JP2009224098A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery suppressing a capacity drop even when the nonaqueous electrolyte secondary battery is charged and discharged at high temperatures, enhancing cycle characteristics even under high temperature environment, and having high capacity and high safety. <P>SOLUTION: An active material A represented by Li<SB>x</SB>CoO<SB>2</SB>and an active material B represented by Li<SB>x</SB>Ni<SB>y</SB>Co<SB>z</SB>M<SB>1-y-z</SB>O<SB>2</SB>are mixed, and a nonaqueous electrolyte is prepared by dissolving at least one kind of lithium salt selected from LiClO<SB>4</SB>, LiPF<SB>6</SB>, LiBF<SB>4</SB>, LiCF<SB>3</SB>SO<SB>3</SB>, LiN(CF<SB>3</SB>SO<SB>2</SB>)<SB>2</SB>, LiN(CF<SB>3</SB>CF<SB>2</SB>SO<SB>2</SB>)<SB>2</SB>, LiN(CF<SB>3</SB>SO<SB>2</SB>)(C<SB>4</SB>F<SB>9</SB>SO<SB>2</SB>), and LiC(CF<SB>3</SB>SO<SB>2</SB>)<SB>3</SB>in a mixed solvent of a cyclic carbonate and a chain carbonate. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a non-aqueous electrolyte secondary battery suitably applied to a battery power source of a small portable electronic device or the like, and more particularly to a non-aqueous electrolyte secondary battery that improves reliability when stored at a high temperature. is there.

  In recent years, portable electronic devices have become increasingly smaller, thinner, lighter, and more advanced, and accordingly, batteries that serve as power sources are also required to be smaller, thinner, lighter, and higher in capacity. A non-aqueous electrolyte secondary battery is most suitable as a small, thin, light and high capacity battery. Of these, lithium secondary batteries are most suitable. Today, as a battery that can be used repeatedly, it is increasingly applied to mobile electronic devices such as mobile phones and laptop computers.

As such a positive electrode active material for a lithium secondary battery, lithium cobaltate (hereinafter abbreviated as LiCoO ₂ ) or lithium nickelate (hereinafter referred to as LiCoO ₂ ), which can achieve a high capacity density and exhibits good reversibility in a high voltage range. Lithium-containing transition metal oxides such as LiNiO ₂ are used.

These positive electrode active materials are expensive raw materials such as cobalt and nickel. In addition, when the charged lithium secondary battery is intentionally heated, there is a problem that the positive electrode active material and the nonaqueous electrolyte react to generate heat. In addition, lithium secondary batteries using spinel-type composite oxides such as lithium manganate (hereinafter abbreviated as LiMn ₂ O ₄ ) using relatively inexpensive manganese as a raw material have been studied. In LiMn ₂ O _4, when intentionally heating the lithium secondary battery in the charged state, the lithium secondary positive electrode active material and the nonaqueous electrolyte may react, using, for example, LiCoO ₂ and LiNiO ₂ as a positive electrode active material Compared to secondary batteries, it has a feature that it does not easily generate heat. However, there is a problem that the capacity density is small as compared with a lithium secondary battery using a cobalt-based material such as LiCoO ₂ or a nickel-based material such as LiNiO ₂ as a positive electrode active material.

  In order to solve these problems, lithium secondary batteries in which two or more types are mixed instead of using these lithium-containing transition metal oxides alone as a positive electrode active material have been proposed (for example, Patent Documents 1 to 5). reference).

On the other hand, a porous polyolefin, which is a thermoplastic resin, is often used for the separator of the nonaqueous electrolyte secondary battery from the viewpoint of safety. When a failure such as an external short circuit occurs, the isolation membrane softens as the battery suddenly increases in temperature due to the short circuit, and the micropores (innumerable small holes) in the isolation membrane collapse, losing ionic conductivity, and current. Has a function (so-called shutdown function). However, when the temperature of the battery continues to rise after the shutdown, the separator film melts and heat shrinks, and a short circuit area between the positive and negative electrodes expands (so-called meltdown). Therefore, efforts have been made to improve both shutdown performance and meltdown resistance, but there is a conflicting problem that increasing the thermal meltability to improve shutdown performance lowers the meltdown temperature. . In order to solve this problem, a composite separator comprising a porous polyolefin layer and a heat resistant resin layer as a separator has been proposed. As one of them, a separator made of a heat-resistant nitrogen-containing aromatic polymer (aramid or polyamideimide) layer containing ceramic powder and a porous polyolefin layer has been proposed (see, for example, Patent Document 6).
Japanese Patent Laid-Open No. 11-3698 JP-A-10-27611 JP 2002-145623 A JP 2002-1003007 A JP 2007-188703 A Japanese Patent No. 3175730

Patent Document 1 proposes a lithium secondary battery using a mixture of three kinds of LiMn ₂ O ₄ , LiNiO ₂ , and LiCoO ₂ as a positive electrode active material. However, when such a mixture is used, since LiMn ₂ O ₄ having a low discharge capacity per unit weight is used, the discharge capacity per unit weight of the mixture is also low.
As a lithium-containing transition metal oxide, a positive electrode active material in which a plurality of transition metals of cobalt, nickel, and manganese are dissolved is proposed. The positive electrode active material in solid solution has different electric characteristics such as electric capacity, reversibility, operating voltage, and safety depending on the type of transition metal to be dissolved. For example, in the case of using _LiNi 0.8 _Co 0.2 _{O 2} was a solid solution nickel 80% of LiCoO ₂ cobalt as the positive electrode active material, in the case of using LiCoO ₂ alone capacity density 140~160mAh / g As compared with the above, a high capacity density of 180 to 200 mAh / g can be achieved.

Patent Document 2 proposes LiNi _0.75 Co _0.2 Mn _0.05 O _{2 and the} like in order to improve the characteristics of LiNi _0.8 Co _0.2 O ₂ . Patent Document 3 discloses LiNi _x Mn _1-x M _y O ₂ (where 0.30 ≦ x ≦ 0.65, 0 ≦ y ≦ 0.2, and M is Fe, Co, Cr, Al , Ti, Ga, In, and Sn). A lithium-containing transition metal oxide represented by a metal element has been proposed. Patent Document 4 discloses Li _x Ni _y Mn _1-yz M _z O ₂ (where x is 0.9 ≦ x ≦ 1.2, y is 0.40 ≦ y ≦ 0.60, z Is a lithium-containing transition metal oxide represented by 0 ≦ z ≦ 0.2 and M is selected from any one of Fe, Co, Cr, and Al atoms, and Li _x CoO ₂ (where x Is a mixture with a lithium-cobalt composite oxide represented by 0.9 ≦ x ≦ 1.1.

  However, in any positive electrode active material, a positive electrode active material satisfying all of charge / discharge capacity, cycle characteristics, reliability at high temperature storage, and safety has not been obtained. In particular, regarding the reliability after high-temperature storage in a charged lithium secondary battery, it was found that the reliability is determined by the type of transition metal. This is because the positive electrode active material in a charged state reacts with the nonaqueous electrolyte during high-temperature storage, and a part of the transition metal (Co, Ni, Mn, etc.) in the positive electrode active material is dissolved in the nonaqueous electrolyte. It is. As a result, it is assumed that the positive electrode active material is deteriorated.

Patent Document 5 discloses Li _x CoO ₂ , Li _x Co _1-y M _y O ₂ , and Li _x Ni _y Mn _z M _1-y in order to improve the reliability after such high-temperature storage. _-Z O ₂ has been proposed to be mixed, but in either case, it is possible to provide a battery having a lower capacity than a nickel positive electrode such as LiNiO _{2 and} a higher capacity than conventional LiCoO _2. There is a problem that it cannot be done. In addition, since Li _x Ni _y Mn _z M _1-yz O ₂ contains Mn, elution of Mn occurs in a higher temperature environment such as 85 ° C. or higher, so that capacity deterioration becomes significant. Had problems.

In addition, when a heat resistant resin is used for the separator as in Patent Document 6, the safety of the battery can be improved, but there is a problem that the reliability during high temperature storage is lowered. As a heat resistant resin used for the separator, aramid is obtained by polymerizing an organic substance having an amine group represented by paraphenylenediamine and an organic substance having a chlorine group represented by terephthalic acid chloride. However, a chlorine group remains at the terminal group during polymerization. Polyamideimide is obtained by reacting trimellitic anhydride monochloride with diamine. However, as in the case of aramid, a chlorine group remains at the terminal group during synthesis. The remaining chlorine groups are liberated in the non-aqueous electrolyte by being stored for a long time in a high temperature environment. If liberated chlorine is present in the vicinity of the positive electrode active material, a part of the dissolved transition metal undergoes a complexing reaction with chlorine, and the amount of transition metal elution increases and the number of sites that function as the positive electrode active material decreases. It is considered that the capacity is significantly reduced.

  Therefore, in view of the above-described conventional problems, the present invention suppresses the deterioration of the discharge characteristics of the nonaqueous electrolyte secondary battery even when the nonaqueous electrolyte secondary battery has a high capacity and is stored at a high temperature. It aims at providing the nonaqueous electrolyte secondary battery excellent in the reliability at the time of high temperature storage.

In order to solve the above problems, a non-aqueous electrolyte secondary battery of the present invention is a non-aqueous electrolyte secondary battery comprising a negative electrode having an active material capable of inserting and extracting lithium, a non-aqueous electrolyte, a separator, and a positive electrode. In the battery, the active material of the positive electrode is a mixture of an active material A and an active material B, and the active material A is a lithium composite oxide represented by Li _x CoO ₂ (0.9 ≦ x ≦ 1.2). , The active material B is Li _x Ni _y Co _z M _1-yz O ₂ (0.9 ≦ x ≦ 1.2, 0.3 ≦ y ≦ 0.9, 0.05 ≦ z ≦ 0.5, 0.01 ≦ 1-yz ≦ 0.3, and M is Mg, Ba, Al, Ti, Sr, Ca, V, Fe, Cu, Bi, Y, Zr, Mo, Tc, Ru, And at least one selected from Ta, W, and Re), and the non-aqueous electrolyte is a cyclic carbonate. At least one selected from ethylene carbonate, propylene carbonate, and butylene carbonate, and chain carbonates such as dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, di-n-propyl carbonate, methyl-n-propyl carbonate, ethyl-n LiClO ₄ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (CF ₃₎ which is a lithium salt in at least one mixed solvent selected from -propyl carbonate, methyl-i-propyl carbonate, and ethyl-i-propyl carbonate At least one selected from SO ₂ ) ₂ , LiN (CF ₃ CF ₂ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ), and LiC (CF ₃ SO ₂ ) ₃ This is a non-aqueous electrolyte secondary battery in which seeds are dissolved.

In the nonaqueous electrolyte secondary battery of the present invention, the active material of the positive electrode is a mixture of the active material B and the active material C, and the active material B is Li _x Ni _y Co _z M _1-yz O ₂ ( 0.9 ≦ x ≦ 1.2, 0.3 ≦ y ≦ 0.9, 0.05 ≦ z ≦ 0.5, 0.01 ≦ 1-yz ≦ 0.3, and M is At least one selected from Mg, Ba, Al, Ti, Sr, Ca, V, Fe, Cu, Bi, Y, Zr, Mo, Tc, Ru, Ta, W, and Re) Lithium composite oxide, positive electrode active material C is Li _x Co _1-y M _y O ₂ (0.9 ≦ x ≦ 1.2, 0.005 ≦ y ≦ 0.1, M is Mg, Al At least selected from Ti, Sr, Mn, Ni, Ca, V, Fe, Y, Zr, Mo, Tc, Ru, Ta, W, Re, Yb, Cu, Zn, and Ba And a nonaqueous electrolyte is at least one selected from cyclic carbonates such as ethylene carbonate, propylene carbonate, and butylene carbonate, and chain carbonates such as dimethyl carbonate, diethyl carbonate, Lithium salt in at least one mixed solvent selected from ethyl methyl carbonate, di-n-propyl carbonate, methyl-n-propyl carbonate, ethyl-n-propyl carbonate, methyl-i-propyl carbonate, and ethyl-i-propyl carbonate LiClO ₄ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (CF ₃ CF ₂ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C ₄ A nonaqueous electrolyte secondary battery in which at least one selected from F ₉ SO ₂ ) and LiC (CF ₃ SO ₂ ) ₃ is dissolved.

By doing this, even when the non-aqueous electrolyte secondary battery is stored at a high temperature, it is possible to suppress deterioration of the discharge characteristics of the battery and obtain a non-aqueous electrolyte secondary battery excellent in reliability at high-temperature storage. it can.

  According to the present invention, even when the nonaqueous electrolyte secondary battery is stored at a high temperature, the deterioration of the discharge characteristics of the battery is suppressed, and the nonaqueous electrolyte secondary battery having a high capacity and excellent reliability during high temperature storage is provided. A secondary battery can be provided.

The nonaqueous electrolyte secondary battery of the present invention comprises a negative electrode having an active material capable of inserting and extracting lithium, a nonaqueous electrolyte, a separator, and a positive electrode. The active material of the positive electrode is a mixture of active material A and active material B. The active material A is a lithium composite oxide represented by Li _x CoO ₂ (0.9 ≦ x ≦ 1.2). The active material B is Li _x Ni _y Co _z M _1-yz O ₂ (0.9 ≦ x ≦ 1.2, 0.3 ≦ y ≦ 0.9, 0.05 ≦ z ≦ 0.5, 0 .01 ≦ 1-yz ≦ 0.3, and M is Mg, Ba, Al, Ti, Sr, Ca, V, Fe, Cu, Bi, Y, Zr, Mo, Tc, Ru, Ta, A lithium composite oxide represented by at least one selected from W and Re). The non-aqueous electrolyte is at least one selected from cyclic carbonates such as ethylene carbonate, propylene carbonate, and butylene carbonate, and chain carbonates such as dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, di-n-propyl carbonate, methyl- At least one mixed solvent selected from n-propyl carbonate, ethyl-n-propyl carbonate, methyl-i-propyl carbonate, and ethyl-i-propyl carbonate is a lithium salt, LiClO ₄ , LiPF ₆ , LiBF ₄ , LiCF _{3 SO 3, LiN (CF 3} SO 2) 2, LiN (CF 3 CF 2 SO 2) 2, LiN (CF 3 SO 2) (C 4 F 9 SO 2), and LiC _(CF 3 S Is characterized in that from _{2) 3} are dissolved least one selected.

  By doing so, it is possible to obtain a non-aqueous electrolyte secondary battery having the characteristics of both the positive electrode active material A having a high average voltage during discharge and the positive electrode active material B having a high capacity and high thermal stability. it can. In particular, when the charged nonaqueous electrolyte secondary battery is exposed to a high temperature environment, even if the positive electrode active material B reacts with the nonaqueous electrolyte, the amount of transition metal in the positive electrode active material B dissolved in the nonaqueous electrolyte Less. As a result, the deterioration of the positive electrode active material is suppressed, and the electrical characteristics of the nonaqueous electrolyte secondary battery after high temperature storage are improved. This is because Co and M are present in the positive electrode active material B, so that the crystal structure of the positive electrode active material is stable even in a high charge state. Furthermore, it is considered that the conductive path in the positive electrode plate is secured by mixing the positive electrode active material A having relatively high conductivity.

  In one embodiment of the present invention, the mixing ratio of the active material B is preferably 10 to 90% by weight ratio with respect to the sum of the active material B and the active material A, and more preferably 15 to 50%. By doing so, it is possible to obtain a non-aqueous electrolyte secondary battery having a good balance of charge / discharge capacity, cycle characteristics, reliability during high-temperature storage, and safety.

In the nonaqueous electrolyte secondary battery of the present invention, the active material B and the active material C are mixed as the active material of the positive electrode. The active material B is Li _x Ni _y Co _z M _1-yz O ₂ (0.9 ≦ x ≦ 1.2, 0.3 ≦ y ≦ 0.9, 0.05 ≦ z ≦ 0.5, 0 .01 ≦ 1-yz ≦ 0.3, and M is Mg, Ba, Al, Ti, Sr, Ca, V, Fe, Cu, Bi, Y, Zr, Mo, Tc, Ru, Ta, A lithium composite oxide represented by at least one selected from W and Re). The positive electrode active material C is Li _x Co _1-y M _y O ₂ (0.9 ≦ x ≦ 1.2, 0.005 ≦ y ≦ 0.1, and M is Mg, Al, Ti, Sr, Mn, Lithium composite oxide represented by at least one selected from Ni, Ca, V, Fe, Y, Zr, Mo, Tc, Ru, Ta, W, Re, Yb, Cu, Zn, and Ba) It is. The non-aqueous electrolyte is at least one selected from cyclic carbonates such as ethylene carbonate, propylene carbonate, and butylene carbonate, and chain carbonates such as dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, di-n-propyl carbonate, methyl At least one mixed solvent selected from -n-propyl carbonate, ethyl-n-propyl carbonate, methyl-i-propyl carbonate, and ethyl-i-propyl carbonate is a lithium salt, LiClO ₄ , LiPF ₆ , LiBF ₄ , _{LiCF 3 SO 3, LiN (CF} 3 SO 2) 2, LiN (CF 3 CF 2 SO 2) 2, LiN (CF 3 SO 2) (C 4 F 9 SO 2), and LiC (CF ₃ O ₂₎ is characterized in that it is dissolved at least one selected from _3.

  By doing so, it is possible to obtain a non-aqueous electrolyte secondary battery having the characteristics of both the positive electrode active material C having a high average voltage during discharge and the positive electrode active material B having a high capacity and high thermal stability. it can. In particular, when the charged nonaqueous electrolyte secondary battery is exposed to a high temperature environment, even if the positive electrode active material B reacts with the nonaqueous electrolyte, the amount of transition metal in the positive electrode active material B dissolved in the nonaqueous electrolyte Less. As a result, the deterioration of the positive electrode active material is suppressed, and the electrical characteristics of the nonaqueous electrolyte secondary battery after high temperature storage are improved. This is because Co and M are present in the positive electrode active material B, so that the crystal structure of the positive electrode active material is stable even in a high charge state. Furthermore, it is considered that the conductive path in the positive electrode plate is secured by mixing the positive electrode active material C having relatively high conductivity.

  In one embodiment of the present invention, the mixing ratio of the active material B is preferably 10 to 90%, more preferably 15 to 50% in terms of a weight ratio with respect to the sum of the active material B and the active material C.

As the non-aqueous electrolyte, in order to suppress the reaction between the non-aqueous electrolyte and the positive electrode active material in a high temperature environment, as described above, at least one selected from ethylene carbonate, propylene carbonate, and butylene carbonate, which are cyclic carbonates, And chain carbonates such as dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, di-n-propyl carbonate, methyl-n-propyl carbonate, ethyl-n-propyl carbonate, methyl-i-propyl carbonate, and ethyl-i-propyl at least one solvent mixture of lithium salt chosen from _{carbonate, LiClO 4, LiPF 6, LiBF} 4, LiCF 3 SO 3, LiN (CF 3 SO 2) 2, LiN (CF 3 CF 2 SO 2) _{, LiN (CF 3 SO 2)} (C 4 F 9 SO 2), and _LiC (CF 3 _{SO 2)} is preferably composed mainly of at least one selected from _3.

  By doing so, it is possible to obtain a non-aqueous electrolyte secondary battery having a good balance of charge / discharge capacity, cycle characteristics, reliability during high-temperature storage, and safety.

  In one embodiment of the present invention, it is preferable that 50% or more of ethylene carbonate is contained in cyclic carbonate. By doing so, it is possible to obtain a nonaqueous electrolyte secondary battery that is stable in a high temperature environment and excellent in charge and discharge characteristics.

  In one embodiment of the present invention, it is preferable that ethyl methyl carbonate is included as the chain carbonate. By doing so, it is possible to obtain a nonaqueous electrolyte secondary battery that is stable in a high temperature environment and excellent in charge and discharge characteristics.

In one embodiment of the present invention, the chain carbonate is preferably a mixed solvent of diethyl carbonate and ethyl methyl carbonate, and the proportion of diethyl carbonate is higher than that of ethyl methyl carbonate. By doing so, since the decomposition of the solvent in the electrolyte under a high temperature environment is suppressed, a nonaqueous electrolyte secondary battery that is stable under a high temperature environment and excellent in charge / discharge characteristics can be obtained.

  The cyclic carbonate as the high dielectric constant solvent and the chain carbonate as the low viscosity solvent can be arbitrarily selected and used in combination. The high dielectric constant solvent and the low viscosity solvent are used in a volume ratio (high dielectric constant solvent: low viscosity solvent) in a mixing ratio of 10:90 to 40:10, preferably 10:50 to 70:30. . The chain carbonate is used in a volume ratio (EMC: DEC) of 45:55 to 10:90, preferably 40:60 to 30:70.

In one embodiment of the present invention, it is preferable that LiPF ₆ is included as a lithium salt. By doing so, it is possible to obtain a nonaqueous electrolyte secondary battery that is stable in a high temperature environment and excellent in charge and discharge characteristics.

  These electrolytes are used in the above non-aqueous solvent in a concentration of usually 0.1 to 3.0 mol / L, preferably 0.5 to 1.6 mol / L.

In one embodiment of the present invention, it is preferable that the lithium salt is a mixed salt of LiPF ₆ and LiBF ₄ and the proportion of LiPF ₆ is larger than that of LiBF ₄ . By doing so, decomposition of the electrolyte in the electrolyte under a high temperature environment is suppressed, so that a nonaqueous electrolyte secondary battery that is stable under a high temperature environment and excellent in charge / discharge characteristics can be obtained. These electrolytes are used in a weight ratio (LiPF ₆ : LiBF ₄ ) of 100: 1 to 55:45, preferably 100: 2 to 70:30.

  In one embodiment of the present invention, the nonaqueous electrolyte preferably contains at least one cyclic ester selected from vinylene carbonate, vinylethylene carbonate, γ-butyrolactone, and γ-valerolactone. In particular, it is preferable to use a mixture of vinylene carbonate (VC) and vinyl ethylene carbonate (VEC), and the amount added is 0.1% to 10% in total, preferably 1% to 5% by weight. . By doing so, a stable film is formed on the negative electrode surface, and decomposition of the electrolyte in the electrolyte under high temperature environment is suppressed. Therefore, non-water that is stable under high temperature environment and has excellent charge / discharge characteristics. An electrolyte secondary battery can be obtained.

  In one embodiment of the present invention, the nonaqueous electrolyte preferably contains at least one selected from ethylene sulfite, 1,3-propane sultone, sulfolane, tetrahydrofuran sulfite, and sulfolene. By adding such a sulfur-containing compound, a stable film is formed on the surface of the positive electrode, and decomposition of the electrolyte in the electrolyte in a high temperature environment is suppressed. A nonaqueous electrolyte secondary battery having excellent discharge characteristics can be obtained.

In one embodiment of the present invention, the non-aqueous electrolyte is methylamine, ethylamine, trimethylamine, triethylamine, ethylenediamine, 1,4-ethylenediamine, hexamethylenediamine, pyridine, hexahydropyridine, morpholine, quinuclidine, aniline, tetra It is preferable that at least one organic solvent selected from methylethylenediamine and etheramines is contained. By adding such a nitrogen-containing compound, in particular, a stable film is formed on the surface of the positive electrode containing Li _x Ni _y Co _z M _1-yz O ₂ , and the electrolyte in the electrolyte in a high temperature environment Therefore, it is possible to obtain a nonaqueous electrolyte secondary battery that is stable in a high temperature environment and has excellent charge / discharge characteristics.

Hereinafter, the isolation film will be described. The separator film is not particularly limited, and a porous sheet or nonwoven fabric made of polyolefin such as polyethylene (hereinafter abbreviated as PE) or polypropylene (hereinafter abbreviated as PP), an inorganic microporous film, or the like may be used. The thickness of the organic microporous film is preferably 10 to 40 μm. The inorganic microporous film is, for example, a film in which an inorganic filler such as alumina and silica and an organic binder for binding the inorganic filler are mixed as a binder. The inorganic microporous film may be interposed between the positive electrode plate and the negative electrode plate. As a method of interposing an inorganic microporous film between the positive electrode plate and the negative electrode plate, an inorganic microporous film may be formed on the surface of the positive electrode plate, or an inorganic microporous film may be formed on the surface of the negative electrode plate. An inorganic microporous film may be formed on the surface of the plate. The thickness of the inorganic microporous film is preferably 1 to 20 μm. Moreover, you may use both an inorganic microporous film and an organic microporous film. The thickness of the inorganic microporous film when both the inorganic microporous film and the organic microporous film are used is preferably 1 to 10 μm.

  In one embodiment of the present invention, the separator is preferably a porous film containing a heat-resistant resin containing chlorine, and the positive electrode active material preferably contains at least one lithium-containing composite oxide having Al in the composition. . In this way, even when chlorine remaining as the end group of the heat-resistant resin that constitutes the separator is released during the high-temperature cycle, this chlorine preferentially forms a complex with Al to form other transition metals. Elution can be suppressed. This is because Al has a higher stabilization constant in complex formation than transition metals such as Co, Ni, and Mn, and is preferentially complexed with chlorine. Thereby, elution of main constituent elements (Co, Ni, etc.) into the non-aqueous electrolyte can be suppressed, and a non-aqueous electrolyte secondary battery having a good balance between cycle characteristics and safety at high temperatures can be obtained.

  In one embodiment of the present invention, it is preferable that the heat resistant resin of the separator is at least one of aramid and polyamideimide. These heat-resistant resins are soluble in polar organic solvents for both aramids and polyamide-imides, have excellent film-forming properties, easily form a porous film, and have extremely high nonaqueous electrolyte retention and heat resistance. This is because it has characteristics.

  In one embodiment of the present invention, the separator is preferably a laminate of a porous membrane formed of a heat resistant resin and a porous polyolefin. It is preferable to use PE or PP as the porous polyolefin. There is a method of providing a porous film formed of a heat-resistant resin on a porous polyolefin. The reverse method may also be used. For example, when aramid is used as the heat resistant resin, it is dissolved in a polar solvent such as N-methylpyrrolidone (hereinafter abbreviated as NMP), and then applied to a substrate such as a glass plate or a stainless steel plate. By making it dissociate, a porous film of a single heat resistant resin can be obtained. On the other hand, an NMP solution in which aramid is dissolved is coated on a porous polyolefin substrate such as PE or PP, whereby a separator film in which a heat resistant resin and a porous polyolefin are laminated can be obtained.

  In one embodiment of the present invention, the separator is preferably a laminate of a porous membrane made of a heat resistant resin and a filler and a porous polyolefin. For example, a porous film having higher heat resistance can be formed by adding an inorganic oxide as a filler to an NMP solution in which aramid is dissolved. As the inorganic oxide filler, it is preferable to use at least one of alumina, zeolite, silicon nitride, silicon carbide, titanium oxide, zirconium oxide, magnesium oxide, zinc oxide, silicon dioxide, and the like. Such an inorganic oxide filler has organic electrolyte resistance and does not cause side reactions that adversely affect battery characteristics even under a redox potential. Therefore, it is preferable to select a chemically stable and high-purity one.

As a method for producing Li _x Ni _y Co _z M _1-yz O ₂ , for example, a mixture of a cobalt compound, a lithium compound, and a nickel compound is mixed in a solid phase in an inert gas atmosphere or in the air. Examples thereof include a method of baking at 500 to 1000 ° C. by a method and a method of baking at 500 to 850 ° C. by a molten salt method.

  Examples of the nickel raw material used for the positive electrode active material include oxides (NiO, etc.), hydroxides (NiOH), oxyhydroxides (NiOOH), and the like. As the cobalt raw material, a trivalent cobalt compound is more preferable. These cobalt raw materials may be used independently and may use 2 or more types together.

  In addition to the positive electrode active material of the present invention, the positive electrode plate may contain a binder, a conductive agent, a solvent and the like as necessary. The method for producing the positive electrode plate is not particularly limited. For example, a binder, a thickener, a conductive agent, a solvent, etc. are added to the positive electrode material as necessary to form a slurry, which is applied to the current collector substrate. And it can manufacture a positive electrode plate by drying. Further, the positive electrode plate can be roll-formed as it is to form a sheet electrode, or a pellet electrode can be formed by compression molding.

  The binder used for manufacturing the electrode is not particularly limited as long as it is a material that is stable with respect to the solvent and electrolyte used in manufacturing the electrode. Specific examples thereof include polyvinylidene fluoride (hereinafter abbreviated as PVDF), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), isopropylene rubber, butadiene rubber, ethylene propylene diethane polymer (EPDM) and the like. Can be mentioned.

  Examples of the thickener include carboxymethyl cellulose (hereinafter abbreviated as CMC), methyl cellulose (MC), hydroxymethyl cellulose (HMC), ethyl cellulose, polyvinyl alcohol (PVA), oxidized starch, phosphorylated starch, and casein.

  Examples of the conductive agent include metal materials such as copper and nickel, and carbon materials such as graphite and carbon black.

  The positive electrode current collector may be made of a metal such as aluminum, titanium, or tantalum or an alloy thereof, but aluminum or an alloy thereof is particularly preferable because it is lightweight and advantageous in energy density.

  The negative electrode contains graphite as its component. As long as graphite can occlude and release lithium, its physical properties are not particularly limited. Preference is given to artificial graphite and purified natural graphite produced by high-temperature heat treatment of soot graphite pitch obtained from various raw materials, or materials obtained by subjecting these graphite to various surface treatments containing pitch. A negative electrode material capable of inserting and extracting lithium can be further mixed with these graphite materials. As negative electrode materials capable of occluding and releasing lithium other than graphite, non-graphite carbon materials such as non-graphite carbon or low-temperature calcined carbon, metal oxide materials such as tin oxide and silicon oxide, lithium metal and various other materials A lithium alloy can be illustrated. These negative electrode materials are used as a mixture of two or more as required.

  It does not specifically limit about the method of manufacturing a negative electrode plate, It can manufacture according to said manufacturing method of a positive electrode plate. As for the shape, a binder, a conductive agent, a solvent, etc. are added to the negative electrode material as necessary and mixed, and then applied to the current collector substrate to form a sheet electrode, or press molding to form a pellet electrode It can be.

  As the material for the current collector for the negative electrode, metals such as copper, nickel, and stainless steel can be used. Among these, copper foil is preferable because it can be easily processed into a thin film and is low in cost.

The separator used in the present invention is not particularly limited, but a porous sheet or nonwoven fabric made of polyolefin such as polyethylene (PE) or polypropylene (PP), or an inorganic microporous membrane may be used. The thickness of the organic microporous film is preferably 10 to 40 μm. The inorganic microporous film is, for example, a film in which an inorganic filler such as alumina and silica and an organic binder for binding the inorganic filler are mixed as a binder. The inorganic microporous film may be interposed between the positive electrode plate and the negative electrode plate. As a method of interposing an inorganic microporous film between the positive electrode plate and the negative electrode plate, an inorganic microporous film may be formed on the surface of the positive electrode plate, or an inorganic microporous film may be formed on the surface of the negative electrode plate. An inorganic microporous film may be formed on the surface. The thickness of the inorganic microporous film is preferably 1 to 20 μm. Moreover, you may use both an inorganic microporous film and an organic microporous film. The thickness of the inorganic microporous film when both the inorganic microporous film and the organic microporous film are used is preferably 1 to 10 μm.

  The method for producing the lithium secondary battery of the present invention having the negative electrode plate, the positive electrode plate and the non-aqueous electrolyte is not particularly limited, and can be appropriately selected from commonly employed methods.

  In addition, the shape of the battery is not particularly limited, and a cylinder type in which a sheet electrode and a separator are spiraled, a cylinder type having an inside-out structure in which a pellet electrode and a separator are combined, a coin type in which a pellet electrode and a separator are stacked, and the like are used. Is possible.

  Hereinafter, a prismatic nonaqueous electrolyte secondary battery according to an embodiment of the present invention will be described with reference to FIGS. 1 is a perspective view of a flat rectangular nonaqueous electrolyte secondary battery, FIG. 2 is an enlarged sectional view taken along the line AA in FIG. 1, and FIG. 3 is an enlarged sectional view taken along the line BB in FIG. Show.

  In FIG. 2, a flat prismatic battery 1 includes an electrode plate group 5 in which a positive electrode plate 2 and a negative electrode plate 3 are stacked with a separator 4 and a nonaqueous electrolyte contained in a bottomed cylindrical battery case 6. Has been. As the separator, a porous polyethylene separator having a thickness of 20 μm is used. The battery case 6 is made of aluminum (hereinafter abbreviated as Al) metal. At the opening end of the battery case 6, a sealing plate 8 having a projection 7 serving as a negative terminal is welded and sealed with a laser. The protrusion 7 that is insulated from the sealing plate 8 is welded by a laser through the frame body 10 through the negative electrode plate 3 and the lead wire 9. Further, in FIG. 3, the sealing plate 8 is welded by a laser through the frame body 10 through the positive electrode plate 2 and the lead wire 11. The size of the battery is 50 mm long, 34 mm wide, 5 mm wide, and the battery capacity is 900 mAh.

  As the negative electrode active material, a material obtained by subjecting purified natural graphite to a surface treatment containing pitch is used. This negative electrode active material, CMC as a thickener, and SBR as a binder are blended in a weight ratio of 100: 2: 2, and mixed while adding water as a solvent to obtain a negative electrode slurry. This negative electrode slurry is applied onto a 10 μm thick copper foil as a current collector, and dried at 200 ° C. to remove water. Then, it rolls using a roll press, cut | disconnects to a predetermined dimension, and the negative electrode plate 3 is produced.

  Below, the positive electrode active material and nonaqueous electrolyte used for the positive electrode plate 2 are demonstrated in detail about this invention. This invention is not limited to the Example described below, In the range which does not change the summary, it can change suitably and can implement.

(I) Preparation of positive electrode active material LiNi _0.8 Co _0.15 Al _0.05 O ₂ Nickel sulfate, cobalt sulfate, and aluminum sulfate were mixed in an aqueous solution mixed at a molar ratio of 80: 15: 5 with water. An aqueous sodium oxide solution was added to obtain a nickel-cobalt-aluminum (hereinafter abbreviated as Ni-Co-Al) coprecipitated hydroxide. The Ni—Co—Al coprecipitated hydroxide was filtered, washed with water, dried in air, and then calcined at 400 ° C. for 5 hours to obtain Ni—Co—Al oxide powder. The obtained powder and lithium carbonate powder were mixed, put into a rotary kiln, and preheated at 650 ° C. for 10 hours in an air atmosphere. Next, the preheated mixture was heated in an electric furnace to 950 ° C. in 2 hours. By baking at 950 ° C. 10 hours to obtain a positive electrode active material _{LiNi 0.8 Co 0.15 Al 0.05 O 2} .

Next, as a positive electrode active material, Li _x CoO ₂ and LiNi _0.8 Co _0.15 Al _0.05 O ₂ prepared in (i) were mixed at a weight ratio of 70:30. This positive electrode active material, acetylene black as a conductive agent, and PVDF were blended in a weight ratio of 100: 2: 2, and mixed while adding N-methylpyrrolidone (hereinafter abbreviated as NMP) as a solvent, A positive electrode slurry was obtained. This positive electrode slurry was applied onto a 15 μm thick Al foil as a current collector, and dried at 150 ° C. to remove NMP. Then, it rolled using the roll press, cut | disconnected to the predetermined dimension, and produced the positive electrode plate 2. FIG.

The non-aqueous electrolyte was prepared by dissolving LiPF ₆ at 1 mol / L in a solvent mixed so that the volume ratio of EC and EMC was 3: 7.

  A battery was prepared using the positive electrode plate 2 thus prepared, the prepared nonaqueous electrolyte, and a porous polyethylene separator having a thickness of 20 μm as a separator. The produced battery was designated as battery A1 of Example 1.

A positive electrode active material was prepared in the same manner as in (i) except that an aqueous solution in which nickel sulfate, cobalt sulfate, and aluminum sulfate were mixed at a molar ratio of 77: 3: 20 was used, and the positive electrode active material LiNi _{0 .7} Co _0.1 Al _0.2 O ₂ was obtained. A battery produced in the same manner as in Example 1 except that a mixture of Li _x CoO ₂ and LiNi _0.7 Co _0.1 Al _0.2 O ₂ was used as the positive electrode active material. Battery A2.

A positive electrode active material was prepared in the same manner as (i) except that nickel sulfate, cobalt sulfate, and aluminum sulfate were mixed at a molar ratio of 30:50:20, and the positive electrode active material LiNi _0.3 Co _{0 was} prepared. _.5 Al _0.2 O ₂ was obtained. A battery produced in the same manner as in Example 1 was used, except that a mixture of Li _x CoO ₂ and LiNi _0.3 Co _0.5 Al _0.2 O ₂ was used as the positive electrode active material. Battery A3.

A positive electrode active material was prepared in the same manner as in (i) except that nickel sulfate, cobalt sulfate, and aluminum sulfate were mixed at a molar ratio of 84: 15: 1, and the positive electrode active material LiNi _0.84 Co _{0 was} prepared. _.15 Al _0.01 O ₂ was obtained. A battery produced in the same manner as in Example 1 except that a mixture of Li _x CoO ₂ and LiNi _0.84 Co _0.15 Al _0.01 O ₂ was used as the positive electrode active material. Battery A4.

A positive electrode active material was prepared in the same manner as (i) except that nickel sulfate, cobalt sulfate, and aluminum sulfate were mixed at a molar ratio of 75: 5: 20, and the positive electrode active material LiNi _0.75 Co _{0 was} prepared. _.05 Al _0.2 O ₂ was obtained. A battery produced in the same manner as in Example 1 except that a mixture of Li _x CoO ₂ and LiNi _0.75 Co _0.05 Al _0.2 O ₂ was used as the positive electrode active material. Battery A5.

As a positive electrode active material, except that Li _x CoO ₂ and LiNi _0.8 Co _0.15 Al _0.05 O ₂ prepared in (i) were mixed at a weight ratio of 95: 5, A battery produced in the same manner as in Example 1 was designated as Battery A6 of Example 6.

As the positive electrode active material, except that Li _x CoO ₂ and LiNi _0.8 Co _0.15 Al _0.05 O ₂ prepared in (i) were mixed at a weight ratio of 90:10, A battery produced in the same manner as in Example 1 was designated as Battery A7 of Example 7.

As the positive electrode active material, except that Li _x CoO ₂ and LiNi _0.8 Co _0.15 Al _0.05 O ₂ prepared in (i) were mixed at a weight ratio of 10:90, A battery produced in the same manner as in Example 1 was designated as Battery A8 of Example 8.

As the positive electrode active material, except that Li _x CoO ₂ and LiNi _0.8 Co _0.15 Al _0.05 O ₂ prepared in (i) were mixed at a weight ratio of 5:95, A battery produced in the same manner as in Example 1 was designated as Battery A9 of Example 9.

As a positive electrode active material, except that Li _x CoO ₂ and LiNi _0.8 Co _0.15 Al _0.05 O ₂ prepared in (i) were mixed at a weight ratio of 85:15, A battery produced in the same manner as in Example 1 was designated as Battery A10 of Example 10.

As the positive electrode active material, except that Li _x CoO ₂ and LiNi _0.8 Co _0.15 Al _0.05 O ₂ prepared in (i) were mixed at a weight ratio of 50:50, A battery produced in the same manner as in Example 1 was designated as Battery A11 of Example 11.

A positive electrode active material was prepared in the same manner as in Example 1 except that an aqueous solution in which nickel sulfate, cobalt sulfate, and magnesium sulfate were mixed at a molar ratio of 80: 15: 5 was used, and the positive electrode active material LiNi _{0 .8} Co _0.15 Mg _0.05 O ₂ was obtained. A battery produced in the same manner as in Example 1 except that a mixture of Li _x CoO ₂ and LiNi _0.8 Co _0.15 Mg _0.05 O ₂ was used as the positive electrode active material. Battery A12.

A positive electrode active material was prepared in the same manner as in Example 1 except that an aqueous solution in which nickel sulfate, cobalt sulfate, and calcium sulfate were mixed at a molar ratio of 80: 15: 5 was used, and the positive electrode active material LiNi _{0 .8} Co _0.15 Ca _0.05 O ₂ was obtained. A battery produced in the same manner as in Example 1 was used except that a mixture of Li _x CoO ₂ and LiNi _0.8 Co _0.15 Ca _0.05 O ₂ was used as the positive electrode active material. Battery A13.

A positive electrode active material was produced in the same manner as in Example 1 except that an aqueous solution in which nickel sulfate, cobalt sulfate, and titanium sulfate were mixed at a molar ratio of 80: 15: 5 was used, and the positive electrode active material LiNi _{0 .8} Co _0.15 Ti _0.05 O ₂ was obtained. A battery produced in the same manner as in Example 1 except that a mixture of Li _x CoO ₂ and LiNi _0.8 Co _0.15 Ti _0.05 O ₂ was used as the positive electrode active material. Battery A14.

A positive electrode active material was prepared in the same manner as in Example 1 except that an aqueous solution in which nickel sulfate, cobalt sulfate, and vanadium sulfate were mixed at a molar ratio of 80: 15: 5 was used, and the positive electrode active material LiNi _{0 .8} Co _0.15 V _0.05 O ₂ was obtained. Li _x C as positive electrode active material
A battery produced in the same manner as in Example 1 except that a mixture of oO _{2 and} this LiNi _0.8 Co _0.15 V _0.05 O ₂ was used was designated as battery A15 of Example 15.

A positive electrode active material in the same manner as in Example 1 except that an aqueous solution in which nickel sulfate, cobalt sulfate, aluminum sulfate, and magnesium sulfate were mixed at a molar ratio of 80: 15: 2.5: 2.5 was used. Then, a positive electrode active material LiNi _0.8 Co _0.15 Al _0.025 Mg _0.025 O ₂ was obtained. A battery produced in the same manner as in Example 1 except that a mixture of Li _x CoO ₂ and LiNi _0.8 Co _0.15 Al _0.025 Mg _0.025 O ₂ was used as the positive electrode active material. Was designated as Battery A16 of Example 16.

A positive electrode active material in the same manner as in Example 1 except that an aqueous solution in which nickel sulfate, cobalt sulfate, aluminum sulfate, and titanium sulfate were mixed at a molar ratio of 80: 15: 2.5: 2.5 was used. To obtain a positive electrode active material LiNi _0.8 Co _0.15 Al _0.025 Ti _0.025 O ₂ . A battery produced in the same manner as in Example 1 except that a mixture of Li _x CoO ₂ and LiNi _0.8 Co _0.15 Al _0.025 Ti _0.025 O ₂ was used as the positive electrode active material. Was designated as Battery A17 of Example 17.

As a positive electrode active material, Li _x Co _0.995 Mg _0.005 O ₂ and LiNi _0.8 Co _0.15 Al _0.05 O ₂ prepared in (i) were mixed at a weight ratio of 70:30. A battery produced in the same manner as in Example 1 was used as the battery A18 of Example 18 except that the obtained battery was used.

As a positive electrode active material, Li _x Co _0.98 Mg _0.02 O ₂ and LiNi _0.8 Co _0.15 Al _0.05 O ₂ prepared in (i) were mixed at a weight ratio of 70:30. A battery produced in the same manner as in Example 1 was used as the battery A19 of Example 19 except that the obtained battery was used.

As a positive electrode active material, Li _x Co _0.9 Mg _0.1 O ₂ and LiNi _0.8 Co _0.15 Al _0.05 O ₂ prepared in (i) were mixed at a weight ratio of 70:30. A battery produced in the same manner as in Example 1 was used as the battery A20 of Example 20, except that the obtained battery was used.

As the positive electrode active material, Li _x Co _0.98 Al _0.02 O ₂ and LiNi _0.8 Co _0.15 Al _0.05 O ₂ prepared in (i) were mixed at a weight ratio of 70:30. A battery produced in the same manner as in Example 1 was used as the battery A21 of Example 21, except that the obtained battery was used.

As the positive electrode active material, Li _x Co _0.98 Ti _0.02 O ₂ and LiNi _0.8 Co _0.15 Al _0.05 O ₂ prepared in (i) were mixed at a weight ratio of 70:30. A battery produced in the same manner as in Example 1 was used as the battery A22 of Example 22 except that the obtained battery was used.

As a positive electrode active material, Li _x Co _0.98 Mn _0.02 O ₂ and LiNi _0.8 Co _0.15 Al _0.05 O ₂ prepared in (i) were mixed at a weight ratio of 70:30. A battery produced in the same manner as in Example 1 was used as the battery A23 of Example 23 except that the obtained battery was used.

As a positive electrode active material, Li _x Co _0.98 Ni _0.02 O ₂ and LiNi _0.8 Co _0.15 Al _0.05 O ₂ prepared in (i) were mixed at a weight ratio of 70:30. A battery produced in the same manner as in Example 1 was used as the battery A24 of Example 24 except that the obtained battery was used.

As a positive electrode active material, Li _x Co _0.98 V _0.02 O ₂ and LiNi _0.8 Co _0.15 Al _0.05 O ₂ prepared in (i) were mixed at a weight ratio of 70:30. A battery produced in the same manner as in Example 1 was used as Battery A25 of Example 25 except that the obtained battery was used.

As the positive electrode active material, Li _x Co _0.98 Mo _0.02 O ₂ and LiNi _0.8 Co _0.15 Al _0.05 O ₂ prepared in (i) were mixed at a weight ratio of 70:30. A battery produced in the same manner as in Example 1 was used as the battery A26 of Example 26 except that the obtained battery was used.

As the positive electrode active material, Li _x Co _0.975 Mg _0.02 Al _0.005 O ₂ and LiNi _0.8 Co _0.15 Al _0.05 O ₂ prepared in (i) are in a weight ratio of 70:30. A battery produced in the same manner as in Example 1 was used as Battery A27 of Example 27, except that the mixture at a ratio of

As a positive electrode active material, Li _x Co _0.975 Mg _0.02 Ti _0.005 O ₂ and LiNi _0.8 Co _0.15 Al _0.05 O ₂ prepared in (i) are in a weight ratio of 70:30. A battery produced in the same manner as in Example 1 was used as Battery A28 of Example 28, except that the battery was mixed at a ratio of.

As a positive electrode active material, Li _x Co _0.97 Mg _0.02 Al _0.005 Ti _0.005 O ₂ and LiNi _0.8 Co _0.15 Al _0.05 O ₂ prepared in (i) are in a weight ratio. A battery produced in the same manner as in Example 1 was used as Battery A29 of Example 29, except that a mixture at a ratio of 70:30 was used.

Example 1 except that an electrolyte prepared by dissolving LiPF ₆ to 2.0 mol / L in a solvent mixed so that the volume ratio of EC and EMC was 3: 7 was used as the nonaqueous electrolyte. A battery produced in the same manner was designated as a battery A30 of Example 30.

Example 1 except that an electrolyte prepared by dissolving LiPF ₆ to 1.6 mol / L in a solvent mixed so that the volume ratio of EC and EMC was 3: 7 was used as the nonaqueous electrolyte. A battery produced in the same manner was designated as a battery A31 of Example 31.

Example 1 except that an electrolyte prepared by dissolving LiPF ₆ to 0.8 mol / L in a solvent mixed so that the volume ratio of EC and EMC was 3: 7 was used as the non-aqueous electrolyte. A battery produced in the same manner was designated as a battery A32 of Example 32.

Example 1 except that an electrolyte prepared by dissolving LiPF ₆ to 0.5 mol / L in a solvent mixed so that the volume ratio of EC and EMC was 3: 7 was used as the non-aqueous electrolyte. A battery produced in the same manner was designated as a battery A33 of Example 33.

Example 1 except that an electrolyte prepared by dissolving LiPF ₆ to 0.4 mol / L in a solvent mixed so that the volume ratio of EC and EMC was 3: 7 was used as the nonaqueous electrolyte. A battery produced in the same manner was designated as battery A34 of Example 34.

Except that an electrolyte prepared by dissolving LiPF ₆ to 1 mol / L in a solvent mixed so that the volume ratio of EC, EMC, and DEC was 3: 5: 2 was used as the nonaqueous electrolyte. A battery produced in the same manner as in Example 1 was designated as Battery A35 of Example 35.

Except that an electrolyte prepared by dissolving LiPF ₆ to 1 mol / L in a solvent mixed so that the volume ratio of EC, EMC, and DEC was 3: 4: 3 was used as the nonaqueous electrolyte. A battery produced in the same manner as in Example 1 was designated as Battery A36 of Example 36.

Except that an electrolyte prepared by dissolving LiPF ₆ to 1 mol / L in a solvent mixed so that the volume ratio of EC, EMC, and DEC was 3: 3: 4 was used as the nonaqueous electrolyte. A battery produced in the same manner as in Example 1 was designated as Battery A37 of Example 37.

Except that an electrolyte prepared by dissolving LiPF ₆ to 1 mol / L in a solvent mixed so that the volume ratio of EC, EMC, and DEC was 3: 2: 5 was used as the nonaqueous electrolyte. A battery produced in the same manner as in Example 1 was designated as Battery A38 of Example 38.

The same procedure as in Example 1 was used except that an electrolyte prepared by dissolving LiPF ₆ to 1 mol / L in a solvent mixed so that the volume ratio of EC and DEC was 3: 7 was used as the nonaqueous electrolyte. The battery thus prepared was designated as battery A39 of Example 39.

As a non-aqueous electrolyte, an electrolyte prepared by dissolving LiPF ₆ to 0.6 mol / L and LiBF ₄ to 0.4 mol / L in a solvent mixed so that the volume ratio of EC and EMC is 3: 7 is used. A battery produced in the same manner as in Example 1 except that it was used was designated as Battery A40 of Example 40.

As a non-aqueous electrolyte, an electrolyte prepared by dissolving LiPF ₆ to 0.8 mol / L and LiBF ₄ to 0.2 mol / L in a solvent mixed so that the volume ratio of EC and EMC is 3: 7 is used. A battery produced in the same manner as in Example 1 except that it was used was designated as Battery A41 of Example 41.

As a non-aqueous electrolyte, an electrolyte prepared by dissolving LiPF ₆ to 0.95 mol / L and LiBF ₄ to 0.05 mol / L in a solvent mixed so that the volume ratio of EC and EMC is 3: 7 is used. A battery produced in the same manner as in Example 1 except that it was used was designated as Battery A42 of Example 42.

As a non-aqueous electrolyte, LiPF ₆ is 0.8 mol / L and LiN (CF ₃ CF ₂ SO ₂ ) ₂ is 0.2 mol / L in a solvent mixed so that the volume ratio of EC and EMC is 3: 7. A battery produced in the same manner as in Example 1 was used as Battery A43 of Example 43 except that the electrolyte prepared by dissolution as described above was used.

As a non-aqueous electrolyte, LiPF ₆ was 0.8 mol / L, LiBF ₄ was 0.1 mol / L, LiN (CF ₃ CF ₂ SO ₂ ) in a solvent mixed so that the volume ratio of EC and EMC was 3: 7. A battery produced in the same manner as in Example 1 was used as Battery A44 of Example 44 except that an electrolyte prepared by dissolving ₂ so as to be 0.1 mol / L was used.

As a non-aqueous electrolyte, an electrolyte prepared by dissolving LiPF ₆ to 0.4 mol / L and LiBF ₄ to 0.6 mol / L in a solvent mixed so that the volume ratio of EC and EMC is 3: 7 is used. A battery produced in the same manner as in Example 1 except that it was used was designated as Battery A45 of Example 45.

A non-aqueous electrolyte was prepared by dissolving LiPF ₆ in a solvent mixed so that the volume ratio of EC and EMC was 3: 7, and 1% VC was added as an additive. A battery produced in the same manner as in Example 1 except that it was used was designated as Battery A46 of Example 46.

A non-aqueous electrolyte was prepared by dissolving LiPF ₆ in a solvent mixed so that the volume ratio of EC and EMC was 3: 7 so that LiPF ₆ would be 1 mol / L, and further adding 3% VC as an additive. A battery produced in the same manner as in Example 1 except that it was used was designated as Battery A47 of Example 47.

A non-aqueous electrolyte was prepared by dissolving LiPF ₆ in a solvent mixed so that the volume ratio of EC and EMC was 3: 7 to 1 mol / L, and further adding 1% VEC as an additive. A battery produced in the same manner as in Example 1 except that it was used was designated as Battery A48 of Example 48.

A non-aqueous electrolyte was prepared by dissolving LiPF ₆ at 1 mol / L in a solvent mixed so that the volume ratio of EC and EMC was 3: 7. Further, VC was 2% and VEC was 1 as an additive. A battery produced in the same manner as in Example 1 except that the electrolyte added in% was used as battery A49 of Example 49.

A non-aqueous electrolyte is prepared by dissolving LiPF ₆ in a solvent mixed so that the volume ratio of EC and EMC is 3: 7 to 1 mol / L, and further adding 1% ES as an additive. A battery produced in the same manner as in Example 1 except that it was used was designated as Battery A50 of Example 50.

As a non-aqueous electrolyte, LiP was added to a solvent mixed so that the volume ratio of EC and EMC was 3: 7.
A battery produced in the same manner as in Example 1 except that an electrolyte prepared by dissolving F ₆ at 1 mol / L and further adding 1% of 1,3-PS as an additive was used. Battery A51.

A non-aqueous electrolyte is prepared by dissolving LiPF ₆ in a solvent mixed so that the volume ratio of EC and EMC is 3: 7 to 1 mol / L, and further adding 1% SUL as an additive. A battery produced in the same manner as in Example 1 except that it was used was designated as Battery A52 of Example 52.

A non-aqueous electrolyte is prepared by dissolving LiPF ₆ in a solvent mixed so that the volume ratio of EC and EMC is 3: 7 so that the concentration of LiPF ₆ is 1 mol / L, and further adding 1% THFS as an additive. A battery produced in the same manner as in Example 1 except that it was used was designated as Battery A53 of Example 53.

A non-aqueous electrolyte was prepared by dissolving LiPF ₆ in a solvent mixed so that the volume ratio of EC and EMC was 3: 7 to 1 mol / L, and 1% ES, 1, 3 as an additive. A battery produced in the same manner as in Example 1 except that an electrolyte containing 1% of -PS was used was designated as battery A54 of Example 54.

As a non-aqueous electrolyte, an electrolyte prepared by dissolving LiPF ₆ in a solvent mixed so that the volume ratio of EC and EMC is 3: 7 to 1 mol / L and further adding 1% of methylamine as an additive A battery produced in the same manner as in Example 1 except that was used was designated as Battery A55 of Example 55.

A non-aqueous electrolyte was prepared by dissolving LiPF ₆ in a solvent mixed so that the volume ratio of EC and EMC was 3: 7 so that 1 mol / L of LiPF ₆ was added, and further adding 1% of ethylamine as an additive. A battery produced in the same manner as in Example 1 except that it was used was designated as Battery A56 of Example 56.

A non-aqueous electrolyte was prepared by dissolving LiPF ₆ in a solvent mixed so that the volume ratio of EC and EMC was 3: 7 so that 1 mol / L of LiPF ₆ was added, and further adding 1% of trimethylamine as an additive. A battery produced in the same manner as in Example 1 except that it was used was designated as Battery A57 of Example 57.

A non-aqueous electrolyte was prepared by dissolving LiPF ₆ in a solvent mixed so that the volume ratio of EC and EMC was 3: 7 so that LiPF ₆ would be 1 mol / L, and further adding 1% ethylenediamine as an additive. A battery produced in the same manner as in Example 1 except that it was used was designated as Battery A58 of Example 58.

A non-aqueous electrolyte was prepared by dissolving LiPF ₆ at 1 mol / L in a solvent mixed so that the volume ratio of EC and EMC was 3: 7, and 1% 1,4-ethylenediamine was further added as an additive. A battery produced in the same manner as in Example 1 except that the added electrolyte was used was designated as battery A59 of Example 59.

A non-aqueous electrolyte was prepared by dissolving LiPF ₆ at 1 mol / L in a solvent mixed so that the volume ratio of EC and EMC was 3: 7, and 1% hexamethylenediamine was added as an additive. A battery produced in the same manner as in Example 1 except that the electrolyte was used was designated as battery A60 of Example 60.

A non-aqueous electrolyte is prepared by dissolving LiPF ₆ in a solvent mixed so that the volume ratio of EC and EMC is 3: 7 to 1 mol / L, and further adding 1% pyridine as an additive. A battery produced in the same manner as in Example 1 except that it was used was designated as Battery A61 of Example 61.

A non-aqueous electrolyte was prepared by dissolving LiPF ₆ in a solvent mixed so that the volume ratio of EC and EMC was 3: 7 to 1 mol / L, and further adding 1% aniline as an additive. A battery produced in the same manner as in Example 1 except that it was used was designated as Battery A62 of Example 62.

As a non-aqueous electrolyte, it was prepared by dissolving so that LiPF ₆ would be 1 mol / L in a solvent mixed so that the volume ratio of EC and EMC was 3: 7, and further 1% methylamine and ethylenediamine as additives. A battery produced in the same manner as in Example 1 except that 1% added electrolyte was used was designated as Battery A63 of Example 63.

  A battery produced in the same manner as in Example 1 except that an aramid-porous PE laminated film in which a layer made of an aramid resin as a heat-resistant resin was formed on a porous PE thin film having a thickness of 16 μm was used as the separator. Was designated as Battery A64 of Example 64.

The method for producing the aramid-porous PE laminated film is as follows. 6.5 parts by weight of dry anhydrous calcium chloride (hereinafter abbreviated as CaCl ₂ ) is added to 100 parts by weight of NMP, and heated to 80 ° C. in a reaction vessel to be completely dissolved to prepare a CaCl ₂ added NMP solution. did. The CaCl ₂ added NMP solution was returned to room temperature, it was added p-phenylenediamine 3.2 parts by weight, and completely dissolved. Thereafter, the reaction vessel was placed in a constant temperature bath at 20 ° C., 5.8 parts by weight of terephthalic acid dichloride was added dropwise over 1 hour, and polyparaphenylene terephthalamide (hereinafter abbreviated as PPTA) was synthesized by a polymerization reaction. Then, it was left in a constant temperature bath at 20 ° C. for 1 hour, replaced with a vacuum chamber after the reaction was completed, and deaerated by stirring for 30 minutes under reduced pressure. The obtained polymerization liquid was further diluted with a CaCl ₂ -added NMP solution to prepare an NMP solution of an aramid resin having a PPTA concentration of 1.4% by weight. The NMP solution of aramid resin thus obtained is coated thinly on a porous PE with a doctor blade, dried with hot air at 80 ° C. (wind speed 0.5 m / sec), and washed thoroughly with pure water. The remaining CaCl ₂ was removed and the aramid resin layer was made porous and dried again. Thereby, an aramid-porous PE laminated film having a total thickness of 20 μm was produced. When the amount of residual chlorine in this separator was measured by chemical analysis, it was 650 μg with respect to 1 g of separator.

A battery produced in the same manner as in Example 1 except that an amideimide-porous PE laminated film in which a layer made of an amideimide resin was formed on the porous PE thin film was used as the separator.
5 battery A65.

  The method for producing the amidoimide-porous PE laminated film is as follows. Trimellitic anhydride monochloride and diamine were mixed in an NMP solvent at room temperature to obtain an NMP solution of polyamic acid. This NMP solution of polyamic acid is coated thinly on a porous PE with a doctor blade, dried with hot air at 80 ° C. (wind speed 0.5 m / sec), dehydrated and closed to form polyamideimide, and the total thickness is 20 μm. An amidoimide-porous PE laminated film was obtained. When the amount of residual chlorine in this separator was measured by chemical analysis, it was 830 μg with respect to 1 g of separator.

  A battery produced in the same manner as in Example 1 except that a porous aramid resin single membrane was used as a separator was designated as battery A66 of Example 66.

  The method for producing the porous aramid resin single membrane is as follows. An aramid resin NMP solution is coated on a smooth stainless steel (hereinafter abbreviated as SUS) plate using a doctor blade, dried with hot air at 80 ° C. (wind speed 0.5 m / sec), and an aramid having a thickness of 20 μm. A single layer film was obtained. When the amount of residual chlorine in this separator was measured by chemical analysis, it was 1800 μg with respect to 1 g of separator.

  A battery produced in the same manner as in Example 1 except that a filler / aramid-porous PE laminated film in which a layer made of fine particle alumina and an aramid resin was formed as a filler on a porous PE thin film was used as the separator film. Was designated as Battery A67 of Example 67.

  The method for producing the filler / aramid-porous PE laminated film is as follows. 200 parts by weight of fine particle alumina is added to 100 parts by weight (solid content) of NMP solution of aramid resin and stirred. The dispersion is thinly coated on the porous PE with a doctor blade, and heated at 80 ° C. 0.5 m / sec) to obtain a filler / aramid-porous PE laminated film having a total thickness of 20 μm. When the amount of residual chlorine in this separator was measured by chemical analysis, it was 600 μg per 1 g of separator.

(Comparative Example 1)
A battery produced in the same manner as in Example 1 except that Li _x CoO ₂ was used as the positive electrode active material was designated as battery B1 of Comparative Example 1.

(Comparative Example 2)
A battery produced in the same manner as in Example 1 except that Li _x Co _0.98 Mg _0.02 O ₂ was used as the positive electrode active material was designated as a battery B2 of Comparative Example 2.

(Comparative Example 3)
A battery produced in the same manner as in Example 1 was used as Battery B3 of Comparative Example 3, except that Li _x Co _0.975 Mg _0.02 Al _0.005 O ₂ was used as the positive electrode active material.

(Comparative Example 4)
A battery produced in the same manner as in Example 1 except that Li _x Co _0.9 Mg _0.1 O ₂ was used as the positive electrode active material was designated as a battery B4 of Comparative Example 4.

(Comparative Example 5)
A battery produced in the same manner as in Example 1 except that LiNi _0.8 Co _0.15 Al _0.05 O ₂ was used as the positive electrode active material was designated as a battery B5 of Comparative Example 5.

(Comparative Example 6)
A battery manufactured in the same manner as in Example 1 was compared except that a mixture of Li _x CoO ₂ and LiNi _1/3 Mn _1/3 Co _1/3 O ₂ at 70:30 was used as the positive electrode active material. The battery was B6 of Example 6.

(Comparative Example 7)
Example 1 except that a mixture of Li _x Co _0.98 Mg _0.02 O ₂ and LiNi _1/3 Mn _1/3 Co _1/3 O ₂ at 70:30 was used as the positive electrode active material. A battery produced in the same manner was designated as a battery B7 of Comparative Example 7.

  The high-temperature storage characteristic evaluation of the batteries A1 to A67 and the batteries B1 to B7 produced as examples and comparative examples and a 150 ° C. heating test were performed.

  The evaluation method of the high temperature storage characteristics is as follows. The batteries of these examples and comparative examples were subjected to a 3-cycle charge / discharge test at 20 ° C. with a current value at which charging was completed in 1 hour at a charge end voltage of 4.2 V and a discharge end voltage of 2.5 V. The discharge capacity was taken as the initial capacity. Thereafter, a storage test was conducted at 85 ° C. for 7 days, and a charge / discharge test was conducted in the same manner as the measurement of the initial capacity. The discharge capacity at the third cycle was defined as the discharge capacity after storage.

  The evaluation method of the heating test is as follows. First, it was charged in a normal temperature atmosphere at 1 ItA until the end voltage reached 4.30V. Thereafter, the battery was allowed to stand in a thermostat and heated from room temperature to 150 ° C. at a rate of 5 ° C./min. After heating, the sample was allowed to stand for 3 hours in an atmosphere of 150 ° C., and the maximum temperature reached by heat generation of the battery was measured. The smaller the heat generated by the battery, the higher the maximum temperature reached on the battery surface is close to 150 ° C., and the higher the thermal stability of the battery. Here, in consideration of the variation of the charging voltage of 4.20 V that is normally used in an electronic device or the like, the evaluation was performed with a charging voltage of 4.25 V or more.

  The evaluation results of the high-temperature storage characteristics and the evaluation results of the 150 ° C. heating test of the batteries A1 to A67 and the batteries B1 to B7 produced as examples and comparative examples are shown in (Table 1) to (Table 4).

From the results of (Table 1) to (Table 4), it can be seen that the batteries A1 to A67 are superior in capacity retention after storage at 85 ° C. compared to the batteries B1 to B7. This and _{Li x Co 1-y M y} O 2 of _Li x CoO ₂ or the positive electrode active material C of the positive electrode active material A, the positive electrode active material B and _{Li x Ni y Co z M 1} -y-z O 2 This is probably because the amount of transition metal in the positive electrode active material dissolved in the non-aqueous electrolyte could be reduced by mixing.

In addition, compared with the batteries B1 to B5, the battery B6 and the battery B7 have better capacity retention ratio after storage at 85 ° C., but the effect is more excellent in the batteries A1 to A67, which is 85 ° C. It is presumed that Mn in Li _x Ni _1/3 Mn _1/3 Co _1/3 O ₂ was dissolved in the nonaqueous electrolyte in a higher temperature environment.

In the batteries A1 to A5, although a large difference is not seen, the capacity retention rate after storage at 85 ° C. is improved when the amount of Co in Li _x Ni _y Co _z M _1-yz O ₂ increases. There was a trend. This is presumed to be because the crystal structure of Li _x Ni _y Co _z M _1-yz O ₂ is stabilized by Co.

In the batteries A6 to A11, since the capacity retention ratio after storage at 85 ° C. does not change, Li _x CoO ₂ of the positive electrode active material A or Li _x Co _{1- y My} O ₂ of the positive electrode active material C and the positive electrode active material It can be seen that the effect of mixing B Li _x Ni _y Co _z M _1-yz O ₂ is not significantly affected by the mixing ratio. In addition, although there is no significant difference, the batteries A7 and A8 and the batteries A10 and A11 tend to have a better capacity retention rate after storage at 85 ° C than the batteries A6 and A9. It was. From this, the mixing ratio of LiCoO ₂ and Li _x Ni _y Co _z M _1-yz O ₂ is preferably in the range of 10 to 90%, particularly in the range of 15 to 50% of the amount of LiCoO ₂ , 85 It was found that the capacity retention rate after storage at 0 ° C. was high and showed good characteristics.

Moreover, according to batteries A12 to A14, when an element other than Al is used for M in Li _x Ni _y Co _z M _1-yz O ₂ , for example, elements such as Mg, Ca, Ti, and V It was also found that good high-temperature storage characteristics can be obtained by using, and the same effect as when Al is used can be obtained. In addition, it was confirmed that good characteristics can be obtained when a transition metal element is used.

  Further, from the results of the batteries A16 and A17, it was found that the same effect can be obtained when there are two types of M, for example, when Al and Mg or Al and Ti are used. In addition, it was confirmed that good characteristics were obtained when various combinations of transition metal elements were used, or when combinations of two or more transition metal elements were used.

According to the battery _{A18~A20, Li x Co 1-y} M y O 2 and _{Li x Ni y Co z M 1} -y-z O 2 and even when mixed with, for _example, Li x _{Co 1-y} Even when Mg _y O ₂ was used, it was found that the same effect as when Li _x CoO ₂ and Li _x Ni _y Co _z M _1-yz O ₂ were mixed was obtained. In addition, although not so large, it can be seen that the battery A19 and A20 have higher capacity retention ratios after storage at 85 ° C. than the battery A1, and exhibit good characteristics. This is because the addition of Mg in _Li x CoO _2, the crystal structure of Li x CoO ₂ is presumed to stabilize.

In addition, according to the batteries A21 to A26, when an element other than Mg is used for M in Li _x Co _1-y M _y O ₂ , for example, elements such as Al, Ti, Mn, Ni, V, and Mo It was found that even when used, good high-temperature storage characteristics were obtained, and the same effect as when Co was used was obtained. In addition, it was confirmed that good characteristics can be obtained when a transition metal element is used.

  Further, from the results of the batteries A27 to A29, it was found that the same effect can be obtained when M is two or more, for example, when Mg and Al, Mg and Ti, or Mg, Al and Ti are used. In addition, it was confirmed that good characteristics can be obtained when various combinations of metal elements are used.

In the batteries A30 to A34, the salt concentration of the lithium salt LiPF ₆ in the non-aqueous electrolyte tends to be slightly improved when the salt concentration is high, but largely does not depend on the salt concentration, and the same effect is obtained. I found out that Further, in the results of the battery A30 and the battery A31, the capacity retention rate after storage at 85 ° C. is almost the same, so that the effect of improving the salt concentration is estimated to be up to 1.6 mol / L. Such an increase in the salt concentration causes an increase in the viscosity of the electrolyte and a decrease in productivity due to a decrease in the pouring property of the electrolyte. Therefore, the salt concentration should be 1.6 mol / L or less. Is preferred. In addition, in the results of the batteries A33 and A34, the salt concentration decreased from 0.5 mol / L to 0.4 mol / L, and the capacity retention rate after storage at 85 ° C. decreased. / L or more is preferable. Therefore, 0.5 to 1.6 mol / L is preferable.

In comparison between the battery A1 and the batteries A35 to A39, it was found that the capacity retention rate after storage at 60 ° C. was improved when the ratio of DEC was larger for the solvent in the nonaqueous electrolyte. This is presumably because the reaction in which the solvent in the electrolyte is simultaneously decomposed when the metal is eluted from the positive electrode active material is suppressed in a high temperature environment. In addition, when the DEC is 40% or more, the effect of improving the storage characteristics is not so much obtained, but when the DEC ratio is 50% or more, the charge / discharge characteristics under a low temperature environment tend to be lowered. It is preferable that about 20% EMC is contained because a well-balanced electrical characteristic can be obtained.

From the results of the battery A1 and the batteries A40 to A42, it was found that the capacity retention rate after storage at 85 ° C. was improved by mixing LiPF ₆ and LiBF ₄ with respect to the lithium salt in the nonaqueous electrolyte. Further, it was found that the mixing amount of LiBF _{4 only} needs to be mixed as much as possible. This is presumably because decomposition of the electrolytic solution is suppressed because a protective film of LiBF ₄ is formed on the electrode plate.

Moreover, from the result of the battery A45, as for the mixing ratio of LiPF ₆ and LiBF ₄ , when the amount of LiBF ₄ increased, the capacity retention rate after storage at 85 ° C. tended to decrease. This is presumed to be because the LiBF ₄ is decomposed and consumed, so that the lithium salt concentration is extremely lowered.

In the battery A43 and the battery A44, as for the type of lithium salt in the non-aqueous electrolyte, when other salts are used, for example, when LiPF ₆ and LiN (CF ₃ CF ₂ SO ₂ ) ₂ are mixed, LiPF ₆ and It has been found that the same effect can be obtained when LiBF ₄ and LiN (CF ₃ CF ₂ SO ₂ ) ₂ are mixed. Furthermore, in the battery A44, it is presumed that the capacity retention rate after storage at 85 ° C. is improved due to the effect of mixing LiPF ₆ and LiBF ₄ . In addition, it was confirmed that good characteristics can be obtained when various lithium salts are used or when a combination of two or more lithium salts is used.

  In the comparison of the results of the battery A1 and the batteries A46 to A48, it was found that the capacity retention rate after storage at 85 ° C. was improved by adding VC or VEC to the nonaqueous electrolyte. This is presumed to be because a high-quality film is formed on the surface of the electrode plate due to the decomposition product of the additive, and metal elution from the positive electrode active material and decomposition of the electrolyte are suppressed in a high temperature environment. Further, from the result of the battery A49, it was found that the same effect can be obtained even when two kinds of added solvents, for example, two kinds of VC and VEC are mixed and used. In addition, it was confirmed that good characteristics can be obtained when various cyclic esters are used or when a combination of two or more kinds of cyclic esters is used.

  In comparison of results between battery A1 and batteries A50-A53, capacity retention after storage at 85 ° C is improved by adding sulfur-containing compounds such as ES, 1,3-PS, SUL, and THFS to the non-aqueous electrolyte I found out that This is presumed to be because a film made of a degradable organism of the additive is formed on the surface of the positive electrode plate, and the metal elution from the positive electrode active material and the decomposition of the electrolyte are suppressed in a high temperature environment. Further, from the result of the battery A54, it was found that the same effect can be obtained even when two kinds of added solvents, for example, two kinds of ES and 1,3-PS are mixed and used. In addition, it was confirmed that good characteristics can be obtained when various sulfur-containing compounds are used or when a combination of two or more kinds of sulfur-containing compounds is used.

In comparison of the results of battery A1 and batteries A55 to A62, by adding a nitrogen-containing compound such as methylamine, ethylamine, trimethylamine, ethylenediamine, 1,4-ethylenediamine, hexamethylenediamine, pyridine or aniline to the non-aqueous electrolyte It was found that the capacity retention rate after storage at 85 ° C. was significantly improved. This is because, by adding a nitrogen-containing compound, a stable coating is formed on the surface of the positive electrode, particularly containing Li _x Ni _y Co _z M _1-yz O ₂ , and the metal from the positive electrode active material in a high temperature environment It is estimated that elution and decomposition of the electrolyte in the electrolyte are suppressed. In addition, compared with batteries A55 to A57, batteries A58 to A60 have a slightly improved capacity retention rate after storage at 85 ° C. Therefore, the more nitrogen is contained in the compound, the more the effect appears. It is assumed that this is because. Moreover, from the result of battery A63,
It was found that the same effect can be obtained when two kinds of solvent are added, for example, a mixture of two kinds of methylamine and ethylenediamine. In addition, it was confirmed that good characteristics can be obtained when various nitrogen-containing compounds are used or when a combination of two or more types of nitrogen-containing compounds is used.

  In comparison of the results of the battery A1 and the batteries A64 to A67, instead of the porous polyethylene separator, an aramid-porous PE laminated film, an amideimide-porous PE laminated film, a porous aramid resin single film, It was found that the capacity retention rate after storage at 85 ° C. was improved by using the filler / aramid-porous PE laminated film.

  In addition, from the highest reached temperature at 150 ° C. heating, the batteries A1 to A67 all have lower maximum reached temperature at 150 ° C. heating and improved thermal stability than the batteries B1 to B7. It is suggested.

  In addition, since the maximum temperature reached when the batteries A64 to A67 are heated at 150 ° C. is lower than that of the batteries A1 to A63, by using a porous film containing a heat-resistant resin containing chlorine as a separator, Furthermore, it is possible to provide a thermally stable nonaqueous electrolyte battery.

  As mentioned above, although various combinations have been shown in the embodiments, the present invention is not limited to the described embodiments, and various combinations that can be easily inferred from the gist of the invention are possible.

  As described above, according to the present invention, it is possible to realize a non-aqueous electrolyte secondary battery excellent in reliability during high-temperature storage while maintaining charge / discharge capacity, cycle characteristics, and safety.

In this example, as the positive electrode active material B, Li _x Ni _y Co _z Al _1-yz O ₂ , Li _x Ni _y Co _z Mg _1-yz O ₂ , Li _x Ni _y Co _z Ca _{1 -y-z O 2, Li x} Ni y Co z Ti 1-y-z O 2, Li x Ni y Co z V 1-y-z O 2, Li x Ni y Co z (AlMg) 1-y- _z O _2, and _{Li x Ni y Co z (AlTi} ) has been described using _{1-y-z O 2,} Li x Ni y Co z Ba 1-y-z O 2, Li x Ni y Co _z Sr _1-yz O ₂ , Li _x Ni _y Co _z Fe _1-yz O ₂ , Li _x Ni _y Co _z Cu _1-yz O ₂ , Li _x Ni _y Co _z Bi _{1-y -z O 2, Li x Ni y} Co z Y 1-y-z O _{, Li x Ni y Co z Zr} 1-y-z O 2, Li x Ni y Co z Mo 1-y-z O 2, Li x Ni y Co z Tc 1-y-z O 2, Li x Ni y Co _z Ru _1-yz O ₂ , Li _x Ni _y Co _z Ta _1-yz O ₂ , Li _x Ni _y Co _z W _1-yz O ₂ , and Li _x Ni _y Co _z Re ₁ The same effect can be obtained when _{-yzO 2} is used.

Further, in this example, as the positive electrode active material C, Li _x Co _1-y Mg _y O ₂ , Li _x Co _1-y Al _y O ₂ , Li _x Co _1-y Ti _y O ₂ , Li _x Co _{1− y Mn y O 2, Li x} Co 1-y Ni y O 2, Li x Co 1-y V y O 2, Li x Co 1-y Mo y O 2, Li x Co 1-y (MgAl) y O ₂ , Li _x Co _1-y (MgTi) _y O ₂ , Li _x Co _1-y (MgAlTi) _y O _{2 In} the case of using, but as M of Li _x Co _1-y M _y O ₂ , M was selected from Mg, Al, Ti, Sr, Mn, Ni, Ca, V, Fe, Y, Zr, Mo, Tc, Ru, Ta, W, Re, Yb, Cu, Zn, and Ba The same effect can be obtained when at least one kind is used. It is.

  The nonaqueous electrolyte secondary battery of the present invention is useful as a main power source for electronic devices and the like. For example, it is suitable for use as a main power source for consumer mobile tools such as mobile phones and laptop computers, a main power source for power tools such as an electric screwdriver, and an industrial main power source such as an EV car.

Perspective view of flat rectangular nonaqueous electrolyte secondary battery AA arrow enlarged sectional view of FIG. BB arrow enlarged sectional view of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Battery 2 Positive electrode plate 3 Negative electrode plate 4 Separation film 5 Electrode plate group 6 Battery case 7 Negative electrode terminal 8 Sealing plate 9 Negative electrode lead wire 10 Frame body 11 Positive electrode lead wire

Claims (13)

In a non-aqueous electrolyte secondary battery comprising an active material capable of inserting and extracting lithium, a non-aqueous electrolyte, a separator, and a positive electrode,
The active material of the positive electrode is a mixture of active material A and active material B,
The active material A is a lithium composite oxide represented by Li _x CoO ₂ (0.9 ≦ x ≦ 1.2),
The active material B is Li _x Ni _y Co _z M _1-yz O ₂ (0.9 ≦ x ≦ 1.2, 0.3 ≦ y ≦ 0.9, 0.05 ≦ z ≦ 0.5, 0.01 ≦ 1-yz ≦ 0.3,
And M is at least one selected from Mg, Ba, Al, Ti, Sr, Ca, V, Fe, Cu, Bi, Y, Zr, Mo, Tc, Ru, Ta, W, and Re) Lithium composite oxide represented by
The non-aqueous electrolyte is at least one selected from cyclic carbonates such as ethylene carbonate, propylene carbonate, and butylene carbonate, and chain carbonates such as dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, di-n-propyl carbonate, methyl At least one mixed solvent selected from -n-propyl carbonate, ethyl-n-propyl carbonate, methyl-i-propyl carbonate, and ethyl-i-propyl carbonate is a lithium salt, LiClO ₄ , LiPF ₆ , LiBF ₄ , _{LiCF 3 SO 3, LiN (CF} 3 SO 2) 2, LiN (CF 3 CF 2 SO 2) 2, LiN (CF 3 SO 2) (C 4 F 9 SO 2), and LiC (CF SO ₂₎ at least one was dissolved in non-aqueous electrolyte secondary batteries are selected from _3. In a non-aqueous electrolyte secondary battery comprising a negative electrode having an active material capable of inserting and extracting lithium, a non-aqueous electrolyte, a separator, and a positive electrode,
The active material of the positive electrode is a mixture of active material B and active material C,
The active material B is Li _x Ni _y Co _z M _1-yz O ₂ (0.9 ≦ x ≦ 1.2, 0.3 ≦ y ≦ 0.9, 0.05 ≦ z ≦ 0.5, 0.01 ≦ 1-yz ≦ 0.3,
And M is at least one selected from Mg, Ba, Al, Ti, Sr, Ca, V, Fe, Cu, Bi, Y, Zr, Mo, Tc, Ru, Ta, W, and Re) Lithium composite oxide represented by
The positive electrode active material C is Li _x Co _1-y M _y O ₂ (0.9 ≦ x ≦ 1.2, 0.005 ≦ y ≦ 0.1, and M is Mg, Al, Ti, Sr, Mn Li, Ni, Ca, V, Fe, Y, Zr, Mo, Tc, Ru, Ta, W, Re, Yb, Cu, Zn, and Ba) Is a thing,
The non-aqueous electrolyte is at least one selected from cyclic carbonates such as ethylene carbonate, propylene carbonate, and butylene carbonate, and chain carbonates such as dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, di-n-propyl carbonate, methyl At least one mixed solvent selected from -n-propyl carbonate, ethyl-n-propyl carbonate, methyl-i-propyl carbonate, and ethyl-i-propyl carbonate is a lithium salt, LiClO ₄ , LiPF ₆ , LiBF ₄ , _{LiCF 3 SO 3, LiN (CF} 3 SO 2) 2, LiN (CF 3 CF 2 SO 2) 2, LiN (CF 3 SO 2) (C 4 F 9 SO 2), and LiC (CF SO ₂₎ at least one was dissolved in non-aqueous electrolyte secondary batteries are selected from _3. The non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein a mixing ratio of the active material B is 10 to 90% by weight ratio with respect to a sum of the active material B and the active material A or C. The non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein a mixing ratio of the active material B is 10 to 50% in a weight ratio with respect to a sum of the active material B and the active material A or C. The non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein the chain carbonate is a mixed solvent of diethyl carbonate and ethyl methyl carbonate, and the proportion of diethyl carbonate is higher than that of ethyl methyl carbonate. 3. The nonaqueous electrolyte secondary battery according to claim 1, wherein the lithium salt is a mixed salt of LiPF ₆ and LiBF ₄ , and the proportion of LiPF ₆ is greater than that of LiBF ₄ . The nonaqueous electrolyte secondary battery according to claim 1, wherein the nonaqueous electrolyte contains at least one cyclic ester selected from vinylene carbonate, vinylethylene carbonate, γ-butyrolactone, and γ-valerolactone. The nonaqueous electrolyte according to claim 1 or 2, wherein the nonaqueous electrolyte contains at least one sulfur-containing organic solvent selected from ethylene sulfite, 1,3-propane sultone, sulfolane, tetrahydrofuran sulfite, and sulfolene. Electrolyte secondary battery. The non-aqueous electrolyte is at least selected from methylamine, ethylamine, trimethylamine, triethylamine, ethylenediamine, 1,4-ethylenediamine, hexamethylenediamine, pyridine, hexahydropyridine, morpholine, quinuclidine, aniline, tetramethylethylenediamine, and etheramines. The nonaqueous electrolyte secondary battery according to claim 1 or 2, comprising a kind of nitrogen-containing organic solvent. The nonaqueous electrolyte secondary battery according to claim 1 or 2, wherein the separator is a porous film containing a heat-resistant resin containing chlorine. The nonaqueous electrolyte secondary battery according to claim 1, wherein the separator is a laminated film of a heat resistant resin and a porous polyolefin. The non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein the separator is a laminated film of a layer made of a heat resistant resin and a filler and a porous polyolefin. The nonaqueous electrolyte secondary battery according to any one of claims 10 to 12, wherein the heat resistant resin is at least one of aramid and polyamideimide.

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