Journal of Energy Storage 7 (2016) 121–130

Contents lists available at ScienceDirect

Journal of Energy Storage

journal homepage: www.elsevier.com/locate/est

Effects of surfactants on sulfation of negative active material in lead

acid battery under PSOC condition
Robab Khayat Ghavami* , Fatemeh Kameli, Ali Shirojan, Amir Azizi
R & D Center, Tavan MFG. Co., P.O. Box 19575-361, Tehran, I.R., Iran

A R T I C L E I N F O A B S T R A C T

Article history:
Received 8 December 2015 Lead–acid battery performance is severely limited to negative plate sulfation (irreversible formation of
Received in revised form 6 June 2016 lead sulfate).The influence of surfactants types in lead-acid battery electrolyte has been investigated on
Accepted 13 June 2016 the sulfation of negative active material (NAM) under high-rate partial-state-of-charge (HRPSoC)
Available online xxx opreation. However, it is still an open investigation to explore that how to make the lead sulfate crystals
more electrochemically active and how surfactants affect on their pattern growth. This research
Keywords: demonstrates that various surfactants have different effects on NAM sulfation using XRD (X-ray
Lead-acid battery diffraction), SEM (scanning electron microscopy), CV (cyclic voltammetry) and EIS (electrochemical
Performance
impedance spectroscopy) techniques, which in some cases their behaviors are conversely. Amongst all
Sulfation
tested surfactants, the cell with anionic sodium dodecyl sulfate surfactant (SDS) exhibits the longest cycle
Partial-state-of-charge regime
Surfactant life with the least overcharge and fine PbSO4 crystals. The cell with cationic cethyl trimethyl ammonium
bromide (CTAB) surfactant shows opposite effects.
ã 2016 Elsevier Ltd. All rights reserved.

1. Introduction expander component (lignosulfonate), being a surface active

polymer, is adsorbed on the Pb surface and prevents the formation
Irreversible formation of the lead sulfate in negative active of a continuous PbSO4 layer on the electrode surface [9]. The other
material (NAM), which is called sulfation or hard sulfate, has expander component, barium sulfate, provides nuclei for the
plagued battery engineers for many years. It has also been a main growth of numerous small PbSO4 crystals, forming a porous layer
cause of failures in lead-acid batteries. This type of lead sulfate instead of the continuous PbSO4 film [10].
cannot, or only partially, be returned to its electrochemically active Many efforts have been performed on the development of
state. Thus, a corresponding loss of capacity and hydrogen several new features like stop-start cycling in micro hybrid
evolution take place in early stages of the charging. Usually, vehicles, but this application requires battery that operates
negative plates have more trends to be sulfated, than positive continuously at partial-state-of-charge (PSoC) condition and also
plates [1]. to be charged and discharged at high rates (HRPSoC) [11–15].
It is important to know that how the sulfation occurs in Different methods were suggested e.g. addition of carbon black
negative plates. The kinetic and mechanism of lead sulfate [16] and Bismuth material [17] electrochemical conversion of lead
formation on the lead electrodes in sulfuric acid solution progress sulfate to lead which prepared from lead acetate and sodium
in three main mechanisms [2–5]: (a) dissolution-precipitation sulfate solution in presence of SDS and poly(vinyl pyrrolidone)
reaction [6] (b) solid-state mechanism [7] (c) a complex path way (PVP) [18] in order to overcome formation of large lead sulfate
[8]. during cycling. Many researchers have reported that the
In order to avoid the formation of hard sulfate during cycling, adsorption of surfactants on the metal surface can markedly
the negative paste must be contained the expanders. Nowadays, change the corrosion-resisting property of metal [19,20] that help
advances in lead-acid batteries include the usage of additives and to realize the relations between the adsorption and corrosion
the modified charging methods to obtain the beneficial effect on inhibition.
the charge acceptance and the crystal morphology. The organic Surfactants have been widely applied in battery systems to
improve the electrochemical performance through increment of
the hydrogen evolution potential, inhibition of the metal corrosion
and/or modification the crystals morphology. Surfactants with a
* Corresponding author. long hydrophobic C H chain and a hydrophilic head group can be
E-mail address: robab.ghavami@gmail.com (R. Khayat Ghavami).

http://dx.doi.org/10.1016/j.est.2016.06.002
2352-152X/ã 2016 Elsevier Ltd. All rights reserved.
122 R. Khayat Ghavami et al. / Journal of Energy Storage 7 (2016) 121–130

adsorbed at hydrophobic electrode surface. They change the electrode for measuring the potential of negative plate during
electrode/solution interface properties that affect on the electro- cycling. All potentials were reported with respect to this electrode.
chemical process of electro active species [21,22]. According to A sulfuric acid electrolyte with 1.28 s.g. was used in this
Ritchie [23,24] and Willihnganz [25], the lead sulfate crystals with experiment. There was 1.89 cm3 of sulfuric acid solution for every
high porosity are formed during discharge as the consequence of gram of paste. The cells with different kinds of surfactant are
partial coverage of lead sulfate by the organic material adsorption, presented in Table 1. The surfactant content in H2SO4 solution was
while a limitation of the lead crystals size occurs during charge. It determined 50 ppm that was below the critical micelle concentra-
has been also found that presence of perfluorinated surfactant in tion point (CMC) for every surfactant. All electrochemical
positive active materials (PAM) cause excellent surface activity measurements and cycling tests were carried out by using battery
and/or cycle life [19]. In our previous researches [26,27], the test system, Solartron 1470A, at 25  C.
influences of surfactants on performance characteristics of Zn- Calculation of the conversion indicator is a rapid and useful
MnO2 batteries was reported that their behaviors are very complex procedure for investigation of additives affects on charging ability
and depend on their concentration and negative or positive of negative plates, which is proposed by Lam [17]. Although the
charged head groups of surfactants. It was found that the conversion indicator is not as same as charging efficiency, but these
adsorption of surfactants on electrodes can have large effects on two parameters have a close relation. On the other hand, the higher
kinetic of electron transfer and consequently on the pattern conversion indicator causes to the greater charging efficiency. The
growth of metal atoms. conversion indicator refers to ratio between charge input (Icttp) up
With regard to behavior of the negative plates, which markedly to the turning point and the previous discharge capacity (Idtd) that
affects on the PSoC service in lead-acid cells, the effect of can be calculated by the following equation:
surfactants (cationic cetyl trimethyl ammonium bromide (CTAB),
Ic ttp =Id td  100%
anionic sodium dodecyl benzene sulfonate (SDBS), sodium dodecyl
sulfate (SDS) and nonionic t-octyl phenoxy poly ethoxy ethanol
(Triton X-100) are determined with the aim to suppress the 2.2. Cycling regimes Zero percent SoC/full-charge cycling and PSoC
accumulation of large lead sulfate to improve the performance of cycling regime
lead-acid cells under PSoC duty. The electrochemical character-
izations are performed by cyclic voltammetry (CV) and the The effect of surfactant on the performance characteristic of the
electrochemical impedance spectroscopy (EIS) in a three-electrode negative plate was determined from the performed initial capacity
system. In this research, different techniques have been employed tests on cells. The negative plate was discharged at 2.2A (1 h rate)
for characterization of negative electrodes such as scanning until the potential fell to 0.6 V, which corresponds to state of
electron microscopy (SEM) and X-ray diffraction (XRD) that proved charge (SoC0).
to be particularly successful. In PSoC cycling regime, the cells were successfully operated in
14 cycles through four different PSoC windows, respectively, 90–
2. Experimental methods 60%, 70–40%, 80–40% and 90–40%, (Fig. 1). In each PSoC window,
the cell was discharged at 2.2A and recharged at 1.1A with an equal
2.1. Cell construction for investigation negative plate properties amount of charge input and charge output. End-of-discharge (EoD)
and end-of-charge (EoC) potentials of the negative plates were
Charge/discharge cycles were carried out in laboratory cells. All recorded during cycling. The conversion indicator was determined
positive and negative plates and separators, which have been for each cycle.
applied in this research, were furnished by Niru Battery Company. In PSoC operation, the battery cycles over a relatively small
The negative electrode paste was prepared with 4.5% sulfuric acid/ range centered on some intermediate state-of-charge, which
leady oxide ratio (75% degree of oxidation), 0.4% Vanispers-A, 0.8% causes PSoC operation to offer two major advantages.
BaSO4 and 0.2% Carbon black and their grids are consist of Pb-
0.09 wt% Ca-0.3wt%Sn in (12 V sealed battery 3Ah) 12SB3 1. It avoids the battery spending time near the gassing zone at top-
motorcycle battery. of-charge.
The used flooded cells comprised of two positive and one 2. It does not give rise to large volume change related stresses in
negative plate with dimensions (68 mm *40 mm *2.9 mm as height, the active masses [28].
width and thickness, respectively) and poly vinyl chloride (PVC) as
separator sheets. The nominal capacity of mentioned cell was
2.1 Ah when discharged at the 5-h rate (C5/5 = 2.1A.h). The amount
of negative active materials in each electrode was about 28 g. 2.3. Scanning electron microscopy(SEM)/X-ray diffraction(XRD)
Surfactant was added to electrolyte solution after formation. The
cell was then charged fully with a constant current of 0.5 A for 10 h. The negative plates are rinsed with double distillated water to
A mercury/mercurous sulfate electrode was used as reference remove the H2SO4 and dried under vacuum with appropriate

Table 1
The specifications of different kinds of surfactants and their cells name.

Surfactant Kinds of Concentration Abbreviated cell Molecular Chemical Critical micelle concentration (CMC)
surfactant (ppm) name weight formula (mM)
Cetyl trimethyl ammonium bromide cationic 50 CTAB-NAM 364.45 C19H42BrN 1
(CTAB)
Sodium dodecyl benzene solfonate anionic 50 SDBS-NAM 348.48 C18H29NaO3S 1.6
(SDBS)
Sodium dodecyl solfate (SDS) anionic 50 SDS-NAM 288.372 NaC12H25SO4 8
t-octyl phenoxy polyethoxyethanl Non-ionic 50 TX-100-NAM 647 C14H22O 0.22–0.24
(Triton X-100) (C2H4O)n
Without surfactant – – standard-NAM – –
 R. Khayat Ghavami et al. / Journal of Energy Storage 7 (2016) 121–130 123

Fig. 1. PSoC cycling regime.

conditions. Scanning Electron microscopy (SEM) was used to study commercially available lead salts have very low solubility in
the morphology of negative plate after PSoC cycling. X-ray concentrated sulfuric acid solutions, it is very difficult to identify
diffraction (XRD) patterns were recorded using a Philips Xpert the nature of the dissolved species in very strong acidic medium.
diffractometer and Cu Ka radiation (l = 0.15418 nm) to determine Thus, a saturated solution of Pb2+ ions was prepared in 1.5 M H2SO4
composition of discharged plates. The size of PbSO4 particles for to assist stronger anodic film formation.
different discharged negative plates was calculated from the full The impedance spectrum was measured in the frequency range
width at the half maximum (FWHM) of [2 1 1] diffraction lines 105–1 Hz with amplitude of the sine signal of 5 mV after 50th cyclic
using Sherrer equation. voltammetry test to understand properties of the formed films by
means of Autolab PGSTAT 30 at open circuit potential.
2.4. Cyclic voltammetry and impedance measurements
3. Results and discussion
Electrochemical laboratory tests were carried out with a pure
lead electrode embedded in Teflon polymer to have a flat circular 3.1. Performance of cells under SoC0 and simulated PSoC duty
exposed area of about 1 cm2 as working electrode. Also, a larger
platinum sheet and a Hg/Hg2SO4 electrode with a Luggin capillary The negative plates were discharged at 2.2 A (1 h rate) until the
were used as a counter and reference electrode in all experiments. potential fell to 0.6 V in SoC0 test. The discharge curves of all cells
Pre-treatment of lead electrode surface was implemented as are shown in Fig. 2. It presents that the addition of anionic SDBS to
described by Francia et al. [29]. Cyclic voltammetry was performed electrolyte provides the highest discharge capacity, causing deeply
after addition of chosen surfactant to the solution (50 ppm) by discharge of NAM compared with standard cell. In contrast to
means of Autolab PGSTAT 30 in the range 1.3 V to 0.7 V at a SDBS, CTAB-NAM cell shows the lowest discharge capacity. SDS-
constant scan rate of 5 mV s 1 at room temperature. Since the NAM and TX-100-NAM cells almost have the same capacity but

Fig. 2. The first discharge curves and initial capacity for all cells.
124 R. Khayat Ghavami et al. / Journal of Energy Storage 7 (2016) 121–130

SDS-NAM cell has a bit larger capacity than TX-100-NAM cell. All of SDS-NAM. In comparison with acidic medium without surfactant
these surfactant-NAMs present more capacity compared with (standard), the EoDP of the plate in presence of CTAB decreases
standard. slowly over 29 cycles, and then the experiences rapid decline to
In PSoC condition, all plates, which have been cycled under 0.6 V.
different state of charge windows were particularly discharged and The EoDP of SDS plate decreases with cycling, but at a much
charged with an equal output and input charge. Therefore, in each slower rate than the others. This cell completed 56 cycles.
PSoC cycle, the plates always receive insufficient charge, which EoCP of CTAB-NAM, SDBS-NAM and standard cell stayed mainly
causes the decrease in the end-of-discharge potential (EoDP) of at 1.45 V but EoCP of TX-100-NAM and SDS-NAM is respectively
plates during cycling. This feature is indicative of undercharging of maintained at 1.35 and 1.4 V for longer time in all SoC windows.
plates, whilst an increase in the end-of-charge potential (EoCP) The EoCP values of all plates are decreased as follows:
suggests overcharging. The charging is sufficient when the EoDP is SDS-NAM > TX-100-NAM > standard > SDBS-NAM > CTAB-NAM
constant. Therefore, the cationic CTAB surfactant decreases the over-
The EoDP and EoCP of negative plate are shown in Fig. 3(a). All charging potential. Probably, CTAB accelerates the accumulation of
plates display a decrease in the EoDP, the overall decline is faster in large lead sulfate by enhancing the evolution of hydrogen.
this order: CTAB-NAM > standard > SDBS-NAM > TX-100-NAM >

Fig. 3. Negative plates performance in the presence of various surfactants in electrolyte (a) EoC and EoD potential (b) The percent of conversion indicator.
 R. Khayat Ghavami et al. / Journal of Energy Storage 7 (2016) 121–130 125

Fig. 4. The X-ray diffraction patterns of the discharged negative plates after PSoC cycling, the labeled diffraction lines refer to (*: Pb), (S: PbSO4), (B: Basic lead sulfate) and
(without symbol: PbSO4). The inset images show the surface photographs (a) Standard-NAM, (b) CTAB-NAM, (c) SDBS-NAM, (d) SDS-NAM and (e) TX-100-NAM.
126 R. Khayat Ghavami et al. / Journal of Energy Storage 7 (2016) 121–130

The conversion indicator of all cells is presented in Fig. 3(b). In Table 2

The amounts of PbSO4 formed and the size of PbSO4 particles in the discharged
90–60% SoC window, conversion indicators of all plates start to
NAM after PSOC cycling for all cells with different kinds of surfactant.
increase. The conversion indicator of the standard cell has high
starting value compared with SDS-NAM, but it becomes constant Sample Amount of PbSO4 (wt%) Particle size (Å)
to about 93%. After early cycles, the conversion indicator of CTAB- CTAB-NAM 79.9 610.3
NAM cell falls slowly. At the first cycle, SDS-NAM cell shows low Standard-NAM 68.1 483.3
SDBS-NAM 78.9 386.7
value of conversion indicator but it starts to increase at much rapid
SDS-NAM 48.4 366.1
rate, which approach to 100%. TX-100-NAM 62 366.2
In 70–40%, conversion indicator of standard and SDBS-NAM
have almost similar changes and SDBS-NAM displays a close
performance to standard. They decrease slowly at first and then
remain constant at 86%. This factor for CTAB-NAM is constant at
84% initially and then rapid decline to 77%. On the other hand, it Table 2 shows the size of PbSO4 particles and the amounts of
displays the lowest charging ability and the shortest cycle life. TX- PbSO4 formed in all cells. The size of PbSO4 particles was calculated
100-NAM cell maintains conversion indicator for about 95% but at from scherrer equation of [2 1] PbSO4 diffraction lines, which had
end of window, it falls to 92%. In this window, SDS-NAM shows minimum overlapping. The size of the formed PbSO4 particles
decrease in conversion indicator and then remains constant at shows decrease in this order: CTAB-NAM > Standard > SDBS-NAM >
about 93%. SDS-NAM and TX-100-NAM. According to Table 2, it is concluded
In 80–40% window, SDS-NAM cell shows improving effects over that large amount of PbSO4 crystals were formed in CTAB-NAM
the TX-100-NAM cell while both of them become constant at 89% negative plate, then the cell rapidly lost capacity on cycling
and 86%, respectively. Standard-NAM fails after 37 cycles while its because of limited discharge of the negative plate in presence of
conversion indicator is 78%. SDBS-NAM cell completes 42 cycles cationic CTAB surfactant. As a result, the premature failing of CTAB-
and it fails at 74%. NAM cell is due to the formation of coarse PbSO4 crystals with the
In 90–40% window, the conversion indicator of SDS-NAM is largest in size. The conversion of lead to lead sulfate affected by
almost constant all over the window. It completes 56 cycles and surfactant molecules due to the changes in intensity of the
shows the longest cycle life. In the other words, SDS-NAM cell characteristic X-ray diffraction lines for PbSO4 crystals and the
shows the best charging ability at the end of cycling. TX-100-NAM corresponding electrochemical capacity of these cells. Thus, the
cell fails after 48 cycles while it has lower value of conversion improvement of PSoC cycling in SDS-NAM cell can be related to the
indicator than SDS-NAM cell in last two windows. formation of the modified PbSO4 crystals with small size.
The above results show clearly that cycle life increases in this
order:
CTAB-NAM < SDBS-NAM < standard < TX-100-NAM < SDS- 3.3. SEM characterization
NAM
There is another important finding from this study. The The morphology of NAM crystals growth in the discharged cells
negative plates had the best charging ability when cycled over a was observed by scanning electron microscopy (SEM). Fig. 5 shows
low and narrow PSoC window, e.g. 70–40% SoC. In most widows for the SEM micrographs of the discharged NAM after PSoC cycling.
SDS–NAM and TX-100-NAM cells, there were low fluctuations by In standard (see Fig. 5(a)), there are different forms of micron
conversion indicator. As a result, homogenous reactions take place dimensional particles with round and needle shapes and many
on NAM because of less hydrogen evolution and high charge created macro pores after PSoC cycling that cause to decline the
acceptance during cycling. In contrast to above cells (SDBS–NAM), mechanical strength.
standard and CTAB-NAM cells presented low charging ability. In Fig. 5(b), there are large (10 mm) and non-uniform particles
of PbSO4 with dendritic and needle forms on negative plate which
3.2. XRD characterization is a common occurrence in the presence of CTAB. It is clear that the
macro pores and the needle growth of negative materials are
The phase composition of the NAM after PSoC cycling was decreased in absence of cationic surfactant, as shown in Fig. 5(a).
determined by X-Ray (XRD) analysis. Fig. 4 shows the photographs Therefore, the formation of large and the dendritic lead sulfate
of the discharged negative plates that have been taken from the crystals with low reactivity caused the premature failing of CTAB-
surface; the images have been presented with the corresponded NAM cell in high-rate PSoC cycling.
XRD diffractograms. The labeled diffraction lines in Fig. 4 refer to In SDBS-NAM (Fig. 5(c)), the discharged plate consists of mainly
(*: Pb), (S: PbSO4), (B: Basic lead sulfate), (without label: lead micro particles in tetragonal shapes that were identified as PbSO4
sulfate). particles with the size range almost less than 10 mm. It can be
Fig. 4 shows the changes in intensity of the characteristic observed in Fig. 5(c) that lots of particles were formed with
diffraction lines for PbSO4 (3.00 Å) in NAM plate after PSOC cycling. submicron size on large particles surface, which are growing in the
The intensity of the PbSO4 diffraction line changed in presence of empty spaces and probably managed to make micropores during
surfactants (see Fig. 4(b) and (d)). The difference among of cycling.
diffraction lines on X-Ray diffractograms show that the preferred In Fig. 5(d), the surface morphology, the crystal shape, and the
growth of the lead sulfate grains could occur in presence of particles size of NAM are markedly affected by SDS surfactant. This
surfactants. Hence, the crystallographic orientation could be plate consisted of regular and well-defined particles of PbSO4 in
changed by the surfactant adsorption because of the metal surface the presence of SDS. It is obvious that the discharged plate contains
energy modification [30–32]. The set of images that were taken many submicron particles or is made of the poly nano sized crystals
from the discharged NAM after PSoC cycling, show the largest with fine pores that cause suitable mechanical strength on the
macropores and the most destruction of negative plate in presence surface of the discharged plate during cycling.
of CTAB (Fig. 4(b)). However, SDS-NAM cell (Fig. 4(d)) presents a Fig. 5(e) exhibits that the discharged plate of Tx-100-NAM is
uniform structure and very fine pores while the appearance images comprised of larger crystals size and more macropores compared
of other plates show that macropores size are between CTAB-NAM with SDS-NAM. In addition, the nucleation centers on each crystal
and SDS-NAM plates (Fig. 4(a), (c) and (e)). and crystals reactivity decline during cycling.
 R. Khayat Ghavami et al. / Journal of Energy Storage 7 (2016) 121–130 127

Fig. 5. Scanning electron micrographs of NAM after PSoC cycling at 25  C. (a) Standard-NAM, (b) CTAB-NAM, (c) SDBS-NAM, (d) SDS-NAM and (e) TX-100-NAM.

3.4. Cyclic voltammetry oxidation and reduction peaks of SDS surfactant are much stronger
than Standard that is because of difference in conductivity of the
Fig. 6 shows the voltammogram curves in the range of 1.3 V to formed PbSO4. Pavlov [33] suggested that decreasing peak current
0.7 V with a constant scan rate of 5 mV s 1 at room temperature originated from the diminishing surface area due to formation of a
for standard (Fig. 6(a)) and SDS surfactant (Fig. 6(b)) at 1, 10th, less porous film during the cyclic process. Therefore, in this study
20th, 30th, 40th and 50th cycle. It can be observed that during a the applied SDS surfactant can improve electrochemical properties
voltammetric cycle one single electrochemical reaction, which is of the anodic film during cycling, which ensures a better
related to conversion of lead to lead sulfate occurs in the anodic conductivity of the anodic film on lead electrode.
branch of cycle. However, in the cathodic branch, hydrogen ion Mac Donald shows that in the case of an electrode which a
discharge partly occurs together with lead sulfate reduction. All resistive layer is formed, the trend of a voltammetric curve is traced
three processes are influenced by the presence of surfactant. The by a linear potential scan and depends on the change of the layer

Fig. 6. Cyclic voltammograms of a pure lead electrode in 1.5 M H2SO4 (a) standard, (b) containing 50 ppm of SDS.
128 R. Khayat Ghavami et al. / Journal of Energy Storage 7 (2016) 121–130

resistance [34]. According to such interpretation, the slope of the

voltammetric curves is affected by the porosity and thickness of
the layer, which is being formed. In the case of the lead in sulphuric
acid, the changes of the contact resistance are caused by the lead
sulfate layer [29]. When considering the trend and shape of the
voltammetric curves, it must be noted that the SDS surfactant
modify both the anodic and the cathodic branches of the
voltammetric cycles because in the former case, they affect the
structure of the formed lead sulfate while, in the latter case, they
exert an influence on the formation of lead crystals and on
hydrogen evolution.
The voltammetric curves provide the reliable information about
the amount of charge, which has been stored in anodic and
cathodic part of cyclic voltametry when using surfactant, as shown
in Table 3. The area under the anodic and cathodic peaks gives the
involved charge in anodic (Qa) and cathodic (Qc) reaction. The
highest amount of electrical charges (Qa and Qc) were specified in
presence of SDS (as seen in Table 3) compared with standard
Fig. 7. Impedance data on the Nyquist plot determined in the frequency range
during cycling. Adsorption of SDS on the lead surface is induced to
105  1 Hz, in 1.5 M H2SO4 from surface of the grown film after50th cyclic
observe about tenfold increment in Qa compared with standard at voltametry scanning with SDS surfactant and without surfactant (standard).
50th cycle. Since lead sulfate is formed more easily on the lead
surface due to high reactivity of the lead surface with SDS but standard causes the formation of high resistive PbSO4 layer on
adsorption. It concluded that SDS adsorption notably affects both the lead surface with the low capacitance.
cathodic and anodic electrochemical behavior of lead in sulphuric
acid, namely it affects both hydrogen evolution and lead sulfate 3.6. Mechanism of lead sulfate accumulation in negative plates under
formation. HRPSoC duty

3.5. Electrochemical impedance spectroscopy When a PbSO4 layer is formed and passivates the electrode
surface, the stability of the passivated surface depends on structure
The EIS is a powerful, nondestructive, and informative of PbSO4 layer, which formed under different conditions [36].
technique that has been usually used in studies of lead-acid Researchers believe that dissolution-participation processes in
batteries [35]. This method was used to investigate the anodic negative plate reaction actually proceed in two stages during
charge transfer resistance of anodic film that was formed after charging, dissolution of lead sulfate (chemical reaction), deposi-
cyclic voltametry at open circuit potential and 25  C. The tion of metallic lead (electrochemical reaction), and a solid-state
impedance spectrum is measured in the frequency range 105– reaction can take place by direct attack of sulfate anion on lead
1 Hz with amplitude of the sine signal of 5 mV after 50th cyclic sulfate [37]. During charging, most of PbSO4 crystals have been
voltammetry test to understand properties of the formed films. converted to lead and correspondingly the sulfuric acid concen-
Fig. 7 displays the Nyquist plots that are obtained from surface of tration is increased. Further, dissolution of PbSO4 to Pb2+ and SO42
the SDS film and the standard film. The EIS data reveals that each decrease. If the dissolution of PbSO4 is hindered, hydrogen can also
impedance diagram almost consists of semicircles (capacitive be evolved during the early stages of the charging process.
loops). The charge transfer resistance (Rct) and double-layer Therefore, charging of the negative plate after deep discharge at
capacitance (Cdl) for SDS surfactant and standard were estimated high-rate is difficult. High-rate discharge cannot proceed into the
from a semi-circular fit with Ri (RctC) equivalent circuit in the interior of the plate, but it stops at the surface. Thus, the utilization
Nyquist plots that Rct Cdl parallel circuit with Ri, the ohmic of the active material is low. Consequently, the relative density of
resistance is in series. This circuit represents the model of a simple the acid during charge is still at high level that it decreases the
faradic reaction. Ri, the ohmic resistance is determined mainly by dissolution of PbSO4.
the conductivity of the electrolyte and the electrical pathway. Rct The competition between growth and nucleation determines
and Cdl describe the transient behavior, which is caused by the the granularity of the deposit. The growth form is confined by faces
charge-transfer reaction in combination with the double-layer having the lowest normal growth rate as described by Buderski
capacitance at the surface of the electrodes. Table 4 shows that the [30]. More fibrous and dendritic structures were obtained in CTAB-
lowest charge transfer resistance and the largest electrode NAM compared with the other cells. In other word, the large
capacitance presents with SDS. It is clear that anionic SDS developed crystal faces parallel to the surface could be seen. Thus,
surfactant diminishes the electrode surface resistance and the growth rate was more than nucleation rate. It is clear that
improves the electrode conductivity with the high capacitance, adsorption of cationic CTAB surfactant could prevent the dissolu-
tion process of lead sulfate and/or inhibit the diffusion of SO42 and
HSO4 species towards the bulk solution during charging. Thus,
Table 3 when the negative plate potential move toward more negative
Effect of SDS surfactant on the amount of charge stored in anodic and cathodic
branch vs. number of cycles on the lead electrode in 1.5 M H2SO4 compared with
standard. Table 4
Charge transfer resistance (Rct) and double-layer capacitance (Cdl) of the formed
cycle number 1 10 20 30 40 50 films on the lead electrode surface in presence of SDS surfactant and free surfactant
standard Qa(C) 0.091 0.10 0.106 0.24 0.38 0.39 solutions which calculated from corresponded Nyquist plots.
Qc(C) 0.069 0.065 0.15 0.5 0.66 0.75
Electrolyte additive Rct(V) Cdl(mf)
SDS Qa(C) 0.73 1.13 1.67 2.22 2.71 3.10 standard 4.71 0.18
Qc(C) 0.64 1.12 1.70 2.38 3.01 3.53 SDS 1.87 8.50
 R. Khayat Ghavami et al. / Journal of Energy Storage 7 (2016) 121–130 129

Fig. 8. Conceptual scheme of surfactant effect on NAM properties.

potential during cycling then hydrogen evolution is began. Hence, 4. Conclusion

over charge factor will increase by cycling and eventually gas
evolution will cause that outward growth and swelling of crystals The performance and cycle life of lead–acid battery are severely
that were very important event on NAM plate in presence of CTAB. limited due to the sulfation of negative plate. In the negative paste,
The lead surface was converted to spongy shape with large pores. a surface active substance (e.g. lignosulfonate) as organic expander
At last, the cell will be unable to provide sufficient power. The is applied to prevent the formation of a passivating PbSO4 layer
cationic CTAB molecules can be adsorbed on the negative charge (sulfation) on the lead surface. This organic expander is adsorbed
electrode by ion pairing because the adsorbate contains positive on the lead surface and prevents the deposition of a continuous
charge (C19H42N+) and substrate has strongly negative sites. Thus, PbSO4 passivating layer during battery discharge. However, they
CTAB can completely block electrode surface and subsequently contribute to the formation of a porous sulfate layer instead.
sulfate ions may be adsorbed on the electrode surface by attraction In this research, the effects of different kinds of surfactants on
between positive head groups of CTAB and sulfate anions. Since the the irreversible lead sulfate formation in NAM were examined by
reduction rate of PbSO4 depends on diffusion of SO42 and HSO4 addition of surfactant in lead-acid battery electrolyte. Amongst of
species towards the bulk solution and Pb2+ ions towards reaction four tested cells under PSOC cycling, the parameters of charge
sites [38,39], probably positive head groups of CTAB surfactant acceptance, cycle life and hydrogen evolution potential were
impede of such diffusion. Consequently, the relative density of acid increased more in SDS-NAM cell. In contrast, these parameters had
is increased in micropores during charge then dissolution of PbSO4 the most decrease in CTAB-NAM cell. Coarse needle shaped crystals
is decreased. Fig. 8 shows a conceptual scheme of surfactant effect of PbSO4 were grown on the discharged negative plate in presence
on NAM properties. of cationic CTAB surfactant. However, PbSO4 crystals were
The interpretations of the findings that were obtained from observed as fine and uniform shapes in presence of anionic SDS
amphotericTX-100 surfactant are more complex. Tx-100-NAM cell surfactant. Anionic SDBS surfactant could not perform as well as
completed more cycles than standard but it had shorter cycle life anionic SDS surfactants. Amphoteric Tx-100 surfactant had better
compared with SDS-NAM cell. effects than CTAB and SDBS on the electrochemical properties.
Negative head groups of SDS (C12 H 25 SO42 ) and SDBS Besides, different techniques such as CV and EIS were employed
(C16H29OSO2 ) surfactants can adsorb perpendicularly on the to investigate the effect of SDS on the lead pure electrode. The
metallic lead surface by gathering their hydrophilic head groups superior increment in the anodic peak current of cyclic voltametry
and sulfate ions. The formation of lead sulfate proceeds differently was observed in presence of SDS compared with the standard cell,
in presence of SDS and SDBS surfactants under high-rate discharge which is related to more reactivity of lead electrode surface.
due to the different type of polar and non-polar groups that was Impedance data confirmed a better conductivity of the grown
proved by the obtained results. The non-polar fraction of the anodic film on the lead electrode. The research founded that
organic molecule which is mainly constituted by aromatic rings anionic SDS surfactant diminished the electrode surface resistance
and hydrocarbon chains can be easily adsorbed at the negative and improved the electrode conductivity with high capacitance
active material. While the polar groups i.e. sulphonate and sulfate compared with standard cell. Thus, it managed to make a
groups are facing out to the aqueous electrolyte phase, due to conductive network through the control of uniform growth of
hydrophilic properties. Thus, the non-polar groups are important negative plate material, the crystallization process of lead sulfate
for covering metallic lead and decreasing or increasing in the metal and altering the shape and size of PbSO4 crystals by control of
surface energy [29]. It seems that formation of fine crystals is growth rate. We have concluded that the relative importance of
energetically more favorable in presence of anionic SDS surfactant hydrophobicity and the charged head groups of surfactants are the
when compared with others. This effect can be mainly related to key factors for explaining their efficiencies in the negative plates.
kind of surfactants. Since, the adsorption of SDS molecules succeed
in increase of negative active material reactivity and granularity
through decreasing the charge transfer resistance and increasing References
the double layer capacitance of the formed lead sulfate during
[1] P. Ruetschi, Aging mechanisms and service life of lead-acid batteries, J. Power
cycling that causes the longest cell cycle life and the lowest Sources 127 (2004) 33–44.
hydrogen evolution amongst all cells. [2] K. Uosaki, K. Konishi, M. Koinuma, Langmuir 13 (1997) 3557–3562.
130 R. Khayat Ghavami et al. / Journal of Energy Storage 7 (2016) 121–130

[3] J.R. Vilche, F.E. Varela, Reaction model development for the Pb/PbSO4 system, J. [21] M.J. Rosen, Surfactant and Interfacial Phenomena, Third ed., JohnWiley, New
Power Sources 64 (1997) 39–45. York, 2004, pp. 39.
[4] Y. Guo, M. Wu, S. Hua, A study of the passivation mechanism of negative plates [22] P.P. Xie, X.X. Chen, F. Wang, C.G. Hu, S.S. Hu, Electrochemical behaviors of
in lead/acid batteries, J. Power Sources 64 (1997) 65–69. adrenaline at acetylene black electrode in the presence of sodium dodecyl
[5] G. Petkova, P. Nikolov, D. Pavlov, Influence of polymer additive on the sulfate, Colloids Surf. B 48 (2006) 17–23.
performance of lead-acid battery negative plates, J. Power Sources 158 (2006) [23] E.J. Ritchie, Addition agents for negative plates of lead-acid storage batteries,
841–845. Trans. Electrochem. Soc. 92 (1947) 229–257.
[6] K. Das, K. Bose, Linear potential sweep voltammetric studies on lead in [24] E.J. Ritchie, Addition agents for negative plates of Lead-Acid storage batteries:
aqueous sulphuric acid.I. Effect of acid concentration, B. Electrochem. 2 (1986) II. pure organic compounds, J. Electrochem. Soc. 100 (1953) 53–59.
387–390. [25] E. Willihnganz, Storage battery addition agents, J. Electrochem. Soc. 92 (1947)
[7] F.E. Varela, M.E. Vela, J.R. Vilche, A study of the passivation mechanism of 281–302.
negative plates in lead/acid batteries A.J. Arvia, Electrochim. Acta 38 (1993) [26] R.K. Ghavami, Z. Rafiei, Performance improvements of alkaline batteries by
1513–1520. studying the effects of different kinds of surfactant and different derivatives of
[8] S.B. Hall, G.A. Wright, A conductive film model for the lead anode in sulfuric benzene on the electrochemical properties of electrolytic zinc, J. Power
acid, Corros. Sci. 31 (1990) 709. Sources 162 (2006) 893–899.
[9] A.A. Abdul Azim, A.A. Ismail, Evaluation of expanders used in negative lead [27] R.K. Ghavami, Z. Rafiei, S.M. Tabatabaei, Effects of cationic CTAB and anionic
battery electrode, J. Appl. Electrochem. 4 (1974) 1351–1356. SDBS surfactants on the performance of Zn–MnO2 alkaline batteries, J. Power
[10] D. Pavlov, P. Nikolov, T. Rogachev, Influence of expander components on the Sources 164 (2007) 934–946.
processes at the negative plates of lead-acid cells on high-rate partial-state-of- [28] H. Newnham, W.G.A. Baldsing, New operational strategies for gelled-
charge cycling. Part I: effect of lignosulfonates and BaSO4 on the processes of electrolyte lead/acid batteries, J. Power Sources 59 (1996) 137–141.
charge and discharge of negative plates, J. Power Sources 195 (2010) [29] C. Francia, M. Maja, P. Spinelli, Electrochemical characterisation of expander
4435–4443. materials, J. Power Sources 95 (2001) 119–124.
[11] P.T. Moseley, D.A.J. Rand, B. Monahov, Designing lead-acid batteries to meet [30] E. Buderski, G. Staikov, W.J. Lorenz, Electrochemical Phase Formation and
energy and power requirements of future automobiles, J. Power Sources 219 Growth, VCH, Weinhiem, 1996.
(2012) 75–79. [31] W. Zhang, Z. Shan, K. Zhu, S. Liu, X. Liu, J. Tian, LiMnPO4 nanoplates grown via a
[12] P.T. Moseley, D. Rand, High-rate partial-state-of-charge operation of VRLA facile surfactant-mediated solvothermal reaction for high-performance Li-ion
batteries, J. Power Sources 127 (2004) 27–32. batteries, Electrochim. Acta 153 (2015) 385–392.
[13] D.A.J. Rand, P.T. Moseley, J. Garche, C.D. Parker (Eds.), Valve Regulated Lead- [32] D.Y. Li, J.A. Szpunar, A Monte Carlo simulation approach to the texture
acid Batteries, Elsevier, 2004. formation during electrodeposition—II. Simulation and experiment,
[14] J. Gou, A. Lee, J. Pyko, Modeling of the cranking and charging processes of Electrochim. Acta 42 (1997) 47–60.
conventional valve regulated lead acid (VRLA) batteries in micro-hybrid [33] D. Pavlov, Processes of formation of divalent lead oxide compounds on anodic
applications, J. Power Sources 263 (2014) 186–194. oxidation of lead in sulphuric acid, Electrochim. Acta 13 (1968) 2051–2061.
[15] J. Albers, E. Meissner, S. Shirazi, Lead-acid batteries in micro-hybrid vehicles, J. [34] D.D. Mac Donald, Transient Techniques in Electrochemistry, Plenum Press,
Power Sources 196 (2011) 3993–4002. New York, 1977.
[16] E. Ebner, D. Burow, A. Börger, M. Wark, P. Atanassova, J. Valenciano, Carbon [35] J. Kowal, H. Budde-Meiwes, D.U. Sauer, Interpretation of processes at positive
blacks for the extension of the cycle life in flooded lead acid batteries for and negative electrode by measurement and simulation of impedance spectra.
micro-hybrid applications, J. Power Sources 239 (2013) 483–489. Part II: concentration limitation, J. Power Sources 207 (2012) 45–50.
[17] L.T. Lam, H. Ceylana, N.P. Haigha, J.E. Manders, Influence of bismuth on the [36] D. Pavlov, R. Popova, Mechanism of passivation processes of the lead sulphate
charging ability of negative plates in lead–acid batteries, J. Power Sources 107 electrode, Electrochim. Acta 15 (9) (2016) 1483–1491.
(2002) 155–161. [37] L.T. Lam, N.P. Haigh, C.G. Phyland, A.J. Urban, Failure mode of valve-regulated
[18] Y. Liu, P. Gao, X. Bu, G. kuang, W. Liu, L. Lei, Nanocrosses of lead sulphate as the lead-acid batteries under high-rate partial-state-of-charge operation, J. Power
negative active material of lead acid batteries, J. Power Sources 263 (2014) 1–6. Sources 133 (2004) 126–134.
[19] Z. Shi, Y.H. Zhou, C.S. Cha, Influence of perfluorinated surfactants on the [38] N. Boudieb, M. Bounoughaz, A. Bouklachi, The effect of surfactants on the
positive active-material of lead/acid batteries, J. Power Sources 70 (1998) efficiency of lead acid batteries, Proc. Soc. Behav. Sci. 195 (2015) 1618–1622.
205–213. [39] B. Rezaei, E.H. Keshian, A.R. Hajipour, Application of ionic liquids as an
[20] S.S. Hu, K.B. Wu, H.C. Yi, D.F. Cui, Voltammetric behavior and determination of electrolyte additive on the electrochemical behavior of lead acid battery, J.
estrogens at nafion-modified glassy carbon electrode in the presence of Solid State Electrochem. 15 (2011) 421–430.
cetyltrimethylammonium bromide, Anal. Chim. Acta 464 (2002) 209–216.