Solid electrolyte, and solid electrolyte membrane and all-solid-state rechargeable battery which comprise same

Abstract

The present invention relates to a solid electrolyte, and a solid electrolyte membrane and an all-solid-state rechargeable battery which comprise same, the solid electrolyte comprising argyrodite-type sulfide-based solid electrolyte particles and a lithium salt located on the surfaces of the particles, wherein the lithium salt has F and P-O functional groups.

Description

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

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

[0002] Lithium secondary batteries, which offer high energy density and portability, are primarily used as power sources for mobile information terminals such as mobile phones, laptops, and smartphones. Recently, active research is underway to utilize high-energy-density lithium secondary batteries as power sources for hybrid and electric vehicles, or as power storage devices.

[0003] Commercially available lithium secondary batteries use electrolytes containing flammable organic solvents, posing safety concerns that can lead to explosion or fire in the event of collisions, penetration, or other problems. Therefore, all-solid-state secondary batteries, which utilize solid electrolytes instead of the electrolyte, have been proposed. All-solid-state secondary batteries are composed entirely of solid materials, eliminating the risk of electrolyte leakage and explosion, making them safer. Furthermore, they facilitate the production of thin batteries, allowing for a reduced anode thickness, improving high-speed charge / discharge performance and enabling high-voltage operation and high-energy density.

[0004] Sulfide-based solid electrolytes with high ionic conductivity are mainly used as solid electrolytes. Among them, argyrodite-type sulfide-based solid electrolytes have an ionic conductivity of 10, which is the ionic conductivity of a typical liquid electrolyte at room temperature. -4 10 inland -2 It can exhibit high ionic conductivity approaching the S / cm range, and has the advantage of having soft mechanical properties, which can form close bonds between solid electrolytes and between the solid electrolyte and the positive active material. Accordingly, all-solid-state secondary batteries using argyrodite-type sulfide-based solid electrolytes can exhibit improved rate characteristics, Coulombic efficiency, and cycle life characteristics.

[0005] However, argyrodite-type sulfide-based solid electrolytes are very vulnerable to moisture and air, and when exposed to air during the manufacturing process, distribution process, or battery operation, they react with H2O, CO2, O2, etc. to generate byproducts such as hydrogen sulfide, and there is a problem that their performance deteriorates, such as surface damage or rapid drop in ionic conductivity.

[0006] It improves the moisture stability of argyrodite-type sulfide-based solid electrolytes, realizes stable ionic conductivity, and enhances performance such as life characteristics of all-solid-state secondary batteries.

[0007] In one embodiment, a solid electrolyte is provided, which comprises argyrodite-type sulfide-based solid electrolyte particles and a lithium salt positioned on the surface of the particles, wherein the lithium salt has F and PO functional groups.

[0008] In another embodiment, a solid electrolyte membrane comprising the solid electrolyte is provided.

[0009] In another embodiment, an all-solid-state secondary battery is provided, comprising a positive electrode, a negative electrode, and a solid electrolyte layer positioned between the positive electrode and the negative electrode, wherein at least one of the positive electrode, the negative electrode, and the solid electrolyte layer comprises the solid electrolyte.

[0010] According to one embodiment, a solid electrolyte comprises an argyrodite-type sulfide, yet exhibits excellent atmospheric stability and level stability. This effectively suppresses the continuous decrease in ionic conductivity over time due to atmospheric exposure, and provides relatively stable resistance values ​​that facilitate the smooth movement of lithium ions. Solid electrolyte membranes and all-solid-state secondary batteries utilizing this electrolyte can exhibit outstanding electrochemical properties, including excellent cycle life.

[0011] Figures 1 and 2 are cross-sectional views schematically showing an all-solid-state secondary battery according to one embodiment.

[0012] Figure 3 is a graph showing the change in weight of a symmetrical cell according to exposure time after leaving the solid electrolyte membranes of Example 1, Comparative Example 1, and Comparative Example 2 in a dry room.

[0013] Figure 4 is a graph showing the change in ionic conductivity retention rate according to exposure time after leaving the solid electrolyte membranes of Example 1, Comparative Example 1, and Comparative Example 2 in a dry room.

[0014] Below, specific implementation examples are described in detail to facilitate their implementation by those skilled in the art. However, the present invention may be implemented in various different forms and is not limited to the implementation examples described herein.

[0015] The terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

[0016] Here, “combination of these” means a mixture, laminate, composite, copolymer, alloy, blend, reaction product, etc. of the components.

[0017] It should be understood that the terms "include," "comprising," or "having" herein are intended to specify the presence of a feature, number, step, component, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0018] To clearly illustrate various layers and regions in the drawings, their thicknesses are enlarged, and similar parts are designated by the same drawing reference numerals throughout the specification. When an element such as a layer, film, region, or plate is said to be "over" or "on" another element, this includes not only the case where it is "directly over" the other element, but also the case where there are other elements in between. Conversely, when an element is said to be "directly over" another element, it means that there are no other elements in between.

[0019] Also, here, “layer” includes not only the shape formed on the entire surface when observed in a plan view, but also the shape formed on a portion of the surface.

[0020] The average particle size can be measured by methods well known to those skilled in the art, for example, by measuring with a particle size analyzer, or by measuring with a transmission electron microscope image or a scanning electron microscope image. Alternatively, the average particle size can be obtained by measuring using dynamic light scattering, performing data analysis, counting the number of particles for each particle size range, and calculating from the counted number. Unless otherwise defined, the average particle size can mean the diameter (D50) of particles in a particle size distribution that have a cumulative volume of 50% by volume. In addition, unless otherwise defined, the average particle size can be obtained by randomly measuring the sizes (diameters or major axis lengths) of about 20 particles in a scanning electron microscope image to obtain a particle size distribution, and taking the diameter (D50) of particles in the particle size distribution that have a cumulative volume of 50% by volume as the average particle size.

[0021] Here, “or” is not interpreted in an exclusive sense, for example, “A or B” is interpreted to include A, B, A+B, etc.

[0022] “Metal” is interpreted as a concept that includes common metals, transition metals, and metalloids (semi-metals).

[0023] solid electrolyte

[0024] In one embodiment, a solid electrolyte is provided, which comprises argyrodite-type sulfide-based solid electrolyte particles and a lithium salt positioned on the surface of the particles, wherein the lithium salt has F and PO functional groups.

[0025] In the lithium salt, the PO functional group has a high affinity for the argyrodite-type sulfide-based solid electrolyte particles and can be stably attached to the surface of the particles, and further, the F functional group has strong hydrophobicity and can effectively prevent moisture from coming into contact with the particles. This lithium salt can be evenly attached to the surface of the argyrodite-type sulfide-based solid electrolyte particles and effectively suppress deterioration due to moisture.

[0026] These solid electrolytes can control chemical side reactions and maintain high ionic conductivity characteristics even in a dry room process exposure environment. For example, the solid electrolyte can effectively suppress weight loss that occurs when exposed to a dry room or the atmosphere. Since the lithium salt protects the surface of the argyrodite-type sulfide-based solid electrolyte particles, side reactions and irreversibility on the particle surface due to exposure to the atmosphere can be suppressed, and the content of byproducts generated by the side reactions can be reduced, thereby improving the ionic conductivity retention characteristics and enhancing the performance of the all-solid-state secondary battery.

[0027] The lithium salt may include, but is not limited to, LiPOF4, LiPO2F2, Li2PO3F, or combinations thereof.

[0028] In the lithium salt, the PO functional group may be, for example, a PO2 functional group. The PO2 functional group has high affinity for the argyrodite-type sulfide-based solid electrolyte particles, and therefore, a lithium salt containing the PO2 functional group can be stably attached to the surface of the particles and evenly distributed on the surface of the particles.

[0029] The lithium salt may be included in an amount of 1 mol% to 30 mol% based on 100 mol% of the azirodite-type sulfide-based solid electrolyte particles and the lithium salt, for example, 2 mol% to 25 mol%, 3 mol% to 20 mol%, 4 mol% to 18 mol%, or 5 mol% to 15 mol%. When the lithium salt is included in the above range, the surface of the azirodite-type sulfide-based solid electrolyte particles is sufficiently protected, thereby ensuring moisture stability and improving lithium ion conductivity.

[0030] The lithium salt may be partially present on the surface of the argyrodite-type sulfide-based solid electrolyte particles, may be coated in an island shape, or may be present in a continuous film shape. For example, the solid electrolyte may include argyrodite-type sulfide-based solid electrolyte particles and a coating layer positioned on the surface of the particles, wherein the coating layer may include a lithium salt containing F and PO functional groups.

[0031] The above argyrodite-type sulfide-based solid electrolyte particles include argyrodite-type sulfide, and may include, for example, a compound represented by the following chemical formula 11.

[0032] [Chemical Formula 11]

[0033] (Li a M 1 b M 2 c )(P d M 3 e )(S f M 4 g )X h

[0034] In the above chemical formula 11, 4≤a≤8, and M 1 is Mg, Ca, Cu, Ag, or a combination thereof, and 0≤b<0.5, and M 2 is Na, K, or a combination thereof, 0≤c<0.5, and M3 is Sn, Zn, Si, Sb, Ge, or a combination thereof, and 0 <d<4, 0≤e<1 이고, M 4 is N,O,SO n , or a combination thereof, and 1.5≤n≤5, 3≤f≤12, 0≤g<2, and X is F, Cl, Br, I, or a combination thereof, and 0≤h≤2.

[0035] For example, in chemical formula 11, a halide element (X) may be included as an essential element, in which case 0 <h≤2로 표시될 수 있다. 일 예로 화학식 11에 M 1 Elements may be required, in which case 0 <b<0.5로 표시될 수 있다. 화학식 11에서 M 3 can be understood as an element substituted in place of P and 0 <e<1일 수 있다. 화학식 11에서 M 4 is substituted in the S position, for example, 0 <g<2일 수 있으며 S의 비율인 f는 예를 들어 3≤f≤7일 수 있다. M 4 Go SO n If SO n It can be, for example, S4O6, S3O6, S2O3, S2O4, S2O5, S2O6, S2O7, S2O8, SO4, or SO5, and can be, for example, SO4.

[0036] For example, in chemical formula 11, a+b+c+h=7, d+e=1, and f+g+h=6.

[0037] As a specific example, argyrodite-type sulfide-based solid electrolyte particles include Li3PS4 and Li7P3S. 11 , Li7PS6, Li6PS5Cl, Li6PS5Br, Li 5.8 PS 4.8 Cl 1.2 , Li 6.2 PS 5.2 Br 0.8 , Li 5.75 PS 4.75 Cl 1.25 , (Li 5.69 Cu 0.06 )PS4.75 Cl 1.25 , (Li 5.72 Cu 0.03 )PS 4.75 Cl 1.25 , (Li 5.69 Cu 0.06 )P(S 4.70 (SO4) 0.05 )Cl 1.25 , (Li 5.69 Cu 0.06 )P(S 4.60 (SO4) 0.15 )Cl 1.25 , (Li 5.72 Cu 0.03 )P(S 4.725 (SO4) 0.025 )Cl 1.25 , (Li 5.72 Na 0.03 )P(S 4.725 (SO4) 0.025 )Cl 1.25 , Li 5.75 P(S 4.725 (SO4) 0.025 )Cl 1.25 , or combinations thereof, but are not limited thereto.

[0038] Sulfide-based solid electrolytes containing these argyrodite-type sulfides have an ionic conductivity of 10 that of typical liquid electrolytes at room temperature. -4 10 inland -2 It has a high ionic conductivity approaching the S / cm range, can form a close bond between a positive electrode active material and a solid electrolyte without causing a decrease in ionic conductivity, and further can form a close interface between an electrode layer and a solid electrolyte layer. An all-solid-state secondary battery including this can have improved battery performance, such as rate characteristics, Coulombic efficiency, and cycle life characteristics.

[0039] An argyrodite-type sulfide-based solid electrolyte can be manufactured, for example, by mixing lithium sulfide and phosphorus sulfide, and optionally, lithium halide. After mixing these, a heat treatment may be performed. The heat treatment may include, for example, two or more heat treatment steps. Here, manufacturing an argyrodite-type sulfide-based solid electrolyte may include, for example, a first heat treatment of mixing raw materials and calcining at 120°C to 350°C, and a second heat treatment of mixing the resultant of the first heat treatment again and calcining at 350°C to 800°C.

[0040] The average particle diameter (D) of the above argyrodite-type sulfide-based solid electrolyte particles 50 ) may be 5.0 ㎛ or less, for example, 0.1 ㎛ to 5.0 ㎛, 0.5 ㎛ to 5.0 ㎛, 0.5 ㎛ to 4.0 ㎛, 0.5 ㎛ to 3.0 ㎛, 0.5 ㎛ to 2.0 ㎛, or 0.5 ㎛ to 1.0 ㎛. The solid electrolyte particles may be small particles having a size of 0.1 ㎛ to 1.5 ㎛, large particles having a size of 2.0 ㎛ to 5.0 ㎛, or a mixture thereof. The average particle diameter of the solid electrolyte particles may be measured by an electron microscope image, and for example, a particle size distribution may be obtained by measuring the size (diameter or major axis length) of about 20 particles in a scanning electron microscope image, and D50 may be calculated from this.

[0041] The above solid electrolyte can be manufactured by mixing argyrodite-type sulfide-based solid electrolyte particles and a lithium salt having F and PO functional groups.

[0042] At this time, the lithium salt may be mixed in an amount of 1 mol% to 30 mol% with respect to the total of 100 mol% of the argyrodite-type sulfide-based solid electrolyte particles and the lithium salt, for example, 2 mol% to 25 mol%, 3 mol% to 20 mol%, 4 mol% to 18 mol%, or 5 mol% to 15 mol%.

[0043] Additionally, the mixing may be performed at a temperature range of, for example, 5°C to 50°C, or 10°C to 40°C, or at room temperature, and may be performed for 30 seconds to 1 hour, 30 seconds to 30 minutes, 30 seconds to 20 minutes, or 30 seconds to 10 minutes.

[0044] The method for manufacturing the above solid electrolyte may be a type of solid-state or dry coating method.

[0045] solid electrolyte membrane

[0046] In one embodiment, a solid electrolyte membrane comprising the aforementioned solid electrolyte is provided. The solid electrolyte membrane according to one embodiment can achieve high ionic conductivity by comprising the aforementioned solid electrolyte, and can achieve high ionic conductivity retention even after long-term exposure due to high moisture stability, and can improve battery safety and life characteristics by reducing side reactions of the solid electrolyte due to moisture.

[0047] The above solid electrolyte membrane may include argyrodite-type sulfide-based solid electrolyte particles and a lithium salt containing F and PO functional groups, and the lithium salt may be uniformly dispersed in the solid electrolyte membrane.

[0048] The above solid electrolyte membrane can be manufactured by a conventional solvent-casting method, and in this case, it is possible to manufacture a solid electrolyte membrane with a low ion conductivity reduction rate.

[0049] In addition to the above-described solid electrolyte, the above-described solid electrolyte membrane may further include another oxide-based solid electrolyte, such as a halide-based solid electrolyte, and may optionally further include a binder.

[0050] Oxide-based solid electrolyte

[0051] Oxide-based solid electrolytes include, for example, Li 1+x Ti 2-x Al(PO4)3(LTAP)(0≤x≤4), Li 1+x+y Al x Ti2-x Si y P 3-y O 12 (0 <x<2, 0≤y<3), BaTiO3, Pb(Zr,Ti)O3(PZT), Pb 1-x La x Zr 1-y Ti y O3(PLZT)(0≤x<1, 0≤y<1), PB(Mg3Nb 2 / 3 )O3-PbTiO3(PMN-PT), HfO2, SrTiO3, SnO2, CeO2, Na2O, MgO, NiO, CaO, BaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiO2, lithium phosphate (Li3PO4), lithium titanium phosphate (Li x Ti y (PO4)3, 0 <x<2, 0<y<3), Li 1+x+y (Al, Ga) x (Ti, Ge) 2-x Si y P 3-y O 12 (0≤x≤1, 0≤y≤1), lithium lanthanum titanate (Li x La y TiO3, 0 <x<2, 0<y<3), Li2O, LiAlO2, Li2O-Al2O3-SiO2-P2O5-TiO2-GeO2계 세라믹스, 가넷(Garnet)계 세라믹스 Li 3+x La3M2O 12 (M= Ta, Te, Nb, or Zr; x is an integer from 1 to 10), or mixtures thereof.

[0052] Halide-based solid electrolyte

[0053] A halide-based solid electrolyte contains a halogen element as a main component, and may mean that the ratio of the halide element to all elements constituting the solid electrolyte is 50 mol% or more, 70 mol% or more, 90 mol% or more, or 100 mol%. For example, the halide-based solid electrolyte may not contain a sulfur element.

[0054] The above halide-based solid electrolyte may contain a lithium element, a metal element other than lithium, and a halogen element. The metal element other than lithium may be Al, As, B, Bi, Ca, Cd, Co, Cr, Fe, Ga, Hf, In, Mg, Mn, Ni, Sb, Sc, Sn, Ta, Ti, Y, Zn, Zr, or a combination thereof. The halogen element may be F, Cl, Br, I, or a combination thereof, and may be Cl, Br, or a combination thereof, for example. The halide-based solid electrolyte may contain, for example, Li a M1X6 (M is Al, As, B, Bi, Ca, Cd, Co, Cr, Fe, Ga, Hf, In, Mg, Mn, Ni, Sb, Sc, Sn, Ta, Ti, Y, Zn, Zr, or a combination thereof, X is F, Cl, Br, I, or a combination thereof, and 2≤a≤3) can be represented. The halide-based solid electrolyte is, for example, Li2ZrCl6, Li 2.7 Y 0.7 Zr 0.3 Cl6, Li 2.5 Y 0.5 Zr 0.5 Cl6, Li 2.5 In 0.5 Zr 0.5 Cl6, Li2In 0.5 Zr 0.5 Cl6, Li3YBr6, Li3YCl6, Li3YBr2Cl4, Li3YbCl6, Li 2.6 Hf 0.4 Yb 0.6 Cl6, or combinations thereof, but is not limited thereto.

[0055] The binder may include, for example, nitrile-butadiene rubber, hydrogenated nitrile-butadiene rubber, styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, fluoroelastomer, polydimethylsiloxane, polyethylene oxide, polyvinylpyrrolidone, polyvinylpyridine, chlorosulfonated polyethylene, polyvinyl alcohol, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polyethylene, polypropylene, ethylene propylene copolymer, ethylene propylene diene copolymer, polyamideimide, polyimide, poly(meth)acrylate, polyacrylonitrile, polystyrene, polyurethane, or a combination thereof.

[0056] The content of the binder relative to 100 wt% of the above solid electrolyte membrane may be about 0.1 wt% to 5 wt%, or 0.5 wt% to 3 wt%.

[0057] The above solid electrolyte membrane may optionally further include an alkali metal salt, and / or an ionic liquid, and / or a conductive polymer.

[0058] The above alkali metal salt may be, for example, a lithium salt. The content of the lithium salt in the solid electrolyte layer may be 1 M or more, for example, 1 M to 4 M. In this case, the lithium salt may improve ion conductivity by enhancing the lithium ion mobility of the solid electrolyte layer.

[0059] The lithium salt may be applied without limitation on type, and may include, for example, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiSCN, LiN(CN)2, lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiDFOB), lithium difluorobis(oxalato)phosphate (LiDFBP), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(pentafluoroethanesulfonyl)imide (LiBETI), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, or a combination thereof.

[0060] For example, the lithium salt may be an imide-based lithium salt such as LiTFSI, LiFSI, LiBETI, or a combination thereof. The imide-based lithium salt can maintain or improve ionic conductivity by appropriately maintaining chemical reactivity with the ionic liquid.

[0061] The above ionic liquid has a melting point below room temperature and is a salt or room-temperature molten salt that is liquid at room temperature and consists only of ions.

[0062] The above ionic liquid comprises a) one or more cations selected from ammonium, pyrrolidinium, pyridinium, pyrimidinium, imidazolium, piperidinium, pyrazolium, oxazolium, pyridazinium, phosphonium, sulfonium, triazolium, and mixtures thereof, and b) BF4. - , PF6 - , AsF6 - , SbF6 - , AlCl4 - , HSO4 - , ClO4 - , CH3SO3 - , CF3CO2 - , Cl - , Br - , I - , BF4- , SO4 - , CF3SO3 - , (FSO2)2N - , (C2F5SO2)2N - , (C2F5SO2)(CF3SO2)N - , and (CF3SO2)2N - It may be a compound containing one or more anions selected from among.

[0063] The ionic liquid may be at least one selected from the group consisting of, for example, N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide, N-butyl-N-methylpyrrolidinium bis(3-trifluoromethylsulfonyl)imide, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide, and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide.

[0064] In the above solid electrolyte layer, the weight ratio of the solid electrolyte and the ionic liquid may be 0.1:99.9 to 90:10, for example, 10:90 to 90:10, 20:80 to 90:10, 30:70 to 90:10, 40:60 to 90:10, or 50:50 to 90:10. A solid electrolyte layer satisfying the above range can maintain or improve ionic conductivity by improving the electrochemical contact area with the electrode. Accordingly, the energy density, discharge capacity, rate characteristics, etc. of the all-solid-state secondary battery can be improved.

[0065] All-solid-state secondary battery

[0066] In one embodiment, an all-solid-state secondary battery comprising the above-described solid electrolyte is provided. The all-solid-state secondary battery comprises a positive electrode, a negative electrode, and a solid electrolyte membrane positioned between the positive electrode and the negative electrode. The above-described solid electrolyte may be included in at least one of the positive electrode, the negative electrode, and the solid electrolyte membrane. In one example, an all-solid-state secondary battery is provided comprising a positive electrode, a negative electrode, and a solid electrolyte membrane containing the above-described solid electrolyte.

[0067] FIG. 1 is a cross-sectional view of an all-solid-state secondary battery according to an embodiment. Referring to FIG. 1, the all-solid-state secondary battery (100') may have a structure in which an electrode assembly in which a negative electrode (400) including a negative electrode collector (401) and a negative electrode active material layer (403), a solid electrolyte layer (300), and a positive electrode (200) including a positive electrode active material layer (203) and a positive electrode collector (201) are laminated is housed in a battery case. The all-solid-state secondary battery (100') may further include an elastic layer (500) on the outer side of at least one of the positive electrode (200) and the negative electrode (400). Although FIG. 1 illustrates one electrode assembly including a negative electrode (400), a solid electrolyte layer (300), and a positive electrode (200), an all-solid-state secondary battery may be manufactured by laminating two or more electrode assemblies.

[0068] cathode

[0069] An anode for an all-solid-state secondary battery comprises a current collector and a negative electrode active material layer positioned on the current collector. The negative electrode active material layer comprises a negative electrode active material, may further comprise a binder and / or a conductive material, and may optionally comprise the solid electrolyte described above.

[0070] The above negative electrode active material includes a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide.

[0071] The material capable of reversibly intercalating / deintercalating the lithium ions may include a carbon-based negative electrode active material, for example, crystalline carbon, amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite such as natural graphite or artificial graphite in an amorphous, plate-like, flake-like, spherical, or fibrous form, and examples of the amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, calcined coke, and the like.

[0072] As the above lithium metal alloy, an alloy of lithium and a metal selected from the group consisting of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn can be used.

[0073] As the material capable of doping and dedoping the lithium, a Si-based negative electrode active material or a Sn-based negative electrode active material can be used, and the Si-based negative electrode active material may be silicon, a silicon-carbon composite, or SiO. x (0 < x < 2), Si-Q alloy (wherein Q is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, Group 15 elements, Group 16 elements, transition metals, rare earth elements, and combinations thereof, and is not Si), Sn-based negative electrode active materials include Sn, SnO2, Sn-R alloy (wherein R is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, Group 15 elements, Group 16 elements, transition metals, rare earth elements, and combinations thereof, and is not Sn), and at least one of these may be mixed with SiO2 for use. The above elements Q and R may be selected from the group consisting of 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, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof.

[0074] For example, the negative active material may include silicon-carbon composite particles. The average particle diameter (D50) of the silicon-carbon composite particles may be, for example, 0.5 μm to 20 μm. The average particle diameter (D50) is measured by a particle size analyzer and refers to the diameter of particles having a cumulative volume of 50% by volume in a particle size distribution. With respect to 100 wt% of the silicon-carbon composite particles, silicon may be included in an amount of 10 wt% to 60 wt% and carbon may be included in an amount of 40 wt% to 90 wt%. The silicon-carbon composite particles may include, for example, a core including silicon particles and a carbon coating layer positioned on a surface of the core. The average particle diameter (D50) of the silicon particles in the core may be, for example, 10 nm to 1 μm, or 10 nm to 200 nm. The silicon particles may exist as silicon alone, in the form of a silicon alloy, or in an oxidized form. The oxidized form of silicon is SiO x (0 <x<2)로 표시될 수 있다. 또한, 상기 탄소 코팅층의 두께는 약 5 nm 내지 100 nm일 수 있다.

[0075] For example, the silicon-carbon composite particle may include a core including silicon particles and crystalline carbon, and a carbon coating layer located on the surface of the core and including amorphous carbon. For example, in the silicon-carbon composite particle, the amorphous carbon may not be present in the core but may be present only in the carbon coating layer. The crystalline carbon may be artificial graphite, natural graphite, or a combination thereof, and the amorphous carbon may be formed from coal pitch, mesophase pitch, petroleum pitch, coal oil, petroleum heavy oil, or a polymer resin (phenol resin, furan resin, polyimide resin, etc.). At this time, the content of the crystalline carbon may be 10 wt% to 70 wt%, and the content of the amorphous carbon may be 20 wt% to 40 wt% with respect to 100 wt% of the silicon-carbon composite particle.

[0076] In the above silicon-carbon composite particle, the core may include a void in the central portion. The radius of the void may be 30% to 50% of the radius of the silicon-carbon composite particle.

[0077] The silicon-carbon composite particles described above can effectively suppress problems such as volume expansion, structural collapse, or particle crushing due to charge and discharge, thereby preventing the phenomenon of conductive path disconnection, realizing high capacity and high efficiency, and are advantageous for use under high voltage or fast charging conditions.

[0078] The above Si-based negative electrode active material or Sn-based negative electrode active material can be used in combination with a carbon-based negative electrode active material. When the Si-based negative electrode active material or Sn-based negative electrode active material and the carbon-based negative electrode active material are used in combination, the mixing ratio can be 1:99 to 90:10 by weight.

[0079] The content of the negative active material in the above negative active material layer may be 95 wt% to 99 wt% with respect to the total weight of the negative active material layer.

[0080] In one embodiment, the negative electrode active material layer further includes a binder and may optionally further include a conductive material. The content of the binder in the negative electrode active material layer may be 1 wt% to 5 wt% based on the total weight of the negative electrode active material layer. In addition, when the negative electrode active material layer further includes a conductive material, the negative electrode active material layer may include 90 wt% to 98 wt% of the negative electrode active material, 1 wt% to 5 wt% of the binder, and 1 wt% to 5 wt% of the conductive material.

[0081] The above binder serves to adhere the negative electrode active material particles well to each other and also to adhere the negative electrode active material well to the current collector. The binder may be an insoluble binder, a water-soluble binder, or a combination thereof.

[0082] The above-mentioned non-aqueous binder may include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer containing ethylene oxide, an ethylene propylene copolymer, polystyrene, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or a combination thereof.

[0083] The water-soluble binder may be a rubber-based binder or a polymer resin binder. The rubber-based binder may be selected from styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, fluororubber, and combinations thereof. The polymer resin binder may be selected from polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenol resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0084] When a water-soluble binder is used as the negative electrode binder, a cellulose-based compound capable of imparting viscosity as a type of thickener may be further included. The cellulose-based compound may be a mixture of one or more of carboxymethyl cellulose, hydroxypropylmethyl cellulose, methyl cellulose, or an alkali metal salt thereof. The alkali metal may be Na, K, or Li. The amount of the thickener used may be 0.1 to 3 parts by weight based on 100 parts by weight of the negative electrode active material.

[0085] The above conductive material is used to provide conductivity to the electrode, and in the battery to be formed, any material that does not cause a chemical change and is electronically conductive can be used. Examples of conductive materials that can be used include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based materials including copper, nickel, aluminum, silver, etc. and in the form of metal powder or metal fiber; conductive polymers such as polyphenylene derivatives; or conductive materials including mixtures thereof.

[0086] The negative electrode current collector may be selected from the group consisting of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof.

[0087] precipitation cathode

[0088] As another example, the negative electrode for an all-solid-state secondary battery may be a precipitation-type negative electrode. The precipitation-type negative electrode may refer to a negative electrode that does not include a negative electrode active material when the battery is assembled, but in which lithium metal or the like is precipitated or deposited on the negative electrode when the battery is charged, and this acts as a negative electrode active material.

[0089] Fig. 2 is a schematic cross-sectional view of an all-solid-state secondary battery including a precipitation-type negative electrode. Referring to Fig. 2, the precipitation-type negative electrode (400') may include a current collector (401) and a negative electrode coating layer (405) positioned on the current collector. An all-solid-state secondary battery including such a precipitation-type negative electrode (400') starts initial charging in a state in which no negative electrode active material is present, and during charging, high-density lithium metal is precipitated or deposited between the current collector (401) and the negative electrode coating layer (405) or on the negative electrode coating layer (405) to form a lithium metal layer (404), which may function as a negative electrode active material. Accordingly, in an all-solid-state secondary battery that has been charged more than once, the precipitation-type negative electrode (400') may include, for example, a current collector (401), a lithium metal layer (404) positioned on the current collector, and a negative electrode coating layer (405) positioned on the metal layer. The lithium metal layer (404) refers to a layer in which lithium metal or the like is precipitated during the charging process of the battery, and may be referred to as a metal layer, a lithium layer, a lithium deposition layer, or a negative electrode active material layer.

[0090] In this case, the aforementioned area or first solid electrolyte layer can be said to be a surface in contact with the cathode coating layer (405).

[0091] The above cathode coating layer (405) may be referred to as a lithium electrodeposition induction layer or a cathode catalyst layer, and may include a metal, carbon material, or a combination thereof that acts as a catalyst.

[0092] The metal may be a lithium-philic metal, and may include, for example, gold, platinum, palladium, silicon, silver, aluminum, bismuth, tin, zinc, or a combination thereof, and may be composed of one type of these or may be composed of several types of alloys. When the metal is present in the form of particles, the average particle diameter (D50) thereof may be about 4 μm or less, and may be, for example, 10 nm to 4 μm.

[0093] The carbon material may be, for example, crystalline carbon, amorphous carbon, or a combination thereof. The crystalline carbon may be, for example, natural graphite, artificial graphite, mesophase carbon microbeads, or a combination thereof. The amorphous carbon may be, for example, carbon black, activated carbon, acetylene black, Denka black, Ketjen black, or a combination thereof.

[0094] When the above-described negative electrode coating layer (405) includes both the metal and the carbon material, the mixing ratio of the metal and the carbon material may be, for example, a weight ratio of 1:10 to 2:1. In this case, the precipitation of lithium metal can be effectively promoted and the characteristics of the all-solid-state secondary battery can be improved. The above-described negative electrode coating layer (405) may include, for example, a carbon material supported with a catalytic metal, or may include a mixture of metal particles and carbon material particles.

[0095] The above-described cathode coating layer (405) may include, for example, the above-described lithium-philic metal and amorphous carbon, in which case the precipitation of the lithium metal may be effectively promoted. As a specific example, the cathode coating layer (405) may include a composite in which a lithium-philic metal is supported on amorphous carbon.

[0096] The above cathode coating layer (405) may further include a binder, and the binder may be, for example, a conductive binder. In addition, the above cathode coating layer (405) may further include general additives such as fillers, dispersants, and ionic conductive agents.

[0097] The thickness of the cathode coating layer (405) may be, for example, 100 nm to 20 ㎛, or 500 nm to 10 ㎛, or 1 ㎛ to 5 ㎛.

[0098] The above-described precipitated negative electrode (400') may further include, for example, a thin film on the surface of the current collector, i.e., between the current collector and the negative electrode coating layer. The thin film may include an element capable of forming an alloy with lithium. The element capable of forming an alloy with lithium may be, for example, gold, silver, zinc, tin, indium, silicon, aluminum, bismuth, etc., and may be composed of one type thereof or may be composed of multiple types of alloys. The thin film may further flatten the precipitated form of the lithium metal layer (404) and further improve the characteristics of the all-solid-state secondary battery. The thin film may be formed by, for example, a vacuum deposition method, a sputtering method, a plating method, etc. The thickness of the thin film may be, for example, 1 nm to 500 nm.

[0099] The lithium metal layer (404) may include lithium metal or a lithium alloy. The lithium alloy may be, for example, a Li-Al alloy, a Li-Sn alloy, a Li-In alloy, a Li-Ag alloy, a Li-Au alloy, a Li-Zn alloy, a Li-Ge alloy, or a Li-Si alloy.

[0100] The thickness of the lithium metal layer (404) may be 1 μm to 500 μm, 1 μm to 200 μm, 1 μm to 100 μm, or 1 μm to 50 μm. If the thickness of the lithium metal layer (404) is too thin, it may be difficult to perform the role of a lithium storage, and if it is too thick, the battery volume may increase and performance may deteriorate.

[0101] When such a precipitation-type cathode is applied, the cathode coating layer (405) can play a role in protecting the lithium metal layer (404) and suppressing the precipitation growth of lithium deadlight. Accordingly, short-circuiting and capacity reduction of the all-solid-state battery can be suppressed, and the life characteristics can be improved.

[0102] anode

[0103] In one embodiment, the device comprises a current collector and a positive electrode active material layer positioned on the current collector, wherein the positive electrode active material layer comprises a positive electrode active material and a solid electrolyte, and may optionally comprise a binder and / or a conductive material. In this case, the positive electrode active material layer may comprise the aforementioned solid electrolyte.

[0104] positive electrode active material

[0105] The above-mentioned positive electrode active material can be applied without limitation as long as it is generally used in all-solid-state secondary batteries. For example, the above-mentioned positive electrode active material may be a compound capable of reversible intercalation and deintercalation of lithium, and may include a compound represented by any one of the following chemical formulas.

[0106] Li a A 1-b X b D2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5);

[0107] Li a A 1-b X b O 2-c D c (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05);

[0108] Li a E 1-b X b O 2-c D c (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05);

[0109] Li a E 2-b X b O 4-c D c (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05);

[0110] Li a Ni 1-b-c Co b X c D α(0.90 ≤ a ≤1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.5, 0 <α ≤ 2);

[0111] Li a Ni 1-b-c Co b X c O 2-α T α (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2);

[0112] Li a Ni 1-b-c Co b X c O 2-α T2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2);

[0113] Li a Ni 1-b-c Mr b X c D α (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2);

[0114] Li a Ni 1-b-c Mr b X c O 2-α T α (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2);

[0115] Li a Ni 1-b-c Mr b X c O 2-α T2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2);

[0116] Li a Ni b HAVE BEEN c G d O2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1);

[0117] The a Nor b Co c Mn d G e O2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤0.5, 0.001 ≤ e ≤ 0.1);

[0118] The a NiG b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1);

[0119] The a CoG b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1);

[0120] The a Mn 1-b G b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1);

[0121] The a Mn2G b O4(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1);

[0122] The a Mn 1-g G g PO4(0.90 ≤ a ≤ 1.8, 0 ≤ g ≤ 0.5);

[0123] QO2; QS2; LiQS2;

[0124] V2O5; LiV2O5;

[0125] LiZO2;

[0126] LiNiVO4;

[0127] The (3-f) J2(PO4)3(0 ≤ f ≤ 2);

[0128] The (3-f) Fe2(PO4)3(0 ≤ f ≤ 2);

[0129] The a FePO4(0.90 ≤ a ≤ 1.8).

[0130] In the above chemical formulas, A is selected from the group consisting of Ni, Co, Mn, and combinations thereof; X is selected from the group consisting of Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements, and combinations thereof; D is selected from the group consisting of O, F, S, P, and combinations thereof; E is selected from the group consisting of Co, Mn, and combinations thereof; T is selected from the group consisting of F, S, P, and combinations thereof; G is selected from the group consisting of Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, and combinations thereof; Q is selected from the group consisting of Ti, Mo, Mn, and combinations thereof; Z is selected from the group consisting of Cr, V, Fe, Sc, Y, and combinations thereof; J is selected from the group consisting of V, Cr, Mn, Co, Ni, Cu, and combinations thereof.

[0131] The above-mentioned positive electrode active material may be, for example, lithium cobalt oxide (LCO), lithium nickel oxide (LNO), lithium nickel cobalt oxide (NC), lithium nickel cobalt aluminum oxide (NCA), lithium nickel cobalt manganese oxide (NCM), lithium nickel manganese oxide (NM), lithium manganese oxide (LMO), or lithium iron phosphate (LFP).

[0132] The positive electrode active material may include, for example, a lithium nickel-based oxide represented by the following chemical formula 11, a lithium cobalt-based oxide represented by the following chemical formula 12, a lithium iron phosphate-based compound represented by the following chemical formula 13, a cobalt-free lithium nickel-manganese-based oxide represented by the following chemical formula 14, or a combination thereof.

[0133] [Chemical Formula 11]

[0134] Li a1 Ni x1 M 1 y1 M 2 z1 O 2-b1 Xb1

[0135] In the above chemical formula 11, 0.9≤a1≤1.8, 0.3≤x1≤1, 0≤y1≤0.7, 0≤z1≤0.7, 0.9≤x1+y1+z1≤1.1, and 0≤b1≤0.1, and M 1 and M 2 are each independently one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, and Zr, and X is one or more elements selected from the group consisting of F, P, and S.

[0136] In the above chemical formula 1, 0.6≤x1≤1, 0≤y1≤0.4, and 0≤z1≤0.4, or 0.8≤x1≤1, 0≤y1≤0.2, and 0≤z1≤0.2.

[0137] [Chemical Formula 12]

[0138] Li a2 Co x2 M 3 y2 O 2-b2 X b2

[0139] In the above chemical formula 12, 0.9≤a2≤1.8, 0.7≤x2≤1, 0≤y2≤0.3, 0.9≤x2+y2≤1.1, and 0≤b2≤0.1, and M 3 is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Se, Si, Sn, Sr, Ti, V, W, Y, Zn and Zr, and X is one or more elements selected from the group consisting of F, P and S.

[0140] [Chemical Formula 13]

[0141] Li a3 Fe x3 M 4 y3 PO 4-b3 X b3

[0142] In the above chemical formula 13, 0.9≤a3≤1.8, 0.6≤x3≤1, 0≤y3≤0.4, and 0≤b3≤0.1, and M 4 is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Mg, Mn, Mo, Ni, Se, Si, Sn, Sr, Ti, V, W, Y, Zn and Zr, and X is one or more elements selected from the group consisting of F, P and S.

[0143] [Chemical Formula 14]

[0144] Li a4 Ni x4 Mn y4 M 5 z4 O 2-b4 X b4

[0145] In the above chemical formula 14, 0.9≤a2≤1.8, 0.8≤x4<1, 0 <y4≤0.2, 0≤z4≤0.2, 0.9≤x4+y4+z4≤1.1, 및 0≤b4≤0.1이고 M 5 is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, and Zr, and X is one or more elements selected from the group consisting of F, P, and S.

[0146] The average particle diameter (D50) of the positive electrode active material may be 1 μm to 25 μm, for example, 3 μm to 25 μm, 1 μm to 20 μm, 1 μm to 18 μm, 3 μm to 15 μm, or 5 μm to 15 μm. For example, the positive electrode active material may include small particles having an average particle diameter (D50) of 1 μm to 9 μm and large particles having an average particle diameter (D50) of 10 μm to 25 μm. A positive electrode active material having such a particle diameter range can be harmoniously mixed with other components within a positive electrode active material layer and can realize high capacity and high energy density. Here, the average particle diameter may be obtained by selecting 20 or so random particles from a scanning electron microscope image of the positive electrode active material, measuring their particle diameters (diameter, major axis, or major axis length), obtaining a particle size distribution, and then taking the diameter (D50) of particles having a cumulative volume of 50% by volume from the particle size distribution as the average particle diameter.

[0147] The above-mentioned positive electrode active material may be in the form of a secondary particle formed by agglomeration of a plurality of primary particles, or may be in the form of a single particle. In addition, the above-mentioned positive electrode active material may be spherical or nearly spherical in shape, or may be polyhedral or irregular in shape.

[0148] Meanwhile, the positive electrode active material may include a buffer layer on the particle surface. The buffer layer may be expressed as a coating layer, a protective layer, etc., and may play a role in lowering the interfacial resistance between the positive electrode active material and the sulfide-based solid electrolyte particles. For example, the buffer layer may include a lithium-metal-oxide, wherein the metal may be one or more elements selected from the group consisting of Al, B, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ta, V, W, and Zr. The lithium-metal-oxide is excellent in lowering the interfacial resistance between the positive electrode active material and the solid electrolyte particles while improving the performance of the positive electrode active material by facilitating the movement of lithium ions and electron conduction.

[0149] The positive electrode active material may be included in an amount of 55 wt% to 99 wt% based on 100 wt% of the positive electrode active material layer, for example, 65 wt% to 95 wt%, or 75 wt% to 91 wt%.

[0150] bookbinder

[0151] The above binder serves to adhere the positive electrode active material particles well to each other and also to adhere the positive electrode active material well to the current collector, and representative examples thereof include, but are not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc.

[0152] The content of the binder in the positive electrode active material layer may be approximately 0.1 wt% to 5 wt% with respect to 100 wt% of the positive electrode active material layer.

[0153] Challenge

[0154] The above-described positive electrode active material layer may further include a conductive material. The conductive material is used to provide conductivity to the electrode, and any material that does not cause a chemical change and is electronically conductive in the battery to be constructed may be used. Examples of conductive materials that may be used include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, carbon nanotube, etc.; metal-based materials containing copper, nickel, aluminum, silver, etc. in the form of metal powder or metal fiber; conductive polymers such as polyphenylene derivatives; or conductive materials including mixtures thereof.

[0155] The content of the conductive material in the positive electrode active material layer may be 0 wt% to 3 wt%, 0.01 wt% to 2 wt%, or 0.1 wt% to 1 wt% with respect to 100 wt% of the positive electrode active material layer.

[0156] With respect to 100 wt% of the above positive electrode active material layer, the solid electrolyte may be included in an amount of 0.1 wt% to 35 wt%, for example, 1 wt% to 35 wt%, 5 wt% to 30 wt%, 8 wt% to 25 wt%, or 10 wt% to 20 wt%.

[0157] In addition, in the positive electrode active material layer, 65 wt% to 99 wt% of the positive electrode active material and 1 wt% to 35 wt% of the solid electrolyte may be included based on the total weight of the positive electrode active material and the solid electrolyte, for example, 80 wt% to 90 wt% of the positive electrode active material and 10 wt% to 20 wt% of the solid electrolyte may be included. When the solid electrolyte is included in the positive electrode in such an amount, the efficiency and life characteristics of the all-solid-state battery can be improved without reducing the capacity.

[0158] Aluminum foil may be used as the positive electrode current collector, but is not limited thereto.

[0159] The above-mentioned all-solid-state secondary battery may be a unit cell having a structure of positive electrode / solid electrolyte layer / negative electrode, a bi-cell having a structure of negative electrode / solid electrolyte layer / positive electrode / solid electrolyte layer / negative electrode, or a laminated battery in which the structure of the unit cell is repeated.

[0160] The shape of the above-mentioned all-solid-state secondary battery is not particularly limited, and may be, for example, coin-shaped, button-shaped, sheet-shaped, stacked, cylindrical, flat, etc. In addition, the above-mentioned all-solid-state secondary battery can be applied to large-scale batteries used in electric vehicles, etc. For example, the above-mentioned all-solid-state secondary battery can be used in hybrid vehicles such as plug-in hybrid electric vehicles (PHEVs). In addition, it can be used in fields requiring a large amount of power storage, and for example, it can be used in electric bicycles or power tools, etc. In addition, the above-mentioned all-solid-state secondary battery can be used in various fields such as portable electronic devices.

[0161] Hereinafter, examples and comparative examples of the present invention are described. The following examples are merely examples of the present invention, and the present invention is not limited to the following examples.

[0162] Example 1

[0163] 1. Preparation of solid electrolyte

[0164] A solid electrolyte was prepared by mixing 90 molar parts of argyrodite-type sulfide-based solid electrolyte particles (Li6PS5Cl, D50=3.5㎛) and 10 molar parts of LiPO2F2 using a Lab. Milling machine at room temperature for about 1 minute at 10,000 rpm.

[0165] 2. Manufacturing of solid electrolyte membranes

[0166] The solid electrolyte was added to an isobutyryl isobutyrate (IBIB) solvent containing an acrylic binder and mixed to prepare a slurry. The slurry contained 98 wt% of the solid electrolyte and 2 wt% of the binder. The slurry was applied onto a release PET film using a blade coater and dried to prepare a solid electrolyte membrane having a thickness of approximately 100 to 150 μm.

[0167] 3. Manufacturing of all-solid-state secondary batteries

[0168] LiNi coated with Li2O-ZrO2 0.8 Co 0.15 Mn 0.05 A positive electrode composition was prepared by mixing 85 wt% of an O2 positive electrode active material, 13.5 wt% of a lithium argyrodite-type solid electrolyte Li6PS5Cl, 1.0 wt% of a polyvinylidene fluoride binder, and 0.5 wt% of a carbon nanotube conductive material. The prepared positive electrode composition was coated on a positive electrode current collector using a bar coater, and dried and rolled to prepare a positive electrode.

[0169] Primary entry (D 50 ) carbon black with an average particle diameter (D) of about 30 nm 50 ) was prepared by mixing silver (Ag) having a diameter of approximately 60 nm in a weight ratio of 3:1, and 0.25 g of the above complex was added to 2 g of an NMP solution containing 7 wt% of polyvinylidene fluoride binder and mixed to prepare a negative electrode coating layer composition. This was applied to a nickel foil current collector using a bar coater and vacuum-dried to prepare a deposition-type negative electrode in which a negative electrode coating layer was formed on the current collector.

[0170] A unit cell was manufactured by stacking a positive electrode, a solid electrolyte membrane, and a negative electrode in that order, and then this was placed in a laminate film and subjected to warm isostatic pressing (WIP) at 80°C and 500 MPa for 30 minutes to manufacture an all-solid-state secondary battery.

[0171] Comparative Example 1

[0172] A solid electrolyte membrane and an all-solid-state secondary battery were manufactured in substantially the same manner as in Example 1, except that the argyrodite-type sulfide-type solid electrolyte particles (Li6PS5Cl, D50=3.5㎛) themselves were used as the solid electrolyte, without mixing the argyrodite-type sulfide-type solid electrolyte particles with LiPO2F2.

[0173] Comparative Example 2

[0174] A solid electrolyte was prepared in substantially the same manner as in Example 1, except that 10 molar parts of LiI were used instead of LiPO2F2, and then a solid electrolyte membrane and an all-solid-state secondary battery were prepared.

[0175] Evaluation Example 1: Moisture Safety Evaluation

[0176] The solid electrolyte powders manufactured in Example 1, Comparative Example 1, and Comparative Example 2 were pressurized at 4 tons for 2 minutes to prepare samples, and the weight of each sample was measured. The samples were left in a dry room with a dew point of -45°C or lower, and the weight change of the samples after 3 days and 7 days was measured. The weight after leaving was divided by the initial weight and then multiplied by 100, and the value was shown as the weight change rate (%) in Table 1 and Fig. 3 below.

[0177] In addition, the samples before being stored in the dry room, the samples after being stored for 3 days, and the samples after being stored for 7 days were used as solid electrolyte membranes, and these were sandwiched between lithium metals to manufacture symmetrical cells, and then the ionic conductivity was measured. The ionic conductivity after being stored was divided by the ionic conductivity before being stored (σ exp / σ ini ) multiplied by 100 is shown as the ionic conductivity retention rate (%) in Table 1 and Figure 4 below.

[0178] Ionic conductivity was measured by electrochemical impedance spectroscopy (EIS). CellTest from Solartron was used as the EIS equipment, and analysis was performed from 0.05 Hz to 1 MHz under a voltage condition of 10 mV. The Nyquist plot was obtained through impedance analysis, and the ionic conductivity of the solid electrolyte membrane was calculated from this.

[0179] Dry room exposure (days) Weight change rate (%) Ionic conductivity retention rate (%) Example 13100.0979.37100.2576.6 Comparative example 13100.1871.87100.3665.4 Comparative example 23100.9363.67101.2853.9

[0180] Referring to Table 1 and FIGS. 3 and 4 above, it can be confirmed that Example 1 has a lower initial weight gain rate than Comparative Examples 1 and 2, and also has a lower weight gain rate after exposure to a dry room, and the ionic conductivity retention rate is also maintained at a higher level. That is, it can be seen that the solid electrolyte of Example 1 has improved moisture stability. Comparing the ionic conductivity retention rates of Example 1 and Comparative Example 1, it can be seen that the ionic conductivity of Example 1 improved by about 7.5% or more compared to Comparative Example 1 after 3 days of exposure, and improved by about 11% or more after 7 days of exposure. It is understood that a lithium salt containing both a moisture defense functional group (F) and a functional group (PO) having an affinity for a sulfide-based solid electrolyte is stably coated on the surface of the solid electrolyte particles, and this effectively suppresses solid electrolyte deterioration due to moisture exposure. In addition, it is understood that the weight increase due to adsorption and reaction upon moisture exposure is suppressed due to the moisture reactivity suppression effect of the solid electrolyte.

[0181] The results of Comparative Example 2 show that not all lithium salts exhibit the same effect, and that the affinity with the solid electrolyte and the performance of protecting the solid electrolyte from moisture vary depending on the structural characteristics of the anion of the lithium salt.

[0182] Although the preferred embodiments have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concepts defined in the following claims also fall within the scope of the present invention.

[0183] [Explanation of symbols]

[0184] 100: All-solid-state battery 200: Cathode

[0185] 201: Cathode current collector 203: Cathode active material layer

[0186] 300: Solid electrolyte layer 400: Cathode

[0187] 401: Negative current collector 403: Negative active material layer

[0188] 400': Precipitation type cathode 404: Lithium metal layer

[0189] 405: Cathode coating layer 500: Elastic layer

Claims

1. Comprising argyrodite-type sulfide-based solid electrolyte particles and a lithium salt located on the surface of the particles, A solid electrolyte wherein the lithium salt has F and PO functional groups.

2. In paragraph 1, The above lithium salt is a solid electrolyte comprising LiPOF4, LiPO2F2, Li2PO3F, or a combination thereof.

3. In paragraph 1, A solid electrolyte wherein the lithium salt has F and PO2 functional groups.

4. In paragraph 1, A solid electrolyte wherein the lithium salt is included in an amount of 1 mol% to 30 mol% with respect to 100 mol% of the lithium salt and the argyrodite-type sulfide-based solid electrolyte particles.

5. In paragraph 1, A solid electrolyte wherein the lithium salt is included in an amount of 3 mol% to 20 mol% with respect to 100 mol% of the lithium salt and the argyrodite-type sulfide-based solid electrolyte particles.

6. In paragraph 1, A solid electrolyte having an average particle diameter of the above-mentioned argyrodite-type sulfide-based solid electrolyte particles of 0.1 ㎛ to 5.0 ㎛.

7. In paragraph 1, The above argyrodite-type sulfide-based solid electrolyte particles are Li3PS4, Li7P3S. 11 , Li7PS6, Li6PS5Cl, Li6PS5Br, Li 5.8 PS 4.8 Cl 1.2 , Li 6.2 PS 5.2 Br 0.8 , Li 5.75 PS 4.75 Cl 1.25 , (Li 5.69 Cu 0.06 )PS 4.75 Cl 1.25 , (Li 5.72 Cu 0.03 )PS 4.75 Cl 1.25 , (Li 5.69 Cu 0.06 )P(S 4.70 (SO4) 0.05 )Cl 1.25 , (Li 5.69 Cu 0.06 )P(S 4.60 (SO4) 0.15 )Cl 1.25 , (Li 5.72 Cu 0.03 )P(S 4.725 (SO4) 0.025 )Cl 1.25 , (Li 5.72 Na 0.03 )P(S 4.725 (SO4) 0.025 )Cl 1.25 , Li 5.75 P(S 4.725 (SO4) 0.025 )Cl 1.25 , or a solid electrolyte comprising a combination thereof.

8. A solid electrolyte membrane comprising a solid electrolyte according to any one of claims 1 to 7.

9. Bipolar, cathode, and An all-solid-state secondary battery comprising a solid electrolyte layer positioned between a positive electrode and a negative electrode, An all-solid-state secondary battery, wherein at least one of the positive electrode, negative electrode, and solid electrolyte layers comprises a solid electrolyte according to any one of claims 1 to 7.

Images