JP2014197460A - Electrochemical device manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing an electrochemical device having higher quality retention performance and capable of improving battery performance.
An electrolysis in which a laminated body in which a positive electrode 10p and a negative electrode 10n formed in a substantially rectangular sheet shape are arranged to face each other with a separator interposed therebetween and an electrolyte solution are sealed in a film-shaped outer package 100. A method for manufacturing a device, the step of irradiating a plasma discharge on a surface of a region of an outer package 100 to be bonded to seal the laminate and the electrolyte, and the outer package 100 irradiated with the plasma discharge Bonding the surface of the regions.
[Selection] Figure 4

Description

  The present invention relates to an electrochemical device such as a battery, and more particularly to a method for manufacturing an electrochemical device.

  In recent years, various thin electronic devices such as electronic paper, IC tags, IC cards, and electronic keys have been put into practical use. The power source for these thin electronic devices is similarly required to have a thin shape, and a laminate type battery is usually incorporated. Also, as a large-capacity battery that is a power source for electric vehicles and a transportable power source, a laminate type battery is used to reduce the mounting location and installation location. As an example of this laminate type battery, for example, in Patent Document 1, a lithium terminal of a type in which a metal terminal connected to each of a positive electrode and a negative electrode of a lithium battery main body is sandwiched in a protruding state and thermally bonded to be sealed. A laminate for a battery is disclosed.

JP 2006-281613 A

  The laminated body of patent document 1 is trying to improve the sealing performance as a laminate type battery by improving physical properties, such as electrolyte solution resistance, corrosion resistance, and water vapor | steam barrier property, as laminated body itself. However, even if the sealing performance of the laminate itself is improved, it is difficult to ensure the sealing performance required for the battery unless the portion to be joined to seal the laminate has sufficient sealing performance. is there. For example, when the laminate is sealed by heat fusion, if the bondability of the heat fused portion is not sufficient, the container sealed by heat fusion when stored or used under high humidity conditions In some cases, moisture may enter from the outside, which may cause deterioration of battery characteristics such as battery swelling and increased internal resistance. It is known that such inadequate bonding is particularly likely to occur at the tabs protruding from the battery electrodes.

  The present invention solves the above problems, and provides a method for producing an electrochemical device that can prevent characteristic deterioration as much as possible throughout the use period and storage period, and has higher quality retention performance. One purpose.

In order to achieve the above object, one embodiment of the present invention provides:
A manufacturing method of an electrochemical device in which a laminate and an electrolytic solution in which a positive electrode and a negative electrode formed in a substantially rectangular sheet shape are arranged to face each other via a separator are sealed in a film-shaped exterior body,
Irradiating plasma discharge to the surface of the region of the exterior body that will be joined together to seal the laminate and the electrolyte; and
Joining the surface areas of the outer package irradiated with the plasma discharge;
have.

  In addition, the method for manufacturing an electrochemical device may include a step of irradiating plasma discharge to the surface of the positive electrode and / or the surface of the negative electrode constituting the laminate.

  According to the above-described embodiment of the present invention, it is possible to provide a method for manufacturing an electrochemical device that can prevent characteristic deterioration as much as possible throughout the use period and the storage period, and has higher quality retention performance.

FIG. 1 is a perspective view showing an example of the appearance of a general laminate type electrochemical device 1. FIG. 2 is a cross-sectional view of the electrochemical device 1 of FIG. FIG. 3 is a schematic diagram showing a manufacturing process of the electrochemical device 1 of the present embodiment. FIG. 4 is a schematic diagram showing a manufacturing process of the electrochemical device 1 of the present embodiment. FIG. 5 is a diagram showing changes over time in battery thickness and internal resistance in the electrochemical device 1 according to the embodiment of the present invention and the comparative example. FIG. 6 is a diagram showing high-rate discharge characteristics in the electrochemical device 1 according to the embodiment of the present invention and a comparative example.

  Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a diagram illustrating the appearance of a laminate type electrochemical device 1 according to an embodiment of the present invention. As shown in FIG. 1, the electrochemical device 1 is configured such that a power generation element including an electrolytic solution is housed in an exterior body 100. An electrode plate (tab) 40 connected to the positive electrode and negative electrode terminals of the power generation element and connected to an external device is exposed to the outside of the outer package 100.

  The exterior body 100 is configured by bonding edges of four sides of two substantially rectangular laminate films. In general, a laminate film has a metal thin film made of aluminum or the like as a base material, and a protective layer made of a resin such as polyester or nylon is provided on the outer side of the electrochemical device 1, that is, the front surface of the outer package 100. On the other side, that is, the inner surface of the electrochemical device 1 is provided with a heat-sealing layer made of a heat-fusible resin.

  In FIG. 2, the example of the cross-sectional view of the electrochemical device 1 of FIG. 1 is shown. In FIG. 2, the power generation element 20 of the electrochemical device 1 includes a positive electrode active material 11 p and a negative electrode active material 11 n coated on the surface of a sheet-like conductor 11 serving as a current collector in a substantially rectangular shape, A negative electrode 10n and a separator 30 are provided.

  The sheet-like conductor 11 has a planar shape in which an electrode terminal serving as a power outlet is provided on one side of a substantially rectangular shape. The power generation element 20 is configured such that the positive electrode 10p and the negative electrode 10n are disposed to face each other through the separator 30 so that the positive electrode active material 11p and the negative electrode active material 11n face each other. The power generation element 20 is housed in a sealed state in the exterior body 100 together with the electrolytic solution. A tab 40 for connecting to an external circuit is fused to the electrode terminal formed on the sheet-like conductor 11 by a method such as ultrasonic welding.

  In the example shown in FIG. 2, the power generation element 20 is shown as a single layer structure in which a pair of positive electrode 10 p and negative electrode 10 n are arranged to face each other with a separator 30 interposed therebetween. In addition to such a single layer structure, as is well known, the electrochemical device 1 can also be configured as a multilayer structure having a combination of a plurality of positive electrodes 10p and negative electrodes 10n. Further, the relationship between the shape and relative size of each element shown in FIG. 2 is an example for explanation, and it is needless to say that it can be appropriately changed according to a design requirement or the like.

  Next, a method for manufacturing the electrochemical device 1 according to this embodiment will be described. 3 and 4 schematically show the production process of the electrochemical device 1 according to the present invention. First, as shown in FIG. 3, the exterior body 100 which seals the electric power generation element 20 and electrolyte solution in the bag shape is prepared. In the example of FIG. 3, only the side to which the positive electrode 10p of the outer package 100 is attached is shown for easy understanding. On one surface of the outer package 100, a sheet-like positive electrode 10p formed by applying the positive electrode active material 11p to the sheet-like conductor 11 is disposed so that the positive electrode active material 11p is exposed. In this state, the plasma discharge is applied to the positive electrode 10p and the entire inner surface of the exterior body 100 on which the positive electrode 10p is disposed. 3 and 4, the region irradiated with the plasma discharge is indicated as a plasma irradiation region 150 (dotted dot display portion in the figure).

  FIG. 4 illustrates in more detail the process of irradiating the positive electrode 10p and the inner surface of the outer package 100 with plasma. FIG. 4 schematically shows a state in which the inner surface of the outer package 100 in FIG. 3 is viewed in the direction of arrow A from the side where the positive electrode 10p is attached. In FIG. 4, the exterior body 100 used as four sets of laminate type batteries is arrange | positioned along with the horizontal direction, and the four positive electrodes 10p are affixed. Thus, since plasma irradiation is performed in a state where the positive electrode 10p is attached to the outer package 100, the treatment of the inner surface of the outer package 100 and the treatment of the surface of the positive electrode 10p can be performed collectively. Note that five or more sets of exterior bodies 100 may be juxtaposed for batch processing.

  The plasma discharge generating work 250 provided in the plasma discharge generating device 200 is disposed in proximity to the inner surface of the outer package 100 of FIG. 4 and the positive electrode 10p attached thereto, and the outer package 100 including the tab 40 portion. A plasma discharge 260 is applied to the inner surface of the electrode and the surface of the positive electrode 10p. After the plasma irradiation treatment, the outer packaging body 100 opposite to the separator 30 and the negative electrode 10n is disposed on the positive electrode 10p, the electrolyte is injected, and then the outer packaging body 100 around the configured power generation element 20 is thermally melted. The laminate type battery in which the power generating element 20 is sealed together with the electrolytic solution is obtained. Note that the plasma discharge conditions can be set as appropriate in accordance with the specifications of the exterior body 100 and the like.

As an effect of irradiating the inner surface of the outer package 100 formed of a resin material with plasma discharge, a polar group is generated on the inner surface of the outer package 100 irradiated with plasma discharge to perform chemical modification. , Increase the affinity when heat-sealing. In addition, due to the plasma discharge irradiation, dirt such as a sebum film adhering to the inner surface of the outer package 100 is decomposed and removed into CO ₂ or the like, so that the inner surface of the outer package 100 becomes clean. By these actions, the adhesive strength between the inner surfaces of the exterior material 100 is improved. As a result, the sealing performance of the power generation element 20 of the outer package 100 is improved, and the quality retention performance during use as a battery or during storage is improved.

  Moreover, since the so-called surface roughening effect and hydrophilic functional groups are imparted to the surface of the positive electrode active material 11p of the positive electrode 10p by plasma discharge, so that the hydrophilicity of the surface of the positive electrode active material 11p is improved. Since the liquid stain of the electrolytic solution is improved, the internal resistance of the finished battery can be reduced, and the performance of the battery can be improved.

  In this embodiment, plasma irradiation is performed only on the positive electrode 10p. However, plasma irradiation may be performed on the negative electrode active material 11n of the negative electrode 10n or both of the positive electrode 10p and the negative electrode 10n. The same battery performance improvement effect can be obtained.

  As described above, according to the manufacturing method of the present embodiment, the inner surface of the exterior body 100 to be heat-sealed is irradiated with plasma, so that the strength of the heat-sealed portion is improved, and thereby, from the outside. The sealing performance of the exterior body 100 is improved, for example, moisture intrusion into the exterior body 100 is prevented, thereby improving the quality retention performance as a battery. Further, the internal resistance is reduced by the moderate surface roughening effect of the positive electrode 10p and the liquid stain of the electrolytic solution due to the addition of the hydrophilic functional group, and the battery performance can be improved.

  The effect of the embodiment described above will be described more specifically. Table 1 shows the results of the peel strength test performed on the electrochemical device 1 manufactured by the manufacturing method of the present embodiment and the electrochemical device (comparative example) manufactured without plasma treatment. The thermal fusion treatment was performed at a temperature of 190 ° C. for 2 seconds. The peel strength test was carried out by preparing a fusion sample having a size of 2.5 mm × 4 mm for PPa (modified polypropylene) and aluminum and PPa and PPa as an evaluation of adhesion between materials. The test speed was set at 10 mm / min, and the maximum value obtained was recorded as the intensity. The test was carried out five times for each material for this embodiment and the comparative example, and the average value was evaluated. In Table 1, the processed product of the present embodiment is displayed as a relative value with the peel strength value in the unprocessed case being 100.

  As shown in Table 1, in the PPa / Al outer package 100, when the plasma treatment of this embodiment was performed, the peel strength was improved by about 30% compared to the untreated one. Further, in the PPa / PPa outer package 100, when the plasma treatment of the present embodiment was performed, the peel strength was improved by about 50% compared to the untreated one. Thus, since the strength of the joint portion by heat fusion of the outer package 100 is increased, in the electrochemical device 1 in which the plasma treatment of the present embodiment is performed, the sealing performance of the power generation element 20 by the outer package 100 is increased, and the quality is maintained. Performance is improved.

  FIG. 5 shows the internal resistance with respect to the storage days and the rate of change of the battery thickness for the electrochemical device 1 of the present embodiment and the plasma-untreated comparative example. As a sample, a laminate cell having a thickness of 0.45 mm or less and a size of 27 mm × 22 mm was used. The storage conditions were a temperature of 60 ° C. and a relative humidity of 90%. As is clear from FIG. 5, the electrochemical device 1 in this embodiment has a small increase in battery thickness during storage and a long time until the internal resistance reaches a maximum as compared with the comparative example. Specifically, regarding the internal resistance, in the untreated comparative example shown by the broken line, the internal resistance becomes maximal after 40 days of storage and the function as a battery is lost, whereas the book shown by the solid line In the case of the embodiment, the number of storage days retaining the battery function is extended to 60 days. This is because the welded portion strength due to thermal fusion of the outer package 100 is increased, so that an increase in battery thickness due to expansion of the outer package 100 during storage is suppressed, and thereby an increase in internal resistance due to deformation of the power generation element 20 is also suppressed. This is probably because of this.

  Next, changes in internal resistance in the discharge test will be described. About the electrochemical device 1 which implemented the plasma processing of this embodiment, and the untreated comparative example, the discharge test was implemented on the same conditions with the discharge rate of 1 mA and the temperature of 23 degreeC, and internal resistance was measured. The results are shown in Table 2. Samples of this embodiment and five comparative examples are prepared for each sample, compared with the average value of the measurement results, and the change between the initial resistance value and the resistance value after discharge is the case of untreated. Displayed as a relative change of 100.

  As is apparent from Table 2, in the electrochemical device 1 of the present embodiment, both the initial resistance value of the internal resistance and the resistance value after discharge are smaller by about 20% than in the comparative example without plasma treatment. It was. This is considered to be due to the effect of reducing the internal resistance due to the improvement of the hydrophilicity by the plasma treatment of the surface of the positive electrode active material 11p and the improvement of the liquid stain of the electrolytic solution thereby. Thereby, the battery capacity in this embodiment increased about 1.2 times with respect to the comparative example.

  FIG. 6 shows changes in voltage when the discharge rate is 1 mA constant current for the electrochemical device 1 of the present embodiment and the comparative example without plasma treatment. As shown in the drawing, the plateau voltage of the present embodiment is higher than that of the comparative example due to the decrease in the internal resistance.

  As described above, according to the embodiment of the present invention, the manufacturing method according to the embodiment of the present invention increases the strength of the exterior body 100 due to thermal fusion. In the chemical device 1, the sealing performance of the power generation element 20 is improved, and the quality retention performance is improved. In addition, the reduction in internal resistance has the effect of improving high rate characteristics and improving battery capacity.

DESCRIPTION OF SYMBOLS 1 Electrochemical device 10p Positive electrode 10n Negative electrode 11 Sheet-like electroconductive material 11p Positive electrode active material 11n Negative electrode active material 20 Electric power generation element 30 Separator 40 Tab 100 Outer body 150 Plasma treatment area | region 200 Plasma discharge generator 250 Plasma discharge generation work 260 Plasma discharge

Claims (2)

A manufacturing method of an electrochemical device in which a laminate and an electrolytic solution in which a positive electrode and a negative electrode formed in a substantially rectangular sheet shape are arranged to face each other via a separator are sealed in a film-shaped exterior body,
Irradiating plasma discharge to the surface of the region of the exterior body that will be joined together to seal the laminate and the electrolyte; and
Joining the surface areas of the outer package irradiated with the plasma discharge;
The manufacturing method of the electrochemical device which has this. A method for producing an electrochemical device according to claim 1,
The manufacturing method of the electrochemical device which has a step which irradiates plasma discharge to the surface of the said positive electrode which comprises the said laminated body, and the surface of the said negative electrode, or any one surface.