JP2008135334A - Negative electrode plate for nonaqueous electrolyte secondary battery, and nonaqueous electrolyte secondary battery using this negative electrode plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a negative electrode plate for a nonaqueous electrolyte secondary battery which is most suitable for an EV, HEV or the like superior in cycle characteristics and charging load characteristics although employing a water-based binder, and to provide the nonaqueous electrolyte secondary battery using this negative electrode plate. <P>SOLUTION: In the negative electrode plate for the nonaqueous electrolyte secondary battery in which a negative electrode active material mixture layer containing the water-based binder and an negative electrode active material is formed on the surface of a negative electrode core, a polymer layer having a three-dimensional network structure formed by applying an organic solvent solution of a polymer compound is coated on the surface of the negative electrode mixture layer. The coated amount of the polymer layer having this three-dimensional network structure is preferably 4% or less of negative electrode active material weight in the negative electrode active material mixture. Moreover, it is preferable that the negative electrode active material is a carbonaceous material, the water-based binder is composed of a mixture of carboxymethyl cellulose and styrene-butadiene rubber, and the polymer layer having the three-dimensional network structure is composed of polyvinylidene fluoride. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a negative electrode plate for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery using the negative electrode plate, and particularly an electric vehicle excellent in cycle characteristics and charge load characteristics while using an aqueous binder ( EV), a negative electrode plate for a non-aqueous electrolyte secondary battery that is optimal for a hybrid electric vehicle (HEV), and the like, and a non-aqueous electrolyte secondary battery using the negative electrode plate.

  Emission regulations such as carbon dioxide gas have been strengthened against the backdrop of an increasing environmental protection movement, and the automobile industry is actively developing EVs and HEVs as well as automobiles that use fossil fuels such as gasoline, diesel oil and natural gas. Has been done. In addition, the rapid rise in fossil fuel prices in recent years is a tailwind for the development of these EVs and HEVs. In the field of batteries for EVs and HEVs, nonaqueous electrolyte secondary batteries represented by lithium ion secondary batteries having a higher energy density than other batteries have attracted attention. The share is showing a big growth.

  FIG. 1 is a perspective view showing a conventional cylindrical non-aqueous electrolyte secondary battery cut in the longitudinal direction. In this nonaqueous electrolyte secondary battery 10, a wound electrode body 14 in which a positive electrode 11 and a negative electrode 12 are wound via a separator 13 is disposed, and insulating plates 15 and 16 are disposed above and below the wound electrode body 14, respectively. After that, it is housed in a steel cylindrical battery outer can 17 that also serves as the negative electrode terminal, and the current collecting tab 12a of the negative electrode 12 is welded to the inner bottom portion 17a of the battery outer can 17 and the current collecting tab 11a of the positive electrode 11 is welded. Is welded to the bottom plate portion of the current interrupting sealing body 18 incorporating the safety device, and a predetermined non-aqueous electrolyte is injected from the opening of the battery outer can 17. Manufactured by sealing. Such a non-aqueous electrolyte secondary battery has an excellent effect that the battery performance and the battery reliability are high.

  As a positive electrode active material in such a non-aqueous electrolyte secondary battery, LixMO2 (where M is at least one of Co, Ni, and Mn) capable of reversibly occluding and releasing lithium ions. Lithium transition metal composite oxides represented, that is, LiCoO2, LiNiO2, LiNiyCo1-yO2 (y = 0.01 to 0.99), LiMnO2, LiMn2O4, LiCoxMnyNizO2 (x + y + z = 1), LiFePO4, or the like alone or in combination Are used as a mixture.

  In addition, as the negative electrode active material, a material mainly composed of carbon such as natural graphite, artificial graphite, carbon black, coke, glassy carbon, carbon fiber, or a mixture of one or more of these fired bodies is used. Has been.

  By the way, the increase in capacity of the battery can be achieved by increasing the density of the active material mixture applied to the surface of the current collector. However, if the density of the active material mixture is increased, the capacity of the active material mixture layer is increased. A space | gap reduces and the amount of non-aqueous electrolyte solution which can be hold | maintained in an active material mixture layer reduces. When charging / discharging is repeated in this state, the nonaqueous solvent (organic solvent) in the nonaqueous electrolytic solution is decomposed, so that the amount of the nonaqueous electrolytic solution in the active material mixture layer further decreases. In particular, when an aqueous binder is used at the time of adjusting the active material mixture, the ability to hold the electrolytic solution of the aqueous binder may be low, and charging and discharging may be impossible at a relatively early stage. The decrease in the amount of the non-aqueous electrolyte in the active material mixture layer during charging / discharging is caused by organicity on the electrode surface during the charge / discharge process when a carbonaceous material such as graphite or amorphous carbon is used as the negative electrode active material. Since the solvent is reductively decomposed, it is particularly prominent. The aqueous binder refers to one obtained by dissolving or dispersing in water one or more compounds composed of a thermoplastic resin, a resin having rubber elasticity, a polysaccharide and the like.

In order to solve the problems such as decomposition of the non-aqueous electrolyte when the carbon material is used as the negative electrode active material as described above, the following Patent Document 1 discloses an ionic polymer, a water-soluble high concentration on the surface of the carbon negative electrode. A non-aqueous electrolyte layer that forms a coating layer made of either a molecule or an alkali metal salt, improves the wettability between the carbon negative electrode and the non-aqueous electrolyte layer, and suppresses the decomposition of the non-aqueous electrolyte layer. An invention of a secondary battery is disclosed. Similarly, in Patent Document 2 below, a polymer layer that swells or wets with a nonaqueous electrolyte such as a porous lithium ion conductive polymer, polyvinylidene fluoride (PVdF), polyvinyl chloride, or polyacrylonitrile is used as a positive electrode. An invention of a cylindrical non-aqueous battery that is excellent in charge / discharge characteristics after that, without being depleted of an electrolyte solution between the positive electrode and the negative electrode even when left at high temperature by being provided between the negative electrode and the negative electrode has been disclosed. .
JP-A-11-129992 JP-A-11-26025

  In the invention of the non-aqueous electrolyte secondary battery disclosed in Patent Document 1, a negative electrode active material comprising a mixture of a binder resin composition and N-methylpyrrolidone (NMP) using a carbonaceous material as the negative electrode active material. A negative electrode is prepared using a mixture, and a coating layer made of any one of an ionic polymer, a water-soluble polymer, and an alkali metal salt is formed on the surface of the negative electrode, and is disclosed in Patent Document 2 above. In the invention of a cylindrical non-aqueous battery, a carbonaceous material is used as a negative electrode active material, and a negative electrode is produced using a negative electrode active material mixture made of a mixture of PVdF and NMP as a binder.

  In general, the reason for using a binder that dissolves or disperses in an organic solvent such as NMP in the production of the negative electrode active material mixture is to prevent deterioration of battery performance due to residual moisture when the battery is assembled. . Then, as in the inventions disclosed in Patent Documents 1 and 2, if a non-aqueous electrolyte secondary battery is manufactured using a negative electrode using a material having a property of being dissolved or dispersed in an organic solvent such as NMP as a binder, Since the retention capacity of the non-aqueous electrolyte is greater than when a water-based binder is used, cycle characteristics are improved.

  However, when using an organic solvent such as NMP in the production of the negative electrode active material mixture, it is necessary to take measures to prevent problems in the working environment and external discharge of the organic solvent. It is requested to refrain as much as possible. Therefore, while using a water-based binder, holding a non-aqueous electrolyte equivalent to or higher than that of using a polymer material that dissolves or disperses in an organic solvent such as NMP as a binder when forming a negative electrode plate A negative electrode plate capable of exhibiting characteristics is required.

  As a result of various studies to solve the problems of the prior art, the inventors have dissolved it in an organic solvent on the surface of the negative electrode plate on which a negative electrode active material mixture using an aqueous binder is provided. When a polymer layer having a three-dimensional network structure is formed by applying the polymer compound solution, a large amount of non-aqueous electrolyte can be retained in the three-dimensional network structure. The present inventors have found that a negative electrode for a non-aqueous electrolyte secondary battery excellent in cycle characteristics and charge load characteristics can be obtained while reducing the amount of organic solvent used during the production of the present invention.

  That is, the present invention is excellent in cycle characteristics and charge load characteristics while using a negative electrode plate provided with a negative electrode active material mixture using a water-based binder, and can charge and discharge large currents such as EV and HEV. It is an object of the present invention to provide a negative electrode plate for a nonaqueous electrolyte secondary battery that is optimal for the required application and a nonaqueous electrolyte secondary battery using the negative electrode plate.

  The above object of the present invention can be achieved by the following configurations. That is, the negative electrode plate for a nonaqueous electrolyte secondary battery of the present invention is a negative electrode for a nonaqueous electrolyte secondary battery in which a negative electrode active material mixture layer containing an aqueous binder and a negative electrode active material is formed on the surface of the negative electrode core. In the plate, the surface of the negative electrode active material mixture layer is covered with a polymer layer having a three-dimensional network structure formed by applying an organic solvent solution of a polymer compound.

  As an aqueous binder used for the negative electrode plate for a non-aqueous electrolyte secondary battery of the present invention, a thermoplastic resin, a polymer having rubber elasticity, a compound such as a polysaccharide, or a mixture thereof is used by dispersing in water. Can do. Specifically, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene copolymer, styrene butadiene rubber (SBR), polybutadiene, butyl rubber, fluororubber, polyethylene oxide, polyvinyl pyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile. , Polystyrene, ethylene-propylene-diene copolymer, polyvinyl pyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenol resin, epoxy resin, polyvinyl alcohol, carboxymethyl cellulose, cellulose resin such as hydroxypropyl cellulose, etc. It can be selected appropriately. In general, carboxymethyl cellulose (CMC) is often used in combination with other binders as a thickener, but CMC alone is sometimes used as a function as a binder. In the case of CMC, CMC is also treated as being included in the aqueous binder.

  Moreover, as a negative electrode active material that can be used for the negative electrode plate for a nonaqueous electrolyte secondary battery of the present invention, natural graphite, artificial graphite, carbon black, coke, glassy carbon, carbon fiber, or one of these fired bodies Or what mixed carbon, such as what mixed multiple types, is preferable.

  In the negative electrode plate for a non-aqueous electrolyte secondary battery according to the present invention, the coating amount of the polymer layer having the three-dimensional network structure is 4% or less of the mass of the negative electrode active material in the negative electrode active material mixture layer. It is characterized by being.

  In the negative electrode plate for a non-aqueous electrolyte secondary battery according to the present invention, the negative electrode active material is a carbonaceous material, the aqueous binder is a mixture of CMC and SBR, and has a three-dimensional network structure. The molecular layer is made of PVdF.

  The nonaqueous electrolyte secondary battery of the present invention includes a negative electrode plate for a nonaqueous electrolyte secondary battery according to any one of the above inventions, and a positive electrode plate in which a positive electrode active material mixture is formed on the surface of a positive electrode core. And a non-aqueous electrolyte.

  As the positive electrode active material used in the nonaqueous electrolyte secondary battery of the present invention, LixMO2 capable of reversibly occluding and releasing lithium ions (provided that M is at least one of Co, Ni, and Mn) LiCoO2, LiNiO2, LiNiyCo1-yO2 (y = 0.01 to 0.99), LiMnO2, LiMn2O4, LiCoxMnyNizO2 (x + y + z = 1), or LiFePO4 alone or A plurality of types can be mixed and used.

  In addition, carbonates, lactones, ethers, esters, and the like can be used as the nonaqueous solvent (organic solvent) constituting the nonaqueous solvent-based electrolyte used in the nonaqueous electrolyte secondary battery of the present invention. Two or more of these solvents can be mixed and used. Among these, carbonates, lactones, ethers, ketones, esters and the like are preferable, and carbonates are more preferably used.

  Specific examples include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), cyclopentanone, sulfolane, 3-methylsulfolane, 2,4-dimethylsulfolane, 3-methyl. -1,3-oxazolidine-2-one, dimethyl carbonate (DMC), methyl ethyl carbonate (MEC), diethyl carbonate (DEC), methyl propyl carbonate, methyl butyl carbonate, ethyl propyl carbonate, ethyl butyl carbonate, dipropyl carbonate, γ -Butyrolactone, γ-valerolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, methyl acetate, ethyl acetate, 1,4-dio Xanthan can be mentioned.

  In addition, as a solute of the nonaqueous electrolyte used in the nonaqueous electrolyte secondary battery of the present invention, a lithium salt generally used as a solute in the nonaqueous electrolyte secondary battery can be used. Such lithium salts include LiPF6, LiBF4, LiCF3SO3, LiN (CF3SO2) 2, LiN (C2F5SO2) 2, LiN (CF3SO2) (C4F9SO2), LiC (CF3SO2) 3, LiC (C2F5SO2) 3, LiAsF6, LiClO4, Examples include Li2B10Cl10, Li2B12Cl12, and mixtures thereof. Among these, LiPF6 (lithium hexafluorophosphate) is preferably used. The amount of solute dissolved in the non-aqueous solvent is preferably 0.5 to 2.0 mol / L.

  By providing the above configuration, the present invention has the following excellent effects. That is, according to the negative electrode plate for a non-aqueous electrolyte secondary battery of the present invention, it is formed by applying an organic solvent solution of a polymer compound to the surface of a negative electrode active material mixture layer containing an aqueous binder and a negative electrode active material. Since the polymer layer having a three-dimensional network structure is coated, even if the amount of the non-aqueous electrolyte contained in the negative electrode active material mixture layer is small, it is provided on the surface of the negative electrode active material mixture layer. Since the non-aqueous electrolyte can be held in the polymer layer having a three-dimensional network structure, the non-aqueous electrolyte in the negative electrode active material mixture may be decomposed by repeating the charge / discharge cycle. In addition, since the nonaqueous electrolytic solution retained in the polymer layer having a three-dimensional network structure is supplied into the negative electrode active material mixture, it is possible to suppress liquid withering in the negative electrode active material mixture layer. . Therefore, when the negative electrode plate for a non-aqueous electrolyte secondary battery of the present invention is used, a non-aqueous electrolyte secondary battery having excellent charge / discharge cycle characteristics and excellent discharge load characteristics can be obtained.

  In addition, according to the negative electrode plate for a non-aqueous electrolyte secondary battery of the present invention, the coating amount of the polymer layer having a three-dimensional network structure is good at 4% or less of the negative electrode active material mass in the negative electrode active material mixture. There is an effect of improving the charge / discharge cycle characteristics. If the coating amount of the polymer layer having the three-dimensional network structure exceeds 4% of the mass of the negative electrode active material in the negative electrode active material mixture, the internal resistance of the polymer layer having the three-dimensional network structure increases. Although the effect of improving the characteristics can be expected, the charge load characteristics are lowered. Note that even if the coating amount of the polymer layer having the three-dimensional network structure is small, the effect of improving the cycle characteristics is produced, so the lower limit should be over 0%.

  In addition, carbonaceous materials such as graphite and amorphous carbon as a negative electrode active material have a discharge potential comparable to that of lithium metal or lithium alloy, but have high safety because dendrite does not grow, Furthermore, it is known to have excellent properties such as excellent initial efficiency, good potential flatness, and high density, but it decomposes the non-aqueous electrolyte on the electrode surface. It has the property of being easy. According to the negative electrode plate for a non-aqueous electrolyte secondary battery of the present invention, a polymer having a three-dimensional network structure using a mixture of CMC and SBR as an aqueous binder while using a carbonaceous material as a negative electrode active material. Since PVdF was used as the layer, the effect of the present invention was remarkably exhibited.

  In addition, according to the nonaqueous electrolyte secondary battery of the present invention, since the negative electrode plate for a nonaqueous electrolyte secondary battery is used, the effect of the invention of the negative electrode plate for a nonaqueous electrolyte secondary battery is achieved. A non-aqueous electrolyte secondary battery that can be obtained is obtained.

  Hereinafter, the best mode for carrying out the present invention will be described in detail using examples and comparative examples. However, the following examples illustrate non-aqueous electrolyte secondary batteries for embodying the technical idea of the present invention, and are not intended to specify the present invention to these examples. The present invention can be equally applied to various modifications without departing from the technical idea shown in the claims.

[Production of positive electrode]
Lithium cobaltate (LiCoO2) as the positive electrode active material uses lithium carbonate (Li2CO3) as the starting material and tricobalt tetroxide (Co3O4) as the cobalt source, and weighs a predetermined amount of these and mixes them. After that, it was baked at 850 ° C. for 24 hours in an air atmosphere to obtain lithium cobalt oxide. This was ground to an average particle size of 14 μm with a mortar to obtain a positive electrode active material. 90 parts by mass of the positive electrode active material thus produced, 5 parts by mass of graphite powder as a conductive agent, and 5 parts by mass of PVdF powder as a binder are dispersed in an NMP solution to produce a positive electrode active material. A slurry was prepared. Next, this positive electrode active material slurry was applied to both surfaces of a positive electrode core body made of an aluminum foil having a thickness of 15 μm by a doctor blade method, and then passed through a dryer to remove NMP necessary for slurry preparation. A positive electrode plate was produced by rolling to a thickness of 140 μm using a roll press.

[Production of negative electrode plate]
A negative electrode active material mixture slurry was prepared by dispersing 97 parts by mass of graphite powder as a negative electrode active material, 1 part by mass of CMC, and 2 parts by mass of SBR, and uniformly mixing in water. Next, this negative electrode active material mixture slurry was applied to both surfaces of a negative electrode core made of a copper foil having a thickness of 10 μm by a doctor blade method, and then passed through a dryer to remove water necessary for slurry preparation. Then, a negative electrode plate was produced by rolling to a thickness of 125 μm using a roll press. Next, PVdF dissolved in NMP is applied to the surface by a doctor blade method so that the mass ratio with respect to the negative electrode active material is 2%, dried to remove NMP, and a polymer layer having a three-dimensional network structure is formed. The negative electrode plate of Example 1 was produced by coating. The amount of active material applied to each of the positive electrode and the negative electrode is such that the charge capacity ratio (negative electrode charge capacity / positive electrode charge capacity) at the portion where the positive electrode plate and the negative electrode plate face each other is 1 at the charge voltage as the design standard. .1 (hereinafter the same).

[Preparation of non-aqueous electrolyte]
What melt | dissolved LiPF6 as electrolyte salt in the ratio of 1.0 mol / L in the nonaqueous solvent which mixed EC, EMC, and DEC by the ratio of 20:50:30 (1 atmosphere, 25 degreeC conversion). A non-aqueous electrolyte was used.

[Production of battery]
Using the positive electrode plate, the negative electrode plate, and the non-aqueous electrolyte prepared as described above, and using a polyethylene microporous membrane as a separator, the cylindrical non-electrode of Example 1 configured as shown in FIG. A water electrolyte secondary battery was produced. The design capacity of this cylindrical nonaqueous electrolyte secondary battery is 2200 mAh.

  In Example 2, a negative electrode plate was prepared in the same manner as in Example 1 except that the amount of the PVdF layer covering the surface of the negative electrode active material mixture layer was 4% by mass ratio to the negative electrode active material. Then, the other configurations were the same as those of Example 1, and a nonaqueous electrolyte secondary battery of Example 2 was produced.

  In Example 3, a negative electrode plate was prepared in the same manner as in Example 1 except that the amount of the PVdF layer covering the surface of the negative electrode active material mixture layer was 5% by mass ratio to the negative electrode active material. The other configurations were the same as in Example 1, and a nonaqueous electrolyte secondary battery of Example 3 was produced.

[Comparative Example 1]
In Comparative Example 1, a negative electrode plate was prepared in the same manner as in Example 1 except that the PVdF layer was not provided on the surface of the negative electrode plate, and all other configurations were the same as in Example 1, Comparative Example 1. A non-aqueous electrolyte secondary battery was prepared.

[Comparative Example 2]
In Comparative Example 2, a negative electrode active material mixture slurry was prepared by uniformly mixing in an NMP solution at a ratio of 95 parts by mass of graphite powder and 5 parts by mass of PVdF during the production of the negative electrode plate. The active material mixture slurry was applied to both surfaces of a negative electrode core made of a copper foil having a thickness of 10 μm by a doctor blade method, and then passed through a dryer to remove NMP necessary for slurry preparation, and then a roll press machine The negative electrode plate of Comparative Example 2 was produced by rolling to a thickness of 125 μm. A PVdF layer is not provided on the surface of the negative electrode plate of Comparative Example 2. Using the negative electrode plate of Comparative Example 2, a nonaqueous electrolyte secondary battery of Comparative Example 2 was produced in the same manner as in Example 1.

[Comparative Example 3]
In Comparative Example 3, when preparing the negative electrode plate, a negative electrode active material mixture slurry was prepared by mixing uniformly in an NMP solution at a ratio of 95 parts by mass of graphite powder and 5 parts by mass of PVdF. The active material mixture slurry was applied to both surfaces of a negative electrode core made of a copper foil having a thickness of 10 μm by a doctor blade method, and then passed through a dryer to remove NMP necessary for slurry preparation, and then a roll press machine Was used to roll to a thickness of 125 μm to prepare a negative electrode plate. Next, a polymer layer having a three-dimensional network structure is formed by applying PVdF dissolved in NMP to the surface by a doctor blade method so that the mass ratio to the active material is 2%, and drying to remove NMP. The negative electrode plate of Comparative Example 3 was produced. Then, the other configurations were the same as in Example 1, and a nonaqueous electrolyte secondary battery of Comparative Example 3 was produced.

[Measurement of cycle characteristics and charge load characteristics]
For the six types of batteries of Examples 1 to 3 and Comparative Examples 1 to 3 manufactured as described above, the cycle characteristics and the charge load characteristics were measured as follows. The cycle characteristics are measured by charging at 25 ° C. with a constant current of 1 It = 2200 mA until the battery voltage reaches 4.20 V, and then charging with a constant voltage of 4.20 V until the current reaches 1/50 It = 44 mA. Subsequently, the battery was discharged at a constant current of 1 It at 25 ° C. until the battery voltage reached 2.75V. The discharge capacity at this time was determined as the discharge capacity of the first cycle. Next, the above charge / discharge cycle was repeated 300 times, and the discharge capacity at the 300th time was determined as the discharge capacity at the 300th cycle. And the cycle characteristic value was calculated | required with the following formulas. The results are summarized in Table 1.
Cycle characteristic value (%)
= (Discharge capacity at 300th cycle / Discharge capacity at 1st cycle) × 100

In addition, the charge load characteristic is that the battery whose discharge capacity is measured at the first cycle is charged at a constant current until the battery voltage reaches 4.20 V at 1 It at 25 ° C., and then the battery voltage becomes 2.75 V at 1 It. The charge capacity when discharged until is obtained as a 1 It charge capacity, then charged until the battery voltage reaches 4.20 V at a constant current of 3 It = 6600 mA, and then the battery voltage reaches 2.75 V at a constant current of 1 It. The charge capacity when discharged was determined as a 3 It charge capacity, and the charge load characteristics were determined by the following calculation formula. The results are summarized in Table 1.
Charging load characteristics (%)
= (3It charge capacity / 1It charge capacity) × 100

  From the results shown in Table 1, the following can be understood. That is, from the comparison of the results of Comparative Example 1 and Comparative Example 2 that do not include a polymer layer having a three-dimensional network structure on the surface of the negative electrode plate, the cycle characteristics of the battery of Comparative Example 1 using an aqueous binder are non-aqueous. It turns out that cycling characteristics are falling rather than the battery of the comparative example 2 which uses a binder. This is because the negative electrode plate using a water-based binder has a lower ability to hold a non-aqueous electrolyte than a negative electrode plate using a non-aqueous binder. This indicates that the non-aqueous electrolyte of the battery is exhausted.

  On the other hand, the battery of Example 1 provided with a polymer layer having a three-dimensional network structure on the surface of the negative electrode active material mixture layer while using the same aqueous binder has such a polymer layer. It can be seen that the cycle characteristics are greatly increased as compared with the battery of Comparative Example 1 that is not present. The difference in configuration between the battery of Example 1 and the battery of Comparative Example 1 is only the presence or absence of a polymer layer having a three-dimensional network structure on the surface of the negative electrode active material mixture layer. It is clear that the presence of non-aqueous electrolyte leads to improvement of cycle characteristics. The presence or absence of this polymer layer has little influence on the charge load characteristics.

  In addition, while using the negative electrode active material mixture layer of the same composition using an aqueous binder, the amount of the polymer layer having a three-dimensional network structure coated on the surface of the negative electrode active material mixture layer is different 1. When the results of Example 2 and Example 3 are compared, up to 4% of the polymer layer having a three-dimensional network structure hardly affects cycle characteristics and charge load characteristics. When the amount of the polymer layer is more than 4%, the cycle characteristics are deteriorated and the charge load characteristics are greatly deteriorated. This is because, in the battery of Example 3, the amount of the polymer layer having a three-dimensional network structure is large, so the thickness of the polymer layer is increased, and a large amount of nonaqueous electrolyte is retained in the polymer layer. Even if this is done, the internal resistance of the polymer layer increases, which is thought to have led to a significant decrease in charge load characteristics. Therefore, it can be seen that the amount of the polymer layer having a three-dimensional network structure is preferably 4% or less with respect to the mass of the active material in the negative electrode active material mixture layer.

FIG. 6 is a front view of a conventional cylindrical nonaqueous electrolyte secondary battery seen through.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Nonaqueous electrolyte secondary battery 11 Positive electrode 11a Positive electrode current collection tab 12 Negative electrode 12a Negative electrode current collection tab 13 Separator 14 Winding electrode body 17 Battery exterior can 18 Current interruption sealing body

Claims (4)

In the negative electrode plate for a non-aqueous electrolyte secondary battery in which a negative electrode active material mixture layer containing an aqueous binder and a negative electrode active material is formed on the surface of the negative electrode core,
A surface of the negative electrode active material mixture layer is coated with a polymer layer having a three-dimensional network structure formed by applying an organic solvent solution of a polymer compound. Negative electrode plate for batteries.   2. The nonaqueous electrolyte secondary battery according to claim 1, wherein a coating amount of the polymer layer having the three-dimensional network structure is 4% or less of a negative electrode active material mass in the negative electrode active material mixture. Negative electrode plate.   2. The negative electrode active material is a carbonaceous material, the aqueous binder is made of a mixture of carboxymethyl cellulose and styrene butadiene rubber, and the polymer layer having the three-dimensional network structure is made of polyvinylidene fluoride. Or the negative electrode plate for nonaqueous electrolyte secondary batteries of 2.   It has the negative electrode plate for nonaqueous electrolyte secondary batteries in any one of Claims 1-3, the positive electrode plate in which the positive electrode active material mixture was formed in the surface of a positive electrode core, and a nonaqueous electrolyte. A non-aqueous electrolyte secondary battery.

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