Method for manufacturing solid-state battery

Abstract

The present invention addresses the problem of providing a method for easily manufacturing a solid-state battery in which the charging rate and initial characteristics are improved. The method comprises: a first processing step for causing a current to pass through a solid-state battery before initial charging, at a temperature of 25-90°C and at a rate of 0.001-0.5C; a holding step for holding the solid-state battery at a temperature of 25-90°C after the first processing step; and a second processing step that is performed after the holding step as an initial charging step for charging the solid-state battery to a depth of charge of 50-100% in SOC and then discharging the same. Preferably, the holding time in the holding step is at least 10 minutes. Further preferably, in the first processing step, a current is passed through the solid-state battery to a depth of charge of 1-105% in SOC.

Description

Solid-state battery manufacturing method

[0001] The present invention relates to a method for manufacturing a solid-state battery.

[0002] In recent years, CO ２ Secondary batteries have been attracting attention as an effort to prevent global warming by reducing CO2 emissions. Among them, solid-state batteries are expected to be put to practical use as they combine safety and high energy density. However, solid-state batteries have the problem that it is more difficult to improve their initial characteristics and charge rate than batteries with liquid electrolytes. One possible solution to this problem is to improve the adhesion between the solid electrolyte and the active material.

[0003] For the purpose of increasing the adhesion between the solid electrolyte and the active material, for example, Patent Document 1 proposes producing a solid-state battery by pressurizing an electrode group including electrodes and a solid electrolyte layer located between the electrodes at a pressure of 400 MPa or more and 1500 MPa or less.

[0004] US2021 / 0119246A1

[0005] However, the method described in Patent Document 1 requires the application of pressure under high pressure conditions to enhance adhesion between the electrode and the solid electrolyte layer, which requires the use of, for example, a large press. Therefore, the method described in Patent Document 1 is not suitable for the simple manufacture of solid-state batteries. Therefore, an object of the present invention is to provide a method for easily manufacturing solid-state batteries having good battery characteristics.

[0006] As a result of intensive research to solve the above-mentioned problems, the present inventors unexpectedly found that by subjecting a battery before its initial charge to a specific pretreatment, it is possible to increase the adhesion between the electrodes and the solid electrolyte layer without applying excessive pressure to them. That is, the present invention solves the above-mentioned problems by providing a method for manufacturing a solid-state battery, the method comprising: a first treatment step of applying a current to a solid-state battery before its initial charge at a temperature of 25°C to 90°C and at a rate of 0.001 C to 0.5 C; a standing step of leaving the solid-state battery at a temperature of 25°C to 90°C after the first treatment step; and a second treatment step as an initial charging step of charging the solid-state battery to a charge depth of 50% to 105% and then discharging the battery after the standing step.

[0007] The present invention will be described below based on preferred embodiments. The present invention relates to a method for manufacturing a solid-state battery. In this specification, a solid-state battery refers to a battery having a solid electrolyte layer. A solid-state battery is a battery that does not contain any liquid or gel-like substance as an electrolyte, or a battery that contains, for example, 50% by mass or less, particularly 30% by mass or less, and particularly 10% by mass or less of a liquid or gel-like substance as an electrolyte. The solid-state battery obtained by this manufacturing method has a positive electrode layer, a negative electrode layer, and a solid electrolyte layer located between the positive electrode layer and the negative electrode layer. There are no particular limitations on the types of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer. Any materials can be used for the positive electrode layer, the negative electrode layer, and the solid electrolyte layer as long as the completed solid-state battery operates properly.

[0008] The solid-state battery may be a primary battery or a secondary battery. Examples of the solid-state battery include, but are not limited to, lithium ion batteries and sodium ion batteries. The materials of the positive electrode layer, negative electrode layer, and solid electrolyte layer constituting the solid-state battery are selected appropriately depending on the type of the solid-state battery. When the solid-state battery is, for example, a lithium ion battery, the following materials can be used as the positive electrode layer, negative electrode layer, and solid electrolyte layer.

[0009] Examples of the positive electrode active material constituting the positive electrode layer include lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, Ni-Co-Mn ternary lithium composite oxide (NCM), and Ni-Co-Al ternary lithium composite oxide (NCA).

[0010] Examples of the negative electrode active material constituting the negative electrode layer include carbon-based materials such as graphite, artificial graphite, natural graphite, and non-graphitizable carbon (hard carbon), silicon, metallic lithium, and lithium titanate.

[0011] Examples of solid electrolytes constituting the solid electrolyte layer include sulfide solid electrolytes, oxide solid electrolytes, and nitride solid electrolytes. The sulfide solid electrolyte may be crystalline or amorphous. The sulfide solid electrolyte preferably contains, for example, lithium (Li), sulfur (S), and an M element. The M element is preferably at least one of phosphorus (P), germanium (Ge), antimony (Sb), silicon (Si), tin (Sn), aluminum (Al), titanium (Ti), iron (Fe), nickel (Ni), cobalt (Co), and manganese (Mn). In particular, it is preferable that the M element contains at least phosphorus (P), and more preferably, the M element is only P. The sulfide solid electrolyte preferably contains a halogen (X) element in addition to the Li, S, and M elements. Examples of the X element include fluorine (F), chlorine (Cl), bromine (Br), and iodine (I). The X element may be one of these elements, or a combination of two or more of them. From the viewpoint of facilitating the production of an argyrodite-type crystal structure (described later) by a solid-state reaction and increasing lithium ion conductivity, the solid electrolyte preferably contains at least Cl or Br as the X element, and more preferably contains Cl and Br.

[0012] In the sulfide solid electrolyte, it is preferable to set the molar ratio of X element to P element (X / P) to a relatively high value. For example, the X / P is preferably 1.1 or more, more preferably 1.5 or more, and even more preferably 1.8 or more. On the other hand, the X / P is preferably 4.0 or less, more preferably 3.5 or less, and even more preferably 2.4 or less. When the X / P is within the predetermined range, the sulfide solid electrolyte exhibits superior lithium ion conductivity. Furthermore, when the sulfide solid electrolyte is used in a solid-state battery, the solid-state battery exhibits superior battery characteristics. The X / P can be measured, for example, by ICP atomic emission spectroscopy.

[0013] In the sulfide solid electrolyte, the molar ratio of S element to P element (S / P) is, for example, preferably 4.9 or less, more preferably 4.5 or less, and even more preferably 4.2 or less. On the other hand, the S / P is preferably 3.2 or more, more preferably 3.5 or more, and even more preferably 3.8 or more. When the S / P is within the specified range, the sulfide solid electrolyte exhibits better lithium ion conductivity. Furthermore, when the solid electrolyte of the present invention is used in a solid battery, the solid battery exhibits better battery characteristics. The S / P can be measured, for example, by ICP atomic emission spectroscopy.

[0014] In particular, the use of a sulfide solid electrolyte that contains the above-mentioned elements and also contains a crystalline phase having an argyrodite-type crystal structure is preferable, as this significantly enhances the advantages of the present invention. Whether or not a sulfide solid electrolyte contains a crystalline phase having an argyrodite-type crystal structure can be determined by analyzing solid electrolyte particles using X-ray diffraction or X-ray total scattering.

[0015] The positive electrode layer can be produced, for example, by applying a positive electrode mixture containing the above-mentioned positive electrode active material powder, conductive additive, and solid electrolyte powder to the surface of the positive electrode current collector, or by rolling the mixture using a roll press, etc. The positive electrode current collector can be made of metals such as stainless steel, gold, platinum, zinc, nickel, tin, aluminum, molybdenum, niobium, tantalum, tungsten, titanium, etc., and alloys thereof.

[0016] The negative electrode layer is produced, for example, by applying a negative electrode mixture containing the above-described negative electrode active material powder and solid electrolyte powder to the surface of a negative electrode current collector. In this manufacturing method, a negative electrode of a solid battery called an anode-free battery may be used. The negative electrode used in an anode-free battery may be composed of a negative electrode current collector and a negative electrode layer disposed on the negative electrode current collector, containing a solid electrolyte but not containing a negative electrode active material. Specifically, this negative electrode has a negative electrode current collector and a negative electrode layer containing a solid electrolyte and a conductive additive but not containing a negative electrode active material. Alternatively, the negative electrode used in an anode-free battery has a negative electrode current collector and a negative electrode layer containing carbon that does not occlude Li elements. By using a negative electrode used in an anode-free battery, lithium ions migrated from the positive electrode during charging are deposited as metallic lithium on the negative electrode current collector, and the metallic lithium functions as the negative electrode active material. In other words, it is a so-called in-situ deposition type negative electrode. In this case, the use of a specific carbonaceous material and a Li conductive material such as Ag can suppress the growth of metallic lithium crystals into a dendritic shape compared to conventional in-situ deposition-type anodes, thereby suppressing battery short-circuiting. This not only improves the initial characteristics and charge rate, but also makes it easy to obtain a solid-state battery that can effectively prevent battery short-circuiting.

[0017] The solid electrolyte layer can be produced, for example, by dropping a slurry containing the above-mentioned solid electrolyte, binder, and solvent onto a substrate and scraping it off with a doctor blade or the like; by contacting the substrate with the slurry and then cutting it with an air knife; or by forming a coating film by screen printing or the like, followed by heat drying to remove the solvent. Alternatively, the solid electrolyte layer can be produced by compacting a powder of the solid electrolyte by pressing or the like, and then processing it appropriately. Instead of the above methods, a solid electrolyte sheet in which the solid electrolyte is supported on a porous support may be used as the solid electrolyte layer. The porous support is preferably one that can impart self-supporting properties and appropriate flexibility to the solid electrolyte sheet. From this perspective, a fiber sheet such as various nonwoven fabrics can be used as the porous support.

[0018] After the positive electrode layer, negative electrode layer, and solid electrolyte layer are manufactured, the solid electrolyte layer is then disposed between the positive electrode layer and the negative electrode layer, and these three components are sealed in a container. This results in a solid-state battery in a state before initial charging (hereinafter also referred to as a "pre-charged battery"). The three components may be subjected to a pressure treatment before, while, or after being placed in the container. This increases adhesion between the three components, thereby improving the properties of the manufactured solid-state battery. For example, the initial properties and charge rate properties can be improved. In particular, it is preferable to perform the pressure treatment in one or more of the following steps: (i) the first treatment step, (ii) the standing step, and (iii) the second treatment step, described below, in order to improve the properties of the manufactured solid-state battery, such as the initial properties and charge rate.

[0019] The pressure applied in the pressure treatment does not need to be as high as, for example, the value described in Patent Document 1 mentioned above. This is because the present invention employs means other than pressure to enhance the adhesion between the electrode and the solid electrolyte layer. However, applying high pressure is not prohibited. In this manufacturing method, the pressure applied in the pressure treatment is preferably, for example, 100 MPa or more, more preferably 300 MPa or more, and even more preferably 600 MPa or more. On the other hand, the pressure is preferably, for example, 700 MPa or less. In the pressure treatment, applying heat, for example, at 25°C to 150°C, simultaneously with the application of pressure is preferable, as this effectively improves the adhesion between the electrode and the solid electrolyte layer. This also eliminates the need for a large press machine in the pressure treatment in this manufacturing method, making it possible to easily manufacture a solid-state battery.

[0020] In this manufacturing method, a solid-state battery is manufactured as a finished product by subjecting a pre-charged battery to the following treatments. The treatments applied to the pre-charged battery are broadly divided into (i) a first treatment step, (ii) a leaving step, and (iii) a second treatment step. In the first treatment step, the pre-charged battery is subjected to a treatment of passing a current at a rate of 0.001 C to 0.5 C at a temperature of 25° C. to 90° C. In the leaving step, the pre-charged battery subjected to the first treatment step is left in a predetermined environment. In the second treatment step, the pre-charged battery subjected to the leaving step is charged and discharged under predetermined conditions to give the battery capacity, thereby obtaining a finished solid-state battery.

[0021] In a solid-state battery manufactured through the above steps, it is believed that a good interface is formed on the surface of the solid electrolyte particles. The presence of this interface allows smooth exchange of lithium ions between the solid electrolyte particles and the active material particles. As a result, problems such as localized current concentration within the battery are less likely to occur. As a result, the solid-state battery manufactured by this method has improved characteristics, such as initial characteristics and charge rate characteristics. Each step will be explained below using the example of manufacturing a lithium-ion battery as a solid-state battery.

[0022] (i) First Treatment Step In this step, current is applied to the pre-charged battery at a predetermined rate. Specifically, current is applied at a rate of preferably 0.5 C or less, more preferably 0.2 C or less, even more preferably 0.1 C or less, and even more preferably 0.01 C or less. By applying current at a rate below this value, a solid battery with improved initial characteristics and charge rate can be easily obtained. The current application rate is preferably 0.001 C or more, more preferably 0.005 C or more, even more preferably 0.01 C or more, and even more preferably 0.05 C or more. Applying current at a rate above this value can also easily obtain a solid battery with improved initial characteristics and charge rate. In this step, current may be applied while maintaining a constant rate, or the rate may be varied within a range of 0.001 C to 0.5 C. From the perspective of more easily obtaining a solid battery with improved initial characteristics and charge rate, it is desirable to apply current while maintaining a constant rate. "While the rate is kept constant" includes both the case where the rate is completely constant and the case where the rate fluctuates within a range of ±5%.

[0023] In this process, maintaining the ambient temperature during energization within a predetermined range is advantageous from the viewpoint of easily obtaining a solid-state battery with improved initial characteristics and a charge rate. Specifically, provided that the energization rate is within the above-mentioned range, the ambient temperature during energization is preferably set to 25°C or higher, more preferably 30°C or higher, even more preferably 45°C or higher, and even more preferably 60°C or higher. Furthermore, provided that the energization rate is within the above-mentioned range, the ambient temperature during energization is preferably set to 90°C or lower, even more preferably 70°C or lower, and even more preferably 60°C or lower. In this process, energization may be performed while maintaining a constant ambient temperature, or may be performed while varying the temperature within a range of 25°C or higher and 90°C or lower. From the viewpoint of more easily obtaining a solid-state battery with improved initial characteristics and a charge rate, it is desirable to perform energization while maintaining a constant ambient temperature. Note that, depending on the type of battery being energized, heat may be generated by energization, causing the battery to exhibit a temperature different from the ambient temperature. However, the temperature during energization in this process refers to the ambient temperature at which the battery is placed before charging.

[0024] The current application in this step is preferably carried out until the SOC (depth of charge) is, for example, preferably 1% or more, more preferably 3% or more, even more preferably 5% or more, and even more preferably 10% or more. By applying current at a depth of charge equal to or greater than this value, a solid battery with improved initial characteristics and charge rate can be easily obtained. The depth of charge is, for example, preferably 100% or less, more preferably 90% or less, and even more preferably 80% or less. By applying current at a depth of charge equal to or greater than this value, a solid battery with improved initial characteristics and charge rate can be easily obtained.

[0025] (ii) Standing Step After the first treatment step is completed, the pre-charged battery is then subjected to the standing step. During this step, the pre-charged battery is not charged or discharged. Furthermore, no other operations, including charging and discharging, are performed on the pre-charged battery. It is preferable that the standing step be performed immediately after the completion of the first treatment step, i.e., that the standing step be performed without interruption after the completion of the first treatment step, from the viewpoint of easily obtaining a solid-state battery with improved initial characteristics and charge rate. In other words, it is preferable that no steps be performed between the first treatment step and the standing step.

[0026] In this step, it is preferable to leave the pre-charged battery subjected to the first treatment step in an environment with an ambient temperature of 25°C or higher, for example. This makes it possible to easily obtain a solid-state battery with improved initial characteristics and charge rate. From the viewpoint of making this advantage even more pronounced, it is preferable to leave the pre-charged battery subjected to the first treatment step in an environment with an ambient temperature of 25°C or higher, desirably 30°C or higher, particularly 50°C or higher, and especially 60°C or higher. The leaving temperature is, for example, preferably 90°C or lower, more preferably 70°C or lower, and even more preferably 60°C or lower. Leaving the pre-charged battery at an ambient temperature below this value also makes it possible to easily obtain a solid-state battery with improved initial characteristics and charge rate.

[0027] In this step, the pre-charged battery may be left standing while the ambient temperature is kept constant, or may be left standing while the temperature is changed within a range of 25° C. to 90° C. From the viewpoint of more easily obtaining a solid-state battery with improved initial characteristics and charge rate, it is desirable to leave the battery standing while the ambient temperature is kept constant.

[0028] The ambient temperature used in this step may be the same as or different from the ambient temperature used in the first treatment step described above. Ａ and the ambient temperature T in the first step １ If different from Ａ >T １ Alternatively, T Ａ <T １In order to avoid impairing the active state of each material constituting the solid-state battery and to avoid changing the shape and performance of the precipitated Li, the ambient temperature T Ａ is the ambient temperature T １ It is preferable that it is higher than

[0029] Ambient temperature T during the leaving process Ａ and the ambient temperature T in the first step １ If they are different, the difference between them is ΔT １ =|T Ａ -T １ From the viewpoint of easily obtaining a solid state battery with improved initial characteristics and charging rate, the value of | is, for example, preferably 65°C or less, more preferably 45°C or less, even more preferably 30°C or less, even more preferably 10°C or less, and particularly preferably 5°C or less.

[0030] In this step, the time for leaving the battery before charging is preferably, for example, 10 minutes or more, more preferably 30 minutes or more, and even more preferably 60 minutes or more, from the viewpoint of easily obtaining a solid-state battery with improved initial characteristics and charge rate. From the same viewpoint as above, the time for leaving the battery before charging is preferably, for example, 1,440 minutes or less, more preferably 720 minutes or less, and even more preferably 300 minutes or less.

[0031] (iii) Second Treatment Step: In this step, the pre-charged battery subjected to the standing step is subjected to the second treatment step as an initial charging step to give the battery a capacity and obtain a finished solid-state battery. This step is preferably performed immediately after the standing step, i.e., the second treatment step is performed without interruption after the standing step, from the viewpoint of easily obtaining a solid-state battery with improved initial characteristics and charge rate. In other words, it is preferable that no other step is performed between the standing step and the second treatment step. In this step, charging is performed, for example, to a charge depth of preferably 50% or more, more preferably 70% or more, even more preferably 85% or more, and even more preferably 100%, provided that the SOC (depth of charge) is higher than that in the first treatment step. Meanwhile, the charge depth is preferably 105% or less, more preferably 100% or less, and even more preferably 90% or less. By charging at a charge depth within the above range, a solid-state battery with improved initial characteristics and charge rate can be easily obtained. Here, an SOC of 100% is defined as the state in which a battery is charged at a constant current of 0.1 C up to 4.2 V in an environment of 25°C or 60°C using an electrode composition described in the Examples below, and then charged at a constant voltage until the current reached 0.01 C at the time the battery reached 4.2 V.

[0032] The charge rate when charging at the above-mentioned depth of charge is, for example, preferably 0.001 C or more, more preferably 0.005 C or more, even more preferably 0.01 C or more, and even more preferably 0.05 C or more. On the other hand, the charge rate is, for example, preferably 0.5 C or less, more preferably 0.3 C or less, even more preferably 0.1 C or less, and even more preferably 0.01 C or less. By keeping the charge rate within the above range, a solid battery with improved initial characteristics and charge rate can be easily obtained. In this step, charging may be performed while maintaining a constant rate, or the rate may be changed. From the viewpoint of more easily obtaining a solid battery with improved initial characteristics and charge rate, it is desirable to charge while maintaining a constant rate.

[0033] In this step, as in the first treatment step described above, maintaining the ambient temperature during charging within a predetermined range is advantageous from the viewpoint of easily obtaining a solid-state battery with improved initial characteristics and charge rate. The ambient temperature during charging is, for example, preferably 25°C or higher, more preferably 30°C or higher, and even more preferably 60°C or higher. On the other hand, the ambient temperature during charging is, for example, preferably 90°C or lower, more preferably 70°C or lower, and even more preferably 60°C or lower. In this step, charging may be performed while the ambient temperature is kept constant, or may be performed while the temperature is changed. From the viewpoint of more easily obtaining a solid-state battery with improved initial characteristics and charge rate, it is desirable to pass current while the ambient temperature is kept constant.

[0034] In this process, after charging to a predetermined depth of charge under the above conditions, discharging is then performed to obtain a solid-state battery as a final product. Discharging is preferably performed at a rate of 0.001 C or higher, more preferably 0.005 C or higher, even more preferably 0.01 C or higher, and even more preferably 0.05 C or higher. Meanwhile, the discharge rate is preferably 0.5 C or lower, more preferably 0.3 C or lower, even more preferably 0.1 C or lower, and even more preferably 0.01 C or lower. Discharging at a rate within the above range can easily produce a solid-state battery with improved initial characteristics and charge rate. In this process, discharging may be performed while maintaining a constant rate, or while varying the rate. From the viewpoint of more easily obtaining a solid-state battery with improved initial characteristics and charge rate, it is desirable to discharge while maintaining a constant rate.

[0035] Discharging is preferably terminated when a predetermined voltage is reached, and the rate is preferably within the range of 0.01 C to 0.1 C. Discharging is preferably carried out at the same ambient temperature as charging.

[0036] The ambient temperature used in the leaving step (charging and discharging) may be the same as or different from the ambient temperature used in the leaving step described above. Ａand the ambient temperature T in the second treatment step ２ If different from Ａ >T ２ Alternatively, T Ａ <T ２ In order to avoid impairing the active state of each material constituting the solid-state battery and to avoid changing the shape and performance of the precipitated Li, the ambient temperature T Ａ is the ambient temperature T ２ The ambient temperatures in the charging step and the discharging step can be set independently of each other.

[0037] Ambient temperature T during the leaving process Ａ and the ambient temperature T2 in the second treatment step are different, the difference between them, ΔT ２ =|T Ａ -T ２ From the viewpoint of easily obtaining a solid-state battery with improved initial characteristics and charging rate, the value of | is, for example, preferably 65°C or less, more preferably 45°C or less, even more preferably 30°C or less, even more preferably 10°C or less, and particularly preferably 5°C or less.

[0038] The above-described process results in the production of a desired solid-state battery. In this solid-state battery, a favorable interface is formed on the surface of the solid electrolyte particles, allowing smooth exchange of lithium ions between the solid electrolyte particles and the active material particles. As a result, problems such as localized current concentration within the battery are less likely to occur, resulting in improved initial characteristics and charging rate of the solid-state battery.

[0039] In relation to the above-described embodiments, the present invention further discloses the following methods for manufacturing a solid-state battery. [1] A method for manufacturing a solid-state battery, comprising: a first processing step of applying current to a solid-state battery before initial charging at a temperature of 25°C to 90°C and at a rate of 0.001 C to 0.5 C; a leaving step of leaving the solid-state battery at a temperature of 25°C to 90°C after the first processing step; and a second processing step as an initial charging step of charging the solid-state battery to a charge depth of 50% to 105% SOC and discharging the battery after the leaving step. [2] The manufacturing method according to [1], wherein the leaving time in the leaving step is 10 minutes or longer. [3] The manufacturing method according to [1] or [2], wherein the first processing step is a step of applying current to a charge depth of 1% to 100% SOC. [4] The manufacturing method according to any one of [1] to [3], wherein the solid-state battery includes a solid electrolyte, and the solid electrolyte includes lithium (Li), sulfur (S), and M (M is at least one of phosphorus (P), germanium (Ge), antimony (Sb), silicon (Si), tin (Sn), aluminum (Al), titanium (Ti), iron (Fe), nickel (Ni), cobalt (Co), and manganese (Mn)). [5] The manufacturing method according to [4], wherein the solid electrolyte further includes a halogen (X). [6] The manufacturing method according to [5], wherein the solid electrolyte includes a crystalline phase having an argyrodite-type crystal structure.

[0040] The present invention will be described in more detail below with reference to examples, but the scope of the present invention is not limited to these examples.

[0041] [Definition of SOC] With the electrode composition of the example, a battery was charged at a constant current of 0.1 C up to 4.2 V in an environment of 25° C. or 60° C., and when the battery reached 4.2 V, it was charged at a constant voltage until the current reached 0.01 C. This was defined as an SOC of 100%. Note that an SOC of 100% at 25° C. is described in Comparative Example 1, and an SOC of 100% at 60° C. is described in Comparative Example 2.

[0042] [Example 1] (1) Manufacture of a battery before charging LiNi was used as the positive electrode active material. ０．６ Co ０．２ Mn ０．２ O ２The negative electrode active material was graphite powder. The solid electrolyte was Li ５．８ P.S. ４．４ Br ０．８ Cl ０．８ A sulfide solid electrolyte powder having an argyrodite-type crystal structure was used. The positive electrode active material, solid electrolyte, carbon-based conductive additive, and binder were mixed in a mortar in a mass ratio of 85:12:1:2, and repeatedly pressed using a roll press until the mixture reached the desired thickness to form a positive electrode layer, resulting in a positive electrode. Separately, graphite, solid electrolyte, and binder were weighed in a mass ratio of 67:30:3, and an appropriate amount of a tetralin and anisole mixed solvent was added as a solvent. The mixture was then mixed using a rotation / revolution mixer (Awatori Rentaro®) to prepare an electrode mixture. The electrode mixture was applied to a stainless steel current collector foil using a doctor blade to form a coating. This coating was then vacuum dried at 120°C for 6 hours to form a negative electrode layer, resulting in a negative electrode. The above-mentioned negative electrode was punched out to a size of 25 mm x 25 mm. The punched negative electrode was superimposed on a 25 mm x 25 mm solid electrolyte layer and a 20 mm x 20 mm positive electrode layer, and then a pressure of 700 MPa was applied by cold isostatic pressing (CIP) to produce an all-solid-state battery.

[0043] (2) First Treatment Step The ambient temperature was set to 25° C., and current was applied to the pre-charged battery at a constant rate of 0.1 C. The current was applied until the SOC reached 5%.

[0044] (3) Leaving Step The ambient temperature continued to be 25° C., and the pre-charged battery was left for the time shown in Table 1. During this time, no operation was performed on the pre-charged battery.

[0045] (4) Second Treatment Step: While the ambient temperature remained at 25°C, the pre-charged battery was charged until the charge cut-off current reached 0.01 C. The charge rate was constant at 0.1 C. Next, while the ambient temperature remained at 25°C, the battery was discharged until the cell voltage reached 2.5 V. The discharge rate was constant at 0.1 C. In this way, the desired lithium ion solid state secondary battery was obtained. The area capacity of the positive electrode was 1.3 mA / cm. ２ It was decided.

[0046] [Examples 2 to 5 and Comparative Examples 1 and 2] Lithium ion solid state secondary batteries were obtained in the same manner as in Example 1, except that the conditions for the first treatment step, the standing step, and the second treatment step were as shown in Tables 1 to 4 below.

[0047] [Evaluation] As shown in Tables 2 to 4, the lithium ion solid state secondary batteries obtained in the Examples and Comparative Examples were evaluated for charge capacity, discharge capacity, and 0.5 C charge rate characteristics.

[0048]

[0049]

[0050]

[0051]

[0052] As is clear from the results shown in Tables 1 to 4, the solid state batteries obtained in the examples have improved initial characteristics and rate characteristics compared to the solid state batteries obtained in the comparative examples.

[0053] As described above in detail, the present invention provides a method for easily producing a solid-state battery having good battery characteristics.

Claims

1. A method for manufacturing a solid-state battery, comprising: a first processing step of applying current to a solid-state battery before initial charging at a rate of 0.001 C or more and 0.5 C or less at a temperature of 25°C or more and 90°C or less; a leaving step of leaving the battery at a temperature of 25°C or more and 90°C or less after the first processing step; and a second processing step as an initial charging step of charging the battery to a charge depth of 50% or more and 105% or less SOC and then discharging the battery after the leaving step.

2. The method of claim 1, wherein the leaving time in the leaving step is 10 minutes or more.

3. The manufacturing method according to claim 1 or 2, wherein the first treatment step is a step of energizing the battery to a charging depth of 1% or more and 100% or less of SOC.

4. The manufacturing method according to claim 1 or 2, wherein the solid-state battery includes a solid electrolyte, and the solid electrolyte includes lithium (Li), sulfur (S), and M (wherein M is at least one of phosphorus (P), germanium (Ge), antimony (Sb), silicon (Si), tin (Sn), aluminum (Al), titanium (Ti), iron (Fe), nickel (Ni), cobalt (Co), and manganese (Mn)).

5. The manufacturing method according to claim 4, wherein the solid electrolyte further contains a halogen (X) element.

6. The method of claim 5, wherein the solid electrolyte contains a crystalline phase having an argyrodite-type crystal structure.

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