Method of manufacturing unit cell of all-solid rechargeable battery

Abstract

A method of manufacturing a unit cell of an all-solid rechargeable battery is provided. The method of manufacturing a unit cell of an all-solid rechargeable battery, according to one embodiment, comprises: a first step of continuously supplying an anode electrode plate in a reel state; a second step of putting, onto the anode electrode plate, a cathode electrode plate, in a sheet state, with a cathode active material layer, and defining a unit cell; a third step of arranging a step compensation member on the anode electrode plate at the outside of the cathode electrode plate in the unit cell, so as to compensate for a step that is set as the height from the anode electrode plate inner surface facing the cathode electrode plate to the cathode electrode plate outer surface facing the opposite side of the anode electrode plate; a fourth step of performing roll-pressing by passing the step compensation member and the cathode electrode plate arranged on the anode electrode plate through a pair of press rolls; and a fifth step of cutting, into the unit cells, the anode electrode plate and the cathode electrode plate integrated by the roll-pressing.

Description

Method for manufacturing unit cells of all-solid-state secondary batteries

[0001] The present disclosure relates to a method for manufacturing a unit cell of an all-solid-state secondary battery.

[0002] Recent industrial demands have led to the active development of batteries with high energy density and safety. For example, lithium-ion batteries are being used not only in information and communication devices, but also in the automotive sector. Safety is particularly important in the automotive sector, as it is directly related to life.

[0003] Lithium-ion batteries currently on the market use electrolytes containing flammable organic solvents, which poses a risk of overheating and fire in the event of a short circuit. To address this issue, all-solid-state secondary batteries using solid electrolytes are being proposed.

[0004] All-solid-state secondary batteries do not use flammable organic solvents, significantly reducing the risk of fire or explosion even if a short circuit occurs. Therefore, these all-solid-state batteries significantly improve safety compared to lithium-ion batteries that use electrolytes.

[0005] The above-described information disclosed in the background technology of this invention is only intended to improve understanding of the background of the present disclosure and may therefore include information that does not constitute prior art.

[0006] One embodiment provides a method for manufacturing a unit cell of an all-solid-state secondary battery that minimizes damage to an electrode plate due to a difference in thickness when roll pressing a unit cell of an all-solid-state secondary battery.

[0007] A method for manufacturing a unit cell of an all-solid-state secondary battery according to one embodiment includes a first step of continuously supplying a negative electrode plate in a reel state, a second step of forming a unit cell by inserting a positive electrode plate having a positive electrode active material layer in a single sheet state onto the negative electrode plate and pressing the positive electrode plate, a third step of compensating for a step difference set as a height from an inner surface of the negative electrode plate to an outer surface of the positive electrode plate by arranging a step compensation member on the negative electrode plate at an outer edge of the positive electrode plate in the unit cell, a fourth step of roll-pressing the positive electrode plate and the step compensation member arranged on the negative electrode plate while passing them between a pair of press rolls, and a fifth step of cutting the negative electrode plate and the positive electrode plate integrated with the roll press into the unit cell.

[0008] The second step may include inserting the positive electrode plate having a positive electrode active material layer on the positive electrode current collector and a solid electrolyte layer on the positive electrode active material layer.

[0009] In the above first step, the negative electrode plate having a solid electrolyte layer can be inserted onto the negative electrode current collector.

[0010] The above third step can supply the step compensation member in a continuous structure corresponding to a plurality of the unit cells.

[0011] The second step supplies the positive electrode plate having a lead tab on one side, and the third step can compensate for the step by arranging a unit compensation part corresponding to the unit cell in the step compensation member on the outer side of the positive electrode plate.

[0012] The third step may form a first gap (G1) between the outer surface of the positive electrode plate and the inner surface of the unit compensation part based on the direction of progression of the unit cell.

[0013] The third step can be performed so that the upper surface of the positive electrode plate has a first height difference (ΔH1) higher than the upper surface of the unit compensation part when viewed based on the roll press direction of the unit cell.

[0014] The third step can supply the step compensation member having a thickness of 80 to 90% of the combined thickness of the positive electrode plate and the solid electrolyte layer.

[0015] The third step can make the upper surface of the positive electrode plate have a second height difference (ΔH2) lower than the upper surface of the unit compensation part when viewed based on the roll press direction of the unit cell.

[0016] The above third step can supply the step compensation member having a thickness of 80 to 110% of the total thickness of the current collector of the positive electrode plate and the positive electrode active material layer.

[0017] The above third step can be supplied by forming the step compensation member into a square frame structure corresponding to the outer periphery of the unit cell formed in a rectangular shape.

[0018] The third step may supply adhesive tape or paper tape as the step compensation member.

[0019] The fourth step may further include a step of continuously removing the pressurized step compensation member.

[0020] In one embodiment, a negative electrode plate is continuously supplied in a reel state, a positive electrode plate having a positive electrode active material layer is inserted in a single sheet state onto the negative electrode plate, and a step compensation member is placed on the negative electrode plate located at the outer side of the positive electrode plate in a unit cell before pressing, thereby compensating for a step set as the height from the inner surface of the negative electrode plate to the outer surface of the positive electrode plate, thereby minimizing damage to the plates due to a thickness difference when roll pressing a unit cell of a secondary battery.

[0021] Figure 1 is a cross-sectional view showing an all-solid-state secondary battery according to one embodiment of the present invention.

[0022] FIG. 2 is a cross-sectional view showing the formation of a lithium metal layer of an all-solid-state secondary battery according to one embodiment.

[0023] Figure 3 is a flowchart of a method for manufacturing a unit cell of an all-solid-state secondary battery according to a first embodiment of the present invention.

[0024] Figure 4 is a side view of a method for manufacturing a unit cell of an all-solid-state secondary battery according to a first embodiment of the present invention.

[0025] Figure 5 is a plan view of Figure 4.

[0026] Fig. 6 is a cross-sectional view showing the height relationship between the unit cell and the step compensation member of Fig. 4.

[0027] FIG. 7 is a cross-sectional view showing the height relationship between a unit cell and a step compensation member in a method for manufacturing a unit cell of an all-solid-state secondary battery according to a second embodiment of the present invention.

[0028] Figure 8 is a side view of a method for manufacturing a unit cell of an all-solid-state secondary battery according to a third embodiment of the present invention.

[0029] Figure 9 is a plan view of Figure 8.

[0030] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present invention. The present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0031] Additionally, throughout the specification, whenever a part is said to "include" a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated.

[0032] 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 is another element in between. Conversely, when an element is said to be "directly over" another element, it means that there is no other element in between.

[0033] Furthermore, the term "layer" here includes not only shapes formed on the entire surface when observed in a plan view, but also shapes formed on a portion of the surface. Here, "or" is not interpreted in an exclusive sense; for example, "A or B" is interpreted to include A, B, A+B, etc.

[0034] Cathode for all-solid-state secondary batteries

[0035] In one embodiment, a positive electrode for an all-solid-state secondary battery is provided, comprising a current collector and a positive electrode active material layer positioned on the current collector, wherein the positive electrode active material layer comprises at least one of a positive electrode active material, a sulfide-based solid electrolyte, a binder, and a conductive material. However, without limitation thereto, the positive electrode for an all-solid-state secondary battery may comprise more or less components than the components described above.

[0036] In one embodiment, the positive electrode for the all-solid-state secondary battery is manufactured by applying a positive electrode composition including at least one of a positive electrode active material, a sulfide-based solid electrolyte, a binder, and a conductive agent to a current collector, followed by drying and rolling.

[0037] positive electrode active material

[0038] 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.

[0039] Li a A 1-b X b D2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5);

[0040] 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);

[0041] 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);

[0042] 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);

[0043] 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);

[0044] 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);

[0045] 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);

[0046] 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);

[0047] 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);

[0048] 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);

[0049] 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);

[0050] Li a Ni b Co c Mr 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);

[0051] Li a NiG bO2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1);

[0052] Li a CoG b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1);

[0053] Li a Mn 1-b G b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1);

[0054] Li a Mn2G b O4(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1);

[0055] Li a Mn 1-g G g PO4(0.90 ≤ a ≤ 1.8, 0 ≤ g ≤ 0.5);

[0056] QO2; QS2; LiQS2;

[0057] V2O5; LiV2O5;

[0058] LiZO2;

[0059] LiNiVO4;

[0060] Li (3-f) J2(PO4)3(0 ≤ f ≤ 2);

[0061] Li (3-f) Fe2(PO4)3(0 ≤ f ≤ 2);

[0062] Li a FePO4(0.90 ≤ a ≤ 1.8).

[0063] 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.

[0064] 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).

[0065] The above positive electrode active material may include a lithium nickel-based oxide represented by the following chemical formula 1, a lithium cobalt-based oxide represented by the following chemical formula 2, a lithium iron phosphate-based compound represented by the following chemical formula 3, or a combination thereof.

[0066] [Chemical Formula 1]

[0067] Li a1 Ni x1 M 1 y1 M 2 1-x1-y1 O2

[0068] In the above chemical formula 1, 0.9≤a1≤1.8, 0.3≤x1≤1, 0≤y1≤0.7, and M 1 and M2 is one or more elements independently selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, F, Fe, Mg, Mn, Mo, Nb, P, S, Si, Sr, Ti, V, W, and Zr.

[0069] [Chemical Formula 2]

[0070] Li a2 Co x2 M 3 1-x2 O2

[0071] In the above chemical formula 2, 0.9≤a2≤1.8, 0.6≤x2≤1, and M 3 is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Cr, Cu, F, Fe, Mg, Mn, Mo, Nb, P, S, Si, Sr, Ti, V, W, and Zr.

[0072] [Chemical Formula 3]

[0073] Li a3 Fe x3 M 4 (1-x3) PO4

[0074] In the above chemical formula 3, 0.9≤a3≤1.8, 0.6≤x3≤1, and M 4 is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, F, Fe, Mg, Mn, Mo, Nb, P, S, Si, Sr, Ti, V, W, and Zr.

[0075] 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, 5 μm to 25 μm, 5 μm to 20 μm, 8 μm to 20 μm, or 10 μm to 18 μm. A positive electrode active material having such a particle diameter range can be harmoniously mixed with other components within the positive electrode active material layer and can realize high capacity and high energy density.

[0076] 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.

[0077] Sulfide-based solid electrolyte

[0078] Sulfide-based solid electrolytes include, for example, Li2S-P2S5, Li2S-P2S5-LiX (where X is a halogen element, for example, I or Cl), Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z. m S n (m, n are integers, Z is Ge, Zn or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (p, q are integers, and M is P, Si, Ge, B, Al, Ga or In), or a combination thereof.

[0079] Such sulfide-based solid electrolytes can be obtained, for example, by mixing Li2S and P2S5 in a molar ratio of 50:50 to 90:10, or 50:50 to 80:20, and optionally heat-treating them. Within the above mixing ratio range, a sulfide-based solid electrolyte having excellent ionic conductivity can be produced. Here, the ionic conductivity can be further improved by further including other components such as SiS2, GeS2, and B2S3.

[0080] Methods for mixing sulfur-containing raw materials for producing sulfide-based solid electrolytes include mechanical milling or the solution method. Mechanical milling involves placing the starting raw materials in a reactor and vigorously stirring them with a ball mill or similar device to finely atomize and mix them. Using the solution method, the starting raw materials are mixed in a solvent to obtain a solid electrolyte as a precipitate. Furthermore, heat treatment after mixing can solidify the crystals of the solid electrolyte and improve ionic conductivity. For example, a sulfide-based solid electrolyte can be produced by mixing sulfur-containing raw materials and heat-treating them twice or more, resulting in a sulfide-based solid electrolyte with high ionic conductivity and robustness.

[0081] For example, the sulfide-based solid electrolyte particles may include argyrodite-type sulfides. The argyrodite-type sulfides may include, for example, Li a M b P c S d A e (wherein a, b, c, d and e are all 0 or more and 12 or less, M is a metal other than Li or a combination of multiple metals other than Li, and A is F, Cl, Br, or I) and a specific example is Li 7-x PS 6-x A x (x is 0.2 or more and 1.8 or less, and A is F, Cl, Br, or I) can be expressed by the chemical formula. The above argyrodite-type sulfide is specifically Li3PS4, Li7P3S 11 , Li7PS6, Li6PS5Cl, Li6PS5Br, Li 5.8 PS 4.8 Cl 1.2 , Li 6.2 PS 5.2 Br 0.8 It could be the back.

[0082] Sulfide-based solid electrolyte particles containing these argyrodite-type sulfides have an ionic conductivity of 10, which is the ionic conductivity of a typical liquid electrolyte 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 can further form a close interface between the electrode layer and the solid electrolyte layer. An all-solid-state battery including this can have improved battery performance, such as rate characteristics, Coulombic efficiency, and cycle life characteristics.

[0083] An argyrodite-type sulfide-based solid electrolyte can be prepared, for example, by mixing lithium sulfide, phosphorus sulfide, and optionally, a lithium halide. After mixing, a heat treatment may be performed. The heat treatment may include, for example, two or more heat treatment steps.

[0084] According to one embodiment, the average particle diameter (D50) of the sulfide-based solid electrolyte particles may be 5.0 ㎛ or less, for example, 0.1 ㎛ to 5.0 ㎛, 0.1 ㎛ to 4.0 ㎛, 0.1 ㎛ to 3.0 ㎛, 0.5 ㎛ to 2.0 ㎛, or 0.1 ㎛ to 1.5 ㎛. Alternatively, the sulfide-based solid electrolyte particles may be small particles having an average particle diameter (D50) of 0.1 ㎛ to 1.0 ㎛, or may be large particles having an average particle diameter (D50) of 1.5 ㎛ to 5.0 ㎛, depending on the location or purpose of use. The sulfide-based solid electrolyte particles having such a particle diameter range can effectively penetrate between solid particles in a battery, and have excellent contact with an electrode active material and connectivity between solid electrolyte particles. The average particle size of the sulfide-based solid electrolyte particles may be measured from a microscope image, for example, by measuring the sizes of about 20 particles in a scanning electron microscope image to obtain a particle size distribution and calculating D50 from this.

[0085] The content of the solid electrolyte in the positive electrode for the all-solid-state battery may be 0.5 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%. This is the content relative to the total weight of components in the positive electrode, and specifically, it can be said to be the content relative to the total weight of the positive electrode active material layer.

[0086] In one embodiment, the positive electrode active material layer may include 50 wt% to 99.35 wt% of the positive electrode active material, 0.5 wt% to 35 wt% of the sulfide-based solid electrolyte, 0.1 wt% to 10 wt% of the fluorine-based resin binder, and 0.05 wt% to 5 wt% of the vanadium oxide, based on 100 wt% of the positive electrode active material layer. When this content range is satisfied, the positive electrode for an all-solid-state secondary battery can implement high capacity and high ionic conductivity while maintaining high adhesiveness, and the viscosity of the positive electrode composition can be maintained at an appropriate level, thereby improving processability.

[0087] bookbinder

[0088] The 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.

[0089] Challenge

[0090] The above-described positive electrode active material layer may further include a conductive material. The conductive material is used to impart conductivity to the electrode, and may include, for example, carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, and carbon nanotubes; metal-based materials containing copper, nickel, aluminum, silver, and the like in the form of metal powder or metal fibers; conductive polymers such as polyphenylene derivatives; or combinations thereof.

[0091] The conductive material may be included in an amount of 0.1 wt% to 5 wt%, or 0.1 wt% to 3 wt%, based on the total weight of each component of the positive electrode for the all-solid-state battery, or based on the total weight of the positive electrode active material layer. Within the above content range, the conductive material can improve electrical conductivity without degrading battery performance.

[0092] When the positive electrode active material layer further includes a conductive material, the positive electrode active material layer may include 45 wt% to 99.25 wt% of the positive electrode active material, 0.5 wt% to 35 wt% of the sulfide-based solid electrolyte, 0.1 wt% to 10 wt% of the fluorine-based resin binder, 0.05 wt% to 5 wt% of the vanadium oxide, and 0.1 wt% to 5 wt% of the conductive material, based on 100 wt% of the positive electrode active material layer.

[0093] Meanwhile, the positive electrode for the lithium secondary battery may further include an oxide-based inorganic solid electrolyte in addition to the above-described solid electrolyte. The oxide-based inorganic solid electrolyte may be, for example, Li 1+x Ti 2-x Al(PO4)3(LTAP)(0≤x≤4), Li 1+x+y Al x Ti 2-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 Zr1-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= Te, Nb, or Zr; x is an integer from 1 to 10), or a combination thereof.

[0094] All-solid-state secondary battery

[0095] In one embodiment, an all-solid-state secondary battery is provided, which includes the aforementioned positive electrode and negative electrode and a solid electrolyte layer positioned between the positive electrode and negative electrode. The all-solid-state secondary battery may also be referred to as an all-solid-state battery or an all-solid-state lithium secondary battery.

[0096] Fig. 1 is a cross-sectional view of an all-solid-state secondary battery according to one 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 current 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 current collector (201) are laminated is housed in a case such as a pouch. 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 battery may be manufactured by laminating two or more electrode assemblies.

[0097] cathode

[0098] An anode for an all-solid-state battery may include, for example, a current collector and a layer of anode active material positioned on the current collector. The layer of anode active material includes a cathode active material and may further include a binder, a conductive material, and / or a solid electrolyte.

[0099] The above negative active material may include 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.

[0100] 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.

[0101] As the above lithium metal alloy, an alloy of lithium and one or more metals selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn can be used.

[0102] 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 합금(상기 Q는 알칼리 금속, 알칼리 토금속, 13족 원소, 14족 원소, 15족 원소, 16족 원소, 전이금속, 희토류 원소 및 이들의 조합으로 이루어진 군에서 선택되는 원소이며, Si은 아님), 상기 Sn계 음극 활물질로는 Sn, SnO2, Sn-R 합금(상기 R은 알칼리 금속, 알칼리 토금속, 13족 원소, 14족 원소, 15족 원소, 16족 원소, 전이금속, 희토류 원소 및 이들의 조합으로 이루어진 군에서 선택되는 원소이며, Sn은 아님) 등을 들 수 있고, 또한 이들 중 적어도 하나와 SiO2를 혼합하여 사용할 수도 있다. 상기 원소 Q 및 R로는 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, 및 이들의 조합으로 이루어진 군에서 선택되는 것을 사용할 수 있다.

[0103] The silicon-carbon composite may be, for example, a silicon-carbon composite including a core comprising crystalline carbon and silicon particles and an amorphous carbon coating layer positioned on the surface of the core. The crystalline carbon may be artificial graphite, natural graphite, or a combination thereof. As the amorphous carbon precursor, coal pitch, mesophase pitch, petroleum pitch, coal oil, petroleum heavy oil, or a polymer resin such as a phenol resin, a furan resin, or a polyimide resin may be used. At this time, the content of silicon may be 10 wt% to 50 wt% with respect to the total weight of the silicon-carbon composite. In addition, the content of the crystalline carbon may be 10 wt% to 70 wt% with respect to the total weight of the silicon-carbon composite, and the content of the amorphous carbon may be 20 wt% to 40 wt% with respect to the total weight of the silicon-carbon composite. In addition, the thickness of the amorphous carbon coating layer may be 5 nm to 100 nm.

[0104] The average particle diameter (D50) of the above silicon particles may be 10 nm to 20 μm, for example, 10 nm to 500 nm. The silicon particles may exist in an oxidized form, and at this time, the atomic content ratio of Si:O in the silicon particles, which indicates the degree of oxidation, may be 99:1 to 33:67. The silicon particles may be SiO x It can be a particle, in which case SiO x In the range of x, it can be greater than 0 and less than 2. Here, the average particle diameter (D50) is measured by a particle size analyzer using laser diffraction and means the diameter of particles having a cumulative volume of 50% by volume in the particle size distribution.

[0105] 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. The mixing ratio of the Si-based negative electrode active material or Sn-based negative electrode active material and the carbon-based negative electrode active material can be 1:99 to 90:10 by weight.

[0106] 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.

[0107] 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.

[0108] The above binder serves to adhere the negative active material particles well to each other and also to adhere the negative active material well to the current collector. The binder may include an insoluble binder, a water-soluble binder, or a combination thereof.

[0109] The above-described non-aqueous binder may include, for example, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer comprising ethylene oxide, an ethylene propylene copolymer, polystyrene, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or a combination thereof.

[0110] 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.

[0111] When a water-soluble binder is used as the negative electrode binder, a thickener capable of imparting viscosity may be used together, and the thickener may include, for example, a cellulose-based compound. The cellulose-based compound may include carboxymethyl cellulose, hydroxypropylmethyl cellulose, methyl cellulose, an alkali metal salt thereof, or a combination thereof. Na, K, or Li may be used as the alkali metal. 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.

[0112] The conductive material is used to provide conductivity to the electrode, and may include, for example, carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, and carbon nanotubes; metal-based materials in the form of metal powder or metal fibers, including copper, nickel, aluminum, and silver; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0113] The negative electrode current collector may be selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and a combination thereof.

[0114] As another example, the negative electrode for the all-solid-state battery may be a precipitation-type negative electrode. The precipitation-type negative electrode refers 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 when the battery is charged, and this acts as a negative electrode active material.

[0115] FIG. 2 is a schematic cross-sectional view of an all-solid-state secondary battery including a precipitation-type negative electrode according to one embodiment. 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 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 upon charging, high-density lithium metal or the like is precipitated between the current collector (401) and 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 battery that has been charged at least once, the precipitation-type negative electrode (400') may include 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 above lithium metal layer (404) refers to a layer in which lithium metal, etc. is precipitated during the charging process of the battery, and may be referred to as a metal layer or a negative electrode active material layer.

[0116] The above cathode coating layer (405) may include a metal, a carbon material, or a combination thereof that acts as a catalyst.

[0117] The metal 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 an alloy of several types. When the metal is present in the form of particles, the average particle diameter (D50) thereof may be about 4 μm or less, for example, 10 nm to 4 μm.

[0118] 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.

[0119] 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 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.

[0120] The above cathode coating layer (405) may include, for example, the metal and amorphous carbon, in which case it can effectively promote the precipitation of lithium metal.

[0121] The above cathode coating layer (405) may further include a binder, and the binder may be a conductive binder. In addition, the above cathode coating layer (405) may further include general additives such as fillers, dispersants, and ionic conductive agents.

[0122] 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 ㎛.

[0123] 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 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.

[0124] solid electrolyte layer

[0125] The solid electrolyte layer (300) may include a sulfide-based solid electrolyte, an oxide-based solid electrolyte, etc. The specific details of the sulfide-based solid electrolyte and the oxide-based solid electrolyte are as described above.

[0126] In one example, the solid electrolyte included in the positive electrode (200) and the solid electrolyte included in the solid electrolyte layer (300) may include the same compound or different compounds. For example, when both the positive electrode (200) and the solid electrolyte layer (300) include an argyrodite-type sulfide-based solid electrolyte, the overall performance of the all-solid-state secondary battery may be improved. In addition, for example, when both the positive electrode (200) and the solid electrolyte layer (300) include the above-described coated solid electrolyte, the all-solid-state secondary battery may implement high capacity and high energy density while implementing excellent initial efficiency and lifespan characteristics.

[0127] Meanwhile, the average particle diameter (D50) of the solid electrolyte included in the positive electrode (200) may be smaller than the average particle diameter (D50) of the solid electrolyte included in the solid electrolyte layer (300). In this case, the energy density of the all-solid-state battery can be maximized while increasing the mobility of lithium ions, thereby improving the overall performance. For example, the average particle diameter (D50) of the solid electrolyte included in the positive electrode (200) may be 0.1 ㎛ to 1.0 ㎛, or 0.1 ㎛ to 0.8 ㎛, and the average particle diameter (D50) of the solid electrolyte included in the solid electrolyte layer (300) may be 1.5 ㎛ to 5.0 ㎛, or 2.0 ㎛ to 4.0 ㎛, or 2.5 ㎛ to 3.5 ㎛. When this particle size range is satisfied, the energy density of the all-solid-state secondary battery can be maximized while lithium ion transport is facilitated, resistance is suppressed, and the overall performance of the all-solid-state secondary battery can be improved. Here, the average particle diameter (D50) of the solid electrolyte can be measured using a particle size analyzer using laser diffraction. Alternatively, the particle size can be measured by selecting 20 or so random particles from a microscope image such as a scanning electron microscope, obtaining a particle size distribution, and calculating the D50 value from this.

[0128] The above solid electrolyte layer may further include a binder in addition to the solid electrolyte. At this time, the binder may be styrene butadiene rubber, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, an acrylate polymer, or a combination thereof, but is not limited thereto, and any binder used in the relevant technical field may be used. The acrylate polymer may be, for example, butyl acrylate, polyacrylate, polymethacrylate, or a combination thereof.

[0129] The above solid electrolyte layer can be formed by adding a solid electrolyte to a binder solution, coating the same on a base film, and drying the same. The solvent of the binder solution may be isobutyryl isobutyrate, xylene, toluene, benzene, hexane, or a combination thereof. Since the solid electrolyte layer formation process is widely known in the art, a detailed description thereof will be omitted.

[0130] The thickness of the solid electrolyte layer may be, for example, 10 ㎛ to 150 ㎛.

[0131] The above solid electrolyte layer may further include an alkali metal salt, and / or an ionic liquid, and / or a conductive polymer.

[0132] 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.

[0133] The above lithium salts include, for example, LiSCN, LiN(CN)2, Li(CF3SO2)3C, LiC4F9SO3, LiN(SO2CF2CF3)2, LiCl, LiF, LiBr, LiI, LiB(C2O4)2, LiBF4, LiBF3(C2F5), lithium bis(oxalato)borate (LiBOB), lithium oxalyldifluoroborate (LIODFB), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(trifluoro methanesulfonyl)imide (LiTFSI, LiN(SO2CF3)2), lithium bis(fluorosulfonyl)imide (LiFSI, It may include LiN(SO2F)2), LiCF3SO3, LiAsF6, LiSbF6, LiClO4 or mixtures thereof.

[0134] In addition, the lithium salt may be an imide-based one, and for example, the imide-based lithium salt may include lithium bis(trifluoro methanesulfonyl)imide (LiTFSI, LiN(SO2CF3)2), lithium bis(fluorosulfonyl)imide (LiFSI, LiN(SO2F)2). The lithium salt may maintain or improve ionic conductivity by appropriately maintaining chemical reactivity with an ionic liquid.

[0135] 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.

[0136] The above ionic liquid may be a compound including a) one or more cations selected from ammonium-based, pyrrolidinium-based, pyridinium-based, pyrimidinium-based, imidazolium-based, piperidinium-based, pyrazolium-based, oxazolium-based, pyridazinium-based, phosphonium-based, sulfonium-based, triazolium-based, and mixtures thereof, and b) one or more anions selected from 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-.

[0137] 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.

[0138] 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 battery can be improved.

[0139] The above-mentioned all-solid-state battery may be a unit battery having a structure of positive electrode / solid electrolyte layer / negative electrode, a bi-cell having a structure of positive electrode / solid electrolyte layer / negative electrode / solid electrolyte layer / positive electrode, or a laminated battery in which the structure of the unit battery is repeated.

[0140] The shape of the above-mentioned all-solid-state 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 battery can be applied to large-scale batteries used in electric vehicles, etc. For example, the above-mentioned all-solid-state battery can be used in hybrid vehicles such as plug-in hybrid electric vehicles (PHEVs). In addition, it can be used in fields requiring large amounts of power storage, and for example, it can be used in electric bicycles or power tools.

[0141] The press process of an all-solid-state secondary battery is performed after the coating process of one electrode plate of the positive or negative electrode is completed to increase the capacity density of the active material on the electrode plate and to increase the bonding force between the electrode current collector and the active material.

[0142] The roll press process compresses an electrode plate to a desired thickness by passing it between two rolls. To achieve the desired thickness, the roll press process is performed at high temperature and high pressure.

[0143] In addition, all-solid-state secondary batteries require a pressing process to pressurize the stacked unit cells of anode / solid electrolyte / cathode, thereby densifying the solid electrolyte and reducing the electrical resistance at the interface between the solid electrolyte and the electrode plate. To improve the productivity of the pressing process, the embodiments of the present invention exemplify a roll press.

[0144] In the case of roll pressing, when roll pressing a unit cell containing two or more positive and negative electrode plates, the electrode plates are fed in as sheets or fed while being unwound onto a reel without length restrictions. At this time, a difference in thickness exists between neighboring unit cells, and if roll pressing is performed while this difference in thickness exists, the electrode plates may be damaged.

[0145] FIG. 3 is a flowchart of a method for manufacturing a unit cell of an all-solid-state secondary battery according to a first embodiment of the present invention, FIG. 4 is a side view of a method for manufacturing a unit cell of an all-solid-state secondary battery according to a first embodiment of the present invention, and FIG. 5 is a plan view of FIG. 4.

[0146] Referring to FIGS. 3 and 4, the first embodiment provides a method for manufacturing a unit cell of an all-solid-state secondary battery to minimize damage to an electrode plate due to a difference in thickness when roll-pressing a unit cell before pressurization.

[0147] The method for manufacturing a unit cell of the first embodiment includes a first step (ST1), a second step (ST2), a third step (ST3), a fourth step (ST4), and a fifth step (ST5). The first step (ST1) is performed by continuously supplying a negative electrode plate (10) while winding it on a reel (41) and then unwinding it. Since the negative electrode plate (10) is continuously supplied, a roll press can be continuously implemented without a separate transport means.

[0148] In the second step (ST2), a positive electrode plate (20) having a positive active material layer is inserted and laminated on a negative electrode plate (10) in a single sheet state. That is, the second step (ST2) forms a unit cell (UC1) before pressurization. Since the positive electrode plate (20) is inserted in single sheets, it is possible to prevent accumulation of misalignment with the negative electrode plate (10).

[0149] In the third step (ST3), a step compensation member (30) is placed on the negative electrode plate (10) located on the outer side of the positive electrode plate (20) in the pre-pressurized unit cell (UC1). The step compensation member (30) compensates for the step difference set as the height from the inner surface of the negative electrode plate (10) to the outer surface of the positive electrode plate (20). That is, since the step compensation member (30) removes the step difference formed between adjacent pre-pressurized unit cells (UC1), when the pre-pressurized unit cells (UC1) are roll pressed, the pressure load is concentrated on the outer edges of the unit cells (UC1), which can prevent the edges from being damaged.

[0150] Step 4 (ST4) is to roll press the positive electrode plate (20) and the step compensation member (30) placed on the negative electrode plate (10) while passing them between a pair of press rolls (40) to pressurize and form a unit cell (UC2). The press rolls (40) press the unit cells (UC1) and the step compensation member (30).

[0151] The negative electrode plate (10) can be unwound from the wound reel (41) and can be subjected to tensile force due to the press rolls (40) being driven to rotate. In the fifth step (ST5), the negative electrode plate (10) and positive electrode plate (20) that are integrated with the roll press are cut to complete the unit cell (UC3). At this time, the step compensation member (30) is also cut together with the unit cell (UC3).

[0152] Fig. 6 is a cross-sectional view illustrating the height relationship between the unit cell of Fig. 4 and the step compensation member. Referring to Fig. 6, the second step (ST2) includes installing a positive electrode plate (20) having a positive electrode active material layer (22) on a positive electrode current collector (21) and a solid electrolyte layer (50) on the positive electrode active material layer (22). That is, the positive electrode plate (20) is installed on the negative electrode plate (10).

[0153] Referring again to FIGS. 4 and 5, the third step (ST3) supplies the step compensation member (30) in a continuous structure corresponding to a plurality of unit cells (UC1, UC2). For convenience, in the first embodiment, the step compensation member (30) is provided in a length corresponding to four unit cells (UC1, UC2).

[0154] Step 2 (ST2) supplies a positive electrode plate (20) having a lead tab (202) on one side. The lead tab (202) of the positive electrode plate (20) is positioned on the opposite side to the lead tab (102) of the negative electrode plate (10) in a direction orthogonal to the direction of travel. That is, the lead tabs (102, 202) are pulled out in opposite directions in the unit cell (UC3).

[0155] Step 3 (ST3) compensates for the step difference by arranging each unit compensation member (301) corresponding to the unit cell (UC1) in the step compensation member (30) on the outer surface of the positive electrode plate (20). As an example, the step compensation member (30) may be formed in a rectangular shape and may be formed in a square frame structure corresponding to the outer surface of the unit cell (UC1).

[0156] This square frame structure facilitates handling of the step compensation member (30) by connecting each unit compensation member (301) to each other while compensating for the step between the unit cells (UC1). The third step (ST3) supplies the step compensation member (30) of the corresponding square frame structure.

[0157] Accordingly, the step compensation member (30) has a receiving groove (31) corresponding to the lead tab (202) of the positive electrode plate (20) to receive the lead tab (202) and prevent excessive increase in thickness in the lead tab (202) portion. As an example, the step compensation member (30) may be formed of an adhesive tape or paper tape made of a synthetic resin film material.

[0158] The third step (ST3) forms a first gap (G1) between the outer surface of the positive electrode plate (20) and the inner surface of the unit compensation part (301) based on the direction of progression of the unit cells (UC1, UC2) (progressing from left to right in FIG. 4). The closer the unit compensation part (301) gets to the positive electrode plate (20), the smaller the first gap (G1).

[0159] When pressurizing the roll, the compressed unit compensation part (301) effectively prevents damage to the positive electrode active material layer (22), but as the first gap (G1) becomes smaller, the compressed unit compensation part (301) is deformed, which may push the positive electrode active material layer (22) laterally and disturb the alignment of the positive electrode plate (20) and the negative electrode plate (10).

[0160] Therefore, the first gap (G1) is positioned as close as possible to the positive electrode active material layer (22) without the unit compensation part (301) being deformed and reaching the positive electrode active material layer (22) when the roll press is applied, thereby preventing damage to the positive electrode active material layer (22). Since the paper tape is less compressible than the adhesive tape, it can have a smaller thickness than the adhesive tape, and can have a smaller first gap (G1) than the adhesive tape.

[0161] In the third step (ST3), when viewed from the roll press direction (up-down direction in FIG. 4) of the unit cells (UC1, UC2), the upper surface of the positive electrode plate (20) has a first height difference (ΔH1) that is higher than the upper surface of the unit compensation part (301). In other words, the unit compensation part (301) is formed lower than the positive electrode plate (20).

[0162] As an example, the third step (ST3) supplies a step compensation member (30) having a thickness (H2) of 80 to 90% of the combined thickness (H1) of the positive electrode plate (20) and the solid electrolyte layer (50) (H2=0.8 to 0.9H1). The step compensation member (30) includes a unit compensation portion (301). When the thickness (H2) of the step compensation member (30) is less than 80% of the thickness (H1), damage to the positive electrode active material layer (22) may begin. When the thickness (H2) is 80 to 90% of the thickness (H1), damage to the positive electrode active material layer (22) can be effectively prevented.

[0163] Referring back to FIGS. 4 to 6, in the fourth step (ST4) of roll pressing the unit cells (UC1, UC2), the step compensation member (30), i.e., the unit compensation portion (301), is first pressed by the press roll (40), then the positive electrode collector (21) of the unit cell (UC1) is pressed, and after the pressurization of the unit cell (UC1) is completed, the step compensation member (30) is continuously pressed again. In this way, when the unit cell (UC1) is roll pressed, the step compensation member (30) is first pressed and entered at the start and end of the press roll (40) and finally pressed and exited, so that damage to the positive electrode active material layer (22) can be prevented despite the first height difference (ΔH1). Due to the square frame structure of the step compensation member (30), damage to the positive electrode active material layer (22) can be effectively prevented in the longitudinal direction of the press roll (40).

[0164] Step 5 (ST5) removes the step compensation member (30) from the pressurized unit cell (UC3), thereby completing the final unit cell (not shown). These unit cells can be stacked to assemble an all-solid-state secondary battery of the required capacity.

[0165] Hereinafter, various embodiments of the present invention will be described. Compared to the first embodiment and the previously described embodiments, descriptions of identical components will be omitted, and descriptions of different components will be provided.

[0166] Fig. 7 is a cross-sectional view illustrating the height relationship between a unit cell and a step compensation member in a method for manufacturing a unit cell of an all-solid-state secondary battery according to a second embodiment of the present invention. Referring to Fig. 7, in the method for manufacturing a unit cell of an all-solid-state secondary battery according to the second embodiment, a first step (ST1) includes inserting an anode plate (210) having a solid electrolyte layer (250) onto an anode current collector (11).

[0167] In the third step (ST3), when viewed from the roll press direction (up-down direction in FIG. 4) of the unit cells (UC1, UC2), the upper surface of the positive electrode plate (20) has a second height difference (ΔH2) lower than the upper surface of the unit compensation part (302). In other words, the unit compensation part (302) is formed higher than the positive electrode plate (20).

[0168] As an example, the third step (ST3) supplies a step compensation member (30) having a thickness (H4) of 80 to 110% of the combined thickness (H3) of the positive electrode current collector (21) and the positive electrode active material layer (22) (H4=0.8 to 1.1H3). The step compensation member (30) includes a unit compensation portion (301). If the thickness (H4) of the step compensation member (30) is less than 80% of the thickness (H3), damage to the positive electrode active material layer (22) may begin. If the thickness (H4) of the step compensation member (30) is more than 110% of the thickness (H3), the step compensation member (30) may be compressed and deformed, thereby pushing the side of the positive electrode active material layer (22), thereby disturbing the alignment of the positive electrode plate (20) and the negative electrode plate (210). When the thickness (H4) is 80 to 110% of the thickness (H3), damage to the positive electrode active material layer (22) can be effectively prevented.

[0169] Referring back to FIGS. 4, 5 and 7, in the fourth step (ST4) of roll pressing the unit cells (UC1, UC2), the step compensation member (30), i.e., the unit compensation portion (302), is first sufficiently pressed by the press roll (40), then the positive electrode collector (21) of the unit cell (UC1) is pressed, and after the pressurization of the unit cell (UC1) is completed, the step compensation member (30) is sufficiently pressed again. In this way, when roll pressing the unit cell (UC1), the step compensation member (30) is first sufficiently pressed and enters at the start and end of the press roll (40) and then finally pressurized and exits, so that damage to the positive electrode active material layer (22) can be prevented despite the second height difference (ΔH2). Due to the square frame structure of the step compensation member (30), damage to the positive electrode active material layer (22) can be effectively prevented in the longitudinal direction of the press roll (40).

[0170] In the first embodiment, the step compensation member (30) having a thickness (H2) of 80 to 90% of the thickness (H1) can prevent damage to the positive electrode active material layer (22) while minimizing the decrease in the pressing density of the positive electrode active material layer (22).

[0171] In contrast, in the second embodiment, the step compensation member (30) mainly functions to prevent damage to the positive electrode active material layer (22) in a portion having a thickness (H4) of 90 to 110% of the thickness (H3), thereby further preventing damage to the positive electrode active material layer (22). In addition, in the second embodiment, the step compensation member (30) mainly functions to increase the pressing density of the positive electrode active material layer (22), as in the first embodiment, in a portion having a thickness (H4) of 80 to 90% of the thickness (H3).

[0172] Fig. 8 is a side view of a method for manufacturing a unit cell of an all-solid-state secondary battery according to a third embodiment of the present invention, and Fig. 9 is a plan view of Fig. 8. Referring to Figs. 8 and 9, in the method for manufacturing a unit cell of an all-solid-state secondary battery according to the third embodiment, the fourth step (ST24) further includes a step of continuously removing a pressed step compensation member (303).

[0173] That is, in the fourth step (ST24), after the roll press is performed, the step compensation member (303) is removed. To this end, in the third step (ST23), the unwinding reel (305) supplies the step compensation member (303) from the entry side of the press roll (40), and in the fourth step (ST24), the rewinding reel (306) removes the step compensation member (303) from the exit side of the press roll (40). Accordingly, the third embodiment can facilitate the supply and removal of the step compensation member (303) compared to the first embodiment.

[0174] In this case, the fifth step (ST25) completes the unit cell (UC23) by cutting the negative electrode plate (10) and positive electrode plate (20) integrated with a roll press. At this time, the step compensation member (303) is not included in the cutting target, so the burden on the cutting unit is reduced.

[0175] The above description is only one embodiment for implementing the all-solid-state secondary battery according to the present disclosure, and the present disclosure is not limited to the above-described embodiment, and as claimed in the following claims, it will be understood that the technical spirit of the present disclosure encompasses a range in which various modifications can be implemented without departing from the gist of the present disclosure by anyone having ordinary skill in the art to which the invention pertains.

[0176] - Explanation of symbols -

[0177] 10: Negative electrode plate 11: Negative current collector

[0178] 20: Positive electrode plate 21: Positive current collector

[0179] 22: Positive active material layer 30: Step compensation member

[0180] 31: Receiving groove 40: Press rolls

[0181] 41: Reel 50: Solid electrolyte layer

[0182] 102: 202: Lead tab 210: Negative electrode plate

[0183] 250: Solid electrolyte layer 301: Unit compensation section

[0184] 303: Step compensation member G1: First gap

[0185] H1, H2, H3, H4: Thickness UC1, UC2, UC3, UC23: Unit cell

[0186] ΔH1: First height difference ΔH2: Second height difference

Claims

1. The first step is to continuously supply the negative electrode plate in a reel state; A second step in which a positive electrode plate having a positive active material layer is placed on the negative electrode plate in a single sheet state to define a unit cell; A third step of compensating for a step difference set as a height from an inner surface of the negative electrode plate facing the positive electrode plate to an outer surface of the positive electrode plate facing the opposite side of the negative electrode plate by arranging a step difference compensation member on the negative electrode plate located on the outer side of the positive electrode plate in the unit cell; A fourth step of roll pressing the positive electrode plate and the step compensation member placed on the negative electrode plate while passing them between a pair of press rolls; and A fifth step of cutting the negative electrode plate and the positive electrode plate integrated with the roll press into the unit cell. A method for manufacturing a unit cell of an all-solid-state secondary battery including a .

2. In paragraph 1, The second step above is A method for manufacturing a unit cell of an all-solid-state secondary battery, comprising: providing a positive electrode active material layer on a positive electrode current collector; and inserting a positive electrode plate having a solid electrolyte layer on the positive electrode active material layer.

3. In paragraph 1, The above first step is A method for manufacturing a negative electrode plate of an all-solid-state secondary battery, wherein the negative electrode plate having a solid electrolyte layer is inserted on a negative electrode current collector.

4. In paragraph 1, The third step above is A method for manufacturing a unit cell of an all-solid-state secondary battery, wherein the step compensation member is supplied in a continuous structure corresponding to a plurality of the unit cells.

5. In paragraph 4, The second step above supplies the positive electrode plate having a lead tab on one side, The third step above is A method for manufacturing a unit cell of an all-solid-state secondary battery, wherein a unit compensation part corresponding to the unit cell in the above step compensation member is arranged on the outer side of the positive electrode plate to compensate for the step difference.

6. In paragraph 5, The third step above is A method for manufacturing a unit cell of an all-solid-state secondary battery, wherein a first gap (G1) is formed between the outer surface of the positive electrode plate and the inner surface of the unit compensation portion, based on the direction of progression of the unit cell.

7. In paragraph 6, The third step above is A method for manufacturing a unit cell of an all-solid-state secondary battery, wherein the upper surface of the positive electrode plate has a first height difference (ΔH1) higher than the upper surface of the unit compensation part, based on the roll press direction of the unit cell.

8. In paragraph 7, The third step above is A method for manufacturing a unit cell of an all-solid-state secondary battery, wherein the step compensation member has a thickness of 80 to 90% of the combined thickness of the positive electrode plate and the solid electrolyte layer.

9. In paragraph 6, The third step above is A method for manufacturing a unit cell of an all-solid-state secondary battery, wherein the upper surface of the positive electrode plate has a second height difference (ΔH2) lower than the upper surface of the unit compensation part, based on the roll press direction of the unit cell.

10. In paragraph 9, The third step above is A method for manufacturing a unit cell of an all-solid-state secondary battery, which supplies the step compensation member having a thickness of 80 to 110% of the total thickness of the current collector and the positive electrode active material layer of the positive electrode plate.

11. In paragraph 4, The third step above is A method for manufacturing a unit cell of an all-solid-state secondary battery, wherein the step compensation member is formed into a square frame structure corresponding to the outer surface of the unit cell formed in a rectangular shape.

12. In paragraph 1, The third step above is A method for manufacturing a unit cell of an all-solid-state secondary battery, wherein an adhesive tape or paper tape is supplied as the step compensation member.

13. In paragraph 1, The above 4th step is A method for manufacturing a unit cell of an all-solid-state secondary battery, further comprising a step of continuously removing the pressurized step compensation member.

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