JP2010165591A - Method of manufacturing battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a battery capable of improving productivity without causing changes in composition of electrolyte. <P>SOLUTION: The method of manufacturing a battery includes (a) a process in which a positive electrode 11 and a negative electrode 12 are wound or laminated with a separator 13 interposed in between and an electrode group 20 is constructed, (b) a process in which the electrode group is housed in a battery can 15, and (c) a process in which an electrolyte is impregnated in the electrode group while impressing voltage between the positive electrode and the negative electrode. Thus, the time required for filling the electrolyte solution can be shortened. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a battery manufacturing method, and more particularly, to an improvement in a technique for injecting an electrolyte into a battery.

  Lithium ion secondary batteries are generally composed of a positive electrode core material, a positive electrode made of composite lithium oxide supported on the positive electrode core material, a negative electrode core material, and a negative electrode made of a material capable of entering and exiting lithium ions supported on the negative electrode core material. And a non-aqueous electrolyte (electrolyte). The positive electrode and the negative electrode are wound together with a separator interposed between both electrodes, and constitute a columnar electrode plate group. The electrode plate group is placed in a bottomed cylindrical container that also serves as a negative electrode terminal, and an electrolyte is injected in this state.

In recent years, along with the increase in the density of lithium ion secondary batteries, the time required for injecting the electrolyte is increasing, which is an obstacle to improving the productivity.
Then, in order to improve the pouring property of electrolyte solution, utilizing a surfactant is proposed (refer patent document 1).

JP 2003-223926 A

  However, according to the proposed method, the surfactant is mixed in the electrolytic solution, so that the composition of the electrolytic solution changes. Further, since the surfactant usually has a salt and a highly polar functional group, it is difficult to say that the surfactant is an electrochemically stable substance. For this reason, there exists a possibility of producing side reactions, such as a surfactant decomposing | disassembling and generating gas in a battery.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a battery manufacturing method capable of improving productivity without causing a change in the composition of the electrolyte.

In order to achieve the above object, the method for producing a battery of the present invention comprises (a) a step of forming a positive electrode group, a negative electrode, and a plate group including a separator that separates both electrodes,
(B) including a step of accommodating the electrode plate group in a container; and (c) impregnating the electrode group with an electrolyte while applying a voltage between the positive electrode and the negative electrode.

Here, in the manufacturing method of the present invention, the applied voltage is preferably an alternating current.
The applied voltage is more preferably 0.1 to 2.0V.
The electrolyte is preferably a gel electrolyte.
The electrolyte preferably contains a non-aqueous solvent and a lithium salt.

  According to the present invention, the electrode group is impregnated with the electrolyte while a voltage is applied between the positive electrode and the negative electrode. Thereby, the electrolyte can be rapidly impregnated in the positive electrode and the negative electrode of the electrode plate group by utilizing the electrocapillary phenomenon. Thereby, productivity at the time of manufacturing a battery can be improved.

  A representative example of a battery to which the production method of the present invention is applied is a lithium ion secondary battery. The lithium ion secondary battery includes a positive electrode composed of a positive electrode core material and a composite lithium oxide supported on the positive electrode core material, and a negative electrode composed of a negative electrode core material and a material capable of entering and exiting lithium ions supported on the negative electrode core material. To do. Each of the positive electrode and the negative electrode has a strip shape, and has a core material exposed portion at one end portion along the longitudinal direction thereof. An aluminum foil or the like is preferably used for the positive electrode core material, but is not limited thereto. Moreover, although copper foil etc. are used preferably for a negative electrode core material, it is not limited to this.

  In order to obtain such an electrode plate, first, an electrode mixture paste is prepared by mixing a composite lithium oxide or a material capable of entering and exiting lithium ions with a dispersion medium, and the electrode mixture paste is applied to a predetermined end. It can be obtained by applying to both surfaces of the strip-shaped core material except for drying. The end portion of the core material to which the electrode mixture paste is not applied may be only one end portion along the longitudinal direction or both end portions along the longitudinal direction.

  The columnar electrode plate group is formed by winding a positive electrode and a negative electrode with a separator interposed between the two electrodes, and is placed in a bottomed cylindrical metal container that also serves as a negative electrode terminal. An electrolytic solution (electrolyte) is further injected into the container, and the electrode plate group is impregnated with the injected electrolytic solution. Thereafter, the opening of the container is sealed by a sealing body having a positive electrode terminal, and the battery is completed by covering the exterior material.

  In the injection / impregnation step of the electrolytic solution, the electrode plate group is impregnated with the electrolytic solution while applying a voltage between the positive electrode and the negative electrode. At this time, it is preferable to apply an AC voltage having a frequency of 0.1 to 10 Hz and a voltage of 0.1 to 2 V between the positive electrode and the negative electrode. Here, the reason why the voltage is applied between the positive electrode and the negative electrode is to make the positive electrode and the negative electrode easily impregnated with the electrolyte using the electrocapillary phenomenon. The electrocapillary phenomenon is a phenomenon in which, when a potential difference is applied between the electrolytic solution and the electrode, the interfacial tension of the electrolytic solution changes according to the applied potential difference.

  In particular, in an alkaline solution, the potential of the electrode is lower than that of a standard hydrogen electrode (SHE), and when the electrode functions as a cathode, the potential difference between the electrode and the electrolyte is relatively small. Therefore, the interfacial tension on the electrode surface becomes extremely small due to electrocapillary phenomenon. Therefore, by applying an AC voltage to the positive electrode and negative electrode of the battery, the positive electrode and the negative electrode function alternately as a cathode, and only by applying a relatively small voltage between the positive electrode and the negative electrode, The impregnation of the electrolyte solution can be promoted at the same time.

Further, the voltage range is 0.1 to 2V because if the potential difference between the electrolyte and the electrode is about 1.5V, for example, the interface tension hardly decreases even if the potential difference is increased further, while 2V It is because electrolysis will be caused when exceeding.
In addition, the frequency of the alternating current applied is set to 10 Hz or less because a certain amount of time is required for the wetting of the substance. Therefore, in order to proceed with the impregnation of the electrolytic solution, the frequency of the alternating current applied is preferably as small as possible. Because. On the other hand, the frequency of the alternating current to be applied is 0.1 Hz or more, in order to promote the impregnation of the electrolytic solution in both the positive electrode and the negative electrode, it is necessary to apply the alternating current over at least one cycle, This is because if the frequency is further reduced, it takes too much time.

  In the present invention, after applying a DC voltage for a predetermined time so that either the positive electrode or the negative electrode functions as a cathode, the polarity is changed and a DC voltage of the same voltage is applied for the same time. This can also be realized.

The negative electrode includes at least a negative electrode active material made of a material that allows lithium ions to enter and exit, a binder, and a thickener.
As the negative electrode active material, it is possible to use various natural graphites, various artificial graphites, petroleum coke, carbon fibers, organic polymer fired products, silicon-containing composite materials such as oxides and silicides, various metals or alloy materials. it can.

  As the negative electrode binder, a rubbery polymer is used from the viewpoint of improving the lithium ion acceptability as described above. As such a rubbery polymer, those containing styrene units and butadiene units are preferably used. For example, a styrene-butadiene copolymer (SBR), a modified SBR, or the like can be used, but it is not limited thereto.

  The rubber-like polymer constituting the negative electrode binder can be used in combination with a thickener made of a water-soluble polymer. Here, as the water-soluble polymer, a cellulose-based resin is preferable, and carboxymethyl cellulose (CMC) is particularly preferable.

  The amount of the binder composed of a rubbery polymer and the thickener composed of a water-soluble polymer contained in the negative electrode is 0.1 to 5 parts by weight and 0.1 to 5 parts by weight per 100 parts by weight of the negative electrode active material, respectively. Part.

The positive electrode includes at least a positive electrode active material made of a composite lithium oxide, a binder, and a conductive agent.
Composite lithium oxides include lithium cobaltate (LiCoO2), lithium cobaltate modified, lithium nickelate (LiNiO2), lithium nickelate modified, lithium manganate (LiMn2O4), lithium manganate modified, these In the oxide, a part of Co, Mn, or Ni is preferably substituted with another transition metal element. Some modified bodies contain elements such as aluminum and magnesium. There are also those containing at least two of cobalt, nickel and manganese. Mn-based lithium-containing transition metal oxides such as LiMn2O4 are particularly promising because they exist abundantly on the earth and are inexpensive.

  The binder for the positive electrode is not particularly limited, and polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), or the like can be used. PTFE is preferably used in combination with CMC, polyethylene oxide (PEO), or the like that serves as a thickener for the raw material paste of the positive electrode mixture layer. PVDF has a single function as a binder and a function as a thickener by using n-methylpyrrolidinone (NMP) as a solvent.

  As the conductive agent for the positive electrode, acetylene black, ketjen black, various graphites and the like can be used. These may be used alone or in combination of two or more.

  As the non-aqueous electrolyte, it is preferable to use a non-aqueous solvent that dissolves a lithium salt as a solute. As the lithium salt, lithium hexafluorophosphate (LiPF 6), lithium perchlorate (LiClO 4), lithium borofluoride (LiBF 4) or the like is preferably used. As the nonaqueous solvent, ethylene carbonate (EC), propylene carbonate is used. (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC) and the like are preferably used. Although a nonaqueous solvent can also be used individually by 1 type, it is preferable to use 2 or more types in combination. The solute concentration dissolved in the non-aqueous solvent is generally 0.5 to 2 mol / L. Also,

  Use vinylene carbonate (VC), cyclohexylbenzene (CHB), modified products of VC and CHB, etc. to form a good film on the positive electrode and / or negative electrode and to ensure stability during overcharge. You can also.

  The separator is not particularly limited as long as it is made of a material that can withstand the usage environment of the lithium ion battery, but a microporous sheet made of a polyolefin resin is generally used. In addition, as the polyolefin resin, polyethylene, polypropylene, or the like is used. The microporous sheet may be a single layer film made of one kind of polyolefin resin or a multilayer film made of two or more kinds of polyolefin resins. Although the thickness of a separator is not specifically limited, From a viewpoint of maintaining the design capacity of a battery, it is preferable that it is 8-30 micrometers.

Next, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to these.
Example 1
This will be described with reference to FIG.

(A) Production of positive electrode 3 kg of lithium cobaltate and 1 kg of PVDF # 1320 (N-methyl-2-pyrrolidone (NMP) solution containing 12% by weight of PVDF) as a positive electrode binder manufactured by Kureha Chemical Co., Ltd. Then, 90 g of acetylene black and an appropriate amount of NMP were stirred with a double-arm kneader to prepare a positive electrode mixture paste. This paste was applied to both surfaces of a 15 μm-thick aluminum foil 11b as a positive electrode core material, dried and then rolled to form a positive electrode mixture layer 11a. At this time, a core material exposed portion having a width of 5 mm was left at one end portion along the longitudinal direction of the aluminum foil 11b. Further, the thickness of the electrode plate made of the aluminum foil 11b and the positive electrode mixture layer 11a was controlled to 160 μm. Thereafter, the electrode plate was slit to a width that can be inserted into a can-shaped battery case of a cylindrical battery (Part No. 18650) to obtain a hoop of the positive electrode 11.

(B) Production of negative electrode 3 kg of artificial graphite, 75 g of JSR product number 0656 (an aqueous dispersion containing 40% by weight of styrene-butadiene copolymer (rubber particles)) as a binder for the negative electrode, 30 g of CMC as a thickener and an appropriate amount of water were stirred with a double-arm kneader to prepare a negative electrode mixture paste. This paste was applied to both sides of a 10 μm-thick copper foil 12b as a negative electrode core material, dried and rolled to form a negative electrode mixture layer 12a. At this time, a core material exposed portion having a width of 5 mm was left at one end portion along the longitudinal direction of the copper foil 12b. Further, the thickness of the electrode plate made of the copper foil 12b and the negative electrode mixture layer 12a was controlled to 180 μm. Then, the electrode plate was slit to a width that can be inserted into the battery can 15 of the cylindrical battery (product number 18650), and a hoop of the negative electrode 12 was obtained.

(C) Preparation of non-aqueous electrolyte solution In a mixed solvent containing ethylene carbonate (EC), dimethyl carbonate (DMC), and methyl ethyl carbonate (MEC) in a volume ratio of 2: 3: 3, LiPF6 was added at a concentration of 1 mol / L. It melt | dissolved and also 3 weight% of vinylene carbonate (VC) was added, and electrolyte solution was prepared.

(D) Structure of electrode plate group Each of the positive electrode 11 and the negative electrode 12 is cut at a predetermined length, and a microporous sheet 13 made of polyethylene resin and having a thickness of 20 μm is interposed between the electrodes as a separator. A columnar electrode plate group 20 was configured. However, in the winding process, the core material exposed portions of the positive electrode 11 and the negative electrode 12 were protruded by about 2 mm from the end portions of the other electrode on one and the other end surfaces of the columnar electrode plate group, respectively.

(E) Production of current collector part While rotating the electrode plate group around the winding axis, while pressing a predetermined jig against the exposed part of the positive electrode core member on one end face of the electrode plate group, The jig was moved from the outer peripheral side toward the center. As a result, the core material exposed portion was sequentially bent from the outer peripheral side toward the inner peripheral side, and a flat positive electrode current collector 21 was formed. Similarly, while pressing the jig against the exposed portion of the negative electrode core material on the other end face of the electrode plate group, the jig is moved from the outer peripheral side of the end face toward the center to form a flat negative electrode current collector 22. did.

(F) Attaching the current collector plate The flat positive electrode current collector 21 and negative electrode current collector 22 were pressed against the flat positive electrode current collector 18 and negative electrode current collector 19, respectively. In this state, the positive electrode current collector 18 and the negative electrode current collector 19 were welded to the positive electrode current collector 21 and the negative electrode current collector 22 by irradiating a laser beam radially from the outside of each current collector.

(G) Electrolyte Injection / Impregnation and Battery Assembly One end of the positive electrode lead 18 a was welded to the positive electrode current collector plate 18, and one end of the negative electrode lead 19 a was welded to the negative electrode current collector plate 19. Next, the electrode plate group was accommodated in the inner space of the battery can 15. A separator was interposed between the electrode plate group and the inner surface of the battery can 15. The other end of the positive electrode lead 18 a was welded to the back surface of the battery lid 6. The other end of the negative electrode lead 19 a was welded to the inner bottom surface of the battery can 15.
Thereafter, 5.5 g of a nonaqueous electrolytic solution was injected into the inner space of the battery can 15. Then, the electrode group was vacuum impregnated with the electrolytic solution. At this time, an AC voltage having a frequency of 1.0 Hz and a voltage of 1.2 V was applied between the positive electrode and the negative electrode for 30 seconds.
As a result, the electrolyte injection / impregnation step was completed in 3 minutes.

  Then, the opening of the battery can 15 was closed with the battery lid 6, and the opening end of the battery can 15 was caulked and sealed with an insulating packing 17 disposed on the periphery of the battery lid 6. Thus, a cylindrical lithium ion secondary battery was completed.

Example 2
When the electrode plate is vacuum impregnated with the electrolyte, a DC voltage of 1.2 V is applied between the positive electrode and the negative electrode for 30 seconds, and then the DC voltage of the same voltage is changed for 30 seconds by changing the polarity. A lithium ion secondary battery was produced in the same manner as in Example 1 except that it was applied.
Here, the step of injecting and impregnating the electrolyte was completed in 2.5 minutes.

<< Comparative Example 1 >>
A lithium ion secondary battery was produced in the same manner as in Example 1 except that no voltage was applied between the positive electrode and the negative electrode when the electrode plate group was vacuum impregnated with the electrolyte.
Here, the step of pouring and impregnating the electrolytic solution was completed in 7 minutes.

<Evaluation>
From the above results, it was found that impregnation of the injected electrolyte solution was accelerated by application of voltage.

  The method for producing a battery of the present invention can reduce the time for injecting the electrolyte solution of a highly densified battery, and thus can improve the productivity of a high capacity battery such as a lithium ion secondary battery. .

It is a longitudinal cross-sectional view of a lithium ion secondary battery.

11 Positive electrode 12 Negative electrode 13 Separator 15 Battery can 20 Electrode plate group

Claims (5)

(A) a step of constituting an electrode plate group including a positive electrode, a negative electrode, and a separator that separates both electrodes;
(B) A method of manufacturing a battery, comprising: housing the electrode plate group in a container; and (c) impregnating the electrode group with an electrolyte while applying a voltage between the positive electrode and the negative electrode.   The manufacturing method according to claim 1, wherein the applied voltage is an alternating current.   The manufacturing method according to claim 1 or 2, wherein the applied voltage is 0.1 to 2.0V.   The manufacturing method according to claim 1, wherein the electrolyte is a gel electrolyte.   The manufacturing method according to claim 1, wherein the electrolyte contains a nonaqueous solvent and a lithium salt.

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