JP2012156061A - Secondary battery and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary battery which can realized improved adhesive strength between a current collector and an anode mixture layer by dispersing a binding member over the entire mixture layer.SOLUTION: In a secondary battery provided by the present invention, an anode 84 comprises an anode current collector 82 and an anode mixture layer 90 which is a mixture layer formed on the current collector and including at least anode active materials 85 and binding members 86. The binding members included in the anode mixture layer have a particle size distribution having two peaks, a first peak of relatively small particle size and a second peak of relatively large particle size. An average particle size of the binding member in a lower layer part 94 of the anode mixture layer when it is halved in the thickness direction, which is close to the anode current collector, is larger than an average particle size of the binding member in an upper layer part 92 of the anode mixture layer when it is halved in the thickness direction, which is apart from the anode current collector toward an opposite electrode side.

Description

  The present invention relates to a secondary battery and a manufacturing method thereof. In particular, the present invention relates to a negative electrode having a configuration in which a negative electrode material containing a negative electrode active material is held by a negative electrode current collector, and a method of manufacturing the negative electrode.

  Lithium-ion secondary batteries, nickel-metal hydride batteries, and other secondary batteries are important as, for example, power sources mounted on vehicles that use electricity as a drive source, or power sources used in personal computers, portable terminals, and other electrical products. It is growing. In particular, a lithium ion secondary battery that is lightweight and has a high energy density is expected to be preferably used as a high-output power source for mounting on a vehicle.

  In a lithium ion secondary battery having a typical configuration, a negative electrode material mainly composed of a substance (electrode active material) capable of reversibly occluding and releasing lithium ions on a conductive member (electrode current collector) is layered. An electrode having a formed configuration (hereinafter, this layered product is referred to as a “negative electrode mixture layer”) is provided. For example, the electrode active material (that is, the negative electrode active material) used for the negative electrode includes a carbon material such as natural graphite. Such a negative electrode is typically a paste-like composition obtained by dispersing a negative electrode active material and a binder (binder) or the like in an appropriate solvent (for example, water) and kneading (a slurry-like composition for a paste-like composition). And an ink-like composition are prepared, and this is applied to a negative electrode current collector (for example, a copper material) and dried. Patent documents 1-5 are mentioned as conventional technology about this kind of negative electrode provided with a negative electrode compound material layer.

Japanese Patent Application Laid-Open No. 11-337772 JP 2007-123141 A JP 09-185960 A JP 2008-31164 A JP 2010-182626 A

By the way, when the paste-like composition applied on the negative electrode current collector is dried to form the negative electrode mixture layer, the solvent in the composition evaporates from the surface of the composition. In some cases, the binder contained in the composition moves and is unevenly distributed (migrated) on the surface of the composition. As a result, there is a problem that sufficient adhesion cannot be obtained in the negative electrode current collector and the negative electrode mixture layer. In order to deal with such a problem, a solution containing a binder (hereinafter also referred to as “binder solution”) is applied in advance (pre-coating) to the surface of the negative electrode current collector, and then the negative electrode active material is added. There has been proposed a method of applying a paste-like composition.
However, when the binder contained in the binder solution is composed of one kind of binder having a predetermined average particle size, the binder is still unevenly distributed in the negative electrode mixture layer, and the negative electrode current collector There is a risk that sufficient adhesion between the body and the negative electrode mixture layer cannot be obtained.

  Therefore, the present invention has been created to solve the above-described conventional problems, and its purpose is to disperse the binder throughout the negative electrode composite material layer, thereby collecting the current collector and the composite material layer. It is providing the secondary battery which can implement | achieve the improvement of adhesive force. Another object is to provide a method for manufacturing a secondary battery including the negative electrode disclosed herein.

In order to achieve the above object, the present invention provides a secondary battery including a positive electrode and a negative electrode. That is, in the secondary battery disclosed herein, the negative electrode is a negative electrode current collector and a negative electrode composite material that is a composite material layer formed on the current collector and includes at least a negative electrode active material and a binder. And a layer. The binder contained in the negative electrode composite material layer has a particle size distribution having two peaks, a first peak having a relatively small particle size and a second peak having a relatively large particle size. . The above-mentioned bonding in the lower layer portion adjacent to the negative electrode current collector when the negative electrode mixture layer is bisected in the thickness direction (typically at the position where the upper layer portion and the lower layer portion have the same thickness). The average particle diameter of the binder is larger than the average particle diameter of the binder in the upper layer part farther away from the negative electrode current collector when the negative electrode composite material layer is divided into two in the thickness direction.
In the present specification, the “secondary battery” refers to a general power storage device that can be repeatedly charged and discharged, and is a term including a so-called storage battery such as a lithium ion secondary battery and a power storage element such as an electric double layer capacitor.
In the present specification, “average particle size” and “peak value (peak particle size)” in a predetermined particle size distribution refer to values measured optically. Typically, it refers to a measured value based on a laser diffraction / scattering method (a variety of particle size distribution measuring devices are commercially available).

The secondary battery provided by the present invention has a particle size distribution in which the binder contained in the negative electrode composite material layer has two different particle size peaks, and is a lower layer of the negative electrode composite material layer. The average particle size of the binder contained in the portion is larger than the average particle size of the binder contained in the upper layer portion of the negative electrode mixture layer.
In this way, the binder having a relatively large particle size is preferentially disposed in the lower layer portion (the negative electrode current collector side) of the negative electrode mixture layer, and the binder having a relatively small particle size is the negative electrode mixture layer. Since it is preferentially placed in the upper layer part (surface layer side of the negative electrode composite material layer), excessive migration (specifically, the binder is unevenly distributed on the upper layer part (particularly the surface part) of the negative electrode composite material layer) As a result, it is possible to achieve a good dispersive arrangement of the binder in the negative electrode mixture layer (in particular, to prevent the binder from being insufficient in a region close to the current collector). Adequate adhesion is obtained between the body and the negative electrode mixture layer.

  In a preferred aspect of the secondary battery disclosed herein, the particle size value of the first peak is in the range of 80 nm to 160 nm, the particle size value of the first peak is A, and The value of B / A, which is the ratio when the particle size value of the peak of 2 is B, is 2 to 3.2. According to this configuration, since the dispersion state of the binder becomes better in the negative electrode mixture layer, higher adhesion can be obtained between the negative electrode current collector and the negative electrode mixture layer.

  In another preferred embodiment of the secondary battery disclosed herein, when the negative electrode mixture layer is 100% by mass, the binder contained in the negative electrode mixture layer is 0.2% by mass to 0.8% by mass. The negative electrode mixture layer containing the binder in such a ratio has sufficient adhesion between the negative electrode current collector and the negative electrode mixture layer, and the internal resistance of the battery (specifically, by reducing the amount of the binder) In particular, a reduction in reaction resistance) can be realized. Preferably, the negative electrode active material is a carbon material capable of reversibly occluding and releasing lithium ions.

In addition, according to the present invention, as another aspect for realizing the above object, a positive electrode in which a positive electrode mixture layer including a positive electrode active material is formed on a positive electrode current collector, and a negative electrode active material is included on the negative electrode current collector. There is provided a method for producing a secondary battery comprising a negative electrode on which a negative electrode mixture layer is formed. That is, in the method of manufacturing a secondary battery disclosed herein, in the step of forming the negative electrode, the first binder having the first average particle diameter and the average particle diameter larger than the first average particle diameter are formed. The second binder having the second average particle diameter and the solvent are mixed, and the first peak corresponding to the first binder and the second binder corresponding to the second binder are mixed. Preparing a binder solution having a particle size distribution having two peaks and a peak, preparing a paste-like composition for forming a negative electrode mixture layer containing at least the negative electrode active material and a solvent, the above prepared The method includes applying a binder solution to the surface of the negative electrode current collector and applying the prepared composition for forming a negative electrode mixture layer on the applied binder solution.
In the present specification, the “binder solution” is a term that includes a solution obtained by dissolving a binder in a predetermined solvent and a dispersion obtained by dispersing the binder in a predetermined solvent.

  In the method for manufacturing a secondary battery according to the present invention, as a result of mixing the first binder and the second binder having different average particle diameters, the particles having two peaks different in particle size distribution are obtained. The adhesive solution is applied to the negative electrode current collector, and then the paste-like composition is applied onto the solution before the binder solution is dried. The applied binder solution and the paste-like composition are mixed with each other when the negative electrode mixture layer is formed (typically during drying). At this time, the binder having a relatively small particle size moves together with the solvent to the upper layer portion of the negative electrode mixture layer (that is, the surface layer side of the negative electrode mixture layer) in the drying process of the negative electrode mixture layer (paste coating product). On the other hand, the binder having a relatively large particle diameter remains in the lower layer portion (negative electrode current collector side) of the negative electrode mixture layer and is predominantly disposed in the lower layer portion. For this reason, according to the method of this structure, it can prevent that an excessive migration generate | occur | produces in the formed negative electrode compound material layer. Specifically, it is possible to prevent the binder from being insufficient in the lower layer portion of the negative electrode mixture layer and to realize a good dispersion state of the binder throughout the negative electrode mixture layer. And a negative electrode mixture layer, a negative electrode having sufficient adhesion can be formed. In addition, since the binder can be dispersed well, a sufficient adhesion can be obtained even if the binder content is reduced as compared with the conventional one.

In a preferred aspect of the method for manufacturing a secondary battery disclosed herein, a binder having the first average particle diameter in the range of 80 nm to 160 nm is used as the first binder. As said 2nd binder, the said 1st average particle diameter is set to A, and the average when the value of B / A which is a ratio when said 2nd average particle diameter is set to B is 2-3. Use a binder with a particle size.
By using a binder having such an average particle size, a negative electrode having higher adhesion can be formed between the negative electrode current collector and the negative electrode mixture layer.

  In another preferred embodiment of the secondary battery manufacturing method disclosed herein, the amount of the binder solution applied per unit area is 100% by mass of the formed negative electrode mixture layer. It adjusts so that the binder contained in this negative electrode compound material layer may be 0.2 mass%-0.8 mass%. By using a binder of such a ratio, a negative electrode that has sufficient adhesion between the negative electrode current collector and the negative electrode mixture layer and can realize a reduction in reaction resistance due to the reduction of the binder. Can be formed. Preferably, the negative electrode is a negative electrode for a lithium ion secondary battery, and a carbon material capable of reversibly occluding and releasing lithium ions is used as the negative electrode active material.

  The secondary battery disclosed here has a negative electrode that has sufficient adhesion between the negative electrode current collector and the negative electrode mixture layer and is excellent in reliability. Since such a secondary battery is excellent in reliability as described above, it can be suitably used as a power source for a motor (electric motor) mounted on a vehicle such as an automobile. Accordingly, the present invention provides a vehicle including such a secondary battery as a power source.

It is a perspective view which shows typically the external shape of the lithium ion secondary battery which concerns on one Embodiment of this invention. It is sectional drawing which follows the II-II line | wire in FIG. It is sectional drawing which shows typically the structure of the negative electrode which concerns on one Embodiment of this invention. 3 is a flowchart for explaining a method of manufacturing a secondary battery according to an embodiment of the present invention. It is a graph which shows adhesive strength. It is a graph which shows the relationship between adhesive strength and a particle size ratio. It is a graph which shows initial stage resistance. It is a scanning electron microscope (SEM) photograph which shows the state of the negative electrode which concerns on Example 5 after EPMA analysis. It is a scanning electron microscope (SEM) photograph which shows the state of the negative electrode which concerns on Example 9 after EPMA analysis. It is a side view which shows typically the vehicle (automobile) provided with the secondary battery which concerns on this invention.

  Hereinafter, preferred embodiments of the present invention will be described. It should be noted that matters other than matters specifically mentioned in the present specification and necessary for carrying out the present invention can be grasped as design matters of those skilled in the art based on the prior art in this field. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field.

  As one preferred embodiment of the method for producing a secondary battery disclosed herein, a method for producing a lithium ion secondary battery in which an electrode mixture layer is formed on the surface of an electrode current collector is taken as an example. Although described in detail, the present invention is not intended to limit the application target of the present invention to such a battery and a manufacturing method thereof.

  As shown in FIG. 4, the manufacturing method of the lithium ion secondary battery disclosed here includes a binder solution preparing step (step S10), a composition preparing step (step S20), and a binder solution applying step. (Step S30) and a composition application | coating process (step S40) are included.

  First, the binder solution preparation step (S10) will be described. In the binder solution preparation step, the first binder having the first average particle size and the second having a second average particle size that is larger than the first average particle size. The binder and the solvent are mixed to have a particle size distribution having two peaks, a first peak corresponding to the first binder and a second peak corresponding to the second binder. Preparing a dressing solution is included.

As said binder (binder), the thing similar to the binder used for the negative electrode of a general lithium ion secondary battery can be employ | adopted suitably. For example, when an aqueous composition is used to form the negative electrode mixture layer, a polymer material that dissolves or disperses in water can be preferably used. Polymer materials that disperse in water (water dispersible) include rubbers such as styrene butadiene rubber (SBR) and fluorine rubber; fluorine resins such as polyethylene oxide (PEO) and polytetrafluoroethylene (PTFE); vinyl acetate Examples thereof include copolymers.
Here, the “aqueous composition” is a concept indicating a composition using water or a mixed solvent mainly composed of water (aqueous solvent) as the predetermined solvent (dispersion medium). As the solvent other than water constituting the mixed solvent, one or more organic solvents (lower alcohol, lower ketone, etc.) that can be uniformly mixed with water can be appropriately selected and used.

The average particle size (eg, the median diameter (D ₅₀ ) in the particle size distribution measured based on the laser diffraction / scattering method) of the constituent particles (typically primary particles) of the binder is typically about It is in the range of 80 nm to 520 nm (for example, approximately 80 nm to 360 nm).
The binder solution contains binders (particles) having different average particle sizes. Typically, the binder solution has a first binder having a first average particle size and a second average particle size that is larger than the first average particle size. And a second binding material. Here, the total content of the first binder and the second binder contained in the binder solution is 0.2% by mass when the negative electrode mixture layer described later is 100% by mass. It may be in the range of ˜5% by mass (eg, 0.2% by mass to 0.8% by mass, preferably 0.4% by mass to 0.8% by mass). Moreover, it is preferable that the mass ratio of the 1st binder and the 2nd binder contained in a binder solution exists in the range of 3: 2-1: 1. Note that the first binder and the second binder may be the same type of material. For example, the first binder and the second binder may both be SBR. Alternatively, the first binder and the second binder may be different materials. Typically, a combination of similar materials having different average particle diameters, particularly a combination of SBRs can be preferably employed.

  The average particle diameter (first average particle diameter) C of the first binder is approximately in the range of 80 nm to 160 nm (for example, 80 nm to 110 nm), and the average particle diameter (first of the second binder) (Average particle size 2) D is approximately in the range of 160 nm to 520 nm (for example, 160 nm to 360 nm), and the ratio of the second average particle size D to the first average particle size C, that is, the value of D / C. Is in the range of about 2 to 3.2 (for example, preferably in the range of about 2.3 to 3.2, more preferably in the range of about 2.4 to 2.9). Preferably there is. When D / C is too smaller than 2, the effect of mixing two kinds of binders having different particle sizes becomes small, and the uneven distribution of the binder in the negative electrode mixture layer can be effectively prevented. There is a possibility that it cannot be done. Further, when D / C is too larger than 3.2, the concentration of the binder is high in the upper part (that is, the surface layer side of the negative electrode composite layer) and the lower part (negative electrode current collector side) in the negative electrode mixture layer. There is a risk that the adhesion between the negative electrode current collector and the negative electrode mixture layer may be reduced because a layer is formed (that is, the binder is segregated), and the intermediate layer is less likely to peel off. is there.

  Since the binder solution contains the first binder and the second binder having different average particle sizes, the particle size distribution (particle size distribution) of the entire binder is The bimodal particle size distribution has two peaks, a first peak corresponding to one binder and a second peak corresponding to the second binder.

  Next, the composition preparation step (S20) will be described. The composition preparation step includes preparing a paste-like composition for forming a negative electrode mixture layer (hereinafter sometimes simply referred to as “composition”) including at least a negative electrode active material and a solvent. .

The negative electrode active material used for the negative electrode of the lithium ion secondary battery disclosed here is not particularly limited in its composition and shape as long as it is a negative electrode active material having a property capable of realizing the object of the present invention. For example, carbon materials such as graphite (graphite), oxide materials such as lithium / titanium oxide Li ₄ Ti ₅ O ₁₂ ), metals such as tin, aluminum (Al), zinc (Zn), silicon (Si), or these Examples thereof include metal materials made of metal alloys mainly composed of these metal elements. A typical example is a powdery carbon material made of graphite or the like. For example, natural graphite and artificial graphite can be preferably used.

Moreover, as a thickener used for the negative electrode of the lithium ion secondary battery disclosed here, a polymer material that is dissolved or dispersed in water or a solvent (organic solvent) may be employed. Examples of water-soluble (water-soluble) polymer materials include cellulose polymers such as carboxymethyl cellulose (CMC), methyl cellulose (MC), cellulose acetate phthalate (CAP), and hydroxypropylmethyl cellulose (HPMC); polyvinyl alcohol ( PVA); and the like. A cellulose derivative such as CMC is preferably used from the viewpoints of workability and stability during kneading (preparation) of the composition for forming a negative electrode mixture layer.
What is necessary is just to select suitably the addition amount (content) of a thickener according to the kind and quantity of a negative electrode active material, for example, when a negative mix layer is 100 mass%, about 0.5 mass%-10 mass. It can be made into the mass% (for example, about 1 mass%-5 mass%).

  The operation of mixing (kneading) the negative electrode active material and the thickening material in a solvent can be performed using, for example, a suitable kneader (planetary mixer, homodisper, clear mix, fill mix, etc.). In preparing the paste-like composition, first, the negative electrode active material and the thickener are kneaded with a small amount of solvent (for example, water), and then the obtained kneaded product is diluted with an appropriate amount of solvent. Also good. Although not particularly limited, in order to improve the drying efficiency, the solid content concentration of the paste-like composition for forming a negative electrode mixture layer (non-volatile content, that is, the proportion of the negative electrode mixture layer forming component. Hereinafter referred to as “NV”). .) Is, for example, preferably about 45% by mass or more (typically 50 to 80% by mass).

Next, the binder solution application step (S30) and the composition application step (S40) will be described. The binder solution application step includes applying the prepared binder solution to the surface of the negative electrode current collector. In addition, the composition application step includes applying the prepared composition for forming a negative electrode mixture layer before the solution is dried on the binder solution applied to the surface of the negative electrode current collector. ing.
As the negative electrode current collector, a conductive member made of a metal having good conductivity is preferably used, like the current collector used in the negative electrode of a conventional lithium ion secondary battery. For example, a copper material, a nickel material, or an alloy material mainly composed of them can be used. The shape of the negative electrode current collector can vary depending on the shape of the lithium ion secondary battery, and is not particularly limited, and may be various forms such as a rod shape, a plate shape, a sheet shape, a foil shape, and a mesh shape.
As a method of applying the binder solution and the composition, a technique similar to a conventionally known method can be appropriately employed. For example, by using an appropriate coating apparatus such as a gravure coater, comma coater, slit coater, die coater, etc., the binder solution is applied to the surface of the negative electrode current collector, and the composition is applied onto the binder solution. It can apply | coat suitably. The coating amount of the binder solution is approximately per one surface of the current collector on a solids basis ^{0.01mg / cm 2 ~0.5mg / cm 2} (0.02mg / cm 2 ~0.3mg / cm 2), the coating amount of the composition is approximately per one surface of the current collector on a solids basis ^{2mg / cm 2 ~20mg / cm 2} (3mg / cm 2 ~15mg / cm 2).

  Next, the binder solution and the negative electrode mixture layer forming composition are simultaneously dried by an appropriate drying means (for example, a drying furnace) (typically, the drying temperature is 70 ° C. to 200 ° C., preferably 120 ° C. The drying time is 10 seconds to 120 seconds, preferably 30 seconds to 60 seconds.), And the solvent in the binder solution and the composition is removed to form the negative electrode mixture layer. Then, it compresses (presses) as needed. Thereby, a negative electrode provided with a negative electrode current collector and a negative electrode mixture layer formed on the negative electrode current collector can be produced. As the compression method, a conventionally known compression method such as a roll press method or a flat plate press method can be employed.

Next, the structure of the negative electrode produced by the above production method will be described. FIG. 3 is a cross-sectional view schematically showing the structure of the negative electrode 84 according to one embodiment of the present invention.
As shown in FIG. 3, the negative electrode 84 according to this embodiment includes a negative electrode current collector 82 and a negative electrode mixture layer 90 formed on the current collector 82. The negative electrode mixture layer 90 includes graphite particles 85 as a negative electrode active material and a binder 86. The binder 86 is composed of a first binder 87 having the first average particle diameter and a second binder 88 having the second average particle diameter.
Since the binder 86 included in the negative electrode mixture layer 90 according to the present embodiment includes the first binder 87 and the second binder 88 having different average particle diameters, they are relatively Have a particle size distribution having two peaks, a first peak having a small particle size and a second peak having a relatively large particle size. Further, the second binder 88 having a relatively large average particle diameter is disposed predominantly on the negative electrode current collector 82 side, and the first binder 87 having a relatively small average particle diameter is predominantly disposed on the counter electrode side. Therefore, a favorable dispersion arrangement of the binders 87 and 88 in the negative electrode mixture layer 90 is realized, and the negative electrode mixture layer 90 is disposed in the vicinity of the negative electrode current collector 82 and the lower layer portion 94. Divided in the thickness direction into the upper layer portion 92 that is further to the counter electrode (typically positive electrode) side than the negative electrode current collector 82 (typically bisected in the thickness direction as shown by the two-dot chain line in FIG. 3). ), The average particle size of the binder 86 in the lower layer portion 94 is larger than the average particle size of the binder 86 in the upper layer portion 92.
At this time, the particle diameter value (mode diameter) A in the first peak is in the range of 80 nm to 160 nm (for example, 80 nm to 110 nm), and the particle diameter value (mode diameter) B in the second peak is about 160 nm. In the range of ˜520 nm (for example, 160 nm to 360 nm), and the ratio of the second particle size value B to the first particle size value A, that is, the value of B / A is in the range of about 2 to 3.2. (It is more preferable to be in the range of about 2.3 to 3.2, and more preferably in the range of about 2.4 to 2.9.). By being in such a range, since the dispersion state of the binder becomes better in the negative electrode mixture layer, a higher adhesion can be obtained between the negative electrode current collector 82 and the negative electrode mixture layer 90.

Next, the process of forming the positive electrode containing a positive electrode active material is demonstrated. First, a paste-like composition for forming a positive electrode mixture layer is prepared by dispersing a positive electrode active material, a conductive material, a binder (binder) and the like in a predetermined solvent.
Examples of the positive electrode active material include a lithium-containing compound (for example, a lithium transition composite oxide) that is a material capable of inserting and extracting lithium ions and includes a lithium element and one or more transition metal elements. For example, lithium cobalt composite oxide (LiCoO ₂ ), lithium nickel composite oxide (LiNiO ₂ ), lithium manganese composite oxide (LiMn ₂ O ₄ ), or nickel-cobalt-based LiNi _x Co _1-x O ₂ ( 0 <x <1), cobalt / manganese-based LiCo _x Mn _1-x O ₂ (0 <x <1), nickel / manganese-based LiNi _x Mn _1-x O ₂ (0 <x <1) and LiNi as represented by _{x Mn 2-x O 4 (} 0 <x <2), a so-called binary lithium-containing composite oxide containing two kinds of transition metal elements, or nickel cobalt containing three transition metal elements A ternary lithium-containing composite oxide such as manganese may be used.
In addition, a polyanionic compound (for example, LiFePO ₄₎ whose general formula is represented by LiMPO _4, LiMVO _4, or Li ₂ MSiO ₄ (wherein M is at least one element of Co, Ni, Mn, and Fe), etc. ₄ , LiMnPO ₄ , LiFeVO ₄ , LiMnVO ₄ , Li ₂ FeSiO ₄ , Li ₂ MnSiO ₄ , Li ₂ CoSiO ₄ ) may be used as the positive electrode active material.

  As said binder (binder), the thing similar to the binder used for the positive electrode of a common lithium ion secondary battery can be employ | adopted suitably. When preparing a water-based composition, what is used for the said negative electrode can be employ | adopted suitably. When preparing a solvent-based composition, a polymer material that can be dissolved in an organic solvent (non-aqueous solvent) such as polyvinylidene fluoride (PVDF) or polyvinylidene chloride (PVDC) can be used. Here, the “solvent-based composition” is a concept indicating a composition in which the dispersion medium of the positive electrode active material is mainly an organic solvent. As the organic solvent, for example, N-methylpyrrolidone (NMP) can be used.

  The conductive material is not limited to a specific conductive material as long as it is conventionally used in this type of lithium ion secondary battery. For example, carbon materials such as carbon powder and carbon fiber can be used. As the carbon powder, various carbon blacks (for example, acetylene black, furnace black, ketjen black, etc.), carbon powders such as graphite powder can be used. Among these, you may use together 1 type, or 2 or more types.

Then, the prepared composition for forming a positive electrode mixture layer is applied to the surface of the positive electrode current collector, dried to form a positive electrode mixture layer, and then compressed (pressed) as necessary. Thereby, a positive electrode provided with a positive electrode current collector and a positive electrode mixture layer containing a positive electrode active material can be produced.
As the positive electrode current collector, a conductive member made of a metal having good conductivity is preferably used, like the current collector used in the positive electrode of a conventional lithium ion secondary battery. For example, an aluminum material or an alloy material mainly composed of an aluminum material can be used. The shape of the positive electrode current collector can be the same as the shape of the negative electrode current collector.

Next, a process of constructing a lithium ion secondary battery by accommodating the negative electrode (negative electrode sheet) 84 manufactured by applying the above-described method and the prepared positive electrode together with an electrolyte in a battery case will be described. The negative electrode and the positive electrode are laminated together with a total of two separator sheets and wound to produce a wound electrode body. Next, the wound electrode body is accommodated in a battery case (for example, a flat rectangular parallelepiped case), and an electrolytic solution is injected into the battery case. And a lithium ion secondary battery can be constructed | assembled by sealing the opening part of a battery case with a cover body. Here, as the electrolytic solution, the same non-aqueous electrolytic solution conventionally used for lithium ion secondary batteries can be used without any particular limitation. Such a nonaqueous electrolytic solution typically has a composition in which a supporting salt is contained in a suitable nonaqueous solvent. As said non-aqueous solvent, 1 type, or 2 or more types selected from EC, PC, DMC, DEC, EMC etc. can be used, for example. Further, as the supporting salt (supporting electrolyte), for _example, it can be used lithium salts such as LiPF 6, LiBF _4. Examples of the separator sheet include those made of a porous polyolefin resin or the like.

Hereinafter, although one form of the lithium ion secondary battery constructed as described above will be described with reference to the drawings, the present invention is not intended to be limited to such an embodiment. That is, the binder 86 included in the negative electrode mixture layer 90 has a particle size distribution having two peaks, a first peak having a relatively small particle size and a second peak having a relatively large particle size. The average particle size of the binder 86 in the lower layer portion 94 of the negative electrode mixture layer 90 is constructed as long as the average particle size of the binder 86 in the upper layer portion 92 of the negative electrode mixture layer 90 is larger. There is no particular limitation on the shape (outer shape and size) of the lithium ion secondary battery. In the following embodiment, a lithium ion secondary battery having a configuration in which a wound electrode body and an electrolytic solution are housed in a rectangular battery case will be described as an example.
In addition, in the following drawings, the same code | symbol is attached | subjected to the member and site | part which show | plays the same effect | action, and the overlapping description may be abbreviate | omitted. Moreover, the dimensional relationship (length, width, thickness, etc.) in each drawing does not necessarily reflect the actual dimensional relationship.

FIG. 1 is a perspective view schematically showing a lithium ion secondary battery 10 according to the present embodiment. FIG. 2 is a longitudinal sectional view taken along line II-II in FIG.
As shown in FIG. 1, the lithium ion secondary battery 10 according to this embodiment includes a battery case 15 made of metal (a resin or a laminate film is also suitable). The case (outer container) 15 includes a flat cuboid case main body 30 having an open upper end, and a lid body 25 that closes the opening 20. The lid body 25 seals the opening 20 of the case main body 30 by welding or the like. On the upper surface of the case 15 (that is, the lid body 25), a positive electrode terminal 60 electrically connected to the positive electrode sheet (positive electrode) 64 of the wound electrode body 50 and a negative electrode terminal electrically connected to the negative electrode sheet 84 of the electrode body. 80 is provided. In addition, as in the case of the conventional lithium ion secondary battery, the lid 25 has a safety valve (not shown) for discharging the gas generated inside the case 15 to the outside of the case 15 when the battery is abnormal. Is provided. In the case 15, the positive electrode sheet 64 and the negative electrode sheet 84 are laminated together with a total of two separator sheets 95 and wound, and then the obtained wound body is crushed from the side direction and ablated. A flat wound electrode body 50 and the electrolyte solution are accommodated.

  At the time of the above lamination, as shown in FIG. 2, the positive electrode mixture layer non-formed portion of the positive electrode sheet 64 (that is, the portion where the positive electrode current collector 62 is exposed without forming the positive electrode mixture layer 66) and the negative electrode sheet The negative electrode composite material layer non-formed portion 84 (that is, the portion where the negative electrode current collector 82 is exposed without forming the negative electrode composite material layer 90) protrudes from both sides in the width direction of the separator sheet 95. And the negative electrode sheet 84 are overlapped with a slight shift in the width direction. As a result, in the lateral direction with respect to the winding direction of the wound electrode body 50, the electrode mixture layer non-forming portions of the positive electrode sheet 64 and the negative electrode sheet 84 are respectively wound core portions (that is, the positive electrode mixture layer forming portion of the positive electrode sheet 64. And a portion where the negative electrode mixture layer forming portion of the negative electrode sheet 84 and the two separator sheets 95 are wound tightly) protrude outward. The positive electrode terminal 60 is joined to the protruding portion on the positive electrode side, and the positive electrode sheet 64 and the positive electrode terminal 60 of the wound electrode body 50 formed in the flat shape are electrically connected. Similarly, the negative electrode terminal 80 is joined to the negative electrode side protruding portion, and the negative electrode sheet 84 and the negative electrode terminal 80 are electrically connected. The positive and negative electrode terminals 60 and 80 and the positive and negative electrode current collectors 62 and 82 can be joined by, for example, ultrasonic welding, resistance welding, or the like.

  EXAMPLES Examples relating to the present invention will be described below, but the present invention is not intended to be limited to those shown in the examples.

[Preparation of negative electrode sheet]
<Example 1>
Natural graphite having an average particle diameter of 10 μm as a negative electrode active material, CMC as a thickener, a first SBR having an average particle diameter C of 102 nm as a binder, and a second SBR having an average particle diameter D of 206 nm Weigh so that the mass ratio with SBR is 98.2: 1: 0.4: 0.4, disperse natural graphite and CMC in ion-exchanged water, and knead in a 5-L capacity biaxial planetary kneader. Thus, a paste-like composition for forming a negative electrode mixture layer according to Example 1 having an NV of 50% was prepared.
In addition, a binder solution according to Example 1 having 10% NV including the first SBR and the second SBR was prepared. At this time, the ratio of the average particle diameter (D / C) between the first SBR and the second SBR was 2.02.
And after apply | coating the binding material solution which concerns on Example 1 on both surfaces of 10-micrometer-thick copper foil with the application amount per surface 0.304mg / cm < ² > using a gravure coater, before this binding material solution dries The composition for forming a negative electrode mixture layer according to Example 1 was applied onto the binder solution at a coating amount of 15.08 mg / cm ² per side using a comma coater (two-layer coating). At this time, it apply | coated so that the total application amount of the said binder material solution and the composition for negative electrode compound-material layer formation might be 7.6 mg / cm < ² > (solid basis) per single side. Then, it was dried at 150 ° C. for 20 seconds. After drying, the coated material was pressed to prepare a negative electrode sheet according to Example 1 including a negative electrode mixture layer having a density of 1.5 g / cm ³ .

<Example 2>
The mass ratio of natural graphite, CMC, first SBR having an average particle diameter C of 80 nm, and second SBR having an average particle diameter D of 206 nm is 98.2: 1: 0.4: 0.4 A binder solution according to Example 2 of NV 10% containing the weighed first SBR and second SBR was prepared. At this time, the value of the average particle diameter ratio (D / C) was 2.58. A negative electrode sheet according to Example 2 was produced in the same manner as in Example 1 except that the binder solution according to Example 2 was used.
<Example 3>
The mass ratio of natural graphite, CMC, first SBR with an average particle size C of 80 nm, and second SBR with an average particle size D of 250 nm is 98.2: 1: 0.4: 0.4 A binder solution according to Example 3 of NV 10% containing the weighed first SBR and second SBR was prepared. At this time, the average particle size ratio (D / C) was 3.13. A negative electrode sheet according to Example 3 was produced in the same manner as in Example 1 except that the binder solution according to Example 3 was used.
<Example 4>
The mass ratio of natural graphite, CMC, first SBR with an average particle size C of 102 nm, and second SBR with an average particle size D of 152 nm is 98.2: 1: 0.4: 0.4 A binder solution according to Example 4 of NV 10% containing the weighed first SBR and second SBR was prepared. At this time, the ratio of the average particle diameter (D / C) was 1.49. A negative electrode sheet according to Example 4 was produced in the same manner as in Example 1 except that the binder solution according to Example 4 was used.
<Example 5>
The mass ratio of natural graphite, CMC, first SBR having an average particle diameter C of 80 nm, and second SBR having an average particle diameter D of 206 nm is 98.6: 1: 0.2: 0.2 A composition for forming a paste-like negative electrode mixture layer according to Example 5 in which natural graphite and CMC are dispersed in ion-exchanged water and kneaded in a 5-liter biaxial planetary kneader and NV is 50%. A product was prepared.
Moreover, the binder solution which concerns on Example 5 of NV10% containing the said 1st SBR and 2nd SBR was prepared. At this time, the ratio of the average particle diameter (D / C) of the first SBR and the second SBR was 2.58. A negative electrode sheet according to Example 5 was produced in the same manner as in Example 1 except that the composition according to Example 5 and the binder solution were used.

<Example 6>
NV10% containing the first SBR weighed so that the mass ratio of natural graphite, CMC, and first SBR having an average particle size C of 80 nm is 98.2: 1: 0.8 A binder solution according to Example 6 was prepared. A negative electrode sheet according to Example 6 was produced in the same manner as in Example 1 except that the binder solution according to Example 6 was used.
<Example 7>
NV10% containing the first SBR weighed so that the mass ratio of natural graphite, CMC, and first SBR having an average particle size C of 102 nm is 98.2: 1: 0.8 A binder solution according to Example 7 was prepared. A negative electrode sheet according to Example 7 was produced in the same manner as in Example 1 except that the binder solution according to Example 7 was used.
<Example 8>
In Example 8 of NV 10% containing the first SBR weighed so that the mass ratio of natural graphite, CMC, and the first SBR having an average particle diameter C of 80 nm was 98: 1: 1. Such a binder solution was prepared. A negative electrode sheet according to Example 8 was produced in the same manner as in Example 1 except that the binder solution according to Example 8 was used.
<Example 9>
Weighing so that the mass ratio of natural graphite, CMC, and the first SBR having an average particle size C of 80 nm is 98.2: 1: 0.8, these materials are dispersed in ion-exchanged water, A paste-like composition for forming a negative electrode mixture layer according to Example 9 having an NV of 50% was prepared. And the composition which concerns on Example 9 was apply | coated to both surfaces of 10-micrometer-thick copper foil using the gravure coater by the coating amount per one side 7.6 mg / cm < ² > (solid basis). Then, it was dried at 150 ° C. for 20 seconds. After drying, the coated material was pressed to prepare a negative electrode sheet according to Example 9 including a negative electrode mixture layer having a density of 1.5 g / cm ³ .

[Peel strength test]
A 90 ° peel test was performed on the negative electrode sheets according to Examples 1 to 9 manufactured as described above in accordance with JIS K6854-1. That is, each negative electrode sheet is fixed to a frame of a tensile tester, and either one of the negative electrode mixture layers formed on both surfaces of the negative electrode current collector is partially peeled off from the negative electrode current collector. The material layer was fixed to a tension jig (for example, a clamp). The tensile jig was pulled upward at a rate of 20 mm / min in the vertical direction, and the peel strength (tensile strength) [N / m] when the negative electrode composite layer was peeled from the negative electrode current collector was measured. The measurement results are shown in Table 1, Table 2 and FIG. FIG. 6 shows the relationship between the adhesion strength and the particle size ratio.

  As shown in Table 1, Table 2 and FIG. 5, when the content of the binder is the same, the adhesion strength of the negative electrode formed by the composition containing one type of SBR as in Example 9 is the lowest, Next, it was confirmed that the adhesion strength of the negative electrode formed by applying the composition after applying the binder solution containing one type of SBR as in Example 6 and Example 7 was low. The adhesion strength of the negative electrodes formed by applying the composition after applying the binders containing two types of SBR having different average particle diameters as in Examples 1 to 4, were Example 6, Example 7 and Example 9. It has confirmed that it had high adhesive strength compared with the negative electrode which concerns on. In particular, it was confirmed that the negative electrodes according to Examples 1 to 3 had high adhesion strength. As shown in FIG. 6, it was confirmed that the adhesion strength was high when the particle size ratio (D / C) was 2 to 3.2. It was confirmed that D / C is preferably in the range of 2.3 to 3.2, and more preferably in the range of 2.4 to 2.9. Further, it was confirmed that the negative electrodes according to Examples 1 to 3 showed high adhesion strength although the content of SBR (binder) was 2 mass% lower than that of the negative electrode according to Example 9. It was. Moreover, although the negative electrode which concerns on Example 5 compared with the negative electrode which concerns on Examples 6-9, the content of SBR contained in a negative electrode compound material layer is half (it is 60% reduction about Example 8). It was confirmed that the adhesive strength higher than that of the negative electrodes according to Examples 6 to 9 was obtained.

<EPMA analysis>
With respect to the negative electrode sheets of Example 5 and Example 9 produced as described above, each negative electrode sheet was dyed with bromine, and elemental analysis was performed using EPMA (Electron Probe Micro Analyzer). 8 and 9 are scanning electron microscope (SEM) photographs showing the state of the negative electrode sheet after EPMA analysis. As shown in FIG. 9, in the negative electrode sheet formed by single-layer coating, it was confirmed that the binder (white portion in the figure) was unevenly distributed on the counter electrode side (upper side in the figure) in the negative electrode mixture layer. It was done. On the other hand, as shown in FIG. 8, in the negative electrode sheet formed by the method according to the present invention, it was confirmed that the binder (white portion in the figure) was well dispersed in the negative electrode mixture layer.

[Construction of lithium ion secondary battery]
The mass ratio of LiNi _1/3 Mn _1/3 Co _1/3 O ₂ as the positive electrode active material, acetylene black (AB) as the conductive material, and PVDF as the binder is 90: 5: 5. Thus, these materials were dispersed in NMP to prepare a paste-like composition for forming a positive electrode mixture layer according to Example 1. The positive electrode sheet according to Example 1 in which the paste is applied onto a 15 μm-thick aluminum foil at a coating amount of 6 mg / cm ² per side and processed by a roll press to provide a positive electrode mixture layer on the aluminum foil. Produced.
Then, the prepared positive electrode sheet according to Example 1 and the negative electrode sheet according to Example 1 were disposed opposite to each other with a separator sheet (polypropylene / polyethylene composite porous film) having a thickness of 25 μm interposed therebetween, and this was used as an electrolyte solution. And the lithium ion secondary battery which concerns on Example 1 was constructed | assembled by accommodating in a laminate type case (laminate film). As the electrolytic solution, a solution obtained by dissolving 1 mol / L LiPF ₆ in a mixed solvent of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) in a volume ratio of 3: 3: 4 was used. . Further, secondary batteries according to Examples 2 to 9 were constructed in the same manner as the lithium ion secondary battery according to Example 1 using the negative electrode sheets according to Examples 2 to 9.

<Initial resistance (DCIR) measurement test>
The initial resistance (DCIR, direct current internal resistance) was calculated for the lithium ion secondary batteries according to Examples 1 to 9 manufactured as described above. That is, each battery was adjusted to a SOC (State of Charge) 60% charge state by constant current constant voltage (CC-CV) charging. Thereafter, discharging was performed at 25 ° C. with a current value of 4 C for 10 seconds, and the initial resistance [mΩ] was calculated from the voltage drop amount 10 seconds after the start of discharge. The measurement results are shown in Table 1, Table 2 and FIG.
As shown in Table 1, Table 2, and FIG. 7, it can be confirmed that there is almost no difference in the initial resistance depending on the coating method and the average particle size and type of SBR contained in the negative electrode mixture layer. It was confirmed that it depends on the content of SBR contained in the material layer. That is, as the SBR content increases, the initial resistance increases, and as the SBR content decreases, the initial resistance decreases.

  From the above measurement results, the negative electrode mixture layer containing two types of binders having different average particle sizes and having a particle size ratio of 2 to 3.2 has high adhesion strength even with fewer binders. It was confirmed that the initial resistance can be reduced.

[Preparation of negative electrode sheet]
<Example 10>
The mass ratio of natural graphite having an average particle diameter of 10 μm as the negative electrode active material, CMC, first SBR having an average particle diameter C of 102 nm, and second SBR having an average particle diameter D of 206 nm is 98: 1: 0.5: 0.5, natural graphite and CMC are dispersed in ion-exchanged water, kneaded in a 5 L capacity biaxial planetary kneader, and pasty according to Example 10 with an NV of 50% A negative electrode mixture layer forming composition was prepared.
Moreover, the binder solution which concerns on Example 10 of NV10% containing the said 1st SBR and 2nd SBR was prepared. A negative electrode sheet according to Example 10 was produced in the same manner as in Example 1 except that the composition according to Example 10 and the binder solution were used.
<Example 11>
Example 11 was repeated in the same manner as Example 10 except that the mass ratio of natural graphite, CMC, first SBR, and second SBR was 98.2: 1: 0.4: 0.4. Such a negative electrode sheet was prepared.
<Example 12>
Example 12 was repeated in the same manner as in Example 10 except that the mass ratio of natural graphite, CMC, first SBR, and second SBR was 98.4: 1: 0.3: 0.3. Such a negative electrode sheet was prepared.
<Example 13>
Example 13 was repeated in the same manner as Example 10 except that the mass ratio of natural graphite, CMC, first SBR, and second SBR was 98.6: 1: 0.2: 0.2. Such a negative electrode sheet was prepared.
<Example 14>
Example 14 was repeated in the same manner as in Example 10 except that the mass ratio of natural graphite, CMC, first SBR, and second SBR was 98.8: 1: 0.1: 0.1. Such a negative electrode sheet was prepared.

<Example 15>
The mass ratio of natural graphite, CMC, first SBR with an average particle size C of 80 nm, and second SBR with an average particle size D of 206 nm is 98: 1: 0.5: 0.5 Then, these materials were dispersed in ion-exchanged water to prepare a paste-like composition for forming a negative electrode mixture layer according to Example 15 having an NV of 50%. A negative electrode sheet according to Example 15 was produced in the same manner as in Example 9, except that the composition according to Example 15 was used.
<Example 16>
In the same manner as in Example 15 except that the mass ratio of natural graphite, CMC, first SBR, and second SBR was 98.2: 1: 0.4: 0.4, Such a negative electrode sheet was prepared.
<Example 17>
Example 17 was carried out in the same manner as Example 15 except that the mass ratio of natural graphite, CMC, first SBR, and second SBR was 98.4: 1: 0.3: 0.3. Such a negative electrode sheet was prepared.
<Example 18>
As in Example 15, except that the mass ratio of natural graphite, CMC, first SBR, and second SBR was 98.6: 1: 0.2: 0.2. Such a negative electrode sheet was prepared.
<Example 19>
Example 19 was repeated in the same manner as in Example 15 except that the mass ratio of natural graphite, CMC, first SBR, and second SBR was 98.8: 1: 0.1: 0.1. Such a negative electrode sheet was prepared.

<Example 20>
Weigh natural graphite, CMC, and first SBR having an average particle size C of 80 nm so that the mass ratio is 98: 1: 1, and disperse natural graphite and CMC in ion-exchanged water. The paste-like composition for forming a negative electrode mixture layer according to Example 20 having an NV of 50% was prepared by kneading with a biaxial planetary kneader.
Moreover, the binder solution which concerns on Example 20 of NV10% containing said 1st SBR was prepared. A negative electrode sheet according to Example 20 was produced in the same manner as in Example 1 except that the composition according to Example 20 and the binder solution were used.
<Example 21>
A negative electrode sheet according to Example 21 was produced in the same manner as Example 20, except that the mass ratio of natural graphite, CMC, and first SBR was 98.2: 1: 0.8.
<Example 22>
A negative electrode sheet according to Example 22 was produced in the same manner as in Example 20, except that the mass ratio of natural graphite, CMC, and first SBR was 98.4: 1: 0.6.
<Example 23>
A negative electrode sheet according to Example 23 was produced in the same manner as in Example 20 except that the mass ratio of natural graphite, CMC, and first SBR was 98.55: 1: 0.45.
<Example 24>
A negative electrode sheet according to Example 24 was produced in the same manner as in Example 20, except that the mass ratio of natural graphite, CMC, and first SBR was 98.8: 1: 0.2.

<Example 25>
The weight ratio of natural graphite, CMC, and first SBR having an average particle size C of 80 nm is 98: 1: 1, these materials are dispersed in ion-exchanged water, and NV is 50%. A paste-like composition for forming a negative electrode mixture layer according to Example 25 was prepared. A negative electrode sheet according to Example 25 was produced in the same manner as in Example 9, except that the composition according to Example 25 was used.
<Example 26>
A negative electrode sheet according to Example 26 was produced in the same manner as in Example 25 except that the mass ratio of natural graphite, CMC, and first SBR was 98.2: 1: 0.8.
<Example 27>
A negative electrode sheet according to Example 27 was produced in the same manner as in Example 25 except that the mass ratio of natural graphite, CMC, and first SBR was 98.4: 1: 0.6.
<Example 28>
A negative electrode sheet according to Example 28 was produced in the same manner as in Example 25 except that the mass ratio of natural graphite, CMC, and first SBR was set to 98.55: 1: 0.45.
<Example 29>
A negative electrode sheet according to Example 29 was produced in the same manner as in Example 25 except that the mass ratio of natural graphite, CMC, and first SBR was 98.8: 1: 0.2.

<Bend resistance evaluation test>
The negative electrode sheets according to Example 10 to Example 29 produced as described above were subjected to a bending resistance (flexibility) evaluation test according to JIS K5600-5-1. That is, when each negative electrode sheet was wound around a cylindrical core material, the minimum value of the diameter (core diameter) of the core material that did not crack in the negative electrode mixture layer of the negative electrode sheet was measured. The measurement results are shown in Tables 3 to 6. In Example 19 and Example 29, SBR was not sufficiently dispersed in the negative electrode mixture layer, and therefore cracks occurred at the time of forming the negative electrode mixture layer.

  As shown in Tables 3 to 6, when the SBR content is 1% by mass and 0.8% by mass, the minimum diameter of the core material is 2 μm, and the coating method and the type of SBR It was confirmed that there was no difference in bending resistance. However, when the core diameter indicating the bending resistance required for the negative electrode composite material layer in this evaluation test is 50 μm, the negative electrode sheet prepared by coating one layer of two types of SBR and one layer of one type of SBR. As shown in Examples 17 and 27, the negative electrode sheet produced by coating can reduce the SBR content only to 0.6% by mass, and the negative electrode sheet produced by coating one kind of SBR by two layers. As shown in Example 23, the SBR content can only be reduced to 0.45% by mass, but the negative electrode sheet formed by the two-layer coating using two types of SBR is SBR as shown in Example 14. It was confirmed that sufficient bending resistance was provided even if the content was reduced to 0.2% by mass.

  As mentioned above, although the specific example of this invention was demonstrated in detail, these are only illustrations and do not limit a claim. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

  The lithium ion secondary battery 10 according to the present invention can be used as a secondary battery for various applications. For example, as shown in FIG. 10, it can be suitably used as a power source for a vehicle driving motor (electric motor) mounted on a vehicle 100 such as an automobile. The type of vehicle 100 is not particularly limited, but is typically a hybrid vehicle, an electric vehicle, a fuel cell vehicle, or the like. Such lithium ion secondary battery 10 may be used alone, or may be used in the form of an assembled battery that is connected in series and / or in parallel.

DESCRIPTION OF SYMBOLS 10 Lithium ion secondary battery 15 Battery case 20 Opening part 25 Cover body 30 Case main body 40 Safety valve 50 Winding electrode body 60 Positive electrode terminal 62 Positive electrode current collector 64 Positive electrode sheet (positive electrode)
66 Positive electrode mixture layer 80 Negative electrode terminal 82 Negative electrode current collector 84 Negative electrode sheet (negative electrode)
85 Graphite material 86 Binder 87 First binder 88 Second binder 90 Negative electrode mixture layer 92 Upper layer portion 94 Lower layer portion 95 Separator sheet 100 Vehicle (automobile)

Claims (8)

A secondary battery comprising a positive electrode and a negative electrode,
The negative electrode includes a negative electrode current collector, and a negative electrode composite material layer formed on the current collector and including at least a negative electrode active material and a binder,
The binder contained in the negative electrode composite material layer has a particle size distribution having two peaks, a first peak having a relatively small particle size and a second peak having a relatively large particle size. ,
The average particle size of the binder in the lower layer portion adjacent to the negative electrode current collector when the negative electrode mixture layer is divided into two in the thickness direction is the negative electrode current collection when the negative electrode mixture layer is divided into two in the thickness direction. The secondary battery which is larger than the average particle diameter of the said binder in the upper layer part which left | separated the counter electrode side rather than the electric body. The particle size value of the first peak is in the range of 80 nm to 160 nm,
The value of B / A, which is the ratio when the particle size value of the first peak is A and the particle size value of the second peak is B, is 2 to 3.2. Secondary battery.   The said binding material contained in this negative electrode composite material layer is 0.2 mass%-0.8 mass% when said negative electrode composite material layer is 100 mass%, 2 of Claim 1 or 2 Next battery.   4. The secondary battery according to claim 1, wherein the negative electrode active material is a carbon material capable of reversibly occluding and releasing lithium ions. 5. A secondary battery comprising: a positive electrode in which a positive electrode mixture layer including a positive electrode active material is formed on a positive electrode current collector; and a negative electrode in which a negative electrode mixture layer including a negative electrode active material is formed on a negative electrode current collector. A method of manufacturing comprising:
In the step of forming the negative electrode,
A first binder having a first average particle size, a second binder having a second average particle size that is larger than the first average particle size, and a solvent are mixed. Preparing a binder solution having a particle size distribution having two peaks, a first peak corresponding to the first binder and a second peak corresponding to the second binder,
Preparing a paste-like composition for forming a negative electrode mixture layer containing at least the negative electrode active material and a solvent;
Applying the prepared binder solution to the surface of the negative electrode current collector;
Applying the prepared composition for forming a negative electrode mixture layer on the applied binder solution;
A method for manufacturing a secondary battery. As the first binder, a binder having the first average particle diameter in the range of 80 nm to 160 nm is used.
As the second binder, an average value of D / C, which is a ratio when the first average particle diameter is C and the second average particle diameter is D, is 2 to 3.2. The manufacturing method of Claim 5 using the binder of a particle size.   The amount of the binder solution applied per unit area is 0.2% by mass to 0.00% by weight of the binder contained in the negative electrode mixture layer when the formed negative electrode mixture layer is 100% by mass. The manufacturing method of Claim 5 or 6 adjusted so that it may become 8 mass%. The negative electrode is a negative electrode for a lithium ion secondary battery,
The production method according to any one of claims 5 to 7, wherein a carbon material capable of reversibly occluding and releasing lithium ions is used as the negative electrode active material.