JP4599050B2 - Nonaqueous electrolyte secondary battery - Google Patents

Description

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

  In recent years, electronic devices such as mobile communication devices, notebook computers, palmtop computers, integrated video cameras, portable CD (MD) players, cordless telephones, etc. have been reduced in size and weight. As a power source, a battery having a small size and a large capacity is particularly demanded.

  Examples of batteries that are widely used as power sources 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, the 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 small and lightweight, has a high unit cell voltage, and a high energy density. It is attracting attention because it is obtained.

In Patent Document 1, the basic composition is LiMeO ₂ (Me is one or more 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 rays is used. A lithium transition metal composite oxide is described in which a relationship of β ₍₁₀₄₎ ≧ β ₍₀₀₃₎ is established between the half-value width β ₍₁₀₄₎ of the diffraction peak and the half-value width β ₍₀₀₃₎ of the (003) plane diffraction peak. Has been. In this publication, when the value of I ₍₀₀₃₎ / I ₍₁₀₄₎ exceeds 4, the primary particles are strongly oriented, and Li occlusion / desorption at the positive electrode is not smoothly performed. It is described that the lithium secondary battery has low power characteristics.

Patent Document 2 discloses a diffraction peak intensity (I003) on the (003) plane of 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 non-aqueous electrolyte secondary battery comprising a positive electrode plate having an intensity ratio (I003 / I104) of 2θ to 44.5 ± 1.0 degrees (104) plane diffraction peak intensity (I104) of 2 or more and less than 5 Is described. This publication describes that a battery having an intensity ratio (I003 / I104) of 5 or more has a strong orientation of the (003) plane of the electrode plate itself, thus preventing ion diffusion and being inferior in high-rate discharge performance. ing.
Japanese Patent Laid-Open No. 2001-167761 Japanese Patent Laid-Open No. 11-154509

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

A first nonaqueous electrolyte secondary battery according to the present invention is a nonaqueous electrolyte secondary battery comprising a positive electrode including a positive electrode active material, a negative electrode, and a nonaqueous electrolyte.
The positive electrode active material has a particle size (D10) with a volume cumulative frequency of 10% of 0.1 μm or more and 4.5 μm or less, and (003) plane peak intensity I ₀₀₃ and (104) plane peak intensity in powder X-ray diffraction. the ratio (I ₀₀₃ / I ₁₀₄₎ greater than 5 with I _104, at 500, and the lithium composite oxide powder molar ratio of Li and _Co (X _Li / X Co) contains 1.02 to 2 More than 50% by weight ,
The nonaqueous electrolyte contains a nonaqueous solvent containing 0.01% by volume or more and 10% by volume or less of a sultone compound having at least one double bond in the ring.

A second non-aqueous electrolyte secondary battery according to the present invention is a non-aqueous electrolyte secondary battery comprising 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 mass % of lithium cobalt-containing composite oxide particles having a peak intensity ratio satisfying the following formula (1):
The positive electrode active material particles have a volume cumulative frequency 10% particle size (D10) of 0.1 μm or more and 4.5 μm or less, and the molar ratio of lithium and cobalt of the positive electrode active material particles satisfies the following formula (2):
The nonaqueous electrolyte contains a nonaqueous solvent containing 0.01% by volume or more and 10% by volume or less of a sultone compound having at least one double bond in the ring.

500 ≧ (I ₀₀₃ / I ₁₀₄ )> 5 (1)
1.02 ≦ (Y _Li / Y _Co ) ≦ 2 (2)
However, 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. 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.

  ADVANTAGE OF THE INVENTION According to this invention, the nonaqueous electrolyte secondary battery by which the swelling at the time of storing in a high temperature environment in a charging state was suppressed 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 comprising a positive electrode including a positive electrode active material, a negative electrode, and a nonaqueous electrolyte,
The positive electrode active material has a particle size (D10) with a volume cumulative frequency of 10% of 0.1 μm or more and 4.5 μm or less, a peak intensity ratio satisfying the following formula (A), and a molar ratio of lithium and cobalt is B) including a lithium composite oxide powder satisfying the formula,
The non-aqueous electrolyte contains a non-aqueous solvent containing 0.01% by volume to 10% by volume of a sultone compound having at least one double bond in the ring.

500 ≧ (I ₀₀₃ / I ₁₀₄ )> 5 (A)
2 ≧ (X _Li / X _Co ) ≧ 1.02 (B)
However, _I003 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 even when the positive electrode potential reaches a high potential (around 4.2 V) by charging, the structural phase transition from hexagonal to monoclinic crystal is unlikely to occur. It has the feature that it can charge and discharge efficiently. In addition, those that maintain a highly symmetric hexagonal state at a high positive electrode potential are more active than those in which a monoclinic phase transition occurs due to an increase in the positive electrode potential. Such an oxide in a highly active state can react rapidly with the sultone compound in the non-aqueous electrolyte under a high temperature environment. Therefore, the positive electrode containing the lithium composite oxide powder described above can quickly form a protective film with a sultone compound on the surface when stored in a high temperature environment in a charged state, so that the oxidative decomposition reaction of the nonaqueous electrolyte Can be suppressed. As a result, since the amount of gas generated when the secondary battery is stored in a high temperature environment in a charged state can be reduced, it is possible to suppress battery swelling.

  Hereinafter, the positive electrode, the negative electrode, and the nonaqueous electrolyte will be described.

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

The reason why the molar ratio (X _Li / X _Co ) of lithium (X _Li ) to 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 of constituent elements (for example, oxides and hydroxides) and then firing in air or in an oxygen atmosphere. When the molar ratio (X _Li / X _Co ) is less than 1.02, the grain growth rate during firing is slow, and the crystallinity and orientation of the crystal are low, so the positive electrode potential reached a high potential by charging. Sometimes structural phase transition reactions are likely to occur. For this reason, the reactivity with a sultone compound may be inferior, and there is a fear that the amount of gas generated when stored in a high temperature environment in a charged state may increase. The upper limit of the molar ratio (X _Li / X _Co ) is desirably 1.1 for the reason described below.

When the molar ratio (X _Li / X _Co ) is greater than 1.1, there is a high possibility that the alkali melting does not proceed completely during firing of the positive electrode active material and Li remains. When this residual alkali content is large, it causes gelation of the binder and causes troubles during coating. A more preferable 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. There may be one kind of additive element or two or more kinds.

  The lithium composite oxide preferably accounts for 50% or more of the positive electrode active material.

The reason why the ratio (I ₀₀₃ / I ₁₀₄ ) of the peak intensity I ₀₀₃ on the ( ₀₀₃ ) plane and the peak intensity I ₁₀₄ on the (104) plane in powder X-ray diffraction is limited to the above range will be described. Those having a peak intensity ratio (I ₀₀₃ / I ₁₀₄ ) of less than 5 are low in crystallinity and crystal orientation, so that a structural phase transition reaction is likely to occur at a high potential, and the reactivity with a sultone compound is poor. There is a risk that the amount of gas generated when stored in a high temperature environment in a charged state will increase. A more preferable range of the peak intensity ratio (I ₀₀₃ / I ₁₀₄ ) is 7 or more. In addition, since the peak intensity ratio is greater than 500 and the peak derived from the (104) plane is not detected, it may have a crystal structure that does not occlude lithium, so the upper limit of the peak intensity ratio is 500 is desirable.

The reason why the particle size (D10) with a volume cumulative frequency of 10% of the lithium composite oxide is defined in the above range will be described. The lithium composite oxide powder having a peak intensity 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 has secondary agglomerated particles. There are few and is 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 decreases, so the rate of formation of the protective coating on the positive electrode surface becomes slow, and the gas when stored in a high temperature environment in a charged state The amount generated may increase. Moreover, 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 preferably 3 μm or less. In addition, when D10 is less than 0.1 μm, the ratio of particles having low crystallinity and crystal orientation is high due to insufficient grain growth during firing. There is a risk that the amount of gas generated will increase. Therefore, it is desirable that the lower limit value of D10 is 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 to each other. Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), polyethersulfone, ethylene-propylene-diene copolymer (EPDM), and styrene-butadiene rubber (SBR). be able to.

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

  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 produced, for example, by suspending a conductive agent and a binder in an appropriate 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 side or both sides of the current collector.

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

Examples of the carbonaceous material include graphite materials, carbonaceous materials such as graphite, coke, carbon fiber, spherical carbon, pyrolytic vapor phase carbonaceous material, and resin fired body; thermosetting resin, isotropic pitch, mesophase pitch, and the like. Graphite material obtained by performing heat treatment at 500 to 3000 ° C. on carbon-based carbon, mesophase pitch-based carbon fiber, mesophase microspheres, etc. (especially, mesophase pitch-based carbon fiber is preferable because of high capacity and charge / discharge cycle characteristics) or And carbonaceous materials. Among them, it is preferable to use a graphite material having a graphite crystal having a (002) plane spacing _d002 of 0.34 nm or less. A nonaqueous electrolyte secondary battery including a negative electrode containing such a graphite material as a carbonaceous material can greatly improve battery capacity and large current discharge characteristics. More preferably, the surface interval _d002 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), carboxymethyl cellulose (CMC), and the like. Can be used.

Mixing ratio of the carbonaceous material and the binder, carbonaceous material 90-98 wt%, is preferably in the range of the binder 2-20% by weight.

  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, kneaded with a carbonaceous material that occludes / releases lithium ions and a binder in the presence of a solvent, and the resulting suspension is applied to a current collector and dried, followed by a desired pressure. It is produced by pressing once or multistage pressing 2-5 times.

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

  In this electrode group, for example, (i) whether the positive electrode and the negative electrode are wound in a spiral shape 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) winding the positive electrode and the negative electrode in a spiral shape with a separator interposed therebetween, and then compressing in the radial direction, or (iv) bending the positive electrode and the negative electrode one or more times with a separator interposed therebetween, Or (v) It is produced by a method of 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 integrated strength of the positive electrode, the negative electrode, and the separator. It is also possible to heat at the time of pressing.

  The electrode group can contain an adhesive polymer in order to increase the integrated strength of the positive electrode, the negative electrode, and the separator. Examples of the adhesive polymer 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 film, a woven fabric, a non-woven fabric, a laminate of the same material or different materials among these can be used. Examples of the material for forming the separator include polyethylene, polypropylene, ethylene-propylene copolymer, and ethylene-butene copolymer. As a material for forming the separator, one type or two or more types selected from the types described above can be used.

  The thickness of the separator is preferably 30 μm or less, and more preferably 25 μm or less. Moreover, it is preferable that the lower limit of thickness is 5 micrometers, and a more preferable lower limit is 8 micrometers.

  The separator preferably has a heat shrinkage rate of 20% or less at 120 ° C. for 1 hour. The heat shrinkage rate is more preferably 15% or less.

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

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

  The width of the separator is desirably wider than the width of the positive electrode and the negative electrode. By adopting such a configuration, it is possible to prevent the positive electrode and the negative electrode from coming into direct contact without a separator.

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

  The nonaqueous solvent and electrolyte contained in the liquid nonaqueous electrolyte and the gel-like nonaqueous electrolyte will be described.

  The non-aqueous solvent includes a sultone compound 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 general formula shown in the following chemical formula 1 or at least one H of the sultone compound A is substituted with a hydrocarbon group The sultone compound B can be used. In the present application, sultone compound A or sultone compound B may be used alone, or both sultone compound A and 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.

  Since a sultone compound having at least one double bond in the ring opens a double bond by reaction with the positive electrode to cause a polymerization reaction, a lithium ion-permeable protective film can be formed on the surface of the positive electrode. Among the sultone compounds, a compound in which sultone compound A has m = 3 and n = 4, that is, 1,3-propene sultone (PRS), or a compound in which 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 very thick, the lithium ion permeability is lowered, and the discharge capacity at a temperature lower than room temperature is lowered. Furthermore, in order to keep the discharge capacity high even at a low temperature such as −20 ° C., the ratio of the sultone compound is desirably 4% or less. Further, in order to sufficiently secure the formation amount of the protective film, it is desirable to secure a sultone compound ratio of at least 0.01% by volume. Furthermore, when the ratio of the sultone compound is 0.1% by volume or more, the protective function by 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 EC content in the non-aqueous solvent is desirably in the range of 25% by volume to 50% by volume. As a result, a non-aqueous electrolyte having high conductivity and appropriate viscosity can be obtained. Further preferred EC content is in the range of 25% to 45% by volume.

  As the non-aqueous solvent, other solvents can be used in combination with the sultone compound and EC. Other solvents include, for example, chain carbonate {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), Examples include furan (F), thiophene (TIOP), catechol carbonate (CATC), ethylene sulfite (ES), 12-crown-4 (Crown), and tetraethylene glycol dimethyl ether (Ether). The type of the other solvent can be one type or two or more types.

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

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

  The liquid non-aqueous electrolyte may contain a surfactant such as trioctyl phosphate (TOP). The addition amount of the surfactant is preferably 3% or less, and more preferably in the range of 0.1 to 1%.

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

  The container in which the electrode group and nonaqueous electrolyte described above are stored will be described.

  The shape of the container can be, for example, a bottomed cylindrical shape, a bottomed rectangular tube shape, 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 of, for example, iron, stainless steel, or aluminum.

  The thicknesses of the metal plate and the metal film are desirably 0.4 mm or less, more preferably 0.3 mm or less, and most preferably 0.25 mm or less. Moreover, since there exists a possibility that sufficient intensity | strength may not be acquired when thickness is thinner than 0.05 mm, it is preferable that the lower limit of the thickness of a metal plate and a metal film shall be 0.05 mm.

  The resin layer contained in the film can be formed from, for example, polyolefin (for example, polyethylene, 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 arranged on both sides of the metal layer are integrated. The metal layer is responsible for blocking moisture and maintaining the shape of the container. Examples of the metal layer include aluminum, stainless steel, iron, copper, and nickel. Among these, 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, but may be formed from a combination of two or more types of metal layers. Of the two protective layers, the protective layer in contact with the outside serves to prevent damage to the metal layer. This external protective layer is formed of one type of resin layer or two or more types of resin layers. On the other hand, the internal protective layer plays a role of preventing the metal layer from being corroded by the non-aqueous electrolyte. This internal protective layer is formed of one type of resin layer or two or more types of resin layers. Moreover, the thermoplastic resin for sealing a container by heat seal can be distribute | arranged on the surface of this internal protective layer.

  The thickness of the film including the resin layer is desirably 0.3 mm or less, a more preferable range is 0.25 mm or less, a further preferable range is 0.15 mm or less, and a most preferable range is 0.12 mm or less. . Moreover, since it will become easy to deform | transform and damage when thickness is thinner than 0.05 mm, it is preferable that the lower limit of the thickness of a film shall be 0.05 mm.

A second non-aqueous electrolyte secondary battery according to the present invention is a non-aqueous electrolyte secondary battery comprising 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 mass % of lithium cobalt-containing composite oxide particles having a peak intensity ratio satisfying the following formula (C):
The positive electrode active material particles have a volume cumulative frequency 10% particle size (D10) of 0.1 μm or more and 4.5 μm or less, and the molar ratio of lithium and cobalt of the positive electrode active material particles satisfies the following formula (D):
The non-aqueous electrolyte contains a non-aqueous solvent containing 0.01% by volume to 10% by volume of a sultone compound having at least one double bond in the ring.

500 ≧ (I ₀₀₃ / I ₁₀₄ )> 5 (C)
1.02 ≦ (Y _Li / Y _Co ) ≦ 2 (D)
However, 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. 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 sides of the current collector and containing the positive electrode active material particles, a binder, and a conductive agent.

The reason why the molar ratio of lithium to cobalt (Y _Li / Y _Co ) in the positive electrode active material particles is specified in 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 the appropriate value, so that it is not possible to suppress battery swelling during high-temperature storage.

In particular, when the molar ratio of Co in the elements other than Li and O in the positive electrode active material is 0.9 or more and 1 or less, the molar ratio (Y _Li / Y _Co ) is set to 1.02 to 1.1. By making it into this range, the reactivity of the lithium cobalt-containing composite oxide particles with the sultone compound can be made higher, and the charge high-temperature storage characteristics can be made more excellent. In this case, the more preferable value of the 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 mass . In lithium cobalt-containing composite oxide particles having a peak intensity ratio greater 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 single particles tends to be high There is. Accordingly, when the particle size (D10) with a volume cumulative frequency of 10% of the positive electrode active material particles is larger than 4.5 μm, the reaction area of the positive electrode with the non-aqueous electrolyte decreases, so that the rate of formation of the protective film on the positive electrode surface is increased. There is a risk that the amount of gas generated when stored in a high temperature environment in a charged state is increased. Moreover, 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 preferably 3 μm or less. Further, when D10 is less than 0.1 μm, the ratio of particles having low crystallinity and crystal orientation becomes high, and there is a risk that the amount of gas generated when stored in a high temperature environment in a charged state may increase. Therefore, it is desirable that the lower limit value of D10 is 0.1 μm (more preferably 0.5 μm).

The higher the content of 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 of the positive electrode with the sultone compound. it can. Therefore, in order to sufficiently reduce the amount of gas generated when 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 60% by mass or more. More preferably, it is more preferably 70% by mass or more.

  The lithium cobalt-containing composite oxide particles 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. There may be one kind of additive element or two or more kinds. Among these, a composition represented by the following formula (E) is preferable.

_{Li a Co b M1 c O 2} (E)
However, M1 is one or more elements selected from the group consisting of Ni, Mn, B, Al and Sn, and the molar ratios a, b and c are 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, all the particles may not have the same composition, and if the peak intensity ratio is larger than 5, it may be composed of two or more kinds of particles having different compositions. good.

  Moreover, although the said positive electrode active material particle may be formed from the lithium cobalt containing complex oxide particle mentioned above, you may contain other particles other than lithium cobalt containing complex oxide particle.

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, it is possible to suppress peeling of the protective film from the surface of the positive electrode due to repeated expansion and contraction in the charge / discharge cycle. 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 the calculation, so the peak intensity ratio is 2 or more and less than 5. It is preferable. A more preferable range of the peak intensity ratio is greater than 2 and 4.95 or less.

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 The proportion in the particles is preferably in the range of 0.1 mass % or more and less than 50 mass %. A more preferable range is 0.5 to 48% by mass .

  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 kind of element different from the constituent elements can be added to each composite oxide. Examples of the additive element include Ni, Mn, Al, Sn, Fe, Cu, Cr, Zn, Mg, and Si. , P, F, Cl, B, and the like. Among these, a lithium-containing composite oxide having a composition represented by the following formula (F) is preferable.

Li _x Ni _y Co _z M 2 _w O ₂ (F)
However, M2 is one or more elements selected from the group consisting of Mn, B, Al and Sn, and the molar ratios x, y, z and w are 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 ratio x, y, z are 0.97 ≦ x ≦ 1.03, 0.75 ≦ y ≦ 0.9, and 0.1 ≦ z ≦ 0.25. A more preferable range of the molar ratio w is 0 ≦ w ≦ 0.07, a more preferable range is 0 ≦ w ≦ 0.05, and a most preferable range is 0 ≦ w ≦ 0.03. In order to sufficiently obtain the effect of adding the element M2, the lower limit value of the molar ratio w is preferably set to 0.001.

  In this lithium-containing composite oxide particle, not all particles may 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 kinds of particles having different compositions. Also good.

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

  The positive electrode is produced, for example, by suspending a conductive agent and a binder in an appropriate 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 second non-aqueous electrolyte secondary battery according to the present invention described above contains 50% by mass of lithium cobalt-containing composite oxide particles having a peak intensity ratio (I ₀₀₃ / I ₁₀₄ ) greater than 5. The sultone compound in the non-aqueous electrolyte in a high-temperature environment because D10 is 0.1 μm or more and 4.5 μm or less and the molar ratio (Y _Li / Y _Co ) is in the range of 1.02 to 2. It can react quickly. Therefore, when 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. As a result, since the amount of gas generated when the secondary battery is stored in a high temperature environment in a charged state can be reduced, it is possible to suppress battery swelling.

  A thin, square, and cylindrical nonaqueous electrolyte secondary battery as an example of the first and second nonaqueous 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 nonaqueous electrolyte secondary battery as an example of the nonaqueous electrolyte secondary battery according to the present invention, and FIG. 2 shows the thin nonaqueous electrolyte secondary battery of FIG. 1 along the short side direction. FIG. 3 is a cutaway partial sectional view, FIG. 3 is a partially cutaway perspective view showing a rectangular nonaqueous electrolyte secondary battery as an example of the nonaqueous electrolyte secondary battery according to the present invention, and FIG. 4 is a nonaqueous electrolyte secondary battery according to the present invention. It is a fragmentary sectional view which shows the cylindrical nonaqueous electrolyte secondary battery which is 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 nonaqueous electrolyte is held in the electrode group 2. A part of the edge of the container body 1 is wide and functions as the lid plate 6. The container body 1 and the cover plate 6 are each composed of a laminate film. The laminate film includes an external protective layer 7, an internal protective layer 8 containing a thermoplastic resin, and a metal layer 9 disposed between the external protective layer 7 and the internal protective layer 8. A lid 6 is fixed to the container body 1 by heat sealing using a 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, and each is pulled 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. In the electrode group 13, a positive electrode 14, a separator 15 and a negative electrode 16 are laminated in this order and wound in a flat shape. A spacer 17 having an opening near the center is disposed above the electrode group 13.

  The nonaqueous electrolyte is held in the electrode group 13. A sealing plate 18 b having an explosion-proof mechanism 18 a 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 disposed in a circular hole of the sealing plate 18b via a hermetic seal. The negative electrode tab 20 drawn 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 a container 12 that also serves as a positive electrode terminal.

  Next, a cylindrical nonaqueous electrolyte secondary battery will be described.

  A bottomed cylindrical container 21 made of stainless steel has an insulator 22 disposed at the bottom. The electrode group 23 is accommodated in the container 21. The electrode group 23 has a structure in which a belt-like material in which a positive electrode 24, a separator 25, a negative electrode 26, and a separator 25 are laminated is wound in a spiral shape so that the separator 25 is located outside.

  A nonaqueous electrolyte is accommodated in the container 21. An insulating paper 27 having an opening at the center is disposed above the electrode group 23 in the container 21. The insulating sealing plate 28 is disposed 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. 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 which is a negative electrode terminal through a negative electrode 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 ) shown in Table 1 below were prepared. The volume cumulative frequency 10% particle size D10 and the peak intensity ratio (I ₀₀₃ / I ₁₀₄ ) were measured by the method described below.

<Measurement of D10>
That is, the particle diameter of the lithium composite oxide particles and the occupied volume of 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 be 10% of the total was defined as the particle size with a volume accumulation frequency of 10%.

<Measurement of peak intensity ratio>
For the X-ray diffraction measurement, RINT2000 manufactured by Rigaku Denki Co., Ltd. was used. The test was performed under the following equipment conditions using Cu-Kα1 (wavelength: 1.5405 mm) as the 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 under the conditions of 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 defined as the (104) plane peak, and the peak at 2θ = 18.8 ° ± 0.1 ° was defined as the (003) plane peak. The peak intensity (cps) was obtained by subtracting the background from the measured value of the diffraction pattern expressed on the 2θ axis.

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

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

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

<Separator>
A separator made of a microporous polyethylene film 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 nonaqueous electrolyte was prepared by dissolving lithium hexafluorophosphate (LiPF ₆ ) in the obtained nonaqueous solvent so that the concentration thereof was 1 mol / L.

<Production of electrode group>
After the positive electrode lead made of a strip-shaped aluminum foil (thickness 100 μm) is ultrasonically welded to the positive electrode current collector, and the negative electrode lead made of a strip-shaped nickel foil (thickness 100 μm) is ultrasonically welded to the negative electrode current collector The positive electrode and the negative electrode were spirally wound through the separator therebetween, and then formed into a flat shape to produce an electrode group.

  The electrode group was stored in an aluminum square can having a wall thickness of 0.25 mm. Subsequently, the electrode group in the metal can was vacuum-dried at 80 ° C. for 12 hours to remove moisture contained in the electrode group and the metal can.

  Subsequently, the liquid nonaqueous electrolyte is injected into the electrode group in the metal can so that the amount per battery capacity 1Ah is 4.8 g, and the injection hole is sealed by welding, whereby the structure shown in FIG. A rectangular nonaqueous 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 nonaqueous electrolyte secondary battery was assembled in the same manner as described in Example 1 except that the composition of the nonaqueous electrolyte was changed as shown in Table 2 below.

  In Table 2, DEC represents diethyl carbonate, GBL represents γ-butyrolactone, PC represents propylene carbonate, and BTS represents 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 rectangular nonaqueous electrolyte secondary battery was assembled in the same manner as described in Example 1.

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

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

(Comparative Examples 6-8)
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 diameter D10 as shown in Table 3 below, A rectangular nonaqueous electrolyte secondary battery was assembled in the same manner as described in Example 1.

  About the obtained secondary battery of Examples 1-13 and Comparative Examples 1-8, the charge high temperature storage characteristic was evaluated on the conditions demonstrated below, and the result is shown in the following Table 2 and Table 4.

(Charge high temperature storage characteristics)
For each secondary battery, as an initial charge / discharge process, constant current / constant voltage charge was performed at room temperature at 0.2 C (130 mA) to 4.2 V for 15 hours, and then discharged at room temperature at 0.2 C to 3.0 V. .

  Next, the thickness of the battery container after charging at a charge rate of 1 C and a charge end voltage of 4.2 V and storing for 120 hours in an environment at a temperature of 80 ° C. is measured. The rate of change was determined.

{(T ₁ −t ₀ ) / t ₀ } × 100 (%) (2)
Where t ₀ is the thickness of the battery container just before storage, and t ₁ is the thickness of the battery container after 120 hours of storage.

As 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 containing a certain lithium composite oxide powder and a sultone compound having at least one double bond in the ring are expanded when stored in a charged state in an environment at 80 ° C. However, compared with the secondary battery of Comparative Examples 1-8, it can be understood that it is small.

The molar ratio (X _Li / X _Co ) of the secondary batteries of Comparative Examples 1 to 4 to which no sultone compound was added, the secondary battery of Comparative Example 5 using PS having no double bond as an additive, and Both the secondary batteries of Comparative Examples 6 and 7 having a peak intensity ratio (I ₀₀₃ / I ₁₀₄ ) of 5 or less and the secondary battery of Comparative Example 8 having a D10 exceeding 4.5 μm are less than 1.02. The battery swollen when stored in a charged state in an environment at 80 ° C. was as large as 4% or more.

(Example 14)
70% by mass 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 (D10 of 1.8 μm) by I ₀₀₃ / I ₁₀₄₎ is mixed with 30% by weight 50 of Li _1.05 Co _0.97 Sn _0.03 O ₂ particles (second active material particles), to obtain a positive electrode active material particles. The following table shows D10 of the obtained positive electrode active material particles, the molar ratio (Y _Li / Y _Co ) of the positive electrode active material particles, and the molar ratio of Co when the elements other than Li and O in the positive electrode active material are 1. As shown in FIG.

  A square nonaqueous 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)
The composition of the first positive electrode active material and the second positive electrode active material, the peak intensity ratio (I ₀₀₃ / I ₁₀₄ ) and D10, the mass ratio of the first positive electrode active material in the positive electrode active material, and the positive electrode active material The examples described above 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 shown in Table 5 below. A prismatic nonaqueous electrolyte secondary battery having the same configuration as described in 1 was obtained.

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

  Moreover, about Examples 14-18 and Example 1 mentioned above, the charging / discharging test of 1C of charge / discharge rates, 4.2V of charge end voltages, and the end-of-discharge voltage of 3.0V is done, and charge / discharge is carried out in the environment of temperature 20 degreeC. The discharge capacity retention ratio after repeating 500 times was calculated with the capacity of the first discharge as 100%, and the results are shown in Table 6 below.

As apparent from Tables 5 and 6, Examples 14 to 14 provided with positive electrodes each 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 ) greater than 5. In the battery No. 15, either the thickness change rate or the cycle maintenance rate is improved as compared with Example 1. And a positive electrode including a lithium cobalt-containing composite oxide having a peak intensity ratio (I ₀₀₃ / I ₁₀₄ ) of greater than 5 and a lithium-containing composite oxide having a peak intensity ratio of (I ₀₀₃ / I ₁₀₄ ) of less than 5. In the secondary batteries of Examples 16 to 18, the capacity retention rate at 500 cycles was higher than that of Example 1.

(PRS detection method)
For 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 decomposed | disassembled in the following glove boxes and took out the electrode group. The electrode group was put in a centrifuge tube, dimethyl sulfoxide (DMSO) -d ₆ was added and sealed, removed from the glove box, and centrifuged. Thereafter, a mixed solution of the electrolytic solution and the DMSO-d ₆ was collected from the centrifuge tube in the glove box. About 0.5 ml of the mixed solvent was put into a 5 mmφ NMR sample tube and subjected to NMR measurement. The apparatus used for the NMR measurement is JNM-LA400WB manufactured by JEOL Ltd., the observation nucleus is ¹ H, the observation frequency is 400 MHz, and the residual proton signal slightly contained in dimethyl sulfoxide (DMSO) -d ₆ is used as an internal reference. (2.5 ppm). The measurement temperature was 25 ° C. ^{In the 1} HNMR spectrum, the peak corresponding to EC is around 4.5 ppm, and the peak corresponding to PRS is around 5.1 ppm (P ₁ ), 7.05 ppm (P ₂ ) and 7. It was observed 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 ¹³ CNMR measurement was performed using an observation frequency of 100 MHz and dimethyl sulfoxide (DMSO) -d ₆ (39.5 ppm) as an internal reference substance, a peak corresponding to EC was around 66 ppm and a peak corresponding to PRS was 74 ppm. It was observed in the vicinity of 124 ppm and 140 ppm. From this result, it was confirmed that PRS was contained in the nonaqueous solvent present in the secondary battery of Example 1 after the initial charge / discharge process.

  The present invention is not limited to the above-described embodiments, and can be similarly applied to combinations of other types of positive electrode, negative electrode, separator, and container.

  Further, the present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

The perspective view which shows the thin nonaqueous electrolyte secondary battery which is an example of the nonaqueous electrolyte secondary battery concerning this invention. The fragmentary sectional view which cut | disconnected the thin nonaqueous electrolyte secondary battery of FIG. 1 along the short side direction. The partial notch perspective view which shows the square nonaqueous electrolyte secondary battery which is an example of the nonaqueous electrolyte secondary battery which concerns on this invention. The fragmentary sectional view which shows the cylindrical nonaqueous electrolyte secondary battery which is an example of the nonaqueous electrolyte secondary battery which concerns on this invention. FIG. 3 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 symbols

  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 terminal.

Claims (4)

In a non-aqueous electrolyte secondary battery comprising 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 size (D10) with a volume cumulative frequency of 10% of 0.1 μm or more and 4.5 μm or less, and (003) plane peak intensity I ₀₀₃ and (104) plane peak intensity in powder X-ray diffraction. the ratio (I ₀₀₃ / I ₁₀₄₎ greater than 5 with I _104, at 500, and the lithium composite oxide powder molar ratio of Li and _Co (X _Li / X Co) contains 1.02 to 2 More than 50% by weight ,
The non-aqueous electrolyte contains a non-aqueous solvent containing a sultone compound having at least one double bond in the ring in an amount of 0.01% by volume to 10% by volume . A non-aqueous electrolyte secondary battery comprising 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 mass % of lithium cobalt-containing composite oxide particles having a peak intensity ratio satisfying the following formula (1):
The positive electrode active material particles have a volume cumulative frequency 10% particle size (D10) of 0.1 μm or more and 4.5 μm or less, and the molar ratio of lithium and cobalt of the positive electrode active material particles satisfies the following formula (2):
The non-aqueous electrolyte contains a non-aqueous solvent containing a sultone compound having at least one double bond in the ring in an amount of 0.01% by volume to 10% by volume .
500 ≧ (I ₀₀₃ / I ₁₀₄ )> 5 (1)
1.02 ≦ (Y _Li / Y _Co ) ≦ 2 (2)
However, 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. 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 contain lithium-containing composite oxide particles having a peak intensity ratio satisfying the following formula (3).
2 ≦ (I ₀₀₃ / I ₁₀₄ ) <5 (3)
However, I ₀₀₃ in the lithium-containing composite oxide peak intensity of (003) plane in a powder X-ray diffraction of the particles (cps), I ₁₀₄ is a peak intensity of the powder in the X-ray diffraction (104) plane (cps) is there.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the sultone compound is composed of at least one of 1,3-propene sultone and 1,4-butylene sultone.

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