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Definitions

• the present disclosure relates to an electrode mixture, an electrode, and a secondary battery.
• Non-aqueous electrolyte secondary batteries such as lithium-ion secondary batteries are notebook personal computers because of their high voltage, high energy density, low self-discharge, low memory effect, and ultra-light weight.
• Patent Document 1 describes a solvent, a positive electrode active material, and the surface of the positive electrode active material, and the solvent.
• a composite positive electrode active material containing a first binder insoluble in water, a fibrous carbon material having an average fiber diameter of 40 nm or less and an average aspect ratio of 500 or more, and a second binder soluble in the solvent.
• the mass% of the first binder is 0.2 to 1.5 mass% with respect to the total mass of the composite positive electrode active material, and the mass% of the fibrous carbon material with respect to the total mass of the total solid content is It is 0.01 to 0.5% by mass, and the mass% of the second binder with respect to the total mass of the total solid content is 0.1 to 0.5% by mass, and the specific surface area of the positive electrode active material is a ( m 2 / g), where b (mass%) is the mass% of the first binder with respect to the total mass of the composite positive electrode active material, b / a is 5.0 or less.
• the positive electrode mixture slurry is described.
• the present disclosure provides an electrode mixture capable of forming an electrode mixture layer having excellent flexibility and adhesion to a current collector and forming a secondary battery having excellent battery characteristics. With the goal.
• an electrode mixture containing a lithium-containing transition metal oxide, a conductive auxiliary agent, a binder and an organic solvent, wherein the conductive auxiliary agent is a multi-walled carbon nanotube, a carbon nanohorn, a carbon nanofiber, or a fullerene.
• Fluoride-containing which contains at least one nanocarbon material selected from the group consisting of and graphene
• the binder contains a vinylidene fluoride unit and a fluorinated monomer unit (excluding the vinylidene fluoride unit).
• an electrode mixture containing a copolymer and having a content of vinylidene fluoride units in the fluorine-containing copolymer of more than 50 mol% and 99 mol% or less with respect to all monomer units.
• the nanocarbon material is at least one selected from the group consisting of multi-walled carbon nanotubes and graphene.
• the content of vinylidene fluoride units in the fluorine-containing copolymer is preferably 57.0 mol% or more and 97.0 mol% or less with respect to all the monomer units.
• the fluorinated monomer unit is preferably a tetrafluoroethylene unit.
• the content of the binder is preferably 0.3 to 3.0% by mass with respect to the total mass of the lithium-containing transition metal oxide, the conductive auxiliary agent and the binder.
• the content of the conductive auxiliary agent is preferably 0.3 to 3.0% by mass with respect to the total mass of the lithium-containing transition metal oxide, the conductive auxiliary agent and the binder.
• the binder preferably further contains polyvinylidene fluoride.
• an electrode including a current collector and an electrode mixture layer provided on one side or both sides of the current collector and formed by the electrode mixture.
• a secondary battery provided with the above electrodes is provided.
• an electrode mixture capable of forming an electrode mixture layer having excellent flexibility and adhesion to a current collector and forming a secondary battery having excellent battery characteristics. can do.
• the electrode mixture of the present disclosure contains a lithium-containing transition metal oxide, a conductive auxiliary agent, a binder and an organic solvent.
• the electrode mixture of the present disclosure contains a lithium-containing transition metal oxide.
• the lithium-containing transition metal oxide functions as a positive electrode active material or a negative electrode active material in the electrode mixture layer.
• the electrode mixture of the present disclosure can be used as a positive electrode mixture when it contains a lithium-containing transition metal oxide that functions as a positive electrode active material, and contains a lithium-containing transition metal oxide that functions as a negative electrode active material. In some cases, it can be used as a negative electrode mixture.
• the electrode mixture of the present disclosure is preferably a positive electrode mixture. That is, the electrode mixture of the present disclosure preferably contains a lithium-containing transition metal oxide as the positive electrode active material.
• transition metal of the lithium-containing transition metal oxide V, Ti, Cr, Mn, Fe, Co, Ni, Cu and the like are preferable.
• lithium-containing transition metal oxide that functions as a positive electrode active material examples include a lithium-cobalt composite oxide such as LiCoO 2 , a lithium-nickel composite oxide such as LiNiO 2 , LiMnO 2 , LiMn 2 O 4 , and Li 2 MnO.
• Lithium-manganese composite oxides such as 3 and some of the transition metal atoms that are the main components of these lithium-containing transition metal oxides are Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn. , Mg, Ga, Zr, Si and the like substituted with other metals.
• substituted ones are LiNi 0.5 Mn 0.5 O 2 , LiNi 0.85 Co 0.10 Al 0.05 O 2 , LiNi 0.82 Co 0.15 Al 0.03 O 2 , LiNi 0.80 Co 0.15 Al 0.05 O 2 , LiNi 1/3 Co 1/3 Mn 1/3 O 2 , LiMn 1.8 Al 0.2 O 4 , LiMn 1.5 Ni 0.5 O 4 , Li 4 Ti 5 O 12 and the like can be mentioned.
• a lithium-containing transition metal phosphoric acid compound can also be used as the lithium-containing transition metal oxide that functions as the positive electrode active material.
• the lithium-containing transition metal phosphoric acid compound include iron phosphates such as LiFePO 4 , Li 3 Fe 2 (PO 4 ) 3 , LiFeP 2 O 7 , and cobalt phosphates such as LiCoPO 4 , and lithium-containing thereof.
• Some of the transition metal atoms that are the main constituents of transition metal phosphate compounds are Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Nb, Si, etc. Examples thereof include those replaced with the metal of.
• a lithium-nickel-based composite oxide As the lithium-containing transition metal oxide that functions as a positive electrode active material, a lithium-nickel-based composite oxide is preferable, and the general formula (1): General formula (1): Li y Ni 1-x M x O 2 (In the formula, x is 0.01 ⁇ x ⁇ 0.5, y is 0.9 ⁇ y ⁇ 1.2, and M represents a metal atom (excluding Li and Ni).)
• the lithium-nickel composite oxide represented by is more preferable. Such a lithium-containing transition metal oxide containing a large amount of Ni is beneficial for increasing the capacity of the secondary battery.
• x is a coefficient satisfying 0.01 ⁇ x ⁇ 0.5, and a secondary battery having a higher capacity can be obtained. Therefore, 0.05 ⁇ x ⁇ 0. It is 4, and more preferably 0.10 ⁇ x ⁇ 0.3.
• examples of the metal atom of M include V, Ti, Cr, Mn, Fe, Co, Cu, Al, Zn, Mg, Ga, Zr, Si and the like.
• examples of the metal atom of M include transition metals such as V, Ti, Cr, Mn, Fe, Co, and Cu, or the above transition metals, and Al, Ti, V, Cr, Mn, Fe, Co, Cu, Zn, Combination with other metals such as Mg, Ga, Zr and Si is preferable.
• Lithium-containing transition metal oxides that function as positive electrode active materials include LiNi 0.80 Co 0.15 Al 0.05 O 2 , LiNi 0.82 Co 0.15 Al 0.03 O 2 , and LiNi 0.33 Mn. 0.33 Co 0.33 O 2 , LiNi 0.5 Mn 0.3 Co 0.2 O 2 , LiNi 0.6 Mn 0.2 Co 0.2 O 2 , LiNi 0.8 Mn 0.1 Co 0 At least one selected from the group consisting of .1 O 2 and LiNi 0.90 Mn 0.05 Co 0.05 O 2 is preferable, and LiNi 0.82 Co 0.15 Al 0.03 O 2 and LiNi At least one selected from the group consisting of 0.6 Mn 0.2 Co 0.2 O 2 and LiNi 0.8 Mn 0.1 Co 0.1 O 2 is more preferable.
• a lithium / nickel-based composite oxide represented by the general formula (1) may be used in combination with a positive electrode active material different from this.
• the different positive electrode active materials are LiCoO 2, LiMnO 2 , LiMn 2 O 4 , Li 2 MnO 3, LiMn 1.8 Al 0.2 O 4, Li 4 Ti 5 O 12, LiFePO 4 , Li 3 Fe. 2 (PO 4 ) 3 , LiFeP 2 O 7, LiCoPO 4 , Li 1.2 Fe 0.4 Mn 0.4 O 2 , LiNiO 2 , and the like can be mentioned.
• lithium-containing transition metal oxide that functions as a negative electrode active material examples include Li 4 + x Ti 5 O 12 (0 ⁇ x ⁇ 3) having a spinel structure and Li 2 + y Ti 3 O 7 (0 ⁇ ) having a ramsteride structure.
• lithium titanate such as y ⁇ 3).
• the lithium-containing transition metal oxide one in which a substance having a composition different from that of the lithium-containing transition metal oxide is attached to the surface of the lithium-containing transition metal oxide can also be used.
• Surface adhering substances include aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, bismuth oxide and other oxides, lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate. , Sulfates such as aluminum sulfate, carbonates such as lithium carbonate, calcium carbonate, magnesium carbonate and the like.
• These surface adhering substances are, for example, a method of dissolving or suspending in a solvent to impregnate and add to a lithium-containing transition metal oxide and drying, or dissolving or suspending a surface adhering substance precursor in a solvent to dissolve or suspend a lithium-containing transition metal oxide.
• a method of dissolving or suspending in a solvent to impregnate and add to a lithium-containing transition metal oxide and drying or dissolving or suspending a surface adhering substance precursor in a solvent to dissolve or suspend a lithium-containing transition metal oxide.
• the amount of the surface adhering substance is preferably 0.1 ppm or more, more preferably 1 ppm or more, still more preferably 10 ppm or more, preferably 20% or less, more preferably 10% by mass with respect to the lithium-containing transition metal oxide. Hereinafter, it is more preferably used at 5% or less.
• the surface adhering substance can suppress the oxidation reaction of the non-aqueous electrolytic solution on the surface of the lithium-containing transition metal oxide, and can improve the battery life. However, if the adhering amount is too small, the effect is sufficient. If it is not expressed and is too much, resistance may increase because it inhibits the ingress and egress of lithium ions.
• the shape of the lithium-containing transition metal oxide particles a mass, a polyhedron, a spherical shape, an elliptical spherical shape, a plate shape, a needle shape, a columnar shape, etc., which are conventionally used, are used. It is preferable that the secondary particles are formed by forming secondary particles and the shape of the secondary particles is spherical or elliptical spherical.
• the active material in the electrode expands and contracts with the charge and discharge, so that the stress tends to cause deterioration such as destruction of the active material and breakage of the conductive path.
• the primary particles aggregate to form the secondary particles rather than the single particle active material containing only the primary particles because the stress of expansion and contraction is alleviated and deterioration is prevented.
• the expansion and contraction of the electrode during charging and discharging is also smaller, and the electrode is manufactured. Even when mixed with the conductive auxiliary agent, it is preferable because it is easy to be mixed uniformly.
• the tap density of the lithium-containing transition metal oxide is usually 1.3 g / cm 3 or more, preferably 1.5 g / cm 3 or more, more preferably 1.6 g / cm 3 or more, and most preferably 1.7 g / cm 3. That is all.
• the tap density of the lithium-containing transition metal oxide is lower than the above lower limit, the amount of dispersion medium required for forming the electrode mixture layer increases, and the required amount of the conductive auxiliary agent and the binder increases, so that the electrode mixture layer is formed.
• the filling rate of the lithium-containing transition metal oxide is restricted, and the battery capacity may be restricted.
• the tap density of the lithium-containing transition metal oxide is determined by passing a sieve having a mesh size of 300 ⁇ m, dropping a sample into a tapping cell of 20 cm 3 to fill the cell volume, and then using a powder density measuring instrument (for example, Seishin Enterprise Co., Ltd.).
• the tap density is defined as the density obtained from the volume and the weight of the sample at that time by performing tapping with a stroke length of 10 mm 1000 times using a tap densor manufactured by Seishin Enterprise Co., Ltd.
• the median diameter d50 (secondary particle diameter when the primary particles aggregate to form secondary particles) of the lithium-containing transition metal oxide particles is usually 0.1 ⁇ m or more, preferably 0.5 ⁇ m or more, and more. It is preferably 1 ⁇ m or more, most preferably 3 ⁇ m or more, usually 20 ⁇ m or less, preferably 18 ⁇ m or less, more preferably 16 ⁇ m or less, and most preferably 15 ⁇ m or less.
• the electrode mixture of the present disclosure has excellent coatability.
• the electrode mixture of the present disclosure can form a high-density electrode mixture layer.
• the median diameter d50 in the present disclosure is measured by a known laser diffraction / scattering type particle size distribution measuring device.
• LA-920 manufactured by HORIBA is used as the particle size distribution meter
• a 0.1 mass% sodium hexametaphosphate aqueous solution is used as the dispersion medium used in the measurement, and the measured refractive index is set to 1.24 after ultrasonic dispersion for 5 minutes. Is measured.
• the average primary particle diameter of the lithium-containing transition metal oxide is usually 0.01 ⁇ m or more, preferably 0.05 ⁇ m or more, and more preferably 0. It is 08 ⁇ m or more, most preferably 0.1 ⁇ m or more, usually 3 ⁇ m or less, preferably 2 ⁇ m or less, still more preferably 1 ⁇ m or less, and most preferably 0.6 ⁇ m or less.
• the average primary particle size of the lithium-containing transition metal oxide is within the above range, spherical secondary particles can be easily formed, the powder filling property is excellent, and the crystallinity is also excellent. Therefore, the electrode mixture of the present disclosure is provided.
• the primary particle size is measured by observation using a scanning electron microscope (SEM). Specifically, in a photograph at a magnification of 10000, the longest value of the intercept by the left and right boundary lines of the primary particles with respect to the horizontal straight line is obtained for any 50 primary particles, and the average value is taken. Be done.
• the BET specific surface area of the lithium-containing transition metal oxide is usually 0.2 m 2 / g or more, preferably 0.3 m 2 / g or more, more preferably 0.4 m 2 / g or more, and usually 4.0 m 2 / g. Hereinafter, it is preferably 2.5 m 2 / g or less, and more preferably 1.5 m 2 / g or less.
• the electrode mixture of the present disclosure has excellent coatability, and is even more excellent in flexibility and adhesion to the current collector.
• the agent layer can be formed, and a secondary battery having more excellent battery characteristics can be formed.
• the BET specific surface area is determined by pre-drying the sample at 150 ° C. for 30 minutes using a surface area meter (for example, a fully automatic surface area measuring device manufactured by Okura Riken Co., Ltd.), and then the relative pressure of nitrogen with respect to atmospheric pressure. It is defined by the value measured by the nitrogen adsorption BET 1-point method by the gas flow method using a nitrogen-helium mixed gas accurately adjusted so that the value of is 0.3.
• a surface area meter for example, a fully automatic surface area measuring device manufactured by Okura Riken Co., Ltd.
• a general method is used as a method for producing an inorganic compound.
• various methods can be considered for producing spherical or elliptical spherical lithium-containing transition metal oxides.
• transition metal raw materials such as transition metal nitrates and sulfates and, if necessary, raw materials of other elements.
• a solvent such as water
• the pH is adjusted while stirring to prepare and recover a spherical precursor, which is dried as necessary, and then LiOH, Li 2 CO 3 , Li NO.
• the raw material of the above is dissolved or pulverized and dispersed in a solvent such as water, and dried and molded with a spray dryer or the like to obtain a spherical or elliptical spherical precursor, which is then Li OH, Li 2 CO 3 , Li NO 3 or the like.
• a Li source such as 3 and, if necessary, raw materials of other elements are dissolved or pulverized and dispersed in a solvent such as water, and dried and molded with a spray dryer or the like to obtain a spherical or elliptical spherical precursor. Examples thereof include a method of calcining this at a high temperature to obtain a lithium-containing transition metal oxide.
• lithium-containing transition metal oxide may be used alone, or two or more types having different compositions or different powder physical characteristics may be used in combination in any combination and ratio.
• the content of the lithium-containing transition metal oxide in the electrode mixture it is possible to form an electrode mixture layer that is more excellent in flexibility and adhesion to the current collector, and is even more excellent in battery characteristics. Since the next battery can be formed, it is preferably 95.0 to 99.8% by mass, more preferably 96.0 to 99.8 to the total mass of the lithium-containing transition metal oxide, the conductive auxiliary agent and the binder. It is 99.4% by mass, more preferably 96.5 to 99.0% by mass.
• the conductive auxiliary agent contained in the electrode mixture of the present disclosure contains at least one nanocarbon material selected from the group consisting of multi-walled carbon nanotubes, carbon nanohorns, carbon nanofibers, fullerenes and graphene. Since the electrode mixture of the present disclosure contains a specific nanocarbon material as a conductive auxiliary agent, the electrode mixture of the present disclosure is used to form an electrode mixture layer of an electrode of a secondary battery. It is possible to obtain an electrode mixture layer having excellent adhesion to the current collector without impairing the flexibility. Furthermore, the secondary battery provided with such an electrode mixture layer exhibits a high high-temperature storage capacity retention rate, a low resistance increase rate, and a low gas amount change rate, and is excellent in battery characteristics.
• the nanocarbon material is a material formed by carbon atoms having a size of nanometer size.
• the shape of the nanocarbon material may be cylindrical, hollow needle-shaped, hollow rod-shaped, hollow particle-shaped or sheet-shaped. Further, the nanocarbon material preferably has conductivity.
• the nanocarbon material may be at least one selected from the group consisting of multi-walled carbon nanotubes, carbon nanohorns, carbon nanofibers, fullerene and graphene, and is not particularly limited, but depends on flexibility and adhesion to a current collector. At least selected from the group consisting of multi-walled carbon nanotubes, carbon nanohorns and graphene because a more excellent electrode mixture layer can be formed and a secondary battery having better battery characteristics can be formed. One is preferable, at least one selected from the group consisting of multi-walled carbon nanotubes and graphene is more preferable, and multi-walled carbon nanotubes are further preferable. As the nanocarbon material, one type may be used alone, or two or more types may be used in combination in any combination and ratio.
• Graphene is a two-dimensional material and is distinguished from carbon nanotubes known as one-dimensional materials. Further, the carbon nanotube has a shape in which a graphene sheet is rolled into a cylinder.
• the single-walled ones are called single-walled carbon nanotubes (SWNTs)
• the multi-walled ones are called multi-walled carbon nanotubes (MWNTs).
• the conductive auxiliary agent contained in the electrode mixture of the present disclosure contains a conductive auxiliary agent other than the nanocarbon material.
• the conductive auxiliary agent other than the nanocarbon material include carbon black such as acetylene black and Ketjen black; natural graphite; and metal powder such as nickel and aluminum.
• carbon black is preferable, and acetylene black is more preferable.
• a secondary battery that can form an electrode mixture layer that is more excellent in flexibility and adhesion to the current collector and that is more excellent in battery characteristics can be obtained. Since it can be formed, it is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and further, based on the total mass of the lithium-containing transition metal oxide, the conductive auxiliary agent, and the binder. It is preferably 0.3% by mass or more, particularly preferably 0.5% by mass or more, preferably 3.0% by mass or less, more preferably 2.5% by mass or less, still more preferably 2 It is 0.0% by mass or less, and particularly preferably 1.6% by mass or less.
• a secondary battery that can form an electrode mixture layer that is more excellent in flexibility and adhesion to the current collector and that is more excellent in battery characteristics can be obtained. Since it can be formed, it is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and further, based on the total mass of the lithium-containing transition metal oxide, the conductive auxiliary agent, and the binder. It is preferably 0.2% by mass or more, still more preferably 0.3% by mass or more, particularly preferably 0.5% by mass or more, preferably 3.0% by mass or less, and more preferably. It is 2.5% by mass or less, more preferably 2.0% by mass or less, and particularly preferably 1.6% by mass or less.
• the electrode mixture of the present disclosure contains a nanocarbon material and a conductive auxiliary agent other than the nanocarbon material as the conductive auxiliary agent
• the content ratio of the nanocarbon material and the other conductive auxiliary agent is Since it is possible to form a more excellent electrode mixture layer due to its flexibility and adhesion to the current collector, and it is possible to form a secondary battery having even better battery characteristics, the mass ratio (nanocarbon material).
• Mass of conductive aid other than / mass of nanocarbon material preferably 1/99 to 99/1, more preferably 10/90 to 95/5, and even more preferably 20/80 to 90/. It is 10.
• the binder contained in the electrode mixture of the present disclosure contains a fluorine-containing copolymer containing a vinylidene fluoride unit (VdF unit) and a fluorinated monomer unit (excluding VdF unit).
• fluorinated monomer examples include tetrafluoroethylene (TFE), vinyl fluoride, trifluoroethylene, chlorotrifluoroethylene (CTFE), fluoroalkyl vinyl ether, and hexafluoropropylene (HFP).
• TFE tetrafluoroethylene
• CFE chlorotrifluoroethylene
• HFP fluoroalkyl vinyl ether
• HFP hexafluoropropylene
• (Perfluoroalkyl) ethylene, 2,3,3,3-tetrafluoropropene and trans-1,3,3,3-tetrafluoropropene examples include tetrafluoroethylene (TFE), vinyl fluoride, trifluoroethylene, chlorotrifluoroethylene (CTFE), fluoroalkyl vinyl ether, and hexafluoropropylene (HFP).
• the fluorinated monomer unit (excluding the VdF unit) may or may not have a polar group.
• the content of the VdF unit of the fluorine-containing copolymer is more than 50 mol% and 99 mol% or less with respect to all the monomer units.
• the content of VdF units is in the above range, it is possible to form an electrode mixture layer having excellent flexibility and adhesion to a current collector, and to form a secondary battery having excellent battery characteristics. Can be done. If the content of the fluorine-containing copolymer in VdF units is too small, sufficient adhesion of the electrode mixture layer to the current collector may not be obtained, or excellent battery characteristics of the secondary battery may not be obtained.
• a secondary battery capable of forming an electrode mixture layer having more excellent flexibility and adhesion to a current collector and having more excellent battery characteristics can be obtained. Since it can be formed, it is preferably 57.0 mol% or more, more preferably 60.0 mol% or more, still more preferably 63.0 mol% or more, based on all the monomer units. It is preferably 99.0 mol% or less, more preferably 97.0 mol% or less, further preferably 95.0 mol% or less, particularly preferably 90.0 mol% or less, and most preferably. Is 85.0 mol% or less.
• the content of the fluorinated monomer unit (excluding the VdF unit) of the fluorine-containing copolymer may be less than 50 mol% and is not particularly limited, but is preferable with respect to all the monomer units. It is 1.0 mol% or more, more preferably 3.0 mol% or more, further preferably 5.0 mol% or more, particularly preferably 10.0 mol% or more, and most preferably 15. It is 0 mol% or more, preferably 43.0 mol% or less, more preferably 40.0 mol% or less, and further preferably 37.0 mol% or less.
• the electrode mixture of the present disclosure has flexibility and adhesion to a current collector. Therefore, a more excellent electrode mixture layer can be formed, and a secondary battery having more excellent battery characteristics can be formed.
• composition of the fluorine-containing copolymer can be measured, for example, by 19 F-NMR measurement.
• the fluorine-containing copolymer may further contain a non-fluorinated monomer unit.
• the non-fluorinated monomer may be a non-fluorinated monomer having no polar group such as ethylene or propylene, or a non-fluorinated monomer having a polar group (hereinafter referred to as a polar group-containing monomer). ) Etc. can be mentioned.
• a polar group is introduced into the fluorine-containing copolymer, whereby excellent adhesion between the positive electrode mixture layer and the current collector can be obtained. Be done.
• the polar group that the fluorine-containing copolymer can have is selected from the group consisting of a carbonyl group-containing group, an epoxy group, a hydroxy group, a sulfonic acid group, a sulfate group, a phosphoric acid group, an amino group, an amide group and an alkoxy group.
• At least one selected from the group consisting of a carbonyl group-containing group, an epoxy group and a hydroxy group is more preferable, and a carbonyl group-containing group is further preferable.
• the hydroxy group does not include a hydroxy group that constitutes a part of the carbonyl group-containing group.
• the amino group is a monovalent functional group obtained by removing hydrogen from ammonia, a primary or secondary amine.
• a group represented by the general formula: -COOR R represents a hydrogen atom, an alkyl group or a hydroxyalkyl group
• a carboxylic acid anhydride group is preferable.
• the number of carbon atoms of the alkyl group and the hydroxyalkyl group is preferably 1 to 16, more preferably 1 to 6, and further preferably 1 to 3.
• the carbonyl group-containing group the general formula: -X-COOR (X is mainly composed of 2 to 15 atoms, and the molecular weight of the atomic group represented by X is preferably 350 or less.
• R is a hydrogen atom.
• the number of carbon atoms of the alkyl group and the hydroxyalkyl group is preferably 1 to 16, more preferably 1 to 6, and further preferably 1 to 3.
• the amide group includes a group represented by the general formula: -CO-NRR'(R and R'independently represent a hydrogen atom or a substituted or unsubstituted alkyl group), or a general formula:-. Bonds represented by CO-NR "-(R” represents a hydrogen atom, a substituted or unsubstituted alkyl group or a substituted or unsubstituted phenyl group) are preferable.
• polar group-containing monomer examples include hydroxyalkyl (meth) acrylates such as hydroxyethyl acrylate and 2-hydroxypropyl acrylate; alkylidene malonic acid esters such as dimethyl methylidene malonate; vinyl carboxymethyl ether, vinyl carboxyethyl ether and the like.
• Vinyl carboxyalkyl ethers such as 2-carboxyethyl acrylate and 2-carboxyethyl methacrylate; acryloyloxyethyl succinic acid, acryloyloxypropyl succinic acid, methacryloyloxyethyl succinic acid, acryloyloxyethyl phthalic acid, (Meta) acryloyloxyalkyldicarboxylic acid esters such as methacryloyloxyethyl phthalic acid; monoesters of unsaturated dibasic acids such as maleic acid monomethyl ester, maleic acid monoethyl ester, citraconic acid monomethyl ester, citraconic acid monoethyl ester; general Equation (2): (In the formula, R 1 to R 3 independently represent a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms. R 4 represents a single bond or a hydrocarbon group having 1 to 8
• polar group-containing monomer unit that can be contained in the fluorine-containing copolymer
• a unit based on the monomer (2) represented by the general formula (2) is preferable.
• Y 1 represents an inorganic cation and / or an organic cation.
• the inorganic cation include cations such as H, Li, Na, K, Mg, Ca, Al and Fe.
• the organic cation, NH 4, NH 3 R 5 , NH 2 R 5 2, NHR 5 3, NR 5 4 (R 5 are independently. Represents an alkyl group having 1 to 4 carbon atoms) cations such as Can be mentioned.
• H Li, Na, K, Mg, Ca, Al, NH 4 are preferable, H, Li, Na, K, Mg, Al, NH 4 are more preferable, and H, Li, Al, NH 4 Is more preferable, and H is particularly preferable.
• Specific examples of the inorganic cation and the organic cation are described by omitting the reference numerals and valences for convenience.
• R 1 to R 3 independently represent a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms.
• the hydrocarbon group is a monovalent hydrocarbon group.
• the hydrocarbon group preferably has 4 or less carbon atoms.
• Examples of the hydrocarbon group include an alkyl group having the above carbon number, an alkenyl group, an alkynyl group and the like, and a methyl group or an ethyl group is preferable.
• R 1 and R 2 are preferably hydrogen atoms, methyl groups or ethyl groups independently, and R 3 is preferably hydrogen atoms or methyl groups.
• R 4 represents a single bond or a hydrocarbon group having 1 to 8 carbon atoms.
• the hydrocarbon group is a divalent hydrocarbon group.
• the hydrocarbon group preferably has 4 or less carbon atoms.
• Examples of the hydrocarbon group include the above-mentioned alkylene group having carbon number and alkenylene group, and among them, at least one selected from the group consisting of a methylene group, an ethylene group, an ethylidene group, a propylidene group and an isopropylidene group is selected.
• a methylene group is more preferred.
• Examples of the monomer (2) include (meth) acrylic acid and its salt, vinylacetic acid (3-butenoic acid) and its salt, 3-pentenoic acid and its salt, 4-pentenoic acid and its salt, and 3-hexenoic acid. And salts thereof, 4-heptenoic acid and salts thereof, and at least one selected from the group consisting of 5-hexenoic acid and salts thereof, preferably 3-butenoic acid and salts thereof, and 4-pentenoic acid and salts thereof. At least one selected from the group consisting of salts is more preferred.
• the content of the polar group-containing monomer unit of the fluorine-containing copolymer is preferably 0 with respect to all the monomer units. It is 0.05 to 2.0 mol%, more preferably 0.10 mol% or more, further preferably 0.25 mol% or more, particularly preferably 0.40 mol% or more, and more preferably. It is 1.5 mol% or less.
• the content of the polar group-containing monomer unit in the fluorine-containing copolymer can be measured by acid-base titration of the acid group, for example, when the polar group is an acid group such as a carboxylic acid.
• fluorine-containing copolymer examples include a VdF / TFE copolymer, a VdF / HFP copolymer, a VdF / TFE / HFP copolymer, and a VdF / TFE / 2,3,3,3-tetrafluoropropene copolymer.
• VdF / TFE / (meth) acrylic acid copolymer VdF / HFP / (meth) acrylic acid copolymer, VdF / CTFE copolymer, VdF / TFE / 4-pentenoic acid copolymer, VdF / TFE / 3-butenoic acid copolymer, VdF / TFE / HFP / (meth) acrylic acid copolymer, VdF / TFE / HFP / 4-pentenoic acid copolymer, VdF / TFE / HFP / 3-butenoic acid copolymer Combined, VdF / TFE / 2-carboxyethyl acrylate copolymer, VdF / TFE / HFP / 2-carboxyethyl acrylate copolymer, VdF / TFE / acryloyloxyethyl succinic acid copolymer, VdF / TFE
• fluorine-containing copolymers it is possible to form an electrode mixture layer having more excellent flexibility and adhesion to a current collector, and to form a secondary battery having more excellent battery characteristics. Therefore, a fluorine-containing copolymer composed of only VdF units, TFE units, and arbitrary non-fluorinated monomer units is preferable.
• the molar ratio of VdF units to TFE units is preferably more than 50/50 and 99/1 or less, more preferably. Is 57/43 to 97/3, more preferably 60/40 to 95/5, particularly preferably 63/37 to 90/10, and most preferably 63/37 to 85/15.
• the weight average molecular weight (in terms of polystyrene) of the fluorine-containing copolymer is preferably 50,000 to 3,000, more preferably 80,000 or more, further preferably 100,000 or more, particularly preferably 200,000 or more, and more preferably. It is 2400000 or less, more preferably 220000 or less, and particularly preferably 20000 or less.
• the weight average molecular weight can be measured by gel permeation chromatography (GPC) using dimethylformamide as a solvent.
• the number average molecular weight (in terms of polystyrene) of the fluorine-containing copolymer is preferably 20,000 to 1500,000, more preferably 40,000 or more, further preferably 70,000 or more, particularly preferably 140,000 or more, and more preferably. It is 1400000 or less, more preferably 120000 or less, and particularly preferably 110000 or less.
• the number average molecular weight can be measured by gel permeation chromatography (GPC) using dimethylformamide as a solvent.
• the melting point of the fluorine-containing copolymer is preferably 100 to 170 ° C, more preferably 110 to 165 ° C, and even more preferably 120 to 163 ° C.
• the melting point is raised from 30 ° C. to 220 ° C. at a rate of 10 ° C./min using a differential scanning calorimetry (DSC) device, then lowered to 30 ° C. at 10 ° C./min, and again at 10 ° C./min. Obtained as the temperature with respect to the maximum value in the heat of fusion curve when the temperature is raised to 220 ° C at a rate.
• DSC differential scanning calorimetry
• the fluorine-containing copolymer preferably has a breaking point elongation of 100% or more.
• the elongation at the breaking point is more preferably 200% or more, further preferably 300% or more.
• the break point elongation can be measured by the following method. That is, a fluorine-containing copolymer solution obtained by dissolving a fluorine-containing copolymer in N-methyl-2-pyrrolidone (NMP) so as to have a concentration of 10 to 20% by mass was cast on a glass plate 100. It is dried at ° C. for 12 hours and then dried under vacuum at 100 ° C. for 12 hours to obtain a film having a thickness of 50 to 100 ⁇ m. The film is punched into a dumbbell shape and the elongation at break at 25 ° C. is measured by an autograph.
• NMP N-methyl-2-pyrrolidone
• the fluorine-containing copolymer preferably has a storage elastic modulus of 1100 MPa or less at 30 ° C. and a storage elastic modulus of 500 MPa or less at 60 ° C.
• the storage elastic modulus of the fluorine-containing copolymer at 30 ° C. is more preferably 800 MPa or less, still more preferably 600 MPa or less.
• the storage elastic modulus of the fluorine-containing copolymer at 60 ° C. is more preferably 350 MPa or less.
• the storage elastic modulus of the fluorine-containing copolymer at 30 ° C. is preferably 100 MPa or more, more preferably 150 MPa or more, and further preferably 200 MPa or more.
• the storage elastic modulus of the fluorine-containing copolymer at 60 ° C. is preferably 50 MPa or more, more preferably 80 MPa or more, and further preferably 130 MPa or more.
• the storage elastic modulus of a sample having a length of 30 mm, a width of 5 mm, and a thickness of 50 to 100 ⁇ m was measured by a dynamic viscoelastic device DVA220 manufactured by IT Measurement Control Co., Ltd. in a tensile mode, a grip width of 20 mm, and a measurement temperature of -30. It is a measured value at 30 ° C. and 60 ° C. when measured under the conditions of ° C. to 160 ° C., a heating rate of 2 ° C./min, and a frequency of 1 Hz.
• the measurement sample is, for example, a fluorine-containing copolymer solution obtained by dissolving a fluorine-containing copolymer in N-methyl-2-pyrrolidone (NMP) so as to have a concentration of 10 to 20% by mass on a glass plate. It can be produced by casting it into a polymer, drying it at 100 ° C. for 12 hours, and further drying it under vacuum at 100 ° C. for 12 hours, and cutting the obtained film having a thickness of 50 to 100 ⁇ m into a length of 30 mm and a width of 5 mm. can.
• NMP N-methyl-2-pyrrolidone
• the weight increase rate of the fluorine-containing copolymer after being immersed in an electrolytic solution at 60 ° C. for 1 week is preferably 250% by mass or less, and more preferably 200% by mass or less.
• the weight increase rate of the fluorine-containing copolymer after being immersed in the electrolytic solution at 60 ° C. for 1 week is more preferably 180% by mass or less, particularly preferably 160% by mass or less, and 105% by mass or more. It may be there.
• the weight increase rate can be obtained by the following method.
• An NMP solution (8% by mass) of the fluorine-containing copolymer is cast on a glass petri dish and vacuum-dried at 100 ° C. for 12 hours to prepare a film having a thickness of 200 ⁇ m of the fluorine-containing copolymer.
• the obtained film was punched to a size of 6 mm ⁇ and placed in a sample bottle containing an electrolytic solution (a solution in which LiPF 6 was dissolved in a solvent of 3/7 (volume ratio) of ethylene carbonate / ethyl methyl carbonate at a concentration of 1 M). After allowing to stand at ° C. for 1 week, the weight increase rate is determined.
• the binder contained in the electrode mixture of the present disclosure further contains polyvinylidene fluoride (PVdF).
• PVdF polyvinylidene fluoride
• VdF Polyvinylidene fluoride
• VdF units Polyvinylidene fluoride
• VdF units may be a VdF homopolymer consisting of only VdF units, VdF units and It may be a polymer containing a unit based on a monomer copolymerizable with VdF.
• the monomer copolymerizable with VdF is preferably a monomer different from tetrafluoroethylene (TFE). That is, PVdF preferably does not contain TFE units.
• examples of the monomer copolymerizable with VdF include a fluorinated monomer and a non-fluorinated monomer, and a fluorinated monomer is preferable.
• examples of the fluorinated monomer include vinyl fluoride, trifluoroethylene, chlorotrifluoroethylene (CTFE), fluoroalkyl vinyl ether, hexafluoropropylene (HFP), (perfluoroalkyl) ethylene, 2,3,3,3. -Tetrafluoropropene, trans-1,3,3,3-tetrafluoropropene and the like can be mentioned.
• examples of the non-fluorinated monomer include ethylene and propylene.
• At least one fluorinated monomer selected from the group consisting of CTFE, fluoroalkyl vinyl ether, HFP and 2,3,3,3-tetrafluoropropene is preferred, and at least one fluorinated monomer selected from the group consisting of CTFE, HFP and fluoroalkyl vinyl ethers is more preferred.
• the content of the monomer unit copolymerizable with VdF is preferably 0 to 5.0 mol%, more preferably 0 to 3.0 mol%, based on all the monomer units. Is.
• the content of the fluorinated monomer unit copolymerizable with VdF is preferably less than 5.0 mol%, more preferably less than 3.0 mol%, based on all the monomer units. It is more preferably less than 1.0 mol%.
• composition of PVdF can be measured, for example, by 19 F-NMR measurement.
• the PVdF may have a polar group.
• a fluorine-containing copolymer and PVdF having a polar group as the binder, it is possible to form an electrode mixture layer that is more excellent in flexibility and adhesion to the current collector, and is even more excellent in battery characteristics.
• a secondary battery can be formed.
• the polar group is not particularly limited as long as it is a functional group having polarity, but while maintaining the excellent flexibility of the electrode mixture layer to be formed and the excellent battery characteristics of the secondary battery to be formed. Since the adhesion of the formed electrode mixture layer to the current collector can be further improved, a carbonyl group-containing group, an epoxy group, a hydroxy group, a sulfonic acid group, a sulfate group, a phosphoric acid group, and an amino group can be obtained.
• At least one selected from the group consisting of a group, an amide group and an alkoxy group is preferable, at least one selected from the group consisting of a carbonyl group-containing group, an epoxy group and a hydroxy group is more preferable, and a carbonyl group-containing group is further added.
• the hydroxy group does not include a hydroxy group that constitutes a part of the carbonyl group-containing group.
• the amino group is a monovalent functional group obtained by removing hydrogen from ammonia, a primary or secondary amine.
• the carbonyl group-containing group As the carbonyl group-containing group, the current collector of the electrode mixture layer to be formed while maintaining the excellent flexibility of the electrode mixture layer to be formed and the excellent battery characteristics of the secondary battery to be formed.
• a group represented by the general formula: -COOR (R represents a hydrogen atom, an alkyl group or a hydroxyalkyl group) or a carboxylic acid anhydride group is preferable because the adhesion to the group can be further improved.
• General formula: The group represented by ⁇ COOR is more preferable.
• the number of carbon atoms of the alkyl group and the hydroxyalkyl group is preferably 1 to 16, more preferably 1 to 6, and further preferably 1 to 3.
• the carbonyl group-containing group the general formula: -X-COOR (X is mainly composed of 2 to 15 atoms, and the molecular weight of the atomic group represented by X is preferably 350 or less.
• R is a hydrogen atom.
• the number of carbon atoms of the alkyl group and the hydroxyalkyl group is preferably 1 to 16, more preferably 1 to 6, and further preferably 1 to 3.
• the amide group includes a group represented by the general formula: -CO-NRR'(R and R'independently represent a hydrogen atom or a substituted or unsubstituted alkyl group), or a general formula:-. Bonds represented by CO-NR "-(R” represents a hydrogen atom, a substituted or unsubstituted alkyl group or a substituted or unsubstituted phenyl group) are preferable.
• the polar group can be introduced into PVdF by polymerizing VdF and a monomer having the polar group (hereinafter, referred to as a polar group-containing monomer), or a compound having PVdF and the polar group. Although it can be introduced into PVdF by reacting with, it is preferable to polymerize VdF and the above-mentioned polar group-containing monomer from the viewpoint of productivity.
• PVdF containing a VdF unit and a polar group-containing monomer unit By polymerizing VdF and the above-mentioned polar group-containing monomer, PVdF containing a VdF unit and a polar group-containing monomer unit can be obtained. That is, PVdF maintains the excellent flexibility of the formed electrode mixture layer and the excellent battery characteristics of the formed secondary battery, and the adhesion of the formed electrode mixture layer to the current collector. It is preferable to contain the above-mentioned polar group-containing monomer unit, because the above-mentioned polar group-containing monomer unit can be further improved.
• the content of the polar group-containing monomer unit is preferably 0.001 to 5.0 mol%, more preferably 0.01 to 3.0 mol%, based on all the monomer units. , More preferably 0.10 to 1.5 mol%.
• the content of the polar group-containing monomer unit in PVdF can be measured by acid-base titration of the acid group, for example, when the polar group is an acid group such as a carboxylic acid.
• polar group-containing monomer examples include hydroxyalkyl (meth) acrylates such as hydroxyethyl acrylate and 2-hydroxypropyl acrylate; (meth) acrylic acid, crotonic acid, vinyl acetic acid (3-butenoic acid), and 3-pentenoic acid.
• the polar group-containing monomer or a group reactive with PVdF is used as the compound having the polar group.
• a silane-based coupling agent or a titanate-based coupling agent having a hydrolyzable group and a titanate-based coupling agent can be used.
• the hydrolyzable group is preferably an alkoxy group.
• PVdF it is also possible to use a PVdF obtained by partially defluorinating the PVdF with a base and then further reacting the partially defluorinated hydrogenated PVdF with an oxidizing agent.
• the oxidizing agent include hydrogen peroxide, hypochlorite, palladium halide, chromium halide, alkali metal permanganate, peracid compound, alkyl peroxide, alkyl persulfate and the like.
• the content of PVdF in VdF units is such that an electrode mixture layer having more excellent flexibility and adhesion to a current collector can be formed, and a secondary battery having more excellent battery characteristics can be formed. Therefore, it is preferably more than 95.0 mol%, more preferably more than 97.0 mol%, and further preferably more than 99.0 mol% with respect to all the monomer units. Further, the content of PVdF in VdF units is such that an electrode mixture layer having more excellent flexibility and adhesion to a current collector can be formed, and a secondary battery having more excellent battery characteristics can be formed. It is preferably 95.0 to 99.99 mol%, more preferably 97.0 mol% or more, still more preferably 98.5 mol% or more, based on all the monomer units. , More preferably 99.99 mol% or less, still more preferably 99.90 mol% or less.
• the weight average molecular weight (in terms of polystyrene) of PVdF is such that an electrode mixture layer having better flexibility and adhesion to a current collector can be formed, and a secondary battery having better battery characteristics can be formed. It is preferably 50,000 to 3,000,000, more preferably 80,000 or more, further preferably 100,000 or more, particularly preferably 200,000 or more, more preferably 2400000 or less, still more preferably 220000 or less. Yes, particularly preferably 20000 or less.
• the weight average molecular weight can be measured by gel permeation chromatography (GPC) using N, N-dimethylformamide as a solvent.
• PVdF (A) can be formed because it is possible to form an electrode mixture layer having excellent flexibility and adhesion to a current collector, and it is possible to form a secondary battery having very excellent battery characteristics. ) May have a weight average molecular weight of 1,000,000 or more, or 1500,000 or more.
• the number average molecular weight of PVdF (in terms of polystyrene) is such that an electrode mixture layer having better flexibility and adhesion to a current collector can be formed, and a secondary battery having better battery characteristics can be formed. It is preferably 20000 to 1500,000, more preferably 40,000 or more, further preferably 70,000 or more, particularly preferably 140000 or more, more preferably 140000 or less, still more preferably 120000 or less. Yes, particularly preferably 110000 or less.
• the number average molecular weight can be measured by gel permeation chromatography (GPC) using dimethylformamide as a solvent.
• the melting point of PVdF is preferably 100 to 240 ° C.
• the melting point can be determined as the temperature with respect to the maximum value in the heat of fusion curve when the temperature is raised at a rate of 10 ° C./min using a differential scanning calorimetry (DSC) device.
• DSC differential scanning calorimetry
• PVdF can be produced by a conventionally known method such as solution polymerization or suspension polymerization by appropriately mixing VdF, the above-mentioned polar group-containing monomer, and an additive such as a polymerization initiator.
• the storage elastic modulus of PVdF at 30 ° C. is preferably 2000 MPa or less, more preferably 1800 MPa or less.
• the storage elastic modulus of PVdF at 60 ° C. is preferably 1500 MPa or less, more preferably 1300 MPa or less.
• the storage elastic modulus of PVdF at 30 ° C. is preferably 1000 MPa or more, more preferably 1100 MPa or more.
• the storage elastic modulus of PVdF at 60 ° C. is preferably 600 MPa or more, more preferably 700 MPa or more.
• the storage elastic modulus of PVdF can be measured by the same method as the storage elastic modulus of the fluorine-containing copolymer.
• the mass ratio of PVdF to the fluorine-containing copolymer (PVdF / fluorine-containing copolymer) in the binder is flexibility and adhesion to the current collector. It is preferably 99/1 to 1/99, more preferably 97, because a more excellent electrode mixture layer can be formed and a secondary battery having more excellent battery characteristics can be formed. It is / 3 to 3/97, more preferably 95/5 to 5/95, further preferably 90/10 to 10/90, and particularly preferably 85/15 to 15/85, which is the most. It is preferably 80/20 to 40/60.
• the binder may contain other polymers in addition to PVdF and a fluorine-containing copolymer.
• other polymers include polymethacrylate, polymethylmethacrylate, polyacrylonitrile, polyimide, polyamide, polyamideimide, polycarbonate, styrene rubber, butadiene rubber and the like.
• an electrode mixture layer having more excellent flexibility and adhesion to the current collector can be formed, and a secondary battery having more excellent battery characteristics can be formed. It is preferably 1% by mass or more, more preferably 3% by mass or more, further preferably 5% by mass or more, and particularly preferably 10% by mass or more, based on the mass of the binder. Most preferably, it is 15% by mass or more, and may be 100% by mass or less.
• the content of the binder in the electrode mixture it is possible to form an electrode mixture layer having more excellent flexibility and adhesion to the current collector, and to form a secondary battery having more excellent battery characteristics. Therefore, it is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and further preferably 0, based on the total mass of the lithium-containing transition metal oxide, the conductive auxiliary agent, and the binder. .3% by mass or more, particularly preferably 0.5% by mass or more, preferably 3.0% by mass or less, more preferably 2.5% by mass or less, still more preferably 2.0% by mass. % Or less.
• the electrode mixture of the present disclosure further contains an organic solvent.
• the organic solvent include nitrogen-containing organic solvents such as N-methyl-2-pyrrolidone, N, N-dimethylacetamide and dimethylformamide; ketone solvents such as acetone, methyl ethyl ketone, cyclohexanone and methyl isobutyl ketone; ethyl acetate, Ester solvent such as butyl acetate; Ether solvent such as tetrahydrofuran and dioxane; ⁇ -methoxy-N, N-dimethylpropionamide, ⁇ -n-butoxy-N, N-dimethylpropionamide, ⁇ -n-hexyloxy- ⁇ -alkoxypropionamides such as N, N-dimethylpropionamide; Further, general-purpose organic solvents having a low boiling point such as a mixed solvent thereof can be mentioned.
• N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone and ⁇ -alkoxypropion are excellent in coatability.
• At least one selected from the group consisting of amides is preferable, and at least one selected from the group consisting of N-methyl-2-pyrrolidone and N, N-dimethylacetamide is more preferable.
• the contents of the lithium-containing transition metal oxide, the binder, and the carbon nanomaterial in the electrode mixture of the present disclosure are determined in consideration of the coatability to the current collector, the thin film formation property after drying, and the like.
• the total content of the lithium-containing transition metal oxide, the binder and the carbon nanomaterial in the electrode mixture is preferably 50 to 90% by mass, more preferably 60 to 80% by mass.
• the electrode mixture of the present disclosure can be prepared by mixing a lithium-containing transition metal oxide, a binder, a nanocarbon material, an organic solvent, and if necessary, other components.
• the order in which each component is mixed is not particularly limited.
• the binder, the nanocarbon material, and the organic solvent may be mixed, and then the lithium-containing transition metal oxide and other components may be mixed.
• a composite material of the binder and the lithium-containing transition metal oxide is obtained by spraying a solution or dispersion of the binder onto the lithium-containing transition metal oxide and drying the composite material.
• the nanocarbon material, the organic solvent and other components may be mixed.
• the binder be used in a small particle size having an average particle size of 1000 ⁇ m or less, particularly 50 to 350 ⁇ m, in order to enable rapid dissolution in an organic solvent.
• the electrodes of the present disclosure include a current collector and an electrode mixture layer.
• the electrode mixture layer is formed by using the electrode mixture of the present disclosure, and may be provided on one side of the current collector or on both sides.
• the electrode of the present disclosure includes an electrode mixture layer formed by using the electrode mixture of the present disclosure, it is excellent in flexibility and the current collector and the electrode mixture layer are sufficiently adhered to each other. Moreover, it is possible to form a secondary battery having excellent battery characteristics.
• the density of the electrode mixture layer is preferably 2.0 to 5.0 g / cm 3 , and more preferably 2.5 to 5.0 g / cm 3 .
• the density of the electrode mixture layer can be calculated from the mass and volume of the electrode mixture layer.
• the thickness of the electrode mixture layer is preferably 20 ⁇ m or more, more preferably 45 ⁇ m or more, further preferably 55 ⁇ m or more, and particularly preferably 60 ⁇ m or more, because even higher battery characteristics can be obtained. It is preferably 170 ⁇ m or less, and more preferably 150 ⁇ m or less. Further, the thickness of the electrode mixture layer may be 85 ⁇ m or less, or less than 69 ⁇ m.
• the thickness of the electrode mixture layer can be measured with a micrometer.
• the thickness of the electrode mixture layer in the present disclosure is the thickness per one side when the electrode mixture layers are provided on both sides of the current collector.
• Examples of the current collector included in the electrodes of the present disclosure include metal foils such as iron, stainless steel, copper, aluminum, nickel, and titanium, metal nets, and the like, and among them, aluminum foil is preferable.
• the electrodes of the present disclosure can be suitably manufactured by a manufacturing method of applying the electrode mixture of the present disclosure to a current collector. After applying the electrode mixture, the coating film may be further dried and the obtained dried coating film may be pressed.
• the amount of the electrode mixture applied to the current collector is preferably 15 mg / cm 2 or more, more preferably 17.5 mg / cm 2 or more, preferably 60 mg / cm 2 or less, and more preferably. Is 50 mg / cm 2 or less.
• the coating amount of the electrode mixture is the dry weight of the electrode mixture per unit area.
• a secondary battery including the above-mentioned electrodes is provided.
• the secondary battery of the present disclosure includes an electrode formed by using the electrode mixture of the present disclosure, it exhibits a high high temperature storage capacity retention rate, a low resistance increase rate, and a low gas amount change rate, and is excellent in battery characteristics.
• the secondary battery of the present disclosure preferably includes a positive electrode, a negative electrode, and a non-aqueous electrolytic solution, and one or both of the positive electrode and the negative electrode are the above-mentioned electrodes. Further, the secondary battery of the present disclosure preferably includes a positive electrode, a negative electrode, and a non-aqueous electrolytic solution, and the positive electrode is the above-mentioned electrode.
• the non-aqueous electrolyte solution is not particularly limited, but is propylene carbonate, ethylene carbonate, butylene carbonate, ⁇ -butyl lactone, 1,2-dimethoxyethane, 1,2-diethoxyethane, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate and the like.
• One or more of the known solvents of the above can be used. Any conventionally known electrolyte can be used, and LiClO 4 , LiAsF 6 , LiPF 6 , LiBF 4 , LiCl, LiBr, CH 3 SO 3 Li, CF 3 SO 3 Li, cesium carbonate and the like can be used.
• the electrodes of the present disclosure are excellent in flexibility, the current collector and the electrode mixture layer are sufficiently adhered to each other, and a secondary battery having excellent battery characteristics can be formed. Therefore, it can be suitably used as an electrode for a wound type secondary battery. Further, the secondary battery of the present disclosure may be a winding type secondary battery.
• the electrodes of the present disclosure are useful not only for lithium ion secondary batteries using the liquid electrolyte described above, but also for polymer electrolyte lithium secondary batteries for non-aqueous electrolyte secondary batteries. It is also useful for electric double layer capacitors.
• ⁇ Content of acrylic acid unit in PVdF The content of acrylic acid units in PVdF was measured by acid-base titration of carboxylic acid groups. Specifically, about 0.5 g of PVdF was dissolved in acetone at a temperature of 70 to 80 ° C. 5 ml of water was added dropwise under vigorous stirring to avoid coagulation of PVdF. Titration with aqueous NaOH solution having a concentration of 0.1 N was performed with a neutral transition at about -270 mV until complete neutralization of acidity. From the measurement results, the amount of the substance contained in the acrylic acid unit contained in 1 g of PVdF was determined, and the content of the acrylic acid unit was calculated.
• A, B, C, D The following peak areas (A, B, C, D) were determined by F-NMR measurement, and the ratio of VdF units to TFE units was calculated.
• ⁇ Melting point> Using a differential scanning calorimetry (DSC) device, the temperature is raised from 30 ° C. to 220 ° C. at a rate of 10 ° C./min, then lowered to 30 ° C. at 10 ° C./min, and again at a rate of 10 ° C./min at 220 ° C. The temperature with respect to the maximum value in the heat of fusion curve when the temperature was raised to the maximum was determined as the melting point.
• DSC differential scanning calorimetry
• a test piece was prepared by punching the positive electrode prepared in Examples and Comparative Examples with a hand punch of ⁇ 13 mm, the total thickness of the test piece was measured with a micrometer having a minimum scale of 1 ⁇ m, and the positive electrode current collector was measured from these measured values. It was calculated from the value obtained by subtracting the thickness.
• a test piece was prepared by punching the positive electrodes prepared in Examples and Comparative Examples with a hand punch of ⁇ 13 mm, and the mass and area of the test piece were measured. Then, the density of the positive electrode mixture layer was calculated from the mass of the test piece and the positive electrode current collector, the area of the test piece, and the thickness of the positive electrode mixture layer obtained by the above method.
• a 2 cm ⁇ 10 cm test piece was prepared by cutting off the prepared positive electrode before pressing. The test piece was pressed to prepare a test piece after density adjustment in which the density of the positive electrode mixture layer was 3.6 g / cc. After the density was adjusted, the test piece was wound around a round bar having a diameter of 5 mm and a diameter of 3 mm, and the positive electrode mixture layer was visually confirmed and evaluated according to the following criteria.
• ⁇ No cracks were observed.
• ⁇ Cracks were observed, but no breakage of the positive electrode mixture layer and the positive electrode current collector was observed.
• X The positive electrode mixture layer and the positive electrode current collector were broken.
• NMC622 LiNi 0.6 Mn 0.2 Co 0.2 O 2
• NMC811 LiNi 0.8 Mn 0.1 Co 0.1 O 2
• NCA LiNi 0.82 Co 0.15 Al 0.03
• O 2 AB Acetylene Black CNT: Multi-walled carbon nanotube, manufactured by Sinano, trade name LB136-43 Graphene: Made by Sanjun Chukasha, trade name GNP-N
• Example 1 (Preparation of positive electrode mixture)
• the fluorine-containing copolymer (a) as a binder was dissolved in N-methyl-2-pyrrolidone (NMP) to prepare a fluorine-containing copolymer (a) solution having a concentration of 8% by mass.
• NMP N-methyl-2-pyrrolidone
• a solution of the fluorine-containing copolymer (a), NMC622 as a positive electrode active material, acetylene black (AB) as a conductive additive, and multi-walled carbon nanotubes (CNT) were mixed using a stirrer and shown in Table 1.
• a mixed solution having a composition ratio (active material / conductive additive / binder) was obtained.
• NMP was further added to the obtained mixed solution and mixed to prepare a positive electrode mixture having a solid content concentration of 71% by mass.
• the obtained positive electrode mixture is uniformly applied to one side of the positive electrode current collector (aluminum foil having a thickness of 20 ⁇ m), the NMP is completely volatilized, and then a pressure of 10 tons is applied using a roll press machine.
• the positive electrode current collector aluminum foil having a thickness of 20 ⁇ m
• the NMP is completely volatilized
• a pressure of 10 tons is applied using a roll press machine.
• Table 1 shows the amount of the positive electrode mixture applied per side, the thickness of the positive electrode mixture layer in the positive electrode per side, the density of the positive electrode mixture layer, and the adhesion of the positive electrode mixture layer to the positive electrode current collector.
• the prepared positive electrode was cut into a size of 500 mm ⁇ 700 mm (with a positive electrode terminal), and a strip-shaped negative electrode was cut into a size of 502 mm ⁇ 702 mm (with a negative electrode terminal), and a lead body was welded to each terminal. Further, a polypropylene film separator having a thickness of 20 ⁇ m was cut into a size of 504 mm ⁇ 800 mm, and the positive electrode and the negative electrode were wound so as to sandwich the separator and placed in the packaging material.
• an electrolytic solution (a solvent in which ethylene carbonate and ethyl methyl carbonate are mixed at a volume ratio of 3/7 and LiPF 6 is dissolved at a concentration of 1 mol / liter) is put in a packaging material, sealed, and wound-wound laminated battery.
• an electrolytic solution a solvent in which ethylene carbonate and ethyl methyl carbonate are mixed at a volume ratio of 3/7 and LiPF 6 is dissolved at a concentration of 1 mol / liter
• the battery is charged to 4.2 V with a constant current of 0.2 C, charged with a constant voltage of 4.2 V until the current value reaches 0.05 C, and with a constant current of 0.2 C.
• the current was discharged to 0 V, and the initial discharge capacity was determined.
• charging was carried out with a constant voltage of 4.2 V until the current value became 0.05 C, and the initial resistance was measured.
• 1C represents a current value that discharges the reference capacity of the battery in 1 hour
• 5C is a current value that is 5 times that value
• 0.1C is a current value that is 1/10 of that
• 0.2C Represents a current value of 1/5 of that.
• the wound-type laminated battery for which the initial characteristic evaluation was completed was stored at a high temperature under the condition of 85 ° C. for 36 hours. After the battery was sufficiently cooled, the volume of the battery was measured by the Archimedes method, and the rate of change in the amount of gas was calculated from the volume change before and after storage at high temperature based on the following formula. Next, the battery was discharged to 3 V at 0.5 C at 25 ° C., the residual capacity after high temperature storage was determined, and the high temperature storage capacity retention rate (%) was determined based on the following formula.
• the battery was charged to 4.2 V with a constant current of 0.2 C, charged to a current value of 0.05 C with a constant voltage of 4.2 V, and then discharged to 3 V at 0.5 C. Then, after charging to 4.2V with a constant current of 0.2C, charging is performed with a constant voltage of 4.2V until the current value reaches 0.05C, the resistance after high temperature storage is measured, and based on the following formula. The resistance increase rate (%) was calculated.
• This composite NMC622 was used as a positive electrode active material, and a positive electrode mixture was prepared in the same manner as in Example 1. Then, a positive electrode was prepared using the obtained positive electrode mixture and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 2.
• the positive electrode active material, the conductive auxiliary agent and the binder with respect to the total mass of the positive electrode active material, the conductive auxiliary agent and the binder in the positive electrode mixture.
• the content ratio of is described.
• the positive electrode mixture contains two types of conductive auxiliary agents, the content ratio of each conductive auxiliary agent in the positive electrode mixture is described separately.
• the positive electrode mixture is 96 with respect to the total mass of the positive electrode active material, the conductive auxiliary agent and the binder. It means that it contains 9.9% by mass of positive electrode active material, 1.2% by mass of acetylene black, 0.4% by mass of multi-layer carbon nanotubes and 1.5% by mass of binder.
• Example 14> (Preparation of positive electrode mixture)
• the fluorine-containing copolymer (a) as a binder was dissolved in N-methyl-2-pyrrolidone (NMP) to prepare a fluorine-containing copolymer (a) solution having a concentration of 8% by mass.
• NMP N-methyl-2-pyrrolidone
• a solution of the fluorine-containing copolymer (a), NMC811 as the positive electrode active material, acetylene black (AB) as the conductive additive, and multi-walled carbon nanotubes (CNT) were mixed using a stirrer and shown in Table 3.
• a mixed solution having a composition ratio (active material / conductive additive / binder) was obtained.
• NMP was further added to the obtained mixed solution and mixed to prepare a positive electrode mixture having a solid content concentration of 71% by mass.
• the obtained positive electrode mixture is uniformly applied to one side of the positive electrode current collector (aluminum foil having a thickness of 20 ⁇ m), the NMP is completely volatilized, and then a pressure of 10 tons is applied using a roll press machine.
• the positive electrode current collector aluminum foil having a thickness of 20 ⁇ m
• the NMP is completely volatilized
• a pressure of 10 tons is applied using a roll press machine.
• Table 3 shows the amount of the positive electrode mixture applied per side, the thickness of the positive electrode mixture layer in the positive electrode per side, the density of the positive electrode mixture layer, and the adhesion of the positive electrode mixture layer to the positive electrode current collector.
• the prepared positive electrode was cut into a size of 500 mm ⁇ 700 mm (with a positive electrode terminal), and a strip-shaped negative electrode was cut into a size of 502 mm ⁇ 702 mm (with a negative electrode terminal), and a lead body was welded to each terminal. Further, a polypropylene film separator having a thickness of 20 ⁇ m was cut into a size of 504 mm ⁇ 800 mm, and the positive electrode and the negative electrode were wound so as to sandwich the separator and placed in the packaging material.
• an electrolytic solution (a solvent in which ethylene carbonate and ethyl methyl carbonate are mixed at a volume ratio of 3/7 and LiPF 6 is dissolved at a concentration of 1 mol / liter) is put in a packaging material, sealed, and wound-wound laminated battery.
• an electrolytic solution a solvent in which ethylene carbonate and ethyl methyl carbonate are mixed at a volume ratio of 3/7 and LiPF 6 is dissolved at a concentration of 1 mol / liter
• the battery is charged to 4.1 V with a constant current of 0.2 C, charged with a constant voltage of 4.1 V until the current value reaches 0.05 C, and with a constant current of 0.2 C.
• the current was discharged to 0 V, and the initial discharge capacity was determined.
• charging was carried out with a constant voltage of 4.1 V until the current value became 0.05 C, and the initial resistance was measured.
• 1C represents a current value that discharges the reference capacity of the battery in 1 hour
• 5C is a current value that is 5 times that value
• 0.1C is a current value that is 1/10 of that
• 0.2C Represents a current value of 1/5 of that.
• the wound-type laminated battery for which the initial characteristic evaluation was completed was stored at a high temperature under the condition of 70 ° C. for 96 hours. After the battery was sufficiently cooled, the volume of the battery was measured by the Archimedes method, and the rate of change in the amount of gas was calculated from the volume change before and after storage at high temperature based on the following formula. Next, the battery was discharged to 3 V at 0.5 C at 25 ° C., the residual capacity after high temperature storage was determined, and the high temperature storage capacity retention rate (%) was determined based on the following formula.
• the battery was charged to 4.1 V with a constant current of 0.2 C, charged to a current value of 0.05 C with a constant voltage of 4.1 V, and then discharged to 3 V at 0.5 C. Then, after charging to 4.1V with a constant current of 0.2C, charging is carried out with a constant voltage of 4.1V until the current value reaches 0.05C, the resistance after high temperature storage is measured, and based on the following formula. The resistance increase rate (%) was calculated.
• This composite NMC811 was used as a positive electrode active material, and a positive electrode mixture was prepared in the same manner as in Example 14. Then, a positive electrode was prepared using the obtained positive electrode mixture and evaluated in the same manner as in Example 14. The evaluation results are shown in Table 4.
• Example 27> (Preparation of positive electrode mixture)
• the fluorine-containing copolymer (a) as a binder was dissolved in N-methyl-2-pyrrolidone (NMP) to prepare a fluorine-containing copolymer (a) solution having a concentration of 8% by mass.
• NMP N-methyl-2-pyrrolidone
• a solution of the fluorine-containing copolymer (a), NCA as a positive electrode active material, acetylene black (AB) as a conductive additive, and multi-walled carbon nanotubes (CNT) were mixed using a stirrer and shown in Table 5.
• a mixed solution having a composition ratio (active material / conductive additive / binder) was obtained.
• NMP was further added to the obtained mixed solution and mixed to prepare a positive electrode mixture having a solid content concentration of 71% by mass.
• the obtained positive electrode mixture is uniformly applied to one side of the positive electrode current collector (aluminum foil having a thickness of 20 ⁇ m), the NMP is completely volatilized, and then a pressure of 10 tons is applied using a roll press machine.
• the positive electrode current collector aluminum foil having a thickness of 20 ⁇ m
• the NMP is completely volatilized
• a pressure of 10 tons is applied using a roll press machine.
• Table 5 shows the amount of the positive electrode mixture applied per side, the thickness of the positive electrode mixture layer in the positive electrode per side, the density of the positive electrode mixture layer, and the adhesion of the positive electrode mixture layer to the positive electrode current collector.
• the prepared positive electrode was cut into a size of 500 mm ⁇ 700 mm (with a positive electrode terminal), and a strip-shaped negative electrode was cut into a size of 502 mm ⁇ 702 mm (with a negative electrode terminal), and a lead body was welded to each terminal. Further, a polypropylene film separator having a thickness of 20 ⁇ m was cut into a size of 504 mm ⁇ 800 mm, and the positive electrode and the negative electrode were wound so as to sandwich the separator and placed in the packaging material.
• an electrolytic solution (a solvent in which ethylene carbonate and ethyl methyl carbonate are mixed at a volume ratio of 3/7 and LiPF 6 is dissolved at a concentration of 1 mol / liter) is put in a packaging material, sealed, and wound-wound laminated battery.
• an electrolytic solution a solvent in which ethylene carbonate and ethyl methyl carbonate are mixed at a volume ratio of 3/7 and LiPF 6 is dissolved at a concentration of 1 mol / liter
• the battery is charged to 4.0 V with a constant current of 0.2 C, charged with a constant voltage of 4.0 V until the current value reaches 0.05 C, and with a constant current of 0.2 C.
• the current was discharged to 0 V, and the initial discharge capacity was determined.
• charging was carried out with a constant voltage of 4.0 V until the current value became 0.05 C, and the initial resistance was measured.
• 1C represents a current value that discharges the reference capacity of the battery in 1 hour
• 5C is a current value that is 5 times that value
• 0.1C is a current value that is 1/10 of that
• 0.2C Represents a current value of 1/5 of that.
• the wound-type laminated battery for which the initial characteristic evaluation was completed was stored at a high temperature under the condition of 60 ° C. for 720 hours. After the battery was sufficiently cooled, the volume of the battery was measured by the Archimedes method, and the rate of change in the amount of gas was calculated from the volume change before and after storage at high temperature based on the following formula. Next, the battery was discharged to 3 V at 0.5 C at 25 ° C., the residual capacity after high temperature storage was determined, and the high temperature storage capacity retention rate (%) was determined based on the following formula.
• the battery was charged to 4.0 V with a constant current of 0.2 C, charged to a current value of 0.05 C at a constant voltage of 4.0 V, and then discharged to 3 V at 0.5 C. Then, after charging to 4.0V with a constant current of 0.2C, charging is performed with a constant voltage of 4.0V until the current value reaches 0.05C, the resistance after high temperature storage is measured, and based on the following formula. The resistance increase rate (%) was calculated.
• Examples 28 to 39 and Comparative Examples 11 to 14> The same as in Example 27, except that the binder was appropriately dissolved so that the concentration of the binder solution was 5 to 8% by mass, and the type of binder, the type of conductive auxiliary agent, the composition ratio, etc. were changed as described in each table. To prepare a positive electrode mixture. Then, a positive electrode was prepared using the obtained positive electrode mixture and evaluated in the same manner as in Example 27. The results are shown in Tables 5 and 6.
• ⁇ Comparative Example 15> The aqueous dispersion of the fluorine-containing copolymer (c) was sprayed onto the NCA and dried to prepare a composite NCA.
• This composite NCA was used as a positive electrode active material, and a positive electrode mixture was prepared in the same manner as in Example 27. Then, a positive electrode was prepared using the obtained positive electrode mixture and evaluated in the same manner as in Example 27. The evaluation results are shown in Table 6.

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