WO2014171290A1

WO2014171290A1 - Lithium ion secondary battery and production method therefor

Info

Publication number: WO2014171290A1
Application number: PCT/JP2014/058934
Authority: WO
Inventors: 上羽悠介; 澤田学; 田中陽介
Original assignee: 株式会社村田製作所
Priority date: 2013-04-16
Filing date: 2014-03-27
Publication date: 2014-10-23

Abstract

Provided are a lithium ion secondary battery which is superior in safety and enables the realization of high energy density and high power density at a low cost without using a polymer separator such as a porous polyolefin separator, and a production method therefor. A ceramic separator layer (11) which comprises a composite material including insulating inorganic microparticles and an organic material and which has lithium ion permeability is disposed on the surface of a positive electrode (1) and/or a negative electrode (2), and a lithium ion permeable gel-containing layer (12) which includes a gel having electron insulating properties and lithium ion permeability is disposed on the surface of the ceramic separator layer (11). The gel included in the lithium ion permeable gel-containing layer is a gel having a chemical crosslink structure. The ceramic separator layer is disposed on the positive electrode and/or the negative electrode, and the lithium ion permeable gel-containing layer is formed thereupon so as to prevent the occurrence of defects such as flaking in the ceramic separator layer.

Description

Lithium ion secondary battery and manufacturing method thereof

The present invention relates to a battery, and more particularly, to a lithium ion secondary battery using a ceramic separator, which is excellent in economic efficiency and high in reliability, and a manufacturing method thereof.

A lithium ion secondary battery includes, for example, a positive electrode formed by applying a positive electrode active material (lithium composite oxide) to a sheet-like current collector foil (such as an aluminum foil or a copper foil), and a negative electrode active material. An electricity storage element constituted by laminating a negative electrode formed by coating a substance (activated carbon, carbon, etc.) via a separator for preventing a short circuit due to contact between the positive and negative electrodes, and an electrolytic solution, It has a structure accommodated in the exterior body.

As such a battery, Patent Document 1 discloses a separator in which inorganic fine particles are dispersed in an organic polymer, instead of a conventionally used separator such as a polyolefin-based stretched film (hereinafter referred to as “polyolefin-based separator”). (Hereinafter also referred to as “ceramic separator”), as schematically shown in FIG. 4, a nonaqueous electrolyte battery in which the ceramic separator 111 is disposed between the positive electrode 101 and the negative electrode 102 has been proposed. Yes.

The ceramic separator 111 used in Patent Document 1 described above does not deform and shrink even at high temperatures. Therefore, even when the ceramic separator 111 is exposed to an unintended high temperature, the positive electrode and the negative electrode are not short-circuited by the contraction, heat generation, smoke generation, ignition, and the like are prevented, and safety can be improved. For example, the safety that does not ignite in the nail cutting test is due to this feature.

However, when an electrode having a large surface irregularity is employed, since the electronic insulation cannot be maintained only by the ceramic separator, there is actually no battery on the market in a configuration that maintains the electronic insulation only by the ceramic separator 111. .

In addition, if a ceramic separator is used to meet the demand for low cost and low resistance, the film thickness must be reduced. However, if an electrode with large surface irregularities is used, if the ceramic separator is thinned, the electronic insulating property Can not be secured. On the other hand, increasing the film thickness of the ceramic separator in order to ensure electronic insulation can ensure electronic insulation, but increasing the film thickness has the problem of increasing costs and increasing resistance. . As described above, in the case of the configuration shown in FIG. 4, the actual situation is that all of low cost, low resistance, and electronic insulation cannot be satisfied.

Further, in Patent Document 2, as schematically shown in FIG. 5, a porous insulating layer (HRL) (substantially ceramic separator) 111 and a porous insulator (general) are provided between the positive electrode 101 and the negative electrode 102. A non-aqueous electrolyte battery has been proposed in which a polyolefin-based separator 112 is used.
The porous insulating layer 111 is formed of a mixture of insulating inorganic fine particles and a binder (binder) made of an organic polymer, and is substantially the same as a ceramic separator.

In the case of the configuration of Patent Document 2, a porous insulating layer (ceramic separator) made of a mixture of a porous insulator 112, which is a polyolefin-based separator, and a binder (binder) made of insulating inorganic fine particles and an organic polymer. ) 111 is interposed between the positive electrode 101 and the negative electrode 102, and by interposing a porous insulating layer (ceramic separator) 111 that does not shrink even at high temperatures, shorting, heat generation, and ignition of the positive electrode and the negative electrode are suppressed and prevented. While improving the safety, the porous insulator 112, which is a polyolefin-based separator excellent in electronic insulation, can ensure the electronic insulation between the positive and negative electrodes, but the porous insulator is a polyolefin-based separator. Since 112 is used in combination, there are the following problems.

(A) The cost of the polyolefin separator occupies a high proportion of the cost of the battery, which causes an increase in cost.
(B) Polyolefin-based separators have high resistance and lead to deterioration of power characteristics. Therefore, as countermeasures, it is conceivable to reduce the film thickness or increase the porosity. This is a major factor that hinders performance. In addition, it is conceivable to increase the number of stacked layers in order to ensure power characteristics, but this causes an increase in cost.
(C) The film thickness of the polyolefin-based separator is usually as thick as 20 to 30 μm, and there is a problem that the energy density per volume decreases, and a battery with a higher energy density can be designed as the separator film thickness decreases. It is very difficult to reduce the film thickness of the polyolefin separator due to handling problems.

Further, in Patent Document 3, as schematically shown in FIG. 6, (a) a first insulating layer (ion-permeable gel) 113 and (b) a second insulating layer (between the positive electrode 101 and the negative electrode 102 ( A lithium ion secondary battery including a ceramic separator 111 having lithium ion permeability) and (c) a porous insulator (porous polyolefin separator) 112 has been proposed.

In the case of the configuration of Patent Document 3, since the ceramic separator (second insulating layer) 111 and the porous polyolefin-based separator (porous insulator) 112 are provided, the above-described problem with respect to Patent Document 2 just applies. In addition, since one additional component of the ion-permeable gel (first insulating layer) 113 is added, problems such as high cost, high resistance, reduced energy density, and reduced power density become more serious.

JP 2006-164761 A International Publication No. 2005-098997 Pamphlet JP 2010-267475 A

The present invention solves the above-described problems, and can achieve high energy density and high power density at low cost without using a polymer separator such as a porous polyolefin separator, and is excellent in safety. Another object of the present invention is to provide a lithium ion secondary battery and a method for manufacturing the same.

In order to solve the above problems, the lithium ion secondary battery of the present invention is
A battery element including a positive electrode, a negative electrode, a ceramic separator layer and a lithium ion permeable gel-containing layer disposed so as to be interposed between the positive electrode and the negative electrode, and an electrolyte, and the battery element are accommodated With an exterior body,
The ceramic separator layer is made of a composite material containing insulating inorganic fine particles and an organic substance, has lithium ion permeability, and is disposed on at least one surface of the positive electrode and the negative electrode.
The lithium ion permeable gel-containing layer includes a gel having electronic insulation and lithium ion permeability, and is disposed on the surface of the ceramic separator layer.

In the present invention, a ceramic separator layer having lithium ion permeability and electronic insulation is used.
Further, as the lithium ion permeable gel-containing layer, a layer containing a gel having an electronic insulating property while having lithium ion permeability is used.
The lithium ion permeable gel-containing layer may contain an insulating inorganic powder such as ceramic.

In the lithium ion secondary battery of the present invention, the ceramic separator layer is provided on both surfaces of the positive electrode and the negative electrode, and the lithium ion permeable gel-containing layer is provided on the surface of the positive electrode. It is also possible to adopt a configuration in which the ceramic separator layer is disposed so as to be positioned between the ceramic separator layer provided on the surface of the negative electrode.

In the lithium ion secondary battery of the present invention, the ceramic separator layer is disposed on one surface of the positive electrode and the negative electrode, and a lithium ion permeable gel-containing layer is formed on the surface of the ceramic separator layer. However, a ceramic separator layer is provided on both surfaces of the positive electrode and the negative electrode, and a lithium ion permeable gel-containing layer is provided on the surface of each ceramic separator layer or one of the ceramic separator layers. In such a case, lithium ion that can realize high energy density and high power density at low cost without using a polymer separator such as a porous polyolefin separator, and also has excellent safety. A secondary battery can be obtained.

Moreover, it is preferable that the gel contained in the lithium ion permeable gel-containing layer is a gel having a chemical crosslinking structure.

When a gel having a chemically crosslinked structure is used as the gel contained in the lithium ion permeable gel-containing layer, the gel having the chemically crosslinked structure is mechanically rigid. It is possible to provide a sufficient function of ensuring electronic insulation between the negative electrodes, and the present invention can be more effectively realized. In general, since a gel having a chemical cross-linking structure is excellent in swelling property, it is possible to hold an electrolytic solution more and contribute to improvement in battery life.

In addition, the method for producing the lithium ion secondary battery of the present invention includes:
A battery element including a positive electrode, a negative electrode, a ceramic separator layer and a lithium ion permeable gel-containing layer disposed so as to be interposed between the positive electrode and the negative electrode, and an electrolyte, and the battery element are accommodated A method for producing a lithium ion secondary battery comprising an exterior body,
A step of forming a ceramic separator layer having a lithium ion permeability on a surface of at least one of a positive electrode and a negative electrode made of a composite material containing insulating inorganic fine particles and an organic substance;
On the surface of the ceramic separator layer, a step of forming a lithium ion permeable gel-containing layer containing a gel having electronic insulation and lithium ion permeability;
A positive electrode or a negative electrode provided with the ceramic separator layer and the lithium ion permeable gel-containing layer, and a negative electrode or positive electrode not provided with the ceramic separator layer and the lithium ion permeable gel-containing layer are joined together; Forming a battery element comprising a pair of negative electrodes.

In addition, another method for producing a lithium ion secondary battery of the present invention is as follows.
A battery element including a positive electrode, a negative electrode, a ceramic separator layer and a lithium ion permeable gel-containing layer disposed so as to be interposed between the positive electrode and the negative electrode, and an electrolyte, and the battery element are accommodated A method for producing a lithium ion secondary battery comprising an exterior body,
A step of forming a ceramic separator layer made of a composite material containing insulating inorganic fine particles and an organic material on both surfaces of the positive electrode and the negative electrode and having lithium ion permeability;
On the surface of the ceramic separator layer, a step of forming a lithium ion permeable gel-containing layer containing a gel having electronic insulation and lithium ion permeability;
A positive electrode or a negative electrode provided with the ceramic separator layer and the lithium ion permeable gel-containing layer, and a negative electrode or positive electrode provided with the ceramic separator layer and the lithium ion permeable gel-containing layer. And a step of forming a battery element including a positive electrode and a negative electrode as a pair, with the ceramic separator layer and the lithium ion permeable gel-containing layer interposed therebetween.

Since the lithium ion secondary battery of the present invention has a ceramic separator layer disposed on at least one surface of the positive electrode and the negative electrode, and a lithium ion permeable gel-containing layer is formed on the surface of the ceramic separator layer, For example, even when there are irregularities on the surface of the positive electrode or negative electrode and it is not easy to achieve sufficient reliability by securing sufficient electronic insulation with a ceramic separator layer alone, a porous polymer separator is used. It is possible to obtain a lithium ion battery that can realize high safety, high energy density, and high power density at low cost without requiring use.

In addition, by providing a lithium ion permeable gel-containing layer on the ceramic separator layer, defects (so-called powder fall) during handling of the ceramic separator layer, or pinholes or defects in the ceramic separator layer are caused. It is possible to suppress or prevent the occurrence of such as, but this is because the lack of ceramic separator layer (powder falling) caused by external factors such as friction between the ceramic separator layer and other members is lithium ion permeable. This is because defects such as penetrating pinholes suppressed by the gel-containing layer or generated in the ceramic separator layer are complemented by the lithium ion-permeable gel-containing layer.

The ceramic separator layer is basically composed of a ceramic and a binder, but as the ceramic ratio increases, the resistance to lithium ion permeation decreases, while the binder decreases, so the strength of the ceramic separator layer is It is easy to cause loss (powders) due to external factors. The resistance of the ceramic separator layer and the ease of occurrence of chipping (powder falling) are in a trade-off relationship. On the other hand, generation | occurrence | production of defects, such as powder fall, can be suppressed by providing a lithium ion permeable gel content layer on the surface of a ceramic separator layer like this invention.

Further, when the surface of the positive electrode or the negative electrode has irregularities (protrusions) and the convex portions are exposed on the surface of the ceramic separator layer, and there is no lithium ion permeable gel-containing layer, Although a short circuit is caused by contact, a short circuit defect can be suppressed because the lithium ion permeable gel-containing layer disposed on the surface of the ceramic laminate reinforces the ceramic separator layer. Therefore, according to the present invention, a lithium ion secondary battery having sufficient characteristics and reliability can be realized without employing a porous polymer separator.

In addition, according to the present invention, the lithium ion permeable gel-containing layer reinforces the ceramic separator layer, and the ceramic ratio is increased compared to the case where the ceramic separator layer is used alone, so that the low resistance design can be achieved. Therefore, it is possible to obtain a high-performance lithium ion secondary battery including a ceramic separator layer that has excellent electronic insulation, low resistance, and excellent lithium ion permeability.

In the present invention, the ceramic separator layer may be formed on either the positive electrode or the negative electrode, but may be formed on both the positive electrode and the negative electrode.
The lithium ion permeable gel-containing layer formed on the ceramic separator layer may contain an insulating inorganic powder such as ceramic.

As described above, according to the present invention, since it is not necessary to use a porous polymer separator, the following effects can be obtained.

(1) The cost of a porous polymer separator (for example, a porous polyolefin separator) occupies a high proportion of the cost of battery constituent materials. Reduction can be achieved.

(2) In addition, when the lithium ion secondary battery is a laminated battery, a high-resistance polymer separator is not required, so the number of layers required to obtain the desired power characteristics can be suppressed. Therefore, the cost can be reduced also from this aspect.

(3) The thickness of the porous polymer separator (for example, a porous polyolefin separator) is usually 20 to 30 μm. By eliminating the need for such a large polymer separator, energy per volume is obtained. The density can be increased (that is, since the presence of a porous polymer separator does not contribute to the development of energy (or capacity), the energy density can be improved by making this polymer separator unnecessary). .

The method for producing a lithium ion secondary battery according to the present invention includes forming a ceramic separator layer having lithium ion permeability on a surface of at least one of a positive electrode and a negative electrode, which is made of a composite material including insulating inorganic fine particles and an organic substance. In addition, after forming a lithium ion permeable gel-containing layer containing a gel having electronic insulation and lithium ion permeability on the surface of the ceramic separator layer, the ceramic separator layer and the lithium ion permeable gel-containing layer were provided. Since the positive electrode or the negative electrode is joined to the negative electrode or the positive electrode that does not include the ceramic separator layer and the lithium ion permeable gel-containing layer, a battery element including the positive electrode and the negative electrode as a pair is formed. The surface is covered with a lithium ion permeable gel-containing layer Therefore, the lithium ion permeable gel-containing layer has lithium ion permeability and electronic insulation. Therefore, it is possible to manufacture a lithium ion secondary battery having sufficient characteristics and reliability without using a porous polymer separator.

Further, a ceramic separator layer made of a composite material containing insulating inorganic fine particles and an organic substance is formed on both surfaces of the positive electrode and the negative electrode, and a lithium ion permeable ceramic separator layer is formed. After forming a lithium ion permeable gel-containing layer including a gel having lithium ion permeability, a positive electrode or a negative electrode including the ceramic separator layer and the lithium ion permeable gel-containing layer, the ceramic separator layer, and the lithium ion permeable gel A negative electrode or a positive electrode provided with a containing layer is joined so that a ceramic separator layer and a lithium ion-permeable gel-containing layer are interposed between the positive electrode and the negative electrode, so as to form a battery element comprising a positive electrode and a negative electrode as a pair. Even when the ceramic separator layer is used, the surface of the ceramic separator layer Since it is handled in a state covered with an ion-permeable gel-containing layer, it is possible to suppress or prevent the occurrence of powder falling, and the lithium-ion-permeable gel-containing layer is permeable to lithium ions. Therefore, it is possible to manufacture a lithium ion secondary battery having sufficient characteristics and reliability without using a porous polymer separator.

It is a figure which shows typically the structure of the lithium ion secondary battery (battery element) concerning embodiment of this invention. It is a figure which shows typically the modification of the lithium ion secondary battery (battery element) concerning embodiment of this invention. It is a figure which shows typically the other modification of the lithium ion secondary battery (battery element) concerning embodiment of this invention. It is a figure which shows typically the structure of the conventional lithium ion secondary battery disclosed by patent document 1. FIG. It is a figure which shows typically the structure of the conventional lithium ion secondary battery disclosed by patent document 2. FIG. It is a figure which shows typically the structure of the conventional lithium ion secondary battery disclosed by patent document 3. FIG.

Hereinafter, embodiments of the present invention will be shown, and features of the present invention will be described in detail.

[Embodiment 1]
<Production of lithium ion secondary battery>
(Step 1) Preparation of positive electrode active material slurry
88 g of lithium manganate (manufactured by Toda Kogyo Co., Ltd., HPM-7051, average particle diameter D ₅₀ = 6.1 μm), 2 g of graphite (manufactured by Timcal, KS-6), 6 g of graphite (manufactured by Timcal, Super P Li) Was weighed.

Then, each weighed material was put into a 1000 mL pot, and PSG grinding media having a diameter of 1.0 mm and 200 g of N-methylpyrrolidone (hereinafter referred to as NMP) as a solvent were added. Then, the mixture was dispersed by mixing at 150 rpm for 24 hours using a rolling ball mill. As a result, the secondary particles of lithium manganate were crushed, and the average particle diameter D ₅₀ was 2.1 μm.

40 g of a 10% by mass NMP solution of polyvinylidene fluoride (manufactured by Kureha Co., Ltd., # 7208) is added to the solution in which each material is dispersed as described above, and further mixed at 150 rpm for 4 hours using a rolling ball mill. Then, a positive electrode active material slurry was prepared.

(Step 2) Preparation of negative electrode active material slurry 91 g of lithium titanate (Ishihara Sangyo Co., Ltd., XA-105, median diameter 6.7 μm), 4 g of acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd., HS-100) Weighed.

Then, each weighed material was put in a 1000 mL pot, and 200 g of NMP was added as a PSZ grinding medium having a diameter of 1.0 mm and a solvent. Then, the mixture was dispersed by mixing at 150 rpm for 24 hours using a rolling ball mill. As a result, the secondary particles of lithium titanate were crushed, and the average particle diameter D ₅₀ was 2.3 μm.

50 g of a 10% by mass NMP solution of polyvinylidene fluoride (manufactured by Kureha Co., Ltd., # 7208) is added to the solution in which each material is dispersed as described above, and further mixed at 150 rpm for 4 hours using a rolling ball mill. Thus, a slurry for negative electrode active material was prepared.

(Step 3) Production of Positive Electrode The positive electrode active material slurry produced in (Step 1) above was coated on a positive electrode current collector foil made of aluminum foil (manufactured by Tokai Toyo Aluminum Sales Co., Ltd., thickness 20 μm) and dried. The positive electrode was produced by post-pressing. Further, an aluminum tab was attached to the exposed portion of the positive electrode current collector foil to produce a lead electrode.

(Step 4) Production of Negative Electrode The negative electrode active material slurry produced in the above (Step 2) was coated on a negative electrode current collector foil made of rolled copper foil (manufactured by Nippon Foil Co., Ltd., thickness 10 μm) and dried. A negative electrode was produced by post-pressing. Further, a nickel tab was attached to the exposed portion of the negative electrode current collector foil to produce a lead electrode.

(Step 5) Formation of ceramic separator layer A 500 mL pot was charged with 100 g of spherical alumina powder (manufactured by Denki Kagaku Kogyo Co., Ltd., average particle diameter D ₅₀ = 0.3 μm) and 80 g of NMP as a solvent. Further, PSZ grinding media having a diameter of 5 mm were put, and the mixture was dispersed by mixing at 150 rpm for 16 hours using a rolling ball mill.

Thereafter, 67.8 g of a binder solution (20 mass% NMP solution) of PVDF-HFP (manufactured by Arkema Co., Ltd., Kynar # 2850) was added and mixed for 4 hours at 150 rpm using a rolling ball mill, and PVC (pigment volume concentration) 80 % Slurry for ceramic separator layer.

The prepared slurry for ceramic separator layer was coated on the negative electrode prepared in the above (Step 4) with a bar coater and then dried to form a ceramic separator layer having a thickness of 13 μm.

(Step 6) Production of Lithium Ion-permeable Gel-Containing Layer (Precursor) First, a 20% by mass methyl ethyl ketone (hereinafter MEK) solution of polybutyl methacrylate (manufactured by Aldrich, hereinafter PBMA) was produced. The prepared PBMA MEK solution was coated with a bar coater on the negative electrode on which the ceramic separator layer was formed in the above (Step 5), and then dried, whereby the film thickness was formed on the negative electrode via the ceramic separator layer. A 1.0 μm lithium ion permeable gel-containing layer (precursor) was formed.

(Step 7) Production of Battery Cell As shown in FIG. 1, the positive electrode 1 produced in the above (Step 3), the ceramic separator layer 11 produced in the above (Step 6), and the lithium ion permeable gel-containing layer (precursor) The battery element 20 including a pair of electrodes (a positive electrode and a negative electrode) was manufactured by facing the negative electrode 2 provided with the body 12.

Then, the produced battery element was sandwiched between two laminates, and three sides were subjected to thermocompression bonding with an impulse sealer to produce a laminate package (exterior body) having an opening on one side.

Next, an electrolytic solution was injected into the inside of the opening of the laminate package. As the electrolytic solution, an electrolytic solution in which lithium hexafluorophosphate (LiPF ₆ ) was dissolved in a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 3: 7 so as to be 1 M was used. . Here, the lithium ion permeable gel-containing layer (precursor) is impregnated with the electrolytic solution, whereby the original lithium ion permeable gel-containing layer is formed.
Finally, a lithium ion secondary battery (battery cell) was produced by vacuum-sealing the opening of the laminate package.

<Evaluation of characteristics>
In order to evaluate the characteristics of the lithium ion secondary battery (battery cell) produced as described above, the presence or absence of occurrence of short-circuit failure was confirmed for 10 lithium ion secondary batteries. Judgment of short circuit was made by leaving the cell to 2.2V for 1 week and measuring the cell voltage, and the cell having a voltage of 2.1V or higher was regarded as a non-defective product, and the cell having a voltage of less than 2.1V was regarded as short circuit. The results are shown in Table 1.

For comparison, lithium prepared in exactly the same manner except that the formation of the lithium ion permeable gel-containing layer in (Step 6) is not performed (that is, the lithium ion permeable gel-containing layer is not formed). The same evaluation was performed on an ion secondary battery (a lithium ion secondary battery having only a ceramic separator layer between the positive electrode and the negative electrode). The results are also shown in Table 1.

As shown in Table 1, in the case of the lithium ion secondary battery according to Embodiment 1 of the present invention, occurrence of a short circuit was observed in only one of the 10 lithium ion secondary batteries used for evaluation.

On the other hand, in the case of the comparative lithium ion secondary battery not provided with the lithium ion permeable gel-containing layer, occurrence of a short circuit was observed in all of the ten lithium ion secondary batteries used for evaluation.

From the above results, it can be seen that short-circuit defects can be suppressed and prevented when a ceramic separator layer and a lithium ion permeable gel-containing layer are used in combination. This is because the lithium ion permeable gel-containing layer complements defects such as through pin holes generated in the ceramic separator layer, or due to external factors such as friction between the ceramic separator layer and other members. This is because, for example, the lack (powder omission) is suppressed by the lithium ion permeable gel-containing layer.

[Embodiment 2]
<Production of lithium ion secondary battery>
(Step 1) Preparation of positive electrode active material slurry Lithium iron phosphate (Mitsui Zosen Co., Ltd., EF014-LCC, average particle diameter D ₅₀ = 13.2 μm) 84 g, acetylene black (Denki Kagaku Kogyo Co., Ltd., HS −100) 12 g, N-methylpyrrolidone (hereinafter referred to as NMP) 100 g, and 40 g of a 10% by mass NMP solution of polyvinylidene fluoride (manufactured by Kureha Co., Ltd., # 7208) were weighed and stirred with a planetary mixer to obtain a positive electrode active A material slurry was prepared.

(Step 2) Preparation of negative electrode active material slurry: 85 g of graphite (manufactured by Mitsubishi Chemical Corporation, GTR6, average particle diameter D ₅₀ = 11.0 μm), 15 g of conductive additive (manufactured by Hitachi Chemical Co., Ltd., SMSC10-4V3), NMP 100g and polyvinylidene fluoride (manufactured by Kureha Co., Ltd., # 7305) 10 mass% NMP solution 53g were weighed and stirred with a planetary mixer to prepare a slurry for negative electrode active material.

(Step 5) Formation of ceramic separator layer A 500 mL pot was charged with 100 g of spherical alumina powder (manufactured by Denki Kagaku Kogyo Co., Ltd., average particle diameter D ₅₀ = 0.3 μm) and 80 g of NMP as a solvent. Further, PSZ grinding media having a diameter of 5 mm were put, and the mixture was dispersed by mixing at 150 rpm for 16 hours using a rolling ball mill.
Thereafter, 67.8 g of a binder solution (20 mass% NMP solution) of PVDF-HFP (manufactured by Arkema Co., Ltd., Kynar # 2850) was added, mixed for 4 hours at 150 rpm using a rolling ball mill, and PVC (pigment volume concentration) 80 % Slurry for ceramic separator layer.
The prepared slurry for ceramic separator layer was coated on the negative electrode prepared in the above (Step 4) with a bar coater and then dried to form a ceramic separator layer having a thickness of 13 μm.

(Step 6) Preparation of lithium ion permeable gel-containing layer (precursor) On the ceramic separator layer formed on the negative electrode in the above (Step 5), 1% by weight of benzophenone was dissolved to give 0.5% ethylene. 2-ethylhexyl acrylate (manufactured by Nacalai Tesque) containing glycol diacrylate (manufactured by Aldrich) was applied with a bar coater after nitrogen bubbling for 10 minutes. Then, photopolymerization by UV was performed in a nitrogen atmosphere to form a lithium ion permeable gel-containing layer (precursor) having a chemical cross-linking structure with a film thickness of 2.1 μm.

(Step 7) Production of Battery Cell As shown in FIG. 1, the positive electrode 1 produced in the above (Step 3) (ie, the positive electrode in which neither the ceramic separator layer nor the lithium ion permeable gel-containing layer is formed) ) And the negative electrode 2 provided with the ceramic separator layer 11 and the lithium ion permeable gel-containing layer (precursor) 12 produced in the above (Step 6) are opposed to each other from a pair of electrodes (positive electrode and negative electrode). A battery element 20 was produced.

<Evaluation of characteristics>
In order to evaluate the characteristics of the lithium ion secondary battery (battery cell) produced as described above, the presence or absence of occurrence of short-circuit failure was confirmed for 10 lithium ion secondary batteries. Judgment of a short circuit was made by leaving the cell to 3.5 V for 1 week, and measuring the voltage of the cell after 1 week, and determining a cell of 3.4 V or higher as a non-defective product and a cell of less than 3.4 V as a short circuit. The results are shown in Table 2.

For comparison, lithium prepared in exactly the same manner except that the formation of the lithium ion permeable gel-containing layer in (Step 6) is not performed (that is, the lithium ion permeable gel-containing layer is not formed). The same evaluation was performed for an ion secondary battery (a lithium ion secondary battery having only a ceramic separator layer between the positive electrode and the negative electrode). The results are also shown in Table 2.

As shown in Table 2, in the case of the lithium ion secondary battery according to Embodiment 2 of the present invention, no short circuit was observed in all of the 10 lithium ion secondary batteries used for evaluation.

On the other hand, in the case of the comparative lithium ion secondary battery in which the lithium ion permeable gel-containing layer is not formed, occurrence of a short circuit is observed in all of the ten lithium ion secondary batteries used for evaluation. It was.

In addition, it was confirmed that the short-circuit suppressing effect is particularly large when the lithium ion permeable gel-containing layer includes a gel having a chemical cross-linking structure.

[Modification]
In the first and second embodiments, a ceramic separator layer is formed on the surface of the negative electrode, and a lithium ion permeable gel-containing layer is formed on the ceramic separator layer. The positive electrode and the negative electrode were joined to form a battery element without forming the conductive gel-containing layer (see FIG. 1). On the contrary, a ceramic separator layer was formed on the surface of the positive electrode, A lithium ion permeable gel-containing layer is formed on the ceramic separator layer, and the positive electrode and the negative electrode are joined to the negative electrode without forming the ceramic separator layer and the lithium ion permeable gel-containing layer. As shown, the positive electrode 1, the ceramic separator layer 11 formed on the surface thereof, and the lithium ion permeability formed on the surface thereof. And Le-containing layer 12, it is also possible to prepare a battery element 20 and a negative electrode 2. In this case as well, the same effects as those in the first and second embodiments can be obtained.

Moreover, after forming a ceramic separator layer on both surfaces of the positive electrode and the negative electrode, and further forming a lithium ion permeable gel-containing layer on the ceramic separator layer, the positive electrode and the negative electrode are sandwiched between the ceramic separator layer and By bonding so that the lithium ion permeable gel-containing layer is interposed, as shown in FIG. 3, the positive electrode 1, the negative electrode 2, and the ceramic separator layer 11 (11 a, 11 a, 11 provided on the surfaces of the positive electrode 1 and the negative electrode 2). 11b) and a battery element 20 having a structure including the lithium ion permeable gel-containing layer 12 positioned between the ceramic separator layers 11 (11a and 11b) can be formed. In this case as well, the same effects as those in the first and second embodiments can be obtained.

The present invention is not limited to the above embodiment, and relates to specific constituent materials and forming methods such as a positive electrode and a negative electrode, a lithium ion permeable gel-containing layer, a ceramic separator layer, and the type of electrolytic solution. Various applications and modifications can be made within the scope of the invention.

DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Negative electrode 11 (11a, 11b) Ceramic separator layer 12 Lithium ion permeable gel content layer 20 Battery element

Claims

A battery element including a positive electrode, a negative electrode, a ceramic separator layer and a lithium ion permeable gel-containing layer disposed so as to be interposed between the positive electrode and the negative electrode, and an electrolyte, and the battery element are accommodated With an exterior body,
The ceramic separator layer is made of a composite material containing insulating inorganic fine particles and an organic substance, has lithium ion permeability, and is disposed on at least one surface of the positive electrode and the negative electrode.
The lithium ion permeable gel-containing layer includes a gel having electronic insulation properties and lithium ion permeability, and is disposed on a surface of the ceramic separator layer.
The ceramic separator layer is provided on the surfaces of both the positive electrode and the negative electrode,
The lithium ion permeable gel-containing layer is disposed between the ceramic separator layer provided on the surface of the positive electrode and the ceramic separator layer provided on the surface of the negative electrode. The lithium ion secondary battery according to claim 1.
3. The lithium ion secondary battery according to claim 1, wherein the gel contained in the lithium ion permeable gel-containing layer is a gel having a chemical cross-linking structure.
A battery element including a positive electrode, a negative electrode, a ceramic separator layer and a lithium ion permeable gel-containing layer disposed so as to be interposed between the positive electrode and the negative electrode, and an electrolyte, and the battery element are accommodated A method for producing a lithium ion secondary battery comprising an exterior body,
A step of forming a ceramic separator layer having a lithium ion permeability on a surface of at least one of a positive electrode and a negative electrode made of a composite material containing insulating inorganic fine particles and an organic substance;
On the surface of the ceramic separator layer, a step of forming a lithium ion permeable gel-containing layer containing a gel having electronic insulation and lithium ion permeability;
A positive electrode or a negative electrode provided with the ceramic separator layer and the lithium ion permeable gel-containing layer, and a negative electrode or positive electrode not provided with the ceramic separator layer and the lithium ion permeable gel-containing layer are joined together; Forming a battery element comprising a negative electrode as a pair. A method for producing a lithium ion secondary battery, comprising:
A battery element including a positive electrode, a negative electrode, a ceramic separator layer and a lithium ion permeable gel-containing layer disposed so as to be interposed between the positive electrode and the negative electrode, and an electrolyte, and the battery element are accommodated A method for producing a lithium ion secondary battery comprising an exterior body,
A step of forming a ceramic separator layer made of a composite material containing insulating inorganic fine particles and an organic material on both surfaces of the positive electrode and the negative electrode and having lithium ion permeability;
On the surface of the ceramic separator layer, a step of forming a lithium ion permeable gel-containing layer containing a gel having electronic insulation and lithium ion permeability;
A positive electrode or a negative electrode provided with the ceramic separator layer and the lithium ion permeable gel-containing layer, and a negative electrode or positive electrode provided with the ceramic separator layer and the lithium ion permeable gel-containing layer. And a step of forming a battery element comprising a positive electrode and a negative electrode as a pair, with the ceramic separator layer and the lithium ion permeable gel-containing layer interposed therebetween. A battery manufacturing method.