JP3443764B2 - Non-aqueous electrolyte battery - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte battery having improved reliability at high temperatures.

[0002]

2. Description of the Related Art Lithium secondary batteries are lead batteries and Ni-M.
The battery has a higher voltage and a higher energy density than an aqueous secondary battery such as an H battery. In such a lithium secondary battery, various non-aqueous solvents that can withstand a high voltage of about 4 V are used as a solvent for dissolving the electrolyte.

[0003]

Such a non-aqueous solvent does not cause any problem during normal use of the battery, but if the battery becomes hot or short-circuited for some reason, it will react at the interface with the electrode. May occur, which may accelerate the temperature rise of the battery and cause the battery to ignite.

Such a phenomenon is unique to the non-aqueous solvent and has not been observed in the case of the aqueous solvent used in the conventional battery. Therefore, in order to prevent such problems, a non-aqueous solvent having low reactivity and a solid electrolyte battery that does not use a solvent are being developed.

However, it is difficult to replace the currently used non-aqueous solvent with another solvent without deteriorating the performance, and the solid electrolyte also has a large resistance value, so that the battery performance, especially the large current characteristic is large. Is difficult to maintain.

[0006] Therefore, it is an object of the present invention to provide a non-aqueous electrolyte battery which can solve the above-mentioned problems while directly utilizing the advantages of the non-aqueous solvent.

[0007]

DISCLOSURE OF THE INVENTION The present invention relates to a non-aqueous electrolyte battery, a diaphragm between an electrode and a separator, which does not hinder the movement of electrolyte ions in the electrolytic solution between them and suppresses the movement of a solvent. Is provided.
The invention of claim 1 is a non-aqueous electrolyte battery in which a positive electrode and a negative electrode are arranged with a separator interposed therebetween, and the separator, the positive electrode, and the negative electrode are impregnated with a non-aqueous electrolytic solution, wherein the positive electrode and the negative electrode are made of metal. An active material layer is formed on the metal foil so as to leave a portion where the active material layer is not formed at the end of the foil, and is gel-like at least between the separator and the positive electrode or between the separator and the negative electrode. A diaphragm made of an electrolyte membrane is provided, and the entire exposed surface of the active material layer is covered with the gel electrolyte membrane. Further, the invention of claim 2 is a method for producing a non-aqueous electrolyte battery, in which a positive electrode and a negative electrode are arranged with a separator interposed therebetween, and the separator, the positive electrode, and the negative electrode are impregnated with a non-aqueous electrolytic solution, wherein the electrode Or apply a paste that will be a gel electrolyte membrane on the separator surface,
By drying and injecting an electrolytic solution, at least between the separator and the positive electrode or before the separator and
Serial and providing a diaphragm made of the gel electrolyte film between the negative electrode.

As described above, by providing the diaphragm made of a gel electrolyte membrane between the separator and the positive electrode or between the separator and the negative electrode, the electrolyte is easy to move but the solvent is difficult to move. Even if an abnormal exothermic reaction of the non-aqueous solvent locally occurs, the supply of the so-called non-aqueous solvent, which is a fuel, of the exothermic reaction held in the separator or the counter electrode to the electrode is hindered, and the abnormal exothermic reaction spreads. Is prevented and the reaction is suppressed. Therefore, the gel electrolyte membrane is more preferably a gel electrolyte membrane.

Further, the gel electrolyte membrane is excellent in that it can be easily formed by a method such as applying it to a separator or an electrode, and that it is easy to obtain one having high conductivity. Further, it is preferable to impregnate the electrode and the separator with the same type of electrolytic solution, but in this case, a gel electrolyte membrane is preferable because the same electrolytic solution can be easily retained.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The diaphragm used in the non-aqueous electrolyte battery of the present invention is composed of a gel electrolyte membrane, and its thickness is preferably 2 μm or more and 12 μm or less. This is because when it is less than 2 μm, it is difficult to prevent the movement of the non-aqueous solvent that constitutes the non-aqueous electrolyte between the electrode and the separator, and when it exceeds 12 μm, the resistance of the electrolyte membrane increases and the internal resistance This is because the use capacity of the battery is reduced due to the increase. Further, within this range, it is preferable that the thickness be as thin as possible in order to reduce the resistance component and increase the volumetric efficiency, and it is preferable that the thickness be around 2 μm.

The above-mentioned film thickness means the average film thickness, but when the surface of the electrode has irregularities and the gel electrolyte film is soft, this film thickness may change locally. Therefore, in this case, it is more preferable that the thickness of the thinnest portion is 2 μm or more and 12 μm or less,
Even more preferably, the thickness of the thinnest portion is 2μ.
It is preferable that the thickness of the thickest part is 12 μm or less.

The gel electrolyte membrane constituting the diaphragm used in the non-aqueous electrolyte battery of the present invention has a structure in which a solid substance is contained in the gel electrolyte membrane, preferably in the electrolyte membrane. It is preferable that the structure includes a fine solid substance having a size that can be accommodated. Furthermore, this solid material is preferably made of a heat-resistant material that fluidizes at a temperature higher than the temperature at which the gel state of the gel electrolyte begins to collapse. This is because when the battery temperature rises, the gel state of the electrolyte membrane collapses depending on the temperature and the retained non-aqueous solvent begins to move, and the gel electrolyte membrane functions as a diaphragm for the non-aqueous solvent. However, it is possible to prevent the non-aqueous solvent from starting to move up to a higher temperature by mixing the solid substance made of the heat-resistant material.
Incidentally, it is preferable that the solid matter is contained so as to be uniformly distributed in the film.

The shape of the solid material is preferably granular or acicular, and the material may be organic or inorganic.
For example, a polyimide resin or a ceramic-based inorganic insulating solid, for example, a metal oxide insulator such as aluminum oxide or magnesium oxide or a metal nitride insulator such as aluminum nitride can be used. In particular, ceramic-based inorganic insulating solid particles are widely stable to non-aqueous solvents, and these particles act as spacers between the separator and the electrode to prevent the diaphragm from being partially collapsed. Is preferable because it always maintains a stable diaphragm and also functions as a film thickness control material for the electrolyte membrane.

The gel electrolyte membrane is prepared, for example, by swelling and moistening the electrolytic solution with a polymer simple substance such as polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, nitrile rubber or the like or a polymer to which a plasticizer is added. Therefore, it is preferable to use the same electrolytic solution as that used for the battery to be produced.

In the present invention, the presence of a free electrolytic solution is indispensable. As the electrolytic solution, for example, one in which an electrolyte is dissolved in an organic solvent can be used. As a solvent, propylene carbonate, ethylene carbonate, methyl ethyl carbonate, dimethyl carbonate, γ-butyl lactone, 1,
2-dimethoxyethane, methyl propionate, butyl propionate and the like are used alone or in combination, and L
iPF ₆ , LiClO ₄ , LiBF ₄ , LiCF ₃ SO ₃ ,
LiAsF ₆ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₂
A solution in which an electrolyte salt such as SO ₂ ) ₃ is dissolved can be used.

The simplest method for providing a gel electrolyte membrane as a diaphragm between the electrode and the separator is to apply a paste that forms a gel electrolyte membrane on the surface of the electrode or the separator. , It is good to solidify the paste as soon as possible after application. This is to prevent the paste serving as the electrolyte membrane from penetrating into the separator or the electrode, and to prevent the amount of the electrolytic solution held in the separator and the electrode from being reduced as much as possible. As a result, the characteristics peculiar to the non-aqueous electrolyte battery in which the non-aqueous electrolyte is retained are maximally retained.

[0017]

The present invention will be described in more detail by taking a lithium secondary battery as an example.

To 87 wt% of LiCoO ₂ particles and 5 wt% of acetylene black particles, 8 wt% of PVDF dissolved in an NMP (N-methylpyrrolidone) solvent was added to form a paste, which was then applied on an aluminum foil having a thickness of 20 μm.
This was dried at 100 ° C. to prepare a positive electrode sheet. The active material layer formed by coating had a thickness of 70 μm on each side, and was formed on both sides of the aluminum foil.

PVDF dissolved in NMP solvent in 86 wt% of graphite particles and 6 wt% of acetylene black particles
8 wt% was added to form a paste, and the paste was applied on a copper foil having a thickness of 15 μm and dried at 90 ° C. to prepare a negative electrode sheet. The thickness of the active material layer formed by coating is 80 on one side.
μm, formed on both sides of the copper foil.

Then, a gel electrolyte membrane was formed on the surface of each active material layer of the positive electrode sheet and the negative electrode sheet. The gel electrolyte membrane was prepared as follows. 30 wt% of PVDF copolymer resin and 70 wt% of MgO particles having an average particle diameter of 0.2 μm are mixed, and N
MP solvent was added to form a paste, which was applied onto the electrode and immediately dried by vacuum drying at 80 ° C. for 60 minutes.
Then, by injecting the electrolyte solution shown below, the electrolyte solution permeates and swells into the PVDF-based copolymer membrane, and a gel electrolyte membrane is formed. In the battery of the present invention, PVDF
When using a polymer, it is preferable to use a PVDF copolymer.

The positive electrode sheet and the negative electrode sheet produced as described above are superposed with a 25 μm-thick polyethylene separator interposed therebetween and wound up into a cylindrical wound laminated body, which is nickel-plated on the inner surface. The container was inserted into an iron container, the inside of the container was evacuated, an electrolytic solution was injected, the container was sealed, and a cylindrical lithium secondary battery was produced. The electrolyte used was LiPF ₆ dissolved in a 2: 1 mixed solvent of EC and DEC at 1 mol / l.

FIG. 1 is a schematic sectional view showing the structure of a battery element of the battery of this embodiment. As shown in the figure, in the battery of this example, the gel electrolyte film 4 was interposed between the positive electrode active material layer 1 and the separator 2 and between the negative electrode active material layer 3 and the separator 2, and A separator made of a gel electrolyte film is provided between the separator and the separator. Both the positive electrode active material layer 1 and the negative electrode active material layer 3 are
In order to more effectively function the gel-like electrolyte membrane 4 as a diaphragm, the aluminum foil 5 and the copper foil 6 are formed on the foil so as to leave a portion where the active material layer is not formed at the end portions, A paste serving as a gel electrolyte is applied to the active material layer including the portion not formed so that the entire exposed surface of the active material layer is covered with the gel electrolyte film 4 including the end portions thereof. There is. As described above, in the present invention, the diaphragm is preferably formed so as to completely separate the electrolytic solution on the electrode side and the electrolytic solution on the separator side, and more preferably, the electrode active material as in this example is used. It is preferable to form the material layer so as to completely cover it and to isolate it.

In this embodiment, M is contained in the gel electrolyte membrane.
Although the gO particles were mixed, for comparison, one in which the MgO particles were not mixed was prepared. As a result, the capacity of the non-mixed battery was smaller than that of the mixed battery. Moreover, it was difficult to form a gel electrolyte membrane only on the electrode surface.

Based on these results, as a result of further examination, in the production of the battery of the present invention, in particular, the battery in which the electrodes are porous, when the gel electrolyte film is formed by applying the paste, Is preferably prepared by mixing fine solid matter such as granules into the paste, which suppresses the penetration of the coating layer formed by the paste into the electrode, and forms a gel electrolyte membrane only on the surface. It is easy to form.

Further, in the battery of the present invention, especially in the non-aqueous electrolyte lithium secondary battery, the ionic conductivity of the gel electrolyte can be improved by mixing fine solid matter such as particles into the gel electrolyte membrane. Therefore, it is possible to obtain an output characteristic equivalent to that of a conventional battery in which a diaphragm made of a gel electrolyte membrane is not provided. Therefore, it is preferable to mix a fine solid substance into the gel electrolyte membrane. In addition, as the material of the solid material,
In addition to the above MgO, metal oxide insulator particles such as Al ₂ O ₃ are particularly preferable.

FIG. 2 is a diagram showing the measurement results of the relationship between the thickness of the gel electrolyte membrane and the discharge capacity of the battery of this example. The discharge was performed at a current of 600 mA in the range of 4.1V to 3.0V. The measurement was carried out in the above-mentioned battery production process, in which gel electrolyte membranes having an average film thickness of 1, 2, 4, 6, 10, 12, 15 μm were produced and used. This was done by measuring the characteristics of the battery.

From the figure, the thickness of the gel electrolyte membrane is 12
It can be seen that when the thickness exceeds μm, the capacity sharply decreases. As a result of further study based on this result, it was found that in the non-aqueous electrolyte lithium secondary battery as in this example, the thickness of the gel electrolyte membrane should be 12 μm or less.

Furthermore, after charging each of the above batteries to 4.2V, an internal short-circuit test was conducted by piercing the batteries with nails. As a result, smoke was observed for the gel-free electrolyte membrane and the 1 μm-thick one. On the other hand, at 2 μm or more, no abnormality was observed. Based on this result, as a result of further examination, in the non-aqueous electrolyte lithium secondary battery as in this example,
The thickness of the gel electrolyte membrane is preferably 2 μm or more.

[0029]

According to the invention described in claim 1, the reliability of the non-aqueous electrolyte battery at high temperature can be further improved even when the conventional non-aqueous electrolyte is used as it is. Further, according to the invention of claim 2, a non-aqueous electrolyte battery in which a diaphragm made of a gel electrolyte membrane is provided at least between the separator and the positive electrode or between the separator and the negative electrode can be obtained by a simple method. it can.

By setting the thickness of the diaphragm made of a gel electrolyte membrane to 2 μm or more and 12 μm or less, the reliability of the non-aqueous electrolyte battery at high temperature can be more reliably improved and a large capacity can be obtained. A battery is obtained. Furthermore, by including a solid substance in the gel electrolyte membrane, the reliability of the non-aqueous electrolyte battery at high temperatures can be further improved and a battery having a large capacity can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing the structure of a battery element of an example battery.

FIG. 2 is a diagram showing a measurement result obtained by measuring a relationship between a thickness of a gel electrolyte membrane of an example battery and a discharge capacity.

[Explanation of symbols]

1 Positive electrode active material layer 2 separator 3 Negative electrode active material layer 4 Gel electrolyte membrane

Continuation of front page (56) Reference JP-A-11-273735 (JP, A) JP-A-9-289040 (JP, A) JP-A-2-291607 (JP, A) JP-A-9-22728 (JP , A) JP-A-10-21964 (JP, A) JP-A-8-171938 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01M 10/40 H01M 4/02- 4/04 H01M 2820-2/34

Claims (2)

(57) [Claims] 1. A non-aqueous electrolyte battery in which a positive electrode and a negative electrode are arranged with a separator interposed therebetween, and the separator, the positive electrode, and the negative electrode are impregnated with a non-aqueous electrolytic solution, wherein the positive electrode and the negative electrode.
Is left on the edge of the metal foil where the active material layer is not formed.
Active material layer is formed on the metal foil in Suyo, at least prior to
Serial separator and or between the separator and the positive electrode
A separator made of a gel electrolyte membrane is provided between the negative electrode and the entire exposed surface of the active material layer is the gel electrolyte membrane.
A non-aqueous electrolyte battery characterized by being covered . Across 2. A separator and the positive electrode and the negative electrode is arranged, the separator, the positive electrode, a method of manufacturing a non-aqueous electrolyte battery nonaqueous electrolyte is impregnated in the negative electrode, the electrode also
Apply a paste that will form a gel electrolyte membrane to the separator surface.
And cloth, dried by pouring the electrolytic solution, by providing a diaphragm made of the gel electrolyte film between the or between the separator <br/> data of at least the separator the cathode the anode A method for manufacturing a non-aqueous electrolyte battery , comprising: