KR20160088121A - Positive active material for lithium rechargeable battery, lithium rechargeable battery including the same, and manufacturing method for the same - Google Patents

Abstract

The present invention relates to a positive electrode active material for a lithium secondary battery and a lithium secondary battery comprising the same and, more specifically, to a positive electrode active material for a lithium secondary battery having a novel structure and a lithium secondary battery comprising the same, where the oxidation number of Ni and Co maintains plus trivalent by inserting Li into a transition metal layer, and the oxidation number of Mn maintains plus tetravalent, so stability is structurally maintained.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positive active material for a lithium secondary battery and a lithium secondary battery comprising the positive active material and a lithium secondary battery including the same.

The present invention relates to a positive electrode active material for a lithium secondary battery and a lithium secondary battery comprising the same. More specifically, Li ions are inserted into a transition metal layer to maintain the oxidation number of Ni and the oxidation number of Co at +3, 4, a lithium secondary battery including the same, and a method of manufacturing the same.

Recently, with the rapid development of electronic, communication, and computer industries, the use of portable electronic products such as a camcorder, a mobile phone, and a notebook PC has become common, thereby demanding a lightweight, long-lasting, and reliable battery.

Particularly, since the lithium secondary battery has an operating voltage of 3.7 V or higher and a higher energy density per unit weight than a nickel-cadmium battery or a nickel-hydrogen battery, the demand for a lithium secondary battery as a power source for driving these portable electronic information communication devices It is increasing day by day.

In recent years, studies on a power source for an electric vehicle by hybridizing an internal combustion engine with a lithium secondary battery have been actively conducted in the United States, Japan, and Europe. The development of plug-in hybrid (P-HEV) batteries for vehicles with a mileage less than 60 miles a day is underway in the United States. The P-HEV battery is a battery having characteristics close to those of an electric vehicle, and development of a high capacity battery is a great challenge. In particular, it is a great challenge to develop a cathode material having a high tap density of 2.0 g / cc or more and a high capacity characteristic of 230 mAh / g or more.

LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , LiFePO ₄ and the like are currently commercially available or under development. Of these, LiCoO ₂ is an excellent material having stable charge / discharge characteristics, excellent electron conductivity, high cell voltage, high stability, and flat discharge voltage characteristics. However, Co has a low reserves, high price, and toxicity to the human body, so development of other cathode materials is desired. In addition, it has a disadvantage in that the crystalline structure is unstable due to the lithium removal during charging.

LiNi _{1 - x} Co _x O ₂ (x: 0.1-0.3) material in which a portion of nickel was substituted with cobalt exhibited excellent charge / discharge characteristics and lifetime characteristics, but did not solve the thermal stability problem. In addition, in European Patent No. 0872450, Li _a Co _b Mn _c M _d Ni _{1 - (b + c + d)} O ₂ (M = B, Al, Si, Fe, Cr, Cu, Zn, W, Ti, and Ga). However, the thermal stability of the Ni system still can not be solved.

It is an object of the present invention to provide a cathode active material having a novel structure which is structurally stable and does not deteriorate capacity characteristics upon charge and discharge.

In order to solve the problems of the prior art as described above, the present invention provides a superstructure having a layered Lombohydral R-3m structure, in which Li is substituted for some transition metal layers and oxidation number of Mn is +4, That is, the present invention provides a positive electrode active material for a lithium secondary battery, which exhibits a structure in which two structures coexist.

In the positive electrode active material for a lithium secondary battery according to the present invention, the oxidation number of Ni and Co is maintained at +3.

The positive electrode active material for a lithium secondary battery according to the present invention comprises Li _a [Ni _x Co _y Mn _z ] O ₂ , 0.95 <a <1.05, x? 0.85, 0 <y <0.075, 0.075 <z <0.15, y / z < 1). &Lt; / RTI &gt;

Cathode active material for a lithium secondary battery according to the invention is characterized by represented by _{Li [Ni 0 .85 Co 0 .05} Mn 0 .10] O 2.

The positive electrode active material for a lithium secondary battery according to the present invention is characterized in that a diffraction pattern due to Mn ^{4 +} appears in the Lombohydral R-3m structure in a layer at a TEM peak.

The positive electrode active material for a lithium secondary battery according to the present invention is characterized in that a peak due to the superstructure is exhibited at an XRD peak in the range of 20 to 20 in the range of 20 to 25.

The present invention also provides a lithium secondary battery comprising the cathode active material for a lithium secondary battery according to the present invention.

The present invention also relates to

Adding a precursor including nickel, cobalt and manganese, an ammonia solution, and a basic solution to a reactor at the same time, mixing, precipitating and stirring to precipitate the metal complex hydroxide;

Filtering and washing the metal complex hydroxide, followed by drying; And

Mixing the metal complex oxide with a lithium salt and then performing heat treatment;

A method for producing a lithium secondary battery positive electrode active material,

Wherein the heat treatment is performed at a temperature of 670 to 750 ° C. in the step of heat-treating the lithium salt after mixing the lithium salt.

The positive electrode active material for a lithium secondary battery according to the present invention is structurally stable by allowing Li to be inserted into the transition metal layer to maintain the oxidation number of Ni and the oxidation number of Co at +3 and maintain the oxidation number of Mn at +4, The life characteristics and the capacity characteristics of the lithium secondary battery including the cathode active material for the secondary battery are greatly improved.

FIGS. 1 to 3 show the results of XRD measurements of the cathode active material prepared in one embodiment of the present invention and a comparative example.
FIG. 4 shows TEM images of the cathode active material prepared in Examples of the present invention.
5 and 6 show X-ray absorption spectra of Mn and Ni for the cathode active material prepared in the examples 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>

4 liters of distilled water was placed in a coprecipitation reactor (capacity 4 L, output of a rotary motor was 80 W or more), nitrogen gas was supplied to the reactor at a rate of 0.7 liter / min to remove dissolved oxygen, lt; / RTI &gt;

An aqueous metal solution and an ammonia solution mixed in a molar ratio of nickel sulfate, cobalt sulfate and manganese sulfate of 85: 5: 10 were continuously introduced into the reactor, respectively. The pH was adjusted by feeding sodium hydroxide solution for pH adjustment.

The impeller speed was adjusted to 1000 rpm. The flow rate was adjusted so that the average residence time of the solution in the reactor was about 6.35 hours and the reaction was allowed to continue to be obtained after the reaction reached a steady state. The metal complex hydroxide was filtered, washed with water, and dried in a 110 占 폚 hot air dryer for 15 hours.

After mixing with the metal complex hydroxide and the lithium salt, the mixture was calcined at a temperature of 730 캜 for 15 hours to obtain a cathode active material powder represented by Li [Ni _{0 .85} Co _{0 .05} Mn _{0 .10} ] O ₂ .

< Comparative Example  1>

The cathode active material powder was prepared in the same manner as in Example 1 except that the aqueous metal solution in which the molar ratio of nickel sulfate, cobalt sulfate, and manganese sulfate was 85: 7.5: 7.5 was continuously introduced into the reactor in Example 1 .

< Experimental Example > XRD  Measure

XRD was measured for the cathode active material prepared in Example 1 and Comparative Example 1, and the results are shown in FIGS. 1 to 3.

In FIG. 3, it can be seen that Li is substituted for the transition metal layer in the case of the cathode active material according to the embodiment of the present invention, and a peak due to a superstructure in which the oxidation number of Mn is +4 is present.

< Experimental Example > TEM  Measure

TEM photographs of the cathode active material prepared in Example 1 were measured and the results are shown in FIG.

As shown in FIG. 4, a diffraction pattern of superstructure indicated by small points (indicated by arrows) due to Mn ^{4 +} appears in the original diffraction pattern (red circle) due to the layered Rombohydral structure.

Also, it can be seen that the superstructure appears regularly in FIG. 4 because the regular arrangement of Mn ^{4 +} is contained in the lattice of the basic rombo hydral structure.

< Experimental Example > X-ray absorption spectrum measurement

The X-ray absorption spectra of Mn and Ni were measured for the cathode active material prepared in Example 1, and the results are shown in FIG. 5 and FIG.

5 and 6, it can be seen that the positive electrode active material prepared in Example 1 has an oxidation number of Mn of +4 and an oxidation number of Ni of +3 due to the superstructure present therein.

< Manufacturing example > Battery Manufacturing

Super P as a cathode active material and a conductive material prepared in Example 1 and Comparative Example 1, and polyvinylidene fluoride (PVdF) as a binder were mixed at a weight ratio of 85: 7.5: 7.5, respectively, to prepare a slurry.

The slurry was uniformly applied to an aluminum foil having a thickness of 20 占 퐉, and vacuum dried at 120 占 폚 to prepare a positive electrode.

Using the prepared anode and lithium foil as counter electrodes, a porous polyethylene membrane (Celgard 2300, thickness: 25 μm) was used as a separator, and ethylene carbonate and ethyl methyl carbonate were mixed at a volume ratio of 3: 7 Coin cells were prepared according to a conventionally known production process using a liquid electrolyte in which LiPF ₆ was dissolved in the solvent at a concentration of 1.2M.

< Experimental Example > Charging and discharging  Measurement of capacity and life characteristics

The charge / discharge test and the cycle characteristics of the cells using the active materials prepared in Examples 1 to 12 and Comparative Examples 1 to 8 were measured and shown in Table 1.

The charging and discharging characteristics of the battery proceeded by 10 times for each sample under the condition of 0.1 C at 2.7 to 4.5 V, and the average value was taken. The lifetime characteristic was 60 C at 0.5 C and 25 C at 25 C Respectively.

As shown in Table 1, the active material according to the present invention exhibits excellent initial charge-discharge capacity and efficiency, and excellent lifetime characteristics even in 100 cycles, as compared with the active material of the comparative example.

division 0.2 C Initial discharge capacity
( mAh / g) 100th cycle
Capacity retention rate (0.2 C)
(%) DSC  Maximum exotherm peak temperature
(° C) Example  One 210.9 88.8 233.6 Comparative Example  One 211.8 75.2 222.8

< Experimental Example > DSC Through Thermal stability  Measure

The anode including the active materials prepared in Example 1 and Comparative Example 1 was charged at 4.3 V and measured at a rate of 10 ° C / min using a differential scanning calorimeter (DSC) Are shown in Table 1 above.

Table 1 shows that the DSC maximum exothermic peak temperature of the active material prepared in the example of the present invention is significantly improved compared with the comparative example.

Claims (8)

It is a layered Rombohydral R-3m structure,
And a superstructure in which Li is substituted in the transition metal layer so that the oxidation number of Mn is +4 is present in the positive electrode active material for a lithium secondary battery.
The method according to claim 1,
And the oxidation number of Ni and Co is maintained at +3.
The method according to claim 1,
The positive electrode active material for a lithium secondary battery according to claim ₁ , wherein Li _a Ni _x Co _y Mn _z O ₂ (0.95 <a <1.05, x 0.85, 0 <y <0.075, 0.075 <z <0.15, y / z < Wherein the positive electrode active material is a positive electrode active material for a lithium secondary battery.
The method according to claim 1,
The cathode active material for a lithium secondary battery is a lithium secondary battery positive electrode active material, characterized in that represented by _{Li [Ni 0 .85 Co 0 .05} Mn 0 .10] O 2.
The method according to claim 1,
Wherein the positive electrode active material for a lithium secondary battery exhibits a peak due to the superstructure at an XRD peak in a range of 20 in a range of 20 to 25. The positive electrode active material for a lithium secondary battery according to claim 1,
The method according to claim 1,
The cathode active material for a lithium secondary battery is a lithium secondary battery positive electrode active material, it characterized in that a diffraction pattern may appear due to the Mn ^{+ 4} in rombo hydroxide barrels R-3m structure of the layer in the TEM peak.
A lithium secondary battery comprising the cathode active material for a lithium secondary battery according to any one of claims 1 to 6.
Adding a precursor including nickel, cobalt and manganese, an ammonia solution, and a basic solution to a reactor at the same time, mixing, precipitating and stirring to precipitate the metal complex hydroxide;
Filtering and washing the metal complex hydroxide, followed by drying; And
Mixing the metal complex oxide with a lithium salt and then performing heat treatment;
A method for producing a lithium secondary battery positive electrode active material,
Wherein the heat treatment is performed at a temperature of 670 to 750 占 폚 in the step of mixing the lithium salt and heat treating the lithium salt.

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