JP6954224B2 - Manufacturing method of all-solid-state battery - Google Patents

Description

The present disclosure relates to a method for manufacturing an all-solid-state battery.

The all-solid-state battery is a battery having a solid electrolyte layer between the positive electrode layer and the negative electrode layer, and has an advantage that the safety device can be easily simplified as compared with a liquid-based battery having an electrolytic solution containing a flammable organic solvent. Has.

For example, Patent Document 1 includes an assembly step for producing a battery precursor and an initial charging step for first charging the battery precursor within a range of an environmental temperature of 15 ° C. or higher and 50 ° C. or lower. A method for manufacturing a solid electrolyte battery is disclosed. Further, in Patent Document 2, an all-solid-state secondary battery having a constant voltage charging step of performing constant voltage charging while applying a restraining pressure of 0.1 MPa to 10 MPa to the battery in a temperature environment of 40 ° C. to 60 ° C. The manufacturing method of is disclosed. Further, Patent Document 3 states that, in the first charge, the charge capacity when a constant current charge is performed at 0.3 C or more and 3.6 C or less and up to 3.6 V is 50 mAh / g or more and 90 mAh / g or less. Batteries are disclosed.

On the other hand, although it is not a technique relating to an all-solid-state battery, in Patent Document 4, a pre-doping step of pre-doping an alloy-based negative electrode at a low charging rate and an initial charging step of performing initial charging at a higher charging rate than at the time of pre-doping are described. A method for manufacturing a lithium ion power storage device having the above is disclosed.

JP-A-2002-376676 Japanese Unexamined Patent Publication No. 2016-081790 Japanese Unexamined Patent Publication No. 2014-137868 Japanese Unexamined Patent Publication No. 2012-212629

Since the Si-based negative electrode active material has a large theoretical capacity, it is easy to increase the energy density of an all-solid-state battery using the Si-based negative electrode active material. On the other hand, since the volume of the Si-based negative electrode active material changes greatly during charging / discharging, the resistance tends to increase due to the charging / discharging cycle. Therefore, an all-solid-state battery that suppresses an increase in resistance due to a charge / discharge cycle is desired. Further, from the viewpoint of manufacturing equipment cost, it is desired to shorten the initial charging time.

The present disclosure has been made in view of the above circumstances, and provides a method for manufacturing an all-solid-state battery capable of obtaining an all-solid-state battery in which an increase in resistance due to a charge / discharge cycle is suppressed while shortening the initial charging time. The main purpose is to do.

In the present disclosure, an initial charging step of performing an initial charge of an all-solid-state battery having a negative electrode layer containing a Si-based negative electrode active material under the conditions of an environmental temperature of 30 ° C. or higher and 60 ° C. or lower and a charging rate of 1C or higher and lower than 4C is performed. Provided is a method for manufacturing an all-solid-state battery.

According to the present disclosure, by performing initial charging at a predetermined environmental temperature and charging rate, it is possible to obtain an all-solid-state battery in which an increase in resistance due to a charge / discharge cycle is suppressed while shortening the initial charging time.

In the present disclosure, it is possible to obtain an all-solid-state battery in which an increase in resistance due to a charge / discharge cycle is suppressed while shortening the initial charging time.

It is a flowchart which shows an example of the manufacturing method of the all-solid-state battery of this disclosure. It is the schematic sectional drawing which shows an example of the all-solid-state battery in this disclosure. It is a graph which shows the result of the resistance increase rate in Examples 1 to 3 and Comparative Example 2. It is a graph which shows the result of the initial discharge capacity in Examples 1 to 3 and Comparative Example 2. It is a graph which shows the result of the initial resistance in Examples 1 and 4 and Comparative Examples 3 and 4.

Hereinafter, the method for manufacturing the all-solid-state battery of the present disclosure will be described in detail.

FIG. 1 is a flowchart showing an example of the manufacturing method of the all-solid-state battery of the present disclosure. First, an all-solid-state battery (all-solid-state battery before initial charging) having a negative electrode layer containing a Si-based negative electrode active material is prepared. The all-solid-state battery is initially charged at a predetermined environmental temperature and charging rate (initial charging step). As a result, an all-solid-state battery after initial charging can be obtained.

FIG. 2 is a schematic cross-sectional view showing an example of the all-solid-state battery in the present disclosure. The all-solid-state battery 10 shown in FIG. 2 is a battery having a positive electrode layer 1, a solid electrolyte layer 3, and a negative electrode layer 2 in this order. Further, the all-solid-state battery 10 has a positive electrode current collector 4 that collects electricity from the positive electrode layer 1, a negative electrode current collector 5 that collects electricity from the negative electrode layer 2, and a battery case 6.

According to the present disclosure, by performing initial charging at a predetermined environmental temperature and charging rate, it is possible to obtain an all-solid-state battery in which an increase in resistance due to a charge / discharge cycle is suppressed while shortening the initial charging time. Here, as described above, the all-solid-state battery using the Si-based negative electrode active material can easily achieve high energy density. On the other hand, since the volume of the Si-based negative electrode active material changes greatly during charging / discharging, the resistance tends to increase due to the charging / discharging cycle.

Therefore, as a result of diligent research conducted by the present inventors, it is said that an increase in resistance due to a charge / discharge cycle can be suppressed by positively forming a specific Li storage field in the Si-based negative electrode active material at the time of initial charging. I got the knowledge. Specifically, the Si-based negative electrode active material reacts with Li to form an alloy during initial charging, but Li is desorbed from the alloyed Si-based negative electrode active material by the subsequent discharge. The desorbed portion is amorphized and remains, and reacts preferentially with Li. Therefore, by positively forming such a Li storage yard, the stress concentration at the time of reacting with Li is relaxed, and the increase in resistance is suppressed. In the present disclosure, by raising the environmental temperature at the time of initial charging higher than before, the formation reaction of the Li storage yard can be promoted, and the increase in resistance due to the charge / discharge cycle can be suppressed.

Further, when the charging rate is low, the reaction between the active material and the Li ion becomes rate-determining instead of the diffusion reaction of the Li ion, and the Li storage yard is likely to be formed uniformly. On the other hand, when the charging rate is high, the reaction between the active material and the Li ion becomes rate-determining, and the Li storage yard is likely to be formed unevenly. Specifically, since only the Si-based negative electrode active material existing at a position close to the solid electrolyte layer reacts with Li, the Li storage yard is likely to be unevenly formed. As a result, the stress concentration at the time of reacting with Li is less likely to be relaxed, and the resistance is likely to increase due to the charge / discharge cycle. On the other hand, in the present disclosure, by raising the environmental temperature at the time of initial charging higher than before, it is possible to suppress the uneven formation of the Li storage yard. Therefore, even when the initial charge is performed at a high charge rate, it is possible to obtain an all-solid-state battery in which the resistance increase due to the charge / discharge cycle is suppressed.

Further, in the present disclosure, the initial charging time can be shortened by performing the initial charging at a high charging rate. For example, if the initial charge is performed at a low charge rate, the initial charge time becomes longer. In that case, as the battery production scale increases, the charge / discharge equipment (for example, the number of power supply units, the number of battery restraint jigs, the number of charge / discharge equipment shelves, the installation area) becomes large, and the manufacturing equipment cost increases sharply. .. On the other hand, in the present disclosure, it is possible to obtain an all-solid-state battery in which an increase in resistance due to a charge / discharge cycle is suppressed even when the initial charge is performed at a high charge rate. Therefore, the initial charging time can be shortened, and an increase in manufacturing equipment cost can be suppressed. Further, in the present disclosure, by specifying the upper limit of the environmental temperature in the initial charge, it is possible to suppress the decrease in the initial discharge capacity due to the deterioration of the positive electrode active material.

The method for manufacturing an all-solid-state battery of the present disclosure includes an initial charging step in which an all-solid-state battery having a negative electrode layer containing a Si-based negative electrode active material is initially charged at a predetermined ambient temperature and charging rate. The initial charging process can also be regarded as an activation process that activates the all-solid-state battery. Further, in the present disclosure, "initial" and "first time" are clearly distinguished. "Initial" is a concept that includes "first time", but is a broader concept than "first time". For example, the first charge literally means the first charge, but the initial charge does not necessarily have to be the first charge. For example, even if charging / discharging that does not meet the above conditions is performed several times for the purpose of avoiding infringement of rights, if charging that meets the above conditions is subsequently performed, the step is the initial stage in the present disclosure. Corresponds to the charging process. The initial charge is preferably, for example, the first charge or more and the tenth charge or less.

1. 1. Charging conditions In this disclosure, initial charging is performed at a predetermined environmental temperature and charging rate. The environmental temperature at the time of initial charging is usually 30 ° C. or higher, may be 35 ° C. or higher, or may be 40 ° C. or higher. If the environmental temperature at the time of initial charging is too low, the formation reaction of the Li storage yard may not be promoted. On the other hand, the environmental temperature at the time of initial charging is usually 60 ° C. or lower, and may be 55 ° C. or lower. If the environmental temperature at the time of initial charging is too high, the initial discharge capacity may decrease due to deterioration of the positive electrode active material. The all-solid-state battery is usually manufactured in an environment in which the temperature and humidity are adjusted for the purpose of performing an accurate quality inspection and the like. Therefore, for example, even when the outside air temperature is high in summer, the all-solid-state battery is manufactured in an environment where the temperature is adjusted to be lower.

Further, the charging rate at the time of initial charging is usually 1C or more, may be 1.5C or more, or may be 2C or more. If the charging rate is too low, it may not be possible to shorten the initial charging time. On the other hand, the charging rate at the time of initial charging is usually less than 4C, may be 3.5C or less, or may be 3C or less. If the charge rate is too high, it may not be possible to suppress the increase in resistance due to the charge / discharge cycle. The charging rate refers to the relative ratio of the charging current value to the battery capacity. For example, in a battery having a constant capacity of 40 Ah, charging at a charging rate of 1 C means charging at 40 A.

In the initial charging step, it is preferable to charge the battery to a predetermined high battery voltage. By increasing the battery voltage at the time of initial charging, more Li storage areas can be formed. In the present disclosure, it is preferable to perform the initial charge until the battery voltage becomes larger than 4.45 V, more preferably to perform the initial charge until the battery voltage becomes 4.50 V or more, and the battery voltage becomes 4.55 V or more. It is more preferable to perform the initial charge until it becomes. If the battery voltage at the time of initial charging is too high, the initial discharge capacity may decrease due to deterioration of the positive electrode active material. Further, the initial charging method is not particularly limited, and a method using a general charging / discharging device can be adopted.

2. All-solid-state battery The all-solid-state battery in the present disclosure is a battery having a solid electrolyte layer between a positive electrode layer and a negative electrode layer. Further, the negative electrode layer contains at least a Si-based negative electrode active material. The all-solid-state battery preferably has a positive electrode current collector that collects electricity from the positive electrode layer and a negative electrode current collector that collects electricity from the negative electrode layer. Further, the all-solid-state battery before the initial charge may be prepared by making the all-solid-state battery by oneself, or may be prepared by purchasing from another person.

(1) Negative electrode layer The negative electrode layer in the present disclosure is a layer containing at least a Si-based negative electrode active material. Further, the negative electrode layer may further contain at least one of a solid electrolyte, a conductive auxiliary agent and a binder, if necessary.

The Si-based negative electrode active material is an active material that contains a Si element and can be alloyed with Li. Examples of the Si-based negative electrode active material include Si simple substance and Si alloy. The Si alloy preferably contains a Si element as a main component. The ratio of the Si element in the Si alloy may be, for example, 50 mol% or more, 70 mol% or more, or 90 mol% or more.

_{The average particle size (D 50} ) of the Si-based negative electrode active material is not particularly limited, but is, for example, 10 nm or more, and may be 100 nm or more. On the other hand, the average particle size (D ₅₀ ) of the Si-based negative electrode active material is, for example, 50 μm or less, and may be 20 μm or less.

The ratio of the Si-based negative electrode active material in the negative electrode layer is, for example, 20% by volume or more, 30% by volume or more, or 40% by volume or more. On the other hand, the ratio of the Si-based negative electrode active material may be, for example, 80% by volume or less, 70% by volume or less, or 60% by volume or less.

Examples of the solid electrolyte include inorganic solid electrolytes such as sulfide solid electrolytes and oxide solid electrolytes. The sulfide solid electrolyte, for _{example, Li 2 S-P 2 S} 5, Li 2 S-P 2 S 5 -Li 3 PO 4, LiI-P 2 S 5 -Li 3 PO 4, Li 2 S-P 2 _{S 5 -LiI, Li 2 S-} P 2 S 5 -LiI-LiBr, Li 2 S-P 2 S 5 -Li 2 O, Li 2 S-P 2 S 5 -Li 2 O-LiI, Li 2 S- P ₂ O ₅ , LiI-Li ₂ S-P ₂ O ₅ , Li ₂ S-SiS ₂ , Li ₂ S-SiS _2- LiI, Li ₂ S-SiS _2- LiI-LiBr, Li ₂ S-SiS _2- LiBr, Li ₂ S-SiS _2- LiCl, Li ₂ S-SiS _2- B ₂ S _3- LiI, Li ₂ S-SiS _2- P ₂ S ₅ -Li I, Li _{2 SB 2} S ₃ , Li ₂ SP ₂ S _{5- Z m} S _n (where m and n are positive numbers. Z is any of Ge, Zn, Ga), Li ₂ S-GeS ₂ , Li ₂ S-SiS _2- Li ₃ PO ₄ , Li ₂ S-SiS _{2 -Li x} MO _y (where x, y are positive numbers, M is any of P, Si, Ge, B, Al, Ga, In). Be done. The above description of "Li ₂ SP ₂ S ₅ " means a sulfide solid electrolyte made by using a raw material composition containing _{Li 2} S and P ₂ S _{5, and the same applies to other descriptions.} ..

Examples of the conductive auxiliary agent include a carbon material. Examples of the carbon material include particulate carbon materials such as acetylene black (AB) and Ketjen black (KB), and fibrous carbon materials such as carbon fibers, carbon nanotubes (CNT), and carbon nanofibers (CNF). .. The ratio of the conductive auxiliary agent in the negative electrode layer is not particularly limited and can be appropriately set. On the other hand, by increasing the proportion of the conductive auxiliary agent, it is possible to suppress the uneven formation of the Li storage yard even when the initial charge is performed at a high charging rate. The proportion of the conductive auxiliary agent in the negative electrode layer is, for example, 4.2% by volume or more, 4.8% by volume or more, or 7.0% by volume or more. On the other hand, the proportion of the conductive auxiliary agent is, for example, 9.2% by volume or less, and may be 8.1% by volume or less.

Examples of the binder include rubber-based binders such as butylene rubber (BR) and styrene-butadiene rubber (SBR), and fluoride-based binders such as polyvinylidene fluoride (PVDF). The thickness of the negative electrode layer is, for example, 1 μm or more, and may be 3 μm or more. On the other hand, the thickness of the negative electrode layer is, for example, 300 μm or less, and may be 100 μm or less.

(2) Positive Electrode Layer The positive electrode layer in the present disclosure is a layer containing at least a positive electrode active material. Further, the positive electrode layer may further contain at least one of a solid electrolyte, a conductive auxiliary agent and a binder, if necessary.

Examples of the positive electrode active material include an oxide active material. Examples of the oxide active material include rock salt layered active materials _{such as LiCoO 2} , LiMnO ₂ , LiNiO ₂ , LiVO ₂ , LiNi _1/3 Co _1/3 Mn _1/3 O _{2 , LiMn 2} O ₄ , Li ₄ Examples thereof include spinel-type active materials such as Ti ₅ O ₁₂ and Li (Ni _0.5 Mn _1.5 ) O ₄ , and olivine-type active materials such as _{LiFePO 4} , LiMnPO ₄ , LiNiPO ₄ , and LiCoPO _4. Further, as an oxide active material, for _{example, Li 1 + x Mn 2-} x-y M y O 4 (M is, Al, Mg, Co, Fe, Ni, at least one of Zn, 0 <x + y < 2) with The represented LiMn spinel active material, lithium titanate, may be used.

It is preferable that a coat layer containing a Li ion conductive oxide is formed on the surface of the positive electrode active material. This is because the side reaction between the positive electrode active material and the solid electrolyte can be suppressed. Examples of the Li ion conductive oxide include LiNbO ₃ , Li ₄ Ti ₅ O ₁₂ , and Li ₃ PO ₄ . The thickness of the coat layer is, for example, 0.1 nm or more, and may be 1 nm or more. On the other hand, the thickness of the coat layer is, for example, 100 nm or less, and may be 20 nm or less. The coverage of the coat layer on the surface of the positive electrode active material is, for example, 50% or more, preferably 80% or more.

The solid electrolyte, the conductive auxiliary agent, and the binder used for the positive electrode layer are the same as those for the negative electrode layer described above. The thickness of the positive electrode layer is, for example, 1 μm or more, and may be 3 μm or more. On the other hand, the thickness of the positive electrode layer is, for example, 300 μm or less, and may be 100 μm or less.

(3) Solid Electrolyte Layer The solid electrolyte layer in the present disclosure is a layer formed between a positive electrode layer and a negative electrode layer. In addition, the solid electrolyte layer contains at least a solid electrolyte, and may further contain a binder, if necessary.

The solid electrolyte and the binder used in the solid electrolyte layer are the same as in the case of the negative electrode layer described above. The content of the solid electrolyte in the solid electrolyte layer is, for example, 10% by weight or more, and may be 50% by weight or more. On the other hand, the content of the solid electrolyte in the solid electrolyte layer may be 100% by weight or less than 100% by weight. The thickness of the solid electrolyte layer is, for example, 0.1 μm or more, and may be 1 μm or more. The thickness of the solid electrolyte layer is, for example, 300 μm or less, and may be 100 μm or less.

(4) Other Configuration The all-solid-state battery in the present disclosure usually has a positive electrode current collector that collects electricity in the positive electrode layer and a negative electrode current collector that collects electricity in the negative electrode layer. Examples of the material of the positive electrode current collector include SUS, aluminum, nickel, iron, titanium and carbon. On the other hand, examples of the material of the negative electrode current collector include SUS, copper, nickel and carbon. The thickness and shape of the positive electrode current collector and the negative electrode current collector are preferably selected as appropriate according to the application of the battery. Further, as the battery case used in the present disclosure, a battery case of a general battery can be used, and examples thereof include a battery case made of SUS.

Further, the all-solid-state battery in the present disclosure may have a restraining jig that applies a restraining pressure to at least the positive electrode layer, the solid electrolyte layer, and the negative electrode layer in the thickness direction. The restraining pressure is, for example, 3 MPa or more, and may be 5 MPa or more. On the other hand, the restraining pressure is, for example, 100 MPa or less, 50 MPa or less, or 20 MPa or less.

(5) All-solid-state battery In the all-solid-state battery of the present disclosure, a part of the Si-based negative electrode active material is amorphized by initial charging. That is, the amorphization rate of the Si-based negative electrode active material increases before and after the initial charging. The amorphization rate can be determined, for example, by observation with a transmission electron microscope (TEM).

Further, the all-solid-state battery in the present disclosure may be a primary battery or a secondary battery, but the latter is preferable. This is because it can be charged and discharged repeatedly and is useful as an in-vehicle battery, for example. The secondary battery also includes the use as a primary battery of the secondary battery (use for the purpose of discharging only once after charging). Examples of the shape of the all-solid-state battery include a coin type, a laminated type, a cylindrical type, and a square type.

Further, the all-solid-state battery in the present disclosure may have only one power generation element of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer, or may have two or more power generation elements. In the latter case, the plurality of power generation elements may be connected in parallel or in series.

3. 3. Method for manufacturing an all-solid-state battery system In the present disclosure, in the present disclosure, a manufacturing of an all-solid-state battery system having an all-solid-state battery having a negative electrode layer containing a Si-based negative electrode active material and a control device for controlling charging and discharging of the all-solid-state battery. A method of manufacturing an all-solid-state battery system that comprises an initial charging step of performing initial charging at a particular ambient temperature and charging rate.

The initial charging process is basically the same as described above. Further, in the initial charging step, it is preferable to perform initial charging to a voltage higher than the battery voltage controlled by the control device. The control device has at least a function of controlling the upper limit of the battery voltage. That is, when the battery voltage increases due to charging during normal use, charging is stopped when the value reaches a predetermined value. The upper limit of the battery voltage is usually 4.35 V or less, may be 4.30 V or less, or may be 4.25 V or less. Further, the control device preferably has a function of controlling the lower limit of the battery voltage. That is, when the battery voltage drops due to the discharge during normal use, the discharge is stopped when the value reaches a predetermined value. The lower limit of the battery voltage is appropriately set according to the application of the all-solid-state battery system, and is not particularly limited, but may be, for example, 2 V or more, 2.5 V or more, or 3.0 V or more. In the present disclosure, a general control device can be used.

The present disclosure is not limited to the above embodiment. The above embodiment is an example, and any object having substantially the same structure as the technical idea described in the claims of the present disclosure and exhibiting the same effect and effect is the present invention. Included in the technical scope of the disclosure.

[Manufacturing example]
(Preparation of negative electrode layer)
Polypropylene (PP) container made, heptane and the heptane solution containing butylene rubber (BR) based binder at a ratio of 5 wt%, and a negative electrode active material (Si), a sulfide solid electrolyte _(Li including LiI 2 S- P ₂ S ₅ based glass ceramics, the average particle diameter _D 50 = 1.5 [mu] m), was added conductive auxiliary agent and (VGCF), and stirred for 30 seconds with an ultrasonic dispersing device (manufactured by SMT Ltd. UH-50). After that, it was shaken for 30 minutes with a shaker (Shibata Scientific Technology Co., Ltd., TTM-1). As a result, a negative electrode slurry was obtained. The obtained negative electrode slurry was applied onto a negative electrode current collector (Cu foil) by a blade method using an applicator, and dried on a hot plate at 100 ° C. for 30 minutes. From the above, a negative electrode laminate having a negative electrode layer and a negative electrode current collector was obtained.

(Preparation of positive electrode layer)
A heptane solution containing heptane and a butylene rubber (BR) -based binder in a proportion of 5% by weight in a polypropylene (PP) container, and a positive electrode active material (LiNi _1/3 Co _1/3 Mn _1/3 O ₂₎ , average. Particle size D ₅₀ = 4 μm), sulfide solid electrolyte (Li _{2 SP 2} S ₅ glass ceramics containing Li I, average particle size D ₅₀ = 0.8 μm), and a conductive additive (VGCF) are added. Then, the mixture was stirred with an ultrasonic disperser (UH-50 manufactured by SMT) for 30 seconds. After that, it was shaken for 3 minutes with a shaker (Shibata Scientific Technology Co., Ltd., TTM-1). Further, the mixture was stirred with an ultrasonic disperser for 30 seconds and shaken with a shaker for 3 minutes. As a result, a positive electrode slurry was obtained. The obtained positive electrode slurry was applied onto a positive electrode current collector (Al foil, SDX manufactured by Showa Denko KK) by a blade method using an applicator, and dried on a hot plate at 100 ° C. for 30 minutes. From the above, a positive electrode laminate having a positive electrode layer and a positive electrode current collector was obtained.

(Preparation of solid electrolyte layer)
A heptane solution containing heptane and a butylene rubber (BR) binder in a proportion of 5% by weight in a polypropylene (PP) container, and a sulfide solid electrolyte (Li _{2 SP 2} S ₅ glass ceramics containing LiI). Was added, and the mixture was stirred with an ultrasonic disperser (UH-50 manufactured by SMT) for 30 seconds. Then, it was shaken for 30 minutes with a shaker (TTM-1 manufactured by Shibata Scientific Technology Co., Ltd.). As a result, a solid electrolyte slurry was obtained. The obtained slurry was applied onto a release sheet (Al foil) by a blade method using an applicator, and dried on a hot plate at 100 ° C. for 30 minutes. From the above, a transfer member having a solid electrolyte layer and a release sheet was obtained. A total of three transfer members were prepared in the same manner.

(Manufacturing of evaluation battery)
The negative electrode laminate and the transfer member were arranged so that the negative electrode layer and the solid electrolyte layer were in contact with each other. A pressure of 5 kN / cm was applied to the obtained laminate using a roll press under the conditions of a gap between rolls of 100 μm and a feed rate of 0.5 m / min. Then, the release sheet was peeled off to obtain a first laminated body. Next, the positive electrode laminate and the transfer member were arranged so that the positive electrode layer and the solid electrolyte layer were in contact with each other. A pressure of 5 kN / cm was applied to the obtained laminate using a roll press under the conditions of a gap between rolls of 100 μm and a feed rate of 0.5 m / min. Then, the release sheet was peeled off to obtain a second laminated body.

The first laminated body and the second laminated body were punched out in a circular shape. The first laminate and the transfer member were arranged so that the solid electrolyte layer of the first laminate and the solid electrolyte layer of the transfer member were in contact with each other, and the release sheet of the transfer member was peeled off to obtain a third laminate. Next, the third laminated body and the second laminated body were arranged so that the solid electrolyte layer of the third laminated body and the solid electrolyte layer of the second laminated body were in contact with each other. The obtained laminate was pressed under the conditions of a temperature of 130 ° C. and a pressure of 200 MPa. A restraining pressure of 10 MPa was applied to the obtained laminate using a restraining jig to obtain an evaluation battery.

[Example 1]
The evaluation battery obtained in Production Example 1 was charged and discharged under the following conditions. Unless otherwise specified, the environmental temperature in each operation was set to 25 ° C. First, as the initial charging, constant current-constant voltage charging (termination current 1 / 100C) was performed up to 4.55V at an environmental temperature of 40 ° C. and a 0.5 hour rate (2C). Next, as the initial discharge, constant current-constant voltage discharge was performed up to 2.5 V. Next, the initial discharge capacity was obtained by performing constant current-constant voltage charging up to 4.35 V and constant current-constant voltage discharge up to 2.5 V. Next, in order to adjust the SOC (state of charge), constant current-constant voltage charging was performed up to 3.9 V, and constant current-constant voltage discharge was performed up to 3.7 V. Next, the battery was discharged at a current value of 17.15 mA / cm ² for 5 seconds, and the voltage change ΔV before and after that was divided by the current value to obtain the initial resistance. Next, the cycle of charging to 4.22 V at a 0.5 hour rate (2C) and then discharging to 3.14 V was repeated 300 times. Next, in order to adjust the SOC (state of charge), constant current-constant voltage charging was performed up to 3.9 V, and constant current-constant voltage discharge was performed up to 3.7 V. Next, the battery was discharged at a current value of 17.15 mA / cm ² for 5 seconds, and the voltage change ΔV before and after that was divided by the current value to obtain the resistance after the cycle test. The ratio of the resistance after the cycle test to the initial resistance was defined as the resistance increase rate.

[Example 2]
Charging and discharging were carried out in the same manner as in Example 1 except that the environmental temperature in the initial charging was changed to 50 ° C.

[Example 3]
Charging and discharging were carried out in the same manner as in Example 1 except that the environmental temperature in the initial charging was changed to 60 ° C.

[Comparative Example 1]
Charging and discharging were carried out in the same manner as in Example 1 except that the environmental temperature in the initial charging was set to 25 ° C. and the charging rate in the initial charging was changed to a 10-hour rate (0.1C).

[Comparative Example 2]
Charging and discharging were carried out in the same manner as in Example 1 except that the environmental temperature in the initial charging was changed to 25 ° C. The results of the resistance increase rate and the initial discharge capacity in Examples 1 to 3 and Comparative Example 2 are shown in FIGS. 3 and 4, respectively. The resistance increase rate in FIG. 3 is a relative value when the resistance increase rate in Comparative Example 1 is 1. The initial discharge capacity in FIG. 4 is a relative value when the initial discharge capacity in Comparative Example 1 is 1.

As shown in FIG. 3, in Examples 1 to 3, the rate of increase in resistance after the cycle test was lower than that in Comparative Example 2. This is because by raising the initial charging temperature (environmental temperature at the time of initial charging), the Li ion conductivity of the solid electrolyte contained in the negative electrode layer increased, and the amount of Li storage in the negative electrode active material (Si) increased. It is presumed that there is. In addition, the results of Example 1 and Comparative Example 2 suggest that the resistance increase rate after the cycle test is low even when the initial charging temperature is, for example, 30 ° C. Further, as shown in FIG. 4, the initial discharge capacities of Examples 1 to 3 were substantially the same as the initial discharge capacities of Comparative Example 2. Comparing Examples 1 to 3, there was a tendency that the initial discharge capacity slightly decreased as the initial charge temperature increased. It is presumed that if the initial charge temperature is too high, the positive electrode active material deteriorates and the initial discharge capacity decreases. On the other hand, it was suggested that the initial discharge capacity is unlikely to decrease when the initial charge temperature is 60 ° C. or lower.

[Example 4]
Charging and discharging were performed in the same manner as in Example 1 except that the charging rate in the initial charging was changed to the 0.33 hour rate (3C).

[Comparative Example 3]
Charging and discharging were performed in the same manner as in Example 1 except that the charging rate in the initial charging was changed to a 10-hour rate (0.1 C).

[Comparative Example 4]
Charging and discharging were performed in the same manner as in Example 1 except that the charging rate in the initial charging was changed to the 0.25 hour rate (4C). The results of the initial resistance in Examples 1 and 4 and Comparative Examples 3 and 4 are shown in FIG. The initial resistance in FIG. 5 is a relative value when the initial resistance in Comparative Example 1 is 1.

As shown in FIG. 5, Examples 1 and 4 having a high charge rate obtained initial resistance equivalent to that of Comparative Example 3 having a high charge rate. That is, even if the charging rate was increased, the increase in the initial resistance was suppressed. This is because by raising the initial charge temperature (environmental temperature at the time of initial charge), the Li ion conductivity of the solid electrolyte contained in the negative electrode layer increases, and the diffusion reaction of Li ions is rate-determining even at a high charge rate. It is presumed that this is because it was possible to suppress the situation. Moreover, from the results of Example 1 and Comparative Example 3, it was suggested that the increase in the initial resistance was suppressed even when the initial charge rate was 1C, for example. On the other hand, in Comparative Example 4, the initial resistance increased significantly. It is presumed that if the charging rate is too high, the diffusion reaction of Li ions becomes rate-determining. Therefore, it was confirmed that the initial charge rate is preferably less than 4C.

1 ... Positive electrode layer 2 ... Negative electrode layer 3 ... Solid electrolyte layer 4 ... Positive electrode current collector 5 ... Negative electrode current collector 10 ... All-solid-state battery

Claims (1)

An all-solid-state battery having an initial charging step in which an all-solid-state battery having a negative electrode layer containing a Si-based negative electrode active material is initially charged under the conditions of an environmental temperature of 40 ° C. or higher and 60 ° C. or lower and a charging rate of 2 C or higher and 3 C or lower. Battery manufacturing method.

Images