JP6426542B2 - Electrode forming paste and non-aqueous electrolyte secondary battery - Google Patents

Description

  The present invention relates to an electrode forming paste and a non-aqueous electrolyte secondary battery.

  In recent years, nonaqueous electrolyte secondary batteries such as lithium ion secondary batteries and nickel hydrogen batteries are important as power supplies for vehicles mounted with electricity as a driving source, or as power supplies mounted on personal computers, portable terminals and other electric products etc. Is rising. In particular, a lithium ion secondary battery which is light in weight and capable of obtaining a high energy density is preferably used as a high output power supply for vehicle mounting.

  A typical secondary battery of this type has an electrode having a structure in which an active material layer mainly composed of an active material capable of reversibly absorbing and desorbing chemical species serving as charge carriers is formed on a current collector. Have. The active material layer is a paste or slurry composition (hereinafter sometimes referred to as "electrode forming paste") prepared by adding an appropriate solvent to the active material together with a binder and a thickener, and collecting the current collector. It is formed by applying to the body (typically coating and drying). Patent document 1 is mentioned as a prior art regarding the manufacturing method of the said electrode.

International Publication No. 2012/046305

  By the way, in order to manufacture the said electrode efficiently, it is desirable to highly solidify this paste and to reduce a solvent so that the paste for electrode formation may dry easily. However, when the paste for electrode formation is highly solidified, the viscosity of the paste, particularly the viscosity of the paste at a high shear rate, is significantly increased. Therefore, the coating property at the time of coating this paste on a current collector may be impaired, and a streak or thickness unevenness may occur on the coated surface.

  This invention is made in view of this point, The main objective is to provide the paste for electrode formation excellent in coating property. Another object of the present invention is to provide a non-aqueous electrolyte secondary battery provided with an electrode having a smooth surface by adopting the electrode-forming paste.

  In order to achieve the above object, the present invention provides a paste for forming an electrode of a non-aqueous electrolyte secondary battery. The electrode-forming paste contains an active material, a binder, a thickener, a dispersant, and a solvent. The dispersant is a urethane compound represented by the following general formula.

Here, in the formula (A), X and Z are each independently a group selected from the group consisting of cholesteryl group, lanosteryl group, agnosteryl group and lanolin group. Y is a divalent organic residue derived from a diisocyanate compound. OR, OR ′ and OR ′ ′ are each independently an oxyalkylene group having 2 to 4 carbon atoms. A and d each is an integer of 1 to 15, b is an integer of 30 to 300, c Is an integer of 1 or more.

  Thus, the paste for electrode formation excellent in coating property can be implement | achieved by including the urethane compound represented by the said Formula (A) as a dispersing agent. Since the paste for electrode formation is excellent in coatability, for example, an electrode having a smooth surface can be easily formed with a constant thickness.

  In a preferable embodiment of the paste for electrode formation disclosed herein, the content of the dispersing agent is 0.1 parts by mass or more (eg, 0.1 parts by mass to 0.5 parts by mass) with respect to 100 parts by mass of the active material. Department). Within the range of the content of such a dispersant, the coatability of the paste can be further improved. On the other hand, when the content of the dispersant is too large, the resistance (particularly, the resistance in the low temperature range) of the electrode formed using the paste may tend to increase.

  In a preferable embodiment of the paste for electrode formation disclosed herein, the content of the thickener is at least 0.7 parts by mass with respect to 100 parts by mass of the active material. Thus, by containing the thickener in a predetermined ratio, the temporal stability of the paste (the difficulty of settling the solid content in the paste) can be improved better, and the solid content in the paste settles. Can effectively prevent various problems (eg, clogging of piping of coating apparatus, uneven distribution of active material and binder, increase in internal resistance and decrease in adhesion between active material layer and current collector, etc.) .

In a preferred embodiment of the paste for electrode formation disclosed herein, the viscosity of the paste at a shear rate of 1000 s ⁻¹ is 998 mPa · s or less. A paste with a low viscosity at such a high shear rate has high flowability (it is easy to pass through a narrow and narrow flow path of a coating apparatus) and good coatability. Therefore, when the paste is applied to the current collector, it is possible to prevent the occurrence of streaks and thickness unevenness on the coated surface. Here, the viscosity is a viscosity which can be measured by a commercially available shear viscometer. For example, by using a cone-plate viscometer such as a standard rheometer in the art, the viscosity can be easily measured under the conditions of the shear rate range as described above.

  In a preferable embodiment of the paste for electrode formation disclosed herein, c in the formula (A) is an integer of 1 or more and 4 or less. A dispersant having such [OCO-NH-Y-CO- (OR ') b] repeating units can effectively reduce the viscosity of the paste at high shear rates.

  In another aspect, the present invention provides a non-aqueous electrolyte secondary battery including an electrode having an active material layer formed on a current collector. The active material layer contains an active material, a binder, a thickener and a dispersant. The dispersant is a urethane compound represented by the following general formula (A). The content of the dispersing agent contained in the active material layer is 0.1 parts by mass to 0.5 parts by mass with respect to 100 parts by mass of the active material. Such a non-aqueous electrolyte secondary battery can be a high performance secondary battery with excellent electrode smoothness and low internal resistance.

Here, in the formula (A), X and Z are each independently a group selected from the group consisting of cholesteryl group, lanosteryl group, agnosteryl group and lanolin group. Y is a divalent organic residue derived from a diisocyanate compound. OR, OR ′ and OR ′ ′ are each independently an oxyalkylene group having 2 to 4 carbon atoms. A and d each is an integer of 1 to 15, b is an integer of 30 to 300, c Is an integer of 1 or more (for example, 1 or more and 4 or less).

  In a preferred embodiment of the non-aqueous electrolyte secondary battery disclosed herein, the content of the thickener contained in the active material layer is at least 0.7 parts by mass with respect to 100 parts by mass of the active material. is there. Such a non-aqueous electrolyte secondary battery can be, for example, a high-performance secondary battery in which the active material layer does not easily come off from the current collector and the internal resistance is low.

It is a graph which shows the relationship between a shear rate and paste viscosity. It is a graph which shows the relationship between a shear rate and paste viscosity. It is a graph which shows the relationship between a shear rate and paste viscosity. It is a figure showing typically the battery composition concerning one embodiment of the present invention. It is a figure for demonstrating the winding electrode body which concerns on one Embodiment of this invention.

Hereinafter, preferred embodiments of the present invention will be described. The matters other than the matters specifically mentioned in the present specification and necessary for the implementation of the present invention can be understood as the design matters of those skilled in the art based on the prior art in the relevant field. The present invention can be implemented based on the contents disclosed in the present specification and common technical knowledge in the field.
In the present specification, the term "secondary battery" refers to a battery that can be repeatedly charged in general, a so-called chemical battery involving a chemical reaction such as a lithium ion secondary battery, a nickel hydrogen battery, a nickel cadmium battery, etc. It is a term that includes so-called physical batteries such as capacitors. Further, in the present specification, the “active material” refers to an active material capable of reversibly absorbing and desorbing (typically inserting and desorbing) a chemical species serving as a charge carrier in a secondary battery. Moreover, the viscosity of the paste referred to in the present specification indicates the value of the viscosity measured at normal temperature. Here, “normal temperature” refers to a temperature range of 15 to 35 ° C., and typically refers to a temperature range of 20 to 30 ° C. (eg, 25 ° C.). For example, the viscosity of the paste is set to 25 ° C. with a cone plate of a cone plate type viscometer, temperature is adjusted for 1 minute after the paste is dropped, and then the measured value is employed.

  The electrode forming paste according to the present invention is a paste for forming an electrode of a non-aqueous electrolyte secondary battery. Hereinafter, the present invention will be described in detail by taking a negative electrode forming paste for forming a negative electrode of a lithium ion secondary battery as an example, but the application of the present invention is not intended to be limited to such a battery and an electrode.

<Paste for negative electrode formation>
The paste for forming a negative electrode disclosed herein is a composition in which a negative electrode active material, a binder, a thickener and a dispersant are mixed together with a solvent, and the negative electrode active material, the binder, the thickener and the dispersant are high. Included are pastes or slurried compositions contained in solid content. That is, the paste for forming a negative electrode disclosed herein contains a negative electrode active material, a binder, a thickener, a dispersant, and a solvent.

<Anode active material>
As a negative electrode active material used for the said paste for negative electrode formation, it can be used, without specifically limiting 1 type, 2 or more types of a substance conventionally used for a lithium ion secondary battery. Preferable examples include carbon-based materials such as natural graphite, artificial graphite, graphite, amorphous carbon and the like. As such a material (typically in the form of particles), for example, a material powder prepared by a conventionally known method can be used as it is. For example, a material powder substantially constituted by particles having an average particle diameter (D50 diameter) based on a laser diffraction / scattering method in a range of about 5 μm to 25 μm (preferably 8 μm to 15 μm) is preferably used as a negative electrode active material Can. As the tap density of the negative electrode active material, a is approximately 0.9g ^/ cm ³ ~1.2g ^/ cm 3 suitable, preferably ^{0.95g / cm 3 ~1.15g / cm 3} . Here, the tap density is a density measured after tapping with a powder reduction degree measuring device of tapping type and solidification by the impact. By using the negative electrode active material having such a tap density, the coatability of the paste can be better improved without adversely affecting the battery performance.

<Binder>
As a binder used for the said paste for negative electrode formation, there exists a function which couple | bonds active materials with each other or between an active material and a collector, and a soluble and dispersible material can be used for the solvent to be used. For example, in the paste for forming a negative electrode using an aqueous solvent, water dispersible polymers such as styrene butadiene block copolymer (SBR), acrylic acid modified SBR resin (SBR latex), gums such as gum arabic; It can be adopted. Among them, styrene butadiene block copolymer (SBR) can be preferably used. Moreover, in the paste for negative electrode formation using a non-aqueous solvent, polyvinylidene fluoride (PVDF), polyvinylidene chloride (PVDC), polyethylene oxide (PEO), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) Polymers such as fluorocarbon resins such as tetrafluoroethylene-hexafluoropropylene copolymer (FEP) and ethylene-tetrafluoroethylene copolymer (ETFE) can be preferably employed. Such materials may be used alone or in combination of two or more. The content of the binder is not particularly limited, but approximately 0.1 parts by mass to 10 parts by mass is appropriate with respect to 100 parts by mass of the negative electrode active material, preferably 0.5 parts by mass to 5 parts by mass, more preferably 0.8 parts by mass to 2 parts by mass.

<Thickener>
As a thickener used for the paste for negative electrode formation, a material having a function of thickening the paste can be used. For example, carboxymethylcellulose (CMC; typically sodium salt), hydroxyethylcellulose (HEC), hydroxypropylcellulose (HPC), methylcellulose (MC), cellulose acetate phthalate (CAP), hydroxypropylmethylcellulose (HPMC), hydroxypropyl Cellulose derivatives such as methyl cellulose phthalate (HPMCP) or polyvinyl alcohol (PVA) can be mentioned. Among these, cellulose derivatives (eg, CMC) can be particularly preferably used. Such materials may be used alone or in combination of two or more. The content of the thickener is not particularly limited, but approximately 0.5 parts by mass to 5 parts by mass is appropriate with respect to 100 parts by mass of the negative electrode active material, and preferably 0.7 parts by mass to 2 parts by mass, Preferably, it is 0.7 parts by mass to 1 part by mass. Thus, by containing a thickener in a predetermined ratio, the temporal stability of the paste can be better improved without adversely affecting the battery performance.

<Dispersing agent>
The paste for forming a negative electrode disclosed herein further contains a urethane compound represented by the following general formula (A) as a dispersant. Thus, the paste for electrode formation excellent in coating property can be implement | achieved by including the compound represented by following formula (A) as a dispersing agent.

Here, in the formula (A), X and Z are each independently a group selected from the group consisting of cholesteryl group, lanosteryl group, agnosteryl group and lanolin group. Y is a divalent organic residue derived from a diisocyanate compound. OR, OR ′ and OR ′ ′ are each independently an oxyalkylene group having 2 to 4 carbon atoms. A and d each is an integer of 1 to 15, b is an integer of 30 to 300, c Is an integer of 1 or more.

  In the urethane compound represented by the above formula (A), X and Z are each independently a group selected from cholesteryl group, lanosteryl group, agnosteryl group and lanolin group. X and Z may be the same or different combinations. As a preferable example of the above-mentioned compound, a urethane compound in which X is a group selected from cholesteryl group, lanosteryl group and agnosteryl group, and Z is a group selected from cholesteryl group, lanosteryl group, agnosteryl group and lanolin group is exemplified. . Among them, a urethane compound in which X is a cholesteryl group or a lanosteryl group and Z is a group selected from a lanosteryl group, an agnosteryl group and a lanolin group is preferable. The lanolin group can also be referred to as a group having a skeleton derived from lanolin alcohol.

  In the urethane compound represented by the formula (A), Y is a divalent organic residue derived from a diisocyanate compound. The diisocyanate compound is not particularly limited. Examples of the diisocyanate compound include aliphatic diisocyanate compounds, aromatic diisocyanate compounds and alicyclic diisocyanates; and the like.

  Examples of aliphatic diisocyanate compounds include methylene diisocyanate, dimethylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, and the like. Hexamethylenediisocyanate, heptamethylenediisocyanate, octamethylenediisocyanate, nonamethylenediisocyanate, decamethylenediisocyanate, dipropyl ether diisocyanate, 2, 2- Dimethylpentanediisocyanate, 3-methoxyhexanediisocyanate, 2,2,4-trimethylpentanediisocyanate, 3-butoxyhexanediisocyanate, 1,4-butylene glycoldipropyl ether -Terdiisocyanate, metaxylylene diisocyanate, paraxylylene diisocyanate Cyanate - DOO and tetramethyl xylylene diisocyanate - DOO; and the like. Among them, pentamethylene diisocyanate, hexamethylene diisocyanate and heptamethylene diisocyanate are preferable.

  Examples of aromatic diisocyanate compounds include metaphenylene diisocyanate, paraphenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, Dimethylbenzenediisocyanate, ethylbenzenediisocyanate, isopropylbenzenediisocyanate, biphenyldiisocyanate, tolidinediisocyanate, 3,3'-dimethoxybiphenyldiisocyanate, Naphthalene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,2'-dimethyldiphenylmethane-4,4'-diisocyanate, 3,3'-dimethoxydiphenylmethane-4,4'-diisocyanate -4,4,4'-Dimethoxydiphenylmethane-3,3'-diisocyanate, 4,4'-di Butoxy diphenylmethane-3,3'-diisocyanate - DOO and 2,2'-dimethyl-5,5'-dimethoxy-4,4'-diisocyanate - DOO; and the like.

  Examples of alicyclic diisocyanate compounds include cyclohexyl diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate and dicyclohexylmethane-4,4'-diisocyanate; It is illustrated.

  In the urethane compound represented by the above formula (A), OR, OR ′ and OR ′ ′ are oxyalkylene groups having 2 to 4 carbon atoms. When the carbon number is less than 2 or more than 4 when the coatability is lowered Examples of the oxyalkylene group having 2 to 4 carbon atoms include an oxyethylene group, an oxypropylene group, an oxybutylene group, etc. (OR) a, (OR ′) b and (OR ′ ′) d Is a random polymerization chain or block polymerization chain of two or more oxyalkylene groups, or a combination thereof. The oxyalkylene groups may be the same or different combinations.

  In the urethane compound represented by the above formula (A), a and d each represent a repeating unit of OR and OR ′ ′ a and d each is an integer of 1 to 15, and preferably 1 to 10 More preferably, it is 1 to 8. If a, d is less than 1, the reaction may not proceed well, while if it exceeds 15, the coatability may decrease.

  In the urethane compound represented by the above formula (A), b represents a repeating unit of OR '. b is an integer of 30 to 300, preferably 40 to 250, and more preferably 50 to 200. When b is less than 30 or more than 300, the coatability may be reduced.

  In the urethane compound represented by the above formula (A), c represents a repeating unit in [OCO-NH-Y-CO- (OR ') b], and is an integer of 1 or more (preferably 1 or more and 4 or less) is there. When c is less than 1, the coatability may be reduced.

  As a method of synthesizing the above-mentioned dispersant, it can be synthesized using a known urethanation reaction. For example, it can be synthesized by reacting polyether monool, polyether diol and diisocyanate for 2 to 10 hours. For example, in the case of synthesis from a polyether monool, a polyether diol and a diisocyanate, a synthesis method by one-step preparation may be used, and after reacting a polyether diol with a diisocyanate, a polyether mono io is produced. The reaction may be carried out by reacting with polyester, or by reacting polyester monool with diisocyanate and then reacting with polyether. By-products may be produced by the reaction, but can be suitably used in a mixture with by-products.

  As reaction temperature, about 40-130 degreeC is suitable, Preferably it is 70-100 degreeC. If the temperature is less than 40 ° C., the reaction may be slow and the reaction may take too long to complete, and if the temperature is higher than 130 ° C., abnormal side reactions may occur, which is not preferable.

  In these reactions, a solvent may be used if necessary. The solvent preferably does not contain active hydrogen. For example, toluene and xylene as aromatic solvents, petroleum ether and n-hexane as aliphatic solvents, cyclohexane, cyclohexanone and decalin as alicyclic solvents, chloroform as halogen-containing solvents, carbon tetrachloride, ethylene Examples of ester solvents such as dichloride and chlorobenzene, ethyl acetate, butyl acetate and pentyl acetate, and ketone solvents such as methyl ethyl ketone, diethyl ketone and methyl isobutyl ketone.

  In addition, a catalyst may be used for the urethanization reaction, if necessary. As a catalyst used for the urethanization reaction, for example, amine compounds such as triethylamine, triethylenediamine, heptamethyldiethylenetriamine, N-methylmorpholine and benzyltriethylammonium hydroxide, etc., metal-containing compounds such as stannous chloride and stannous chloride And tin octylate, lead octylate, dibutyltin dilaurate, cobalt naphthenate, lead naphthenate, potassium naphthenate and antimony trichloride. The amount of catalyst added is suitably about 0.001% by mass to 1% by mass with respect to the total mass of the charge. Moreover, as an addition method, although it adds normally to the reaction initial stage, you may add separately in reaction.

The content of the dispersant is not particularly limited, but is preferably about 0.1 parts by mass or more, preferably 0.2 parts by mass or more, and more preferably 0.3 parts by mass with respect to 100 parts by mass of the negative electrode active material. It is more than mass part. Within the range of the content of such a dispersant, the coatability of the paste can be further improved. On the other hand, when the content of the dispersant is too large, the resistance (particularly, the resistance in the low temperature range) of the electrode formed using the paste may tend to increase.
From the viewpoint of reducing the resistance, for example, the content of the dispersant is suitably 0.5 parts by mass or less, preferably 0.4 parts by mass or less, with respect to 100 parts by mass of the negative electrode active material.

<Solvent>
As the solvent for dispersing the negative electrode active material, the binder, the thickener and the dispersant described above, those used in conventional paste materials of this type can be used without particular limitation, and aqueous solvents and non-aqueous solvents Any of (eg, N-methyl pyrrolidone (NMP)) can be used. Typically, water or a mixed solvent composed mainly of water is preferably used. As solvent components other than water which comprises this mixed solvent, 1 type, or 2 or more types of organic solvents (lower alcohol, lower ketone, etc.) which can be mixed uniformly with water can be selected suitably, and can be used. For example, it is preferable to use an aqueous solvent in which 80% by mass or more (more preferably 90% by mass or more, further preferably 95% by mass or more) of the aqueous solvent is water. Particularly preferred examples include aqueous solvents substantially consisting of water.

<Solid fraction>
Although the solid content can be suitably selected according to the purpose for the paste for negative electrode formation disclosed here, it is preferable to set it as 55 mass% or more which usually becomes easy to dry, for example, 59 mass%-75 mass%. Is more preferably in the range of 60 to 70% by mass, and particularly preferably in the range of 60 to 65% by mass.

<Viscosity>
Moreover, the paste for negative electrode formation disclosed here may be a thing with favorable coating property, although it is high solid content. For example, the viscosity α at a shear rate of 1000 s ⁻¹ is α ≦ 1000 mPa · s (eg, 500 mPa · s ≦ α ≦ 1000 mPa · s), preferably α ≦ 998 mPa · s, more preferably α ≦ 980 mPa · s, in particular Preferably, it may be α ≦ 950 mPa · s. Shear rate: The paste for negative electrode formation which set viscosity (alpha) in 1000 s < ^-1 > to (alpha) <= 1000 mPa * s has high fluidity | liquidity (it is easy to pass the thin narrow channel of die-coaters etc.), and its coatability is favorable. Therefore, when the paste is applied to the current collector, it is possible to prevent the occurrence of streaks and thickness unevenness on the coated surface.

As a preferable example of the paste for forming a negative electrode disclosed herein, one having a viscosity α of 1000 mPa · s or less at a shear rate of 1000 s ⁻¹ and a solid content in a range of 55 to 70% by mass, In the range where the viscosity α is 998 mPa · s or less and the solid content is in the range of 59 to 70% by mass, the viscosity α is 980 mPa · s or less and the solid content is in the range 60 to 70% by mass A certain thing, etc. are mentioned. By having both the viscosity α and the solid content in such a predetermined range, it is possible to obtain a negative electrode forming paste which satisfies both of good coatability which can not be obtained conventionally and high drying efficiency. it can.

The paste for forming a negative electrode disclosed herein has a viscosity β of 1000 mPa · s ≦ β (for example, 1000 mPa · s ≦ β ≦ 30000 mPa · s) at a shear rate of 1 s ⁻¹ , preferably 2000 mPa · s ≦ β. It may be ≦ 25000 mPa · s, more preferably 3000 mPa · s ≦ β ≦ 15000 mPa · s. The paste for forming a negative electrode disclosed herein exhibits a temporal stability suitable for applying the paste to a current collector by having a viscosity of 1000 mPa · s ≦ β. That is, the paste for forming a negative electrode, in which the viscosity β at a shear rate of 1 s ^-1 is 1000 mPa · s ≦ β, is excellent in the temporal stability during standing (when left at room temperature without performing operations such as stirring) Therefore, when the paste is applied to a current collector, the solid content in the paste can be maintained in a good dispersion state without settling. Therefore, various problems due to the solid content in the paste settling out (for example, clogging of piping such as die coater, uneven distribution of negative electrode active material and binder, increase in internal resistance accompanying it, negative electrode active material layer and negative electrode current collector And the like) can be prevented.
That is, by simultaneously having the viscosity α and β such that α ≦ 1000 mPa · s and 1000 mPa · s ≦ β, both the temporal stability and the coatability of the paste are good, so that the coating failure It is possible to form a high-performance negative electrode with a smooth internal surface, a negative electrode active material layer that is difficult to peel off from the negative electrode current collector, and lower internal resistance while avoiding generation.

  Here, in the conventional paste for forming a negative electrode which does not contain the above-described urethane compound as a dispersant, the present inventor prepares a plurality of pastes adjusted to various different solid fractions, changes the shear rate and changes the viscosity of the paste. It was measured. Among these, about the paste adjusted to 52 mass%, 56 mass%, and 60 mass% solid content, the result of having performed viscosity measurement is shown in FIG. Here, 1 part by mass of CMC was used as a thickener with respect to 100 parts by mass of the active material.

As shown in FIG. 1, as the solid content of the paste increased to 52% by mass, 56% by mass, and 60% by mass, the viscosity of the paste tended to increase. In particular, the viscosity of the paste at a shear rate of 1000 s ^-1 was significantly increased. As described above, when the paste viscosity in the high shear rate region is increased, the coating property may be deteriorated as described above. Although it is conceivable to reduce the addition amount of the thickener (CMC) in order to suppress such viscosity increase, simply reducing the addition amount of the thickener reduces the paste viscosity as a whole. For example, FIG. 2 shows changes in paste viscosity when the solid content is fixed at 60% by mass and the addition amount of CMC is adjusted to 0.4 parts by mass, 0.7 parts by mass, and 1 part by mass. As shown in FIG. 2, as the amount of CMC added decreases, the viscosity in the high shear rate region tends to decrease, but the viscosity in the low shear rate region also tends to decrease accordingly. Therefore, the viscosity at a shear rate of 1 s ⁻¹ is less than 1000 mPa · s only by reducing the addition amount of the thickener, and the temporal stability of the paste is impaired.

On the other hand, the paste for forming a negative electrode disclosed herein contains a urethane compound represented by the above-mentioned formula (A) as a dispersant, so that even a high solid content such as 60% by mass or more can be obtained, Shear rate: It is possible to effectively suppress the increase in viscosity of the paste in the vicinity of 1000 s ⁻¹ . Moreover, the paste viscosity in shear rate: 1s < ^-1 > vicinity can be maintained highly viscous by including a thickener in a predetermined | prescribed ratio. That is, by intentionally using the dispersant represented by the formula (A) in combination with a thickener having a predetermined ratio, the viscosity α at a shear rate of 1000 s ⁻¹ is high despite the high solid content. A paste having a viscosity of α ≦ 1000 mPa · s and a viscosity β of 1000 mPa · s ≦ β at a shear rate of 1 s ⁻¹ can be easily realized, and a good coating which could not be obtained conventionally It can be set as the optimal paste for negative electrode formation which satisfies both of property and favorable aging stability.

  The paste for negative electrode formation disclosed here can be typically prepared by kneading the said negative electrode active material, a binder, a thickener, a dispersing agent (urethane compound), and a solvent. Preferably, first, the negative electrode active material, the thickener and the solvent are mixed to form a paste, and then a binder is further added and kneaded. The solvent may be divided into a plurality of times and charged in small amounts. The dispersant may be added from the beginning together with the negative electrode active material and the thickener, may be added together with the binder, and may be added last after adding the binder. Also, the dispersing agent may be diluted with a solvent so as to have an appropriate viscosity and then added. Although the apparatus used for the said kneading | mixing is not specifically limited, For example, extrusion-type kneaders, such as a planetary mixer, a disper, a ball mill, a kneader, a mixer, etc. are mentioned. The paste for negative electrode formation which has the viscosity mentioned above can be suitably prepared by mixing various paste materials in such a procedure, and mutually kneading together.

  When forming the negative electrode, the paste for forming a negative electrode is applied to a negative electrode current collector to form a negative electrode active material layer on the negative electrode current collector. For the negative electrode current collector, for example, a metal foil suitable for the negative electrode can be suitably used. For example, copper foil is used as a negative electrode current collector. The operation for applying the paste for forming a negative electrode to the current collector can be performed in the same manner as in the case of producing a conventional negative electrode for a lithium ion secondary battery. For example, using a suitable coating apparatus (die coater, slit coater, comma coater, etc.), a predetermined amount of the paste for forming a negative electrode is applied to a uniform thickness on the negative electrode current collector. Then, the solvent in the paste for negative electrode formation is removed by volatilizing the solvent in the paste for negative electrode formation with a drying furnace. A negative electrode active material layer is formed by removing the solvent from the negative electrode forming paste. Thus, the negative electrode in which the negative electrode active material layer is formed on the negative electrode current collector can be obtained. After drying, the thickness and density of the negative electrode active material layer can be appropriately adjusted by applying an appropriate press treatment (for example, a roll press treatment) as necessary.

  Thus, the negative electrode current collector has a configuration in which the negative electrode active material layer including the negative electrode active material, the binder, the thickener, and the dispersant (the urethane compound represented by the formula (A)) is held. A negative electrode can be obtained. In a preferable aspect, the content of the dispersant contained in the negative electrode active material layer is 0.1 parts by mass to 0.5 parts by mass with respect to 100 parts by mass of the negative electrode active material. The content of the thickener contained in the negative electrode active material layer is 0.5 parts by mass or more (preferably 0.7 parts by mass or more) with respect to 100 parts by mass of the negative electrode active material. Such a negative electrode is formed using the paste for forming a negative electrode which satisfies both the coating property and the temporal stability, so that it is a high performance negative electrode having excellent smoothness and lower electrode resistance. obtain. Such a negative electrode can be preferably used as a component of various types of batteries or a component of an electrode assembly incorporated in the battery because it has higher performance.

  For example, a negative electrode formed using any of the negative electrode-forming pastes disclosed herein, a positive electrode, an electrolyte disposed between the positive and negative electrodes, and a separator (solid which is typically separated between the positive and negative electrodes) (Which may be omitted in batteries using electrolytes in the form of gel or gel).) And preferably used as a component of a lithium ion secondary battery. The structure (for example, a metal casing or a laminate film structure) or the size of an outer container constituting such a battery, or the structure of an electrode body having a positive and negative electrode current collector as a main component (for example, a wound structure or a laminated structure) There is no particular restriction on etc.

  The other materials and members constituting the lithium ion secondary battery provided with the negative electrode formed using the paste for forming a negative electrode disclosed herein may be the same as those conventionally provided in the same kind of battery, and there are no particular limitations. Absent. Hereinafter, the other components will be described with reference to the schematic diagrams shown in FIGS. 4 and 5. FIG. 4 is a cross-sectional view of a lithium ion secondary battery 100 according to an embodiment of the present invention. FIG. 5 is a view showing an electrode assembly 40 incorporated in the lithium ion secondary battery 100. In the lithium ion secondary battery 100, as the negative electrode (negative electrode sheet) 60, the negative electrode (negative electrode sheet) 60 manufactured using the above-described paste for forming a negative electrode is used.

  A lithium ion secondary battery 100 according to an embodiment of the present invention is configured in a flat rectangular battery case (i.e., an outer container) 20 as shown in FIG. 4. In the lithium ion secondary battery 100, as shown in FIGS. 4 and 5, the flat wound electrode body 40 is accommodated in the battery case 20 together with the liquid electrolyte (electrolyte solution) 80.

  The battery case 20 has a box-shaped (that is, a bottomed rectangular parallelepiped) case body 21 having an opening at one end (corresponding to the upper end of the battery 100 in a normal use state), and is attached to the opening It is comprised from the cover body (sealing plate) 22 which consists of a rectangular-shaped plate member which block | closes an opening part. The material of the battery case 20 may be the same as that used in a conventional lithium ion secondary battery, and is not particularly limited. A battery case 20 mainly composed of a lightweight, thermally conductive metal material is preferable, and aluminum or the like is exemplified as such a metal material.

  As shown in FIG. 4, the lid 22 is provided with a positive electrode terminal 23 and a negative electrode terminal 24 for external connection. Between the two terminals 23 and 24 of the lid 22, a thin-walled safety valve 30 configured to release the internal pressure when the internal pressure of the battery case 20 rises above a predetermined level, and a liquid injection port 32 are formed. It is done. In addition, in FIG. 4, the said liquid injection port 32 is sealed by the sealing material 33 after liquid injection.

  As shown in FIG. 5, the wound electrode body 40 has a total of two sheets of a long sheet-like positive electrode (positive electrode sheet 50) and a long sheet-like negative electrode (negative electrode sheet 60) similar to the positive electrode sheet 50. And a long sheet-like separator (separators 72 and 74).

  The positive electrode sheet 50 includes a strip-shaped positive electrode current collector 52 and a positive electrode active material layer 53. For the positive electrode current collector 52, for example, a metal foil suitable for the positive electrode can be suitably used. In this embodiment, an aluminum foil is used as the positive electrode current collector 52. An uncoated portion 51 is set along the edge on one side in the width direction of the positive electrode current collector 52. In the illustrated example, the positive electrode active material layer 53 is held on both sides of the positive electrode current collector 52 except for the uncoated portion 51 set in the positive electrode current collector 52. The positive electrode active material layer 53 contains positive electrode active material particles, a conductive material, and a binder.

  As the positive electrode active material, a material capable of absorbing and desorbing lithium ions is used, and one or two or more kinds of substances conventionally used in lithium ion secondary batteries (for example, oxides of layered structure and oxides of spinel structure) Is used without particular limitation. For example, lithium-containing transition metal oxides such as lithium nickel based composite oxides, lithium cobalt based composite oxides, lithium manganese based composite oxides and the like can be mentioned.

  The positive electrode active material layer 53 is prepared, for example, by mixing the above-described positive electrode active material particles, a conductive material, and a binder with a solvent to prepare a positive electrode forming paste, coating (coating and drying) on the positive electrode current collector 52, and rolling It is formed by doing. In addition, the paste for positive electrode formation may also contain the urethane compound represented by said Formula (A) as a dispersing agent like the paste for negative electrode formation. As a solvent for the paste, both aqueous solvents and non-aqueous solvents (for example, N-methylpyrrolidone (NMP)) can be used. As a conductive material, carbon materials, such as carbon powder and carbon fiber, are illustrated, for example. As the conductive material, one selected from such conductive materials may be used alone, or two or more may be used in combination. As the carbon powder, carbon powders such as various carbon blacks (for example, acetylene black (AB), oil furnace black, graphitized carbon black, carbon black, graphite, ketjen black), graphite powder and the like can be used. As the binder, polyvinylidene fluoride (PVdF), polyvinylidene chloride (PVdC), polyacrylonitrile (PAN) or the like can be preferably employed.

  As shown in FIG. 5, the negative electrode sheet 60 includes a strip-like negative electrode current collector 62 and a negative electrode active material layer 63. For the negative electrode current collector 62, for example, a metal foil suitable for the negative electrode can be suitably used. In this embodiment, a strip-shaped copper foil is used for the negative electrode current collector 62 as described above. An uncoated portion 61 is set along the edge on one side in the width direction of the negative electrode current collector 62. The negative electrode active material layer 63 is held on both sides of the negative electrode current collector 62 except for the uncoated portion 61 set in the negative electrode current collector 62. As described above, the negative electrode active material layer 63 contains the negative electrode active material, the binder, the thickener, and the urethane compound (dispersant) represented by the formula (A). The method for producing the negative electrode sheet is as described above, and thus the description thereof is omitted.

  The separators 72 and 74 are members for separating the positive electrode sheet 50 and the negative electrode sheet 60, as shown in FIG. In this example, the separators 72 and 74 are formed of a band-like sheet material having a predetermined width and having a plurality of minute holes. For the separators 72 and 74, for example, a separator having a single layer structure made of a porous polyolefin resin or a separator having a laminated structure can be used. In addition, a layer of insulating particles may be further formed on the surface of the sheet material made of such a resin. Here, as particles having insulating properties, inorganic fillers having insulating properties (for example, fillers such as metal oxides and metal hydroxides) or resin particles having insulating properties (for example, particles such as polyethylene and polypropylene) It may consist of. In this example, as shown in FIG. 3, the width b1 of the negative electrode active material layer 63 is slightly wider than the width a1 of the positive electrode active material layer 53. Furthermore, the widths c1 and c2 of the separators 72 and 74 are slightly wider than the width b1 of the negative electrode active material layer 63 (c1, c2> b1> a1).

  In this embodiment, as shown in FIG. 5, the wound electrode body 40 is flatly pressed and bent in one direction orthogonal to the winding axis WL. In the example shown in FIG. 5, the uncoated portion 51 of the positive electrode current collector 52 and the uncoated portion 61 of the negative electrode current collector 62 are spirally exposed on both sides of the separators 72 and 74. In this embodiment, as shown in FIG. 4, the middle portion of the uncoated portion 51 is gathered and welded to the current collecting tabs 25 and 26 of the electrode terminals (internal terminals) disposed inside the battery case 20. Be done. Reference numerals 25a and 26a in FIG. 4 indicate the welds.

  Then, the wound electrode body 40 is accommodated in the main body 21 from the upper end opening of the case main body 21, and the opening is sealed by welding with the lid 22 or the like. Further, the electrolytic solution 80 is disposed (injected) in the case main body 21 from the liquid injection port 32.

As the electrolyte solution (non-aqueous electrolyte solution) 80, the same non-aqueous electrolyte solution conventionally used for lithium ion secondary batteries can be used without particular limitation. Such non-aqueous electrolytes typically have a composition in which a suitable non-aqueous solvent contains a supporting salt. Examples of the non-aqueous solvent include ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 1,3-dioxolane and the like. One or two or more selected from the group can be used. Further, as the supporting salt, for _{example, LiPF 6, LiBF 4, LiAsF} 6, LiCF 3 SO 3, LiC 4 F 9 SO 3, LiN (CF 3 SO 2) 2, LiC (CF 3 SO 2) _3, etc. Lithium salts can be used.

  Thereafter, the liquid injection port 32 is sealed by the sealing material 33, and the assembly of the lithium ion secondary battery 100 according to the present embodiment is completed. The sealing process of the case 20 and the placement (injection) process of the electrolytic solution may be the same as the method performed in the manufacture of a conventional lithium ion secondary battery, and do not characterize the present invention. Thus, the construction of the lithium ion secondary battery 100 according to the present embodiment is completed.

  As described above, the lithium ion secondary battery 100 constructed in this manner is formed using the paste for forming a negative electrode having a suitable viscosity including the urethane compound (dispersant) represented by the formula (A) as described above. Since it has been described, it exhibits excellent battery performance. For example, by constructing a battery using the above negative electrode, at least one (preferably all) of excellent input / output characteristics, high cycle durability, good production stability, good production efficiency is satisfied. A lithium ion secondary battery can be provided.

  EXAMPLES The test examples of the present invention will be described below, but the present invention is not intended to be limited to those shown in the specific examples. In the following description, "part" or "%" means "part by mass" or "% by mass".

<< Synthesis of Urethane Compounds >>
The urethane compound (dispersant) used in Examples and Comparative Examples was synthesized as follows.

<Production Example 1>
431 parts of ethylene oxide adduct of cholesterol (average number of added moles: 1), polyethylene glycol (number average molecular weight: 1,350) in a 2000 ml four-necked flask equipped with a thermometer, nitrogen inlet tube and high viscosity stirrer ) Was dehydrated at 80 to 90 ° C. under low pressure (5 to 10 mmHg) for 3 hours to make the water content of the system 0.03%. Next, the reaction solution is cooled to 70 ° C., 168 parts of hexamethylene diisocyanate is added, and the mixture is reacted under nitrogen flow at 85 to 90 ° C. until the isocyanate content is 0% (3 hours). A reaction product (dispersant 1) was obtained.

<Production Example 2>
43.0 parts of ethylene oxide adduct of cholesterol (average number of added moles: 1), ethylene oxide adduct of lanosterol in a 2000 mL four-necked flask equipped with a thermometer, nitrogen inlet tube and high viscosity stirrer Add 47.0 parts of the average added number of moles: 1) and 1320 parts of polyethylene glycol (number average molecular weight 13200), dehydrate at 80 to 90 ° C for 3 hours under low pressure (5 to 10 mmHg), The content is 0.03%. Then, it is cooled to 70 ° C., 33.6 parts of hexamethylene diisocyanate is added, and the mixture is reacted at 85 to 90 ° C. under nitrogen flow until the isocyanate content is 0% (3 hours), light yellow viscous A liquid reaction product (dispersant 2) was obtained.

<Production Example 3>
524 parts of ethylene oxide adduct of cholesterol (average number of added moles: 15) and ethylene oxide adduct of agnosterol (average of 15 mol) in a 2000 ml four-necked flask equipped with a thermometer, a nitrogen introducing pipe and a stirrer for high viscosity Add 543 parts of added moles: 15) and 675 parts of polyethylene glycol (number average molecular weight: 1350), dehydrate at 80 to 90 ° C under low pressure (5 to 10 mmHg) for 3 hours, and set the water content of the system to 0 .03%. Next, the reaction solution is cooled to 70 ° C., 168 parts of hexamethylene diisocyanate is added, and the mixture is reacted under nitrogen flow at 85 to 90 ° C. until the isocyanate content is 0% (3 hours). A reaction product (dispersant 3) was obtained.

Production Example 4
105 parts of ethylene oxide adduct of cholesterol (average number of added moles: 15), lanolin alcohol ethylene oxide adduct (average addition, in a 2000 ml four-necked flask equipped with a thermometer, a nitrogen inlet tube and a stirrer for high viscosity 105 parts of moles and 1320 parts of polyethylene glycol (number average molecular weight 13200) are dehydrated at 80 to 90 ° C. for 3 hours under low pressure (5 to 10 mmHg), and the water content of the system is 0. It is 03%. Then, it is cooled to 70 ° C., 33.6 parts of hexamethylene diisocyanate is added, and the mixture is reacted at 85 to 90 ° C. under nitrogen flow until the isocyanate content is 0% (3 hours), light yellow viscous A liquid reaction product (dispersant 4) was obtained.

<Production Example 5>
129 parts of ethylene oxide adduct of ranosterol (average number of added moles: 5) and polyethylene glycol (number average molecular weight 6600) in a 2000 ml four-necked flask equipped with a thermometer, a nitrogen inlet tube and a stirrer for high viscosity 1320 parts) was dehydrated at 80 to 90 ° C. for 3 hours under low pressure (5 to 10 mmHg) to make the water content of the system 0.03%. Next, the mixture is cooled to 70 ° C., 50.4 parts of hexamethylene diisocyanate is added, and the mixture is reacted under nitrogen flow at 85 to 90 ° C. until the isocyanate content is 0% (3 hours), light yellow viscous A liquid reaction product (dispersant 5) was obtained.

<Production Example 6>
32.4 parts of ethylene oxide adduct of ranosterol (average number of added moles: 5) and ethylene oxide adduct of agnosterol in a 2000 ml four-necked flask equipped with a thermometer, a nitrogen inlet tube and a stirrer for high viscosity Add 32.4 parts of (average added mole number: 5) and 1320 parts of polyethylene glycol (number average molecular weight 6600) and dehydrate at 80 to 90 ° C for 3 hours under low pressure (5 to 10 mmHg). The water content was 0.03%. Then, it is cooled to 70 ° C., 42 parts of hexamethylene diisocyanate is added, and the mixture is reacted under nitrogen flow at 85 to 90 ° C. until the isocyanate content becomes 0% (3 hours), light yellow viscous liquid A reaction product (dispersant 6) was obtained.

Production Example 7
129 parts of ethylene oxide adduct of ranosterol (average number of added moles: 5), lanolin alcohol ethylene oxide adduct (average addition, in a 2000 ml four-necked flask equipped with a thermometer, nitrogen inlet tube and high viscosity stirrer 121 parts of mol number: 5) and 1320 parts of polyethylene glycol (number average molecular weight 6600) are dehydrated at 80 to 90 ° C. for 3 hours under low pressure (5 to 10 mmHg), and the water content of the system is 0. It is 03%. Next, the solution is cooled to 70 ° C., 67.2 parts of hexamethylene diisocyanate is added, and the mixture is reacted under nitrogen flow at 85 to 90 ° C. until the isocyanate content becomes 0% (3 hours), light yellow viscous A liquid reaction product (dispersant 7) was obtained.

<Production Example 8>
In a 2000 ml four-necked flask equipped with a thermometer, a nitrogen inlet tube and a stirrer for high viscosity, 129 parts of ethylene oxide adduct of gonosterol (average number of added moles: 5), lanolin alcohol ethylene oxide adduct (average 121 parts of added moles: 13) and 1320 parts of polyethylene glycol (number average molecular weight 6600), dehydrated at 80 to 90 ° C. under low pressure (5 to 10 mmHg) for 3 hours, and the water content of the system was 0 .03%. Next, the solution is cooled to 70 ° C., 67.3 parts of hexamethylene diisocyanate is added, and the mixture is reacted under nitrogen flow at 85 to 90 ° C. until the isocyanate content is 0% (3 hours), light yellow viscous A liquid reaction product (dispersant 8) was obtained.

<Production Example 9>
121 parts of ethylene oxide adduct of cholesterol (average number of added moles: 5), polyethylene glycol (number average molecular weight 6600) in a 2000 ml four-necked flask equipped with a thermometer, nitrogen inlet tube and high viscosity stirrer 1320 parts) was dehydrated at 80 to 90 ° C. for 3 hours under low pressure (5 to 10 mmHg) to make the water content of the system 0.03%. Then, it is cooled to 70 ° C., 50.5 parts of hexamethylene diisocyanate is added, and the mixture is reacted at 85 to 90 ° C. under nitrogen flow until the isocyanate content is 0% (3 hours), light yellow viscous A liquid reaction product (dispersant 9) was obtained.

<Comparative Production Example 1>
105 parts of ethylene oxide adduct of cholesterol (average number of added moles: 15) and polyethylene glycol (number average molecular weight 17600) in a 2000 ml four-necked flask equipped with a thermometer, nitrogen inlet tube and high viscosity stirrer 880 parts) was dehydrated at 80 to 90 ° C. for 3 hours under low pressure (5 to 10 mmHg) to make the water content of the system 0.03%. Next, it is cooled to 70 ° C., 16.8 parts of hexamethylene diisocyanate is added, and the mixture is reacted under nitrogen flow at 85 to 90 ° C. until the isocyanate content becomes 0% (3 hours), light yellow viscous A liquid reaction product (comparative compound 1) was obtained.

<Comparative Production Example 2>
1047 parts of ethylene oxide adduct of cholesterol (average number of added moles: 15) is placed in a 2000 ml four-necked flask equipped with a thermometer, a nitrogen inlet tube and a stirrer for high viscosity, under low pressure (5 to 10 mmHg) The system was dehydrated at 80-90.degree. C. for 3 hours to make the water content of the system 0.03%. Next, the reaction solution is cooled to 70 ° C., 84.1 parts of hexamethylene diisocyanate is added, and the mixture is reacted at 85 to 90 ° C. under a nitrogen stream until the isocyanate content is 0% (3 hours), light yellow viscous A liquid reaction product (comparative compound 2) was obtained.

Comparative Production Example 3
342 parts of ethylene oxide adduct of cholesterol (average number of moles added: 30) and polyethylene glycol (number average molecular weight 6600) in a 2000 ml four-necked flask equipped with a thermometer, nitrogen inlet tube and high viscosity stirrer 1320 parts) was dehydrated at 80 to 90 ° C. for 3 hours under low pressure (5 to 10 mmHg) to make the water content of the system 0.03%. Then, it is cooled to 70 ° C., 50.5 parts of hexamethylene diisocyanate is added, and the mixture is reacted at 85 to 90 ° C. under nitrogen flow until the isocyanate content is 0% (3 hours), light yellow viscous A liquid reaction product (Compound 3) was obtained.

Comparative Production Example 4
169 parts of ethylene oxide adduct of lauryl alcohol (average number of added moles: 15) and polyethylene glycol (number average molecular weight) in a 2000 ml four-necked flask equipped with a thermometer, nitrogen inlet tube and stirrer for high viscosity 13200 parts were added and dehydrated at 80 to 90 ° C. for 3 hours under low pressure (5 to 10 mmHg) to make the water content of the system 0.03%. Then, it is cooled to 70 ° C., 33.6 parts of hexamethylene diisocyanate is added, and the mixture is reacted at 85 to 90 ° C. under nitrogen flow until the isocyanate content is 0% (3 hours), light yellow viscous A liquid reaction product (comparative compound 4) was obtained.

<Comparative Production Example 5>
1564 parts of ethylene oxide adduct of cholesterol (average number of moles added: 80), polyethylene glycol (number average molecular weight: 220) in a 2000 ml four-necked flask equipped with a thermometer, a nitrogen inlet tube and a stirrer for high viscosity 22.0 parts) and dehydrated at 80 to 90 ° C. for 3 hours under low pressure (5 to 10 mmHg) to make the water content of the system 0.03%. Then, it is cooled to 70 ° C., 50.5 parts of hexamethylene diisocyanate is added, and the mixture is reacted at 85 to 90 ° C. under nitrogen flow until the isocyanate content is 0% (3 hours), light yellow viscous A liquid reaction product (Compound 5) was obtained.

<Comparative Production Example 6>
391 parts of ethylene oxide adduct of cholesterol (average number of added moles: 80), polyethylene glycol (number average molecular weight 31,000) in a 2000 ml four-necked flask equipped with a thermometer, a nitrogen introducing tube and a stirrer for high viscosity 775 parts) and dehydrated at 80 to 90 ° C. for 3 hours under low pressure (5 to 10 mmHg) to make the water content of the system 0.03%. Then, it is cooled to 70 ° C., 12.6 parts of hexamethylene diisocyanate is added, and the mixture is reacted under nitrogen flow at 85 to 90 ° C. until the isocyanate content becomes 0% (3 hours), light yellow viscous A liquid reaction product (comparative compound 6) was obtained.

<< Preparation of paste for negative electrode formation >>
The paste for negative electrode formation was prepared as follows.

Example 1
100 parts of natural graphite powder (average particle diameter: 12.2 μm, tap density: 1.13 g / cm ³ ) as a negative electrode active material, 0.7 part of CMC as a thickener and water are sequentially introduced into a planetary mixer After kneading in a paste form, 1 part of SBR as a binder was added, and 0.3 parts of the dispersing agent 1 obtained in the above-mentioned Production Example 1 was further added to prepare a paste for forming a negative electrode. The final solid content of the negative electrode-forming paste was adjusted to 60%.

Examples 2 to 6
In Examples 2 to 6, a paste for forming a negative electrode is prepared in the same manner as in Example 1 except that the dispersants 2 to 6 obtained in the above Production Examples 2 to 6 are used instead of the dispersant 1 respectively. did.

Example 7
Example 7 is the same as Example 1 except that the dispersant 7 obtained in the above Production Example 7 was used instead of the dispersant 1 and the amount of the dispersant 7 used was changed to 0.1 parts. The paste for negative electrode formation was prepared in the procedure of 5.

Example 8
Example 8 is the same as Example 1 except that the dispersant 8 obtained in the above Production Example 8 is used instead of the dispersant 1 and the amount of the dispersant 8 used is changed to 0.5 parts. The paste for negative electrode formation was prepared in the procedure of 5.

Example 9
Example 9 is the same as Example 1 except that the dispersant 9 obtained in the above Production Example 9 was used instead of the dispersant 1 and the amount of the dispersant 9 used was changed to 0.7 parts. The paste for negative electrode formation was prepared in the procedure of 5.

Comparative Example 1
In Comparative Example 1, a paste for forming a negative electrode was prepared in the same manner as in Example 1 except that Dispersant 1 was not used.

Comparative Examples 2 to 7
In Comparative Examples 2 to 7, in the same manner as in Example 1, except that the comparative compounds 1 to 6 obtained in Comparative Production Examples 1 to 6 were used instead of Dispersant 1, a paste for forming a negative electrode. Was prepared.

Comparative Example 8
In Comparative Example 8, a non-ion comprising ethylene oxide adduct of lauryl alcohol (average added mole number: 2.2, trade name: BLAUNON EL-1502.2: manufactured by Aoki Yushi Kogyo Co., Ltd.) in place of dispersant 1 A negative electrode-forming paste was prepared in the same manner as in Example 1 except that a surfactant was used.

Comparative Example 9
In Comparative Example 9, in place of Dispersant 1, a nonionic surfactant comprising ethylene oxide adduct of lauryl alcohol (average added mole number: 7, trade name: BLAUNON EL-1507: manufactured by Aoki Yushi Kogyo Co., Ltd.) A negative electrode-forming paste was prepared in the same manner as in Example 1 except that it was used.

Comparative Example 10
In Comparative Example 10, in place of Dispersant 1, a nonionic surfactant comprising ethylene oxide adduct of lauryl alcohol (average number of added moles: 21, trade name: BLAUNON EL-1521: manufactured by Aoki Yushi Kogyo Co., Ltd.) A negative electrode-forming paste was prepared in the same manner as in Example 1 except that it was used.

Comparative Example 11
In Comparative Example 11, the same procedure as in Example 1 except that an anionic surfactant made of sodium alkylbenzene sulfonate (trade name: Neoperex G-65: manufactured by Kao Corporation) was used in place of Dispersant 1 The paste for negative electrode formation was prepared by this.

Comparative Example 12
In Comparative Example 12, Example 1 was used except that, in place of Dispersant 1, an anionic surfactant consisting of a sodium salt of β-naphthalenesulfonic acid formalin condensate (trade name: Demol RN: manufactured by Kao Corporation) was used. The paste for negative electrode formation was prepared in the same procedure as the above.

Comparative Example 13
The procedure of Comparative Example 13 is the same as that of Example 1 except that an anionic surfactant made of polyacrylic acid sodium salt (trade name: Sokalan PA 25 CL: manufactured by BASF) is used instead of the dispersant 1. The paste for negative electrode formation was prepared.

The viscosity of the paste for negative electrode formation of each example is set to 25 ° C. by using a commercially available rheometer (manufactured by Toki Sangyo Co., Ltd .: RE 115 H), and the temperature is adjusted for 1 minute, and then the shear rate is 1000 s. ^It measured by ^-1 . The results are shown in the corresponding column of Table 1. Moreover, about the paste for negative electrode formation of Example 8, paste viscosity was measured, changing in the shear rate of 1-5000 s < ^-1 >. The results are shown in FIG.

Furthermore, the cell for evaluation (design capacity 14.2 mAh) was constructed | assembled using the paste for negative electrode formation of Examples 1-9, and IV resistance of the battery was evaluated. In Comparative Examples 1 to 13, the viscosity α of the paste at a shear rate of 1000 s ⁻¹ was high, and the coatability was deteriorated, so streaks were generated on the coated surface of the negative electrode active material layer, and an appropriate negative electrode sheet was obtained. It could not be made. Therefore, the IV resistance of the battery is not measured.

«Fabrication of negative electrode sheet»
The negative electrode sheet was produced as follows. The paste for forming a negative electrode of Examples 1 to 9 was applied onto a copper foil (negative electrode current collector) and dried to form a negative electrode active material layer. Then, the negative electrode active material layer was rolled to prepare a negative electrode sheet. Also in any negative electrode sheet, the coated surface was free from streaks and thickness unevenness, and a negative electrode sheet with a smooth surface was obtained.

«Production of positive electrode sheet»
The positive electrode sheet was produced as follows. The mass ratio of these materials is 93: 4: 3 such as LiNi _1/3 Co _1/3 Mn _1/3 O ₂ powder as a positive electrode active material, AB as a conductive material, and PVdF as a binder The mixture was kneaded with NMP to prepare a paste for forming a positive electrode. This paste was applied onto an aluminum foil (positive electrode current collector) and dried to form a positive electrode active material layer. Then, the positive electrode active material layer was rolled to prepare a positive electrode sheet.

«Construction of lithium ion secondary battery»
The negative electrode sheet and the two positive electrode sheets are alternately laminated so that the positive electrode active material layer and the negative electrode active material layer face each other, and a separator (PP (polypropylene) / PE (polyethylene) / PP A porous sheet laminated with polypropylene) was used to insert an electrode body. This electrode body was inserted into a laminate bag together with a non-aqueous electrolyte to construct a lithium ion secondary battery for testing (laminate cell). As a non-aqueous electrolytic solution, LiPF ₆ as a supporting salt is used in a mixed solvent containing ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) in a volume ratio of 3: 3: 4. The one contained at a concentration of about 1 mol / liter was used.

  After adjusting each cell for evaluation to a state of charge of approximately 30% of the initial capacity (SOC 30%), discharge for 2 seconds at a current value of 3C under an environment atmosphere of -30 ° C, and 2 seconds from the start of discharge The subsequent voltage value was measured to calculate the IV resistance. The results are shown in the corresponding column of Table 1. In addition, each column of "a, d", "b", "c", "X", "Z" of Table 1 is respectively a, d, b, c, X, Z of said Formula (A). It corresponds.

As shown in Table 1, in the paste for forming a negative electrode according to Comparative Examples 2 to 13, the viscosity α at a shear rate of 1000 s ⁻¹ is warped as compared with the paste of Comparative Example 1 in which no dispersant is added. It has been on the rise. On the other hand, in the paste for forming a negative electrode according to Examples 1 to 9, X and Z in the above-mentioned formula (A) are a group selected from cholesteryl group, lanosteryl group, agnosteryl group and lanolin group, and OR, OR ' And OR ′ ′ is an oxyalkylene group having 2 to 4 carbon atoms, a and d are integers of 1 to 15, b is an integer of 30 to 300, and c is an integer of 1 or more. In Examples 1 to 9, the viscosity α at a shear rate of 1000 s ⁻¹ was lower than that in Comparative Example 1. In addition, in Examples 1 to 9, By using the paste, a negative electrode sheet having a smooth surface without streaks and thickness unevenness on the coated surface was obtained, and from this result, the viscosity at a high shear rate was obtained by using the dispersant according to Examples 1 to 9. Reduction effect As a result, it was confirmed that a smooth electrode could be produced, and the paste for forming a negative electrode according to Example 8 had a shear rate of 1 s ⁻¹ as shown in FIG. The viscosity β at the time was 1000 mPa · s or more, and it was confirmed that good results were obtained also with respect to the temporal stability of the paste.

In the case of the paste for forming a negative electrode tested here, the viscosity α at a shear rate of 1000 s ⁻¹ can realize a low viscosity of 1000 mPa · s or less by setting the content of the dispersant to 0.1 part or more. The From the viewpoint of improving the coatability better, the content of the dispersant is preferably approximately 0.1 part or more. However, even when the content of the dispersing agent is less than 0.1 part, the coating property can be improved as compared with the embodiment of Comparative Example 1 which does not contain the dispersing agent. Moreover, the battery constructed using the paste for forming a negative electrode according to Example 9 in which the content of the dispersing agent is 0.7 parts is lower than the batteries constructed using the pastes of Examples 1 to 8: The IV resistance tended to increase. From the viewpoint of reducing the resistance, the content of the dispersant is preferably 0.5 parts or less.

  The electrode forming paste and the non-aqueous electrolyte secondary battery according to one embodiment of the present invention have been described above, but the paste and the non-aqueous electrolyte secondary battery according to the present invention are limited to any of the above-described embodiments. And, various modifications are possible. For example, the type of the battery is not limited to the above-described lithium ion secondary battery, but may be a battery of various contents different in electrode assembly material and electrolyte. In addition, the size and other configurations of the battery can also be appropriately changed depending on the application (typically for on-vehicle use).

  Moreover, although the case where a negative electrode was formed using the paste for negative electrode formation containing the dispersing agent represented by said Formula (A) was illustrated in embodiment mentioned above, the kind of electrode is not limited to this. For example, the positive electrode may be formed using a paste for forming a positive electrode containing the dispersant represented by the formula (A).

  As described above, the present invention can contribute to the performance improvement of non-aqueous electrolyte secondary batteries (for example, lithium ion secondary batteries). The present invention is suitable for a non-aqueous electrolyte secondary battery for a vehicle drive power source such as a hybrid vehicle or a drive battery of an electric vehicle. That is, the non-aqueous electrolyte secondary battery can be suitably used, for example, as a vehicle drive power source for driving a motor (electric motor) of a vehicle such as a car. The vehicle drive power source may be a battery pack in which a plurality of non-aqueous electrolyte secondary batteries are combined.

Reference Signs List 20 battery case 40 wound electrode body 50 positive electrode sheet 52 positive electrode current collector 53 positive electrode active material layer 60 negative electrode sheet 62 negative electrode current collector 63 negative electrode active material layer 72, 74 separator 80 electrolyte solution 100 lithium ion secondary battery

Claims (7)

A paste for forming an electrode of a non-aqueous electrolyte secondary battery,
Containing active material, binder, thickener, dispersant and solvent,
The dispersant has the following general formula (A):
(In the formula (A), X and Z each independently represent a group selected from the group consisting of cholesteryl group, lanosteryl group, agnosteryl group and lanolin group. Y is a divalent derived from a diisocyanate compound OR, OR ′ and OR ′ ′ each independently represent an oxyalkylene group having 2 to 4 carbon atoms, a and d each represents an integer of 1 to 15, and b is 30 to 300. And c is an integer greater than or equal to 1.);
In Ri urethane compound der represented,
The paste for electrode formation whose content of the said dispersing agent is 0.1 mass part-0.5 mass part with respect to 100 mass parts of said active materials . The electrode forming paste according to claim 1, wherein a content of the thickener is at least 0.7 parts by mass with respect to 100 parts by mass of the active material. Shear rate: viscosity of the paste at the time of 1000 s ^-1 is less than 998mPa · s, claim 1 or 2, wherein the electrode forming paste. The electrode formation paste according to any one of claims 1 to 3 , wherein c in the formula (A) is an integer of 1 or more and 4 or less. A non-aqueous electrolyte secondary battery comprising an electrode having an active material layer formed on a current collector,
The active material layer includes an active material, a binder, a thickener, and a dispersant.
The dispersant has the following general formula (A):
(In the formula (A), X and Z each independently represent a group selected from the group consisting of cholesteryl group, lanosteryl group, agnosteryl group and lanolin group. Y is a divalent derived from a diisocyanate compound OR, OR ′ and OR ′ ′ each independently represent an oxyalkylene group having 2 to 4 carbon atoms, a and d each represents an integer of 1 to 15, and b is 30 to 300. And c is an integer greater than or equal to 1.);
Is a urethane compound represented by
Content of the said dispersing agent contained in the said active material layer is 0.1 mass part-0.5 mass part with respect to 100 mass parts of said active materials, non-aqueous electrolyte secondary battery. The nonaqueous electrolyte secondary battery according to claim 5 , wherein a content of the thickener contained in the active material layer is at least 0.7 parts by mass with respect to 100 parts by mass of the active material. C in the formula (A) is 1 to 4 integer, a non-aqueous electrolyte secondary battery according to claim 5 or 6.