WO2014077663A1

WO2014077663A1 - Anode active material for sodium secondary battery and method for producing same

Info

Publication number: WO2014077663A1
Application number: PCT/KR2013/010521
Authority: WO
Inventors: 선양국; 오승민; 장민우
Original assignee: 한양대학교 산학협력단
Priority date: 2012-11-19
Filing date: 2013-11-19
Publication date: 2014-05-22

Abstract

The present invention relates to an anode active material for a sodium secondary battery and a method for producing same and, more specifically, to an anode active material, having a new O₃structure, for a sodium secondary battery and a method for producing same. The anode active material for a sodium secondary battery according to the present invention has an O₃structure and thus is structurally stable, unlike conventional anode active materials, and accordingly, a sodium battery comprising the anode active material for a sodium secondary battery according to the present invention exhibits excellent lifespan characteristics.

Description

Cathode active material for sodium secondary battery and manufacturing method thereof

The present invention relates to a cathode active material for a sodium secondary battery and a method for manufacturing the same, and more particularly, to a cathode active material for a sodium secondary battery having a new O ₃ structure and a method for manufacturing the same.

Currently, as a secondary battery having a high energy density, a lithium ion secondary battery using a nonaqueous electrolyte solution in which an electrolyte salt is dissolved in a nonaqueous solvent and moving lithium ions between a positive electrode and a negative electrode so that charge and discharge is performed is widely used. Lithium ion batteries using an intercalation reaction of lithium ions using lithium transition metal oxides are commercially available as positive electrode materials. However, since lithium included in the lithium ion battery is expensive, there is a need for a battery having a lower cost and a higher capacity.

Recently, research on sodium ion secondary batteries using sodium ions instead of lithium ions has begun. Since sodium has abundant resource reserves, if a secondary battery using sodium ions can be manufactured instead of lithium ions, the secondary battery can be manufactured at low cost.

Japanese Unexamined Patent Application Publication No. 2007-287661 has a positive electrode made of a composite metal oxide obtained by firing a raw material having a composition ratio of Na, Mn and Co (Na: Mn: Co) of 0.7: 0.5: 0.5 and a negative electrode made of sodium metal. Secondary batteries are described in detail. Further, Japanese Patent Laid-Open No. 2005-317511 discloses α-NaFeO ₂ having a hexagonal crystal (layered rock salt) crystal structure as a sum metal oxide, specifically, by mixing Na ₂ O ₂ and Fe ₃ O ₄ . This composite metal oxide was obtained by baking at 600-700 degreeC in air. However, the conventional sodium secondary battery cannot be said to have sufficient lifespan characteristics, that is, a discharge capacity retention rate when repeated charging and discharging.

An object of the present invention is to provide a cathode active material for a sodium secondary battery of a novel composition with improved life characteristics and a method of manufacturing the same in order to solve the problems of the prior art as described above.

The present invention to solve the above problems Na _x [Ni _y Fe _z Mn _1-yz ] O ₂ (0.8≤x≤1.2, 0.05≤y≤0.9, 0.05≤z≤0.9, 0.05≤1-yz≤ 0.9), which provides a cathode active material for a sodium secondary battery having an O ₃ crystal structure.

The cathode active material for sodium secondary battery according to the present invention is a spherical particle having a particle size of 5 to 15 μm, and the particle size distribution is monodisperse.

The cathode active material for sodium secondary battery according to the present invention is characterized in that 2θ in XRD shows three peaks in a range of 30 ° to 40 °.

The cathode active material for a sodium secondary battery according to the present invention is characterized in that the peak (104) having a main peak in the range of 2θ in the range of 40 ° to 45 ° in XRD.

The cathode active material for sodium secondary battery according to the present invention is characterized in that the tap density is 1.0 to 2.4 g / cc.

The present invention also provides

Mixing a positive electrode active material precursor for a sodium secondary battery and a sodium compound; And

It provides a method for producing a cathode active material for sodium secondary battery according to the present invention comprising a heat treatment step.

In the method for producing a cathode active material for sodium secondary battery according to the present invention, the cathode active material precursor for sodium secondary battery is characterized in that represented by any one of the following formulas (1) to (3).

[Formula 1] Ni _x Fe _y Mn _1-xy (OH) _2,

[Formula 2] Ni _x Fe _y Mn _1-xy C ₂ O _4,

[Ni _x Fe _y Mn _1-xy ] ₃ O ₄

(In the above Chemical Formulas 1 to 3 0.05≤x≤0.9, 0.1≤y≤0.9, 0.05≤1-xy≤0.9 )

The cathode active material precursor for sodium secondary battery is preferably prepared by the co-precipitation method, such as the application No. 10-2012-0130824 of the inventors filed on November 19, 2012.

That is, the cathode active material precursor for sodium secondary battery

(a) adding distilled water and a first pH adjusting agent to the coprecipitation reactor, and maintaining the pH inside the reactor at 6.5 to 7.5 while supplying air or nitrogen gas and stirring;

(b) continuously adding a second pH adjusting agent into the reactor and mixing to adjust the pH in the reactor to 6.5 to 11; And

(c) adding an aqueous solution of a transition metal compound containing an equivalent ratio of nickel salt, iron salt, and manganese salt and a complexing agent to form cathode active material precursor particles for a sodium secondary battery.

In the method of preparing a cathode active material precursor for a sodium secondary battery, the second pH adjusting agent in the step (b) is characterized in that selected from the group consisting of ammonium oxalate, NaOH and KOH.

In the method of preparing a cathode active material precursor of the present invention, when KOH or NaOH is added to the second pH adjusting agent in the step (b), the pH in the reactor is adjusted to 9 to 11, and the ammonium oxalate is used as the second pH adjusting agent. In the case of adding the pH in the reactor is characterized in that to adjust to 6.5 to 11.

In the method for preparing a cathode active material precursor for a sodium secondary battery of the present invention, the nickel salt in the step (c) is selected from the group consisting of nickel sulfate, nickel nitrate, nickel chloride, and nickel fluoride, and the iron salt is iron sulfate, It is selected from iron nitrate, iron chloride, iron fluoride, and the manganese salt is characterized in that it is selected from manganese sulfate, manganese nitrate, manganese chloride, manganese fluoride.

In the method for preparing a cathode active material precursor for a sodium secondary battery of the present invention, the complexing agent in the step (c) is an aqueous ammonia solution (NH ₄ OH), ammonium sulfate ((NH ₄ ) ₂ SO ₄ ), ammonium nitrate (NH ₄ NO ₃ ) and first ammonium phosphate ((NH ₄ ) ₂ HPO ₄ ).

In the method for preparing a cathode active material precursor for a sodium secondary battery of the present invention, the ratio of the concentration of the complexing agent and the concentration of the aqueous solution of the transition metal compound in the step (c) is 0.8 to 1.2.

In the method for producing a cathode active material for sodium secondary battery according to the present invention, the sodium compound is characterized in that one of sodium carbonate, sodium nitrate, sodium acetate, sodium hydroxide, sodium hydroxide hydrate, sodium oxide or a combination thereof.

In the method for producing a cathode active material for sodium secondary battery according to the present invention, in the step of mixing the cathode active material precursor for sodium secondary battery and the sodium compound, the sodium compound per 1 mol of the cathode active material precursor for sodium secondary battery is mixed in a ratio of 1.0 to 1.5 mol It is characterized by.

In the method for producing a cathode active material for sodium secondary battery according to the present invention, the heat treatment step is characterized in that the heat treatment at 800 ℃ to 1000 ℃.

The sodium secondary battery positive electrode active material according to the present invention is structurally stable in the O ₃ structure unlike the prior art, and thus the sodium battery including the sodium secondary battery positive electrode active material according to the present invention exhibits excellent life characteristics.

1 to 4 show SEM pictures of the precursor prepared in the embodiment of the present invention.

5 to 8 show the results of measuring the particle size distribution of the precursor prepared in the embodiment of the present invention.

Figure 9 shows the results of measuring the XRD of the precursor prepared in the embodiment of the present invention.

Figure 10 shows the results of measuring the particle size distribution of the precursor prepared in the embodiment of the present invention.

11 and 12 show SEM photographs of the precursors prepared in Examples of the present invention.

13 and 14 show the results of measuring the particle size distribution of the precursor prepared in Examples of the present invention.

15 to 22 show XRD results of the cathode active materials prepared in Examples of the present invention.

23 to 33 show the results of measuring the life characteristics or charge and discharge characteristics of the sodium secondary battery including the positive electrode active material prepared in the embodiment of the present invention.

Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited by these.

<실시예 1 내지 4><Examples 1 to 4>

The reactor was charged with 4 L of distilled water and stirred at 1000 rpm while adding ammonia to maintain the reactor internal pH at 7 and the internal temperature at 50 ° C. 4 M NaOH solution was added as a second pH adjusting agent to adjust the pH inside the reactor to 10.2 and maintained for 30 minutes.

NiSO ₄ ㆍ 6H ₂ O, FeSO ₄ ㆍ 7H ₂ O, MnSO ₄ ㆍ 5H ₂ O as an aqueous solution of a transition metal compound were mixed in an equivalent ratio, and introduced into the reactor together with NH ₄ OH as a complexing agent, A precursor was prepared.

Except for adjusting the mixing ratio of the transition metal compound aqueous solution in Example 1 as shown in Table 1 below as shown in Table 1 Ni _0.25 Fe _0.35 Mn _0.4 (OH) ₂ , Ni _0.25 Fe _0.5 Mn The precursors of Examples 2-4 were prepared, represented by _0.25 (OH) ₂ and Ni _0.15 Fe _0.35 Mn _0.5 (OH) ₂ .

Table 1

division	Precursor composition
Example 1	Ni _0.25 Fe _0.25 Mn _0.5 (OH) ₂
Example 2	Ni _0.25 Fe _0.35 Mn _0.4 (OH) ₂
Example 3	Ni _0.25 Fe _0.5 Mn _0.25 (OH) ₂
Example 4	Ni _0.15 Fe _0.35 Mn _0.5 (OH) ₂
Example 5	Ni _0.25 Fe _0.5 Mn _0.25 C ₂ O ₄
Example 6	Ni _0.2 Fe _0.6 Mn _0.2 C ₂ O ₄
Example 7	Ni _0.17 Fe _0.66 Mn _0.17 C ₂ O ₄
Example 8	Ni _0.2 Fe _0.55 Mn _0.25 C ₂ O ₄
Example 9	Ni _0.3 Fe _0.45 Mn _0.25 C ₂ O ₄
Example 10	Ni _0.35 Fe _0.4 Mn _0.25 C ₂ O ₄
Example 11	(Ni _0.25 Fe _0.5 Mn _0.25 ) ₃ O ₄
Example 12	(Ni _0.25 Fe _0.25 Mn _0.5 ) ₃ O ₄

<실험예 1> SEM 사진 측정Experimental Example 1 SEM Photographic Measurement

SEM pictures of the precursors prepared in Examples 1 to 4 were measured and shown in FIGS. 1 to 4.

<실험예 2> 입도 분포 측정Experimental Example 2 Particle Size Distribution Measurement

The particle size distribution of the precursors prepared in Examples 1 to 4 was measured and shown in FIGS. 5 to 8. 5 to 8, it can be seen that the particle size of the precursor particles is monodisperse.

Examples 5 to 10 Ni _xx Fe _yy Mn _1-x-y1-x-y C ₂₂ O ₄₄ Precursor manufacturing

In the same manner as in Example 1 except that the pH inside the reactor was adjusted to 7 using ammonia as the first pH regulator, and the pH inside the reactor was adjusted to 7 using an aqueous 0.5M ammonium oxalate solution as the second pH regulator. The precursors of Examples 5 to 10 of the composition as shown in Table 1 were prepared.

<실험예 3> XRD 측정Experimental Example 3 XRD Measurement

XRDs of the precursors prepared in Examples 5 to 7 were measured and shown in FIG. 9.

<실험예 4> 입도 분포 측정Experimental Example 4 Measurement of Particle Size Distribution

The particle size distribution of the precursors prepared in Examples 5 to 7 was measured and shown in FIG. 10.

<실시예 11, 12><Examples 11 and 12>

The internal pH of the reactor was adjusted to 7 using ammonia as the first pH regulator, and the internal pH of the reactor was adjusted to 9.2 by adding 4 M NaOH as the second pH regulator (Ni). The precursors of Example 11 and Example 12, which are represented by _0.25 Fe _0.5 Mn _0.25 ) ₃ O ₄ and (Ni _0.25 Fe _0.25 Mn _0.5 ) ₃ O ₄ , were prepared.

<실험예5> SEM 사진 측정Experimental Example 5 SEM Photographic Measurement

SEM photographs of the precursors prepared in Examples 11 and 12 were measured and shown in FIGS. 11 and 12.

<실험예6> 입도 분포 측정Experimental Example 6 Measurement of Particle Size Distribution

Particle size distributions of the precursors prepared in Examples 11 and 12 were measured and shown in FIGS. 13 and 14. It can be seen from FIG. 13 and FIG. 14 that the particle size distribution is monodisperse.

<실시예 13 내지 24> 양극활물질의 제조 <Examples 13 to 24> Preparation of a positive electrode active material

In Table 1, the precursors prepared in Examples 1 to 12 and sodium carbonate were mixed and stirred as the sodium compound, followed by heat treatment to prepare the cathode active materials of Examples 13 to 24.

<실험예> XRD 측정Experimental Example XRD Measurement

The results of measuring XRD of the cathode active materials of Examples 13 to 16 are shown in FIGS. 15 to 18, and the results of XRD measurement of the cathode active materials of Examples 17 to 19 are shown in FIG. 19. The results of measuring XRD with respect to the positive electrode active materials of 20 to 22 are shown in FIG. 20, and the results of measuring XRD with respect to the positive electrode active materials of Examples 23 and 24 are shown in FIGS. 21 and 22.

In FIGS. 15 to 22, the cathode active material for the sodium secondary battery prepared in Examples of the present invention exhibits three peaks in a range of 30 ° to 40 ° in 2RD in XRD, and O ₃ in a range of 40 ° to 45 ° in 2θ. It can be seen that the (104) main peak, which is characteristic of the crystal structure, appears.

<제조예> 전지의 제조Preparation Example Production of Battery

Composite metal oxide E1, acetylene black (manufactured by Denki Chemical Co., Ltd.) as a conductive material, and PVDF (PolyVinylidene DiFluoride Polyflon) as a binder are used as the composite metal oxide E1. : Conductive material: Binder = 85: 10: 5 (weight ratio), each weighed so as to have a composition.

Thereafter, first, the composite metal oxide and acetylene black are sufficiently mixed with an agate mortar, and N-methyl-2-pyrrolidone (NMP: manufactured by Tokyo Kasei Kogyo Co., Ltd.) is appropriately added to the mixture, followed by addition. PVDF was added to the mixture to make it uniform and slurryed. The obtained slurry was apply | coated to the thickness of 100 micrometers using an applicator on the aluminum foil of 40 micrometers thickness which is an electrical power collector, it was put into a drier, and it dried sufficiently, removing NMP, and the positive electrode sheet was obtained. After punching this positive electrode sheet to 1.5 cm in diameter with the electrode puncher, it fully crimped | bonded by the hand press and manufactured the positive electrode.

An anode prepared with aluminum foil facing downward was placed in the recess of the lower part of the coin cell (manufactured by Hosen Kabushiki Co., Ltd.), followed by 1 M NaClO ₄ / propylene carbonate + 2 vol% fluoroethylene carbonate as a nonaqueous electrolyte. A sodium secondary battery was produced by combining (FEC, Fluoro Ethylene Carbonate), a polypropylene porous membrane (thickness 20 µm) as a separator, and sodium metal as a negative electrode.

<실험예> 충방전 특성 측정Experimental Example Measurement of Charge and Discharge Characteristics

The charge and discharge characteristics of the sodium secondary battery including the active materials of Examples 13 to 19 and 23 made of the precursors of Examples 1 to 7 and 11 were measured and the results are shown in Table 2 below.

TABLE 2

division	Sintering condition and charging / discharging condition	0.2C 1 ^st	1 ^st Efficiency
Example 1 Example 13	Ni _0.25 Fe _0.25 Mn _0.5 (OH) ₂ precursor / Na 95%, sintered at 970 ° C / 24h, 4.3V	155.5 mAh / g	94.1%
Example 2 Example 14	Ni _0.25 Fe _0.35 Mn _0.4 (OH) ₂ Precursor / Na 98%, 900 ° C / 24h Sintered, 4.3V	180.1 mAh / g	101.2%
	Ni _0.25 Fe _0.35 Mn _0.4 (OH) ₂ precursor / Na 98%, sintered at 930 ° C / 24h, 4.3V	176.3 mAh / g	100.9%
	Ni _0.25 Fe _0.35 Mn _0.4 (OH) ₂ Precursor / Na 98%, 970 ° C / 24h Sintered, 4.3V	166.2 mAh / g	95.4%
Example 3 Example 15	Ni _0.25 Fe _0.5 Mn _0.25 (OH) _{2 /} Na 98%, 970 ° C / 24h Sintered, 3.9V	130.7 mAh / g	91.6%
Example 4 Example 16	Ni _0.15 Fe _0.35 Mn _0.5 (OH) ₂ precursor / Na 98%, sintered at 970 ° C / 24h, 4.3V	141.3 mAh / g	104%
Example 5 Example 17	Ni _0.25 Fe _0.5 Mn _0.25 C ₂ O ₄ Precursor / Na 98%, 950 ° C / 24h Sintered, 3.9V	135.7 mAh / g	93.4%
Example 6 Example 18	Ni _0.2 Fe _0.6 Mn _0.2 C ₂ O ₄ Precursor / Na 98%, sintered at 950 ° C / 24h, 3.8V	123.0 mAh / g	93.6%
Example 7 Example 19	Ni _0.17 Fe _0.66 Mn _0.17 C ₂ O ₄ , Precursor / Na 98%, sintered at 950 ° C / 24h, 3.7V	116.8 mAh / g	91.8%
Example 11 Example 23	(Ni _0.25 Fe _0.5 Mn _0.25 ) ₃ O ₄ precursor / Na 98%, sintered at 970 ° C / 24h, 3.9V	124.3 mAh / g	92.1%

In Table 2, in the case of a battery including a sodium battery cathode active material having a crystal structure of O ₃ prepared according to the present invention, the initial charge and discharge efficiency was found to be 90% or more.

<실험예> 수명 특성 측정Experimental Example Measurement of Life Characteristics

The charge and discharge characteristics of the sodium secondary battery including the active material of the O ₃ crystal structure of Examples 13 to 16 and Example 23 made of the precursors of Examples 1 to 4 and Example 11 are measured in Table 3 below. 27 shows the results of measuring charge and discharge characteristics of the sodium secondary battery including the active material having the O ₃ crystal structure of Examples 17 to 19 made of the precursors of Examples 5 to 7. FIG.

TABLE 3

division	0.2C 1^st	0.2C 20^th	0.2C retention	0.5C 1^st	0.5C 20^th	0.5C retention
Example 1 Example 13	155.5 mAh / g	130.2 mAh / g	83.7%	106.9 mAh / g	96.0 mAh / g	89.8%
Example 2 Example 14	180.1 mAh / g	141.3 mAh / g	78.5%	125.6 mAh / g	117.5 mAh / g	93.6%
	176.3 mAh / g	140.5 mAh / g	76.7%	125.9 mAh / g	117.8 mAh / g	93.6%
	166.2 mAh / g	124.6 mAh / g	75.0%	107.7 mAh / g	95.1 mAh / g	88.3%
Example 3 Example 15	130.7 mAh / g	122.0 mAh / g	93.3%	114.3 mAh / g	105.4 mAh / g	92.2%
Example 4 Example 16	141.3 mAh / g	119.9 mAh / g	84.9%	90.7 mAh / g	81.7 mAh / g	90.1%
Example 11 Example 23	124.3 mAh / g	114.7 mAh / g	92.3%	106.5 mAh / g	100.7 mAh / g	94.6%

In Table 2 and FIG. 27, the sodium secondary battery including the active material having the O ₃ crystal structure according to the present invention shows that the charge and discharge efficiency up to 20 cycles has a very high lifespan characteristic of about 90%.

<실험예>충방전 특성 및 수명 특성 측정Experimental Example Measurement of charge and discharge characteristics and lifetime characteristics

The charge and discharge characteristics of the sodium secondary battery including the active material prepared in Examples 13 to 16 are measured in FIGS. 23 to 26, and the charge and discharge characteristics and lifetime characteristics of the sodium secondary batteries of Examples 17 to 19 were measured. The results are shown in FIGS. 27 and 28, and the results of measuring charge and discharge characteristics and life characteristics of the sodium secondary battery including the active materials prepared in Examples 17 and 20 to 22 are shown in FIGS. 29 to 31. 32 and 33 show the results of measuring charge and discharge characteristics and lifespan characteristics of a sodium secondary battery including an active material having an O ₃ crystal structure formed at 23 and 24.

Claims

Na x [Ni y Fe z Mn 1-yz ] O 2 (0.8 ≦ x ≦ 1.2, 0.05 ≦ y ≦ 0.9, 0.05 ≦ z ≦ 0.9, 0.05 ≦ 1-yz ≦ 0.9), and is an O 3 crystal structure. Cathode active material for sodium secondary battery.
The method of claim 1,

The cathode active material for sodium secondary battery is a spherical particle having a particle size of 5 to 15 ㎛, the particle size distribution is a cathode active material for sodium secondary battery, characterized in that the monodisperse type.
The method of claim 1,

The cathode active material for sodium secondary battery is a cathode active material for sodium secondary battery, characterized in that 2θ in the XRD shows three peaks in the range of 30 ° to 40 °.
The method of claim 3, wherein

The cathode active material for sodium secondary battery is a cathode active material for sodium secondary battery, characterized in that the peak (104) peak in the range 2θ is 40 ° to 45 ° in XRD.
The method of claim 1,

The cathode active material for sodium secondary battery is a cathode active material for sodium secondary battery, characterized in that the tap density is 1.0 to 2.4 g / cc.
Mixing a positive electrode active material precursor for a sodium secondary battery and a sodium compound; And

Heat treatment step; comprising

A method for producing a cathode active material for sodium secondary battery according to claim 1.
The method of claim 6,

The cathode active material precursor for the sodium secondary battery is a method for producing a cathode active material for sodium secondary battery which is represented by any one of the following formula (1).

[Formula 1] Ni x Fe y Mn 1-xy (OH) 2,

[Formula 2] Ni x Fe y Mn 1-xy C 2 O 4,

[Ni x Fe y Mn 1-xy ] 3 O 4

(In the above Chemical Formulas 1 to 3 0.05≤x≤0.9, 0.1≤y≤0.9, 0.05≤1-xy≤0.9 )
The method of claim 6,

The sodium compound is sodium carbonate, sodium nitrate, sodium acetate, sodium hydroxide, sodium hydroxide hydrate, sodium oxide or a method for producing a positive electrode active material for sodium secondary battery, characterized in that any one of them.
The method of claim 6,

The sodium compound per one mole of the positive electrode active material precursor for the sodium secondary battery is a method for producing a positive electrode active material for sodium secondary battery, characterized in that the mixture of 1.0 to 1.5 moles.
The method of claim 6,

In the heat treatment step, the cathode active material for a sodium secondary battery, characterized in that the heat treatment at 800 ℃ to 1000 ℃.