JP2006108047A - Manufacturing method of battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve filling speed of an electrolytic liquid in a battery assembling process. <P>SOLUTION: The manufacturing method of a battery has a positive electrode fabrication process for fabricating a positive electrode having a positive electrode active material, a negative electrode fabrication process for fabricating a negative electrode active material, and a plasma treatment process for treating at least one of the positive electrode and the negative electrode under atmospheric pressure or nearby the atmospheric pressure by glow discharge plasma. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a battery manufacturing method.

A battery is manufactured by winding or laminating a positive electrode and a negative electrode to form a power generation element, and housing the power generation element in a battery container.
By the way, in recent years, attempts have been made to increase the density of the mixture layer in order to improve the discharge capacity of the battery. However, when the density of the mixture layer is increased, voids in the mixture layer are reduced, and the electrolyte solution is reduced. When pouring, the electrolytic solution hardly permeates, and as a result, the battery manufacturing time tends to be longer. Therefore, in order to shorten the injection time, it is considered that the electrolytic solution is heated to reduce its viscosity so as to easily penetrate into the mixture layer (for example, see Patent Document 1).
JP 2001-110399 A

However, when the electrolytic solution is heated, there is a problem that the electrolytic solution evaporates to change its concentration or the electrolytic solution is thermally deteriorated.
In addition, although a method of applying an electrolytic solution by pressurizing when injecting a liquid is conceivable, it is necessary to provide a pressurizer for pressurization, and there is a problem that a battery manufacturing apparatus is increased in size and cost. .
The present invention has been completed based on the above circumstances, and an object of the present invention is to provide a method for manufacturing a battery that solves the above-described problems and improves the rate of electrolyte injection.

  The inventors of the present invention have made extensive studies in order to shorten the time for injecting the electrolyte. As a result, when the plasma treatment by glow discharge was performed on the positive electrode or the negative electrode under atmospheric pressure or a pressure in the vicinity of the positive electrode or the negative electrode before the electrolyte solution injection, the electrolyte solution easily penetrated and the injection time was shortened. I found it. The present invention has been made based on this finding.

  That is, the invention of claim 1 includes a positive electrode manufacturing step for manufacturing a positive electrode provided with a positive electrode active material, a negative electrode manufacturing step for manufacturing a negative electrode provided with a negative electrode active material, and at least one of the positive electrode and the negative electrode at atmospheric pressure or A battery manufacturing method comprising: a plasma processing step of processing with glow discharge plasma under a nearby pressure.

  According to a second aspect of the present invention, in the first aspect of the present invention, the electrode after the plasma treatment step is stored at −10 to 20 ° C.

When plasma surface treatment by glow discharge is performed on the positive electrode or the negative electrode under atmospheric pressure or a pressure in the vicinity thereof, functional groups such as carbonyl groups and hydroxyl groups are formed on the carbon and binder on the surface of the positive electrode or negative electrode.
Since these functional groups have high affinity for the electrolytic solution, the wettability of the electrode with respect to the electrolytic solution is improved and the electrolytic solution is not repelled. As a result, the electrolytic solution easily penetrates into the electrode, and the injection time is shortened.
Further, since the glow discharge is performed under atmospheric pressure, it is not necessary to introduce equipment for reducing the pressure as in the case of glow discharge under reduced pressure, and the production line can be simplified and the cost can be reduced. . Furthermore, since it is glow discharge, the value of current flowing through the electrode is lower than that of arc discharge, and there is no fear of electrode damage.

  By the way, when the plasma-treated electrode is stored in an atmosphere higher than 20 ° C., the modified portion is caused by molecular motion of the modified portion of the electrode surface (the portion where a functional group such as a carbonyl group or a hydroxyl group is formed). There is a possibility that the effect of the surface modification may be reduced because the active material particles or the binder is immersed. According to the invention of claim 2, since the storage temperature of the treated electrode before the injection after the plasma surface treatment is set to −10 to 20 ° C. or less, the molecular motion of the modified portion is suppressed, and the modified portion is It remains on the surface as it is, the wettability of the electrode to the electrolyte is further increased, and the injection time is further shortened.

  The battery manufacturing method of the present invention includes a positive electrode manufacturing step for manufacturing a positive electrode provided with a positive electrode active material, a negative electrode manufacturing step for manufacturing a negative electrode including a negative electrode active material, and at least one of the positive electrode and the negative electrode at atmospheric pressure or And a plasma processing step of processing with glow discharge plasma under a nearby pressure.

For the positive electrode, a solvent is added to a mixture of a positive electrode active material and carbon as a conductive additive and a binder to form a paste, this paste is applied onto a current collector, dried, and then compression molded with a roll press, or the positive electrode The active material is manufactured by a method of directly attaching the active material on the current collector by sputtering or the like.
The positive electrode active material is not particularly limited, and a known positive electrode active material can be used. In the case of a non-aqueous electrolyte secondary battery, a lithium-containing composite metal oxide, that is, a cobalt oxide containing lithium , A manganese oxide containing lithium, a nickel oxide containing lithium or a composite oxide thereof, or a mixture thereof, and is not particularly limited, for example, a basic expressed by LiMO ₂ (where M is one or more transition metals) as compound mainly composed of lithium transition metal complex oxide having a _structure, LiCoO 2, LiNiO ₂ and the like, _{also, LiMnO 4, LiMn 2 O 4} , LiM y Mn 2-y O 4 (M = Cr, Co, Ni) or the like, or a composite oxide or a mixture thereof can also be used. When a compound mainly composed of a lithium transition metal composite oxide having a basic structure represented by LiMO ₂ (wherein M is one or more transition metals) is used as the transition metal M particularly from the high discharge voltage. It is desirable to select from Co, Ni, and Mn.

  Further, the carbon contained in the conductive auxiliary agent of the positive electrode is not particularly limited, and graphite, carbon black and the like can be used. In addition, an organic compound such as polyaniline can be mixed with the conductive auxiliary agent. It is.

  The binder for the positive electrode is not particularly limited, and cellulose, carboxymethyl cellulose, styrene-butadiene rubber, isoprene rubber, butadiene rubber, ethylene-propylene rubber, syndiotactic 1,2-polybutadiene, ethylene-vinyl acetate copolymer , Propylene-α-olefin (carbon number 2 to 12) copolymer, polyvinylidene fluoride, polytetrafluoroethylene, polytetrafluoroethylene-ethylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer Etc. can be used.

For the negative electrode, a solvent is added to a mixture of a negative electrode active material such as graphite and a binder to form a paste, this paste is applied onto a current collector, dried, and then compression molded with a roll press, or a negative electrode active material is sputtered. It is manufactured by a method of directly attaching on a current collector by a method or the like, a method of directly attaching metallic lithium or a lithium alloy on the current collector, a method of directly attaching on a current collector by a vacuum deposition method, or the like.
The carbon of the negative electrode active material is not particularly limited. For example, carbon such as known cokes, glassy carbons, graphites, natural graphite, artificial graphite, non-graphitizable carbons, pyrolytic carbons, carbon fibers, etc. A quality material can be used. Furthermore, you may mix SiOx (0 <= x <= 2), SnOx (0 <= x <= 2), etc. in a negative electrode active material.

  The binder for the negative electrode is not particularly limited. Styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVdF), cellulose, carboxymethylcellulose, isoprene rubber, butadiene rubber, ethylene-propylene rubber, syndiotactic 1,2-polybutadiene. , Ethylene-vinyl acetate copolymer, propylene-α-olefin (2 to 12 carbon atoms) copolymer, polytetrafluoroethylene, polytetrafluoroethylene-ethylene copolymer, vinylidene fluoride-hexafluoropropylene-tetra A fluoroethylene copolymer or the like can be used.

Next, the plasma treatment process will be described. In this step, the positive electrode or negative electrode produced as described above is treated with glow discharge plasma under atmospheric pressure or a pressure in the vicinity thereof.
The treatment with glow discharge plasma under atmospheric pressure or a pressure in the vicinity thereof uses a reactive gas under a pressure of 90 kPa to 110 kPa and applies a high frequency electric field to cause discharge between opposing electrodes, and the plasma by discharge. Surface treatment is performed by exposing the surface of the electrode to be treated to the reaction gas in a state.
By adjusting the pressure within this range, the pressure can be easily adjusted.
As an apparatus used in this step, a known apparatus that generates glow discharge plasma at a pressure near atmospheric pressure can be used.
For example, an example thereof will be described with reference to the schematic cross-sectional view of FIG. 1. An electric field is applied to the electrodes 2 and 3 from the high-voltage power supply 1, a processing gas is supplied from the arrow 6 and introduced between the electrodes, and is converted into plasma. A device can be used in which a gas in a plasma state is blown onto the electrode 7 for processing, and the gas after the processing is exhausted in the direction of the arrow 8. In FIG. 1, reference numerals 4 and 5 are the foundations of the plasma processing apparatus.
As the process gas is not particularly limited, N ₂ gas, O ₂ gas, a mixed gas of N ₂ and O _2, air, an inert gas such as argon or helium can be used. When a mixed gas of N ₂ and O ₂ is used, the mixing ratio is not particularly limited, but N ₂ : O ₂ = 80: 20 (volume ratio) is preferable. In particular, if air is used as the processing gas, it is not necessary to provide a processing gas supply device, so that the cost can be reduced.

  Next, battery assembly will be described. In this step, the electrode is wound or laminated via a separator to form a power generation element, and the obtained power generation element is housed in a battery container. In these battery manufacturing processes, the electrolyte may be injected before the power generating element is stored in the battery container or after the power generating element is stored in the battery container.

  The separator used here is not particularly limited, and a woven fabric, a non-woven fabric, a synthetic resin microporous membrane, or the like can be used. In particular, a synthetic resin microporous membrane can be suitably used. Among these, polyolefin microporous membranes such as polyethylene and polypropylene microporous membranes or microporous membranes composed of these are preferably used in terms of thickness, membrane strength, membrane resistance, and the like.

The electrolyte is not particularly limited and can be appropriately selected depending on the type of battery. In the case of a non-aqueous electrolyte secondary battery, for example, a mixed solvent of ethylene carbonate and methyl ethyl carbonate or ethylene carbonate and dimethyl A mixed solvent with carbonate is used. Propylene carbonate, butylene carbonate, vinylene carbonate, trifluoropropylene carbonate, γ-butyrolactone, 2-methyl-γ-butyllactone, acetyl-γ-butyrolactone, γ-valerolactone, sulfolane, 1,2-dimethoxy Ethane, 1,2-diethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 3-methyl-1,3-dioxolane, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate , Dipropyl carbonate, methyl propyl carbonate, ethyl isopropyl carbonate, dibutyl carbonate and the like may be used alone or in combination of two or more thereof. In this case, the electrolyte salt as a solute of the nonaqueous electrolytic solution is not particularly limited. For example, LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiCF ₃ CF ₂ SO ₃ , LiCF ₃ CF ₂ CF ₂ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ or the like can be used alone or in admixture of two or more.

  In addition, it is preferable to store the plasma-treated positive electrode or negative electrode at −10 to 20 ° C. in the state of an electrode, or in a state of being wound or laminated to form a power generation element.

When the plasma-treated electrode is stored in an atmosphere at a temperature higher than 20 ° C., the modified portion is caused by molecular motion of the modified portion of the electrode surface (the portion where a functional group such as a carbonyl group or a hydroxyl group is formed). This is because it may sink into the electrode and reduce the effect of surface modification.
On the other hand, if the temperature is lower than −10 ° C., the size of the equipment for cooling is increased, and energy consumption for cooling is increased, resulting in inefficiency.

  Therefore, by setting the storage temperature to −10 ° C. to 20 ° C., the size of the cooling equipment is increased and the energy consumption is saved, while the molecular motion of the modified portion is suppressed, and the modified portion remains on the surface as it is. You can do that.

EXAMPLES Hereinafter, although an Example demonstrates this invention in more detail, this invention is not limited to an Example.
<Example 1>
(1) Production of positive electrode The paste of the positive electrode mixture was prepared by mixing 94 parts by weight of LiCoO _{2 as} an active material, 3 parts by weight of acetylene black as a conductive material, and 3 parts by weight of polyvinylidene fluoride (PVdF) as a binder. N-methyl-2-pyrrolidone was added as appropriate and dispersed. The paste was uniformly applied to an aluminum current collector with a thickness of 20 μm, dried, and then compression-molded with a roll press to produce a strip-shaped positive electrode having a width of 26 mm and a length of 530 mm.

(2) Production of negative electrode The negative electrode mixture paste was prepared by mixing 97 parts by weight of flake graphite, 2 parts by weight of styrene-butadiene rubber (SBR) and 1 part by weight of carboxymethylcellulose (CMC), and adding purified water as appropriate. And dispersed to prepare. The paste was uniformly applied to a 10 μm thick copper current collector, dried, and then compression-molded with a roll press to prepare a strip-shaped negative electrode having a width of 27 mm and a length of 480 mm.

(3) Plasma treatment Using positive pressure plasma surface treatment apparatus AP-T02 manufactured by Sekisui Chemical Co., Ltd., the positive electrode is treated under an atmospheric pressure, a treatment gas; a mixed gas of N ₂ and O ₂ (N ₂ : O ₂ = 8: 2 (volume ratio)), applied voltage; 270 V, treatment time of 10 seconds, and treatment with atmospheric pressure glow discharge plasma.
The negative electrode was treated with atmospheric pressure glow discharge plasma using the same atmospheric pressure plasma surface treatment apparatus used for the treatment of the positive electrode under the same conditions as the treatment of the positive electrode.

(4) Battery assembly The positive electrode and negative electrode after plasma treatment were stored at 25 ° C. for 3 days, and then the positive electrode and negative electrode were wound through a separator of a microporous polyethylene film having a thickness of 25 microns to form a power generation element. After the power generation element is stored in a rectangular battery container having a width of 30 mm, a height of 48 mm, a thickness of 4.15 mm, and an internal capacity of 4.2 ml, the electrolyte is added so that the electrolyte does not overflow from the container at 25 ° C. The liquid was poured while adjusting the liquid volume.
As the electrolytic solution, ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at a volume ratio of 30:70, and LiPF ₆ dissolved in 1.2 mol / liter of this solution was used.

<Example 2>
The negative electrode was plasma-treated under the same conditions as in Example 1. The positive electrode was not plasma treated. Otherwise, the battery was fabricated in the same manner as in Example 1.

<Example 3>
Using the same atmospheric pressure plasma surface treatment apparatus as that used in Example 1, the negative electrode was processed under atmospheric pressure; a mixed gas of N ₂ and O ₂ (N ₂ : O ₂ = 8: 2 (volume ratio)) ), Applied voltage: 270 V, treatment with an atmospheric pressure glow discharge plasma at a treatment time of 5 seconds. The positive electrode was not plasma treated. Otherwise, the battery was fabricated in the same manner as in Example 1.

<Example 4>
Using the same atmospheric pressure plasma surface treatment apparatus as used in Example 1, the negative electrode was treated with atmospheric pressure glow discharge plasma under a treatment gas: N ₂ , an applied voltage: 200 V, and a treatment time of 10 seconds under atmospheric pressure. The positive electrode was not plasma treated. Otherwise, the battery was fabricated in the same manner as in Example 1.

<Example 5>
Using the same atmospheric pressure plasma surface treatment apparatus as used in Example 1, the negative electrode was treated with atmospheric pressure glow discharge plasma under a treatment gas; N ₂ , an applied voltage: 200 V, and a treatment time of 5 seconds under atmospheric pressure. The positive electrode was not plasma treated. Otherwise, the battery was fabricated in the same manner as in Example 1.

<Example 6>
Using the same atmospheric pressure plasma surface treatment apparatus as used in Example 1, the negative electrode was treated with atmospheric pressure glow discharge plasma at atmospheric pressure under a treatment gas; O ₂ , an applied voltage: 270 V, and a treatment time of 10 seconds. The positive electrode was not plasma treated. Otherwise, the battery was fabricated in the same manner as in Example 1.

<Example 7>
Using the same atmospheric pressure plasma surface treatment apparatus as used in Example 1, the negative electrode was treated with atmospheric pressure glow discharge plasma under a treatment pressure of O ₂ , an applied voltage of 270 V, and a treatment time of 5 seconds under atmospheric pressure. The positive electrode was not plasma treated. Otherwise, the battery was fabricated in the same manner as in Example 1.

<Example 8>
Using the same atmospheric pressure plasma surface treatment apparatus as that used in Example 1, the positive electrode was treated at atmospheric pressure; a mixed gas of N ₂ and O ₂ (N ₂ : O ₂ = 8: 2 (volume ratio)) ), An applied voltage: 270 V, and a treatment time of 10 seconds. The negative electrode was not plasma treated. Otherwise, the battery was fabricated in the same manner as in Example 1.

<Example 9>
Polyvinylidene fluoride (PVdF) was used in place of styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC) when producing the negative electrode, and the negative electrode was plasma treated under the same conditions as in Example 1. The positive electrode was not plasma treated. Otherwise, the battery was fabricated in the same manner as in Example 1.

<Example 10>
The negative electrode was plasma-treated under the same conditions as in Example 1. The positive electrode was not plasma treated. The negative electrode after the plasma treatment was stored at 20 ° C. for 3 days. Otherwise, the battery was fabricated in the same manner as in Example 1.

<Example 11>
The negative electrode was plasma-treated under the same conditions as in Example 1. The positive electrode was not plasma treated. The negative electrode after the plasma treatment was stored at 0 ° C. for 3 days. Otherwise, the battery was fabricated in the same manner as in Example 1.

<Example 12>
The negative electrode was plasma-treated under the same conditions as in Example 1. The positive electrode was not plasma treated. The negative electrode after the plasma treatment was stored at −10 ° C. for 3 days. Otherwise, the battery was fabricated in the same manner as in Example 1.

<Example 13>
In the plasma treatment of the positive electrode and the negative electrode, in the same manner as in Example 1 except that air was used instead of the mixed gas of N ₂ and O ₂ (volume ratio N ₂ : O ₂ = 8: 2) as the treatment gas. A battery of Example 13 was produced.

<Comparative Example 1>
The positive electrode and the negative electrode were subjected to plasma jet treatment by atmospheric pressure arc discharge.
Specifically, in the case of the positive electrode, the same belt-like positive electrode as used in Example 1 was surface-treated by atmospheric pressure arc discharge under the condition of an interelectrode distance of 3 cm. In the case of the negative electrode, the same strip-like negative electrode as used in Example 1 was subjected to surface treatment by atmospheric pressure arc discharge under the condition of an interelectrode distance of 3 cm. In addition, the positive electrode and the negative electrode after the surface treatment by atmospheric pressure arc discharge were found to have damaged and damaged surfaces. Therefore, it could not be used for a battery and a battery could not be produced.

<Comparative example 2>
Neither the positive electrode nor the negative electrode was plasma-treated. Otherwise, the battery was fabricated in the same manner as in Example 1.

<Test method>
For the batteries of Examples 1 to 13 and Comparative Example 2, the contact angle with water, the presence or absence of dropping of the mixture, and the liquid injection time were measured. In Comparative Example 1, no battery was produced.
(1) Measurement of contact angle with water About the electrode before battery assembly, the contact angle with respect to water was measured by the sessile drop method described in JIS R3257.
The “wetability” of the materials was compared by “contact angle with water”. When an organic solvent was used instead of water, the absolute value of the contact angle changed, but the relative contact angle was large. Since the relationship does not change, the relationship of “contact angle with respect to organic solvent” can be estimated from the data of “contact angle with respect to water”.
(2) Presence / absence of removal of mixture In the electrodes used in the batteries of Examples 1 to 13 and Comparative Example 2, the presence or absence of removal of the mixture was examined by visual observation of the electrode after plasma treatment.
(3) Measurement of injection time After storing the power generation element in the battery container, 1.75 ml of electrolyte was injected while adjusting the injection volume, and the time from the start of injection to the end of injection was measured. did.

<Experimental result>
For the batteries of Examples 1 to 13 and Comparative Examples 1 and 2, Tables 1 and 2 summarize the plasma treatment conditions of the electrodes used, the contact angle with water, the presence or absence of removal of the mixture, and the injection time. It was. In the table, “None” in the column of contact angle with water indicates that the contact angle is not measured.

実施例１〜実施例１３では、比較例２の非プラズマ処理のものよりも注液時間が短くなっていることが確認された。

In Examples 1 to 13, it was confirmed that the injection time was shorter than that of the non-plasma-treated one of Comparative Example 2.

In Example 1, since both the positive and negative electrodes were plasma-treated, the injection time was shorter than in Example 2 in which only the negative electrode was treated under the same conditions and in Example 8 in which only the positive electrode was treated. Also, in Example 9 using a binder other than SBR, the liquid injection time is shorter than in Comparative Example 2, and therefore the liquid injection time can be shortened by plasma treatment regardless of the type of binder. confirmed. Further, when a mixed gas of N ₂ and O ₂ is used (Examples 1 to 3, 8 to 12), when air is used (Example 13), when N ₂ is used (Examples 4 to 5). In each case where O ₂ was used (Example 7), the liquid injection time was shorter than that of Comparative Example 2, so that the liquid injection time was shortened by plasma treatment regardless of the type of processing gas. It was confirmed that
In addition, when Example 1 and Example 13 are compared, when the processing gas is a mixed gas of N ₂ and O ₂ (volume ratio N ₂ : O ₂ = 8: 2) and in the case of air, the injection time is Since almost no difference is observed, it is preferable to use air as the processing gas.

  Next, the contact angle between the negative electrode and water will be examined. In each of Examples 1 to 7 and Examples 10 to 12 in which the negative electrode was treated with atmospheric pressure glow discharge plasma, it was confirmed that the contact angle was extremely small compared to the untreated negative electrode.

Next, the storage temperature of the treated electrode will be examined. Example 2 (storage temperature; 25 ° C.), Example 10 (storage temperature; 20 ° C.), Example 11 (storage temperature 0 ° C.), and Example 12 (storage temperature−10 ° C.) were assembled after the plasma treatment step. Since the storage temperature of the negative electrode before the process is different and the other conditions are the same, these injection times are compared.
The liquid injection time in the assembly process of these examples tended to be shorter when the storage temperature was lowered, and the tendency was remarkable at 0 ° C. or lower. On the other hand, when the storage temperature is lower than −10 ° C., the equipment becomes larger and the energy consumption for cooling increases, which is inefficient. Therefore, it was found that the storage temperature after the plasma treatment is desirably −10 to 20 ° C.

  In addition, what was processed by the atmospheric pressure arc discharge of the comparative example 1 was not able to be used as an electrode because the electrode was severely damaged due to a large current value passed through the electrode, and the mixture had already partially dropped.

It is a conceptual diagram explaining the example of the apparatus used for a plasma treatment process.

Claims (2)

A positive electrode manufacturing process for manufacturing a positive electrode including a positive electrode active material, a negative electrode manufacturing process for manufacturing a negative electrode including a negative electrode active material, and glow discharge plasma under atmospheric pressure or a pressure in the vicinity of at least one of the positive electrode and the negative electrode. And a plasma processing step of processing by the battery. The battery manufacturing method according to claim 1, wherein the electrode after the plasma treatment step is stored at −10 to 20 ° C.

Images