JP2008103245A - Sulfide based secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sulfide based secondary battery which traps hydrogen sulfide gas formed by deterioration and breakage of a battery and detoxifies it. <P>SOLUTION: This is the sulfide based secondary battery 1 which contains a sulfur compound in a battery cell 10 to generate the hydrogen sulfide gas by decomposition, and in which the outer peripheral part of the battery cell 10 is covered by a material 31 to trap the hydrogen sulfide gas and detoxify it. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a sulfide-based secondary battery.

In recent years, the demand for secondary batteries such as lithium batteries used in personal digital assistants, portable electronic devices, small household power storage devices, motorcycles powered by motors, electric vehicles, hybrid electric vehicles, etc. has increased. .
As the applications used expand, further improvements in safety and performance of secondary batteries are required.

In order to ensure the safety of the lithium battery, it is effective to use an inorganic solid electrolyte instead of the organic solvent electrolyte.
Inorganic solid electrolytes are generally nonflammable in nature and are safer materials than commonly used organic solvent electrolytes. Therefore, development of an all-solid lithium battery with high safety using the electrolyte is desired.

For this reason, various applications have been filed for secondary batteries with regard to safety measures relating to short circuits and damage within the battery.
As described above, in general, an all-solid-state secondary battery composed of an inorganic material member is considered to be safe against short-circuiting or breakage, but in the case of a sulfide-based secondary battery, the inside of the battery In addition, since sulfur compounds that react with water and generate hydrogen sulfide gas are included, if the battery is damaged, such sulfur compounds may react with moisture in the air to generate hydrogen sulfide gas. is there.

  Patent Document 1 discloses a battery that is sealed with an adhesive resin and is provided with a safety valve mechanism that is opened on the exterior material when the internal pressure increases. In the technique disclosed in Patent Document 1, when gas is generated inside the battery due to a short circuit or the like, the device is devised to prevent the battery from bursting by releasing pressure.

  Patent Document 2 discloses a non-aqueous electrolyte secondary battery in which at least one of a positive electrode and a negative electrode includes an active material having a porous polymer electrolyte having a shutdown function on its surface. In this battery, when the battery is short-circuited and a large current flows in a part of the battery and becomes locally high in temperature, the porous polymer electrolyte is dissolved by this heat and an insulating film is formed. As a result, the internal resistance is increased, no more current flows, heat generation is stopped, and a technique for preventing battery explosion and the like is employed.

  Patent Document 3 discloses an explosion-proof secondary battery in which a thermal fuse is provided on a lid member of a battery case. In this battery, when the internal temperature of the battery rises due to overfilling, overdischarge, etc., a device is devised to prevent the battery from bursting by operating the thermal fuse to cut off the energization.

  In Patent Document 1, no measures are taken for the gas released to the outside due to depressurization, and neither Patent Document 2 nor Patent Document 3 takes measures when the current interruption fails. That is, there is no description of safety measures for hydrogen sulfide generated due to sulfide inside the battery.

JP 11-31505 A JP 2000-58065 A JP 2003-257212 A

  An object of the present invention is to provide a sulfide-based secondary battery that traps and renders harmless hydrogen sulfide gas generated by battery deterioration or breakage.

According to the present invention, the following sulfide-based secondary battery is provided.
1. The battery cell contains a sulfur compound that generates hydrogen sulfide gas by decomposition,
A sulfide-based secondary battery in which an outer peripheral portion of the battery cell is covered with a substance that traps hydrogen sulfide gas and makes it non-toxic.

  2. The sulfide secondary battery according to claim 1, wherein the substance for detoxifying the hydrogen sulfide gas is an alkaline compound.

3. A lead frame extending from the battery cell through a substance that detoxifies the hydrogen sulfide gas;
The sulfide secondary battery according to 1 or 2, wherein at least a portion of the lead frame that is in contact with a substance that detoxifies the hydrogen sulfide gas is covered with a substance that does not react with the substance that detoxifies the hydrogen sulfide gas.

  ADVANTAGE OF THE INVENTION According to this invention, when the battery is aged, short-circuited, or when the battery is damaged, it is possible to provide a sulfide-based secondary battery that is designed to be safe by trapping generated hydrogen sulfide gas and detoxifying it.

  The sulfide-based secondary battery of the present invention includes, in the battery cell, a material made from a sulfur compound that generates hydrogen sulfide gas by reacting with water, such as lithium sulfide or diphosphorus pentasulfide. Furthermore, the battery of the present invention covers the outer periphery of the battery cell with a substance that traps and detoxifies hydrogen sulfide gas.

FIG. 1 is a cross-sectional view showing a sulfide-based secondary battery according to an embodiment of the present invention.
As shown in FIG. 1, the sulfide-based secondary battery 1 includes a battery cell 10, an exterior material 30 that covers the battery cell 10, and hydrogen sulfide gas that is provided between the battery cell 10 and the exterior material 30. And a substance 31.
The battery cell 10 includes a negative electrode 12, a positive electrode 13, a solid electrolyte 14 sandwiched between the negative electrode 12 and the positive electrode 13, lead frames (electrode terminal portions) 15 and 16, and an interior material 20. . One end of each of the lead frames 15 and 16 is connected to the negative electrode 12 and the positive electrode 13 via a current collector (not shown), and the other end extends to the outside of the exterior member 30. The interior material 20 encloses the negative electrode 12, the positive electrode 13, and the solid electrolyte 14.
The end portions of the interior material 20 and the exterior material 30 are sealed by thermocompression bonding, for example, via a heat-fusible sealing material.
In addition, you may reinforce by providing a support | pillar between the exterior material 30 and the interior material 20. FIG.

In the sulfide-based secondary battery of the present invention, the lead frames 15 and 16 are preferably covered with a substance that does not react with the detoxifying substance.
FIG. 2 is a schematic view of a sulfide-based secondary battery coated with a lead frame. The lead frames 15 and 16 extend from the current collector 19 through the interior material 20 and the exterior material 30 to the outside. In order to prevent erosion by the detoxifying substance 31, the portions of the lead frames 15, 16 (exposed to the detoxifying substance 31) outside the interior material 20 and inside the exterior material 30 are coated 18. Has been.
The material for coating the lead frames 15 and 16 is preferably a polyolefin resin having excellent chemical resistance such as polystyrene, polypropylene, or polyethylene. However, not limited to the above, various synthetic resins and coating materials can be used.

  In the embodiment shown in FIGS. 1 and 2, the entire interior including the sealing portion of the interior material 20 is covered with a hydrogen sulfide detoxification layer, and the exterior material 30 is provided on the outside thereof, as shown in FIG. Only the outside of the solid electrolyte 14 and the electrodes 12 and 13 may be covered with the sulfurized water detoxification layer 31. Depending on the application, a mode of covering only one side as shown in FIG. 4 may be employed.

  The above embodiment is a single secondary battery, but if it has a structure capable of detoxifying hydrogen sulfide gas outside the battery cell, it is a parallel, series battery, or a battery module in which this is integrated. It is also possible to apply the present invention.

An alkaline substance can be exemplified as a substance that reacts with hydrogen sulfide to trap hydrogen sulfide gas chemically or physically (such as adsorption) to detoxify it. Since hydrogen sulfide gas is weakly acidic when dissolved in water, it can be absorbed by an alkaline substance.
The alkaline substance can be used as an aqueous solution, slurry, gel, or powder.

In consideration of the stability of the whole battery, a powder or granular solid is preferable. When using an alkaline aqueous solution, it is preferable to impregnate a water-absorbing polymer compound and use it as a gel. Further, a slurry-like or gel-like alkaline substance can be used by being enclosed in a microcapsule having air permeability. Further, when a powdery alkaline substance is used, it can be mixed with a resin that does not react with the alkaline substance, molded, and used as a sheet. For example, a mode in which the sheet-like material is sandwiched between the exterior material 30 and the interior material 20 shown in FIG. 1 can be used. In this case, a multilayer sheet having the sheet-like material as an intermediate layer can also be employed.
The alkaline substance may be strong alkaline or weak alkaline, but a weak alkaline substance is preferable in view of safety in handling. Examples of strong alkaline compounds include Group Ia hydroxides of the Periodic Table, and examples include NaOH and KOH. Examples of weak alkaline compounds include Group IIa hydroxides of the Periodic Table, and examples include Ca (OH) ₂ and Mg (OH) ₂ .

  Furthermore, in addition to the above-mentioned chemical adsorption, those that adsorb gas bodies such as activated carbon and silica gel can be used as physical adsorption.

  A moisture-proof sheet can be used as the exterior material and interior material used in the present invention.

  As the exterior material, a moisture-proof multilayer film composed of a metal foil layer for enhancing airtightness and a resin layer (polymer film layer) for maintaining strength can be used. The metal foil material is not particularly limited as long as it is lightweight and flexible and chemically stable, but aluminum is advantageous from the viewpoint of physical properties and cost. The polymer film material may be polyamide resin such as nylon, polyethylene terephthalate, or polyolefin resin such as polyethylene or polypropylene, but polyethylene terephthalate or nylon resin is advantageous in terms of mechanical strength.

  In addition, since it is optimal to seal by heat sealing, it is desirable that the inside of the battery of the moisture-proof multilayer film is a heat sealing resin layer, but it is also possible to seal using an adhesive resin It is. As the heat sealing resin, polyolefin resins such as polyethylene and polypropylene, polyamide resins such as nylon, vinyl acetate resins, acrylic resins, epoxy resins, and the like can be used, and are not particularly limited.

  A general-purpose laminate resin can be used as the moisture-proof multilayer film composed of such a heat-sealing resin layer and a metal foil layer.

The substance constituting the lithium ion conductive solid electrolyte used in the sulfide-based secondary battery of the present invention is not particularly limited as long as it is a substance containing sulfide or sulfide, and is an organic compound, an inorganic compound, or an organic compound. A material composed of both inorganic compounds can be used, and those known in the lithium ion battery field can be used.
In particular, sulfide-based inorganic solid electrolytes are known to have higher ionic conductivity than other inorganic compounds, and inorganic solid electrolytes described in JP-A-4-202024 can be used. Specifically, an inorganic solid electrolyte in which Li ₃ PO ₄ , a halogen, and a halogen compound are appropriately added to an inorganic solid electrolyte composed of a combination of Li ₂ S and SiS ₂ , GeS ₂ , P ₂ S ₅ , B ₂ S _3. Can be used.

Since lithium ion conductivity is high, lithium ion conduction generated from lithium sulfide and diphosphorus pentasulfide, or lithium sulfide and simple phosphorus and simple sulfur, as well as lithium sulfide, diphosphorus pentasulfide, simple phosphorus and / or simple sulfur It is preferable to use a conductive inorganic solid electrolyte. Hereinafter, a preferable solid electrolyte will be described.
The lithium ion conductive inorganic solid electrolyte can be produced from lithium sulfide and diphosphorus pentasulfide (P ₂ S ₅ ) and / or simple phosphorus and simple sulfur. Specifically, it can be produced by melting these raw materials and then rapidly cooling them. In addition, sulfide glass obtained by treating these raw materials by a mechanical milling method (hereinafter, sometimes referred to as MM method), or a heat-treated product thereof.

As lithium sulfide, those commercially available without limitation can be used, but those having high purity are preferable as described below.
Lithium sulfide preferably has a total content of lithium salts of sulfur oxides of 0.15% by mass or less, more preferably 0.1% by mass or less, and a content of lithium N-methylaminobutyrate is preferably 0. .15% by mass or less, more preferably 0.1% by mass or less. When the total content of the lithium salt of sulfur oxide is 0.15% by mass or less, the solid electrolyte obtained by the melt quenching method or the mechanical milling method described later is a glassy electrolyte (fully amorphous). That is, when the total content of the lithium salt of sulfur oxide exceeds 0.15% by mass, the obtained electrolyte is a crystallized product from the beginning, and the ionic conductivity of this crystallized product is low. Furthermore, even if the crystallized product is subjected to the following heat treatment, the crystallized product is not changed, and there is a possibility that a lithium ion conductive inorganic solid electrolyte having high ion conductivity cannot be obtained.

Further, when the content of lithium N-methylaminobutyrate is 0.15% by mass or less, the deteriorated product of lithium N-methylaminobutyrate does not deteriorate the cycle performance of the lithium battery.
Thus, in order to obtain a high ion conductive electrolyte, it is necessary to use lithium sulfide with reduced impurities.

The method for producing lithium sulfide used for producing the high ion conductive electrolyte is not particularly limited as long as it is a method that can reduce at least the impurities.
For example, it can also be obtained by purifying lithium sulfide produced by the following method.

Among the following production methods, the method a or b is particularly preferable.
a. A method in which lithium hydroxide and hydrogen sulfide are reacted at 0 to 150 ° C. in an aprotic organic solvent to produce lithium hydrosulfide, and this reaction solution is then desulfurized at 150 to 200 ° C. -330312).
b. A method of directly producing lithium sulfide by reacting lithium hydroxide and hydrogen sulfide at 150 to 200 ° C. in an aprotic organic solvent (Japanese Patent Laid-Open No. 7-330312).
c. A method of reacting lithium hydroxide and a gaseous sulfur source at a temperature of 130 to 445 ° C. (Japanese Patent Laid-Open No. 9-283156).

There is no restriction | limiting in particular as a purification method of the lithium sulfide obtained as mentioned above. As a preferable purification method, for example, the method described in International Publication No. WO2005 / 40039 and the like can be mentioned.
Specifically, the lithium sulfide obtained as described above is washed at a temperature of 100 ° C. or higher using an organic solvent. The organic solvent used for washing is preferably an aprotic polar solvent, and more preferably, the aprotic organic solvent used for lithium sulfide production and the aprotic polar organic solvent used for washing are the same. .

Examples of the aprotic polar organic solvent preferably used for washing include aprotic polar organic compounds such as amide compounds, lactam compounds, urea compounds, organic sulfur compounds, cyclic organophosphorus compounds, Or it can use suitably as a mixed solvent. In particular, N-methyl-2-pyrrolidone (NMP) is selected as a good solvent.
The amount of the organic solvent used for washing is not particularly limited, and the number of times of washing is not particularly limited, but is preferably 2 or more. Cleaning is preferably performed under an inert gas such as nitrogen or argon.
The washed lithium sulfide is dried at a temperature equal to or higher than the boiling point of the organic solvent used for washing for 5 minutes or more, preferably about 2 to 3 hours or more under an inert gas stream such as nitrogen under normal pressure or reduced pressure. Thus, lithium sulfide suitably used in the present invention can be obtained.

P ₂ S ₅ can be used without particular limitation as long as it is industrially manufactured and sold. In place of P ₂ S ₅ , elemental phosphorus (P) and elemental sulfur (S) in a corresponding molar ratio can also be used. Simple phosphorus (P) and simple sulfur (S) can be used without particular limitation as long as they are industrially produced and sold.

  In the present invention, as the solid electrolyte, both a glassy solid electrolyte and a solid electrolyte containing a crystal component (glass ceramic solid electrolyte) can be used. The type should be selected according to the required characteristics. Both may be used.

The mixing molar ratio of the lithium sulfide to diphosphorus pentasulfide or simple phosphorus and simple sulfur is usually 50:50 to 80:20, preferably 60:40 to 75:25.
Particularly preferably, it is about Li ₂ S: P ₂ S ₅ = 68: 32 to 74:26 (molar ratio).

Examples of the method for producing a sulfide glass that is a glassy electrolyte include a melt quenching method and a mechanical milling method.
In the case of the melt quenching method, a predetermined amount of P ₂ S ₅ and Li ₂ S are mixed in a mortar, and the pellets are placed in a carbon-coated quartz tube and sealed in a vacuum. After reacting at a predetermined reaction temperature, the glass is put into ice and quenched to obtain a sulfide glass.
The reaction temperature at this time is preferably 400 ° C to 1000 ° C, more preferably 800 ° C to 900 ° C. Moreover, reaction time becomes like this. Preferably it is 0.1 to 12 hours, More preferably, it is 1 to 12 hours. The quenching temperature of the reaction product is usually 10 ° C. or lower, preferably 0 ° C. or lower, and the cooling rate is about 1 to 10,000 K / sec, preferably 1 to 1000 K / sec.

In the case of the MM method, sulfide glass is obtained by mixing a predetermined amount of P ₂ S ₅ and Li ₂ S in a mortar and reacting for a predetermined time by a mechanical milling method.
The mechanical milling method using the above raw materials can be reacted at room temperature. According to the MM method, since a glassy electrolyte can be produced at room temperature, there is an advantage that a raw material is not thermally decomposed and a glassy electrolyte having a charged composition can be obtained. Further, the MM method has an advantage that the glassy electrolyte can be made into fine powder simultaneously with the production of the glassy electrolyte.
Although various types of pulverization methods can be used for the MM method, it is particularly preferable to use a planetary ball mill. The planetary ball mill can efficiently generate very high impact energy by rotating the platform while the pot rotates.

Although the rotation speed and rotation time of the MM method are not particularly limited, the faster the rotation speed, the faster the glassy electrolyte production rate, and the longer the rotation time, the higher the conversion rate of the raw material into the glassy electrolyte.
The electrolyte thus obtained is a glassy electrolyte and usually has an ionic conductivity of about 1.0 × 10 ^{−5 to} 8.0 × 10 ⁻⁴ (S / cm).
As conditions for the MM method, for example, when a planetary ball mill is used, the rotational speed may be set to several tens to several hundreds of revolutions / minute, and the treatment may be performed for 0.5 hours to 100 hours.
Although specific examples of the sulfide glass by the melt quenching method and the MM method have been described above, manufacturing conditions such as temperature conditions and processing time can be appropriately adjusted according to the equipment used.

Thereafter, the obtained sulfide glass is heat-treated at a predetermined temperature to produce a solid electrolyte containing a crystal component.
The heat treatment temperature for producing such a solid electrolyte is preferably 190 ° C to 340 ° C, more preferably 195 ° C to 335 ° C, and particularly preferably 200 ° C to 330 ° C. When the temperature is lower than 190 ° C., it may be difficult to obtain a crystal with high ion conductivity. When the temperature is higher than 340 ° C., a crystal with low ion conductivity may be generated.
In the case of a temperature of 190 ° C. or higher and 220 ° C. or lower, the heat treatment time is preferably 3 to 240 hours, particularly preferably 4 to 230 hours. Moreover, in the case of the temperature higher than 220 degreeC and 340 degrees C or less, 0.1 to 240 hours are preferable, 0.2 to 235 hours are especially preferable, Furthermore, 0.3 to 230 hours are preferable. If the heat treatment time is shorter than 0.1 hour, it may be difficult to obtain a crystal with high ion conductivity, and if it is longer than 240 hours, a crystal with low ion conductivity may be formed.

The lithium ion conductive inorganic solid electrolyte containing the crystal component thus obtained usually has an ionic conductivity of about 7.0 × 10 ^{−4 to} 5.0 × 10 ⁻³ (S / cm). It is.
This lithium ion conductive inorganic solid electrolyte has 2θ = 17.8 ± 0.3 deg, 18.2 ± 0.3 deg, 19.8 ± 0.3 deg, X-ray diffraction (CuKα: λ = 1.5418４), It is preferable to have diffraction peaks at 21.8 ± 0.3 deg, 23.8 ± 0.3 deg, 25.9 ± 0.3 deg, 29.5 ± 0.3 deg, 30.0 ± 0.3 deg. A solid electrolyte having such a crystal structure has extremely high lithium ion conductivity.

The lithium ion conductive solid material used in the present invention is a solid electrolyte containing a lithium (Li) element, a phosphorus (P) element and a sulfur (S) element, and the following (1) and (2) It is preferable to satisfy the following condition.
(1) The solid ³¹ P-NMR spectrum of the solid electrolyte has peaks due to crystals at 90.9 ± 0.4 ppm and 86.5 ± 0.4 ppm.
(2) The ratio (xc) of crystals that produce the peak (1) in the solid electrolyte is 60 mol% to 100 mol%.

The two peaks of condition (1) are observed when a high ion conductive crystal component is present in the solid electrolyte. Specifically, it is a peak caused by P ₂ S ₇ ^4- and PS ₄ ^3- in the crystal.

Condition (2) defines the ratio xc of the crystal in the solid electrolyte. When a high ion conductive crystal component is present in a predetermined amount or more, specifically 60 mol% or more in the solid electrolyte, lithium ions move mainly through the high ion conductive crystal. Therefore, the lithium ion conductivity is improved as compared with the case of moving a non-crystalline portion (glass portion) in the solid electrolyte or a crystal lattice (for example, P ₂ S ₆ ⁴⁻ ) that does not exhibit high ion conductivity. The ratio xc is preferably 65 mol% to 100 mol%. The crystal ratio xc can be controlled by adjusting the heat treatment time and temperature of the sulfide glass as a raw material.

The solid ³¹ P-NMR spectrum can be measured, for example, using a JNM-CMXP302 NMR apparatus manufactured by JEOL Ltd., with an observation nucleus of ³¹ P, an observation frequency of 121.339 MHz, a measurement temperature of room temperature, and a measurement method. Performed as MAS method.
The method of measuring the ratio xc is to calculate the resonance line observed at 70 to 120 ppm in a solid ³¹ P-NMR spectrum into a Gaussian curve using a nonlinear least square method and calculate from the area ratio of each curve. For details, refer to Japanese Patent Application No. 2005-356889.

In this solid electrolyte, the spin-lattice relaxation time T _1Li at room temperature (25 ° C.) measured by a solid ⁷ Li-NMR method is preferably 400 ms or less. The relaxation time T _1Li is an index of molecular mobility in a solid electrolyte including a glass state or a crystalline state and a glass state, and when T _1Li is short, the molecular mobility increases. Accordingly, since lithium ions are easily diffused during discharge, the ion conductivity is increased. In the present invention, as described above, since a high ion conductive crystal component is contained in a predetermined amount or more, T _1Li can be 400 ms or less. T _1Li is preferably 350 ms or less.

The spin-lattice relaxation time T _1Li of ⁷ Li can be obtained, for example, as follows.
When a JNM-CMXP302 NMR apparatus manufactured by JEOL Ltd. is used and measured under the following conditions, a ⁷ Li-NMR spectrum having a peak in the range of 0-1 ppm is obtained.
NMR measurement conditions Observation nucleus: ⁷ Li
Observation frequency: 116.489 MHz
Measurement temperature: Room temperature (25 ° C)
Measurement method: Saturation recovery method (Pulse sequence: see FIG. 7 of Japanese Patent Application No. 2005-356889)
90 ° pulse width: 4μs
Magic angle rotation speed: 6000Hz
Wait time until the next pulse application after FID measurement: 5s
Integration count: 64 times

The chemical shift is determined using LiBr (chemical shift -2.04 ppm) as an external reference.
T 1 _Li is determined by optimizing the change in the intensity of this peak obtained when measurement is performed while changing τ in FIG. 7 using the nonlinear least square method.

M (τ) = M (∞) (1-e ^{−τ / T1Li} )

M (τ): Peak intensity at τ

This solid electrolyte has a decomposition voltage of at least 10V or more. In addition, while maintaining the characteristic that the lithium ion transport number is 1, it exhibits extremely high lithium ion conductivity of 10 ⁻³ S / cm level at room temperature. Therefore, it is extremely suitable as a material for a solid electrolyte of a lithium battery. Moreover, it is a solid electrolyte excellent in heat resistance.

  The electrolyte layer constituting the sulfide-based secondary battery can be manufactured, for example, by forming a particulate lithium ion conductive solid material by a blast method or an aerosol deposition method. Also, a lithium ion conductive solid material can be formed by a cold spray method, a sputtering method, a vapor deposition method (CVD), a thermal spraying method, or the like.

Further, there is a method in which a solution in which a solid electrolyte is mixed with a solvent and a binder (such as a binder and a polymer compound) is applied and applied, and then the solvent is removed to form a film. Also, the solid electrolyte itself, solid electrolyte and binder (binder, polymer compound, etc.) and support (materials and compounds to reinforce the strength of the solid electrolyte layer and prevent short circuit of the solid electrolyte itself) are mixed -It is also possible to form a film by pressing the combined electrolyte under pressure.
The blasting method and the aerosol deposition method described above are preferable because a film can be formed in a temperature range that does not change the state of the solid electrolyte under a simple apparatus and room temperature conditions.
The thickness of the electrolyte is 1 to 500 μm, more preferably 1 to 50 μm, and still more preferably 1 to 30 μm.

  In the secondary battery of the present invention, as a current collector, a plate or foil made of copper, magnesium, stainless steel, titanium, iron, cobalt, nickel, zinc, aluminum, germanium, indium, lithium, or an alloy thereof. The body can be used.

  In a solid electrode material (electrode material) that is a member of a solid secondary battery, in order to improve ion conductivity in addition to electron conductivity, the particles of the electrode material are in close contact with each other, and the junction points and surfaces between the particles It is important to secure a larger number of ion conduction paths. Therefore, for example, a method of mixing an ion conductive active material such as an electrolyte to obtain an electrode material is used. In addition, the smaller the space generated in the gap between the polar material particles (the ratio of the volume of the polar material particles to the volume of the polar material particles: the porosity), the denser the polar material layer is and the higher the ionic conductivity.

The electrode that can be used in the present invention can be produced by forming the above-mentioned electrode material (positive electrode material or negative electrode material) in a film shape on at least a part of the current collector. Examples of the film forming method include a blast method, an aerosol deposition method, a cold spray method, a sputtering method, a vapor deposition method, and a thermal spray method, as in the production of the battery member described above. By forming a film by such a method, the porosity of the electrode material layer can be further reduced, and the ionic conductivity can be improved.
Moreover, it is possible to manufacture an electrode layer by the other similar method described in the manufacturing method of a solid electrolyte layer.
The blasting method and the aerosol deposition method are preferred because a film can be formed in a temperature range that does not change the crystal state of the electrolyte under a simple apparatus and room temperature conditions.

As a positive electrode material, what is used as a positive electrode active material in the battery field | area can be used. For example, in the sulfide system, titanium sulfide (TiS ₂ ), molybdenum sulfide (MoS ₂ ), iron sulfide (FeS, FeS ₂ ), copper sulfide (CuS), nickel sulfide (Ni ₃ S ₂ ), and the like can be used. Preferably, TiS ₂ can be used.
In the oxide system, bismuth oxide (Bi ₂ O ₃ ), bismuth lead acid (Bi ₂ Pb ₂ O ₅ ), copper oxide (CuO), vanadium oxide (V ₆ O ₁₃ ), lithium cobalt oxide (LiCoO ₂ ) Lithium nickelate (LiNiO ₂ ), lithium manganate (LiMnO ₂ ), and the like can be used. It is also possible to use a mixture of these. Preferably, lithium cobaltate can be used.
In addition to the above, niobium selenide (NbSe ₃ ) can be used.

  As the conductive auxiliary agent, a substance having electrical conductivity for allowing electrons to move smoothly in the positive electrode active material may be appropriately added. The electrically conductive substance is not particularly limited, but a conductive substance such as acetylene black, carbon black and carbon nanotube or a conductive polymer such as polyaniline, polyacetylene and polypyrrole may be used alone or in combination. Can be used.

As a negative electrode material, what is used as a negative electrode active material in the battery field | area can be used. For example, carbon materials, specifically artificial graphite, graphite carbon fiber, resin-fired carbon, pyrolytic vapor-grown carbon, coke, mesocarbon microbeads (MCMB), furfuryl alcohol resin-fired carbon, polyacene, pitch-based carbon Examples include fibers, vapor grown carbon fibers, natural graphite, and non-graphitizable carbon. Or it may be a mixture thereof. Preferably, it is artificial graphite.
In addition, metallic lithium, metallic indium, metallic aluminum, metallic silicon, or an alloy combined with these metals themselves, other elements, or compounds can be used as the negative electrode material.
Furthermore, you may mix and use the solid electrolyte material used for an electrolyte layer with an pole material.

The sulfide-based secondary battery of the present invention can be manufactured by bonding and joining the above-described battery members and / or electrode members. As a method of joining, there are a method of laminating each member, pressurizing and pressure bonding, a method of pressing through two rolls (roll to roll), and the like.
Moreover, you may join to the joining surface through the active material which has ion conductivity, and the adhesive material which does not inhibit ion conductivity.
In joining, heat fusion may be performed as long as the crystal structure of the solid electrolyte does not change.
In addition, since the secondary battery of the present invention can be thinned, it can be stacked to obtain a high output. Furthermore, a high degree of integration is possible.

[Production Example 1]
(1) Production of lithium sulfide (Li ₂ S) In a 10 liter autoclave equipped with a stirring blade, N-methyl-2-pyrrolidone (NMP) 3326.4 g (33.6 mol) and lithium hydroxide 287.4 g (12 mol) ) And heated to 300 rpm and 130 ° C. After the temperature rise, hydrogen sulfide was blown into the liquid at a supply rate of 3 liters / minute for 2 hours. Subsequently, this reaction solution was heated in a nitrogen stream (200 cc / min) to dehydrosulfide a part of the reacted hydrogen sulfide. As the temperature increased, water produced as a by-product due to the reaction between hydrogen sulfide and lithium hydroxide started to evaporate, but this water was condensed by the condenser and extracted out of the system. While water was distilled out of the system, the temperature of the reaction solution rose, but when the temperature reached 180 ° C., the temperature increase was stopped and the temperature was kept constant. After the dehydrosulfurization reaction was completed (about 80 minutes), the reaction was completed to obtain lithium sulfide.

(2) Purification of lithium sulfide After decanting NMP in the 500 mL slurry reaction solution (NMP-lithium sulfide slurry) obtained in (1) above, 100 mL of dehydrated NMP was added and stirred at 105 ° C. for about 1 hour. did. NMP was decanted at that temperature. Further, 100 mL of NMP was added, stirred at 105 ° C. for about 1 hour, NMP was decanted at that temperature, and the same operation was repeated a total of 4 times. After completion of the decantation, lithium sulfide was dried at 230 ° C. (temperature higher than the boiling point of NMP) under a nitrogen stream for 3 hours under normal pressure. The impurity content in the obtained lithium sulfide was measured.

Incidentally, lithium sulfite _(Li 2 _SO 3), the content of each sulfur oxide lithium sulfate _(Li 2 SO ₄₎ and lithium thiosulfate _{(Li 2 S 2 O 3)} , and N- methylamino acid lithium (LMAB) Was quantified by ion chromatography. As a result, the total content of sulfur oxides was 0.13% by mass, and LMAB was 0.07% by mass.

(3) Manufacture of glassy solid electrolyte Alumina balls having a mixture of Li ₂ S and P ₂ S ₅ (manufactured by Aldrich) prepared as described above in a molar ratio of 70:30 to about 1 g and a particle diameter of 10 mmΦ 10 pieces are put in a 45 mL alumina container, and a planetary ball mill (manufactured by Fritsch: Model No. P-7) is used in nitrogen, at room temperature (25 ° C.) at a rotation speed of 370 rpm, and mechanical milling for 20 hours. As a result, a sulfide-based glass (solid electrolyte) that was a white-yellow powder was obtained.

(4) Production of Crystallized Solid Electrolyte The sulfide-based glass powder produced in (3) above was baked at 300 ° C. for 2 hours in nitrogen to obtain a sulfide-based crystallized glass. In addition, the ionic conductivity of this sulfide type crystallized glass was 2.0 * 10 < ^-3 > S / cm.
(5) Preparation of three-layer pellet Three-layer pellet using carbon graphite (manufactured by TIMCAL, SFG-15) as the negative electrode active material and lithium cobaltate (LiCoO ₂ ) as the positive electrode active material. Was made.
In the three-layer pellet, a lithium ion conductive solid electrolyte (the powder of the sulfide-based crystallized glass of (4) above) and carbon graphite were mixed at a mass ratio of 1: 1 to obtain a negative electrode material. Moreover, what mixed lithium cobaltate and lithium ion conductive solid electrolyte (the powder of the sulfide type crystallized glass of said (4)) by the mass ratio of 8: 5 was used as positive electrode material.
For the production of the pellets, a commercially available pellet molding machine was used, and the negative electrode material, the sulfide crystallized glass (150 mg) of the solid electrolyte (150 mg), and the positive electrode material (20 mg) were sequentially placed in the pellet molding machine. A pressure of 20 t / cm ² was applied to produce a three-layer pellet of a positive electrode, a solid electrolyte, and a negative electrode.

[Example 1]
(1) Production of Laminated Battery (Battery Cell) FIG. 5A is an exploded sectional view of a laminated battery (battery cell). 20 is a moisture-proof multilayer film (inside PP layer) composed of a polyethylene terephthalate layer (12 μm) / aluminum foil layer (7 μm) / polypropylene layer (PP) (70 μm), 12 is a negative electrode, 13 is a positive electrode, and 14 is a solid Electrolyte layers, 15 and 16 are electrode terminals made of SUS, and 17 is a polyethylene piece of a heat-sealing sealant. In addition, the negative electrode 12, the positive electrode 13, and the solid electrolyte layer 14 used what was manufactured as a three-layer pellet by said (5). A SUS current collector (not shown) having a thickness of 0.3 mm and the same shape as a 10 mmφ pellet is inserted between the electrode terminals 15 and 16 and the electrode materials 12 and 13. 16 were joined by welding.
In the configuration of FIG. 5A, the periphery of the moisture-proof multilayer film 20 is hot-pressed, and the polyethylene piece 17 is thermally melted to seal the current collector, the negative electrode 12, the positive electrode 13, and the entire solid electrolyte layer 14 with the multilayer film 20. Thus, a laminated battery 10 was manufactured (FIG. 5B). In the sealing process, sealing was performed while depressurizing so that no gas portion remained between the film and the battery.
The laminate battery 10 had an initial charge / discharge efficiency of 82% and an operating potential of 3.3V.

(2) Exterior of Laminate Battery (Battery Cell) The electrode terminals 15 and 16 were covered and coated (not shown) with molten PP, leaving part of the ends of the electrode terminals 15 and 16 of the laminate battery 10. Then, as shown in FIG.5 (c), the moisture-proof multilayer film 30 (the same thing as the moisture-proof multilayer film as described in said (1)) is laminated | stacked so that the laminated battery 10 whole may be covered, and the polyethylene piece 32 is attached. Using, the outer peripheral portion was subjected to thermocompression bonding while leaving a part of the opening 33.
Granular magnesium hydroxide having an average particle diameter of 1 mm is injected from the opening 33, spread over the whole 20 and the remaining opening 33 is sealed by heat fusion using a polyethylene piece 32 (FIG. 5). (D)), a sulfide-based secondary battery 1 was manufactured.

(3) Battery Evaluation A nail penetration test, which is a technique for confirming battery safety, was performed on the battery prepared in (2). Even after 10 minutes from the time when the nail was pierced, the hydrogen sulfide detector installed at a position 1 m away from the battery did not react.
The nail penetration test is a safety test based on the UL (Underwriters Laboratories Inc.) standard.
As the hydrogen sulfide detector, a cosmos gas detector XS-2000 was used.

[Example 2]
In order to maintain the strength, as shown in FIG. 3, a battery was manufactured in the same manner as in Examples 1 (1) and (2) except that the exterior material 30 was crimped at the same position as the crimping portion of the interior material 20.
The manufactured battery was subjected to a nail penetration test similar to that in Example 1 (3), but similar results were obtained.

[Comparative Example 1]
The same nail penetration test as in Example 1 (3) was performed on the laminate battery without exterior as shown in FIG. 5B manufactured in Example 1 (1).
As a result, the hydrogen sulfide detector alarm started to sound immediately after the nail was pierced.

  The sulfide-based secondary battery of the present invention can be used as a battery for a portable information terminal, a portable electronic device, a small household power storage device, a motorcycle using a motor as a power source, an electric vehicle, a hybrid electric vehicle, or the like.

It is sectional drawing which shows the sulfide type secondary battery which concerns on one Embodiment of this invention. It is the schematic of the sulfide type secondary battery which coated the lead frame. It is sectional drawing which shows the sulfide type secondary battery which concerns on other embodiment of this invention. It is sectional drawing which shows the sulfide type secondary battery which concerns on other embodiment of this invention. 3 is a diagram showing a method for manufacturing the sulfide-based secondary battery of Example 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sulfide secondary battery 10 Battery cell, laminated battery 12 Negative electrode 13 Positive electrode 14 Solid electrolyte 15, 16 Lead frame 17 Polyethylene piece 18 Lead frame coating 19 Current collector 20 Interior material 30 Exterior material 31 Detoxification substance 32 Polyethylene piece 33 Opening 34 Magnesium hydroxide slurry

Claims (3)

The battery cell contains a sulfur compound that generates hydrogen sulfide gas by decomposition,
A sulfide-based secondary battery in which an outer peripheral portion of the battery cell is covered with a substance that traps hydrogen sulfide gas and makes it non-toxic.   The sulfide-based secondary battery according to claim 1, wherein the substance that detoxifies the hydrogen sulfide gas is an alkaline compound. A lead frame extending from the battery cell through a substance that detoxifies the hydrogen sulfide gas;
3. The sulfide-based secondary according to claim 1, wherein at least a portion of the lead frame in contact with a substance that detoxifies the hydrogen sulfide gas is covered with a substance that does not react with the substance that detoxifies the hydrogen sulfide gas. battery.

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