WO2014163357A1 - Precursor for producing lithium-rich cathode active material, and lithium-rich cathode active material produced thereby - Google Patents

Abstract

The present invention relates to a precursor for producing lithium-rich cathode active material, and lithium-rich cathode active material produced by means of same, and more specifically, to a new precursor for producing lithium-rich cathode active material, and lithium-rich cathode active material produced by means of same, in which dissimilar metals Al and A are substituted, thereby mitigating the problems of conventional lithium-rich cathode active material to significantly improve capacity and life-span characteristics.

Description

Precursor for producing lithium excess positive electrode active material and lithium excess positive electrode active material produced thereby

The present invention relates to a precursor for preparing a lithium excess positive electrode active material and a lithium excess positive electrode active material prepared thereby, and more particularly, to improve the problem of the conventional lithium excess positive electrode active material, a new lithium excess positive electrode greatly improved capacity characteristics and life characteristics The present invention relates to a precursor for preparing an active material and a lithium excess cathode active material prepared thereby.

Lithium batteries are widely used in home appliances because of their relatively high energy density. Rechargeable batteries are also called secondary cells, and lithium ion secondary cells generally include a negative electrode material that introduces lithium.

Currently, the positive electrode active materials of lithium ion secondary batteries include lithium-containing cobalt oxides such as LiCoO ₂ in a layered structure, lithium-containing nickel oxides such as LiNiO _{2 in a} layered structure, and LiMn ₂ O _{4 in a} spinel crystal structure. Lithium-containing manganese oxides and the like are used, and graphite-based materials are mainly used as the negative electrode active material.

LiCoO ₂ has been widely used because of its excellent physical properties such as excellent cycle characteristics, but it is low in safety, and has a limitation in using it as a power source in fields such as electric vehicles because it is expensive due to resource limitations of cobalt as a raw material. LiNiO ₂ is difficult to apply to the actual production process at a reasonable cost, due to the characteristics of the manufacturing method.

On the other hand, lithium manganese oxides such as LiMnO ₂ , LiMn ₂ O ₄ has the advantage of using a resource-rich and environmentally friendly manganese as a raw material, attracting a lot of attention as a cathode active material that can replace LiCoO ₂ . However, these lithium manganese oxides also have the disadvantage of poor cycle characteristics. LiMnO ₂ has a small initial capacity and has a disadvantage of requiring dozens of charge and discharge cycles to reach a constant capacity.

In addition, LiMn ₂ O ₄ has a disadvantage in that the capacity is severely degraded as the cycle continues, and particularly, the cycle characteristics are sharply degraded due to decomposition of the electrolyte and elution of manganese at a high temperature of 50 ° C. or higher.

Recently, there is a proposal to increase the theoretical usable capacity by introducing Li ₂ MnO ₃ to increase the stability of the layered cathode active material. Such a cathode active material has a characteristic of showing a flat section in a high voltage section of 4.3V to 4.6V during charging. Such a flat section is known as a section in which lithium is inserted into the cathode while lithium (Li) and oxygen (O) are separated from the crystal structure of Li ₂ MnO ₃ . Li ₂ MnO ₃ cannot be used as an insertion electrode in a lithium battery. This is because the insertion space of the four-sided structure facing the neighboring eight-sided structure is inefficiently desirable to accommodate additional lithium. Manganese ions are tetravalent and are not easily oxidized at actual potential, so lithium extraction is not possible. However, according to Rossouw et al in the Materials Research Bulletin (Volume 26, page 463 (1991)), the Li ₂ O from Li ₂ MnO ₃ structure by a chemical process for the production of _{Li 2-x MnO 3-x} / 2 By elimination, Li ₂ MnO ₃ can be electrochemically active and this process is accompanied by some H ⁺ -Li ⁺ ion exchange. Lithium batteries have been reported by Kalyani et al. In the Journal of Power Sources (Volume 80, page 103 (1999)) and by Robertson et al. In the Chemistry of Materials (Volume 15, page 1984, (2003)). by removing the Li ₂ O is Li ₂ MnO _3, but also can be electrochemically active, these active electrodes is not desirable, the performance of the lithium battery.

As such, when Li _2-x MnO _{3-x / 2} electrodes are used alone, US Pat. Nos. 6,677,082 and 6,680,143 describe composite electrodes, such as Li ₂ MnO ₃ and LiMO ₂ , although they tend to lose capacity during cycling of lithium batteries. When the components are used in two component electrode systems such as xLi ₂ MnO ₃ · (lx) LiMO ₂ (M = Mn, Ni, Co), all of which have a layered structure, they can have high efficiency in improved electrochemical properties. Is shown.

However, the cathode active material of the composite electrode structure is electrochemically active due to the desorption of lithium and oxygen in the high voltage section of 4.3V to 4.6V, and the capacity can be increased due to the existence of the flat section. However, the oxygen gas generated inside the battery is highly likely to decompose and decompose the electrolyte at high voltages, and the crystal structure is physically and chemically deformed through repeated charging and discharging, thereby lowering the rate characteristic. There is a problem of deterioration.

In addition, since the end section of the discharge voltage is lowered, it does not contribute to the capacity when used as a mobile phone, or when used in a vehicle, the power is low and becomes an unusable depth of charge (SOC) area, thereby increasing the power output in the actual battery. There is a problem that can not be achieved.

Therefore, there is a high need for a technology that can fundamentally solve these problems.

An object of the present invention is to improve the problems of the conventional lithium excess positive electrode active material as described above, to provide a precursor for producing a lithium excess positive electrode active material greatly improved capacity characteristics and life characteristics and a lithium excess positive electrode active material produced thereby.

The present invention provides a precursor for producing a lithium excess positive electrode active material represented by the following formula (1) to solve the above problems.

Ni _α Mn _β-y Co _γ-δ Al _δ A _y CO ₃

(In Formula 1, A is selected from the group consisting of Mg, Ti, and Zr, α is 0.05 to 0.4, β is 0.5 to 0.8, γ is 0 to 0.4, δ is 0.001 to 0.1, y Is 0.001 to 0.1)

Particle diameter of the precursor for producing a lithium excess positive electrode active material of the present invention is characterized in that 5 to 25 μm.

The present invention also provides a lithium excess cathode active material prepared from the precursor for preparing the lithium excess cathode active material and represented by the following Chemical Formula 2.

Li _{1 + x} Ni _α Mn _β-y Co _γ-δ Al _δ A _y O ₂

(In Formula 2, x is 0.2 to 0.7, A is selected from the group consisting of Mg, Ti, and Zr, α is 0.05 to 0.4, β is 0.5 to 0.8, γ is 0 to 0.4, δ Is 0.001 to 0.1 and y is 0.001 to 0.1)

Lithium excess cathode active material according to the present invention is xLiMAl _δ O ₂ · (1-x) Li ₂ Mn _{1 - y} A _y O ₃ (0 <x <1, M is a combination of Ni, Co, and Mn, A is Selected from the group consisting of Mg, Ti, and Zr, α is 0.05 to 0.4, β is 0.5 to 0.8, γ is 0 to 0.4, δ is 0.001 to 0.1, and y is 0.001 to 0.1). It is characterized by. That is, lithium overdose positive electrode active material according to the present invention is a layer-phase and the Li ₂ Mn ₁ represented by LiMAl _δ O _{2 -} is composed of a layer-phase represented by the _y A _y O _3, at layer-phase represented by LiMAl _δ O ₂ As Al displaces M and the dissimilar metal A displaces Mn in the layered system represented by Li ₂ Mn _y O ₃ , dissimilar metal A is involved in the electrochemical activation of Li ₂ MnO ₃ to improve the high voltage lifetime characteristics. In addition, it shows the effect of preventing the elution of Mn.

In the case of M in Formula 2, when the dissimilar metal A replaces the Co site in an excessive amount, output and capacity may decrease due to a decrease in the Co content, so that the substitution amount of Al is preferably 0.001 to 0.1, and as the dissimilar metal A, Substitution of Mn in excess leads to a decrease in capacity, so the substitution amount of dissimilar metal A is preferably 0.001 to 0.1, more preferably 0.02 to 0.05.

In the lithium excess positive electrode active material according to the present invention, the following relational expression is satisfied between the content δ of Al, the content x of Li, and the content y of dissimilar metal A in the general formula (2).

x ≥δ

y ≥δ

The lithium excess cathode active material according to the present invention is characterized in that it is in the form of a layered composite or solid solution.

Particle strength of the lithium excess positive electrode active material according to the invention is characterized in that more than 115 Mpa.

The lithium excess positive electrode active material precursor and the lithium excess positive electrode active material prepared according to the present invention can manufacture a battery having a high voltage capacity and improved lifespan characteristics by controlling the type and amount of metal added during the production of a carbonate precursor. have.

1 and 2 show the results of measuring the SEM photograph and EDS of the precursor for preparing a lithium excess positive electrode active material prepared in one embodiment of the present invention.

3 and 4 show the results of SEM and EDS measurement of the precursor for preparing a lithium excess cathode active material prepared in another embodiment of the present invention.

5 and 6 show the results of SEM and EDS measurements of the lithium excess cathode active material prepared in one embodiment of the present invention.

7 and 8 show the results of SEM and EDS measurements of the lithium excess cathode active material prepared in another embodiment of the present invention.

9 and 10 show the results of measuring the charge and discharge characteristics for the coin cell (Coin half cell) using the lithium excess positive electrode active material prepared in one embodiment of the present invention.

11 and 12 show the results of measuring the life characteristics of a coin cell (Coin half cell) using the lithium excess positive electrode active material prepared in one embodiment of the present invention.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the present invention is not limited by the following examples.

< Example > Lithium Excess Cathode active material  Precursor Synthesis for Manufacturing

Nickel sulfate hexahydrate (NiSO ₄ · 6H ₂ O) and cobalt sulfate hexahydrate (CoSO ₄ · 7H ₂ O), manganese sulfate hydrate (MnSO ₄ · 7H ₂ O), aluminum sulfate as an aluminum compound, TiO ₂ as a dissimilar metal The mixed metal mixed solution was added to the coprecipitation reactor, and the coprecipitation reaction was carried out for 50 hours by continuously supplying the reactor with a pH of 8 to 10 using 28% ammonia water as a complexing agent and Na ₂ CO ₃ as a carbonate compound. The slurry solution in the reactor was filtered and washed with distilled water of high purity, and dried in a vacuum oven at 110 ° C. for 12 hours to obtain a nickel cobalt manganese aluminum titanium metal composite carbonate compound. The composition of the transition metal composite carbonate compound obtained was Ni _0.2 Co _0.07 Mn _0.67 Al _0.03 Ti _0.03 CO ₃ .

Table 1

	Ni	Co	Mn	Al	Ti	Zr	Mg
Example 1	20	7	67	3	3	0	0
Example 2	20	7	67	3	0	3	3
Example 3	20	7	67	3	0	0	One
Example 4	20	7	67	3	0	0	2
Comparative Example 1	20	10	70	0	0	0	0
Comparative Example 2	20	7	70	3	0	0	0
Comparative Example 3	20	7	67	0	3	0	0
Comparative Example 4	20	7	67	0	0	3	3
Comparative Example 5	20	7	64	3	6	0	0
Comparative Example 6	20	7	64	3	0	6	6

The precursors of Examples 2 to 4 and Comparative Examples 1 to 6 were synthesized in the same manner as described above, except that a metal mixed solution containing heterogeneous metals was prepared in the same composition ratio as in Table 1.

<Experimental Example> SEM photograph and EDS measurement

The results of measuring the SEM photograph and EDS of the precursor prepared in the composition of Example 3 are shown in Figures 1 and 2, the SEM photograph and EDS of the precursor for preparing a lithium excess positive electrode active material prepared in the composition of Example 4 One result is shown in FIGS. 3 and 4.

In the SEM measurement results of FIGS. 1 and 3, it can be confirmed that the Al ₂ O ₃ coated on the surface is agglomerated, and the doped Al and Mg are uniformly doped throughout the particles from the EDS measurement results of FIGS. 2 and 4. Can be.

< Example > Lithium Excess Cathode active material  synthesis

The Examples 1 to 4 and the positive electrode active material in lithium excess after the heat treatment and pulverization on the mixture, 900 ℃ the Li ₂ CO ₃ as an equivalent ratio of the carbonate precursor and a lithium compound prepared in Comparative Example was prepared.

<Experimental Example> SEM photograph and EDS measurement

SEM pictures and EDS results of the lithium excess positive electrode active material prepared in the composition of Example 3 are shown in FIGS. 5 and 6, SEM pictures and EDS of the lithium excess positive electrode active material prepared in the composition of Example 4 The measured results are shown in FIGS. 7 and 8.

Experimental Example Measurement of Battery Characteristics

The lithium excess positive electrode active material prepared in the compositions of Examples 1 to 4 and Comparative Examples 1 to 6 was mixed with carbon black and PVDF [Poly (vinylidene fluoride)] as a binder and NMP as an organic solvent in a weight ratio of 94: 3: 3. To prepare a slurry.

The slurry was coated on Al foil having a thickness of 20 μm and then dried to prepare a positive electrode. Coin half cell (CR2016) was assembled using a porous polyethylene film (Cell Guard 2502) as a metal lithium as a cathode and a separator as a cathode, and 1.1M LiPF ₆ EC / EMC / DEC solution was used as an electrolyte. It was.

The discharge capacity and lifespan characteristics of the battery thus prepared were measured and shown in Table 2 below.

TABLE 2

	Discharge Capacity / mAhg-1	Room temperature lifespan after 50 times /%
Example 1	249	95
Example 2	250	96
Comparative Example 1	261	87
Comparative Example 2	259	93
Comparative Example 3	254	92
Comparative Example 4	253	93
Comparative Example 5	240	92
Comparative Example 6	239	93

As shown in Table 2, in the case of the lithium excess positive electrode active material prepared according to the embodiment of the present invention, it can be seen that the discharge capacity and the life characteristics are improved than in the comparative example.

The results of measuring charge and discharge characteristics of the CR2016 coin half cell using the lithium excess cathode active material prepared in the composition of Examples 3 and 4 are shown in FIGS. 9 to 10.

< Experimental Example > Life characteristics measurement

The lifespan characteristics of the CR2016 coin half cell using the lithium excess cathode active material prepared in the composition of Examples 3 and 4 prepared in the above experimental example were measured and the results are shown in FIGS. 11 and 12.

11 and 12 in the case of CR2016 coin cell using a lithium excess cathode active material prepared in the composition of Examples 3 and 4 of the present invention, it can be seen that the capacity is maintained up to 40 cycles.

Experimental Example Particle Strength Measurement

Particle strength was measured for the lithium excess positive electrode active material prepared in the compositions of Examples 3 and 4 and the lithium excess positive electrode active material prepared in the compositions of Comparative Examples 1 and 2 and the results are shown in Table 3 below.

TABLE 3

	ID	Particle hardness
Comparative Example 1	bare	101
Comparative Example 2	Al 0.3	111
Example 3	Al 0.3 Mg1	116
Example 4	Al 0.3 Mg2	116

The lithium excess positive electrode active material precursor and the lithium excess positive electrode active material prepared according to the present invention can manufacture a battery having a high voltage capacity and improved lifespan characteristics by controlling the type and amount of metal added during the production of a carbonate precursor. have.

Claims (7)

1. A precursor for producing a lithium excess positive electrode active material represented by the following formula (1).

   Ni _α Mn _β-y Co _γ-δ Al _δ A _y CO ₃

   (In Formula 1, A is selected from the group consisting of Mg, Ti, and Zr, α is 0.05 to 0.4, β is 0.5 to 0.8, γ is 0 to 0.4, δ is 0.001 to 0.1, y Is 0.001 to 0.1)
2. The method of claim 1,

   Particle diameter of the precursor for producing the lithium excess positive electrode active material is a precursor for producing a lithium excess positive electrode active material, characterized in that 5 to 25 ㎛.
3. A lithium excess cathode active material prepared by using the precursor for producing a lithium excess cathode active material according to claim 1 or 2, and represented by the following Chemical Formula 2.

   Li _{1 + x} Ni _α Mn _β-y Co _γ-δ Al _δ A _y O ₂

   (In Formula 2, x is 0.2 to 0.7, A is selected from the group consisting of Mg, Ti, and Zr, α is 0.05 to 0.4, β is 0.5 to 0.8, γ is 0 to 0.4, δ Is 0.001 to 0.1 and y is 0.001 to 0.1)
4. The method of claim 3, wherein

   The lithium excess positive electrode active material is xLiMAl _δ O _2. (1-x) Li ₂ Mn _{1 - y} A _y O ₃ (0 <x <1, M is a combination of Ni, Co, and Mn, A is Mg, Ti , And Zr, and a metal selected from the group consisting of δ is 0.001 to 0.1, and y is 0.001 to 0.1).
5. The method of claim 3, wherein

   The lithium excess positive electrode active material is a lithium excess positive electrode active material, characterized in that the layered composite or solid solution form.
6. The method of claim 3, wherein

   Lithium excess cathode active material, characterized in that the following relational expression is satisfied between the content δ of Al, the content x of Li and the content y of dissimilar metal A.

   x ≥δ

   y ≥δ
7. The method of claim 3, wherein

   The lithium excess positive electrode active material, characterized in that the particle strength of the lithium excess positive electrode active material is 115 Mpa or more.

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