JP2007242454A - Nonaqueous electrolytic solution secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolytic solution secondary battery in which reliability in high temperature storage is improved without reducing mass productivity and battery capacity. <P>SOLUTION: This is the nonaqueous electrolytic solution secondary battery which is equipped with an electrode group, nonaqueous electrolytic solution, and a gas absorbing agent to absorb gas generated in the battery, in which the electrode group includes a positive electrode having lithium containing complex oxide as a positive electrode material, a negative electrode having a material capable of storing and releasing metal lithium or lithium ion as a negative electrode material, and a separator interposed between the positive electrode and the negative electrode, in which the nonaqueous electrolytic solution contains nonaqueous solvent and lithium salt dissolved in it, and in which the gas absorbing agent contains a mesoporous material modified by amine. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a non-aqueous electrolyte secondary battery having excellent reliability.

  In recent years, consumer electronic devices such as cellular phones, portable personal computers, and portable video cameras are rapidly becoming portable and cordless. For this reason, as a power source for driving these electronic devices, there is an increasing demand for a secondary battery that is small and light and has a high energy density.

From the above viewpoints, non-aqueous electrolysis using a lithium-containing composite oxide as a positive electrode active material and lithium metal, a lithium alloy, a carbon material capable of occluding and releasing lithium ions, a silicon compound, a tin compound, etc. as a negative electrode active material Liquid secondary batteries are being developed. In such a battery, a microporous membrane such as polyethylene (PE) or polypropylene (PP) is mainly used as a separator, and as a non-aqueous electrolyte, LiBF ₄ , LiPF ₆ or the like is used in an aprotic non-aqueous solvent. A solution in which the lithium salt is dissolved is used.

  Since the non-aqueous electrolyte secondary battery as described above has a high electromotive force, the non-aqueous solvent in the non-aqueous electrolyte is easily decomposed when stored at a high temperature in a charged state. It is known that when the non-aqueous solvent is decomposed, a gas mainly composed of carbon dioxide is generated.

  The generated gas increases the battery internal pressure. For this reason, for example, in the case of a rectangular battery, deformation or breakage of the outer case occurs. In the case of a cylindrical battery, the internal pressure operation type current interruption mechanism provided in the sealing plate in order to ensure the safety at the time of overcharge causes malfunction.

  Thus, since the nonaqueous solvent secondary battery containing a nonaqueous solvent cannot avoid the decomposition of the nonaqueous solvent, a means for suppressing the above problems is strongly demanded. For example, in order to suppress an increase in battery internal pressure due to cracked gas, use of various absorbents that absorb carbon dioxide has been studied (see Patent Document 1 and Patent Document 2). In Patent Document 1, as a carbon dioxide absorbent, a group I or group II metal hydroxide, oxide or carbonate, or zeolite of the periodic table, an iron-based oxygen scavenger having carbon dioxide absorption capacity, metallic lithium, The use of metallic calcium, metallic magnesium or the like is disclosed. Patent Document 2 discloses the use of porous glass, silica gel, activated alumina, activated carbon, activated clay and the like as a carbon dioxide absorbent.

  As described above, in a non-aqueous electrolyte secondary battery, studies have been conventionally made to suppress a decrease in reliability associated with an increase in internal pressure due to the generation of carbon dioxide. However, with the above-described configuration, it is difficult to stably suppress an increase in battery internal pressure for a long period of time. Because, as described in Patent Document 3, when the gas absorbent is arranged so as to be in contact with the non-aqueous electrolyte, the gas absorbent is wetted with the non-aqueous solvent, and functions as a gas absorbent. It is because is inhibited.

On the other hand, conventionally, it has been proposed to use SrO, CaO, BaO, MgO or the like as a gas absorbent and arrange the gas absorbent so as not to come into direct contact with a nonaqueous solvent (see Patent Document 4). It has also been proposed to use a gas absorbent comprising a gas absorbent material and a lyophobic material for a non-aqueous solvent (see Patent Document 3).
Japanese Patent Laid-Open No. 10-255860 Japanese Patent Laid-Open No. 11-307131 Japanese Patent Laid-Open No. 2003-77549 JP-A-11-54154

However, it is difficult to dispose the gas absorbent so as not to come into direct contact with the non-aqueous solvent, which is not preferable from the viewpoint of mass productivity.
In addition, when using a gas absorbent consisting of a gas absorbent material and a lyophobic material for a non-aqueous solvent, the lyophobic material does not have a gas absorbing ability. It is lower than Therefore, in order to suppress a decrease in reliability due to an increase in the internal pressure of the battery due to the generation of carbon dioxide, a large amount of gas absorbent must be added to the battery, and the gas absorbent is installed in the battery. It is necessary to provide a large space. If a large space is provided in the battery, the volume that the electrode group can occupy in the battery is reduced, resulting in a problem that the battery capacity is reduced.

  In view of the above problems, an object of the present invention is to provide a non-aqueous electrolyte secondary battery that has improved reliability during high-temperature storage without reducing mass productivity and battery capacity.

As a result of the inventors' extensive research, the present invention shows that a mesoporous material modified with amine selectively absorbs carbon dioxide, and its gas absorption ability does not decrease even when it is in contact with a non-aqueous electrolyte. Based on finding.
That is, the present invention includes an electrode group, a non-aqueous electrolyte, and a gas absorbent that absorbs gas generated in the battery, and the electrode group includes a positive electrode using a lithium-containing composite oxide as a positive electrode material, metallic lithium or Including a negative electrode having a negative electrode material as a material capable of inserting and extracting lithium ions, and a separator interposed between the positive electrode and the negative electrode, the non-aqueous electrolyte includes a non-aqueous solvent and a lithium salt dissolved therein, The gas absorbent relates to a non-aqueous electrolyte secondary battery including a mesoporous material modified with an amine. In this non-aqueous electrolyte secondary battery, the electrode group, the non-aqueous electrolyte, and the gas absorbent are preferably housed in a battery case, and the battery case is preferably sealed.

  The mesoporous material is preferably mesoporous silica. The gas absorbent is preferably formed by reacting an amino group-containing silane coupling agent with a mesoporous material.

  In the non-aqueous electrolyte secondary battery, the amount of carbon dioxide adsorbed by the gas absorbent is preferably 0.9 mol or more per kg of the gas absorbent in an environment of 60 ° C. and 15 kPa.

  The gas absorbent preferably contains 3.5 mol or more of amino groups derived from the amine per kg.

Pore volume of the gas absorbent is preferably 2.0 cm ³ or less 0.07 cm ³ or more per gas absorbent 1g.

  The gas absorbent may be in contact with the non-aqueous electrolyte, or may be included in an insulating component disposed in the battery. When the gas absorbent is included in the insulating component, the insulating component is more preferably a separator.

  The end-of-charge voltage of the nonaqueous electrolyte secondary battery is preferably 4.3 V or higher.

  The nonaqueous electrolyte secondary battery of the present invention includes a gas absorbent containing a mesoporous material modified with an amine. Even when this gas absorbent is in contact with the non-aqueous electrolyte, the ability of absorbing gas such as carbon dioxide generated in the battery during high temperature storage does not decrease. Therefore, the arrangement location of the gas absorbent is not limited. For this reason, it is not necessary to ensure the place where a gas absorbent is installed in the battery. Therefore, the reliability at high temperature storage can be improved without reducing mass productivity and battery capacity.

  The non-aqueous electrolyte secondary battery of the present invention includes an electrode group, a non-aqueous electrolyte, and a gas absorbent that absorbs gas generated in the battery. The electrode group includes a positive electrode using a lithium-containing composite oxide as a positive electrode material, a negative electrode using a metal lithium or a substance capable of inserting and extracting lithium ions as a negative electrode material, and a separator interposed between the positive electrode and the negative electrode. The non-aqueous electrolyte contains a non-aqueous solvent and a lithium salt dissolved therein.

  A positive electrode can be comprised from the positive electrode collector and the positive mix layer carry | supported on it, for example. Similarly, the negative electrode can be composed of a negative electrode current collector and a negative electrode mixture layer carried thereon. In this case, the positive electrode material and the negative electrode material are included in the positive electrode mixture layer and the negative electrode mixture layer, respectively.

  The gas absorbent includes a mesoporous material modified with an amine. The mesoporous material functions as a support for fixing amino groups having carbon dioxide adsorption ability in the pores at high density. The amino group fixed in the pores of the mesoporous material is an adsorption field of carbon dioxide, and carbamate is generated by the reaction of this amino group and carbon dioxide. In this way, carbon dioxide is fixed to the amino group.

Such a gas absorbent can selectively absorb carbon dioxide without being wetted by the non-aqueous solvent contained in the non-aqueous electrolyte. Therefore, it is possible to install this gas absorbent in a place that is in direct contact with a non-aqueous solvent, such as a positive electrode mixture layer, a negative electrode mixture layer, and a separator. For this reason, since it is not necessary to provide a space for disposing the gas absorbent in the battery, implementation is facilitated, which is preferable from the viewpoint of mass productivity.
Moreover, since the lyophobic material for the non-aqueous solvent is not required, the ability of the gas absorbent can be maximized.
Furthermore, as described above, since it is not necessary to provide a space for disposing the gas absorbent in the battery, it is not necessary to reduce the size of the positive electrode and the negative electrode. Therefore, the battery capacity is not reduced.

  The mesoporous material is a material having pores (mesopores) having a pore diameter of 2 to 50 nm. Examples thereof include mesoporous silica and mesoporous materials composed of metallosilicates containing heteroatoms, non-silicon oxides, sulfides, phosphates, platinum, and the like.

  FIG. 1 shows an example of the structure of mesoporous silica. The mesoporous silica shown in FIG. 1 has a form in which a plurality of cylindrical bodies 1 containing silicon atoms are gathered with their openings directed in the same direction. Note that the mesoporous material may have a structure other than this.

The mesoporous material is modified with an amine. By thus modifying with an amine, for example, an amino group is introduced into the inner wall of the mesopores of the mesoporous material.
At this time, the amine to be modified may have one or more amino groups in the molecule. In the amino group to be introduced, the hydrogen atom may be substituted with another substituent or may not be substituted. For example, when a substituted amino group is introduced into the mesopore, the amino group may be a primary amino group, a secondary amino group, or a tertiary amino group.
Moreover, you may use the above amino groups in combination of 2 or more types.
Furthermore, the amino group may have a spacer portion such as a hydrocarbon chain interposed between the inner wall of the mesoporous material.

  When the hydrogen atom of the amino group is substituted, the substituent is preferably a methyl group, an ethyl group, a propyl group, a phenyl group or the like.

  Such a gas absorbent can be produced by reacting a molecule having one or more amino groups in the molecule with a mesoporous material. For example, it can be formed by a graft method using a mesoporous material and a silane coupling agent having an organic functional group.

  First, a mesoporous material and a silane coupling agent are chemically reacted. This reaction is preferably performed in a predetermined solvent. That is, it is preferable to mix the mesoporous material and the silane coupling agent with a predetermined solvent to obtain a reaction mixture. The reaction temperature is not particularly limited. In addition, it is preferable to react the mesoporous material and the silane coupling agent while heating the reaction mixture to the boiling point of the solvent contained and refluxing the reaction mixture. Thereby, reaction with a mesoporous material and a silane coupling agent can be accelerated | stimulated.

  Examples of the solvent used in the above reaction include organic solvents such as methanol, ethanol, isopropanol, benzene, (dehydrated) toluene, xylene, acetone, ethyl acetate, methyl cellosolve, and tetrahydrofuran. Of these, (dehydrated) toluene is preferred.

  Subsequently, the mesoporous material in which the silane coupling agent is introduced into the pores can be obtained by filtering the mixture after the reaction, washing the filtered solid content, and drying.

The organic functional group possessed by the silane coupling agent may or may not be an amino group. When the organic functional group of the silane coupling agent is an amino group, the amino group is introduced into the mesopores of the mesoporous material by the above reaction.
When the organic functional group of the silane coupling agent is not an amino group, the organic functional group is substituted with an amino group. Substitution of an organic functional group to an amino group can be performed by a known method.

  Thus, in the present invention, amino groups are introduced into the mesopores of the mesoporous material using the graft method. In the impregnation method, the gas absorption component 3 may block the mesopores 4 of the mesoporous material 2 as shown in FIG. For this reason, a specific surface area becomes small and the adsorption speed of gas becomes slow. On the other hand, by using the graft method, as shown in FIG. 3, compared with the conventional impregnation method, the mesopores 4 of the mesoporous material 2 are not clogged with the gas-absorbing component (amino). It is possible to introduce the group 3) uniformly and at a high density. For this reason, compared with the gas absorbent produced by the impregnation method, the gas adsorption rate can be improved.

  As the silane coupling agent, both those having an amino group and those having no amino group can be used as described above. Examples thereof include 3-aminopropyltriethoxysilane, N-methyl-3-aminopropyltriethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, N- (2-aminoethyl). -3-aminopropylmethyldimethoxysilane, (3-trimethoxysilylpropyl) diethylenetriamine, γ-methacryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, methyltrimethoxysilane , Methyltriethoxysilane, vinyltriacetoxysilane, γ-methacryloxypropyltrimethoxysilane, hexamethyldisilazane, γ-anilinopropyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyl Lutris (β-methoxyethoxy) silane, N-vinylbenzyl-aminoethyl-γ-aminopropyltrimethoxysilane (hydrochloride), γ-chloropropyltrimethoxysilane, γ-chloropropylmethyldimethoxysilane, methyltrichlorosilane, dimethyl Dichlorosilane, trimethylchlorosilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, p-aminophenyltrimethoxysilane, N, N-dimethyl-3-aminopropyltrimethoxysilane Etc. These silane coupling agents may be used alone or in combination of two or more.

  Among these, those having an amino group in the molecule (amino group-containing silane coupling agent) are preferable. In particular, 3-aminopropyltriethoxysilane, N-methyl-3-aminopropyltriethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3- At least one amino group-containing silane coupling agent selected from the group consisting of aminopropylmethyldimethoxysilane and (3-trimethoxysilylpropyl) diethylenetriamine is preferred. The amino-containing silane coupling agent may have two or more amino groups in the molecule.

The amount of the silane coupling agent bound to the mesoporous material is about 0.1 to 75% by weight, preferably about 1 to 60% by weight, more preferably about 2.5 to about the total of the mesoporous material and the silane coupling agent. 50% by mass. If the amount of the silane coupling agent is less than about 0.1% by mass, the CO ₂ adsorption capacity becomes too small. When the amount exceeds about 75% by mass, the amount of the silane coupling agent becomes excessive, which is not economical. The amount of the silane coupling agent bonded to the mesoporous material is determined by subjecting the mesoporous material bonded with the silane coupling agent to thermogravimetric analysis or chemical analysis and measuring the contents of C, H, and N. Can do.

  As the mesoporous material, mesoporous silica is most preferable among the above. Mesoporous silica is mainly characterized by having a substantially uniform pore diameter in the range of 2 nm to 50 nm, a regular structure, and a large specific surface area and pore volume. For example, when mesoporous silica and zeolite are compared, the pore diameter of mesoporous silica is larger than the pore diameter of zeolite. For this reason, mesoporous silica can introduce relatively large molecules into its pores. That is, when the silane coupling agent is chemically bonded in the pores, mesoporous silica has a greater degree of freedom than zeolite. In addition, since mesoporous silica has a substantially uniform pore diameter, it is considered that more uniform chemical modification is possible than a substance having non-uniform pores. For these reasons, mesoporous silica is preferable among the mesoporous materials.

The adsorption capacity of the gas absorbent for carbon dioxide is not particularly limited, but a larger one is desirable. Therefore, it is desirable to use an adsorbent having an adsorption amount of carbon dioxide of 0.9 mol / kg or more in an environment of 60 ° C. and 15 kPa, assuming a state where carbon dioxide starts to be generated in the battery at a high temperature.
The adsorption capacity of the gas absorbent for carbon dioxide can be controlled by adjusting the amount of amino groups introduced into the mesopores.

The pore volume of the gas absorbent is preferably 0.07 to 2.0 cm ³ per 1 g of the gas absorbent, and more preferably 0.11 to 0.88 cm ³ . When the pore volume is smaller than 0.07 cm ³ / g, the carbon dioxide adsorption ability is lowered and a sufficient effect is not exhibited. When the pore volume is larger than 2.0 cm ³ / g, the strength of the gas absorbent is lowered and handling becomes difficult.

The content of the amino group derived from the amine in the gas absorbent is preferably 3.5 mol or more per kg of the gas absorbent. If the content of the amino group is less than 3.5 mol / kg, the number of sites that trap carbon dioxide is reduced, so that the adsorption capacity is lowered. For this reason, the effect of this invention is not fully exhibited.
Moreover, it is preferable that content of an amino group is 10 mol / kg or less. This is because if the amino group content is more than 10 mol / kg, the pores are blocked, and the adsorption rate of carbon dioxide is remarkably reduced.

  Since the nonaqueous electrolyte secondary battery of the present invention contains a gas absorbent, the end-of-charge voltage can be set to 4.3 V or higher. In a conventional battery that does not include a gas absorbent, if the end-of-charge voltage is 4.3 V or more, a large amount of gas is generated in the battery during high-temperature storage in a charged state, and the battery may be damaged. However, by adding a gas absorbent into the battery, the gas absorbent absorbs the gas generated in the battery. For this reason, even if it is charged to a high voltage and stored at a high temperature in that state, its reliability can be maintained.

  Even if the gas absorbent is in contact with the non-aqueous solvent contained in the non-aqueous electrolyte, the carbon dioxide adsorption capacity does not decrease. For this reason, the gas absorbent is not limited, but can be added to a portion in contact with the non-aqueous electrolyte, for example, a positive electrode mixture layer, a negative electrode mixture layer, and / or a separator.

As described above, the positive electrode and the negative electrode can be composed of a current collector and a mixture layer supported thereon. For example, the positive electrode is obtained by mixing a positive electrode material (positive electrode active material), a binder, a solvent, and a thickener as necessary to obtain a slurry, applying the slurry onto a current collector, and drying the slurry. . The negative electrode is also produced in the same manner as the positive electrode.
Therefore, when the gas absorbent is contained in the positive electrode mixture layer and / or the negative electrode mixture layer, the gas absorbent may be added to the slurry in the slurry kneading step, or the kneaded slurry may be added to the slurry after kneading. It may be added.
When the gas absorbent is added to the mixture layer, the amount is preferably 0.1 to 10 parts by weight per 100 parts by weight of the active material. When the amount of the gas absorbent added to the mixture layer is extremely small, the resulting gas absorption effect is reduced. On the other hand, when the amount of addition is remarkably large, the amount of active material that can be filled in the mixture layer is reduced, so that the battery capacity is significantly reduced. A more preferable addition amount of the gas absorbent is 0.5 to 5 parts by weight per 100 parts by weight of the active material.

  Further, since the gas absorbent has high insulating properties, it may be installed directly in the battery in the form of powder, for example. Further, from the viewpoint of not causing a decrease in battery capacity, the gas absorbent may be molded and used together with a resin on an insulating part installed in the battery. For example, in the case of a cylindrical battery, a gas absorbent is molded together with a resin as an insulating plate disposed above and below the electrode group, and in the case of a square battery, an insulating frame disposed above the electrode group. Is possible.

  As the resin used for molding the gas absorbent, a resin having a melting point of 100 ° C. or higher is preferable. Such resins include polyethylene resin (PE), polypropylene resin (PP), ethylene tetrafluoride / perfluoroalkoxy vinyl ether copolymer resin (PFA), polyphenylene sulfide resin (PPS) from the viewpoint of chemical stability. ), Polyethylene terephthalate resin (PET), and phenol resin are preferably used.

  Moreover, you may form the porous layer containing such a gas absorbent on a positive electrode and / or a negative electrode.

  Alternatively, the gas absorbent can be used as a separator by kneading together with a resin such as an acrylic rubber-based resin, a fluorine-based resin, a polyethylene oxide-based resin, or a polyacrylonitrile-based resin and molding it into a thin film. At this time, a laminate in which a porous film made of a polyolefin-based resin such as polyethylene or polypropylene and a thin film containing a gas absorbent, which has been conventionally used as a separator, can be used as a separator. Alternatively, a gas absorbent may be impregnated inside the porous membrane as described above.

In the present invention, a lithium-containing composite oxide is used as the positive electrode material. Although the lithium-containing composite oxide has a high capacity, it is highly reactive with a non-aqueous electrolyte and easily generates CO ₂ gas when stored at a high temperature in a charged state. Therefore, by adding a gas absorbent in the battery, even when the lithium-containing composite oxide is used as the positive electrode material and stored in a charged state at a high temperature, the generated CO ₂ gas can be absorbed. For this reason, the reliability of a battery can be improved.

Examples of the lithium-containing composite oxide include lithium-containing transition metal oxides. Examples _{thereof, Li x CoO 2, Li x} NiO 2, Li x MnO 2, Li x Co y Ni 1-y O 2, Li x Co f V 1-f O z, Li x Ni 1-y M y O ₂ (M = Ti, V, Mn, or Fe), Li _x Co _a Ni _{b McO 2} (M = Ti, Mn, Al, Mg, Fe, or Zr), Li _x Mn ₂ O ₄ , and _{li x Mn 2-y M y} O 4 (M = Na, Mg, Sc, Y, Fe, Co, Ni, Ti, Zr, Cu, Zn, Al, Pb , or Sb,) and the like. Here, x = 0 to 1.2, y = 0 to 0.9, f = 0.9 to 0.98, z = 2.0 to 2.3, a + b + c = 1, 0 ≦ a ≦ 1, 0 ≦ b ≦ 1, 0 ≦ c <1. In addition, x value is a value at the time of preparation of the oxide, and it increases / decreases by charging / discharging. Moreover, these oxides may be used independently and may be used in combination of 2 or more type.

Examples of the lithium-containing transition metal oxide include lithium carbonate, nitrate, oxide or hydroxide, and transition metal carbonate, nitrate, oxide or hydroxide of cobalt, manganese, nickel and the like. Can be prepared by a method of mixing, pulverizing and firing at a desired ratio. Alternatively, it can be synthesized by solution reaction.
The lithium-containing transition metal oxide is preferably synthesized by a firing method, and the firing temperature is preferably a temperature at which a part of the mixed compound is decomposed and melted, for example, 250 to 1500 ° C. The firing time is preferably 1 to 80 hours. The firing gas atmosphere may be any of air, an oxidizing atmosphere, and a reducing atmosphere, and is not particularly limited.

  The positive electrode mixture layer contains a conductive agent in addition to the positive electrode material. As the conductive agent, an electronically conductive material that does not cause a chemical change in a configured battery can be used. Examples of such materials include graphites such as natural graphite (flaky graphite, etc.), artificial graphite, carbon blacks such as acetylene black, ketjen black, channel black, furnace black, lamp black and thermal black, carbon Examples include fibers. These may be used alone or in combination of two or more. Among these conductive agents, artificial graphite and acetylene black are particularly preferable.

  The amount of the conductive agent in the positive electrode mixture layer is not particularly limited, but is preferably 1 to 50% by weight of the positive electrode mixture layer, and particularly preferably 1 to 30% by weight. For example, when carbon or graphite is used as the conductive agent, the amount is preferably 2 to 15% by weight of the positive electrode mixture layer.

Next, the negative electrode and nonaqueous electrolyte used in the nonaqueous electrolyte secondary battery of the present invention will be described.
As the negative electrode and the non-aqueous electrolyte, a negative electrode and a non-aqueous electrolyte conventionally used in non-aqueous electrolyte secondary batteries can be used without particular limitation.

  As described above, the negative electrode can also be composed of, for example, a negative electrode current collector and a negative electrode mixture layer carried thereon. The negative electrode mixture layer includes a negative electrode material that is a main material constituting the negative electrode mixture layer. As this negative electrode material, lithium metal, lithium alloy alloys, intermetallic compounds, carbon materials, organic compounds, inorganic compounds, metal complexes, organic polymer compounds, and other compounds capable of inserting and extracting lithium ions can be used. . These may be used alone or in combination of two or more. Among these, a carbon material is particularly preferable.

The average particle size of the carbon material is preferably from 0.1 to 60 μm, particularly preferably from 0.5 to 30 μm. The specific surface area of the carbon material is preferably 1 to 10 m ² / g. Among these, graphite having a carbon hexagonal plane interval (d ₀₀₂ ) of 3.35 to 3.4 mm and a crystallite size (Lc) in the c-axis direction of 100 mm or more is particularly preferable.

The non-aqueous electrolyte contains a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent. The non-aqueous solvent is preferably a cyclic carbonate such as ethylene carbonate or propylene carbonate, a chain carbonate such as dimethyl carbonate, diethyl carbonate or ethyl methyl carbonate, or a cyclic carboxylic acid ester such as γ-butyrolactone or γ-valerolactone. Used. These may be used alone or in combination of two or more.
As the lithium salt, LiPF ₆ , LiBF ₄ or the like can be used. These may be used alone or in combination of two or more.

  As the separator, an insulating microporous thin film having a large ion permeability and a predetermined mechanical strength is used. Especially, it is preferable to use as a separator the sheet | seat or nonwoven fabric produced from the olefin polymer and glass fiber etc. which contain at least 1 sort (s) of polypropylene, polyethylene, etc. from an organic solvent resistance and hydrophobic viewpoint. In addition, the separator preferably has a function of closing the holes at a certain temperature or higher and increasing the internal resistance.

The pore diameter of the separator pores is desirably in a range in which the active material, binder and / or conductive agent desorbed from the positive electrode and / or the negative electrode does not permeate, for example, 0.01 to 1 μm is desirable. . The porosity of the separator is determined according to the permeability of electrons and ions, the material of the separator, the film thickness, and the like, but is generally desirably 30 to 80%.
The thickness of the separator is generally 10 to 300 μm.

  Moreover, what laminated | stacked the thin film containing a gas absorbent and the said porous membrane, a sheet | seat, or a nonwoven fabric can also be used as a separator.

  The shape of the battery is not particularly limited, and may be any of a cylindrical shape, a flat shape, and a square shape. In order to ensure safety even in the case of malfunction, the battery is, for example, a pressure relief safety valve that releases the gas in the battery when the internal pressure of the battery reaches a predetermined pressure, and the internal pressure of the battery becomes a predetermined pressure. It is preferable to provide a safety valve that cuts off the current when

  Hereinafter, the present invention will be specifically described based on examples.

<Synthesis of gas absorbent>
(I) Production of mesoporous materials Various mesoporous silicas were produced by the following method.

(Preparation of mesoporous silica SBA-15)
Polyethylene oxide chain - polypropylene oxide chain - a triblock copolymer (EO ₂₀ PO ₇₀ EO ₂₀ (Aldrich)) having a polyethylene oxide chain 50 g, to a solution prepared by dissolving in distilled water 1.3dm ^3, tetraethoxysilane (Kishida 110 g of Chemical Co., Ltd. was added and stirred for 5 minutes.

Next, 175 cm ³ of 36 vol% hydrochloric acid (manufactured by Wako Pure Chemical Industries, Ltd.) was added to this solution over 30 minutes. Thereafter, the mixture was stirred at 35 ° C. for 20 hours, and further stirred at 95 ° C. for 24 hours.

The produced solid was collected by suction filtration and washed with 4 dm ³ of distilled water. This solid was dried in a thermostatic bath maintained at 70 ° C. for 12 hours and then calcined at 550 ° C. for 8 hours to obtain mesoporous silica SBA-15.

(Preparation of mesoporous silica wSBA-15)
6.0 g of mesoporous silica SBA-15 was added to 250 cm ³ of distilled water at 95 ° C. and boiled for 2 hours. Then, the solid substance collect | recovered by suction filtration was dried for 12 hours in the thermostat hold | maintained at 60 degreeC, and mesoporous silica wSBA-15 was obtained.

(Preparation of mesoporous silica MSU-H)
To a solution of 50 g of a triblock copolymer having a polyethylene oxide chain-polypropylene oxide chain-polyethylene oxide chain (EO ₂₀ PO ₇₀ EO ₂₀ (Aldrich)) in 1.4 dm ³ of distilled water, glacial acetic acid (Kishida Chemical ( 15 cm ³ ) and 72.5 cm ³ of sodium silicate solution (No. 3) (manufactured by Kishida Chemical Co., Ltd.) were added. The solution was stirred at 45 ° C. for 20 hours and then further stirred at 100 ° C. for 20 hours.
The produced solid was collected by suction filtration and washed with 4 dm ³ of distilled water. This solid was dried in a thermostatic bath maintained at 60 ° C. for 12 hours and then calcined at 550 ° C. for 8 hours to obtain mesoporous silica MSU-H.

(Preparation of mesoporous silica wMSU-H)
6.0 g of mesoporous silica MSU-H was added to 250 cm ³ of distilled water at 95 ° C. and boiled for 2 hours. Then, the solid substance collect | recovered by suction filtration was dried for 12 hours in the thermostat hold | maintained at 60 degreeC, and mesoporous silica wMSU-H was obtained.

(Preparation of mesoporous silica MCM-48)
In 110 cm ³ of distilled water, 15 g of hexadecyltrimethylammonium bromide (manufactured by Nacalai Tesque) and 2 g of sodium hydroxide (manufactured by Wako Pure Chemical Industries, Ltd.) were dissolved at 60 ° C. To this solution, 20 g of tetraethoxysilane (manufactured by Kishida Chemical Co., Ltd.) was added. Thereafter, the solution was stirred at 60 ° C. for 1.5 hours, then transferred to an autoclave and further heated at 90 ° C. for 72 hours.
The produced solid was collected by suction filtration and washed with distilled water. This solid was dried in a thermostatic bath maintained at 60 ° C. for 12 hours and then calcined at 500 ° C. for 12 hours to obtain mesoporous silica MCM-48.

(Preparation of mesoporous silica wMCM-48)
6.0 g of mesoporous silica MCM-48 was added to 250 cm ³ of distilled water at 95 ° C. and boiled for 2 hours. Then, the solid substance collect | recovered by suction filtration was dried for 12 hours in the thermostat hold | maintained at 60 degreeC, and mesoporous silica wMCM-48 was obtained.

(Preparation of mesoporous silica SBA-3)
In 120 cm ³ of distilled water, 4.4 g of hexadecyltrimethylammonium bromide (manufactured by Nacalai Tesque) and 20 cm ³ of 36 vol% hydrochloric acid (manufactured by Wako Pure Chemical Industries, Ltd.) are dissolved, and further 10 g of tetraethoxysilane ( Kishida Chemical Co., Ltd.) was added. After this time, the solution was stirred at room temperature for 4 hours.
The produced solid was collected by suction filtration and washed with distilled water. This solid was dried at room temperature for 12 hours and then calcined at 500 ° C. for 4 hours to obtain mesoporous silica SBA-3.

(Ii) Production of gas absorbent (production of gas absorbent APS / SBA-15 (g))
The mesoporous silica SBA-15 obtained as described above was dried in a constant temperature bath at 120 ° C. Thereafter, a predetermined amount of mesoporous silica SBA-15 was added to dehydrated toluene (manufactured by Wako Pure Chemical Industries, Ltd.), and the mixture was stirred. Next, a predetermined amount of 3-aminopropyltriethoxysilane (APS) (manufactured by Aldrich), which is an amino group-containing silane coupling agent, was added to the mixture. Thereafter, this mixture was stirred while refluxing at 110 ° C. for 24 hours in an inert gas argon stream.

  Thereafter, the mixture was allowed to cool to room temperature, and the solid material collected by suction filtration was washed with dehydrated toluene (manufactured by Wako Pure Chemical Industries, Ltd.). Next, the solid substance was dried in a constant temperature bath at 60 ° C. for 12 hours to obtain a gas absorbent APS / SBA-15 (g) into which an amino group was introduced.

(Production of MAPS / SBA-15 (g))
Gas absorbent MAPS / SBA-15 (g) was used in the same manner as APS / SBA-15 (g) except that N-methyl-3-aminopropyltriethoxysilane (MAPS) was used instead of APS. Obtained.

(Production of AEAPS / SBA-15 (g))
A gas absorbent AEAPS / SBA- was used in the same manner as APS / SBA-15 (g) except that N- (2-aminoethyl) -3-aminopropyltrimethoxysilane (AEAPS) was used instead of APS. 15 (g) was obtained.

(Production of AEAPMS / SBA-15 (g))
A gas absorbent AEAPMS / SBA- was used in the same manner as APS / SBA-15 (g) except that N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane (AEAPMS) was used instead of APS. 15 (g) was obtained.

(Production of TA / SBA-15 (g))
Gas absorbent TA / SBA-15 (g) was obtained in the same manner as APS / SBA-15 (g) except that (3-trimethoxysilylpropyl) diethylenetriamine (TA) was used instead of APS. .

(Production of APS / wSBA-15 (g))
A gas absorbent APS / wSBA-15 (g) was obtained in the same manner as APS / SBA-15 (g) except that mesoporous silica wSBA-15 was used instead of mesoporous silica SBA-15.

(Production of AEAPS / wSBA-15 (g))
A gas absorbent AEAPS / wSBA-15 (g) was obtained in the same manner as APS / wSBA-15 (g) except that AEAPS was used instead of APS.

(Production of TA / wSBA-15 (g))
Gas absorbent TA / wSBA-15 (g) was obtained in the same manner as APS / wSBA-15 (g) except that TA was used instead of APS.

(Production of APS / MSU-H (g))
A gas absorbent APS / MSU-H (g) was obtained in the same manner as APS / SBA-15 (g) except that mesoporous silica MSU-H was used instead of mesoporous silica SBA-15.

(Production of TA / MSU-H (g))
In the same manner as APS / SBA-15 (g), except that mesoporous silica MSU-H was used instead of mesoporous silica SBA-15 and TA was used instead of APS, gas absorbent TA / MSU-H ( g) was obtained.

(Preparation of APS / MCM-48 (g))
A gas absorbent APS / MCM-48 (g) was obtained in the same manner as APS / SBA-15 (g) except that mesoporous silica MCM-48 was used instead of mesoporous silica SBA-15.

(Production of TA / MCM-48 (g))
Gas absorbent TA / MCM-48 (as in APS / SBA-15 (g), except that mesoporous silica MCM-48 was used instead of mesoporous silica SBA-15, and TA was used instead of APS. g) was obtained.

(Preparation of APS / wMCM-48 (g))
A gas absorbent APS / wMCM-48 (g) was obtained in the same manner as APS / SBA-15 (g) except that mesoporous silica wMCM-48 was used instead of mesoporous silica SBA-15.

(Production of TA / wMCM-48 (g))
The gas absorbent TA / wMCM-48 (g) was used in the same manner as APS / SBA-15 (g) except that mesoporous silica wMCM-48 was used instead of mesoporous silica SBA-15 and TA was used instead of APS. g) was obtained.

(Production of APS / SBA-3 (g))
A gas absorbent APS / SBA-3 (g) was obtained in the same manner as APS / SBA-15 (g) except that mesoporous silica SBA-3 was used instead of mesoporous silica SBA-15.

(Production of TA / wMSU-H (g) (1))
The mesoporous silica wMSU-H was dried for 6 hours in a thermostatic bath maintained at 120 ° C. 5.0 g of dried mesoporous silica wMSU-H was added to 250 cm ³ of dehydrated toluene (manufactured by Wako Pure Chemical Industries, Ltd.) and stirred for 5 minutes, and then 50 cm ³ of TA was added thereto. This mixture was stirred while refluxing at 110 ° C. for 24 hours in an argon gas stream. After this time, the mixture was cooled to room temperature.

The cooled mixture was then filtered with suction to recover the solid. The solid content was washed with dehydrated toluene 200 cm ³ (manufactured by Wako Pure Chemical Industries, Ltd.) and then dried overnight in a thermostatic bath maintained at 60 ° C., and the gas absorbent TA / wMSU-H ( g) (1) was obtained.

(Production of TA / wMSU-H (g) (2))
The gas absorbent TA / wMSU-H (g) (1) obtained as described above was further treated with TA in the same manner as described above, so that the absorbent TA / wMSU-H (g) (2) was obtained.

(Production of APS / SBA-15 (i))
A gas absorbent APS / SBA-15 (i) was produced by the impregnation method as follows.
After adding APS to SBA-15 with stirring, the mixture was allowed to stand for 24 hours in a desiccator at 25 ° C. saturated with water vapor. Then, it was further left for 24 hours in a desiccator at 60 ° C. saturated with water vapor. Then, this mixture was dried overnight in a 60 degreeC thermostat, and absorbent APS / SBA-15 (i) processed with the amino group containing silane coupling agent was obtained.

(Iii) Evaluation of physical properties of mesoporous silica and gas absorbent The various mesoporous silica and gas absorbent obtained were measured for their specific surface area, average pore diameter and pore volume by the BET method using N ₂ gas. The obtained results are shown in Table 1.

  Further, the content (number of moles) of amino groups introduced per 1 kg of the gas absorbent was measured by thermogravimetric analysis and chemical analysis of C, H, and N elements. The obtained results are shown in Table 1.

Furthermore, the CO ₂ adsorption capacity of the gas absorbent was measured by the method shown below. Here, the test apparatus for examining the CO ₂ adsorption ability of the produced gas absorbent is composed of a gas absorbent filling column, a raw material gas cylinder, a vacuum pump, and a switching valve. This apparatus can perform tests such as adsorption / desorption of CO ₂ under a constant temperature and pressure condition by opening and closing a predetermined switching valve with a sequence controller.
A breakthrough curve was created by adsorbing 15% by volume of CO ₂ , 12% by volume of water, and the remaining N ₂ to 1.5 g of gas absorbent in an environment of 60 ° C., and CO _{2 at} 15 kPa. The amount of adsorption was estimated. The obtained results are shown in Table 1.

Example 1
(A) Production of positive electrode LiCoO ₂ (average particle diameter 8 μm, specific surface area 4.2 m ² / g by BET method) was used as a positive electrode active material, and 3 parts by weight of acetylene black as a conductive agent was added to 100 parts by weight of this active material. 4 parts by weight of polyvinylidene fluoride as a binder, 2 parts by weight of APS / SBA-15 (g) as a gas absorbent, and an appropriate amount of N-methyl-2-pyrrolidone are stirred and mixed. Thus, a paste-like positive electrode mixture was obtained. Polyvinylidene fluoride was used in a state of being previously dissolved in N-methyl-2-pyrrolidone.

  Next, the said paste-form positive mix was apply | coated to both surfaces of the collector which consists of 20-micrometer-thick aluminum foil, the coating film was dried, and it rolled with the roller. The obtained electrode plate was cut into a predetermined size to obtain a positive electrode.

Hereinafter, a method for preparing LiCoO ₂ used as the positive electrode active material will be described.
First, an aqueous metal salt solution in which cobalt sulfate was dissolved was prepared. The aqueous metal salt solution was maintained at 50 ° C. with stirring, and an aqueous solution containing 30% by weight of sodium hydroxide was dropped into the aqueous solution and neutralized to produce a precipitate of cobalt hydroxide.
The cobalt hydroxide precipitate was filtered, washed with water, dried in air, and then calcined at 400 ° C. for 5 hours to obtain cobalt oxide. The obtained cobalt oxide was confirmed to be a single phase by powder X-ray diffraction.

Next, the obtained cobalt oxide and lithium carbonate were mixed so that the ratio of the number of Co atoms to the number of Li atoms was 1: 1. This mixture was calcined at 950 ° C. for 10 hours. Thereafter, the fired product was pulverized to obtain a powder having a cumulative 50% particle size of 8 μm obtained by a laser diffraction method, thereby obtaining the target LiCoO ₂ . The obtained LiCoO ₂ was confirmed to have a single phase of hexagonal crystal structure by powder X-ray diffraction.

(B) Production of negative electrode 2.5 parts by weight of styrene-butadiene rubber as a binder was mixed with 100 parts by weight of flaky graphite that had been pulverized and classified so that the average particle diameter was about 20 μm. To this mixture, a CMC aqueous solution containing 1 part by weight of carboxymethylcellulose (CMC) per 100 parts by weight of flaky graphite was added, and stirred and mixed to obtain a paste-like negative electrode mixture.

  Next, the paste-like negative electrode mixture was applied to both surfaces of a current collector made of a copper foil having a thickness of 15 μm, and the coating film was dried and rolled with a roller. The obtained electrode plate was cut into a predetermined size to obtain a negative electrode.

(C) Battery assembly A square nonaqueous electrolyte secondary battery (thickness 5.2 mm, width 34 mm, height 50 mm, design capacity 800 mAh) was assembled using the positive electrode and the negative electrode obtained as described above. . FIG. 4 is a perspective view in which a part of the prismatic battery manufactured in the example is cut out.

This rectangular battery was assembled as follows.
The strip-shaped positive electrode and the negative electrode were wound in a spiral shape through a separator made of a microporous polyethylene resin having a thickness of 25 μm to produce the electrode plate group 11. An aluminum positive electrode lead 12 and a nickel negative electrode lead 13 were welded to the positive electrode and the negative electrode, respectively. An insulating frame 16 made of polyethylene resin was mounted on the upper part of the electrode plate group and housed inside an aluminum battery case 14 having a thickness of 0.25 mm. The other end of the positive electrode lead 12 was spot welded to the inner surface of the aluminum sealing plate 15. The other end of the negative electrode lead 13 was spot welded to the lower part of a nickel negative electrode terminal 17 attached to the center of the sealing plate 15 via an insulating material 19.
Next, the open end of the battery case 14 and the peripheral edge of the sealing plate 15 were laser welded. Then, a predetermined amount of non-aqueous electrolyte was injected from the injection port, and finally the injection port was sealed with an aluminum plug 18 to complete the battery.

In the non-aqueous electrolyte, 1 part by weight of vinylene carbonate is added to 100 parts by weight of a mixed solvent of ethylene carbonate and ethyl methyl carbonate in a volume ratio of 30:70, and LiPF ₆ is dissolved to a concentration of 1.0 mol / L. What was done was used.

Example 2
A battery was fabricated in the same manner as in Example 1 except that APS / SBA-15 (i) was used as the gas absorbent.

Example 3
A battery was fabricated in the same manner as in Example 1 except that MAPS / SBA-15 (g) was used as the gas absorbent.

Example 4
A battery was fabricated in the same manner as in Example 1, except that AEAPS / SBA-15 (g) was used as the gas absorbent.

Example 5
A battery was fabricated in the same manner as in Example 1 except that AEAPMS / SBA-15 (g) was used as the gas absorbent.

Example 6
A battery was fabricated in the same manner as in Example 1 except that TA / SBA-15 (g) was used as the gas absorbent.

Example 7
A battery was fabricated in the same manner as in Example 1 except that APS / wSBA-15 (g) was used as the gas absorbent.

Example 8
A battery was fabricated in the same manner as in Example 1, except that AEAPS / wSBA-15 (g) was used as the gas absorbent.

Example 9
A battery 9 was produced in the same manner as in Example 1 except that TA / wSBA-15 (g) was used as the gas absorbent.

Example 10
A battery was fabricated in the same manner as in Example 1 except that APS / MSU-H (g) was used as the gas absorbent.

Example 11
A battery was fabricated in the same manner as in Example 1 except that TA / MSU-H (g) was used as the gas absorbent.

Example 12
A battery was produced in the same manner as in Example 1 except that TA / wMSU-H (g) (1) was used as the gas absorbent.

Example 13
A battery was fabricated in the same manner as in Example 1 except that TA / wMSU-H (g) (2) was used as the gas absorbent.

Example 14
A battery was fabricated in the same manner as in Example 1 except that APS / MCM-48 (g) was used as the gas absorbent.

Example 15
A battery was fabricated in the same manner as in Example 1 except that TA / MCM-48 (g) was used as the gas absorbent.

Example 16
A battery was fabricated in the same manner as in Example 1 except that APS / wMCM-48 (g) was used as the gas absorbent.

Example 17
A battery was fabricated in the same manner as in Example 1 except that TA / wMCM-48 (g) was used as the gas absorbent.

Example 18
A battery was fabricated in the same manner as in Example 1, except that APS / SBA-3 (g) was used as the gas absorbent.

<< Comparative Example 1 >>
A battery was fabricated in the same manner as in Example 1 except that the gas absorbent was not used.

<< Comparative Example 2 >>
As a gas absorbent, Y-type zeolite (manufactured by Tosoh Corporation) (specific surface area 410 m ² / g, average pore diameter 0.74 nm, pore volume 0.48 cm ³ / g, CO ₂ adsorption amount 0.03 mol / kg) Using. A battery was fabricated in the same manner as in Example 1 except for this.

<< Comparative Example 3 >>
A battery was fabricated in the same manner as in Example 1 except that mesoporous silica SBA-15 was used instead of the gas absorbent.

<< Comparative Example 4 >>
A battery was fabricated in the same manner as in Example 1 except that mesoporous silica wSBA-15 was used instead of the gas absorbent.

<< Comparative Example 5 >>
A battery was fabricated in the same manner as in Example 1 except that mesoporous silica MSU-H was used instead of the gas absorbent.

<< Comparative Example 6 >>
A battery was fabricated in the same manner as in Example 1 except that mesoporous silica wMSU-H was used instead of the gas absorbent.

<< Comparative Example 7 >>
A battery was fabricated in the same manner as in Example 1 except that mesoporous silica MCM-48 was used instead of the gas absorbent.

<< Comparative Example 8 >>
A battery was fabricated in the same manner as in Example 1 except that mesoporous silica wMCM-48 was used instead of the gas absorbent.

<< Comparative Example 9 >>
A battery was fabricated in the same manner as in Example 1 except that mesoporous silica SBA-3 was used instead of the gas absorbent.

《Experimental evaluation》
(I) Initial charging / discharging Each of the batteries of Examples 1 to 18 and Comparative Examples 1 to 9 was repeated three times in a 25 ° C. environment, and the following charging / discharging cycle was repeated three times to perform acclimation charging / discharging. . The charging was constant current charging with a current value of 160 mA and a charge end voltage of 4.2 V. The discharge was a constant current discharge with a current value of 160 mA and a discharge end voltage of 3.0 V. In this break-in charging / discharging, it was confirmed that the discharge capacity in the second cycle almost coincided with the discharge capacity in the third cycle.

  Next, one of each of these batteries was subjected to a high-temperature storage test at a charging voltage of 4.2 V, 4.3 V, or 4.4 V.

(Ii) 4.2V high-temperature storage test The battery in the discharged state after the completion of the initial charge / discharge was charged with a constant voltage of 4.2V for 2 hours in a 25 ° C environment. In this charging, the maximum current value was set to 800 mA. The battery thickness in a charged state was measured using a micrometer, and the thickness was defined as T1. The measurement position was the center of the case. Thereafter, it was left in an 80 ° C. environment for 48 hours. The battery after standing was cooled to 25 ° C., the battery thickness was measured in the same manner, and the thickness was defined as T2. The amount of swelling of the battery was defined as T2-T1, and this amount of swelling was used as an index of the amount of deformation of the battery case due to gas generation during high-temperature storage. The obtained results are shown in Table 2.

(Iii) 4.3V high-temperature storage test The amount of battery swelling was measured in the same manner as the 4.2V high-temperature storage test except that the charge voltage value was 4.3V. The obtained results are shown in Table 2.

(Iv) 4.4V high-temperature storage test The amount of battery swelling was measured in the same manner as the 4.2V high-temperature storage test except that the charging voltage value was 4.4V. The obtained results are shown in Table 2.
Table 2 also shows the types of gas absorbents used.

Compared with the battery of Comparative Example 1 in which no gas absorbent was added, the batteries of Examples 1 to 18 in which mesoporous silica modified with amine was added as a gas absorbent were used in the high-temperature storage test at any voltage value. It can be seen that the swelling of the battery can be suppressed. On the other hand, the battery of Comparative Example 2 using Y-type zeolite, which is a general gas absorbent, resulted in almost no battery swelling. This is because, when mesoporous silica modified with amine was used as a gas absorbent, the adsorption ability of CO ₂ gas could be maintained without being wetted by the polar organic solvent which is the main component of the non-aqueous electrolyte, This is probably because the Y-type zeolite has been wetted by the polar organic solvent and has lost its original ability to adsorb CO ₂ gas.
As described above, even when the gas absorbent containing the mesoporous silica modified with amine is disposed at a position in contact with the non-aqueous electrolyte, it does not lose its ability to absorb CO ₂ gas and swells when the battery is stored at high temperature. It became clear that the deformation due to can be suppressed.

Moreover, it turns out that the battery of Comparative Examples 3-9 using only various mesoporous silica has the effect which hardly suppresses the swelling of a battery. This is because, as shown in Table 1, the mesoporous silica is for absorption incompetent of CO ₂ gas, in order to impart the absorption capacity of the CO ₂ gas in the mesoporous silica must be modified with amine I know that there is.

Furthermore, the battery of Example 1 and the battery of Example 2 using the same amino group-containing silane coupling agent (APS) and mesoporous silica (SBA-15) and using a gas absorbent prepared by different modification methods were compared. Then, it can be seen that the battery of Example 2 has a smaller swelling suppression effect than the battery of Example 1. As shown in Table 1, the gas absorbent APS / SBA-15 (i) used in the battery of Example 2 contained a relatively large amount of amine and exhibited a certain amount of CO ₂ adsorption. It is extremely small among gas absorbents that do not have pores and also use a specific surface area. Therefore, during high-temperature storage test, not follow the CO ₂ adsorption rate of the gas absorbent for the occurrence rate of CO ₂ that occurs in the battery, resulting in increased pressure inside the battery, the deformation of the battery case caused It is estimated that From this result, it can be seen that it is preferable to use a graft method to introduce an amino group into a mesoporous material.

Next, FIG. 5 shows the CO ₂ adsorption amount of the gas absorbent used in the batteries of Examples 1 and 3 to 18 and the charging voltage value of 4.2 V (diamond), 4.3 V (square) or 4.4 V. (Triangle) shows the relationship with the battery bulge during the high temperature storage test. FIG. 5 also shows the amount of swelling of the battery of Comparative Example 1 in the high temperature storage test at each voltage value.

At any charge voltage, the greater the amount of CO ₂ adsorbed by the gas absorbent, the greater the effect of suppressing battery swelling during high-temperature storage. If the CO ₂ adsorption amount of the gas absorbent is 0.25 mol / kg or more, the effect of suppressing battery swelling is recognized, but in order to remarkably improve the reliability during high temperature storage, a gas absorbent is added. It is desirable to make it about half of the swelling amount of the battery of Comparative Example 1 that does not exist. From this viewpoint, it is preferable to use a gas absorbent having a CO ₂ adsorption amount of 0.9 mol / kg or more, and it is more preferable to use a gas absorbent having an adsorption amount of 1.5 mol / kg or more.

In addition, by using a gas absorbent having a CO ₂ adsorption amount of 0.9 mol / kg or more, a battery that does not contain a gas absorbent even when a high voltage charge such as 4.3 V or 4.4 V is performed. It becomes possible to give the reliability at the time of high temperature storage equivalent to or higher than that when charging at 4.2V. Therefore, in the battery of the present invention including the gas absorbent, the charging voltage can be set to 4.3 V or higher.

  FIG. 6 shows the relationship between the amino group content of the gas absorbent used in the batteries of Examples 1 and 3 to 18 and the battery swelling during the high temperature storage test at each charging voltage. FIG. 6 also shows the amount of swelling of the battery of Comparative Example 1 in the high-temperature storage test at each voltage value.

  At any charge voltage, as the content of amino groups contained in the gas absorbent increased, the effect of suppressing battery swelling during high-temperature storage became significant. When the amino group content is 2.0 mol / kg or more, the effect of suppressing battery swelling is recognized, but in order to significantly improve the reliability during high-temperature storage, Comparative Example 1 in which no gas absorbent is added. It is desirable to make it about half the amount of battery swelling. From this viewpoint, it is preferable to use a gas absorbent having an amino group content of 3.5 mol / kg or more.

  FIG. 7 shows the pore volume of a gas absorbent having an equivalent amino group content (5.1 to 6.0 mol / kg) (Examples 2, 9, 12, 15 and 17) and high-temperature storage at each charging voltage. The relationship with the battery swelling at the time is shown. FIG. 7 also shows the amount of swelling of the battery of Comparative Example 1 in the high temperature storage test at each voltage value.

At any charge voltage, the effect of suppressing battery swelling during high-temperature storage became large as the pore volume of the gas absorbent generally increased. When the pore volume per 1 g of the gas absorbent was 0.025 cm ³ or more, the effect of suppressing battery swelling was recognized, and the effect of suppressing swelling increased to a pore volume of 0.07 cm ³ / g. When the pore volume was larger than 0.07 cm ³ / g, even if the pore volume increased, the swelling suppression effect was the same as or larger than that when the pore volume was 0.07 cm ³ / g. . On the other hand, when the pore volume of the gas absorbent is larger than 2.0 cm ³ / g, the strength of the gas absorbent is lowered and handling becomes difficult. From the above results, in order to obtain the effect of suppressing swelling stable cell pore volume of the gas absorber is preferably 0.07 cm ³ / g or more 2.0 cm ³ / g or less.

  In the following examples, the type of the positive electrode active material was changed.

Example 19
A battery was fabricated in the same manner as in Example 13, except that LiCo _0.975 Mg _0.020 Al _0.005 O ₂ (average particle diameter: 8 μm, specific surface area by BET method: 3.9 m ² / g) was used as the positive electrode active material.

A method for preparing LiCo _0.975 Mg _0.020 Al _0.005 O ₂ used as the positive electrode active material will be described below.
First, an aqueous metal salt solution in which cobalt sulfate and magnesium sulfate were dissolved at a predetermined ratio was prepared. The aqueous metal salt solution is maintained at 50 ° C. with stirring, and an aqueous solution containing 30% by weight of sodium hydroxide is dropped into the aqueous solution and neutralized to produce a precipitate of magnesium-containing cobalt hydroxide by a coprecipitation method. I let you.
The magnesium-containing cobalt hydroxide precipitate was filtered, washed with water, dried in air, and then calcined at 400 ° C. for 5 hours to obtain magnesium-containing cobalt oxide. The obtained magnesium-containing cobalt oxide was confirmed by powder X-ray diffraction to be a single phase, and magnesium being in solid solution.

Next, the obtained magnesium-containing cobalt oxide, aluminum hydroxide, and lithium carbonate were mixed so that the ratio of the number of (Co + Mg + Al) atoms to the number of Li atoms was 1: 1. This mixture was calcined at 950 ° C. for 10 hours, and then pulverized to obtain a powder having a cumulative 50% particle size of 8 μm obtained by laser diffraction, thereby obtaining the target LiCo _0.975 Mg _0.020 Al _0.005 O ₂ . The obtained LiCo _0.975 Mg _0.020 Al _0.005 O ₂ was confirmed by powder X-ray diffraction to have a single phase having a hexagonal crystal structure.

<< Comparative Example 9 >>
A battery was fabricated in the same manner as in Example 19 except that the gas absorbent was not used.

Example 20
Except that LiNi _1/3 Mn _1/3 Co _1/3 O ₂ (average particle size 10 μm, specific surface area 3.2 B ² / g by BET method) was used as the positive electrode active material, the same as Example 13 A battery was produced.

A method for preparing LiNi _1/3 Mn _1/3 Co _1/3 O ₂ used as the positive electrode active material will be described below.
First, an aqueous metal salt solution in which nickel sulfate, manganese sulfate and cobalt sulfate were dissolved at a predetermined ratio was prepared. The aqueous metal salt solution is maintained at 50 ° C. with stirring, and an aqueous solution containing 30% by weight of sodium hydroxide is dropped into the aqueous solution and neutralized, whereby a ternary hydroxide Ni _1/3 Mn is obtained. _{A 1/3} Co _1/3 (OH) ₂ precipitate was produced by coprecipitation.
The ternary hydroxide precipitate is filtered, washed with water, dried in air, and then calcined at 400 ° C. for 5 hours to form the ternary oxide Ni _1/3 Mn _1/3 Co _{1. / 3} O was obtained. The obtained ternary oxide was confirmed to be a single phase by powder X-ray diffraction.

Next, the obtained ternary oxide and lithium hydroxide monohydrate were mixed so that the ratio of the number of (Ni + Mn + Co) atoms to the number of Li atoms was 1: 1. This mixture is calcined in dry air at 1000 ° C. for 10 hours, and then pulverized to obtain a powder having a cumulative 50% particle size of 10 μm obtained by a laser diffraction method, whereby the target LiNi _1/3 Mn _1/3 Co _1/3 O ₂ was obtained. The obtained LiNi _1/3 Mn _1/3 Co _1/3 O ₂ was confirmed to have a single phase of hexagonal structure by powder X-ray diffraction.

<< Comparative Example 10 >>
A battery was fabricated in the same manner as in Example 20 except that the gas absorbent was not used.

<< Example 21 >>
A battery was fabricated in the same manner as in Example 13, except that LiNi _0.82 Co _0.15 Al _0.03 O ₂ (average particle diameter 9 μm, specific surface area 4.1 m ² / g by BET method) was used as the positive electrode active material.

A method for preparing LiNi _0.82 Co _0.15 Al _0.03 O ₂ used as the positive electrode active material will be described below.
First, an aqueous metal salt solution in which nickel sulfate and cobalt sulfate were dissolved at a predetermined ratio was prepared. The aqueous metal salt solution is maintained at 50 ° C. with stirring, and an aqueous solution containing 30% by weight of sodium hydroxide is dropped into the aqueous solution and neutralized to thereby precipitate cobalt-containing nickel hydroxide by coprecipitation. Generated.
The precipitate of cobalt-containing nickel hydroxide was filtered, washed with water, dried in air, and then calcined at 600 ° C. for 5 hours to obtain cobalt-containing nickel oxide. It was confirmed by powder X-ray diffraction that the obtained cobalt-containing nickel oxide was a single phase, and cobalt was in solid solution.

Next, the obtained cobalt-containing nickel oxide, aluminum hydroxide, and lithium hydroxide monohydrate were mixed so that the ratio of the number of (Ni + Co + Al) atoms to the number of Li atoms was 1: 1. . This mixture was calcined at 740 ° C. for 10 hours, and then pulverized to obtain a powder having an accumulated 50% particle size of 9 μm obtained by laser diffraction, thereby obtaining the target LiNi _0.82 Co _0.15 Al _0.03 O ₂ . The obtained LiNi _0.82 Co _0.15 Al _0.03 O ₂ was confirmed by powder X-ray diffraction to have a single phase having a hexagonal crystal structure, and Al was dissolved.

<< Comparative Example 11 >>
A comparative battery 11 was produced in the same manner as in Example 21 except that the gas absorbent was not used.

  The produced batteries 19 to 21 and comparative batteries 9 to 11 were subjected to initial charge and discharge as described above, and then subjected to a 4.2 V high-temperature storage test. The obtained results are shown in Table 3.

  Even if the kind of the positive electrode active material is changed, in the batteries of Examples 19 to 21 to which the gas absorbent was added, the battery swelling was suppressed as compared with the batteries of Comparative Examples 9 to 11 to which no gas absorbent was added. The effect of adding the absorbent was recognized.

  In the following examples, the part where the gas absorbent was added was changed.

Example 22
(I) Production of positive electrode A positive electrode was produced in the same manner as in Example 1 except that the gas absorbent was not added.

(Ii) Production of negative electrode A negative electrode was produced in the same manner as in Example 1.

(Iii) Battery assembly As an insulating frame to be installed on top of the electrode plate group, 0.1 g of polypropylene and 0.12 g of gas absorbent (TA / wMSU-H (g) (2)) are heated and kneaded. A battery was obtained in the same manner as in Example 1 except that the molded one was used.

<< Example 23 >>
(I) Production of positive electrode A positive electrode was produced in the same manner as in Example 1 except that the gas absorbent was not added.

(Ii) Production of negative electrode A negative electrode was produced in the same manner as in Example 1.

(Iii) Battery assembly In place of the 25 μm microporous polyethylene resin separator used in Example 1, an ion-permeable insulation formed by molding a copolymer of vinylidene fluoride and propylene hexafluoride to which a gas absorbent was added The membrane was used as a separator. A battery was obtained in the same manner as in Example 1 except for this.

A method for preparing the ion-permeable insulating film will be described below.
An appropriate amount of N-methyl-2-pyrrolidone was added to 10 parts by weight and 90 parts by weight of a gas absorbent (TA / wMSU-H (g) (2)) of a copolymer of polyvinylidene fluoride containing 10% by weight of propylene hexafluoride. Was added and stirred and mixed to obtain a slurry. This slurry was applied onto a 30 μm polyethylene terephthalate film and dried to obtain a target 25 μm ion-permeable insulating film. The produced ion-permeable insulating film was peeled from the polyethylene terephthalate film, and the insulating film was used as a separator.

The manufactured batteries of Examples 22 and 23 were subjected to the initial charge / discharge as described above, and then subjected to a 4.2 V high-temperature storage test. Table 4 shows the obtained results. In addition, the third discharge capacity in the initial charge / discharge is defined as the initial capacity, and the value is also shown in Table 4.
Table 4 also shows the results of Example 13 and Comparative Example 1.

  In the battery of Example 13 in which the gas absorbent was added to the positive electrode mixture layer, the battery swelling in the high temperature storage test was suppressed, but the proportion of the positive electrode active material contained in the positive electrode mixture layer was reduced. For this reason, as a result, the initial capacity of the battery of Example 13 is somewhat lower than that of the battery of Comparative Example 1. On the other hand, in the battery of Example 22 (insulation frame) and the battery of Example 23 (separator) in which the gas absorbent is incorporated as an insulating part in the battery, the ratio of the positive electrode active material contained in the positive electrode mixture layer is set as follows. Since it is not reduced, battery swelling can be suppressed without causing a reduction in initial capacity.

  As described above, from the viewpoint of achieving both high capacity and high temperature reliability, the gas absorbent is preferably molded as an insulating component disposed in the battery and provided in the battery. Although the example which added the gas absorber to the insulating frame or separator for square batteries was given in the said Example, the form is not specifically limited. For example, if an insulating component arranged so as to be in contact with the generated gas in the battery contains a gas absorbent, the effect can be exhibited.

  According to the present invention, the reliability of the battery during high-temperature storage can be improved. Therefore, the non-aqueous electrolyte secondary battery of the present invention can be used, for example, as a power source for portable electronic devices that require high reliability. Further, the present invention can be widely applied to an electric vehicle, a large battery used for power storage, and the like.

It is a perspective view which shows an example of the shape of mesoporous silica. The cross-sectional schematic diagram of the mesoporous material modified with amine by the impregnation method is shown. The cross-sectional schematic diagram of the mesoporous material modified with amine by the grafting method is shown. It is the perspective view which notched a part of the square nonaqueous electrolyte battery produced in the Example. It is a graph showing the relationship between the battery swelling during CO ₂ adsorption amount and the high-temperature storage test gas absorbent. It is a graph which shows the relationship between the amine content of a gas absorbent, and the battery swelling at the time of a high temperature storage test. It is a graph which shows the relationship between the pore volume of a gas absorbent, and the battery swelling at the time of a high temperature storage test.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cylindrical body 2 Mesoporous material 3 Gas absorption component 4 Mesopore 11 Electrode board group 12 Positive electrode lead 13 Negative electrode lead 14 Battery case 15 Sealing plate 16 Insulating frame 17 Negative electrode terminal 18 Sealing 19 Insulating material

Claims (10)

A gas absorbent that absorbs gas generated in the electrode group, non-aqueous electrolyte and battery,
The electrode group includes a positive electrode using a lithium-containing composite oxide as a positive electrode material, a negative electrode using a metal lithium or a substance capable of occluding and releasing lithium ions as a negative electrode material, and a separator interposed between the positive electrode and the negative electrode Including
The non-aqueous electrolyte includes a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent,
The gas absorbent is a non-aqueous electrolyte secondary battery including a mesoporous material modified with an amine.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the mesoporous material is mesoporous silica.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the gas absorbent is formed by reacting an amino group-containing silane coupling agent and the mesoporous material.   The nonaqueous electrolyte secondary battery according to claim 1, wherein the amount of carbon dioxide adsorbed by the gas absorbent is 0.9 mol or more per kg of the gas absorbent in an environment of 60 ° C and 15 kPa.   The nonaqueous electrolyte secondary battery according to claim 1, wherein the gas absorbent includes 3.5 mol or more of amino groups derived from the amine per 1 kg of the gas absorbent. The pore volume of the gas absorber is a non-aqueous electrolyte secondary battery according to claim 1 wherein the gas absorbent 2.0cm ³ or less is 0.07 cm ³ or more per 1g.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the gas absorbent is in contact with the non-aqueous electrolyte.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the gas absorbent is contained in an insulating component disposed in the battery.   The non-aqueous electrolyte secondary battery according to claim 8, wherein the insulating component is a separator.   The non-aqueous electrolyte secondary battery according to claim 1, wherein an end-of-charge voltage of the battery is 4.3 V or more.

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