JP6287108B2 - Non-aqueous electrolyte secondary battery for X-ray analysis - Google Patents

Description

  The present invention relates to a non-aqueous electrolyte secondary battery, and more particularly to a non-aqueous electrolyte secondary battery for X-ray analysis suitable for grasping the internal state of the battery using X-ray analysis.

In recent years, non-aqueous electrolyte secondary batteries, particularly lithium secondary batteries, have attracted attention as power sources for portable devices such as mobile phones, PHS (simple mobile phones), small computers, power storage power sources, and electric vehicle power sources. .
This non-aqueous electrolyte secondary battery is generally composed of a positive electrode having a positive electrode active material as a main component, a negative electrode having a negative electrode active material as a main component, and a non-aqueous electrolyte. There are an external hard pack type and a soft pack type (laminate cell) externally covered with an aluminum laminate film.

As a positive electrode active material constituting such a nonaqueous electrolyte secondary battery, a lithium-containing transition metal oxide typified by lithium cobaltate is used, and a carbonaceous material typified by graphite (graphite) is used as the negative electrode active material. Is obtained by dissolving an electrolyte salt typified by lithium hexafluorophosphate (LiPF ₆ ) in a non-aqueous electrolyte in which a high-melting-point solvent ethylene carbonate and a low-melting-point solvent diethyl carbonate are combined. Widely used.

By the way, in advancing battery research, it is important to elucidate the charging / discharging mechanism of the battery, and many studies have been made on the analysis method therefor.
As an analysis method for elucidating the charge / discharge mechanism, Ex-Situ analysis, in which a battery is disassembled and a constituent material such as a positive electrode is taken out and analyzed, has been the mainstream analysis method up to now.
However, in recent years, attention has been focused on an analysis method of In-Situ analysis in which various analyzes are performed while charging and discharging without disassembling the battery.

In the analysis using this In-Situ analysis, analysis using X-rays is an effective analysis method for elucidating the mechanism. However, in a battery used for normal research, a material that blocks X-rays such as metal is used in a member itself constituting the battery (for example, Patent Document 1).
When the battery is made of such a material that blocks X-rays, the X-rays cannot be sufficiently transmitted, and there remains a problem in the analysis accuracy when performing in-situ analysis.

JP 2012-119093 A

  Therefore, in view of the above problems, the present invention provides a non-aqueous electrolyte secondary battery that can improve X-ray permeability, and can be easily and inexpensively manufactured with high accuracy and high reliability. For the purpose.

  As a result of intensive studies on a battery capable of obtaining high analytical accuracy when evaluating a positive electrode active material using X-rays, the present inventors have determined the X-ray permeability of the constituent materials of the battery and the structure in which each material is used. Obtaining the knowledge that the X-ray permeability of the battery is improved and the analysis accuracy is improved by the change, and the present invention has been completed.

That is, the first invention according to the present invention is an X-ray composed of at least a positive electrode and a negative electrode arranged opposite to each other with a separator, and a non-aqueous electrolyte and a battery container containing the positive electrode, the negative electrode, and the non-aqueous electrolyte. An analytical non-aqueous electrolyte secondary battery, wherein at least a part of the negative electrode is made of metal lithium or lithium alloy having a thickness of 0.5 to 2.0 mm, which is a material capable of transmitting X-rays, At least a portion of the battery container is made of a laminate made of only an organic resin film having a thickness of 0.2 mm or less, which is a material that can transmit X-rays, and is made of a material that can transmit X-rays of the negative electrode. Arranged in the battery container so that the part and the part of the battery container made of X-ray transmissive material are aligned on the X-ray irradiation path in the X-ray analysis. A non-aqueous electrolyte for X-ray analysis comprising an electric current collector capable of electrical continuity with the outside of the battery on at least a part of the outer periphery of the negative electrode that does not interfere with the path of irradiated X-rays in the negative electrode. Next battery.

  A second invention of the present invention is a non-aqueous electrolyte secondary battery for X-ray analysis, characterized in that the current collector in the first invention is arranged on the entire outer periphery of the negative electrode.

  According to a third aspect of the present invention, the negative electrode current collector in the first and second aspects is selected from one metal selected from the group consisting of Cu, Fe, and Ni, or from the above group A non-aqueous electrolyte secondary battery for X-ray analysis, which is an alloy of two or more metals.

  According to a fourth aspect of the present invention, there is provided a non-aqueous electrolyte secondary battery for X-ray analysis, wherein the negative electrode current collector is made of Cu and the positive electrode current collector is made of Al. It is.

In a fifth aspect of the present invention, the oxygen permeability of the organic resin film in the first aspect is 5 ml / (m ² · 24 hr · MPa) or less, and the water vapor permeability is 0.5 g / (m ² · d ) A non-aqueous electrolyte secondary battery for X-ray analysis characterized by the following.

  According to the present invention, it is possible to manufacture a battery with improved X-ray permeability. Therefore, X-ray analysis with high accuracy and high reliability can be easily and inexpensively measured. The value is extremely great.

It is the schematic which shows the structure of the laminate cell battery 10 used in the Example, (a) is the schematic of the battery structure seen from the positive electrode side, (b) is the schematic of the battery structure seen from the negative electrode side. It is the a-a 'line sectional view of Drawing 1 showing the structure of lamination cell battery 10 used in the example.

The non-aqueous electrolyte secondary battery for X-ray analysis according to the present invention (hereinafter sometimes simply referred to as “battery”) has a positive electrode and a negative electrode containing a positive electrode active material made of a lithium transition metal composite oxide via a separator. The nonaqueous electrolyte secondary battery is disposed so as to face each other and is covered with a battery container.
This battery has a negative electrode made of a material at least partially transparent to X-rays. In general, a negative electrode in which a negative electrode active material such as graphite is laminated on a copper foil is used. However, when a material having low X-ray transmission such as copper is used, X-rays do not pass and X-ray analysis becomes difficult. .

For this reason, in a non-aqueous electrolyte secondary battery for X-ray analysis, a portion that transmits irradiated X-rays during X-ray analysis is made of a material that can transmit X-rays.
The X-ray transmissive material is preferably lithium or lithium metal. Lithium can be used as a negative electrode active material and has conductivity. Therefore, it is not necessary to arrange an electric current collector on the entire surface of the negative electrode, and it is sufficient even if there is no electric current collector in a portion that transmits X-rays. Can be made to act as a negative electrode.

Furthermore, since the negative electrode needs to be electrically connected to the outside, it is preferable to arrange the electric current collector on a part of the outer periphery that does not interfere with the X-ray path. By attaching a lead wire or the like to the current collector, electrical continuity with the outside is efficiently performed.
The position where the current collector is stacked may be a position that does not interfere with the X-ray path of the irradiated X-ray, but is stacked at least on a part of the outer periphery of the negative electrode in order to maintain a high degree of freedom in X-ray measurement. It is preferable. Furthermore, in order to improve electrical conductivity, it is preferable to arrange | position to the whole outer peripheral part of a negative electrode.

Here, the negative electrode current collector is preferably one kind of metal selected from the group consisting of Cu, Fe, and Ni, or an alloy of two or more kinds of metals selected from the group. By using these metals or alloys, embrittlement of the current collector due to lithium doping is suppressed, and charging and discharging can be repeated.
Further, the positive electrode also requires an electric current collector to ensure electrical continuity with the outside, and it is desirable to use Al as the electric current collector.
By attaching a lead wire or the like to the current collector, electrical continuity with the outside can be efficiently performed. Further, the aluminum constituting the positive electrode preferably has a thickness of 40 μm or less so as not to prevent X-ray transmission.

  Therefore, the configuration of the electric current collector in the electrode of the non-aqueous electrolyte secondary battery for X-ray analysis is preferably a combination in which the negative electrode current collector is made of Cu and the positive electrode current collector is made of Al. Thereby, the electrical conductivity of a collector is high and the battery excellent in charging / discharging efficiency is obtained.

Next, in the non-aqueous electrolyte secondary battery for X-ray analysis according to the present invention, at least a part of the battery container is made of a material capable of transmitting X-rays, like the negative electrode.
Since a metal battery container is difficult to transmit X-rays, X-ray analysis can be performed by changing a part thereof to a material that can transmit X-rays.
For example, light metal foil such as beryllium or aluminum, resin, glass, or the like is used as the X-ray transmissive material. However, since changing the material of the battery container is costly, it is preferable to use a laminated cell as the battery container.

  The laminate generally used as a battery container is laminated with an aluminum foil, but can transmit X-rays. Furthermore, in order to increase the X-ray transmittance and improve the accuracy of X-ray analysis, the laminate is preferably made of only an organic resin film. As the organic resin, polyethylene terephthalate (PET), nylon, or the like is mainly used. However, the material is not particularly limited as long as the hermeticity in the battery is ensured.

In the case of using a laminate composed only of an organic resin film, the oxygen permeability of the organic resin film is 5 ml / (m ² · 24 hr · MPa) or less and the water vapor permeability is 0.5 g / (m) in order to prevent deterioration of the battery. ² · d) or less.
When the oxygen permeability is 5 ml / (m ² · 24 hr · MPa) and the water vapor permeability exceeds 0.5 g / (m ² · d), oxygen and moisture that have entered the battery react with the non-aqueous electrolyte. This may cause deterioration of the electrolyte and generation of gas, which may significantly impair battery performance. Here, the organic resin film may be surface-treated with a ceramic or the like within a range not deteriorating the X-ray permeability in order to improve oxygen permeability and water vapor permeability. The thickness of the laminate made of this organic resin film is preferably 0.2 mm or less so as not to prevent the transmission of X-rays.

Furthermore, it is important that the portions made of a material that can transmit X-rays are arranged in a straight line on the X-ray path of irradiated X-rays.
In such a state, a path through which irradiated X-rays can be transmitted is ensured. As a result, the X-ray transmittance is improved, and a highly accurate non-aqueous electrolyte secondary battery for X-ray analysis can be obtained.
Hereinafter, the non-aqueous electrolyte secondary battery for X-ray analysis of the present invention will be clarified while explaining the respective configurations of the battery.

(1) Positive electrode First, the positive electrode mixture which forms a positive electrode, and each material which comprises it are demonstrated.
As a material constituting the positive electrode, a material constituting a general battery is used. Specifically, it is composed of at least a positive electrode active material, a conductive material, and a binder, and other materials can be added as necessary to improve or stabilize battery performance.

The mixing ratio of the respective materials in the positive electrode mixture is also an important factor that determines the performance of the nonaqueous electrolyte secondary battery. When the total mass of the solid content of the positive electrode mixture is 100 parts by mass, the content of the positive electrode active material is 60 to 95 parts by mass, and the content of the conductive material is the same as the positive electrode of a general non-aqueous electrolyte secondary battery. 1 to 20 parts by mass and the binder content is preferably 1 to 20 parts by mass.
The above materials are mixed to obtain a positive electrode mixture. The obtained positive electrode mixture may be pressed by a roll press or the like to increase the electrode density as necessary. In this way, a sheet-like positive electrode can be produced. The sheet-like positive electrode can be cut into an appropriate size according to the intended battery and used for battery production.

In producing this positive electrode, as the positive electrode active material, for example, a lithium transition metal composite oxide such as LiCoO ₂ , LiNiO _2, or LiMn ₂ O ₄ is used.
In addition, in the non-aqueous electrolyte secondary battery for X-ray analysis, the positive electrode active material contained in the positive electrode is controlled in the range of 5 to 10 mg / cm ² , thereby providing an excellent balance of X-ray transmittance and absorption rate. When used for X-ray analysis of an active material, high analysis accuracy is obtained.
If the positive electrode active material is produced with a basis weight of less than 5 mg / cm ² , the X-ray absorption rate is too low, which hinders analysis accuracy. If the basis weight is 10 mg / cm ² or more, the absorption of X-rays is too large, and the X-rays may be blocked. Therefore, preferably by controlling the positive electrode active material in the range of 5 to 10 mg / cm ^2, and even more preferably from 7 mg / cm ^2.

  In the non-aqueous electrolyte secondary battery for X-ray analysis, the thickness of the positive electrode, excluding the current collector, is preferably about 0.01 to 0.05 mm in order to increase the X transmittance for X-ray analysis. Is preferably small.

  Examples of the conductive agent used include graphite (natural graphite, artificial graphite, expanded graphite, etc.), carbon black materials such as acetylene black and ketjen black. As the binder, for example, polyvinylidene fluoride, polytetrafluoroethylene, ethylene propylene diene rubber, fluororubber, styrene butadiene, cellulose resin, polyacrylic acid, and the like can be used.

  In addition, the binder plays a role of holding the active material particles. For example, a fluorine-containing resin such as polytetrafluoroethylene, polyvinylidene fluoride, or fluororubber, or a thermoplastic resin such as polypropylene or polyethylene may be used. it can. Activated carbon can be added to the positive electrode mixture to increase the electric double layer capacity.

(2) Negative electrode As shown above, it is preferable to use metallic lithium or a lithium alloy for the negative electrode. Since these have strength and conductivity capable of constituting an electrode, an electric current collector can be eliminated in a portion that transmits X-rays.
The lithium metal or lithium alloy constituting the negative electrode preferably has a thickness in the range of 0.5 to 2.0 mm so as not to prevent X-ray transmission.

(3) Separator A separator is interposed between the positive electrode and the negative electrode.
This separator has functions such as insulation between the positive electrode and the negative electrode, and also holds an electrolytic solution, and those used in general non-aqueous electrolyte secondary batteries can be used. For example, a separator having a necessary function such as a porous film such as polyethylene (PE), polypropylene (PP), or a laminate thereof may be used as a separator used in a general non-aqueous electrolyte secondary battery. For example, there is no particular limitation.

(4) Non-aqueous electrolyte The non-aqueous electrolyte is obtained by dissolving a lithium salt as an electrolyte in an organic solvent. Examples of the organic solvent include cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, and trifluoropropylene carbonate; chain carbonates such as diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, and dipropyl carbonate; and tetrahydrofuran, 2- One kind selected from ether compounds such as methyltetrahydrofuran and dimethoxyethane, sulfur compounds such as ethylmethylsulfone and butanesultone, phosphorus compounds such as triethyl phosphate and trioctyl phosphate, etc. are used alone or in admixture of two or more. be able to.

As the electrolyte, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiN (CF ₃ SO ₂ ) ₂ , and complex salts thereof can be used. Furthermore, the non-aqueous electrolyte solution may contain a radical scavenger, a surfactant, a flame retardant, and the like.

(5) Configuration of Battery The positive electrode and negative electrode described above are laminated through a separator to form an electrode body, and this electrode body is impregnated with the non-aqueous electrolyte. Each of the positive electrode and the negative electrode is connected to an external terminal to conduct. The non-aqueous electrolyte secondary battery for X-ray analysis can be completed by sealing the above structure with an organic resin laminate as a battery container.

  Hereinafter, the non-aqueous electrolyte secondary battery for X-ray analysis according to the present invention will be further described with reference to examples.

The laminated cell battery 10 of the non-aqueous electrolyte secondary battery for X-ray analysis which concerns on Example 1 shown in FIGS. 1 and 2 was produced, and the X-ray transmittance was verified.
1A is a schematic diagram of a battery structure viewed from the positive electrode side, and FIG. 1B is a schematic diagram of the battery structure viewed from the negative electrode side. 1 and 2, 1 is a positive electrode, 2 is a separator, 3 is a negative electrode, 4 is a laminate (battery container), 5 is a tab lead, 6c is an electric current collector (positive electrode), 6a is an electric current collector (negative electrode), 7 is a sealing agent (for example, thermocompression bonding agent) that seals between the laminate (battery container) and the tab lead, and the “open arrow” in FIG. 2 indicates the X-ray irradiation direction.

As the negative electrode 3, metal lithium having a thickness of 2 mm is used, and a Cu current collector (negative electrode) 6 a is disposed as shown in FIGS. 1 and 2, and the positive electrode 1 has LiNi _0.82 Co _{0. 15} Al _0.03 O ₂ and aluminum foil with a thickness of 20 μm were used for the current collector (positive electrode) 6c, respectively, and the laminate 4 to be packaged had a thickness of 0.1 mm and an oxygen permeability of 5 ml / (m ² · 24hr · MPa), the water vapor permeability using an organic resin film of ^{0.5g / (m 2 · d)} . X-ray transmittance was measured with an X-ray output of 8 keV.
The X-ray transmittance was 90%, and good results with high transmittance were obtained.

Other than using an aluminum laminate film having a thickness of 0.1 mm, an oxygen transmission rate of 5 ml / (m ² · 24 hr · MPa), and a water vapor transmission rate of 0.5 g / (m ² · d) for the laminated laminate 4 Produced a laminated cell battery 10 according to Example 2 in the same manner as in Example 1, and measured the X-ray transmittance.
The X-ray transmittance was 84%, and good results with high transmittance were obtained.

(Comparative Example 1)
A laminate cell of Comparative Example 1 in the same manner as in Example 1 except that a negative electrode obtained by laminating carbon powder as a negative electrode active material to a thickness of 50 μm on a copper foil of 15 μm thickness of the current collector (negative electrode) 6a was used. A battery was prepared and the X-ray transmittance was measured.
The X-ray transmittance was 44%, and X-ray analysis by X transmission from the outside of the battery was difficult.

(Comparative Example 2)
A laminate cell of Comparative Example 2 in the same manner as in Example 2 except that a negative electrode obtained by laminating carbon powder as a negative electrode active material to a thickness of 50 μm on a 15 μm thick copper foil of the current collector (negative electrode) 6a was used. A battery was prepared and the X-ray transmittance was measured.
The X-ray transmittance was 38%, and X-ray analysis by X transmission from the outside of the battery was difficult.

1 Positive electrode 2 Separator 3 Negative electrode 4 Laminate (battery container)
5 Tab lead 6c Electric current collector (positive electrode)
6a Electric current collector (negative electrode)
7 Sealant (Thermo-compression bonding agent)
10 Laminated cell battery (non-aqueous electrolyte secondary battery for X-ray analysis)

Claims (5)

A non-aqueous electrolyte secondary battery for X-ray analysis comprising a positive electrode and a negative electrode disposed opposite to each other via at least a separator, and a non-aqueous electrolyte solution and a battery container storing the positive electrode, the negative electrode and the non-aqueous electrolyte solution,
At least a part of the negative electrode is made of metal lithium or lithium alloy having a thickness of 0.5 to 2.0 mm, which is a material capable of transmitting X-rays, and at least a part of the battery container is made of X-rays. It consists of a laminate consisting only of an organic resin film having a thickness of 0.2 mm or less, which is a permeable material,
The portion of the negative electrode made of an X-ray transmissive material and the portion of the battery container made of an X-ray transmissive material are aligned on the X-ray irradiation path in X-ray analysis. And an electric current collector that allows electrical continuity with the outside of the battery on at least a part of the outer periphery of the negative electrode that does not interfere with the irradiation X-ray path in the negative electrode. A non-aqueous electrolyte secondary battery for X-ray analysis.   2. The non-aqueous electrolyte secondary battery for X-ray analysis according to claim 1, wherein the current collector is disposed on the entire outer periphery of the negative electrode.   The negative electrode current collector is one metal selected from the group consisting of Cu, Fe and Ni, or an alloy of two or more metals selected from the group. 3. A nonaqueous electrolyte secondary battery for X-ray analysis according to 1 or 2. The negative electrode current collector is made of Cu,
The non-aqueous electrolyte secondary battery for X-ray analysis according to claim 3, wherein the positive electrode current collector is made of Al. The oxygen permeability of the organic resin film is 5 ml / (m ² · 24 hr · MPa) or less,
^{2. The} nonaqueous electrolyte secondary battery for X-ray analysis according to claim 1, wherein the water vapor permeability is 0.5 g / (m ² · d) or less.

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