JPH09320638A - Nonaqueous secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the cycle characteristic of a nonaqueous secondary battery which has a positive electrode whose active material is a lithium-containing transition metal oxide, a negative electrode whose active material is a carbon material, an organic solvent type electrolyte, and a separator. SOLUTION: This battery has a positive electrode 1 whose active material is a lithium-containing transition metal oxide, a negative electrode 2 whose active material is a carbon material, an organic solvent type electrolyte 4, and a separator 5. In this case, for an infrared PAS spectrum on the side of the separator 3 opposite to the negative electrode 2, obtained through PAS (photoacoustic spectrometry) at a modulation frequency of 1.6kHz, the ratio of characteristic absorption peak intensity (photoacoustic signal intensity) in the vicinity of 1739cm<-1> to characteristic absorption peak intensity (photoacoustic signal intensity) in the vicinity of 2922cm<-1> is set to range from not less 0.001 to not more than 0.1.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a non-aqueous secondary battery, and more particularly to a non-aqueous secondary battery having excellent cycle characteristics.

[0002]

2. Description of the Related Art A non-aqueous secondary battery represented by a lithium secondary battery has a large discharge capacity, a high voltage and a high energy density, and therefore, there are great expectations for its development.

In this non-aqueous secondary battery, an organic solvent-based electrolytic solution in which a lithium salt is dissolved in an organic solvent is used, and lithium or a lithium alloy is used as a negative electrode active material.
When these negative electrode active materials are used, an internal short circuit is likely to occur, which causes deterioration of battery characteristics and has a problem in safety. Therefore, in place of lithium or a lithium alloy, use of a carbon material such as activated carbon or graphite as a negative electrode active material has been studied in JP-A-6-84515.

However, when the above carbon material is used, the electrolytic solution reacts with lithium on the surface of the carbon material,
There is a problem that retention (difference between charge capacity and discharge capacity) becomes large and it is difficult to obtain a battery having excellent cycle characteristics.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the problems in the conventional non-aqueous secondary battery as described above and to provide a non-aqueous secondary battery having excellent cycle characteristics.

[0006]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have utilized the information obtained by the reaction between the electrolytic solution on the surface of the carbon material of the negative electrode and lithium. It was found that a non-aqueous secondary battery having excellent cycle characteristics can be obtained by using a carbon material having the above characteristics as a negative electrode, and completed the present invention.

That is, the present invention provides a non-aqueous secondary battery having a positive electrode having a lithium-containing transition metal oxide as an active material, a negative electrode having a carbon material as an active material, an organic solvent-based electrolyte and a separator. 1.6 kHz PAS
Regarding the infrared PAS spectrum on the side of the separator facing the negative electrode obtained by the analytical method, the characteristic absorption peak intensity (photoacoustic signal intensity) of the product near 1739 cm ⁻¹ and 29
The non-aqueous secondary battery is characterized in that the ratio with respect to the characteristic absorption peak intensity (photoacoustic signal intensity) of the separator near 22 cm ⁻¹ is 0.001 or more and 0.1 or less.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The PAS analysis method referred to in the present invention means Photoacoustic Spectrosc.
OPS (photoacoustic spectroscopy), and this PAS analysis method is a method of irradiating a sample with intermittent light and finally detecting a periodic thermal change generated in the sample as a pressure change,
In-situ measurement is possible.

More specifically, first, when the modulated infrared light is absorbed by the sample, heat corresponding to the incident light is generated. The generated heat causes a pressure change in the surrounding gas layer, and this change is detected by the high-sensitivity microphone. Then, a spectrum similar to a normal infrared absorption spectrum is obtained by subjecting this to a Fourier transform.

In the present invention, the side of the separator facing the negative electrode is analyzed without PAS analysis of the carbon material itself of the negative electrode for the following reason. That is, many electrolytes are adsorbed on the surface of the carbon material of the negative electrode, and many peaks based on their functional groups overlap, so when peak intensity is quantified, each peak point overlaps and quantifies. While the error becomes large, almost no peaks other than the peaks due to the separator and the product on the carbon material surface are detected in the analytical peak of the separator,
This is because it is easy to consider.

According to the present invention, as a result of the measurement by the PAS analysis method, the peak intensity around 1739 cm ^-1 and 2922 by the PAS analysis method on the side of the separator facing the negative electrode are measured.
cm ^-1 ratio of the peak intensity in the vicinity of 1739cm ^-1 / 292
It was found that the cycle characteristics can be improved when 2 cm ⁻¹ is 0.001 or more and 0.1 or less.

In the present invention, the characteristic absorption peak of the infrared PAS spectrum obtained by PAS analysis measurement shifts to some extent (the peak position changes) depending on the battery system.
Therefore, the characteristic absorption peak intensity near 1739 cm ^-1 is 1
Among the characteristic absorption peaks in the range of 650 to 1800 cm ^-1 , they do not overlap with other peaks, no interaction is observed even if the amount of the product on the surface of the separator increases, and it can be distinguished from the peak of the separator. Say,
It is preferable to select the one having the maximum intensity from the peaks satisfying the condition of. The modulation frequency of 1.6 kHz is used because the peaks satisfying the conditions (1) to (3) can be most conspicuously confirmed.

In the present invention, the characteristic absorption peak near 1739 cm ⁻¹ is the ν out of the bonds constituting the product of the reaction between the electrolytic solution and lithium on the surface of the carbon material.
It is considered to be a peak based on stretching vibration of a C = O (ester) group. Since the functional group of the product exhibiting this characteristic absorption peak is considered to also contribute to ionic conduction, when a product having these functional groups is formed on the surface of the carbon material, the product is Prevents direct contact between the surface of the carbon material and the organic solvent of the electrolytic solution that inactivates the surface of the carbon material, and when lithium ions dope the carbon material, the reaction between the organic solvent of the electrolytic solution and lithium is suppressed. Therefore, it is considered that the cycle characteristics are improved.

The peak near 2922 cm ^-1 indicates the C--H bond of the separator material, and serves as a standard for measuring the amount of the product on the surface of the carbon material attached to the surface of the separator facing the negative electrode. It is a thing. That is,
As the characteristic absorption peak of the separator that becomes the reference,
Asymmetric stretching vibration of νC—H group near 2922 cm ⁻¹ is used. The characteristic absorption peak near 2922 cm ^{−1 of} this separator does not overlap with other peaks of 2800 to 3000 cm ⁻¹ , and no interaction is observed even if the amount of hydrocarbons in the separator is large. Of the peaks satisfying the above conditions, it is preferable to select the peak having the maximum intensity.

Therefore, in the present invention, the ratio of the characteristic absorption peak intensity near 1739 cm ^-1 and the characteristic absorption peak intensity near 2922 cm ^-1 obtained by PAS analysis is
It shows whether there are many products on the surface of the carbon material,
The characteristic absorption peak intensity of the product near 1739 cm ^-1 and 2
A large ratio with the characteristic absorption peak intensity of hydrocarbons in the separator near 922 cm ^-1 means that there are many products formed by the reaction of the electrolyte and lithium on the surface of the carbon material of the negative electrode. However, when the above peak intensity ratio is too large, the resistance increases due to the above products, and the cycle characteristics deteriorate.

On the other hand, the fact that the peak intensity ratio is small means that the amount of the product on the surface of the carbon material is small, and when the peak intensity ratio is too small, the electrolysis during the charge / discharge reaction by the product is caused. The effect of suppressing the reaction between the liquid and lithium is not sufficiently exhibited, and in this case also, the cycle characteristics deteriorate.

The inventors of the present invention conducted extensive studies on the relationship between the peak intensity ratio and the cycle characteristics, and as a result, 173
The characteristic absorption peak intensity of the product near 9 cm ^-1 and 2922
It has been found that the cycle characteristics can be improved when the ratio of the characteristic absorption peak intensity of hydrocarbon of the separator in the vicinity of cm ⁻¹ is 0.001 or more and 0.1 or less. If the peak intensity ratio is larger or smaller than the above range, as described above, the cycle characteristics are deteriorated, although the reasons are different.

Up to now, XP has been used to analyze the surface of the carbon material.
S (X-ray photoelectron spectroscopy) and FTIR / ATR (Fourier transform infrared attenuated total reflection) have been performed, but these are ex-situ extraction from the negative electrode.
Since it is a method of analysis under (outside the system) conditions, the measurement sample can be analyzed only in the oxidized state, and the reaction form between the electrolytic solution and lithium on the carbon material surface of the negative electrode in the battery can be directly confirmed. Therefore, it was not possible to obtain useful information regarding the cycle characteristics, but the P
According to the AS analysis method, the same condition as in the battery, in-
In situ conditions, the surface of the carbon material of the negative electrode can be analyzed, and by using this PAS analysis method, not the negative electrode itself but the side of the separator facing the negative electrode can be measured.
Information related to cycle characteristics can be derived.

In the present invention, the substance serving as the precursor of the negative electrode active material can be doped or dedoped with lithium ions, and examples thereof include pyrolytic carbons, cokes, glassy carbons and organic polymers. A compound fired body, mesocarbon microbeads, carbon fiber, activated carbon and the like can be used. The carbon material used as the negative electrode active material in the present invention is obtained by carbonizing each of the substances listed above.

In the present invention, various methods are conceivable as a method for producing a carbon material surface having a predetermined peak intensity ratio by the PAS analysis method. For example, carbon dioxide is bubbled in the electrolytic solution or liquid carbon dioxide is used. Although a method of dissolving carbon can be used, it is difficult to control these so that the film thickness becomes constant.

Therefore, as a result of various investigations, the present inventors have found that the simplest and most inexpensive method is as follows.
It has been found that a carbon material that can serve as the negative electrode active material of the present invention can be produced by subjecting a battery to aging.

Explaining this aging, first, the produced battery is subjected to CVCC charging (constant current and constant voltage charging) at a low rate. The state of charge of the battery at that time is preferably 30 to 100% charged, and particularly preferably 60 to 100% charged.

Then, the battery in this charged state is
It is stored in a temperature range of 80 ° C., preferably 40 to 70 ° C. for a predetermined time. This is because if the temperature is lower than 30 ° C., the temperature is too low, so that it becomes difficult to generate a certain amount of product on the surface of the carbon material, and if the temperature is higher than 80 ° C., decomposition of the electrolytic solution is likely to occur. Because it will be. And
By such aging, a carbon material surface suitable for charging and discharging can be prepared.

In the present invention, examples of the positive electrode active material include lithium nickel oxide, lithium manganese oxide and lithium cobalt oxide (these are usually represented by LiNiO ₂ , LiMnO ₂ and LiCoO ₂ , respectively, The ratio of these Li and Ni, the ratio of Li and Mn, L
The ratio of i to Co is often deviated from the stoichiometric composition) and the like, and a lithium-containing transition metal oxide is used alone or as a mixture of two or more kinds.

Then, the positive electrode contains, if necessary, a conductive auxiliary agent such as phosphorus (scaly) graphite, acetylene black or carbon black, and, for example, polyvinylidene fluoride or polytetrafluoroethylene. , A positive electrode mixture prepared by adding a binder such as ethylene propylene diene terpolymer is pressure-molded, or a solvent is further added to form a paste, which is then formed into a metal foil (for example, aluminum foil, titanium foil, platinum foil, etc.). ) Is applied to a current collector made of, for example, and dried. However, the method for producing the positive electrode is not limited to the above-described example.

In the present invention, in the negative electrode, if necessary, a binder such as polyvinylidene fluoride, polytetrafluoroethylene, ethylene propylene diene terpolymer, etc. is appropriately added to the above-mentioned substance as the negative electrode active material precursor, The negative electrode mixture prepared by mixing is pressure-molded, or a solvent is further added to form a paste, and the paste is a metal foil (eg, copper foil, nickel foil, etc.)
It is produced by incorporating an electrode body produced through a process of coating and drying on a current collector made of, for example, into a battery and aging it so that the carbon material has a specific peak intensity ratio. However, the manufacturing method of the electrode body as the precursor of the negative electrode is not limited to the method exemplified above.

The electrolytic solution is prepared by dissolving an electrolyte in an organic solvent. At that time, it is preferable to use an ester having a high dielectric constant or an ether or an ester having a low viscosity.

Examples of the ester having a high dielectric constant include, for example,
Propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), gamma-
Butyrolactone (γ-BL) and the like can be mentioned.

Examples of ethers having a low viscosity include, for example,
1,2-dimethoxyethane (DME), dioxolane (DO), tetrahydrofuran (THF), 2-methyl-tetrahydrofuran (Me-THF), diethyl ether (DEE) and the like can be mentioned. Examples of low-viscosity esters include methyl ethyl carbonate (ME
C), diethyl carbonate (DEC) and the like.

In addition, imide type organic solvents, sulfur-containing or fluorine-containing organic solvents, trialkyl phosphates and the like can be used.

In the present invention, as the electrolyte of the electrolytic solution, for example, LiClO ₄ , LiPF ₆ , LiBF ₄ ,
LiAsF ₆ , LiSbF ₆ , LiCF ₃ SO ₃ , Li
CF ₃ CO _2, etc., and other Li ₂ C ₂ F ₄ (S
O ₃ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃
SO ₂ ) ₃ , LiC _n F _{2n + 1} SO ₃ (n ≧ 2) and the like are used alone or in combination of two or more. Among them, LiPF ₆ and LiC _n F _{2n + 1} SO ₃ (n ≧ 2) are preferably used because of good charge / discharge characteristics. The concentration of these electrolytes in the electrolytic solution is not particularly limited, but is usually 0.1 to 2 mol / l, particularly 0.4 to 1.4 m.
ol / l is preferred.

[0032]

Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to only those examples.

Example 1 As a negative electrode active material precursor, carbon microbeads extracted from petroleum pitch were heat-treated at 3000 ° C., and bulk carbon was pulverized to prepare a powder having an average particle size of 10 μm.
The interlayer distance d ₀₀₂ of this powder was 3.36Å, and the crystallite size Lc in the c-axis direction was 1334Å. 9 parts by weight of this powder and polyvinylidene fluoride 1 as a binder
By weight, N-methyl-2-pyrrolidone is used as a solvent to prepare a negative electrode mixture slurry, which is evenly applied on both surfaces of a negative electrode current collector made of strip-shaped copper foil and dried, and then by a roller press. It was compression-molded and the lead body was welded to produce a strip-shaped electrode body as a precursor of the negative electrode.

Next, 90 parts by weight of LiCoO ₂ was mixed with 6 parts of graphite.
Parts by weight and 4 parts by weight of polyvinylidene fluoride are added and mixed,
It was dissolved with N-methylpyrrolidone to form a slurry. This positive electrode mixture slurry is uniformly applied to both sides of a positive electrode current collector made of an aluminum foil having a thickness of 20 μm, dried, and then compression-molded by a roller press machine to weld a lead body to form a strip-shaped positive electrode. Was produced.

After the strip-shaped electrode body as a precursor of the negative electrode was superposed on the strip-shaped positive electrode through a separator made of a microporous polyethylene film having a thickness of 25 μm and spirally wound into a spiral electrode body, Outer diameter 15 mm, height 40 mm
The battery was filled in a cylindrical battery case having a bottom and the lead bodies of the positive and negative electrode bodies were welded, and then the electrolytic solution was injected into the battery case.

The above-mentioned electrolytic solution was prepared by dissolving LiPF ₆ in ethyl methyl carbonate and then adding and mixing ethylene carbonate. LiPF ₆ was prepared by mixing ethylene carbonate (EC) and ethyl methyl carbonate (M
EC) in a mixed solvent with a volume ratio of 1: 1 is 1.0 mol /
1 is a dissolved organic solvent-based electrolytic solution. The composition of this electrolytic solution is represented by 1.0 mol / l LiPF ₆ / EC: MEC (volume ratio 1: 1).

Then, the opening of the battery case was sealed according to a conventional method to produce a cylindrical non-aqueous secondary battery having the structure shown in FIG.

Explaining the battery shown in FIG. 1, 1 is the positive electrode and 2 is the negative electrode. However, in FIG. 1, in order to avoid complication, the current collector and the like used in manufacturing the positive electrode 1 and the negative electrode 2 are not shown. 3 is a separator, and 4 is an electrolytic solution.

5 is a battery case made of stainless steel,
This battery case 5 also serves as a negative electrode terminal. An insulator 6 made of a polytetrafluoroethylene sheet is arranged at the bottom of the battery case 5, and an insulator 7 made of a polytetrafluoroethylene sheet is also arranged at the inner periphery of the battery case 5. The spiral electrode body composed of the negative electrode 2 and the separator 3, the electrolyte 4, and the like are accommodated in the battery case 5.

Reference numeral 8 is a stainless steel sealing plate, and a gas vent hole 8a is provided at the center of the sealing plate 8. Reference numeral 9 denotes an annular packing made of polypropylene, reference numeral 10 denotes a flexible thin plate made of titanium, and reference numeral 11 denotes an annular, thermally deformable member made of polypropylene.

The thermal deformation member 11 acts to change the breaking pressure of the flexible thin plate 10 by being deformed by the temperature.

Reference numeral 12 is a nickel-plated terminal plate made of rolled steel. The terminal plate 12 is provided with a cutting edge 12a and a gas discharge hole 12b. When the internal pressure rises and the flexible thin plate 10 is deformed due to the increase in the internal pressure, the cutting blade 12a breaks the flexible thin plate 10 to discharge the gas inside the battery from the gas discharge hole 12b to the outside of the battery. In addition, the battery is designed to be prevented from being broken under high pressure.

Reference numeral 13 is an insulating packing, and 14 is a lead body. This lead body 14 electrically connects the positive electrode 1 and the sealing plate 8, and the terminal plate 12 comes into contact with the sealing plate 8 to make a positive electrode terminal. Acts as. Reference numeral 15 is a lead body that electrically connects the negative electrode 2 and the battery case 5.

After charging this battery at 0.2C for 8 hours,
It was stored at 60 ° C. for 10 hours and aged. After discharging this battery, the battery was decomposed in an argon atmosphere in a glove box (dew point temperature of -40 ° C or lower), the separator was washed with ethyl methyl carbonate, vacuum dried, and sampled and sealed in a PAS cell. After that, FT the PAS cell
The sample was set in the -IR sample chamber, the inside of the PAS cell was replaced with He (helium), and FT-IR analysis was performed on the negative electrode side of the separator.

The PAS analysis conditions are as shown in Table 1 below.

[0046]

[Table 1] * 1: Made by Mattson, USA * 2: Made by MTEC, USA

The infrared PAS spectrum of the side of the separator facing the negative electrode obtained by PAS analysis and measurement under the above conditions for the battery of Example 1 is shown in FIG. Also,
The detail of the A portion of FIG. 2 is enlarged and shown in FIG.

As shown in these figures, the position of the characteristic absorption peak of the product on the carbon material surface of the negative electrode was 1739 cm ^-1.
The position of the characteristic absorption peak of the polyethylene separator is 2922 cm ^-1 , and the peak intensity ratio is 17
The value of 39cm ^-1 / 2922cm ^-1 was 0.0136.

Example 2 A sample was prepared in the same manner as in Example 1 except that instead of aging under the condition of 60 ° C. for 10 hours in Example 1, the sample was stored at 45 ° C. for 10 hours and aged. ,
PAS analysis was performed. As a result, the position of the characteristic absorption peak and separator characteristic absorption peak of the product of the negative electrode carbon material surface of this second embodiment, both the same as in Example 1, the peak intensity ratio 1736cm ^-1 / 2922cm ^{- 1}
The value of was 0.0086.

Example 3 A sample was prepared in the same manner as in Example 1 except that aging was carried out by storing at 60 ° C. for 10 hours instead of aging at 60 ° C. for 10 hours in Example 1. ,
PAS analysis was performed. As a result, the position of the characteristic absorption peak and separator characteristic absorption peak of the product of the negative electrode carbon material surface of this third embodiment, both the same as in Example 1, the peak intensity ratio 1737cm ^-1 / 2922cm ^{- 1}
The value of was 0.0871.

Example 4 As an electrolytic solution, LiPF ₆ was added to diethyl carbonate (D
EC) and then ethylene carbonate (EC)
Was added and mixed to prepare a composition of 1.0 mol / l L
A sample was prepared in the same manner as in Example 1 except that an organic solvent-based electrolytic solution represented by iPF ₆ / EC: DEC (volume ratio 1: 1) was used, and PAS analysis was performed. As a result, the position of the characteristic absorption peak of the product on the carbon material surface of the negative electrode of Example 4 was 1738 cm ⁻¹ , and the peak intensity ratio was 17
The value of 38cm ^-1 / 2922cm ^-1 was 0.0082.

Example 5 Instead of LiPF ₆ as the electrolyte, C ₄ F ₉ SO ₃ Li was used.
A sample was prepared in the same manner as in Example 1 except that was used, and PAS analysis was performed. As a result, the position of the characteristic absorption peak of the product on the carbon material surface of the negative electrode of Example 5 was 1
Is 740 cm ^-1, the peak intensity ratio 1740 cm ^-1 / 2
The value at 922 cm ^-1 was 0.0075.

Example 6 As a negative electrode active material precursor, coke heat-treated at 1200 ° C. was pulverized to prepare a powder of 10 μm. The interlayer distance d ₀₀₂ of this powder was 3.43Å, and the crystallite size Lc in the c-axis direction was 32Å. A sample was prepared in the same manner as in Example 1 except that this powder was used, and PAS analysis was performed.

As a result, the position of the characteristic absorption peak of the product on the carbon material surface of the negative electrode of Example 6 was 1735 cm ^-1.
And the peak intensity ratio is 1735 cm ^-1 / 2922 cm ^-1
The value of was 0.0125.

Example 7 A sample was prepared in the same manner as in Example 1 except that a microporous polypropylene film was used as the separator.
S analysis was performed. As a result, the position of the characteristic absorption peak of the product on the carbon material surface of the negative electrode of Example 7 was 1680c.
m ⁻¹ , and the position of the characteristic absorption peak of the separator is 28
70 cm ^-1 , with a peak intensity ratio of 1680 cm ^-1
The value of / 2870 cm ^-1 was 0.0035.

Comparative Example 1 A sample was prepared in the same manner as in Example 1 except that aging was performed by storing at 80 ° C. for 20 days instead of aging at 60 ° C. for 10 hours in Example 1. ,
PAS analysis was performed. As a result, the position of the characteristic absorption peak and separator characteristic absorption peak of the product of the negative electrode carbon material surface of Comparative Example 1, both the same as in Example 1, the peak intensity ratio 1737cm ^-1 / 2922cm ^{- 1}
The value of was 0.2551.

Comparative Example 2 A sample was prepared in the same manner as in Example 1 except that instead of aging under the condition of 60 ° C. for 10 hours in Example 1, the sample was stored at 25 ° C. for 10 hours and aged. ,
PAS analysis was performed. As a result, the position of the characteristic absorption peak and separator characteristic absorption peak of the product of the negative electrode carbon material surface in Comparative Example 2, both the same as in Example 1, the peak intensity ratio 1739cm ^-1 / 2922cm ^{- 1}
Was 0.0005.

The batteries of Examples 1 to 7 and Comparative Examples 1 and 2 were charged and discharged at a voltage of 2.7 to 4.2 V at 0.5 C, and the discharge capacity dropped to 95% of the initial discharge capacity. The number of cycles to do was examined. The number of cycles and the peak intensity ratio (for the infrared PAS spectrum of the side of the separator facing the negative electrode, obtained by PAS analysis measurement: 1
Characteristic absorption peak intensity around 739 cm ^-1 and 2922 cm
Table 2 shows the relationship with the characteristic absorption peak intensity near ^-1 ).

[0059]

[Table 2]

As shown in Table 2, the peak intensity ratio, that is, the infrared PAS spectrum of the side of the separator facing the negative electrode obtained by PAS analysis measurement was 1739.
cm ^-1 ratio of the characteristic absorption peak intensity and 2922cm ^-1 characteristic absorption peak intensity near the vicinity is within the range of 0.001 to 0.1 Examples 1 to 7, the peak intensity ratio is outside the above range Compared with Comparative Examples 1 and 2, the number of cycles (the number of cycles until the discharge capacity decreased to 95% of the initial discharge capacity) was large, and the cycle characteristics were excellent.

That is, also in Comparative Example 1 in which the peak intensity ratio is larger than 0.1, the peak intensity ratio is 0.001.
The smaller Comparative Example 2 also had a smaller number of cycles than Examples 1 to 7 and did not have sufficient cycle characteristics.

[0062]

INDUSTRIAL APPLICABILITY As described above, the present invention provides a non-aqueous electrolyte having a positive electrode having a lithium-containing transition metal oxide as an active material, a negative electrode having a carbon material as an active material, an organic solvent-based electrolyte and a separator. In the secondary battery, the infrared PAS on the side facing the negative electrode of the separator obtained by PAS analysis measurement
For spectrum, by a 0.001 to 0.1 the ratio of the characteristic absorption peak intensity at around the characteristic absorption peak intensity and 2922cm ^-1 in the vicinity of 1739cm ^-1,
It was possible to provide a non-aqueous secondary battery having excellent cycle characteristics.

[Brief description of drawings]

FIG. 1 is a cross-sectional view schematically showing an example of a non-aqueous secondary battery of the present invention.

2 is a modulation frequency of 1.6 k for the battery of Example 1. FIG.
It is a figure which shows the infrared PAS spectrum of the side which opposes the negative electrode of the separator obtained by PAS analysis measurement of Hz.

FIG. 3 is an enlarged view of part A of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Negative electrode 3 Separator 4 Electrolyte

Claims (1)

[Claims] 1. A non-aqueous secondary battery having a positive electrode using a lithium-containing transition metal oxide as an active material, a negative electrode using a carbon material as an active material, an organic solvent-based electrolyte and a separator at a modulation frequency of 1.6 kHz. PAS (photoacoustic spectroscopy)
Regarding the infrared PAS spectrum of the side of the separator facing the negative electrode obtained by analytical measurement, the characteristic absorption peak intensity (photoacoustic signal intensity) near 1739 cm ^-1 and 2922c
A non-aqueous secondary battery having a ratio with a characteristic absorption peak intensity (photoacoustic signal intensity) in the vicinity of m ⁻¹ of 0.001 or more and 0.1 or less.