WO2007066639A1 - Lithium ion secondary battery - Google Patents

Lithium ion secondary battery Download PDF

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Publication number
WO2007066639A1
WO2007066639A1 PCT/JP2006/324225 JP2006324225W WO2007066639A1 WO 2007066639 A1 WO2007066639 A1 WO 2007066639A1 JP 2006324225 W JP2006324225 W JP 2006324225W WO 2007066639 A1 WO2007066639 A1 WO 2007066639A1
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WIPO (PCT)
Prior art keywords
positive electrode
negative electrode
active material
battery
electrode active
Prior art date
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PCT/JP2006/324225
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French (fr)
Japanese (ja)
Inventor
Tsuyoshi Hatanaka
Hideaki Fujita
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Matsushita Battery Industrial Co., Ltd.
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Publication of WO2007066639A1 publication Critical patent/WO2007066639A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0568—Liquid materials characterised by the solutes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the 002-tium secondary battery Due to its high degree of energy, the 002-tium secondary battery has become widespread as a source for consumer equipment, for example, mobile phones, sons, and other information devices.
  • secondary batteries are also nowadays attracting attention as a power source for electric vehicles, especially for electric vehicles ().
  • the secondary battery for mobile use will be put into practical use.
  • a secondary battery for operation needs to generate a large current that is ten times as high as that of a general consumer lithium secondary battery at a time rate of 20 to 40C, though it is a short time. In order to obtain higher output power, it is necessary to suppress the resistance of the rechargeable lithium battery.
  • a high-power pond for use is required to discharge at a large current of 20 to 40C at a time rate of around 0, although the time is around 0.
  • a high-power pond for use is required to discharge at a large current of 20 to 40C at a time rate of around 0, although the time is around 0.
  • 0007 Cations such as thium compounds, are used as positive electrodes.
  • a possible way to improve the electrons when used as a quality is to include acetyl black or ketchin black as a conductive material in the positive electrode.
  • 009 including positive electrode current collector and positive electrode formed thereon, negative electrode A positive electrode, a negative electrode formed on the positive electrode, a battery disposed between the positive electrode and the negative electrode, and a solvent containing a thiium salt dissolved in the solvent.
  • a positive electrode 7 to 3 a positive electrode 35 to 55, and a concentration of the thiium salt in the range .multidot.2 o to 2 o. In the 001 0 thium ion secondary battery, it is preferable that it is 35 to 50 of the negative electrode.
  • FIG. 12 is a graph showing an example of the characteristics of a thium ion secondary battery.
  • 3 is a graph showing the relationship with the concentration output property of the contained thium salt measured in 2.
  • 3 is a graph showing the relationship between the output characteristics of the positive electrode measured in 2 3.
  • 43 is a graph showing the relationship between the output characteristics of tin black in the positive electrode layer, measured in 4 3.
  • 5 is a graph showing the relationship between the output characteristics of the negative electrode measured at 54.
  • the thium-ion secondary battery of the present invention includes a positive electrode current collector and a positive electrode formed thereon, a negative electrode current collector and a negative electrode formed thereon, and a battery disposed between the positive electrode and the negative electrode. Containing a metal case containing solvent, and a solvent containing thiium salt dissolved in the solvent. It is equipped with. , Positive electrode and. , The positive electrode occupies 7 to 3. It is 35 to 55. As described above, the concentration of the thiium salt in the positive electrode, the concentration of the non-medium thium salt in the positive electrode, and the amount of the agent contained in the positive electrode can be optimized to suppress the addition of the reaction. I can do it. Therefore, a battery having excellent output performance can be obtained.
  • the positive electrode also contains a high concentration of thion ions. Therefore, when the discharge is carried out at, the difference between the content of thiium ion and the content of nearby thiium ion becomes large, and the content of thium ion from the surface to the surface becomes faster.
  • the concentration of thium salt is ⁇ 2 ⁇ ⁇ o.
  • the amount of the 006 agent is 7 to 3, and preferably 7 to 3. If the amount of agent is less than that of positive electrode 7, the output performance is improved. The fruit is obtained. When the amount of the agent is larger than that of the positive electrode 3, the amount of the substance contained in the positive electrode is large, and the amount of thium ion that can reach the positive electrode surface is reduced. Therefore, the output performance is reduced. Included in 01717 are, for example, acetyl black, ketch black, fan black, lap black, zabla, and other bombs, carbon, and metals.
  • the reaction at the negative electrode may be delayed and the battery power may decrease. Therefore, it is preferable to increase the output of the negative electrode by optimizing the negative electrode.
  • the negative electrode is preferably 35 to 50, and more preferably 35 to 45. In the thium-ion secondary battery, it has a negative polarity of 30. As a matter of fact, the negative electrode is larger than the negative electrode in consumer lithium ion secondary batteries. For this reason, the movement of thium ions at the negative electrode is easy, and the thium ions move from the negative electrode to the positive electrode during discharge. Therefore, it is possible to further improve the battery performance.
  • the titanium salt conventionally used in the field can be used.
  • P B etc. can be used.
  • thiium oxide for quality, it is possible to use thiium oxide in the field.
  • Such compounds include, for example, thallium compounds, thimium compounds, and thallium compounds. Above all, thirium oxide is preferred because it is relatively inexpensive.
  • Quality of 7 to 2 is preferred.
  • the quality is 7, the amount of fine powder increases and it becomes difficult to handle the positive electrode quality. If the quality exceeds 20, the reaction product may decrease and the output may decrease. In addition, in the case of high-powered ponds, the design will be thin. this Therefore, the quality of the positive electrode is large and the production yield may be reduced.
  • 002 is, in the field, reversibly sucking and
  • capable materials include metals, carbon materials, compounds and elementary compounds.
  • Examples of the constituent metals include metals capable of forming alloys such as () and (S). Instead of metal, a metal element capable of forming an alloy can be used.
  • Examples of the raw material include various types, shavings, upper, carbon, spherical, various types, and raw materials.
  • Examples of the elementary compound include SO (05 .95), and elemental compounds, compounds and bodies. It should be noted that the gold, the compound, and the S part in the body are replaced by at least one element selected from the group consisting of Bo Co Ca CC eba, W, Z, C, and S. For example,
  • the negative electrode is a body such as S S, an elemental compound, and / or a negative electrode.
  • 002 Quality, 7 to 2 is preferred.
  • the quality reaches 7%, the amount of fine powder increases and it becomes difficult to handle the negative electrode quality. If the quality exceeds 20, the product of the negative electrode quality may decrease and the output performance may decrease. For high-powered ponds, the design will be thin. For this reason, the quality of the negative electrode is large and the production yield may be reduced.
  • 024 it may be composed of only the negative electrode material. Also, it may be included.
  • the body such as S, the element compound, the compound, and the fact that it adheres to the current collector does not contain only the negative electrode material.
  • the negative electrode can be controlled by adjusting the deposition amount, the deposition time, and / or the deposition degree when the negative electrode quality is negotiated on the current collector.
  • the positive electrode and the agent may contain
  • P Bohoffiden
  • P Terafuchi
  • the P positive electrode is 2 to 5 and the P positive electrode is 7 to 7.
  • P and tin butadiene (SBR) can be used as the negative electrode.
  • SBR tin butadiene
  • the negative electrode of P is 5 to 2 and the negative electrode of S R is from 5 to 5.
  • the public materials can be used in the field as the material for the current collector, the negative electrode current collector and the electrode.
  • the solvent contained can be a public solvent in the field.
  • the quality is mixed with an agent for imparting.
  • This mixture can be mixed with a solution of and a dispersion of to obtain a positive electrode. At this time, it is adjusted so that it becomes 45 to 65 of the space.
  • a methices (CC) can be used.
  • the CC of the CC solution can be, for example:
  • the obtained strip is applied to, for example, a positive electrode current collector surface made of an aluminum foil, And then, for example, drying through a furnace adjacent to
  • the positive electrode can be obtained by rolling with a press. Incidentally, at this time, by changing the rolling force, the value of the positive electrode can be adjusted to a predetermined value. It is possible to do so by using the body of the device, for example, the data, the data, etc. , For example, can be done by pressing.
  • As a material for forming the current collector for example, an aluminum foil can be used.
  • 003 for example, can be produced as follows.
  • This soot is processed, for example, on the surface of the negative electrode current collector, and then dried, for example, through a furnace adjacent to, to obtain. By rolling this, a negative electrode can be obtained. Note that, similarly to the above, by changing the force of the negative electrode at this time, it is possible to adjust it to a predetermined value.
  • poles As in the case of poles, one can use methices and that can.
  • the body of the chair for example, a printer, a printer, or the like. However, for example, it can be done by push or the like.
  • the material for forming the pole current collector can be used.
  • 003 and can be determined, for example, by mercury porosimetry.
  • 0032 for example, can be assembled as follows.
  • a set is placed between the positive electrode and the negative electrode obtained as described above to obtain a laminate. Then, get Then, place it in the battery case, and seal the battery case to complete the battery.
  • a case made of aluminium a case made of iron with a plated inner surface, or a case made of aluminium, may be used as the case. It may have a misaligned shape such as a case, cylinder, or square shape.
  • the cross-section of the group is the same as that of the battery case, but the shape of the positive electrode, the negative electrode, etc., in which the shape of the circle is selected, is selected from the materials conventionally used in the field. You can
  • the 003 pond can be evaluated, for example, as follows.
  • the battery is charged to a predetermined value (S a e Of Cage S C).
  • the pond is discharged for 0 for a time rate of C, and the discharge pond is brought to 30 state. This left pond is charged with the same (C) as the discharge. After that, the pond will be suspended for 30 minutes. After completing this condition, the above cycle is also applied at an hourly rate of 2C 5C C 20C 30C and 40C.
  • the quality of the composition is represented by Co
  • the coated powder was applied to the surface of the anode current collector (20) and dried. Then, a positive electrode was obtained by pressing so as to obtain 40 of the positive electrode.
  • the positive electrode had a length of 80 and a length of 2500.
  • the quality, a solution of methices (CC), and thimbulium (SBR) were mixed to obtain a negative electrode s.
  • the negative electrode material C C S R was 00: 0: 5.
  • the obtained 004 was applied to the surface of the current collector (0 is) of and dried.
  • a negative electrode was obtained by pressing so as to obtain 40 of the obtained negative electrode.
  • the size of the negative electrode was 85 and the length was 2650.
  • a pond was prepared using the obtained positive electrode and electrode.
  • a laminate was obtained by arranging a metal between the positive electrode and the negative electrode.
  • Chicabone was prepared by dissolving 6 Ht (P) in the solvent in which Mechicabone was mixed in 2 at each step.
  • the battery was tested and then jigged. Always first
  • the battery was activated by performing initial charge and then activated. The same applies to the other batteries of this embodiment and Embodiments 2 to 4. 004 I turned on the power as shown below. First, the battery was charged at a flow rate of 0.2 C at a battery pressure of 4.2. Then, the battery was discharged at a flow of 0.2C until the battery pressure dropped to 3 *, and then charged at a flow of 0.2C until the battery pressure became 4.2. This cycle was repeated 2 times, and the battery was charged up to 00 C and left in the environment C for 7 hours.
  • Batteries 2 to 4 were produced in the same manner as the batteries, except that the concentration of the thium salt was set to • 2 o, • 8, or 2 ⁇ o.
  • Comparison 2 was prepared in the same manner as the battery, except that the concentration of the thiium salt was set to • O o or 2.2 °.
  • the output performance was evaluated in the above-mentioned ponds of 005 cells and batteries ⁇ 4 and ⁇ 2, and the pond value was calculated. , 3 ⁇ 0.
  • this test was performed at 60 C and 25 C.
  • the reason for conducting the test at 60 OC depends on the control system, but is mainly used in the condition where OC is about 60.
  • the charging current reached a maximum value of 0C, and the charging was performed at 0C above 20C, and by adjusting the charging interval, the same amount of discharged electricity was charged.
  • the output was improved.
  • concentration of thium salt exceeded o, the output was slightly reduced, but sufficient output was maintained.
  • concentration of thium salt exceeds ⁇ , it is considered that the output is slightly decreased because the amount of thion ion is decreased.
  • the output level was significantly lower than that of Battery 2 in which the concentration of thium salt was ⁇ 2 o.
  • the reason for this is that when the thixium content is o, when the battery is discharged with a large current, the battery pressure drops abruptly at 0 after the beginning of discharge, and the property and note are lost. Is considered to be.
  • the thium salt is released from the liquid. Since it is expected to be below 20oC around the pond, it can be used for batteries containing such high concentration of thium salt. It is possible.
  • the concentration of the contained thium salt is 2 o to 2 o.
  • the positive electrode was changed.
  • the quality of the positive electrode current collection battery was the same as that of the battery. 005 (5 to 7)
  • Batteries 5 to 7 were prepared in the same manner as the battery by adjusting the force at the time of extension and adjusting the positive electrode to 350 or 55.
  • Comparisons 3 to 4 were prepared in the same manner as in the case where the positive electrode was adjusted to 30 or 60 by adjusting the elongation force.
  • the value of the 005 pond was determined in the same manner as the implementation. The results are shown in Fig. 3. The result of the battery (of: 40) is also shown in 3.
  • the output is excellent when it is in the range of ⁇ 60 from the positive electrode.
  • (2) is high, it is easy for thium ions to diffuse from the cathode to the positive electrode part, and therefore it is easy for thium ions to be supplied to the positive electrode surface.
  • the black fiber which is, also aggregates to a high density. At this time, the thium-iot contained in this will occur. Therefore, it is considered that the reason why the output power is large when the temperature is above 35 of the positive electrode is that the thium ion is easily scattered from the substance because the temperature is so high.
  • the amount of tin black (B) was changed. Even in the pond, the batteries had the same quality per positive electrode current collection.
  • Batteries 8 to 9 were prepared in the same manner as the battery, except that tin black was used as the positive electrode 7 or 3.
  • Comparisons 5 to 6 were made in the same manner as the battery, except that tin black was used as the positive electrode 6 or 5.
  • the batteries 40 to 9 and 5 to 6 were the positive electrodes.
  • the value of the 006 pond was determined in the same manner as the implementation. The results are shown in Fig. 4. In addition, 4 shows the result of the battery (0 of acetyl black).
  • the output performance is excellent when it is 7 to 3 of acetyl black ().
  • the effect of improving output performance cannot be obtained. There are 3 and many of them. For this reason, the amount of the liquid retained in is large, and the amount of thium ions reaching the positive electrode surface is thought to decrease. Moreover, it is considered that when the temperature is high, it causes the generation of thionium on the positive electrode surface from the material.
  • the deterioration of the negative electrode causes deterioration of the negative electrode quality, and in some cases, there are problems caused by the deterioration of the negative electrode quality. For this reason, it is considered that the output performance decreased when the negative electrode was 55.
  • the negative electrode has a value of 35 to 50.
  • Ketchin Black was used, or when a mixture of Chin Black and Ketchin Black was used, the results similar to those of Examples 1 to 4 were obtained.
  • a thium ion secondary battery with excellent output performance could be obtained by setting the content of thium in the range of -2 o to 2 o and the positive electrode of 35 to 55.
  • the above-mentioned, 006-Am thium-ion secondary battery has excellent output performance, so it can be suitably used, for example, as a power source for electric vehicles and vehicles.

Abstract

Disclosed is a lithium ion secondary battery comprising a electrode plates group including a positive electrode, a negative electrode and a separator arranged between the positive electrode and the negative electrode; a battery case for housing the electrode plates group; and a nonaqueous electrolyte solution containing a lithium salt dissolved in a nonaqueous solvent. The positive electrode comprises a positive electrode mix layer formed on a positive electrode collector, and the positive electrode mix layer contains a positive electrode active material and a conductive agent. The negative electrode comprises a negative electrode active material layer formed on a negative electrode collector. When such a lithium secondary battery is used for an HEV or the like, it is required high output characteristics enabling large current discharge such as an hour rate of 20-40C, though it is for a short time period such as 10 seconds or so. In the lithium secondary battery, 7-13% by weight of the positive electrode mix layer is composed of the conductive agent, the positive electrode mix layer have a porosity of 35-55%, and the concentration of lithium salt contained in the nonaqueous electrolyte solution is from 1.2 mol/L to 2 mol/L. Consequently, the output characteristics of the lithium secondary battery are improved.

Description

明 細 書 Specification
リチウムイオン二次電池 Lithium ion secondary battery
技術分野 Technical field
[0001] 本発明は、リチウムイオン二次電池、特に正極および非水電解液の改良に関する。 [0001] The present invention relates to lithium ion secondary batteries, particularly to improvements in positive electrodes and non-aqueous electrolytes.
背景技術 Background technology
[0002] リチウムイオン二次電池は、エネルギー密度が高いために、民生用、例えば、携帯 電話、パソコンなどの通信 ·情報機器用の電源として広く普及している。さらに、今日 では、リチウムイオン二次電池は、電気自動車、特にハイブリッド電気自動車 (HEV) のモーター駆動用電源としても注目されている。一方で、環境問題およびエネルギ 一問題への意識の高まりから、モーター駆動用リチウムイオン二次電池の早期実用 化が期待されている。 [0002] Due to their high energy density, lithium ion secondary batteries are widely used as power sources for consumer devices, such as mobile phones, personal computers, and other communications and information devices. Furthermore, lithium-ion secondary batteries are now attracting attention as a power source for driving the motors of electric vehicles, especially hybrid electric vehicles (HEVs). On the other hand, with increasing awareness of environmental and energy issues, there are expectations for the early commercialization of lithium-ion secondary batteries for motor drives.
[0003] 例えば、 HEV車両の加速性能、登坂性能および燃費を向上させるために、モータ 一駆動用リチウムイオン二次電池には、高い出力特性が強く要求される。例えば、モ 一ター駆動用リチウムイオン二次電池は、短時間ではあるが、時間率 20〜40Cという 一般的な民生用リチウムイオン二次電池の数十倍の大電流を生じさせる必要がある 。このような高出力特性を得るためには、リチウムイオン二次電池の内部抵抗を小さく 抑える必要がある。 [0003] For example, in order to improve the acceleration performance, hill-climbing performance, and fuel efficiency of HEV vehicles, high output characteristics are strongly required for lithium-ion secondary batteries for driving motors. For example, a lithium ion secondary battery for driving a motor needs to generate a large current at a time rate of 20 to 40C, several tens of times as large as a typical consumer lithium ion secondary battery, albeit for a short time. In order to obtain such high output characteristics, it is necessary to keep the internal resistance of a lithium-ion secondary battery low.
[0004] そこで、例えば、以下のような試みが行われている。 [0004] Therefore, for example, the following attempts have been made.
(1)極板面積を大きくすることによって、極板単位面積あたりの電流密度を小さくし、 電流負荷がかかった時の電圧降下を小さく抑える。 (1) By increasing the electrode plate area, the current density per unit area of the electrode plate is reduced, and the voltage drop when a current load is applied is suppressed.
(2)集電用電極リードの改良、集電リードと正負極板との溶接条件の改良などによつ て、部品抵抗を小さくする。 (2) Reduce component resistance by improving current collecting electrode leads and improving welding conditions between current collecting leads and positive and negative electrode plates.
(3)正極活物質として、ニッケル酸リチウム、コバルト酸リチウムなどのような電子伝導 性の低いリチウム含有複合酸化物を主に用いる場合には、正極合剤層中に、ァセチ レンブラックなどの導電剤をさらに加える。これにより、極板の電子伝導性を高くし、内 部抵抗を低く抑える。 (3) When a lithium-containing composite oxide with low electronic conductivity, such as lithium nickelate or lithium cobaltate, is mainly used as the positive electrode active material, a conductive material such as acetylene black may be added to the positive electrode mixture layer. Add more agent. This increases the electron conductivity of the electrode plate and keeps the internal resistance low.
このような取り組みの結果、現在、 2500W/kg程度の出力特性を示す高出力タイ プのリチウムイオン二次電池が得られてレ、る。 As a result of these efforts, we are currently producing high-output tires with output characteristics of approximately 2500W/kg. A new lithium-ion secondary battery was obtained.
[0005] また、正極合剤層の多孔度が 25%以下である高密度の正極を用いた場合でも、ハ ィレート特性および低温特性が劣化しなレ、非水電解質二次電池を提供するために、 最も高いイオン伝導度を与える濃度よりも高い濃度で溶質を含む非水電解質を用い ることが提案されている（特許文献 1参照）。 [0005] In addition, to provide a non-aqueous electrolyte secondary battery in which the hyrate characteristics and low-temperature characteristics do not deteriorate even when a high-density positive electrode in which the porosity of the positive electrode mixture layer is 25% or less is used. It has been proposed to use a non-aqueous electrolyte containing a solute at a concentration higher than the concentration that gives the highest ionic conductivity (see Patent Document 1).
特許文献 1 :特開 2003— 173821号公報 Patent document 1: Japanese Patent Application Publication No. 2003-173821
発明の開示 Disclosure of invention
発明が解決しょうとする課題 Problems that the invention seeks to solve
[0006] 上記のように、 HEV用のような高出力用途の電池には、 10秒前後の短時間ではあ る力 時間率 20〜40Cという大電流で放電することが要求される。電池の出力特性 を向上させるためには、電池内の電子伝導性を如何に高くするかということ、および 放電反応を維持するために正極活物質表面へのリチウムイオンの供給量を如何に 増加させるかということが重要になる。 [0006] As mentioned above, batteries for high-output applications such as HEVs are required to discharge at a high current with a power-time rate of 20 to 40C for a short time of around 10 seconds. In order to improve the output characteristics of a battery, it is important to determine how to increase the electronic conductivity within the battery, and how to increase the amount of lithium ions supplied to the surface of the positive electrode active material in order to maintain the discharge reaction. That is important.
[0007] ニッケル酸リチウム、コバルト酸リチウムなどのリチウム含有複合酸化物を正極活物 質として使用した場合に、電子伝導性を向上させる方法としては、アセチレンブラック またはケッチェンブラックを導電剤として正極合剤層に含ませることが考えられる。民 生用のリチウムイオン二次電池においては、正極活物質 100重量部あたり 5重量部 程度の導電剤が正極に添加されている。 [0007] When a lithium-containing composite oxide such as lithium nickelate or lithium cobaltate is used as a positive electrode active material, a method for improving electronic conductivity is to use acetylene black or Ketjenblack as a conductive agent to synthesize the positive electrode. It is conceivable to include it in the agent layer. In consumer lithium ion secondary batteries, approximately 5 parts by weight of a conductive agent is added to the positive electrode per 100 parts by weight of the positive electrode active material.
[0008] 出力特性を向上させるために、アセチレンブラック、ケッチェンブラックなどの導電 剤を、民生用電池の場合と比べて多く添カ卩し、極板の電子伝導性を高めることが考 えられる。し力 ながら、単に導電剤の含有量を増加しただけでは、導電剤の比較的 高密度の凝集物が極板内に形成され、その凝集物に非水電解液が吸収および保持 されてしまう。本発明者らの検討から、このような高密度の凝集物に保持された非水 電解液中のリチウムイオンは、正極活物質近傍へ拡散するのに時間を要し、その結 果、放電反応において、正極活物質へ移動するリチウムイオンの量が不足し、出力 特性が低下することがわかった。 [0008] In order to improve the output characteristics, it may be possible to add more conductive agents such as acetylene black or Ketjen black than in the case of consumer batteries to increase the electronic conductivity of the electrode plates. . However, if the content of the conductive agent is simply increased, relatively high-density aggregates of the conductive agent will be formed within the electrode plate, and the nonaqueous electrolyte will be absorbed and retained in the aggregates. The inventors have found that lithium ions in the non-aqueous electrolyte held in such high-density aggregates take time to diffuse into the vicinity of the positive electrode active material, and as a result, the discharge reaction slows down. It was found that the amount of lithium ions moving to the positive electrode active material was insufficient, resulting in a decrease in output characteristics.
課題を解決するための手段 Means to solve problems
[0009] 本発明は、正極集電体およびその上に形成された正極合剤層を含む正極と、負極 集電体およびその上に形成された負極活物質層を含む負極と、正極と負極の間に 配置されたセパレータとを備える極板群、極板群を収容する電池ケース、ならびに非 水溶媒とその非水溶媒に溶解されたリチウム塩を含む非水電解液を具備し、正極合 剤層は正極活物質および導電剤を含み、導電剤は正極合剤層の 7重量％〜： 13重 量％を占め、正極合剤層の多孔度は 35%〜55%であり、非水電解液におけるリチ ゥム塩の濃度は 1. 2mol/L〜2mol/Lであるリチウムイオン二次電池に関する。 [0009] The present invention provides a positive electrode including a positive electrode current collector and a positive electrode mixture layer formed thereon, and a negative electrode. An electrode plate group comprising a negative electrode including a current collector and a negative electrode active material layer formed thereon, and a separator disposed between the positive electrode and the negative electrode, a battery case housing the electrode plate group, and a non-aqueous solvent. The positive electrode mixture layer includes a non-aqueous electrolyte containing a lithium salt dissolved in the non-aqueous solvent, and the positive electrode mixture layer contains a positive electrode active material and a conductive agent, and the conductive agent accounts for 7% by weight of the positive electrode mixture layer to 13% by weight. %, the porosity of the positive electrode mixture layer is 35% to 55%, and the concentration of lithium salt in the nonaqueous electrolyte is 1.2 mol/L to 2 mol/L.
[0010] 上記リチウムイオン二次電池において、負極活物質層の多孔度は 35%〜50%で あることが好ましい。 [0010] In the above lithium ion secondary battery, the porosity of the negative electrode active material layer is preferably 35% to 50%.
発明の効果 Effect of the invention
[0011] 本発明においては、正極合剤層に含まれる導電剤の量、正極合剤層の多孔度、お よび非水電解液に含まれるリチウム塩の濃度を調節してレ、るので、高負荷で放電し た場合でも、電圧降下を抑えることができる。このため、出力特性に優れたリチウムィ オン二次電池を供給することが可能となる。 [0011] In the present invention, the amount of conductive agent contained in the positive electrode mixture layer, the porosity of the positive electrode mixture layer, and the concentration of lithium salt contained in the nonaqueous electrolyte are adjusted. Even when discharging under high load, the voltage drop can be suppressed. This makes it possible to supply lithium-ion secondary batteries with excellent output characteristics.
図面の簡単な説明 Brief description of the drawing
[0012] [図 1]リチウムイオン二次電池の電流一電圧特性の一例を示すグラフである。 [0012] [FIG. 1] A graph showing an example of current-voltage characteristics of a lithium ion secondary battery.
[図 2]実施例 1で測定した、非水電解液に含まれるリチウム塩の濃度と出力特性との 関係を示すグラフである。 [Figure 2] A graph showing the relationship between the concentration of lithium salt contained in the non-aqueous electrolyte and the output characteristics measured in Example 1.
[図 3]実施例 2で測定した、正極合剤層の多孔度と出力特性との関係を示すグラフあ る。 [Figure 3] There is a graph showing the relationship between the porosity of the positive electrode mixture layer and the output characteristics measured in Example 2.
[図 4]実施例 3で測定した、正極合剤層へのアセチレンブラックの添加量と出力特性 との関係を示すグラフである。 [FIG. 4] A graph showing the relationship between the amount of acetylene black added to the positive electrode mixture layer and the output characteristics measured in Example 3.
[図 5]実施例 4で測定した、負極活物質層の多孔度と出力特性との関係を示すグラフ である。 [FIG. 5] A graph showing the relationship between the porosity of the negative electrode active material layer and the output characteristics measured in Example 4.
発明を実施するための最良の形態 BEST MODE FOR CARRYING OUT THE INVENTION
[0013] 本発明のリチウムイオン二次電池は、正極集電体およびその上に形成された正極 合剤層を含む正極と、負極集電体およびその上に形成された負極活物質層を含む 負極と、正極と負極との間に配置されたセパレータとを備える極板群、極板群を収容 する金属製ケース、ならびに非水溶媒と非水溶媒に溶解されたリチウム塩を含む非 水電解液を具備する。正極合剤層は、正極活物質および導電剤を含む。導電剤は、 正極合剤層の 7重量％〜： 13重量％を占める。正極合剤層の多孔度は、 35%〜55 %である。非水電解液におけるリチウム塩の濃度は、 1. 2mol/L〜2mol/Lである 上記のように、正極合剤層の多孔度、非水電解液中のリチウム塩の濃度、および正 極合剤層に含まれる導電剤の量を最適化することにより、反応抵抗の増加を抑制す ること力 Sできる。このため、出力特性に優れた電池を得ることができる。 [0013] The lithium ion secondary battery of the present invention includes a positive electrode including a positive electrode current collector and a positive electrode mixture layer formed thereon, and a negative electrode current collector and a negative electrode active material layer formed thereon. An electrode plate group comprising a negative electrode and a separator disposed between the positive electrode and the negative electrode, a metal case housing the electrode plate group, and a non-aqueous solvent containing a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent. A water electrolyte is provided. The positive electrode mixture layer contains a positive electrode active material and a conductive agent. The conductive agent accounts for 7% to 13% by weight of the positive electrode mixture layer. The porosity of the positive electrode mixture layer is 35% to 55%. The concentration of lithium salt in the non-aqueous electrolyte is 1.2 mol/L to 2 mol/L. As mentioned above, the porosity of the positive electrode mixture layer, the concentration of lithium salt in the non-aqueous electrolyte, and the positive electrode composition By optimizing the amount of conductive agent contained in the agent layer, it is possible to suppress the increase in reaction resistance. Therefore, a battery with excellent output characteristics can be obtained.
[0014] ポータブル機器などの電源として用いられる民生用のリチウムイオン二次電池では 、正極合剤層の多孔度は、約 25%である。一方、本発明においては、正極合剤層の 多孔度を 35%〜55%と高くしている。これにより、正極活物質表面近傍へ、リチウム イオンが移動しやすくなる。また、正極合剤層の多孔度を上記範囲にする場合、正極 を作製するときに、極板を圧延するときの圧力を高くする必要がない。このため、導電 剤の凝集物の密度を低くすることができる。よって、凝集物に含まれるリチウムイオン 力 正極活物質表面近傍に移動しやすくなる。正極合剤層の多孔度は、 35〜45% であることが好ましい。 [0014] In consumer lithium ion secondary batteries used as power sources for portable devices, the porosity of the positive electrode mixture layer is approximately 25%. On the other hand, in the present invention, the porosity of the positive electrode mixture layer is set to be as high as 35% to 55%. This facilitates the movement of lithium ions to the vicinity of the surface of the positive electrode active material. Furthermore, when the porosity of the positive electrode mixture layer is within the above range, there is no need to increase the pressure when rolling the electrode plate when producing the positive electrode. Therefore, the density of the conductive agent aggregates can be lowered. Therefore, the lithium ions contained in the aggregates tend to move near the surface of the positive electrode active material. The porosity of the positive electrode mixture layer is preferably 35 to 45%.
[0015] 非水電解液に含まれるリチウム塩の濃度は、 1. 2〜2mol/Lと通常のリチウム塩の 濃度よりも高い。例えば、時間率 20C〜40Cという高い電流値で放電を行った場合、 正極活物質表面付近のリチウムイオン濃度は、急速に低下する。非水電解液中のリ チウム塩の濃度を 1. 2mol/L〜2mol/Lとすることにより、正極活物質表面近傍の リチウムイオン濃度を高くすることができる。 [0015] The concentration of lithium salt contained in the nonaqueous electrolyte is 1.2 to 2 mol/L, which is higher than the concentration of normal lithium salt. For example, when discharging is performed at a high current value of 20C to 40C, the lithium ion concentration near the surface of the positive electrode active material rapidly decreases. By setting the concentration of lithium salt in the nonaqueous electrolyte to 1.2 mol/L to 2 mol/L, the lithium ion concentration near the surface of the positive electrode active material can be increased.
さらには、リチウム塩の濃度が高い非水電解液を用いることにより、正極合剤層の導 電剤の凝集物にも、高濃度のリチウムイオンを含む非水電解液が含まれることになる Furthermore, by using a non-aqueous electrolyte with a high concentration of lithium salt, the aggregates of the conductive agent in the positive electrode mixture layer will also contain the non-aqueous electrolyte containing a high concentration of lithium ions.
。よって、高い電流値で放電を行った場合、凝集物に含有されているリチウムイオン 濃度と活物質表面付近のリチウムイオン濃度との差が大きくなり、凝集物から活物質 表面へのリチウムイオンの拡散速度が速くなる。 . Therefore, when discharging at a high current value, the difference between the lithium ion concentration contained in the aggregates and the lithium ion concentration near the active material surface becomes large, and the lithium ions diffuse from the aggregates to the active material surface. speed increases.
なお、リチウム塩の濃度は、 1. 2〜： 1. 75mol/Lであることが好ましい。 Note that the concentration of the lithium salt is preferably 1.2 to 1.75 mol/L.
[0016] 導電剤の量は、正極合剤層の 7〜： 13重量％であり、 7〜： 11重量％であることが好ま しい。導電剤の量が、正極合剤層の 7重量％より少なくなると、出力特性を向上させる 効果が得られにくくなる。導電剤の量が、正極合剤層の 13重量％より大きくなると、 正極合剤層に含まれる導電剤の凝集物の量が多くなり、正極活物質表面に到達す ることができるリチウムイオンの量が減少する。このため、出力特性が低下する。 [0016] The amount of the conductive agent is 7 to 13% by weight, preferably 7 to 11% by weight of the positive electrode mixture layer. When the amount of conductive agent is less than 7% by weight of the positive electrode mixture layer, the output characteristics are improved. It becomes difficult to obtain an effect. When the amount of the conductive agent exceeds 13% by weight of the positive electrode mixture layer, the amount of conductive agent aggregates contained in the positive electrode mixture layer increases, and the number of lithium ions that can reach the surface of the positive electrode active material increases. quantity decreases. Therefore, the output characteristics deteriorate.
[0017] 正極合剤層に含まれる導電剤としては、例えば、黒鉛類、アセチレンブラック、ケッ チェンブラック、ファーネスブラック、ランプブラック、サーマルブラック等のカーボンブ ラック類、炭素繊維、および金属繊維が用いることができる。 [0017] As the conductive agent contained in the positive electrode mixture layer, for example, graphites, carbon blacks such as acetylene black, Ketjen black, furnace black, lamp black, and thermal black, carbon fibers, and metal fibers can be used. Can be done.
[0018] また、正極が高出力化されている一方で、負極が高出力化されていない場合には 、負極における充放電反応が律速段階となって、電池の出力が低下することがある。 よって、負極活物質層の多孔度を最適化することによって、負極を高出力化すること が好ましい。 [0018] Furthermore, if the output of the positive electrode is increased while the output of the negative electrode is not increased, the charge/discharge reaction at the negative electrode may become the rate-determining step, resulting in a decrease in the output of the battery. Therefore, it is preferable to increase the output of the negative electrode by optimizing the porosity of the negative electrode active material layer.
本発明において、負極活物質層の多孔度は、 35〜50%とすることが好ましぐ 35 〜45%であることがさらに好ましい。民生用のリチウムイオン二次電池において、負 極活物質層の多孔度は約 30%である。本発明では、負極活物質層の多孔度を、民 生用リチウムイオン二次電池における負極活物質層の多孔度よりも大きくしている。こ のため、負極活物質層内でのリチウムイオンの移動が容易となり、放電反応中におい て、リチウムイオンが負極から正極へ移動しやくなる。よって、電池の出力特性をさら に向上することが可能となる。 In the present invention, the porosity of the negative electrode active material layer is preferably 35 to 50%, more preferably 35 to 45%. In consumer lithium-ion secondary batteries, the porosity of the negative electrode active material layer is approximately 30%. In the present invention, the porosity of the negative electrode active material layer is made larger than the porosity of the negative electrode active material layer in consumer lithium ion secondary batteries. Therefore, the movement of lithium ions within the negative electrode active material layer becomes easy, and during the discharge reaction, the lithium ions easily move from the negative electrode to the positive electrode. Therefore, it becomes possible to further improve the output characteristics of the battery.
[0019] 非水電解液に含まれるリチウム塩としては、当該分野で従来から用いられているリ チウム塩を用いることができる。そのようなリチウム塩としては、 LiPF、 LiBFなどを用 [0019] As the lithium salt contained in the non-aqueous electrolyte, lithium salts conventionally used in the field can be used. LiPF, LiBF, etc. are used as such lithium salts.
6 4 レ、ることができる。 6 4 les, can.
[0020] 正極活物質としては、当該分野で公知の、リチウム含有複合酸化物を用いることが できる。このような複合酸化物としては、例えば、リチウムニッケル複合酸化物、リチウ ムコバルト複合酸化物、およびリチウムマンガン複合酸化物が挙げられる。中でも、 比較的安価であるため、 Niを含むリチウム複合酸化物が好ましい。 [0020] As the positive electrode active material, a lithium-containing composite oxide known in the art can be used. Examples of such composite oxides include lithium-nickel composite oxide, lithium-cobalt composite oxide, and lithium-manganese composite oxide. Among these, lithium composite oxide containing Ni is preferred because it is relatively inexpensive.
正極活物質の平均粒子径は、 7 ！〜 20 z mであることが好ましい。正極活物質 の平均粒子径が 7 z m未満になると、微粉の量が増加し、正極活物質の取り扱いが 困難となる。正極活物質の平均粒子径が 20 z mを超えると、反応面積が減少し出力 特性が低下することがある。また、高出力用途の電池では極板を薄く設計する。この ため、正極活物質の平均粒子径が大きいと、製造歩留まりが低下することがある。 The average particle diameter of the positive electrode active material is 7! ~20 zm is preferred. When the average particle diameter of the positive electrode active material is less than 7 zm, the amount of fine powder increases, making it difficult to handle the positive electrode active material. If the average particle diameter of the positive electrode active material exceeds 20 zm, the reaction area may decrease and the output characteristics may deteriorate. In addition, batteries for high-power applications are designed with thin plates. this Therefore, if the average particle diameter of the positive electrode active material is large, the manufacturing yield may decrease.
[0021] 負極活物質としては、当該分野で公知の、リチウムを可逆的に吸蔵および放出可 能な材料を用いることができる。このような材料としては、例えば、金属繊維、炭素材 料、錫化合物、珪素化合物等が挙げられる。金属繊維を構成する金属としては、例 えば、珪素（Si)、錫（Sn)などのような Liと合金を形成することが可能な金属が挙げら れる。なお、金属繊維の代わりに、 Liと合金を形成することが可能な金属粒子を用い ることちでさる。 [0021] As the negative electrode active material, materials known in the art that are capable of reversibly intercalating and deintercalating lithium can be used. Examples of such materials include metal fibers, carbon materials, tin compounds, and silicon compounds. Examples of the metal constituting the metal fiber include metals that can form an alloy with Li, such as silicon (Si) and tin (Sn). Note that metal particles that can form an alloy with Li can be used instead of metal fibers.
炭素材料としては、例えば、各種天然黒鉛、コータス、黒鉛化途上炭素、炭素繊維 、球状炭素、各種人造黒鉛、および非晶質炭素が挙げられる。 Examples of carbon materials include various natural graphites, cortus, under-graphitized carbon, carbon fibers, spherical carbon, various artificial graphites, and amorphous carbon.
珪素化合物としては、例えば、 SiO (0. 05 < χ< 1. 95)、ならびに珪素を含む合 金、化合物および固溶体が挙げられる。なお、前記合金、化合物および固溶体にお レヽて、 Siのー咅力 B、 Mg、 Ni、 Ti、 Mo、 Co、 Ca、 Cr、 Cu、 Fe、 Mn、 Nb、 Ta、 V、 W、 Zn、 C、 N、および Snからなる群から選択される少なくとも 1種の元素で置換され ていてもよい。 Examples of silicon compounds include SiO (0.05<χ<1.95), and alloys, compounds, and solid solutions containing silicon. In addition, regarding the alloys, compounds and solid solutions mentioned above, the force of Si is B, Mg, Ni, Ti, Mo, Co, Ca, Cr, Cu, Fe, Mn, Nb, Ta, V, W, Zn, It may be substituted with at least one element selected from the group consisting of C, N, and Sn.
錫ィ匕合物としては、 ί列えば、 Ni Sn、 Mg Sn、 SnO (0 < y< 2)、 SnO、および Sn Examples of tin compounds include Ni Sn, Mg Sn, SnO (0 < y< 2), SnO, and Sn.
2 4 2 y 2 2 4 2 y 2
SiOが挙げられる。 An example is SiO.
3 3
なお、上記以外にも、リチウムを可逆的に吸蔵および放出可能な酸化物、窒化物、 各種合金材料等を負極活物質として用いることができる。 In addition to the above, oxides, nitrides, various alloy materials, etc. that can reversibly insert and release lithium can be used as the negative electrode active material.
これらの材料は、単独で用いてもよいし、 2種以上を組み合わせて用いてもよい。 These materials may be used alone or in combination of two or more.
[0022] 上記のうちでも、容量密度が高いことから、負極活物質としては、 Si、 Snなどの単体[0022] Among the above, simple substances such as Si and Sn are recommended as negative electrode active materials because of their high capacity density.
、珪素化合物、および/または錫化合物を負極活物質として用いることが好ましい。 , a silicon compound, and/or a tin compound are preferably used as the negative electrode active material.
[0023] 負極活物質の平均粒子径は、 7 μ m〜20 μ mであることが好ましレ、。負極活物質 の平均粒子径が 7 z m未満になると、微粉の量が増加し、負極活物質の取り扱いが 困難となる。負極活物質の平均粒子径が 20 z mを超えると、負極活物質の反応面積 が減少し、出力特性が低下することがある。また、高出力用途の電池では、極板を薄 く設計する。このため、負極活物質の平均粒子径が大きいと、製造歩留まりが低下す ること力 sある。 [0023] The average particle diameter of the negative electrode active material is preferably 7 μm to 20 μm. When the average particle size of the negative electrode active material is less than 7 zm, the amount of fine powder increases, making it difficult to handle the negative electrode active material. When the average particle diameter of the negative electrode active material exceeds 20 zm, the reaction area of the negative electrode active material decreases, and the output characteristics may deteriorate. In addition, batteries for high-power applications are designed with thin plates. Therefore, if the average particle size of the negative electrode active material is large, the manufacturing yield may be reduced.
[0024] 負極活物質層は、負極活物質のみから構成されていてもよいし、負極活物質の他 に、導電剤、結着剤等を含んでいてもよい。 [0024] The negative electrode active material layer may be composed only of the negative electrode active material, or may be composed of other negative electrode active materials. In addition, a conductive agent, a binder, etc. may be included.
例えば、上記のような、 Si、 Snなどの単体、珪素化合物、錫化合物等を、集電体上 に蒸着させることにより、負極活物質のみからなり、導電剤、結着剤等を含まない活 物質層を形成することができる。この場合、負極活物質層の多孔度は、集電体上に 負極活物質を条約する際の蒸着エネルギー、蒸着時間、および Zまたは蒸着速度 を調整することにより、制卸すること力 Sできる。 For example, by vapor-depositing elements such as Si, Sn, silicon compounds, tin compounds, etc. on a current collector, an active material consisting only of negative electrode active materials and containing no conductive agent, binder, etc. can be obtained. A material layer can be formed. In this case, the porosity of the negative electrode active material layer can be controlled by adjusting the deposition energy, deposition time, and deposition rate when depositing the negative electrode active material on the current collector.
[0025] 正極合剤層は、正極活物質および導電剤の他に、結着剤を含んでいてもよい。正 極合剤層に含まれる結着剤としては、例えば、ポリフッ化ビニリデン (PVDF)および ポリテトラフルォロエチレン (PTFE)を用いることができる。結着性、電池容量および 出力特性の観点から、 PVDFの添力卩量は正極合剤層の 2〜5重量％であることが好 ましぐ PTFEの添力卩量は正極合剤層の 1〜7重量％であることが好ましい。 [0025] The positive electrode mixture layer may contain a binder in addition to the positive electrode active material and the conductive agent. As the binder contained in the positive electrode mixture layer, for example, polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE) can be used. From the viewpoint of binding properties, battery capacity, and output characteristics, it is preferable that the amount of PVDF added is 2 to 5% by weight of the positive electrode mixture layer.The amount of added volume of PTFE is preferably 1% by weight of the positive electrode mixture layer. Preferably it is ~7% by weight.
[0026] 負極活物質層が結着剤を含む場合、負極活物質層に含まれる結着剤としては、例 えば、 PVDFおよびスチレン一ブタジエンゴム（SBR)を用いることができる。結着性、 電池容量および出力特性の観点から、 PVDFの添加量は負極活物質層の 5〜： 12重 量％であることが好ましぐ SBRの添加量は負極活物質層の 1〜5重量％であること が好ましい。 [0026] When the negative electrode active material layer contains a binder, for example, PVDF and styrene-butadiene rubber (SBR) can be used as the binder contained in the negative electrode active material layer. From the viewpoint of binding properties, battery capacity and output characteristics, it is preferable that the amount of PVDF added is 5 to 12% by weight of the negative electrode active material layer, and the amount of SBR added is 1 to 5% by weight of the negative electrode active material layer. Preferably, it is % by weight.
[0027] 正極集電体、負極集電体およびセパレータを構成する材料には、当該分野で公知 の材料を用いることができる。非水電解液に含まれる非水溶媒には、当該分野で公 知の材料を用いることができる。 [0027] Materials known in the art can be used for the materials constituting the positive electrode current collector, negative electrode current collector, and separator. Materials known in the art can be used as the nonaqueous solvent contained in the nonaqueous electrolyte.
[0028] 以下、本発明のリチウムイオン二次電池の作製方法について説明する。 [0028] Hereinafter, a method for manufacturing a lithium ion secondary battery of the present invention will be explained.
正極は、例えば、以下のようにして作製することができる。 The positive electrode can be produced, for example, as follows.
正極活物質を、導電性を付与するための導電剤などと混合する。この混合物を、増 粘剤の水溶液と、結着剤の水分散液とともに混合して、正極合剤層形成用ペースト を得ることができる。このとき、ペーストの固形分率は、 45重量％〜65重量％になる ように調整される。ペーストの固形分には、正極活物質、導電剤、結着剤等が含まれ る。増粘剤としては、例えば、カルボキシメチルセルロース（CMC)を用いることがで きる。 CMC水溶液における CMCの濃度は、例えば、 1重量％とすることができる。 The positive electrode active material is mixed with a conductive agent for imparting conductivity. This mixture can be mixed with an aqueous solution of a thickener and an aqueous dispersion of a binder to obtain a paste for forming a positive electrode mixture layer. At this time, the solid content of the paste is adjusted to 45% to 65% by weight. The solid content of the paste includes the positive electrode active material, conductive agent, binder, etc. As the thickener, for example, carboxymethyl cellulose (CMC) can be used. The concentration of CMC in the CMC aqueous solution can be, for example, 1% by weight.
[0029] 次に、得られたペーストを、例えば、アルミニウム箔からなる正極集電体の両面に、 塗工し、次いで、例えば、塗工機に隣接されている乾燥炉の中を通して乾燥して、極 板を得る。この極板を、例えば、ロールプレスによって、圧延することにより、正極を得 ること力 Sできる。なお、この圧延工程において、圧延の圧力を変化させることにより、 正極合剤層の多孔度を所定の値に調整することができる。ペーストの集電体への塗 ェは、例えば、ダイコーター、コンマコーターなどを用いて行うことができる。極板の圧 延は、例えば、ロールプレス等により行うことができる。正極集電体を構成する材料と しては、例えば、アルミニウム箔を用いることができる。 [0029] Next, the obtained paste is applied to both sides of a positive electrode current collector made of aluminum foil, for example. The electrode plate is obtained by coating and then drying, for example through a drying oven adjacent to the coating machine. By rolling this electrode plate using, for example, a roll press, a positive electrode can be obtained. In addition, in this rolling process, the porosity of the positive electrode mixture layer can be adjusted to a predetermined value by changing the rolling pressure. The paste can be applied to the current collector using, for example, a die coater, a comma coater, or the like. The electrode plate can be rolled by, for example, a roll press. As a material constituting the positive electrode current collector, for example, aluminum foil can be used.
[0030] 負極は、例えば、以下のようにして作製することができる。 [0030] The negative electrode can be produced, for example, as follows.
負極活物質と、増粘剤の水溶液と、結着剤とを混合して、負極活物質層形成用ぺ 一ストを得ることができる。このペーストを、例えば、負極集電体の両面に塗工し、次 いで、例えば、塗工機に隣接されている乾燥炉の中を通して乾燥して、極板を得る。 この極板を、圧延することにより、負極を得ること力 sできる。なお、上記と同様に、負極 活物質層の多孔度は、この圧延工程における圧延の圧力を変化させることにより、所 定の値に調整することができる。 A paste for forming a negative electrode active material layer can be obtained by mixing a negative electrode active material, an aqueous solution of a thickener, and a binder. This paste is applied, for example, to both sides of a negative electrode current collector, and then dried, for example, through a drying oven adjacent to a coating machine, to obtain an electrode plate. By rolling this electrode plate, a negative electrode can be obtained. Note that, similarly to the above, the porosity of the negative electrode active material layer can be adjusted to a predetermined value by changing the rolling pressure in this rolling step.
正極の場合と同様に、増粘剤には、カルボキシメチルセルロースを用いることができ As in the case of the positive electrode, carboxymethyl cellulose can be used as a thickener.
、その濃度は、 1重量％とすることができる。また、ペーストの集電体への塗工は、例 えば、ダイコーター、コンマコーターなどを用いて行うことができる。極板の圧延は、例 えば、ロールプレス等により行うことができる。負極集電体を構成する材料としては、 例えば、銅箔を用いることができる。 , its concentration can be 1% by weight. Furthermore, the paste can be applied to the current collector using, for example, a die coater, a comma coater, or the like. The electrode plate can be rolled using, for example, a roll press. As a material constituting the negative electrode current collector, for example, copper foil can be used.
[0031] 正極合剤層および負極活物質層の多孔度は、例えば、水銀ポロシメーターによつ て測定することができる。 [0031] The porosity of the positive electrode mixture layer and the negative electrode active material layer can be measured using, for example, a mercury porosimeter.
[0032] 電池は、例えば、以下のようにして組み立てることができる。 [0032] The battery can be assembled, for example, as follows.
上記のようにして得られた正極と負極との間に、セパレータを配置し、積層体を得る 。その積層体を捲回して、極板群を得る。得られた極板群を、電池ケース内に収容し 、非水電解液を注液し、電池ケースを密閉して、電池を完成する。 A separator is placed between the positive electrode and negative electrode obtained as described above to obtain a laminate. The laminate is wound to obtain an electrode plate group. The obtained electrode plate group is housed in a battery case, a nonaqueous electrolyte is injected, and the battery case is sealed to complete the battery.
[0033] 電池ケースとしては、例えば、アルミニウム製のケース、内面がニッケルメツキされた 鉄製のケース、またはアルミニウムラミネートフィルムからなるケースを用いることがで きる。電池ケースの形状は、円筒型、角型など、いずれの形状であってもよい。極板 群の横断面は、電池ケースの形状にあわせて、円形、楕円形等の形状が選択される 正極リード、負極リード等を構成する材料としては、当該分野で従来から用いられて レ、る材料を用いることができる。 [0033] As the battery case, for example, a case made of aluminum, a case made of iron whose inner surface is plated with nickel, or a case made of aluminum laminate film can be used. The shape of the battery case may be any shape, such as cylindrical or square. pole plate The cross section of the group is selected to be circular, elliptical, etc. in accordance with the shape of the battery case. Materials for forming the positive electrode lead, negative electrode lead, etc. are materials conventionally used in the relevant field. can be used.
[0034] 電池の出力特性は、例えば、以下のようにして評価することができる。 [0034] The output characteristics of the battery can be evaluated, for example, as follows.
まず、電池を、所定の充電状態（State of Charge : S〇C)まで充電する。充電後 の電池は、 25°Cで 10時間以上放置する。 First, the battery is charged to a predetermined state of charge (S〇C). After charging, leave the battery at 25°C for at least 10 hours.
[0035] 次いで、その電池を、時間率 1Cの電流値で 10秒間放電し、放電後の電池を、 30 秒間休止状態とする。この後、放置後の電池を、放電時と同じ電流値（1C)で 10秒 間充電する。充電終了後 30秒間、その電池を休止状態とする。この休止状態の終了 後、上記のような充放電サイクルを、時間率 2C、 5C、 10C、 20C、 30Cおよび 40C の電流値においても行う。 [0035] Next, the battery is discharged for 10 seconds at a current value at a time rate of 1C, and the battery after discharge is placed in a resting state for 30 seconds. After this, charge the battery for 10 seconds at the same current value (1C) as when discharging. The battery will be in hibernation mode for 30 seconds after charging is complete. After the end of this rest state, charge and discharge cycles as described above are also carried out at current values at time rates of 2C, 5C, 10C, 20C, 30C and 40C.
[0036] 各電流値で放電が開始されてから 10秒後の電池電圧を測定し、電流 電圧特性（ I V特性）図を作成する。 I V特性図の一例を図 1に示す。ここで、図 1の横軸は、 放電電流の時間率を示す。なお、図 1において、横軸の値は、放電電流であるため、 マイナス表示されている。 [0036] The battery voltage is measured 10 seconds after discharge starts at each current value, and a current-voltage characteristic (IV characteristic) diagram is created. Figure 1 shows an example of the IV characteristic diagram. Here, the horizontal axis in Fig. 1 indicates the time rate of the discharge current. Note that in Figure 1, the value on the horizontal axis is the discharge current, so it is displayed as a negative value.
[0037] 得られた I V特性図を用レ、、任意の電圧 (V)における電流値 (I)を読み取り、その 積 (V X I)を、その電池の出力値とする。 [0037] Using the obtained IV characteristic diagram, read the current value (I) at any voltage (V), and take the product (V x I) as the output value of the battery.
[0038] なお、上記では、放電開始から 10秒後の電圧を測定している力 放電開始から測 定を行うなでの時間は、電池の用途によって変わることがある。 [0038] Note that in the above, the voltage is measured 10 seconds after the start of discharge, and the time from the start of discharge to which the measurement is performed may vary depending on the use of the battery.
実施例 Example
[0039] 《実施例 1》 [0039] 《Example 1》
以下、実施例に基づいて、本発明を具体的に説明する。 Hereinafter, the present invention will be specifically explained based on Examples.
(電池 1) (Battery 1)
(正極の作製） (Preparation of positive electrode)
正極を、上記で説明した方法と同様にして作製した。 A positive electrode was produced in a manner similar to that described above.
正極活物質として、組成式 LiNi Co Al Oで表されるリチウムニッケル複合酸 As a positive electrode active material, lithium nickel composite acid represented by the composition formula LiNi Co Al O
0.8 0.15 0.05 2 0.8 0.15 0.05 2
化物を用いた。導電剤としては、アセチレンブラックを用いた。 正極活物質と導電剤とを、所定の割合で混合した。この混合物を、増粘剤である力 ルポキシメチルセルロース（CMC)の 1重量％水溶液および結着剤であるポリテトラフ ルォロエチレン (PTFE)の水分散液とともに混合して、正極合剤層形成用ペーストを 得た。正極活物質と CMCと PTFEとの重量比は、 100 : 1. 5 : 1. 2とした。また、ァセ チレンブラックは、正極合剤層の 10重量％となるような量で、前記ペーストに含まれ た。 A chemical compound was used. Acetylene black was used as the conductive agent. A positive electrode active material and a conductive agent were mixed at a predetermined ratio. This mixture was mixed with a 1% by weight aqueous solution of polypoxymethylcellulose (CMC) as a thickener and an aqueous dispersion of polytetrafluoroethylene (PTFE) as a binder to obtain a paste for forming the positive electrode mixture layer. Ta. The weight ratio of the positive electrode active material, CMC, and PTFE was 100:1.5:1.2. Furthermore, acetylene black was included in the paste in an amount that was 10% by weight of the positive electrode mixture layer.
[0040] 得られたペーストを、アルミニウム箔製の正極集電体 (厚さ 20 μ m)の両面に塗布し 、乾燥した。得られた極板を、正極合剤層の多孔度が 40%になるように、ロールプレ スによって圧延して、正極を得た。ここで、正極のサイズは、幅 80mm、長さ 2500m mとした。 [0040] The obtained paste was applied to both sides of a positive electrode current collector (thickness: 20 μm) made of aluminum foil and dried. The obtained electrode plate was rolled using a roll press so that the porosity of the positive electrode mixture layer was 40% to obtain a positive electrode. Here, the size of the positive electrode was 80 mm in width and 2500 mm in length.
[0041] (負極の作製） [0041] (Preparation of negative electrode)
負極も、上記で説明した方法と同様にして作製した。 The negative electrode was also produced in the same manner as described above.
負極活物質として人造黒鉛 (大阪ガス (株)製のメソカーボンマイクロビーズ (MCM B) )を用いた。 Artificial graphite (mesocarbon microbeads (MCM B) manufactured by Osaka Gas Co., Ltd.) was used as the negative electrode active material.
負極活物質と、カルボキシメチルセルロース（CMC)の 1重量％水溶液と、結着剤 であるスチレンブタジエンゴム（SBR)とを混合して、負極活物質層形成用ペーストを 得た。ここで、負極活物質と CMCと SBRとの重量比は、 100 : 1. 0 : 1. 5とした。 A paste for forming a negative electrode active material layer was obtained by mixing the negative electrode active material, a 1% by weight aqueous solution of carboxymethyl cellulose (CMC), and styrene butadiene rubber (SBR) as a binder. Here, the weight ratio of the negative electrode active material, CMC, and SBR was set to 100:1.0:1.5.
[0042] 得られたペーストを、銅箔製の負極集電体 (厚さ 10 μ ΐη)の両面に塗布し、乾燥し た。その後、得られた極板を、負極活物質層の多孔度が 40%になるように、ロールプ レスによって圧延して、負極を得た。ここで、負極のサイズは、幅 85mm、長さ 2650 mmとしに。 [0042] The obtained paste was applied to both sides of a copper foil negative electrode current collector (thickness: 10 μΐη) and dried. Thereafter, the obtained electrode plate was rolled using a roll press so that the porosity of the negative electrode active material layer was 40% to obtain a negative electrode. Here, the size of the negative electrode is 85 mm in width and 2650 mm in length.
[0043] 次いで、得られた正極および負極を用いて、角型電池を作製した。 [0043] Next, a square battery was produced using the obtained positive electrode and negative electrode.
まず、正極と負極との間にセパレータを配置して、積層体を得た。得られた積層体 を捲回して、極板群を得た。正極と負極には、それぞれアルミニウム製の正極リード およびニッケル製の負極リードの一端を溶接しておいた。 First, a separator was placed between a positive electrode and a negative electrode to obtain a laminate. The obtained laminate was wound to obtain an electrode plate group. One end of an aluminum positive electrode lead and a nickel negative electrode lead were welded to the positive and negative electrodes, respectively.
この極板群を、その上部にポリエチレン樹脂製の絶縁体を装着して、アルミニウム 製の角形電池ケース（92mm X 95mm X 15mm)に揷入した。正極リードの他端は、 アルミニウム製封口板にスポット溶接した。負極リードの他端は、封口板の中心部に あるニッケノレ製負極端子の下部にスポット溶接した。なお、負極端子と封口板は、絶 縁されている。 This group of electrode plates was placed in a rectangular aluminum battery case (92 mm x 95 mm x 15 mm) with a polyethylene resin insulator attached to the top. The other end of the positive electrode lead was spot welded to an aluminum sealing plate. Place the other end of the negative electrode lead in the center of the sealing plate. Spot welded to the bottom of a negative electrode terminal made by Nikkenore. Note that the negative electrode terminal and the sealing plate are insulated.
[0044] 電池ケースの開口端部と封口板の周縁部とをレーザー溶接してから、封口板に設 けてある注入口から所定量の非水電解液を注液した。最後に注入口をアルミニウム 製の封栓で塞ぎ、レーザー溶接で密封して、電池 1を完成させた。電池 1の容量は約 5 Ahであった。 [0044] After laser welding the open end of the battery case and the peripheral edge of the sealing plate, a predetermined amount of non-aqueous electrolyte was injected from the injection port provided in the sealing plate. Finally, the injection port was plugged with an aluminum stopper and sealed using laser welding to complete Battery 1. The capacity of battery 1 was approximately 5 Ah.
[0045] 非水電解液は、エチレンカーボネートとジメチルカーボネートを 2 : 8の体積比で混 合した非水溶媒に、 6フッ化リン酸リチウム (LiPF )を、 1. 5molZLの濃度で溶解す [0045] The non-aqueous electrolyte is prepared by dissolving lithium hexafluorophosphate (LiPF) at a concentration of 1.5 molZL in a non-aqueous solvent that is a mixture of ethylene carbonate and dimethyl carbonate at a volume ratio of 2:8.
6 6
ることにより調製した。 It was prepared by
セパレータには、ポリプロピレン層とポリエチレン層とからなる 2層多孔質フィルム（ 厚さ 25 x m)を用いた。 A two-layer porous film (thickness: 25 x m) consisting of a polypropylene layer and a polyethylene layer was used as the separator.
[0046] 得られた電池 1につレ、て、初期充放電およびエージングを行った。通常、初期充放 電は電池を活性化させることを目的として行われる。本実施例では、電池 1について 、初期充放電を行うことにより活性化させ、活性化させた状態でエージング処理を行 つた。なお、このことは、本実施例の他の電池、および実施例 2〜4でも同様である。 [0046] One of the obtained batteries was subjected to initial charging/discharging and aging. Normally, initial charging and discharging is performed for the purpose of activating the battery. In this example, Battery 1 was activated by performing initial charging and discharging, and aging treatment was performed in the activated state. Note that this also applies to the other batteries of this example and Examples 2 to 4.
[0047] 初期充放電を以下のようにして行った。まず、電池 1を、時間率 0. 2Cの定電流で、 電池電圧が 4. 2Vになるなで充電した。その後、電池 1を、 0. 2Cの定電流で、電池 電圧が 3. 0Vに低下するまで放電し、次いで、 0. 2Cの定電流で、電池電圧が 4. 2 Vになるまで充電する充放電サイクルに供した。この充放電サイクルを 2回繰り返した [0047] Initial charging and discharging was performed as follows. First, battery 1 was charged with a constant current at a time rate of 0.2C until the battery voltage reached 4.2V. After that, battery 1 was discharged at a constant current of 0.2C until the battery voltage dropped to 3.0V, and then charged at a constant current of 0.2C until the battery voltage reached 4.2V. It was subjected to a discharge cycle. This charge/discharge cycle was repeated twice.
[0048] エージングは、上記初期充放電を行った電池 1を、 100%の SOCとなるまで充電し[0048] Aging is performed by charging Battery 1, which has undergone the initial charging and discharging described above, until it reaches 100% SOC.
、その充電後の電池を、環境温度 60°Cで 7日間放置することにより行った。 After charging, the battery was left at an environmental temperature of 60°C for 7 days.
[0049] (電池 2〜4) [0049] (Battery 2-4)
非水電解液のリチウム塩の濃度を、 1. 2mol/L、 1. 8molZL、または 2. Omol/ Lとしたこと以外は、電池 1と同様にして、電池 2〜4を作製した。 Batteries 2 to 4 were produced in the same manner as Battery 1, except that the concentration of lithium salt in the nonaqueous electrolyte was 1.2 mol/L, 1.8 molZL, or 2.0 mol/L.
[0050] (比較電池:!〜 2) [0050] (Comparison battery:!~2)
非水電解液のリチウム塩の濃度を、 1. Omol/Lまたは 2. 2mol/Lとしたこと以外 は、電池 1と同様にして、比較電池 1〜2を作製した。 [0051] エージング処理後の、電池 1〜4および比較電池 1〜2の各電池について、出力特 性を、上記のようにして評価し、各電池の出力値を算出した。出力算出電圧は、 3. 0 Vとした。ここで、本試験は、 60%の SOCおよび 25°Cの環境温度で行った。 60%の S〇Cで試験を行うのは、制御システムに依存する力 HEV用電池は、 SOCがおよ そ 60%である状態を中心として使用されるからである。 Comparative batteries 1 and 2 were produced in the same manner as battery 1 except that the concentration of lithium salt in the nonaqueous electrolyte was set to 1. Omol/L or 2.2 mol/L. [0051] After the aging treatment, the output characteristics of each battery, Batteries 1 to 4 and Comparative Batteries 1 to 2, were evaluated as described above, and the output value of each battery was calculated. The calculated output voltage was 3.0 V. Here, this test was conducted at 60% SOC and an ambient temperature of 25°C. The reason for testing at 60% S〇C is that HEV batteries are mainly used at a SOC of approximately 60%, which is dependent on the control system.
また、放電下限電圧は 2. 0Vとし、電池電圧が、放電中にこの電圧を下回った場合 は、そこで試験を終了した。 In addition, the discharge lower limit voltage was set at 2.0V, and if the battery voltage fell below this voltage during discharge, the test was terminated at that point.
充電上限電圧は 4. 5Vとした。なお、電流値が 20Cを超えるような高負荷充電では 、分極が大きぐ 10秒間の充電ができない場合がある。そこで、充電電流は 10Cを最 大値とし、 20C以上の電流値での放電後は、 10Cで充電を行レ、、充電時間を調整す ることによって放電電気量と同じ電気量を充電することとした。 The upper limit charging voltage was set to 4.5V. Note that in high-load charging where the current value exceeds 20C, polarization may be so large that charging for 10 seconds may not be possible. Therefore, the maximum charging current is 10C, and after discharging at a current value of 20C or higher, charging is performed at 10C.By adjusting the charging time, it is possible to charge the same amount of electricity as the discharged amount. And so.
また、本出力特性試験において、各電池につき、 5個のセルを試験し、各セルの結 果の平均値を、その電池の出力値とした。 In addition, in this output characteristic test, five cells were tested for each battery, and the average value of the results for each cell was taken as the output value of that battery.
得られた結果を図 2に示す。 The results obtained are shown in Figure 2.
[0052] 図 2に示されるように、非水電解液中に含まれるリチウム塩の濃度が 1. 5mol/L程 度までは、出力特性が向上していた。リチウム塩の濃度が 1. 5mol/Lを超えると、出 力特性がほんのわずか低下していたが、十分な出力特性は維持されていた。なお、 リチウム塩の濃度が 1. 5mol/Lを超えた場合に、出力特性が若干低下するのは、リ チウムイオン伝導性が低下したためであると考えられる。 [0052] As shown in Figure 2, the output characteristics improved up to a concentration of lithium salt contained in the non-aqueous electrolyte of about 1.5 mol/L. When the concentration of lithium salt exceeded 1.5 mol/L, the output characteristics decreased only slightly, but sufficient output characteristics were maintained. Note that when the concentration of lithium salt exceeds 1.5 mol/L, the output characteristics deteriorate slightly, which is thought to be due to a decrease in lithium ion conductivity.
[0053] リチウム塩濃度が 1. Omol/Lである比較電池 1は、リチウム塩の濃度が 1. 2mol/ Lである電池 2と比較して、出力値が大きく低下していた。比較電池 1の出力特性が 大きく低下するのは、リチウム塩濃度が 1. Omol/Lである場合、電池が大電流で放 電されると、放電開始後 10秒後に、電池電圧が急激に低下し、 I一 V特性の直線性 が失われるためであると考えられる。 [0053] Comparative battery 1, in which the lithium salt concentration was 1.0 mol/L, had a significantly lower output value than battery 2, in which the lithium salt concentration was 1.2 mol/L. The reason why the output characteristics of Comparative Battery 1 decreases significantly is that when the lithium salt concentration is 1.0mol/L, when the battery is discharged with a large current, the battery voltage drops rapidly 10 seconds after the start of discharge. This is thought to be due to the loss of linearity of the I-V characteristics.
[0054] リチウム塩の濃度が 2. Omol/Lを超えると、非水電解液へのリチウム塩の溶解が 困難となる。特に、 0°C以下の低温では、リチウム塩が非水電解液から析出すると考 えられる。 HEV用電池の使用温度範囲の下限は一 20°C以下であると予想されるた め、このような高濃度のリチウム塩を含む非水電解液は、 HEV用の電池に使用でき ないと考えられる。 [0054] When the concentration of the lithium salt exceeds 2.0 mol/L, it becomes difficult to dissolve the lithium salt in the non-aqueous electrolyte. In particular, at low temperatures below 0°C, lithium salts are thought to precipitate from the non-aqueous electrolyte. Since the lower limit of the operating temperature range of HEV batteries is expected to be below -20°C, non-aqueous electrolytes containing such high concentrations of lithium salts cannot be used in HEV batteries. It is thought that there is no.
[0055] 以上の結果から、非水電解液に含まれるリチウム塩の濃度は、 1. 2mol/L〜2mo [0055] From the above results, the concentration of lithium salt contained in the non-aqueous electrolyte is 1.2 mol/L to 2 mo
1/Lであることが必要である。 It needs to be 1/L.
[0056] 《実施例 2》 [0056] 《Example 2》
本実施例では、正極合剤層の多孔度を変化させた。なお、本実施例の電池におい て、正極集電体単位面積あたりの正極活物質の担持量は、電池 1と同一とした。 In this example, the porosity of the positive electrode mixture layer was changed. In the battery of this example, the amount of positive electrode active material supported per unit area of the positive electrode current collector was the same as in Battery 1.
[0057] (電池 5〜7) [0057] (Battery 5-7)
圧延時の圧力を調節して、正極合剤層の多孔度を、 35%、 50%または 55%とした こと以外は、電池 1と同様にして、電池 5〜7を作製した。 Batteries 5 to 7 were produced in the same manner as Battery 1, except that the pressure during rolling was adjusted to set the porosity of the positive electrode mixture layer to 35%, 50%, or 55%.
[0058] (比較電池 3〜4) [0058] (Comparative batteries 3 to 4)
圧延時の圧力を調節して、正極合剤層の多孔度を、 30%または 60%としたこと以 外は、電池 1と同様にして、比較電池 3〜4を作製した。 Comparative batteries 3 to 4 were produced in the same manner as battery 1, except that the pressure during rolling was adjusted to set the porosity of the positive electrode mixture layer to 30% or 60%.
[0059] 各電池の出力値を、実施例 1と同様にして求めた。結果を図 3に示す。なお、図 3に は、電池 1 (正極合剤層の多孔度： 40%)の結果も示す。 [0059] The output value of each battery was determined in the same manner as in Example 1. The results are shown in Figure 3. Furthermore, Figure 3 also shows the results for Battery 1 (porosity of positive electrode mixture layer: 40%).
[0060] 図 3から、正極合剤層の多孔度が 35%〜60%の範囲にある場合に、出力特性に 優れていることがわかる。これには 3つの理由が考えられる。 （1)正極合剤層の多孔 度が高いほど、正極合剤層に非水電解液が多量に保持されるため、放電に必要なリ チウムイオンが正極活物質近傍に数多く存在する。 （2)正極合剤層の多孔度が高い と、リチウムイオンがセパレータから正極合剤層内部に拡散しやすくなるため、リチウ ムイオンが正極活物質表面に供給されやすくなる。 （3)正極合剤層の多孔度が 30% 程度のような高密度の正極の場合には、導電剤であるアセチレンブラックも高密度に 凝集する。このとき、この凝集物に含まれたリチウムイオンの拡散が起こりに《なる。 よって、正極合剤層の多孔度が 35%以上である場合に、出力特性が大きく向上する のは、導電剤の凝集物の密度がそれほど高くないために、リチウムイオンが、その凝 集物から拡散しやすいためであると考えられる。 [0060] From FIG. 3, it can be seen that the output characteristics are excellent when the porosity of the positive electrode mixture layer is in the range of 35% to 60%. There are three possible reasons for this. (1) The higher the porosity of the positive electrode mixture layer, the larger the amount of non-aqueous electrolyte retained in the positive electrode mixture layer, and the more lithium ions necessary for discharge are present near the positive electrode active material. (2) If the porosity of the positive electrode mixture layer is high, lithium ions will more easily diffuse from the separator into the inside of the positive electrode mixture layer, making it easier for lithium ions to be supplied to the surface of the positive electrode active material. (3) In the case of a high-density cathode where the porosity of the cathode mixture layer is approximately 30%, the acetylene black, which is a conductive agent, also aggregates at a high density. At this time, diffusion of lithium ions contained in the aggregates occurs. Therefore, when the porosity of the positive electrode mixture layer is 35% or more, the output characteristics are greatly improved because the density of the conductive agent aggregates is not so high, and the lithium ions are separated from the aggregates. This is thought to be because it spreads easily.
[0061] なお、多孔度が 60%である比較電池 4の場合には、正極の強度が弱くなるため、正 極の製造中における活物質の脱落が激しくなると考えられる。このため、実際の生産 において、不良発生率が高くなることが予想される。 [0062] 以上の検討結果から、正極合剤層の多孔度は 35%〜55%の範囲にある必要があ る。 [0061] In the case of Comparative Battery 4 with a porosity of 60%, the strength of the positive electrode is weakened, so it is thought that the active material falls off more frequently during the production of the positive electrode. For this reason, it is expected that the defect rate will increase in actual production. [0062] From the above study results, the porosity of the positive electrode mixture layer needs to be in the range of 35% to 55%.
[0063] 《実施例 3》 [0063] 《Example 3》
本実施例では、導電剤であるアセチレンブラック (AB)の量を変化させた。本実施 例の電池においても、正極集電体単位面積あたりの正極活物質の担持量は、電池 1 と同一とした。 In this example, the amount of acetylene black (AB), which is a conductive agent, was varied. In the battery of this example as well, the amount of positive electrode active material supported per unit area of the positive electrode current collector was the same as in Battery 1.
[0064] (電池 8〜9) [0064] (Battery 8~9)
アセチレンブラックの添カ卩量を、正極合剤層の 7重量％または 13重量％としたこと 以外は、電池 1と同様にして、電池 8〜9を作製した。 Batteries 8 to 9 were produced in the same manner as Battery 1 except that the amount of acetylene black added was 7% or 13% by weight of the positive electrode mixture layer.
[0065] (比較電池 5〜6) [0065] (Comparison batteries 5-6)
アセチレンブラックの添カ卩量を、正極合剤層の 6重量％または 15重量％としたこと 以外は、電池 1と同様にして、比較電池 5〜6を作製した。 Comparative batteries 5 and 6 were produced in the same manner as battery 1 except that the amount of acetylene black added was 6% or 15% by weight of the positive electrode mixture layer.
なお、電池 8〜9および比較電池 5〜6において、正極合剤層の多孔度は、 40%と した。 Note that in Batteries 8 to 9 and Comparative Batteries 5 to 6, the porosity of the positive electrode mixture layer was 40%.
[0066] 各電池の出力値を、実施例 1と同様にして求めた。結果を図 4に示す。なお、図 4に は、電池 1 (アセチレンブラックの添カ卩量： 10重量0 /0)の結果も示す。 [0066] The output value of each battery was determined in the same manner as in Example 1. The results are shown in Figure 4. Furthermore, Figure 4 also shows the results for Battery 1 (amount of acetylene black added: 10 weight 0/0 ).
[0067] 図 4力 、アセチレンブラック (AB)の添カ卩量が 7重量0/。〜 13重量0 /0である場合に、 出力特性に優れていることがわかる。導電剤の添加量が 7重量％より少ないと、出力 特性を向上させる効果が得られなくなる。導電剤の添加量が 13重量％より多いと、導 電剤の凝集物自体の量が多くなる。このため、凝集物に保持される非水電解液の量 も多くなり、正極活物質表面に到達するリチウムイオンの量が減少すると考えられる。 さらに、凝集物の密度が高い場合には、凝集物から正極活物質表面へのリチウムィ オンの拡散が生じに《なると考えられる。 [0067] Figure 4: The amount of acetylene black (AB) added is 7 % by weight. ~13It can be seen that the output characteristics are excellent when the weight is 0/0 . If the amount of the conductive agent added is less than 7% by weight, the effect of improving output characteristics cannot be obtained. If the amount of the conductive agent added is more than 13% by weight, the amount of the conductive agent aggregate itself increases. Therefore, it is thought that the amount of non-aqueous electrolyte retained in the aggregates increases, and the amount of lithium ions reaching the surface of the positive electrode active material decreases. Furthermore, if the density of the aggregates is high, it is thought that diffusion of lithium ions from the aggregates to the surface of the positive electrode active material will occur.
[0068] 以上の結果から、導電剤は、正極合剤層の 7〜： 13重量％を占める必要がある。 [0068] From the above results, the conductive agent needs to account for 7 to 13% by weight of the positive electrode mixture layer.
[0069] 《実施例 4》 [0069] 《Example 4》
次に、負極合剤の多孔度について検討した。 Next, we examined the porosity of the negative electrode mixture.
(電池 10〜： 13) (Battery 10~: 13)
圧延時の圧力を調節して、負極活物質層の多孔度を、 30%、 35%、 50%または 5 5%としたこと以外は、電池 1と同様にして、電池 10〜： 13を作製した。 By adjusting the pressure during rolling, the porosity of the negative electrode active material layer can be adjusted to 30%, 35%, 50%, or 5%. Batteries 10 to 13 were produced in the same manner as Battery 1 except that the concentration was 5%.
[0070] 各電池の出力値を、実施例 1と同様にして求めた。結果を図 5に示す。なお、図 5に は、電池 1 (負極活物質層の多孔度： 40%)の結果も示す。 [0070] The output value of each battery was determined in the same manner as in Example 1. The results are shown in Figure 5. Furthermore, Figure 5 also shows the results for Battery 1 (porosity of negative electrode active material layer: 40%).
[0071] 図 5から、負極活物質層の多孔度が 35〜50%の範囲にある場合に、出力特性に 優れていることがわかる。また、他のリチウム塩濃度でも、図 5と同様の傾向を示した。 [0071] From FIG. 5, it can be seen that the output characteristics are excellent when the porosity of the negative electrode active material layer is in the range of 35 to 50%. In addition, other lithium salt concentrations showed the same trends as in Figure 5.
[0072] 放電反応において、負極活物質から非水電解液中へ移動したリチウムイオンは、 正極へと拡散する。この拡散が遅いと、正極において、リチウムイオンが不足する、つ まり、反応抵抗が高くなると考えられる。負極活物質層の多孔度が低い場合には、リ チウムイオン力 負極からセパレータへと拡散しにくくなる。このため、正極へのリチウ ムイオンの移動量が少なくなり、反応抵抗が増加したと考えられる。 [0072] In the discharge reaction, lithium ions that have moved from the negative electrode active material into the nonaqueous electrolyte diffuse into the positive electrode. If this diffusion is slow, there will be a shortage of lithium ions at the positive electrode, which means that the reaction resistance will increase. If the porosity of the negative electrode active material layer is low, it becomes difficult for lithium ions to diffuse from the negative electrode to the separator. For this reason, it is thought that the amount of lithium ions transferred to the positive electrode decreased and the reaction resistance increased.
[0073] 正極の場合と同様に、負極活物質層の多孔度が 55%程度になると、負極活物質 層の強度が低下し、塗工後の圧延工程や正極ゃセパレータと捲回する構成工程な どにおいて、負極活物質の脱落したり、その脱落物が原因となる短絡不良が発生し たりする。このため、負極活物質層の多孔度が 55%である場合、出力特性が低下し たと考えられる。 [0073] As in the case of the positive electrode, when the porosity of the negative electrode active material layer reaches approximately 55%, the strength of the negative electrode active material layer decreases, and the rolling process after coating and the construction process of winding the positive electrode with a separator decreases. In such cases, the negative electrode active material may fall off, or short circuits may occur due to the falling material. For this reason, it is thought that when the porosity of the negative electrode active material layer was 55%, the output characteristics decreased.
よって、負極活物質層の多孔度は、 35〜50%であることが好ましい。 Therefore, the porosity of the negative electrode active material layer is preferably 35 to 50%.
[0074] なお、導電剤として、ケッチェンブラックを用いた場合、またはアセチレンブラックお よびケッチェンブラックの混合物を使用した場合にも、実施例:!〜 4の結果と同様の結 果が得られた。 [0074] Furthermore, when Ketjen black was used as the conductive agent, or when a mixture of acetylene black and Ketjen black was used, results similar to those of Examples ! to 4 were obtained. Ta.
[0075] 以上の結果から、導電剤の含有量が正極合剤層の 7重量％〜： 13重量％の範囲と し、非水電解液中のリチウム塩濃度を 1. 2mol/L〜2. Omol/Lの範囲とし、正極 合剤層の多孔度を 35%〜55%の範囲とすることによって、出力特性に優れるリチウ ムイオン二次電池が得られることがわかった。 [0075] From the above results, the content of the conductive agent was set in the range of 7% to 13% by weight of the positive electrode mixture layer, and the lithium salt concentration in the nonaqueous electrolyte was set to 1.2mol/L to 2.2mol/L. It was found that a lithium ion secondary battery with excellent output characteristics could be obtained by setting the porosity of the positive electrode mixture layer to a range of Omol/L and a range of 35% to 55%.
産業上の利用可能性 Industrial applicability
[0076] 本発明のリチウムイオン二次電池は、出力特性に優れているため、例えば、電気自 動車や HEV用の電源として好適に用いることができる。 [0076] Since the lithium ion secondary battery of the present invention has excellent output characteristics, it can be suitably used as a power source for electric vehicles and HEVs, for example.

Claims

請求の範囲 The scope of the claims
[1] 正極集電体および前記正極集電体上に形成された正極合剤層を含む正極と、負 極集電体および前記負極集電体上に形成された負極活物質層を含む負極と、前記 正極と前記負極の間に配置されたセパレータとを備える極板群、前記極板群を収容 する電池ケース、ならびに非水溶媒と前記非水溶媒に溶解されたリチウム塩を含む 非水電解液を具備し、 [1] A positive electrode including a positive electrode current collector and a positive electrode mixture layer formed on the positive electrode current collector, and a negative electrode including a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector. and a separator disposed between the positive electrode and the negative electrode, a battery case housing the electrode plate group, and a non-aqueous solvent containing a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent. Equipped with an electrolyte,
前記正極合剤層が、正極活物質および導電剤を含み、 The positive electrode mixture layer includes a positive electrode active material and a conductive agent,
前記導電剤が、前記正極合剤層の 7重量％〜 13重量％を占め、 The conductive agent accounts for 7% to 13% by weight of the positive electrode mixture layer,
前記正極合剤層の多孔度力 35 %〜 55 %であり、 The positive electrode mixture layer has a porosity of 35% to 55%,
前記非水電解液における前記リチウム塩の濃度力 1. 2mol/L〜2mol/Lであ る、リチウムイオン二次電池。 A lithium ion secondary battery, wherein the concentration of the lithium salt in the non-aqueous electrolyte is 1.2 mol/L to 2 mol/L.
[2] 前記負極活物質層の多孔度が 35%〜50%である、請求項 1に記載のリチウムィォ ン二次電池。 [2] The lithium ion secondary battery according to claim 1, wherein the negative electrode active material layer has a porosity of 35% to 50%.
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CN108780930A (en) * 2016-01-13 2018-11-09 弗莱克斯电子有限责任公司 The method of discharge period is estimated during high rate cell discharge
CN108780930B (en) * 2016-01-13 2021-09-07 弗莱克斯电子有限责任公司 Method for estimating discharge duration during high rate battery discharge

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