Solid electrolyte and all-solid-state battery comprising same

Abstract

The present invention relates to a solid electrolyte comprising: sulfide-based solid electrolyte particles; and a plurality of La-containing fine particles disposed on the surface of the sulfide-based solid electrolyte particles.

Description

Solid electrolyte and all-solid-state battery containing the same

[0001] The present invention relates to a solid electrolyte and an all-solid-state battery including the same.

[0002]

[0003] Research on the safety issues and energy density of high-capacity batteries is attracting attention, and all-solid-state batteries are gaining attention as next-generation batteries.

[0004] The above all-solid-state battery is a battery that ensures battery safety because it replaces the liquid electrolyte that causes explosion with a solid electrolyte, does not use a flammable solvent in the battery, and thus does not cause any ignition or explosion due to a reaction such as the decomposition reaction of a conventional electrolyte.

[0005] Additionally, since lithium metal or a lithium alloy can be used as the negative electrode material, the energy density for the mass and volume of the battery can be improved.

[0006] The solid electrolyte used in the above-mentioned all-solid-state battery is generally an inorganic solid electrolyte, and various studies are being conducted on a sulfide-based solid electrolyte having a composition such as Li6PS5Cl, which has an argyrodite structure among the above-mentioned all-solid-state batteries.

[0007] Although argyrodite-based sulfide solid electrolytes have high lithium ion conductivity, they have a problem with poor moisture stability, such as the S element among the constituent elements reacting sensitively with moisture in the air, causing a sharp decrease in ion conductivity.

[0008] To solve this problem, there have been attempts to control the composition itself, such as by introducing doping elements into the basic argyrodite-based solid electrolyte, or to improve moisture stability through surface modification. However, there is currently no technology to fundamentally prevent the reaction between the argyrodite-based solid electrolyte and moisture in the atmosphere.

[0009]

[0010] Accordingly, one object of the present invention is to provide a solid electrolyte having high ionic conductivity as a sulfide-based solid electrolyte, and improved moisture stability by fundamentally controlling the reaction with moisture in the atmosphere, a method for producing the same, and an all-solid-state battery including the same.

[0011]

[0012] One embodiment of the present invention provides a solid electrolyte comprising: sulfide-based solid electrolyte particles; and a plurality of La-containing fine particles arranged on the surface of the sulfide-based solid electrolyte particles.

[0013] The above sulfide-based solid electrolyte particles may be argyrodite-based solid electrolyte particles.

[0014] The above-mentioned plurality of La-containing fine particles may exist in a form in which they are attached to each other and spaced apart from each other on the surface of the sulfide-based solid electrolyte particles.

[0015] The above La-containing fine particles may include La oxide.

[0016] The above La-containing fine particles may include a La2O3 phase.

[0017] The above La-containing fine particles may further include a La(OH)3 phase.

[0018] The content of the above La-containing fine particles may be 2 to 30 wt% based on the total weight of the solid electrolyte.

[0019] The ratio of the average particle diameter (D50) of the La-containing fine particles to the average particle diameter (D50) of the sulfide-based solid electrolyte may be 0.0005 to 0.017.

[0020] The average particle diameter (D50) of the above sulfide-based solid electrolyte may be 0.6 to 12.0 μm.

[0021] The average particle diameter (D50) of the above La-containing fine particles may be 5 to 400 nm.

[0022] The above solid electrolyte can exhibit a first peak in the range of 30.2˚≤2θ≤30.3˚ when analyzing an X-ray diffraction (XRD) pattern.

[0023] The solid electrolyte may have a decrease in the first peak intensity of 20% or less when exposed to an air atmosphere of 25°C and a relative humidity of 40% for 60 minutes.

[0024] The above solid electrolyte can exhibit a second peak in the range of 25.5˚≤2θ≤25.7˚ when analyzing an X-ray diffraction (XRD) pattern.

[0025] The solid electrolyte may have a decrease in the second peak intensity of 20% or less when exposed to an air atmosphere of 25°C and a relative humidity of 40% for 60 minutes.

[0026]

[0027] A solid electrolyte according to one embodiment of the present invention can not only realize excellent ionic conductivity but also improve stability against moisture in the air by further including La-containing fine particles on the surface of a sulfide-based solid electrolyte.

[0028]

[0029] Figure 1 is a conceptual diagram of a solid electrolyte according to one embodiment of the present invention.

[0030] Figure 2 is an SEM image of a solid electrolyte manufactured according to Example 2, Example 3, and Reference Example 3.

[0031] Figure 3 shows the results of an X-ray diffraction pattern analysis over time when the solid electrolyte manufactured according to Comparative Example 1 is exposed to an air atmosphere with a relative humidity of 40%.

[0032] Figure 4 shows the results of an X-ray diffraction pattern analysis over time when a solid electrolyte manufactured according to Example 2 is exposed to an air atmosphere with a relative humidity of 40%.

[0033] Figure 5 shows the results of an X-ray diffraction pattern analysis over time when the solid electrolyte manufactured according to Example 3 is exposed to an air atmosphere with a relative humidity of 40%.

[0034] Figure 6 shows the results of an X-ray diffraction pattern analysis over time when the solid electrolyte manufactured according to Reference Example 3 is exposed to an air atmosphere with a relative humidity of 40%.

[0035] The terms first, second, and third, etc., are used to describe, but are not limited to, various parts, components, regions, layers, and / or sections. These terms are used only to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Accordingly, a first part, component, region, layer, or section described below may be referred to as a second part, component, region, layer, or section without departing from the scope of the present invention.

[0036] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the present invention. As used herein, the singular forms "singular" and "comprising" include plural forms as well, unless the context clearly dictates otherwise. The word "comprising" as used herein specifies a particular feature, region, integer, step, operation, element, and / or component, but does not exclude the presence or addition of other features, regions, integers, steps, operations, elements, and / or components.

[0037] When a part is referred to as being "on" or "over" another part, it can be directly on or over the other part, or there may be other parts intervening. Conversely, when a part is referred to as being "directly on" another part, there are no other parts intervening.

[0038] Although not defined otherwise, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention pertains. Terms defined in commonly used dictionaries are further interpreted to have meanings consistent with the relevant technical literature and the present disclosure, and are not to be construed as ideal or overly formal unless otherwise defined.

[0039] Also, unless otherwise stated, % means weight%, and 1 ppm is 0.0001 weight%.

[0040] In this specification, the term "combination(s) thereof" described in the expression in the Makushi format means one or more mixtures or combinations selected from the group consisting of the components described in the expression in the Makushi format, and means including any one or more selected from the group consisting of said components.

[0041] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0042]

[0043] 1. Solid electrolyte

[0044] Figure 1 is a conceptual diagram of a solid electrolyte according to one embodiment of the present invention.

[0045] Referring to FIG. 1, a solid electrolyte according to one embodiment of the present invention includes sulfide-based solid electrolyte particles.

[0046] The above sulfide-based solid electrolyte particles may be, more specifically, argyrodite-based solid electrolyte particles. Accordingly, excellent ionic conductivity can be achieved.

[0047] The above argyrodite-based solid electrolyte is not particularly limited as long as it has an argyrodite-based crystal structure.

[0048] The above argyrodite-based solid electrolyte may optionally further include other doping elements as needed in addition to the basic elements Li, P, S, and halogen elements.

[0049] The above other doping elements may be, for example, Al, Zr, Zn, Si, Sn, B, C, Ga, Ge, Na, Mg, Ca or a combination thereof.

[0050] However, although these sulfide-based solid electrolyte particles have excellent ionic conductivity immediately after synthesis, there is a problem in that S, one of the constituent elements, reacts with moisture in the air, causing deterioration of the crystal structure and rapid deterioration of the ionic conductivity.

[0051] Accordingly, a solid electrolyte according to one embodiment of the present invention further includes a plurality of La-containing fine particles arranged on the surface of sulfide-based solid electrolyte particles. By further including the La-containing fine particles in the solid electrolyte, moisture stability can be improved, thereby reducing deterioration in ionic conductivity over time immediately after synthesis. More specifically, the La-containing fine particles have a stronger reactivity with atmospheric moisture than the sulfide-based solid electrolyte, and when present in a complexed form with the sulfide-based solid electrolyte, they participate in a reaction with atmospheric moisture before the sulfide-based solid electrolyte. Through this, the moisture stability of the sulfide-based solid electrolyte can be improved.

[0052] In addition, the La-containing fine particles can have moisture removed when subjected to heat treatment. Therefore, after the La-containing fine particles in the solid electrolyte have reacted to a certain extent with atmospheric moisture, moisture within the La-containing fine particles can be removed again through heat treatment, thereby achieving a continuous improvement in moisture stability.

[0053] The above heat treatment may be a low-temperature heat treatment, and may be performed, for example, at a temperature of 100 to 500°C for 1 to 8 hours. When the heat treatment temperature and time satisfy the above range, the deterioration of the crystal structure of the sulfide-based solid electrolyte can be prevented, thereby achieving a continuous improvement in moisture stability without a significant deterioration in ionic conductivity.

[0054] At this time, the sulfide-based solid electrolyte particles and La-containing fine particles may exist in a complexed form through physical or chemical bonding.

[0055] In addition, the plurality of La-containing fine particles may exist in a form in which they are attached to each other and spaced apart from each other on the surface of the sulfide-based solid electrolyte particles.

[0056] The above La-containing fine particles may include, for example, a phase of La2O3, La(OH)3, LaCl3, LaC, LaPO4, LaI3, LaNO3 or a combination thereof.

[0057] The above La-containing fine particles may more specifically include La oxide. Among La compounds, La oxide in particular has a higher reactivity with moisture than other types of compounds, so that the effect of improving moisture stability can be more preferably implemented.

[0058] The above La oxide may include, for example, a phase of La2O3, La(OH)3 or a combination thereof.

[0059] More specifically, the La-containing fine particles include a La2O3 phase and may further include a La(OH)3 phase. The La(OH)3 phase may be a product generated when the La-containing fine particles react with moisture in the air.

[0060] That is, the above La-containing fine particles may simultaneously include La2O3 phase and La(OH)3 phase over time after the solid electrolyte is manufactured.

[0061] In addition, the content of the La-containing fine particles may be 2 to 30 wt%, and more specifically, 2 to 25 wt% or 2 to 22 wt%, based on the total weight of the solid electrolyte. If the content of the La-containing fine particles is too low, the aforementioned moisture stability improvement effect may be minimal. If the content of the La-containing fine particles is too high, there may be a problem of deterioration of ionic conductivity due to increased resistance.

[0062] In addition, the ratio of the average particle diameter (D50) of the La-containing fine particles to the average particle diameter (D50) of the sulfide-based solid electrolyte may be 0.0005 to 0.017, and more specifically, 0.0007 to 0.015. If the ratio of the average particle diameter of the La-containing fine particles to the average particle diameter of the sulfide-based solid electrolyte is too small, there may be a problem of uneven dispersion. If the ratio of the average particle diameter of the La-containing fine particles to the average particle diameter of the sulfide-based solid electrolyte is too large, the La-containing fine particle coating on the sulfide-based solid electrolyte may not be properly formed, which may cause a problem of minimal improvement in moisture stability.

[0063] The average particle size (D50) of the above sulfide-based solid electrolyte may be 0.6 to 12.0 μm, more specifically 1.0 to 12.0 μm. If the average particle size of the sulfide-based solid electrolyte is too small, agglomeration problems may occur. If the average particle size of the sulfide-based solid electrolyte is too large, a problem of increased lithium ion resistance in the cell may occur.

[0064] The average particle diameter (D50) of the above La-containing fine particles may be 5 to 400 nm, and more specifically, 5 to 300 nm. If the average particle diameter of the La-containing fine particles is too small, there may be a problem of uneven dispersion. If the average particle diameter of the La-containing fine particles is too large, the La-containing fine particle coating may not be properly formed on the sulfide-based solid electrolyte, which may cause a problem of minimal improvement in moisture stability.

[0065] Meanwhile, in this specification, the average particle diameter (D50) can be defined as the particle diameter corresponding to 50% of the volume accumulation amount in the particle diameter distribution curve. The average particle diameter (D50) can be measured using, for example, the laser diffraction method. The laser diffraction method can generally measure particle diameters from the submicron range to several millimeters, and can obtain results with high reproducibility and high resolution.

[0066]

[0067] The above solid electrolyte can exhibit a first peak in the range of 30.2˚≤2θ≤30.3˚ when analyzing an X-ray diffraction (XRD) pattern. The peak in the above range may indicate an argyrodite-based crystal phase, and excellent ionic conductivity can be achieved by having the first peak.

[0068] At this time, when the solid electrolyte is exposed to an air atmosphere of 25°C and a relative humidity of 40% for 60 minutes, the decrease rate of the first peak intensity may be 20% or less, and more specifically, 16% or less. That is, the solid electrolyte according to the present invention has improved moisture stability, and can well maintain the argyrodite crystal structure even when exposed for 60 minutes under the above conditions. Accordingly, the first peak intensity can be well maintained, and deterioration of ionic conductivity can be prevented.

[0069] The above solid electrolyte may exhibit a second peak in the range of 25.5˚≤2θ≤25.7˚ when analyzing an X-ray diffraction (XRD) pattern. The peak in the above range may indicate an argyrodite-based crystal phase, and excellent ionic conductivity can be achieved by having the second peak.

[0070] At this time, when the solid electrolyte is exposed to an air atmosphere of 25°C and a relative humidity of 40% for 60 minutes, the decrease rate of the second peak intensity may be 20% or less, and more specifically, 19% or less. That is, the solid electrolyte according to the present invention has improved moisture stability, and can well maintain the argyrodite crystal structure even when exposed to an environment under the above conditions for 60 minutes. Accordingly, the second peak intensity can be well maintained, and deterioration of ionic conductivity can be prevented.

[0071]

[0072] 2. Solid electrolyte manufacturing method

[0073] A method for manufacturing a solid electrolyte according to another embodiment of the present invention is very simple and economical, as it is possible to obtain a solid electrolyte by preparing a sulfide-based solid electrolyte and La-containing fine particles and simply mixing them.

[0074] More specifically, a method for manufacturing a solid electrolyte according to another embodiment of the present invention may include a step of preparing a sulfide-based solid electrolyte; a step of preparing La-containing fine particles; and a step of mixing the sulfide-based solid electrolyte and the La-containing fine particles.

[0075] Hereinafter, a method for manufacturing a solid electrolyte according to another embodiment of the present invention will be described in detail step by step.

[0076]

[0077] First, prepare a sulfide-based solid electrolyte.

[0078] The above sulfide-based solid electrolyte can be prepared by purchasing a commercially available sulfide-based solid electrolyte, or can be manufactured according to a manufacturing method of a sulfide-based solid electrolyte common in the art.

[0079] The above sulfide-based solid electrolyte may be, more specifically, an argyrodite-based solid electrolyte.

[0080] The above argyrodite-based solid electrolyte can be manufactured, for example, by a step of forming a mixture by mixing a lithium raw material, a phosphorus raw material, and a halogen element raw material; and a step of heat-treating the mixture to form a sulfide-based solid electrolyte having an argyrodite-based crystal structure.

[0081] The above lithium raw material may be, for example, Li2S, Li2S2, or a combination thereof, but is not necessarily limited thereto.

[0082] The above raw material may be, for example, P2S5, P2O5 or a combination thereof, but is not necessarily limited thereto.

[0083] The above halogen element raw material may be, for example, LiF, LiCl, LiBr, LiI, or a combination thereof, but is not necessarily limited thereto. More specifically, the above halogen element raw material may be LiCl.

[0084] The above mixing can be performed by mechanical mixing or chemical mixing.

[0085] The above mechanical mixing can be performed by, for example, a planetary mill, a paint shaker, a ball mill, a bead mill, a homogenizer, a hammer mill, a turbo mill, a disc mill, a planetary mill, a mechanofusion mill, etc.

[0086] The above chemical mixing can be performed, for example, by melt quenching.

[0087] The above mixing can be performed for 4 to 12 hours, specifically 6 to 10 hours, and more specifically 7 to 9 hours. If the mixing time is too short, the mixing will not be sufficient, and thus the synthesis of the solid electrolyte may not proceed well in the heat treatment process described later. If the mixing time is too long, the mixing will be completed after a certain period of time, and even if the mixing is performed further, the mixing state will remain the same, which may cause problems in terms of process efficiency.

[0088] The above mixing can be performed at a rotation speed of 100 to 500 rpm, specifically 150 to 450 rpm, and more specifically 200 to 400 rpm. If the rotation speed is too slow, the balls may not be able to enter the inside of the powder particles, which may result in a problem of less overall mixing of the powder particles or less atomization of the powder particles due to low energy. On the other hand, if the rotation speed is too fast, the powder particles may be concentrated in one area, which may result in a problem of less even mixing.

[0089] Of course, if a doping element is to be introduced into the argyrodite-based solid electrolyte, the doping raw material can be further mixed in when forming the mixture.

[0090] Next, optionally, after the step of forming the mixture, a step of compressing the mixture to form pellets may be further included.

[0091] At this time, the compression can be performed at a pressure of 100 to 500 Mpa, specifically 150 to 450 Mpa, more specifically 200 to 400 Mpa. If the pressure is too low, a problem may arise in that the interfacial resistance may increase due to insufficient bonding between the powder particles. On the other hand, if the pressure is too high, the bonding between the powder particles may already occur, and the bonding state may not change even if further pressure is applied, which may cause a problem in terms of process efficiency. Therefore, it is desirable in terms of productivity to form pellets at an appropriate pressure.

[0092] Next, the mixture is heat-treated to form a sulfide-based solid electrolyte having an argyrodite-based crystal structure.

[0093] At this time, the heat treatment can be performed at a temperature of 400 to 700°C, and more specifically, can be performed at 500 to 600°C. If the heat treatment temperature is too low, the synthesis of a solid electrolyte having an argyrodite crystal structure may not occur sufficiently, or the solid electrolyte may be synthesized in an amorphous crystal structure, which may reduce the ionic conductivity of the solid electrolyte. If the heat treatment temperature is too high, the elements forming the solid electrolyte may vaporize, resulting in the loss of the solid electrolyte, or an impurity phase may be generated, which may reduce the ionic conductivity of the solid electrolyte.

[0094] In addition, the heat treatment may be performed for 2 to 8 hours, and more specifically, for 3 to 5 hours. If the heat treatment time is too short, the synthesis of the solid electrolyte having an argyrodite crystal structure may not occur sufficiently, or the solid electrolyte may be synthesized in an amorphous crystal structure, which may reduce the ionic conductivity of the solid electrolyte. If the heat treatment time is too long, the elements constituting the solid electrolyte may vaporize, resulting in the loss of the solid electrolyte, or an impurity phase may be generated, which may reduce the ionic conductivity of the solid electrolyte.

[0095] Additionally, the heat treatment may be performed in an inert gas atmosphere. Since the heat treatment is performed in an inert gas atmosphere, there may be an advantage in that contact with atmospheric moisture can be prevented. The inert gas atmosphere may be, for example, an Ar, N2, H2, or He atmosphere, and more specifically, an Ar atmosphere.

[0096] A sulfide-based solid electrolyte can be manufactured through the above series of steps.

[0097] The average particle diameter (D50) of the above sulfide-based solid electrolyte may be 3 to 7 μm. The technical significance of controlling the average particle diameter of the sulfide-based solid electrolyte is as described above and therefore is omitted.

[0098]

[0099] Next, prepare La-containing fine particles.

[0100] The above La-containing fine particles can be prepared by obtaining commercially available La-containing fine particles.

[0101] At this time, the composition of the La-containing fine particles is omitted as mentioned above.

[0102] In addition, the average particle diameter (D50) of the La-containing fine particles may be 5 to 400 nm. The technical significance of controlling the average particle diameter of the La-containing fine particles is as described above, and therefore is omitted.

[0103] In addition, the ratio of the average particle diameter (D50) of the La-containing fine particles to the average particle diameter (D50) of the sulfide-based solid electrolyte may be 0.0005 to 0.017. The technical significance of controlling the ratio of the average particle diameter (D50) of the La-containing fine particles to the average particle diameter (D50) of the sulfide-based solid electrolyte is as described above, and therefore is omitted.

[0104]

[0105] Next, the above sulfide-based solid electrolyte and La-containing fine particles are mixed to form a solid electrolyte according to the present invention.

[0106] As such, the solid electrolyte according to the present invention can be manufactured by simply mixing the sulfide-based solid electrolyte and La-containing fine particles, making the manufacturing method very simple and economical. Furthermore, as described in the experimental examples described below, the inventors of the present invention were able to confirm that even when the sulfide-based solid electrolyte and La-containing fine particles are simply mixed, they exhibit a complex structure in which they are physically or chemically bonded and attached. The inventors believe that this is due to the attractive force caused by van der Waals between the particles.

[0107] The above mixing can be performed by mechanical mixing.

[0108] The above mechanical mixing can be performed by, for example, a planetary mill, a paint shaker, a ball mill, a bead mill, a homogenizer, a hammer mill, a turbo mill, a disc mill, a planetary mill, a mechanofusion mill, etc.

[0109] At this time, the mixing can be performed at a stirring speed of 50 to 150 rpm. If the stirring speed is too slow, there may be a problem of uneven coating. If the stirring speed is too fast, there may be a problem of particle damage.

[0110] Meanwhile, the amount of La-containing fine particles to be introduced may be 2 to 30 wt% based on the total weight of the solid electrolyte. The technical significance of controlling the content of La-containing fine particles is as described above and therefore is omitted.

[0111]

[0112] 3. All-solid-state battery

[0113] Another embodiment of the present invention provides an all-solid-state battery comprising a positive electrode layer; a negative electrode layer, and a solid electrolyte layer positioned between the positive electrode layer and the negative electrode layer, wherein at least one of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer comprises the above-described solid electrolyte.

[0114]

[0115] (bipolar layer)

[0116] More specifically, the above positive electrode layer may include a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector.

[0117] The above-described positive electrode active material layer may further include, for example, a positive electrode active material and optionally a solid electrolyte as needed. The solid electrolyte included in the positive electrode active material layer may be the same as or different from the solid electrolyte according to one embodiment of the present invention, and may be the same as or different from the solid electrolyte included in the solid electrolyte layer.

[0118] A cathode active material is a material that can reversibly absorb and desorb lithium ions. Examples of cathode active materials include, but are not limited to, lithium transition metal oxides such as lithium cobalt oxide (LCO), lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminum oxide (NCA), lithium nickel cobalt manganese oxide (NCM), lithium manganate, and lithium iron phosphate; nickel sulfide, copper sulfide, lithium sulfide, iron oxide, or vanadium oxide; and the like. Any material used as a cathode active material in the relevant technical field may be used. The cathode active materials may be singly or as a mixture of two or more.

[0119] The above lithium transition metal oxide is, for example, Li a A 1-b B b D2 (in the above formula, 0.90 ≤ a ≤ 1, and 0 ≤ b ≤ 0.5); Li a E 1-b B b O 2-c D c (In the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); LiE2-b B b O 4-c D c (In the above formula, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li a Ni 1-b-c Co b B c D α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li a Ni 1-b-c Co b B c O 2-α F α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Co b B c O 2-α F2 (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Mn b B c D α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li a Ni 1-b-c Mn b B c O 2-α F α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Mn b B c O 2-α F2 (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni b E c Gd O2 (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1); Li a Ni b Co c Mn d GeO2 (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, 0.001 ≤ e ≤ 0.1); Li a NiG b O2 (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a CoG b O2 (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a MnG b O2 (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a Mn2G b O4 (wherein 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); QO2; QS2; LiQS2; V2O5; LiV2O5; LiIO2; LiNiVO4; Li (3-f) J2(PO4)3(0 ≤ f ≤ 2); Li (3-f)Fe2(PO4)3(0 ≤ f ≤ 2); A compound represented by any one of the chemical formulas of LiFePO4. In this compound, A is Ni, Co, Mn, or a combination thereof; B is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D is O, F, S, P, or a combination thereof; E is Co, Mn, or a combination thereof; F is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; Q is Ti, Mo, Mn, or a combination thereof; I is Cr, V, Fe, Sc, Y, or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof. It is also possible to use a compound having a coating layer added to the surface of this compound, and it is also possible to use a mixture of the above-mentioned compound and the compound having a coating layer added. The coating layer added to the surface of these compounds includes a coating element compound of, for example, an oxide, a hydroxide, an oxyhydroxide of the coating element, an oxycarbonate of the coating element, or a hydroxycarbonate of the coating element of the coating element. The compound forming the coating layer is amorphous or crystalline. The coating elements included in the coating layer are Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or a mixture thereof. The method for forming the coating layer is selected within a range that does not adversely affect the physical properties of the positive electrode active material. The coating method includes, for example, spray coating and dipping. Since the specific coating method is well understood by those working in the relevant field, a detailed description thereof will be omitted.

[0120] The positive electrode active material layer may include, for example, a binder. The binder may include, but is not limited to, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, and the like, and any binder used in the art may be used.

[0121] The positive electrode active material layer may include, for example, a conductive material. The conductive material may include, but is not limited to, graphite, carbon black, acetylene black, Ketjen black, carbon fiber, metal powder, etc., and any conductive material used in the relevant technical field may be used.

[0122] The positive electrode active material layer may further include, for example, additives such as fillers, coating agents, dispersants, and ion conductive aids in addition to the above-described positive electrode active material, solid electrolyte, binder, and conductive agent.

[0123] As fillers, coating agents, dispersants, ion conductive aids, etc. that the positive electrode active material layer may include, known materials generally used in electrodes of all-solid-state secondary batteries can be used.

[0124] The positive electrode collector may be, for example, a plate or foil made of indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof. The thickness of the positive electrode collector may be, for example, 1 um to 100 um, 1 um to 50 um, 5 um to 25 um, or 10 um to 20 um.

[0125]

[0126] (cathode layer)

[0127] The above negative electrode layer may more specifically include a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector.

[0128] The above negative electrode active material layer may include, for example, a negative electrode active material and a binder, and may optionally further include a solid electrolyte as needed.

[0129] The above negative electrode active material may include, for example, a carbon-based negative electrode active material, a metal / metalloid negative electrode active material, or a combination thereof.

[0130] The above carbon-based negative electrode active material may be amorphous carbon, crystalline carbon, or a mixture or composite thereof. The amorphous carbon may be, for example, carbon black (CB), acetylene black (AB), furnace black (FB), ketjen black (KB), graphene, etc., but is not necessarily limited thereto, and any material classified as amorphous carbon in the relevant technical field may be used. Amorphous carbon is carbon that has no crystallinity or very low crystallinity, and is distinguished from crystalline carbon or graphitic carbon. The crystalline carbon may be, for example, natural graphite, artificial graphite, or a combination thereof.

[0131] The metal / metalloid negative electrode active material includes at least one selected from the group consisting of lithium (Li), gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn), but is not necessarily limited thereto, and any metal negative electrode active material or metalloid negative electrode active material that forms an alloy or compound with lithium in the relevant technical field may be used.

[0132] The binder included in the negative electrode active material layer may be, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, etc., but is not necessarily limited thereto, and any binder used in the relevant technical field may be used. The binder may be composed of a single binder or a plurality of different binders.

[0133] By including a binder in the negative electrode active material layer, the negative electrode active material layer is stabilized on the negative electrode current collector. Furthermore, cracking of the negative electrode active material layer is suppressed despite changes in volume and / or relative position of the negative electrode active material layer during the charge / discharge process.

[0134] The negative active material layer may further include additives used in conventional all-solid-state batteries, such as fillers, coating agents, dispersants, and ion conductive aids.

[0135] The all-solid-state battery may further include a second negative electrode active material layer disposed between the negative electrode current collector and the negative electrode active material layer during charging. The second negative electrode active material layer may be deposited between the negative electrode current collector and the negative electrode current collector during the charging process, or may be further disposed on the negative electrode active material layer during electrode assembly. The second negative electrode active material layer may be a metal layer containing lithium or a lithium alloy. The lithium alloy includes, but is not limited to, a Li-Al alloy, a Li-Sn alloy, a Li-In alloy, a Li-Ag alloy, a Li-Au alloy, a Li-Zn alloy, a Li-Ge alloy, a Li-Si alloy, and the like, and any lithium alloy used in the art may be used. The second negative electrode active material layer may be made of one of these alloys and / or lithium, or may be made of multiple types of alloys and / or lithium.

[0136] The negative electrode current collector may be composed of, for example, a material that does not react with lithium, i.e., does not form an alloy or compound. The negative electrode current collector may include, but is not limited to, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni), and any material that is used as an electrode current collector in the art may be used. The negative electrode current collector may be composed of one of the above-described metals, or may be composed of an alloy or a coating material of two or more metals. The negative electrode current collector may be, for example, in the form of a plate or foil.

[0137] When the negative electrode active material layer includes a solid electrolyte, the solid electrolyte included in the negative electrode active material layer may be the same as or different from the solid electrolyte according to one embodiment of the present invention, and may be the same as or different from the solid electrolyte included in the solid electrolyte layer.

[0138]

[0139] (solid electrolyte layer)

[0140] The above solid electrolyte layer can be manufactured by mixing and drying the above-described solid electrolyte and binder, or by rolling the above-described solid electrolyte powder into a certain shape under a pressure of 1 ton to 10 tons.

[0141] At this time, the solid electrolyte may be in the form of a powder or a molded product. The solid electrolyte in the form of a molded product may be in the form of, for example, pellets, sheets, thin films, etc., but is not necessarily limited to these and may have various forms depending on the intended use.

[0142] The above solid electrolyte layer may further include a solid electrolyte such as a conventional sulfide-based solid electrolyte and / or an oxide-based solid electrolyte in addition to the above-described solid electrolyte, if necessary.

[0143] The above binder may be, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polyvinyl alcohol, etc., but is not limited thereto, and any binder used in the relevant technical field may be used. The binder of the solid electrolyte layer may be the same as or different from the binders of the positive and negative electrode layers.

[0144]

[0145] Another embodiment of the present invention provides an electric vehicle including the all-solid-state battery.

[0146]

[0147] Hereinafter, embodiments of the present invention will be described in more detail through examples. However, the following examples are merely preferred embodiments of the present invention, and the present invention is not limited to the following examples.

[0148]

[0149] Example 1

[0150] Argyrodite-based solid electrolyte powder with the composition Li6PS5Cl was prepared using a conventional manufacturing method. At this time, the average particle diameter (D50) of the solid electrolyte was 1.1 μm.

[0151] Afterwards, La2O3 (aldrich) powder was prepared. At this time, the average particle diameter (D50) of the La2O3 particles was 10 nm.

[0152] Thereafter, the above solid electrolyte powder and La2O3 powder were placed in a reactor and mixed at a stirring speed of 100 rpm for 2 minutes using a planetary mixer to prepare a solid electrolyte. At this time, the amount of La2O3 powder added was adjusted so that the content of La2O3 powder was 3 wt% relative to the total weight of the solid electrolyte.

[0153]

[0154] Comparative Example 1

[0155] An argyrodite-based solid electrolyte powder having a composition of Li6PS5Cl was prepared using a conventional manufacturing method, and a solid electrolyte was manufactured in the same manner as in Example 1, except that La2O3 powder was not mixed.

[0156]

[0157] Other Examples and Reference Examples

[0158] A solid electrolyte was manufactured in the same manner as in Example 1, except that the average particle diameter (D50) of the solid electrolyte particles, the average particle diameter (D50) of the La2O3 particles, and the content of La2O3 were changed as shown in Table 1 below.

[0159]

[0160] Table 1 below summarizes the process conditions of the above examples, comparative examples, and reference examples.

[0161] Solid electrolyte average particle size (D50, μm)La-containing fine particles average particle size (D50, nm)La-containing fine particles content (wt%)La-containing fine particles / solid electrolyte average particle size ratio Comparative example 13.1-0-Reference example 10.71010.0143Example 11.11030.0091Example 22.11050.0048Example 33.310100.0030Example 45.410150.0019Example 510.610200.0009Reference example 40.51050.0200Reference example 50.11050.1000Reference example 6350050.1667Reference example 73100050.3333

[0162]

[0163] Table 2 below shows the results of the physical property evaluation experiment of the solid electrolyte according to Experimental Examples 1 and 2 described below.

[0164] First peak reduction rate (%)Second peak reduction rate (%)Ionic conductivity before exposure to air (mS / cm)Ionic conductivity after exposure to air (mS / cm)Moisture stability (%)Comparative example 129273.22.0865Reference example 131321.51.0570Example 115191.81.4480Example 212172.82.3283Example 31082.01.6683Example 4572.62.2185Example 5453.73.2989Reference example 439450.50.3876Reference example 541490.10.0875Reference example 641492.82.0071Reference example 740422.21.5269

[0165]

[0166] Experimental Example 1: Evaluation of Solid Electrolyte SEM Images

[0167] SEM (scanning electron microscope) images of the solid electrolytes manufactured according to Example 2, Example 3, and Reference Example 3 were observed, and are shown in Fig. 2, respectively.

[0168] Referring to FIG. 2, it was confirmed that the solid electrolyte according to the examples and reference examples exhibited a complex structure in which multiple La-containing fine particles were attached to the surface of sulfide-based solid electrolyte particles.

[0169]

[0170] Experimental Example 2: Evaluation of X-ray diffraction patterns of solid electrolytes

[0171] An XRD (X-ray diffraction) diffraction analysis experiment was conducted on solid electrolytes manufactured according to examples, comparative examples, and reference examples.

[0172] At this time, for each Example, Comparative Example, and Reference Example, X-ray diffraction analysis was performed immediately after manufacturing and X-ray diffraction analysis was performed in parallel after exposure for a certain period of time in an air atmosphere of 25℃ and a relative humidity of 40%. At this time, it was confirmed that the solid electrolytes manufactured according to the Example, Comparative Example, and Reference Example all exhibited the first peak, which was the maximum peak, in the range of 30.2˚≤2θ≤30.3˚, and the second peak, which was the second maximum peak, in the range of 25.5˚≤2θ≤25.7˚. Thereafter, the decrease rates of each of the first peak intensity and the second peak intensity after 60 minutes were derived as percentages (%), and these are shown in Table 2 above.

[0173] Figures 3 to 6 are the results of X-ray diffraction pattern analysis over time of solid electrolytes manufactured according to Comparative Example 1, Example 2, Example 3, and Reference Example 3, respectively.

[0174]

[0175] Referring to Table 2 and FIGS. 3 to 6, the solid electrolyte of the example includes La-containing fine particles, and as a result of appropriately controlling the content of the La-containing fine particles and the average particle size ratio of the La-containing fine particles to the solid electrolyte, it was confirmed that the first and second peak intensity reduction rates were significantly reduced. This can be interpreted as a result of the solid electrolyte of the example having improved moisture stability, thereby reducing the degradation of the argyrodite crystal structure.

[0176] Meanwhile, in the case of Comparative Example 1, where the La-containing fine particles were not complexed, it was confirmed that the reduction rates of the first and second peaks were large, and accordingly, it was confirmed that the moisture stability was deteriorated and the deterioration of the argyrodite crystal structure progressed.

[0177] In the case of Reference Example 1, it was confirmed that the reduction rates of the first and second peaks were large as a result of the content of La-containing fine particles being too small. This can be interpreted as a result of the deterioration of the argyrodite crystal structure progressing as the effect of improving moisture stability due to the inclusion of La fine particles was weaker than in the example.

[0178] In addition, in the case of Reference Examples 4 to 7, where the average particle size ratio of La-containing fine particles to the solid electrolyte was too large, it was confirmed that the reduction rates of the first and second peaks were large. Through this, it was confirmed that the average particle size ratio of La-containing fine particles to the solid electrolyte was also a factor affecting the effect of improving moisture stability, and that the effect of improving moisture stability in Reference Examples 4 to 7 was weaker than in the examples.

[0179]

[0180] Experimental Example 3: Evaluation of Solid Electrolyte Ionic Conductivity and Moisture Stability

[0181] (1) Evaluation of ionic conductivity before exposure to air (25℃)

[0182] We conducted experiments to evaluate the ionic conductivity of solid electrolytes using a pressure powder cell. Specifically, the synthesized solid electrolyte was pulverized and then manufactured into pellets under a pressure of 300 MPa. The cell was then manufactured using SUS as the working electrode at a pressure of 700 MPa. Impedance was then measured at 25°C with a voltage of 10 mV applied.

[0183] (2) Evaluation of ionic conductivity after exposure to air (25℃)

[0184] In a dry room with a dew point of approximately -40°C, 2 g of a solid electrolyte in powder form was left for approximately 12 hours, then recovered and the impedance was re-measured using the same method as above.

[0185] (3) Moisture stability evaluation

[0186] Moisture stability was derived by converting the value of ionic conductivity after atmospheric exposure to the value of ionic conductivity before atmospheric exposure derived above into a percentage (%).

[0187]

[0188] Referring to Table 2, it was confirmed that the solid electrolytes of Examples 1 to 5 not only had excellent ionic conductivity before exposure to the atmosphere, but also had significantly improved moisture stability.

[0189] On the other hand, in the case of Comparative Example 1, it was confirmed that the moisture stability was significantly deteriorated as a result of the La-containing fine particles not being complexed.

[0190] In the case of Reference Example 1, it was confirmed that the moisture stability improvement effect was deteriorated compared to the example due to the content of La-containing fine particles being too low.

[0191] In the case of Reference Examples 4 to 7, it was confirmed that the effect of improving moisture stability was deteriorated compared to the examples because the ratio of the average particle diameter of the La-containing fine particles to the average particle diameter of the solid electrolyte was too large, and in particular, in the case of Reference Examples 4 and 5, it was confirmed that the ionic conductivity before exposure to the atmosphere was also too deteriorated.

[0192]

[0193] Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications can be made within the scope of the patent claims, the detailed description of the invention, and the attached drawings, and it is obvious that this also falls within the scope of the present invention.

[0194] Accordingly, the actual scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. Sulfide-based solid electrolyte particles; and A solid electrolyte comprising a plurality of La-containing fine particles arranged on the surface of the above sulfide-based solid electrolyte particles.

2. In paragraph 1, The above sulfide-based solid electrolyte particles are solid electrolyte particles of the argyrodite type.

3. In paragraph 1, A solid electrolyte in which the above-mentioned plurality of La-containing fine particles exist in a form of being attached and spaced apart from each other on the surface of sulfide-based solid electrolyte particles.

4. In paragraph 1, The above La-containing fine particles are a solid electrolyte containing La oxide.

5. In paragraph 1, The above La-containing fine particles are a solid electrolyte including a La2O3 phase.

6. In paragraph 1, The above La-containing fine particles are a solid electrolyte further comprising a La(OH)3 phase.

7. In paragraph 1, A solid electrolyte having a content of the above La-containing fine particles of 2 to 30 wt% based on the total weight of the solid electrolyte.

8. In paragraph 1, A solid electrolyte wherein the ratio of the average particle diameter (D50) of the La-containing fine particles to the average particle diameter (D50) of the sulfide-based solid electrolyte is 0.0005 to 0.

017.

9. In paragraph 1, A solid electrolyte having an average particle diameter (D50) of 0.6 to 12.0 μm.

10. In paragraph 1, A solid electrolyte having an average particle diameter (D50) of the above La-containing fine particles of 5 to 400 nm.

11. In paragraph 1, The above solid electrolyte is a solid electrolyte that exhibits a first peak in the range of 30.2˚≤2θ≤30.3˚ when analyzed by X-ray diffraction (XRD) pattern.

12. In paragraph 11, The above solid electrolyte is a solid electrolyte in which the first peak intensity decreases by 20% or less when exposed to an air atmosphere of 25°C and a relative humidity of 40% for 60 minutes.

13. In paragraph 1, The above solid electrolyte is a solid electrolyte that exhibits a second peak in the range of 25.5˚≤2θ≤25.7˚ when analyzed by X-ray diffraction (XRD) pattern.

14. In paragraph 13, The above solid electrolyte is a solid electrolyte in which the second peak intensity decreases by 20% or less when exposed to an air atmosphere of 25°C and a relative humidity of 40% for 60 minutes.

15. An all-solid-state battery comprising a solid electrolyte according to paragraph 1.

Images