Positive active material for all-solid-state rechargeable batteries, preparation method thereof, positive electrode for all-solid-state rechargeable batteries, and all-solid-state rechargeable batteries

Abstract

The present invention relates to a positive active material for all-solid-state rechargeable batteries, a preparation method thereof, a positive electrode for all-solid-state rechargeable batteries, and all-solid-state rechargeable batteries, the positive active material comprising lithium transition metal composite oxide particles and a coating layer positioned on the surface of each lithium transition metal composite oxide particle, wherein the coating layer comprises: coating particles containing a metal oxide; and a low-melting metal oxide including phosphorus oxide, lead oxide, vanadium oxide, or a combination thereof.

Description

Cathode active material for all-solid-state secondary batteries and method for manufacturing the same, cathode for all-solid-state secondary batteries, and all-solid-state secondary batteries

[0001] The invention relates to a positive electrode active material for an all-solid-state secondary battery and a method for manufacturing the same, a positive electrode for an all-solid-state secondary battery, and an all-solid-state secondary battery.

[0002] Lithium-ion batteries, which offer high energy density and portability, are primarily used as the power source for mobile information terminals such as mobile phones, laptops, and smartphones. Recently, active research is being conducted to utilize high-energy-density lithium-ion batteries as power sources for driving or energy storage in hybrid and electric vehicles.

[0003] Various cathode active materials are being investigated to realize lithium secondary batteries suitable for these applications. Among them, lithium nickel-based oxides, lithium nickel manganese cobalt composite oxides, lithium nickel cobalt aluminum composite oxides, and lithium cobalt oxides are primarily used as cathode active materials. However, these cathode active materials face problems such as structural collapse or cracking due to repeated charge-discharge cycles, which degrades the long-term lifespan of the lithium secondary battery and increases resistance, resulting in unsatisfactory capacity characteristics. Therefore, there is a need to develop new cathode active materials that can secure long-term lifespan characteristics while achieving high capacity and high energy density.

[0004] Meanwhile, with recent reports regarding the explosion risk of batteries using liquid electrolytes, the development of all-solid-state secondary batteries is actively underway. However, solid electrolytes present several challenges compared to liquid electrolytes, including lower ionic conductivity, resistance occurring at the interfaces with solid particles such as cathode active materials within the battery, and reduced ionic conductivity performance due to the formation of depletion layers caused by the junction of solids. Consequently, there is a need for the development of cathode active materials that can be used with such solid electrolytes, as well as cathode active materials capable of improving the overall performance of all-solid-state secondary batteries, such as capacity and lifespan characteristics.

[0005] In one embodiment, a dry coating method that does not use organic solvents is applied to enable mass production, and a coating layer is uniformly formed on the surface of the positive active material to suppress side reactions between the positive active material and the solid electrolyte, thereby reducing resistance. The present invention provides a positive active material, a method for manufacturing the same, and a positive electrode and an all-solid-state secondary battery comprising the same.

[0006] One embodiment provides a positive electrode active material for an all-solid-state secondary battery comprising lithium transition metal composite oxide particles and a coating layer located on the surface of the lithium transition metal composite oxide particles, wherein the coating layer comprises coating particles including a metal oxide and a low-temperature molten metal oxide including phosphorus oxide, lead oxide, vanadium oxide, or a combination thereof.

[0007] One embodiment provides a method for manufacturing a positive electrode active material for an all-solid-state secondary battery, comprising dry mixing lithium transition metal composite oxide particles, coating particles containing a metal oxide, and low-temperature molten metal oxide, and heat treating the result of the dry mixing at 300°C to 500°C.

[0008] One embodiment provides a positive electrode for an all-solid-state secondary battery comprising a positive current collector and a positive active material layer positioned on the positive current collector and comprising the aforementioned positive active material.

[0009] One embodiment provides an all-solid-state secondary battery comprising the aforementioned anode, cathode, and a solid electrolyte layer located between the anode and the cathode.

[0010] According to one embodiment, mass production can be realized by applying a dry coating method that does not use an organic solvent, and a cathode active material and a method for manufacturing the same can be provided, which can reduce resistance by suppressing side reactions between the cathode active material and the solid electrolyte by uniformly forming a coating layer on the surface of the cathode active material.

[0011] A positive electrode for a lithium secondary battery according to one embodiment, a lithium secondary battery including the same, and an all-solid-state secondary battery can achieve excellent capacity and lifespan characteristics.

[0012] FIG. 1 is a cross-sectional view schematically showing the structure of an all-solid-state secondary battery according to one embodiment.

[0013] FIG. 2 is a cross-sectional view schematically showing the structure of an all-solid-state secondary battery including a precipitation type negative electrode according to one embodiment.

[0014] Figure 3 shows a scanning electron microscope (SEM) image of the surface of the positive electrode active material prepared in Example 1.

[0015] Figure 4 shows a scanning electron microscope (SEM) image of the surface of the positive electrode active material prepared in Comparative Example 1.

[0016] Figure 5 shows a scanning electron microscope (SEM) image of the surface of the positive electrode active material prepared in Comparative Example 2.

[0017] Figure 6 shows a scanning electron microscope (SEM) image of the surface of the positive electrode active material prepared in Comparative Example 3.

[0018] Specific embodiments are described below 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.

[0019] The terms used herein are for describing exemplary embodiments only and are not intended to limit the invention. The singular expression includes the plural expression unless the context clearly indicates otherwise.

[0020] Here, "combinations of these" refers to mixtures of components, laminates, composites, copolymers, alloys, blends, reaction products, etc.

[0021] The terms "include," "equip," or "have" used herein are intended to specify the existence of the implemented features, numbers, steps, components, or combinations thereof, and should be understood as not excluding in advance the existence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0022] In the drawings, thicknesses have been enlarged to clearly represent various layers and regions, and the same reference numerals have been used for similar parts throughout the specification. When a part such as a layer, film, region, or plate is described as being "on" or "on" another part, this includes not only cases where it is "immediately on" another part, but also cases where there is another part in between. Conversely, when a part is described as being "immediately on" another part, it means that there is no other part in between.

[0023] In addition, the term “layer” here includes not only shapes formed on the entire surface when viewed in a plan view, but also shapes formed on some surfaces.

[0024] The average particle size can be measured by methods widely known to those skilled in the art, for example, by measuring with a particle size analyzer, or by using transmission electron microscope or scanning electron microscope images. Alternatively, the average particle size value can be obtained by measuring using dynamic light scattering, performing data analysis to count the number of particles for each particle size range, and then calculating from this. Unless otherwise defined, the average particle size is the diameter (D) of the particle at which the cumulative volume in the particle size distribution is 50 volume percent. 50 It may mean ). In addition, unless otherwise defined, the average particle size is obtained by measuring the size (diameter or length of the major axis) of approximately 20 randomly selected particles from scanning electron microscope images to obtain a particle size distribution, and the diameter (D) of the particle with a cumulative volume of 50% in the said particle size distribution. 50 It may be that ) was taken as the average particle size.

[0025] Here, “or” is not interpreted in an exclusive sense; for example, “A or B” is interpreted to include A, B, A+B, etc.

[0026] The term “metal” is interpreted as a concept that includes ordinary metals, transition metals, and metalloids (semimetals).

[0027] Cathode active material for all-solid-state secondary batteries

[0028] One embodiment provides a positive electrode active material for an all-solid-state secondary battery comprising lithium transition metal composite oxide particles and a coating layer located on the surface of the lithium transition metal composite oxide particles, wherein the coating layer comprises coating particles including a metal oxide and a low-temperature molten metal oxide including phosphorus oxide, lead oxide, vanadium oxide, or a combination thereof.

[0029] In all-solid-state secondary batteries, side reactions between the positive active material and the solid electrolyte within the positive electrode can cause degradation of battery characteristics and lifespan. To address this, a coating layer containing a metal oxide or a lithium metal oxide is formed on the surface of the positive active material.

[0030] In order to effectively suppress side reactions between the aforementioned positive active material and the solid electrolyte, it is important to uniformly form a coating layer on the surface of the active material. However, in the case of coating technology using a wet process, which is mainly used to form a uniform coating layer, the process cost is high, making it difficult to apply to mass production processes. Furthermore, in the case of the above wet process, since the use of organic solvents is involved during the process, residual carbon remains on the surface of the final positive active material even after heat treatment, which causes an increase in resistance or side reactions, thereby deteriorating charge / discharge and lifespan characteristics.

[0031] Meanwhile, in order to reduce process costs, facilitate application to mass production processes, and avoid the use of organic solvents, it is necessary to apply a dry process rather than a wet process. However, in the case of coating technology using a dry process, the coating is mainly formed in an island form rather than a continuous film form, making it difficult to form a uniform coating layer on the surface of the cathode active material.

[0032] Accordingly, in one embodiment, a positive electrode active material is proposed that achieves a thin and uniform coating on the surface while performing coating by a dry method to reduce process costs, effectively apply to mass production processes, and avoid using organic solvents.

[0033] Specifically, the cathode active material according to one embodiment introduces a low-temperature molten metal oxide, which melts at a low temperature together with the coating particles, into a coating layer located on the surface of lithium transition metal composite oxide particles. This allows only the low-temperature molten metal oxide to melt during mixing and low-temperature heat treatment by a dry process, thereby uniformly coating the surface of the lithium transition metal composite oxide particles and improving coverage by the coating material. Furthermore, since the dry process can be effectively applied, the use of organic solvents during the manufacturing process can be avoided, thereby suppressing the increase in resistance or side reactions caused by residual carbon. Through this, when the cathode active material according to one embodiment is used as the cathode of an all-solid-state secondary battery, side reactions between the cathode active material and the solid electrolyte can be suppressed, thereby improving efficiency and lifespan performance.

[0034] A positive electrode active material for an all-solid-state secondary battery according to one embodiment comprises: lithium transition metal composite oxide particles; and a coating layer located on the surface of the lithium transition metal composite oxide particles.

[0035] Lithium transition metal complex oxide particles

[0036] A positive electrode active material for an all-solid-state secondary battery according to one embodiment comprises lithium transition metal composite oxide particles. The lithium transition metal composite oxide particles represent a type of core having a particle shape and containing a lithium transition metal composite oxide, and any commonly used positive electrode active material can be applied without limitation. The lithium transition metal composite oxide particles may be a compound capable of reversible intercalation and deintercalation of lithium, and may include a compound represented by any one of the following chemical formulas.

[0037] Li a A 1-b X b D2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5);

[0038] Li aA 1-b X b O 2-c D c (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05);

[0039] Li a HAVE BEEN 1-b X b O 2-c D c (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05);

[0040] Li a HAVE BEEN 2-b X b O 4-c D c (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05);

[0041] Li a Ni 1-b-c Co b X c D α (0.90 ≤ a ≤1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.5, 0 <α ≤ 2);

[0042] Li a Ni 1-b-c Co b X c O 2-α T α (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2);

[0043] Li a Ni 1-b-c Co b X c O 2-α T2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2);

[0044] Li a Ni 1-b-c Mr b X c D α(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2);

[0045] Li a Ni 1-b-c Mr b X c O 2-α T α (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2);

[0046] Li a Ni 1-b-c Mr b X c O 2-α T2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2);

[0047] Li a Ni b HAVE BEEN c G d O2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1);

[0048] Li a Ni b Co c Mr d G e O2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤0.5, 0.001 ≤ e ≤ 0.1);

[0049] Li a NiG b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1);

[0050] Li a CoG b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1);

[0051] Li a Mr 1-b G b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1);

[0052] Li a Mn2G b O4(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1);

[0053] Li a Mn 1-g G g PO4(0.90 ≤ a ≤ 1.8, 0 ≤ g ≤ 0.5);

[0054] QO2; QS2; LiQS2;

[0055] V2O5; LiV2O5;

[0056] LiZO2;

[0057] LiNiVO4;

[0058] Li (3-f) J2(PO4)3(0 ≤ f ≤ 2);

[0059] Li (3-f) Fe2(PO4)3(0 ≤ f ≤ 2);

[0060] Li a FePO4(0.90 ≤ a ≤ 1.8).

[0061] In the above chemical formulas, A is selected from the group consisting of Ni, Co, Mn, and combinations thereof; X is selected from the group consisting of Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements, and combinations thereof; D is selected from the group consisting of O, F, S, P, and combinations thereof; E is selected from the group consisting of Co, Mn, and combinations thereof; T is selected from the group consisting of F, S, P, and combinations thereof; G is selected from the group consisting of Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, and combinations thereof; Q is selected from the group consisting of Ti, Mo, Mn, and combinations thereof; Z is selected from the group consisting of Cr, V, Fe, Sc, Y, and combinations thereof; and J is selected from the group consisting of V, Cr, Mn, Co, Ni, Cu, and combinations thereof.

[0062] Lithium transition metal composite oxides may include, for example, lithium cobalt oxide (LCO), lithium nickel oxide (LNO), lithium nickel cobalt oxide (NC), lithium nickel cobalt aluminum oxide (NCA), lithium nickel cobalt manganese oxide (NCM), lithium nickel manganese oxide (NM), lithium manganese oxide (LMO), lithium iron phosphate compound (LFP), or a combination thereof.

[0063] The lithium transition metal complex oxide may be, for example, a lithium nickel-based oxide represented by the following chemical formula 1, a lithium cobalt-based oxide represented by the following chemical formula 2, a lithium iron phosphate-based compound represented by the following chemical formula 3, a cobalt-free lithium nickel-manganese-based oxide represented by the following chemical formula 4, or a combination thereof.

[0064] [Chemical Formula 1]

[0065] Li a1 Ni x1 M 1 y1 M 2 z1 O 2-b1 X b1

[0066] In the above chemical formula 1, 0.9≤a1≤1.8, 0.3≤x1≤1, 0≤y1≤0.7, 0≤z1≤0.7, 0.9≤x1+y1+z1≤1.1, and 0≤b1≤0.1, and M 1 and M 2 are identical or different from each other and are each independently one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Zn, and Zr, and X is one or more elements selected from the group consisting of F, P, and S, and

[0067] [Chemical Formula 2]

[0068] Li a2 Co x2 M 3 y2 O 2-b2 Xb2

[0069] In the above chemical formula 2, 0.9≤a2≤1.8, 0.7≤x2≤1, 0≤y2≤0.3, 0.9≤x2+y2≤1.1, and 0≤b2≤0.1, and M 3 is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Se, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is one or more elements selected from the group consisting of F, P, and S, and

[0070] [Chemical Formula 3]

[0071] Li a3 Fe x3 M 4 y3 PO 4-b3 X b3

[0072] In the above chemical formula 3, 0.9≤a3≤1.8, 0.6≤x3≤1, 0≤y3≤0.4, and 0≤b3≤0.1, and M 4 is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Mg, Mn, Mo, Ni, Se, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is one or more elements selected from the group consisting of F, P, and S, and

[0073] [Chemical Formula 4]

[0074] Li a4 Ni x4 Mn y4 M 5 z4 O 2-b4 X b4

[0075] In the above chemical formula 4, 0.9≤a4≤1.8, 0.8≤x4<1, 0 <y4≤0.2, 0≤z4≤0.2, 0.9≤x4+y4+z4≤1.1, 및 0≤b4≤0.1이고 M 5is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, and Zr, and X is one or more elements selected from the group consisting of F, P, and S.

[0076] For example, the lithium transition metal composite oxide may be a lithium nickel-based oxide represented by Chemical Formula 1, for instance, a high-nickel-based oxide. For example, the nickel content relative to 100 mol% of the metal excluding lithium in the lithium transition metal composite oxide may be 80 mol% or more, or 90 mol% or more, or 91 mol% or more, or 94 mol% or more. For example, in Chemical Formula 1, 0.8≤x1≤1, 0≤y1≤0.2, and 0≤z1≤0.2, or 0.9≤x1≤1, 0≤y1≤0.1, and 0≤z1≤0.1, or 0.91≤x1≤1, 0≤y1≤0.09, and 0≤z1≤0.09, and 0.94≤x1≤1, 0≤y1≤0.06, and 0≤z1≤0.06. For example, 0.8≤x1<1, 0 <y1≤0.2, 및 0≤z1≤0.2이거나 0.9≤x1<1, 0<y1≤0.1, 및 0≤z1≤0.1일 수 있다. 이러한 고니켈계 산화물은 높은 용량을 구현할 수 있어 최근의 고용량 고밀도의 요구를 충족하기에 적절할 수 있다. 다만, 고니켈계 산화물을 포함하는 양극 활물질은 충방전에 따른 부피 변화가 8% 가량으로 크기 때문에 고체 전해질과 장시간 접촉을 유지하는 것이 어려운데, 일 구현예에 따른 코팅층을 도입함으로써 고체 입자들 간의 장시간 접착력을 구현하면서 리튬 이온의 이동을 원활하게 할 수 있다.

[0077] For example, the average particle size (D) of particles containing lithium transition metal complex oxides 50) can be 1 μm to 25 μm, for example, 2 μm to 20 μm, or 3 μm to 18 μm. Here, the average particle size is obtained by obtaining a particle size distribution by measuring the size (diameter or length of the major axis) of about 20 randomly selected particles from electron microscope images such as a scanning electron microscope, and the diameter (D) of the particle whose cumulative volume is 50 volume% in the particle size distribution. 50 It may be that ) was taken as the average particle size.

[0078] For example, particles containing a lithium transition metal complex oxide may be in the form of secondary particles formed by the aggregation of multiple primary particles, single particles, or a mixture thereof. The secondary particles may be in a polycrystalline form. A single particle refers to a particle that exists independently without grain boundaries within the particle and consists of a single particle; it may refer to a single particle, monolithic structure, monolithic structure, or non-aggregated particle that exists in an independent phase without mutual aggregation in terms of morphology, and may be a single crystal, for example.

[0079] For example, particles containing a lithium transition metal composite oxide may include large particles with an average particle size of 9 μm to 25 μm and small particles with an average particle size of 1 μm to 8 μm. In this case, with respect to the total sum of large particles and small particles at 100 wt%, the large particles may be included at 60 wt% to 95 wt% and the small particles at 5 wt% to 40 wt%, for example, the large particles may be included at 70 wt% to 90 wt% and the small particles at 10 wt% to 30 wt%. When composed of a mixture of large particles and small particles, a high energy density battery can be realized.

[0080] For example, an allele is in the form of a secondary particle composed of multiple primary particles, and a subatomic particle may be in the form of a secondary particle composed of multiple primary particles or in the form of a single particle.

[0081] For example, the average particle size of the coarse particles may be 9 µm to 20 µm, or 10 µm to 15 µm. The average particle size of the fine particles may be 1 µm to 7 µm, 1 µm to 6 µm, or 2 µm to 5 µm. Here, too, the average particle size is determined by obtaining a particle size distribution by randomly measuring the size (diameter or length of the major axis) of about 20 particles from electron microscope images, such as those of a scanning electron microscope, and the diameter (D) of the particle whose cumulative volume is 50 volume% in the particle size distribution. 50 It may be that ) was taken as the average particle size.

[0082] coating layer

[0083] The coating layer may be described as a buffer layer or a protective layer, and the coating layer comprises coating particles including metal oxides, and low-temperature molten metal oxides including phosphorus oxide, lead oxide, vanadium oxide, or a combination thereof.

[0084] In one embodiment, the coating particles comprise a metal oxide, and the metal oxide may be a metal oxide having a melting point higher than the melting point of the low-temperature molten metal oxide described below, for example, a metal oxide having a melting point greater than 500°C, greater than 600°C, or greater than 1,000°C. As an example, the metal of the metal oxide may comprise Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Nb, Si, Sr, Ti, W, Y, Zn, Zr, or a combination thereof. For example, the metal oxide may include aluminum oxide, boron oxide, barium oxide, calcium oxide, cerium oxide, cobalt oxide, chromium oxide, copper oxide, iron oxide, magnesium oxide, manganese oxide, molybdenum oxide, nickel oxide, neobium oxide, silicon oxide, strontium oxide, titanium oxide, tungsten oxide, yttrium oxide, zinc oxide, zirconium oxide, or a combination thereof. If these conditions are met, the movement of lithium ions on the surface of the positive electrode active material is made smoother, the structural stability of the positive electrode active material is improved, and interfacial resistance can be reduced by lowering reactivity with the solid electrolyte.

[0085] The coating layer comprises a low-temperature molten metal oxide, and the low-temperature molten metal oxide may refer to a metal oxide that can be melted in a temperature range of 300°C to 500°C and evenly distributed on the surface of the positive electrode active material. In one embodiment, the coating layer of the positive electrode active material comprises phosphorus oxide, lead oxide, vanadium oxide, or a combination thereof as the low-temperature molten metal oxide. By including the aforementioned low-temperature molten metal oxide, which can be melted at a low temperature, in the coating layer, a thin and uniform coating layer can be formed on the surface of the positive electrode active material even when the coating layer is formed by a dry process. As a result, side reactions between the positive electrode active material and the solid electrolyte within the positive electrode of the all-solid-state secondary battery can be effectively suppressed, thereby improving efficiency and lifespan performance.

[0086] In one example, the low-temperature molten metal oxide may further include lithium, for example, lithium phosphorus oxide, lithium lead oxide, lithium vanadium oxide, or a combination thereof. If this is satisfied, the movement of lithium ions on the surface of the positive electrode active material can be further enhanced, and this can contribute to the improvement of charge / discharge characteristics and lifespan performance.

[0087] In one embodiment, in the coating layer, the coating particles may exist in an island form, and the low-temperature molten metal oxide may exist in a continuous film form. As described above, since the low-temperature molten metal oxide melts at a low temperature, during the dry mixing and low-temperature post-heat treatment process by the dry process method, the low-temperature molten metal oxide can melt and be uniformly distributed on the surface of the anode active material and can also exist in a continuous film form. On the other hand, since the coating particles do not melt during the aforementioned low-temperature post-heat treatment process and remain as they are, they may exist in an island form in the coating layer. According to one embodiment, even if the coating layer is formed by the dry process method, the coating particles and the low-temperature molten metal oxide do not aggregate or exist locally, and can be formed well with a uniform thickness on the surface of the anode active material. Accordingly, the capacity and lifespan performance of the anode active material can be improved.

[0088] For example, the low-temperature molten metal oxide can connect the spaces between the coating particles, and the coating particles and the low-temperature molten metal oxide can exist separately in the coating layer. In this case, while improving the structural stability of the positive electrode active material, a coating layer can be uniformly formed on the surface of the positive electrode active material to suppress the reaction between the positive electrode active material and the solid electrolyte, thereby further improving capacity and lifespan performance.

[0089] In one embodiment, the average particle size (D) of the coating particles 50 The wavelength may be 5 nm to 500 nm, 10 nm to 200 nm, 50 nm to 150 nm, or 100 nm to 150 nm. When this is satisfied, the positive electrode active material can be effectively protected while suppressing the increase in resistance caused by the coating, and the electrochemical properties of the lithium secondary battery can be improved by improving ion conductivity.

[0090] For example, the thickness of the coating layer may be 5 nm to 1 μm, 10 nm to 500 nm, 20 nm to 400 nm, 50 nm to 200 nm, or 100 nm to 150 nm. Within this range, the increase in resistance caused by the coating can be suppressed, while effectively protecting the positive active material and suppressing the reaction between the positive active material and the solid electrolyte.

[0091] For example, the coating layer may be formed with a uniform thickness without being locally present or aggregated on the surface of the positive active material. For example, the standard deviation of the coating layer thickness may be 10% or less, or 5% or less relative to the diameter of the positive active material, and may be 100 nm or less, 50 nm or less, or 30 nm or less.

[0092] For example, the content of the coating particles in the coating layer may be 0.1 to 1.0 molar, 0.1 to 0.5 molar, or 0.1 to 0.4 molar relative to 100 molar parts of the lithium transition metal composite oxide particles. Within this range, the coating particles can adequately protect the positive electrode active material in the coating layer without acting as a resistor, and can exist well with a uniform thickness without aggregating or existing locally on the surface of the positive electrode active material, thereby effectively improving the lifespan characteristics without reducing the capacity of the positive electrode active material. If the content of the coating particles is excessive, the coating layer may become thick and act as a resistive layer, which may reduce the charge / discharge capacity of the positive electrode active material. Conversely, if the content of the coating particles is too low, it may fail to adequately perform the buffering role, which may reduce the lifespan characteristics of the positive electrode active material.

[0093] In one embodiment, the content of the low-temperature molten metal oxide in the coating layer may be 0.01 to 0.5 mol, 0.05 to 0.4 mol, or 0.1 to 0.3 mol relative to 100 mol of the lithium transition metal composite oxide particles. Within this range, the positive electrode active material can be protected while suppressing the increase in resistance caused by the coating, and the reaction between the positive electrode active material and the solid electrolyte can be effectively suppressed by forming a uniform coating layer on the surface, which is advantageous for improving capacity and lifespan performance.

[0094] For example, the average particle size (D) of the lithium transition metal composite oxide particles. 50 ) and the average particle size (D) of the coating particles. 50 The ratio of ) may be 500:1 to 10:1, 300:1 to 50:1, or 250:1 to 100:1.

[0095] Method for manufacturing a positive electrode active material for an all-solid-state secondary battery

[0096] One embodiment provides a method for manufacturing a positive electrode active material for an all-solid-state secondary battery, comprising dry mixing lithium transition metal composite oxide particles, coating particles containing a metal oxide, and low-temperature molten metal oxide, and heat treating the result of the dry mixing at 300°C to 500°C.

[0097] The following describes a method for manufacturing a positive electrode active material for an all-solid-state secondary battery according to one embodiment. In the following description, explanations that overlap with the previously mentioned content regarding the positive electrode active material are omitted, and the processes for manufacturing the positive electrode active material for an all-solid-state secondary battery according to one embodiment are described in detail.

[0098] First, lithium transition metal composite oxide particles, coating particles containing metal oxides, and low-temperature molten metal oxides are dry-mixed. The above manufacturing method applies a coating process using a dry method, and since it does not use organic solvents or expensive coating raw materials and allows the use of existing equipment, it is possible to manufacture cathode active materials economically and in an environmentally friendly manner, and mass production can be realized. According to the above manufacturing method, a cathode active material can be synthesized in which coating particles containing metal oxides and a coating layer containing low-temperature molten metal oxides are formed, and a coating layer of appropriate content and thickness can be formed in a good form, thereby manufacturing a cathode active material with improved capacity and lifespan performance. Such a cathode active material has low reactivity with sulfide-based solid electrolyte particles and low interfacial resistance, so it can be applied to all-solid-state secondary batteries to improve capacity characteristics, rate characteristics, and lifespan characteristics.

[0099] As the lithium transition metal composite oxide particles, coating particles containing metal oxides, and low-temperature molten metal oxides have been described above, a detailed explanation is omitted.

[0100] In a method for manufacturing a positive electrode active material for an all-solid-state secondary battery according to one embodiment, dry mixing means mixing without a solvent and can be understood as a solid-state coating method. This is distinguished from wet coating methods or liquid coating methods.

[0101] For example, the coating particles may be added in an amount of 0.1 to 1.0 molar relative to 100 molar parts of the lithium transition metal composite oxide particles, for example, in an amount of 0.1 to 0.5 molar, or in an amount of 0.1 to 0.4 molar. Within this range, the coating particles are introduced in an appropriate amount to form a coating layer of appropriate thickness, which can sufficiently perform the role of protecting the positive electrode active material and produce a positive electrode active material that exists with a uniform thickness without aggregating or existing locally on the surface of the positive electrode active material. If the amount of coating particles added is excessive, the coating layer becomes thick and may act as a resistive layer, thereby reducing the charge / discharge capacity of the positive electrode active material. If the amount of coating particles added is too small, it may not sufficiently perform the buffering role, which may reduce the lifespan characteristics of the positive electrode active material.

[0102] For example, the low-temperature molten metal oxide may be added in an amount of 0.01 to 0.5 molar parts relative to 100 molar parts of the lithium transition metal composite oxide particles, for example, in an amount of 0.05 to 0.4 molar parts or 0.1 to 0.3 molar parts. Within this range, the increase in resistance caused by the coating containing the low-temperature molten metal oxide can be suppressed while protecting the positive electrode active material, and a uniform coating layer is formed on the surface to effectively suppress the reaction between the positive electrode active material and the solid electrolyte, which can be advantageous for improving capacity and lifespan performance.

[0103] For example, the average particle size (D) of the coating particles. 50 ) is the average particle size (D) of the coating particles. 50The wavelength may be 5 nm to 500 nm, 10 nm to 200 nm, 50 nm to 150 nm, or 100 nm to 150 nm. When this is satisfied, the positive electrode active material can be effectively protected while suppressing the increase in resistance caused by the coating, and the electrochemical properties of the lithium secondary battery can be improved by improving ion conductivity.

[0104] For example, the low-temperature molten metal oxide introduced during the dry mixing process may be in the form of particles, and the particles may be 5 nm to 500 nm, 5 nm to 200 nm, 50 nm to 150 nm, or 80 nm to 130 nm. When these conditions are met, it may be advantageous to form a coating layer of appropriate thickness while suppressing the increase in resistance caused by the coating containing the low-temperature molten metal oxide, and to form a uniform coating layer on the surface of the positive electrode active material. Through this, the reaction between the positive electrode active material and the solid electrolyte within the positive electrode can be effectively suppressed, and it may be more advantageous to secure excellent capacity and lifespan performance.

[0105] Next, the product of the above dry mixing can be heat-treated at 300°C to 500°C, for example, at 300°C to 450°C, or at 300°C to 400°C. In this range, the low-temperature molten metal oxide can be melted and uniformly distributed on the surface of the positive electrode active material, thereby forming a thin and uniform coating layer on the surface of the positive electrode active material, which can effectively suppress side reactions between the positive electrode active material and the solid electrolyte.

[0106] In one embodiment, the heat treatment may be performed in an oxygen atmosphere for 5 to 25 hours, 10 to 20 hours, or 15 to 20 hours. Under these conditions, a well-uniform coating layer can be formed.

[0107] anode

[0108] One embodiment provides a positive electrode for an all-solid-state secondary battery comprising a positive current collector and a positive active material layer positioned on the positive current collector and comprising the aforementioned positive active material.

[0109] The positive active material layer of the positive electrode according to one embodiment comprises the aforementioned positive active material, and in addition to the positive active material, may further comprise a binder, a conductive material, a solid electrolyte, or a combination thereof.

[0110] bookbinder

[0111] The above binder serves to adhere the positive active material particles well to each other and also to adhere the positive active material well to the positive current collector. Representative examples include polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, diacetylcellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc., but are not limited thereto.

[0112] The content of the binder in the above positive active material layer may be approximately 0.1% to 5% by weight with respect to 100% by weight of the positive active material layer.

[0113] Challenge

[0114] The above positive active material layer may further include a conductive material. The conductive material is used to impart conductivity to the electrode, and any electronically conductive material that does not cause chemical changes can be used in the battery being constructed. Examples include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, carbon nanotube, etc.; metal-based materials in the form of metal powder or metal fibers containing copper, nickel, aluminum, silver, etc.; conductive polymers such as polyphenylene derivatives; or conductive materials including mixtures thereof.

[0115] The content of the conductive material in the above positive active material layer may be 0% to 3% by weight, 0.01% to 2% by weight, or 0.1% to 1% by weight with respect to 100% by weight of the positive active material layer.

[0116] Aluminum foil may be used as the anode current collector, but is not limited thereto.

[0117] solid electrolyte

[0118] The above solid electrolyte may be an inorganic solid electrolyte, such as a sulfide-based solid electrolyte or an oxide-based solid electrolyte.

[0119] In one embodiment, the solid electrolyte may be a sulfide-based solid electrolyte with excellent ion conductivity. The sulfide-based solid electrolyte particles are, for example, Li2S-P2S5, Li2S-P2S5-LiX (where X is a halogen element, for example, I or Cl), Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n(m and n are integers, and Z is Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (p, q are integers, and M is P, Si, Ge, B, Al, Ga or In), or may include a combination thereof.

[0120] Such sulfide-based solid electrolytes can be obtained, for example, by mixing Li2S and P2S5 in a molar ratio of 50:50 to 90:10 or 50:50 to 80:20 and optionally heat-treating. Within the above mixing ratio range, a sulfide-based solid electrolyte having excellent ionic conductivity can be manufactured. Additionally, ionic conductivity may be further improved by including other components such as SiS2, GeS2, B2S3, etc.

[0121] Mechanical milling or the solution method can be applied as mixing methods for sulfur-containing raw materials to manufacture sulfide-based solid electrolytes. Mechanical milling is a method in which starting materials are placed in a ball mill reactor and vigorously stirred to finely atomize and mix them. When using the solution method, starting materials are mixed in a solvent to obtain a solid electrolyte as a precipitate. Furthermore, if heat treatment is performed after mixing, the crystals of the solid electrolyte can become more robust and the ionic conductivity can be improved. For example, a sulfide-based solid electrolyte can be manufactured by mixing sulfur-containing raw materials and heat-treating them two or more times; in this case, a robust sulfide-based solid electrolyte with high ionic conductivity can be produced.

[0122] Sulfide-based solid electrolyte particles according to one embodiment can be manufactured, for example, by mixing sulfur-containing raw materials and calcining at 120°C to 350°C in a first heat treatment, and by mixing the results of the first heat treatment and calcining at 350°C to 800°C in a second heat treatment. The first heat treatment and the second heat treatment can each be carried out in an inert gas or nitrogen atmosphere. The first heat treatment can be performed for 1 to 10 hours, and the second heat treatment can be performed for 5 to 20 hours. Through the first heat treatment, the effect of milling small raw materials can be obtained, and through the second heat treatment, the final solid electrolyte can be synthesized. Through two or more such heat treatments, a high-performance sulfide-based solid electrolyte with high ion conductivity and robustness can be obtained, and such a solid electrolyte can be considered suitable for mass production. The temperature of the first heat treatment may be, for example, 150°C to 330°C or 200°C to 300°C, and the temperature of the second heat treatment may be, for example, 380°C to 700°C or 400°C to 600°C.

[0123] For example, the sulfide-based solid electrolyte particles may include an argyrodite-type sulfide. The argyrodite-type sulfide-based solid electrolyte particles have an ionic conductivity of 10 at room temperature, which is the ionic conductivity of a typical liquid electrolyte. -4 to 10 -2 It has high ionic conductivity close to the S / cm range and can form a tight bond between the positive active material and the solid electrolyte without causing a decrease in ionic conductivity, and furthermore, can form a tight interface between the electrode layer and the solid electrolyte layer. An all-solid-state secondary battery including this can improve battery performance such as rate characteristics, Coulomb efficiency, and life characteristics.

[0124] The azirodite-type sulfide-based solid electrolyte particles may include, for example, a compound represented by the chemical formula 11 below.

[0125] [Chemical Formula 11]

[0126] (Li a M 1 b M 2 c )(P d M 3 e )(S f M 4 g )X h

[0127] In the above chemical formula 11, 4≤a≤8, and M 1 is Mg, Cu, Ag, or a combination thereof, 0≤b<0.5, and M 2 is Na, K, or a combination thereof, 0≤c<0.5, and M 3 is Sn, Zn, Si, Sb, Ge, or a combination thereof, and 0 <d<4, 0≤e<1 이고, M 4 is O, SO n , or a combination thereof, 1.5≤n≤5, 3≤f≤12, 0≤g<2, X is F, Cl, Br, I, or a combination thereof, and 0≤h≤2.

[0128] For example, in Chemical Formula 11, a halide element (X) may be required to be included, in which case 0 <h≤2로 표시될 수 있다. 일 예로 화학식 11에 M 1 An element may be required, in which case 0 <b<0.5로 표시될 수 있다. 화학식 11에서 M 3 can be understood as an element substituted in the P position, and 0 <e<1일 수 있다. 화학식 11에서 M 4 is substituted in the S position, for example, 0 <g<2일 수 있으며 S의 비율인 f는 예를 들어 3≤f≤7일 수 있다. M 4 ga SO n In the case of SO n It can be, for example, S4O6, S3O6, S2O3, S2O4, S2O5, S2O6, S2O7, S2O8, SO4, or SO5, and as an example, it can be SO4.

[0129] For example, in chemical formula 11, a+b+c+h=7, d+e=1, and f+g+h=6.

[0130] As a specific example, azirodite-type sulfide-based solid electrolyte particles include Li3PS4 and Li7P3S 11 , Li7PS6, Li6PS5Cl, Li6PS5Br, Li 5.8 PS 4.8 Cl 1.2 , Li 6.2 PS 5.2 Br 0.8 , Li 5.75 PS 4.75 Cl 1.25 , (Li 5.69 Cu 0.06 )PS 4.75 Cl 1.25 , (Li 5.72 Cu 0.03 )PS 4.75 Cl 1.25 , (Li 5.69 Cu 0.06 )P(S 4.70 (SO4) 0.05 )Cl 1.25 , (Li 5.69 Cu 0.06 )P(S 4.60 (SO4) 0.15 )Cl 1.25 , (Li 5.72 Cu 0.03 )P(S 4.725 (SO4) 0.025 )Cl 1.25 , (Li 5.72 Na 0.03 )P(S 4.725 (SO4) 0.025 )Cl 1.25 , Li 5.75 P(S 4.725 (SO4) 0.025 )Cl 1.25 , or a combination thereof may be included, but is not limited thereto.

[0131] An azirodite-type sulfide-based solid electrolyte can be prepared by mixing, for example, lithium sulfide and phosphorus sulfide, and optionally lithium halide. After mixing these, heat treatment may be performed. The heat treatment may include, for example, two or more heat treatment steps. Here, preparing an azirodite-type sulfide-based solid electrolyte may include, for example, a first heat treatment in which raw materials are mixed and calcined at 120°C to 350°C, and a second heat treatment in which the result of the first heat treatment is mixed again and calcined at 350°C to 800°C.

[0132] Average particle size of sulfide-based solid electrolyte particles (D 50 ) may, for example, be 0.1 μm to 5.0 μm or 0.1 μm to 3.0 μm, and may be fine particles of 0.1 μm to 1.9 μm or coarse particles of 2.0 μm to 5.0 μm. The sulfide-based solid electrolyte particles may be a mixture of fine particles with an average particle size of 0.1 μm to 1.9 μm and coarse particles with an average particle size of 2.0 μm to 5.0 μm. The average particle size of the sulfide-based solid electrolyte particles may be measured using electron microscope images, for example, by measuring the size (diameter or length of the major axis) of about 20 particles from scanning electron microscope images to obtain a particle size distribution, where D 50 It could be that it was calculated.

[0133] The solid electrolyte may include oxide-based inorganic solid electrolytes in addition to sulfide-based materials. The oxide-based inorganic solid electrolyte is, for example, Li 1+x Ti 2-x Al(PO4)3(LTAP)(0≤x≤4), Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 (0 <x<2, 0≤y<3), BaTiO3, Pb(Zr,Ti)O3(PZT), Pb 1-x La x Zr 1-y Tiy O3(PLZT)(0≤x<1, 0≤y<1), PB(Mg3Nb 2 / 3 )O3-PbTiO3(PMN-PT), HfO2, SrTiO3, SnO2, CeO2, Na2O, MgO, NiO, CaO, BaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiO2, Lithium Phosphate (Li3PO4), Lithium Titanium Phosphate (Li x Ti y (PO4)3, 0 <x<2, 0<y<3), Li 1+x+y (Al, Ga) x (Ti, Ge) 2-x Si y P 3-y O 12 (0≤x≤1, 0≤y≤1), lithium lanthanum titanate(Li x La y TiO3, 0 <x<2, 0<y<3), Li2O, LiAlO2, Li2O-Al2O3-SiO2-P2O5-TiO2-GeO2계 세라믹스, 가넷(Garnet)계 세라믹스 Li 3+x La3M2O 12 (M= Te, Nb, or Zr; x is an integer from 1 to 10), or may include a mixture thereof.

[0134] Solid electrolytes are in the form of particles, and the average particle size (D 50 The ) may be 5.0 μm or less, for example, 0.1 μm to 5.0 μm, 0.5 μm to 5.0 μm, 0.5 μm to 4.0 μm, 0.5 μm to 3.0 μm, 0.5 μm to 2.0 μm, or 0.5 μm to 1.0 μm. Such a solid electrolyte can effectively penetrate between the positive electrode active materials, and has excellent contact with the positive electrode active materials and connectivity between the solid electrolyte particles.

[0135] With respect to 100 weight% of the positive active material layer, the solid electrolyte may be included in an amount of 0.1 weight% to 35 weight%, for example, 1 weight% to 35 weight%, 5 weight% to 30 weight%, 8 weight% to 25 weight%, or 10 weight% to 20 weight%.

[0136] In addition, regarding the total sum of the positive active material and the solid electrolyte in the positive active material layer of 100 wt%, 65 wt% to 99 wt% of the positive active material and 1 wt% to 35 wt% of the solid electrolyte may be included, for example, 80 wt% to 90 wt% of the positive active material and 10 wt% to 20 wt% of the solid electrolyte may be included. When the solid electrolyte is included in the positive electrode in such a content, the efficiency and lifespan characteristics of the all-solid-state battery can be improved without reducing the capacity.

[0137] All-solid-state secondary battery

[0138] In one embodiment, an all-solid-state secondary battery is provided, comprising the aforementioned positive electrode, negative electrode, and a solid electrolyte layer located between the positive electrode and the negative electrode.

[0139] FIG. 1 is a cross-sectional view of an all-solid-state secondary battery according to one embodiment. Referring to FIG. 1, the all-solid-state secondary battery (100) may have a structure in which an electrode assembly is housed in a battery case, wherein the electrode assembly comprises a negative electrode (400) including a negative electrode current collector (401) and a negative electrode active material layer (403), a solid electrolyte layer (300), and a positive electrode (200) including a positive electrode active material layer (203) and a positive electrode current collector (201). The all-solid-state secondary battery (100) may further include an elastic layer (500) on the outer side of at least one of the positive electrode (200) and the negative electrode (400). FIG. 1 illustrates a single electrode assembly including a negative electrode (400), a solid electrolyte layer (300), and a positive electrode (200), but an all-solid-state secondary battery may be manufactured by stacking two or more electrode assemblies.

[0140] cathode

[0141] A negative electrode for an all-solid-state secondary battery comprises, for example, a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector. The negative electrode active material layer comprises a negative electrode active material and may further comprise a binder and / or a conductive material.

[0142] The negative electrode active material includes a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide.

[0143] A material capable of reversibly intercalating / deintercalating the above lithium ions may include a carbon-based negative electrode active material, for example, crystalline carbon, amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite such as amorphous, plate-like, flake-like, spherical, or fibrous natural graphite or artificial graphite, and examples of the amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, calcined coke, etc.

[0144] As the above lithium metal alloy, an alloy of a metal selected from the group consisting of lithium, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn may be used.

[0145] As a material capable of doping and undoping the above lithium, a Si-based negative electrode active material or a Sn-based negative electrode active material may be used, and the Si-based negative electrode active material may include silicon, a silicon-carbon composite, or SiO₂. x(0 <x≤2), Si-Q 합금(상기 Q는 알칼리 금속, 알칼리 토금속, 13족 원소, 14족 원소, 15족 원소, 16족 원소, 전이금속, 희토류 원소 및 이들의 조합으로 이루어진 군에서 선택되는 원소이며, Si은 아님), 상기 Sn계 음극 활물질로는 Sn, SnO2, Sn-R 합금(상기 R은 알칼리 금속, 알칼리 토금속, 13족 원소, 14족 원소, 15족 원소, 16족 원소, 전이금속, 희토류 원소 및 이들의 조합으로 이루어진 군에서 선택되는 원소이며, Sn은 아님) 등을 들 수 있고, 또한 이들 중 적어도 하나와 SiO2를 혼합하여 사용할 수도 있다. 상기 원소 Q 및 R로는 Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, 및 이들의 조합으로 이루어진 군에서 선택되는 것을 사용할 수 있다.

[0146] For example, the negative electrode active material may include silicon-carbon composite particles. The average particle size (D) of the silicon-carbon composite particles 50 ) may be, for example, 0.5 μm to 20 μm. With respect to 100 wt% of the silicon-carbon composite particles, silicon may be included in an amount of 10 wt% to 60 wt% and carbon may be included in an amount of 40 wt% to 90 wt%. The silicon-carbon composite particles may include, for example, a core containing silicon particles and a carbon coating layer located on the surface of the core. The average particle size (D) of the silicon particles in the core 50) may be 10 nm to 1 µm, or 10 nm to 200 nm. The silicon particles may exist as silicon alone, in the form of a silicon alloy, or in an oxidized form. The oxidized form of silicon is SiO x (0 <x≤2)로 표시될 수 있다. 또한, 상기 탄소 코팅층의 두께는 약 5 nm 내지 100 nm일 수 있다.

[0147] For example, the silicon-carbon composite particles may comprise a core containing silicon particles and crystalline carbon, and a carbon coating layer located on the surface of the core containing amorphous carbon. For example, in the silicon-carbon composite particles, the amorphous carbon may not be present in the core but only in the carbon coating layer. The crystalline carbon may be artificial graphite, natural graphite, or a combination thereof, and the amorphous carbon may be formed from coal-based pitch, mesophase pitch, petroleum-based pitch, coal-based oil, petroleum-based heavy oil, or a polymer resin (phenol resin, furan resin, polyimide resin, etc.). In this case, the content of crystalline carbon may be 10% to 70% by weight and the content of amorphous carbon may be 20% to 40% by weight with respect to 100% by weight of the silicon-carbon composite particles.

[0148] In silicon-carbon composite particles, the core may include a void in the central portion. The radius of the void may be 30% to 50% of the radius of the silicon-carbon composite particle.

[0149] Silicon-carbon composite particles effectively suppress problems such as volume expansion, structural collapse, or particle fragmentation due to charging and discharging, thereby preventing the interruption of conductive paths and enabling the realization of high capacity and high efficiency, making them advantageous for use under high voltage or high-speed charging conditions.

[0150] Si-based negative electrode active material or Sn-based negative electrode active material may be used in combination with carbon-based negative electrode active material. When Si-based negative electrode active material or Sn-based negative electrode active material and carbon-based negative electrode active material are mixed and used, the mixing ratio may be 1:99 to 90:10 by weight.

[0151] The content of the negative electrode active material for 100 weight% of the negative electrode active material layer may be 95 weight% to 99 weight%.

[0152] In one embodiment, the negative electrode active material layer further comprises a binder and optionally further comprises a conductive material. The content of the binder may be 1% to 5% by weight with respect to 100% by weight of the negative electrode active material layer. Additionally, when further comprising a conductive material, the negative electrode active material layer may comprise 90% to 98% by weight of the negative electrode active material, 1% to 5% by weight of the binder, and 1% to 5% by weight of the conductive material.

[0153] The binder serves to effectively bond the negative electrode active material particles to each other and also to effectively bond the negative electrode active material to the negative electrode current collector. As the binder, a water-insoluble binder, a water-soluble binder, or a combination thereof may be used.

[0154] Examples of water-insoluble binders include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, ethylene propylene copolymer, polystyrene, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or combinations thereof.

[0155] Examples of water-soluble binders include rubber-based binders or polymer resin binders. The rubber-based binder may be selected from styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, fluororubber, and combinations thereof. The polymer resin binder may be selected from polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, ethylenepropylenediene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0156] When a water-soluble binder is used as the cathode binder, a cellulose-based compound capable of imparting viscosity as a type of thickener may be further included. As this cellulose-based compound, one or more types such as carboxymethyl cellulose, hydroxypropylmethyl cellulose, methyl cellulose, or alkali metal salts thereof may be mixed and used. Na, K, or Li may be used as the alkali metal. The content of such a thickener may be 0.1 to 3 parts by weight per 100 parts by weight of the cathode active material.

[0157] A conductive material is used to impart conductivity to an electrode, and any electronically conductive material that does not cause chemical changes can be used in the battery being constructed. Examples include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, carbon nanotube; metal-based materials in the form of metal powder or metal fibers including copper, nickel, aluminum, silver, etc.; conductive polymers such as polyphenylene derivatives; or conductive materials including mixtures thereof.

[0158] As a cathode current collector, a material selected from the group consisting of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof may be used.

[0159] Alternatively, as another example, the negative electrode for an all-solid-state secondary battery may be a precipitation-type negative electrode, unlike the one described above. The precipitation-type negative electrode may refer to a negative electrode that does not contain a negative electrode active material during battery assembly, but in which lithium metal, etc. is precipitated or electrodeposited on the negative electrode during battery charging, and which acts as the negative electrode active material.

[0160] FIG. 2 is a schematic cross-sectional view of an all-solid-state secondary battery including a precipitation type negative electrode. Referring to FIG. 2, the precipitation type negative electrode (400') may include a negative electrode current collector (401) and a negative electrode coating layer (405) located on the negative electrode current collector. An all-solid-state secondary battery having such a precipitation type negative electrode (400') starts initial charging in a state where no negative electrode active material is present, and during charging, a high-density lithium metal is precipitated or electrodeposited between the negative electrode current collector (401) and the negative electrode coating layer (405), or on the negative electrode coating layer (405), to form a lithium metal layer (404), which can serve as a negative electrode active material. Accordingly, in a solid-state secondary battery that has undergone one or more charges, the precipitation type negative electrode (400') may include, for example, a negative electrode current collector (401), a lithium metal layer (404) located on the negative electrode current collector, and a negative electrode coating layer (405) located on the metal layer. The lithium metal layer (404) refers to a layer in which lithium metal, etc. is precipitated during the charging process of the battery, and may be referred to as a metal layer, a lithium layer, a lithium electrodeposition layer, or a negative electrode active material layer.

[0161] The negative electrode coating layer (405) may be a lithium electrodeposition inducing layer or a negative electrode catalyst layer, and may include a metal, carbon material, or a combination thereof that acts as a catalyst.

[0162] The above metal may be a lithium-friendly metal and may include, for example, gold, platinum, palladium, silicon, silver, aluminum, bismuth, tin, zinc, or a combination thereof, and may be composed of one of these or may be composed of several types of alloys. When the metal exists in the form of particles, its average particle size (D 50 ) can be about 4 μm or less, and for example, 10 nm to 4 μm.

[0163] The carbon material may be, for example, crystalline carbon, amorphous carbon, or a combination thereof. Crystalline carbon may be, for example, natural graphite, artificial graphite, mesophase carbon micro beads, or a combination thereof. Amorphous carbon may be, for example, carbon black, activated carbon, acetylene black, Denka black, Ketjen black, or a combination thereof.

[0164] When the negative electrode coating layer (405) includes both the metal and the carbon material, the mixing ratio of the metal and the carbon material may be, for example, a weight ratio of 1:10 to 2:1. In this case, the precipitation of lithium metal can be effectively promoted and the characteristics of the all-solid-state secondary battery can be improved. The negative electrode coating layer (405) may include, for example, a carbon material supported with a catalyst metal, or may include a mixture of metal particles and carbon material particles.

[0165] The cathode coating layer (405) may, for example, include the metal and amorphous carbon, and in this case, can effectively promote the precipitation of lithium metal.

[0166] The cathode coating layer (405) may further include a binder, and the binder may be, for example, a conductive binder. In addition, the cathode coating layer (405) may further include general additives such as fillers, dispersants, ion conductive agents, etc.

[0167] The thickness of the cathode coating layer (405) may be, for example, 100 nm to 20 μm, or 500 nm to 10 μm, or 1 μm to 5 μm.

[0168] The precipitation type cathode (400') may, for example, further include a thin film on the surface of the cathode current collector, that is, between the cathode current collector and the cathode coating layer. The thin film may include an element capable of forming an alloy with lithium. The element capable of forming an alloy with lithium may be, for example, gold, silver, zinc, tin, indium, silicon, aluminum, bismuth, etc., and may be composed of one of these or composed of several types of alloys. The thin film can further flatten the precipitation shape of the lithium metal layer (404) and further improve the characteristics of the all-solid-state secondary battery. The thin film may be formed by, for example, vacuum deposition, sputtering, plating, etc. The thickness of the thin film may be, for example, 1 nm to 500 nm.

[0169] The lithium metal layer (404) may include lithium metal or a lithium alloy. The lithium alloy may be, for example, 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, or a Li-Si alloy.

[0170] The thickness of the lithium metal layer (404) may be 1 µm to 500 µm, 1 µm to 200 µm, 1 µm to 100 µm, or 1 µm to 50 µm. If the thickness of the lithium metal layer (404) is too thin, it is difficult to perform the function of a lithium storage tank, and if it is too thick, the battery volume may increase and performance may deteriorate.

[0171] When such a precipitation type cathode is applied, the cathode coating layer (405) can protect the lithium metal layer (404) and suppress the precipitation growth of lithium deadlite. Accordingly, short circuits and capacity degradation of the all-solid-state battery are suppressed, and lifespan characteristics can be improved.

[0172] solid electrolyte layer

[0173] The solid electrolyte layer (300) may include a sulfide-based solid electrolyte, an oxide-based solid electrolyte, etc. Since the details regarding the sulfide-based solid electrolyte and the oxide-based solid electrolyte are as described above, a detailed explanation is omitted.

[0174] Meanwhile, the average particle size (D) of the solid electrolyte included in the solid electrolyte layer (300) 50 ) is the average particle size (D) of the solid electrolyte contained in the anode (200). 50 It may be larger than ). In this case, overall performance can be improved by increasing the mobility of lithium ions while maximizing the energy density of the all-solid-state secondary battery. For example, the average particle size (D) of the solid electrolyte included in the positive electrode (200) 50 ) may be 0.1 μm to 1.9 μm, or 0.1 μm to 1.0 μm, and the average particle size (D) of the solid electrolyte included in the solid electrolyte layer (300) 50 ) may be 2.0 μm to 5.0 μm, or 2.0 μm to 4.0 μm, or 2.5 μm to 3.5 μm. When such particle size ranges are satisfied, the energy density of the all-solid-state secondary battery is maximized, while lithium ion transport is facilitated to suppress resistance, thereby improving the overall performance of the all-solid-state secondary battery. Here, the average particle size (D) of the solid electrolyte 50 ) may be measured using a particle size analyzer utilizing laser diffraction.

[0175] The solid electrolyte layer (300) may further include a binder in addition to the solid electrolyte. In this case, the binder may be styrene butadiene rubber, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, acrylate-based polymer, or a combination thereof, but is not limited thereto, and any material used as a binder in the relevant technical field may be used. The acrylate-based polymer may be, for example, butyl acrylate, polyacrylate, polymethacrylate, or a combination thereof.

[0176] A solid electrolyte layer (300) can be formed by adding a solid electrolyte to a binder solution, coating the solution onto a substrate film, and drying it. The solvent of the binder solution may be octyl acetate, isobutyryl isobutylate, xylene, toluene, benzene, hexane, or a combination thereof. Since the process of forming the solid electrolyte layer is widely known in the field, a detailed description will be omitted.

[0177] The thickness of the solid electrolyte layer (300) can be, for example, 10 μm to 150 μm.

[0178] The solid electrolyte layer (300) may further include an alkali metal salt, and / or an ionic liquid, and / or a conductive polymer.

[0179] The alkali metal salt may be, for example, a lithium salt. The content of the lithium salt in the solid electrolyte layer may be 1 M or more, for example, 1 M to 4 M. In this case, the lithium salt can improve ion conductivity by improving the lithium ion mobility of the solid electrolyte layer.

[0180] Lithium salts may be applied without limitation of type and may include, for example, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiSCN, LiN(CN)2, lithium bis(oxalateto)borate (LiBOB), lithium difluoro(oxalateto)borate (LiDFOB), lithium difluorobis(oxalateto)phosphate (LiDFBP), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(pentafluoroethanesulfonyl)imide (LiBETI), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, or combinations thereof.

[0181] For example, the lithium salt may be an imide-based lithium salt such as LiTFSI, LiFSI, LiBETI, or a combination thereof. Imide-based lithium salts can maintain or improve ionic conductivity by appropriately maintaining chemical reactivity with ionic liquids.

[0182] Ionic liquids are salts or room temperature molten salts that have a melting point below room temperature, are in a liquid state at room temperature, and consist only of ions.

[0183] The ionic liquid comprises a) one or more cations selected from ammonium, pyrrolidinium, pyridinium, pyrimidinium, imidazolium, piperidinium, pyrazolium, oxazolium, pyridazinium, phosphonium, sulfonium, triazolium, and mixtures thereof, and b) BF4 - , PF6 - , AsF6 - , SbF6 - , AlCl4 - , HSO4 - , ClO4 - , CH3SO3 - , CF3CO2 - , Cl - , Br - , I - , BF4 -, SO4 - , CF3SO3 - , (FSO2)2N - , (C2F5SO2)2N - , (C2F5SO2)(CF3SO2)N - , and (CF3SO2)2N - It may be a compound containing one or more anions selected from among.

[0184] The ionic liquid may be one or more selected from the group consisting of, for example, N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide, N-butyl-N-methylpyrrolidinium bis(3-trifluoromethylsulfonyl)imide, 1-butyl-3-methylimidazoliium bis(trifluoromethylsulfonyl)amide, and 1-ethyl-3-methylimidazoliium bis(trifluoromethylsulfonyl)amide.

[0185] The weight ratio of the solid electrolyte to the ionic liquid in the solid electrolyte layer may be 0.1:99.9 to 90:10, and for example, 10:90 to 90:10, 20:80 to 90:10, 30:70 to 90:10, 40:60 to 90:10, or 50:50 to 90:10. A solid electrolyte layer satisfying the above range can maintain or improve ionic conductivity by increasing the electrochemical contact area with the electrode. Accordingly, the energy density, discharge capacity, rate characteristics, etc. of the all-solid-state secondary battery can be improved.

[0186] The all-solid-state secondary battery may be a unit cell having a structure of a positive electrode / solid electrolyte layer / negative electrode, a bicell having a structure of a positive electrode / solid electrolyte layer / negative electrode / solid electrolyte layer / positive electrode, or a stacked battery in which the structure of the unit cell is repeated.

[0187] The shape of the all-solid-state secondary battery is not particularly limited and may be, for example, coin-type, button-type, sheet-type, stacked-type, cylindrical-type, flat-type, etc. In addition, the all-solid-state secondary battery can be applied to large batteries used in electric vehicles, etc. For example, the all-solid-state secondary battery can be used in hybrid vehicles such as plug-in hybrid electric vehicles (PHEVs). In addition, it can be used in fields requiring a large amount of power storage, for example, in electric bicycles or power tools. Furthermore, the above-mentioned all-solid-state secondary battery can be used in various fields such as portable electronic devices.

[0188] Examples and comparative examples of the present invention are described below. The following examples are merely illustrative of the present invention, and the present invention is not limited to the following examples.

[0189] Example 1

[0190] 1. Preparation of cathode active material

[0191] Average particle size (D 50 ) is approximately 13 µm and is in the form of secondary particles LiNi 0.945 Co 0.04 Al 0.015 O2 was prepared as lithium transition metal composite oxide particles. 100 molar parts of the lithium transition metal composite oxide particles, 0.1 molar parts of zirconium oxide (ZrO2), and 0.25 molar parts of phosphate oxide (P2O5) were placed in a Henschel mixer and mixed to proceed with coating. At this time, the mixer was operated at low, medium, and high speeds to ensure even coating without layer separation. Subsequently, the final cathode active material with a coating layer was prepared by heat treatment at 300°C for 15 hours in an oxygen atmosphere.

[0192] 2. Manufacture of the anode

[0193] A cathode composition was prepared by mixing 85 wt% of the manufactured cathode active material, 13.44 wt% of an azirodite-type solid electrolyte of Li6PS5Cl, 1 wt% of a PVdF binder, 0.4 wt% of a carbon nanotube conductive material, and 0.16 wt% of hydrogenated nitrile butadiene rubber (HNBR) as a dispersant in an octyl acetate (OA) solvent. The cathode was prepared by coating the composition onto a cathode current collector and drying it at 80°C.

[0194] 3. Manufacturing of all-solid-state secondary batteries

[0195] Carbon black with a primary particle size of approximately 30 nm and an average particle size (D 50 An Ag / C composite was prepared by mixing silver (Ag) with a thickness of approximately 60 nm in a weight ratio of 3:1, and 0.25 g of the composite was added to 2 g of an NMP solution containing 7 wt% of a polyvinylidene fluoride binder and mixed to prepare a cathode coating layer composition. This was applied onto a cathode current collector and dried to prepare a precipitation type cathode with a cathode coating layer formed on the cathode current collector.

[0196] An azirodite-type solid electrolyte of Li6PS5Cl was added to an OA solvent containing an acrylic binder and mixed to prepare a composition for forming a solid electrolyte layer. The composition was cast onto a release film and dried at 80°C to prepare a solid electrolyte layer.

[0197] The prepared positive electrode, negative electrode, and solid electrolyte layer were cut, and the solid electrolyte layer was laminated onto the positive electrode, followed by the lamination of the negative electrode. The mixture was sealed in a pouch form and subjected to high-temperature hydrostatic pressing (WIP) at 85°C at 500 MPa for 30 minutes to manufacture an all-solid-state secondary battery.

[0198] Comparative Example 1

[0199] A positive active material and an all-solid-state secondary battery were prepared in substantially the same manner as in Example 1, except that zirconium oxide was not used in the preparation of the positive active material above.

[0200] Comparative Example 2

[0201] A positive electrode active material and an all-solid-state secondary battery were prepared in substantially the same manner as in Example 1, except that phosphorus oxide was not used in the preparation of the positive electrode active material.

[0202] Comparative Example 3

[0203] Except for using the lithium transition metal composite oxide particles prepared in Example 1 as the positive active material itself when manufacturing the positive active material, the positive active material and the all-solid-state secondary battery were manufactured in substantially the same manner as in Example 1.

[0204] To aid understanding, the design details of the cathode active materials for Example 1 and Comparative Examples 1 to 3 are briefly shown in Table 1 below.

[0205] Coating Method ZrO2 Coating Content (Moll%) P2O5 Coating Content (Moll%) Coating Heat Treatment Temperature Example 1: Dry Coating 0.1 0.25 300 ℃ Comparative Example 1: Dry Coating -0.25 300 ℃ Comparative Example 2: 0.1 -300 ℃ Comparative Example 3: No Coating -300 ℃

[0206] Evaluation Example 1: Evaluation of Charge / Discharge Characteristics of All-Solid State Secondary Battery

[0207] The all-solid-state secondary batteries prepared in Example 1 and Comparative Examples 1 to 3 were charged at 45°C with a constant current of 0.1C to an upper limit voltage of 4.25V and with a constant voltage of 0.05C, then discharged at 0.1C to a cutoff voltage of 2.5V, and then charged the batteries in the same process and discharged at a high rate of 0.33C and 1.0C to a cutoff voltage of 2.5V to evaluate the rate characteristics of the batteries, and subsequently charged again in the same process and discharged at 0.1C to a cutoff voltage of 2.5V to evaluate the recovery capacity.

[0208] In Table 2 below, the ratio of the initial discharge capacity to the high-rate discharge capacity was calculated and expressed as the discharge rate, and the ratio of the initial discharge capacity to the recovery capacity was calculated and expressed as the recovery rate to show the high-rate characteristics and recovery characteristics of the battery.

[0209] Initial Discharge Capacity (mAh / g) 0.33C Discharge Rate (%) 1.0C Discharge Rate (%) Recovery Rate (%) Example 1 19 59 2.68 3.9 95.9 Comparative Example 1 19 49 2.58 1.4 95.3 Comparative Example 2 20 49 0.77 9.7 93.5 Comparative Example 3 20 19 1.37 4.6 93.8

[0210] Referring to Table 2, Example 1 has a coating layer formed on the surface of the positive electrode active material with a high coverage rate using zirconium oxide and phosphorus oxide. During initial charging and discharging, the coating layer acts as some resistance, resulting in a low initial discharge capacity, but side reactions are suppressed, and it can be confirmed that it exhibits excellent high-rate characteristics and recovery rate.

[0211] Comparative Example 1 does not use zirconium oxide during coating, so compared to Example 1, the coating layer is formed with a relatively low coverage rate, and it can be confirmed that the high rate characteristics and recovery rate are inferior to those of Example 1.

[0212] Comparative Example 2 does not use phosphorus oxide during coating, so the coating rate on the surface of the positive active material is low, resulting in low resistance due to the coating layer and high initial discharge capacity during initial charging and discharging. However, a resistance layer is formed due to side reactions occurring during initial charging and discharging, showing low high-rate characteristics. Additionally, it can be confirmed that the recovery rate is also inferior as side reactions continue to occur due to repeated charging and discharging.

[0213] It can be confirmed that Comparative Example 3 does not form a coating layer, and thus exhibits low high-rate characteristics and recovery rate similar to Comparative Example 2.

[0214] Evaluation Example 2: Evaluation of Lifespan Characteristics of All-Solid State Secondary Batteries

[0215] For the all-solid-state secondary batteries prepared in Example 1 and Comparative Examples 1 to 3, as in Evaluation Example 1, charging and discharging were performed at 45°C with a constant current of 0.1C to an upper limit voltage of 4.25V and at a constant voltage of 0.05C, followed by discharging at 0.1C to a cutoff voltage of 2.5V. Additionally, charging and discharging at 0.33C within a voltage range of 2.5V to 4.25V at 45°C were repeated 20 times, and the ratio of the discharge capacity of 20 cycles to the discharge capacity of 1 cycle, i.e., the capacity retention rate during the life cycle, was evaluated. The results are shown in Table 3 below.

[0216] Initial Discharge Capacity (mAh / g) Capacity Retention Rate (%) (20 Cycles) Example 1 1629 2.7 Comparative Example 1 1599 2.0 Comparative Example 2 1628 8.9 Comparative Example 3 1587 0.8

[0217] Referring to Table 3, it can be confirmed that Example 1, which has a high coverage rate due to low-temperature molten metal oxide, has a high lifespan retention rate up to 20 charge-discharge cycles.

[0218] Comparative Example 1 shows a lower lifespan retention rate compared to Example 1, but shows a higher capacity retention rate compared to Comparatives 2 and 3 due to the relatively high coverage rate formed by low-temperature molten metal oxide.

[0219] Comparative Examples 2 and 3 can be seen to have inferior lifespan retention rates because they cannot effectively suppress side reactions during lifespan evaluation due to the low coverage rate.

[0220] Evaluation Example 3: Evaluation of Surface Coating Condition

[0221] The surfaces of the cathode active materials prepared in Example 1 and Comparative Examples 1 to 3 were photographed using SEM, and photographs at magnification of X40.0K are shown in Figures 3 to 6, respectively.

[0222] Referring to FIGS. 3 to 6, the positive electrode active material prepared in Example 1 has a shape in which the surface of the active material and the island-type zirconium oxide coating layer applied to the surface are well covered by a phosphate coating layer, which is a low-temperature molten metal oxide, whereas in Comparative Example 1, only the phosphate coating layer covering the surface is observed, and in Comparative Example 2, only the island-type zirconium oxide coating layer on the surface is observed, so it can be seen that there is a large exposed surface of the active material.

[0223] Although preferred embodiments have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concepts defined in the following claims are also included within the scope of the present invention.

[0224] [Explanation of the symbol]

[0225] 100: All-solid-state secondary battery 200: Cathode

[0226] 201: Positive current collector 203: Positive active material layer

[0227] 300: Solid electrolyte layer 400: Cathode

[0228] 401: Cathode current collector 403: Cathode active material layer

[0229] 400': Precipitation type cathode 404: Lithium metal layer

[0230] 405: Cathode coating layer 500: Elastic layer

Claims

1. Lithium transition metal complex oxide particles, and It includes a coating layer located on the surface of the above lithium transition metal composite oxide particles, and The above coating layer Coating particles containing metal oxides, and A positive electrode active material for an all-solid-state secondary battery comprising a low-temperature molten metal oxide including phosphorus oxide, lead oxide, vanadium oxide, or a combination thereof.

2. In Paragraph 1, A positive electrode active material for an all-solid-state secondary battery, wherein the coating particles in the above coating layer exist in an island form.

3. In Paragraph 1, In the above coating layer, the low-temperature molten metal oxide exists in the form of a continuous film. A positive electrode active material for an all-solid-state secondary battery.

4. In Paragraph 1, The metal of the above metal oxide comprises Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Nb, Si, Sr, Ti, W, Y, Zn, Zr, or a combination thereof, for a positive electrode active material for an all-solid-state secondary battery.

5. In Paragraph 1, The above metal oxide comprises aluminum oxide, boron oxide, barium oxide, calcium oxide, cerium oxide, cobalt oxide, chromium oxide, copper oxide, iron oxide, magnesium oxide, manganese oxide, molybdenum oxide, nickel oxide, neobium oxide, silicon oxide, strontium oxide, titanium oxide, tungsten oxide, yttrium oxide, zinc oxide, zirconium oxide, or a combination thereof, forming a positive electrode active material for an all-solid-state secondary battery.

6. In Paragraph 1, The above low-temperature molten metal oxide is a positive electrode active material for an all-solid-state secondary battery that further contains lithium.

7. In Paragraph 1, The above low-temperature molten metal oxide is a positive electrode active material for an all-solid-state secondary battery, further comprising lithium phosphorus oxide, lithium lead oxide, lithium vanadium oxide, or a combination thereof.

8. In Paragraph 1, The content of the low-temperature molten metal oxide in the coating layer is 0.01 to 0.5 molar parts relative to 100 molar parts of the lithium transition metal complex oxide particles, and A positive electrode active material for an all-solid-state secondary battery, wherein the content of the coating particles is 0.1 to 1.0 molar relative to 100 molar parts of the lithium transition metal composite oxide particles.

9. In Paragraph 1, A positive electrode active material for an all-solid-state secondary battery, wherein the average particle size of the coating particles is 5 nm to 500 nm.

10. In Paragraph 1, A positive electrode active material for an all-solid-state secondary battery, wherein the thickness of the coating layer is 5 nm to 1 μm.

11. In Paragraph 1, A positive electrode active material for an all-solid-state secondary battery in which the low-temperature molten metal oxide connects the coating particles.

12. In Paragraph 1, A positive electrode active material for an all-solid-state secondary battery in which the coating particles and the low-temperature molten metal oxide exist separately in the coating layer.

13. In Paragraph 1, The above lithium transition metal composite oxide is a positive electrode active material for an all-solid-state secondary battery, wherein the lithium transition metal composite oxide is a lithium nickel-based oxide represented by the following chemical formula 1, a lithium cobalt-based oxide represented by the following chemical formula 2, a lithium iron phosphate-based compound represented by the following chemical formula 3, a cobalt-free lithium nickel-manganese-based oxide represented by the following chemical formula 4, or a combination thereof: [Chemical Formula 1] Li a1 Ni x1 M 1 y1 M 2 z1 O 2-b1 X b1 In the above chemical formula 1, 0.9≤a1≤1.8, 0.3≤x1≤1, 0≤y1≤0.7, 0≤z1≤0.7, 0.9≤x1+y1+z1≤1.1, and 0≤b1≤0.1, and M 1 and M 2 are identical or different from each other and are each independently one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Zn, and Zr, and X is one or more elements selected from the group consisting of F, P, and S, and [Chemical Formula 2] Li a2 Co x2 M 3 y2 O 2-b2 X b2 In the above chemical formula 2, 0.9≤a2≤1.8, 0.7≤x2≤1, 0≤y2≤0.3, 0.9≤x2+y2≤1.1, and 0≤b2≤0.1, and M 3 is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Se, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is one or more elements selected from the group consisting of F, P, and S, and [Chemical Formula 3] Li a3 Fe x3 M 4 y3 PO 4-b3 X b3 In the above chemical formula 3, 0.9≤a3≤1.8, 0.6≤x3≤1, 0≤y3≤0.4, and 0≤b3≤0.1, and M 4 is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Mg, Mn, Mo, Ni, Se, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is one or more elements selected from the group consisting of F, P, and S, and [Chemical Formula 4] Li a4 Ni x4 Mr y4 M 5 z4 O 2-b4 X b4 In the above chemical formula 4, 0.9≤a4≤1.8, 0.8≤x4<1, 0 <y4≤0.2, 0≤z4≤0.2, 0.9≤x4+y4+z4≤1.1, 및 0≤b4≤0.1이고 M 5 is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, and Zr, and X is one or more elements selected from the group consisting of F, P, and S.

14. In Paragraph 13, The above lithium transition metal complex oxide is a lithium nickel-based oxide represented by the above chemical formula 1, and 0.8≤x1<1, 0 <y1≤0.2, 및 0≤z1≤0.2를 만족하는 고니켈계 산화물인 전고체 이차 전지용 양극 활물질.

15. In Paragraph 13, The above lithium transition metal composite oxide is a lithium nickel-based oxide represented by the above chemical formula 1, and 0.9≤x1<1, 0 <y1≤0.1, 및 0≤z1≤0.1를 만족하는 고니켈계 산화물인 전고체 이차 전지용 양극 활물질.

16. In Paragraph 1, A positive electrode active material for an all-solid-state secondary battery, wherein the average particle size of the lithium transition metal composite oxide particles is 1 μm to 25 μm.

17. In Paragraph 1, A positive electrode active material for an all-solid-state secondary battery, wherein the ratio of the average particle size of the lithium transition metal composite oxide particles to the average particle size of the coating particles is 500:1 to 10:

1.

18. Dry-mix lithium transition metal composite oxide particles, coating particles containing metal oxide, and low-temperature molten metal oxide, and, A method for manufacturing a positive electrode active material for an all-solid-state secondary battery, comprising heat-treating the result of the above dry mixing at 300 ℃ to 500 ℃.

19. In Paragraph 18, A method for manufacturing a positive electrode active material for an all-solid-state secondary battery, wherein the above heat treatment is carried out in an oxygen atmosphere for 5 to 25 hours.

20. In Paragraph 18, The coating particles are added in an amount of 0.1 to 1.0 molar relative to 100 molar parts of the lithium transition metal composite oxide particles, and A method for manufacturing a positive electrode active material for an all-solid-state secondary battery, wherein the low-temperature molten metal oxide is added in an amount of 0.01 to 0.5 molar parts relative to 100 molar parts of the lithium transition metal composite oxide particles.

21. In Paragraph 18, A method for manufacturing a positive electrode active material for an all-solid-state secondary battery, wherein the metal oxide is in the form of particles and the average particle size of the particles is 5 nm to 500 nm.

22. Positive current collector, and A positive electrode for an all-solid-state secondary battery, positioned on the positive electrode current collector and comprising a positive electrode active material layer according to any one of claims 1 to 17.

23. In Paragraph 22, The above-mentioned positive active material is a positive electrode for an all-solid-state secondary battery that further comprises a sulfide-based solid electrolyte.

24. In Paragraph 23, A positive electrode for an all-solid-state secondary battery, wherein, based on 100 weight% of the total of the positive electrode active material and the sulfide-based solid electrolyte, the positive electrode active material is included in an amount of 65 weight% to 99 weight% and the sulfide-based solid electrolyte is included in an amount of 1 weight% to 35 weight%.

25. In Paragraph 23, The above sulfide-based solid electrolyte comprises an azirodite-type sulfide, is in the form of particles, and is a positive electrode for an all-solid-state secondary battery having an average particle size of 0.1 μm to 3.0 μm.

26. Anode pursuant to Paragraph 22, cathode, and All-solid-state secondary battery comprising a solid electrolyte layer located between the anode and the cathode.

27. In Paragraph 26, The above cathode comprises a cathode current collector and a cathode coating layer located on the cathode current collector and containing a lithium-friendly metal, a carbon material, or a combination thereof. An all-solid-state secondary battery comprising a lithium metal layer formed by charging between the above-mentioned negative electrode current collector and the above-mentioned negative electrode coating layer.

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