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

Abstract

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...

A Mathematical Model for the Simulation of New and Aged Automotive Lead-Acid Batteries

“…The first mathematical models appeared at the beginning of the 1970s when computers enabled the development of this kind of application. These models, [1][2][3][4][5][6][7][8][9][10][11] detailed in Table I, were progressively applied to the lead-acid electrodes and cells of flooded batteries. Since the 1990s, they have been applied to sealed batteries.…”

“…11 The results obtained at a high current density ͑Ͼ100 mA/cm 2 ͒ and a normal acid concentration ͑5 M͒ demonstrate that the available capacity of the negative electrode is limited by a thickness of insulating PbSO 4 like in the positive one. More recently, the positive electrode gassing of sealed battery, under pulse current in charge, was studied by Guo et al 6 The proposed model showed that the electrode polarization, oxygen evolution, and loss of water can be inhibited by using a pulse discharge and/or by prolonging the off time of the pulse charge.…”

Mathematical Modeling of Current-Interrupt and Pulse Operation of Valve-Regulated Lead Acid Cells

“…It should be noted that there are reports in the literature of considerable higher exchange current densities for the reaction. For example, LaFollette and Bennion 28 use a value of 1.78 mA/cm 2 , while Guo et al 29 and Carr and Hampson 30 use 0.32 mA/cm 2 , all three authors suggesting that the electrode reaction is facile. The latter value appears to have originated from a paper by Aguf, 31 where the exchange current density of this reaction was measured using impedance spectroscopy.…”

Investigation of Active Mass Utilization of Positive Plate in Automotive Lead-Acid Batteries

“…The pulsedcurrent charge not only shortens the charge time but also overcomes PCL 2 and hence prolongs the cycle life of the batteries. [9][10][11][12] In an optimized design, the ratio of the active mass between the positive and negative plates is important to the battery life. 13,14 As the utilization of PAM is much lower than that of the negative active mass, great attention has been paid to the investigations on PAM utilization in the past decades.…”