JP2009146811A - Positive electrode body for lithium-ion secondary battery and lithium-ion secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lithium-ion secondary battery capable of preventing oxidative destruction or ignition of electrolyte solution even at overcharge or high temperature, and yet with high energy density. <P>SOLUTION: The positive electrode bodies 100, 200 are to include an oxygen-absorbing substance 1 having a lithium-ion absorbing and desorbing capacity, and moreover, having an oxygen-absorbing capacity at overcharge and containing lithium-content complex oxide, and a positive electrode active substance 2, respectively. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a positive electrode body for a lithium ion secondary battery and a lithium ion secondary battery, and more particularly to a lithium ion secondary battery with improved safety.

  In recent years, from the viewpoint of protecting the global environment, a high-performance and high-capacity high-performance power supply is required to be applied to electric vehicles, hybrid vehicles, and the like as low-pollution vehicles. Among these, the lithium ion secondary battery is small, light, and has a high capacity, and can be suitably used for the automobile and the like, and its performance is improved every day. Also, in fields other than the above-mentioned automobiles and the like, the mobile tools such as information-related devices and communication devices represented by mobile phones and laptop computers can be made smaller and higher performance by worldwide spread. Lithium ion secondary batteries are preferably used.

  Generally, a lithium ion secondary battery has a structure having a positive electrode body and a negative electrode body, and a separator that is impregnated with a non-aqueous electrolyte and sandwiched between the two electrode bodies. Further, the positive electrode body and the negative electrode body are formed by providing a positive electrode layer or a negative electrode layer obtained by mixing a positive electrode active material or a negative electrode active material with a conductive material or a binder on a current collector such as a metal foil. Yes.

As described above, the lithium ion secondary battery has a positive electrode active material and a non-aqueous electrolyte as its constituent elements. The positive electrode active material is known to release oxygen when overcharged, at high temperatures, etc., and in conventional lithium ion secondary batteries, the oxygen and non-aqueous electrolyte are in contact with each other. The oxidation reaction may lead to heat generation, ignition, explosion, and the like. Further, the cycle characteristics of the lithium ion secondary battery are deteriorated due to the oxidative decomposition of the nonaqueous electrolytic solution.
Therefore, a highly safe lithium ion secondary battery that can suppress the oxidation reaction even during overcharge or high temperature is desired, and various proposals have been made. As one of the methods for improving safety, there is a lithium ion secondary battery using an oxygen absorbing material as shown below.

Patent Document 1 discloses a lithium ion secondary battery composed of a positive electrode composed of a conductive agent and a positive electrode active material on which an oxygen absorbing material composed of a metal oxide is fixed, a negative electrode, and an electrolyte. It is described that oxygen generated from the positive electrode at a high temperature can be captured by such a configuration. Patent Document 2 discloses a secondary battery having an oxygen storage material mainly composed of cerium oxide and / or an oxygen storage material mainly composed of a cerium composite oxide containing cerium and zirconium and / or yttrium as constituent elements. For this positive electrode, it is described that oxygen generated from the positive electrode active material can be captured by an oxygen storage material. Further, Patent Document 3 discloses a material in which a coating layer containing an oxygen storage material mainly composed of a cerium composite oxide is formed on the surface of a positive electrode active material.
Japanese Patent Laid-Open No. 11-144734 JP 2006-114256 A JP 2006-32325 A

  However, in the lithium ion secondary battery as described above, the oxygen absorbing material contained in the positive electrode layer does not contribute to the absorption and release of lithium ions, and the lithium ion absorption and release amount of the positive electrode body is reduced. The energy density of the positive electrode body was low. In addition, the presence of the oxygen-absorbing material may inhibit lithium ion absorption / release of the positive electrode active material. Therefore, the conventional lithium ion secondary battery cannot satisfy both of the improvement in safety and the increase in energy density, and cannot be said to have sufficient performance.

  The present invention has been made in view of the above-described problems, and efficiently absorbs oxygen released from the positive electrode active material during overcharge and suppresses a decrease in energy density related to lithium ion absorption / release. The main purpose is to provide a secondary battery.

  In order to solve the above-mentioned problems, the inventor has intensively studied, and as a result, the positive electrode layer contains oxygen absorbing material having oxygen absorbing ability at the time of overcharge and having lithium ion absorbing / releasing ability. It has been found that ignition and the like due to release can be prevented, and the decrease in the energy density can be suppressed. The configuration of the present invention will be described below.

  1st this invention is a positive electrode body provided with the positive electrode layer containing a positive electrode active material and an oxygen absorption material, The said oxygen absorption material has lithium ion absorption-and-release capability, And it has oxygen absorption capability, The oxygen-absorbing material includes a lithium-containing composite oxide, which is a positive electrode body for a lithium ion secondary battery. As used herein, “including a positive electrode active material and an oxygen absorbing material” means that the positive electrode layer includes at least a positive electrode active material and an oxygen absorbing material, and additionally includes a conductive material, a binder, and the like. Also good. In addition, “a positive electrode body including a positive electrode layer” means that the positive electrode layer is an essential constituent element, and a positive electrode current collector or the like may be included. Furthermore, “having lithium ion absorption and release ability and oxygen absorption ability” means capturing oxygen released from the positive electrode active material during overcharge etc. while having lithium ion storage and release ability. Means that you can.

In the first aspect of the present invention, “having a lithium-containing composite oxide” means that at least a lithium-containing composite oxide is used as the oxygen-absorbing substance. The lithium-containing composite oxide is not particularly limited as long as it is a substance that can absorb oxygen and has an ability to absorb and release lithium ions during overcharge. Examples thereof include W-based composite oxides. Among these, LiMoO ₂ and LiWO ₂ are preferable because they have both excellent oxygen absorption ability and lithium ion absorption / release ability.

  In the first aspect of the present invention, the positive electrode active material is preferably coated with an oxygen absorbing material. As used herein, “covered with an oxygen-absorbing material” means that it is sufficient that an oxygen-absorbing material exists on the surface of the positive electrode active material and in the vicinity of the surface. Need not be tied together. However, from the viewpoint of efficiently absorbing oxygen by the oxygen absorbing material, it is preferable that the oxygen absorbing material is in contact with the surface of the positive electrode active material. By covering the surface of the positive electrode active material with the oxygen absorbing material, oxygen released from the positive electrode active material is efficiently captured.

  2nd this invention is a lithium ion secondary battery provided with the positive electrode body which is 1st this invention.

The positive electrode body according to the first aspect of the present invention includes a material having both an oxygen absorption capacity and a lithium absorption / release capacity as an oxygen absorption material in the positive electrode layer, without reducing the capacity of the lithium ion secondary battery, The safety can be improved. Further, by making the oxygen-absorbing substance a lithium-containing composite oxide, particularly LiMoO ₂ or LiWO ₂ , a positive electrode having a high oxygen-absorbing ability at the time of overcharge and a high density with respect to lithium ion absorption / release. It can be a body, and both improvement in safety and maintenance of energy density can be achieved.

  In the first aspect of the present invention, since the surface of the positive electrode active material is coated with an oxygen absorbing material, oxygen released from the surface of the positive electrode active material is efficiently captured by the oxygen absorbing material, and safety is improved. Figured.

  According to the second aspect of the present invention, a lithium ion secondary battery having a high safety and a high capacity, including the high performance positive electrode body, can be obtained.

  Embodiments of the present invention will be described below. In addition, embodiment shown below is an illustration and this invention is not limited to the following embodiment.

  The lithium ion secondary battery provided with the positive electrode body of the present invention can have the same basic configuration as the conventional one. For example, it can be configured to include a positive electrode body and a negative electrode body, and a separator impregnated in an organic electrolyte typified by a non-aqueous electrolyte and sandwiched between the two electrode bodies. . In addition, the positive electrode body and the negative electrode body are usually formed by providing a positive electrode layer or a negative electrode layer obtained by mixing a positive electrode active material or a negative electrode active material with a conductive material or a binder on a current collector such as a metal foil. Has been. In the present invention, by improving the configuration of the positive electrode body among the above configurations, a lithium ion secondary battery having high safety and high capacity is obtained. Hereinafter, the respective configurations of the positive electrode body and the lithium ion secondary battery of the present invention will be described in order with reference to FIGS.

<1. Positive electrode body 100, 200>
1A and 1B are diagrams schematically showing a positive electrode body of the present invention. As shown in FIGS. 1 (a) and 1 (b), the positive electrode body 100, 200 of the present invention requires an oxygen absorbing material 1 having a lithium ion absorbing / releasing capability and an oxygen absorbing capability, and a positive electrode active material 2. As a constituent element, a configuration that is conventionally used and applied to a positive electrode body, such as a conductive material 3 such as carbon particles and a current collector 20 as a current collecting base material, may be included. By including the essential components, the positive electrode bodies 100 and 200 having higher safety and higher capacity than the conventional positive electrode bodies can be obtained.

(1.1. Oxygen absorbing material 1)
The oxygen-absorbing substance 1 of the present invention is a material in which the effects of the present invention are suitably achieved, can efficiently capture oxygen released from the positive electrode active substance 2 during overcharge, and can absorb and release lithium ions. If it comprises, it will not specifically limit. Specifically, lithium containing complex oxides, such as Li-Mo type complex oxide and Li-W type complex oxide, are mentioned. In the present invention, it is particularly preferable that LiMoO ₂ having an oxygen absorption capacity and a high lithium ion absorption / release capacity is included. Hereinafter, the lithium ion absorption / release capability and the oxygen absorption capability of LiMoO ₂ will be described with reference to FIG.

FIG. 2A shows the state of the positive electrode active material 2 and the oxygen absorbing material 1 in the vicinity of 3.5 V (vs. Li ^/ Li ⁺ ). Here, vs. Li / Li ⁺ indicates that the potential reference is the potential at which lithium is electrodeposited. As shown in FIG. 2 (a), if they contain LiMoO ₂ in an oxygen-absorbing material, LiMoO ₂ is a Li ⁺ desorbed at around 3.5V (vs.Li/Li ^+), the MoO ₂ (below (See Equation 1). That is, in the vicinity of 3.5 V (vs. Li ^/ Li ⁺ ), both the oxygen absorbing material 1 and the positive electrode active material 2 have the ability to absorb and release lithium ions. Further, although the positive electrode active material 2 releases lithium ions, the release of oxygen due to decomposition is suppressed. Next, when the voltage is further increased from the state of FIG. 1A and an overcharged state is reached, the positive electrode active material is decomposed as shown in FIG. Is released (see Equation 2 below). At this time, since the oxygen absorbing material 1 is maintained in a state containing MoO ₂ as described above, it has oxygen absorbing ability. That is, oxygen released from the positive electrode active material 2 reaches the surface of the adjacent oxygen absorbing material 1 and is absorbed by MoO ₂ in the oxygen absorbing material 1. At this time, MoO ₂ becomes MoO ₃ by an oxidation reaction (see the following formula 3).

  Thus, the oxygen-absorbing substance 1 of the present invention has a lithium ion absorption / release capability at a specific potential, and can contribute to charging / discharging of the lithium ion secondary battery. Furthermore, since the oxygen absorbing material 1 changes to a form having excellent oxygen absorbing ability after lithium ion release at the specific potential or higher (during overcharge), oxygen released from the positive electrode active material 2 is efficiently used. Can absorb well. Therefore, the positive electrode bodies 100 and 200 including the oxygen absorbing material 1 have high safety and can maintain the energy density in a high density state.

  The specific shape of the oxygen-absorbing substance 1 is not particularly limited, such as powder / particle shape, columnar shape (columnar shape, quadrangular columnar shape, needle shape, curved shape, etc.). In the present invention, from the viewpoint of forming a positive electrode body suitably used for a lithium ion secondary battery, for example, the shape of the oxygen-absorbing substance 1 can be made into particles. The particulate oxygen-absorbing substance has an average particle size (measurement method is particle size distribution measurement by laser diffraction method, observation by SEM, etc.), preferably 100 μm or less, more preferably 10 μm or less, and 1 μm or less. More preferably. When the shape of the oxygen absorbing material 1 is out of the above range, oxygen may not be sufficiently absorbed with respect to the oxygen release of the positive electrode active material 2 at the time of overcharging, and the lithium ion absorbing / releasing ability may be reduced. This may lead to a decrease in the function as the positive electrode body.

  The amount of the oxygen-absorbing substance 1 contained in the positive electrode layer 10 is preferably 1% by mass or more and 30% by mass or less, more preferably 1% by mass or more and 20% by mass or less, based on the positive electrode layer 10 as a whole. More preferably, the content is 1% by mass or more and 10% by mass or less. When the content of the oxygen-absorbing material 1 is too small, sufficient oxygen-absorbing ability cannot be imparted to the positive electrode layer. On the other hand, when the content is too large, the amount of the positive-electrode active material 2 is decreased. The function as the positive electrode body may be reduced, such as reduction.

(1.2. Positive electrode active material 2)
The positive electrode active material 2 of the present invention is not particularly limited as long as it is conventionally used. Specifically, a lithium-containing composite oxide system represented by lithium cobalt oxide system, lithium nickel oxide system, lithium manganese oxide system, etc., a composite oxide doped with a different metal element, and Other examples include oxides and sulfides of different metals, and organic compounds such as polyaniline and polypyrrole. Among these, those based on lithium cobalt oxide are preferably used. Specifically, for example, a composite oxide represented by Li _y MO _z can be used. Here, M is mainly composed of Co and includes transition metals such as Ni, V, and Ti. Moreover, it is preferable that the range of the value of y and z is y = 0.02-2.2 and z = 1.4-3. In particular, LiCoO ₂ is preferable because it is general and highly versatile.

  The shape of the positive electrode active material 2 is not particularly limited as long as it is a shape suitably used as a positive electrode body of a lithium ion secondary battery, and is powder / particle shape (spherical, polyhedral shape, etc.), columnar shape (columnar shape, square shape). Various shapes such as a columnar shape and a needle shape) can be used. When the positive electrode active material 2 is powder / particulate, the average particle diameter is not particularly limited as long as it can be used as a positive electrode active material of a lithium ion secondary battery. On the other hand, when the columnar positive electrode active material 2 is used, it is not particularly limited as long as the size can be suitably used for the positive electrode layer of the lithium ion secondary battery. Specifically, the length is as follows. The columnar positive electrode active material 2 in the range of 1 μm to 50 μm can be suitably used.

  The amount of the positive electrode active material 2 contained in the positive electrode layer 10 is preferably 70% by mass or more, more preferably 80% by mass or more, and more preferably 90% by mass or more based on the whole positive electrode layer 10. Is more preferable. When the content of the positive electrode active material 2 is too small, sufficient lithium ion absorption / release ability may not be imparted. Conversely, when the content is too large, the amount of the oxygen absorbing material 1 decreases and sufficient oxygen absorption capacity is obtained. May not be obtained, and may reduce the safety of lithium ions.

(1.3. Positive Electrode Layers 10, 11)
The positive electrode layer 10 or 11 contains at least the oxygen absorbing material 1 and the positive electrode active material 2. Further, in the positive electrode layer 10 or 11, it is necessary that the surface of the positive electrode active material 2 is coated with the oxygen absorbing material 1 or the oxygen absorbing material 1 and the positive electrode active material 2 are mixed. The A method for coating the surface of the positive electrode active material 2 with the oxygen-absorbing material 1 is not particularly limited, and a conventionally known coating method can be used. Specifically, the oxygen-absorbing material 1 and the positive electrode active material 2 are mixed by mechanical mixing such as a ball mill or manual mixing such as a mortar using a solvent or the like, the mixed slurry is dried, and further, heat treatment, By performing pressure treatment or the like, the surface of the positive electrode active material 2 can be coated with the oxygen absorbing material 1. In the present invention, as described above, since the binding between the oxygen-absorbing material 1 and the positive electrode active material 2 is not required with respect to the coating, it may be merely mixed. The positive electrode layers 10 and 11 are formed on the positive electrode current collector 20 together with the conductive material 3 and the additive as necessary, as shown in a method for manufacturing the positive electrode bodies 100 and 200 described later.

  In the present invention, the oxygen absorbing material 1 and the positive electrode active material 2 as described above are included in the positive electrode layers 10 and 11 as essential elements. By including the essential element, even when oxygen is released from the positive electrode active material 2 during overcharge, the oxygen absorbing material 1 can efficiently absorb oxygen, and the oxygen absorbing material 2 Since it has the ability to absorb and release lithium ions, the energy density is not reduced. Accordingly, a lithium ion secondary battery with high safety and high capacity can be obtained. Hereinafter, other components that can be included in the positive electrode bodies 100 and 200 of the present invention will be described.

(1.4. Conductive material 3)
As shown in FIG. 1B, the positive electrode body 200 may contain a conductive material that can be generally used, such as carbon, as the conductive material 3 in the positive electrode layer 11. By including the conductive material 3, the electron conductivity of the positive electrode layer can be increased. The shape of the conductive material 3 is not particularly limited, and may be included in the form of particles, columns, or the like. Moreover, it is preferable that the electrically conductive material 3 is contained to such an extent that the lithium ion absorption / release capability and the oxygen absorption capability are not reduced excessively. Specifically, if it is contained in an amount of about 1% by mass or more and 10% by mass or less based on the whole positive electrode layer 11, it can be suitably used as a positive electrode layer of a lithium ion secondary battery. Examples of the material constituting the conductive material 3 include various metals such as carbon and Pt, but carbon black, acetylene black, graphite and the like are preferable from the viewpoint of low cost and high versatility.

(1.5. Positive Current Collector 20)
The positive electrode body 100, 200 of the present invention is provided with a positive electrode current collector 20. The positive electrode current collector 20 is usually disposed on the surface of the positive electrode layers 10 and 11. The positive electrode current collector 20 collects current from the positive electrode layers 10 and 11, and the material thereof is not particularly limited as long as it has conductivity. Specifically, for example, aluminum, stainless steel, nickel, iron, titanium and the like can be mentioned, and among them, aluminum is preferable. The positive electrode current collector 20 may be a dense metal current collector or a porous metal current collector. Moreover, what vapor-deposited the said conductive material on the surface of polymer films, such as PET, and a conductive polymer film may be sufficient.

<2. Manufacturing Method of Positive Electrode Body 100, 200>
The positive electrode bodies 100 and 200 of the present invention are not particularly limited as long as the positive electrode layers 10 and 11 can be formed on the positive electrode current collector 20, and can be manufactured using a conventional method. Specifically, first, a mixture of the oxygen absorbing material 1 and the positive electrode active material 2 or the positive electrode active material 2 coated with the oxygen absorbing material 1 and, if necessary, a conductive material 3 and the addition described later. A positive electrode layer mixture is prepared by mixing an agent and the like. Next, a solvent is added to the mixture to prepare a mixture slurry. Then, the slurry is applied onto the positive electrode current collector 20 using a coating device or the like, and dried using a drying device or the like, thereby forming and integrally forming the positive electrode layers 10 and 11 on the positive electrode current collector 20. The positive electrode bodies 100 and 200 can be obtained.

   The slurry preparation solvent can be used without particular limitation as long as it does not affect the function of the material that can constitute the positive electrode layers 10 and 11 of the present invention, such as the oxygen-absorbing substance 1. Examples include water, N-methyl-2-pyrrolidone, methyl ethyl ketone, acetone, methanol, ethanol and the like. The slurry is prepared by dispersing the various constituent materials in a solvent appropriately selected from these solvents. At this time, it is preferable to disperse using a dispersant, an additive or the like. The slurry is in a state where each element is uniformly dispersed in the solvent. The slurry is applied on the positive electrode current collector 20 and dried.

  The coating device is not particularly limited as long as the slurry can be uniformly coated on the positive electrode current collector 20, but includes, for example, a forward roll, a reverse roll, a gravure, a doctor blade, a slot die, a spray coating device, and the like. Can be used. Further, the drying device used in the above drying is not particularly limited as long as it can remove excess volatile components in the slurry, which is not preferable to remain in the positive electrode layer. An infrared device, an electromagnetic induction device, a microwave device, or the like can be used.

  By combining the positive electrode body 100 or 200 with the negative electrode body 400, the separator 500, the electrolyte, and the like as shown in FIG. 3, a high-capacity and high-power lithium ion secondary battery 1000 can be obtained. it can. Hereinafter, other configurations included in the lithium ion secondary battery 1000 of the present invention will be described.

<3. Negative electrode body 400>
The negative electrode body 400 includes a negative electrode layer 40 including a negative electrode active material and the negative electrode current collector 30. The negative electrode body 400 that can be used in the lithium ion secondary battery 1000 of the present invention is not particularly limited as long as it is generally used as shown below, and can be appropriately selected.

(3.1. Negative electrode layer 40)
The negative electrode active material contained in the negative electrode layer 40 of the present invention is not particularly limited as long as it is a material capable of occluding and releasing lithium ions and generally used as a negative electrode active material. Is possible. Specific examples include carbon-based active materials such as graphite and coke, metallic lithium, lithium transition metal nitride, other metals, and silicon. Further, the shape of the negative electrode active material can be appropriately selected from powder / particle form, columnar form, and the like, similar to the positive electrode active material.

  The negative electrode layer 40 of the present invention may contain a conductive material in addition to the negative electrode active material. Examples of the conductive material include a conductive material containing copper in addition to the conductive material used for the positive electrode. The shape is not particularly limited like that used for the positive electrode of the conductive material, and the content can be adjusted as appropriate.

(3.2. Negative electrode current collector 30)
The negative electrode current collector 30 of the present invention can be used without particular limitation as long as it is generally used. The negative electrode current collector 30 collects current from the negative electrode layer 40. Specifically, a metal foil such as copper or nickel, a metal film deposited on the surface of a polymer film such as PET, or a conductive material. A polymer film or the like can be used. Among these, it is preferable to use a copper foil from the viewpoint of conductivity.

<4. Separator 500>
The separator 500 that can be used in the present invention is not particularly limited as long as it is a commonly used separator for a lithium ion secondary battery. The material constituting the separator 500 is not particularly limited as long as lithium ions can move in the layer structure or in the voids in the layer. Specifically, for example, inorganic particles such as alumina, silica, magnesium oxide, titanium oxide, zirconia, silicon carbide, silicon nitride, or polyethylene (PE), polypropylene (PP), polystyrene, polyester, polyacrylonitrile, cellulose, Examples thereof include organic resins such as polyimide and polyamide, and mixtures and molded bodies of the above-described inorganic particles and organic resins.

  The positive electrode layers 10 and 11, the negative electrode layer 40, and the separator 500 can appropriately include a binder, a solvent, various additives, and the like as described in the method for manufacturing the positive electrode body. The binder is used to bind the current collector and the active material, the active materials, or the separator particles. Specifically, a fluororesin, fluororubber, latex, a cellulose derivative, etc. are mentioned, for example. Examples of the various additives include a dispersant, a surfactant, a rheology adjusting material, and the like.

<5. Electrolyte (Electrolyte)>
In this invention, it has electrolyte which contains lithium salt normally in the electrode layer in the electrode body mentioned above, and in a separator. The electrolyte can be used in various states such as liquid, gel, and solid. Among these, a liquid electrolyte is preferable. In consideration of the effect of the present invention, an organic nonaqueous electrolytic solution is particularly preferable among the liquid electrolytes. The organic non-aqueous electrolyte has good lithium ion conductivity and can be a high-performance lithium ion secondary battery 1000.

The non-aqueous electrolyte usually has a lithium salt and a non-aqueous solvent. Any lithium salt can be used as long as it is a lithium salt used in a general lithium ion secondary battery. Specific examples include LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiClO ₄ , LiN (CF ₃ SO ₂ ) ₂ , LiCF ₃ SO ₃ , LiCF ₃ CO _2, and lithium imide salt. On the other hand, the non-aqueous solvent is not particularly limited as long as it can dissolve the lithium salt. For example, propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, 1,2-dimethoxyethane, 1 , 2-diethoxyethane, acetonitrile, propionitrile, tetrahydrofuran, 2-methyltetrahydrofuran, dioxane, 1,3-dioxolane, nitromethane, N, N-dimethylformamide, dimethyl sulfoxide, sulfolane, γ-butyrolactone and the like. In the present invention, these non-aqueous solvents may be used alone or in combination of two or more. In addition to the above, a room temperature molten salt can also be used as the non-aqueous electrolyte.

<6. Lithium ion secondary battery 1000>
A lithium ion secondary battery 1000 can be obtained by combining the above components and stacking them as shown in FIG. In FIG. 3, the lithium ion secondary battery 1000 of the present invention has a configuration including the positive electrode body 200, but the positive electrode body 100 can be used instead of the positive electrode body 200. By having either of the positive electrode bodies 100 and 200, safety against oxygen release from the positive electrode active material 2 during overcharge is increased, and a high energy density can be maintained, resulting in a high capacity. A lithium ion secondary battery can be obtained. In addition, a decrease in cycle characteristics due to oxidative decomposition of the nonaqueous electrolytic solution can be suppressed. The lithium ion secondary battery 1000 of the present invention can be manufactured by a conventional manufacturing method. As a specific example, it is manufactured as follows.

  First, the positive electrode body 100 or 200 manufactured by the method for manufacturing a positive electrode body is placed on the separator 500 so that the positive electrode layer and the separator 500 are in contact with each other. Next, the slurry in which the constituent material of the negative electrode layer 40 is dispersed is applied on the negative electrode current collector 30, and formed and integrated through a drying process, thereby producing the negative electrode body 400. The negative electrode body 400 is placed on the side of the separator 500 opposite to the positive electrode body so that the negative electrode layer 40 and the separator 500 are in contact with each other. Thereafter, after the positive electrode layer, the separator, and the negative electrode layer are filled with the predetermined electrolyte, the positive electrode body and the negative electrode body are inserted into a battery case or the like while holding the separator, and the lithium ion secondary is inserted. It can be a battery. In the present invention, the positive electrode body and the negative electrode body may be separately disposed on the separator as described above, or may be simultaneously disposed. Further, after installing the negative electrode body, the positive electrode body may be installed.

  In manufacturing the lithium ion secondary battery 1000, a coating device, a drying device, or the like is used. As the coating apparatus and the drying apparatus, those described in the method for manufacturing the positive electrode body can be used as appropriate.

  Examples are shown below. However, the following embodiment is a form shown for explaining the present invention in detail, and the present invention is not limited to the embodiment shown below without departing from the gist thereof, and can be arbitrarily modified. Can be implemented.

  In the examples, a coin-type battery was used as the lithium ion secondary battery. Each configuration will be described below.

<Examples and comparative examples>
i) Positive electrode preparation The positive electrode bodies of Examples and Comparative Examples were prepared by the following methods.

For the examples, LiCoO ₂ was used as the positive electrode active material, and LiMoO ₂ was used as the oxygen absorbing material. These, in mass _{ratio, LiCoO 2: LiMoO 2 = 90} %: and 10% become so prepared, respectively, they were mixed by a ball mill. Furthermore, the positive electrode mixture was produced by adding carbon black as a conductive material to the mixture. The positive electrode mixture was made into a slurry by adding N-methyl-2-pyrrolidone (NMP) in which polyvinylidene fluoride (PVDF) was dissolved. The slurry containing the positive electrode mixture was applied onto an aluminum foil as a current collector and dried to prepare a positive electrode body of an example.
On the other hand, the positive electrode body of the comparative example used LiCoO ₂ as a positive electrode active material and did not contain an oxygen absorbing material. Other configurations were the same as in the example.

ii) Negative electrode, separator, electrolyte, and lithium ion secondary battery In both Examples and Comparative Examples, lithium metal was used as the negative electrode, and a PP porous separator was used as the separator. As the electrolytic solution, ethylene carbonate (EC) and dimethyl carbonate (DMC) mixed at a volume ratio of 3: 7, and lithium hexafluorophosphate (LiPF ₆ ) as a supporting salt at a concentration of 1 mol / L. What was dissolved was used. The positive electrode, the separator, and the negative electrode were stacked and impregnated with the electrolytic solution, thereby producing coin type lithium ion secondary batteries of Examples and Comparative Examples.

iii) Evaluation of Lithium Ion Secondary Battery For each of the lithium ion secondary batteries prepared above, first, the battery was charged to 4.3 V, then discharged to 3.0 V, and the discharge capacity was measured. Thereafter, the battery was recharged to 4.3 V, the positive electrode body was taken out, and the total calorific value of the electrode was measured by a differential scanning calorimeter (DSC). Table 1 shows the results.

  From the results shown in Table 1, it can be seen that when the lithium ion secondary battery of the example is overcharged, the total calorific value is reduced as compared with the lithium ion secondary battery of the comparative example. Moreover, there is almost no difference from the comparative example regarding the discharge capacity. Therefore, by using a substance having both oxygen absorbing ability and lithium ion absorbing / releasing ability as an oxygen absorbing substance, it is possible to reduce the calorific value while suppressing a decrease in energy density. It can be seen that a high-capacity lithium ion secondary battery can be obtained.

  Although the present invention has been described with reference to the most practical and preferred embodiments at the present time, the present invention is not limited to the embodiments disclosed herein. The positive electrode body and the lithium ion secondary battery with such a change are also within the technical scope of the present invention without departing from the spirit or concept of the invention that can be read from the claims and the entire specification. It must be understood as included.

It is a figure which shows schematically the positive electrode body of this invention. It is a figure which shows roughly the absorption / release of the lithium ion of the positive electrode active material and an oxygen absorption material, and the absorption / release of oxygen under charge and overcharge. It is a figure which shows roughly the lithium ion secondary battery with which one form of the positive electrode bodies of this invention was provided.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Oxygen absorption material 2 Positive electrode active material 3 Conductive material 10 Positive electrode layer 11 Positive electrode layer 20 Positive electrode collector 30 Negative electrode collector 40 Negative electrode layer 100, 200 Positive electrode body 400 Negative electrode body 500 Separator 1000 Lithium ion secondary battery

Claims (4)

A positive electrode body comprising a positive electrode layer containing a positive electrode active material and an oxygen absorbing material, wherein the oxygen absorbing material has a lithium ion absorption / release capability, and has an oxygen absorption capability,
The positive electrode body for a lithium ion secondary battery, wherein the oxygen-absorbing substance contains a lithium-containing composite oxide. The positive electrode body for a lithium ion secondary battery according to claim 1, wherein the lithium-containing composite oxide contains LiMoO ₂ . The positive electrode body for a lithium ion secondary battery according to claim 1 or 2, wherein a surface of the positive electrode active material is coated with the oxygen absorbing material. A lithium ion secondary battery comprising the positive electrode body according to any one of claims 1 to 3.

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