JP2013058377A - Lithium ion battery and manufacturing method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology which inhibits bumping when a gas in a battery case is vented.SOLUTION: A lithium ion battery is manufactured through a housing process, a decompression process, and a sealing process. In the housing process, a battery structure 4 including a positive electrode, a negative electrode, and a separator, a porous body 8 having open holes, and an electrolytic solution are housed in a battery case 2 so that the battery structure 4 and the porous body 8 are immersed in the electrolytic solution. In the decompression process, the battery case 2 is exposed to a decompression environment with an opening 10a of the battery case 2 after the housing process kept open. In the sealing process, the opening 10a is sealed while the battery case 2 remains exposed to the decompression environment.

Description

  The present invention relates to a lithium ion battery and a manufacturing method thereof.

  In a lithium ion battery, by repeatedly charging and discharging, the electrolyte in the battery case is decomposed to generate gas. Therefore, as the battery is used, gas accumulates in the battery case and the internal pressure of the battery increases. When the internal pressure of the battery reaches a predetermined value, the safety valve provided in the battery case is activated, and the gas in the battery case is released. The battery reaches the end of its life as the safety valve is activated. If the amount of gas mixed in the battery case at the manufacturing stage is large, the internal pressure of the battery may reach a predetermined value earlier than planned, and the safety valve may operate earlier than the original life. Therefore, at the manufacturing stage, it is required to reduce the amount of gas mixed in the battery case as much as possible. In the technique of Patent Document 1, the battery structure and the electrolytic solution are housed in a container, and then the gas in the battery case is degassed. This reduces the amount of gas present in the battery case before use.

JP 2009-224252 A

  As in Patent Document 1, if the gas is removed from the battery case, it is possible to suppress the internal pressure of the battery from reaching a predetermined value earlier than planned. Examples of the gas introduced into the battery case at the manufacturing stage include dissolved gas dissolved in the electrolytic solution. This dissolved gas is typically removed by exposing the battery case before sealing to a reduced pressure environment to bring the gas dissolved in the electrolyte into a supersaturated state. However, when the dissolved gas becomes supersaturated, bumping may occur in the battery case. As a result, the electrolytic solution may jump out of the battery case. When the electrolytic solution jumps out of the battery case, the manufacturing process becomes complicated, or the amount of the electrolytic solution in the battery case varies. That is, the yield in the manufacturing process of a lithium ion battery falls. An object of the technology disclosed in the present specification is to provide a technology for suppressing bumping when degassing a battery case in a lithium ion battery.

  The method for producing a lithium ion battery disclosed in the present specification is characterized in that gas is removed from the battery case while the porous body is accommodated in the battery case. The porous body has open pores. When the porous body is used to vent the battery case (exposing the battery case to a reduced pressure environment), bubbles are supplied from the porous body to the electrolyte. Supplying bubbles from the porous body to the electrolyte prevents the electrolyte from boiling. The gas (mainly dissolved gas) introduced into the battery case together with the battery structure, electrolyte, etc. is discharged outside the battery case while being taken into the bubbles generated from the porous body. That is, the technology disclosed in the present specification is to supply gas (bubbles) into the battery case using a porous body, despite performing gas venting in order to reduce the amount of gas in the battery case. This is an extremely novel technology that has never existed before. In the following description, the gas introduced into the battery case together with the battery structure, the electrolytic solution, and the like is sometimes referred to as introduced gas, and the gas (bubbles) generated from the porous body may be simply referred to as “bubbles”. As used herein, “open pores” means that pores formed in a porous body communicate with the outside of the porous body.

  The method for manufacturing a lithium ion battery disclosed in the present specification includes a housing process, a pressure reducing process, and a sealing process. In the housing step, the battery structure including the positive electrode, the negative electrode, and the separator, the porous body having open pores, and the electrolytic solution are placed in a state where the battery structure and the porous body are immersed in the electrolytic solution. Store in battery case. In the decompression step, the battery case is exposed to a decompression environment with a part of the battery case after the housing step being opened. In the sealing step, the opening of the battery case is sealed with the battery case exposed to a reduced pressure environment.

  By exposing the battery case to a reduced pressure environment, bubbles are generated from the porous body and the electrolytic solution is prevented from bumping. At this time, since the pores of the porous body are evacuated under reduced pressure, no gas remains. According to said manufacturing method, degassing in a battery case can be performed, suppressing bumping of electrolyte solution. In addition, the parts (positive electrode, negative electrode, and separator) constituting the battery structure also have holes and can be regarded as a porous body in a broad sense. In particular, the separator has a hole for allowing lithium ions to pass therethrough. However, a separator of a lithium ion battery typically has 0.02 to 2 μm holes. Bubbles generated from holes of such a size are crushed by the pressure of the electrolyte, and have no effect of suppressing bumping. In the manufacturing method disclosed in the present specification, a porous body having open pores is used separately from the battery structure. Since bubbles of a size that is not crushed by the pressure of the electrolytic solution can be supplied into the electrolytic solution, when degassing, the bubbles are reliably supplied into the electrolytic solution, and bumping can be suppressed.

  In the decompression step, typically, a battery case is placed in a decompression container, and the interior of the decompression container is decompressed. In the decompression step, it is preferable that the battery case is disposed in the decompression container in a state where the opening of the battery case is located on the upper side in the gravity direction, and the decompression container is decompressed. Bubbles generated from the porous body move in the electrolytic solution toward the upper side in the gravity direction of the battery case (the opposite side to the gravity, that is, the vertical direction). Therefore, if the decompression step is performed in a state where the opening of the battery case is on the upper side in the gravity direction, bubbles generated from the porous body can reach the opening while taking in a large amount of gas generated from the electrolytic solution. The “accommodating step” is preferably performed outside the decompression vessel in order to leave bubbles inside the porous body.

  As described above, the bubbles generated from the small-sized holes are crushed by the pressure of the electrolytic solution. If the pore size of the porous body is 5 μm or more, bubbles generated from the porous body are not crushed by the pressure of the electrolytic solution. On the other hand, if the pore size of the porous body is too large, the pores of the porous body are filled with the electrolytic solution before the battery case is exposed to the reduced pressure environment. However, if the pore size of the porous body is 100 μm or less, the open pores of the porous body are not filled with the electrolyte before the decompression step is performed. Therefore, it is desirable that the pore diameter of the open pores of the porous body is 5 to 100 μm.

  A lithium ion battery disclosed in the present specification includes a battery structure including a positive electrode, a negative electrode, and a separator, a porous body having open pores, an electrolytic solution in which the battery structure and the porous body are immersed, and a battery case It has. In this lithium ion battery, the battery structure, the electrolytic solution, and the porous body are sealed in the battery case in a state where the open pores of the porous body are filled with the electrolytic solution. The pore diameter of the open pores of the porous body is desirably 5 to 100 μm.

  The battery case may include a first end provided with a sealing portion and a second end facing the inner surface of the first end. In this case, it is preferable that the porous body is disposed closer to the second end than the center between the first end and the second end. The “sealing portion” here refers to a portion where the opening of the battery case when degassing is sealed after degassing. That is, this lithium ion battery is a form in which the porous body is disposed at a location sufficiently away from the opening for venting.

  The battery case may include a side wall connecting the first end and the second end. In this case, it is preferable that the porous body is disposed between the side wall of the battery case and the battery structure. If the porous body is disposed between the side wall of the battery case and the battery structure, bubbles generated from the porous body can be prevented from entering the battery structure. As a result, it is possible to suppress the bubbles generated from the porous body from staying in the battery structure and increasing the internal pressure of the battery. That is, the form in which the porous body is disposed between the side wall of the battery case and the battery structure is a form in which the gas that increases the internal pressure of the battery is reliably removed from the battery case.

  According to the technique disclosed in this specification, bumping when degassing the battery case can be suppressed.

A sectional view of a lithium ion battery of a 1st embodiment is shown. Sectional drawing of a laminated battery structure is shown. The external view of a wound battery structure is shown. The figure explaining the manufacturing method of the lithium ion battery of 1st Embodiment is shown (1). The figure explaining the manufacturing method of the lithium ion battery of 1st Embodiment is shown (2). Sectional drawing of the lithium ion battery of 2nd Embodiment is shown. Sectional drawing of the lithium ion battery of 3rd Embodiment is shown.

(First embodiment)
A lithium ion battery 100 shown in FIG. 1 includes a battery structure 4, a porous body 8, an electrolytic solution, and a battery case 2. In the drawing, wirings connected to the battery structure 4 are omitted. The battery structure 4 and the porous body 8 are accommodated in the battery case 2. The electrolytic solution fills the space 6 in the battery case 2. Therefore, the battery structure 4 and the porous body 8 are immersed in the electrolytic solution. The electrolyte also fills the gaps of the battery structure 4 and the pores of the porous body 8. A sealing portion 10 is provided on the upper end 2 u of the battery case 2. No sealing portion is provided at the lower end 2b at a position facing the inner surface of the upper end 2u. The upper end 2u and the lower end 2b are connected by a side wall 2s. The sealing unit 10 will be described later. In the present embodiment, the upper end 2u provided with the sealing portion 10 corresponds to the first end described in the claims. The lower end 2b corresponds to the second end described in the claims. The shape of the battery case 2 is not limited, and may be, for example, a cylindrical shape, a rectangular parallelepiped shape, or a sheet shape formed of a film. Hereinafter, the lithium ion battery 100 will be described in detail. Note that the terms “upper end 2 u” and “lower end 2 b” are for convenience to indicate the part of the battery case 2. When the lithium ion battery 100 is used, it does not mean that the “lower end 2b” is used with the lower side in the direction of gravity (the direction of gravity).

(Porous body)
The porous body 8 is disposed in the vicinity of the lower end 2b of the battery case 2. That is, the porous body 8 is disposed on the lower end 2b side from the center of the upper end 2u and the lower end 2b where the sealing portion 10 is provided. In the lithium ion battery 100, the porous body 8 is disposed between the lower end 2 b and the battery structure 4. In other words, the battery structure 4 is disposed between the porous body 8 and the sealing portion 10.

  The porous body 8 has open pores of 5 to 100 μm, and the open pores are filled with the electrolytic solution. As the porous body 8, it is used in polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), polyolefin, polyamide, and other resins, minerals, foam metal, glass, nonwoven fabric, wood, ceramics, nickel metal hydride batteries. A separator or the like can be used. In particular, a separator used in a nickel metal hydride battery has a pore size adjusted to an appropriate value and is suitable as the porous body 8.

(Battery structure)
The battery structure 4 may be a stacked type in which a plurality of electrode pairs (positive electrode and negative electrode) opposed via a separator are laminated, or a sheet-like cell having an electrode pair opposed via a separator is spiral. It may be a wound type that has been processed. Below, the battery structure 4 is demonstrated in detail.

  FIG. 2 shows a cross section of the stacked battery structure 4. The battery structure 4 includes a plurality of electrode pairs 20 in which the positive electrode 12 and the negative electrode 16 face each other with the separator 14 interposed therebetween. The positive electrode 12 and the negative electrode 16 are alternately laminated, and a separator 14 is interposed between the positive electrode 12 and the negative electrode 16. In the lithium ion battery 100, the surface 4s of the battery structure 4 faces the side wall 2s of the battery case 2 (see also FIG. 1). In addition, one end 4 u in a direction orthogonal to the stacking direction of the positive electrode 12 and the negative electrode 16 faces the sealing portion 10 of the battery case 2. The other end 4 b in the direction orthogonal to the stacking direction of the positive electrode 12 and the negative electrode 16 faces the lower end 2 b of the battery case 2.

  FIG. 3 shows the appearance of the wound battery structure 4a. The battery structure 4a is obtained by processing a pair of electrodes 20a in which the positive electrode sheet 12a and the negative electrode sheet 16a face each other via a separator 14a in a spiral shape. Specifically, the battery structure 4a is obtained by winding a sheet-like electrode pair 20a in which a separator 14a, a positive electrode sheet 12a, a separator 14a, and a negative electrode sheet 16a are stacked in this order using a winding machine. In the lithium ion battery 100, one end 4u in the winding axis direction of the battery structure 4a faces the sealing portion 10 (see also FIG. 1). In the battery structure 4a, the separator 14a corresponds to the surface 4s of the battery structure 4a.

(Positive electrode)
The positive electrode 12 and the positive electrode sheet 12a have a positive electrode current collector and a positive electrode active material. As the positive electrode current collector, aluminum (Al), nickel (Ni), titanium (Ti), or a composite material thereof can be used. As the positive electrode active material, trivalent manganese oxides such as Li ₂ MnO ₃ , Li (NiCoMn) _0.33 O ₂ and Li (NiMn) _0.5 O ₂ , and trivalents such as LiMn ₂ O ₄ and LiMnO ₂ are used. manganese _oxide, can be used _{LiNiO 2, LiCoO 2, LiNi 0.8} Co 0.15 Al 0.05 O 2 and the like. The positive electrode 12 and the positive electrode sheet 12a are formed by attaching a positive electrode active material together with a conductive material, a binder, and the like to a positive electrode current collector as necessary.

(Negative electrode)
The negative electrode 16 and the negative electrode sheet 16a have a negative electrode current collector and a negative electrode active material. As the negative electrode current collector, aluminum, nickel, copper (Cu), or a composite material thereof can be used. Carbon materials such as alkali metals such as lithium (Li) and sodium (Na), transition metal oxides containing alkali metals, natural graphite, mesocarbon microbeads, highly oriented graphite, hard carbon, and soft carbon as negative electrode active materials A silicon simple substance, a silicon-containing alloy, or a silicon-containing oxide can be used. The negative electrode 16 and the negative electrode sheet 16a are formed by attaching a negative electrode active material together with a conductive material, a binder and the like to a negative electrode current collector as necessary.

(Separator)
The separator 14 is interposed between the positive electrode 12 and the negative electrode 16 and insulates the positive electrode 12 and the negative electrode 16. Similarly, the separator 14a insulates the positive electrode sheet 12a and the negative electrode sheet 16a. The separators 14 and 14a are porous and can contain an electrolytic solution therein. The holes formed in the separators 14 and 14a are preferably 0.02 to 2 μm. As the separator, a porous film made of a polyolefin-based resin such as polyethylene (PE) or polypropylene (PP), or a woven or non-woven fabric made of polypropylene, polyethylene terephthalate (PET), methyl cellulose or the like can be used.

(Electrolyte)
The electrolytic solution is preferably a nonaqueous electrolytic solution in which a supporting salt (electrolyte) is dissolved in a nonaqueous solvent. As the non-aqueous solvent, ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), or a mixture thereof can be used. Moreover, as a supporting salt (electrolyte), for _example, can be used LiPF _6, LiBF 4, LiAsF _6, and the like.

(Production method)
With reference to FIG.4 and FIG.5, the manufacturing method of the lithium ion battery 100 is demonstrated. As shown in FIG. 4, after the battery structure 4 and the porous body 8 are accommodated in the battery case 2, an electrolytic solution is supplied into the battery case 2, and the battery structure 4 and the porous body 8 are made of the electrolytic solution. Immerse. With the opening 10a of the battery case 2 positioned on the upper side in the direction of gravity (that is, with the opening 10a facing the opposite side of gravity), the battery case 2 is disposed in the decompression vessel 30. As described above, the porous body 8 has pores of 5 to 100 μm. Therefore, at this stage, the electrolytic solution does not fill the pores of the porous body 8.

  Thereafter, the inside 32 of the decompression container 30 is decompressed. Bubbles 40 are generated from the porous body 8. The bubble 40 moves in the electrolytic solution toward the opening 10a. Further, when the inside 32 of the decompression container 30 is decompressed, the dissolved gas dissolved in the electrolytic solution becomes saturated, and gas is generated in the electrolytic solution. The bubble 40 moves in the electrolytic solution while taking in dissolved gas. Therefore, even if the pressure in the container 32 is reduced, it is possible to prevent bumping of the electrolyte due to the supersaturated state of the dissolved gas in the battery case 2.

  After the generation of the bubbles 40 from the porous body 8 is completed, the opening 10a is sealed as shown in FIG. The opening 10a is sealed while maintaining the pressure in the container 32 in a reduced pressure state. By forming the sealing portion 10 in a reduced pressure state, it is possible to prevent the gas from being mixed into the battery case 2 again.

  As described above, by using the porous body 8, the gas in the battery case 2 can be removed while preventing the electrolytic solution from bobbing. In the lithium ion battery manufactured by the above manufacturing method, the electrolyte does not spout outside the battery case during the manufacturing process, so that the electrolyte in the battery case is maintained at a desired amount. Therefore, the quality of the lithium ion battery is stabilized.

(Second Embodiment)
In the lithium ion battery 200 shown in FIG. 6, a recess 22 is formed in the lower end 2 b of the battery case 2. In other words, the recess 22 is formed at a position facing the inner surface of the upper end 2 u of the battery case 2. The porous body 8 is disposed in the recess 22. The width 22 w of the recess 22 is smaller than the width 4 w of the battery structure 4. In the lithium ion battery 200, it is possible to prevent a problem that the porous body 8 is sandwiched between the battery structure 4 and the battery case 2. The battery structure 4 can suppress the movement of bubbles generated from the porous body 8 from being restricted.

(Third embodiment)
In the lithium ion battery 300 shown in FIG. 7, the porous body 8 is disposed between the side wall 2 s of the battery case 2 and the surface 4 s of the battery structure 4. With such an arrangement, the bubbles generated from the porous body 8 can be prevented from entering between the electrodes. It is possible to suppress the bubbles from remaining in the battery case 2.

  Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. In addition, the technical elements described in the present specification or drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in the present specification or the drawings can achieve a plurality of objects at the same time, and has technical utility by achieving one of the objects.

2: Battery case 4: Battery structure 8: Porous body 12: Positive electrode 14: Separator 16: Negative electrode 100: Lithium ion battery

Claims (7)

A battery structure including a positive electrode, a negative electrode, and a separator, a porous body having open pores, and an electrolyte solution, such that the battery structure body and the porous body are immersed in the electrolyte solution A housing process for housing in the case;
A decompression step of exposing the battery case to a decompression environment in a state where a part of the battery case after the housing step is opened
A sealing step of sealing the opening in a state where the battery case is exposed to the reduced pressure environment;
A method of manufacturing a lithium ion battery comprising:   2. The decompression step, wherein the battery case is disposed in the decompression container in a state where the opening of the battery case is located on the upper side in the direction of gravity, and the interior of the decompression container is decompressed. Method for producing a lithium ion secondary battery.   3. The method of manufacturing a lithium ion battery according to claim 1, wherein a hole diameter of the open hole is 5 to 100 μm. A battery structure including a positive electrode, a negative electrode, and a separator;
A porous body having open pores;
An electrolyte in which the battery structure and the porous body are immersed;
Battery case, and
A lithium ion battery in which the battery structure, the electrolyte, and the porous body are sealed in the battery case in a state where the open pores of the porous body are filled with the electrolyte.   The lithium ion battery according to claim 4, wherein a hole diameter of the open hole is 5 to 100 μm. The battery case includes a first end provided with a sealing portion and a second end facing the inner surface of the first end,
6. The lithium ion battery according to claim 4, wherein the porous body is disposed closer to the second end than the center of the first end and the second end. The battery case includes a side wall connecting the first end and the second end;
The lithium ion battery according to claim 6, wherein the porous body is disposed between the side wall of the battery case and the battery structure.

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