JP2012094407A - Active material for nonaqueous electrolyte secondary battery, electrode plate for nonaqueous electrolyte secondary battery, nonaqueous electrolyte secondary battery and battery pack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an active material for a nonaqueous electrolyte secondary battery which is superior in cycle characteristics, and to provide an electrode plate for the nonaqueous electrolyte secondary battery, the nonaqueous electrolyte secondary battery, and a battery pack.SOLUTION: Disclosed is the active material for the nonaqueous electrolyte secondary battery. The active material for the nonaqueous electrolyte secondary battery is constituted of a core body, and a shell body which is fixed and adhered to the core body so as to cover at least a part of the surface of the core body. Both the core body and the shell body are made of an electrode active material. The core body is made of a particle-like electrode active material and the shell body is made of an electrode active material having an olivine structure.

Description

  The present invention relates to an active material for a non-aqueous electrolyte secondary battery, an electrode plate for a non-aqueous electrolyte secondary battery, a non-aqueous electrolyte secondary battery, and a battery pack.

  A non-aqueous electrolyte secondary battery represented by a lithium ion secondary battery has a high energy density and a high voltage, and is gradually charged when the battery is charged before being completely discharged, which is called a memory effect at the time of charge / discharge. Since there is no phenomenon in which the battery capacity decreases, it is used in various fields such as portable devices, notebook computers, and portable devices.

Currently, as a measure to prevent global warming, efforts to reduce CO ₂ emissions are being carried out on a global scale. By reducing the dependence on oil and allowing it to travel with a low environmental load, it can greatly reduce CO ₂ emissions. There is an urgent need to develop and promote next-generation clean energy vehicles represented by plug-in hybrid vehicles and electric vehicles that can contribute. If non-aqueous electrolyte secondary batteries can be used as the driving force for these next-generation clean energy vehicles, there is no need to rely on gasoline, which can greatly contribute to CO ₂ reduction and greatly prevent global warming. Can contribute. On the other hand, in order to use non-aqueous electrolyte secondary batteries as the driving force for next-generation clean energy vehicles, high durability that does not deteriorate cycle characteristics even when charging and discharging are repeated Is required.

  Currently, various proposals of non-aqueous electrolyte secondary batteries include a positive electrode plate, a negative electrode plate, a separator, and a non-aqueous electrolyte solution. As the positive electrode plate, one having a positive electrode active material layer containing positive electrode active material particles on the surface of a current collector such as a metal foil is generally used. Moreover, as a negative electrode plate, what equips the collector surface, such as copper and aluminum, with the negative electrode active material layer containing a negative electrode active material particle is common.

Examples of electrode active materials such as a positive electrode active material and a negative electrode active material include composite oxides of transition metal oxides such as manganese, nickel, cobalt, iron, and titanium and alkali metals such as sodium and lithium. ing. Conventionally, these electrode active materials are produced by a method of firing an alkali metal compound and a transition metal compound. For example, a method of firing a mixture of manganese oxide and a lithium material to obtain LiMn ₂ O ₄ (patented) Literature 1) or a mixture of a nickel compound such as lithium nickel carbonate or nickel nitrate and a lithium compound such as lithium nitrate or lithium carbonate is fired in the air or in an oxygen atmosphere to obtain a composite oxide of lithium and nickel. Method (Patent Document 2), Method of obtaining a powder solid obtained by spray-drying a solid-liquid mixture obtained by pulverizing a lithium compound and a transition metal compound in an aqueous medium in the presence of oxygen (Patent Document 3) Etc. are known.

JP-A-4-198028 JP-A-6-231767 JP 2009-277667 A

  However, since the electrode active material obtained by the method proposed in Patent Documents 1 to 3 is manufactured by firing a mixture of metal compounds in a solid state, the electrode active material is heated at a high temperature in order to complex the metal compounds. When firing at a high temperature, particles of the obtained metal composite compound are welded together to form a single crystal structure. However, in a secondary battery using active material particles having a single crystal structure as an electrode, if charging / discharging is repeated, the active material particles gradually deteriorate due to expansion and contraction of the active material particles, so that sufficient charging / discharging can be performed. It is known to disappear. That is, a conventional non-aqueous electrolyte secondary battery using active material particles having a single crystal structure as an electrode does not always satisfy the charge / discharge cycle characteristics (durability).

  The present invention has been made in view of such a situation, and even when charging and discharging are repeatedly performed, deterioration due to expansion and contraction hardly occurs, and the active material for a non-aqueous electrolyte secondary battery excellent in cycle characteristics An object is to provide an electrode plate for a non-aqueous electrolyte secondary battery, a non-aqueous electrolyte secondary battery, and a battery pack.

  The present invention for solving the above problems is an active material for a non-aqueous electrolyte secondary battery, wherein the active material for a non-aqueous electrolyte secondary battery includes at least one of a core body and a surface of the core body. The core body and the shell body are both made of an electrode active material, and the core body is a particulate electrode active material, and the shell body Is an electrode active material having an olivine structure.

  The electrode active material having an olivine structure may be a lithium composite phosphate, and the metal phosphate compound is any one of lithium iron phosphate, lithium manganese phosphate, and lithium manganese manganese phosphate. May be.

  Further, at the interface between the core body and the shell body, the core body and the shell body may be connected so that the crystal structure is discontinuous.

  Further, the present invention for solving the above problems is an electrode plate for a non-aqueous electrolyte secondary battery comprising a current collector and an electrode active material layer, wherein the electrode active material layer includes an active material, The active material is an active material for a non-aqueous electrolyte secondary battery having the above characteristics.

  Further, the present invention for solving the above problems, the present invention for solving the above problems, a positive electrode plate, a negative electrode plate, a separator provided between the positive electrode plate and the negative electrode plate, A non-aqueous electrolyte secondary battery comprising at least a non-aqueous electrolyte, wherein one or both of the positive electrode plate and the negative electrode plate have the above-mentioned characteristics. It is characterized by being.

  In addition, the present invention for solving the above-mentioned problems includes the following: a storage case, a non-aqueous electrolyte secondary battery including a positive electrode terminal and a negative electrode terminal, and overcharge and overdischarge protection A battery pack comprising at least a protective circuit having a function, wherein the storage case includes the non-aqueous electrolyte secondary battery and the protection circuit, wherein the non-aqueous electrolyte secondary battery has the above characteristics. It is a nonaqueous electrolyte secondary battery which has.

  According to the active material for a non-aqueous electrolyte secondary battery of the present invention (hereinafter also simply referred to as “active material”), the cycle characteristics are not deteriorated even when charging and discharging are repeated. Durability can be improved compared to other active materials.

  In addition, according to the electrode plate for a non-aqueous electrolyte secondary battery of the present invention (hereinafter, also simply referred to as “electrode plate”), an electrode plate having the above-described effects of the active material can be provided.

  Moreover, according to the non-aqueous electrolyte secondary battery of the present invention, a non-aqueous electrolyte secondary battery exhibiting the effects of the electrode plate can be provided.

  Moreover, according to the battery pack of this invention, the battery pack which has the effect of said nonaqueous electrolyte secondary battery can be provided.

It is sectional drawing of the active material for nonaqueous electrolyte secondary batteries of this invention. It is sectional drawing of the active material for nonaqueous electrolyte secondary batteries of this invention. It is a cyclic voltammogram which shows the result of the cyclic voltammetry test using the metal oxide which shows alkali metal ion insertion elimination reaction. It is a cyclic voltammogram which shows the result of the cyclic voltammetry test using the metal oxide which does not show alkali metal ion insertion elimination reaction. It is sectional drawing of the positive electrode plate for nonaqueous electrolyte secondary batteries of this invention. It is the schematic which shows an example of the nonaqueous electrolyte secondary battery of this invention. It is a sectional exploded view showing an example of a battery pack of the present invention.

  Hereinafter, the active material for a non-aqueous electrolyte secondary battery of the present invention will be specifically described with reference to FIGS. 1 and 2 are schematic cross-sectional views of the active material of the present invention, and FIG. 1 is a cross-sectional view of the active material of the present invention in which the entire surface of the core body is covered with a shell body. 2 is a cross-sectional view of the active material of the present invention in which a part of the surface of the core body is covered with a shell body. In the following description, unless otherwise specified, an active material for a lithium ion secondary battery will be described as an example of the active material for a non-aqueous electrolyte secondary battery of the present invention. Moreover, as a nonaqueous electrolyte secondary battery active material, the active material used for a positive electrode plate is demonstrated to an example.

<< Active material for non-aqueous electrolyte secondary battery >>
As shown in FIGS. 1 and 2, the active material 10 for a non-aqueous electrolyte secondary battery of the present invention (hereinafter simply referred to as the active material of the present invention) includes a core body 11 and at least one of the surfaces of the core body. The core body and the shell body are both made of an electrode active material, and the electrode active material of the shell body is an electrode active material having an olivine structure. Hereinafter, the core body 11 and the shell body 12 will be specifically described.

<Core body>
The core body 11 constituting the active material 10 of the present invention is made of a particulate electrode active material, and this electrode active material is generally chargeable / dischargeable used in an electrode plate for a non-aqueous electrolyte secondary battery. If it is an electrode active material, it will not specifically limit. For example, specific examples of the core body 11 that can be used for the positive electrode plate of a lithium ion secondary battery include LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiFeO ₂ , Li ₄ Ti ₅ O ₁₂ , LiFePO ₄ , Examples thereof include electrode active material particles such as lithium transition metal composite oxides such as LiNi _1/3 Mn _1/3 Co _1/3 O ₂ and LiNi _0.80 Co _0.15 Al _0.05 O ₂ . Specific examples of the core body 11 in the sodium ion secondary battery include electrode active material particles such as NaCoO ₂ , NaNi _0.3 Mn _0.7 O ₂ , and NaNi _0.1 Cr _0.9 O ₂ . Hereinafter, a core body made of an electrode active material may be simply referred to as a core body.

  It does not specifically limit about the particle diameter of the electrode active material of the core body 11, A thing of arbitrary magnitude | sizes can be selected suitably, and can be used. However, the total amount of the surface area of the active material 10 of the present invention can be increased as the particle diameter of the core body 11 is smaller. Therefore, when higher input / output characteristics are required, it is desirable to select a material having a small particle diameter, specifically, less than 10 μm as the electrode active material of the core body 11.

  The particle diameter of the core 11 shown in the present invention and the present specification is an average particle diameter (volume median particle diameter: D50) measured by laser diffraction / scattering particle size distribution measurement. The particle diameter of the core 11 is determined by identifying the measured electron microscope observation data using a particle recognition tool, and displaying a graph of particle size distribution based on the shape data acquired from the recognized particle image. It can be created and calculated from this particle size distribution graph. The particle size distribution graph can be created, for example, by using an image analysis type particle size distribution measurement software (manufactured by Mount Tech Co., Ltd., MAC VIEW) based on an electron microscope observation result.

<Shell body>
The shell body 12 is made of an electrode active material, and is fixed to the outside of the particulate core body 11 described above. As shown in FIG. 1, the shell body 12 may be fixed so as to cover the entire surface of the core body 11 as shown in FIG. Further, it may be fixed so as to be scattered on the surface of the core body 11. In this case, a part of the surface of the core body 11 is exposed. Alternatively, instead of the film-like shell body 12, a plurality of fine-particle shell bodies 12 may be fixed to at least a part of the surface of the core body 11.

  In this way, the inventors of the present invention make the active material 10 have a dual structure of the core body 11 and the shell body 12, and the electrode active material of the shell body 12 is an electrode active material having an olivine structure. It has been found that the characteristics are improved. Therefore, the active material 10 of the present invention has a double structure in which at least part of the surface of the core body 11 is fixed so as to be covered with the shell body 12, and the core body 11 and the shell body 12 are both It is an electrode active material, and the electrode active material of the shell body 12 consists of an electrode active material which has an olivine structure.

  In the above configuration, the mechanism for improving the cycle characteristics is presumed to be as follows. An electrode active material having an olivine structure has a stable crystal structure even when charging / discharging is repeated (even when alkali metal ions are repeatedly put in and out), and has a characteristic that deterioration due to expansion and contraction is small. It is thought to have. The active material 10 of the present invention has a structure in which at least a part of the surface of the electrode active material of the core body 11 is fixed so as to be covered with the electrode active material (shell body 12) having the olivine structure. The exposure of the core body 11 is limited to the extent that the shell body 12 is fixed to the surface of 11. Therefore, it is possible to reduce the burden of taking in and out alkali metal ions with respect to the electrode active material of the core body 12 during charging and discharging, and it is possible to prevent the core body 11 from being deteriorated due to expansion and contraction.

  Furthermore, as described above, the shell body fixed to the surface of the core body 11 is less likely to be deteriorated due to the addition and removal of alkali metal ions even when charging and discharging are repeated. As a result, it is estimated that the entire active material 10 can be prevented from being deteriorated due to repeated charging and discharging, and the cycle characteristics can be improved.

  Further, in addition to the above effects, the active material 10 of the present invention has the shell body 12 fixed so as to cover at least a part of the surface of the core body 11, so that the active material 10 is not covered by the shell body 12. The contact surface between the water electrolyte and the core body 11 can be reduced. Thereby, formation of the reaction film with the non-aqueous electrolyte considered to be formed by decomposing the non-aqueous electrolyte can be produced on the shell body 12 side, and deterioration of the core body 11 can be prevented.

  As an electrode active material having an olivine structure, a lithium composite phosphor oxide having an olivine structure can be preferably used. Lithium composite phosphorous oxide has a stable crystal structure among electrode active materials having an olivine structure, and hardly deteriorates even when charging and discharging are repeated. Examples of such lithium composite phosphate include lithium iron phosphate, lithium manganese phosphate, lithium cobalt phosphate, lithium iron manganese phosphate and the like.

  Whether the shell body 12 is an electrode active material having an olivine structure can be confirmed by X-ray diffraction of the shell body 12. Specifically, whether or not the shell body 12 is an electrode active material having an olivine structure by setting the shell body 12 in an X-ray diffractometer (Smart Lab manufactured by Rigaku Corporation) and confirming an X-ray diffraction spectrum. Can be confirmed.

  The mixing ratio of the core body 11 and the shell body 12 constituting the active material 10 of the present invention is not particularly limited, and is appropriately determined according to the type and size of the electrode active material that is the core body 11 and the shell body 12. Can be set. In addition, when there are few compounding quantities of the shell body 12 in the active material 10, there exists a possibility that a cycle characteristic cannot fully be aimed at. Therefore, considering this point, when the mass ratio of the core body 11 is 100 parts by mass, the mass ratio of the shell body 12 is preferably 5 parts by mass or more and 30 parts by mass or less.

  Further, when the shell body 12 is fixed in such a manner as to cover a part of the surface of the core body 11, the area covered by the shell body 12 is less than 20% with respect to the total surface area of the core body 11. In this case, the effect of suppressing the expansion and contraction of the core body 11 during charging and discharging is reduced. Considering such points, the area covered by the shell body 12 with respect to the total surface area of the core body 11 is preferably 20% or more.

  On the other hand, when the shell body 12 is fixed so as to cover the entire surface of the core body 11, the electrode active material (electrode active material having an olivine structure) of the shell body 12 permeates (permeates) the non-aqueous electrolyte. It is preferable that it is possible. By making the electrode active material of the shell body 12 into an electrode active material that can permeate the non-aqueous electrolyte, the non-aqueous electrolyte and the core body 12 can be brought into contact with each other. The function as a substance can be fully exhibited.

  Examples of the electrode active material that can permeate the non-aqueous electrolyte include a porous electrode active material and a microcrystalline electrode active material. By using the electrode active material of the shell body 12 as such an electrode active material, even if a reaction film that is considered to be formed by decomposing the electrolytic solution is formed on the shell body 12, it is difficult for the deterioration to proceed.

  Note that whether or not the shell body 12 can permeate the non-aqueous electrolyte, that is, whether it has a porous structure exemplified above or a microcrystalline structure is scanned. It can be confirmed with a scanning electron microscope (magnification: 10,000 to 50,000 times).

(Combination of core body 11 and shell body 12)
As described above, a chargeable / dischargeable electrode active material can be used as the core body 11 fixed to the surface of the shell body 12. Since the shell body 12 constituting the active material 10 of the present invention is an electrode active material having an olivine structure, the electrode active material of the core body 11 is also an electrode active material having an olivine structure, such as described above. Lithium composite phosphorous oxide is preferable in that the voltage can be easily controlled in order to function both as active materials. Note that the active material 10 of the present invention has a double structure of the core body 11 and the shell body 12, and the core body 11 and the shell body 12 can be clearly distinguished. Therefore, even if the electrode active materials of the core body 11 and the shell body 12 are both electrode active materials having an olivine structure, the core body 11 and the shell body 12 at the interface between the core body 11 and the shell body 12. Are connected so that the crystal structure is discontinuous. The active material 10 connected so that the crystal structure is discontinuous at the interface between the core body 11 and the shell body 12 can be formed by, for example, a method of forming the active material 10 described later.

  Whether or not the core body 11 and the shell body 12 are connected so that the crystal structure is discontinuous can be confirmed by observing at a magnification of 2 million using a transmission electron microscope.

  Moreover, although there is no limitation in particular also about the thickness of the shell body 12, it is preferable that it is 5 nm-500 nm.

The presence or absence of an alkali metal ion insertion / elimination reaction of the electrode active material can be confirmed by an electrochemical measurement (cyclic voltammetry: CV) method. The CV test will be described below. Specifically, the electrode potential is swept from 3.0 V to 4.3 V in the appropriate voltage range of the active material, for example, assuming lithium ions as alkali metal ions and the electrode active material is LiMn ₂ O _4. After that, the operation of returning to 3.0 V again is repeated about three times. The scanning speed is preferably 1 mV / sec. For example, in the case of LiMn ₂ O ₄ , as shown in FIG. 3, an oxidation peak corresponding to an alkali metal ion desorption reaction of LiMn ₂ O ₄ appears in the vicinity of about 3.9 V, and an alkali metal in the vicinity of about 4.1 V. A reduction peak corresponding to the ion insertion reaction appears, whereby the presence or absence of an alkali metal ion insertion / desorption reaction can be confirmed. Further, as shown in FIG. 4, when no peak appears, it can be determined that there is no alkali metal ion insertion / desorption reaction.

  As described above, the active material 10 of the present invention has been described focusing on the active material used for the positive electrode plate of the non-aqueous electrolyte secondary battery. However, the active material 10 of the present invention is not limited to the non-aqueous electrolyte secondary battery. It can also be used for a negative electrode plate. In this case, it is comprised from the core body 11 and the shell body fixed so that at least one part of the surface of this core body 11 may be covered, and the shell body 12 has the olivine structure which can be used for the electrode plate of a negative electrode plate. Any electrode active material may be used. As such an electrode active material, a material suitable for the negative electrode plate can be appropriately selected from the olivine-type electrode active materials described in the above positive electrode plate and other electrode active materials having an olivine structure. .

<Formation method of active material>
Next, an example of a forming method for forming the active material 10 of the present invention will be described. In addition, the active material 10 of this invention is not limited to the following formation methods. Moreover, although the formation method of the active material shown below has demonstrated centering on the formation method of the active material 10 used for a positive electrode plate, the electrode active material of the shell body 12 is heated by heating the core body 11 electrode. The active material 10 used for a negative electrode plate can be formed by preparing the active material formation liquid which selected the metal element containing compound used as a substance suitably, and heating at appropriate heating temperature.

(Formation of an active material in which at least a part of the surface of the core body is fixed with a film-like shell body)
The active material 10 in which at least a part of the surface of the core body is fixed with a film-like shell body is one type or an electrode active material having an olivine structure by heating with the electrode active material particles of the core body 11 or An active material forming liquid in which two or more metal element-containing compounds and a solvent are mixed is prepared, and this is a temperature equal to or higher than a temperature at which the metal element-containing compound becomes an electrode active material (shell body 12) having an olivine structure, For example, it can be formed by heating at a temperature equal to or higher than the temperature at which the metal element-containing compound is thermally decomposed and the electrode active material having an olivine structure is deposited.

(Metal element-containing compounds)
The metal element-containing compound is a precursor of an electrode active material (shell body 12) having an olivine structure. Therefore, any metal element-containing compound may be used as long as it can generate an electrode active material (shell body 12) having an olivine structure by being heated.

  Examples of the metal element-containing compound that becomes an electrode active material having an olivine structure by heating include lithium compounds, iron compounds, phosphorus compounds, manganese compounds, cobalt compounds, and the like. These compounds include chlorides, nitrates, It is used in the form of sulfate, perchlorate, acetate, phosphate, bromate, oxalate, carbonate, lactate, ammonium salt and the like. Of these, chlorides, nitrates, and acetates, which are easily available, are preferable, and acetates having good film forming properties for a wide range of current collectors can be preferably used.

For example, as an electrode active material having an olivine structure, a metal element-containing compound in the case of forming lithium iron phosphate includes a lithium compound (for example, LiCl), an iron compound (for example, FeCl ₂ ), a phosphorus compound (for example, NH _4). PH ₂ O ₂ ). In addition, examples of the metal element compound for forming lithium manganese phosphate having an olivine structure include a lithium compound, a manganese compound (for example, Mn (CH ₃ COO) ₂ .4H ₂ O), and a phosphorus compound. In addition, examples of the metal element-containing compound for forming lithium iron manganese phosphate having an olivine structure include a lithium compound, a manganese compound, an iron compound, and a phosphorus compound.

Examples of the lithium compound include lithium citrate tetrahydrate, lithium perchlorate trihydrate, lithium acetate dihydrate, lithium nitrate, lithium phosphate, and lithium carbonate. Examples of the iron compound include Iron (II) chloride tetrahydrate, iron (III) citrate, iron (II) acetate, iron (II) oxalate dihydrate, iron (III) nitrate nonahydrate, iron (II) lactate Hydrates, iron (II) sulfate heptahydrate and the like can be mentioned. Examples of manganese compounds include manganese acetate, (III) dihydrate, manganese (II) nitrate hexahydrate, manganese (II) sulfate pentahydrate, manganese (II) oxalate dihydrate, manganese ( III) Acetylacetonate, manganese carbonate and the like. Examples of the phosphorus compound include lithium phosphate used as a lithium compound, orthophosphoric acid (H ₃ PO ₄ ), condensed phosphoric acid, ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ ), diammonium hydrogen phosphate ( (NH ₄ ) ₂ HPO ₄ ), ammonium hypophosphite (NH ₄ PH ₂ O ₂ ), or the like can be used.

  When the electrode active material (shell body 12) having an olivine structure is lithium iron phosphate, the mixing ratio of the lithium compound, the iron compound, and the phosphorus compound is not particularly limited, but the ratio of each element in the compound is Li: Fe: When P = X: Y: 1, the ratio of 1 ≦ X <2, 1 ≦ Y <2 is preferable, and the ratio of 1 ≦ X <1.2, 1 ≦ Y <1.2 is more preferable. When the lithium composite compound produced is lithium manganese phosphate, the compounding ratio of the lithium compound, manganese compound, and phosphorus compound is 1 ≦ a <2, 1 ≦ when Li: Mn: P = a: b: 1. The ratio of b <2 is preferable, and the ratio of 1 ≦ a <1.2 and 1 ≦ b <1.2 is more preferable.

(solvent)
Solvents for dissolving the metal element-containing compound are, for example, water, NMP (N-methyl-2-pyrrolidone), methanol, ethanol, n-propanol, iso-propanol, n-butanol, iso-butanol, 2-butanol. , Lower alcohols such as t-butanol, ketones such as acetylacetone, diacetyl, benzoylacetone, ketoesters such as ethyl acetoacetate, ethyl pyruvate, ethyl benzoylacetate, ethyl benzoylformate, toluene, ethylene glycol, diethylene glycol, polyethylene glycol and These mixed solvents can be mentioned.

  Then, the active material forming liquid prepared as described above is heated at a temperature equal to or higher than the temperature at which the metal element-containing compound becomes an electrode active material having an olivine structure. The active material 10 of the present invention is formed by adhering an electrode active material (shell body 12) having a structure.

  Specifically, for example, an electrode having an olivine structure is obtained by heating an active material forming liquid containing a metal element-containing compound in a reducing gas atmosphere and / or an inert gas atmosphere to thermally decompose the metal element-containing compound. An active material can be formed. The electrode active material (shell body 12) having an olivine structure formed at this time is directly fixed to the surface of the core body 11 in the state of a film. Further, the shell body 12 is fixed so as to cover the entire surface of the core body 11 or the shell body 12 so as to cover a part of the surface of the core body 11 by appropriately changing the blending amount of the metal element-containing compound. Can be fixed.

  Examples of the method for heating the active material forming liquid include a method in which the active material forming liquid is put in a container such as a crucible and heated in a heating furnace, and a method in which the active material forming liquid is sprayed and heated in the heating furnace. As mentioned above, in the method of spraying and heating the active material forming liquid, an active material having a smaller particle diameter can be obtained as compared with the method of heating the active material forming liquid in a container such as a crucible.

  The reducing gas atmosphere for heating is realized by a reducing gas such as hydrogen gas or carbon monoxide gas, and the inert gas atmosphere is realized by an inert gas such as argon gas or nitrogen gas. If it is an active gas atmosphere, it will not specifically limit. Further, a reducing gas and an inert gas can be used in combination. Any heating method can be used as long as the metal element-containing compound can be heated to a temperature capable of pyrolysis. For example, a hot plate, an oven, a heating furnace, an infrared heater, a halogen heater, a hot air blower, or the like is used. Or a method of using two or more in combination.

  About the heating temperature, the metal element-containing compound used may be a temperature at which the electrode active material (shell body 12) having an olivine structure, for example, a temperature at which the metal element-containing compound used can be thermally decomposed, It can set suitably according to the metal element containing compound used. This temperature varies depending on the metal element-containing compound contained in the active material forming liquid, and is generally in the temperature range of 150 ° C to 800 ° C.

(Formation method of an active material in which at least a part of the surface of the core body is fixed with a fine particle shell body)
The active material forming liquid described above is heated at a higher temperature than in the case of forming a film-like shell body, thereby forming the active material 10 in which at least a part of the surface of the core body is fixed with the fine-particle shell body. be able to.

<< Electrode plate for non-aqueous electrolyte secondary battery >>
Next, the electrode plate for a non-aqueous electrolyte secondary battery of the present invention (hereinafter referred to as the electrode plate of the present invention) will be described with reference to FIG. Although the following description will focus on the case where the electrode plate for a non-aqueous electrolyte secondary battery of the present invention is a positive electrode plate, the non-aqueous electrolyte secondary battery of the present invention can also be used as a negative electrode plate. .

  The electrode plate (positive electrode plate) 20 of the present invention comprises a current collector 21 and a positive electrode active material layer 22 formed on the current collector, and the positive electrode active material layer 22 is the active material of the present invention described above. It is composed of a substance 10 and a binding substance 23. Since the active material which comprises the positive electrode active material layer 22 is the active material 10 demonstrated above, the positive electrode plate 20 of this invention can be made into the positive electrode plate 20 which improved cycling characteristics. Hereinafter, the current collector 21 and the positive electrode active material layer 22 will be described more specifically.

(Current collector)
The current collector 21 used in the present invention is not particularly limited as long as it is generally used as a current collector for a positive electrode plate for a nonaqueous electrolyte secondary battery. For example, a current collector formed of a simple substance such as an aluminum foil or a nickel foil or an alloy can be preferably used. The current collector 21 used in the present invention is a current collector that is subjected to surface processing on the surface (the surface of the current collector) on which the positive electrode active material layer 22 is scheduled to be formed, if necessary. Also good. As the current collector 21 whose surface is processed on its surface, a current collector in which a conductive material is laminated on the surface of a material having a current collecting function, chemical polishing treatment, corona treatment, and oxygen plasma treatment were performed. Examples include current collectors. That is, the current collector 21 is not only a current collector made of only a material having a current collecting function, but also has a surface laminated with a substance for ensuring conductivity, or some surface treatment. Also included. In addition, the surface of the current collector referred to in the present invention refers to the surface of a material having a current collecting function in the current collector 21 formed only from a material having a current collecting function, and has a current collecting function. In the case where surface processing or a conductive material is laminated on the entire surface of the material, the surface processing surface or the surface of the conductive material is referred to. In addition, in the case where a part of the surface of the material having a current collecting function is subjected to a surface processing treatment or a conductive material, the surface processing surface, the surface of the conductive material, or these surfaces A portion where a processing treatment or a conductive substance is not stacked (that is, a surface of a material having a current collecting function).

  Although the thickness of the collector 21 will not be specifically limited if it is the thickness which can generally be used as a collector of the positive electrode plate for nonaqueous electrolyte secondary batteries, It is preferable that it is 10-100 micrometers, and is 15-50 micrometers. It is more preferable.

(Positive electrode active material layer)
The positive electrode active material layer 22 in the present invention contains the active material 10 of the present invention described above and the binder material 23.

  The layer thickness of the positive electrode active material layer 22 is not particularly limited, and can be appropriately designed in consideration of electric capacity and input / output characteristics required for the positive electrode plate, and is generally about 300 nm to 200 μm.

  Moreover, it is preferable that the positive electrode active material layer 2 has voids to such an extent that the electrolytic solution can permeate, and the porosity is preferably 10% or more and 70% or less. The porosity can be measured with Autopore IV 9500 manufactured by Shimadzu Corporation.

  As the active material 10, the active material 10 described above can be used as it is, and the description thereof is omitted here.

(Binder)
There is no particular limitation on the active material 10, the current collector 21, and the binding material 23 for fixing the active material 10, and a resin binder or metal oxide can be used alone or in combination. Examples of the resin binder include polyvinylidene fluoride (PVDF) and styrene butadiene rubber (SBR). As the metal oxide, LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiFeO ₂ , Li ₄ Ti ₅ O ₁₂ , LiFePO ₄ , LiNi _1/3 Mn _1/3 Co _1/3 O ₂ , LiNi _0.80 Co _Examples thereof include metal oxides such as lithium transition metal composite oxides such as _0.15 Al _0.05 O ₂ . The metal oxide may exhibit an alkali metal ion insertion / release reaction or may not exhibit an alkali metal ion insertion / release reaction. A method of manufacturing the positive electrode plate in which the current collector 21 and the active material 10 and the active materials 10 are fixed to each other with a resin binder and metal oxide will be described later.

(Other materials)
The positive electrode active material layer 22 may be composed of only the active material 10 and the binder material 23, but may be formed by adding further additives without departing from the gist of the present invention. For example, according to the present invention, good conductivity can be exhibited without using a conductive material exemplified by a conductive carbon material such as carbon black, but better conductivity is desired. Depending on the case or the type of active material particles, a conductive material may be used.

  Further, the conductive material may cover the shell body 12. In order to cover the shell body surface with the conductive material, carbon as a conductive material can be obtained by heating sugars such as sugar alcohol, sugar ester, and cellulose, such as sucrose. The covering mode of the conductive material can be confirmed by observation with a transmission electron microscope. Moreover, when applying an electrode active material layer forming solution, in order to form a coating film favorable, you may further contain resin, such as a viscosity modifier.

(Method for manufacturing electrode plate)
Below, an example of the manufacturing method for manufacturing the electrode plate of this invention is demonstrated. As a method for producing the electrode plate of the present invention, there are a method using a conventionally known resin binder as a binding material and a method using a metal oxide as a binding material. This will be specifically described below. Hereinafter, although a positive electrode plate will be mainly described as an electrode plate, the negative electrode plate can be manufactured by appropriately selecting a current collector and an active material 10 that are suitable for the negative electrode plate.

(1) Manufacturing method of electrode plate using resinous binding material as binding material Conventionally known method is appropriately selected as a manufacturing method of electrode plate using resinous binding material as binding material. Can be used. For example, the positive electrode plate 20 can be manufactured by applying and drying an electrode active material layer forming solution containing the active material 10 and a resin binder on the current collector 21.

  Examples of the resin binder include polyester resin, polyamide resin, polyacrylate resin, polycarbonate resin, polyurethane resin, cellulose resin, polyolefin resin, polyvinyl resin, fluorine resin, and polyimide resin. Among these, a fluororesin is preferable as a resin binder, and polyvinylidene fluoride is particularly preferable.

  The electrode active material layer forming solution is prepared by mixing the active material 10, an appropriately selected resin binder, and other components as necessary. For example, the active material 10 and an appropriately selected binder are put into an organic solvent such as toluene, methyl ethyl ketone, N-methyl-2-pyrrolidone, or a mixture thereof, and a conductive material is further added as necessary. In addition, it is dissolved or dispersed by a dispersing machine such as a homogenizer, a ball mill, a sand mill or a roll mill to prepare an electrode active material layer forming solution. The blending ratio at this time is preferably such that the total amount of the active material 10 and the binder is about 40 to 80 parts by mass when the entire electrode active material layer forming solution is 100 parts by mass. Further, the mixing ratio of the active material 10 and the resin binder may be the same as the conventional one, and is preferably about active material: binder = 5: 5 to 9: 1 (mass ratio).

  The method for coating the electrode active material layer forming solution on the current collector 21 is not particularly limited, and a general coating method can be appropriately selected and used. For example, the electrode active material layer forming solution can be applied to an arbitrary region on the surface of the current collector 21 by printing, spin coating, dip coating, bar coating, spray coating, or the like. In addition, when the surface of the current collector 21 is porous, has a large number of irregularities, or has a three-dimensional structure, it can be manually applied in addition to the above method. . The current collector 21 used in the present invention can be further improved in film formability of the positive electrode active material layer 22 by performing a corona treatment, an oxygen plasma treatment, or the like in advance as necessary.

  Further, the coating amount of the electrode active material layer forming solution is not particularly limited, but it is preferable that the coating is performed in such a range that the thickness after heating becomes the thickness of the positive electrode active material layer 22 described above. .

  As a heat source in drying after coating, hot air, infrared rays, microwaves, high frequencies, or a combination thereof can be used. When using resin-made binders, you may further press after drying. The pressing can be performed by drying the electrode active material layer forming solution formed on the current collector 21 as necessary to remove the solvent, and then pressing. The pressing method is performed by applying a slurry-like electrode active material layer forming solution containing a conventional resin binder on the current collector 21 and drying it, and then performing the same method as the pressing performed. Can do. Thus, the manufacturing method of this invention can increase a volume energy density by implementing a press process. The press pressure in the press is not particularly limited. However, when performing the press, it is desirable to adjust the press pressure in consideration of the content of the solute contained in the electrode active material layer forming solution and the heating conditions in the heating process. .

(2) Manufacturing method of electrode plate using metal oxide as binder The electrode plate 20 using metal oxide as the binder is composed of an active material 10, a binder precursor containing a metal element-containing compound, and a solvent. The electrode active material layer forming solution is prepared using the other materials described above as necessary, and the solution can be manufactured by applying the solution onto the current collector 21 and then heating it. .

  As the metal element-containing compound, a compound similar to the metal element-containing compound described in the method for producing the active material 10 can be appropriately selected and used, and description thereof is omitted here. The same applies to the solvent for preparing the electrode active material layer forming solution. Also, as the coating method, the various methods described above can be appropriately selected and used.

As described above, the heating temperature may be at or above the temperature at which the metal element-containing compound becomes a shell body, for example, the temperature at which the metal element-containing compound is thermally decomposed. Also, the heating method and the heating device can be the same as those described in the method for manufacturing the positive electrode plate 20 described above. The metal oxide obtained by heating the metal element-containing compound may be a metal oxide that exhibits an alkali metal ion insertion / release reaction, or a metal oxide that does not exhibit an alkali metal ion insertion / release reaction. There may be. Therefore, the metal element-containing compound can be appropriately set depending on the obtained metal oxide.

  Further, the heating atmosphere is not particularly limited, and can be appropriately determined in consideration of the material used for manufacturing the electrode plate, the heating temperature, the oxygen potential of the metal element contained in the metal element-containing compound, and the like. For example, as the inert gas atmosphere, argon gas, nitrogen gas, and reducing gas atmosphere include hydrogen gas, carbon monoxide gas, a gas atmosphere in which the inert gas and the reducing gas are mixed, or an air atmosphere. . For example, an air atmosphere is preferable in that a special atmosphere adjustment is not necessary and the heating process can be easily performed. In particular, when an aluminum foil is used as a current collector, it is preferable that the aluminum foil is not oxidized even if the heating step is performed in an air atmosphere.

(Non-aqueous electrolyte secondary battery)
Next, the nonaqueous electrolyte secondary battery of the present invention will be described with reference to FIG. FIG. 6 is a schematic diagram showing an example of the re-nonaqueous electrolyte secondary battery 100 of the present invention. As shown in FIG. 6, the non-aqueous electrolyte secondary battery of the present invention includes a positive electrode plate 20 in which an electrode active material layer 22 is provided on one surface side of a current collector 21, and a collector combined therewith. The electric body 55 includes a negative electrode plate 50 having an electrode active material layer 54 provided on one surface side thereof, and a separator 70 provided between the positive electrode plate 20 and the negative electrode plate 50. It is accommodated in the container comprised by this, and the structure sealed in the state with which the nonaqueous electrolyte solution 90 was filled in the container is taken.

  Here, the non-aqueous electrolyte secondary battery of the present invention requires the electrode plate 20 for the non-aqueous electrolyte secondary battery described above as one of the positive electrode plate 20, the negative electrode plate 50, or both electrode plates. It is characterized in that it is used as a configuration of The nonaqueous electrolyte secondary battery 100 of the present invention is not particularly limited with respect to other requirements as long as it satisfies this requirement, and a conventionally known negative electrode plate, nonaqueous electrolyte solution, and container are appropriately selected and used. However, the present invention is not limited to the form shown in FIG.

(Electrode plate)
As the non-aqueous electrolyte secondary battery of the present invention, the non-aqueous electrolyte secondary battery of the present invention is used by using the electrode plate of the present invention described above for either one or both of the positive electrode plate 20 and the negative electrode plate 50. The battery 100 also exhibits the performance of the electrode plate. Therefore, when the electrode plate described above is used as the positive electrode plate, a conventionally known negative electrode plate for a nonaqueous electrolyte secondary battery can be appropriately selected and used as the negative electrode plate. As a conventionally known negative electrode plate, a copper foil such as an electrolytic copper foil or a rolled copper foil having a thickness of about 5 to 50 μm is used as a current collector, and an electrode active material in the negative electrode plate is formed on at least a part of the current collector surface. What was formed by apply | coating a layer forming solution, drying, and pressing as needed is used. The electrode active material layer forming solution in the negative electrode plate generally includes an active material made of a carbonaceous material such as natural graphite, artificial graphite, amorphous carbon, carbon black, or a material obtained by adding a different element to these components, Alternatively, negative electrode active material particles such as metal oxides such as Li ₄ Ti ₅ O ₁₂ , metal lithium and alloys thereof, tin, silicon, and alloys thereof, materials capable of occluding and releasing alkali metal ions, and resin binders In general, other additives such as a conductive material are dispersed and mixed as necessary. However, the present invention is not limited to this. Moreover, the positive electrode plate using the active material 10 of the present invention and the negative electrode plate using the active material of the present invention can be used together.

(Non-aqueous electrolyte)
The non-aqueous electrolyte 90 used in the present invention is not particularly limited as long as it is generally used as a non-aqueous electrolyte for a non-aqueous electrolyte secondary battery, but when used for a lithium ion secondary battery. For this, a nonaqueous electrolytic solution in which a lithium salt is dissolved in an organic solvent is preferably used.

Examples of the lithium salt include inorganic lithium salts such as LiClO ₄ , LiBF ₄ , LiPF ₆ , LiAsF ₆ , LiCl, and LiBr; LiB (C ₆ H ₅ ) ₄ , LiN (SO ₂ CF ₃ ) ₂ , LiC ( Organic compounds such as SO ₂ CF ₃ ) ₃ , LiOSO ₂ CF ₃ , LiOSO ₂ C ₂ F ₅ , LiOSO ₂ C ₄ F ₉ , LiOSO ₂ C ₅ F ₁₁ , LiOSO ₂ C ₆ F ₁₃ , and LiOSO ₂ C ₇ F ₁₅ Typical examples include lithium salts.

  Examples of the organic solvent used for dissolving the lithium salt include cyclic esters, chain esters, cyclic ethers, and chain ethers.

  As a structure of the battery manufactured using the positive electrode plate, the negative electrode plate, the separator, and the nonaqueous electrolytic solution, a conventionally known structure can be appropriately selected and used. For example, the structure which winds a positive electrode plate and a negative electrode plate in the shape of a spiral via the separator like a polyethylene porous film, and accommodates in a battery container is mentioned. As another aspect, a structure in which a positive electrode plate and a negative electrode plate cut into a predetermined shape are stacked and fixed via a separator, and this is housed in a battery container may be employed. In any structure, after the positive electrode plate and the negative electrode plate are stored in the battery container, the lead wire attached to the positive electrode plate is connected to the positive electrode terminal provided in the outer container, while the lead wire attached to the negative electrode plate Is connected to a negative electrode terminal provided in the outer container, and the battery container is further filled with a nonaqueous electrification solution and then sealed to produce a nonaqueous electrolyte secondary battery.

(Battery pack)
Next, a battery pack 200 configured using the nonaqueous electrolyte secondary battery 100 of the present invention will be described with reference to FIG. FIG. 7 is a schematic exploded view showing an example of the battery pack 200 of the present invention.

  As shown in FIG. 7, the battery pack 200 is configured such that the nonaqueous electrolyte secondary battery 100 is housed in a resin container 36 a, a resin container 36 b, and an end case 37. Further, a protection circuit for preventing overcharge and overdischarge between one end face of the nonaqueous electrolyte secondary battery, which is a face including the positive electrode terminal 32 and the negative electrode terminal 33, and the end case 37. A substrate 34 is provided.

  The protection circuit board 34 includes an external connection connector 35. The external connection connector 35 is connected to an external connection window 38a provided in the resin container 36a and an external connection window 38b provided in the end case 37. Inserted and connected to external terminals. The protection circuit board 34 is mounted with a charge / discharge safety circuit (not shown) for controlling charge / discharge, a wiring circuit for connecting the external connection terminal and the nonaqueous electrolyte secondary battery 100, and the like. .

  As the battery pack 200, a configuration of a conventionally known battery pack can be appropriately selected except that the non-aqueous electrolyte secondary battery 100 using the electrode plate 20 of the present invention is used. Although not shown, the battery pack 200 includes a positive electrode lead plate connected to the positive electrode terminal 32, a negative electrode lead plate connected to the negative electrode terminal 33, and an insulator between the nonaqueous electrolyte secondary ground 100 and the end case 37. Etc. may be provided as appropriate.

  In addition, the nonaqueous electrolyte secondary battery 100 of the present invention using the electrode plate 20 of the present invention has functions other than the use mode for the battery pack, such as a function of blocking the excessive current, battery temperature monitoring, etc. in the protection circuit. And the protection circuit may be used by being integrated with the non-aqueous electrolyte secondary battery. In such an embodiment, the battery pack can be used as a secondary battery having a protection function and a protection circuit without constituting a battery pack, and is highly versatile. In addition, some aspects demonstrated above are only illustrations, and do not limit use of the positive electrode plate 20 of this invention, or the nonaqueous electrolyte secondary battery 100 of this invention at all.

  Next, the present invention will be described more specifically with reference to examples and comparative examples. Hereinafter, unless otherwise specified, parts or% is based on mass.

Example 1
LiCl [molecular weight: 42.39]: 4.2 g, FeCl ₂ .4H ₂ O [molecular weight: 198.81] 19.8 g, NH ₄ PH ₂ O ₂ [molecular weight: 83.0 g] 8.3 g, sucrose 3 g Pure water: 30 g was added and mixed to obtain a raw material liquid for producing lithium iron phosphate having an olivine structure as a shell body. Subsequently, positive electrode active material particles (LiCoO ₂ ): 10 g having an average particle diameter of 1 μm were mixed with 10 g of the above raw material liquid to obtain an active material raw material liquid. The active material raw material liquid is placed in an electric furnace (high-temperature atmosphere box furnace, manufactured by Koyo Thermo System Co., Ltd., KB8610N-VP) in an argon nitrogen atmosphere, heated to 500 ° C. over 1 hour, and then heated to 500 ° C. While maintaining, heating was performed for 1 hour to obtain an active material for lithium ion secondary battery. Next, 10 g of the lithium ion secondary battery active material (lithium iron phosphate-coated lithium cobalt oxide) particles obtained above, 1 g of acetylene black HS-100 (manufactured by Denki Kagaku Kogyo Co., Ltd.) as the conductive material, and 0.2 g of VGCF (manufactured by Showa Denko Co., Ltd.) and 1.3 g of PVDF (manufactured by Kureha Co., Ltd., KF # 1100) are prepared as a resin binder, and NMP (Mitsubishi Chemical Corporation) as a solvent. Manufactured): A PVDF resin solution dissolved in 10 g was dispersed and stirred with an Excel auto homogenizer (Nihon Seiki Seisakusho Co., Ltd.) at a rotation speed of 7000 rpm for 15 minutes to prepare a positive electrode active material layer forming slurry.

Then, the positive electrode active material layer-forming slurry was applied onto a 15 μm-thick aluminum foil used as a positive electrode current collector so that the coating amount of the positive electrode active material layer after drying was 72 g / m ^2. Was dried in an air atmosphere at 120 ° C. for 20 minutes to form an electrode active material layer for the positive electrode on the surface of the current collector. Further, using a roll press machine, the electrode active material layer was pressed under the conditions of applied pressure: 0.1 ton / cm and speed of 10 mm / second, and then vacuum dried at 140 ° C. for 5 minutes for positive electrode use. An electrode plate was obtained. And it cut | judged to the predetermined | prescribed magnitude | size (disk 15 mm in diameter), and was set as the positive electrode plate of Example 1. FIG.

(Example 2)
Instead of the raw material liquid for the shell body of Example 1, Li (CH ₃ COO) · 2H ₂ O [Molecular weight: 102.02]: 3.0 g, Mn (CH ₃ COO) ₂ · 4H ₂ O [Molecular weight: 245.09]: 7.5 g, NH ₄ PH ₂ O ₂ [molecular weight: 83.0 g]: 2.5 g, 1 g of dextrin and 20 g of pure water are mixed and mixed, and lithium manganese phosphate having an olivine structure as a shell body A positive electrode plate of Example 2 was obtained in the same manner as in Example 1 except that the raw material liquid for producing was used.

(Example 3)
Active material obtained in Example 1: 10 g, 1.0 g of acetylene black HS-100 (manufactured by Denki Kagaku Kogyo Co., Ltd.) as a conductive material, 0.2 g of VGCF (manufactured by Showa Denko KK), and Li (CH ₃ COO) · 2H ₂ O [molecular weight: 102.02]: 1 g as a precursor solution to be a binder, Mn (NO ₃ ) ₂ · 6H ₂ O [molecular weight: 287.04]: 5. 7 g, pure water: 2 g, a resin material (hydroxyethylcellulose) 0.1 g as a viscosity modifier added with 5 g of a viscosity adjusting solution prepared by dissolving 4.9 g of pure water was mixed and dispersed, and an Excel auto homogenizer ( Nippon Seiki Seisakusho Co., Ltd.) was stirred at 7000 rpm for 15 minutes to prepare a positive electrode active material layer forming slurry.

Then, the positive electrode active material layer forming slurry was applied onto a 15 μm thick aluminum foil used as a positive electrode current collector so that the applied amount of the positive electrode active material layer after drying was 72 g / m ^2. In a nitrogen atmosphere electric furnace (high temperature atmosphere box furnace, manufactured by Koyo Thermo Systems Co., Ltd., KB8610N-VP), heated up from room temperature (25 ° C.) to 450 ° C. over 1 hour, Then, heating was continued for 10 minutes while maintaining the temperature at 450 ° C., and then left to reach room temperature. A positive electrode plate having a positive electrode active material layer formed on the current collector was obtained. And it cut | judged to the predetermined | prescribed magnitude | size (a 15-mm diameter disc), and made this into the positive electrode plate of Example 3.

Example 4
Titanium diisopropoxybis (acetylacetonate) (manufactured by Matsumoto Co., Ltd., TC-100) 5.0 g as a precursor solution to be a binder, 0.1 g of a resin material (hydroxyethylcellulose) as a viscosity modifier A mixture obtained by adding 5 g of a viscosity adjusting solution dissolved in 4.9 g of pure water is mixed and dispersed, and stirred with an Excel auto homogenizer (Nihon Seiki Seisakusho Co., Ltd.) at a rotational speed of 7000 rpm for 15 minutes, and the positive electrode active material layer A positive electrode plate of Example 4 was obtained in the same manner as Example 3 except that the forming slurry was prepared.

(Comparative Example 1)
Positive electrode active material particles having an average particle diameter of 1 μm as a raw material of the positive electrode active material LiCoO ₂ : 10 g, 1 g of acetylene black HS-100 (manufactured by Denki Kagaku Kogyo Co., Ltd.) as a conductive material, and VGCF (manufactured by Showa Denko KK) 0.2 g of resin, and 1.3 g of PVDF (manufactured by Kureha Co., Ltd., KF # 1100) as a resin binder are prepared and dispersed in 10 g of NMP (manufactured by Mitsubishi Chemical Corporation) as a solvent. Then, the mixture was stirred with an Excel auto homogenizer (Nihon Seiki Seisakusho Co., Ltd.) at a rotational speed of 7000 rpm for 15 minutes to prepare a positive electrode active material layer forming slurry.
Furthermore, it was applied on an aluminum foil so that the coating amount after drying was 77 g / m ^2, and dried in an air atmosphere at 120 ° C. using an oven, and an electrode active material for a positive electrode on the surface of the current collector A layer was formed. Further, using a roll press machine, the electrode active material layer was pressed under the conditions of applied pressure: 0.1 ton / cm and speed of 10 mm / second, and then vacuum dried at 140 ° C. for 5 minutes for positive electrode use. An electrode plate was obtained. And it cut | judged to the predetermined | prescribed magnitude | size (a 15-mm diameter disc), and was set as the positive electrode plate of the comparative example 1.

(Comparative Example 2)
In place of the shell body raw material liquid of Example 1, Li (CH ₃ COO) · 2H ₂ O [Molecular weight: 102.02]: 2.0 g, Mn (CH ₃ COO) ₂ · 4H ₂ O [Molecular weight: 245.09]: 4.9 g of pure water: 10 g was added and mixed, and all were the same as in Example 1 except that the raw material liquid for producing lithium manganate having a layered structure was used as a shell body. The positive electrode plate of Example 2 was obtained.

(Battery characteristics evaluation)
<Production of tripolar coin cell>
Lithium hexafluorophosphate (LiPF ₆ ) is added as a solute to a mixed solvent of ethylene carbonate (EC) / dimethyl carbonate (DMC) (volume ratio = 1: 1), and the concentration of LiPF _{6 as} the solute is 1 mol. The non-aqueous electrolyte was prepared by adjusting the concentration to be / L. Using the examples and comparative examples prepared as described above as the positive electrode plate as the working electrode, the metal lithium plate as the counter electrode plate and the reference electrode plate, the non-aqueous electrolyte prepared above as the electrolyte, Assembled. About this test cell, the following charging / discharging test was done and the 1C 500 cycle characteristic test was done.

(Charge / discharge test)
In the test cell, in order to perform the discharge test of the working electrode, first, the test cell was fully charged according to the following charge test (charge test and discharge test).

(Charge test)
The test cell was charged at a constant current (685 μA) under an environment of 25 ° C. until the voltage reached 4.2 V, and after the voltage reached 4.2 V, the voltage did not exceed 4.2 V. As described above, the current (discharge rate: 0.5 C) was decreased until it became 5% or less, and the battery was charged at a constant voltage, fully charged, and then suspended for 10 minutes. Here, the above-mentioned “0.5 C” means a current value (current value reaching the end-of-discharge voltage) at which the constant current discharge is performed using the tripolar coin cell and the discharge is completed in 2 hours. To do.

(Discharge test)
Thereafter, the fully charged test cell was subjected to constant current (685 μA) (discharge rate: 0) in an environment of 25 ° C. until the voltage was changed from 4.2 V (full charge voltage) to 3.0 V (discharge end voltage). 0.5C), the cell voltage (V) is plotted on the vertical axis, the discharge time (h) is plotted on the horizontal axis, a discharge curve is prepared, and the initial discharge capacity (μAh) of the positive electrode plate is obtained.

(Cycle characteristic test)
The cycle characteristic test was carried out by a charge / discharge test in the case where the initial discharge capacity (μAh) obtained above was set to a discharge rate of 1C and the discharge rate was 1C. The charge / discharge test was conducted by repeating the first charge test and discharge test as one cycle for 500 cycles, and the 500 cycle discharge capacity retention rate (%) was calculated. The 500 cycle discharge capacity retention rate (%) is shown in Table 1 below. The 500 cycle discharge capacity retention rate (%) is a value calculated by dividing the discharge capacity (mAh) after 500 cycles by the discharge capacity (mAh) after 1 cycle and multiplying by 100.

  As is clear from Table 1, Examples 1 and 2 using an active material in which a core body is covered with a shell body having an olivine structure are comparative examples 1 and 1 having no olivine structure (layered). It was confirmed that the cycle characteristics were excellent as compared with Comparative Example 1 using an active material in which the core body was covered with a shell body having a structure.

DESCRIPTION OF SYMBOLS 10 ... Active material for non-aqueous electrolyte secondary battery 11 ... Core body 12 ... Shell body 20 ... Positive electrode plate for non-aqueous electrolyte secondary battery 21, 55 ... Current collector 22 ... positive electrode active material layer 32 ... positive electrode terminal 33 ... negative electrode terminal 34 ... protective circuit board 35 ... external connector 36a, 36b ... resin container 37 ... end case 38a, 38b ... External connection window 70 ... Separator 81, 82 ... Exterior 100 ... Non-aqueous electrolyte secondary battery 200 ... Battery pack

Claims (7)

An active material for a non-aqueous electrolyte secondary battery,
The non-aqueous electrolyte secondary battery active material is composed of a core body and a shell body fixed so as to cover at least a part of the surface of the core body,
The core body and the shell body are both made of an electrode active material,
The core body is a particulate electrode active material,
The active material for a non-aqueous electrolyte secondary battery, wherein the shell body is an electrode active material having an olivine structure.   The active material for a nonaqueous electrolyte secondary battery according to claim 1, wherein the electrode active material having an olivine structure is a lithium composite phosphorous oxide.   3. The non-aqueous electrolyte according to claim 1, wherein the lithium composite phosphate is any one of lithium iron phosphate, lithium manganese phosphate, lithium iron manganese phosphate, and lithium cobalt phosphate. 4. Active material for secondary batteries.   4. The structure according to claim 1, wherein the core body and the shell body are connected so that the crystal structure is discontinuous at an interface between the core body and the shell body. 5. The active material for nonaqueous electrolyte secondary batteries as described in 2. An electrode plate for a non-aqueous electrolyte secondary battery comprising a current collector and an electrode active material layer,
The electrode active material layer is composed of an active material and a binder material,
The said active material is an active material for nonaqueous electrolyte secondary batteries of any one of Claims 1 thru | or 4, The electrode plate for nonaqueous electrolyte secondary batteries characterized by the above-mentioned. A non-aqueous electrolyte secondary battery comprising at least a positive electrode plate, a negative electrode plate, a separator provided between the positive electrode plate and the negative electrode plate, and a non-aqueous electrolyte solution,
Either the said positive electrode plate or the said negative electrode plate is an electrode plate for nonaqueous electrolyte secondary batteries of Claim 5, The nonaqueous electrolyte secondary battery characterized by the above-mentioned. A storage case; a non-aqueous electrolyte secondary battery including a positive electrode terminal and a negative electrode terminal; and a protection circuit having an overcharge and over-discharge protection function, wherein the storage case includes the non-aqueous electrolyte secondary battery and the In a battery pack configured to contain a protection circuit,
The battery pack, wherein the non-aqueous electrolyte secondary battery is the non-aqueous electrolyte secondary battery according to claim 6.

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