KR102444283B1 - All Solid secondary battery, and method for preparing all solid secondary battery - Google Patents

Abstract

The solid battery 1 includes a negative electrode layer 9 containing a negative electrode active material, a positive electrode layer 5 containing a positive electrode active material, and a negative electrode layer 9 and a positive electrode layer 5 between the negative electrode layer 9 and the positive electrode layer 5 . ) and a solid electrolyte layer (7) provided so as to be in contact with each other. Let the total volume of the negative electrode layer 9, the positive electrode layer 5 and the solid electrolyte layer 7 be V _p , and the pressure of the negative electrode layer 9 and the positive electrode layer 5 and the solid electrolyte layer 7 as a whole is 980 MPa. If the volume under V ₉₈₀ is defined as {(Vp-V ₉₈₀ ) / Vp × 100} ≤ 3%.

Description

All-solid-state secondary battery, and all-solid-state secondary battery manufacturing method {All Solid secondary battery, and method for preparing all solid secondary battery}

It relates to a solid-state battery and a method for manufacturing the same.

Recently, the development of batteries with high energy density and safety has been actively carried out in response to industrial demands. For example, lithium ion batteries are being put to practical use not only in the fields of information-related devices and communication devices, but also in the fields of automobiles. In the automotive field, safety is especially important because it is related to life.

Lithium ion batteries currently on the market use an electrolyte solution containing a combustible organic solvent, and thus there is a possibility of overheating and fire when a short circuit occurs. On the other hand, a solid battery using a solid electrolyte instead of an electrolyte has been proposed.

According to the solid batteries described in Patent Documents 1 to 3, by not using a flammable organic solvent, even if a short circuit occurs, the possibility of occurrence of a fire or explosion can be greatly reduced. Therefore, there is a possibility that such a solid battery can greatly improve safety compared to a lithium ion battery using an electrolyte.

Patent Document 1: Japanese Patent Laid-Open No. 2012-104270

Patent Document 2: Korean Patent Publication No. WO2012/164723

Patent Document 3: Japanese Patent Laid-Open No. 2014-120199

However, in the conventional solid battery described above, since the electrolyte is solid, if the contact between the positive electrode layer and the solid electrolyte and between the negative electrode layer and the solid electrolyte is not sufficiently maintained, the resistance in the battery increases, making it difficult to exhibit excellent battery characteristics.

Here, in order to lower the resistance in the battery, charging and discharging may be performed while applying an external pressure to the solid battery. However, in that case, since a structure for applying an external pressure is separately required, the product cost increases and the energy density of the solid battery also decreases.

One aspect is to provide a solid battery with high safety and capable of exhibiting excellent battery characteristics.

according to one embodiment

a negative electrode layer including an anode active material;

a positive electrode layer comprising a positive electrode active material; and

There is provided a solid electrolyte layer disposed between the negative electrode layer and the positive electrode layer so as to be in contact with the negative electrode layer and the positive electrode layer, respectively, and satisfying Equation 1 below:

<Equation 1>

{(V _p -V ₉₈₀ ) / V _p ㅧ 100} - 3%

In the above formula,

V _p is the total volume of the cathode layer, the anode layer and the solid electrolyte layer,

V ₉₈₀ is the total volume of the negative electrode layer, the positive electrode layer and the solid electrolyte layer under a pressure of 980 MPa.

According to one aspect, according to the solid battery, it is possible to exhibit high safety and excellent battery characteristics.

1 is a cross-sectional view of a solid-state cell according to an exemplary embodiment.
2 is a cross-sectional view showing a step of consolidating a battery material using hydrostatic pressure.
3 is a cross-sectional view showing an embodiment in which uniaxial press working is performed in the consolidation process of the laminate.
4 shows the relationship between the ratio of the initial discharge capacity value when the initial discharge capacity is 100% when pressurized at a hydrostatic pressure of 980 MPa in a solid battery and the porosity based on V ₉₈₀ when pressurized at a hydrostatic pressure of 980 MPa. is a graph representing
5 is a diagram showing the relationship between the cell resistance and the porosity on the basis of V980 when pressurized with a hydrostatic pressure of ₉₈₀ MPa in a solid battery.
6 is a diagram showing the relationship between the cycle retention rate and the porosity based on V ₉₈₀ when pressurized with a hydrostatic pressure of 980 MPa in a solid battery.
<Explanation of symbols for main parts of the drawing>
1: solid battery 3: positive electrode current collector layer
5: Anode layer 7: Solid electrolyte layer
9: negative electrode layer 11: negative electrode current collector layer
13: support 14: exterior body
15: protective body 17: pressurized medium
19: pressure 21: hydrostatic pressure
24: laminated body 25: press

Hereinafter, an all-solid-state secondary battery and an all-solid-state secondary battery manufacturing method according to exemplary embodiments will be described in more detail with reference to the accompanying drawings. In the present specification and drawings, components having substantially the same functional configuration are referred to by the same reference numerals, and repeated descriptions will be omitted.

A solid battery according to an embodiment includes an anode layer including an anode active material; a positive electrode layer comprising a positive electrode active material; and a solid electrolyte layer disposed between the cathode layer and the anode layer so as to be in contact with the cathode layer and the anode layer, respectively, satisfying Equation 1 below:

<Equation 1>

{(V _p -V ₉₈₀ ) / V _p × 100} ≤ 3%

In the above formula, V _p is the total volume of the negative electrode layer, the positive electrode layer and the solid electrolyte layer, and V ₉₈₀ is the total volume of the negative electrode layer, the positive electrode layer and the solid electrolyte layer under a pressure of 980 MPa.

For example, when the total volume of the negative electrode layer, the positive electrode layer, and the solid electrolyte layer is V _p , and the volume when the entire negative electrode layer, the positive electrode layer, and the solid electrolyte layer are pressurized at a pressure of 980 MPa is V ₉₈₀ Equation 1 above holds.

In the present specification, {(V _p -V ₉₈₀ ) / V _p × 100} may be referred to as “porosity based on V ₉₈₀ ”. The {(V _p -V ₉₈₀ ) / V _p × 100} is the total volume of the negative electrode layer, the positive electrode layer, and the solid electrolyte layer under the pressure of 980 MPa compared to the volume occupied by V ₉₈₀ and the negative electrode layer, the positive electrode layer and the solid electrolyte layer. It corresponds to the rate of increase in V _p , the volume occupied by the volume under a certain pressure. Since this increase in volume will eventually be occupied by voids, {(V _p -V ₉₈₀ ) / V _p × 100} can be referred to as a relative porosity of V _p with respect to V ₉₈₀ .

The pressure in the solid-state cell may be hydrostatic pressure. For example, the pressure may be a pressure applied by a press. The pressure at which V _p satisfying Equation 1 is obtained may be 450 Mpa or more. That is, V _p is the total volume of the negative electrode layer, the positive electrode layer, and the solid electrolyte layer under a pressure of 450 MPa or more.

In the solid battery, a porosity based on V ₉₈₀ may be 2.5% or less. For example, the porosity based on V ₉₈₀ may be 2.0% or less. For example, the porosity based on V ₉₈₀ may be 1.5% or less. For example, the porosity based on V ₉₈₀ may be 1.0% or less.

(Embodiment)

- Construction of a solid-state battery -

1 is a cross-sectional view illustrating a solid-state battery according to an embodiment disclosed herein. This figure schematically shows the configuration of the solid battery 1 for easy understanding, and the ratio of the thickness of each layer may be different from the example of FIG. 1 .

As shown in FIG. 1 , the solid battery 1 of this embodiment has a negative electrode current collector layer 11 , a negative electrode layer 9 , a solid electrolyte layer 7 and a positive electrode layer 5 installed in order from the bottom, and A positive electrode current collector layer (3) is provided.

The solid electrolyte layer 7 formed between the cathode layer 9 and the anode layer 5 is in direct contact with the cathode layer 9 and the anode layer 5, respectively. The negative electrode layer 9, the solid electrolyte layer 7, and the positive electrode layer 5 are each composed of powder and press-molded. In addition, the planar shape of the solid battery 1 is not specifically limited, A circular shape, a quadrilateral, etc. may be sufficient.

The negative electrode current collector layer 11 is made of a conductor, and is made of, for example, a metal such as copper (Cu), nickel (Ni), stainless steel, or a nickel-plated steel sheet. The thickness of the negative electrode current collector layer 11 is, for example, about 10 μm to 20 μm.

The negative electrode layer 9 includes an anode active material in powder form. The average particle diameter of the negative active material may be, for example, in the range of 5 μm to 20 μm. The content of the anode active material of the anode layer 9 may be, for example, in the range of 60 wt% to 95 wt%. The negative electrode layer 9 may further include a binder that does not cause a chemical reaction with the solid electrolyte layer 7 , a solid electrolyte material in powder form, a conductive material, and the like.

As the negative active material, various known materials may be used, but a carbon active material, a metal active material, an oxide active material, and the like may be used. Examples of the carbon active material include graphite such as artificial graphite and natural graphite, and amorphous carbon such as hard carbon and soft carbon. Examples of the metal active material include lithium (Li), indium (In), aluminum (Al), silicon (Si), and tin (Sn). _As an oxide active material, _Nb2O5 , _Li4Ti5O12 , _SiO , _etc. can be illustrated, for example. These negative active materials may be used alone, or two or more of them may be used together. Although the thickness of the cathode layer 9 is not specifically limited, For example, it is about 50 micrometers - 300 micrometers.

The solid electrolyte layer 7 is composed of a solid electrolyte in powder form. The average particle diameter of the solid electrolyte may be, for example, in the range of 1 μm to 10 μm. As the solid electrolyte, for example, a sulfide-based solid electrolyte containing at least lithium (Li), phosphorus (P) and sulfur (S) may be used. Examples of the sulfide-based solid electrolyte include Li ₂ SP ₂ S ₅ . This sulfide-based solid electrolyte exhibits good lithium ion conductivity and contains sulfides such as SiS ₂ , GeS ₂ , and B ₂ S ₃ in addition to Li ₂ SP ₂ S ₅ . Although the thickness of the solid electrolyte layer 7 is not specifically limited, For example, it is about 10 micrometers - 200 micrometers.

In addition, as the solid electrolyte, an inorganic solid electrolyte to which Li ₃ PO ₄ , halogen, a halogen compound, and the like is added may be used.

The Li ₂ SP ₂ S ₅ may be obtained by heating Li ₂ S and P ₂ S ₅ to a melting temperature or higher, melting and mixing both at a predetermined ratio, maintaining the mixture for a predetermined time, and then quenching the mixture. This Li ₂ SP ₂ S ₅ can also be obtained by treating a powder of Li ₂ S and P ₂ S ₅ according to a mechanical milling method. The mixing ratio of Li ₂ S and P ₂ S ₅ is usually 50:50 to 80:20 in molar ratio, preferably 60:40 to 75:25.

The positive electrode layer 5 includes a positive electrode active material in powder form. The average particle diameter of the positive active material may be, for example, in the range of 2 μm to 10 μm. The content of the positive electrode active material in the positive electrode layer 5 may be, for example, in the range of 65% by weight to 95% by weight. The positive electrode layer 5 may further include a binder that does not cause a chemical reaction with the solid electrolyte layer 7 , a solid electrolyte material in powder form, a conductive material, and the like. Any material capable of reversibly occluding and releasing lithium ions can be used as a positive electrode active material. For example, lithium cobalt oxide (LCO), lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminum oxide (NCA), lithium nickel cobalt manganese oxide (NCM), lithium manganese oxide, lithium iron phosphate, Nickel sulfide, copper sulfide, sulfur, iron oxide, vanadium oxide, etc. can be illustrated. Such a positive active material may be used alone, or two or more types may be used together.

For example, the positive active material may be one or more of a composite oxide of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof, and specific examples thereof include Li _a A _1-b B _b D ₂ (wherein 0.90 ≤ a ≤ 1, and 0 ≤ b ≤ 0.5); Li _a E _1-b B _b O _2-c D _c (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); LiE _2-b B _b O _4-c D _c (wherein 0 ≤ b ≤ 0.5 and 0 ≤ c ≤ 0.05); Li _a Ni _1-bc Co _b B _c D _α (where 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li _a Ni _1-bc Co _b B _c O _2-α F _α (wherein 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α <2); Li _a Ni _1-bc Co _b B _c O _2-α F ₂ (wherein 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α <2); Li _a Ni _1-bc Mn _b B _c D _α (wherein 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li _a Ni _1-bc Mn _b B _c O _2-α F _α (wherein 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α <2); Li _a Ni _1-bc Mn _b B _c O _2-α F ₂ (wherein 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α <2); Li _a Ni _b E _c G _d O ₂ (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1); Li _a Ni _b Co _c Mn _d GeO ₂ (wherein, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, 0.001 ≤ e ≤ 0.1); Li _a NiG _b O ₂ (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li _a CoG _b O ₂ (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li _a MnG _b O ₂ (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li _a Mn ₂ G _b O ₄ (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); QO ₂ ; QS ₂ ; LiQS ₂ ; V ₂ O ₅ ; LiV ₂ O ₅ ; LiIO 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); A compound represented by any one of the chemical formulas of LiFePO ₄ may be used.

In the above formula, A is Ni, Co, Mn, or a combination thereof; B is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D is O, F, S, P, or a combination thereof; E is Co, Mn, or a combination thereof; F is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; Q is Ti, Mo, Mn, or a combination thereof; I is Cr, V, Fe, Sc, Y, or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof.

Among the above-described positive active materials, a lithium salt of a transition metal oxide having a layered rock salt structure may be used. Here, the "rock salt structure" is a sodium chloride type structure, which is a type of crystal structure, and refers to a structure in which the face-centered cubic lattice formed by each of the cations and anions is shifted by only 1/2 of the corners of the unit lattice. For example, Li _1-xyz Ni _x Co _y Al _z O ₂ (NCA) or Li _1-xyz Ni _x Co _y Mn _z O ₂ (NCM) (0<x<1, 0<y<1, 0< A lithium salt of a ternary transition metal oxide represented by z<1 and x+y+z<1) may be used as the positive electrode active material.

A compound having a coating layer on the surface of the compound that can be used as the positive electrode active material specifically disclosed above may be used, or a mixture of the compound and the compound having a coating layer may be used. The coating layer may include a coating element compound of oxide or hydroxide of the coating element, oxyhydroxide of the coating element, oxycarbonate of the coating element, or hydroxycarbonate of the coating element. The compound constituting these coating layers may be amorphous or crystalline. As the coating element included in the coating layer, Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or a mixture thereof may be used. In the coating layer forming process, any coating method may be used as long as the compound can be coated by a method that does not adversely affect the physical properties of the positive electrode active material (eg, spray coating, dipping method, etc.) by using these elements in the compound. Since the content can be well understood by those engaged in the field, a detailed description thereof will be omitted.

Examples of the anode layer conductive material include graphite, carbon black, acetylene black, ketjen black, carbon fiber, and metal powder.

The positive electrode layer may additionally include a solid electrolyte. As the solid electrolyte for the positive electrode layer, a conventionally known solid electrolyte can be used without limitation. Specifically, Li ₃ N, LISICON, lithium oxynitride (LIPON), Thio-LISICON (Li _3.25 Ge _0.25 P _0.75 S ₄ ), Li ₂ O-Al ₂ O ₃ -TiO ₂ -P ₂ O ₅ (LATP ) can be exemplified. In addition, examples of the solid electrolyte having high ionic conductivity include Li ₂ SP ₂ S ₅ , Li ₃ PS ₄ , Li ₇ P ₃ S ₁₁ , Li ₆ PS ₅ Cl, Li ₃ PO ₄ , and the like.

The ionic conductivity of Li ₃ PO ₄ is 10 ^-4 to 10 ^-3 S/cm. The ionic conductivity of Li ₇ P ₃ S ₁₁ is 10 ^-3 to 10 ^-2 S/cm. The ionic conductivity of Li ₆ PS ₅ Cl is 10 ^-4 to 10 ^-3 S/cm. The ionic conductivity of Li ₃ PO ₄ is 10 ^-5 to 10 ^-4 S/cm.

As the binder, for example, a non-polar resin having no polar functional group can be used. Therefore, the positive electrode layer binder is inert to a reactive solid electrolyte, particularly a sulfide-based solid electrolyte. Examples of the positive electrode layer binder include styrene-based thermoplastic elastomers such as SBS (styrene butadiene block copolymer), SEBS (styrene ethylene butadiene styrene block copolymer), styrene-(styrene butadiene)-styrene block copolymer, SBR ( styrene-butadiene rubber), BR (butadiene rubber), NR (natural rubber), IR (isoprene rubber), EPDM (ethylene-propylene-diene terpolymer) and partially or fully hydrogenated products thereof. . In addition, polystyrene, polyolefin, olefinic thermoplastic elastomer, polycycloolefin, silicone resin, etc. can be used as the binder. Although the thickness of the anode layer 5 is not specifically limited, For example, it is about 50 micrometers - 350 micrometers.

The positive electrode current collector layer 3 is made of a conductor, and is made of, for example, a metal such as aluminum (Al) or stainless steel. Although the thickness of the positive electrode current collector layer 3 is not specifically limited, For example, it is about 10 micrometers - 20 micrometers.

The planar areas of the negative electrode current collector layer 11, the negative electrode layer 9, the solid electrolyte layer 7, the positive electrode layer 5, and the positive electrode current collector layer 3 may be the same as in FIG. 1, and the positive electrode layer ( 5) and the planar area of the positive electrode current collector layer 3 are smaller than those of the negative electrode current collector layer 11, the negative electrode layer 9 and the solid electrolyte layer 7, while the positive electrode layer 5 and the positive electrode current collector It may be provided so that the planar outer shape of the layer 3 is inside the planar outer shape of the negative electrode current collector layer 11 , the negative electrode layer 9 and the solid electrolyte layer 7 (refer to FIG. 3 ). The negative electrode layer 9; When pressure is applied to the solid electrolyte layer 7 and the anode layer 5 , the outward protrusion of the anode layer 5 can be prevented, thereby making it difficult to cause a short circuit.

Let V _p be the total volume of the negative electrode layer 9 , the positive electrode layer 5 , and the solid electrolyte layer 7 in the solid battery 1 of the embodiment, and the negative electrode layer 9 and the positive electrode layer 5 ) and the volume when the entire solid electrolyte layer 7 is pressurized with a hydrostatic pressure of 980 MPa is V ₉₈₀ , {(V _p -V ₉₈₀ ) / V _p × 100} - 3% can be established have. In addition, in the present specification, {(V _p -V ₉₈₀ ) / V _p × 100} is referred to as “porosity based on V ₉₈₀ ”, and a general porosity ratio (hereinafter “ true porosity").

When the negative electrode layer 9, the positive electrode layer 5 and the solid electrolyte layer 7 are formed using a general method for manufacturing a conventional lithium ion battery, generally {(V _p -V ₉₈₀ ) / V _p x 100} becomes greater than 3%. In contrast, in the solid battery 1 of the embodiment, the negative electrode layer 9, the solid electrolyte layer 7 and the positive electrode layer 5 so that {(V _p -V ₉₈₀ ) / V _p × 100} ≤ 3% Since this is consolidated, the contact between the negative electrode active material and the solid electrolyte and the contact between the positive electrode active material and the solid electrolyte can be sufficiently ensured. Accordingly, it is possible to keep the electrical resistance between the negative electrode layer 9 and the solid electrolyte layer 7 and the electrical resistance between the positive electrode layer 5 and the solid electrolyte layer 7 small, respectively, even when no external pressure is applied during operation. As a result, the solid battery 1 of one embodiment can become possible to exhibit excellent battery characteristics.

In addition, since a structure for applying an external pressure to the solid battery 1 of the embodiment is not required, a reduction in product cost can be achieved. In addition, high energy density can be obtained. In addition, since the solid-state battery 1 of the embodiment is an all-solid-state battery, the risk of fire or the like can be extremely low compared to a battery using a combustible organic electrolyte.

Here, the negative electrode layer 9, the positive electrode layer 5 and the solid electrolyte layer 7 are pressurized at a hydrostatic pressure of 980 MPa or more by pressing the entire negative electrode layer 9, the positive electrode layer 5 and the solid electrolyte layer 7 formed by coating or the like. Since the volume does not decrease even if a hydrostatic pressure of 980 MPa is applied again after the production of the solid battery 1 in the case of consolidation, {(V _p -V ₉₈₀ ) / V _p × 100} = 0%.

In addition, the fact that battery characteristics can be improved by setting the porosity of the negative electrode layer 9, the positive electrode layer 5, and the solid electrolyte layer 7 within an appropriate range means that even when the constituent materials of the solid electrolyte layer 7 are different. may be the same.

This is because the fact that the contact between solid particles is a factor influencing the characteristics of a solid battery is common regardless of the constituent materials of the solid electrolyte. Therefore, if {(V _p -V ₉₈₀ ) / V _p × 100} ≤ 3% holds even in the solid electrolyte other than the sulfide type (eg, oxide type and phosphoric acid type), the solid electrolyte according to the embodiment (1 ), it may be possible to exhibit excellent battery properties such as

In addition, although the monopolar type solid-state battery 1 is shown in FIG. 1, the solid-state battery 1 may be a bipolar type. In addition, the monopolar battery structure of FIG. 1 may be stacked several times.

In addition, the solid battery 1 does not necessarily need to be an all-solid-state lithium ion secondary battery, but may be an all-solid-type alkali ion secondary battery (for example, an all-solid-type sodium ion secondary battery).

In addition, the solid battery 1 according to the embodiment may be in a vacuum laminate-packed state with a metal foil or a plastic film. Also in this case, the solid battery 1 of the embodiment can exhibit excellent battery characteristics even without receiving external pressure. In the solid battery 1 of the embodiment, the pressure applied to the negative electrode layer 9 , the positive electrode layer 5 , and the solid electrolyte layer 7 from the outside in the atmosphere may be equal to or less than atmospheric pressure.

- Manufacturing method of solid-state battery -

As an example of a method for manufacturing the solid battery 1, there is a method using a coating. First, a powdered positive electrode active material, a solid electrolyte, a conductive aid, a binder, etc. are added and mixed in an appropriate solvent to prepare a coating solution for the positive electrode layer 5 . Then, the coating solution is applied to one surface of the positive electrode current collector layer 3 and dried. In the above process, a non-polar solvent having low reactivity with a sulfide-based solid electrolyte is used. For example, aromatic hydrocarbons such as xylene, toluene, and ethylbenzene, and aliphatic hydrocarbons such as pentane, hexane, and heptane can be used as the solvent.

Meanwhile, a powdered negative electrode active material, a solid electrolyte, a conductive aid, and a binder are added to the solvent and mixed to prepare a coating solution for the negative electrode layer 9 . Then, the coating solution is applied to one surface of the negative electrode current collector layer 11 and dried.

Next, a coating solution for an electrolyte layer in which a sulfide-based solid electrolyte and a binder are added to a solvent and mixed is prepared. Next, the coating solution is applied to one surface of the negative electrode current collector layer 11 on which the negative electrode layer material is applied and dried.

Each of the positive electrode current collector layer 3 and the negative electrode current collector layer 11 is cut to an appropriate size. Next, the negative electrode current collector layer 11 and the positive electrode current collector so that the surface on which the electrolyte material is applied among one surface of the negative electrode current collector layer 11 and the surface on which the positive electrode layer material is applied among the one surface of the positive electrode current collector layer 3 are bonded After overlapping the layers (3), the consolidation process is performed as follows. Here, the overlapping of the negative electrode current collector layer 11 and the positive electrode current collector layer 3 is referred to as a “stacked body for batteries”.

2 is a cross-sectional view showing a process of consolidation of a battery material using hydrostatic pressure. As shown, the battery stack 24 is sealed by an exterior body 14 made of metal foil or the like after the battery stack is disposed on the support 13 made of a rigid plate.

Next, the battery stack 24 and the support 13 are sealed with a protective body 15 made of a resin film or the like, and are immersed in a pressurized medium 17 filled in a high-pressure container (not shown). In this state, the negative electrode layer 9, the solid electrolyte layer 7 and the positive electrode layer 5 are consolidated by applying the pressure 19 from above to the pressurized medium 17 in the container. According to this method, the hydrostatic pressure 21 of a desired value can be applied to the negative electrode layer 9, the solid electrolyte layer 7, and the positive electrode layer 5 from the side and top.

In this step, since the bonding between the negative electrode layer 9 and the solid electrolyte layer 7 and the bonding between the positive electrode layer 5 and the solid electrolyte layer 7 are sufficiently secured, the electrical resistance of the battery can be reduced. In addition, since the densities of the negative electrode layer 9, the solid electrolyte layer 7 and the positive electrode layer 5 can be increased, the current density of the solid battery 1 can be improved.

The value of the hydrostatic pressure applied to the battery stack 24 from the side and from above in the consolidation step is not particularly limited, but if it is 450 MPa or more, the V ₉₈₀ of the negative electrode layer 9, the solid electrolyte layer 7 and the positive electrode layer 5 The porosity based on can be made 3% or less. In this way, it is possible to produce a solid battery 1 exhibiting excellent cycle retention and initial discharge capacity. For example, in the consolidation process, the hydrostatic pressure applied from the side and the top to the battery stack 24 may be 500 MPa or more. For example, in the consolidation process, the value of the hydrostatic pressure applied from the side and the top to the battery stack 24 may be 550 MPa or more. For example, in the consolidation process, the value of the hydrostatic pressure applied to the battery stack 24 from the sides and from above may be 600 MPa or more. For example, the value of the hydrostatic pressure applied from the side and the top to the battery stack 24 in the consolidation process may be 650 MPa or more. For example, the value of the hydrostatic pressure applied from the side and the top to the battery stack 24 in the consolidation process may be 700 MPa or more.

In addition, even if the hydrostatic pressure applied to the battery stack is too high, it is difficult to bring the true porosity close to zero, and the facility for applying the hydrostatic pressure becomes large. Therefore, the hydrostatic pressure applied to the battery stack may be 980 MPa or less.

In a case where the support 13 is not installed because hydrostatic pressure is applied in a state where the support 13 is installed under the anode current collector layer 11 in one process, or an elastic body under the anode current collector layer 11 It is possible to significantly reduce the deformation of the manufactured solid battery 1 compared to the case of installing the. Also, in the consolidation process, different hydrostatic pressures may be applied to a portion of the laminate 24 in contact with the support 13 and a portion not in contact with the support 13 .

The support 13 used in one process may have a thickness to obtain sufficient rigidity, for example, may have a thickness of about 3 mm to 5 mm. The support 13 may be made of, for example, metal, for example, made of aluminum.

After the above process, the solid battery 1 in the pressurized medium is removed, the protective body 15 is removed, and the support 13 is separated from the solid battery 1 to manufacture the solid battery 1 of one embodiment. .

In addition, although the case where hydrostatic pressure is applied to the laminated body 24 was demonstrated in one Embodiment, as shown in FIG. 3, the compaction of the laminated body 24 by axial press working, such as a roll press and a double-sided press, was demonstrated. can be carried out. In the case of axial press working, the planar area of the positive electrode layer 5 and the positive electrode current collector 3 is made smaller than that of the solid electrolyte layer 7, the negative electrode layer 9, and the negative electrode current collector layer 11, and the positive electrode layer (5) and the positive electrode collector 3 so that the planar outlines of the solid electrolyte layer 7, the negative electrode layer 9 and the negative electrode collector layer 11 fit inside the planar outlines of the positive electrode layer 5 and the positive electrode collector All (3) can be placed.

For example, the pressure applied to the laminate 24 by the press may be 450 MPa or more. For example, the pressure applied to the laminate 24 by the press may be 500 MPa or more. For example, the pressure applied to the laminate 24 by the press may be 550 MPa or more. For example, the pressure applied to the laminate 24 by the press may be 600 MPa or more. For example, the pressure applied to the laminate 24 by the press may be 650 MPa or more. For example, the pressure applied to the laminate 24 by the press may be 700 MPa or more.

For example, the pressure applied to the laminate 24 by the press may be 980 MPa or less.

According to this method, even when the laminate 24 is sandwiched by the press 25 and the positive electrode layer 5 is spread outward, the positive electrode layer 5 is attached to the negative electrode layer 9 and the negative electrode current collector layer 11 . contact can be effectively prevented.

In addition, the structure and manufacturing method of the solid battery 1 demonstrated above are an example of embodiment, and you may change a structural member, a manufacturing procedure, etc. suitably.

<Example>

Next, an embodiment of the solid-state battery 1 according to an embodiment will be described. In addition, the operations in each of the following examples and comparative examples were all held in a dry room at a dew point temperature - 55°C or lower.

[Example 1]

- Formation of anode layer -

Powdered LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (positive electrode active material), powdered Li ₂ SP ₂ S ₅ (sulfide-based solid electrolyte) and vapor-grown carbon fiber powder (conductive auxiliary) were mixed in a weight ratio of 60:35:5 was weighed, and then, a xylene solution in which butadiene rubber, a binder, was dissolved in these mixed powders was added so that the binder was 2 wt% based on the total weight of the mixed powder, and mixed using a rotating and revolving mixer to apply the coating solution for the positive electrode layer was prepared.

Then, the coating solution was applied on an aluminum foil (positive electrode current collector) having a thickness of 12 μm using a desktop screen printing machine. Thereafter, the aluminum foil coated with the coating solution was dried at 40° C. for 10 minutes using a hot plate, and then vacuum dried at 40° C. for 12 hours. Therefore, an anode layer was formed on the aluminum foil. The thickness of the anode layer was 300 μm.

- Formation of cathode layer -

Next, graphite powder (negative electrode active material), Li ₂ SP ₂ S ₅ (sulfide-based solid electrolyte) and vapor-grown carbon fiber powder (conductive auxiliary) were weighed in a weight ratio of 60:35:5, and then the mixed powder A xylene solution in which butadiene rubber as a binder was dissolved was added to 3 wt% of the binder based on the total weight of the mixed powder, and mixed using a rotating and revolving mixer to prepare a coating solution for the negative electrode layer. Next, the negative electrode layer coating solution was applied to a 10 μm-thick copper foil (negative electrode current collector) using a desktop screen printing machine.

The copper foil coated with the coating solution was dried at 40°C for 10 minutes using a hot plate and then vacuum dried at 40°C for 12 hours. Thereby, the negative electrode layer was formed in the copper foil. Next, using a roll press having a roll gap of 50 µm, the copper foil with the negative electrode layer (that is, the negative electrode structure) was rolled. The total thickness of the cathode layer and the copper foil was about 120 μm.

- Formation of electrolyte layer -

A xylene solution in which a binder was dissolved was added to powder Li ₂ SP ₂ S ₅ (sulfide-based solid electrolyte) and mixed using a rotational revolution mixer. Thereby, a coating solution of the electrolyte layer was prepared.

Then, the coating solution of the electrolyte layer was applied on the negative electrode structure using a desktop screen printing machine. Thereafter, the negative electrode structure was dried at 40° C. for 10 minutes using a hot plate, and then vacuum dried at 40° C. for 12 hours. Thus, a solid electrolyte layer was formed on the anode structure. After drying, the thickness of the solid electrolyte layer was 70 μm.

- Fabrication of solid-state batteries -

Negative electrode structure After punching a hole in the sheet-shaped negative electrode structure with the solid electrolyte layer and the sheet-shaped positive current collector layer with the positive electrode layer formed thereon with a Thompson blade, respectively, the negative electrode structure and the positive electrode current collector layer were combined with the solid electrolyte layer and the positive electrode The layers were stacked in contact with each other. In this state, a vacuum laminate pack of the laminate was performed. Here, the solid electrolyte layer of the anode structure was made to be 0.7 mm larger in the upper, lower, left and right sides, respectively, than the anode layer.

Next, the laminate was placed on an aluminum plate (support) having a thickness of 3 mm, and a vacuum lamination pack of the laminate including the support was performed. This laminate was immersed in a pressurized medium as shown in Fig. 2, and hydrostatic pressure treatment (consolidation step) was performed at 455 MPa. Thereby, the solid battery 1 single cell (single cell) was produced.

[Example 2-5]

A solid battery according to Examples 2-5 was manufactured in the same manner as in Example 1 except for the consolidation process. The example in which the hydrostatic pressure was set to 490 MPa in the consolidation process was set to Example 2, the example in which the hydrostatic pressure was set to 525 MPa, the example in which the hydrostatic pressure was set to 525 MPa, the example in which the hydrostatic pressure was set to 675 MPa, and the example in which the hydrostatic pressure was set to 980 MPa was set to Example 5.

[Comparative Example 1-6]

Solid batteries according to Comparative Examples 1 to 6 were manufactured in the same manner as in Example 1 except for the consolidation process. An example in which the compaction process was not performed was designated as Comparative Example 1. In addition, the example in which the hydrostatic pressure was 75 MPa was Comparative Example 2, the example in which the hydrostatic pressure was 150 MPa was Comparative Example 3, the example in which the hydrostatic pressure was 225 MPa was Comparative Example 4, and the example in which the hydrostatic pressure was 375 MPa was Comparative Example 5.

- Measurement of porosity based on V ₉₈₀ -

First, the total volume Vp of the negative electrode layer, the solid electrolyte layer, and the positive electrode layer of the solid battery is punched into these layers with a size of φ13 mm, and the film thickness and weight are measured using a film thickness meter and a scale, respectively. did.

Then, a laminate composed of the negative electrode current collector layer, the negative electrode layer, the solid electrolyte layer, the positive electrode layer and the positive electrode current collector layer was placed on an aluminum plate (support) having a thickness of 3 mm with the negative electrode current collector layer facing down. This laminate was immersed in a pressurized medium as shown in FIG. 2 in a vacuum laminate pack state for each aluminum plate. Next, a hydrostatic pressure of 980 MPa was applied to the laminate by applying a pressure in the pressurized medium from above. After that, take out the laminate from the vacuum laminate pack and measure the total volume (V ₉₈₀ ) of the negative electrode layer, the solid electrolyte layer, and the positive electrode layer with a size of φ13 mm in these layers and measure the film thickness and weight with a film thickness meter and a scale, respectively. was measured and calculated using

By calculating the value of {(V _p -V ₉₈₀ ) / V _p × 100} from the measured values obtained above, the porosity based on V ₉₈₀ was obtained.

- Measurement of cycle retention rate -

A solid battery was placed in a constant temperature bath at 25° C., and charging and discharging were performed at a current density of 0.5 mA/cm ² and 4V-2.5V. The discharge capacity of the first cycle was 100%, and the ratio of the discharge capacity of the 50th cycle was calculated as the cycle maintenance rate.

- cell resistance -

A solid battery was placed in a constant temperature bath at 25° C., and charging and discharging were performed at a current density of 0.5 mA/cm ² and 4V-2.5V. Impedance (cell resistance) was measured in the state of charge of the fifth cycle.

- Initial discharge capacity -

A solid battery was placed in a constant temperature bath at 25° C., and charging and discharging were performed at a current density of 0.5 mA/cm ² and 4V-2.5V. The ratio of the initial discharge capacity when the initial discharge capacity of the solid battery in the case of consolidation using a hydrostatic pressure of 980 MPa (Example 5) was set to 100% was calculated.

- Measurement result -

Table 1 shows the measurement results of the solid batteries according to Examples 1 to 5 and Comparative Examples 1 to 6.

hydrostatic pressure
[MPa] porosity
[%] cycle maintenance
[%] cell resistance
[Ω] Initial discharge capacity
[%] Comparative Example 1 0 32.4 0.0 0 Comparative Example 2 75 16.5 23.4 816 28 Comparative Example 3 150 13.2 40.7 654 42 Comparative Example 4 225 10.6 55.3 382 52 Comparative Example 5 300 7.7 66.8 243 64 Comparative Example 6 375 6.0 73.5 198 69 Example 1 455 3.0 95.0 40 95 Example 2 490 1.8 96.3 38 96 Example 3 525 1.2 96.8 31 98 Example 4 675 0.6 97.0 29 99 Example 5 980 0.0 98.0 27 100

In addition, the relationship between the initial discharge capacity and the porosity based on V ₉₈₀ is shown in FIG. 4 , the relationship between the cell resistance and the porosity based on V ₉₈₀ is shown in FIG. 5 , and the cycle maintenance ratio and V ₉₈₀ are shown in FIG. The relationship with the porosity as a reference is shown in FIG. 6 .

From the results of Examples 1 to 5 shown in Table 1, it was confirmed that when compaction was performed at a hydrostatic pressure of 455 MPa or more, the porosity based on V ₉₈₀ was 3% or less.

In addition, as shown in FIG. 5 , when the porosity with respect to _V980 was 3% or less, it was confirmed that the cell resistance was significantly lower than when the porosity exceeded 3%.

In addition, as shown in FIGS. 4 and 6 , in Examples 1 to 5 in which the porosity with respect to V ₉₈₀ is 3% or less, the initial discharge capacity is larger than Comparative Examples 1 to 6, and also discharges after 50 cycles of charging and discharging. It was also confirmed that the capacity was well maintained.

In addition, from the results for Comparative Examples 1 to 6, it was confirmed that as the hydrostatic pressure of the consolidation treatment decreased, the cell resistance increased, the initial discharge capacity decreased, and the cycle maintenance rate decreased.

As described above, the solid-state battery according to the present embodiment can be applied to various portable devices, vehicles, and the like.

An exemplary embodiment has been described in detail above with reference to the accompanying drawings, but the present inventive concept is not limited to these examples. It is obvious that those with ordinary knowledge in the technical field to which this creative idea belongs can derive various changes or modifications within the scope of the technical idea described in the claims, and these are of course also the technical scope of this creative idea will belong to

Claims (20)

positive electrode current collector layer;
a negative electrode layer including an anode active material;
a positive electrode layer comprising a positive electrode active material; and
and a sulfide-based solid electrolyte layer disposed between the cathode layer and the anode layer so as to be in contact with the cathode layer and the anode layer, respectively,
The positive electrode layer is in contact with the positive electrode current collector layer,
The planar area of the anode layer is smaller than the planar area of the cathode layer and the solid electrolyte layer,
The planar shape of the anode layer is disposed inside the planar shape of the cathode layer and the solid electrolyte layer,
A solid-state battery satisfying Equation 1 below:
<Equation 1>
{(V _p -V ₉₈₀ ) / V _p × 100} < 1.8%
In the above formula,
V _p is the total volume of the cathode layer, the anode layer and the solid electrolyte layer,
V ₉₈₀ is the total volume of the negative electrode layer, the positive electrode layer and the solid electrolyte layer under a pressure of 980 MPa. The solid-state cell of claim 1 , wherein the pressure is hydrostatic pressure. The solid battery according to claim 1, wherein the pressure at which Vp satisfying Equation (1) is obtained is greater than 490 MPa. The solid battery according to claim 1, wherein the negative electrode layer, the positive electrode layer, and the solid electrolyte layer are each made of powder. The solid battery of claim 1, wherein the negative electrode layer, the positive electrode layer and the solid electrolyte layer are consolidated. The solid battery according to claim 1, wherein the solid electrolyte layer is made of a sulfide-based solid electrolyte containing at least lithium, phosphorus, and sulfur. The solid battery according to claim 1, wherein the solid electrolyte comprises Li ₂ SP ₂ S ₅ . The solid battery according to claim 1, wherein the pressure applied to the negative electrode layer, the positive electrode layer, and the solid electrolyte layer from the outside in the atmosphere is equal to or lower than atmospheric pressure. According to claim 1, 25 ℃ of the solid battery, a current density of 0.5mA/cm ² When charging and discharging between 4V-2.5V, the discharge capacity in the 50th cycle with respect to the discharge capacity in the first cycle is 96 % solid cells. The solid battery according to claim 1, wherein the cell resistance after charging in the fifth cycle is less than 38Ω when charging and discharging between 25° C., 0.5mA/cm ² , and 4V-2.5V of the solid battery. The method according to claim 1, wherein at 25° C. of the solid battery, a current density of 0.5 mA/cm ² , and charging and discharging between 4V-2.5V, {(V _p -V ₉₈₀ )/V _p ×100}=0% A solid cell with an initial discharge capacity of more than 96% of {(V _p -V ₉₈₀ ) /V _p ×100} <1.8% for the discharge capacity of the solid cell. delete The solid battery according to claim 1, wherein the positive electrode layer, the negative electrode layer and the solid electrolyte layer are consolidated by pressing. The solid cell of claim 1 , wherein the solid cell is an all solid cell. The solid battery according to claim 1, wherein the solid battery is an alkali ion secondary battery. 16. A method for manufacturing a solid battery according to any one of claims 1 to 11 and 13 to 15, comprising:
manufacturing a solid battery satisfying Equation 1 below, comprising a step of consolidating the laminate by applying pressure to a laminate having a negative electrode layer, a positive electrode layer, and a solid electrolyte layer formed between the negative electrode layer and the positive electrode layer; Way:
<Equation 1>
{(V _p -V _r ) / V _p × 100} < 1.8%
In the above formula,
V _p is the total volume after consolidation of the negative electrode layer, the positive electrode layer and the solid electrolyte layer,
V ₉₈₀ is the volume when a pressure of 980 MPa is applied to all of the negative electrode layer, the positive electrode layer and the solid electrolyte layer. 17. The method of claim 16, wherein the pressure is hydrostatic pressure. The method according to claim 16, wherein in the step of consolidating the laminate, hydrostatic pressure is applied to the laminate formed on a support made of a rigid plate, so that a portion of the laminate in contact with the support and a portion not in contact with the support are mutually A method of manufacturing a solid battery that applies different hydrostatic pressures. The method for manufacturing a solid battery according to claim 18, wherein, in the step of consolidating the laminate, the hydrostatic pressure applied to a portion of the laminate that is not in contact with the support is set to more than 490 MPa. The method of claim 16, wherein the pressure is applied by a press.

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