KR102013827B1 - Electrode active material-solid electrolyte composite, method for manufacturing the same, and all solid state rechargeable lithium battery including the same - Google Patents

Abstract

Based on the aqueous solution process, various methods for forming a solid electrolyte coating layer on the surface of the electrode active material particles to obtain a composite.

Description

ELECTRODE ACTIVE MATERIAL-SOLID ELECTROLYTE COMPOSITE, METHOD FOR MANUFACTURING THE SAME, AND ALL SOLID STATE RECHARGEABLE LITHIUM BATTERY INCLUDING THE SAME

ELECTRODE ACTIVE MATERIAL-SOLID ELECTROLYTE COMPOSITE, METHOD FOR MANUFACTURING THE SAME, AND ALL SOLID STATE RECHARGEABLE LITHIUM BATTERY INCLUDING THE SAME

Lithium secondary batteries have been mainly applied to small fields such as mobile devices and notebook computers, but recently, the research direction has been extended to medium and large fields such as energy storage systems (ESS) and electric vehicles (EVs). have.

In the case of such a medium-large lithium secondary battery, unlike a small battery, the operating environment (for example, temperature and impact) is not only severe but also requires more batteries. Therefore, it is necessary to secure safety with excellent performance or an appropriate price. have.

Most commercially available lithium secondary batteries use organic liquid electrolytes in which lithium salts are dissolved in a flammable organic solvent, and thus pose a potential risk of ignition and explosion, including leakage.

Accordingly, using a solid electrolyte in place of the organic liquid electrolyte has been in the spotlight as an alternative to overcome the safety problem. Specifically, a battery using a solid electrolyte, that is, an all-solid-state battery may be classified into a thin film type and a thick film type. Among these, the thick-film all-solid-state battery is a so-called composite-type all-solid-state battery, and is a form in which an organic liquid electrolyte is simply replaced with a solid electrolyte in a commercially available lithium secondary battery.

In order to express the performance of such an all-solid-state battery, it is required to have excellent contact characteristics between the particles of the solid electrolyte and the active material in the all-solid-state battery to the extent that the theoretical capacity of the active material on which it is based can be fully expressed. Pharaoh is not meeting that level of demand.

In order to solve the problems discussed above, based on the aqueous solution process, various methods for forming a solid electrolyte coating layer on the surface of the electrode active material particles to obtain a composite.

In one embodiment of the present invention, the electrode active material particles; And a solid electrolyte coating layer disposed on the surface of the electrode active material particles.

However, the solid electrolyte coating layer includes a solid electrolyte, and the solid electrolyte includes an amorphous sulfide-based compound represented by Formula 1 below.

[Formula 1] Li _a M _b S _c X ¹ _d

In Formula 1, M is Sn, Mg, Ba, B, Al, Ga, In, Si, Ge, Pb, N, P, As, Sb, Bi, Ti, V, Cr, Mn, Fe, Co, Ni , Cu, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Hf, Ta, W, or La, X ¹ is F, Cl, Br, I, Se, Te, or O, 0 <a ≦ 6, 0 <b ≦ 6, 0 <c ≦ 6, and 0 ≦ d ≦ 6.

Specifically, the weight ratio of the coating layer in the composite to the electrode active material particles may be 0.1: 99.9 to 50:50.

10^-4 S/cm 이상일 수 있다. 이 경우, 상기 화학식 1에서, M은 Sn일 수 있고, 3.5<a≤4.5일 수 있고, 0.5<b≤1.5일 수 있고, 3.5<c≤4.5일 수 있다. The solid electrolyte has a lithium ion conductivity of 1.0 at 30 ° C.

It may be at least 10 ^-4 S / cm. In this case, in Chemical Formula 1, M may be Sn, 3.5 <a ≦ 4.5, 0.5 <b ≦ 1.5, and 3.5 <c ≦ 4.5.

The electrode active material particles may be a compound capable of reversible intercalation and deintercalation of lithium. In addition, the electrode active material particles, Li, Nb, Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr or a coating element containing a mixture thereof The coating layer containing a compound of, or a mixture of the compounds may be located on the surface.

Specifically, the electrode active material particles are lithium (Li), lithium metal (Li-metal) oxide, carbon-based material, oxide, silicon (Si), tin (Sn), germanium (Ge), sulfur (S), At least one selected from the group comprising derivatives thereof, and mixtures thereof.

For example, the lithium metal (Li-metal) oxide, cobalt, manganese, nickel or a combination thereof metal; And lithium; at least one of complex oxides.

In another embodiment of the present invention, preparing a first mixture comprising an electrode active material particles, a crystalline sulfide-based compound represented by Formula 1, and water (H ₂ O); It provides a method for producing an electrode active material-solid electrolyte composite comprising a; and heat-treating the first mixture.

However, in the step of heat-treating the first mixture; water in the first mixture is removed, and the crystalline sulfide compound is converted to amorphous and coated on the surface of the electrode active material particles.

[Formula 1] Li _a M _b S _c X ¹ _d

In Formula 1, M is Sn, Mg, Ba, B, Al, Ga, In, Si, Ge, Pb, N, P, As, Sb, Bi, Ti, V, Cr, Mn, Fe, Co, Ni , Cu, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Hf, Ta, W, or La, X ¹ is F, Cl, Br, I, Se, Te, or O, 0 <a ≦ 6, 0 <b ≦ 6, 0 <c ≦ 6, and 0 ≦ d ≦ 6.

Specifically, preparing the first mixture; may include mixing the electrode active material particles, the crystalline sulfide compound, and the water at the same time.

Independently, preparing the first mixture; may include mixing the crystalline sulfide-based compound and the water and then adding and mixing the electrode active material particles.

In preparing the first mixture, regardless of the mixing order of the components, the total amount of the electrode active material particles and the crystalline sulfide compound may be 300 to 600 mg per 1 mL of the solvent. In addition, the weight ratio of the crystalline sulfide-based compound: electrode active material particles in the first mixture may be mixed to be 0.1: 99.9 to 50:50.

The heat treatment of the first mixture may be performed for 6 to 10 hours in a temperature range of 200 to 450 ° C. or less, for example, in a temperature range of 280 to 320 ° C. or less. At this time, the pressure may be in the range of 0 to 760 torr.

After preparing the first mixture, the first mixture may be filtered to further remove impurities in the first mixture.

Before preparing the first mixture, a crystalline sulfide compound represented by Chemical Formula 1 may be further included.

Specifically, the step of preparing the crystalline sulfide-based compound represented by the formula (1), so as to satisfy the stoichiometric molar ratio of the formula (1), a lithium raw material; The M raw material; And dry mixing the S raw material; And heat treating the dry mixture.

More specifically, the step of heat-treating the dry mixture may be performed for 5 to 30 hours in a temperature range of 400 to 700 ℃ and vacuum conditions.

Lithium or sodium raw material to satisfy the stoichiometric molar ratio of Chemical Formula 1 'M raw material; And dry mixing the S raw material; by adding the X ¹ raw material.

On the other hand, in another embodiment of the present invention, the electrode active material particles; And a solid electrolyte coating layer positioned on a surface of the electrode active material particles.

However, the solid electrolyte coating layer includes a solid electrolyte, and the solid electrolyte includes a crystalline compound represented by any one of the following Chemical Formulas 2 to 4.

[Formula 2] _x (LiX ² _e H _f )- _(1-x) (Li _a M _b S _c X ¹ _d )

[Formula 3] _x (Li _e X ³ _f O _g )- _(1-x) (Li _a M _b S _c X ¹ _d )

[Formula 4] _x (LiX ⁴ _e H _f )- _(1-x) (Li _a M _b S _c X ¹ _d )

In Formulas 2 to 4, each independently of each other, M is Sn, Mg, Ba, B, Al, Ga, In, Si, Ge, Pb, N, P, As, Sb, Bi, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Hf, Ta, W, or La, X ¹ is F, Cl, Br, I, Se , Te, or O, 0 <a ≦ 6, 0 <b ≦ 6, 0 <c ≦ 6, 0 ≦ d ≦ 6, and x is 0.1 to 0.5.

In Formula 2, X ² is F, Cl, Br, or I, 0 <e ≦ 6, and 0 ≦ f ≦ 6.

In Formula 3, X ³ is Mg, Ba, P, As, Sb, B, S, Se, or Mg, 0 <e ≦ 6, 0 <f ≦ 6, and 0 <g ≦ 6.

In Formula 4, X ⁴ is B, Mg, or N, 0 <e ≦ 4, and 0 <f ≦ 6.

Specifically, the solid electrolyte, at least one or more of the range 2θ is 16.5 to 17 °, the range 17 to 18 °, the range 18.5 to 19 °, the range 25 to 26 °, and the range 26 to 26.5 °. In, XRD peak by Cu Kα X-rays (X-rα) may appear. The solid electrolyte at this time, the crystal structure may be orthorhombic (orthorhombic).

In Chemical Formulas 2 to 4, each independently, x may be 0.3 to 0.5.

10^-4 S/cm 이상일 수 있다.In addition, the solid electrolyte has a lithium ion conductivity of 1.0 at 30 ° C.

It may be at least 10 ^-4 S / cm.

In another embodiment of the present invention, preparing a second mixture comprising an ion conductive additive, an electrode active material particles, a crystalline sulfide compound represented by Formula 1, and water (H ₂ O); And heat-treating the second mixture.

However, in the step of heat-treating the second mixture; water in the second mixture is removed, and the ion conductive additive and the crystalline sulfide compound are coated on the surface of the electrode active material particles.

[Formula 1] Li _a M _b S _c X ¹ _d

In Formula 1, M is Sn, Mg, Ba, B, Al, Ga, In, Si, Ge, Pb, N, P, As, Sb, Bi, Ti, V, Cr, Mn, Fe, Co, Ni , Cu, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Hf, Ta, W, or La, X ¹ is F, Cl, Br, I, Se, Te, or O, 0 <a ≦ 6, 0 <b ≦ 6, 0 <c ≦ 6, and 0 ≦ d ≦ 6.

Specifically, preparing the second mixture; may include mixing the ion conductive additive, the electrode active material particles, the crystalline sulfide compound, and the water at the same time.

Independently, preparing the second mixture; may include mixing the ion conductive additive, the crystalline sulfide compound, and the water, and then adding and mixing the electrode active material particles.

In preparing the second mixture, regardless of the preparation method, the total amount of the electrode active material particles and the crystalline sulfide compound may be 300 to 600 mg per 1 mL of the solvent.

In addition, the step of heat-treating the second mixture; may be performed at a pressure in the range of 0 to 760 torr for 6 to 10 hours at a temperature range of 180 to 220 ℃.

The ion conductive additive may be represented by any one of the following Chemical Formulas 5 to 7.

[Formula 5] LiX ²

[Formula 6] Li _a X ³ _b O _c

[Formula 7] LiX ⁴ _a H _b

X ² in Formula 5 is F, Cl, Br, or I. In Formula 6, X ³ is Mg, Ba, P, As, Sb, B, S, Se, or Mg, 0 <a ≦ 6, 0 <b ≦ 6, and 0 <c ≦ 6. In Formula 7, X ⁴ is B, Mg, or N, 0 <a ≦ 4, and 0 <b ≦ 6.

In another embodiment of the present invention, an anode layer; Solid electrolyte layer; And a negative electrode layer, wherein the above-described composite is included in at least one electrode layer of the positive electrode layer and the negative electrode layer.

Composites according to an embodiment of the present invention can be excellently expressed in ionic conductivity and contact properties with the active material.

The property may be due to being prepared in an aqueous solution process.

Figure 1 shows a process of coating a solid electrolyte on the surface of the electrode active material particles in an aqueous solution process.
FIG. 2A shows the XRD pattern according to the heat treatment temperature of the solid electrolyte particle 1 (aqueous solution step).
Figure 2b shows the XRD pattern for each heat treatment temperature of the solid electrolyte particles 1 (methanol process).
FIG. 2C shows the XRD pattern according to the LiI: Li ₄ SnS ₄ molar ratio and the heat treatment temperature of the solid electrolyte particle 2 (aqueous solution step).
2D shows the LiI: Li ₄ SnS ₄ molar ratio and XRD pattern of solid electrolyte particle 2 (methanol process).
3A and 3B show the heat treatment temperature and the ionic conductivity by molar ratio of LiI: Li ₄ SnS ₄ in relation to the solid electrolyte particles 1 and 2 (aqueous solution process).
4A is FESEM and EDXS of surface coated active material particles (aqueous solution process).
4B is a FESEM for the cross section of surface coated active material particles (aqueous solution process).
FIG. 5A shows the rate-specific characteristics of the cell to which each is applied, with respect to simple mixtures of the active material and the solid electrolyte and surface coated active material particles (aqueous solution process).
FIG. 5B shows the discharge characteristics for each C-rate of the battery to which each of the batteries is applied, with respect to simple mixtures of the active material and the solid electrolyte and surface-coated active material particles (aqueous solution process).
5C shows the life characteristics of a battery to which the surface-coated active material particles (aqueous solution process) are applied.

Hereinafter, embodiments of the present invention will be described in detail. However, this is presented as an example, by which the present invention is not limited and the present invention is defined only by the scope of the claims to be described later.

In general, an all-solid-state battery includes two electrode layers and a solid electrolyte layer positioned therebetween. Specifically, the solid electrolyte layer includes a solid electrolyte, and at least one electrode layer also includes a solid electrolyte, thereby ensuring ion conductivity by the solid electrolyte.

Meanwhile, the electrode layer includes an electrode active material together with a solid electrolyte, and the contact property between the solid electrolyte and the electrode active material particles in the electrode layer affects the performance of the all-solid-state battery. Solid electrolytes known to date have poor contact characteristics with electrode active material particles, and thus, it is difficult to fully express the theoretical capacity of the electrode active material in the electrode layer.

Embodiments of the present invention present a composite in which the solid electrolyte is coated on the surface of the electrode active material particles.

In particular, there are two kinds of solid electrolytes applicable to the composite. The two solid electrolytes basically have excellent ion conductivity as an ion transfer medium, and have excellent ductility to improve contact characteristics with electrode active material particles.

Hereinafter, to distinguish the two solid electrolytes, they will be referred to as solid electrolyte 1 and solid electrolyte 2 arbitrarily. In addition, the electrode active material particles coated with the solid electrolyte 1 will be referred to as a composite 2 and the electrode active material particles coated with the solid electrolyte 2 will be referred to as a composite 2.

Composite 1 and preparation method thereof

In one embodiment of the present invention, the electrode active material particles; And a solid electrolyte coating layer disposed on the surface of the electrode active material particles. However, the solid electrolyte coating layer includes a solid electrolyte, and the solid electrolyte includes an amorphous sulfide-based compound represented by Formula 1 below.

In another embodiment of the present invention, preparing a first mixture comprising an electrode active material particles, a crystalline sulfide-based compound represented by Formula 1, and water (H ₂ O); It provides a method for producing an electrode active material-solid electrolyte composite comprising a; and heat-treating the first mixture. However, in the step of heat-treating the first mixture; water in the first mixture is removed, and the crystalline sulfide compound is converted to amorphous and coated on the surface of the electrode active material particles.

[Formula 1] Li _a M _b S _c X ¹ _d

In Formula 1, M is Sn, Mg, Ba, B, Al, Ga, In, Si, Ge, Pb, N, P, As, Sb, Bi, Ti, V, Cr, Mn, Fe, Co, Ni , Cu, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Hf, Ta, W, or La, X ¹ is F, Cl, Br, I, Se, Te, or O, 0 <a ≦ 6, 0 <b ≦ 6, 0 <c ≦ 6, and 0 ≦ d ≦ 6.

In general, even if a substance is represented by the same chemical formula, its chemical properties may be expressed differently depending on the crystal structure of the substance.

For example, in the case of a solid electrolyte represented by the same chemical formula, it is known that ionic conductivity is higher and ductility is improved when it is amorphous than when it is crystalline.

In this regard, the solid electrolyte 1 is represented by Formula 1, and is amorphous. Accordingly, it has the same chemical formula and has higher ionic conductivity than crystalline, and is advantageous for being in intimate contact with the electrode active material based on improved ductility.

In addition, the solid electrolyte 1 may be amorphous, because it is manufactured through a process using water as a solvent (hereinafter, referred to as an "aqueous solution process") according to one embodiment of the present invention. If an organic solvent such as methanol is used instead of water (hereinafter referred to as an "organic solvent process"), crystalline particles containing sulfide-based compounds represented by the same chemical formula but crystalline can be obtained.

Hereinafter, the composite 1 according to the embodiments of the present invention and a manufacturing method thereof will be described in detail.

Raw Material of Solid Electrolyte 1 (crystalline Sulfide Compound)

Specifically, the raw material for producing the solid electrolyte 1 is a crystalline sulfide compound represented by the same chemical formula.

The crystalline sulfide compound that is the raw material may be prepared by a dry process. In this regard, before the step of preparing the first aqueous solution, the step of preparing a crystalline sulfide-based compound represented by Formula 1; may further comprise a.

Specifically, the step of preparing the crystalline sulfide-based compound represented by the formula (1), so as to satisfy the stoichiometric molar ratio of the formula (1), a lithium raw material; The M raw material; And dry mixing the S raw material; and heat treating the dry mixture.

More specifically, to satisfy the stoichiometric molar ratio of Chemical Formula 1, lithium or sodium raw material '' M raw material; And dry mixing the S raw material; in the dry mixing process, by adding the X ¹ raw material.

In this regard, the step of heat-treating the dry mixture may be carried out under vacuum conditions in a temperature range of 400 to 700 ℃, specifically 400 to 650 ℃ for 5 to 30 hours, specifically 5 to 24 hours. have. At such time, temperature, and atmospheric conditions, the crystalline sulfide compound represented by Chemical Formula 1 may be formed.

Electrode active material particles

The electrode active material particles may be lithium cobalt oxide used in Examples described later. However, the present invention is not limited thereto, and lithium (Li), lithium metal (Li-metal) oxides, carbon-based materials, oxides, silicon (Si), tin (Sn), germanium (Ge), sulfur (S), and the like It may include at least one electrode active material selected from the group comprising derivatives, and mixtures thereof.

Specifically, the electrode active material may be a positive electrode active material, and as the positive electrode active material, a compound capable of reversible intercalation and deintercalation of lithium (lithiated intercalation compound) may be used.

For example, the lithium metal oxide (Li-metal) oxide is a compound capable of reversible intercalation and deintercalation of lithium, a metal which is cobalt, manganese, nickel or a combination thereof; And one or more of composite oxides of lithium can be used.

Specific examples thereof may be a compound represented by any one of the following formulas. Li _a A _1-b R _b D ₂ (wherein 0.90 ≦ a ≦ 2.1, specifically 0.90 ≦ a ≦ 1.8 and 0 ≦ b ≦ 0.5); Li _a E _1-b R _b O _2-c D _c (wherein 0.90 ≦ a ≦ 2.1, specifically 0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.5, and 0 ≦ c ≦ 0.05); LiE _2-b R _b 0 _4-c D _c (wherein 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05); Li _a Ni _1-bc Co _b R _c D ₂ (wherein 0.90 ≦ a ≦ 2.1, specifically 0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05); Li _a Ni _1-bc Co _b R _c O _2-α Z _α (wherein 0.90 ≦ a ≦ 2.1, specifically 0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05 and 0 <α <2); Li _a Ni _1-bc Co _b R _c O _2-α Z _α (wherein 0.90 ≦ a ≦ 2.1, specifically 0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05 and 0 <α <2); Li _a Ni _1-bc Mn _b R _c D _α (wherein 0.90 ≦ a ≦ 2.1, specifically 0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, and 0 <α ≦ 2); Li _a Ni _1-bc Mn _b R _c O _2-α Z _α (wherein 0.90 ≦ a ≦ 2.1, specifically 0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05 and 0 <α <2); Li _a Ni _1-bc Mn _b R _c O _2-α Z _α (wherein 0.90 ≦ a ≦ 2.1, specifically 0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05 and 0 <α <2); Li _a Ni _b E _c G _d O ₂ (wherein 0.90 ≦ a ≦ 2.1, specifically 0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.9, 0 ≦ c ≦ 0.5, and 0.001 ≦ d ≦ 0.1); Li _a Ni _b Co _c Mn _d GeO ₂ (wherein 0.90 ≤ a ≤ 2.1, specifically 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5 and 0.001 ≤ e ≤ 0.1); Li _a NiG _b O ₂ (wherein 0.90 ≦ a ≦ 2.1, specifically 0.90 ≦ a ≦ 1.8 and 0.001 ≦ b ≦ 0.1); Li _a CoG _b O ₂ (wherein 0.90 ≦ a ≦ 2.1, specifically 0.90 ≦ a ≦ 1.8 and 0.001 ≦ b ≦ 0.1); Li _a MnG _b O ₂ (wherein 0.90 ≦ a ≦ 2.1, specifically 0.90 ≦ a ≦ 1.8 and 0.001 ≦ b ≦ 0.1); Li _a Mn ₂ G _b O ₄ (wherein 0.90 ≦ a ≦ 2.1, specifically 0.90 ≦ a ≦ 1.8 and 0.001 ≦ b ≦ 0.1); QO ₂ ; QS ₂ ; LiQS ₂ ; V ₂ O ₅ ; LiV ₂ O ₅ ; LiTO ₂ ; LiNiVO ₄ ; Li _(3-f) J ₂ (PO ₄ ) ₃ (0 ≦ f ≦ 2); Li _(3-f) Fe ₂ (PO ₄ ) ₃ (0 ≦ f ≦ 2); And LiFePO ₄ .

In each of the formulas above, A is Ni, Co, Mn, or a combination thereof; R is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements or combinations thereof; D is O, F, S, P or a combination thereof; E is Co, Mn or a combination thereof; Z is F, S, P or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V or a combination thereof; Q is Ti, Mo, Mn or a combination thereof; T is Cr, V, Fe, Sc, Y or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu or a combination thereof.

On the other hand, as a representative example of the carbon-based material may be used crystalline carbon, amorphous carbon or a combination thereof. Examples of the crystalline carbon include graphite such as amorphous, plate, flake, spherical or fibrous natural graphite or artificial graphite. Examples of the amorphous carbon include soft carbon (soft carbon) Or hard carbon, mesophase pitch carbide, calcined coke, or the like.

Of course, one having a coating layer on the surface of the compound (ie, the electrode active material) may be used, or a compound having the compound and the coating layer may be used in combination. The coating layer may include an oxide of a coating element, a hydroxide of a coating element, an oxyhydroxide of a coating element, an oxycarbonate of a coating element, or a hydroxycarbonate of a coating element. The compounds constituting these coating layers may be amorphous or crystalline. Li, Nb, Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr or a mixture thereof may be used as the coating element. In addition, the coating layer may be formed in the form of a compound of the coating elements, a mixture of the compound. For example, the compound of the coating elements may be one of O, C, H, S, Se, F, Cl, Br, I, and combinations thereof, and a compound of the coating element. The coating layer forming process may use any coating method as long as it does not adversely affect the physical properties of the positive electrode active material by using such elements in the compound (for example, spray coating, dipping, etc.). Details that will be well understood by those in the field will be omitted.

First Mixture Manufacturing Process

The first mixture is prepared by mixing the crystalline sulfide compound which is the production raw material, the electrode active material particles, and the water.

Specifically, preparing the first mixture; may include mixing the electrode active material particles, the crystalline sulfide compound, and the water at the same time.

Independently, preparing the first mixture; may include mixing the crystalline sulfide-based compound and the water and then adding and mixing the electrode active material particles.

In the evaluation examples described below, the composite 1 obtained in the case of simultaneous mixing of the electrolyte, the active material, and water (Coated 1), and in the case of adding the active material after the electrolyte and water mixing (Coated 2) were evaluated. According to the evaluation result, it can be confirmed that excellent battery performance of both (Coated 1 and 2) is secured, and the battery performance of the latter (Coated 2) is further improved.

In the preparation of the first mixture, regardless of the mixing order of the constituents, it can be mixed so that the total amount of the electrode active material particles and the crystalline sulfide-based compound is 300 to 600 mg per 1 mL of the solvent. This is merely an example, and it is sufficient that the crystalline sulfide compound in the first mixture is completely dissolved.

In addition, the weight ratio of the crystalline sulfide-based compound: electrode active material particles in the first mixture may be mixed to be 0.1: 99.9 to 50:50. When satisfying this, in the finally obtained composite 1, the weight ratio of the coating layer: electrode active material particles may also be in the range of 0.1: 99.9 to 50:50. When the weight ratio range is satisfied, the thickness of the coating layer may be formed on the surface of the electrode active material particles having a diameter of 5 to 30 μm to 0.05 to 0.5 μm, and the coating layer may provide an improved ion transfer path between the electrode active material particles. Can be.

After preparing the first mixture, the first mixture may be filtered to further remove impurities in the first mixture. Thus, a higher purity final material can be obtained.

First Mixture Heat Treatment Process

As mentioned above, during the heat treatment of the first mixture, water in the first mixture is removed, and the crystalline compound which is the raw material for preparation is converted to amorphous and coated on the surface of the electrode compound particles.

In this regard, the heat treatment of the first mixture may be performed at a temperature range of 200 ° C. to 450 ° C., specifically, at a temperature range of 280 to 450 ° C. Specifically, in the temperature range of 280 ° C or more and 320 ° C or less, the crystalline compound which is the raw material for manufacture may be almost converted to amorphous. However, in the temperature range of more than 320, specifically 450, the crystallinity of the manufacturing raw material may be restored.

However, even when heat-treated in the temperature range of 280 or more and 450 ° C. or less using the same raw material, the organic solvent process does not convert to amorphous and still crystalline particles can be obtained. This fact is confirmed by the evaluation example mentioned later.

In addition, the heat treatment of the first mixture may be performed at a pressure in the range of 0 to 760 torr, for example, 0 to 0.1 torr, for 6 to 10 hours.

Final Substance (Compound 1)

According to the heat treatment of the first mixture, Composite 1 according to one embodiment of the present invention is obtained.

The solid electrolyte 1 included in the coating layer of the composite 1 may include a sulfide-based compound having M in the formula 1 of Sn, 3.5 <a ≦ 4.5, 0.5 <b ≦ 1.5, and 3.5 <c ≦ 4.5. have. Based on the chemical formula in this case, it can have a better ion conductivity.

10^-4 S/cm 이상으로, 우수한 이온 전도성을 가질 수 있다.Specifically, the solid electrolyte 1 has a lithium ion conductivity of 1.0 at 30 ° C.

At 10 ⁻⁴ S / cm or more, it may have excellent ion conductivity.

In addition, since the solid electrolyte 1 is amorphous, the ductility of the solid electrolyte 1 may be improved than that of the crystalline particles of the raw material, and the contact characteristics with the electrode active material may be improved.

As described above, in the composite 1, the weight ratio of the coating layer: the electrode active material particles may also be in the range of 0.1: 99.9 to 50:50. When the weight ratio range is satisfied, the thickness of the coating layer may be formed on the surface of the electrode active material particles having a diameter of 5 to 30 μm to 0.05 to 0.5 μm, and the coating layer may provide an improved ion transfer path between the electrode active material particles. Can be.

Composite 2 and its manufacturing method

In another embodiment of the present invention, the electrode active material particles; And a solid electrolyte coating layer positioned on a surface of the electrode active material particles. However, the solid electrolyte coating layer includes a solid electrolyte, and the solid electrolyte includes a crystalline compound represented by any one of the following Chemical Formulas 2 to 4.

[Formula 1] Li _a M _b S _c X ¹ _d

[Formula 2] _x (LiX ² _a H _b )- _(1-x) (Li _a M _b S _c X ¹ _d )

[Formula 3] _x (Li _a X ³ _b O _c )- _(1-x) (Li _a M _b S _c X ¹ _d )

[Formula 4] _x (LiX ⁵ _a H _b )- _(1-x) (Li _a M _b S _c X ¹ _d )

In Formula 1, M is Sn, Mg, Ba, B, Al, Ga, In, Si, Ge, Pb, N, P, As, Sb, Bi, Ti, V, Cr, Mn, Fe, Co, Ni , Cu, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Hf, Ta, W, or La, X ¹ is F, Cl, Br, I, Se, Te, or O, 0 <a ≦ 6, 0 <b ≦ 6, 0 <c ≦ 6, and 0 ≦ d ≦ 6.

In Formulas 2 to 4, each independently of each other, M is Sn, Mg, Ba, B, Al, Ga, In, Si, Ge, Pb, N, P, As, Sb, Bi, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Hf, Ta, W, or La, X ¹ is F, Cl, Br, I, Se , Te, or O, 0 <a ≦ 6, 0 <b ≦ 6, 0 <c ≦ 6, 0 ≦ d ≦ 6, and x is 0.1 to 0.5.

In Formula 2, X ² is F, Cl, Br, or I. In Formula 3, X ³ is Mg, Ba, P, As, Sb, B, S, Se, or Mg, 0 <a ≦ 6, 0 <b ≦ 6, and 0 <c ≦ 6. In Formula 4, X ⁴ is B, Mg, or N, 0 <a ≦ 4, and 0 <b ≦ 6.

In another embodiment of the present invention, preparing a second mixture comprising an ion conductive additive, an electrode active material particles, a crystalline sulfide compound represented by Formula 1, and water (H ₂ O); And heat-treating the second mixture. However, in the step of heat-treating the second mixture; water in the second mixture is removed, and the ion conductive additive and the crystalline sulfide compound are coated on the surface of the electrode active material particles.

Solid electrolyte 2 included in the coating layer of the composite 2, using the same raw material as the above-described solid electrolyte 1, using an ion conductive additive further, is prepared by an aqueous solution process. Accordingly, the compound included in the solid electrolyte 2 is represented by any one of Formulas 2 to 4.

However, since the solid electrolyte 2 has a crystalline structure unlike the solid electrolyte 1, the ion conductive additive plays a role of lowering the crystallization temperature in the manufacturing process.

If an organic solvent such as methanol is used instead of water (hereinafter referred to as "organic solvent process"), amorphous particles containing sulfide-based compounds represented by the same chemical formula can be obtained.

Of course, it is as described above that the material represented by the same chemical formula is higher in ion conductivity, ductility, etc. when amorphous than when crystalline. However, compared with water, organic solvents, such as methanol, are not easy to handle, are harmful substances to which the discharge | emission is restricted, and there exists a problem of being expensive.

Since the solid electrolyte 2 has a crystalline structure, the ionic conductivity, ductility, etc. may be slightly reduced than in the amorphous case, but the reduction of the ionic conductivity may be minimized by additionally using lithium compound particles having lithium ion conductivity. It can take advantage of the process of using water, which is easy to handle, safe and inexpensive solvent.

Hereinafter, the composite 2 according to the embodiments of the present invention and a manufacturing method thereof will be described in detail. However, the content not described below is the same as the description of the complex 1.

Manufacturing raw materials

Specifically, the production raw material of the solid electrolyte 2 may be the same crystalline particles as the production raw material of the solid electrolyte 1. Thus, redundant descriptions are omitted.

Meanwhile, the ion conductive additive may include a lithium compound represented by any one of the following Chemical Formulas 5 to 7.

[Formula 5] LiX ²

[Formula 6] Li _a X ³ _b O _c

[Formula 7] LiX ⁴ _a H _b

In Formula 5, X ² is F, Cl, Br, or I,

In Chemical Formula 6, X ³ is Mg, Ba, P, As, Sb, B, S, Se, or Mg, 0 <a ≦ 6, 0 <b ≦ 6, 0 <c ≦ 6,

In Formula 7, X ⁴ is B, Mg, or N, 0 <a ≦ 4, and 0 <b ≦ 6.

Second Mixture Manufacturing Process

In addition to the crystalline sulfide type compound which is the said manufacturing raw material, the said electrode active material particle, and the said water, the said ion conductive additive is mixed, and the said 2nd mixture is manufactured. That is, the second mixture further includes the ion conductive additive than the first mixture.

In the second aqueous solution, the molar ratio of the crystalline sulfide compound and the ion conductive addition may be determined according to the composition of the desired solid electrolyte 2. Specifically, the molar ratio of the ion conductive additive: the crystalline sulfide compound in the second aqueous solution may be 1: 9 to 5: 5.

If the ion conductive additive is included in excess of the above range, the crystallinity of the finally obtained solid electrolyte 2 is increased, and the crystal phase of the additive is separately present, so that ion conductivity may be lowered and battery performance may be deteriorated. . On the other hand, when a small amount of the ion conductive additive is included in less than the above range, the effect of improving the ion conductivity may be minimally expressed.

Specifically, when the molar ratio is 3: 7 to 4: 6, and when the heat treatment temperature is properly controlled in the heat treatment process described later, ionic conductivity similar to that of the solid electrolyte 1 may be expressed.

Second mixture heat treatment process

As mentioned above, in the heat treatment process of the second mixture, water in the second aqueous solution is removed, and a crystalline compound including the compound represented by any one of Formulas 2 to 4 is coated on the surface of the electrode active material particles. Can be.

At this time, the ion conductive additive in the second mixture serves to lower the crystallization temperature, the heat treatment temperature of the second mixture may be lower than the heat treatment temperature of the first mixture.

Specifically, the heat treatment of the second mixture may be performed at a temperature range of 180 to 220 ° C. This range is the range which can obtain the solid electrolyte 2 with the lowest crystallinity as possible.

In addition, the heat treatment of the second mixture may be performed at a pressure ranging from 6 to 10 hours, 0 to 760 torr, for example, 0 to 0.1 torr.

Final material (complex 2)

Specifically, in the final composite 2 obtained, the solid electrolyte 2 included in the coating layer has a 2θ of 16.5 to 17 °, a range of 17 to 18 °, a range of 18.5 to 19 °, a range of 25 to 26 °, and 26 In at least one or more of the range of 26.5 ° to, XRD peak by Cu Kα X-ray (X-rα) may appear. This may mean that the crystal structure of the solid electrolyte 2 is orthorhombic.

In addition, in Chemical Formulas 2 to 4, each independently, M may be a Sn, 3.5 <a ≦ 4.5, 0.5 <b ≦ 1.5, and 3.5 <c ≦ 4.5, and may include a sulfide-based compound. Based on the chemical formula in this case, it can have a better ion conductivity.

In addition, in Chemical Formulas 2 to 4, each independently, x may be 0.1 to 0.5, specifically, 0.3 to 0.5.

10^-4 S/cm 이상으로, 우수한 이온 전도성을 가질 수 있다.The solid electrolyte 2 has a lithium ion conductivity of 1.0 at 30 ° C.

At 10 ⁻⁴ S / cm or more, it may have excellent ion conductivity.

All-solid-state battery

In another embodiment of the present invention, an anode layer; Solid electrolyte layer; And a cathode layer; And an electrode layer of at least one of the positive electrode layer and the negative electrode layer comprises the composite 1 or the composite 2.

Specifically, the all-solid-state battery includes the complex 1 or the complex 2 having the excellent characteristics in the electrode layer, so that unlike the general all-solid-state battery, the all-solid-state battery does not include a separate solid electrolyte (the following third solid electrolyte). In addition, the performance of the all-solid-state battery is improved, and the improved performance can be maintained stably.

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

Example 1 (Aqueous solution process)

(1) Preparation of LSS for Characteristic Evaluation of Solid Electrolyte 1

First, crystalline Li ₄ SnS ₄ particles were prepared. Specifically, Li ₂ S (purity 99.9%, alfa-aesar), Sn (purity 99.8%, alfa-aesar), and S (purity 99.5%, alfa-aesar) are selected from Li _4. After mixing according to the stoichiometric molar ratio of SnS ₄ and heat-treating at 650 ° C. for 24 hours under vacuum conditions, crystalline Li ₄ SnS ₄ particles could be obtained. This is represented by "SS-LSS" in the drawing of the evaluation example mentioned later.

Thereafter, the crystalline Li ₄ SnS ₄ particles were dissolved in water to prepare a first solution. At this time, the total amount of the first solution 100% by weight, the crystalline Li ₄ SnS ₄ particles are included 9.1% by weight, the water was to be included as a balance.

The first solution was filtered to remove the impurities by solid / liquid separation, and the filtrate was heat-treated under vacuum conditions for 6 hours. (However, the temperature conditions at this time depend on the evaluation example mentioned later.) As a result, the powder containing the solid electrolyte particle 1 was finally obtained.

The said solid electrolyte particle 1 is represented by the combination of "LSS" and "heat processing temperature" in the drawing of the evaluation example mentioned later. For example, when heat treated at 200 ° C., it is indicated as LSS200.

(2) Preparation of xLiI- (1-x) LSS for Evaluation of Solid Electrolyte 2 Properties

In the same process as the solid electrolyte particle 1, crystalline Li ₄ SnS ₄ particles were prepared. Subsequently, the first solution was prepared by dissolving the crystalline Li ₄ SnS ₄ particles and LiI, a kind of ion conductive additive, in water. In this first solution, the molar ratio of the crystalline Li ₄ SnS ₄ particles and the LiI depends on the evaluation example described later.

Thereafter, in the same process as above, the first solution is filtered to remove impurities by solid / liquid separation, and the filtrate is heat-treated at a specific temperature in a vacuum for a predetermined time to finally obtain a powder containing solid electrolyte particles 2. Could.

The said solid electrolyte particle 2 is represented by the combination of "xLiI- (1-x) LSS" and "heat treatment temperature" in the drawing of the evaluation example mentioned later. For example, when the molar ratio of LiI: LSS is 0.2: 0.8 and heat-treated at 200 ° C, it is represented as 0.2 LiI-0.8LSS200.

(2) Preparation of pellets for the evaluation of solid electrolyte 1 and 2 properties

The solid electrolyte particles 1 and the solid electrolyte particles 2 were each molded into a form suitable for evaluation.

Specifically, 120 mg of the solid electrolyte particles 1 or 2 were put in a cylindrical frame of f 13 mm, respectively, and pressed in a pressure of 370 Mpa to form a pellet.

(3) Surface coating of electrode active material particles using solid electrolyte particles

According to FIG. 1, the surface of the electrode active material was coated using solid electrolyte particles 1 and 2, respectively.

1) Electrode active material particle manufacturing process (LiNbO ₃ coated LCO particles)

First, crystalline LiCoO ₂ (hereinafter LCO) powder was prepared. On the surface of the LCO particles, a lithium-metal oxide (LiNbO ₃ ) coating layer was formed before forming a solid electrolyte (Li ₄ SnS ₄ or _x LiI- _(1-x) Li ₄ SnS ₄ ) coating layer.

Specifically, lithium ethoxide (Li (OC ₂ H ₅ )) and niobium ethoxide (Nb (OC ₂ H ₅ ) ₅ ) in a molar ratio of 1: 1 (Li (OC ₂ H ₅ ): (Nb (OC ₂ H ₅ ) ₅ ) This mixture was dissolved in ethanol (C ₂ H ₅ OH) to prepare a coating solution, and the content of the mixture in the total amount of the coating solution was 10% by weight.

For the LCO powder, the coating solution was mixed. At this time, the weight ratio of the coating liquid: LCO powder was 99.7: 0.3. Thereafter, ethanol was removed by evaporation under heat treatment at 60 ° C., and then heat-treated for 1 hour in an air atmosphere at 400 ° C. to finally obtain LiNbO ₃ coated LCO particles.

2) coating process

On the surface of the electrode active material particles, a solid electrolyte 1 or 2 was coated by an aqueous solution process.

2-1) Simultaneous Mixing of Electrolyte, Active Material, and Water (Coated 1)

The first crystalline Li ₄ SnS ₄ particles, the electrode active material particles, and water were simultaneously mixed to prepare a first mixture. Independently of this, the crystalline Li ₄ SnS ₄ particles, the LiI, the electrode active material particles, and water were simultaneously mixed to prepare a second mixture.

In the preparation of the first mixture and the second mixture, when the total of the solid components (ie, the solid electrolyte particles and the electrode active material particles) was 300 mg, the solvent, water, was 1 mL.

The mixture was filtered to remove impurities by solid / liquid separation, and the filtrate was heat-treated for a certain time at a specific temperature under vacuum conditions. (The temperature and time conditions at this time are based on the evaluation example mentioned later.)

2-2) Add Active Material after Mixing Electrolyte and Water (Coated 2)

After mixing the crystalline Li ₄ SnS ₄ particles and water first, the electrode active material particles were added to prepare a first mixture. Independently, after mixing the crystalline Li ₄ SnS ₄ particles, the LiI, and water, the electrode active material particles were added to prepare a second mixture.

Specifically, when preparing the first mixture and the second mixture, the crystalline Li ₄ SnS ₄ particles in the solution before the addition of the electrode active material was dispersed uniformly. The electrolyte solution was filtered to solidify / liquid to remove impurities.

Thereafter, the electrode active material particles were added to the filtered electrolyte solution. When the total of the solid components (ie, the solid electrolyte particles and the electrode active material particles) became 300 mg, water as a solvent was 1 mL.

Then, the mixed solution was heat-treated at a specific temperature for a certain time under vacuum conditions. (The temperature and time conditions at this time are based on the evaluation example mentioned later.)

3) As a result, the surface-coated active material particles could be obtained.

(4) anode layer manufacturing

 f 13 mm into a cylindrical mold, 15 mg of the surface-coated active material particles were pressed in a pressure of 370 Mpa to form a pellet.

(5) all-solid-state battery manufacturing

The all-solid-state battery was produced so that the laminated structure of FIG. 1 might be satisfied.

First, 120 mg of LGPS solid electrolyte powder and 30 mg of LPS solid electrolyte powder were sequentially stacked in a cylindrical frame of f 13 mm, and formed into pellets by applying a pressure of 74 MPa. This gave a solid electrolyte film in the form of an LGPS / LPS bi-layer.

The anode layer and the cathode layer were attached to both surfaces of the solid electrolyte film, respectively. Specifically, in the solid electrolyte film, 15 mg of the positive electrode layer was attached to the surface where the LGPS is located, and a negative electrode layer was attached to the surface where the LPS is located. Thereafter, finally, a pressure of 370 MPa was applied to obtain an all-solid-state battery satisfying the laminated structure of FIG. 1.

Comparative Example 1 (Methanol Process)

(1) Preparation of LSS and xLiI- (1-x) LSS

Unlike using water as a solvent in the entire process of Example 1, a solution process using methanol as a solvent, solid electrolyte particles 1 (Li ₄ SnS ₄ ) and solid electrolyte particles 2 ( _x LiI- _(1-x) Li ₄ SnS ₄ ) were prepared respectively.

(2) Surface coating of electrode active material particles using solid electrolyte particles

In addition, by using the solid electrolyte particles 1 (Li ₄ SnS ₄ ) and solid electrolyte particles 2 ( _x LiI- _(1-x) Li ₄ SnS ₄ ) prepared by the methanol process, a solution process using methanol as a solvent , Surface coated LCO particles were prepared. Other process conditions were the same as Example 1 except having changed the solvent.

(3) anode layer manufacturing

In the same manner as in Example 1, 15 mg of the surface-coated active material particles in Comparative Example 2 was put into a cylindrical frame of f 13 mm and pressed at a pressure of 370 Mpa to form a pellet. This was used as an anode layer.

(4) all-solid-state battery manufacturing

An all-solid-state battery was produced in the same manner as in Example 1 except that the positive electrode layer of Comparative Example 1 was used instead of the positive electrode layer of Example 1.

Comparative Example 2 (Dry Mixture)

(1) anode layer manufacturing

Each solid electrolyte particle of Li ₄ SnS ₄ or _x LiI- _(1-x) Li ₄ SnS ₄ of Example 1 was simply mixed with electrode active material particles.

Specifically, the electrode active material particles and the solid electrolyte particles are mixed so that the weight ratio is 85:15 (active material: solid electrolyte), the total weight is 15 mg, put into a cylindrical frame of f 13 mm and 370 Mpa It was pressed in the pressure of to form a pellet (pellet).

(2) all-solid-state battery manufacturing

In addition, except having used the positive electrode layer of the comparative example 2 instead of the positive electrode layer of Example 1, except having carried out similarly to Example 1, the all-solid-state battery was produced.

Evaluation Example 1 (XRD)

 (1) LSS (aqueous process vs. methanol process)

1) When preparing the solid electrolyte particles 1 in Example 1, the heat treatment temperature of the aqueous solution was changed to 200, 240, 280, 320, or 450 ℃. Thus, LSS200, LSS240, LSS280, LSS320, and LSS450 were obtained, respectively, and compared with the SS-LSS used as a raw material, the XRD pattern was confirmed (FIG. 2A).

In FIG. 2A, SS-LSS is Cu in the range 2θ is 16.5 to 17 °, the range 17 to 18 °, the range 18.5 to 19 °, the range 25 to 26 °, and the range 26 to 26.5 °, respectively. It can be seen that the XRD peak due to Kα X-ray (X-rα) appears. Accordingly, it can be seen from the XRD that the SS-LSS is a crystalline particle having an orthorhombic crystal structure.

In contrast, LSS200, LSS240, LSS280, LSS320, and LSS450 do not exhibit characteristic peaks of SS-LSS. Specifically, LSS200, LSS240, LSS280, and LSS320 are almost amorphous because only peaks due to impurities appear in each XRD.

Therefore, when preparing the solid electrolyte particles 1 (LSS) by the aqueous solution process, when the heat treatment at 200 to 450 ℃, specifically 200 to 320 ℃, the amorphous particles are obtained, thereby excellent ionic conductivity and ductility Inferred to be expressed.

2) In the preparation of the solid electrolyte particles 1 in Comparative Example 1, the heat treatment temperature of the methanol process was varied to 200, 320, or 450 ° C. For each particle thus obtained, an XRD pattern was confirmed in comparison with SS-LSS used as a raw material (FIG. 2B).

According to Figure 2b, when heat treated at 320 ℃ using a methanol process, a characteristic peak of SS-LSS appears.

3) Thus, when the same raw material SS-LSS is used and the heat treatment temperature is in the range of 200 to 450 ° C., it can be seen that amorphous particles are obtained by the aqueous solution process and crystalline particles are obtained by the methanol process.

(2) xLiI- (1-x) LSS (aqueous process vs. methanol process)

1) In preparing the solid electrolyte particles 2 in Comparative Example 1, the heat treatment temperature of the aqueous solution was fixed at 200 ° C., but the molar ratio of LiI: Li ₄ SnS ₄ was varied. For each particle thus obtained, XRD pattern was confirmed in comparison with SS-LSS used as a raw material in Example 1 (FIG. 2D).

In FIG. 2D, when the methanol process is used, crystallization of LSS is not performed at 200 ° C., regardless of LiI addition.

2) In preparing the solid electrolyte particles 2 in Example 1, the molar ratio of LiI: Li ₄ SnS ₄ is 2: 8, 3: 7, or 4: 6, and the heat treatment temperature of the aqueous solution is different from 200 ° C. or 320 ° C. It was. This yields 0.2LiI-0.8LSS200, 0.3LiI-0.7LSS200, 0.4LiI-0.6LSS200, 0.2LiI-0.8LSS320, and 0.4LiI-0.6LSS320, respectively, and compared with Solid Electrolyte Particle 1 (LSS200) of Example 1 The XRD pattern was confirmed (FIG. 2C).

In Figure 2c, 0.2LiI-0.8LSS200, 0.3LiI-0.7LSS200, 0.4LiI-0.6LSS200, 0.2LiI-0.8LSS320, and 0.4LiI-0.6LSS320 In common, it can be seen that some characteristic peaks of SS-LSS appear have. This involves that LiI lowers the crystallization temperature in the aqueous solution process, so that some crystallized particles are formed.

More specifically, when the molar ratio of the same LiI: Li ₄ SnS ₄ , it is confirmed that the higher the heat treatment temperature, the better the characteristic peak of SS-LSS appears. Thus, in the preparation of the solid electrolyte particles 2, it can be seen that in order to lower the degree of crystallization as much as possible, heat treatment must be performed at a lower temperature than in the preparation of the solid electrolyte particles 1.

On the other hand, for 0.3LiI-0.7LSS200 and 0.4LiI-0.6LSS200 (particularly the latter), characteristic peaks due to LiI also appear. These can offset the decrease in ionic conductivity due to the crystallization of LSS by LiI.

3) Therefore, when the same raw material SS-LSS is used, the crystallization temperature of the LSS is lowered by LiI according to the aqueous solution process, but the molar ratio of LiI: LSS that can adequately offset the decrease in ion conductivity due to the crystallization of LSS by LiI. It can be seen that can control.

Evaluation Example 2 (lithium ion conductivity)

(1) LSS and xLiI- (1-x) LSS (aqueous solution process)

Example 1 The process was controlled to yield LSS200, LSS240, LSS280, LSS320, LSS450, 0.4LiI-0.6LSS200, and 0.4LiI-0.6LSS320, respectively, and measured their lithium ion conductivity at 30 ° C (FIG. 3A).

According to FIG. 3A, it can be seen that LSS200, LSS240, LSS280, LSS320, LSS450, 0.4LiI-0.6LSS200, and 0.4LiI-0.6LSS320 all secure lithium ion conductivity at least 1.0 * 10 ^-5 S / cm at 30 ° C. Can be.

Furthermore, in the case of the solid electrolyte particles 1, when the heat treatment temperature is in the range of 280 to 320 ° C. (ie, LSS280 and LSS320), lithium ion conductivity of more than 1.0 * 10 ⁻⁴ S / cm appears. This is inferred to be due to the almost amorphous and dehydration of LSS in this temperature range.

In addition, in the case of the solid electrolyte particle 2, when the heat treatment temperature is 200 ° C. (that is, 0.4LiI-0.6LSS200), lithium ion conductivity of more than 1.0 * 10 ⁻⁴ S / cm appears. From this, it can be seen that the lowering of the crystallization temperature of the LSS is due to LiI, but it is also due to the LiI that offsets the decrease in the ionic conductivity due to the crystallization of the LSS.

(2) xLiI- (1-x) LSS (aqueous solution process)

Meanwhile, Example 1 process was controlled to obtain LSS200, 0.2LiI-0.8LSS200, 0.3LiI-0.7LSS200, and 0.4LiI-0.6LSS320, and 0.5LiI-0.5LSS200, respectively, and their lithium ion conductivity at 30 ° C. It was measured (FIG. 3B).

In FIG. 3B, all of LSS200, 0.2LiI-0.8LSS200, 0.3LiI-0.7LSS200, and 0.4LiI-0.6LSS320, and 0.5LiI-0.5LSS200, lithium ion conductivity of at least 1.0 * 10 ^-5 S / cm at 30 ° C. It can be seen that is secured.

Furthermore, in the case of solid electrolyte particles 2 having a heat treatment temperature of 200 ° C., when the molar ratio of LiI: LSS is 2: 8 to 3: 7 (that is, 0.2LiI-0.8LSS200, and 0.3LiI-0.7LSS200), almost 1.0 * 10 Lithium ion conductivity of ^-4 S / cm level is shown, especially when the molar ratio of LiI: LSS is 4: 6 (ie 0.4LiI-0.6LSS200), lithium ion conductivity is greater than 1.0 * 10 ^-4 S / cm. This is due to the optimum heat treatment temperature and the optimum molar ratio of LiI: LSS.

Evaluation Example 3 (FESEM, HRTEM, and EDXS; LSS aqueous solution process)

Figure 4 relates to the active material particles surface-coated with LSS320 in Example 1.

Specifically, looking at the FESEM and EDXS of the surface-coated active material particles (Fig. 4a), it appears that the distribution of Co located inside the active material particles and the distribution of Sn and S located on the surface thereof are almost identical. From this, it can be seen that the solid electrolyte is evenly coated on the surface of the active material particles by the aqueous solution process.

Also, look at the FESEM for the cross-section cutting the active material particle surface coated with a FIB (Fig. 4b), LCO surface can be seen that the LSS coating layer present on the thin, on such LiNbO ₂ coating layer is coated with a LiNbO _2. This is also consistent with the elemental distribution seen in EDXS for this cross section.

Evaluation Example 4 (Characteristics by Rate, Discharge Characteristics by C-rate, and Lifetime Characteristics; Aqueous Process vs. Dry Mixing)

LCO particles surface-coated with LSS320 in an aqueous solution process according to Example 1 were evaluated for battery application. However, for the active material surface-coated by the process of simultaneously mixing the electrolyte, the active material, and water (Coated 1), and the case of the active material surface-coated by the process of adding the active material after mixing the electrolyte and water (Coated 2), respectively It was.

On the other hand, a cell (shown as p-LCO) with a mixture of LCO (bare) and LSS320 applied to the positive electrode layer and a cell (shown with w-LCO) with a mixture of LCO and LSS320 surface-treated with water were applied to the positive electrode layer. .

Specifically, for each battery, the discharge rate is changed and the rate-specific characteristics are evaluated while imposing conditions of 3.0 to 4.3 V (V vs. Li / Li ⁺ ) at room temperature (FIG. 5A), and the discharge characteristics for each C-rate. Was evaluated (FIG. 5B).

5A and 5B, when only LCO (bare) and LSS320 are mixed, when LCO and LSS320 surface-treated with water are mixed, an electrolyte, an active material, and a surface-coated active material by a process of simultaneously mixing water ( Coated 1), the process of adding the active material after mixing the electrolyte and water, in the order of the surface-coated active material (Coated 2), the characteristics of the rate and the discharge characteristics of the C-rate was excellent.

As a result, the contact property between the active material and the solid electrolyte is improved through water, and it can be seen that the property is more excellent when the solid electrolyte is coated on the surface of the active material.

As a result of performing charge / discharge cycles 80 times for Coated 2 having the best rate-specific characteristics and discharge characteristics for each C-rate (FIG. 5C), it can be seen that there is almost no capacity reduction compared to the initial stage.

Evaluation Example 5 (resistance characteristics, discharge voltage characteristics of the electrode layer; aqueous solution process vs. dry mixing)

Regarding the LCO particles surface-coated with LSS320 in an aqueous solution process according to Example 1, the electrode resistance characteristics (FIG. 7A) and the discharge voltage characteristics (FIG. 7B) were evaluated. However, for the active material surface-coated by the process of simultaneously mixing the electrolyte, the active material, and water (Coated 1), and the case of the active material surface-coated by the process of adding the active material after mixing the electrolyte and water (Coated 2), respectively It was.

In addition, the positive electrode (indicated by p-LCO) to which a mixture of LCO (bare) and LSS320 was applied, and the positive electrode (indicated by w-LCO) to which a mixture of LCO and LSS320 surface-treated with water were also evaluated.

In general, since the semicircle size of the impedance analysis graph corresponds to the resistance size, it is possible to determine the resistance characteristics accordingly. In this regard, referring to FIG. 7A, when LCO (bare) and LSS320 are simply mixed, when LCO and LSS320 surface-treated with water are mixed, an electrolyte, an active material, and an active material surface-coated by simultaneously mixing water ( Coated 1), the process of adding the active material after mixing the electrolyte and water, in the case of the surface-coated active material (Coated 2), it can be seen that the resistance is small.

This resistance characteristic evaluation result corresponds to the characteristic evaluation result for each rate confirmed by the evaluation example 1. Furthermore, it corresponds to the discharge voltage characteristic evaluation result shown in FIG. 7B.

The present invention is not limited to the above embodiments, but may be manufactured in various forms, and a person skilled in the art to which the present invention pertains has another specific form without changing the technical spirit or essential features of the present invention. It will be appreciated that the present invention may be practiced as. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive.

Claims (15)

delete delete delete delete delete delete Preparing a first mixture including electrode active material particles, a crystalline sulfide compound represented by Chemical Formula 1, and water (H ₂ O) as a solvent; And
Heat treating the first mixture; including,
Heat-treating the first mixture;
Water in the first mixture is removed,
The crystalline sulfide compound is converted to amorphous and coated on the surface of the electrode active material particles,
Heat treatment of the first mixture is performed at a temperature range of 200 to 320 ℃,
Method for preparing an electrode active material-solid electrolyte composite:
[Formula 1]
Li _a M _b S _c X ¹ _d
In Formula 1, M is Sn, X ¹ is F, Cl, Br, I, Se, Te, or O, 0 <a≤6, 0 <b≤6, 0 <c≤6, 0 ≦ d ≦ 6.
The method of claim 7, wherein
Preparing the first mixture;
Simultaneously mixing the electrode active material particles, the crystalline sulfide compound, and the water;
Method for producing an electrode active material-solid electrolyte composite.
The method of claim 7, wherein
Preparing the first mixture;
Mixing the crystalline sulfide compound and the water, and then adding and mixing the electrode active material particles;
Method for producing an electrode active material-solid electrolyte composite.
The method of claim 7, wherein
In the step of preparing the first mixture;
Per 1 mL of the solvent, the total amount of the electrode active material particles and the crystalline sulfide compound is mixed so as to be 300 to 600 mg,
Method for producing an electrode active material-solid electrolyte composite.
The method of claim 7, wherein
In the step of preparing the first mixture;
The crystalline sulfide-based compound in the first mixture: to be mixed so that the weight ratio of the particles of the electrode active material is 0.1: 99.9 to 50:50,
Method for producing an electrode active material-solid electrolyte composite.
The method of claim 7, wherein
Heat-treating the first mixture;
It is carried out in a temperature range of 280 to 320 ℃ or less,
Method for producing an electrode active material-solid electrolyte composite.
The method of claim 7, wherein
Heat-treating the first mixture;
That is performed for 6 to 10 hours,
Method for producing an electrode active material-solid electrolyte composite.
The method of claim 7, wherein
Heat-treating the first mixture;
To be carried out at a pressure in the range of 0 to 760 torr,
Method for producing an electrode active material-solid electrolyte composite.
delete

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