Solid electrolyte layer and production method of the same, and solid-state battery

Abstract

To provide a solid electrolyte layer capable of suppressing increase of resistance and a production method of the same, and a solid-state battery.SOLUTION: A production method of a solid electrolyte layer 30 includes: providing a slurry including a solid electrolyte 20, a binder, and a dispersion medium; coating a support medium 10 having pores 12 with the slurry; and drying the support medium 10 coated with the slurry to remove the dispersion medium, where the slurry is coated so that the thickness of the solid electrolyte 20 becomes 1.1 times or more and 3.3 times or less of the thickness of the support medium after drying. A solid electrolyte layer 30 obtained by the same, and a solid-state battery including the same are also provided.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a solid electrolyte layer, a method for manufacturing the same, and a solid-state battery. [Background technology]

[0002] The solid electrolyte layer has the function of conducting lithium ions and also functions as a separator to prevent short-circuiting between the negative electrode active material layer and the positive electrode active material layer. To improve energy density, it is preferable to form the separator as thin as possible. However, it is difficult to make a thin film of solid electrolyte stand on its own. Therefore, solid electrolyte layers with a support are being considered.

[0003] For example, Patent Document 1 discloses a solid electrolyte sheet, which is a sheet containing a nonwoven fabric and a solid electrolyte on the surface and inside of the nonwoven fabric, wherein the weight of the nonwoven fabric per square meter is 8 g or less and the thickness of the nonwoven fabric is 10 μm or more and 25 μm or less.

[0004] Patent Document 2 discloses a method for producing a solid electrolyte layer used in an all-solid-state battery, the method comprising: a preparation step of preparing a slurry containing a solid electrolyte, a binder, and a dispersion medium; a placement step of arranging a support having pores on a first release film; a coating step of applying the slurry to the support to impregnate the support with the slurry; a drying step of drying the support to which the slurry has been applied to remove the dispersion medium; and a pressing step of arranging a second release film on the surface of the support opposite to the first release film after the drying, and pressing the first release film, the support, and the second release film in the stacking direction. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-31789 [Patent Document 2] Japanese Patent Application Publication No. 2023-90080 Summary of the Invention [Problem to be solved by the invention]

[0006] Both of the solid electrolyte layers disclosed in Patent Documents 1 and 2 have a problem in that the resistance may increase.

[0007] An object of the present disclosure is to provide a solid electrolyte layer capable of suppressing an increase in resistance, a method for manufacturing the same, and a solid-state battery. [Means for solving the problem]

[0008] The present disclosure achieves the above object by the following means. <Aspect 1> Providing a slurry containing a solid electrolyte, a binder, and a dispersion medium; applying the slurry to a porous support; and drying the support coated with the slurry to remove the dispersion medium; Including, The slurry is applied so that the thickness of the solid electrolyte after drying is 1.1 to 3.3 times the thickness of the support. Method for manufacturing a solid electrolyte layer. Aspect 2: The method for producing a solid electrolyte layer according to Aspect 1, wherein the density of the slurry is 0.85 to 1.15 times the density of the support. <Embodiment 3> A support having pores, and A solid electrolyte present on the surface and inside of the support Including, The thickness of the solid electrolyte is 1.1 times or more and 3.3 times or less the thickness of the support. Solid electrolyte layer. A solid-state battery comprising the solid electrolyte layer according to Aspect 3. [Effects of the Invention]

[0009] According to the present disclosure, by setting the thickness of the solid electrolyte membrane to a predetermined range of ratios relative to the thickness of the support, it is possible to provide a solid electrolyte layer, a manufacturing method thereof, and a solid-state battery that can avoid exposure of the support and suppress an increase in resistance. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view schematically illustrating an example of a solid electrolyte layer obtained by the method for producing a solid electrolyte layer according to the present disclosure. [Figure 2] FIG. 2 is an explanatory diagram showing an example of a method for squeezing a support coated with a slurry. [Figure 3] FIG. 3 is a cross-sectional schematic diagram showing an example of a solid state battery including the solid electrolyte layer of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present disclosure will be described in detail. Note that the present disclosure is not limited to the following embodiments, and various modifications can be made within the scope of the gist of the present disclosure. In addition, in the description of the drawings, the same elements are given the same reference numerals, and duplicated descriptions will be omitted.

[0012] In the context of the present disclosure, a "solid-state battery" refers to a battery that uses at least a solid electrolyte as the electrolyte, and thus a solid-state battery may use a combination of a solid electrolyte and a liquid electrolyte as the electrolyte. Also, in the context of the present disclosure, a solid-state battery may be an all-solid-state battery, i.e., a battery that uses only a solid electrolyte as the electrolyte.

[0013] <<Method for manufacturing solid electrolyte layer>> The method for producing a solid electrolyte layer according to the present disclosure includes: providing a slurry containing a solid electrolyte, a binder, and a dispersion medium; applying the slurry to a porous support; and drying the support coated with the slurry to remove the dispersion medium; Including, The slurry is applied so that the thickness of the solid electrolyte after drying is 1.1 to 3.3 times the thickness of the support.

[0014] The solid electrolyte layer obtained by the method for producing a solid electrolyte according to the present disclosure (hereinafter sometimes referred to as the "production method according to the present disclosure") has a cross-sectional structure as shown in FIG. 1. FIG. 1 is a schematic cross-sectional view showing an example of a solid electrolyte layer obtained by the method for producing a solid electrolyte layer according to the present disclosure. The solid electrolyte layer 30 includes a support 10 having pores 12, and a solid electrolyte 20 present on a surface 14 of the support 10 and inside the support 10.

[0015] In the manufacturing method of the present disclosure, the slurry is applied so that, after drying, the thickness t2 of the solid electrolyte 20 is 1.1 to 3.3 times the thickness t1 of the support 10, as shown in FIG. 1.

[0016] Without being bound by theory, when the thickness t2 of the solid electrolyte 20 is not excessively large relative to the thickness t1 of the support 10, the solid electrolyte 20 is sufficiently supported by the support 10. Therefore, cracks are less likely to occur in the solid electrolyte 20, and as a result, exposure of the support 10 on the surface of the solid electrolyte layer 30 can be suppressed.

[0017] Since the thickness t2 of the solid electrolyte 20 is not excessively thin relative to the thickness t1 of the support 10, the support 10 can be sufficiently covered with the solid electrolyte 20. As a result, the support 10 can be prevented from being exposed on the surface of the solid electrolyte layer 30.

[0018] Generally, the support 10 is made of an insulating material, and therefore, when the support 10 is exposed on the surface of the solid electrolyte layer 30, the resistance of the solid electrolyte layer 30 increases. For this reason, by preventing the support 10 from being exposed on the surface of the solid electrolyte layer 30, an increase in the resistance of the solid electrolyte layer 30 can be prevented.

[0019] Generally, when the support 10 swells due to the binder and dispersant in the slurry during application of the slurry, the expanded shape of the support 10 is maintained even after the support to which the slurry has been applied is dried and the dispersant is removed.

[0020] In the past, the expansion of the support 10 was not taken into consideration, and it is believed that the solid electrolyte 20 was not adequately supported by the support to prevent cracks from occurring in the solid electrolyte 20, or that the support 10 was not adequately covered with the solid electrolyte 20.

[0021] The manufacturing method of the present disclosure includes slurry provision, slurry application, and dispersion medium removal, each of which will be described below.

[0022] <Slurry provided> A slurry containing a solid electrolyte, a binder, and a dispersion medium is provided. In addition to the solid electrolyte, the binder, and the dispersion medium, the slurry may optionally contain, for example, a conductive aid. The slurry may be purchased commercially or prepared by the user. When the slurry is prepared by the user, examples of the method for preparing the slurry include a method of kneading a composition containing a solid electrolyte, a binder, and a dispersion medium. Examples of the kneading method include a method using a general kneading device such as a dissolver, a homomixer, a kneader, a roll mill, a sand mill, an attritor, a ball mill, a vibrator mill, a high-speed impeller mill, an ultrasonic homogenizer, or a shaker. The solid electrolyte, the binder, the dispersion medium, and the conductive additive will each be described later.

[0023] The density of the slurry is preferably 0.85 times or more, 0.88 times or more, 0.90 times or more, 0.92 times or more, 0.94 times or more, or 0.96 times or more, and preferably 1.15 times or less, 1.12 times or less, 1.00 times or less, or 0.98 times or less, relative to the density of the support. This allows the solid electrolyte to remain inside the support during the stages of slurry application and dispersion medium removal, and the solid electrolyte to adhere as evenly as possible to both surfaces of the support.

[0024] <Slurry coating> The slurry is applied to a support having pores. By applying the slurry to the support, the support is impregnated with the slurry. This allows the slurry to fill the pores of the support while leaving the slurry on the surface of the support. The method for applying the slurry is not particularly limited, but examples thereof include dipping, doctor blade, die coating, gravure coating, spray coating, electrostatic coating, and bar coating.

[0025] In the slurry coating, the thickness of the solid electrolyte is 1.1 to 3.3 times the thickness of the support after drying. If the thickness of the solid electrolyte is 1.1 times or more the thickness of the support, the support can be sufficiently covered with the solid electrolyte. From this perspective, the thickness of the solid electrolyte may be 1.2 times or more, 1.3 times or more, 1.4 times or more, 1.5 times or more, or 1.6 times or more the thickness of the support. If the thickness of the solid electrolyte is 3.3 times or less the thickness of the support, the solid electrolyte can be sufficiently supported by the support, and cracks are less likely to occur in the solid electrolyte. From this perspective, the thickness of the solid electrolyte may be 3.0 times or less, 2.7 times or less, 2.6 times or less, 2.5 times or less, 2.4 times or less, 2.3 times or less, 2.2 times or less, 2.1 times or less, or 2.0 times or less the thickness of the support.

[0026] As described above, the support generally swells when the slurry is applied, and the expanded shape of the support is maintained even after the dispersion medium is removed. Since the degree of expansion of the support is relatively stable, the slurry may be applied to the support in consideration of the expansion of the support.

[0027] In order to ensure that the thickness of the solid electrolyte and the thickness of the support are within the above-mentioned ranges, it is preferable to sandwich the support coated with the slurry between opposing members and squeeze the support coated with the slurry.

[0028] 2 is an explanatory diagram showing an example of a method for squeezing a support coated with a slurry. The support 10 coated with the slurry 22 is sandwiched between opposing members 40, and the support 10 coated with the slurry 22 is pulled up in the direction of the arrow and squeezed. The distance between the opposing members 40 may be the same as t2 in FIG. 1. In other words, the distance between the opposing members 40 may be the same as the thickness of the solid electrolyte 20 after drying (after removal of the dispersion medium).

[0029] <Dispersion medium removal> The support coated with the slurry is dried to remove the dispersion medium. The drying method is not particularly limited as long as it can remove the dispersion medium, and examples thereof include well-known methods such as warm air and / or hot air drying, infrared drying, reduced pressure drying, and dielectric heating drying. Examples of the drying atmosphere include an inert gas atmosphere such as an argon gas atmosphere and / or a nitrogen gas atmosphere, air atmosphere, and vacuum.

[0030] The drying temperature is not particularly limited, but is preferably a temperature at which the solid electrolyte does not deteriorate. The drying temperature may be, for example, 100°C or higher, 120°C or higher, or 130°C or higher, and may be 200°C or lower, 180°C or lower, or 160°C or lower. The drying time is not particularly limited and can be adjusted as appropriate.

[0031] 《Solid electrolyte layer》 The solid electrolyte layer according to the present disclosure comprises: a support having pores; and A solid electrolyte present on the surface and inside of the support Including, The thickness of the solid electrolyte membrane is 1.1 times or more and 3.3 times or less the thickness of the support.

[0032] For the structure of the solid electrolyte layer, reference can be made to FIG. 1 and the description of "<Method for manufacturing the solid electrolyte layer>" already described.

[0033] 《Solid-state battery》 3 is a cross-sectional schematic diagram showing an example of a solid-state battery including a solid electrolyte layer according to the present disclosure. In a solid-state battery 60, an anode current collector layer 52, an anode active material layer 54, a solid electrolyte layer 30, a cathode active material layer 56, and a cathode current collector layer 58 are stacked in this order. The support 10 is omitted for the solid electrolyte layer 30. The anode current collector layer 52, the anode active material layer 54, the cathode active material layer 56, and the cathode current collector layer 58 may be formed in a known manner, and an outline thereof will be described below. Each layer is stacked by a known method.

[0034] <<Solid Electrolyte Layer, Manufacturing Method Thereof, and Components of Solid-State Battery>> Hereinafter, each component of the solid electrolyte layer, the manufacturing method thereof, and the solid state battery according to the present disclosure will be described.

[0035] <Solid electrolyte> The material of the solid electrolyte is not particularly limited, and may be, for example, a sulfide solid electrolyte, an oxide solid electrolyte, or a polymer electrolyte.

[0036] Examples of sulfide solid electrolytes include, but are not limited to, sulfide-based amorphous solid electrolytes, sulfide-based crystalline solid electrolytes, and argyrodite-type solid electrolytes. Specific examples of sulfide solid electrolytes include Li2S-P2S5-based (Li7P3S 11 , Li3PS4, Li8P2S9, etc.), Li2S-SiS2, LiI-Li2S-SiS2, LiI-Li2S-P2S5, LiI-LiBr-Li2S-P2S5, Li2S-P2S5-GeS2(Li 13 GeP3S 16 , Li 10 GeP2S 12 etc.), LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, Li 7-x PS 6-x Cl x etc.; or combinations thereof, but are not limited to these.

[0037] An example of an oxide solid electrolyte is Li7La3Zr2O 12 , Li 7-x La3Zr 1-x Nbx O 12 , Li 7-3x La3Zr2Al x O 12 , Li 3x La 2 / 3-x TiO3, Li 1+x Al x Ti 2-x (PO4)3, Li 1+x Al x Ge 2-x (PO4)3, Li3PO4, or Li 3+x PO 4-x N x (LiPON), etc.; or combinations thereof.

[0038] The sulfide solid electrolyte and the oxide solid electrolyte may be glass or crystallized glass (glass ceramics).

[0039] Examples of polymer electrolytes include, but are not limited to, polyethylene oxide (PEO), polypropylene oxide (PPO), and copolymers thereof.

[0040] The ratio of the solid electrolyte to the solid components of the slurry is, for example, 70% by mass or more and 99% by mass or less. The solid electrolyte may have a particle shape, for example. The particle size (D50) of the solid electrolyte may be, for example, 10 nm or more and 50 μm or less. D50 can be calculated, for example, from measurements using a laser diffraction particle size distribution analyzer or a scanning electron microscope (SEM). The ionic conductivity (25°C) of the solid electrolyte is preferably high. The ionic conductivity (25°C) of the solid electrolyte is, for example, 1×10 -4 S / cm or more, 1×10 -3 It may be S / cm or more.

[0041] <Binder> The binder is not particularly limited. The binder may be, for example, polyvinylidene fluoride (PVdF), butadiene rubber (BR), polytetrafluoroethylene (PTFE), styrene butadiene rubber (SBR), or other materials, but is not limited to these. The binder is not particularly limited, and one type may be used alone, or two or more types may be used in combination. The proportion of the binder in the solid components of the slurry is, for example, 1% by mass or more and 30% by mass or less.

[0042] <Dispersion medium> Examples of the dispersion medium include esters such as butyl butyrate, dibutyl ether, and ethyl acetate, ketones such as diisobutyl ketone (DIBK), methyl ketone, and methyl propyl ketone, aromatic hydrocarbons such as xylene, benzene, and toluene, alkanes such as heptane, dimethylbutane, and methylhexane, and amines such as tributylamine and allylamine. The proportion of the dispersion medium in the slurry is adjusted so that the solid content of the slurry is, for example, 30% by mass to 50% by mass.

[0043] <Conductive additive> The conductive additive is not particularly limited. Examples of the conductive additive include, but are not limited to, vapor-grown carbon fiber (VGCF), acetylene black (AB), ketjen black (KB), carbon nanotubes (CNT), and carbon nanofibers (CNF). The conductive additive may be, for example, particulate or fibrous, and its size is not particularly limited. The conductive additive is not particularly limited, and one type may be used alone, or two or more types may be used in combination.

[0044] <Negative electrode current collector layer> The material used for the negative electrode current collector layer is not particularly limited, and any material commonly used for a negative electrode current collector in a battery can be appropriately used. Examples of materials used for the negative electrode current collector layer include, but are not limited to, Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, stainless steel, and a carbon sheet. The negative electrode current collector layer may have a coating layer on its surface for the purpose of adjusting resistance, etc.

[0045] <Negative electrode active material layer> The negative electrode active material layer contains at least a negative electrode active material, and may further contain, optionally, a solid electrolyte, a conductive additive, a binder, etc. The negative electrode active material layer may also contain various other additives. The contents of the negative electrode active material, solid electrolyte, conductive additive, binder, etc. in the negative electrode active material layer may be appropriately determined depending on the desired battery performance.

[0046] As the negative electrode active material, various materials can be used that have a potential (charge / discharge potential) at which they absorb and release lithium ions that is lower than that of the positive electrode active material described below. The material for the negative electrode active material is not particularly limited, and may be metallic lithium or a material capable of absorbing and releasing metal ions such as lithium ions. Examples of materials capable of absorbing and releasing metal ions such as lithium ions include alloy-based negative electrode active materials, carbon materials, and lithium titanate (Li4Ti5O 12 ) and the like can be mentioned, but are not limited to these.

[0047] The alloy-based negative electrode active material is not particularly limited, and examples thereof include Si alloy-based negative electrode active materials and Sn alloy-based negative electrode active materials. Examples of Si alloy-based negative electrode active materials include silicon, silicon oxide, silicon carbide, silicon nitride, and solid solutions thereof. The Si alloy-based negative electrode active material may contain metal elements other than silicon, such as Fe, Co, Sb, Bi, Pb, Ni, Cu, Zn, Ge, In, Sn, and Ti. Examples of Sn alloy-based negative electrode active materials include tin, tin oxide, tin nitride, and solid solutions thereof. The Sn alloy-based negative electrode active material may contain metal elements other than tin, such as Fe, Co, Sb, Bi, Pb, Ni, Cu, Zn, Ge, In, Ti, and Si.

[0048] The carbon material is not particularly limited, and examples thereof include hard carbon, soft carbon, graphite, and the like.

[0049] <Cathode active material layer> The positive electrode active material layer contains at least a positive electrode active material, and may further contain, optionally, a solid electrolyte, a conductive additive, a binder, etc. The positive electrode active material layer may also contain various other additives. The contents of the positive electrode active material, solid electrolyte, conductive additive, binder, etc. in the positive electrode active material layer may be appropriately determined depending on the desired battery performance.

[0050] The material of the positive electrode active material is not particularly limited as long as it can absorb and release lithium ions. Examples of the positive electrode active material include lithium cobalt oxide (LiCoO), lithium nickel oxide (LiNiO), lithium manganese oxide (LiMnO), and nickel-cobalt-manganese oxide (NCM:LiCO 1 / 3 Ni 1 / 3 Mn 1 / 3 O2), lithium nickel-cobalt-aluminate (LiNi 0.8 (CoAl) 0.2 O2), Li 1+x Mn 2-x-y M yThe material may be, but is not limited to, a different element-substituted Li-Mn spinel having a composition represented by O4 (M is one or more metal elements selected from Al, Mg, Co, Fe, Ni, and Zn).

[0051] The positive electrode active material may have a coating layer, although it is not particularly limited. The coating layer is a layer containing a substance that has lithium ion conductivity, low reactivity with the positive electrode active material and the solid electrolyte, and can maintain the shape of the coating layer without flowing even when in contact with the active material and the solid electrolyte. Specific examples of materials that constitute the coating layer include LiNbO3 and Li4Ti5O 12 , Li3PO4, etc., but are not limited to these.

[0052] For the solid electrolyte, conductive additive, and binder that can be contained in the positive electrode active material layer, reference can be made to the above description of "<Negative electrode active material layer>".

[0053] <Positive electrode current collector layer> The material used for the positive electrode current collector layer is not particularly limited, and any material commonly used for a battery positive electrode current collector can be appropriately adopted. Examples of materials used for the positive electrode current collector layer include, but are not limited to, Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, and stainless steel. The positive electrode current collector layer may have a coating layer on its surface for purposes such as adjusting resistance. The positive electrode current collector layer may also be a metal foil or a substrate on which the above metals are plated or vapor-deposited. [Example]

[0054] <Sample Preparation> Each sample was prepared as follows.

[0055] The sulfide solid electrolyte was weighed to 99% by mass and the styrene butadiene rubber (SBR) binder to 1% by mass. These were added to a dispersion medium so that the solid content was 30% by mass or more and 50% by mass or less, and ultrasonic dispersion treatment was performed for 1 minute using an ultrasonic dispersion device. This produced a slurry for the solid electrolyte layer.

[0056] After immersing a nonwoven fabric as a support in the slurry, the nonwoven fabric to which the slurry had adhered was squeezed using the member 40 shown in Fig. 3, and the slurry was applied to the nonwoven fabric. The basis weight, including the nonwoven fabric, was 1 mg / cm 3 More than 10mg / cm 3 It was as follows.

[0057] The squeezed nonwoven fabric was hung up to dry, and a sample was obtained.

[0058] "evaluation" The surface of each sample was observed using a laser microscope to check whether the nonwoven fabric was exposed on the surface of the solid electrolyte layer. For the samples of Examples 1 to 4, the cross section of the sample was observed under a microscope to check the thickness t of the nonwoven fabric after drying. 1b was measured.

[0059] Thickness of the support (nonwoven fabric) after drying t 1b It was confirmed that in all of the samples of Examples 1 to 4, in which the ratio of the thickness t2 of the solid electrolyte to the thickness t2 was within the predetermined range, the nonwoven fabric was not exposed on the surface of the solid electrolyte layer.

[0060] On the other hand, in the sample of Comparative Example 1, the solid electrolyte was not sufficiently supported by the support, causing cracks on the surface of the solid electrolyte layer and exposing the nonwoven fabric, while in the sample of Comparative Example 2, the support was not sufficiently covered with the solid electrolyte, causing the nonwoven fabric to be exposed.

[0061] For the samples of Comparative Examples 1 and 2, the thickness t of the support (nonwoven fabric) after drying 1b The ratio of the thickness of the solid electrolyte t2 to the thickness of the solid electrolyte (t2 / t 1b ) but the thickness of the support (nonwoven fabric) before coating, t 1a The ratio of the thickness of the solid electrolyte t2 to the thickness of the solid electrolyte (t2 / t 1a In the samples of Examples 1 to 4, the thickness (t 1a ) to the thickness of the support (nonwoven fabric) after drying (t 1b) was 1.278 times at maximum. Using this value, the t2 / t 1a from t2 / t 1b From these converted values, the t2 / t 1b The sample of Comparative Example 2 exceeds the upper limit of t2 / t 1b It can be understood that the lower limit of

[0062] These findings confirm the effects of the solid electrolyte layer and the manufacturing method thereof according to the present disclosure, and also suggest that a solid battery including the solid electrolyte layer according to the present disclosure will achieve the desired effects.

[0063] [Table 1] [Explanation of symbols]

[0064] 10 Support 12 Vacancies 14 Surface 20 Solid electrolyte 22 Slurry 30 Solid electrolyte layer 40 components 52 Negative electrode current collector layer 54 Negative electrode active material layer 56 Cathode active material layer 58 Positive electrode current collector layer

Claims

1. providing a slurry containing a solid electrolyte, a binder, and a dispersion medium; applying the slurry to a porous support; and drying the support coated with the slurry to remove the dispersion medium; Including, The slurry is applied so that the thickness of the solid electrolyte after drying is 1.1 times or more and 3.3 times or less the thickness of the support. Method for manufacturing a solid electrolyte layer.

2. The method for producing a solid electrolyte layer according to claim 1 , wherein the density of the slurry is 0.85 to 1.15 times the density of the support.

3. a support having pores; and A solid electrolyte present on the surface and inside of the support Including, The thickness of the solid electrolyte is 1.1 times or more and 3.3 times or less the thickness of the support. Solid electrolyte layer.

4. A solid-state battery comprising the solid electrolyte layer according to claim 3 .

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