JPH09219188A - Nonaqueous electrolyte secondary battery, and manufacture of it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the shelf life characteristic of electric discharge capacity, by coating respective powder surfaces of carbon material, capable of doping and dedoping the Li-containing composite oxide and Li ion of positive and negative electrode active material, by a resin protective coat, unsoluble for both the nonaqueous solvent of a nonaqueous electrolyte, and the binder resin dissolving solvent for an electrode fixture. SOLUTION: A negative electrode 1 is formed by using powder obtained by drying slurry, wherein PVDF and NMP are mixed in a negative electrode active material fine particle wherein a carbon material fine particle is dispersed in a water solution of PVA and then dried. A positive electrode active material fine particle can be obtained by dispersing a fine particle, obtained by powdering LiCo O2 wherein lithium carbonate and cobalt carbonate are mixed to be baked, and grapnite in the water solution of PVA to be dried. A positive electrode 2 is formed by using a positive electrode mixture powder, obtained by drying slurry wherein the PVDF and NMP are added to the fine particle. A separator 3 is interposed between the negative and positive electrodes 1 and 2, to be housed in a negative electrode battery can 4, into which an electrolyte is injected, and then to seal the battery can 4 by a sealing gasket 6. This can improve the shelf life characteristic of electric discharge capacity.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a positive electrode containing a lithium-containing composite oxide, a negative electrode containing a carbon material capable of doping and dedoping lithium ions, and a lithium salt electrolyte dissolved in a non-aqueous solvent. Non-aqueous electrolyte secondary battery comprising the following non-aqueous electrolyte.

[0002]

2. Description of the Related Art In recent years, due to advances in electronic technology, high performance, miniaturization, and portability of electronic devices have advanced, and the demand for high energy density batteries used in these portable electronic devices has increased. Conventionally, nickel-cadmium batteries and lead batteries have been used as secondary batteries used in these electronic devices.
In reality, the requirements for a battery having a low V), a large battery weight and a large battery volume, and a high energy density have not been met.

Recently, as a battery system satisfying these requirements, a non-aqueous electrolyte secondary battery having a negative electrode made of metallic lithium or a lithium alloy has attracted attention and has been actively studied. However, in the case of non-aqueous electrolyte secondary batteries that use metallic lithium as the negative electrode, the cycle life and rapid charging characteristics are practically sufficient due to the dissolution of metallic lithium, the generation of dendrites at the time of cracking, and the miniaturization of precipitated lithium. There is a problem that it does not exhibit various characteristics.

[0004] In order to solve these problems,
Research and development of a lithium-ion non-aqueous electrolyte secondary battery in which a material capable of doping and de-doping with lithium ions, for example, a carbon material as a negative electrode is active. Non-aqueous electrolyte secondary battery using such a negative electrode, since lithium does not exist in the metal state, there is no problem related to deterioration of cycle characteristics and rapid charge characteristics due to the metal lithium negative electrode,
It exhibits excellent battery characteristics. Further, as compared with the nickel-cadmium battery, the low self-discharge property required for the secondary battery is improved, and there is an advantage that there is no memory effect. Furthermore, by using a lithium-containing composite oxide having a high redox potential for the positive electrode, the voltage of the battery (about 4.2 V) is increased, so that a battery having a high energy density can be realized.

By the way, as one of the typical forms of such a lithium ion non-aqueous electrolyte secondary battery, a coin type as shown in FIG. 1 is known. In this coin-type battery, a disk-shaped negative electrode 1 and a positive electrode 2 are mixed with, for example, 1 mol / mL of LiPF ₆ in a mixed solvent of propylene carbonate and dimethyl carbonate (1: 1 (volume ratio)).
It has a structure in which it is housed in a negative electrode battery can 4 and a positive electrode battery can 5, respectively, via a separator 3 made of polypropylene nonwoven fabric impregnated with an electrolytic solution dissolved at a ratio of 1, and they are caulked via a sealing gasket 6. .

In this case, the negative electrode 1 has a powder of carbon material capable of doping and dedoping lithium ions as described above and polyvinylidene fluoride (PVD) which is a binder resin.
F) and N-methylpyrrolidone capable of dissolving PVDF are added to prepare a negative electrode mixture slurry, which is spread on a vat and dried by hot air at about 220 ° C. It is produced from the negative electrode mixture powder by a heat compression molding method. The positive electrode 2 is also made of lithium-containing composite oxide powder, conductive material carbon black, and binder resin polyvinylidene fluoride (PVDF).
In the same manner as in the case of producing the negative electrode 1, is charged into N-methylpyrrolidone capable of dissolving PVDF to prepare a positive electrode mixture slurry, which is spread on a vat and dried to be crushed. It is produced from the obtained positive electrode mixture powder by a heat compression molding method.

In the case of a spiral type non-aqueous electrolyte secondary battery, an electrode body is used in which the positive electrode mixture slurry and the negative electrode mixture slurry described above are applied to a current collector and dried. doing.

[0008]

However, even the non-aqueous electrolyte secondary battery configured as described above has a problem that the discharge capacity after long-term storage is reduced and the storage characteristics are deteriorated. This tendency is particularly strong when a lithium-containing composite oxide containing nickel is used as the positive electrode active material.

The present invention is intended to solve the problems of the above-mentioned conventional techniques, and uses a lithium-containing composite oxide as a positive electrode active material, and carbon that can be doped and dedoped with lithium ions as a negative electrode active material. It is an object of the present invention to improve the storage characteristics of the non-aqueous electrolyte secondary battery using the material, regarding the charge / discharge efficiency.

[0010]

The present inventor has found that one of the major causes of the deterioration of the storage characteristics related to the discharge capacity of a non-aqueous electrolyte secondary battery is that the non-aqueous solvent is the surface of the electrode active material during charging and discharging. This is because it is oxidized or reduced. Therefore, in order to reduce the discharge capacity after long-term storage, the surface of the electrode active material should be
If a protective film that is lithium ion conductive but does not dissolve in the non-aqueous electrolyte is formed, improvement of storage characteristics can be expected, and further,
Considering that the electrode mixture is slurried at the time of producing the electrode, if the protective film is not dissolved in the solvent used when producing the electrode mixture slurry, it can be surely performed even after the battery is assembled. They have found that a protective film can be left on the surface of an electrode active material, and have completed the present invention.

That is, the present invention provides a positive electrode containing a lithium-containing composite oxide, a negative electrode containing a carbon material capable of doping and dedoping lithium ions, and a non-aqueous electrolysis obtained by dissolving a lithium salt electrolyte in a non-aqueous solvent. In a non-aqueous electrolyte secondary battery including a liquid, a positive electrode or a negative electrode, a lithium-containing composite oxide powder or carbon material powder coated with a protective film, respectively, and a fluorine-based binder resin binder resin It is formed from a positive electrode mixture slurry or a negative electrode mixture slurry obtained by mixing in a dissolving solvent, and the protective film is dissolved in both the nonaqueous solvent of the nonaqueous electrolytic solution and the binder resin dissolving solvent. Provided is a non-aqueous electrolyte secondary battery, which is characterized by being formed from a non-resin.

The present invention also provides a positive electrode containing a lithium-containing composite oxide, a negative electrode containing a carbon material capable of doping and dedoping lithium ions, and a non-aqueous electrolysis obtained by dissolving a lithium salt electrolyte in a non-aqueous solvent. In a method for producing a non-aqueous electrolyte secondary battery including a liquid, (a) a lithium-containing composite oxide powder or a carbon material powder, a non-aqueous solvent of the non-aqueous electrolyte and a solvent for dissolving a binder resin. And (b) mixing the powder coated with the protective film and a fluorine-based binder resin in a solvent for dissolving the binder resin, the positive electrode mixture slurry or the negative electrode mixture slurry. And (c) forming a positive electrode or a negative electrode from the positive electrode mixture slurry or the negative electrode mixture slurry, respectively.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.

First, the non-aqueous electrolyte secondary battery of the present invention will be described.

The non-aqueous electrolyte secondary battery of the present invention comprises a positive electrode containing a lithium-containing composite oxide as a positive electrode active material, a negative electrode containing a carbon material capable of doping and dedoping lithium ions as a negative electrode active material, and lithium. And a non-aqueous electrolytic solution obtained by dissolving a salt electrolyte in a non-aqueous solvent.

Here, the positive electrode is formed from a positive electrode mixture slurry obtained by mixing powder of lithium-containing composite oxide and a fluorine-based binder resin in a solvent for dissolving the binder resin, and the negative electrode is It is formed from a negative electrode mixture slurry obtained by mixing a powder of a carbon material capable of doping and dedoping lithium ions and a fluorine-based binder resin in a solvent for dissolving the binder resin. Then, at least one of the powder of the lithium-containing composite oxide and the powder of the carbon material, preferably both, is a protective film made of a resin that is insoluble in both the non-aqueous solvent of the non-aqueous electrolyte and the solvent for dissolving the binder resin. It is covered. By forming such a protective film, it is possible to suppress or prevent the non-aqueous solvent of the non-aqueous electrolyte from directly contacting the electrode active material during charge and discharge, and suppress the decomposition reaction of the non-aqueous solvent. be able to. Therefore, it is possible to greatly suppress the deterioration of the storage characteristics related to the discharge capacity. In addition, it is possible to reduce the manufacturing cost of the battery by reducing the amount of the fluorine-based binder used.

The material constituting such a protective film varies depending on the types of the non-aqueous solvent of the non-aqueous electrolyte used and the solvent for dissolving the binder, and examples thereof include polyvinyl alcohol (PVA) and polytetrafluoroethylene (PT).
FE), polyethylene (PE), styrene butadiene rubber (SBR), polyvinylidene fluoride (PVDF), etc. can be mentioned. Among them, PVA and PTFE can be preferably used.

Polyvinylidene fluoride (PVDF)
In the case of functioning as a protective film, it is preferable that the compound is adhered to the surface of the electrode active material and then heat-treated to be crystallized (or fiberized) so as not to be dissolved in the organic solvent.

In the present invention, the formation of the protective film on the powder of the electrode active material can be carried out according to various known methods, but it is particularly preferable that the electrode active material is immersed in a solution of a resin for forming the protective film. The substance is dispersed, and the dispersion (slurry) is spray-dried and granulated. As a result, the surface of the powder of the spherical electrode active material can be covered with a thin protective film.

Such a spray dry granulation method can be carried out by using various known spray dryers,
For example, use a disk type spray drying device, a parallel countercurrent pressure nozzle spray drying device, a cocurrent pressure nozzle spray drying device, or a countercurrent pressure nozzle spray drying device. You can

The average particle size of the individual spherical particles of the powder of the electrode active material coated with the protective film by such spray-dry granulation is preferably in consideration of handleability and moldability. Is 50 to 500 μm, more preferably 50 to 300 μm.

If the content of the resin for forming the protective film in the electrode mixture slurry (solid content) is too small, a sufficient addition effect cannot be obtained. Of 0.1 to 5% by weight, and more preferably 0.1 to 3% by weight.

As the lithium-containing composite oxide which is the positive electrode active material, those which have been conventionally used as the positive electrode active material of the lithium ion secondary battery can be used.

[0024]

Embedded image Li _x MO ₂ (1) (where M is a transition metal, preferably Co, Ni and Mn
X is 0.05 ≦ x ≦ 1.10
Is a number that satisfies. )) Can be preferably used. Here, the value of x in the formula changes within the range of 0.05 ≦ x ≦ 1.10 depending on the charge / discharge state. Specific examples of such a compound of formula (1) include L
Examples thereof include iCoO ₂ , LiNiO ₂ , and LiNi _y Co _(1-y) O ₂ (where O <y <1). When the transition metal M is Mn, Li _x Mn ₂ O ₄ and Li _x MnO
Any of the _two can be used.

Such a lithium-containing composite oxide is, for example, a salt of each of lithium and transition metal M, for example,
Carbonates, nitrates, sulfates, oxides, hydroxides, halides and the like can be used as raw materials for production. For example, the lithium salt raw material and the transition metal M salt raw material may be weighed according to a desired composition, sufficiently mixed, and then heated and baked in a temperature range of 600 ° C. to 1000 ° C. in an oxygen-existing atmosphere. . In this case, the method of mixing each component is not particularly limited, and the powdery salts may be mixed in a dry state as they are, or the powdery salts may be dissolved in water to prepare an aqueous solution. May be mixed.

As the carbon material as the negative electrode active material, one that can be doped with lithium ions and dedoped is used. As such a carbon material, a low crystalline carbon material obtained by firing at a relatively low temperature of 2000 ° C. or less, a highly crystalline carbon material obtained by treating a raw material that is easily crystallized at a high temperature near 3000 ° C., and the like are used. be able to. For example, pyrolytic carbons, cokes (pitch cokes, needle cokes, petroleum cokes, etc.), artificial graphites, natural graphites,
Glassy carbons, organic polymer compound fired bodies (furan resin etc. fired at appropriate temperature and carbonized), carbon fiber,
Activated carbon or the like can be used. Above all, (00
2) A low crystalline carbon material having a surface spacing of 3.70 angstroms or more, a true density of less than 1.70 g / cc, and having no exothermic peak at 700 ° C. or more in a differential thermal analysis in an air stream, or a negative electrode mixture. The true specific gravity with high agent filling is 2.10
A highly crystalline carbon material having g / cc or more can be preferably used.

As the fluorine-based binder resin to be added to the negative electrode mixture or the positive electrode mixture, those which are stable without being decomposed during charging and discharging and which are soluble in a solvent for making the negative electrode mixture or the positive electrode mixture into a slurry are used. Can be used. As such a fluorine-based binder resin, in addition to PVDF described above, polyhexafluoropropylene, polytrifluoroethylene chloride, polypentafluoropropylene, etc. can be used. Above all, it is preferable to use PVDF.

The positive electrode mixture preferably contains a known material such as carbon black or graphite as a conductive material.

As the solvent for dissolving the binder resin, various polar solvents capable of dissolving the above-mentioned fluorine-based binder resin can be used. For example, dimethylformamide, dimethylacetamide, methylformamide, N-methylpyrrolidone. Etc. can be used, and particularly when PVDF is used as the fluorine-based binder resin, N-methylpyrrolidone can be preferably used.

When the content of the fluorine-based binder resin in the positive electrode mixture slurry (solid content) is too small, the moldability is lowered, and when it is too large, the content of the electrode active material is relatively lowered and the battery characteristics are lowered. Therefore, 0.3 to 7% by weight, preferably 0.5 to 5% by weight,
It is more preferably 0.5 to 4% by weight.

When the content of the fluorine-based binder resin in the negative electrode mixture slurry (solid content) is too small, the moldability is lowered, and when it is too large, the content of the electrode active material is relatively lowered. Since it is feared that the battery characteristics may deteriorate, 1.0 to 20% by weight, preferably 1.5 to 15%
%, More preferably 1.5 to 12% by weight.

As the non-aqueous solvent used in the present invention, a non-aqueous solvent conventionally used in lithium ion secondary batteries can be used. For example, propylene carbonate, ethylene carbonate, carbonic acid which are high dielectric constant solvents. Cyclic carbonates such as butylene and γ-butyrolactone, low-viscosity solvents such as 1,2-dimethoxyethane, 2-methyltetrahydrofuran, dimethyl carbonate, methyl ethyl carbonate,
Diethyl carbonate etc. can be mentioned. Above all, a mixed solvent of propylene carbonate and diethyl carbonate can be preferably used.

The lithium salt electrolyte used in preparing the non-aqueous electrolyte by dissolving it in the non-aqueous solvent as described above is generally Li used for lithium batteries.
ClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiC
1, LiBr, CH ₃ SO ₃ Li, CF ₃ SO ₃ Li and the like can be mentioned. These can be used alone or in combination of two or more.

The other configurations of the separator, the battery can and the like of the non-aqueous electrolyte secondary battery of the present invention can be the same as those of the conventional lithium ion non-aqueous electrolyte secondary battery.

Further, the non-aqueous electrolyte secondary battery of the present invention can be manufactured by the same process as the conventional one except that the process for manufacturing the positive electrode or the negative electrode is carried out as follows.

(Process for Producing Positive Electrode or Negative Electrode) (a) Resin that does not dissolve the lithium-containing composite oxide powder or the carbon material powder in both the non-aqueous solvent of the non-aqueous electrolyte and the solvent for dissolving the binder resin It is covered with a protective film consisting of. Specifically, the powder of the lithium-containing composite oxide or the powder of the carbon material is added to the solution of the resin that is insoluble in both the non-aqueous solvent of the non-aqueous electrolytic solution and the solvent for dissolving the binder resin, and the mixture is uniformly added. Disperse. The dispersion (slurry)
By spray-drying granulation with, the surface of the powder of the lithium-containing composite oxide or the powder of the carbon material can be coated with the protective film.

(B) Next, the powder coated with the protective film and the fluorine-based binder resin are mixed in a solvent for dissolving the binder resin by a conventional method to prepare a positive electrode mixture slurry or a negative electrode mixture slurry. .

(C) In the case of producing a spiral electrode, the positive electrode mixture slurry or the negative electrode mixture slurry is applied to the current collector by a coater, dried, and wound by a separator to form the electrode. Can be made. Further, in the case of producing a coin-type pellet electrode, the positive electrode mixture slurry or the negative electrode mixture slurry may be poured into a flat bat or the like, dried with hot air to be powdered, and press-molded.

The shape of the non-aqueous electrolyte secondary battery of the present invention described above is not particularly limited, and various shapes such as a cylindrical shape, a square shape, a coin shape, and a button shape may be used as necessary. Can be

[0040]

The present invention will be described below in more detail with reference to examples.

Example 1 (Preparation of Negative Electrode) Pitch coke was ground with a stainless ball having a diameter of 12.7 mm in a vibration mill for 15 minutes to prepare a carbon material having an average particle size of 33 μm. The true density of this carbon material was 2.03 g / cm ³ , and the true density was 002 by X-ray diffraction.
The interplanar spacing was 3.46 Å, and the crystal thickness Lc in the C-axis direction was 40 Å.

90 parts by weight of the obtained carbon material powder having an average particle diameter of 33 μm was dispersed in an aqueous solution in which 0.1 part by weight of PVA (molecular weight 10000) as a protective film forming resin was dispersed to obtain a powder. The dispersion is put into a spray dryer (manufactured by Sakamoto Giken) having a hot air temperature of 120 ° C. and dried to have an average particle size of 1
A nearly spherical spherical negative electrode active material powder having a size of 00 μm was obtained.

Next, 10 parts by weight of PVDF was mixed with 90 parts by weight of the obtained negative electrode active material powder, and N-methylpyrrolidone (NMP) was further added to prepare a negative electrode mixture slurry. A negative electrode mixture powder was obtained by opening in a vat and drying by blowing hot air at 120 ° C.
This negative electrode mixture powder was molded into a pellet-shaped negative electrode 1 having a diameter of 16 mm at a pressure of 5 ton / cm ² . The obtained negative electrode 1
Had a volume density (d) of 1.25 g / ml.

(Preparation of Positive Electrode) 0.5 mol of lithium carbonate and 1 mol of cobalt carbonate were mixed, and the mixture was mixed in air at 900 ° C.
LiCoO ₂ was obtained by firing for a time. This Li
CoO ₂ is crushed with a bowl mill to obtain L with an average particle size of 10 μm.
iCoO ₂ powder was obtained.

The obtained LiCoO ₂ having an average particle size of 10 μm
93.9 parts by weight of powder and graphite 6 as a conductive material
Parts by weight as a resin for forming a protective film (PVA (molecular weight 1
0000) 0.1 part by weight is dispersed in a dissolved aqueous solution, and the resulting dispersion is put into a spray dryer (manufactured by Sakamoto Giken) having a hot air temperature of 120 ° C. and dried to obtain an average particle size of 10
A substantially spherical positive electrode active material powder of 0 μm was obtained.

Next, P is added to the obtained positive electrode active material powder.
VDF (3 parts by weight) was mixed, and N-methylpyrrolidone was further added to prepare a positive electrode mixture slurry, which was dried by blowing hot air at 120 ° C. into a flat vat to obtain a positive electrode mixture powder. Obtained. This positive electrode material mixture powder was molded into a pellet-shaped positive electrode 2 having a diameter of 15.5 mm at a pressure of 5 ton / cm ² . The volume density (d) of the obtained positive electrode 2 was 3.5 g / ml.

(Preparation of coin type lithium ion non-aqueous electrolyte secondary battery) The obtained negative electrode 1 and positive electrode 2 were placed in a negative electrode battery can 4 via a separator 3 made of polypropylene nonwoven fabric, and then the negative electrode battery can. After injecting an electrolyte solution in which LiPF ₆ was dissolved at a ratio of 1 mol / 1 in a mixed solvent of propylene carbonate and dimethyl carbonate (1: 1 (volume ratio)) in 4, a positive electrode battery can was inserted through a sealing gasket 6. By crimping No. 5, coin type lithium ion non-aqueous electrolyte secondary battery (diameter 25 m as shown in FIG. 1
m, thickness 2.5 mm).

Examples 2 to 7 Coin type lithium ion non-aqueous electrolyte secondary batteries were prepared in the same manner as in Example 1 except that the amount of PVA shown in Table 1 was used.

Example 8 In the same manner as in Example 1 except that an emulsion containing 1.0 part by weight of PTFE (T-30J, manufactured by Mitsui Fluorochemicals Co., Ltd.) was used in place of the aqueous solution of PVA, coin type lithium ion non-ion was used. A water electrolyte secondary battery was produced.

Example 9 A coin type lithium ion non-aqueous electrolyte solution 2 was prepared in the same manner as in Example 1 except that a toluene solution containing 1.0 part by weight of polyethylene (PE) having a molecular weight of 10,000 was used in place of the PVA aqueous solution. A secondary battery was produced.

Example 10 Coin-type lithium ion non-aqueous electrolysis was carried out in the same manner as in Example 1 except that a toluene solution containing 1.0 part by weight of styrene-butadiene rubber (SBR) having a molecular weight of 10,000 was used in place of the PVA aqueous solution. A liquid secondary battery was produced.

Comparative Example 1 A coin type lithium ion non-aqueous electrolyte secondary battery was manufactured in the same manner as in Example 1 except that the positive electrode and the negative electrode manufactured as described below were used.

(Preparation of Positive Electrode) 1 part by weight of LiCoO _{2 having an} average particle size of 10 μm (without protective film) not covered with a protective film as in Example 1 and graphite 6 as a conductive material
Parts by weight and polyvinylidene fluoride (P
VDF) (3 parts by weight), and then N-methylpyrrolidone was added as a dispersant and mixed to prepare a positive electrode mixture slurry.

This slurry was placed in a flat vat and
It was dried by blowing warm air of 20 ° C. The obtained positive electrode mixture was pulverized to prepare a pellet-shaped positive electrode (volume density (d) = 3.5 g / ml) in the same manner as in Example 1.

(Preparation of Negative Electrode) Pitch coke powder having an average particle size of 33 μm and not covered with a protective film as in Example 1 (true density = 2.03 g / cm ³ , (002) surface spacing =
3.46 Å, C-axis direction crystal thickness Lc = 40
90 parts by weight) and 9 parts by weight of polyvinylidene fluoride (PVDF) as a binder,
Further, N-methylpyrrolidone was added as a dispersant and mixed to prepare a negative electrode mixture slurry.

This slurry is placed in a flat vat to
It was dried by blowing warm air of 50 ° C. The obtained negative electrode mixture was pulverized and a pellet-shaped negative electrode (volume density (d) = 1.25 g / ml) was produced in the same manner as in Example 1.

Comparative Example 2 A coin type lithium ion non-aqueous electrolyte solution was prepared in the same manner as in Example 1 except that a toluene solution containing 1.0 part by weight of butyl rubber (BR) having a molecular weight of 10,000 was used in place of the PVA aqueous solution. A secondary battery was produced.

(Evaluation) With respect to the non-aqueous electrolyte secondary batteries of Examples and Comparative Examples, the charge end voltage was 4.
Charging is performed at 20 V and a charging current of 1 mA, and then constant current discharging is performed at a discharging current of 1 mA or 5 mA up to an end voltage of 3.0 V. At this time, the discharging capacity (initial discharging capacity (mA
h)) was measured. Table 1 shows the results.

Next, after the same charge, the discharge capacity (discharge capacity after storage (mAh)) after standing for one month at room temperature was measured, and the capacity after storage when the initial discharge capacity was 100%. The retention rate was calculated. Table 1 shows the results.

[0060]

[Table 1] Protective film vs. NMP and protective film Discharge capacity (mAh) Capacity retention Example resin Resin solubility Soluble usage (wt%) Retention rate after initial storage (%) 1 PVA None 0.1 60.0 54.0 90 2 PVA None 0. 2 59.9 54.5 9 1 3 PVA None 0.5 59.7 54.9 9 2 4 PVA None 1.0 59.4 56.4 95 5 PVA None 2.0 58.8 56.4 96 6 PVA None 3.0 58.2 55.9 967 PVA None 5.0 57.0 54.2 95 8 No PTFE 1.0 59.4 56.4 959 9 PE swell 1.0 59.4 56.4 95 10 SBR swell 1.0 59.4 56.4 95 Comparative Example 1 − − − 60.0 51.0 85 2 BR dissolved 1.0 59.4 51.0 85

From the results shown in Table 1, in the case of the non-aqueous electrolyte secondary batteries of Examples 1 to 7, both the positive electrode active material and the negative electrode active material were NMP which was the non-aqueous solvent of the electrolytic solution and the binder dissolving resin. It can be seen that the capacity retention rate is significantly improved as compared with the battery of Comparative Example 1 which is a conventional non-aqueous electrolyte secondary battery which is not covered with PVA because it is coated with PVA insoluble in.

Similarly, in the case of the non-aqueous electrolyte secondary battery of Example 8 in which PTFE was used instead of PVA, the non-aqueous electrolyte secondary battery of Comparative Example 1 which was an uncoated conventional non-aqueous electrolyte secondary battery was also compared. It can be seen that the capacity retention rate is remarkably improved.

PE or SBR swelling in the non-aqueous solvent of the electrolytic solution and NMP which is a binder dissolving resin.
In the case of the non-aqueous electrolyte secondary batteries of Examples 9 and 10 in which the protective film was formed with, PE and SBR do not dissolve in the non-aqueous solvent of the electrolyte and NMP which is a binder-dissolving resin, and therefore the capacity retention ratio It can be seen that is significantly improved.

On the other hand, in the case of the non-aqueous electrolyte secondary battery of Comparative Example 2 in which the protective film is formed of BR which dissolves in the non-aqueous solvent of the electrolytic solution and NMP which is the binder dissolving resin,
It can be seen that the effect of forming the protective film is not obtained.

[0065]

According to the present invention, a non-aqueous electrolyte secondary battery using a lithium-containing composite oxide as a positive electrode active material and a carbon material capable of doping and dedoping lithium ions as a negative electrode active material. The storage characteristics relating to the discharge capacity can be improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a non-aqueous electrolyte secondary battery of the present invention.

[Explanation of symbols]

1 negative electrode, 2 positive electrode, 3 separator, 4 negative electrode battery can, 5 positive electrode battery can, 6 sealing gasket

Claims (7)

[Claims] 1. A positive electrode containing a lithium-containing composite oxide,
In a non-aqueous electrolyte secondary battery comprising a negative electrode containing a carbon material capable of doping and de-doping lithium ions, and a non-aqueous electrolyte solution obtained by dissolving a lithium salt electrolyte in a non-aqueous solvent,
The positive electrode or the negative electrode is a positive electrode mixture slurry obtained by mixing a powder of a lithium-containing composite oxide or a powder of a carbon material, each of which is coated with a protective film, and a fluorine-based binder resin in a solvent for dissolving a binder resin. Alternatively, the non-aqueous liquid is formed from a negative electrode mixture slurry, and the protective film is formed from a resin that is insoluble in both the non-aqueous solvent of the non-aqueous electrolytic solution and the solvent for dissolving the binder resin. Electrolyte secondary battery. 2. The non-aqueous electrolyte secondary battery according to claim 1, wherein both the positive electrode and the negative electrode each contain a powder of a lithium-containing composite oxide and a powder of a carbon material which are coated with a protective film. 3. The non-aqueous electrolyte secondary battery according to claim 1, wherein the protective film is polyvinyl alcohol or polytetrafluoroethylene. 4. The non-aqueous electrolyte secondary battery according to claim 3, wherein the fluorine-based binder resin is polyvinylidene fluoride. 5. The non-aqueous electrolyte solution according to claim 3, wherein the non-aqueous solvent of the non-aqueous electrolyte solution is a mixed solvent of cyclic carbonate and dialkyl carbonate, and the solvent for dissolving the binder resin is N-methylpyrrolidone. Next battery. 6. A positive electrode containing a lithium-containing composite oxide,
In a method for producing a non-aqueous electrolyte secondary battery comprising a negative electrode containing a carbon material capable of doping and dedoping lithium ions, and a non-aqueous electrolyte solution obtained by dissolving a lithium salt electrolyte solution in a non-aqueous solvent: ( a) a step of coating the lithium-containing composite oxide powder or the carbon material powder with a protective film made of a resin that is insoluble in both the non-aqueous solvent of the non-aqueous electrolyte and the solvent for dissolving the binder resin; (b) A step of preparing a positive electrode mixture slurry or a negative electrode mixture slurry by mixing the powder coated with a protective film and a fluorine-based binder resin in a solvent for dissolving the binder resin; and (c) positive electrode mixture slurry or negative electrode A method of manufacturing, comprising a step of forming a positive electrode or a negative electrode from a mixture slurry. 7. In step (a), a lithium-containing composite oxide powder or a carbon material powder is dispersed in a solution containing a resin for forming a protective film, and the resulting dispersion is spray-dried. The powder containing a lithium-containing composite oxide or the powder containing a carbon material is coated with a protective film by granulating.
The manufacturing method as described.