Patent Application
20170092975
1. Field
The present disclosure relates to a composite electrolyte film, an electrochemical cell including the composite electrolyte film, and methods of preparing the composite electrolyte film.
2. Description of the Related Art
It is known that a metal air cell, which is a type of an electrochemical cell, includes an anode capable of depositing/dissolving metal ions, a cathode configured to oxidize/reduce oxygen in air, and a metal ion conductive media disposed between the cathode and the anode.
Since the metal air cell uses a metal itself as the anode and does not need to store air that is a positive electrode active material, the metal air cell is suitable for implementation of a high capacity cell. A theoretical energy density per unit weight of the metal air cell is very high, for example, about 3,500 Wh/kg or more. In a metal air cell, it is desirable to block oxygen such that a metal anode is not oxidized by oxygen. To this end, the metal air cell uses an oxygen barrier film, such as a ceramic solid electrolyte film, which has a low oxygen transmission rate. Since the ceramic solid electrolyte film is heavy and thick, a volume and a weight of a metal air cell, including the ceramic solid electrolyte film, increases. Accordingly, an energy density of the metal air cell decreases. In addition, the ceramic solid electrolyte film is brittle and inductile. Therefore, there is a need for an electrolyte film that is light, thin, and flexible and is capable of blocking oxygen. In addition, there is a need for a metal air cell that includes the electrolyte film to have an improved energy density.
Provided is a composite electrolyte film having a 2D nanostructure.
Provided is an electrochemical cell including the composite electrolyte film.
Provided are methods of preparing the composite electrolyte film.
Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented exemplary embodiments.
According to an aspect of an exemplary embodiment, a composite electrolyte film includes: a composite electrolyte layer including: a first domain including a plurality of two-dimensional nanostructures; and a second domain which is disposed in an interstitial space between neighboring two-dimensional nanostructures of the plurality of two-dimensional nanostructures, wherein the plurality of two-dimensional nanostructures include a first electrolyte.
According to an aspect of another exemplary embodiment, an electrochemical cell includes an electrode-film assembly including: a cathode; an anode; and the composite electrolyte film which is disposed between the cathode and the anode.
According to an aspect of another exemplary embodiment, a method of preparing a composite electrolyte film includes: providing a porous membrane; forming a two-dimensional nanostructure on a first surface of the porous membrane; and impregnating an electrolyte into the porous membrane and the two-dimensional nanostructure to prepare the composite electrolyte film.
These and/or other aspects will become apparent and more readily appreciated from the following description of the exemplary embodiments, taken in conjunction with the accompanying drawings in which:
Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. In this regard, the present exemplary embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, the exemplary embodiments are merely described below, by referring to the figures, to explain aspects. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. “Or” means “and/or.” Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list.
It will be understood that when an element is referred to as being “on” another element, it can be directly on the other element or intervening elements may be present therebetween. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present.
It will be understood that, although the terms “first,” “second,” “third” etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer, or section. Thus, “a first element,” “component,” “region,” “layer,” or “section” discussed below could be termed a second element, component, region, layer, or section without departing from the teachings herein.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms, including “at least one,” unless the content clearly indicates otherwise. “At least one” is not to be construed as limiting “a” or “an.” It will be further understood that the terms “comprises” and/or “comprising,” or “includes” and/or “including” when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof.
Furthermore, relative terms, such as “lower” or “bottom” and “upper” or “top,” may be used herein to describe one element's relationship to another element as illustrated in the Figures. It will be understood that relative terms are intended to encompass different orientations of the device in addition to the orientation depicted in the Figures. For example, if the device in one of the figures is turned over, elements described as being on the “lower” side of other elements would then be oriented on “upper” sides of the other elements. The exemplary term “lower,” can therefore, encompasses both an orientation of “lower” and “upper,” depending on the particular orientation of the figure. Similarly, if the device in one of the figures is turned over, elements described as “below” or “beneath” other elements would then be oriented “above” the other elements. The exemplary terms “below” or “beneath” can, therefore, encompass both an orientation of above and below.
“About” or “approximately” as used herein is inclusive of the stated value and means within an acceptable range of deviation for the particular value as determined by one of ordinary skill in the art, considering the measurement in question and the error associated with measurement of the particular quantity (i.e., the limitations of the measurement system). For example, “about” can mean within one or more standard deviations, or within ±30%, 20%, 10% or 5% of the stated value. “2D nanostrucutres” as used herein means a structure defined by two dimensions having micrometer scale or greater scale respectively and one dimension having nanometer scale. The nanometer scale may be 1 nm to 999 nm and the micrometer scale or greater scale may be 1 micormeter or greater.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
Exemplary embodiments are described herein with reference to cross section illustrations that are schematic illustrations of idealized embodiments. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments described herein should not be construed as limited to the particular shapes of regions as illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, a region illustrated or described as flat may, typically, have rough and/or nonlinear features. Moreover, sharp angles that are illustrated may be rounded. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the precise shape of a region and are not intended to limit the scope of the present claims.
Hereinafter, according to exemplary embodiments, a composite electrolyte film, an electrochemical cell including the composite electrolyte film, and a method of preparing the composite electrolyte film will be disclosed in further detail.
A composite electrolyte film according to an exemplary embodiment may include a composite electrolyte layer including a first domain that includes a plurality of two-dimensional (2D) nanostructures; and a second domain that is disposed in, e.g., occupies, interstitial spaces between neighboring two-dimensional nanostructures of the plurality of 2D nanostructures, and wherein the plurality of two-dimensional nanostructures includes a first electrolyte.
Since the composite electrolyte film includes the plurality of 2D nanostructures, and the plurality of 2D nanostructures have barrier characteristics of preventing diffusion of oxygen from a cathode to the composite electrolyte film, a lithium anode may be protected from oxygen. The composite electrolyte film may function as an anode protection film or an oxygen barrier film. In addition, since the composite electrolyte film includes the first electrolyte disposed between the plurality of 2D nanostructures, the composite electrolyte film may have suitable ion conductivity (i.e., ionic conductivity). The composite electrolyte film may provide suitable ion conductivity and suitable oxygen barrier characteristics at the same time. Since the composite electrolyte film is flexible, the composite electrolyte film may be molded in various shapes. Since the composite electrolyte film is light in weight, compared to an inorganic material including a ceramic, an electrochemical cell including the composite electrolyte film has improved energy density.
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For example, the plurality of 2D nanostructures 110 may include deformed graphene. For example, the plurality of 2D nanostructures 110 may include at least one selected from wrinkled graphene and crumpled graphene, but are not limited thereto. The plurality of 2D nanostructures 110 may include any suitable deformed graphene as long as the deformed graphene is applicable to a 2D nanostructure in the art. Since the deformed graphene is able to increase the interspacing of graphene at the time of forming the first domain 101 within the composite electrolyte layer 100, the second domain 102 may be more easily impregnated. Accordingly, ion conductivity may be improved.
For example, the plurality of 2D nanostructures 110 may include a metal oxide nanosheet. For example, the plurality of 2D nanostructures 110 may be an oxide nanosheet that includes at least one selected from titanium (Ti), manganese (Mn), niobium (Nb), ruthenium (Ru), tungsten (W), tantalum (Ta), lanthanum (La), europium (Eu), strontium (Sr), virginium (Vi), calcium (Ca), and sodium (Na). For example, the plurality of 2D nanostructures 110 may have a layered perovskite structure. For example, the plurality of 2D nanostructures 110 may include at least one nanosheet selected from TiO2, Ti0.91O2, Ti0.87O2, Ti3O7, Ti4O9, Ti5O11, MnO2, Mn3O7, Nb3O8, Nb6O17, LaNb2O7, La0.90Eu0. 05Nb2O7, Eu0.56Ta2O7, SrTa2O7, Bi2SrTa2O9, Ca2Nb3O10, Sr2Nb3O10, NaCaTa3O10, CaLaNb2TiO10, La2Ti2NbO10, Ba5Ta4O15, W2O7, RuO2.1, Cs4W11O36, TaO3, TiNbO5, Ti2NbO7, and TiTaO5.
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The solid electrolyte may be an electrolyte that can maintain a fixed shape at room temperature and has suitable lithium ion conductivity. The liquid electrolyte may be a flowable electrolyte which has suitable lithium ion conductivity and does not maintain a fixed shape at room temperature such that a shape of the flowable electrolyte is determined according to a shape of a container containing the flowable electrolyte. The gel electrolyte may be a solid electrolyte which contains a liquid.
Even when the composite electrolyte layer 100 includes a liquid electrolyte as the first electrolyte, the composite electrolyte layer 100 may be in a solid state or a gel state at room temperature according to a content of the 2D nanostructures 110.
In the composite electrolyte layer 100, the first electrolyte may include at least one selected from a polymeric ionic liquid (PIL), an ion conductive inorganic material, and an ion conductive polymer.
For example, in the composite electrolyte layer 100, examples of the first electrolyte may include at least one selected from a solid electrolyte including a polymeric ionic liquid (PIL) and a lithium salt, a solid or gel electrolyte including a polymeric ionic liquid, an ionic liquid, and a lithium salt, a solid electrolyte including an ion conductive polymer and a lithium salt, a solid electrolyte including an ion conductive inorganic material, and a solid electrolyte including an electron conductive polymer, but are not limited thereto. The first electrolyte may include any suitable solid electrolyte as long as the solid electrolyte is applicable to an electrolyte of an electrochemical cell in the art.
Examples of the lithium salt included in the first electrolyte may include at least one selected from LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, LiN(CxF2x+1SO2)(CyF2y+1SO2) (where each of x and y is a natural number), LiCl, and LiI, but are not limited thereto. The lithium salt may include any suitable material as long as the material is applicable to a lithium salt in the art.
The ionic liquid included in the first electrolyte may be expressed by the following Formula 1 or 2:
wherein
denotes a 3-to 31-membered ring including at least one heteroatom and 2 to 30 carbon atoms and is selected from an unsubstituted or substituted carbon ring, an unsubstituted or substituted aryl ring, and an unsubstituted or substituted heteroaryl ring; X is —N(R1)(R2), or —P(R1)(R2); and Y− is an anion, and
wherein X is —N(R1)(R2)(R3), or —P(R1)(R2)(R3); R1 to R3 are each independently selected from: a hydrogen atom, an unsubstituted or substituted C1-C30 alkyl group, an unsubstituted or substituted C1-C30 alkoxy group, an unsubstituted or substituted C6-C30 aryl group, an unsubstituted or substituted C6-C30 aryloxy group, an unsubstituted or substituted C3-C30 heteroaryl group, an unsubstituted or substituted C3-C30 heteroaryloxy group, an unsubstituted or substituted C4-C30 cycloalkyl group, an unsubstituted or substituted C3-C30 heterocycloalkyl group, and an unsubstituted or substituted C2-C100 alkylene oxide group; R11 is selected from an unsubstituted or substituted C1-C30 alkyl group, an unsubstituted or substituted C1-C30 alkoxy group, an unsubstituted or substituted C6-C30 aryl group, an unsubstituted or substituted C6-C30 aryloxy group, an unsubstituted or substituted C3-C30 heteroaryl group, an unsubstituted or substituted C3-C30 heteroaryloxy group, an unsubstituted or substituted C4-C30 cycloalkyl group, an unsubstituted or substituted C3-C30 heterocycloalkyl group, and an unsubstituted or substituted C2-C100 alkylene oxide group; and Y−is an anion.
For example,
of Formula 1 may be expressed by the following Formula 3, and
of Formula 2 may be a cation expressed by the following Formula 4:
wherein Z denotes nitrogen (N) or phosphorus (P); and R12 to R18 are each independently selected from a hydrogen atom, an unsubstituted or substituted C1-C30 alkyl group, an unsubstituted or substituted C1-C30 alkoxy group, an unsubstituted or substituted C6-C30 aryl group, an unsubstituted or substituted C6-C30 aryloxy group, an unsubstituted or substituted C3-C30 heteroaryl group, an unsubstituted or substituted C3-C30 heteroaryloxy group, an unsubstituted or substituted C4-C30 cycloalkyl group, an unsubstituted or substituted C3-C30 heterocycloalkyl group, and an unsubstituted or substituted C2-C100 alkylene oxide group, and
wherein Z denotes N or; and R12 to R18 are each independently selected from a hydrogen atom, an unsubstituted or substituted C1-C30 alkyl group, an unsubstituted or substituted C1-C30 alkoxy group, an unsubstituted or substituted C6-C30 aryl group, an unsubstituted or substituted C6-C30 aryloxy group, an unsubstituted or substituted C3-C30 heteroaryl group, an unsubstituted or substituted C3-C30 heteroaryloxy group, an unsubstituted or substituted C4-C30 cycloalkyl group, an unsubstituted or substituted C3-C30 heterocycloalkyl group, and an unsubstituted or substituted C2-C100 alkylene oxide group.
For example, the ionic liquid may include at least one selected from [emim]Cl/AlCl3(emim=ethyl methyl imidazolium), [bmpyr]NTf2(bmpyr=butyl methyl pyridinium), [bpy]Br/AlCl3(bpy4=4,4′-bipyridine), [choline]Cl/CrCl3.6H2O, [Hpy(CH2)3pyH][NTf2]2 (NTf=trifluoromethanesulfonimide), [emim]OTf/[hmim]I(hmim=hexyl methyl imidazolium), [choline]Cl/HOCH2CH2OH, [Et2MeN(CH2CH2OMe)]BF4 (Et=ethyl, Me=methyl, Pr=propyl, Bu=butyl, Ph=phenyl, Oct=octyl, and Hex=hexyl), [Bu3PCH2CH2C8F17]OTf(OTf=trifluoromethane sulfonate), [bmim]PF6(bmim=butyl methyl imidazolium), [bmim]BF4, [omim]PF6(omim=octyl methyl imidazolium), [Oct3PC18H37]I, [NC(CH2)3mim]NTf2(mim=methyl imidazolium), [Pr4N][B(CN)4], [bmim]NTf2, [bmim]Cl, [bmim][Me(OCH2CH2)2OSO3], [PhCH2mim]OTf, [Me3NCH(Me)CH(OH)Ph]NTf2, [pmim][(HO)2PO2](pmim=propyl methyl imidazolium), [b(6-Me)quin]NTf2(bquin=butyl quinolinium, [bmim][Cu2Cl3], [C18H37OCH2mim]BF4(mim=methyl imidazolium), [heim]PF6(heim=hexyl ethyl imidazolium), [mim(CH2CH2O)2CH2CH2mim][NTf2]2(mim=methyl imidazolium), [obim]PF6(obim=octyl butyl imidazolium), [oquin]NTf2(oquin=octyl quinolinium), [hmim][PF3(C2F5)3], [C14H29mim]Br(mim=methyl imidazolium), [Me2N(C12H25)2]NO3, [emim]BF4, [mm(3-NO2)im][dinitrotriazolate], [MeN(CH2CH2OH)3], [MeOSO3], [Hex3PC14H29]NTf2, [emim][EtOSO3], [choline][ibuprofenate], [emim]NTf2, [emim][(EtO)2PO2], [emim]Cl/CrCl2, and [Hex3PC14H29]N(CN)2, but is not necessarily limited thereto. The ionic liquid may include any suitable material as long as the material is applicable to an ionic liquid in the art.
For example, the ionic liquid may include at least one selected from N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium tetrafluoroborate ([DEME][BF4]), diethylmethylammonium trifluoromethanesulfonate ([dema][TfO]), dimethylpropylammonium trifluoromethanesulfonate ([dmpa][TfO]), diethylmethylammonium trifluoromethanesulfonylimide ([DEMA][TFSI]), and methylpropylpiperidinium trifluoromethanesulfonylimide ([mpp][TFSI]), but is not necessarily limited thereto. The ionic liquid may include any suitable ionic material as long as the ionic material is applicable to an electrolyte in the art.
The PIL included in the first electrolyte may include a repeating unit that includes i) at least one cation selected from an ammonium cation, a pyrrolidinium cation, a pyridinium cation, a pyrimidinium cation, an imidazolium cation, a piperidinium cation, a pyrazolium cation, an oxazolium cation, a pyridazinium cation, a phosphonium cation, a sulfonium cation, a triazole cation, and mixtures thereof and includes ii) at least one anion selected from BF4—, PF6—, AsF6—, SbF6—, AlCl4—HSO4—, ClO4—CH3SO3—, CF3CO2—, (CF3SO2)2N—, Cl—, Br—, I—, BF4—, SO4−, PF6—, ClO4—, CF3SO3—, CF3CO2—, (C2F5SO2)2N—, (C2F5SO2)(CF3SO2)N—, NO3−, Al2Cl731 , AsF631 , SbF6−, CF3COO31 , CH3COO−, CF3SO3−, (CF3SO2)3C−, (CF3CF2SO2)2N−, (CF3)2PF431 , (CF3)3PF3−, (CF3)4PF2−, (CF3)5PF−, (CF3)6P−, SF5CF2SO3−, SF5CHFCF2SO3−, CF3CF2(CF3)2CO−, (CF3SO2)2CH−, (SF5)3C−, (O(CF3)2C2(CF3)2O)2PO−, and (CF3SO2)2N−.
Examples of the PIL may include at least one selected from poly(diallyldimethylammonium) bis(trifluoromethanesulfonyl)imide (DAM TFSI), 1-Allyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, and poly((N-Methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide).
Examples of the ion conductive inorganic material included in the first electrolyte may include at least one selected from a glassy or amorphous metal ion conductor, a ceramic active metal ion conductor, and a glass-ceramic active metal ion conductor, but are not limited thereto. The ion conductive inorganic material may include any suitable material as long as the material is applicable to an ion conductive inorganic material in the art. The ion conductive inorganic material may be an ion conductive inorganic particle.
Examples of the ion conductive inorganic material may include at least one selected from BaTiO3, Pb(Zr,Ti)O3 (PZT), Pb1−xLaxZr1−yTiyO3 (PLZT) (where 0≦x<1, and 0≦y<1), Pb(Mg3Nb2/3)O3—PbTiO3(PMN—PT), HfO2, SrTiO3, SnO2, CeO2, Na2O, MgO, NiO, CaO, BaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiO2, SiC, lithium phosphate (Li3PO4), lithium titanium phosphate (LixTiy(PO4)3, where 0<x<2, and 0<y<3), lithium aluminum titanium phosphate (LixAlyTiz(PO4)3, where 0<x<2, 0<y<1, and 0<z<3), Li 1+x+y (Al, Ga)x(Ti, Ge)2−xSiyP3−yO12 (where 0≦x≦1, and 0≦y≦1) lithium lanthanum titanate (e.g., LixLayTiO3, where 0<x<2, and 0<y<3), lithium germanium thiophosphate (e.g., LixGeyPzSw, where 0<x<4, 0<y<1, 0<z<1, and 0<w<5), lithium nitride (e.g., LixNy, where 0<x<4, and 0<y<2), SiS2 (LixSiySz, where 0<x<3, 0<y<2, and 0<z<4)-based glass, P2S5 (e.g., LixPySz, where 0<x<3, 0<y<3, and 0<z<7)-based glass, Li2O, LiF, LiOH, Li2CO3, LiAlO2, a Li2O—Al2O3—SiO2—P2O5—TiO2—GeO2-based ceramic, and a garnet-based ceramic (e.g., Li3+xLa3M2O12, where M=Te, Nb, or Zr).
The ion conductive polymer included in the first electrolyte may be a polymer that includes an ion conductive repeating unit on a main chain or a side chain. The ion conductive repeating unit may include any unit as long as the unit has suitable ion conductivity. For example, the ion conductive repeating unit may include at least one selected from a C1 to C20 alkylene oxide unit such as ethylene oxide, a hydrophilic unit, and the like.
Examples of the ion conductive polymer may include at least one ion conductive repeating unit selected from an ether-based monomer, an acryl-based monomer, a methacryl-based monomer, and a siloxane-based monomer. “Acryl” includes acrylic and (C1 to C20 alkyl)acrylate, and “methacryl” includes methacrylic and (C1 to C20 alkyl)methacrylate.
Examples of the ion conductive polymer may include at least one selected from polyethylene oxide, polypropylene oxide, polymethyl methacrylate, polyethyl methacrylate, polydimethylsiloxane, polyacrylic acid, polymethacrylic acid, polymethyl acrylate, polyethyl acrylate, poly(2-ethylhexyl acrylate), poly butyl methacrylate, poly(2-ethylhexyl methacrylate), poly(decyl acrylate), and polyethylene vinyl acetate.
Examples of the ion conductive polymer may include at least one selected from a polyethylene (PE) derivative, a polyethylene oxide (PEO) derivative, a polypropylene oxide (PPO) derivative, a phosphate ester polymer, polyester sulfide, polyvinyl alcohol (PVA), polyvinylidene fluoride (PVdF), and a polymer including an ionic dissociable group such as lithium-exchanged Nafion (lithium Nafion), but are not limited thereto. The ion conductive polymer may include any suitable material as long as the material is applicable to an ion conductive polymer in the art.
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For example, the adhesive layer 150 may include a polymer oppositely charged to the 2D nanostructures 110 included in the composite electrolyte layer 100. For example, the adhesive layer 150 may include a polymer which is positively charged, i.e., oppositely charged to the negatively charged 2D nanostructures 110 included in the composite electrolyte layer 100. The positively charged polymer may include polyethyleneimine, but is not necessarily limited thereto. The positively charged polymer may include any suitable material as long as the material is applicable to a positively charged material in the art.
Since the adhesive material 150 including a positively or negatively charged polymer is disposed on the porous membrane 210, a surface of the porous membrane 210 may be negatively or positively charged, i.e., oppositely charged to the positively or negatively charged polymer. For example, as the surface of the porous membrane 210 is negatively charged through a corona treatment, the positively charged polymer may be easily disposed on the porous membrane 210 due to electrostatic attraction.
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For example, since an ion conductive polyelectrolyte is impregnated in a flow path formed by connecting the plurality of pores 220 irregularly arranged in the porous membrane 210, the ion conductive polyelectrolyte may be exposed on a first surface of the porous membrane 210 and a second surface, which is opposite to the first surface to thereby provide a transfer path of active metal ions.
For example, although not illustrated in
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For example, a concentration of the second electrolyte at a middle point between the first surface 203 and the second surface 204 of the ion conductive substrate 200 may be less than a concentration of the second electrolyte at each of the first surface 203 of the ion conductive substrate 200 and the second surface 204, which is opposite to the first surface 203. That is, the second electrolyte may have a U-shaped or V-shaped concentration gradient in which the concentration of the second electrolyte decreases and then increases in a thickness direction (e.g., a y direction) of the ion conductive substrate 200. In the ion conductive substrate 200, a profile of the concentration gradient in the second electrolyte may be symmetric with respect to the middle point between the first surface 203 and the second surface 204 of the ion conductive substrate 200. The concentration of the second electrolyte may be greatest at each of the first surface 203 of the ion conductive substrate 200 and the second surface 204, which is opposite to the first surface 203. The concentration of the second electrolyte may be the least at any point within the ion conductive substrate 200. For example, there may be no second electrolyte at a certain point within the ion conductive substrate 200. The concentration of the second electrolyte at the middle point between the first surface 203 and the second surface 204 of the ion conductive substrate 200 may be less than the concentration of the second electrolyte at each of the first surface 203 and the second surface 204 of the ion conductive substrate 200, thereby reducing an interfacial resistance when the ion conductive substrate 200 comes into contact with other electrochemical cell members, for example, a cathode and an anode.
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For example, the porous membrane 210 included in the ion conductive substrate 200 may include a polymer having suitable gas and moisture barrier characteristics. Since the porous membrane 210 included in the ion conductive substrate 200 blocks a gas and moisture, the ion conductive substrate 200 may protect an anode. Therefore, the composite electrolyte film 400 including the ion conductive substrate 200 may function as a protective membrane. In an embodiment, the polymer having gas and moisture barrier characteristics as a water vapor transmission rate of less than about 1 g/m2 per day, or about 0.001 g/m2 per day to about 1 g/m2 per day, or about 0.01 g/m2 per day to about 0.5 g/m2 per day, when measured using a 25 micrometer film and 25° C.
Examples of the polymer having the gas and moisture barrier characteristics may include at least one selected from poly(2-vinyl pyridine); polytetrafluoroethylene; a tetrafluoroethylene-hexafluoropropylene copolymer; polychlorotrifluoroethylene; a perfluoroalkoxy copolymer; fluorinated cyclic ether; polyethylene oxide diacrylate; polyethylene oxide dimethacrylate; polypropylene oxide diacrylate; polypropylene oxide dimethacrylate; polymethylene oxide diacrylate; polymethylene oxide dimethacrylate; poly((C1 to C20)alkyldiol diacrylate); poly((C1 to C20)alkyldiol dimethacrylate); polydivinylbenzene; polyether; polycarbonate; polyamide; polyester; polyvinyl chloride; polyimide; polycarboxylic acid; polysulfonic acid; polyvinyl alcohol; polysulfone; polystyrene; polyethylene; polypropylene; poly(p-phenylene); polyacetylene; poly(p-phenylene vinylene); polyaniline; polypyrrole; polythiophene; poly(2,5-ethylene vinylene); polyacene; poly(naphthalene-2,6-diyl); polyethylene oxide; polypropylene oxide; polyvinylidene fluoride; a copolymer of vinylidene fluoride and hexafluoropropylene; polyvinyl acetate; poly(vinyl butyral-co-vinyl alcohol-co-vinyl acetate); poly(methyl methacrylate-co-ethyl acrylate); polyacrylonitrile; polyvinyl chloride-co-vinyl acetate; poly(l-vinylpyrrolidone-co-vinyl acetate); polyvinylpyrrolidone; polyacrylate; polymethacrylate; polyurethane; polyvinyl ether; acrylonitrile-butadiene rubber; styrene-butadiene rubber; acrylonitrile-butadiene-styrene rubber; a sulfonated styrene/ethylene-butylene triblock copolymer; a polymer obtained from at least one acrylate monomer selected from ethoxylated neopentyl glycol diacylate, ethoxylated bisphenol A diacrylate, ethoxylated aliphatic urethane acrylate, an ethoxylated (C1 to C20)alkylphenol acrylate, and a (C1 to C20)alkyl acrylate; polyvinyl alcohol; polyimide; an epoxy resin; and an acrylic resin, but are not limited thereto. The polymer having the gas and moisture barrier characteristics may include any suitable polymer as long as the polymer has suitable gas and moisture barrier characteristics in the art.
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A lithium metal thin film may be used as the anode 600 of the electrochemical cell 900 as it is. When the lithium metal thin film is used as the anode 600 as it is, a volume and a weight occupied by a current collector may be reduced, thereby improving the energy density of the electrochemical cell 900. Alternatively, the lithium metal thin film may be used in a state of being disposed on a conductive substrate that is a current collector. The lithium metal thin film may be integrated within the current collector. Examples of the current collector may include at least one selected from stainless steel, copper, nickel, iron, and titanium, but are not limited thereto. The current collector may include any suitable metallic substrate as long as the metallic substrate has suitable conductivity and is applicable to the art.
An alloy of a lithium metal and other negative electrode active material may be used as the anode 600 of the electrochemical cell 900. The other negative electrode active material may include a lithium-alloyable metal. Examples of the lithium-alloyable metal may include at least one selected from silicon (Si), tin (Sn), aluminum (Al), germanium (Ge), lead (Pb), bismuth (Bi), antimony (Sb), and a Si—Y′ alloy (where Y′ includes one selected from an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element, a transition metal, a rare earth element, and combinations thereof and does not include Si), or may include an Sn—Y″ alloy (where Y″ includes one selected from an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element, a transition metal, a rare earth element, and combinations thereof and does not include Sn). The elements Y′ and Y″ may each independently include at least one selected from magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), radium (Ra), scandium (Sc), yttrium (Y), titanium (Ti), zirconium (Zr), hafnium (Hf), rutherfordium (Rf), vanadium (V), niobium (Nb), tantalum (Ta), dubnium (Db), chromium (Cr), molybdenum (Mo), tungsten (W), seaborgium (Sg), technetium (Tc), rhenium (Re), bohrium (Bh), iron (Fe), lead (Pb), ruthenium (Ru), osmium (Os), hassium (Hs), rhodium (Rh), iridium (Ir), palladium (Pd), platinum (Pt), copper (Cu), silver (Ag), gold (Au), zinc (Zn), cadmium (Cd), boron (B), aluminum (Al), gallium (Ga), tin (Sn), indium(In), titanium (Ti), germanium (Ge), phosphorus (P), arsenic (As), antimony (Sb), bismuth (Bi), sulfur (S), selenium (Se), tellurium (Te), polonium (Po), and combinations thereof. For example, a lithium alloy may include at least one selected from a lithium-aluminum alloy, a lithium-silicon alloy, a lithium-tin alloy, lithium-silver alloy, and a lithium-lead alloy.
In the electrochemical cell 900, a thickness of the anode 600 may be about 10 μm or more. The thickness of the anode 600 may be in the range of about 10 μm to about 20 μm, about 20 μm to about 60 μm, about 60 μm to about 100 μm, about 100 μm to about 200 μm, about 200 μm to about 600 μm, about 600 μm to about 1000 μm, about 1 mm to about 6 mm, about 6 mm to about 10 mm, about 10 mm to about 60 mm, about 60 mm to about 100 mm, or about 100 mm to about 600 mm.
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The positive current collector may include a netlike or mesh-shaped porous body so as to permit rapid diffusion of oxygen and may include a porous metal plate such as stainless steel, nickel, or aluminum. The positive current collector is not limited thereto, and may include any suitable material as long as the material is applicable to a current collector in the art. In order to prevent oxidation of the current collector, the current collector may be covered with an oxidation-resistant metal or an alloy film.
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The negative current collector may include a porous metal plate such as stainless steel, nickel, or aluminum, but is not limited thereto. The negative current collector may include any suitable material as long as the material is applicable to a current collector in the art.
In the electrochemical cell 900, the electrode-film assembly 700 may include at least one folded portion. Since the electrode-film assembly 700 includes at least one folded portion, the electrochemical cell 900 may be easily molded in various shapes.
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In the electrochemical cell 900, the electrode-film assembly 700 may be folded multiple times in a thickness direction of the electrode-film assembly 700 to provide a three-dimensional (3D) electrochemical cell.
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For example, the electrochemical cell 900 may be a metal air cell.
In the metal air cell, a cathode 500 using oxygen as a positive electrode active material may include a conductive material. The conductive material may be a porous particle. The cathode 500 may include any suitable material as the positive electrode active material without limitation as long as the material has suitable porosity and conductivity. For example, the cathode 500 may include a carbon-based material having porosity. Examples of the carbon-based material may include at least one selected from carbon black, graphite, graphene, activated carbon, a carbon fiber, and a carbon nanotube.
In addition, examples of the positive electrode active material may include metallic conductive materials such as metal fibers and metal meshes. Furthermore, examples of the positive electrode active material may include metallic powders such as copper powders, silver powders, nickel powders, and aluminum powders. The positive electrode active material may include an organic conductive material such as a polyphenylene derivative. The conductive material may be used solely or in a combination comprising at least one of the foregoing.
A catalyst for oxidizing/reducing oxygen may be added to the cathode 500 of the metal air cell. Examples of the catalyst may include at least one selected from a noble metal-based catalyst such as platinum, gold, silver, palladium, ruthenium, rhodium, and osmium; an oxide-based catalyst such as manganese oxide, iron oxide, cobalt oxide, and nickel oxide; and an organic metal-based catalyst such as cobalt phthalocyanine; but are not limited thereto. The catalyst may include any suitable material as long as the material is applicable to a catalyst for oxidizing/reducing oxygen in the art. A combination comprising at least one of the foregoing may be used.
In addition, the catalyst may be impregnated in a carrier. Examples of the carrier may include at least one selected from oxide, zeolite, a clay mineral, and carbon. Examples of the oxide may include at least one selected from alumina, silica, zirconium oxide, and titanium dioxide. Examples of the oxide may include an oxide including at least one selected from cerium (Ce), praseodymium (Pr), samarium (Sm), europium (Eu), terbium (Tb), thulium (Tm), ytterbium (Yb), antimony (Sb), bismuth (Bi), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), niobium (Nb), molybdenum (Mo), and tungsten (W). Examples of the carbon may include at least one selected from carbon black such as ketjen black, acetylene black, channel black, or lamp black, graphite such as natural graphite, artificial graphite, or expanded graphite, activated carbon, and a carbon fiber, but are not limited thereto. The carbon may include any suitable material as long as the material is applicable to a carrier in the art.
The cathode 500 of the metal air cell may additionally include a binder. Examples of the binder may include at least one selected from a thermoplastic resin and a thermosetting resin. Examples of the binder may include at least one selected from polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrene-butadiene rubber, a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, a vinylidene fluoride hexafluoropropylene copolymer, a vinylidene fluoride/chlorotrifluoroethylene copolymer, an ethylene-tetrafluoroethylene copolymer, a polychloro-trifluoroethylene copolymer, a vinylidene fluoride-pentafluoro propylene copolymer, a propylene-tetrafluoroethylene copolymer, an ethylene-chloro-trifluoroethylene copolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, a vinylidene fluoride-perfluoroalkyl vinyl ether-tetrafluoroethylene copolymer, and an ethylene-acrylic acid copolymer, which are used solely or in combination. However, the binder is not limited thereto and may include any suitable material as long as the material is applicable to a binder in the art.
The cathode 500 of the metal air cell may additionally include an ion conductive polyelectrolyte. Examples of the ion conductive polyelectrolyte may include at least one selected from polyethylene oxide (PEO), polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), and polyvinyl sulfone, e.g., a polymer which is doped with lithium. For example, an ion conductive polymer solid electrolyte may be polyethylene oxide doped with a lithium salt. The doped lithium salt may be substantially the same as a lithium salt included in the first to third electrolyte described above.
The cathode 500 of the metal air cell may be prepared by, for example, mixing the conductive material, the binder, and the catalyst for oxidizing/reducing oxygen, adding an appropriate solvent to the resultant mixture to prepare a cathode slurry, and applying the prepared cathode slurry on a surface of a current collector to dry the resultant structure or selectively compression-molding the prepared cathode slurry on the current collector so as to improve an electrode density. In addition, the cathode 500 of the metal air cell may selectively include lithium oxide. Furthermore, the catalyst for oxidizing/reducing oxygen may be selectively omitted.
An anode 600 of the metal air cell may include at least one selected from an alkali metal (e.g., lithium, sodium, or potassium), an alkaline earth metal (e.g., calcium, magnesium, or barium), and/or a transition metal (e.g., zinc), and may include alloys thereof.
The aforementioned composite electrolyte film 400 may be disposed between the cathode 500 and the anode 600 of the metal air cell. Since the composite electrolyte film 400 is disposed between the cathode 500 and the anode 600, it may be possible to efficiently prevent oxygen and moisture from being transferred from the cathode 500 to the anode 600. Accordingly, the deterioration of the metal air cell may be prevented. In addition, since the composite electrolyte film 400 is light in weight, it may be possible to improve the energy density of the metal air cell. The metal air cell may be, for example, a lithium air battery or a sodium air battery.
Alternatively, the electrochemical cell 900 may be a lithium secondary cell.
The lithium secondary cell may be, for example, a lithium sulfur secondary cell or a lithium ion secondary cell.
In the lithium sulfur secondary cell, examples of a positive electrode active material in a cathode 500 may include at least one selected from elemental sulfur (S8) and an elemental sulfur-containing compound. Examples of the elemental sulfur-containing compound may include at least one selected from Li2Sn (n≧1), dissolved in a catholyte, an organic sulfur compound, and a carbon-sulfur polymer ((C2Sx)n, where x=2.5 to 50, and n≧2).
In the lithium sulfur secondary cell, examples of a negative electrode active material in an anode 600 may include a carbonaceous material as a material that is capable of reversibly intercalating/deintercalating lithium ions.
The carbonaceous material may include any suitable carbon-based negative electrode active material that is used in the lithium sulfur secondary cell. Representative examples of the carbonaceous material may include one selected from crystalline carbon and amorphous carbon. In addition, representative examples of a material, which is able to reversibly react with the lithium ions to form a lithium-containing compound, may include at least one selected from tin oxide (SnO2), titanium nitrate, and silicon (Si), but are not limited thereto. A lithium alloy may include an alloy of lithium and a metal that includes at least one selected from sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr), beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), radium (Ra), aluminum (Al), and tin (Sn).
In the lithium ion secondary cell, examples of a positive electrode active material in a cathode 500 may include a compound (lithiated intercalation compound) that is capable of reversibly intercalating/deintercalating lithium ions. Examples of the positive electrode active material may include at least one selected from lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, and lithium manganese oxide, but are not limited thereto. The positive electrode active material may include any suitable positive electrode active material as long as the positive electrode active material is applicable to the art.
Specifically, examples of the positive electrode active material may include at least one selected from lithium cobalt oxide expressed by Formula LiCoO2; lithium nickel oxide expressed by Formula LiNiO2; lithium manganese oxide expressed by Formula Li1+xMn2−xO4 (where, x is 0 to 0.33), LiMnO3, LiMn2O3, or LiMnO2; lithium copper oxide expressed by Formula Li2CuO2; lithium iron oxide expressed by Formula LiFe3O4; lithium vanadium oxide expressed by Formula LiV3O8; copper vanadium oxide expressed by Formula Cu2V2O7; vanadium oxide expressed by Formula V2O5; lithium nickel oxide expressed by Formula LiNi1-MxO2 (where, M=Co, Mn, Al Cu, Fe, Mg, B (boron), or Ga, and x=0.01 to 0.3); lithium manganese composite oxide expressed by Formula LiMn2−xMxO2 (where, M=Co, Ni, Fe, Cr, Zn or Ta, and x=0.01 to 0.1) or Li2Mn3MO8 (where, M=Fe, Co, Ni, Cu, or Zn); lithium manganese oxide expressed by Formula LiMn2O4, in which some of Li are substituted with alkaline earth metal ions; a disulfide compound; and iron molybdenum oxide expressed by Formula Fe2(MoO4)3.
In the lithium ion secondary cell, examples of a negative electrode active material in an anode 600 may include at least one selected from Si, SiOx (0<x<2, for example, x is 0.5 to 1.5), Sn, SnO2, and a silicon-containing metal alloy. Examples of a metal, which is capable of forming the silicon-containing metal ally, may include at least one selected from Al, Sn, Ag, Fe, Bi, Mg, Zn, In, Ge, Pb, and Ti.
Specifically, examples of the negative electrode active material may include one selected from lithium-alloyable metals/metalloids, alloys thereof, and oxides thereof. Examples of the lithium-alloyable metals/metalloids may include at least one selected from Si, Sn, Al, Ge, Pb, Bi, Sb, and a S—Y′ alloy (where Y′ includes one selected from an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element, a transition metal, a rare earth element, and combinations thereof and does not include Si), may include an Sn—Y″ alloy (where Y″ includes one selected from an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element, a transition metal, a rare earth element, and combinations thereof and does not include Sn), or may include MnOx (0<x≦2). The elements Y′ and Y″ may include at least one selected from Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ti, Ge, P, As, Sb, Bi, S, Se, Te, and Po. Examples of oxides of the lithium-alloyable metals/metalloids may include at least one selected from lithium titanium oxide, vanadium oxide, lithium vanadium oxide, SnO2, and SiOx (0<x<2).
Examples of the negative electrode active material may include a mixture of a carbon-based material and at least one selected from the above-described silicon, silicon oxides, and silicon-containing metal alloy, and may include a composite of a carbon-based material and at least one selected from the above-described silicon, silicon oxides, and silicon-containing metal alloy.
The negative electrode active material may have a simple particle shape and may have a nano-sized nanostructure. For example, the negative electrode active material may have any suitable shape and may be in a form such as nanoparticles, nanowires, nanorods, nanotubes, and nanobelts.
The aforementioned composite electrolyte film 400 may be disposed between the cathode 500 and the anode 600 of the lithium secondary cell. Since the composite electrolyte film 400 is disposed between the cathode 500 and the anode 600, it may be possible to more efficiently prevent oxygen and moisture from being transferred the anode 600. Accordingly, it may be possible to prevent the deterioration of the lithium secondary cell, in particular, a lithium anode. In addition, since the composite electrolyte film 400 is light in weight, it may be possible to improve the energy density of the lithium secondary cell.
According to an exemplary embodiment, a method of preparing a composite electrolyte film may include preparing a porous membrane; forming a 2D nanostructure layer on a first surface of the porous membrane; and preparing a composite electrolyte film by impregnating an electrolyte in the porous membrane and the 2D nanostructure layer.
According to the method of preparing the composite electrolyte film, it may be possible to more easily prepare a composite electrolyte film that is light in weight, thin, and flexible and is capable of blocking oxygen. In addition, it may be possible to manufacture an electrochemical cell that includes the composite electrolyte film to have an improved energy density.
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The electrochemical cell may be used to provide a lithium primary cell or a lithium secondary cell. A shape of the electrochemical cell is not particularly limited and may have, for example, a coin shape, a button shape, a sheet shape, a laminate shape, a cylindrical shape, a flat shape, or a horn shape. In addition, the electrochemical cell may also be used as a large-sized cell used in an electric vehicle or the like.
The term “air” used in the specification is not limited to air in the atmosphere and may include one selected from a pure oxygen gas and combinations of gases including oxygen. A broad definition with respect to the term “air” may be applied to all of applications, for example, an air cell, an air electrode, and the like.
Hereinafter, the present disclosure will be described in more detail through Examples and Comparative Examples. However, Examples are provided to illustrate the present disclosure and not to limit it.
A mixture solution of water and ethanol (mixed in a volume ratio of about 1:1) was prepared, wherein the mixture solution includes about 0.025 weight % of graphene oxide (UHC-GO-175 manufactured by Graphene Supermarket). Interspacing (d002) of graphene oxide (GO) was about 0.81 nanometers (nm).
A porous separator coated with graphene oxide was prepared by coating a first surface of a 12 micrometer (μm)-thickness porous separator (TM123AHS manufactured by SK Innovation) with the mixture solution using a vacuum filtration apparatus. A weight of the coated graphene oxide layer was about 0.05 milligrams per square centimeter (mg/cm2).
A polyethylene oxide (PEO) solution was obtained by dissolving about 16.32 grams (g) of polyethylene oxide (PEO, 182028 manufactured by Sigma-Aldrich) with a weight average molecular weight (Mw) of 600,000 in about 150 mL of acetonitrile. LiTFSi was introduced into the obtained PEO solution while stirring the solution such that a molar ratio of ethylene oxide (EO) to lithium (Li) was about 18:1 to form a resultant solution. The resultant solution was coated on the first surface of the porous separator, coated with graphene oxide, to a thickness of about 150 μm and the coated solution was vacuum dried at a temperature of about 80° C. for about 4 hours. Then, the resultant solution was coated on a second surface of the porous separator to a thickness of about 150 μm and the coated solution was vacuum dried at a temperature of about 80° C. for about 4 hours to prepare a laminate. A composite electrolyte film having a shape of a free standing film was prepared by disposing the laminate between polytetrafluoroethylene (PTFE) films, hot-pressing the laminate and the PTFE films at a pressure of about 2 kilograms-force per square centimeter (kgf/cm2) at a temperature of about 120° C. for about 1 hour using a press, and quickly cooling the hot-pressed laminate and PTFE films. After the hot-pressing, the hot-pressed laminate and PTFE films were cooled to a temperature of about 80° C. within about 1 minute through the quick cooling and may be cooled to a temperature of about 30° C. for about 20 minutes.
A SEM image of a cross section in the prepared porous separator coated with graphene oxide was illustrated in
A SEM image of a cross section in the prepared composite electrolyte film impregnated with an electrolyte was illustrated in
Although not illustrated in
A thickness of the composite electrolyte film was about 24 μm.
In the composite electrolyte film, a composition ratio of the porous separator to the electrolyte was about 1:2.6 based on weight.
In the composite electrolyte film, a composition ratio of a 2D nanostructure to the electrolyte was about 1:1 based on weight.
A composite electrolyte film was prepared in the same manner as Example 1 except that reduced graphene oxide (rGO) was used instead of graphene oxide.
Interspacing (d002) of reduced graphene oxide (rGO) was about 0.39 nm.
A thickness of the composite electrolyte film was about 31 μm.
Reduced graphene oxide (rGO) was prepared as follows.
About 80 mL of an aqueous solution was prepared, wherein the aqueous solution includes 0.025 weight % of graphene oxide (UHC-GO-175 manufactured by Graphene Supermarket). A reduced graphene oxide dispersed solution was prepared by mixing about 2 mL of an ammonia solution (NH4OH, 28%, A0628 manufactured by SAMCHUN Chemical) for improving dispersibility and about 40 μL of hydrazine hydrate (225819 manufactured by Sigma-Aldrich) as a reducing agent into the aqueous solution, and stirring the resultant mixture at a temperature of about 90° C. for about 1 hour.
A TiO2 nanosheet was prepared.
A mixture of a TiO2 powder, a K2CO3 powder, a Li2CO3 powder, and a MoO3 powder with a molar ratio of 1.73:1.67:0.135:1.27 was heat-treated to obtain a sintered material including two phases, i.e., K0.8Ti1.73Li0.27O4 phase and K2MoO4 phase. The heat-treatment was performed by maintaining the mixture at a temperature of 1,100° C. for 12 hours and slowly cooling the mixture to a temperature of 800° C. for 83.3 hours to grow a single crystal.
The obtained sintered material was mixed into water to dissolve a water-soluble flux, i.e., K2MoO4 in the water and remove K2MoO4 to thereby obtain a K0.8Ti1.73Li0.27O4 powder having a layered structure and including potassium disposed between layers.
15 g of the K0.8Ti1.73Li0.27O4 powder was impregnated in 1 L of a 1 M HCl solution and was maintained for 3 days in the state of being impregnated in the HCl solution. The HCl solution was changed with a fresh solution every 24 hours to substitute the potassium disposed between the layers with hydrogen.
A powder was obtained by pouring copious amounts of water into the HCl solution impregnated with the K0.8Ti1.73Li0.27O4, completely removing HCl through filtration, and then, drying the HCl-removed solution.
0.8 g of the obtained powder and 0.73 g of tetrabutylammonium hydroxide were introduced into 200 ml of deionized water, and then, were left for 10 days or more to obtain a TiO2 nanosheet exfoliated from a hydrogen-substituted sintered material due to interspacing increased while tetrabutylammonium ions were disposed between layers. Centrifuation was performed on the exfoliated TiO2 nanosheet at 2,000 rpm for 30 minutes to prepare the TiO2 nanosheet. A SEM image of the prepared TiO2 nanosheet is illustrated in
An aqueous solution including 0.05 wt % of the prepared TiO2 nanosheet was prepared.
A surface of a separator (Celgard 3501) was negatively charged by performing a corona treatment on one surface of the separator such that a polymer adhesive layer can be easily formed on a substrate.
Positively charged 0.01 wt % aqueous solution of polyethyleneimine (PEI, Mn=25,000) was electrostatically dip-coated on the negatively charged surface of the separator to form a polymer adhesive layer on the separator.
The prepared aqueous solution including the TiO2 nanosheet was coated on the polymer adhesive layer on the separator by using a vacuum filtration apparatus. A coated TiO2 nanosheet layer had a weight of about 0.0025 mg/cm2. A SEM image of the separator coated with the TiO2 nanosheet layer is iilustrated in
A gel electrolyte, which was obtained by mixing a polymeric ionic liquide (PIL), an ionic liquid (IL), and a lithium salt, was used as an electrolyte.
TFSI anion-substituted PDDA-TFSI was obtained by sequentially introducing 200 g of poly(diallyldimethylammonium chloride) (PDDA manufactured by Sigma-Aldrich, Mw=400,000, 20 wt % aqueous solution) and 100 ml of an aqueous solution including 40 g of lithium bis(trifluoromethane sulfonyl)imide (LiTFSI) into water and stirring the resultant aqueous solution for 1 hour.
A uniform electrolyte solution was prepared by mixing PDDA-TFSI obtained through filtration and drying, 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR1,4-TFSI), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) with a weight ratio of 42.6:45:12.4 into an acetonitrile solvent.
A porous separator coated with a TiO2 thin film layer was introduced into the uniform electrolyte solution, so that the uniform electrolyte solution was impregnated into the porous separator. A composite electrolyte film impregnated with an electrolyte was prepared by taking the porous separator out from the uniform electrolyte solution and additionally removing a solvent from the porous separator through vacuum drying. The composite electrolyte film had a thickness of about 85 μm.
A composite electrolyte film was prepared in the same manner as Example 1 except that a graphene oxide coating layer was omitted.
A 260 μm-thickness LICGC™ (LATP manufactured by Ohara Company) film, i.e., an inorganic lithium ion conductor was used as a composite electrolyte film as it is.
Carbon black (Printex® manufactured by Orion Engineered Chemicals in U.S.A.), i.e., a carbon-based porous particle, and a polytetrafluoroethylene (PTFE) binder (powder manufactured by Sigma-Aldrich) were prepared in a weight ratio of about 1:0.2.
A rectangular porous particle layer having an area of about 6 cm2 (2 cm×3 cm) and a thickness of about 30 μm was prepared by mechanically kneading the prepared carbon black and PTFE binder, pressing the kneaded carbon black and PTFE binder to a thickness of about 30 μm using a roll press, and drying the pressed carbon black and PTFE binder at a temperature of about 60° C. in an oven.
A polyethylene oxide (PEO) solution was obtained by dissolving 16.32 g of polyethylene oxide (PEO, 182028 manufactured by Sigma-Aldrich) with an average Mw of 600,000 in about 150 mL of acetonitrile. First electrolyte films were prepared by introducing LiTFSi into the obtained PEO solution such that a molar ratio of EO to Li was about 18:1, coating, with the resultant solution, a 50 μm-thickness Teflon film to a thickness of about 100 μm while stirring the resultant solution, and vacuum-drying the resultant solution and the Teflon film at a temperature of about 80° C. for about 4 hours.
A laminate was prepared by respectively disposing the obtained first electrolyte films on first and second surfaces of the rectangular porous particle layer. A cathode having a shape of a free standing film was prepared by disposing the laminate between PTFE films and hot-pressing the laminate and the PTFE films at a temperature of about 120° C. using a press. A thickness of the cathode was about 33 μm.
In the cathode, a composition ratio of the carbon black to a first electrolyte was about 1:2.4 based on weight.
The composite electrolyte film prepared in Example 1 was used.
A cathode-film laminate was prepared by disposing two cathodes, i.e., cathode film, (each of the films has an area of about 1 cm×3 cm) were disposed on a first surface of an electrolyte film (about 2.4 cm×3.4 cm) so as to be spaced apart by a gap of about 0.5 mm from each other. A cathode-film assembly having a shape of a free standing film was prepared by disposing the cathode-film laminate between PTFE films, hot-pressing the cathode-film laminate and the PTFE films at a temperature of about 100° C. for about 10 minutes, and quickly cooling the cathode-film laminate and the PTFE films in a state of being pressured for about 20 minutes. After the hot-pressing, the hot-pressed laminate and PTFE films were cooled to a temperature of about 80° C. within about 1 minute through the quick cooling and may be cooled to a temperature of about 30° C. for about 20 minutes.
A carbon paper (about 2 cm×3 cm, 25BA manufactured by SGL in Germany), that is, a gas diffusion layer was disposed between the two cathodes while the cathode-film assembly was folded such that the two cathodes faced each other.
A gas diffusion layer/cathode/electrolyte film/anode structure was prepared by disposing an lithium metal having a thickness of about 30 μm and an area of about 2.15 cm×3 cm on a second surface of the electrolyte film and folding the lithium metal and the cathode-film assembly including the gas diffusion layer such that the lithium metal was symmetric with the cathode with respect to the electrolyte film.
A portion of the gas diffusion layer protruding from a cathode area may function as a positive current collector. A Cu sheet was disposed on one surface of the lithium metal to be used as a negative current collector.
A lithium air cell was manufactured by respectively disposing end plates on the negative current collector and an anode opposite to the negative current collector. For example,
A lithium air cell was manufactured in the same manner as Example 4 except that the composite electrolyte film prepared in Example 2 was used.
A lithium air cell was manufactured in the same manner as Example 4 except that the composite electrolyte film prepared in Example 3 was used.
Lithium air cells were manufactured in the same manner as Example 3 except that the composite electrolyte films prepared in Comparative Examples 1 and 2 were respectively used.
A cathode-film laminate was prepared by disposing a cathode having an area of about 104.5 cm2 (about 5 cm×20.9 cm) on a first surface of the composite electrolyte film (about 5.2×22 cm) prepared in Example 1. A cathode-film assembly having a shape of a free standing film was prepared by disposing the cathode-film laminate between PTFE films, hot-pressing the cathode-film laminate and the PTFE films at a temperature of about 100° C. for about 10 minutes, and quickly cooling the cathode-film laminate and the PTFE films in a state of being pressured for about 20 minutes.
A cathode/electrolyte film/anode structure was prepared by disposing and assembling the cathode-film assembly and a lithium metal having a thickness of about 30 μm and an area of about 5 cm×20.9 cm in assembly equipment.
In addition, in the assembly equipment, the cathode/electrolyte film/anode structure was folded at an angle of about 180° to surround a gas diffusion layer having an area of about 5 cm×2 cm such that the gas diffusion layer was disposed on the cathode of the cathode/electrolyte film/anode structure and was re-folded at an angle of about 180° in an opposite direction. An operation of folding the cathode/electrolyte film/anode structure at the angle of about 180° was performed 10 times to manufacture a 3D lithium air cell. For example 10 may be referenced for the 3D lithium air cell.
Five 3D lithium air cells were laminated to manufacture a lithium air cell module.
A portion protruding from a cathode area of the gas diffusion layer may function as a positive current collector. A Cu sheet was disposed on one surface of the lithium metal to be used as a negative current collector. End plates were disposed on the negative current collector and an anode opposite to the negative current collector, respectively.
A thickness, a weight per unit area, an ionic resistance, an oxygen transfer rate, and flexibility were measured with respect to each of the composite electrolyte films prepared in Examples 1 to 3 and Comparative Examples 1 and 2. The measurement results were shown in Table 1 below.
The ionic resistance of the composite electrolyte film was measured in a 2-probe method using Solartron 1260A Impedance/Gain-Phase Analyzer. A current density was about 0.4 A/cm2, an amplitude was about ±10 mV, and a frequency range was from about 0.1 Hz to about 10 KHz.
The oxygen transfer rate was obtained by measuring an oxygen transfer rate of a composite electrolyte film having an area of about 1 cm2 in an influent oxygen atmosphere having room temperature and a pressure of about 760 mmHg using an oxygen transfer rate tester (MOCON OX-TRAN Model 2/21).
The flexibility was determined according to whether the composite electrolyte film was fractured by applying a force to the composite electrolyte film in a thickness direction thereof. “X” means that the composite electrolyte film was fractured, and “0” means that the composite electrolyte was not fractured but folded.
As shown in Table 1, the composite electrolyte films of Examples 1 to 3 have a considerably reduced weight and ion resistance and excellent flexibility compared to the ceramic solid electrolyte film of Comparative Example 2. In addition, the composite electrolyte films of Examples 1 and 2 has a considerably reduced oxygen transfer rate compared to the composite electrolyte film of Comparative Example 1.
That is, the composite electrolyte films of Examples 1 to 3 had improved ion conductivity and oxygen barrier characteristics at the same time.
The oxygen transfer rate of the composite electrolyte film of Comparative Example 1 was unmeasurable due to a too high oxygen transfer rate thereof.
The ceramic solid electrolyte film of the Comparative Example 2 was fractured (brittle) when the ceramic solid electrolyte film was folded by applying a force to the ceramic solid electrolyte film in a thickness direction thereof.
It was confirmed that the lithium air cells operated by performing a charge/discharge cycle on each of the lithium air cells manufactured in Examples 4 to 6 and the lithium air cell module manufactured in Example 5, the charge/discharge cycle including discharging each of the lithium air cells and the lithium air cell module to about 1.7 V (vs. Li) at a constant current of about 0.24 mA/cm2 and charging each of the lithium air cells and the lithium air cell module to about 4.3 V (vs. Li) with the same current in an oxygen atmosphere having a pressure of about 1 atm and a temperature of about 60°.
Therefore, a lithium air cell, which was excellent in oxygen barrier characteristics, flexible, thin, and light in weight and had a reduced volume and an improved energy density, was implemented.
According to an aspect, an energy density of an electrochemical cell may be improved by employing a composite electrolyte film having a novel structure.
It should be understood that exemplary embodiments described herein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each exemplary embodiment should typically be considered as available for other similar features or aspects in other exemplary embodiments.
While an exemplary embodiment has been disclosed with reference to the figures, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope as defined by the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2015-0136557 | Sep 2015 | KR | national |
| 10-2016-0120748 | Sep 2016 | KR | national |
This application is a continuation in part of U.S. patent application Ser. No. 15/149,364, filed on May 9, 2016, and claims priority to and the benefit of Korean Patent Application No. 10-2015-0136557, filed on Sep. 25, 2015, and Korean Patent Application No. 10-2016-0120748, filed on Sep. 21, 2016, in the Korean Intellectual Property Office, and all the benefits accruing therefrom under 35 U.S.C. §119, the contents of which are incorporated herein in their entirety by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 15149364 | May 2016 | US |
| Child | 15272947 | US |
