On the behaviour of carbon black in positive lead-acid battery electrodes

The addition of carbon black to the positive paste led to an alteration in structure of the PbO₂/PbSO₄ electrode due to an increase in porosity, in active mass coarsening and in the /-PbO₂ ratio. These structural effects are explained as being caused by the ability of carbon black to increase the water-accumulating capacity of the paste, to influence the local formation conditions and to participate in the charge transport within the unformed mass. Oxidative removal of carbon black from the active mass was studied.     

Studies on the microstructure of the positive lead-acid battery plate and its electrochemical reactivity

It has been shown that the physicochemical properties of PbO₂ in the positive plate of a lead-acid battery relates to the PbO₂ crystal size growth during charge/discharge cycling. It was found that there were two types of PbO₂ present in an uncycled positive plate thermally decomposed into tet-PbO: One with, and the other without, forming -PbO _x . The degree of crystallinity was found to be lower in the surface layer of PbO₂ crystals than in the interior. The degree of crystallinity of PbO₂ crystals increased with cycling, and at the same time the size of PbO₂ crystals became larger, causing decrease in the specific surface area and surface roughness. It was also concluded that the electrochemical reactivity of the surface layer of PbO₂ was strongly influenced by the properties of the PbO₂ crystal lattice characterized by the formula PbO_2-(xH₂O).     

Theory of porous electrodes—XI. The positive plate of the lead-acid battery

Partial differential equations describing the transport of mass and electricity in the pores of the positive electrode of a lead acid battery were derived. The theory is based on exact transport equations and on the assumption that the solid porous matrix has a metallic conductivity. Volume changes in both phases are taken into account. Numerical solutions obtained on a computer are presented for the case where the influence of electrolyte between the electrodes can be neglected. The solutions depend on the product of electrode thickness times current density, and on the initial porosity.     

Application of a novel gelled-electrolyte in valve-regulated lead-acid batteries with tubular positive plates

A polysiloxane-based gel electrolyte (PBGE) was prepared and used as a novel gel electrolyte in valve-regulated lead-acid (VRLA) batteries with tubular positive plates. Cyclic voltammetry (CV) and scanning electron microscopy (SEM) indicated that PBGE is more stable than fumed-silica gel electrolyte (FSGE). The properties of AGM (absorptive glass mat)-PBGE and PVC-FSGE tubular batteries were investigated by electrochemical techniques. The results showed that the AGM-PBGE tubular batteries have higher initial discharge capacity and better high-low temperature performance than PVC-FSGE. The improved electrochemical performance of the AGM-PBGE batteries may result from the high charge efficiency and the open three-dimensional network structure of PBGE. SEM and X-ray diffraction (XRD) spectroscopy showed that PBGE facilitates the conversion of the active-mass to lead dioxide, presenting a high formation efficiency. The addition of PBGE instead of FSGE not only simplifies the manufacturing process of tubular gel batteries, but also improves the utilization efficiency of positive active material (PAM), thus enhancing the battery performance and reducing the manufacturing cost.     

The discharge behaviour of the porous lead electrode in the lead-acid battery. I. Experimental investigations

The discharge kinetics of the porous lead electrode have been investigated experimentally as a function of extent of discharge and the concentration of lignosulphonate expander. The results show that the kinetic model previously suggested for the recharge reaction can also be fitted to the anodic polarization curves. The structural changes in the electrode have been studied with SEM and electron microprobe analysis. These studies show that the higher discharge capacity at higher discharge currents of electrodes with organic expander in comparison to electrodes without expander is due to the formation of larger lead sulphate crystals in the former case. The discharge capacity at high current density (1000 A m^–2) is limited by depletion of sulphuric acid in the pores only at concentrations lower than the normal.     

The influence of different factors on the porous structure of the positive electrode in lead-acid batteries

Geometric structure measurements of positive electrodes have been determined by measuring cumulative pore volume, pore size distribution, porosity, pore specific surface area and BET specific surface area. The influence of technological parameters such as concentration of SO₄²⁻ ions in the paste, the temperature of the paste and the quality of oxides on the structure of porous positive electrode have been studied. The relation between BET specific surface area and the electrical capacity of the positive electrode is shown and interpreted.     

The discharge behaviour of the porous lead electrode in the lead-acid battery. II. Mathematical model

A mathematical model for the porous lead electrode in the lead-acid battery has been derived in order to explain the limited discharge capacity at high rates of discharge. By comparison with experimental discharge curves the model predicts that the discharge process is ended by a coverage of the electroactive surface of lead by lead sulphate, even at current densities around 1000 A m^–2. Only at concentrations lower than the normal (4–5 M) and very high current densities will depletion of sulphuric acid become a limitation. By using an expression which relates, the local maximum utilization of the active material to the time integral of the local current density in a way which resembles the empirical Peukert equation, final lead sulphate distributions can be predicted with a maximum in the centre of the electrode, which is in agreement, with measurements.     

Use of a PbO2 electrode of a lead-acid battery for the electrochemical degradation of methylene blue

In this work, the electrochemical degradation efficiency of synthetic azo dye, methylene blue, at positive electrode PbO₂ of lead-acid battery was investigated. The structure and morphology of the electrode was investigated by X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray spectrometry. The influence of several operating parameters on electro-oxidation of 100 mL of methylene blue solution 100 mg/L was studied. Results indicated that lead-acid battery electrode is effective for removing color and chemical oxygen demand (COD). It is found that current density, the stirring speed, and the supporting electrolyte concentration have a positive effect on decolorization and mineralization, and no significant effect of the distance between the electrodes on methylene blue degradation and COD removal was observed. By contrast, the percentage of color and COD removal decreases with increasing of pH. Kinetic analysis of the results revealed that the COD removal follows a pseudo-first-order kinetics.     

Developments in the soluble lead-acid flow battery

The history of soluble lead flow batteries is concisely reviewed and recent developments are highlighted. The development of a practical, undivided cell is considered. An in-house, monopolar unit cell (geometrical electrode area 100 cm²) and an FM01-LC bipolar (2 × 64 cm²) flow cell are used. Porous, three-dimensional, reticulated vitreous carbon (RVC) and planar, carbon-HDPE composite electrodes have been used in laboratory flow cells. The performance of such cells under constant current density (10–160 mA cm⁻²) cycling is examined using a controlled flow rate (mean linear flow velocity <14 cm s^-1) at a temperature of approximately 298 K. Voltage versus time and voltage versus current density relationships are considered. High charge (<90%), voltage (<80%) and energy (<70%) efficiencies are possible. Possible failure modes encountered during early scale-up from a small, laboratory flow cell to larger, pilot-scale cells are discussed.     

The effect of sodium polymethacrylate on the rheology of the positive paste and performance of the lead-acid battery

Due to its rheological properties, positive lead-acid battery paste can be difficult to spread on lead current collectors accurately and efficiently under industry machinery and setting. Sodium polymethacrylate dispersant was studied as an effective positive paste additive that could lower the yield stress of the paste without affecting paste density and battery performance. Under a four-blade vane rheometer setup, stress growth and oscillatory amplitude strain sweep experiments evaluated the rheological properties of positive paste with the addition of varying amounts of sodium polymethacrylate. Further, the electrochemical effects of sodium polymethacrylate were also evaluated in 2V batteries by testing positive active material utilization and cycle life.     

Dependence of the properties of the lead-acid battery positive plate paste on the processes occurring during its production

The phase composition, microstructure, porosity, density and consistency of positive plate pastes prepared at 35 and 80° C were determined as functions of the amount of H₂SO₄. It was found that the phase composition of the paste is determined by the H₂SO₄ oxidized lead powder ratio and by the temperature at which the paste is mixed. The paste density is determined by the liquid powder ratio. The total pore volume is controlled by the paste density while the average pore radius and the consistency are determined by the phase composition. Stoichiometric calculations were made for the phase composition of the pastes. It is concluded that the paste represents a non-equilibrium system consisting of crystalline basic lead sulphates and oxides and amorphous sulphate-containing components.     

Corrosion behavior of a positive graphite electrode in vanadium redox flow battery

The graphite plate is easily suffered from corosion because of CO₂ evolution when it acts as the positive electrode for vanadium redox flow battery. The aim is to obtain the initial potential for gas evolution on a positive graphite electrode in 2 mol dm⁻³ H₂SO₄ + 2 mol dm⁻³ VOSO₄ solution. The effects of polarization potential, operating temperature and polarization time on extent of graphite corrosion are investigated by potentiodynamic and potentiostatic techniques. The surface characteristics of graphite electrode before and after corrosion are examined by scanning electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. The results show that the gas begins to evolve on the graphite electrode when the anodic polarization potential is higher than 1.60 V vs saturated calomel electrode at 20 °C. The CO₂ evolution on the graphite electrode can lead to intergranular corrosion of the graphite when the polarization potential reaches 1.75 V. In addition, the functional groups of COOH and CO introduced on the surface of graphite electrode during corrosion can catalyze the formation of CO₂, therefore, accelerates the corrosion rate of graphite electrode.     

提高锂离子电池正极材料LiFePO4电导率的方法

橄榄石型结构的LIFePO<,4>作为一种新型的锂离子电池正极材料,具有材料来源广泛、价格便宜、理论比容量高(约170 mAh/g)、热稳定性好、无吸湿性、对环境友好等优点,近年来引起人们的广泛关注,可望成为新一代首选替代LiCoO<,2>的锂离子二次电池正极材料.分析了锂离子电池正极材料橄榄石型LiFePO<,4>的...     

Dissolution of pastes in lead-acid battery recycling plants

The dissolution of the active materials of lead-acid batteries in fluoboric electrolyte has been studied. The use of redox couples such as Ti³⁺/Ti⁴⁺ is proposed for an efficient and quick dissolution of lead and lead dioxide mixtures. For PbO₂ and Pb electrodeposited on platinum electrodes the rate of dissolution in HBF₄ (200 g dm⁻³) containing Ti ions (0.3m) corresponds to a current density of 400 A cm⁻² and 160 A cm⁻², respectively. Dissolved oxygen has a marked influence on lead dissolution acting as an oxidizer of Ti³⁺ to Ti⁴⁺. It has also been shown that the Fe²⁺/Fe³⁺ couple can be used, although with lower benefits. For industrial applications, a concentration of Ti ions of about 0.051m and the use of a counter-current electrolyte flow in the electrolysis cell can advantageously accomplish the leaching process of pastes and slimes in a batteries recycling plant.     

Investigation of Ir-modified carbon felt as the positive electrode of an all-vanadium redox flow battery

Porous graphite felts have been used as electrode materials for all-vanadium redox flow batteries due to their wide operating potential range, stability as both an anode and a cathode, and availability in high surface area. In this paper, the carbon felt was modified by pyrolysis of Ir reduced from H₂IrCl₆. ac impedance and steady-state polarization measurements showed that the Ir-modified materials have improved activity and lowered overpotential of the desired V(IV)/V(V) redox process. Ir-modification of carbon felt enhanced the electro-conductivity of electrode materials. The Ir-material, when coated on the graphite felt electrode surface, lowered the cell internal resistance. A test cell was assembled with the Ir-modified carbon felt as the activation layer of the positive electrode, the unmodified raw felt as the activation layer of the negative electrode. At an operating current density of 20 mA cm⁻², a voltage efficiency of 87.5% was achieved. The resistance of the cell using Ir-modified felt decreased 25% compared to the cell using non-modified felt.     

铅酸蓄电池酸性水处理实践

分析了拆解铅酸蓄电池过程中CX预处理系统循环水水质差的原因,通过添加絮凝剂、改变部分设备功能等,解决了CX预处理系统在拆解铅酸蓄电池过程中出现的水质问题,成功实现了CX预处理系统高效运行的目标。     

A modelling approach to the optimizaton of lead-acid battery electrodes

A resistive grid model was used to study the current and ohmic overpotential distributions along the surface of lead-acid battery electrodes. Analyses were made under two different regimes: the initial behaviour at high current densities and the response with time at low current densities. At high discharge currents the theoretical results show that the geometry of the electrodes and the position of the lug play the most important role in controlling the magnitude of ohmic losses. The best geometry is a square grid with the lug positioned at the upper centre of the electrode. At low discharge currents the model was used to follow the current distribution along the electrode surface as a function of time. In this last study the appearance, for long discharge times, of short-circuited concentration microcells localized in certain regions of the electrode surface was noted. The other regions of the electrode supply the external discharge current and the excess current necessary to charge the internal microcell.     

含添加剂PVA的胶体铅酸电池电解质性能

为改善胶体电解质的物理性质,提高电化学性能,制备了不同聚乙烯醇（PVA）含量的胶体电解质,黏度、强度和胶凝时间测试结果表明,黏度随PVA含量的提高而增加,在含量0.0050%之后增加显著;加入0.0025%和0.0050% PVA,凝胶强度增大,胶凝时间延长,凝胶性能得到改善,但继续提高PVA含量对改善电解质的物理性质不利。循环伏安和交流阻抗测试结果表明,加入0.0050% PVA可提高电极的反应电流和电量,有利于提高活性物质的利用率、析氧过电位,抑制自放电,降低电解质的阻抗、电化学反应的电荷转移电阻和电容。     

‘Breathing’ of the lead-acid battery negative plate during cycling

By measuring the thickness of the negative plates with and without an expander, during cycling, it was established that the active mass volume pulsates, expanding during discharge and shrinking during charge. This phenomenon is due to the mechanical stress in the lead skeleton structure caused by the PbSO₄ crystals. At each pulsation of the plate, slight changes in the structural parameters of the active mass are observed. These changes accumulate during cycling causing expansion or shrinking of the active mass. As a result of this the capacity of the plate decreases. These changes in the plate structure depend strongly on the expander.     

锂离子电池正极材料磷酸亚铁锂的改性进展

橄榄石型结构的磷酸亚铁锂(L iFePO4)作为一种新型的锂离子电池正极材料,具有材料来源广泛、价格便宜、理论比容量高(约170 mA.h/g)、热稳定性好、无吸湿性、对环境友好等优点,可望成为新一代首选的可替代钴酸锂(L iCoO2)的锂离子二次电池正极材料。分析了锂离子电池正极材料橄榄石型磷酸亚铁锂的结构特点和锂离子在充放电时的脱嵌模型,评述了近年来国内外对于改善磷酸亚铁锂的电化学性能所进行的改性研究,重点介绍了优化合成工艺、提高离子扩散效率、添加导电材料等方法对锂离子电池正极材料磷酸亚铁锂的影响,并对其发展方向作了展望。