JP2004172114A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery having an improved charge-discharge cycle life. <P>SOLUTION: This nonaqueous electrolyte secondary battery is provided with: a positive electrode containing a positive electrode active material containing lithium composite oxide powder; a negative electrode; and a nonaqueous electrolyte. The nonaqueous electrolyte secondary battery is characterized by that the lithium composite oxide powder contains secondary agglomerated particles, and has a composition containing Li and an element M (the element M is at least one kind selected form a group comprising Ni and Co) at a mol ratio (X<SB>Li</SB>/X<SB>M</SB>) in the range of 0.95-1.02; in the lithium composite oxide powder, the ratio (I<SB>003</SB>/I<SB>104</SB>) of the peak intensity of the (003) surface to the peak intensity I<SB>104</SB>of the (I<SB>104</SB>) surface is not less than 2 and less than 5, and the particle diameter (D90) at a volume cumulative frequency of 90% is 10-25 μm; and the nonaqueous electrolyte contains a sultone compound having at least one double bond in each ring. <P>COPYRIGHT: (C)2004,JPO

Description

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

  In recent years, in order to reduce the size and weight of electronic devices such as mobile communication devices, notebook computers, palmtop computers, integrated video cameras, portable CD (MD) players, and cordless telephones, these electronic devices have been developed. In particular, a small-sized and large-capacity battery is demanded as a power source for the battery.

  Examples of batteries that are widely used as power supplies for these electronic devices include primary batteries such as alkaline manganese batteries, and secondary batteries such as nickel cadmium batteries and lead storage batteries. Among them, a non-aqueous electrolyte secondary battery using a lithium composite oxide for the positive electrode and a carbonaceous material capable of occluding and releasing lithium ions for the negative electrode is smaller, lighter, has a higher cell voltage, and has a higher energy density. It is noted because it can be obtained.

Patent Literature 1 discloses, as a positive electrode active material of a nonaqueous electrolyte secondary battery, a general formula (I) represented by Li _v-x1 Ni _1-x2 M _x O ₂ and a mirror index hkl of X-ray diffraction of (003) ) And (104) plane, diffraction peak ratio (003) / (104) is 1.2 or more, average particle diameter D is 5 to 100 μm, 10% of particle size distribution is 0.5D or more, and 90% is 2D or less. Is described.

However, a secondary battery provided with a positive electrode containing such a lithium nickel composite oxide has a problem that the charge / discharge cycle life is short because an oxidative decomposition reaction of the nonaqueous electrolyte occurs.
JP-A-10-69910

  An object of the present invention is to provide a non-aqueous electrolyte secondary battery having an improved charge / discharge cycle life.

The first nonaqueous electrolyte secondary battery according to the present invention is a nonaqueous electrolyte secondary battery including a positive electrode including a positive electrode active material containing a lithium composite oxide powder, a negative electrode, and a nonaqueous electrolyte,
The lithium composite oxide powder contains secondary aggregated particles, and has a molar ratio of Li and the element M (the element M is at least one selected from the group consisting of Ni and Co) (X _Li / X _M ) in the range of 0.95 to 1.02, and the ratio (I) of the peak intensity I ₀₀₃ on the ( ₀₀₃ ) plane to the peak intensity I ₁₀₄ on the (104) plane in powder X-ray diffraction. ₀₀₃ / I ₁₀₄ ) is 2 or more and less than 5, and the particle diameter (D90) at a volume cumulative frequency of 90% is in the range of 10 μm to 25 μm;
The non-aqueous electrolyte contains a sultone compound having at least one double bond in a ring.

A second nonaqueous electrolyte secondary battery according to the present invention is a nonaqueous electrolyte secondary battery including a positive electrode including positive electrode active material particles containing lithium composite oxide particles, a negative electrode, and a nonaqueous electrolyte. hand,
The lithium composite oxide particles have a composition including at least one element M selected from the group consisting of Ni and Co, have a particle form including secondary aggregated particles, and have a peak intensity ratio of the following ( 1) satisfying the equation,
The content of the lithium composite oxide particles in the positive electrode active material particles is 50% by weight or more,
The molar ratio of the positive electrode active material particles satisfies the following equation (2), and the particle diameter (D90) of the positive electrode active material particles at a volume accumulation frequency of 90% is in the range of 10 μm to 25 μm;
The non-aqueous electrolyte contains a sultone compound having at least one double bond in a ring.

2 ≦ (I ₀₀₃ / I ₁₀₄ ) <5 (1)
0.95 ≦ (Y _Li / Y _M ) ≦ 1.02 (2)
Here, I ₀₀₃ is the peak intensity (cps) of the (003) plane in the powder X-ray diffraction of the lithium composite oxide particles, and I ₁₀₄ is the peak intensity (cps) of the (104) plane in the powder X-ray diffraction. , Y _Li is the number of moles of lithium in the positive electrode active material particles, Y _M is the number of moles of the element M in the positive electrode active material particles, and the element M is at least one selected from the group consisting of Ni and Co. Kind.

  According to the present invention, a non-aqueous electrolyte secondary battery having an improved charge / discharge cycle life can be provided.

  The first and second nonaqueous electrolyte secondary batteries according to the present invention will be described.

A first nonaqueous electrolyte secondary battery according to the present invention is a nonaqueous electrolyte secondary battery including a positive electrode including a positive electrode active material containing a lithium composite oxide powder, a negative electrode, and a nonaqueous electrolyte. ,
The lithium composite oxide powder contains secondary agglomerated particles, the molar ratio satisfies the following formula (A), the peak intensity ratio satisfies the following formula (B), and the particle diameter at which the volume cumulative frequency is 90%. (D90) is in the range of 10 μm to 25 μm,
The non-aqueous electrolyte includes a sultone compound having at least one double bond in a ring.

2 ≦ (I ₀₀₃ / I ₁₀₄ ) <5 (A)
0.95 ≦ (X _Li / X _M ) ≦ 1.02 (B)
Here, I ₀₀₃ is the peak intensity (cps) of the (003) plane in the powder X-ray diffraction of the lithium composite oxide powder, and I ₁₀₄ is the peak intensity (cps) of the (104) plane in the powder X-ray diffraction. , X _Li is the number of moles of lithium in the lithium composite oxide powder, X _M is the number of moles of element M in the lithium composite oxide powder, and the element M is selected from the group consisting of Ni and Co At least one type.

  The above-mentioned sultone compound can form a lithium ion permeable protective film on the positive electrode surface by opening a double bond and causing a polymerization reaction at the time of initial charge. On the other hand, the lithium composite oxide powder has a small expansion and contraction due to occlusion and release of lithium, and at the same time, a protective coating is formed not only on the surfaces of the secondary aggregated particles but also on the gaps between the primary particles. The coating can form a complex network structure. As a result, since the protective film can be prevented from peeling off from the positive electrode during the charge / discharge cycle, the oxidative decomposition reaction of the nonaqueous electrolyte can be suppressed, and the charge / discharge cycle life of the secondary battery can be improved. it can.

  Hereinafter, the positive electrode, the negative electrode, and the non-aqueous electrolyte will be described.

1) Positive Electrode The positive electrode includes a current collector and a positive electrode layer supported on one or both surfaces of the current collector and containing the positive electrode active material, the binder, and the conductive agent.

  The lithium composite oxide is synthesized, for example, by mixing compounds (for example, oxides and hydroxides) of the respective constituent elements and then firing the mixture in air or an oxygen atmosphere.

The reason why the molar ratio (X _Li / X _M ) between lithium (X _Li ) and the element M (X _M ) in the lithium composite oxide is in the range of 0.95 to 1.02 will be described. When the molar ratio (X _Li / X _M ) is less than 0.95, crystallinity is remarkably reduced, and there is a possibility that occlusion and release of lithium hardly occur. On the other hand, when the molar ratio (X _Li / X _M ) exceeds 1.02, although the crystallinity is excellent, since the grain growth proceeds during firing, the ratio of single particles becomes high. As a result, not only does the expansion and contraction accompanying the occlusion and release of lithium increase, but also the protective coating covering the primary particles becomes isolated and a network structure cannot be obtained. And the cycle life of the charge and discharge may be shortened. A more preferable range of the molar ratio (X _Li / X _M ) is 0.97 to 1.02, and a further preferable range is 0.99 to 1.02.

  Examples of the lithium composite oxide include a lithium nickel composite oxide, a lithium cobalt composite oxide, and a lithium nickel cobalt composite oxide. The lithium composite oxide may contain lithium and an element other than the element M. Examples of such elements include Mn, Al, Sn, Fe, Cu, Cr, Zn, Mg, Si, P, F, Cl, and B. The type of the additive element may be one type or two or more types.

  It is preferable that the lithium composite oxide accounts for 50% or more of the positive electrode active material.

The reason for limiting the ratio (I ₀₀₃ / I ₁₀₄ ) of the peak intensity I ₀₀₃ on the ( ₀₀₃ ) plane to the peak intensity I ₁₀₄ on the (104) plane in the powder X-ray diffraction will be described. Those having a peak intensity ratio (I ₀₀₃ / I ₁₀₄ ) of 5 or more have excellent crystallinity, but exhibit plate-likeness due to the progress of grain growth, that is, the ratio of single particles having high crystal orientation is increased. In addition, the expansion and contraction accompanying the occlusion and release of lithium are large, and the protective coating covering each primary particle is isolated, and a network structure cannot be obtained. As a result, the protection film is easily peeled off by repeating the charge / discharge cycle, and the charge / discharge cycle life may be shortened. By setting the peak intensity ratio (I ₀₀₃ / I ₁₀₄ ) to 2 or more and less than 5, the ratio of secondary aggregated particles can be increased, and the expansion and contraction rate accompanying the occlusion and release of lithium is reduced. be able to. When the crystal has no orientation and is completely isotropic, the peak intensity ratio (I ₀₀₃ / I ₁₀₄ ) is 2 in calculation. A more preferable range of the peak intensity ratio (I ₀₀₃ / I ₁₀₄ ) is more than 2 and not more than 4.95.

  The reason why the particle diameter (D90) of the lithium composite oxide powder at a volume accumulation frequency of 90% is defined in the above range will be described. If D90 is less than 10 μm, since the number of primary particles constituting the secondary aggregated particles tends to be small, the contact area between the secondary aggregated particles and the protective film is insufficient, and the protective film is easily peeled off. The charge / discharge cycle life may be shortened. On the other hand, when the D90 exceeds 25 μm, since the number of primary particles constituting the secondary agglomerated particles is large, the protective film is not spread inside the secondary agglomerated particles, and only the surface of the secondary agglomerated particles is covered with the protective film. It is close to the state that is being done. For this reason, peeling of the protective film easily occurs during the charge / discharge cycle, and the charge / discharge cycle life may be shortened. A more preferred range for D90 is from 10 μm to 20 μm.

  Examples of the conductive agent include acetylene black, carbon black, and graphite.

  The binder has a function of holding the active material on the current collector and connecting the active materials. As the binder, for example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), polyethersulfone, ethylene-propylene-diene copolymer (EPDM), styrene-butadiene rubber (SBR), or the like is used. be able to.

  The mixing ratio of the positive electrode active material, the conductive agent and the binder is preferably in the range of 80 to 95% by weight of the positive electrode active material, 3 to 20% by weight of the conductive agent, and 2 to 7% by weight of the binder.

  As the current collector, a conductive substrate having a porous structure or a non-porous conductive substrate can be used. These conductive substrates can be formed from, for example, aluminum, stainless steel, or nickel.

  The positive electrode is manufactured, for example, by suspending a conductive agent and a binder in a suitable solvent in a positive electrode active material, applying the suspension to a current collector, and drying to form a thin plate.

2) Negative electrode The negative electrode includes a current collector and a negative electrode layer supported on one or both surfaces of the current collector.

  The negative electrode layer includes a carbonaceous material that stores and releases lithium ions and a binder.

Examples of the carbonaceous material include a graphite material or a carbonaceous material such as graphite, coke, carbon fiber, spherical carbon, pyrolysis gas phase carbonaceous material, and resin fired body; thermosetting resin, isotropic pitch, mesophase pitch Graphitic material obtained by performing a heat treatment at 500 to 3000 ° C. on a base carbon, a mesophase pitch-based carbon fiber, a mesophase small sphere or the like (in particular, a mesophase pitch-based carbon fiber is preferable because the capacity and charge / discharge cycle characteristics are increased) or Carbonaceous material; and the like. Among them, it is preferable to use a graphitic material having graphite crystals in which the (002) plane spacing d ₀₀₂ is 0.34 nm or less. A nonaqueous electrolyte secondary battery provided with a negative electrode containing such a graphite material as a carbonaceous material can significantly improve the battery capacity and large current discharge characteristics. More preferably, the plane distance d ₀₀₂ is 0.337 nm or less.

  Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), ethylene-propylene-diene copolymer (EPDM), styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC). Can be used.

  The mixing ratio of the carbonaceous material and the binder is preferably in the range of 90 to 98% by weight of the carbonaceous material and 2 to 20% by weight of the binder.

  As the current collector, a conductive substrate having a porous structure or a non-porous conductive substrate can be used. These conductive substrates can be formed from, for example, copper, stainless steel, or nickel.

  The negative electrode is, for example, kneading a carbonaceous material that absorbs and releases lithium ions and a binder in the presence of a solvent, applies the obtained suspension to a current collector, and after drying, applies a desired pressure. By pressing once or multi-stage pressing 2 to 5 times.

  An electrode group is manufactured using the positive electrode and the negative electrode as described above.

  This electrode group is, for example, whether (i) the positive electrode and the negative electrode are spirally wound with a separator interposed therebetween, or (ii) the positive electrode and the negative electrode are wound in a flat shape with a separator interposed therebetween. (Iii) the positive electrode and the negative electrode are spirally wound with a separator interposed therebetween, and then compressed in the radial direction; or (iv) the positive electrode and the negative electrode are bent one or more times with the separator interposed therebetween. Alternatively, it is produced by a method of (v) laminating a positive electrode and a negative electrode with a separator interposed therebetween.

  The electrode group need not be pressed, but may be pressed to increase the integration strength of the positive electrode, the negative electrode, and the separator. In addition, heating can be performed at the time of pressing.

  The electrode group may contain an adhesive polymer in order to increase the integration strength of the positive electrode, the negative electrode, and the separator. Examples of the polymer having the adhesive property include polyacrylonitrile (PAN), polyacrylate (PMMA), polyvinylidene fluoride (PVdF), polyvinyl chloride (PVC), and polyethylene oxide (PEO). .

  As a separator used for this electrode group, a microporous membrane, a woven fabric, a nonwoven fabric, a laminate of the same material or a different material among them, or the like can be used. Examples of the material forming the separator include polyethylene, polypropylene, an ethylene-propylene copolymer, and an ethylene-butene copolymer. As the material for forming the separator, one or more kinds selected from the above-mentioned kinds can be used.

  The thickness of the separator is preferably 30 μm or less, and more preferably 25 μm or less. The lower limit of the thickness is preferably 5 μm, and more preferably 8 μm.

  The separator preferably has a heat shrinkage at 120 ° C. for one hour of 20% or less. More preferably, the heat shrinkage is 15% or less.

  The separator preferably has a porosity in the range of 30 to 60%. A more preferred range of porosity is 35-50%.

The separator preferably has an air permeability of 600 seconds / 100 cm ³ or less. The air permeability means the time (seconds) required for 100 cm ³ of air to pass through the separator. The upper limit of the air permeability is more preferably set to 500 seconds / 100 cm ³ . Further, the lower limit of the air permeability is preferably 50 seconds / 100 cm ³ , and more preferably 80 seconds / 100 cm ³ .

  It is desirable that the width of the separator be wider than the width of the positive electrode and the width of the negative electrode. With such a configuration, it is possible to prevent the positive electrode and the negative electrode from directly contacting each other without passing through the separator.

3) Non-aqueous electrolyte As the non-aqueous electrolyte, those having a substantially liquid or gel form can be used.

  The non-aqueous solvent and the electrolyte contained in the liquid non-aqueous electrolyte and the gel non-aqueous electrolyte will be described.

  Non-aqueous solvents include sultone compounds having at least one double bond in the ring.

Here, as the sultone compound having at least one double bond in the ring, the sultone compound A represented by the following general formula 1 or at least one H of the sultone compound A is substituted with a hydrocarbon group. Sultone compound B can be used. In the present application, the sultone compound A or the sultone compound B may be used alone, or both the sultone compound A and the sultone compound B may be used.

In Chemical Formula 1, C _m H _n is a linear hydrocarbon group, and m and n are integers of 2 or more that satisfy 2m> n.

  The sultone compound having at least one double bond in the ring opens a double bond by the reaction with the positive electrode to cause a polymerization reaction, so that a lithium ion permeable protective film can be formed on the surface of the positive electrode. Among the sultone compounds, a compound having m = 3 and n = 4 in the sultone compound A, that is, 1,3-propene sultone (PRS) or a compound having m = 4 and n = 6, that is, 1 , 4-butylene sultone (BTS). As the sultone compound, 1,3-propene sultone (PRS) or 1,4-butylene sultone (BTS) may be used alone, or these PRS and BTS may be used in combination.

  The ratio of the sultone compound is desirably 10% by volume or less. This is because, when the ratio of the sultone compound exceeds 10% by volume, the protective film becomes extremely thick, the lithium ion permeability is reduced, and the discharge capacity at a temperature lower than room temperature is reduced. Further, in order to keep the discharge capacity high even at a low temperature such as -20 ° C., the ratio of the sultone compound to be contained is preferably 4% by volume or less. In addition, in order to ensure a sufficient amount of the protective film formed, it is desirable to secure at least 0.01% by volume of the sultone compound. Furthermore, if the ratio of the sultone compound is 0.1% by volume or more, the protective function of the protective film can be sufficiently exhibited even at a higher temperature such as 65 ° C.

  It is desirable that the non-aqueous solvent further contains ethylene carbonate (EC). The content of EC in the non-aqueous solvent is desirably in the range of 25% by volume to 50% by volume. Thereby, a non-aqueous electrolyte having high conductivity and appropriate viscosity can be obtained. A more preferred EC content is in the range of 25% to 45% by volume.

  As the nonaqueous solvent, other solvents can be used in combination with the sultone compound and EC. Other solvents include, for example, chain carbonates (eg, methyl ethyl carbonate (MEC), diethyl carbonate (DEC), dimethyl carbonate (DMC), etc.), vinylene carbonate (VC), vinyl ethylene carbonate (VEC), phenylethylene Carbonate (phEC), propylene carbonate (PC), γ-butyrolactone (GBL), γ-valerolactone (VL), methyl propionate (MP), ethyl propionate (EP), 2-methylfuran (2Me-F), Furan (F), thiophene (TIOP), catechol carbonate (CATC), ethylene sulfite (ES), 12-crown-4 (crown), tetraethylene glycol dimethyl ether (Ether), and the like can be given. The types of other solvents can be one or more.

Examples of the electrolyte dissolved in the non-aqueous solvent include lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), and lithium arsenide hexafluoride. (LiAsF ₆ ), lithium trifluorometasulfonate (LiCF ₃ SO ₃ ), lithium bistrifluoromethylsulfonylimide [LiN (CF ₃ SO ₂ ) ₂ ], LiN (C ₂ F ₅ SO ₂ ) ₂ and other lithium salts Can be mentioned. The type of electrolyte used can be one or more.

  The amount of the electrolyte dissolved in the non-aqueous solvent is desirably 0.5 to 2.5 mol / L. A more preferred range is 1 to 2.5 mol / L.

  It is desirable that the liquid nonaqueous electrolyte contains a surfactant such as trioctyl phosphate (TOP) in order to improve the wettability with the separator. The amount of the surfactant added is preferably 3% or less, and more preferably in the range of 0.1 to 1%.

  It is preferable that the amount of the liquid non-aqueous electrolyte is 0.2 to 0.6 g per 100 mAh of battery unit capacity. A more preferable range of the mass of the liquid non-aqueous electrolyte is 0.25 to 0.55 g / 100 mAh.

  A container in which the above-described electrode group and the non-aqueous electrolyte are stored will be described.

  The shape of the container can be, for example, a cylindrical shape with a bottom, a rectangular tube with a bottom, a bag shape, a cup shape, or the like.

  This container can be formed, for example, from a film including a resin layer, a metal plate, a metal film, or the like.

  The resin layer included in the film can be formed from, for example, polyolefin (for example, polyethylene or polypropylene), polyamide, or the like. Among films including a resin layer, it is desirable to use a laminate film in which a metal layer and protective layers disposed on both surfaces of the metal layer are integrated. The metal layer plays a role of blocking moisture and a shape of the container. Examples of the metal layer include aluminum, stainless steel, iron, copper, and nickel. Among them, aluminum that is lightweight and has a high function of blocking moisture is preferable. The metal layer may be formed from one type of metal, or may be formed from a combination of two or more types of metal layers. Of the two protective layers, a protective layer in contact with the outside serves to prevent damage to the metal layer. This external protective layer is formed from one type of resin layer or two or more types of resin layers. On the other hand, the inner protective layer plays a role of preventing the metal layer from being corroded by the non-aqueous electrolyte. This internal protective layer is formed from one type of resin layer or two or more types of resin layers. In addition, a thermoplastic resin for sealing the container by heat sealing can be provided on the surface of the internal protective layer.

  The thickness of the film including the resin layer is preferably 0.3 mm or less, more preferably 0.25 mm or less, further preferably 0.15 mm or less, and most preferably 0.12 mm or less. . When the thickness is less than 0.05 mm, the film is easily deformed or damaged. Therefore, the lower limit of the thickness of the film is preferably set to 0.05 mm.

  The metal plate and the metal film can be formed from, for example, iron, stainless steel, and aluminum.

  The thickness of the metal plate and the metal film is desirably 0.4 mm or less, a more preferred range is 0.3 mm or less, and a most preferred range is 0.25 mm or less. If the thickness is smaller than 0.05 mm, sufficient strength may not be obtained. Therefore, the lower limit of the thickness of the metal plate and the metal film is preferably set to 0.05 mm.

A second nonaqueous electrolyte secondary battery according to the present invention is a nonaqueous electrolyte secondary battery including a positive electrode including positive electrode active material particles containing lithium composite oxide particles, a negative electrode, and a nonaqueous electrolyte. hand,
The lithium composite oxide particles have a composition including at least one element M selected from the group consisting of Ni and Co, have a particle form including secondary aggregated particles, and have a peak intensity ratio of the following ( C) satisfying the formula,
The content of the lithium composite oxide particles in the positive electrode active material particles is 50% by weight or more,
The molar ratio of the positive electrode active material particles satisfies the following formula (D), and the particle diameter (D90) of the positive electrode active material particles having a volume accumulation frequency of 90% is in the range of 10 μm to 25 μm.
A non-aqueous electrolyte secondary battery is provided, wherein the non-aqueous electrolyte includes a sultone compound having at least one double bond in a ring.

2 ≦ (I ₀₀₃ / I ₁₀₄ ) <5 (C)
0.95 ≦ (Y _Li / Y _M ) ≦ 1.02 (D)
Here, I ₀₀₃ is the peak intensity (cps) of the (003) plane in the powder X-ray diffraction of the lithium composite oxide particles, and I ₁₀₄ is the peak intensity (cps) of the (104) plane in the powder X-ray diffraction. , Y _Li is the number of moles of lithium in the positive electrode active material particles, Y _M is the number of moles of the element M in the positive electrode active material particles, and the element M is at least one selected from the group consisting of Ni and Co. Kind.

  The second non-aqueous electrolyte secondary battery according to the present invention can have the same configuration as that described in the first non-aqueous electrolyte secondary battery except for the positive electrode. Hereinafter, the positive electrode will be described.

  The positive electrode includes a current collector, and a positive electrode layer supported on one or both surfaces of the current collector and containing the positive electrode active material particles, a binder, and a conductive agent.

By setting the peak intensity ratio (I ₀₀₃ / I ₁₀₄ ) of the lithium composite oxide particles containing the element M to 2 or more and less than 5, it is possible to increase the ratio of secondary aggregated particles, The rate of expansion and contraction associated with release can be reduced. When the crystal has no orientation and is completely isotropic, the peak intensity ratio (I ₀₀₃ / I ₁₀₄ ) is 2 in calculation. A more preferable range of the peak intensity ratio (I ₀₀₃ / I ₁₀₄ ) is more than 2 and not more than 4.95.

Since the lithium composite oxide particles having a peak intensity ratio (I ₀₀₃ / I ₁₀₄ ) of 2 or more and less than 5 are contained in the positive electrode active material particles by 50% by weight or more, the molar ratio of the positive electrode active material particles (Y _Li / Y _M ) becomes substantially equal to the molar ratio of the lithium composite oxide particles. Therefore, if the molar ratio (Y _Li / Y _M ) is less than 0.95, there is a possibility that the occlusion and release of lithium in the positive electrode active material hardly occur due to a decrease in crystallinity of the lithium composite oxide particles. On the other hand, when the molar ratio (Y _Li / Y _M ) is larger than 1.02, although the crystallinity of the lithium composite oxide particles is excellent, the ratio of single particles in the lithium composite oxide particles increases, so that the lithium occlusion is increased. -Not only the expansion and contraction accompanying the release are increased, but also the protective coating covering the primary particles is isolated, making it difficult to obtain a network structure. As a result, the protective film is easily peeled off in the charge / discharge cycle, and the life of the charge / discharge cycle may be shortened. A more preferable range of the molar ratio (Y _Li / Y _M ) is 0.97 to 1.02, and a still more preferable range is 0.99 to 1.02.

  Since the content of the lithium composite oxide particles in the positive electrode active material particles is 50% by weight or more, the particle size distribution of the lithium composite oxide particles is largely reflected in the particle size distribution of the positive electrode active material particles. When the particle diameter (D90) of the positive electrode active material particles having a volume accumulation frequency of 90% is less than 10 μm, the number of primary particles constituting the secondary aggregated particles of the lithium composite oxide particles tends to be small. The contact area between the aggregated particles and the protective film is reduced, and the protective film is easily peeled. Therefore, there is a possibility that a long charge / discharge cycle life cannot be obtained. On the other hand, when the D90 is larger than 25 μm, the number of primary particles constituting the secondary aggregated particles of the lithium composite oxide particles tends to be large. In many cases, only the surface of the grains is covered with a protective coating. For this reason, peeling of the protective film easily occurs during the charge / discharge cycle, and a long charge / discharge cycle life may not be obtained. A more preferred range for D90 is from 10 μm to 20 μm.

  The larger the content of the lithium composite oxide particles in the positive electrode active material particles, the better the adhesion between the positive electrode and the protective coating. Therefore, in order to obtain a longer charge / discharge cycle life, the content of the lithium composite oxide particles in the positive electrode active material particles is more preferably 60% by weight or more, and further preferably 70% by weight or more. .

  Examples of the lithium composite oxide containing the element M include a lithium nickel composite oxide, a lithium cobalt composite oxide, and a lithium nickel cobalt composite oxide. Other types of elements can be added to the lithium composite oxide from the viewpoint of improving characteristics and the like. Examples of such elements include Mn, Al, Sn, Fe, Cu, Cr, Zn, Mg, Si, P, F, Cl, and B. The type of the additive element may be one type or two or more types.

  Among them, a composition represented by the following formula (E) or (F) is preferable.

_{Li a Co b M1 c O 2} (E)
Here, M1 is at least one element selected from the group consisting of Ni, Mn, B, Al and Sn, and the molar ratios a, b and c are respectively 0.95 ≦ a ≦ 1. 05, 0.95 ≦ b ≦ 1.05, 0 ≦ c ≦ 0.05, 0.95 ≦ b + c ≦ 1.05. More preferable ranges of the molar ratios a, b, and c are 0.97 ≦ a ≦ 1.03, 0.97 ≦ b ≦ 1.03, and 0.001 ≦ c ≦ 0.03, respectively.

_{Li x Ni y Co z M2 w} O 2 (F)
Here, M2 is at least one element selected from the group consisting of Mn, B, Al and Sn, and the molar ratios x, y, z and w are respectively 0.95 ≦ x ≦ 1. 05, 0.7 ≦ y ≦ 0.95, 0.05 ≦ z ≦ 0.3, 0 ≦ w ≦ 0.1, 0.95 ≦ y + z + w ≦ 1.05. More preferable ranges of the molar ratios x, y, and z are 0.97 ≦ x ≦ 1.03, 0.75 ≦ y ≦ 0.9, and 0.1 ≦ z ≦ 0.25. The more preferable range of the molar ratio w is 0 ≦ w ≦ 0.07, the further preferable range is 0 ≦ w ≦ 0.05, and the most preferable range is 0 ≦ w ≦ 0.03. In order to sufficiently obtain the effect of adding the element M2, the lower limit of the molar ratio w is preferably set to 0.001.

  In the lithium composite oxide particles described above, not all the particles need to have the same composition, and if the peak intensity ratio is 2 or more and less than 5, the particles are composed of two or more types of particles having different compositions. May be.

  In addition, the positive electrode active material particles may be formed from the lithium composite oxide particles described above, but may include particles other than the lithium composite oxide particles.

Examples of the other particles include lithium-containing composite oxide particles having a peak intensity ratio (I ₀₀₃ / I ₁₀₄ ) of more than 5. Since the lithium-containing composite oxide particles have a high activity in a charged state, the positive electrode containing the lithium-containing composite oxide particles can quickly react with the sultone compound in the nonaqueous electrolyte in a high-temperature environment. it can. As a result, when the battery is stored in a high temperature environment in a charged state, a protective film made of a sultone compound can be quickly formed on the surface of the positive electrode, so that the oxidative decomposition reaction of the nonaqueous electrolyte can be suppressed. Accordingly, the amount of gas generated when the secondary battery is stored in a high temperature environment in a charged state can be reduced, so that the battery can be prevented from swelling, the charge / discharge cycle life is long, and the charge A secondary battery in which swelling during storage is suppressed can be realized. A more preferred range of the peak intensity ratio (I ₀₀₃ / I ₁₀₄ ) is 7 or more. Further, those having a peak intensity ratio of more than 500 and those in which a peak derived from the (104) plane is not detected may have a crystal structure that does not occlude lithium. It is desirable to set it to 500.

In order to realize a secondary battery excellent in both charge / discharge cycle life and charge / high-temperature storage characteristics, the lithium-containing composite oxide particles having a peak intensity ratio (I ₀₀₃ / I ₁₀₄ ) of more than 5 in the positive electrode active material particles are required. It is preferable that the ratio be in the range of 0.1% by weight or more and less than 50% by weight. A more preferred range is from 0.5 to 48% by weight.

  Examples of the lithium-containing composite oxide include a lithium-cobalt composite oxide. At least one element different from the constituent elements can be added to the lithium-containing composite oxide. Examples of the additional elements include Ni, Mn, Al, Sn, Fe, Cu, Cr, Zn, and Mg. , Si, P, F, Cl, B and the like. Further, the composition of the lithium-containing composite oxide may be represented by the above-described formula (E) or (F).

  In the lithium-containing composite oxide particles, not all the particles need to have the same composition, and if the peak intensity ratio is larger than 5, two or more particles having different compositions may be used.

  Examples of the conductive agent, the binder, and the current collector may be the same as those described in the first nonaqueous electrolyte secondary battery.

  The positive electrode is manufactured, for example, by suspending a conductive agent and a binder in a suitable solvent in a positive electrode active material, applying the suspension to a current collector, and drying to form a thin plate.

The positive electrode active material particles used in the second non-aqueous electrolyte secondary battery according to the present invention described above contain lithium composite oxide particles containing the element M in an amount of 50% by weight or more, and the lithium composite oxide particles have a peak. The strength ratio (I ₀₀₃ / I ₁₀₄ ) is 2 or more and less than 5, and has a particle form including secondary aggregated particles, and the molar ratio (Y _Li / Y _M ) of the positive electrode active material particles is 0.95 to 0.95. Since the particle diameter (D90) of the positive electrode active material particles having a volume accumulation frequency of 90% is within the range of 10 μm to 25 μm in the range of 1.02 and the positive electrode active material particles react with the sultone compound and have a lithium ion permeable A protective coating can be formed. Since this protective coating is formed not only on the surface of the secondary aggregated particles but also on the gap between the primary particles, it can have a complicated network structure. As a result, since the protective film can be prevented from peeling off from the positive electrode during the charge / discharge cycle, the oxidative decomposition reaction of the nonaqueous electrolyte can be suppressed, and the charge / discharge cycle life of the secondary battery can be improved. it can.

  A thin, square, cylindrical non-aqueous electrolyte secondary battery as an example of the non-aqueous electrolyte secondary battery according to the present invention will be described in detail with reference to FIGS.

  FIG. 1 is a perspective view showing a thin non-aqueous electrolyte secondary battery which is an example of the non-aqueous electrolyte secondary battery according to the present invention. FIG. 2 shows the thin non-aqueous electrolyte secondary battery of FIG. FIG. 3 is a partially cutaway perspective view showing a rectangular non-aqueous electrolyte secondary battery which is an example of the non-aqueous electrolyte secondary battery according to the present invention, and FIG. 4 is a non-aqueous electrolyte secondary battery according to the present invention. FIG. 2 is a partial cross-sectional view illustrating a cylindrical non-aqueous electrolyte secondary battery as an example of a battery.

  First, a thin nonaqueous electrolyte secondary battery will be described.

  As shown in FIG. 1, an electrode group 2 is accommodated in a container body 1 having a rectangular cup shape. The electrode group 2 has a structure in which a laminate including a positive electrode 3, a negative electrode 4, and a separator 5 disposed between the positive electrode 3 and the negative electrode 4 is wound into a flat shape. The non-aqueous electrolyte is held by the electrode group 2. A part of the edge of the container body 1 is wide and functions as a cover plate 6. The container body 1 and the lid plate 6 are each formed of a laminated film. The laminate film includes an outer protective layer 7, an inner protective layer 8 containing a thermoplastic resin, and a metal layer 9 disposed between the outer protective layer 7 and the inner protective layer 8. The lid 6 is fixed to the container main body 1 by heat sealing using the thermoplastic resin of the inner protective layer 8, whereby the electrode group 2 is sealed in the container. A positive electrode tab 10 is connected to the positive electrode 3, and a negative electrode tab 11 is connected to the negative electrode 4. Each of the negative electrodes 4 is drawn out of the container and serves as a positive electrode terminal and a negative electrode terminal.

  Next, the prismatic nonaqueous electrolyte secondary battery will be described.

  As shown in FIG. 3, an electrode group 13 is accommodated in a bottomed rectangular cylindrical container 12 made of metal such as aluminum. The electrode group 13 has a structure in which a positive electrode 14, a separator 15, and a negative electrode 16 are laminated in this order and wound flat. The spacer 17 having an opening near the center is disposed above the electrode group 13.

  The non-aqueous electrolyte is held by the electrode group 13. A sealing plate 18b having an explosion-proof mechanism 18a and having a circular hole opened near the center is laser-welded to the opening of the container 12. The negative electrode terminal 19 is arranged in a circular hole of the sealing plate 18b via a hermetic seal. The negative electrode tab 20 pulled out from the negative electrode 16 is welded to the lower end of the negative electrode terminal 19. On the other hand, a positive electrode tab (not shown) is connected to the container 12 also serving as a positive electrode terminal.

  Next, the cylindrical non-aqueous electrolyte secondary battery will be described.

  A cylindrical container 21 made of stainless steel and having a bottom has an insulator 22 disposed at the bottom. The electrode group 23 is housed in the container 21. The electrode group 23 has a structure in which a band formed by laminating the positive electrode 24, the separator 25, the negative electrode 26, and the separator 25 is spirally wound so that the separator 25 is located outside.

  The container 21 contains a non-aqueous electrolyte. An insulating paper 27 having a central opening is disposed above the electrode group 23 in the container 21. The insulating sealing plate 28 is arranged in the upper opening of the container 21, and the sealing plate 28 is fixed to the container 21 by caulking the vicinity of the upper opening inward. The positive terminal 29 is fitted in the center of the insulating sealing plate 28. One end of the positive electrode lead 30 is connected to the positive electrode 24, and the other end is connected to the positive electrode terminal 29. The negative electrode 26 is connected to the container 21 as a negative terminal via a negative lead (not shown).

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings described above.

(Example 1)
<Preparation of positive electrode>
Lithium composite oxide particles having the composition shown in Table 1 below and having a volume cumulative frequency 90% particle size D90 and a peak intensity ratio (I ₀₀₃ / I ₁₀₄ ) shown in Table 1 below were prepared. As a result of observation with a scanning electron microscope (SEM), it was confirmed that the lithium composite oxide particles contained secondary aggregated particles. The volume cumulative frequency 90% particle size D90 and the peak intensity ratio (I ₀₀₃ / I ₁₀₄ ) were measured by the method described below.

<Measurement of D90>
That is, the particle size of the lithium composite oxide particles and the volume occupied by the particles in each particle size section are measured by a laser diffraction / scattering method. The particle size when the volume of the particle size section was accumulated to 90% of the total was defined as the volume cumulative frequency 90% particle size.

<Measurement of peak intensity ratio>
For the X-ray diffraction measurement, RINT2000 manufactured by Rigaku Corporation was used. The measurement was performed under the following instrument conditions using Cu-Kα1 (wavelength: 1.5405 °) as an X-ray source. The tube voltage was 40 kV, the current was 40 mA, the divergence slit was 0.5 °, the scattering slit was 0.5 °, and the light receiving slit width was 0.15 mm. In addition, a monochromator was used. The measurement was performed at a scanning speed of 2 ° / min, a scanning step of 0.01 °, and a scanning axis of 2θ / θ. The peak at 2θ = 45.0 ° ± 0.5 ° was the peak on the (104) plane, and the peak at 2θ = 18.8 ° ± 0.2 ° was the peak on the (003) plane. The peak intensity (cps) was obtained by subtracting the background from the measured value of the diffraction pattern represented by the 2θ axis.

  To 90% by weight of the lithium composite oxide powder, 5% by weight of acetylene black and a solution of 5% by weight of polyvinylidene fluoride (PVdF) in N-methyl-2-pyrrolidone (NMP) were added and mixed to prepare a slurry. . The slurry was applied to both sides of a current collector made of aluminum foil having a thickness of 15 μm, dried, and pressed to produce a positive electrode having a structure in which a positive electrode layer was supported on both sides of the current collector. In addition, the thickness of the positive electrode layer was 60 μm per side.

<Preparation of negative electrode>
As a carbonaceous material, 95% by weight of a powder having a mesophase pitch-based carbon fiber heat-treated at 3000 ° C. (having a (002) plane spacing (d ₀₀₂ ) of 0.336 nm as determined by powder X-ray diffraction), and polyvinylidene fluoride ( (PVdF) was mixed with 5% by weight of a dimethylformamide (DMF) solution to prepare a slurry. The slurry was applied on both sides of a current collector made of a copper foil having a thickness of 12 μm, dried, and pressed to produce a negative electrode having a structure in which a negative electrode layer was supported on the current collector. The thickness of the negative electrode layer was 55 μm per one side.

The plane distance d ₀₀₂ of the (002) plane of the carbonaceous material was determined from the powder X-ray diffraction spectrum by the half-width half-point method. At this time, scattering correction such as Lorentz scattering was not performed.

<Separator>
A separator made of a microporous polyethylene membrane having a thickness of 25 μm was prepared.

<Preparation of non-aqueous electrolyte>
A non-aqueous solvent is prepared by mixing ethylene carbonate (EC), γ-butyrolactone (GBL) and 1,3-propene sultone (PRS) such that the volume ratio (EC: GBL: PRS) is 33: 66: 1. did. A liquid non-aqueous electrolyte was prepared by dissolving lithium tetrafluoroborate (LiBF ₄ ) in the obtained non-aqueous solvent so as to have a concentration of 1.5 mol / L.

<Preparation of electrode group>
The positive electrode current collector of the positive electrode is ultrasonically welded to a positive electrode lead made of a band-shaped aluminum foil (thickness: 100 μm), and the negative electrode current collector is ultrasonically welded to a negative electrode lead made of a band-shaped nickel foil (thickness: 100 μm). After the positive electrode and the negative electrode were spirally wound between the positive electrode and the negative electrode with the separator interposed therebetween, the positive electrode and the negative electrode were formed into a flat shape to form an electrode group.

  A 100 μm-thick laminated film in which both surfaces of an aluminum foil were covered with polyethylene was formed into a rectangular cup shape by a press machine, and the electrode group was housed in the obtained container.

  Next, moisture contained in the electrode group and the laminated film was removed by subjecting the electrode group in the container to vacuum drying at 80 ° C. for 12 hours.

  Subsequently, the liquid non-aqueous electrolyte was injected into the electrode group in the container so that the amount per 1 Ah of the battery capacity became 4.8 g, and sealed by heat sealing to obtain the structure shown in FIGS. Then, a thin nonaqueous electrolyte secondary battery having a thickness of 3.6 mm, a width of 35 mm, and a height of 62 mm was assembled.

(Examples 2 to 8)
A thin non-aqueous electrolyte secondary battery was assembled in the same manner as described in Example 1 except that the composition of the non-aqueous electrolyte was changed as shown in Table 2 below.

  In Table 2, DEC indicates diethyl carbonate, MEC indicates methyl ethyl carbonate, PC indicates propylene carbonate, and BTS indicates 1,4-butylene sultone.

(Examples 9 to 17)
Except that the molar ratio of Li and the element M (X _Li / X _M ), the peak intensity ratio (I ₀₀₃ / I ₁₀₄ ), and the volume cumulative frequency 90% particle size D90 are changed as shown in Table 1 below, are as described above. A thin non-aqueous electrolyte secondary battery was assembled in the same manner as described in Example 1.

(Comparative Examples 1 to 5)
A thin non-aqueous electrolyte secondary battery was assembled in the same manner as described in Example 1 except that the composition of the non-aqueous electrolyte was changed as shown in Table 4 below.

  In Table 4, EC indicates ethylene carbonate, MEC indicates methyl ethyl carbonate, PRS indicates 1,3-propene sultone, DEC indicates diethyl carbonate, GBL indicates γ-butyrolactone, PC indicates propylene carbonate, and PS indicates propane sultone.

(Comparative Examples 6 to 10)
Except that the molar ratio of Li to the element M (X _Li / X _M ), the peak intensity ratio (I ₀₀₃ / I ₁₀₄ ), and the volume cumulative frequency 90% particle size D90 are changed as shown in Table 3 below, are as described above. A thin non-aqueous electrolyte secondary battery was assembled in the same manner as described in Example 1.

  The charge and discharge cycle characteristics of the obtained secondary batteries of Examples 1 to 17 and Comparative Examples 1 to 10 were evaluated under the conditions described below, and the results are shown in Tables 2 and 4 below.

(Charge / discharge cycle characteristics)
For each secondary battery, as a first charge / discharge step, constant-current / constant-voltage charging was performed at room temperature at 0.2 C (130 mA) to 4.2 V for 15 hours, and then discharged at room temperature to 0.2 V at 3.0 V. .

  Next, as charge / discharge cycle characteristics, a charge / discharge test was performed at a charge / discharge rate of 1 C, a charge end voltage of 4.2 V, and a discharge end voltage of 3.0 V, and after charge / discharge was repeated 500 times in an environment at a temperature of 20 ° C. The discharge capacity retention ratio (the capacity of the first discharge was defined as 100%) was determined.

As is clear from Tables 1 to 4, when the molar ratio (X _Li / X _M ) is in the range of 0.95 to 1.02 and the peak intensity ratio (I ₀₀₃ / I ₁₀₄ ) is 2 or more and less than 5, , And the secondary batteries of Examples 1 to 17 containing a lithium composite oxide having a D90 in the range of 10 μm to 25 μm and a sultone compound having at least one double bond in the ring were prepared in Comparative Examples 1 to 10. It can be understood that the capacity retention rate at the time of 500 cycles is higher than that of the secondary battery. Above all, the secondary batteries of Examples 1 to 12 and 14 to 17 had a higher capacity retention rate at 500 cycles than the secondary batteries of Example 13 in which D90 exceeded 20 μm.

  The secondary batteries of Comparative Examples 1 to 4 to which no sultone compound was added and the secondary battery of Comparative Example 5 using PS having no double bond as an additive had a peak intensity ratio larger than 5 and D90. And the secondary batteries of Comparative Examples 7 and 10 having a molar ratio of greater than 1.02 and a peak intensity ratio of greater than 5 and a secondary battery of Comparative Example 7 having a molar ratio of greater than 1.02, The secondary battery of Comparative Example 8 in which the peak intensity ratio is greater than 5 and D90 is less than 10 μm, and the secondary battery of Comparative Example 9 in which D90 is greater than 25 μm both have a capacity retention rate at 500 cycles of 70%. Did not meet.

(Example 18)
70% by weight of LiCoO ₂ particles (first active material particles) having a D90 of 15.25 μm and a peak intensity ratio (I ₀₀₃ / I ₁₀₄ ) of 3.4, and a peak intensity ratio of D90 of 14.93 μm ( Positive electrode active material particles were obtained by mixing 30% by weight of LiNi _0.8 Co _0.2 Mn _0.06 O ₂ particles (I ₀₀₃ / I ₁₀₄ ) of 3.8 (second active material particles). As a result of observation by a scanning electron microscope (SEM), it was confirmed that some of the first active material particles were in the form of secondary aggregated particles.

Table 5 below shows D90 of the obtained positive electrode active material particles and the molar ratio (Y _Li / Y _M ).

  A thin non-aqueous electrolyte secondary battery having the same configuration as that described in Example 1 was obtained except that the obtained positive electrode active material particles were used.

(Examples 19 to 24)
The composition, peak intensity ratio (I ₀₀₃ / I ₁₀₄ ) and D90 of the first active material and the second active material, the compounding ratio of the first active material in the positive electrode active material particles, and D90 of the positive electrode active material particles And a thin non-aqueous electrolyte secondary battery having the same configuration as that described in Example 1 except that positive electrode active material particles having a molar ratio (Y _Li / Y _M ) as shown in Table 5 below are used. Got.

  With respect to the obtained secondary batteries of Examples 18 to 24, the capacity retention at 500 cycles was measured in the same manner as described in Example 1 described above, and the results are shown in Table 6 below. For the secondary batteries of Examples 18 to 24 and Example 1 described above, the charging / high-temperature storage characteristics were evaluated under the conditions described below, and the results are shown in Table 6 below.

(Charge high temperature storage characteristics)
Each secondary battery was charged at a charge rate of 1 C and a charge end voltage of 4.2 V, and after being stored in an environment at a temperature of 80 ° C. for 120 hours, the thickness of the battery container was measured. The thickness change rate of the container was determined.

{(T ₁ −t ₀ ) / t ₀ } × 100 (%) (I)
Here, t ₀ is the thickness of the battery container immediately before storage, and t ₁ is the thickness of the battery container 120 hours after storage.

As is clear from Tables 5 and 6, an implementation was provided with a positive electrode including a positive electrode active material composed of two types of lithium cobalt-containing composite oxides having a peak intensity ratio (I ₀₀₃ / I ₁₀₄ ) of 2 or more and less than 5. The batteries of Examples 18 and 19 had a higher cycle maintenance ratio and a slightly better thickness change ratio than Example 1.

Further, a lithium element M-containing composite oxide having a peak intensity ratio (I ₀₀₃ / I ₁₀₄ ) of 2 or more and less than 5 and a lithium-containing composite oxide having a peak intensity ratio (I ₀₀₃ / I ₁₀₄ ) of more than 5 In the secondary batteries of Examples 20 to 24 including the positive electrode containing, the swelling at the time of high-temperature charging storage was able to be reduced as compared with Example 1 while setting the capacity retention rate at the time of 500 cycles to a high value. .

  In the above-described examples, the mole number of the element M in the positive electrode active material particles is the mole number of the contained element when Ni or Co is included in the positive electrode active material particles. When Ni and Co are contained in the positive electrode active material particles, it is the total number of moles of Ni and Co.

(Method of detecting PRS)
Further, with respect to the secondary battery of Example 1, after the initial charge / discharge step, the circuit was opened for 5 hours or more to sufficiently settle the potential, and then the Ar concentration was 99.9% or more and the dew point was −50 ° C. It was disassembled in the following glove box, and the electrode group was taken out. Claw said electrode group into a centrifuge tube, and sealed by the addition of dimethyl sulfoxide (DMSO) -d _6, taken out from the glove box and centrifuged. Then, in the glove box were taken mixed solution of the said electrolyte DMSO-d ₆ from the centrifuge tube. About 0.5 ml of the mixed solvent was placed in a 5 mmφ NMR sample tube, and NMR measurement was performed. The apparatus used for NMR measurement was JNM-LA400WB manufactured by JEOL Ltd., an observing nucleus is ¹ H, observation frequency is 400MHz, dimethyl sulfoxide (DMSO) internal reference residual proton signals included slightly in -d ₆ (2.5 ppm). The measurement temperature was 25 ° C. ^{In the 1} H NMR spectrum, the peak corresponding to EC is around 4.5 ppm, and the peak corresponding to PRS is around 5.1 ppm (P ₁ ), around 7.05 ppm (P ₂ ), and 7.0 as shown in the spectrum shown in FIG. It was observed at around 2 ppm (P ₃ ). From these results, it was confirmed that PRS was contained in the nonaqueous solvent present in the secondary battery of Example 1 after the initial charge / discharge step.

Further, when the observation frequency was set to 100 MHz and ¹³ C NMR measurement was performed using dimethyl sulfoxide (DMSO) -d ₆ (39.5 ppm) as an internal reference substance, the peak corresponding to EC was around 66 ppm, and the peak corresponding to PRS was 74 ppm. In the vicinity, at around 124 ppm, and at around 140 ppm, it was also confirmed from the results that PRS was contained in the non-aqueous solvent present in the secondary battery of Example 1 after the initial charge / discharge step.

Further, when the ratio of the PRS NMR integrated intensity to the EC NMR integrated intensity in the ¹ H NMR spectrum was determined, it was confirmed that the ratio of PRS to the entire non-aqueous solvent was smaller than before the secondary battery was assembled. did it.

  The present invention is not limited to the above-described embodiment, and is similarly applicable to combinations of other types of positive electrodes, negative electrodes, separators, and containers.

  Further, the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the gist thereof at the stage of implementation. Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above embodiments. For example, some components may be deleted from all the components shown in the embodiment. Further, components of different embodiments may be appropriately combined.

FIG. 1 is a perspective view showing a thin non-aqueous electrolyte secondary battery which is an example of a non-aqueous electrolyte secondary battery according to the present invention. FIG. 2 is a partial cross-sectional view of the thin non-aqueous electrolyte secondary battery of FIG. 1 cut along a short side direction. 1 is a partially cutaway perspective view showing a rectangular non-aqueous electrolyte secondary battery as an example of the non-aqueous electrolyte secondary battery according to the present invention. FIG. 1 is a partial cross-sectional view showing a cylindrical non-aqueous electrolyte secondary battery as an example of a non-aqueous electrolyte secondary battery according to the present invention. FIG. 4 is a characteristic diagram showing a ¹ HNMR spectrum of PRS contained in the nonaqueous electrolyte of the nonaqueous electrolyte secondary battery of Example 1.

Explanation of reference numerals

  DESCRIPTION OF SYMBOLS 1 ... Container main body, 2 ... Electrode group, 3 ... Positive electrode, 4 ... Negative electrode, 5 ... Separator, 6 ... Cover plate, 7 ... External protective layer, 8 ... Internal protective layer, 9 ... Metal layer, 10 ... Positive electrode terminal, 11 ... negative electrode terminal.

Claims (4)

In a nonaqueous electrolyte secondary battery including a positive electrode including a positive electrode active material containing a lithium composite oxide powder, a negative electrode, and a nonaqueous electrolyte,
The lithium composite oxide powder contains secondary aggregated particles, and has a molar ratio of Li and the element M (the element M is at least one selected from the group consisting of Ni and Co) (X _Li / X _M ) in the range of 0.95 to 1.02, and the ratio (I) of the peak intensity I ₀₀₃ on the ( ₀₀₃ ) plane to the peak intensity I ₁₀₄ on the (104) plane in powder X-ray diffraction. ₀₀₃ / I ₁₀₄ ) is 2 or more and less than 5, and the particle diameter (D90) at a volume cumulative frequency of 90% is in the range of 10 μm to 25 μm;
The non-aqueous electrolyte secondary battery according to claim 1, wherein the non-aqueous electrolyte includes a sultone compound having at least one double bond in a ring. A positive electrode including positive electrode active material particles containing lithium composite oxide particles, a negative electrode, a non-aqueous electrolyte secondary battery including a non-aqueous electrolyte,
The lithium composite oxide particles have a composition including at least one element M selected from the group consisting of Ni and Co, have a particle form including secondary aggregated particles, and have a peak intensity ratio of the following ( 1) satisfying the equation,
The content of the lithium composite oxide particles in the positive electrode active material particles is 50% by weight or more,
The molar ratio of the positive electrode active material particles satisfies the following equation (2), and the particle diameter (D90) of the positive electrode active material particles at a volume accumulation frequency of 90% is in the range of 10 μm to 25 μm;
The non-aqueous electrolyte secondary battery according to claim 1, wherein the non-aqueous electrolyte includes a sultone compound having at least one double bond in a ring.
2 ≦ (I ₀₀₃ / I ₁₀₄ ) <5 (1)
0.95 ≦ (Y _Li / Y _M ) ≦ 1.02 (2)
Here, I ₀₀₃ is the peak intensity (cps) of the (003) plane in the powder X-ray diffraction of the lithium composite oxide particles, and I ₁₀₄ is the peak intensity (cps) of the (104) plane in the powder X-ray diffraction. , Y _Li is the number of moles of lithium in the positive electrode active material particles, Y _M is the number of moles of element M in the positive electrode active material particles, and the element M is at least one selected from the group consisting of Ni and Co. Kind. The non-aqueous electrolyte secondary battery according to claim 2, wherein the positive electrode active material particles further include lithium-containing composite oxide particles having a peak intensity ratio satisfying the following expression (3).
(I ₀₀₃ / I ₁₀₄ )> 5 (3)
Here, I ₀₀₃ is the peak intensity (cps) of the (003) plane in the powder X-ray diffraction of the lithium-containing composite oxide particles, and I ₁₀₄ is the peak intensity (cps) of the (104) plane in the powder X-ray diffraction. is there.   The non-aqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein the sultone compound is composed of at least one of 1,3-propene sultone and 1,4-butylene sultone.

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