize the washing procedures to balance the removal of RLC with the preservation of the cathode's electrochemical performance and stability.Here we want to point the effectiveness of washing procedure on NMC811 morphology, structural stability and electrochemistry. Additionally, our studies addressed the effects of calendar aging of active powders, i.e. prolonged shelf-storage in an ambient conditions for washed and unwashed samples, especially an influence of LiOH and Li2CO3 on structural parameters, electrodes preparation and electrochemical behavior. We want to open the discussion about preferable strategy on storage of Ni-rich NMCThe work was supported by the University of Warsaw through Action I.3.4. “The circular economy – energy storage”: "New electrode materials for next generation Li-ion batteries" (project no. PSP 501-D112-20-0001340) within the “Excellence Initiative – Research University (2020-2026)” programme of the Ministry of Science and Higher Education, Poland.ReferencesArai, H., Okada, S., Ohtsuka, H., Ichimura, M., Yamaki, J., 1995. Solid State Ion 80, 261–269.Hartmann, L., Ching, C.H., Kipfer, T., Koch, M., Gasteiger, H.A., 2022. J Electrochem Soc 169, 070516.Jung, R., Metzger, M., Maglia, F., Stinner, C., Gasteiger, H.A., 2017. J Phys Chem Lett 8, 4820–4825.Teichert, P., Eshetu, G.G., Jahnke, H., Figgemeier, E., 2020. Batteries 6, 8.Xie, H., Hu, G., Du, K., Peng, Z., Cao, Y., 2016. J Alloys Compd 666, 84–87.

Cathode Electrochemical Performance of PEMFCs with Compressed Gas Diffusion Layer: A Pore-Scale Investigation

Proton exchange membrane fuel cells (PEMFCs) are one of the most promising power sources in the fields of vehicle and ship power. Compression caused by assembly pressure, freeze-thaw cycles, and mechanical vibration can cause changes in the microstructure of the gas diffusion layer (GDL), thereby affecting the mass transfer and electrochemical reaction processes inside the PEMFC. In this paper, a three-dimensional single-phase multi-component lattice Boltzmann (LB) model is established to investigate the effects of binder volume fraction and compression on the cathode electrochemical performance. The stochastic reconstruction method is employed to generate 20 GDLs with different binder volume fractions and compression ratios. Afterward, the reactive gas flow within the 20 GDLs is simulated, and the distribution of oxygen mole fraction, water vapor mole fraction, and the current density are analyzed. The simulation results demonstrate that the mean current density decreases with the increase of the compression ratio, and the optimal binder volume fraction of 20% resulted in the highest current density. This paper enriches the research on the cathode electrochemical performance of PEMFCs at the pore scale and provides a guideline for optimizing the GDL design.

Recent Report on the Hydrothermal Growth of LiFePO4 as a Cathode Material

Various growth processes have been utilized for the development of lithium iron phosphate including microwave treatment, spray thermal decomposition, sol-gel and the hydrothermal route. However, microwave treatment, spray process and sol-gel suffer from high costs and difficulties in controlling growth parameters. In this review paper, recent synthetic strategies, including the raw materials utilized for the hydrothermal growth of lithium iron phosphate, their effect on the basic characteristics and, as a consequence, the electrochemical performance of cathodes, are reported. The advantages of the hydrothermal process, including high material stability, eco-friendliness, low production costs and material abundance, are explained along with the respective processing parameters, which can be easily tuned to modify lithium iron phosphate characteristics such as structure, morphology and particle size. Specifically, we focus on strategies that were applied in the last three years to improve the performance and electrochemical stability of the cathode utilizing carbon-based materials, N-doped graphene oxide and multi-wall carbon nanotubes (MWCNTs), along with the addition of metallic nanoparticles such as silver. Finally, future perspectives on the hydrothermal process are discussed including the simultaneous growth of powders and solid-state electrodes (i.e., growth of lithium iron phosphate on a rigid substrate) and the improvement in morphology and orientation for its establishment and standardization for the growth of energy storage materials.

Improved electrochemical performance in Sc-doped nanocrystalline LiMn2O4

• Design of stable interfaces for cathode nanomaterials enhanced capacity in Li-ion battery. • Sc 3+ spontaneously segregates to both surfaces and grain boundaries in LiMn 2 O 4 nanoparticles. • Sc 3+ -LMO showed capacity retention of 97.3% compared LMO with only 88.3%. Jahn-Teller effects have been widely known to cause capacity fading in LiMn 2 O 4 (LMO) cathode materials due to Mn dissolution from the cathode/electrolyte interfaces. This effect is more pronounced in nanoscale materials due to their high surface reactivity. Although surface coatings can help mitigate the phenomenon, there is still limited understanding of the correlation between the spontaneous segregation of dopants to interfaces and the cathode electrochemical performance. This work demonstrates that an interfacial dopant, Sc 3+ , selected on a thermodynamic principle, segregates to surfaces and grain boundaries and acts as a system stabilizer. The electrochemical performance in Li/LMO half-cells showed nanostructured Sc 3+ -doped LMO delivers capacity retention of 97.3% after 50 cycles at 0.2C compared to an equivalent undoped LMO with only 88.3%. Sc-doping reduces the charge transfer resistance while maintaining its high characteristic diffusion coefficient (D Li+ ) of 9.089 × 10 -11 cm 2 /s. The work highlights that understanding the thermodynamic stabilization of cathode materials can provide a pathway to advance cathode technologies even beyond Lithium.

Enhanced electrochemical performance of O3-type NaNi0.5Mn0.3Co0.2O2 cathodes for sodium-ion batteries via Al-doping

O3-type NaNi0.5Mn0.3Co0.2O2 based positive electrode materials are very promising for sodium-ion batteries. However, the irreversible phase transition due to structural deformation leads to sluggish kinetics, rapid capacity fade, and low C-rate performance, limiting its wide practical applications. The partial substitution of Co3+ (0.545 Å) by Al3+ (0.535 Å) ions in the transition-metal layer in NaNi0.5Mn0.3Co0.2-xAlxO2 (0.01 ≤ x ≤ 0.02) is an effective strategy to address the issue of structural deformation and thus to improve the electrochemical performance of NaNi0.5Mn0.3Co0.2O2 cathode. Solution combustion synthesis of NaNi0.5Mn0.3Co0.2-xAlxO2 (x = 0.01, 0.02) shows O3-type structure of NaNi0.5Mn0.3Co0.2−xAlxO2 material with the space group of R3¯m. The composition with an overall x = 0.02 Al doping delivers an initial 120 mAh g−1 capacity at a 0.1 C rate. It retains 90 % capacity even after 200 cycles than the other stoichiometric aluminum substitution, x = 0.01 (77 %). Moreover, the NaNi0.5Mn0.3Co0.18Al0.02O2 shows a good capacity of ~ 83 mAh g−1 even at a high C-rate of 5 C, almost 70 % of the initial capacity at the 0.1 C rate. The Al-substitute NaNi0.5Mn0.3Co0.2−xAlxO2 cathode's electrochemical performance is attributed to the enhancement in the structural stability of the sodium layered transition metal oxide after the partial substitution of Co3+ by Al3+ ion. Finally, the practical sodium-ion full cells are realized using a hard carbon-based anode and NaNi0.5Mn0.3Co0.18Al0.02O2 cathode, showing 91 % capacity retention at the end of 100th cycles with an OCV of 3.5 V.

Boosting fast and stable symmetric sodium-ion storage by synergistic engineering and amorphous structure

Tuning the microstructure and crystallinity of electrode materials is a great challenge and crucial for the development of high-performance sodium-ion batteries (SIBs). Herein, we develop a series of rationally designed carbon-coated V2O5 core-shell nanostructures (S-V2O5-HS, S-V2O5-HCS, P-V2O5/C-SCS, A-V2O5/C-SCS, and A-V2O5/C-WCS) in which the phase (single/polycrystalline, amorphous), microstructure (hollow, solid, porous) for the V2O5 core, and the thickness of the carbon shell are controlled via a one-pot solvothermal method followed by a single calcination process, and the performance differences between them are systematically studied. In this composite of amorphous carbon-coated V2O5 well-defined porous core-shell heterostructure (A-V2O5/C-WCS), synergistically the amorphous V2O5 core accelerates ions diffusion, carbon shell boosts the electronic conductivity, and the defect-rich porous structure lowers the binding energy compared to its counterparts as confirmed by DFT calculations and electrochemical results. Out of the ordinary, the A-V2O5/C-WCS used as a symmetric electrode for SIBs exhibits an excellent rate capability of 148 mAh g−1 at 5.0 A g−1 and outstanding ultralong cyclic stability (95% capacity retentions over 3000 cycles at 2.0 A g−1), when applied as a cathode (1.5–4.0 V) and anode (0.01–3.0 V) for SIBs. The A-V2O5/C-WCS displays a fully pseudocapacitive manner over the whole voltage thus the electrochemical performance of cathode and anode are well-matched. Impressively, the symmetric full-cell possesses a superior energy density of 219 Wh kg−1 at a high specific density of 6.0 KW kg−1 and superior cycling stability (95% capacity retained over 1200 cycles at 1.0 A g−1), demonstrating the great potential for practical application.

Effect of sediment embedding ratio on the cathode electrochemical performance in marine microbial fuel cells on ocean floor

In the long-term electricity generation and driving sensor work process of marine sediment microbial fuel cells(MSMFCs), its cathode in the seawater may be embedded into the marine sediment, which will affect the electrochemical performance and lead to MSMFCs failure. The article simulated the embedding ratio of cathodes in sediment in the laboratory: 1/3, 1/2, 2/3, in order to investigate the changes of the electrochemical performance of the cathode and the electricity generation performance of MSMFCs. The results show that: the open circuit potential dropped and the required longer steady time with the higher embedding ratio of the cathode. Its capacitance decreased gradually, and the minimum capacitance was 32 F/cm2 (2/3 group), which was 0.72 times of the Blank. The kinetic activity decreased firstly and then increased, and its maximum activity was 1.61 times of the Blank (2/3 group); The maximum power density of the MSMFCs was 140.83 mW/m2 (1/3 group), which was 1.21 times of the Blank. With the increase of embedding ratio of the cathode in the marine sediment, its electrochemical performance and electricity generation performance of MSMFCs both fluctuates, but the normal operation of MSMFCs can still be ensured.

Enhanced electrochemical properties of LiMn2O4 cathode by adding halloysite nanotubes as additive

Halloysite nanotubes (HNTs) were used as an electrode additive to prepare a LiMn2O4/halloysite composite cathode to improve the cycle and rate performance of LiMn2O4–Zn batteries. The composite electrode was characterized by XRD, FTIR, SEM, and TEM. Electrochemical performance of batteries using composite electrode was evaluated by CV, EIS, rate and cycle test. SEM image revealed that the hollow halloysite nanotubes were well dispersed in the prepared cathode. The electrochemical performance test results showed that the battery with LiMn2O4/halloysite composite cathode containing 3 wt% HNTs exhibited the higher specific discharge capacity, better rate capability and cyclability than that of the battery using the conventional LiMn2O4 cathode without any HNTs additive. The improved electrochemical performance of LiMn2O4 cathode was attributed to the three-dimensional network channels formed by the hollow HNTs. Li+ could migrate rapidly in the halloysite nanotubes filled with water-based electrolytes, and the negative electric surface of halloysite could be another pathway for Li+ migration in the electric field. The efficient Li+ transmission effectively reduced the concentration polarization during the charge-discharge process and promoted the improvement of the LiMn2O4 cathode electrochemical performance.

Understanding the calendering processability of Li(Ni0.33Mn0.33Co0.33)O2-based cathodes

The calendering process aims at enhancing the electrode energy density, and improving the electronic conductivity, and determines the final porous electrode micro/mesostructure. In this sense, one of the main parameters of interest is its impact in the electrode porosity (ε) and the electrochemical performance. Here, we present a systematic study of the calendering conditions (applied calender pressure and roll temperature) effect on the final NMC-based electrodes ε in terms of the active material/carbon additive/binder composition and the amount of solvent used during the preparation of the slurries. The calendering processability was assessed through the cathodes compressibility resistance and minimal attainable ε, the electrode mechanical properties (hardness and elastic deformability), the pore size distribution, the electrode film mesostructure and the C-rate cathode electrochemical performance. Based on our results, it was found that the distribution and organization of the inactive carbon black (CB)/PVdF phase and the electrode mesostructure are the key parameters that control the cathode processability through calendering. Electrodes with high CB/PVdF content and prepared with higher amounts of solvent in the slurry ensure a good electronic conductivity and a film-like structure of the electronic conducting phase around the NMC particles which upon calendering outputs a better electrochemical performance.

Sulfur nanoparticles/Ti3C2Tx MXene with an optimum sulfur content as a cathode for highly stable lithium-sulfur batteries.

Lithium-sulfur batteries have a high theoretical energy density but they need better sulfur host materials to retain the lithium polysulfide shuttle effect, which results in the batteries' capacity fading. Titanium carbide MXene (Ti3C2Tx MXene) is an excellent host for the sulfur cathode because of its layered-stacked structure and many surface termination groups. The sulfur content in S/Ti3C2Tx MXene composites is an important factor affecting the cathodes' electrochemical performance. In this work, S/Ti3C2Tx MXene composites with different sulfur contents are prepared by a one-step hydrothermal process, and the influence of the sulfur content in the S/Ti3C2Tx MXene composite on the S/Ti3C2Tx MXene cathode's electrochemical performance is studied. When the mass ratio of sulfur to MXene in the reactant is 4 : 1, the sulfur nanoparticles are uniformly filled in the layered-stacked structure. The layered-stacked structure can buffer the volume expansion of sulfur during cycling and the surface termination groups exhibit strong adsorption of LiPSn. Thus, the S/MXene composite with an optimum sulfur content (67.0 wt%) demonstrates an excellent electrochemical performance, including a high initial reversible capacity (1277 mA h g-1 at 0.5 C) and the best cycling performance (1059 mA h g-1 at 0.5 C after 100 cycles). This work offers a guide to developing advanced S-based cathode materials with an appropriate S content for lithium sulfur batteries.

Improved thermal expansion and electrochemical performance of La1−xSrxFe0.7Ni0.3O3−δ cathodes for intermediate-temperature SOFCs

Perovskite oxides of composition La1−xSrxFe0.7Ni0.3O3−δ (LSFN-x, 0 ≤ x ≤ 0.4) were evaluated as candidate cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs). Their crystal structures, electrical conductivity, thermal expansion coefficient (TEC), and electrochemical performance were investigated as a function of their Sr content. An orthorhombic structure was obtained when 0.3 equivalents of Ni were substituted at the Fe sites, resulting in LaFe0.7Ni0.3O3−δ, and the crystal structure was transformed from orthorhombic to hexagonal upon the substitution of Sr at La sites. Sr doping was found to increase the TEC of the LSFN material, resulting in a good thermal match with the commonly used Gd0.1Ce0.9O2−δ (GDC) electrolyte. The LSFN-0.2 also exhibited good chemical compatibility with the GDC electrolyte at temperatures <1000 °C. A gradual increase in electrical conductivity with increasing Sr content was observed because of the increase in the concentration of electronic defects. The cathode electrochemical performance was investigated by AC impedance spectroscopy. Among the LSFN series, LSFN-0.2 exhibited the lowest polarization resistance value of 0.065 Ω cm2 at 800 °C. The substitution of Sr can promote charge transfer and the adsorption/dissociation of oxygen molecules, thereby decreasing the polarization resistance of the LSFN material. X-ray photoelectron spectroscopy measurements were conducted to elucidate the cause of the performance improvement. The results indicated that the LSFN-0.2 material has potential applications as cathode material for IT-SOFCs.

La0.6Sr0.4Co0.2Fe0.8O3−δ powder: a simple microstructure modification strategy for enhanced cathode electrochemical performance

A simple strategy of producing well-dispersed La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) cathode nanopowders that utilizes a dispersing agent is presented. The cathode nanopowder was synthesized by employing a dispersing agent-assisted sol–gel method. Two types of dispersing agents were applied as the synthesizing aids in this study which are the activated carbon (AC) and ethylene glycol (EG). The synthesized cathode powder was systematically characterized by X-ray diffraction (XRD), thermogravimetric analyzer (TGA), field emission scanning electron microscopy (FESEM), and BET surface area analyzer. The electrochemical properties of the fabricated cell were evaluated using electrochemical impedance spectroscopy (EIS). TGA analysis shows that both dispersing agents decomposed below 600 °C. The XRD analysis demonstrates that the single-phase LSCF perovskite is attainable at the calcination temperature of 700 °C for 5 h. FESEM results are in accordance with the BET analysis in which application of the dispersing agents produced more dispersed cathode powders and larger surface area. The electrochemical performances of the LSCF cathode modified with the AC and EG are respectively in the average of six- and eightfolds higher as compared with the pristine LSCF. The dispersing reaction of AC and EG and their influences on the cathode microstructure and performance are also thoroughly discussed.

Development of Pr2-xSrxCuO4±δ mixed ion-electron conducting system as cathode for intermediate temperature solid oxide fuel cell

Mixed ionic-electronic conducting oxides Pr2-xSrxCuO4±δ (x = 0, 0.2, 0.4, 0.5 and 0.6) are synthesized by combusting mixed precursors (metal acetates) under microwave heating followed by microwave sintering at 1000 °C for 4 h. Each composition of Pr2-xSrxCuO4±δ solid solutions crystalizes into tetragonal structure within one single phase across the compositional range 0 ≤ x ≤ 0.5. The T′-phase Pr2CuO4±δ transforms to the T*-phase at x = 0.4. Crystallite size reduces from 801(9) to 728(6) nm with an increase in the Sr content. The maximum dc-conductivity (σdc = 63.1(2) S cm−1 at 700 °C) and minimum activation energy (Ea = 0.118(3) eV, below pseudo-transition temperature 620 °C) in Pr1.6Sr0.4CuO4±δ is ascribed to optimum concentration of extrinsic dissociated defects. The performance of electrochemical symmetrical cells (Pr2-xSrxCuO4±δ/ Ce0.9Gd0.1O1.95/ Pr2-xSrxCuO4±δ) prepared using inkjet printing is found to be superior than spin coated (cathode) symmetrical cells. Increase in oxygen ion conductivity and surface oxygen exchange reaction rate with increasing Sr dopant concentration improve overall electrochemical performance of cathode. Minimum electrode polarization resistances 0.30(7) Ω cm2 and 0.21(3) Ω cm2 (at 700 °C) are obtained for symmetrical cells of Pr1.6Sr0.4CuO4±δ cathode using spin-coating and inkjet printing methods, respectively. Electrochemical impedance spectroscopy studies suggest that the charge transfer step is the rate-limiting step during oxygen reduction reaction.

A facile solution to mature cathode modified by hydrophobic dimethyl silicon oil (DMS) layer for electro-Fenton processes: Water proof and enhanced oxygen transport

Water flooding in the microporous cathode is poisonous but inevitable for oxygen reduction reaction (ORR) in electro-Fenton (EF) processes. To meet this challenge, a facile modification was reported to stabilize performance of cathode through the infiltration process, which selecting superior CB-PTFE electrode as backbone and dimethyl silicon oil (DMS) as maturation layer. Characterized by FE-SEM, EDS, BET, XRD, the matured cathode was proved to be wrapped uniformly by DMS. Electrochemical performances of cathodes were evaluated by CA, CV, EIS and CP measurements in oxygen “starvation” condition. These results proved that the maturation layer improved the electrocatalysis on 2e− ORR, the service lifetime from 1.68 h to 18.34 h, the working range of current density from 70 to 110 A m−2 and reduced the oxygen diffusion resistance from 74.23 to 8.07 Ω. Besides, H2O2 generation and oxygen utilization of 2%DMS cathode respectively reached 126.7 mg L−1 and 83.49% in 60 min, which were rarely influenced by pH and aeration rate even after water flooding process. 2%DMS layer served as the accelerated oxygen transport channel can explain the enhanced oxygen transport. The simulated contaminated solution containing a fungicide-flutriafol (FTF) was obtained 100% removal in about 40 min and 48.88% TOC removal in 2 h. The lifetime tests revealed much more stable decay of FTF under the broader operational condition.

Synthesis, microstructure, and electrochemical performance of Li-rich layered oxide cathode materials for Li-ion batteries

Li-rich layered oxides Li1.2Mn0.54Ni0.13Co0.13O2 were synthesized by modified Pechini method using various compositions of the reaction mixture. Difference in the electrochemical performance of cathodes on their basis is explained by different morphology and microstructure of the materials. The porous hierarchical structure favors a better electrochemical performance. The presence of defects, including crystal twins, in the samples is considered to be a major reason that leads to their poor cyclability and rate capability.

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...

Novel Processing of Cathodes for Solid Oxide Fuel Cells

Solid-oxide fuel cells (SOFCs) are electrochemical devices that efficiently convert chemical energy of fuels into electricity.[1] However, they typically operate at high temperature (800–1000 °C) causing substantial challenges in cost and material compatibility. SOFC that can work at intermediate temperature (IT) (500–750 °C) is thus more attractive.[2] SOFC is generally composed of anode, electrolyte and cathode. A practical cathode for SOFCs should possess sufficiently high thermo-mechanical stability, good thermal and chemical compatibility with the electrolyte, high chemical stability against the surrounding atmosphere, good electro-catalytic activity for oxygen reduction reaction (ORR), as well as high electrical conductivity.[1] However, the current widely used cathode, lanthanum strontium manganite (LSM), rapidly loses activity below 800 °C.[3] According to numerical calculations, the efforts to optimize the oxygen surface exchange reaction are required while very high ionic conductivities are not necessary in order to achieve the goal of a highly active cathode.[4] Nano-sized palladium (Pd) and platinum (Pt) show very high activity towards oxygen activation, which can substantially increase the cathode electrochemical performance by improving the surface properties. However, precious metals are expensive and undergo sintering. Silver is a good alternative for its relatively low price and high electrocatalytic activity for oxygen activation, however more easily sintered than Pt and Pd resulting in the electrode deactivation.[5] As the electrodes and the dense electrolyte are sintered together in SOFC, the deactivated electrodes are normally neither regenerable nor replaceable, what brings the end of the SOFC. On the other hand, the Ag-doped perovskites have promoted catalytic oxidation of CO, CH4, n-hexane, and NO,[6] which was significantly improved by the partial substitution of Ag into the A-site of perovskite together with the additional formation of the oxygen vacancy and the metallic Ag on the surface of the perovskite forming composite materials. [7, 8] Among several ways to process the composites, infiltration has shown promising results bringing the possibility to tailor electronic, ionic and mixed ionic electronic conductivities in a porous backbone of proton conducting oxides. [9, 10] The exsolution of nickel, ruthenium, silver or other metal nanoparticles has been investigated in reducing conditions for the design of the electrodes for SOFC. [11-13] The development of highly electrochemically active cathodes for SOFCs requires the optimization of materials composition together with micro- and nanostructures in order to form stable and catalytically active composite electrodes. Here we report on the novel heterostructured silver nanoparticle-decorated perovskite composites La0.95-xSrxMn1-y-z(Fe,Ni,Zn,Mg)zNbyO3-δ – 0.05Ag (exLSAMN) as highly active and durable cathodes for SOFCs, derived from single phase La0.95-xSrxAg0.05Mn1-y-z(Fe,Ni,Zn,Mg)zNbyO3-δ (LSAMN) perovskite precursors through an exsolution process. We report LSAMN as a novel precursor which can develop into high-performance nanosized silver modified LSM-based electrode under cathodic polarization or reducing atmosphere with improved stability and in situ electrochemical regeneration capability. The LSAMN materials were synthesized by solid state reaction and wet chemical synthesis method in order to compare the activity. The electrochemical intercalation/de-intercalation of metal catalysts is a conceptually attractive approach that is also applicable for the development of other metal-modified oxide electrodes. The composite formation and properties were tailored by changing the synthesis route and thermal treatment. A thorough description of the synthesis methods is presented as well as a careful characterization of the microstructure and phase composition of the resulting composite electrodes. The performance of the new composite cathodes with gadolinia-doped ceria (CGO) electrolyte is demonstrated. The exLSAMN electrode showed fairly high electrochemical activity and low area specific resistance (ASR). These unique features make the new materials highly promising cathodes for SOFCs at intermediate temperatures. References A. B. Stambouli, E. Traversa, Renew. Sust. Ener. Rev., 6 (2002) 433.J. A. Kilner, M. Burriel, Ann. Rev. Materi. Res., 44 (2014) 365.S. P. Jiang, J. Mater. Sci., 43 (2008) 6799.J. Fleig, J. Pow. Sour., 105 (2002) 228.T. Z. Sholklapper et al. J. Pow. Sour., 175 (2008) 206.D. Y. Yoon et al. J. Catal., 319 (2014) 182.K. Wang et al. Catalysis Today, 158 (2010) 423.G. Pecchi et al. App. Catalysis A: General, 371 (2009) 78.C. Duan et al. Science, 349 (2015) 1321.C. Duan et al. Energy Environ. Sci., 10 (2017) 176.Y. Zhu et al. Nano Lett., 16 (2016) 512.J. T. S. Irvine et al. Nature Energy, 1 (2016) 15014.G. Tsekouras, D. Neagu, J. T. S. Irvine, Energy Environ. Sci., 6 (2013) 256.