KR20230145831A - Positive electrode for all solid state battery, preparing method thereof, and all solid state battery - Google Patents

Abstract

It includes a current collector, and a positive electrode active material layer located on the current collector and containing positive electrode active material particles and a sulfide-based solid electrolyte, and includes a coating layer located on the surface of the positive electrode active material particles and/or the surface of the positive electrode active material layer. The present invention relates to an anode for an all-solid-state battery in which the coating layer contains a lithium salt, a method for manufacturing the same, and an all-solid-state battery.

Description

Anode for all-solid-state battery, manufacturing method thereof, and all-solid-state battery comprising the same {POSITIVE ELECTRODE FOR ALL SOLID STATE BATTERY, PREPARING METHOD THEREOF, AND ALL SOLID STATE BATTERY}

It relates to an anode for an all-solid-state battery, a method of manufacturing the same, and an all-solid-state battery containing the same.

Lithium secondary batteries, which have high energy density and are easy to carry, are mainly used as a driving power source for mobile information terminals such as mobile phones, laptops, and smartphones. Recently, research has been actively conducted to use lithium secondary batteries with high energy density as a driving power source or power storage power source for hybrid vehicles or electric vehicles.

Since commercially available lithium secondary batteries use an electrolyte containing a flammable organic solvent, there is a safety problem in that they may explode or catch fire when problems such as collision or penetration occur. Accordingly, semi-solid batteries or all-solid batteries that avoid the use of electrolytes have been proposed. An all-solid-state battery is a battery in which all materials are made of solid, especially a battery that uses a solid electrolyte. These all-solid-state batteries are safe as there is no risk of explosion due to electrolyte leakage, and have the advantage of being easy to manufacture thin batteries.

All-solid-state batteries generally use sulfide-based solid electrolytes with excellent ionic conductivity. However, sulfide-based solid electrolytes have a problem in that irreversible lithium loss occurs at the interface due to high reactivity with the positive electrode active material. In particular, sulfide-based solid electrolytes are prone to side reactions and interface deterioration at the interface with the high-nickel-based positive electrode active material. Accordingly, there is a problem in which the capacity and lifespan of the all-solid-state battery are rapidly reduced.

This relates to the development of a protective layer (buffer layer) on the surface of the positive electrode active material particle or positive active material layer of an all-solid-state battery. It lowers the reactivity between the positive electrode active material and the sulfide-based solid electrolyte, suppresses irreversible lithium loss at the interface, and lithium ions. It reduces the interfacial resistance (charge-transfer resistance) for smooth movement and improves the high-voltage stability of the sulfide-based solid electrolyte, improving the electrochemical properties such as capacity, initial charge and discharge efficiency, rate characteristics, and lifespan of the all-solid-state battery. Let's do it.

In one embodiment, it includes a current collector, and a positive electrode active material layer located on the current collector and containing positive electrode active material particles and a sulfide-based solid electrolyte, and located on the surface of the positive electrode active material particles and/or the surface of the positive electrode active material layer. It provides a positive electrode for an all-solid-state battery, including a coating layer, wherein the coating layer includes a lithium salt.

In another embodiment, a positive electrode active material, a lithium salt, and lithium hydroxide are mixed and heat treated to prepare a coated positive electrode active material, a positive electrode composition is prepared by mixing the coated positive electrode active material and a sulfide-based solid electrolyte, and the positive electrode composition is prepared. A method for manufacturing a positive electrode for an all-solid-state battery is provided, including coating and drying the positive electrode current collector.

Another embodiment provides an all-solid-state battery including the above-described positive electrode, the negative electrode, and a solid electrolyte layer located between the positive electrode and the negative electrode.

In the positive electrode for an all-solid-state battery according to an embodiment, the reactivity between the positive electrode active material and the sulfide-based solid electrolyte is lowered, thereby suppressing irreversible lithium loss at the interface, and reducing the interfacial resistance so that lithium ions can be smoothly charged and discharged. The high voltage stability of the solid electrolyte is improved. Accordingly, the electrochemical properties of the all-solid-state battery according to one embodiment may be improved, such as capacity, initial charge/discharge efficiency, rate characteristics, and lifespan.

1 and 2 are cross-sectional views schematically showing an all-solid-state battery according to an embodiment.
Figure 3 is a Nyquist Plot showing the impedance of the batteries of Example 1 and Comparative Example 1 after full charging at 4.25V.
Figure 4 is a Nyquist diagram showing the impedance of the batteries of Examples 1 to 3 after full charging at 4.25V.
Figure 5 is a graph measuring the change in interfacial resistance over time while maintaining a constant voltage state for the batteries of Example 1 and Comparative Example 1 after charging at 4.25V.
Figure 6 is a Nyquist diagram showing the impedance of the batteries of Example 4 and Comparative Example 2 after full charging at 4.25V.

Hereinafter, specific implementation examples will be described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein.

The terminology used herein is for the purpose of describing example implementations only and is not intended to limit the invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

Here, “a combination thereof” means a mixture of constituents, a laminate, a composite, a copolymer, an alloy, a blend, a reaction product, etc.

Here, terms such as “comprise,” “comprise,” or “have” are intended to designate the presence of implemented features, numbers, steps, components, or a combination thereof, but are intended to indicate the presence of one or more other features, numbers, or steps. , components, or combinations thereof should be understood as not excluding in advance the existence or possibility of addition.

In the drawings, the thickness is enlarged to clearly express various layers and regions, and similar reference numerals are given to similar parts throughout the specification. When a part of a layer, membrane, region, plate, etc. is said to be “on” or “on” another part, this includes not only cases where it is “directly above” another part, but also cases where there is another part in between. Conversely, when a part is said to be “right on top” of another part, it means that there is no other part in between.

Also, here, “layer” includes not only the shape formed on the entire surface when observed in plan view, but also the shape formed on some surfaces.

In addition, the average particle diameter and average size can be measured by methods well known to those skilled in the art, for example, by measuring with a particle size analyzer, or by transmission electron micrograph or scanning electron micrograph. . Alternatively, the size, etc. may be measured using a dynamic light scattering method, data analysis may be performed, the number of particles may be counted for each particle size range, and the average particle diameter value may be obtained by calculating from this. Unless otherwise defined, the average particle diameter refers to the diameter (D50) of particles with a cumulative volume of 50% by volume in the particle size distribution as measured by a particle size analyzer.

Here, “or” is not interpreted in an exclusive sense; for example, “A or B” is interpreted as including A, B, A+B, etc.

Anode for all-solid-state battery

In one embodiment, it includes a current collector, and a positive electrode active material layer located on the current collector and containing positive electrode active material particles and a sulfide-based solid electrolyte, and located on the surface of the positive electrode active material particles and/or the surface of the positive electrode active material layer. It provides a positive electrode for an all-solid-state battery, including a coating layer, wherein the coating layer includes a lithium salt.

The coating layer is a type of surface protective layer or buffer layer, and may uniformly cover the surface of the positive electrode active material particles or may also cover the shape of an island, and may be the surface opposite to the surface of the positive active material layer in contact with the current collector, that is, a solid surface. It may be formed in the form of a film on the surface in contact with the electrolyte layer.

The coating layer can be said to be an ion conductive protective layer and a lithium-rich protective layer. The coating layer can suppress side reactions at the interface between the positive electrode active material and the sulfide-based solid electrolyte, while simultaneously facilitating the movement of lithium ions and improving the robustness of the interface. The coating layer according to one embodiment is characterized by high lithium ion conductivity, high chemical resistance and high voltage resistance, and low interfacial resistance.

In general, layered positive electrode active materials such as lithium nickel-based oxide exhibit a high electrochemical potential of 4.2 V or more (vs. Li ⁺ /Li). This high potential acts as a driving force to move lithium ions from the solid electrolyte side to the positive electrode side or vice versa. However, due to the fact that there is a large gap between the reduction potential of the positive electrode active material and the oxidation potential of the sulfide-based solid electrolyte, and the bonding strength of Li-O is much greater than that of Li-S, the interface between the positive electrode active material and the sulfide-based solid electrolyte There is a region of rapid lithium concentration decrease due to weak molecular bonds. That is, a lithium reduction layer, which is a space charge region, is formed at the interface between the anode and the solid electrolyte. This lithium reduction layer can act to increase the interfacial resistance and polarization. Accordingly, it is necessary to form a protective layer (buffer layer) on the anode of an all-solid-state battery that can reduce interfacial resistance and capacity reduction. This protective layer is characterized by limited ionic conductivity depending on the coating thickness, degree of uniformity, and composition. Previously, many oxide-based protective layers, such as LiNbO ₃ , Li ₃ BO ₃ , and Li ₂ ZrO ₃ , have been developed. In one embodiment, the interfacial resistance can be further lowered compared to existing protective layer materials, thereby improving the mobility characteristics of lithium, greatly improving the charge/discharge efficiency and capacity of the battery, and a coating layer that can improve high voltage stability. provides.

_The ^lithium _salt in the _{coating layer can be referred to as} Li ⁺ , LiCl, LiI, lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(oxalato)borate (LiBOB), lithium difluoro. It may include (oxalato)borate (LiDFOB), lithium difluorobis(oxalato)phosphate, lithium tetrafluoro(oxalato)phosphate, or a combination thereof.

In addition to the lithium salt, the coating layer may further include lithium oxide (Li ₂ O), lithium carbonate (Li ₂ CO ₃ ), lithium hydroxide (LiOH), lithium complex oxide, or a combination thereof. Here, the lithium composite oxide contains lithium along with Al, B, Ca, Co, Ga, K, Mg, Na, Nb, Si, Sn, Ta, Ti, V, W, Y, Zr, or a combination thereof. It means oxide.

In the coating layer, the lithium salt may form a composite with lithium oxide (Li ₂ O), lithium carbonate (Li ₂ CO ₃ ), lithium hydroxide (LiOH), lithium complex oxide, or a combination thereof. This coating layer has high lithium ion conductivity, is structurally stable, and can further lower the interface resistance between the positive electrode active material and the sulfide-based solid electrolyte.

The lithium carbonate and lithium hydroxide can also be understood as residual lithium on the surface of the positive electrode active material. In addition, the lithium composite oxide is, for example, LiNbO ₃ , Li ₃ BO ₃ , Li ₂ CO ₃ , Li ₄ Ti ₅ O ₁₂ , LiTaO ₃ , LiAlO ₂ , Li ₂ ZrO ₃ , Li ₂ SiO _3, Li ₃ BO ₃ - It may include Li ₂ CO ₃ , LiNb _0.5 Ta _0.5 O ₃ , or a combination thereof.

The lithium salt in the coating layer may have a lithium-rich structure. That is, the coating layer may further include lithium-rich lithium salt. The lithium-rich means that a compound containing lithium contains more lithium than the specified amount. For example, the coating layer may include a lithium-rich lithium salt represented by Li _x -PF _6-y (0<x≤6, 0≤y≤5). In the lithium-rich lithium salt chemical formula, x and y may be, for example, 1≤x≤6 and 0≤y≤5, or 1<x≤6 and 0≤y≤5. This coating layer has very high lithium ion conductivity, is structurally stable, and is advantageous in lowering the interfacial resistance.

The coating layer may be in the form of a continuous film or layer, or may be in the form of an island, but the form is not limited.

The coating layer may be included in an amount of 0.05 mole parts to 5.0 mole parts based on 100 mole parts of the positive electrode active material particles, for example, 0.1 mole part to 4 mole part, 0.1 mole part to 3 mole part, 0.1 mole part to 2 mole part, or 0.1 mole part to 1.0 mole part. You can. When this range is satisfied, the coating layer can dramatically lower the interfacial resistance, increase lithium ion conductivity, and improve the overall electrochemical performance of the all-solid-state battery.

Meanwhile, the positive electrode active material particles may include a lithium nickel-based composite oxide, for example, a high nickel-based composite oxide having a nickel content of 80 mol% or more based on the total elements excluding lithium and oxygen. The lithium nickel-based composite oxide refers to an oxide further containing lithium, nickel, and optionally other elements, and may be an oxide with a layered structure.

While high-nickel-based cathode active materials can achieve high capacity, there is a problem in all-solid-state batteries that their capacity rapidly decreases due to their high reactivity with sulfide-based solid electrolytes. In one embodiment, even when a high nickel-based positive electrode active material is used, the existing problem can be solved by sufficiently suppressing the interfacial reactivity by applying a lithium salt-containing coating layer, and compared to existing protective layer materials, the interfacial resistance is further lowered and the lithium ion conductivity is improved. By increasing , the electrochemical properties of the all-solid-state battery can be improved.

The content of nickel in the high nickel-based positive electrode active material may be 60 mol% or more, for example, 70 mol% or more, 80 mol% or more, 85 mol% or more, or 90 mol% based on the total amount of elements excluding lithium and oxygen. It may be more than, 100 mol% or less, 99.9 mol% or less, or 99 mol% or less.

The lithium nickel-based composite oxide may be specifically represented by Formula 1 below.

[Formula 1]

Li _a1 Ni _x1 M ¹ _y1 M ² _1-x1-y1 O ₂

In Formula 1, 0.9≤a1≤1.8, 0.6≤x1≤1, 0≤y1≤0.4, and M ¹ and M ² are each independently Al, B, Ba, Ca, Ce, Co, Cr, F, Fe. , Mg, Mn, Mo, Nb, P, S, Si, Sr, Ti, V, W, Zr, or a combination thereof.

In Formula 1, 0.7≤x1≤1 and 0≤y1≤0.3, or 0.8≤x1≤1 and 0≤y1≤0.2, 0.85≤x1≤1 and 0≤y1≤0.15, or 0.9≤x1≤1 and 0≤ y1≤0.1.

For example, the lithium nickel-based composite oxide may be a lithium nickel cobalt-based oxide represented by Formula 2 below.

[Formula 2]

Li _a2 Ni _x2 Co _y2 M ³ _1-x2-y2 O ₂

In Formula 2, 0.9≤a2≤1.8, 0.6≤x2<1, 0<y2≤0.4, and M ³ is Al, B, Ba, Ca, Ce, Cr, F, Fe, Mg, Mn, Mo, Nb, P, S, Si, Sr, Ti, V, W, Zr, or a combination thereof.

In Formula 2, 0.7≤x2≤1 and 0≤y2≤0.3, or 0.8≤x2≤1 and 0≤y2≤0.2, 0.85≤x2≤0.99 and 0.01≤y2≤0.15, or 0.9≤x2≤0.99 and 0.01≤y2 It can be ≤0.1.

For example, the lithium nickel-based composite oxide may be represented by Formula 3 below. The compound represented by Formula 3 below can be referred to as lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminum oxide.

[Formula 3]

Li _a3 Ni _x3 Co _y3 M ⁴ _z3 M ⁵ _1-x3-y3-z3 O ₂

In Formula 3, 0.9≤a3≤1.8, 0.6≤x3≤0.98, 0.01≤y3≤0.39, 0.01≤z3≤0.39, M ⁴ is Al, Mn, or a combination thereof, and M ⁵ is B, Ba, Ca, Ce, Cr, F, Fe, Mg, Mo, Nb, P, S, Si, Sr, Ti, V, W, Zr, or a combination thereof.

In Formula 3, for example, it may be 0.8≤x3≤0.98, 0.01≤y3≤0.19, and 0.01≤z3≤0.19, or 0.9≤x3≤0.98, 0.01≤y3≤0.09, and 0.01≤z3≤0.09.

The average particle diameter (D50) of the positive electrode active material may be 1 ㎛ to 25 ㎛, for example, 4 ㎛ to 25 ㎛, 5 ㎛ to 20 ㎛, 8 ㎛ to 20 ㎛, or 10 ㎛ to 18 ㎛. A positive electrode active material having this particle size range can be harmoniously mixed with other components within the positive active material layer and can achieve high capacity and high energy density. The average particle diameter is obtained by randomly measuring the size (diameter or long axis length) of about 30 particles in an optical microscope photo such as a scanning electron microscope to obtain a particle size distribution, and in the particle size distribution, the diameter of the particle with a cumulative volume of 50% by volume (D50) may be taken as the average particle size. In a positive electrode for an all-solid-state battery, it is important to properly control the average particle size of the positive electrode active material particles, the average particle size of the sulfide-based solid electrolyte, which will be described later, and the ratio of these average particle sizes. By adjusting these, the performance of the all-solid-state battery can be maximized. .

The positive electrode active material may be in the form of secondary particles made by agglomerating a plurality of primary particles, or may have a monolith structure. Additionally, the positive electrode active material may be spherical or close to a spherical shape, or may be polyhedral or amorphous.

Based on the total weight of the positive electrode active material layer, the positive electrode active material may be included in an amount of 55% by weight to 99.9% by weight, for example, 55% by weight to 99.7% by weight, or 74% by weight to 89.8% by weight. When included within the above range, the capacity of the all-solid-state battery can be maximized while the lifespan characteristics can be improved.

The sulfide-based solid electrolyte is, for example, Li ₂ SP ₂ S ₅ , Li ₂ SP ₂ S ₅ --LiX (X is a halogen element), Li ₂ SP ₂ S ₅ -Li ₂ O, Li ₂ SP ₂ S ₅ -Li ₂ O-LiI, Li ₂ S-SiS ₂ , Li ₂ S-SiS ₂ -LiI, Li ₂ S-SiS ₂ -LiBr, Li ₂ S-SiS ₂ -LiCl, Li ₂ S-SiS ₂ -B ₂ S ₃ -LiI, Li ₂ S-SiS ₂ -P ₂ S ₅ -LiI, Li ₂ SB ₂ S ₃ , Li ₂ SP ₂ S ₅ -Z _m S _n (m and n are each integers, Z is Ge, Zn or Ga), Li ₂ S-GeS ₂ , Li ₂ S-SiS ₂ -Li ₃ PO ₄ , Li ₂ S-SiS ₂ -Li _p MO _q (p, q are integers, M are P, Si, Ge, B, Al, Ga or In), or a combination thereof.

As an example, the sulfide-based solid electrolyte may include argyrodite-type sulfide. The azyrodite-type sulfide is, for example, Li _a M _b P _c S _d A _e (a, b, c, d and e are all 0 or more and 12 or less, and M is Ge, Sn, Si, or a combination thereof , A is F, Cl, Br, or I), and specifically Li ₃ PS ₄ , Li ₇ P ₃ S ₁₁ , Li ₆ PS ₅ Cl, Li ₆ PS ₅ Br, Li ₆ PS ₅ I, etc. there is. This azyrodite-type sulfide has a high ionic conductivity close to the 10 ^-4 to 10 ^-2 S/cm range, which is the ionic conductivity of a typical liquid electrolyte at room temperature, and thus binds closely to the positive electrode active material without causing a decrease in ionic conductivity. can be formed, and further, a tight interface can be formed between the electrode layer and the solid electrolyte layer. All-solid-state batteries containing this can have improved battery performance such as rate characteristics, coulombic efficiency, and lifespan characteristics.

The sulfide-based solid electrolyte may be amorphous or crystalline, or may be a mixture thereof.

The sulfide-based solid electrolyte is in the form of particles, and its average particle diameter (D50) may be 5.0 ㎛ or less, for example, 0.1 ㎛ to 5.0 ㎛, 0.5 ㎛ to 5.0 ㎛, 0.5 ㎛ to 4.0 ㎛, 0.5 ㎛ to 3.0 ㎛. , 0.5 μm to 2.0 μm, or 0.5 μm to 1.0 μm. A sulfide-based solid electrolyte that satisfies this particle size range can effectively penetrate between positive electrode active materials and has excellent contact with the positive electrode active material and connectivity between electrolyte particles. The average particle diameter is obtained by randomly measuring the size (diameter or long axis length) of about 50 particles in an optical microscope photograph such as a runner electron microscope to obtain a particle size distribution, and in the particle size distribution, the diameter of the particle with a cumulative volume of 50% by volume ( D50) may be taken as the average particle diameter.

In addition to the sulfide-based solid electrolyte described above, the positive electrode may further include an oxide-based inorganic solid electrolyte. The oxide-based inorganic solid electrolyte is, for example, Li _1+x Ti _2-x Al(PO ₄ ) 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), BaTiO ₃ , Pb(Zr,Ti)O ₃ (PZT), Pb _1-x La _x Zr _1-y Ti _y O ₃ (PLZT )(0≤x<1, 0≤y<1), PB(Mg ₃ Nb _2/3 )O ₃ -PbTiO ₃ (PMN-PT), HfO ₂ , SrTiO ₃ , SnO ₂ , CeO ₂ , Na ₂ O , MgO, NiO, CaO, BaO, ZnO, ZrO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , TiO ₂ , SiO ₂ , lithium phosphate (Li ₃ PO ₄ ), lithium titanium phosphate (Li _x Ti _y (PO ₄ ) 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 TiO ₃ , 0<x<2, 0<y<3), Li ₂ O, LiAlO ₂ , Li ₂ O-Al ₂ O ₃ -SiO ₂ -P ₂ O ₅ -TiO ₂ -GeO _2- based ceramics, Garnet-based ceramics Li _3+x La ₃ M ₂ O ₁₂ (M=Te, Nb, or Zr; x is an integer from 1 to 10), Or it may include a mixture thereof.

Based on the total weight of the positive electrode active material layer, the solid electrolyte may be included in an amount of 0.1% by weight to 45% by weight, for example, 1% by weight to 35% by weight, 5% by weight to 30% by weight, and 8% by weight to 25% by weight. %, or 10% to 20% by weight. Additionally, based on the total weight of the positive electrode active material and solid electrolyte in the positive electrode active material layer, 65% to 99% by weight of the positive electrode active material and 1% to 35% by weight of the solid electrolyte may be included, for example, 80% to 80% by weight of the positive electrode active material. It may contain 90% by weight and 10% to 20% by weight of solid electrolyte. When the solid electrolyte is included in the positive electrode in this amount, the efficiency and lifespan characteristics of the all-solid-state battery can be improved without reducing the capacity.

bookbinder

The positive active material layer may optionally further include a binder. The binder serves to adhere the positive electrode active material particles to each other and also to adhere the positive electrode active material to the current collector. Examples of the binder include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymer containing ethylene oxide, polyvinyl pyrroli. Money, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyethylene, polypropylene, styrene butadiene rubber, acrylated styrene butadiene rubber, polyacrylonitrile, Examples include, but are not limited to, epoxy resin, nylon, poly(meth)acrylate, and polymethyl(meth)acrylate.

Among them, the binder according to one embodiment is polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polytetrafluoroethylene, styrene butadiene rubber, polyacrylonitrile, and polymethyl (meth)acrylate. There may be one or more selected from among. These binders can be well dissolved in the dispersion medium, the compound represented by Formula 1 and the compound represented by Formula 2, and thus uniform coating is possible and excellent electrode plate performance can be achieved.

The binder is present in an amount of 0% to 5% by weight, 0.1% to 4% by weight, or 0.1% to 3% by weight, based on the total weight of each component of the positive electrode for an all-solid-state battery, or based on the total weight of the positive electrode active material layer. It can be included as a percentage. In the above content range, the binder can sufficiently demonstrate adhesive ability without deteriorating battery performance.

conductive material

The positive active material layer may optionally further include a conductive material. The conductive material is used to provide conductivity to the electrode, and any electronically conductive material can be used as long as it does not cause chemical change. The conductive material includes, for example, carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; Metallic substances containing copper, nickel, aluminum, silver, etc. and in the form of metal powder or metal fiber; Conductive polymers such as polyphenylene derivatives; Or it may include a mixture thereof.

The conductive material may be included in an amount of 0% to 5% by weight, or 0.1% to 3% by weight, based on the total weight of each component of the positive electrode for an all-solid-state battery, or based on the total weight of the positive electrode active material layer. Within the above content range, the conductive material can improve electrical conductivity without deteriorating battery performance.

The positive electrode active material layer includes 55% by weight to 99.7% by weight of the positive electrode active material, based on the total weight of the positive electrode active material, solid electrolyte, binder, and conductive material; 0.1% to 35% by weight of solid electrolyte; 0.1% to 5% by weight binder; And it may include 0.1% by weight to 5% by weight of a conductive material. As a specific example, 74% to 89.8% by weight of positive electrode active material; 10% to 20% by weight of solid electrolyte; 0.1% to 3% by weight binder; And 0.1% by weight to 3% by weight of a conductive material may be included. When mixed in the above content range, the lifespan characteristics of the battery can be improved while maximizing the capacity.

In the positive electrode for an all-solid-state battery, the current collector may be aluminum, but is not limited thereto.

Method for manufacturing anode for all-solid-state battery

In one embodiment, a positive electrode active material, a lithium salt, and lithium hydroxide are mixed and heat treated to prepare a coated positive electrode active material, a positive electrode composition is prepared by mixing the coated positive electrode active material and a sulfide-based solid electrolyte, and the positive electrode composition is prepared as a base material. Provides a method for manufacturing an anode for an all-solid-state battery, including applying and drying. Accordingly, the above-described positive electrode can be manufactured.

In the above manufacturing method, the positive electrode active material, lithium salt, and sulfide-based solid electrolyte are the same as described above, so detailed descriptions are omitted. The coated positive electrode active material means that a lithium salt-containing coating layer is formed on the surface of the positive electrode active material particles.

In the step of mixing the positive electrode active material, lithium salt, and lithium hydroxide, the lithium salt is added in an amount of 0.05 mole part to 5.0 mole part, 0.05 mole part to 3.0 mole part, 0.05 mole part to 2.0 mole part, and 0.1 mole part to 1.0 mole part, based on 100 parts by weight of the cathode active material. It may be mixed in molar parts, or 0.1 molar parts to 0.5 molar parts. Additionally, the lithium hydroxide may be mixed in an amount of 0.05 mole part to 5.0 mole, 0.05 mole part to 3.0 mole, 0.1 mole part to 2.0 mole part, or 0.1 mole part to 1.0 mole part with respect to 100 parts by weight of the positive electrode active material. When mixed in the above content range, the positive electrode active material can be uniformly coated with a lithium salt or a lithium-rich lithium salt-containing coating layer, effectively lowering the interfacial resistance, and improving lithium ion conductivity.

In the method of manufacturing the positive electrode, a metal compound or metalloid compound may be further mixed with the positive electrode active material, the lithium salt, and the lithium hydroxide. Here, the metal compound or metalloid compound is a compound containing Al, B, Ca, Co, Ga, K, Mg, Na, Nb, Si, Sn, Ta, Ti, V, W, Y, Zr, or a combination thereof. means. This may mean a precursor of a metal or metalloid element to be present in the coating layer. When these metal compounds or metalloid compounds are further mixed, lithium composite oxide may be formed in addition to the lithium salt in the coating layer, and the lithium salt and the lithium composite oxide may be in the form of a composite in the coating layer. . The lithium composite oxide includes Al, B, Ca, Co, Ga, K, Mg, Na, Nb, Si, Sn, Ta, Ti, V, W, Y, along with lithium, as described in the positive electrode portion for an all-solid-state battery. It means an oxide containing Zr, or a combination thereof. If both lithium salt and lithium complex oxide are present in the coating layer, the interfacial resistance can be further lowered, lithium ion conductivity can be increased, and the structural stability of the coating layer can be improved. Additionally, lower interfacial resistance characteristics can be achieved compared to existing protective layers containing only lithium composite oxide.

The metal compound or metalloid compound may be mixed in an amount of 0.05 mole part to 3.0 mole part, for example, 0.05 mole part to 2.0 mole part, or 0.1 mole part to 1.0 mole part, based on 100 parts by weight of the positive electrode active material. Within the above range, low interfacial resistance and high lithium ion conductivity can be achieved.

The heat treatment step may be carried out in an oxygen atmosphere at a temperature of, for example, 100°C to 700°C, or 100°C to 500°C, or 200°C to 400°C, and may be carried out for 1 hour to 12 hours, or 2 hours to 6 hours. You can. In this case, a structurally stable coating layer can be formed.

The step of preparing the coated positive electrode active material, that is, the step of coating by adding lithium salt and lithium hydroxide to the positive electrode active material, may be performed wet, for example, may be performed by a sol-gel method, or may be performed dry. . When coating is performed in a wet manner, the positive electrode active material, lithium salt, and lithium hydroxide can be mixed in an aqueous solvent, then dried and heat treated.

The mixing ratio of the positive electrode active material and the sulfide-based solid electrolyte in the positive electrode composition is as described above. The positive electrode composition may optionally further include an oxide-based solid electrolyte, a binder, and/or a conductive material, and the content range is as described above.

solid-state battery

In one embodiment, an all-solid-state battery is provided including the above-described positive electrode, the negative electrode, and a solid electrolyte layer located between the positive electrode and the negative electrode. These all-solid-state batteries can achieve high capacity, have high initial efficiency, excellent rate characteristics, and excellent lifespan characteristics. The all-solid-state battery can be expressed as an all-solid secondary battery, an all-solid lithium secondary battery, etc.

1 is a cross-sectional view of an all-solid-state battery according to one embodiment. Referring to Figure 1, the all-solid-state battery 100 includes a negative electrode 400 including a negative electrode current collector 401 and a negative electrode active material layer 403; Solid electrolyte layer 300; Additionally, the electrode superstructure in which the positive electrode 200 including the positive electrode active material layer 203 and the positive electrode current collector 201 is stacked may be stored in a case such as a pouch. Although FIG. 1 shows one electrode assembly including a cathode 400, a solid electrolyte layer 300, and an anode 200, an all-solid-state battery can also be manufactured by stacking two or more electrode assemblies.

The all-solid-state battery 100 may further include an elastic sheet 500 outside at least one of the positive electrode 200 and the negative electrode 400. The elastic sheet 500 may be expressed as a buffer layer or an elastic layer, and serves to ensure good contact between solid components by uniformly transmitting pressure to the electrode laminate, and to relieve stress transmitted to the solid electrolyte, etc. It can play a role in suppressing the occurrence of cracks in the solid electrolyte due to stress accumulation due to changes in the thickness of the electrode during charging and discharging.

cathode

For example, a negative electrode for an all-solid-state battery may include a current collector and a negative electrode active material layer located on the current collector. The negative electrode active material layer includes a negative electrode active material and may further include a binder, a conductive material, and/or a solid electrolyte.

The anode active material may include 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.

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

The alloy of the lithium metal includes lithium and one selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al and Sn. Alloys with the above metals may be used.

As the material capable of doping and dedoping lithium, a Si-based negative electrode active material or a Sn-based negative electrode active material can be used, and the Si-based negative electrode active material includes silicon, silicon-carbon composite, SiO _x (0<x<2), Si -Q alloy (Q is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, Group 15 elements, Group 16 elements, transition metals, rare earth elements, and combinations thereof, but not Si. ), the Sn-based negative electrode active materials include Sn, SnO ₂ , and Sn-R alloy (where R is an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element, a Group 15 element, a Group 16 element, a transition metal, a rare earth element, and elements selected from the group consisting of combinations thereof, but not Sn), and the like, and at least one of these may be mixed with SiO ₂ . The elements Q and R include 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, One selected from the group consisting of S, Se, Te, Po, and combinations thereof can be used.

For example, the silicon-carbon composite may be a silicon-carbon composite including a core containing crystalline carbon and silicon particles and an amorphous carbon coating layer located on the surface of the core. The crystalline carbon may be artificial graphite, natural graphite, or a combination thereof. As the amorphous carbon precursor, coal-based pitch, mesophase pitch, petroleum-based pitch, coal-based oil, petroleum-based heavy oil, or polymer resin such as phenol resin, furan resin, and polyimide resin can be used. At this time, the content of silicon may be 10% by weight to 50% by weight based on the total weight of the silicon-carbon composite. In addition, the content of the crystalline carbon may be 10% by weight to 70% by weight based on the total weight of the silicon-carbon composite, and the content of the amorphous carbon may be 20% by weight to 40% by weight based on the total weight of the silicon-carbon composite. there is. Additionally, the thickness of the amorphous carbon coating layer may be 5 nm to 100 nm.

The average particle diameter (D50) of the silicon particles may be 10nm to 20㎛, for example, 10nm to 200nm. The silicon particles may exist in an oxidized form, and in this case, the atomic content ratio of Si:O in the silicon particles, which indicates the degree of oxidation, may be 99:1 to 33:67. The silicon particles may be SiO _x particles, and in this case, the SiO _x x range may be greater than 0 and less than 2.

The Si-based negative electrode active material or Sn-based negative electrode active material may be used by mixing with a carbon-based negative electrode active material. Si-based negative electrode active material or Sn-based negative electrode active material; and a carbon-based negative active material; the mixing ratio may be 1:99 to 90:10 in weight ratio.

The content of the negative electrode active material in the negative electrode active material layer may be 95% by weight to 99% by weight based on the total weight of the negative electrode active material layer.

In one embodiment, the negative electrode active material layer further includes a binder and, optionally, may further include a conductive material. The content of the binder in the negative electrode active material layer may be 1% by weight to 5% by weight based on the total weight of the negative electrode active material layer. In addition, when a conductive material is further included, the negative electrode active material layer may include 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.

The binder serves to adhere the negative electrode active material particles to each other and also helps the negative electrode active material to adhere to the current collector. The binder may be a water-insoluble binder, a water-soluble binder, or a combination thereof.

The water-insoluble binder includes polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, ethylene propylene copolymer, polystyrene, polyvinylpyrrolidone, polyurethane, and polytetrafluoride. Ethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamidoimide, polyimide, or combinations thereof may be mentioned.

Examples of the water-soluble binder include a rubber binder or a polymer resin binder. The rubber-based binder may be selected from styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, fluorine rubber, and combinations thereof. The polymer resin binder is polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, poly It may be selected from ester resin, acrylic resin, phenol resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

When a water-soluble binder is used as the negative electrode binder, it may further include a cellulose-based compound capable of imparting viscosity. As this cellulose-based compound, one or more types of carboxymethyl cellulose, hydroxypropylmethyl cellulose, methyl cellulose, or alkali metal salts thereof can be used. Na, K, or Li can be used as the alkali metal. The amount of the thickener used may be 0.1 to 3 parts by weight based on 100 parts by weight of the negative electrode active material.

The conductive material is used to provide conductivity to the electrode, and any material that has electronic conductivity without causing chemical change can be used. The conductive material includes, for example, carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; Metallic substances containing copper, nickel, aluminum, silver, etc. in the form of metal powder or metal fiber; Conductive polymers such as polyphenylene derivatives; Or it may include a mixture thereof.

The negative electrode current collector may be selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof.

Meanwhile, as an example, the anode for an all-solid-state battery may be a precipitation-type anode. The precipitation-type negative electrode refers to a negative electrode that does not have a negative electrode active material when the battery is assembled, but lithium metal, etc. is precipitated and acts as a negative electrode active material when the battery is charged.

Figure 2 is a schematic cross-sectional view of an all-solid-state battery including a precipitated negative electrode. Referring to FIG. 2, the precipitated negative electrode 400' may include a current collector 401 and a negative electrode catalyst layer 405 located on the current collector. In an all-solid-state battery having such a precipitation-type negative electrode 400', initial charging begins in the absence of a negative electrode active material, and during charging, a high density of lithium metal, etc. is deposited between the current collector 401 and the negative electrode catalyst layer 405. A lithium metal layer 404 is formed, which can serve as a negative electrode active material. Accordingly, in an all-solid-state battery that has been charged at least once, the precipitated negative electrode 400' includes a current collector 401, a lithium metal layer 404 located on the current collector, and a negative electrode catalyst layer located on the metal layer ( 405) may be included. 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 or a negative electrode active material layer.

The cathode catalyst layer 405 may include metal and/or carbon material that acts as a catalyst.

The metal 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 several types of alloys. there is. The average particle diameter (D50) of the metal may be about 4 ㎛ or less, for example, 10 nm to 4 ㎛, 10 nm to 2 ㎛, or 10 nm to 1 ㎛.

The carbon material may be, for example, crystalline carbon, non-graphitic carbon, or a combination thereof. For example, the crystalline carbon may be at least one selected from natural graphite, artificial graphite, mesophase carbon microbeads, and combinations thereof. The non-graphitic carbon may be at least one selected from carbon black, activated carbon, acetylene black, Denka black, Ketjen black, furnace black, graphene, and combinations thereof.

When the cathode catalyst layer 405 includes both the metal and the carbon material, the mixing ratio of the metal and the carbon material is, for example, 1:10 to 1:2, 1:10 to 2:1, and 5:1 to 1:1. The weight ratio may be 1:1, or 4:1 to 2:1. In this case, the precipitation of lithium metal can be effectively promoted and the characteristics of the all-solid-state battery can be improved. For example, the cathode catalyst layer 405 may include a carbon material on which a catalyst metal is supported, or may include a mixture of metal particles and carbon material particles.

The cathode catalyst layer 405 may further include a binder, and the binder may be, for example, a conductive binder. Additionally, the cathode catalyst layer 405 may further include general additives such as fillers, dispersants, and ion conductive materials.

The thickness of the cathode catalyst layer 405 may be, for example, 1 μm to 20 μm, 2 μm to 10 μm, or 3 μm to 7 μm. Additionally, the thickness of the negative electrode catalyst layer 405 may be 50% or less, 20% or less, or 5% or less of the thickness of the positive electrode active material layer. If the thickness of the cathode catalyst layer 405 is too thin, it may be collapsed by the lithium metal layer 404, and if the thickness is too thick, the density of the all-solid-state battery may decrease and internal resistance may increase.

For example, the precipitated negative electrode 400' may further include a thin film on the surface of the current collector, that is, between the current collector and the negative electrode catalyst layer. The thin film may contain an element that can form an alloy with lithium. Elements that can form an alloy with lithium may be, for example, gold, silver, zinc, tin, indium, silicon, aluminum, bismuth, etc., and may be composed of one type or several types of alloys. The thin film can further flatten the precipitation form of the lithium metal layer 404 and further improve the characteristics of the all-solid-state battery. The thin film may be formed by, for example, vacuum deposition, sputtering, or plating methods. The thickness of the thin film may be, for example, 1 nm to 800 nm, or 100 nm to 500 nm.

The lithium metal layer 404 may include lithium metal or lithium alloy. The lithium alloy may be, for example, a Li-Al alloy, Li-Sn alloy, Li-In alloy, Li-Ag alloy, Li-Au alloy, Li-Zn alloy, Li-Ge alloy, or Li-Si alloy. .

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 role of a lithium storage, and if it is too thick, the battery volume may increase and performance may deteriorate.

When applying such a precipitation-type cathode, the cathode catalyst layer 405 may play a role in protecting the lithium metal layer 404 and suppressing the precipitation growth of lithium deadlight. Accordingly, short circuit and capacity degradation of the all-solid-state battery can be suppressed and lifespan characteristics can be improved.

solid electrolyte layer

The solid electrolyte layer 300 includes a solid electrolyte and may include the above-described sulfide-based solid electrolyte, oxide-based solid electrolyte, or solid polymer electrolyte. Since the solid electrolyte is the same as described in the anode for an all-solid-state battery, detailed description will be omitted.

The solid electrolyte layer may further include a binder in addition to the solid electrolyte. At this time, the binder may be styrene butadiene rubber, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, acrylate polymer, or a combination thereof, but is not limited thereto, and the binder used in the art is You can use anything. The acrylate-based polymer may be, for example, butyl acrylate, polyacrylate, polymethacrylate, or a combination thereof.

The solid electrolyte layer can be formed by adding a solid electrolyte to a binder solution, coating it on a base film, and drying it. The solvent of the binder solution may be isobutyryl isobutyrate, xylene, toluene, benzene, hexane, or a combination thereof, or may be a compound represented by Formula 1 and/or a compound represented by Formula 2. there is. Since the solid electrolyte layer forming process is widely known in the art, detailed description will be omitted.

The thickness of the solid electrolyte layer may be, for example, 10 ㎛ to 150 ㎛.

The solid electrolyte layer may further include an alkali metal salt, and/or an ionic liquid, and/or a conductive polymer.

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

The lithium salt is, for example, LiSCN, LiN(CN) ₂ , Li(CF ₃ SO ₂ ) ₃ C, LiC ₄ F ₉ SO ₃ , LiN(SO ₂ CF ₂ CF ₃ ) ₂ , LiF, LiCl, LiBr, LiI , LiB(C ₂ O ₄ ) ₂ , LiPF ₆ , LiBF ₄ , LiBF ₃ (C ₂ F ₅ ), lithium bis(oxalato)borate (LiBOB), lithium oxalyldifluoroborate (LIODFB), lithium difluoride Low(oxalato)borate (LiDFOB), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), LiCF ₃ SO ₃ , LiAsF ₆ , LiSbF ₆ , LiClO ₄ or a mixture thereof.

Additionally, the lithium salt may be an imide-based salt, and may include, for example, LiTFSI, LiFSI, or a combination thereof. The imide-based lithium salt can maintain or improve ionic conductivity by maintaining appropriate chemical reactivity with ionic liquid.

The ionic liquid has a melting point below room temperature and is in a liquid state at room temperature and refers to a salt consisting of only ions or a room temperature molten salt.

The ionic liquid is a) ammonium-based, pyrrolidinium-based, pyridinium-based, pyrimidinium-based, imidazolium-based, piperidinium-based, pyrazolium-based, oxazolium-based, pyridazinium-based, phosphonium-based, sulfonium-based, At least one cation selected from the triazolium system and mixtures thereof, and b) BF ₄ -, PF ₆ -, AsF ₆ -, SbF ₆ -, AlCl ₄ -, HSO ₄ -, ClO ₄ -, CH ₃ SO ₃ -, CF ₃ CO ₂ -, Cl-, Br-, I-, BF ₄ -, SO ₄ -, CF ₃ SO ₃ -, (FSO ₂ ) ₂ N-, (C ₂ F ₅ SO ₂ )2N-, (C ₂ It may be a compound containing one or more anions selected from F ₅ SO ₂ )(CF ₃ SO ₂ )N-, and (CF ₃ SO ₂ ) ₂ N-.

The ionic liquid is, for example, N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide N-butyl-N-methylpyrrolidium bis(3-trifluoromethylsulfonyl) an imide, one selected from the group consisting of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide It could be more than that.

The weight ratio of the solid electrolyte and the ionic liquid in the solid electrolyte layer may be 0.1:99.9 to 90:10, 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 that satisfies the above range can maintain or improve ionic conductivity by improving the electrochemical contact area with the electrode. Accordingly, the energy density, discharge capacity, and rate characteristics of the all-solid-state battery can be improved.

The all-solid-state battery according to one embodiment can be manufactured by preparing a laminate by sequentially stacking a positive electrode, a solid electrolyte, and a negative electrode, and optionally attaching an elastic sheet to the outer surface of the positive electrode and/or negative electrode and then pressing it. The pressurization may be performed at a temperature of, for example, 25°C to 90°C, and may be performed at a pressure of 550 MPa or less, or 500 MPa or less, for example, 400 MPa to 500 MPa. The pressing may be, for example, isostatic press, roll press or plate press.

The all-solid-state battery may be a unit cell having a structure of anode/solid electrolyte layer/cathode, a bicell having a structure of anode/solid electrolyte layer/cathode/solid electrolyte layer/anode, or a stacked battery in which the structure of the unit cell is repeated. You can.

The shape of the all-solid-state battery is not particularly limited, and may be, for example, coin-shaped, button-shaped, sheet-shaped, stacked-shaped, cylindrical, flat, etc. Additionally, the all-solid-state battery can also be applied to medium to large-sized batteries used in electric vehicles, etc. For example, the all-solid-state battery can also be used in hybrid vehicles such as plug-in hybrid electric vehicles (PHEV). In addition, it can be applied to an energy storage system (ESS) that requires large amounts of power storage, and can also be applied to electric bicycles or power tools.

Hereinafter, examples and comparative examples of the present invention will be described. The following examples are only examples of the present invention, and the present invention is not limited to the following examples.

Example 1

1. Preparation of positive electrode active material

Li _1.06 Ni _0.90 Co _0.07 Mn _0.03 O ₂ Prepare a positive electrode active material, add the positive electrode active material and ethanol solvent to a stirrer at a weight ratio of 1:1, and add 0.1 mole part of LiPF ₆ and 0.5 mole of LiOH based on 100 parts by weight of the positive electrode active material. Add and mix. Afterwards, the coated positive electrode active material is manufactured by drying at 150°C for more than 2 hours and then heat treating at 300°C for 4 hours under O ₂ conditions.

2. Manufacturing of all-solid-state battery

The coated positive electrode active material was used, an azirodite-based solid electrolyte (Li ₆ PS ₅ Cl, D50=1㎛) was used as a solid electrolyte, and carbon nanofibers (CNF) were used as a conductive agent. A positive electrode composition is prepared by mixing these materials in a weight ratio of positive electrode active material:conductive agent:solid electrolyte = 60:5:35.

A positive electrode was manufactured by uniformly distributing the positive electrode composition on a solid electrolyte (Li ₆ PS ₅ Cl, D50 = 3㎛) filled in a torque cell with a diameter of 13 mm. The solid electrolyte was first filled by pressing with hand pressing, and the positive electrode composition was put on the solid electrolyte layer and then plate pressed for 2 minutes at a pressure of 4 tons per unit area to form a negative electrode/solid electrolyte/positive electrode structure. A torque cell was manufactured. The cathode used lithium metal with a thickness of 40㎛, and the torque cell was fastened with a torque of 4N·m.

Example 2

A positive electrode active material and an all-solid-state battery were manufactured in the same manner as in Example 1, except that 0.25 mole part of LiPF ₆ was mixed in the production of the positive electrode active material.

Example 3

A positive electrode active material and an all-solid-state battery were manufactured in the same manner as in Example 1, except that 0.5 mole part of LiPF ₆ was mixed in the production of the positive electrode active material.

Example 4

A positive electrode active material and an all-solid-state battery were manufactured in the same manner as in Example 1, except that 0.25 mole part of Zr(OC ₃ H ₇ ) ₄ was further mixed in the production of the positive electrode active material.

Comparative Example 1

An all-solid-state battery was manufactured in the same manner as Example 1, except that Li _1.06 Ni _0.90 Co _0.07 Mn _0.03 O ₂ on which no coating layer was formed was used as the positive electrode active material.

Comparative Example 2

A positive electrode active material and an all-solid-state battery were manufactured in the same manner as Example 4, except that LiPF ₆ was not mixed in the production of the positive electrode active material. That is, the positive electrode active material of Comparative Example 2 is a lithium zirconium composite oxide prepared by mixing 0.5 mole part of LiOH and 0.25 mole part of Zr(OC ₃ H ₇ ) ₄ with 100 parts by weight of Li _1.06 Ni _0.90 Co _0.07 Mn _0.03 O ₂ and heat treatment. It is a positive electrode active material coated with .

Evaluation Example 1: Interface resistance evaluation

The impedance of the all-solid-state secondary batteries manufactured according to Examples 1 to 3 and Comparative Example 1 was measured using an impedance analyzer (Solartron 1260A Impedance/Gain-Phase Analyzer) with an amplitude of ±10 mV and a frequency of 10 mHz to 1 MHz, This was expressed as a Nyquist Plot expressed on the complex plane. The all-solid-state secondary battery manufactured according to Examples 1 to 3 and Comparative Example 1 was charged to SOC (Site of Charge) 100 at 0.1C-rate under 4.25V CCCV/CC conditions at 45°C, and a current of 0.05C rate. After the cut-off, there was a stabilization time of 1 hour, and the measurements were made in a fully charged state. The interfacial resistance of the battery is determined by the position and size of the semicircle.

Figure 3 is a Nyquist diagram of Example 1 and Comparative Example 1, and Figure 4 is a Nyquist diagram of Examples 1 to 3.

Referring to FIG. 3, it can be seen that the size of the semicircle of Example 1 is smaller than that of Comparative Example 1, resulting in lower interfacial resistance (charge-transfer resistance, R _ct ). That is, compared to the positive electrode active material of Comparative Example 1 in which no coating layer or buffer layer was formed, the positive electrode active material of Example 1 in which the LiPF ₆ lithium salt-containing coating layer was formed was confirmed to have further improved interface stability.

Referring to FIG. 4, the interfacial resistance of Examples 1 to 3 is lower than that of Comparative Example 1 of FIG. 3, and as the lithium salt coating amount increases, the interfacial resistance increases, and an appropriate interface is obtained in the coating range of 0.10 to 0.50 mole part. It can be confirmed that resistance can be displayed.

It is understood that such low interfacial resistance facilitates insertion and detachment of lithium ions during charging and discharging, and greatly improves battery capacity by maintaining constant charging and discharging efficiency (coulombic efficiency).

In addition, considering that the interfacial resistance of the examples was drastically lowered compared to Comparative Example 1, the surface of the positive electrode active material particles of the examples was uniformly coated with lithium salt, lithium-rich lithium salt, or a complex of lithium salt and lithium carbonate. I understand.

Evaluation Example 2: All-solid-state battery performance evaluation

The all-solid-state batteries manufactured in Examples 1 to 3 and Comparative Example 1 were charged to an upper limit voltage of 4.25V under constant current/constant voltage (CC/CV) conditions of 0.1C at 45°C, and then charged at a current rate of 0.05C while maintaining the constant voltage. After cut-off, initial charging and discharging was performed by discharging at 0.1C to a final voltage of 2.5V, and the initial charging capacity, initial discharging capacity, and initial charging and discharging efficiency are shown in Table 1 below.

In addition, in order to evaluate the rate characteristics, the all-solid-state batteries of Examples 1 to 3 and Comparative Example 1 were charged and discharged as above except that the C-rate was changed from 0.1C to 0.33C, and 0.1C The ratio of 0.33C discharge capacity to discharge capacity was calculated and shown in Table 1 below. Similarly, charging was performed at 0.1C and discharging was performed at 1.0C, and then the ratio of 1.0C discharge capacity to 0.1C discharge capacity was calculated and shown in Table 1 below.

Additionally, in order to evaluate the recovery capacity after high-rate discharge of 1.0C, discharge was performed at 0.1C after low-rate charging of 0.1C, and the recovery discharge capacity is shown in Table 1 below. Afterwards, charging was performed again at 0.1C, and the charging capacity after recovery is shown in Table 1 below.

In Table 1 below, each data is the arithmetic average of data measured three times each.

initial charge and discharge rate characteristics recovery capacity Initial charge capacity
(mAh/g) Initial discharge capacity
(mAh/g) Initial efficiency (%) 0.33C (%) 1.0C (%) Recovery discharge capacity
(mAh/g) Charge capacity after recovery
(mAh/g) Comparative Example 1 233.1 198.1 85.0 88.4 79.7 179.6 177.4 Example 1 225.1 205.2 91.2 93.7 86.9 202.3 202.3 Example 2 225.4 203.0 90.1 92.9 85.5 199.7 199.6 Example 3 222.2 193.9 87.3 90.3 81.1 185.3 185.7

Referring to Table 1, in the case of the all-solid-state batteries of Examples 1 to 3, both initial charge and discharge efficiency and rate characteristics were improved compared to the all-solid-state battery of Comparative Example 1, and the high-rate recovery discharge capacity and charge capacity after recovery were higher. It can be seen that it appears high. This can be said to be a characteristic resulting from improved mobility (kinetic properties) of lithium ions in the example. Additionally, these results can be viewed as an indicator of the structural stability of the coating layer.

Evaluation Example 3: Evaluation of withstand voltage characteristics

The batteries manufactured in Example 1 and Comparative Example 1 were charged to 4.25 V as in Evaluation Example 2 above, then cut-off at a current of 0.05C rate while maintaining a constant voltage of 4.25V, and charged for 1 hour. A stabilization time of . Afterwards, resistance was measured at 45°C using an impedance analyzer under equilibrium voltage. The amplitude was ±10 mV and the frequency range was 10 mHz to 1 MHz. In the same manner as above, the cell was charged again to 4.25V at a constant current of 0.1C rate, then maintained at constant voltage for 12 hours, and a stabilization time of 1 hour was allowed. Resistance measurements were repeated in the same manner at 12-hour intervals for up to 60 hours, and the interfacial resistance value was calculated from the measured Nyguist plot, and the results are shown in FIG. 5.

Referring to Figure 5, it can be seen that in the case of Comparative Example 1, the interfacial resistance continuously increases, but in the case of Example 1, the interfacial resistance does not increase over a long period of time, showing low interfacial resistance characteristics.

Evaluation Example 4: Interface resistance evaluation

The impedance of the all-solid-state secondary batteries manufactured according to Example 4 and Comparative Example 2 was measured in the same manner as Evaluation Example 1, and the impedance according to the measurement frequency is shown in FIG. 6 as a Nyquist diagram.

Referring to FIG. 6, compared to Comparative Example 2 in which a positive electrode active material coated with lithium zirconium complex oxide was applied, in Example 4 in which a positive electrode active material coated with lithium zirconium complex oxide and lithium salt was applied, the size of the semicircle was smaller, so that the interface It can be seen that the resistance was lowered, and thus the interfacial stability was further improved.

Evaluation Example 5: All-solid-state battery performance evaluation

The all-solid-state batteries manufactured in Example 4 and Comparative Example 2 were evaluated for initial charge/discharge efficiency, rate characteristics, and recovery capacity in the same manner as in Evaluation Example 2, and the results are shown in Table 2 below. In Table 2 below, each data is the arithmetic average of data measured three times each.

initial charge and discharge rate characteristics recovery capacity Initial charge capacity (mAh/g) Initial discharge capacity (mAh/g) Initial efficiency (%) 0.33C (%) 1.0C (%) Recovery discharge capacity (mAh/g) Charge capacity after recovery (mAh/g) Comparative Example 2 225.1 205.2 91.2 93.7 86.9 202.3 202.3 Example 4 226.0 208.6 92.3 94.3 87.9 206.5 206.6

Referring to Table 2 above, in the case of the all-solid-state battery of Example 4, both initial charge and discharge efficiency and rate characteristics were improved compared to the all-solid-state battery of Comparative Example 2, and the recovery discharge capacity and charge capacity after recovery were further increased. You can check it. Although the preferred embodiments have been described in detail above, the scope of the present invention is not limited thereto. In addition, various modifications and improvements made by those skilled in the art using the basic concept defined in the claims should also be understood as falling within the scope of the present invention.

100: all-solid-state battery 200: anode
201: positive electrode current collector 203: positive electrode active material layer
300: solid electrolyte layer 400: cathode
401: negative electrode current collector 403: negative electrode active material layer
400': Precipitated cathode 404: Lithium metal layer
405: cathode catalyst layer 500: elastic layer

Claims (20)

house collector, and
A positive electrode active material layer located on the current collector and containing positive electrode active material particles and a sulfide-based solid electrolyte,
It includes a coating layer located on the surface of the positive electrode active material particles and/or the surface of the positive active material layer,
An anode for an all-solid-state battery, wherein the coating layer contains a lithium salt. In paragraph 1:
The lithium salt is LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiAlO ₂ , LiAlCl ₄ , LiPO ₂ F ₂ , LiF, LiBr, LiCl, LiI, lithium bis(fluorosulfonyl)imide (LiFSI) ), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiDFOB), lithium difluorobis(oxalato) ) A positive electrode for an all-solid-state battery containing phosphate, lithium tetrafluoro(oxalato)phosphate, or a combination thereof. In paragraph 1:
The coating layer further includes lithium oxide (Li ₂ O), lithium carbonate (Li ₂ CO ₃ ), lithium hydroxide (LiOH), lithium complex oxide, or a combination thereof,
The lithium complex oxide is an oxide containing Al, B, Ca, Co, Ga, K, Mg, Na, Nb, Si, Sn, Ta, Ti, V, W, Y, Zr, or a combination thereof along with lithium. Phosphorus, anode for all-solid-state batteries. In paragraph 3,
The lithium salt is a positive electrode for an all-solid-state battery in which the lithium salt forms a composite with the lithium oxide, lithium carbonate, lithium hydroxide, lithium composite oxide, or a combination thereof. In paragraph 1:
The coating layer is a positive electrode for an all-solid-state battery further comprising a lithium-rich lithium salt represented by Li _x -PF _6-y (0<x≤6, 0≤y≤5). In paragraph 1:
The coating layer is a positive electrode for an all-solid-state battery in the form of a continuous film or island. In paragraph 1:
The positive electrode for an all-solid-state battery wherein the coating layer is included in an amount of 0.05 mole parts to 5.0 mole parts based on 100 mole parts of the positive electrode active material particles. In paragraph 1:
A positive electrode for an all-solid-state battery, wherein the positive electrode active material particles include a lithium nickel-based composite oxide represented by the following formula (1):
[Formula 1]
Li _a1 Ni _x1 M ¹ _y1 M ² _1-x1-y1 O ₂
In Formula 1, 0.9≤a1≤1.8, 0.6≤x1≤1, 0≤y1≤0.4, and M ¹ and M ² are each independently Al, B, Ba, Ca, Ce, Co, Cr, F, Fe. , Mg, Mn, Mo, Nb, P, S, Si, Sr, Ti, V, W, Zr, or a combination thereof. In paragraph 1:
The average particle diameter (D50) of the positive electrode active material is 1 ㎛ to 25 ㎛,
An anode for an all-solid-state battery wherein the sulfide-based solid electrolyte has an average particle diameter (D50) of 0.5 ㎛ to 5.0 ㎛. In paragraph 1:
The sulfide-based solid electrolyte is Li ₂ SP ₂ S ₅ , Li ₂ SP ₂ S ₅ --LiX (X is a halogen element), Li ₂ SP ₂ S ₅ -Li ₂ O, Li ₂ SP ₂ S ₅ -Li ₂ O-LiI, Li ₂ S-SiS ₂ , Li ₂ S-SiS ₂ -LiI, Li ₂ S-SiS ₂ -LiBr, Li ₂ S-SiS ₂ -LiCl, Li ₂ S-SiS ₂ -B ₂ S ₃ - LiI, Li ₂ S-SiS ₂ -P ₂ S ₅ -LiI, Li ₂ SB ₂ S ₃ , Li ₂ SP ₂ S ₅ -Z _m S _n (m, n are each integers, and Z is Ge, Zn or Ga Lim), Li ₂ S-GeS ₂ , Li ₂ S-SiS ₂ -Li ₃ PO ₄ , Li ₂ S-SiS ₂ -Li _p MO _q (p, q are integers, M is P, Si, Ge, B , Al, Ga or In), or a combination thereof. In paragraph 1:
The anode for an all-solid-state battery, wherein the sulfide-based solid electrolyte includes an azyrodite-type sulfide. In paragraph 1:
The positive electrode active material layer is based on 100% by weight of the positive active material layer,
55% to 99.9% by weight of positive electrode active material;
0.1% to 45% by weight of solid electrolyte;
0% to 5% by weight of conductive agent; and
An anode for an all-solid-state battery comprising 0% to 5% by weight of a binder. Prepare a coated positive electrode active material by mixing the positive electrode active material, lithium salt, and lithium hydroxide and heat treating,
Prepare a positive electrode composition by mixing the coated positive electrode active material and the sulfide-based solid electrolyte,
A method of producing a positive electrode for an all-solid-state battery comprising applying the positive electrode composition to a substrate and drying it. In paragraph 13:
The lithium salt is LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiAlO ₂ , LiAlCl ₄ , LiPO ₂ F ₂ , LiF, LiBr, LiCl, LiI, lithium bis(fluorosulfonyl)imide (LiFSI) ), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiDFOB), lithium difluorobis(oxalato) ) A method for producing a positive electrode for an all-solid-state battery containing phosphate, lithium tetrafluoro(oxalato)phosphate, or a combination thereof. In paragraph 13:
A method of producing a positive electrode for an all-solid-state battery, wherein 0.05 mole part to 5.0 mole part of the lithium salt and 0.05 mole part to 5.0 mole part of the lithium hydroxide are mixed with 100 parts by weight of the positive electrode active material. In paragraph 13:
A method of producing a positive electrode for an all-solid-state battery, wherein the positive electrode active material includes a lithium nickel-based composite oxide represented by the following formula (1):
[Formula 1]
Li _a1 Ni _x1 M ¹ _y1 M ² _1-x1-y1 O ₂
In Formula 1, 0.9≤a1≤1.8, 0.6≤x1≤1, 0≤y1≤0.4, and M ¹ and M ² are each independently Al, B, Ba, Ca, Ce, Co, Cr, F, Fe. , Mg, Mn, Mo, Nb, P, S, Si, Sr, Ti, V, W, Zr, or a combination thereof. In paragraph 13:
Further mixing a metal compound or metalloid compound with the positive electrode active material, the lithium salt, and the lithium hydroxide,
The metal compound or metalloid compound is a compound containing Al, B, Ca, Co, Ga, K, Mg, Na, Nb, Si, Sn, Ta, Ti, V, W, Y, Zr, or a combination thereof. Method for manufacturing an anode for a phosphorus all-solid-state battery. In paragraph 17:
A method of producing a positive electrode for an all-solid-state battery, wherein the metal compound or metalloid compound is mixed in an amount of 0.05 mole part to 3.0 mole part based on 100 parts by weight of the positive electrode active material. In paragraph 13:
A method of manufacturing a positive electrode for an all-solid-state battery, wherein the heat treatment is carried out at 100°C to 700°C for 1 hour to 12 hours. An anode according to any one of claims 1 to 12,
cathode, and
An all-solid-state battery comprising a solid electrolyte layer located between the anode and the cathode and containing a sulfide-based solid electrolyte.