WO2015025466A1 - 正極活物質層上に熱暴走抑制層を具備する正極を有するリチウムイオン二次電池 - Google Patents
正極活物質層上に熱暴走抑制層を具備する正極を有するリチウムイオン二次電池 Download PDFInfo
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- WO2015025466A1 WO2015025466A1 PCT/JP2014/003787 JP2014003787W WO2015025466A1 WO 2015025466 A1 WO2015025466 A1 WO 2015025466A1 JP 2014003787 W JP2014003787 W JP 2014003787W WO 2015025466 A1 WO2015025466 A1 WO 2015025466A1
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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
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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
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
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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
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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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
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/362—Composites
- H01M4/366—Composites as layered products
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- H—ELECTRICITY
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- 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
- H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
- H01M4/386—Silicon or alloys based on silicon
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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
- H01M4/36—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
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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
- H01M4/36—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
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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
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
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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
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/028—Positive electrodes
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- 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 lithium ion secondary battery having a positive electrode provided with a thermal runaway suppression layer on the positive electrode active material layer.
- secondary batteries are recognized as essential for mobile devices such as mobile phones and laptop computers.
- lithium ion secondary batteries are widely used because of their small size and large capacity, and are also used in aircraft and automobiles.
- research on lithium ion secondary batteries has been actively conducted for the purpose of providing better lithium ion secondary batteries.
- Patent Document 1 describes a lithium ion secondary battery that did not ignite as a result of a nail penetration test.
- the lithium ion secondary battery disclosed in Patent Document 1 is obtained by dividing an electrode into sheets having a specific shape.
- Patent Document 2 includes a positive electrode including a first positive electrode active material layer containing LiNiO 2 and a second positive electrode active material layer containing Li 2 FeSiO 4 or LiFePO 4, and Cu 6 Sn 6 as a negative electrode active material.
- a lithium ion secondary battery having a negative electrode and having a lithium amount in the second positive electrode active material layer equal to or greater than the irreversible capacity of the negative electrode active material is described, but there is no mention of a nail penetration test.
- Patent Document 1 defines the area and shape of a sheet obtained by dividing an electrode and the distance between a positive electrode current collector and a negative electrode current collector with a certain relational expression.
- the present invention has been made in view of such circumstances, and provides a lithium ion secondary battery that can suppress temporal and spatial concentration of heat generation due to a chemical reaction between a positive electrode and a nonaqueous electrolyte during an internal short circuit.
- the purpose is to do.
- the present inventor has intensively studied the components of the lithium ion secondary battery while repeating trial and error.
- the inventor has found that a lithium ion secondary battery in which a thermal runaway suppression layer containing a specific compound is provided on a positive electrode active material layer in a specific range is excellent in stability even during an internal short circuit. It came to complete.
- the lithium ion secondary battery of the present invention is excellent in stability even when an internal short circuit occurs.
- the numerical range “a to b” described in this specification includes the lower limit “a” and the upper limit “b”.
- the numerical range can be configured by arbitrarily combining these upper limit value and lower limit value and the numerical values listed in the examples.
- numerical values arbitrarily selected from the numerical value range can be used as upper and lower numerical values.
- a current collector refers to a chemically inert electronic high conductor that keeps a current flowing through an electrode during discharge or charging of a lithium ion secondary battery.
- a material of the current collector at least one selected from silver, copper, gold, aluminum, magnesium, tungsten, cobalt, zinc, nickel, iron, platinum, tin, indium, titanium, ruthenium, tantalum, chromium, molybdenum, or Examples thereof include metal materials such as stainless steel and carbon materials such as graphite.
- aluminum is preferable as the material of the positive electrode current collector
- copper is preferable as the material of the negative electrode current collector.
- 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 10 ⁇ m to 100 ⁇ m.
- Li a Ni b Co c Mn d De O f (0.2 ⁇ a ⁇ 1, b + c + d + e 1, 0 ⁇ e ⁇ 1, D is Li, Fe, Cr At least one element selected from Cu, Zn, Ca, Mg, S, Si, Na, K, and Al, and a lithium-containing composite oxide represented by 1.7 ⁇ f ⁇ 2.1) has a high capacity.
- the positive electrode active material layer is a layer having a positive electrode active material formed on the current collector.
- the positive electrode active material layer includes a binder and / or a conductive aid as necessary.
- the binder plays a role of binding the active material to the surface of the current collector.
- binders fluorine-containing resins such as polyvinylidene fluoride, polytetrafluoroethylene and fluororubber, thermoplastic resins such as polypropylene and polyethylene, imide resins such as polyimide and polyamideimide, carboxymethylcellulose, methylcellulose and styrene-butadiene rubber
- imide resins such as polyimide and polyamideimide
- carboxymethylcellulose methylcellulose and styrene-butadiene rubber
- binders can be added to the active material layer alone or in combination of two or more.
- the amount of the binder used is not particularly limited, but a range of 1 to 50 parts by mass of the binder is preferable with respect to 100 parts by mass of the active material. This is because when the amount of the binder is too small, the moldability of the electrode and the active material layer is lowered, and when the amount of the binder is too large, the energy density of the electrode is lowered.
- Conductive aid is added to increase conductivity.
- Examples of the conductive aid include carbon black, graphite, acetylene black, ketjen black (registered trademark), and vapor grown carbon fiber (Vapor Grown Carbon Fiber). These conductive assistants can be added to the active material layer alone or in combination of two or more.
- the amount of the conductive aid used is not particularly limited, but for example, the conductive aid can be 1 to 30 parts by weight with respect to 100 parts by weight of the active material.
- the lithium-containing transition metal oxide in the positive electrode active material layer is preferably in the range of 50 to 99 parts by mass, more preferably in the range of 70 to 97 parts by mass, 85 A range of ⁇ 95 parts by mass is particularly preferable.
- the surface of the current collector can be formed using a conventionally known method such as a roll coating method, a dip coating method, a doctor blade method, a spray coating method, or a curtain coating method. What is necessary is just to apply
- a composition for forming an active material layer containing an active material and, if necessary, a binder and / or a conductive aid is prepared, and an appropriate solvent is added to the composition to obtain a paste-like liquid.
- the pasty liquid may be prepared using a solution in which a binder is dissolved in a solvent in advance or a dispersed suspension.
- the solvent examples include N-methyl-2-pyrrolidone, methanol, ethanol, methyl isobutyl ketone, and water.
- the paste-like liquid is applied to the surface of the current collector and then dried. Drying may be performed under normal pressure conditions or under reduced pressure conditions using a vacuum dryer. What is necessary is just to set drying temperature suitably, and the temperature beyond the boiling point of the said solvent is preferable. What is necessary is just to set drying time suitably according to an application quantity and drying temperature.
- a compression step may be added to the dried current collector on which the active material layer is formed.
- the lithium ion secondary battery of the present invention includes a thermal runaway suppression layer formed on the positive electrode active material layer and including a lithium silicate transition metal lithium salt.
- the lithium silicate transition metal lithium salt does not substantially function as an active material capable of occluding lithium ions and exists as a high resistance compound.
- the lithium silicate transition metal lithium salt functions as a high resistance compound, it is possible to suppress a significant current from being generated between the positive electrode and the negative electrode.
- the lithium ion secondary battery of the present invention can suppress contact between the organic solvent constituting the electrolytic solution and the lithium-containing composite oxide. As a result, since the above chain reaction can be suppressed, the lithium ion secondary battery of the present invention can prevent thermal runaway.
- the transition metal lithium salt contained in the thermal runaway suppression layer also has oxygen in the molecule, since the binding energy of the oxygen-silicon bond is high, such oxygen is not normally released.
- the layer formed on the positive electrode active material layer and containing a lithium silicate transition metal lithium salt has a thermal runaway suppression effect.
- the lithium silicate transition metal lithium salt simply becomes a high resistance compound, and therefore it is not preferable to exist in an excessive amount in the positive electrode.
- the ratio is 1.5 or more, there is no hindrance to the normal operation of the lithium ion secondary battery, but from the viewpoint of the discharge capacity of the lithium ion secondary battery, the ratio is in the range of 2 to 10. Is preferable, and the range of 2.1 to 9 is more preferable, and the range of 2.2 to 5 is particularly preferable.
- Patent Document 2 discloses a positive electrode including a first positive electrode active material layer containing LiNiO 2 and a second positive electrode active material layer containing Li 2 FeSiO 4 or LiFePO 4, and Cu as a negative electrode active material.
- a lithium ion secondary battery having a negative electrode containing 6 Sn 6 and having a lithium amount in the second positive electrode active material layer equal to or greater than an irreversible capacity of the negative electrode active material is described.
- excess Li 2 FeSiO 4 or LiFePO 4 simply becomes a high resistance compound. Therefore, in the lithium ion secondary battery disclosed in Patent Document 2, the second positive electrode active material layer It is not preferable that the amount of lithium exceeds the amount corresponding to the irreversible capacity of the negative electrode active material.
- the total amount of lithium in the thermal runaway suppression layer is preferably less than the amount corresponding to the irreversible capacity of the negative electrode active material.
- the irreversible capacity of the negative electrode active material is a capacity calculated by subtracting the initial discharge capacity from the initial charge capacity of the lithium ion secondary battery, and therefore can be easily calculated by a person skilled in the art by a simple experiment. .
- silicate transition metal lithium salt examples include compounds represented by Li 2 MSiO 4 (M is one or more elements selected from transition elements).
- Specific examples of the lithium silicate transition metal lithium salt include, for example, Li 2 FeSiO 4 , Li 2 MnSiO 4 , Li 2 NiSiO 4 , Li 2 CoSiO 4 , Li 2 Fe 0.9 Co 0.1 SiO 4 , Li 2 Fe 0. .75 Co 0.25 SiO 4 , Li 2 Fe 0.5 Co 0.5 SiO 4 , and Li 2 Fe 0.25 Co 0.75 SiO 4 .
- the thermal runaway suppression layer contains a binder and / or a conductive aid as necessary.
- the binder described in the description of the active material layer can be added to the thermal runaway suppressing layer alone or in combination of two or more.
- the amount of the binder used is not particularly limited, but a range of 1 to 50 parts by mass of the binder is preferable with respect to 100 parts by mass of the lithium silicate transition metal. This is because if the amount of the binder is too small, the moldability of the thermal runaway suppressing layer is lowered, and if the amount of the binder is too large, the thermal runaway suppressing effect of the thermal runaway suppressing layer is lowered.
- the conductive auxiliary agent those described in the description of the active material layer can be added to the thermal runaway suppressing layer alone or in combination of two or more.
- the amount of the conductive aid used is not particularly limited, but for example, it can be 1 to 30 parts by weight of the conductive aid with respect to 100 parts by weight of the lithium silicate transition metal salt.
- a conventionally known method such as a roll coating method, a dip coating method, a doctor blade method, a spray coating method, or a curtain coating method may be used.
- a suitable solvent is added to a mixture in which a lithium silicate transition metal lithium salt and, if necessary, a binder and / or a conductive additive are mixed to form a paste-like thermal runaway suppression layer forming composition.
- the composition for forming a thermal runaway suppression layer is applied to the surface of the positive electrode active material layer and then dried. Drying may be performed under normal pressure conditions or under reduced pressure conditions using a vacuum dryer. What is necessary is just to set drying temperature suitably, and the temperature beyond the boiling point of the said solvent is preferable. What is necessary is just to set drying time suitably according to an application quantity and drying temperature. In order to increase the density of the thermal runaway suppression layer, a compression step may be added to the dried positive electrode on which the thermal runaway suppression layer is formed.
- the thickness of the thermal runaway suppression layer is not particularly limited, but is preferably in the range of 1 to 20 ⁇ m, more preferably in the range of 3 to 15 ⁇ m, and particularly preferably in the range of 4 to 10 ⁇ m.
- the lithium ion secondary battery of the present invention has a negative electrode including a negative electrode active material.
- a lithium ion secondary battery such as a carbon-based material capable of inserting and extracting lithium, an element capable of being alloyed with lithium, a compound having an element capable of being alloyed with lithium, or a polymer material
- a known material employed as a material for the negative electrode active material may be used alone or in combination.
- the carbon-based material include non-graphitizable carbon, artificial graphite, natural graphite, cokes, graphites, glassy carbons, organic polymer compound fired bodies, carbon fibers, activated carbon, and carbon blacks.
- the organic polymer compound fired body refers to a material obtained by firing and carbonizing a polymer material such as phenols and furans at an appropriate temperature.
- elements that can be alloyed with lithium include Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Ti, Ag, Zn, Cd, Al, Ga, In, Si. , Ge, Sn, Pb, Sb, Bi can be exemplified, and Si or Sn is particularly preferable.
- compounds having elements that can be alloyed with lithium include ZnLiAl, AlSb, SiB 4 , SiB 6 , Mg 2 Si, Mg 2 Sn, Ni 2 Si, TiSi 2 , MoSi 2 , CoSi 2 , NiSi 2 , CaSi 2, CrSi 2, Cu 5 Si, FeSi 2, MnSi 2, NbSi 2, TaSi 2, VSi 2, WSi 2, ZnSi 2, SiC, Si 3 N 4, Si 2 N 2 O, SiO v (0 ⁇ v ⁇ 2), SnO w (0 ⁇ w ⁇ 2), SnSiO 3 , LiSiO or LiSnO can be exemplified, and among these, a compound containing Si is preferable, and SiO x (0.5 ⁇ x ⁇ 1.5) is particularly preferable. . Further, examples of the compound having an element capable of alloying with lithium include tin alloys (Cu—Sn alloy, Co—Sn alloy, etc.). Specific
- the negative electrode only needs to include a current collector and a negative electrode active material layer containing a negative electrode active material formed on the current collector.
- the current collector the above-described current collector may be adopted as appropriate.
- the negative electrode active material layer includes a binder and / or a conductive aid as necessary. And what is necessary is just to employ
- the above-described method may be used to form the negative electrode active material layer on the current collector.
- the amount of the positive electrode active material in the positive electrode and the amount of the negative electrode active material in the negative electrode may be appropriately determined so as to obtain a desired battery capacity in view of the lithium occlusion performance and release performance of both active materials.
- the lithium ion secondary battery of the present invention preferably has a separator for separating the positive electrode and the negative electrode and allowing ions to pass while preventing a short circuit of the battery due to contact between the two electrodes.
- a separator a known one used in a lithium ion secondary battery may be used.
- a porous film using one or more synthetic resins such as polytetrafluoroethylene, polypropylene, polyethylene, polyester, and polyamide is used. It can be illustrated.
- the separator may have a single-layer structure using a single synthetic resin or a laminated structure in which a plurality of synthetic resin layers are stacked.
- the thickness of the separator is not particularly limited, but is preferably in the range of 5 ⁇ m to 100 ⁇ m, more preferably in the range of 10 ⁇ m to 50 ⁇ m, and particularly preferably in the range of 15 ⁇ m to 30 ⁇ m.
- the lithium ion secondary battery of the present invention preferably has an electrolytic solution or a solid electrolyte serving as a medium for ions to move between the positive electrode and the negative electrode.
- the electrolytic solution is a solution containing a solvent and an electrolyte dissolved in the solvent.
- As the electrolytic solution or the solid electrolyte a known one used in a lithium ion secondary battery may be used.
- Examples of the solvent used in the electrolytic solution include non-aqueous solvents such as cyclic esters, chain esters, ethers, and fluorine-containing cyclic esters.
- examples of 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.
- Fluorine-containing cyclic esters are those in which a part of the hydrogen constituting the cyclic ester is substituted with fluorine, and include fluoroethylene carbonate, 4,4-difluoroethylene carbonate, 4,5-difluoroethylene carbonate, and trifluoropropylene carbonate. Can be illustrated.
- a plurality of the above-described solvents may be used in combination as the solvent for the electrolytic solution.
- Examples of the electrolyte of the lithium ion secondary battery 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 concentration of the electrolyte in the electrolytic solution is preferably in the range of 0.5 to 1.7 mol / L.
- a positive electrode having a current collector, a positive electrode active material layer and a thermal runaway suppression layer, and a negative electrode having a current collector and a negative electrode active material layer are prepared by the method described above.
- a separator is sandwiched between both electrodes to form an electrode body.
- an electrolytic solution is added to the electrode body to obtain a lithium ion secondary battery.
- the shape of the lithium ion secondary battery is not particularly limited, and various shapes such as a cylindrical shape, a laminated shape, a coin shape, and a laminated shape can be employed.
- Example 1 The lithium ion secondary battery of the present invention was manufactured as follows.
- a lithium-containing metal oxide having a layered rock salt structure represented by LiNi 5/10 Co 2/10 Mn 3/10 O 2 as a positive electrode active material, 5 parts by mass of acetylene black as a conductive auxiliary agent, and a binder 3 parts by mass of polyvinylidene fluoride as an agent was mixed. This mixture was dispersed in an appropriate amount of N-methyl-2-pyrrolidone to prepare a slurry. An aluminum foil having a thickness of 20 ⁇ m was prepared as a positive electrode current collector. The slurry was applied to the surface of the aluminum foil using a doctor blade so as to form a film. The aluminum foil coated with the slurry was dried at 80 ° C. for 20 minutes to remove N-methyl-2-pyrrolidone by volatilization to obtain an aluminum foil on which a positive electrode active material layer was formed.
- Li 2 FeSiO 4 which is a lithium silicate transition metal
- acetylene black which is a conductive additive
- polyvinylidene fluoride which is a binder
- the said composition for thermal runaway suppression layer formation was apply
- the mass ratio of LiNi 5/10 Co 2/10 Mn 3/10 O 2 to the mass of Li 2 FeSiO 4 contained in the positive electrode was 9.
- a rectangular sheet (27 ⁇ 32 mm, thickness 25 ⁇ m) made of a polypropylene resin film was prepared as a separator.
- a separator was sandwiched between the thermal runaway suppression layer on the positive electrode and the negative electrode active material layer on the negative electrode to form an electrode plate group.
- the electrode plate group was covered with a set of two laminated films, and the three sides were sealed, and then an electrolyte solution was injected into the bag-like laminated film.
- an electrolytic solution a solution in which LiPF 6 was dissolved to 1 mol / L in a solvent obtained by mixing 4 parts by volume of fluoroethylene carbonate, 26 parts by volume of ethylene carbonate, 30 parts by volume of methyl ethyl carbonate, and 40 parts by volume of dimethyl carbonate was used. .
- the remaining one side of the laminate film was sealed to obtain a laminate type lithium ion secondary battery in which the four sides were hermetically sealed and the electrode plate group and the electrolyte were sealed.
- the amount of lithium in the thermal runaway suppression layer is less than the amount corresponding to the irreversible capacity of the negative electrode active material.
- the positive electrode and negative electrode of the lithium ion secondary battery of Example 1 are provided with tabs that can be electrically connected to the outside, and a part of this tab extends to the outside of the lithium ion secondary battery.
- Example 2 The lithium of Example 2 was the same as Example 1 except that the mass ratio of LiNi 5/10 Co 2/10 Mn 3/10 O 2 to the mass of Li 2 FeSiO 4 contained in the positive electrode was set to 4. An ion secondary battery was obtained. Note that the total mass of LiNi 5/10 Co 2/10 Mn 3/10 O 2 and Li 2 FeSiO 4 contained in the positive electrode of Example 2 is the same as that of Example 1. In the lithium ion secondary battery of Example 2, the amount of lithium in the thermal runaway suppression layer is less than the amount corresponding to the irreversible capacity of the negative electrode active material.
- Example 3 was the same as Example 1 except that the mass ratio of LiNi 5/10 Co 2/10 Mn 3/10 O 2 to the mass of Li 2 FeSiO 4 contained in the positive electrode was 7/3. A lithium ion secondary battery was obtained. Note that the total mass of LiNi 5/10 Co 2/10 Mn 3/10 O 2 and Li 2 FeSiO 4 contained in the positive electrode of Example 3 is the same as that of Example 1. In the lithium ion secondary battery of Example 3, the amount of lithium in the thermal runaway suppression layer is less than the amount corresponding to the irreversible capacity of the negative electrode active material.
- Example 4 is the same as Example 1 except that the mass ratio of LiNi 5/10 Co 2/10 Mn 3/10 O 2 to the mass of Li 2 FeSiO 4 contained in the positive electrode is 1.5. A lithium ion secondary battery was obtained. Note that the total mass of LiNi 5/10 Co 2/10 Mn 3/10 O 2 and Li 2 FeSiO 4 contained in the positive electrode of Example 4 is the same as that of Example 1. In the lithium ion secondary battery of Example 4, the amount of lithium in the thermal runaway suppression layer is equal to or greater than the amount corresponding to the irreversible capacity of the negative electrode active material.
- Comparative Example 1 The lithium of Comparative Example 1 was the same as Example 1 except that the mass ratio of LiNi 5/10 Co 2/10 Mn 3/10 O 2 to the mass of Li 2 FeSiO 4 contained in the positive electrode was set to 1. An ion secondary battery was obtained. Note that the total mass of LiNi 5/10 Co 2/10 Mn 3/10 O 2 and Li 2 FeSiO 4 contained in the positive electrode of Comparative Example 1 is the same as that of Example 1.
- Comparative Example 2 A lithium ion secondary battery of Comparative Example 2 was obtained in the same manner as in Example 1 except that the thermal runaway suppression layer was not formed on the positive electrode.
- the mass of LiNi 5/10 Co 2/10 Mn 3/10 O 2 contained in the positive electrode of Comparative Example 2 is the same as that of Example 1 LiNi 5/10 Co 2/10 Mn 3/10 O 2 and Li 2 FeSiO. It is the same as the total amount of four masses.
- the lithium ion secondary battery to be measured is CCCV charged (constant current constant voltage charge) to 25 ° C, 1C rate, voltage 4.5V, and then CC discharged (constant current discharge) to 2.5V at 0.33C rate.
- the initial adjustment was made. With respect to the lithium ion secondary battery subjected to the initial adjustment, CCCV charge was performed up to 25 ° C., 1 C rate, voltage 4.5 V, and then CC discharge was performed up to 2.5 V at a 0.33 C rate.
- a value obtained by dividing the discharge amount by the total mass of the positive electrode active materials LiNi 5/10 Co 2/10 Mn 3/10 O 2 and Li 2 FeSiO 4 in the positive electrode was defined as the discharge capacity.
- the lithium ion secondary battery in which the mass ratio of the lithium-containing composite oxide in the active material layer to the mass of the lithium silicate transition metal in the thermal runaway suppression layer is 1.5 or more It can be seen that the discharge capacity is superior to the discharge capacity of the lithium ion secondary battery having no thermal runaway suppression layer.
- the discharge capacity of the lithium ion secondary battery of Example 1-3 in which the amount of lithium in the thermal runaway suppression layer is less than the amount corresponding to the irreversible capacity of the negative electrode active material is remarkably excellent.
- Example 3 For the lithium ion secondary batteries of Example 3 and Comparative Example 2, the following nail penetration test was performed, and the state of the lithium ion secondary battery during an internal short circuit was observed. The results are shown in Table 2.
- a laminated lithium ion secondary battery was stacked so that the battery capacity was equivalent to 4 Ah.
- the laminated laminate type lithium ion secondary battery was charged at a constant voltage until it became stable at a potential of 4.1 V, 4.2 V, or 4.3 V.
- the laminated laminate type lithium ion secondary battery after charging was placed on a constraining plate having a hole with a diameter of 20 mm.
- a restraint plate was placed on a press machine with a nail attached to the top. Until the nail penetrates the laminated laminated lithium ion secondary battery on the restraining plate and the tip of the nail is located inside the hole of the restraining plate, the nail is moved from the top to the bottom at 20 mm / sec. Moved at a speed of.
- the state of the battery after nail penetration was observed at room temperature and atmospheric conditions.
- the nail used had a diameter of 8 mm and a tip angle of 60 °, and the nail material was S45C defined by JIS G 4051.
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Abstract
Description
本発明のリチウムイオン二次電池を以下のとおり製造した。
正極に含まれるLi2FeSiO4の質量に対するLiNi5/10Co2/10Mn3/10O2の質量比を4としたこと以外は、実施例1と同様の方法で、実施例2のリチウムイオン二次電池を得た。なお、実施例2の正極に含まれるLiNi5/10Co2/10Mn3/10O2及びLi2FeSiO4の質量の合計量は、実施例1のそれと同じである。実施例2のリチウムイオン二次電池において、熱暴走抑制層のリチウム量は負極活物質の不可逆容量に相当する量未満である。
正極に含まれるLi2FeSiO4の質量に対するLiNi5/10Co2/10Mn3/10O2の質量比を7/3としたこと以外は、実施例1と同様の方法で、実施例3のリチウムイオン二次電池を得た。なお、実施例3の正極に含まれるLiNi5/10Co2/10Mn3/10O2及びLi2FeSiO4の質量の合計量は、実施例1のそれと同じである。実施例3のリチウムイオン二次電池において、熱暴走抑制層のリチウム量は負極活物質の不可逆容量に相当する量未満である。
正極に含まれるLi2FeSiO4の質量に対するLiNi5/10Co2/10Mn3/10O2の質量比を1.5としたこと以外は、実施例1と同様の方法で、実施例4のリチウムイオン二次電池を得た。なお、実施例4の正極に含まれるLiNi5/10Co2/10Mn3/10O2及びLi2FeSiO4の質量の合計量は、実施例1のそれと同じである。実施例4のリチウムイオン二次電池において、熱暴走抑制層のリチウム量は負極活物質の不可逆容量に相当する量以上である。
正極に含まれるLi2FeSiO4の質量に対するLiNi5/10Co2/10Mn3/10O2の質量比を1としたこと以外は、実施例1と同様の方法で、比較例1のリチウムイオン二次電池を得た。なお、比較例1の正極に含まれるLiNi5/10Co2/10Mn3/10O2及びLi2FeSiO4の質量の合計量は、実施例1のそれと同じである。
正極に熱暴走抑制層を形成しなかったこと以外は、実施例1と同様の方法で、比較例2のリチウムイオン二次電池を得た。なお、比較例2の正極に含まれるLiNi5/10Co2/10Mn3/10O2の質量は、実施例1のLiNi5/10Co2/10Mn3/10O2及びLi2FeSiO4の質量の合計量と同じである。
実施例1-4、比較例1-2のリチウムイオン二次電池につき、以下の試験を行い、リチウムイオン二次電池の放電容量を測定した。結果を表1に示す。
Claims (5)
- 集電体と、該集電体上に形成され、層状岩塩構造の一般式:LiaNibCocMndDeOf(0.2≦a≦1、b+c+d+e=1、0≦e<1、DはLi、Fe、Cr、Cu、Zn、Ca、Mg、S、Si、Na、K、Alから選ばれる少なくとも1の元素、1.7≦f≦2.1)で表されるリチウム含有複合酸化物を含む正極活物質層と、該正極活物質層上に形成され、ケイ酸遷移金属リチウム塩を含む熱暴走抑制層とを具備する正極と、
負極活物質を具備する負極とを有し、
前記正極において、前記ケイ酸遷移金属リチウム塩の質量に対する前記リチウム含有複合酸化物の質量比が1.5以上であることを特徴とするリチウムイオン二次電池。 - 前記熱暴走抑制層におけるリチウム合計量が前記負極活物質の不可逆容量に相当する量未満である請求項1に記載のリチウムイオン二次電池。
- 前記一般式において、0<b<1、0<c<1及び0<d<1である請求項1又は2に記載のリチウムイオン二次電池。
- 前記ケイ酸遷移金属リチウム塩がLi2MSiO4(Mは遷移元素から選択される単独又は複数の元素である。)である請求項1~3のいずれかに記載のリチウムイオン二次電池。
- 前記負極活物質がSiを含む請求項1~4のいずれかに記載のリチウムイオン二次電池。
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DE112014003824.5T DE112014003824T5 (de) | 2013-08-22 | 2014-07-17 | Lithiumionensekundärbatterie mit positiver Elektrode, die eine Schicht zur Unterdrückung eines thermischen Durchgehens auf der Aktivmaterialschicht der positiven Elektrode umfasst |
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US20180145317A1 (en) * | 2016-11-18 | 2018-05-24 | Semiconductor Energy Laboratory Co., Ltd. | Positive electrode active material, method for manufacturing positive electrode active material, and secondary battery |
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