JP2004172113A - Non-aqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery restrained from swelling when stored in a charged state and in a high-temperature environment. <P>SOLUTION: This nonaqueous electrolyte secondary battery is equipped with: a positive electrode 3 containing a positive electrode active material; a negative electrode 4; and a nonaqueous electrolyte. The nonaqueous electrolyte secondary battery is characterized by that the positive electrode active material contains lithium composite oxide powder wherein the particle diameter (D10) at a volume cumulative frequency of 10% is below 4.5 μm, the ratio (I<SB>003</SB>/I<SB>104</SB>) of the peak intensity I<SB>003</SB>of the (003) surface to the peak intensity I<SB>104</SB>of the (104) surface in a powder X-ray diffraction is larger than 5, and the mol ratio (X<SB>Li</SB>/X<SB>Co</SB>) of Li to Co is above 1.02; 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 Document 1 discloses that the basic composition is LiMeO ₂ (Me is at least one selected from Ni and Co), the crystal structure is a layered rock salt structure, and the (104) plane obtained by X-ray diffraction analysis using CuKα radiation. Described is a lithium transition metal composite oxide in which the relationship of β ₍₁₀₄₎ ≧ β ₍₀₀₃₎ is established between the half width of the diffraction peak β ₍₁₀₄₎ and the half width of the diffraction peak on the (003) plane β _(003). Have been. According to this publication, when the value of I ₍₀₀₃₎ / I ₍₁₀₄₎ exceeds 4, the primary particles are in a strongly oriented state, and the occlusion and desorption of Li in the positive electrode are not performed smoothly. It is described that the lithium secondary battery has low power characteristics.

Patent Document 2 discloses a diffraction peak intensity (1003) of the (003) plane at 2θ = 18.5 ± 0.5 degrees measured by X-ray diffraction using LiCoO ₂ as an active material and CuKα as a radiation source. And a positive electrode plate having an intensity ratio (I003 / I104) of 2 to less than 5 with respect to the diffraction peak intensity (I104) of the (104) plane at 2θ = 44.5 ± 1.0 degrees. Is described. This publication describes that batteries with an intensity ratio (I003 / I104) of 5 or more have a strong orientation of the (003) plane of the electrode plate itself, which impedes diffusion of ions and is inferior in high-rate discharge performance. ing.
JP 2001-167761 A JP-A-11-154509

  An object of the present invention is to provide a nonaqueous electrolyte secondary battery in which swelling when stored in a charged state in a high-temperature environment is suppressed.

The first nonaqueous electrolyte secondary battery according to the present invention is a positive electrode including a positive electrode active material, a negative electrode, a nonaqueous electrolyte secondary battery including a nonaqueous electrolyte,
The positive electrode active material has a particle diameter (D10) at a volume accumulation frequency of 10% of 4.5 μm or less, and a peak intensity I ₀₀₃ of a ( ₀₀₃ ) plane and a peak intensity I ₁₀₄ of a (104) plane in powder X-ray diffraction. A lithium composite oxide powder having a ratio (I ₀₀₃ / I ₁₀₄ ) of greater than 5 and containing Li and Co at a molar ratio (X _Li / X _Co ) of 1.02 or more;
The non-aqueous electrolyte contains a sultone compound having at least one double bond in a ring.

The second non-aqueous electrolyte secondary battery according to the present invention is a non-aqueous electrolyte secondary battery including a positive electrode including positive electrode active material particles, a negative electrode, and a non-aqueous electrolyte,
The positive electrode active material particles contain more than 50% by weight of lithium cobalt-containing composite oxide particles having a peak intensity ratio satisfying the following formula (1),
The particle diameter (D10) at a volume accumulation frequency of 10% of the positive electrode active material particles is 4.5 μm or less, and the molar ratio of lithium to cobalt in the positive electrode active material particles satisfies the following formula (2);
The non-aqueous electrolyte contains a sultone compound having at least one double bond in a ring.

(I ₀₀₃ / I ₁₀₄ )> 5 (1)
1.02 ≦ (Y _Li / Y _Co ) ≦ 2 (2)
Here, I ₀₀₃ is the peak intensity (cps) of the (003) plane in the powder X-ray diffraction of the lithium cobalt-containing composite oxide particles, and I ₁₀₄ is the peak intensity (cps) of the (104) plane in the powder X-ray diffraction. Wherein Y _Li is the number of moles of lithium in the positive electrode active material particles, and Y _Co is the number of moles of cobalt in the positive electrode active material particles.

  According to the present invention, it is possible to provide a nonaqueous electrolyte secondary battery in which swelling when stored in a high temperature environment in a charged state is suppressed.

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

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, a negative electrode, and a nonaqueous electrolyte,
The positive electrode active material has a particle diameter (D10) at a volume accumulation frequency of 10% of 4.5 μm or less, a peak intensity ratio satisfying the following formula (A), and a molar ratio of lithium and cobalt satisfying the following formula (B). Including a lithium composite oxide powder that satisfies
The non-aqueous electrolyte includes a sultone compound having at least one double bond in a ring.

(I ₀₀₃ / I ₁₀₄ )> 5 (A)
(X _Li / X _Co ) ≧ 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, and X _Co is the number of moles of cobalt in the lithium composite oxide powder.

  The lithium composite oxide powder described above has high crystallinity, and is unlikely to undergo a structural phase transition from hexagonal to monoclinic even when the positive electrode potential reaches a high potential (around 4.2 V) by charging. It has the feature that it can be charged and discharged efficiently. Further, those that maintain a highly symmetric hexagonal state at a high positive electrode potential are more active than those that have undergone a monoclinic phase transition due to an increase in the positive electrode potential. An oxide in such a high activity state can quickly react with a sultone compound in a nonaqueous electrolyte under a high temperature environment. Therefore, the positive electrode containing the above-described lithium composite oxide powder can quickly form a protective film of a sultone compound on the surface thereof when stored in a high temperature environment in a charged state, and thus the oxidative decomposition reaction of the nonaqueous electrolyte. Can be reduced. As a result, the amount of gas generated when the secondary battery is stored in a charged state under a high-temperature environment can be reduced, so that the battery can be prevented from swelling.

  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 reason why the molar ratio (X _Li / X _Co ) between lithium (X _Li ) and cobalt (X _Co ) in the lithium composite oxide is 1.02 or more will be described. 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. When the molar ratio (X _Li / X _Co ) was less than 1.02, the positive electrode potential reached a high potential by charging because the grain growth rate during firing was low and the crystallinity and crystal orientation were low. Sometimes a structural phase transition reaction is likely to occur. For this reason, the reactivity with the sultone compound may be inferior, and the amount of gas generated during storage in a charged state in a high-temperature environment may increase. The upper limit of the molar ratio (X _Li / X _Co ) is preferably set to 1.1 for the reason described below.

When the molar ratio (X _Li / X _Co ) is larger than 1.1, the possibility that alkali melting does not completely proceed during the firing of the positive electrode active material and Li remains is increased. If this residual alkali content is large, it causes gelling of the binder and causes trouble during coating. A more preferred value of the upper limit of the molar ratio (X _Li / X _Co ) is 1.08.

  The lithium composite oxide may contain elements other than lithium and cobalt. Examples of such elements include Ni, 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 less than 5 have low crystallinity and crystal orientation, so that a structural phase transition reaction at a high potential is likely to occur, and the reactivity with a sultone compound is poor. When stored in a high temperature environment in a charged state, the amount of gas generated may increase. 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.

The reason for defining the particle diameter (D10) of the lithium composite oxide having a volume accumulation frequency of 10% in the above range will be described. A lithium composite oxide powder having a peak intensity ratio (I ₀₀₃ / I ₁₀₄ ) of greater than 5 and a molar ratio (X _Li / X _Co ) of Li and Co of 1.02 or more has a secondary agglomerated particle. Fewer, substantially composed of single particles. Therefore, when D10 is larger than 4.5 μm, the reaction area of the positive electrode with the non-aqueous electrolyte is reduced, so that the formation speed of the protective film on the positive electrode surface is reduced, and the gas when stored in a charged state in a high-temperature environment is reduced. There is a risk that the amount generated will increase. Further, since the bulk density of the lithium composite oxide powder is reduced, the energy density of the positive electrode may be reduced. D10 is more desirably 3 μm or less. Further, those having a D10 of less than 0.1 μm have a high ratio of particles having low crystallinity and low crystal orientation due to insufficient grain growth at the time of firing. Gas generation amount may increase. Therefore, it is desirable that the lower limit of D10 be 0.1 μm (more preferably 0.5 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 by 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.

  The liquid non-aqueous electrolyte may contain a surfactant such as trioctyl phosphate (TOP). 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 from, for example, a metal plate, a metal film, a film including a resin layer, or the like.

  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.

  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 second non-aqueous electrolyte secondary battery according to the present invention is a non-aqueous electrolyte secondary battery including a positive electrode including positive electrode active material particles, a negative electrode, and a non-aqueous electrolyte,
The positive electrode active material particles contain more than 50% by weight of lithium cobalt-containing composite oxide particles having a peak intensity ratio satisfying the following formula (C),
The particle diameter (D10) of the positive electrode active material particles having a volume cumulative frequency of 10% is 4.5 μm or less, and the molar ratio of lithium to cobalt in the positive electrode active material particles satisfies the following formula (D);
The non-aqueous electrolyte includes a sultone compound having at least one double bond in a ring.

(I ₀₀₃ / I ₁₀₄ )> 5 (C)
1.02 ≦ (Y _Li / Y _Co ) ≦ 2 (D)
Here, I ₀₀₃ is the peak intensity (cps) of the (003) plane in the powder X-ray diffraction of the lithium cobalt-containing composite oxide particles, and I ₁₀₄ is the peak intensity (cps) of the (104) plane in the powder X-ray diffraction. Wherein Y _Li is the number of moles of lithium in the positive electrode active material particles, and Y _Co is the number of moles of cobalt in the positive electrode active material particles.

  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.

The reason for defining the molar ratio of lithium to cobalt (Y _Li / Y _Co ) in the positive electrode active material particles within the above range will be described. If the molar ratio (Y _Li / Y _Co ) is less than 1.02 or greater than 2, the lithium-cobalt ratio of the lithium-cobalt-containing composite oxide particles having a peak intensity ratio (I ₀₀₃ / I ₁₀₄ ) of more than 5 ( X _Li / X _Co ) deviates from an appropriate value, so that the battery swelling during high-temperature storage during charging cannot be suppressed.

In particular, when the molar ratio of Li in the positive electrode active material and Co in elements other than O is 0.9 or more and 1 or less, the molar ratio (Y _Li / Y _Co ) is set to 1.02 to 1.1. Within this range, the reactivity of the lithium-cobalt-containing composite oxide particles with the sultone compound can be increased, and the charge / high-temperature storage characteristics can be further improved. In this case, the more preferable upper limit of the molar ratio (Y _Li / Y _Co ) is 1.08.

The particle size distribution of the positive electrode active material particles largely reflects the particle size distribution of the lithium cobalt-containing composite oxide particles contained in the positive electrode active material particles in an amount of more than 50% by weight. In the lithium-cobalt-containing composite oxide particles having a peak intensity ratio larger than 5, when the molar ratio of the positive electrode active material (Y _Li / Y _Co ) is in the range of 1.02 to 2, the abundance ratio of the single particles tends to be high. There is. Accordingly, when the particle diameter (D10) of the positive electrode active material particles having a volume cumulative frequency of 10% is larger than 4.5 μm, the reaction area of the positive electrode with the nonaqueous electrolyte decreases, and the formation rate of the protective film on the positive electrode surface decreases. There is a possibility that the amount of gas generated when the battery is stored under a high temperature environment in a charged state will increase. Further, since the bulk density of the lithium-cobalt-containing composite oxide particles is reduced, the energy density of the positive electrode may be reduced. D10 is more desirably 3 μm or less. Further, when D10 is less than 0.1 μm, the ratio of particles having low crystallinity and low crystal orientation is increased, so that the amount of gas generated during storage in a charged state in a high-temperature environment may increase. Therefore, it is desirable that the lower limit of D10 be 0.1 μm (more preferably 0.5 μm).

  The higher the content of the lithium-cobalt-containing composite oxide particles in the positive electrode active material particles, the higher the crystallinity and crystal orientation of the positive electrode active material particles, and the higher the reactivity with the sultone compound of the positive electrode. it can. Therefore, in order to sufficiently reduce the amount of gas generated when the battery is stored in a high temperature environment in a charged state, the content of the lithium-cobalt-containing composite oxide particles in the positive electrode active material particles should be set to 60% by weight or more. More preferably, the content is more preferably 70% by weight or more.

  The lithium-cobalt-containing composite oxide particles may contain an element other than lithium and cobalt. Examples of such elements include Ni, 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) 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.

  In the above-described lithium-cobalt-containing composite oxide particles, not all particles need to have the same composition, and if the peak intensity ratio is larger than 5, even if the particles are composed of two or more types of particles having different compositions. good.

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

Examples of the other particles include lithium-containing composite oxide particles having a peak intensity ratio (I ₀₀₃ / I ₁₀₄ ) of 2 or more and less than 5. By adding the lithium-containing composite oxide particles to the positive electrode, peeling of the protective film from the positive electrode surface due to repeated expansion and contraction in the charge / discharge cycle can be suppressed, and the protective film formed on the positive electrode surface can be prevented from peeling off. Since the stability can be increased, the charge / discharge cycle life of the secondary battery can be improved while having excellent charge / high-temperature storage characteristics. When the crystal has no orientation and is completely isotropic, the peak intensity ratio (I ₀₀₃ / I ₁₀₄ ) is 2 in calculation, so that the peak intensity ratio is 2 or more and less than 5. Is preferred. A more preferable range of the peak intensity ratio is larger than 2 and equal to or smaller than 4.95.

In order to realize a secondary battery excellent in both charge / discharge cycle life and charge / high-temperature storage characteristics, a positive electrode active material of lithium-containing composite oxide particles having a peak intensity ratio (I ₀₀₃ / I ₁₀₄ ) of 2 or more and less than 5 It is preferable that the proportion in the particles 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 manganese composite oxide, a lithium nickel composite oxide, a lithium cobalt composite oxide, and a lithium nickel cobalt composite oxide. At least one element different from the constituent elements can be added to each composite oxide. Examples of the additional elements include Ni, Mn, Al, Sn, Fe, Cu, Cr, Zn, Mg, and Si. , P, F, Cl, B and the like. Among them, a lithium-containing composite oxide having a composition represented by the following formula (F) is preferable.

_{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-containing composite oxide particles, not all the particles need to have the same composition, and if the peak intensity ratio is 2 or more and less than 5, it is composed of two or more types of particles having different compositions. Is also good.

  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 used in the above-described second nonaqueous electrolyte secondary battery according to the present invention contains lithium cobalt-containing composite oxide particles having a peak intensity ratio (I ₀₀₃ / I ₁₀₄ ) of more than 5 by 50% by weight. Since it contains a larger amount, D10 is 4.5 μm or less, and the molar ratio (Y _Li / Y _Co ) is in the range of 1.02 to 2, it quickly reacts with the sultone compound in the non-aqueous electrolyte under a high temperature environment. be able to. Therefore, when the battery is stored in a high temperature environment in a charged state, a protective film of the 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. As a result, the amount of gas generated when the secondary battery is stored in a charged state under a high-temperature environment can be reduced, so that the battery can be prevented from swelling.

  The thin, square, and cylindrical non-aqueous electrolyte secondary batteries, which are examples of the first and second non-aqueous electrolyte secondary batteries 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 of 10% particle diameter D10 and a peak intensity ratio (I ₀₀₃ / I ₁₀₄ ) having the values shown in Table 1 below were prepared. The volume cumulative frequency 10% particle diameter D10 and the peak intensity ratio (I ₀₀₃ / I ₁₀₄ ) were measured by the method described below.

<Measurement of D10>
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 10% of the total was defined as the volume cumulative frequency 10% 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 = 45.2 ° ± 0.1 ° was the peak on the (104) plane, and the peak at 2θ = 18.8 ° ± 0.1 ° 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), methyl ethyl carbonate (MEC) and 1,3-propene sultone (PRS) so that the volume ratio (EC: MEC: PRS) is 33: 66: 1. did. A liquid non-aqueous electrolyte was prepared by dissolving lithium hexafluorophosphate (LiPF ₆ ) in the obtained non-aqueous solvent so as to have a concentration of 1 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.

  The electrode group was housed in an aluminum square can having a thickness of 0.25 mm. Next, moisture contained in the electrode group and the metal can was removed by subjecting the electrode group in the metal can to vacuum drying at 80 ° C. for 12 hours.

  Subsequently, a liquid non-aqueous electrolyte was injected into the electrode group in the metal can so that the amount per 1 Ah of the battery capacity was 4.8 g, and the injection hole was sealed by welding to form the above-described structure shown in FIG. And a rectangular non-aqueous electrolyte secondary battery having a thickness of 4.8 mm, a width of 30 mm, and a height of 48 mm was assembled.

(Examples 2 to 8)
A prismatic 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, GBL indicates γ-butyrolactone, PC indicates propylene carbonate, and BTS indicates 1,4-butylene sultone.

(Examples 9 to 13)
Except for changing the molar ratio of Li and Co (X _Li / X _Co ), the peak intensity ratio (I ₀₀₃ / I ₁₀₄ ), and the volume cumulative frequency 10% particle size D10 as shown in Table 1 below, A prismatic nonaqueous electrolyte secondary battery was assembled in the same manner as described in Example 1.

(Comparative Examples 1 to 5)
A prismatic 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 8)
Except for changing the molar ratio of Li and Co (X _Li / X _Co ), the peak intensity ratio (I ₀₀₃ / I ₁₀₄ ), and the volume cumulative frequency 10% particle size D10 as shown in Table 3 below, A prismatic nonaqueous electrolyte secondary battery was assembled in the same manner as described in Example 1.

  With respect to the obtained secondary batteries of Examples 1 to 13 and Comparative Examples 1 to 8, charging high-temperature storage characteristics were evaluated under the conditions described below, and the results are shown in Tables 2 and 4 below.

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

{(T ₁ −t ₀ ) / t ₀ } × 100 (%) (2)
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 apparent from Tables 1 to 4, when D10 is 4.5 μm or less, the peak intensity ratio (I ₀₀₃ / I ₁₀₄ ) is larger than 5, and the molar ratio (X _Li / X _Co ) is 1.02 or more. The secondary batteries of Examples 1 to 13 each containing a certain lithium composite oxide powder and a sultone compound having at least one double bond in the ring swelled when stored in a charged state under an environment of 80 ° C. However, it can be understood that they are smaller than the secondary batteries of Comparative Examples 1 to 8.

The molar ratio (X _Li / X _Co ) of the secondary batteries of Comparative Examples 1 to 4 in which no sultone compound was added and the secondary battery of Comparative Example 5 in which PS having no double bond was used as an additive was used. The secondary batteries of Comparative Examples 6 and 7 having a peak intensity ratio (I ₀₀₃ / I ₁₀₄ ) of less than 5 and a peak intensity ratio (I ₀₀₃ / I ₁₀₄ ) of 5 or less, and the secondary battery of Comparative Example 8 having a D10 of more than 4.5 μm were both used. The battery swelling when stored in a charged state under an environment of 80 ° C. was as large as 4% or more.

(Example 14)
70% by weight of Li _1.04 CoO ₂ particles (first active material particles) having a D10 of 2.9 μm and a peak intensity ratio (I ₀₀₃ / I ₁₀₄ ) of 30, and a peak intensity ratio of D10 of 1.8 μm ( _Positive electrode active material particles were obtained by mixing Li _1.05 Co _0.97 Sn _0.03 O ₂ particles (I ₀₀₃ / I ₁₀₄ ) of 50 (second active material particles) with 30% by weight. The following table shows the D10 of the obtained positive electrode active material particles, the molar ratio of the positive electrode active material particles (Y _Li / Y _Co ), and the molar ratio of Co when the element other than Li and O in the positive electrode active material was set to 1. It is shown in FIG.

  A rectangular 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 15 to 18)
Composition, peak intensity ratio (I ₀₀₃ / I ₁₀₄ ) and D10 of the first positive electrode active material and the second positive electrode active material, the weight ratio of the first positive electrode active material in the positive electrode active material, and the positive electrode active material Except that the molar ratio (Y _Li / Y _Co ), D10, and the molar ratio of Co when the elements other than Li and O in the positive electrode active material are set to 1 are as shown in Table 5 below, the above-described example was used. A square non-aqueous electrolyte secondary battery having the same configuration as that described in 1 was obtained.

  With respect to the obtained secondary batteries of Examples 14 to 18, the thickness change rate of the battery container was measured in the same manner as described in Example 1 described above, and the results are shown in Table 6 below.

  Further, for Examples 14 to 18 and Example 1 described above, 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. The discharge capacity retention ratio after 500 repetitions was calculated assuming that the capacity of the first discharge was 100%, and the results are shown in Table 6 below.

As is clear from Tables 5 and 6, Examples 14 to 15 provided with a positive electrode containing a positive electrode active material composed of two kinds of lithium cobalt-containing composite oxides having a peak intensity ratio (I ₀₀₃ / I ₁₀₄ ) of more than 5 The battery No. 15 is better in either the thickness change rate or the cycle maintenance rate as compared with the first embodiment. Also includes a positive electrode containing a peak intensity ratio (I ₀₀₃ / I ₁₀₄₎ greater than 5 lithium cobalt-containing complex oxide and the peak intensity ratio (I ₀₀₃ / I ₁₀₄₎ is a lithium-containing composite oxide of less than 5 In each of the secondary batteries of Examples 16 to 18, the capacity retention rate at the time of 500 cycles was higher than that of Example 1.

(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.

  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 non-aqueous electrolyte secondary battery including a positive electrode including a positive electrode active material, a negative electrode, and a non-aqueous electrolyte,
The positive electrode active material has a particle diameter (D10) at a volume accumulation frequency of 10% of 4.5 μm or less, and a peak intensity I ₀₀₃ of a ( ₀₀₃ ) plane and a peak intensity I ₁₀₄ of a (104) plane in powder X-ray diffraction. A lithium composite oxide powder having a ratio (I ₀₀₃ / I ₁₀₄ ) of greater than 5 and containing Li and Co at a molar ratio (X _Li / X _Co ) of 1.02 or more;
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, a negative electrode, a non-aqueous electrolyte secondary battery including a non-aqueous electrolyte,
The positive electrode active material particles contain more than 50% by weight of lithium cobalt-containing composite oxide particles having a peak intensity ratio satisfying the following formula (1),
The particle diameter (D10) at a volume accumulation frequency of 10% of the positive electrode active material particles is 4.5 μm or less, and the molar ratio of lithium to cobalt in the positive electrode active material particles satisfies the following formula (2);
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.
(I ₀₀₃ / I ₁₀₄ )> 5 (1)
1.02 ≦ (Y _Li / Y _Co ) ≦ 2 (2)
Here, I ₀₀₃ is the peak intensity (cps) of the (003) plane in the powder X-ray diffraction of the lithium cobalt-containing composite oxide particles, and I ₁₀₄ is the peak intensity (cps) of the (104) plane in the powder X-ray diffraction. Wherein Y _Li is the number of moles of lithium in the positive electrode active material particles, and Y _Co is the number of moles of cobalt in the positive electrode active material particles. 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).
2 ≦ (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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