Improved performance of the rechargeable hybrid aqueous battery at near full state-of-charge

Article abstract of DOI:10.1016/j.electacta.2018.03.152

For the first time, a green lignin/silica nanocomposite (LSC) is introduced to the rechargeable hybrid aqueous Zn/LiMn₂O₄ battery (ReHAB) as additive in the cathode formulation. Lignin acts as a key role to regulate and control the structure of LSC, intending to enhance the stability of the ReHAB by improving the float charge performance while maintaining other electrochemical performances of the battery. The lignin/silica nanocomposites (LSCs) are characterized by X-ray diffraction, scanning electron microscopy, surface area and porosimetry analyzer, and transmission electron microscopy. The results show that amorphous, uniform and mesoporous LSC-1 is prepared at the mass ratio of 1:2 of lignin to silica. LSC-1 used as the cathode additive improves the float charge performance of ReHAB via decreasing the float charge capacity by 57%. To compensate the loss of conductivity caused by LSC-1 and increase the capacity of the battery, graphene (G) is added. Compared to the reference battery, battery using the cathode containing 3 wt% combined additive of LSC-1 and G at mass ratio of 1:1, has 50% lower float charge capacity, higher rate performance and better cyclability. Up to a discharge capacity of 95 mAh g^?1 is still obtained after 300 cycles of 100% depth-of-discharge.

Full text of DOI:10.1016/j.electacta.2018.03.152

Accepted Manuscript
Improved performance of the rechargeable hybrid aqueous battery at near full state-
of-charge
Wenlong Xiong, Dongjie Yang, Jian Zhi, Tuan K.A. Hoang, Xueqing Qiu, P. Chen
PII:
S0013-4686(18)30669-8
10.1016/j.electacta.2018.03.152
EA 31518
DOI:
Reference:
To appear in: Electrochimica Acta
Received Date: 15 January 2018
Revised Date: 23 March 2018
Accepted Date: 24 March 2018
Please cite this article as: W. Xiong, D. Yang, J. Zhi, T.K.A. Hoang, X. Qiu, P. Chen, Improved
performance of the rechargeable hybrid aqueous battery at near full state-of-charge, Electrochimica Acta
(2018), doi: 10.1016/j.electacta.2018.03.152.
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ACCEPTED MANUSCRIPT
Improved performance of the rechargeable hybrid
aqueous battery at near full state-of-charge
Wenlong Xionga,b,c†, Dongjie Yanga,c†, Jian Zhib, Tuan K. A. Hoangb, Xueqing
Qiua,c,**, P. Chenb,*
a
School of Chemistry and Chemical Engineering, South China University of
Technology, Guangzhou 510640, China
b
Department of Chemical Engineering and Waterloo Institute of Nanotechnology,
University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L3G1,
Canada
c
Guangdong Engineering Research Center for Green Fine Chemicals, South China
University of Technology, Guangzhou 510640, China
† These authors equally contributed to this work.
*Corresponding Author
P. Chen
E-mail: p4chen@uwaterloo.ca. Tel.: +1-519-888-4567 ext. 35586. Fax:
+1-519-888-4347.
**Corresponding Author
Xueqing Qiu
E-mail: xueqingqiu66@163.com. Tel.: +86-20-8711-4722. Fax: +86-20-8711-4721.

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Abstract: For the first time, a green lignin/silica nanocomposite (LSC) is introduced
to the rechargeable hybrid aqueous Zn/LiMn2O4 battery (ReHAB) as additive in the
cathode formulation. Lignin acts as a key role to regulate and control the structure of
LSC, intending to enhance the stability of the ReHAB by improving the float charge
performance while maintaining other electrochemical performances of the battery.
The lignin/silica nanocomposites (LSCs) are characterized by X-ray diffraction,
scanning electron microscopy, surface area and porosimetry analyzer, and
transmission electron microscopy. The results show that amorphous, uniform and
mesoporous LSC-1 is prepared at the mass ratio of 1:2 of lignin to silica. LSC-1 used
as the cathode additive improves the float charge performance of ReHAB via
decreasing the float charge capacity by 57%. To compensate the loss of conductivity
caused by LSC-1 and increase the capacity of the battery, graphene (G) is added.
Compared to the reference battery, battery using the cathode containing 3 wt%
combined additive of LSC-1 and G at mass ratio of 1:1, has 50% lower float charge
capacity, higher rate performance and better cyclability. Up to a discharge capacity of
95 mAh·g-1 is still obtained after 300 cycles of 100% depth-of-discharge.
Keywords: lignin/silica nanocomposite; graphene; hybrid aqueous batteries; float
charge capacity.

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1. Introduction
Aqueous rechargeable lithium ion batteries (ARLB) are promising alternative
energy storage systems to store electricity generated from renewable and clean energy
resources (e.g., solar, wind, and biomass energy), partly because ARLB can overcome
some disadvantages of lithium ion batteries, i.e., the high cost and safety problems,
and environment pollution problem of commercially aqueous Pb-acid or Ni–Cd
batteries, i.e., the heavy metal pollution and corrosion of strong acid and alkaline
electrolyte [1–4]. The LiMn2O4 based ARLB, one typical aqueous batteries, is born in
1994 [5] and has been proven that it can function at good rate capability and
cyclability [1–4,6,7]. A rechargeable hybrid aqueous battery (ReHAB), using
commercial LiMn2O4 as the active material in the cathode, zinc as the anode, and an
aqueous solution containing Li+ and Zn2+ as the electrolyte, has been being developed
by our group [8]. Importance of the ReHAB is attributed to its environmental
friendliness, inherent non-flamability, low cost, and reasonable energy density [8].
To apply this low cost ReHAB as power storage (e.g. interface with grid to regulate
and store electricicity from wind mill) or as uninterruptible power supply (UPS), the
energy spent to maintain the battery at it 100% charged state should be as small as
possible. The process applying a small current to maintain battery at fully charged
state is called float charge. Low float charge current or low float charge capacity are
the most beneficial criterion for electricity stores. Extensive efforts have been made
continuously to improve the performances of the ReHAB to promote the progress of
its commercialization. These efforts focus on the chemical modification of LiMn2O4

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in the cathode [8,9], the modification of zinc anode via electroplating [10,11], and in
particular, the physical modification of electrolytes, for example, the aqueous
electrolyte with thiourea as additive [12] and a series of gel electrolytes [13–17]. In
fact, the physical modification is very important because simple method is always
easily scaled up. Except for the physical modification of electrolytes, the physical
modification of cathode should be an approach to improve the performances of the
ReHAB. Cathode modification is important in many types of rechargeable batteries.
For instance, an appropriate amount of additive, silica, has significant improvement
on the performances of Li-S batteries, when it is blended into the cathode [18–20].
The dissolution of Mn2+ derived from the decomposition of LiMn2O4 into the
electrolyte appears in the ReHAB [8,21,22]. This problem cause poor float charge
performance of the ReHAB. That is to say, the float charge performance of the
ReHAB could be improved by slowing down the diffusion of Mn2+ into the electrolyte.
In fact, silica, a material attracted substantial academic and industrial interest, has
been proven that it can effectively adsorb Mn2+ [23].
Silica can be prepared by many methods, such as sol-gel, microemulsion,
precipitation, or commercial fuming [24]. Comparing with the other methods, the
precipitated silica may be the most appropriate candidate additive for the ReHAB
because of its ease of preparation and very low cost. However, the dispersity of silica
is low owing to the agglomeration caused by the luxuriant silanol (Si–OH) groups on
its surface [24]. Besides the traditional approaches, which are the addition of
expensive and toxic modifiers in the precipitation process, people have found out

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some novel, cheap, and renewable modifiers, for example, lignin, to tackle the issue
of agglomeration between precipitated silica particles by preparing the precipitated
lignin/silica composite (LSC) [25–27].
Lignin, which accounts for 15–40 wt% of wood, is the second most abundant
biopolymer and the largest natural renewable resource of aromatic compounds on the
earth [28,29]. Despite the traditional low-valued uses of industrial lignin, the novel
applications are focused on introducing industrial lignin into different high
value-added areas, such as nanomaterials [30–32], UV-absorbent additives for
polymers [27,33], sun blocker for sunscreens [34,35] and lignin/silica composites
(LSCs) [25–27,36]. Especially, LSCs have opened up several promising application
areas for lignin [37–39]. As far as we know, there are no reports referring to the use of
LSCs as additives in batteries. Inspired from the successful experience of silica
additive in the cathode of Li-S batteries [18–20], here we add LSC to the cathode of
ReHAB for the first time.
In the present study, the uniform LSC was prepared by a simple one-pot method
[27], and used as additives to modify the cathode of ReHAB. The LSC prepared at the
mass ratio of 1:2 of lignin to silica was found to be able to significantly improve the
float charge performance of ReHAB by decreasing the float charge capacity. However,
it also dramatically decreases the discharge capacity of ReHAB due to its insulation.
To compensate the loss of conductivity caused by LSC, graphene (G) is employed as
a additive for the cathode of ReHAB due to its superior electronic conductivity [40–
44]. Benefiting from the cooperation of LSC and G, ReHAB using the cathode

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containing LSC and G as a combined additive (LSC + G) can operate at a very low
float charge capacity and high discharge capacity. The capacity retention after 300
cycles at 1 C of ReHAB using the cathode cotaining LSC + G is very close to that of
the battery using reference cathode and much higher than that of the battery using
cathode only containing G as the additive. The float charge performance is
emphatically considered in this study because the ReHAB is a promising alternative
for the application of UPS. In this regard, float charge performance is the most
important criterion [13].
2. Experimental
2.1 Materials
The source and pretreatment of pine alkali lignin (AL) were presented in our
previous work [26]. LiMn2O4 was purchased from Shanshan Co. (Changsha, China).
Graphene (G) was purchased from Tanyuan Technology Co., Ltd. (Changzhou, China).
Other reagents, such as sodium metasilicate pentahydrate (Na2SiO3·5H2O), 60 wt%
3-chloro-2-hydroxypropyltrimethylammonium chloride (CHPTMAC) aqueous
solution, ammonium chloride, lithium hydroxide, and sodium hydroxide, were of
analytical grade and purchased from Sigma-Aldrich Co.. Sulfuric acid (95−98 wt%,
ACS plus grade) was purchased from Fisher Scientific Co..
2.2 Synthesis of Quaternized alkali lignin (QAL)
The QAL was synthesized following the same processes presented in our previous

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work [27].
2.3 Preparation of LSCs and silica
The LSCs were prepared following the same process presented in our previous
work [27]. Three LSCs, named as LSC-1, LSC-2, and LSC-3, were prepared based on
the different initial mass ratios of QAL to SiO2 (QAL: SiO2 = 0.5, 1.0, 1.5,
respectively).
The preparation process of silica was almost the same as the one of LSC, except the
addition process of QAL. Na2SiO3·5H2O (5.3 g) was first dissolved in an
ethanol-water mixture (the volume ratio of absolute ethanol to deionized water was
1:6). The mixture was stirring for 30 min at 35 ºC. Subsequently, the mixture was
adjusted to a pH of 10.5 using aqueous ammonium chloride solution (2 M) and then
stirred for 3 h. After that, the mixture was adjusted to a pH of 7.0 using aqueous
sulfuric acid (20 wt%) and then stirred for 30 min. When the reaction came to the end,
the mixture was aged for 1 h at 40 ºC. Finally, the silica was collected by suction
filtration, washed several times with neutral deionized water and dried in an oven at
60 ºC.
2.4 Preparation of cathodes, anode, electrolytes, and batteries
The reference cathode was prepared by mixing LiMn2O4 (Shanshan Co.), KS-6
graphite (Imerys Graphite & Carbon), and polyvinylidene fluoride (PVdF, Kynar®,
HSV900) (86:7:7 wt%) in n-methyl-2-pyrrolidone (NMP, Sigma-Aldrich Co., 99.5%

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purity) for 10 min with Planetary Centrifugal Mixer (AR-100, ThinkUSA). The slurry
was coated on a conductive polyethylene (PE) film (All-Spec 854-36150) and placed
in 60 °C vacuum oven for 6 h. The dried slurry with substrate of PE film was cut in a
disk with 12 mm diameter to be used as the cathode. The loading of cathode is 5−7
mg of LiMn2O4 per cm2. The other cathodes with additives were prepared by mixing
LiMn2O4, KS-6 graphite, PVDF (86:7:7 wt%), and different additives (LSC, G, and
LSC+G) in NMP with Planetary Centrifugal Mixer, respectively. It should be note that
each additive was blended with KS first, and then the mixture of additive and KS-6
was mixed with LiMn2O4 and PVDF in NMP. The dosages of the additives were
determined based on the mass of LiMn2O4. The other procedures were the same as the
reference one.
The zinc anode was prepared by polishing the commercial zinc foil (Rotometals,
99.6% purity) using 0.3 ꢀm polishing powder (Boehler) dispersed in deionized water
and a nanocloth (Boehler). Each side of the zinc foil was polished for 10 min. The
polished zinc foil was washed with deionized water, followed by rinsing with ethanol
and dried at 60 °C under vacuum for 30 min. Zinc anode was obtained by cutting
from the polished zinc foil to round shape disk with diameter of 12 mm.
The electrolyte was prepared by dissolving 2 M zinc sulfate heptahydrate (Alfa
Aesar Co., 98%) and 1 M lithium sulfate (Sigma-Aldrich Co., 98%) in deionized
water. The pH of the solution was adjusted to 4.00 ± 0.05 using sulfuric acid or
lithium hydroxide solution.
The cathode, Absorbed Glass Mat (AGM, NSG Co.) separator, electrolyte, and zinc

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anode were assembled into a coin cell (CR 2025).
2.5 Characterization
LSCs and the prepared silica were characterized by a powder X-ray diffraction
(XRD, D8 Discover, Brüker) instrument equipped with a Cu Kα radiation source,
with a scan speed of 1° per minute, ranging from 10° to 90°, an accelerated surface
area and porosimetry analyzer (ASAP2020, Micromeritics) using a 20-point nitrogen
adsorption and desorption program based on the Brunauer–Emmett–Teller (BET)
method, a field emission scanning electron microscopy (SEM, Merlin, Zeiss Corp.,
Germany) at 10 kV, and a transmission electron microscopy (TEM, LIBRA® 200 MC,
Zeiss Corp., Germany).
2.6 Electrochemical measurements
The float charge performance, which was presented by the float charge capacity,
was tested by an NEWARE battery tester (NEWARE Battery Test System, Neware Co.
Ltd., China) at room temperature. The test program was charging the battery from 1.4
to 2.1 V (vs Zn2+/Zn) by a constant current (CC) mode at 0.2 C rate (1 C is defined as
115 mAh·g-1), then charging the battery to maintain it at 2.1 V by a constant voltage
(CV) mode for 24 h, and finally discharging the battery to 1.4 V by the CC mode at
0.2 C rate. The open circuit voltage (OCV) was measured following the test of float
charge performance. For this purpose, the battery voltage was recorded when the
battery was at resting state, e.g. not charging or discharging , and finally discharging

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the battery to 1.4 V by the CC mode at 0.2 C rate.
The rate performance of the battery was tested by the NEWARE battery tester at
various CC charge−CC discharge rates from 0.2 C to 4 C at room temperature.
The galvanostatic charge-discharge cycling of the batteries was carried out between
1.4 and 2.1 V, in CC−CV mode at room temperature at 1 C rate with the NEWARE
battery tester. The current cutoff during CV charging was set at 10% of the charging
current in the CC charging step at 1 C rate.
Cyclic voltammetry (CV) tests were conducted on a multichannel potentiostat
(VMP3, Biologic) between 1.4 and 2.1 V at a scan rate of 0.1 mV·s−1. In addition, AC
impedance measurements were performed with amplitude of 10 mV at the applied
frequency range from 0.1 Hz to 1 MHz after the batteries were cycled for 10 cycles at
1 C rate. With the same running program, AC impedance was implemented on a
three-electrode cell with the battery cathode as the working electrode (WE), platinum
as the counter electrode (CE), and standard calomel electrode (SCE) as the reference
electrode (RE). These data were fitted by using ZView and the Li+ diffusion
coefficient was calculated for each of the cathode (Supporting information).
3. Results and discussion
3.1 Specific surface areas, pore volume distributions, and TEM images of LSCs
The N2 adsorption–desorption isotherms on LSCs prepared with different initial
mass ratios of silica and QAL are presented Fig. 1(a). All of the samples are
amorphous materials, as evidenced by the XRD results in Fig. S1 (Supporting

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information). The lower portion of the loop is traced out on adsorption, and the upper
portion on desorption. At low relative pressure (P/P0 < 0.4), the quantity absorbed of
N2 almost accounts for half of the total adsorbed nitrogen for each material. This
suggests that the materials possess some porous characteristics [13]. The hysteresis
loops observed in the adsorption–desorption isotherm of all samples, which resembled
type IV of Brunauer’s classification [45], indicate all the samples possess mesoporous
structure. The hysteresis loop in the adsorption–desorption isotherm of LSC-1 is
markedly bigger than that of the other two samples, which means there are more
abundant mesopores in LSC-1. When it comes to high relative pressure (P/P0 > 0.9),
the capillary condensation occurs in the adsorption–desorption isotherm of each
sample may be owing to the small sizes of particles in the materials [46].
The pore volume curves are shown in Fig. 1(b). Obviously, the tendency of pore
volume distribution and pore size of LSC-1 are different from that of the other two
samples. There are some micropores (pore size less than 2 nm) that cannot be
measured by the instrument in silica (Fig. S2, Supporting information), LSC-2 and
LSC-3, but they are absent in LSC-1 with average pore width of 3.45 nm (Table S1,
Supporting information). It indicates that the prepared LSC will be uniform
mesoporous materials when the initial mass ratio of QAL and silica is 0.5:1. This is
because the negatively protogenous silica crystal nucleus are easier bonded to the
three-dimensional network structure of QAL by the strong interaction between the
surface acidic groups of silica and the basic cationic quaternary ammonium groups in
QAL, to prevent the protogenous silica crystal nucleus from aggregating into

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non-porous or microporous silica by themselves. If the initial mass ratio of QAL and
silica reaches 1.0:1 and 1.5:1, the self-aggregation of QAL in aqueous solution will be
enhanced due to the increase of the concentration of QAL [47–49], resulting in the
loss of ability to control the formation of mesoporous structures. In particular, when
the initial mass ratio of QAL and silica reaches to 1.5:1, the uniform spherical
morphology of the prepared LSC-3 is destroyed compared with that of silica, LSC-1
and LSC-2, as evidenced by the SEM images in Fig. S3 (Supporting information).
There is some shapeless QAL coating on the surface of particles owing to the
enhancement of self-aggregation of QAL, because the self-aggregation of lignin
derivatives increases when the concentration increases in aqueous solution [47–49].
This is further demonstrating the self-aggregation of QAL will inhibit the formation
of uniform spherical LSC with mesoporous structures.
In fact, the formation of LSC includes two steps in the one-pot method [27]. The
first one is the generation of silica at pH 10.5 accompanied by the formation of pore
structure and the second one is the deposition of QAL on silica to form the LSC along
with the pH decreasing from 10.5 to 7. According to our results in Fig. 1, 0.5 is the
opportune initial mass ratio of QAL to SiO2 to prepare the LSC with pure mesopore.
Comparing the data of LSC-1 with LSC-2 in Table S1 (Supporting information), the
pore volume obviously decreases along with the increase of QAL. However,
comparing the data of LSC-2 with LSC-3 in Table S1 (Supporting information), the
pore volume doesn’t change too much along with the increase of QAL. This suggests
that the formation of pore structure of LSC in the first step is almost the same after the

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initial mass ratio of QAL to SiO2 reaches to a certain value (≥ 1). So the pore volume
of LSC is almost maintained although the initial mass ratio of QAL to SiO2 increases
from 1.0 to 1.5. In the premise of similar first step, too much QAL aggregation will
affect the second step, which is reflected by the significantly decrease in BET surface
area, comparing the data of LSC-2 with LSC-3 in Table S1 (Supporting information).
TEM is employed to further characterize the structure of LSCs. As shown in Fig.
S4 (Supporting information), the precipitated silica is uniform and amorphous, which
is consistent with the results of XRD and SEM analyses. In addition, there seems to
be some irregular pores in the silica particle, as evidenced by the transmission of light
of particles in Fig. S4. Compared to the structure of silica, the LSC-1 and LSC-2 are
also uniform and amorphous. However, the surface of LSC-1 and LSC-2 are majorly
coated with QAL, as evidenced by the obvious core-shell structure in Fig. 2. The
irregular pores are also existed in the LSC-1 particles but nearly absent in the LSC-2
particles, which means too much QAL will inhibit the formation of pore structure. It
is hard to distinguish the differnece between the pores in silica and LSC-1 only
depended on the TEM images in Fig. S4 and Fig. 2, but the BET method and pore size
distribution can distinguish it. According to the analyses of N2 adsorption–desorption
isotherms, pore size distributions, and TEM images, it can be determined that LSC-1
is the pure mesoporous material.
3.2 Float charge performances of the batteries
High float charge capacity/current is one of the major drawbacks for aqueous

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lithium batteries. Thus, minimization of the float charge capacity is highly desirable
while quite challenging in designing highly stable aqueous batteries. Table 1 presents
the discharge capacity and float charge capacity at 0.2 C of the batteries based on the
different cathodes with or without additives. The data in this table is aimed at
evaluating which LSC is the best for improving the float charge performance, which
is presented by the decrease of the float charge capacity of the battery. After mixing 2
wt% of silica into the cathode, the float charge capacity of the battery decreases from
14.3 to 9.4 mAh·g-1 (Table S2, Supporting information). This is a good and the
decrease of the float charge capacity may be contributed by the following approach.
The mesoporous silica possesses the ability to adsorb Mn2+ according to Yang’s
research [23]. There are some mesopores in the precipitated silica according to the
results of N2 adsorption–desorption isotherm and pore volume curve (Fig. S2,
Supporting information). Hence, the mesopores in silica may contribute to improving
the float charge performance, because the mesopores may adsorb Mn2+ derived from
the decomposition of LiMn2O4 in the acidic electrolyte to prevent it from dissolving
into the electrolyte. Meanwhile, the discharge capacity also decreases from 119.1 to
113.8 mAh·g-1 (Table S2, Supporting information), because the loss of the
conductivity of the cathode inevitably results in a slight decrease of the discharge
capacity.
The precipitated silica can improve the float charge performance of the cathode, but
the enhancement is not very significant. The silica based composites may be an
attemptable approach. Because many kinds of composites can exert multiple

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advantages of the different components in the composites, and some of the advantages
are even much better than a single component. Herein presents the amorphous LSC,
which is prepared by a novel, simple and environmentally friendly one-pot method in
an aqueous solution. This idea is evidenced to be practicable by the data presented in
Table 1. After mixing 2 wt% of LSC-1 into the cathode, it shows the biggest ability to
decrease the float charge capacity, which is decreased from 14.3 to 6.1 mAh·g-1,
approximately 57.3% lower. If the lignin content in the LSC increases, the float
charge capacity will also increase. This suggests that purely mesoporous LSC-1
possesses stronger ability to improve the float charge performance of the batteries
than that of silica, LSC-2 and LSC-3 with micropores and some small size mesopores.
According to Yang’s research [23], the bigger the average pore size within the range
of 10 nm of mesopores, the stronger the adsorption capacity of Mn2+. Therefore, it can
be expected that the purely mesoporous LSC-1 can adsorb more Mn2+ derived from
the decomposition of LiMn2O4 in the mild acidic electrolyte, because there are more
large mesopores within the pore size range of 10 nm in LSC-1 than that of in silica,
LSC-2, and LSC-3 based on the results of pore volume curves. In addition, the
cathode containing LSC-3 shows the worst float charge performance, which also may
be due to the non-uniform particle morphology of LSC-3, as evidenced by the SEM
images presented in the Fig. S3 (Supporting information). This indicates that the
uniform morphology of LSC is also request for improving the float charge
performance of the battery. According to the analyses in part 3.1, LSC-3 doesn’t have
the similar pore structure as that of LSC-1 to hold the Mn2+ and includes too much

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lignin aggregates while lignin itself increases the float charge capacity (Table S2,
Supporting information). Therefore, the float charge capacity of LSC-3 increases
more than that of LSC-1. Because the purpose of the research is to improve the float
charge performance by decreasing the float charge capacity, LSC-1 is considered as
the most promising additive to achieve this goal. However, the most urgent issue of
LSC-1 is that the discharge capacity of battery using the cathode containing LSC-1
decreases due to the loss of conductivity of the cathode.
In order to compensate the loss of conductivity caused by LSC-1, graphene, an
excellent material with extraordinary electronic transport property, is also introduced
into the cathode as a partner with LSC-1. The results of float charge performance of
the battery using cathode with LSC, G (graphene) and LSC+G are presented in Table
2, respectively. The discharge capacity of battery using the cathode containing 2 wt%
G increase from 119.1 to 122.1 mAh·g-1, and meanwhile, the float charge capacity
decrease from 14.3 to 9.9 mAh·g-1 compared to the battery using reference cathode.
As described in part 2.4 of the experimental section, the conductive carbon (KS-6) is
mixed with G first, that is, part of the surface of KS-6 is modified by G. There is a
published paper proving that the oxidation/consumption of KS-6 on the
cathode/electrolyte interface is inhibited after the LMO cathode is coated with
reduced graphene oxide [44], which helps to reduce the float charge capacity.
Therefore, the oxidation/consumption of KS-6 on the cathode/electrolyte interface
should be suppressed more or less because of the surface modifaction of KS-6 by G,
leading to the decrease in float charge capacity. The ability of G to improve the float

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charge performance is not better than that of LSC-1, but the ability of G to increase
the discharge capacity is superior to that of LSC-1.
After mixing both LSC-1 and G into the cathode, there are some different results
under the condition of different mass ratios of LSC-1 and G. When the cathode is
blended with 2 wt% LSC-1+G at the mass ratio of 1:1, the discharge capacity increase
from 110.1 to 115.5 mAh·g-1 and the float charge capacity also increase from 6.1 to
7.9 compared to that of the cathode with 2 wt% LSC-1. The discharge capacity (115.5
mAh·g-1) of battery using the cathode containing 2 wt% LSC-1+G (1:1) is still lower
than that of the reference cathode (119.1 mAh·g-1), indicating that the G cannot
completely compensate the loss of conductivity caused by LSC-1 at this condition. If
the dosage of LSC-1+G (1:1) increases to 3 wt%, the discharge capacity reaches to
122.1 mAh·g-1 and the float charge capacity just slightly increase to 7.2 mAh·g-1
compared to that of the cathode containing 2 wt% LSC-1. It indicates that battery
using the cathode containing 3 wt% LSC-1+G (1:1) possesses higher discharge
capacity and much lower float charge capacity than that of the battery using reference
cathode. Especially the float charge capacity is reduced by approximately 50%, which
is an exciting result. If the dosage of LSC-1+G (1:1) in the cathode continuously
increase to 4 wt%, the discharge capacity will further go up to 124.7 mAh·g-1, but the
float charge capacity will also dramatically go up to 12.4 mAh·g-1 compared to that of
battery using the cathode containing 3 wt% LSC-1+G (1:1). These results suggest that
LSC-1 and G can play a synergistic interaction to slightly increase the discharge
capacity and significantly decrease the float charge capacity at an appropriate

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formula.
When the total dosage of LSC-1 and G in the cathode is fixed at 4 wt%, the float
charge performance is not as good as that of the cathode containing 3 wt% LSC-1+G
(1:1), although the mass ratio of LSC-1 to G changes from 1:1 to 2:1. In order to
clearly show the float charge performance, an assistant parameter FC/DC, the value of
dividing the discharge capacity by the float charge capacity, is artificially defined to
represent the float charge performance only when the discharge capacity is higher
than the reference one or at least closed to the reference one. The lower the FC/DC is,
the better the float charge performance is. The FC/DC of battery using the reference
cathode, the cathode containing 2 wt% G, 3 wt% LSC-1+G (1:1), 4 wt% LSC-1+G
(1:1), and 4 wt% LSC-1+G (1.5:1) is 12.0%, 8.1%, 5.9%, 9.9%, and 8.6%,
respectively. Obviously the float charge performance of the battery using cathode
containing 3 wt% LSC-1+G (1:1) is the best.
3.3 Rate capabilities of the batteries
Fig. 3 presents the rate performance of the batteries assembled by the reference
cathode, cathode containing 2 wt% LSC-1, cathode containing 2 wt %G, and the
different LSC-1+G based cathodes, respectively. After the cathode is mixed with 2 wt%
LSC-1, the discharge capacities are sharply decreased at each rate compared to the
reference cathode, which means LSC-1 can dramatically decrease the rate
performance of the battery. The battery using cathode containing 2 wt% G can
maintain the discharge capacities at 0.5 C, 1 C and 2 C, slightly increase the discharge

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capacity at 0.2 C, and obviously increase the discharge capacity at 4 C compared to
the battery using reference cathode, which means G can improve the rate performance
of the battery. The battery using cathode containing 3 wt% LSC-1+G (1:1) has the
similar trend on the rate performance, maintaining the discharge capacities at 0.5 C, 1
C and 2 C and slightly increasing the discharge capacities at 0.2 C and 4 C compared
to the battery using reference cathode. Subsequently the rate performances are not
obviously promoted when the dosage or mass ratio of LSC-1 and G changes. Hence,
among the cathodes using LSC-1 and G as the additives together, the cathode
containing 3 wt% LSC-1+G (1:1) is considered as the best and selected to evaluate
the cycle performance according to the analyses of float charge performance and rate
performance.
3.4 Cyclabilities of the batteries
Fig. 4 presents constant current−constant voltage (CC−CV) cycling performances
of batteries at 1 C for up to 300 cycles. Capacity fading is observed on all batteries
owing to unwanted side reactions, including the manganese dissolution, water
decomposition, hydrogen evolution, and Zn corrosion [13,21,22,50]. The discharge
capacity of battery using the cathode containing 2 wt% LSC-1 on the first cycle is
104.5 mAh·g-1, which is much lower than the 114.7 mAh·g-1 of the battery using
reference cathode. The discharge capacity of battery using the cathode containing 2 wt%
G on the first cycle is 120.8 mAh·g-1, which is much higher than that of the battery
using reference cathode. The discharge capacity of battery using the cathode

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containing 3 wt% LSC-1+G (1:1) is 122.3 mAh·g-1 on the first cycle, which is also
much higher than that of the battery using reference cathode. This suggests that the
LSC-1 and G combined additives can perform the ability of G to increase the capacity
of the battery owing to the successful compensation on the loss of conductivity of the
cathode caused by LSC-1. After 300 cycles the discharge capacity of battery using the
cathode containing 3 wt% LSC-1+G (1:1) is 94.3 mAh·g-1, which is still higher than
the 91.3 mAh·g-1 of the battery using reference cathode. For the battery using cathode
containing 2 wt% G, the most serious issue is that the capacity retention is lower than
that of the reference battery, that is to say, the discharge capacity will decrease faster
than that of the reference one. This issue can almost be fixed by LSC-1, which can
increase the capacity retention of the battery for up to 250 cycles. The final capacity
retention of the battery using cathode containing 3 wt% LSC-1+G (1:1) is 77.0%,
which is very close to the 79.6% of the battery using reference cathode and much
higher than the 70.8% of the battery using cathode containing 2 wt% G. Hence, the
battery using the cathode containing 3 wt% LSC-1+G (1:1) can inherit the ability to
increase the discharge capacity of G and the ability to maintain the capacity retention
of LSC-1, leading to a higher discharge capacity than the reference one for up to 300
cycles at 1 C.
3.5 OCV, PEIS and CV of the batteries
Fig. 5 presents the open circuit voltages (OCV) versus time of the fully charged
coin cells using reference cathode, cathode containing LSC-1, G, and LSC-1+G,

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respectively. OCV of 1966.4 mV is observed for the battery using cathode containing
2 wt% LSC-1 after 24 h monitoring. The OCV value is much lower than that of the
reference ones at 1979.8 mV. This disadvantage of LSC-1 is nearly fixed by G, as
evidenced by the result that the OCV of 1977.1 mV is observed for the battery using
cathode containing 3 wt% LSC-1+G (1:1) after 24 h monitoring, which is very close
to that of the reference ones at 1979.8 mV.
Potential static impedance spectroscopy (PEIS) results from three-electrode-cell
(WE: the cathode of the battery, CE: Pt, RE: SCE) are presented in Fig. 6. The Li+
diffusivity can be calculated based on the PEIS data [44] and the relative fitting
results are shown in Table 3. They correlate well with the battery performance. The
cathode with 2 wt% LSC-1 has slightly higher Ohmic and charge transfer resistances
because LSC-1 is insulating. Furthermore, the Li+ diffusivity decreases by ca. 21%.
This slow diffusion limits the battery performance at high rate capability and
decreases the initial discharge capacity at 4 C. When adding graphene into the
electrode, the Li+ diffusivity is enhanced by a large margin of 75% and the charge
transferred resistance decreases by nearly half. This explains the improved
performance in rate, specific discharge capacity. However, the float charge capacity
increases compared with that of LSC-1. A balance between graphene and LSC-1 (3 wt%
of LSC-1 : G = 1 : 1) would solve the problem nicely. The rate capability and specific
discharge capacity are improved while the float charge capacity is kept at low level.
The cyclic voltammetry (CV) results of battery using the reference cathode and the
cathode containing 3 wt% LSC-1+G (1:1) are shown in Fig. S5 (Supporting

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information), respectively. All currents at 1C rate are normalized to the electrode
loadings. In the CV results, the two steps of intercalation/extraction of Li+ into/out of
the LiMn2O4 lattice are presented by the two distinctive pairs of reduction/oxidation
peaks. It is observed that there is slight increase in the current of the battery using
cathode containing 3 wt% LSC-1+G (1:1) compared to that of the reference battery,
suggesting that the internal resistance and kinetics of electrochemical reactions in the
batteries are slightly altered. This is expected because G improves the conductivity of
the cathode owing to its excellent electrochemical activity, although LSC-1 is
electrochemically inert under the testing conditions and in the voltage window of
1.4−2.1 V vs. Zn2+/Zn. Meanwhile, the potentials vs. Zn2+/Zn of different cathodes are
almost the same. This indicates that different types of cathodes exert similar
electrochemistry impacts on the intercalation and deintercalation of Li+ into and out of
the cathode. That is to say, 3 wt% LSC-1+G (1:1) just slightly enhances the speed
rather than changes the approach of the intercalation and extraction of Li+ into and out
of the cathode.
4. Conclusions
In this work, the performance of the ReHAB was optimized by a new formulation
of the cathode containing a combined additive of lignin/silica composite (LSC) and
graphene (G). After mixing 3 wt% of LSC-1+G (1:1) into the cathode, the overall
performance of the battery is superior to that of the reference battery as evidenced by
the following details. The float charge capacity decreases from 14.3 to 7.2 mAh·g-1,

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which is accounted for a decrease of 49.7%. The rate performance is improved as
evidenced by the increase of discharge capacity at 0.2 C and 4 C and the maintenance
of discharge capacity at 0.5 C, 1 C, and 2 C. For the cycling performance, the initial
discharge capacity increases from 114.7 to 122.3 mAh·g-1 and the discharge capacity
after 300 cycles is still higher than that of the battery using reference cathode. This
study demonstrates that the performance of ReHAB can be greatly improved through
cathode formulation, meanwhile, contributes to promoting the progress in research of
high value-added application of renewable lignin resources.
Acknowledgements
This research is financially supported by the National Natural Science Foundation
of China (No. 21436004), Natural Science Foundation of Guangdong
Province (2017A030308012), Positec Canada Ltd., and Chinese Scholarship Council
(CSC).
References
[1]
Y.G. Wang, J. Yi, Y.Y. Xia, Recent progress in aqueous lithium-ion batteries, Adv.
Energy Mater. 2 (2012) 830.
[2]
W. Tang, Y.S. Zhu, Y.Y. Hou, L.L. Liu, Y.P. Wu, K.P. Loh, H.P. Zhang, K. Zhu,
Aqueous rechargeable lithium batteries as an energy storage system of superfast
charging, Energy Environ. Sci. 6 (2013) 2093.
[3]
H. Kim, J. Hong, K.-Y. Park, H. Kim, S.-W. Kim, K. Kang, Aqueous rechargeable

ACCEPTED MANUSCRIPT
Li and Na ion batteries, Chem. Rev. 114 (2014) 11788.
[4]
[5]
[6]
[7]
[8]
[9]
N. Alias, A.A. Mohamad, Advances of aqueous rechargeable lithium-ion battery:
a review, J. Power Sources 274 (2015) 237.
W. Li, J.R. Dahn, D.S. Wainwright, Rechargeable lithium batteries with aqueous
electrolytes, Science 264 (1994) 1115.
L. Tian, A.B. Yuan, Electrochemical performance of nanostructured spinel
LiMn2O4 in different aqueous electrolytes, J. Power Sources 192 (2009) 693.
H. Manjunatha, G.S. Suresh, T.V. Venkatesha, Electrode materials for aqueous
rechargeable lithium batteries, J. Solid State Electrochem. 15 (2011) 431.
J. Yan, J. Wang, H. Liu, Z. Bakenov, D. Gosselink, P. Chen, Rechargeable hybrid
aqueous batteries, J. Power Sources 216 (2012) 222.
G.H. Yuan, J.T. Bai, T.N.L. Doan, P. Chen, Synthesis and electrochemical
investigation of nanosized LiMn2O4 as cathode material for rechargeable hybrid
aqueous batteries, Mater. Lett. 137 (2014) 311.
[10]
[11]
[12]
K.E.K. Sun, T.K.A. Hoang, T.N.L. Doan, Y. Yu, X. Zhu, Y. Tian, P. Chen,
Suppression of dendrite formation and corrosion on zinc anode of secondary
aqueous batteries, ACS Appl. Mater. Interfaces 9 (2017) 9681.
K.E.K. Sun, T.K.A. Hoang, T.N.L. Doan, Y. Yu, P. Chen, Highly sustainable zinc
anodes for a rechargeable hybrid aqueous battery, Chem. Eur. J. 23 (2017). DOI:
10.1002/chem.201704440
X.W. Wu, Y.H. Li, C.C. Li, Z.X. He, Y.H. Xiang, L.Z. Xiong, D. Chen, Y. Yu, K.
Sun, Z.Q. He, P. Chen, The electrochemical performance improvement of

ACCEPTED MANUSCRIPT
LiMn2O4/Zn based on zinc foil as the current collector and thiourea as an
electrolyte additive, J. Power Sources 300 (2015) 453.
[13]
[14]
[15]
[16]
C.Y. Lu, T.K.A. Hoang, T.N.L. Doan, H.B. Zhao, R. Pan, L. Yang, W.S. Guan, P.
Chen, Rechargeable hybrid aqueous batteries using silica nanoparticle doped
aqueous electrolytes, Appl. Energy 170 (2016) 58.
C.Y. Lu, T.K.A. Hoang, T.N.L. Doan, M. Acton, H.B. Zhao, W.S. Guan, P. Chen,
Influence of different silica gelling agents on the performance of aqueous gel
electrolytes, J. Ind. Eng. Chem. 42 (2016) 101.
T.K.A. Hoang, T.N.L. Doan, C.Y. Lu, M. Ghaznavi, H.B. Zhao, P. Chen,
Performance of thixotropic gel electrolytes in the rechargeable aqueous
Zn/LiMn2O4 battery, ACS Sustainable Chem. Eng. 5 (2017) 1804.
T.K.A. Hoang, M. Acton, H.T.H. Chen, Y. Huang, T.N.L. Doan, P. Chen,
Sustainable gel electrolyte containing Pb2+ as corrosion inhibitor and dendrite
suppressor for the zinc anode in the rechargeable hybrid aqueous battery, Mater.
Today Energy 4 (2017) 34.
[17]
T.K.A. Hoang, T.N.L. Doan, J.H. Cho, J.Y.J. Su, C. Lee, C.Y. Lu, P. Chen,
Sustainable gel electrolyte containing pyrazole as corrosion inhibitor and dendrite
suppressor for aqueous Zn/LiMn2O4 battery, ChemSusChem 10 (2017) 2816.
X.L. Ji, S. Evers, R. Black, L.F. Nazar, Stabilizing lithium–sulphur cathodes
using polysulphide reservoirs, Nat. Commun. 2 (2011) 325.
[18]
[19]
S. Evers, L.F. Nazar, New approaches for high energy density lithium–sulfur
battery cathodes, Accounts Chem. Res. 46 (2013) 1135.

ACCEPTED MANUSCRIPT
[20]
[21]
[22]
[23]
M. Kim, S.-H. Kang, J. Manuel, X.H. Zhao, K.K. Cho, J.H. Ahn, Investigation
into the role of silica in lithium polysulfide adsorption for lithium sulfur battery,
Mater. Res. Bull. 69 (2015) 29.
G.J. Xu, Z.H. Liu, C.J. Zhang, G.L. Cui, L.Q. Chen, Strategies for improving the
cyclability and thermo-stability of LiMn2O4-based batteries at elevated
temperatures, J. Mater. Chem. A 3 (2015) 4092.
A. Konarov, D. Gosselink, Y.G. Zhang, Y. Tian, D. Askhatova, P. Chen,
Self-discharge of rechargeable hybrid aqueous battery, ECS Electrochem. Lett. 4
(2015) A151.
H. Yang, R. Xu, X.M. Xue, F.T. Li, G.T. Li, Hybrid surfactant-templated
mesoporous silica formed in ethanol and its application for heavy metal removal,
J. Hazard. Mater. 152 (2008) 690.
[24]
[25]
H. Zou, S.S. Wu, J. Shen, Polymer/silica nanocomposites: preparation,
characterization, properties, and applications, Chem. Rev. 108 (2008) 3893.
Y.N. Qu, Y.M. Tian, B. Zou, J. Zhang, Y.H. Zheng, L.L. Wang, Y. Li, C.G. Rong,
Z.C. Wang, A novel mesoporous lignin/silica hybrid from rice husk produced by a
sol–gel method, Bioresource Technol. 101 (2010) 8402.
[26]
W.L. Xiong, D.J. Yang, R.S. Zhong, Y. Li, H.F. Zhou, X.Q. Qiu, Preparation of
lignin-based silica composite submicron particles from alkali lignin and sodium
silicate in aqueous solution using a direct precipitation method, Ind. Crops Prod.
74 (2015) 285.
[27]
W.L. Xiong, X.Q. Qiu, D.J. Yang, R.S. Zhong, Y. Qian, Y.Y. Li, H. Wang, A

ACCEPTED MANUSCRIPT
simple one-pot method to prepare UV-absorbent lignin/silica hybrids based on
alkali lignin from pulping black liquor and sodium metasilicate, Chem. Eng. J.
326 (2017) 803.
[28]
A.J. Ragauskas, G.T. Beckham, M.J. Biddy, R. Chandra, F. Chen, M.F. Davis,
B.H. Davison, R.A. Dixon, P. Gilna, M. Keller, P. Langan, A.K. Naskar, J.N.
Saddler, T.J. Tschaplinski, G.A. Tuskan, C.E. Wyman, Lignin valorization:
improving lignin processing in the biorefinery, Science 344 (2014) 1246843.
T. Aro, P. Fatehi, Production and application of lignosulfonates and sulfonated
lignin, ChemSusChem 10 (2017) 1861.
[29]
[30]
Y. Qian, Y.H. Deng, X.Q. Qiu, H. Li, D.J. Yang, Formation of uniform colloidal
spheres from lignin, a renewable resource recovered from pulping spent liquor,
Green Chem. 16 (2014) 2156.
[31]
[32]
[33]
[34]
S.S. Nair, S. Sharma, Y.Q. Pu, Q.N. Sun, S.B. Pan, J.Y. Zhu, Y.L. Deng, A.J.
Ragauskas, High shear homogenization of lignin to nanolignin and thermal
stability of nanolignin-polyvinyl alcohol blends, ChemSusChem 7 (2014) 3513.
Y.Y. Li, X.Q. Qiu, Y. Qian, W.L. Xiong, D.J. Yang, pH-responsive lignin-based
complex micelles: preparation, characterization and application in oral drug
delivery, Chem. Eng. J. 327 (2017) 1176.
Y. Qian, X.Q. Qiu, X.W. Zhong, D.L. Zhang, Y.H. Deng, D.J. Yang, S.P. Zhu,
Lignin reverse micelles for UV-absorbing and high mechanical performance
thermoplastics, Ind. Eng. Chem. Res. 54 (2015) 12025.
Y. Qian, X.Q. Qiu, S.P. Zhu, Lignin: a nature-inspired sun blocker for

ACCEPTED MANUSCRIPT
broad-spectrum sunscreens, Green Chem. 17 (2015) 320.
[35]
[36]
[37]
[38]
[39]
Y. Qian, X.Q. Qiu, S.P. Zhu, Sunscreen performance of lignin from different
technical resources and their general synergistic effect with synthetic sunscreens,
ACS Sustainable Chem. Eng. 4 (2016) 4029.
Ł. Klapiszewski, M. Nowacka, G. Milczarek, T. Jesionowski, Physicochemical
and electrokinetic properties of silica/lignin biocomposites, Carbohyd. Polym. 94
(2013) 345.
T. Jesionowski, Ł. Klapiszewski, G. Milczarek, Structural and electrochemical
properties of multifunctional silica/lignin materials, Mater. Chem. Phys. 147
(2014) 1049.
Ł. Klapiszewski, P. Bartczak, M. Wysokowski, M. Jankowska, K. Kabat, T.
Jesionowski, Silica conjugated with kraft lignin and its use as a novel ‘green’
sorbent for hazardous metal ions removal, Chem. Eng. J. 260 (2015) 684.
Ł. Klapiszewski, T. Rzemieniecki, M. Krawczyk, D. Malina, M. Norman, J.
Zdarta, I. Majchrzak, A. Dobrowolska, K. Czaczyk, T. Jesionowski, Kraft
lignin/silica–AgNPs as a functional material with antibacterial activity, Colloids
Surfaces B 134 (2015) 220.
[40]
[41]
P.C. Lian, X.F. Zhu, H.F. Xiang, Z. Li, W.S. Yang, H.H. Wang, Enhanced cycling
performance of Fe3O4–graphene nanocomposite as an anode material for
lithium-ion batteries, Electrochim. Acta 56 (2010) 834.
P.C. Lian, X.F. Zhu, S.Z. Liang, Z. Li, W.S. Yang, H.H. Wang, High reversible
capacity of SnO2/graphene nanocomposite as an anode material for lithium-ion

ACCEPTED MANUSCRIPT
batteries, Electrochim. Acta 56 (2011) 4532.
[42]
[43]
[44]
Y.J. Mai, X.L. Wang, J.Y. Xiang, Y.Q. Qiao, D. Zhang, C.D. Gu, J.P. Tu,
CuO/graphene composite as anode materials for lithium-ion batteries,
Electrochim. Acta 56 (2011) 2306.
G.H. Yuan, J.T. Bai, T.N.L. Doan, P. Chen, Synthesis and electrochemical
properties of LiFePO4/graphene composite as a novel cathode material for
rechargeable hybrid aqueous battery, Mater. Lett. 158 (2015) 248.
J. Zhi, A.Z. Yazdi, G. Valappil, J. Haime, P. Chen, Artificial solid electrolyte
interphase for aqueous lithium energy storage systems, Sci. Adv. 3 (2017)
e1701010.
[45]
[46]
[47]
S. Brunaue, P.H. Emmett, E. Telle, Adsorption of gases in multimolecular layers,
J. Am. Chem. Soc. 60 (1938) 309.
F. Lu, S.-H. Wu, Y. Hung, C.-Y. Mou, Size effect on cell uptake in
well-suspended, uniform mesoporous silica nanoparticles, Small 5 (2009) 1408.
Yu.M. Chernoberezhskii, A.A. Atanesyan, A.B. Dyagileva, A.V. Lorentsson, T.V.
Leshchenko, Effect of the concentration of sulfate lignin on the aggregation
stability of its aqueous dispersions, Colloid J. 64 (2002) 637.
[48]
[49]
X.Q. Qiu, Q. Kong, M.S. Zhou, D.J. Yang, Aggregation behavior of sodium
lignosulfonate in water solution, J. Phys. Chem. B 114 (2010) 15857.
M.F. Yan, D.J. Yang, Y.H. Deng, P. Chen, H.F. Zhou, X.Q. Qiu, Influence of pH
on the behavior of lignosulfonate macromolecules in aqueous solution, Colloids
Surf. A: Physicochem. Eng. Aspects 371 (2010) 50.