JP6936661B2 - Manufacturing method of all-solid-state battery - Google Patents

Description

The present invention relates to a method for manufacturing an all-solid-state battery including a solid electrolyte layer.

Among various secondary batteries being developed, the lithium ion secondary battery (LIB), which can easily obtain a high energy density, is the most promising. On the other hand, with the expansion of battery applications, large batteries such as automobile batteries and stationary batteries are attracting attention. Ensuring safety is even more important for large batteries than for small batteries. An all-solid-state battery using an inorganic solid electrolyte is expected to be easier to secure safety and to have a higher capacity even if the size is increased, as compared with a LIB using an electrolytic solution.

An all-solid-state battery generally includes a positive electrode, a negative electrode, and a group of electrodes having a solid electrolyte layer interposed between them. The solid electrolyte layer contains a solid electrolyte, and the positive electrode and the negative electrode contain an active material and a solid electrolyte, respectively. In an all-solid-state battery, all charge / discharge reactions occur at the interface between solids. Therefore, in an all-solid-state battery, unlike a battery using an electrolytic solution, the contact resistance at the interface between solids greatly affects the performance of the battery.

Patent Document 1 proposes the use of a sulfide-based solid electrolyte for the positive electrode and the electrolyte layer from the viewpoint of enhancing the output characteristics of the all-solid LIB. In Patent Document 1, a positive electrode mixture is placed on an electrolyte layer formed by pressure molding and further pressure molded, and an indium foil is placed on the side of the electrolyte layer opposite to the positive electrode mixture to produce a battery. There is.

Japanese Unexamined Patent Publication No. 2010-24039

However, in Patent Document 1, since the positive electrode mixture is merely pressure-molded on the electrolyte layer, the contact resistance at the interface between the solid and the solid, such as the interface between the active material particles and the solid electrolyte particles, is reduced. Has its limits.

One aspect of the present invention is a first step of assembling an all-solid-state battery including an electrode group including a positive electrode, a solid electrolyte layer, and a negative electrode.
The second step of heating the all-solid-state battery at a temperature of 80 ° C. or higher in an uncharged state, and
After the second step, a third step of cooling the all-solid-state battery to a temperature of 45 ° C. or lower in an uncharged state is provided.
The solid electrolyte layer and at least one of the positive electrode and the negative electrode each contain a solid electrolyte.
In the first step, a laminate in which the positive electrode, the solid electrolyte layer, and the negative electrode are laminated is formed, and the laminate is pressurized.
The present invention relates to a method for producing an all-solid-state battery, wherein in the second step, the temperature at which the all-solid-state battery is heated is lower than the temperature at which the phase transition, the glass transition, or the chemical change of the solid electrolyte occurs.

In the all-solid-state battery obtained by the manufacturing method according to the above aspect, high output can be ensured and high cycle characteristics can be ensured.

It is a vertical cross-sectional view which shows typically the electrode group included in the all-solid-state battery obtained by the manufacturing method which concerns on one Embodiment of this invention.

The method for manufacturing an all-solid-state battery according to an embodiment of the present invention includes a step of assembling an all-solid-state battery including an electrode group including a positive electrode, a solid electrolyte layer, and a negative electrode (first step), and an all-solid-state battery. A step of heating at a temperature of 80 ° C. or higher in an uncharged state (second step), and a step of cooling the all-solid-state battery to a temperature of 45 ° C. or lower in an uncharged state after the second step (third step). , Equipped with. The solid electrolyte layer and at least one of the positive electrode and the negative electrode each contain a solid electrolyte. In the first step, a laminate in which the positive electrode, the solid electrolyte layer, and the negative electrode are laminated is formed, and the laminate is pressurized. In the second step, the temperature at which the all-solid-state battery is heated is lower than the temperature at which the phase transition, glass transition, or chemical change of the solid electrolyte occurs.

In the electrodes and the solid electrolyte layer of the all-solid-state battery, the solid electrolyte generally exists in the form of particles, and the active material particles and the solid electrolyte particles are in contact with each other. Since there is no electrolytic solution in the all-solid-state battery, the contact resistance at the interface between the solid electrolyte particles and the solid electrolyte particles and the active material particles tends to affect the output and the capacity.

In the present embodiment, when assembling the all-solid-state battery, the laminate in which the positive electrode, the solid electrolyte layer and the negative electrode are laminated is pressed, and the assembled all-solid-state battery is heated to 80 ° C. or higher and the solid electrolyte in an uncharged state. Heat at a temperature lower than the temperature at which the phase transition, glass transition, or chemical change occurs. Therefore, the solid electrolyte particles can be appropriately and slowly blended in a state where the solid electrolyte particles are in contact with each other or the solid electrolyte particles and the active material particles are in contact with each other or in close proximity to each other. As a result, the solid electrolyte particles or the solid electrolyte particles and the active material particles can be brought into close contact with each other. Therefore, high output can be secured. In order to secure high output, it is also important to pressurize the laminate to reduce the voids in each layer as much as possible so that the solid electrolyte particles or the solid electrolyte particles and the active material particles are in contact with each other or in close contact with each other. Is. By heating at the above temperature in such a state, it becomes possible to blend the solid electrolyte particles with each other or the solid electrolyte particles and the active material particles. In this way, the contact state between the solids is improved. Further, by cooling the uncharged all-solid-state battery to 45 ° C. or lower after heating, the composition of the solid electrolyte particles and the active material particles may be changed or altered, or the interface between the solid electrolyte particles and the active material particles may be secondary. The reaction is suppressed. Therefore, it becomes easy to secure a high discharge capacity even after repeating the charge / discharge cycle, and it is possible to suppress the deterioration of the cycle characteristics.

Even if the all-solid-state battery once charged is subjected to the heating step, the output does not improve. Further, if the heated all-solid-state battery is charged and discharged without being cooled, the output may be lowered, and the charge / discharge efficiency and the cycle characteristics may be lowered. This is because when the all-solid-state battery, which is heated in the charged state, is charged and discharged without cooling, a side reaction occurs during charging, which increases resistance and releases oxygen from the active material. This is thought to be due to the deterioration of the material and the change or alteration of the composition of the electrolyte and active material due to the action of heat. Therefore, in the present embodiment, it is important to heat the uncharged all-solid-state battery and to cool the heated all-solid-state battery in the uncharged state.

An uncharged all-solid-state battery is an all-solid-state battery that has never been charged. Generally, an all-solid-state battery is subjected to a break-in charge / discharge (preliminary charge / discharge) before being charged / discharged. The uncharged all-solid-state battery in the present specification is an all-solid-state battery before running-in charging and discharging.

The temperature at which a phase transition, glass transition, or chemical change of a solid electrolyte occurs is the temperature at which a phase transition such as crystallization, transition melting, etc. of the solid electrolyte occurs, the glass transition point, or various chemical changes (eg, thermal decomposition, combustion, etc.). It means the temperature at which oxidation, reduction, etc. occur. That is, in the present embodiment, the all-solid-state battery is heated at a temperature at which these transitions and changes do not occur.

The method for manufacturing the all-solid-state battery according to the present embodiment will be described in more detail below.
The method for manufacturing an all-solid-state battery includes a first step of assembling the all-solid-state battery, a second step of heating the uncharged all-solid-state battery, and a third step of cooling the heated all-solid-state battery in the uncharged state. Be prepared.

(First step)
In the first step, for example, an all-solid-state battery is assembled by accommodating a group of electrodes in a battery case.
The electrode group is formed by forming a laminate in which a positive electrode, a solid electrolyte layer, and a negative electrode are laminated, and pressurizing the laminate. The order of forming the electrodes and the solid electrolyte layer is not particularly limited. For example, the laminate is prepared by forming a solid electrolyte layer, then forming one electrode of a positive electrode and a negative electrode on one main surface of the solid electrolyte layer, and forming the other electrode on the other main surface. You may. Further, a laminate may be produced by forming one electrode of a positive electrode and a negative electrode, forming a solid electrolyte layer on the one electrode, and forming the other electrode on the solid electrolyte layer. The mold is filled with the material of one of the positive electrode and the negative electrode, the material of the solid electrolyte layer is filled therein, and the material of the other electrode is filled therein, and the laminate is compressed. Alternatively, an electrode group) may be formed.

In the present embodiment, the solid electrolyte layer and at least one of the positive electrode and the negative electrode each contain a solid electrolyte. Then, in the process of assembling the all-solid-state battery, a laminate of the positive electrode, the solid electrolyte layer, and the negative electrode is formed, and the laminate is pressurized. Therefore, prior to the heating step of the battery, it becomes easy to bring the solid electrolyte particles into contact with each other or the solid electrolyte particles and the active material particles contained in the electrode.

In the first step, an electrode group may be formed by pressurizing the laminated body, and the formed electrode group may be housed in the battery case. The battery case may be housed in the battery case and then the laminated body is pressurized. A group of electrodes may be formed within. For example, when the battery case is a laminated film or the like, the laminated body may be pressurized together with the battery case after the laminated body is housed in the battery case.

The pressure when pressurizing the laminate is, for example, 200 MPa or more, and from the viewpoint of further enhancing the adhesion between the solid electrolyte layer and the positive electrode and / or the negative electrode, it is preferably 300 MPa or more or 500 MPa or more, preferably 700 MPa or more. Alternatively, it is more preferably 900 MPa or more. The upper limit of the pressure is not particularly limited, but is, for example, 1500 MPa or less. When the pressurization is performed a plurality of times, the pressurization may be performed at the same pressure, or the pressure may be changed. When the pressurization is performed a plurality of times, for example, the pressurizing pressure may be gradually increased.

One end of the lead is connected to the positive electrode and the negative electrode of the electrode group, respectively. The other end of the lead is electrically connected to an external terminal exposed to the outside of the battery case.
The configuration of the electrode group will be described in more detail below.

(electrode)
The solid electrolyte may be contained in at least one of the positive electrode and the negative electrode, but if it is contained in both of them, the effect of reducing the contact resistance between the particles in the second step can be easily obtained. In particular, in the positive electrode, the potential is likely to change due to resistance, so that the effect of the second step is likely to appear remarkably.

The positive electrode and the negative electrode each usually include an electrode mixture containing an active material and a solid electrolyte. Each of these electrodes can be obtained by forming an electrode mixture and applying pressure. An electrode may be formed by forming an electrode mixture layer on the surface of the current collector. The film formation can be carried out by a known procedure, but a dry film formation is preferable because it is simple and cost-effective.

The pressurization of the electrode mixture layer is preferably performed at a pressure of 100 MPa or more, more preferably 150 MPa or more. The upper limit of the pressure at this time is not particularly limited, but since the laminated body is pressurized with the above pressure, the pressure may be less than 200 MPa. The pressurization of the electrode mixture layer may be performed at least once, or may be performed a plurality of times. When the pressurization is performed a plurality of times, the pressurization may be performed at the same pressure, or the pressure may be changed. For example, when the electrode mixture layer of the other electrode is formed on the solid electrolyte layer after laminating one electrode and the solid electrolyte layer, the laminate is formed after being pressed with such a pressure once. It is preferable to form an electrode group by pressurizing with the above-mentioned pressure (pressure of 200 MPa or more).

(Active material)
As the active material used for the positive electrode, those used as the positive electrode active material in the all-solid-state battery can be used without particular limitation. Taking an all-solid LIB as an example, examples of the positive electrode active material include lithium-containing oxides containing, for example, cobalt, nickel, and / or manganese [for example, lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO). ₂ ), Lithium nickel cobalt oxide (LiNi _0.85 Co _0.15 O ₂ etc.), Lithium nickel cobalt manganate (LiNi _1/3 Co _1/3 Mn _1/3 O ₂ etc.), Lithium manganate (spinnel type lithium manganate (such as spinel type lithium manganate) LiMn ₂ O ₄ etc.), etc.], oxides such as complex oxides with excess Li (Li ₂ MnO _3- LiM ¹ O ₂ ), and compounds other than oxides can also be mentioned. Examples of compounds other than oxides include olivine compounds (LiM ¹ PO ₄ ) and sulfur-containing compounds (Li ₂ S, etc.). In the above formula, M ¹ represents a transition metal. The positive electrode active material may be used alone or in combination of two or more. From the viewpoint that a high capacity can be easily obtained, a lithium-containing oxide containing at least one selected from the group consisting of Co, Ni and Mn is preferable. The lithium-containing oxide may further contain a main group element such as Al. Examples of the lithium-containing oxide containing Al include aluminum-containing lithium nickel cobalt oxide.

Among the positive electrode active materials, a lithium-containing oxide containing Ni is preferable from the viewpoint of stability of the crystal structure, reduction of charge / discharge hysteresis, and easy increase of electron conductivity. Examples of such a positive electrode active material include oxides represented by _{the formula (1): Li 1 + x} ( _Ny1 M _1-y1 ) _1-x O _2. In formula (1), M is at least one selected from the group consisting of Co, Mn, Fe, and Al, and contains Co as an essential component. It is preferable that x is 0 ≦ x ≦ 1/3. When x is in such a range, the capacity of the metal oxide can be increased and charging / discharging can be stably performed. The molar ratio y1 of Ni to the total of Ni and M satisfies 0.2 ≦ y1 ≦ 0.9. The element M preferably contains Co and / or Al, and may contain Co and / or Al and other elements. The element M is preferably composed of only Ni, and is also preferably a combination of Ni and Co, Mn, Fe, and / or Al.

In the above formula (1), the metal oxide is described as carbon dioxide, but the oxygen coefficient “2” may be “2 ± δ”, and the oxygen coefficient is 2 ± δ ( A) and the metal oxide of the formula (1) are also included in the present embodiment. Here, δ is an excess oxygen amount or an oxygen deficiency amount, and is, for example, 0 to 0.2.

Specific examples of the metal oxide of the formula (1) include _{Li 1 + x} (Ni _0.8 Co _0.15 Al _0.05 ) _1-x O _2, LiNi _1/3 Co _1/3 such as _{LiNi 0.8} Co _0.15 Al _0.05 O _2. Examples thereof include Mn _1/3 O _{2, LiNi 0.5} Co _0.2 Mn _0.3 O ₂ , LiNi _0.6 Co _0.2 Mn _0.2 O _2, LiNi _0.8 Co _0.1 Mn _0.1 O _2.

As the active material used for the negative electrode, a known negative electrode active material used in an all-solid-state LIB can be used. Taking an all-solid LIB as an example, examples of the negative electrode active material include a carbonaceous material capable of inserting and desorbing lithium ions, a metal capable of alloying and dealloying lithium ions, and the like. Examples include simple substances of semi-metals, alloys, or compounds. Examples of the carbonaceous material include graphite (natural graphite, artificial graphite, etc.), hard carbon, amorphous carbon, and the like. Examples of simple substances and alloys of metals and semimetals include lithium metals, alloys, and Si alone. Examples of the compound include oxides, sulfides, nitrides, hydrides, VDD (lithium silicide and the like) and the like. Examples of the oxide include titanium oxide and silicon oxide. As the negative electrode active material, one type may be used alone, or two or more types may be used in combination. For example, a silicon oxide and a carbonaceous material may be used in combination. Among the negative electrode active materials, graphite is preferable, and coated particles containing graphite particles and amorphous carbon that coats the graphite particles may be used.

Since the particles of the carbonaceous material such as graphite are relatively hard, it is generally difficult to reduce the contact resistance with the solid electrolyte particles. However, in the present embodiment, since the all-solid-state battery is heated by the second step, the carbonaceous material is used. Even when the particles of the material are used, the compatibility with the solid electrolyte particles can be improved.

(Solid electrolyte)
As the solid electrolyte used for the electrode (specifically, the electrode mixture layer), a solid electrolyte exhibiting ionic conductivity is used. As the solid electrolyte, an inorganic solid electrolyte such as a sulfide (sulfide-based solid electrolyte) or a hydride (hydride-based solid electrolyte) is preferable. The hydride also includes a solid electrolyte, commonly referred to as a complex hydride.

The temperature at which the solid electrolyte undergoes a phase transition, a glass transition, or a chemical change is, for example, greater than 210 ° C and may be 220 ° C or higher.

The solid electrolyte will be described by taking the case of an all-solid LIB as an example. For example, at least selected from the group consisting of Li, S, Group 13 element, Group 14 element, and Group 15 element of the periodic table. Those containing one kind of element (for example, sulfide) are preferable. The elements of Groups 13 to 15 of the periodic table are not particularly limited, and examples thereof include P, Si, Ge, As, Sb, and Al, and P, Si, and Ge are preferable. Of these, a solid electrolyte containing Li, P, and S (for example, a sulfide) is preferable.

Examples of the sulfide, and Li ₂ S, Group 13 elements of the periodic table, Group 14 elements, and at least one or more kinds of sulfides containing one element selected from the group consisting of Group 15 Those containing and are preferable. Specific examples of sulfides include Li ₂ S-SiS ₂ , Li ₂ S-P ₂ S ₅ , Li ₂ S-GeS ₂ , Li ₂ S-B ₂ S ₃ , Li ₂ S-Ga ₂ S ₃ , Li. ₂ S-Al ₂ S ₃ , Li ₂ S-GeS _2- P ₂ S ₅ , Li ₂ S-Al ₂ S _3- P ₂ S ₅ , Li _{2 SP 2} S ₃ , Li ₂ SP ₂ S _3- P ₂ S ₅ , LiX-Li ₂ S-P ₂ S ₅ , LiX-Li ₂ S-SiS ₂ , LiX-Li _{2 SB 2} S ₃ (X: I, Br, Cl, or I), etc. Can be mentioned.

Examples of the hydride include a complex hydride of lithium borohydride. Examples of the complex hydride include LiBH _4- LiI-based complex hydride, LiBH _4- LiNH _2- based complex hydride, LiBH _4- P ₂ S ₅ , LiBH _4- P ₂ I _{4 and the} like.
As the solid electrolyte, one type may be used alone, or two or more types may be used in combination, if necessary.
The solid electrolytes contained in the positive electrode and the negative electrode may be of the same type or may be different.

If necessary, known components used in the electrodes in all-solid-state batteries, such as binders, conductive auxiliaries, and other additives, may be added to each electrode.

The current collector can be used without particular limitation as long as the metal ions do not elute and diffuse into the electrode material or the solid electrolyte at a high temperature. Examples of the form of such a current collector include a metal foil, a plate-like body, an aggregate of powders, and the like, and a film formed of a material of the current collector may be used. The metal foil may be an electrolytic foil, an etched foil, or the like. It is desirable that the current collector has a strength that does not wavy or tear when forming the electrode mixture layer or the active material layer.

Examples of the material of the current collector used for the positive electrode include materials stable at the redox potential of the positive electrode, for example, aluminum, magnesium, stainless steel, titanium, iron, cobalt, zinc, tin, or alloys thereof. .. Examples of the material of the current collector used for the negative electrode include materials stable at the redox potential of the negative electrode, such as copper, nickel, stainless steel, titanium, and alloys thereof.

The thickness of the current collector can be appropriately selected from the range of, for example, 5 μm to 300 μm. The thickness of the current collector is preferably 10 μm to 50 μm.

(Solid electrolyte layer)
The solid electrolyte layer contains a solid electrolyte. The solid electrolyte layer can be formed by forming a solid electrolyte film and applying pressure. The solid electrolyte can be formed by a known procedure, but from the viewpoint of easily ensuring high ionic conductivity, a dry film formation is preferable, and it is preferable not to use a binder such as a resin during the film formation. ..

The pressure of the solid electrolyte layer is preferably, for example, 100 MPa or more, and more preferably 150 MPa or more. The upper limit of the pressure at this time is not particularly limited, but since the laminated body is pressurized with the above pressure, the pressure may be less than 200 MPa. The pressurization of the solid electrolyte layer may be performed at least once, or may be performed a plurality of times. When the pressurization is performed a plurality of times, the pressurization may be performed at the same pressure, or the pressure may be changed. For example, when both electrodes are formed first and a solid electrolyte layer is formed between the electrodes, both electrodes and a solid electrolyte film arranged between these electrodes are once pressed at such a pressure. After pressurizing, it is preferable to form an electrode group by pressurizing the formed laminate at the above-mentioned pressure (pressure of 200 MPa or more).

Examples of the solid electrolyte include solid electrolytes exemplified for electrodes, and sulfides and hydrides are preferable.
The solid electrolyte used may be the same for the positive electrode and / or the negative electrode, and may be different from any electrode.

If necessary, a known additive used for the solid electrolyte layer of the all-solid-state battery may be added to the solid electrolyte layer. From the viewpoint of ensuring high ionic conductivity in the solid electrolyte layer, it is preferable to prepare the solid electrolyte layer without using an organic component such as a dispersion medium or a binder, as in the case of the electrode mixture layer.
The thickness of the solid electrolyte layer is, for example, 20 μm to 200 μm.

(Second step)
In the second step, the uncharged all-solid-state battery is heated at a temperature of 80 ° C. or higher and lower than the temperature at which the phase transition, glass transition, or chemical change of the solid electrolyte occurs. When heated at a temperature higher than the temperature at which the phase transition, glass transition, or chemical change of the solid electrolyte occurs, the solid electrolyte is altered at the interface between the solid electrolyte particles and the interface between the active material particles and the solid electrolyte particles, and by-products are generated. It happens. As a result, the resistance at the interface becomes high, and the output cannot be improved.

Although it depends on the type of solid electrolyte, the heating temperature is preferably 100 ° C. or higher. Further, from the viewpoint of easily improving the contact state between the solid electrolyte particles and between the solid electrolyte particles and the active material particles, the heating temperature is higher than the temperature at which the phase transition, the glass transition, or the chemical change of the solid electrolyte occurs. It may be as low as possible, but the temperature is preferably 5 ° C. or higher or 10 ° C. or higher, and more preferably 50 ° C. or higher or 100 ° C. or higher. For the same reason, the heating temperature is preferably 210 ° C. or lower or 200 ° C. or lower, and more preferably 150 ° C. or lower or 120 ° C. or lower. These lower limit values and upper limit values can be arbitrarily combined. The heating temperature may be, for example, 80 ° C. or higher and 210 ° C. or lower, 80 ° C. or higher and 200 ° C. or lower, 80 ° C. or higher and 150 ° C. or lower, or 80 ° C. or higher and 120 ° C. or lower. The heating temperature is preferably lower than the melting point or decomposition temperature of the constituent members of the all-solid-state battery (for example, resin members such as insulating materials, packages, and sealants).

The heating of the all-solid-state battery may be performed under pressure. The pressure when pressurizing the all-solid-state battery is, for example, 0.5 MPa or more and 100 MPa or less, preferably 1 MPa or more and 80 MPa or less, and further preferably 10 MPa or more and 80 MPa or less or 30 MPa or more and 80 MPa or less. When the all-solid-state battery is heated while applying such pressure, the adhesion between the solid electrolyte particles and the solid electrolyte particles and the active material particles tends to increase, which is advantageous in reducing the contact resistance.

The time for heating the all-solid-state battery may be appropriately determined within a range in which the solid electrolyte particles or the solid electrolyte particles and the active material particles can be blended with each other. The heating time is, for example, 0.5 hour to 10 hours, preferably 1 hour to 6 hours, and more preferably 1 hour to 4 hours.

(Third step)
In the third step, the all-solid-state battery heated in the second step is cooled in an uncharged state. By cooling the heated battery before charging and discharging, including pre-charging and discharging, it is possible to suppress side reactions and suppress composition changes and alterations of solid electrolyte particles and / or active material particles. can.

The cooling temperature may be 45 ° C. or lower, preferably 40 ° C. or lower, and more preferably room temperature (for example, 10 ° C. or higher and 35 ° C. or lower) or lower. By cooling the all-solid-state battery to such a temperature, it is possible to suppress side reactions, composition changes and alterations of the solid electrolyte particles and / or the active material particles. The lower limit of the cooling temperature is not particularly limited, but is, for example, 10 ° C. or higher.

In the manufacturing method according to the present embodiment, in the electrode group of the all-solid-state battery, the solid electrolyte particles contained in the electrodes and the solid electrolyte layer or the solid electrolyte particles are formed by pressurizing the laminate of the positive electrode, the solid electrolyte layer, and the negative electrode. And the active material particles are in contact with or close to each other. Then, the particles in contact or close contact with each other can be appropriately adapted when heating the uncharged battery, and the solid electrolyte particles and the solid electrolyte particles and the active material particles can be brought into close contact with each other. .. Therefore, in the all-solid-state battery obtained by such a manufacturing method, the contact resistance at the interface between the solid electrolyte particles and the interface between the solid electrolyte particles and the active material particles is reduced, and a high output can be obtained. Further, by cooling the heated all-solid-state battery in an uncharged state, side reactions can be suppressed, and composition changes and alterations of solid electrolyte particles and active material particles can be suppressed. Therefore, in the all-solid-state battery, high cycle characteristics can be ensured. The present embodiment also includes an all-solid-state battery obtained by such a manufacturing method.

FIG. 1 is a vertical cross-sectional view schematically showing a group of electrodes included in an all-solid-state battery obtained by the manufacturing method according to the present embodiment. The electrode group 1 included in the all-solid-state battery includes a positive electrode 2, a negative electrode 4, and a solid electrolyte layer 3 interposed between them. The positive electrode 2 includes a positive electrode current collector 2b and a positive electrode mixture layer 2a supported on the current collector 2b. The negative electrode 4 includes a negative electrode current collector 4b and a negative electrode mixture layer 4a supported on the negative electrode current collector 4b. The positive electrode 2 and the negative electrode 4 are arranged so that the positive electrode mixture layer 2a and the negative electrode mixture layer 4a face each other. The solid electrolyte layer 3 is arranged between the positive electrode mixture layer 2a and the negative electrode mixture layer 4a. The positive electrode 2, the solid electrolyte layer 3, and the negative electrode 4 contain a solid electrolyte. In the positive electrode 2, the solid electrolyte layer 3 and the negative electrode 4, the solid electrolyte particles, the solid electrolyte particles and the active material particles are blended with each other by the pressurization of the laminate of the positive electrode, the solid electrolyte layer and the negative electrode and the heating step described above. The contact state at the interface between particles is improved, and the contact resistance is reduced.

The positive electrode mixture layer 2a, the negative electrode mixture layer 4a, and the solid electrolyte layer 3 in FIG. 1 have a disk shape having substantially the same size, and are laminated with the solid electrolyte layer 3 sandwiched between them. Is forming. An insulator 5 is mounted on the side surface of the laminate 6 so as to cover the side surface of the negative electrode mixture layer 4a and the side surface of the solid electrolyte layer 3 on the negative electrode mixture layer 4a side. The positive electrode current collector 2b and the negative electrode current collector 4b are circular or polygonal (square or the like) metal foils having a size larger than that of the positive electrode mixture layer 2a and the negative electrode mixture layer 4a. The positive electrode current collector 2b and the negative electrode current collector 4b are formed so as to have substantially the same size as the laminated body 6 with the insulator 5 attached.

The all-solid-state battery is not limited to the example shown in FIG. 1, and may be of various types such as a round type, a cylindrical type, a square type, and a thin layer flat type. The electrode group may include a plurality of positive electrodes and / or a plurality of negative electrodes.

[Example]
Hereinafter, the present invention will be specifically described based on Examples and Comparative Examples, but the present invention is not limited to the following Examples.

Example 1
An all-solid-state battery having the electrode group shown in FIG. 1 was produced by the following procedure.
(1) Assembly of all-solid-state battery (a) Preparation of solid electrolyte layer 3 A cylindrical mold (inner diameter 10 mm, height 30 mm) made of cold die steel (SKD) is erected and installed, and a bottom plate is placed on the bottom of the cylindrical mold. I inserted a short pin. _{In this state, 90 mg of a Li 2 SP 2} S ₅ solid solution, which is a lithium ion conductive solid electrolyte, was packed in a layer in a cylindrical mold. Then, a long columnar pin having a size matching the inner diameter of the cylindrical die is inserted into the inside from the top of the cylindrical die, and the solid electrolyte layer is pressed once at a pressure of 188 MPa in the thickness direction of the layer. 3 was prepared.

(B) Preparation of Negative Electrode Mixture Layer 4a Graphite and Li _{2 SP 2} S ₅ solid solution were thoroughly mixed in a mortar using a mass ratio of 6: 4. 15 mg of the obtained mixture was layered on the solid electrolyte layer 3 in the cylindrical mold prepared in (a). Then, the negative electrode mixture layer 4a was produced by pressurizing and pressing three times in the thickness direction of the layer. The pressure of the pressure press was 188 MPa each time.

Next, the short pin was taken out with the cylindrical mold turned upside down, the short pin was inserted into the negative electrode mixture layer 4a side, and the cylindrical mold was arranged so that the short pin was at the bottom. Next, the solid electrolyte layer 3 and the negative electrode mixture layer 4a were pressed from the solid electrolyte layer 3 side using a long pin.

(C) Preparation of positive electrode mixture layer 2a LiNi _0.8 Co _0.15 Al _0.05 O ₂ and Li _{2 SP 2} S ₅ solid solution are used in a mass ratio of 7: 3 and mixed thoroughly in a mortar to form a mixture. Got 20 mg of the mixture is packed in a layer on the solid electrolyte layer 3 in the cylindrical die described later, and pressure-pressed three times in the order of 376 MPa, 752 MPa, and 1050 MPa in the thickness direction of the layer to obtain a positive electrode ( A positive electrode mixture layer 2a) was produced.

(D) Assembly of an all-solid-state battery A cylindrical laminate 6 in a state in which the solid electrolyte layer 3 is sandwiched between the positive electrode mixture layer 2a and the negative electrode mixture layer 4a formed as in (a) to (c). Removed from the mold. An insulator 5 (inner diameter 11 mm, height 200 μm) having a hole in the center was arranged on one surface of a stainless steel plate (length 40 mm × width 40 mm, thickness 300 μm) as the negative electrode current collector 4b. Then, the laminated body 6 (outer diameter 10 mm) was housed in the hole of the insulator 5 so that the negative electrode mixture layer 4a was in contact with the negative electrode current collector 4b. Next, the electrode group 1 was produced by arranging a stainless steel plate (length 40 mm × width 40 mm, thickness 300 μm) as the positive electrode current collector 2b on the positive electrode mixture layer 2a of the laminated body 6. The insulator 5 is arranged so as to suppress contact between the negative electrode mixture layer 4a and the negative electrode current collector 4b and the positive electrode mixture layer 2a and the positive electrode current collector 2b.

The electrode group 1 was housed in a laminated cell having a negative electrode lead and a positive electrode lead, and the gas in the cell was sealed while being sucked by a vacuum pump. In this way, an all-solid-state battery was produced.

(2) Heating and cooling of the all-solid-state battery The uncharged all-solid-state battery produced in (1) above is pressurized at 58.8 MPa and allowed to stand still in a constant temperature bath set at a temperature of 100 ° C. for 3 hours. Heated by placing. After heating, the uncharged all-solid-state battery was cooled to room temperature (25 ° C.).

(3) Evaluation (a) Output characteristics The all-solid-state battery obtained in (2) above is placed in a constant temperature bath set at 25 ° C., the battery temperature is maintained at 25 ° C., and the pressure is increased at 58.8 MPa. bottom. In this state, a current of 0.1 C was used to charge the battery to a final charge voltage of 4.2 V, and then a current of 0.1 C or 2.0 C was used to discharge the battery to a final discharge voltage of 2.8 V. The charge capacity (initial charge capacity) and discharge capacity (initial discharge capacity) at this time were determined.
Further, the ratio of the discharge capacity at 2.0C to the discharge capacity at 0.1C (discharge capacity retention rate) (%) was obtained and used as an index of the output characteristics. The larger this value is, the higher the output characteristic is.

(B) Cycle characteristics An all-solid-state battery is charged with a current of 0.1 C to a final charge voltage of 4.2 V, and then discharged with a current of 0.1 C to a final discharge voltage of 2.8 V. With one cycle, the ratio of the discharge capacity after 5 cycles to the initial discharge capacity (capacity retention rate after the cycle) (%) was determined.

Example 2
An all-solid-state battery was prepared and evaluated in the same manner as in Example 1 except that the uncharged all-solid-state battery was heated at 120 ° C.

Example 3
An all-solid-state battery was prepared and evaluated in the same manner as in Example 1 except that the uncharged all-solid-state battery was heated at 80 ° C.

Example 4
An all-solid-state battery was prepared and evaluated in the same manner as in Example 1 except that the uncharged all-solid-state battery was heated at 100 ° C. without pressurization.

Example 5
An all-solid-state battery was prepared and evaluated in the same manner as in Example 1 except that the uncharged all-solid-state battery was heated at 120 ° C. without pressurization.

Example 6
An all-solid-state battery was prepared and evaluated in the same manner as in Example 1 except that the uncharged all-solid-state battery was heated at 80 ° C. without pressurization.

Comparative Example 1
The evaluation was performed using the assembled battery in the same manner as in Example 1 except that the step of heating the uncharged all-solid-state battery was not performed.

Comparative Example 2
The uncharged all-solid-state battery assembled in the same procedure as in Example 1 was charged with a current of 0.1 C to a final charge voltage of 4.2 V to bring it into a fully charged state. The heating step was performed in the same manner as in Example 1 except that the fully charged all-solid-state battery was used instead of the uncharged all-solid-state battery. The same evaluation as in Example 1 was performed using a heated, fully charged all-solid-state battery. However, regarding the charge capacity and discharge capacity, a fully charged all-solid-state battery is once discharged with a current of 0.1 C up to a discharge end voltage of 2.8 V, and then a charge end voltage of 4.2 V is further applied with a current of 0.1 C. It was determined when charging to 2.8 V and then when discharging to a discharge end voltage of 2.8 V with a current of 0.1 C.

Comparative Example 3
The all-solid-state battery was charged to full charge in the same manner as in Comparative Example 2, and then discharged to a discharge end voltage of 2.8 V with a current of 0.1 C (end-of-discharge state). The heating step was performed in the same manner as in Example 1 except that the discharged all-solid-state battery was used instead of the uncharged all-solid-state battery. The same evaluation as in Example 1 was performed using a heated and discharged all-solid-state battery.
The results of Examples 1 to 6 and Comparative Examples 1 to 3 are shown in Table 1.

As shown in Table 1, the charge capacity and discharge capacity at 0.1 C are not so different between Examples 1 to 6 and Comparative Examples 1 to 3, but in the examples, the discharge capacity at 2.0 C is Comparative Example. It is much higher than the above, and the output characteristics are improved. It is considered that this is because the contact state between the solid electrolyte particles and the interface between the solid electrolyte particles and the active material particles was improved by pressurizing the electrodes and the solid electrolyte layer and heating the uncharged all-solid-state battery. Be done. Further, in the examples, a high capacity retention rate of 99.4% or more was obtained after 5 cycles of charging and discharging.

Comparative Example 4
After heating the all-solid-state battery produced in the same manner as in Example 2, the battery was placed in a constant temperature bath set at 120 ° C. without cooling, the battery temperature was maintained at 120 ° C., and the pressure was increased at 58.8 MPa. .. In this state, in (3) and (a) of Example 1, charging and discharging are performed with a current of 0.1 C, the initial charge capacity and the initial discharge capacity are measured, and the ratio of the initial discharge capacity to the initial charge capacity (0. 1C charge / discharge efficiency) (%) was determined. In addition, the cycle characteristics of (3) and (b) of Example 1 were evaluated. Further, the discharge capacity after 15 cycles of charge / discharge is obtained under the same charge / discharge conditions as in (3) and (b) of Example 1, and the initial discharge capacity is obtained in the same manner as in the case of 5 cycles of charge / discharge. The ratio (capacity retention rate) (%) was calculated.
Further, also in Example 3 above, the 0.1C charge / discharge efficiency and the capacity retention rate at the time of 15 cycle charge / discharge were determined as in the case of Comparative Example 4. The results of Comparative Example 4 and Example 3 are shown in Table 2.

As shown in Table 2, in Example 3, the capacity retention rate during 5-cycle charge / discharge is extremely high at 99.5%, and a high capacity retention rate of 98.8% is obtained even during 15-cycle charge / discharge. rice field. On the other hand, in Comparative Example 4 in which the uncharged battery was heated and then charged / discharged in the heated state, the capacity retention rate at the time of 5 cycles of charging / discharging was 91.7%, and the capacity at the time of 15 cycles of charging / discharging. The maintenance rate dropped significantly to 60.7%. As described above, in the battery of Example 3 in which the uncharged battery is heated, cooled, and then charged / discharged, high cycle characteristics can be ensured. Further, in Example 3, the initial 0.1C charge / discharge efficiency is higher than that in Comparative Example 4.

According to the manufacturing method of the present invention, an all-solid-state battery having high output and excellent cycle characteristics can be manufactured. The obtained all-solid-state battery can be charged and discharged well even at a high rate and has excellent cycle characteristics, and is therefore useful for various applications requiring high output and high cycle characteristics.

1: Electrode group 2: Positive electrode, 2a: Positive electrode mixture layer, 2b: Positive electrode current collector, 3: Solid electrolyte layer, 4: Negative electrode, 4a: Negative electrode mixture layer, 4b: Negative electrode current collector, 5: Insulation Body, 6: Laminate

Claims (8)

The first step of assembling an all-solid-state battery including an electrode group including a positive electrode, a solid electrolyte layer, and a negative electrode.
After the first step, the second step of heating the all-solid-state battery at a temperature of 80 ° C. or higher in an uncharged state, and
After the second step, a third step of cooling the all-solid-state battery to a temperature of 45 ° C. or lower in an uncharged state is provided.
The solid electrolyte layer and at least one of the positive electrode and the negative electrode each contain a solid electrolyte.
Wherein the first step includes the positive electrode, and the solid electrolyte layer, and the step of the negative electrode is pressurized at a first pressure higher than 300MPa laminates stacked, and a step of releasing the first pressure,
A method for producing an all-solid-state battery, wherein in the second step, the temperature at which the all-solid-state battery is heated is lower than the temperature at which the phase transition, glass transition, or chemical change of the solid electrolyte occurs. The method for manufacturing an all-solid-state battery according to claim 1, wherein in the second step, the all-solid-state battery is heated while pressurizing the all-solid-state battery with a second pressure. The method for manufacturing an all-solid-state battery according to claim 2, wherein the second pressure is 0.5 MPa or more and 100 MPa or less. In the second step, the temperature for heating the all-solid-state battery is 80 ° C. or higher and 210 ° C. or lower.
The method for producing an all-solid-state battery according to any one of claims 1 to 3, wherein the solid electrolyte contains at least one selected from the group consisting of a sulfide-based solid electrolyte and a hydride-based solid electrolyte. The method for producing an all-solid-state battery according to any one of claims 1 to 4, wherein the solid electrolyte contains Li, P, and S. The method for producing an all-solid-state battery according to any one of claims 1 to 5, wherein the solid electrolyte layer does not contain an organic binder. The positive electrode contains a positive electrode active material and contains a positive electrode active material.
The positive electrode active material has the formula (1): Li _{1 + x} ( _Ny1 M _1-y1 ) _1-x O ₂
(In the formula, M is at least one selected from the group consisting of Co, Mn, Fe, and Al, and Co is contained as an essential component. X satisfies 0 ≦ x ≦ 1/3, and y1 is. , 0.2 ≦ y1 ≦ 0.9.)
The method for producing an all-solid-state battery according to any one of claims 1 to 6 , which comprises an oxide represented by. The negative electrode contains a negative electrode active material and contains a negative electrode active material.
The method for producing an all-solid-state battery according to any one of claims 1 to 7 , wherein the negative electrode active material contains a carbonaceous material capable of inserting and removing lithium ions.

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