TWI755429B - Adhesive for lithium ion battery and electrode and separator using the same - Google Patents

Abstract

The present invention provides a non-aqueous electrode or a separator for use in a lithium ion battery having excellent cycle life characteristics at high temperature. The binder of the present invention is a non-aqueous binder used in electrodes or separators for lithium ion batteries in which cellulose nanofibers are composited with thermoplastic fluorine-based resins, wherein the cellulose nanofibers have a diameter of (diameter) of 0.002 μm or more and 1 μm or less, fiber length of 0.5 μm or more and 10 mm or less, and aspect ratio (fiber length of cellulose nanofibers/fiber diameter of cellulose nanofibers) of 2 or more and 100,000 or less cellulose.

Description

Adhesive for lithium ion battery and electrode and separator using the same

The present invention relates to binders used in electrodes or separators of lithium ion batteries, electrodes and separators using the same.

The use of secondary batteries has expanded from electronic equipment to automobiles, large-scale power storage systems, etc., and its market size is expected to grow to an industry of more than 10 trillion yen. In particular, information communication devices such as mobile phones, smart phones, and tablet terminals have been widely used, and the penetration rate in the world has exceeded 30%.

In addition, the application scope of secondary batteries has also expanded to the power sources of next-generation vehicles such as electric vehicles (EV), plug-in hybrid electric vehicles (PHEV), and hybrid electric vehicles (HEV). In addition, secondary batteries have been used as a backup power source for households, storage of natural energy, load balancing, etc., as a result of the Great East Japan Earthquake in 2011, and the use of secondary batteries tends to expand. In this way, secondary batteries have become indispensable in the introduction of energy-saving technologies or new energy technologies.

It is known that secondary batteries are mainly alkaline secondary batteries such as nickel-cadmium (Ni-Cd) batteries or nickel-hydrogen (Ni-MH) batteries, but due to their small size, light weight, high voltage, and no memory effect. Such characteristics, the use of lithium-ion batteries, which are non-aqueous electrolyte secondary batteries, is increasing. A lithium ion battery is composed of a positive electrode, a negative electrode, a separator, an electrolyte or electrolyte, and a cell body (battery case).

Electrodes such as positive and negative electrodes are composed of active materials, conductive additives, binders and current collectors. Generally speaking, the electrodes are mixed with active materials, conductive additives, and binders into a solvent such as an organic solvent or water to form a slurry, which is then coated on the current collector (mainly, the positive electrode is aluminum, and the negative electrode is copper. or nickel), after drying, it is produced by rolling by rolling or the like.

The positive active materials are mainly lithium cobalt oxide (LiCoO ₂ ), ternary materials (Li(Ni, Co, Mn)O ₂ ), nickel-cobalt-lithium aluminate (Li(Ni, Co, Al)O ₂ ), etc. It has been widely used as a positive electrode material for practical batteries. Recently, research and development of positive electrode materials such as lithium excess solid solution materials (Li ₂ MnO ₃ -LiMO ₂ ) and lithium silicate materials (Li ₂ MSiO ₄ ) have also been actively conducted.

LiCoO ₂ shows a discharge voltage above 3.7V (vs. Li/Li ⁺ ), and the effective discharge capacity is about 150mAh/g. It can obtain stable cycle life characteristics, so it is mainly used in mobile devices. However, since large batteries such as those used in vehicles (EVs, PHEVs, HEVs) or power storage are susceptible to fluctuations in the market price of cobalt (Co), ternary systems (Li(Ni, Co,Mn)O ₂ ), hereinafter referred to as NCM) positive electrode or nickel-cobalt-lithium aluminate (Li(Ni, Co, Al)O ₂ , hereinafter referred to as NCA) positive electrode, or the like.

The charge-discharge characteristics of NCM can be adjusted by changing the molar ratio of three transition metal elements including nickel (Ni), cobalt (Co), and manganese (Mn).

For NCM positive electrodes before 2015, the molar ratio of the mainstream transition metal is Ni:Co:Mn=1:1:1 (Li(Ni _0.33 Co _0.33 Mn _0.33 )O ₂ , hereinafter referred to as NCM111); Since 2016, a material (Li(Ni _0.5 Co _0.2 Mn _0.3 )O ₂ , hereinafter referred to as NCM523) in which the amount of Co is decreased and the amount of Ni is increased, and Ni:Co:Mn=5:2:3, has become popular. In recent years, Ni:Co:Mn=6:2:2 material (Li(Ni _0.6 Co _0.2 Mn _0.2 )O ₂ ) or Ni: Co: Mn=8:1: 1 material (Li(Ni _0.8 Co _0.1 ) Research and development of NCM positive electrodes such as Mn _0.1 )O ₂ ) are being actively conducted.

NCA is a positive electrode material in which Co is substituted into the Ni site of lithium nickelate (LiNiO ₂ ) and aluminum (Al) is added. In general NCA, the molar ratio of Ni, Co, and Al is Ni is 0.65 or more and 0.95 or less, Co is 0.1 or more and 0.2 or less, and Al is 0.01 or more and 0.20 or less. The NCA with this element ratio suppresses the movement of Ni cations, improves thermal stability and durability compared to LiNiO ₂ , and obtains a larger discharge capacity than LiCoO ₂ .

Compared with LiCoO ₂ , these nickel-lithium NMC positive electrodes or NCA positive electrodes are expected to have higher capacity and lower cost.

Negative active materials are mainly graphite (black lead), hard carbon (hard to black lead carbon), soft carbon (easy black lead carbon), lithium titanate (Li ₄ Ti ₅ O ₁₂ ), etc., which have been widely used as practical materials. The negative electrode material of the battery. Recently, these materials have been mixed with silicon (Si)-based materials or tin (Sn)-based materials to increase the capacity of negative electrodes.

The effective discharge capacity of black lead series is 340~360mAh/g, showing a value almost close to the theoretical capacity of 372mAh/g, showing excellent cycle life characteristics.

Hard carbon and soft carbon are amorphous carbon materials, the effective discharge capacity is 150~250mAh/g, the discharge capacity is lower than that of crystalline graphite, but the output characteristics are superior.

The effective capacity of Li ₄ Ti ₅ O ₁₂ is 160~180mAh/g, and the discharge capacity is lower than that of graphite or amorphous carbon material, but the potential during charging is about 1.5V away from the lithium precipitation potential, and the dendrite of lithium There is less risk of precipitation.

Si-based materials or Sn-based materials are classified as alloy-based materials, and the effective capacitance is 3000~3600mAh/g for Si and 700~900mAh/g for Sn.

After drying the positive electrode or negative electrode, and then rolling, it is used to shrink the volume of the active material layer of the electrode, that is, the coating layer composed of the active material, the conductive agent, and the binder, so as to make it and the active material layer. The contact area between the conductive aid or the current collector increases. Thereby, the electron conduction network of the active material layer is firmly constructed, and the electron conductivity is improved.

The binder is used to bond the active material with the active material, the active material with the conductive auxiliary, the active material with the current collector, and the conductive auxiliary with the current collector. Adhesives can be roughly divided into: "solution type", which is dissolved in a solvent and used in a liquid state; "dispersion type (emulsion, latex type)", which is used by dispersing solid content in a solvent; "Reactive type" used to react with heat or light.

In addition, depending on the type of solvent, the binder can be classified into an aqueous system and an organic solvent system. For example, polyvinylidene fluoride (PVdF), which is a typical plastic fluorine-based resin, is a solvent-based binder, and N-methyl-2-pyrrolidone (NMP) is used in the production of electrode paste. organic solvent. Styrene butadiene rubber (SBR) is a dispersion-type adhesive, which is used by dispersing SBR fine particles in water. Polyimide (PI) is a reactive binder. The PI precursor is dissolved or dispersed in a solvent such as NMP, and then heat treated to generate imidization (dehydration reaction and cyclization reaction) and cross combined reaction to obtain strong PI.

唑(PBO)等。 Although it depends on the molecular weight or substituent of the adhesive, there are dissolving adhesives such as polyvinylidene fluoride (PVdF), ethylene-vinyl acetate (EVA) and the like. In addition, dispersion-type adhesives include styrene butadiene rubber (SBR), polytetrafluoroethylene (PTFE), urethane rubber, polypropylene (PP), polyethylene (PE), polyvinyl acetate ( PVAc), nitrocellulose, cellulose nanofibers, etc. Reactive adhesives include polyimide (PI), polyamide (PA), polyamide imide (PAI), polybenzimidazole (PBI), polybenzyl

azole (PBO) etc.

In addition, organic solvent-based binders such as NMP swell in high-temperature electrolytes and increase electrode resistance, so it is difficult to use them in high-temperature environments. In particular, the thermoplastic fluorine-based resin has a property that the swelling ratio increases as the temperature rises. For example, according to Patent Document 1, it is described that PVdF is swelled by an electrolyte solution in a high temperature environment of 50°C or higher, the bonding force becomes weak, the electrode resistance increases, and the high temperature durability is poor.

Water-based dissolving adhesives have poor oxidation resistance or reduction resistance, and are often gradually decomposed due to repeated charge and discharge, so that sufficient life characteristics cannot be obtained. In addition, since the ion conductivity is low, the output characteristics are lacking. Although the dispersion type binder has the advantage of using water in the solvent, it is easy to lose the dispersion stability depending on the degree of acid or alkali (pH), water concentration or ambient temperature, and segregation, agglomeration, Precipitation etc. In addition, the binder fine particles dispersed in water have a particle size of less than 1 μm, and when the water vaporizes due to drying, the particles fuse with each other to form a thin film. Since this film has no electrical conductivity (electrical conductivity) and ionic conductivity, only a slight deviation in the usage amount will have a great influence on the output characteristics or life characteristics of the battery.

When an electrode slurry is produced with an aqueous binder as the solvent type, when an active material containing Li is added, the slurry becomes alkaline (pH value rises). When the pH value of the slurry is 11 or more, there is a problem that it is difficult to obtain a uniform electrode due to the reaction with the aluminum current collector at the time of coating.

Therefore, there has been proposed a method of coating the surface of the particles of the positive electrode active material with carbon, ceramics, or the like. By coating the particle surface of the positive electrode active material with carbon or ceramics, even if an aqueous binder is used, the direct contact between the solvent and the active material is reduced, and the pH value of the slurry can be suppressed from rising.

For example, according to Non-Patent Document 1, it is described that polyvalent anion systems such as lithium iron phosphate (LiFePO ₄ ), which are positive electrode active materials, are coated with carbon on the particle surfaces, so even if an aqueous binder is used, the solvent and the positive electrode active material are still The direct contact is reduced, and the pH value can be suppressed. In addition, the battery using acrylic binder and PVdF binder in the positive electrode showed cycle life characteristics at 60°C, while the positive electrode using PVdF binder in the positive electrode gradually decreased the system capacity; The positive electrode with acrylic binder shows superior high temperature durability.

For example, in Patent Document 2, as the reasons why it is difficult to use a water-based binder for the positive electrode like the negative electrode, there are listed: (1) Since the positive electrode active material contacts and reacts with water, the lithium of the positive electrode active material is eluted, and the positive electrode capacity decreases; ( 2) Oxidative decomposition of the water-based binder occurs during charging; (3) It is difficult to disperse the slurry; and so on, in terms of battery characteristics, there is a possibility that the positive electrode capacity and cycle characteristics may decrease. Therefore, according to Patent Document 2, by using Li _α M _β O _γ (where M is selected from the group consisting of Al, Ti, Cr, Mn, Fe, Co, Ni, Cu, zr, Nb, Mo , Ag, Ta, W, Ir one or more metal elements of the group, 0≦α≦6, 1≦β≦5, 0<γ≦12) The active material of the compound shown in It can prevent the lithium of the positive electrode active material from dissolving and the capacity of the positive electrode active material is reduced. It can prevent the oxidative decomposition of the water-based binder during charging, and can be used as a positive electrode for lithium ion secondary batteries with excellent high temperature characteristics.

However, commercially available lithium (Li)-containing active materials sometimes contain lithium hydroxide (LiOH) as an impurity. The reason for this has not been elucidated, but it is considered that the starting material used for synthesizing the Li-containing active material remains, or the active material itself generates lithium hydroxide, or the like.

In particular, among the Li-containing active materials, positive active materials such as NCM, NCA, LiNiO ₂ , Li ₂ MnO ₃ -LiMO ₂ , and Li ₂ MSiO ₄ contain a large amount of lithium hydroxide and show strong alkalinity. Therefore, in the production step of the slurry, when a plastic fluororesin binder is used, the slurry may be gelled. It is difficult to manufacture electrodes from the gelled slurry, and gas may be generated during charging.

For example, in Patent Document 3, it is described that in general, lithium hydroxide is a cause of reacting with a binder to rapidly increase the viscosity of the slurry or to gel the slurry in the production process of the positive electrode mixture slurry. Therefore, according to Patent Document 3, it is proposed that the surface of the nickel-based lithium-nickel composite oxide particles has high elution-suppressing ability to the solution by three-dimensionally cross-linking the polymer, and also has ionic conductivity by coating. Coated nickel-based lithium-nickel composite oxide particles with non-electron-conductive polymer and electron-conductive polymer with both electron conductivity and ion conductivity improve atmospheric stability without adversely affecting battery characteristics.

According to Patent Document 4, it is disclosed that a LiFePO ₄ /SiO-based lithium ion secondary battery using PI for the positive electrode and the negative electrode can stably charge and discharge even at a high temperature of 120°C.

Reactive adhesives are excellent in heat resistance, adhesion, and chemical resistance. Among them, PI-based adhesives show high heat resistance and adhesiveness. Even active materials with large volume changes can still obtain stable life characteristics, and the adhesives are not easy to swell even in high-temperature electrolytes.

As a reinforcing material for the binder, Patent Document 5 discloses an electrode structure for an electric storage device, which is characterized by compounding cellulose nanofibers with a binder containing a water-soluble polymer, and has Si as its main component. Active materials, and conductive auxiliary materials, binders, current collectors.

Cellulose nanofibers are hydrophilic and are often dispersed in water. However, Patent Document 6 discloses cellulose nanofibers dispersed in NMP that does not contain water in a dispersion medium. By mixing the cellulose dispersion with the resin, it can be expected to increase the functionality of the resin utilizing the light weight, high strength, high elastic modulus, low coefficient of linear thermal expansion, and high heat resistance of cellulose.

In addition to the above-mentioned binders, there are almost no reported examples in the field of lithium ion batteries, but Patent Document 7 and Non-Patent Documents 2 and 3 disclose technologies using inorganic binders for secondary battery electrodes.

Such lithium-ion batteries are widely used in various shapes such as cylindrical, square, and laminated (pouch) types. In addition, in the battery with a small capacity, the cylindrical type is used in terms of pressure resistance or sealing easiness, and the battery with a large capacity is in a square type because of the ease of handling.

In addition, when focusing on the electrode structure of a lithium ion battery, two types of the laminated type and the wound type are generally used. That is, in a laminated type battery, an electrode group in which positive electrodes and negative electrodes are alternately laminated via separators is accommodated in a battery case. Most of the multilayer batteries have a square battery case. On the other hand, the wound-type battery is accommodated in the battery cell (battery case) in a state in which the positive electrode and the negative electrode sandwich the separator and are wound into a spiral shape. The winding type battery case is like a cylindrical type or a square type.

[Prior Art Literature] [Patent Literature]

Patent Document 1: Japanese Patent Re-List No. 2014/057627

Patent Document 2: Japanese Patent No. 5999683

Patent Document 3: Japanese Patent No. 6102837

Patent Document 4: Japanese Patent Laid-Open No. 2013-084521

Patent Document 5: Japanese Patent Laid-Open No. 2016-021332

Patent Document 6: Japanese Patent Laid-Open No. 2015-101694

Patent Document 7: Japanese Patent No. 6149147

[Non-patent literature]

Non-Patent Document 1: Mukai Takashi et al.: Industrial Materials, vol. 63, No. 12, pp. 18-23 (2015)

Non-Patent Document 2: Mukai Takashi et al.: Material Stage, vol.17, No.5, pp.29-33 (2017)

Non-Patent Document 3: Mukai Takashi et al.: "Lithium-ion secondary battery ~Component design method and evaluation method suitable for high capacity and characteristic improvement~", Chapter 4, Section 2, Intelligence Agency Co., Ltd., pp.210 -220 (2017)

As described above, the high-temperature durability of the electrode system using the thermoplastic fluorine-based resin as a binder deteriorates. On the other hand, as in Patent Documents 1 to 5 or Non-Patent Documents 1 to 3, if a water-based binder or a PI-based binder is used as the electrode binder, the high-temperature durability can be improved. However, when an active material containing a large amount of Li comes into contact with water or moisture, the electrode capacity decreases and the cycle life characteristics also deteriorate. If the surface of the particles of the active material containing Li is covered with carbon or ceramics, the direct contact between water and the active material is suppressed, and the pH value of the slurry can be suppressed from rising. However, during the mixing (kneading) step of the slurry, if the When the coating on the surface of the active material particles is peeled off, the pH of the slurry rises in one go. Furthermore, even if the solvent type is an organic solvent-based binder, in a PI-based binder in which a dehydration reaction is induced by heat treatment, the moisture generated when the electrode is dried comes into contact with the Li-containing active material.

In addition, PI-based adhesives are insoluble in almost all organic solvents due to their excellent chemical resistance. Therefore, in the preparation of the electrode slurry, polyamic acid, which is a PI precursor, is dissolved in NMP and used, and it is heated at 200° C. or higher to carry out imidization reaction (dehydration cyclization). reaction) to obtain PI. Then, after the imidization reaction, heat treatment is performed at a higher temperature to cause a crosslinking reaction, and PI with high mechanical strength is obtained. From the viewpoint of electrode life, the heat treatment temperature is preferably such a high temperature that PI does not carbonize. However, if the PI precursor is mixed with a strong alkaline Li-containing active material, the PI precursor will segregate, making it difficult to produce a uniformly dispersed slurry, and it is also difficult to adjust the viscosity of the slurry. Furthermore, the heat treatment at 200° C. or higher also leads to an increase in power consumption at the time of electrode production.

Patent Document 5 discloses that, as a reinforcing material for an electrode, by mixing cellulose nanofibers with a binder and compounding, a machine can be obtained that can withstand the stress that occurs during volume expansion and contraction during lithium insertion and extraction reactions. strength. It can be considered that by compounding cellulose nanofibers into a water-soluble binder, the mechanical strength of the electrode is improved, and even if an active material with a drastic volume change is used, the damage of the conductive network caused by charge and discharge can be suppressed.

However, the Li-containing active material has little volume change due to charge and discharge. Thus, the destruction of the conductive network due to the volume change hardly occurs. In addition, the mechanical strength of the electrode is independent of the swellability between the electrolytes at high temperature. Therefore, even if the mechanical strength of the adhesive is improved, the improvement of the cycle life characteristics at high temperature cannot be expected.

In addition, the binder is a water-soluble polymer, and is not suitable for Li-containing active substances that are materials that are not suitable for contact with moisture. Most of the water-based adhesives (dissolving, dispersing, and reactive types using water as a solvent) are oxidized and decomposed during charging. Therefore, even if the strength of the water-based adhesive is improved, the properties of the electrode at high temperatures (durability or cycle life characteristics, output characteristics, etc.) have not been significantly improved. In addition, if the water-soluble binder is in contact with the strong alkaline Li-containing active material, not only the pH value of the slurry will rise, but also the salting out of the binder or the viscosity of the slurry will change significantly.

Patent Document 6 discloses cellulose nanofibers dispersed in NMP without water in a dispersion medium. However, in the case of using only the cellulose nanofibers dispersed in NMP as a binder, if the slurry to which the active material is added is mixed by a self-revolving mixer or the like, there is a problem of aggregation.

In addition, when the solid content of the cellulose nanofibers dispersed in NMP exceeds 10 mass %, the solid content cannot be increased because the cellulose nanofibers tend to aggregate. The electrode slurry is a slurry with low solid content if cellulose nanofibers with low solid content are used. If the slurry is applied to the current collector, the cellulose nanofibers aggregate when the electrode is dried, it is difficult to obtain a uniform electrode, and the drying time increases. In addition, since the density of the slurry is low, a practical electrode capacity cannot be obtained without increasing the coating amount of the slurry per unit area.

However, the inventors have reviewed the electrodes using cellulose nanofibers as binders and found that, despite the above problems, even in a high temperature environment of 80°C, they did not absorb the electrolyte and swell , which can function as an electrode that exhibits superior cycle life characteristics at high temperatures. In addition, when the conventional thermoplastic fluorine-based resin is only used for adhesion, the color changes to black when lithium hydroxide is added, and gelation occurs easily, but the cellulose nanofibers dispersed in NMP are not confirmed to gel even if lithium hydroxide is added. gelling phenomenon. However, in addition to the above-mentioned problems, it is known that electrodes composed of only cellulose nanofibers as binders have poor output characteristics compared with electrodes using thermoplastic fluorine-based resins as binders. That is, it was shown that most of the conventional cellulose nanofibers are not suitable as binders for electrodes.

Patent Document 7 discloses that an electrode using a silicate-based or phosphate-based inorganic binder has less swelling of the active material layer even when it comes into contact with a high-temperature electrolyte. However, the inorganic binder has a larger specific gravity than the conventional binder (resin binder), so the electrode energy density per unit weight tends to be lower.

However, even if the active material or conductive aid contained in the electrode slurry is uniformly dispersed, for example, if it is left to stand, aggregation or sedimentation occurs over time. In particular, the larger the specific gravity of the active material, the more the active material settles to the bottom due to gravity, so it is easy to become an electrode that loses uniformity in the electrode fabrication process. Therefore, an electrode slurry that does not easily aggregate or settle even if it is left to stand for a long period of time is required.

As mentioned above, the inventors of the present application have repeatedly reviewed the application of the binder using cellulose nanofibers, and found that there are still many problems when only using cellulose nanofibers as the electrode binder, and the practicality cannot be established. the electrode. Therefore, the inventors of the present invention and others have repeatedly studied the binders of thermoplastic fluorine-based resins that combine cellulose nanofibers and binders. The present invention can solve the above-mentioned conventional problems or problems newly discovered by the inventors of the present application.

The binder of the present invention is a non-aqueous binder in an electrode for a lithium ion battery in which cellulose nanofibers and a thermoplastic fluororesin are composited, and characterized in that the diameter (diameter) of the cellulose nanofibers Cellulose having a fiber length of 0.002 μm or more and 1 μm or less, a fiber length of 0.5 μm or more and 10 mm or less, and an aspect ratio (fiber length of cellulose nanofibers/fiber diameter of cellulose nanofibers) of 2 to 100,000. According to this configuration, a binder for electrodes can be obtained that suppresses swelling of the electrode active material layer in the electrolyte solution at 60° C. or higher, and improves cycle life characteristics and output characteristics at high temperatures. In addition, since the thermoplastic fluorine-based resin contains cellulose nanofibers, even if a positive electrode material containing Li is used, gelation of the slurry does not easily occur.

Cellulose nanofibers are a group of cellulose fibers in which cellulose, which is a constituent material such as wood, is physically or chemically decomposed to a maximum fiber diameter of 1 μm or less. In addition, cellulose nanofibers obtained from animals, algae, or bacteria may also be used.

In addition, in the present invention, the fiber length is a value measured by a fiber length measuring machine (manufactured by KAJAANI AUTOMATION, FS-200). In addition, the fiber diameter can be measured by the same apparatus.

More specifically, the fiber diameter (diameter) is preferably 0.002 μm or more and 1 μm or less, the fiber length of the cellulose nanofibers is 0.05 μm or more and 1 μm or less, and the aspect ratio (fiber length of cellulose nanofibers/ The fiber diameter of cellulose nanofibers) is 10 or more and 100,000 or less cellulose nanofibers; more preferably, the fiber length of cellulose nanofibers is 0.2 μm or more, and the aspect ratio (cellulose fiber length / cellulose fiber The fiber diameter) is 20 or more and 50,000 or less cellulose nanofibers.

In general, cellulose nanofibers are made of cellulose materials (precursors of cellulose nanofibers), that is, chemically treated pulp of wood such as kraft pulp and sulfite pulp, cotton pulp such as cotton linter or lint, and straw pulp. Or non-wood pulp such as bagasse pulp, recycled pulp from waste paper, cellulose isolated from seaweed, man-made cellulose fibers, bacterial cellulose fibers caused by acetic acid bacteria, cellulose from animals such as sea squirts Fibers and the like are produced as starting materials.

In the present invention, the cellulose nanofibers are not particularly limited as long as they satisfy the aforementioned fiber diameter, fiber length, and aspect ratio. In this cellulose nanofiber, the above-mentioned cellulose material (cellulose nanofiber precursor) is subjected to a cellulose swelling step, and is mixed by a homomixer, a homogenizer, an ultrasonic dispersion treatment, a pulper, a refiner, and a spiral mixer. Machines, paddle mixers, dispersing mixers, turbo mixers, ball mills, bead mills and mills can be produced by fine fibrillation.

In the cellulose swelling step, a swelling agent and a liquid medium with a hydroxyl group (-OH) having a function as a dispersing solvent can be used to mix it. Coagulation or sedimentation is not easy to occur, and the NMP concentration can be effectively increased in the following step (C), and the liquid medium with -OH is preferably water and/or alcohols. Examples of alcohols include methanol, ethanol, propanol, butanol and the like. Here, when the liquid medium containing cellulose and -OH is 100% by mass, the cellulose is preferably 0.1% by mass or more and 20% by mass or less, more preferably 1% by mass or more and 15% by mass or less .

The cellulose nanofibers thus obtained contain a large amount of water and a liquid medium having -OH such as alcohols. Therefore, when it is mixed with the thermoplastic fluororesin dissolved in NMP, the thermoplastic fluororesin is salted out by water or alcohols, and the function as a binder for electrodes cannot be effectively exhibited.

In the case of using a thermoplastic fluororesin dispersed in a liquid medium having -OH such as water and/or alcohols, cellulose nanofibers are not contained in the thermoplastic fluororesin, and the thermoplastic fluororesin and It is a simple mixture of cellulose nanofibers, so it is difficult to effectively suppress the swelling of the electrode active material layer in a high temperature electrolyte.

That is, the cellulose nanofibers are preferably composited with a thermoplastic fluorine-based resin.

Here, the so-called "composite" and "mixed" are different concepts. The mixed adhesive is a simple collection of cellulose nanofibers and thermoplastic fluorine-based resins. In contrast, the composite adhesive is in the composition of the adhesive. A binder that allows cellulose nanofibers to exist in a dispersed state in a thermoplastic fluororesin matrix. For example, an adhesive containing cellulose nanofibers inside a thermoplastic resin is a composite adhesive.

That is, in order to obtain a composite adhesive, a liquid in which cellulose nanofibers are dispersed in NMP is an essential material.

However, since the cellulose nanofibers are in a liquid state dispersed in a liquid medium having -OH such as water and/or alcohols, it is necessary to prepare a liquid in which the cellulose nanofibers are dispersed in NMP. In the liquid in which the cellulose nanofibers are dispersed, even if the water and/or alcohol is removed by heating or filtration only once, the cellulose nanofibers will aggregate irreversibly and cannot be restored to the original dispersed state. . Therefore, even if NMP is added and mixed to the cellulose nanofibers from which the solvent has been completely removed, a liquid in which the cellulose nanofibers are dispersed in NMP cannot be obtained.

Therefore, it is necessary to replace the cellulose nanofibers dispersed in a liquid medium having -OH such as water and/or alcohols with NMP while maintaining the dispersed liquid state.

The liquid in which the cellulose nanofibers are dispersed in NMP can be produced by going through the following steps (B) and (C).

That is, it can be produced by a method comprising the following steps: a liquid in which cellulose nanofibers are dispersed in NMP, and the sum of the cellulose nanofibers, the liquid medium having -OH, and NMP is set to 100 mass. In the case of %, the liquid medium in which the cellulose nanofibers are dispersed is mixed with NMP so that the solid content of the cellulose nanofibers is 0.1% by mass or more and 20% by mass or less, to obtain cellulose nanofibers containing With the step (B) of the liquid of above-mentioned liquid medium and NMP; And while stirring the above-mentioned liquid of containing cellulose nanofibers and above-mentioned liquid medium and NMP, make above-mentioned liquid medium evaporate, and improve the step (C of NMP concentration) ).

The above-mentioned step (C) preferably removes water by heating under reduced pressure. Specifically, the above step (C) is preferably a step of heating to 25°C or more and 150°C or less under a pressure of 10 hPa or more and 900 hPa or less, and evaporating the liquid medium to increase the NMP concentration. According to this method, the above-mentioned liquid medium can be efficiently removed, and a liquid in which cellulose nanofibers are dispersed in high-purity NMP can be obtained. When the pressure exceeds 900 hPa, unless the heating temperature is raised, it is difficult to remove the above-mentioned liquid medium, and NMP is also likely to be vaporized simultaneously with the above-mentioned liquid medium. If it is less than 10 hPa, NMP is easily vaporized even at room temperature (for example, 25°C), and the scale of the apparatus required for depressurization increases. The pressure is more preferably 50 hPa or more and 800 hPa or less, and more preferably 100 hPa or more and 700 hPa or less. Within this pressure range, the above-mentioned liquid medium can be effectively removed by setting the temperature to 25° C. or higher and 150° C. or lower. Here, the reason for setting the temperature to 150° C. or lower is not only to suppress the vaporization of NMP, but also to suppress the yellowing (color change) of the cellulose nanofibers and prevent the flexibility and mechanical strength of the cellulose nanofibers from decreasing. The reason for making it 25 degreeC or more is to improve the removal rate of the said liquid medium.

After the step (C), it is preferable to include the step (D) of irradiating the liquid in which the cellulose nanofibers are dispersed in the NMP with ultrasonic waves having an oscillation frequency of 10 kHz or more and 200 kHz or less and an amplitude of 1 μm or more and 200 μm or less. More preferably, the irradiated ultrasonic wave has a vibration frequency of 15 kHz or more and 100 kHz or less, and a vibration amplitude of 10 μm or more and 100 μm or less.

This is because, under such conditions, the cellulose nanofibers are uniformly defibrated by the shock wave of the cavity generated by the ultrasonic irradiation, thereby improving the dispersibility and storage stability.

The irradiation time of ultrasonic waves is not particularly limited, but is preferably 1 minute or more, more preferably 3 minutes or more and 60 minutes or less.

The above-mentioned binder contains 5 to 80% by mass of cellulose nanofibers, when the total solid content of the cellulose nanofibers and the thermoplastic fluorine-based resin is 100% by mass, and contains a thermoplastic fluorine-based resin. Resin is 20 mass % or more and 95 mass % or less. According to this structure, the function as a binder for electrodes with more excellent output characteristics can be exhibited. In addition, aggregation or sedimentation is unlikely to occur in the slurry production process, thereby improving the yield in electrode production.

When the total solid content of the cellulose nanofibers and the thermoplastic fluororesin is 100% by mass, the cellulose nanofibers are adjusted to be 5% by mass or more and the thermoplastic fluororesin to be 95% by mass or less. , will improve the resistance to electrolyte swelling, improve the cycle life characteristics and output characteristics at high temperature. The reason for this is presumably because the cellulose nanofibers are dispersed in the matrix of the thermoplastic fluororesin, and the cellulose nanofibers suppress the swelling of the thermoplastic fluororesin by the electrolyte. By adjusting the content of cellulose nanofibers to 80% by mass or less and the thermoplastic fluororesin to be 20% by mass or more, the thermoplastic fluororesin in the electrode binder absorbs the electrolyte at high temperature, but the cellulose nanofibers absorb the electrolyte. The fiber inhibits the swelling of the electrode active material layer, so the conductive network of the active material layer is not easily damaged, and can impart ionic conductivity to the adhesive, thereby obtaining an electrode adhesive with improved output characteristics. Therefore, in the case of only thermoplastic fluorine-based resin, although the electrolyte is absorbed at high temperature and ionic conductivity is imparted to the binder, swelling of the electrode active material layer cannot be suppressed, and the conductive network of the electrode active material layer is destroyed. Therefore, this situation can be suppressed by containing 5 mass % or more of cellulose nanofibers. The cellulose nanofibers alone can suppress the swelling of the electrode active material layer at high temperatures, but lack ionic conductivity. Therefore, this situation can be improved by containing 20 mass % or more of the thermoplastic fluorine-based resin that absorbs the electrolyte. More preferably, it contains 10 mass % or more and 75 mass % or less of cellulose nanofibers, and the thermoplastic fluorine-based resin contains 25 mass % or more and 90 mass % or less, and more preferably contains 20 mass % or more of cellulose nanofibers and 70 mass % or less, and the thermoplastic fluorine-based resin is 30 mass % or more and 80 mass % or less.

The above-mentioned cellulose nanofibers preferably contain cellulose nanofibers in which a part of the hydroxyl group is substituted with a carboxyl group by a polyacid half-ester (SA) treatment. The presence of carboxyl (-COOH) groups on the surface of the cellulose nanofibers can induce repulsion between the cellulose nanofibers. According to this configuration, it is possible to make a binder for electrodes that can suppress swelling of the electrode active material layer in an electrolyte solution of 80°C or higher, and improve cycle life characteristics and output characteristics at high temperatures. In addition, even if the proportion of thermoplastic fluorine-based resin in the binder is reduced, aggregation or sedimentation is unlikely to occur in the slurry manufacturing process, which further improves the yield of electrode manufacturing.

The polybasic acid half-esterification treatment refers to a treatment in which a carboxyl group is introduced into the cellulose surface by half-esterifying a polybasic acid anhydride with respect to a part of the hydroxyl group of cellulose.

The step (A) of the polyacid half-esterification treatment is preferably performed before the step (B). That is, it is preferable that the polybasic acid half-esterified cellulose nanofibers are subjected to the polybasic acid half-esterification treatment of the cellulose material in advance. Specifically, it is preferable to mix the cellulose material (cellulose nanofiber precursor) and the polybasic acid anhydride, which are the starting materials, with a pressure kneader or a single-shaft or above extrusion kneader at a temperature of 80°C or higher and After mixing at a temperature of 150 or lower, the polybasic acid anhydride is half-esterified to a part of the hydroxyl groups present on the surface of cellulose, and the carboxyl group is introduced, and then it is produced by the above-mentioned cellulose microfibrillation method. Before the step (B), the cellulose nanofibers with excellent storage stability can be obtained by performing the polybasic acid half-esterification treatment on the cellulose in the step (A).

Furthermore, after the polybasic acid half-esterification treatment, ethylene oxide addition treatment or propylene oxide addition treatment may be performed as a secondary treatment of cellulose nanofibers.

The composite binder is prepared by dissolving a thermoplastic fluororesin in a liquid in which cellulose nanofibers are dispersed in NMP, thereby obtaining a thermoplastic fluororesin in NMP and dispersing cellulose nanofibers. liquid. Alternatively, a liquid in which cellulose nanofibers are dispersed in NMP may be mixed with a thermoplastic fluororesin dissolved in NMP.

The liquid in which the thermoplastic fluororesin is dissolved in NMP and the cellulose nanofibers are dispersed is obtained when the total solid content of the cellulose nanofibers and the thermoplastic fluororesin is 100% by mass. Step (E) of dissolving the thermoplastic fluororesin in NMP by mixing the cellulose nanofibers at 5% by mass to 80% by mass and the thermoplastic fluororesin at 20% by mass and 95% by mass or less. ), can manufacture adhesives for lithium-ion batteries.

Examples of the thermoplastic fluorine-based resin include polyvinylidene fluoride (PVdF), vinylidene fluoride copolymer, polytetrafluoroethylene (PTFE), polyvinyl fluoride, polytrifluoride, polychlorotrifluoride, A difluoroethylene-chloroethylene trifluoride copolymer, a difluoroethylene-tetrafluoroethylene copolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, etc., can be used by one type or two or more types. Moreover, these may be a homopolymer, a copolymer, and a terpolymer. Among them, it is preferable to contain polyvinylidene fluoride (PVdF) from the viewpoint of high ion conductivity of the electrode, and excellent oxidation resistance and reduction resistance.

The PVdF is preferably an average molecular weight (number average molecular weight: Mn) of 100,000 or more and 5,000,000 or less from the viewpoint of easy electrolyte retention and excellent adhesion to the current collector. If the average molecular weight is less than 100,000, the adhesiveness with the current collector is insufficient, or the viscosity of the adhesive becomes low, so that the coating amount per unit area increases, and it is difficult to obtain an electrode with a high basis weight capacity. When the temperature exceeds 5 million, it is not easy to dissolve in NMP, or the viscosity of the binder increases, so the slurry generates intense heat during mixing. If the slurry cannot be cooled (can not be kept below 80°C), the electrode slurry is easy to gel. . More preferably, the average molecular weight of PVdF is 110,000 or more and 3,000,000 or less, and more preferably 120,000 or more and 1,500,000 or less.

PVdF is usually obtained by suspension polymerization or emulsion polymerization of vinylidene fluoride together with additives such as a polymerization initiator, suspending agent, or emulsifier in a suitable reaction medium. The molecular weight of this PVdF can be adjusted using a known polymerization degree adjuster, chain transfer agent, or the like.

In the present invention, the number-average molecular weight means the result of measurement by gel permeation chromatography, which has been widely used as a method for measuring the molecular weight of polymers. As measurement conditions, the value measured by an ultraviolet detector using NMP in which 0.01 mol/L of lithium bromide is dissolved can be used with an HLC8020 apparatus manufactured by Tosoh Corporation.

The above-mentioned adhesive is an adhesive in which thermoplastic fluorine-based resin is dissolved in NMP, and cellulose nanofibers are dispersed in NMP. When the total mass is 100 mass %, the total of the solid content of the cellulose nanofibers and the thermoplastic fluorine-based resin is preferably 3 mass % or more and 30 mass % or less. Here, in order to avoid the contact of NMP and the Li-containing active material with water as much as possible, the water content is preferably as small as possible. Specifically, it is 1000 ppm or less, preferably 500 ppm or less, more preferably 100 ppm or less.

According to this configuration, gelation does not easily occur when the Li-containing active material is added to manufacture the slurry, or aggregates or sedimentation does not easily occur during the manufacturing process of the slurry, the coating property of the electrode is also excellent, and the electrode manufacturing process is improved. Yield.

The thus-produced binder is used as an electrode binder for a lithium ion battery, and the current collector is coated and formed, whereby it can function well as a positive electrode or a negative electrode for the lithium ion battery. In addition, an electrode binder can also be used as a reference electrode. Moreover, it can also be used as a binder for electrodes used in electric storage devices such as electric double layer capacitors, ion capacitors, sodium ion batteries, magnesium ion batteries, calcium ion batteries, alkaline secondary batteries, and primary batteries.

The electrode is composed of, for example, the binder of the present invention, an active material, and a conductive assistant.

For the electrode system, for example, to a mixture (electrode mixture) containing an active material, a conductive assistant, a binder, etc., NMP, etc. are added as a slurry solvent and fully kneaded to obtain an electrode mixture slurry, and this slurry is applied to the current collector. The bulk surface is dried and the electrodes can be formed under control of the desired thickness and density. In the case of producing a lithium ion battery equipped with this electrode, the battery elements (counter electrode, separator, electrolyte, etc.) of a known lithium secondary battery can be used, and assembled into a laminated or wound lithium ion battery according to an ordinary method. Battery.

The conductive auxiliary agent for electrodes is not particularly limited as long as it has conductivity (electrical conductivity), and metals, carbon materials, conductive polymers, conductive glass, and the like can be used. Among them, a carbon material is preferable because the conductivity of the electrode active material can be expected to be improved by adding a small amount. Specifically, for example, acetylene black (AB), ketjen black (KB), furnace black (FB), thermal black, lamp black, groove black, roll black, disc black, carbon black (CB), carbon fiber (for example, Vapor-grown carbon fibers (VGCF), carbon nanotubes (CNTs), carbon nanohorns, graphite, graphene, glassy carbon, amorphous carbon, etc., can be used one or more of them.

When the total of the active material, the binder, and the conductive aid contained in the electrode is 100% by mass, the conductive aid is preferably contained in 0 to 20% by mass. That is, a conductive auxiliary agent is contained as needed. When it exceeds 20 mass %, since the ratio of the active material as a battery is small, the electrode capacity density tends to become low.

The binder for electrodes is not particularly limited as long as it contains the binder of the present invention. As the binder that can be contained in addition to the binder of the present invention, it can be commonly used as a binder for electrodes, such as polyimide (PI), polyamide, polyamideimide, polyaramide, Ethylene-vinyl acetate copolymer (EVA), styrene-ethylene-butylene-styrene copolymer (SEBS), polyvinyl butyraldehyde (PVB), ethylene vinyl alcohol, polyethylene (PE), polypropylene (PP) ), epoxy resin, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), nylon, polyvinyl chloride, polysiloxane, nitrile rubber, cyanoacrylate, urea Resin, melamine resin, phenol resin, polyvinylpyrrolidone, vinyl acetate, polystyrene, propylene chloride, resorcinol resin, polyaromatic, modified polysiloxane, polybutene, butyl rubber, 2 -Materials such as acrylic acid, these may be used individually by 1 type, and may contain 2 or more types together.

In addition, the binder may contain inorganic particles such as ceramics and carbon. In this case, the particle size of the ceramic or carbon is preferably in the range of 0.01 to 20 μm, more preferably in the range of 0.05 to 10 μm. In addition, in the present invention, the particle diameter means the volume-based median diameter (D50) of the laser diffraction-scattering particle size distribution measurement method, and the same applies hereinafter.

When the total of the active material, the binder, and the conductive aid contained in the electrode is 100% by mass, the binder is preferably contained at 0.1% by mass or more and 60% by mass or less, more preferably 0.5% by mass or more and 30% by mass or less , and more preferably 1 mass % or more and 15 mass % or less.

If the binder content is less than 0.1 mass %, the mechanical strength of the electrode is low, and the active material tends to fall off, and the cycle life characteristics of the battery may deteriorate. On the other hand, when it exceeds 60 mass %, the ion conductivity is low, or the resistance is high, and the ratio of the active material as a battery is small, so that the electrode capacity density tends to be low.

The current collector used for the electrode is not particularly limited as long as it has conductivity and can energize the held active material. For example, conductive substances such as C, Ti, Cr, Ni, Cu, Mo, Ru, Rh, Ta, W, Os, Ir, Pt, Al, and Au, and alloys containing two or more of these conductive substances can be used ( e.g. stainless steel). In the case of using a conductive material other than the above-mentioned conductive material, for example, it may be a multilayer structure in which iron is coated with a dissimilar metal such as Al, Ni, or C.

From the viewpoint of high electrical conductivity and good stability in the electrolyte, the current collector is preferably C, Ti, Cr, Au, Fe, Cu, Ni, Al, stainless steel, or the like; further, from the viewpoint of material cost, In other words, C, Cu, Ni, Al, stainless steel, etc. are preferable. In addition, when iron is used as the current collector base material, it is preferable to cover the current collector base material with Ni, Cu, Al, and C in order to prevent oxidation of the surface of the current collector base material.

The shape of the current collector is not particularly limited, and there are foil-shaped substrates, three-dimensional substrates, and the like, and these may also be current collectors having through holes. Among these, a three-dimensional base material is preferable because the packing density of the active material can be increased. Examples of the three-dimensional base material include nets, woven fabrics, non-woven fabrics, embossed bodies, expanded bodies, or foamed bodies. Among them, in terms of the shape and output characteristics of the current collector base material, embossed bodies or foamed bodies are preferred. Bubbles.

In addition, as described in the patent document (Japanese Patent No. 6149147), in this electrode, the inorganic skeleton-forming agent may be applied to the active material layer or the like, so that the inorganic skeleton-forming agent may penetrate into the active material layer. Thereby, even if an alloy-based active material in which the active material expands and contracts rapidly during charge and discharge is used, the expansion and contraction are allowed, and there is an effect of suppressing the occurrence of wrinkles or cracks in the current collector of the electrode.

When the inorganic skeleton-forming agent is applied to the active material, the electrode is preferably one-side-coated electrode with the skeleton-forming agent per unit area of 0.001 mg/cm ² or more and 10 mg/cm ² or less, more preferably 0.01 mg/cm 2 or more. mg/cm ² or more and 3 mg/cm ² or less. In an electrode coated on both sides or an electrode filled with an active material layer on a three-dimensional substrate, the skeleton-forming agent per unit area of the electrode is preferably 0.002 mg/cm ² or more and 20 mg/cm ² or less, more preferably 0.02 mg/cm ² or more and 6 mg/cm ² or less.

The inorganic framework-forming agent may be silicate-based, phosphate-based, sol-based, cement-based, or the like. Such as lithium silicate, sodium silicate, potassium silicate, cesium silicate, guanidine silicate, ammonium silicate, silicon fluoride, boron hydrochloric acid, lithium aluminate, sodium aluminate, potassium Aluminate, aluminosilicate, lithium aluminate, sodium aluminate, potassium aluminate, polyaluminum chloride, polyaluminum sulfate, polyaluminum silicate sulfate, aluminum sulfate, aluminum nitrate, ammonium alum, lithium alum, sodium alum , potassium alum, chromium alum, iron alum, manganese alum, nickel ammonium sulfate, diatomaceous earth, polyzirconoxane, polytantaoxane, mullite, white carbon, silica sol, colloidal silica, hair Fumed silica, alumina sol, colloidal alumina, fumed alumina, zirconia sol, colloidal zirconia, fumed zirconia, magnesia sol, colloidal magnesia, fumed magnesia, calcium oxide sol, colloidal oxidation Calcium, fumed calcium oxide, titanium oxide sol, colloidal titanium oxide, fumed titanium oxide, zeolite, silicoaluminophosphate zeolite, sepiolite, montmorillonite, kaolin, saponite, aluminum phosphate, magnesium phosphate, calcium phosphate Salt, Iron Phosphate, Copper Phosphate, Zinc Phosphate, Titanium Phosphate, Manganese Phosphate, Barium Phosphate, Tin Phosphate, Low Melting Glass, Plaster of Paris, Gypsum, Magnesium Cement, Lead Oxide Cement, Portland Cement , Inorganic materials such as blast furnace cement, fly ash cement, silica cement, phosphoric acid cement, concrete, solid electrolyte, etc. These can be used alone or in combination of two or more.

In addition, in this electrode, when the total solid content of the active material, the conductive aid, the binder, and the skeleton-forming agent is 100% by mass, the skeleton-forming agent is preferably 0.01% by mass or more and 50% by mass or less, more preferably 0.1% by mass. % by mass or more and 30% by mass or less, more preferably 0.2% by mass or more and 20% by mass or less.

The electrode slurry using the binder of the present invention uses an active material containing Li, and the slurry is not easily gelled. Therefore, if the active material used in the electrode is a lithium-ion battery that can be used for storage, The active material that releases lithium ions is not particularly limited.

For example, as the positive electrode active material, well-known ones containing alkali metal transition metal oxides, vanadium-based, sulfur-based, solid solution systems (lithium-excess type, sodium-excess type, potassium-excess type), carbon-based, organic-based, etc. can be used. electrode. For example, as the negative electrode active material, known electrodes containing graphite, hard carbon, soft carbon, lithium titanate, alloy-based materials, conversion materials, and the like can be used.

Alloy-based materials include, for example, Mg, Al, Si, Ca, Mn, Fe, Co, Zn, Ge, Ag, In, Sn, Sb, Pb, etc., as well as oxides such as SiO, SnO, SnO ₂ , SnSO ₄ , etc. compounds, chalcogenides such as SnS, SnS ₂ , and SnSe, halides such as SnF ₂ , SnCl ₂ , SnI ₂ , and SnI ₄ , etc.

Here, the so-called Li-containing active material is a compound composed of at least lithium (Li), a transition metal (M), and oxygen, and examples thereof include LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , NCM, NCA, and LiMn ₂ O _{4 .} , LiFePO ₄ , Li ₄ Ti ₅ O ₁₂ , Li ₂ MnO ₃ -LiMO ₂ (M=Ni, Co, Mn, Ti), Li ₂ MSiO ₄ (Fe, Ni, Co, Mn), etc.

The electrode is made by mixing the active material, binder, and conductive auxiliary agent added as needed and making it into a slurry, coating or filling the current collector, drying it temporarily, and rolling it at a temperature of 60°C or higher and 280°C or lower. heat treatment, whereby electrodes are obtained. The temporary drying is not particularly limited as long as it is a method that can volatilize and remove the solvent in the slurry, and for example, a method of performing heat treatment in the atmosphere at a temperature of 50° C. or higher and 200° C. or lower is exemplified.

In addition, by setting the heat treatment after calendering to 60°C or higher and 280°C or lower, the solvent and water in the slurry can be removed as much as possible, and the carbonization of the binder (especially the carbonization of cellulose nanofibers can be prevented) ). It is preferably 100°C or higher and 250°C or lower, more preferably 105°C or higher and 200°C or lower, still more preferably 110°C or higher and 180°C or lower.

In addition, the heat treatment time can be performed by holding for 0.5 to 100 hours. The heat treatment environment can be in the atmosphere, but in order to prevent the current collector from oxidizing, it is preferable to conduct the treatment in a non-oxidizing environment. The so-called non-oxidizing environment means an environment in which the amount of oxygen present is less than that in the air. For example, it can be a reduced pressure environment, a vacuum environment, a hydrogen environment, a nitrogen environment, a rare gas environment, or the like.

Furthermore, the electrodes include a negative electrode and a positive electrode, and the negative electrode and the positive electrode are mainly different from each other only in the current collector and the active material, and the manufacturing method is the same.

In addition, in the case of using an electrode of a material having irreversible capacity, it is preferable to release the irreversible capacity by doping with lithium. The lithium doping method is not particularly limited, for example: (i) Partial attachment of the non-active material layer on the electrode current collector, injection of metallic lithium to form a local battery, doping in the electrode active material layer The method of lithium; (ii) the method of doping lithium in the electrode active material layer by attaching to the active material layer on the electrode current collector, injecting metal lithium to make it forcibly short-circuited, and doping lithium in the electrode active material layer; (iii) on the active material A method of forming a metal lithium film by evaporation or sputtering, and doping lithium in an electrode active material by solid-phase reaction; (iv) Electrochemically doping lithium in an electrolyte before the electrode is formed method; (v) a method of adding lithium metal to the active material powder and mixing it, and doping the active material with lithium, and the like.

3.2mm)所測定之值。其中，未滿1μm之厚度可為藉由橫裁割器切斷對象物，藉SEM觀察其剖面而測定的值。分隔件基材之空孔率(空隙率)若為20~90%之範圍內，則無特別限定。於此，空隙率係由分隔件之表觀密度與構成材料之固形份之真密度，藉下式算出的值。 In addition, the adhesive of the present invention can also be coated on the surface of the separator. According to this configuration, a separator having high strength and excellent heat resistance, excellent adhesion to electrodes, and improved cycle life characteristics can be obtained. In addition, the adhesive of the present invention can be coated on one side or both sides of the separator base material (raw material), or can be filled in the separator base material. Here, the separator base material can be used by ordinary users of lithium ion batteries. That is, as the thickness of a separator base material, if it exists in the range of 1-50 micrometers, it will not specifically limit. The so-called thickness in the present invention refers to the use of a micrometer (manufactured by Mitsutoyo, high-precision digital liquid crystal micrometer MDH-25M, measuring force of 7~9N, measuring surface size

3.2mm) measured value. However, the thickness of less than 1 μm may be a value measured by cutting the object with a cross cutter and observing its cross section with SEM. The porosity (void ratio) of the separator base material is not particularly limited as long as it is in the range of 20 to 90%. Here, the void ratio is a value calculated by the following formula from the apparent density of the separator and the true density of the solid content of the constituent material.

Porosity (%)=100-(apparent density of separator/true density of solid content of material)×100

The pore diameter of the separator base material is not particularly limited as long as it is in the range of 0.001 to 10 μm.

Here, the pore size refers to the hexane vapor permeability measured by a nano-pore size distribution analyzer (Nano Perm Porometer, manufactured by Seiwa Industrial Co., Ltd.), using He gas as a carrier gas, and a 50% permeation flow diameter.

The material of the separator base material is not particularly limited as long as it is a material that is insoluble in the solvent of the electrolyte solution and has excellent oxidation resistance and reduction resistance. For example, polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), polyimide (PI), polyaramide, polyamide imide, polycarbonate , Resin materials such as polyacetal, polyphenylene ether, polyether ketone, polysaccharide, polyester, polyacrylonitrile (PAN), polytetrafluoroethylene (PTFE), etc., from the standpoint of whether the separator has blocking properties, Preferably, it is a resin material containing PP or PE. Generally, PP, PE, PET, etc. have excellent water repellency, so when using water as a solvent adhesive (aqueous adhesive), since the substrate is pulled away from the coating layer, it is difficult to form a uniform surface coating phase. In addition, polyolefin resins such as PP and PE hardly have polar groups for chemical bonding, and the surface free energy is low, so even non-aqueous fluorine-based resins have weak adhesion and are easy to peel off. On the other hand, since the adhesive of the present invention is non-aqueous, the above-mentioned water detachment does not occur. In addition, although the fluororesin itself contained in the adhesive of the present invention cannot be expected to adhere to the polyolefin-based resin itself, the inclusion of cellulose nanofibers allows them to penetrate into the pores existing on the surface of the substrate. Or micro-concave and convex and hardened, so it can be physically bonded. Therefore, the adhesive of the present invention is different from the conventional water-based adhesive or simple fluorine-based resin, and will improve the bonding strength with the separator.

The thickness of the surface coating layer of the adhesive is preferably 0.01 μm or more and 3 μm or less on one side from the viewpoint of excellent heat resistance and adhesion to the electrodes. The coating quality per unit area of the surface coating layer is preferably within the range of 0.001 to 5 g/m ² on one side. In the case of double-sided coating or filling on non-woven fabrics, the standard of double-sided coating can be used.

The surface coating methods of the adhesive include: a method of immersing a spacer base material in a tank storing the adhesive of the present invention; a method of dropping or coating the surface of the spacer base material with the adhesive of the present invention; Spraying, screen printing, curtain coating, spin coating, gravure coating, wire bar coating, die coating, etc. The adhesive coated on the surface of the base material of the separator penetrates into the inside of the hole of the separator, and is physically bonded by the anchoring effect. Then, the separator body is dried by warm air at 60°C to 160°C, heating, etc., to vaporize the solvent of the binder. Thereby, the adhesive is formed on the surface of the separator substrate.

In addition, the shape of the separator base material includes, for example, a microporous film, a woven fabric, a non-woven fabric, and a powder compact, and is not particularly limited.

In order not to be melted due to local heat generation during a short circuit, the separator can also be a separator coated or filled with a ceramic (inorganic filler) layer on the above-mentioned separator base material. At this time, the ceramic layer is a porous layer composed of at least the binder of the present invention and the ceramic powder (inorganic filler), and gas or liquid can pass therethrough. The material coated on the surface of the separator substrate, even if it does not contain ceramics, still improves the heat resistance of the separator and has the effect of improving the liquid retention of the electrolyte. Furthermore, by containing the ceramic powder, not only the heat resistance and the liquid retention of the electrolyte solution are further improved, but also the input and output characteristics of the battery are also improved. The ceramic powder is not particularly limited as long as it is a material that is insoluble in the solvent of the electrolyte solution, and has excellent oxidation resistance and reduction resistance. For example, silicon dioxide (SiO ₂ ), aluminum oxide (Al ₂ O ₃ ), magnesium oxide (MgO), calcium oxide (CaO), zirconium oxide (ZrO), yttrium oxide (Y ₂ O ₃ ), titanium oxide ( TiO ₂ ), aluminum oxide hydroxide (AlOOH), aluminum oxide (Al(OH) ₃ ), magnesium hydroxide (Mg(OH) ₂ ), barium titanate (BaTiO ₃ ), aluminum nitride (AlN), nitride Silicon (Si ₃ N ₄ ), calcium carbonate (CaCO ₃ ), magnesium carbonate (MgCO ₃ ), boron nitride (BN), silicon carbide (SiC), lithium metatitanate (Li ₂ TiO ₃ ), lithium titanate ( Li ₂ Ti ₅ O ₁₂ ), trilithium phosphate (Li ₃ PO ₄ ) and other oxides or hydroxides, nitrides, carbides, and the like. If the particle size of the ceramic powder is too small, the Gurley value tends to increase, and if it is too large, the strength of the ceramic layer tends to decrease easily. Therefore, the particle size of the ceramic powder is preferably in the range of 0.001 to 3 μm, more preferably in the range of 0.01 to 1 μm. The shape of the ceramic powder is not particularly limited, and may be spherical, elliptical, chamfered, ribbon, fibrous, sheet, doughnut, or hollow. The ceramic layer is not particularly limited as long as the binder of the present invention contains 0.1 mass % or more when the binder of the present invention and the ceramic powder are taken as 100 mass %, but from the viewpoint of the adhesiveness with the separator base material Specifically, it is preferably 1 mass % or more, more preferably 2 mass % or more. The binder of the present invention is preferably 90% by mass or less, more preferably 80% by mass or less, from the viewpoint of the input-output characteristics of the battery. The porosity of the ceramic layer is preferably in the range of 20 to 80%, more preferably in the range of 50 to 70%. By adjusting within this range, even if the electrode volume changes accompanying the charging and discharging of the battery, the separator is still easy to follow the electrode change, so the separator is not easily worn out, and the safety of the battery in the medium and long term is increased. The thickness of the ceramic layer is preferably 0.5 μm or more on one side from the viewpoint of excellent heat resistance and adhesion to the electrodes. The coating quality per unit area of the ceramic layer varies depending on the materials used, and is preferably in the range of 0.1 to 60 g/m ² . The coating or filling method of the ceramic layer can be formed by the same method as the above-mentioned surface coating of the adhesive.

For the application of the adhesive or the ceramic layer, from the viewpoint of excellent resistance to lithium dendritic crystals of the separator, the Gurley value of the separator is preferably controlled to be 5000sec/100mL or less. The same is true for filled dividers. The Gurley value in the present invention refers to an index related to the penetration rate of the separator, and is determined in accordance with the JIS P8117 standard. In general, the Gorie number can be reduced by increasing the pore size of the spacer substrate or by increasing the number of pores. In addition, the Goley value can also be reduced by reducing the thickness of the ceramic layer or increasing the particle size of the ceramic. By making the separator with a small Gore value, excellent I/O characteristics can be obtained, but if the Gore value exceeds 5000sec/100mL, the possibility of short circuit due to lithium dendrites generated by overcharge increases. On the other hand, it is preferable to control the Goliath value of a separator to 50 sec/100mL or more from a viewpoint of being excellent in the input-output characteristic of a battery. Therefore, the preferred Collier value of the separator is in the range of 50sec/100mL~5000sec/100mL, and more preferably in the range of 70sec/100mL~2000sec/100mL.

By applying the adhesive of the present invention to the separator, the effect of suppressing the short circuit of the battery due to the melting of the separator base material due to local heat generation at the time of short circuit can be expected. In addition, when the battery is charged, the presence of the adhesive of the present invention on the surface of the separator on the positive electrode side can prevent direct contact between the separator substrate and the positive electrode, inhibit the oxidation of the separator substrate, and thus suppress the self-discharge of the battery. In addition, since the heat resistance of the separator is improved, the safety against nail penetration or overcharging is improved.

For example, in the case of a battery using the above-mentioned electrodes, a battery structure in which the positive electrode and the negative electrode are joined via a separator and sealed in a state of being immersed in an electrolyte solution can be considered. In addition, the battery structure is not limited to this, and can be applied to existing battery forms, structures, and the like, such as a laminated battery and a wound battery.

The battery may be a lithium ion battery using an electrode including a binder containing cellulose nanofibers in a thermoplastic fluororesin for at least one of the positive electrode and the negative electrode.

The electrolyte used in this battery may be a liquid or solid that can move lithium ions from the positive electrode to the negative electrode, or from the negative electrode to the positive electrode, and the same electrolyte used in a known lithium ion battery can be used. For example, electrolytic solutions, gel electrolytes, solid electrolytes, ionic liquids, and molten salts may be mentioned. Here, the term "electrolyte solution" refers to a state in which the electrolyte is dissolved in the solvent.

Since the electrolyte solution must contain lithium ions, it is not particularly limited as long as it can be used by a lithium ion battery, and is composed of an electrolyte salt and an electrolyte solvent.

Since the electrolyte salt must contain lithium ions, the electrolyte salt is not particularly limited as long as the electrolyte salt can be used by a lithium ion battery, but a lithium salt is preferred. As this lithium salt, a lithium hexafluorophosphate (LiPF ₆ ), lithium perchlorate (LiClO ₄ ), lithium tetrafluoroborate (LiBF ₄ ), lithium trifluoromethanesulfonate (LiCF ₃ SO ₄ ), bistrifluoromethane can be used Lithium sulfonimide (Li(SO ₂ CF ₃ ) ₂ ), lithium bis-pentafluoroethane sulfonimide (LiN(SO ₂ C ₂ F ₅ ) ₂ ), lithium bis-oxalate borate (LiBC ₄ O ₈ ), etc. At least one or more of the constituted groups. Among the above-mentioned lithium salts, LiPF ₆ is particularly preferred because of its high degree of electronegativity and easy ionization. If it is an electrolyte solution containing LiPF ₆ , the charge-discharge cycle characteristics are excellent, and the charge-discharge capacity of the secondary battery can be improved.

The solvent for the above electrolyte is not particularly limited as long as it can be used in a lithium ion battery. For example, a solvent selected from the group consisting of propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate can be used. (DEC), ethyl methyl carbonate (EMC), diphenyl carbonate, γ-butyrolactone (GBL), γ-valerolactone, methyl formate (MF), 2-methyltetrahydrofuran, 1,3- Dioxolane, 4-methyl-1,3-dioxolane, dimethoxyethane (DME), 1,2-diethoxyethane, diethyl ether, cyclobutane , tetrahydrofuran (THF), methylcyclobutane, nitromethane, N,N-dimethylformamide, dimethylsulfoxide, vinylene carbonate (VC), vinylethylene carbonate (EVC), At least one of the group consisting of fluoroethylene carbonate (FEC) and ethylene sulfite (ES), and among them, at least one of PC, EC, DMC, DEC, EMC, etc. is preferably used. Particularly preferred are mixtures of cyclic carbonates such as EC and PC, and chain carbonates such as DMC, DEC, and EMC. The mixing ratio of the cyclic carbonate and the chain carbonate can be arbitrarily adjusted within the range of 10 to 90% by volume of the total of the cyclic carbonate and the chain carbonate.

Among them, a solvent containing an electrolyte of VC, ECV, FEC, and ES is more preferable. VC, ECV, FEC, and ES are preferably contained in 0.1 to 20 mass %, more preferably 0.2 to 10 mass %, when the electrolytic solution (total amount of electrolyte and solvent) is 100 mass %.

As the concentration of this lithium salt in the electrolyte, preferably 0.5 to 2.5 mol/L, more preferably 0.8 to 1.6 mol/L.

The electrolyte solution is particularly preferably an electrolyte solution containing at least LiPF ₆ as an electrolyte salt, and an electrolyte solvent containing an aprotic cyclic carbonate and an aprotic chain carbonate. The battery with the electrolyte of this composition and the electrode using the binder of the present invention is heated to a temperature of 50°C or more, and the thermoplastic fluorine-based resin of the binder used in the electrode absorbs lithium hexafluorophosphate and aprotic carbonate. Polymer gels with excellent ionic conductivity can be formed.

Moreover, by this polymer gel, the separator which is in physical contact with the electrode can also be integrated. Through the integration, the adhesive strength between the electrode and the separator is increased, which can effectively prevent the positional deviation of the separator and the electrode caused by external factors such as vibration or impact, which helps to improve the safety of the battery. Here, in the case where the binder does not contain cellulose nanofibers, the thermoplastic fluorine-based resin gels by increasing the temperature, but at the same time the electrode active material layer swells and the conductive network is destroyed, so the resistance of the electrode is increase. Once the thermoplastic fluororesin swells in the electrolyte, the electrode cannot be restored to its original state. That is, the cellulose nanofibers contained in the binder suppress the swelling of the electrode, and the thermoplastic fluorine-based resin gels, thereby suppressing the increase in the resistance of the electrode, and at the same time, the electrode and the separator are adhered through the binder. , and a battery in which the separator and the electrode are integrated can be fabricated.

The term "integration" in the present invention means that the electrodes and separators should be separate battery components originally, but due to the heat treatment, the electrodes and separators are adhered and fixed to each other and are in a state that is difficult to peel off easily. More specifically, according to the JISZ0237 standard, when the electrode and the separator are subjected to a peeling test at an angle of 180 degrees, the adhesive force is 0.01N/25mm or more, and when peeled, the separator has 0.1mg/ ^cm2 or more. A state in which the mass per unit area fluctuates, or the partition is extended and broken. The mass change of the separator refers to a phenomenon in which the peeled member (electrode active material layer, separator base material, separator coating layer) adheres to the opposite side, and the mass changes.

The battery may be a lithium ion battery using an electrode provided with a binder containing cellulose nanofibers in a thermoplastic fluorine-based resin on at least one of the positive electrode and the negative electrode.

The battery can be filled with an electrode group that is laminated or wound through a separator between the positive electrode and the negative electrode, together with an electrolyte solution containing lithium hexafluorophosphate and aprotic carbonate, and sealed in the cell body. When the temperature of the cell body is above 50°C and below 120°C, pressure is applied perpendicularly to the extending direction of the electrode from the outside of the cell body, and the electrode provided with the binder of thermoplastic fluororesin containing cellulose nanofibers is attached to the electrode. It is manufactured by step (F) of integrating the spacer. More preferably, the temperature of the cell body is 55°C or higher and 95°C or lower.

By setting the temperature of the cell body to 50°C or higher, the binder contained in the electrode will absorb the electrolyte and gel, thereby improving the ionic conductivity of the electrode. When the temperature exceeds 120° C., the electrolytic solution is vaporized and gas is likely to be contained inside the battery. In addition, when the separator contains a polyolefin-based resin, the polyolefin-based resin softens and there is an increased risk of short-circuiting the battery.

By applying pressure perpendicular to the extending direction of the electrode from the outside of the cell body, the electrode and the separator can be easily adhered and bonded.

The pressure varies depending on the size of the battery, the number of layers of electrodes, or the number of windings, and is not particularly limited. For example, the pressure may be maintained at 0.1 Pa or more for 10 seconds or more.

The above-mentioned step (F) can also be used to charge or discharge the battery.

The lithium ion battery thus obtained can suppress the swelling of the electrode active material layer caused by the electrolyte even in a temperature environment of 60°C or higher, and can be made into a battery with improved cycle life characteristics and output characteristics at high temperatures. In addition, the high-temperature storage characteristics and productivity of the battery were also good. Therefore, the lithium ion battery of the present invention takes advantage of such characteristics, and is used in information communication equipment such as mobile phones, smart phones, tablet terminals, electric vehicles (EV), plug-in hybrid electric vehicles (PHEV), and hybrid electric vehicles ( HEV), in-vehicle power supplies such as idling and stalling vehicles, home backup power supplies, natural energy storage, load balancing and other large-scale power storage systems, etc., can be widely used in the same applications as those used in lithium-ion batteries known in the past. in use.

The adhesive of the present invention is not easy to absorb the electrolyte and swell at high temperature by being used in the electrode of the lithium ion battery, and the ion conductivity is also excellent. In addition, even if an active material containing Li is used in this binder, the gelation of the slurry does not easily occur.

FIG. 1 shows the batteries of the examples (Example 1, Example 2, Reference Example 1) with electrodes containing the binder material A as the electrode binder, and electrodes with only the binder material G as the electrode binder. A graphical representation of the comparison of the battery (Comparative Example 1).

FIG. 2 shows the batteries of the examples (Examples 3 to 5, Reference Example 2) with electrodes containing the binder material B as the electrode binder, and batteries with electrodes using only the binder material G as the electrode binder. (Comparative Example 1) A diagram for comparison.

FIG. 3 shows the batteries of the examples (Examples 6 to 8, Reference Example 3) with electrodes containing the binder material C as the electrode binder, and batteries with electrodes using only the binder material G as the electrode binder. (Comparative Example 1) A diagram for comparison.

FIG. 4 shows the batteries of the examples with electrodes containing the binder material D as the electrode binder (Examples 9 to 11), and the batteries with electrodes using only the binder material G as the electrode binder (Comparative Example 1). ) for comparison.

FIG. 5 shows the batteries of the examples with electrodes containing the binder material E as the electrode binder (Examples 12 to 14), and the batteries with electrodes using only the binder material G as the electrode binder (Comparative Example 1). ) for comparison.

FIG. 6 shows a battery with electrodes containing the binder material F as an electrode binder (Reference Examples 4 to 6) and a battery with electrodes using only the binder material G as the electrode binder (Comparative Example 1). ) for comparison.

FIG. 7 shows the batteries of the examples (Example 1, Example 2, Reference Example 1) with electrodes containing the binder material A as the electrode binder, and electrodes with only the binder material G as the electrode binder. A graphical representation of the comparison of the battery (Comparative Example 1).

FIG. 8 shows the batteries of the examples (Examples 3 to 5, Reference Example 2) with electrodes containing the binder material B as the electrode binder, and the batteries with electrodes using only the binder material G as the electrode binder. (Comparative Example 1) A diagram for comparison.

FIG. 9 shows the batteries of the examples (Examples 6 to 8, Reference Example 3) with electrodes containing the binder material C as the electrode binder, and the batteries with electrodes using only the binder material G as the electrode binder. (Comparative Example 1) A diagram for comparison.

FIG. 10 shows the batteries of the examples with electrodes containing the binder material D as the electrode binder (Examples 9 to 11), and the batteries with electrodes using only the binder material G as the electrode binder (Comparative Example 1). ) for comparison.

FIG. 11 shows the battery of the example with the electrode containing the binder material E as the electrode binder (Example 14), and the battery with the electrode using only the binder material G as the electrode binder (Comparative Example 1). Graphics for comparison.

FIG. 12 shows a battery with electrodes containing the binder material F as an electrode binder (Reference Examples 4 to 6) and a battery with electrodes using only the binder material G as the electrode binder (Comparative Example 1). ) for comparison.

FIG. 13 shows the batteries of the examples (Example 15, Example 16, Reference Example 7) with electrodes containing the binder material A as the electrode binder, and electrodes with only the binder material G as the electrode binder. A graphical representation of the comparison of the battery (Comparative Example 2).

FIG. 14 shows the batteries of the examples (Example 15, Example 16, Reference Example 7) with electrodes containing the binder material A as the electrode binder, and electrodes with only the binder material G as the electrode binder. A graphical representation of the comparison of the battery (Comparative Example 2).

FIG. 15 shows the results of confirming the gelation resistance of the adhesives of the examples (gelation resistance tests 1 and 2).

FIG. 16 is a graph showing a comparison between batteries provided with test separators 1 to 4 (Examples 17 to 20) and batteries using an uncoated separator (Comparative Example 3).

[Example]

The present invention will be specifically described below based on the examples, but the following examples do not limit the present invention.

[1. Material production of composite adhesive]

Table 1 shows the materials (adhesive materials A to G) used for making the composite adhesive.

Binder material A is a liquid in which untreated cellulose nanofibers are dispersed in NMP. The production method of the binder material A is to add an equal volume or more of NMP to a liquid (solid ratio of 5% by mass) in which untreated cellulose nanofibers are dispersed in water, and use a rotary evaporator (200hPa, 70~90°C). , 160 rpm), and after evaporating water while stirring, it was produced by irradiating ultrasonic waves (frequency 38 kHz, 1 minute). When the solid ratio of the binder material A exceeds 7% by mass, aggregation and sedimentation are likely to occur, so the solid ratio was set to 4.4% by mass. In addition, a liquid in which cellulose nanofibers were dispersed in water was a commercially available crystalline cellulose powder (manufactured by Asahi Kasei Chemical Co., Ltd., registered trademark: CEOLUS FD-101, average particle size 50 μm, bulk density 0.3 g/cc ), was added so that the cellulose would be 4 mass % with respect to the total amount of the aqueous dispersion, put into a stone mortar type defibrillation treatment device, and was prepared by passing through the stone mortars 10 times.

The binder material B is a liquid in which the half-esterified cellulose nanofibers are dispersed in NMP. The manufacturing method of the binder material B is the same as that of the binder material A except that a liquid (solid ratio of 5 mass %) in which the half-esterified cellulose nanofibers are dispersed in water is used. In the binder material B, when the solid ratio exceeds 10 mass %, aggregation and sedimentation tend to occur, so the solid ratio is set to 4.1 mass %. In addition, the liquid in which the half-esterified cellulose nanofibers were dispersed in water was obtained by dispersing untreated commercially available crystalline cellulose powder (manufactured by Asahi Kasei Chemical Co., Ltd., registered trademark: CEOLUS FD-101, average particle size). diameter 50μm, bulk density 0.3g/cc) and succinic anhydride in a ratio of 86.5:13.5, and then reacted in a vessel heated to 130°C, after which the total amount of cellulose relative to the aqueous dispersion was 4wt % was added, put into a stone mortar type defibrillation treatment device, and was prepared by passing through the stone mortar 10 times.

The binder material C is a liquid in which cellulose nanofibers with secondary propylene oxide added are dispersed in NMP after half-esterification of cellulose. The production method of the binder material C is to use a liquid (solid ratio of 5 mass %) in which the cellulose nanofibers to which propylene oxide is added secondary are dispersed in water after half-esterification of cellulose. The rest is the same as the adhesive material B. In the binder material C, when the solid ratio exceeds 10 mass %, aggregation and sedimentation are likely to occur, so the solid ratio is set to 3.3 mass %. In addition, the liquid in which the cellulose nanofibers subjected to the addition treatment of propylene oxide were dispersed in water was obtained by dispersing untreated commercially available crystalline cellulose powder (manufactured by Asahi Kasei Chemical Co., Ltd., registered trademark: CEOLUS FD-101, Average particle size 50μm, bulk density 0.3g/cc) and succinic anhydride were blended in a ratio of 86.5:13.5, and then reacted in a vessel heated to 130°C, after which propylene oxide was further added relative to the weight of cellulose 4.5 wt %, reacted at 140 ° C, and then added 4 wt % of this cellulose relative to the total amount of the aqueous dispersion, put it into a stone mortar type defibrillation treatment device, and made it pass through the stone mortar for 10 times. modulation.

The binder material D is a liquid in which cellulose nanofibers containing lignin obtained from hardwood are dispersed in NMP. The manufacturing method of the binder material D is the same as that of the binder material A except that a liquid obtained by dispersing cellulose nanofibers containing lignin obtained from hardwood trees in water is used. When the solid ratio of the binder material D exceeds 2 mass %, aggregation and sedimentation are likely to occur, so the solid ratio is set to 1.5 mass %. In addition, cellulose nanofibers containing lignin obtained from hardwood trees were dispersed in water, and 4 wt % of cellulose was added to the total amount of the aqueous dispersion, and put into a stone mortar-type defibrillation treatment device to make it. It is prepared by processing 10 times between stone mortars.

The binder material E is a liquid in which cellulose nanofibers containing lignin obtained from conifers are dispersed in NMP. The manufacturing method of the binder material E is the same as that of the binder material A except that cellulose nanofibers produced from conifers are used. In the binder material E, when the solid ratio exceeds 2 mass %, aggregation and sedimentation are likely to occur, so the solid ratio is set to 1.3 mass %. In addition, the cellulose nanofibers containing lignin obtained from conifers were dispersed in water, and 4 wt % of cellulose was added to the total amount of the aqueous dispersion, and put into a stone mortar-type defibrillation treatment device to make it. It is prepared by processing 10 times between stone mortars.

The binder material F is a liquid in which nanoclay (SUMECTON SAN, manufactured by KUNIMINE INDUSTRIAL CO., LTD., 4% dispersion viscosity 4000 mPa·s) is dispersed in NMP. In the binder material F, when the solid content ratio exceeds 4 mass %, since foaming is intense, the solid content ratio is set to 1.9 mass %. The manufacturing method of the binder material F is to add an equal volume or more of NMP to a liquid (solid ratio 4 mass %) in which nanoclay is dispersed in water, and use a rotary evaporator (200hPa, 70~90°C, 160rpm), After evaporating water while stirring, it was produced by irradiating ultrasonic waves (frequency: 38 kHz, 1 minute).

The binder material G is a liquid obtained by dissolving PVdF in NMP, and was produced by mixing NMP and PVdF (mass average molecular weight: 280,000) with a self-revolving mixer (manufactured by THINKY, 2000 rpm, 30 minutes). The binder material G was made into a solid ratio of 12 mass %.

[2. Production of adhesive]

The electrode binder is made into a fixed composition as shown in the following table 3, using the binder materials A to G, with a self-revolving mixer (Thinky, Lentaro, 2000 rpm, 30 minutes), making NMP as the Solvent-based composite adhesive.

[3. Production of paste and electrodes] <Relevant review of slurry coagulation and sedimentation properties, etc.>

A test to confirm the properties related to the cohesion and settling properties of the slurry.

The NCA electrode paste is composed of NCA (LiNi _0.8 Co _0.15 Al _0.05 O ₂ ) as an active material, acetylene black as a conductive assistant, and a predetermined electrode binder shown in Table 4, at a solid ratio of 94:2:4 mass % The mixture was prepared and kneaded using an auto-revolution mixer (manufactured by THINKY, Lentaro, 2000 rpm, 15 minutes) to form a slurry.

As shown in Table 4, after observing the coagulation state, sedimentation state, and foaming state of the slurry, the aluminum current collector with a thickness of 20 μm was coated with a doctor blade, and the coating property of the slurry was observed.

It can be seen from Table 4 that the cellulose nanofibers contained in the binder were treated with polybasic acid half-ester (SA) treatment or further treated with propylene oxide as compared with the untreated ones. The slurry of the secondary treated cellulose nanofibers is preferred. Moreover, from the overall tendency, as the content of PVdF increases, the cohesiveness tends to be improved, and it can be seen that the coating property is close to the slurry with only PVdF.

<Production of NCA Electrode>

The test electrodes 1 to 25 were coated with the slurries (slurry 1 to 25) shown in Table 4 on an aluminum foil with a thickness of 20 μm using an applicator, and after being temporarily dried at 80° C., rolled by rolling, and dried under reduced pressure ( 160°C, 12 hours) and produced. The capacity density of each NCA positive electrode was set to 2.1 mAh/cm ² . Among them, with regard to the test electrode 13, the test electrode 17, and the test electrode 21, since the solid content of the slurry was too low, it was not possible to produce electrodes with a capacity density exceeding 1 mAh/cm ² . From these results, it was found that the solid ratio of the binder material is preferably 2 mass % or more.

<Production of NCM523 Electrode>

The test electrodes 26 to 29 are composed of NCM (LiNi _0.5 Co _0.2 Mn _0.3 O ₂ ) as the active material, acetylene black as the conductive assistant, and the predetermined electrode binder shown in Table 5 as the electrode binder, according to the solid ratio of 94 : 2:4 mass % blended, kneaded using a self-revolution mixer (manufactured by THINKY, Lentaro, 2000 rpm, 15 minutes) to form a slurry, and applied the slurry on an aluminum foil with a thickness of 20 μm using an applicator. After being temporarily dried at 80° C., it was rolled by roll pressing and dried under reduced pressure (160° C., 12 hours) to produce. The capacity density of each NCM523 positive electrode was set to 2.5 mAh/cm ² .

[4. Fabrication of NCA/Si full cell]

The NCA/Si all-electrodes of Examples 1 to 14, Reference Examples 1 to 6, and Comparative Example 1 were test cells provided with the test electrodes shown in Table 6. The test cells used NCA electrodes (test electrodes) as positive electrodes, Si electrodes as negative electrodes, glass nonwoven fabrics (GA-100) as separators, and 1 mol/L LiPF ₆ (EC: DEC=50: 50 vol%) as electrolytes , +VC1 mass %) to make CR2032 coin cell batteries.

For the Si electrode system, Si, PVdF (mass average molecular weight: 280,000), and acetylene black were prepared at a solid ratio of 94:2:4 mass %, and kneaded using a self-revolution mixer (manufactured by THINKY, Lentaro, 2000 rpm, 15 minutes). , apply the slurry to a stainless steel foil with a thickness of 8 μm, dry it temporarily at 100°C, and use a gravure coater to apply an alkali metal silicate aqueous solution (A ₂ O·nSiO ₂ ; n=3.2, A= Li, Na, K) and dried under reduced pressure (160° C., 12 hours) to prepare. The capacity density of the Si electrode was set at 4.5 mAh/cm ² . Here, the reason why the alkali metal silicate aqueous solution is applied to the Si electrode is that, as described in Patent Document 7, in order to prolong the life of the Si electrode, the test cell is used to improve the high-temperature durability without being limited by the characteristics of the Si negative electrode. speed.

In the present invention, the term "full cell" refers to a battery evaluated without using metallic lithium as a counter electrode, and the term "half cell" refers to a battery in which metallic lithium is used for the counter electrode.

<Cycle life characteristics at 60°C>

A test for evaluating the cycle life characteristics in a 60° C. environment was conducted with respect to the test cells of Examples 1 to 14, Reference Examples 1 to 6, and Comparative Example 1.

The charge-discharge test is based on the conditions of an ambient temperature of 60°C and a cut-off potential of 4.25~2.7V. Repeat charging and discharging.

In addition, the so-called charge-discharge rate refers to the constant current discharge of a battery cell with a metric capacity value, and the current value that becomes a complete discharge in 1 hour is set as an index of "1C-rate"; for example, The current value for complete discharge in 5 hours was recorded as "0.2C-rate", and the current value for complete discharge in 10 hours was recorded as "0.1C-rate".

Fig. 1 shows the comparison between the batteries with electrodes containing the binder material A as the electrode binder (Example 1, Example 2, and Reference Example 1), and the batteries with electrodes using only the binder material G as the electrode binder (Example 1, Example 2, Reference Example 1) Comparative Example 1) Illustration for comparison.

FIG. 2 shows the comparison between the batteries with electrodes containing the binder material B as the electrode binder (Examples 3 to 5, Reference Example 2), and the batteries with electrodes using only the binder material G as the electrode binder (Comparative example). 1) Diagram for comparison.

FIG. 3 shows the comparison between the batteries with electrodes containing the binder material C as the electrode binder (Examples 6 to 8, Reference Example 3), and the batteries with electrodes using only the binder material G as the electrode binder (Comparative example). 1) Diagram for comparison.

FIG. 4 shows the comparison between the batteries with electrodes containing the binder material D as the electrode binder (Examples 9 to 11) and the batteries with electrodes using only the binder material G as the electrode binder (Comparative Example 1). 's icon.

FIG. 5 shows a comparison between batteries with electrodes containing binder material E as an electrode binder (Examples 12 to 14) and a battery with electrodes using only binder material G as an electrode binder (Comparative Example 1). 's icon.

FIG. 6 shows a comparison between the batteries with electrodes containing the binder material F as the electrode binder (Reference Examples 4 to 6), and the batteries with electrodes using only the binder material G as the electrode binder (Comparative Example 1) 's icon.

It can be seen from FIG. 1 to FIG. 6 that the battery containing any one of the binder materials A to E in the electrode binder (Examples 1 to 14) is compared with that only the binder material G constitutes the electrode binder. The battery (Comparative Example 1) has significantly improved cycle life characteristics. On the other hand, batteries containing the binder material F in the electrode binder (Reference Examples 4 to 6) did not have the effect of improving the lifespan, but deteriorated performance even with the same nanoscale particles. From these results, it is known that the inclusion of cellulose nanofibers in the electrode binder has the effect of improving the cycle life characteristics of the battery at high temperature.

<Cycle life characteristics at 80°C>

A test for evaluating the cycle life characteristics in an environment of 80° C. for the test batteries of Examples 1 to 14, Reference Examples 1 to 6, and Comparative Example 1.

The charge-discharge test is based on the conditions of an ambient temperature of 80°C and a cut-off potential of 4.25~2.7V. Repeat charging and discharging.

FIG. 7 is a diagram showing the comparison between the batteries with electrodes containing the binder material A as the electrode binder (Example 1, Example 2, and Reference Example 1), and the batteries with electrodes using only the binder material G as the electrode binder (Example 1, Example 2, Reference Example 1) Comparative Example 1) Illustration for comparison.

FIG. 8 is a diagram showing the comparison between the batteries with electrodes containing the binder material B as the electrode binder (Examples 3 to 5, Reference Example 2), and the batteries with electrodes using only the binder material G as the electrode binder (Comparative example). 1) Diagram for comparison.

FIG. 9 is a diagram showing the comparison between the batteries with electrodes containing the binder material C as the electrode binder (Examples 6 to 8, Reference Example 3), and the batteries with electrodes using only the binder material G as the electrode binder (Comparative example). 1) Diagram for comparison.

FIG. 10 shows the comparison between the batteries with electrodes containing the binder material D as the electrode binder (Examples 9 to 11) and the batteries with electrodes using only the binder material G as the electrode binder (Comparative Example 1). 's icon.

FIG. 11 is a diagram showing a comparison between a battery (Example 14) having an electrode containing a binder material E as an electrode binder, and a battery having an electrode using only the binder material G as an electrode binder (Comparative Example 1) Show.

FIG. 12 shows the comparison between the batteries with electrodes containing the binder material F as the electrode binder (Reference Examples 4 to 6), and the batteries with electrodes using only the binder material G as the electrode binder (Comparative Example 1) 's icon.

It can be seen from FIG. 7 to FIG. 12 that the battery containing any one of the binder materials A to E in the electrode binder (Examples 1 to 14) is compared with that only the binder material G constitutes the electrode binder. The battery (Comparative Example 1) has significantly improved cycle life characteristics. On the other hand, batteries containing the binder material F in the electrode binder (Reference Examples 4 to 6) did not have the life-improving effect even with the same nanoscale particles. From these results, it is known that the inclusion of cellulose nanofibers in the electrode binder has the effect of improving the cycle life characteristics of the battery at high temperature. In particular, the batteries (Examples 1 to 8, Reference Examples 1 to 3) containing any one of the binder materials A to C in the electrode binder showed particularly significant differences.

At 80°C, as the amount of cellulose nanofibers contained in the binder of the test electrode increased, although the cycle life characteristics at high temperature tended to improve, the output characteristics tended to decrease.

[5. Fabrication of NCM523/SiO full cell]

The NCM523 electrodes of Example 15, Example 16, Reference Example 7, and Comparative Example 2 were test cells provided with the electrode binders shown in Table 7. The test cell used NCM523 electrode (test electrode) as positive electrode, SiO electrode as negative electrode, polyolefin microporous membrane (PP/PE/PP) as separator, and 1 mol/L LiPF ₆ (EC: DEC) as electrolyte =50:50vol%) to make CR2032 coin-type battery.

SiO electrode system: SiO, PVA (polymerization degree: 2800), acetylene black, and VGCF are prepared in a solid ratio of 94:10:4:1 mass %, and kneaded using a self-revolution mixer (manufactured by THINKY, Lentaro, 2000 rpm, 15 minutes). , the slurry was applied to a copper foil having a thickness of 40 μm, and was temporarily dried at 80° C., and then dried under reduced pressure (160° C., 12 hours). The capacity density of the SiO electrode was set to 3.2 mAh/cm ² . In addition, the SiO electrode is a SiO electrode obtained by disassembling a half-cell after the irreversible capacity is eliminated by fabricating a half-cell using metallic lithium as a counter electrode in advance before assembling the full-cell.

<Cycle life characteristics at 30°C>

A test for evaluating the cycle life characteristics in a 30° C. environment was performed on the test cells of Example 15, Example 16, Reference Example 7, and Comparative Example 2.

The charge-discharge test is based on the conditions of an ambient temperature of 30°C and a cut-off potential of 4.3~2.5V, and repeated charge-discharge at 0.2C-rate.

FIG. 13 shows the comparison between the batteries with electrodes containing the binder material A as the electrode binder (Example 15, Example 16, Reference Example 7), and the batteries with electrodes using only the binder material G as the electrode binder (Example 15, Example 16, Reference Example 7) Comparative Example 2) Illustration for comparison.

It can be seen from FIG. 13 that under the environment of 30°C, the cycle life characteristics are not much different.

<Cycle life characteristics at 60°C>

A test for evaluating the cycle life characteristics in a 60° C. environment was carried out for the test batteries of Example 15, Example 16, Reference Example 7 and Comparative Example 2.

The charge-discharge test is based on the conditions of the ambient temperature of 60°C and the cut-off potential of 4.3~2.5V, and repeated charge and discharge at 0.2C-rate.

Fig. 14 shows the comparison between the batteries with electrodes containing the binder material A as the electrode binder (Example 15, Example 16, Reference Example 7), and the batteries with electrodes using only the binder material G as the electrode binder (Example 15, Example 16, Reference Example 7) Comparative Example 2) Illustration for comparison.

As can be seen from FIG. 14 , in an environment of 60° C., by including the binder material A, the cycle life characteristics can be improved. In particular, the ratio of the binder material A to the binder material G, the larger the binder material A, the greater the effect.

[6. Confirmation of gelation resistance]

A test to check whether the adhesive is gelled by strong alkali.

(Gelification resistance test 1)

Gelation resistance test 1 series Lithium hydroxide (LiOH) 2 mass % was added to the binder 4, and after stirring using a self-revolving mixer (manufactured by THINKY, Lentaro, 2000 rpm, 15 minutes), it was left to stand at 25°C for 12 Hour.

(Gelification resistance test 2)

Gelation resistance test 2 series Lithium hydroxide (LiOH) 2 mass % was added to the binder 25, and after stirring using a self-revolving mixer (manufactured by THINKY, Lentaro, 2000 rpm, 15 minutes), it was left to stand at 25°C for 12 Hour.

FIG. 15 shows the results of confirming the gelation resistance of the adhesive. As can be seen from FIG. 15 , in the gelation resistance test 2, the color changed immediately after the addition of LiOH; in contrast, in the gelation resistance test 1, there was no color change even after being left for 12 hours. In addition, in the gelation resistance test 2, PVdF gelled and changed into a gum-like substance after being left to stand for 12 hours. In contrast, the gelation resistance test 1 did not lose the fluidity of the adhesive.

[7. Fabrication of surface-coated separators]

The test separators 1 to 4 have a predetermined solid composition as shown in Table 8. Binder 5 and alumina (particle size: 200 nm) are used, and are kneaded by a self-revolving mixer (manufactured by THINKY, Lentaro, 2000 rpm, 30 minutes). , the slurry was coated on one side to a polypropylene (PP) microporous membrane with a thickness of 16 μm, and after being temporarily dried at 70° C., it was dried under reduced pressure (80° C., 24 hours) to prepare. The thicknesses of the surface coating layers of the test separators 1 to 4 were respectively 4 μm. In addition, as a comparative example, an uncoated PP microporous film was used as the test separator 5 .

The test cells of Example 17, Example 18, Example 19, Example 20, and Comparative Example 3 were test cells provided with separators 1 to 5 shown in Table 8. The test cell (NCM111/black lead full cell) used the NCM111 electrode as the positive electrode, the graphite electrode as the negative electrode, the test separators 1~5 as the separator, and 1 mol/L LiPF ₆ as the electrolyte (EC: DEC=50 : 50vol%), assemble a CR2032 coin cell battery, and place it at 80 °C for 1 hour. In addition, the coating layer of the separator was provided on the positive electrode side.

The NCM111 electrode is prepared by mixing NCM111, PVdF (mass average molecular weight: 280,000), and acetylene black at a solid ratio of 91:5:4 mass %, and kneading using a self-revolving mixer (manufactured by THINKY, Lentaro, 2000 rpm, 15 minutes), The slurry was applied to an aluminum foil having a thickness of 15 μm, and was temporarily dried at 80° C., and then dried under reduced pressure (160° C., 12 hours) to prepare. The capacity density of one side of the NCM111 electrode was set to 2.5mAh/cm ² .

The graphite electrode system was prepared by mixing graphite, SBR, carboxymethyl cellulose (CMC), acetylene black, and VGCF in a solid ratio of 93.5:2.5:1.5:2:0.5 mass %, using a self-revolution mixer (Thinky, Lentaro, 2000 rpm, 15 minutes) kneading, apply|coat the slurry to the copper foil of thickness 10 micrometers, dry it temporarily at 80 degreeC, and then dry it under reduced pressure (160 degreeC, 12 hours), and manufacture. The capacity density of one side of the graphite electrode was set to 3.0 mAh/cm ² . Also, the black lead electrode in this test did not eliminate the irreversible capacity.

<Cycle life characteristics at 60°C>

A test for evaluating the cycle life characteristics in the environment of 60° C. for the test cells of Examples 17 to 20 and Comparative Example 3.

The charge-discharge test is based on the conditions of an ambient temperature of 60°C and a cut-off potential of 4.3~2.5V. After 2 cycles of charge and discharge at 0.1C-rate, after 3 cycles of charge and discharge at 0.2C-rate, repeat the charge and discharge at 1C-rate. .

FIG. 16 is a graph showing a comparison between batteries provided with test separators 1 to 4 (Examples 17 to 20) and batteries using an uncoated separator (Comparative Example 3).

As can be seen from FIG. 16 , by providing the coating layer on the surface of the separator, the cycle life characteristics can be improved. In particular, when Al ₂ O ₃ is contained, the effect becomes large.

<Sting Security>

A test was conducted for the safety of the battery (Example 21 ) using the surface-coated separator. In addition, as a comparison, a battery (Comparative Example 4) using an uncoated separator was produced and subjected to the same test.

The test method is a nail penetration test in which the laminated battery is nailed and the state of smoke or ignition of the laminated battery is examined. In the test, in addition to being used in an aluminum laminate case, a black lead negative electrode (capacity density on both sides of 6mAh/cm ² ), a separator, and an NCM111 positive electrode (capacity density on both sides of 5mAh/cm ² ) were laminated in multiple layers. The same as Example 21 and Example 20 except for the 1.2 Ah laminate battery in which the electrolyte was sealed. Comparative Example 4 is the same as Comparative Example 3.

3mm，圓型)依速度1mm/sec穿刺至貫通為止，測定電池電壓與釘溫度、外殼溫度。 The nail penetration test is performed by charging the battery to 4.2V at 0.1C-rate, then pierce the center of the battery with an iron nail (

3mm, round type) puncture at a speed of 1mm/sec until it penetrates, and measure the battery voltage, nail temperature, and case temperature.

In the battery using the uncoated separator (Comparative Example 4), when nailing was performed, the battery voltage dropped to 0 V, and a large amount of smoke was generated. This is due to the heat generated when a short circuit occurs inside the battery, and the separator melts, resulting in an overall short circuit.

On the other hand, the battery (Example 21) in which a ceramic layer consisting of the binder 5 and Al ₂ O ₃ was formed on the surface of the separator maintained a voltage of 3 V or more even when nailing was performed , No smoke, the temperature of the shell or nail is below 50 ℃, almost no heat caused by short circuit occurs. This is considered to be due to the fact that even when a short circuit occurs inside the battery, heat is generated, the separator is not melted, and a complete short circuit is prevented.

As above, the preferred embodiments of the present invention have been described with reference to the drawings, but various additions, changes, or deletions can be made without departing from the scope of the present invention. For example, the ratio of the cellulose nanofibers to the thermoplastic fluorine-based resin is not limited to the values of the above-mentioned embodiments. Furthermore, in the above-mentioned embodiments, PVdF as the thermoplastic fluororesin may be a polymer, a copolymer, or a copolymer, and the mass average molecular weight is not limited to 280,000. In addition, cellulose nanofibers containing anionic groups such as carboxylic acid groups, sulfonic acid groups, phosphoric acid groups, and sulfuric acid groups are also included in the scope of the present invention. In addition, the active material is not limited to NCA or NCM523, and may be any material capable of reversibly occluding and releasing Li ions. Accordingly, such ones are also included within the scope of the present invention.

Claims (20)

A binder, which is a non-aqueous binder in an electrode or a separator for a lithium ion battery composited with a cellulose nanofiber and a thermoplastic fluorine-based resin, wherein the above-mentioned cellulose nanofiber fiber diameter (( Fibers with a diameter) of 0.002 μm or more and 1 μm or less, a fiber length of 0.5 μm or more and 10 mm or less, and an aspect ratio (fiber length of cellulose nanofibers/fiber diameter of cellulose nanofibers) of 2 or more and 100,000 or less When the total solid content of the cellulose nanofibers and the thermoplastic fluorine-based resin is 100% by mass, the cellulose nanofibers are contained at 5% by mass to 50% by mass, and the thermoplastic fluorine-based resin 50 Mass % or more and 95 mass % or less; cellulose nanofibers exist in a dispersed state in the thermoplastic fluororesin. The adhesive according to claim 1, wherein the cellulose nanofibers comprise cellulose nanofibers in which a part of the hydroxyl group is partially substituted with a carboxyl group after being half-esterified with a polybasic acid. The adhesive of claim 1, wherein the cellulose nanofibers comprise cellulose nanofibers subjected to ethylene oxide addition treatment or propylene oxide addition treatment. The adhesive of claim 2, wherein the cellulose nanofibers comprise cellulose nanofibers subjected to ethylene oxide addition treatment or propylene oxide addition treatment. The adhesive according to claim 1, wherein the thermoplastic fluorine-based resin contains polyvinylidene fluoride or a copolymer of vinylidene fluoride. The adhesive according to claim 2, wherein the thermoplastic fluorine-based resin contains polyvinylidene fluoride or a copolymer of vinylidene fluoride. The adhesive according to claim 3, wherein the thermoplastic fluorine-based resin contains polyvinylidene fluoride or a copolymer of vinylidene fluoride. The adhesive according to claim 4, wherein the thermoplastic fluorine-based resin contains a polymer Difluorovinylidene or difluorovinylidene copolymer. The adhesive according to any one of claims 1 to 8, wherein the thermoplastic fluorine-based resin is dissolved in N-methyl-2-pyrrolidone, and dispersed in N-methyl-2-pyrrolidone Binder for cellulose nanofibers; when the total mass of cellulose nanofibers, thermoplastic fluorine-based resin and N-methyl-2-pyrrolidone in the above-mentioned binder is 100% by mass, cellulose The total of the solid content of the nanofibers and the thermoplastic fluorine-based resin is 3% by mass or more and 30% by mass or less. An electrode using the adhesive of any one of claims 1 to 9. The electrode of claim 10, comprising a polymer gel containing lithium hexafluorophosphate, cyclic carbonate and chain carbonate, wherein the polymer gel is a composite of cellulose nanofibers. The electrode of claim 10 or 11 uses an active material containing Li. A separator using the adhesive of any one of claims 1 to 9. The separator according to claim 13, comprising a polymer gel containing lithium hexafluorophosphate, cyclic carbonate, and chain carbonate, wherein the polymer gel is a composite of cellulose nanofibers. A battery, a lithium ion battery using the electrode of any one of claims 10 to 12, characterized in that the electrode is a battery in which the electrode and the separator are integrated; The electrodes and separators are bonded to make them integrated. A battery, a lithium ion battery using the separator of claim 13 or 14, characterized in that: The separator is used in a battery in which the electrode and the separator are integrated; the electrode and the separator are bonded and integrated through the adhesive used in the separator. An electrical apparatus provided with at least one of the battery of claim 15 and the battery of claim 16. A manufacturing method of an adhesive for lithium ion batteries, belonging to the adhesive for lithium ion batteries in which a thermoplastic fluorine-based resin is dissolved in N-methyl-2-pyrrolidone, and a liquid in which cellulose nanofibers are dispersed A production method comprising: a step (E) of setting the total of the solid content of the cellulose nanofibers and the thermoplastic fluorine-based resin to 100% by mass, wherein the cellulose nanofibers are 5% by mass or more and 50% by mass. The thermoplastic fluorine-based resin is dissolved in N-methyl-2-pyrrolidone, and the thermoplastic fluorine-based resin is mixed so that the thermoplastic fluorine-based resin is 50 mass % or more and 95 mass % or less by mass % or less; cellulose nanofibers are used in thermoplastic It exists in a dispersed state in the fluorine-based resin. A manufacturing method of a lithium ion battery, which is a manufacturing method of a lithium ion battery using the electrode of any one of claims 10 to 12 in at least one of the positive electrode and the negative electrode, comprising: step (F), adding the positive electrode to the positive electrode. The electrode group that is laminated or wound with a separator between the negative electrode and the electrolyte solution containing lithium hexafluorophosphate and aprotic carbonate is sealed and sealed in the cell body, and then heated to a temperature of 50°C or higher in the cell body. In the state below 120°C, from the outside of the cell body, pressure is applied perpendicularly to the extending direction of the electrode, and the electrode and the separator are integrated with the binder for compounding the thermoplastic fluorine-based resin and the cellulose nanofiber. A method of manufacturing a lithium ion battery using at least claim 13 or 14 The manufacturing method of the lithium ion battery of the separator, which comprises: step (F), between the positive electrode and the negative electrode through the separator to make the electrode group laminated or wound, and the electrolysis containing lithium hexafluorophosphate and aprotic carbonate After the battery is sealed and sealed, the temperature of the battery body is heated to a state where the temperature of the battery body is above 50°C and below 120°C. From the outside of the battery body, pressure is applied vertically to the extending direction of the electrode, which will have the ability to make thermoplastic fluorine The electrode and the separator are integrated as a binder of resin and cellulose nanofibers.

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