JP6631831B2 - Electrode for secondary battery, secondary battery, and method of manufacturing these - Google Patents
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Description
本発明は、二次電池用電極及び二次電池並びにこれらの製造方法に関する。 The present invention relates to an electrode for a secondary battery, a secondary battery, and a method for producing the same.
リチウムイオン二次電池は、充放電容量が高く、高出力化が可能な二次電池である。現在、リチウムイオン二次電池は、主として携帯電子機器用の電源として用いられており、更に、今後普及が予想される電気自動車用の電源として期待されている。 A lithium ion secondary battery is a secondary battery having a high charge / discharge capacity and a high output. At present, lithium ion secondary batteries are mainly used as power supplies for portable electronic devices, and are also expected to be used as power supplies for electric vehicles, which are expected to spread in the future.
通常、リチウムイオン二次電池用電極は、導電性を向上させるために活物質粉末の他にアセチレンブラックやケッチェンブラック（登録商標）のような微細な導電助剤を混合して作製される。このような従来電極では、数十ｎｍ程度の微細な導電助剤間の無数の点接触の連続によって電極合材層の導電性が担保されている。導電助剤間で点接触している箇所には接触抵抗が存在し、サイクルや保存等の過程において接触抵抗が増加し、さらに切断（導電パス切れ）することで劣化が進行する恐れがある。点接触を減らす手段として、比較的粒径の大きな導電助剤の導入が考えられる。特許文献１には、保存特性の向上のために平均粒径０．０１〜１μｍの炭素粒子からなる第１導電助剤中に平均粒径８〜４５μｍの炭素粒子を第２導電助剤として添加することが開示されている。また、特許文献２には、抵抗減少のために粒径の大きな第２導電助剤を導入することが開示されている。
Generally, an electrode for a lithium ion secondary battery is prepared by mixing a fine conductive additive such as acetylene black or Ketjen Black (registered trademark) in addition to the active material powder in order to improve conductivity. In such a conventional electrode, the conductivity of the electrode mixture layer is ensured by continuous countless point contacts between fine conductive aids of about several tens of nanometers. Contact resistance exists at points where the conductive assistants are in point contact, and the contact resistance increases in the course of cycling, storage, and the like, and further deterioration may occur due to further cutting (breaking of the conductive path). As a means for reducing the point contact, introduction of a conductive aid having a relatively large particle size can be considered.
しかしながら、単に第１導電助剤より粒径が少し大きいだけの第２導電助剤を添加するだけでは、導電パス切れを効果的に抑制するには不十分である。また、第２導電助剤の粒径が大きすぎる場合には電極内の導電性にバラツキが生じ、反応ムラによる電極の劣化が起こる場合がある。そこで、導電助剤についてより好ましい粒径設計が求められている。
本発明はかかる事情に鑑みてなされたものであり、適切な粒径設計がなされた導電助剤を有する二次電池用電極及び二次電池並びにこれらの製造方法を提供することを課題とする。
However, simply adding the second conductive assistant having a slightly larger particle size than the first conductive assistant is not enough to effectively suppress the disconnection of the conductive path. If the particle size of the second conductive additive is too large, the conductivity in the electrode varies, and the electrode may deteriorate due to uneven reaction. Therefore, a more preferable particle size design for the conductive auxiliary agent is required.
The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a secondary battery electrode and a secondary battery having a conductive aid with an appropriate particle size design, and a method for manufacturing these.
本発明者は鋭意探求の結果、サイクル後の電池の内部抵抗増加を低く抑えることができる、導電助剤の粒径と電極活物質の粒径との新たな関係を見出した。 As a result of intensive investigation, the present inventor has found a new relationship between the particle size of the conductive additive and the particle size of the electrode active material, which can suppress the increase in internal resistance of the battery after cycling.
本発明の二次電池用電極の製造方法は、平均粒径Ｄ（μｍ）の電極活物質と、平均粒径ｄｃ１（μｍ）の第１導電助剤と、前記ｄｃ１（μｍ）よりも大きい平均粒径ｄｃ２（μｍ）であり且つ前記ｄｃ２（μｍ）が以下の式（１）の条件を満たす第２導電助剤と、を選択する選択工程と、
前記電極活物質と前記第１導電助剤と前記第２導電助剤とを有する電極合材を集電体上に塗布して電極合材層を形成する電極形成工程と、をもつことを特徴とする。
Ｄ×（（３／２）１／２−１）≦ｄｃ２≦Ｄ・・・式（１）
Method of manufacturing a secondary battery electrode of the present invention includes an electrode active material having an average particle diameter D ([mu] m), a first conductive additive having an average particle diameter d c1 ([mu] m), than the d c1 (μm) A selection step of selecting a second conductive auxiliary agent having a large average particle diameter d c2 (μm) and the d c2 (μm) satisfying the following expression (1):
An electrode forming step of forming an electrode mixture layer by applying an electrode mixture having the electrode active material, the first conductive auxiliary, and the second conductive auxiliary on a current collector. And
D × ((3/2) 1/2 −1) ≦ d c2 ≦ D Expression (1)
本発明の二次電池用電極は、平均粒径Ｄ（μｍ）の電極活物質と、平均粒径ｄｃ１（μｍ）の第１導電助剤と、前記ｄｃ１（μｍ）よりも大きい平均粒径ｄｃ２（μｍ）であり且つ前記ｄｃ２（μｍ）が以下の式（１）の条件を満たす第２導電助剤とを有することを特徴とする。
Ｄ×（（３／２）１／２−１）≦ｄｃ２≦Ｄ・・・式（１）
The electrode for a secondary battery according to the present invention includes an electrode active material having an average particle diameter D (μm), a first conductive additive having an average particle diameter d c1 (μm), and an average particle having a diameter larger than d c1 (μm). It is characterized by having a diameter d c2 (μm) and the second conduction aid having the d c2 (μm) satisfying the following expression (1).
D × ((3/2) 1/2 −1) ≦ d c2 ≦ D Expression (1)
本発明の二次電池は、上記記載の二次電池用電極の製造方法により製造された二次電池用電極、又は上記記載の二次電池用電極を有することを特徴とする。 A secondary battery of the present invention is characterized by having the secondary battery electrode manufactured by the above-described method for manufacturing a secondary battery electrode or the secondary battery electrode described above.
本発明は上記の構成を具備しているため、適切な粒径設計がなされた導電助剤を有する二次電池用電極及び二次電池並びにこれらの製造方法を提供することができる。 Since the present invention has the above-described configuration, it is possible to provide an electrode for a secondary battery and a secondary battery having a conductive auxiliary agent having an appropriately designed particle size, and a method for manufacturing the same.
本発明の実施形態に係る二次電池用電極及びその製造方法並びに二次電池について詳細に説明する。なお、本明細書において、電極合材は、集電体に塗布する前の電極活物質等を含む混合物（固形分）をいう。電極合材層は、集電体上に電極合材を塗布して形成された層（固形分）をいう。Ｍ*、ｍｃ１ *、ｍｃ２ *が、順に、電極合材層を１００質量％としたときの電極合材層中の電極活物質、第１導電助剤、及び第２導電助剤の質量比（質量％）であるとして記述するが、Ｍ*、ｍｃ１ *、ｍｃ２ *が、順に、電極合材を１００質量％としたときの電極合材中の電極活物質、第１導電助剤、及び第２導電助剤の質量比（質量％）であると読み替えてもよい。 An electrode for a secondary battery, a method for manufacturing the same, and a secondary battery according to an embodiment of the present invention will be described in detail. In the present specification, the electrode mixture refers to a mixture (solid content) containing an electrode active material and the like before being applied to a current collector. The electrode mixture layer refers to a layer (solid content) formed by applying the electrode mixture on the current collector. M * , mc1 * , and mc2 * are, in order, the mass of the electrode active material, the first conductive additive, and the second conductive additive in the electrode mixture layer when the electrode mixture layer is 100% by mass. Although described as a ratio (% by mass), M * , mc1 * , and mc2 * are, in order, the electrode active material and the first conductive additive in the electrode mixture when the electrode mixture is 100% by mass. It may be read as the mass ratio (% by mass) of the agent and the second conductive additive.
（二次電池用電極の製造方法及び二次電池用電極）
本発明の二次電池用電極の製造方法は、選択工程と電極形成工程とを有する。選択工程と電極形成工程の間に、調整工程、又は／及び決定工程を行っても良い。以下、選択工程、調整工程、決定工程、及び電極形成工程について順に説明する。各工程で述べる電極活物質、第１導電助剤及び第２導電助剤の平均粒径などの関係は、電極活物質、第１導電助剤及び第２導電助剤が単分散の球体であるとした場合の理想モデルに基づくパラメータである。
(Method of manufacturing electrode for secondary battery and electrode for secondary battery)
The method for manufacturing an electrode for a secondary battery of the present invention includes a selecting step and an electrode forming step. An adjusting step and / or a determining step may be performed between the selecting step and the electrode forming step. Hereinafter, the selecting step, the adjusting step, the determining step, and the electrode forming step will be described in order. The relationship between the average particle size of the electrode active material, the first conductive auxiliary, and the second conductive auxiliary described in each step is such that the electrode active material, the first conductive auxiliary, and the second conductive auxiliary are monodispersed spheres. Is a parameter based on the ideal model.
（１）選択工程
選択工程では、平均粒径Ｄ（μｍ）の電極活物質と、平均粒径ｄｃ１（μｍ）の第１導電助剤と、平均粒径ｄｃ２（μｍ）の第２導電助剤とを選択する。ここで、第２導電助剤の平均粒径ｄｃ２（μｍ）は、第１導電助剤の平均粒径ｄｃ１（μｍ）よりも大きく（ｄｃ２＞ｄｃ１）、且つ、電極活物質の平均粒径Ｄ（μｍ）と以下の式（１）の関係を有する。
Ｄ×（（３／２）１／２−１）≦ｄｃ２≦Ｄ・・・式（１）
(1) Selection Step In the selection step, an electrode active material having an average particle diameter D (μm), a first conductive auxiliary having an average particle diameter d c1 (μm), and a second conductive agent having an average particle diameter d c2 (μm) are used. Auxiliary and select. Here, the average particle size d c2 (μm) of the second conductive additive is larger than the average particle size d c1 (μm) of the first conductive additive (d c2 > d c1 ), and the average particle size of the electrode active material. The average particle diameter D (μm) has the relationship of the following equation (1).
D × ((3/2) 1/2 −1) ≦ d c2 ≦ D Expression (1)
式（１）は、電極活物質、第１導電助剤及び第２導電助剤が電極合材層の中で導電性を高める配置にするためのこれらの平均粒径の範囲を示している。これらの平均粒径の範囲は、電極合材層が正極合材層である場合又は／及び負極合材層である場合のいずれにも適用できる。電極活物質が導電性に乏しく導電助剤を必要とする場合に、本実施形態を特に有効に適用できる。 Formula (1) shows the range of the average particle size of the electrode active material, the first conductive auxiliary agent, and the second conductive auxiliary agent so that the electrode active material and the second conductive auxiliary agent are arranged to increase the conductivity in the electrode mixture layer. These ranges of the average particle size can be applied to both cases where the electrode mixture layer is a positive electrode mixture layer and / or a case where the electrode mixture layer is a negative electrode mixture layer. This embodiment can be applied particularly effectively when the electrode active material has poor conductivity and requires a conductive assistant.
図１に示すように、電極活物質３の表面は、第１導電助剤１により被覆されている。第１導電助剤１よりも平均粒径が大きい第２導電助剤２は、電極活物質３間の隙間４を埋めることで、第２導電助剤２により電極活物質３間の長距離導電性を確保する。本明細書において、「隙間」とは、少なくとも３つの電極活物質３で囲まれている立体的な空間をいう。
As shown in FIG. 1, the surface of the electrode
第２導電助剤の平均粒径ｄｃ２（μｍ）の上限は、電極活物質の平均粒径Ｄ（μｍ）である。ｄｃ２（μｍ）がＤ（μｍ）よりも大きい場合には、電極合材層に導電ムラが生じるおそれがある。ｄｃ２（μｍ）の上限はＤ×４／５であることが好ましい。 The upper limit of the average particle diameter d c2 (μm) of the second conductive additive is the average particle diameter D (μm) of the electrode active material. When d c2 (μm) is larger than D (μm), there is a possibility that conductive unevenness may occur in the electrode mixture layer. The upper limit of d c2 (μm) is preferably D × 4/5.
第２導電助剤の平均粒径ｄｃ２（μｍ）の下限は、Ｄ×（（３／２）１／２−１）である。ｄｃ２（μｍ）がＤ×（（３／２）１／２−１）未満の場合には、第２導電助剤が、隙間を囲む電極活物質と接しにくくなり、隙間での導電性に貢献しないおそれがある。 The lower limit of the average particle size d c2 (μm) of the second conductive additive is D × ((3/2) 1/2 −1). When d c2 (μm) is less than D × ((3/2) 1/2 −1), the second conductive assistant becomes less likely to be in contact with the electrode active material surrounding the gap, and the conductivity in the gap is reduced. May not contribute.
電極活物質が最密構造をとった場合、第２導電助剤の平均粒径ｄｃ２（μｍ）の下限は、電極活物質間の隙間にちょうど収まる大きさである。これを以下に詳細に説明する。 When the electrode active material has a close-packed structure, the lower limit of the average particle diameter d c2 (μm) of the second conductive additive is a size that fits in the gap between the electrode active materials. This will be described in detail below.
図２は、最密構造をもって配置された電極活物質３を示している。電極活物質３は粒径Ｄ（μｍ）の球、第２導電助剤２は粒径ｄｃ２（μｍ）の球とする。
FIG. 2 shows the electrode
最密構造となるように高密度に配置された電極活物質３の間には、隙間４が形成される。隙間４にちょうど収まる大きさの第２導電助剤２の中心は、隙間４を囲む４つの電極活物質３の中心を結んで形成される正四面体６の重心に位置する。
A gap 4 is formed between the electrode
正四面体とその重心の関係を図３に示す。図３において、Ａ、Ｂ、Ｃ、Ｄは、正四面体の頂点を示し、Ｇは正四面体の重心を示し、Ｇ１は頂点Ｂ、Ｃ、Ｄで囲まれる三角形ＢＣＤの重心を示し、Ｇ２は頂点Ａ、Ｃ、Ｄで囲まれる三角形ＡＣＤの重心を示し、Ｇ３は頂点Ａ、Ｂ、Ｄで囲まれる三角形ＡＢＤの重心を示し、Ｇ４は頂点Ａ、Ｂ、Ｃで囲まれる三角形ＡＢＣの重心を示している。頂点Ａ、頂点Ｂ、重心Ｇ１で囲まれる三角形ＡＢＧ１は、∠ＡＧ１Ｂを直角とし、線分ＡＢの長さをＤ（μｍ）とする。線分ＢＣの中心をＰとすると、∠ＢＰＧ１は直角であり、∠Ｇ１ＢＰは３０°である。線分ＢＰの長さは１／２×Ｄである。三平方の定理より、線分ＢＧ１の長さはＤ／√３であり、線分ＡＧ１の長さは√（２／３）×Ｄである。正四面体の重心の性質より、線分ＧＧ１の長さと線分ＧＡの長さとの比は１：３である。線分ＡＧの長さはＤ×√（２／３）×３／４である。 FIG. 3 shows the relationship between the tetrahedron and its center of gravity. In FIG. 3, A, B, C, and D indicate the vertices of the regular tetrahedron, G indicates the center of gravity of the regular tetrahedron, G 1 indicates the center of gravity of the triangle BCD surrounded by the vertices B, C, and D, G 2 indicates the center of gravity of the triangle ACD surrounded by vertices A, C, and D, G 3 indicates the center of gravity of the triangle ABD surrounded by vertices A, B, and D, and G 4 is surrounded by vertices A, B, and C The center of gravity of the triangle ABC is shown. Vertex A, vertex B, triangle ABG 1 surrounded by the center of gravity G 1 is a right angles ∠AG 1 B, the length of the line segment AB and D ([mu] m). Assuming that the center of the line segment BC is P, ∠BPG 1 is a right angle, and ∠G 1 BP is 30 °. The length of the line segment BP is ×× D. From the Pythagorean theorem, length of the segment BG 1 is a D / √3, the length of the line segment AG 1 is √ (2/3) × D. From the nature of the centroid of the tetrahedron, the ratio of the length of the line segment GA line segment GG 1 1: 3. The length of the line segment AG is D × √ (2/3) × 3/4.
以上から、隣り合う電極活物質３の中心間を結んで形成される正四面体の重心と、電極活物質３の中心との間の距離Ｅ（μｍ）は、Ｄ×√（２／３）×３／４で表される。図２に示すように、第２導電助剤２は隙間４を囲む電極活物質３と接しているため、隙間４にちょうど収まる大きさの第２導電助剤２の半径は、隣り合う電極活物質３の中心間を結んで形成される正四面体の重心と、電極活物質３の中心との間の距離Ｅから電極活物質３の粒径Ｄ（μｍ）の半値を引いた値（Ｄ×√（２／３）×３／４−１／２×Ｄ）に等しい。第２導電助剤の半径の２倍が粒径ｄｃ２（μｍ）である。したがって、隙間４にちょうど収まる大きさの第２導電助剤の粒径ｄｃ２は、２×（Ｄ×√（２／３）×３／４−１／２×Ｄ）＝Ｄ（（３／２）１／２−１）となる。よって、第２導電助剤の平均粒径ｄｃ２（μｍ）は、正極活物質の平均粒径Ｄ（μｍ）との間で式（１）の関係をもつ。
From the above, the distance E (μm) between the center of gravity of the tetrahedron formed by connecting the centers of the adjacent electrode
選択工程に先立って、電極活物質の平均粒径Ｄ（μｍ）、第１導電助剤の平均粒径ｄｃ１（μｍ）、及び第２導電助剤の平均粒径ｄｃ２（μｍ）の少なくとも１つを測定するとよい。選択工程では、予め測定したＤ（μｍ）、ｄｃ１（μｍ）、及びｄｃ２（μｍ）の少なくとも１つに基づいて、ｄｃ２＞ｄｃ１であり且つ上記の式（１）を満たす関係になるように、測定していないＤ（μｍ），ｄｃ１（μｍ）、及びｄｃ２（μｍ）の残りのパラメータを決定することがよい。 Prior to the selection step, at least one of the average particle diameter D (μm) of the electrode active material, the average particle diameter d c1 (μm) of the first conductive auxiliary, and the average particle diameter d c2 (μm) of the second conductive auxiliary. You may want to measure one. In the selection step, based on at least one of D (μm), d c1 (μm) , and d c2 (μm) measured in advance, the relation of d c2 > d c1 and satisfying the above expression (1) is satisfied. The remaining parameters of D (μm), d c1 (μm) , and d c2 (μm), which have not been measured, may be determined.
各平均粒径Ｄ（μｍ）、ｄｃ１（μｍ）、ｄｃ２（μｍ）は、各成分のＤ５０、即ち体積基準で測定したメディアン径を意味する。各平均粒径Ｄ（μｍ），ｄｃ１（μｍ）、ｄｃ２（μｍ）は、レーザ回折粒度分布測定法により測定することができる。電極活物質の平均粒径Ｄ（μｍ）、第１導電助剤の平均粒径ｄｃ１（μｍ）、及び第２導電助剤の平均粒径ｄｃ２（μｍ）は、ｄｃ２＞ｄｃ１であり且つ上記の式（１）を満たす関係になるように、粉砕、分級などにより調整することがよい。 The average particle diameters D (μm), d c1 (μm) and d c2 (μm) mean the D50 of each component, that is, the median diameter measured on a volume basis. Each average particle diameter D (μm), dc1 (μm) , dc2 (μm) can be measured by a laser diffraction particle size distribution measurement method. The average particle diameter D of the electrode active material ([mu] m), the average particle of the first conductive additive diameter d c1 ([mu] m), and the average particle diameter d c2 (μm) of the second conductive additive, in d c2> d c1 It is preferable to adjust by pulverization, classification and the like so as to satisfy the above-mentioned expression (1).
また、予め電極活物質の平均粒径Ｄ（μｍ）を測定してもよい。測定されたＤ（μｍ）に基づいて上記の式（１）の条件を満たす平均粒径ｄｃ２（μｍ）の第２導電助剤を選択してもよい。 Further, the average particle diameter D (μm) of the electrode active material may be measured in advance. Based on the measured D (μm), a second conductive additive having an average particle diameter d c2 (μm) satisfying the condition of the above formula (1) may be selected.
更に、Ｄ（μｍ）、ｄｃ１（μｍ）、及びｄｃ２（μｍ）は、以下の範囲にあることが好ましい。 Further, it is preferable that D (μm), d c1 (μm), and d c2 (μm) are in the following ranges.
電極活物質の平均粒径Ｄは、０．６μｍ以上６０μｍ以下であることがよく、更に、１μｍ以上３０μｍ以下であることが好ましい。電極活物質の平均粒径Ｄが過小である場合には、電極活物質が取り扱いにくくなるおそれがある。電極活物質の平均粒径Ｄが過大である場合には、電荷担体が電極活物質の内部まで到達しにくくなり、電池容量及びレート特性が低下するおそれがある。 The average particle diameter D of the electrode active material is preferably 0.6 μm or more and 60 μm or less, and more preferably 1 μm or more and 30 μm or less. If the average particle size D of the electrode active material is too small, the electrode active material may be difficult to handle. If the average particle diameter D of the electrode active material is too large, the charge carriers will not easily reach the inside of the electrode active material, and the battery capacity and rate characteristics may be reduced.
第１導電助剤の平均粒径ｄｃ１は、０．００３μｍ以上０．３μｍ以下であることがよく、更に０．０１μｍ以上０．１μｍ以下であり、０．０２μｍ以上０．０８μｍであることがより好ましい。第１導電助剤の平均粒径ｄｃ１が過小である場合には、第１導電助剤の取り扱い性が低下するおそれがある。第１導電助剤の平均粒径ｄｃ１が過大である場合には、電極活物質の表面を均一に被覆しにくくなり、電極活物質表面の導電性が低下するおそれがある。 The average particle diameter d c1 of the first conductive additive may be at 0.3μm or less than 0.003 .mu.m, and is further 0.01μm or 0.1μm or less, to be 0.08μm or more 0.02μm More preferred. When the average particle diameter dc1 of the first conductive additive is too small, the handleability of the first conductive additive may be reduced. If the average particle diameter dc1 of the first conductive additive is too large, it is difficult to uniformly cover the surface of the electrode active material, and the conductivity of the electrode active material surface may be reduced.
第２導電助剤の平均粒径ｄｃ２は、０．３μｍ以上３０μｍ以下であることがよく、更に、１μｍ以上１０μｍ以下であることが好ましく、２μｍ以上８μｍ以下であることが最も好ましい。この場合には、本発明の課題をより効果的に達成できる。 The average particle diameter dc2 of the second conductive additive is preferably 0.3 μm or more and 30 μm or less, more preferably 1 μm or more and 10 μm or less, and most preferably 2 μm or more and 8 μm or less. In this case, the object of the present invention can be achieved more effectively.
第２導電助剤の平均粒径ｄｃ２（μｍ）と第１導電助剤の平均粒径ｄｃ１（μｍ）との比率（ｄｃ２／ｄｃ１）は、１０以上１０００以下がよく、更に５０以上５００以下であることが好ましく、７０以上２５０以下であることが望ましい。上記の比率（ｄｃ２／ｄｃ１）が過小の場合には、第２導電助剤の平均粒径と第１導電助剤の平均粒径が近すぎて、これらを区別して用いることの意義が失われるおそれがある。 The ratio (d c2 / d c1 ) of the average particle size d c2 (μm) of the second conductive auxiliary to the average particle size d c1 (μm) of the first conductive auxiliary is preferably 10 or more and 1000 or less, and more preferably 50 or less. It is preferably from 500 to 500, and more preferably from 70 to 250. When the above ratio (d c2 / d c1 ) is too small, the average particle size of the second conductive additive is too close to the average particle size of the first conductive additive, and it is meaningful to use these separately. May be lost.
本実施形態において用いる電極活物質は、リチウムイオンなどの金属イオンを吸蔵及び放出し得る物質である。本実施形態において用いる電極活物質は、導電性に乏しいため、電極合材層に導電助剤を混合する必要性が大きいものがよい。本実施形態において用いる電極活物質は、正極活物質及び負極活物質のいずれでもよい。電極合材層が正極合材層である場合の電極活物質は、特に正極活物質といい、電極合材層が負極合材層である場合の電極活物質は、特に負極活物質という。 The electrode active material used in the present embodiment is a material that can occlude and release metal ions such as lithium ions. Since the electrode active material used in the present embodiment has poor conductivity, it is preferable that the need to mix a conductive additive into the electrode mixture layer is great. The electrode active material used in the present embodiment may be either a positive electrode active material or a negative electrode active material. The electrode active material when the electrode mixture layer is a positive electrode mixture layer is particularly called a positive electrode active material, and the electrode active material when the electrode mixture layer is a negative electrode mixture layer is particularly called a negative electrode active material.
正極活物質としては、リチウム複合金属酸化物が挙げられる。リチウム複合金属酸化物としては、一般式：ＬｉａＮｉｂＣｏｃＭｎｄＤｅＯｆ(０．２≦ａ≦１．２、ｂ＋ｃ＋ｄ＋ｅ＝１、０≦ｅ＜１、ＤはＬｉ、Ｆｅ、Ｃｒ、Ｃｕ、Ｚｎ、Ｃａ、Ｍｇ、Ｓ、Ｓｉ、Ｎａ、Ｋ、Ａｌ、Ｚｒ、Ｔｉ、Ｐ、Ｇａ、Ｇｅ、Ｖ、Ｍｏ、Ｎｂ、Ｗ、Ｌａから選ばれる少なくとも１の元素、１．７≦ｆ≦２．１) で表される層状化合物、Ｌｉ２ＭｎＯ３を挙げることができる。また、リチウム複合金属酸化物としては、一般式：ＬｉｘＡｙＭｎ２-ｙＯ4（Ａは、遷移金属元素、Ｌｉ、Ｃａ、Ｍｇ、Ｓ、Ｓｉ、Ｎａ、Ｋ、Ａｌ、Ｐ、Ｇａ、及びＧｅから選ばれる少なくとも１種の元素、０＜ｘ≦２．２、０≦ｙ≦１）で表されるスピネル型化合物、及びスピネル型化合物と層状化合物の混合物で構成される固溶体、ＬｉＭＰＯ４、ＬｉＭＶＯ４又はＬｉ２ＭＳｉＯ４（式中のＭはＣｏ、Ｎｉ、Ｍｎ、Ｆｅのうちの少なくとも一種から選択される）などで表されるポリアニオン系化合物であってもよい。
Examples of the positive electrode active material include a lithium composite metal oxide. As the lithium composite metal oxide represented by the general formula: Li a Ni b Co c Mn d D e O f (0.2 ≦ a ≦ 1.2, b + c + d + e = 1,0 ≦ e <1, D is Li, Fe, At least one element selected from Cr, Cu, Zn, Ca, Mg, S, Si, Na, K, Al, Zr, Ti, P, Ga, Ge, V, Mo, Nb, W and La; 1.7 ≦ f ≦ 2.1) lamellar compound represented by, may be mentioned
例えば、層状化合物としては、ＬｉＮｉ０．５Ｃｏ０．２Ｍｎ０．３Ｏ２、ＬｉＮｉ０．５Ｃｏ０．３Ｍｎ０．２Ｏ２、ＬｉＮｉ1/3Ｃｏ1/3Ｍｎ1/3Ｏ２、ＬｉＮｉ０．５Ｍｎ０．５Ｏ２、ＬｉＮｉ０．７５Ｃｏ０．１Ｍｎ０．１５Ｏ２、ＬｉＭｎＯ２、ＬｉＮｉＯ２、及びＬｉＣｏＯ２から選ばれる少なくとも一種が挙げられる。スピネル型化合物としては、例えば、ＬｉＮｉ０．５Ｍｎ１．５Ｏ４、ＬｉＭｎ２Ｏ４が挙げられる。ポリアニオン系化合物としては、例えば、ＬｉＦｅＰＯ４、ＬｉＣｏＰＯ４、Ｌｉ２ＣｏＰＯ４Ｆ、Ｌｉ２ＭｎＳｉＯ４、Ｌｉ２ＦｅＳｉＯ４が挙げられる。 For example, as the layered compound, LiNi 0.5 Co 0.2 Mn 0.3 O 2 , LiNi 0.5 Co 0.3 Mn 0.2 O 2 , LiNi 1/3 Co 1/3 Mn 1/3 O 2 , LiNi 0.5 Mn 0.5 O 2 , at least one selected from LiNi 0.75 Co 0.1 Mn 0.15 O 2 , LiMnO 2 , LiNiO 2 , and LiCoO 2 . Examples of the spinel-type compound include LiNi 0.5 Mn 1.5 O 4 and LiMn 2 O 4 . Examples of the polyanionic compound include LiFePO 4 , LiCoPO 4 , Li 2 CoPO 4 F, Li 2 MnSiO 4 , and Li 2 FeSiO 4 .
負極活物質としては、リチウムイオンなどの金属イオンを吸蔵及び放出し得る材料が使用可能である。したがって、負極活物質は、リチウムイオンなどの金属イオンを吸蔵及び放出可能である単体、合金または化合物であるとよい。たとえば、負極活物質として、ケイ素などが挙げられる。ケイ素などを負極活物質に採用すると、ケイ素１原子が複数のリチウムと反応するため、高容量の活物質となるが、リチウムの吸蔵及び放出に伴う体積の膨張及び収縮が顕著となるとの問題が生じる恐れがあるため、当該恐れの軽減のために、ケイ素単体と二酸化ケイ素に不均化するＳｉＯｘ（０．３≦ｘ≦１．６）などのケイ素系材料を採用することが好ましい。 As the negative electrode active material, a material that can occlude and release metal ions such as lithium ions can be used. Therefore, the negative electrode active material is preferably a simple substance, an alloy, or a compound capable of inserting and extracting metal ions such as lithium ions. For example, silicon or the like can be used as the negative electrode active material. When silicon or the like is used for the negative electrode active material, one atom of silicon reacts with a plurality of lithium atoms, resulting in a high-capacity active material. However, there is a problem that the expansion and contraction of volume due to occlusion and release of lithium become remarkable. In order to reduce such a risk, it is preferable to employ a silicon-based material such as SiO x (0.3 ≦ x ≦ 1.6) that disproportionates to silicon alone and silicon dioxide.
また、負極活物質して、Ｎｂ２Ｏ５、ＴｉＯ２、Ｌｉ４Ｔｉ５Ｏ１２、ＷＯ２、ＭｏＯ２、Ｆｅ２Ｏ３等の酸化物、又は、Ｌｉ３−ｘＭｘＮ（Ｍ＝Ｃｏ、Ｎｉ、Ｃｕ）で表される窒化物を採用しても良い。 In addition, as a negative electrode active material, an oxide such as Nb 2 O 5 , TiO 2 , Li 4 Ti 5 O 12 , WO 2 , MoO 2 , Fe 2 O 3 , or Li 3-x M x N (M = A nitride represented by (Co, Ni, Cu) may be employed.
負極活物質として導電性材料を用いる場合にも本発明を適用できる。本発明の第１導電助剤と第２導電助剤を本発明の粒径設計を適用することで、導電性の負極活物質間の導電パス切れを抑制できる。負極活物質として用い得る導電性材料としては、例えば、Ｌｉや、炭素、ゲルマニウム、錫などの１４族元素、アルミニウム、インジウムなどの１３族元素、亜鉛、カドミウムなどの１２族元素、アンチモン、ビスマスなどの１５族元素、マグネシウム、カルシウムなどのアルカリ土類金属、銀、金などの１１族元素が挙げられる。これらは、合金又は化合物として用いることができる。合金又は化合物の具体例としては、Ａｇ−Ｓｎ合金、Ｃｕ−Ｓｎ合金、Ｃｏ−Ｓｎ合金等の錫系材料、各種黒鉛などの結晶性炭素系材料、ハードカーボンやソフトカーボンなどの非晶質炭素系材料が挙げられる。 The present invention can be applied to a case where a conductive material is used as the negative electrode active material. By applying the particle size design of the first conductive assistant and the second conductive assistant of the present invention to the particle size design of the present invention, disconnection of a conductive path between conductive negative electrode active materials can be suppressed. Examples of the conductive material that can be used as the negative electrode active material include Li, Group 14 elements such as carbon, germanium, and tin; Group 13 elements such as aluminum and indium; Group 12 elements such as zinc and cadmium; and antimony and bismuth. Group 15 elements, alkaline earth metals such as magnesium and calcium, and Group 11 elements such as silver and gold. These can be used as alloys or compounds. Specific examples of alloys or compounds include tin-based materials such as Ag-Sn alloys, Cu-Sn alloys, and Co-Sn alloys, crystalline carbon-based materials such as various graphites, and amorphous carbons such as hard carbon and soft carbon. System material.
本発明の実施形態に係る二次電池用電極に用いる電極活物質は、必ずしも上に挙げたもの単一で用いる必要はなく、2種類以上を含む混合電極活物質として用いても良い。 The electrode active material used for the secondary battery electrode according to the embodiment of the present invention does not necessarily need to be used alone as described above, and may be used as a mixed electrode active material including two or more types.
第１導電助剤及び第２導電助剤は、化学的に不活性な電子高伝導体であれば良く、炭素質微粒子であるカーボンブラック、黒鉛、アセチレンブラック、ケッチェンブラック（登録商標）、気相法炭素繊維（Vapor Grown Carbon Fiber：ＶＧＣＦ）、及び各種金属粒子などが例示される。これらを単独又は二種以上組み合わせて第１導電助剤及び第２導電助剤として用いるとよい。 The first conductive assistant and the second conductive assistant may be chemically inert high electron conductors, and may be carbon fine particles such as carbon black, graphite, acetylene black, Ketjen black (registered trademark), Examples include phase-process carbon fiber (Vapor Grown Carbon Fiber: VGCF) and various metal particles. These may be used alone or in combination of two or more as the first conductive auxiliary and the second conductive auxiliary.
（２）調整工程
調整工程では、電極合材層を１００質量％としたときの電極活物質の質量比及び第２導電助剤の質量比を百分率でＭ＊（質量％）及びｍｃ２ ＊（質量％）とし、電極活物質の真密度をρ（ｇ／ｃｍ３）とし、第２導電助剤の真密度をρｃ２（ｇ／ｃｍ３）とし、電極活物質の平均粒径をＤ（μｍ）とし、第２導電助剤の平均粒径をｄｃ２（μｍ）としたときに、Ｍ＊（質量％）とｍｃ２ ＊（質量％）が以下の式（２）の条件を満たすように、電極活物質と第２導電助剤との配合比を調整する。
０．１＜（Ｍ＊×ρｃ２×ｄｃ２ ３）／（ｍｃ２ ＊×ρ×Ｄ３）＜１０・・・式（２）
(2) Adjustment Step In the adjustment step, the mass ratio of the electrode active material and the mass ratio of the second conductive additive, assuming that the electrode mixture layer is 100% by mass, are expressed as percentages of M * (mass%) and mc2 * ( Mass%), the true density of the electrode active material is ρ (g / cm 3 ), the true density of the second conductive additive is ρ c2 (g / cm 3 ), and the average particle size of the electrode active material is D ( μm) and the average particle size of the second conductive additive is d c2 (μm), so that M * (mass%) and m c2 * (mass%) satisfy the condition of the following formula (2). Next, the mixing ratio of the electrode active material and the second conductive additive is adjusted.
0.1 <(M * × ρ c2 × d c2 3 ) / ( mc2 * × ρ × D 3 ) <10 Expression (2)
図２に示すように、電極合材層において電極活物質３が最密配置され、立方または六方最密構造をとる場合、電極活物質３の数と電極活物質３間の隙間４の数はほぼ等しくなる。電極活物質３間の隙間４の多くには第２導電助剤が収まることがよい。このため、電極合材層における電極活物質３の数と第２導電助剤２の数とがほぼ等しいことがよい。
As shown in FIG. 2, when the electrode
電極合材層における電極活物質の数は、電極合材層における電極活物質の総体積Ｖ（ｃｍ３）を、電極活物質１個当たりの体積Ｗ（ｃｍ３）で除することにより求められる。電極合材層の中の電極活物質の総質量をＭ（ｇ）とし、電極活物質の真密度をρ（ｇ／ｃｍ３）とし、電極活物質の平均粒径をＤ（μｍ）としたとき、電極合材層における電極活物質の数Ｎは、以下の式（３）で表される。
Ｎ＝Ｖ／Ｗ＝１０１２×（Ｍ／ρ）／（４π×（Ｄ／２）３／３）・・・式（３）
The number of the electrode active materials in the electrode mixture layer is determined by dividing the total volume V (cm 3 ) of the electrode active materials in the electrode mixture layer by the volume W (cm 3 ) per electrode active material. . The total mass of the electrode active material in the electrode mixture layer was M (g), the true density of the electrode active material was ρ (g / cm 3 ), and the average particle size of the electrode active material was D (μm). At this time, the number N of the electrode active materials in the electrode mixture layer is represented by the following equation (3).
N = V / W = 10 12 × (M / ρ) / (4π × (D / 2) 3/3) ··· (3)
電極合材層における第２導電助剤の数ｎｃ２は、電極合材層における第２導電助剤の総体積ｖｃ２（ｃｍ３）を、第２導電助剤１個当たりの体積ｗｃ２（ｃｍ３）で除することにより求められる。電極合材層中の第２導電助剤の総質量をｍｃ２（ｇ）とし、第２導電助剤の真密度をρｃ２（ｇ／ｃｍ３）とし、第２導電助剤の平均粒径をｄｃ２（μｍ）としたときに、電極合材層における第２導電助剤の数ｎｃ２は、以下の式（４）で表される。
ｎｃ２＝ｖｃ２／ｗｃ２＝１０１２×（ｍｃ２／ρｃ２）／（４π×（ｄｃ２／２）３／３）・・・式（４）
The number nc2 of the second conductive assistants in the electrode mixture layer is determined by dividing the total volume v c2 (cm 3 ) of the second conductive assistants in the electrode mixture layer by the volume w c2 (per second conductive assistant). cm 3 ). The total mass of the second conductive additive in the electrode mixture layer is mc2 (g), the true density of the second conductive additive is ρc2 (g / cm 3 ), and the average particle size of the second conductive additive is Is defined as d c2 (μm), the number nc2 of the second conductive assistant in the electrode mixture layer is represented by the following equation (4).
n c2 = v c2 / w c2 = 10 12 × (m c2 / ρ c2) / (4π × (d c2 / 2) 3/3) ··· (4)
電極合材層における電極活物質の数Ｎと第２導電助剤の数ｎｃ２との比率（Ｎ／ｎｃ２）は、以下の式（５）により表される。
Ｎ／ｎｃ２＝（（Ｍ／ρ）／（４π×（Ｄ／２）３／３））／（（ｍｃ２／ρｃ２）／（４π×（ｄｃ２／２）３／３））＝（Ｍ×ρｃ２×ｄｃ２ ３）／（ｍｃ２×ρ×Ｄ３）・・・式（５）
The ratio between the number n c2 number N and a second conductive additive of the electrode active material in the electrode mixture layer (N / n c2) is represented by the following equation (5).
N / n c2 = ((M / ρ) / (4π × (D / 2) 3/3)) / ((m c2 / ρ c2) / (4π × (d c2 / 2) 3/3)) = (M × ρ c2 × d c2 3) / (m c2 × ρ × D 3) ··· (5)
ここで、電極合材層を１００質量％としたときの電極活物質の質量比及び第２導電助剤の質量比をＭ＊（質量％）及びｍｃ２ ＊（質量％）としたときに、式（５）は、（Ｍ＊×ρｃ２×ｄｃ２ ３）／（ｍｃ２ ＊×ρ×Ｄ３）と等しい。 Here, when the mass ratio of the electrode active material and the mass ratio of the second conductive additive when the electrode mixture layer is 100 mass% are M * (mass%) and mc2 * (mass%), equation (5) is equal to (M * × ρ c2 × d c2 3) / (m c2 * × ρ × D 3).
（Ｍ＊×ρｃ２×ｄｃ２ ３）／（ｍｃ２ ＊×ρ×Ｄ３）が０．１以下の場合には、電極活物質間の隙間の数に対して第２導電助剤が多くなり、隙間での導電性に貢献しない第２導電助剤が多くなるおそれがある。電極活物質が相対的に少なくなり、電池の容量が低下するおそれがある。一方、（Ｍ＊×ρｃ２×ｄｃ２ ３）／（ｍｃ２ ＊×ρ×Ｄ３）が１０以上の場合には、電極活物質間の隙間の多くに第２導電助剤が入らず、隙間の導電性を図ることができず、電池の内部抵抗が増加するおそれがある。 If (M * × ρ c2 × d c2 3) / (m c2 * × ρ × D 3) is 0.1 or less, many second conductive auxiliary agent to the number of gaps between the electrode active material Therefore, there is a possibility that the amount of the second conductive aid that does not contribute to the conductivity in the gap increases. There is a possibility that the electrode active material becomes relatively small and the capacity of the battery is reduced. On the other hand, if (M * × ρ c2 × d c2 3) / (m c2 * × ρ × D 3) is 10 or more, not a second conductive additive from entering the number of gaps between the electrode active material, The gap cannot be made conductive, and the internal resistance of the battery may increase.
（Ｍ＊×ρｃ２×ｄｃ２ ３）／（ｍｃ２ ＊×ρ×Ｄ３）は０．３以上４以下であることが好ましく、更には、０．５以上３．５以下であることが最も望ましい。この場合には、電池の内部抵抗を更に抑制できる。 (M * × ρ c2 × d c2 3) / (m c2 * × ρ × D 3) is preferably 0.3 to 4, further, it is 0.5 to 3.5 Most desirable. In this case, the internal resistance of the battery can be further suppressed.
調整工程に先立って、電極活物質の真密度ρ（ｇ／ｃｍ３）及び第２導電助剤の真密度ρｃ２（ｇ／ｃｍ３）を測定することがよい。測定などによって既知となったρ（ｇ／ｃｍ３）及びρｃ２（ｇ／ｃｍ３）に基づいて、電極合材層の中のＭ（ｇ）とｍｃ２（ｇ）が式（２）の条件を満たすように調整するとよい。また、予め電極合材層における電極活物質の質量比Ｍ＊（質量％）を決定しておき、Ｍ＊（質量％）と既知のρ（ｇ／ｃｍ３）及びρｃ２（ｇ／ｃｍ３）に基づいて、式（２）の条件を満たすように、電極合材層における第２導電助剤の質量比ｍｃ２ ＊（質量％）を決定してもよい。 Prior to the adjustment step, it is preferable to measure the true density ρ (g / cm 3 ) of the electrode active material and the true density ρ c2 (g / cm 3 ) of the second conductive additive. Based on ρ (g / cm 3 ) and ρ c2 (g / cm 3 ) known by measurement and the like, M (g) and m c2 (g) in the electrode mixture layer are calculated according to the formula (2). It is advisable to adjust to meet the conditions. Further, the mass ratio M * (mass%) of the electrode active material in the electrode mixture layer is determined in advance, and M * (mass%) and known ρ (g / cm 3 ) and ρ c2 (g / cm 3) ), The mass ratio mc2 * (mass%) of the second conductive additive in the electrode mixture layer may be determined so as to satisfy the condition of Expression (2).
電極合材層における電極活物質の質量比Ｍ＊（質量％）と第２導電助剤の質量比ｍｃ２ ＊（質量％）とが、式（２）の条件を満たすようにするためには、集電体上に塗布する前の電極合材の中のＭ＊（質量％）とｍｃ２ ＊（質量％）が式（２）の条件を満たすようにすればよい。 In order for the mass ratio M * (mass%) of the electrode active material and the mass ratio m c2 * (mass%) of the second conductive additive in the electrode mixture layer to satisfy the condition of the expression (2), It suffices that M * (mass%) and mc2 * (mass%) in the electrode mixture before being applied onto the current collector satisfy the condition of Expression (2).
（３）決定工程
更に、電極合材層の中の第１導電助剤の個数と第１導電助剤１個当たりの断面積との積をＳｃ１（ｍ２）とし、電極合材層の中の電極活物質の総表面積をＳ（ｍ２）とし、電極合材層の中の第２導電助剤の総表面積をＳｃ２（ｍ２）としたとき、Ｓｃ１（ｍ２）及びＳｃ２（ｍ２）が以下の式（６）の条件を満たすように、第１導電助剤及び第２導電助剤の量を決定する決定工程を行うとよい。
Ｓ＋Ｓｃ２≦Ｓｃ１・・・・式（６）
(3) Determination Step Further, the product of the number of the first conductive assistants in the electrode mixture layer and the cross-sectional area per one first conductive assistant is S c1 (m 2 ), and When the total surface area of the electrode active material in the electrode is S (m 2 ) and the total surface area of the second conductive additive in the electrode mixture layer is S c2 (m 2 ), S c1 (m 2 ) and S c It is preferable to perform a determining step of determining the amounts of the first conductive auxiliary agent and the second conductive auxiliary agent so that c2 (m 2 ) satisfies the condition of the following expression (6).
S + S c2 ≦ S c1 Equation (6)
電極合材層の中の第１導電助剤の個数と第１導電助剤１個当たりの断面積との積であるＳｃ１（ｍ２）は、電極合材層に含まれる第１導電助剤全体で被覆可能な被覆面積を意味している。第１導電助剤１個当たりの断面積は、第１導電助剤を球体であると想定したときの該球体の中心を通る断面の面積をいう。 S c1 (m 2 ), which is the product of the number of first conductive assistants in the electrode mixture layer and the cross-sectional area per first conductive assistant, is the first conductive assistant included in the electrode mixture layer. It means the coverage area that can be covered with the whole agent. The cross-sectional area per 1st electric conduction auxiliary agent means the area of the cross section which passes through the center of the spherical object, assuming that the 1st electric conduction auxiliary agent is a sphere.
電極活物質全体をできるだけ効率的にムラなく反応させるためには、第1導電助剤が電極活物質表面全体を被覆し集電できるようにすることが望ましい。そのため、第1導電助剤は少なくとも電極活物質表面を被覆できる量を用いるのが望ましい。異なる粒径の材料からなる電極合材層を形成する場合、図４に示すように、第１導電助剤１は、電極活物質３の表面だけでなく、第２導電助剤２の表面も被覆することが想定される。このため、第１導電助剤１の被覆面積は、電極活物質３の表面積と第２導電助剤２の表面積の合計と同じかそれよりも大きいことがよい。この場合、第１導電助剤１は、電極活物質３の表面全体を被覆するに十分な被覆面積をもつことになり、電極合材層内の抵抗を更に低くすることができるとともに、効率的な反応および集電が可能となる。
In order to make the entire electrode active material react as efficiently and uniformly as possible, it is desirable that the first conductive assistant covers the entire surface of the electrode active material so that current can be collected. Therefore, it is desirable to use the first conductive additive in an amount that can cover at least the surface of the electrode active material. When forming the electrode mixture layers made of materials having different particle diameters, as shown in FIG. 4, the first
決定工程では、電極合材層における第１導電助剤の個数と第１導電助剤１個当たりの断面積との積Ｓｃ１（ｍ２）、電極活物質の総表面積Ｓ（ｍ２）、及び第２導電助剤の総表面積Ｓｃ２（ｍ２）を、以下の式（７）、式（８）、式（９）、式（１０）、式（１１）に従って計算することがよい。 In the determination step, the product S c1 (m 2 ) of the number of the first conductive assistants and the cross-sectional area per one first conductive assistant in the electrode mixture layer, the total surface area S (m 2 ) of the electrode active material, And the total surface area S c2 (m 2 ) of the second conductive additive may be calculated according to the following equations (7), (8), (9), (10), and (11).
第１導電助剤の平均粒径をｄｃ１（μｍ）としたとき、第１導電助剤１個当たりの体積ｗｃ１（ｃｍ３）は、次の式（７）で表される。
ｗｃ１（ｃｍ３）＝４π×（ｄｃ１×１０−４／２）３／３＝π×（ｄｃ１×１０−４）３／６＝π×ｄｃ１ ３×１０−１２／６・・・式（７）
Assuming that the average particle size of the first conductive assistant is d c1 (μm), the volume w c1 (cm 3 ) per one first conductive assistant is represented by the following equation (7).
w c1 (cm 3) = 4π × (d c1 × 10 -4 / 2) 3/3 = π × (d c1 × 10 -4) 3/6 = π × d
電極合材層における第１導電助剤の総質量をｍｃ１（ｇ）とし、第１導電助剤の真密度をρｃ１（ｇ／ｃｍ３）としたとき、第１導電助剤の総質量ｍｃ１（ｇ）中の第１導電助剤の個数ｎｃ１は、以下の式（８）で表される。
ｎｃ１（個）＝（ｍｃ１／ρｃ１）×（１／ｗｃ１）＝（ｍｃ１／ρｃ１）×（１／（π×ｄｃ１ ３×１０−１２／６））＝６ｍｃ１×１０１２／（π×ρｃ１×ｄｃ１ ３）・・・式（８）
When the total mass of the first conductive additive in the electrode mixture layer is m c1 (g) and the true density of the first conductive additive is ρ c1 (g / cm 3 ), the total mass of the first conductive additive is The number n c1 of the first conductive assistants in m c1 (g) is represented by the following equation (8).
n c1 (number) = (m c1 / ρ c1 ) × (1 / w c1) = (m c1 / ρ c1) × (1 / (π × d
第１導電助剤１個当たりの断面積（ｍ２）と第１導電助剤の個数ｎｃ１との積Ｓｃ１（ｍ２）は、次の式（９）で表される。
Ｓｃ１（ｍ２）＝π（ｄｃ１×１０−６／２）２×ｎｃ１＝π（ｄｃ１×１０−６／２）２×６ｍｃ１×１０１２／（π×ρｃ１×ｄｃ１ ３）＝３ｍｃ１／（２ρｃ１×ｄｃ１）・・・式（９）
The product S c1 (m 2 ) of the cross-sectional area (m 2 ) per one first conductive assistant and the number n c1 of the first conductive assistant is represented by the following equation (9).
S c1 (m 2 ) = π (d c1 × 10 −6 / 2) 2 × n c1 = π (d c1 × 10 −6 / 2) 2 × 6 m c1 × 10 12 / (π × ρ c1 × d c1) 3 ) = 3m c1 / (2ρ c1 × d c1 ) Equation (9)
第２導電助剤のＢＥＴ比表面積をｓｃ２（ｍ２／ｇ）とし、電極合材層の中の第２導電助剤の総質量をｍｃ２（ｇ）としたとき、電極合材層の中の第２導電助剤の総表面積Ｓｃ２（ｍ２）は、以下の式（１０）で表される。
Ｓｃ２（ｍ２）＝ｓｃ２×ｍｃ２・・・式（１０）
When the BET specific surface area of the second conductive additive is s c2 (m 2 / g) and the total mass of the second conductive additive in the electrode mixture layer is mc2 (g), the electrode mixture layer The total surface area S c2 (m 2 ) of the second conductive auxiliary agent is represented by the following equation (10).
S c2 (m 2 ) = s c2 × m c2 Equation (10)
電極活物質のＢＥＴ比表面積をｓａｍ（ｍ２／ｇ）とし、電極合材層の中の電極活物質の総質量をＭ（ｇ）としたとき、電極合材層の中の電極活物質の総表面積Ｓ（ｍ２）は、以下の式（１１）で表される。
Ｓ（ｍ２）＝ｓａｍ×Ｍ・・・式（１１）
Assuming that the BET specific surface area of the electrode active material is s am (m 2 / g) and the total mass of the electrode active material in the electrode mixture layer is M (g), the electrode active material in the electrode mixture layer is the total surface area S of the (m 2) is expressed by the following equation (11).
S (m 2 ) = s am × M Equation (11)
式（６）に式（９）、式（１０）、及び式（１１）を代入すると、Ｓ＋Ｓｃ２≦Ｓｃ１は、以下の式（１２）で表すことができる。
ｓａｍ×Ｍ＋ｓｃ２×ｍｃ２≦３ｍｃ１／（２ρｃ１×ｄｃ１）・・・式（１２）
By substituting the equations (9), (10), and (11) into the equation (6), S + S c2 ≦ S c1 can be expressed by the following equation (12).
s am × M + s c2 × m c2 ≦ 3m c1 / (2ρ c1 × d c1 ) formula (12)
電極合材層を１００質量％としたときに、百分率で、電極活物質の質量比をＭ＊、第１導電助剤の質量比をｍｃ１ ＊、第２導電助剤の質量比をｍｃ２ ＊とした時には、式（１２）は、以下の（１３）で表わされる。
ｓａｍ×Ｍ＊＋ｓｃ２×ｍｃ２ ＊≦３ｍｃ１ ＊／（２ρｃ１×ｄｃ１）・・・式（１３）
Assuming that the electrode mixture layer is 100% by mass, the mass ratio of the electrode active material is M * , the mass ratio of the first conductive additive is m c1 * , and the mass ratio of the second conductive additive is m c2. When * is given, the equation (12) is represented by the following (13).
s am × M * + s c2 × m c2 * ≦ 3m c1 * / (2ρ c1 × d c1) ··· formula (13)
選択工程または調整工程の後に、上記の式（６）または式（１３）の関係をもつように電極合材層における電極活物質の質量比Ｍ＊、第１導電助剤の質量比ｍｃ１ ＊、及び第２導電助剤の質量比ｍｃ２ ＊を決定するとよい。 After the selection step or the adjustment step, the mass ratio M * of the electrode active material and the mass ratio m c1 * of the first conductive additive in the electrode mixture layer are set so as to satisfy the above formula (6) or (13) . , And the mass ratio mc2 * of the second conductive additive may be determined.
電極合材層全体を１００質量％としたときに、電極活物質の質量比Ｍ＊は、５５質量％以上９９質量％以下であることがよく、更に、８０質量％以上９８質量％以下、８５質量％以上９８質量％以下であることが好ましい。電極活物質の質量比Ｍ＊が小さすぎる場合には、電池の容量が低下するおそれがある。 When the entire electrode mixture layer is 100% by mass, the mass ratio M * of the electrode active material is preferably 55% by mass or more and 99% by mass or less, and more preferably 80% by mass or more and 98% by mass or less. It is preferable that the content is not less than 98% by mass and not more than 98% by mass. If the mass ratio M * of the electrode active material is too small, the capacity of the battery may be reduced.
電極合材層全体を１００質量％としたときに、第１導電助剤の質量比ｍｃ１ ＊及び第２導電助剤の質量比ｍｃ２ ＊の合計（ｍｃ１ ＊＋ｍｃ２ ＊）は、０．５質量％以上５０質量％がよく、更に１質量％以上３０質量％以下が好ましい。この場合には、電極合材層内の導電性を向上または維持しつつ電池の容量低下を抑制できる。 When the entire electrode mixture layer is 100% by mass, the total ( mc1 * + mc2 * ) of the mass ratio mc1 * of the first conductive additive and the mass ratio mc2 * of the second conductive additive is 0. It is preferably from 0.5% by mass to 50% by mass, more preferably from 1% by mass to 30% by mass. In this case, a decrease in the capacity of the battery can be suppressed while improving or maintaining the conductivity in the electrode mixture layer.
電極合材層において、電極活物質の質量比Ｍ＊と、第１導電助剤の質量比ｍｃ１ ＊及び第２導電助剤の質量比ｍｃ２ ＊の合計（ｍｃ１ ＊＋ｍｃ２ ＊）と割合は、Ｍ＊：（ｍｃ１ ＊＋ｍｃ２ ＊）＝９９：１〜７０：３０であるのが好ましい。第１導電助剤及び第２導電助剤が少なすぎると効率のよい導電パスを形成できず、また、導電助剤が多すぎると電極のエネルギー密度が低くなるためである。 In the electrode mixture layer, the mass ratio M * of the electrode active material, the sum of the mass ratio mc1 * of the first conductive additive and the mass ratio mc2 * of the second conductive additive ( mc1 * + mc2 * ) ratio, M *: (m c1 * + m c2 *) = 99: 1~70: is preferably 30. If the first and second conductive assistants are too small, an efficient conductive path cannot be formed, and if the first and second conductive assistants are too large, the energy density of the electrode becomes low.
（４）電極形成工程
次に、電極形成工程において、上記の工程で設定した条件を満たす電極活物質と第１導電助剤と第２導電助剤とを有する電極合材を集電体上に塗布して電極合材層を形成する。集電体上に電極合材層を形成した後に、各電極合材層に含まれる電極活物質、第１導電助剤及び第２導電助剤が、上記（１）〜（３）の各工程の条件を満たすことを確認してもよい。
(4) Electrode Forming Step Next, in the electrode forming step, an electrode mixture containing an electrode active material, a first conductive auxiliary, and a second conductive auxiliary that satisfies the conditions set in the above step is placed on the current collector. Apply to form an electrode mixture layer. After forming the electrode mixture layer on the current collector, the electrode active material, the first conductive auxiliary, and the second conductive auxiliary contained in each of the electrode composite layers are subjected to the steps (1) to (3). May be confirmed.
電極合材には、電極活物質、第２導電助剤及び第１導電助剤の他に、必要に応じて結着剤を含む。結着剤は電極活物質及び導電助剤を集電体の表面に繋ぎ止める役割を果たすものである。結着剤としては、ポリフッ化ビニリデン、ポリテトラフルオロエチレン、フッ素ゴム等の含フッ素樹脂、ポリプロピレン、ポリエチレン等の熱可塑性樹脂、ポリイミド、ポリアミドイミド等のイミド系樹脂、アルコキシシリル基含有樹脂を例示することができる。 The electrode mixture contains, as necessary, a binder in addition to the electrode active material, the second conductive auxiliary, and the first conductive auxiliary. The binder plays a role of binding the electrode active material and the conductive assistant to the surface of the current collector. Examples of the binder include polyvinylidene fluoride, polytetrafluoroethylene, fluorine-containing resins such as fluorine rubber, polypropylene, thermoplastic resins such as polyethylene, polyimide, imide resins such as polyamideimide, and alkoxysilyl group-containing resins. be able to.
電極合材中の結着剤の配合割合は、質量比で、電極活物質：結着剤＝９９：１〜７０：３０であるのが好ましい。結着剤が少なすぎると電極の成形性が低下し、また、結着剤が多すぎると電極のエネルギー密度と導電性が低くなるためである。 It is preferable that the compounding ratio of the binder in the electrode mixture is, in terms of mass ratio, electrode active material: binder = 99: 1 to 70:30. If the amount of the binder is too small, the formability of the electrode is reduced, and if the amount of the binder is too large, the energy density and the conductivity of the electrode are reduced.
集電体の表面に電極合材層を形成させるには、ロールコート法、ダイコート法、ディップコート法、ドクターブレード法、スプレーコート法、カーテンコート法などの従来から公知の方法を用いて、集電体の表面に電極合材を塗布すればよい。具体的には、電極合材に適当な溶剤を加えてペースト状にしてから、集電体の表面に塗布した後、乾燥して電極合材層を形成する。溶剤としては、Ｎ−メチル−２−ピロリドン、メタノール、メチルイソブチルケトン、水を例示できる。電極密度を高めるべく、乾燥後の電極合材層を圧縮しても良い。 In order to form the electrode mixture layer on the surface of the current collector, a conventionally known method such as a roll coating method, a die coating method, a dip coating method, a doctor blade method, a spray coating method, and a curtain coating method is used. The electrode mixture may be applied to the surface of the electric body. Specifically, an appropriate solvent is added to the electrode mixture to form a paste, which is then applied to the surface of the current collector and then dried to form an electrode mixture layer. Examples of the solvent include N-methyl-2-pyrrolidone, methanol, methyl isobutyl ketone, and water. In order to increase the electrode density, the dried electrode mixture layer may be compressed.
電極合材層の圧縮は、厚み方向に電極を加圧するとよい。加圧により電極合材層の中の電極活物質を最密構造に近い状態に配置することができる。しかも、第２導電助剤を電極活物質間の隙間により好適に配置することができる。 The compression of the electrode mixture layer is preferably performed by pressing the electrode in the thickness direction. By pressing, the electrode active material in the electrode mixture layer can be arranged in a state close to a close-packed structure. In addition, the second conductive additive can be more suitably arranged in the gap between the electrode active materials.
集電体は、リチウムイオン二次電池の放電又は充電の間、電極に電流を流し続けるための化学的に不活性な電子高伝導体をいう。集電体としては、銀、銅、金、アルミニウム、タングステン、コバルト、亜鉛、ニッケル、鉄、白金、錫、インジウム、チタン、ルテニウム、タンタル、クロム、モリブデンから選ばれる少なくとも一種、並びにステンレス鋼などの金属材料を例示することができる。集電体は公知の保護層で被覆されていても良い。集電体の表面を公知の方法で処理したものを集電体として用いても良い。 The current collector refers to a chemically inert high-electron conductor for continuously supplying a current to an electrode during discharging or charging of a lithium ion secondary battery. As the current collector, at least one selected from silver, copper, gold, aluminum, tungsten, cobalt, zinc, nickel, iron, platinum, tin, indium, titanium, ruthenium, tantalum, chromium, molybdenum, and stainless steel A metal material can be exemplified. The current collector may be covered with a known protective layer. A current collector whose surface is treated by a known method may be used as the current collector.
集電体は箔、シート、フィルム、線状、棒状、メッシュなどの形態をとることができる。そのため、集電体として、例えば、銅箔、ニッケル箔、アルミニウム箔、ステンレス箔などの金属箔を好適に用いることができる。集電体が箔、シート、フィルム形態の場合は、その厚みが１μｍ〜１００μｍの範囲内であることが好ましい。 The current collector may be in the form of a foil, a sheet, a film, a line, a bar, a mesh, or the like. Therefore, for example, a metal foil such as a copper foil, a nickel foil, an aluminum foil, and a stainless steel foil can be suitably used as the current collector. When the current collector is in the form of a foil, sheet, or film, the thickness is preferably in the range of 1 μm to 100 μm.
本発明の二次電池用電極は、上記の製造方法により製造された電極である。本発明の二次電池用電極は、電極活物質、第１導電助剤、及び第２導電助剤を有し、上記の式（１）の関係をもつ電極活物質及び第２導電助剤を有する。この関係をもつ電極活物質、第１導電助剤及び第２導電助剤を有する電極によれば、電池の内部抵抗及びその増加を低く抑えることができる。さらに、電極活物質、第１導電助剤、及び第２導電助剤は、式（２）、式（６）、式（１３）の少なくとも１種の関係をもつことが好ましい。この関係をもつ電極活物質、第１導電助剤及び第２導電助剤を有する電極によれば、電池の内部抵抗及びその増加を更に低く抑えることができる。 The electrode for a secondary battery of the present invention is an electrode manufactured by the above manufacturing method. The electrode for a secondary battery of the present invention includes an electrode active material, a first conductive auxiliary, and a second conductive auxiliary, and includes the electrode active material and the second conductive auxiliary having the relationship of the above formula (1). Have. According to the electrode having the electrode active material, the first conductive auxiliary, and the second conductive auxiliary having this relationship, the internal resistance of the battery and the increase thereof can be suppressed. Further, it is preferable that the electrode active material, the first conductive auxiliary, and the second conductive auxiliary have at least one of the relations of the formulas (2), (6), and (13). According to the electrode having the electrode active material, the first conductive auxiliary, and the second conductive auxiliary having this relationship, the internal resistance of the battery and the increase thereof can be further suppressed.
（二次電池）
本実施形態の二次電池は、上記の二次電池用電極を備えている。二次電池は、非水系の電解液を用いた非水二次電池であるとよい。上記の二次電池用電極は、正極、負極のいずれでもよく、また、正極及び負極とも上記の二次電池用電極であってもよい。
(Rechargeable battery)
The secondary battery of the present embodiment includes the above-described secondary battery electrode. The secondary battery is preferably a non-aqueous secondary battery using a non-aqueous electrolyte. The above-mentioned secondary battery electrode may be either a positive electrode or a negative electrode, and both the positive electrode and the negative electrode may be the above-mentioned secondary battery electrode.
二次電池には必要に応じてセパレータが用いられる。セパレータは、電極と負極とを隔離し、両極の接触による電流の短絡を防止しつつ、金属イオンを通過させるものである。セパレータとしては、ポリテトラフルオロエチレン、ポリプロピレン、ポリエチレン、ポリイミド、ポリアミド、ポリアラミド（Ａｒｏｍａｔｉｃ ｐｏｌｙａｍｉｄｅ）、ポリエステル、ポリアクリロニトリル等の合成樹脂、セルロース、アミロース等の多糖類、フィブロイン、ケラチン、リグニン、スベリン等の天然高分子、セラミックスなどの電気絶縁性材料を１種若しくは複数用いた多孔体、不織布、織布などを挙げることができる。また、セパレータは多層構造としてもよい。 A separator is used for the secondary battery as needed. The separator separates the electrode and the negative electrode, and prevents metal current from being short-circuited due to contact between the two electrodes, and allows metal ions to pass through. Examples of the separator include synthetic resins such as polytetrafluoroethylene, polypropylene, polyethylene, polyimide, polyamide, polyaramide, polyester, and polyacrylonitrile; polysaccharides such as cellulose and amylose; and natural resins such as fibroin, keratin, lignin, and suberin. Examples thereof include a porous body, a nonwoven fabric, and a woven fabric using one or a plurality of electric insulating materials such as polymers and ceramics. Further, the separator may have a multilayer structure.
正極及び負極に必要に応じてセパレータを挟装させ電極体とする。電極体は、正極、セパレータ及び負極を重ねた積層型、又は、正極、セパレータ及び負極を捲いた捲回型のいずれの型にしても良い。正極の集電体および負極の集電体から外部に通ずる正極端子および負極端子までの間を、集電用リード等を用いて接続した後に、電極体に電解液を加えて二次電池とするとよい。 A separator is interposed between the positive electrode and the negative electrode as necessary to form an electrode body. The electrode body may be any of a stacked type in which a positive electrode, a separator, and a negative electrode are stacked, or a wound type in which a positive electrode, a separator, and a negative electrode are wound. After connecting the current collector of the positive electrode and the current collector of the negative electrode to the positive electrode terminal and the negative electrode terminal leading to the outside using a current collecting lead or the like, and then adding an electrolytic solution to the electrode body to form a secondary battery, Good.
非水系の電解液は、有機溶媒に電解質である金属塩を溶解させたものである。有機溶媒として、非プロトン性有機溶媒、たとえばプロピレンカーボネート（ＰＣ）、エチレンカーボネート（ＥＣ）、ジメチルカーボネート（ＤＭＣ）、ジエチルカーボネート（ＤＥＣ）、エチルメチルカーボネート(ＥＭＣ)等から選ばれる一種以上を用いることができる。また、溶解させる電解質としては、ＬｉＣｌＯ４、ＬｉＡｓＦ６、ＬｉＰＦ６、ＬｉＢＦ４、ＬｉＣＦ３ＳＯ３、ＬｉＮ（ＣＦ３ＳＯ２）２等のリチウム塩を用いることができる。 The non-aqueous electrolyte solution is obtained by dissolving a metal salt as an electrolyte in an organic solvent. As the organic solvent, use of an aprotic organic solvent, for example, one or more selected from propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and the like Can be. As an electrolyte to be dissolved, a lithium salt such as LiClO 4 , LiAsF 6 , LiPF 6 , LiBF 4 , LiCF 3 SO 3 , and LiN (CF 3 SO 2 ) 2 can be used.
非水系の電解液として、例えば、エチレンカーボネート、ジメチルカーボネート、プロピレンカーボネート、ジメチルカーボネートなどの有機溶媒にＬｉＣｌＯ４、ＬｉＰＦ６、ＬｉＢＦ４、ＬｉＣＦ３ＳＯ３等のリチウム金属塩を０．５ｍｏｌ／Ｌから１．７ｍｏｌ／Ｌ程度の濃度で溶解させた溶液を使用することができる。 As a non-aqueous electrolyte, for example, a lithium metal salt such as LiClO 4 , LiPF 6 , LiBF 4 , and LiCF 3 SO 3 is added to an organic solvent such as ethylene carbonate, dimethyl carbonate, propylene carbonate, and dimethyl carbonate from 0.5 mol / L. A solution dissolved at a concentration of about 1.7 mol / L can be used.
本発明の二次電池の形状は特に限定されるものでなく、円筒型、角型、コイン型、ラミネート型等、種々の形状を採用することができる。 The shape of the secondary battery of the present invention is not particularly limited, and various shapes such as a cylindrical type, a square type, a coin type, and a laminate type can be adopted.
本発明の二次電池は、車両に搭載してもよい。車両は、その動力源の全部あるいは一部に二次電池による電気エネルギーを使用している車両であればよく、たとえば、電気車両、ハイブリッド車両などであるとよい。車両に二次電池を搭載する場合には、二次電池を複数直列に接続して組電池とするとよい。二次電池を搭載する機器としては、車両以外にも、パーソナルコンピュータ、携帯通信機器など、電池で駆動される各種の家電製品、オフィス機器、産業機器などが挙げられる。さらに、本発明の二次電池は、風力発電、太陽光発電、水力発電その他電力系統の蓄電装置及び電力平滑化装置、船舶等の動力及び／又は補機類の電力供給源、航空機、宇宙船等の動力及び／又は補機類の電力供給源、電気を動力源に用いない車両の補助用電源、移動式の家庭用ロボットの電源、システムバックアップ用電源、無停電電源装置の電源、電動車両用充電ステーションなどにおいて充電に必要な電力を一時蓄える蓄電装置に用いてもよい。 The secondary battery of the present invention may be mounted on a vehicle. The vehicle may be a vehicle that uses electric energy from a secondary battery for all or a part of its power source, and may be, for example, an electric vehicle or a hybrid vehicle. When a secondary battery is mounted on a vehicle, a plurality of secondary batteries may be connected in series to form an assembled battery. Examples of the device on which the secondary battery is mounted include, in addition to vehicles, various home appliances, office devices, industrial devices, and the like, which are driven by a battery, such as personal computers and portable communication devices. Furthermore, the secondary battery of the present invention is a power storage device and a power smoothing device for wind power generation, solar power generation, hydroelectric power generation and other power systems, power supply sources for motive power of ships and the like and / or auxiliary equipment, aircraft, spacecraft And / or power supply for auxiliary equipment, auxiliary power supply for vehicles that do not use electricity as power source, power supply for mobile home robots, power supply for system backup, power supply for uninterruptible power supply, electric vehicle It may be used for a power storage device that temporarily stores the power required for charging at a charging station for use.
以上、本発明の実施形態を説明したが、本発明は、上記実施形態に限定されるものではない。本発明の要旨を逸脱しない範囲において、当業者が行い得る変更、改良等を施した種々の形態にて実施することができる。 The embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments. The present invention can be implemented in various forms with modifications, improvements, and the like that can be made by those skilled in the art without departing from the gist of the present invention.
（実施例１）
本実施例１のリチウムイオン二次電池は、正極と、負極と、電解液と、セパレータとを有する。
(Example 1)
The lithium ion secondary battery of Example 1 has a positive electrode, a negative electrode, an electrolyte, and a separator.
正極は、正極合材層と、正極合材層で被覆された集電体とからなる。正極合材層は、正極活物質と、第１導電助剤と、第２導電助剤と、結着剤とを有する。正極活物質は、平均粒径Ｄが６μｍのＬｉＮｉ０．５Ｃｏ０．２Ｍｎ０．３Ｏ２からなる。第１導電助剤は、アセチレンブラック（ＡＢ）からなり、平均粒径ｄｃ１は０．０３５μｍである（デンカブラック粒状品（商品名）、電気化学工業株式会社製）。第２導電助剤は、黒鉛からなり、平均粒径ｄｃ２は３．５μｍである（製品名ＫＳ６Ｌ、ＩＭＥＲＹＳ製造）。結着剤は、ポリフッ化ビニリデン（ＰＶＤＦ、クレハバッテリーマテリアルスジャパン製、商品番号＃７３００）からなる。集電体は、厚み２０μｍのアルミニウム箔からなる。正極合材層を１００質量％としたときの、正極活物質の質量比Ｍ＊と第１導電助剤の質量比ｍｃ１ ＊と第２導電助剤の質量比ｍｃ２ ＊と結着剤の質量比は、百分率で、９０：５：３：２である。 The positive electrode includes a positive electrode mixture layer and a current collector covered with the positive electrode mixture layer. The positive electrode mixture layer has a positive electrode active material, a first conductive auxiliary, a second conductive auxiliary, and a binder. The positive electrode active material is made of LiNi 0.5 Co 0.2 Mn 0.3 O 2 having an average particle diameter D of 6 μm. The first conductive additive consists of acetylene black (AB), the average particle diameter d c1 is 0.035 .mu.m (Denka Black granule (trade name), manufactured by Denki Kagaku Kogyo Co., Ltd.). The second conductive additive is made of graphite, the average particle diameter d c2 is 3.5 [mu] m (product name KS6L, IMERYS production). The binder is made of polyvinylidene fluoride (PVDF, manufactured by Kureha Battery Materials Japan, product number # 7300). The current collector is made of an aluminum foil having a thickness of 20 μm. When the positive-electrode mixture layer is 100 mass%, the mass ratio m c2 * and a binder mass ratio m c1 * and the second conductive additive weight ratio M * a first conductive additive of the positive electrode active material The mass ratio is 90: 5: 3: 2 in percentage.
正極を作製するために、以下の各工程を行った。 The following steps were performed to produce a positive electrode.
（１）選択工程
まず、正極活物質としてのＬｉＮｉ０．５Ｃｏ０．２Ｍｎ０．３Ｏ２、結着剤としてのＰＶＤＦ、及び第１導電助剤及び第２導電助剤としてのＡＢを準備した。正極活物質の平均粒径Ｄ及び第１導電助剤の平均粒径ｄｃ１をレーザ回折法により測定した。Ｄは６μｍであり、ｄｃ１は０．０３５μｍであった。Ｄを用いて式（１）に従って、第２導電助剤の平均粒径ｄｃ２の範囲を求めたところ、６（（３／２）1/2―１）≦ｄｃ２≦６、すなわち１．３≦ｄｃ２≦６であった。この範囲に入り、且つｄｃ１よりも大きい平均粒径ｄｃ２の第２導電助剤を選択した。選択された第２導電助剤の平均粒径ｄｃ２は３．５μｍであった。
(1) Selection Step First, LiNi 0.5 Co 0.2 Mn 0.3 O 2 as a positive electrode active material, PVDF as a binder, and AB as a first conductive auxiliary and a second conductive auxiliary were added. Got ready. The average particle diameter d c1 having an average particle diameter D and the first conductive additive of the positive electrode active material was measured by a laser diffraction method. D was 6 μm and d c1 was 0.035 μm. According to equation (1) using the D, it was determined the range of the average particle diameter dc2 of the second conductive additive, 6 ((3/2) 1/2 -1 ) ≦ d c2 ≦ 6, i.e. 1.3 ≦ d c2 ≦ 6. A second conductive auxiliary agent having an average particle diameter dc2 that falls within this range and is larger than dc1 was selected. The average particle size dc2 of the selected second conductive additive was 3.5 μm.
（２）調整工程
既知の正極活物質の真密度ρ、第１導電助剤（ＡＢ）の真密度ρｃ１、及び第２導電助剤（黒鉛）の真密度ρｃ２を確認した。正極活物質の真密度ρは４．７０g/cm3であった。第１導電助剤の真密度ρｃ１は１．９５g/cm3であった（「ナノマテリアル情報提供シート」（材料名アセチレンブラック、電気化学工業株式会社提供）に掲載のアセチレンブラックの真密度１．８―２．１g/cm3の平均値）。第２導電助剤の真密度ρｃ２は２．２６g/cm3であった（ＩＭＥＲＹＳ分析表掲載）。集電体上に形成される正極合材層における正極活物質の質量比Ｍ＊及び第２導電助剤の質量比ｍｃ２ ＊が、式（２）の関係を満たすように、正極活物質と第２導電助剤との配合比を調整した。本実施例１では、Ｍ＊は９０質量％とし、ｍｃ２ ＊は３質量％とした。（Ｍ＊×ρｃ２×ｄｃ２ ３）／（ｍｃ２ ＊×ρ×Ｄ３）は２．８６であった。
(2) the true density of the adjustment process known positive electrode active material [rho, was confirmed true density [rho c2 true density [rho c1, and a second conductive additive of the first conductive additive (AB) (graphite). The true density ρ of the positive electrode active material was 4.70 g / cm 3 . The true density ρ c1 of the first conductive additive was 1.95 g / cm 3 (
（３）決定工程
既知の正極活物質の比表面積ｓａｍ、及び第２導電助剤の比表面積ｓｃ２を、ＢＥＴ法により確認した。正極活物質の比表面積ｓａｍは、０．４３ｍ２／ｇであり、第２導電助剤の比表面積ｓｃ２は、１９．２ｍ２／ｇであった。正極合材層を１００質量％としたときの正極活物質の質量比Ｍ＊、第１導電助剤の質量比ｍｃ１ ＊及び第２導電助剤の質量比ｍｃ２ ＊が式（１３）の条件を満たすように、Ｍ＊、ｍｃ１ ＊及びｍｃ２ ＊を決定した。本実施例１では式（１３）の左辺（ｓａｍ×Ｍ＊＋ｓｃ２×ｍｃ２ ＊）は９６．３ｍ２であり、式（１３）の右辺（３ｍｃ１ ＊／（２ρｃ１×ｄｃ１））は１０９．９ｍ２とした。式（１３）の関係を満足するように、ｍｃ１ ＊を５質量％と決定した。
(3) determining step known positive electrode active specific surface area s am substance, and a specific surface area s c2 of the second conductive additive, was confirmed by the BET method. The specific surface area s am of the positive electrode active material is 0.43 m 2 / g, a specific surface area s c2 of the second conductive additive was 19.2 m 2 / g. When the positive-electrode mixture layer is 100 mass% mass ratio M * of the positive electrode active material, the mass ratio of the mass ratio m c1 * and the second conductive additive of the first conductive additive m c2 * is the formula (13) M * , mc1 * and mc2 * were determined to satisfy the conditions. In Example 1 the left-hand side of equation (13) (s am × M * + s c2 × m c2 *) is 96.3m 2, wherein the right-hand side of (13) (3m c1 * / (2ρ c1 × d c1) ) Was 109.9 m 2 . Mc1 * was determined to be 5% by mass so as to satisfy the relationship of Expression (13).
また、正極合材層１００ｇの中の第１導電助剤の個数と第１導電助剤１個当たりの断面積との積をＳｃ１とし、正極活物質の総表面積をＳとし、第２導電助剤の総表面積をＳｃ２としたとき、Ｓｃ１及びＳｃ２は式（６）の条件を満たすように決定した。式（９）によりＳｃ１を求めたところ、１０９．９ｍ２であった。式（１０）によりＳｃ２を求めたところ、５７．６ｍ２であった。式（１１）によりＳを求めたところ、３８．７ｍ２であった。Ｓｃ１、Ｓ、及びＳｃ２は、式（６）の関係を満足した。 The product of the number of the first conductive assistants in the positive electrode mixture layer 100g and the cross-sectional area per one first conductive assistant is Sc1 , the total surface area of the positive electrode active material is S, and the second conductive agent is S2. Assuming that the total surface area of the auxiliaries is Sc2 , Sc1 and Sc2 were determined so as to satisfy the condition of equation (6). Was determined the S c1 by the equation (9), it was 109.9m 2. Was determined the S c2 by the equation (10) was 57.6m 2. When S was determined by the equation (11), it was 38.7 m 2 . S c1 , S, and S c2 satisfied the relationship of Expression (6).
式（６）及び式（１３）を満たす正極活物質、第１導電助剤及び第２導電助剤の量として、Ｍ＊を９０質量％、ｍｃ１ ＊を５質量％、ｍｃ２ ＊を３質量％と決定した。 As the amounts of the positive electrode active material, the first conductive auxiliary agent, and the second conductive auxiliary agent that satisfy the formulas (6) and (13), M * is 90% by mass, mc1 * is 5% by mass, and mc2 * is 3%. % By mass.
（４）正極形成工程
正極形成工程において、上記の正極活物質、第１導電助剤、及び第２導電助剤に加えて結着剤を添加し混合して正極合材を得た。正極合材を１００質量％としたときの、正極活物質、第１導電助剤、第２導電助剤、及び結着剤の質量比は百分率で９０質量％、５質量％、３質量％、２質量％とした。正極合材に、溶剤としてのＮ−メチル−２−ピロリドン（ＮＭＰ）を添加してペーストとした。このペーストを、集電体としてのアルミニウム箔の表面にドクターブレードを用いて塗布し、８０℃で２０分間乾燥することで、ＮＭＰを揮発により除去して、正極合材層を形成した。乾燥後の正極合材層の目付は６ｍｇ／ｃｍ２とした。表面に正極合材層を形成したアルミニウム箔を、ロ−ルプレス機を用い圧縮し、アルミニウム箔と正極合材層とを強固に密着接合させた。接合物を１２０℃で６時間、真空乾燥機で加熱し、所定の形状に切り取り（２５ｍｍ×３０ｍｍ）、正極合材層の厚さが２５μｍ程度の正極を得た。
(4) Positive electrode forming step In the positive electrode forming step, a binder was added and mixed in addition to the positive electrode active material, the first conductive auxiliary, and the second conductive auxiliary to obtain a positive electrode mixture. When the positive electrode mixture was 100% by mass, the mass ratio of the positive electrode active material, the first conductive auxiliary, the second conductive auxiliary, and the binder was 90% by mass, 5% by mass, 3% by mass, It was 2% by mass. N-methyl-2-pyrrolidone (NMP) as a solvent was added to the positive electrode mixture to form a paste. This paste was applied to the surface of an aluminum foil as a current collector using a doctor blade, and dried at 80 ° C. for 20 minutes to remove NMP by volatilization to form a positive electrode mixture layer. The basis weight of the positive electrode mixture layer after drying was 6 mg / cm 2 . The aluminum foil having the positive electrode mixture layer formed on its surface was compressed by using a roll press, and the aluminum foil and the positive electrode mixture layer were firmly adhered to each other. The bonded article was heated at 120 ° C. for 6 hours by a vacuum dryer, cut into a predetermined shape (25 mm × 30 mm), and a positive electrode having a positive electrode mixture layer thickness of about 25 μm was obtained.
負極は、負極合材層と、負極合材層で被覆された集電体とからなる。負極合材層は、負極活物質と結着剤とを有する。負極を作製するために、負極活物質としての黒鉛９８質量部と、結着剤としてスチレン−ブタジエンゴム（ＳＢＲ）１質量部及びカルボキシメチルセルロース（ＣＭＣ）１質量部とを混合した。この混合物を適量のイオン交換水に分散させてスラリー状の負極合材を作製した。このスラリー状の負極合材を負極用集電体である厚み２０μｍの銅箔にドクターブレードを用いて膜状になるように塗布して負極合材層を形成した。乾燥後の負極合材層の目付は４ｍｇ／ｃｍ２とした。負極合材層を形成した集電体を８０℃で２０分間乾燥後プレスし、接合物を１２０℃で６時間、真空乾燥機で加熱し、所定の形状に切り取り（２６ｍｍ×３１ｍｍ）、負極合材層の厚さが３４μｍ程度の負極を得た。 The negative electrode includes a negative electrode mixture layer and a current collector covered with the negative electrode mixture layer. The negative electrode mixture layer has a negative electrode active material and a binder. In order to produce a negative electrode, 98 parts by mass of graphite as a negative electrode active material, 1 part by mass of styrene-butadiene rubber (SBR) and 1 part by mass of carboxymethyl cellulose (CMC) as a binder were mixed. This mixture was dispersed in an appropriate amount of ion-exchanged water to prepare a slurry-like negative electrode mixture. The slurry-like negative electrode mixture was applied to a 20 μm-thick copper foil as a negative electrode current collector using a doctor blade so as to form a film, thereby forming a negative electrode mixture layer. The basis weight of the negative electrode mixture layer after drying was 4 mg / cm 2 . The current collector on which the negative electrode mixture layer was formed was dried at 80 ° C. for 20 minutes and then pressed. The joined body was heated at 120 ° C. for 6 hours with a vacuum dryer, cut into a predetermined shape (26 mm × 31 mm), and A negative electrode having a material layer thickness of about 34 μm was obtained.
電解液を作製するために、エチレンカーボネート（ＥＣ）とジエチルカーボネート（ＤＥＣ）との混合溶媒を調製した。混合溶媒の成分比率は、体積比でＥＣ／ＤＥＣ＝３：７とした。混合溶媒に、電解質としてのＬｉＰＦ６を１ｍｏｌ／Ｌとなるように溶解させて、電解液とした。 In order to prepare an electrolytic solution, a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) was prepared. The component ratio of the mixed solvent was EC / DEC = 3: 7 by volume. LiPF 6 as an electrolyte was dissolved at 1 mol / L in a mixed solvent to prepare an electrolyte.
上記の正極、負極及び電解液を用いて、ラミネート型リチウムイオン二次電池を製作した。詳しくは、正極および負極の間に、セパレータとしてポリプロピレン／ポリエチレン／ポリプロピレンの３層構造の多孔質樹脂膜からなる矩形状シート（２７×３２ｍｍ、厚さ２５μｍ）を挟装して極板群とした。この極板群を二枚一組のラミネートフィルムで覆い、三辺をシールした後、袋状となったラミネートフィルムに上記電解液を注入した。その後、残りの一辺をシールすることで、四辺が気密にシールされ、極板群および電解液が密閉されたラミネート型リチウムイオン二次電池を得た。なお、正極および負極は外部と電気的に接続可能なタブを備え、このタブの一部はラミネート型リチウムイオン二次電池の外側に延出している。 Using the positive electrode, the negative electrode, and the electrolytic solution described above, a laminated lithium ion secondary battery was manufactured. Specifically, a rectangular sheet (27 × 32 mm, thickness 25 μm) formed of a porous resin film having a three-layer structure of polypropylene / polyethylene / polypropylene was sandwiched between the positive electrode and the negative electrode to form an electrode plate group. . This electrode plate group was covered with a set of two laminated films, and after sealing three sides, the above-mentioned electrolytic solution was injected into the bag-shaped laminated film. Thereafter, by sealing the remaining one side, the four sides were hermetically sealed to obtain a laminated lithium ion secondary battery in which the electrode group and the electrolyte were sealed. Note that the positive electrode and the negative electrode have tabs that can be electrically connected to the outside, and some of these tabs extend outside the laminated lithium ion secondary battery.
得られたリチウムイオン二次電池のサイクル試験前後の交流インピーダンスを測定した。サイクル試験を行う際は、常温（２５℃）に制御された恒温器内において、１Ｃレートの電流負荷にて４．１ＶまでＣＣ充電（定電流充電）後、３．０ＶまでＣＣ放電（定電流放電）を行い、これを２００サイクル繰り返した。なお、例えば１Ｃとは、１時間で電池を完全充電または放電させるための、一定の電流値を意味する。交流インピーダンスは、電圧を３．５Ｖに調整したサイクル試験前後のリチウムイオン二次電池について、Ｓｏｌａｔｒｏｎ １４７０５５ＢＥＣ（ソーラトロン社）を用いて周波数０．０２Ｈｚ〜１ＭＨｚの範囲で測定した。結果を図５に示す。 The AC impedance of the obtained lithium ion secondary battery before and after the cycle test was measured. When performing the cycle test, in a thermostat controlled at room temperature (25 ° C.), CC charge up to 4.1 V (constant current charge) at a current load of 1 C rate, and then discharge CC to 3.0 V (constant current charge). This was repeated for 200 cycles. In addition, for example, 1C means a constant current value for fully charging or discharging a battery in one hour. The AC impedance of the lithium ion secondary batteries before and after the cycle test in which the voltage was adjusted to 3.5 V was measured using Solatron 147055BEC (Solartron) in a frequency range of 0.02 Hz to 1 MHz. The results are shown in FIG.
測定により得られた複素インピーダンス平面プロットには、二つの円弧がみられた。図中左側（つまり複素インピーダンスの実部が小さい側）の円弧を第１円弧と呼ぶ。図中右側の円弧を第２円弧と呼び、これらの円弧の大きさを基に電子抵抗（導電パスの抵抗）を解析した。解析結果を図５に示す。図５に示すように、実施例１では2つの円弧の増大は見られず、電子抵抗上昇が抑制されていることが考えられる。 Two arcs were observed in the complex impedance plane plot obtained by the measurement. The arc on the left side in the figure (that is, the side on which the real part of the complex impedance is small) is called a first arc. The arc on the right side in the figure is called a second arc, and the electronic resistance (resistance of the conductive path) was analyzed based on the size of these arcs. FIG. 5 shows the analysis result. As shown in FIG. 5, in Example 1, no increase in two arcs was observed, and it is considered that the increase in electronic resistance was suppressed.
（比較例１）
本比較例１のリチウムイオン二次電池は、正極合材層に第２導電助剤を含めておらず、正極活物質と第１導電助剤と結着剤の配合比を９０質量％：８質量％：２質量％にした点を除いて、実施例１のリチウムイオン二次電池と同様である。
(Comparative Example 1)
In the lithium ion secondary battery of Comparative Example 1, the positive electrode mixture layer did not include the second conductive additive, and the mixing ratio of the positive electrode active material, the first conductive additive, and the binder was 90% by mass: 8. Mass%: The same as the lithium ion secondary battery of Example 1 except that the mass% was set to 2% by mass.
正極を製造する工程は、次のようにした。
即ち、（１）選択工程は、実施例１の選択工程と同様に行った。用いた正極活物質及び第１導電助剤は、実施例１の正極活物質及び第１導電助剤と同じであり、これらの平均粒径Ｄ、ｄｃ１、真密度ρ、ρｃ１及び比表面積ｓａｍは、実施例１と同じとした。
The process for manufacturing the positive electrode was as follows.
That is, (1) the selecting step was performed in the same manner as the selecting step of Example 1. The positive electrode active material and the first conductive auxiliary used were the same as the positive electrode active material and the first conductive auxiliary of Example 1, and their average particle diameter D, d c1 , true density ρ , ρ c1 and specific surface area sam was the same as in Example 1.
（２）調整工程では、集電体上に形成される正極合材層における正極活物質の質量比Ｍ＊は９０質量％とした。第２導電助剤を用いていないため、式（２）は計算できなかった。 (2) In the adjusting step, the mass ratio M * of the positive electrode active material in the positive electrode mixture layer formed on the current collector was set to 90% by mass. Equation (2) could not be calculated because the second conductive additive was not used.
（３）決定工程において、正極活物質の質量比Ｍ＊、及び第１導電助剤の質量比ｍｃ１ ＊を用いて式（１３）を計算した。式（１３）の左辺（ｓａｍ×Ｍ＊＋ｓｃ２×ｍｃ２ ＊）は３８．７ｍ２であり、式（１３）の右辺（３ｍｃ１ ＊／（２ρｃ１×ｄｃ１））は１７５．８ｍ２であった。
また、正極合材層１００ｇの中の第１導電助剤の個数と第１導電助剤１個当たりの断面積との積をＳｃ１とし、正極活物質の総表面積をＳとしたとき、式（９）によりＳｃ１を求めたところ、１７５．８ｍ２であった。式（１０）によりＳｃ２を求めたところ０ｍ２であった。式（１１）によりＳを求めたところ、３８．７ｍ２であった。Ｓｃ１、Ｓ、及びＳｃ２は、式（６）の関係を満足した。正極活物質、及び第１導電助剤及び第２導電助剤の量として、Ｍ＊を９０質量％、ｍｃ１ ＊を８質量％、ｍｃ２ ＊を０質量％と決定した。
(3) In the determining step, the mass ratio of the positive electrode active material M *, and were calculated equation (13) using a mass ratio m c1 * of the first conductive additive. Left (s am × M * + s c2 × m c2 *) of formula (13) is 38.7m 2, the right side of the equation (13) (3m c1 * / (2ρ c1 × d c1)) is 175.8m It was 2 .
When the product of the number of the first conductive assistants in the positive electrode mixture layer 100g and the cross-sectional area per one first conductive assistant is Sc1, and the total surface area of the positive electrode active material is S, the following equation is obtained. (9) was determined to S c1, it was 175.8m 2. Was 0 m 2 was determined to S c2 by the equation (10). When S was determined by the equation (11), it was 38.7 m 2 . S c1 , S, and S c2 satisfied the relationship of Expression (6). As the amount of the positive electrode active material, and the first conductive additive and a second conductive additive, an M * 90 wt%, m c1 * 8 wt%, and the m c2 * is determined as 0 mass%.
（４）正極形成工程は、正極合材を１００質量％としたときの、正極活物質、第１導電助剤、第２導電助剤、及び結着剤の質量比は百分率で９０質量％、８質量％、０質量％、２質量％とした点を除いて、実施例１の（４）正極形成工程と同様に行った。以上により、比較例１の正極を得た。 (4) In the positive electrode forming step, the mass ratio of the positive electrode active material, the first conductive auxiliary agent, the second conductive auxiliary agent, and the binder when the positive electrode mixture is 100% by mass is 90% by mass, The process was performed in the same manner as in the positive electrode forming step (4) of Example 1, except that 8% by mass, 0% by mass and 2% by mass were used. Thus, a positive electrode of Comparative Example 1 was obtained.
得られた比較例１の正極を用いて、実施例１と同様にリチウムイオン二次電池を作製し、これを比較例１のリチウムイオン二次電池とした。 Using the obtained positive electrode of Comparative Example 1, a lithium ion secondary battery was fabricated in the same manner as in Example 1, and this was used as the lithium ion secondary battery of Comparative Example 1.
比較例１のリチウムイオン二次電池のサイクル試験前後のインピーダンスを測定した。その結果を図６に示した。また、図６に示すように、図５の実施例１の結果に比べて、左側の第1円弧が大きくなった。これは、正極活物質間で導電パス切れが生じて、正極の電子抵抗が上昇したものと考えられる。 The impedance of the lithium ion secondary battery of Comparative Example 1 before and after the cycle test was measured. FIG. 6 shows the result. Also, as shown in FIG. 6, the first arc on the left side was larger than the result of Example 1 in FIG. This is considered to be due to the fact that the conductive path was cut between the positive electrode active materials and the electronic resistance of the positive electrode increased.
また、表１には、実施例１及び比較例１の式（１）、式（２）、及び式（６）のパラメータを示した。表２、表３には、実施例１及び比較例１におけるリチウムイオン二次電池の第１円弧の抵抗、サイクル試験後の抵抗増加量及び抵抗増加率を求めた。サイクル試験前の第１円弧の抵抗をＺbeforeとし、サイクル試験後の第１円弧の抵抗をＺafterとしたとき、抵抗増加率（％）は、１００×（Ｚafter−Ｚbefore）／Ｚbeforeで計算される。表２は、第１円弧の抵抗を小数第４位で四捨五入して小数第３位までで表した値を用いて計算した結果を示し、表３は、第１円弧の抵抗を小数第３位で四捨五入して小数第２位までで表した値を用いて計算した結果を示す。表２及び表３の抵抗増加率（％）はいずれも小数第２位を四捨五入して小数第１位までの値とした。 Table 1 shows the parameters of the formulas (1), (2), and (6) of Example 1 and Comparative Example 1. In Tables 2 and 3, the resistance of the first arc, the resistance increase after the cycle test, and the resistance increase rate of the lithium ion secondary batteries in Example 1 and Comparative Example 1 were obtained. When the resistance of the first arc before the cycle test is Z before and the resistance of the first arc after the cycle test is Z after , the resistance increase rate (%) is 100 × (Z after −Z before ) / Z before Is calculated by Table 2 shows the results obtained by rounding the resistance of the first arc to the fourth decimal place and using values expressed to the third decimal place, and Table 3 shows the resistance of the first arc to the third decimal place. The result calculated using the value rounded down to the second decimal place is shown. Each of the resistance increase rates (%) in Tables 2 and 3 was rounded to the first decimal place to be a value up to the first decimal place.
表２及び表３に示すように、実施例１の二次電池の第1円弧の抵抗増加率は比較例１の二次電池のそれに比べ、大幅に抑えられていた。このことは、実施例１で、正極合材層の中に第２導電助剤を導入したことにより、正極合材層において導電パスの切断が生じにくくなったためであると考えられる。 As shown in Tables 2 and 3, the resistance increase rate of the first arc of the secondary battery of Example 1 was significantly suppressed as compared with that of the secondary battery of Comparative Example 1. This is considered to be because the introduction of the second conductive additive into the positive electrode mixture layer in Example 1 made it difficult to cut the conductive path in the positive electrode mixture layer.
（実施例２）
実施例２のリチウムイオン二次電池は、正極の正極合材層を１００質量％としたときの、正極活物質の質量比Ｍ＊と第１導電助剤の質量比ｍｃ１ ＊と第２導電助剤の質量比ｍｃ２ ＊と結着剤の質量比は、百分率で、９０：７．１３：０．８７：２である点で、実施例１のリチウムイオン二次電池と相違する。
(Example 2)
In the lithium ion secondary battery of Example 2, the mass ratio M * of the positive electrode active material, the mass ratio m c1 * of the first conductive additive, and the second conductivity were calculated when the positive electrode mixture layer of the positive electrode was 100% by mass. The lithium ion secondary battery of Example 1 is different from the lithium ion secondary battery of Example 1 in that the mass ratio mc2 * of the auxiliary agent and the mass ratio of the binder are 90: 7.13: 0.87: 2 in percentage.
正極を製造する工程は、次のようにした。
即ち、（１）選択工程は、実施例１の選択工程と同様に行った。用いた正極活物質、第１導電助剤及び第２導電助剤は、実施例１の正極活物質、第１導電助剤及び第２導電助剤と同じであり、これらの平均粒径Ｄ、ｄｃ１、ｄｃ２、真密度ρ、ρｃ１、ρｃ２及び比表面積ｓａｍ、ｓｃ２は、実施例１と同じとした。
The process for manufacturing the positive electrode was as follows.
That is, (1) the selecting step was performed in the same manner as the selecting step of Example 1. The positive electrode active material, the first conductive auxiliary, and the second conductive auxiliary used were the same as the positive electrode active material, the first conductive auxiliary, and the second conductive auxiliary of Example 1, and had an average particle diameter D, d c1 , d c2 , true densities ρ , ρ c1 , ρ c2 and specific surface areas s am , sc 2 were the same as in Example 1.
（２）調整工程では、集電体上に形成される正極合材層における正極活物質の質量比Ｍ＊は９０質量％とし、第２導電助剤の質量比ｍｃ２ ＊は０．８７質量％とした。式（２）の（Ｍ＊×ρｃ２×ｄｃ２ ３）／（ｍｃ２ ＊×ρ×Ｄ３）は９．８５であった。 (2) In the adjusting step, the mass ratio M * of the positive electrode active material in the positive electrode mixture layer formed on the current collector is 90% by mass, and the mass ratio m c2 * of the second conductive additive is 0.87% by mass. %. Formula (2) (M * × ρ c2 × d c2 3) / (m c2 * × ρ × D 3) was 9.85.
（３）決定工程では、式（１３）の左辺（ｓａｍ×Ｍ＊＋ｓｃ２×ｍｃ２ ＊）は５５．４ｍ２であり、式（１３）の右辺（３ｍｃ１ ＊／（２ρｃ１×ｄｃ１））は１５６．７ｍ２であった。式（１３）の関係を満足するように、ｍｃ１ ＊を７．１３質量％と決定した。
また、正極合材層１００ｇの中の第１導電助剤の個数と第１導電助剤１個当たりの断面積との積をＳｃ１とし、正極活物質の総表面積をＳとし、第２導電助剤の総表面積をＳｃ２としたとき、Ｓｃ１及びＳｃ２は式（６）の条件を満たすように決定した。式（９）によりＳｃ１を求めたところ、１５６．７ｍ２であった。式（１０）によりＳｃ２を求めたところ、１６．７ｍ２であった。式（１１）によりＳを求めたところ、３８．７ｍ２であった。Ｓｃ１、Ｓ、及びＳｃ２は、式（６）の関係を満足した。式（６）及び式（１３）を満たす正極活物質、第１導電助剤及び第２導電助剤の量として、Ｍ＊を９０質量％、ｍｃ１ ＊を７．１３質量％、ｍｃ２ ＊を０．８７質量％と決定した。
(3) In the determining step, the left side (s am × M * + s c2 × m c2 *) of formula (13) is 55.4M 2, right side of equation (13) (3m c1 * / (2ρ c1 × d c1 )) was 156.7 m 2 . Mc1 * was determined to be 7.13% by mass so as to satisfy the relationship of the expression (13).
The product of the number of the first conductive assistants in the positive electrode mixture layer 100g and the cross-sectional area per one first conductive assistant is Sc1 , the total surface area of the positive electrode active material is S, and the second conductive agent is S2. Assuming that the total surface area of the auxiliaries is Sc2 , Sc1 and Sc2 were determined so as to satisfy the condition of equation (6). Was determined the S c1 by the equation (9), it was 156.7m 2. Was determined the S c2 by the equation (10) was 16.7 m 2. When S was determined by the equation (11), it was 38.7 m 2 . S c1 , S, and S c2 satisfied the relationship of Expression (6). As the amounts of the positive electrode active material, the first conductive auxiliary, and the second conductive auxiliary that satisfy the formulas (6) and (13), M * is 90% by mass, m c1 * is 7.13% by mass, and m c2 *. Was determined to be 0.87% by mass.
（４）正極形成工程は、正極合材を１００質量％としたときの、正極活物質、第１導電助剤、第２導電助剤、及び結着剤の質量比は百分率で９０質量％、７．１３質量％、０．８７質量％、２質量％とした点を除いて、実施例１の（４）正極形成工程と同様に行った。以上により、実施例２の正極を得た。 (4) In the positive electrode forming step, the mass ratio of the positive electrode active material, the first conductive auxiliary agent, the second conductive auxiliary agent, and the binder when the positive electrode mixture is 100% by mass is 90% by mass, Except that 7.13 mass%, 0.87 mass%, and 2 mass% were used, it carried out similarly to (4) positive electrode formation process of Example 1. Thus, a positive electrode of Example 2 was obtained.
得られた実施例２の正極を用いて、実施例１と同様にリチウムイオン二次電池を作製し、これを実施例２のリチウムイオン二次電池とした。 Using the obtained positive electrode of Example 2, a lithium ion secondary battery was fabricated in the same manner as in Example 1, and this was used as the lithium ion secondary battery of Example 2.
（実施例３）
実施例３のリチウムイオン二次電池は、正極の正極合材層を１００質量％としたときの、正極活物質の質量比Ｍ＊と第１導電助剤の質量比ｍｃ１ ＊と第２導電助剤の質量比ｍｃ２ ＊と結着剤の質量比は、百分率で、９０：７．６：０．４：２である点で、実施例１のリチウムイオン二次電池と相違する。
(Example 3)
The lithium ion secondary battery of Example 3, when the positive-electrode mixture layer of the positive electrode is 100 mass%, the mass ratio m c1 * and the second conductive mass ratio M * a first conductive additive of the positive electrode active material The lithium ion secondary battery of Example 1 is different from the lithium ion secondary battery of Example 1 in that the mass ratio of the auxiliary agent, mc2 *, and the mass ratio of the binder are 90: 7.6: 0.4: 2 in percentage.
正極を製造する工程は、次のようにした。
即ち、（１）選択工程は、実施例１の選択工程と同様に行った。用いた正極活物質、第１導電助剤及び第２導電助剤は、実施例１の正極活物質、第１導電助剤及び第２導電助剤と同じであり、これらの平均粒径Ｄ、ｄｃ１、ｄｃ２、真密度ρ、ρｃ１、ρｃ２及び比表面積ｓａｍ、ｓｃ２は、実施例１と同じとした。
The process for manufacturing the positive electrode was as follows.
That is, (1) the selecting step was performed in the same manner as the selecting step of Example 1. The positive electrode active material, the first conductive auxiliary, and the second conductive auxiliary used were the same as the positive electrode active material, the first conductive auxiliary, and the second conductive auxiliary of Example 1, and had an average particle diameter D, d c1 , d c2 , true densities ρ , ρ c1 , ρ c2 and specific surface areas s am , sc 2 were the same as in Example 1.
（２）調整工程では、集電体上に形成される正極合材層における正極活物質の質量比Ｍ＊は９０質量％とし、第２導電助剤の質量比ｍｃ２ ＊は０．４質量％とした。式（２）の（Ｍ＊×ρｃ２×ｄｃ２ ３）／（ｍｃ２ ＊×ρ×Ｄ３）は２１．５であった。 (2) In the adjusting step, the mass ratio M * of the positive electrode active material in the positive electrode mixture layer formed on the current collector is 90% by mass, and the mass ratio mc2 * of the second conductive additive is 0.4% by mass. %. Formula (2) (M * × ρ c2 × d c2 3) / (m c2 * × ρ × D 3) was 21.5.
（３）決定工程では、式（１３）の左辺（ｓａｍ×Ｍ＊＋ｓｃ２×ｍｃ２ ＊）は４６．４ｍ２であり、式（１３）の右辺（３ｍｃ１ ＊／（２ρｃ１×ｄｃ１））は１６７．０ｍ２であった。式（１３）の関係を満足するように、ｍｃ１ ＊を７．６質量％と決定した。
また、正極合材層１００ｇの中の第１導電助剤の個数と第１導電助剤１個当たりの断面積との積をＳｃ１とし、正極活物質の総表面積をＳとし、第２導電助剤の総表面積をＳｃ２としたとき、Ｓｃ１及びＳｃ２は式（６）の条件を満たすように決定した。式（９）によりＳｃ１を求めたところ、１６７．０ｍ２であった。式（１０）によりＳｃ２を求めたところ、７．７ｍ２であった。式（１１）によりＳを求めたところ、３８．７ｍ２であった。Ｓｃ１、Ｓ、及びＳｃ２は、式（６）の関係を満足した。式（６）及び式（１３）を満たす正極活物質、第１導電助剤及び第２導電助剤の量として、Ｍ＊を９０質量％、ｍｃ１ ＊を７．６質量％、ｍｃ２ ＊を０．４質量％と決定した。
(3) In the determining step, the left side (s am × M * + s c2 × m c2 *) of formula (13) is 46.4M 2, right side of equation (13) (3m c1 * / (2ρ c1 × d c1)) was 167.0m 2. Mc1 * was determined to be 7.6% by mass so as to satisfy the relationship of Expression (13).
The product of the number of the first conductive assistants in the positive electrode mixture layer 100g and the cross-sectional area per one first conductive assistant is Sc1 , the total surface area of the positive electrode active material is S, and the second conductive agent is S2. Assuming that the total surface area of the auxiliaries is Sc2 , Sc1 and Sc2 were determined so as to satisfy the condition of equation (6). Was determined the S c1 by the equation (9), it was 167.0m 2. Was determined the S c2 by the equation (10), it was 7.7 m 2. When S was determined by the equation (11), it was 38.7 m 2 . S c1 , S, and S c2 satisfied the relationship of Expression (6). As the amounts of the positive electrode active material, the first conductive auxiliary agent, and the second conductive auxiliary agent that satisfy the formulas (6) and (13), M * is 90% by mass, mc1 * is 7.6% by mass, and mc2 *. Was determined to be 0.4% by mass.
（４）正極形成工程は、正極合材を１００質量％としたときの、正極活物質、第１導電助剤、第２導電助剤、及び結着剤の質量比は百分率で９０質量％、７．６質量％、０．４質量％、２質量％とした点を除いて、実施例１の（４）正極形成工程と同様に行った。以上により、実施例３の正極を得た。 (4) In the positive electrode forming step, the mass ratio of the positive electrode active material, the first conductive auxiliary agent, the second conductive auxiliary agent, and the binder when the positive electrode mixture is 100% by mass is 90% by mass, Except that 7.6% by mass, 0.4% by mass, and 2% by mass were carried out, the same procedure as in (4) the positive electrode forming step of Example 1 was performed. Thus, a positive electrode of Example 3 was obtained.
得られた実施例３の正極を用いて、実施例１と同様にリチウムイオン二次電池を作製し、これを実施例３のリチウムイオン二次電池とした。 Using the obtained positive electrode of Example 3, a lithium ion secondary battery was produced in the same manner as in Example 1, and this was used as the lithium ion secondary battery of Example 3.
（実施例４）
実施例４のリチウムイオン二次電池は、正極の正極合材層を１００質量％としたときの、正極活物質の質量比Ｍ＊と第１導電助剤の質量比ｍｃ１ ＊と第２導電助剤の質量比ｍｃ２ ＊と結着剤の質量比は、百分率で、９０：７．９２：０．０８：２である点で、実施例１のリチウムイオン二次電池と相違する。
(Example 4)
In the lithium ion secondary battery of Example 4, the mass ratio M * of the positive electrode active material, the mass ratio m c1 * of the first conductive additive, and the second conductivity were defined assuming that the positive electrode mixture layer of the positive electrode was 100% by mass. The lithium ion secondary battery of Example 1 is different from the lithium ion secondary battery of Example 1 in that the mass ratio mc2 * of the assistant and the mass ratio of the binder are 90: 7.92: 0.08: 2 in percentage.
正極を製造する工程は、次のようにした。
即ち、（１）選択工程は、実施例１の選択工程と同様に行った。用いた正極活物質、第１導電助剤及び第２導電助剤は、実施例１の正極活物質、第１導電助剤及び第２導電助剤と同じであり、これらの平均粒径Ｄ、ｄｃ１、ｄｃ２、真密度ρ、ρｃ１、ρｃ２及び比表面積ｓａｍ、ｓｃ２は、実施例１と同じとした。
The process for manufacturing the positive electrode was as follows.
That is, (1) the selecting step was performed in the same manner as the selecting step of Example 1. The positive electrode active material, the first conductive auxiliary, and the second conductive auxiliary used were the same as the positive electrode active material, the first conductive auxiliary, and the second conductive auxiliary of Example 1, and had an average particle diameter D, d c1 , d c2 , true densities ρ , ρ c1 , ρ c2 and specific surface areas s am , sc 2 were the same as in Example 1.
（２）調整工程では、集電体上に形成される正極合材層における正極活物質の質量比Ｍ＊は９０質量％とし、第２導電助剤の質量比ｍｃ２ ＊は０．０８質量％とした。式（２）の（Ｍ＊×ρｃ２×ｄｃ２ ３）／（ｍｃ２ ＊×ρ×Ｄ３）は１０７．４であった。 (2) In the adjusting step, the mass ratio M * of the positive electrode active material in the positive electrode mixture layer formed on the current collector is 90% by mass, and the mass ratio mc2 * of the second conductive additive is 0.08% by mass. %. Formula (2) (M * × ρ c2 × d c2 3) / (m c2 * × ρ × D 3) was 107.4.
（３）決定工程では、式（１３）の左辺（ｓａｍ×Ｍ＊＋ｓｃ２×ｍｃ２ ＊）は４０．２ｍ２であり、式（１３）の右辺（３ｍｃ１ ＊／（２ρｃ１×ｄｃ１））は１７４．１ｍ２であった。式（１３）の関係を満足するように、ｍｃ１ ＊を７．９２質量％と決定した。
また、正極合材層１００ｇの中の第１導電助剤の個数と第１導電助剤１個当たりの断面積との積をＳｃ１とし、正極活物質の総表面積をＳとし、第２導電助剤の総表面積をＳｃ２としたとき、Ｓｃ１及びＳｃ２は式（６）の条件を満たすように決定した。式（９）によりＳｃ１を求めたところ、１７４．１ｍ２であった。式（１０）によりＳｃ２を求めたところ、１．５ｍ２であった。式（１１）によりＳを求めたところ、３８．７ｍ２であった。Ｓｃ１、Ｓ、及びＳｃ２は、式（６）の関係を満足した。式（６）及び式（１３）を満たす正極活物質、第１導電助剤及び第２導電助剤の量として、Ｍ＊を９０質量％、ｍｃ１ ＊を７．９２質量％、ｍｃ２ ＊を０．０８質量％と決定した。
(3) In the determining step, the left side (s am × M * + s c2 × m c2 *) of formula (13) is 40.2M 2, right side of equation (13) (3m c1 * / (2ρ c1 × d c1)) was 174.1m 2. Mc1 * was determined to be 7.92% by mass so as to satisfy the relationship of Expression (13).
The product of the number of the first conductive assistants in the positive electrode mixture layer 100g and the cross-sectional area per one first conductive assistant is Sc1 , the total surface area of the positive electrode active material is S, and the second conductive agent is S2. Assuming that the total surface area of the auxiliaries is Sc2 , Sc1 and Sc2 were determined so as to satisfy the condition of equation (6). Was determined the S c1 by the equation (9), it was 174.1m 2. Was determined the S c2 by the equation (10), it was 1.5 m 2. When S was determined by the equation (11), it was 38.7 m 2 . S c1 , S, and S c2 satisfied the relationship of Expression (6). As the amounts of the positive electrode active material, the first conductive auxiliary agent, and the second conductive auxiliary agent that satisfy the formulas (6) and (13), M * is 90% by mass, mc1 * is 7.92% by mass, and mc2 *. Was determined to be 0.08% by mass.
（４）正極形成工程は、正極合材を１００質量％としたときの、正極活物質、第１導電助剤、第２導電助剤、及び結着剤の質量比は百分率で９０質量％、７．９２質量％、０．０８質量％、２質量％とした点を除いて、実施例１の（４）正極形成工程と同様に行った。以上により、実施例４の正極を得た。 (4) In the positive electrode forming step, the mass ratio of the positive electrode active material, the first conductive auxiliary agent, the second conductive auxiliary agent, and the binder when the positive electrode mixture is 100% by mass is 90% by mass, Except that 7.92 mass%, 0.08 mass%, and 2 mass% were used, the same procedure as in (4) the positive electrode forming step of Example 1 was performed. Thus, a positive electrode of Example 4 was obtained.
得られた実施例４の正極を用いて、実施例１と同様にリチウムイオン二次電池を作製し、これを実施例４のリチウムイオン二次電池とした。 Using the obtained positive electrode of Example 4, a lithium ion secondary battery was produced in the same manner as in Example 1, and this was used as the lithium ion secondary battery of Example 4.
（比較例２）
本比較例２のリチウムイオン二次電池は、正極合材層に第１導電助剤を含めておらず、正極活物質と第２導電助剤と結着剤の配合比を９０質量％：８質量％：２質量％にした点を除いて、実施例１のリチウムイオン二次電池と同様である。
(Comparative Example 2)
The lithium ion secondary battery of Comparative Example 2 did not include the first conductive additive in the positive electrode mixture layer, and the compounding ratio of the positive electrode active material, the second conductive additive, and the binder was 90% by mass: 8. Mass%: The same as the lithium ion secondary battery of Example 1 except that the mass% was set to 2% by mass.
正極を製造する工程は、次のようにした。
即ち、（１）選択工程では、実施例１の選択工程と同様に行った。用いた正極活物質及び第２導電助剤は、実施例１の正極活物質及び第２導電助剤と同じであり、これらの平均粒径Ｄ、ｄｃ２、真密度ρ、ρｃ２及び比表面積ｓａｍ、ｓｃ２は、実施例１と同じとした。
The process for manufacturing the positive electrode was as follows.
That is, (1) the selecting step was performed in the same manner as the selecting step of the first embodiment. The positive electrode active material and the second conductive auxiliary used were the same as the positive electrode active material and the second conductive auxiliary of Example 1, and their average particle diameter D, d c2 , true density ρ , ρ c2, and specific surface area s am and sc2 were the same as in Example 1.
（２）調整工程では、集電体上に形成される正極合材層における正極活物質の質量比Ｍ＊は９０質量％とし、第２導電助剤の質量比ｍｃ２ ＊は２質量％とした。式（２）の（Ｍ＊×ρｃ２×ｄｃ２ ３）／（ｍｃ２ ＊×ρ×Ｄ３）は１．０７であった。 (2) In the adjusting step, the mass ratio M * of the positive electrode active material in the positive electrode mixture layer formed on the current collector is 90% by mass, and the mass ratio mc2 * of the second conductive additive is 2% by mass. did. Formula (2) (M * × ρ c2 × d c2 3) / (m c2 * × ρ × D 3) was 1.07.
（３）決定工程では、正極活物質の質量比Ｍ＊、及び第２導電助剤の質量比ｍｃ２ ＊を用いて式（１３）を計算した。式（１３）の左辺（ｓａｍ×Ｍ＊＋ｓｃ２×ｍｃ２ ＊）は１９２．３ｍ２であり、式（１３）の右辺（３ｍｃ１ ＊／（２ρｃ１×ｄｃ１））は０であった。
また、正極合材層１００ｇの中の第１導電助剤の個数と第１導電助剤１個当たりの断面積との積をＳｃ１とし、正極活物質の総表面積をＳとし、第２導電助剤の総表面積をＳｃ２とし、式（９）によりＳｃ１を求めたところ、０ｍ２であった。式（１０）によりＳｃ２を求めたところ、１５３．６ｍ２であった。式（１１）によりＳを求めたところ、３８．７ｍ２であった。Ｓｃ１、Ｓ、及びＳｃ２は、式（６）の関係を満足しなかった。正極活物質、及び第１導電助剤及び第２導電助剤の量として、Ｍ＊を９０質量％、ｍｃ１ ＊を０質量％、ｍｃ２ ＊を８質量％と決定した。
(3) In the determining step, the mass ratio of the positive electrode active material M *, and were calculated equation (13) using a mass ratio m c2 * of the second conductive additive. Left (s am × M * + s c2 × m c2 *) of formula (13) is 192.3m 2, right side of equation (13) (3m c1 * / (2ρ c1 × d c1)) is 0 met Was.
The product of the number of the first conductive assistants in the positive electrode mixture layer 100g and the cross-sectional area per one first conductive assistant is Sc1 , the total surface area of the positive electrode active material is S, and the second conductive agent is S2. the total surface area of the auxiliary and S c2, was determined to S c1 by the equation (9), it was 0 m 2. Was determined the S c2 by the equation (10), it was 153.6m 2. When S was determined by the equation (11), it was 38.7 m 2 . S c1 , S, and S c2 did not satisfy the relationship of Expression (6). As the amount of the positive electrode active material, and the first conductive additive and a second conductive additive, an M * 90 wt%, the m c1 * 0 wt%, it was determined to 8% by weight of m c2 *.
（４）正極形成工程は、正極合材を１００質量％としたときの、正極活物質、第１導電助剤、第２導電助剤、及び結着剤の質量比は百分率で９０質量％、０質量％、８質量％、２質量％とした点を除いて、実施例１の（４）正極形成工程と同様に行った。以上により、比較例２の正極を得た。 (4) In the positive electrode forming step, the mass ratio of the positive electrode active material, the first conductive auxiliary agent, the second conductive auxiliary agent, and the binder when the positive electrode mixture is 100% by mass is 90% by mass, Except that 0 mass%, 8 mass%, and 2 mass% were used, the same procedure as in (4) the positive electrode forming step of Example 1 was performed. Thus, a positive electrode of Comparative Example 2 was obtained.
得られた比較例２の正極を用いて、実施例１と同様にリチウムイオン二次電池を作製し、これを比較例２のリチウムイオン二次電池とした。 Using the obtained positive electrode of Comparative Example 2, a lithium ion secondary battery was fabricated in the same manner as in Example 1, and this was used as a lithium ion secondary battery of Comparative Example 2.
実施例２〜４及び比較例２の各種パラメータを表１に示した。また、実施例２〜４及び比較例２のリチウムイオン二次電池のサイクル試験前後のインピーダンスを、実施例１と同様に測定し、その結果を表２、表３に示した。 Table 1 shows various parameters of Examples 2 to 4 and Comparative Example 2. The impedance of the lithium ion secondary batteries of Examples 2 to 4 and Comparative Example 2 before and after the cycle test was measured in the same manner as in Example 1, and the results are shown in Tables 2 and 3.
第１導電助剤及び第２導電助剤とも正極に含む実施例１〜４のリチウムイオン二次電池については、第１導電助剤及び第２導電助剤の一方を正極に含む比較例１，２のリチウムイオン二次電池に比べて、サイクル試験後の抵抗増加率が格段に低かった。実施例１〜４の中でも、式（２）の条件を満たしている実施例１，２のリチウムイオン二次電池については、式（２）の条件を満たしていない実施例３，４に比べて、抵抗増加率が低かった。表２と表３とでは、抵抗増加率が異なるが、第１円弧の抵抗を小数第３位までもとめて計算した表２の値の方が表３の値よりも信頼性が高い値であると考えられる。 Regarding the lithium ion secondary batteries of Examples 1 to 4 including both the first conductive auxiliary and the second conductive auxiliary in the positive electrode, Comparative Examples 1 and 2 including one of the first conductive auxiliary and the second conductive auxiliary in the positive electrode As compared with the lithium ion secondary battery of No. 2, the rate of increase in resistance after the cycle test was significantly lower. Among Examples 1 to 4, the lithium ion secondary batteries of Examples 1 and 2 satisfying the condition of Expression (2) are compared with Examples 3 and 4 not satisfying the condition of Expression (2). , The rate of increase in resistance was low. Although the resistance increase rate is different between Table 2 and Table 3, the value of Table 2 calculated by ascertaining the resistance of the first arc to the third decimal place has a higher reliability value than the value of Table 3. it is conceivable that.
１：第１導電助剤、２：第２導電助剤、３：電極活物質、４：隙間 1: first conductive assistant, 2: second conductive assistant, 3: electrode active material, 4: gap
Claims (10)
前記電極活物質と前記第１導電助剤と前記第２導電助剤とを有する電極合材を集電体上に塗布して電極合材層を形成する電極形成工程と、をもち、
さらに、前記電極形成工程の前に、前記電極合材層を１００質量％としたときの前記電極活物質の質量比及び前記第２導電助剤の質量比を百分率でＭ ＊ 及びｍ ｃ２ ＊ とし、前記電極活物質の真密度をρ（ｇ／ｃｍ ３ ）とし、前記第２導電助剤の真密度をρ ｃ２ （ｇ／ｃｍ ３ ）とし、前記電極活物質の平均粒径をＤ（μｍ）とし、前記第２導電助剤の平均粒径をｄ ｃ２ （μｍ）としたときに、前記Ｍ ＊ と前記ｍ ｃ２ ＊ が以下の式（２）の条件を満たすように、前記電極活物質と前記第２導電助剤との配合比を調整する調整工程をもつことを特徴とする二次電池用電極の製造方法。
Ｄ×（（３／２）１／２−１）≦ｄｃ２≦Ｄ・・・式（１）
０．１＜（Ｍ ＊ ×ρ ｃ２ ×ｄ ｃ２ ３ ）／（ｍ ｃ２ ＊ ×ρ×Ｄ ３ ）＜１０・・・式（２） An electrode active material having an average particle diameter D (μm), a first conductive auxiliary having an average particle diameter d c1 (μm), and an average particle diameter d c2 (μm) larger than d c1 (μm); a selection step of selecting a second conductive additive whose d c2 (μm) satisfies the condition of the following formula (1);
Chi also, the electrode forming step of forming an electrode composite layer is applied onto a current collector and electrode composite having said electrode active material and the first conductive additive the second conductive additive,
Further, before the electrode forming step, and M * and m c2 * mass ratio and mass ratio of the second conductive additive of the electrode active material upon the electrode mixture layer is 100 mass% in percentage The true density of the electrode active material is ρ (g / cm 3 ), the true density of the second conductive additive is ρ c2 (g / cm 3 ), and the average particle size of the electrode active material is D (μm ), And when the average particle size of the second conductive additive is d c2 (μm) , the electrode active material is set such that the M * and the m c2 * satisfy the condition of the following formula (2). manufacturing method of the second conductive auxiliary and the secondary battery electrode, wherein also One possible adjustment step of adjusting a mixing ratio of the.
D × ((3/2) 1/2 −1) ≦ d c2 ≦ D Expression (1)
0.1 <(M * × ρ c2 × d c2 3 ) / ( mc2 * × ρ × D 3 ) <10 Expression (2)
前記電極活物質と前記第１導電助剤と前記第２導電助剤とを有する電極合材を集電体上に塗布して電極合材層を形成する電極形成工程と、をもち、
さらに、前記電極形成工程の前に、前記電極合材層の中の前記第１導電助剤の個数と前記第１導電助剤１個当たりの断面積との積をＳ ｃ１ （ｍ ２ ）とし、前記電極合材層の中の前記電極活物質の総表面積をＳ（ｍ ２ ）とし、前記電極合材層の中の前記第２導電助剤の総表面積をＳ ｃ２ （ｍ ２ ）としたとき、前記Ｓ，前記Ｓ ｃ１ （ｍ ２ ）及び前記Ｓ ｃ２ （ｍ ２ ）が以下の式（６）の条件を満たすように、前記電極合材層に含める前記電極活物質、前記第１導電助剤及び前記第２導電助剤の質量比を決定する決定工程をもつことを特徴とする二次電池用電極の製造方法。
Ｄ×（（３／２）１／２−１）≦ｄｃ２≦Ｄ・・・式（１）
Ｓ + Ｓ ｃ２ ≦ Ｓ ｃ１ ・・・・式（６） An electrode active material having an average particle diameter D (μm), a first conductive auxiliary having an average particle diameter d c1 (μm), and an average particle diameter d c2 (μm) larger than d c1 (μm); a selection step of selecting a second conductive additive whose d c2 (μm) satisfies the condition of the following formula (1);
Chi also, the electrode forming step of forming an electrode composite layer is applied onto a current collector and electrode composite having said electrode active material and the first conductive additive the second conductive additive,
Further, before the electrode forming step, the product of the number of the first conductive assistants in the electrode mixture layer and the cross-sectional area per one first conductive assistant is S c1 (m 2 ). The total surface area of the electrode active material in the electrode mixture layer was S (m 2 ), and the total surface area of the second conductive additive in the electrode mixture layer was S c2 (m 2 ). The electrode active material and the first conductive material included in the electrode mixture layer so that S, S c1 (m 2 ), and S c2 (m 2 ) satisfy the condition of the following equation (6). method of manufacturing aids and secondary battery electrode, wherein also One possible a determination step of determining the mass ratio of the second conductive additive.
D × ((3/2) 1/2 −1) ≦ d c2 ≦ D Expression (1)
S + S c2 ≤ S c1 ······
前記電極活物質と前記第１導電助剤と前記第２導電助剤とを有する電極合材を集電体上に塗布して電極合材層を形成する電極形成工程と、をもち、
さらに、前記電極形成工程の前に、前記電極活物質の比表面積をｓ ａｍ （ｍ ２ ／ｇ）とし、前記第２導電助剤の比表面積をｓ ｃ２ （ｍ ２ ／ｇ）とし、前記第１導電助剤の真密度をρ ｃ１ （ｇ／ｃｍ ３ ）とし、前記第１導電助剤の平均粒径をｄ ｃ１ （μｍ）とし、前記電極合材層を１００質量％としたときの前記第１導電助剤の質量比、前記第２導電助剤の質量比、及び正極活物質の質量比をｍ ｃ１ ＊ 、ｍ ｃ２ ＊ 、Ｍ ＊ としたとき、前記Ｍ ＊ 、前記ｍ ｃ１ ＊ 及び前記ｍ ｃ２ ＊ が以下の式（１３）の条件を満たすように、前記電極合材層に含める前記正極活物質、前記第１導電助剤及び前記第２導電助剤の質量比を決定する工程をもつことを特徴とする二次電池用電極の製造方法。
Ｄ×（（３／２）１／２−１）≦ｄｃ２≦Ｄ・・・式（１）
ｓ ａｍ ×Ｍ ＊ ＋ｓ ｃ２ ×ｍ ｃ２ ＊ ≦３ｍ ｃ１ ＊ ／（２ρ ｃ１ ×ｄ ｃ１ ）・・・式（１３） An electrode active material having an average particle diameter D (μm), a first conductive auxiliary having an average particle diameter d c1 (μm), and an average particle diameter d c2 (μm) larger than d c1 (μm); a selection step of selecting a second conductive additive whose d c2 (μm) satisfies the condition of the following formula (1);
Chi also, the electrode forming step of forming an electrode composite layer is applied onto a current collector and electrode composite having said electrode active material and the first conductive additive the second conductive additive,
Further, before the electrode forming step, the specific surface area of the electrode active material is set to s am (m 2 / g), and the specific surface area of the second conductive additive is set to sc 2 (m 2 / g). 1 When the true density of the conductive additive is ρ c1 (g / cm 3 ), the average particle size of the first conductive additive is d c1 (μm), and the electrode mixture layer is 100% by mass. the weight ratio of the first conductive additive, the weight ratio of the second conductive additive, and m c1 * the mass ratio of the positive electrode active material, m c2 *, when the M *, wherein M *, wherein m c1 * and wherein m c2 * is to satisfy the condition of following equation (13), the positive electrode active material including the electrode mixture layer, the step of determining the mass ratio of the first conductive additive and the second conductive additive method of manufacturing a secondary battery electrode, characterized in that One also.
D × ((3/2) 1/2 −1) ≦ d c2 ≦ D Expression (1)
s am × M * + s c2 × m c2 * ≦ 3m c1 * / (2ρ c1 × d c1) ··· formula (13)
前記電極合材層を１００質量％としたときの前記電極活物質の質量比及び前記第２導電助剤の質量比を百分率でＭ ＊ 及びｍ ｃ２ ＊ とし、前記電極活物質の真密度をρ（ｇ／ｃｍ ３ ）とし、前記第２導電助剤の真密度をρ ｃ２ （ｇ／ｃｍ ３ ）とし、前記電極活物質の平均粒径をＤ（μｍ）とし、前記第２導電助剤の平均粒径をｄ ｃ２ （μｍ）としたときに、前記Ｍ ＊ と前記ｍ ｃ２ ＊ が以下の式（２）の条件を満たすことを特徴とする二次電池用電極。
Ｄ×（（３／２）１／２−１）≦ｄｃ２≦Ｄ・・・式（１）
０．１＜（Ｍ ＊ ×ρ ｃ２ ×ｄ ｃ２ ３ ）／（ｍ ｃ２ ＊ ×ρ×Ｄ ３ ）＜１０・・・式（２） An electrode active material having an average particle diameter D (μm), a first conductive auxiliary having an average particle diameter d c1 (μm), and an average particle diameter d c2 (μm) larger than d c1 (μm); an electrode mixture layer having a second conductive additive having d c2 (μm) satisfying the following expression (1) :
The mass ratio of the electrode active material and the mass ratio of the second conductive additive when the electrode mixture layer is 100% by mass are expressed as M * and mc2 * in percentage, and the true density of the electrode active material is expressed as ρ. (G / cm 3 ), the true density of the second conductive additive is ρ c2 (g / cm 3 ), the average particle size of the electrode active material is D (μm), An electrode for a secondary battery , wherein, when the average particle diameter is d c2 (μm), the M * and the m c2 * satisfy the following expression (2) .
D × ((3/2) 1/2 −1) ≦ d c2 ≦ D Expression (1)
0.1 <(M * × ρ c2 × d c2 3 ) / ( mc2 * × ρ × D 3 ) <10 Expression (2)
前記電極合材層の中の前記第１導電助剤の個数と前記第１導電助剤１個当たりの断面積との積をＳ ｃ１ （ｍ ２ ）とし、前記電極合材層の中の前記電極活物質の総表面積をＳ（ｍ ２ ）とし、前記電極合材層の中の前記第２導電助剤の総表面積をＳ ｃ２ （ｍ ２ ）としたとき、前記Ｓ、前記Ｓ ｃ１ （ｍ ２ ）及び前記Ｓ ｃ２ （ｍ ２ ）が以下の式（６）の条件を満たすことを特徴とする二次電池用電極。
Ｄ×（（３／２）１／２−１）≦ｄｃ２≦Ｄ・・・式（１）
Ｓ + Ｓ ｃ２ ≦ Ｓ ｃ１ ・・・・式（６） An electrode active material having an average particle diameter D (μm), a first conductive additive having an average particle diameter d c1 (μm), and an average particle diameter d c2 (μm) larger than d c1 (μm); an electrode mixture layer having a second conductive additive having d c2 (μm) satisfying the following expression (1) :
The product of the number of the first conductive assistants in the electrode mixture layer and the cross-sectional area per one first conductive assistant is S c1 (m 2 ), and the product in the electrode mixture layer is When the total surface area of the electrode active material is S (m 2 ), and the total surface area of the second conductive additive in the electrode mixture layer is S c2 (m 2 ), the S and the S c1 (m 2 ) and an electrode for a secondary battery, wherein S c2 (m 2 ) satisfies the condition of the following expression (6) .
D × ((3/2) 1/2 −1) ≦ d c2 ≦ D Expression (1)
S + S c2 ≤ S c1 ······
前記電極活物質の比表面積をｓ ａｍ （ｍ ２ ／ｇ）とし、前記第２導電助剤の比表面積をｓ ｃ２ （ｍ ２ ／ｇ）とし、前記第１導電助剤の真密度をρ ｃ１ （ｇ／ｃｍ ３ ）とし、前記第１導電助剤の平均粒径をｄ ｃ１ （μｍ）とし、前記電極合材層を１００質量％としたときの前記第１導電助剤の質量比、前記第２導電助剤の質量比、及び正極活物質の質量比をｍ ｃ１ ＊ 、ｍ ｃ２ ＊ 、Ｍ ＊ としたとき、前記Ｍ ＊ 、前記ｍ ｃ１ ＊ 及び前記ｍ ｃ２ ＊ が以下の式（１３）の条件を満たすことを特徴とする二次電池用電極。
Ｄ×（（３／２）１／２−１）≦ｄｃ２≦Ｄ・・・式（１）
ｓ ａｍ ×Ｍ ＊ ＋ｓ ｃ２ ×ｍ ｃ２ ＊ ≦３ｍ ｃ１ ＊ ／（２ρ ｃ１ ×ｄ ｃ１ ）・・・式（１３） An electrode active material having an average particle diameter D (μm), a first conductive auxiliary having an average particle diameter d c1 (μm), and an average particle diameter d c2 (μm) larger than d c1 (μm); an electrode mixture layer having a second conductive additive having d c2 (μm) satisfying the following expression (1) :
The specific surface area of the electrode active material is s am (m 2 / g), the specific surface area of the second conductive auxiliary is s c2 (m 2 / g), and the true density of the first conductive auxiliary is ρ c1. (G / cm 3 ), the average particle size of the first conductive additive is d c1 (μm), and the mass ratio of the first conductive additive when the electrode mixture layer is 100% by mass. the weight ratio of the second conductive additive, and the mass ratio of the positive electrode active material m c1 *, m c2 *, when the M *, wherein M *, wherein m c1 * and the m c2 * the following equation (13 An electrode for a secondary battery , which satisfies condition (1) .
D × ((3/2) 1/2 −1) ≦ d c2 ≦ D Expression (1)
s am × M * + s c2 × m c2 * ≦ 3m c1 * / (2ρ c1 × d c1) ··· formula (13)
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