ISSN 10876596, Glass Physics and Chemistry, 2013, Vol. 39, No. 5, pp. 570–578. © Pleiades Publishing, Ltd., 2013. Original Russian Text © O.A. Shilova, V.N. Antipov, P.A. Tikhonov, I.Yu. Kruchinina, M.Yu. Arsent’ev, T.I. Panova, L.V. Morozova, V.V. Moskovskaya, M.V. Kalinina, I.N. Tsvetkova, 2013, published in Fizika i Khimiya Stekla.
Ceramic Nanocomposites Based on Oxides of Transition Metals for Ionistors O. A. Shilova, V. N. Antipov, P. A. Tikhonov, I. Yu. Kruchinina, M. Yu. Arsent’ev, T. I. Panova, L. V. Morozova, V. V. Moskovskaya, M. V. Kalinina, and I. N. Tsvetkova Grebenshchikov Institute of Silicate Chemistry, Russian Academy of Sciences, nab. Makarova 2, St. Petersburg, 199034 Russia email: tikhonov_p
[email protected] Received August 17, 2012
Abstract—Lowtemperature synthesis methods are used to produce nanoceramic materials for electrodes of the following ionistors: (ZrO2)0.6(In2O3)0.4, praseodymium cobaltite, as well as neodymium, lanthanum, and nickel chromites; they operate in the presence of an ionconducting phosphorosilicate separator membrane and phosphate impregnation. Film electrodes of ionistors are fabricated that consist of nanocrystalline oxide materials deposited as a thin film on a porous electroconductive metal substrate, i.e., foamed nickel. The MnO2–foamed nickel electrode has a specific capacity of 45.0 F g–1, which is compared with that of indus trial supercapacitors. Keywords: ceramics, membrane, electric conductivity, electrodes, electrolyte, foamed nickel, supercapaci tors DOI: 10.1134/S1087659613050179
INTRODUCTION At present, an increase in energy costs makes power consumption and energy saving issues even more top ical in various fields of electronics, electrical engineer ing, electrical systems of vehicles, power engineering when energy collection and recuperation systems for wind and solar power plants are developed, and unin terrupted power supplies. Electrolytic capacitors, accumulators, or batteries are used, depending on the mode of power consumption and the field of applica tion. However, these devices cannot always fully solve the problem of a selfcontained power supply. Accord ing to experts, supercapacitors represent a way of ensuring efficient power consumption. The development and production of supercapaci tors or ionistors is a promising research trend in mod ern materials science. They are devices for the accu mulation and storage of energy combining high spe cific power, a long service life, and low power consumption. Ionistors have a number of advantages over other power sources, such as batteries and accu mulators, i.e., a wide temperature range, a long service life, and cyclic stability [1–3]. Supercapacitors represent the most striking devel opment in capacitormaking during the last decade. The prefix “super” is added due to their capacity that is approximately by three orders of magnitude higher than the capacity of traditional capacitors with similar dimensions. As analytical experts of globally known industrial companies believe, the compound growth
rate for the global supercapacitor market for 2008– 2014 will amount to 27% and sales will substantially increase [4, 5]. There are two types of supercapacitors, i.e., super capacitors with a double electrical layer or electro chemical supercapacitors and supercapacitors with the pseudocapacity effect [6–8]. The charge that can be accumulated by a supercapacitor with the pseudocapacity effect can exceed 10–100 times the charge that can be accumulated by its analogs based on the double electricallayer principle [6]. In capacitors with a double electrical layer, the electrode is mainly made of carbon, nanotubes, fullerenes, carbon nanofibers, and other materials. The main drawback of these capacitors with carbon electrodes is the high cost, which is determined by substantial production power inputs and a short ser vice life. For an electrode made of oxides of transition metals with a high specific capacity and a low specific electric resistance, this problem can be solved and the field of application of the supercapacitors can be con siderably widened. Among oxides of transition metals, RuO2 possesses the greatest specific capacity. Pure RuOxHy is a mixed electron–proton conductor with a high specific capacity (720–900 F/g). Extensive studies of ruthe nium oxide were mainly carried out for military pur poses where the cost issue is less urgent than in com mercial applications. The efforts of research institutes from all over the world are aimed at the search for
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Table 1. Composition and properties of supercapacitor electrodes based on oxides of transition metals [9] Production method
Specific capacity, F g ⎯1
Sol–gel Sol–gel and electrophoresis deposition Sol–gel Sol–gel and electrochemical Hardening of V2O5 powder –
650–720 100–720 290 250 350 200
Electrode material RuO2 MnO2 CoOx NiOx V2O5 Iron oxides
alternative and cheaper materials to replace RuO2. Table 1 presents the values of the specific capacity of the electrodes based on some oxides of transition met als for capacitors [9]. The main requirements for oxide electrode materi als are a high specific electric conductivity at low tem peratures (25–700°C). Oxides of the transition metals with a variable valence cause the occurrence of redox processes at the electrode–electrolyte interface, thus giving rise to an increase in the specific capacity. The accumulation of charge in ionistors of the new generation occurs both due to electrostatic processes in the double electrical layer at the electrode–electro lyte interface and due to reversing Faraday processes, such as redox reactions that induce pseudocapacity; this implies the need to develop electrode and electro lyte materials with the required properties. The production of a working cell of the ionistors requires the availability of electrodes and an electro lyte, as well as nanocomposites for the separator mem brane to be developed. In the last few years, the devel opment of ionexchange membranes (IEMs) has been one of the important aspects of creating protoncon ducting membranes [10]. Perfluorinated sulfonic cat ionite membranes patented by the E.I. du Pont de Nemours and Company (United States) are currently the only commercial IEM with the abovementioned properties. An analog of these membranes was devel oped in the Plastpolymer JSC (Russia) [11]. Alterna tive variants of creating protonconducting mem branes with improved characteristics, which are the basis for the material for separator membranes of supercapacitors, are searched for all over the world. The aim of this work is to develop ionistors of the new generation, made of advanced functional materi als based on nanocrystalline oxide electrode and elec trolyte materials with reproducible characteristics. SYNTHESIS AND STUDY METHODS In this work, the oxide electrode materials and the phosphorosilicate membranes were synthesized using lowtemperature methods, i.e., the sol–gel method, chemical deposition, the cocrystallization of salt solu tions with mechanochemical activation, which made it possible to produce nanocomposites with a specified GLASS PHYSICS AND CHEMISTRY
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composition, as well as high mechanical, electrical, and other properties [12–18]. The sol–gel synthesis method is based on the tran sition of a fluid solution of silicon alcoxyl compounds, e.g., tetraethyl ortosilicate, tetramethyl ortosilicate, and others to a gel due to the hydrolysis and polycon densation reactions, followed by the transformation of the gel to a monolithic composite, powder, or thin coating [15, 16]. The synthesis of an inorganic poly mer in the presence of an organic polymer may yield hybrid materials that possess flexibility and a high pro ton conductivity (4 × 10–2–8 × 10–1 S/cm); they are formed by spilling [19]. When using the reverse coprecipitation method (RCM), we used diluted solutions of nitrates (not more than 0.1 M) as the reagents to be precipitated and a water solution of ammonia NH4OH as the pre cipitating agent [17, 18, 20]. This method yielded gel like precipitates of the hydroxides of the precipitated substances, i.e., hydroxides of zirconium, indium, niobium, titanium, and aluminum. The structure and properties of these hydroxides depend on many pro cess factors such as the pH of the fluid and the concen trations of the precipitated substances, as well as the precipitating agent, the precipitation rate, the proce dures of the agitation of the precipitate, the process temperature, and the duration of the length of the pre cipitate in the mother solution. The optimal conditions of the coprecipitation of solid solutions, i.e., the gelation rate and the pH of the fluid are developed based on the data on the potentio metric titration of the nitrates of zirconium, indium, aluminum, rare earth elements, and their mixtures in the specified stoichiometric ratios for each given com position. The cocrystallization method favors the reactions of the chemical components at the ion–molecular level and, in our case, implies the use of nitrates of chrome, lanthanum, neodymium, cobalt, iron, and other elements followed by their mixing and evapora tion in a water bath, as well as the cooling of the over saturated solutions until the formation of crystalline hydrates. These powders were then compacted and shaped into the form of an electrode and sintered at a temperature of 1200°C for 2 h until the required 2013
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oxides of chrome, neodymium, cobalt, nickel, lantha num, and other elements appeared [13, 19]. Mechanochemical synthesis was carried out at a relatively low temperature at which the formation of a perfect crystalline structure was hampered [21]. The mechanochemical activation of the powders was per formed in a Fritch planetarytype mill for 1 h at the mass ratio charge : balls = 1 : 1 with addition of ethyl alcohol; the specimens shaped as electrodes were then formed and sintered at 1200–1250°C. Electric Conductivity The ceramic specimens were shaped as parallelepi peds and silver paste based on the colophonyturpen tine binder was then applied on their ends. The con ductivity of the ceramics was measured in the temper ature range of 500–1000 K; no measurements were carried out at higher temperatures because of the risk of the melting of the silver contacts preapplied to the substrate. The electrical characteristics were measured using a hardware and software complex for studying the electrical properties of nanocrystalline ceramics [19]. The complex included a temperaturecontrolled heater, a temperature controller, two thermocouples, and a programmed measuring unit. The results were automatically stored in a computer. The relative conductivity measurement error in the range of 500–1000 K is ~20%. The electric conductivity was calculated using the following formula:
()
σ=G l , S where σ is the specific conductivity; G is the conduc tivity; l is the specimen thickness; and S is the speci men thickness. An electrodes–electrolyte working cell was fabri cated with KOH used as the electrolyte. In order to test the produced film electrode materials, i.e., to deter mine their specific capacity, we designed a setup con sisting of a B543A power supply, a diode limiter, and a hardware and software complex. The open porosity of the ceramic specimens was determined in accordance with GOST 473.481 [17]. The pH was measured using a 150 M pH tester. Xray phase analysis (XRPA) was carried out in a DRON3 diffractometer; the diffraction patterns were identified using the data from the file of ASTM inter national standards. Differential thermal analysis (DTA) was performed in a Q1000 derivatograph (MOM Co.) in the temper ature range of 20–800°C. EXPERIMENTAL The nanocrystalline solid solutions and the com posites we synthesized from the ZrO2–In2O3, ZrO2–
Al2O3–TiO2–Nb2O5, Pr2O3–CoO, Cr2O3–Fe2O3– MnO2, CoO–CeO2, CeO2–Ta2O5, Pr2O3–CoO, NiO–CoO, and NiO–Nd2O3 systems, as well as neodymium, lanthanum, and nickel complex chromites, were studied as the materials for the accu mulating electrodes. These materials possess catalytic activity due to the redox processes related to the vari able valence of Cr, Ni, Pr, Nb, Co, Nd, and Ti, as well as high electric conductivity. Table 2 presents the results of measuring the spe cific electric conductivity of the ceramic electrode composites under study. The materials based on the ZrO2–In2O3 system, as well as neodymium, lanthanum, and nickel complex chromites, meet the specified requirements, since at 300 K, their specific electric conductivity that contrib utes to the charge accumulation process is 3 × 10–3– 10 S cm–1. In order to confirm this conclusion, the temperature dependences of the specific electric con ductivity of some of the best ceramic electrode nano composites are shown in Fig. 1. The crystalline struc ture features and the physicochemical properties of these electrode materials were studied. Neodymium, lanthanum, and nickel complex chromites were synthesized by cocrystallization (Fig. 2). Table 3 presents the chemical compositions, the structures, and the open porosity of the selected elec trode materials, as well as the conditions of their syn thesis and sintering. The open porosity was deter mined by the hydrostatic method. It can be seen from Table 3 that, at temperatures above 700°C, lanthanum and neodymium complex chromites have the orthor hombic perovskite (RP) structure. At a temperature of 1100°C, the phase transition of orthorhombic perovs kite to rhombohedral perovskite (RP), whose structure is retained up to 1300°C, occurs. No such structural transformation occurs in neodymium and nickel com plex chromites (compositions 4 and 5 in Table 3) and the OP structure is retained in neodymium complex chromite up to 1300°C. Figure 3 shows the diffraction pattern of lanthanum and neodymium chromites with the OP structure obtained after sintering at 800°C. The average grain size of lanthanum and neodymium chromites reaches 30–110 nm at temperatures of 800 and 1300°C. The grain size of the synthesized nanoc eramics was calculated by the Scherrer formula D = 0.9 λ/(β cosθ) [22], where D is the average grain size; λ is the CuKα wavelength; and β is the halfwidth of the diffraction peak. In order to produce the electrode material in the ZrO2–In2O3 system, we selected the compound with the (ZrO2)0.6(In2O3)0.4 composition (Table 3) synthe sized by the reverse coprecipitation of zirconium and indium hydroxides. Solutions of zirconium and indium nitrates (~0.2 M) and a water solution of ammonia (~1 M) were used as the original reagents.
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Table 2. Compositions of synthesized ceramic materials and some of their physicochemical properties Specimen no. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
Production method
Specimen composition (La2O3)0.45(CaO)0.05(Cr2O3)0.50 (Nd2O3)0.45(CaO)0.05(Cr2O3)0.50 (Y2O3)0.45(CaO)0.05(Cr2O3)0.50 (La2O3)0.45(CaO)0.05(Cr2O3)0.45(NiO)0.05 (Nd2O3)0.45(CaO)0.05(Cr2O3)0.45(NiO)0.05 (Y2O3)0.45(CaO)0.05(Cr2O3)0.45(NiO)0.05 (ZrO2)0.6(In2O3)0.4 (ZrO2)0.7(Al2O3)0.3 (ZrO2)0.4(Al2O3)0.6 (ZrO2)0.3(Al2O3)0.7 [(ZrO2)0.4(Al2O3)0.6]0.4(TiO2)0.6 [(ZrO2)0.4(Al2O3)0.6]0.4(TiO2)0.4(Nb2O5)0.2 (Cr2O3)0.4(Fe2O3)0.3(MnO2)0.3 (CoO)0.7(CeO2)0.3 (CeO2)0.3(Ta2O5)0.7 (Pr2O3)0.5(CoO)0.5 (NiO)0.5(CoO)0.5 (NiO)0.5(Nd2O3)0.5 Combined MnO2–foamed nickel electrode (110 ppi, ppi is the number of pores per inch)
σ (25°C), S cm–1
C × 10–3, F g–1
3 × 10–2 4 × 10–1 3 × 10–3 4 × 10–1 8 × 10–1 1 × 10–1 10 1.2 × 10–13 6 × 10–14 2.5 × 10–15 1.2 × 10–7 1.2 × 10–7 1.2 × 10–6 6 × 10–8 1 × 10–6 4.7 × 10–3 10–2 1.3 × 10–1 1.4
3.6 1.4 0.42 9.3 11 0.41 2.5 0.41 0.18 0.18 0.06 0.05 0.25 0.41 0.10 0.79 1100 4.5 45000
P, %
Cocrystallization
Coprecipitation
Cocrystallization
37 40 45 39 42 43 20 15 15 18 20 23 15 19 15 18 35 32
Spray pyrolysis
P is the open porosity; and σ is the specific electric conductivity in air at 25°C.
Table 3. Chemical composition, structure, open porosity (P) of (ZrO2)0.6(In2O3)0.4 and lanthanum and neodymium chromites, as well as conditions of their synthesis and sintering Specimen no.
Specimen composition (by synthesis conditions)
Synthesis conditions
1
(ZrO2)0.6(In2O3)0.4
Coprecipitation at 700°C for 2 h
2 3 4 5
LaCrO3 NdCrO3 (La, Ni)CrO3 (Nd, Ni)CrO3
Cocrystallization at 800°C for 2 h
Sintering condi tions
Structure
P, %
1300°C, 2 h
F+C
20
1300°C, 2 h
RP OP RP OP
37 40 39 42
F is the fluorite structure; C is the Tl2O3like bcc structure; RP is the rhombohedral perovskite structure; and OP is the orthorhombic perovskite structure.
An analysis of the pH curves of the process of hydrox ide precipitation has shown that the pH of zirconium hydroxide precipitation is 2.3 and that of indium hydroxide precipitation is 3.8; therefore, during direct precipitation, Zr(OH)4 will be the first to precipitate and then In(OH)3 will precipitate (Fig. 4a). Precipita tion was accompanied by agitation at the minimum rate (Vpr = 0.02 cm3/s) and a low temperature, which gives rise to increased dispersity, as well as to the reduced size and strength of the agglomerates. GLASS PHYSICS AND CHEMISTRY
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The gellike precipitate was filtered to separate it from the mother solution and was then frozen at a temperature of –25°C for 20 h to reduce the degree of agglomeration. The synthesized powder was studied by the DTA method. It has been found that, in the temperature range of 100–350°C, dehydration processes occur, nitrogen oxides are removed, the hydroxides decom pose, and an Xray amorphous substance is formed; at a temperature of 400°C, crystallization begins and a powder precursor is formed (Fig. 4b). According to the 2013
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logσ, S/cm
2 1
1
0
2 3
–1 –2 –3 –4 –5 4 –6
5 6 10
15
20
25
30
104/T, K–1
Fig. 1. Temperature dependences of specific electric conductivity of electrode materials of different compositions: (1) (ZrO2)0.6(In2O3)0.4; (2) (Nd2O3)0.45(CaO)0.05(Cr2O3)0.45(NiO)0.05; (3) (La2O3)0.45(CaO)0.05(Cr2O3)0.45(NiO)0.05; (4) (Cr2O3)0.4(Fe2O3)0.3(MnO2)0.3; (5) (Pr2O3)0.5(CoO)0.5; (6) [(ZrO2)0.4(Al2O3)0.6]0.4(TiO2)0.4(Nb2O5)0.2.
XRPA data, at a temperature of 700°C, a twophase product appears, which contains the fluoritelike cubic solid solutions based on ZrO2 and on the body centered structure based on In2O3. The average grain size of these phases is 52 to 57 nm. Figure 5 shows the diagram of the synthesis of the ceramic electrode material of the ZrO2–In2O3 system. It has been found that neodymium and lanthanum complex chromites are ptype semiconductors; this mechanism is attributed to the formation of vacancies in the oxygen sublattice (Vo¨) by the jump mechanism 4+ 3+ (OO2− + 2CrCr + VOii + ½O2), which reduces 2CrCr the number of sources of charge carriers (Cr4+) [23]. The alloying of lanthanum and neodymium chromites by nickel oxide increases their specific elec tric conductivity, which is caused by the additional 2+ + electric transfer of nickel (Ni 3+ Ni Ni Ni + p ). The specific capacity of the ceramic electrode materials was measured using an Impedansmetr Z2000 instrument at room temperature and frequen cies of 10 and 1000 Hz. The performance characteris tics of these ceramic electrodes; i.e., the specific elec tric conductivity and specific capacity were measured in the cell we developed that contained an ioncon ducting separator membrane compatible with the electrodes and a fluid phosphate electrolyte (Table 2).
It can be seen from Table 2 that the considered ceramic materials of the ionistor electrode have an insufficiently high specific capacity, which necessi tates the further search for techniques to produce new composite materials for electrodes and substrates [24]. We developed an alternative approach to the solu tion of the problem of creating ionistor electrodes based on the process of producing a new type of film electrodes that ensured the most important optimal and reproducible characteristics of ionistors, such as the specific capacity and the charge–discharge rate. This method for producing the film electrodes of ionistors employs the deposition of a thin layer of nanocrystalline oxide materials on a porous electro conductive metal substrate made of foamed nickel [19]. Diluted solutions of Co, Ni, and Mn nitrates in various concentration ratios were used as the materials deposited on the substrate. In order to form oxide lay ers, a thin layer of the mixture of the deposited hydrox ides or nitrates was applied to the foam nickel substrate using the sol–gel method of aerosol sputtering; these specimens were then dried at a temperature of 90°C and sintered in a furnace at temperatures of 360– 370°C. The thin oxide layers were also formed by spray pyrolysis [25].
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Mixing of solutions of nitrates (0.2 M) in a specified stoichiometric oxide ratio
Evaporation of mixture of nitrates for 5 h to produce oversaturated solution
Cooling of oversaturated solution at 3–5°C and formation of crystalline hydrate
Dehydration, decomposition of nitrates, and crystallization at 500°C to produce powdered precursor with grain size of ~ 8–10 nm
Heat treatment of powdered precursor in temperature range of 800–1400°C and control over phase formation process using XRPA. Average crystallite size of chromites varies from 20 to 110 nm Fig. 2. Diagram of synthesis of lanthanum and neodymium chromites by cocrystallization of salts.
A model supercapacitor was developed that con sisted of combined oxide electrodes and an inorganic electrolyte. The following electrochemical processes caused by the variable valence of, e.g., Co and Ni and contribut ing to charge accumulation occur at the electrode– electrolyte interface: Co3O4 + H2O + OH– = 3CoOOH + e– and Ni(OH)2 + OH ⎯ = NiOOH + H2O + e–. The pseudocapacity properties of Mn oxide in the electrolyte based on an ionic fluid, i.e., 1ethyl3methylimidazoline dicyanamide were stud ied in [26] using Xray photoelectron spectroscopy (XPS). Figure 6 shows the Mn 2p3/2 Xray photoelec tron spectra of the materials based on Mn oxide pre
I, arb. units
100 75 50 25 0 15
20
25
30
35 40 45 2θ, deg
50
55
60
65
polarized by voltages of +0.5 and –1.5 V, respectively; a change in the chemical state apparently occurs. With allowance for the data on values of the binding energy for Mn2O3 (641 eV) and MnO2 (642 eV) presented in the literature, it can be asserted that, in the case of polarization by a voltage of +0.5 V, Mn exists mainly in the quadruplecharged state; when a voltage of ⎯1.5 V is applied, Mn exists in both the triplecharged and the quadruplecharged states. This fact confirms the occurrence of Faraday redox reactions of Mn oxide in this electrolyte. Thus, it can be concluded that, in these ionistors with the electrodes based on the oxides of transition metals, the socalled Faraday pseudocapacity accu mulates in addition to the accumulation of the energy or charge on the double electrical layer. The charge–discharge galvanostatic curves for the supercapacitors with the foamed nickel–Mn2O3, foamed nickel–50NiO ⋅ 50Mn2O3 (mol %), foamed nickel–5La2O3 ⋅ 95Mn2O3 (mol %), and foamed nickel–50CoO ⋅ 50NiO (mol %) film electrodes were obtained using the test apparatus; the voltage range was 0–0.5 V, the current density was 50 mA/mm2, and the 1 M solution of KOH was used as the electrolyte. The values of the average specific capacity of these electrodes were then calculated. The average specific capacity of the film electrodes was calculated by the following equation [27]:
Fig. 3. Diffraction pattern of lanthanum and neodymium chromites with orthorhombic perovskite (OR) structure produced during sintering at 800°C. GLASS PHYSICS AND CHEMISTRY
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C= 2013
I , (d V dt )m
(1)
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(b) 2 1
9
450°C
8 7 DTA
pH
6 5 4
250°C
3 2
320°C
1 4
8
12
16 20 24 VNH OH, mL
28
32
4
Fig. 4. (a) pH curves for precipitation of (1) zirconium and (2) indium hydroxides; (b) results of thermal analysis of precipitated zirconium and indium hydroxides.
where I (mA) and dV/dt (mV s–1) are the galvanostatic current and the slope of the linear and symmetric por tion of the time dependence of the voltage, respec tively; and m (g) is the total weight of the two elec trodes; i.e., the weight of the electroactive material plus the weight of the substrate. The conclusion was drawn that the values of the specific capacity depend on the oxide layer composition and the electrolyte composition, as well as the quality and porosity of the substrate material; as the pore size in foamed nickel decreases in transition from 70 to 110 ppi, where ppi is the number of pores per inch, the value of the specific capacity approximately doubles. The best results were obtained for the electrode material that consisted of foamed nickel with 110 ppi and Mn2O3 using the 1 M solution of combined oxide electrodes and an inor ganic electrolyte as the electrolyte. Small (up to
5 mol %) additives of La2O3 to Mn2O3 lead to an increase in the specific capacity by ~10% compared to the specific capacity of the electrode with the active layer based on Mn2O3. For example, it has been found using Xray phase analysis that Mn2O3 produced by spray pyrolysis has the bixbyitelike cubic structure (Fig. 7). Table 4 pre sents the crystalline structure characteristics of Mn2O3. The average grain size of the Mn2O3 phase is ~29 nm. The synthesis and study of the physicochemical properties of the ceramic electrodes operating in the presence of the ionconducting phosphorosilicate separator membrane and phosphate impregnation, as well as the film electrodes operating in the inorganic electrolyte, have yielded the values of the specific capacity that is the governing characteristic of a super
Table 4. Xray structural characteristics of Mn2O3 powder produced by spray pyrolysis Reflection no. 1 2 3 4 5 6 7 8 9 10
2θ
dhkl
I0/I
hkl
23.065 26.497 32.890 35.634 38.156 42.463 46.874 49.413 55.162 65.748
3.8529 3.3612 2.7210 2.5175 2.3567 2.1271 1.9367 1.8430 1.6637 1.4191
56 53 100 29 38 27 20 18 33 20
211 220 222 321 400 411 420 431 440 622
Elementary cell parameters a = 9.39 Å
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Structure Bixbyitelike cubic structure
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CERAMIC NANOCOMPOSITES BASED ON OXIDES Mixture of solutions of zirconium and indium nitrates (~ 0.2 M)
577 MnO2
Mn2O3
Ammonia water solution (~ 1 M) 1 Intensity, arb. units
Mixing, gelation, and precipitation
Filtration and drying of precipitate at 100–120°C
Ultrasonic treatment of precipitate for 30 min to reduce degree of agglomeration
2
Heating at 400–500°C for 1 h to produce powdered precursor with a grain size of 3–5 nm Heat treatment of powdered precursor in temperature range of 600–1300°C control over the phaseformation process using XRPA and DTA. Average crystallite size of the phase formed varies from 10 to 60 nm
635
640 645 Binding energy, eV
Fig. 6. Mn 2p3/2 Xray photoelectron spectra of materials based on Mn oxide prepolarized by voltage of (1) +0.5 V and (2) –1.5 V in electrolyte based on ionic fluid (1ethyl3methylimidazoline dicyanamide).
Fig. 5. Diagram of synthesis of (ZrO2)0.6(In2O3)0.4 nanoc rystalline composition by coprecipitation of hydroxides.
3
capacitor (Table 2). It can be seen from Table 2 that the film electrodes are the most efficient since they have the highest values of the specific capacity similar to those of industrial supercapacitors.
I, arb. units
100
1
The (ZrO2)0.6(In2O3)0.4 nanoceramic materials, neodymium, lanthanum, and nickel complex chromites, as well as nickel, praseodymium, cerium cobaltites, etc., for the supercapacitor electrodes with an open porosity of ~15–45%, an average grain size of 30–110 nm, and a specific electric conductivity of ~3 × 10–3–10 S cm–1 at 300 K were produced using the lowtemperature synthesis methods, i.e., the coprecipitation of hydroxides and the cocrystalliza tion of nitrate solutions. The ionconducting separator membranes com patible with these ceramic electrodes in the presence of phosphate impregnation were synthesized from sil ica gels doped with orthophosphoric acid using the solgel method. In order to improve considerably the performance characteristics of supercapacitor electrodes, the film electrodes were produced that consisted of thin layers of nanocrystalline oxide materials deposited on the Vol. 39
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2 4
50
15 20
CONCLUSIONS
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650
30
5
6 7
40 2θ, deg
9 10
8
50
60
Fig. 7. Diffraction pattern of Mn2O3 powder produced by spray pyrolysis (Table 4).
porous electroconductive metal substrate made of foamed nickel; these electrodes operate in the inor ganic electrolyte. The MnO2–foamed nickel electrode has a specific capacity of 45.0 F g ⎯1. The further search for oxide electrode materials compatible with the heterophase phosphorosilicate membrane will favor the development of a new type of supercapacitor. ACKNOWLEDGMENTS This study was supported by grant no. MK 64457.2010.3 of the President of the Russian Federa tion for the government’s support of young Russian 2013
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Translated by D. Tkachuk
GLASS PHYSICS AND CHEMISTRY
Vol. 39
No. 5
2013
