KR20210154134A - Lithium secondary battery - Google Patents

Abstract

The present invention relates to a lithium secondary battery including a positive electrode, a negative electrode and a non-aqueous electrolyte, and more specifically, to a lithium secondary battery, wherein the positive electrode includes a positive electrode active material including a lithium-metal oxide in which at least one kind among metals has a continuous concentration gradient from a central unit to a surface unit, and the non-aqueous electrolyte includes lithium salt, a polyfunctional nitrile compound and an organic solvent, thereby improving high-temperature storage characteristics and lifespan characteristics.

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 high voltage charging characteristics.

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, a longer lifespan is required, and as the capacity of the battery increases, the need for charging at a high voltage is also increasing. However, when charging at a high voltage, the amount of lithium ions occluded and desorbed from the positive electrode active material increases, which increases the instability of the structure of the positive electrode active material, and promotes the decomposition of the electrolyte on the surface of the positive electrode, thereby reducing the life of the battery. there is a problem. Conventional lithium transition metal oxides or composite oxides used as positive electrode active materials for lithium secondary batteries have limitations in lifespan characteristics and high voltage charging.

In order to solve this problem, Korean Patent Application Laid-Open No. 2006-0134631 discloses a cathode active material having a core-shell structure in which a core part and a shell part are made of different lithium transition metal oxides, but the improvement in lifespan characteristics is still insufficient. Not only that, but the charging problem at high voltage has not been solved.

Patent Document 1: Korean Patent Publication No. 2006-0134631

An object of the present invention is to provide a lithium secondary battery having excellent lifespan characteristics and excellent charging characteristics at high voltage.

A lithium secondary battery according to exemplary embodiments may include a positive electrode including a positive electrode active material including lithium metal oxide particles containing nickel; a negative electrode opposite to the positive electrode; and an electrolyte solution including a lithium salt, an organic solvent, and a polyfunctional nitrile compound, wherein the lithium metal oxide particles are between the central portion and the surface portion of the lithium metal oxide particles, and nickel decreases from the central portion to the surface portion direction. It includes a concentration gradient section having a concentration gradient, and the content of the polyfunctional nitrile compound may be 0.1 to 10% by weight based on 100% by weight of the total non-aqueous electrolyte.

In an embodiment, the lithium metal oxide particles may further contain a metal having a constant concentration in the concentration gradient section.

In an embodiment, the lithium metal oxide particles may further contain a metal having a concentration gradient increasing from the center to the surface portion in the concentration gradient section.

In one embodiment, the lithium metal oxide particles may be represented by the following 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 and B; 0<x≤1.1, 2≤y≤2.02, 0<a<1, 0<b<1, 0<c<1, 0<a+b+c≤1).

In an embodiment, in the concentration gradient section, at least one of M2 and M3 may have a concentration gradient that increases from the central portion to the surface portion.

In an embodiment, in the concentration gradient section, M2 may have a constant concentration, and M3 may have a concentration gradient that increases from the center to the surface portion.

In one embodiment, M2 and M3 may be Co and Mn, respectively.

In one embodiment, 0.6≤a≤0.95 and 0.05≤b+c≤0.4 may be.

In an embodiment, 0.7≤a≤0.9 and 0.1≤b+c≤0.3.

In an embodiment, the lithium metal oxide particles may include rod-type primary particles.

In one embodiment, the polyfunctional nitrile compound may be a dinitrile compound, a trinitrile compound, or a mixture thereof.

In an embodiment, the concentration gradient section may be formed entirely from the central portion to the surface portion.

The lithium secondary battery of the present invention has significantly improved lifespan characteristics and excellent charging characteristics at a high voltage by combining a positive electrode active material containing a metal having a continuous concentration gradient and a non-aqueous electrolyte containing a specific additive.

1 is a diagram schematically illustrating a position for measuring a concentration of a lithium-metal oxide according to an embodiment.
2 is a TEM photograph of the lithium-metal oxide of Example 1.
3 is a TEM photograph of the lithium-metal oxide of Comparative Example 1.

The present invention relates to a lithium secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte, wherein the positive electrode includes a positive active material comprising a lithium-metal oxide in which at least one of the metals has a continuous concentration gradient from the center to the surface portion, The non-aqueous electrolyte includes a lithium salt, a polyfunctional nitrile compound, and an organic solvent, and relates to a lithium secondary battery having improved high-temperature storage characteristics and lifespan characteristics.

Hereinafter, the present invention will be described in more detail.

cathode active material

The positive active material according to the present invention includes a lithium-metal oxide in which at least one of the metals has a continuous concentration gradient from the central portion to the surface portion. Such a positive active material has excellent high temperature storage characteristics as well as excellent lifespan characteristics compared to a positive electrode active material having no change in concentration.

In the present invention, that the metal among lithium-metal oxides has a continuous concentration gradient from the center to the surface means that metals other than lithium have a concentration distribution that changes with a constant tendency from the center to the surface of the lithium-metal oxide particles. it means. 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 positive electrode active material according to the present invention includes at least one metal having a concentration gradient. Accordingly, as an embodiment, the first metal having a concentration gradient section in which the concentration increases from the center to the surface portion and the second metal having a concentration gradient section in which the concentration decreases from the center portion to the surface portion may be included. The first metal or the second metal may be independently of one another.

As another embodiment of the present invention, the positive electrode active material according to the present invention may include a metal having a constant concentration from the center to the surface portion.

Specific examples of the positive electrode active material according to the present invention include a lithium-metal oxide represented by the following formula (1), M1 in the following formula (1), At least one of M2 and M3 has a continuous concentration gradient from the center to the surface:

[Formula 1]

Li _x M1 _a M2 _b M3 _c O _y

(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 becomes,

0<x≤1.1, 2≤y≤2.02, 0≤a≤1, 0≤b≤1, 0≤c≤1, 0<a+b+c≤1).

In one embodiment of the present invention, M1, At least one of M2 and M3 may have a concentration gradient section in which the concentration increases from the central portion to the surface portion, and the rest may have a concentration gradient section in which the concentration decreases from the center portion to the surface portion.

In another embodiment of the present invention, M1, One of M2 and M3 has a concentration gradient section in which the concentration increases from the center to the surface portion, the other has a concentration gradient section in which the concentration decreases from the center portion to the surface portion, and the other one has a constant concentration from the center to the surface portion. can have

As a specific example of the present invention, M1, M2 and M3 may be Ni, Co and Mn, respectively.

The 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 in that the life is charged. does not Accordingly, the positive active material of the present invention may exhibit excellent lifespan characteristics while maintaining high capacity.

For example, in the lithium-metal oxide according to the present invention, the molar ratio of nickel may be 0.6 to 0.95, preferably 0.7 to 0.9. That is, when M1 in Formula 1 is Ni, 0.6≤a≤0.95 and 0.05≤b+c≤0.4, preferably, 0.7≤a≤0.9 and 0.1≤b+c≤0.3.

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 particle size of the lithium-metal oxide according to the present invention is not particularly limited, and may be, for example, 3 to 20 μm.

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 cathode 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.

negative active material

As the negative active material according to 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.

non-aqueous electrolyte

The non-aqueous electrolyte includes a lithium salt as an electrolyte and an organic solvent, and further includes a polyfunctional nitrile compound.

The polyfunctional nitrile compound refers to a compound including at least two nitrile groups, and may be, for example, a dinitrile compound, a trinitrile compound, or a mixture thereof.

When the polyfunctional nitrile compound is used together with the positive electrode active material according to the present invention, it is possible to maintain excellent lifespan characteristics and remarkably improve the high temperature charging characteristics, which is that the polyfunctional nitrile compound is adsorbed on the surface of the positive electrode active material to decompose the electrolyte It is judged to be caused by preventing

Specific examples of the polyfunctional nitrile compound according to the present invention include succinonitrile, sebaconitrile, glutaronitrile, adiponitrile, 1,5-dicynopentane, 1,6-dicyanohexane, 1,7- Dicyanoheptane, 1,8-dicyanooctane, 1,9-dicyanononane, 1,10-dicyanodecane, 1,12-dicyanododecane, tetramethylsuccinonitrile, 2-methylglutaronitrile , 2,4-dimethylglutaronitrile, 2,2,4,4-tetramethylglutaronitrile, 1,4-dicynopentane, 2,5-dimethyl-2,5-hexanedicarbonitrile, 2, 6-dicyanoheptane, 2,7-dicyanooctane, 2,8-dicyanononane, 1,6-dicyanodecane, 1,3,5-hexanetricarbonitrile, 1,3,6-hexanetri Carbonitrile and the like may be used alone or in combination of two or more, but the present invention is not limited thereto. Preferably, it may be at least one selected from the group consisting of succinonitrile, glutaronitrile, adiponitrile, 1,3,5-hexanetricarbonitrile and 1,3,6-hexanetricarbonitrile.

The polyfunctional nitrile compound according to the present invention may be included in an amount of 0.1 to 10% by weight, preferably 0.5 to 7% by weight, and more preferably 1 to 7% by weight based on 100% by weight of the total non-aqueous electrolyte. In the above range, high voltage charging performance may be excellently exhibited.

As the lithium salt, those commonly used in electrolytes for lithium secondary batteries may be used without limitation, and may be expressed as ^{Li +} X ^{− .} The anion of the lithium salt is not particularly limited, but F ^- , Cl ^- , Br ^- , I ^- , NO ₃ ^- , N(CN) ₂ ^- , BF ₄ ^- , ClO ₄ ^- , PF ₆ ^- , (CF ₃ ) ₂ PF ₄ ^- , (CF ₃ ) ₃ PF ₃ ^- , (CF ₃ ) ₄ PF ₂ ^- , (CF ₃ ) ₅ PF ^- , (CF ₃ ) ₆ P ^- , CF ₃ SO ₃ ^- , CF ₃ CF ₂ SO ₃ ^- , (CF ₃ SO ₂ ) ₂ N ^- , (FSO ₂ ) ₂ N ^- _, CF ₃ CF ₂ (CF ₃ ) ₂ CO ^- , (CF ₃ SO ₂ ) ₂ CH ^- , (SF ₅ ) ₃ C ^- , (CF ₃ SO ₂ ) ₃ C ^- , CF ₃ (CF ₂ ) ₇ SO ₃ ^- , CF ₃ CO ₂ ^- , CH ₃ CO ₂ ^- , SCN ⁻ and (CF ₃ CF ₂ SO ₂ ) ₂ N ⁻ and the like can be exemplified.

As the organic solvent, those commonly used in electrolytes for lithium secondary batteries may be used without limitation, representatively propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl Carbonate (dimethyl carbonate, DMC), ethylmethyl carbonate (EMC), methylpropyl carbonate, dipropyl carbonate, dimethylsulfuroxide, acetonitrile, dimethoxyethane, diethoxyethane, vinylene carbonate, sulfolane, gamma-butyrolactone , any one selected from the group consisting of propylene sulfite and tetrahydrofuran, or a mixture of two or more thereof may be used.

secondary battery

The present invention provides a lithium secondary battery manufactured using the positive electrode including the positive electrode active material described above, the negative electrode including the negative electrode active material, and the non-aqueous electrolyte solution described above.

The lithium secondary battery according to the present invention, including the above-described positive active material and non-aqueous electrolyte, can be charged at a charging voltage applied in the art, and has excellent charging characteristics, particularly at a high voltage of 4.3V or higher. For example, even when the charging voltage is 4.3 to 4.5V, excellent lifespan characteristics can be exhibited.

The positive electrode and the negative electrode are prepared by mixing and stirring the positive electrode active material and the negative electrode active material according to the present invention with a solvent and, if necessary, a binder, a conductive material, a dispersing material, etc. It can be manufactured by compression and drying.

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.

A separator is interposed between the positive electrode and the negative electrode. As the separator, a conventional porous polymer film conventionally used as a separator, such as ethylene homopolymer, propylene homopolymer, ethylene/butene copolymer, ethylene/hexene copolymer, and ethylene/ A porous polymer film made of a polyolefin-based polymer such as a methacrylate copolymer may be used alone or by laminating them, or a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high-melting glass fiber, polyethylene terephthalate fiber, etc. can be used, but is not limited thereto. 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.

The non-aqueous electrolyte solution for a lithium secondary battery of the present invention is prepared by injecting it into an electrode structure comprising a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode to form 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 One

<Anode>

As a cathode active material, the total composition is LiNi _{0 . 8} Co _{0 . 1} Mn _{0 . 1} O ₂ , and the surface composition LiNi _{0 from the central composition LiNi 0.84} Co _0.11 Mn _0.05 O _{2 . 78} Co _{0 . 10} Mn _{0 . A} positive electrode mixture was prepared using lithium-metal oxide (hereinafter CAM-10) having a concentration gradient up to 12 O ₂ , Denka Black as a conductive material, PVDF as a binder, and each mass ratio composition of 92: 5: 3 Then, it was coated, dried, and pressed on an aluminum substrate to prepare a positive electrode.

For reference, the concentration gradient of the prepared lithium-metal oxide is shown in Table 1 below, and the concentration measurement position is as shown in FIG. 1 . The measurement positions were measured at intervals of 5/7 μm from the surface for lithium-metal oxide particles having a distance of 5 μm from the center of the particle to the surface.

location Ni Mn Co One 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

<Cathode>

A negative electrode mixture containing 93 wt% of natural graphite (d002 3.358Å) as an anode active material, 5 wt% of a flake type conductive material KS6 as a conductive material, 1 wt% of SBR as a binder, and 1 wt% of a CMC thickener is coated on a copper substrate and dried and press to prepare a negative electrode.

<Evaluation of battery manufacturing and room temperature life characteristics>

The positive and negative electrode plates are stacked by notching each of an appropriate size, and a separator (polyethylene, thickness 25㎛) is interposed between the positive and negative electrode plates to form a cell, 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 electrolyte injection side. 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 %, lithium bis(oxalato)borate (LiBOB) 0.5 wt% and succinonitrile (SN) 0.5 wt% were used.

After that, 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 0.5C 4.2V 0.05C CUT-OFF, discharge condition CC 0.5C 2.5V CUT-OFF).

After repeating charging (CC-CV 2.0C 4.2V 0.05C CUT-OFF) and discharging (CC 2.0C 2.75V CUT-OFF) 500 times with the manufactured cell, the discharge capacity at 500 times is % compared to the one-time discharge capacity was calculated to measure room temperature lifespan characteristics. The results are shown in Table 3 below.

The results are shown in Table 2 below.

Example 2-24

A battery was prepared in the same manner as in Example 1 and lifespan characteristics were evaluated in the same manner as in Example 1, except that the content of succinonitrile and the charging voltage were applied according to Table 2, and the results are shown in Table 2.

comparative example One

LiNi _{0 .8} in the positive electrode active material having a uniform composition in the entire particle of _{Co 0 .1 Mn 0 .1 O 2} ( hereinafter CAM-20) to Example 1, the same manufacturing the cell and the life characteristics, except for using After evaluation, the results are shown in Table 3.

comparative example 2-28

A battery was prepared in the same manner as in Comparative Example 1 and lifespan characteristics were evaluated in the same manner as in Comparative Example 1, except that the content of succinonitrile and the charging voltage were applied according to Table 2, and the results are shown in Table 3.

anode
active material SN
(content, wt%) Charging voltage (V) life span(%)
(500cycle) Example 1 CAM-10 0.5 4.2 80 Example 2 CAM-10 1.0 4.2 80 Example 3 CAM-10 3.0 4.2 79.5 Example 4 CAM-10 5.0 4.2 79 Example 5 CAM-10 7.0 4.2 78.4 Example 6 CAM-10 9.0 4.2 74 Example 7 CAM-10 0.5 4.3 65 Example 8 CAM-10 1.0 4.3 71 Example 9 CAM-10 3.0 4.3 75 Example 10 CAM-10 5.0 4.3 76 Example 11 CAM-10 7.0 4.3 78 Example 12 CAM-10 9.0 4.3 65 Example 13 CAM-10 0.5 4.4 58 Example 14 CAM-10 1.0 4.4 62 Example 15 CAM-10 3.0 4.4 72 Example 16 CAM-10 5.0 4.4 74 Example 17 CAM-10 7.0 4.4 75 Example 18 CAM-10 9.0 4.4 61 Example 19 CAM-10 0.5 4.5 29 Example 20 CAM-10 1.0 4.5 35 Example 21 CAM-10 3.0 4.5 42 Example 22 CAM-10 5.0 4.5 51 Example 23 CAM-10 7.0 4.5 62 Example 24 CAM-10 9.0 4.5 10

anode
active material SN
(content, wt%) Charging voltage (V) life span(%)
(500cycle) Comparative Example 1 CAM-20 0 4.2 70 Comparative Example 2 CAM-20 0.5 4.2 70 Comparative Example 3 CAM-20 1.0 4.2 70 Comparative Example 4 CAM-20 3.0 4.2 69.5 Comparative Example 5 CAM-20 5.0 4.2 69 Comparative Example 6 CAM-20 7.0 4.2 68.8 Comparative Example 7 CAM-20 9.0 4.2 62 Comparative Example 8 CAM-20 0 4.3 50 Comparative Example 9 CAM-20 0.5 4.3 51 Comparative Example 10 CAM-20 1.0 4.3 52 Comparative Example 11 CAM-20 3.0 4.3 54 Comparative Example 12 CAM-20 5.0 4.3 56 Comparative Example 13 CAM-20 7.0 4.3 58 Comparative Example 14 CAM-20 9.0 4.3 45 Comparative Example 15 CAM-20 0 4.4 30 Comparative Example 16 CAM-20 0.5 4.4 31 Comparative Example 17 CAM-20 1.0 4.4 32 Comparative Example 18 CAM-20 3.0 4.4 34 Comparative Example 19 CAM-20 5.0 4.4 36 Comparative Example 20 CAM-20 7.0 4.4 38 Comparative Example 21 CAM-20 9.0 4.4 26 Comparative Example 22 CAM-20 0 4.5 10 Comparative Example 23 CAM-20 0.5 4.5 11 Comparative Example 24 CAM-20 1.0 4.5 12 Comparative Example 25 CAM-20 3.0 4.5 14 Comparative Example 26 CAM-20 5.0 4.5 16 Comparative Example 27 CAM-20 7.0 4.5 18 Comparative Example 28 CAM-20 9.0 4.5 5

Referring to Tables 2 and 3, it can be seen that the batteries of Examples exhibit superior lifespan characteristics and high voltage charging characteristics compared to Comparative Examples.

Specifically, when the charging voltage is 4.2V, it can be seen that the absolute value of the lifetime of the Example is larger than that of the comparative example, and in particular, the life reduction rate is smaller than that of the comparative example. It can be seen that not only the absolute value of the lifetime but also the increase rate of the lifetime is remarkable.

In addition, when the content of SN is 1 to 7wt% at a charging voltage of 4.3V or more, it can be confirmed that the lifespan characteristic is rather increased, and in particular, it can be confirmed that the lifespan increase rate is larger than that of the comparative example in Examples.

In addition, TEM photographs of the positive active material particles of Example 1 and Comparative Example 1 are shown in FIGS. 2 and 3, respectively. Referring to FIGS. 2 (Example 1) and 3 (Comparative Example 1), the primary particles of the positive active material of the Example have a rod-like shape, whereas the positive active material of the Comparative Example has a shape close to a spherical shape, it can be seen that there is

Example 25-24

Except for applying the type of polyfunctional nitrile compound (glutaronitrile (GN), adiponitrile (AN), 1,3,5-hexanetricarbonitrile (HTCN)) and charging voltage according to Table 4 below, A battery was manufactured in the same manner as in Example 9 and lifespan characteristics were evaluated, and the results are shown in Table 4.

anode
active material polyfunctional nitrile Charging voltage (V) life span(%)
(500cycle) Kinds (content, wt%) Example 9 CAM-10 SN 3 4.3 75 Example 2 CAM-10 GN 3 4.3 74 Example 3 CAM-10 AN 3 4.3 75 Example 4 CAM-10 HTCN 3 4.3 75 Example 15 CAM-10 SN 3 4.4 72 Example 6 CAM-10 GN 3 4.4 73 Example 7 CAM-10 AN 3 4.4 72 Example 8 CAM-10 HTCN 3 4.4 73 Example 21 CAM-10 SN 3 4.5 42 Example 10 CAM-10 GN 3 4.5 41 Example 11 CAM-10 AN 3 4.5 42 Example 12 CAM-10 HTCN 3 4.5 42

Referring to Table 4, even when various polyfunctional nitrile compounds are used, similar performance to succinonitrile is shown, and it can be confirmed that excellent lifespan characteristics and high voltage charging characteristics appear.

Claims (12)

a positive electrode including a positive active material including lithium metal oxide particles containing nickel;
a negative electrode opposite to the positive electrode; and
An electrolyte solution comprising a lithium salt, an organic solvent, and a polyfunctional nitrile compound,
The lithium metal oxide particles include a concentration gradient section having a concentration gradient in which nickel decreases from the center to the surface portion between the central portion and the surface portion of the lithium metal oxide particles,
The content of the polyfunctional nitrile compound is 0.1 to 10% by weight of the total 100% by weight of the non-aqueous electrolyte, a lithium secondary battery. The lithium secondary battery of claim 1, wherein the lithium metal oxide particles further contain a metal having a constant concentration in the concentration gradient section. The lithium secondary battery of claim 1 , wherein the lithium metal oxide particles further contain a metal having a concentration gradient that increases from the center to the surface portion in the concentration gradient section. The lithium secondary battery according to claim 1, wherein the lithium metal oxide particles are 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 and B; 0<x≤1.1, 2≤y≤2.02, 0<a<1, 0<b<1, 0<c<1, 0<a+b+c≤1). The lithium secondary battery of claim 4, wherein in the concentration gradient section, at least one of M2 and M3 has a concentration gradient that increases from the central portion to the surface portion. The lithium secondary battery of claim 4 , wherein in the concentration gradient section, M2 has a constant concentration, and M3 has a concentration gradient that increases from the central portion to the surface portion. The lithium secondary battery according to claim 4, wherein M2 and M3 are Co and Mn, respectively. The lithium secondary battery according to claim 4, wherein 0.6≤a≤0.95 and 0.05≤b+c≤0.4. The lithium secondary battery according to claim 4, wherein 0.7≤a≤0.9 and 0.1≤b+c≤0.3. The lithium secondary battery of claim 1, wherein the lithium metal oxide particles include rod-type primary particles. The lithium secondary battery according to claim 1, wherein the polyfunctional nitrile compound is a dinitrile compound, a trinitrile compound, or a mixture thereof. The lithium secondary battery according to claim 1, wherein the concentration gradient section is formed entirely from the central portion to the surface portion.

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