KR20220089311A - Positive active material precursor, preparing method thereof and positive active material for rechargeable lithium battery - Google Patents

Abstract

A cathode active material precursor comprising a compound represented by Formula 1, wherein the cathode active material precursor is composed of secondary particles formed by aggregation of a plurality of primary particles, and the average particle diameter of the secondary particles is 1 μm to 9 μm, The cathode active material precursor has a P-3m1 space group in X-ray diffraction analysis and has a half width at half maximum in the (001) plane of 0.5 or more, a cathode active material precursor for a lithium secondary battery, a method for preparing the same, and a lithium-excess layered cathode active material prepared therefrom will be.
[Formula 1]
Ni _x Mn _y M ¹ _z (OH) ₂
In Formula 1, x+y+z=1, 0<x<0.5, 0.5<y<1, 0≤z<0.5, wherein M ¹ is Co, Mg, Ca, Al, Ti, V, Cr, It is at least one element selected from Zr, Nb, Mo, and W.

Description

A cathode active material precursor for a lithium secondary battery, a manufacturing method thereof, and a cathode active material

A cathode active material precursor for a lithium secondary battery, a method for manufacturing the same, and a cathode active material prepared therefrom.

With the rapid development of electric vehicles and large-capacity energy storage system technologies in recent years, the development of a lithium secondary battery having a high weight and volume energy density at a low price has become very important. In particular, the energy capacity applied to electric vehicles is tens of kwh, and the mileage of electric vehicles depends on the energy density of the battery. In order to compete in terms of price, it is essential to lower the price of lithium batteries applied to electric vehicles.

The cathode active materials that have been studied so far are mainly LiCoO ₂ (lithium cobalt oxide, LCO)-based active materials having a layered structure, LiMnO ₂ having a layered structure, LiMn ₂ O ₄ of a spinel structure using manganese as a transition metal, etc., In addition, research on layered LiNiO ₂ using nickel as a transition metal is also being conducted.

Among the cathode active materials, LiCoO ₂ is widely used for mobile applications due to its excellent lifespan and output characteristics, but has poor structural stability at high voltage and is expensive due to the limited amount of cobalt used, so there is a limitation in price competitiveness. There is a limit to applying it to the same medium/large capacity power source. LiMnO ₂ , LiMn ₂ O ₄ Lithium manganese oxide, such as, is inexpensive and has excellent thermal stability, but has a small capacity, life characteristics, and manganese elution problems due to structural change at high temperatures. Although LiNiO ₂ -based positive electrode active material is relatively inexpensive and exhibits high discharge capacity, there is a problem in that a rapid phase transition of the crystal structure appears at high voltage due to severe volume change due to charging and discharging. Therefore, the development of a high-capacity positive electrode material having a capacity of 200 mAh/g or more through lithium transition metal oxide of LiNiCoMnO ₂ containing 80% or more of nickel is rapidly progressing, but capacity increase through oxidation/reduction reaction of cations has limitations.

Accordingly, in the lithium transition metal oxide containing high manganese content, the lithium content is higher than that of the transition metal, and the lithium excess composition layered oxide exhibits a high capacity of 270 mAh/g or more under a high voltage of 4.5V or more. Research on this is continuously being attempted.

LiNi _x Co _y Mn _1-xy O ₂ and Li ₂ MnO ₃ two types of layered oxides with excess lithium are composed of nano-unit composites, and the Li ₂ MnO ₃ phase has a slow lithium transfer rate and poor electronic conductivity, A high capacity can be obtained only when the size of the cathode active material particles is reduced to a nano size. However, when the lithium-excess layered positive electrode active material made of nanoparticles is applied to an actual electrode, there is a limitation in increasing the bulk energy density due to the low electrode density, and there is a problem in that an excessive amount of a conductive material must be used for electron conduction. Accordingly, research is being conducted to solve this problem by preparing a nickel-manganese hydroxide precursor and preparing a cathode active material having a shape of secondary particles having a size of several μm by aggregation of nano-sized primary particles.

To provide a lithium-excess layered positive electrode active material that has a high tap density and exhibits sufficient capacity even at a low conductive material content, realizing a high capacity, and provides a precursor and a method for preparing a precursor for manufacturing such a positive electrode active material.

In one embodiment, a positive electrode active material precursor comprising a compound represented by Formula 1, wherein the positive electrode active material precursor is composed of secondary particles formed by aggregation of a plurality of primary particles, and the average particle diameter of the secondary particles is 1 μm to 9 μm, the cathode active material precursor has a P-3m1 space group in X-ray diffraction analysis, and provides a cathode active material precursor for a lithium secondary battery having a half width at half maximum in the (001) plane.

[Formula 1]

Ni _x Mn _y M ¹ _z (OH) ₂

In Formula 1, x+y+z=1, 0<x<0.5, 0.5<y<1, 0≤z<0.5, wherein M ¹ is Co, Mg, Ca, Al, Ti, V, Cr, It is at least one element selected from Zr, Nb, Mo, and W.

In another embodiment, distilled water and an aqueous ammonia solution are put into the co-precipitation reactor, air is supplied to the co-precipitation reactor, and an aqueous metal salt solution containing nickel salt and manganese salt, and an aqueous alkali solution for pH adjustment are continuously added and mixed into the co-precipitation reactor. to provide a method for producing a positive electrode active material precursor for a lithium secondary battery comprising obtaining the above-described positive electrode active material precursor.

In another embodiment, a lithium-excess layered positive electrode active material comprising a compound represented by Formula 2, wherein the positive active material is composed of secondary particles formed by aggregation of a plurality of primary particles, and the primary particles are plate-shaped No, the primary particles have an average particle diameter of 10 nm to 950 nm, the secondary particles have an average particle diameter of 1 μm to 9 μm, and the positive electrode active material has a tap density of 1.7 g/cc or more of a lithium excess layer for a lithium secondary battery An upper-level positive electrode active material is provided.

[Formula 2]

Li _a Ni _x2 Mn _y2 M ² _z2 O ₂

In Formula 1, 1.1≤a≤1.5 x2+y2+z2=1, 0<x2<0.5, 0.5<y2<1, 0≤z2<0.5, wherein M ² is Co, Mg, Ca, Al, Ti , V, Cr, Zr, Nb, Mo, and at least one element selected from W.

The positive electrode active material precursor for a lithium secondary battery according to an embodiment and the lithium-excess layered positive electrode active material prepared therefrom have a secondary particle shape in which primary particles are densely formed, high tap density, high capacity, and sufficient even at low conductive material content Capacity can be expressed, and excellent battery characteristics can be exhibited.

1 is a scanning electron microscope photograph of the cathode active material precursor prepared in Example 1. Referring to FIG.
2 is an X-ray diffraction analysis graph of the positive active material precursor prepared in Example 1. Referring to FIG.
3 is a scanning electron microscope photograph of the positive active material prepared in Example 1. Referring to FIG.
4 is an X-ray diffraction analysis graph of the positive active material prepared in Example 1. FIG.
5 is a scanning electron microscope photograph of the cathode active material precursor prepared in Comparative Example 1. Referring to FIG.
6 is an X-ray diffraction analysis graph of the cathode active material precursor prepared in Comparative Example 1. Referring to FIG.
7 is a scanning electron microscope photograph of the positive active material prepared in Comparative Example 1. Referring to FIG.
8 is an X-ray diffraction analysis graph of the positive active material prepared in Comparative Example 1. Referring to FIG.
9 is a graph showing the charge/discharge capacity evaluation of the batteries prepared in Example 1 and Comparative Example 1. Referring to FIG.

Hereinafter, specific embodiments will be described in detail so that those of ordinary skill in the art can easily implement them. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein.

The terminology used herein is used to describe exemplary embodiments only, and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise.

As used herein, "combination of these" means mixtures, laminates, composites, copolymers, alloys, blends, reaction products, and the like of constituents.

Herein, terms such as “comprise”, “comprising” or “have” are intended to designate the presence of an embodied feature, number, step, element, or a combination thereof, but one or more other features, number, or step It should be understood that it does not preclude the possibility of the presence or addition of , components, or combinations thereof.

In order to clearly express the various layers and regions in the drawings, the thickness is enlarged and the same reference numerals are given to similar parts throughout the specification. When a part of a layer, film, region, plate, etc. is said to be “on” or “on” another part, it includes not only cases where it is “directly on” another part, but also cases where another part is in between. Conversely, when we say that a part is "just above" another part, we mean that there is no other part in the middle.

In addition, the "layer" herein includes not only a shape formed on the entire surface when viewed from a plan view, but also a shape formed on a partial surface.

In one embodiment, a positive electrode active material precursor comprising a compound represented by Formula 1, wherein the positive electrode active material precursor is composed of secondary particles formed by aggregation of a plurality of primary particles, and the average particle diameter of the secondary particles is 1 μm to 9 μm, the cathode active material precursor has a P-3m1 space group in X-ray diffraction analysis, and the diffraction peak half width at (001) plane provides a cathode active material precursor for a lithium secondary battery of 0.5 or more.

[Formula 1]

Ni _x Mn _y M ¹ _z (OH) ₂

In Formula 1, x+y+z=1, 0<x<0.5, 0.5<y<1, 0≤z<0.5, wherein M ¹ is Co, Mg, Ca, Al, Ti, V, Cr, It is at least one element selected from Zr, Nb, Mo, and W.

Typically, in order to synthesize a secondary particle-shaped positive electrode active material composed of nano-sized primary particles, a precursor that is a transition metal hydroxide such as nickel, manganese, and cobalt is prepared by a co-precipitation method, and then lithium such as Li ₂ CO ₃ or LiOH A synthesis method of mixing with raw materials and firing at a high temperature of 800°C or higher is mainly used. However, in the case of a lithium-excess layered oxide positive electrode active material, an excess of manganese is required compared to nickel, so a transition metal hydroxide is usually prepared by a co-precipitation method under a nitrogen atmosphere. However, in this case, a precursor having a thick plate-like primary particle shape is synthesized, and an impurity phase such as Mn ₃ O ₄ is present. When synthesizing the positive electrode active material with these precursors, the lithium excess positive electrode active material having large pores inside the secondary particles is mainly synthesized due to the non-uniformity of the plate-shaped particle arrangement, so that the tap density of the positive electrode active material is lowered, and it is sufficient to use an excessive amount of conductive material. Electron conduction can be exhibited, and there is a problem in that the capacitance characteristic is also deteriorated.

On the other hand, the positive electrode active material precursor for a lithium secondary battery according to an embodiment is a precursor for producing an excess lithium layered positive electrode active material, a transition metal hydroxide containing an excess of manganese compared to nickel, and the primary particles are thin and small plate-shaped and dense It is densely packed to form small secondary particles of several μm in size, has low crystallinity, and does not have a Mn ₃ O ₄ phase. The lithium-excess layered positive electrode active material synthesized from these precursors has the shape of small secondary particles of several μm in size in which nano-sized primary particles are densely packed, has a very high tap density, and has a conductive material content of 5 wt% or less during electrode manufacturing. It is also possible to express a sufficiently high dose at this level.

The primary particles of the cathode active material precursor may have a thin and small plate shape, and may have an average long diameter of approximately 10 nm to 950 nm, for example, 50 nm to 900 nm, or 100 nm to 850 nm. The secondary particles composed of these primary particles may be spherical, and the average particle diameter of the secondary particles is 1 μm to 9 μm, for example, 1 μm to 8 μm, 1 μm to 7 μm, 1 μm to 6 μm. , 2 μm to 5 μm or 3 μm to 5 μm. When the long diameter of the primary particles and the particle diameter of the secondary particles of the positive electrode active material precursor satisfy the above ranges, the positive electrode active material prepared therefrom may have a secondary particle shape in which nano-sized primary particles are densely packed, and tap density is high, and while realizing a high capacity, it is possible to express sufficient capacity even with a low content of conductive material.

Here, the average particle diameter or the average long diameter may refer to a measurement through a particle size analyzer that analyzes the size of particles according to diffraction, or may mean a measurement through a scanning electron micrograph or the like.

The cathode active material precursor has a P-3m1 space group in X-ray diffraction analysis, and a full width at half maximum (FWHM) of a diffraction peak in the (001) plane is 0.5 or more, for example, 0.7 or more, 0.9 or more, 1.0 or more, 1.2 or more, 1.4 or more, 1.5 or more, 1.6 or more, 1.7 or more, or 1.8 or more, and may be 3 or less, 2.5 or less, or 2 or less. When the half width of the X-ray diffraction peak at the (001) plane of the positive electrode active material precursor satisfies the above range, crystallinity is sufficiently low, and the positive active material prepared therefrom has a low tap density, high capacity, and sufficient even at low conductive material content. capacity can be expressed. The (001) plane means a lattice plane corresponding to the Miller index (001).

The cathode active material precursor does not include Mn ₃ O ₄ . In general, when a hydroxide of a transition metal containing nickel and manganese is prepared by a co-precipitation method, Mn ₃ O ₄ is generated together, and accordingly, the cathode active material contains Li ₂ MnO ₃ in addition to lithium nickel manganese oxide, Li ₂ MnO ₃ has a slow lithium transfer rate and poor electronic conductivity. On the other hand, the cathode active material precursor according to an embodiment is prepared by a method to be described later, and thus does not have a Mn ₃ O ₄ phase. The positive active material prepared therefrom does not have a Li ₂ MnO ₃ phase, and thus may exhibit sufficient capacity even at a low conductive material content, and may realize high capacity and excellent battery characteristics.

The cathode active material precursor may include a manganese excess transition metal hydroxide having a higher manganese content than nickel, and specifically may include a compound represented by Formula 1 above. In Formula 1, for example, 0<x<0.4, 0.6<y<1, and 0≤z<0.4, may be 0<x<0.3, 0.7<y<1, and 0≤z<0.3, , or 0<x<0.25, 0.75<y<1, and 0≤z<0.25, or 0<x<0.2, 0.8<y<1, and 0≤z<0.2. For example, in Formula 1, x=0.4, y=0.6, and z=0, or x=0.3, y=0.7, and z=0, or x=0.25, y=0.75, and z=0 can be When x, y, and z in Formula 1 satisfy the above ranges, the positive active material formed therefrom may realize ultra-high capacity even at high voltage.

Another embodiment provides a method of manufacturing a cathode active material precursor for a lithium secondary battery. In the manufacturing method, distilled water and an aqueous ammonia solution are put into the co-precipitation reactor, air is supplied to the co-precipitation reactor, and an aqueous metal salt solution containing nickel salt and manganese salt, and an aqueous alkali solution for pH adjustment are continuously added and mixed to the co-precipitation reactor. , including obtaining the above-described positive electrode active material precursor.

In general, when a manganese-excess transition metal hydroxide precursor with a high manganese content compared to nickel is prepared by the co-precipitation method, a method of continuously quantitatively inputting an aqueous metal salt solution and an aqueous alkali solution for pH adjustment while continuously supplying nitrogen to the co-precipitation reactor is used. do. On the other hand, in one embodiment, by changing the supply gas from nitrogen to air, the growth of the particles is appropriately suppressed, and the thin and small primary particles take the form of small secondary particles agglomerated and the crystallinity is low, and Mn ₃ O ₄ is We succeeded in preparing an unformed transition metal hydroxide precursor.

In the manufacturing method, the addition of distilled water and aqueous ammonia solution into the coprecipitation reactor may include, for example, distilled water, aqueous ammonia solution and sodium hydroxide.

In addition, the nickel salt may be, for example, nickel sulfate, nickel nitrate, nickel chloride, nickel fluoride, or a combination thereof. The manganese salt may be, for example, manganese sulfate, manganese nitrate, manganese chloride, manganese fluoride, or a combination thereof. In the metal salt aqueous solution, the manganese content with respect to the total metal content of the metal salt included in the metal salt aqueous solution may be greater than 50 mol%, for example, 60 mol% or more, 65 mol% or more, 70 mol% or more, 75 mol% or more % or more, or 80 mol% or more. In this case, a manganese-excess transition metal hydroxide precursor can be formed, and thus a high-capacity lithium-excess layered positive electrode active material can be prepared.

The aqueous alkali solution for adjusting the pH may include, for example, distilled water, an aqueous ammonia solution, and sodium hydroxide.

The process of continuously adding and mixing the aqueous metal salt solution and the aqueous alkali solution for pH adjustment to the coprecipitation reactor may be performed in a state in which air is continuously supplied.

In addition, the method of preparing the cathode active material precursor does not include supplying nitrogen to the coprecipitation reactor. By using air instead of nitrogen as an injection gas, a desired cathode active material precursor can be synthesized.

Another embodiment provides a method for preparing a lithium-excess layered positive electrode active material for a lithium secondary battery. The method of manufacturing the positive active material includes mixing the above-described positive electrode active material precursor and a lithium raw material and performing heat treatment.

The lithium raw material may include Li ₂ CO ₃ , LiOH, or a combination thereof.

The molar ratio of the cathode active material precursor and the lithium raw material may be 1:1.1 to 1:3, for example, 1:1.1 to 1:2.5, 1:1.1 to 1:2, or 1:1.2 to 1:1.8. can In this case, it is possible to form an excess lithium layered positive electrode active material capable of realizing an ultra-high capacity even at a high voltage.

The heat treatment may be performed, for example, at 800 °C to 1000 °C or 850 °C to 950 °C, and for 4 hours to 24 hours, for example, 5 hours to 15 hours.

In another embodiment, there is provided an excess lithium layered positive electrode active material for a lithium secondary battery prepared from the above-described positive electrode active material precursor. A positive active material according to an embodiment includes a compound represented by Formula 2, wherein the positive active material is composed of secondary particles formed by aggregation of a plurality of primary particles, wherein the primary particles are not plate-shaped, and the primary The average particle diameter of the particles is 10 nm to 950 nm, the average particle diameter of the secondary particles is 1 μm to 9 μm, and the tap density of the positive electrode active material is 1.7 g/cc or more.

[Formula 2]

Li _a Ni _x2 Mn _y2 M ² _z2 O ₂

In Formula 1, 1.1≤a≤1.5 x2+y2+z2=1, 0<x2<0.5, 0.5<y2<1, 0≤z2<0.5, wherein M ² is Co, Mg, Ca, Al, Ti , V, Cr, Zr, Nb, Mo, and at least one element selected from W.

In general, in the case of an excess lithium layered positive electrode active material, the primary particles are irregular and have a large plate shape, and the secondary particles agglomerated therein have large pores. Accordingly, the tap density of the active material is low, the electrode density is low, and there is a limit in increasing the bulk energy density. In addition, such a positive active material contains Li ₂ MnO ₃ in addition to lithium transition metal oxide. Accordingly, lithium conductivity and electronic conductivity are low, so that sufficient capacity can be realized only by using an excess of a conductive material.

On the other hand, the positive electrode active material according to the exemplary embodiment is a layered positive electrode active material with excess lithium, and the primary particles are not plate-shaped, but nano-sized amorphous (does not have a fixed shape), and they are densely packed to form secondary particles of several μm. It has a particle-like shape. Accordingly, the positive active material may exhibit a high tap density of 1.7 g/cc or more. In addition, since the Mn ₃ O ₄ phase is not formed in the precursor, the active material also does not contain Li ₂ MnO ₃ , and thus may exhibit high lithium ion conductivity and electronic conductivity, and the content of the conductive material during electrode manufacturing is 8 wt% or less, or A sufficiently high capacity can be exhibited even at a level of 5% by weight or less.

The average particle diameter of the primary particles of the positive active material may be 10 nm to 950 nm, for example, 10 nm to 900 nm, 50 nm to 850 nm, or 100 nm to 800 nm. The secondary particles of the positive active material may be spherical, and the secondary particles have an average particle diameter of 1 μm to 9 μm, for example, 2 μm to 8 μm, 3 μm to 7 μm, or 3 μm to 6 μm. can When the average particle diameter of the primary particles and the average particle diameter of the secondary particles of the positive active material satisfy the above ranges, it is possible to realize ultra-high capacity at high voltage and high tap density at the same time to realize high energy density.

Here, the average particle diameter may mean measured through a particle size analyzer that analyzes the size of particles according to diffraction, or may mean measured through a scanning electron micrograph or the like.

The positive active material may have a tap density of 1.7 g/cc or more, for example, 1.71 g/cc or more, 1.72 g/cc or more, or 3 g/cc or less, 2.5 g/cc or less, or 2.0 g/cc or less. . When the tap density of the positive electrode active material satisfies the above range, it is possible to realize ultra-high capacity at high voltage and at the same time realize high electrode density and high battery energy density due to the high tap density.

Another embodiment, the positive electrode; cathode; and a non-aqueous electrolyte, wherein the positive electrode provides a lithium secondary battery comprising the positive electrode active material according to the above-described embodiment.

The positive electrode includes a current collector and a positive electrode active material layer disposed on the current collector. The positive active material layer may include a positive active material, and the positive active material may include the positive active material for a lithium secondary battery according to the embodiment described above.

In the cathode active material layer, the content of the cathode active material may be 90 wt% to 99 wt% based on the total weight of the cathode active material layer.

The positive active material layer may further include a binder and/or a conductive material. In this case, the content of the binder and the conductive material may be 1 wt% to 5 wt%, respectively, based on the total weight of the positive electrode active material layer.

The binder serves to well adhere the positive active material particles to each other and also to adhere the positive active material to the current collector. Representative examples of the binder include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer including ethylene oxide, polyvinyl pyrrol Don, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc. may be used, but the present invention is not limited thereto. .

The conductive material is used to impart conductivity to the electrode, and in the configured battery, any electronically conductive material may be used without causing a chemical change. Examples of the conductive material include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, and carbon fiber; Metal-based substances, such as metal powders, such as copper, nickel, aluminum, and silver, or a metal fiber; conductive polymers such as polyphenylene derivatives; or a conductive material containing a mixture thereof.

The positive electrode current collector may be an aluminum foil, a nickel foil, or a combination thereof, but is not limited thereto.

The negative electrode includes a current collector and a negative active material layer formed on the current collector, and the negative active material layer includes a negative electrode active material.

The negative active material includes a material capable of reversibly intercalating/deintercalating lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide.

The material capable of reversibly intercalating/deintercalating lithium ions is a carbon material, and any carbon-based negative active material generally used in lithium ion secondary batteries may be used, and a representative example thereof is crystalline carbon. , amorphous carbon or these may be used together.

The lithium metal alloy includes lithium and Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al and Sn from the group consisting of Alloys of metals of choice may be used.

Materials capable of doping and dedoping lithium include Si, SiO _x (0 < x < 2), Si-Y alloy (where Y is an alkali metal, alkaline earth metal, group 13 element, group 14 element, transition metal, An element selected from the group consisting of rare earth elements and combinations thereof, but not Si), Sn, SnO ₂ , Sn-Y (wherein Y is an alkali metal, an alkaline earth metal, a group 13 element, a group 14 element, a transition metal, a rare earth) It is an element selected from the group consisting of elements and combinations thereof, and is not Sn) and the like.

Examples of the transition metal oxide include vanadium oxide and lithium vanadium oxide. The negative active material layer also includes a binder, and may optionally further include a conductive material.

The binder serves to well adhere the negative active material particles to each other and also to adhere the negative active material to the current collector.

The conductive material is used to impart conductivity to the electrode, and in the configured battery, any electronically conductive material may be used without causing a chemical change.

As the current collector, one selected from the group consisting of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with conductive metal, and combinations thereof may be used.

The negative electrode and the positive electrode are prepared by mixing an active material, a conductive material, and a binder in a solvent to prepare an active material composition, and applying the composition to a current collector. Since such an electrode manufacturing method is widely known in the art, a detailed description thereof will be omitted herein. The solvent may include, but is not limited to, N-methylpyrrolidone.

The electrolyte includes a non-aqueous organic solvent and a lithium salt.

The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move.

The lithium salt is dissolved in an organic solvent, serves as a source of lithium ions in the battery, enables basic lithium secondary battery operation, and promotes movement of lithium ions between the positive electrode and the negative electrode.

Depending on the type of lithium secondary battery, a separator may exist between the positive electrode and the negative electrode. As such a separator, polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof may be used. A polyethylene/polypropylene two-layer separator, a polyethylene/polypropylene/polyethylene three-layer separator, and polypropylene/polyethylene/poly It goes without saying that a mixed multilayer film such as a propylene three-layer separator or the like can be used.

Lithium secondary batteries can be classified into lithium ion batteries, lithium ion polymer batteries, and lithium polymer batteries according to the type of separator and electrolyte used, and can be classified into cylindrical, prismatic, coin-type, pouch-type, etc. according to the shape, According to the size, it can be divided into a bulk type and a thin film type. Since the structure and manufacturing method of these batteries are well known in the art, a detailed description thereof will be omitted.

Hereinafter, Examples and Comparative Examples of the present invention will be described. The following examples are only examples of the present invention, and the present invention is not limited to the following examples.

Example 1

(1) Preparation of a cathode active material precursor

A 20L co-precipitation reactor is used to prepare nickel-manganese co-precipitation hydroxide. First, using 1508 g of NiSO ₄ 6H ₂ O, 2852 g of MnSO 4H ₂ O, and 7879 g of ultrapure water, a 2.5 M aqueous metal salt solution is prepared. Second, NaOH (2093 g, powder), NH ₄ OH (627 g, 24% aqueous solution), and ultrapure water 6279 g are mixed to prepare an aqueous alkali solution for pH adjustment. Third, after the prepared aqueous metal salt solution and the aqueous alkali solution for pH adjustment are put into tank 1 and tank 2, respectively, tank 1 is maintained at 45 ℃ and tank 2 is 10 ℃.

Fourth, 2.5L of ultrapure water, 44g of initial NH ₄ OH, and 3g of initial NaOH were added into the reactor to prepare a base solution, and then air was added as an injection gas, followed by stirring for 10 minutes. Fifth, while introducing air, the metal salt aqueous solution in tank 1 is quantitatively added at 680 g/hr and the alkali aqueous solution for pH adjustment in tank 2 at 432 g/hr to start the co-precipitation reaction.

Sixth, the size of the co-precipitated particles is measured and recorded in units of 10 minutes up to the initial 1 hour and 1 hour after 1 hour, and nickel manganese hydroxide having a final particle size of 3 μm to 5 μm is prepared. A scanning electron microscope photograph showing the shape of the prepared precursor is shown in FIG. 1 , and an X-ray diffraction analysis graph for the precursor is shown in FIG. 2 . The prepared precursor is a composite phase of Ni _0.25 Mn _0.75 (OH) ₂ and Ni _0.25 Mn _0.75 (OOH), and the half value of the X-ray diffraction peak at the (001) plane of the P-3m1 structure of Ni _0.25 Mn _0.75 (OH) ₂ The width (Full Width Half Maximum) was measured to be 1.85.

(2) Preparation of positive electrode active material

The prepared nickel manganese hydroxide and lithium raw material Li ₂ CO ₃ were weighed in a molar ratio of 0.8:1.2, mixed, and calcined at 900° C. for 10 hours while adding air. The growth of the precursor primary particles proceeds to prepare a lithium-excess layered positive electrode active material having a spherical secondary particle shape of about 5 μm composed of primary particles of irregular shape and size. A scanning electron microscope photograph showing the shape of the synthesized positive active material is shown in FIG. 3 , and an X-ray diffraction analysis graph for the positive active material is shown in FIG. 4 .

(3) Preparation of battery

92% of the prepared positive electrode active material, 4% of Super P as a conductive material, and 4% of PVDF as a binder were put in an NMP solution, mixed to prepare a slurry, and then coated on an aluminum current collector to prepare a positive electrode having a thickness of 50 μm , to fabricate a coin half cell using lithium metal as a negative electrode.

Comparative Example 1

In the preparation of the cathode active material precursor of Example 1, a cathode active material precursor, a cathode active material, and a battery (half cell) were prepared in the same manner except that nitrogen was added instead of air during the coprecipitation reaction.

The nickel manganese hydroxide precursor (Ni _0.25 Mn _0.75 (OH) ₂ ) prepared in Comparative Example 1 had a particle diameter of about 3 μm to 5 μm. The shape of the precursor prepared in Comparative Example 1 was photographed with a scanning electron microscope and shown in FIG. 5 , and an X-ray diffraction analysis graph for the precursor is shown in FIG. 6 . In the prepared precursor, a composite phase of Ni _0.25 Mn _0.75 (OH) ₂ and Ni _0.25 Mn _0.75 (OOH) was mainly present, and an Mn ₃ O ₄ impurity phase was present. The X-ray diffraction peak half width of the (001) plane of the P-3m1 structure of Ni _0.25 Mn _0.75 (OH) ₂ was measured to be 0.28.

The shape of the positive active material prepared in Comparative Example 1 was photographed with a scanning electron microscope and shown in FIG. 7 , and an X-ray diffraction analysis graph for the positive active material is shown in FIG. 8 . The average particle diameter of the positive active material of Comparative Example 1 was about 5 μm.

Evaluation Example 1: X-ray diffraction analysis of precursors

X-ray diffraction analysis was performed on the precursor (nickel manganese hydroxide) prepared in Example 1 and the precursor prepared in Comparative Example 1, and the results are shown in FIGS. 2 and 4, respectively, and (001) of the P-3m1 structure The X-ray diffraction peak half width of the surface was measured and shown in Table 1 below.

Peak full width at (001) plane Example 1 1.85 Comparative Example 1 0.28

Referring to Table 1, it can be seen that the half width of Example 1 is 1.85, indicating a value exceeding 0.5.

Evaluation Example 2: Tap Density Analysis of Positive Active Material

The tap densities of the positive active material prepared in Example 1 and the positive active material prepared in Comparative Example 1 were measured, and the results are shown in Table 2 below. For tap density, using a tap density meter (Autotap) of Quantachrome, put 90ml of the synthesized positive active material into a 100ml graduated cylinder, measure the mass up to 0.1g, set the stroke length to 3.2mm, and rotate After tapping 3000 times at a speed of 250 rpm, the volume is measured up to the 1 ml scale, and then the sample weight is divided by the volume.

Tap Density (g/cc) Example 1 1.72 Comparative Example 1 1.56

Referring to Table 2, it can be seen that the tap density of the positive active material prepared in Example 1 is 1.72 g/cc, which is higher than in Comparative Example 1.

Evaluation Example 3: Evaluation of battery charge/discharge characteristics

For the half cells prepared in Example 1 and Comparative Example 1, an initial cycle was performed with 1/20C charge and 1/20C discharge (1C=250mAh/g), the charge cut-off voltage was 4.7V, and the discharge cut-off voltage was 4.7V. was set to 2.5V, and the temperature of the coin cell evaluation chamber was set to 25°C to evaluate the charge/discharge characteristics, and the results are shown in Table 3 and FIG. 9 .

First Charge Capacity (mAh/g) First discharge capacity (mAh/g) Example 1 313.1 226.8 Comparative Example 1 231.5 166.2

Referring to Table 3 and FIG. 9, it can be seen that the battery of Example 1 implements a high discharge capacity even in a positive electrode composition of 92% active material, 4% binder, and 4% conductive material while applying an excess lithium layered positive electrode active material. have.

Although preferred embodiments have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept defined in the following claims are also within the scope of the present invention. will belong

Claims (11)

As a positive electrode active material precursor comprising a compound represented by the following formula (1),
The cathode active material precursor is composed of secondary particles formed by aggregation of a plurality of primary particles,
The secondary particles have an average particle diameter of 1 μm to 9 μm,
The cathode active material precursor has a P-3m1 space group in X-ray diffraction analysis and has a diffraction peak full width at half maximum in the (001) plane of 0.5 or more cathode active material precursor for a lithium secondary battery:
[Formula 1]
Ni _x Mn _y M ¹ _z (OH) ₂
In Formula 1, x+y+z=1, 0<x<0.5, 0.5<y<1, 0≤z<0.5, wherein M ¹ is Co, Mg, Ca, Al, Ti, V, Cr, It is at least one element selected from Zr, Nb, Mo, and W. In claim 1,
The cathode active material precursor is a cathode active material precursor for a lithium secondary battery that does not contain Mn ₃ O ₄ . In claim 1,
The secondary particles have an average particle diameter of 1 μm to 6 μm, a cathode active material precursor for a lithium secondary battery. In claim 1,
The primary particle is a plate-shaped positive electrode active material precursor for a lithium secondary battery. In claim 1,
A cathode active material precursor for a lithium secondary battery, wherein 0<x<0.3, 0.7<y<1, and 0≤z<0.3 in Formula 1 above. Distilled water and ammonia aqueous solution were put into the coprecipitation reactor,
supplying air to the coprecipitation reactor;
An aqueous solution of a metal salt including a nickel salt and a manganese salt, and an aqueous alkali solution for pH adjustment are continuously added to the co-precipitation reactor and mixed, and
A method for producing a cathode active material precursor for a lithium secondary battery comprising obtaining the cathode active material precursor according to any one of claims 1 to 5. In claim 6,
The nickel salt is nickel sulfate, nickel nitrate, nickel chloride, nickel fluoride, or a combination thereof,
The manganese salt is manganese sulfate, manganese nitrate, manganese chloride, manganese fluoride, or a combination thereof. In claim 6,
In the metal salt aqueous solution, the content of manganese with respect to the total metal content of the metal salt included in the metal salt aqueous solution is more than 50 mol% of the method of manufacturing a positive electrode active material precursor for a lithium secondary battery. As a lithium excess layered positive electrode active material comprising a compound represented by Formula 2,
The positive active material is composed of secondary particles formed by aggregation of a plurality of primary particles,
The primary particles are not plate-shaped,
The primary particles have an average particle diameter of 10 nm to 950 nm,
The secondary particles have an average particle diameter of 1 μm to 9 μm,
The tap density of the positive electrode active material is 1.7 g / cc or more lithium excess layered positive electrode active material for a lithium secondary battery:
[Formula 2]
Li _a Ni _x2 Mn _y2 M ² _z2 O ₂
In Formula 1, 1.1≤a≤1.5 x2+y2+z2=1, 0<x2<0.5, 0.5 < y2<1, 0≤z2<0.5, wherein M ² is Co, Mg, Ca, Al, Ti , V, Cr, Zr, Nb, Mo, and at least one element selected from W. In claim 9,
The primary particle is an amorphous lithium-excess layered positive electrode active material for a lithium secondary battery. A positive electrode comprising an excess lithium layered positive electrode active material according to any one of claims 9 or 10;
cathode; and
A lithium secondary battery comprising an electrolyte.

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