JP2012094405A - Active material for nonaqueous electrolyte secondary battery, positive 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 capable of improving the initial charge/discharge efficiency, and to provide a positive 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 electrode active material of the shell body has lower alkali metal ion release potential than that of the core body.

Description

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

  Non-aqueous electrolyte secondary batteries represented by lithium ions have high energy density and high voltage, and when the battery is charged before being completely discharged, the so-called memory effect during charge / discharge, the battery capacity gradually increases. Since there is no decreasing phenomenon, 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 a nonaqueous electrolyte secondary battery as a driving force for a next-generation clean energy vehicle, improvement in initial charge / discharge efficiency 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 a positive electrode active material 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 is common.

  In order to manufacture the electrode plate which is the positive electrode plate or the negative electrode plate, first, the electrode active material particles which are the positive electrode active material particles or the negative electrode active material particles, the resin binder, or further, the conductive material or other materials as necessary. The material is kneaded and / or dispersed in a solvent to prepare a slurry-like electrode active material layer forming liquid. And an electrode plate provided with an electrode active material layer is formed by applying an electrode active material layer forming liquid on the current collector surface, then drying to form a coating film on the current collector, and pressing (for example, Patent Document 1 or Patent Document 2).

JP 2006-310010 A JP 2006-107750 A

  When a voltage is applied to the positive electrode of the battery rechargeable battery, the positive electrode is deficient in electrons, and the negative electrode is fed with electrons through an external circuit. At that time, alkali metal atoms in the positive electrode active material are deprived of electrons and become alkali metal ions. Next, the alkali metal ions are attracted to the negative electrode through the electrolytic solution. Since the positive electrode continues to be deficient in electrons, the stored alkali metal atoms are deprived of electrons and new alkali metal ions are generated. Then, alkali metal ions move to the negative electrode again. The alkali metal ions that have moved to the negative electrode are given electrons on the negative electrode surface, return to the original electrically neutral alkali metal atoms, and are stored in the negative electrode. During discharge, alkali metal atoms in the negative electrode are ionized to generate alkali metal ions, and these alkali metal ions move to the positive electrode through the electrolytic solution, get electrons from the positive electrode, return to the alkali metal atom, and are stored in the positive electrode active material. The

In addition, in a general non-aqueous electrolyte secondary battery in which graphite or the like is used for the negative electrode as described above, the solvent or solute (alkaline) contained in the non-aqueous electrolyte during the initial charge (during initial charge). Metal ions) and the negative electrode active material react to form a SEI (Solid Electrolyte Interface) film on the surface of the negative electrode. The SEI film thus formed prevents the negative electrode active material from reducing the non-aqueous electrolyte.

  However, the formation of this SEI film is not limited to the solvent contained in the nonaqueous electrolytic solution, but the reaction causes alkali metal ions (that is, the active material in the positive active material to be attracted to the negative electrode through the electrolytic solution). Alkali metal ions released by depriving electrons of the constituent alkali metal atoms are consumed. And the alkali metal ion consumed for formation of a SEI film cannot contribute to subsequent charging / discharging reaction, and initial stage charging / discharging efficiency will fall.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an active material for a non-aqueous electrolyte secondary battery that is excellent in initial charge / discharge efficiency, and such a non-aqueous electrolyte secondary battery. A positive electrode plate for a non-aqueous electrolyte secondary battery using a battery active material, a non-aqueous electrolyte secondary battery comprising such a positive electrode plate for a non-aqueous electrolyte secondary battery, and such a non-aqueous electrolyte secondary battery An object is to provide a battery pack provided.

  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 electrode active material of the shell body is more than the electrode active material of the core body. The alkali metal ion emission potential is low.

  Further, the electrode active material of the core body and the electrode active material of the shell body are complex oxides of at least one metal selected from cobalt, nickel, manganese, iron and titanium and lithium. May be. Further, the electrode active material of the shell body may be an electrode active material that can permeate a non-aqueous electrolyte.

  Moreover, this invention for solving the said subject is a positive electrode plate for nonaqueous electrolyte secondary batteries which consists of a collector and an electrode active material layer, Comprising: The said electrode active material layer is an electrode active material, And the electrode active material is an active material for a non-aqueous electrolyte secondary battery having the above characteristics.

  Moreover, this invention for solving the said subject is a non-aqueous electrolyte provided with the positive electrode plate, the negative electrode plate, the separator provided between the said positive electrode plate and the said negative electrode plate, and a non-aqueous electrolyte at least. A secondary battery, wherein the positive electrode plate is a positive electrode plate for a non-aqueous electrolyte secondary battery having the above characteristics.

  Further, the present invention for solving the above-described problems includes at least a storage case, a nonaqueous electrolyte secondary battery including a positive electrode terminal and a negative electrode terminal, and a protection circuit having an overcharge and overdischarge protection function, A battery pack in which the non-aqueous electrolyte secondary battery and the protection circuit are housed in a storage case, wherein the non-aqueous electrolyte secondary battery has the above characteristics. It is characterized by being.

  According to the active material for a non-aqueous electrolyte secondary battery of the present invention (hereinafter also simply referred to as “active material”), during the initial charge, alkali metal ions are first released from the electrode active material of the shell body. Metal ions are consumed to form the SEI coating. Therefore, since the alkali metal ions released from the electrode active material of the core body are not consumed at all for the formation of the SEI film, the initial charge / discharge efficiency is improved as compared with the conventional active material consisting only of the electrode active material of the core body. Can be achieved.

  In addition, according to the positive electrode plate for a non-aqueous electrolyte secondary battery of the present invention (hereinafter, also simply referred to as “positive electrode plate”), a positive electrode plate having the 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 positive 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.

<< 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 releases alkali metal ions more than the electrode active material of the core body. It is characterized by a low potential. 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 the electrode active material can be charged / discharged generally used in a positive 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 in the lithium ion secondary battery include LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiFeO ₂ , Li ₄ Ti ₅ O ₁₂ , LiFePO ₄ , LiNi _1/3 Mn _1. Electrode active material particles such as lithium transition metal composite oxides such as _{/ 3} Co _1/3 O ₂ and LiNi _0.80 Co _0.15 Al _0.05 O ₂ can be given. 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.

  In the present invention, the alkali metal ion release potential of the electrode active material of the core body 11 and the electrode active material of the shell body 12 described later means a potential at which oxidation corresponding to an alkali metal ion desorption reaction starts. The alkali metal ion emission potential can be confirmed by an electrochemical measurement (cyclic voltammetry: CV) method. The electrochemical measurement (cyclic voltammetry: CV) method refers to an appropriate voltage range (for example, A1 (V) to A2 (V)) of the electrode active material from A1 (V) at a scanning speed of 1 mV / sec. In this test, the operation of sweeping back to A2 (V) and then returning to A1 (V) is repeated three times to confirm the presence or absence of an alkali metal ion insertion / release reaction. In addition, an appropriate voltage range means the voltage range which can confirm the presence or absence of the peak which shows the insertion-release reaction of the alkali metal ion used for a test in a cyclic voltammetry test.

Specifically, the case where the electrode active material is LiMn ₂ O ₄ will be described as an example, and the alkali metal ion (lithium ion) emission potential will be described. When the electrode active material is LiMn ₂ O ₄ , the scanning speed is 1 mV / second, and after sweeping from 3.0 V to 4.3 V, which is an appropriate voltage range, the operation of returning to 3.0 V again is performed about three times. repeat. At this time, as shown in FIG. 3, oxidation corresponding to an alkali metal ion (lithium ion) elimination reaction of LiMn ₂ O ₄ starts from about 3.75 V, and an oxidation peak appears at about 3.9 V. A reduction peak corresponding to an alkali metal ion (lithium ion) insertion reaction appears in the vicinity of 1 V, and the presence or absence of an alkali metal ion insertion and desorption reaction can be confirmed. Since the alkali metal ion release potential in the present invention is a potential at which oxidation corresponding to an alkali metal ion elimination reaction starts, 3.75 V is the alkali metal ion release potential when the active material is LiMn ₂ O _4. It becomes. Similarly, the alkali metal ion emission potential can be confirmed for other active materials.

The alkali metal ion release potential of the electrode active material calculated according to the above method is shown below.
Li ₄ Ti ₅ O ₁₂・ ・ ・ 1.3V
LiFeO ₂ ... 3.0V
LiFePO ₄ ... 3.1V
LiNi _0.80 Co _0.15 Al _0.05 O ₂ ... 3.3V
LiNiO ₂ 3.5V
LiCoO ₂ ... 3.6V
LiNi _1/3 Mn _1/3 Co _1/3 O ₂ ... 3.65V
LiMn ₂ O ₄ ... 3.75V

  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 having a lower alkali metal ion emission potential than the electrode active material of the core body 11, 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. 1, or as shown in FIG. The body 12 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.

  The shell body 12 is made of an electrode active material, and has a lower alkali metal ion emission potential than the electrode active material of the core body 11 described above. Therefore, the alkali metal ions released from the core body 11 during the initial charge can be improved in the initial charge / discharge efficiency without being consumed for the formation of the SEI film.

  Below, the mechanism which has the said effect is demonstrated more concretely. The active material 10 of the present invention includes a core body 11 and a shell body 12 fixed so as to cover at least a part of the surface of the core body 11, and the core body 11 and the shell body 12 are both electrode active materials. For this reason, a reaction occurs in which alkali metal ions are released from the core body 11 and the shell body 12 during initial charging. Here, in the present invention, since the alkali metal ion release potential of the shell body 12 showing this alkali metal ion desorption reaction is lower than the alkali metal ion release potential of the core body 11, immediately after the start of initial charging, The shell body 12 releases alkali metal ions earlier than the core body 11 releases alkali metal ions.

  As described above, since the alkali metal ions are consumed for the formation of the SEI film of the negative electrode active material during the initial charging, in the present invention, the alkali metal released from the shell body 12 exhibiting the alkali metal ion elimination reaction. Ions will be consumed for the formation of the SEI film during the initial charge. Then, in the active material 10 of the present invention, the alkali metal ions released from the core body 11 at the time of initial charging are not consumed at all for the formation of the SEI film. For example, a conventional active material composed only of the core body electrode active material is used. It can be considered that the improvement of the initial charge / discharge efficiency was realized as compared with the case of using the substance.

  In addition, when the alkali metal ion emission potential of the shell body 12 is higher than the alkali metal ion emission potential of the core body 11, the alkali metal ions are first released from the core body 11 during the initial charging, and this is released. Alkali metal ions are consumed to form the SEI coating. Then, for example, as in the case of the conventional active material composed only of the electrode active material of the core body, the initial charge / discharge efficiency is reduced, and it is considered that the improvement of the initial charge / discharge efficiency is realized as in the present invention. I can't.

  In addition, since the active material 10 of the present invention has a double structure of the core body 11 and the shell body 12, the contact surface between the core body 11 and the nonaqueous electrolytic solution is reduced, and the electrolytic solution can be decomposed. A possible reaction film with the electrolytic solution can be formed on the shell body 12 side. Thereby, deterioration of the core body 11 can be improved. Further, since the outer surface of the shell body 12 has a large surface area, the reaction with the electrolytic solution increases, and as a result, the output increases.

  Moreover, as an electrode active material of the shell body 12 which comprises the active material 10 of this invention, even if it is other than the material quoted above, it has a function as an electrode active material, and (2) the core body 11 Any material that satisfies the two conditions that the alkali metal ion emission potential is lower than the alkali metal ion emission potential of the electrode active material is not limited to the above-mentioned materials. For example, Li, Be, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Rb, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, Cs, Ba, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl, Pb, Bi, Fr, Ra, And a metal element such as Ce, one metal oxide of these metal elements, or a composite metal oxide containing two or more metal elements, and satisfying the above two conditions, It can be used as an electrode active material for the shell body 12 constituting the active material 10.

  Although the alkali metal ions released from the shell body 12 are consumed for forming the SEI film, not all the alkali metal ions released from the shell body 12 are consumed. That is, once the SEI film is formed by alkali metal ions released from the shell body 12, no further alkali metal ions released from the shell body are consumed. Therefore, the electric capacity of the positive electrode plate 20 increases as “the electric capacity of the core body 11” + “the electric capacity of the shell body 12 after initial charging”. That is, according to the active material 10 of the present invention, it can be said that the capacity of the active material is increased as compared with the conventional active material made of only the electrode active material of the core body 11.

  As described above, in the present invention, the shell body only needs to be fixed so as to cover at least a part of the surface of the electrode active material that is the core body 11, and as described above, the surface of the core body 11 The shell body 12 may be fixed so as to cover the entire surface. When the shell body 12 is fixed so as to cover the entire surface of the core body 11, the electrode active material of the shell body 12 may be an electrode active material that can permeate (penetrate) the nonaqueous electrolytic solution. preferable. 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. Can function as a substance.

  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).

  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 the improvement of an initial stage charge / discharge efficiency 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.

  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.

Further, the presence or absence of an alkali metal ion insertion / release reaction of the electrode active material of the core body 11 and the electrode active material of the shell body 12 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, assuming, for example, 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.

<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.

(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 heated from the electrode active material particles of the core body 11 described above and the electrode active material of the core body 11 by heating. An active material forming liquid prepared by mixing one or two or more metal element-containing compounds to be an electrode active material (shell body 12) having a low alkali metal ion emission potential and a solvent is prepared, and the resulting mixture is used as a metal element-containing solution. It can be formed by heating at a temperature equal to or higher than the temperature at which the compound becomes the shell body 12, for example, at a temperature equal to or higher than the temperature at which the metal element-containing compound is thermally decomposed.

(Metal element-containing compounds)
The metal element-containing compound is a precursor of the electrode active material of the shell body 12. Accordingly, any metal element-containing compound can be used as long as it can generate an electrode active material of the shell body 12 having a lower alkali metal ion emission potential than the electrode active material of the core body 11 by heating. Also good.

  Whether or not the electrode active material of the shell body 12 produced from the metal element-containing compound to be used exhibits an alkali metal ion insertion / desorption reaction is determined based on an active material layer forming liquid containing the metal element-containing compound in a preliminary experiment. An electrode active material can be formed by coating on a substrate and heating it, and can be confirmed by a cyclic voltammetry method.

  As the metal element-containing compound, a lithium element-containing compound and one or more metal element-containing compounds containing any metal element selected from cobalt, nickel, manganese, iron or titanium are preferably used. Can do. The metal element-containing compound may be an inorganic metal element-containing compound in which no carbon is contained in the compound, or an organometallic element-containing compound constituted by containing carbon in the compound. Also good. In the present invention and the present specification, the inorganic metal element-containing compound and the organic metal-containing compound may be simply referred to as a metal element-containing compound.

  Examples of the metal element-containing compound include chloride, nitrate, sulfate, perchlorate, acetate, phosphate, bromate, carbonate, etc. of other metal elements such as lithium element or cobalt. it can. Among them, in the present invention, chloride, nitrate, and acetate are preferably used because they are easily available as general-purpose products. In particular, nitrate is preferably used because it has good film forming properties for a wide variety of current collectors.

For example, as the metal element-containing compound for generating LiCoO ₂ as the electrode active material of the shell body 12, a Li element-containing compound and a Co element-containing compound can be used in combination as main raw materials, and further, if necessary Other raw materials can also be used in combination. Examples of the Li element-containing compound include lithium citrate tetrahydrate, lithium perchlorate trihydrate, lithium acetate dihydrate, lithium nitrate, lithium phosphate, and lithium carbonate. Examples of the Co element-containing compound include cobalt (II) chloride hexahydrate, cobalt (II) formate dihydrate, cobalt (III) acetylacetonate, cobalt (II) acetylacetonate dihydrate, and acetic acid. Cobalt (II) tetrahydrate, cobalt (II) oxalate dihydrate, cobalt (II) nitrate hexahydrate, cobalt (II) ammonium chloride hexahydrate, sodium cobalt (III) nitrite, and Examples thereof include cobalt (II) sulfate heptahydrate, cobalt carbonate, and the like. The combination ratio (Li: Co = X: 1) of the Li element-containing compound and the Co element-containing compound used as the main raw material is not particularly limited, but is preferably 1 ≦ X <2, and preferably 1 ≦ X ≦ 1. 2 is more preferable.

(solvent)
The solvent for dissolving the metal element-containing compound may be any solvent that can dissolve the metal element-containing compound, and a conventionally known solvent can be appropriately selected and used. For example, water, lower alcohols such as NMP (N-methyl-2-pyrrolidone), methanol, ethanol, n-propanol, iso-propanol, n-butanol, iso-butanol, 2-butanol, t-butanol, acetylacetone, diacetyl And ketones such as benzoylacetone, ketoesters such as ethyl acetoacetate, ethyl pyruvate, ethyl benzoylacetate and ethyl benzoylformate, toluene, ethylene glycol, diethylene glycol, polyethylene glycol, and mixed solvents thereof.

  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 the shell body 12, so that the electrode active material of the core body 11 is formed on the surface of the electrode active material particles of the core body 11. The active material 10 of the present invention is formed by adhering an electrode active material (shell body 12) having a lower alkali metal ion emission potential than the material. Further, the electrode active material of the shell body 12 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. However, in the method in which the metal element-containing compound is heated by spraying the active material forming liquid in a temperature atmosphere equal to or higher than the temperature at which the shell body 12 is formed, compared to the method of heating the active material forming liquid in a container such as a crucible, An active material having a smaller particle size can be obtained.

  About the heating temperature in heating, what is necessary is just the temperature at which the metal element-containing compound used becomes the shell body 12, for example, a temperature at which the metal element-containing compound used can be thermally decomposed, depending on the metal element-containing compound used. Can be set as appropriate. Although there is no limitation in particular about the upper limit of heating temperature, when heating temperature is too high, there exists a possibility that the active material formed may fuse | melt. Therefore, in consideration of this point, the upper limit of the heating temperature can be determined. In general, the upper limit value of the heating temperature is preferably 600 ° C. or less.

  Further, the heating method is not particularly limited as long as it is a heating method or a heating apparatus that can heat the active material forming liquid at a temperature at which the metal element-containing compound becomes the shell body 12 having the above characteristics. For example, a method of using any one of a hot plate, an oven, a heating furnace, an infrared heater, a halogen heater, a hot air blower, etc., or a combination of two or more can be mentioned.

(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 in which at least a part of the surface of the core body is fixed with the fine-particle shell body is formed by heating the above-described active material forming liquid at a higher temperature than when the film-like shell body 12 is formed. can do.

<< Positive electrode plate for non-aqueous electrolyte secondary battery >>
Next, the positive electrode plate 20 for a nonaqueous electrolyte secondary battery of the present invention (hereinafter referred to as the positive electrode plate of the present invention) will be described with reference to FIG. The positive electrode plate 20 of the present invention includes a current collector 21 and a positive electrode active material layer 22 formed on the current collector. The positive electrode active material layer 22 includes the active material 10 of the present invention described above, It is composed of a binder material 23. Since the active material constituting the positive electrode active material layer 22 is the active material 10 described above, the positive electrode plate 20 of the present invention can be the positive electrode plate 20 with improved initial charge / discharge efficiency. 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, it may be formed by further containing a resin such as a viscosity modifier. A viscosity modifier is good also as using in order to form a coating film favorable, when apply | coating a positive electrode active material layer forming solution.

(Method for manufacturing positive electrode plate)
Below, an example of the manufacturing method for manufacturing the positive electrode plate 20 of this invention is demonstrated. As a method for producing the positive electrode plate 20 of the present invention, there are a method using a conventionally known resin binder as a binder and a method using a metal oxide as a binder. Specific explanation is given below.

(1) Method for Producing Positive Plate Using Resin Binder as Binder Material As a method for producing a positive plate using resin binder as the binder material, a conventionally known method is appropriately selected. Can be used. For example, the positive electrode plate 20 can be manufactured by applying and drying a positive 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 positive 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 a positive electrode active material layer forming solution. The blending ratio at this time is preferably set so that the total amount of the active material 10 and the binder is about 40 to 80 parts by mass when the entire positive 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 positive 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 positive 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 further improve the film forming property of the positive electrode active material layer 22 by performing corona treatment, oxygen plasma treatment, or the like in advance as necessary.

  Further, the coating amount of the positive 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 positive 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 positive 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 the press is performed, it is desirable to adjust the press pressure in consideration of the content of the solute contained in the positive electrode active material layer forming solution and the heating conditions in the heating process. .

(2) Method for producing positive electrode plate using metal oxide as binder material Positive electrode plate 20 using metal oxide as a binder material includes an active material 10, a binder precursor containing a metal element, a solvent, and a necessary material. Depending on the above, the positive electrode active material layer forming solution can be prepared using the other materials described above, and the solution can be coated on the current collector 21 and then heated.

  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 positive electrode active material layer forming solution. Also, as the coating method, the various methods described above can be appropriately selected and used. 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.

  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.

  Also, the heating atmosphere is not particularly limited, and can be appropriately determined in consideration of the material used for manufacturing the positive 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 view showing an example of the non-aqueous 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 a positive 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 a negative 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 nonaqueous electrolyte secondary battery of the present invention is characterized in that the positive electrode plate 20 for a nonaqueous electrolyte secondary battery described above is used as an essential configuration as a positive electrode plate. 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. In addition, about the positive electrode plate for nonaqueous electrolyte secondary batteries of this invention, it is as having demonstrated above, and detailed description is abbreviate | omitted.

(Positive electrode plate)
The nonaqueous electrolyte secondary battery of the present invention is characterized in that the positive electrode plate 20 of the present invention is used as the positive electrode plate. The positive electrode plate 20 of the present invention is composed of the active material 10 whose initial charge / discharge efficiency is improved. Therefore, by using the positive electrode plate 20, the performance of the positive electrode plate is exhibited also in the non-aqueous electrolyte secondary battery 100 of the present invention.

(Negative electrode plate)
As the negative electrode plate, a conventionally known negative electrode plate for a non-aqueous electrolyte secondary battery can be appropriately selected and used. Generally, 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 the negative electrode plate is formed on at least a part of the current collector surface. The electrode active material layer forming solution is applied, dried, and pressed as necessary. The electrode active material layer forming liquid 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.

(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. When used, 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 nonaqueous electrolyte secondary battery 100 using the positive 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 non-aqueous electrolyte secondary battery 100 of the present invention using the positive electrode plate 20 of the present invention has functions such as an overcurrent blocking function and a battery temperature monitor in addition to the protection circuit, in addition to the usage mode for the battery pack. 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
Li (CH ₃ COO) · 2H ₂ O [molecular weight: 102.02]: 5 g added with 5 g of pure water, and titanium chelating agent (Ti (Oi-C ₃ H ₇ ) ₂ (C ₆ H ₁₄ O ₃ N) ₂ ): 16 g was used as a shell raw material solution. Subsequently, positive electrode active material particles (LiMn ₂ O ₄ ): 10 g serving as a core body were mixed with 10 g of the above raw material liquid to obtain an electrode active material raw material liquid. This electrode 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 air atmosphere, heated to 450 ° C. over 1 hour, and then heated to 450 ° C. The mixture was heated for 10 minutes while maintaining the temperature to obtain an active material. Next, a positive electrode active material layer forming slurry for forming a positive electrode active material layer in the positive electrode plate was prepared as follows. Active material: 10 g, 1 g of acetylene black HS-100 (manufactured by Denki Kagaku Kogyo Co., Ltd.) as the conductive material, 0.2 g of VGCF (manufactured by Showa Denko Co., Ltd.), and PVDF (resin binder) Prepare 1.3g of Kureha Co., Ltd., KF # 1100), disperse the PVDF resin solution dissolved in 10g of NMP (Mitsubishi Chemical Co., Ltd.) as solvent, Excel Auto Homogenizer (Nippon Seiki Seisakusho Co., Ltd.) The mixture 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 80 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 shell body raw material liquid of Example 1, Li (CH ₃ COO) · 2H ₂ O [molecular weight: 102.02]: 10 g and Co (NO ₃ ) ₂ · 6H ₂ O [molecular weight: 290.9] A positive electrode plate of Example 2 was obtained in the same manner as in Example 1 except that a shell material solution in which 30 g and 30 g of methanol were mixed was used.

(Example 3)
Active material obtained in Example 2: 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 80 g / m ^2. Is installed in an electric furnace (high temperature atmosphere box furnace, manufactured by Koyo Thermo Systems Co., Ltd., KB8610N-VP) in a nitrogen atmosphere, heated up from room temperature (25 ° C.) to 480 ° C. over 1 hour, and then Heating was continued for 30 minutes while maintaining the temperature at 480 ° C., and then allowed to stand until room temperature was reached, whereby a positive electrode plate having a positive electrode active material layer formed on a current collector was obtained. Subsequently, it was cut into a predetermined size (a disk having a diameter of 15 mm), and this was used as 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)
LiMn ₂ O ₄ powder having an average particle size of 4 μm: 10 g, acetylene black (Denka Black, manufactured by Denki Kagaku Kogyo Co., Ltd.): 1.2 g as a conductive material, and PVDF (manufactured by Kureha Co., KF # 1100): 0 as a binder NMP (manufactured by Mitsubishi Chemical Corporation) as an organic solvent: Disperse the PVDF resin solution dissolved in 10 g, and stir for 15 minutes at 7000 rpm with an Excel auto homogenizer (Nihon Seiki Seisakusho Co., Ltd.). A material layer forming slurry was prepared. This positive electrode active material layer forming slurry was applied so that the coating amount after drying was 80 g / m ^2, and was dried in an air atmosphere at 120 ° C. for 20 minutes using an oven to form on the surface of the current collector. An electrode active material layer for the positive electrode 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 magnitude | size (a 15-mm diameter disc), and was set as the positive electrode plate of the comparative example 1.

(Comparative Example 2)
Instead of the shell body raw material liquid of Example 1, Li (CH ₃ COO) · 2H ₂ O [molecular weight: 102.02]: 2 g and Mn (CH ₃ COO) ₂ · 4H ₂ O [molecular weight: 245. [09]: Using a shell raw material liquid in which 9 g of methanol and 11 g of methanol are mixed, the positive active material particles (LiMn ₂ O ₄ ) having an average particle diameter of 4 μm as the core body of Example 1 are used. Te, the cathode active having an average particle size of 5μm material LiCoO _2: using 10 g, except that the coating amount after drying was coated to a 59 g / m ^2, the same procedure as in example 1, Comparative example 2 The positive electrode plate 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, The assembly was subjected to the following charge / discharge test.

(Initial charging test)
The test cell is charged with a constant current (1000 μA) under a 25 ° C. environment until the voltage reaches 4.3 V. After the voltage reaches 4.3 V, the voltage does not exceed 4.3 V. As described above, the current (discharge rate: 1C) was decreased until it became 5% or less, and the battery was charged at a constant voltage, fully charged, and then rested for 10 minutes. Here, “1C” means a current value (current value reaching the discharge end voltage) at which constant current discharge is performed using the tripolar coin cell and discharge is completed in one hour.

(Initial discharge test)
Thereafter, the fully charged test cell was fixed at a constant current (discharge rate: 1 C) in a 25 ° C. environment until the voltage changed from 4.3 V (full charge voltage) to 3.0 V (discharge end voltage). Current discharge was performed, the cell voltage (V) on the vertical axis and the discharge time (h) on the horizontal axis, a discharge curve was prepared, and the initial discharge capacities (μAh) of the positive plates of Examples and Comparative Examples were determined.

(Calculation of initial charge / discharge efficiency (%))
Initial charge / discharge efficiency% = {(initial discharge capacity) ÷ (initial charge capacity)} × 100 Table 1 shows the results of the above-described Examples and Comparative Examples.

  As can be seen from the above table, each of the positive electrode plates of Examples 1 and 2 of the present invention has an active material composed of a core body and a shell body, and the alkali metal ion emission potential of the shell body is The initial charge / discharge efficiency is improved as compared with Comparative Example 1 having no shell body and Comparative Example 2 in which the alkali metal ion release potential of the core body is lower than the alkali metal ion release potential of the shell body. Has been confirmed.

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 (6)

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 active material for a non-aqueous electrolyte secondary battery, wherein the electrode active material of the shell body has a lower alkali metal ion release potential than the electrode active material of the core body.   The electrode active material of the core body and the electrode active material of the shell body are complex oxides of at least one metal selected from cobalt, nickel, manganese, iron, and titanium and lithium. The active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein the active material is a non-aqueous electrolyte secondary battery.   The active material for a non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein the electrode active material of the shell body is an electrode active material capable of transmitting a non-aqueous electrolyte. A positive 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,
A positive electrode plate for a non-aqueous electrolyte secondary battery, wherein the active material is the active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 3. 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,
The said positive electrode plate is a positive electrode plate for nonaqueous electrolyte secondary batteries of Claim 4, 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 5.

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