JP2005276604A - Electrode for lithium secondary battery and lithium secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode for a lithium secondary battery and the lithium secondary battery which are superior in short-time output characteristics at low temperatures in a simple and inexpensive way while maintaining a high energy density. <P>SOLUTION: The electrode for the lithium secondary battery is the electrode for the lithium battery having an active material capable of storing or releasing Li ions, at least one kind of material having an electric double layer capacitance or a pseudo-electric double layer capacitance in which a sudden discharge potential descent of the active material at the low temperatures is enabled to suppress, at least one kind of conductive agent, and at least one kind of water soluble organic compound, and a material having the electric double layer capacitance or a pseudo-electric double layer capacitance has an acidic surface functional group. The lithium secondary battery is the battery using this electrode as the positive electrode. With this electrode for the lithium secondary battery, the lithium secondary battery is obtained in which the short-time output at the low temperatures is improved and in which an environmental load is less in manufacturing, and which is inexpensive. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electrode for a lithium secondary battery and a lithium secondary battery, and more particularly to an electrode for a lithium secondary battery that exhibits high output at a low temperature and a lithium secondary battery using the electrode as a positive electrode.

  In recent years, high-performance lithium secondary batteries have been developed as clean energy sources for notebook computers, small portable devices, or automobiles. The on-vehicle power supply has severer usage conditions compared to consumer applications. Specifically, in-vehicle power supplies require high energy density, have high output characteristics at room temperature, and need to start an engine in a cold region. ) For a short time output characteristic for several seconds.

  For example, in order to solve the improvement in battery characteristics such as higher output at room temperature, attempts have been made to reduce the resistance by reducing the electrode thin film, and lithium secondary batteries with improved characteristics to some extent have been provided. ing.

  However, in the above-described prior art lithium secondary battery, a large increase in internal resistance due to the battery material itself (particularly a significant increase in charge transfer resistance at the solid-liquid interface) occurs at a low temperature. The output characteristics were not obtained, and it was very difficult to satisfy the required characteristics.

  Therefore, a material having an electric double layer capacity (for example, carbon having a high specific surface area), a Li-containing transition metal oxide as a positive electrode, a negative electrode containing a carbon material capable of inserting and extracting lithium ions, and an organic containing a lithium salt A lithium secondary battery using an electrolytic solution has been proposed (see, for example, Patent Document 1). Here, the material having the electric double layer capacity functions as a capacitor component that can be charged / discharged at a high speed during discharge, so that the battery voltage drop speed with increasing time constant becomes slow. As a result, the lithium secondary battery using this lithium secondary battery electrode can improve short-time output characteristics at low temperatures.

  Usually, such a lithium battery electrode is formed by applying a paste obtained by dissolving or suspending an active material, a material having an electric double layer capacity, and a binder in an organic solvent to the surface of a current collector made of a metal foil or the like. Are made. However, it has been pointed out that organic solvents have a large environmental impact and cost.

Then, the paste preparation process using the binder which changes an organic solvent into the water which does not have an environmental impact and is low cost, and is further dispersible with water is disclosed (for example, refer patent document 2). However, it has been difficult to produce a paste by using water to disperse a material having an active material, an electric double layer capacity, or a pseudo electric double layer capacity. In other words, these materials have a large specific surface area, and the surface is lipophilic and repels water, so that aggregation is likely to occur. For this reason, there is a problem that pasting is not sufficient, it is difficult to produce a uniform electrode, and desired characteristics cannot be obtained.
JP 2003-234099 A JP 2002-42817 A

  The present invention has been made in view of the above circumstances, and is a lithium secondary battery excellent in short-time output characteristics at low temperatures (hereinafter referred to as low-temperature output) simply and inexpensively while maintaining a high energy density. Providing an electrode for use and a lithium secondary battery is a problem to be solved.

  As a result of intensive studies for the purpose of solving the above problems, the present inventors have found that an active material capable of inserting and extracting Li ions, at least one material having an electric double layer capacity or a pseudo electric double layer capacity, and hydrophilicity An electrode for a lithium battery having a composite layer containing at least one water-soluble organic compound for dispersing a low-density material, wherein the material having the electric double layer capacity or pseudo electric double layer capacity is an acidic surface functional It is characterized by having a group. By employing the electrode for a lithium secondary battery of the present invention as an electrode of a lithium secondary battery, low temperature output can be satisfied easily and inexpensively while maintaining a high energy density. A material having an electric double layer capacity or a pseudo electric double layer capacity can suppress a rapid discharge potential drop at a low temperature of the active material.

  In the electrode for a lithium secondary battery of the present invention, as a means for improving the low temperature output, a material having an electric double layer capacity or a pseudo electric double layer capacity is contained in the electrode mixture in addition to the active material. A material having an electric double layer capacity or a pseudo electric double layer capacity is made hydrophilic by introducing an acidic surface functional group so as to be mixed with water, and dispersibility is improved also by a water-soluble organic compound contained therein. As a result, the active material and the material having the electric double layer capacity or pseudo electric double layer capacity can be well dispersed in water, so that the effect of including the material having the electric double layer capacity or pseudo electric double layer capacity is sufficiently exhibited. In addition, the environmental load and cost can be reduced due to the fact that water can be used as the solvent.

  Further, the lithium secondary battery of the present invention comprises an active material capable of inserting and extracting Li ions, at least one material having an electric double layer capacity or a pseudo electric double layer capacity, and at least one water-soluble organic compound. A lithium secondary battery using an electrode for a lithium secondary battery having a composite material layer, wherein the material having an electric double layer capacity or pseudo electric double layer capacity has an acidic surface functional group .

  In the present specification, a material having an electric double layer capacity or a pseudo electric double layer capacity is hereinafter referred to as an “electric double layer material”.

  The electric double layer material has an acidic functional group, so that the surface of the electric double layer material can be made hydrophilic and can be made into a paste using water as a solvent, contributing to the improvement of battery characteristics. Yes.

  The lithium secondary battery of the present invention includes an electric double layer material having an acidic surface functional group in the positive electrode of the lithium secondary battery, so that lithium having a low temperature output easily and inexpensively while maintaining a high energy density. It is a secondary battery.

(Electrode for lithium secondary battery)
The electrode for a lithium secondary battery of the present invention has a composite layer containing an active material capable of inserting and extracting Li ions, at least one electric double layer material, and at least one water-soluble organic compound. The electric double layer material has an acidic surface functional group. The acidic surface functional group is a functional group mainly introduced into the surface, but it does not exclude having inside.

  Examples of the electric double layer material include a carbon material and a conductive polymer material. In order to obtain a practical electric double layer capacity in a carbon material, it is required to have a high specific surface area and high conductivity. Examples of the carbon material having a high specific surface area include activated carbon and carbon black. Here, the starting material of the carbon material is an organic compound and often has some kind of functional group. However, since a normal carbon material is heat-treated at a high temperature, the starting material has Almost no functional group remains and has a lipophilic surface. Further, in the conductive polymer material, the acidic surface functional group that exhibits hydrophilicity has a small contribution to the conductivity, and does not have an acidic surface functional group unless special treatment is performed during synthesis.

  The amount of the acidic surface functional group possessed by the electric double layer material can be defined by the ion exchange capacity. For example, it is 0.30 meq / g or more, preferably 0.35 meq / g or more, more preferably 1.0 meq / g or more, and preferably 3.0 meq / g or less. When it is 0.30 meq / g or more, it can be easily pasted. The acidic surface functional group traps lithium ions that are cations. Therefore, by setting it to 3.0 meq / g or less, the trap of lithium ions becomes negligible, and an increase in resistance value caused by the influence on the movement of lithium ions can be suppressed.

  The amount of the acidic surface functional group possessed by the electric double layer material can also be defined by the O / C ratio (oxygen / carbon ratio). For example, it is 0.05 or more, preferably 0.08 or more. When it is 0.05 or more, a paste can be easily formed. The O / C ratio is calculated from the area ratio of the peak derived from oxygen and the peak derived from carbon measured by X-ray photoelectron spectroscopy (XPS). When the O / C ratio was measured using an actual sample having an ion exchange capacity of 0.6 meq / g, it was 0.089.

  Even if the range of ion exchange capacity is not included in the preferable range, the range of O / C ratio may be included in the preferable range. On the contrary, even if the range of the ion exchange capacity is included in the preferable range, the range of the O / C ratio may not be included in the preferable range. In the electric double layer material employed in the present invention, if any value of the ion exchange capacity and the O / C ratio is within the preferred range, the amount of the acidic surface functional group is judged to be within the preferred range. Needless to say, it is more preferable that both values fall within the preferred range.

  The method for introducing the acidic surface functional group is not particularly limited. For example, a carboxy group or a phenolic OH group can be introduced by heating in the presence of oxygen. Moreover, it can introduce | transduce by making it react in oxygen atmosphere after low temperature plasma irradiation, or making it contact with a flame. A chemical method is simple and preferable.

When the electric double layer material is a carbon material, the amount and type of acidic surface functional groups can be determined by the BOEHM method. The BOEHM method is a method in which surface oxides present on the surface of activated carbon are neutralized with alkali, and the amount and type of acidic surface functional groups are determined from the amount of alkali consumed by neutralization. The types of acidic surface functional groups are classified as follows.
I: Carboxyl group
II: Lactone group
III: Phenolic hydroxyl group
IV: Carbonyl group The amount of the acidic functional group can be determined from the total amount of these functional groups I to IV.

  When the electric double layer material is a conductive polymer material, the introduced functional group may not be the above, but the total amount of the functional group can be obtained by the same neutralization titration method.

The electric double layer material desirably has a powder compression resistance of 10 ⁷ Ωcm or less when compressed at 15.7 MPa (converted from 160 kgf / cm ² ). Desirably, it is 10 ⁶ Ωcm or less. By having high electrical conductivity, it has higher output characteristics at room temperature.

  The amount of the electric double layer material that can maintain the energy density of the lithium secondary battery at a sufficient level is preferably 20% by mass or less, more preferably 13. The amount added is 3% by mass.

  The electric double layer material preferably has a capacitance at −30 ° C. of 93 F / g or more. When the electric double layer material has a capacitance of 93 F / g or more at −30 ° C., a high low-temperature output can be exhibited.

The electric double layer material is desirably either a carbon material or a conductive polymer material having a specific surface area of 1200 m ² / g or more. The specific surface area can be measured by the BET method using nitrogen gas. In the carbon material, when the specific surface area is 1200 m ² / g or more, sufficient adsorption of electrolyte ions can be realized, so that sufficient battery characteristics can be achieved. Furthermore, when the specific surface area is 3000 m ² / g or less, the handleability at the time of electrode preparation is improved (improvement of bulk density, etc.).

  The pores of the electric double layer material preferably have a large pore diameter in order to improve low temperature output. When the pore diameter is large, a decrease in ion mobility and a decrease in wettability of the electrolyte due to an increase in the viscosity of the electrolyte at low temperatures can be effectively prevented, resulting in an improvement in low-temperature output.

  In order to achieve both energy density and low temperature output characteristics, the electric double layer material has a pore diameter of 2 nm or more (preferably defining 50 nm as the upper limit of the pore diameter) and a pore volume of 0.418 mL / It is preferable to contain g or more electric double layer material in the composite layer of the electrode for lithium secondary battery. The pore volume is a method of calculating the pore distribution by nitrogen gas adsorption, and can be measured by a BJH (Barrett-Joyner-Halenda) method suitable for analyzing pores of 2 nm or more.

  The conductive polymer material as the electric double layer material is a material having a pseudo electric double layer capacity by a redox reaction in part or all of the battery operating voltage range. For example, conductive polymer materials include polyaniline, poly (P-phenylene), poly (2,5-pyridinediyl), polyphenylene sulfide, polyphenylene oxide, polythiophene, polypyrrole, polyacene, polyazulene, polyphenylene vinylene, and derivatives thereof. Can be mentioned. The derivative can be selected within a range that does not impair the conductivity. A preferable conductive polymer material differs depending on the case where it is used for the positive electrode and the negative electrode, respectively. What has good voltage matching with the active material adopted for the positive and negative electrodes (that is, the potential of high capacity charge / discharge is close to the Li-based potential) may be selected.

  As an acidic surface functional group of the conductive polymer material, for example, a carboxyl group, a hydroxyl group, a sulfone group, a methoxy group or the like can be arbitrarily introduced to make it hydrophilic.

  Even if the electric double layer material is only used for either the positive or negative electrode, a sufficient low-temperature output improvement effect can be exhibited. It is preferable to employ it for an electrode having a large reaction resistance of the active material. In general, it is preferably applied to the positive electrode. Needless to say, the above configuration is more effective when applied to both the positive electrode and the negative electrode.

  The water-soluble organic compound is desirably anionic or nonionic with an HLB of 4 or more, and is preferably selected from a polymer material that also functions as a binder. HLB means the hydrophilic / lipophilic balance, and is a value calculated based on the number of Davis groups determined for each hydrophilic group or lipophilic group [HLB = 7 + Σ (the number of hydrophilic groups) + Σ (the number of lipophilic groups) ]]. Examples of the polymer material as the water-soluble organic compound include celluloses such as methylcellulose (MC), carboxymethylcellulose (CMC), ethylcellulose (EC), hydroxyethylcellulose (HEC), hydroxypropylmethylcellulose (HPMC), and hydroxyethylmethylcellulose (HEMC). And polyacrylates, polyethylene oxide (PEO), and polyvinyl alcohol (PVA). In addition, various anionic dispersants, various nonionic dispersants, and the like can be given. It is desirable to use one or more of these materials.

  The manufacturing method of the electrode for lithium batteries is not specifically limited. For example, a composite paste is prepared by dissolving or suspending an active material, an electric double layer material, a water-soluble organic compound, and a conductive agent or binder contained as necessary in an aqueous solvent (such as water). It can be produced by applying and drying the composite paste on the surface of an appropriate current collector or the like.

(Application to positive electrode)
When the electrode for a lithium secondary battery of the present invention is used for a positive electrode, a positive electrode active material is employed as the active material.

  The positive electrode is composed of a positive electrode active material, an electric double layer material, a conductive agent, and a binder. When the electrode for the lithium secondary battery of the present invention is used for a positive electrode, the electric double layer material includes activated carbon, carbon aerogel, expanded carbon, expanded carbon, hard carbon, and other carbonaceous materials, As the molecular material, polyaniline, a derivative thereof, and the like having good voltage matching with the battery material can be used. The electric double layer material is preferably activated carbon capable of easily obtaining a pore structure having a high specific surface area at low cost.

The activated carbon activation method is not particularly limited. Water vapor activation, CO ₂ activation, chemical activation and the like can be mentioned. Two or more of these activation methods may be combined. However, it is preferable that chemical activation (at least, the presence of enlarged macropores is small and volumetric efficiency is good) is performed at least. In addition, as chemicals to be activated, potassium hydroxide, sodium hydroxide, lithium hydroxide, zinc chloride and the like have the effect of eroding and dissolving a part of the raw material, so that mesopores having a high electric double layer capacity at low temperature The above pores are preferable because they are easy to make. Of these, potassium hydroxide is preferably used in terms of increasing the specific surface area and the mesopore volume.

  The raw material for the activated carbon is not particularly limited. For example, phenolic materials and woody materials (cellulosic materials such as wood chips and coconut shells, and starch materials such as chestnuts) can be mentioned. A woody material is preferable because chemicals such as potassium hydroxide, sodium hydroxide, lithium hydroxide, and zinc chloride are easily penetrated to form mesopores.

  The size of the pores is mainly classified as follows according to IUPAC (International Union of Pure and Applied Chemistry).

Micropores: 2 nm or less (regions that are mainly attracting attention as materials for conventional electric double layer capacitors)
Mesopore: 2 nm to 50 nm (region in which pore volume is defined in the present invention)
Macropores: 50 nm or more positive electrode active material, at least one element formula _{Li x Ni 1-y M y} O 2 (M is Co, Mn, Al, B, Ti, Mg, selected from among Fe, 0 <x It is preferable to use a positive electrode active material made of a compound represented by ≦ 1.2, 0 <y ≦ 0.25). Furthermore, a value obtained by dividing the sum of the diffraction intensity I ₀₀₆ attributed to the 006 plane and the diffraction intensity I ₁₀₂ attributed to the 102 plane by the crystal structure analysis using X-ray diffraction by the diffraction intensity I ₁₀₁ attributed to the 101 plane ( It is preferable to use a positive electrode active material in which I ₀₀₆ + I ₁₀₂ ) / I ₁₀₁ is 0.36 to 0.42. LiNi _0.82 Co in which only the intensity ratio (I ₀₀₆ + I ₁₀₂ ) / I ₁₀₁ was changed by changing the mixing ratio of raw materials at the time of active material synthesis, firing temperature, and atmosphere (oxygen concentration, dew point, CO ₂ content, etc.) As a result of producing _0.15 Al _0.03 O ₂ , when the strength ratio was larger than 0.42, the internal resistance after cycle evaluation increased rapidly. This is thought to be due to the fact that crystal defects in the initial stage inhibit diffusion of lithium ions to become a resistance component, further generation of an impurity layer accompanying charge / discharge cycles, and increase in strain due to expansion and contraction of the active material. Further, when the peak intensity ratio (I ₀₀₆ + I ₁₀₂ ) / I ₁₀₁ is smaller than 0.36, it is considered that the number of crystal defects decreases and the inhibition of lithium ion diffusion decreases, but the rate of increase in internal resistance increases. The reason for this is not clear, but it seems that a small amount of crystal defects suppresses the change in the crystal structure of the active material to some extent in a state like a pinning effect of strain. Moreover, this effect is not impaired even if it mixes positive electrode active materials, such as another lithium oxide, in arbitrary ratios as a positive electrode active material, and it is a lithium secondary battery.

  The positive electrode active material desirably has an average particle size of 2 to 15 μm. When the average particle size is 2 μm or less, the reactivity with the electrolytic solution increases, and the discharge capacity deterioration and the internal resistance increase in the charge / discharge cycle may increase. On the other hand, when the average particle size is 15 μm or more, the filling property to the electrode is poor and the battery capacity may be reduced.

The positive electrode active material is preferably a BET specific surface area measured by nitrogen gas adsorption is 0.2m ² /g~1.5m ² / g. When the BET specific surface area is 0.2 m ² / g or less, the wettability with the electrolytic solution is poor and the effective discharge capacity is reduced. Further, when the BET specific surface area is 1.5 m ² / g or more, the reactivity with the electrolytic solution is increased, and the discharge capacity deterioration and the internal resistance increase in the charge / discharge cycle are increased.

  The amount of the electric double layer material such as activated carbon in the positive electrode mixture layer is preferably 13.3% by mass or less in order to achieve a sufficient energy density of the lithium secondary battery. If added more than this, the energy density of the lithium secondary battery at room temperature decreases due to the decrease in electrode density.

As the conductive agent, it is desirable to use carbon black having a specific surface area of 30 m ² / g or more by the BET method. It is preferably 500 m ² / g or more, more preferably 700 m ² / g or more, and preferably 3000 m ² / g or less, more preferably 2000 m ² / g or less. Such a high specific surface area carbon black is not particularly limited, and examples thereof include special furnace black (for example, “Ketjen Black” manufactured by Ketjen Black International).

  In addition, the average particle diameter of carbon black is preferably 1 nm or more and preferably 5 nm or more from the viewpoint of production as a primary particle diameter, and usually from the aspect of imparting conductivity to the electrode active material-containing composition. It is preferably 500 nm or less and 100 nm or less.

If the specific surface area of the carbon black in the present invention is less than 30 m ² / g, the effect of improving the low-temperature output tends to be reduced, whereas if it is 3000 m ² / g or more, the bulk density as the electrode active material-containing layer is reduced, The capacity per volume becomes small.

  As the water-soluble organic compound, an anionic or HLB which is a water-soluble organic compound constituting the electrode in the present invention is selected from nonionic polymers having 4 or more, and has an excellent function as a dispersant and has an adhesive property. High CMC and PEO are desirable. CMC and PEO also function as a binder.

  Furthermore, it is desirable to add an aqueous dispersion resin having flexibility and excellent electrolytic solution resistance as a binder. By adding the aqueous dispersion resin, the electrode has flexibility at the time of manufacture, so that the electrode layer is prevented from being damaged due to cracking or dropping off of the composite layer when handling or winding the sheet-like positive electrode. can do.

  Moreover, by being excellent in electrolytic solution resistance, swelling and dissolution with respect to the electrolytic solution can be prevented, and damage to the electrode can also be prevented.

  Examples of the aqueous dispersion resin include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), and tetrafluoroethylene. Fluorine resin resins such as ethylene-ethylene copolymer (ETFE), tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether copolymer (EPE), acrylic resins, olefins such as polyethylene and polyolefin, polyimide resins, etc. And water-dispersed resin having excellent organic solvent resistance. In particular, it is desirable to use PTFE excellent in electrolytic solution resistance.

(Application to negative electrode)
When the electrode for a lithium secondary battery of the present invention is used for a negative electrode, a negative electrode active material is employed as the active material.

  When the electrode for a lithium secondary battery of the present invention is used for a negative electrode, the electric double layer material may be a conductive high-capacity material having a pseudo electric double layer capacity, in which Li ions do not intercalate and are not reduced at the negative electrode potential. It is preferable to employ a molecular material. This is because an irreversible capacity tends to increase in a carbon material such as activated carbon in which Li ions are intercalated. In particular, polythiophene, polyacetylene, poly (2,5-pyridinediyl), poly-p-phenylene and the like, which are n-type conductive polymer materials that are not easily reduced, are preferable.

  The negative electrode active material is not particularly limited as long as it is a material that can occlude and release lithium ions. Examples thereof include carbonaceous materials such as lithium metal, graphite, and amorphous carbon. A carbonaceous material that is an intercalating material that can be occluded / released electrochemically without causing precipitation of dendritic lithium that causes lithium to be short-circuited or the like is more preferable. Since the carbonaceous material has a relatively large specific surface area and a high rate of occlusion / release of lithium ions, it has the effect of improving the output / regeneration density particularly at room temperature.

The negative electrode active material preferably has a BET specific surface area of 3.5 m ² / g or less. The BET specific surface area of the negative electrode active material is more preferably 3.0 m ² / g or less. By setting the specific surface area of the negative electrode active material to 3.5 m ² / g or less, side reactions caused by the negative electrode active material and the electrolytic solution can be suppressed. As a result, the life of the lithium secondary battery can be extended.

  The method for producing the negative electrode active material is not particularly limited. Since the specific surface area greatly affects the specific surface area of the raw material, the raw material is preferably fired after being pulverized and / or classified under predetermined conditions. Moreover, you may grind | pulverize and / or classify | categorize after baking.

(Lithium secondary battery)
The lithium secondary battery of the present invention is a lithium secondary battery using the lithium battery electrode as a positive electrode or a negative electrode. In particular, application to the positive electrode is effective and preferable. Since the lithium battery electrode of the present invention is as described above, further description is omitted. For electrodes not employing the lithium battery electrode of the present invention, known electrodes can be employed as they are. Furthermore, an electrode in which the electric double layer material is omitted from the above-described positive and negative electrodes of the present invention can be employed.

  The lithium secondary battery of the present invention is a battery that employs the above-mentioned electrode for a lithium secondary battery, and conventionally known ones can be used for other elements such as an electrolytic solution and a separator. Further, the lithium secondary battery of the present invention is not particularly limited in its shape, and can be batteries having various shapes such as a coin shape, a cylindrical shape, and a square shape.

The electrolytic solution is preferably obtained by dissolving a supporting salt in a solvent. Examples of the solvent include 1,2-dimethoxyethane, 1,2-diethoxyethane, propylene carbonate, ethylene carbonate, γ-butyrolactone, tetrahydrofuran, 1,3-dioxolane, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, and the like. Single or 2 or more types of mixed solvents are mentioned. Examples of the supporting salt include LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiClO ₄ , LiPF ₆ , LiBF ₄ , LiN (CF ₃ SO ₂ ) (CF ₃ SO ₂ ), LiN (C ₄ F ₉ SO ₂ ) ( CF ₃ SO ₂ ), LiN (C ₂ F ₅ SO ₂ ) (C ₂ F ₅ SO ₂ ) and other supporting salts may be used alone or in combination of two or more.

  As the separator, a microporous polypropylene film, a microporous polyethylene film, a polymethylpentene nonwoven fabric separator or the like having a thickness of 10 to 50 (μm) and a porosity of 30 to 70% can be used.

  As one form of the lithium secondary battery of the present invention, a configuration of a cylindrical lithium secondary battery is given.

  Cylindrical lithium secondary batteries are housed in a predetermined cylindrical case together with a wound body in which a positive electrode and a negative electrode are formed into a sheet shape, stacked together via a separator and wound in a spiral shape, and an electrolyte filling the gap. It is a thing. Further, the positive electrode and the positive electrode terminal portion of the case, and the negative electrode and the negative electrode terminal portion of the case are electrically joined to each other.

  The method for producing the lithium secondary battery of the present invention is not particularly limited. For example, in the above cylindrical lithium secondary battery, a sheet-like positive and negative electrode is manufactured, the positive electrode and the negative electrode are wound with a separator interposed therebetween, and an electrode body is manufactured. And enclosed in a case. A cylindrical lithium secondary battery can be manufactured by such a procedure.

  The lithium secondary battery of the present invention has a slow battery voltage drop speed with an increase in time constant, and the lithium secondary battery using the lithium secondary battery electrode of the present invention has a short-time output at a low temperature. Shows the effect of obtaining an improved lithium secondary battery. The lithium battery of the present invention is a lithium secondary battery having excellent low-temperature output characteristics, and can be suitably used as an in-vehicle power source.

  Hereinafter, the present invention will be described using examples.

  As an example of the present invention, an electrode for a lithium secondary battery and a lithium secondary battery were produced. The measurement of the surface functional group, capacitance, particle size, specific surface area, and pore distribution of the activated carbon used as the electric double layer material in the positive electrode of the lithium secondary battery was performed according to the following procedure. .

<< Measurement of acidic surface functional groups: BOEHM method >>
1 g of electric double layer material was accurately weighed into each of three 50 ml centrifuge tubes. 30 mL of one of the following three types of alkaline solutions was added to each centrifuge tube and shaken for 6 hours.
(1) 0.1 mol / L sodium hydroxide aqueous solution (2) 0.05 mol / L sodium carbonate aqueous solution (3) 0.01 mol / L sodium hydrogen carbonate aqueous solution After shaking, the electric double layer material and the aqueous phase are centrifuged. And the supernatant was filtered through a membrane filter (0.45 μm). 20 ml of this filtrate was titrated under the following conditions. (1) to (3) The amount of the acidic surface functional group was calculated from the sum of the titration values in the alkaline solution.
・ Apparatus: COM-2500 type Hiranuma automatic titration apparatus Hiranuma Sangyo Co., Ltd.
・ Titration solution: 0.1 mol / L hydrochloric acid aqueous solution ・ Maximum dropping amount: 30 mL
<Capacitance measurement>
An electrochemical capacitor was produced, and the produced electrochemical capacitor was charged at a constant temperature of −30 ° C. using a potentio galvanostat (HA-501G manufactured by Hokuto Denko Corporation) at an applied voltage of 2.0 V for 5 minutes. After a rest time of 2 minutes, the battery was discharged at 0.3 mA. The electrostatic capacity is 1.0 V from the charging voltage, and the slope dV / dt shown in the figure is obtained by the least square method from the relationship between the voltage and time of the discharge curve shown in FIG. The electrostatic capacity per unit was determined.

  Here, C is the capacitance per activated carbon mass, I is the current, dV / dt is the slope in FIG. 1, and W is the activated carbon mass per single electrode.

<Measurement of particle size>
The particle size distribution was measured using “HRA9320-X100 type microtrack” manufactured by Nikkiso Co., Ltd., and the average particle size D50 was determined.

<< Measurement of specific surface area >>
The specific surface area by nitrogen adsorption BET method was measured using “NOVA2000 type BET specific surface area measuring device” manufactured by Canterchrome.

<< Measurement of pore distribution >>
The measurement was performed under the following conditions using a “BELSORP 36 high-precision fully automatic gas adsorption device” manufactured by Nippon Bell Co., Ltd. Adsorption gas: N2, dead volume: He, adsorption temperature: liquid nitrogen temperature (77K), pretreatment for measurement: vacuum degassing at 150 ° C, measurement mode: adsorption / desorption at isothermal, measurement range: relative pressure (P / P0) ) = 0.00 to 0.99, Equilibrium time: 180 sec for each equilibrium relative pressure, Analytical method: BJH method, Pore diameter range: 20.0 mm to 400 mm (Because the minimum change width of P / P0 is 0.05, the lower limit is 20) .0Å was 19.2Å or 21.6Å, so it was closer to 19.2Å).

<Measurement of peel strength>
After the electrode is punched out with a length of 55 mm and a width of 30 mm, a polyester tape (612S manufactured by Teraoka Seisakusho Co., Ltd., 612S) having a length of 100 mm and a width of 6 mm is sufficiently adhered to the center of the width of the punched electrode. Thereby, the peel strength measuring electrode (see FIG. 2) with the tape portion extending in the 45 mm length direction is obtained.

  In the obtained electrode with tape, an electrode portion to which no tape is attached is fixed with a jig, and a tape portion protruding from the electrode in the length direction is sandwiched between load cells. The peel strength was measured by moving the load cell at −200 mm / min in the −X direction shown in FIG.

(Example 1)
(Activated carbon)
First, activated carbon as an electric double layer material is carbonized using coconut shell as a raw material, then an alkali solution is included, a water vapor activation method is performed, and then heat treatment is performed in an oxygen atmosphere to impart an acidic functional group. Manufactured by. The amount of the acidic functional group of the obtained activated carbon was 1.15 meq / g, the pore volume with a pore diameter of 20 mm or more by the BJH method was 1.501 mL / g, and the BET specific surface area was 1900 m ² / g.
(Positive electrode for capacitance measurement)
N-methyl was added to a mixture comprising 35 parts by mass of the activated carbon, 50 parts by mass of acetylene black (HS-100, manufactured by Denki Kagaku Kogyo Co., Ltd.) having a specific surface area of 40 m ² / g as a conductive agent, and 15 parts by mass of polyvinylidene fluoride as a binder. -2-Pyrrolidone was added and kneaded, coated on a 15 μm aluminum foil, and then dried in the air at 60 ° C. for 3 hours. After drying, the sheet is punched to a diameter of 15 mm, the punched sheet is pressed, the thickness excluding the aluminum foil is 50 μm (the total thickness of the sheet including the aluminum foil is 65 μm), and the mass excluding the aluminum foil is 2. 0 mg of polarizable electrode was obtained.
(Negative electrode for capacitance measurement)
98 parts by weight of flaky graphite and 2 parts by weight of carboxymethylcellulose sodium salt aqueous solution are mixed so that the solid content of sodium carboxymethylcellulose as an anionic water-soluble organic compound is 1 part by weight, and further an aqueous dispersion resin As follows, water was added to a mixture consisting of 1 part by mass of SBR, kneaded, applied onto a 10 μm copper foil, and then dried in the air at 60 ° C. for 3 hours. After drying, the sheet is punched to a diameter of 15 mm, the punched sheet is pressed, the thickness excluding the copper foil is 50 μm (the total thickness of the sheet including the aluminum foil is 65 μm), and the mass excluding the copper foil is 2. 0 mg of negative electrode was obtained.

  Thus, by using the negative electrode which is not affected by the acidic surface functional group, the capacitance of only the positive electrode can be accurately measured. These positive and negative electrodes were vacuum-dried at 120 ° C., then transferred into a glove box in an argon atmosphere, and faced through a microporous separator (trade name: UP3025, manufactured by Ube Industries) to form an element, 1 mol / L A cell was prepared by impregnating a mixed solution composed of 30 parts by mass of ethylene carbonate containing 30 parts by mass of ethyl carbonate, 30 parts by mass of ethyl methyl carbonate, and 40 parts by mass of dimethyl carbonate. The cell was inserted into a coin type case made of stainless steel (SUS316) and an insulating gasket made of polypropylene, and the coin type case was caulked and sealed to obtain a coin type electrochemical capacitor. It was 110 F / g when the electrostatic capacitance in -30 degreeC of the obtained electrochemical capacitor was measured. That is, the produced activated carbon had a capacitance at −30 ° C. of 110 F / g.

  Using this electric double layer material, a lithium secondary battery was produced by the following procedure.

(Manufacture of positive electrode)
To 87 parts by mass of lithium nickel oxide as a positive electrode active material, 2.6 parts by mass of Ketjen black (manufactured by Ketjen Black International: ECP-600JD) as a conductive agent, and 4 parts by mass of the activated carbon as an electric double layer material, 2% by weight carboxymethylcellulose sodium salt aqueous solution is mixed so that the solid content of sodium carboxymethylcellulose as an anionic water-soluble organic compound is 1 part by mass, and further polyethylene oxide powder as a nonionic water-soluble organic compound (HLB20) 1 part by mass and a predetermined amount of water were mixed and stirred for 30 minutes with a circulating stirrer. Thereafter, PTFE having a solid content ratio of about 50% as an aqueous dispersion resin was added so that the solid content of PTFE was 1 part by mass, and the mixture was stirred for 10 minutes using a circulating stirrer. The total solid content at the time of manufacturing the positive electrode was 97.6 parts by mass. The paste thus obtained was applied onto both sides of an aluminum foil with a comma coater at a basis weight of 4.92 (mg / cm ² ) per side. Next, this electrode was passed through a roll press to increase the electrode density to 2.10 (g / cm ³ ). Next, this electrode was cut into a width of 5.4 (cm) and a length of 90 (cm), and an electrode mixture for a length of 2.5 (cm) was scraped off as a lead tab weld for extracting current. The effective reaction area of this electrode is 5.4 (cm) × 87.5 (cm) × 2 = 945 (cm ² ). The peel strength of the electrode was 119 mN.

(Manufacture of negative electrode)
In the negative electrode, 98 parts by mass of flaky graphite as a negative electrode active material and a 2% by weight carboxymethylcellulose sodium salt aqueous solution are mixed so that the solid content of sodium carboxymethylcellulose as an anionic water-soluble organic compound is 1 part by mass. Further, 1 part by mass of SBR as an aqueous dispersion resin and a predetermined amount of water were mixed, and a paste in which graphite was dispersed was applied to a copper foil on a copper foil using a comma coater in the same manner as the positive electrode 3.36 mg / mg cm ² ). Thereafter, an electrode having an electrode density increased to 1.28 (g / cm ³ ) was produced through a roll press. Next, this electrode was cut into a width of 5.6 (cm) and a length of 94 (cm), and an electrode mixture for a length of 0.5 (cm) was scraped off as a lead tab weld for taking out the electrode. The effective reaction area of this electrode is 5.6 (cm) × 93.5 (cm) × 2 = 1047.2 (cm ² ).

(Battery assembly)
The sheet-like positive electrode and the sheet-like negative electrode obtained above were wound with a separator interposed therebetween to form a wound electrode body. A separator made of polyethylene having a thickness of 25 μm was used. The obtained wound electrode body was inserted into the case and held in the case. At this time, the current collecting lead having one end welded to the lead tab weld portion of the sheet-like positive electrode and the sheet-like negative electrode was joined to the positive electrode terminal or the negative electrode terminal of the case. Then, after inject | pouring electrolyte solution in the case where the winding type electrode body was hold | maintained, the case was sealed and sealed.

  The cylindrical lithium secondary battery of this example having a diameter of 18 mm and an axial length of 65 mm was manufactured by the above procedure.

(Comparative Example 1)
Activated carbon was produced in the same manner as in Example 1 except that heat treatment was not performed in an oxygen atmosphere. The amount of the acidic functional group is 0.22 meq / g, the pore volume with a pore diameter of 20 mm or more by the BJH method is 1.360 mL / g, the BET specific surface area is 1900 m ² / g, and the capacitance at −30 ° C. is 110 F / g.

  Using this activated carbon, an attempt was made to produce a positive electrode in the same manner as in Example 1. However, agglomeration occurred frequently at the time of producing the paste, a sufficiently dispersed paste could not be produced, and a battery could not be produced.

(Example 2)
The lithium secondary battery is the same as that of Example 1 except that activated carbon obtained by subjecting activated carbon as an electric double layer material to chemical activation simultaneously with carbonization of a wood chip material is used.

In addition, the amount of acidic functional groups of the activated carbon produced from the wood chips used in this example is 0.68 meq / g, the pore volume of pore diameters of 20 mm or more is 1.464 mL / g, and the BET specific surface area is 1800 m ² / g. The electrostatic capacity at −30 ° C. was 108 F / g, and the peel strength of the electrode was 87 mN.

(Example 3)
The lithium secondary battery is the same as that of Example 1 except that activated carbon obtained by a steam activation method using wood chips as a raw material is used as the electric double layer material.

In addition, the acidic functional group amount of the activated carbon used in this example is 0.39 meq / g, the pore volume of pore diameter 20 mm or more is 0.418 mL / g, the BET specific surface area is 1200 m ² / g, at −30 ° C. The capacitance was 93 F / g, and the peel strength of the electrode was 64 mN.

Example 4
Except for the use of carbon materials obtained by carbonization, steam activation, and heat treatment in an oxygen atmosphere using carbon aerogel (MarkeTech International Inc.) as a raw material by supercritical drying of polyvinylidene fluoride as the electric double layer material A lithium secondary battery similar to that of Example 1.

The amount of acidic functional groups of the carbon material used in this example is 0.36 meq / g, the pore volume with a pore diameter of 20 mm or more by the BJH method is 1.650 mL / g, the BET specific surface area is 1200 m ² / g, The capacitance at −30 ° C. was 105 F / g, and the peel strength of the electrode was 57 mN.

(Example 5)
The lithium secondary battery is the same as that of Example 1 except that polyaniline having a sulfone group introduced therein is used as the electric double layer material.

  The amount of acidic functional groups of the polyaniline used in this example was 1.0 meq / g, the capacitance at −30 ° C. was 105 F / g, and the peel strength of the electrode was 210 mN.

(Comparative Example 2)
As the electric double layer material, activated carbon obtained by a steam activation method using phenol as a raw material was used.

In addition, the acidic functional group amount of the activated carbon used in this example is 0.26 meq / g, the pore volume of pore diameter 20 mm or more is 0.153 mL / g, the BET specific surface area is 2000 m ² / g, at −30 ° C. The capacitance was 63 F / g.

  Using this activated carbon, an attempt was made to produce a positive electrode in the same manner as in Example 1. However, agglomeration occurred frequently at the time of producing the paste, a sufficiently dispersed paste could not be produced, and a battery could not be produced.

(Comparative Example 3)
As the electric double layer material, activated carbon obtained by an alkali activation method using phenol as a raw material was used.

In addition, the acidic functional group amount of the activated carbon of the activated carbon used in this example is 0.20 meq / g, the pore volume of pore diameter 20 mm or more is 0.167 mL / g, the BET specific surface area is 2300 m ² / g, −30 The capacitance at 0 ° C. was 80 F / g.

  Using this activated carbon, an attempt was made to produce a positive electrode in the same manner as in Example 1. However, agglomeration occurred frequently at the time of producing the paste, a sufficiently dispersed paste could not be produced, and a battery could not be produced.

(Example 6)
A lithium secondary battery was produced in the same manner as in Example 1 except that the activated carbon as the electric double layer material was changed to 5 parts by mass. The total solid content at the time of producing the positive electrode was 98.6 parts by mass, and the basis weight was 4.96 (mg / cm ² ).

(Example 7)
A lithium secondary battery was produced in the same manner as in Example 1 except that 10 parts by mass of activated carbon as the electric double layer material was added so that the solid content of PTFE was 4 parts by mass in order to improve the peel strength. In addition, the total of solid content at the time of manufacture of a positive electrode was 105.6 mass parts, and the fabric weight was 5.31 (mg / cm < ² >).

(Example 8)
A lithium secondary battery was produced in the same manner as in Example 1 except that the active carbon as an electric double layer material was added in an amount of 15 parts by mass and the solid content of PTFE was 6 parts by mass in order to improve the peel strength. The total solid content at the time of manufacturing the positive electrode was 112.6 parts by mass, and the basis weight was 5.67 (mg / cm ² ).

Example 9
A lithium secondary battery was produced in the same manner as in Example 1 except that the active carbon as an electric double layer material was 20 parts by mass and that the solid content of PTFE was 11 parts by mass in order to improve the peel strength. The total solid content at the time of manufacturing the positive electrode was 119.6 parts by mass, and the basis weight was 60.2 (mg / cm ² ).

(Example 10)
Example 9 is a lithium secondary battery manufactured in the same manner as in Example 1 except that the positive electrode shown below was used. The positive electrode active material was coated with 86.9 parts by mass of the lithium nickel oxide as the positive electrode active material and 4.1 parts by mass of Ketjen black (product number: ECP-600JD) as the conductive agent.

  As a method for coating the active material with the conductive agent, a film forming apparatus using a mechanochemical reaction shown in FIG. 3 was used. This film forming apparatus has a rotating drum 1 having an internal space 10, and a press shear head 3, a fixed shaft 2, a first arm 4, a claw 5, and a second arm 6 are provided in the internal space 10. ing.

  The pressing shear head 3 is provided with a slight gap with respect to the inner peripheral surface of the rotary drum 1. The pressure shearing head 3 has a surface that is provided outwardly in the radial direction of the rotating drum 1 and has a larger curvature than the inner peripheral surface of the rotating drum 1, and the side opposite to the surface is fixed to the tip of the first arm 4. Has been. The other end of the first arm 4 is fixed to a fixed shaft 2 inside the rotary drum 1.

  The fixed shaft 2 has a second arm at a predetermined angle behind the first arm 4 when the rotary drum 1 is rotated (that is, the rotary drum 1 rotates clockwise in FIG. 2). One end of 6 is fixed. A claw 5 extending to the vicinity of the inner peripheral surface of the rotary drum 1 is fixed to the other end of the second arm 6.

  The mixed powder was put into the internal space 10 of the film forming apparatus, and the rotary drum 1 was rotated at a predetermined rotation speed for a predetermined time (processing time). In the rotary drum 1, a mechanochemical action is produced on the mixed powder by the press shear force between the press shear head 3 and the inner peripheral surface of the rotary drum 1, and the surface of each particle of lithium nickel oxide is coated with ketjen black. I was able to. Since the mixed powder was appropriately drawn off by the claw 5 inside the rotating drum 1, the coating action of the mixed powder proceeded as a whole.

On the active material coated with the above ketjen black, 3 parts by mass of activated carbon (same as used in Example 2) and 6 parts by mass of a conductive agent as electrochemical acetylene black (HS-100) having a specific surface area of 40 m ² / g ) A carboxymethylcellulose sodium salt aqueous solution with a concentration of 2 parts by mass is mixed so that the solid content of sodium carboxymethylcellulose as an anionic water-soluble organic compound is 1 part by mass, and further polyethylene as a nonionic water-soluble organic compound 1 part by mass of oxide powder and a predetermined amount of water are mixed and stirred for 30 minutes with a circulating stirrer. Thereafter, PTFE having a solid content ratio of about 50% as an aqueous dispersion resin is added so that the solid content of PTFE is 1 part by mass, and the mixture is stirred for 10 minutes using a circulation type stirrer. In addition, the sum total of the solid content at the time of manufacture of a positive electrode is 97.6 mass parts. The paste thus obtained was applied onto both sides of an aluminum foil with a comma coater at a basis weight of 4.92 (mg / cm ² ) per side.

(Example 11)
Example 10 is a lithium secondary battery produced in the same manner as in Example 1 except that the negative electrode shown below was used.

(Manufacture of negative electrode)
As a negative electrode active material, 98 parts by mass of flaky graphite and 1.3% by mass of poly (3,4-ethylenedioxythiophene) / polystyrenesulfonic acid aqueous solution as a pseudo electric double layer material so that the solid content becomes 2 parts by mass. Mixed. Subsequently, a 2% by mass aqueous solution of sodium carboxymethylcellulose was mixed so that the solid content of sodium carboxymethylcellulose as an anionic water-soluble organic compound was 1 part by mass, and further 1 part by mass of SBR was added as an aqueous dispersion resin. A paste in which graphite was dispersed was prepared by mixing with a fixed amount of water. The prepared paste was coated on a copper foil with a basis weight of 3.37 (mg / cm ² ) on a copper foil using a comma coater, then passed through a roll press machine, and the electrode density was 1.28 (g / cm ³ ). An electrode raised up to 2 mm was produced. In addition, the sum total of the solid content at the time of manufacture of a negative electrode was 102 mass parts.

  The amount of acidic functional groups of poly (3,4-ethylenedioxythiophene) used in this example was 0.36 meq / g, and the capacitance at −30 ° C. was 105 F / g.

(Evaluation)
As evaluation of each battery of the examples and comparative examples, the initial battery capacity, room temperature output and low temperature output were measured. The measurement results are shown in Tables 1 and 2. Each capacity and output were measured by the following measurement procedure.

《Battery initial capacity》
The first time, CC-CV charge was performed to 4.1 (V) with a charge current of 250 (mA), and CC discharge was performed to 3.0 (V) with a discharge current of 333 (mA). Next, CC-CV charge is performed to 4.1 (V) at a charge current of 1000 (mA), and CC discharge is performed four times to 3.0 (V) at a discharge current of 1000 (mA), and then a charge current of 1000 (mA). CC-CV charge up to 4.1 (V) and CC discharge to 3.0 (V) at a discharge current 333 (mA), and the discharge capacity at this time was defined as the battery initial capacity. The measurement was performed in an atmosphere at 25 ° C.

《Room temperature output》
After the initial discharge capacity measurement, the temperature was kept at 25 ° C., and the battery was CC-CV charged to 3.750 V (SOC 60%) at a charging current of 1000 mA. After that, 300 mA, 900 mA, 2.7 A, 5.4 A, and 8.1 A were each discharged for 10 seconds and charged for 10 seconds in order, and each current value and closed circuit battery voltage were approximated to a straight line, and the straight line was 3.0 V. The output was obtained by reading the current value at the point of crossing and multiplying the current value by 3V. All measurements were performed at 25 ° C.

<Low temperature output>
After the initial discharge capacity measurement, the temperature was kept at 25 ° C., and the battery was CC-CV charged to 3.618 V (SOC 40%) at a charging current of 1000 mA.

  Thereafter, discharging the two points in the order of 100 mA, 200 mA, 300 mA, 400 mA, 600 mA, and 1000 mA for 2 seconds each, repeating the charging for 2 seconds, measuring the current value and the closed circuit battery voltage at each point, The current value at the point where the straight line connecting the points crossed 3.0V was read, and the output was obtained by multiplying the current value by 3V. All measurements were performed at -30 ° C.

  Tables 1 and 2 show the results.

  From Table 1 and Table 2, it was revealed that the batteries of each Example were excellent in battery capacity, output at low temperature and room temperature. In particular, each comparative example was found to have almost no peel strength due to poor dispersion of activated carbon.

  Since the lithium secondary battery of each Example has sufficient output characteristics even at a low temperature of −30 ° C., it has been clarified that the lithium secondary battery can be used as an in-vehicle secondary battery such as an electric vehicle.

It is the figure which showed the relationship between the voltage of the discharge curve, and time in the measurement of an electrostatic capacitance. It is the schematic diagram which showed a mode that peel strength was measured in an Example. It is sectional drawing which showed the outline of the structure of the film forming apparatus used in the Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Rotary drum 10 ... Internal space 2 ... Fixed axis | shaft 3 ... Pressing shear head 4 ... 1st arm 5 ... Claw 6 ... 2nd arm

Claims (16)

An electrode for a lithium battery having a composite layer including an active material capable of inserting and extracting Li ions, at least one material having electric double layer capacity or pseudo electric double layer capacity, and at least one water-soluble organic compound. There,
The electrode for a lithium secondary battery, wherein the material having the electric double layer capacity or the pseudo electric double layer capacity has an acidic surface functional group.   The electrode for a lithium secondary battery according to claim 1, wherein the material having the electric double layer capacity or pseudo electric double layer capacity has an acidic surface functional group of 0.30 meq / g or more.   The electrode for a lithium secondary battery according to claim 1, wherein the material having the electric double layer capacity or the pseudo electric double layer capacity has an O / C ratio of 0.05 or more. _2. The lithium secondary material according to claim 1, wherein the material having the electric double layer capacity or the pseudo electric double layer capacity has a powder compression resistance of 10 ⁷ Ωcm or less when compressed at 15.7 MPa (160 kgf / cm ₂ ). Battery electrode.   2. The lithium secondary according to claim 1, wherein the content of the material having the electric double layer capacity or the pseudo electric double layer capacity is 13.3 mass% or less when the entire composite material layer is 100 mass%. Battery electrode. ^{2. The} electrode for a lithium secondary battery according to claim 1, wherein the material having the electric double layer capacity or the pseudo electric double layer capacity is at least one of a carbon material and a conductive polymer material having a specific surface area of 1200 m ² / g or more. .   The lithium secondary material according to claim 6, wherein the material having the electric double layer capacity or the pseudo electric double layer capacity is a carbon material having pores having a pore diameter of 2 nm or more and a pore volume of 0.418 mL / g or more. Battery electrode.   The electrode for a lithium secondary battery according to claim 1, wherein the water-soluble organic compound is anionic or nonionic with an HLB of 4 or more. For a lithium secondary battery having a composite layer including an active material capable of inserting and extracting Li ions, at least one material having electric double layer capacity or pseudo electric double layer capacity, and at least one water-soluble organic compound A lithium secondary battery using an electrode,
The lithium secondary battery, wherein the material having the electric double layer capacity or the pseudo electric double layer capacity has an acidic surface functional group.   The lithium secondary battery according to claim 9, wherein the material having the electric double layer capacity or the pseudo electric double layer capacity has an acidic surface functional group of 0.30 meq / g or more.   The lithium secondary battery according to claim 9, wherein the material having the electric double layer capacity or the pseudo electric double layer capacity has an O / C ratio of 0.05 or more. The lithium secondary material according to claim 9, wherein the material having the electric double layer capacity or the pseudo electric double layer capacity has a powder compression resistance of 10 ⁷ Ωcm or less when compressed at 15.7 MPa (160 kgf / cm ² ). battery.   10. The lithium secondary according to claim 9, wherein a content of the material having the electric double layer capacity or the pseudo electric double layer capacity is 13.3 mass% or less when the entire composite material layer is 100 mass%. battery. The lithium secondary battery according to claim 9, wherein the material having the electric double layer capacity or the pseudo electric double layer capacity is at least one of a carbon material and a conductive polymer material having a specific surface area of 1200 m ² / g or more.   The lithium secondary material according to claim 9, wherein the material having the electric double layer capacity or the pseudo electric double layer capacity is a carbon material having pores having a pore diameter of 2 nm or more and a pore volume of 0.418 mL / g or more. Battery electrode.   The electrode for a lithium secondary battery according to claim 9, wherein the water-soluble organic compound is anionic or nonionic with an HLB of 4 or more.

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