Solid electrolyte membrane and all-solid-state battery comprising same

Abstract

Disclosed are a solid electrolyte membrane and an all-solid-state battery comprising same, the solid electrolyte membrane comprising: a solid electrolyte; and a block copolymer comprising a unit structure derived from an aromatic vinyl monomer and a unit structure derived from a conjugated diene-based monomer.

Description

Solid electrolyte membrane and all-solid-state battery containing the same

[0001] It relates to a solid electrolyte membrane and an all-solid-state battery including the same.

[0002] Secondary batteries are devices that convert external electrical energy into chemical energy, store it, and then generate electricity when needed. They are also called rechargeable batteries. Conventional secondary batteries include lead-acid batteries, nickel-cadmium (NiCd), nickel-metal hydride (NiMH), and lithium secondary batteries. Compared to disposable primary batteries, secondary batteries offer economic and environmental advantages.

[0003] Meanwhile, as market demands for lighter, thinner, and smaller devices, such as portable devices and automotive accessories, grow, so does the need for technological development in secondary batteries, which serve as the energy source for these devices. In particular, as various types of electric vehicles become commercially available, the development of secondary batteries that reduce manufacturing costs and weight while extending their lifespan is becoming increasingly important. Efforts have been made to improve lithium secondary batteries, which boast lightweight characteristics, high energy density, high operating potential, and long cycle life.

[0004] Typically, lithium secondary batteries are manufactured by mounting an electrode assembly consisting of a cathode, anode, and a separator within a cylindrical or square metal can or a pouch-shaped case made of aluminum laminate sheet, and injecting an electrolyte into the electrode assembly. Because these lithium secondary batteries require a case with a fixed space, such as a cylindrical, square, or pouch-shaped case, the development of various types of portable devices is limited. Therefore, there is a need for the development of a novel form of lithium secondary battery that is easily reconfigurable.

[0005] Meanwhile, conventional lithium secondary battery electrolytes have primarily been liquid electrolytes containing lithium salts dissolved in non-aqueous organic solvents. However, liquid electrolytes pose safety concerns, as the organic solvent is more likely to evaporate or leak, and combustion or explosion can occur depending on ambient temperature and the temperature of the battery itself.

[0006] All-solid-state batteries, which utilize solid electrolytes, offer the advantage of safe and simple electrode assembly fabrication due to the elimination of organic solvents. However, all-solid-state batteries have limitations: their actual energy density and output fall short of those of conventional lithium secondary batteries using liquid electrolytes.

[0007] Furthermore, because all-solid-state batteries feature an electrolyte membrane containing a solid electrolyte positioned between the anode and cathode, they are larger and heavier than conventional lithium secondary batteries, resulting in lower volumetric and weight-based energy densities. To prevent this, thinning the electrolyte membrane can lead to short circuits between the anode and cathode.

[0008] Nitrile-butadiene rubber (NBR) has been primarily used as a binder for solid electrolyte membranes used in all-solid-state batteries. However, when manufacturing thin-walled solid electrolyte membranes containing a nitrile-butadiene rubber binder, they suffer from poor moisture stability, mechanical properties, and manufacturing processability.

[0009] In this way, solid electrolyte membranes for all-solid-state batteries need to be manufactured as thin films for high energy density and low resistance, but even these thin films must satisfy various mechanical properties.

[0010] Therefore, there is a need to develop a solid electrolyte membrane for all-solid-state batteries that not only has excellent ionic conductivity but also ensures flexibility.

[0011] (Prior art literature)

[0012] (Patent Document)

[0013] (Patent Document 0001) Republic of Korea Publication Patent No. 10-2021-0098246

[0014] The description of this specification was created in consideration of the problems of the prior art described above, and was completed by confirming that ionic conductivity and flexibility can be improved by using a specific block copolymer as a binder and controlling the content of unit structures derived from each monomer, the ratio of linear structures and branched structures, and molecular weight.

[0015] Accordingly, the purpose of the present specification is to provide a solid electrolyte membrane for an all-solid-state battery having excellent ionic conductivity and flexibility.

[0016] In addition, another object of the present invention is to provide an all-solid-state battery including the above-mentioned solid electrolyte membrane.

[0017] According to one aspect, a solid electrolyte membrane is provided, comprising: a solid electrolyte; and a block copolymer including a unit structure derived from an aromatic vinyl monomer and a unit structure derived from a conjugated diene monomer.

[0018] In one embodiment, the unit structure content derived from the aromatic vinyl monomer may be 15 to 45 parts by weight based on 100 parts by weight of the block copolymer.

[0019] In one embodiment, at least some of the block copolymers may include branched structures within the chains.

[0020] In one embodiment, the proportion of the block copolymer containing a branched structure may be 5 to 50 wt%.

[0021] In one embodiment, the weight average molecular weight of the block copolymer may be 5,000 to 1,000,000 g / mol.

[0022] In one embodiment, the block copolymer is soluble in a non-polar solvent at room temperature.

[0023] In one embodiment, the block copolymer can bind to at least a portion of the solid electrolyte surface.

[0024] In one embodiment, the ionic conductivity of the solid electrolyte membrane may be 1.2 to 10 mS / cm.

[0025] According to another aspect, an all-solid-state battery is provided, which includes a positive electrode, a negative electrode, and a solid electrolyte membrane interposed therebetween, wherein the solid electrolyte membrane is the solid electrolyte membrane described above.

[0026] According to one aspect, a solid electrolyte membrane having excellent balance between ionic conductivity and flexibility can be provided.

[0027] In addition, an all-solid-state battery having excellent characteristics can be provided by using such a solid electrolyte membrane.

[0028] It should be understood that the effects of one aspect of this specification are not limited to the effects described above, but include all effects that can be inferred from the detailed description or claims of this specification.

[0029] FIG. 1 is a schematic diagram of a solid electrolyte and a block copolymer binder according to one aspect of the present specification.

[0030] FIG. 2 is a photograph of a solid electrolyte membrane for an all-solid-state battery according to one embodiment of the present specification.

[0031] FIG. 3 is a photograph of a solid electrolyte membrane for an all-solid-state battery according to another embodiment of the present specification.

[0032] FIG. 4 is a graph showing the characteristics of an all-solid-state battery including a solid electrolyte membrane according to another embodiment of the present specification.

[0033] Hereinafter, aspects of this specification will be described with reference to the attached drawings. However, the descriptions herein may be implemented in various different forms and are therefore not limited to the examples described herein. Furthermore, to clearly illustrate aspects of this specification, portions irrelevant to the description in the drawings have been omitted, and similar parts have been designated with similar drawing reference numerals throughout the specification.

[0034] Throughout the specification, when a part is said to be "connected" to another part, this includes not only "directly connected" but also "indirectly connected" with other elements intervening. Furthermore, when a part is said to "include" a component, this does not exclude other components, but rather implies that the other components may be included, unless otherwise specifically stated.

[0035] When a range of numerical values ​​is stated herein, unless the specific range is otherwise specified, the values ​​have the precision of the significant figures provided according to the standard rules in chemistry for significant figures. For example, the number 10 includes the range of 5.0 to 14.9, and the number 10.0 includes the range of 9.50 to 10.49.

[0036] Hereinafter, one aspect of this specification will be described in detail with reference to the attached drawings.

[0037] solid electrolyte membrane

[0038] A solid electrolyte membrane according to one aspect may include a solid electrolyte; and a block copolymer including a unit structure derived from an aromatic vinyl monomer and a unit structure derived from a conjugated diene monomer.

[0039] Secondary batteries are devices that store and use energy through charging and discharging, which convert electrical and chemical energy. Among these, lithium secondary batteries utilize the movement of lithium ions and electrons.

[0040] In conventional lithium secondary batteries, lithium ions are transported through a liquid electrolyte containing a lithium salt dissolved in an organic solvent. The organic solvents used in this process are highly volatile and prone to ignition or explosion, so technology to replace them is being developed.

[0041] All-solid-state batteries, which replace liquid electrolytes with solid electrolytes, are considered essential technologies for manufacturing high-output, high-energy-density lithium secondary batteries because they have excellent stability and a low risk of fire or explosion.

[0042] However, solid electrolytes have lower ionic conductivity than liquid electrolytes. Furthermore, when the charge and discharge cycle is repeated, the volume of the components constituting the battery cell changes, causing the individual components to become separated from each other, preventing ionic conduction and reducing capacity.

[0043] To solve these problems, it is necessary to thin the solid electrolyte membrane and apply a binder with excellent elasticity to minimize capacity loss due to volume change.

[0044] Meanwhile, solid electrolyte membranes are manufactured by applying a slurry of a particulate solid electrolyte and binder in a solvent onto a release film, drying the slurry, and removing the release film. Therefore, the solid electrolyte and binder must be well dispersed in the solvent without any side reactions.

[0045] The above solid electrolyte may be at least one selected from the group consisting of a sulfide-based solid electrolyte, an oxide-based solid electrolyte, and a polymer-based solid electrolyte.

[0046] The sulfide-based solid electrolyte may be a material containing sulfur (S) and having conductivity of metal ions of Group 1 or Group 2 of the periodic table used in secondary batteries. For example, it may be a Li-PS-based glass or Li-PS-based glass ceramic having conductivity of lithium ions.

[0047] Examples of the above sulfide-based solid electrolyte may include at least one selected from the group consisting of Li6PS5Cl, Li6PS5Br, Li6PS5I, Li2S-P2S5, Li2S-LiI-P2S5, Li2S-LiI-Li2O-P2S5, Li2S-LiBr-P2S5, Li2S-Li2OP2S5, Li2S-Li3PO4-P2S5, Li2S-P2S5-P2S5, Li2S-P2S5-SiS2, Li2S-P2S5-SnS, Li2S-P2S5-Al2S3, Li2S-GeS2, and Li2S-GeS2-ZnS. Among these, Li6PS5Cl, Li6PS5Br, and Li6PS5I are also called argyrodite type solid electrolytes. Meanwhile, trace elements may be doped into the solid electrolyte, for example, Li6PS5Cl doped with bromine (Br).

[0048] The oxide-based solid electrolyte may be a material containing oxygen (O) and having the conductivity of a metal ion of Group 1 or Group 2 of the periodic table used in a secondary battery. For example, an LLTO-based compound, Li6La2CaTa2O 12 , Li6La2ACaNb2O 12 , Li6La2ASrNb2O 12 , Li2Nd3TeSbO 12 , Li3BO 2.5 N 0.5 , Li9SiAlO8, LAGP compounds, LATP compounds, Li 1+x Ti 2-x Al x Si y (PO4) 3-y (Here, 0≤x≤1, 0≤y≤1), LiAlxZr 2-x(PO4)3(where, 0≤x≤1, 0≤y≤1), LiTixZr 2-x (PO4)3 (wherein, 0≤x≤1, 0≤y≤1), may be at least one selected from the group consisting of LISICON compounds, LIPON compounds, perovskite compounds, NASICON compounds, and LLZO compounds.

[0049] Meanwhile, a polymer-based solid electrolyte may be a polymer resin complexed with a salt of a Group 1 or 2 metal ion used in secondary batteries. For example, a polymer resin may be added to a solvated lithium salt.

[0050] Salts of the above metal ions are, for example, metal cations and F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - , (CF3CF2SO2)2N - It may be an ionic compound in which anions such as , etc. are combined.

[0051] The polymer resin includes, for example, polyether polymers, polycarbonate polymers, acrylate polymers, polysiloxane polymers, phosphazene polymers, polyethylene derivatives, alkylene oxide derivatives such as polyethylene oxide, phosphoric acid ester polymers, agitation lysine, polyester sulfides, polyvinyl alcohol, polyvinylidene fluoride, polymers containing ionic dissociation groups, branched copolymers in which an amorphous polymer such as PMMA, polycarbonate, polysiloxane (PDMS) or phosphazene is copolymerized as a comonomer in a PEO (polyethylene oxide) main chain, comb-like polymers, and cross-linked polymer resins.

[0052] In the above solid electrolyte membrane, the content of the solid electrolyte may be 90 to 99.5 wt%, for example, 90 wt%, 90.5 wt%, 91 wt%, 91.5 wt%, 92 wt%, 92.5 wt%, 93 wt%, 93.5 wt%, 94 wt%, 94.5 wt%, 95 wt%, 95.5 wt%, 96 wt%, 96.5 wt%, 97 wt%, 97.5 wt%, 98 wt%, 98.5 wt%, 99 wt%, 99.5 wt%, or a range between any two of these values. The higher the proportion of the solid electrolyte, the higher the ionic conductivity of the solid electrolyte membrane may be; however, if the block copolymer is insufficient, the adhesion between the solid electrolytes may be insufficient, making it difficult to maintain the membrane shape.

[0053] The above block copolymer functions as a binder that interconnects solid electrolytes, which are particulate materials, in a solid electrolyte membrane.

[0054] The above block copolymer comprises a unit structure derived from an aromatic vinyl monomer and a unit structure derived from a conjugated diene monomer. Here, the inclusion of a unit structure derived from a monomer means that the polymer or copolymer is manufactured by polymerizing the monomer. In such a polymer or copolymer, each monomer exists in one or more repeating structures to form a polymer chain. This repeating structure is called a unit structure, and a single monomer can exist in various forms of unit structures.

[0055] An aromatic vinyl monomer refers to a monomer having a cyclic structure with a conjugated pi electron system, i.e., an aromatic ring structure and a vinyl structure with a carbon-carbon double bond. For example, the monomer may be at least one selected from the group consisting of styrene, α-methylstyrenevinyltoluene, t-butylstyrene, halogen-substituted styrene, 1,3-dimethylstyrene, 2,4-dimethylstyrene, and ethylstyrene, but is not limited thereto. The conjugated structure of such an aromatic vinyl monomer can increase the ionic conductivity of a solid electrolyte membrane.

[0056] The unit structure content derived from the aromatic vinyl monomer may be 15 to 45 parts by weight, for example, 15 parts by weight, 17.5 parts by weight, 20 parts by weight, 22.5 parts by weight, 25 parts by weight, 27.5 parts by weight, 30 parts by weight, 32.5 parts by weight, 35 parts by weight, 37.5 parts by weight, 40 parts by weight, 42.5 parts by weight, 45 parts by weight, or a range between any two of these values. When the unit structure content derived from the aromatic vinyl monomer satisfies the above range, the flexibility and ion conductivity of the solid electrolyte membrane can be excellent in balance.

[0057] As the content of unit structures derived from aromatic vinyl monomers increases, the copolymer chains become relatively rigid, and cohesion increases in certain regions of the polymer chains, which can enhance adhesive strength. Furthermore, the ionic conductivity of the solid electrolyte membrane can be improved. On the other hand, if the content of unit structures derived from aromatic vinyl monomers increases excessively, the flexibility of the polymer chains decreases, which can deteriorate the physical properties of the solid electrolyte membrane. For example, the flexibility of the electrolyte membrane may be reduced, and peeling from the release film may become difficult.

[0058] A conjugated diene monomer refers to a hydrocarbon compound having a structure in which two carbon-carbon double bonds are directly connected by a carbon-carbon single bond. For example, the conjugated diene monomer may be at least one selected from the group consisting of, but is not limited to, 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2,3-dimethylbutadiene, 2-phenyl-1,3-butadiene, 2-chloro-1,3-butadiene, 1,3-pentadiene, 2-methyl-1,3-pentadiene, 3-methyl-1,3-pentadiene, 4-methyl-1,3-pentadiene, 1,3-hexadiene, 2-ethyl-1,3-butadiene, 2,4-hexadiene, and cyclo-1,3-hexadiene.

[0059] The unit structure derived from the conjugated diene monomer may have more than one form. For example, the unit structure derived from 1,3-butadiene may have a cis-1,4 structure, a trans-1,4 structure, and a vinyl-1,2 structure within the polymer chain. In the copolymer, the cis-1,4 structure has high crystallinity and a glass transition temperature (T g ) may be low. In addition, the trans-1,4 structure may have relatively low crystallinity. On the other hand, the vinyl-1,2 structure has a high glass transition temperature (T g ) can have.

[0060] The unit structure derived from the conjugated diene monomer can impart elasticity to the copolymer. If the block copolymer used as a binder has elasticity, it can prevent capacity loss due to volume changes of each component in a battery including a solid electrolyte membrane.

[0061] Meanwhile, the copolymer may be a block copolymer in which a single type of structure is dominant in a certain region of the polymer chain. For example, it may be a region composed of a unit structure derived from a conjugated diene monomer, i.e., a form in which aromatic vinyl blocks are bonded to both ends of a conjugated diene block. An example of such a block copolymer is a styrene-butadiene-styrene block copolymer.

[0062] Such polymer structures can be confirmed by a variety of conventional methods, including Fourier transform infrared (FT-IR) spectroscopy, nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), and the Koldhof method. For example, block structures can be confirmed by the Koldhof method, which involves staining a specific unit structure in a copolymer with osmic acid and then observing it with a transmission electron microscope.

[0063] In one example, the block copolymer may have a linear structure. Here, the linear structure may mean a form in which one unit structure is connected to two or fewer unit structures. The block copolymer may account for 50 wt% or more of the total unit structure, for example, 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, 85 wt%, 90 wt%, 95 wt%, 100 wt%, or a range between any two of these values. If the proportion of the linear structure in the block copolymer is high, the adhesion speed of the binder may be increased.

[0064] Meanwhile, the block copolymer may include a branched structure within the chain. Here, a branched structure may mean that one unit structure is connected to three or more unit structures. For example, when a coupling agent is added during polymerization of the block copolymer, one unit structure derived from the coupling agent may combine with three or more other unit structures to form a branched structure. The compound used as the coupling agent may include vinylalkylalkoxysilane, epoxyalkylalkoxysilane, mercaptoalkylalkoxysilane, vinylhaloalkoxysilane, alkylacyloxysilane, and the like.

[0065] For example, the coupling agent is dimethyldichlorosilane, trimethylchlorosilane, methyldichlorosilane, methyltrichlorosilane, phenyltrichlorosilane, vinyltrichlorosilane, tetrachlorosilane, triethoxysilylpropyldiethylamine, vinyltrimethoxysilane, vinyltriethoxysilane, 2-(3,4epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-Methacryloxypropylmethyldiethoxysilane, 3-Acryloxypropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3 dimethylbutylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, N-(vinylbenzyl)-2-aminoethyl-3-aminopropyltrimethoxysilane hydrochloride, tris-(trimethoxysilylpropyl)isocyanurate, vinyltris(methoxyethoxy)silane, methacryloxypropyltrimethoxysilane, 3-ureidopropyltrialkoxysilane, 3-mercaptopropylmethyldimethoxysilane, It may be at least one selected from the group consisting of 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-isocyanatopropyltriethoxysilane, 3-thiocyanatopropyltrimethoxysilane, 3-thiocyanatopropyltriethoxysilane, 3,3'-bis(trimethoxysilylpropyl)polysulfide, 3,3'-bis(triethoxysilylpropyl)polysulfide, 3,3'-bis(trimethoxysilylpropyl)tetrasulfide, 3,3'-bis(triethoxysilylpropyl)tetrasulfide, 3,3'-bis(trimethoxysilylpropyl)disulfide, 3,3'-bis(triethoxysilylpropyl)disulfide, and 3-(trimethoxysilyl)propylsuccinic anhydride, but is not limited thereto.

[0066] The proportion of copolymers containing such branched structures can be directly or indirectly confirmed using various known methods. For example, after forming a branched structure using a coupling agent, the proportion can be confirmed using gel permeation chromatography (GPC). In the GPC measurement results, the molecular weight of the branched block copolymer may be located in a region higher than the molecular weight of the linear block copolymer. Therefore, the proportion of the block copolymer containing the branched structure can be confirmed from the area ratio of the region with relatively high molecular weight. Meanwhile, the content of the branched structure can also be indirectly confirmed from the ratio of the Mooney viscosity and the solution viscosity.

[0067] The proportion of the block copolymer having a branched structure may be 5 to 50 wt%, for example, 5 wt%, 7.5 wt%, 10 wt%, 12.5 wt%, 15 wt%, 17.5 wt%, 20 wt%, 22.5 wt%, 25 wt%, 27.5 wt%, 30 wt%, 32.5 wt%, 35 wt%, 37.5 wt%, 40 wt%, 42.5 wt%, 45 wt%, 47.5 wt%, 50 wt%, or a range between two of these values.

[0068] In particular, if the block copolymer has a form in which at least a portion of a branched structure is mixed, the ion conductivity and flexibility of the solid electrolyte membrane are excellent, and it can be easily peeled off from the release film.

[0069] In one example, even if the block copolymer has a low content of unit structures derived from aromatic vinyl monomers, ionic conductivity can be improved by increasing the proportion of branched structures. As a result, a solid electrolyte membrane with excellent ionic conductivity and flexibility can be formed.

[0070] The weight average molecular weight of the above block copolymer is 5,000 to 1,000,000 g / mol, for example, 5,000 g / mol, 10,000 g / mol, 15,000 g / mol, 20,000 g / mol, 25,000 g / mol, 30,000 g / mol, 35,000 g / mol, 40,000 g / mol, 45,000 g / mol, 50,000 g / mol, 55,000 g / mol, 60,000 g / mol, 65,000 g / mol, 70,000 g / mol, 75,000 g / mol, 80,000 g / mol, 85,000 g / mol, 90,000 g / mol, 95,000 g / mol, 100,000 g / mol, 125,000 g / mol, 150,000 g / mol, 175,000 g / mol, 200,000 g / mol, 225,000 g / mol, 250,000 g / mol, 300,000 g / mol, 350,000 g / mol, 400,000 g / mol, 450,000 g / mol, 500,000 g / mol, 550,000 g / mol, 600,000 g / mol, 650,000 g / mol, 700,000 g / mol, 750,000 g / mol, 800,000 g / mol, 850,000 g / mol, 900,000 g / mol, The molecular weight of the block copolymer may be 950,000 g / mol, 1,000,000 g / mol, or a range between two of these values. If the molecular weight of the block copolymer is high, the flexibility and ionic conductivity of the solid electrolyte membrane manufactured using the block copolymer may be excellent. However, if the molecular weight of the block copolymer is excessively high, the viscosity of the slurry for manufacturing the solid electrolyte membrane may become too high, or the dispersibility in the solvent may be reduced.

[0071] That is, by controlling the content of the unit structure derived from the aromatic vinyl monomer, the proportion of the branched structure, and the weight average molecular weight in relation to the above block copolymer as a binder, the flexibility and ion conductivity of the solid electrolyte membrane, which are in a complementary relationship, can be controlled in a balanced manner.

[0072] Meanwhile, the block copolymer can be dissolved in a non-polar solvent at room temperature. The non-polar solvent may be at least one selected from the group consisting of benzene, toluene, xylene, hexane, cyclohexane, methylcyclohexane, ethylcyclohexane, nonane, decane, decalin, tetralin, dodecane, dibromomethane, dichloromethane, chloroform, butyl butyrate, hexyl butyrate, and isobutylisobutyrate. The non-polar solvents described above have little or no reactivity with solid electrolytes, but it was difficult to dissolve and disperse conventional binder copolymers in non-polar solvents. On the other hand, the block copolymer according to one aspect of the present disclosure can be well dispersed to form a slurry even in a solvent that has little or no reactivity with solid electrolytes.

[0073] The above block copolymer can be produced by polymerizing an aromatic vinyl monomer and a conjugated diene monomer in the presence of a catalyst. Here, an anionic polymerization initiator such as an organic lithium compound such as n-butyl lithium can be used as the catalyst, but is not limited thereto.

[0074] As a means of controlling the structure of the above block copolymer, a randomizing agent can be added during polymerization to control the polymerization reaction rate. Alternatively, the desired structure can be formed by exploiting the difference in reactivity between the aromatic vinyl monomer and the conjugated diene monomer. Furthermore, a coupling agent can be added to form a branched structure.

[0075] In the above solid electrolyte membrane, the block copolymer may be combined with at least a portion of the solid electrolyte surface. The block copolymer can form a solid electrolyte membrane in the form of a so-called free-standing or self-supporting film through bonding between solid electrolyte particles. Such a film can maintain its shape even without a support.

[0076] Therefore, the solid electrolyte membrane can replace the role of the separator included in a conventional secondary battery. Since the separator is interposed between the positive and negative electrodes and plays a role in preventing short circuits, the solid electrolyte membrane must also be able to prevent damage due to external impacts or internal factors of the battery. If the solid electrolyte membrane is rigid, it can easily be damaged and cause a short circuit, so a solid electrolyte membrane with excellent flexibility is required. Using a flexible solid electrolyte membrane can increase the speed of the continuous process during the manufacturing of battery cells.

[0077] In the above solid electrolyte membrane, the content of the block copolymer may be 0.5 to 10 wt%, for example, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, 5.5 wt%, 6 wt%, 6.5 wt%, 7 wt%, 7.5 wt%, 8 wt%, 8.5 wt%, 9 wt%, 9.5 wt%, 10 wt%, or a range between any two of these values. The block copolymer, which is a binder during ion conduction in the solid electrolyte membrane, may act as a type of resistor. On the other hand, if the content of the block copolymer is insufficient, it may be difficult to form and maintain a free-standing film.

[0078] The thickness of the above solid electrolyte membrane may be in the range of 30 to 200 μm, for example, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 75 μm, 100 μm, 125 μm, 150 μm, 175 μm, 200 μm, or a range between any two of these values. When this range is satisfied, a battery using the above solid electrolyte membrane can have excellent stability and performance in a balanced manner.

[0079] The ionic conductivity of the solid electrolyte membrane may be in a range of 1.2 to 10 mS / cm, for example, 1.2 mS / cm, 1.5 mS / cm, 2.5 mS / cm, 5 mS / cm, 7.5 mS / cm, 10 mS / cm, or a range between any two of these values.

[0080] The above solid electrolyte membrane can be manufactured by mixing a solid electrolyte, a block copolymer, and a solvent to prepare a slurry, applying the slurry to one surface of a release film, drying the slurry, and then removing the release film.

[0081]

[0082] All-solid-state batteries

[0083] According to another aspect, an all-solid-state battery is an all-solid-state battery including a positive electrode, a negative electrode, and a solid electrolyte membrane interposed therebetween, wherein the solid electrolyte membrane may be the solid electrolyte membrane described above.

[0084] In one example, the all-solid-state battery may be a type of lithium secondary battery, wherein the types of the positive and negative electrodes are not limited. For example, it may be a lithium-air battery, a lithium oxide battery, a lithium-sulfur battery, or a lithium metal battery.

[0085] The positive or negative electrode may be formed by forming a layer on at least one surface of the current collector, which is a mixture of a positive or negative electrode active material and, if necessary, a conductive material and a binder. This mixed layer may be formed by applying a slurry containing the active material, the conductive material, and the binder mixed in a solvent onto the current collector, and then drying and removing the solvent.

[0086] Methods for applying the electrode slurry include doctor blade, die casting, comma coating, and screen printing. Furthermore, the electrode slurry can be molded onto a separate substrate and then bonded or laminated to the current collector. The coating thickness can be controlled by adjusting the concentration of the slurry solution or the number of coating cycles.

[0087] The drying process involves drying the slurry coated on the collector to remove the solvent and moisture. The specific method may vary depending on the solvent used. For example, it is performed in a vacuum oven at 50 to 200°C. Other drying methods include drying using warm air, hot air, or low-humidity air, vacuum drying, and drying using irradiation with infrared or electron beams. Typically, drying takes between 30 seconds and 24 hours.

[0088] A cooling process may be added after the drying process. An example of a cooling process is slow cooling to room temperature to ensure the binder's recrystallized structure is well formed.

[0089] Additionally, if necessary, a rolling process may be performed after the drying process to compress the electrode to a desired thickness to increase the capacity density of the electrode and enhance the adhesion between the current collector and the active materials. This rolling process can be performed using known methods, such as passing the electrode between rotating rolls or using a flat plate press.

[0090] The above positive electrode active material is, for example, a layered compound such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or a compound in which some of these are substituted with a transition metal, chemical formula Li 1+x Mn 2-x Lithium manganese oxides such as O4(0≤x≤0.33), LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, Cu2V2O7; chemical formula LiNi 1-x M x Ni-site lithium nickel oxide represented by O2 (M = Co, Mn, Al, Cu, Fe, Mg, B or Ga; 0.01≤x≤0.3); chemical formula LiMn 2-x M xLithium manganese composite oxides expressed as O2 (M = Co, Ni, Fe, Cr, Zn or Ta; 0.01≤x≤0.1) or Li2Mn3MO8 (M = Fe, Co, Ni, Cu or Zn); LiNi x Mn 2-x Lithium manganese composite oxides with spinel structure represented by O4; LiCoPO4; LiFePO4; Elemental sulfur (S8); Li2Sn(n=1), organosulfur compounds or carbon-sulfur polymers (C2S x ) n : It may include sulfur series compounds such as x=2.5~50, n=2), but is not limited thereto.

[0091] Lithium ion (Li) is used as the negative electrode active material. + ) can be used. For example, carbonaceous materials such as crystalline artificial graphite, crystalline natural graphite, amorphous hard carbon, low-crystalline soft carbon, carbon black, acetylene black, Ketjen black, Super-P, graphene, and fibrous carbon, Si-based materials, Li x Fe2O3(0≤x≤1), Li x WO2(0≤x≤1), Sn x Me 1-x Me´ y O z (Me: Mn, Fe, Pb, Ge; Me´Al, B, P, Si, elements of group 1, 2, and 3 of the periodic table, halogens; 0 <x≤1; 1≤y≤3; 1≤z≤8) 등의 금속 복합 산화물; 리튬 금속; 리튬 합금; 규소계 합금; 주석계 합금; SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, Bi2O5등의 금속 산화물; 폴리아세틸렌 등의 도전성 고분자; Li-Co-Ni 계 재료; 티타늄 산화물; 리튬 티타늄 산화물 등일 수 있으나, 이에 한정되는 것은 아니다.

[0092] The current collector is intended to support the electrode active material, and its type is not limited as long as it has excellent conductivity and is electrochemically stable under the conditions of use of the all-solid-state battery. For example, the current collector may be at least one selected from the group consisting of carbon, copper, aluminum, stainless steel, titanium, silver, palladium, and nickel, or an alloy of two or more thereof. Alternatively, the current collector surface may be surface-treated with at least one of carbon, nickel, titanium, and silver.

[0093] Meanwhile, by forming fine irregularities on the surface of the collector, the bonding strength with the positive electrode active material can be strengthened, and various forms such as films, sheets, foils, meshes, nets, porous bodies, foams, and non-woven fabrics can be used.

[0094] Meanwhile, a conductive material is a material that electrically connects an electrolyte and an electrode active material and serves as a path for electrons to move from a current collector to the electrode active material. As long as it does not cause chemical changes under the conditions of use of the all-solid-state battery and has porosity and conductivity, it can be used without restriction.

[0095] Examples of conductive materials include porous carbon-based materials, metallic fibers, metallic powders, and organic conductive materials. Carbon-based materials include carbon black, graphite, graphene, activated carbon, carbon fibers, and carbon nanotubes. Metallic fibers or powders include copper, silver, nickel, and aluminum. Polyphenylene derivatives are examples of organic conductive materials.

[0096] There is no limitation on the type of electrode binder as long as it can increase the bonding strength between the components constituting the electrode and between these components and the current collector. Examples include fluororesin binders such as polyvinylidene fluoride (PVdF) and polytetrafluoroethylene (PTFE); rubber binders such as styrene butadiene rubber (SBR), acrylonitrile-butidiene rubber, and styrene-isoprene rubber; cellulose binders such as carboxylmethyl cellulose (CMC), starch, hydroxypropyl cellulose, and regenerated cellulose; polyalcohol binders; polyolefin binders such as polyethylene and polypropylene; polyimide binders; polyester binders; silane binders, etc.

[0097] The method for manufacturing an all-solid-state battery is not particularly limited, and any known method can be utilized.

[0098] For example, a cell can be manufactured by compressing a solid electrolyte membrane between the anode and cathode. The assembled cell can then be installed within an outer packaging material and sealed using processes such as heating and compression. Examples of such outer packaging materials include laminate packs made of aluminum, stainless steel, or other materials, as well as cylindrical or square metal containers.

[0099] The above-mentioned all-solid-state battery can have various shapes such as cylindrical, laminated, and coin-shaped depending on the outer packaging material used.

[0100] Hereinafter, examples of this specification will be described in more detail. However, the experimental results below represent only representative experimental results among the examples above, and the scope and content of this specification cannot be interpreted as being reduced or limited by these examples. The effects of each of the various implementation examples of this specification that are not explicitly presented below will be specifically described in the relevant sections.

[0101] Experimental Example 1

[0102] -Example 1A: A solution styrene-butadiene rubber having a styrene content of 21 wt%, a vinyl content of 63 wt%, and a Tg of -28°C was set as Example 1A.

[0103] -Example 1B: Styrene-butadiene rubber (emulsion styrene-butadiene rubber) manufactured by low-temperature emulsion polymerization with a styrene content of 23.5 wt% was set as Example 1B.

[0104] -Example 1C: Acrylonitrile butadiene rubber containing 34 wt% acrylonitrile was set as Example 1C.

[0105] -Example 1D: A linear styrene-butadiene-styrene copolymer having a styrene content of 40.5 wt% and a weight average molecular weight of 50,000 g / mol was set as Example 1D.

[0106] -Example 1E: The content of cis-1,4 group is 96 wt% or more, and the Raw Mooney viscosity (ML) 1+4 @100℃) was set as Example 1E for butadiene rubber with a temperature of 43.

[0107] -Solid electrolyte: Agrhodite (Li6PS5Cl) was set as the solid electrolyte material used in the experimental example.

[0108] The dispersibility of the binder was confirmed by mixing 5 parts by weight of each of the binders of Examples 1A to 1E with 100 parts by weight of xylene or isobutyl isobutyrate solvent.

[0109] Next, 495 parts by weight of a solid electrolyte was added to prepare a solid electrolyte slurry, and the binder stability upon addition of the electrolyte was confirmed.

[0110] The above slurry was applied onto a polyethylene terephthalate release film and dried at room temperature for 2 hours and at 70°C for 5 hours to form a solid electrolyte membrane. The ionic conductivity of the solid electrolyte membrane was measured, and the membrane was separated from the release film to determine its physical properties. The results are shown in Table 1 and Figure 2 below.

[0111] Dispersible Stable Membrane PropertiesDispersible Stable Membrane PropertiesExample 1A○○×○○×Example 1B○○×○△×Example 1C△×××--Example 1D○△○○△○Example 1E○○○○△×

[0112] In the table above, among the evaluation items, those that are excellent are marked with ○, those that are usable but cannot be identified with △, and those that cannot be used due to poor characteristics are marked with ×.

[0113] Referring to Table 1, the binder of Example 1A was easily broken due to insufficient flexibility of the electrolyte membrane during the process of separating it from the release film when dispersed in isobutylene isobutyrate. The binder of Example 1B could not be used because the electrolyte membrane did not peel off from the release film. The binder of Example 1C could not be dispersed because the electrolyte and binder coagulated with each other. The binder of Example 1D had a very low viscosity, making it difficult to confirm stability, but the flexibility of the electrolyte membrane manufactured from it was the best among the electrolyte membranes of Example 1. The binder of Example 1E had a problem of easily breaking when manufacturing the electrolyte membrane using isobutylene isobutyrate.

[0114] Meanwhile, as a result of examining the ion conductivity characteristics of the electrolyte membranes of Examples 1A, 1B, and 1D, which are capable of measuring ion conductivity among the electrolyte membranes manufactured in Example 1, Example 1D showed the best ion conductivity, Example 1B showed slightly inferior ion conductivity to Example 1D, and Example 1A showed significantly inferior ion conductivity to Example 1D.

[0115]

[0116] Experimental Example 2

[0117] In Experimental Example 1, the styrene-butadiene-styrene copolymer of Example 1D, which enabled the production of the best electrolyte membrane, was prepared as a binder with different properties as follows.

[0118] -Example 2A: A linear styrene-butadiene-styrene copolymer having a styrene content of 40.5 wt% and a weight average molecular weight of 50,000 g / mol was set as Example 2A.

[0119] -Example 2B: A linear styrene-butadiene-styrene copolymer having a styrene content of 31.5 wt% and a weight average molecular weight of 50,000 g / mol was set as Example 2B.

[0120] -Example 2C: A branched styrene-butadiene-styrene copolymer having a styrene content of 31.5 wt% and a weight average molecular weight of 50,000 g / mol was set as Example 2C.

[0121] - Example 2D: A styrene-butadiene-styrene copolymer having a styrene content of 20 wt% and a weight-average molecular weight of 190,000 g / mol was set as Example 2D. The copolymer of Example 2D was generally linear, but some branched structures were mixed in among the polymer chains.

[0122] -Example 2E: A styrene-butadiene-styrene copolymer having a styrene content of 45 wt% and a weight average molecular weight of 220,000 g / mol was set as Example 2E. The copolymer of Example 2E was generally linear, but some branched structures were mixed in among the polymer chains.

[0123] -Solid electrolyte: Agrhodite (Li6PS5Cl) was set as the solid electrolyte material used in the experimental example.

[0124] The binder of any one of Examples 2A to 2C and the isobutyl isobutyrate solvent were mixed at a weight ratio of 1:20 to check the dispersibility of the binder.

[0125] Next, 49 parts by weight (2 wt% binder) or 49 parts by weight (5 wt% binder) of the solid electrolyte were added to 1 part by weight of the binder to prepare a solid electrolyte slurry. The slurry was applied onto a polyethylene terephthalate release film and dried at room temperature for 2 hours and at 70°C for 5 hours to form a solid electrolyte membrane. The ionic conductivity of the solid electrolyte membrane was measured, separated from the release film, and the physical properties of the solid electrolyte membrane were confirmed. The results are shown in Table 2 and Fig. 3 below. Here, the ionic conductivity was determined as a reference (100) for the electrolyte membrane to which the binder of Example 2A was applied at 2 wt% and 5 wt%, respectively, and a higher number was assigned as the better value.

[0126] ClassificationBinder DispersibilityBinder ContentIonic ConductivityFlexibilityExample 2A-1◎2 wt% 100○Example 2A-25 wt% 100○Example 2B-1○2 wt% 91.9○Example 2B-25 wt% 96.4○Example 2C-1○2 wt% 86.9○Example 2C-25 wt% 101.8○Example 2D-1○2 wt% 105.1○Example 2D-25 wt% 112.5○Example 2E-1○2 wt% 112.1○Example 2E-25 wt% 119.6○

[0127] According to Experimental Example 2, the higher the styrene content of the styrene-butadiene-styrene copolymer binder, the lower the flexibility and the more difficult it is to peel the electrolyte membrane from the release film. In addition, it is believed that when the copolymer has a branched structure, the electrolyte membrane is easier to peel and has better flexibility. Meanwhile, the characteristics of the electrolyte membrane may vary depending on the balance of styrene content, copolymer chain structure, and molecular weight. It was confirmed that the ionic conductivity tends to increase as the styrene content increases, but even at a low styrene content, if the copolymer includes a branched structure and has a high molecular weight, it may be advantageous in terms of ionic conductivity and flexibility.

[0128]

[0129] Experimental Example 3

[0130] A cathode was manufactured by mixing NCM811 cathode active material, carbon fiber conductive material, agarodite solid electrolyte, and polytetrafluoroethylene binder in a weight ratio of 84:0.2:14.8:1 and then rolling.

[0131] A negative electrode was manufactured by applying a mixture of carbon black negative active material and polyvinylidene fluoride to a thickness of 150 μm on a SUS negative electrode collector with a thickness of 10 μm.

[0132] An electrolyte membrane of Examples 2A-1, 2D-1, and 2E-1 was interposed between the manufactured positive and negative electrodes, and then pressurized to manufacture an all-solid-state battery in the form of a monocell.

[0133] The charge / discharge characteristics of the all-solid-state battery manufactured by repeating charge / discharge under the conditions of 3.0~4.25 V, 1 C were measured, and the results are shown in Fig. 4.

[0134] The description of this specification above is for illustrative purposes only, and those skilled in the art will readily appreciate that aspects of this specification can be readily modified into other specific forms without altering the technical concepts or essential features described herein. Therefore, the examples described above should be understood as illustrative in all respects and not limiting. For example, components described as being single may be implemented in a distributed manner, and similarly, components described as being distributed may be implemented in a combined manner.

[0135] The scope of this specification is indicated by the claims, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included within the scope of this specification.

Claims

1. Solid electrolyte; and A block copolymer comprising a unit structure derived from an aromatic vinyl monomer and a unit structure derived from a conjugated diene monomer; Solid electrolyte membrane.

2. In paragraph 1, The unit structure content derived from the above aromatic vinyl monomer is 15 to 45 parts by weight based on 100 parts by weight of the above block copolymer. Solid electrolyte membrane.

3. In paragraph 1, At least some of the above block copolymers comprise a branched structure within the chain, Solid electrolyte membrane.

4. In paragraph 3, The proportion of the above block copolymer containing a branched structure is 5 to 50 wt%, Solid electrolyte membrane.

5. In paragraph 1, The weight average molecular weight of the above block copolymer is 5,000 to 1,000,000 g / mol. Solid electrolyte membrane.

6. In paragraph 1, The above block copolymer is soluble in a non-polar solvent at room temperature, Solid electrolyte membrane.

7. In paragraph 1, The above block copolymer is bonded to at least a portion of the solid electrolyte surface, Solid electrolyte membrane.

8. In paragraph 1, The ionic conductivity of the above solid electrolyte membrane is 1.2 to 10 mS / cm. Solid electrolyte membrane.

9. An all-solid-state battery comprising a positive electrode, a negative electrode, and a solid electrolyte membrane interposed therebetween, The above solid electrolyte membrane is an all-solid-state battery according to any one of claims 1 to 8.

Images