Method for activating all-solid-state battery

Abstract

The present invention relates to a method for activating an all-solid-state battery comprising a positive electrode, a negative electrode, and a solid electrolyte layer interposed between the positive electrode and the negative electrode, the method comprising: a first charging step of charging the all-solid-state battery at a first current density; and a first discharging step of discharging the all-solid-state battery at a second current density greater than the first current density after the first charging step.

Description

Activation method of all-solid-state batteries

[0001] This application claims the benefit of priority from Republic of Korea Patent Application No. 10-2023-0187488, dated December 20, 2023, and all contents of that Republic of Korea patent application are incorporated herein by reference.

[0002] The present invention relates to a method for activating an all-solid-state battery.

[0003] Lithium secondary batteries have been mainly applied to small fields such as mobile devices and laptop computers, but recently, the research direction is expanding to medium and large fields such as energy storage systems (ESS) and electric vehicles (EVs).

[0004] For these medium and large-sized lithium secondary batteries, unlike small ones, the operating environment (e.g., temperature, shock) is harsher, and more batteries must be used, so safety must be secured along with excellent performance and an appropriate price.

[0005] Most commercially available lithium secondary batteries utilize organic liquid electrolytes, which consist of lithium salts dissolved in flammable organic solvents. This poses a potential risk of leakage, fire, and explosion. Therefore, replacing these liquid electrolytes with solid electrolytes is gaining attention as a viable solution to address these safety concerns.

[0006] Lithium secondary batteries using solid electrolytes offer increased safety, improved reliability by preventing electrolyte leakage, and the ease of manufacturing thin batteries. Furthermore, the use of lithium metal as the anode enhances energy density. Consequently, solid electrolytes are attracting attention as next-generation batteries, promising applications in both compact secondary batteries and high-capacity secondary batteries for electric vehicles.

[0007] However, lithium secondary batteries using solid electrolytes have lower ionic conductivity than liquid electrolytes, and their output characteristics deteriorate, especially at low temperatures. Furthermore, solid electrolytes have lower surface adhesion to active materials than liquid electrolytes, and the volume of the active material expands during the charge / discharge process, increasing interfacial resistance. Furthermore, solid electrolytes are distributed in a non-contact state with the electrode active material, which reduces output characteristics and capacity compared to the amount of conductive material introduced.

[0008] In addition, even in the case of lithium secondary batteries using solid electrolytes, lithium dendrites are inevitably generated during the charging and discharging process of the battery, and lithium dendrites formed in a dendritic shape can grow by penetrating the solid electrolyte as described above, causing reversible lithium loss and short-circuiting of the battery, and are evaluated as factors that have a negative impact on the lifespan of lithium secondary batteries.

[0009] As a solution to these problems, a 'pressurization process' is implemented to apply external force during the operation of lithium secondary batteries using solid electrolytes. However, it is difficult to completely resolve the problem caused by lithium dendrites growing unevenly due to these external factors.

[0010] [Prior Art Literature]

[0011] [Patent Document]

[0012] (Patent Document 1) Republic of Korea Patent Publication No. 10-2016-0091375 (August 2, 2016)

[0013] The purpose of the present invention is to provide a method for activating an all-solid-state battery, which improves the lifespan characteristics of the battery by suppressing the formation of lithium dendrites in the all-solid-state battery through a process of high-rate discharge at a current density greater than the current density at the time of initial charging in the activation process of the all-solid-state battery.

[0014] One embodiment of the present invention provides a method for activating an all-solid-state battery including a positive electrode, a negative electrode, and a solid electrolyte layer interposed between the positive electrode and the negative electrode, the method comprising a first charging step of charging the all-solid-state battery at a first current density, and a first discharging step of discharging the all-solid-state battery at a second current density greater than the first current density after the first charging step.

[0015] The range of the above first current density may be 0.05 to 0.33 C.

[0016] The range of the second current density may be 1.0 to 2.5 C.

[0017] The charging and discharging process, in which the first charging step and the first discharging step are performed as one cycle, may be performed 3 to 10 times.

[0018] The negative electrode may include a current collector, and a lithium precipitation layer may be formed between the negative electrode and the solid electrolyte layer after the first charging step.

[0019] The thickness of the lithium precipitation layer may be 20 to 40 μm.

[0020] The above positive electrode may include at least one of a sulfide-based solid electrolyte, an oxide-based solid electrolyte, and a polymer-based solid electrolyte.

[0021] According to the present invention, by performing a high-rate discharge at a current density greater than the current density at which an all-solid-state battery is initially charged, the formation of lithium dendrites is suppressed, or poor interface contact within the battery caused by uneven electrode formation due to unevenly deposited lithium dendrites is resolved, thereby improving the capacity and life characteristics of an all-solid-state battery.

[0022] Figure 1 is a graph showing the life characteristics of an all-solid-state battery according to an activation method of an all-solid-state battery according to one embodiment and a comparative example of the present invention.

[0023] Hereinafter, embodiments of the present invention will be described in detail. Prior to this, terms and words used in this specification and claims should not be interpreted as limited to their conventional or dictionary meanings. Rather, they should be interpreted with meanings and concepts that conform to the technical spirit of the present invention, based on the principle that the inventor can appropriately define the concept of a term to best explain his or her invention. Accordingly, the configurations described in the embodiments described in this specification are merely the most preferred embodiments of the present invention and do not represent all of the technical spirit of the present invention. Therefore, it should be understood that various equivalents and modified examples may exist as of the time of this application.

[0024] Throughout this 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.

[0025] Additionally, the description that concretizes or adds components can be applied to all inventions unless there are special limitations, and is not limited to a specific invention.

[0026] Additionally, throughout the description and claims of the invention herein, the singular includes the plural unless otherwise stated.

[0027] Additionally, throughout the description and claims of the present invention, the term "or" includes "and" unless otherwise stated. Therefore, "comprising A or B" means all three cases of including A, including B, or including A and B.

[0028] Additionally, all numerical ranges include the extreme values ​​and all intermediate values ​​between them, unless explicitly stated otherwise.

[0029]

[0030] Activation method of all-solid-state batteries

[0031] Hereinafter, the method for activating the all-solid-state battery of the present invention will be described in detail.

[0032] The method for activating an all-solid-state battery of the present invention is a method for activating an all-solid-state battery including a positive electrode, a negative electrode, and a solid electrolyte layer interposed between the positive electrode and the negative electrode, comprising a first charging step of charging the all-solid-state battery at a first current density, and a first discharging step of discharging the all-solid-state battery at a second current density greater than the first current density after the first charging step.

[0033] Recently, in order to solve the problems caused by leakage, ignition, and explosion of the electrolyte that occur due to the use of liquid electrolytes in existing lithium-ion batteries, all-solid-state batteries that use solid-state electrolytes are being actively studied. Among these, research is also being actively conducted on the so-called "lithium precipitation type negative electrode" in which lithium is precipitated between the negative electrode current collector and the solid electrolyte layer during the operation of the all-solid-state battery, forming a lithium precipitation layer.

[0034] The above lithium precipitation type negative electrode may generally include a lithium precipitation layer including a composite in which metal nanoparticles capable of forming an alloy with lithium metal are supported on a carbon-based material or the like, as the metal nanoparticles have a lithophilic property with lithium metal.

[0035] In the case of an all-solid-state battery including such a lithium precipitation type negative electrode, as the charging and discharging process of the battery progresses, a phenomenon occurs in which lithium is precipitated or dissolved in the lithium precipitation layer formed between the solid electrolyte layer and the negative electrode current collector. At this time, the lithium precipitation may occur unevenly according to the reaction area depending on the electrode structure or external pressurization conditions of the all-solid-state battery.

[0036] In this way, lithium precipitated in an uneven manner in the lithium precipitation layer forms lithium dendrites in the form of resins, which grow by penetrating the solid electrolyte layer of the all-solid-state battery, thereby acting as a potential factor that can cause reversible lithium loss and short circuit of the all-solid-state battery.

[0037] To solve the problems of these all-solid-state batteries, all-solid-state batteries are usually operated in an environment where external pressure is applied, but the problem of unbalanced growth of lithium dendrite is not completely resolved even under the above-mentioned operating pressure conditions.

[0038] The present invention has been devised to solve a problem caused by unbalanced growth of lithium dendrites, particularly in an all-solid-state battery including a 'lithium precipitation layer' between a solid electrolyte layer and a negative electrode current collector, and the problem is solved by activating the all-solid-state battery through a first charging step of charging the all-solid-state battery including a positive electrode, a negative electrode, and a solid electrolyte layer interposed between the positive electrode and the negative electrode at a first current density and a first discharging step of discharging the all-solid-state battery at a second current density, and performing a high-rate discharging process in which the second current density of the discharging step is greater than the first current density of the first charging step.

[0039] An all-solid-state battery according to the present invention includes a positive electrode, a negative electrode, and a solid electrolyte layer interposed between the positive electrode and the negative electrode.

[0040] In one embodiment of the present invention, the positive electrode may include a positive electrode current collector and a positive electrode active material layer.

[0041] The above-mentioned positive electrode current collector is a conductive member that functions as a path for electrons that are emitted from the positive electrode toward an external load or that flow from a power source toward the positive electrode according to a battery reaction.

[0042] The above-described positive electrode current collector may generally have a thickness of 3 to 500 μm. The positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. The current collector may also form fine irregularities on its surface to increase the adhesive strength of the positive electrode active material, and may be in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0043] In addition, the above-mentioned positive electrode current collector may have a single-layer structure made of a single material, or may have a laminated structure in which layers made of such materials are appropriately combined. In the case of the current collector for reducing weight, it may include at least a conductive resin layer made of a conductive resin.

[0044] The above positive electrode active material layer may include a positive electrode active material, a solid electrolyte, a conductive material, and a binder.

[0045] There is no particular limitation on the material, as long as it is a lithium composite oxide material capable of reversible insertion and de-insertion of lithium ions. For example, it may include at least one of a composite oxide of cobalt, manganese, nickel, iron, or a combination thereof; and lithium.

[0046] For a more specific example, as the positive electrode active material, a compound represented by any one of the following chemical formulas may be used: Li a A 1-b R bD2 (in the above formula, 0.90 ≤ a ≤ 1.8 and 0 ≤ b ≤ 0.5); Li a E 1-b R b O 2-c D c (In the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, and 0 ≤ c ≤ 0.05); LiE 2-b R b O 4-c D c (In the above formula, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li a Ni 1-b-c Co b R c D α (In the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05 and 0 < α ≤ 2); Li a Ni 1-b-c Co b R c O 2-α Z α (In the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05 and 0 < α < 2); Li a Ni 1-b-c Co b R c O 2-α Z2 (in the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05 and 0 < α < 2); Li a Ni 1-b-c Mn b R c D α (In the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05 and 0 < α ≤ 2); Li a Ni 1-b-c Mn b R c O 2-α Z α (In the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05 and 0 < α < 2); Lia Ni 1-b-c Mn b R c O 2-α Z2 (in the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05 and 0 < α < 2); Li a Ni b E c G d O2 (in the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5 and 0.001 ≤ d ≤ 0.1); Li a Ni b Co c Mn d G e O2 (in the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, and 0 ≤ e ≤ 0.1); Li a NiG b O2 (in the above formula, 0.90 ≤ a ≤ 1.8 and 0.001 ≤ b ≤ 0.1); Li a CoG b O2 (in the above formula, 0.90 ≤ a ≤ 1.8 and 0.001 ≤ b ≤ 0.1); Li a MnG b O2 (in the above formula, 0.90 ≤ a ≤ 1.8 and 0.001 ≤ b ≤ 0.1); Li a Mn2G b O4 (wherein 0.90 ≤ a ≤ 1.8 and 0.001 ≤ b ≤ 0.1); QO2; QS2; LiQS2; V2O5; LiV2O5; LiTO2; LiNiVO4; Li (3-f) J2(PO4)3(0 ≤ f ≤ 2); Li (3-f) Fe2(PO4)3(0 ≤ f ≤ 2); and LiFePO4.

[0047] In the above chemical formula, A is Ni, Co, Mn or a combination thereof; R is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element or a combination thereof; D is O, F, S, P or a combination thereof; E is Co, Mn or a combination thereof; Z is F, S, P or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V or a combination thereof; Q is Ti, Mo, Mn or a combination thereof; T is Cr, V, Fe, Sc, Y or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu or a combination thereof.

[0048] In one embodiment of the present invention, the positive electrode active material may be included in an amount of 50 to 95 parts by weight based on 100 parts by weight of the entire positive electrode active material layer. For example, the content of the positive electrode active material may be 50 parts by weight or more, 60 parts by weight or more, 70 parts by weight or more, 75 parts by weight or more, 78 parts by weight or more, or 80 parts by weight or more, and may be 95 parts by weight or less, 90 parts by weight or less, or 85 parts by weight or less, based on 100 parts by weight of the entire positive electrode active material layer.

[0049] If the content of the positive electrode active material is less than 50 parts by weight based on 100 parts by weight of the entire positive electrode active material layer, there may be a problem of a decrease in the capacity and total energy density of the electrode, and if it exceeds 95 parts by weight, there may be a problem of an increase in the interfacial resistance between the positive electrode active material and the solid electrolyte due to an increase in voids in the positive electrode active material layer. Therefore, in the case of the positive electrode active material layer for an all-solid-state battery according to the present invention, it is necessary to appropriately control the content of the positive electrode active material within the above range.

[0050] The conductive material is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and examples thereof include graphite such as natural graphite or artificial graphite; carbon black such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and summer black; conductive fibers such as carbon fiber or metal fiber; metal powders such as fluorinated carbon, aluminum, and nickel powder; conductive whiskey such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives. The conductive material may be included in an amount of about 0.01 to 10 parts by weight, or 0.01 to 5 parts by weight, or 0.01 to 3 parts by weight, based on 100 parts by weight of the total positive electrode active material layer.

[0051] The above binder is a component added in consideration of the binding properties of the positive active material, solid electrolyte, and conductive material included in the positive active material layer, and may be any type of binder as long as it can be used for electrode formation in the technical field to which the present invention pertains. For example, the binder may be at least one selected from the group consisting of nitrile-butadiene rubber (NBR), polystyrene, and styrene-butadiene rubber (SBR), and preferably, the binder may be a butadiene rubber series binder such as nitrile-butadiene rubber (NBR) or styrene-butadiene rubber (SBR). The binder may be included in an amount of about 0.1 to 10 parts by weight based on 100 parts by weight of the entire positive active material layer.

[0052] If the content of the above binder is less than 0.1 parts by weight based on 100 parts by weight of the entire positive electrode active material layer, the adhesive strength of the electrode may decrease, which may cause problems with the processability and stability of the coated product. If it exceeds 10 parts by weight, the resistance of the electrode may increase, which may reduce the cell life and output characteristics. Therefore, it is appropriately adjusted within the above range.

[0053] In one embodiment of the present invention, the solid electrolyte may include at least one of a sulfide-based solid electrolyte, an oxide-based solid electrolyte, and a polymer-based solid electrolyte, and specifically, the solid electrolyte may include a sulfide-based solid electrolyte.

[0054] The sulfide-based solid electrolyte included in the above positive electrode active material layer may be, for example, represented by the following chemical formula 1.

[0055] [Chemical Formula 1]

[0056] Li a M b S c X d

[0057] In the above chemical formula 1, M is Sn, Mg, Ba, B, Al, Ga, In, Si, Ge, Pb, N, P, As, Sb, Bi, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Hf, Ta, W, or La, X is F, Cl, Br, I, Se, Te, or O, and 0 <a≤6, 0<b≤6, 0<c≤6 및 0<d≤6이다.

[0058] For example, in the above chemical formula 1, M can be B, Si, Ge, P or N.

[0059] For example, in the above chemical formula 1, X can be F, Cl, Br, I or O.

[0060] For example, the sulfide-based solid electrolyte represented by the above chemical formula 1 may be Li2S-P2S5-LiBr, Li2S-P2S5-LiCl-LiBr, Li2S-SiS2-LiBr, Li2S-P2S5, Li2S-P2S5-LiCl, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-GeS2, Li2S-SiS2-Li3PO4, or a combination thereof.

[0061] The above sulfide-based solid electrolyte may have an argyrodite-type crystal structure. Since the sulfide-based solid electrolyte has an argyrodite-type crystal structure, the purity and crystallinity of the sulfide-based solid electrolyte are high, and a stable interfacial phase is formed, thereby achieving a high energy density while significantly improving potential stability and ionic conductivity.

[0062] Examples of the above oxide-based solid electrolyte include compounds having a NASICON-type structure. An example of a compound having a NASICON-type structure is a compound having the general formula Li 1+x Al x Ge 2-x A compound (LAGP) represented by (PO4) 3 (0 ≤ x ≤ 2), general formula Li 1+x Al x Ti 2-x (PO4) 3 (0 ≤ x ≤ 2) compounds (LATP) are also mentioned. Also, other examples of oxide solid electrolytes include LiLaTiO (e.g., Li 0.34 La 0.51 TiO3), LiPON (e.g. Li 2.9 PO 3.3 N 0.46 ), LiLaZrO (e.g. Li7La3Zr2O 12 ) can be cited.

[0063] The above solid electrolyte may be included in an amount of 5 to 49 parts by weight based on 100 parts by weight of the entire positive electrode active material layer.

[0064] The content of the solid electrolyte may be, for example, 5 parts by weight or more, 6 parts by weight or more, 7 parts by weight or more, 8 parts by weight or more, 9 parts by weight or more, 10 parts by weight or more, 11 parts by weight or more, 12 parts by weight or more, 13 parts by weight or more, 14 parts by weight or more, 15 parts by weight or more, 16 parts by weight or more, 17 parts by weight or more, 18 parts by weight or more, 19 parts by weight or more, 19.4 parts by weight or more, and 49 parts by weight or less, 45 parts by weight or less, 40 parts by weight or less, 35 parts by weight or less, 30 parts by weight or less, 25 parts by weight or less, 24 parts by weight or less, 23 parts by weight or less, 22 parts by weight or less, 21 parts by weight or less, or 20 parts by weight or less, based on 100 parts by weight of the entire positive electrode active material layer. Preferably, the content of the solid electrolyte may be included in an amount of 12 to 20 parts by weight based on 100 parts by weight of the entire positive electrode active material layer.

[0065] If the content of the above solid electrolyte is less than 5 parts by weight based on 100 parts by weight of the entire positive electrode active material layer, there may be a problem that the voids in the positive electrode active material layer increase, causing the interfacial resistance between the positive electrode active material and the solid electrolyte to increase, resulting in a decrease in the capacity and total energy density of the electrode. If it exceeds 49 parts by weight, there may be a problem that the capacity and total energy density of the electrode to decrease. Therefore, it is necessary to appropriately adjust the content of the solid electrolyte within the above range.

[0066] The shape of the solid electrolyte may include, for example, a particle shape such as a sphere, an ellipse, a sphere, a thin film shape, etc., but when the shape of the solid electrolyte is a particle shape, the average particle diameter may be 0.1 to 5 ㎛. For example, the average particle diameter of the solid electrolyte may be 0.1 to 3 ㎛, 0.1 to 2 ㎛, 0.1 to 1 ㎛, 0.1 to 0.9 ㎛, 0.1 to 0.8 ㎛, 0.1 to 0.7 ㎛, 0.1 to 0.6 ㎛, or 0.1 to 0.5 ㎛. The average particle diameter of the solid electrolyte may be, for example, a volume-converted median diameter (D50) measured using a laser particle size distribution meter.

[0067] If the average particle size of the above solid electrolyte is less than 0.1 ㎛, the solid electrolyte particles may easily clump together or may not be uniformly distributed, causing them to be concentrated within the electrode, and there may be a problem that it may be difficult to form an effective interface between the positive electrode active material and the solid electrolyte. If it exceeds 5 ㎛, there may be a problem that pores may be generated in the positive electrode active material layer, reducing the ionic conductivity of the electrode. Therefore, it is desirable to appropriately adjust the solid electrolyte to have an average particle size within the above range.

[0068] The above-mentioned positive electrode active material layer can be manufactured according to a method widely known in the art, and is not limited to a specific manufacturing method, but for example, it can be manufactured by a dry electrode process method in which the positive electrode active material, a solid electrolyte, a conductive material, and a binder are mixed to manufacture a dough and then the manufactured dough is sheeted, or a wet process in which the positive electrode mixture is manufactured in a slurry state by mixing in a solvent and then the positive electrode mixture is applied to a positive electrode current collector.

[0069] The above-described positive electrode active material layer may further include additives such as fillers, coating agents, dispersants, and ion-conducting aids in addition to the above-described positive electrode active material, solid electrolyte, conductive agent, and binder. The fillers, coating agents, dispersants, ion-conducting aids, and the like may be known materials generally used in electrodes of all-solid-state batteries.

[0070] The thickness of the positive electrode active material layer may vary depending on the configuration of the intended all-solid-state battery, but is preferably in the range of 0.1 µm to 1,000 µm, and more preferably 40 µm to 100 µm.

[0071] The above solid electrolyte layer is a layer interposed between the positive electrode and the negative electrode, which contains a solid electrolyte as its main component. The solid electrolyte layer contains a solid electrolyte, and the solid electrolyte may be the same as or different from the solid electrolyte contained in the positive electrode active material layer. Since the specific type thereof is the same as that described for the positive electrode active material layer, a detailed description thereof will be omitted.

[0072] The elastic modulus of the solid electrolyte layer, i.e., Young's modulus, may be, for example, 35 GPa or less, 30 GPa or less, 27 GPa or less, 25 GPa or less, or 23 GPa or less. The elastic modulus of the solid electrolyte layer, i.e., Young's modulus, may be, for example, 10 to 35 GPa, 15 to 35 GPa, 15 to 30 GPa, or 15 to 25 GPa. Since the solid electrolyte layer has an elastic modulus in this range, pressurization and / or sintering of the solid electrolyte included in the solid electrolyte layer may be performed more easily.

[0073] The above solid electrolyte layer further includes, for example, a binder. The binder included in the solid electrolyte layer is not limited to, but may include, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, etc., and any binder used in the relevant technical field may be used. The binder of the solid electrolyte layer may be the same as or different from the binder of the positive electrode active material layer.

[0074] The thickness of the solid electrolyte layer may vary depending on the configuration of the intended all-solid-state battery, and from the viewpoint of improving the volumetric energy density of the battery, it may be preferably 600 μm or less, more preferably 500 μm or less or 400 μm or less. Meanwhile, there is no particular limitation on the lower limit of the thickness of the solid electrolyte layer, but it may preferably be 1 μm or more, 5 μm or more, or 10 μm or more.

[0075] In one embodiment of the present invention, the negative electrode may include a negative electrode current collector, and may include a lithium precipitation layer formed by precipitation of lithium between the solid electrolyte layer and the negative electrode current collector according to charge and discharge operation of the all-solid-state battery.

[0076] The above-described negative current collector is a conductive member that functions as a path for electrons that are emitted from the negative electrode toward the power source or that flow into the negative electrode from an external source according to the charge / discharge behavior of the battery. The negative current collector is composed of, for example, a material that does not react with lithium, i.e., does not form an alloy or a compound. The material constituting the negative current collector is, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni), but is not necessarily limited thereto, and any material that is used as an electrode current collector in the relevant technical field may be used. The negative current collector may be composed of one type of the above-described metal, or may be composed of an alloy or a coating material of two or more types of metals. The negative current collector is, for example, in the form of a plate or a foil.

[0077] The above negative electrode may further include additives used in conventional all-solid-state batteries, such as fillers, dispersants, and ionic conductors.

[0078] In one embodiment of the present invention, a lithium precipitation layer may further be included between the negative electrode current collector and the solid electrolyte layer.

[0079] The above lithium precipitation layer is formed as lithium metal is precipitated on the negative electrode current collector during the charging process of the all-solid-state battery, and the lithium precipitation layer composed of the lithium metal precipitated in this way can function as the negative electrode active material layer of the all-solid-state battery according to the present invention. Therefore, in the charging step of the all-solid-state battery, lithium ions are precipitated on the negative electrode current collector, and the thickness of the lithium precipitation layer increases, and conversely, in the discharging step, the thickness of the lithium precipitation layer decreases as the lithium metal in the lithium precipitation layer is dissolved (or ionized).

[0080] For example, the thickness of the lithium precipitation layer when the all-solid-state battery is fully charged may be 20 to 40 μm.

[0081] The above all-solid-state battery can be manufactured by manufacturing the positive electrode, the solid electrolyte layer, and the negative electrode separately and then sequentially stacking them.

[0082] In one embodiment of the present invention, the electrode assemblies stacked in the above order may be structured to be housed in a case such as a pouch. In addition, two or more electrode assemblies may be stacked to produce an all-solid-state battery.

[0083] The above-described all-solid-state battery may further include an elastic sheet on the outer side of at least one of the positive electrode current collector and the negative electrode current collector. The elastic sheet may be expressed as a buffer layer or an elastic layer, and may serve to ensure uniform transmission of pressure to the electrode stack to improve contact between solid components, and may also alleviate stress transmitted to the solid electrolyte, etc., and may serve to suppress cracks from occurring in the solid electrolyte due to stress accumulation according to changes in the thickness of the electrode during charge and discharge.

[0084] In one embodiment of the present invention, an all-solid-state battery having the above-described positive electrode, negative electrode, and a solid electrolyte layer interposed between the positive electrode and negative electrode undergoes a first charging step of charging at a first current density, and lithium is precipitated in a space portion between the solid electrolyte layer and the negative electrode current collector to form the lithium precipitation layer.

[0085] However, the solid electrolyte layer and the negative electrode current collector are both made of solid materials, and therefore have numerous irregularities on their surfaces. As the charging stage of the all-solid-state battery progresses, there is a strong tendency for lithium metal to precipitate starting from the portion where the irregularities of the solid electrolyte layer and the negative electrode current collector come into contact to form a contact point.

[0086] In addition, lithium metal grown based on this tendency forms lithium dendrites in the form of resins, and the lithium dendrites grow by penetrating the solid electrolyte layer, thereby causing reversible lithium loss in the all-solid-state battery and short circuiting of the battery.

[0087] In one embodiment of the present invention, an all-solid-state battery that has undergone a first charging step of charging at the first current density undergoes a first discharging step of discharging at a second current density greater than the first current density, thereby causing lithium metal to react with lithium metal having a relatively long length and induce dissolution, thereby suppressing the growth of lithium dendrites in the dendritic form, by reacting with lithium metal formed in a lithium precipitation layer, that is, starting from a point where the irregularities of the solid electrolyte layer and the negative electrode current collector come into contact to form a contact point.

[0088] In other words, in the process of performing the first discharge step, if a low-rate discharge process using a current density similar to that of the first charge step is performed, the lithium metal formed in the lithium precipitation layer is uniformly distributed to the entire area of ​​the lithium precipitation layer as lithium ions (Li). + ), so that the morphology of the lithium metal formed in the first charging step is maintained as it is, and it is difficult to suppress the growth of lithium dendrites formed as the charging and discharging process of the all-solid-state battery is repeated. On the other hand, the method for activating an all-solid-state battery according to the present invention has the effect of suppressing the growth of such lithium dendrites by performing a high-rate discharge process using a second current density greater than the first current density in the first discharge step.

[0089] In one embodiment of the present invention, the first current density of the first charging step may have a range of 0.05 to 0.33 C, for example, 0.08 to 0.3 C, preferably 0.1 to 0.25 C.

[0090] If the first current density of the first charging step is less than 0.05 C, there is a concern that productivity may decrease as the time required for activation of the all-solid-state battery increases, and if it exceeds 0.33 C, there may be a problem that non-uniform precipitation of lithium metal between the solid electrolyte layer and the negative electrode current collector becomes more severe.

[0091] In one embodiment of the present invention, the second current density of the first discharge step may have a range of 1 to 2.5 C, for example, 1.25 to 2.25 C, preferably 1.5 to 2 C.

[0092] When the second current density of the first discharge step is less than 1 C, the effect of suppressing the formation of lithium dendrites as charging and discharging continues may be minimal as the lithium metal formed in the lithium precipitation layer in the discharge step of the all-solid-state battery does not dissolve from its peak, and when it exceeds 2.5 C, there may be a problem in that the all-solid-state battery is not sufficiently discharged as the internal resistance increases due to the large current.

[0093] In one embodiment of the present invention, when the first charging step and the first discharging step are defined as 'one cycle' of the charging and discharging process, the charging and discharging process can be performed 3 to 10 times.

[0094] If the above charging and discharging process is performed less than 3 times, the planarization effect of the lithium metal formed in the lithium precipitation layer during the discharge stage of the all-solid-state battery may be minimal, and if the above charging and discharging process exceeds 10 times, the planarization of the lithium metal may have already progressed sufficiently and there may be no additional planarization effect.

[0095] As described above, the all-solid-state battery according to the present invention stably exhibits excellent discharge capacity, output characteristics, and capacity retention rate, and is therefore useful in portable devices such as mobile phones, laptop computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs).

[0096] Accordingly, according to another embodiment of the present invention, a battery module including the all-solid-state battery as a unit cell and a battery pack including the same are provided.

[0097] The above battery module or battery pack can be used as a power source for one or more medium- to large-sized devices, such as a power tool; an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0098] Below, specific embodiments of the present invention are presented. However, the embodiments described below are intended solely to specifically illustrate or explain the present invention and are not intended to limit the scope of the invention. Furthermore, any details not described herein are technically feasible to those skilled in the art and thus are omitted.

[0099]

[0100] Manufacturing example: Manufacturing of all-solid-state batteries

[0101] (1) Manufacturing of anode

[0102] Based on 100 parts by weight of the total positive electrode layer, LiNi having a particle size (D50) of 5㎛ as the positive electrode active material 0.8 Co 0.1 Mn 0.1 78 parts by weight of O2 powder, 19.5 parts by weight of lithium argyrodite-type solid electrolyte Li6PS5Cl, 1.5 parts by weight of carbon black conductive agent, and 1.0 parts by weight of styrene-butadiene rubber (SBR) binder are added to a xylene solvent, 2 mm zirconia balls are added, and the mixture is stirred with a sinky mixer to prepare a slurry.

[0103] The manufactured slurry is applied to one side of an aluminum current collector having a thickness of 15 μm, which is a positive electrode current collector, and dried in a vacuum oven at 100°C for 8 hours to prepare a positive electrode of an all-solid-state battery.

[0104] (2) Manufacturing of solid electrolyte layer

[0105] A lithium argyrodite-type solid electrolyte Li6PS5Cl is added to a binder solution in which an acrylic binder (SX-A334, Zeon) is dissolved in an isobutyl isobutyrate (IBIB) solvent, and the solution is stirred in a sinky mixer to adjust the viscosity to an appropriate level. After adjusting the viscosity, 2 mm zirconia balls are added and stirred again in a sinky mixer to prepare a slurry. The slurry contains 98.5 wt% of the solid electrolyte and 1.5 wt% of the binder. The slurry is applied on a release PET film using a bar coater and dried at room temperature to prepare a solid electrolyte layer.

[0106] (3) Manufacturing of all-solid-state batteries

[0107] The prepared positive electrode and solid electrolyte layer are cut together with a negative electrode current collector made of nickel foil, and the positive electrode, solid electrolyte layer, and negative electrode current collector are laminated in that order, then sealed in a pouch shape and subjected to a warm isostatic press (WIP) at a high temperature of 80°C and 500 MPa for 30 minutes to manufacture an all-solid-state battery.

[0108] In a pressurized state, the thickness of the positive electrode is about 100 μm, the thickness of the negative electrode current collector is about 7 μm, and the thickness of the solid electrolyte layer is about 60 μm.

[0109]

[0110] Example 1: Activation of an all-solid-state battery

[0111] The all-solid-state battery manufactured in the above manufacturing example was subjected to a first charging step at a first current density of 0.1 C until the battery voltage became 4.2 V, and then a first discharging step was performed at a second current density of 1.5 C until the battery voltage became 3.0 V.

[0112] After repeating the above charge / discharge cycle 5 times, which is one cycle, 50 charge / discharge cycles were performed at 0.33 C.

[0113] The discharge capacity for each cycle was measured using a charge / discharge evaluation device “TOSCAT-3000” (trade name, manufactured by Toyo Systems).

[0114]

[0115] Comparative Example 1: Activation of an All-Solid-State Battery

[0116] The all-solid-state battery manufactured in the above manufacturing example was subjected to a first charging step at a first current density of 0.1 C until the battery voltage became 4.2 V, and then a first discharging step was performed at a first current density of 0.1 C until the battery voltage became 3.0 V.

[0117] After repeating the above charge / discharge cycle 5 times, which is one cycle, 50 charge / discharge cycles were performed at 0.33 C.

[0118] The discharge capacity for each cycle was measured using a charge / discharge evaluation device “TOSCAT-3000” (trade name, manufactured by Toyo Systems).

[0119]

[0120] The capacity retention rate of the discharge capacity of the all-solid-state battery according to Example 1 and Comparative Example 1 was measured, and the results are shown in Fig. 1.

[0121] Referring to FIG. 1, in the case of the all-solid-state battery according to Example 1, it can be confirmed that the capacity retention rate is greatly improved compared to the all-solid-state battery according to Comparative Example 1 at the 50th cycle point as a result of performing a high-rate discharge through a second current density greater than the first current density in the first discharge step.

[0122] This can be understood as an improvement in the lifespan characteristics of the all-solid-state battery, as the lithium metal formed in the lithium precipitation layer is dissolved into lithium ions from its tip during the discharge step at a higher current density than during the charge step, thereby suppressing the formation of dendrites.

[0123]

[0124] Although the preferred embodiments of the present invention 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 concept of the present invention defined in the following claims also fall within the scope of the present invention.

Claims

1. Bipolar; cathode; and A method for activating an all-solid-state battery including a solid electrolyte layer interposed between the positive and negative electrodes, A first charging step of charging the above-mentioned all-solid-state battery at a first current density; and It comprises a first discharging step for discharging at a second current density greater than the first current density after the first charging step. Method for activating an all-solid-state battery.

2. In paragraph 1, The range of the above first current density is 0.05 to 0.33 C. Method for activating an all-solid-state battery.

3. In paragraph 1, The range of the second current density is 1.0 to 2.5 C, Method for activating an all-solid-state battery.

4. In paragraph 1, The charging and discharging process, which comprises the first charging step and the first discharging step as one cycle, is performed 3 to 10 times. Method for activating an all-solid-state battery.

5. In paragraph 1, The above cathode comprises a current collector, Characterized in that after the first charging step, a lithium precipitation layer is formed between the negative electrode and the solid electrolyte layer. Method for activating an all-solid-state battery.

6. In paragraph 5, The thickness of the lithium precipitation layer is 20 to 40 ㎛. Method for activating an all-solid-state battery.

7. In paragraph 1, The above anode comprises at least one of a sulfide-based solid electrolyte, an oxide-based solid electrolyte, and a polymer-based solid electrolyte. Method for activating an all-solid-state battery.

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