JP2010262821A - Method of manufacturing secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a secondary battery capable of impregnating electrolytic liquid uniformly in a short time. <P>SOLUTION: The method is provided for manufacturing the secondary battery which has a battery case and a positive and a negative electrode group housed in the battery case, with electrolytic liquid impregnated in the electrode group. The method includes a gas housing step in which a part of solvent constituting the electrolytic liquid is housed in evaporation state into the battery case wherein the electrode group is housed, a liquefaction step in which the solvent in an evaporation state housed in the battery case after the gas housing step is liquefied, and a liquid filling step in which remaining liquid which is not housed in the gas housing step out of the electrolytic liquid is filled into the battery case after the liquefaction step. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a secondary battery including a step of injecting a non-aqueous electrolyte. More specifically, the present invention relates to a method for manufacturing a secondary battery in which a non-aqueous electrolyte is impregnated into an electrode body obtained by winding or laminating a positive electrode plate and a negative electrode plate with a separator interposed therebetween.

  For example, there is a secondary battery manufactured by inserting a positive electrode plate and a negative electrode plate wound through a separator into a case, and injecting and sealing an electrolyte. In such a secondary battery manufacturing process, in the process of injecting and impregnating an electrolytic solution, generally a waiting time is required for the impregnation to proceed. Therefore, conventionally, many ideas have been made to make the process related to the injection as short as possible. In particular, many methods for reducing the pressure inside the battery case have been proposed in order to allow the electrolytic solution to enter the pores of the separator or the like.

  For example, the present applicant has previously proposed a method in which only a thin electrolytic solution or solvent is first injected, and then a thick electrolytic solution is injected after evacuation (see Patent Document 1). By doing so, it was said that it was possible to prevent scattering of the electrolyte due to evacuation and to prevent surrounding contamination. Patent Document 2 proposes a method in which the electrolyte solution is divided and injected by repeating a cycle of a normal pressure state and a reduced pressure state while the electrolyte solution of the battery case is heated. Impregnation in a short time is possible by reducing the viscosity of the electrolyte by heating and repeating relatively weak pressure reduction.

  In addition, Patent Document 3 describes a manufacturing method in which the inside of a chamber is depressurized, then the nonaqueous electrolytic solution is injected after being replaced with a gas that can be dissolved in the nonaqueous electrolytic solution, and then the pressure is reduced to remove the remaining gas. A method has been proposed. Since the replacement of the gas with the non-aqueous electrolyte is promoted, it is said that the injection time can be shortened.

JP-A-2005-203120 JP 2004-241222 A JP 2007-335181 A

  However, in recent years, with the increase in the capacity of secondary batteries, the density of electrode plates and the concentration of electrolytes have increased, and it has become increasingly time for impregnation. Therefore, it is desired to shorten the time required for this injection process.

  The present invention has been made to solve the problems of the conventional method for manufacturing a secondary battery. That is, an object of the present invention is to provide a method for manufacturing a secondary battery that can be uniformly impregnated with an electrolytic solution in a short time.

  A method of manufacturing a secondary battery according to the present invention for the purpose of solving this problem includes a battery case and a group of positive and negative electrodes housed in the battery case, and the electrode body group is impregnated with an electrolyte. A method for producing a secondary battery, comprising: a gas containing step in which a part of a solvent constituting the electrolyte is contained in a vaporized state inside a battery case containing an electrode assembly; A liquefaction process for liquefying the vaporized solvent contained in the battery case after the process, and the remaining liquid that was not accommodated in the gas containment process was injected into the battery case after the liquefaction process. And a liquid injection step.

  According to the method for manufacturing a secondary battery of the present invention, a part of the solvent is contained in a gas and then liquefied. Gas diffuses rapidly in the space, and diffuses throughout the battery case in a short time. Since it is liquefied after that, a part of the solvent adheres as a liquid at various points in the battery case. Since the remainder of the electrolyte is injected into the battery case, the impregnation speed is high. Since it is guided by the presence of some of the solvent that has been previously injected and adhered, it reaches every corner of the battery case. Therefore, it is a method that can uniformly impregnate the electrolyte in a short time.

Furthermore, in the present invention, it is desirable that the remaining liquid contained in the liquid injection step in the electrolytic solution contains a solvent having a higher boiling point than the solvent contained in the gas containing step.
If it is such, the solvent accommodated in a gas accommodation process will be easily vaporized by raising temperature.

Further, in the present invention, it is desirable that the gas containing step is by heating the inside of the battery case, and the liquefaction step is by cooling the inside of the battery case.
If it is such, in a gas accommodation process, it can be made into a vaporization state easily, after inject | pouring appropriate quantity of the solvent accommodated. Furthermore, it can be easily liquefied. In order to be able to do this, it is preferable to select a solvent whose vaporized environment is within a range of, for example, 1 atm and less than 100 ° C.

  According to the method for manufacturing a secondary battery of the present invention, the electrolytic solution can be uniformly impregnated in a short time.

It is process drawing which shows the procedure of the liquid injection process which concerns on manufacture of the secondary battery of this form.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the best mode for embodying the present invention will be described in detail with reference to the accompanying drawings. This embodiment is a method of manufacturing a flat wound lithium ion secondary battery, and the present invention is applied to a method of manufacturing a battery by injecting a non-aqueous electrolyte.

  In the secondary battery manufacturing method of the present embodiment, first, a battery cell before the electrolyte is injected is manufactured, and then a nonaqueous electrolyte is injected and sealed. A battery cell is one in which an electrode plate group is enclosed in a battery case. Therefore, the production of battery cells will be briefly described. First, battery cases and electrode plate groups are manufactured. The electrode plate group is formed by sandwiching a separator between positive and negative electrode plates and winding it into a flat shape. Alternatively, it may be cylindrical or flat.

  Positive and negative electrode plates are manufactured by applying an active material paste to a metal foil and drying and rolling. The separator is a sheet made of insulating resin. These electrode plates are wound with a separator between them and placed in a battery case. Then, a sealing plate is attached to the opening of the battery case. At this stage, the liquid injection port is opened in the sealing plate. For the steps up to here, a manufacturing method similar to the conventional one may be adopted.

The positive electrode plate is made of aluminum foil coated with a positive electrode active material capable of inserting and extracting lithium ions. As the positive electrode active material, for example, a lithium composite oxide such as lithium nickelate (LiNiO ₂ ), lithium manganate (LiMnO ₂ ), lithium cobaltate (LiCoO ₂ ) or the like is used. The negative electrode plate is a copper foil coated with a negative electrode active material capable of inserting and extracting lithium ions. Examples of the negative electrode active material include carbon-based materials such as amorphous carbon, non-graphitizable carbon, graphitizable carbon, and graphite.

  Next, an electrolytic solution is injected into the battery case in this state according to the procedure shown in FIG. In this embodiment, a substance that can be used as a solvent for an electrolytic solution and can be vaporized by heating to a certain degree (hereinafter referred to as a first electrolytic solution) is first injected in a small amount and vaporized in a battery case. Then, after the gas is filled in the battery case, it is cooled and liquefied. As a result, the first electrolytic solution is condensed in various places in the battery case. In this state, the remaining electrolytic solution (hereinafter referred to as the second electrolytic solution) can be poured to quickly impregnate.

  As a 1st electrolyte solution, while being a liquid at room temperature (about 20-30 degreeC) among the substances used as a solvent of a nonaqueous electrolyte solution, the heating which does not affect an electrode plate group (for example, 40 to 80 ° C.). For example, methyl acetate (boiling point 56.9 ° C.), ethyl acetate (boiling point 77 ° C.) and the like are preferable. The second electrolytic solution is obtained by dissolving an electrolyte in an organic solvent. A substance that has been widely used as a non-aqueous electrolyte may be used. This is liquid at room temperature. In general, a substance having a lower boiling point than the second electrolytic solution may be selected as the first electrolytic solution as compared with the boiling point.

As an organic solvent for the second electrolyte, for example, an ester solvent such as propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC), or methyl ethyl carbonate (MEC), or γ-butylactone as an ester solvent. An organic solvent containing an ether solvent such as (γ-BL) or diethoxyethane (DEE) can be used. In addition, as a salt that is an electrolyte, lithium salts such as lithium perchlorate (LiClO ₄ ), lithium borofluoride (LiBF ₄ ), and lithium hexafluorophosphate (LiPF ₆ ) can be used.

  In the liquid injection process of the present embodiment, liquid injection is performed while controlling the temperature and pressure inside the battery case in which the electrode body is housed. First, the inside of the battery case is heated to about 100 ° C. (step 1), and vacuuming is performed (step 2). Thereby, moisture, air, impurities, etc. in the battery case are removed.

  Next, the environment in the battery case is adjusted to a temperature at which the first electrolytic solution is vaporized (step 3). This temperature may be determined according to the type of solvent selected as the first electrolytic solution. Then, the first electrolytic solution is injected into the battery case (step 4). After this step 4, the injected first electrolyte becomes gas soon in the battery case. In this embodiment, methyl acetate is used as the first electrolytic solution, and the temperature is adjusted to about 60 ° C. in Step 3.

  Therefore, the first electrolytic solution that has become a gas easily diffuses in the battery case and spreads throughout the battery case. In particular, since the air is evacuated in advance, almost no air remains in the battery case. And the 1st electrolyte solution of the vaporization state can penetrate | penetrate easily into fine places, such as the clearance gap between electrode plate groups, and the pore of a separator. Step 3 and step 4 correspond to a gas containing step.

  Further, after allowing a sufficient amount of time for the gas of the first electrolyte to diffuse, the temperature is lowered until the interior of the battery case reaches room temperature (for example, 25 ° C.) (step 5). As a result, the first electrolytic solution is liquefied in the battery case. Since the first electrolytic solution is diffused in the battery case in the previous stage, dew condensation occurs on the electrode plate, the surface of the separator, and the like. That is, it is in a state of being uniformly attached to each part of the electrode body. Therefore, this step 5 corresponds to a liquefaction step.

  In step 4, the first electrolytic solution is poured in such a degree that the surface of the electrode plate or separator can be sufficiently wetted in step 5. In addition, after injecting the liquid in step 4, the heating in step 3 may be performed. Also by this procedure, the battery case can be filled with the first electrolytic solution that has become a gas. In addition, you may preheat the 1st electrolyte solution to such an extent that it does not evaporate before injection. Further, it may be vaporized in advance and injected as a gas. In steps 3 to 5, instead of vaporization or liquefaction due to temperature adjustment, pressure adjustment may be used. Moreover, you may use temperature and a pressure together.

  Next, while the inside of the battery case is kept at about room temperature, the remainder of the electrolytic solution, that is, the second electrolytic solution is injected (step 6). Since the second electrolytic solution is liquid at room temperature, this step 6 is a step of injecting a liquid electrolytic solution. This step 6 corresponds to a liquid injection step. The liquid injection method in this step is basically the same as the conventional procedure. That is, after pouring an appropriate amount of electrolyte, the inside of the battery case is depressurized and waits for the electrolyte to be impregnated. Usually, in order to shorten the required time, the entire predetermined amount of electrolyte is not injected all at once, but dividedly. Then, by repeating injection and decompression several times, the entire amount is impregnated in a relatively short time.

  By this step 6, the first electrolytic solution and the second electrolytic solution that have already been injected are mixed. The first electrolyte also becomes part of the electrolyte. When the second electrolyte is impregnated by a predetermined amount, the battery case inlet is sealed (step 7). This completes the liquid injection process of this embodiment.

  In this embodiment, the battery case is preliminarily filled with the first electrolytic solution in a gaseous state, and dew condensation is caused in the battery case. That is, the electrode plate group is once wetted with the first electrolytic solution. Therefore, the second electrolytic solution is guided to the first electrolytic solution and easily impregnated in the gaps of the electrode plates, the pores of the separator, and the like. That is, since the impregnation speed is high, the time required for injecting the second electrolytic solution is considerably shortened compared to the conventional one. Therefore, even if the time required for the dew condensation of the first electrolytic solution is taken into consideration, the liquid injection process can be performed in a shorter time than the conventional required time.

The inventors of the present invention performed injections according to the embodiment of the present embodiment and Comparative Examples 1 and 2 and compared the required time. In this experiment, a liquid injection process was performed in the manufacturing process of a lithium ion secondary battery using LiCoO _{2 as} the positive electrode active material and carbon as the negative electrode active material. The secondary battery used in this experiment has an electrode body volume of about 120 cm ³ and a battery case volume of about 300 cm ³ . This is a size generally used for, for example, a hybrid vehicle.

In this experiment, 0.8 g of methyl acetate was used as the first electrolytic solution. Further, as the second electrolytic solution, a solution obtained by dissolving 1 mol / l LiPF ₆ in a mixed solvent of ethylene carbonate and diethyl carbonate was used. 100 g of the second electrolytic solution was injected. Also, among the steps shown in FIG. 1, step 1, step 2, and step 7 were performed in the same manner in any of the examples and comparative examples 1 and 2.

In the examples, liquid injection was performed along the liquid injection process of this embodiment. That is, first, the first electrolytic solution was injected and vaporized to fill the battery case, and then condensed (Steps 3 to 5). Then, the 2nd electrolyte solution was inject | poured (process 6). On the other hand, in Comparative Examples 1 and 2, the following liquid injection process was performed without using steps 3 to 5 of this embodiment.
In Comparative Example 1, 100.8 g of an electrolytic solution obtained by mixing the first electrolytic solution and the second electrolytic solution in advance was prepared and injected at room temperature.
In Comparative Example 2, first, 0.8 g of the first electrolytic solution was injected at room temperature, and then 100 g of the second electrolytic solution was injected. That is, the first electrolytic solution was not vaporized and remained liquid after the injection.

  The inventor further tried the procedure of injecting the second electrolyte solution in Examples and Comparative Examples 1 and 2 when the entire amount was injected at once and then the pressure was reduced, and when the divided injection was divided into multiple times. I made a mistake and searched for what would be the shortest injection process. As a result, the injection process in the shortest time was as follows. In both Comparative Examples 1 and 2, the required time hardly changed even when only the second electrolytic solution not containing the first electrolytic solution was injected.

In this example, the second electrolytic solution was injected by a total of three times of the following (A-1) to (A-3) and reduced pressure. The total time required to impregnate all 100 g of the second electrolyte by this procedure was about 17 minutes.
(A-1) Injection of about 50 g of the second electrolytic solution → 60 seconds depressurization at −50 kPa (A-2) Injection of about 30 g of the second electrolytic solution → Depressurization of 60 seconds at −20 kPa (A-3) Second electrolytic solution Total remaining injection → Depressurized for 120 seconds at -10kPa

In Comparative Example 1, the liquid was divided into five times by the following procedures (B-1) to (B-5). The total time required was about 24 minutes.
(B-1) Mixed electrolyte solution injection about 50 g → reduced pressure at −50 kPa for 60 seconds (B-2) Mixed electrolyte solution injection about 20 g → reduced pressure at −30 kPa for 60 seconds (B-3) Mixed electrolyte solution injection about 10 g → −20 kPa (B-4) Reduced pressure by -10 kPa for 60 seconds (B-5) Reduced pressure by -100 kPa for 120 seconds.

In Comparative Example 2, the liquid was divided into five times according to the following procedures (C-1) to (C-5). The total time required was about 23 minutes.
(C-1) Continuous injection of 0.8 g of the first electrolytic solution and about 50 g of the second electrolytic solution
→ -60 kPa for 60 seconds (C-2) injection of about 20 g of the second electrolyte → -30 kPa for 60 seconds (C-3) injection of about 10 g of the second electrolyte → -20 kPa for 60 seconds (C- 4) Injection of about 10 g of the second electrolyte solution → 60 seconds depressurization at −10 kPa (C-5) Second electrolyte injection of all remaining amount → 120 seconds depressurization at −10 kPa

  Therefore, according to the example of the present embodiment, it was confirmed that the liquid injection process could be completed in a considerably short time as compared with Comparative Examples 1 and 2. In the example, since the impregnation greatly progressed by a single pressure reduction, the amount of electrolyte that can be injected thereafter could be increased. Therefore, the injection process could be completed in a sufficiently short time even if the number of injection and decompression divisions was reduced. On the other hand, in Comparative Examples 1 and 2, the progress of impregnation was slow, and it was necessary to slightly increase the number of times of injection and decompression. As a result, as a whole, the injection process required a considerably long time compared to the examples.

  As described in detail above, according to the liquid injection process of this embodiment, first, only the first electrolytic solution is injected, vaporized in the battery case, and filled inside. Therefore, the first electrolytic solution spreads to the details in the battery case. In this state, the temperature of the battery case is lowered to liquefy the first electrolytic solution. Thereby, the inside of the battery case becomes wet with the first electrolytic solution. Then, when the second electrolytic solution is injected, the first electrolytic solution can be used as priming water and impregnated quickly. Accordingly, the electrolyte solution can be uniformly impregnated in a short time to the details of the electrode plate group.

In addition, this form is only a mere illustration and does not limit this invention at all. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof.
For example, the above-described divided injection procedure is an example, and the injection amount, the decompression time, the decompression pressure, etc. of each time may be appropriately selected according to the configuration of the secondary battery and various conditions. Further, the materials of the first and second electrolytes and the amount of injection thereof may be appropriately selected according to the use and size of each secondary battery.

Claims (3)

In a method of manufacturing a secondary battery having a battery case and a positive and negative electrode body group housed in the battery case, the electrode body group being impregnated with an electrolyte solution,
A gas containing step in which a part of the solvent constituting the electrolytic solution is contained in a vaporized state inside the battery case containing the electrode group; and
A liquefaction step for liquefying the vaporized solvent housed inside the battery case after the gas containment step;
A method for manufacturing a secondary battery, comprising: injecting the remaining liquid of the electrolyte solution that has not been stored in the gas storage step into the battery case after the liquefaction step. In the manufacturing method of the secondary battery according to claim 1,
The method of manufacturing a secondary battery, wherein the remaining liquid contained in the liquid injecting step of the electrolyte contains a solvent having a boiling point higher than that of the solvent contained in the gas containing step. In the manufacturing method of the secondary battery according to claim 1 or 2,
The gas containing step is by heating the inside of the battery case,
The method for producing a secondary battery, wherein the liquefaction step is performed by cooling the inside of the battery case.

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