Activation method of all-solid-state battery

Abstract

The present invention relates to an activation method for an all-solid-state battery, the all-solid-state battery comprising: a positive electrode, a negative electrode, and a solid electrolyte layer sandwiched 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

Technical Field

[0001] This application claims priority to Korean Patent Application No. 10-2023-0187488, filed on December 20, 2023, the disclosure of which is incorporated herein by reference as part of this specification.

[0002] This invention relates to an activation method for an all-solid-state battery. Background Technology

[0003] Although lithium-ion batteries are primarily used in small applications such as mobile devices and laptops, research has recently expanded to medium and large applications such as energy storage systems (ESS) and electric vehicles (EVs).

[0004] These medium and large-sized lithium rechargeable batteries, unlike small lithium rechargeable batteries, operate in more demanding environments (such as temperature and shock) and require more batteries. Therefore, they need to ensure safety while maintaining good performance and affordable prices.

[0005] Most commercially available lithium-ion batteries currently use organic liquid electrolytes, which are lithium salts dissolved in flammable organic solvents. This poses potential risks of leakage, fire, and explosion. Therefore, the use of solid electrolytes to replace organic liquid electrolytes as an alternative to overcome these safety issues has attracted attention.

[0006] Lithium-ion batteries using solid electrolytes offer advantages such as improved safety, enhanced reliability through prevention of electrolyte leakage, and ease of manufacturing thin batteries. Furthermore, lithium metal can be used as a negative electrode to improve energy density, and it holds promise for applications in small secondary batteries and high-capacity secondary batteries for electric vehicles, making it a next-generation battery.

[0007] However, lithium-ion batteries using solid electrolytes have lower ionic conductivity and poorer output characteristics compared to liquid electrolytes, especially at low temperatures. Furthermore, there are other issues such as: poorer surface adhesion between solid electrolytes and active materials compared to liquid electrolytes; increased interfacial resistance due to volume expansion of active materials during charging and discharging; and the fact that solid electrolytes are distributed without direct contact with electrode active materials, leading to a decrease in output or capacity characteristics relative to the amount of conductive material used.

[0008] Furthermore, in the case of lithium secondary batteries using solid electrolytes, lithium dendrites are inevitably generated during the battery charging and discharging process. The dendritic lithium dendrites can grow through the solid electrolyte, causing reversible lithium loss and battery short circuits. This is considered a factor that adversely affects the lifespan of lithium secondary batteries.

[0009] As a solution to this problem, an external force is applied during the operation of lithium secondary batteries using solid electrolytes through a "pressurization process." However, even this external factor cannot completely solve the problem caused by the uneven growth of lithium dendrites.

[0010] [Existing Technical Documents]

[0011] [Patent Literature]

[0012] (Patent Document 1) Korean Patent Application Publication No. 10-2016-0091375 (August 2, 2016) Summary of the Invention

[0013] [Technical Issues]

[0014] The purpose of this invention is to provide a method for activating an all-solid-state battery by discharging the battery at a high rate with a current density higher than that at the initial charging stage to suppress the formation of lithium dendrites in the all-solid-state battery, thereby improving the battery's lifespan characteristics.

[0015] [Technical Solution]

[0016] An example of the present invention provides an activation method for an all-solid-state battery, the all-solid-state battery comprising: a positive electrode, a negative electrode, and a solid electrolyte layer sandwiched 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.

[0017] The first current density can be from 0.05 to 0.33 C.

[0018] The second current density can be from 1.0 to 2.5 C.

[0019] The first charging step and the first discharging step are defined as one cycle, which can be performed 3 to 10 times.

[0020] The negative electrode may include a current collector, wherein a lithium deposition layer is formed between the negative electrode and the solid electrolyte layer after the first charging step.

[0021] The thickness of the lithium deposited layer can be 20 to 40 μm.

[0022] The positive electrode may contain one or more of the following: sulfide solid electrolyte, oxide solid electrolyte, and polymer solid electrolyte.

[0023] [Beneficial Effects]

[0024] According to the present invention, by discharging the all-solid-state battery at a high rate with a current density higher than that used for initial charging of the battery, the formation of lithium dendrites can be suppressed or the interface contact defects of the battery caused by unevenly precipitated lithium dendrites can be resolved, thereby improving the capacity and lifespan characteristics of the all-solid-state battery. Attached Figure Description

[0025] Figure 1 The graph illustrates the lifetime characteristics of all-solid-state batteries prepared by the activation methods of the all-solid-state batteries of the embodiments and comparative examples of the present invention. Detailed Implementation

[0026] The following provides a detailed description of examples of the present invention. The terms and words used in this specification and claims should not be construed as having their conventional or dictionary meanings, but rather should be interpreted as meanings and concepts consistent with the technical concept of the invention, based on the principle that the inventor can define the concepts of the terms in a manner they deem appropriate in order to best illustrate their invention. Therefore, it should be understood that the configurations described in the examples herein are merely the most preferred embodiments of the invention and do not represent all the technical concepts of the invention; various equivalents and modifications may exist at the time of application.

[0027] Throughout this specification, whenever any part “contains” any ingredient, unless otherwise expressly stated, it means that it may contain more other ingredients, rather than that it does not contain any other ingredients.

[0028] Furthermore, unless otherwise specified, descriptions of limiting or further specifying ingredients may apply to any invention and are not limited to any particular invention.

[0029] Furthermore, throughout the specification and claims of this invention, unless otherwise stated, singular terms include plural terms.

[0030] Furthermore, throughout the entire specification and claims of this invention, unless otherwise stated, "or" includes "and". Therefore, "comprising A or B" means all three of the above: comprising A, comprising B, or comprising both A and B.

[0031] Furthermore, all numerical ranges include the values ​​at both ends and all intermediate values ​​in between, unless explicitly stated otherwise.

[0032] Activation method of all-solid-state batteries

[0033] The activation method of the all-solid-state battery of the present invention will be described in detail below.

[0034] The activation method of the all-solid-state battery of the present invention activates an all-solid-state battery comprising a positive electrode, a negative electrode and a solid electrolyte layer sandwiched between the positive electrode and the negative electrode. The method includes: 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.

[0035] In recent years, in order to solve the problems of electrolyte leakage, fire and explosion caused by the use of liquid electrolytes in traditional lithium-ion batteries, research is being actively conducted on all-solid-state batteries using solid electrolytes. Among them, research on the so-called "lithium deposition negative electrode" technology, in which lithium is deposited between the negative electrode current collector and the solid electrolyte layer to form a lithium deposition layer during the driving process of all-solid-state batteries, is being actively carried out.

[0036] The lithium-deposited negative electrode may include a lithium-deposited layer containing a composite of metal nanoparticles that are generally lithiophilic to lithium metal and thus can form alloys with lithium metal, immersed in a carbon-based material.

[0037] In the case of an all-solid-state battery containing this lithium-deposited negative electrode, as the battery is charged and discharged, lithium deposition or dissolution occurs in the lithium deposition layer formed between the solid electrolyte layer and the negative electrode current collector. Lithium deposition may occur unevenly depending on the reaction area of ​​the electrode structure of the all-solid-state battery or the external pressure conditions.

[0038] Therefore, lithium deposited in the lithium deposition layer in a biased manner forms dendritic lithium dendrites, which grow through the solid electrolyte layer of the all-solid-state battery, potentially leading to reversible lithium loss and battery short circuits.

[0039] To address this issue with all-solid-state batteries, they are typically driven under external pressure. However, even under these pressure conditions, the unbalanced growth of lithium dendrites has not been completely resolved.

[0040] The present invention aims to solve the problem caused by unevenly grown lithium dendrites (especially in all-solid-state batteries containing a "lithium deposited layer" between the solid electrolyte layer and the negative electrode current collector), and solves the problem by a first charging step of charging the all-solid-state battery, which includes a positive electrode, a negative electrode and a solid electrolyte layer sandwiched between the positive and negative electrodes, at a first current density, and a first discharging step of discharging the battery at a second current density, wherein the second current density of the discharging step is greater than the first current density of the first charging step, as a high-rate discharge process.

[0041] The all-solid-state battery of the present invention comprises a positive electrode, a negative electrode, and a solid electrolyte layer sandwiched between the positive electrode and the negative electrode.

[0042] In one embodiment of the present invention, the positive electrode may include a positive current collector and a positive active material layer.

[0043] The positive current collector is a conductive component that depends on the battery response as a channel for electrons to flow from the positive terminal to the external load or from the power source to the positive terminal.

[0044] The thickness of the positive electrode current collector can typically range from 3 μm to 500 μm. There are no particular limitations on the positive electrode current collector, as long as it has high conductivity and does not cause chemical changes in the battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel with a surface treated with carbon, nickel, titanium, or silver can be used. The current collector can also have fine irregularities formed on its surface to increase the adhesion of the positive electrode active material, and it can take the form of a film, sheet, foil, mesh, porous material, foam, non-woven fabric, etc.

[0045] Furthermore, the positive current collector can be a single-layer structure of a single material, or a laminated structure comprising any suitable combination of these materials. From the perspective of reducing the weight of the current collector, it can include at least a conductive resin layer composed of a conductive resin.

[0046] The positive electrode active material layer may include positive electrode active material, solid electrolyte, conductive material and binder.

[0047] There are no particular restrictions, as long as it is a lithium composite oxide material capable of reversibly inserting and extracting lithium ions. For example, it can contain one or more of cobalt, manganese, nickel, iron, or combinations thereof with lithium in a composite oxide.

[0048] As a more specific example, compounds represented by any of the following chemical formulas can be used as positive electrode active materials: Li a A 1-b R b D2 (where 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5); Li a E 1-b R b O 2-c D c (Where, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); LiE 2-b R b O 4-c D c (Where, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li a Ni 1-b-c Co b R c D α(wherein, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0< α ≤ 2); Li a Ni 1-b-c Co b R c O 2-α Z α (wherein, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤0.05, 0 < α < 2); Li a Ni 1-b-c Co b R c O 2-α Z2 (wherein, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Mn b R c D α (wherein, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c≤ 0.05, 0 < α ≤ 2); Li a Ni 1-b-c Mn b R c O 2-α Z α (wherein, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Mn b R c O 2-α Z2 (wherein, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni b E c G d O2 (of which, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1); Li a Ni b Co c Mn d G e O2 (of which, 0.90 ≤ a ≤ 1.8, 0 ≤ b≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤0.5, 0 ≤ e ≤ 0.1); Li a NiGb O2 (where 0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li a CoG b O2 (where 0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li a MnG b O2 (where 0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li a Mn2G b O4 (where 0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); QO2; QS2; LiQS2; V2O5; LiV2O5; LiTO2; LiNiVO4; Li (3-f) J2(PO4)3 (where 0 ≤ f ≤ 2); Li (3-f) Fe2(PO4)3 (where 0 ≤ f ≤ 2); and LiFePO4.

[0049] In the above formula, A is Ni, Co, Mn or a combination thereof; R is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements 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 any combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V or any combination thereof; Q is Ti, Mo, Mn or any combination thereof; T is Cr, V, Fe, Sc, Y or any combination thereof; J is V, Cr, Mn, Co, Ni, Cu or any combination thereof.

[0050] In one embodiment of the present invention, based on a total of 100 parts by weight of the positive electrode active material layer, the content of the positive electrode active material can be from 50 parts by weight to 95 parts by weight. For example, based on all 100 parts by weight of the positive electrode active material layer, the content of the positive electrode active material can 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 is less than 95 parts by weight, less than 90 parts by weight, or less than 85 parts by weight.

[0051] If the content of positive active material is less than 50 parts by weight based on 100 parts by weight of the total positive active material layer, there may be a problem of reduced electrode capacity and overall energy density. If it exceeds 95 parts by weight, there may be a problem of increased interfacial resistance between the positive active material and the solid electrolyte due to increased porosity in the positive active material layer. Therefore, for the positive active material layer of the all-solid-state battery of the present invention, the content of positive active material needs to be appropriately controlled within the above range.

[0052] There are no particular restrictions on conductive materials, as long as they are conductive and do not cause chemical changes in the battery. Examples include graphite, such as natural or artificial graphite; carbon black, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermally cracked carbon black; conductive fibers, such as carbon fibers or metal fibers; fluorides; metal powders, such as aluminum or nickel powder; conductive whiskers, such as zinc oxide or potassium titanate; conductive metal oxides, such as titanium dioxide; and conductive materials, such as polyphenylene derivatives. Based on 100 parts by weight of all positive electrode active material layers, the content of conductive material can be 0.01 to 10 parts by weight, or 0.01 to 5 parts by weight, or 0.01 to 3 parts by weight.

[0053] The binder is a component added to improve the adhesion of the positive electrode active material, solid electrolyte, and conductive material contained in the positive electrode active material layer. It can be any type applicable to electrode formation in this technical field, for example, at least one selected from the group consisting of nitrile rubber (NBR), polystyrene, and styrene-butadiene rubber (SBR), preferably a binder from the butadiene rubber family, such as nitrile rubber (NBR) or styrene-butadiene rubber (SBR). Based on 100 parts by weight of the total positive electrode active material layer, the binder content can be from 0.1 to 10 parts by weight.

[0054] If the binder content is less than 0.1 parts by weight based on 100 parts by weight of the total positive electrode active material layer, the electrode adhesion may decrease, which may cause problems with processability and the stability of the coated product. If it exceeds 10 parts by weight, the electrode resistance may increase, which may reduce battery life and output characteristics. Therefore, it should be appropriately adjusted within the above range.

[0055] In one embodiment of the present invention, the solid electrolyte may include one or more of sulfide solid electrolytes, oxide solid electrolytes and polymer solid electrolytes, and more specifically, the solid electrolyte may include sulfide solid electrolytes.

[0056] The sulfide-based solid electrolyte contained in the positive electrode active material layer can be represented, for example, by the following chemical formula 1.

[0057] [Chemical Formula 1]

[0058] Li a M b S c X d

[0059] Where 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, and X is F, Cl, Br, I, Se, Te, or O, and 0 <a≤6,0<b≤6,0<c≤6,0<d≤6。

[0060] For example, in chemical formula 1, M can be B, Si, Ge, P, or N.

[0061] For example, in chemical formula 1, X can be F, Cl, Br, I, or O.

[0062] For example, the sulfide solid electrolyte represented by the above chemical formula 1 can 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 any combination thereof.

[0063] Sulfide solid electrolytes can possess a sulforaphite-germanium ore-type crystal structure. Due to this structure, sulfide solid electrolytes exhibit high purity and crystallinity, can form stable interfacial phases, possess high energy density, and significantly improve potential stability and ionic conductivity.

[0064] This oxide-based solid electrolyte includes, for example, compounds having a NASICON structure. Examples of compounds having a NASICON structure include those derived from the general formula Li. 1+x Al x Ge 2-x Compounds represented by (PO4)3 (where 0 ≤ x ≤ 2) (LAGP), and compounds derived from the general formula Li 1+x Al x Ti 2-x Compounds represented by (PO4)3 (where 0 ≤ x ≤ 2) (LATP). Other examples of oxide solid electrolytes include LiLaTiO (e.g., Li... 0.34 La 0.51 TiO3), LiPON (e.g., Li 2.9 PO3.3 N 0.46 ) and LiLaZrO (e.g., Li7La3Zr2O) 12 ).

[0065] Based on 100 parts by weight of all positive electrode active material layers, the content of solid electrolyte can be 5 to 49 parts by weight.

[0066] Based on 100 parts by weight of the entire positive electrode active material layer, the content of the solid electrolyte can 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, less than 49 parts by weight, less than 45 parts by weight, less than 40 parts by weight, less than 35 parts by weight, less than 30 parts by weight, less than 25 parts by weight, less than 24 parts by weight, less than 23 parts by weight, less than 22 parts by weight, less than 21 parts by weight, or less than 20 parts by weight. Preferably, based on 100 parts by weight of the entire positive electrode active material layer, the content of the solid electrolyte can be 12 to 20 parts by weight.

[0067] If the solid electrolyte content is less than 5 parts by weight based on 100 parts by weight of the total positive electrode active material layer, the electrode capacity and overall energy density may decrease due to the increased porosity in the positive electrode active material layer and the increased interfacial resistance between the positive electrode active material and the solid electrolyte. If it exceeds 49 parts by weight, the electrode capacity and overall energy density may decrease. Therefore, the solid electrolyte content needs to be appropriately adjusted within the above range.

[0068] The solid electrolyte can be in the shape of particles such as spheres or ellipses, or in the shape of a thin film, but when the solid electrolyte is in the shape of particles, the average particle size can be from 0.1 to 5 μm. For example, the average particle size of the solid electrolyte can be 0.1 to 3 μm, 0.1 to 2 μm, 0.1 to 1 μm, 0.1 to 0.9 μm, 0.1 to 0.8 μm, 0.1 to 0.7 μm, 0.1 to 0.6 μm, or 0.1 to 0.5 μm. The average particle size of the solid electrolyte can be, for example, the volume equivalent median diameter (D50) measured by a laser particle size analyzer.

[0069] If the average particle size of the solid electrolyte is less than 0.1 μm, there may be problems such as the solid electrolyte particles being prone to agglomeration or not being able to disperse uniformly and may be biased in the electrode, and it may be difficult to form an effective interface between the positive electrode active material and the solid electrolyte. If it exceeds 5 μm, there may be problems such as voids being generated in the positive electrode active material layer and the ionic conductivity of the electrode being reduced. Therefore, it is preferable to adjust the average particle size of the solid electrolyte appropriately within the above range.

[0070] The positive electrode active material layer can be prepared according to methods known in the art, and is not limited to a specific preparation method. However, it can be prepared by, for example, a dry electrode process (preparing agglomerates by mixing positive electrode active material, solid electrolyte, conductive material and binder, and then forming the agglomerates into sheets), or by a wet process (preparing a slurry of the positive electrode mixture by mixing in a solvent and coating the positive electrode mixture onto the positive electrode current collector).

[0071] In addition to the aforementioned positive electrode active material, solid electrolyte, conductive material, and binder, the positive electrode active material layer may also contain additives such as fillers, coatings, dispersants, and ion-conducting agents. Fillers, coatings, dispersants, and ion-conducting agents can be any known materials commonly used in all-solid-state battery electrodes.

[0072] The thickness of the positive electrode active material layer can vary depending on the target configuration of the all-solid-state battery, but is preferably, for example, 0.1 μm to 1,000 μm, more preferably 40 μm to 100 μm.

[0073] The solid electrolyte layer is a layer containing a solid electrolyte as its main component, located between the positive and negative electrodes. This solid electrolyte layer contains a solid electrolyte, which may be the same as or different from the solid electrolyte contained in the positive electrode active material layer. Its specific type is the same as described in the positive electrode active material layer description, therefore its specific description is omitted.

[0074] The elastic modulus or Young's modulus of the solid electrolyte layer can be, for example, below 35 GPa, below 30 GPa, below 27 GPa, below 25 GPa, or below 23 GPa. Alternatively, the elastic modulus or Young's modulus of the solid electrolyte layer can be, for example, from 10 to 35 GPa, from 15 to 35 GPa, from 15 to 30 GPa, or from 15 to 25 GPa. Because the solid electrolyte layer has an elastic modulus within this range, it is easier to pressurize and / or sinter the solid electrolyte contained within the solid electrolyte layer.

[0075] The solid electrolyte layer also includes, for example, an adhesive. The adhesive included in the solid electrolyte layer can be, for example, but not limited to, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, or any other adhesive used in the art. The adhesive of the solid electrolyte layer may be the same as or different from the adhesive of the positive electrode active material layer.

[0076] The thickness of the solid electrolyte layer can vary depending on the configuration of the target all-solid-state battery. From the perspective of improving the volumetric energy density of the battery, it is preferably 600 μm or less, more preferably 500 μm or less, or 400 μm or less. On the other hand, there is no particular limitation on the lower limit of the thickness of the solid electrolyte layer, but it is preferably 1 μm or more, 5 μm or more, or 10 μm or more.

[0077] In one embodiment of the present invention, the negative electrode may include a negative current collector and may include a lithium deposition layer formed by lithium deposition between the solid electrolyte layer and the negative current collector during the charging and discharging of the all-solid-state battery.

[0078] A negative electrode current collector is a conductive component that acts as a channel for electrons to flow from the negative electrode to the power source or from an external load to the negative electrode, depending on the charging and discharging behavior of the battery. The negative electrode current collector is made of, for example, a material that does not react with lithium, i.e., a material that does not form alloys or compounds. The material constituting the negative electrode current collector can be, for example, but is not limited to, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni), as long as it is used as an electrode current collector in the art. The negative electrode current collector can be made of one of the above-mentioned metals, or it can be made of an alloy or coating material of two or more metals. The negative electrode current collector is, for example, in the form of a plate or foil.

[0079] The negative electrode may also contain additives used in traditional all-solid-state batteries, such as fillers, dispersants, and ion conductors.

[0080] In one embodiment of the present invention, a lithium deposition layer may also be included between the negative electrode current collector and the solid electrolyte layer.

[0081] During the charging process of an all-solid-state battery, a lithium deposition layer is formed by the deposition of lithium metal on the negative electrode current collector. This lithium deposition layer, composed of deposited lithium metal, functions as the negative electrode active material layer of the all-solid-state battery of this invention. Therefore, during the charging process of the all-solid-state battery, the thickness of the lithium deposition layer increases as lithium ions are deposited on the negative electrode current collector. Conversely, during the discharging process, the thickness of the lithium deposition layer decreases as the lithium metal in the lithium deposition layer dissolves (or ionizes).

[0082] For example, the thickness of the lithium deposited layer in a fully charged all-solid-state battery can be 20 to 40 μm.

[0083] All-solid-state batteries can be fabricated by separately manufacturing such a positive electrode, a solid electrolyte layer, and a negative electrode, and then stacking them in sequence.

[0084] In one embodiment of the invention, the electrode assemblies stacked in the above order can be a structure housed within a casing (e.g., a bag). All-solid-state batteries can also be fabricated by stacking two or more electrode assemblies.

[0085] The all-solid-state battery may include an elastic sheet on the outside of at least one of the positive and negative current collectors. The elastic sheet may function as a buffer layer or elastic layer, which allows pressure to be uniformly transmitted to the electrode stack to ensure good contact of the solid components. It can also alleviate the stress transmitted to the solid electrolyte and suppress cracking of the solid electrolyte caused by stress accumulation due to changes in electrode thickness during charging and discharging.

[0086] In one embodiment of the present invention, a first charging step is performed on an all-solid-state battery having the above-mentioned positive electrode, negative electrode and a solid electrolyte layer sandwiched between the positive electrode and the negative electrode, charging at a first current density, so that lithium is deposited in the space between the solid electrolyte layer and the negative electrode current collector, thereby forming a lithium deposition layer.

[0087] However, since both the solid electrolyte layer and the negative electrode current collector are made of solid materials, they have many uneven surfaces. As the charging phase of the all-solid-state battery progresses, there is a strong tendency for lithium metal to detach from the parts where the uneven surfaces of the solid electrolyte layer and the negative electrode current collector come into contact with each other.

[0088] Moreover, lithium metal that grows in this way will form lithium dendrites, which can grow through the solid electrolyte layer, resulting in reversible lithium loss and battery short circuits in all-solid-state batteries.

[0089] In one embodiment of the present invention, a first discharge step is performed on an all-solid-state battery that has undergone a first charging step at a first current density, and a second discharge step at a second current density higher than the first current density is performed. This causes lithium metal to react with lithium metal of relatively high length deposited at the point where the tip of the lithium metal in the lithium deposited layer, specifically the point where the solid electrolyte layer and the unevenness of the negative electrode current collector come into contact with each other, and induces dissolution, thereby suppressing the growth of lithium dendrites.

[0090] In other words, during the first discharge step, if a low-rate discharge process using a current density similar to that of the first charging step is performed, the lithium metal formed in the lithium deposited layer will uniformly dissolve into lithium ions (Li) throughout the entire region of the lithium deposited layer. +This maintains the morphology of the lithium metal formed in the first charging step, making it difficult to suppress the growth of lithium dendrites formed by repeated charge-discharge cycles of the all-solid-state battery. However, the activation method of the all-solid-state battery of the present invention uses a second current density higher than the first current density to perform a high-rate discharge process in the first discharge step, which has the effect of suppressing the growth of these lithium dendrites.

[0091] In one embodiment of the invention, the first current density of the first charging step may be in the range of 0.05 to 0.33C, for example 0.08 to 0.3C, preferably 0.1 to 0.25C.

[0092] If the first current density of the first charging step is less than 0.05 C, there is a risk of decreased productivity due to the long activation time required for the all-solid-state battery. If it exceeds 0.33 C, there is a problem of uneven lithium metal deposition and growth between the solid electrolyte layer and the negative electrode current collector.

[0093] In one embodiment of the invention, the second current density of the first discharge step may be in the range of 1 to 2.5 C, for example 1.25 to 2.25 C, preferably 1.5 to 2 C.

[0094] If the second current density of the first discharge step is less than 1 C, the effect of suppressing lithium dendrite formation as charging and discharging continue may not be significant because the lithium metal formed in the lithium deposited layer during the discharge step of the all-solid-state battery does not dissolve from the tip. If it exceeds 2.5 C, there may be a problem that the all-solid-state battery is not fully discharged due to the increase in internal resistance caused by the large current.

[0095] In one embodiment of the invention, when the first charging step and the first discharging step are defined as “one cycle” of the charge-discharge process, the charge-discharge process can be performed 3 to 10 times.

[0096] If the above charge-discharge process is performed less than 3 times, the planarization effect of lithium metal formed in the lithium deposited layer during the discharge step of the all-solid-state battery may not be obvious. If the above charge-discharge process is performed more than 10 times, the planarization of lithium metal may have been fully completed, resulting in no further planarization effect.

[0097] As described above, the all-solid-state battery of the present invention exhibits excellent discharge capacity, output characteristics and capacity retention, making it suitable for portable devices such as mobile phones, laptops, and digital cameras, as well as electric vehicles such as hybrid electric vehicles (HEVs).

[0098] Therefore, 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.

[0099] The battery module or battery pack can be used to power one or more of the following medium to large-sized devices: power tools; electric vehicles, including electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); or energy storage systems.

[0100] [Example]

[0101] Specific embodiments of the present invention will be described below. However, the following embodiments are merely intended to illustrate or describe the present invention and are not intended to limit the present invention. Furthermore, any matters not described herein can be fully inferred by those skilled in the art and are therefore omitted here.

[0102] Manufacturing example: Manufacturing of all-solid-state batteries

[0103] (1) Manufacturing of the positive electrode

[0104] Based on a total of 100 parts by weight of the positive electrode layer, 78 parts by weight of LiNi with a particle size (D50) of 5 μm are used as the positive electrode active material. 0.8 Co 0.1 Mn 0.1 O2 powder, 19.5 parts by weight of lithium sulfide silver germanium mineral type solid electrolyte Li6PS5Cl, 1.5 parts by weight of carbon black conductive material and 1.0 parts by weight of styrene-butadiene rubber (SBR) binder were added to xylene solvent, 2 mm zirconia balls were added, and they were stirred with a Thinky mixer to prepare a slurry.

[0105] The prepared slurry was coated onto one side of an aluminum current collector with a thickness of 15 μm, which served as the positive electrode current collector, and dried in a vacuum oven at 100°C for 8 hours to prepare the positive electrode of the all-solid-state battery.

[0106] (2) Preparation of solid electrolyte layer

[0107] An acrylic adhesive (SX-A334, Zeon) was dissolved in isobutyl isobutyrate (IBIB) solvent. A lithium-sulfur silver-germanium ore-type solid electrolyte, Li6PS5Cl, was added, and the mixture was stirred with a Thinky mixer to adjust the viscosity to a suitable level. After viscosity adjustment, 2 mm zirconia balls were added, and the mixture was stirred again with a Thinky mixer to prepare a slurry. This slurry contained 98.5% by weight of solid electrolyte and 1.5% by weight of adhesive. The slurry was coated onto a release PET film using a rod coater and dried at room temperature to prepare the solid electrolyte layer.

[0108] (3) Manufacturing of all-solid-state batteries

[0109] The prepared positive electrode and solid electrolyte were cut together with the nickel foil negative electrode current collector, stacked in the order of positive electrode, solid electrolyte layer and negative electrode current collector, sealed in a bag, and subjected to high temperature at 80℃ and 500 MPa for 30 minutes, and then subjected to warm isostatic pressing (WIP) to obtain an all-solid-state battery.

[0110] Under pressure, the thickness of the positive electrode is approximately 100 μm, the thickness of the negative electrode current collector is approximately 7 μm, and the thickness of the solid electrolyte layer is approximately 60 μm.

[0111] Example 1: Activation of all-solid-state batteries

[0112] The all-solid-state battery prepared in the manufacturing example was charged at a first current density of 0.1 C until the battery voltage reached 4.2 V, and then discharged at a second current density of 1.5 C until the battery voltage reached 3.0 V.

[0113] The above charge-discharge process is defined as one cycle, repeated 5 times, and then 50 cycles at 0.33 C.

[0114] The discharge capacity of each cycle was measured using the charge-discharge evaluation equipment "TOSCAT-3000" (trade name, Toyo System).

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

[0116] The all-solid-state battery prepared in the manufacturing example is charged at a first current density of 0.1 C until the battery voltage is 4.2 V, and then discharged at a first current density of 0.1 C until the battery voltage is 3.0 V.

[0117] The above charge-discharge process is defined as one cycle, repeated 5 times, and then 50 cycles at 0.33 C.

[0118] The discharge capacity of each cycle was measured using the charge-discharge evaluation equipment "TOSCAT-3000" (trade name, Toyo System).

[0119] The capacity retention rate of the all-solid-state batteries of Example 1 and Comparative Example 1 was measured, and the results are shown in... Figure 1 .

[0120] See Figure 1 As can be seen, for the all-solid-state battery of Example 1, as a result of high-rate discharge at a second current density higher than the first current density in the first discharge step, the capacity retention rate at 50 cycles is significantly improved compared with the all-solid-state battery of Comparative Example 1.

[0121] This can be understood as follows: as the discharge step proceeds at a higher current density than the charging step, the lithium metal formed in the lithium deposited layer dissolves into lithium ions from the tip, thus suppressing dendrite formation and improving the lifespan characteristics of the all-solid-state battery.

[0122] While the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto. Various modifications and improvements made by those skilled in the art using the basic concept of the present invention as defined in the appended claims are also within the scope of the present invention.

Claims

1. A method for activating an all-solid-state battery, the all-solid-state battery comprising: a positive electrode; negative electrode; and The solid electrolyte layer sandwiched between the positive and negative electrodes The method includes: The first charging step involves charging the all-solid-state battery at a first current density. as well as A first discharge step is performed after the first charging step, discharging the all-solid-state battery at a second current density greater than the first current density.

2. The activation method for the all-solid-state battery as described in claim 1, in, The first current density is 0.05 to 0.33 C.

3. The activation method for the all-solid-state battery as described in claim 1, in, The second current density is 1.0 to 2.5 C.

4. The activation method for the all-solid-state battery as described in claim 1, in, The first charging step and the first discharging step are defined as one cycle, and the cycle is performed 3 to 10 times.

5. The activation method for the all-solid-state battery as described in claim 1, in, The negative electrode includes a current collector. In this process, a lithium deposition layer is formed between the negative electrode and the solid electrolyte layer after the first charging step.

6. The activation method for the all-solid-state battery as described in claim 5, in, The thickness of the lithium deposited layer is 20 to 40 μm.

7. The activation method for the all-solid-state battery as described in claim 1, in, The positive electrode comprises at least one of sulfide solid electrolytes, oxide solid electrolytes, and polymer solid electrolytes.

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