KR20160023496A - Manufacturing method of cobalt free concentration gradient cathod active material and cobalt free concentration gradient cathod active material made by the same - Google Patents

Abstract

The present invention relates to a manufacturing method of a cobalt-free concentration gradient positive electrode active material, and a cobalt-free concentration gradient positive electrode active material manufactured thereby. According to the manufacturing method of a cobalt-free concentration gradient positive electrode active material, an M element is uniformly doped on an internal side and a surface of particles manufactured by initially and simultaneously coprecipitating the M element added by a coprecipitation technique, thereby showing an effect of improving lifespan properties.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cobalt-free gradient cathode active material and a cobalt-free gradient cathode active material,

The present invention relates to a process for producing a non-cobalt concentration gradient cathode active material and a non-cobalt concentration gradient cathode active material produced thereby.

BACKGROUND ART A nonaqueous electrolyte secondary battery or a lithium ion secondary battery is widely used as a power source for a portable device such as a cellular phone or a notebook computer. The non-aqueous electrolyte secondary battery is indispensable to today's ubiquitous network society, and the capacity of the non-aqueous electrolyte secondary battery is urgently required in the future. In recent years, a non-aqueous electrolyte secondary battery has been adopted as a power tool power source. In the future, the use of non-aqueous electrolyte secondary batteries is expected to be extended to power sources for hybrid vehicles and the like.

Since the lithium ion secondary battery was mass produced in 1991, to date, the energy density of the battery has doubled from 280 Wh / L to 580 Wh / L. Meanwhile, the basic design of using LiCoO _{2 for the} cathode active material and graphite for the cathode has not been changed. However, the technology of improving the cell structure and increasing the density is already close to the limit, and development of a new material having high capacity, high performance and high safety is expected.

In this background, as a promising material to replace LiCoO ₂ , tribological "lithium nickel manganese cobalt oxide (LMNCO)" containing three elements of nickel, manganese and cobalt has been actively studied.

An example of "lithium nickel manganese cobalt oxide (LMNCO)" is Li _{1 + x} M _{1 -x} 0 ₂ where M = Mn _1/3 Ni _1/3 Co _1/3 O ₂ . "Lithium nickel manganese cobalt oxide (LMNCO)" is highly active, easy to manufacture, and generally has a low cost because it has a relatively low content of cobalt. However, this compound has a disadvantage that the reverseble capacity is relatively low. Generally, between 4.3 V and 3.0 V, the capacity is less than about 160 mAh / g, and the capacity of lithium nickel oxide based cathode active material (LNO) is compared to 185-195 mAh / g. The disadvantage of the "lithium nickel manganese cobalt oxide" cathode active material (LNMCO) compared to the lithium nickel oxide based positive electrode active material (LNO) is the relatively low crystallographic density, which also has a small volumetric capacity ; And relatively low electronic conductivity.

Lithium nickel manganese cobalt oxide cathode active material (LNMCO) has a low propensity to react with electrolytes at higher temperatures and a much higher intrinsic capacity (which is typically characterized by dissolution of Mn) compared to lithium nickel oxide based cathode active material (LNO) . In general, the base content increases and safety performance tends to deteriorate with increasing Ni: Mn ratio. On the other hand, high Mn content is known to help improve safety.

High base content is associated with moisture sensitivity. In this regard, the lithium nickel manganese oxide cathode active material (LMNO) is less sensitive than the lithium nickel oxide based cathode active material (LNO) but is more sensitive than the lithium nickel manganese cobalt oxide cathode active material (LMNCO). Immediately after the preparation, a well prepared lithium nickel manganese oxide cathode active material (LMNO) sample has a relatively low surface base content and, if well-prepared, most surface bases are not Li ₂ CO ₃ type bases. However, in the presence of moisture, airborne CO ₂ or organic radicals react with LiOH-type bases to form Li ₂ CO ₃ type bases. Similarly, since the consumed LiOH is slowly reformed by Li from bulk, the total amount of base (total base = Li ₂ CO ₃ + moles of LiOH-type base) increases. At the same time, moisture (ppm H ₂ O) increases. Therefore, the above process is not very good for battery production. Li ₂ CO ₃ and water are known to cause serious swelling and poor slurry stability.

Accordingly, there is a need for research to improve the properties of the non-cobalt lithium nickel manganese oxide cathode active material.

Disclosure of Invention Technical Problem [8] Accordingly, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a novel method for preparing a non-cobalt lithium nickel manganese oxide cathode active material.

The present invention also aims to provide a non-cobalt lithium nickel manganese oxide cathode active material produced by the production method of the present invention.

The present invention has been made to solve the above problems

Preparing a first metal salt aqueous solution for forming a center portion and a second metal salt aqueous solution for forming a surface portion containing a manganese compound, a nickel compound and an M-containing compound (M is at least one selected from the group consisting of aluminum, magnesium and titanium) ;

Introducing the second metal salt aqueous solution to the first metal salt aqueous solution while increasing the proportion of the second metal salt aqueous solution from 0 v% to 100 v%, introducing the mixture into the reactor, and mixing the basic compounds to prepare transition metal hydroxide particles by coprecipitation;

Mixing the hydroxide and the lithium compound; And

Calcining the mixture;

Cobalt < / RTI > concentration gradient cathode active material.

The concentration of nickel in the aqueous solution of the first metal salt for forming the center portion is preferably 0.8 mol% to 0.95 mol%, the concentration of manganese is 0.05 mol% to 0.2 mol% .

The concentration of nickel in the second metal salt aqueous solution for forming the surface portion is 0.4 mol% to 0.6 mol%, the concentration of manganese is 0.4 mol% to 0.6 mol% .

In the method for producing a cathode-free, cobalt-free slurry cathode active material according to the present invention, the concentration of M metal in the first metal salt aqueous solution for forming the center portion is 0.001 to 0.1 mol%. The method for producing a non-cobalt concentration gradient cathode active material according to the present invention is characterized in that at the time of the coprecipitation reaction, the M compound is contained in the aqueous solution of the first metal salt for forming the center portion and the aqueous solution of the second metal salt for forming the surface portion at a constant concentration, .

In the method for producing a positive electrode active material of a non-cobalt concentration gradient according to the present invention, the M metal concentration of the second metal salt aqueous solution for forming the surface portion is 0.001 to 0.1 mol%.

In the method for producing a cobalt-free concentration gradient cathode active material according to the present invention, the M compound is a sulfate salt or an oxalate salt.

In the method for producing a cobalt-free gaseous cathode active material according to the present invention, in the step of firing the mixture, heat treatment is performed at 700 to 900 ° C for 8 to 12 hours.

The present invention also provides a non-cobalt-concentration gradient cathode active material, which is produced by the production method according to the present invention and has a concentration gradient of nickel and manganese from the center of grains to the surface thereof, .

≪ Formula 1 > LiNiaMnbM1-a-bO2

(Wherein 0.9? X? 1.1, 0.5? A? 1.0, 0? B? 0.5, 0? 1-ab?

The method of producing a cobalt-free cathode active material according to the present invention is characterized in that M element added in addition to nickel manganese is mixed with nickel manganese simultaneously from the initial stage of coprecipitation so that M is uniformly doped into the surface of the thus- And the lifetime characteristics are improved.

1 is a SEM photograph of a cobalt-doped gradient cathode active material prepared according to an embodiment of the present invention.
FIGS. 2 to 4 show the results of measurement of initial charging / discharging characteristics of a battery including a non-cobalt concentration gradient cathode active material manufactured according to an embodiment of the present invention.
FIGS. 5 to 7 show the results of measurement of the C-rate characteristics of a battery including a non-cobalt concentration gradient cathode active material manufactured according to an embodiment of the present invention.
FIGS. 8 to 10 illustrate results of measurement of lifetime characteristics of a battery including a non-cobalt concentration gradient cathode active material manufactured according to an embodiment of the present invention.

Hereinafter, the present invention will be described in more detail by way of examples. However, the present invention is not limited by the following examples.

< Example  1>

A first metal salt aqueous solution containing 10 mol%, 89.995 mol% and 0.005 mol% of a magnesium sulfate compound as a M compound, and a second metal salt aqueous solution containing 50 mol%, 49.995 mol% and 0.005 mol% A second aqueous metal salt solution for forming part was prepared.

14 liters of distilled water was placed in a coprecipitation reactor (capacity 50 L, output of a rotary motor 1.0 KW), nitrogen gas was supplied to the reactor at a rate of 5 liters / minute to remove dissolved oxygen and the temperature of the reactor lt; / RTI &gt;

The first metal salt aqueous solution for forming the center portion and the second metal salt aqueous solution for forming the surface portion were mixed at a constant ratio and charged at a rate of 0.9 liter / hour. Further, an ammonia solution having a concentration of 14M was continuously introduced into the reactor at 0.09 liter / hour. In order to adjust the pH, a 4M aqueous NaOH solution was supplied to maintain the pH in the reactor at 11.

Then, the impeller speed of the reactor was adjusted to 600 rpm, and the coprecipitation reaction was performed until the diameter of the obtained precipitate became 8 to 9 탆. At this time, the flow rate was adjusted so that the average residence time of the solution in the reactor was about 18 hours. After the reaction reached a steady state, a steady state duration was given to the reactant to obtain a more dense coprecipitated compound. The compound was filtered, washed with water, and then dried in a hot air dryer at 110 DEG C for 10 hours to obtain an active material precursor.

Li ₂ CO ₃ as a lithium salt was mixed with the active material precursor to obtain Li / M ratio of 1.01, followed by heating at a heating rate of 2.5 ° C / min and holding at 880 ° C for 10 hours to obtain final active material particles.

< Example  2 to 10>

Except that the ratio of the lithium salt to be added to the first metal salt aqueous solution for forming the center portion and the M metal species and the hydroxide in the second metal salt aqueous solution for forming the surface portion in Example 1 was adjusted as shown in Table 1 The active material particles of Examples 2 to 10 were produced in the same manner as in Example 1 above.

< Experimental Example  1> SEM  Photo measurement

SEM photographs of the cathode active materials prepared in Examples 1 to 9 were measured and the results are shown in FIG.

< Experimental Example  2> Measurement of particle characteristics

The D50 values of the cathode active materials prepared in Examples 1 to 9 were measured. Tap density and BET surface area were measured and the results are shown in Table 2 below.

< Experimental Example  3> Charging and discharging  Capacity, and cycle characteristics

Each of the active materials prepared in Examples 1 to 9 and the active materials prepared in the above Comparative Examples were used to prepare a positive electrode and applied to a cylindrical lithium secondary battery. The initial charge-discharge characteristics, life characteristics, and C-rate characteristics of the battery using the active materials prepared in Examples 1 to 9 were measured, and the results are shown in FIGS. 2 to 11.

As shown in FIGS. 2 to 4, the initial charge and discharge characteristics of the battery using the active material prepared according to the present invention were not improved as compared with the comparative example. However, as shown in FIGS. 5 to 7 and 8 to 10, -rate characteristics and life characteristics are greatly improved.

Claims (8)

Preparing a first metal salt aqueous solution for forming a center portion and a second metal salt aqueous solution for forming a surface portion containing a manganese compound, a nickel compound and an M-containing compound (M is at least one selected from the group consisting of aluminum, magnesium and titanium) ;
The ratio of the second metal salt aqueous solution for forming the surface portion to the first metal salt aqueous solution for forming the central portion is increased from 0 v% to 100 v%, and the mixture is introduced into the reactor, and the basic compound is mixed and the transition metal hydroxide particles ;
Mixing the hydroxide and the lithium compound; And
Calcining the mixture;
Wherein the non-cobalt concentration gradient cathode active material is a non-cobalt concentration gradient cathode active material.
The method according to claim 1,
Wherein the concentration of nickel in the first metal salt aqueous solution for forming the center portion is 0.8 mol% to 0.95 mol%, and the concentration of manganese is 0.05 mol% to 0.2 mol%.
The method according to claim 1,
Wherein the concentration of nickel in the second metal salt aqueous solution for surface part formation is 0.4 mol% to 0.6 mol%, and the concentration of manganese is 0.4 mol% to 0.6 mol%.
The method according to claim 1,
Wherein the M metal concentration of the first metal salt aqueous solution for forming the center portion is 0.001 to 0.1 mol%.
The method according to claim 1,
Wherein the M compound is a sulfate salt or an oxalate salt.
The method according to claim 1,
Wherein the M metal concentration of the first metal salt aqueous solution for forming the center portion is the same as the M metal concentration of the second metal salt aqueous solution for surface portion forming.
The method according to claim 1,
Wherein the heat treatment is performed at 700 to 900 DEG C for 8 to 12 hours in the step of firing the mixture.
A process for producing a nickel-manganese composite oxide according to any one of claims 1 to 7, wherein the concentration of nickel and manganese in the grains from the center of grains to the surface is in the range of from 0.1 to 10, Cathode active material.
& _{Lt ;} Formula 1 > Li _x Ni _a Mn _b M _{1-a b} O ₂
(Wherein 0.9? X? 1.1, 0.5? A? 1.0, 0? B? 0.5, 0? 1-ab?

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