KR20140119620A - Precusor for lithium rich active material and lithium rich active material made by the same - Google Patents

Abstract

The present invention relates to a precursor for manufacturing a lithium-rich positive electrode material and a lithium-rich positive electrode material manufactured thereby. More specifically, the present invention relates to a new precursor for manufacturing a lithium-rich positive electrode material and a lithium-rich positive electrode material manufactured thereby, whose capacity and life service are significantly improved by resolving existing problems of the lithium-rich positive electrode material with replacing AI and A which are dissimilar metals.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a precursor for the production of a lithium excessive amount of a cathode active material, and a lithium excess amount of a cathode active material produced thereby.

The present invention relates to a precursor for the production of a lithium-excess cathode active material and a lithium-over-capacity cathode active material prepared thereby, and more particularly to a lithium-excess cathode active material having improved lithium- A precursor for producing an active material, and a lithium-over-capacity cathode active material produced thereby.

Lithium batteries are widely used in consumer electronics due to their relatively high energy density. A rechargeable battery is also referred to as a secondary battery, and a lithium ion secondary battery generally includes a cathode material that introduces lithium.

At present, as the positive electrode active material of the lithium ion secondary battery, lithium-containing cobalt oxide such as LiCoO2 of a layered structure, lithium-containing nickel oxide such as LiNiO2 of a layered structure, LiMn ₂ O ₄ of a spinel crystal structure Lithium-containing manganese oxide, and the like are used. As the negative electrode active material, a graphite-based material is mainly used.

LiCoO2 is widely used today because it has excellent physical properties such as excellent cycle characteristics, but its safety is low, and it is expensive due to the resource limit of cobalt as a raw material, and there is a limit to mass use as a power source for fields such as electric vehicles. LiNiO ₂ is difficult to apply to actual mass production process at a reasonable cost due to its characteristics depending on the manufacturing method.

On the other hand, lithium manganese oxides such as LiMnO ₂ and LiMn ₂ O ₄ have the advantage of using manganese which is rich in resources and environment-friendly as a raw material, and thus attracts much attention as a cathode active material that can replace LiCoO ₂ . However, these lithium manganese oxides also have a disadvantage of poor cycle characteristics and the like. LiMnO ₂ has a disadvantage in that the initial capacity is small and dozens of charge-discharge cycles are required until a certain capacity is reached.

In addition, LiMn ₂ O ₄ has a disadvantage in that the cycle capacity is seriously deteriorated as the cycle continues, and in particular, at a high temperature of 50 ° C or higher, the cycle characteristics are drastically lowered due to decomposition of the electrolytic solution and elution of manganese.

Recently, there is a proposal to increase the theoretical available capacity by increasing the stability of the layered positive electrode active material by introducing Li ₂ MnO ₃ . Such a cathode active material exhibits a flat section at a high voltage section of 4.3 V to 4.6 V at the time of charging. This flat region is known as a region where lithium (Li) and oxygen (O) are separated from the crystal structure of Li ₂ MnO ₃ and lithium is inserted into the cathode. Li ₂ MnO ₃ can not 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 not desirable inefficiently to accommodate additional lithium. Lithium extraction is not possible because the manganese ion is quaternary and is not easily oxidized at the actual potential. However, according to Rossouw et al in the Materials Research Bulletin (Volume 26, page 463 (1991)), Li 2 - x MnO 3 -x / 2 Li 2 O from Li ₂ MnO ₃ structure by a chemical treatment to produce the By removal, Li ₂ MnO ₃ can be electrochemically activated, and this process is accompanied by some H + - Li + ion exchange. Reported by Robertson et al. In Kalyani et al., Journal of Power Sources (Volume 80, page 103 (1999)) and in Chemistry of Materials (Volume 15, page 1984, (2003) Li ₂ MnO ₃ can also be electrochemically activated by removing Li ₂ O, but the performance of such an activated electrode in a lithium battery is undesirable.

Although the Li _{2 - x} MnO _{3 - x / 2} electrode alone tends to lose its capacity during cycling of the lithium battery, US Pat. Nos. 6,677,082 and 6,680,143 disclose a composite electrode such as Li ₂ MnO ₃ And LiMO ₂ components are used in an electrode system of two components such as xLi ₂ MnO _3. (Lx) LiMO ₂ (M = Mn, Ni, Co) having a layered structure, the improved electrochemical properties provide high efficiency It can be seen that

However, the cathode active material having such a composite electrode structure is electrochemically active due to desorption of lithium and oxygen at a high voltage range of 4.3 V to 4.6 V, and the capacity can be increased due to the existence of the flat section However, there is a high possibility of decomposition of electrolyte and gas generation at a high voltage due to oxygen gas generated inside the battery, and the crystal structure is physically and chemically deformed through repeated charge and discharge, thereby deteriorating the rate characteristic. As a result, .

In addition, since the terminal region of the discharge voltage is lowered, the battery can not contribute to the capacity when used in a cellular phone, or when the battery is used in an automobile, the battery is in an unusable region of charge (SOC) It can not be achieved.

Therefore, there is a high need for a technique capable of fundamentally solving such problems.

It is an object of the present invention to provide a precursor for the production of a lithium-excess cathode active material having improved capacity characteristics and life characteristics, and to provide a lithium-over-capacity cathode active material as described above.

The present invention provides a precursor for the production of a lithium-excess cathode active material represented by the following general formula (1).

[Chemical Formula 1] Ni _α Mn _y Co _{β- γ-δ} A _δ Al _y CO ₃

(Wherein A is a tetravalent ion selected from Ti and Zr,? Is 0.05 to 0.4,? Is 0.5 to 0.8,? Is 0 to 0.4,? Is 0.001 to 0.1, y is 0.001 Lt; / RTI >

The present invention also provides a lithium-excess cathode active material obtained from the cathode active material precursor for lithium secondary batteries and represented by the following formula (2).

???????? Li _{1 + x} Ni _? Mn _{? -Y} Co _{? -Δ} Al _? A _y O ₂ ?????

X is from 0.2 to 0.7, A is selected tetravalent ion of Ti and Zr,? Is 0.05 to 0.4,? Is 0.5 to 0.8,? Is 0 to 0.4,? Is 0.001 to 0.1 And y is 0.001 to 0.1.

The positive electrode active material according to the present invention _{xLiMAl δ O 2 · (1-} x) Li 2 Mn 1 - a combination of _{y A y O 3 (0 <} x <1, M ' is Ni, Co, and Mn, A is Ti , And Zr). That is, the positive electrode active material according to the present invention is composed of a layer-phase represented by the layer-phase and _{Li 2 Mn 1-y A y} O 3 represented by LiMAl _δ O _2, the aluminum in the layer offset represented by LiMAl _δ O ₂ Co is substituted and the dissimilar metal A substitutes for Mn in the layer system represented by Li ₂ Mn _y O ₃ , thereby exhibiting the effect of improving the high-voltage lifetime characteristics by involvement of the dissimilar metal A in the electrochemical activation of Li ₂ MnO ₃ And at the same time, the elution of Mn is prevented.

However, when the dissimilar metal A substitutes for the Co moiety excessively, the output and capacity decrease may occur as the Co content decreases. Therefore, the substitution amount of Al is preferably 0.001 to 0.1, and when the dissimilar metal A is substituted with Mn in excess The substitution amount of the dissimilar metal A is preferably 0.001 to 0.1, more preferably 0.02 to 0.05.

In the cathode active material according to the present invention, the following relation is satisfied between the content of Al, the content x of Li and the content y of the dissimilar metal A:

x?

y?

The cathode active material according to the present invention is characterized by being in the form of a composite or solid solution of a layered structure.

The precursor for the lithium-overbased cathode active material according to the present invention and the lithium-over-capacity cathode active material produced thereby can improve the high-voltage capacity and improve the life characteristics of the battery by controlling the kind and amount of the metal added in the production of the carbonate precursor have.

FIGS. 1 and 2 show SEM photographs and EDS measurements of precursors prepared in one embodiment of the present invention.
FIGS. 3 and 4 show SEM photographs and EDS measurements of the precursor prepared in another embodiment of the present invention. FIG.
FIGS. 5 and 6 show SEM photographs and EDS measurements of the lithium-excessive cathode active material prepared in one embodiment of the present invention.
FIGS. 7 and 8 show SEM photographs and EDS measurements of the lithium-excessive cathode active material prepared in another embodiment of the present invention.
9 and 10 illustrate the results of measurement of the charge / discharge characteristics of a coin half cell using the lithium oversized cathode active material prepared in one embodiment of the present invention.
FIGS. 11 and 12 illustrate results of measurement of lifetime characteristics for a coin half cell using the lithium oversized cathode active material manufactured in an embodiment of the present invention. FIG.

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 > Precursor synthesis

Nickel sulfate hexahydrate (NiSO ₄ .6H ₂ O), cobalt sulfate heptahydrate (CoSO ₄ .7H ₂ O), manganese sulfate hydrate (MnSO ₄ .7H ₂ O), aluminum sulphate as an aluminum compound, TiO ₂ as a dissimilar metal The mixed metal solution was introduced into a coprecipitation reactor, and 28% ammonia water as a complexing agent and Na ₂ CO ₃ as a carbonate compound were continuously supplied to the reactor while adjusting the pH to 8 to 10, followed by a coprecipitation reaction for 50 hours The slurry solution in the reactor was filtered and washed with high purity distilled water and dried in a vacuum oven at 110 ° C for 12 hours to obtain a nickel cobalt manganese aluminum titanium composite metal carbonate compound. The composition of the transition metal complex carbonate compound was _{Ni 0 .2 Co 0 .07 Mn 0} .67 Al 0 .03 Ti 0 .03 CO 3.

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 5 were synthesized in the same manner as described above, except that a metal mixed solution containing a dissimilar metal was prepared in the composition ratio as shown in Table 1 above.

< Experimental Example > SEM  Photos and EDS  Measure

SEM photographs and EDS measurements of precursors prepared with the composition of Example 3 are shown in Figs. 1 and 2, and SEM photographs and EDS of the precursors prepared with the composition of Example 4 are shown in Fig. 3 And FIG. 4, respectively.

1 and 3, the surface-coated Al ₂ O ₃ And it is confirmed from the EDS measurement results of FIGS. 2 and 4 that the doped Al and Mg are uniformly doped into the entire grain.

< Example > Cathode active material  synthesis

The carbonate precursors prepared in Examples 1 to 4 and Comparative Examples were mixed with Li ₂ CO ₃ in an equivalent ratio as a lithium compound, and the mixture was heat-treated at 900 ° C. and pulverized to synthesize a lithium-excessive cathode active material.

< Experimental Example > SEM  Photos and EDS  Measure

SEM photographs and EDS of the cathode active material prepared in the composition of Example 3 are shown in FIGS. 5 and 6, and SEM photographs and EDS of the cathode active material prepared in the composition of Example 4 are shown in FIG. 7 and 8.

< Experimental Example > Measurement of battery characteristics

The lithium excessive amount of the cathode active material prepared in the compositions of Examples 1 to 4 and Comparative Example 1 was mixed with carbon black and PVDF [poly (vinylidene fluoride)] as a binder in a weight ratio of 94: 3: 3 with NMP as an organic solvent, .

The slurry was coated on Al foil having a thickness of 20 탆 and dried to prepare a positive electrode. A CR2016 coin half cell was fabricated using a porous polyethylene film (Cell Guard 2502) as a negative electrode and a porous polyethylene film (Cell Guard 2502) as a separator. The electrolyte solution was a 1.1M LiPF ₆ EC / EMC / DEC solution Respectively.

The discharge capacity and lifetime characteristics of the battery thus prepared were measured and shown in Table 2 and FIG. 3 below.

Discharge capacity
/ mAhg-1 After 50 times
Normal temperature service life
/% 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 and FIG. 3, the lithium oversolding cathode active material prepared according to the example of the present invention shows improved discharge capacity and lifetime characteristics as compared with the comparative example.

The charging / discharging characteristics of the CR2016 coin half cell using the lithium excessive amount of the cathode active material prepared in the compositions of Examples 3 and 4 were measured, and the results are shown in FIG. 9 to FIG.

< Experimental Example > Life characteristics measurement

The lifetime characteristics of the CR2016 coin half cell using the lithium excessive amount of the cathode active material prepared in the examples 3 and 4 prepared in the above Experimental Example were measured and the results are shown in FIG. 11 and FIG.

In FIGS. 11 and 12, it can be seen that the capacity of the CR2016 coin half cell using the lithium-excessive cathode active material prepared according to the compositions of Examples 3 and 4 of the present invention is maintained up to 40 cycles.

< Experimental Example > Particle strength measurement

Particulate strength of the lithium-excessive cathode active material prepared in the compositions of Examples 3 and 4 and the lithium-excessive cathode active material prepared in the compositions of Comparative Examples 1 and 2 were measured, and the results are shown in Table 3 below.

Claims (7)

A precursor for the production of a lithium-excessive amount of a cathode active material represented by the following formula (1).
[Chemical Formula 1] Ni _α Mn _{β-γ-δ y} Co _y Al _δ A CO ₃
(Wherein A is selected from the group consisting of Mg, Ti and Zr,? Is 0.05 to 0.4,? Is 0.5 to 0.8,? Is 0 to 0.4,? Is 0.001 to 0.1, y Is 0.001 to 0.1)
The method according to claim 1,
Wherein the precursor for producing a cathode active material has a particle diameter of 5 to 25 占 퐉.
A lithium-excessive amount of the cathode active material, which is produced by the precursor for producing a lithium-excessive amount of the cathode active material according to claim 1 or 2, and is represented by the following formula (2).
[Chemical Formula 2] Li _x Ni _{1 + α β-} Mn _y Co _γ-δ A _δ Al _y O ₂
X is from 0.2 to 0.7, A is selected from the group consisting of Mg, Ti, and Zr,? Is from 0.05 to 0.4, beta is from 0.5 to 0.8, y is from 0 to 0.4, and? Is 0.001 to 0.1, and y is 0.001 to 0.1)
The method of claim 3,
The positive electrode active material is _{xLiMAl δ O 2 · (1-} x) Li 2 Mn 1 - a combination of _{y A y O 3 (0 <} x <1, M ' is Ni, Co, and Mn, A is Mg, Ti, And Zr, wherein? Is from 0.001 to 0.1, and y is from 0.001 to 0.1. &Lt; RTI ID = 0.0 &gt; 11. &lt; / RTI &gt;
The method of claim 3,
Wherein the lithium excessive amount of the positive electrode active material is in the form of a composite or solid solution of a layered structure.
The method of claim 3,
Wherein the following relationship is satisfied between the content of Al, the content x of Li, and the content of y of the dissimilar metal A:
x?
y?
The method of claim 3,
Wherein the lithium overbased cathode active material has a particle strength of 115 or more.

Images