KR102387401B1 - Lithium secondary battery - Google Patents

Abstract

The present invention relates to a lithium secondary battery, and more particularly, comprising a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode; The positive electrode includes a first lithium-metal oxide in which at least one of the metals has a continuous concentration gradient region between at least a portion of the central portion and the surface portion of the particle, and a constant concentration of at least one of the metals between the central portion and the surface portion of the particle. By including the second lithium-metal oxide having a region, lifespan characteristics and penetration stability may be excellent.

Description

Lithium secondary battery {LITHIUM SECONDARY BATTERY}

The present invention relates to a lithium secondary battery, and more particularly, to a lithium secondary battery having excellent lifespan characteristics and penetration stability.

BACKGROUND With the rapid development of electronics, communication, and computer industries, portable electronic communication devices, such as camcorders, mobile phones, and notebook PCs, are admirably developing. Accordingly, the demand for lithium secondary batteries as a power source capable of driving them is increasing day by day. In particular, as an eco-friendly power source, R&D is being actively carried out in Japan, Europe, and the United States as well as in Korea in relation to the application of electric vehicles, uninterruptible power supplies, power tools, and satellites.

Among the currently applied secondary batteries, the lithium secondary battery developed in the early 1990s contains an anode made of a carbon material capable of occluding and releasing lithium ions, a cathode made of lithium-containing oxide, etc., and lithium salt dissolved in an appropriate amount in a mixed organic solvent. It is composed of a non-aqueous electrolyte.

However, as the application range of the lithium secondary battery is expanded, the need to use the lithium secondary battery even in a harsher environment such as a high temperature or low temperature environment is increasing.

However, lithium transition metal oxide or composite oxide used as a positive electrode active material of a lithium secondary battery has a problem in that the metal component is separated from the positive electrode when stored at a high temperature in a fully charged state, and thus is placed in a thermally unstable state. In addition, when a forcible internal short circuit occurs due to an external shock, there is a problem in that the amount of heat generated inside the battery is rapidly increased to cause ignition.

In order to solve this problem, Korean Patent Application Laid-Open No. 2006-0134631 discloses a cathode active material having a core-shell structure made of a lithium transition metal oxide having a different core and a different shell. Insufficient stability.

Korean Patent Publication No. 2006-0134631

An object of the present invention is to provide a lithium secondary battery having excellent lifespan characteristics and penetration stability.

According to an embodiment of the present invention, it includes a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode; The positive electrode includes a first lithium-metal oxide in which at least one of the metals has a continuous concentration gradient in at least a portion between the center portion of the particle and the surface portion, and a second lithium in which the metal has a constant concentration from the center portion of the particle to the surface portion. - A lithium secondary battery comprising a positive active material including a metal oxide, wherein the second lithium-metal oxide is represented by the following formula (1) is provided:

[Formula 1]

Li _x M1 _a M2 _b M3 _c O _y

(wherein, M1, M2 and M3 are 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, W and B 0<x≤1.1, 2≤y≤2.02, 0<a+b+c≤1, 0.58≤a≤0.62, 0.18≤b≤0.22, and 0.18≤c≤0.22).

In addition, the other one of the metal forming the first lithium-metal oxide has a constant concentration from the center of the particle to the surface, a lithium secondary battery is provided.

In addition, the first lithium-metal oxide has a concentration in which the concentration decreases in at least a portion between the first metal having a concentration gradient section in which the concentration increases in at least a portion between the center portion of the particle and the surface portion in the center of the particle and the surface portion in the center of the particle. A lithium secondary battery comprising a second metal having an inclined section is provided.

In addition, the first lithium-metal oxide is represented by the following formula (2), a lithium secondary battery is provided:

[Formula 2]

Li _x M4 _a M5 _b M6 _c O _y

(wherein, M4, M5 and M6 are 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, W and B is selected from, 0<x≤1.1, 2≤y≤2.02, and 0<a+b+c≤1, M4, Any one of M5 and M6 has a concentration gradient section in which the concentration increases at least partly between the center of the particle and the surface part, and the other one has a concentration gradient zone in which the concentration decreases at least partly between the center part of the particle and the surface part. and the other one has a constant concentration from the center of the particle to the surface).

In addition, in the first lithium-metal oxide, in the total particle concentration, M4 is Ni, 0.6≤a≤0.95 and 0.05≤b+c≤0.4, a lithium secondary battery is provided.

In addition, the first lithium-metal oxide is 0.7≤a≤0.9 and 0.1≤b+c≤0.3, a lithium secondary battery is provided.

In addition, the M4, A lithium secondary battery is provided, wherein M5 and M6 are Ni, Co and Mn, respectively.

In addition, the second lithium-metal oxide is 0.59≤a≤0.61, 0.19≤b≤0.21, and 0.19≤c≤0.21, a lithium secondary battery is provided.

In addition, the shape of the primary particles constituting the first lithium-metal oxide includes a rod-type shape, a lithium secondary battery is provided.

In addition, a mixed weight ratio of the first lithium-metal oxide and the second lithium-metal oxide is 60:40 to 10:90, a lithium secondary battery is provided.

In addition, a mixed weight ratio of the first lithium-metal oxide and the second lithium-metal oxide is 40:60 to 10:90, a lithium secondary battery is provided.

In addition, the second lithium-metal oxide has a size (D ₅₀ ) of 3 to 15 μm, a lithium secondary battery is provided.

In addition, the second lithium-metal oxide has a size (D ₅₀ ) of 7 to 15 μm, a lithium secondary battery is provided.

In addition, the density of the electrode of the positive electrode is 3.0 to 3.9 g / cc, a lithium secondary battery is provided.

The lithium secondary battery according to the present invention may exhibit significantly improved effects in both lifespan characteristics and penetration durability.

Figure 1 (a) schematically shows a cross section of the first lithium-metal oxide particles.
Figure 1 (b) schematically shows the metal concentration measurement position of the lithium-metal oxide particles used in Examples and Comparative Examples with respect to the concentration gradient layer.

One embodiment of the present invention is

a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode; The positive electrode includes a first lithium-metal oxide in which at least one of the metals has a continuous concentration gradient in at least a portion between the center portion of the particle and the surface portion, and a second lithium in which the metal has a constant concentration from the center portion of the particle to the surface portion. -A positive active material including a metal oxide, wherein the second lithium-metal oxide is represented by the following formula (1):

[Formula 1]

Li _x M1 _a M2 _b M3 _c O _y

(wherein, M1, M2 and M3 are 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, W and B 0<x≤1.1, 2≤y≤2.02, 0<a+b+c≤1, 0.58≤a≤0.62, 0.18≤b≤0.22 and 0.18≤c≤0.22),

It relates to a lithium secondary battery having excellent lifespan characteristics and penetration stability.

Hereinafter, specific embodiments of the present invention will be described. However, this is merely an example, and the present invention is not limited thereto.

In this specification, the meaning of "first" and "second" does not mean limiting the number of objects modified by "first" and "second", but only a meaning of distinguishing objects to be modified from each other does not

lithium secondary battery

The lithium secondary battery of the present invention includes a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode.

anode

The positive electrode according to the present invention includes a first lithium-metal oxide in which at least one of the metals has a continuous concentration gradient in at least a portion between the center portion of the particle and the surface portion, and the metal has a constant concentration from the center portion of the particle to the surface portion. and a positive active material including a second lithium-metal oxide.

In the present invention, that the metal forming the lithium-metal oxide has a continuous concentration gradient in at least a portion between the central portion and the surface portion means that the metals other than lithium are lithium-metal oxide particles in at least a portion between the center portion and the surface portion. It means to have a concentration distribution that changes with a constant trend. A constant trend means that the overall concentration change trend decreases or increases, and does not exclude having a value opposite to the trend at some points.

In the present invention, the central portion of the particle means within a radius of 0.2 μm from the center of the active material particle, and the surface portion of the particle means within 0.2 μm from the outermost part of the particle.

The present invention provides a positive electrode active material in which at least one of the metals includes a first lithium-metal oxide having a continuous concentration gradient in at least a portion between the central portion of the particle and the surface portion, thereby improving the lifespan characteristics and penetration characteristics of a lithium secondary battery. It can be effective, and by mixing the second lithium-metal oxide having excellent thermal stability because the Ni content is small, the lifespan characteristics and penetration characteristics of the lithium secondary battery can be remarkably excellent.

The second lithium-metal oxide of the positive electrode active material according to the present invention is represented by the following Chemical Formula 1:

[Formula 1]

Li _x M1 _a M2 _b M3 _c O _y

(wherein, M1, M2 and M3 are 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, W and B is selected from, 0<x≤1.1, 2≤y≤2.02, and 0<a+b+c≤1)

In addition, the metal included in the second lithium-metal oxide according to the present invention represented by Formula 1 is 0.58≤a≤0.62, 0.18≤b≤0.22 and 0.18≤c≤0.22, preferably 0.59≤a≤ 0.61, 0.19≤b≤0.21, and 0.19≤c≤0.21. When the first lithium-metal oxide satisfies the entire particle concentration range described above, lifespan characteristics and penetrating characteristics of the lithium secondary battery may be more excellent.

The first lithium-metal oxide of the positive active material according to an embodiment of the present invention may be represented by the following Chemical Formula 2:

[Formula 2]

Li _x M4 _a M5 _b M6 _c O _y

(wherein, M4, M5 and M6 are 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, W and B 0<x≤1.1, 2≤y≤2.02, and 0<a+b+c≤1).

The first lithium-metal oxide according to the present embodiment represented by Formula 2 includes at least one metal having a concentration gradient. Accordingly, as an embodiment, a first metal having a concentration gradient section in which the concentration increases in at least a portion between the central portion and the surface portion and a second metal having a concentration gradient section in which the concentration decreases in at least a portion between the center portion and the surface portion may include The first metal or the second metal may be independently of one another.

As another embodiment of the present invention, the first lithium-metal oxide according to the present invention may include a metal having a constant concentration from the center to the surface of the metals forming the lithium-metal oxide.

The first lithium-metal oxide according to the present invention may have, for example, 0.6≤a≤0.95 and 0.05≤b+c≤0.4, preferably 0.7≤a≤0.9 and 0.1≤ in terms of the total particle concentration b+c≤0.3, more preferably 0.77≤a≤0.83, 0.07≤b≤0.13, and 0.07≤c≤0.13, even more preferably 0.79≤a≤0.81, 0.09≤b≤0.11 and 0.09≤c≤0.11. The lithium secondary battery including the first lithium-metal oxide may have better lifespan characteristics and penetration characteristics.

The mixing weight ratio of the first lithium-metal oxide and the second lithium-metal oxide according to the present invention may be, for example, 60:40 to 10:90, preferably 40:60 to 10:90, within the above range. In the above-described effect of the present invention may be more excellent.

In addition, the density of the electrode of the positive electrode according to the present invention may be 3.0 to 3.9 g/cc, preferably 3.2 to 3.8 g/cc.

As a specific example of the lithium-metal oxide according to the present invention, M4 may be Ni, more preferably M4, M5 and M6 may be Ni, Co and Mn, respectively.

The first lithium-metal oxide according to the present invention may have a relatively high content of nickel (Ni). When nickel is used, it helps to improve battery capacity. In the conventional positive electrode active material structure, when the content of nickel is large, there is a problem that the life is reduced, but in the case of the positive active material according to the present invention, the content of nickel in the first lithium-metal oxide Even if there are many of these, life characteristics do not fall. Accordingly, the positive active material of the present invention may exhibit excellent lifespan characteristics while maintaining high capacity.

In this aspect, the first lithium-metal oxide according to the present invention may have, for example, a molar ratio of nickel included in the range of 0.6 to 0.95, preferably 0.7 to 0.9.

The lithium-metal oxide according to the present invention does not specifically limit the particle shape, but preferably, the primary particle may have a rod-type shape.

The first and second lithium-metal oxides according to the present invention do not specifically limit the particle size (D ₅₀ ), for example, the particle size (D ₅₀ ) may be 3 to 15 μm, respectively, preferably The second lithium-metal oxide may be 7 to 15 μm. When the first lithium-metal oxide or the second lithium-metal oxide satisfies the particle size in the above-mentioned range, lifespan characteristics or penetration stability may be more excellent.

The positive electrode active material according to the present invention may further include a coating layer on the above-described lithium-metal oxide. The coating layer may include a metal or a metal oxide. For example, it may include Al, Ti, Ba, Zr, Si, B, Mg, P and alloys thereof, or an oxide of the metal.

If necessary, the positive active material according to the present invention may be doped with the above-described lithium-metal oxide with a metal or a metal oxide. The dopable metal or metal oxide may be Al, Ti, Ba, Zr, Si, B, Mg, P and alloys thereof, or an oxide of the metal.

The lithium-metal oxide according to the present invention may be prepared using a co-precipitation method.

Hereinafter, an embodiment of a method for manufacturing a cathode active material according to the present invention will be described.

First, metal precursor solutions having different concentrations are prepared. The metal precursor solution is a solution including a precursor of at least one metal to be included in the positive electrode active material. Metal precursors are typically halides, hydroxides, acid salts of metals, and the like.

The metal precursor solution to be prepared obtains two types of precursor solutions, a precursor solution having a concentration of the composition of the central portion of the positive electrode active material to be prepared, and a precursor solution having a concentration corresponding to the composition of the surface portion, respectively. For example, in the case of manufacturing a metal oxide positive active material containing nickel, manganese, and cobalt in addition to lithium, a precursor solution having concentrations of nickel, manganese and cobalt corresponding to the central composition of the positive active material and the surface portion composition of the positive electrode active material Prepare a precursor solution having concentrations of nickel, manganese and cobalt corresponding to .

Next, a precipitate is formed while mixing the two kinds of metal precursor solutions. Upon mixing, the mixing ratio of the two metal precursor solutions is continuously changed to correspond to the concentration gradient in the desired active material. Thus, the precipitate has a concentration gradient in the concentration of the metal in the active material. Precipitation may be performed by adding a chelating reagent and a base upon mixing.

After the prepared precipitate is heat-treated, mixed with lithium salt and heat-treated again, the positive electrode active material according to the present invention can be obtained.

The positive electrode according to the present invention is prepared by mixing and stirring the positive electrode active material with a solvent, if necessary, a binder, a conductive material, a dispersing material, etc. to prepare a slurry, then applying (coating) it to a current collector of a metal material, compressing it, and drying it. can do.

As a binder, those used in the art may be used without particular limitation, for example, vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (polyvinylidenefluoride, PVDF), An organic binder such as polyacrylonitrile and polymethylmethacrylate, or an aqueous binder such as styrene-butadiene rubber (SBR) may be used together with a thickener such as carboxymethyl cellulose (CMC).

As the conductive material, a conventional conductive carbon material may be used without particular limitation.

The current collector made of a metal material has high conductivity and is a metal to which the positive or negative electrode active material mixture can easily adhere, and any metal that has no reactivity in the voltage range of the battery may be used. Non-limiting examples of the positive electrode current collector include a foil made of aluminum, nickel, or a combination thereof, and non-limiting examples of the negative electrode current collector include copper, gold, nickel, or a copper alloy or a combination thereof. foil, etc.

cathode

The negative electrode according to the present invention may be used without any particular limitation as long as it is commonly used in the art.

As the negative active material usable in the present invention, any one known in the art capable of occluding and deintercalating lithium ions may be used without particular limitation. For example, a carbon material such as crystalline carbon, amorphous carbon, carbon composite material, carbon fiber, lithium metal, an alloy of lithium and other elements, silicon or tin may be used. Examples of the amorphous carbon include hard carbon, coke, mesocarbon microbead (MCMB) calcined at 1500° C. or lower, mesophase pitch-based carbon fiber (MPCF), and the like. As crystalline carbon, there are graphite-based materials, specifically natural graphite, graphitized coke, graphitized MCMB, graphitized MPCF, and the like. As another element alloying with lithium, aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin, gallium or indium may be used.

The size of the graphite used in the present invention is not particularly limited, but may have an average particle diameter of 5 to 30 μm.

The negative electrode according to the present invention prepares a slurry by mixing and stirring a solvent, a binder, a conductive material, a dispersing material, etc., with the above-described negative active material, if necessary, and then coating (coating) it on a current collector of a metal material, compressing it, and drying it The same material and method as the above-described positive electrode may be applied to the solvent, binder, conductive material, dispersing material, and manufacturing method.

separator

As the separator, conventional porous polymer films conventionally used as separators, for example, polyolefin-based polymers such as ethylene homopolymer, propylene homopolymer, ethylene/butene copolymer, ethylene/hexene copolymer, and ethylene/methacrylate copolymer The porous polymer film produced by . As a method of applying the separator to a battery, in addition to winding, which is a general method, lamination, stacking, and folding of a separator and an electrode are possible.

non-aqueous electrolyte

In addition, the lithium secondary battery according to the present invention may further include a non-aqueous electrolyte, and the non-aqueous electrolyte includes a lithium salt as an electrolyte and an organic solvent, and the lithium salt is commonly used in electrolytes for lithium secondary batteries. Examples of the organic solvent include propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethylmethyl carbonate ( EMC), methylpropyl carbonate, dipropyl carbonate, dimethylsulfuroxide, acetonitrile, dimethoxyethane, diethoxyethane, vinylene carbonate, sulfolane, gamma-butyrolactone, propylene sulfite and tetrahydrofuran from the group consisting of Any one selected or a mixture of two or more of them may be used.

The non-aqueous electrolyte is injected into an electrode structure comprising a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode to prepare a lithium secondary battery.

The external shape of the lithium secondary battery of the present invention is not particularly limited, but may be a cylindrical shape using a can, a prismatic shape, a pouch type, or a coin type.

Hereinafter, preferred embodiments are presented to help the understanding of the present invention, but these examples are merely illustrative of the present invention and do not limit the appended claims, and are within the scope and spirit of the present invention. It is obvious to those skilled in the art that various changes and modifications are possible, and it is natural that such variations and modifications fall within the scope of the appended claims.

Example N6-A-1

As the first lithium-metal oxide, the overall composition is Li _{1 . 0} Ni _{0 . 80} Co _{0 . 11} Mn _{0 . 09} O ₂ , and the composition on the central side is Li _{1 . 0} Ni _{0 . 802} Co _{0 . 11} Mn ₀ . ₀₈₈ (positions 1 to 12 in Table 1) and the composition on the surface side is Li _{1 . 0} Ni _{0 . 77} Co _{0 . 11} Mn _{0 . 12} O ₂ (positions 12-5 to 13 in Table 1), and a concentration gradient layer is formed in the region between the center side and the surface side (positions 12 to 12-4 in Table 1) nickel Lithium-metal oxide (CAM10) having a concentration gradient of manganese and manganese was used.

Specifically, the concentration gradient of the first lithium-metal oxide is shown in Table 1 below (concentration measurement according to the position from the center to the surface of the lithium-metal oxide particle), and the concentration gradient layer and the concentration measurement position are shown in FIG. It's like a bar. The measurement position is for lithium-metal oxide particles with a distance of 4.8 μm from the center of the particle to the surface of the lithium-metal oxide at positions 1 to 12 from the center of the lithium-metal oxide to the surface according to an interval of 0.4 μm from the center. Molar ratio values of each metal included were measured, and 0.04 μm (40 nm) intervals were measured between positions 12 and 13. Measured values of the metal concentration measured at intervals of 0.04 μm (40 nm) between positions 12 and 13 are at positions 12-1, 12-2, 12-3, 12-4, 12-5, 12-6, 12-7, 12-8, 12-9.

In addition, the overall composition of the second lithium-metal oxide is Li _{1 . 0} Ni _{0 . 6} Co _{0 . 2} Mn _{0 . 2} O ₂ (NCM622, D ₅₀ : 3 μm) was used, and the first lithium-metal oxide and the second lithium-metal oxide were mixed in a weight ratio of 9:1 to prepare a positive active material.

Denka Black was used as a conductive material and PVDF was used as a binder, and the positive electrode active material, conductive material, and binder containing the first lithium-metal oxide and the second lithium-metal oxide were used as a positive electrode slurry in a weight ratio of 92:5:3, respectively. After preparing, it was coated, dried, and pressed on an aluminum substrate to prepare a positive electrode. At this time, the density of the positive electrode after pressing was 3.3 g/cc.

location (number) Molar ratio of Ni Co molar ratio Molar ratio of Mn One 0.802 0.110 0.088 2 0.801 0.111 0.088 3 0.802 0.110 0.088 4 0.802 0.110 0.088 5 0.803 0.111 0.086 6 0.802 0.110 0.088 7 0.802 0.110 0.088 8 0.802 0.109 0.089 9 0.801 0.110 0.089 10 0.802 0.110 0.088 11 0.802 0.108 0.090 12 0.800 0.110 0.090 12-1 0.794 0.110 0.096 12-2 0.789 0.109 0.102 12-3 0.782 0.110 0.108 12-4 0.777 0.110 0.113 12-5 0.770 0.110 0.120 12-6 0.771 0.110 0.119 12-7 0.770 0.110 0.120 12-8 0.769 0.111 0.120 12-9 0.770 0.109 0.121 13 0.770 0.110 0.120

<Cathode>

A negative electrode slurry containing 93% by weight of natural graphite as an anode active material, 5% by weight of KS6, a flake type conductive material as a conductive material, 1% by weight of SBR as a binder, and 1% by weight of CMC as a thickener is coated, dried and pressed on a copper substrate. A negative electrode was prepared.

<Battery>

The positive electrode plate and the negative electrode plate are stacked by notching each to an appropriate size, and a separator (polyethylene, thickness 25㎛) is interposed between the positive and negative electrode plates to form a battery, and the tab of the positive electrode and the tab of the negative electrode are welded, respectively. did The welded anode/separator/cathode combination was placed in a pouch and sealed on three sides except for the side where the electrolyte was injected. In this case, the part with the tab is included in the sealing part. After injecting electrolyte into the remaining part, the remaining side was sealed and impregnated for more than 12 hours. The electrolyte solution was prepared by preparing a 1M LiPF ₆ solution with a mixed solvent of EC/EMC/DEC (25/45/30; volume ratio), then vinylene carbonate (VC) 1wt%, 1,3-propensultone (PRS) 0.5wt % and lithium bis(oxalato)borate (LiBOB) of 0.5 wt% was used.

Thereafter, pre-charging was performed for 36 minutes at a current (2.5A) corresponding to 0.25C. After 1 hour of degasing and aging for 24 hours or more, chemical charge and discharge were performed (charge condition CC-CV 0.2C 4.2V 0.05C CUT-OFF, discharge condition CC 0.2C 2.5V CUT-OFF). After that, standard charge/discharge was performed (charge condition CC-CV 0.5 C 4.2V 0.05C CUT-OFF, discharge condition CC 0.5C 2.5V CUT-OFF).

Example N6-A-2 to N6-A-9

The batteries of Examples N6-A-2 to N6-A-9 contained the first lithium-metal oxide and the second lithium-metal oxide in a weight ratio of 8:2, 7:3, 6:4, 5:5, It was prepared in the same manner as in Example N6-A-1, except that 4:6, 3:7, 2:8 and 1:9 were mixed.

Example N6-B-1 to N6-B-9

Examples N6-B-1 to N6-, except that the particle size (D ₅₀ ) of the second lithium-metal oxide was 4.5 μm, the rest were the same as those of Examples N6-A-1 to N6-A-9. A battery of B-9 was prepared.

Example N6-C-1 to N6-C-9

Examples N6-C-1 to N6-Examples N6-A-1 to N6-A-9 except that the particle size (D ₅₀ ) of the second lithium-metal oxide was 7.0 μm A cell of C-9 was prepared.

Example N6-D-1 to N6-D-9

Examples N6-D-1 to N6-Examples N6-A-1 to N6-A-9 except that the particle size (D ₅₀ ) of the second lithium-metal oxide was 10 μm. A battery of D-9 was prepared.

Example N6-E-1 to N6-E-9

Examples N6-E-1 to N6-Examples N6-A-1 to N6-A-9 except that the particle size (D ₅₀ ) of the second lithium-metal oxide was 15 μm. A battery of E-9 was prepared.

comparative example N6-A-1

Li _1.0 Ni _0.8 Co _0.1 Mn _0.1 O ₂ (CAM20) having a uniform composition throughout the particles was used as the first lithium-metal oxide, and the first lithium-metal oxide and the second lithium-metal oxide were used in a weight ratio of 10:0. A battery was manufactured in the same manner as in Example N6-A-1 except for mixing.

comparative example N6-A-2 to N6-A-10

In the batteries of Comparative Examples N6-A-2 to N6-A-10, each of the first lithium-metal oxide and the second lithium-metal oxide had a weight ratio of 9:1, 8:2, 7:3, 6:4, It was prepared in the same manner as in Comparative Example N6-A-1, except that 5:5, 4:6, 3:7, 2:8, and 1:9 were mixed.

comparative example N6-A-11

A battery was manufactured in the same manner as in Example N6-A-1 except that the first lithium-metal oxide and the second lithium-metal oxide were mixed in a weight ratio of 10:0.

comparative example N6-B-1 to N6-B-19

Comparative Examples N6-B-1 to N6-, except that the particle size (D ₅₀ ) of the second lithium-metal oxide was 4.5 μm, the rest were the same as those of Comparative Examples N6-A-2 to N6-A-10. A battery of B-9 was prepared.

comparative example N6-C-1 to N6-C-9

Comparative Examples N6-C-1 to N6-Excluding that the particle size (D ₅₀ ) of the second lithium-metal oxide was 7.0 μm, the rest were the same as those of Comparative Examples N6-A-2 to N6-A-10 A cell of C-9 was prepared.

comparative example N6-D-1 to N6-D-9

Comparative Examples N6-D-1 to N6-Excluding that the particle size (D ₅₀ ) of the second lithium-metal oxide was 10 μm, the rest were the same as those of Comparative Examples N6-A-2 to N6-A-10 A battery of D-9 was prepared.

comparative example N6-E-1 to N6-E-9

Comparative Examples N6-E-1 to N6-, except that the particle size (D ₅₀ ) of the second lithium-metal oxide was 15 μm, the rest were the same as those of Comparative Examples N6-A-2 to N6-A-10. A battery of E-9 was prepared.

Test Methods

1. Room temperature life characteristics

After repeating charging (CC-CV 2.0 C 4.2V 0.05C CUT-OFF) and discharging (CC 2.0C 2.75V CUT-OFF) 500 times with the cells prepared in Examples and Comparative Examples, the discharge capacity at 500 times The room temperature life characteristics were measured by calculating as a percentage of the discharge capacity at one time.

The results are shown in Table 2 below.

2. Penetration stability evaluation

After charging the batteries prepared in Examples and Comparative Examples (1C 4.2V 0.1C CUT-OFF), 3mm diameter nails were penetrated from the outside at a speed of 80mm/sec to check whether ignition or explosion occurred.

The results are shown in Tables 2 to 6 below.

Table 2 shows examples and comparative examples in which the particle size (D ₅₀ ) of the second lithium-metal oxide is 3 μm.

Table 3 shows examples and comparative examples in which the particle size (D ₅₀ ) of the second lithium-metal oxide is 4.5 μm.

Table 4 shows examples and comparative examples in which the particle size (D ₅₀ ) of the second lithium-metal oxide is 7 μm.

Table 5 shows examples and comparative examples when the particle size (D ₅₀ ) of the second lithium-metal oxide is 10 μm.

Table 6 shows examples and comparative examples in which the particle size (D ₅₀ ) of the second lithium-metal oxide is 15 μm.

division first lithium-metal oxide Second Lithium-Metal Oxide
(D ₅₀ : 3㎛)
Mixing ratio (wt%) 500 times
Lifespan maintenance rate (%) Penetration evaluation result Example N6-A-1 CAM10 10 81.6 utterance Example N6-A-2 CAM10 20 81.3 utterance Example N6-A-3 CAM10 30 82.9 utterance Example N6-A-4 CAM10 40 83.6 utterance Example N6-A-5 CAM10 50 84.4 utterance Example N6-A-6 CAM10 60 85 not ignited Example N6-A-7 CAM10 70 85.9 not ignited Example N6-A-8 CAM10 80 86.3 not ignited Example N6-A-9 CAM10 90 87 not ignited Comparative Example N6-A-1 CAM20 0 69.9 utterance Comparative Example N6-A-2 CAM20 10 70.3 utterance Comparative Example N6-A-3 CAM20 20 70.6 utterance Comparative Example N6-A-4 CAM20 30 71 utterance Comparative Example N6-A-5 CAM20 40 71.3 utterance Comparative Example N6-A-6 CAM20 50 71.5 utterance Comparative Example N6-A-7 CAM20 60 71.8 utterance Comparative Example N6-A-8 CAM20 70 72 utterance Comparative Example N6-A-9 CAM20 80 72.4 utterance Comparative Example N6-A-10 CAM20 90 72.8 utterance Comparative Example N6-A-11 CAM10 0 81.1 utterance

division first lithium-metal oxide Second Lithium-Metal Oxide
(D ₅₀ : 4.5㎛)
Mixing ratio (wt%) 500 times
Lifespan maintenance rate (%) Penetration evaluation result Example N6-B-1 CAM10 10 81.7 utterance Example N6-B-2 CAM10 20 82.5 utterance Example N6-B-3 CAM10 30 83.1 utterance Example N6-B-4 CAM10 40 83.7 utterance Example N6-B-5 CAM10 50 84.4 utterance Example N6-B-6 CAM10 60 85.3 not ignited Example N6-B-7 CAM10 70 85.9 not ignited Example N6-B-8 CAM10 80 86.7 not ignited Example N6-B-9 CAM10 90 87.3 not ignited Comparative Example N6-B-1 CAM20 10 70.4 utterance Comparative Example N6-B-2 CAM20 20 70.8 utterance Comparative Example N6-B-3 CAM20 30 71 utterance Comparative Example N6-B-4 CAM20 40 71.4 utterance Comparative Example N6-B-5 CAM20 50 71.7 utterance Comparative Example N6-B-6 CAM20 60 72.1 utterance Comparative Example N6-B-7 CAM20 70 72.6 utterance Comparative Example N6-B-8 CAM20 80 72.9 utterance Comparative Example N6-B-9 CAM20 90 73.2 utterance

division first lithium-metal oxide Second Lithium-Metal Oxide
(D ₅₀ : 7㎛)
Mixing ratio (wt%) 500 times
Lifespan maintenance rate (%) Penetration evaluation result Example N6-C-1 CAM10 10 81.9 utterance Example N6-C-2 CAM10 20 82.5 utterance Example N6-C-3 CAM10 30 83.5 utterance Example N6-C-4 CAM10 40 84.2 not ignited Example N6-C-5 CAM10 50 85.1 not ignited Example N6-C-6 CAM10 60 85.9 not ignited Example N6-C-7 CAM10 70 86.6 not ignited Example N6-C-8 CAM10 80 87.7 not ignited Example N6-C-9 CAM10 90 88.3 not ignited Comparative Example N6-C-1 CAM20 10 70.3 utterance Comparative Example N6-C-2 CAM20 20 70.7 utterance Comparative Example N6-C-3 CAM20 30 71.2 utterance Comparative Example N6-C-4 CAM20 40 71.6 utterance Comparative Example N6-C-5 CAM20 50 72.1 utterance Comparative Example N6-C-6 CAM20 60 72.5 utterance Comparative Example N6-C-7 CAM20 70 72.7 utterance Comparative Example N6-C-8 CAM20 80 73.1 utterance Comparative Example N6-C-9 CAM20 90 73.6 not ignited

division first lithium-metal oxide Second Lithium-Metal Oxide
(D ₅₀ : 10㎛)
Mixing ratio (wt%) 500 times
Lifespan maintenance rate (%) Penetration evaluation result Example N6-D-1 CAM10 10 82 utterance Example N6-D-2 CAM10 20 82.9 utterance Example N6-D-3 CAM10 30 83.7 utterance Example N6-D-4 CAM10 40 84.8 not ignited Example N6-D-5 CAM10 50 85.6 not ignited Example N6-D-6 CAM10 60 86.6 not ignited Example N6-D-7 CAM10 70 87.5 not ignited Example N6-D-8 CAM10 80 88.5 not ignited Example N6-D-9 CAM10 90 89.3 not ignited Comparative Example N6-D-1 CAM20 10 70.5 utterance Comparative Example N6-D-2 CAM20 20 70.8 utterance Comparative Example N6-D-3 CAM20 30 71.3 utterance Comparative Example N6-D-4 CAM20 40 71.9 utterance Comparative Example N6-D-5 CAM20 50 72.3 utterance Comparative Example N6-D-6 CAM20 60 72.8 utterance Comparative Example N6-D-7 CAM20 70 73.1 utterance Comparative Example N6-D-8 CAM20 80 73.5 not ignited Comparative Example N6-D-9 CAM20 90 74 not ignited

division first lithium-metal oxide Second Lithium-Metal Oxide
(D ₅₀ : 15㎛)
Mixing ratio (wt%) 500 times
Lifespan maintenance rate (%) Penetration evaluation result Example N6-E-1 CAM10 10 82 utterance Example N6-E-2 CAM10 20 83.1 utterance Example N6-E-3 CAM10 30 84.1 utterance Example N6-E-4 CAM10 40 85.2 not ignited Example N6-E-5 CAM10 50 86.3 not ignited Example N6-E-6 CAM10 60 87.2 not ignited Example N6-E-7 CAM10 70 88.3 not ignited Example N6-E-8 CAM10 80 89.4 not ignited Example N6-E-9 CAM10 90 90.4 not ignited Comparative Example N6-E-1 CAM20 10 70.6 utterance Comparative Example N6-E-2 CAM20 20 71.2 utterance Comparative Example N6-E-3 CAM20 30 71.6 utterance Comparative Example N6-E-4 CAM20 40 71.9 utterance Comparative Example N6-E-5 CAM20 50 72.5 utterance Comparative Example N6-E-6 CAM20 60 73.1 utterance Comparative Example N6-E-7 CAM20 70 73.4 utterance Comparative Example N6-E-8 CAM20 80 74.1 not ignited Comparative Example N6-E-9 CAM20 90 74.6 not ignited

As shown in Tables 2 to 6, it was confirmed that the batteries of Examples exhibited superior lifespan characteristics and penetration stability compared to Comparative Examples.

Specifically, when the Examples and Comparative Examples were compared over the entire range of the mixing ratio of the first lithium-metal oxide and the second lithium-metal oxide, it was found that the Examples had more cases of non-ignition than the Comparative Examples.

In addition, with respect to the particle size (D ₅₀ ) of the second lithium-metal oxide, it was found that the lifespan characteristics and penetration stability of the battery improved from Example A to Example E.

On the other hand, in the embodiments, when the mixing weight ratio of the first lithium-metal oxide and the second lithium-metal oxide is 40:60 to 10:90, the penetration stability is obtained regardless of the size (D ₅₀ ) of the second lithium-metal oxide. I was able to confirm that it was excellent,

When the size (D ₅₀ ) of the second lithium-metal oxide was 7 to 15 μm, it was confirmed that the mixed weight ratio of the first lithium-metal oxide and the second lithium-metal oxide exhibiting a non-ignition effect upon penetration was the widest. .

Claims (16)

A positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode,
The anode is
a first lithium-metal oxide particle comprising Ni, wherein the Ni has a continuous concentration gradient region in at least a portion of a center portion and a surface portion of the particle; and
Containing Ni, Ni has a constant concentration region between the central portion and the surface portion of the second lithium-metal oxide particles; Containing a cathode active material comprising;
In the concentration gradient region of the first lithium-metal oxide particles, Ni has a concentration gradient decreasing from the particle center to the surface direction,
The second lithium-metal oxide particles have a particle size (D ₅₀ ) of 7 to 15 μm,
A mixing weight ratio of the first lithium-metal oxide particles and the second lithium-metal oxide particles is 60:40 to 10:90, a lithium secondary battery. The lithium secondary battery according to claim 1 , wherein one type other than Ni among the metals forming the first lithium-metal oxide particles has a constant concentration region between the center portion and the surface portion of the particles. The lithium secondary battery according to claim 1, wherein one type other than Ni among the metals forming the first lithium-metal oxide particles has a concentration gradient in which the concentration increases from the particle center to the surface direction in the concentration gradient region. The lithium secondary battery according to claim 1, wherein the first lithium-metal oxide particles are represented by the following Chemical Formula 2:
[Formula 2]
Li _x M4 _a M5 _b M6 _c O _y
(wherein M4 is Ni, M5 and M6 are selected from the group consisting of Co, Mn, Na, Mg, Ca, Ti, V, Cr, Cu, Zn, Ge, Sr, Ag, Ba, Zr, Nb, Mo, Al, Ga, W and B and 0<x≤1.1, 2≤y≤2.02, and 0<a+b+c≤1). The lithium secondary battery according to claim 4, wherein the first lithium-metal oxide particles have 0.6≤a≤0.95 and 0.05≤b+c≤0.4 in total particle concentration. The lithium secondary battery according to claim 5, wherein the first lithium-metal oxide particles are 0.7≤a≤0.9 and 0.1≤b+c≤0.3. The lithium secondary battery according to claim 4, wherein M5 and M6 are Co and Mn, respectively. The lithium secondary battery according to claim 1, wherein the second lithium-metal oxide particle is represented by the following Chemical Formula 1:
[Formula 1]
Li _x M1 _a M2 _b M3 _c O _y
(wherein M1 is Ni, M2 and M3 are selected from the group consisting of Co, Mn, Na, Mg, Ca, Ti, V, Cr, Cu, Zn, Ge, Sr, Ag, Ba, Zr, Nb, Mo, Al, Ga, W and B and 0<x≤1.1, 2≤y≤2.02, 0<a+b+c≤1, 0.58≤a≤0.62, 0.18≤b≤0.22, and 0.18≤c≤0.22). The lithium secondary battery of claim 1, wherein the first lithium-metal oxide particles include rod-shaped primary particles. delete delete delete delete The method according to claim 1, The density of the electrode of the positive electrode is 3.0 to 3.9 g / cc, lithium secondary battery. The method according to claim 1, wherein the first lithium-metal oxide particle or the second lithium-metal oxide particle contains at least one element selected from the group consisting of Al, Ti, Ba, Zr, Si, B, Mg and P. A lithium secondary battery comprising a coating or doping. delete

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