WO2015011884A1 - Électrode positive pour pile rechargeable à électrolyte non aqueux, et pile rechargeable à électrolyte non aqueux - Google Patents

Électrode positive pour pile rechargeable à électrolyte non aqueux, et pile rechargeable à électrolyte non aqueux Download PDF

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WO2015011884A1
WO2015011884A1 PCT/JP2014/003603 JP2014003603W WO2015011884A1 WO 2015011884 A1 WO2015011884 A1 WO 2015011884A1 JP 2014003603 W JP2014003603 W JP 2014003603W WO 2015011884 A1 WO2015011884 A1 WO 2015011884A1
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positive electrode
metal oxide
secondary battery
aqueous secondary
transition metal
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PCT/JP2014/003603
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Japanese (ja)
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直人 安田
雄太 中川
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株式会社豊田自動織機
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to a positive electrode for a non-aqueous secondary battery and a non-aqueous secondary battery.
  • Non-aqueous secondary batteries such as lithium ion secondary batteries are small and have high energy density, and are widely used as power sources for portable electronic devices.
  • the positive electrode active material containing Ni has low thermal stability, and it has been reported that the battery ignites at high temperatures. The reason is considered that oxygen is released from the positive electrode active material at a high temperature because the bonding force between nickel and oxygen is weak. A technique for increasing the thermal stability of the positive electrode is required.
  • Patent Document 1 in a winding structure in which a positive electrode and a negative electrode are wound through a separator, a positive electrode active material is provided on the outer peripheral surface side of the current collector at the outermost peripheral portion of the positive electrode. A portion where the containing coating film is not formed is provided. The portion where the positive electrode active material-containing coating film is not formed is opposed to the negative electrode through the separator, and the lead body welded to the negative electrode current collector is not directly opposed to the positive electrode through the separator.
  • the positive electrode active material does not exist in the short-circuit portion at the outermost peripheral portion of the positive electrode. A battery having this configuration is less likely to reach a thermal runaway temperature even if it generates heat, and is highly safe.
  • LiNi 0.5 Mn 1.5 O 4 having a spinel structure has a high upper limit potential of 4.5 V (Li reference) or more, and is used as a positive electrode active material for high voltage use.
  • a battery using a high-voltage positive electrode active material is charged and discharged at a high potential, and it has been pointed out that the cycle characteristics of the battery deteriorate due to oxidative decomposition of the electrolytic solution.
  • the causes of the oxidative decomposition of the electrolytic solution are considered to be that the positive electrode is exposed to a high oxidation state and that the positive electrode active material is easily dissolved in an acid such as hydrofluoric acid generated by the decomposition of the electrolytic solution. Therefore, development of a positive electrode material having a function of improving the stability of the battery at a high potential is desired.
  • the inventor of the present application diligently searched to develop a highly safe non-aqueous secondary battery by a method different from the technique described in Patent Document 1 above.
  • This invention is made
  • Another problem is to provide a positive electrode for a non-aqueous secondary battery and a non-aqueous secondary battery that can be used stably even at a high potential.
  • the positive electrode for a non-aqueous secondary battery of the present invention has a positive electrode active material having a Ni-containing metal oxide containing Ni and a transition metal oxide having a transition element, and the transition element can be taken after the initial charge. It has an oxidation number smaller than the maximum oxidation number.
  • the positive electrode for a non-aqueous secondary battery of the present invention has a transition metal oxide having a transition element in addition to a positive electrode active material having a Ni-containing metal oxide.
  • the transition element contained in the transition metal oxide has an oxidation number smaller than the maximum oxidation number that can be taken after the first charge. For this reason, heat_generation
  • Example 1 and Comparative Example 1 The DSC curve of Example 1 and Comparative Example 1 is shown.
  • the discharge capacities of Examples 3 and 4 and Comparative Example 2 when a cycle test is performed at 25 ° C. are shown.
  • the discharge capacities of Examples 3 and 4 and Comparative Example 2 when a cycle test is performed at 60 ° C. are shown.
  • the positive electrode for non-aqueous secondary battery and the non-aqueous secondary battery of the present invention will be described in detail.
  • the positive electrode for a non-aqueous secondary battery of the present invention has a Ni-containing metal oxide and a transition metal oxide.
  • the negative electrode active material and the SEI film (passive film) formed on the surface of the negative electrode active material react with the electrolytic solution and generate heat.
  • the separator is decomposed to further promote heat generation.
  • the Ni-containing metal oxide in the positive electrode contains nickel element.
  • the binding force of the Ni—O bond in the Ni-containing metal oxide is smaller than that of other metal-oxygen bonds.
  • the Ni—O bond in the Ni-containing metal oxide is decomposed, and the Ni-containing metal oxide releases oxygen.
  • the released oxygen causes a violent oxidation (exothermic) reaction with the organic solvent of the electrolyte, causing thermal runaway.
  • the transition element in the transition metal oxide contained in the positive electrode has an oxidation number smaller than the maximum oxidation number that can be taken after the initial charge.
  • the transition metal oxide absorbs oxygen before the oxygen released from the Ni-containing metal oxide reacts with the electrolyte.
  • the oxidation number of the transition element in the transition metal oxide is smaller than the maximum oxidation number that the transition element can take.
  • the transition element in the transition metal oxide is oxidized by oxygen to increase the oxidation number, and oxygen is absorbed by the transition metal oxide. For this reason, the calorific value of the positive electrode is greatly suppressed in the temperature range where oxygen is released from the Ni-containing metal oxide. Also, the stable temperature range of the positive electrode can be expanded to the high temperature side.
  • the transition element in the transition metal oxide contained in the positive electrode has an oxidation number smaller than the maximum oxidation number that can be taken after the initial charge.
  • the transition element in the transition metal oxide absorbs oxygen and increases its valence. For this reason, the oxidative decomposition of electrolyte solution is suppressed effectively.
  • the non-aqueous electrolyte has a compound having fluorine
  • the decomposition of the compound contained in the non-aqueous electrolyte is suppressed and the generation of hydrofluoric acid is suppressed. Dissolution of the positive electrode active material by hydrofluoric acid is prevented. This effect is remarkably exhibited when the potential is high.
  • the transition element contained in the transition metal oxide includes a transition element whose valence does not change by the initial charge and a transition element whose valence decreases by the initial charge.
  • the transition metal oxide has a transition element having an oxidation number smaller than the maximum possible oxidation number after the initial charge means that the transition element (for example, Fe) whose valence is reduced by the initial charge is the initial charge. Later, it means having a valence less than the maximum valence.
  • a transition element (for example, Mn, Co) whose valence does not change by the first charge has a valence smaller than the maximum valence both before and after the first charge.
  • the upper limit potential for charging the Ni-containing metal oxide contained in the positive electrode is preferably 4.5 V (Li counter electrode reference) or more.
  • the upper limit potential of charging is a value converted to a lithium counter electrode based on the charge and discharge curves of the positive and negative electrodes measured in advance.
  • Such Ni-containing metal oxides include LiNi 0.5 Mn 1.5 O 4 , LiNi 0.5 Co 0.2 Mn 0.3 O 2 , and LiNi 1/3 Co 1/3 Mn 1/3 O 2. Can be mentioned.
  • the transition metal oxide has a transition element. Unlike the Ni-containing metal oxide of the positive electrode active material, the transition metal oxide does not participate in the battery reaction or has a much smaller reaction amount than the Ni-containing metal oxide even though it participates in the battery reaction. At least in the operating potential range of the battery, it is preferable that the transition metal oxide does not participate in the battery reaction or has a much smaller reaction amount than the Ni-containing metal oxide even though it participates in the battery reaction.
  • the transition element in the transition metal oxide has an oxidation number smaller than the maximum possible oxidation number after the first charge.
  • Transition elements are elements that can take several oxidation numbers. Transition elements are more likely to be oxidized and oxygen uptake than typical elements. If the transition element has an oxidation number smaller than the maximum possible oxidation number, the transition element is easily oxidized, and the oxidation number can be increased toward the maximum oxidation number.
  • the average oxidation number of the transition element in the transition metal oxide is, for example, preferably from 1 to less than 3, and more preferably from 1 to less than 2, although it depends on the type of the transition element. In this case, the transition element is easily oxidized and easily absorbs oxygen.
  • the transition element in the transition metal oxide is preferably oxidized more easily than Ni contained in the Ni-containing metal oxide. That is, the transition element in the transition metal oxide preferably has a lower standard reduction potential than Ni contained in the Ni-containing metal oxide. In this case, oxygen released from the Ni-containing metal oxide can be immediately absorbed by the transition metal oxide.
  • the transition metal oxide contains one or more transition elements.
  • the transition element contained in the transition metal oxide may be a transition element other than Ni. This is because Ni has a weak binding force with O (oxygen), and therefore when the transition metal oxide contains Ni, the oxygen absorption performance of the transition metal oxide is reduced.
  • the transition metal oxide is a first transition element (3d transition element). Examples of the transition element include Mn, Co, Fe, Cu, and the like.
  • the transition metal oxide contains at least a transition element and an oxygen element.
  • the transition metal oxide may be composed of only a transition element and an oxygen element, and the transition metal oxide in this case is represented by the general formula: M 1 x O y (M 1 is one selected from the transition elements) As described above, x and y are integers of 1 or more) (Expression 1).
  • Transition element M 1 in the transition metal oxide for example, Mn, Co, Fe, Cu, V and the like.
  • M 1 in Formula 1 may be a transition element that does not participate in the battery reaction. When the transition metal oxide is a compound represented by Formula 1, the transition metal oxide does not participate in the battery reaction.
  • the transition metal oxide may contain a metal element other than the transition element.
  • the general formula is M 2 z M 1 x O y (M 1 is one or more selected from the transition elements, M 1 2 is a metal element other than a transition element, and x, y, and z are integers of 1 or more) (Expression 2).
  • M 1 in the formula 2 is the same as M 1 in formula 1.
  • Examples of M 2 in Formula 2 include Li and Na.
  • M 2 in Formula 2 may be a cation as an ionic conductor. In this case, the transition metal oxide decomposes and discharges the cation M 2 during the first charge, and the cation M 2 is doped into the negative electrode active material. Most of the transition metal oxides are preferably M 1 x O y not containing M 2 .
  • Table 1 lists the maximum oxidation number of the transition element that can be contained in the transition metal oxide, the oxidation number that is smaller than the maximum oxidation number and that can be taken, and the transition metal oxide containing the transition element.
  • the transition metal oxide is not limited to those listed in Table 1.
  • MnO and CoO are preferable. Furthermore, MnO is desirable. Metals Fe and Cu generated from FeO and Cu 2 O are easy to dissolve when the voltage is high, but metals Mn and Co generated from MnO and CoO are difficult to dissolve even when the voltage is high. MnO is stable in the atmosphere and can absorb oxygen at room temperature.
  • the transition metal oxide is preferably a compound having an inverted fluorite structure.
  • the transition metal oxide is preferably a compound having a reverse fluorite structure and including a lithium element, a transition element, and an oxygen element.
  • Such compounds include the formula: Li a M 1 b O c (4.5 ⁇ a ⁇ 6.5, 0.5 ⁇ b ⁇ 1.5, 3.5 ⁇ c ⁇ 4.5, M 1 : Co, It may be a lithium metal composite oxide represented by at least one selected from the group consisting of Mn and Fe.
  • the transition metal oxide is preferably composed of at least one selected from the group consisting of Li 6 MnO 4 , Li 6 CoO 4 , and Li 5 FeO 4 .
  • These compounds are lithium metal composite oxides having an inverted fluorite structure.
  • the lithium metal composite oxide decomposes during the initial charge to generate MnO, CoO, and FeO, respectively, and releases lithium ions.
  • the negative electrode active material can be doped with lithium, and the discharge capacity can be increased.
  • transition elements contained in MnO, CoO, and FeO have an oxidation number smaller than the maximum oxidation number, and can absorb oxygen released from the positive electrode active material.
  • transition metal oxides When these transition metal oxides absorb oxygen, the oxidation number of the transition element contained in the transition metal oxide is increased to MnO 2 , CoO 2 , and Fe 2 O 3 .
  • the above compound having an inverted fluorite structure can serve as a lithium doping material and an oxygen absorbing material. For this reason, the thermal runaway of the battery by combustion is suppressed. Further, when the electrolytic solution contains fluorine, the generation of hydrofluoric acid can be suppressed and dissolution of the positive electrode active material can be suppressed.
  • the positive electrode active material contained in the positive electrode has a Ni-containing metal oxide having at least Ni (nickel) and O (oxygen).
  • Ni-containing metal oxide has the formula: LiNi 1-xy Co x Mn y O 2 (0 ⁇ x ⁇ 1,0 ⁇ y ⁇ 1,0 ⁇ 1-xy), or / and Formula: LiNi 2-xy Co x Mn y O 4 (0 ⁇ x ⁇ 2, 0 ⁇ y ⁇ 2, 0 ⁇ 2-xy) is preferable.
  • Formula: LiNi 1-xy Co x Mn y O 2 (0 ⁇ x ⁇ 1,0 ⁇ y ⁇ 1,0 ⁇ 1-xy) compound represented by is a layered compound.
  • Ni-containing metal oxides include LiNi 1/3 Co 1/3 Mn 1/3 O 2 , LiNi 0.5 Co 0.2 Mn 0.3 O 2 , LiNiO 2 , LiNi 1-x Co x O. 2 (0 ⁇ x ⁇ 1), LiNi 0.5 Mn 1.5 O 4 and the like.
  • the Ni-containing metal oxide used as the positive electrode active material may be based on the above composition formula as a basic composition, and a metal element included in the basic composition may be substituted with another metal element, Mg, etc. Other metal elements may be added to the basic composition to form a metal oxide.
  • the positive electrode active material may contain other positive electrode active material components responsible for the battery reaction in addition to the Ni-containing metal oxide.
  • other positive electrode active material components include LiMn 2 O 4 and LiMnO 2 .
  • the content of the transition metal oxide when the Ni-containing metal oxide as the positive electrode active material is 100 parts by mass is preferably 5 parts by mass or more and 40 parts by mass or less, and more preferably 10 parts by mass or more and 20 parts by mass or more. It is preferable that it is below mass parts. In this case, oxygen released from the Ni-containing metal oxide can be sufficiently absorbed by the transition metal oxide, and the thermal stability of the positive electrode is excellent.
  • the positive electrode preferably has a positive electrode mixture having a positive electrode active material and a transition metal oxide, and a current collector whose surface is coated with the positive electrode mixture.
  • the positive electrode current collector is not particularly limited as long as it is a metal that can withstand a voltage suitable for the active material to be used. For example, silver, copper, gold, aluminum, tungsten, cobalt, zinc, nickel, iron, platinum, tin , Indium, titanium, ruthenium, tantalum, chromium, molybdenum, and metal materials such as stainless steel.
  • the positive electrode for a non-aqueous secondary battery includes a current collector and a positive electrode mixture that covers the surface of the current collector and has the positive electrode active material and the transition metal oxide, and the positive electrode mixture is 100 masses. %,
  • the content of the transition metal oxide contained in the positive electrode mixture is preferably 1% by mass to 15% by mass, and more preferably 5% by mass to 10% by mass. preferable. In this case, the oxygen absorption performance of the transition metal oxide can be improved while increasing the battery capacity.
  • the current collector can take the form of a foil, a sheet, a film, a linear shape, a rod shape, a mesh, or the like. Therefore, for example, a metal foil such as a copper foil, a nickel foil, an aluminum foil, and a stainless steel foil can be suitably used as the current collector.
  • a metal foil such as a copper foil, a nickel foil, an aluminum foil, and a stainless steel foil can be suitably used as the current collector.
  • the thickness is preferably in the range of 1 ⁇ m to 100 ⁇ m.
  • the positive electrode mixture may contain a conductive additive.
  • the conductive assistant is added to increase the conductivity of the electrode.
  • Examples of the conductive assistant include carbon black, graphite, acetylene black (AB), ketjen black (KB), and vapor grown carbon fiber (Vapor Grown Carbon Fiber: VGCF).
  • the amount of the conductive aid used is not particularly limited, but can be, for example, 1 to 30 parts by mass with respect to 100 parts by mass of the positive electrode active material.
  • the positive electrode mixture may contain a binder.
  • the binder serves to bind the active material, transition metal oxide and conductive additive to the surface of the current collector.
  • the binder include fluorine-containing resins such as polyvinylidene fluoride, polytetrafluoroethylene, and fluororubber, thermoplastic resins such as polypropylene and polyethylene, imide resins such as polyimide and polyamideimide, and alkoxysilyl group-containing resins. be able to.
  • a conventionally known method such as a roll coating method, a die coating method, a dip coating method, a doctor blade method, a spray coating method, or a curtain coating method is used.
  • the positive electrode mixture may be applied to the surface of the current collector.
  • an active material layer-forming composition containing an active material, a transition metal oxide and, if necessary, a binder and a conductive aid is prepared, and an appropriate solvent is added to the composition to make a paste. Then, after applying to the surface of the current collector, it is dried.
  • the solvent include N-methyl-2-pyrrolidone, methanol, methyl isobutyl ketone, and water. In order to increase the electrode density, the dried product may be compressed.
  • Non-aqueous secondary battery of the present invention includes the positive electrode for a non-aqueous secondary battery, a negative electrode, and a non-aqueous electrolyte.
  • the above-mentioned positive electrode for a non-aqueous secondary battery contains a transition metal oxide.
  • the transition element in the transition metal oxide has an oxidation number smaller than the maximum possible oxidation number after the first charge.
  • the transition metal oxide absorbs oxygen. In the temperature range where oxygen is released from the Ni-containing metal oxide, the calorific value of the positive electrode is greatly suppressed.
  • the non-aqueous electrolyte has a compound having fluorine, decomposition of the compound contained in the non-aqueous electrolyte is suppressed, and the generation of hydrofluoric acid is suppressed. Dissolution of the positive electrode active material by hydrofluoric acid is prevented.
  • the negative electrode used in the non-aqueous secondary battery of the present invention has a current collector and a negative electrode mixture bonded to the surface of the current collector.
  • the negative electrode mixture has a negative electrode active material.
  • the negative electrode mixture preferably contains a conductive additive or / and a binder in addition to the negative electrode active material.
  • the conductive auxiliary agent and / or binder that may be contained in the negative electrode mixture the same conductive assistant or / and binder as may be contained in the positive electrode mixture can be used.
  • the negative electrode current collector is not particularly limited as long as it is a metal that can withstand a voltage suitable for the active material to be used, and for example, the one described for the positive electrode current collector can be adopted.
  • the negative electrode active material a material that can occlude and release metal ions such as lithium ions can be used. Therefore, there is no particular limitation as long as it is a simple substance, alloy, or compound that can occlude and release metal ions such as lithium ions.
  • a negative electrode active material Li, group 14 elements such as carbon, silicon, germanium and tin, group 13 elements such as aluminum and indium, group 12 elements such as zinc and cadmium, group 15 elements such as antimony and bismuth, magnesium , Alkaline earth metals such as calcium, and group 11 elements such as silver and gold may be employed alone.
  • silicon or the like is employed as the negative electrode active material, one silicon atom reacts with a plurality of lithiums.
  • the alloy or compound in which other elements such as transition are combined in a simple substance such as a negative electrode active material.
  • the alloy or compound include tin-based materials such as Ag—Sn alloy, Cu—Sn alloy, Co—Sn alloy, carbon-based materials such as various graphites, SiOx (0 which disproportionates into silicon simple substance and silicon dioxide). .3 ⁇ x ⁇ 1.6), silicon simple substance, or a composite of a silicon-based material and a carbon-based material.
  • the non-aqueous electrolyte used for the non-aqueous secondary battery of the present invention has a non-aqueous solvent and an electrolyte dissolved in the non-aqueous solvent.
  • cyclic esters include ethylene carbonate, propylene carbonate, butylene carbonate, gamma butyrolactone, vinylene carbonate, 2-methyl-gamma butyrolactone, acetyl-gamma butyrolactone, and gamma valerolactone.
  • chain esters examples include dimethyl carbonate, diethyl carbonate, dibutyl carbonate, dipropyl carbonate, methyl ethyl carbonate, propionic acid alkyl ester, malonic acid dialkyl ester, and acetic acid alkyl ester.
  • ethers include tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-diethoxyethane, and 1,2-dibutoxyethane. These nonaqueous solvents may be used alone or in combination with the electrolyte.
  • Examples of the electrolyte include lithium salts such as LiClO 4 , LiAsF 6 , LiPF 6 , LiBF 4 , LiCF 3 SO 3 , and LiN (CF 3 SO 2 ) 2 .
  • the non-aqueous electrolyte may have a compound having fluorine.
  • the compound in the electrolytic solution may be decomposed under high voltage to generate hydrofluoric acid.
  • the generated hydrofluoric acid is immediately absorbed by the transition metal oxide having a transition metal having a valence smaller than the maximum valence. For this reason, the amount of hydrofluoric acid in the electrolyte is extremely reduced.
  • the positive electrode active material that has come into contact with the electrolytic solution is prevented from being dissolved by hydrofluoric acid, and the cycle characteristics are improved.
  • examples of the compound having fluorine include fluorinated ethylene carbonate as a non-aqueous solvent
  • examples of the electrolyte include LiAsF 6 , LiPF 6 , LiBF 4 , LiCF 3 SO 3 , LiN (CF 3 SO 2 ) 2, and the like. It is done.
  • a separator is used for non-aqueous secondary batteries as necessary.
  • the separator separates the positive electrode and the negative electrode and allows metal ions such as lithium ions to pass while preventing a short circuit of current due to contact between the two electrodes.
  • a separator is sandwiched between the positive electrode and the negative electrode as necessary to form an electrode body.
  • the electrode body may be either a stacked type in which the positive electrode, the separator and the negative electrode are stacked, or a wound type in which the positive electrode, the separator and the negative electrode are sandwiched.
  • the positive electrode for a non-aqueous secondary battery according to this example includes a current collector and a positive electrode mixture that covers the current collector.
  • the positive electrode mixture includes a positive electrode active material and a transition metal oxide.
  • the positive electrode active material is made of LiNi 0.5 Mn 0.3 Co 0.2 O 2 having a layered structure.
  • the transition metal oxide is made of Li 6 MnO 4 .
  • the content of Li 6 MnO 4 is 4% by mass and the content of LiNi 0.5 Mn 0.3 Co 0.2 O 2 is 90% by mass when the entire positive electrode mixture is 100% by mass.
  • the positive electrode mixture further contains 3% by mass of acetylene black as a conductive additive and 3% by mass of PVdF as a binder.
  • the current collector is made of an aluminum foil having a thickness of 20 ⁇ m.
  • the electrolytic solution is composed of a mixed solvent and LiPF 6 as a lithium salt.
  • the mixed solvent consists of ethylene carbonate (EC) and diethyl carbonate (DEC).
  • the volume ratio of EC to DEC in the mixed solvent was 3: 7.
  • the concentration of LiPF 6 in the electrolytic solution is 1 mol / L.
  • This half cell was charged to 4.5 V at the Li reference potential. Thereafter, the half cell was disassembled and the positive electrode was taken out.
  • This positive electrode was subjected to differential scanning calorimetry.
  • 3 mg of this positive electrode and 1.8 ⁇ L of the electrolytic solution were placed in a stainless steel pan, and the pan was sealed. Using a sealed pan, under a nitrogen atmosphere, the heating rate was 20 ° C / min.
  • Differential scanning calorimetry was performed under the conditions of the above to obtain a DSC curve. Rigaku DSC8230 was used as a differential scanning calorimeter. The measured DSC curve of Example 1 is shown in FIG.
  • the main calorific value was 500 J / g, and the main exothermic reaction temperature was 271 ° C.
  • the main calorific value was measured in the range of 250 to 300 ° C. where main heat generation occurred in the positive electrode.
  • Example 1 The positive electrode of this example is different from Example 1 in that it does not contain a transition metal oxide. Others are the same as in the first embodiment.
  • Example 2 For this positive electrode, a half cell was prepared in the same manner as in Example 1 and charged to 4.5V. Thereafter, the half cell was disassembled, and the positive electrode was taken out. Differential scanning calorimetry was performed on the positive electrode in the same manner as in Example 1 to obtain a DSC curve.
  • the DSC curve of Comparative Example 1 is shown in FIG. Moreover, as shown in Table 2, the main calorific value was 750 J / g, and the main exothermic reaction temperature was 258 ° C.
  • the positive electrode of Example 1 had less main heat generation and a higher main exothermic reaction temperature than the positive electrode of Comparative Example 1.
  • the reason is considered as follows. Li 6 MnO 4 is decomposed by charging to produce MnO. MnO absorbed oxygen released from the Ni-containing metal oxide to become MnO 2 , and the calorific value was suppressed.
  • the positive electrode of Example 1 was produced by decomposing the transition metal oxide Li 6 MnO 4 in addition to the Ni-containing metal oxide LiNi 0.5 Mn 0.3 Co 0.2 O 2 as the positive electrode active material. Contains MnO. In the vicinity of 230 to 240 ° C., MnO starts absorbing oxygen released from the Ni-containing metal oxide and generates MnO 2 as represented by the following formula (3). In the vicinity of 240 to 270 ° C., MnO 2 is actively generated. In the vicinity of 270 to 280 ° C., Mn in MnO 2 begins to release O (oxygen), and O 2 oxygen reacts with the electrolyte and generates heat, as shown in the following formula (4).
  • Example 1 Li 6 MnO 4 absorbs oxygen released from the Ni-containing metal oxide at around 255 ° C. For this reason, reaction of oxygen and electrolyte solution is suppressed. Further, MnO 2 that has absorbed oxygen releases oxygen at around 275 ° C., and oxygen and the electrolytic solution react. Thus, the main exothermic reaction temperature between oxygen and the electrolyte shifts to the high temperature side. Therefore, the stable temperature range of the positive electrode can be expanded to the high temperature side.
  • the transition metal oxide having an inverse fluorite structure in addition to the Li 6 MnO 4, Li 6 CoO 4, Li 5 FeO 4 may be used.
  • Li 6 CoO 4 and Li 5 FeO 4 are both decomposed into CoO and FeO during the initial charge.
  • CoO and FeO are oxides that do not participate in the battery reaction and can absorb oxygen. For this reason, the oxygen released from the Ni-containing metal oxide of the positive electrode active material is absorbed to improve the stability of the positive electrode.
  • Example 2 The positive electrode of this example is different from Example 1 in that MnO is used instead of Li 6 MnO 4 as a transition metal oxide.
  • the content of MnO was 4% by mass when the entire positive electrode mixture was 100% by mass.
  • a half cell was prepared in the same manner as in Example 1 and charged to 4.5 V on the basis of the Li counter electrode. Thereafter, the half cell was disassembled, and the positive electrode was taken out. Differential scanning calorimetry was performed on the positive electrode in the same manner as in Example 1, and the DSC curve was observed.
  • LiNi 0.5 Mn 1.5 O 4 having a spinel structure As the positive electrode active material, LiNi 0.5 Mn 1.5 O 4 having a spinel structure was used. In this LiNi 0.5 Mn 1.5 O 4 , primary particles aggregated to form secondary particles. The primary particle size was about 200 nm, the secondary particle size was 15 ⁇ m, and the specific surface area was 8.5 m 2 / g.
  • the positive electrode active material 80 parts by weight of the positive electrode active material, 10 parts by weight of acetylene black, and 10 parts by weight of PVdF were mixed with an NMP solvent to form a slurry.
  • the slurry was applied to one side of a 15 ⁇ m thick aluminum foil so that the slurry had a thickness of 20 ⁇ m and a solid content of about 7 mg / cm 2 , dried and pressed to obtain a positive electrode.
  • This positive electrode was punched into a diameter of 14 mm.
  • metallic lithium was used.
  • separator a polyethylene nonwoven fabric having a thickness of 25 ⁇ m was used.
  • the electrolytic solution is composed of a mixed solvent composed of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) and LiPF 6 as a lithium salt.
  • EC ethylene carbonate
  • EMC ethyl methyl carbonate
  • LiPF 6 LiPF 6 as a lithium salt.
  • the concentration of LiPF 6 in the electrolytic solution is 1.2 mol / L. Using these, a 2032 type coin battery was produced. All battery fabrication operations were performed in a glove box filled with argon gas. The obtained battery was referred to as Example 1.
  • Example 3 A slurry was prepared by mixing 76 parts by weight of the positive electrode active material, 4 parts by weight of commercially available 5 ⁇ m MnO, 10 parts by weight of acetylene black, and 10 parts by weight of PVDF with an NMP solvent.
  • the positive electrode active material was the same as in Comparative Example 2.
  • a battery was produced in the same manner as in Comparative Example 2 using this slurry. This battery was referred to as Example 3.
  • Example 4 A slurry was prepared by mixing 71.3 parts by weight of the positive electrode active material, 8.7 parts by weight of Li 6 MnO 4 , 10 parts by weight of acetylene black, and 10 parts by weight of PVdF with an NMP solvent.
  • the positive electrode active material was the same as in Comparative Example 2.
  • a battery was produced in the same manner as in Comparative Example 2 using this slurry. This battery was referred to as Example 4.
  • ⁇ Cycle test> A cycle test was performed on the batteries of Comparative Example 2 and Examples 3 and 4.
  • the conditions of the cycle test are as follows: the positive electrode active material LiNi 0.5 Mn 1.5 O 4 has a capacity of 120 mAh / g. After the elapse of time, the battery was discharged to 3.0 V at a 0.1 C rate with a rest time of 10 minutes. Charging and discharging were taken as one cycle and repeated 50 cycles.
  • the test was performed in an environment of 25 ° C. and 60 ° C., respectively.
  • FIG. 2 shows the discharge capacity of each battery when the cycle test is conducted at 25 ° C.
  • FIG. 3 shows the discharge capacity of each battery when the cycle test is conducted at 60 ° C.
  • Examples 3 and 4 had a higher discharge capacity during the cycle than Comparative Example 2.
  • the difference in discharge capacity between Examples 3 and 4 and Comparative Example 2 was large at a high temperature of 60 ° C. Under high temperature, LiPF 6 in the electrolytic solution is easily decomposed to generate hydrofluoric acid.
  • Example 3 since the generated hydrofluoric acid was absorbed by MnO, it is considered that the superiority with Comparative Example 2 was increased at high temperatures.
  • Li 6 MnO 4 releases Li and decomposes into MnO at the time of charging, particularly at the first charging. MnO absorbs hydrofluoric acid generated in the electrolytic solution. For this reason, it is considered that the cycle characteristics of the battery of Example 5 were improved as compared with Comparative Example 2.

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Abstract

La présente invention porte sur une électrode positive pour pile rechargeable à électrolyte non aqueux, l'électrode positive étant très sûre et pouvant être utilisée d'une manière stable à un potentiel élevé. Une pile rechargeable à électrolyte non aqueux est également décrite. Cette électrode positive pour pile rechargeable à électrolyte non aqueux comprend: un matériau actif d'électrode positive comprenant un oxyde métallique contenant Ni; et un oxyde de métal de transition comprenant un élément de transition. Après la charge initiale, l'élément de transition a un nombre d'oxydation inférieur au nombre d'oxydation maximal que ledit élément de transition peut avoir.
PCT/JP2014/003603 2013-07-25 2014-07-07 Électrode positive pour pile rechargeable à électrolyte non aqueux, et pile rechargeable à électrolyte non aqueux WO2015011884A1 (fr)

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CN108736060A (zh) * 2017-04-24 2018-11-02 丰田自动车株式会社 锂离子二次电池及其制造方法
CN108767242A (zh) * 2018-05-02 2018-11-06 温州玖源锂电池科技发展有限公司 一种可预锂化的锂离子启停电源及其制备方法
WO2020090591A1 (fr) * 2018-10-30 2020-05-07 パナソニックＩｐマネジメント株式会社 Batterie secondaire
JP7531971B2 (ja) 2021-05-25 2024-08-13 エルジー エナジー ソリューション リミテッド 正極スラリーおよびそれを用いたリチウム二次電池用正極

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JP7531971B2 (ja) 2021-05-25 2024-08-13 エルジー エナジー ソリューション リミテッド 正極スラリーおよびそれを用いたリチウム二次電池用正極

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