JP2003217671A - Manufacturing method for gastight battery and sealing evaluation method for gastight battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for a gastight battery hard to expand in initial charging. <P>SOLUTION: According to this manufacturing method for the gastight battery, a power generation element having a positive electrode, a separator, a negative electrode and a nonaqueous battery electrolyte is enclosed in a case made of a laminated film of a metal sheet and a resin film, or a metal-made can to manufacture a uncharged battery, and subsequently the uncharged battery is charged in a pressurized gas. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a sealed battery and a method for evaluating its sealing property, and more specifically, it has a large discharge capacity during initial charging and after charge / discharge cycles.
The present invention also relates to a method for manufacturing a sealed battery whose overall shape is thin, and a method for evaluating the sealing property of the sealed battery.

[0002]

2. Description of the Related Art In recent years, with the progress of various electronic devices such as mobile phones and personal computers, secondary batteries, which are the power sources thereof, have been made smaller, thinner, lighter, larger in capacity, and have higher functions. There is a constant demand for lower prices and lower prices. In order to meet such demands, for example, in the field of prismatic batteries, conventionally, of power generating elements composed of a positive electrode, a separator and a negative electrode, for example, one having a higher energy density as an active material material constituting the positive electrode or the negative electrode is selected. Or
The separator can be made thinner to increase the capacity of the power generation element per unit volume, and the material of the battery can can be made of a lighter material such as Al.
Measures such as conversion to are adopted. However, none of these measures have necessarily met the required performance levels.

By the way, recently, the following thin batteries have begun to be marketed as batteries intended to be made thinner, smaller and lighter. A general method for manufacturing such a thin battery will be described below. In the case of this thin battery,
First, for example, a laminated film having a three-layer structure in which a resin film is laminated on both sides of a thin metal sheet is prepared as an exterior member. Then, for example, cup molding is performed on the above-mentioned exterior member to form a recess having a size capable of accommodating a power generation element described later.

On the other hand, a sheet in which a slurry of a positive electrode active material is coated on the surface of a current collector made of a metal foil having a thickness of the order of μm, and an external (positive electrode) terminal is connected to the current collector. A sheet-shaped negative electrode in which a negative electrode active material is coated on the surface of a current collector and an external (negative electrode) terminal is connected to the current collector. A separator is inserted between the two and then wound in a cylindrical shape. Then, the cylindrical body is crushed in the radial direction to manufacture a flat power generating element. At this time, the positive electrode and the negative electrode are aligned so that the respective external terminals described above face the same direction.

After the power generating element is housed in the concave portion of the exterior member, the exterior member is folded in two to cover the entire power generating element, and one peripheral edge is removed and the other peripheral edge is heat-melted. By performing the bonding treatment, the exterior member is formed into a bag shape in which one end is opened and the remaining peripheral portion is a heat-sealed portion. Then, after injecting a predetermined electrolytic solution from the above-mentioned opening, heat sealing treatment is also applied to the opening to seal it,
The power generation element is enclosed in the exterior member. The two external terminals extending from the power generation element in the same direction are
It extends outside from any one of the above-mentioned heat-sealing parts (three places).

Since these assembled batteries are in an uncharged state at that time, they are used for actual use after being initially charged. Charging at that time is usually performed in the atmosphere.

[0007]

By the way, when the uncharged battery is charged for the first time immediately after the production, gas is generated to increase the internal pressure of the battery or expand the active material. Therefore, there is also a problem that the battery after initial charging swells and cannot maintain a desired thickness. In particular, in the case of the thin battery that pursues weight reduction, downsizing, and thinning, the amount of gas generation increases, and the increase in internal pressure and twisting of the battery due to the decrease in free space inside the battery. Is likely to occur, and since the exterior member is soft and therefore easily deformed, the swelling of the battery during initial charging tends to occur frequently.

To solve such a problem, for example, the gas generated at the first charge is exhausted to the outside of the exterior member or the exterior can to have a desired thickness, and then the exhaust port is sealed. The so-called open charging method is implemented. In addition, a so-called press charging method is also used in which an uncharged battery is fixed with a mold or a jig and the battery is initially charged in that state. However, in the case of the open charging method, the electrolytic solution overflows from the exhaust port together with the exhaust gas, so that the peripheral equipment is contaminated or corroded, and a countermeasure is required. In addition, in the case of the press charging method, complicated work such as mounting and demounting the uncharged battery in the mold or jig is required, and since the uncharged battery is fixed by applying pressure, the battery is damaged. There is a problem that there are things to do.

The present invention solves the above-mentioned problems in the conventional method implemented to suppress the expansion of the battery at the time of initial charging, and at the same time, finishes the thickness to a desired thickness even after the initial charging. It is also an object of the present invention to provide a method for manufacturing a sealed battery, which is capable of improving the discharge capacity and the cycle life characteristics. Another object of the present invention is to provide a simple and reliable method for evaluating the sealing property of a sealed battery.

[0010]

In order to achieve the above object, in the present invention, a power generating element having a positive electrode, a separator, a negative electrode and a non-aqueous electrolyte is composed of a laminated film of a metal sheet and a resin film. A method for manufacturing a sealed battery, which is characterized in that an uncharged battery is manufactured by enclosing it in an outer member or a metal outer can, and then the uncharged battery is charged in a pressurized gas. .

Further, after performing a pressure treatment on the sealed battery in a pressurized gas, the sealed battery is taken out into the atmosphere, and the time-dependent change in the outer diameter of the sealed battery is measured. If there is no change, it is determined that the sealability is good, and a sealability evaluation method for a sealed battery is provided.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION First, the manufacturing method of the present invention will be described in detail by taking a sealed non-aqueous electrolyte thin battery as an example. The manufacturing method of the present invention is roughly carried out through the following steps. First step: production of power generation element.

Second step: encapsulating the power generating element with an exterior member,
A step of making one peripheral portion of the exterior member open and subjecting the other peripheral portion to heat fusion treatment. Third step: a step of injecting the non-aqueous electrolytic solution through the above-mentioned opening and then subjecting the opening to heat fusion treatment to seal the power generation element in the exterior member. Fourth step: a step of charging (initial charging) the uncharged battery obtained in the third step in a pressurized gas.

The manufacturing method of the present invention is completed by the above four steps. Below, each process is demonstrated one by one. In the first step, the power generation element is manufactured. The power generation element is composed of a positive electrode, a negative electrode, and a separator sandwiched between them, which will be described later. First, the positive electrode has a structure in which a positive electrode active material is carried in layers on both sides or one side of a current collector made of, for example, Al foil. Specifically, a slurry obtained by mixing a positive electrode active material, a binder and a non-aqueous solvent is applied in layers on the surface of a current collector, and then the non-aqueous solvent is volatilized, and the whole is applied by, for example, roll pressing. It is manufactured by pressure forming.

Here, as the positive electrode active material, a Li composite oxide having a high energy density is suitable. For example, Li
CoO ₂ , LiNiO ₂ , Li _x Ni _y Co _1-y O ₂ (where x and y are different depending on the charged state of the battery, but usually 0 <x
<1, 0.7 <y <1), Li _x Co _y
Sn _z O ₂ (where x, y, and z are each 0.05
≤ x ≤ 1.10, 0.85 ≤ y ≤ 1.00, 0.001 ≤ z
A number satisfying ≦ 0.10) and the like.

Of these, Li _x Co _y Sn _z O ₂
Is preferred. This is because the material powder has a small particle size and is uniform, and when used as an active material, the battery has excellent cycle life characteristics. In this compound, if the index z is smaller than 0.001, it becomes difficult to control the particle size, and if the index z is larger than 0.10, the capacity is lowered. Therefore, the index z is set within the above range.

Such a Li complex oxide contains a carbonate, a nitrate, an oxide or a hydroxide of Li and a carbonate, a nitrate, an oxide or a hydroxide such as Co, Mn or Ni in a predetermined ratio. The mixed powder obtained by mixing and crushing can be produced by firing in an oxygen atmosphere at a temperature of 600 to 1000 ° C. Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), ethylene-propylene-diene copolymer (EPDM), styrene-butadiene rubber (SBR).
Etc. can be used.

In addition to the slurry prepared from these materials,
For example, when an appropriate amount of a conductive material such as carbon black or graphite is added, the conductivity of the active material layer is improved and the utilization factor is improved. Examples of the non-aqueous solvent include N-methylpyrrolidone, acetic acid esters, ethyl cellosolve, and the like.

Next, the negative electrode is manufactured by slurry coating as in the case of the positive electrode, and a layer of the negative electrode active material is formed on both surfaces or one surface of the current collector. In that case, for example, a sheet or mesh of Cu or Ni is used as the current collector. The negative electrode active material may be any as long as it can absorb and desorb Li ions, and examples thereof include graphite, coke such as petroleum coke, pitch coke and needle coke, pyrolytic carbon, Examples thereof include carbides of organic polymer materials such as phenol resin, metallic Li, polyacetylene, and polypyrrole.

Further, as the binder, in addition to the above-mentioned binders used in the slurry for the positive electrode, carboxymethyl cellulose is also suitable. As the separator interposed between the positive electrode and the negative electrode, for example, a microporous membrane made of polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-butene copolymer, or a woven fabric made of fibers of these materials. And non-woven fabric.

In the production of the power generating element, first, the positive electrode, the first separator, the negative electrode and the second separator described above are superposed on each other, and the laminated sheet-like material is arranged with a core material on the negative electrode side, for example. The positive electrode is placed on the outer side, the material is spirally wound, and then the core material is extracted to produce a cylindrical product. In addition,
Prior to this winding, the active material layers of the positive electrode and the negative electrode are partially removed to expose the surface of the current collector, and external terminals in the form of lead pieces are connected to each current collector by, for example, a welding method.

Then, the above-mentioned cylindrical material is heated to a temperature of 60 to 1
While heating at 00 ° C, preferably 80 to 95 ° C, in the radial direction is 9.8 MPa to 29.4 MPa, preferably 11.8 MPa to 21.
Pressurize with a pressure of 6 MPa. As a result, as shown in FIG. 1, a power generating element 1 is obtained which is shaped into a flat shape as a whole, and the positive electrode terminal 2 and the negative electrode terminal 3 extend in the same direction from one of the winding cross sections. .

FIG. 2 which is a sectional view taken along the line II-II of FIG. 1 shows the sectional structure of the power generating element 1 in the vicinity of the positive electrode terminal. As is clear from FIG. 2, the power generating element 1 includes a positive electrode 4 composed of positive electrode active material layers 4b and 4b carried on both sides of a current collector 4a, and a negative electrode carried on both sides of a current collector 5a. The negative electrode 5 including the active material layers 5b and 5b is the separator 6
A plurality of units that are stacked via the above are alternately stacked, and the above-described second separator is interposed between the units. The positive electrode terminal 2 is welded to the current collector 4a of the positive electrode 4 in the outermost layer unit.

Here, the material of the positive electrode terminal 2 and the negative electrode terminal 3 is largely premised to be a material that does not elute in the non-aqueous electrolyte solution described later, and on top of that, the corrosion resistance to the non-aqueous electrolyte solution is good. In addition, it is preferable that the material does not increase the impedance of the manufactured battery. Specifically, Al or Al alloy is used for the positive electrode terminal 2, and Cu or Ni is used for the negative electrode terminal 3.

In the case of Al or Al alloy, for example,
Anodized at 15 V in a phosphoric acid aqueous solution having a concentration of 100 g / L or a sulfuric acid aqueous solution having a concentration of 100 g / L,
What was anodized at 20 V in a 75 g / L chromic acid aqueous solution, what was surface-treated by immersing it in a 140 g / L sodium hydroxide aqueous solution, sodium chromate: sulfuric acid: water mass ratio Of which surface treatment is performed by immersing in a solution having a temperature of 3:30:10 at a temperature of 60 to 70 ° C. is a porous alumina having fine protrusions with a height of several nm to several thousands nm on the surface. Since the film is formed, it is possible to improve the corrosion resistance and the adhesiveness with the sealant film forming the exterior member described later.

When the negative electrode terminal 3 is made of Ni alone, since the impedance of Ni is high, abnormal heating occurs due to resistance loss when the manufactured battery is externally short-circuited, and the terminal is likely to melt. From such a thing,
As the negative electrode terminal 3, it is preferable to use, for example, Cu, which has excellent conductivity, as a base material and which is plated with Ni. The above-mentioned power generation element is composed of a positive electrode, a separator and a negative electrode, but this power generation element is stored in an exterior member and then injected with a non-aqueous electrolyte solution. It becomes a power generation element having an electrolytic solution.

However, the power generating element usable in the present invention is not limited to this, and for example, a polymer gel electrolyte in which a non-aqueous electrolyte is impregnated in a polymer material, or an all-solid-state polymer is used. A solid electrolyte may be arranged between the positive electrode and the negative electrode. The polymer material used for the above-mentioned polymer gel electrolyte is not particularly limited, but for example, polyacrylonitrile resin, polyethylene oxide resin, polyether resin, polyester resin, polyacrylate Examples of such resins include fluororesins and fluororesins.

The power generating element 1 manufactured in this way is
Next, it is transferred to the second step. First, in the second step, a laminated film having a three-layer structure in which resin films are laminated on both surfaces of a metal sheet is used as an exterior member. The metal sheet functions as a barrier for preventing the non-aqueous electrolyte solution and the gas generated in the battery from permeating to the outside, and a sheet made of Al or Al alloy is usually used.

In this exterior member, one of the resin films directly forms a heat-sealed portion having high liquid-tightness and air-tightness at the time of heat-sealing treatment so as to seal the power generating element in the outer-sealed member. Contribute to. In that respect, this resin film is hereinafter referred to as a sealant film. On the other hand, the resin film laminated on the other side of the metal sheet is
At the time of manufacturing the battery, it becomes a film that constitutes the outer surface of the battery without being involved in the formation of the heat-sealed portion, protects the metal sheet, and at the same time contributes to ensuring the strength of the battery. Therefore, this resin film is made of a material having rigidity.

Of these two types of resin films, the sealant film is preferably an unstretched film made of a material that does not dissolve or swell in contact with the non-aqueous electrolyte. Examples of materials for such a film include polyolefins such as unstretched polypropylene (PP) and linear low density polyethylene (LLDPE), ethylene / vinyl acetate copolymer (EVA), ionomer (IO), polyamide ( PA), nylon (N
y), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyvinyl chloride (P
VC), polyvinylidene chloride (PVDC), polyvinyl alcohol (PVA), ethylene / vinyl alcohol (EVOH), polycarbonate (PC), polystyrene (PS), polyacrylonitrile (PAN), ethylene / acrylic acid copolymer (EAA) , Ethylene / methacrylic acid copolymer (EMAA), ethylene / methyl acrylate copolymer (EMA), ethylene / methyl methacrylate copolymer (EMMA), ethylene / ethyl acrylate copolymer (EEA), polymethylpentene (PM)
P) etc. can be mentioned.

Then, using these materials as a base polymer,
For example, when an acid anhydride such as maleic anhydride is graft-polymerized, the film of the material has an improved adhesive force with a metal and is sealed by a heat fusion treatment without using an adhesive insulating film described later. This is preferable not only because it enhances the stopping effect, but also because the adhesiveness with the metal increases, so that the sealing effect at the location where the external terminal is located can be enhanced.

On the other hand, as the material of the resin film having rigidity, for example, biaxially oriented polyolefin such as biaxially oriented polyethylene (PE) or polypropylene (PP),
Examples thereof include polyethylene terephthalate (PET) and polyamide (PA). In the second step, the short side is slightly longer than the long side of the power generating element 1 to be accommodated, and the long side is slightly more than twice the short side of the power generating element 1 as shown in FIG. , A resin film 7c having rigidity with the sealant film 7b sandwiching the metal sheet 7a
An exterior member 7 having a three-layer structure formed by laminating and is prepared. Then, for example, cup molding is performed on the right half of the exterior member 7 from the sealant film 7b side to form the power generating element 1
The recessed portion 8 having a size capable of accommodating the is formed.

A plasma irradiation process is performed in advance on a peripheral edge portion (hatched portion in FIG. 3) of the sealant film 7b in this exterior member, that is, a portion which is subjected to heat fusion treatment as described later and converted into a heat fusion treatment portion. It is preferable to set. When this plasma irradiation treatment is performed, the high-energy plasma particles are combined with the dirt attached to the irradiation-treated surface to remove the surface dirt, and the irradiation-treated surface is cleaned. Further, the chemical bond on the irradiation-treated surface is changed, and a hydrophilic group such as an OH group is introduced on the surface to improve the adhesiveness. Furthermore, the low-activity molecular layer on the irradiated surface is decomposed to form a highly-active oxide layer, which improves the wettability of the surface. Also, unevenness at the atomic level occurs on the irradiated surface. .

Therefore, when the surface of the resin or metal is subjected to the plasma irradiation treatment, the wettability of the surface of the resin or metal is improved and the contact angle with water is reduced, so that the resin and the metal, or the resin and the resin. The adhesion between the two is improved. In the present invention, a plasma irradiation process that exerts such an effect is applied to the peripheral portions of the sealant films 7b, 7b to be heat-sealed to each other to clean the peripheral surface, and in the subsequent steps. It is preferable to ensure the airtightness and the liquidtightness of the heat-sealed portion formed.

In the present invention, this plasma irradiation treatment may be carried out in the atmosphere using a commercially available plasma irradiation device (for example, ST-7000 manufactured by Keyence Corporation). For example, as shown in FIG. 4, the outer portion of the plasma 10 generated in a barrel shape between the electrodes 9a and 9b is irradiated onto the peripheral portion of the exterior member 7 running in the direction perpendicular to the paper surface. Good. At this time, the distance between the plasma and the exterior member is about 5 to 50 mm, and the irradiation time is 1 to
If the time is about 3 seconds, suitable surface cleaning can be achieved.

After accommodating the power generating element 1 in the recess 8,
The left half of the exterior member 7 is folded in two near the boundary line l ₀ with the recess 8 and folded to cover the upper surface of the power generation element 1 housed in the recess 8. As a result, as shown in FIG.
The entire power generating element 1 housed in the recess 8 is the exterior member 7.
The intermediate member A encapsulated in is manufactured.

In this intermediate member A, the upper exterior member portion and the lower exterior member portion directly overlap with each other. 2
As shown in FIG. 6, the side edge portions of the portions are in contact with each other at the portions where the plasma irradiation treatment is performed on the sealant films 7b, 7b, and the other peripheral edge portions, that is, the external terminals. In the peripheral edge portion where 2 and 3 are extended, the state where the plasma irradiation treatment points of the sealant films 7b and 7b are in contact with each other and the external terminals 2 and 3 from above and below in the plasma irradiation treatment points of the sealant films 7b and 7b. There is a trapped condition.
The outer surface of the intermediate member A is composed of a resin film 7c having rigidity.

Then, of the above-mentioned three peripheral portions,
A heat fusion treatment is applied to the other two places, leaving one place. In that case, one of the two peripheral portions is the peripheral portion from which the external terminal extends. Therefore, at this time, the exterior member 7 is formed into a bag shape with one peripheral edge opened, and the power generation element 1 is accommodated therein.

Of the above-mentioned peripheral portions, when heat-sealing the peripheral portions where the external terminals 2 and 3 extend, as shown in FIG. 6, the sealant films 7b and 7b of the exterior member and the external terminals are formed. It is preferable to interpose the adhesive insulating film 11 between the two (3). Then, the plasma irradiation process described above is applied to the respective surfaces of the external terminal 2 (3) and the adhesive insulating film 11.

By doing so, the respective materials are firmly adhered to each other during the heat-sealing process, and the liquid-sealing property and air-tightness of the formed heat-sealing portion are improved. As such an adhesive insulating film, it is preferable that the adhesive insulating film has the same properties and moldability as those of the sealant film, and has excellent adhesiveness to the external terminal which is a metal. For example, a resin obtained by graft-polymerizing an acid anhydride such as maleic anhydride with the above-mentioned resin used for the sealant film as a base can be used.

The adhesive insulating film may be of the same system as that of the sealant film or of a different system. The throwing power becomes uniform, and the reliability of the formed heat-sealed portion (sealing structure) increases. In the next third step, the non-aqueous electrolytic solution is injected from the opening in the bag-shaped exterior member formed in the second step, and then the opening is also subjected to heat fusion treatment. As a result, as shown in FIG. 7, all of the three peripheral portions of the exterior member 7 are heat-sealed portions, the power generating element 1 is sealed in the recess 8, and from one end It is possible to obtain an uncharged thin battery in which the external terminals 2 and 3 are extended.

In the third step, it is preferable that the heat-sealing process is performed in a state where the inside of the bag-shaped exterior member is deaerated beforehand under reduced pressure. The air contained in the power generating element 1 is removed, and the impregnation speed of the non-aqueous electrolyte into the power generating element is increased,
In addition, the entire power generation element can be uniformly impregnated with the non-aqueous electrolytic solution. As such a method, a method of degassing the inside of the exterior member under reduced pressure and then injecting a non-aqueous electrolyte solution to seal it, and a method of injecting the non-aqueous electrolyte solution into the exterior member under an air atmosphere and then decompressing A method of degassing and finally sealing can be adopted.

The non-aqueous electrolytic solution injected at this time is a non-aqueous solvent in which the electrolyte is dissolved.
For example, lithium perchlorate (LiClO ₄ ), lithium tetrafluoroborate (LiBF ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium hexafluoroarsenate (LiAs)
F ₆ ), lithium trifluoromethanesulfonate (Li
_{CF 3 SO 3), LiN (} CF 3 SO 2) 2, lithium bis [5-fluoro-2 Orato 1-benzene - sulfonato (2)] and the like borate.

As the non-aqueous solvent, for example, γ-butyrolactone, ethylene carbonate, propylene carbonate, diethyl carbonate, methyl ethyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 1,3- Dioxolane,
Methyl sulfolane, acetonitrile, propyl nitrile, anisole, acetic acid ester, propionic acid ester and the like can be used. These may be used alone or as a mixture of two kinds.

When a surfactant such as trioctyl phosphate (TOP) or di-n-butyl carbonate (DNBC) is added to these non-aqueous solvents, the wettability of the resulting non-aqueous electrolyte with respect to the separator is improved. It is suitable for improvement. The electrolyte concentration in the non-aqueous electrolyte solution is 0.1.
It is preferably 5 mol / L or more.

As a non-aqueous electrolyte, a mixture of ethylene carbonate (EC) and γ-butyrolactone (γ-BL) was used as a non-aqueous solvent, and lithium tetrafluoroborate (LiB
With those and F ₄₎ the electrolyte, even to increase the degree of vacuum during vacuum degassing, evaporation is hard to occur, since the foaming is small, it is easy to cell production. In that case, EC is γ-B
Since the viscosity is higher than L and the capacity at low temperature is small,
The higher the EC ratio in the mixture, the more easily the low temperature characteristics of the manufactured thin battery deteriorate. On the contrary, in the case of γ-BL, the higher the ratio is, the better the low temperature characteristic is.
Since it easily reacts with the negative electrode (carbon) at a high temperature, the capacity of the manufactured battery is greatly reduced at a high temperature.

From the above, when the nonaqueous solvent of EC and γ-BL is used, the EC / γ-BL ratio (volume ratio)
Is preferably 2/1 to 1/5. Also, LiB
The amount of F ₄ added is 0.75 to 2 mo based on the total amount of the non-aqueous solvent.
It is preferably 1 / L. If it is less than 0.75 mol / L, it becomes difficult to manufacture a thin battery having a desired capacity, and 2
If it is more than mol / L, the cycle life characteristics of the battery are likely to be deteriorated, and the non-aqueous electrolyte becomes expensive.

In the above series of manufacturing methods,
It is preferable to subject the manufactured positive and negative electrodes and one or more separators to plasma irradiation treatment. This is because the wettability of the power generation element is improved as a whole when the non-aqueous electrolyte solution is injected in the third step, so that the non-aqueous electrolyte solution is smoothly impregnated into the power generation element and the impregnation speed can be shortened. . This means that under the recent circumstances where it is required to increase the energy density, the power generation element is housed in the exterior member without any gap, which makes it difficult to smoothly impregnate the nonaqueous electrolyte into the power generation element. Considering that
It can be said that this is a preferable effect.

In the fourth step, the uncharged thin battery thus obtained is initially charged. Specifically, an uncharged thin battery is housed in a pressure container, and each of the positive electrode terminal and the negative electrode terminal of the thin battery is provided through the wall of the pressure container and is It connects with the connection terminal connected with the charging device arrange | positioned at through a lead wire, and performs initial charge, pressurizing the said thin battery with the pressurization gas mentioned later. Also, once
You may pressurize and may perform the first charge after that.

By the initial charging under the pressure, expansion of the active material and expansion of the thin battery due to gas generation are suppressed. At the same time, the pressure applied to the non-aqueous electrolyte in the battery increases the impregnation rate of the non-aqueous electrolyte into the power generation element, which results in uniform impregnation of the non-aqueous electrolyte, resulting in an increase in discharge capacity and cycle life characteristics. It is possible to obtain effects such as improvement of. Examples of the pressurized gas used include dry air, carbon dioxide gas, nitrogen gas, inert gas and the like. From the viewpoint of preventing water from entering the inside of the battery, it is preferable that none of them contains water.

When carbon dioxide gas is used as the pressurized gas, a part of the carbon dioxide gas penetrates into the battery from the exterior member to form a stable solid electrolyte interface (SEI) in the power generating element.
This is preferable because it improves the cycle life of the non-aqueous electrolyte. The pressure of the pressurized gas is 0.3 to 1 in gauge pressure.
It is preferably set to 5 MPa. When the pressure is lower than 0.3 MPa, the effect of suppressing the expansion of the battery is poor.

When the pressure of the pressurized gas is increased, the effect of suppressing the expansion of the battery is increased, and the impregnation speed of the non-aqueous electrolyte into the power generating element can be increased, but on the other hand, the pressure is increased. Accordingly, it is necessary to make the pressure vessel a pressure resistant structure, and it becomes difficult to penetrate the wall of the pressure vessel to dispose the connection terminal. Therefore, the upper limit of the applied pressure is about 15 MPa in gauge pressure. Set to.

If the non-aqueous electrolytic solution is not completely impregnated into the power generating element during the initial charging, the charging proceeds only in the portion where the non-aqueous electrolytic solution is impregnated. Then, the charging progresses in a state in which the rate is substantially higher than that in a state in which the entire power generating element is completely impregnated with the non-aqueous electrolytic solution, that is, in a so-called full impregnation state. Therefore, the discharge capacity of the obtained battery is lowered, and the battery characteristics such as cycle life characteristics are deteriorated. Moreover, the battery characteristics described above vary due to the variation in the impregnation state of the non-aqueous electrolyte.

For this reason, it is necessary to carry out the initial charging in a fully impregnated state. In the case of this thin battery,
Capacitance and / or impedance between the positive electrode and the negative electrode can be measured by a non-destructive test to determine the impregnation state of the non-aqueous electrolyte into the power generation element. The non-destructive test is based on the following points. That is, since the relative permittivity of the non-aqueous electrolyte is orders of magnitude larger than the relative permittivity of the void (air portion) of the power generating element, the non-aqueous electrolyte impregnates the void of the power generating element and the void becomes non-aqueous. This is because when the electrolyte is replaced, the capacitance measured between the positive electrode and the negative electrode greatly increases, and similarly, the impedance of the non-aqueous electrolyte is orders of magnitude smaller than the impedance of the void. When the void is replaced with the non-aqueous electrolyte, the impedance measured between the positive electrode and the negative electrode is reduced by an order of magnitude.

Therefore, in the present invention, the capacitance or / and the impedance of the manufactured thin battery is measured, and when the measured value matches the value in the fully-impregnated state, which was previously obtained by an experiment. First, it is determined that the impregnation is complete. Next, the sealability evaluation method of the present invention will be described. This evaluation method, the thin battery manufactured by the method of the present invention described above is taken out of the pressurized container into the atmosphere, the change over time of the outer shape of the battery is observed, and the change is recognized as insufficient sealing property, This is a method of judging that no change is recognized as having sufficient sealing property.

If, in the third step, there is an insufficient fusion-bonding portion during the heat-sealing treatment of the exterior member, the pressurized gas of the fourth step is applied to the battery, and the pressurized gas is discharged. Penetrates into the inside of the battery from a location where fusion is insufficient. Then, when the battery is taken out of the pressurized container into the atmosphere, the internal pressure of the battery rises due to the intrusion of the pressurized gas, so that the exterior member expands based on the differential pressure between the internal pressure and the atmospheric pressure. .

That is, a battery having an insufficient sealing property is taken out from the pressure vessel into the atmosphere and, at the same time, it is swollen and becomes thicker. However, in the case of a battery having a sufficient sealing property, the above phenomenon does not occur,
The thickness of the pressurized container is maintained even when taken out into the atmosphere. Thus, according to the sealability evaluation method of the present invention,
It is possible to judge whether the sealing property of the battery is good or bad very easily and surely.

Although the above description has been made on the case of a thin battery using a laminated film as the exterior member, the method of the present invention is not limited to this, and for example, a metal such as Al is used as the exterior member. It can also be applied to a sealed battery using an outer can made of.

[0059]

EXAMPLES Example 1. Production of positive electrode LiCoSn _0.02 O _{2 with} average particle size of 3 μm (positive electrode active material)
89 parts by mass, graphite powder (conductive filler: KS6 manufactured by Lonza Co., Ltd.) 6 parts by mass, polyvinylidene fluoride (binder: # 1100 manufactured by Kureha Chemical Co., Ltd.) 3 parts by mass, and N-methylpyrrolidone (solvent) 25 The mixture consisting of parts by mass was uniformly sheared and stirred, and then dispersed by a bead mill to prepare a slurry having an apparent viscosity of 7,500 mPa · s.

Then, the above-mentioned slurry is uniformly applied to both sides of a strip-shaped Al foil having a thickness of 20 μm, the non-aqueous solvent is dried and removed, and the mixture is pressure-molded by a roll press machine and then cut into a predetermined size to form a strip-shape. Was manufactured. Then, the Al foil at one end of the positive electrode is exposed, and the length is 50 mm and the width is 5 m.
An external (positive electrode) terminal made of Al and having a thickness of 0.1 mm was welded and attached.

2. Manufacture of Negative Electrode 50 parts by mass of scaly graphite was dispersed in 1.5 parts by mass of carboxymethyl cellulose to prepare a masterbatch coating. To this coating material (51.5 parts by mass), 50 parts by mass of carbon fiber was added, which was then shear-dispersed, 2.4 parts by mass of styrene-butadiene rubber latex was further added, and the whole was uniformly mixed and stirred to give an apparent viscosity of 4500 mPa. A slurry of s was prepared.

Then, a strip-shaped Cu foil having a thickness of 10 μm was evenly applied on both sides, dried, pressure-molded by a roll press machine, and then cut into a predetermined size to produce a strip-shaped negative electrode. A Cu foil at one end of this negative electrode was exposed, and a Ni external (negative electrode) terminal having a length of 50 mm, a width of 5 mm and a thickness of 0.1 mm was welded and attached thereto. 3. Manufacturing thickness of power generation element 25μm, porosity 50%, air permeability 300sec / 10
Prepare a separator consisting of a 0 cc polyethylene microporous membrane, stack the positive electrode, negative electrode, and separator in the order positive electrode / separator / negative electrode / separator, and then use a core with a flat cross-sectional shape and place the positive electrode on the outside. Then, it was wound into a spiral shape, and was further heated and pressed at a temperature of 90 ° C. and a pressure of 1.7 MPa using a hydraulic press machine to manufacture a flat power generating element.

4. Manufacture of thin battery A stretched nylon film (resin film having rigidity) having a thickness of 25 μm, an Al foil (metal sheet) having a thickness of 40 μm, and a maleinized polypropylene film (sealant film) having a thickness of 70 μm are used in this order with a urethane adhesive. An exterior member formed by bonding and laminating was prepared. The melting point of the sealant film is 138 ° C.

[0064] After forming the concave portion by performing a cup molded from the sealant film side of the exterior member, and cut into strips to the exterior member 7 shown in FIG. 3, and by the end l ₀ of the recess 8 a boundary recess The part where no mark was formed was bent by a molding machine at 180 ° C. so that the sealant films faced each other vertically. Then, the whole was developed again, and a plasma irradiation process was applied to the shaded portion in FIG.

Then, the power generation element contains 300 pp of water.
After vacuum-drying at a temperature of 60 ℃ until it becomes less than m,
Plasma was also applied to the surfaces of the two exterior terminals. Next, the power generating element described above is housed in the recess of the exterior member, and the other exterior member is bent again to form the intermediate member A shown in FIG.
Assembled. In this process, an adhesive insulating film, which has been subjected to plasma irradiation treatment in advance, is interposed between the external terminal and the sealant film (there are two upper and lower portions) at the peripheral portion where the external terminal extends. I dressed up.

Then, first, a heat fusion treatment using a press head (pressure 0.2 MPa) at a temperature of 210 ° C. is applied to one peripheral edge portion on the short side of the intermediate member A for 5 seconds, and then,
The same heat fusion treatment was performed for 5 seconds also on the peripheral portion where the external terminal extends, and the exterior member was formed into a bag shape with one of the long sides open. Then, in a vacuum atmosphere of 1 Torr or less, the nonaqueous electrolytic solution was injected into the exterior member through the opening described above. As the non-aqueous electrolyte, trioctyl phosphate (TOP) is added in an amount of 0.5% by mass to a mixed solution of ethylene carbonate (EC) and γ-butyrolactone (γ-BL) in a volume ratio of 1: 3. Li, as a solvent
A solution was used in which BF ₄ was dissolved at a concentration of 1.25 mol / L.

Then, the above-mentioned opening was heat-sealed under the same conditions as described above, and the excess exterior member was cut and removed to manufacture an uncharged thin battery. Next, the thin battery was placed in an autoclave (pressurized container), dry air was pressed into the container, and pressure treatment was performed for 10 minutes at a gauge pressure of 0.5 MPa. And finally, while maintaining the pressurized state, the temperature is 20 ° C.
At a temperature of 45 ° C and a temperature of 0.2C (150m
The initial charge is performed for 8 hours under the conditions of A), and the external dimensions are 62 m in length.
m, width 35mm, thickness 3.8mm, rated capacity 750mAh
A thin non-aqueous electrolyte secondary battery of (0.2C) was manufactured.

For comparison, a thin nonaqueous electrolyte secondary battery was manufactured in the same manner as in Example except that the initial charging was performed in the atmosphere at a temperature of 20 ° C. 5. Performance evaluation The thickness and discharge capacity of the battery were measured immediately after the end of initial charging. Further, the thickness, discharge capacity, and discharge capacity retention rate of the battery after 1C / 1C-500 cycle charge / discharge were measured.
The above results are collectively shown in Table 1.

[0069]

[Table 1]

As is clear from Table 1, the batteries manufactured by the method of Example have a smaller thickness after initial charging and a larger discharge capacity than the battery manufactured by the method of Comparative Example. In that case, if the temperature at the time of initial charging is high, the thickness after initial charging becomes slightly thick, but the discharge capacity becomes large. In addition, the battery manufactured by the method of Example has a smaller thickness and a higher discharge capacity retention rate than the battery manufactured by the method of Comparative Example even after cycle charging and discharging.

[0071]

As is clear from the above description, according to the method of the present invention, since the assembled uncharged battery is initially charged in the pressurized gas, the expansion of the battery is suppressed, and at the same time, the non-aqueous electrolyte is Since the power generating element is effectively impregnated under pressure, it is possible to manufacture a battery having a small thickness and an improved discharge capacity and a discharge capacity retention rate after cycle charge / discharge, and its industrial value is great.

Further, when the battery is assembled in the method of the present invention, the power generating elements such as the positive electrode, the negative electrode and the separator are irradiated with plasma, so that the wettability with the electrolytic solution is improved and a battery having a high energy density is manufactured. You can

[Brief description of drawings]

FIG. 1 is a perspective view showing a power generation element.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is a perspective view showing a state in which a power generation element is housed in an exterior member.

FIG. 4 is an explanatory diagram for explaining a plasma irradiation process.

5 is a perspective view showing an intermediate member A. FIG.

FIG. 6 is a cross-sectional view showing a state of a portion (peripheral portion) where an external terminal is located.

FIG. 7 is a perspective view showing a thin battery of the present invention.

[Explanation of symbols]

1 power generation element 2 External terminal (positive terminal) 3 External terminal (negative terminal) 4 positive electrode 4a Current collector 4b Positive electrode active material layer 5 Negative electrode 5a Current collector 5b Negative electrode active material layer 6 separator 7 Exterior material 7a metal sheet 7b sealant film 7c Resin film with rigidity 8 recess 9a, 9b electrodes 10 plasma 11 Adhesive insulating film

Continued front page    (72) Kenji Tsuchiya             8th Shinsugita Town, Isogo Ward, Yokohama City, Kanagawa Prefecture             Ceremony company Toshiba Yokohama office (72) Inventor Toru Yajima             8th Shinsugita Town, Isogo Ward, Yokohama City, Kanagawa Prefecture             Ceremony company Toshiba Yokohama office F-term (reference) 5H028 AA01 BB01 BB10 BB11 BB15                       HH05 HH09                 5H029 AJ11 AJ14 AK03 AL06 AL07                       AM03 AM04 AM05 BJ04 CJ28                       DJ02 DJ03 EJ12 HJ04

Claims (6)

[Claims] 1. An uncharged battery is obtained by encapsulating a power generation element having a positive electrode, a separator, a negative electrode, and a non-aqueous electrolyte in an exterior member made of a laminated film of a metal sheet and a resin film or a metal exterior can. A method for manufacturing a sealed battery, comprising manufacturing and then charging the uncharged battery in a pressurized gas. 2. The uncharged battery is housed inside a pressure vessel, and the uncharged battery is charged from a charging device arranged outside the pressure vessel via a terminal penetrating the pressure vessel. The method for manufacturing the sealed battery according to claim 1. 3. The method for manufacturing a sealed battery according to claim 1, wherein the pressurized gas is dry air, nitrogen, carbon dioxide, or an inert gas. 4. The pressure of the pressurized gas is 0.
It is 1-15 MPa, The manufacturing method of the sealed battery in any one of Claims 1-3. 5. The method for manufacturing a sealed battery according to claim 1, wherein the battery is charged in a heated state. 6. The sealed battery is subjected to a pressure treatment in a pressurized gas and then taken out into the atmosphere, and the time-dependent change in the outer shape of the sealed battery is measured.
A method for evaluating the sealing property of a sealed battery, which is characterized in that the sealing property is judged to be good when it does not change.