JP5295664B2 - Nonaqueous electrolyte battery electrode and nonaqueous electrolyte battery - Google Patents

Abstract

An electrode for a non-aqueous electrolyte battery for reducing internal resistance includes a current collector formed of aluminum foil or aluminum alloy foil, and an active material-containing layer formed on a surface of the current collector and containing an active material, a conductive agent and a binder. The conductive agent comprises a carbon particle group containing first carbon particles each exhibiting an aspect ratio of more than one. A portion of each of the first carbon particles is embedded into the current collector to the depth corresponding to 20 to 50% of the thickness of the current collector. A major axis of each of the first carbon particles has a length of 1.05 to 1.50 times as large as the thickness of the active material-containing layer.

Description

  The present invention relates to a nonaqueous electrolyte battery electrode and a nonaqueous electrolyte battery.

  In a high-power nonaqueous electrolyte battery intended to flow a large current, it is necessary to reduce the internal resistance of an electrode composed of a current collector and an active material containing layer. For example, Patent Document 1 discloses an electrode having a structure in which the maximum distance between the current collector and the active material-containing layer is shortened by arranging a plurality of current collectors in the active material-containing layer. Although this electrode can be expected to reduce the diffusion resistance in the active material-containing layer, it is difficult to reduce the interface resistance between the active material-containing layer and the current collector, which is another factor of the electrode internal resistance. This interfacial resistance is remarkable when a metal that forms a strong oxide film on the surface such as aluminum is used for the current collector.

  Patent Document 2 discloses an electrode in which a conductive layer having a low electrical resistance is disposed between a current collector and an active material-containing layer. Although this electrode can be expected to reduce the above-mentioned interface resistance, the effect of reducing the above-mentioned diffusion resistance cannot be obtained.

Furthermore, since the electrodes described in Patent Documents 1 and 2 both newly include a member that does not contribute to power generation in the active material-containing layer, the energy density with respect to the volume of the nonaqueous electrolyte battery including this electrode is reduced. .
JP 2006-286427 A JP 2000-277393 A

  The present invention provides a nonaqueous electrolyte battery electrode with reduced internal resistance, and a nonaqueous electrolyte battery that includes this electrode and has excellent output characteristics.

According to the first aspect of the present invention, a current collector made of an aluminum foil or an aluminum alloy foil, and an active material-containing layer formed on the current collector surface and containing an active material, a conductive agent, and a binder,
The conductive agent is composed of 30 to 60% by weight of carbon particles including the first carbon particles and 40 to 70% by weight of fine carbon powder compared to the first carbon particles,
The first carbon particles have an aspect ratio exceeding 1, and a part of the first carbon particles is buried in the current collector at a depth of 20 to 50% with respect to the thickness of the current collector, and the first carbon particles Provides a nonaqueous electrolyte battery electrode characterized in that the major axis has a length of 1.05 to 1.50 times the thickness of the active material-containing layer.

  According to a second aspect of the present invention, there is provided a nonaqueous electrolyte battery comprising the nonaqueous electrolyte battery electrode as at least one of a positive electrode and a negative electrode.

  ADVANTAGE OF THE INVENTION According to this invention, the electrode for nonaqueous electrolyte batteries with reduced internal resistance can be provided.

  According to the present invention, a nonaqueous electrolyte battery excellent in output characteristics can be provided by providing the electrode.

  Hereinafter, a nonaqueous electrolyte battery electrode and a nonaqueous electrolyte battery according to embodiments of the present invention will be described in detail.

  An electrode for a non-aqueous electrolyte battery according to an embodiment includes a current collector made of an aluminum foil or an aluminum alloy foil, and an active material formed on one or both sides of the current collector and including an active material, a conductive agent, and a binder A content layer. The conductive agent contains a carbon particle group including first carbon particles having an aspect ratio exceeding 1. A part of the first carbon particles is embedded in the current collector at a depth of 20 to 50% with respect to the thickness of the current collector. The length is 1.05-1.50 times the thickness. For example, during the press for forming the active material-containing layer on the current collector, the first carbon particles are partly applied to the current collector by applying a force that partially penetrates the current collector. It can be buried.

  Here, the thickness of the active material-containing layer means the thickness of the active material-containing layer on one side of the current collector.

  The embedded depth of a part of the first carbon particles in the current collector can be confirmed by an electron microscope. That is, it was confirmed by whether or not carbon particles partially embedded at a depth of 20 to 50% with respect to the current collector thickness exist in the electron microscope field of the electrode cross section selected at random.

  Part of the first carbon particles embedded in the current collector preferably includes one of opposing ends (both ends) extending in the long axis direction. In this case, the first carbon particles are erected with respect to the current collector. Such a state is preferable because the energy density per unit volume is increased.

  Here, the major axis of the first carbon particles can be determined as follows. That is, when an electrode cross section is observed with an electron microscope, a circle having a minimum diameter (referred to as a minimum circumscribed circle) is drawn among circles enclosing the first carbon particles (that is, a circumscribed circle). When the minimum circumscribed circle and the contact point where the contour lines of the carbon particles intersect are connected, the longest segment is defined as the longest segment.

  This will be described with reference to FIG. A circle C is a minimum circumscribed circle of the scaly first carbon particles 101. The circle C is in contact with the contour line of the first carbon particle 101 at points P1 to P3. When the lengths of straight lines connecting points P1 and P2, points P2 and P3, and points P3 and P1 are L12, L23, and L31, respectively, the longest of these line segments is L12. is there. Therefore, the long axis of the carbon particle 101 shown in FIG. 5 is the line segment L12.

  The aspect ratio can be determined as follows. That is, after the major axis is determined by the above-described method, the line segment having the maximum length among the segment segments in which the straight line perpendicular to the major axis is divided by the contour line of the first carbon particles is defined as the minor axis. .

  Thus, when the short axis and the long axis are determined, the aspect ratio can be obtained by the following equation.

Aspect ratio = (major axis) / (minor axis)
In FIG. 5, the major axis is L12 and the minor axis is L4. Therefore, the aspect ratio can be obtained as L12 / L4.

  It is preferable that the aspect ratio exceeds 1 (for example, 1.5 or more). When the aspect ratio is about 1, the first carbon particles are almost spherical. In such a case, the energy density per unit volume is extremely low. For this reason, the aspect ratio is required to exceed 1. On the other hand, if the aspect ratio exceeds 100, the first carbon particles become structurally weak. For this reason, when a pressure is applied during pressing, the first carbon particles may be structurally destroyed. When the first carbon particles are destroyed, the conductive path is interrupted, making it difficult to solve the problem. Therefore, the aspect ratio is preferably 1.5 to 100. A more preferred aspect ratio is 1.5-20.

  The length of the long axis of the first carbon particles can also be confirmed by an electron microscope. That is, the embedded depth in the current collector is 20 to 50% within the electron microscope field of the electrode cross section selected at random, and the major axis is 1.05 to 1.50 times the active material containing layer thickness. It was confirmed by whether or not carbon particles were present.

  The first carbon particles having the aspect ratio are preferably scaly carbon particles made of graphite or coke. The first carbon particles are preferably carbon particles having a network structure. The first carbon particles having a network structure can maintain a conductive path by another network even when a part of the structure is destroyed.

  When the buried depth of the first carbon particles in the current collector is less than 20% of the thickness of the current collector, the anchor effect, i.e., current collection, caused by part of the first carbon particles biting into the current collector. It becomes difficult to sufficiently achieve the effect of reducing the interface resistance between the body and the active material-containing layer. On the other hand, when the buried depth of the first carbon particles in the current collector exceeds 50% with respect to the thickness of the current collector, the current collector resistance decreases as the current collector volume decreases at the buried portion. May increase. More preferably, the buried depth of the first carbon particles in the current collector is 20 to 40% with respect to the thickness of the current collector. Here, the thickness of the current collector means the average thickness of the current collector on which the active material-containing layer is formed. This average thickness can be obtained, for example, by measuring 20 points with a micrometer and calculating the average value.

  In the first carbon particles having a buried depth of 20 to 50% in the current collector, when the length of the major axis is less than 1.05 times the thickness of the active material-containing layer, the effect of shortening the conductive path length and There is a possibility that it may be difficult to obtain the effect of reducing the resistance at the interface between the current collector and the active material-containing layer. On the other hand, when the length of the major axis of the first carbon particles having a buried depth of 20 to 50% in the current collector exceeds 1.50 times the thickness of the active material-containing layer, the first carbon particles are (Active material-containing layer) It becomes a shape that rises from the surface, a semi-short is likely to occur, and there is a concern about a decrease in safety. More preferably, the length of the major axis of the first carbon particles is 1.10 to 1.45 times the thickness of the active material-containing layer.

  In a form in which a part of the first carbon particles is buried in the current collector, a part of the end opposite to the part of the first carbon particles buried (hereinafter referred to as the other part) is the thickness of the active material-containing layer. It is preferable to be located on the surface side from the intermediate portion. In this way, by positioning the other part of the first carbon particles on the surface side from the intermediate part of the thickness of the active material-containing layer, the path length of the conductive path can be made closer to the shortest distance between the active material and the current collector. Therefore, further reduction effect of internal resistance can be expected.

  In particular, the other part of the first carbon particles preferably reaches the surface of the active material-containing layer.

  Here, “has reached the surface” means that the other part of the first carbon particles is located on the surface of the active material layer (the surface opposite to the surface where the current collector and the active material layer are in contact). To do.

  In addition, when the first carbon particle does not reach the surface of the active material layer (the surface opposite to the surface where the current collector and the active material layer are in contact), the other side opposite to the portion embedded in the current collector The other part is preferably located within a depth range (excluding the active material-containing layer surface) corresponding to the average particle diameter of the active material from the surface toward the current collector.

Position a portion of the first carbon particles are buried in the current collector is preferably to electrode area is 1 × 10 ³ cells / m ² ~1 × 10 ⁸ cells / m ^2. By defining the number of buried portions of the first carbon particles with respect to the current collector as described above, the reaction can be rapidly advanced at any location in the active material layer.

A preferred form of the first carbon particles present in the active material layer, a portion of the first carbon particles, based on the electrode area on the current collector 1 × 10 ³ cells / m ² to 1 × 10 ⁸ cells / m ² And the other part of the first carbon particles reaches the surface of the active material-containing layer.

  A preferable form of the conductive agent has a composition composed of a carbon particle group having an aspect ratio of more than 1 such as graphite and coke, and carbon powder such as carbon black finer than the first carbon particles and fibrous carbon. Carbon black is preferably acetylene black or ketjen black, for example. The conductive agent is preferably contained in a proportion of 30 to 60% by weight of carbon particle group and 40 to 70% by weight of carbon powder. The active material-containing layer containing the conductive agent having such a composition has sufficient strength to withstand the winding during the production of the electrode group in addition to the effect of reducing the internal resistance described later.

  The carbon particle group has an aspect ratio exceeding 1, and one end in the major axis direction is embedded in the current collector at a depth of less than 20% with respect to the thickness of the current collector, or in the major axis direction. It is preferable that one end further contains second carbon particles that are not buried in the current collector. The second carbon particles include carbon particles having a long axis similar to that of the first carbon particles having a length of 1.05 to 1.50 times the thickness of the active material-containing layer, and a long axis corresponding to the first carbon particles. In comparison, it is allowed to contain short carbon particles. In such a carbon particle group including the first and second carbon particles, the first carbon particles are desirably contained in a proportion of 10 to 80% by weight, more preferably 20 to 60% by weight.

  The current collector made of aluminum foil or aluminum alloy foil is preferably roughened by etching, for example. The roughened current collector increases the contact area with the active material-containing layer, so that the interface resistance can be reduced. However, a current collector made of a roughened aluminum foil or aluminum alloy foil forms a stronger oxide film on the surface than a non-roughened current collector. For this reason, the interface resistance between the current collector and the active material-containing layer is not sufficiently reduced. In the electrode according to the embodiment, a part of carbon particles having an aspect ratio exceeding 1 contained in the conductive agent is buried in the current collector at a depth of 20 to 50% with respect to the thickness of the current collector. Since the anchor effect can reduce the influence of the oxide film resistance, the internal resistance is reduced.

  Etching for roughening can employ a chemical etching method or an electrolytic etching method. Electrolytic etching is performed by immersing the aluminum foil or aluminum alloy foil in an electrolytic bath containing chloride ions heated to 60 to 120 ° C. as an anode, and applying a DC or AC voltage of 20 to 1000 V, so that the foil surface has a smooth foil area. The surface is roughened from several times to 120 times. The roughening magnification is calculated by measuring the capacitance of the aluminum foil or aluminum alloy foil. When a roughened aluminum foil or aluminum alloy foil is sandwiched between metal electrodes and a voltage (V [V]) is applied, a charge (Q [C]) shown in the following formula (1) is stored in proportion to the voltage. .

Q = CV (1)
The proportionality constant C [F] in equation (1) is the capacitance. This capacitance C is defined by the following equation (2): electrode area S, interelectrode distance t, dielectric relative permittivity ξ (7 to 8 for aluminum oxide film), vacuum permittivity ξ ₀ (= 8 .85 × 10 ⁻¹² ).

ξ ₀ · ξ · (S / t) (2)
The surface roughening magnification is calculated by dividing the electrode area S obtained from the equation (2) by the smooth area s. The roughening magnification is preferably 10 to 120 times.

  Such an aspect ratio exceeds 1, one end in the major axis direction is buried in the current collector at a depth of 20 to 50% with respect to the thickness of the current collector, and the major axis contains the active material. An electrode structure including first carbon particles having a length of 1.05 to 1.50 times the thickness of the layer as one component of the conductive agent will be described more specifically with reference to FIGS. 1 and 2, an active material-containing layer 2 containing an active material, a conductive agent, and a binder is formed on one surface of a current collector 1 made of an aluminum foil or an aluminum alloy foil. The conductive agent which is one component of the active material-containing layer 2 has an aspect ratio of more than 1, and one end in the major axis direction of the current collector 1 is 20 to 50% of the thickness of the current collector 1 The first carbon particles 3 buried at a depth are included. The first carbon particles 3 have a major axis length (L) of 1.05 to 1.50 times the thickness of the active material-containing layer 2. In the carbon particles 3, the other end opposite to one end in the long axis direction embedded in the current collector 1 reaches the surface of the active material containing layer 2.

  The nonaqueous electrolyte battery according to the embodiment includes the above-described electrode for nonaqueous electrolyte battery as at least one of a positive electrode and a negative electrode. A non-aqueous electrolyte battery electrode will be described in detail below in terms of (1) a form provided for both the positive electrode and the negative electrode, (2) a form provided with only the positive electrode, and (3) a form provided with only the negative electrode.

(1) A form in which both the positive electrode and the negative electrode are the electrodes for a non-aqueous electrolyte battery described above <Positive electrode>
The positive electrode is a current collector made of an aluminum foil or aluminum alloy foil, and is supported on one or both surfaces of the current collector. The positive electrode active material, the conductive agent (including the first carbon particles in the above-described form), and the binder And a positive electrode active material-containing layer. In this positive electrode, for example, a conductive agent and a binder are added to the positive electrode active material, these are suspended in an appropriate solvent, and the suspension (slurry) is applied to a current collector, dried and pressed to form a belt shape. It is produced by making an electrode.

  The aluminum foil or aluminum alloy foil constituting the current collector desirably has an average crystal grain size of 50 μm or less, more preferably 30 μm or less, and still more preferably 5 μm or less. By setting the average crystal grain size of the aluminum foil or aluminum alloy foil to 50 μm or less, the strength of the aluminum foil or aluminum alloy foil can be dramatically increased. For this reason, it is possible to increase the positive electrode capacity by increasing the pressure during pressing to increase the density of the positive electrode active material-containing layer.

The average crystal grain size can be determined by the following method. The structure of the current collector surface is observed with an optical microscope, and the number (n) of crystal grains present within 1 mm × 1 mm is determined. Using this n, the average crystal grain area S is determined from S = 1 × 10 ⁶ / n (μm ² ). The average crystal particle diameter d (μm) is calculated from the obtained S value by the following formula (3).

d = 2 (S / π) ^1/2 (3)
The average crystal grain size of the aluminum foil or aluminum alloy foil changes under complex influences from a plurality of factors such as material structure, impurities, processing conditions, heat treatment history, and annealing conditions. The crystal grain size can be adjusted by combining the above factors in the production process of the current collector.

  The thickness of the aluminum foil or aluminum alloy foil is desirably 20 μm or less, more preferably 1.50 μm or less. The aluminum foil preferably has a purity of 99% or more. The aluminum alloy is preferably an alloy containing elements such as magnesium, zinc, and silicon. Transition metals such as iron, copper, nickel and chromium contained as alloy components are preferably 1% by weight or less.

  As described above, the surface of the aluminum foil or aluminum alloy foil is preferably roughened.

Examples of the positive electrode active material include manganese dioxide (MnO ₂ ), iron oxide, copper oxide, nickel oxide, Li _a MnO ₂ , lithium nickel composite oxide (eg, Li _a NiO ₂ ), and lithium cobalt composite oxide (Li _a CoO _2). ), Lithium nickel cobalt composite oxide {for example, LiNi _1-ef Co _e MfO ₂ , where M is at least one element selected from the group consisting of Al, Cr and Fe, 0 ≦ e ≦ 0.5, 0 ≦ f ≦ 0.1}, lithium manganese cobalt composite oxide {for example, LiMn _1-gh Co _g M _h O ₂ , where M is at least one element selected from the group consisting of Al, Cr and Fe, 0 ≦ g ≦ 0.5, 0 ≦ h ≦ 0.1}, lithium manganese nickel composite compound {for example, LiMn _j Ni _j M _1-2j O ₂ , where M is a group consisting of Co, Cr, Al and Fe At least one element selected from _1/3 ≦ j ≦ 1/2, LiMn _1/3 Ni _1/3 Co _1/3 O ₂ , LiMn _1/2 Ni _1/2 O ₂ }, spinel type lithium manganese Complex oxide (Li _a Mn _2-b M _b O ₄ , where M is at least one element selected from the group consisting of Al, Cr, Ni and Fe), spinel type lithium manganese nickel complex oxide (Li _a Mn _2-b Ni _b O ₄ ), lithium phosphorous oxide having an olivine structure (such as Li _a FePO ₄ , Li _a Fe _1-b Mn _b PO ₄ , Li _a CoPO ₄ ), iron sulfate (Fe ₂ (SO _{4 3} ) and vanadium oxide (for example, V ₂ O ₅ ). Here, a, b, and c are preferably 0 to 1. Examples of the positive electrode active material include conductive polymer materials such as polyaniline and polypyrrole, disulfide polymer materials, sulfur (S), organic materials such as carbon fluoride, and inorganic materials.

  More preferable positive electrode active materials are lithium nickel composite oxide, lithium cobalt composite oxide, lithium nickel cobalt composite oxide, lithium manganese nickel composite compound, spinel type lithium manganese composite oxide, spinel type lithium manganese nickel composite oxide, lithium Manganese cobalt composite oxide and lithium iron phosphate can be used. According to these positive electrode active materials, a high battery voltage can be obtained. Spinel type lithium manganese composite oxide and lithium iron phosphate are more preferable because of their large electric resistance.

  For example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), or fluorine-based rubber can be used as the binder.

  The mixing ratio of the positive electrode active material, the conductive agent and the binder is preferably 73 to 95% by weight of the positive electrode active material, 3 to 20% by weight of the conductive agent, and 2 to 7% by weight of the binder.

<Negative electrode>
The negative electrode includes a current collector made of an aluminum foil or an aluminum alloy foil, a negative electrode active material, a conductive agent (including the first carbon particles having the form described above) and a binder supported on one or both sides of the current collector. And a negative electrode active material-containing layer containing an agent. In this negative electrode, for example, a conductive agent and a binder are added to a powdered negative electrode active material, these are suspended in an appropriate solvent, and this suspension (slurry) is applied to a current collector, dried and pressed. It is produced by forming a strip electrode.

  The aluminum foil or aluminum alloy foil constituting the current collector desirably has an average crystal grain size of 50 μm or less, more preferably 30 μm or less, and still more preferably 5 μm or less. The average crystal grain size can be determined by the method described above. By setting the average crystal grain size of the aluminum foil or aluminum alloy foil to 50 μm or less, the strength of the aluminum foil or aluminum alloy foil can be dramatically increased. For this reason, it is possible to increase the negative electrode capacity by increasing the pressure during pressing to increase the density of the negative electrode active material-containing layer. Further, it is possible to prevent the current collector from being dissolved and corroded in an overdischarge cycle under a high temperature environment (40 ° C. or higher). For this reason, an increase in negative electrode impedance can be suppressed. Furthermore, output characteristics, quick charge, and charge / discharge cycle characteristics can also be improved.

  The average crystal grain size of the aluminum foil or aluminum alloy foil changes under complex influences from a plurality of factors such as material structure, impurities, processing conditions, heat treatment history, and annealing conditions. The crystal grain size can be adjusted by combining the above factors in the production process of the current collector.

  The thickness of the aluminum foil or aluminum alloy foil is desirably 20 μm or less, more preferably 1.50 μm or less. The aluminum foil preferably has a purity of 99% or more. The aluminum alloy is preferably an alloy containing elements such as magnesium, zinc, and silicon. Transition metals such as iron, copper, nickel and chromium contained as alloy components are preferably 1% by weight or less.

  As described above, the surface of the aluminum foil or aluminum alloy foil is preferably roughened.

As the negative electrode active material, for example, a carbonaceous material or a metal compound is used. Examples of the carbonaceous material include natural graphite, artificial graphite, coke, vapor-grown carbon fiber, mesophase pitch-based carbon fiber, spherical carbon, and resin-fired carbon. . More preferable carbonaceous materials include vapor grown carbon fiber, mesophase pitch carbon fiber, and spherical carbon. The carbonaceous material preferably has a (002) plane spacing d ₀₀₂ of 0.340 nm or less by X-ray diffraction.

  As the metal compound, for example, a metal oxide, a metal sulfide, or a metal nitride can be used.

The metal oxide is, for example, a titanium-containing metal composite oxide, for example, an amorphous tin oxide such as SnB _0.4 P _0.6 O _3.1 , a tin silicon oxide such as SnSiO ₃ , a silicon oxide such as SiO, or a tungsten oxide such as WO _3. You can list things. Of these, titanium-containing metal composite oxides are preferable. The titanium-containing metal composite oxide is selected from the group consisting of ramsteride type Li _{2 + f} Ti ₃ O ₇ (−1 ≦ f ≦ 3), Ti and P, V, Sn, Cu, Ni and Fe, for example. Examples thereof include metal composite oxides containing at least one element. Examples of the metal composite oxide containing at least one element selected from the group consisting of Ti and P, V, Sn, Cu, Ni and Fe include TiO ₂ —P ₂ O ₅ , TiO ₂ —V _2. O ₅ , TiO ₂ —P ₂ O ₅ —SnO ₂ , TiO ₂ —P ₂ O ₅ —MeO (Me is at least one element selected from the group consisting of Cu, Ni and Fe). This metal complex oxide has a low crystallinity and preferably has a microstructure in which a crystal phase and an amorphous phase coexist or exist alone. Such a microstructured metal composite oxide can greatly improve the cycle performance. Among these, lithium titanium oxide, metal composite oxide containing at least one element selected from the group consisting of Ti and P, V, Sn, Cu, Ni, and Fe are preferable.

As the metal sulfide, titanium sulfide such as TiS ₂ , molybdenum sulfide such as MoS ₂ , and iron sulfide such as FeS, FeS ₂ , and LixFeS ₂ can be used.

  As the metal nitride, for example, lithium cobalt nitride (for example, LisCotN, 0 <s <4, 0 <t <0.5) can be used.

  Spinel type lithium titanate is more preferable because of its large electric resistance.

  Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine rubber, and styrene butadiene rubber.

  The blending ratio of the negative electrode active material, the conductive agent and the binder is preferably in the range of 73 to 96% by weight of the negative electrode active material, 2 to 20% by weight of the conductive agent, and 2 to 7% by weight of the binder.

(2) Form in which only the positive electrode is the electrode for a non-aqueous electrolyte battery described above <Positive electrode>
The positive electrode is the same as that described in (1) above.

<Negative electrode>
The negative electrode includes a current collector made of an aluminum foil or an aluminum alloy foil, and a negative electrode active material-containing layer that is supported on one or both sides of the current collector and includes a negative electrode active material and a binder. In this negative electrode, for example, a conductive agent and a binder are added to a powdered negative electrode active material, these are suspended in an appropriate solvent, and this suspension (slurry) is applied to a current collector, dried and pressed. It is produced by forming a strip electrode.

  The current collector and the binder are the same as those described in (1) above.

  As the negative electrode active material, for example, lithium metal or a lithium alloy can be used.

  Examples of the lithium alloy include a lithium aluminum alloy, a lithium zinc alloy, a lithium magnesium alloy, a lithium silicon alloy, and a lithium lead alloy. When using lithium alloy foil, you may use alloy foil as a negative electrode as it is.

  When the negative electrode active material is used in combination with a conductive agent, the carbonaceous material or metal compound described in (1) above can be used. This conductive agent has a different form from the conductive agent described in the above (1) (including the first carbon particles having the form described above), for example, carbon black (acetylene black and ketjen black are preferred), graphite, coke, Examples thereof include fibrous carbon.

  The mixing ratio of the negative electrode active material, the conductive agent and the binder is preferably in the range of 73 to 98% by weight of the negative electrode active material, 0 to 20% by weight of the conductive agent, and 2 to 7% by weight of the binder.

(3) Form in which only the negative electrode is the electrode for a non-aqueous electrolyte battery described above <Positive electrode>
The positive electrode has a different form from the conductive agent described in (1) (including the first carbon particles having the form described above), such as carbon black (acetylene black and ketjen black are preferred), graphite, coke, and fibrous. Except for using a conductive agent made of carbon or the like, it has essentially the same composition and structure as described in (1) above.

<Negative electrode>
The negative electrode is the same as that described in (1) above.

  The non-aqueous electrolyte battery according to the embodiment includes the above-described non-aqueous electrolyte battery electrode as at least one of a positive electrode and a negative electrode, and battery resistance [mΩ] at a state of charge (SOC) of 50%. And (battery resistance) [mΩ] × (battery capacity) [Ah] are preferably less than 10 mΩAh.

  When the value of (battery resistance) [mΩ] × (battery capacity) [Ah] exceeds 10 mΩAh, it means that the resistance component other than the electrode resistance is large, and the resistance component other than the electrode resistance is a large current during large current charge / discharge. There is a risk that the output characteristics may be deteriorated due to an obstacle to the flow. The resistance component other than the electrode resistance component includes, for example, a separator resistance, a resistance of the current collector and a current extraction part, a nonaqueous electrolyte resistance, an interface resistance between the current collector and the active material, and a resistance caused by an interlayer distance between the positive electrode and the negative electrode. Can be mentioned.

  Such a nonaqueous electrolyte battery (rectangular nonaqueous electrolyte battery) will be described in detail with reference to FIG. 3 and FIG. FIG. 3 is a partially cutaway perspective view showing the nonaqueous electrolyte battery according to the embodiment, and FIG. 4 is an enlarged sectional view of a portion A in FIG.

  For example, an aluminum rectangular lid 12 is attached to an opening of a bottomed rectangular cylinder 11 made of aluminum. The flat electrode group 13 is accommodated in the bottomed rectangular cylinder 11. As shown in FIG. 4, the electrode group 13 is produced by winding the positive electrode 14 and the negative electrode 15 in a spiral shape so that the separator 16 is positioned on the outer peripheral surface with the separator 16 interposed therebetween, and press molding. The positive electrode 14 includes, for example, a current collector 14a and a positive electrode active material-containing layer 14b formed on both surfaces of the current collector 14a. The positive electrode lead tab 17 is integrally connected to the current collector 14 a of the positive electrode 14. The negative electrode 15 includes, for example, a current collector 15a and a negative electrode active material-containing layer 15b formed on both surfaces of the current collector 15a. The negative electrode lead tab 18 is integrally connected to the current collector 15a. The nonaqueous electrolytic solution is accommodated in the bottomed rectangular cylinder 11.

  For example, the belt-like positive electrode terminal 19 is inserted into the lid body 12. A positive lead tab 17 is connected to the vicinity of the end of the positive terminal 19 located in the bottomed rectangular cylinder 11. For example, the strip-like negative electrode terminal 20 is inserted into the lid 12 by a hermetic seal with a glass material 21 interposed, for example. A negative electrode lead tab 18 is connected near the end of the negative electrode terminal 20 located in the bottomed rectangular cylinder 11. The negative electrode terminal 20 may be attached to the lid 12 by caulking through a resin instead of a glass material.

  The separator and non-aqueous electrolyte will be described in detail below.

  Examples of the separator include polyethylene (PE), polypropylene (PP), polytetrafluoroethylene (PTFE), polytetrafluoroethylene-perfluoroalkoxyethylene (PFA), polyhexafluoropropylene (HFP), and polytetrafluoroethylene-hexafluoro. Porous films and synthetic resins containing organic polymers such as propylene (FEP), polyethylene-tetrafluoroethylene (ETFE), polyethylene terephthalate (PET), polyamide, polyimide, cellulose, cellulose polyethylene, polyvinylidene fluoride (PVdF) A nonwoven fabric made of glass or a nonwoven fabric made of glass fiber can be used.

  The nonaqueous electrolyte includes a nonaqueous solvent and an electrolyte salt dissolved in the nonaqueous solvent. The non-aqueous solvent may contain a polymer.

Examples of the electrolyte salt include LiPF ₆ , LiBF ₄ , Li (CF ₃ SO ₂ ) ₂ N (bistrifluoromethanesulfonylamide lithium; commonly known as LiTFSI), LiCF ₃ SO ₃ (commonly known as LiTFS), and Li (C ₂ F ₅ SO ₂ ). ₂ N (bis pentafluoroethanesulfonyl amide lithium; called _{LiBETI), LiClO 4, LiAsF 6} , LiSbF 6, bisoxalato Lato lithium borate _{(LiB (C 2 O 4)} 2 ( known as LiBOB)), difluoro (tri-fluoro-2 - oxide-2-trifluoromethyl - methylpropionate diisocyanatohexane (2 -) - 0,0) lithium borate _{(LiBF2 (OCOOC (CF 3)} 2) ( aka LiBF ₂ (HHIB))) lithium salt be used, such as Can do. These electrolyte salts may be used alone or in combination of two or more. Particularly preferred are LiPF ₆ and LiBF ₄ .

  The electrolyte salt concentration is preferably 1.0 to 3 mol / L. Such regulation of the electrolyte concentration makes it possible to further improve the performance when a high load current is passed while suppressing the influence of an increase in viscosity due to an increase in the electrolyte salt concentration.

  The non-aqueous solvent is not particularly limited. For example, propylene carbonate (PC), ethylene carbonate (EC), 1,2-dimethoxyethane (DME), γ-butyrolactone (GBL), tetrahydrofuran (THF), 2 -Use methyltetrahydrofuran (2-MeHF), 1,3-dioxolane, sulfolane, acetonitrile (AN), diethyl carbonate (DEC), dimethyl carbonate (DMC), methyl ethyl carbonate (MEC), dipropyl carbonate (DPC) Can do. These solvents may be used alone or in combination of two or more. The non-aqueous solvent is preferably γ-butyrolactone when the thermal stability is important. In addition, when the non-aqueous solvent requires thermal stability as well as low temperature performance, it preferably contains all three components of EC, PC, and GBL. By including all three cyclic carbonate-based solvents (EC, PC and GBL), high thermal stability and improvement in low-temperature performance considered to be associated with increased entropy can be expected. Since the cyclic carbonate has a higher viscosity than the chain carbonate, the cycle characteristics when using a non-aqueous solvent comprising the cyclic carbonate can be greatly improved.

  An additive may be added to the non-aqueous electrolyte. Although an additive is not specifically limited, For example, vinylene carbonate (VC), vinylene acetate (VA), vinylene butyrate, vinylene hexanate, vinylene crotonate, catechol carbonate can be used. The amount of the additive is 0.1 to 3% by weight, more preferably 0.5 to 1% by weight, based on the nonaqueous electrolyte.

  The non-aqueous electrolyte battery electrode according to the embodiment described above can significantly reduce the internal resistance as compared with the conventional electrode.

  That is, since the aluminum foil or aluminum alloy foil that is the current collector has a strong oxide film formed on the surface, the interface resistance between the active material-containing layer and the current collector is increased.

  According to the embodiment, the conductive agent includes first carbon particles having an aspect ratio of more than 1 and embedded in one end of the major axis direction at a depth of 20 to 50% with respect to the thickness of the current collector. The so-called high anchor effect that the first carbon particles bite into the current collector can be exhibited. For this reason, it becomes possible to reduce the interface resistance between the active material-containing layer and the current collector interface, which is another factor of the electrode internal resistance.

  In addition, since the conventional electrode has a structure in which the active material surface is covered with a fine powder conductive agent such as carbon black, the conductive path from the active material to the current collector during large current charge / discharge is the active material surface. It becomes a path to transmit. As a result, the path length of the conductive path is longer than the shortest distance from the active material to the current collector.

  According to the embodiment, the first carbon particles in the conductive agent mainly have a major axis length of 1.05 to 1.50 times the thickness of the active material-containing layer. Acts as a conductive path. For this reason, the path length of the conductive path can be made closer to the shortest distance between the active material and the current collector than the conventional electrode. As a result, it becomes possible to reduce the diffusion resistance in the electron transfer which is one of the factors of the internal resistance.

  Therefore, according to the embodiment, the diffusion resistance in electron transfer can be reduced only by controlling the size of the first carbon particles in the conductive agent that is a constituent component of the active material-containing layer, and the active material-containing layer and the current collector can be reduced. The interface resistance of the interface can be reduced. As a result, a new member, such as a conductive layer, becomes unnecessary as in the case of conventional electrodes, so that an electrode for a nonaqueous electrolyte battery that achieves a reduction in internal resistance without reducing effective energy density is obtained. Is possible.

  In addition, according to the embodiment, a nonaqueous electrolyte battery having excellent large current discharge characteristics can be realized by providing the electrode for a nonaqueous electrolyte battery with reduced internal resistance as at least one of the positive electrode and the negative electrode. Can do. In particular, by making the value obtained by multiplying the battery resistance [mΩ] and the battery capacity [Ah] less than 10 mΩAh, a non-aqueous electrolyte battery with even more excellent large current discharge characteristics can be realized.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings described above.

Example 1
<Preparation of positive electrode>
LiCoO ₂ (d50: 5.5 μm) was prepared as the positive electrode active material, graphite and acetylene black (d50: 35 nm) as the conductive agent, and PVdF as the binder. The graphite used had a particle size distribution of d50: 12 μm and d90: 32 μm by a laser particle size distribution meter. Moreover, the average value of the aspect ratio of the graphite was 3.2 by image analysis of the scanning electron microscope image.

Next, 88 parts by weight of LiCoO ₂ , 3 parts by weight of graphite, 4 parts by weight of acetylene black and 5 parts by weight of PVdF were dispersed in a solvent of N-methylpyrrolidone (NMP) to prepare a slurry. This slurry was applied to both sides of a 15 μm thick aluminum foil current collector, dried, and press-molded to produce a positive electrode in which an active material-containing layer having a thickness of 28 μm on one side was formed on both sides of the current collector. did.

  The cross section of the obtained positive electrode was observed with an electron microscope. As a result, it was confirmed that one end in the major axis direction of graphite having an aspect ratio exceeding 1 was embedded in the aluminum foil current collector at a depth of up to 28% of the current collector thickness. It was done. The major axis length of graphite having a buried depth of 20 to 28% in the current collector was 1.09 to 1.32 times the thickness of the active material-containing layer.

The portion of the graphite where one end of the long axis is buried in the current collector at a depth of 20 to 28% of its thickness and the other end reaches the surface of the active material containing layer is the electrode area of 1 m ² from the value of the particle size distribution of the graphite. Per 1 × 10 ⁴ to 1 × 10 ⁷ points are expected.

<Production of negative electrode>
Li ₄ Ti ₅ O ₁₂ as a negative electrode active material, graphite as a conductive agent, and PVdF as a binder were prepared. The graphite used had a particle size distribution of d50: 19 μm and d90: 41 μm by a laser particle size distribution meter. Moreover, the average value of the aspect ratio of the graphite was 3.4 by image analysis of the scanning electron microscope image.

Next, 89 parts by weight of Li ₄ Ti ₅ O ₁₂ , 6 parts by weight of graphite and 5 parts by weight of PVdF were dispersed in a solvent of N-methylpyrrolidone (NMP) to prepare a slurry. This slurry was applied to both sides of a 15 μm thick aluminum foil current collector, dried, and press-molded to produce a negative electrode in which an active material-containing layer having a thickness of 35 μm on one side was formed on both sides of the current collector. did.

  The cross section of the obtained negative electrode was observed with an electron microscope. As a result, it was confirmed that one end in the major axis direction of graphite having an aspect ratio exceeding 1 was embedded in an aluminum foil current collector at a depth of up to 24% of the current collector thickness. It was done. The major axis length of graphite having an embedded depth of 20 to 24% in the current collector was 1.07 to 1.33 times the thickness of the active material-containing layer.

The portion of the graphite where one end of the long axis is buried in the current collector at a depth of 20 to 24% of the thickness and the other end reaches the surface of the active material containing layer is the electrode area of 1 m ² from the value of the particle size distribution of the graphite. Per 1 × 10 ⁴ to 1 × 10 ⁷ points are expected.

<Preparation of non-aqueous electrolyte>
A non-aqueous electrolyte was prepared by mixing 2M LiBF ₄ in a mixed solvent in which EC, PC, and GBL were mixed at a volume ratio of 1: 1: 4.

<Battery assembly>
A container with a bottomed rectangular tube made of aluminum with a thickness of 0.3 mm and an aluminum lid with a positive electrode terminal inserted and a negative electrode terminal inserted by caulking through an insulating resin are prepared. did. After impregnating a separator made of a polyethylene porous film with a non-aqueous electrolyte, the positive electrode is covered with this separator, and the negative electrode is overlapped with the separator so as to face the positive electrode and wound in a spiral shape, extending from the positive electrode and the negative electrode, respectively. A spiral electrode group having a lead tab was prepared. This electrode group was pressed into a flat shape. Connect the positive electrode lead tab of the electrode group formed into a flat shape to one end of the positive electrode terminal of the lid, connect the negative electrode lead tab to one end of the negative electrode terminal, insert the electrode group into the interior through the opening of the container together with the lid body, The lid was welded to the opening of the container. Through these steps, a prismatic nonaqueous electrolyte battery having the structure shown in FIG. 1 and having a thickness of 3.0 mm, a width of 35 mm, a height of 62 mm, and a capacity of 700 mAh was manufactured.

(Example 2)
A non-aqueous electrolyte battery similar to that of Example 1 was manufactured, except that an aluminum foil roughened about 80 times the smooth area was used as the positive and negative electrode current collector.

  The cross section of the obtained positive electrode was observed with an electron microscope. As a result, one end in the major axis direction of the carbon particles described in Example 1 has a portion that is buried in the aluminum foil current collector at a depth of up to 35% with respect to the current collector thickness. confirmed.

  Moreover, the cross section of the obtained negative electrode was observed with the electron microscope. As a result, one end in the major axis direction of the carbon particles described in Example 1 has a portion embedded in the current collector thickness of the aluminum foil at a depth of up to 33% with respect to the current collector thickness. confirmed.

  Furthermore, in the positive electrode and the negative electrode, one end of the major axis is buried in the current collector at a depth of 20 to 35% and 20 to 33% of the thickness, respectively, and the other portion of the graphite reaching the surface of the active material containing layer is This is expected to be the same as in Example 1.

(Example 3)
A non-aqueous electrolyte battery similar to that of Example 1 was manufactured, except that the slurry used for the production of the positive and negative electrodes was a slurry whose NMP amount was reduced and the solid content ratio was increased by 3% by weight as compared with Example 1.

  The cross section of the obtained positive electrode was observed with an electron microscope. As a result, one end in the major axis direction of the carbon particles described in Example 1 was buried in the aluminum foil current collector at a depth of up to 27% with respect to the thickness of the current collector, and further opposite to the buried one end. It was confirmed that the other end of the side had a part reaching the surface of the active material-containing layer.

  Moreover, the cross section of the obtained negative electrode was observed with the electron microscope. As a result, one end in the major axis direction of the carbon particles described in Example 1 was buried in the aluminum foil current collector at a depth of up to 33% with respect to the thickness of the current collector, and further opposite to the buried one end. It was confirmed that the other end of the side had a part reaching the surface of the active material-containing layer.

  Further, in the positive electrode and the negative electrode, one end of the major axis is buried in the current collector at a depth of 20 to 27% and 20 to 33% of the thickness, respectively, and the other portion of the graphite reaching the surface of the active material containing layer is This is expected to be the same as in Example 1.

Example 4
The graphite in the positive electrode conductive agent is a value measured by a laser particle size distribution meter, d50: 24 μm, d90: 56 μm, the thickness of the active material containing layer of the positive electrode is 52 μm, and the graphite in the negative electrode conductive agent is a laser particle size distribution meter. A nonaqueous electrolyte battery similar to that of Example 1 was prepared except that the thickness of the active material-containing layer of the negative electrode was set to 65 μm, and the values of d50: 26 μm and d90: 65 μm were used. Each graphite used had an average aspect ratio of 3.5 by image analysis of a scanning electron microscope image.

The cross section of the obtained positive electrode was observed with an electron microscope. As a result, it was confirmed that one end in the major axis direction of graphite having an aspect ratio exceeding 1 was embedded in the aluminum foil current collector at a depth of up to 25% of the current collector thickness. It was done. The major axis length of graphite having an embedding depth of 20 to 25% in the current collector was 1.05 to 1.15 times the thickness of the active material-containing layer. The portion of the graphite in which one end of the long axis is buried in the current collector at a depth of 20 to 25% of the thickness and the other end reaches the surface of the active material containing layer is determined from the value of the particle size distribution of the graphite. It is expected to exist in the range of 1 × 10 ⁴ to 1 × 10 ⁷ points per 1 m ² .

The cross section of the obtained negative electrode was observed with an electron microscope. As a result, it was confirmed that one end in the long axis direction of the carbon particles had a portion buried in the aluminum foil current collector at a depth of 22% at the maximum with respect to the current collector thickness. The major axis length of graphite having a buried depth of 20 to 22% in the current collector was 1.06 to 1.18 times the thickness of the active material-containing layer. The portion of the graphite where one end of the long axis is buried in the current collector at a depth of 20 to 22% of the thickness and the other end reaches the surface of the active material containing layer is determined from the value of the particle size distribution of the graphite. It is expected to exist in the range of 1 × 10 ⁴ to 1 × 10 ⁷ points per 1 m ² .

(Example 5)
Coke (value by laser particle size distribution meter, d50: 24 μm, d90: 56 μm) is used instead of graphite in the positive electrode conductive agent, and coke (value by laser particle size distribution meter, d50: 26 μm) instead of graphite in the negative electrode conductive agent. , D90: 65 μm), a non-aqueous electrolyte battery similar to that of Example 1 was manufactured.

  The coke used for the positive electrode conductive agent had an average aspect ratio of 4.1 by image analysis of a scanning electron microscope image. The coke used for the negative electrode conductive agent had an average aspect ratio of 4.5 by image analysis of a scanning electron microscope image.

The cross section of the obtained positive electrode was observed with an electron microscope. As a result, it was confirmed that one end in the major axis direction of the carbon particles had a portion embedded in the current collector thickness of the aluminum foil at a maximum depth of 27% with respect to the current collector thickness. The major axis length of coke having a buried depth of 20 to 27% in the current collector was 1.10 to 1.50 times the thickness of the active material-containing layer. Further, the portion of the coke in which one end of the long axis is buried in the current collector at a depth of 20 to 27% of the thickness and the other end reaches the surface of the active material containing layer is the electrode area from the value of the particle size distribution of graphite. It is expected to be present in a range of 1 m ² per 2 × 10 ⁴ ~2 × 10 ⁷ points.

The cross section of the obtained negative electrode was observed with an electron microscope. As a result, it was confirmed that one end in the major axis direction of the carbon particles had a portion buried in the current collector thickness of the aluminum foil at a maximum depth of 25% with respect to the current collector thickness. The major axis length of coke having a buried depth of 20 to 25% in the current collector was 1.12 to 1.48 times the thickness of the active material-containing layer. Further, the portion of the coke in which one end of the long axis is buried in the current collector at a depth of 20 to 27% of the thickness and the other end reaches the surface of the active material containing layer is the electrode area from the value of the particle size distribution of graphite. It is expected to be present in a range of 1 m ² per 2 × 10 ⁴ ~2 × 10 ⁷ points.

(Example 6)
A nonaqueous electrolyte battery similar to that of Example 1 was produced except that graphite in the negative electrode conductive agent had values of d50: 12 μm and d90: 32 μm as measured by a laser particle size distribution meter. In addition, the average value of the aspect ratio of the graphite used for the negative electrode conductive agent was 3.0 by image analysis of a scanning electron microscope image.

  The cross section of the obtained negative electrode was observed with an electron microscope. As a result, graphite having a major axis length of 0.94 times the thickness of the active material-containing layer is a current collector having an aluminum foil at one end in the major axis direction. It was confirmed to have a portion buried at a depth of%.

(Example 7)
A nonaqueous electrolyte battery similar to that of Example 1 was produced except that the graphite in the positive electrode conductive agent used the values measured by a laser particle size distribution meter, d50: 9 μm, d90: 20 μm. In addition, the average value of the aspect ratio of the graphite used for the positive electrode conductive agent was 3.1 by image analysis of a scanning electron microscope image.

  The cross section of the obtained positive electrode was observed with an electron microscope. As a result, graphite having a major axis length of 0.75 times the maximum of the thickness of the active material-containing layer is a maximum of the collector thickness of the aluminum foil at one end in the major axis direction with respect to the current collector thickness. It was confirmed to have a portion buried at a depth of 2%.

(Example 8)
A non-aqueous electrolyte battery similar to that of Example 1 was manufactured, except that the slurry used for the production of the positive electrode was used in which the amount of NMP was increased and the solid content ratio was increased by 2% by weight compared to Example 1.

  The cross section of the obtained positive electrode was observed with an electron microscope. As a result, the graphite was partially buried in the aluminum foil current collector at a depth of 22% at maximum with respect to the current collector thickness. Furthermore, it was confirmed that the graphite has a part where the other part on the opposite side reaches the surface of the active material containing layer.

Example 9
A nonaqueous electrolyte battery similar to that of Example 1 was manufactured except that graphite having a particle size distribution of d50: 9 μm and d90: 30 μm was used as a positive electrode conductive agent by a laser particle size distribution meter. The cross section of the obtained positive electrode was observed with an electron microscope. As a result, one end of the long axis direction of the carbon particle is buried in the current collector of aluminum foil at a depth of up to 24% with respect to the thickness of the current collector, and the other end of the long axis of the carbon particle is the active material. It was confirmed to have a site at a position of 5 μm from the surface of the containing layer.

(Comparative Example 1)
Graphite in the positive electrode conductive agent was a value measured by a laser particle size distribution meter, d50: 9 μm, d90: 20 μm, and graphite in the negative electrode conductive agent was a value measured by a laser particle size distribution meter, d50: 12 μm, d90: 32 μm. A nonaqueous electrolyte battery similar to that of Example 1 was manufactured. In addition, the average value of the aspect ratio of the graphite used for the positive electrode conductive agent was 3.1 by image analysis of a scanning electron microscope image. The graphite used for the negative electrode conductive agent had an average aspect ratio of 3.0 by image analysis of a scanning electron microscope image.

  The cross section of the obtained positive electrode was observed with an electron microscope. As a result, graphite having a major axis length of 0.75 times the maximum of the thickness of the active material-containing layer is a maximum of the collector thickness of the aluminum foil at one end in the major axis direction with respect to the current collector thickness. It was confirmed to have a portion buried at a depth of 2%.

  The cross section of the obtained negative electrode was observed with an electron microscope. As a result, graphite having a major axis length of 0.94 times the thickness of the active material-containing layer is a current collector having an aluminum foil at one end in the major axis direction. It was confirmed to have a portion buried at a depth of%.

(Comparative Example 2)
A nonaqueous electrolyte battery similar to that of Comparative Example 1 was produced, except that an aluminum foil roughened about 80 times the smooth area was used as the current collector for the positive and negative electrodes.

  The cross section of the obtained positive electrode was observed with an electron microscope. As a result, the graphite described in Comparative Example 1 having a major axis length of 0.75 times the maximum of the thickness of the active material-containing layer is a collector whose aluminum axis is one end in the major axis direction. It was confirmed to have a portion buried at a depth of a maximum of 12% with respect to the thickness.

  The cross section of the obtained negative electrode was observed with an electron microscope. As a result, the graphite described in Comparative Example 1 having a major axis length of 0.94 times the thickness of the active material-containing layer is a collector with an aluminum foil at one end in the major axis direction. It was confirmed to have a portion buried at a maximum depth of 11% with respect to the thickness.

(Comparative Example 3)
Graphite in the positive electrode conductive agent is a value measured by a laser particle size distribution meter, d50: 18 μm, d90: 45 μm, and the thickness of the active material-containing layer of the positive electrode is 52 μm. A nonaqueous electrolyte battery similar to that of Example 1 was manufactured, except that the values of d50: 20 μm and d90: 50 μm were used, and the thickness of the negative electrode active material-containing layer was set to 65 μm. In addition, the average value of the aspect ratio of the graphite used for the positive electrode conductive agent was 3.2 by image analysis of a scanning electron microscope image. Moreover, the average value of the aspect ratio of the graphite used for the negative electrode conductive agent was 3.6 by image analysis of a scanning electron microscope image.

  The cross section of the obtained positive electrode was observed with an electron microscope. As a result, it was confirmed that one end in the major axis direction of the graphite had a portion buried in the current collector thickness of the aluminum foil at a maximum depth of 1% with respect to the current collector thickness.

  The cross section of the obtained negative electrode was observed with an electron microscope. As a result, it was confirmed that one end in the major axis direction of the graphite had a portion buried in the current collector thickness of the aluminum foil at a maximum depth of 1% with respect to the current collector thickness.

  About the nonaqueous electrolyte battery obtained by Examples 1-9 and Comparative Examples 1-3, the resistance value of 50% of charge depth was measured with the following method.

That is, after charging the battery to a fully charged state, half of the battery capacity was discharged to bring the charging depth to 50%. The discharge was performed for 0.2 seconds at a current value of _0.2 C at 0.2 C, and the voltage value E ₁ “V” at this time was read. After an open circuit state for 1 minute, 0 at a battery capacity of 0.2 C. .Charge for 2 seconds, and after an open circuit state for 1 minute, discharge for ₁₀ seconds with 10C current value I ₁₀ [A] of the battery capacity, and read voltage value E ₂ [V] at this time The battery resistance was determined by substituting these current values and voltage values into the following equation (4).

Battery resistance [Ω] = (E ₁ −E ₂ ) / (I ₁₀ −I _0.2 ) (4)
Moreover, about the nonaqueous electrolyte battery obtained in Examples 1-9 and Comparative Examples 1-3, the output was measured with the following method.

  That is, first, after the battery state was set to a charge depth of 50% by the same method as the battery resistance measurement, discharging was performed at 1C for 10 seconds, and the voltage Ea [V] at this time was measured. After charging for capacity compensation, discharging at 10 C for 10 seconds was performed, and the voltage Eb [V] at this time was measured. Based on these results, a current-voltage correlation diagram was created, the current value Ia [A] when the battery voltage reached 1 V was calculated by extrapolation, and the output was calculated by substituting it into the following equation (5). .

Output [W] = 1 [V] × Ia [A] (5)
The resistance values and outputs of the nonaqueous electrolyte batteries of Examples 1 to 9 and Comparative Examples 1 to 3 are shown in Table 1 below. Table 1 below shows the thicknesses of the active material-containing layers of the positive electrode and the negative electrode, the maximum embedment depth of graphite or coke in the current collector in the positive electrode and the negative electrode [simply “maximum embedment depth of carbon particles in the current collector” Say "Sa"].

  As apparent from Table 1, when Examples 1 and 5 were compared with Comparative Example 1, the aspect ratio exceeded 1, and the aluminum foil current collector was buried at a depth of 20 to 50% with respect to its thickness. A positive electrode and a negative electrode having a structure in which a conductive agent containing carbon particles (graphite or coke) having a major axis length of 1.05 to 1.50 times the active material-containing layer thickness is contained in the active material-containing layer. The batteries of Examples 1 and 5 provided have improved output characteristics as compared with the battery of Comparative Example 1 containing carbon particles having a shallow buried depth in the current collector and a short major axis length as a conductive agent. Recognize.

  Comparing the batteries of Example 1 and Example 2, it can be seen that the battery of Example 2 using a roughened aluminum foil as the current collector has lower resistance and higher main force.

  When the batteries of Example 1 and Example 3 are compared, the battery of Example 3 in a form in which the other end of the carbon particle embedded in the current collector is opposite to the other end in the long axis direction reaches the surface of the active material-containing layer. It can be seen that the resistance is lower and the output is higher.

  The relationship between Example 1 and Comparative Example 1 (the thickness of the active material-containing layer of the positive electrode and the negative electrode is 28 μm and 35 μm, respectively) and the relationship between Example 4 and Comparative Example 3 (the thickness of the active material-containing layer of the positive electrode and the negative electrode is From the comparison of 52 μm and 65 μm, respectively, it can be seen that a battery with a value of (battery resistance) [mΩ] × (battery capacity) [Ah] smaller than 10 [mΩAh] has a higher output.

  When Examples 1 and 8 are compared with Comparative Example 1, it is preferable for one end of the long axis of the carbon particles to be buried in the current collector to increase the output of the battery, but one end of the long axis is not included. It can be seen that substantially the same effect can be obtained even if part of the structure is buried.

  When Examples 1 and 9 are compared with Comparative Example 1, it is preferable that a part of the carbon particles reach the surface of the active material-containing layer, but the same is true even if the depth corresponding to the active material particle size is submerged. It can be seen that higher output of the battery can be achieved.

The schematic sectional drawing which shows the electrode which concerns on embodiment. The schematic sectional drawing which shows the electrode which concerns on embodiment. The partial notch side view which shows an example of the nonaqueous electrolyte battery concerning this invention. The expanded sectional view of the A section of FIG. Explanatory drawing for determining the long axis of a 1st carbon particle.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Current collector, 2 ... Active material containing layer, 3 ... Carbon particle, 11 ... Bottomed rectangular cylinder, 12 ... Rectangular lid, 13 ... Electrode group, 15 ... Positive electrode, 15a ... Current collector, 15b ... Positive electrode Active material containing layer, 16 ... negative electrode, 16a ... current collector, 16b ... negative electrode active material containing layer, 17 ... separator.

Claims (16)

A current collector made of aluminum foil or aluminum alloy foil, and an active material-containing layer formed on the surface of the current collector and containing an active material, a conductive agent and a binder;
The conductive agent is composed of 30 to 60% by weight of carbon particles including the first carbon particles and 40 to 70% by weight of fine carbon powder compared to the first carbon particles,
The first carbon particles have an aspect ratio exceeding 1, and a part of the first carbon particles is buried in the current collector at a depth of 20 to 50% with respect to the thickness of the current collector, and the first carbon particles Has a length of 1.05 to 1.50 times the thickness of the active material-containing layer.   2. The nonaqueous electrolyte battery according to claim 1, wherein a part of the first carbon particles embedded in the current collector includes one of opposing ends extending in a major axis direction of the first carbon particles. Electrode.   3. The nonaqueous electrolyte battery according to claim 1, wherein a part of the first carbon particles opposite to a part embedded in the current collector reaches the surface of the active material containing layer. 4. Electrode.   A part of the first carbon particles embedded in the current collector includes one of opposing ends extending in the major axis direction, and the other of the opposing ends extending in the major axis direction reaches the surface of the active material containing layer. The electrode for a nonaqueous electrolyte battery according to any one of claims 1 to 3. Wherein the first carbon particles, a portion of the opposite side corresponds to an average particle size of the active material toward the collector from the active material-containing layer surface against a portion to be buried in the collector The electrode for a nonaqueous electrolyte battery according to any one of claims 1 to 4, wherein the electrode is located within a depth range.   6. The electrode for a nonaqueous electrolyte battery according to claim 1, wherein a surface of the current collector on which the active material-containing layer is formed is roughened.   The electrode for a nonaqueous electrolyte battery according to claim 6, wherein a roughening ratio of the current collector is 10 to 120 times.   The carbon particle group has an aspect ratio exceeding 1, and one end in the major axis direction is buried in the current collector at a depth of less than 20% with respect to the thickness of the current collector, or the major axis direction 8. The electrode for a nonaqueous electrolyte battery according to claim 1, further comprising second carbon particles that are not embedded in the current collector. The electrode for a nonaqueous electrolyte battery according to claim 8, wherein the carbon particle group is graphite or coke, and the carbon powder is carbon black. The electrode for a nonaqueous electrolyte battery according to any one of claims 1 to 8, wherein the aspect ratio of the first carbon particles is 1.5 to 100. Nonaqueous of the buried depth of the first carbon particles, according to any one of claims 1 to 8 and 10, characterized in that from 20 to 40% of the thickness of the current collector relative to the current collector Electrode battery electrode. The long axis of the first carbon particles, for a non-aqueous electrolyte battery according to any one of the active claims 1, wherein the material is 1.10 to 1.45 times the thickness of the layer containing 8,10 electrode. The electrode is a positive electrode, and the active material of the positive electrode is lithium nickel composite oxide, lithium cobalt composite oxide, lithium nickel cobalt composite oxide, lithium manganese nickel composite oxide, spinel type lithium manganese composite oxide, lithium manganese cobalt composite The electrode for a nonaqueous electrolyte battery according to any one of claims 1 to 12 , wherein the electrode is selected from an oxide or lithium iron phosphate. The electrode is a negative electrode, and the active material of the negative electrode is lithium titanium oxide or a metal composite oxide containing at least one element selected from the group consisting of Ti and P, V, Sn, Cu, Ni and Fe. It claims 1 to 12 non-aqueous electrolyte battery electrode according to any one characterized in that it is selected. At least a non-aqueous electrolyte battery characterized by comprising as one of claims 1 to 14 or a non-aqueous electrolyte electrode The positive electrode and the negative electrode for battery according. The nonaqueous electrolyte battery according to claim 15 , wherein a value obtained by multiplying the battery resistance [mΩ] and the battery capacity [Ah] is less than 10 mΩAh.

Images