JP7329014B2 - Method for manufacturing laminated secondary battery - Google Patents

Description

The present invention relates to a method for manufacturing a laminated secondary battery.

Secondary batteries such as lithium-ion secondary batteries are lighter and have higher energy density than existing batteries, and are therefore preferably used as high-output power sources for vehicles or power sources for personal computers and portable terminals. As one form of this type of secondary battery, there is a laminate type battery in which an electrode assembly is housed in an electrode package using a laminate film.

A laminate type battery is typically constructed by sandwiching an electrode body having a positive electrode and a negative electrode as a power generation element between a pair of laminate films, and applying pressure and heat to the periphery of the laminate film. . Electrode bodies, which are power generation elements, typically include a positive electrode sheet in which a positive electrode active material layer is formed on a sheet-like positive electrode current collector, and a negative electrode active material layer is formed on a sheet-like negative electrode current collector. It is a structure in which a negative electrode sheet and a negative electrode sheet are stacked or wound with a separator interposed therebetween. Therefore, in the conventional battery manufacturing method, it takes a long time to impregnate the inside of the electrode body with the electrolyte.

For example, Patent Literature 1 discloses an electrolytic solution impregnation method characterized by impregnating an electrolytic solution by applying an alternating voltage or an alternating current between a positive electrode and a negative electrode. It is described that this improves the impregnating property of the electrolytic solution.

JP 2012-28290 A

By the way, in recent years, for the purpose of further increasing the capacity of the secondary battery, the size of the electrode body is also increased. By increasing the capacity per unit battery, when mounted in a limited space such as a vehicle, the gap (dead space) is reduced compared to mounting multiple small batteries as in the past. Since it can be mounted with a large capacity, it can be preferably used as a driving power supply that requires a high capacity.

For example, a large-sized electrode body (hereinafter also referred to as a large-sized electrode body) having an electrode area of 20 cm×40 cm or more is being studied. When such a large-sized electrode body is impregnated with an electrolytic solution by a conventional method, it is difficult to uniformly impregnate the entire large-sized electrode body with the electrolytic solution due to the large electrode area.

The present invention has been made in view of such circumstances, and its main purpose is to provide a method for manufacturing a laminate type secondary battery in which even a large electrode body can be uniformly impregnated with an electrolytic solution. be.

In order to achieve the above object, there is provided a method for manufacturing a laminate type battery disclosed herein. The production method disclosed herein includes a step of housing a large electrode body having at least a positive electrode and a negative electrode and having an electrode area of 20 cm × 40 cm or more in a laminated outer package; a laminated outer package containing the large electrode body. a step of injecting an electrolytic solution into the inner space of the body to construct a laminate type battery; and a step of impregnating the large-sized electrode body with the electrolytic solution. The electrolytic solution impregnation step includes a process of leaving the laminated battery in which the electrolytic solution is injected for two hours or more, a process of initially charging the laminated battery after the standing, and a laminate after the initial charging. and a process of repeating charge-discharge cycles for the model battery at least four times.
The impregnation of the electrolyte solution into the large-sized electrode body is promoted by allowing the electrolyte solution to stand still for two hours or more and performing initial charge and charge/discharge cycles. According to such a configuration, even a large-sized electrode body having an electrode area of 20 cm×40 cm or more can be uniformly impregnated with the electrolytic solution.

In a preferred aspect of the production method disclosed herein, the positive electrode includes a positive electrode current collector and a positive electrode active material layer formed on the current collector, and the average film thickness of the positive electrode active material layer is The positive electrode active material layer has a thickness of 100 μm or more and contains a positive electrode active material having an average particle size of 10 μm or less.
According to such a configuration, even if the electrode has a relatively large average film thickness and the positive electrode active material has a relatively small average particle diameter and is densified, the non-aqueous electrolytic solution can be preferably impregnated. can provide.

In a preferred aspect of the production method disclosed herein, the stationary treatment is performed in an environment of 30°C or higher and 80°C or lower.
According to such a configuration, the viscosity of the non-aqueous electrolyte can be lowered, and the impregnation of the non-aqueous electrolyte can be promoted more favorably.

In a preferred aspect of the manufacturing method disclosed herein, the amount of the electrolytic solution to be injected in the step of constructing the laminate type battery is predetermined, and the injection of the electrolytic solution is performed at a predetermined level. It is performed at least three times or more while providing intervals.
According to such a configuration, it is possible to more uniformly impregnate the large-sized electrode body with the electrolytic solution.

1 is an explanatory diagram schematically showing a laminate-type battery according to one embodiment; FIG. 1 is a flowchart of a method for manufacturing a laminate type battery according to one embodiment; FIG. Figure 3 is a flow diagram illustrating one embodiment of the impregnation process of Figure 2; FIG. 4 is a diagram schematically showing the result of AC impedance measurement of a laminate type battery; FIG. 4 is a diagram schematically showing XRF mapping according to an embodiment; FIG. 5 is a diagram schematically showing XRF mapping according to a comparative example;

Hereinafter, preferred embodiments of the technology disclosed herein will be described with reference to the drawings as appropriate. Matters other than those specifically mentioned in this specification that are necessary for implementation (for example, the general configuration and construction process of a laminate type battery) can be understood by those skilled in the art based on the prior art in the relevant field. It can be grasped as a design matter. The technology disclosed herein can be implemented based on the content disclosed in this specification and common general technical knowledge in the field. Further, in the following drawings, the symbol X indicates the long side direction of the laminate type battery, and the symbol Y indicates the short side direction of the laminate type battery. Members and parts having the same action are denoted by the same reference numerals, and redundant description may be omitted or simplified. Also, the dimensional relationships (length, width, height, etc.) do not reflect actual dimensional relationships.
In this specification, the notation "A to B (where A and B are arbitrary values)" indicating a range means from A to B or less.

Here, first, the configuration of the laminate type secondary battery will be described, and then the method for manufacturing the laminate type battery according to one embodiment will be described.
In this specification, the term "laminate type battery" refers to a battery in general that uses a laminate film as an exterior body and accommodates an electrode body therein. The laminate type battery may be, for example, a so-called storage battery (chemical battery) such as a lithium ion secondary battery or a nickel hydrogen battery, or a capacitor (physical battery) such as an electric double layer capacitor.

<Laminate type battery>
FIG. 1 is a plan view schematically showing a laminate type battery 1 according to one embodiment. The laminate-type battery 1 includes a laminate outer package 10, an electrode assembly 20 housed in the laminate outer package 10, and a non-aqueous electrolyte (not shown). The laminated outer body 10 is bag-shaped, and the peripheral edge portion of the space for accommodating the electrode body 20 is sealed by thermal welding (heat sealing). A positive electrode terminal 30 and a negative electrode terminal 40 protrude outside the laminated outer package 10 . The positive terminal 30 and the negative terminal 40 extend from the inside of the laminated outer package 10 to the outside. The positive terminal 30 and the negative terminal 40 are external terminals.

The laminate outer package 10 is an insulating container that accommodates the electrode assembly 20 . The configuration of the laminate outer package 10 may be the same as that conventionally known, and is not particularly limited. The laminate outer package 10 is typically composed of a laminate film having a multilayer structure. The laminate outer body 10 has, for example, a three-layer structure, and is configured by laminating a sealant layer, a gas barrier layer, and a protective layer in this order from the side closer to the electrode body 20 .

The laminated outer body 10 is formed by heat-sealing and sealing the ends of two laminated films having a multilayer structure. Since the sealant layer is a layer that enables this thermal welding, it is located on the innermost layer of the laminate outer body 10 , that is, on the side closest to the electrode body 20 . The sealant layer may have the same structure as the sealant layer of a conventional laminated outer body. For example, the sealant layer is made of thermoplastic resin such as polyethylene, polypropylene, polystyrene, and polyvinyl chloride.

The gas barrier layer is a layer that blocks entry and exit of moisture, air, or gas generated inside the laminate-type battery 1 inside and outside the laminate-type battery 1 . The gas barrier layer may have the same structure as the gas barrier layer of a conventional laminated exterior body. For example, the gas barrier layer is composed of metal materials such as aluminum, iron, and stainless steel. Among them, aluminum is preferable from the viewpoint of cost and weight reduction.

The protective layer is a layer for improving the durability of the laminated exterior body 10 . The protective layer is positioned closer to the outer surface than the gas barrier layer. The protective layer may be the outermost layer of the laminated outer body 10 . The protective layer may have the same structure as the protective layer of a conventional laminate outer package. For example, the protective layer is made of polyester such as PET, polyamide (nylon), or the like.

In addition, the case where the laminate outer package 10 has a three-layer structure composed of a sealant layer, a gas barrier layer, and a protective layer has been described above. However, the multilayer structure of the laminate outer package 10 is not limited to this. For example, the number of layers may be 4 or more, or about 4 to 10 layers. As an example, an adhesive layer may be provided between the layers described above for adhering both layers to each other. The adhesive layer may be made of resin such as polyamide (nylon), for example. As another example, a print layer, a flame-retardant layer, a surface protective layer, and the like may be further provided on the protective layer, for example, as the outermost layer.

The electrode assembly 20 includes a positive electrode, a negative electrode, and a separator (not shown). The electrode body 20 is characterized by being a large-sized electrode body compared with the conventional one. Specifically, it is an electrode body having an electrode area of 20 cm×40 cm or more. The electrode area of the electrode body 20 may be, for example, 20 cm×40 cm or more and 25 cm×45 cm or less. The electrode body 20 is typically a laminated electrode body (laminated electrode body) in which a rectangular positive electrode and a rectangular negative electrode are stacked via a separator.

The positive electrode includes a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector. Examples of positive electrode current collectors include metal materials having good electrical conductivity, such as aluminum, nickel, titanium, and stainless steel. Among them, aluminum (for example, aluminum foil) is particularly preferable. The thickness of the positive electrode current collector is not particularly limited, but is, for example, 5 μm or more and 35 μm or less, preferably 7 μm or more and 20 μm or less.

The positive electrode active material layer contains at least a positive electrode active material capable of reversibly intercalating and deintercalating charge carriers. As the positive electrode active material, for example, a lithium-transition metal composite oxide such as a lithium-nickel-based composite oxide, a lithium-transition metal phosphate compound (eg, LiFePO ₄ ), or the like can be preferably used. Among them, a positive electrode active material having an average particle size of 10 μm or less (for example, 0.1 μm or more and 10 μm or less) can be preferably used. By setting the average particle size of the positive electrode active material within the above range, the contact area with the conductive material can be suitably secured, and the electrode density can be improved, so that a good conductive path is formed in the positive electrode active material layer. . Examples of positive electrode active materials having an average particle size of 10 μm or less include lithium phosphate compounds such as lithium iron phosphate (LiFePO ₄ ).
In the present specification, the "average particle size" refers to particles corresponding to a cumulative frequency of 50% by volume from the fine particle side with a small particle size in a volume-based particle size distribution based on a general laser diffraction/light scattering method. The diameter (D ₅₀ , also referred to as median diameter).

The positive electrode active material layer may contain substances other than the positive electrode active material, such as a conductive material and a binder. As the conductive material, for example, carbon black such as acetylene black (AB) and other carbon materials (such as graphite) can be preferably used. As the binder, fluorine-based binders such as polyvinylidene fluoride (PVdF) and polytetrafluoroethylene (PTFE), and rubber-based binders such as styrene-butadiene rubber (SBR) can be preferably used. In addition, the positive electrode active material layer may contain materials other than those described above (for example, various additives, etc.) as long as the effects of the present invention are not impaired.

The content of the positive electrode active material in the positive electrode active material layer (that is, the ratio of the positive electrode active material to the total mass of the positive electrode active material layer) is preferably approximately 60% by mass or more from the viewpoint of energy density. For example, it is more preferably 75% by mass to 95% by mass, and even more preferably 80% by mass to 95% by mass. Also, the content of the conductive material in the positive electrode active material layer is, for example, preferably 1% by mass to 10% by mass, more preferably 1% by mass to 8% by mass. The content of the binder in the positive electrode active material layer is, for example, preferably 0.5% by mass to 5% by mass, more preferably 1% by mass to 3% by mass. In addition, when various additives such as thickeners are included, the content of the additive in the positive electrode active material layer is, for example, preferably 7% by mass or less, more preferably 5% by mass or less. .

In a preferred embodiment, the positive electrode active material layer has an average thickness of 100 μm or more per side of the positive electrode current collector. From the viewpoint of achieving high capacity, the average thickness of the positive electrode active material layer may be, for example, 100 μm or more and 200 μm or less, or 110 μm or more and 190 μm or less. The density of the positive electrode active material layer is preferably 2.0 g/cm ³ or more and 3.0 g/cm ^{3 or} less, and more preferably 2.1 g/cm ³ or more and 2.5 g from the viewpoint of realizing gas discharge and energy density. /cm ³ or less.

The negative electrode includes a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector. The negative electrode current collector is composed of, for example, a metal material such as copper having good conductivity, an alloy mainly composed of copper, nickel, titanium, or stainless steel. Among them, copper (for example, copper foil) can be preferably used. The thickness of the negative electrode current collector may be, for example, approximately 5 μm to 20 μm, preferably 8 μm to 15 μm.

The negative electrode active material layer contains at least a negative electrode active material capable of reversibly intercalating and deintercalating charge carriers. Examples of negative electrode active materials include carbon materials such as graphite, hard carbon, and soft carbon. The negative electrode active material is typically particulate. The average particle size of the particulate negative electrode active material is not particularly limited, but is suitably 50 μm or less, typically 20 μm or less, for example 1 μm to 20 μm.

The negative electrode active material layer may contain substances other than the negative electrode active material, such as binders and various additives. As the binder, for example, styrene-butadiene rubber (SBR) or the like can be used. In addition, various additives such as thickening agents, dispersing agents, and conductive agents can be used as appropriate. For example, carboxymethyl cellulose (CMC), methyl cellulose (MC), etc. can be suitably used as thickening agents.

From the viewpoint of energy density, the content of the negative electrode active material in the negative electrode active material layer is preferably approximately 60% by mass or more. For example, it is more preferably 90% by mass to 99% by mass, and even more preferably 95% by mass to 99% by mass. Further, when a binder is used, the content of the binder in the negative electrode active material layer 64 is, for example, preferably 1% by mass to 10% by mass, more preferably 1% by mass to 5% by mass. preferable. When a thickener is used, the content of the thickener in the negative electrode active material layer is, for example, preferably 1% by mass to 10% by mass, more preferably 1% by mass to 5% by mass. preferable.

The average thickness of the negative electrode active material layer may be 100 μm or more and 200 μm or less, or 110 μm or more and 190 μm or less per one side of the negative electrode current collector, from the viewpoint of achieving high capacity. The density of the negative electrode active material layer may be 1.0 g/cm ³ or more and 2.0 g/cm ³ or less, and may be 1.5 g/cm ³ or more and 1.7 g/cm ³ or less.

Examples of separators include porous sheets (films) made of resins such as polyethylene (PE), polypropylene (PP), polyester, cellulose, and polyamide. Such a porous sheet may have a single-layer structure or a laminated structure of two or more layers (for example, a three-layer structure in which PP layers are laminated on both sides of a PE layer). The separator may be provided with a heat resistant layer (HRL).

The non-aqueous electrolyte is typically a liquid in which a supporting salt (e.g., lithium salt, sodium salt, magnesium salt, etc.; lithium salt in a lithium ion secondary battery) is dissolved or dispersed in a non-aqueous solvent. is used.
As the supporting salt, any supporting salt used in conventional non-aqueous electrolyte secondary batteries of this type can be used without particular limitation. For example, lithium salts such as LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiN(CF ₃ SO ₂ ) ₂ and LiC(CF ₃ SO ₂ ) ₃ can be used. Among them, LiPF ₆ can be preferably used. The concentration of the supporting salt is preferably 1.1 mol/L or more and 1.5 mol/L or less, for example.

As the non-aqueous solvent, carbonates, esters, ethers, nitriles, sulfones, lactones and the like can be used without particular limitation. Specifically, ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethylmethyl carbonate (EMC), monofluoroethylene carbonate (MFEC), difluoroethylene carbonate (DFEC) , monofluoromethyldifluoromethyl carbonate (F-DMC), and trifluorodimethyl carbonate (TFDMC). Such non-aqueous solvents can be used singly or in combination of two or more.
In addition, the non-aqueous electrolyte of the non-aqueous secondary battery according to the present embodiment includes, for example, biphenyl (BP), cyclohexylbenzene (CHB), and other gas generating agents; It may contain various additives such as agents, dispersants, and thickeners.

<Method for manufacturing laminated battery>
The manufacturing method disclosed herein typically comprises the following three steps, as shown in FIG. (3) a step of impregnating a large electrode body with an electrolyte (S130); The manufacturing method disclosed herein is characterized by uniformly impregnating the large electrode body with the electrolyte in the electrolyte impregnation step S130. Therefore, the other steps are not particularly limited, and the structure may be the same as that of the conventional manufacturing method of this type. Each step will be described below in order.

In the electrode assembly step S110, the electrode assembly 20 having the positive electrode and the negative electrode described above and having an electrode area of 20 cm×40 cm or more is accommodated in the laminate package 10 . The laminated outer body 10 is typically a rectangular flat sheet having an area larger than that of the electrode body 20 in plan view. The laminated outer body 10 may be prepared, for example, by purchasing a commercially available product. In addition, the electrode body 20 is prepared by, for example, the following process: a process of applying a positive electrode slurry in which a positive electrode active material, a conductive material, and a binder are dispersed in an appropriate solvent on a positive electrode current collector and drying it to prepare a positive electrode. A step of applying a negative electrode slurry obtained by dispersing a negative electrode active material, a binder and a thickener in an appropriate solvent onto a negative electrode current collector and drying it to prepare a negative electrode; It can be produced by a manufacturing method including a step of laminating with intervening and pressing from the lamination direction. A positive electrode terminal 30 is attached to the positive electrode of the electrode assembly 20, and a negative electrode terminal 40 is attached to the negative electrode thereof.

The electrode body 20 used in the manufacturing method disclosed herein is a large electrode body with an electrode area of 20 cm×40 cm or more. Such a large-sized electrode body has the advantage that the capacity per unit battery can be increased and, for example, the battery can be efficiently mounted in a limited space such as under the floor of a vehicle. In a preferred embodiment, the average film thickness of the electrode active material layer (positive electrode active material layer and/or negative electrode active material layer) of the electrode body 20 is 100 μm or more. By increasing the average film thickness of the electrode active material layer compared to the conventional one, it contributes to increasing the capacity of the battery. In a more preferable embodiment, the positive electrode active material contained in the positive electrode active material layer of the electrode body 20 has an average particle size of 10 μm or less. According to such a configuration, the contact area with the conductive material is increased, so that a suitable conductive path is formed in the active material layer, and the output characteristics of the battery are improved.

As described above, when the average particle size of the positive electrode active material is relatively small, the electrode density is improved (in other words, a high energy density is achieved), while the gaps between the particles are reduced and the electrolyte impregnation tends to be difficult. Further, when the positive electrode containing such a positive electrode active material is made relatively thick, it becomes more difficult for the electrolytic solution to impregnate the positive electrode while increasing the capacity. Therefore, in the case of a large-sized electrode body having such a positive electrode, the effect of improving the impregnating property of the electrolytic solution by the manufacturing method disclosed herein is more preferably exhibited.

In the battery construction step S120, an electrolytic solution is injected into the inner space of the laminate outer package containing the large electrode assembly. At the stage when a predetermined amount (predetermined amount) of the electrolytic solution is injected, the laminate outer casing 10 is sealed to construct the laminate type battery 1 .
First, the laminated exterior body 10 is left standing with one of the four sides opened (hereinafter also referred to as an opening). A predetermined amount of electrolytic solution is injected through the opening. Preferably, one of the long sides of the laminated outer body 10 is opened to inject the non-aqueous electrolyte. For injection, a conventionally known electrolyte injection device can be appropriately used.

The predetermined amount of the electrolytic solution may be set to a quantity that allows the electrolytic solution to spread over the entire electrode body 20 . A predetermined amount of the electrolytic solution may be injected all at once, or may be injected in a plurality of times. Preferably, the injection is divided into a plurality of times (for example, 3 to 5 times). More preferably, a predetermined amount of the electrolytic solution is injected in a plurality of times, and each injection is performed under a reduced pressure environment for about 3 minutes (for example, 1 to 5 minutes) with the opening facing upward. It is best to leave it alone. By injecting liquid by such an injecting method, even a large-sized electrode body can be preferably impregnated with the electrolytic solution up to the central portion of the electrode body. After the injection of a predetermined amount of electrolyte is completed, the opening of the laminate outer package 10 is sealed to construct the laminate type battery 1 .
It should be noted that the term "under reduced pressure environment" as used herein may be a state in which the pressure inside the laminate outer package is lower than the atmospheric pressure. Such decompression may be performed by temporarily sealing the opening and decompressing only the inside of the laminated outer package, or by placing the entire laminated outer package containing the large electrode body under a reduced pressure atmosphere and reducing the pressure. . The pressure inside the battery case after decompression is not particularly limited, but is preferably about 1 kPa to 30 kPa, preferably about 5 kPa to 20 kPa.

Although it is not particularly limited, it is preferable to leave the laminated exterior body in which the large-sized electrode body is housed in a high-temperature environment after the electrode body housing step S110 and before starting liquid injection. As an example, it is preferable to heat the laminated outer body 10 containing the large electrode assembly at a temperature of about 40° C. (30° C. to 80° C.) for about 2 hours (eg, 1 to 3 hours). By heating the electrode body 20 and the laminated outer body 10, the viscosity of the injected electrolytic solution can be suitably lowered, and the injection time can be shortened. For temperature control, for example, a constant temperature bath may be used.

The electrolytic solution impregnation step S130 is a step of uniformly impregnating the large electrode body with a predetermined amount of injected electrolytic solution. The electrolytic solution impregnation step S130 disclosed herein includes, as shown in FIG. and a process (S133) of performing a charge/discharge cycle on the model battery.

In the standing process S131, the laminate type battery 1 is left standing with the sealed opening facing upward. In a preferred aspect, the stationary treatment S131 is performed in an environment of about 40° C. (for example, 30° C. or higher and 80° C. or lower). For example, the laminate type battery 1 may be allowed to stand at a temperature of about 40° C. (30° C. or higher and 80° C. or lower) for about 2 hours (for example, 2 to 4 hours). By performing the standing process S131 for a predetermined time in such a temperature environment, the viscosity of the injected electrolytic solution is lowered, and the impregnation of the large electrode body with the electrolytic solution is promoted.

In the initial charging process S132, the laminate type battery 1 is initially charged (conditioned) according to a conventionally known method. Initial charging is a process of charging over the voltage range in which the manufactured secondary battery is used. Thereby, the laminate type battery 1 can be electrochemically activated. For the initial charging, for example, an external power supply may be connected between the positive terminal 30 and the negative terminal 40, and charging to a predetermined voltage (typically, constant current and constant voltage charging) may be performed. The conditions for initial charging are not particularly limited, but the voltage between the positive and negative terminals (typically the highest voltage) is 2.5 V to 4.2 V in a normal temperature environment (eg, 25 ° C. ± 5 ° C.). (Preferably 3.0 V to 4.1 V) after charging at a constant current of about 0.1 C to 10 C, SOC (State of Charge) is about 60 to 100% (typically 80 to 100% It is preferable to perform constant-current constant-voltage charging (CCCV charging) in which charging is performed at a constant voltage until the battery reaches a constant voltage.
Note that "1C" means a current value (current density) that can charge the battery capacity (Ah) predicted from the theoretical capacity of the active material in one hour. Therefore, for example, 1/3C means a current value that can charge the battery capacity in 3 hours, and 20C means a current value that can charge the battery capacity in 1/20 hour.

AC impedance measurement may be performed on the laminate type battery 1 for which the initial charging process S132 has been completed, and the resistance value may be calculated. A relatively high value can be calculated for the resistance value immediately after the initial charging process S131 because the impregnation of the electrolytic solution is still insufficient. Although the details will be described later, by uniformly impregnating the large electrode body with the electrolytic solution, reaction unevenness and the like can be suppressed, and a local increase in resistance value can be suppressed. is lower than the resistance value calculated here.

The resistance value based on AC impedance measurement can be calculated as follows. For example, the impedance can be obtained by passing a direct current between the positive terminal 30 and the negative terminal 40, then measuring the response voltage at each frequency when superimposing a small alternating current with varying frequency. Specifically, the frequency characteristic of impedance can be obtained by Fourier transforming the obtained data. It is preferable to change the frequency of the AC voltage from a high frequency of about 1000000 Hz to a low frequency of about 0.1 Hz. Although the amplitude of the AC voltage is not particularly limited, it can be set to approximately 1 to 10 mV as a guideline.
By fitting the plot obtained by AC impedance measurement to an equivalent circuit and analyzing it, the arc-shaped diameter can be calculated as the reaction resistance.

In the charge/discharge cycle process S133, the charge/discharge cycle is performed on the laminate type battery 1 for which the initial charge process S132 has been completed. A plurality of charge-discharge cycles are performed on the laminate type battery 1, with one cycle (cyc) being a process in which charging and discharging are performed once each. There is a tendency that as the current value of the charge/discharge cycle is increased and the number of cycles is increased, the impregnation of the electrolytic solution is promoted. On the other hand, if the current value is too high or the number of cycles is increased too much, there is a risk that deterioration of the laminate type battery 1 will progress easily due to charging and discharging in the charging and discharging cycle processing S133. From this point of view, the conditions of the charge/discharge cycle can be appropriately set.

In a preferred embodiment, at least 4 or more charge/discharge cycles (for example, about 4 to 6 cycles) are performed in the charge/discharge cycle processing S133. By performing the charge-discharge cycle process S133, the expansion and contraction of the electrode body 20 occur repeatedly and act like a pump, so that impregnation of the non-aqueous electrolyte into the electrode body 20 can be promoted appropriately.

The charge-discharge cycle in the charge-discharge cycle process S133 is performed, for example, in an environment of about 60° C. (for example, 40 to 80° C.) by charging at a constant current to a predetermined potential (charging potential), and then at a constant current. (discharge potential). The voltage between the positive and negative terminals (typically the highest voltage) varies depending on the materials used, but can be, for example, 2.5 V to 4.2 V (preferably 3.0 V to 4.1 V). can. The current value is not particularly limited, but can be, for example, 0.1C to 2C (typically 0.2C to 1.5C, eg 0.3C to 1C). The charge/discharge cycle may be performed by a method of charging and discharging at a constant current (CC charge, CC discharge), or after charging or discharging at a constant current until the predetermined voltage is reached, charging or discharging at a constant voltage. You may perform by a method (CCCV charge, CCCV discharge). In a preferred embodiment, multiple cycles (eg, 2 to 4 cycles) of CC charging and CC discharging may be followed by multiple cycles (eg, 2 to 4 cycles) of CCCV charging and CCCV discharging.
A rest period (a period in which the charging/discharging current is zero) may or may not be provided between charging and discharging. In a preferred embodiment, a rest period of about 10 minutes (eg, about 5 to 15 minutes) should be provided between charging and discharging.

The electrolytic solution impregnation step S130 may be performed while the laminate type battery 1 is restrained. Specifically, a pair of restraining plates are arranged on both sides of the wide surface of the laminated outer body 10, and restrained while a predetermined restraining load is applied. The constraining plate is not particularly limited, but may be a metal member such as stainless steel, and preferably has a thickness of, for example, about 10 to 15 mm. Also, rubber (fluororubber, butyl rubber, ethylene propylene rubber, etc.) is preferably sandwiched between the restraint plate and the laminate outer body 10 . The restraint load is not particularly limited as it may be appropriately adjusted according to the size of the laminate type battery 1, but may be adjusted to 0.2 to 1.5 MPa, for example.

After the electrolytic solution impregnation step S130, in order to confirm whether the large electrode body is uniformly impregnated with the electrolytic solution, impedance measurement may be performed to calculate the resistance value. According to the findings of the present inventors, when the electrolytic solution is uniformly impregnated into the large electrode body, the AC impedance measurement of the laminate type battery 1 immediately after the electrolytic solution impregnation step S130 (more specifically, the charge-discharge cycle treatment S133) and the resistance value based on AC impedance measurement of the laminate type battery 1 which has been allowed to stand for several hours (for example, 1 to 6 hours) after the electrolytic solution impregnation step S130. Although this is not particularly limited, it is inferred as follows. When the electrode body 20 is evenly impregnated with the electrolyte, the electrolyte is favorably retained in the electrode body 20 even after standing for several hours. For this reason, it is presumed that the resistance value does not increase because local increases in resistance due to uneven impregnation of the electrolytic solution in the electrode assembly 20 are suppressed. Therefore, AC impedance measurement is performed immediately after the charge-discharge cycle processing S133 to calculate the resistance value, and after standing for at least one hour or more, the AC impedance measurement is performed again to calculate the resistance value and compare the electrolyte solution. is uniformly impregnated into the electrode assembly 20 or not. According to this method, it is possible to determine whether or not the electrolyte solution is uniformly impregnated on the spot by the AC impedance method without destroying the laminate type battery 1, which is preferable.
It should be noted that such impedance measurement need not be performed for all laminated batteries manufactured by the same manufacturing method. For example, out of several thousand (eg, 1,000 to 3,000) laminated batteries manufactured by a similar manufacturing method, one or more randomly selected batteries (eg, 1 to 10) may be tested. Just do it.

The conditions for leaving the laminate type battery 1 stationary in the impedance measurement are not particularly limited. For example, standing may be carried out in a high temperature environment. For example, the temperature is 40° C. or higher, preferably 50° C. or higher, further 60° C. or higher, and, for example, about 80° C. or lower. Also, the standing time is not particularly limited, but it is typically 1 hour or more (for example, 1 to 8 hours, preferably 4 to 6 hours).

The manufacturing method disclosed herein can be preferably used, for example, in a laminate-type battery having a large-sized electrode body that takes a long time to be impregnated with an electrolytic solution. Furthermore, in a large-sized electrode body containing a positive electrode active material with a small average particle size and having a thick average film thickness of the positive electrode active material layer, it is difficult to uniformly impregnate the electrolytic solution, so that it can be particularly preferably used. A laminate-type battery including a large-sized electrode body having such properties has a high capacity, and thus can be suitably used as a power source (driving power source) for, for example, plug-in hybrid vehicles, hybrid vehicles, electric vehicles, and the like.

Examples of the manufacturing method disclosed here will be described below, but the technology disclosed here is not intended to be limited to those shown in the examples.

<Preparing laminated batteries>
LiFePO ₄ (average particle size D ₅₀ : 10 μm) as a positive electrode active material, acetylene black (AB) as a conductive material, and polyvinylidene fluoride (PVdF) as a binder were mixed so that the mass ratio of these materials was 92: A positive electrode paste was prepared by mixing with N-methylpyrrolidone (NMP) as a solvent at a ratio of 5:3. This positive electrode paste was applied to both sides of a rectangular aluminum foil as a positive electrode current collector. At this time, the average film thickness on one side was set to 100 μm. By drying this, a positive electrode was produced.

Natural graphite (C) as a negative electrode active material, styrene-butadiene rubber (SBR) as a binder, and carboxymethyl cellulose (CMC) as a thickening agent were mixed so that their mass ratio was 98:1:1. , and ion-exchanged water as a solvent to prepare a negative electrode paste. This negative electrode paste was applied to both sides of a rectangular copper foil as a negative electrode current collector. At this time, the average film thickness on one side was set to 100 μm. By drying this, a negative electrode was produced.

A porous polyolefin sheet having a three-layer structure of PP/PE/PP was prepared as a separator.
The positive electrode and the negative electrode prepared above were laminated via the prepared separator to prepare a large electrode body having an electrode area of 20 cm×40 cm. Next, an electrode terminal was attached to each of the positive electrode and the negative electrode of the large electrode body thus produced. This was sandwiched between two laminate films, one long side was opened, and the remaining three sides were thermally welded. As a result, the large electrode body was accommodated inside the laminate outer package. The laminate film used had a sealant layer made of polypropylene, an aluminum deposition layer, and a protective layer made of nylon.

Next, a non-aqueous electrolyte was injected into the inner space of the laminate housing housing the large electrode body. As the non-aqueous electrolyte, LiPF ₆ as a supporting salt was added to a mixed solvent containing ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) at a volume ratio of 30:30:40. A solution dissolved at a concentration of 4 mol/L was prepared.
First, the laminated exterior body in which the large-sized electrode body was housed was allowed to stand in a constant temperature bath at 40° C. for 2 hours. A predetermined amount of the non-aqueous electrolyte was injected through the opening of the laminated exterior body in three portions. It should be noted that each time the solution was injected, it was allowed to stand for 3 minutes under a reduced pressure environment. The opening of the laminate outer package was sealed by heat welding to obtain a laminate type battery for evaluation.

(Example 1)
An electrolytic solution impregnation step was carried out on the laminate-type battery for evaluation. Specifically, the laminate type battery to which the injection of the non-aqueous electrolyte was completed was allowed to stand in a constant temperature bath at 40° C. for 2 hours. After that, in a temperature environment of 25° C., the battery was charged at a rate of ⅓ C until the voltage between the positive and negative terminals reached 3.3 V, and then charged at a constant voltage (CCCV charging). Then, impedance measurement was performed under the conditions of amplitude: 10 mV, measurement frequency range: 1000000 Hz to 0.1 Hz, measurement voltage: 3.3 V, and the obtained plot was fitted to an equivalent circuit and analyzed to obtain a laminate type battery. was calculated. In addition, the results of the impedance measurement here are schematically shown in FIG. 4 as a plot before the charge/discharge cycle (reference A).
Next, the laminate-type battery that has completed the initial charge is charged at a constant current rate of 1/3 C until the voltage between the positive and negative terminals reaches 3.8 V, followed by resting for 10 minutes. One cycle (CC charge/discharge cycle) was a cycle (CC charge/discharge cycle) consisting of constant current discharge at a discharge rate of ⅓ C until the voltage between the charges reached 2.5 V, followed by resting for 10 minutes, and this cycle was repeated for two cycles. Thereafter, constant current charging is performed at a charging rate of 1/5 C until the voltage between the positive and negative terminals reaches 4.0 V, constant voltage charging is performed until the final current (1/100 C) is reached, and then resting for 10 minutes. One cycle (CCCV 2 cycles were repeated as a charge/discharge cycle).

(Example 2 and Comparative Examples 1 to 6)
Example 2 and Comparative Examples 1 to 6 were carried out by changing the conditions of the electrolytic solution impregnation step and the standing condition after the electrolytic solution impregnation step as shown in Table 1. When the number of cycles was 1 and 2, only the CC charge/discharge cycle was performed, and when the number of cycles was 3, the CC charge/discharge cycle was repeated twice and then one CCCV charge/discharge cycle was performed.

<Evaluation of Impregnability of Nonaqueous Electrolyte>
Impedance measurement was performed on the laminate-type battery of Example 1 after the charge-discharge cycle treatment by the method described above, and the resistance value was measured. The results of the impedance measurements here are schematically shown in FIG. 4 as plots after charge-discharge cycles (Reference B). After the charge-discharge cycle treatment, each laminate-type battery for evaluation (Examples 1 and 2 and Comparative Examples 1 to 6) was allowed to stand under the conditions shown in Table 1, impedance was measured, and resistance was measured. The results of the impedance measurements herein are shown in Table 1 and schematically in FIG. 4 as plots AC. Since the resistance value tends to decrease when the large electrode body is uniformly impregnated with the non-aqueous electrolyte, it can be evaluated that the smaller the arc of the plot, the more uniformly the electrolyte is impregnated. Therefore, if the plot after charge-discharge cycles in Example 1 (reference B) matches the plot of each evaluation laminate type battery measured after standing after the electrolyte impregnation step, the large electrode body will not be affected. It can be evaluated that the aqueous electrolyte is uniformly impregnated.
Further, by mapping phosphorus (P) using XRF (X-ray fluorescence spectroscopy), the dispersed state of LiPF ₆ contained as a supporting electrolyte in the non-aqueous electrolyte was confirmed. The XRF mapping diagrams are schematically shown in FIGS. 5 and 6. FIG. Moreover, FIG. 5 shows that phosphorus (P) is well dispersed, and FIG. 6 shows that phosphorus (P) is unevenly distributed, resulting in poor dispersion. The results are shown in Table 1, with "O" when the dispersion state is good and "X" when the dispersion state is poor. When phosphorus (P) is well dispersed, it can be evaluated that the non-aqueous electrolytic solution is uniformly impregnated.

As shown in Table 1, even in the case of a large electrode body having an electrode area of 20 cm × 40 cm or more, in the electrolytic solution impregnation step, the laminate type battery in which the non-aqueous electrolytic solution is injected is left to stand, and the A process of initially charging the laminate type battery after installation and a process of repeating the charging/discharging cycle of the laminate type battery at least four times or more, thereby uniformly impregnating the large electrode body with the non-aqueous electrolyte. can be done.

Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications of the specific examples illustrated above,
Includes changes.

1 Laminated Battery 10 Laminated Outer Body 20 Electrode Body 30 Positive Terminal 40 Negative Terminal

Claims (3)

A rectangular laminated electrode body in which a rectangular positive electrode and a rectangular negative electrode are stacked with a separator interposed therebetween, wherein both the positive electrode and the negative electrode of the rectangular laminated electrode body A step of accommodating a large-sized electrode body having an area of 20 cm × 40 cm or more in a laminated exterior body;
A step of injecting an electrolytic solution into the inner space of the laminate outer package containing the large electrode assembly to construct a laminate type battery;
impregnating the large electrode body with the electrolytic solution;
encompasses
In the step of impregnating the large electrode body with the electrolytic solution ,
A process of leaving the laminate type battery in which the electrolytic solution is injected in an environment of 30 ° C. or higher and 80 ° C. or lower for 2 hours or more;
A process of initially charging the laminate type battery after the process of leaving the laminate type battery in which the electrolytic solution is injected in an environment of 30 ° C. or more and 80 ° C. or less for 2 hours or more;
A process of repeating charge-discharge cycles at least four times or more for the laminate type battery after the initial charge;
A method for manufacturing a laminated battery, comprising: The positive electrode includes a positive electrode current collector and a positive electrode active material layer formed on the current collector,
The average film thickness of the positive electrode active material layer is 100 μm or more,
2. The method of manufacturing a laminate type battery according to claim 1, wherein said positive electrode active material layer contains a positive electrode active material having an average particle size of 10 [mu]m or less. The amount of the electrolyte to be injected in the step of constructing the laminate type battery is predetermined, and the injection of the electrolyte is performed at least three times or more at predetermined intervals. 3. The method for producing a laminate type battery according to claim 1 or 2 .

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