JP4798750B2 - High density electrode and battery using the electrode - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve permeation property of electrolytic solution and retaining property of the electrolytic solution which are the problems in realizing a high density electrode needed to achieve a high energy density battery. <P>SOLUTION: This is the high density electrode which is obtained by containing an electrode active material and a carbon fiber of diameter 1-1,000 nm, and of which the percentage of void is 25% or less, and into which a solid polyelectrolyte is impregnated, and this is the battery using this electrode. <P>COPYRIGHT: (C)2006,JPO&amp;NCIPI

Description

  The present invention relates to a high-density electrode used for a battery having a large electrode bulk density, a large charge / discharge capacity per volume, and excellent charge / discharge cycle characteristics, large current load characteristics, and electrolyte permeability, and a battery using the same. In particular, the present invention relates to a high-density electrode used for a non-aqueous secondary battery and a non-aqueous secondary battery using the same.

  2. Description of the Related Art As mobile devices become smaller and lighter and have higher performance, there is an increasing demand for secondary batteries having high energy density and higher capacities of secondary batteries. Under such circumstances, non-aqueous lithium secondary batteries such as lithium ion batteries and lithium polymer batteries using non-aqueous electrolytes are used as secondary batteries for small portable devices such as mobile phones and video cameras. Due to the characteristic of voltage, it is used in many devices. As a positive electrode material used for these lithium secondary batteries, a metal oxide typified by lithium cobaltate having a large charge / discharge capacity per unit weight at a high potential is used, and as a negative electrode material, a base potential close to Li is used. A carbon material represented by graphite having a large charge / discharge capacity per unit weight is used. However, these electrode materials are used up to the point where the charge / discharge capacity per mass is close to the theoretical value, and the energy density per weight as a battery is approaching its limit. Therefore, new high-capacity cathode materials such as iron olivine compounds and metal sulfides, and new high-capacity anode materials such as tin oxide, silicon oxide, Li alloy, lithium nitride, and composite materials of these and carbon materials have been actively developed. ing.

Moreover, as a secondary battery used for a small portable device, a more compact battery is required, and not only the energy density per mass but also the energy density per volume is required to be high. Therefore, studies have been started to increase the filling amount in the battery container by increasing the density of the electrode, and to increase the energy density per volume of the electrode and the battery.
For example, graphite most frequently used as a negative electrode material has a true density of about 2.2 g / cm ³ , but an electrode density of about 1.5 g / cm ³ is used. By setting this to 1.7 g / cm ³ or more, it is possible to improve the energy density per battery volume, and studies are underway. Also, the true density of lithium cobaltate-based oxide mainly used as a positive electrode material is of the order of 5.1 g / cm ^3, as the electrode density is used in less than 3.3 g / cm ^3, 3 Studies of more than 0.5 g / cm ³ have been made.

  However, by increasing the electrode density, the number of vacancies in the electrode decreases, which usually leads to a shortage of the electrolyte solution that is important for the electrode reaction existing in the vacancies, or slows the penetration of the electrolyte solution into the electrode. The problem arises. When the electrolyte in the electrode is insufficient, the electrode reaction is slowed down, resulting in a problem that the energy density is lowered, the high-speed charge / discharge performance is lowered, and the battery cycle characteristics are lowered. Moreover, when the permeability of the electrolytic solution is slow, the battery manufacturing time becomes long, leading to an increase in manufacturing cost. The problem becomes more prominent when a polymer compound such as a lithium polymer battery is used in part or all of the structure of the electrolytic solution.

JP-A-4-155576 JP-A-4-237971

  An object of the present invention is to improve the electrolyte permeability and electrolyte retention, which are problems in realizing a high-density electrode necessary for achieving a high energy density battery.

  In view of the problems of the high-density electrode, the present inventors have made extensive studies in order to solve the above problems, and as a result, carbon fibers having a fiber diameter of 1 to 1000 nm are added to the electrode active material material to obtain a high density. By producing an electrode, the inventors have found that a high-performance battery with high energy density and good high-speed charge / discharge performance can be obtained without impairing electrolyte permeability, and the present invention has been completed.

The addition of carbon fiber to the electrode material to improve the load characteristics and cycle life of the battery has been studied and put into practical use. For example, in Patent Document 1 (Japanese Patent Laid-Open No. 4-155576) and Patent Document 2 (Japanese Patent Laid-Open No. 4-237971), by adding carbon fiber to a graphite negative electrode, the electrode resistance is lowered and the load characteristics of the battery are reduced. Or improving the strength of the electrode, increasing the resistance to expansion and contraction of the electrode, and improving the cycle life of the battery. Thus, the purpose of adding carbon fiber so far is to lower electrode resistance and improve electrode strength, and electrodes having a normal density with a porosity of more than 25% have been used.
In the present invention, when carbon fiber is added, even in a high-density electrode having a porosity of 25% or less, electrolyte permeability is not significantly reduced, and an electrode having low electrode resistance and good electrode strength can be obtained as usual. It is based on the knowledge of.

  The reason why the electrolyte solution permeability of the high-density electrode is improved by adding the carbon fiber is that fine fibers are appropriately dispersed among the highly compressed active material particles, thereby This is probably because fine voids are maintained.

［式中、Ｒ¹及びＲ³は水素またはアルキル基を表わし、Ｒ²及びＲ⁵はオキシアルキレン、フルオロカーボン、オキシフルオロカーボン及び／またはカーボネート基を含む２価の基を表わし、Ｒ⁴は炭素数１０以下の２価の基を表わす。Ｒ²、Ｒ⁴及びＲ⁵はヘテロ原子を含んでいてもよく、直鎖状、分岐状または環状のいずれの構造を有するものでもよい。ｘは０または１〜１０の整数を示す。但し、同一分子中に複数個の上記一般式（１）または（２）で表される重合性官能基が含まれる場合、それぞれの重合性官能基中のＲ¹、Ｒ²、Ｒ³、Ｒ⁴、Ｒ⁵及びｘは、同一でもよいし異なってもよい。］で示されるユニットをもつ化合物を一種類以上含む前記１〜３１のいずれかに記載の高密度電極。
［３３］高分子固体電解質に用いられる非水系溶媒にエチレンカーボネート、ジエチルカーボネート、ジメチルカーボネート、メチルエチルカーボネート、プロピレンカーボネート、ブチレンカーボネート、及びビニレンカーボネートからなる群から選ばれる少なくとも１種が含まれる前記１〜３２のいずれかに記載の高密度電極。
［３４］前記１〜３３のいずれかに記載の高密度電極を構成要素として含む電池。
［３５］前記１〜３３のいずれかに記載の高密度電極を構成要素として含む二次電池。
［３６］繊維径１〜１０００ｎｍの炭素繊維を０.２〜２０質量％含有し、１００ｍＡｈ／ｇ以上の容量密度を有する電極に、高分子固体電解質が含浸してなることを特徴とするリチウム電池用電極。
［３７］２５℃、１気圧で３μｌのプロピレンカーボネートを５００秒以内で吸液できる前記３６に記載のリチウム電池用電極。
［３８］高分子固体電解質の構成要素として一般式（１）及び／または一般式（２）

［式中、Ｒ¹及びＲ³は水素またはアルキル基を表わし、Ｒ²及びＲ⁵はオキシアルキレン、フルオロカーボン、オキシフルオロカーボン及び／またはカーボネート基を含む２価の基を表わし、Ｒ⁴は炭素数１０以下の２価の基を表わす。Ｒ²、Ｒ⁴及びＲ⁵はヘテロ原子を含んでいてもよく、直鎖状、分岐状または環状のいずれの構造を有するものでもよい。ｘは０または１〜１０の整数を示す。但し、同一分子中に複数個の上記一般式（１）または（２）で表される重合性官能基が含まれる場合、それぞれの重合性官能基中のＲ¹、Ｒ²、Ｒ³、Ｒ⁴、Ｒ⁵及びｘは、同一でもよいし異なってもよい。］で示されるユニットをもつ化合物を一種類以上含む前記３６または３７に記載のリチウム電池用電極。
［３９］高分子固体電解質に用いられる非水系溶媒にエチレンカーボネート、ジエチルカーボネート、ジメチルカーボネート、メチルエチルカーボネート、プロピレンカーボネート、ブチレンカーボネート、及びビニレンカーボネートからなる群から選ばれる少なくとも１種が含まれる前記３６〜３８のいずれかに記載のリチウム電池用電極。 Accordingly, the present invention provides the following high-density electrode and a battery using the electrode.
[1] A high-density electrode comprising a high-density electrode containing an electrode active material and carbon fibers having a fiber diameter of 1 to 1000 nm and a porosity of 25% or less, impregnated with a polymer solid electrolyte.
[2] The high-density electrode as described in 1 above, wherein the carbon fiber is a graphite-based carbon fiber heat-treated at 2000 ° C. or higher.
[3] The high-density electrode according to 1 or 2 above, wherein the carbon fiber is a graphite-based carbon fiber having an oxygen-containing functional group introduced on the surface by oxidation treatment.
[4] The high-density electrode according to any one of 1 to 3, wherein the carbon fiber is a graphite-based carbon fiber containing 0.1 to 100000 ppm of boron.
[5] The high-density electrode according to any one of 1 to 4 above, wherein the amount of carbon fiber in the electrode is 0.05 to 20% by mass.
[6] The high density electrode according to any one of 1 to 5 above, wherein an average aspect ratio of the carbon fiber is 5 to 50000.
[7] The average spacing d ₀₀₂ of (002) plane measured by X-ray diffraction of the graphite carbon fibers, high density electrode according to any one of the at most 0.344 nm 2 to 4.
[8] The high-density electrode according to any one of 1 to 7, wherein the carbon fiber has a hollow structure inside.
[9] The high-density electrode according to any one of 1 to 8, wherein the carbon fiber includes a branched carbon fiber.
[10] The high-density electrode according to any one of 1 to 9, wherein the electrode active material is a carbon-based material.
[11] The high-density electrode as described in 10 above, wherein the carbonaceous material contains Si.
[12] The high-density electrode as described in 10 or 11, wherein the carbon-based material is a non-graphite-based carbon material, and the electrode bulk density is 1.5 g / cm ³ or more.
[13] The high-density electrode according to any one of 10 to 12, wherein the carbon-based material of the electrode active material before electrode molding is a carbonaceous particle that satisfies the following requirements:
(1) The average circularity measured by a flow type particle image analyzer is 0.70 to 0.99,
(2) The average particle diameter by laser diffraction method is 1-50 μm.
[14] The high-density electrode as described in 10, 11 or 13, wherein the carbon-based material contains a graphite-based material of 50% by mass or more and the electrode bulk density is 1.7 g / cm ³ or more.
[15] The high-density electrode as described in 14 above, wherein the graphite material contains boron.
[16] The high-density electrode according to the above 14 or 15, wherein the carbon-based material of the electrode active material before forming the electrode is a carbon particle containing 50% by mass or more of graphite particles satisfying the following requirements:
(1) The average circularity measured by a flow type particle image analyzer is 0.70 to 0.99,
(2) The average particle diameter by laser diffraction method is 1-50 μm.
[17] The high-density electrode according to any one of 14 to 16, wherein the graphite-based material is carbon particles containing 50% by mass or more of graphite particles satisfying the following requirements:
(1) C ₀ of (002) plane in X-ray diffraction measurement is 0.6900 nm, La (crystallite size in the a-axis direction)> 100 nm, Lc (crystallite size in the c-axis direction)> 100 nm,
(2) BET specific surface area of 0.2 to ⁵ m ² / g,
(3) True density is 2.20 g / cm ³ or more,
(4) Laser Raman R value (peak intensity ratio of 1360 cm ^-1 to the peak intensity of 1580 cm ^-1 by laser Raman spectrum) 0.01 to 0.9.
[18] The high-density electrode according to any one of 1 to 9, wherein the electrode active material is a Li alloy.
[19] The high-density electrode according to any one of 1 to 9, wherein the electrode active material is a lithium nitride material.
[20] The high-density electrode according to any one of 1 to 9, wherein the electrode active material is a silicon oxide-based material.
[21] The high-density electrode according to any one of 1 to 9, wherein the electrode active material is a metal oxide material.
[22] The high-density electrode as described in 21 above, wherein the metal oxide material contains 60% by mass or more of a tin oxide material.
[23] The high density electrode as described in 21 above, wherein the cobalt oxide is contained in the metal oxide material in an amount of 60% by mass or more and the electrode bulk density is 3.6 g / cm ³ or more.
[24] The high density electrode as described in 21 above, wherein the metal oxide material contains manganese oxide in an amount of 60% by mass or more and the electrode bulk density is 3.0 g / cm ³ or more.
[25] The high-density electrode as described in 21 above, wherein the metal oxide-based material contains a mixture of cobalt-based oxide and manganese-based oxide in an amount of 80% by mass or more, and the electrode bulk density is 3.4 g / cm ³ or more. .
[26] The high density electrode as described in 21 above, wherein the metal oxide material contains 60% by mass or more of nickel oxide and the electrode bulk density is 3.4 g / cm ³ or more.
[27] The high density electrode as described in 21 above, wherein the metal oxide material contains 60% by mass or more of vanadium oxide, and the electrode bulk density is 2.3 g / cm ³ or more.
[28] The high-density electrode according to any one of 1 to 9, wherein the electrode active material is a metal sulfide-based material.
[29] The high-density electrode according to any one of 1 to 9, wherein the electrode active material is an iron olivine compound.
[30] The carbon fiber having a fiber diameter of 1 to 1000 nm is contained in an amount of 0.2 to 20% by mass, has a capacity density of 100 mAh / g or more, and has high electrolyte permeability. High density electrode.
[31] The high-density electrode as described in 30 above, which can absorb 3 μl of propylene carbonate at 25 ° C. and 1 atm within 500 seconds.
[32] General formula (1) and / or general formula (2) as a constituent of the solid polymer electrolyte

[Wherein R ¹ and R ³ represent hydrogen or an alkyl group, R ² and R ⁵ represent a divalent group containing an oxyalkylene, fluorocarbon, oxyfluorocarbon and / or carbonate group, and R ⁴ represents a carbon number of 10 The following divalent groups are represented. R ² , R ⁴ and R ⁵ may contain a hetero atom, and may have any of a linear, branched or cyclic structure. x represents 0 or an integer of 1 to 10. However, when a plurality of polymerizable functional groups represented by the above general formula (1) or (2) are contained in the same molecule, R ¹ , R ² , R ³ , R in each polymerizable functional group ⁴ , R ⁵ and x may be the same or different. The high-density electrode according to any one of 1 to 31 above, which contains one or more compounds having a unit represented by
[33] The above 1 wherein the non-aqueous solvent used in the polymer solid electrolyte includes at least one selected from the group consisting of ethylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate 33. The high-density electrode according to any one of -32.
[34] A battery comprising the high-density electrode according to any one of 1 to 33 as a constituent element.
[35] A secondary battery including the high-density electrode according to any one of 1 to 33 as a constituent element.
[36] A lithium battery comprising 0.2 to 20% by mass of carbon fibers having a fiber diameter of 1 to 1000 nm and an electrode having a capacity density of 100 mAh / g or more impregnated with a polymer solid electrolyte. Electrode.
[37] The electrode for a lithium battery as described in 36 above, which can absorb 3 μl of propylene carbonate at 25 ° C. and 1 atmosphere within 500 seconds.
[38] The general formula (1) and / or the general formula (2) as a constituent of the solid polymer electrolyte

[Wherein R ¹ and R ³ represent hydrogen or an alkyl group, R ² and R ⁵ represent a divalent group containing an oxyalkylene, fluorocarbon, oxyfluorocarbon and / or carbonate group, and R ⁴ represents a carbon number of 10 The following divalent groups are represented. R ² , R ⁴ and R ⁵ may contain a hetero atom, and may have any of a linear, branched or cyclic structure. x represents 0 or an integer of 1 to 10. However, when a plurality of polymerizable functional groups represented by the above general formula (1) or (2) are contained in the same molecule, R ¹ , R ² , R ³ , R in each polymerizable functional group ⁴ , R ⁵ and x may be the same or different. The electrode for lithium batteries as described in 36 or 37 above, which contains at least one compound having a unit represented by
[39] The above 36, wherein the non-aqueous solvent used for the polymer solid electrolyte includes at least one selected from the group consisting of ethylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate. The electrode for lithium batteries in any one of -38.

The present invention also provides the following high-density electrode.
[40] A high-density electrode using a non-graphitic carbon material as an electrode active material, containing 0.05 to 20% by mass of carbon fibers having a fiber diameter of 1 to 1000 nm, and an electrode bulk density of 1.5 g / cm ³ or more. A high-density electrode characterized by
[41] A high-density electrode having a carbon-based material containing 50% by mass or more of a graphite-based material as an electrode active material, 0.05 to 20% by mass of carbon fibers having a fiber diameter of 1 to 1000 nm, and an electrode bulk density A high-density electrode characterized by being 1.7 g / cm ³ or more.
[42] A high-density electrode using a Li alloy as an electrode active material, containing 0.05 to 20% by mass of carbon fibers having a fiber diameter of 1 to 1000 nm, and an electrode bulk density of 1.0 g / cm ³ or more. High density electrode characterized by
[43] A high-density electrode using a lithium nitride-based material as an electrode active material, containing 0.05 to 20% by mass of carbon fibers having a fiber diameter of 1 to 1000 nm, and having an electrode bulk density of 1.0 g / cm ³ or more. A high-density electrode characterized by being.
[44] A high-density electrode using a silicon oxide-based material such as SiO ₂ as an electrode active material, containing 0.05 to 20% by mass of carbon fibers having a fiber diameter of 1 to 1000 nm and an electrode bulk density of 1.0 g / A high-density electrode characterized by being cm ³ or more.
[45] A high-density electrode having a metal oxide material containing 60% by mass or more of a tin oxide material such as SnO ₂ as an electrode active material, and 0.05 to 20 mass of carbon fiber having a fiber diameter of 1 to 1000 nm. %, And the electrode bulk density is 1.2 g / cm ³ or more.
[46] A high-density electrode using a metal oxide material containing 60% by mass or more of a cobalt-based oxide such as lithium cobaltate as an electrode active material, and 0.05 to 20 carbon fibers having a fiber diameter of 1 to 1000 nm. A high-density electrode comprising mass% and having an electrode bulk density of 3.6 g / cm ³ or more.
[47] A high-density electrode having a metal oxide material containing 60% by mass or more of a manganese oxide such as lithium manganate as an electrode active material, and 0.05 to 20 carbon fibers having a fiber diameter of 1 to 1000 nm. A high-density electrode comprising mass% and having an electrode bulk density of 3.0 g / cm ³ or more.
[48] A high-density electrode comprising a metal oxide material containing 80% by mass or more of a mixture of a cobalt-based oxide such as lithium cobaltate and a manganese-based oxide such as lithium manganate as an electrode active material. A high-density electrode comprising 0.05 to 20% by mass of carbon fibers having a diameter of 1 to 1000 nm and an electrode bulk density of 3.4 g / cm ³ or more.
[49] A high-density electrode having a metal oxide material containing 60% by mass or more of a nickel-based oxide such as lithium nickelate as an electrode active material, and 0.05 to 20 carbon fibers having a fiber diameter of 1 to 1000 nm A high-density electrode comprising mass% and having an electrode bulk density of 3.4 g / cm ³ or more.
[50] A high-density electrode having a metal oxide material containing 60% by mass or more of vanadium oxide such as vanadium pentoxide as an electrode active material, and 0.05 to 20 carbon fibers having a fiber diameter of 1 to 1000 nm. A high-density electrode comprising mass% and having an electrode bulk density of 2.3 g / cm ³ or more.
[51] A high-density electrode using a metal sulfide-based material such as titanium sulfide or molybdenum sulfide as an electrode active material, containing 0.05 to 20% by mass of carbon fiber having a fiber diameter of 1 to 1000 nm, and having an electrode bulk density of A high-density electrode characterized by being 2.0 g / cm ³ or more.
[52] A high-density electrode using an iron olivine compound such as LiFePO ₄ as an electrode active material, containing 0.05 to 20% by mass of carbon fibers having a fiber diameter of 1 to 1000 nm, and an electrode bulk density of 2.5 g / A high-density electrode characterized by being cm ³ or more.
Hereinafter, the present invention will be described in detail.

1. Carbon fiber In general, high-density electrodes are obtained by forming electrode active material powders of several to several tens of μm by high-pressure pressing. Therefore, electrode active material powders are deformed, gaps between the powders are reduced, and electrolyte penetration Is significantly reduced. By adding fine tough fibers that are fine and resistant to pressure deformation, fine voids are formed between the electrode active material powders, and the electrolytic solution easily permeates. If the conductivity between the particles between the electrode active materials is impaired due to voids, the electrode performance will deteriorate, so the added fiber itself is excellent in conductivity, and the fiber length is as long as possible to increase the number of conductive paths. Is preferably long. From such a viewpoint, it is necessary to use conductive, tough and fine carbon fibers as the fibers to be added.

(1-1) Fiber diameter of carbon fiber If the fiber diameter of the carbon fiber used in the high-density electrode of the present invention is too thick, voids in the electrode become too large, and the electrode density cannot be increased. Since the average particle diameter of the active material particles generally used is about several to several tens of μm, the fiber diameter of the carbon fiber is about 1 μm at the maximum. On the other hand, if the fiber diameter is too thin, it is buried between the active material particles, and void formation in the target electrode becomes impossible, which is not preferable. A fiber diameter of about 1 to several nm is required at a minimum. For the above reasons, the fiber diameter of the carbon fiber that can be used for the high-density electrode of the present invention is in the range of 1 to 1000 nm, preferably 5 to 500 nm, and more preferably 10 to 150 nm. In terms of the average fiber diameter, a range of 5 to 500 nm is preferable, and a range of 10 to 200 nm is more preferable.

(1-2) Carbon fiber crystallization degree It is desirable that the carbon fiber crystallization degree, so-called graphitization degree, be higher. In general, the higher the degree of graphitization of the carbon material, the more the layered structure is developed, the harder the carbon material is, and the higher the conductivity is. What is necessary is just to process at high temperature in order to graphitize a carbon material. In this case, the treatment temperature varies depending on the carbon fiber used, but is preferably 2000 ° C. or higher, and more preferably 2500 ° C. or higher. In this case, it is effective to add boron, Si, or the like, which is a graphitization cocatalyst that works to promote the degree of graphitization, before the heat treatment. The addition amount of the cocatalyst is not particularly limited, but if the addition amount is too small, the effect is not obtained, and if it is too much, it remains as an impurity, which is not preferable. A preferable addition amount is in the range of 10 ppm to 50,000 ppm by mass.

Although crystallinity of the carbon fibers is not particularly limited, preferably the average spacing d ₀₀₂ is 0.344nm less by X-ray diffraction method, even more preferably less 0.339 nm, C-axis direction of the thickness of the crystal Lc is 40 nm or less.

(1-3) Carbon fiber fiber length and aspect ratio The carbon fiber fiber length is not particularly limited. As described above, the longer the fiber length, the better the conductivity in the electrode, the strength of the electrode, and the electrolyte solution retention, but it is not preferable if the fiber length is too long because the fiber dispersibility in the electrode is impaired. Although the range of a preferable average fiber length changes with kinds and fiber diameter of the carbon fiber to be used, it is 0.5-100 micrometers, and the thing of 1-50 micrometers is more preferable. When the preferable range of this average fiber length is shown by the average aspect ratio (ratio of the fiber length to the fiber diameter), it is in the range of 5 to 50000, and more preferably in the range of 10 to 15000.

  It is preferable that the carbon fiber is branched (branched) because the conductivity of the entire electrode, the strength of the electrode, and the electrolyte solution retention are further increased. However, if there are too many branched fibers, the dispersibility in the electrode is impaired as with the fiber length. The amount of these branched fibers can be controlled to some extent by the production method and the subsequent pulverization treatment.

(1-4) Carbon Fiber Manufacturing Method The carbon fiber manufacturing method used in the present invention is not particularly limited. Examples thereof include a method in which a polymer is formed into a fiber by a spinning method and heat-treated in an inert atmosphere, and a vapor phase growth method in which an organic compound is reacted at a high temperature in the presence of a catalyst. Carbon fiber obtained by vapor phase growth method, so-called vapor phase carbon fiber, crystal growth direction is almost parallel to the fiber axis, the crystallinity in the fiber length direction of the graphite structure tends to be high, relatively short fiber diameter, A highly conductive and high strength carbon fiber is obtained.

  In order to achieve the object of the present invention, vapor grown carbon fibers in which crystals grow in the fiber axis direction and the fibers branch are suitable. The vapor grown carbon fiber can be produced by, for example, a method in which an organic compound gasified with iron serving as a catalyst is blown into a high temperature atmosphere. As the vapor grown carbon fiber, any of the as-manufactured state, the one heat-treated at about 800-1500 ° C., and the one graphitized at about 2000-3000 ° C. can be used. A suitable one is used, but heat treatment and further graphitization are preferable because carbon crystallinity is advanced and high conductivity and high pressure resistance are provided.

  Moreover, there exists a branched fiber as a preferable form of vapor grown carbon fiber. The branched portion has a hollow structure in which the entire fiber including the portion is in communication with each other, and the carbon layer constituting the cylindrical portion of the fiber is continuous. The hollow structure is a structure in which a carbon layer is wound in a cylindrical shape, and includes a structure that is not a complete cylinder, a structure having a partial cut portion, and a structure in which two stacked carbon layers are combined into one layer. Further, the cross section of the cylinder is not limited to a perfect circle, but includes an ellipse or a polygon.

Vapor-grown carbon fibers often have irregularities and disturbances on the fiber surface, and thus have the advantage of improving the adhesion with the electrode active material. In particular, when carbonaceous powder particles are used as the electrode active material and used as the negative electrode of a secondary battery, the adhesion with the carbonaceous material serving as the nucleus is improved, so that the carbonaceous material and the conductive material are electrically conductive even after repeated charge and discharge. The vapor grown carbon fiber, which also serves as a chemical auxiliary, can be kept in close contact with the vapor grown carbon fiber, and the electron conductivity can be maintained and the cycle characteristics can be improved.
When the vapor grown carbon fiber contains a lot of branched fibers, a network can be formed efficiently, and high electronic conductivity and thermal conductivity are easily obtained. In addition, the active material can be dispersed so as to wrap, increasing the strength of the electrode and maintaining good contact between the particles.

(1-5) Addition amount of carbon fiber The carbon fiber content is preferably in the range of 0.05 to 20% by mass in the high-density electrode, preferably 0.1 to 15% by mass, more preferably 0.5 to 0.5% by mass. 10% by mass. When the content exceeds 20% by mass, the ratio of the electrode active material in the high-density electrode becomes small, so that the electric capacity becomes small. When the content is less than 0.05% by mass, the effect of electrolyte permeability on the high-density electrode does not appear. In order to adjust the content to this range, it can be carried out by adding the same ratio in the production method.

(1-6) Surface Treatment of Carbon Fiber Carbon fiber that has been surface treated to control the dispersion state in the electrode can also be used. The surface treatment method is not particularly limited, and examples thereof include those made hydrophilic by introducing an oxygen-containing functional group by oxidation treatment, and those made hydrophobic by fluorination treatment or silicon treatment. In addition, a phenol resin coating or a mechanochemical treatment may be used. If the surface treatment is excessively performed, the conductivity and strength of the carbon fiber are remarkably impaired, and therefore an appropriate treatment is required.
The oxidation treatment can be performed, for example, by heating the carbon fiber in air at 500 ° C. for about 1 hour. This treatment improves the hydrophilicity of the carbon fiber.

2. Electrode and active material used therefor (2-1) Carbon material-based high-density electrode When the active material that is the main material of the high-density electrode of the present invention is a carbon-based material, the negative electrode of a Li-ion battery or a Li-polymer battery It is mainly used as.
As the carbon-based active material, there are a material mainly composed of a non-graphite carbon material and a material mainly composed of a graphite-based carbon material. Here, “mainly” means that the material occupies 50% by mass or more of the whole, preferably 60% by mass or more, more preferably 80% by mass or more, and particularly preferably 90% by mass or more.

Mainly non-graphitic carbon materials include carbon materials obtained by heat-treating non-graphite polymers such as phenol resins, heat-treated conjugated polymers such as conductive polymers, and substrates formed by thermal CVD. Examples include deposited CVD carbon. Moreover, the thing which increased the electrical capacitance as a negative electrode by mixing Si at the time of heat processing of these materials is mentioned.
Of these non-graphitic carbon materials, spherical ones having as high a degree of circularity as possible are preferable because they can suppress side reactions with the electrolytic solution when used when producing electrode sheets and when used in batteries.
A preferable circularity is 0.70 to 0.99 as an average circularity measured by a flow type particle image analyzer.
The average particle diameter of these non-graphitic carbon materials varies depending on the target electrode sheet shape and is not limited, but generally, the average particle diameter by laser diffraction method is used in the range of 1 to 50 μm.
The bulk density of the high-density electrode using these non-graphitic carbon materials varies with the true density of the carbon-based active material and is not particularly limited. In general, the true density of the non-graphitic carbon material is 1.9 g / cm. It is preferably ³ or more, and the electrode bulk density is preferably 1.5 g / cm ³ or more.

Graphite-based materials are becoming mainstream as carbon-based active material materials for Li-ion batteries. Graphite-based active material has the characteristics that the crystallinity develops, the insertion and release of Li ions occur uniformly, and the diffusion is fast, so that the change in the discharge potential of the battery is small and the high load characteristics are excellent. Yes. These have a high true density of about 2.2 g / cm ³ and are already used at an electrode bulk density of 1.5 g / cm ³ . Furthermore, the porosity is reduced and the use of 1.7 g / cm ³ or more is being studied.
This graphite-based active material is also preferably as high as possible in the circularity, the average circularity measured by a flow type particle image analyzer is 0.70 to 0.99, and the average particle diameter by laser diffraction is about 1 to 50 μm. Is used.
The graphite material preferably has as high crystallinity as possible, and the C ₀ of the 002 plane in X-ray diffraction measurement is 0.6900 nm (d ₀₀₂ = 0.3450 nm) or less, and La (crystallite size in the a-axis direction) It is preferably larger than 100 nm and Lc (crystallite size in the c-axis direction) is preferably larger than 100 nm. The laser Raman R value is 0.01 to 0.9 (R value: peak intensity ratio of 1360 cm ^-1 to the peak intensity of 1580 cm ^-1 by laser Raman spectrum) are preferred, true density 2.20 g / cm ³ or more Is preferred.
Since the graphite-based active material has developed crystallinity, it easily causes a side reaction with the electrolytic solution. Accordingly, it is preferable that the specific surface area is not so high. If it is too low, the wettability with the electrolytic solution and the binder deteriorates, which causes a decrease in electrode strength and a decrease in electrolytic solution retention. A preferable specific surface area is 0.2 to ⁵ m ² / g (by the BET method).

  Heat treatment by adding boron to the graphite-based active material is preferable because it improves crystallinity and improves compatibility with the electrolyte and stability. The addition amount of boron is not particularly limited, but if the addition amount is too small, the effect is not obtained, and if it is too much, it remains as an impurity, which is not preferable. A preferable addition amount is 0.1 mass ppm to 100,000 mass ppm, more preferably in the range of 10 mass ppm to 50,000 mass ppm.

(2-2) Li alloy-based high-density electrode An alloy-based active material, for example, a Li alloy such as a LiAl-based alloy, is partially used as a negative electrode material for a coin-type Li secondary battery. Li alloy is also used for electrodes by pressurizing particles with a press or the like, but since an electrochemical reaction with Li ions takes place on the surface, the permeability of the electrolyte into the electrode becomes more important. This is why, although the theoretical value of the Li insertion / release capacity is high, it can only be used for a low-load battery such as a coin type. If electrolyte permeability is improved as a high-density electrode and an electrochemical reaction of Li ions can be performed inside the electrode, it is promising as a next-generation Li secondary battery. By adding carbon fiber to these Li alloy-based high-density electrodes to improve electrolyte solution permeability, a higher-performance Li-based negative electrode can be obtained. Examples of Li alloys include LiAl alloys, LiSn alloys, LiSi alloys, LiIn alloys, LiPb alloys, LiMg alloys, LiAg alloys, and composite alloys of two or more of these. It is not limited.
In the case of these Li alloys, the bulk density of the electrode varies depending on the type and composition ratio of the metal bonded to Li, but is usually about 0.7 g / cm ^{3. In} the present invention, the bulk density is 1.0 g / cm ^3. Even when the above high-density electrode is used, excellent electrolyte permeability is exhibited.

(2-3) Li-nitride Li-based high-density electrode As next-generation Li secondary battery materials, Li-nitride materials such as Li ₃ N and Li ₃ N _x Co _y have been noticed and developed. Similarly, by including carbon fibers in these materials, a high-density electrode having good electrolyte solution permeability can be obtained.
In the case of these nitrided Li-based materials, the bulk density of the electrode is usually about 0.7 g / cm ³ , but in the present invention, excellent electrolysis is possible even when a high-density electrode having a bulk density of 1.0 g / cm ³ or more is used. Shows liquid permeability.

(2-4) Oxide, sulfide-based high-density electrode Cobalt-based oxide such as lithium cobaltate, manganese-based oxide such as lithium manganate, nickel-based oxide such as lithium nickelate, vanadium such as vanadium pentoxide System oxides and composite oxides and mixtures thereof are currently used as positive electrode active material materials for Li ion batteries. Higher capacity as a battery is being studied by making these positive electrodes into high-density electrodes.

Specifically, the lithium cobalt oxide has a true density of about 5.1 g / cm ³ and is currently used at an electrode bulk density of less than 3.3 g / cm ³ , but by adding carbon fiber to this, Even when the electrode bulk density is 3.6 g / cm ³ , it is possible to suppress a decrease in electrolyte permeability. The true density of lithium manganate is about 4.2 g / cm ³ and is currently used at an electrode bulk density of less than 2.9 g / cm ^3. By adding carbon fiber to this, the electrode bulk density of 3 Even at 0.0 g / cm ³ , it is possible to suppress a decrease in electrolyte permeability. The true density of lithium nickelate is about 5.0 g / cm ³ and is currently used at an electrode bulk density of 3.2 g / cm ³ or less. By adding carbon fiber to this, the electrode bulk density is 3 Even at 0.5 g / cm ³ , a decrease in electrolyte permeability can be suppressed. Vanadium pentoxide has a true density of about 2.9 g / cm ³ and is currently used at an electrode bulk density of 2.0 g / cm ³ or less. By adding carbon fiber to this, an electrode bulk density of 2 Even at 0.3 g / cm ³ , a decrease in electrolyte permeability can be suppressed.

Further, in the case of a mixture of a cobalt-based oxide such as lithium cobaltate and a manganese-based oxide such as lithium manganate, it is currently used at an electrode bulk density of 3.1 g / cm ³ or less. By adding fibers, it is possible to suppress a decrease in electrolyte permeability even at an electrode bulk density of 3.4 g / cm ³ .

The lithium-containing transition metal oxide used as the positive electrode active material of the present invention is preferably lithium and at least one transition metal element selected from Ti, V, Cr, Mn, Fe, Co, Ni, Mo, and W. In which the molar ratio of lithium to transition metal is 0.3 to 2.2. More preferably, the oxide mainly contains at least one transition metal element selected from V, Cr, Mn, Fe, Co, and Ni and lithium, and the molar ratio of lithium to the transition metal is 0.3 to 0.3. The compound of 2.2. In addition, Al, Ga, In, Ge, Sn, Pb, Sb, Bi, Si, P, B, or the like may be contained in a range of less than 30 mole percent with respect to the transition metal present mainly. Among the above positive electrode active materials, the general formula Li _x MO ₂ (M is at least one of Co, Ni, Fe and Mn, x = 0 to 1.2), or Li _y N ₂ O ₄ (N is It is preferable to use at least one material having a spinel structure represented by at least Mn and y = 0-2.

Further, the positive electrode active material _{Li y M a D 1-a} O 2 (M is Co, Ni, Fe, at least one of Mn, D is Co, Ni, Fe, Mn, Al, Zn, Cu, Mo, Ag , W, Ga, In, Sn, Pb, Sb, Sr, B, P, at least one type other than M, y = 0 to 1.2, a = 0.5 to 1.), or _{li z (N b E 1-} b) 2 O 4 (N is Mn, E is Co, Ni, Fe, Mn, Al, Zn, Cu, Mo, Ag, W, Ga, in, Sn, Pb, Sb, It is particularly preferable to use at least one material having a spinel structure represented by at least one of Sr, B, and P, b = 1 to 0.2, and z = 0 to 2.

_{Specifically, Li x CoO 2, Li x} NiO 2, Li x MnO 2, Li x Co a Ni 1-a O 2, Li x Co b V 1-b O z, Li x Co b Fe 1-b _{O 2, Li x Mn 2 O} 4, Li x Mn c Co 2-c O 4, Li x Mn c Ni 2-c O 4, Li x Mn c V 2-c O 4, Li x Mn c Fe 2- _c O ₄ (where x = 0.02 to 1.2, a = 0.1 to 0.9, b = 0.8 to 0.98, c = 1.6 to 1.96, z = 2. 01-2.3.). The most preferred lithium-containing transition metal _{oxides, Li x CoO 2, Li x} NiO 2, Li x MnO 2, Li x Co a Ni 1-a O 2, Li x Mn 2 O 4, Li x Co b V 1 _-b O _z (x = 0.02-1.2, a = 0.1-0.9, b = 0.9-0.98, z = 2.01-2.3). In addition, the value of x is a value before the start of charging / discharging, and increases / decreases by charging / discharging.

As other next-generation Li battery positive electrode materials, metal sulfides such as titanium sulfide and molybdenum sulfide have been actively studied and high-density electrodes are being formed. In the present invention, by adding carbon fibers, it is possible to suppress a decrease in electrolyte permeability even at an electrode bulk density of 2.0 g / cm ³ .
An iron olivine compound such as LiFePO ₄ has a high theoretical capacity, uses iron, is excellent in resource, environmental safety, heat resistance, and the like, and has been energetically studied as a next-generation Li ion positive electrode material. Since the true density of LiFePO ₄ is 3.6 g / cm ^3, which is lower than the positive electrode material (such as lithium cobaltate) currently used in lithium ion batteries, the need for higher density is even higher. In the present invention, by adding carbon fiber, it is possible to suppress a decrease in electrolyte permeability even at an electrode bulk density of 2.5 g / cm ³ . In addition, the conductivity is low, and efficient compounding with a carbon fiber-based conductive material is essential.

The average particle size of the positive electrode active material is not particularly limited, but is usually preferably 0.1 to 50 μm, and the volume of particles of 0.5 to 30 μm is preferably 95% or more. More preferably, the volume occupied by a particle group having a particle size of 3 μm or less is 18% or less of the total volume, and the volume occupied by a particle group of 15 μm or more and 25 μm or less is 18% or less of the total volume. Although the specific surface area is not particularly limited, but is preferably 0.01 to 50 m ² / g by the BET method, particularly preferably 0.2m ² / g~10m ² / g.

As a high-capacity next-generation negative electrode active material for a Li-ion battery, a tin oxide-based material such as SnO ₂ , a titanium oxide-based material such as TiO ₂ , and a silicon oxide-based material such as SiO ₂ are being studied. Tin oxide-based materials are partly used for coin-type Li-ion battery negative electrode materials, but when used in large-sized high-load batteries such as cylinders and squares, the reaction does not occur uniformly, and electrolyte penetration by adding carbon fiber Sexual improvement is necessary. In the case of a tin oxide-based material, the normal electrode has a bulk density of about 1.0 g / cm ³ , but in the present invention, an excellent electrolyte solution can be used as a high-density electrode having a bulk density of 1.2 g / cm ³ or more. It shows the permeability. In the case of a silicon oxide-based material, the bulk density of a normal electrode is about 0.8 g / cm ³ , but in the present invention, an excellent electrolyte solution can be used as a high-density electrode having a bulk density of 1.0 g / cm ³ or more. It shows the permeability.

3. Electrode production The method for producing the high-density electrode of the present invention is not particularly limited, but generally, after mixing the electrode active material, carbon fiber and binder material, coating on a supporting substrate such as a metal current collector, and then drying It can be manufactured by pressing.
As a method for mixing each material, (1) a method in which an electrode active material (including a conductive assistant such as carbon black in some cases; the same applies hereinafter), carbon fiber, and a binder material are mixed at a time; A method of mixing the material and the carbon fiber and then mixing the binder material, (3) A method of mixing the electrode active material and the binder and then mixing the carbon fiber, and (4) A method of mixing the carbon fiber and the binder material, Examples include a method of mixing substance materials.

  Since the dispersion state in the electrode differs depending on the material type, composition ratio, combination, etc., and affects the electrode resistance, liquid absorption, etc., it is necessary to select an optimum mixing method depending on the conditions.

What is necessary is just to stir with a mixer etc., for example, the method of mixing an electrode active material and carbon fiber. Although the stirring method is not particularly limited, for example, apparatuses such as a ribbon mixer, a screw type kneader, a spartan luzer, a redige mixer, a planetary mixer, and a universal mixer can be used.
The method of mixing the binder material into the electrode active material, carbon fiber or a mixture thereof is not particularly limited, but the method of kneading with a solvent after mixing in a dry method, or the method of mixing the electrode material with the solvent by diluting the binder material with the solvent Or the method of knead | mixing with these negative electrode materials is mentioned. These solvent-containing mixtures are coated on a current collector (base material) and formed into a sheet. In order to adjust the viscosity of the solvent-containing mixture, thickening such as polymers such as CMC (sodium carboxymethyl cellulose) and polyethylene glycol is further added. Materials may be added.
As the binder material, known materials such as fluorine-based polymers such as polyvinylidene fluoride and polytetrafluoroethylene, and rubber-based materials such as SBR (styrene butadiene rubber) can be used. As the solvent, a known solvent suitable for each binder, for example, a fluorine-based polymer such as toluene, N-methylpyrrolidone, acetone or the like, and an SBR water such as water can be used.

When the negative electrode material is 100 parts by mass, the amount of the binder used is suitably 0.5 to 20 parts by mass, and particularly preferably about 1 to 15 parts by mass.
The kneading method after the addition of the solvent is not particularly limited. For example, a known apparatus such as a ribbon mixer, a screw type kneader, a spartan luzer, a redige mixer, a planetary mixer, a universal mixer can be used.

The high-density electrode sheet of the present invention can be produced by applying the kneaded mixture to a current collector.
Application to the current collector after kneading can be carried out by a known method, for example, a method of forming by a roll press after applying with a doctor blade or a bar coater.
As the current collector, known materials such as copper, aluminum, stainless steel, nickel and alloys thereof, and carbon sheets can be used.

These coated electrode sheets are dried by a known method, and then formed into a desired thickness and density while adjusting the porosity to 25% or less by a known method such as a roll press or a pressure press.
The pressing pressure may be determined within a range in which the porosity can be adjusted to 25% or less, and cannot be generally specified depending on the electrode active material used, but is usually 1 ton / cm ² or more. The thickness of the electrode sheet varies depending on the shape of the target battery and is not particularly limited, but is usually molded to 0.5 to 2000 μm, preferably 5 to 1000 μm.

4). Battery Production The battery of the present invention uses the above-described high-density electrode for the positive electrode and / or the negative electrode, and can be produced by a known method.
In particular, the above-described high-density electrode can be preferably used as an electrode of a high energy density non-aqueous secondary battery such as a Li ion battery or a Li polymer battery. A typical method for producing a Li ion battery and / or a Li polymer battery will be described below, but is not limited thereto.

The high density electrode sheet produced above is processed into a desired shape and laminated on the positive electrode sheet / separator / negative electrode sheet so that the positive electrode and the negative electrode are not touched, and containers of coin type, square type, cylindrical type, sheet type, etc. Store inside. If there is a possibility that moisture or oxygen has been adsorbed during stacking and storage, it is dried again in an inert atmosphere under reduced pressure and / or a low dew point (-50 ° C. or lower), and then transferred to an inert atmosphere with a low dew point. Next, at least one of an electrolytic solution and / or a solid polymer electrolyte and / or a polymerizable composition is injected, and when the polymerizable composition is injected, the container is sealed after further impregnation with the electrolytic solution. Thus, a Li ion battery or a Li polymer battery can be produced.
The electrode according to the present invention may be impregnated with a thermoplastic polymer as a polymer solid electrolyte, and a battery may be produced by injecting an electrolytic solution before sealing the battery container. In that case, after adding and impregnating the plasticizer to the thermoplastic resin, all or part of the plasticizer may be removed by drying or the like, or the solvent may be replaced with another solvent.

  A known separator can be used, but from the viewpoint of being thin and having high strength, a polyethylene or polypropylene porous microporous film is preferable. The porosity is preferably higher from the viewpoint of ionic conduction, but if it is too high, it will cause a decrease in strength and a short circuit between the positive electrode and the negative electrode, so it is usually used at 30 to 90%, preferably 50 to 80%. is there. The thickness is preferably thin from the viewpoints of ionic conduction and battery capacity, but if it is too thin, it causes a decrease in strength and a short circuit between the positive electrode and the negative electrode, and therefore it is usually 5-100 μm, preferably 5-50 μm. These microporous films can be used in combination of two or more kinds or other separators such as a nonwoven fabric.

  As the electrolyte and electrolyte in a non-aqueous secondary battery, particularly a lithium ion battery and / or a Li polymer battery, known organic electrolytes, inorganic solid electrolytes, and polymer solid electrolytes can be used.

  Non-aqueous solvents used in organic electrolytes (non-aqueous electrolytes) include diethyl ether, dibutyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, diethylene glycol Ethers such as dimethyl ether and ethylene glycol diphenyl ether; formamide, N-methylformamide, N, N-dimethylformamide, N-ethylformamide, N, N-diethylformamide, N-methylacetamide, N, N-dimethylacetamide, N-ethyl Acetamide, N, N-diethylacetamide, N, N-dimethylpropionamide Amides such as hexamethylphosphorylamide; sulfur-containing compounds such as dimethyl sulfoxide and sulfolane; dialkyl ketones such as methyl ethyl ketone and methyl isobutyl ketone; ethylene oxide, propylene oxide, tetrahydrofuran, 2-methoxytetrahydrofuran, 1,2-dimethoxyethane, 1,3 -Cyclic ethers such as dioxolane; carbonates such as ethylene carbonate, butylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, propylene carbonate, vinylene carbonate; γ-butyrolactone; N-methylpyrrolidone; organic solvents such as acetonitrile and nitromethane are preferred. . Furthermore, preferably ethylene carbonate, butylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, propylene carbonate, vinylene carbonate, esters such as γ-butyrolactone, ethers such as dioxolane, diethyl ether, diethoxyethane, dimethyl sulfoxide, Acetonitrile, tetrahydrofuran, etc. are mentioned, Especially preferably, carbonate type nonaqueous solvents, such as ethylene carbonate and propylene carbonate, can be used. These solvents can be used alone or in admixture of two or more.

Lithium salts are used as solutes (electrolytes) for these solvents. Commonly known lithium salts include LiClO ₄ , LiBF ₄ , LiPF ₆ , LiAlCl ₄ , LiSbF ₆ , LiSCN, LiCl, LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiN (CF ₃ SO ₂ ) _{2 and the} like. is there.

The polymer solid electrolyte, polymer and comprising a polyalkylene oxide derivatives and the derivatives such as polyethylene oxide or polypropylene oxide, polyvinylidene fluoride, polyhexafluoropropylene, polycarbonate, phosphate ester polymers, polyalkyl imines, poly Examples include acrylonitrile, poly (meth) acrylic acid esters, polyphosphazenes, polyurethanes, polyamides, polyesters, polysiloxane derivatives, and polymers containing the derivatives.

  Among the above polymer compounds, those containing oxyalkylene such as polyalkylene oxide, polyurethane, and polycarbonate, urethane, and carbonate structures in the molecule have good compatibility with various polar solvents and good electrochemical stability. preferable. From the viewpoint of stability, those having a fluorocarbon group such as polyvinylidene fluoride or polyhexafluoropropylene in the molecule are also preferred. These oxyalkylene, urethane, carbonate, and fluorocarbon groups may be contained in the same polymer. The repeating number of these groups should just be the range of 1-1000 respectively, and the range of 5-100 is preferable.

  In particular, a crosslinked polymer is suitable for the solid polymer electrolyte of the present invention because it retains viscoelastic properties and electrode adhesion and is excellent in strength properties. The term “crosslinking” as used herein includes not only a crosslinked chain formed by a covalent bond, but also a structure in which a side chain is crosslinked by an ionic bond, a hydrogen bond, or the like, or a structure physically crosslinked through various additives. It is out.

［式中、Ｒ¹及びＲ³は水素またはアルキル基を表わし、Ｒ²及びＲ⁵はオキシアルキレン、フルオロカーボン、オキシフルオロカーボン及び／またはカーボネート基を含む２価の基を表わし、Ｒ⁴は炭素数１０以下の２価の基を表わす。Ｒ²、Ｒ⁴及びＲ⁵はヘテロ原子を含んでいてもよく、直鎖状、分岐状または環状のいずれの構造を有するものでもよい。ｘは０または１〜１０の整数を示す。但し、同一分子中に複数個の上記一般式（１）または（２）で表される重合性官能基が含まれる場合、それぞれの重合性官能基中のＲ¹、Ｒ²、Ｒ³、Ｒ⁴、Ｒ⁵及びｘは、同一でもよいし異なってもよい。］で示されるユニットをもつ化合物を一種類以上含むものを挙げることができる。このような高分子固体電解質は、特開平１１−１４９８２４号公報、特開平１１−１４７９８９号公報等に記載されている。 As an example of the polymer solid electrolyte, the general formula (1) and / or the general formula (2) is used as a constituent element thereof.

[Wherein R ¹ and R ³ represent hydrogen or an alkyl group, R ² and R ⁵ represent a divalent group containing an oxyalkylene, fluorocarbon, oxyfluorocarbon and / or carbonate group, and R ⁴ represents a carbon number of 10 The following divalent groups are represented. R ² , R ⁴ and R ⁵ may contain a hetero atom, and may have any of a linear, branched or cyclic structure. x represents 0 or an integer of 1 to 10. However, when a plurality of polymerizable functional groups represented by the above general formula (1) or (2) are contained in the same molecule, R ¹ , R ² , R ³ , R in each polymerizable functional group ⁴ , R ⁵ and x may be the same or different. And those containing one or more compounds having a unit represented by the formula: Such polymer solid electrolytes are described in JP-A-11-149824, JP-A-11-147989, and the like.

  As the organic solvent and solute used in the polymer solid electrolyte, the organic electrolyte can be used. Among these, ethers and carbonates are preferable, and carbonates are particularly preferable.

As the amount of the organic electrolyte added to the polymer solid electrolyte increases, the ionic conductivity of the polymer solid electrolyte improves, and the impregnation rate into the electrode also improves as the viscosity decreases, but the amount added is too large. And the mechanical strength of the polymer solid electrolyte is lowered. The addition amount of the organic electrolyte is particularly preferably 2 to 30 times and 3 to 15 times the mass of the polymer used in the polymer solid electrolyte.
There are no restrictions on the selection of members necessary for battery configuration other than those described above.

Since the electrode of the present invention has a high filling amount of the electrode active material and a high density, the battery can have a high energy density, that is, a battery with a large capacity per electrode volume.
When the electrode is highly filled or densified, the number of vacancies in the electrode decreases, leading to a shortage of the electrolyte solution that is important for the electrode reaction existing in the vacancies, or the penetration of the electrolyte solution into the electrode. As a result, the electrode reaction is delayed, the energy density is lowered, the high-speed charge / discharge performance is lowered, the battery production time is increased, and the production cost is increased. Includes carbon fiber, so that a decrease in the permeability of the electrolytic solution is suppressed and the retention of the electrolytic solution is improved to solve the above problems.

The present invention will be described in more detail below with typical examples. Note that these are merely illustrative examples, and the present invention is not limited thereto.
The physical properties used in the following examples were measured by the following methods.

[1] Average circularity:
The average circularity of the carbon material was measured as follows using a flow particle image analyzer FPIA-2100 (manufactured by Sysmex Corporation).
The sample for measurement was purified by removing fine dust through a 106 μm filter. A sample dispersion for measurement was prepared by adding 0.1 g of the sample into 20 ml of ion-exchanged water and uniformly dispersing 0.1 to 0.5% by mass of an anionic / nonionic surfactant. Dispersion was performed by treating for 5 minutes using an ultrasonic cleaner UT-105S (manufactured by Sharp Manufacturing System).

The outline of the measurement principle and the like is described in “Powder and Industry”, VOL. 32, No. 2, 2000, Japanese Patent Laid-Open No. 8-136439, and the like.
When the dispersion liquid of the measurement sample passes through the flow path of a flat and transparent flow cell (thickness: about 200 μm), strobe light is irradiated at 1/30 second intervals and imaged with a CCD camera. A certain number of the still images were taken and analyzed, and calculated according to the following formula.

  The equivalent circle diameter is the diameter of a true circle having the same projected area as the circumference of the actually imaged particle, and the circumference of the circle obtained from this equivalent circle diameter is divided by the circumference of the actually imaged particle. Value. For example, the value is 1 for a perfect circle, and the value becomes smaller as the shape becomes more complicated. The average circularity is an average value of circularity of each measured particle.

[2] Average particle size:
It measured using the laser diffraction scattering type particle size distribution measuring apparatus Microtrac HRA (made by Nikkiso Co., Ltd.).

[3] Specific surface area:
Using a specific surface area measuring device NOVA-1200 (manufactured by Yuasa Ionics Co., Ltd.), the measurement was performed by the BET method, which is a general method for measuring the specific surface area.

[4] Battery evaluation method:
(1) Electrode kneading paste Electrode active material, acetylene black (abbreviated as AB) manufactured by Denki Kagaku Kogyo Co., Ltd., and carbon fiber are dried at a predetermined composition ratio with a bladed high-speed small mixer (IK mixer). The electrode material mixture was prepared by mixing at 10000 rpm for 30 seconds x 2 times. A KF polymer L1320 (N-methylpyrrolidone (NMP) solution containing 12% by mass of polyvinylidene fluoride (PVDF)) was added to this so that the mass ratio of the electrode material mixture and PVDF was 96: 4. The mixture was kneaded with a planetary mixer to obtain an electrode kneaded paste.

(2) Electrode preparation After adding NMP to the electrode kneaded paste and adjusting the viscosity, rolled foil made by Nippon Foil Co., Ltd. (thickness 18 μm) for the negative electrode, rolled Al produced by Showa Denko KK for the positive electrode Each foil (thickness 25 μm) was applied to a predetermined thickness using a doctor blade. This was vacuum-dried at 120 ° C. for 1 hour and punched out to 18 mmΦ. Further, the punched electrode is sandwiched between super steel press plates, and the press pressure is about 1 × 10 ^{2 to} 3 × 10 ² N / mm ² (1 × 10 ^{3 to} 3 × 10 ³ kg / cm ² ) with respect to the electrode. To a desired electrode density with a thickness of about 100 μm. Then, it dried at 120 degreeC for 12 hours with the vacuum dryer, and was set as the electrode for evaluation.

(3) Evaluation of penetration rate of electrolyte solution and polymer solid electrolyte composition In the atmosphere at 25 ° C, on the electrode (18mmΦ) prepared in (2) above, in the atmosphere at 25 ° C, almost the same as various electrolyte solutions Using a low volatility propylene carbonate (PC) having a viscosity of 3 μl, 3 μl of the PC was dropped into the center of the electrode using a microsyringe, and the time for the PC to permeate into the electrode was measured. The measurement was performed three times, and the average value was used as the evaluation value.

The evaluation of the penetration rate of the polymer solid electrolyte composition was performed by replacing the PC with a mixed solution of the compound for polymer solid electrolyte containing PC.
As the polymerizable compound used in the polymer solid electrolyte composition, the following was obtained with reference to JP-A-11-149824.

化合物ａ（１質量部）及びＰＣ（１２質量部）の混合溶液を組成物ａ−１として得た。同様に、化合物ｂ（１質量部）及びＰＣ（１２質量部）の混合溶液を組成物ｂ−１として得た。

A mixed solution of compound a (1 part by mass) and PC (12 parts by mass) was obtained as composition a-1. Similarly, a mixed solution of compound b (1 part by mass) and PC (12 parts by mass) was obtained as composition b-1.

(4) Production of Li-ion and Li-ion polymer battery test cell A triode cell was produced as follows. The following operation was carried out in a dry argon atmosphere with a dew point of -80 ° C or lower.
In a polypropylene cell with a screw-in lid (inner diameter of about 18 mm), a negative electrode with copper foil prepared in (2) above and a positive electrode with an Al foil separator (polypropylene microporous film (Cell Guard 2400), 25 μm) ) And sandwiched. Further, a reference metal lithium foil (50 μm) was laminated in the same manner. An electrolytic solution was added thereto to obtain a test cell.
For the Li ion polymer battery, the same operation as the above Li ion battery test cell was performed in a dry argon atmosphere with a dew point of −80 ° C. or lower.
In a polypropylene cell with a screw-in lid (inner diameter of about 18 mm), a negative electrode with copper foil prepared in (2) above and a positive electrode with an Al foil separator (polypropylene microporous film (Cell Guard 2400), 25 μm) ) And sandwiched. Further, a reference metal lithium foil (50 μm) was laminated in the same manner. A polymer solid electrolyte composition was added thereto, and a heat treatment was performed at 60 ° C. for 1 hour to obtain a test cell.

(5) Electrolyte and composition for polymer solid electrolyte The electrolyte is a mixture of 8 parts by mass of EC (ethylene carbonate) and 12 parts by mass of DEC (diethyl carbonate), and 1 mol / liter of LiPF ₆ is dissolved as an electrolyte. I got it.
The polymerizable composition for a polymer solid electrolyte is used as an electrolyte with respect to a mixed solution of 1 part by mass of the compound a shown in (3) above, 4 parts by mass of EC (ethylene carbonate) and 6 parts by mass of DEC (diethyl carbonate). After dissolving 1 mol / liter of LiPF ₆ , 0.01 part by mass of bis (4-tert-butylcyclohexyl) peroxydicarbonate was added as a polymerization initiator to obtain a composition a-2.
For compound B having a different molecular weight, the same composition ratio as that of compound a was obtained to obtain composition b-2.

(6) Charge / Discharge Cycle Test A constant current / constant voltage charge / discharge test was conducted at a current density of 0.6 mA / cm ² (equivalent to 0.3 C).
Charging was performed by CC (constant current) at 0.6 mA / cm ² from the rest potential to 4.2 V. Next, it switched to CV (constant volt: constant voltage) charge at 4.2 V, and stopped when the current value dropped to 25.4 μA.
As the discharge, CC discharge was performed at 0.6 mA / cm ² (equivalent to 0.3 C), and cut off at a voltage of 2.7 V.

電極嵩密度は、電極の寸法及び質量より算出した。電極の真密度は、電極活物質、炭素繊維、導電助剤（ＡＢ）、バインダーそれぞれの材料の真密度を比重計で測定し、混合比率で比例計算することにより算出した。 [5] Porosity of electrode:
The porosity of the electrode was calculated based on the following formula.

The electrode bulk density was calculated from the dimensions and mass of the electrode. The true density of the electrode was calculated by measuring the true density of each material of the electrode active material, carbon fiber, conductive additive (AB), and binder with a hydrometer and proportionally calculating the mixture ratio.

Example 1: Electrolyte permeability evaluation of various electrodes Using the following negative electrode active material, positive electrode active material, and carbon fiber, an electrode was prepared by the above methods (1) to (2), and the above (3) PC penetration rate was measured by the method. The composition, density and results of the electrodes are shown in Table 1.

<Negative electrode active material>
MCMB: Osaka Gas Chemical's mesophase spherical graphite particles,
Average particle size: 16.6 μm,
Average circularity: 0.94
X-ray C ₀ : 0.6729 nm, Lc: 84.4 nm,
Raman R value: 0.12,
Specific surface area: 2 m ² / g,
True density: 2.19 g / cm ³ .
SCMG: Spherical graphite particles made by Showa Denko,
Average particle size: 24.5 μm,
Average circularity: 0.934,
X-ray C ₀ : 0.6716 nm, Lc: 459.0 nm,
Raman R value: 0.05,
Specific surface area: 1.1 m ² / g,
True density: 2.17 g / cm ³ .

<Positive electrode active material>
LiCoO ₂ : manufactured by Nippon Chemical Co., Ltd., average particle diameter: 28.9 μm, average circularity: 0.96.
Li ₂ Mn ₂ O ₄ : made by Mitsui Metals, average particle size: 17.4 μm, average circularity: 0.94.

<Carbon fiber>
VGCF: Vapor growth graphite fiber,
Average fiber diameter (from SEM image analysis): 150 nm,
Average fiber length (from SEM image analysis): 8 μm,
Average aspect ratio: 60,
Branching degree (calculated from the SEM image analysis, the number of branches per 1 μm fiber length; the same applies hereinafter): 0.1 / μm,
X-ray _{C 0: 0.6767nm, Lc: 48.0nm} .
VGCF-A: Vapor growth carbon fiber (VGCF non-graphitized, fired at 1200 ° C.),
Average fiber diameter (from SEM image analysis): 150 nm,
Average fiber length (from SEM image analysis): 8 μm,
Average aspect ratio: 70,
Branching degree: 0.1 / μm,
X-ray _{C 0: 0.6992nm, Lc: 3.0nm} .
VGCF-B: Vapor growth graphite fiber (1% boron added during VGCF graphitization),
Average fiber diameter (from SEM image analysis): 150 nm,
Average fiber length (from SEM image analysis): 8 μm,
Average aspect ratio: 55,
Branching degree: 0.1 / μm,
X-ray _{C 0: 0.6757nm, Lc: 72.0nm} .
VGCF-H: Vapor growth graphite fiber (VGCF jet mill pulverization),
Average fiber diameter (from SEM image analysis): 150 nm,
Average fiber length (from SEM image analysis): 5 μm,
Average aspect ratio: 37,
Branching degree: 0.1 / μm,
X-ray _{C 0: 0.6769nm, Lc: 47.0nm} .
VGNF: Vapor growth graphite fiber,
Average fiber diameter (from SEM image analysis): 80 nm,
Average fiber length (from SEM image analysis): 6 μm,
Average aspect ratio: 73
Branching degree: 0.1 / μm,
X-ray _{C 0: 0.6801nm, Lc: 35.0nm} .
VGNT: Vapor growth graphite fiber,
Average fiber diameter (from SEM image analysis): 20 nm
Average fiber length (from SEM image analysis): 6 μm,
Average aspect ratio: 90,
Branching degree: 0.1 / μm,
X-ray _{C 0: 0.6898nm, Lc: 30.0nm} .

As is apparent from Table 1, by adding carbon fiber, the electrolyte penetration rate of various negative electrode materials and positive electrode materials is significantly shortened as compared with the carbon fiber-free product. This improvement in permeability is noticeable in higher density electrode materials. Specifically, when comparing the degree of shortening of the penetration time based on the carbon fiber-free product, when MCMB is used as the active material, the penetration time is reduced by only 53 to 80% at a density of 1.6 g / cm ^3. Although not done, the density is reduced to 20 to 49% at a density of 1.8 g / cm ³ . It can be seen that the electrolyte solution permeability of the electrode material having a higher density is improved in all cases where other active material is used.

Example 2: Evaluation of composition permeability for polymer solid electrolyte of various electrodes In the same manner as in Example 1, the penetration rate of the composition for polymer solid electrolyte was measured. The results are shown in Table 2 together with reference data for comparison.

  As is apparent from Table 2, in the case of an electrode not containing carbon fiber, the permeation rate of the polymer solid electrolyte composition is significantly slower than that of the electrolytic solution (reference), but in the case of an electrode containing carbon fiber. Increases the permeation rate of the composition for polymer solid electrolysis, and the permeation rate also increases in the case of the positive electrode.

Example 3: Charging / discharging cycle characteristics of Li-ion battery test cell The positive and negative electrodes prepared in the same manner as in Example 1 were used in combinations shown in Table 3, and the cycle characteristics were evaluated according to the battery evaluation method described above. The results are also shown in Table 3.

  As is apparent from Table 3, increasing the electrode density increases the capacity per volume of the electrode (volumetric capacity density) and decreases the cycle characteristics, but the rate of decrease in the cycle characteristics is obtained by using an electrode not added with carbon fiber. In the example, it is 20% or less, but in the example using the electrode of the present invention to which carbon fiber is added, it is within 10%.

Example 4: Charging / discharging cycle characteristics of Li-ion polymer battery test cell The positive electrode and negative electrode prepared in the same manner as in Example 3 were combined with the polymer solid electrolyte composition shown in Table 4, and the cycle characteristics were determined according to the battery evaluation method described above. Evaluation was performed. The results are shown in Table 4.

Claims (39)

  A high density electrode comprising a high density electrode containing an electrode active material and carbon fibers having a fiber diameter of 1 to 1000 nm and a porosity of 25% or less, impregnated with a polymer solid electrolyte.   The high-density electrode according to claim 1, wherein the carbon fiber is a graphite-based carbon fiber heat-treated at 2000 ° C. or higher.   The high-density electrode according to claim 1 or 2, wherein the carbon fiber is a graphite-based carbon fiber having an oxygen-containing functional group introduced on the surface by oxidation treatment.   The high-density electrode according to any one of claims 1 to 3, wherein the carbon fiber is a graphite-based carbon fiber containing 0.1 to 100,000 ppm of boron.   The high-density electrode according to any one of claims 1 to 4, wherein the amount of carbon fiber in the electrode is 0.05 to 20% by mass.   The high-density electrode according to any one of claims 1 to 5, wherein an average aspect ratio of the carbon fiber is 5 to 50000. I mean spacing d ₀₀₂ of the graphite carbon fibers by X-ray diffraction (002) plane, dense electrode according to claim 2 or less 0.344 nm.   The high-density electrode according to any one of claims 1 to 7, wherein the carbon fiber has a hollow structure therein.   The high-density electrode according to any one of claims 1 to 8, wherein the carbon fiber includes a branched carbon fiber.   The high-density electrode according to claim 1, wherein the electrode active material is a carbon-based material.   The high-density electrode according to claim 10, wherein the carbon-based material contains Si. The high-density electrode according to claim 10 or 11, wherein the carbon-based material is a non-graphite-based carbon material, and the electrode bulk density is 1.5 g / cm ³ or more. The high-density electrode according to any one of claims 10 to 12, wherein the carbon-based material of the electrode active material before forming the electrode is a carbonaceous particle that satisfies the following requirements:
(1) The average circularity measured by a flow type particle image analyzer is 0.70 to 0.99,
(2) The average particle diameter by laser diffraction method is 1-50 μm. The high-density electrode according to claim 10, 11 or 13, wherein the carbon-based material contains a graphite-based material of 50% by mass or more and an electrode bulk density is 1.7 g / cm ³ or more.   The high-density electrode according to claim 14, wherein the graphite material contains boron. The high-density electrode according to claim 14 or 15, wherein the carbon-based material of the electrode active material before forming the electrode is a carbon particle containing 50% by mass or more of graphite particles satisfying the following requirements:
(1) The average circularity measured by a flow type particle image analyzer is 0.70 to 0.99,
(2) The average particle diameter by laser diffraction method is 1-50 μm. The high-density electrode according to any one of claims 14 to 16, wherein the graphite-based material is carbon particles containing 50% by mass or more of graphite particles satisfying the following requirements:
(1) C ₀ of (002) plane in X-ray diffraction measurement is 0.6900 nm, La (crystallite size in the a-axis direction)> 100 nm, Lc (crystallite size in the c-axis direction)> 100 nm,
(2) BET specific surface area of 0.2 to ⁵ m ² / g,
(3) True density is 2.20 g / cm ³ or more,
(4) Laser Raman R value (peak intensity ratio of 1360 cm ^-1 to the peak intensity of 1580 cm ^-1 by laser Raman spectrum) 0.01 to 0.9.   The high-density electrode according to any one of claims 1 to 9, wherein the electrode active material is a Li alloy.   The high-density electrode according to any one of claims 1 to 9, wherein the electrode active material is a lithium nitride material.   The high-density electrode according to claim 1, wherein the electrode active material is a silicon oxide-based material.   The high-density electrode according to any one of claims 1 to 9, wherein the electrode active material is a metal oxide material.   The high-density electrode according to claim 21, wherein the metal oxide-based material contains tin oxide-based material in an amount of 60% by mass or more. Cobalt oxide contains more than 60 mass% in the metal oxide-based material, high-density electrode according to claim 21 electrode bulk density of 3.6 g / cm ³ or more. Manganese oxide to the metal oxide-based material is contained more than 60 wt%, high-density electrode according to claim 21 electrode bulk density of 3.0 g / cm ³ or more. The high-density electrode according to claim 21, wherein the metal oxide-based material contains a mixture of a cobalt-based oxide and a manganese-based oxide in an amount of 80% by mass or more, and an electrode bulk density is 3.4 g / cm ³ or more. Nickel oxide contains more than 60 mass% in the metal oxide-based material, high-density electrode according to claim 21 electrode bulk density of 3.4 g / cm ³ or more. The high-density electrode according to claim 21, wherein the metal oxide-based material contains 60% by mass or more of vanadium-based oxide and has an electrode bulk density of 2.3 g / cm ³ or more.   The high-density electrode according to claim 1, wherein the electrode active material is a metal sulfide-based material.   The high-density electrode according to any one of claims 1 to 9, wherein the electrode active material is an iron olivine compound.   30. The high-density electrode according to any one of claims 1 to 29, comprising 0.2 to 20% by mass of carbon fiber having a fiber diameter of 1 to 1000 nm and having high electrolyte solution permeability.   The high-density electrode according to claim 30, which can absorb 3 µl of propylene carbonate at 25 ° C and 1 atm within 500 seconds. General formula (1) and / or general formula (2) as a component of the solid polymer electrolyte

[Wherein R ¹ and R ³ represent hydrogen or an alkyl group, R ² and R ⁵ represent a divalent group containing an oxyalkylene, fluorocarbon, oxyfluorocarbon and / or carbonate group, and R ⁴ represents a carbon number of 10 The following divalent groups are represented. R ² , R ⁴ and R ⁵ may contain a hetero atom, and may have any of a linear, branched or cyclic structure. x represents 0 or an integer of 1 to 10. However, when a plurality of polymerizable functional groups represented by the above general formula (1) or (2) are contained in the same molecule, R ¹ , R ² , R ³ , R in each polymerizable functional group ⁴ , R ⁵ and x may be the same or different. The high-density electrode according to any one of claims 1 to 31, comprising at least one compound having a unit represented by   The non-aqueous solvent used for the polymer solid electrolyte includes at least one selected from the group consisting of ethylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate. A high-density electrode according to any one of the above.   A battery comprising the high-density electrode according to claim 1 as a constituent element.   The secondary battery containing the high-density electrode in any one of Claims 1-33 as a component.   A lithium battery electrode, wherein a polymer solid electrolyte is impregnated into an electrode containing 0.2 to 20% by mass of carbon fiber having a fiber diameter of 1 to 1000 nm.   37. The electrode for a lithium battery according to claim 36, which can absorb 3 μl of propylene carbonate at 25 ° C. and 1 atm within 500 seconds. General formula (1) and / or general formula (2) as a component of the solid polymer electrolyte

[Wherein R ¹ and R ³ represent hydrogen or an alkyl group, R ² and R ⁵ represent a divalent group containing an oxyalkylene, fluorocarbon, oxyfluorocarbon and / or carbonate group, and R ⁴ represents a carbon number of 10 The following divalent groups are represented. R ² , R ⁴ and R ⁵ may contain a hetero atom, and may have any of a linear, branched or cyclic structure. x represents 0 or an integer of 1 to 10. However, when a plurality of polymerizable functional groups represented by the above general formula (1) or (2) are contained in the same molecule, R ¹ , R ² , R ³ , R in each polymerizable functional group ⁴ , R ⁵ and x may be the same or different. The electrode for lithium batteries of Claim 36 or 37 containing one or more types of compounds which have a unit shown by this. The non-aqueous solvent used for the polymer solid electrolyte includes at least one selected from the group consisting of ethylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate. An electrode for a lithium battery according to any one of the above.