Fundamental studies of lead-acid cell reactions

The electrode system normalPb/normalPbO normallayer/PbSO4 normalmembrane/H2SO4 solution forms when a lead electrode immersed in an H2SO4 solution is in the potential range between −400 and +960 mV (vs. the normalHg/HgSO4 electrode). When the electrode potential is raised above +960 mV the normalPbO and PbSO4 layers are oxidized to PbO2 . The mechanism of this oxidation is determined by the electric properties and the crystal structure of normalPbO and PbSO4 . The paper deals with the electrochemical behavior of the electrode during potential sweeps from the normalPbO into the PbO2 potential ranges. It was found that first normalPbO is oxidized via solid‐phase reactions to nonstoichiometric PbOn without a change of its crystal structure. This takes place via the electrochemical reactionknormalPbO+m2 H2O=kPbOn+mH++me−which proceeds at the normalPbO/normalsolution interface. Since PbOn is a semiconductor, the oxidation of the Pb2+ ions in its crystal lattice probably takes place through a mechanism in which surface states and mobile acceptors take part. Such are O− and O, evolved during the reaction of oxygen evolution. When n reaches a critical value n=d , α‐PbO2 nucleation commences in the pores of the PbSO4 membrane. When this phase reaches the H2SO4 solution the oxidation of PbSO4 crystals to β‐PbO2 begins. This takes place according to the mechanismdissolution of PbSO4→diffusion of Pb2+ normalions→oxidation of Pb2+ at the PbO2 normalsurface→normalprecipitation of β‐PbO2The dissolution of PbSO4 crystals begins at the apexes of the crystals and continues at their edges and faces.

“…The current passes through a maximum and begins to decrease (Fig. [8][9][10][11]. The water, which is evolved in reaction [8], supplies for some time reaction [4] with OH-ions.…”

Section: Formation Of A-pboz Phase During Pbon Oxidation-mentioning

confidence: 99%

“…During the last decade linear sweep voltammetry was used to study the anodic layer oxidation to PbO2 layer (5)(6)(7)(8)(9)(10)(11). These papers contain considerable information concerning the behavior of the lead electrode both on anodic polarization and cathodic reduction of the PbO2 layer.…”

mentioning

confidence: 99%

Mechanism of the Electrochemical Oxidation of Lead to Lead Dioxide Electrode in H 2 SO 4 Solution

Pavlov

Dinev

1980

“…On the other hand, fundamental studies have been made of specific phenomena in the electrodes of the lead-acid battery. Studies have thus been reported on the electrocrystallizafion of lead dioxide from lead sulfate formed on smooth electrodes of electrodeposited lead dioxide or lead (5)(6)(7)(8).…”

mentioning

confidence: 99%

Recharge Kinetics of the Porous Lead Dioxide Electrode: I . The Effect of Structural Changes

Ekdunge¹,

Simonsson²

1985

The changes in structure and kinetics during charge of the porous PbO2 electrode have been studied by means of electrochemical and structure characterizing methods. It was found that the potentiostatic charge current after an initial period of growth, due to nucleation and growth of PbO2 , is proportional to the decreasing amount of remaining lead sulfate. The polarization curves have a Tafel slope of about 60 mV/decade at overvoltages lower than 0.1V and about 180 mV/decade at higher overvoltages. The form of these curves can be explained by a mechanism with two consecutive single‐electron transfer reactions. The results from these specific studies of the positive electrode and charge experiments with complete lead‐acid cells show that the fastest way to charge lead‐acid batteries is to charge at a constant cell voltage of a value just below that which leads to unacceptable gassing rates.

“…[16][17][18][19][20][21][22] However, from the data in Fig. 2, we believe that PbO 2 electrocrystallization is not a slow step in the pulse charge.…”

Section: Mass Transfer Of O Atoms In Pulse Charge-many Authors Havementioning

confidence: 84%

“…17 and obtain [19] To simplify Eq. 19, we calculate the difference of the following two series [20] where "ϩ" is for on-time and "Ϫ" for off-time. Because the sum of the series on the right of Eq.…”

Section: Mass Transfer Of O Atoms In Pulse Charge-many Authors Havementioning

confidence: 99%

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...