A review of oxygen recombination in the sealed lead-acid cell

A one-dimensional mathematical model of the oxygen-recombination lead-acid cell is developed. The mode] is applied to investigate mechanisms associated with oxygen recombination and species transport during charge. The conditions for rapid transport rates of gaseous oxygen through the separator and dissolved oxygen through the liquid film within the Pb electrode are considered, and these rates are rapid for the conditions investigated. Model predictions show that during charge gas volume increases in the Pb electrode and decreases in the PbO2 electrode. At the onset of oxygen recombination during constant-current charge, the polarization of the Pb electrode is reduced, which results in the prediction of a maximum in cell voltage. This voltage behavior is demonstrated experimentally. The prediction o5 a voltage maximum by the mathematical model occurs when the recombination mechanism is the direct electrochemical reduction of oxygen at the Pb electrode. Model simulation with another recombination mechanism in which oxygen reacts chemically with lead to form lead sulfate does not produce a voltage maximum. A decrease in the amount of gas space surrounding the cell results in predictions o5 increased Pb-electrode depolarization.

Section: Introductionmentioning

confidence: 99%

A Mathematical Model of the Oxygen‐Recombination Lead‐Acid Cell

Bernardi

Carpenter

1995

“…Eq. 17 becomes [33] When m is very large, we can make the following approximation [34] And we can obtain [35]…”

Section: Discussionmentioning

confidence: 99%

“…[33][34][35][36][37] Many authors believe that the adsorption of OH radicals occurs first on the surface of PbO 2 , then two OH radicals dehydrate to form an O atom, and finally two O atoms combine to form oxygen molecules. Among these elementary steps, the first step in which H 2 O is oxidized and OH is adsorbed is rate-determining.…”

Section: Literature Studymentioning

confidence: 99%

“…Kinetics of oxygen evolution.-Much work has been carried out on the mechanism of oxygen evolution on both solid Pb electrodes and porous electrodes, 10,[30][31][32][33] and on the recombination mechanism of oxygen that occurs on the negative plates of VRLA batteries. [33][34][35][36][37] Many authors believe that the adsorption of OH radicals occurs first on the surface of PbO 2 , then two OH radicals dehydrate to form an O atom, and finally two O atoms combine to form oxygen molecules. Among these elementary steps, the first step in which H 2 O is oxidized and OH is adsorbed is rate-determining.…”

mentioning

confidence: 99%

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Rate‐Determining Step Investigations of Oxidation Processes at the Positive Plate during Pulse Charge of Valve‐Regulated Lead‐Acid Batteries

Guo

Groiss

Döring

et al. 1999

In order to develop electric vehicles (EVs), electrochemical scientists and engineers have paid great attention to the study of batteries in recent years. Now, while new types of batteries are still in development, the valve-regulated lead-acid (VRLA) battery is a near-term candidate for EV applications in mass markets. 1 A key usage issue is the possibility of fast recharge. More recently, much work has been carried out on pulse charging of lead-acid batteries. 2-7 The recharge time for valve-regulated lead-acid batteries has been reduced and is now less than 5, 15, and 240 min for 50, 80, and 100% charge. However, many other problems arise from pulse charging such as reduced cycle life of the battery, corrosion of the positive-electrode grid, loss of electrolyte, and thermal management. To enhance the pulse charging of a VRLA battery, it is important to understand the detailed processes during the charge. Therefore, attention has to be paid to the kinetics of important processes during pulse charging. Although many papers have reported on the mechanism of the oxidation processes at the PbSO 4 /PbO 2 electrode and the positive plate, 8-29 this remains a subject of research. It is necessary to study further the electrode kinetics of the positive plate in VRLA batteries under pulse charging conditions. Experimental The tested battery was a 2 V 4.2 Ah VRLA battery with gel electrolyte, produced by Sonnenschein Lead-Acid Battery Company. The pulse charge system, controlled by a computer, is a self-made system. The maximum output current and voltage are 100 A and 10 V, respectively. The rise time of the analog circuit is less than 1 s/A. The control period of the digital circuit is 2 ms. The internal pressures of the gas in the battery were measured by a pressure sensor. The relative pressures of oxygen and hydrogen were measured with a micropipette of 0.5 mm internal diam and 8 cm length, which linked the battery to a quadripole mass spectrometer (Balzers QMS 402). All potentials were measured vs. a Hg/Hg 2 SO 4 /H 2 SO 4 (sp gr 1.28) reference electrode, which was linked to the battery by a proton-conducting polymer bridge. The infrared (IR)-corrected potentials were measured by imposing an instantaneous open circuit. Different interactive pulse charging and discharge/constant-voltage procedures were used, and the current profiles are shown in Fig. 1. Their average current was 15.5 A. The maximum limit voltage with IR compensation was 2.45 V at 25ЊC and it is also compensated by a temperature coefficient with Ϫ4.5 mV/ЊC, to avoid thermal runaway of the VRLA battery. To simulate the situation of a large battery, the test battery was thermally isolated. Literature StudyDuring recent decades, both oxygen evolution and the oxidation of PbSO 4 to PbO 2 have been studied extensively on solid Pb electrodes and on the positive plates of lead-acid batteries. Different models for the kinetics of both reactions have been put forward.A model with hydration structure carried out much work on the kinetic processes of the PbSO 4...

“…properties [22][23][24]. The concentration profile of oxygen in the separator region can be linearized approximately to give the limiting current for diffusion according to Fick's first law…”

mentioning

confidence: 99%

Float Charging of Valve‐Regulated Lead‐Acid Batteries: A Balancing Act Between Secondary Reactions

Berndt¹,

Teutsch²

1996

The behavior of valve‐regulated lead‐acid batteries on float charging is influenced by many interacting parameters. A mathematical model has been developed that describes the effects of kinetic cell parameters, float voltage (or current), and temperature on electrode potentials and rates of electrode reactions. The considered reactions are: hydrogen evolution, oxygen evolution, oxygen reduction, grid corrosion, and discharge of active material that may occur under unfavorable conditions. This model, combined with selected experiments, is a very effective tool for surveying the complex situation during float charging. It can also be applied to vented batteries. With model simulations, some fundamental relationships have been shown: when the oxygen reduction efficiency is near 100%, the kinetics of hydrogen evolution and grid corrosion govern electrode polarization at specified float conditions. To achieve a long service life, the rates of water loss and grid disintegration have to be small, and simultaneously a satisfactory state of charge of the battery is required. Hence, the optimum design of a valve‐regulated battery requires a high and balanced hindrance of hydrogen evolution and grid corrosion. Furthermore, small rates of oxygen evolution are favorable. Oxygen intake from the surroundings by a leakage may cause discharge of the negative electrodes. The model helps to estimate the maximum size of such a leakage that can be tolerated. Temperature has not only a marked effect on all the reaction rates, but also influences electrode polarization and the delicate balance of currents, because the activation energies of the various processes differ.