Electrochemical Characteristics of Capacitor Systems Formed on Chemically Modified Carbon Base
Influence of chemical modification of the activated carbon (AC) material on its specific capacity is found out with the use of methods of impedance spectroscopy, cyclic voltammetry and chronopotentiometry. As shown, a general capacity is the sum of two components, namely, double electric-layer (D...
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Інститут металофізики ім. Г.В. Курдюмова НАН України
2008
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| Цитувати: | Electrochemical Characteristics of Capacitor Systems Formed on Chemically Modified Carbon Base / B.K. Ostafiychuk, I.M. Budzulyak, V.I. Mandzyuk, R.P.Lisovskyy // Наносистеми, наноматеріали, нанотехнології: Зб. наук. пр. — К.: РВВ ІМФ, 2008. — Т. 6, № 4. — С. 1207-1217. — Бібліогр.: 7 назв. — англ. |
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irk-123456789-762272015-02-09T03:01:59Z Electrochemical Characteristics of Capacitor Systems Formed on Chemically Modified Carbon Base Ostafiychuk, B.K. Budzulyak, I.M. Mandzyuk, V.I. Lisovskyy, R.P. Influence of chemical modification of the activated carbon (AC) material on its specific capacity is found out with the use of methods of impedance spectroscopy, cyclic voltammetry and chronopotentiometry. As shown, a general capacity is the sum of two components, namely, double electric-layer (DEL) capacity and pseudocapacity, thus the deposit of the last is insignificant (8—14%). The alloying with rare-earth metals and their compounds results in the rise of specific capacity of AC. Probably, the principal reason of such a growth is transformation of valence bond of carbon material due to introduction of the additional electron states from the implanted metals. As a result, the considerably greater amount of ions (especially, positive ones) will take part in DEL forming, and, consequently, will predetermine growth of specific capacity. З’ясовано вплив хемічної модифікації активованого вуглецевого матеріялу на його питому місткість з використанням метод імпедансної спектроскопії, циклічної вольтамперометрії та хроноамперометрії. Показано, що загальна місткість є сумою двох складових – місткости подвійного електричного шару (ПЕШ) та псевдомісткости, причому, внесок останньої є незначним (8—14%). Леґування рідкоземельними металами та їх сполуками призводить до збільшення питомої місткости активованого вуглецю. Ймовірно, основною причиною такого зростання є трансформація валентної зони вуглецевого матеріялу за рахунок добавляння додаткових електронних станів від втілених матеріялів, в результаті чого значно більша кількість йонів (насамперед, позитивних) буде брати участь у формуванні ПЕШ, а отже, і зумовлювати зростання питомої місткости. Изучено влияние химической модификации активированного углеродного материала на его удельную емкость с использованием методов импедансной спектроскопии, циклической вольтамперометрии и хроноамперометрии. Показано, что общая емкость является суммой двух составляющих – емкости двойного электрического слоя (ДЭС) и псевдоемкости, причем, вклад последней незначителен (8—14%). Легирование редкоземельными металлами и их соединениями увеличивает удельную емкость активированного углерода. Вероятно, основной причиной такого роста является трансформация валентной зоны углеродного материала за счет добавления дополнительных электронных состояний от внедренных материалов, вследствие чего значительно большее количество ионов (в первую очередь, положительных) будет принимать участие в формировании ДЭС, а, следовательно, и обусловливать рост удельной емкости. 2008 Article Electrochemical Characteristics of Capacitor Systems Formed on Chemically Modified Carbon Base / B.K. Ostafiychuk, I.M. Budzulyak, V.I. Mandzyuk, R.P.Lisovskyy // Наносистеми, наноматеріали, нанотехнології: Зб. наук. пр. — К.: РВВ ІМФ, 2008. — Т. 6, № 4. — С. 1207-1217. — Бібліогр.: 7 назв. — англ. 1816-5230 PACS numbers: 81.05.U-, 81.40.Rs, 82.45.Yz, 82.47.Uv, 84.32.Tt http://dspace.nbuv.gov.ua/handle/123456789/76227 en Наносистеми, наноматеріали, нанотехнології Інститут металофізики ім. Г.В. Курдюмова НАН України |
| institution |
Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| collection |
DSpace DC |
| language |
English |
| description |
Influence of chemical modification of the activated carbon (AC) material on its
specific capacity is found out with the use of methods of impedance spectroscopy,
cyclic voltammetry and chronopotentiometry. As shown, a general capacity
is the sum of two components, namely, double electric-layer (DEL) capacity
and pseudocapacity, thus the deposit of the last is insignificant (8—14%). The
alloying with rare-earth metals and their compounds results in the rise of specific
capacity of AC. Probably, the principal reason of such a growth is transformation
of valence bond of carbon material due to introduction of the additional
electron states from the implanted metals. As a result, the considerably
greater amount of ions (especially, positive ones) will take part in DEL forming,
and, consequently, will predetermine growth of specific capacity. |
| format |
Article |
| author |
Ostafiychuk, B.K. Budzulyak, I.M. Mandzyuk, V.I. Lisovskyy, R.P. |
| spellingShingle |
Ostafiychuk, B.K. Budzulyak, I.M. Mandzyuk, V.I. Lisovskyy, R.P. Electrochemical Characteristics of Capacitor Systems Formed on Chemically Modified Carbon Base Наносистеми, наноматеріали, нанотехнології |
| author_facet |
Ostafiychuk, B.K. Budzulyak, I.M. Mandzyuk, V.I. Lisovskyy, R.P. |
| author_sort |
Ostafiychuk, B.K. |
| title |
Electrochemical Characteristics of Capacitor Systems Formed on Chemically Modified Carbon Base |
| title_short |
Electrochemical Characteristics of Capacitor Systems Formed on Chemically Modified Carbon Base |
| title_full |
Electrochemical Characteristics of Capacitor Systems Formed on Chemically Modified Carbon Base |
| title_fullStr |
Electrochemical Characteristics of Capacitor Systems Formed on Chemically Modified Carbon Base |
| title_full_unstemmed |
Electrochemical Characteristics of Capacitor Systems Formed on Chemically Modified Carbon Base |
| title_sort |
electrochemical characteristics of capacitor systems formed on chemically modified carbon base |
| publisher |
Інститут металофізики ім. Г.В. Курдюмова НАН України |
| publishDate |
2008 |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/76227 |
| citation_txt |
Electrochemical Characteristics of Capacitor Systems Formed
on Chemically Modified Carbon Base / B.K. Ostafiychuk, I.M. Budzulyak, V.I. Mandzyuk, R.P.Lisovskyy // Наносистеми, наноматеріали, нанотехнології: Зб. наук. пр. — К.: РВВ ІМФ, 2008. — Т. 6, № 4. — С. 1207-1217. — Бібліогр.: 7 назв. — англ. |
| series |
Наносистеми, наноматеріали, нанотехнології |
| work_keys_str_mv |
AT ostafiychukbk electrochemicalcharacteristicsofcapacitorsystemsformedonchemicallymodifiedcarbonbase AT budzulyakim electrochemicalcharacteristicsofcapacitorsystemsformedonchemicallymodifiedcarbonbase AT mandzyukvi electrochemicalcharacteristicsofcapacitorsystemsformedonchemicallymodifiedcarbonbase AT lisovskyyrp electrochemicalcharacteristicsofcapacitorsystemsformedonchemicallymodifiedcarbonbase |
| first_indexed |
2025-07-06T00:39:45Z |
| last_indexed |
2025-07-06T00:39:45Z |
| _version_ |
1836855995142242304 |
| fulltext |
1207
PACS numbers: 81.05.U-, 81.40.Rs, 82.45.Yz, 82.47.Uv, 84.32.Tt
Electrochemical Characteristics of Capacitor Systems Formed
on Chemically Modified Carbon Base
B. K. Ostafiychuk, I. M. Budzulyak, V. I. Mandzyuk, and R. P. Lisovskyy
Vasyl Stefanyk Precarpathian National University,
Shevchenko Str., 57,
Ivano-Frankivsk, Ukraine
Influence of chemical modification of the activated carbon (AC) material on its
specific capacity is found out with the use of methods of impedance spectros-
copy, cyclic voltammetry and chronopotentiometry. As shown, a general capac-
ity is the sum of two components, namely, double electric-layer (DEL) capacity
and pseudocapacity, thus the deposit of the last is insignificant (8—14%). The
alloying with rare-earth metals and their compounds results in the rise of spe-
cific capacity of AC. Probably, the principal reason of such a growth is trans-
formation of valence bond of carbon material due to introduction of the addi-
tional electron states from the implanted metals. As a result, the considerably
greater amount of ions (especially, positive ones) will take part in DEL form-
ing, and, consequently, will predetermine growth of specific capacity.
З’ясовано вплив хемічної модифікації активованого вуглецевого матеріялу
на його питому місткість з використанням метод імпедансної спектроско-
пії, циклічної вольтамперометрії та хроноамперометрії. Показано, що за-
гальна місткість є сумою двох складових – місткости подвійного електри-
чного шару (ПЕШ) та псевдомісткости, причому, внесок останньої є незна-
чним (8—14%). Леґування рідкоземельними металами та їх сполуками
призводить до збільшення питомої місткости активованого вуглецю. Ймо-
вірно, основною причиною такого зростання є трансформація валентної
зони вуглецевого матеріялу за рахунок добавляння додаткових електро-
нних станів від втілених матеріялів, в результаті чого значно більша кіль-
кість йонів (насамперед, позитивних) буде брати участь у формуванні
ПЕШ, а отже, і зумовлювати зростання питомої місткости.
Изучено влияние химической модификации активированного углеродного
материала на его удельную емкость с использованием методов импедансной
спектроскопии, циклической вольтамперометрии и хроноамперометрии.
Показано, что общая емкость является суммой двух составляющих – ем-
кости двойного электрического слоя (ДЭС) и псевдоемкости, причем, вклад
последней незначителен (8—14%). Легирование редкоземельными метал-
Наносистеми, наноматеріали, нанотехнології
Nanosystems, Nanomaterials, Nanotechnologies
2008, т. 6, № 4, сс. 1207—1217
© 2008 ІМФ (Інститут металофізики
ім. Г. В. Курдюмова НАН України)
Надруковано в Україні.
Фотокопіювання дозволено
тільки відповідно до ліцензії
1208 B. K. OSTAFIYCHUK, I. M. BUDZULYAK, V. I. MANDZYUK et al.
лами и их соединениями увеличивает удельную емкость активированного
углерода. Вероятно, основной причиной такого роста является трансфор-
мация валентной зоны углеродного материала за счет добавления дополни-
тельных электронных состояний от внедренных материалов, вследствие
чего значительно большее количество ионов (в первую очередь, положи-
тельных) будет принимать участие в формировании ДЭС, а, следовательно,
и обусловливать рост удельной емкости.
Key words: activated carbon material, double electric layer, specific capacity,
Nyquist diagram, cyclic voltamogram.
(Received November 21, 2008)
1. INTRODUCTION
The use of various methods of after-activation modification of an acti-
vated carbon (AC) is related to the necessity to improve its parameters as
electrode material of electrochemical capacitors (EC). So it is not possible
to attain the necessary values of given parameters in the process of acti-
vating, in particular, specific resistance and specific capacity of a double
electric layer (DEL) formed by the given material and electrolyte [1].
Coming from general principles of physics and topology of the devel-
oped surface, the principle decision of the indicated problem possible
both due to the increase of the electronic state density in a AC matrix
[2], and due to bringing as soon as possible greater part of the developed
surface in DEL forming, because, as known [3], to 50% of working pores
do not wet by an electrolyte through their chemical-structural features.
One of possibilities of the indicated ideas realization is modification of
AC by its alloying by rare-earth metals and their compounds, that would
give possibility substantially to multiply a DEL capacity, and, accord-
ingly, the capacitors formed on the basis of thus modified AC. Er be-
longs to the first (its percentage in AC makes 0.1, 0.2, and 0.4 wt.%), to
the second–Tm2O3, Eu2O3, Dy2O3, Ho2O3, Pr2O3, content of which in AC
made 0,1 wt.%. The addition of copper was entered in an amount 0.1
wt.% into got alloyed materials (Er, Tm2O3, Eu2O3) with the purpose of
rise of its electronic conductivity. Therefore, the influence of introduc-
tion of the indicated metals into AC on its physical and chemical proper-
ties and operating characteristics of capacitors with a DEL formed on its
base [4] was explored in a given work.
2. EXPERIMENTAL
AC got from fruit stone by them carbonization with a next activation
in the closed reactor at high pressure was used as research objects [5].
The alloying of AC by erbium was carried out with using a nitro-acid
ELECTROCHEMICAL CHARACTERISTICS OF CAPACITOR SYSTEMS 1209
erbium. Investigation of alloying admixtures distribution in AC was
carried out by the method of second ion mass spectrometry on mass-
spectrometer MS-7201 device.
A three-electrode electrochemical cell (Fig. 1) was used for the receipt
of Nyquist diagrams. AC with the proper percentage of the alloyed mate-
rial was used as working electrode, a comparative electrode was similar
to working that, a silver-chlorine electrode Ag/AgCl was as a reference
electrode. A potential of carbon material in relation to the reference elec-
trode made −0.33—−0.28 V. 30% water solution of KOH + 0.3% water
solution of LiOH was used as an electrolyte. The impedance measuring
was conducted with the use of spectrometer Autolab PGSTAT/FRA-2
(Holland) in the frequency interval of 10−2—105
Hz.
The receipt of cyclic voltamperograms of carbon electrodes was con-
ducted in the potential range of −1—0.2 V with the use of above three-
electrode cell with silver-chlorine electrode reference electrode. Scan
rate was 5, 8, 10, 20, 30, 40, and 50 mV/s.
3. RESULTS AND DISCUSSION
It is comfortably to study properties of enough wide rows of the sys-
tems, especially electrochemical ones, after response of this systems to
an external sinusoidal signal. The use of impedance spectroscopy me-
thod for solving of indicated above tasks is most expedient in this plan,
as it enables to conduct research in the enough wide frequency interval
(f = 106—10−3
Hz) [6].
For Er-modified carbon materials, a Nyquist diagram (Fig. 2) pre-
sents by itself a combination of two asymmetric semicircles in the fre-
quencies region of 1—105
Hz. Low-frequency branch tends to infinity at
ω → 0 for AC with 0.1 and 0.2 wt.% Er content that indicates on the
typical behaviour of the capacitor systems. It inclines angularly ∼ 45 to
Fig. 1. Electrochemical cell: 1–glass cell; 2–pressurizing cover; 3–electrolyte;
4–working electrode; 5–reference electrode; 6–comparative electrode.
1210 B. K. OSTAFIYCHUK, I. M. BUDZULYAK, V. I. MANDZYUK et al.
the actual resistance axis for material with 0.4 wt.% Er content that can
specify in the presence of diffusive processes in the explored material,
which are described by an Warburg impedance.
Equivalent schemes, which model electrochemical processes, flowed at
the electrode-electrolyte boundary and in material, testify the in favor of
indicated suppositions (Fig. 3). A relative error for each parameters of
equivalent scheme does not exceed 5%; parameter χ2 = 10—4—10—5
that tes-
tifies to legitimacy of the offered choice.
Resistance Rct corresponds to series equivalent resistance, which con-
sists of the electrolyte resistance, resistance of lead and contacts. Two
R||CPE-links can be linked to heterogeneity of DEL and fractal structure
of electrode, resistance R4 is polarization or electronic resistance of ma-
terial, Cdl–DEL capacity, capacity-type constant phase element CPE3
corresponds to a Faraday capacity; Wo–diffusive Warburg impedance.
The increase of Er percentage results in the insignificant increase of
total resistance R2 + R3 (from 16 to 25 Ohm). It testify that Er intro-
duction blocks the ions C
+
transport through the electrode-electrolyte
boundary and hinders to them to form DEL. Except for it, a growth of
Er content predetermines a forming of heterogeneous DEL and inten-
�
Fig. 2. Nyquist diagram of Er-modified АC.
Fig. 3. Equivalent schemes for Nyquist diagrams obtained for Er-modified
АC: (а) 0.1 and 0.2 wt.% Er content; (б) 0.4 wt.% Er content.
ELECTROCHEMICAL CHARACTERISTICS OF CAPACITOR SYSTEMS 1211
sification of diffusive processes in it–growth of CPE1 and CPE2 pa-
rameters confirm it. The first parameter is the constant phase element
of capacity type (n ∼ 0.83), the second one is of diffusive type
(n ∼ 0.55). The n parameter is in a formula for determination of imped-
ance size of CPE element ZCPE = A−1(jω)−n
and characterize a phase de-
viation. A growth of erbium concentration in AC results in the increase
of CPE3 parameter, which presents by itself the constant phase element
with the heterogeneously distributed capacity (n = 0.82—0.91). Thanks
to it, the total capacity of material is multiplied not only thanks to a
DEL capacity, but also due to faraday processes. Electronic resistance
of material according to impedance spectroscopy data makes 22.6,
22.7, and 24,3 Ohm, respectively. There is a maximum for DEL capac-
ity at 0.2% Er content (Table 1). It is possible to assume that thanks to
an erbium the electronic state density is multiplied at a Fermi level of
carbon material, as a result greater amount C
+
ions take part in DEL
forming. Subsequent erbium introduction results in blocking of work-
ing pores of AC, as a result there is reduction of DEL capacity [7].
The given supposition is confirmed by the results of potentiodynam-
ics researches (Fig. 4). There is the difference of the I—E curves espe-
cially in the region of negative potentials, at which a DEL capacity is
provided by C
+
ions from the electrolyte side. Dissymmetry of given
curves in relation to the zero current line (I = 0) is the characteristic
feature, that specifies on the passing of processes unconnected with
DEL forming (above all Faraday processes).
Introduction of copper in an amount of 0.1 and 0.4 wt.% into Er-
modified material, which has a maximal specific capacity, does not
TABLE 1. Specific capacity of AC, F/g.
Method
Material Impedance
spectrometry
Voltamperometry Chronopotentiometry
АC 56 64 69
АC + 0.1% Er 71 77 73
АC + 0.2% Er 75 83 72
АC + 0.4% Er 59 66 65
АC + 0.2% Er + 0.1% Cu 61 69 68
АC + 0.2% Er + 0.4% Cu 72 81 77
АC + 0.1% Tm2O3 – 68 63
АC + 0.1% Tm2O3
+ 0.1% Cu 89 101 81
АC + 0.1% Eu2O3 80 86 67
АC + 0.1% Eu2O3 + 0.1% Cu 82 84 68
АC + 0.1% Dy2O3 78 83 65
АC + 0.1% Ho2O3 80 83 70
АC + 0.1% Pr2O3 54 59 58
1212 B. K. OSTAFIYCHUK, I. M. BUDZULYAK, V. I. MANDZYUK et al.
change the type of Nyquist diagram noticeably, predetermining the
change of general impedance of the electrochemical system only
(Fig. 5). According to it, an equivalent scheme, which models motion
of electrochemical processes in the explored system, will have a similar
kind (Fig. 3, a).
Electrochemical system made on the Er-modified material basis with
0.1 wt.% Cu content is characterized by the some greater values of R2
and R3 parameters (2.8 and 3.7 Ohm, and 19.1 and 24.9 Ohm, respec-
tively) and practically unchanging electronic resistance R4 (22.8 and
23.2 Ohm, respectively) in comparison with the unalloyed by a copper
material. However, there is the reduction of all three resistances at 0.4
wt.% Cu concentrations in carbon material, especially, electronic one
R4 (14.2 Ohm) that is expressly represented on —ImZ = f(ReZ) depend-
Fig. 4. Cyclic voltamperograms of Er-modified АC.
Fig. 5. Nyquist diagrams for Er- and Er + Cu-modified АC.
ELECTROCHEMICAL CHARACTERISTICS OF CAPACITOR SYSTEMS 1213
ence. Accordingly to Table 1, such modification by a copper does not
lead the specific capacity of carbon material to the improvement, and
can be used with a purpose of the increase of its electronic conductiv-
ity. Except for it, almost the identical capacity of the unalloyed and
alloyed (0.4 wt.%) standards is achieved not due to DEL capacity, but
due to the faraday that conditioned by the passing of mass-transfer
processes (probably, redox reactions).
It is confirmed by the results of voltamperometric researches, accord-
ingly to which there is an ‘influx’ in the negative potential region for a
standard with 0.4 wt.% Cu contents, which is attribute to the faraday
processes (Fig. 6). A horizontal plateau on the anode branch of І—Е-
curve of other standard indicates on that the specific capacity of mate-
rial is provided mainly by DEL capacity.
The use of oxides by rare-earth metals as alloying material (Tm2O3,
Dy2O3, Pr2O3, Eu2O3, Ho2O3) does not change cardinally the general
type of impedance curve (Fig. 7) (except for AV, alloyed by Tm2O3).
However, equivalent schemes, which model electrochemical processes,
some differ. In particular, for AC doped by Dy2O3 and Pr2O3, a scheme
is similar to that on Fig. 3. There is the difference: the constant phase
element CPE3 is the element of capacity type for the first material,
while for the second, diffusive one.
For Eu2O3- and Ho2O3-doped materials, a scheme is the same as well
as for Cr- and Mn- doped AC (Fig. 8) [2]. For AC doped by Tm2O3, we
can not find an equivalent scheme, which would describe satisfactorily
the behaviour of the electrochemical system.
As follows from Table 1, a specific capacity for Eu2O3-, Ho2O3-, and
Dy2O3-doped material is practically identical. Taking into account the
results of impedance spectroscopy and voltamperometry (Fig. 9), it is
Fig. 6. Cyclic voltamperograms of Er + Сu-modified АC.
1214 B. K. OSTAFIYCHUK, I. M. BUDZULYAK, V. I. MANDZYUK et al.
possible to assert that the general specific capacity of the explored ma-
terial is provided by DEL capacity and pseudocapacity. For two other
materials, in which Pr2O3 and Tm2O3 are as alloying additions, the de-
posit of pseudocapacity is unimportant.
Additional alloying of the given materials by copper in an amount of
Fig. 7. Nyquist diagrams of AC doped by oxides of rare-earth metals.
Fig. 8. Equivalent scheme for Nyquist diagram obtained for chemical modi-
fied AC.
TABLE 2. Internal resistance, Оhm.
Method
Material
Impedance spectroscopy Chronopotentiometry
АC + 0.1% Er 22.6 24.3
АC + 0.2% Er 22.7 23.2
АC + 0.4% Er 24.3 29.4
АC + 0.2% Er + 0.1% Cu 23.2 25.2
АC + 0.2% Er + 0.4% Cu 14.2 17.8
АC + 0.1% Tm2O3 39.5 47.3
АC + 0.1% Tm2O3
+ 0.1% Cu 14.9 18.2
АC + 0.1% Eu2O3 9.2 11.3
АC + 0.1% Eu2O3 + 0.1% Cu 7.4 8.4
АC + 0.1% Dy2O3 11.9 13.3
АC + 0.1% Ho2O3 11.7 13.4
АC + 0.1% Pr2O3 30.9 32.8
ELECTROCHEMICAL CHARACTERISTICS OF CAPACITOR SYSTEMS 1215
0.1 wt.% results not only in growth of specific capacity, but also in re-
duction of general impedance of the system (Fig. 10).
Internal resistance, which characterizes electro-physical properties
of electrode carbon material, is no less important parameter. Its de-
termination was conducted by the methods of impedance spectroscopy
and chronopotentiometry. In the first case, the size of internal resis-
tance was got from the results of model, and in the second, with the use
of formula (2 )R U I= Δ , where ΔU–voltage drop on a discharge curve
(Fig. 11), I–discharge current.
The values of internal resistance of the explored materials, got both
methods, are resulted in Table 2.
Fig. 9. Cyclic voltamperograms of АC doped by oxides of rare-earth metals.
а б
Fig. 10. Nyquist diagrams of ACdoped by oxides of rare-earthmetals and copper.
1216 B. K. OSTAFIYCHUK, I. M. BUDZULYAK, V. I. MANDZYUK et al.
It is necessary to remark that a difference between the got values is
not very substantial (it does not exceed 7%). However, the chronopo-
tentiometry method is more exact thanks to the simplicity.
Thus, chemical modification of AC by rare-earth metals and their
compounds results in the rise of specific capacity AC. The principal
reason of such growth, accordingly to previous researches, is trans-
formation of valence area of carbon material due to bringing of the ad-
ditional electronic states from the inculcated metals, as a result the
considerably greater amount of ions (first of all, positive ones) will
take part in DEL forming, and, consequently, to predetermine a
growth of specific capacity.
CONCLUSIONS
The equivalent schemes of capacitor system on modified AC bases are
proposed, which describe satisfactorily electrochemical processes both
on electrode—electrolyte boundary and in AC-matrix.
The general capacity of explored system is the sum of two compo-
nents–DEL capacity and pseudocapacity, thus the deposit of the last
is insignificant (8—14%).
The alloying by rare-earth metals and their compounds can results
in the rise of specific capacity of AC up to 17%.
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Fig. 11. A typical shape of charge—discharge curve.
ELECTROCHEMICAL CHARACTERISTICS OF CAPACITOR SYSTEMS 1217
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