JP2013033641A - Electrode for nonaqueous secondary battery, and nonaqueous secondary battery - Google Patents
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本発明は、非水二次電池用電極及び非水二次電池に関する。 The present invention relates to an electrode for a non-aqueous secondary battery and a non-aqueous secondary battery.
リチウムイオン二次電池に代表される非水二次電池は、エネルギー密度が高いという特徴から、携帯電話やノート型パーソナルコンピューター等の携帯機器の電源として広く用いられている。また、最近では非水二次電池の高性能化に伴い、非水二次電池が携帯機器の電源以外の電源としても用いられようとしている。例えば、産業機械用電源又は車載用電源等に従来より大型の非水二次電池が用いられ始めた。このため、非水二次電池には、従来に増して高出力化と安全性とが要求される。 Non-aqueous secondary batteries represented by lithium ion secondary batteries are widely used as power sources for portable devices such as mobile phones and notebook personal computers because of their high energy density. In recent years, with the improvement in performance of non-aqueous secondary batteries, non-aqueous secondary batteries are also being used as power sources other than the power source of portable devices. For example, a large non-aqueous secondary battery has been used for an industrial machine power supply or a vehicle-mounted power supply. For this reason, non-aqueous secondary batteries are required to have higher output and higher safety than before.
このような非水二次電池の出力特性向上の一つの手法として、正極や負極に用いられる活物質の適切な選定が挙げられ、例えば、高出力時に熱的安定性のあるリチウムチタン複合酸化物やマンガン酸リチウムの使用が検討されている（例えば、特許文献１、特許文献２参照。）。 One method for improving the output characteristics of such a non-aqueous secondary battery is appropriate selection of an active material used for a positive electrode or a negative electrode. For example, a lithium titanium composite oxide having thermal stability at high output And the use of lithium manganate has been studied (for example, see Patent Document 1 and Patent Document 2).
ところで、非水二次電池の高出力化を図るには、正極及び負極の面積を増大させると効果的であることが知られている。正極と負極との対向面積を大きくすること、即ち、電極の反応面積を大きくすることで、大きな電流値での放電が可能になって高出力化を図ることができる。 By the way, it is known that increasing the areas of the positive electrode and the negative electrode is effective for increasing the output of the non-aqueous secondary battery. By increasing the facing area between the positive electrode and the negative electrode, that is, by increasing the reaction area of the electrode, it is possible to discharge at a large current value and increase the output.
非水二次電池に係る電極（正極及び負極）には、例えば、活物質、フッ素樹脂等のバインダ、導電助剤等を含有する電極合剤層を、集電体の表面に形成した態様のものが使用されているが、こうした非水二次電池の有する電極の面積を増大させるには、例えば、活物質の比表面積を大きくする方法が有効である。この場合、活物質の微粒子化が必要となる。ところが、微細な活物質を使用して電極合剤層を形成するには、比較的粒径の大きな活物質を使用して電極合剤層を形成する場合よりも飛躍的に活物質間の導電網の形成が困難になる。これは、以下のような理由によるものと考えられる。即ち、活物質が微細であると、活物質の粒子数が増え、個々の活物質粒子の電気的接触に必要とされる導電助剤量が多くなる。そのため、比較的粒径の大きな活物質を使用した場合と同等程度の導電助剤量では、電極内での導電助剤が不足しがちになって導電網が寸断され、活物質から集電体までの電気抵抗が増大し、却って電池の出力特性が損なわれやすくなると考えられる。 The electrode (positive electrode and negative electrode) related to the non-aqueous secondary battery has, for example, an aspect in which an electrode mixture layer containing an active material, a binder such as a fluororesin, and a conductive additive is formed on the surface of the current collector. In order to increase the area of the electrode of such a non-aqueous secondary battery, for example, a method of increasing the specific surface area of the active material is effective. In this case, it is necessary to make the active material fine particles. However, in order to form an electrode mixture layer using a fine active material, the electrical conductivity between the active materials is dramatically higher than when an electrode mixture layer is formed using an active material having a relatively large particle size. Net formation becomes difficult. This is considered to be due to the following reasons. That is, if the active material is fine, the number of particles of the active material increases, and the amount of conductive auxiliary agent required for electrical contact between the individual active material particles increases. Therefore, when the amount of the conductive auxiliary agent is the same as when using an active material having a relatively large particle size, the conductive auxiliary agent tends to be insufficient in the electrode, and the conductive net is cut off. It is considered that the electrical resistance of the battery increases, and the output characteristics of the battery are easily damaged.
本発明は上記問題を解決したもので、出力特性に優れ、安全性の高い非水二次電池用電極及び非水二次電池を提供するものである。 The present invention solves the above-described problems, and provides an electrode for a non-aqueous secondary battery and a non-aqueous secondary battery that have excellent output characteristics and high safety.
本発明の非水二次電池用電極は、電極活物質と、導電助剤とを含む非水二次電池用電極であって、前記電極活物質の一次粒子の平均粒子径が、１μｍ以下であり、前記導電助剤の分散粒子の平均粒子径が、０．１μｍ以下であり、前記導電助剤の含有量は、前記電極活物質１００質量部に対して、前記導電助剤の分散粒子の平均粒子径を前記電極活物質の分散粒子の平均粒子径で除した値の三乗根に２０を掛けた値以上の質量部であることを特徴とする。 The electrode for non-aqueous secondary battery of the present invention is an electrode for non-aqueous secondary battery containing an electrode active material and a conductive additive, and the average particle diameter of primary particles of the electrode active material is 1 μm or less. And the conductive auxiliary agent dispersed particles have an average particle size of 0.1 μm or less, and the conductive auxiliary agent content of the conductive auxiliary agent dispersed particles is 100 parts by mass of the electrode active material. The mass part is equal to or greater than a value obtained by multiplying the cube root of the value obtained by dividing the average particle diameter by the average particle diameter of the dispersed particles of the electrode active material by 20.
また、本発明の非水二次電池は、正極と、負極と、セパレータと、非水電解質とを含む非水二次電池であって、前記正極は、正極活物質と、正極導電助剤とを含む正極合剤層を備え、前記正極活物質は、スピネル構造を有するリチウムマンガン含有複合酸化物からなり、前記正極導電助剤は、炭素粒子からなり、前記正極活物質の一次粒子の平均粒子径が、１μｍ以下であり、前記正極導電助剤の分散粒子の平均粒子径が、０．１μｍ以下であり、前記正極中の前記正極導電助剤の含有量は、前記正極活物質１００質量部に対して、前記正極導電助剤の分散粒子の平均粒子径を前記正極活物質の分散粒子の平均粒子径で除した値の三乗根に２０を掛けた値以上の質量部であり、前記負極は、負極活物質と、負極導電助剤とを含む負極合剤層を備え、前記負極活物質は、スピネル構造又はラムスデライト構造を有するリチウムチタン複合酸化物からなり、前記負極導電助剤は、炭素粒子からなり、前記負極活物質の一次粒子の平均粒子径が、１μｍ以下であり、前記負極導電助剤の分散粒子の平均粒子径が、０．１μｍ以下であり、前記負極中の前記負極導電助剤の含有量は、前記負極活物質１００質量部に対して、前記負極導電助剤の分散粒子の平均粒子径を前記負極活物質の分散粒子の平均粒子径で除した値の三乗根に２０を掛けた値以上の質量部であることを特徴とする。 The non-aqueous secondary battery of the present invention is a non-aqueous secondary battery including a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte. The positive electrode includes a positive electrode active material, a positive electrode conductive assistant, The positive electrode active material is made of a lithium manganese-containing composite oxide having a spinel structure, the positive electrode conductive additive is made of carbon particles, and the average particle of primary particles of the positive electrode active material The diameter is 1 μm or less, the average particle size of the dispersed particles of the positive electrode conductive auxiliary is 0.1 μm or less, and the content of the positive electrode conductive auxiliary in the positive electrode is 100 parts by mass of the positive electrode active material On the other hand, it is a mass part equal to or greater than the value obtained by multiplying the cube root of the value obtained by dividing the average particle size of the dispersed particles of the positive electrode conductive auxiliary agent by the average particle size of the dispersed particles of the positive electrode active material, The negative electrode includes a negative electrode mixture layer including a negative electrode active material and a negative electrode conductive additive. The negative electrode active material is made of a lithium titanium composite oxide having a spinel structure or a ramsdellite structure, the negative electrode conductive additive is made of carbon particles, and the average particle diameter of primary particles of the negative electrode active material is 1 μm. The average particle diameter of the dispersed particles of the negative electrode conductive auxiliary is 0.1 μm or less, and the content of the negative electrode conductive auxiliary in the negative electrode is based on 100 parts by mass of the negative electrode active material. It is a mass part equal to or more than a value obtained by multiplying the cube root of the value obtained by dividing the average particle size of the dispersed particles of the negative electrode conductive auxiliary agent by the average particle size of the dispersed particles of the negative electrode active material.
本発明によると、微粒子化した活物質を用いることにより生じる電極内の電気抵抗増加を防ぎ、出力特性に優れ、安全性の高い非水二次電池用電極及び非水二次電池を提供できる。 According to the present invention, it is possible to provide an electrode for a non-aqueous secondary battery and a non-aqueous secondary battery that can prevent an increase in electrical resistance in the electrode caused by using a finely divided active material, have excellent output characteristics, and high safety.
本発明の非水二次電池用電極は、電極活物質と、導電助剤とを含む。また、上記電極活物質の一次粒子の平均粒子径は、１μｍ以下であり、上記導電助剤の分散粒子の平均粒子径は、０．１μｍ以下であり、上記導電助剤の含有量は、上記電極活物質１００質量部に対して、上記導電助剤の分散粒子の平均粒子径を上記電極活物質の分散粒子の平均粒子径で除した値の三乗根に２０を掛けた値以上の質量部である。 The electrode for nonaqueous secondary batteries of the present invention contains an electrode active material and a conductive additive. The average particle diameter of the primary particles of the electrode active material is 1 μm or less, the average particle diameter of the dispersed particles of the conductive assistant is 0.1 μm or less, and the content of the conductive assistant is Mass not less than the value obtained by multiplying the cube root of the value obtained by dividing the average particle size of the dispersed particles of the conductive auxiliary agent by the average particle size of the dispersed particles of the electrode active material with respect to 100 parts by mass of the electrode active material. Part.
電池容量を低下させずに出力特性の向上を試みる場合、電極に配合する活物質の質量を維持したままで小粒径化するので、電極中に含まれる活物質の粒子数が増加することになる。そのため、小粒子径化により対応して増加する何らかのパラメータを考慮する必要があり、そのようなパラメータとして活物質の分散粒子の平均粒子径が挙げられる。また、導電助剤についても、活物質に対応した粒子数の導電助剤粒子が必要であり、導電助剤の粒子径が大きくなるに従い、出力特性向上可能な導電網を形成するために必要とされる導電助剤の質量も増加することになる。以上の点から、高速充放電可能な電極を作製するために必要な導電助剤量は、導電助剤の分散粒子の平均粒子径を活物質の分散粒子の平均粒子径で除した値に関連すると考えられる。 When trying to improve output characteristics without reducing battery capacity, the particle size of the active material contained in the electrode increases because the particle size is reduced while maintaining the mass of the active material to be blended in the electrode. Become. For this reason, it is necessary to consider some parameter that increases correspondingly as the particle size is reduced, and an example of such a parameter is the average particle size of dispersed particles of the active material. The conductive auxiliary agent also requires conductive auxiliary particles having the number of particles corresponding to the active material, and is necessary for forming a conductive network that can improve output characteristics as the particle size of the conductive auxiliary agent increases. As a result, the mass of the conductive auxiliary agent also increases. In view of the above, the amount of conductive additive required to produce an electrode capable of high-speed charge / discharge is related to the value obtained by dividing the average particle size of the dispersed particles of the conductive agent by the average particle size of the dispersed particles of the active material. I think that.
一方、高速充放電するためには導電網が孤立することなく連続的につながっていることが必要であるが、どの程度の導電助剤が連続的につながっているかを定量的に評価する技術は存在しなかった。そのため、従来は種々の導電助剤量を検討し、期待される出力特性を達成可能な最も少ない導電助剤量を決定するという方法であった。 On the other hand, in order to charge and discharge at high speed, it is necessary that the conductive network is continuously connected without being isolated, but the technology for quantitatively evaluating how much conductive auxiliary agent is continuously connected is Did not exist. For this reason, conventionally, the amount of various conductive assistants has been examined, and the smallest conductive assistant amount that can achieve the expected output characteristics has been determined.
今回本発明者らが用いた方法では、集束イオンビーム（ＦＩＢ）による断面加工と走査型電子顕微鏡（ＳＥＭ）による断面観察が連続的に可能なＦＩＢ−ＳＥＭ法により、電極の連続断面ＳＥＭ像を撮影し、連続画像を位置補正して３次元可視化ソフトで電極の３次元再構成像を得るものである。ここで、断面方向の分解能は断面の撮影間隔であることから、断面加工ピッチを導電助剤の分散粒子径よりも十分に細かくして行う必要がある。３次元再構成像から導電助剤のみを抽出した再構成像から導電助剤の連続相の体積を算出することが可能となる。得られた導電助剤の連続相の体積は導電助剤量の増減により明らかな違いがみられ、更に連続相の体積が増加することで電池の出力特性が向上することが分かった。 In the method used by the present inventors, a continuous cross-sectional SEM image of an electrode is obtained by a FIB-SEM method in which cross-section processing using a focused ion beam (FIB) and cross-section observation using a scanning electron microscope (SEM) are possible. The three-dimensional reconstructed image of the electrode is obtained by photographing, correcting the position of the continuous image, and using three-dimensional visualization software. Here, since the resolution in the cross-sectional direction is the imaging interval of the cross-section, it is necessary to make the cross-section processing pitch sufficiently finer than the dispersed particle diameter of the conductive additive. It is possible to calculate the volume of the continuous phase of the conductive additive from the reconstructed image obtained by extracting only the conductive additive from the three-dimensional reconstructed image. It was found that the volume of the continuous phase of the obtained conductive auxiliary agent was clearly different depending on the amount of the conductive auxiliary agent, and that the output characteristics of the battery were improved by increasing the volume of the continuous phase further.
上記パラメータと、導電助剤の量及び電池の出力特性との関係を調べたところ、導電助剤の分散粒子の平均粒子径を電極活物質の分散粒子の平均粒子径で除した値の三乗根に係数２０を掛けた値を閾値とし、それ以上の導電助剤量を添加することで、電池の出力特性が向上することを見出した。これは、上記電極の断面分析の結果から、導電助剤の９０％以上が連続相を形成し、集電能力が向上したためと推定される。 When the relationship between the above parameters, the amount of the conductive additive and the output characteristics of the battery was examined, the cube of the value obtained by dividing the average particle size of the dispersed particles of the conductive agent by the average particle size of the dispersed particles of the electrode active material. It has been found that the output characteristics of the battery can be improved by adding a value of the root multiplied by a coefficient of 20 as a threshold and adding a larger amount of conductive assistant. From the result of the cross-sectional analysis of the electrode, it is estimated that 90% or more of the conductive additive formed a continuous phase and the current collecting ability was improved.
また、本発明の非水二次電池は、正極と、負極と、セパレータと、非水電解質とを備える。また、上記正極は、正極活物質と、正極導電助剤とを含む正極合剤層を備え、上記正極活物質は、スピネル構造を有するリチウムマンガン含有複合酸化物からなり、上記正極導電助剤は、炭素粒子からなり、上記正極活物質の一次粒子の平均粒子径が、１μｍ以下であり、上記正極導電助剤の分散粒子の平均粒子径が、０．１μｍ以下であり、上記正極中の上記正極導電助剤の含有量は、上記正極活物質１００質量部に対して、上記正極導電助剤の分散粒子の平均粒子径を上記正極活物質の分散粒子の平均粒子径で除した値の三乗根に２０を掛けた値以上の質量部である。更に、上記負極は、負極活物質と、負極導電助剤とを含む負極合剤層を備え、上記負極活物質は、スピネル構造又はラムスデライト構造を有するリチウムチタン複合酸化物からなり、上記負極導電助剤は、炭素粒子からなり、上記負極活物質の一次粒子の平均粒子径が、１μｍ以下であり、上記負極導電助剤の分散粒子の平均粒子径が、０．１μｍ以下であり、上記負極中の上記負極導電助剤の含有量は、上記負極活物質１００質量部に対して、上記負極導電助剤の分散粒子の平均粒子径を上記負極活物質の分散粒子の平均粒子径で除した値の三乗根に２０を掛けた値以上の質量部である。 The non-aqueous secondary battery of the present invention includes a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte. In addition, the positive electrode includes a positive electrode mixture layer including a positive electrode active material and a positive electrode conductive additive, and the positive electrode active material is composed of a lithium manganese-containing composite oxide having a spinel structure. The positive active material primary particles have an average particle size of 1 μm or less, the positive electrode conductive additive dispersed particles have an average particle size of 0.1 μm or less, and the positive electrode active material has an average particle size of 0.1 μm or less. The content of the positive electrode conductive additive is three times the value obtained by dividing the average particle size of the dispersed particles of the positive electrode conductive agent by the average particle size of the dispersed particles of the positive electrode active material with respect to 100 parts by mass of the positive electrode active material. The mass part is equal to or greater than the value obtained by multiplying the multiplier root by 20. Furthermore, the negative electrode includes a negative electrode mixture layer including a negative electrode active material and a negative electrode conductive additive, and the negative electrode active material is formed of a lithium titanium composite oxide having a spinel structure or a ramsdellite structure, The auxiliary agent is made of carbon particles, the average particle diameter of primary particles of the negative electrode active material is 1 μm or less, the average particle diameter of dispersed particles of the negative electrode conductive auxiliary agent is 0.1 μm or less, and the negative electrode The content of the negative electrode conductive aid in the content was obtained by dividing the average particle size of the dispersed particles of the negative electrode conductive aid by the average particle size of the dispersed particles of the negative electrode active material with respect to 100 parts by mass of the negative electrode active material. The mass part is equal to or greater than the value obtained by multiplying the cube root of the value by 20.
本発明の非水二次電池用電極では、電極の面積を大きくするために、一次粒子の平均粒子径が１μｍ以下の微細な形態の電極活物質を使用し、個々の電極活物質粒子の電気的接触を得るために分散粒子の平均粒子径が０．１μｍ以下の導電助剤を使用することで、個々の電極活物質粒子から集電体までの大電流放電可能な電気的接触を可能にしている。また、本発明の非水二次電池では、上記本発明の非水二次電池用電極を用いることにより、出力特性の向上を達成できる。 In the electrode for a non-aqueous secondary battery of the present invention, in order to increase the area of the electrode, an electrode active material in a fine form in which the average particle diameter of primary particles is 1 μm or less is used, and the electric power of each electrode active material particle In order to obtain electrical contact, a conductive aid having an average particle diameter of dispersed particles of 0.1 μm or less can be used to enable electrical contact capable of discharging a large current from each electrode active material particle to the current collector. ing. Moreover, in the non-aqueous secondary battery of this invention, the improvement of an output characteristic can be achieved by using the said electrode for non-aqueous secondary batteries of this invention.
本発明において、分散粒子の平均粒子径は、レーザー回折式粒度分布測定装置等を用い、水に分散させた試料を測定することにより求められる数平均粒子径をいう。また、一次粒子の平均粒子径は、上記分散粒子が一次粒子のみで構成されている場合は、上記と同様にして求め、二次粒子を形成している場合は、走査型電子顕微鏡で観察される一次粒子１００個の平均粒子径をいう。 In the present invention, the average particle size of dispersed particles refers to the number average particle size obtained by measuring a sample dispersed in water using a laser diffraction particle size distribution measuring device or the like. The average particle diameter of the primary particles is determined in the same manner as described above when the dispersed particles are composed of only primary particles, and is observed with a scanning electron microscope when secondary particles are formed. The average particle diameter of 100 primary particles.
以下、本発明の非水二次電池用電極及び非水二次電池について具体的に説明する。 Hereinafter, the nonaqueous secondary battery electrode and the nonaqueous secondary battery of the present invention will be described in detail.
＜正極＞
正極は、例えば、正極活物質、正極導電助剤、正極バインダ等を含む混合物に、溶剤を加えて十分に混練して得た正極合剤ペーストを、正極集電体の片面又は両面に塗布して乾燥した後に、その正極合剤層を所定の厚さ及び所定の電極密度に制御することにより形成できる。
<Positive electrode>
For the positive electrode, for example, a positive electrode mixture paste obtained by adding a solvent to a mixture containing a positive electrode active material, a positive electrode conductive assistant, a positive electrode binder, and the like and kneading the mixture sufficiently is applied to one or both surfaces of the positive electrode current collector. Then, the positive electrode mixture layer can be formed by controlling the positive electrode mixture layer to a predetermined thickness and a predetermined electrode density.
上記正極活物質は、例えば、リチウム遷移金属複合酸化物等のリチウムイオンを吸蔵・放出可能な正極材料であればよいが、特にスピネル構造を有するリチウムマンガン含有複合酸化物が好ましい。リチウムマンガン含有複合酸化物は熱的安定性が高いことから、充電電流値を大きくしても電池の信頼性及び安全性を確保することが可能となる。 The positive electrode active material may be any positive electrode material capable of occluding and releasing lithium ions, such as lithium transition metal composite oxides, but lithium manganese-containing composite oxides having a spinel structure are particularly preferable. Since the lithium manganese-containing composite oxide has high thermal stability, the reliability and safety of the battery can be ensured even if the charging current value is increased.
上記スピネル構造を有するリチウムマンガン含有複合酸化物としては、ＬｉＭｎ2Ｏ4、ＬｉＮｉ0.5Ｍｎ1.5Ｏ4等の組成で代表されるリチウムマンガン含有複合酸化物やその元素の一部を他の元素、例えばＣａ、Ｍｇ、Ｓｒ、Ｓｃ、Ｚｒ、Ｖ、Ｎｂ、Ｗ、Ｃｒ、Ｍｏ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ｚｎ、Ａｌ、Ｓｉ、Ｇａ、Ｇｅ、Ｓｎ等の元素で置換したリチウムマンガン複合酸化物を用いることができる。これらの正極活物質は、充電の末期に大幅な電圧の変化を示すという特徴を有する。 Examples of the lithium manganese-containing composite oxide having the spinel structure include a lithium manganese-containing composite oxide represented by a composition such as LiMn 2 O 4 and LiNi 0.5 Mn 1.5 O 4 and a part of the element, for example, other elements such as Lithium manganese composite oxide substituted with elements such as Ca, Mg, Sr, Sc, Zr, V, Nb, W, Cr, Mo, Fe, Co, Ni, Cu, Zn, Al, Si, Ga, Ge, Sn Can be used. These positive electrode active materials have a feature that they show a significant voltage change at the end of charging.
また、急速充放電特性を向上させ、高出力の電池を構成するためには、上記正極活物質の一次粒子の平均粒子径は、１μｍ以下であることが必要であり、０．８μｍ以下であることがより好ましい。但し、正極活物質の一次粒子径が小さすぎると、正極合剤層中での正極活物質の分散が困難となり、また、正極合剤層の密度の低下や正極の導電性の低下を招くおそれがあることから、一次粒子の平均粒子径は、０．０１μｍ以上とすることが好ましく、０．０５μｍ以上とすることがより好ましい。 Further, in order to improve the rapid charge / discharge characteristics and constitute a high output battery, the average particle diameter of the primary particles of the positive electrode active material needs to be 1 μm or less, and is 0.8 μm or less. It is more preferable. However, if the primary particle diameter of the positive electrode active material is too small, it is difficult to disperse the positive electrode active material in the positive electrode mixture layer, and the density of the positive electrode mixture layer and the conductivity of the positive electrode may decrease. Therefore, the average particle diameter of the primary particles is preferably 0.01 μm or more, and more preferably 0.05 μm or more.
上記正極活物質の一次粒子は、互いに凝集して二次粒子を形成していてもよく、上記正極活物質は、一次粒子と二次粒子の混合物であってもよい。 The primary particles of the positive electrode active material may be aggregated to form secondary particles, and the positive electrode active material may be a mixture of primary particles and secondary particles.
上記正極導電助剤の分散粒子の平均粒子径は、０．１μｍ以下であることが必要である。０．１μｍ以下の平均粒子径を有する正極導電助剤を用いることで、正極活物質の粒子表面と正極導電助剤との接触面積を増加させ、集電効果を高め、高出力の電池を実現できる。 The average particle diameter of the dispersed particles of the positive electrode conductive auxiliary agent needs to be 0.1 μm or less. By using a positive electrode conductive auxiliary agent having an average particle size of 0.1 μm or less, the contact area between the positive electrode active material particle surface and the positive electrode conductive auxiliary agent is increased, the current collection effect is enhanced, and a high output battery is realized. it can.
本発明において、分散粒子とは、実際に分散した状態での粒子の分散形態をいい、例えば、上記正極導電助剤が一次粒子の状態で完全に単独分散されていれば、分散粒子は一次粒子の分散体を意味し、一次粒子と二次粒子とで混合分散されていれば、分散粒子は一次粒子と二次粒子との混合分散体を意味する。 In the present invention, the dispersed particles refer to a dispersed form of particles in an actually dispersed state. For example, if the positive electrode conductive additive is completely dispersed in the state of primary particles, the dispersed particles are primary particles. If the primary particles and secondary particles are mixed and dispersed, the dispersed particles mean a mixed dispersion of primary particles and secondary particles.
上記正極導電助剤としては、例えば、ケッチェンブラック、アセチレンブラック、繊維状炭素、粉砕した黒鉛等の炭素粒子や、ニッケル粉末等の金属粒子を利用することができる。特に、ケッチェンブラック又はアセチレンブラックからなる炭素粒子が分散粒子径を制御しやすく好ましい。 Examples of the positive electrode conductive assistant include carbon particles such as ketjen black, acetylene black, fibrous carbon, and pulverized graphite, and metal particles such as nickel powder. In particular, carbon particles made of ketjen black or acetylene black are preferable because the dispersed particle size can be easily controlled.
正極中の上記正極導電助剤の含有量は、上記正極活物質１００質量部に対して、上記正極導電助剤の分散粒子の平均粒子径を上記正極活物質の分散粒子の平均粒子径で除した値の三乗根に２０を掛けた値以上の質量部とする。これにより、正極中の上記正極導電助剤の内、９０体積％以上を連続層として形成でき、個々の正極活物質粒子から正極集電体までの電気的接続を確保し、集電効果を高め、高出力の電池を構成することができる。 The content of the positive electrode conductive additive in the positive electrode is calculated by dividing the average particle size of the dispersed particles of the positive electrode conductive agent by the average particle size of the dispersed particles of the positive electrode active material with respect to 100 parts by mass of the positive electrode active material. The mass part is equal to or greater than the value obtained by multiplying the cube root of the obtained value by 20. As a result, 90% by volume or more of the positive electrode conductive additive in the positive electrode can be formed as a continuous layer, ensuring electrical connection from the individual positive electrode active material particles to the positive electrode current collector, and enhancing the current collection effect. A high output battery can be constructed.
本発明において、正極導電助剤が形成する連続層の体積は、ＦＩＢ断面加工装置を備えたＳＥＭを用いて、正極の断面加工とＳＥＭ観察を繰り返すことにより得られる各断面ＳＥＭ像において、観察された正極導電助剤相を市販の画像処理ソフト“アミラ”を用いて三次元に再構成することにより求めるものとする。また、後述の負極導電助剤が形成する連続層の体積も同様にして求めるものとする。 In the present invention, the volume of the continuous layer formed by the positive electrode conductive additive is observed in each cross-sectional SEM image obtained by repeating cross-section processing of the positive electrode and SEM observation using an SEM equipped with a FIB cross-section processing apparatus. The positive electrode conductive auxiliary phase is obtained by three-dimensional reconstruction using commercially available image processing software “Amira”. In addition, the volume of the continuous layer formed by the negative electrode conductive additive described later is obtained in the same manner.
上記正極バインダとしては、ポリフッ化ビニリデン（ＰＶＤＦ）、ポリテトラフルオロエチレン（ＰＴＦＥ）等のフッ素樹脂等が使用できるが、これらに限定されるものではない。 As the positive electrode binder, fluorine resins such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE) can be used, but are not limited thereto.
上記正極集電体としては、構成された電池において実質的に化学的に安定な電子伝導体であれば特に限定されず、例えば、厚さが１０〜３０μｍのアルミニウム又はアルミニウム合金等の金属で構成された箔、パンチングメタル、網、エキスパンドメタル等が用いられる。但し、正極は、正極集電体を用いずに正極合剤層のみで構成することもできる。 The positive electrode current collector is not particularly limited as long as it is a substantially chemically stable electron conductor in the constructed battery. For example, the positive electrode current collector is made of a metal such as aluminum or aluminum alloy having a thickness of 10 to 30 μm. Foil, punched metal, net, expanded metal, etc. are used. However, a positive electrode can also be comprised only with a positive mix layer, without using a positive electrode electrical power collector.
上記溶剤としては、例えば、Ｎ−メチル−２−ピロリドン等が使用できる。 As the solvent, for example, N-methyl-2-pyrrolidone or the like can be used.
上記正極合剤層の厚さ（正極集電体の両面に正極合剤層が形成されている場合には、片面あたりの厚さ。）は、急速充放電特性を向上させるためには、５０μｍ以下とするのが好ましく、４０μｍ以下とするのがより好ましい。但し、正極合剤層が薄すぎると、活物質量が減少して電池容量が低下するおそれがあることから、正極合剤層の厚さは、１５μｍ以上であることが好ましく、２０μｍ以上であることがより好ましい。 The thickness of the positive electrode mixture layer (the thickness per side when the positive electrode mixture layer is formed on both surfaces of the positive electrode current collector) is 50 μm in order to improve rapid charge / discharge characteristics. It is preferable to set it as follows, and it is more preferable to set it as 40 micrometers or less. However, if the positive electrode mixture layer is too thin, the amount of the active material may decrease and the battery capacity may be reduced. Therefore, the thickness of the positive electrode mixture layer is preferably 15 μm or more, and more preferably 20 μm or more. It is more preferable.
正極の厚さは特に限定されないが、通常は１１０〜２３０μｍである。 Although the thickness of a positive electrode is not specifically limited, Usually, it is 110-230 micrometers.
＜負極＞
負極は、例えば、負極活物質、負極導電助剤、負極バインダ等を含む混合物に、溶剤を加えて十分に混練して得た負極合剤ペーストを、負極集電体の片面又は両面に塗布して乾燥した後に、その負極合剤層を所定の厚さ及び所定の電極密度に制御することにより形成できる。
<Negative electrode>
The negative electrode is obtained by, for example, applying a negative electrode mixture paste obtained by sufficiently adding a solvent to a mixture containing a negative electrode active material, a negative electrode conductive additive, a negative electrode binder, etc., on one or both sides of the negative electrode current collector. Then, the negative electrode mixture layer can be formed by controlling the negative electrode mixture layer to a predetermined thickness and a predetermined electrode density.
上記負極活物質は、例えば、天然黒鉛又は塊状黒鉛、鱗片状黒鉛、土状黒鉛等の人造黒鉛等のリチウムイオンを吸蔵・放出可能な負極材料であればよいが、特にスピネル構造又はラムスデライト構造を有するリチウムチタン複合酸化物が好ましい。リチウムチタン複合酸化物は熱的安定性が高く、また、このような負極活物質を用いた負極を有する電池では、リチウムデンドライトが生じにくい。そのため、充電電流値を大きくしても電池の信頼性及び安全性を確保することが可能となる。 The negative electrode active material may be any negative electrode material capable of occluding and releasing lithium ions, such as natural graphite or artificial graphite such as massive graphite, flake graphite, earthy graphite, etc., but in particular a spinel structure or a ramsdellite structure The lithium titanium composite oxide having Lithium titanium composite oxide has high thermal stability, and lithium dendrite hardly occurs in a battery having a negative electrode using such a negative electrode active material. For this reason, it is possible to ensure the reliability and safety of the battery even if the charging current value is increased.
上記スピネル構造を有するリチウムチタン複合酸化物としては、例えば、Ｌｉ4Ｔｉ5Ｏ12、ＬｉＴｉ2Ｏ4等を用いることができ、上記ラムスデライト構造を有するリチウムチタン複合酸化物としては、例えば、Ｌｉ2Ｔｉ3Ｏ7等を用いることができる。 As the lithium titanium composite oxide having the spinel structure, for example, Li 4 Ti 5 O 12 , LiTi 2 O 4 or the like can be used. As the lithium titanium composite oxide having the ramsdellite structure, for example, Li 2 Ti 3 O 7 or the like can be used.
また、急速充放電特性を向上させ、高出力の電池を構成するためには、上記負極活物質の一次粒子の平均粒子径は、１μｍ以下であることが必要であり、０．５μｍ以下であることがより好ましい。但し、負極活物質の一次粒子径が小さすぎると、負極合剤層中での負極活物質の分散が困難となり、また、負極合剤層の密度の低下や負極の導電性の低下を招くおそれがあることから、一次粒子の平均粒子径は、０．０１μｍ以上とすることが好ましく、０．０５μｍ以上とすることがより好ましい。 Further, in order to improve the rapid charge / discharge characteristics and constitute a high output battery, the average particle diameter of the primary particles of the negative electrode active material needs to be 1 μm or less, and is 0.5 μm or less. It is more preferable. However, if the primary particle diameter of the negative electrode active material is too small, it is difficult to disperse the negative electrode active material in the negative electrode mixture layer, and the negative electrode mixture layer may have a reduced density or a negative electrode conductivity. Therefore, the average particle diameter of the primary particles is preferably 0.01 μm or more, and more preferably 0.05 μm or more.
上記負極活物質の一次粒子は、互いに凝集して二次粒子を形成していてもよく、上記負極活物質は、一次粒子と二次粒子の混合物であってもよい。 The primary particles of the negative electrode active material may be aggregated to form secondary particles, and the negative electrode active material may be a mixture of primary particles and secondary particles.
上記負極導電助剤の分散粒子の平均粒子径は、０．１μｍ以下であることが必要である。０．１μｍ以下の平均粒子径を有する負極導電助剤を用いることで、負極活物質の粒子表面と負極導電助剤との接触面積を増加させ、集電効果を高め、高出力の電池を実現できる。 The average particle diameter of the dispersed particles of the negative electrode conductive auxiliary agent needs to be 0.1 μm or less. By using a negative electrode conductive auxiliary agent having an average particle size of 0.1 μm or less, the contact area between the negative electrode active material particle surface and the negative electrode conductive auxiliary agent is increased, the current collection effect is enhanced, and a high output battery is realized. it can.
上記負極導電助剤としては、前述の正極導電助剤と同様のものが使用できる。 As said negative electrode conductive support agent, the thing similar to the above-mentioned positive electrode conductive support agent can be used.
負極中の上記負極導電助剤の含有量は、上記負極活物質１００質量部に対して、上記負極導電助剤の分散粒子の平均粒子径を上記負極活物質の分散粒子の平均粒子径で除した値の三乗根に２０を掛けた値以上の質量部とする。これにより、負極中の上記負極導電助剤の内、９０体積％以上を連続層として形成でき、個々の負極活物質粒子から負極集電体までの電気的接続を確保し、集電効果を高め、高出力の電池を構成することができる。 The content of the negative electrode conductive additive in the negative electrode is calculated by dividing the average particle size of the dispersed particles of the negative electrode conductive aid by the average particle size of the dispersed particles of the negative electrode active material with respect to 100 parts by mass of the negative electrode active material. The mass part is equal to or greater than the value obtained by multiplying the cube root of the obtained value by 20. As a result, 90% by volume or more of the negative electrode conductive additive in the negative electrode can be formed as a continuous layer, ensuring electrical connection from the individual negative electrode active material particles to the negative electrode current collector, and enhancing the current collection effect. A high output battery can be constructed.
上記負極バインダとしては、前述の正極バインダと同様のものが使用できる。 As said negative electrode binder, the thing similar to the above-mentioned positive electrode binder can be used.
上記負極集電体としては、構成された電池において実質的に化学的に安定な電子伝導体であれば特に限定されず、例えば、厚さが５〜３０μｍの銅、ニッケル又はそれらの合金等の金属で構成された箔、パンチングメタル、網、エキスパンドメタル等が用いられる。また、負極集電体としては、負極活物質が前述のスピネル構造又はラムスデライト構造を有するリチウムチタン複合酸化物のみで構成され、負極の電位が１．０Ｖ以上となる範囲で充放電を行う場合には、アルミニウム又はアルミニウム合金で形成された集電体を用いることもできる。但し、負極は、負極集電体を用いずに負極合剤層のみで構成することもできる。 The negative electrode current collector is not particularly limited as long as it is a substantially chemically stable electron conductor in the constructed battery. For example, copper, nickel or an alloy thereof having a thickness of 5 to 30 μm is used. A metal foil, punching metal, net, expanded metal or the like is used. Moreover, as a negative electrode collector, when a negative electrode active material is comprised only with the lithium titanium complex oxide which has the above-mentioned spinel structure or a ramsdellite structure, and it charges / discharges in the range in which the electric potential of a negative electrode becomes 1.0V or more A current collector made of aluminum or an aluminum alloy can also be used. However, a negative electrode can also be comprised only with a negative mix layer, without using a negative electrode collector.
上記溶剤としては、前述の負極に用いたものと同様のものを使用できる。 As said solvent, the thing similar to what was used for the above-mentioned negative electrode can be used.
上記負極合剤層の厚さ（負極集電体の両面に負極合剤層が形成されている場合には、片面あたりの厚さ。）は、急速充放電特性を向上させるためには、５０μｍ以下とするのが好ましく、４０μｍ以下とするのがより好ましい。但し、負極合剤層が薄すぎると、活物質量が減少して電池容量が低下するおそれがあることから、負極合剤層の厚さは、１０μｍ以上であることが好ましい。 The thickness of the negative electrode mixture layer (the thickness per side when the negative electrode mixture layer is formed on both surfaces of the negative electrode current collector) is 50 μm in order to improve rapid charge / discharge characteristics. It is preferable to set it as follows, and it is more preferable to set it as 40 micrometers or less. However, if the negative electrode mixture layer is too thin, the amount of the active material may decrease and the battery capacity may be reduced. Therefore, the thickness of the negative electrode mixture layer is preferably 10 μm or more.
負極の厚さは特に限定されないが、通常は６５〜２２０μｍである。 Although the thickness of a negative electrode is not specifically limited, Usually, it is 65-220 micrometers.
＜セパレータ＞
セパレータとしては、例えば、ポリエチレン（ＰＥ）、ポリプロピレン（ＰＰ）等のポリオレフィン；ポリエチレンテレフタレート（ＰＥＴ）、ポリブチレンテレフタレート（ＰＢＴ）等のポリエステル；ポリフェニレンスルフィド（ＰＰＳ）；等で形成された微孔性フィルム、不織布等を使用できる。セパレータの厚さは特に限定されないが、通常は２５〜９０μｍである。
<Separator>
As the separator, for example, a microporous film formed of polyolefin such as polyethylene (PE) or polypropylene (PP); polyester such as polyethylene terephthalate (PET) or polybutylene terephthalate (PBT); polyphenylene sulfide (PPS); Nonwoven fabrics can be used. Although the thickness of a separator is not specifically limited, Usually, it is 25-90 micrometers.
＜非水電解質＞
非水電解質としては、例えば、リチウム塩を有機溶媒に溶解した溶液（非水電解液）が用いられる。リチウム塩としては、溶媒中で解離してＬｉ+イオンを形成し、電池として使用される電圧範囲で分解等の副反応を起こしにくいものであれば特に制限は無い。
<Nonaqueous electrolyte>
As the non-aqueous electrolyte, for example, a solution (non-aqueous electrolyte) in which a lithium salt is dissolved in an organic solvent is used. The lithium salt is not particularly limited as long as it dissociates in a solvent to form Li + ions and hardly causes side reactions such as decomposition in a voltage range used as a battery.
上記リチウム塩としては、例えば、ＬｉＣｌＯ4、ＬｉＰＦ6、ＬｉＢＦ4、ＬｉＡｓＦ6、ＬｉＳｂＦ6等の無機リチウム塩；ＬｉＣＦ3ＳＯ3、ＬｉＣＦ3ＣＯ2、Ｌｉ2Ｃ2Ｆ4（ＳＯ3）2、ＬｉＮ（ＣＦ3ＳＯ2）2、ＬｉＣ（ＣＦ3ＳＯ2）3、ＬｉＣnＦ2n+1ＳＯ3（２≦ｎ≦７）、ＬｉＮ（ＲｆＯＳＯ2）2〔ここで、Ｒｆはフルオロアルキル基を示す。〕等の有機リチウム塩等を用いることができる。 As the lithium salt, for example, LiClO 4, LiPF 6, LiBF 4, LiAsF 6, LiSbF 6 such as an inorganic lithium salt; LiCF 3 SO 3, LiCF 3 CO 2, Li 2 C 2 F 4 (SO 3) 2, LiN (CF 3 SO 2 ) 2 , LiC (CF 3 SO 2 ) 3 , LiC n F 2n + 1 SO 3 (2 ≦ n ≦ 7), LiN (RfOSO 2 ) 2 [where Rf represents a fluoroalkyl group Show. An organic lithium salt such as can be used.
上記有機溶媒としては、上記リチウム塩を溶解し、電池として使用される電圧範囲で分解等の副反応を起こさないものであれば特に限定されない。例えば、エチレンカーボネート、プロピレンカーボネート、ブチレンカーボネート、ビニレンカーボネート等の環状カーボネート；ジメチルカーボネート、ジエチルカーボネート、メチルエチルカーボネート等の鎖状カーボネート；プロピオン酸メチル等の鎖状エステル；γ−ブチロラクトン等の環状エステル；ジメトキシエタン、ジエチルエーテル、１，３−ジオキソラン、ジグライム、トリグライム、テトラグライム等の鎖状エーテル；ジオキサン、テトラヒドロフラン、２−メチルテトラヒドロフラン等の環状エーテル；アセトニトリル、プロピオニトリル、メトキシプロピオニトリル等のニトリル類；エチレングリコールサルファイト等の亜硫酸エステル類；等が挙げられ、これらは２種以上混合して用いることもできる。より良好な特性の電池とするためには、エチレンカーボネートと鎖状カーボネートとの混合溶媒等、高いイオン伝導率を得ることができる組み合わせで用いることが望ましい。 The organic solvent is not particularly limited as long as it dissolves the lithium salt and does not cause a side reaction such as decomposition in a voltage range used as a battery. For example, cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate and vinylene carbonate; chain carbonates such as dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate; chain esters such as methyl propionate; cyclic esters such as γ-butyrolactone; Chain ethers such as dimethoxyethane, diethyl ether, 1,3-dioxolane, diglyme, triglyme and tetraglyme; cyclic ethers such as dioxane, tetrahydrofuran and 2-methyltetrahydrofuran; nitriles such as acetonitrile, propionitrile and methoxypropionitrile Sulfites such as ethylene glycol sulfite; and the like. These may be used in combination of two or more. In order to obtain a battery having better characteristics, it is desirable to use a combination that can obtain high ionic conductivity, such as a mixed solvent of ethylene carbonate and chain carbonate.
上記非水電解液中のＬｉイオンの濃度は、０．５〜２．０ｍｏｌ／Ｌとすることが好ましい。また、上記非水電解液に安全性、充放電サイクル性、高温貯蔵性等の特性を向上させる目的で、ビニレンカーボネート類、１，３−プロパンサルトン、ジフェニルジスルフィド、シクロヘキシルベンゼン、ビフェニル、フルオロベンゼン、ｔ−ブチルベンゼン等の添加剤を適宜加えることもできる。 The concentration of Li ions in the non-aqueous electrolyte is preferably 0.5 to 2.0 mol / L. In addition, vinylene carbonates, 1,3-propane sultone, diphenyl disulfide, cyclohexyl benzene, biphenyl, and fluorobenzene are used for the purpose of improving safety, charge / discharge cycleability, high-temperature storage properties and the like in the non-aqueous electrolyte. Additives such as t-butylbenzene can also be added as appropriate.
＜電池構成＞
本発明の非水二次電池は、例えば、上述の正極、負極及びセパレータと、非水電解質とを、常法に従い電池容器内に封入して構成される。電池の形態としては、従来公知の非水二次電池と同様に、円筒形や角筒形の外装缶を使用した筒形電池；平面視で円形や角形の扁平形の外装缶を使用した扁平形電池；柔軟性を有する外装体を用いたソフトパッケージ電池；等とすることができる。また、上記外装缶には、スチール製外装缶、アルミニウム製外装缶等を用いることができ、また、上記外装体には、アルミニウム等の金属層と熱可塑性樹脂層とが積層されたラミネートフィルム製外装体等を用いることもできる。
<Battery configuration>
The non-aqueous secondary battery of the present invention is configured, for example, by sealing the above-described positive electrode, negative electrode and separator, and a non-aqueous electrolyte in a battery container according to a conventional method. As for the form of the battery, a cylindrical battery using a cylindrical or rectangular tube-shaped outer can as in the case of a conventionally known non-aqueous secondary battery; a flat shape using a circular or square flat outer can in plan view Battery, a soft package battery using a flexible outer package, and the like. Moreover, a steel outer can, an aluminum outer can, or the like can be used as the outer can, and the outer casing is made of a laminate film in which a metal layer such as aluminum and a thermoplastic resin layer are laminated. An exterior body or the like can also be used.
本発明の非水二次電池は、高出力であることから、産業機械用電源、車載用電源等の用途を始めとして、従来から知られている非水二次電池が適用されている各種用途（携帯機器等の各種電子機器の電源用途等）に好ましく用いることができる。 Since the non-aqueous secondary battery of the present invention has a high output, various uses to which conventionally known non-aqueous secondary batteries are applied, including applications such as industrial machine power supplies and vehicle power supplies. It can be preferably used for (such as power supply for various electronic devices such as portable devices).
以下、実施例に基づいて本発明を説明する。但し、本発明は以下の実施例に限定されるものではない。 Hereinafter, the present invention will be described based on examples. However, the present invention is not limited to the following examples.
（実施例１）
＜正極の作製＞
正極活物質としてＬｉＭｎ2Ｏ4の組成式で表されるスピネル構造のリチウムマンガン含有複合酸化物（一次粒子の平均粒子径：０．１μｍ、分散粒子の平均粒子径：０．３μｍ）１００質量部、正極導電助剤としてアセチレンブラック（分散粒子の平均粒子径：０．０５μｍ）１４質量部、及びバインダとしてＰＶＤＦ３．５質量部を、Ｎ−メチル−２−ピロリドン（ＮＭＰ）を溶剤として均一になるように混合し、正極合剤含有ペーストを調製した。そのペーストを厚さ１５μｍのアルミニウム箔からなる正極集電体の片面に一定厚さで塗布し、１１０±１０℃で乾燥した後、プレス処理により厚さ２０μｍの正極合剤層を形成した。その後、正極合剤層の面積が７２ｍｍ×４０ｍｍとなるように切断して正極を作製した。また、正極合剤層が形成されていない正極の一端部には正極リード端子を形成した。
Example 1
<Preparation of positive electrode>
100 parts by mass of a lithium manganese-containing composite oxide having a spinel structure represented by a composition formula of LiMn 2 O 4 as a positive electrode active material (average particle diameter of primary particles: 0.1 μm, average particle diameter of dispersed particles: 0.3 μm) Further, 14 parts by mass of acetylene black (average particle diameter of dispersed particles: 0.05 μm) as a positive electrode conductive additive, 3.5 parts by mass of PVDF as a binder, and N-methyl-2-pyrrolidone (NMP) as a solvent become uniform. Thus, a positive electrode mixture-containing paste was prepared. The paste was applied to one side of a positive electrode current collector made of an aluminum foil having a thickness of 15 μm, dried at 110 ± 10 ° C., and then a positive electrode mixture layer having a thickness of 20 μm was formed by pressing. Then, it cut | disconnected so that the area of a positive mix layer might be 72 mm x 40 mm, and produced the positive electrode. Moreover, the positive electrode lead terminal was formed in the one end part of the positive electrode in which the positive mix layer was not formed.
＜負極の作製＞
負極活物質としてＬｉ4Ｔｉ5Ｏ12の組成式で表されるスピネル構造のリチウムチタン複合酸化物（一次粒子の平均粒子径：０．０５μｍ、分散粒子の平均粒子径：５μｍ）１００質量部、負極導電助剤としてアセチレンブラック（分散粒子の平均粒子径：０．０５μｍ）８．２質量部、及びバインダとしてＰＶＤＦ９．４質量部を、ＮＭＰを溶剤として均一になるように混合し、負極合剤含有ペーストを調製した。そのペーストを厚さ１０μｍのアルミニウム箔からなる負極集電体の片面に一定厚さで塗布し、１１０±１０℃で乾燥した後、プレス処理により厚さ３５μｍの負極合剤層を形成した。その後、負極合剤層の面積が７４ｍｍ×４０ｍｍとなるように切断して負極を作製した。また、負極合剤層が形成されていない負極の一端部には負極リード端子を形成した。
<Production of negative electrode>
100 parts by mass of a lithium titanium composite oxide having a spinel structure represented by a composition formula of Li 4 Ti 5 O 12 as a negative electrode active material (average particle diameter of primary particles: 0.05 μm, average particle diameter of dispersed particles: 5 μm), Acetylen black (average particle diameter of dispersed particles: 0.05 μm) 8.2 parts by mass as a negative electrode conductive additive and 9.4 parts by mass of PVDF as a binder were mixed so as to be uniform using NMP as a solvent, and a negative electrode mixture A containing paste was prepared. The paste was applied to one side of a negative electrode current collector made of an aluminum foil having a thickness of 10 μm, dried at 110 ± 10 ° C., and a negative electrode mixture layer having a thickness of 35 μm was formed by pressing. Then, it cut | disconnected so that the area of a negative mix layer might be set to 74 mm x 40 mm, and the negative electrode was produced. Moreover, the negative electrode lead terminal was formed in the one end part of the negative electrode in which the negative mix layer was not formed.
＜セパレータ＞
セパレータとして、厚さ１７μｍのポリエチレン製の微多孔フィルムを準備した。
<Separator>
As a separator, a microporous film made of polyethylene having a thickness of 17 μm was prepared.
＜非水電解質＞
非水電解質として、エチレンカーボネートとジメチルカーボネートとを体積比３：７で混合した溶媒中に、ＬｉＰＦ6を１．５ｍｏｌ／Ｌの割合で溶解した非水電解液を準備した。
<Nonaqueous electrolyte>
As a non-aqueous electrolyte, a non-aqueous electrolyte solution in which LiPF 6 was dissolved at a ratio of 1.5 mol / L in a solvent in which ethylene carbonate and dimethyl carbonate were mixed at a volume ratio of 3: 7 was prepared.
＜電池の組み立て＞
上記正極と上記負極との間に上記セパレータを配置して積層電極体を作製し、この積層電極体を、８０ｍｍ×１００ｍｍのアルミニウムラミネートフィルム製の外装体内に挿入し、外装体内に上記非水電解液を注入した後、外装体を封止して、本実施例の非水二次電池を作製した。
<Battery assembly>
The separator is disposed between the positive electrode and the negative electrode to produce a laminated electrode body, and the laminated electrode body is inserted into an exterior body made of an aluminum laminate film of 80 mm × 100 mm, and the nonaqueous electrolysis is disposed in the exterior body. After injecting the liquid, the outer package was sealed to produce a non-aqueous secondary battery of this example.
（比較例１）
正極活物質としてＬｉＭｎ2Ｏ4の組成式で表されるスピネル構造のリチウムマンガン含有複合酸化物（一次粒子の平均粒子径：０．１μｍ、分散粒子の平均粒子径：０．３μｍ）８５質量部、正極導電助剤としてアセチレンブラック（分散粒子の平均粒子径：０．０５μｍ）７質量部、及びバインダとしてＰＶＤＦ８質量部を、ＮＭＰを溶剤として均一になるように混合した正極合剤含有ペーストを用いた以外は、実施例１と同様にして正極を作製し、この正極を用いた以外は、実施例１と同様にして本比較例の非水二次電池を作製した。
(Comparative Example 1)
85 parts by mass of a lithium manganese-containing composite oxide having a spinel structure represented by a composition formula of LiMn 2 O 4 as a positive electrode active material (average particle diameter of primary particles: 0.1 μm, average particle diameter of dispersed particles: 0.3 μm) A positive electrode mixture-containing paste in which 7 parts by mass of acetylene black (average particle diameter of dispersed particles: 0.05 μm) as a positive electrode conductive additive and 8 parts by mass of PVDF as a binder are mixed uniformly using NMP as a solvent is used. A nonaqueous secondary battery of this comparative example was produced in the same manner as in Example 1 except that this positive electrode was used except that the positive electrode was used.
表１に実施例１及び比較例１で用いた電極合剤層の構成を示す。また、表１では、導電助剤量は活物質１００質量部に対する値であり、導電助剤量閾値は活物質１００質量部に対して、導電助剤の分散粒子の平均粒子径を活物質の分散粒子の平均粒子径で除した値の三乗根に２０を掛けた値である。 Table 1 shows the configuration of the electrode mixture layer used in Example 1 and Comparative Example 1. In Table 1, the amount of conductive assistant is a value with respect to 100 parts by mass of the active material, and the threshold value of conductive auxiliary agent is the average particle diameter of dispersed particles of the conductive auxiliary agent with respect to 100 parts by mass of the active material. This is a value obtained by multiplying the cube root of the value divided by the average particle diameter of the dispersed particles by 20.
次に、実施例１及び比較例１の非水二次電池について、下記のとおり導電助剤の連続層形成の評価及び出力特性評価を行った。 Next, the nonaqueous secondary batteries of Example 1 and Comparative Example 1 were evaluated for the formation of a continuous layer of the conductive assistant and the output characteristics as follows.
＜導電助剤の連続相形成の評価＞
各電極についての導電助剤の連続相形成の評価は、導電助剤の全体積に対する導電助剤が形成する連続層の体積の割合を求めることで行った。導電助剤が形成する連続層の体積は、前述のとおり、ＦＩＢ断面加工装置を備えたＳＥＭを用いて、電極の断面加工とＳＥＭ観察を繰り返すことにより得られる各断面ＳＥＭ像において、観察された導電助剤相を画像処理して３次元に再構成することにより求めた。表２に、各電極における断面加工ピッチと、３次元再構成に用いたＳＥＭ像の枚数と、３次元再構成範囲と、得られた導電助剤の連続相の体積割合を示した。
<Evaluation of continuous phase formation of conductive assistant>
Evaluation of the continuous phase formation of the conductive assistant for each electrode was performed by determining the ratio of the volume of the continuous layer formed by the conductive assistant to the total volume of the conductive assistant. As described above, the volume of the continuous layer formed by the conductive additive was observed in each cross-sectional SEM image obtained by repeating cross-section processing of the electrode and SEM observation using the SEM equipped with the FIB cross-section processing apparatus. The conductive auxiliary agent phase was obtained by image processing and reconstructing in three dimensions. Table 2 shows the cross-sectional processing pitch in each electrode, the number of SEM images used for three-dimensional reconstruction, the three-dimensional reconstruction range, and the volume ratio of the obtained continuous phase of the conductive additive.
表２から、正極活物質１００質量部に対する正極導電助剤量が導電助剤量閾値を越えている実施例１では、正極導電助剤の連続相の体積割合は９０％以上であるのに対して、正極活物質１００質量部に対する正極導電助剤量が導電助剤量閾値を下回っている比較例１の正極導電助剤の連続相の体積割合は９０％を下回った。 From Table 2, in Example 1 in which the amount of the positive electrode conductive auxiliary with respect to 100 parts by mass of the positive electrode active material exceeds the threshold value of the conductive auxiliary agent, the volume ratio of the continuous phase of the positive electrode conductive auxiliary is 90% or more. Thus, the volume ratio of the continuous phase of the positive electrode conductive additive of Comparative Example 1 in which the positive electrode conductive additive amount relative to 100 parts by mass of the positive electrode active material is lower than the conductive auxiliary agent amount threshold value was less than 90%.
＜出力特性評価＞
各電池の出力特性評価は、下記のとおり放電容量維持率を求めることで行った。即ち、各電池を、１Ｃの電流値（１２．５ｍＡ）で２．９Ｖまで定電流充電した後、所定の電流値で１．５Ｖまで放電させて、放電容量を測定した。放電電流値は、１Ｃ、２０Ｃ、５０Ｃ、７５Ｃ、１００Ｃとし、各放電電流値での放電容量を測定した。そして、各放電電流値での放電容量を１Ｃでの放電容量で除し、百分率で表して、各放電条件での容量維持率を算出した。より大きな放電電流値での容量維持率が大きいほど、電池の出力特性が優れていることを意味している。図１にその結果を示す。図１では、横軸に放電レート（放電電流値）を、縦軸に容量維持率を示した。図１から明らかなように、実施例１では５０Ｃ以上の放電レートにおいて比較例１を大きく上回る容量維持率を示し、実施例１の電池は、比較例１の電池に比べて高出力の電池であるといえる。
<Output characteristics evaluation>
The output characteristic evaluation of each battery was performed by calculating | requiring the discharge capacity maintenance factor as follows. That is, each battery was charged at a constant current up to 2.9 V at a current value of 1 C (12.5 mA), then discharged to 1.5 V at a predetermined current value, and the discharge capacity was measured. The discharge current values were 1C, 20C, 50C, 75C, and 100C, and the discharge capacity at each discharge current value was measured. Then, the discharge capacity at each discharge current value was divided by the discharge capacity at 1 C, and expressed as a percentage, and the capacity retention rate under each discharge condition was calculated. The larger the capacity retention rate at a larger discharge current value, the better the output characteristics of the battery. The result is shown in FIG. In FIG. 1, the horizontal axis represents the discharge rate (discharge current value), and the vertical axis represents the capacity retention rate. As is clear from FIG. 1, Example 1 shows a capacity maintenance rate that greatly exceeds that of Comparative Example 1 at a discharge rate of 50 C or higher. It can be said that there is.
以上説明したように、本発明は、出力特性に優れ、安全性の高い非水二次電池を提供できる。従って、本発明の非水二次電池は、高出力で且つ高い安全性が要求される産業機械用電源又は車載用電源等として広く利用できる。 As described above, the present invention can provide a non-aqueous secondary battery having excellent output characteristics and high safety. Therefore, the non-aqueous secondary battery of the present invention can be widely used as a power source for industrial machinery or a vehicle-mounted power source that requires high output and high safety.
Claims (6)
前記電極活物質の一次粒子の平均粒子径が、１μｍ以下であり、
前記導電助剤の分散粒子の平均粒子径が、０．１μｍ以下であり、
前記導電助剤の含有量は、前記電極活物質１００質量部に対して、前記導電助剤の分散粒子の平均粒子径を前記電極活物質の分散粒子の平均粒子径で除した値の三乗根に２０を掛けた値以上の質量部であることを特徴とする非水二次電池用電極。 An electrode for a non-aqueous secondary battery comprising an electrode active material and a conductive additive,
The average particle diameter of primary particles of the electrode active material is 1 μm or less,
The average particle diameter of the dispersed particles of the conductive assistant is 0.1 μm or less,
The content of the conductive auxiliary agent is the cube of the value obtained by dividing the average particle size of the dispersed particles of the conductive auxiliary agent by the average particle size of the dispersed particles of the electrode active material with respect to 100 parts by mass of the electrode active material. An electrode for a non-aqueous secondary battery, characterized in that the mass part is equal to or greater than a value obtained by multiplying the root by 20.
前記正極は、正極活物質と、正極導電助剤とを含む正極合剤層を備え、
前記正極活物質は、スピネル構造を有するリチウムマンガン含有複合酸化物からなり、
前記正極導電助剤は、炭素粒子からなり、
前記正極活物質の一次粒子の平均粒子径が、１μｍ以下であり、
前記正極導電助剤の分散粒子の平均粒子径が、０．１μｍ以下であり、
前記正極中の前記正極導電助剤の含有量は、前記正極活物質１００質量部に対して、前記正極導電助剤の分散粒子の平均粒子径を前記正極活物質の分散粒子の平均粒子径で除した値の三乗根に２０を掛けた値以上の質量部であり、
前記負極は、負極活物質と、負極導電助剤とを含む負極合剤層を備え、
前記負極活物質は、スピネル構造又はラムスデライト構造を有するリチウムチタン複合酸化物からなり、
前記負極導電助剤は、炭素粒子からなり、
前記負極活物質の一次粒子の平均粒子径が、１μｍ以下であり、
前記負極導電助剤の分散粒子の平均粒子径が、０．１μｍ以下であり、
前記負極中の前記負極導電助剤の含有量は、前記負極活物質１００質量部に対して、前記負極導電助剤の分散粒子の平均粒子径を前記負極活物質の分散粒子の平均粒子径で除した値の三乗根に２０を掛けた値以上の質量部であることを特徴とする非水二次電池。 A non-aqueous secondary battery including a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte,
The positive electrode includes a positive electrode mixture layer including a positive electrode active material and a positive electrode conductive additive,
The positive electrode active material is composed of a lithium manganese-containing composite oxide having a spinel structure,
The positive electrode conductive assistant is composed of carbon particles,
The average particle diameter of primary particles of the positive electrode active material is 1 μm or less,
The average particle diameter of the dispersed particles of the positive electrode conductive assistant is 0.1 μm or less,
The content of the positive electrode conductive additive in the positive electrode is the average particle size of the dispersed particles of the positive electrode active material is the average particle size of the dispersed particles of the positive electrode active material with respect to 100 parts by mass of the positive electrode active material. A mass part equal to or greater than the value obtained by multiplying the cube root of the divided value by 20;
The negative electrode includes a negative electrode mixture layer including a negative electrode active material and a negative electrode conductive additive,
The negative electrode active material comprises a lithium titanium composite oxide having a spinel structure or a ramsdellite structure,
The negative electrode conductive assistant is composed of carbon particles,
The average particle diameter of primary particles of the negative electrode active material is 1 μm or less,
The average particle size of the dispersed particles of the negative electrode conductive assistant is 0.1 μm or less,
The content of the negative electrode conductive additive in the negative electrode is the average particle size of the dispersed particles of the negative electrode active material as the average particle size of the dispersed particles of the negative electrode active material with respect to 100 parts by mass of the negative electrode active material. A non-aqueous secondary battery having a mass part equal to or greater than a value obtained by multiplying the cube root of the divided value by 20.
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| JP2011169227A JP2013033641A (en) | 2011-08-02 | 2011-08-02 | Electrode for nonaqueous secondary battery, and nonaqueous secondary battery |
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| JP2011169227A JP2013033641A (en) | 2011-08-02 | 2011-08-02 | Electrode for nonaqueous secondary battery, and nonaqueous secondary battery |
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| JP2013033641A true JP2013033641A (en) | 2013-02-14 |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2016042461A (en) * | 2014-08-13 | 2016-03-31 | 三星エスディアイ株式会社Ｓａｍｓｕｎｇ ＳＤＩ Ｃｏ．，Ｌｔｄ． | Positive electrode material, positive electrode including the same and lithium battery including the positive electrode |
| JP2017521822A (en) * | 2014-06-05 | 2017-08-03 | フラウンホッファー−ゲゼルシャフト・ツァー・フォデラング・デル・アンゲワンテン・フォーシュング・エー．ファウ． | Electrical energy storage element and method and apparatus for manufacturing the same |
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2011
- 2011-08-02 JP JP2011169227A patent/JP2013033641A/en not_active Withdrawn
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2017521822A (en) * | 2014-06-05 | 2017-08-03 | フラウンホッファー−ゲゼルシャフト・ツァー・フォデラング・デル・アンゲワンテン・フォーシュング・エー．ファウ． | Electrical energy storage element and method and apparatus for manufacturing the same |
| JP2016042461A (en) * | 2014-08-13 | 2016-03-31 | 三星エスディアイ株式会社Ｓａｍｓｕｎｇ ＳＤＩ Ｃｏ．，Ｌｔｄ． | Positive electrode material, positive electrode including the same and lithium battery including the positive electrode |
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