JP4371721B2 - Method for producing non-aqueous electrolyte secondary battery - Google Patents

Description

【００７８】
前記表１から明らかなように実施例１〜３の非水電解液二次電池は、充電時の電池厚さが比較例１の非水電解液二次電池に比べて薄くなっていることがわかる。
【００７９】
実施例１〜３の非水電解液二次電池は、０．２Ｃ容量が比較例１の非水電解液二次電池と大きな差はないが、やはり大きくなっていることがわかる。
【００８０】
また、放置（貯蔵）条件を２０℃にした実施例１、２の非水電解液二次電池は、高温貯蔵時の電池厚さ変化量（膨れ量）が放置およびガス加圧を施さない比較例１の非水電解液二次電池に比べて小さいことがわかる。なお、放置（貯蔵）条件を４０℃にした実施例３の非水電解液二次電池は実施例１，２の非水電解液二次電池に比べその膨れ量が大きくなっているが、比較例１の非水電解液二次電池よりは小さく効果があることがわかる。
【００８１】
高温貯蔵時の容量回復率は、比較例１の非水電解液二次電池より実施例１〜３の非水電解液二次電池の方がいずれも大きい。
【００８２】
このように実施例１〜３の非水電解液二次電池は、初期特性が比較例１の非水電解液二次電池に比べていずれも向上していることがわかる。
【００８３】
充放電を５００サイクル実施した後の膨れ量は、実施例１〜３の非水電解液二次電池の方が比較例１の非水電解液二次電池に比べて小さく、電池厚さを薄くできることが分かる。５００サイクル後の容量維持率については実施例１〜３の非水電解液二次電池と比較例１の非水電解液二次電池との間で大きな差はないが、定格を満足するものであった。
【００８４】
【発明の効果】
以上詳述したように、本発明によれば初期および長期にわたる充放電においても膨れを防止して設定寸法を有し、かつ初期および長期にわたる充放電時において大きな放電容量を維持することが可能な非水電解液二次電池の製造方法、並び非水電解液二次電池を提供することができる。
【図面の簡単な説明】
【図１】 本発明の方法で製造される角型非水電解液二次電池を示す部分切欠斜視図。
【符号の説明】
１…外装部材、２…金属製の有底矩形筒状外装缶、３…注液孔、４…蓋体、６…電極体（電極群）、７…負極、８…セパレータ、９…正極、１０…封止蓋、１３…負極端子。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery produced by the method.
[0002]
[Prior art]
With the advancement of electronic devices such as mobile phones and personal computers, batteries used in these devices have been constantly required to be smaller, lighter, larger in capacity, higher in performance, and lower in cost. For this reason, in the battery, the electrode material such as the positive electrode active material or the negative electrode active material is changed to a material having higher energy density, the separator is made thinner, the thickness of the metal outer can is reduced, the outer can Improvements such as changing the material of iron from iron to aluminum have been attempted.
[0003]
However, due to these improvements, the amount of gas generated during the initial charge increases, the free space inside the battery decreases, the internal pressure increases, the electrodes are twisted, and the outer can is made of a low elastic material. It becomes easy to deform because it replaced. For this reason, the battery swelled at the time of first charge, and the problem that a desired thickness could not be maintained occurred.
[0004]
For this reason, Patent Document 1 discloses an initial charging process in which an electrolytic solution is quantitatively injected into the battery case from an electrolytic solution injection port, and then the electrolytic solution injection port is temporarily sealed to perform initial charging, and this initial charging step. Thereafter, the step of opening the temporarily sealed electrolyte injection port in an upward state and removing the gas generated in the battery case by the initial charging to the outside and removing the internal pressure after the internal pressure removal step A method of manufacturing a lithium secondary battery having a main sealing step of main sealing an inlet is disclosed.
[0005]
[Patent Document 1]
JP 11-329505 A
[0006]
[Problems to be solved by the invention]
However, the method disclosed in Patent Document 1 has a problem that the gas generated by the initial charge cannot be sufficiently removed from between the electrode plates. This residual gas causes swelling of the lithium secondary battery and deterioration of battery characteristics during charging and discharging.
[0007]
The present invention maintains the exterior member having a metal bottomed rectangular exterior can at a set size even during charging and discharging by sufficiently absorbing the residual gas into the non-aqueous electrolyte, and at the same time has excellent initial characteristics and It is an object of the present invention to provide a method for producing a non-aqueous electrolyte secondary battery having long-term characteristics and a non-aqueous electrolyte secondary battery.
[0008]
[Means for Solving the Problems]
  A method for producing a non-aqueous electrolyte secondary battery according to the present invention includes an electrode group composed of a positive electrode, a negative electrode, and a separator and a non-aqueous electrolyte solution in an exterior member having a metal bottomed rectangular cylindrical outer can. A method of manufacturing a stored nonaqueous electrolyte secondary battery,
  The exterior member in which the electrode group and the non-aqueous electrolyte are accommodated and opened to the outside3.6 to 3.9V voltage conditionDischarging the gas generated by precharging from the open part;
  After sealing the exterior member,1 to 7 days in an atmosphere of 20 to 40 ° CStoring, and
  Sealed exterior member after storageAt a gauge pressure of 0.1 to 15 MPaGas pressurization and further charging
It is characterized by including.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a method for producing a nonaqueous electrolyte secondary battery according to the present invention will be described in detail.
[0011]
(First step)
The positive electrode and the negative electrode are wound, for example, in a spiral shape via a separator to produce a spiral electrode body (electrode group). When applied to a prismatic non-aqueous electrolyte secondary battery, it is wound in a spiral shape and then pressure-molded at room temperature to produce a flat spiral electrode body (electrode group). Subsequently, the spiral electrode body is accommodated in an exterior member having a metal bottomed rectangular tubular exterior can, and further a nonaqueous electrolyte is accommodated in the exterior member.
[0012]
The positive electrode, negative electrode, separator and non-aqueous electrolyte will be described below.
[0013]
1) Positive electrode
The positive electrode includes a current collector and a positive electrode layer that is supported on one or both sides of the current collector and includes an active material.
[0014]
The positive electrode layer includes a positive electrode active material, a binder, and a conductive agent.
[0015]
Examples of the positive electrode active material include various oxides such as manganese dioxide, lithium manganese composite oxide, lithium-containing nickel oxide, lithium-containing cobalt oxide, lithium-containing nickel cobalt oxide, lithium-containing iron oxide, and lithium. Examples thereof include vanadium oxide and chalcogen compounds such as titanium disulfide and molybdenum disulfide. Among them, lithium-containing cobalt oxide (for example, LiCoO₂), Lithium-containing nickel cobalt oxide (eg, LiNi_0.8Co_0.2O₂), Lithium manganese composite oxide (for example, LiMn₂O_FourLiMnO₂) Is preferable because a high voltage can be obtained. Note that one type of oxide or a mixture of two or more types of oxides may be used as the positive electrode active material.
[0016]
Examples of the conductive agent include acetylene black, carbon black, and graphite.
[0017]
The binder has a function of holding the active material on the current collector and connecting the active materials to each other. Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), polyethersulfone, ethylene-propylene-diene copolymer (EPDM), and styrene-butadiene rubber (SBR). be able to.
[0018]
The mixing ratio of the positive electrode active material, the conductive agent and the binder is preferably in the range of 80 to 95% by weight of the positive electrode active material, 3 to 20% by weight of the conductive agent, and 2 to 7% by weight of the binder.
[0019]
As the current collector, for example, a porous conductive substrate or a non-porous conductive substrate can be used. These conductive substrates are made of, for example, aluminum, stainless steel, or nickel.
[0020]
The positive electrode is produced by, for example, preparing a slurry by dispersing a conductive agent and a binder in a suitable solvent in a positive electrode active material, applying the slurry to a current collector, and drying to form a thin plate.
[0021]
2) Negative electrode
The negative electrode includes a current collector and a negative electrode layer supported on one side or both sides of the current collector.
[0022]
The negative electrode layer includes a carbonaceous material that occludes / releases lithium ions and a binder.
[0023]
Examples of the carbonaceous materials include graphite materials, carbonaceous materials such as graphite, coke, carbon fiber, spherical carbon, pyrolytic vapor phase carbonaceous materials, and resin fired bodies, thermosetting resins, isotropic pitches, and mesophase pitch systems. Graphite material or carbon obtained by heat-treating carbon, mesophase pitch-based carbon fiber, mesophase microsphere, etc. (especially mesophase pitch-based carbon fiber is preferable because of its high capacity and charge / discharge cycle characteristics) at 500 to 3000 ° C. A quality material etc. can be mentioned. Among these, the (002) plane spacing d₀₀₂Is preferably a graphite material having a graphite crystal of 0.34 nm or less. A non-aqueous electrolyte secondary battery equipped with a negative electrode containing such a graphite material as a carbonaceous material can greatly improve battery capacity and large current discharge characteristics. Interplanar spacing d of the graphite material₀₀₂Is more preferably 0.337 nm or less.
[0024]
Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), ethylene-propylene-diene copolymer (EPDM), styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), and the like. Can be used.
[0025]
The blending ratio of the carbonaceous material and the binder is preferably in the range of 90 to 98% by weight of the carbonaceous material and 2 to 20% by weight of the binder.
[0026]
As the current collector, for example, a porous conductive substrate or a non-porous conductive substrate can be used. These conductive substrates are made of, for example, copper, stainless steel, or nickel.
[0027]
The negative electrode is prepared, for example, by mixing a carbonaceous material that occludes / releases lithium ions and a binder together with a solvent to prepare a slurry. The slurry is applied to a current collector, dried, and once at a desired pressure. Or by multi-stage pressing 2-5 times.
[0028]
3) Separator
As this separator, a microporous film, a woven fabric, a non-woven fabric, a laminate of the same material or different materials among these can be used. Examples of the material for the separator include polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-butene copolymer, and the like, and one kind or two or more kinds can be used.
[0029]
4) Non-aqueous electrolyte
This nonaqueous electrolytic solution has a composition in which an electrolyte is dissolved in a nonaqueous solvent.
[0030]
Examples of the electrolyte include lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), lithium hexafluorophosphate (LiPF6), lithium hexafluoroarsenate (LiAsF6), and lithium trifluoromethanesulfonate (LiCF3SO3). LiN (CF3SO2) 2, lithium bis [5-fluoro-2-olato-1-benzene-sulfonato (2-)] borate and the like can be used.
[0031]
Examples of the non-aqueous solvent include γ-butyrolactone, ethylene carbonate, propylene carbonate, diethyl carbonate, methyl ethyl carbonate, vinylene carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 1,3-dioxolane. , Methyl sulfolane, acetonitrile, propyl nitrile, anisole, acetic acid ester, propionic acid ester, etc. may be used, and two or more kinds may be mixed and used. It is preferable to add a surfactant such as trioctyl phosphate (TOP) to the non-aqueous solvent. By adding such a surfactant, it becomes possible to improve the wettability of the non-aqueous electrolyte with respect to the separator.
[0032]
The concentration of the electrolyte in the non-aqueous solvent is preferably 0.5 mol / L or more.
[0033]
The exterior member is, for example, a bottomed rectangular tubular exterior can made of a metal such as aluminum or an aluminum alloy, and the aluminum having an electrolyte injection hole joined to the opening of the exterior can by, for example, laser seam welding. It is comprised from the cover body made from aluminum alloy. The outer can is preferably made of aluminum or an aluminum alloy having an elastic modulus of 0.65 to 0.75 GPa and a thickness of 0.1 to 0.3 mm.
[0034]
In order to accommodate the non-aqueous electrolyte in the exterior member composed of the exterior can and the lid, the non-aqueous electrolyte is injected from the liquid injection hole of the lid by, for example, a vacuum injection method. It is preferable to perform this non-aqueous electrolyte injection operation in two steps. Specifically, in the first time, the liquid is injected in an amount corresponding to 70 to 85% of the rated amount of the nonaqueous electrolytic solution, and in the second time, the remaining amount is injected after preliminary charging described later. Avoiding the non-aqueous electrolyte from overflowing from the injection hole when the gas generated during the preliminary charging described later by such two injection operations is discharged to the outside through the injection hole, for example. Is possible.
[0035]
(Second step)
The electrode group and the non-aqueous electrolyte are accommodated, and the gas generated by precharging the metal exterior member opened to the outside is discharged from the open portion.
[0036]
Here, “opened to the outside” means that, for example, when the exterior member is composed of a metal bottomed rectangular cylindrical outer can and a lid body having a liquid injection hole, the liquid injection hole is not sealed. It means the form opened to
[0037]
The preliminary charging is preferably performed under a voltage condition of 3.6 to 3.9 V, for example. This preliminary charging is performed at a rate of 0.5 C, for example, at a potential in the above range for 2 hours. If the precharge potential is less than 3.6 V, gas such as hydrogen gas is generated in the main charge, and the exterior member (particularly the exterior can) may swell. When the precharge potential exceeds 3.9 V, the generation rate of gas such as hydrogen gas in the precharge increases, and there is a possibility that the exterior member (particularly the exterior can) may swell during the precharge.
[0038]
(Third step)
After the exterior member is sealed, it is stored. Gas pressure is applied to the sealed exterior member after storage. Then, this charge is performed and a nonaqueous electrolyte secondary battery is manufactured.
[0039]
Here, “sealing of the exterior member” means, for example, when the exterior member is composed of a metal bottomed rectangular cylindrical exterior can and a lid having a liquid injection hole, for example, a metal rectangular or circular plate The sealing lid which consists of this is joined to the cover body containing a liquid injection hole by welding etc., and the said liquid injection hole is sealed.
[0040]
The storage is preferably left in an atmosphere of 20 to 40 ° C. for 1 to 7 days.
[0041]
The pressurization with the gas can be performed, for example, by a method of setting a sealed exterior member containing an electrode group and a non-aqueous electrolyte in a pressure vessel and supplying a high pressure gas into the pressure vessel.
[0042]
As the gas, for example, air, nitrogen gas, carbon dioxide gas or inert gas can be used, and these gases are preferably dried. In addition, by using a dry gas, moisture permeates into the exterior member and prevents degradation of battery performance due to reaction with an electrolyte in the electrolyte, for example, lithium hexafluorophosphate to generate hydrofluoric acid. Is possible. By using carbon dioxide gas, nitrogen gas, or inert gas as gas, oxygen penetrates into the exterior member and prevents the electrolyte, positive electrode, negative electrode, separator, current collector, etc. from being oxidized, resulting in decreased battery performance Can be prevented.
[0043]
The pressure applied by the gas is preferably 0.1 to 15 MPa as a gauge pressure. When the pressure applied by the gas is less than 0.1 MPa in gauge pressure, the gas (hydrogen, etc.) generated during the preliminary charging is discharged to the outside through the open part (for example, a liquid injection hole) of the exterior member, and the residual gas is not removed. There is a possibility that it is difficult to quickly dissolve in the water electrolyte. On the other hand, when the pressure applied by the gas exceeds 15 MPa in gauge pressure, it is necessary to increase the wall thickness of the container in order to increase the pressure resistance of the pressure container, or the operability may be deteriorated. is there.
[0044]
The “main charging” means charging at a voltage higher than the preliminary charging and a voltage at which a charging reaction between the positive and negative electrodes is sufficiently performed. Specifically, the main charging is performed at 4.2 V, for example, at a rate of 0.2 C for 6 hours.
[0045]
A non-aqueous electrolyte secondary battery (for example, a square non-aqueous electrolyte secondary battery) manufactured by the method according to the present invention has a structure shown in FIG.
[0046]
The square-shaped exterior member 1 has a bottomed rectangular tube shape made of, for example, aluminum or an aluminum alloy, and is hermetically joined to the opening of the exterior can 2 by, for example, laser welding, and has a liquid injection hole 3. It is comprised from the cover body 4 which consists of aluminum or aluminum alloy. The outer can 2 also serves as a positive electrode terminal, for example, and a lower insulating paper 5 is disposed on the bottom surface.
[0047]
An electrode body 6 that is an electrode group is housed in an outer can 2 of the outer member 1. The electrode body 6 is produced, for example, by winding the negative electrode 7, the separator 8, and the positive electrode 9 in a spiral shape so that the positive electrode 9 is located on the outermost periphery, and then press-molding it into a flat shape.
[0048]
The non-aqueous electrolyte is injected into the outer can 2 through the injection hole 3 of the lid 4. After the injection, a sealing lid 10 made of, for example, an aluminum or aluminum alloy disk is joined by ultrasonic welding or the like to seal the exterior member 1. This sealing lid may be a rectangular plate.
[0049]
A spacer 11 made of, for example, synthetic resin having a lead extraction hole in the vicinity of the center is disposed on the electrode body 6 in the outer can 2. In the vicinity of the center of the lid 4, a lead-out hole 12 for the negative electrode terminal is opened. The negative electrode terminal 13 passes through the hole 12 of the lid body 4 and the hole of the spacer 11 and is hermetically sealed at the location of the hole 12 of the lid body 4 via an insulating material 14 made of glass or resin. Yes. A lead 15 is connected to the lower end surface of the negative electrode terminal 13, and the other end of the lead 15 is connected to the negative electrode 7 of the electrode body 6.
[0050]
The upper insulating paper 16 is covered on the entire outer surface of the lid 4. The outer tube 17 is disposed so as to extend from the side surface of the outer can 2 to the periphery of the lower and upper insulating papers 5 and 16, and the lower insulating paper 5 is placed on the bottom surface of the outer can 2 and the upper side Insulating paper 16 is fixed to the outer surface of the lid 4.
[0051]
According to the present invention described above, an exterior member having a bottomed rectangular cylindrical outer can made of metal and containing an electrode group composed of a positive electrode, a negative electrode, and a separator and a non-aqueous electrolyte and opened to the outside is reserved. The gas generated by charging is discharged from the open part, and the exterior member is sealed and stored, and then the sealed exterior member is pressurized with gas and further charged, thereby generating and correcting the gas during the initial charge. The metal exterior member due to the expansion of the negative electrode active material, particularly the expansion of the outer can, can be suppressed, and the separation between the positive electrode and the negative electrode can be prevented. A nonaqueous electrolyte secondary battery capable of maintaining the discharge capacity can be manufactured.
[0052]
That is, during the pre-charging, the charging reaction that occurs between the electrolyte and the positive and negative electrodes generates decomposition gas such as hydrogen, methane, ethylene, carbon monoxide, and the internal pressure of the exterior member increases, and the metal constituting the exterior member The side surface of the manufactured bottomed rectangular cylindrical outer can is spread and the side surface of the outer can expands to increase its thickness (particularly the thickness of the central portion). Accordingly, a gap is generated between the inner surface of the outer can and the electrode group housed in the outer can, and the positive and negative electrodes of the electrode group are separated from each other. Further, the decomposition gas stays between the positive and negative electrodes of the electrode group. When the main charging is performed in such a state, the electrodes are twisted due to the expansion of the active material of the positive and negative electrodes accompanying the main charging, and the finished thickness of the exterior member becomes thicker. In a non-aqueous electrolyte secondary battery, charging is performed in a local overload state, so that lithium ions are electrodeposited to form a thin metallic lithium layer. As a result, the battery becomes thick or the charge / discharge capacity decreases.
[0053]
For this reason, in the present invention, the generated gas can be discharged from the open portion by opening the exterior member to the outside during preliminary charging. As a result, it is possible to prevent swelling of the side surface of the metal bottomed rectangular cylindrical outer can constituting the outer member. However, even if such a method is taken, the generated gas does not fully escape and remains in the exterior member, particularly between the positive and negative electrodes of the electrode group. Cause a drop in
[0054]
Therefore, in the present invention, after the preliminary charging, before the main charging, the exterior member is sealed and sealed, stored, and then pressurized with a high-pressure gas. By storing the exterior member in such a sealed state, and subsequent gas pressurization, a gas such as hydrogen remaining in the exterior member, particularly between the positive and negative electrodes of the electrode group, is removed from the non-aqueous electrolyte solution in the exterior member. (Henry's law) and the electrode group in the outer member can be pressed through the exterior member to return to the shape before precharging without swelling. As a result, it is possible to prevent the inner surface of the exterior member from being separated from the electrode group or between the positive and negative electrode plates. That is, the inner surface of the exterior member (particularly the exterior can) can be in close contact with the outer surface of the electrode group, and the electrodes can be in close contact with each other. In addition, since the space between the positive and negative electrode plates can be reduced, the occurrence of electrodeposition of the metallic lithium can be prevented. Therefore, even if the positive and negative active materials expand in the main charging, it is possible to prevent the electrodes from being twisted, the finished thickness of the battery from becoming thicker, and the metal lithium from being electrodeposited between the electrode plates. Therefore, it is possible to manufacture a non-aqueous electrolyte secondary battery that has a set dimension after the completion of the initial charge and can maintain a high discharge capacity in the initial stage and in the long term.
[0055]
Further, even if the gas pressure is reduced by the combination of the storage and the gas pressurization, a gas such as hydrogen remaining in the exterior member, particularly between the positive and negative electrodes of the electrode group, is removed by non-aqueous electrolysis in the exterior member. It can be effectively dissolved in the liquid. As a result, it is possible to manufacture a non-aqueous electrolyte secondary battery that has excellent charge / discharge characteristics and has set dimensions with a pressurizing facility such as a pressure vessel that is simple in gas pressure and thin in thickness.
[0056]
That is, if the gas remaining between the positive and negative electrodes of the electrode group is dissolved in the non-aqueous electrolyte only by gas pressurization, it is necessary to apply a considerably high gas pressure to the exterior member. For this reason, it is necessary to use a large-scale and complicated pressurization facility, resulting in a decrease in productivity and cost increase of the non-aqueous electrolyte secondary battery.
[0057]
By storing the sealed exterior member containing the electrode group and the non-aqueous electrolyte as in the present invention described above prior to gas pressurization, the state between the positive and negative electrodes of the electrode group after the precharge reaction is stabilized. Then, the gas remaining between the positive and negative electrodes can be dissolved in the non-aqueous electrolyte, and the subsequent gas dissolving operation by gas pressurization can be performed. As a result, in the gas pressurization operation for the exterior member, hydrogen remaining between the positive and negative electrodes of the electrode group in the exterior member under a low pressure condition, that is, a pressurization facility such as a simple and thin pressure vessel. Such gas can be effectively dissolved in the non-aqueous electrolyte in the exterior member.
[0058]
【Example】
Hereinafter, embodiments of the present invention will be described in detail.
[0059]
Example 1
<Preparation of positive electrode>
First, lithium cobalt oxide (LiCoO₂) To 90% by weight of powder, 5% by weight of acetylene black and 5% by weight of polyvinylidene fluoride (PVdF) in dimethylformamide (DMF) were added and mixed to prepare a slurry. The slurry was applied to both surfaces of a current collector made of an aluminum foil having a thickness of 15 μm, then dried and pressed to produce a positive electrode having a structure in which the positive electrode layer was supported on both surfaces of the current collector. The thickness of the positive electrode layer was 60 μm per side.
[0060]
<Production of negative electrode>
Mesophase pitch carbon fiber heat treated at 3000 ° C. as a carbonaceous material [(002) plane spacing determined by powder X-ray diffraction (d₀₀₂) Was 0.336 nm] and a dimethylformamide (DMF) solution containing 5% by weight of polyvinylidene fluoride (PVdF) was mixed to prepare a slurry. This slurry was applied to both sides of a current collector made of a copper foil having a thickness of 12 μm, dried and pressed to prepare a negative electrode having a structure in which the negative electrode layer was supported on the current collector. The thickness of the negative electrode layer was 55 μm per side.
[0061]
Note that the spacing d of the (002) plane of the carbonaceous material₀₀₂Was determined from the powder X-ray diffraction spectrum by the half-width half-point method. At this time, scattering correction such as Lorentz scattering was not performed.
[0062]
<Separator>
Thickness 20μm, porosity 50%, air permeability 300sec / 100cm^ThreeA separator made of a polyethylene microporous membrane was prepared.
[0063]
<Preparation of non-aqueous electrolyte>
Ethylene carbonate (EC) / methyl ethyl carbonate (MEC) / lithium hexafluorophosphate (LiPF)₆ ) = 34.9 / 53.1 / 12 (weight ratio) A non-aqueous electrolyte was prepared by adding 0.5% by weight of vinylene carbonate (VC).
[0064]
<Production of electrode group>
After ultrasonically welding a positive electrode lead made of a strip-shaped aluminum foil with a thickness of 100 μm to the positive electrode current collector, and ultrasonically welding a negative electrode lead made of a strip-shaped nickel foil with a thickness of 100 μm to the negative electrode current collector, The positive electrode and the negative electrode were spirally wound through the separator therebetween, then formed into a flat shape, further heated and compressed with a hydraulic press, and formed into a flat electrode body (electrode group).
[0065]
<Assembly and manufacture of secondary batteries>
The electrode body is inserted into a bottomed rectangular tubular outer can made of aluminum having a wall thickness of 0.25 mm, and an aluminum lid having a liquid injection hole at the upper end opening of the outer can is laser-seam welded to form the electrode. The body was sealed in the exterior member. Subsequently, the exterior member containing the electrode group was vacuum dried at 85 ° C. for 12 hours to remove moisture contained in the electrode group and the exterior member. Subsequently, an amount corresponding to 85% of the rated amount was injected into the electrode group in the exterior member through the liquid injection hole of the lid body. Preliminary charging was performed at 0.5 C (310 mA) for 2 hours in dry nitrogen at room temperature and atmospheric pressure with the liquid injection hole opened, and the generated gas was discharged through the liquid injection hole. Thereafter, the nonaqueous electrolytic solution having the above composition was injected again into the electrode group in the exterior member through the injection hole of the lid body, and the rated amount of the nonaqueous electrolytic solution was accommodated.
[0066]
Next, after completion of the preliminary charging, a sealing lid made of an aluminum disk was joined to the lid body including the liquid injection hole by welding to seal the exterior member. Subsequently, the sealed exterior member was left (stored) in an atmosphere at 20 ° C. for 24 hours, then placed in a pressure resistant container, and dried air compressed at room temperature was fed into the exterior member at 0.9 MPa ( The pressure was applied for 12 hours. As a result, the gas that is generated in the pre-charging and remains without being discharged is dissolved in the non-aqueous electrolyte, and at the same time, a minute gap generated between the outer can and the electrode group and between the positive and negative electrodes of the electrode group is pushed. I crushed it.
[0067]
Finally, by performing main charging for 10 hours under the conditions of 20 ° C., 0.2 C (124 mA), and 4.2 V, the non-rated dimensions are 4.4 mm thick, 30 mm wide, 48 mm high, and the capacity is 620 mAh (0 .2C) prismatic non-aqueous electrolyte secondary battery was manufactured.
[0068]
(Example 2)
A rectangular non-aqueous electrolyte secondary battery of the same type was manufactured in the same manner as in Example 1 except that the standing (storage) condition after the preliminary charging was 168 hours in an atmosphere of 20 ° C.
[0069]
(Example 3)
A rectangular nonaqueous electrolyte secondary battery of the same type was manufactured in the same manner as in Example 1 except that the standing (storage) condition after the preliminary charging was 168 hours in an atmosphere of 40 ° C.
[0070]
(Comparative Example 1)
A rectangular non-aqueous electrolyte secondary battery of the same type was manufactured in the same manner as in Example 1 except that after the preliminary charging, the main charging was performed without performing gas pressurization.
[0071]
(Battery performance test)
The obtained non-aqueous electrolyte secondary batteries of Examples 1 to 3 and Comparative Example 1 were evaluated by the tests described below. The results are shown in Table 1 below.
[0072]
1) Thickness test during charging
The thickness of each secondary battery after charging at 620 mA, 4.2 V, 3 hours at 20 ° C. was determined.
[0073]
2) 0.2C capacity test
Each secondary battery was charged at 620 mA, 4.2 V, 3 hours at 20 ° C., and after 10 minutes of rest, the discharge capacity at 124 mA, 3.0 V cutoff was determined.
[0074]
3) Test of battery thickness and capacity recovery after high temperature storage
Each secondary battery was charged at 620 mA, 4.2 V, 3 hours at 20 ° C., and after 10 minutes of rest, the discharge capacity (reference capacity) at 620 mA, 3.0 V cutoff was measured. Again, charging was performed at 20 ° C. at 620 mA, 4.2 V, and 3 hours. After measuring the battery thickness in this charged state, it was left in a constant temperature bath at 85 ° C. for 24 hours. The battery thickness after standing was measured, and the amount of battery swelling was determined from the difference from the battery thickness before leaving.
[0075]
Furthermore, discharging, charging, discharging (discharging conditions: 620 mA, 3.0 V cut-off, charging conditions: 620 mA, 4.2 V, 3 hours) were repeated, the final discharging capacity was measured, and the obtained discharging capacity was The capacity recovery rate was determined from the value (percentage; maintenance rate) when divided by the reference capacity.
[0076]
4) Test of battery thickness and capacity retention after 500 cycles
After repeating 500 cycles of charging and discharging (charging conditions; 620 mA, 4.2 V, 3 hours, discharging conditions; 620 mA, 3.0 V cutoff) at 20 ° C. under the conditions of 1.0 C / 1.0 C for each secondary battery. The battery thickness and the discharge capacity retention ratio (maintenance ratio relative to the initial discharge capacity) were determined.
[0077]
[Table 1]

[0078]
As is apparent from Table 1, the nonaqueous electrolyte secondary batteries of Examples 1 to 3 are thinner than the nonaqueous electrolyte secondary battery of Comparative Example 1 in charging. Recognize.
[0079]
It can be seen that the nonaqueous electrolyte secondary batteries of Examples 1 to 3 have a 0.2C capacity that is not significantly different from the nonaqueous electrolyte secondary battery of Comparative Example 1, but is still large.
[0080]
In addition, the non-aqueous electrolyte secondary batteries of Examples 1 and 2 in which the storage (storage) conditions were 20 ° C. were compared with the amount of change in battery thickness (expansion amount) during storage at high temperatures without applying gas pressurization. It can be seen that it is smaller than the non-aqueous electrolyte secondary battery of Example 1. In addition, although the nonaqueous electrolyte secondary battery of Example 3 in which the storage (storage) condition was 40 ° C. was larger than the nonaqueous electrolyte secondary battery of Examples 1 and 2, It can be seen that the effect is smaller than that of the non-aqueous electrolyte secondary battery of Example 1.
[0081]
The non-aqueous electrolyte secondary batteries of Examples 1 to 3 have a higher capacity recovery rate during high-temperature storage than the non-aqueous electrolyte secondary battery of Comparative Example 1.
[0082]
Thus, it can be seen that the non-aqueous electrolyte secondary batteries of Examples 1 to 3 have improved initial characteristics as compared with the non-aqueous electrolyte secondary battery of Comparative Example 1.
[0083]
The amount of swelling after 500 cycles of charge / discharge is smaller in the non-aqueous electrolyte secondary battery of Examples 1 to 3 than in the non-aqueous electrolyte secondary battery of Comparative Example 1, and the battery thickness is reduced. I understand that I can do it. Regarding the capacity retention after 500 cycles, there is no significant difference between the non-aqueous electrolyte secondary battery of Examples 1 to 3 and the non-aqueous electrolyte secondary battery of Comparative Example 1, but it satisfies the rating. there were.
[0084]
【The invention's effect】
As described above in detail, according to the present invention, it is possible to prevent swelling during initial and long-term charging / discharging, to have a set dimension, and to maintain a large discharge capacity during initial and long-term charging / discharging. A method for producing a nonaqueous electrolyte secondary battery and a nonaqueous electrolyte secondary battery can be provided.
[Brief description of the drawings]
FIG. 1 is a partially cutaway perspective view showing a prismatic nonaqueous electrolyte secondary battery manufactured by the method of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Exterior member, 2 ... Metal bottomed rectangular cylindrical exterior can, 3 ... Injection hole, 4 ... Cover body, 6 ... Electrode body (electrode group), 7 ... Negative electrode, 8 ... Separator, 9 ... Positive electrode, 10 ... sealing lid, 13 ... negative electrode terminal.

Claims (2)

A method for producing a non-aqueous electrolyte secondary battery in which an electrode group composed of a positive electrode, a negative electrode, and a separator and a non-aqueous electrolyte is housed in an exterior member having a metal bottomed rectangular cylindrical outer can,
A step of pre-charging the exterior member in which the electrode group and the non-aqueous electrolyte are housed and opened to the outside under a voltage condition of 3.6 to 3.9 V and discharging gas generated from the open portion;
After sealing the exterior member, storing in an atmosphere of 20 to 40 ° C. for 1 to 7 days ;
A method for producing a non-aqueous electrolyte secondary battery, comprising the steps of: gas-pressing the sealed exterior member after storage at a gauge pressure of 0.1 to 15 MPa , and further performing main charging. The non-aqueous electrolyte is injected into the exterior tube of the exterior member in two times, before the preliminary charge and before the exterior member is sealed after the preliminary charge, and the first time is the non-aqueous electrolyte. 2. The electrolytic solution is injected into the outer tube in an amount corresponding to 70 to 85% of the rated amount, and the remaining amount of the electrolytic solution is injected into the outer tube in the second time. Of manufacturing a non-aqueous electrolyte secondary battery.

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