KR20030073817A - Synthesis Method of LiFePO4 Powder by Controlling Heat Treatment Atmosphere for Lithium Secondary Battery cathode - Google Patents
Synthesis Method of LiFePO4 Powder by Controlling Heat Treatment Atmosphere for Lithium Secondary Battery cathode Download PDFInfo
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- 239000000843 powder Substances 0.000 title claims abstract description 42
- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 22
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 19
- 238000010438 heat treatment Methods 0.000 title description 13
- 229910052493 LiFePO4 Inorganic materials 0.000 title 1
- 238000001308 synthesis method Methods 0.000 title 1
- 238000000034 method Methods 0.000 claims abstract description 43
- 229910010707 LiFePO 4 Inorganic materials 0.000 claims abstract description 23
- 238000004519 manufacturing process Methods 0.000 claims abstract description 23
- 238000003746 solid phase reaction Methods 0.000 claims abstract description 10
- 239000011261 inert gas Substances 0.000 claims abstract description 6
- 239000002994 raw material Substances 0.000 claims description 15
- 239000000463 material Substances 0.000 claims description 13
- 239000012071 phase Substances 0.000 claims description 12
- 238000000354 decomposition reaction Methods 0.000 claims description 8
- 239000008188 pellet Substances 0.000 claims description 8
- 239000010453 quartz Substances 0.000 claims description 6
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 6
- 239000011521 glass Substances 0.000 claims description 3
- 238000000465 moulding Methods 0.000 claims description 3
- 238000002360 preparation method Methods 0.000 claims 1
- 238000007789 sealing Methods 0.000 abstract description 18
- 238000003980 solgel method Methods 0.000 abstract description 2
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 description 12
- 239000007789 gas Substances 0.000 description 11
- 230000015572 biosynthetic process Effects 0.000 description 8
- 239000001294 propane Substances 0.000 description 6
- 238000003786 synthesis reaction Methods 0.000 description 5
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 4
- 229910012851 LiCoO 2 Inorganic materials 0.000 description 3
- 238000002441 X-ray diffraction Methods 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- 238000004320 controlled atmosphere Methods 0.000 description 3
- 239000004570 mortar (masonry) Substances 0.000 description 3
- 229910052757 nitrogen Inorganic materials 0.000 description 3
- 230000003647 oxidation Effects 0.000 description 3
- 238000007254 oxidation reaction Methods 0.000 description 3
- 229910015643 LiMn 2 O 4 Inorganic materials 0.000 description 2
- 229910013290 LiNiO 2 Inorganic materials 0.000 description 2
- 239000011812 mixed powder Substances 0.000 description 2
- 239000007774 positive electrode material Substances 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 238000007664 blowing Methods 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 238000001878 scanning electron micrograph Methods 0.000 description 1
- 238000010671 solid-state reaction Methods 0.000 description 1
- 230000002194 synthesizing effect Effects 0.000 description 1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Inorganic Chemistry (AREA)
- Materials Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
본 발명은 휴대전원으로서 각광받고 있는 리튬이차전지용 LiFePO4정극 분말의 제조방법에 관한 것으로, 정극 분말의 제조과정 중에 요구되는 환원성 분위기를 원료 물질을 소정 재질의 튜브에 밀봉시키는 수단을 이용하여 제어하는 리튬이차전지용 LiFePO4정극 분말의 제조방법을 개시한다.BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a LiFePO 4 positive electrode powder for a lithium secondary battery, which has been in the spotlight as a portable power source. A method for producing a LiFePO 4 positive electrode powder for a lithium secondary battery is disclosed.
본 발명에 의하면 기존의 고상반응법, 졸겔법 등에서 불활성 기체를 흘려주면서 환원분위기를 조절하는 방법과는 달리 밀봉을 통해 간단하게 환원성 분위기를 제어할 수 있다.According to the present invention, unlike the method of controlling the reducing atmosphere by flowing an inert gas in the conventional solid phase reaction method, sol-gel method, etc., it is possible to simply control the reducing atmosphere through sealing.
Description
본 발명은 휴대전원으로서 각광받고 있는 리튬이차전지용 LiFePO4정극 분말의 제조방법에 관한 것으로 보다 상세하게는 정극 분말의 제조과정 중에 요구되는 환원성 분위기를 원료 물질을 소정 재질의 튜브에 밀봉시키는 수단을 이용하여 제어하는 리튬이차전지용 LiFePO4정극 분말의 제조방법에 관한 것이다.The present invention relates to a method for manufacturing a LiFePO 4 positive electrode powder for lithium secondary batteries, which has been in the spotlight as a portable power source. It relates to a method for producing a LiFePO 4 positive electrode powder for a lithium secondary battery controlled by.
현재까지 정극 물질로는 LiCoO2, LiNiO2, LiMn2O4등이 주로 연구되어 왔으며 상용화에도 성공하고 있다. 하지만 현재 가장 널리 쓰이고 있는 LiCoO2의 경우 그 원료가격이 높으며 환경적인 문제를 발생시키고 있다. 또한 LiCoO2의 대체재료로서 연구되는 LiNiO2의 경우 그 제조가 어렵고 열적 안정성이 떨어지며, LiMn2O4는 고온에서 전극 퇴화가 빠르게 일어나고 전기 전도도가 낮다는 단점을 가지고 있다.Until now, LiCoO 2 , LiNiO 2 , LiMn 2 O 4, etc. have been mainly studied as positive electrode materials, and commercialization has been successful. However, LiCoO 2 , which is the most widely used at present, has a high raw material price and causes environmental problems. In addition, LiNiO 2 , which is studied as a substitute material for LiCoO 2 , is difficult to manufacture and has low thermal stability, and LiMn 2 O 4 has disadvantages of rapid electrode degradation and high electrical conductivity at high temperatures.
새로운 전지재료인 LiFePO4는 환경친화적이고 매장량도 풍부하며 원료가격도 매우 저렴하다. 또한 방전전압이 3.4V vs. Li/Li+로서 기존 재료보다 쉽게 저전력, 저전압을 구현할 수 있으며, 이론 용량이 170mAh/g으로서 전지용량 또한 우수하다. 하지만 이 물질의 문제점은 Fe의 산화수가 2+라는 것인데, 이는 Fe의 안정한 산화수가 3+임에 비추어 볼 때 환원성 분위기가 필요함을 시사하고 있다.LiFePO 4 , a new battery material, is environmentally friendly, has abundant reserves, and has a very low raw material price. In addition, the discharge voltage is 3.4V vs. As Li / Li + , it is possible to realize low power and low voltage more easily than the existing materials. The theoretical capacity is 170mAh / g, and the battery capacity is also excellent. The problem with this material, however, is that the oxidation number of Fe is 2+, suggesting that a reducing atmosphere is necessary in view of the stable oxidation number of Fe.
본 발명의 LiFePO4분말제조에 관련된 선행기술로는 고상반응법, 졸겔(Sol-Gel)법 등이 보고되고 있다. 특히 본 발명과 같은 방법인 기존의 고상반응법의 경우 환원성 분위기를 유지하기 위하여 상형성시 반응성이 없는 N2기체 등을 분당 800cm3정도로 많이 흘려주는데(Journal of the electrochemical society, 148(3) A224, 2001), 이로 인해 그 제조단가가 올라가고 리튬의 휘발 또한 유발될 수 있다. 또한 졸겔(Sol-Gel)법 역시 상형성을 N2기체를 흘려주면서 수행하기 때문에 기존의 고상반응법과 같은 문제점을 가진다(Electrochemical and Solid-State Letters, 4(10) A170, 2001).As a prior art related to the production of LiFePO 4 powder of the present invention, a solid-phase reaction method, a sol-gel (Sol-Gel) method and the like have been reported. In particular, in the conventional solid phase reaction method of the present invention, in order to maintain a reducing atmosphere, N 2 gas or the like which is not reactive during phase formation flows as much as 800 cm 3 per minute (Journal of the electrochemical society, 148 (3) A224 , 2001), which can lead to higher manufacturing costs and volatilization of lithium. In addition, the sol-gel (Sol-Gel) method also has the same problems as the conventional solid-phase reaction method because the phase formation is performed while flowing N 2 gas (Electrochemical and Solid-State Letters, 4 (10) A170, 2001).
고상반응법은 분말을 합성하는데 있어서 가장 기본적인 방법이다. 고상반응법의 경우 환원성 분위기가 필요할 때 주로 Ar, N2등 반응성이 낮은 기체를 흘려주면서 반응을 진행시키게 된다. 하지만 LiFePO4와 같이 Fe의 산화수가 반응 분위기에 매우 민감한 경우에는 기체를 흘려주면서 반응시키는 방법이 비효율적이라는 문제가 있다. 따라서 효율적인 환원성 분위기의 제어는 LiFePO4분말제조의 핵심기술이라 할 수 있다.Solid state reaction is the most basic method for synthesizing powder. In the case of the solid phase reaction method, when a reducing atmosphere is required, the reaction proceeds by flowing a gas having low reactivity such as Ar and N 2 . However, when the oxidation number of Fe is very sensitive to the reaction atmosphere, such as LiFePO 4 , there is a problem that the method of reacting while flowing gas is inefficient. Therefore, the efficient control of reducing atmosphere can be said to be the core technology for the production of LiFePO 4 powder.
본 발명의 목적은 이처럼 환원성 분위기의 제어를 위해 반응성이 낮은 기체를 흘려주면서 반응시키는 종래의 방법을 탈피하여 간단한 밀봉과정을 통해 분위기를 제어하는 방법을 제공함에 있다.An object of the present invention is to provide a method for controlling the atmosphere through a simple sealing process by avoiding the conventional method of reacting while flowing a low-reactivity gas for the control of the reducing atmosphere.
도 1은 합성된 분말의 X-선 회절결과로서, (a)는 밀봉을 한 후 분해시켰을 때의 결과이며 (b), (c), (d)는 밀봉을 한 후 각각 500, 600, 700℃에서 열처리했을 경우의 결과이다.1 is an X-ray diffraction result of the synthesized powder, where (a) is the result of decomposition after sealing and (b), (c) and (d) are 500, 600 and 700 after sealing, respectively. It is the result when heat-processing at ° C.
도 2는 합성된 분말의 미세조직을 나타내는 주사전자현미경 사진이며, (a), (b), (c)는 각각 밀봉을 한 후 500, 600, 700℃에서 열처리했을 경우의 결과이다.Figure 2 is a scanning electron micrograph showing the microstructure of the synthesized powder, (a), (b), (c) is the result when the heat treatment at 500, 600, 700 ℃ after sealing, respectively.
도 3은 500℃에서 상형성시킨 분말의 정전류 충방전 결과이다.3 is a constant current charge and discharge result of the powder phase-forming at 500 ℃.
도 4는 500, 600℃에서 상형성된 분말의 사이클에 따른 용량변화결과이다.Figure 4 is a capacity change result according to the cycle of the powder formed at 500, 600 ℃.
도 5는 원료물질의 분해는 질소 기체 분위기에서 실시하였으며 상형성은 밀봉을 통해 각각 (a) 600℃, (b) 700℃, (c) 800℃에서 시킨 최종 분말의 X-선 회절결과이다.Figure 5 is the decomposition of the raw material was carried out in a nitrogen gas atmosphere and the phase formation is the X-ray diffraction results of the final powder at (a) 600 ℃, (b) 700 ℃, (c) 800 ℃ through the sealing, respectively.
본 발명은 리튬이차전지용 LiFePO4정극 분말의 제조방법으로서,The present invention is a method for producing a LiFePO 4 positive electrode powder for a lithium secondary battery,
정극 분말의 제조과정 중에 요구되는 환원성 분위기를 원료 물질을 소정 재질의 튜브에 밀봉시키는 수단을 이용하여 제어하는 리튬이차전지용 LiFePO4정극 분말의 제조방법을 포함한다.And a method for producing a LiFePO 4 positive electrode powder for a lithium secondary battery, which controls a reducing atmosphere required during the manufacturing process of the positive electrode powder by means of sealing a raw material in a tube of a predetermined material.
본 발명에 사용가능한 튜브의 재질은 환원성 분위기가 요구되는 처리단계에 따라 적절히 선정하여 사용하는 것으로 충분하고 특별한 한정을 요하지는 아니한다. 이들 튜브재질의 예로서는 석영 또는 유리 재질 등이 있으며 이들은 열처리 온도에 따라 적의 선택하여 사용되어진다.The material of the tube usable in the present invention is sufficient to be appropriately selected and used according to the processing step in which a reducing atmosphere is required, and does not require any special limitation. Examples of these tube materials include quartz or glass materials, which are appropriately selected according to the heat treatment temperature.
정극 분말의 제조과정 중 환원성 분위기가 요구되는 단계는 정극 분말의 제조과정 중에서 예를 들면 원료물질의 분해 단계와, 최종 상형성 단계 등의 열처리 단계가 대표적이다. 이들 단계는 종래 주로 Ar, N2등 반응성이 낮은 불활성 기체를 흘려주면서 반응을 수행하던 것에 대해 본 발명에서는 밀봉과정을 통해 수행하여 효율적으로 환원성 분위기를 제어한다. 바람직하기로 상기 원료물질의 분해과정은 환원성 분위기 속에서 300℃부근의 저온에서 10시간 정도 열처리함으로써 진행시키며, 최종 상형성 과정은 환원성 분위기 속에서 바람직하기로는 500-800℃의 온도에서 10∼40시간동안 진행시키는 단계를 포함한다.Reducing atmosphere is required in the production process of the positive electrode powder is typically a heat treatment step, such as decomposition of the raw material material, the final phase forming step of the production process of the positive electrode powder. These steps are performed in the present invention through the sealing process for efficiently performing the reaction while flowing the inert gas, such as Ar, N 2 , which is conventionally low, to effectively control the reducing atmosphere. Preferably, the decomposition of the raw material is carried out by heat treatment for about 10 hours at a low temperature near 300 ℃ in a reducing atmosphere, the final phase forming process is preferably 10 to 40 at a temperature of 500-800 ℃ in a reducing atmosphere Advancing for time.
본 발명의 정극 분말의 제조방법을 구성하는 밀봉과정은, (a) 원료 물질을 펠렛형태로 성형하여 튜브에 삽입하는 단계와, (b) 튜브내의 진공을 뽑는 단계와, (c) 튜브내에 소정의 불활성 기체를 충진하고 외기와 차단하는 단계를 포함한다.The sealing process constituting the method for producing a positive electrode powder of the present invention includes the steps of (a) molding the raw material into pellets and inserting the same into a tube, (b) extracting a vacuum in the tube, and (c) Filling an inert gas and blocking the outside air.
이하 상기 단계를 포함하는 밀봉과정을 구체적인 예를 들어 설명하기로 한다. 먼저 Li, Fe, PO4등의 원료물질을 일정한 몰비로 하여 유발에서 혼합과 분쇄를 수행한다. 석영 튜브 또는 저온열처리의 경우 유리튜브의 한쪽 끝을 프로판 토치(torch) 등을 이용하여 봉한 후 분말을 가압성형하여 펠렛(pellet)으로 만든 후 이를 튜브에 넣고 밀봉되지 않은 튜브의 나머지 끝을 통해 진공을 충분히 뽑는다. 이후 환원성 분위기 조절을 위해 Ar, N2등의 기체를 주입한다. 이렇게 진공을 뽑고 불활성 기체를 채우는 과정을 2∼3회 반복하여 튜브 내의 분위기를 제어하게 된다. 제어된 분위기를 가지는 튜브는 프로판 토치를 이용하여 나머지 한쪽도 밀봉하여 외기와 완전히 차단시킨다.Hereinafter, a sealing process including the above steps will be described with specific examples. First, raw materials such as Li, Fe, and PO 4 are mixed and pulverized in a mortar by using a constant molar ratio. In the case of quartz tube or low temperature heat treatment, one end of the glass tube is sealed by using a propane torch, etc. Pull out enough. Thereafter, gases such as Ar and N 2 are injected to control the reducing atmosphere. The vacuum is removed and the process of filling the inert gas is repeated two or three times to control the atmosphere in the tube. A tube with a controlled atmosphere is also sealed off the outside by using a propane torch to completely block outside air.
상기와 같은 밀봉과정을 통해 최종 제조된 LiFePO4분말은 500℃의 낮은 온도에서 이미 단일상이 나타나서 기존 고상반응법을 이용한 분말합성의 결과보다 그 합성온도가 낮았으며, 미세조직 면에서도 입자가 작아서 분말의 도전성을 향상시킬 수 있음을 확인하였다. 따라서 본 발명에 의해 제조되는 정극 분말은 리튬이차전지용 정극재료로서 매우 유용함을 알 수 있다.The final LiFePO 4 powder prepared through the sealing process as described above has already exhibited a single phase at a low temperature of 500 ° C., and thus its synthesis temperature was lower than that of powder synthesis using a conventional solid phase reaction method. It was confirmed that the conductivity of the powder can be improved. Therefore, it can be seen that the positive electrode powder produced by the present invention is very useful as a positive electrode material for a lithium secondary battery.
이하 본 발명의 내용을 실시예에 의해 보다 상세하게 설명하기로 한다. 다만이들 실시예는 본 발명의 내용을 이해하기 위해 제시되는 것일 뿐 본 발명의 권리범위가 이들 실시예에 한정되어지는 것으로 해석되어져서는 아니된다.Hereinafter, the content of the present invention will be described in more detail with reference to Examples. However, these examples are only presented to understand the content of the present invention and should not be construed that the scope of the present invention is limited to these embodiments.
<실시예 1><Example 1>
Li, Fe, PO4의 원료로서 Li2CO3, Fe(CH3CO2), NH4H2PO4를 각각 사용하였다. 상기 재료들은 아세톤을 베이스로 하여 1:2:2 몰비율로 유발에서 혼합과 분쇄를 수행하였다. 이렇게 혼합된 분말은 일축가압성형을 통해 펠렛(pellet) 형태로 만든 후 밀봉하였다.As a raw material for Li, Fe, PO 4 was used as the Li 2 CO 3, Fe (CH 3 CO 2), NH 4 H 2 PO 4 , respectively. The materials were mixed and ground in mortar at a 1: 2: 2 molar ratio based on acetone. The mixed powder was made into pellets through uniaxial press molding and then sealed.
밀봉 과정은 다음과 같다. 석영튜브(quartz tube)의 한쪽 끝을 프로판 토치(torch)를 이용하여 밀봉한 후 성형된 펠렛을 넣고 로터리 펌프를 이용하여 10mtorr까지 진공을 충분히 뽑았다. 이후 환원성 분위기 조절을 위해 Ar 기체를 주입하였다. 이렇게 진공을 뽑고 Ar 기체를 채우는 과정을 2 내지 3회 반복하여 튜브 내의 분위기를 완벽히 제어하게 된다. 제어된 분위기를 가지는 튜브는 프로판 토치를 이용하여 나머지 한쪽도 밀봉하여 외기와 완벽히 차단시켰다.The sealing process is as follows. One end of the quartz tube (quartz tube) was sealed using a propane torch (torch), and then the molded pellet was put in, and the vacuum was sufficiently extracted to 10 mtorr using a rotary pump. Thereafter, Ar gas was injected to control the reducing atmosphere. This process of extracting the vacuum and filling the Ar gas is repeated two or three times to completely control the atmosphere in the tube. Tubes with a controlled atmosphere were also completely sealed off from outside by using a propane torch to seal the other side.
밀봉을 한 후 300℃에서 10시간 열처리함으로서 원료분말의 분해를 진행시켰다. 분해가 종료된 후 튜브를 깨고 그 속의 펠렛을 분쇄, 혼합하여 다시 펠렛으로 일축가압성형하였다. 그런 다음 환원성 분위기에서의 최종 열처리를 위해 다시 위에 기술한 바와 같은 밀봉과정을 수행하였다. 밀봉 후 최종 열처리는 500∼700℃의 온도에서 20시간동안 진행시켰다.After sealing, the raw material powder was decomposed by heat treatment at 300 ° C. for 10 hours. After the decomposition was completed, the tube was broken, pellets therein were pulverized and mixed, and uniaxially press-molded into pellets. The sealing process was then carried out again for the final heat treatment in a reducing atmosphere. The final heat treatment after sealing was carried out for 20 hours at a temperature of 500 ~ 700 ℃.
상기 과정을 통해 제조된 LiFePO4분말은 500℃의 낮은 온도에서 이미 단일상이 나타남을 X-선 회절결과로서 확인할 수 있으며(도 1), 이는 기존 고상반응법을 이용한 분말합성 결과보다 합성온도 면에서 낮음을 알 수 있다.LiFePO 4 powder prepared through the above process can be confirmed as a result of X-ray diffraction that the single phase already appears at a low temperature of 500 ℃ (Fig. 1), which is a synthesis temperature surface than the conventional synthesis results using the solid-phase reaction method It can be seen from the low.
또한 상기 과정을 거친 분말은 도 2에서 볼 수 있는 바와 같이 미세구조 면에서도 입자가 매우 작아 도전성을 향상시킬 수 있다. 정전류 충방전 결과에서도 전형적인 LiFePO4정극의 전압곡선을 얻을 수 있었으며(도 3), 충방전 사이클 특성 또한 전류밀도를 변화(전류밀도는 10 사이클까지는 0.1C로, 10 사이클 이후부터는 0.2C로 변화)시키면서 실험을 통해 측정해 보았다(도 4). 이에 의하면 전류밀도가 증가할 때 용량이 감소함을 확인할 수 있다.In addition, the powder that has undergone the above process may have very small particles in terms of microstructure, as shown in FIG. 2, to improve conductivity. The voltage curve of a typical LiFePO 4 positive electrode was also obtained from the constant current charge / discharge result (FIG. 3), and the charge / discharge cycle characteristics also changed the current density (the current density changed to 0.1C up to 10 cycles and 0.2C after 10 cycles). It was measured through experiments while (Fig. 4). This confirms that the capacity decreases as the current density increases.
<실시예 2><Example 2>
Li, Fe, PO4의 원료로서 Li2CO3, Fe(CH3CO2), NH4H2PO4를 각각 사용하였다. 상기 재료들은 아세톤을 베이스로 하여 1:2:2 몰비율로 유발에서 혼합과 분쇄를 수행하였다. 이렇게 혼합된 분말은 상기 실시예 1과는 달리 N2기체를 불어주면서 300℃에서 10시간 열처리함으로서 분해시켰다. 분해가 끝난 후 분말을 펠렛형태로 일축가압성형하였다.As a raw material for Li, Fe, PO 4 was used as the Li 2 CO 3, Fe (CH 3 CO 2), NH 4 H 2 PO 4 , respectively. The materials were mixed and ground in mortar at a 1: 2: 2 molar ratio based on acetone. The mixed powder was decomposed by heat treatment at 300 ° C. for 10 hours while blowing N 2 gas unlike in Example 1. After decomposition, the powder was uniaxially pressed into pellets.
최종 열처리를 위해 석영튜브(quartz tube)의 한쪽 끝을 프로판 토치(torch)를 이용하여 밀봉한 후 성형된 펠렛을 넣고 로터리 펌프를 이용하여 10mtorr까지 진공을 충분히 뽑았다. 이후 환원성 분위기 조절을 위해 Ar 기체를 주입하였다. 이렇게 진공을 뽑고 Ar 기체를 채우는 과정을 2 내지 3회 반복하여 튜브 내의 분위기를 완벽히 제어하게 된다. 제어된 분위기를 가지는 튜브는 프로판 토치를 이용하여 나머지 한쪽도 밀봉하여 외기와 완벽히 차단시켰다. 밀봉 후 최종 열처리는 600∼800℃의 온도에서 24시간동안 진행시켰다.For the final heat treatment, one end of the quartz tube was sealed using a propane torch, a molded pellet was put in, and a vacuum was sufficiently extracted to 10 mtorr using a rotary pump. Thereafter, Ar gas was injected to control the reducing atmosphere. This process of extracting the vacuum and filling the Ar gas is repeated two or three times to completely control the atmosphere in the tube. Tubes with a controlled atmosphere were also completely sealed off from outside by using a propane torch to seal the other side. After sealing, the final heat treatment was performed for 24 hours at a temperature of 600 ~ 800 ℃.
위와 같은 과정을 통해 제조된 분말은 600℃의 낮은 온도에서는 Fe 3+ 상이 나타났으나 700℃ 이후부터는 Fe 2+을 가지는 LiFePO4단일상을 합성할 수 있었다(도 5). 따라서 밀봉을 통한 열처리 방법이 Fe 3+을 가지는 상을 환원을 통해 Fe 2+를 가지는 상으로 만드는 데에 매우 효과적임을 알 수 있다.The powder prepared through the above process showed a Fe 3+ phase at a low temperature of 600 ℃ but after 700 ℃ it was possible to synthesize a LiFePO 4 single phase having Fe 2+ (Fig. 5). Therefore, it can be seen that the heat treatment method through sealing is very effective in making a phase having Fe 3+ into a phase having Fe 2+ through reduction.
본 발명에 의하면 기존의 고상반응법, 졸겔법 등에서 불활성 기체를 흘려주면서 환원분위기를 조절하는 방법과는 달리 밀봉을 통해 간단하게 환원성 분위기를 제어할 수 있다. 따라서 LiFePO4정극분말을 제조할 때 경제적인 면 등에서 효율적이며 리튬의 휘발도 방지할 수 있을 뿐만 아니라 저온합성을 가능하게 하여 분말특성을 향상시킬 수 있다.According to the present invention, unlike the method of controlling the reducing atmosphere by flowing an inert gas in the conventional solid phase reaction method, sol-gel method, etc., it is possible to simply control the reducing atmosphere through sealing. Therefore, when manufacturing the LiFePO 4 positive electrode powder, it is economically effective, and can prevent the volatilization of lithium, and also enable low-temperature synthesis to improve the powder properties.
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| KR100500699B1 (en) * | 2003-01-28 | 2005-07-12 | 한국과학기술원 | Synthesis Method of Cathode Powder for Lithium Secondary Battery by Microwave Heating |
| KR100718020B1 (en) * | 2004-09-17 | 2007-05-14 | 주식회사 엘지화학 | Manufacturing Method of LIFFFEP04 |
| KR100762798B1 (en) * | 2006-09-28 | 2007-10-04 | 한국전기연구원 | Carbon coated composite, preparation method thereof, positive electrode active material and lithium secondary battery having same |
| CN100398435C (en) * | 2005-12-21 | 2008-07-02 | 湖南瑞翔新材料有限公司 | Method of synthesizing iron lithium phosphate by vacuum carbon heating reduction |
| CN108011102A (en) * | 2017-10-31 | 2018-05-08 | 昆明理工大学 | A kind of method for preparing olivine-type lithium iron phosphate positive material |
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| KR100233236B1 (en) * | 1996-12-20 | 1999-12-01 | 정선종 | Vanadium Oxide Substituted with Molybdenum and Preparation Method Thereof |
| JP4949543B2 (en) * | 1999-04-06 | 2012-06-13 | ソニー株式会社 | Method for synthesizing LiFePO4 and method for producing nonaqueous electrolyte battery |
| CN1300449A (en) * | 1999-04-06 | 2001-06-20 | 索尼株式会社 | Method for manufacturing active material of positive plate and method for manufacturing nanoqueous electrolyte secondary cell |
| JP3959929B2 (en) * | 2000-04-25 | 2007-08-15 | ソニー株式会社 | Positive electrode and non-aqueous electrolyte battery |
| JP4963330B2 (en) * | 2000-06-29 | 2012-06-27 | 株式会社豊田中央研究所 | Lithium iron composite oxide for positive electrode active material of lithium secondary battery, method for producing the same, and lithium secondary battery using the same |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| KR100500699B1 (en) * | 2003-01-28 | 2005-07-12 | 한국과학기술원 | Synthesis Method of Cathode Powder for Lithium Secondary Battery by Microwave Heating |
| KR100718020B1 (en) * | 2004-09-17 | 2007-05-14 | 주식회사 엘지화학 | Manufacturing Method of LIFFFEP04 |
| CN100398435C (en) * | 2005-12-21 | 2008-07-02 | 湖南瑞翔新材料有限公司 | Method of synthesizing iron lithium phosphate by vacuum carbon heating reduction |
| KR100762798B1 (en) * | 2006-09-28 | 2007-10-04 | 한국전기연구원 | Carbon coated composite, preparation method thereof, positive electrode active material and lithium secondary battery having same |
| CN108011102A (en) * | 2017-10-31 | 2018-05-08 | 昆明理工大学 | A kind of method for preparing olivine-type lithium iron phosphate positive material |
| CN108011102B (en) * | 2017-10-31 | 2020-02-07 | 昆明理工大学 | Method for preparing olivine type lithium iron phosphate anode material |
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