CN111628209A - Lithium secondary battery - Google Patents
Lithium secondary battery Download PDFInfo
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- CN111628209A CN111628209A CN202010301620.4A CN202010301620A CN111628209A CN 111628209 A CN111628209 A CN 111628209A CN 202010301620 A CN202010301620 A CN 202010301620A CN 111628209 A CN111628209 A CN 111628209A
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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
- 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
- H01M10/056—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
- H01M10/0567—Liquid materials characterised by the additives
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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
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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
- 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
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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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- 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
Abstract
Disclosed herein is a lithium secondary battery. The lithium secondary battery includes a positive electrode, a negative electrode, and a non-aqueous electrolyte, and more particularly, the positive electrode includes a positive active material including a lithium-metal oxide in which at least one metal has a continuous concentration gradient from the center to the surface, and the non-aqueous electrolyte includes a lithium salt, a polynitrile compound, and an organic solvent, thereby improving storage characteristics and life characteristics at high voltage/high temperature.
Description
This application is a divisional application of patent applications having application number 2015102960467, application date 2015, 06, 02 and entitled "lithium secondary battery".
Technical Field
The present invention relates to a lithium secondary battery, and more particularly, to a lithium secondary battery having excellent life characteristics and charging characteristics at high voltage/high temperature.
Background
With the rapid development of the electronics, communications and computer industries, portable electronic communication devices such as video cameras, cell phones, notebook computers, etc. have been significantly improved. Therefore, the demand for a lithium secondary battery as a power source for driving the above devices is increasing. In particular, research and development on environmentally friendly power sources applied to, for example, electric vehicles, uninterruptible power supply devices, electric tools, satellites, etc., are actively progressing in japan, europe, the united states, etc., and korea.
Among currently used secondary batteries, a lithium secondary battery, which was studied in the early 90 s of the 20 th century, includes a negative electrode formed of a carbon material or the like, which is capable of absorbing and releasing lithium ions, a positive electrode formed of a lithium-based oxide or the like, and a non-aqueous electrolyte in which a lithium salt is dissolved in an appropriate amount of a composite organic solvent.
However, as the application range of lithium secondary batteries increases, longer life is required, and as the capacity of batteries increases, the demand for charging at high voltage also increases. However, when the battery is charged at a high voltage/high temperature, the amount of lithium ions is greatly increased, and the structural instability of the positive electrode active material is greatly increased, and the decomposition of the electrolyte on the surface of the positive electrode is accelerated, thereby reducing the life span of the battery. Conventional lithium transition metal oxides or composite oxides used for a positive active material of a lithium secondary battery have limitations in life characteristics and charging at high voltage/high temperature.
In order to solve the above problems, korean patent laid-open No. 10-2006-.
[ Prior art documents ]
Prior art document 1: korean patent laid-open No.10-2006-
Disclosure of Invention
The present invention relates to providing a lithium secondary battery having excellent life characteristics and charging characteristics at high voltage/high temperature.
1. A lithium secondary battery comprising:
a positive electrode;
a negative electrode; and
a non-aqueous electrolyte,
wherein the positive electrode comprises a positive electrode active material comprising a lithium-metal oxide in which at least one metal has a continuous concentration gradient from the center to the surface of the positive electrode active material, and
wherein the non-aqueous electrolyte includes a lithium salt, a polynitrile compound, and an organic solvent.
2. In the lithium secondary battery of item 1, wherein the lithium-metal oxide includes at least one metal having a constant concentration from the center to the surface of the positive electrode active material.
3. In the lithium secondary battery of item 1, wherein the lithium-metal oxide includes a first metal having a concentration gradient range in which a concentration increases from a center to a surface of the positive electrode active material and a second metal having a concentration gradient range in which a concentration decreases from the center to the surface of the positive electrode active material.
4. In the lithium secondary battery of item 1, wherein the lithium-metal oxide is represented by the following chemical formula 1, and at least one of M1, M2, and M3 in the following chemical formula 1 has a continuous concentration gradient from the center to the surface of the cathode active material.
[ chemical formula 1]
LixM1aM2bM3cOy
(wherein M1, M2 and M3 are selected from the group consisting of Ni, Co, Mn, Na, Mg, Ca, Ti, V, Cr, Cu, Zn, Ge, Sr, Ag, Ba, Zr, Nb, Mo, Al, Ga and B,
x is more than 0 and less than or equal to 1.1, y is more than or equal to 2 and less than or equal to 2.02, a is more than or equal to 0 and less than or equal to 1, b is more than or equal to 0 and less than or equal to 1, c is more than or equal to 0 and less than or equal to 1, and a + b + c is more than 0 and less than or equal. )
5. In the lithium secondary battery of item 4, wherein at least one of the M1, M2, and M3 has a concentration gradient range in which the concentration increases from the center to the surface, and the rest has a concentration gradient range in which the concentration decreases from the center to the surface.
6. In the lithium secondary battery of item 4, wherein one of the M1, M2, and M3 has a concentration gradient range in which a concentration increases from the center to the surface, and the other has a concentration gradient range in which a concentration decreases from the center to the surface, and the remaining one has a constant concentration from the center to the surface.
7. In the lithium secondary battery of item 4, wherein the M1, M2 and M3 are Ni, Co and Mn, respectively.
8. In the lithium secondary battery of any one of items 4 to 7, wherein M1 is Ni, and 0.6. ltoreq. a.ltoreq.0.95 and 0.05. ltoreq. b + c.ltoreq.0.4.
9. In the lithium secondary battery of any one of items 4 to 7, M1 may be Ni, and 0.7. ltoreq. a.ltoreq.0.9 and 0.1. ltoreq. b + c.ltoreq.0.3.
10. In the lithium secondary battery according to item 1, wherein the primary particles of the lithium-metal oxide are rod-like in shape.
11. In the lithium secondary battery of item 1, wherein the polynitrile compound comprises a dinitrile compound, a dinitrile compound or a mixture thereof.
12. In the lithium secondary battery of item 1, wherein the polynitrile compound includes at least one selected from the group consisting of: succinonitrile, decanedionitrile, glutaronitrile, adiponitrile, 1, 5-dicyanopentane, 1, 6-dicyanohexane, 1, 7-dicyanoheptane, 1, 8-dicyanooctane, 1, 9-dicyanononane, 1, 10-dicyanodecane, 1, 12-dicyanododecane, tetramethylsuccinonitrile, 2-methylglutaronitrile, 2, 4-dimethylglutaronitrile, 2, 4, 4-tetramethylglutaronitrile, 1, 4-dicyanopentane, 2, 5-dimethyl-2, 5-dicyanohexane, 2, 6-dicyanoheptane, 2, 7-dicyanooctane, 2, 8-dicyanononane, 1, 6-dicyanodecane, 1, 3, 5-tricyanohexane and 1, 3, 6-tricyanohexane.
13. In the lithium secondary battery of item 1, wherein the polynitrile compound includes at least one selected from the group consisting of: succinonitrile, glutaronitrile, adiponitrile, 1, 3, 5-tricyanohexane and 1, 3, 6-tricyanohexane.
14. In the lithium secondary battery of item 1, wherein the polynitrile compound is contained in the nonaqueous electrolyte at 0.1 wt% to 10 wt% based on the total amount of the nonaqueous electrolyte.
15. In the lithium secondary battery of item 1, wherein the polynitrile compound is contained in the nonaqueous electrolyte at 0.5 to 7 wt% based on the total amount of the nonaqueous electrolyte.
16. In the lithium secondary battery of item 1, the polynitrile compound is contained in the nonaqueous electrolyte at a concentration of 1 to 7 wt% based on the total amount of the nonaqueous electrolyte.
17. In the lithium secondary battery of item 1, wherein the charging voltage is 4.3V to 4.5V.
Drawings
The above and other objects, features and advantages of the present invention will become more apparent to those skilled in the art by describing in detail exemplary embodiments thereof with reference to the attached drawings, in which:
fig. 1 is a view briefly showing a measurement position for measuring the concentration of lithium-metal oxide according to an embodiment of the present invention;
fig. 2 is a TEM image of a lithium-metal oxide according to example 1 of the present invention; and
fig. 3 is a TEM image of a lithium-metal oxide according to comparative example 1 of the present invention.
Detailed Description
According to the present invention, in a lithium secondary battery including a positive electrode, a negative electrode and a non-aqueous electrolyte, the positive electrode includes a positive active material including a lithium-metal oxide in which at least one metal has a continuous concentration gradient from the center to the surface, and the non-aqueous electrolyte includes a lithium salt, a polynitrile compound and an organic solvent, and thus storage characteristics and life characteristics at high voltage/high temperature are improved.
Hereinafter, the present invention will be described in detail.
Positive electrode active material
The positive electrode active material of the present invention includes a lithium-metal oxide in which at least one metal has a continuous concentration gradient from the center to the surface of the positive electrode active material. The above-described positive electrode active material has excellent storage characteristics and life characteristics, as compared to a positive electrode active material having a constant concentration.
In the present invention, the metal in the lithium-metal oxide has a continuous concentration gradient from the center to the surface of the positive electrode active material, and therefore, the metal other than lithium has a concentration distribution that changes with a constant tendency from the center to the surface of the lithium-metal oxide particle. A constant trend means a trend of decreasing or increasing of the overall concentration change, but does not exclude a value opposite to the above trend at some points.
The center of the particles of the present invention refers to the range from the center of the material particles to a radius of 0.2 μm, and the surface of the particles refers to the range from the outermost surface of the particles to 0.2 μm.
The positive electrode active material of the present invention includes at least one metal having a concentration gradient. Accordingly, the cathode active material may include a first metal having a concentration gradient range that increases from the center to the surface and a second metal having a concentration gradient range that decreases from the center to the surface. The first metal and the second metal may be independently of one or more types.
According to another embodiment of the present invention, the cathode active material of the present invention may include at least one metal having a constant concentration from the center to the surface of the cathode active material.
Specific examples of the cathode active material of the present invention may include a lithium-metal oxide represented by the following chemical formula 1, and in the following chemical formula 1, at least one of M1, M2, and M3 has a continuous concentration gradient from the center to the surface of the cathode active material.
[ chemical formula 1]
LixM1aM2bM3cOy
(wherein M1, M2 and M3 are selected from the group consisting of Ni, Co, Mn, Na, Mg, Ca, Ti, V, Cr, Cu, Zn, Ge, Sr, Ag, Ba, Zr, Nb, Mo, Al, Ga and B,
and x is more than 0 and less than or equal to 1.1, y is more than or equal to 2 and less than or equal to 2.02, a is more than or equal to 0 and less than or equal to 1, b is more than or equal to 0 and less than or equal to 1, c is more than or equal to 0 and less than or equal to 1, and a + b + c is more than 0 and less than or. )
In an embodiment of the present invention, at least one of M1, M2, and M3 has a concentration gradient range that increases from the center to the surface of the cathode active material, and the rest may have a concentration gradient range that decreases from the center to the surface of the cathode active material.
In another embodiment of the present invention, one of M1, M2, and M3 has a concentration gradient range that increases from the center to the surface, and another may have a concentration gradient range that decreases from the center to the surface, and another may have a constant concentration from the center to the surface.
In a specific example of the present invention, M1, M2, and M3 may be Ni, Co, and Mn, respectively.
The lithium-metal oxide of the present invention may include a relatively high content of nickel (Ni). When nickel is used, the battery capacity can be increased, and in the conventional positive active material structure, when the nickel content is high, the lifespan is reduced, but the positive active material of the present invention does not reduce the lifespan even if the nickel content is high. Therefore, the cathode active material of the present invention has excellent life characteristics while maintaining a high capacity.
For example, in the lithium-metal oxide of the present invention, the molar ratio of nickel is 0.6 to 0.95, and preferably 0.7 to 0.9. That is, when M1 in chemical formula 1 is Ni, chemical formula 1 may include 0.6. ltoreq. a.ltoreq.0.95 and 0.05. ltoreq. b + c.ltoreq.0.4, and preferably 0.7. ltoreq. a.ltoreq.0.9 and 0.1. ltoreq. b + c.ltoreq.0.3.
The lithium-metal oxide of the present invention is not limited to a specific particle shape of the lithium-metal oxide, but preferably, the primary particles may be rod-shaped.
The lithium-metal oxide of the present invention is not limited to a specific particle size of the lithium-metal oxide, and for example, the lithium-metal oxide may have a particle size of 3 μm to 20 μm.
The positive electrode active material of the present invention may further include a coating layer on the lithium-metal oxide. The coating may comprise a metal or metal oxide and may, for example, comprise Al, Ti, Ba, Zr, Si, B, Mg, P and alloys thereof, or comprise metal oxides thereof.
The positive electrode active material of the present invention may be the above-described lithium-metal oxide doped with a metal or a metal oxide. Metals or metal oxides suitable for doping may include Al, Ti, Ba, Zr, Si, B, Mg, P, and alloys thereof, or metal oxides thereof.
The lithium-metal oxides of the present invention may be prepared using coprecipitation.
Hereinafter, a method of preparing the cathode active material according to an embodiment of the present invention will be described.
First, metal precursor solutions having different concentrations were prepared. The metal precursor solution includes one or more precursors of at least one type to be included in the positive electrode active material. Examples of the metal precursor may include metal halides, metal hydroxides, acid salts of metals, and the like.
The metal precursor solution to be prepared includes two types of precursor solutions including a precursor solution of a concentration to generate the center of the positive electrode active material and a precursor solution of a concentration to generate the surface. For example, when preparing a metal oxide cathode active material including nickel, manganese, cobalt, and lithium, a precursor solution having a concentration of nickel, manganese, and cobalt corresponding to the center of the cathode active material and a precursor solution having a concentration of nickel, manganese, and cobalt corresponding to the surface are prepared.
Then, the two types of metal precursor solutions are mixed to form a precipitate. During mixing, the mixing ratio of the two types of metal precursor solutions is continuously varied to correspond to the concentration gradient in the desired active material. Thus, the precipitate has a concentration gradient of the active material. Precipitation is performed during mixing by adding a chelating agent and a base.
The prepared precipitate is heat-treated, mixed with a lithium salt, and then heat-treated again, thereby obtaining the positive electrode active material of the present invention.
Negative electrode active material
The anode active material of the present invention may use any material disclosed in the prior art capable of absorbing and releasing lithium ions without limitation. For example, it is possible to use: carbon materials such as crystalline carbon, amorphous carbon, carbon composite, carbon fiber, and the like; lithium metal, alloys of lithium and other elements, silicon, tin, and the like. The amorphous carbon may include hard carbon, coke, mesocarbon microbeads (MCMB) fired at a temperature of less than or equal to 1500 ℃, mesophase pitch-based carbon fibers (MPCF), and the like. The crystalline carbon may include graphite-based materials such as, for example, natural graphite, graphitized coke, graphitized MCMB, graphitized MPCF, among others. Other elements that alloy with lithium may include aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin, gallium, or indium.
Non-aqueous electrolyte
The non-aqueous electrolyte includes a lithium salt as an electrolyte, and an organic solvent, and further includes a polynitrile compound.
The polynitrile compound includes a compound having at least two nitrile groups, and may be, for example, a dinitrile compound, a trinitrile compound, or a mixture thereof.
When the polynitrile compound is used together with the positive electrode active material of the present invention, the charging characteristics at high voltage/high temperature are greatly improved while the life characteristics are excellently maintained, and theoretically, this is caused by adsorption of the polynitrile compound on the surface of the positive electrode active material to prevent decomposition of the electrolyte, but the present invention should not be limited to the above description.
Specific examples of the polynitrile compound may include one or a mixture of two or more of the following: succinonitrile, sebaconitrile, glutaronitrile, adiponitrile, 1, 5-dicyanopentane, 1, 6-dicyanohexane, 1, 7-dicyanoheptane, 1, 8-dicyanooctane, 1, 9-dicyanononane, 1, 10-dicyanodecane, 1, 12-dicyanododecane, tetramethylsuccinonitrile, 2-methylglutaronitrile, 2, 4-dimethylglutaronitrile, 2, 4, 4-tetramethylglutaronitrile, 1, 4-dicyanopentane, 2, 5-dimethyl-2, 5-dicyanohexane, 2, 6-dicyanoheptane, 2, 7-dicyanooctane, 2, 8-dicyanononane, 1, 6-dicyanodecane, 1, 3, 5-tricyanohexane and 1, 3, 6-tricyanohexane and the like, but is not limited thereto. Preferably, the polynitrile compound may include at least one selected from the group consisting of: succinonitrile, glutaronitrile, adiponitrile, 1, 3, 5-tricyanohexane and 1, 3, 6-tricyanohexane.
The polynitrile compound is included in the non-aqueous electrolyte at 0.1 to 10 wt%, preferably 0.5 to 7 wt%, and more preferably 1 to 7 wt%, based on the total amount of the non-aqueous electrolyte. Within the above range, the charging performance at high voltage/high temperature may be excellent.
The conventional lithium salt used in the electrolyte of the lithium secondary battery may be used for the lithium salt without limitation, and may be made of Li+X-And (4) showing. The anion of the above lithium salt is not particularly limited, and may include, for example, F-、Cl-、Br-、I-、NO3 -、N(CN)2 -、BF4 -、ClO4 -、PF6 -、(CF3)2PF4 -、(CF3)3PF3 -、(CF3)4PF2 -、(CF3)5PF-、(CF3)6P-、CF3SO3 -、CF3CF2SO3 -、(CF3SO2)2N-、(FSO2)2N-、CF3CF2(CF3)2CO-、(CF3SO2)2CH-、(SF5)3C-、(CF3SO2)3C-、CF3(CF2)7SO3 -、CF3CO2 -、CH3CO2 -、SCN-、(CF3CF2SO2)2N-And the like.
The organic solvent may be used without limitation for a conventional electrolyte in a lithium secondary battery, and generally any one or a mixture of two or more selected from the following may be used: propylene Carbonate (PC), Ethylene Carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), Ethyl Methyl Carbonate (EMC), propyl methyl carbonate, dipropyl carbonate, dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, vinylene carbonate, sulfolane, γ -butyrolactone, propylene sulfite, and tetrahydrofuran.
Secondary battery
The present invention provides a lithium secondary battery prepared using a positive electrode comprising the above positive electrode active material, a negative electrode comprising a negative electrode active material, and the above non-aqueous electrolyte.
The lithium secondary battery of the present invention, which includes the above-described cathode active material and a non-aqueous electrolyte, can be charged by a charging voltage applied in the related art, and in particular, has excellent charging characteristics at a high voltage of 4.3V or more. For example, the lithium secondary battery has excellent life characteristics at a charging voltage of 4.3V to 4.5V.
The positive electrode and the negative electrode may be prepared by mixing and stirring the above-described positive electrode active material and negative electrode active material of the present invention with a binder, a conductive material, a dispersant as needed to prepare a composition, and coating the above mixture on a current collector of a metal material and performing pressing and drying.
Well-known binders may be used without limitation, for example, organic-based binders such as polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, etc., or aqueous-based binders such as Styrene Butadiene Rubber (SBR), etc., may be used together with a thickener such as carboxymethyl Cellulose (CMD), etc.
A conventional conductive carbon material may be used as the conductive material without limitation.
The current collector of the metal material may use any metal that has high conductivity and may be easily attached to a compound of the positive or negative active material, and does not react in the voltage range of the battery. Non-limiting examples of the positive electrode current collector may include a foil made of aluminum, nickel, or a combination thereof, and non-limiting examples of the negative electrode current collector may include a foil made of copper, gold, nickel, a copper alloy, or a combination thereof.
The separator is interposed between the positive electrode and the negative electrode, and the separator may include a single-layer or multi-layer structure using: general porous polymer films such as polyolefin-based polymers such as ethylene homopolymer, propylene homopolymer, ethylene/butene copolymer, ethylene/hexene copolymer, ethylene/methacrylate copolymer, and the like; or a general porous non-woven fabric such as a non-woven fabric including glass fiber having a high melting point, polyethylene terephthalate fiber, etc., but not limited thereto. The separator may be applied to the battery by a general winding method, lamination (stacking) of the separator and the battery, a folding method, or the like.
A nonaqueous electrolyte is injected into an electrode structure formed of a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, thereby preparing a lithium secondary battery. The shape of the lithium secondary battery of the present invention is not limited, and may have a cylindrical shape, a prismatic shape, a pocket shape, a coin shape, etc. using a can.
Hereinafter, a collector plate (charge collecting plate) for a fuel cell and a stack structure having the same according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. It is important to understand that the present invention may be embodied in many alternate forms and should not be construed as limited to the embodiments set forth herein. While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that there is no intention to limit the invention to the specific forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.
Example 1
< Positive electrode >
Using a catalyst having LiNi0.8Co0.1Mn0.1O2Material of overall composition, that is, having LiNi composed from the center0.84Co0.11Mn0.05O2To surface composition LiNi0.78Co0.10Mn0.12O2A concentration gradient of lithium-metal oxide (hereinafter, CAM-10) as a positive electrode active material, and dan Black (Denka Black) as a conductive material, and PVDF as a binder, to prepare a positive electrode active material mixture having a composition of a weight ratio of 92: 5: 3, and then coating, drying and pressing the positive electrode active material mixture on an aluminum substrate, to prepare a positive electrode.
Here, the concentration gradient of the prepared lithium-metal oxide was the same as in table 1 below, and the position of the measured concentration is shown in fig. 1. The positions measured with respect to the lithium-metal oxide particles having a radius of 5 μm from the center to the surface were spaced 5/7 μm apart from each other.
[ Table 1]
| Position of | Nickel (II) | | Zirconium | |
| 1 | 77.97 | 11.96 | 10.07 | |
| 2 | 80.98 | 9.29 | 9.73 | |
| 3 | 82.68 | 7 | 10.32 | |
| 4 | 82.6 | 7.4 | 10 | |
| 5 | 82.55 | 7.07 | 10.37 | |
| 6 | 83.24 | 5.9 | 10.86 | |
| 7 | 84.33 | 4.84 | 10.83 |
< negative electrode >
On a copper substrate, a negative electrode comprising 93 wt% of natural graphite as a negative electrode active material
A negative electrode active material mixture of 5 wt% of sheet-shaped conductive material KS6 used as a conductive material, 1 wt% of SBR used as a binder, and 1 wt% of CMC used as a thickener was coated, dried, and pressed, thereby preparing a negative electrode.
< evaluation of Life characteristics at Room temperature for Battery production >
The positive electrode plate and the negative electrode plate were engraved with a groove of an appropriate size and stacked, and a separator (polyethylene, thickness 25 μm) was interposed between the positive electrode plate and the negative electrode plate to form a battery, and a tab portion of each positive electrode and a tab portion of the negative electrode were welded. The welded positive electrode/separator/negative active material mixture was inserted into the pouch, and three sides except for the injection side for injecting the electrolyte were sealed. Here, the portion provided with the joint is included in the sealing portion. Electrolyte was injected through the remaining unsealed side and the remaining side was sealed, and then the above structure was immersed for more than 12 hours. An electrolyte was prepared from a 1M LiPF6 solution using a mixed solvent of EC/EMC/DEC (25/45/30; volume ratio), and then 1 wt% of Vinylene Carbonate (VC), 0.5 wt% of 1, 3-propenyl sultone (PRS), 0.5 wt% of lithium bis (oxalato) borate (LiBOB), and 0.5 wt% of Succinonitrile (SN) were added to be used.
Then, a precharge current (2.5A) corresponding to 0.25C was applied for 36 minutes. After 1 hour, the above structure was degassed and aged for more than 24 hours, and then charge-discharge (charge condition CC-CV 0.2C 4.2V0.05CCUT-OFF, discharge condition CC 0.2C2.5V CUT-OFF) was formed. Then, standard charge-discharge (charge condition CC-CV0.5C 4.2.2V 0.05C CUT-OFF, discharge condition CC 0.5C 2.5V CUT-OFF) was performed.
The prepared battery was repeatedly charged (CC-CV 2.0C 4.2V0.05C CUT-OFF) and discharged (CC2.0C2.75V CUT-OFF)500 times, and then the 500 th discharge capacity was calculated with respect to the percentage (%) of the one-time discharge capacity to measure the life characteristics at room temperature. The results are shown in Table 3.
The results are shown in Table 2.
Examples 2 to 24
Batteries were manufactured in the same manner as example 1 except that the succinonitrile content and the charging voltage according to table 2 were used, and the life characteristics were evaluated, and then the results are shown in table 2.
Comparative example 1
Except that LiNi will have a constant composition throughout the particle0.8Co0.1Mn0.1O2(hereinafter, CAM-20) was used as a positive electrode active material, a battery was prepared in the same manner as in example 1, and life characteristics were evaluated, and then the results were shown in table 3.
Comparative examples 2 to 28
Batteries were manufactured in the same manner as comparative example 1 except that the content of succinonitrile and the charging voltage were changed according to table 2, and the life characteristics were evaluated, and then the results are shown in table 3.
[ Table 2]
[ Table 3]
Referring to tables 2 and 3, the batteries of the examples had excellent life characteristics and charge characteristics at high temperatures, as compared to the comparative examples.
In particular, when the charging voltage was 4.2V, the embodiment had a larger lifetime absolute value than the comparative example, in particular, the lifetime reduction in the embodiment was smaller than that in the comparative example, and the comparison was made at 4.3V, 4.4V, 4.5V, respectively, the lifetime increase and the lifetime absolute value were prominent.
In addition, when the SN content at a charge voltage of 4.3V or more is 1 wt% to 7 wt%, the lifetime characteristics are increased, and in particular, the lifetime increase in the examples is more increased than that in the comparative examples.
In addition, fig. 2 and 3 show TEM images of the positive electrode active material particles of example 1 and comparative example 1, respectively. Referring to fig. 2 (example 1) and 3 (comparative example 1), the primary particles of the positive electrode active material of example 1 have a rod shape, while the primary particles of the positive electrode active material of comparative example 1 have a substantially spherical shape.
Examples 24 and 25
Batteries were prepared in the same manner as in example 9, except that the types and charging voltages of polynitrile compounds (glutaronitrile (GN), Adiponitrile (AN), 1, 3, 5-tricyanohexane and 1, 3, 6-tricyanohexane (HTCN)) were changed according to table 4, and the life characteristics were evaluated, and then the results were shown in table 4.
[ Table 4]
Referring to table 4, various polynitrile compounds have similar properties to succinonitrile, and have excellent life characteristics and charging characteristics at high voltage/high temperature.
According to the lithium secondary battery of the present invention, a positive electrode active material including a metal having a continuous concentration gradient is combined with a non-aqueous electrolyte including a specific additive, and thus life characteristics are greatly improved, and charging characteristics at high voltage/high temperature are excellent.
It will be apparent to those skilled in the art that various modifications to the above-described exemplary embodiments of the present invention can be made without departing from the spirit and scope of the invention. It is therefore intended that the invention be construed as including all such modifications, insofar as they come within the scope of the appended claims or the equivalents thereof.
Claims (12)
1. A lithium secondary battery comprising:
a positive electrode, a negative electrode, and a non-aqueous electrolyte,
wherein the positive electrode includes a positive electrode active material including a lithium-metal oxide containing Ni, Co, and Mn with a concentration gradient of at least one of Ni, Co, and Mn,
wherein the non-aqueous electrolyte comprises a lithium salt, a polynitrile compound and an organic solvent,
wherein the polynitrile compound is contained in an amount of 0.1 to 3 wt% based on 100 wt% of the total amount of the non-aqueous electrolyte.
2. The lithium secondary battery according to claim 1,
the concentration of Ni decreases in a direction from the center to the surface of the lithium-metal oxide.
3. The lithium secondary battery according to claim 1,
the concentration of Mn increases in a direction from the center to the surface of the lithium-metal oxide.
4. The lithium secondary battery according to claim 1,
the concentration of Co is constant in the direction from the center to the surface of the lithium-metal oxide.
5. The lithium secondary battery according to claim 1,
the lithium-metal oxide is represented by the following chemical formula 1:
[ chemical formula 1]
LixNiaCobMncOy
Wherein M1, M2 and M3 are selected from the group consisting of Ni, Co, Mn, Na, Mg, Ca, Ti, V, Cr, Cu, Zn, Ge, Sr, Ag, Ba, Zr, Nb, Mo, Al, Ga and B,
and x is more than 0 and less than or equal to 1.1, y is more than or equal to 2 and less than or equal to 2.02, a is more than or equal to 0 and less than or equal to 1, b is more than or equal to 0 and less than or equal to 1, c is more than or equal to 0 and less than or equal to 1, and a + b + c is more than or equal to 0 and less.
6. The lithium secondary battery according to claim 5,
in the chemical formula 1, a is not less than 0.6 and not more than 0.95, and b + c is not less than 0.05 and not more than 0.4.
7. The lithium secondary battery according to claim 5,
in the chemical formula 1, a is not less than 0.7 and not more than 0.9, and b + c is not less than 0.1 and not more than 0.3.
8. The lithium secondary battery according to claim 1,
the primary particles of the lithium-metal oxide are rod-like in shape.
9. The lithium secondary battery according to claim 1,
the polynitrile compound includes a dinitrile compound, or a mixture thereof.
10. The lithium secondary battery according to claim 1,
the polynitrile compound includes at least one selected from the group consisting of: succinonitrile, decanedionitrile, glutaronitrile, adiponitrile, 1, 5-dicyanopentane, 1, 6-dicyanohexane, 1, 7-dicyanoheptane, 1, 8-dicyanooctane, 1, 9-dicyanononane, 1, 10-dicyanodecane, 1, 12-dicyanododecane, tetramethylsuccinonitrile, 2-methylglutaronitrile, 2, 4-dimethylglutaronitrile, 2, 4, 4-tetramethylglutaronitrile, 1, 4-dicyanopentane, 2, 5-dimethyl-2, 5-dicyanohexane, 2, 6-dicyanoheptane, 2, 7-dicyanooctane, 2, 8-dicyanononane, 1, 6-dicyanodecane, 1, 3, 5-tricyanohexane and 1, 3, 6-tricyanohexane.
11. The lithium secondary battery according to claim 1,
the polynitrile compound includes at least one selected from the group consisting of: succinonitrile, glutaronitrile, adiponitrile, 1, 3, 5-tricyanohexane and 1, 3, 6-tricyanohexane.
12. The lithium secondary battery according to claim 1,
the charging voltage of the lithium secondary battery is 4.3V to 4.5V.
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| KR1020150063878A KR102349731B1 (en) | 2014-06-02 | 2015-05-07 | Lithium secondary battery |
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| KR102640842B1 (en) | 2016-06-09 | 2024-02-27 | 삼성에스디아이 주식회사 | Lithium battery |
| CN109148950B (en) | 2017-06-15 | 2020-10-02 | 宁德时代新能源科技股份有限公司 | Electrolyte and battery |
| CN109103489B (en) * | 2017-06-21 | 2020-05-05 | 宁德时代新能源科技股份有限公司 | Electrolyte and battery |
| KR102571672B1 (en) * | 2018-01-17 | 2023-08-25 | 에스케이온 주식회사 | Lithium secondary battery |
| KR102472882B1 (en) * | 2018-01-18 | 2022-11-30 | 에스케이온 주식회사 | Lithium secondary battery |
| CN111326793B (en) | 2018-12-14 | 2021-07-13 | 宁德时代新能源科技股份有限公司 | Lithium ion battery |
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| CN105322223A (en) | 2016-02-10 |
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