JP6236292B2 - Method for producing film-clad battery - Google Patents

Description

  The present invention relates to a method for producing a flat film-clad battery having a laminate film or the like as an exterior body.

  As described in Patent Document 1, a power generation element formed by laminating a positive electrode plate and a negative electrode plate with a separator interposed between them is housed together with an electrolyte in a flat rectangular outer casing, and is connected to a terminal from one side thereof. A film-clad battery in which four sides of the outer package are sealed is known. In the manufacturing process of this type of film-clad battery, two sheets of material are overlapped, and the three sides except one side are sealed to form a bag-like body, and the power generation element is housed inside the opening. After injecting the electrolyte into the bag-like body from one side, the side to be opened is sealed by thermal fusion. Next, after passing through an aging and initial charging process, an opening is provided in the exterior body in a vacuum environment, and a gas venting process for discharging the internal gas is performed. Is obtained.

In the above degassing step, it is generally said that the higher the degree of vacuum (the greater the degree of vacuum, the lower the pressure), the more reliable the internal gas can be discharged. It is said that the environment of standard 0.1-10 <^-5> Pa) is preferable. For example, paragraph [0028] of Patent Document 1 describes that the degassing step is preferably performed in a high vacuum atmosphere of 1 × 10 ⁻³ Pa or less.

JP 2001-93508 A paragraph [0028]

  However, in the degassing process, simply increasing the degree of vacuum cannot sufficiently exhaust the gas inside the exterior body. That is, the gas generated at a position far from the opening requires time to move to the opening, so that even if the degree of vacuum is sufficiently high, it is difficult to exhaust in a short time.

  In addition, when the degree of vacuum is too high, the electrolyte solution boils and volatilizes, which causes a new problem that the amount of decrease in the electrolyte solution increases.

  This invention is made | formed in view of such a situation, and it aims at discharging | emitting internal gas favorably, suppressing volatilization of the electrolyte solution in a degassing process.

  In a film-clad battery to be manufactured according to the present invention, a power generation element formed by laminating a positive electrode plate and a negative electrode plate via a separator is housed together with an electrolyte in a flat exterior body, and a terminal is led out. The exterior body is sealed.

And the manufacturing method of the film-clad battery according to the present invention includes the inside of the exterior body in a part of the exterior body in which the power generating element is sealed together with the electrolytic solution in a predetermined environment whose pressure is lower than the atmospheric pressure. Forming an opening that communicates with the outside, and a gas venting process that exhausts the gas inside the exterior body from the opening. This gas venting process reduces the pressure of the environment in which the exterior body is disposed to a low vacuum The pressure in the environment is kept in the predetermined pressure range by repeating the operation of reducing the pressure when the pressure in the environment rises to a predetermined value within a predetermined pressure range of The predetermined pressure range of the low vacuum is set to a value that prevents the gas inside the outer casing from being discharged well when the pressure is further increased, and the electrolyte is boiled when the pressure is further decreased. Possible value The lower limit value is set, and the predetermined value is a value within a predetermined pressure range of the low vacuum, and is a value near the upper limit value of the predetermined pressure range. It is a period until the pressure increase rate in the environment becomes a predetermined determination value or less .

  According to the present invention, in order to perform degassing within a predetermined pressure range of low vacuum with a low degree of vacuum, it is possible to suppress the volatilization of the electrolytic solution and to maintain the vacuum state for a predetermined period or longer. Even a portion of the gas far from the gas can move to the opening, and the gas inside the exterior body can be discharged well.

The perspective view which shows an example of the film-clad battery used as the object of manufacture which concerns on this invention. Sectional drawing of a film exterior battery similarly. Explanatory drawing which shows a part of manufacturing process of a film-clad battery simply. The top view for demonstrating the manufacturing process of a film-clad battery. Explanatory drawing which shows the change of the vacuum degree in a degassing process.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. First, based on FIG. 1 and FIG. 2, an example of the film-clad battery 1 to be manufactured according to the present invention will be described. The film-clad battery 1 is, for example, a lithium ion secondary battery, and has a flat rectangular external shape as shown in FIG. 1, and a pair of positive electrodes made of conductive metal foil at one end in the longitudinal direction. Negative terminals 2 and 3 are provided.

  As shown in FIG. 2, the film-clad battery 1 is a battery in which a rectangular power generation element 4 is accommodated in an exterior body 5 made of a laminate film together with an electrolytic solution. The power generation element 4 includes a plurality of positive plates 41 and negative plates 42 that are alternately stacked with separators 43 interposed therebetween. For example, the three negative plates 42, the two positive plates 41, and the gap therebetween And four separators 43. That is, in this example, the negative electrode plates 42 are located on both surfaces of the power generation element 4. However, a configuration in which the positive electrode plate 41 is located on the outermost layer of the power generation element 4 is also possible. In addition, the dimension of each part in FIG. 2 is not necessarily exact, and is exaggerated for explanation.

The positive electrode plate 41 is obtained by forming positive electrode active material layers 41b and 41c on both surfaces of a rectangular positive electrode current collector 41a. The positive electrode current collector 41a is made of an electrochemically stable metal foil such as an aluminum foil, an aluminum alloy foil, a copper foil, or a nickel foil. The positive electrode active material layers 41b and 41c are made of, for example, a positive electrode active material made of a lithium composite oxide such as lithium nickelate (LiNiO ₂ ), lithium manganate (LiMnO ₂ ), or lithium cobaltate (LiCoO ₂ ). In addition, a mixture of a conductive additive such as carbon black and a binder is applied to the main surface of the positive electrode current collector 41a, dried and rolled.

  The negative electrode plate 42 is obtained by forming negative electrode active material layers 42b and 42c on both surfaces of a rectangular negative electrode current collector 42a. The negative electrode current collector 42a is made of, for example, an electrochemically stable metal foil such as nickel foil, copper foil, stainless steel foil, or iron foil. The negative electrode active material layers 42b and 42c are made of, for example, a negative electrode active material that occludes and releases lithium ions of the positive electrode active material, such as amorphous carbon, non-graphitizable carbon, graphitizable carbon, or graphite. The mixture of the binder is applied to the main surface of the negative electrode current collector 42a, dried and rolled.

  A part of the longitudinal edge of the negative electrode current collector 42 a extends as an extended portion that does not include the negative electrode active material layers 42 b and 42 c, and the tip thereof is joined to the negative electrode terminal 3. Although not shown in FIG. 2, similarly, a part of the edge in the longitudinal direction of the positive electrode current collector 41a extends as an extension portion that does not include the positive electrode active material layers 41b and 41c, and the tip thereof Is joined to the positive terminal 2.

  The separator 43 has a function of preventing a short circuit between the positive electrode plate 41 and the negative electrode plate 42 and at the same time holding an electrolyte. For example, the separator 43 is made of polyolefin such as polyethylene (PE) or polypropylene (PP). When the overcurrent flows, the pores of the layer are blocked by the heat generation, and the current is cut off. The separator 43 is not limited to a single-layer film such as polyolefin, but may also be a three-layer structure in which a polypropylene film is sandwiched with a polyethylene film, or a laminate of a polyolefin microporous film and an organic nonwoven fabric. .

  Further, the electrolyte solution is not particularly limited, but for example, a non-aqueous electrolyte solution in which a lithium salt is dissolved in an organic solvent can be used as an electrolyte generally used in a lithium ion secondary battery. .

  The exterior body 5 that houses the power generation element 4 having the above-described configuration together with the electrolytic solution is a three-layered structure including a heat-sealing layer 51, a metal layer 52, and a protective layer 53, as shown in an enlarged view in FIG. It consists of a laminated film having a structure. The intermediate metal layer 52 is made of, for example, an aluminum foil, and the heat-sealing layer 51 that covers the inner surface thereof is made of a synthetic resin that can be heat-fused, for example, polypropylene (PP), and is a protection that covers the outer surface of the metal layer 52. The layer 53 is made of a synthetic resin having excellent durability, such as polyethylene terephthalate (PET). A laminate film having a larger number of layers can also be used. In the above example, the synthetic resin layers are laminated on both surfaces of the metal layer 52. However, the synthetic resin layer on the outer side of the metal layer 52 is not necessarily essential, and the configuration includes the synthetic resin layer only on the inner surface. It may be.

  In one example, the outer package 5 has a two-sheet structure of one laminate film disposed on the lower surface side of the power generation element 4 in FIG. 2 and another laminate film disposed on the upper surface side. The four sides around the two laminate films are superposed and heat-sealed to each other. The illustrated example shows such a two-layer exterior body 5. In another example, the exterior body 5 is made of a single relatively large laminate film, and the power generation element 4 is arranged inside in a folded state, and the surrounding three sides are overlapped, and It is the structure which mutually heat-seal | fused.

  The pair of terminals 2 and 3 positioned on the short side of the rectangular film-clad battery 1 are led out to the outside through the bonding surface of the laminate film when the laminate film is heat-sealed.

  The manufacturing procedure of said film-clad battery 1 is demonstrated with reference to FIG. FIG. 3 schematically shows a part of the manufacturing process. First, the positive electrode plate 41, the negative electrode plate 42, and the separator 43 are sequentially laminated, and the positive electrode current collector 41a and the negative electrode current collector 42a are attached to the positive and negative terminals 2 and 3 by spot welding, ultrasonic welding, or the like. 4 is configured. Next, the power generating element 4 is covered with a laminate film that becomes the outer package 5, and the remaining three sides are heat-sealed, leaving one side. Next, an electrolytic solution is filled into the exterior body 5 through one side of the opening. Then, in 1st sealing process S11 of FIG. 3, the one side to open is heat-sealed and the exterior body 5 is made into a sealing state. In the subsequent aging step S12, as described above, the power generation element 4 and the electrolytic solution are sealed inside the exterior body 5, and the battery is charged to an appropriate level, and in this state, aging is performed for a certain time.

  And after completion of aging, in order to discharge | emit the gas which remains inside including the gas generated at the time of aging of the exterior body 5, degassing is implemented in degassing process S13. In this degassing step S13, at least in a vacuum environment where the pressure (atmospheric pressure) is lower than the atmospheric pressure, as shown in FIG. 4, a part of the exterior body 5 whose four sides are sealed is cut using a cutter blade or the like. By doing so, the opening 14 which connects the inside of the exterior body 5 and the exterior is formed. Then, as will be described later, after the pressure (atmospheric pressure) of the environment (space) in which the exterior body 5 is disposed is reduced to a predetermined pressure range Pr within a low vacuum pressure region (JIS standard 100 Pa or more), Thus, the state where the environmental pressure is within the predetermined pressure range Pr is maintained for a predetermined period Th or more.

  When such a degassing step S13 is completed, in the second sealing step S14 of FIG. 3, by heat-sealing along the sealing line 15 inside the opening 14 provided in the exterior body 5, The film-clad battery 1 in which one side including the opening 14 is sealed and the four sides are sealed along the sealing line 13 is obtained. Thereafter, it is charged again for voltage inspection and shipped.

  FIG. 5 shows a change in pressure in the environment, which is a sealed space in which the exterior body 5 is provided, in the gas venting step S13. The vertical axis indicates the pressure in the environment, that is, the degree of vacuum (hPa), and the horizontal axis. Is time (seconds). As shown in the figure, in this embodiment, the pressure in the environment is held for a predetermined period Th within a predetermined pressure range Pr.

  More specifically, first, the pressure is reduced toward the target pressure range Pr (see arrow Y1 in FIG. 5), and the pressure reduction is stopped at time t0 when the pressure is reduced to the vicinity of the pressure range Pr. In this embodiment, when pressure reduction is stopped for the first time (the pressure reducing valve is closed), the pressure continues to decrease for a while, so that it is higher than the target pressure range Pr in anticipation of the overshoot of the pressure decrease. The first pressure reduction is stopped at the pressure stage (t0). Thereafter, as shown by an arrow Y2 in FIG. 5, the gas inside the film-clad battery 1 is released to the outside in the decompression stop state, whereby the pressure in the environment gradually increases, and the upper limit value Pmax of the target pressure range Pr. At a time point t2 when the pressure rises to a predetermined value Ps (Ps <Pmax) in the vicinity, the pressure is reduced for a very short period of time (for example, 0.1 second). For example, the pressure reducing valve is temporarily opened. By performing this temporary pressure reduction, the pressure in the environment is reduced to the vicinity of the lower limit value Pmin of the target pressure range Pr. In other words, a certain time for reducing pressure is set in advance so that the pressure in the environment is reduced to the vicinity of the lower limit value Pmin of the target pressure range Pr.

  The upper limit value Pmax of the pressure range Pr is a value at which the gas inside the exterior body 5 is not discharged well (becomes NG) when the pressure is further increased, and is set to about 13 hPa, for example. The lower limit value Pmin of the pressure range Pr is a value that may cause boiling of the electrolyte when the pressure is further decreased (the degree of vacuum is increased), and is set to about 10 hPa, for example.

  Regarding the completion of the degassing, that is, the end of the holding of the predetermined pressure range Pr, in this embodiment, as shown in FIG. 5, it is noted that the rate of increase in the environmental pressure decreases as the degassing progresses. The pressure rising speed, that is, the pressure gradient (ΔP / t) is monitored, and at the time t3 when the rising speed ΔP / t becomes equal to or less than a predetermined determination value, the gas inside the outer package 5 is sufficiently discharged. The degassing process is finished because it is determined that it has been performed. That is, the period from the time point t1 when the pressure in the environment is reduced to the target pressure range Pr to the end point t3 of the holding is a “predetermined period” necessary for sufficiently discharging the gas inside the exterior body 5. Equivalent to.

[1] As described above, in this embodiment, the degree of vacuum is sufficiently low (that is, the pressure is lower than the high vacuum pressure region (0.1 to 10-5 Pa)) in the degassing process. high) within a predetermined pressure range Pr at low vacuum pressure region (above 100 Pa), sufficient predetermined period T h or more for the gas inside the outer package 5 is discharged, by continuing to hold, the degree of vacuum while sufficiently suppressing the volatilization by the electrolytic solution boiling which occurs when high, a relatively long predetermined time period T h (e.g., 10 seconds or more) over to maintain the vacuum state, the opening 1 4 in the interior of the outer package 5 As for the gas existing at a far position, a time required for the gas to move to the vicinity of the opening 14 is given, and the gas inside the outer package 5 can be discharged well. In addition, since the degree of vacuum is suppressed to a low level, the burden on the decompression device is reduced and the productivity is excellent.

[2] Here, the target pressure range Pr is a pressure region of at least a low vacuum (lower than atmospheric pressure and 100 Pa or more), more specifically, a pressure at which the electrolyte solution may boil. The pressure range Pr is in a range higher than the boiling point (about 10 hPa) of the electrolyte solution , such as about 10 to 13 hPa, which is much lower in vacuum than in the past. The pressure at which the electrolyte boils varies depending on the ambient temperature. Usually, however, the ambient temperature in the decompression chamber is kept substantially constant, so the target pressure range Pr is a predetermined constant pressure range. . Of course, when the atmospheric temperature in the decompression chamber changes, the pressure range Pr may be changed according to the atmospheric temperature.

  [3] Further, in the degassing step, when the pressure in the environment rises to a predetermined value Ps in the vicinity of the upper limit value Pmax of the target pressure range Pr, a simple operation of repeatedly performing pressure reduction for a predetermined time period is repeated. Through appropriate control, the pressure in the environment can be maintained within the target pressure range.

  [4] Further, as the gas inside the outer package 5 is released, the rate of increase in pressure in the environment (rate of decrease in vacuum) also decreases, so that the rate of increase in pressure becomes a predetermined value or less. Until the degassing process is continued, that is, the pressure in the environment is kept within the target pressure range Pr, thereby reducing the remaining gas amount inside the exterior body 5 with simple control with high accuracy. it can.

[5] However, more simply, the predetermined time period T h to keep the pressure range Pr aim, may be constant time set in advance by adaptation. This fixed time varies depending on the size of the outer package 5 and the like, but if it is too short, the gas cannot be sufficiently discharged, and is preferably 10 seconds or longer.

DESCRIPTION OF SYMBOLS 1 ... Film exterior battery 2, 3 ... Terminal 4 ... Power generation element 5 ... Exterior body 14 ... Opening

Claims (1)

Production of a film-clad battery in which a power generation element formed by laminating a positive electrode plate and a negative electrode plate through a separator is housed together with an electrolyte in a flat outer package, and the outer package is sealed in a state where terminals are led out. In the method
In a predetermined environment where the pressure is lower than atmospheric pressure, an opening that communicates the inside and outside of the exterior body is formed in a part of the exterior body in which the power generation element is sealed together with the electrolyte. It has a degassing step of discharging the gas inside the exterior body more,
In this degassing step, the pressure of the environment in which the exterior body is disposed is maintained within a predetermined pressure range of low vacuum for a predetermined period or more , and when the pressure in the environment increases to a predetermined value, the pressure is reduced. By repeating the operation, the pressure in the environment is maintained within a predetermined pressure range,
The predetermined pressure range of the low vacuum is set to a value that prevents the gas inside the outer casing from being discharged well when the pressure is further increased, and the electrolyte is boiled when the pressure is further decreased. It is set so that there is a feared value as the lower limit,
The predetermined value is a value within a predetermined pressure range of the low vacuum, and is a value near an upper limit value of the predetermined pressure range,
The method for producing a film-clad battery, wherein the predetermined period is a period until the rate of increase in pressure in the environment accompanying the execution of the pressure reduction becomes equal to or less than a predetermined determination value .

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