JP4029266B2 - Nonaqueous electrolyte battery and method for producing nonaqueous electrolyte battery - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a non-aqueous electrolyte battery and a method for producing a non-aqueous electrolyte battery.
[0002]
[Prior art]
In recent years, electronic devices such as portable radio telephones, portable personal computers, and portable video cameras have been developed, and various electronic devices have been miniaturized to the extent that they can be carried. Accordingly, a battery having a high energy density and a light weight has been adopted as a built-in battery.
[0003]
A typical battery that satisfies such a requirement uses metallic lithium, a lithium alloy, or carbon capable of reversibly occluding and releasing lithium as a negative electrode active material and using a positive electrode active material capable of reversibly occluding and releasing lithium. LiClO₄, LiPF₆And a non-aqueous electrolyte secondary battery using an aprotic organic solvent in which a lithium salt is dissolved as an electrolyte.
[0004]
In particular, carbon is used as the negative electrode active material, and LiCoO as the positive electrode active material.₂LiNiO₂Or LiMn₂O₄Is suitable for practical use because of its excellent charge / discharge cycle life. LiCoO₂LiNiO₂And LiMn₂O₄The average discharge potential of the positive electrode active material is Li / Li⁺All are 4V or less by reference.
[0005]
In order to further increase the energy density of the battery, Li / Li⁺LiNi with a discharge potential of 4.7 V on the basis_0.5Mn_1.5O₄Attempts have been made to apply a positive electrode active material to a lithium battery (Special Table 2000-515672, Summary of the 41st Battery Discussion Meeting p450, 452, 454, 456 (2000), etc.).
[0006]
The positive electrode and the negative electrode of the non-aqueous electrolyte are both formed into a thin sheet or foil, and are sequentially laminated or spirally wound through a separator. And this laminated body or wound body is housed in a battery container made of a metal can such as stainless steel, nickel-plated iron, or aluminum, and after injecting the electrolyte solution, hermetically sealed with a lid plate, The battery is assembled.
[0007]
In addition, a method using a battery container made of a metal foil laminated with a resin film is also applied. By this method, there is no leakage of the electrolyte solution or intrusion of moisture or the like from the outside of the battery, and the battery can be reduced in weight.
[0008]
A liquid electrolyte is usually used for such a non-aqueous electrolyte battery, but lithium ion conductive glass is used instead of the electrolyte for the purpose of preventing leakage of the electrolyte and improving the safety of the battery. It has been attempted (DENKI KAGAKU 65 (1997) p914). In addition, it has been attempted to produce a lithium ion conductive thin film by a sol-gel method (Journal of the Chemical Society of Japan (1987) No. 11, p1958).
[0009]
Furthermore, for the purpose of eliminating the need for a binder in the electrode, an attempt has been made to coat active material particles with lithium ion conductive glass using a sol-gel method (Japanese Patent Laid-Open No. 2000-311692). In addition, production of an all-solid glass electrolyte lithium secondary battery that does not use any electrolytic solution has been attempted (technology of the latest secondary battery material, supervision: Zenkachi Okumi, CMC, p138-151).
[0010]
[Problems to be solved by the invention]
A nonaqueous electrolyte battery such as a lithium ion battery has a high voltage because the potential of the positive electrode is very noble and the potential of the negative electrode is very base. Therefore, there has been a problem that the battery is easily swelled by a gas generated by the decomposition of the electrolytic solution because the electrolytic solution is oxidatively decomposed at the positive electrode and reductively decomposed at the negative electrode, and self-discharge tends to occur. These problems were particularly remarkable when the battery was left at high temperature.
[0011]
In a conventional battery in which active material particles are coated with lithium ion conductive glass, a conductive material that provides electronic conductivity between the active material particles is not covered with lithium ion conductive glass. Therefore, the oxidation or reductive decomposition of the electrolytic solution at the interface between the conductive material and the electrolytic solution could not be suppressed.
[0012]
The glass electrolyte has a lower ionic conductivity than the non-aqueous electrolyte. In an all-solid glass electrolyte lithium secondary battery, all lithium ion conduction between the positive and negative electrodes must be carried by the glass electrolyte. Therefore, the all-solid glass electrolyte battery has a problem in that charge and discharge at a high rate cannot be performed because of a large IR drop.
[0013]
The present invention has been made in view of the above problems, and by suppressing the decomposition of the electrolyte solution at the positive electrode or the negative electrode, the self-discharge and the swelling of the battery when left at high temperature are suppressed. The present invention provides a nonaqueous electrolyte battery having excellent charge / discharge performance.
[0014]
[Means for Solving the Problems]
  The invention of claim 1The general formula as the positive electrode active material is Li _x Ni _y Mn _2-y O ₄ Lithium-containing composite oxide (0 ≦ x ≦ 1, 0.45 ≦ y ≦ 0.6)And conductive materialPositive electrode,Negative electrodeAnd a non-aqueous electrolyte battery comprising a non-aqueous electrolyte,Positive electrodeIn a state where electronic conduction between the active material particles is maintained by the conductive material,Positive electrodeAt least a part of the surface of the active material particles and the conductive material is covered with lithium ion conductive glass.
[0015]
According to the invention of claim 1, by suppressing the decomposition of the electrolyte solution at the positive electrode or the negative electrode, the self-discharge and the swelling of the battery when left at high temperature are suppressed, and at the same time, the charge / discharge performance at a high rate is immediately improved. A non-aqueous electrolyte battery is obtained.
[0016]
  In the present inventionIn the non-aqueous electrolyte battery, the lithium ion conductive glass is an oxide.Is preferred.
[0017]
  In the present invention, when the lithium ion conductive glass is an oxide,Unlike the case of sulfide, since lithium ion conductive glass is stable against moisture in the air, it is not necessary to manufacture electrodes in a low dew point atmosphere, and the manufacturing cost of the battery can be reduced.
[0018]
  In the present invention, in the non-aqueous electrolyte battery,As positive electrode active materialAnd the general formula is Li_xNi_yMn_2-yO₄Lithium-containing composite oxide satisfying (0 ≦ x ≦ 1, 0.45 ≦ y ≦ 0.6)It is characterized by using.
[0019]
  In the present invention, the positive electrode active materialAsThe general formula is Li_xNi_yMn_2-yO₄Lithium-containing composite oxide satisfying (0 ≦ x ≦ 1, 0.45 ≦ y ≦ 0.6)UseAs a result, since the potential of the positive electrode is noble, the battery voltage becomes high, and a battery with high energy density can be obtained. Since the present invention can suppress the decomposition of the electrolytic solution by covering with lithium ion conductive glass, it is particularly effective in the case where the electrolytic solution is likely to be decomposed because the potential of the positive electrode is noble.
[0020]
  In the present inventionIn the above non-aqueous electrolyte battery, a polymer electrolyte is provided between the active material particles coated with the lithium ion conductive glass.Preferably.By providing a polymer electrolyte between the active material particlesEven when the active material particles expand and contract by volume due to charge and discharge, the lithium ion conductive glass is less likely to be peeled off.
[0021]
  In the present inventionThe polymer electrolyte is a porous polymer electrolyteIs preferred.
[0022]
  When the polymer electrolyte is a porous polymer electrolyte,, Polymer electrolyteofSince ions can diffuse quickly through the electrolytic solution in the hole, the battery has excellent high rate charge / discharge performance.
[0023]
  The invention of claim 2The general formula as the positive electrode active material is Li _x Ni _y Mn _2-y O ₄ Lithium-containing composite oxide (0 ≦ x ≦ 1, 0.45 ≦ y ≦ 0.6)And conductive materialPositive electrode,Negative electrodeAnd a method for producing a non-aqueous electrolyte battery comprising a non-aqueous electrolyte, comprising:Positive electrodeProvided with active material particles and the conductive materialPositiveAfter making the pole,Positive electrodeThe active material particles and the conductive material are covered with lithium ion conductive glass.
[0024]
  Claim2According to the invention, both the active material particles and the conductive material can be covered with the lithium ion conductive glass while the electronic conduction between the active material particles is maintained well by the conductive material.
[0025]
  In the present inventionUses a sol-gel method in the process of coating the active material particles and the conductive material with the lithium ion conductive glass in the method for manufacturing a non-aqueous electrolyte battery.Is preferred.
[0026]
  By using the sol-gel methodThe active material particles and the conductive material can be coated with the lithium ion conductive glass sufficiently and evenly within the active material layer of the electrode and uniformly throughout the electrode.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
  The present inventionThe general formula as the positive electrode active material is Li _x Ni _y Mn _2-y O ₄ Lithium-containing composite oxide (0 ≦ x ≦ 1, 0.45 ≦ y ≦ 0.6)And conductive materialPositive electrode,Negative electrodeAnd a non-aqueous electrolyte battery comprising a non-aqueous electrolyte,Positive electrodeIn a state where electronic conduction between the active material particles is maintained by the conductive material,Positive electrodeAt least a part of the surface of the active material particles and the conductive material is covered with lithium ion conductive glass.
[0028]
A nonaqueous electrolyte battery such as a lithium ion battery has a high voltage because the potential of the positive electrode is very noble and the potential of the negative electrode is very base. Therefore, there has been a problem that the battery is easily swelled by a gas generated by the decomposition of the electrolytic solution because the electrolytic solution is oxidatively decomposed at the positive electrode and reductively decomposed at the negative electrode, and self-discharge tends to occur. These problems were particularly remarkable when the battery was left at high temperature.
[0029]
On the other hand, in a conventional battery in which active material particles are coated with lithium ion conductive glass, a conductive material that provides electronic conductivity between the active material particles is not covered with lithium ion conductive glass. Therefore, the oxidation or reductive decomposition of the electrolytic solution at the interface between the conductive material and the electrolytic solution could not be suppressed.
[0030]
In the present invention, the electrolytic solution is not exposed to the potential of the positive electrode or the negative electrode by covering at least part of the surfaces of both the active material particles and the conductive material with lithium ion conductive glass. Therefore, since oxidative decomposition of the electrolytic solution by the positive electrode or reductive decomposition by the negative electrode is suppressed, battery swelling and self-discharge due to gas generated by the decomposition of the electrolytic solution are suppressed.
[0031]
Therefore, in the present invention, it is sufficient that at least a part of the surface of the active material particles and the conductive material is covered with lithium ion conductive glass, but the surface area of the active material particles and the conductive material that contacts the electrolyte solution is 100. % Is preferably coated with lithium ion conductive glass.
[0032]
The glass electrolyte has a lower ionic conductivity than the non-aqueous electrolyte. In an all-solid glass electrolyte lithium secondary battery, all lithium ion conduction between the positive and negative electrodes must be carried by the glass electrolyte. Therefore, the all-solid glass electrolyte battery has a problem in that charge and discharge at a high rate cannot be performed because of a large IR drop.
[0033]
In the present invention, since the non-aqueous electrolyte is provided, the resistance of the electrolyte between the positive electrode and the negative electrode can be made smaller than that of the all solid state battery. Therefore, the IR drop does not increase even in charge / discharge at a high rate, and the battery has excellent high rate charge / discharge performance. The battery according to the present invention is particularly effective when the non-aqueous electrolyte penetrates into the pores of the electrode. By doing so, most of the lithium ion conduction between the positive and negative electrodes is carried by the non-aqueous electrolyte, and a battery with excellent high rate charge / discharge performance can be obtained.
[0034]
In the present invention, it is important that the active material particles and the conductive material are covered with the lithium ion conductive glass not only on the electrode surface but also inside the active material layer, and in the deepest part of the active material layer. In addition, it is important that the active material particles and the conductive material are coated with lithium ion conductive glass.
[0035]
Lithium ion conductive glass mainly includes oxide type and sulfide type. The latter is intensively researched because it tends to exhibit higher ionic conductivity than the former, but it reacts with trace moisture in the air to release toxic hydrogen sulfide gas. It is difficult to use it.
[0036]
One aspect of the present invention uses an oxide-based lithium ion conductive glass covering the active material particles and the conductive material. Since this oxide-based glass is stable against moisture, it can be easily used industrially. Further, the resistance value of the electrolyte increases in proportion to its thickness.
[0037]
In the present invention, the lithium ion conductive glass is used as a thin film covering the active material particles and the conductive material, so that the ion conductivity as high as that of the sulfide glass is not necessary. Therefore, the battery according to the present invention can provide sufficient performance even when oxide-based glass is used.
[0038]
However, the lithium ion conductive glass used in the present invention is not limited to an oxide-based one, and the following materials are used alone, or two or more kinds of compounds are mixed or dissolved. May be used. Li_{1 + x}Zr₂Si_xP_3-xO₁₂Or Li_{1 + x}Zr_{2-x / 3}Si_xP_3-xO_{12-2x / 3}(1.5 <x <2.2), Li_{1 + x}M_xTi_2-x(PO₄)₃(M = Al, Sc, Y, or La, 0 ≦ x <2), Li_0.5-3xM_{0.5 + x}TiO₃(M = La, Pr, Nd, or Sm, 0 ≦ x ≦ 1/6), Li₂SO₄, Li₄SiO₄, Li₃PO₄, Li₄GeO₄, Li₃VO₄, Li₂MoO₄, Li₄ZrO₄, Li₂CO₃, Li₂O, SiO₂, ZrO₂, V₂O₅, P₂O₅, B₂O₃, Al₂O₃TiO₂, Zn₂GeO₄, Li₂S, SiS₂, Li₂Se, SiSe₂, B₂S₃, P₂S₅, GeS₂, LiI, LiW₂O₇LiNbO₃. Among these, Li₂O and SiO₂, B₂O₃Or P₂O₅An amorphous glass containing is particularly preferred in the present invention.
[0039]
It has been reported that when lithium ion conductive glass is manufactured using the sol-gel method, organic substances remain in the glass depending on the heating temperature after film formation (Journal of Chemical Society of Japan (1987) No. 11, p1958). The lithium ion conductive glass described in the present specification includes those containing such organic substances.
[0040]
Further, the lithium ion conductive glass used in the present invention may be crystalline glass or amorphous glass. However, since there is no grain boundary and the ionic conduction of the whole film is excellent, and there is no directionality in the ionic conduction, it is preferable to use amorphous glass in the present invention.
[0041]
In the present invention, if the lithium ion conductive glass covering the active material particles and the conductive material is too thick, the internal resistance of the battery is increased, and if it is too thin, oxidation or reductive decomposition of the electrolyte solution by the positive electrode or the negative electrode cannot be sufficiently suppressed. . Therefore, the thickness of the lithium ion conductive glass in the present invention is desirably 5 nm or more and 5 μm or less. More preferably, the thickness is 20 nm or more and 1 μm or less.
[0042]
In the present invention, the lithium ion conductive glass covering the active material particles and the conductive material preferably has as low an electronic conductivity as possible and as high a lithium ion conductivity as possible. In particular, the electronic conductivity is 1 × 10^-10S / cm or less, lithium ion conductivity is 1 × 10^-10S / cm or more is preferable. Furthermore, the lithium ion conductivity is preferably 100 times or more higher than the electronic conductivity.
[0043]
Polymer electrolytes such as polyethers in which lithium salts are dissolved are difficult to apply to practical batteries because of insufficient lithium ion conductivity. Therefore, an attempt has been made to apply a gel polymer electrolyte obtained by swelling a polymer with an electrolyte to a battery. Even when the active material particles and the conductive material are coated with such a gel-like polymer electrolyte, the contact area between the active material and the conductive material and the free electrolytic solution is reduced. Or reductive decomposition by the negative electrode is suppressed. However, in this case, since the electrolytic solution penetrates into the polymer electrolyte, the contact between the active material and the conductive material and the electrolytic solution cannot be completely blocked.
[0044]
In contrast, in the present invention, the active material particles and the conductive material are coated using lithium ion conductive glass into which the electrolyte does not penetrate. Therefore, in the present invention, it is possible to completely block the contact between the active material particles and the conductive material and the electrolytic solution. As a result, the present invention can more reliably suppress oxidative decomposition of the electrolytic solution by the positive electrode or reductive decomposition by the negative electrode.
[0045]
  In the present invention, it is coated with lithium ion conductive glass.Positive electrodeThe active material particles have the general formula Li_xNi_yMn_2-yO₄Lithium-containing composite oxide (0 ≦ x ≦ 1, 0.45 ≦ y ≦ 0.6)It is characterized by. This lithium-containing composite oxide has 4.7 V vs. Li / Li⁺Because of this very noble charge / discharge potential, the electrolyte solution is very susceptible to oxidative decomposition when the present invention is not applied. In the present invention,Positive electrodeBy coating both the active material particles and the conductive material with lithium ion conductive glass, the electrolytic solution is not exposed to the potential of the positive electrode. Therefore, 4.7V vs. Li / Li⁺Even when an active material having a very noble charge / discharge potential is used for the positive electrode, oxidative decomposition of the electrolytic solution is suppressed. That is, the present invention is coated with lithium ion conductive glass.Positive electrodeThe active material particles have the general formula Li_xNi_yMn_2-yO₄Lithium-containing composite oxide (0 ≦ x ≦ 1, 0.45 ≦ y ≦ 0.6)IsIn some cases, it is particularly effective.
[0046]
Furthermore, the general formula is Li_xNi_yMn_2-yO₄It has been reported that the lithium-containing composite oxide satisfying (0 ≦ x ≦ 1, 0.45 ≦ y ≦ 0.6) has a problem of elution of manganese into the electrolyte (41st Battery Discussion) Meeting summary p450 (2000). In the present invention, this lithium-containing composite oxide is coated with lithium ion conductive glass. Since manganese ions are larger than lithium ions, they cannot pass through lithium ion conductive glass. Therefore, elution of manganese from the active material particles is suppressed. As a result, the present invention provides a battery having excellent charge / discharge cycle performance and high-temperature storage performance.
[0047]
Further, manganese eluted from the positive electrode is deposited on the negative electrode and degrades the negative electrode. Therefore, the general formula is Li as a positive electrode active material._xNi_yMn_2-yO₄When a lithium-containing composite oxide satisfying (0 ≦ x ≦ 1, 0.45 ≦ y ≦ 0.6) is used, not only the positive electrode but also the negative electrode active material particles should be covered with lithium ion conductive glass. Is effective. By doing so, precipitation of manganese eluted from the positive electrode to the negative electrode is suppressed, and a battery having excellent charge / discharge cycle performance and high-temperature storage performance can be obtained.
[0048]
In the present invention, Li used for the positive electrode active material_xNi_yMn_2-yO₄(0 ≦ x ≦ 1, 0.45 ≦ y ≦ 0.6) does not mean that the ratio of the sum of the number of moles of nickel and manganese and the number of moles of oxygen is strictly limited to 2: 4. , Including oxygen atoms that are excessive or deficient. In addition, nickel or manganese partially substituted with other elements such as cobalt, iron, chromium, zinc, aluminum, vanadium, and the like are also included.
[0049]
If the value of y of the positive electrode active material is within the range of 0.45 ≦ y ≦ 0.6, 4.7 V vs. Li / Li⁺When the region is used for charging and discharging, a practical discharge capacity can be obtained.
[0050]
Further, the value of x of the positive electrode active material uses a range of 0 ≦ x ≦ 1 in the process of actually charging and discharging the battery. Accordingly, when the battery is assembled, the value of x may be larger than 1 and discharge may be performed to a range where x is larger than 1, but the voltage is low and the practical meaning is lost.
[0051]
The general formula used in the present invention is Li_xNi_yMn_2-yO₄As a typical example of the positive electrode active material satisfying (0 ≦ x ≦ 1, 0.45 ≦ y ≦ 0.6), the crystal structure is changed by charge / discharge reaction as described in JP-T-2000-515672. In other words, those having a spinel structure having a small volume change and a small decrease in capacity when charging and discharging are repeated and having a lattice constant of 8.190 angstroms or less are mentioned.
[0052]
  In the present invention, it is coated with lithium ion conductive glass.Positive electrodeA polymer electrolyte is provided between the active material particlesRuIt is preferable. Normal,Positive electrodeSince the active material particles expand and contract by volume due to charge and discharge, there may be a problem that the lithium ion conductive glass covering the particles peels off. In the present invention,Positive electrodeBy providing the polymer electrolyte between the active material particles, the lithium ion conductive glass is pressed against the active material particles, and peeling is less likely to occur. Therefore, even after the charge / discharge cycle,At the positive electrodeThe decomposition of the electrolytic solution is suppressed, and the self-discharge and the swelling of the battery when left at high temperature are suppressed.
[0054]
Polymers used in the present invention include polymers of vinylidene fluoride and hexafluoropropylene, polyethers such as polyethylene oxide and polypropylene oxide, polyacrylonitrile, polyvinylidene fluoride, polyvinyl chloride, poly Use vinylidene chloride, polymethyl methacrylate, polymethyl acrylate, polyvinyl alcohol, polymethacrylonitrile, polyvinyl acetate, polyvinyl pyrrolidone, polyethyleneimine, polybutadiene, polystyrene, polyisoprene, or derivatives thereof alone or in combination. Also good. Moreover, you may use the polymer which copolymerized the various monomers which comprise the said organic polymer. However, since it is excellent in oxidation resistance, fluororesins such as polyvinylidene fluoride and P (VdF / HFP) are particularly suitable for the present invention.
[0055]
  The present inventionUsed inThe porous polymer electrolyte is a polymer porous body in which a polymer portion other than pores is an electrolyte having lithium ion conductivity. Since a high lithium ion diffusion coefficient can be obtained by retaining the organic electrolyte in these pores, batteries using porous polymer electrolytes are much better than those using pore-free polymer electrolytes. High rate discharge performance.
[0056]
In this case as well, as in the case of using a polymer electrolyte without pores, the lithium ion conductive glass is pressed against the active material particles, and peeling does not easily occur. Therefore, even after the charge / discharge cycle, the decomposition of the electrolyte solution at the positive electrode or the negative electrode is suppressed, and the self-discharge and swelling of the battery when left at high temperature are suppressed.
[0057]
In addition, the method for making the porous polymer electrolyte provided in the electrode may be any of a stretching method, a solvent extraction method, a method using a foaming agent, a method of adhering powder, and a method of depositing a solid in a film. . However, since the polymer can be easily made into a three-dimensional continuous porous body, the solvent extraction method is particularly excellent.
[0058]
The solvent extraction method is a method for obtaining a porous solid polymer by using a first solvent that dissolves the solid polymer and a second solvent for extraction that extracts the first solvent from the solid polymer solution. A solid polymer solution in which a solid polymer is dissolved in a first solvent is immersed in a second solvent compatible with the first solvent, whereby the first solvent is removed from the solid polymer solution. The portion of the solid polymer from which the first solvent has been removed becomes pores to form a porous solid polymer. And by this wet method, a through-hole having a circular opening can be formed in the solid polymer.
[0059]
The porosity of the porous polymer in the present invention is desirably 25% to 90%, and the pore diameter is preferably 0.003 μm or more and 10 μm or less. When the polymer is highly porous, when the electrode is observed with an electron microscope or the like, the polymer is observed as a network rather than porous. In this case as well, the porous polymer described in this specification Shall be included.
[0060]
In the conventional method of preparing an electrode after previously coating active material particles with lithium ion conductive glass, the electron conductivity of lithium ion conductive glass is poor, so that the electron conduction network between the active material particles is sufficient. Could not be formed. Furthermore, the conductive material could not be covered with lithium ion conductive glass.
[0061]
  The invention of claim 2,The general formula as the positive electrode active material is Li _x Ni _y Mn _2-y O ₄ Lithium-containing composite oxide (0 ≦ x ≦ 1, 0.45 ≦ y ≦ 0.6)And conductive materialPositive electrode,Negative electrodeAnd a method for producing a non-aqueous electrolyte battery comprising a non-aqueous electrolyte, comprising:Positive electrodeProvided with active material particles and the conductive materialPositive electrodeAfter producingPositive electrodeThe active material particles and the conductive material are covered with lithium ion conductive glass. In this manufacturing method, conductive material andPositive electrodeSince the coating with lithium ion conductive glass is performed while maintaining direct contact with the active material particles, sufficientPositive electrodeAn electron conduction network between the active material particles is obtained. further,Positive electrodeThe active material particles and the conductive material can be simultaneously coated with lithium ion conductive glass.
[0062]
As a method for producing the nonaqueous electrolyte battery according to the present invention, the sol-gel method is excellent. The sol-gel method uses a metal organic or inorganic compound as a solution, advances hydrolysis and polycondensation of the compound in the solution to solidify the sol as a gel, and produces an oxide solid by heating the gel. Is the method. When this method is used, the electrode is immersed in a solution such as a metal alkoxide so that the solution is infiltrated into the hole of the electrode, and then the electrode is pulled up from the solution and heated to deepen the active material layer. Evenly, the active material particles and the conductive material can be covered with the lithium ion conductive glass.
[0063]
In the nonaqueous electrolyte battery according to the present invention, as a short-circuit prevention film used between the positive and negative electrodes, polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, polyethylene, polypropylene, polyethylene and polypropylene, A laminate or the like can be used. In addition, in the case where a short circuit between the positive electrode and the negative electrode is prevented by the polymer film applied to at least one of the positive electrode and the negative electrode, it is not necessary to use a short-circuit preventing film.
[0064]
As the electrolyte solution solvent of the nonaqueous electrolyte battery in the present invention, ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, γ-butyrolactone, sulfolane, dimethyl sulfoxide, acetonitrile, dimethylformamide, dimethylacetamide, Polar solvents such as 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dioxolane, methyl acetate and the like may be used alone, or a mixture thereof.
[0065]
Furthermore, as a salt contained in the non-aqueous electrolyte, LiPF₆, LiBF₄, LiAsF₆LiClO₄, LiSCN, LiI, LiCF₃SO₃, LiCl, LiBr, LiCF₃CO₂, LiPF₃(C₂F₅)₃Or LiN (C₂F₅SO₂)₂A lithium salt such as, or a mixture thereof may be used. Among these salts, LiBF has excellent oxidation resistance and does not dissolve glass.₄And the organic lithium salt is excellent.
[0066]
Furthermore, in the present invention, when vinylene carbonate, vinyl ethylene carbonate or pyridine is contained in the electrolytic solution, the charge / discharge cycle life performance at a particularly high temperature is excellent.
[0068]
Furthermore, as the negative electrode material of the non-aqueous electrolyte battery in the present invention, MCMB, flaky graphite, massive graphite, non-graphitizable carbon, low crystalline carbon, low-temperature calcined carbon, etc., which are spherical graphite, can be used. Also, alloys of Al, Si, Pb, Sn, Zn, Cd, Ge, etc. and lithium, alloys of Sn, Co and Li, LiFe₂O₃Transition metal complex oxides such as MoO₂, Transition metal oxides such as tin oxide, silicon oxides such as SiO, Li₅(Li₃N) or the like, or a metal lithium foil, or a mixture thereof may be used.
[0069]
【Example】
Hereinafter, a preferred embodiment of the present invention will be described.
[0070]
[Example 1]
LiNi_0.5Mn_1.5O₄70 wt%, acetylene black 6 wt% as a conductive material, polyvinylidene fluoride (PVdF) 9 wt% as a binder, and NMP 15 wt% as a solvent for dissolving the binder 120 mm in width and length It was applied onto an aluminum foil having a thickness of 500 mm and a thickness of 20 μm, and dried at 150 ° C. to evaporate NMP. After performing the above operation on both sides of the aluminum foil, pressing was performed to manufacture a positive electrode plate having a mixture layer containing an active material on both sides.
[0071]
The positive electrode active material particles and the conductive material thus produced were coated with lithium ion conductive glass using a sol-gel method. The method is specifically shown below. Lithium metal and a stoichiometric amount of 20 times anhydrous methanol were reacted by reflux in a flask filled with dry nitrogen, and LiOCH₃Was synthesized.
[0072]
Here, an amount of P (OCH calculated so that the molar ratio of Li, P, and Si is 77: 14: 9.₃)₃And Si (OC₂H₅)₄And allowed to react for about 1 hour with sufficient agitation. The positive electrode plate was immersed in the solution thus prepared, and the pressure was reduced to 0.1 Torr and the pressure was increased to atmospheric pressure five times, and the solution was infiltrated into the positive electrode holes. Thereafter, the positive electrode plate was pulled up from the solution and dried by leaving it in a dry box for 12 hours. In this way, the active material particles and the conductive material in the positive electrode were covered with the gel thin film.
[0073]
Further, by heating the positive electrode plate at 300 ° C. for 10 hours, the gel thin film coated with the active material particles and the conductive material was changed to Li₃PO₄And Li₄SiO₄A lithium ion conductive amorphous glass thin film in which a solid solution was formed in a molar ratio of 6: 4.
[0074]
An active material paste in which MCMB 81 wt%, PVdF 9 wt%, and NMP 10 wt%, which is spherical graphite, was applied onto a copper foil having a width of 120 mm, a length of 500 mm, and a thickness of 10 μm, and dried at 150 ° C. to evaporate NMP. After performing this operation on both sides of the copper foil, pressing was performed to manufacture a negative electrode plate having a mixture layer containing an active material on both sides.
[0075]
The positive electrode plate and the negative electrode plate thus prepared are overlapped and wound with a polyethylene film, which is a continuous porous body having a porosity of 40%, interposed therebetween, and the height is 47.0 mm, the width is 22.2 mm, and the thickness is 6.4 mm. Was inserted into an aluminum container, and a prismatic battery was assembled. In this battery, ethylene carbonate and dimethyl carbonate were mixed at a volume ratio of 3: 7, and 1.5 mol / l LiBF was mixed.₄Was added by vacuum injection, and the electrolyte was infiltrated into the holes of the positive electrode, the negative electrode, and the separator. In this way, a battery (A) according to the present invention having a design capacity of 500 mAh was produced.
[0076]
Next, a conventionally known comparative battery (B) is prepared in the same manner as the battery (A) according to the present invention, except that the positive electrode active material particles and the conductive material are not coated with lithium ion conductive glass. Produced.
[0077]
Using the battery (A) and the comparative battery (B) according to the present invention manufactured as described above, the battery is charged to 4.9 V at a current of 0.5 CmA at 25 ° C., and then at a constant voltage of 4.9 V. After charging for 5 hours, the initial discharge capacity was measured by discharging to 3.5 V with a current of 0.2 CmA. Further, at 25 ° C., the battery was charged to 4.9 V at a current of 0.5 CmA, subsequently charged at a constant voltage of 4.9 V for 5 hours, then left at 60 ° C. for 24 hours, and then at 25 ° C., 0.2 CmA of 0.2 CmA Discharge to 3.5V with current. Table 1 shows the initial capacity, the capacity after standing at 60 ° C., and the amount of increase in battery thickness due to standing at 60 ° C.
[0078]
[Table 1]
[0079]
From Table 1, it was found that the battery (A) according to the present invention was less subject to a decrease in capacity and an increase in battery thickness when left at 60 ° C. than the comparative battery (B). This is because the active material particles and the conductive material of the positive electrode were coated with lithium ion conductive glass, so that the electrolytic solution was not exposed to the potential of the active material particles and the conductive material, and the oxidative decomposition of the electrolytic solution was suppressed. This is probably because self-discharge was suppressed. As a result, the amount of gas generated by the decomposition of the electrolytic solution is also reduced, and it is considered that the increase in battery thickness is suppressed.
[0080]
  [Reference example]
  LiNi as positive electrode active material particles_0.5Mn_1.5O₄Instead of LiNi_0.8Co_0.2O₂A positive electrode plate was produced in the same manner as in the battery (A) according to the present invention in Example 1, except that powder was used. In addition,Reference exampleIn, the positive electrode active material particles and the conductive material were not coated with lithium ion conductive glass.
[0081]
An active material paste in which SiO powder 70 wt%, acetylene black 6 wt%, PVdF 9 wt% and NMP 15 wt% are mixed is applied onto a copper foil having a width of 120 mm, a length of 500 mm, and a thickness of 10 μm, and dried at 150 ° C. to evaporate NMP. It was. After performing this operation on both sides of the copper foil, pressing was performed to manufacture a negative electrode plate having a mixture layer containing an active material on both sides.
[0082]
In the negative electrode plate manufactured in this way, the SiO powder and the acetylene black conductive material were changed to lithium ion conductive glass in the same manner as in Example 1 in which the positive electrode active material particles and the conductive material were coated with lithium ion conductive glass. Coated with.
[0083]
  The manufacturing process thereafter is the same as in the case of the battery (A) according to the present invention in Example 1, with a design capacity of 400 mAh.Reference exampleA battery (C) was produced.
[0084]
  Next, except that the negative electrode active material particles and the conductive material were not coated with lithium ion conductive glass,Reference exampleA conventionally known comparative battery (D) was produced in the same manner as the battery (C).
[0085]
  Produced as aboveReference exampleUsing the battery (C) and the comparative battery (D), at 25 ° C., the battery was charged to 4.2 V with a current of 0.5 CmA, subsequently charged with a constant voltage of 4.2 V for 5 hours, and then 0.2 CmA of The initial discharge capacity was measured by discharging to 2.75 V with current. Furthermore, at 25 ° C., the battery was charged to 4.2 V at a current of 0.5 CmA, subsequently charged at a constant voltage of 4.2 V for 5 hours, then left at 60 ° C. for 24 hours, and then at 25 ° C., 0.2 CmA of 0.2 CmA. The battery was discharged to 2.75V with current. Table 2 shows the initial capacity, the capacity after standing at 60 ° C., and the amount of increase in battery thickness due to standing at 60 ° C.
[0086]
[Table 2]
[0087]
  From Table 2,Reference exampleThe battery (C) was found to have less capacity reduction and battery thickness increase due to standing at 60 ° C. than the comparative battery (D). This is because the negative electrode active material particles and the conductive material were coated with lithium ion conductive glass, so that the electrolytic solution was not exposed to the potential of the active material particles and the conductive material, and the reductive decomposition of the electrolytic solution was suppressed. This is probably because self-discharge was suppressed. As a result, the amount of gas generated by the decomposition of the electrolytic solution is also reduced, and it is considered that the increase in battery thickness is suppressed.
[0088]
  [Example 2]
  After coating the positive electrode active material particles and the conductive material with lithium ion conductive glass, the positive electrode active material particles were filled with a copolymer of vinylidene fluoride and hexafluoropropylene (P (VdF / HFP)). A battery (E) according to the present invention was produced in the same manner as the battery (A) according to the present invention except for the above.
[0089]
The filling of P (VdF / HFP) between the active material particles was performed as follows. A positive electrode plate in which active material particles and a conductive material are coated with lithium ion conductive glass is immersed in a paste in which P (VdF / HFP) is dissolved in NMP at a concentration of 6 wt%, and the pressure is reduced to 0.1 Torr. Then, pressurization to atmospheric pressure was repeated 5 times to fill the gaps between the active material particles with P (VdF / HFP) paste. By pulling up this positive electrode plate from the paste and passing between rollers, the polymer paste that did not penetrate into the electrode and adhered to the electrode was removed.
[0090]
Then, this positive electrode plate was dried at 100 ° C. for 30 minutes to remove NMP, and the positive electrode active material particles coated with lithium ion conductive glass were coated with P (VdF / HFP). This P (VdF / HFP) was swollen by the electrolytic solution injected into the battery case to form a lithium ion conductive polymer electrolyte.
[0091]
Further, the battery (F) according to the present invention is the same as the battery (E) according to the present invention except that P (VdF / HFP) coated with the positive electrode active material particles coated with the lithium ion conductive glass is made porous. Was made.
[0092]
P (VdF / HFP) was made porous as follows. After filling the gap between the positive electrode active material particles with P (VdF / HFP) paste, the positive electrode plate is pulled out of the paste and passed between rollers, so that it does not penetrate into the electrode and adheres to the electrode. The polymer paste was removed. This positive electrode plate is 1 × 10^-3The P (VdF / HFP) between the active material particles is communicated by a solvent extraction method in which NMP in which P (VdF / HFP) is dissolved is replaced with water by immersing in a mol / l phosphoric acid aqueous solution for 5 minutes. It was made porous and solidified.
[0093]
This electrode was dried at 100 ° C. for 30 minutes to remove water. In this way, the positive electrode active material particles coated with the lithium ion conductive glass were coated with the porous P (VdF / HFP). This porous P (VdF / HFP) was swollen by the electrolytic solution injected into the battery case to become a lithium ion conductive porous polymer electrolyte.
[0094]
Using the batteries (E) and (F) according to the present invention manufactured as described above and the battery (A) according to the present invention manufactured in Example 1, the current of 0.5 CmA at 25 ° C. is used. The battery was charged to 9V, subsequently charged at a constant voltage of 4.9V for 5 hours, and then discharged to 3.5V with a current of 0.2 CmA as one cycle, and a 50-cycle charge / discharge test was performed.
[0095]
Thereafter, the battery was further charged at 25 ° C. with a current of 0.5 CmA to 4.9 V, subsequently charged with a constant voltage of 4.9 V for 5 hours, then left at 60 ° C. for 24 hours, and then at 25 ° C. with a voltage of 0.00. The battery was discharged to 3.5 V with a current of 2 CmA. Table 3 shows the discharge capacity at the 50th cycle in the cycle test, the discharge capacity after standing at 60 ° C., and the amount of increase in battery thickness due to standing at 60 ° C.
[0096]
[Table 3]
[0097]
From Table 3, it was found that the batteries (E) and (F) according to the present invention had less capacity reduction and increase in battery thickness due to standing at 60 ° C. than the battery (A) according to the present invention. This is because the positive electrode active material particles coated with the lithium ion conductive glass are further coated with the polymer electrolyte, so that the active material particles of the lithium ion conductive glass are caused by the volume expansion / contraction of the positive electrode active material particles due to the charge / discharge cycle. This is thought to be due to the fact that the exfoliation of the film became difficult to occur.
[0098]
Further, using the batteries (E) and (F) according to the present invention, the battery was charged to 4.9 V at a current of 1 CmA at 25 ° C., and subsequently charged at a constant voltage of 4.9 V for 5 hours, and then 0.2 CmA of Discharge to 3.5V with current. After that, the battery was charged again to 4.9 V with a current of 1 CmA, then charged with a constant voltage of 4.9 V for 5 hours, and then discharged to 3.5 V with a current of 2 CmA. Table 5 shows the ratio of the capacity during discharge of 2 CmA to 0.2 CmA of these batteries.
[0099]
[Table 4]
[0100]
From Table 4, in the battery by this invention, it turned out that the fall of the high rate discharge performance by application of a polymer electrolyte is suppressed remarkably by making the polymer electrolyte provided between active material particles porous. This is considered to be because lithium ions can quickly diffuse through the portion of the electrolytic solution in the pores of the porous polymer electrolyte.
[0101]
【The invention's effect】
  As described above, the present inventionAs a positive electrode active material, the general formula is Li _x Ni _y Mn _2-y O ₄ A lithium-containing composite oxide satisfying (0 ≦ x ≦ 1, 0.45 ≦ y ≦ 0.6) was used.In non-aqueous electrolyte batteries,Positive electrodeIn a state where electronic conduction between the active material particles is maintained by the conductive material,Positive electrodeBy assuming that at least a part of the surface of the active material particles and the conductive material is coated with lithium ion conductive glass,Positive electrodeIt is intended to provide a non-aqueous electrolyte battery in which decomposition of the electrolyte solution is suppressed and self-discharge and swelling of the battery when left at high temperature are suppressed.

Claims (2)

Positive general formula as a positive electrode active material and a a conductive material of lithium-containing composite oxide is _{Li x Ni y Mn 2-y} O 4 (0 ≦ x ≦ 1,0.45 ≦ y ≦ 0.6) , a non-aqueous electrolyte battery comprising a negative electrode and the nonaqueous electrolyte, with the electron conduction between the positive electrode active material particles is maintained by the conductive material, at least a portion of the positive electrode active material particles and the conductive material A non-aqueous electrolyte battery coated with lithium ion conductive glass. Positive general formula as a positive electrode active material and a a conductive material of lithium-containing composite oxide is _{Li x Ni y Mn 2-y} O 4 (0 ≦ x ≦ 1,0.45 ≦ y ≦ 0.6) , a method of manufacturing a nonaqueous electrolyte battery comprising a negative electrode and a nonaqueous electrolyte solution, after forming a positive electrode and a said conductive material and said positive electrode active material particles, the positive electrode active material particles and the conductive material A method for producing a non-aqueous electrolyte battery, characterized in that is coated with lithium ion conductive glass.