Cathode Preparation Research Articles

Improved Electrochemical Performance of Li2Mn0.99Zn0.01SiO4/C Cathode Prepared By Sol-Gel Method with Mn3O4

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Solution-Based Preparation of Graphene-Li2s Composite Cathodes for Lithium/Sulfur and Lithium-Ion Batteries

Fully-lithiated lithium sulfide (Li2S, theoretical capacity 1166 mAhg-1) could be a more promising cathode material than sulfur (S), because it is compatible with safer and more stable Li-free anodes (such as graphite or silicon-based ones, to name a few). Unfortunately, Li2S suffers from low electrical and low ionic conductivities as well as the dissolution and shuttling of lithium polysulfides during cycling, as S cathodes do [1]. Due to the high melting point of commercial Li2S (950°C), the preparation of carbon-Li2S composites by melt infiltration is difficult. The large particle size (30-50 µm) makes it challenging to achieve high capacity utilization of this cathode material. The ball milling has been the most common procedure utilized to reduce the size of commercial Li2S powders to improve their rate performance and capacity utilization. Unfortunately, the ball milling procedure does not allow formation of uniform particles with controlled morphology, uniform carbon coating and good electrochemical performance [2, 3].In this research, we report for the first time a simple and versatile solution-based method to prepare the nano-sized Li2S and graphene-Li2S composites that does not induce release of any dangerous gases [4]. As shown in Figure 1, our finding of the lack of alcoholysis of Li2S in ethanol combined with its relatively high solubility allowed the formation of nanostructured Li2S by simple evaporating of ethanol from a Li2S solution. The pure Li2S powder demonstrates good uniformity of the homogeneously precipitated particles, their crystalline cuboid shape and an average size of ~200 nm. As expected, from SEM results, increasing graphene resulted in the reduction of both the average particle size and degree of the Li2S nanoparticle agglomeration.The addition of graphene and other nanostructured carbons in to the solution allows formation of Li2S-containing composites with enhanced electrical conductivity and structural stability. Higher electrolyte molarity was found to enhance cycle stability of the prepared cathodes in half cells (vs. Li foil) due to the reduced polysulfide dissolution [5-7] and maintaining better mechanical properties of a polyvinylidene fluoride (PVDF) binder in a less swollen state [8]. The high rate performance and good cycle stability (less than 15 % degradation after 200 cycles in Figure 2) of the selected graphene-Li2S nanocomposite cathodes suggest a great promise of the proposed method. The proposed methodology opens the door to solution-based fabrication of a variety of other Li2S-containing composites. Further optimization of Li2S-based composites and the formation of shells around the composite particles are explored to further enhance their performance in cells.

Electroless Copper Metallization for Improving Li-Ion Batteries Performances

Electroless metallization, both autocatalytic and galvanic displacement, is a viable process to deposit copper on materials of interests for the production of electrodes in Li-ions batteries. In this work, examples of electroless copper deposition on lithium cobalt oxide (LiCoO2) and silicon particles for cathode and anode preparation respectively will be discussed, evaluating the improvement in the electrochemical behavior of the battery. Lithium cobalt oxide (LiCoO2) is the most widespread used active material in conventional cathodes for lithium-ion batteries. Its structural and electrochemical properties have been extensively studied [1-3]. The value of LiCoO2 charge capacity, 150 mA h g-1, is one of the reasons that prompted research in seeking for alternatives to be used at the positive electrode. Plenty of cathode materials have been studied, for example spinels [2,4] and LiFePO4 [2,5] amongst the others. Moreover, modification of lithium cobalt oxide properties has been achieved by coatings of the active material with different materials and with various techniques [6,7]. In this work, copper coating has been applied on LiCoO2 particles in order to allow the use of water as solvent in the manufacturing process of the cathodes for Li-ion batteries. The deposition was done with autocatalytic technique in a formaldehyde bath, through a two steps process: (i) Pd-activation of the particles and (ii) the growth of the coating on the particles with the reduction of Cu ions. The treatment allowed the deposition of a homogeneous copper layer on the particles. The electrodes manufactured with the coated powders of active material showed an increased electrical conductivity. Electrochemical characterization has been carried out to investigate the nature of the coating, and performances of the obtained cathodes have been evaluated by means of galvanostatic cycling in coin cells after the first 50 cycles at 0.33 C. The presence of copper on the particles of active material has shown its effectiveness under more severe cycling conditions. The coating allows using water as solvent in the preparation of the cathodes, leading to NMP-free manufacturing process of lithium-ion batteries. Electroless copper deposition was used also to coat silicon particles for anode preparation. Both autocatalytic deposition and galvanic displacement in fluoride containing solution have been tested. Silicon particles copper coated are characterized by better performances at the beginning of the cycling test; with cycling, lithiation/delithiation capacity for copper coated electrodes becomes comparable with the one obtained without copper. Acknowledgements With the contribution of the LIFE financial instrument of the European Community - LIFE12 ENV IT 000712 LIFE+ GLEE.

Composite cathode materials Ag-Ba0.5Sr0.5Co0.8Fe0.2O3 for solid oxide fuel cells

Silver-Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) cathodes were prepared in two ways. In the first method, Ag-BSCF composite powder was prepared in ethanol solution, where Ag nanoparticles serving as a component in the preparation of Ag-BSCF composite cathodes had been previously obtained via one-step synthesis in absolute ethanol using a neutral polymer (polyvinylpyrrolidone). To the best of our knowledge, this is the first study to use a Ag sol obtained by the above method for preparation of Ag-BSCF composite powder. Then, a paste containing this powder was screen-printed on a Sm0.2Ce0.8O1.9 electrolyte and sintered at 1,000 °C. In the second technique, an aqueous solution of AgNO3 was added to a previously sintered BSCF cathode, which was then sintered again at 800 °C. The oxygen reduction reaction at the quasi-point BSCF cathode on the Sm0.2Ce0.8O1.9 electrolyte was tested by electrochemical impedance spectroscopy at different oxygen concentrations in three electrode setup. The continuous decrease of polarization resistance was observed under polarization −0.5 V at 600 °C. The comparative studies of both obtained composite Ag-BSCF materials were performed in hydrogen-oxygen IT-SOFC involving samaria-doped ceria as an electrolyte and Ni-Gd0.2Ce0.8O1.9 anode. In both cases, the addition of silver to the cathode caused an increase in current and power density compared with an IT-SOFC built with the same components but involving a monophase BSFC cathode material.

X-ray evaluation of the boundary between polymer electrolyte and platinum and carbon functionalization to conduct protons in polymer electrolyte fuel cells

In polymer electrolyte fuel cells (PEFCs), it is important to secure proximate diffusion paths of reactants and electrons. One approach is to optimize the boundary between polymer electrolyte and Pt nanoparticle surface. Based on synchrotron X-ray absorption fine structure to monitor directly the status of catalysts in PEFCs, it was found that Pt sites were reduced to Pt0 by alcohols contained in polymer electrolyte dispersion solution during the preparation of cathode of PEFC. As in membrane electrolyte assembly, only the Pt sites not covered by polymer electrolyte re-oxidized to Pt2+/4+. Thus, the interface between Pt and polymer electrolyte was evaluated. The other approach is to functionalize carbon surface with sulfonate/sulfate group to conduct protons. Similar level of proton conductivity was observed in current–voltage dependence compared to using polymer electrolyte, but polymer electrolyte was advantageous to lose less voltage for activation. Based on this comparison, optimum catalyst on cathode is proposed comprising surface sulfonate/sulfate group on carbon mixed with polymer electrolyte. Further optimization of cathode catalyst is proposed to functionalize carbon with sulfonate group linked to fluorocarbon branch.

Design of 1kw Al-Air Battery

The author puts forward the design scheme of 1 kw al-air battery based on analysis of key techniques such as the activation and anti-corrosion of aluminum anode, air cathode preparation, catalyst research, electrolyte additive. Function parameters of cell stack are calculated, and introduce its component functions, including control design, functional electrolyte circulation, air transport, DC / AC inverter system and others.

Preparation and electrode properties of composite cathodes based on Bi1−xSrxFeO3−δ with Perovskite-type structure

Abstract Various volume fractions of perovskite-type Bi 0.5 Sr 0.5 FeO 3 − δ (BSF55) and double perovskite PrBaCo 2 O 5+δ (PBCO) composite cathodes were prepared. The chemical compatibility of BSF55–PBCO composite material was confirmed by the absence of a secondary phase after firing below 850 °C for 2 h and annealing below 700 °C for 100 h. The electrode resistance of composite cathodes is indicated by Nyquist plots, all consisting of one arc in the high frequency (HF) range and another in the low frequency (LF) range. At 450 and 500 °C, the resistance in the HF range decreased linearly as the PBCO fraction increased, while BP73 showed the smallest arcs in the LF range. The activation energy of electrode resistance clearly decreased with the addition of up to 30 vol.% PBCO. This implies the mechanism of the oxygen reduction reaction underwent some changes due to the added PBCO. Considering the activation energy of the electrode resistance and the P(O 2 ) dependence of resistance at 700 °C, the addition of PBCO to BSF55 was shown to affect not only the mechanism but also the rate-determining step of oxygen reduction.

Electrocatalytic performance enhancement of La0.6Sr0.4Co0.2Fe0.8O3-δ–Y2O3 stabilized ZrO2 cathodes prepared by an impregnation technique

The electrocatalytic performance of the oxygen-reduction reaction of La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF)–Y2O3 stabilized ZrO2 (YSZ) cathodes prepared by an impregnation technique has been investigated as cathodes for intermediate temperature solid oxide fuel cells. The electrocatalytic activity of LSCF-YSZ cathodes increases with the introduction of LSCF phases to the YSZ scaffold. The introduction of surfactants into LSCF-precursor solutions during preparation has a great effect on the microstructure and electrochemical performance of LSCF-YSZ composite cathodes. N-ethyl-perfluoyooctylsulfonamide (DF10) is a type of commonly used nonionic flusurfactant which affects the LSCF particles' morphology on the YSZ scaffold. Using N-ethyl-perfluoyooctylsulfonamide (DF10) + acetylacetone during the preparation of LSCF-YSZ composite cathodes decreases the electrode polarization resistance (Re) of cathodes from 0.45 to 0.18 Ω cm2. We obtained a notable improvement in the electrochemical performance of LSCF-YSZ-composite cathodes with uniform and continuous LSCF particle distribution on the surface of YSZ scaffold.

Preparation and electrochemical performances of submicro-TiP2O7 cathode for lithium ion batteries

The TiP2O7 with a cubic 3 × 3 × 3 superstructure was synthesized by a liquid-assisted solid-state reaction, and characterized by x-ray diffraction, scanning electron microscopy, cyclic voltammogram, galvanostatic charge/discharge testing, and electrochemical impedance spectroscopy (EIS) technique. The results showed that there was only one step of intercalation into TiP2O7, corresponding to a pair redox (E Li/Li + = 2.74/2.48 V). The initial discharge capacity of TiP2O7 was 110 mAh/g at a current density of 15 mA/g, and the capacity retention was 76.12 % of the initial discharge capacity after 100 cycles. The EIS of TiP2O7 electrode consisted of two semicircles in organic electrolyte, which was attributed to SEI resistance as well as the contact resistance, and charge transfer process, respectively. A suitable model was proposed to explain the impedance response of the insertion TiP2O7 material of lithium ion batteries.

Preparation of Fiber-Type Cathode and Its Electrode Characteristics for Sodium Ion Battery

Fiber-type cathodes composed of Na-Mn-O for use in a sodium ion battery were developed. The active material was synthesized onto carbon fibers by a two-step procedure that included electrodeposition and hydrothermal reactions. The active material shapes were changed depending on the experimental conditions. The scale-shaped material composed of the Na0.91MnO2 phase was formed by the electrodeposition in an Mn(NO3)2 solution, while the circular-shaped one was obtained in the MnSO4 solution. The addition of H2O2 and increase in the hydrothermal temperature helped to decrease the unreacted precursor phase. The scale-shaped cathode mainly composed of the Na0.91MnO2 phase exhibited the highest 185 mAh/g discharge capacity among the fiber-type Na-Mn-O electrodes, indicating that this active material is beneficial for the intercalation and deintercalation of sodium ions. In addition, both the scale-shaped and string-shaped cathodes exhibited similar rate and cycling performances.

The effect of sulfur loading on the electrochemical performance of a sulfur-polymer composite cathode coated on aluminium foil.

A scaling-up investigation of a sulfur-polymer cathode for rechargeable lithium-sulfur batteries is reported. The proposed procedure uses a low cost aluminium current collector and is suitable for mass production of a composite cathode, with sulfur loading levels of up to 5.9 mg cm(-2), and good electrochemical performance.

Preparation of three-dimensional hybrid nanostructure-encapsulated sulfur cathode for high-rate lithium sulfur batteries

A three-dimensional hybrid nanostructure incorporating the merits of the MWCNTs webs (MWCNTs-W) and the reduced graphene oxide (RGO) is designed to improve the high-rate cycling performance of the lithium-sulfur batteries. Owing to the excellent Li+ ion and electronic transport properties of the MWCNTs-W and the RGO, this unique structure can provide a three-dimensional conductive network and promote rapid charge-transfer reaction at the cathode. Furthermore, because of the rough surface and porous structure of the MWCNTs after activation with KOH, and the special adsorption ability of the RGO, the soluble polysulfide intermediates can be effectively trapped in the cathode. Therefore, when evaluating the electrochemical properties of the RGO@MWCNTs-W/S composite as the cathode material for lithium-sulfur batteries, it exhibits an excellent cyclical stability and high rate performance. In particular, even at an ultrahigh rate (5 C), a discharge capacity as high as 620 mAh g−1 is still retained for the RGO@MWCNTs-W/S composite with 68.93 wt% sulfur after 200 cycles, and the average coulombic efficiency is 96%.

Preparation of a fouling-resistant sustainable cathode for a single-chambered microbial fuel cell

Two different binder materials of varying water affinity, viz. poly vinyl alcohol (PVA) and poly-tetrafluoroethylene (PTFE), and biocide vanillin were tested for cathode fouling in a single chamber air-cathode microbial fuel cell (MFC) constructed with a low-cost baked clayware cylinder and operated under fed-batch mode. PVA and PTFE loadings of 0.5 mg/cm(2) were used for MFC-1 and MFC-2, respectively as a binder; and a 1:1 mixture of PVA + PTFE was used as binder in MFC-3 with same binder loading. Vanillin was mixed with PVA and also applied at a loading of 0.5 mg/cm(2) for MFC-4. Results showed organic matter removal efficiencies around 90% for all MFCs both before and after fouling. Coulombic efficiency was, however, found to decrease 50% after fouling in the MFC-3 coated with both PVA and PTFE. After 5 weeks of operation, due to fouling 56, 40 and 69% reduction in power densities were observed in MFC-1, MFC-2 and MFC-3, respectively. In the MFC-4 having PVA and vanillin, the least fouling was observed. A consistent volumetric power of 233 mW/m(3) was observed for MFC-4, thus potentially offering a suitable solution to alleviate the problem of fouling in the making of single-chamber air-cathode MFCs.

Electrochemical properties of LiNiO2 cathode after TiO2 or ZnO addition

LiNiO2 was prepared by solid state reaction, and LiNiO2 was mixed with 1-, 2-, or 5wt% TiO2 or ZnO for the preparation of cathodes for a lithium ion battery. The electrochemical properties of the cathodes were investigated and the effects of the addition of TiO2 or ZnO were discussed. The voltage vs. capacity curves for charge and discharge at different numbers of cycles for LiNiO2, 2wt% TiO2-added LiNiO2, and 2wt% ZnO2-added LiNiO2 showed that in all the samples the first discharge capacity is much smaller than the first charge capacity. The addition of TiO2 or ZnO decreased the discharge capacities, but improved the cycling performance. The discharge capacities of LiNiO2 and 2wt% TiO2-added LiNiO2 decreased as the number of cycles increased. However, the discharge capacity of 2wt% ZnO-added LiNiO2 increased overall as the number of cycles increased. The −dx/|dV| vs. voltage curves for the 1st and 2nd cycles of 0, 1-, 2-, or 5wt% TiO2 or ZnO-added LiNiO2 showed that all the samples underwent four phase transitions during charging and discharging.

Enhanced cyclability of sulfur cathodes in lithium-sulfur batteries with Na-alginate as a binder

Na-alginate as a binder in an aqueous solvent has been applied in the preparation of sulfur cathodes for lithium-sulfur batteries. Their electrochemical performances have been investigated by a charge-discharge cycle test and electrochemical impedance spectroscopy (EIS). The EIS tests indicated that the alginate sulfur cathode had lower resistance and better kinetic characteristics than those of the poly(vinylidene fluoride) (PVDF) sulfur cathode using PVDF as a binder in a N-methy-2-pyrrolidone (NMP) solvent. The charge-discharge tests showed that the discharge capacity and the capacity retention rate of Na-alginate sulfur cathode were 508 mAh·g−1 and 65.4% at the 50th cycle with a current density of 335 mA·g−1. Compared with PVDF sulfur cathode, the alginate sulfur cathode showed a remarkably better cycle performance. These results show that the alginate binder has promising potential for lithium-sulfur battery applications.

Influence of cathode process on the performance of lithium-air batteries

Lithium-air batteries have attracted the widespread concern of electric vehicle industry and the relevant researchers because of the high energy density and environmental friendly characteristics. This article is dedicated to improve the performance of lithium-air batteries by optimizing the cathode preparation process. Therefore, three generally used methods of rolling, coating and spray have been employed, in the present work, to prepare the cathodes and the performance of the resulted lithium-air batteries have been comparatively investigated, analyzed and discussed. The results revealed that the spray method along with nickel foam as substrate is the best approach to prepare high performance cathode, judging from the discharge capacity, discharge voltage and high-rate discharge-ability. Furthermore, an intermediate pressing process is beneficial for improving the performance of cathode from coating method.

Air-cathode preparation with activated carbon as catalyst, PTFE as binder and nickel foam as current collector for microbial fuel cells

A cathode is a critical factor that limits the practical application of microbial fuel cells (MFCs) in terms of cost and power generation. To develop a cost-effective cathode, we investigate a cathode preparation technique using nickel foam as a current collector, activated carbon as a catalyst and PTFE as a binder. The effects of the type and loading of conductive carbon, the type and loading of activated carbon, and PTFE loading on cathode performance are systematically studied by linear sweep voltammetry (LSV). The nickel foam cathode MFC produces a power density of 1190±50mWm−2, comparable with 1320mWm−2 from a typical carbon cloth Pt cathode MFC. However, the cost of a nickel foam activated carbon cathode is 1/30 of that of carbon cloth Pt cathode. The results indicate that a nickel foam cathode could be used in scaling up the MFC system.

Deposition of Fe on graphite felt by thermal decomposition of Fe(CO)5 for effective cathodic preparation of microbial fuel cells

In this paper, an efficient and cost-effective method to prepare cathodes for microbial fuel cells (MFCs) was developed. Fe(CO)5 was decomposed and Fe was deposited on graphite felts for cathodic preparation. The unmodified, Pt modified and Fe modified graphite felts were utilized as cathodes in MFCs and power generation was compared. The maximum power density of MFCs with unmodified, Pt modified and Fe modified cathodes were respectively 288, 866 and 925mW/m3. The internal resistance of MFCs with unmodified, Pt modified and Fe modified cathodes were respectively 505, 384 and 278Ω. The results of multiple analyses confirmed that Fe on cathode was Fe2O3 and FeOOH and Fe(III) oxides as cathodic catalysts improved the electrochemical activity and promoted power generation. The greatest advantage of new method for cathodic preparation was the replacing manual brushing and Nafion solution and decreasing the cost.

Electrochemical Preparation of Ni-Sn Active Cathode and Its Electrocatalytic Hydrogen Evolution Reaction Mechanisms in Alkaline Solution

A simple galvanostatic electrodeposition method was used to synthesize an active Ni-Sn electrode on a Cu foil substrate. Characterization by high-resolution transmission electron microscopy (HRTEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD) revealed that the crystal structures of the deposited films transformed from amorphous structures composed of Ni crystal embryos and amorphous Ni-Sn to Ni3Sn4/Ni3Sn2 mixed crystals with increasing Sn content. Scanning electron microscope (SEM) images indicated that the amorphous Ni-Sn electrode possessed a smooth surface with uniform distribution of small particles, whereas the Ni3Sn4/Ni3Sn2 mixed crystalline electrode exhibited a rough surface composed of lamellar structures. The polarization curves measured in 1 mol·L-1 NaOH solution at 25 °C indicated that the amorphous Ni-Sn electrode showed a smaller overpotential (85 mV) and better electrocatalytic performance for hydrogen evolution than the mixed crystalline electrode. Electrochemical impedance spectroscopy (EIS) results showed that the hydrogen evolution reaction occurs 1479 Acta Phys. ⁃Chim. Sin. 2013 Vol.29 on the Ni-Sn alloy electrode under a mixture of Volmer and Heyrovsky control. The higher activity of the amorphous Ni-Sn electrode was attributed to the faster charge transfer and electrochemical adsorption and desorption rates of hydrogen atoms compared with those on the mixed crystalline electrode.

Electrochemical preparation of ZrO2 nanopowder: Impact of the pulse current on the crystal structure, composition and morphology

Abstract Formation of the negatively charged colloidal zirconia species i.e. [ZrO] − at the cathode surface and low adhesion of the hydroxide deposit to its surface are common problems in the cathodic electrodeposition of zirconia. Deposition experiments with the direct current mode led to the total spallation of the deposit from the cathode surface and no deposit was obtained in practice. In order to minimize these problems, pulse current deposition was applied in the electrodeposition of ZrO 2 . The results showed that the control of the base electrogeneration and deposit formation on the cathode surface is achievable using the pulse current mode. The XRD analysis and SEM observations revealed that the crystal structure, phase content and surface morphology of the prepared zirconia powders are significantly affected by the variation of t off or t on / t off ratio. This work clearly showed that the pulse current electrodeposition can be introduced as an alternative route in the ZrO 2 cathodic electrodeposition and preparation of its nanostructured powder.