Study of electrode processes in Pb/H2SO4 + additive systems

Materialwissenschaft Werkst

2011

Effect of phosphoric acid on the performance of Pb-1.7%Sb grid of lead-acid cell is studied in 5 M H 2 SO 4 by cyclic galvanostatic polarization and impedance spectroscopy. An increase in capacitance to a maximum is recorded during the initial stages of the electro-reduction of PbO 2 into Pb(II) compounds and attributed to concurrent compositional and dimensional changes. These changes include removal of O 2 bubbles, insertion of large amounts of H 2 SO 4 and H 2 O. Efficiency of PbO 2 formation decreases, while its rate of self-discharge increases with increasing the charging current and in the presence of H 3 PO 4 . The charge capacity increases with increasing the discharging current due to the decrease in the self-discharge. The charge capacity is lower in the presence of H 3 PO 4 . On increasing the cycle number, the corrodibility of the grid increases, because more layers of the surface Pb are involved in the self-discharge. H 3 PO 4 significantly retards the effect of cycle number.

Section: Effect Of Charging Currentsupporting

confidence: 71%

Section: Introductionmentioning

confidence: 99%

Effect of phosphoric acid on the performance of low antimony grid of Pb‐acid cell under constant current charging and discharging

El-Rahman¹,

Salih²,

Materialwissenschaft Werkst

2011

“…14,16,17) Some electrochemical studies have indicated improvement of the formation of PbO 2 with the addition of H 3 PO 4 13,14) but the results of other studies supported the opposite effect. 5,7,11,14,22) One of the main reasons of the lead-acid battery failure is the severe corrosion of the anode grid during service due to the self-discharge. The effect of H 3 PO 4 addition on the performance of the battery grids under oxidation and during the self-discharge seems to be an important part in the evaluation of H 3 PO 4 as an economic electrolyte additive.…”

Section: Introductionmentioning

confidence: 60%

Effect of Phosphoric Acid on the Electronic and Diffusion Properties of the Anodic Passive Layer Formed on Pb-1.7%Sb Grid of Lead-acid Batteries

El-Rahman¹,

Salih²,

Journal of Electrochemical Science and Technology

2011

:Potentiostatic oxidation of Pb-1.7%Sb alloy used in the manufacture of grids of lead-acid batteries over the potential range from −1.0 V to 2.3 V in 5 M H 2 SO 4 in the absence and the presence of 0.4 M H 3 PO 4 and the self-discharge characteristics of the oxide layer formed is studied by electrochemical impedance spectroscopy (EIS). Depending on the potential value, sharp variations in resistance and capacitance of the alloy are recorded during the oxidation and they can be used for identification of the various substances involved in passive layer. Addition of H 3 PO 4 is found to deteriorate the insulating properties of the passive layer by the retardation of the formation of PbSO 4 . H 3 PO 4 completely inhibits the current and impedance fluctuations recorded in H 3 PO 4 -free solutions in the potential range 0.5 V-1.7 V. These fluctuations are attributed to the occurrence of competitive redox processes that involve the formation of PbSO 4 , PbOSO 4 , PbO and PbO 2 and the repeated formation and breakdown of the passive layer. Self-discharge experiments indicate that the amount of PbO 2 formed in the presence of H 3 PO 4 is lesser than in the H 3 PO 4 -free solutions. The start of transformation of PbSO 4 into PbO 2 is greatly shortened. H 3 PO 4 facilitates the diffusion process of soluble species through the passive layer (PbSO 4 and basic PbSO 4 ) but impedes the diffusion process through PbO 2 .

“…H 3 PO 4 is reported to be helpful in reduction of the sulfation after deep discharge, 1,[7][8][9][10] increasing the life cycle, 1,7,8,15) slowing down the discharge. 14) It decreases the capacity 11) and increases the overpotentials of both hydrogen and oxygen evolution reactions. 14,16,17) Some electrochemical studies have indicated improvement of the formation of PbO 2 with the addition of H 3 PO 4 13,14) but the results of other studies supported the opposite effect.…”

Section: Introductionmentioning

confidence: 99%

“…14) It decreases the capacity 11) and increases the overpotentials of both hydrogen and oxygen evolution reactions. 14,16,17) Some electrochemical studies have indicated improvement of the formation of PbO 2 with the addition of H 3 PO 4 13,14) but the results of other studies supported the opposite effect. 5,7,11,14,22) One of the main reasons of the lead-acid battery failure is the severe corrosion of the anode grid during service due to the self-discharge.…”

Section: Introductionmentioning

confidence: 99%

Effect of Phosphoric Acid on the Electronic and Diffusion Properties of the Anodic Passive Layer Formed on Pb-1.7%Sb Grid of Lead-acid Batteries

El-Rahman¹,

Salih²,

J. Electrochem. Sci. Technol

2011

Potentiostatic oxidation of Pb-1.7%Sb alloy used in the manufacture of grids of lead-acid batteries over the potential range from −1.0 V to 2.3 V in 5 M H 2 SO 4 in the absence and the presence of 0.4 M H 3 PO 4 and the self-discharge characteristics of the oxide layer formed is studied by electrochemical impedance spectroscopy (EIS). Depending on the potential value, sharp variations in resistance and capacitance of the alloy are recorded during the oxidation and they can be used for identification of the various substances involved in passive layer. Addition of H 3 PO 4 is found to deteriorate the insulating properties of the passive layer by the retardation of the formation of PbSO 4. H 3 PO 4 completely inhibits the current and impedance fluctuations recorded in H 3 PO 4-free solutions in the potential range 0.5 V-1.7 V. These fluctuations are attributed to the occurrence of competitive redox processes that involve the formation of PbSO 4 , PbOSO 4 , PbO and PbO 2 and the repeated formation and breakdown of the passive layer. Self-discharge experiments indicate that the amount of PbO 2 formed in the presence of H 3 PO 4 is lesser than in the H 3 PO 4-free solutions. The start of transformation of PbSO 4 into PbO 2 is greatly shortened. H 3 PO 4 facilitates the diffusion process of soluble species through the passive layer (PbSO 4 and basic PbSO 4) but impedes the diffusion process through PbO 2 .