JP2005519840A - Solid phase heating synthesis method of lithium cobaltate - Google Patents

Abstract

An object of the present invention is to provide a new method for synthesizing lithium cobaltate (LiCoO ₂ ) comprising one-step heat treatment.
Lithium cobaltate is synthesized by a one-step solid-phase heating reaction in which urea is added to a mixture of oxidized lithium and cobalt nitrate as a pyrogen, pulverized and mixed, and then heated at 650 to 700 ° C. in a furnace.

Description

[0001]
[Industrial application fields]
The present invention relates to a new solid phase heating method for synthesizing lithium cobaltate.
[0002]
[Prior art]
Lithium cobaltate is useful as a cathode material for lithium ion secondary batteries and a cathode material for lithium polymer secondary batteries. Lithium cobalt oxide (LiCoO ₂ ) is a positive electrode of lithium ion secondary battery or lithium polymer secondary battery from the viewpoint of high doping / undoping properties of lithium ions and less reduction in discharge capacity than LiNiO ₂ and LiMn ₂ O ₄ electrodes. It is widely used as a cathode. In the field of manufacturing technology of lithium cobaltate (LiCoO ₂ ), sol-gel method and the like using lithium nitrate, lithium hydroxide, lithium acetate or other lithium salt and cobalt nitrate, oxide, hydroxide, sulfate, etc. A method of producing by a mild chemical reaction at a temperature of 350 to 500 ° C. for a long time or by a multi-step reaction has been reported. Usually, these solid-phase heating methods for these oxidizing substances require heating for a long time during the reaction, and require a process of cooling and grinding in the middle. In the literature, other methods for producing lithium cobalt oxide such as vapor deposition by laser pulse, sputtering, and electrostatic spray deposition have been reported.
[0003]
There are the following as well-known documents concerning the synthesis of lithium cobaltate.
1. "Synthesis and electrochemical properties of LiCoO ₂ spinel cathodes"
S. Chol and A. Manthiram, Journal of the Electrochemical Society, Vol.
149 (2) (2002) A162−166
2. "X-ray absorption spectroscopic study of LiAl _y Co _1-y O ₂ cathode for lithium rechargeable batteries" Won-Sub Yoon, Kyung-Keun Lee and Kwang-Bum Kim, Journal of the Electrochemical Society, Vol. 149 (2 (2002) A146-151
3. "High temperature combustion synthesis and electrochemical characterization of LiNiO ₂ , LiCoO ₂ and LiMn ₂ O ₄ for lithium ion secondary batteries" MMRao, C. Liebenow, M. Jayalakshimi, M. Wulff, U. Guth and F. Scholz, J of Solid State Electrochemistry, Vol. 5, Issue 5 (2001) 348-354
4. "Fabrication of LiCoO ₂ thin films by solgel method and characterization as positive electrodes for Li / LiCoO ₂ cells" MN Kim, H. Chung, Y. Park, J. Kim, J. Son, K. Park and H. Kim , Journal of Power Sources, Vol. 99 (2001) 34-40
5. "Preparation and characterization of high density spherical LiNi _0.8 CoO ₂ cathode material for lithium secondary batteries" Jierong Ying, Chunrong Wan, Changyin Jiang and Yangxing Li, J. of Power Sources, Vol. 99 (2001) 78-84
6. "Electrochemical characterization of layered LiCoO ₂ films prepared by electrostatic deposition" Won-Sub Yoon, Sung-Ho Ban, Kyung-Keun Lee, Kwang-Bum Kim, Min-Dyu Kim and Jay Min Lee, J. of Power Sources, Vol. 97-98 (2001) 282-286
7. "Emulsion-derived lithium manganese oxide powder for positive electrodes in lithium ion batteries" Chung-Hsin Lu and Shang-Wei Lin, J. of Power Sources, Vol. 93 (2001) 14-19
8. "Cobalt doped chromium oxides as cathode materials for secondsry batteries for secondary lithium batteries", Dong Zhang, Branko N. Popov, Yury M. Poddrahnsky, Pankaj Arora and Ralph E. White ,. J. of Power Sources, Vol. 83 (1999) 121-127
9. "Synthesis and electrochemical studies of spinel phase LiMn ₂ O ₄ cathodematerials prepared by the pechini process". W. Liu, GC Farringon, F. Chaput and B. Dunn, Journal of the Electrochemical Society, Vol. 143, No. 3 (1996) 879-884
[0004]
The conventional methods described in the above references have several disadvantages and generally involve any or all of the following disadvantages.
[0005]
1. Side reactions occur, leading to unexpected and unwanted side products.
2. Unreacted substances remain as impurities.
3. Incomplete reaction occurs.
4). It takes several steps and a long firing time to synthesize.
5. You need to control the conditions.
6). An unnecessary phase is formed.
[0006]
Therefore, it is important to develop a method that overcomes the disadvantages listed above.
[0007]
[Problems to be solved by the invention]
The main object of the present invention is to provide a new method for synthesizing lithium cobaltate (LiCoO ₂ ), which has not been attempted in the past, and which can avoid the above-mentioned defects.
[0008]
It is another object of the present invention to eliminate the multi-step method found in the prior art and the generation of unnecessary and unexpected by-products and unnecessary phases.
[0009]
[Means for Solving the Problems]
These and other objectives of the present invention are achieved by the new process of the present invention which consists of a one-step solid state thermal reaction between an oxidation liquor and cobalt nitrate.
[0010]
Accordingly, the present invention relates to a method for producing lithium cobaltate by one step treatment of solid-phase thermal reaction, wherein the one step treatment solidifies oxide lithium (Li ₂ O) and cobalt nitrate (Co (NO ₃ ) ₂ ). Mix uniformly in phase, add heat generating material to the mixture, grind, and heat the grinded mixture to a temperature range of 650-700 ° C. to obtain the desired lithium cobaltate.
[0011]
In one embodiment of the present invention, the ratio of the oxidized lithium, cobalt nitrate mixture and heating material is 1: 3. In another embodiment of the invention, the ground mixture is heated in an oven for about 8 hours. In one embodiment of the present invention, the oxidation liquor is mixed with cobalt nitrate in the following ratios.
[0012]
LiO ₂ : Co (NO ₃ ) ₂ = 1: 2
[0013]
In another embodiment of the invention, the pyrogen is selected from urea or ammonium nitrate. In yet another embodiment of the invention, an electric furnace is used for heating. In yet another embodiment of the invention, the material used for the reaction is all solid.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a method of one-step solid-phase heat treatment for synthesizing lithium cobaltate, and the one-step heat treatment involves solid-phase oxidation of lithium (Li ₂ O) and cobalt nitrate (Co (NO ₃ ) ₂ ). And mixing the mixture uniformly, adding a heat-generating substance such as urea or ammonium nitrate to the mixture and pulverizing, and heating the pulverized mixture to a temperature range of 650 to 700 ° C. to obtain the desired lithium cobalt oxide. Become. The ratio of the LI ₂ O + Co (NO ₃ ) ₂ mixture to urea is preferably 1: 3. The ground mixture is heated in an oven for about 8 hours. Li ₂ O is mixed with Co (NO ₃ ) _{2 in} the following preferred ratio.
[0015]
LiO ₂ : Co (NO ₃ ) ₂ = 1: 2
[0016]
Heating is preferably performed in an electric furnace and all raw materials are used in solid form. The following reactions occur during the heat treatment.
[0017]
LiO ₂ + 2Co (NO ₃ ) ₂ + 3O = 2LiCoO ₂ + 4NO ₂ + 2O ₂
This reaction appeared to proceed in a single step, and the product was identified as lithium cobaltate by X-ray diffraction.
[0018]
The LiO ₂ solid material reacts with the Co (NO ₃ ) ₂ solid at moderate temperatures under controlled conditions to produce a very good spinel sample useful as an excellent doping electrode material. The required amount of purified Co (NO ₃ ) _{2 and} the required amount of purified LiO ₂ are mixed at a molar ratio of 2: 1 to form a uniform mixture with urea 3 times by weight percentage. In order to obtain a homogeneous mixture, the mixture is ground with double the amount of anhydrous distilled diethylene carbonate. This mixture is heated to 300 ° C., and further continuously heated at 700 ° C. for 5 hours to synthesize lithium cobaltate (LiCoO ₂ ). It is proved by X-ray analysis that it is lithium cobalt.
[0019]
This reaction can also be performed by changing urea to ammonium nitrate. The LiO ₂ solid material is reacted with the Co (NO ₃ ) ₂ solid at moderate temperature under controlled conditions to produce a very good spinel sample useful as an excellent doping electrode material. The required amount of purified Co (NO ₃ ) ₂ is mixed with the required amount of purified LiO _{2 in} a molar ratio of 2: 1 to form a uniform mixture with 3 times ammonium nitrate by weight percentage. In order to obtain a homogeneous mixture, the mixture is ground with double the amount of anhydrous distilled diethylene carbonate. This mixture is heated to 300 ° C., and further continuously heated at 700 ° C. for 5 hours to synthesize lithium cobaltate (LiCoO ₂ ). It is proved by X-ray analysis that it is lithium cobaltate.
[0020]
The following examples are intended to illustrate the present invention and should not be construed to limit the technical scope of the present invention.
[0021]
Example 1: Synthesis of LiCoO ₂
The LiO ₂ solid material was reacted with the Co (NO ₃ ) ₂ solid at moderate temperatures under controlled conditions to produce a sample with a very good spinel structure useful as an excellent doping electrode material. The required amount of purified Co (NO ₃ ) ₂ was mixed with the required amount of purified LiO _{2 in} a molar ratio of 2: 1 to form a homogeneous mixture with 3 times the urea by weight percentage. In order to obtain a homogeneous mixture, the mixture was ground with double the amount of anhydrous distilled diethylene carbonate. This mixture was heated at 300 ° C. for 3 hours, and further continuously heated at 700 ° C. for 5 hours to produce lithium cobaltate (LiCoO ₂ ). The lithium cobaltate was proved by X-ray analysis (FIG. 1a).
[0023]
Example 2: Synthesis of LiCoO ₂
The LiO ₂ solid material was reacted with the Co (NO ₃ ) ₂ solid at moderate temperatures under controlled conditions to produce a sample with a very good spinel structure useful as an excellent doping electrode material. The required amount of purified Co (NO ₃ ) ₂ was mixed with the required amount of purified LiO _{2 in} a molar ratio of 2: 1 to form a uniform mixture with 3 times ammonium nitrate by weight percentage. In order to obtain a homogeneous mixture, the mixture was ground with double the amount of anhydrous distilled diethylene carbonate. This mixture was heated at 300 ° C. for 3 hours, and further continuously heated at 700 ° C. for 5 hours to produce lithium cobaltate (LiCoO ₂ ). The lithium cobaltate was proved by X-ray analysis (FIG. 1b).
[0025]
Example 3
[0026]
Dry purified LiO ₂ was mixed with dry purified Co (NO ₃ ) ₂ in a 1: 2 ratio using a mortar and pestle, and then 3 times the weight of urea was mixed and placed in an electric furnace. The mixture was first heated at 300 ° C. for 3 hours, followed by heating at 700 ° C. for 5 hours.
[0027]
Ingredient Composition LiO ₂ 0.333 g
Co (NO ₃ ) ₂ O. 667 g
Urea 3.00 g
Preheating temperature 300 ℃
Final temperature 700 ° C
Time 8 hours Product particle size 10-20μm
Product properties Black yield 80% or more 【0028】
Example 4
[0029]
Dry pure ARLiO ₂ was mixed with dry pure Co (NO ₃ ) ₂ in a 1: 2 ratio using a mortar and pestle, then 3 times by weight of ammonium nitrate was mixed, and the final mixture was placed in an electric furnace. Was initially heated at 300 ° C. for 3 hours, followed by heating at 700 ° C. for 5 hours.
[0030]
Ingredient Composition LiO ₂ 0.333 g
Co (NO ₃ ) ₂ O. 667 g
Ammonium nitrate 3.00 g
Preheating temperature 300 ℃
Final temperature 700 ° C
Time 8 hours Product particle size 10-20μm
Product properties Black yield 80% or more 【0031】
Conclusion [0032]
1. Lithium oxide reacts with Co (NO ₃ ) ₂ in a molar ratio of 1: ₂ to form LiCoO ₂ .
2. Heat generating substances such as urea and ammonium nitrate can be used as self-heating substances, and there is no significant change in yield and product composition. These materials are important for the formation of spinel structures.
3. The synthesis temperature is 650-700 ° C.
4). The heating time is only about 8 hours.
[0033]
【The invention's effect】
The main effects of the present invention are as follows.
1. The synthesis method of the present invention is a single-step solid phase heat treatment.
2. LiO ₂ can be used to react with Co (NO ₃ ) ₂ to form LiCoO ₂ suitable for high capacity doping electrode materials.
3. The heating time is only 8 hours, and a considerable heating time can be omitted as compared with the conventional case.
[Brief description of the drawings]
[Figure 1]
FIG. 1 is an X-ray diffraction pattern of lithium cobaltate obtained by the method according to the present invention.

Claims (8)

In a method for synthesizing lithium cobaltate, lithium oxide (LiO ₂ ) and cobalt nitrate (Co (NO ₃ ) ₂ ) are uniformly mixed in a solid phase, and a pyrogen is added to the mixture, followed by pulverization. A production method characterized by a one-step solid-phase heating reaction comprising heating the mixture to 650 to 700 ° C. to obtain lithium cobaltate. The manufacturing method according to claim 1, wherein a mixing ratio of the lithium oxide / cobalt nitrate mixture and the pyrogen is 1: 3. The manufacturing method according to claim 1, wherein the pulverized mixture is heated in a furnace for 8 hours. 2. The method according to claim 1, wherein the mixing ratio of lithium oxide and cobalt nitrate is 1: 2. The method according to claim 1, wherein the exothermic substance is selected from urea or ammonium nitrate. The manufacturing method according to claim 1, wherein an electric furnace is used for the heating. 2. The manufacturing method according to claim 1, wherein the lithium oxide, cobalt nitrate, and the heat generating substance are all solid. The production method according to claim 1, wherein no side reaction occurs.

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