Properties Of Negative Electrodes Research Articles

Fundamental benchmarking of the discharge properties of negative electrodes in lead acid batteries

The unprecedented scale of energy storage deployment needed to allow high penetration of intermittent renewable energy sources into the electrical grid places significant economic cost and performance targets on battery technologies. Lead batteries, owing to their highly abundant and inexpensive raw materials, can be considered an important solution to grid storage as long as they achieve high material utilization, fast recharge rates, and long cycle life. To address the limitations in material utilization, we need to revisit the electrochemical processes during the discharge step and answer the following question: what are the fundamental limits of the discharge reaction? In this work we discuss how well-defined lead metal surfaces with nanometer scale roughness allow us to resolve the accessible discharge capacity for both faradaic and non-faradaic processes as a function of electrolyte concentration and in the presence of traditional additives. The direct connection between PbSO4 layer morphology and discharge rates gives us important insights on the mechanism of discharge as related to the dissolution and passivation events. This work sets the stage for reimagining the design of lead batteries with implications to grid storage applications.

Lithium-ion battery electrode properties of hydrogen boride.

Recently, hydrogen boride (HB) with a pseudo-two-dimensional sheet structure was successfully synthesized, and it is theoretically predicted to have high potential as a negative electrode material for alkali metal ion batteries, making it a promising new candidate. This study represents the first experimental examination of the negative electrode properties of HB. HB was synthesized via cation exchange from MgB2. The confirmation of HB synthesis was achieved through various spectroscopic experiments, including synchrotron radiation X-ray diffraction and X-ray photoelectron spectroscopy, in addition to direct observation using transmission electron microscopy. The HB electrode was prepared by mixing the HB powder sample with conductive additive carbon black and a polymer binder. A test cell was assembled with the HB electrode as the working electrode, and lithium metal as the counter and reference electrodes, and its battery electrode properties were evaluated. Although reversible charge-discharge curves with good reversibility were observed, the reversible capacity was 100 ± 20 mA h g-1 which is significantly smaller than the theoretical predictions. Nitrogen gas adsorption experiments were performed on the HB powder sample to determine the specific surface area indicating that the HB sheets were stacked together. It is plausible to consider that this stacking structure led to a reduced lithium-ion storage capacity compared to the theoretical predictions.

Simple Estimation of Creep Properties of Negative Electrode for Lithium-Ion Battery

The macroscopic creep properties of negative electrodes in lithium-ion batteries and their estimation methods have been investigated based on the microscopic structure of the electrode. Tensile and creep tests were conducted on a negative electrode consisting of carbon powder and polyvinylidene fluoride (PVDF) binder. The stress-strain curve, the time history of the tensile strain, and the creep rupture time were measured in these tests and estimated using the simple model proposed in this study. The proposed model approximates the alignment of carbon particles as body-centered cubic (bcc) or face-centered cubic (fcc). The external load on the model was supported by a PVDF binder located between carbon particles. The test results showed that PVDF binder mechanical properties affect the macroscopic mechanical properties of the negative electrode, including the creep properties. The stress-strain curve and time history of the tensile strain were located between the upper and lower limits of the proposed model. The tensile strength and creep rupture time agree with the lower limit of the proposed model.

The Effect of C45 Carbon Black-Phosphomolybdic Acid Nanocomposite on Hydrogenation and Corrosion Resistance of La2Ni9Co Hydrogen Storage Alloy

In this paper, we analysed the influence of corrosion processes and the addition of a carbon black-heteropoly phosphomolybdic acid (C45-MPA) nanocomposite on the operating parameters of a hydride electrode obtained on the basis of the intermetallic compound La2Ni9Co. The electrochemical properties of negative electrodes for NiMH batteries were studied using galvanostatic charge/discharge curves, the potentiostatic method, and electrochemical impedance spectroscopy (EIS). The morphology and chemical composition analysis of the studied electrodes were investigated by means of scanning electron microscopy (SEM) with supporting energy-dispersive X-ray analysis (EDS). For more structural information, FTIR analysis was performed. The results indicate that the presence of the C45-MPA nanocomposite in the electrode material increased both the discharge capacity of the hydride electrode and the exchange current density of the H2O/H2 system. The heteropoly acid-modified electrode is also more resistant to high discharge current densities due to its catalytic activity.

Influence of the specific surface area of Stöber silica additives on the electrochemical properties of negative electrodes in lead-acid batteries

The surface area of carbon additives has been described as a key property for the enhancement of cycling stability and dynamic charge acceptance (DCA) of negative lead-acid electrodes. However, it is still uncertain if similar performance enhancing effects can be achieved by other inorganic additives of similar structure, or if the electrochemical activity of carbon additives is mandatory for the enhancing effects. In order to elucidate the importance of structure and electrochemical activity of high DCA additives, Stöber silica with tailorable particle size and specific external surface area were prepared and incorporated into negative lead-acid electrodes, combined with the addition of carbon black to ensure high cycling stability. The properties and electrical performance of the negative active material were investigated by electrical tests in 2 V laboratory cells and different physical characterization methods. The overall electrochemical activity in terms of hydrogen evolution and double-layer capacitance was not affected by the silica additive and therefore is also independent of the external surface area. In addition, the silica particles led to a slightly reduced, though steady, mass utilization and discharge capacity. Finally the DCA could not be improved by the Stöber silica additives, which excludes Stöber silica as high DCA additive. In addition, since the DCA performance has not been increased, despite the broad specific surface area range of the additive particles utilized, this study provides a clear indication that the performance enhancement observed with carbon additives also relies on their electrical conductivity.

KCl-Modified Graphite as High Performance Anode Material for Lithium-Ion Batteries with Excellent Rate Performance

Electrochemical properties of a graphite negative electrode of lithium-ion batteries have been enhanced by treating raw graphite with alkali molten salt. Here, the KCl-modified graphite is fabricated via a simple and low-cost technique in which graphite particles and potassium chloride are simply mixed with deionized water and sintered. Compared to the raw material, the rate capability of the graphite modified by potassium is enhanced significantly to 269.7 mAh g–1 at 1 C after 200 cycles which effectively solves the main problem to limit the application of the graphite anode for Li-ion batteries in the field of hybrid vehicles. First-principle calculations have been done to analyze the effect of K-ions on the lithium storage capacity of the graphite. This study provides a scientific basis for adopting the K-modified technique to enhance the electrochemical properties of the negative electrode materials.

Alkali Metal Ion Storage Properties of Single-Walled Carbon Nanotube Encapsulation Systems

Single-walled carbon nanotube (SWCNT) encapsulation systems have been paid much attention since the discovery of C60 peapod in 1998. So far, several kinds of molecules (e.g. coronene, β-carotene, 9,10-dichloroanthracene, water, iodine) have been encapsulated. The eager studies on structural and electronic properties of the encapsulation systems revealed that some of the encapsulated molecules show properties different from their bulk forms. Due to such findings, it has been concluded that the tube interior provides a unique field to the encapsulated molecules to alter their properties. However, there are not many reports describing the applications of encapsulation systems. Lithium ion batteries (LIBs) have been widely used in portable electronic devices such as cell phones and lap-top computers, owing to their high energy density. However, new energy source with higher capacity and better rate performance is required because LIBs are not good enough for larger and higher power machines such as electric vehicles. Recently, metal-air, lithium-sulfur (LIS), sodium-ion batteries and others have been attracting much attention as post-LIB energy devices. LIS battery is one alternative that has higher energy density than LIB has, and is expected to be used for large-scale devices. However, in order for the practical use of LIS battery to be realized, we have to solve the problem that polysulfide ions (Sn−) are easily dissolved in electrolyte. This dissolution problem leads to capacity fading with charge-discharge cycles. Several investigations have been carried out to improve the cycle performance of LIS battery. For example, Kaneko et al. reported the encapsulation of sulfur into the hollow core of single-walled carbon nanotube (SWCNT) [1]. Another post-LIB is sodium-ion battery (SIB) that has received increasing attention in the recent years, because SIB is very advantageous in regards to cost and resources. However, good anode materials having high capacity for SIBs have not been found yet. Graphite, which is used as a negative electrode of LIBs, does not adsorb Na ions. So far, SIB negative electrode properties of several kinds of carbon materials have been studied. Although some kinds of hard-carbons and Na alloys can adsorb and desorb sodium ions, we should explore better anode materials to realize SIBs. Phosphorus is also expected as alternative electrode materials because of its high theoretical capacity (2596 mAh/g) and relatively low volume expansion when adsorbing sodium ions. However, phosphorus electrode still suffers from instability problems, despite the numerous attempts that have been made with different phosphorus polymorphs and/or different kinds of electrode support materials. In the present study, we use the unique environment provided by the hollow core inside SWCNTs to encapsulate both sulfur and phosphorous molecules, in order to address some of the unanswered questions and performance issues of both LIS and SIB. First, we compare the physical stability of sulfur molecules inserted in SWCNTs having different tube diameters, then we report the LIS battery electrode properties of sulfur encapsulated SWCNTs (S@SWCNTs). We also report on the negative electrode properties of phosphorus encapsulated single-walled carbon nanotubes (P@SWCNTs), in which phosphorus atoms are inserted into the pores of SWCNT [2]. Since SWCNTs have good electric conductivity, they should work as a conductive component for the highly resistive phosphorus electrode. In the conference, I will also talk about another types of SWCNT encapsulation systems.

Ti–V–Cr–Ni alloys as high capacity negative electrode active materials for use in nickel–metal hydride batteries

TiV2.1−xCrxNi0.3 (x = 0.1–0.6 and 1.0), TiyV1.7Cr0.4Ni0.3 (y = 0.9–1.1) and TiV1.7Cr0.4Niz (z = 0.3–0.5) alloys were prepared by arc-melting, and their negative electrode properties such as the maximum discharge capacity (Cdis), charge–discharge cycle performance and high-rate dischargeability (HRD) were evaluated. All the alloys consisted of two phases. The V and Cr constituents were mainly distributed in the primary phase, whereas the Ti and Ni constituents were mainly distributed in the secondary phase. The Cmax was dependent on the lattice volume of the primary phase, mole fraction of the primary phase and the plateau potential in charging. The average decrement of discharge capacity (ΔCdis) from Cmax to the discharge capacity at 30th cycle was used as an indicator of charge–discharge cycle performance. The ΔCdis was decreased or cycle performance was improved with the Cr content in the primary phase. The discharge potential at DOD = 50% (ΔE50) was linearly changed with specific discharge current (idis), and the ΔE50/Δidis and charge transfer resistance (Rct) as indicators of HRD were decreased with an increase in the Ni content in the secondary phase.

Study on Taylor Cone and Trajectory of Spinning Jet by Altering the Properties of Negative Electrode

To achieve continuous yarns formed of nanosized filaments during electrospinning, a chemical liquid in a container was used in this study as the collector (i.e. the negative electrode) to convert nanofiber filaments into yarns. This study focuses on analyzing the impact of the chemical solutions employed in the negative electrode on the Taylor cone and trajectory of the fluid jet during the process of electrospinning. The results indicated that only 5wt peregal O solution produced non-interrupted filaments so the spinning system can work continuously for up to 10 hours. Also, the results showed that both the angle and volume of Taylor cone enlarged along with the increase of the electrical conductivity of the negative electrode. When changing the spinning voltage, both the volume of the Taylor cone and the shape of the spinning jet changed significantly.

Lithiation behavior of single-phase Cu–Sn intermetallics and effects on their negative-electrode properties

Single-phase Cu–Sn intermetallics were used to investigate their phase transformations during lithiation/delithiation, together with their negative-electrode properties. The stoichiometric Cu–Sn samples were prepared as thermodynamically warranted phases using a reduction-diffusion method with controlled potentials. Potentiostatic lithiation tests suggested that Cu3Sn directly changes into LixSn, while Cu6Sn5 becomes Li2CuSn before LixSn forms. We also revealed that separation from Li2CuSn into Cu and LixSn occurs at +0.11 to +0.10V vs. Li. Additionally, charging/discharging tests with cutoff potentials of +1.5V to +0.11V showed better cycling performance than that with +1.5V to +0.00V, probably due to the suppression of LixSn formation. Such a tendency can be expected in other Cu6Sn5 electrode materials.

Effect of Pores in Hollow Carbon Nanofibers on Their Negative Electrode Properties for a Lithium Rechargeable Battery

The effect of pores in hollow carbon nanofibers (HCNFs) on their electrochemical performance is investigated because the carbon shell itself acts as a reservoir for accommodating Li-ions through intercalation and simultaneously becomes a transport medium through which Li-ions migrate into the core materials in HCNFs. Porous HCNFs (pHCNFs) are prepared by the coaxial electrospinning of a sacrificial core solution and an emulsified shell solution containing sacrificial islands for pore generation. After a thermal treatment, a systematic study is carried out to relate the resulting pore size in pHCNFs to the sacrificial islands in the emulsified shell. As the pores are introduced in pHCNFs, their initial capacity and reversible capacity rate are proved to increase significantly to 1003 mAhg(-1) and 61.8%, respectively, compared to those (653 mAhg(-1) and 53.9%) of nonporous HCNFs. The increased pore size and expanded graphene layers are believed to facilitate lithium insertion/extraction behavior.

Negative Electrode Properties of Carbon-Coated Si Leaf Powder for Lithium-Ion Batteries

not Available.

Carbon Coating of Si Thin Flakes and Negative Electrode Properties in Lithium-Ion Batteries

Carbon Coating of Si Thin Flakes and Negative Electrode Properties in Lithium-Ion Batteries

Effect of carbon types on the electrochemical properties of negative electrodes for Li-ion capacitors

The electrochemical properties of various carbon materials (graphite and hard carbon) have been investigated for use as a negative electrode for Li-ion capacitors. The rate capabilities of the carbon electrodes are tested up to 40C using both half and full cell configurations. It is found that the capacitance of the hard carbon material at 40C could be maintained up to 70% of that at 0.2C in full cells with an activated carbon positive electrode, which is the best among the carbon materials. The cycle performance of the hard carbon demonstrates that the initial capacitance is retained up to 83% even after 10,000 cycles. The outperforming results could be ascribed to the microstructure of hard carbon, which indicates that hard carbon is more suitable as negative electrode materials for high power energy storage applications.

Negative Electrode Properties of Si Leaf Powder for Li-ion Batteries: Effects of Thickness and Additives

not Available.

Improvement of Negative Electrode Properties of Si Leaf Powder for Lithium-Ion Batteries

not Available.

Negative Electrode Properties of Sn and Si Leaf Powder for Li-ion Batteries

Two kinds of metal thin platelets (Leaf Powder, Oike Co., Ltd.) based on Sn and Si were prepared, and their charge/discharge properties were investigated as alternative negative electrode materials to graphite for Li-ion batteries. One was simple metal platelets (M-LP, thickness: 100 nm) and the other was laminated platelets with an inactive Ni layer (M/Ni/M-LP, thickness: 30/30/30 nm). For both Sn and Si platelets, the shape of thin platelets effectively relieved the stress by volume expansion and shrinkage during the alloying and de-alloying processes, and improved their charge/discharge cycleabilities. Particularly, the Si platelets suppressed their agglomeration and pulverization, and much more remained the shapes than the Sn platelets. The lamination with the inactive Ni layer further improved the cycleability, though the specific capacity decreased by its presence. The alloying and de-alloying reaction with Li+ ion was substantially smooth, which was due to a decrease in the diffusion distance of Li+ ion by using the thin platelets. As a result, the Si/Ni/Si-LP exhibited a good capability over ca. 400 mAh g-1 up to 3C rate.

Negative Electrode Properties of Sn and Si Leaf Powder for Li-ion Batteries

not Available.

Negative electrodes for Li-ion batteries

Graphitized carbons have played a key role in the successful commercialization of Li-ion batteries. The physicochemical properties of carbon cover a wide range; therefore, identifying the optimum active electrode material can be time consuming. The significant physical properties of negative electrodes for Li-ion batteries are summarized, and the relationship of these properties to their electrochemical performance in non-aqueous electrolytes, are discussed in this paper.

Effect of the stoichiometric ratio on electrochemical properties of hydrogen storage alloys for nickel-metal hydride batteries

Effect of stoichiometric ratio on the electrochemical properties of negative electrodes was investigated for alloys with composition Mm(Ni 3.6Mn 0.4Al 0.3Co 0.7) x (Mm = misch metal, 0.88 ⩽ x ⩽ 1.12). The discharge capacity at a current density of 0.2 A g −1 increased with an increase in unit cell volume of the alloys in the range of x = 0.96−1.12. The discharge efficiency increased with increasing x value, and was about 85.2% even at a high current density of ca 2 A g −1 in the case of x = 1.12. The improved high-rate dischargeability was explained on the basis of high diffusibility of hydrogen in the bulk of alloys as the result of the relatively low stability of the hydride, in addition to the high electrocatalytic activity for the hydrogen electrode reactions of the negative electrode.