JP4925614B2 - Positive electrode for non-aqueous electrolyte secondary battery, and non-aqueous electrolyte secondary battery - Google Patents
Positive electrode for non-aqueous electrolyte secondary battery, and non-aqueous electrolyte secondary battery Download PDFInfo
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- JP4925614B2 JP4925614B2 JP2005184294A JP2005184294A JP4925614B2 JP 4925614 B2 JP4925614 B2 JP 4925614B2 JP 2005184294 A JP2005184294 A JP 2005184294A JP 2005184294 A JP2005184294 A JP 2005184294A JP 4925614 B2 JP4925614 B2 JP 4925614B2
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- secondary battery
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- 239000000203 mixture Substances 0.000 claims description 170
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- 229910052744 lithium Inorganic materials 0.000 claims description 59
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Classifications
-
- 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
Description
本発明は、非水電解質二次電池用の正極と、該正極を有する非水電解質二次電池に関するものである。 The present invention relates to a positive electrode for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery having the positive electrode.
リチウムイオン電池に代表される非水電解質二次電池は、容量が大きく、かつ高電圧、高エネルギー密度であることから、ますます需要が増える傾向にある。そして、電池の高容量化や充電電圧の高電圧化も検討されており、電池の放電電力量の増加が見込まれている。 Non-aqueous electrolyte secondary batteries represented by lithium ion batteries have a large capacity, high voltage, and high energy density, and therefore demands are increasing. Further, increasing the capacity of the battery and increasing the charging voltage are also being studied, and an increase in the amount of discharge power of the battery is expected.
リチウムイオン電池などの非水電解質二次電池で使用されている正極は、例えば、正極活物質、導電助剤および結着剤にＮ−メチル−２−ピロリドン（ＮＭＰ）などの溶剤を加えて混合することにより、ペースト状やスラリー状の正極合剤含有組成物を調製し、この正極合剤含有組成物を集電体となる導電性基体の表面に塗布し、溶剤を乾燥除去すると共にプレス処理などを施し、厚みや密度の調整された正極合剤層を形成する工程を経て作製される。 The positive electrode used in a non-aqueous electrolyte secondary battery such as a lithium ion battery is mixed, for example, by adding a solvent such as N-methyl-2-pyrrolidone (NMP) to the positive electrode active material, the conductive additive and the binder. Thus, a paste-like or slurry-like positive electrode mixture-containing composition is prepared, and this positive electrode mixture-containing composition is applied to the surface of the conductive substrate serving as a current collector, and the solvent is dried and removed. And the like, and is formed through a step of forming a positive electrode mixture layer whose thickness and density are adjusted.
このような正極を有する非水電解質二次電池の高容量化を達成する方法としては、例えば、正極の密度（正極合剤層の密度）を高めて、正極における正極活物質の充填量を増加させる方法や、充電電圧を高める方法などがある。このうち、前者の方法としては、例えば、正極に用いる導電助剤の添加量を少なくすることが考えられる。 As a method for achieving a higher capacity of the nonaqueous electrolyte secondary battery having such a positive electrode, for example, the positive electrode density (the density of the positive electrode mixture layer) is increased to increase the filling amount of the positive electrode active material in the positive electrode. And a method for increasing the charging voltage. Among these, as the former method, for example, it is conceivable to reduce the amount of the conductive additive used for the positive electrode.
導電助剤の添加量を少なくすると正極の導電性が低下することから電池特性にとって不利であるが、例えば、粒子径が小さく、比表面積が大きなカーボンブラック系の炭素材料を用いて、この問題を解決する試みがなされている。更に、４．５Ｖ以上の高電圧状態では、支持塩として汎用されているＬｉＰＦ６の錯イオン（ＰＦ６−）が黒鉛相間に挿入され、黒鉛粒子の導電性低下が起こることからも、正極の高容量化、充電電圧の高電圧化に向けて、黒鉛系の炭素材料よりも、非晶質炭素であるカーボンブラック系の導電助剤の適用が検討されている。 If the addition amount of the conductive auxiliary agent is reduced, the conductivity of the positive electrode is lowered, which is disadvantageous for battery characteristics.For example, this problem is solved by using a carbon black-based carbon material having a small particle diameter and a large specific surface area. Attempts have been made to resolve. Furthermore, in a high voltage state of 4.5 V or higher, LiPF 6 complex ions (PF 6− ) widely used as a supporting salt are inserted between the graphite phases, and the conductivity of the graphite particles is lowered. In order to increase the capacity and the charging voltage, the application of a carbon black-based conductive assistant, which is amorphous carbon, is being investigated rather than the graphite-based carbon material.
また、電池の高電圧充電を可能にしてより高容量化を達成するには、例えば、リチウム（Ｌｉ）と、マンガン（Ｍｎ）、ニッケル（Ｎｉ）、コバルト（Ｃｏ）といった遷移金属とを含有するリチウム遷移金属複合酸化物を正極活物質に用いることも考えられる。このようなリチウム遷移金属複合酸化物は、電池の高温貯蔵性の向上にも寄与し得る。 In order to achieve higher capacity by enabling high voltage charging of the battery, for example, lithium (Li) and transition metals such as manganese (Mn), nickel (Ni), and cobalt (Co) are contained. It is also conceivable to use a lithium transition metal composite oxide for the positive electrode active material. Such a lithium transition metal composite oxide can also contribute to the improvement of the high temperature storage property of the battery.
ところで、正極合剤層においては、含有される各成分の分散の均一性を高めることが、正極活物質の利用率を向上させ、電池の容量をより高める観点から要求される。しかし、カーボンブラックなどの粒子径の小さな炭素材料は凝集し易いため、正極合剤層中における導電助剤の分散の均一性を高めるには、この正極合剤層を形成するための正極合剤含有組成物の段階で、導電助剤を含めた各成分をより均一に分散させておくことが望ましい。こうした観点から、特に粒子径の小さな炭素材料を導電助剤に用い、その添加量を低減させるにあたっては、強いせん断力をかけ得る分散装置を用いて各成分の混合物を混練することにより正極合剤含有組成物を調製する必要がある。 Incidentally, in the positive electrode mixture layer, it is required to improve the uniformity of dispersion of each component contained from the viewpoint of improving the utilization rate of the positive electrode active material and further increasing the capacity of the battery. However, since a carbon material such as carbon black having a small particle diameter is likely to aggregate, the positive electrode mixture for forming this positive electrode mixture layer can be used to increase the uniformity of dispersion of the conductive additive in the positive electrode mixture layer. It is desirable to disperse each component including the conductive additive more uniformly at the stage of the containing composition. From such a viewpoint, in particular, when a carbon material having a small particle diameter is used as a conductive auxiliary and the amount of addition is reduced, a mixture of each component is kneaded by using a dispersing device capable of applying a strong shearing force. It is necessary to prepare the containing composition.
しかしながら、上記のようなリチウム遷移金属複合酸化物を正極活物質として用い、強いせん断力をかけつつ混練する方法で調製した正極合剤含有組成物によって作製した正極を用いて電池を構成すると、以下の問題が生じることが本発明者らの検討により判明した。上記のリチウム遷移金属複合酸化物は粒径が数μｍ程度の粒子状であり、更にこれらが凝集した２次粒子の状態で使用されることがあるが、このような正極活物質を用いて強いせん断力をかけつつ混練して正極合剤含有組成物を調製すると、１次粒子の崩落や１次粒子自体の破壊が生じて、正極活物質の比表面積が増大する。このように正極活物質の比表面積が増大すると、正極活物質の加水分解が促進されて炭酸リチウム（Ｌｉ２ＣＯ３）や水酸化リチウム（ＬｉＯＨ）といったアルカリ成分が生成し、正極合剤含有組成物中のアルカリ成分量が増大してしまう。
However, when a battery is configured using a positive electrode mixture prepared by a method in which a lithium transition metal composite oxide as described above is used as a positive electrode active material and kneaded while applying a strong shearing force, The inventors have found that this problem occurs. The lithium transition metal composite oxide is in the form of particles having a particle size of about several μm, and may be used in the form of secondary particles in which they are aggregated. When preparing the positive electrode mixture-containing composition was kneaded while applying a shearing force, and the destruction of collapse and the primary particles themselves of the primary particles occurs, the specific surface area of the positive electrode active material is increased. When the specific surface area of the positive electrode active material increases in this way, hydrolysis of the positive electrode active material is promoted to generate an alkali component such as lithium carbonate (Li 2 CO 3 ) or lithium hydroxide (LiOH), and the positive electrode mixture-containing composition The amount of alkali components in the product will increase.
炭酸リチウムや水酸化リチウムといったアルカリ成分量の多い正極合剤含有組成物を用いて正極合剤層を形成して正極を作製し、これを電池に用いると、例えば電池が高温環境下で貯蔵された際に、正極合剤層中に多量に残存しているこれらのアルカリ成分が分解して二酸化炭素（ＣＯ２）や水素（Ｈ２）といったガスが発生して電池の内圧を上昇させるために、電池の膨れが生じてしまう。 A positive electrode mixture layer is formed using a composition containing a positive electrode mixture containing a large amount of alkali components such as lithium carbonate and lithium hydroxide to produce a positive electrode. When this is used for a battery, for example, the battery is stored in a high temperature environment. In order to increase the internal pressure of the battery by decomposing a large amount of these alkali components remaining in the positive electrode mixture layer and generating gas such as carbon dioxide (CO 2 ) and hydrogen (H 2 ) The battery will swell.
このような事情から、非水電解質二次電池において、正極密度の向上と高電圧充電による高容量化を達成しつつ、高温時の電池の膨れを抑制するには、正極合剤層における炭酸リチウムや水酸化リチウムといったアルカリ成分の量を低減する必要がある。 For these reasons, in nonaqueous electrolyte secondary batteries, lithium carbonate in the positive electrode mixture layer can be used to suppress battery swelling at high temperatures while achieving higher positive electrode density and higher capacity through high voltage charging. It is necessary to reduce the amount of alkali components such as lithium hydroxide.
正極合剤層中のアルカリ成分量を低減する技術としては、例えば特許文献１に、正極合剤層形成用の組成物（正極合剤含有組成物）に有機酸を添加して、アルカリ成分を中和する方法が開示されている。 As a technique for reducing the amount of alkali component in the positive electrode mixture layer, for example, in Patent Document 1, an organic acid is added to a composition for forming a positive electrode mixture layer (positive electrode mixture-containing composition), and an alkali component is added. A method for neutralization is disclosed.
ところが、正極合剤含有組成物に有機酸を添加した場合、アルカリ成分の中和に寄与しなかった未反応の有機酸が残存して正極合剤層中に取り込まれると、電池の高温貯蔵時に該有機酸自体が分解してガスを発生するなどの問題が生じてしまう。よって、こうしたアルカリ成分の中和以外の方法で、アルカリ成分の分解に起因する電池の膨れを抑制する技術が求められる。 However, when an organic acid is added to the positive electrode mixture-containing composition, an unreacted organic acid that has not contributed to neutralization of the alkali component remains and is taken into the positive electrode mixture layer. The organic acid itself decomposes to generate a problem such as generation of gas. Therefore, there is a need for a technique for suppressing battery swelling caused by decomposition of the alkali component by a method other than neutralization of the alkali component.
本発明は上記事情に鑑みてなされたものであり、その目的は、高容量化を達成しつつ高温貯蔵時における安全性に優れた非水電解質二次電池を構成するための正極と、該正極を有する非水電解質二次電池を提供することにある。 The present invention has been made in view of the above circumstances, and an object thereof is to form a positive electrode for constituting a nonaqueous electrolyte secondary battery excellent in safety during high-temperature storage while achieving high capacity, and the positive electrode It is providing the nonaqueous electrolyte secondary battery which has.
上記目的を達成し得た本発明の非水電解質二次電池用の正極は、正極活物質、導電助剤および結着剤を含有する正極合剤で構成された正極合剤層を有してなるものであって、 上記正極合剤は、下記一般式（１）で表されるリチウム遷移金属複合酸化物を正極活物質として含有しており、かつ比表面積が５０〜１０００ｍ２／ｇの炭素材料を導電助剤として含有しており、正極活物質全量中、上記リチウム遷移金属複合酸化物が５０質量％以上であり、上記リチウム遷移金属複合酸化物として、平均粒径が５〜１８μｍであり、かつ比表面積が０．１〜０．４ｍ ２ ／ｇのものを用い、上記正極合剤層中の上記導電助剤の含有量が０．５〜１．５質量％であり、上記正極合剤層の密度が３．２〜３．９ｇ／ｃｍ ３ であり、上記正極合剤２．５ｇを５０ｇの中性の水に浸漬させたときの上澄み液を、濃度が０．０１ｍｏｌ／ｌの硫酸で中和滴定して求められる中和滴定量（Ａ）が、４．５ｍｌ以下であることを特徴とするものである。
Ｌｉ（１＋δ）ＭｎｘＮｉｙＣｏ（１−ｘ−ｙ）Ｏ２ （１）
［上記一般式（１）中、０≦δ≦０．０５、０．１＜ｘ≦０．５、０．１＜ｙ≦０．５、０．６＜ｘ＋ｙ≦１．０、である。］
The positive electrode for a non-aqueous electrolyte secondary battery of the present invention that has achieved the above object has a positive electrode mixture layer composed of a positive electrode mixture containing a positive electrode active material, a conductive additive and a binder. The positive electrode mixture contains a lithium transition metal composite oxide represented by the following general formula (1) as a positive electrode active material, and has a specific surface area of 50 to 1000 m 2 / g. It contains a material as a conductive additive , the lithium transition metal composite oxide is 50% by mass or more in the total amount of the positive electrode active material, and the lithium transition metal composite oxide has an average particle size of 5 to 18 μm. And having a specific surface area of 0.1 to 0.4 m 2 / g, the content of the conductive assistant in the positive electrode mixture layer is 0.5 to 1.5% by mass, density of the material layer is 3.2~3.9g / cm 3, the cathode mixture 2.5 The neutralization titer (A) obtained by neutralizing the supernatant of 50 g of neutral water with sulfuric acid having a concentration of 0.01 mol / l is 4.5 ml or less. It is characterized by.
Li (1 + δ) Mn x Ni y Co (1-xy) O 2 (1)
[In the general formula (1), 0 ≦ δ ≦ 0.05, 0.1 <x ≦ 0.5, 0.1 <y ≦ 0.5, 0.6 <x + y ≦ 1.0. ]
本発明の正極では、上記特定構造のリチウム遷移金属複合酸化物を正極活物質として用い、更に上記特定の比表面積を有する炭素材料を導電助剤として用いることにより、正極合剤層の高密度化と、この正極を有する電池での高電圧充電を可能にして、該電池の高容量化を達成すると共に、上記の中和滴定量（Ａ）を満足させ、正極合剤層中に含有されるアルカリ成分量を制御し、電池の高温貯蔵時における電池内でのガス発生量を抑えて、電池の膨れを抑制し、その安全性を確保している。 In the positive electrode according to the present invention, the density of the positive electrode mixture layer is increased by using the lithium transition metal composite oxide having the specific structure as a positive electrode active material and further using the carbon material having the specific specific surface area as a conductive additive. And enabling high voltage charging in a battery having this positive electrode, achieving a higher capacity of the battery, satisfying the above neutralization titer (A), and contained in the positive electrode mixture layer By controlling the amount of alkali components, the amount of gas generated in the battery during high-temperature storage of the battery is suppressed, the swelling of the battery is suppressed, and its safety is ensured.
また、本発明には、上記本発明の非水電解質二次電池用の正極を有する非水電解質二次電池も包含される。 The present invention also includes a nonaqueous electrolyte secondary battery having a positive electrode for the nonaqueous electrolyte secondary battery of the present invention.
本発明によれば、高容量であり、かつ高温貯蔵時における安全性に優れた非水電解質二次電池を提供できる。 ADVANTAGE OF THE INVENTION According to this invention, the nonaqueous electrolyte secondary battery which is high capacity | capacitance and excellent in the safety | security at the time of high temperature storage can be provided.
本発明の非水電解質二次電池用の正極は、正極活物質、導電助剤および結着剤を含有する正極合剤で構成された正極合剤層を有してなり、該正極合剤２．５ｇを５０ｇの中性の水に浸漬させたときの上澄み液を、濃度が０．０１ｍｏｌ／ｌの硫酸で中和滴定して求められる中和滴定量（Ａ）が、４．５ｍｌ以下である。 The positive electrode for a nonaqueous electrolyte secondary battery of the present invention has a positive electrode mixture layer composed of a positive electrode mixture containing a positive electrode active material, a conductive additive and a binder, and the positive electrode mixture 2 The neutralization titer (A) obtained by neutralizing and titrating the supernatant obtained by immersing 0.5 g in 50 g of neutral water with sulfuric acid having a concentration of 0.01 mol / l is 4.5 ml or less. is there.
正極合剤を中性の水に浸漬させると、該正極合剤中に含有されているアルカリ成分の一部または全部が水中に溶け出す。このように正極の有する正極合剤を水に浸漬させることで水中に溶解し得るアルカリ成分は、該正極を備えた電池の高温貯蔵時におけるガス発生の要因となる。従って、正極の有する正極合剤を中性の水に浸漬させた際に水中に溶け出すアルカリ成分量が少なく、該水の上澄み液を上記濃度の硫酸で中和滴定したときの中和滴定量（Ａ）が４．５ｍｌ以下であれば、該正極を備えた電池を高温環境下で貯蔵しても、ガス発生量が抑えられて、電池の膨れが抑制できる。中和滴定量（Ａ）は、３．３ｍｌ以下であることがより好ましい。 When the positive electrode mixture is immersed in neutral water, some or all of the alkali components contained in the positive electrode mixture are dissolved in water. As described above, the alkaline component that can be dissolved in water by immersing the positive electrode mixture of the positive electrode in water becomes a cause of gas generation during high-temperature storage of a battery including the positive electrode. Therefore, when the positive electrode mixture possessed by the positive electrode is immersed in neutral water, the amount of alkali component that dissolves in the water is small, and the neutralization titration when the water supernatant is neutralized with sulfuric acid at the above concentration. If (A) is 4.5 ml or less, even if the battery provided with the positive electrode is stored in a high-temperature environment, the amount of gas generated is suppressed, and the swelling of the battery can be suppressed. The neutralization titer (A) is more preferably 3.3 ml or less.
すなわち、正極の有する正極合剤層中のアルカリ成分量を低減するには、例えば、正極合剤層を形成するための各材料中のアルカリ成分量を制御することも考えられる。しかしながら、上記の通り、強いせん断力をかけつつ混練することで、正極合剤層を形成するための正極合剤含有組成物を調製した場合には、調製時に炭酸リチウムや水酸化リチウムといったアルカリ成分が増加してしまう。図１および図２に正極合剤層の走査型電子顕微鏡写真を示しているが、正極合剤含有組成物の調製時に強いせん断力をかけつつ混練することで、図１に示すように、活物質粒子同士の衝突、摩擦により、粒子表面から崩落が起こって微粉末が生成し、導電助剤に取り囲まれた形で活物質の微粉末が存在している状態になる［図１中の矢印の箇所］。そのため、活物質の比表面積が増大して加水分解が進み、アルカリ成分が増加してしまう。このような理由により、単にアルカリ成分含有量の少ない材料を用いて正極を作製しても、正極作製工程中に正極合剤中のアルカリ成分量が増大してしまうことから、高温貯蔵時の電池の膨れを抑制することが困難である。一方で、強いせん断力をかけずに混練して調製した正極合剤含有組成物を用いて得られる正極合剤層を有する正極では、図２から見て取れるように活物質粒子の崩落による微粉末は生成しておらず、材料自体の有するアルカリ成分量と、正極の有しているアルカリ成分量は変化しない。そこで、本発明では、使用する材料中のアルカリ成分量ではなく、正極が有している正極合剤（正極合剤層）中のアルカリ成分量を制御することとし、これにより、高温貯蔵時の電池の膨れを抑えて、安全性を確保することに成功したのである。 That is, to reduce the amount of alkali components in the positive electrode mixture layer of the positive electrode, for example, it is conceivable to control the amount of alkali components in each material for forming the positive electrode mixture layer. However, as described above, when a positive electrode mixture-containing composition for forming a positive electrode mixture layer is prepared by kneading while applying a strong shearing force, alkaline components such as lithium carbonate and lithium hydroxide are prepared at the time of preparation. Will increase. FIGS. 1 and 2 show scanning electron micrographs of the positive electrode mixture layer. When the positive electrode mixture-containing composition was prepared, kneading while applying a strong shearing force, as shown in FIG. Due to the collision and friction between the material particles, the particle surface collapses to produce fine powder, and the active material fine powder exists in a form surrounded by the conductive aid [arrow in FIG. Section]. Therefore, the specific surface area of the active material increases, hydrolysis proceeds, and the alkali component increases. For these reasons, even if a positive electrode is simply made using a material having a low alkali component content, the amount of the alkaline component in the positive electrode mixture increases during the positive electrode preparation step. It is difficult to suppress blistering. On the other hand, in the positive electrode having the positive electrode mixture layer obtained by using the positive electrode mixture-containing composition prepared by kneading without applying a strong shearing force, the fine powder due to the collapse of the active material particles can be seen from FIG. It is not generated, and the amount of alkali component of the material itself and the amount of alkali component of the positive electrode do not change. Therefore, in the present invention, not the amount of alkali components in the material to be used, but the amount of alkali components in the positive electrode mixture (positive electrode mixture layer) possessed by the positive electrode is controlled. They succeeded in ensuring safety by suppressing the swelling of the battery.
本発明の正極は、例えば、正極合剤層が集電体（導電性基体）の片面または両面に形成された形態を有しているが、中和滴定量（Ａ）の測定には、正極から正極合剤を剥離して、２．５ｇを計り取り、これを５０ｇの中性の水（ｐＨが７であってイオン交換法によって生成された、ＪＩＳ Ｋ０５５７に規定されるＡ１以上の水）に、マグネティックスターラで１５分撹拌しながら浸漬させ、３０分間放置した後、これをろ過した上澄み液を用いた。中和測定は電位差滴定装置（ＡＴ−４２０：京都電子工業株式会社製）を用いた。中和滴定は上澄み液をマグネティックスターラで撹拌しながら、０．０１ｍｏｌ／ｌの硫酸を間欠滴下して行った。このとき電位差（最大微分値の電位と最小微分値電位との差）が５０ｍＶ以上となったとき、もしくは微分値差（最大微分値と最小微分値との差）が１００ｍＶ／ｍｌ以上となったとき、これを終点として、その２点目を中和滴定量（Ａ）とした。 The positive electrode of the present invention has, for example, a form in which a positive electrode mixture layer is formed on one side or both sides of a current collector (conductive substrate). The positive electrode mixture was peeled from the sample, 2.5 g was weighed out, and 50 g of neutral water (water having a pH of 7 and produced by the ion exchange method, water of A1 or higher as defined in JIS K0557) Then, the sample was immersed in a magnetic stirrer for 15 minutes with stirring, allowed to stand for 30 minutes, and then a supernatant obtained by filtering this was used. Neutralization measurement was performed using a potentiometric titrator (AT-420: manufactured by Kyoto Electronics Industry Co., Ltd.). Neutralization titration was performed by intermittently dropping 0.01 mol / l sulfuric acid while stirring the supernatant with a magnetic stirrer. At this time, the potential difference (difference between the maximum differential value potential and the minimum differential value potential) was 50 mV or more, or the differential value difference (difference between the maximum differential value and the minimum differential value) was 100 mV / ml or more. When this was the end point, the second point was designated as neutralization titer (A).
すなわち、正極合剤層を浸漬した水（上澄み液）には、正極合剤層中に含有されているアルカリ成分である水酸化リチウムや炭酸リチウムが溶出する。上記の滴定によって、下記式（２）および（３）に示す反応により、これらのアルカリ成分のうち、全水酸化リチウムと炭酸リチウムの半分が中和される。更に滴定を続けると、下記式（４）に示すように、残りの炭酸塩が中和される。上記の中和滴定量（Ａ）の測定では、下記式（４）の反応終了時点を中和終了とみなしており、このときの滴定量を、中和滴定量（Ａ）としている。
ＬｉＯＨ＋０．５Ｈ２ＳＯ４ → ０．５Ｌｉ２ＳＯ４＋Ｈ２Ｏ (２）
Ｌｉ２ＣＯ３＋０．５Ｈ２ＳＯ４ → ０．５Ｌｉ２ＳＯ４＋ＬｉＨＣＯ３ (３）
ＬｉＨＣＯ＋０．５Ｈ２ＳＯ４ → ０．５Ｌｉ２ＳＯ４＋ＣＯ２＋Ｈ２Ｏ (４）
That is, lithium hydroxide and lithium carbonate, which are alkali components contained in the positive electrode mixture layer, are eluted in the water (supernatant liquid) in which the positive electrode mixture layer is immersed. By the above titration, half of the total lithium hydroxide and lithium carbonate are neutralized among these alkali components by the reaction shown in the following formulas (2) and (3). When the titration is further continued, the remaining carbonate is neutralized as shown in the following formula (4). In the measurement of the neutralization titer (A), the reaction end point of the following formula (4) is regarded as the end of neutralization, and the titer at this time is defined as the neutralization titer (A).
LiOH + 0.5H 2 SO 4 → 0.5Li 2 SO 4 + H 2 O (2)
Li 2 CO 3 + 0.5H 2 SO 4 → 0.5Li 2 SO 4 + LiHCO 3 (3)
LiHCO + 0.5H 2 SO 4 → 0.5Li 2 SO 4 + CO 2 + H 2 O (4)
中和滴定量（Ａ）の下限については、少ないほど好ましく、０ｍｌであることが最も好ましいが、通常は、０ｍｌとすることは困難である。 The lower limit of the neutralization titer (A) is preferably as small as possible, and most preferably 0 ml, but it is usually difficult to make it 0 ml.
また、本発明の正極における正極合剤は、正極活物質として、上記一般式（１）で表されるリチウム遷移金属複合酸化物（層状構造のリチウム遷移金属複合酸化物）を含有している。このような構造のリチウム遷移金属酸化物を用いることにより、正極容量、すなわち、電池容量を高めることができる。また、上記一般式（１）で表されるリチウム遷移金属複合酸化物は、高電圧下での安定性にも優れていることから、電池の高電圧充電も可能となるため、かかる点においても電池の高容量化が達成できる。 Moreover, the positive electrode mixture in the positive electrode of the present invention contains a lithium transition metal composite oxide represented by the above general formula (1) (a lithium transition metal composite oxide having a layered structure) as a positive electrode active material. By using the lithium transition metal oxide having such a structure, the positive electrode capacity, that is, the battery capacity can be increased. In addition, since the lithium transition metal composite oxide represented by the general formula (1) is excellent in stability under a high voltage, the battery can be charged at a high voltage. Higher battery capacity can be achieved.
上記一般式（１）において、０≦δ≦０．０５、０．１＜ｘ≦０．５、０．６＜ｘ＋ｙ≦１．０である。δが０未満であるか、ｘが０．５を超える場合には、リチウム遷移金属酸化物粒子が脆くなり、正極合剤含有組成物の調製時に崩壊し易くなって、アルカリ成分量の増大を引き起こすことがある。また、δが０．０５を超えるか、ｘが０．１以下であると、正極活物質の合成時に反応せずに残留しているアルカリ成分が増加する。 In the general formula (1), 0 ≦ δ ≦ 0.05, 0.1 <x ≦ 0.5, and 0.6 <x + y ≦ 1.0. When δ is less than 0 or x is more than 0.5, the lithium transition metal oxide particles become brittle and easily collapse during the preparation of the positive electrode mixture-containing composition, increasing the amount of alkali components. May cause. Further, if δ exceeds 0.05 or x is 0.1 or less, the remaining alkali component without reacting during the synthesis of the positive electrode active material increases.
なお、本発明の正極における正極活物質は、全てが上記一般式（１）で表されるリチウム遷移金属複合酸化物であってもよく、他の活物質を併用していてもよい。上記一般式（１）表されるリチウム遷移金属複合酸化物と併用できる他の活物質としては、例えば、スピネル型のリチウム・マンガン複合酸化物（ＬｉＭｎ２−ｐＭｐＯ４：ただし、Ｍ：Ｔｉ，Ｍｇ，Ｃａ，Ｓｒ，Ａｌ，Ｇａ，Ｚｎ，およびＣｕからなる群から選ばれる少なくとも１種の元素，０≦ｐ≦０．１）、コバルト酸リチウム（ＬｉＣｏ１−ｑＭｑＯ２：ただし、Ｍ：Ｔｉ，Ｍｇ，Ｚｒ，Ｎｂ，Ｍｏ，Ｗ，Ａｌ，Ｓｉ，Ｇａ，ＧｅおよびＳｎからなる群から選ばれる少なくとも１種の元素，０≦q≦０．１）などが挙げられる。このような他の活物質を併用する場合には、正極活物質全量中、上記一般式（１）で表されるリチウム遷移金属複合酸化物が、例えば、５０質量％以上であることが好ましく、７０質量％以上であることがより好ましい。 In addition, all the positive electrode active materials in the positive electrode of the present invention may be lithium transition metal composite oxides represented by the above general formula (1), or other active materials may be used in combination. As another active material that can be used in combination with the lithium transition metal composite oxide represented by the general formula (1), for example, spinel type lithium / manganese composite oxide (LiMn 2−p M p O 4 : where M: At least one element selected from the group consisting of Ti, Mg, Ca, Sr, Al, Ga, Zn, and Cu, 0 ≦ p ≦ 0.1, lithium cobaltate (LiCo 1-q M q O 2 : However, M: Ti, Mg, Zr, Nb, Mo, W, Al, Si, Ga, Ge and Sn, at least one element selected from the group consisting of Sn, 0 ≦ q ≦ 0.1), and the like. When such other active material is used in combination, the lithium transition metal composite oxide represented by the general formula (1) in the total amount of the positive electrode active material is preferably, for example, 50% by mass or more, It is more preferable that it is 70 mass% or more.
更に、本発明の正極における正極合剤は、導電助剤として、比表面積が５０ｍ２／ｇ以上１０００ｍ２／ｇ以下の炭素材料を使用する。このような比表面積を有する炭素材料であれば、電池特性の低下を抑制しつつ正極合剤中の含有量の低減が可能であるため、高密度の正極合剤層の形成が可能となり、電池の高容量化を達成できる。上記炭素材料の比表面積は、２００ｍ２／ｇ以上であることがより好ましく、また、８００ｍ２／ｇ以下であることがより好ましい。 Furthermore, the positive electrode mixture in the positive electrode of the present invention uses a carbon material having a specific surface area of 50 m 2 / g or more and 1000 m 2 / g or less as a conductive additive. If the carbon material has such a specific surface area, it is possible to reduce the content in the positive electrode mixture while suppressing deterioration of the battery characteristics, so that a high-density positive electrode mixture layer can be formed. High capacity can be achieved. The specific surface area of the carbon material is more preferably 200 m 2 / g or more, and more preferably 800 m 2 / g or less.
正極合剤に使用し得る導電助剤としては、例えば、天然黒鉛（鱗片状黒鉛など），人造黒鉛などのグラファイト類；アセチレンブラック、ケッチェンブラック、チャンネルブラック、ファーネスブラック、ランプブラック、サーマルブラックなどのカ−ボンブラック類；炭素繊維；などの炭素材料が挙げられる。本発明では、これらの炭素材料のうち、比表面積が上記範囲内にあるものが用いられるが、必要に応じて比表面積が上記範囲内に無いものや、炭素材料以外の導電助剤（例えば、金属繊維などの導電性繊維類；フッ化カーボン；アルミニウムなどの金属粉末類；酸化亜鉛；チタン酸カリウムなどの導電性ウィスカー類；酸化チタンなどの導電性金属酸化物；ポリフェニレン誘導体などの有機導電性材料；など）も併用することができる。上記炭素材料としては、比表面積が上記範囲内のものの入手が容易な点で、アセチレンブラック、ケッチェンブラック、カーボンブラックが特に好ましい。 Examples of conductive aids that can be used in the positive electrode mixture include graphites such as natural graphite (flaky graphite, etc.) and artificial graphite; acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, etc. Carbon blacks; carbon fibers; and the like. In the present invention, among these carbon materials, those having a specific surface area within the above range are used, and those having a specific surface area not within the above range as necessary, or conductive assistants other than the carbon material (for example, Conductive fibers such as metal fibers; carbon fluoride; metal powders such as aluminum; zinc oxide; conductive whiskers such as potassium titanate; conductive metal oxides such as titanium oxide; organic conductivity such as polyphenylene derivatives Materials; etc.) can also be used in combination. As the carbon material, acetylene black, ketjen black, and carbon black are particularly preferable in that a material having a specific surface area within the above range is easily available.
なお、比表面積が上記範囲内の炭素材料と、他の導電助剤（比表面積が上記範囲内にない炭素材料、または炭素材料以外の導電助剤）を併用する場合には、導電助剤全量中、比表面積が上記範囲内の炭素材料が、例えば、３０質量％以上であることが好ましく、７０質量％以上であることがより好ましい。 In addition, when using together the carbon material whose specific surface area is in the above range, and other conductive assistant (carbon material whose specific surface area is not in the above range, or conductive assistant other than carbon material), the total amount of conductive aid Among them, the carbon material having a specific surface area within the above range is, for example, preferably 30% by mass or more, and more preferably 70% by mass or more.
上記の正極活物質と上記の導電助剤を含有する正極合剤において、中和滴定量（Ａ）を上記上限値以下に制御するには、下記の構成を採用することが好ましい。 In the positive electrode mixture containing the above positive electrode active material and the above conductive additive, it is preferable to employ the following configuration in order to control the neutralization titration amount (A) to the upper limit value or less.
上記のような比表面積の炭素材料は、その粒子径が小さく、凝集し易い。そのため、正極合剤層を形成するための正極合剤含有組成物の調製に当たっては、強いせん断力をかけつつ各成分の混合物を混練して、導電助剤の分散の均一性を高めることが要求される。しかしながら、強いせん断力をかけて正極合剤含有組成物を調製すると、上記一般式（１）で表されるリチウム含有複合酸化物粒子の崩壊などによって、アルカリ成分量が増大する。 The carbon material having a specific surface area as described above has a small particle diameter and is likely to aggregate. Therefore, in preparing the positive electrode mixture-containing composition for forming the positive electrode mixture layer, it is required to improve the uniformity of dispersion of the conductive additive by kneading the mixture of each component while applying a strong shearing force. Is done. However, when a positive electrode mixture-containing composition is prepared by applying a strong shearing force, the amount of alkali components increases due to the collapse of the lithium-containing composite oxide particles represented by the general formula (1).
上記リチウム含有複合酸化物粒子は、例えば、その表面に炭酸リチウムといったアルカリ成分で覆われているが、このような粒子（１次粒子）が崩壊などすると、アルカリ成分が付着していない新たな表面が生じ、該表面において、炭酸リチウムや水酸化リチウムといったアルカリ成分が生成する。また、上記リチウム含有複合酸化物は、１次粒子が凝集した２次粒子として使用される場合が多いが、このような２次粒子全体として見れば、その表面に炭酸リチウムが付着していても、個々の１次粒子の表面（特に、２次粒子の表面を形成していない１次粒子の表面）には、炭酸リチウムが付着していないことがあり、このような２次粒子から、１次粒子が崩落して、炭酸リチウムが付着していない表面が露出すると、該表面において、炭酸リチウムや水酸化リチウムといったアルカリ成分が生成する。 The lithium-containing composite oxide particles are, for example, covered with an alkali component such as lithium carbonate on the surface, but when such particles (primary particles) are collapsed, a new surface to which no alkali component is attached. And alkaline components such as lithium carbonate and lithium hydroxide are generated on the surface. In addition, the lithium-containing composite oxide is often used as secondary particles in which primary particles are aggregated. When viewed as such secondary particles as a whole, even if lithium carbonate is attached to the surface thereof, Lithium carbonate may not adhere to the surface of each primary particle (particularly, the surface of the primary particle that does not form the surface of the secondary particle). When the secondary particles collapse and the surface to which lithium carbonate is not attached is exposed, alkali components such as lithium carbonate and lithium hydroxide are generated on the surface.
よって、本発明の正極に使用する正極活物質としては、アルカリ成分含有量の少ないものを使用すること、および上記一般式（１）で表されるリチウム遷移金属複合酸化物として、正極合剤含有組成物の調製時において、１次粒子の崩壊や表面研磨が生じにくく、また１次粒子が崩落し難い２次粒子を形成し得るものを用いること、が好ましい。 Therefore, as a positive electrode active material used for the positive electrode of the present invention, a material having a low alkali component content is used, and as a lithium transition metal composite oxide represented by the general formula (1), a positive electrode mixture is contained. At the time of preparing the composition, it is preferable to use a material that is capable of forming secondary particles in which primary particles are unlikely to collapse and surface polishing, and the primary particles are difficult to collapse.
すなわち、本発明の正極に使用する正極活物質［上記一般式（１）で表されるリチウム遷移金属複合酸化物以外の他の活物質を併用している場合には、該他の活物質も含む全ての正極活物質］としては、例えば、該正極活物質２．５ｇを５０ｇの中性の水に浸漬させたときの上澄み液を、濃度が０．０１ｍｌ／ｌの硫酸で中和滴定して求められる中和滴定量（Ｂ）が３ｍｌ以下であることが好ましい。また、上記中和滴定量（Ａ）と該中和滴定量（Ｂ）との関係が、（Ａ）／（Ｂ）≦２となるものであることがより好ましい。 That is, the positive electrode active material used for the positive electrode of the present invention [when another active material other than the lithium transition metal composite oxide represented by the general formula (1) is used in combination, the other active material is also As all the positive electrode active materials contained, for example, the supernatant obtained when 2.5 g of the positive electrode active material was immersed in 50 g of neutral water was neutralized and titrated with sulfuric acid having a concentration of 0.01 ml / l. It is preferable that the neutralization titer (B) determined in this manner is 3 ml or less. More preferably, the relationship between the neutralization titer (A) and the neutralization titer (B) satisfies (A) / (B) ≦ 2.
すなわち、中和滴定量（Ｂ）が上記のような値の正極活物質であれば、含有しているアルカリ成分量が少なく、また、中和滴定量（Ａ）と中和滴定量（Ｂ）が上記の関係を満足する正極活物質であれば、正極合剤含有組成物の調製時におけるアルカリ成分の生成量が少ない。よって、上記のような特性を有する正極活物質を選択して用いることで、正極に係る正極合剤（正極合剤層）中のアルカリ成分量を低減して、中和滴定量（Ａ）を上記上限値以下に制御することができる。なお、中和滴定量（Ｂ）の測定方法は、上記の中和滴定量（Ａ）と同じである。中和滴定量（Ｂ）は、１ｍｌ以下であることがより好ましく、また、中和滴定量（Ｂ）の下限については、少ないほど好ましく、０ｍｌであることが最も好ましいが、通常は、０ｍｌとすることは困難である。更に（Ａ）／（Ｂ）は、２以下であることが好ましく、１であることが最も好ましい。 That is, if the neutralization titration amount (B) is the positive electrode active material having the above values, the amount of alkali components contained is small, and the neutralization titration amount (A) and the neutralization titration amount (B) Is a positive electrode active material that satisfies the above relationship, the amount of alkali components produced during the preparation of the positive electrode mixture-containing composition is small. Therefore, by selecting and using a positive electrode active material having the above characteristics, the amount of alkali components in the positive electrode mixture (positive electrode mixture layer) relating to the positive electrode is reduced, and the neutralization titration amount (A) is determined. It can be controlled below the upper limit. In addition, the measuring method of neutralization titer (B) is the same as said neutralization titer (A). The neutralization titer (B) is more preferably 1 ml or less, and the lower limit of the neutralization titer (B) is preferably as small as possible, and most preferably 0 ml. It is difficult to do. Further, (A) / (B) is preferably 2 or less, and most preferably 1.
また、正極活物質として用いる上記一般式（１）で表されるリチウム遷移金属複合酸化物は、その平均粒径［積算で５０％となる粒径（Ｄ５０）］が５μｍ以上、より好ましくは１０μｍ以上であって、２５μｍ以下、より好ましくは１５μｍ以下であり、かつ比表面積が、０．１ｍ２／ｇ以上、より好ましくは０．２ｍ２／ｇ以上であって、０．４ｍ２／ｇ以下、より好ましくは０．３以下ｍ２／ｇであることが望ましい。上記一般式（１）で表されるリチウム遷移金属複合酸化物がこのような形態を有している場合には、比較的強固であり、また、凝集性も向上するため、例えば、正極合剤含有組成物の調製の際に強いせん断力をかけて混練しても、該複合酸化物の１次粒子の崩壊が生じにくく、２次粒子からの１次粒子の崩落も抑えられるため、該調製によるアルカリ成分量の増大が抑制できる。更に、リチウム遷移金属複合酸化物粒子に付着しているアルカリ成分（炭酸リチウム）の量も少なくすることができる。よって、上記一般式（１）で表されるリチウム遷移金属複合酸化物として、このような形態のものを選択して用いることで、正極製造に用いる正極活物質の中和滴定量（Ｂ）を上記好適値に制御することが可能であり、更には、正極の有する正極合剤の中和滴定量（Ａ）を上記所定値に制御できる。 Further, the lithium transition metal composite oxide represented by the above general formula (1) used as the positive electrode active material has an average particle size [particle size (D 50 ) of 50% in total] of 5 μm or more, more preferably 10 μm or more, 25 μm or less, more preferably 15 μm or less, and a specific surface area of 0.1 m 2 / g or more, more preferably 0.2 m 2 / g or more, and 0.4 m 2 / g. Below, it is more desirable that it is 0.3 or less m 2 / g. When the lithium transition metal composite oxide represented by the general formula (1) has such a form, it is relatively strong and also improves the cohesiveness. Even if a strong shearing force is applied during the preparation of the containing composition, the primary particles of the composite oxide are unlikely to collapse, and the primary particles are prevented from collapsing from the secondary particles. An increase in the amount of alkali components due to the can be suppressed. Furthermore, the amount of the alkali component (lithium carbonate) adhering to the lithium transition metal composite oxide particles can be reduced. Therefore, by selecting and using the lithium transition metal composite oxide represented by the general formula (1) in such a form, the neutralization titration amount (B) of the positive electrode active material used for positive electrode production can be obtained. It is possible to control to the above-mentioned preferable value, and furthermore, the neutralization titration amount (A) of the positive electrode mixture possessed by the positive electrode can be controlled to the predetermined value.
なお、本明細書でいう上記一般式（１）で表されるリチウム遷移金属複合酸化物の平均粒径は、レーザー式の粒度分布測定装置（マイクロトラック社製「ＨＲＡ（９３２０−Ｘ１００）」」）を用いて、純水に試料を分散させ、光吸収モードの条件で、体積頻度の積算で５０％となる粒径（Ｄ５０）として求めた値である。また、本明細書でいう上記一般式（１）で表されるリチウム遷移金属複合酸化物の比表面積は、Ｎ２ガス吸着を利用した１点式のＢＥＴ測定装置（マウンテック社製「Ｍａｃｓｏｒｂ ＨＭ−１２０１」）を用いて、前処理として、Ｎ２ガスフロー中、１５０℃の環境下で１時間保持した後に測定することにより得られる値である。 The average particle size of the lithium transition metal composite oxide represented by the general formula (1) referred to in the present specification is a laser-type particle size distribution measuring device (“HRA (9320-X100)” manufactured by Microtrack). ) Is used to disperse the sample in pure water, and the value obtained as the particle diameter (D 50 ) of 50% by volume frequency integration under the conditions of the light absorption mode. In addition, the specific surface area of the lithium transition metal composite oxide represented by the general formula (1) referred to in the present specification is a one-point BET measuring device using N 2 gas adsorption (“Macsorb HM-” manufactured by Mountec Co., Ltd.). 1201 ") as a pretreatment, and a value obtained by measuring after holding for 1 hour in an environment of 150 ° C in an N 2 gas flow.
本発明の正極に用いる結着剤としては、熱可塑性樹脂、熱硬化性樹脂のいずれであってもよい。具体的には、例えば、ポリエチレン、ポリプロピレンなどのポリオレフィン；ポリテトラフルオロエチレン（ＰＴＦＥ）、ポリフッ化ビニリデン（ＰＶＤＦ）、テトラフルオロエチレン−ヘキサフルオロエチレン共重合体、テトラフルオロエチレン−ヘキサフルオロプロピレン共重合体（ＦＥＰ）、テトラフルオロエチレン−パーフルオロアルキルビニルエーテル共重合体（ＰＦＡ）、フッ化ビニリデン−ヘキサフルオロプロピレン共重合体、フッ化ビニリデン−クロロトリフルオロエチレン共重合体、エチレン−テトラフルオロエチレン共重合体（ＥＴＦＥ樹脂）、ポリクロロトリフルオロエチレン（ＰＣＴＦＥ）、フッ化ビニリデン−ペンタフルオロプロピレン共重合体、プロピレン−テトラフルオロエチレン共重合体、エチレン−クロロトリフルオロエチレン共重合体（ＥＣＴＦＥ）、フッ化ビニリデン−ヘキサフルオロプロピレン−テトラフルオロエチレン共重合体、フッ化ビニリデン−パーフルオロメチルビニルエーテル−テトラフルオロエチレン共重合体などのフッ素樹脂；スチレンブタジエンゴム（ＳＢＲ）；エチレン−アクリル酸共重合体または該共重合体のＮａ＋イオン架橋体；エチレン−メタクリル酸共重合体または該共重合体のＮａ＋イオン架橋体；エチレン−アクリル酸メチル共重合体または該共重合体のＮａ＋イオン架橋体；エチレン−メタクリル酸メチル共重合体または該共重合体のＮａ＋イオン架橋体；などが挙げられ、これらの材料を１種単独で用いてもよく、２種以上を併用しても構わない。これらの材料の中でも、ＰＶＤＦ、ＰＴＦＥが特に好ましい。 The binder used for the positive electrode of the present invention may be either a thermoplastic resin or a thermosetting resin. Specifically, for example, polyolefins such as polyethylene and polypropylene; polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), tetrafluoroethylene-hexafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer (ETFE resin), polychlorotrifluoroethylene (PCTFE), vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetrafluoroethylene copolymer, ethylene-chloro Fluoropolymers such as trifluoroethylene copolymer (ECTFE), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene copolymer; styrene butadiene rubber (SBR) ); Ethylene-acrylic acid copolymer or Na + ion crosslinked product of the copolymer; ethylene-methacrylic acid copolymer or Na + ion crosslinked product of the copolymer; ethylene-methyl acrylate copolymer or the copolymer Copolymer Na + ion cross-linked product; ethylene-methyl methacrylate copolymer or Na + ion cross-linked product of the copolymer; and the like, and these materials may be used alone or in combination. You may use the above together. Among these materials, PVDF and PTFE are particularly preferable.
本発明の正極は、上記の通り、正極活物質、導電助剤および結着剤を含有する正極合剤で構成される正極合剤層を、集電体となる導電性基体の片面または両面に形成した形態を有している。集電体としては、構成される電池において実質上化学的に安定な電子伝導体であれば特に制限されない。例えば、集電体を構成する材料としては、例えば、アルミニウムやその合金、ステンレス鋼、ニッケルやその合金、チタンやその合金、炭素、導電性樹脂などの他に、アルミニウムまたはステンレス鋼の表面にカーボンまたはチタンを処理させたものなどが用いられる。これらの中でも、アルミニウムおよびアルミニウム合金が特に好ましい。これらの材料は表面を酸化して用いることもできる。また、表面処理により集電体表面に凹凸を付けることが好ましい。集電体の形状としては、フォイルの他、フィルム、シート、ネット、パンチングされたもの、ラス体、多孔質体、発泡体、繊維群の成形体などが挙げられる。集電体の厚みは特に限定されないが、例えば、１〜５００μｍであることが好ましい。 As described above, the positive electrode of the present invention has a positive electrode mixture layer composed of a positive electrode mixture containing a positive electrode active material, a conductive additive, and a binder on one or both surfaces of a conductive substrate serving as a current collector. It has a formed form. The current collector is not particularly limited as long as it is an electron conductor that is substantially chemically stable in the battery that is configured. For example, the material constituting the current collector may be, for example, aluminum or its alloy, stainless steel, nickel or its alloy, titanium or its alloy, carbon, conductive resin, etc. Or what processed titanium is used. Of these, aluminum and aluminum alloys are particularly preferable. These materials can also be used after oxidizing the surface. Moreover, it is preferable to give unevenness | corrugation to the collector surface by surface treatment. Examples of the shape of the current collector include films, sheets, nets, punched materials, lath bodies, porous bodies, foamed bodies, and molded bodies of fiber groups, in addition to foils. Although the thickness of a collector is not specifically limited, For example, it is preferable that it is 1-500 micrometers.
正極合剤含有組成物（ペースト、スラリーなど）の調製方法としては、例えば、（１）導電助剤と結着剤と溶剤を予め強せん断分散装置で混練し、この分散体に正極活物質を添加して、更に強せん断分散装置で混練して調製する方法、（２）正極活物質と結着剤と溶剤との混合物を分散させてペースト状などの分散体とし、これとは別に導電助剤と結着剤と溶剤とを強せん断分散装置で混練して別分散体とし、前者の分散体に後者の別分散体を添加して更に分散させることにより調製する方法、（３）正極活物質と導電助剤と結着剤と溶剤との混合物を強せん断分散装置で混練して調製する方法、などが挙げられる。 As a method for preparing a positive electrode mixture-containing composition (paste, slurry, etc.), for example, (1) a conductive assistant, a binder, and a solvent are kneaded in advance with a strong shearing dispersion device, and a positive electrode active material is added to this dispersion. (2) A mixture of a positive electrode active material, a binder, and a solvent is dispersed to form a dispersion such as a paste. A method of preparing a dispersion by kneading an agent, a binder and a solvent with a strong shearing dispersion device to add another dispersion to the former dispersion, and (3) positive electrode active And a method in which a mixture of a substance, a conductive additive, a binder, and a solvent is kneaded with a high shear disperser.
正極合剤含有組成物の調製に用いる溶剤としては、例えば、ＮＭＰが挙げられる。 Examples of the solvent used for preparing the positive electrode mixture-containing composition include NMP.
正極合剤含有組成物の調製に用いる上記の強せん断分散装置としては、例えば、混練のための２枚のブレードと１本の高速撹拌機を具備する三軸型のプラネタリーミキサー；混練のための２枚のブレードと２本の高速撹拌機を具備する四軸型のプラネタリーミキサー［浅田鉄工社製「プラネタリーディスパ（商品名）」など］；三枚のブレードを有する三軸型のプラネタリーミキサー［井上製作所社製「トリミックス（商品名）」など］；ミルに代表されるメディアミル；ニーダー；連続式２軸混練機；コロイドミル；ロールミル；塗料（正極合剤含有組成物）にジェット流を発生させ、液―液間のせん断により分散を行うホモジナイザー型分散機；機械精度を高め、３０００〜２００００ｍｉｎ−１の高速運転可能な高速回転ホモジナイザー型分散機であるクレアミックス（商品名、エム・テクニック社製）やユニバーサルミキサー（商品名、パウレック社製）；などが例示できる。 Examples of the above-described high shear dispersion device used for the preparation of the positive electrode mixture-containing composition include a triaxial planetary mixer having two blades for kneading and one high-speed stirrer; A four-axis planetary mixer equipped with two blades and two high-speed stirrers (such as “Planetary Dispa (trade name)” manufactured by Asada Tekko Co., Ltd.); a three-axis planetar with three blades Lee mixer [Intrie Corporation's "Trimix (trade name)"etc.]; Media mill represented by mill; Kneader; Continuous twin-screw kneader; Colloid mill; Roll mill; Paint (Positive electrode mixture-containing composition) A homogenizer type disperser that generates a jet flow and disperses by shearing between liquid and liquid; high speed rotating homogenizer capable of high speed operation of 3000 to 20000 min −1 with improved mechanical accuracy Examples include Clairemix (trade name, manufactured by M Technique Co., Ltd.) and universal mixer (trade name, manufactured by POWREC Co., Ltd.).
本発明の正極は、上記の手法によって調製された正極合剤含有組成物を、集電体の片面または両面に塗布し、乾燥して溶剤を除去した後、カレンダー成形などのプレス処理を施して、正極合剤層の厚みと密度を調整する工程を経て作製される。 In the positive electrode of the present invention, the positive electrode mixture-containing composition prepared by the above method is applied to one or both sides of the current collector, dried to remove the solvent, and then subjected to press treatment such as calendering. It is produced through a step of adjusting the thickness and density of the positive electrode mixture layer.
このようにして得られる本発明の正極においては、正極合剤層の密度が、例えば、３．２ｇ／ｃｍ３以上、より好ましくは３．３ｇ／ｃｍ３以上であって、３．９ｇ／ｃｍ３以下であることが望ましい。正極の有する正極合剤層をこのように高密度とすることにより、該正極を有する電池をより高容量のものとすることができる。なお、ここでいう正極合剤層の密度は、以下の方法により測定されるものである。まず、正極を１ｃｍ×１ｃｍの大きさに切り取り、マイクロメータで厚み（ｌ１）を、精密天秤で質量（ｍ１）を測定する。次に、正極合剤層を削り取り、集電体のみを取り出して、その集電体の厚み（ｌｃ）と質量（ｍｃ）を正極と同様に測定する。得られた厚みと質量から、以下の式によって正極合剤層密度（ｄｃａ）を求める（なお、上記の厚みの単位はｃｍ、質量の単位はｇである）。
ｄｃａ＝（ｍ１−ｍｃ）／（ｌ１−ｌｃ）
In the positive electrode of the present invention thus obtained, the density of the positive electrode mixture layer is, for example, 3.2 g / cm 3 or more, more preferably 3.3 g / cm 3 or more, and 3.9 g / cm 3. It is desirable to be 3 or less. By making the positive electrode mixture layer of the positive electrode have such a high density, a battery having the positive electrode can be made to have a higher capacity. In addition, the density of the positive mix layer here is measured by the following method. First, it cuts a positive electrode to a size of 1 cm × 1 cm, a thickness micrometer (l 1), measuring the mass (m 1) a precision balance. Next, we scraped off the positive electrode mixture layer, and extract only the collector, measuring the thickness of the current collector (l c) mass (m c) in the same manner as the positive electrode. From the obtained thickness and mass, the positive electrode mixture layer density (d ca ) is determined by the following formula ( note that the unit of thickness is cm and the unit of mass is g).
d ca = (m 1 −m c ) / (l 1 −l c )
なお、正極合剤層の密度を求める方法は、必ずしも上記方法に限定されるものではなく、正確に求めることができるのであれば、他の方法を用いてもよい。ここで、正極合剤層中の成分組成としては、正極合剤層全量中、例えば、正極活物質の含有量が９６〜９９質量％、導電助剤の含有量が０．５〜１．５質量％、結着剤の含有量が０．５〜２．５質量％であることが好ましい。本発明の正極では、上記特定の比表面積を有する炭素材料を導電助剤に用いることで、正極合剤層中の導電助剤含有量を低減でき、これに伴って結着剤の含有量も低減できることから、正極合剤層の密度をより容易に高めることが可能であり、該正極を有する電池の高容量化を達成できる。 In addition, the method of calculating | requiring the density of a positive mix layer is not necessarily limited to the said method, You may use another method, if it can calculate | require correctly. Here, the component composition in the positive electrode mixture layer is, for example, 96 to 99% by mass of the positive electrode active material and 0.5 to 1.5% of the conductive auxiliary agent in the total amount of the positive electrode mixture layer. It is preferable that the content of the binder is 0.5 to 2.5% by mass. In the positive electrode of the present invention, the conductive material content in the positive electrode mixture layer can be reduced by using the carbon material having the specific surface area as the conductive aid, and the binder content is accordingly reduced. Since the density can be reduced, the density of the positive electrode mixture layer can be increased more easily, and the capacity of the battery having the positive electrode can be increased.
本発明の非水電解質二次電池は、上記本発明の正極を有していればよく、他の構成要素については、従来公知の非水電解質二次電池に採用されている各構成要素を適用することができる。 The non-aqueous electrolyte secondary battery of the present invention only needs to have the positive electrode of the present invention, and for other components, each component employed in a conventionally known non-aqueous electrolyte secondary battery is applied. can do.
本発明の非水電解質二次電池の負極としては、例えば、負極活物質を含有する負極合剤層を集電体表面に形成してなるものが挙げられる。負極合剤層は、負極活物質の他に、結着剤や導電助剤（必要に応じて）を含有しており、例えば、負極活物質および結着剤（更には導電助剤）などを含む混合物（負極合剤）に、適当な溶剤を加えて十分に混練して得られる負極合剤含有組成物（スラリーなど）を、集電体表面に塗布し乾燥することで、所望の厚みとしつつ形成することができる。 As a negative electrode of the nonaqueous electrolyte secondary battery of the present invention, for example, a negative electrode mixture layer containing a negative electrode active material is formed on the current collector surface. The negative electrode mixture layer contains, in addition to the negative electrode active material, a binder and a conductive aid (if necessary). For example, the negative electrode active material and the binder (and further a conductive aid) A negative electrode mixture-containing composition (slurry, etc.) obtained by adding an appropriate solvent to the mixture (negative electrode mixture) and thoroughly kneading is applied to the surface of the current collector and dried to obtain a desired thickness. Can be formed.
負極活物質としては、例えば、天然黒鉛（鱗片状黒鉛）、人造黒鉛、膨張黒鉛などの黒鉛材料；ピッチをか焼して得られるコークスなどの易黒鉛化性炭素質材料；フルフリルアルコール樹脂（ＰＦＡ）やポリパラフェニレン（ＰＰＰ）およびフェノール樹脂を低温焼成して得られる非晶質炭素などの難黒鉛化性炭素質材料；などの炭素材料が挙げられる。また、炭素材料の他に、リチウムやリチウム含有化合物も負極活物質として用いることができる。リチウム含有化合物としては、Ｌｉ−Ａｌなどのリチウム合金や、Ｓｉ、Ｓｎなどのリチウムとの合金化が可能な元素を含む合金が挙げられる。更にＳｎ酸化物やＳｉ酸化物などの酸化物系材料も用いることができる。負極合剤全量中における負極活物質含有量は、例えば、９７〜９９質量％であることが好ましい。 Examples of the negative electrode active material include graphite materials such as natural graphite (flaky graphite), artificial graphite, and expanded graphite; graphitizable carbonaceous materials such as coke obtained by calcining pitch; furfuryl alcohol resin ( Carbon materials such as non-graphitizable carbonaceous materials such as amorphous carbon obtained by low-temperature firing of PFA), polyparaphenylene (PPP), and phenol resins. In addition to the carbon material, lithium or a lithium-containing compound can also be used as the negative electrode active material. Examples of the lithium-containing compound include lithium alloys such as Li—Al, and alloys containing elements that can be alloyed with lithium such as Si and Sn. Furthermore, oxide-based materials such as Sn oxide and Si oxide can also be used. The negative electrode active material content in the total amount of the negative electrode mixture is preferably 97 to 99% by mass, for example.
導電助剤は、電子伝導性材料であれば特に限定されないし、使用しなくても構わない。導電助剤の具体例としては、アセチレンブラック；ケッチェンブラック；チャンネルブラック、ファーネスブラック、ランプブラック、サーマルブラックなどのカーボンブラック類；炭素繊維；などの炭素材料の他、金属繊維などの導電性繊維類；フッ化カーボン；銅、ニッケルなどの金属粉末類；ポリフェニレン誘導体などの有機導電性材料；などが挙げられ、これらを１種単独で用いてもよく、２種以上を併用しても構わない。これらの中でも、アセチレンブラックや炭素繊維が特に好ましい。負極に導電助剤を使用する場合には、負極合剤全量中における導電助剤含有量を１〜１０質量％とすることが望ましい。 The conductive aid is not particularly limited as long as it is an electron conductive material, and may not be used. Specific examples of conductive aids include acetylene black; ketjen black; carbon blacks such as channel black, furnace black, lamp black, and thermal black; carbon materials such as carbon fibers; and conductive fibers such as metal fibers. Carbon fluoride, metal powders such as copper and nickel, organic conductive materials such as polyphenylene derivatives, and the like. These may be used alone or in combination of two or more. . Among these, acetylene black and carbon fiber are particularly preferable. When using a conductive additive for the negative electrode, the conductive auxiliary agent content in the total amount of the negative electrode mixture is preferably 1 to 10% by mass.
負極合剤層に係る結着剤としては、熱可塑性樹脂、熱硬化性樹脂のいずれであってもよい。具体的には、例えば、上記本発明の正極に係る結着剤と同じ材料が使用でき、それらの材料を１種単独で用いてもよく、２種以上を併用しても構わない。その中でも、ＰＶＤＦ、ＳＢＲ、エチレン−アクリル酸共重合体または該共重合体のＮａ＋イオン架橋体、エチレン−メタクリル酸共重合体または該共重合体のＮａ＋イオン架橋体、エチレン−アクリル酸メチル共重合体または該共重合体のＮａ＋イオン架橋体、エチレン−メタクリル酸メチル共重合体または該共重合体のＮａ＋イオン架橋体が特に好ましい。負極合剤全量中における結着剤含有量は、例えば、１〜５質量％であることが望ましい。 As a binder concerning a negative mix layer, any of a thermoplastic resin and a thermosetting resin may be sufficient. Specifically, for example, the same material as the binder according to the positive electrode of the present invention can be used, and these materials may be used alone or in combination of two or more. Among them, PVDF, SBR, ethylene-acrylic acid copolymer or Na + ion crosslinked product of the copolymer, ethylene-methacrylic acid copolymer or Na + ion crosslinked product of the copolymer, ethylene-methyl acrylate A copolymer or a Na + ion crosslinked product of the copolymer, an ethylene-methyl methacrylate copolymer or a Na + ion crosslinked product of the copolymer is particularly preferred. The binder content in the total amount of the negative electrode mixture is preferably, for example, 1 to 5% by mass.
負極に用いる集電体としては、本発明の非水電解質二次電池において、実質上、化学的に安定な電子伝導体であれば特に限定されない。かかる集電体を構成する材料としては、例えば、ステンレス鋼、ニッケルやその合金、銅やその合金、チタンやその合金、炭素、導電性樹脂などの他に、銅またはステンレス鋼の表面にカーボンまたはチタンを処理させたものなどが用いられる。これらの中でも、銅および銅合金が特に好ましい。これらの材料は表面を酸化して用いることもできる。また、表面処理により集電体表面に凹凸を付けることが好ましい。集電体の形状としては、フォイルの他、フィルム、シート、ネット、パンチングされたもの、ラス体、多孔質体、発泡体、繊維群の成形体などが挙げられる。集電体の厚みは特に限定されないが、例えば、１〜５００μｍであることが好ましい。 The current collector used for the negative electrode is not particularly limited as long as it is a substantially chemically stable electronic conductor in the nonaqueous electrolyte secondary battery of the present invention. Examples of the material constituting the current collector include stainless steel, nickel or an alloy thereof, copper or an alloy thereof, titanium or an alloy thereof, carbon, conductive resin, carbon, or the like on the surface of copper or stainless steel. A material obtained by treating titanium is used. Among these, copper and copper alloys are particularly preferable. These materials can also be used after oxidizing the surface. Moreover, it is preferable to give unevenness | corrugation to the collector surface by surface treatment. Examples of the shape of the current collector include films, sheets, nets, punched materials, lath bodies, porous bodies, foamed bodies, and molded bodies of fiber groups, in addition to foils. Although the thickness of a collector is not specifically limited, For example, it is preferable that it is 1-500 micrometers.
なお、負極合剤層を形成するための負極合剤含有組成物に用い得る溶剤としては、例えば、水などが挙げられる。 In addition, as a solvent which can be used for the negative mix mixture containing composition for forming a negative mix layer, water etc. are mentioned, for example.
本発明の非水電解質二次電池に係る非水電解質としては、例えば、下記の非水系溶媒中に、下記の無機イオン塩を溶解させることで調製した溶液（非水電解液）が使用できる。 As the nonaqueous electrolyte according to the nonaqueous electrolyte secondary battery of the present invention, for example, a solution (nonaqueous electrolyte) prepared by dissolving the following inorganic ion salt in the following nonaqueous solvent can be used.
溶媒としては、例えば、エチレンカーボネート（ＥＣ）、プロピレンカーボネート（ＰＣ）、ブチレンカーボネート（ＢＣ）、ジメチルカーボネート（ＤＭＣ）、ジエチルカーボネート（ＤＥＣ）、メチルエチルカーボネート（ＭＥＣ）、γ−ブチロラクトン、１，２−ジメトキシエタン、テトラヒドロフラン、２−メチルテトラヒドロフラン、ジメチルスルフォキシド、１，３−ジオキソラン、ホルムアミド、ジメチルホルムアミド、ジオキソラン、アセトニトリル、ニトロメタン、蟻酸メチル、酢酸メチル、燐酸トリエステル、トリメトキシメタン、ジオキソラン誘導体、スルホラン、３−メチル−２−オキサゾリジノン、プロピレンカーボネート誘導体、テトラヒドロフラン誘導体、ジエチルエーテル、１，３−プロパンサルトンなどの非プロトン性有機溶媒を１種単独で、または２種以上を混合した混合溶媒として用いることができる。 Examples of the solvent include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), γ-butyrolactone, 1, 2 -Dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphate triester, trimethoxymethane, dioxolane derivatives, Sulfolane, 3-methyl-2-oxazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, diethyl ether, 1,3-propane sultone, etc. It can be an aprotic organic solvent singly mixed solvent or a mixture of two or more.
非水電解質に係る無機イオン塩としては、例えば、ＬｉＣｌＯ４ 、ＬｉＰＦ６ 、ＬｉＢＦ４ 、ＬｉＡｓＦ６ 、ＬｉＳｂＦ６ 、ＬｉＣＦ３ＳＯ３ 、ＬｉＣＦ３ＣＯ２ 、Ｌｉ２Ｃ２Ｆ４（ＳＯ３）２、ＬｉＮ（ＣＦ３ＳＯ２）２、ＬｉＣ（ＣＦ３ＳＯ２）３、ＬｉＣｎＦ２ｎ＋１ＳＯ３（ｎ≧２）、ＬｉＮ（ＲｆＯＳＯ２）２〔ここでＲｆはフルオロアルキル基〕などのリチウム塩から選ばれる少なくとも１種が挙げられる。このリチウム塩の電解液中の濃度としては、０．９〜１．８ｍｏｌ／ｌとすることが好ましく、１．０〜１．６ｍｏｌ／ｌとすることがより好ましい。 The inorganic ion salt according to the non-aqueous electrolyte, for example, LiClO 4, LiPF 6, LiBF 4, LiAsF 6, LiSbF 6, LiCF 3 SO 3, LiCF 3 CO 2, Li 2 C 2 F 4 (SO 3) 2, From lithium salts such as LiN (CF 3 SO 2 ) 2 , LiC (CF 3 SO 2 ) 3 , LiC n F 2n + 1 SO 3 (n ≧ 2), LiN (RfOSO 2 ) 2 [where Rf is a fluoroalkyl group] There may be mentioned at least one selected. The concentration of the lithium salt in the electrolytic solution is preferably 0.9 to 1.8 mol / l, and more preferably 1.0 to 1.6 mol / l.
本発明の非水電解質二次電池内では、上記正極と上記負極との間に、上記の非水電解質を含ませたセパレータが配される。セパレータとしては、大きなイオン透過度および所定の機械的強度を有する絶縁性の微多孔性薄膜が用いられる。また、セパレータとしては、一定温度以上（例えば１００〜１４０℃）で構成材料の溶融によって孔が閉塞し、抵抗を上げる機能を有するもの（すなわち、シャットダウン機能を有するもの）が好ましい。セパレータの具体例としては、耐有機溶剤性および疎水性を有するポリオレフィン系ポリマー（ポリエチレン、ポリプロピレンなど）、またはガラス繊維などの材料で構成されるシート（多孔質シート）、不織布若しくは織布；該ポリオレフィン系ポリマーの微粒子を接着剤で固着した多孔質体などが挙げられる。セパレータの孔径は、正負極より脱離した正負極の活物質、導電助剤および結着剤などが通過しない程度であることが好ましく、例えば、０．０１〜１μｍであることが望ましい。セパレータの厚みは、１０〜３００μｍとすることが一般的であるが、本発明では、１２〜２５μｍとすることが好ましい。また、セパレータの空孔率は、構成材料や厚みに応じて決定されるが、３０〜８０％であることが一般的である。 In the nonaqueous electrolyte secondary battery of the present invention, a separator containing the nonaqueous electrolyte is disposed between the positive electrode and the negative electrode. As the separator, an insulating microporous thin film having a large ion permeability and a predetermined mechanical strength is used. Moreover, as a separator, what has a function which a hole obstruct | occludes by fusion | melting of a constituent material above a fixed temperature (for example, 100-140 degreeC), and raises resistance (namely, what has a shutdown function) is preferable. Specific examples of the separator include a polyolefin polymer (polyethylene, polypropylene, etc.) having resistance to organic solvents and hydrophobicity, or a sheet (porous sheet) made of a material such as glass fiber, a nonwoven fabric or a woven fabric; the polyolefin And a porous body in which fine particles of a polymer are fixed with an adhesive. The pore diameter of the separator is preferably such that the active material of the positive and negative electrodes, the conductive auxiliary agent, the binder and the like detached from the positive and negative electrodes do not pass through, and is preferably 0.01 to 1 μm, for example. The thickness of the separator is generally 10 to 300 μm, but is preferably 12 to 25 μm in the present invention. Further, the porosity of the separator is determined according to the constituent material and thickness, but is generally 30 to 80%.
このようにして得られる本発明の非水電解質二次電池の正極は、リチウム金属基準で４．２〜４．５Ｖといった電圧まで充電しても安定しており、このような電圧のうち、より高電圧での充電を行うことで、更なる高容量化が達成できる。 The positive electrode of the non-aqueous electrolyte secondary battery of the present invention thus obtained is stable even when charged to a voltage of 4.2 to 4.5 V on the basis of lithium metal. A further increase in capacity can be achieved by charging at a high voltage.
以上のように、本発明の非水電解質二次電池は、高容量であり、かつ高温貯蔵時における安全性に優れていることから、こうした特性を活かして、主に角形電池が使用されるホータブル機器、例えば、携帯電話、デジタルカメラ、デジタルビデオカメラ、ポータブルオーディオプレイヤーなどの用途に好適に用いることができる。 As described above, the nonaqueous electrolyte secondary battery of the present invention has a high capacity and is excellent in safety during high-temperature storage. Therefore, taking advantage of these characteristics, a hortable type in which square batteries are mainly used is used. It can be suitably used for devices such as mobile phones, digital cameras, digital video cameras, and portable audio players.
以下、実施例に基づいて本発明を詳細に述べる。ただし、下記実施例は、本発明を制限するものではなく、前・後記の趣旨を逸脱しない範囲で変更実施をすることは、全て本発明の技術的範囲に包含される。 Hereinafter, the present invention will be described in detail based on examples. However, the following examples are not intended to limit the present invention, and all modifications made without departing from the spirit of the preceding and following descriptions are included in the technical scope of the present invention.
実施例１
＜正極の作製＞
正極活物質には、Ｌｉ１．００Ｍｎ０．３４Ｎｉ０．３３Ｃｏ０．３３Ｏ２で表されるリチウム遷移金属複合酸化物（マンガン・コバルト置換ニッケル酸リチウム）［すなわち、上記一般式（１）におけるδが０］を用いた。このリチウム遷移金属複合酸化物は、平均粒径が１０μｍ、ＢＥＴ比表面積が０．２５ｍ２／ｇであり、上記の方法によって測定した中和滴定量（Ｂ）は２．０ｍｌであった。
Example 1
<Preparation of positive electrode>
The positive electrode active material includes a lithium transition metal composite oxide (manganese / cobalt-substituted lithium nickelate) represented by Li 1.00 Mn 0.34 Ni 0.33 Co 0.33 O 2 [that is, the above general formula ( Δ in 1) was 0]. This lithium transition metal composite oxide had an average particle size of 10 μm, a BET specific surface area of 0.25 m 2 / g, and the neutralization titer (B) measured by the above method was 2.0 ml.
上記のリチウム遷移金属複合酸化物と、アセチレンブラック［導電助剤、電気化学工業株式会社製「デンカブラック（商品名）」、粉状品、平均１次粒径（電子顕微鏡法）：４０ｎｍ、ＢＥＴ比表面積：６５ｍ２／ｇ、ＤＢＰ吸油量：１８０ｃｃ／１００ｇ］と、ＰＶＤＦのＮＭＰ溶液とを、固形分質量比９８：１；１の比率で混合し、溶剤であるＮＭＰを加えて、エム・テクニック社製の「クレアミックス ＣＬＭ０．８（商品名）」を用いて、回転数：１００００ｍｉｎ−１で３０分間処理を行い、ペースト状の混合物とした。この混合物に、溶剤であるＮＭＰを更に加えて、回転数：１００００ｍｉｎ−１で１５分間処理を行い、正極合剤含有組成物を調製した。 Lithium transition metal composite oxide and acetylene black [conducting aid, “Denka Black (trade name)” manufactured by Denki Kagaku Kogyo Co., Ltd., powdered product, average primary particle size (electron microscopy): 40 nm, BET Specific surface area: 65 m 2 / g, DBP oil absorption: 180 cc / 100 g] and an NMP solution of PVDF were mixed at a solid mass ratio of 98: 1: 1, and NMP as a solvent was added. Using “CLEARMIX CLM0.8 (trade name)” manufactured by Technic Co., Ltd., the mixture was processed for 30 minutes at a rotational speed of 10000 min −1 to obtain a paste-like mixture. NMP which is a solvent was further added to this mixture, and the mixture was treated at a rotational speed of 10000 min −1 for 15 minutes to prepare a positive electrode mixture-containing composition.
上記の正極合剤含有組成物を、集電体であるアルミニウム箔（厚み：１５μｍ）の両面に塗布し、１２０℃で１２時間真空乾燥を施し、更にプレス処理を施して、集電体の両面に、厚みが５２μｍの正極合剤層を有する正極を作製した。上記の方法によって求めたプレス処理後の正極合剤層の密度は、３．４０ｇ／ｃｍ３であった。また、この正極における中和滴定量（Ａ）を上記の方法によって測定した。結果を表１に示す。 The positive electrode mixture-containing composition is applied to both sides of an aluminum foil (thickness: 15 μm), which is a current collector, vacuum-dried at 120 ° C. for 12 hours, and further subjected to a press treatment, whereby both sides of the current collector are applied. In addition, a positive electrode having a positive electrode mixture layer having a thickness of 52 μm was prepared. The density of the positive electrode mixture layer after the press treatment determined by the above method was 3.40 g / cm 3 . Moreover, the neutralization titer (A) in this positive electrode was measured by the above method. The results are shown in Table 1.
＜負極の作製＞
天然黒鉛：９７．５質量％、ＳＢＲ：１．５質量％、およびカルボキシメチルセルロース（増粘剤）：１質量％を、水を用いて混合してスラリー状の負極合剤含有組成物を調製した。この負極合剤含有組成物を、集電体である銅箔（厚み：８μｍ）の両面に塗布し、１２０℃で１２時間真空乾燥を施し、更にプレス処理を施して、集電体の両面に、厚みが６３μｍの負極合剤層を有する負極を作製した。正極合剤層の密度測定方法と同じ方法で求めたプレス処理後の負極合剤層の密度は、１．６５ｇ／ｃｍ３であった。
<Production of negative electrode>
Natural graphite: 97.5% by mass, SBR: 1.5% by mass, and carboxymethylcellulose (thickener): 1% by mass were mixed with water to prepare a slurry-like negative electrode mixture-containing composition. . This negative electrode mixture-containing composition was applied to both sides of a copper foil (thickness: 8 μm) as a current collector, vacuum-dried at 120 ° C. for 12 hours, and further subjected to a press treatment to form both sides of the current collector. A negative electrode having a negative electrode mixture layer with a thickness of 63 μm was prepared. The density of the negative electrode mixture layer after the press treatment obtained by the same method as the method for measuring the density of the positive electrode mixture layer was 1.65 g / cm 3 .
＜電極体の作製＞
上記の正極と負極とを、間にセパレータを挟んで重ね合わせ、これらを巻き取って電極体を作製した。セパレータには、厚みが１８μｍのポリエチレン製多孔膜を用いた。
<Production of electrode body>
The above positive electrode and negative electrode were overlapped with a separator in between, and these were wound up to produce an electrode body. A polyethylene porous film having a thickness of 18 μm was used as the separator.
＜非水電解液の調製＞
ＥＣとＭＥＣとＤＥＣの混合溶媒（体積比が１：１：1）に、１ｍｏｌ／ｌの濃度でＬｉＰＦ６を溶解させて非水電解液（非水電解質）を調製した。
<Preparation of non-aqueous electrolyte>
LiPF 6 was dissolved at a concentration of 1 mol / l in a mixed solvent of EC, MEC and DEC (volume ratio 1: 1: 1) to prepare a non-aqueous electrolyte (non-aqueous electrolyte).
＜電池の組み立て＞
上記の電極体および非水電解液を用いて、角形非水電解質二次電池を組み立てた。組み立て方法は、まず、上記電極体の各端面に集電板を溶接により接合した。次に、集電板のリード部を蓋体に取り付けられている電極端子集電機構と接続した。その後、正極缶の内部に電極体を収容して、正極缶の開口部に蓋体を溶接固定した。最後に蓋体に設けられた注液孔から正極缶内に非水電解液を注入して、厚さ４ｍｍ、幅３４ｍｍ、高さ５０ｍｍで、図３に示す構造で、図４に示す外観の角形非水電解質二次電池を作製した。
<Battery assembly>
A prismatic nonaqueous electrolyte secondary battery was assembled using the above electrode body and nonaqueous electrolyte. In the assembly method, first, a current collector plate was joined to each end face of the electrode body by welding. Next, the lead part of the current collecting plate was connected to an electrode terminal current collecting mechanism attached to the lid. Then, the electrode body was accommodated inside the positive electrode can, and the lid body was welded and fixed to the opening of the positive electrode can. Finally, a non-aqueous electrolyte is injected into the positive electrode can through the injection hole provided in the lid, and the structure shown in FIG. 3 has a thickness of 4 mm, a width of 34 mm, and a height of 50 mm. A square nonaqueous electrolyte secondary battery was produced.
ここで図３および図４に示す電池について説明すると、正極１と負極２は上記のようにセパレータ３を介して渦巻状に巻回した巻回構造の電極体６として、角形の正極缶４に非水電解液とともに収容されている。ただし、図３では、煩雑化を避けるため、正極１や負極２の作製にあたって使用した集電体としての金属箔や非水電解液などは図示していない。 Here, the battery shown in FIGS. 3 and 4 will be described. The positive electrode 1 and the negative electrode 2 are formed into a rectangular positive electrode can 4 as an electrode body 6 having a winding structure wound in a spiral shape through the separator 3 as described above. It is housed with a non-aqueous electrolyte. However, in FIG. 3, in order to avoid complication, a metal foil, a non-aqueous electrolyte, or the like as a current collector used in manufacturing the positive electrode 1 and the negative electrode 2 is not illustrated.
正極缶４はアルミニウム合金製で電池の外装材を構成するものであり、この正極缶４は正極端子を兼ねている。そして、正極缶４の底部にはポリエチレンシートからなる絶縁体５が配置され、上記正極１、負極２およびセパレータ３からなる電極体６からは、正極１および負極２のそれぞれ一端に接続された正極集電板７と負極集電板８が引き出されている。また、正極缶４の開口部を封口するアルミニウム合金製の蓋板９にはポリプロピレン製の絶縁パッキング１０を介してステンレス鋼製の端子１１が取り付けられ、この端子１１には絶縁体１２を介してステンレス鋼製のリード板（電極端子集電機構）１３が取り付けられている。 The positive electrode can 4 is made of an aluminum alloy and constitutes a battery exterior material. The positive electrode can 4 also serves as a positive electrode terminal. And the insulator 5 which consists of a polyethylene sheet is arrange | positioned at the bottom part of the positive electrode can 4, From the electrode body 6 which consists of the said positive electrode 1, the negative electrode 2, and the separator 3, the positive electrode connected to each one end of the positive electrode 1 and the negative electrode 2 A current collector plate 7 and a negative electrode current collector plate 8 are drawn out. A stainless steel terminal 11 is attached to an aluminum alloy cover plate 9 that seals the opening of the positive electrode can 4 via a polypropylene insulating packing 10, and an insulator 12 is connected to the terminal 11. A stainless steel lead plate (electrode terminal current collecting mechanism) 13 is attached.
そして、この蓋板９は上記正極缶４の開口部に挿入され、両者の接合部を溶接することによって、正極缶４の開口部が封口され、電池内部が密閉されている。 And this cover plate 9 is inserted in the opening part of the said positive electrode can 4, and the opening part of the positive electrode can 4 is sealed by welding the junction part of both, and the inside of a battery is sealed.
なお、蓋板９には、注液孔１４が設けられており、電池組み立ての際には、この注液孔１４から電池内に非水電解液が注入され、その後、注液孔１４は封止される。よって、図３では、注液孔１４と表現しているが、完成した電池においては、１４は封止された注液孔の跡である。また、蓋板９には、防爆用の安全弁１５が設けられている。 The lid plate 9 is provided with a liquid injection hole 14. When the battery is assembled, a nonaqueous electrolyte is injected into the battery from the liquid injection hole 14, and then the liquid injection hole 14 is sealed. Stopped. Therefore, in FIG. 3, although expressed as the liquid injection hole 14, in the completed battery, 14 is a mark of the sealed liquid injection hole. The cover plate 9 is provided with an explosion-proof safety valve 15.
この実施例１の電池では、正極リード体７を蓋板９に直接溶接することによって正極缶４と蓋板９とが正極端子として機能し、負極リード体８をリード板１３に溶接し、そのリード板１３を介して負極リード体８と端子１１とを導通させることによって端子１１が負極端子として機能するようになっているが、正極缶４の材質などによっては、その正負が逆になる場合もある。 In the battery of this Example 1, the positive electrode can 4 and the cover plate 9 function as a positive electrode terminal by directly welding the positive electrode lead body 7 to the cover plate 9, and the negative electrode lead body 8 is welded to the lead plate 13. The terminal 11 functions as a negative electrode terminal by conducting the negative electrode lead body 8 and the terminal 11 through the lead plate 13, but depending on the material of the positive electrode can 4, the sign may be reversed. There is also.
図４は上記図３に示す電池の外観を模式的に示す斜視図であり、この図４は上記電池が角形電池であることを示すことを目的として図示されたものであって、この図４では電池を概略的に示しており、電池の構成部材のうち特定のものしか図示していない。また、図３においても、電極体の内周側の部分は断面にしていない。 FIG. 4 is a perspective view schematically showing the external appearance of the battery shown in FIG. 3. FIG. 4 is shown for the purpose of showing that the battery is a square battery. FIG. 1 schematically shows a battery, and only specific members of the battery are shown. Also in FIG. 3, the inner peripheral portion of the electrode body is not cross-sectional.
実施例２
正極活物質に、Ｌｉ１．０２Ｍｎ０．３４Ｎｉ０．３３Ｃｏ０．３３Ｏ２で表されるリチウム遷移金属複合酸化物［すなわち、上記一般式（１）におけるδが０．０２］を用い、正極作製時のプレス処理の条件を調節して、正極合剤層の密度を表１に示すようにした他は、実施例１と同様にして非水電解質二次電池を作製した。実施例２で用いたリチウム遷移金属複合酸化物は、平均粒径が１０μｍ、ＢＥＴ比表面積が０．３０ｍ２／ｇであった。また、上記の方法によって測定した中和滴定量（Ｂ）を表１に示す。
Example 2
Lithium transition metal composite oxide represented by Li 1.02 Mn 0.34 Ni 0.33 Co 0.33 O 2 [that is, δ in the above general formula (1) is 0.02] is added to the positive electrode active material. A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1, except that the conditions of the press treatment during the production of the positive electrode were adjusted and the density of the positive electrode mixture layer was as shown in Table 1. The lithium transition metal composite oxide used in Example 2 had an average particle size of 10 μm and a BET specific surface area of 0.30 m 2 / g. In addition, Table 1 shows the neutralization titer (B) measured by the above method.
実施例３
正極活物質に、Ｌｉ１．０５Ｍｎ０．３４Ｎｉ０．３３Ｃｏ０．３３Ｏ２で表されるリチウム遷移金属複合酸化物［すなわち、上記一般式（１）におけるδが０．０５］を用い、正極作製時のプレス処理の条件を調節して、正極合剤層の密度を表１に示すようにした他は、実施例１と同様にして非水電解質二次電池を作製した。実施例３で用いたリチウム遷移金属複合酸化物は、平均粒径が１０μｍ、ＢＥＴ比表面積が０．２８ｍ２／ｇであった。また、上記の方法によって測定した中和滴定量（Ｂ）を表１に示す。
Example 3
Lithium transition metal composite oxide represented by Li 1.05 Mn 0.34 Ni 0.33 Co 0.33 O 2 [that is, δ in the above general formula (1) is 0.05] is added to the positive electrode active material. A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1, except that the conditions of the press treatment during the production of the positive electrode were adjusted and the density of the positive electrode mixture layer was as shown in Table 1. The lithium transition metal composite oxide used in Example 3 had an average particle size of 10 μm and a BET specific surface area of 0.28 m 2 / g. In addition, Table 1 shows the neutralization titer (B) measured by the above method.
比較例１
正極活物質に、Ｌｉ１．１３Ｍｎ０．３４Ｎｉ０．３３Ｃｏ０．３３Ｏ２で表されるリチウム遷移金属複合酸化物［すなわち、上記一般式（１）におけるδが０．１３］を用い、正極作製時のプレス処理の条件を調節して、正極合剤層の密度を表１に示すようにした他は、実施例１と同様にして非水電解質二次電池を作製した。比較例１で用いたリチウム遷移金属複合酸化物は、平均粒径が１０μｍ、ＢＥＴ比表面積が０．２５ｍ２／ｇであった。また、上記の方法によって測定した中和滴定量（Ｂ）を表１に示す。
Comparative Example 1
Lithium transition metal composite oxide represented by Li 1.13 Mn 0.34 Ni 0.33 Co 0.33 O 2 [that is, δ in the above general formula (1) is 0.13] is added to the positive electrode active material. A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1, except that the conditions of the press treatment during the production of the positive electrode were adjusted and the density of the positive electrode mixture layer was as shown in Table 1. The lithium transition metal composite oxide used in Comparative Example 1 had an average particle size of 10 μm and a BET specific surface area of 0.25 m 2 / g. In addition, Table 1 shows the neutralization titer (B) measured by the above method.
比較例２
正極活物質に、Ｍｎ含有量が多いＬｉ１．００Ｍｎ０．６Ｎｉ０．４Ｏ２で表されるリチウム遷移金属複合酸化物を用い、正極作製時のプレス処理の条件を調節して、正極合剤層の密度を表１に示すようにした他は、実施例１と同様にして非水電解質二次電池を作製した。比較例２で用いたリチウム遷移金属複合酸化物は、平均粒径が１０μｍ、ＢＥＴ比表面積が０．２０ｍ２／ｇであった。また、上記の方法によって測定した中和滴定量（Ｂ）を表１に示す。
Comparative Example 2
Using a lithium transition metal composite oxide represented by Li 1.00 Mn 0.6 Ni 0.4 O 2 having a high Mn content as the positive electrode active material, adjusting the conditions of the press treatment during the production of the positive electrode, A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that the density of the positive electrode mixture layer was as shown in Table 1. The lithium transition metal composite oxide used in Comparative Example 2 had an average particle size of 10 μm and a BET specific surface area of 0.20 m 2 / g. In addition, Table 1 shows the neutralization titer (B) measured by the above method.
比較例３
正極活物質に、Ｎｉ含有量が多いＬｉ１．００Ｎｉ０．８Ｃｏ０．２Ｏ２で表されるリチウム遷移金属複合酸化物を用い、正極作製時のプレス処理の条件を調節して、正極合剤層の密度を表１に示すようにした他は、実施例１と同様にして非水電解質二次電池を作製した。比較例３で用いたリチウム遷移金属複合酸化物は、平均粒径が１０μｍ、ＢＥＴ比表面積が０．３２ｍ２／ｇであった。また、上記の方法によって測定した中和滴定量（Ｂ）を、表１に示す。
Comparative Example 3
Using a lithium transition metal composite oxide represented by Li 1.00 Ni 0.8 Co 0.2 O 2 having a high Ni content as the positive electrode active material, adjusting the conditions of the press treatment during the production of the positive electrode, A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that the density of the positive electrode mixture layer was as shown in Table 1. The lithium transition metal composite oxide used in Comparative Example 3 had an average particle size of 10 μm and a BET specific surface area of 0.32 m 2 / g. Further, Table 1 shows the neutralization titration (B) measured by the above method.
参考例
正極活物質にコバルト酸リチウム（ＬｉＣｏＯ２）を用い、正極作製時のプレス処理の条件を調節して、正極合剤層の密度を表１に示すようにした他は、実施例１と同様にして非水電解質二次電池を作製した。
Reference Example Example 1 except that lithium cobalt oxide (LiCoO 2 ) was used as the positive electrode active material and the density of the positive electrode mixture layer was as shown in Table 1 by adjusting the conditions of the press treatment during the production of the positive electrode. Similarly, a nonaqueous electrolyte secondary battery was produced.
実施例１〜３および比較例１〜３の電池について、下記の各評価を行った。結果を表１に併記する。 The batteries of Examples 1 to 3 and Comparative Examples 1 to 3 were evaluated as follows. The results are also shown in Table 1.
＜放電容量＞
実施例１〜３および比較例１〜３の電池について、４．４Ｖ充電からの放電容量を測定した。測定においては、まず、０．２Ａで４．４Ｖまで定電流充電を行い、その後、電流値が０．０２Ａとなるまで定電圧充電を行った。次に、０．２Ａで３．０Ｖまで定電流放電を行って、電池容量（放電容量）を求めた。なお、充電後の正極の電位は、リチウム金属基準で４．３Ｖとなった。
<Discharge capacity>
About the battery of Examples 1-3 and Comparative Examples 1-3, the discharge capacity from 4.4V charge was measured. In the measurement, first, constant current charging was performed at 0.2 A to 4.4 V, and then constant voltage charging was performed until the current value reached 0.02 A. Next, constant current discharge was performed to 0.2V at 0.2 A, and battery capacity (discharge capacity) was obtained. Note that the potential of the positive electrode after charging was 4.3 V based on the lithium metal.
＜高温貯蔵後の電池膨れ＞
実施例１〜３および比較例１〜３の電池で、上記の放電容量測定を実施したものと別の電池について、上記の放電容量測定と同じ条件で定電流−定電圧充電を行った後に、８０℃の環境下で５日間貯蔵し、取り出した直後の電池の厚みを測定して、貯蔵前の電池の厚みからの変化（膨れ）を求めた。
<Battery swelling after high temperature storage>
After performing constant current-constant voltage charging under the same conditions as in the above discharge capacity measurement for the batteries of Examples 1 to 3 and Comparative Examples 1 to 3 and different batteries from which the above discharge capacity measurement was performed, The battery was stored for 5 days in an environment of 80 ° C., and the thickness of the battery immediately after removal was measured to determine the change (swelling) from the battery thickness before storage.
表１に示す結果から明らかなように、上記一般式（１）で表されるリチウム遷移金属複合酸化物を正極活物質に用い、中和滴定量（Ａ）が上記所定値を満足している実施例１〜３の電池では、放電容量が大きく、高容量化が達成されていると共に、８０℃で５日間貯蔵した後における電池の膨れも、コバルト酸リチウムを正極活物質に用い、４．２Ｖの電圧に充電した参考例の電池と同等程度に抑制できている。なお、参考例の電池を上記実施例と同じく４．４Ｖまで充電した後に貯蔵試験を行ったところ、電池の膨れは１．８５ｍｍとなった。 As is apparent from the results shown in Table 1, the lithium transition metal composite oxide represented by the general formula (1) is used as the positive electrode active material, and the neutralization titration amount (A) satisfies the predetermined value. In the batteries of Examples 1 to 3, the discharge capacity was large and the capacity was increased, and the swelling of the batteries after storage at 80 ° C. for 5 days also used lithium cobaltate as the positive electrode active material. It is suppressed to the same extent as the battery of the reference example charged to a voltage of 2V. In addition, when the storage test was performed after charging the battery of the reference example to 4.4 V as in the above example, the swelling of the battery was 1.85 mm.
実施例４〜６および比較例４〜５
正極活物質に、Ｌｉ１．００Ｍｎ０．３４Ｎｉ０．３３Ｃｏ０．３３Ｏ２で表されるリチウム遷移金属複合酸化物を用い、これらの平均粒径とＢＥＴ比表面積を表２に示すようにし、また、正極作製時のプレス処理の条件を調節して、正極合剤層の密度を表２に示すようにした他は、実施例１と同様にして非水電解質二次電池を作製した。これらの電池に関して、実施例１と同様にして、中和滴定量（Ａ）、中和滴定量（Ｂ）、放電容量、および高温貯蔵後の電池膨れを評価した。結果を表２に併記する。
Examples 4-6 and Comparative Examples 4-5
A lithium transition metal composite oxide represented by Li 1.00 Mn 0.34 Ni 0.33 Co 0.33 O 2 is used as the positive electrode active material, and the average particle diameter and BET specific surface area thereof are shown in Table 2. In addition, a nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that the conditions of the press treatment during production of the positive electrode were adjusted and the density of the positive electrode mixture layer was as shown in Table 2. did. For these batteries, the neutralization titer (A), the neutralization titer (B), the discharge capacity, and the battery swelling after high temperature storage were evaluated in the same manner as in Example 1. The results are also shown in Table 2.
表２に示す結果から明らかなように、平均粒径および比表面積が好適な上記一般式（１）で表されるリチウム遷移金属複合酸化物を正極活物質に用いた実施例４〜６では、電池の高容量化が達成されており、更には、高温貯蔵後の膨れも抑制されている。これに対し、比較例４では、リチウム遷移金属複合酸化物の比表面積が大きく、２次粒子の凝集性が低いために、強いせん断力をかけて正極合剤含有組成物の調製を行ったことにより、２次粒子が崩壊し、アルカリ成分が生成して、正極の正極合剤層中に残存しているアルカリ成分量が増大し、これにより電池の高温貯蔵時にガス発生量が増大して電池の膨れが大きくなったものと推定される。また、比較例５では、リチウム遷移金属複合酸化物の比表面積が非常に大きいために、正極合剤含有組成物の調製前から、リチウム遷移金属複合酸化物中に含有されているアルカリ成分量が多く、これにより電池の高温貯蔵時にガス発生量が増大して電池の膨れが大きくなったものと推定される。 As is clear from the results shown in Table 2, in Examples 4 to 6 in which the lithium transition metal composite oxide represented by the above general formula (1) having a suitable average particle diameter and specific surface area was used as the positive electrode active material, Higher capacity of the battery has been achieved, and furthermore, swelling after high temperature storage is also suppressed. On the other hand, in Comparative Example 4, the lithium transition metal composite oxide had a large specific surface area and low secondary particle agglomeration, so a positive shear mixture-containing composition was prepared by applying a strong shearing force. As a result, the secondary particles collapse, an alkali component is generated, and the amount of the alkali component remaining in the positive electrode mixture layer of the positive electrode increases, thereby increasing the amount of gas generated during high-temperature storage of the battery. It is presumed that the swelling of the swell increased. Moreover, in Comparative Example 5, since the specific surface area of the lithium transition metal composite oxide is very large, the amount of alkali components contained in the lithium transition metal composite oxide before the preparation of the positive electrode mixture-containing composition is increased. In many cases, it is presumed that the amount of gas generated during the high-temperature storage of the battery increased and the swelling of the battery increased.
以上のように、高電圧での充電を可能とし、より高容量の非水電解質二次電池を構成するための正極として、正極活物質に特定構造のリチウム遷移金属複合酸化物を用い、正極合剤含有組成物を強いせん断力をかけて調製する工程を経て作製した該活物質の充填性を高めた高容量の正極を使用するに当たり、該正極の正極合剤中のアルカリ成分量を制御することで、電池の高温貯蔵時における膨れの発生を抑制して、安全性の高い電池を提供することができる。また、正極の正極合剤中のアルカリ成分量を制御するに当たっては、特定の形態を有し、予め含有しているアルカリ成分量が少なく、より強固な正極活物質粒子を用いることで、正極合剤含有組成物の調製時のアルカリ成分の増大も抑えて、正極合剤中のアルカリ成分量が少ない正極を得ることができる。 As described above, a lithium transition metal composite oxide having a specific structure is used as a positive electrode active material as a positive electrode for enabling high-voltage charging and constituting a higher capacity non-aqueous electrolyte secondary battery. When using a high-capacity positive electrode with a high filling capacity of the active material prepared through a step of preparing an agent-containing composition by applying a strong shearing force, the amount of alkali components in the positive electrode mixture of the positive electrode is controlled. Thus, it is possible to provide a highly safe battery by suppressing the occurrence of swelling during high-temperature storage of the battery. In addition, in controlling the amount of the alkali component in the positive electrode mixture of the positive electrode, the positive electrode compound is obtained by using a stronger positive electrode active material particle having a specific form and containing a small amount of alkali component in advance. An increase in the alkali component during preparation of the agent-containing composition can also be suppressed, and a positive electrode with a small amount of alkali component in the positive electrode mixture can be obtained.
１ 正極
２ 負極
３ セパレータ
４ 正極缶
５ 絶縁体
６ 電極体
７ 正極集電板
８ 負極集電板
９ 蓋板
１０ 絶縁パッキング
１１ 端子
１２ 絶縁体
１３ リード板
１４ 注液孔
１５ 安全弁
DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Negative electrode 3 Separator 4 Positive electrode can 5 Insulator 6 Electrode body 7 Positive electrode current collector plate 8 Negative electrode current collector plate 9 Cover plate 10 Insulation packing 11 Terminal 12 Insulator 13 Lead plate 14 Injection hole 15 Safety valve
Claims (6)
上記正極合剤は、一般式Ｌｉ（１＋δ）ＭｎｘＮｉｙＣｏ（１−ｘ−ｙ）Ｏ２（０≦δ≦０．０５、０．１＜ｘ≦０．５、０．１＜ｙ≦０．５、０．６＜ｘ＋ｙ≦１．０）で表されるリチウム遷移金属複合酸化物を正極活物質として含有しており、かつ比表面積が５０〜１０００ｍ２／ｇの炭素材料を導電助剤として含有しており、
正極活物質全量中、上記リチウム遷移金属複合酸化物が５０質量％以上であり、
上記リチウム遷移金属複合酸化物として、平均粒径が５〜１８μｍであり、かつ比表面積が０．１〜０．４ｍ ２ ／ｇのものを用い、
上記正極合剤層中の導電助剤の含有量が０．５〜１．５質量％であり、
上記正極合剤層の密度が３．２〜３．９ｇ／ｃｍ ３ であり、
上記正極合剤２．５ｇを５０ｇの中性の水に浸漬させたときの上澄み液を、濃度が０．０１ｍｏｌ／ｌの硫酸で中和滴定して求められる中和滴定量（Ａ）が、４．５ｍｌ以下であることを特徴とする非水電解質二次電池用の正極。 A positive electrode for a non-aqueous electrolyte secondary battery having a positive electrode mixture layer composed of a positive electrode mixture containing a positive electrode active material, a conductive additive and a binder,
The positive electrode mixture has the general formula Li (1 + δ) Mn x Ni y Co (1-xy) O 2 (0 ≦ δ ≦ 0.05, 0.1 <x ≦ 0.5, 0.1 <y ≦ 0.5, 0.6 <x + y ≦ 1.0) containing a lithium transition metal composite oxide as a positive electrode active material and conducting a carbon material having a specific surface area of 50 to 1000 m 2 / g. Contains as an aid,
In the total amount of the positive electrode active material, the lithium transition metal composite oxide is 50% by mass or more,
As the lithium transition metal composite oxide, one having an average particle diameter of 5 to 18 μm and a specific surface area of 0.1 to 0.4 m 2 / g,
The content of the conductive additive in the positive electrode mixture layer is 0.5 to 1.5% by mass,
The positive electrode mixture layer has a density of 3.2 to 3.9 g / cm 3 ,
The neutralization titer (A) obtained by neutralizing titration of the supernatant obtained by immersing 2.5 g of the positive electrode mixture in 50 g of neutral water with sulfuric acid having a concentration of 0.01 mol / l, A positive electrode for a non-aqueous electrolyte secondary battery, characterized by being 4.5 ml or less.
The nonaqueous electrolyte secondary battery according to claim 5 , wherein a charge end voltage of the positive electrode is 4.2 to 4.5 V based on a lithium metal.
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| JP4766040B2 (en) * | 2007-12-07 | 2011-09-07 | 日亜化学工業株式会社 | A positive electrode active material for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery using the same. |
| JP5428487B2 (en) * | 2009-04-22 | 2014-02-26 | ソニー株式会社 | Positive electrode active material, method for producing positive electrode active material, and non-aqueous electrolyte battery |
| JP5584456B2 (en) * | 2009-12-10 | 2014-09-03 | 日本化学工業株式会社 | Positive electrode active material for lithium secondary battery, method for producing the same, and lithium secondary battery |
| JP5401296B2 (en) * | 2009-12-21 | 2014-01-29 | 株式会社日立製作所 | Positive electrode for lithium ion secondary battery and lithium ion secondary battery |
| JP5685817B2 (en) * | 2010-02-04 | 2015-03-18 | 株式会社村田製作所 | Electrode active material for non-aqueous electrolyte secondary battery and non-aqueous electrolyte secondary battery using the same |
| JP5734708B2 (en) * | 2011-03-14 | 2015-06-17 | 日立マクセル株式会社 | Nonaqueous electrolyte secondary battery and manufacturing method thereof |
| JP6026403B2 (en) * | 2011-03-24 | 2016-11-16 | Ｊｘ金属株式会社 | Positive electrode active material for lithium ion battery, positive electrode for lithium ion battery, and lithium ion battery |
| JP6026404B2 (en) * | 2011-03-24 | 2016-11-16 | Ｊｘ金属株式会社 | Positive electrode active material for lithium ion battery, positive electrode for lithium ion battery, and lithium ion battery |
| JP5894388B2 (en) * | 2011-07-26 | 2016-03-30 | 住友金属鉱山株式会社 | Cathode active material for non-aqueous electrolyte secondary battery, method for producing the same, and non-aqueous electrolyte secondary battery using the same |
| JP6468191B2 (en) * | 2013-09-17 | 2019-02-13 | 三洋電機株式会社 | Nonaqueous electrolyte secondary battery |
| JP6165036B2 (en) * | 2013-11-27 | 2017-07-19 | 株式会社クレハ | Vinylidene fluoride polymer aqueous composition and use thereof |
| JP2016136489A (en) * | 2015-01-23 | 2016-07-28 | 株式会社豊田自動織機 | Positive electrode and lithium ion secondary electrode |
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| EP1372202B8 (en) * | 2001-03-14 | 2013-12-18 | GS Yuasa International Ltd. | Positive electrode active material and nonaqueous electrolyte secondary cell comprising the same |
| JP4404179B2 (en) * | 2001-12-06 | 2010-01-27 | ソニー株式会社 | Positive electrode active material and secondary battery using the same |
| JP2004071518A (en) * | 2002-08-05 | 2004-03-04 | Kee:Kk | Compound for positive electrode containing modified polyvinylidene fluoride |
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