KR100723973B1 - Core-shell cathode active materials with high safety and high capacity for lithium secondary batteries, Method of preparing thereof And the product thereby - Google Patents

Core-shell cathode active materials with high safety and high capacity for lithium secondary batteries, Method of preparing thereof And the product thereby Download PDF

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KR100723973B1
KR100723973B1 KR1020050106990A KR20050106990A KR100723973B1 KR 100723973 B1 KR100723973 B1 KR 100723973B1 KR 1020050106990 A KR1020050106990 A KR 1020050106990A KR 20050106990 A KR20050106990 A KR 20050106990A KR 100723973 B1 KR100723973 B1 KR 100723973B1
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active material
cathode active
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lithium secondary
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선양국
신호석
이기수
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한양대학교 산학협력단
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    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
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Abstract

본 발명은 코어부는 고용량의 삼성분계 양극 활물질을 쉘부는 안정성이 높은 이성분계 층상계 양극 활물질로 이루어진 코어쉘 구조를 갖는 리튬이차전지용 양극 활물질에 관한 것이다. 본 발명에 따른 코어쉘 구조를 가지는 리튬이차전지용 양극 활물질의 구성에 의하면 용량과 충전밀도가 높고 우수한 열적 안정성 효과가 있다.  The present invention relates to a cathode active material for a lithium secondary battery having a core shell structure composed of a high-capacity samsung-based positive electrode active material and a shell part of a bicomponent layered cathode active material having high stability. According to the configuration of the cathode active material for a lithium secondary battery having a core shell structure according to the present invention, the capacity and the charging density are high, and there is an excellent thermal stability effect.

코어쉘 구조, 공침법, 양극 활물질, 고용량, 열적 안정성 Core Shell Structure, Coprecipitation Method, Cathode Active Material, High Capacity, Thermal Stability

Description

열적 안정성이 우수하고 용량이 높은 코어쉘 구조를 가지는 리튬이차전지용 양극 활물질, 그 제조 방법 및 그를 사용한 리튬이차전지{Core-shell cathode active materials with high safety and high capacity for lithium secondary batteries, Method of preparing thereof And the product thereby}Core-shell cathode active materials with high safety and high capacity for lithium secondary batteries, Method of preparing Technical And the product hence}

도 1은 [Ni1/3Co1/3Mn1/3](OH)2 의 양극 활물질 전구체 분말의 FE-SEM 사진.1 is a FE-SEM photograph of the positive electrode active material precursor powder of [Ni 1/3 Co 1/3 Mn 1/3 ] (OH) 2 .

도 2는 [(Ni1/3Co1/3Mn1/3)x(Ni1/2Mn1/2)1-x)](OH)2 의 양극 활물질 전구체 분말의 FE-SEM 사진,2 is a FE-SEM photograph of the positive electrode active material precursor powder of [(Ni 1/3 Co 1/3 Mn 1/3 ) x (Ni 1/2 Mn 1/2 ) 1-x )] (OH) 2 ,

도 3은 Li[(Ni1/3Co1/3Mn1/3)x(Ni1/2Mn1/2)1-x)]O2 양극 활물질 소결체 분말의 FE-SEM 사진. 3 is a FE-SEM photograph of a powder of Li [(Ni 1/3 Co 1/3 Mn 1/3 ) x (Ni 1/2 Mn 1/2 ) 1-x )] O 2 positive electrode active material.

도 4는 (a) Li[Ni1/3Co1/3Mn1/3]O2, (b) Li[(Ni1/3Co1/3Mn1/3)x(Ni1/2Mn1/2)1-x)O2, (c) Li[Ni1/2Mn1/2]O2 양극 활물질 소결체 분말입자의 엑스선 회절패턴(XRD).4 shows (a) Li [Ni 1/3 Co 1/3 Mn 1/3 ] O 2, (b) Li [(Ni 1/3 Co 1/3 Mn 1/3 ) x (Ni 1/2 Mn 1/2 ) 1-x ) O 2, (c) X-ray diffraction pattern (XRD) of sintered powder particles of Li [Ni 1/2 Mn 1/2 ] O 2 cathode active material.

도 5는 (a) Li[Ni1/3Co1/3Mn1/3]O2, (b) Li[(Ni1/3Co1/3Mn1/3)x(Ni1/2Mn1/2)1-x)O2, (c) Li[Ni1/2Mn1/2]O2의 3.0∼4.3V 충전-방전 0.2C 조건에서 실험한 싸이클에 따른 방전용량그래프,5 shows (a) Li [Ni 1/3 Co 1/3 Mn 1/3 ] O 2, (b) Li [(Ni 1/3 Co 1/3 Mn 1/3 ) x (Ni 1/2 Mn 1/2 ) 1-x ) O 2, (c) of Li [Ni 1/2 Mn 1/2 ] O 2 Discharge capacity graph according to cycle tested under 3.0 ~ 4.3V charge-discharge 0.2C condition,

도 6은 (a) Li[Ni1/3Co1/3Mn1/3]O2, (b) Li[(Ni1/3Co1/3Mn1/3)x(Ni1/2Mn1/2)1-x)O2, (c) Li[Ni1/2Mn1/2]O2의Li[Ni1/2Mn1/2]O2의 4.3V 만충전 후 시차중량열분석에 관한 데이터그래프이다. 6 shows (a) Li [Ni 1/3 Co 1/3 Mn 1/3 ] O 2, (b) Li [(Ni 1/3 Co 1/3 Mn 1/3 ) x (Ni 1/2 Mn 1/2 ) 1-x ) O 2, (c) Differential weight train after 4.3V full charge of Li [Ni 1/2 Mn 1/2 ] O 2 of Li [Ni 1/2 Mn 1/2 ] O 2 Data graph of the analysis.

본 발명은 코어쉘 구조를 갖는 리튬이차전지용 양극 활물질 및 그 제조 방법에 관한 것으로, 보다 상세하게는 코어부는 고용량의 삼성분계 양극 활물질과 쉘부는 안정성이 높은 이성분계 층상계 양극 활물질로 구성되어 용량과 충전밀도가 높고 수명특성이 개선되며 열적 안전성이 우수한 코어쉘 구조를 갖는 양극 활물질 및 그 제조방법에 관한 것이다. The present invention relates to a cathode active material for a lithium secondary battery having a core shell structure, and a method of manufacturing the same. More specifically, the core part is composed of a high-capacity samsung-based cathode active material and a shell part composed of a highly stable two-component layered cathode active material. The present invention relates to a cathode active material having a core shell structure having high packing density, improved life characteristics, and excellent thermal safety, and a method of manufacturing the same.

리튬이온이차전지는 소형, 경량, 대용량 전지로서 1991년에 등장한 이래, 휴대기기의 전원으로서 널리 사용되었다. 최근 들어 전자, 통신, 컴퓨터산업의 급속한 발전에 따라 캠코더, 휴대폰, 노트북PC등이 출현하여 눈부신 발전을 거듭하고 있으며, 이들 휴대용 전자정보통신기기들을 구동할 동력원으로서 리튬이온이차전지에 대한 수요가 나날이 증가하고 있다. Li-ion secondary batteries have been widely used as power sources for portable devices since they emerged in 1991 as small, light and large capacity batteries. Recently, with the rapid development of electronics, telecommunications, and computer industry, camcorders, mobile phones, notebook PCs, etc. have emerged and are developing remarkably, and the demand for lithium ion secondary battery as a power source to drive these portable electronic information communication devices is increasing day by day. It is increasing.

특히 최근에는 내연기관과 리튬이차전지를 혼성화(hybrid)한 전기자동차용 동력원에 관한 연구가 미국, 일본 및 유럽 등에서 활발히 진행 중에 있다. 그러나 전기자동차용의 대형 전지로서 에너지 밀도 관점에서 리튬이온전지사용을 고려하고 있지만, 아직도 개발 시작 단계이고 특히 안전성의 관점에서 니켈 수소 전지가 사 용되고 있으며, 최대의 당면 과제는 높은 가격과 안전성이다. In particular, research on power sources for electric vehicles that hybridize an internal combustion engine and a lithium secondary battery has been actively conducted in the United States, Japan, and Europe. However, although the use of lithium ion batteries is considered as a large battery for electric vehicles in terms of energy density, nickel hydride batteries are still being used in the development stage, especially in terms of safety, and the biggest challenge is high price and safety. .

특히, 현재 상용화되어 사용되고 있는 LiCoO2나 LiNiO2와 같은 양극 활물질은 어느 것이나 충전시의 탈 리튬에 의하여 결정 구조가 불안정하여 열적 특성이 매우 열악한 단점을 가지고 있다. In particular, the positive electrode active materials such as LiCoO 2 and LiNiO 2 which are currently commercially used have a disadvantage in that the crystal structure is unstable due to de-lithography at the time of charging and thus the thermal characteristics are very poor.

즉, 과충전 상태의 전지를 200∼270 ℃에 가열하면, 급격한 구조 변화가 발생하게 되며, 그러한 구조변화로 인해 격자내의 산소가 방출되는 반응이 진행된다 (J.R.Dahn et al., Solid State Ionics ,69,265(1994))．That is, when a battery in an overcharged state is heated to 200 to 270 ° C., a drastic structural change occurs, and a reaction of releasing oxygen in the lattice proceeds due to such a structural change (JRDahn et al., Solid State Ionics, 69,265). (1994).

현재 시판되는 소형 리튬이온이차전지는 양극에 LiCoO2를, 음극에 탄소를 사용한다. LiCoO2는 안정된 충·방전특성, 우수한 전자전도성, 높은 안정성 및 평탄한 방전전압 특성을 갖는 뛰어난 물질이나, 코발트는 매장량이 적고 고가인 데다가 인체에 대한 독성이 있기 때문에 다른 양극 재료 개발이 요망된다. Commercially available small lithium ion secondary batteries use LiCoO 2 for the positive electrode and carbon for the negative electrode. LiCoO 2 is an excellent material having stable charging and discharging characteristics, excellent electronic conductivity, high stability, and flat discharge voltage characteristics. However, cobalt is low in reserve, expensive, and toxic to human body.

LiCoO2와 같은 층상 구조를 갖는 LiNiO2는 방전용량이 크지만 순수한 층상 구조를 갖는 물질을 합성하기 어렵고, 충전 후 반응성이 매우 좋은 Ni4+ 이온 때문에 록솔트(rocksalt)형 구조를 갖는 LixNi1-xO로 전이 되면서 과량의 산소를 방출하므로 수명 및 열적 불안정성 때문에 아직 상품화되지 못하고 있다. LiNiO 2 having a layered structure such as LiCoO 2 has a large discharge capacity but is difficult to synthesize a material having a pure layered structure, and Li x Ni having a rocksalt type structure because of Ni 4+ ions which are highly reactive after charging. Excess oxygen is released as it transitions to 1-x O, which has not yet been commercialized due to lifetime and thermal instability.

최근 LiCoO2 대체 재료로 가장 각광받는 층상 결정구조를 갖는 재료로 니켈-망간과 니켈-코발트-망간이 각각 1:1 혹은 1:1:1로 혼합된 Li[Ni1/2Mn1/2]O2와 Li[Ni1/3Co1/3Mn1/3]O2 등을 들 수 있다. 이 재료들은 LiCoO2에 비해 저가격, 고용량, 우수한 열적 안정성 등의 특성을 나타내나, LiCoO2에 비해 낮은 전자전도도로 인해 고율특성과 저온특성이 열악하며, 낮은 탭 밀도로 인해 용량이 높음에도 불구하고 전지의 에너지 밀도가 향상되지 않는다. 특히 이 재료들을 전자전도도가 낮아 (J. of Power Sources, 112(2002) 41-48) 전기자동차용 하이브리드(hybrid) 전원으로 사용하기에는 고출력 특성이 LiCoO2나 LiMn2O4에 비해 떨어진다. Li[Ni1/2Mn1/2]O2와 Li[Ni1/3Co1/3Mn1/3]O2 등의 일반적인 제법으로는 수용액 중에서 중화반응을 이용하여 2 혹은 3원소를 동시에 침전시켜 수산화물이나 산화물 형태의 전구체를 얻고, 이 전구체를 수산화리튬과 혼합, 소성하는 방법이다. 통상적인 공침 반응과는 달리, 망간을 포함한 공침 입자는 불규칙 판상을 나타내는 것이 보통이며, 탭 밀도가 니켈이나 코발트에 비해 반 정도에 지나지 않는다. 예를 들면, 일본 특개2002-201028에는 불활성 침전법에 의한 종래의 반응기를 사용하였으며, 이때 생성된 침전물의 입자는 입도 분포가 아주 넓고 1차 입자의 형태가 입자마다 다르다. 더욱이 최근에는 일본 특평2003-238165, 특평2003-203633, 특평2003-242976A, 특평2003-197256A, 특평2003-86182, 특평2003-68299 및 특평2003-59490과 한국특허10-2003-0026826과 10-2003-0084702에는 니켈과 망간 염을 혹은 니켈, 망간 및 코발트 염을 수용액에 용해 한 후, 알칼리 용액을 동시에 반응기에 투입하여 환원제나 불활성 가스로 퍼지 하면서 금속 수산화물이나 산화물을 얻고, 이 전구체를 수산화리튬과 혼합 후 소성하여 충방전 가역성과 열적 안정성이 향상된 고용량 양극 활물질 제조에 관한 기술이 공지되어 있다. Recently, LiCoO 2 has the most popular layered crystal structure. Li [Ni 1/2 Mn 1/2 ] in which nickel-manganese and nickel-cobalt-manganese are mixed 1: 1 or 1: 1: 1. O 2 , Li [Ni 1/3 Co 1/3 Mn 1/3 ] O 2 , and the like. The materials and exhibit characteristics such as low cost, high capacity and excellent thermal stability as compared to LiCoO 2, and due to the low electronic conductivity than LiCoO 2 poor high rate characteristics and low-temperature properties, despite the capacity high due to low tap density The energy density of the battery does not improve. In particular, these materials have low electron conductivity (J. of Power Sources, 112 (2002) 41-48), which are less powerful than LiCoO 2 or LiMn 2 O 4 for use as hybrid power sources for electric vehicles. Common methods, such as Li [Ni 1/2 Mn 1/2 ] O 2 and Li [Ni 1/3 Co 1/3 Mn 1/3 ] O 2 , are used to neutralize two or three elements simultaneously using neutralization in an aqueous solution. Precipitation is carried out to obtain a precursor in the form of a hydroxide or oxide, which is mixed with lithium hydroxide and calcined. Unlike conventional coprecipitation reactions, coprecipitation particles containing manganese usually exhibit irregular platelets, and the tap density is only about half that of nickel or cobalt. For example, Japanese Patent Laid-Open No. 2002-201028 uses a conventional reactor by an inert precipitation method, wherein the produced precipitated particles have a very large particle size distribution and the shape of primary particles varies from particle to particle. More recently, Japanese Patent Application Nos. 2003-238165, 2003-203633, 2003-242976A, 2003-197256A, 2003-86182, 2003-86182, 2003-68299 and 2003-59490, and 10-2003-0026826 and 10-2003 In -0084702, nickel and manganese salts or nickel, manganese and cobalt salts are dissolved in an aqueous solution, and then an alkali solution is simultaneously introduced into the reactor to purge with a reducing agent or an inert gas to obtain metal hydroxides and oxides, and the precursors BACKGROUND ART A technique for preparing a high capacity positive electrode active material having improved charge / discharge reversibility and thermal stability by mixing after firing is known.

Li[Ni1/2Mn1/2]O2와 Li[Ni1/3Co1/3Mn1/3]O2 등은 LiNixCo1-2xMnxO2에(0.0 ≤x≤1.0) 포함된 한 형태로 Ni이 2가, Co가 3가, Mn이 4가 산화상태를 가지기 때문에 Mn 3가에 의해 기인되는 얀-텔러 뒤틀림(Jahn-Teller distortion)으로 인해 구조전이가 발생치 않아 수명특성이 우수하다. 충전시 리튬의 탈리에 따른 산화/환원종은 Ni2+/Ni4+, Co3+/Co4+으로 알려져 있다. Mn의 산화수를 4+로 고정시키면서 이러한 전기화학 반응의 활성종인 Ni과 Co의 양을 증가시켜야 고용량 재료 합성이 가능하다. Li [Ni 1/2 Mn 1/2 ] O 2 and Li [Ni 1/3 Co 1/3 Mn 1/3 ] O 2 are used in LiNi x Co 1-2x Mn x O 2 (0.0 ≤ x ≤ 1.0 ), Ni-divalent, Co-trivalent, and Mn tetravalent oxidized states that there is no structural transition due to Jahn-Teller distortion caused by Mn trivalent. Excellent service life Oxidation / reduction species due to desorption of lithium during charging is known as Ni 2+ / Ni 4+ , Co 3+ / Co 4+ . It is necessary to increase the amount of Ni and Co, the active species of this electrochemical reaction, while fixing the oxidation number of Mn to 4+ to enable high capacity material synthesis.

이에 본 발명은 상기 종래 기술의 제반 문제점을 해결하기 위하여 안출된 것으로, 수산화염 공침법을 사용하여 코어부는 고용량의 삼성분계 양극 활물질로 전해질과 접하는 쉘부는 안정성이 높은 이성분계 층상계 양극 활물질로 구성되어 용량과 충전밀도가 높고 수명특성이 개선되며 열적 안전성이 우수한 코어쉘 구조를 갖는 양극 활물질을 제공함에 있다.Accordingly, the present invention has been made to solve the above-mentioned problems of the prior art, the core portion using a hydroxide co-precipitation method of the shell portion contacting the electrolyte with a high-capacity samsung-based cathode active material is composed of a two-component layer-based cathode active material with high stability Accordingly, the present invention provides a cathode active material having a core shell structure having high capacity, high packing density, improved life characteristics, and excellent thermal safety.

또한, 본 발명의 다른 목적은 상기 코어쉘 구조를 갖는 양극 활물질의 제조방법을 제공함에 있다. In addition, another object of the present invention to provide a method for producing a positive electrode active material having the core shell structure.

또한, 본 발명의 다른 목적은 상기 코어쉘 구조를 갖는 양극 활물질을 이용한 리튬이차전지를 제공함에 있다. In addition, another object of the present invention to provide a lithium secondary battery using the positive electrode active material having the core shell structure.

상기 목적을 달성하기 위하여 본 발명은 코어쉘 구조를 가지는 리튬이차전지용 양극 활물질에 있어서, 코어부는 조성식 Liδ[NixCo1-2xMnx]O2(1.0≤δ<1.2, 0.3<x<0.45),쉘부는 Liδ[Nix'Mn1-x']O2 (1.0≤δ<1.2, 0.49<x'<0.55)로 이루어진 것을 특징으로 하는 코어쉘 구조를 가지는 리튬이차전지용 양극 활물질을 제공한다. The present invention to achieve the above object, according to a lithium secondary battery positive electrode active material having a core-shell structure, the core portion composition formula Li δ [Ni x Co 1-2x Mn x] O 2 (1.0≤δ <1.2, 0.3 <x < 0.45), the shell portion Li δ [Ni x ' Mn 1-x' ] O 2 (1.0≤δ <1.2, 0.49 <x '<0.55) The cathode active material for a lithium secondary battery having a core shell structure, characterized in that to provide.

상기 쉘부의 두께는 전체 양극 활물질 두께의 7~80%인 것을 특징으로 한다. 상기 코어부 평균입경은 5 내지 15㎛이고, 상기 양극 활물질의 전체입자의 평균입경은 16 내지 25㎛인 것을 특징으로 한다.The thickness of the shell portion is characterized in that 7 to 80% of the total thickness of the positive electrode active material. The core particle average particle diameter is 5 to 15㎛, the average particle diameter of all the particles of the positive electrode active material is characterized in that 16 to 25㎛.

본 발명은 상기 코어쉘 구조를 가지는 리튬이차전지용 양극 활물질을 이용한 것을 특징으로 하는 리튬이차전지를 제공한다.The present invention provides a lithium secondary battery using a cathode active material for a lithium secondary battery having the core shell structure.

또한, 본 발명은 니켈, 망간, 코발트계 전이금속 수용액, 암모니아 수용액 및 염기성 수용액을 반응기에 동시에 혼합하여 구형의 침전물을 얻는 제1단계; 상기 침전물 위에 전이금속혼합계 수용액, 암모니아 수용액 및 염기성 수용액을 반응기에 동시에 혼합하여 전이금속수산화물이 덮여진 코어쉘 복합금속수산화물의 침전물을 얻는 제2단계; 상기 침전물을 건조 또는 열처리하여 코어쉘 복합금속수산화물 또는 코어쉘 복합금속산화물을 얻는 제3단계; 상기 코어쉘 복합금속수산화물 또는 코어쉘 복합금속산화물에 리튬염을 혼합하여 코어쉘 리튬복합금속산화물을 얻는 제4단계를 포함하는 것을 특징으로 하는 코어쉘 구조를 가지는 리튬이차전지용 양극 활물질의 제조방법을 제공한다. In addition, the present invention is a first step of obtaining a spherical precipitate by simultaneously mixing nickel, manganese, cobalt-based transition metal aqueous solution, aqueous ammonia solution and basic aqueous solution in the reactor; A second step of obtaining a precipitate of the core-shell composite metal hydroxide covered with the transition metal hydroxide by simultaneously mixing the transition metal mixed solution, the ammonia solution and the basic aqueous solution on the precipitate on the precipitate; Drying or heat treating the precipitate to obtain a core-shell composite metal hydroxide or a core-shell composite metal oxide; The method of manufacturing a cathode active material for a lithium secondary battery having a core shell structure comprising the fourth step of obtaining a core shell lithium composite metal oxide by mixing lithium salt with the core shell composite metal hydroxide or core shell composite metal oxide. to provide.

본 발명은 상기 제1단계에서 전구체로서 2종 이상의 금속염을 포함하는 수용액을 혼합하여 사용하고, 암모니아와 금속염의 몰 비는 0.2 내지 0.4, 반응 용액의 pH는 10.5 내지 12로 조절하여 10 내지 20 시간 반응시키는 것을 특징으로 한다.The present invention uses a mixture of an aqueous solution containing two or more metal salts as a precursor in the first step, the molar ratio of ammonia and metal salt is 0.2 to 0.4, the pH of the reaction solution is adjusted to 10.5 to 12 for 10 to 20 hours It is characterized by reacting.

상기 제2단계는 반응시간을 1 내지 10시간으로 조절하여 쉘층의 두께를 조절하는 것을 특징으로 한다.The second step is characterized by adjusting the thickness of the shell layer by adjusting the reaction time to 1 to 10 hours.

상기 제3단계는 110℃에서 15시간 건조시키거나, 400~550℃에서 5 내지 10시간 가열하는 것을 특징으로 한다.The third step may be dried at 110 ° C. for 15 hours or heated at 400 to 550 ° C. for 5 to 10 hours.

상기 제4단계는 300~550℃에서 5시간 유지시켜 예비 소성하는 단계, 700℃ 내지 1100℃에서 공기나 산소의 산화성 분위기에서 10 내지 20시간 소성하는 단계, 600~750℃에서 10시간 어닐링하는 것을 특징으로 한다.The fourth step is a step of preliminary firing by maintaining for 5 hours at 300 ~ 550 ℃, 10 to 20 hours firing in an oxidizing atmosphere of air or oxygen at 700 ℃ to 1100 ℃, annealing for 10 hours at 600 ~ 750 ℃ It features.

상기 코발트계 전이금속수용액의 반응 분위기는 질소 흐름하, pH는 10.5내지 12.5이내, 반응온도는 30 내지 80℃이며, 반응교반기 rpm은 500내지 2000이내인 것을 특징으로 한다.The reaction atmosphere of the cobalt-based transition metal solution is nitrogen flow, the pH is 10.5 to 12.5, the reaction temperature is 30 to 80 ℃, the reaction stirrer rpm is characterized in that within 500 to 2000.

이하, 본 발명에 따른 코어쉘 구조를 가지는 리튬이차전지용 양극 활물질 및 그 제조방법에 대해 상세하게 설명한다.Hereinafter, a cathode active material for a lithium secondary battery having a core shell structure according to the present invention and a method of manufacturing the same will be described in detail.

본 발명에 의한 코어쉘 구조를 가지는 리튬이차전지용 양극 활물질 제조방법은 니켈, 망간, 코발트계 전이금속 수용액, 암모니아 수용액 및 염기성 수용액을 반응기에 동시에 혼합하여 구형의 침전물을 얻는 제1단계; 상기 침전물 위에 전이 금속혼합계 수용액, 암모니아 수용액 및 염기성 수용액을 반응기에 동시에 혼합하여 전이금속수산화물이 덮여진 코어쉘 복합금속수산화물의 침전물을 얻는 제2단계; 상기 침전물을 건조 또는 열처리하여 코어쉘 복합금속수산화물 또는 코어쉘 복합금속산화물을 얻는 제3단계; 상기 코어쉘 복합금속수산화물 또는 코어쉘 복합금속산화물에 리튬염을 혼합하여 코어쉘 리튬복합금속산화물을 얻는 제4단계를 포함한다.Method for producing a cathode active material for a lithium secondary battery having a core shell structure according to the present invention comprises the first step of obtaining a spherical precipitate by simultaneously mixing nickel, manganese, cobalt-based transition metal aqueous solution, ammonia aqueous solution and basic aqueous solution in the reactor; A second step of obtaining a precipitate of a core-shell composite metal hydroxide covered with a transition metal hydroxide by simultaneously mixing a transition metal mixed solution, an ammonia solution and a basic aqueous solution on the precipitate on a reactor; Drying or heat treating the precipitate to obtain a core-shell composite metal hydroxide or a core-shell composite metal oxide; And a fourth step of obtaining a core shell lithium composite metal oxide by mixing lithium salt with the core shell composite metal hydroxide or core shell composite metal oxide.

상기 방법에 의해 제조된 리튬이차전지용 양극 활물질의 코어부는 조성식 Liδ[NixCo1-2xMnx]O2, 쉘부는 Liδ[NixMn1-x]O2로 이루어진 코어쉘 구조를 특징으로 한다. The core portion of the cathode active material for a lithium secondary battery manufactured by the above method has a core shell structure composed of a composition formula Li δ [Ni x Co 1-2x Mn x ] O 2 and a shell portion Li δ [Ni x Mn 1-x ] O 2 . It features.

상기 반응기는 회전날개가 역날개식으로 설계되고, 1∼4개의 배플(baffle)이 내벽과 2∼3cm 이격된 구조이며, 또한 이 배플들은 반응기 코어부의 상하부분의 혼합을 균일하게 하기위하여 원통을 설치하였다. 역날개식 설계도 상하 균일 혼합을 위한 것이고, 반응기의 내면에 설치된 배플(baffle)을 내벽과 이격시키는 것은 물결의 세기와 방향를 조절하며, 터블런트(turbulent) 효과를 증대시켜 반응액의 지역적 불균일성을 해결하기 위한 것이다.The reactor is designed in the reverse wing of the rotary wing, the structure of 1 to 4 baffles spaced 2 to 3cm away from the inner wall, and these baffles are used to uniformly mix the upper and lower parts of the reactor core. Installed. The reverse wing design is also designed for uniform mixing up and down, and the separation of the baffles installed on the inner surface of the reactor from the inner wall controls the intensity and direction of the waves and increases the turbulent effect to solve the local nonuniformity of the reaction solution. It is to.

본 발명의 양극 활물질 제조방법인 금속수산화법은 기존의 금속용액에 암모니아수를 먼저 섞은 후 침전시키는 암모니아 혼합법(Ammonia complex method)과는 달리 2종 이상의 금속염 수용액, 암모니아 수용액, NaOH 수용액을 각각 반응기에 투입함으로써, 망간 이온의 초기 산화를 방지하여 입자의 균일성과 금속원소들이 균일하게 분포된 침전물을 얻을 수 있다. In the method of manufacturing a cathode active material of the present invention, unlike the ammonia complex method, in which ammonia water is first mixed with a conventional metal solution and then precipitated, two or more kinds of metal salt, ammonia, and NaOH solutions are respectively added to the reactor. By introducing, it is possible to prevent the initial oxidation of manganese ions to obtain a precipitate in which the uniformity of particles and metal elements are uniformly distributed.

이하 본 발명의 층상 암염 구조와 코어쉘 구조를 가지는 리튬이차전지용 양극 활물질제조방법인 금속수산화법에 대하여 상세히 살펴보도록 한다. Hereinafter, the metal hydroxide method, which is a method of manufacturing a cathode active material for a lithium secondary battery having a layered rock salt structure and a core shell structure, will be described in detail.

먼저 Ni:Co:Mn을 a:b:1-(a+b) 로 원하는 일정 비율로 증류수에 용해한다. 이때 치환 금속염은 2종 이상으로 선택되도록 하는 것이 바람직하다. 상기 전이금속혼합계 수용액과 암모니아 수용액 및 염기성 수용액을 반응기에 넣어 혼합한다. First, Ni: Co: Mn is dissolved in distilled water in a desired ratio as a: b: 1- (a + b). At this time, it is preferable that the substituted metal salt is selected from two or more kinds. The transition metal mixed aqueous solution, ammonia aqueous solution and basic aqueous solution are mixed in a reactor.

이때, 상기 전이금속혼합계 수용액은 1M 내지 3M 농도의 것을 사용하고, 암모니아 수용액은 금속 수용액 농도의 20% 내지 40%의 농도, NaOH 수용액은 4M 내지 5M 농도의 것을 사용하는 것이 바람직하다. At this time, it is preferable that the transition metal mixed aqueous solution is used in the concentration of 1M to 3M, the aqueous ammonia solution is used in the concentration of 20% to 40% of the metal aqueous solution concentration, the NaOH aqueous solution is used in the concentration of 4M to 5M.

암모니아 수용액의 농도를 금속 수용액 농도의 20% 내지 40%로 하는 것은 암모니아는 금속 전구체와 1 대 1로 반응하지만, 중간 생성물이 다시 암모니아로 회수되어 사용될 수 있기 때문이며, 나아가 이것이 양극 활물질 결정성을 높이고 안정화하기 위한 최적의 조건이기 때문이다. The concentration of the aqueous ammonia solution is 20% to 40% of the aqueous metal solution concentration because the ammonia reacts with the metal precursor one-to-one, but the intermediate product can be recovered and used as ammonia again. This is because it is an optimal condition for stabilization.

또한, 상기 혼합용액의 pH는 10.5 내지 12로 유지되도록 상기 NaOH 수용액을 주입하며, 상기 반응기 내에서의 반응시간은 10∼20시간으로 조절하는 것이 바람직하다. In addition, the NaOH aqueous solution is injected so that the pH of the mixed solution is maintained at 10.5 to 12, and the reaction time in the reactor is preferably adjusted to 10 to 20 hours.

상기 1단계를 보다 구체적으로 설명하면, 먼저 니켈, 망간, 코발트 금속염들을 증류수에 용해한 후, 암모니아 수용액, NaOH 수용액과 함께 각각 반응기에 투입하여 침전이 일어나도록 한다. 공침법은 수용액 중에서 중화반응을 이용하여 2원소 이상을 동시에 침전시켜 복합수산화물을 얻는 방법이다. To describe the first step in more detail, first, nickel, manganese, cobalt metal salts are dissolved in distilled water, and then introduced into the reactor with an aqueous ammonia solution and an aqueous NaOH solution to precipitate. The coprecipitation method is a method of obtaining a composite hydroxide by simultaneously depositing two or more elements by using a neutralization reaction in an aqueous solution.

여기에서 상기 혼합용액이 상기 반응기 내에 체류하는 평균시간은 6시간으로 조절하고, pH는 10.5 내지 11.5로, 반응온도는 30내지 80℃이며, 반응교반기 rpm은 500내지 2000이내로 유지한다. 이렇게 반응기의 온도를 높이는 이유는 생성된 코발트 수산화물이 낮은 온도에서는 착염 형태로 침전되기 때문에 고밀도 복합수산화물을 얻기 어렵기 때문이다. Here, the average time the mixed solution stays in the reactor is adjusted to 6 hours, the pH is 10.5 to 11.5, the reaction temperature is 30 to 80 ℃, the reaction stirrer rpm is maintained within 500 to 2000. The reason for raising the temperature of the reactor is that it is difficult to obtain a high-density complex hydroxide because the cobalt hydroxide produced is precipitated in complex salt form at a low temperature.

다음으로 코어부를 형성하는 전구체 수산화물을 얻은 후에는 쉘부를 조성하는 금속염을 같은 반응조건에서 1∼10시간 동안 반응시켜 코어쉘 구조의 복합수산화물을 얻는다. 쉘부의 두께는 반응기 내에서의 쉘부 전구체의 합성 시간으로 조절한다. Next, after obtaining the precursor hydroxide forming the core portion, the metal salt forming the shell portion is reacted under the same reaction conditions for 1 to 10 hours to obtain a composite hydroxide having a core shell structure. The thickness of the shell portion is controlled by the synthesis time of the shell portion precursor in the reactor.

공침법으로 제조된 삼성분계 양극 활물질에 의해 형성된 1차입자의 평균입경은 5 내지 15㎛이고, 상기 1차 입자 표면을 덮어싼 이성분계 양극 활물질에 의해 형성된 2차입자의 평균입경은 16 내지 25㎛인 것이 바람직하다. The average particle diameter of the primary particles formed by the co-precipitation-based positive electrode active material is 5 to 15 μm, and the average particle diameter of the secondary particles formed by the bicomponent positive electrode active material covering the surface of the primary particles is 16 to 25 μm. It is preferable.

왜냐하면, 1차입자의 평균입경을 5∼15㎛로 하는 것에 의해 충방전의 반응성을 높이고 전지의 고율특성을 향상시키는 한편, 2차입자의 평균입경을 16∼25㎛로 하는 것에 의해 코어쉘 구조를 가지는 리튬이차전지용 양극 활물질의 충전성을 높이고 코팅력을 향상시켜 전극을 고용량화 할 수 있기 때문이다. This is because the average particle diameter of the primary particles is 5 to 15 µm, thereby improving the reactivity of charging and discharging and improving the high rate characteristics of the battery, while having the core shell structure by setting the average particle diameter of the secondary particles to 16 to 25 µm. This is because the electrode can be increased in capacity by increasing the filling property of the cathode active material for a lithium secondary battery and improving the coating power.

또한 코어쉘 구조에서 코어부 Liδ[NixCo1-2xMnx]O2(1.0≤δ<1.2, 0.3<x<0.45)의 특성을 살리기 위해 쉘부에 입혀지는 Liδ[Nix'Mn1-x']O2(1.0≤δ<1.2, 0.49<x'<0.55)의 두께는 전체 이중층 양극 활물질 두께의 7%이상 80%이하가 되도록 하는 것이 바람직하다. 더욱 특성을 살리기 위해서는 30% 이하 더욱 바람직하게는 20%이하로 하는 것이 바람직하다. Also the core portion in the core-shell structure Li δ [Ni x Co 1-2x Mn x] O 2 (1.0≤δ <1.2, 0.3 <x <0.45) Li δ [Ni x 'Mn which is coated with the shell part in order to save the characteristics of the The thickness of 1-x ' ] O 2 (1.0≤δ <1.2, 0.49 <x'<0.55) is preferably 7% or more and 80% or less of the thickness of the entire double layer positive electrode active material. In order to further utilize the properties, it is preferable to make it 30% or less, more preferably 20% or less.

하지만 쉘부에 입혀지는 Liδ[Nix'Mn1-x']O2의 두께가 7% 미만이면 쉘부 조성의 특성이 떨어진다. However, if the thickness of Li δ [Ni x ' Mn 1-x' ] O 2 applied to the shell portion is less than 7%, the characteristics of the shell portion composition are inferior.

또한, 코어부 조성식 Liδ[NixCo1-2xMnx]O2에서 Ni, Co 및 Mn의 산화수는 +2, +3, +4가이나 쉘부에 입혀지는 양극 활물질 Liδ[Nix'Mn1-x']O2 에서 Ni의 산화수는 +2가, Mn의 산화수는 +4가인 것이 바람직하다. In addition, in the core composition formula Li δ [Ni x Co 1-2x Mn x ] O 2 , the oxidation number of Ni, Co, and Mn is +2, +3, +4, but the positive electrode active material Li δ [Ni x ' is applied to the shell portion. In Mn 1-x ' ] O 2 , the oxidation number of Ni is +2, and the oxidation number of Mn is +4.

특히, Mn의 산화수가 +4가인 것은 기존 사방정계나 층상구조 LiMnO2에서 Mn의 +3가, +4가 산화/환원반응에 의해 야기된 구조전이(얀-텔러 효과)를 방지 할 수 있어 충방전시 구조 안정화를 꾀하여 수명특성을 향상 시킬 수 있다. In particular, the +4 valence of Mn can prevent the structural transition (yan-teller effect) caused by the oxidation / reduction reaction of +3 of Mn and +4 in existing tetragonal or layered LiMnO 2 . Structural stabilization during discharging can improve lifespan.

다음으로 얻어진 코어쉘 복합금속수산화물을 증류수로 세척한 후에 여과하여 110℃에서 15시간 건조하거나 400~550℃에서 5 내지 10시간 열처리하여 전구체로 사용한다. Next, the obtained core-shell composite metal hydroxide is washed with distilled water, filtered and dried at 110 ° C. for 15 hours or heat-treated at 400 to 550 ° C. for 5 to 10 hours to be used as a precursor.

다음으로 상기 코어쉘 복합금속수산화물 또는 복합금속산화물과 리튬염을 충분히 혼합하는 건식방법이나, 상기 이중층 복합금속수산화물 또는 복합금속산화물과 리튬염을 구연산, 주석산, 글리콜산, 말레인산 등과 같은 킬레이팅제가 혼합된 수용액에 혼합하는 습식방법을 사용하여 증류수를 제거한다. Next, a dry method of sufficiently mixing the core shell composite metal hydroxide or composite metal oxide and lithium salt, or a chelating agent such as citric acid, tartaric acid, glycolic acid, maleic acid, etc. is mixed with the double layer composite metal hydroxide or composite metal oxide and lithium salt. Distilled water is removed using a wet method of mixing in the aqueous solution.

마지막으로 300~550℃에서 5시간 유지시켜 예비 소성하는 단계, 700℃ 내지 1100℃에서 공기나 산소의 산화성 분위기에서 10 내지 20시간 소성하는 단계, 600~750℃에서 10시간 어닐링단계를 거쳐 코어쉘 구조를 가지는 리튬이차전지용 양극 활물질을 제조한다. Finally, pre-firing by maintaining at 300 ~ 550 ℃ for 5 hours, firing for 10 to 20 hours in the oxidizing atmosphere of air or oxygen at 700 ℃ to 1100 ℃, annealing step at 600 ~ 750 ℃ for 10 hours A cathode active material for a lithium secondary battery having a structure is prepared.

상기 방법으로 제조된 코어쉘 구조를 가지는 리튬이차전지용 양극 활물질의 비표적은 3㎡/g 이하인 것이 바람직하다. 왜냐하면 비표적이 3㎡/g 이상이면 전해액과의 반응성이 증가되어 가스발생이 증대되기 때문이다. It is preferable that the specific target of the positive electrode active material for lithium secondary batteries which has the core-shell structure manufactured by the said method is 3 m <2> / g or less. This is because when the specific target is 3 m 2 / g or more, the reactivity with the electrolyte is increased and gas generation is increased.

본 발명은 상기 코어쉘 구조를 가지는 리튬이차전지용 양극 활물질을 이용한 것을 특징으로 하는 리튬이차전지를 제공한다.The present invention provides a lithium secondary battery using a cathode active material for a lithium secondary battery having the core shell structure.

상기 반응기는 회전날개가 역날개식으로 설계되고, 1∼4개의 배플(baffle)이 내벽과 2∼3cm 이격된 구조이며, 또한 이 배플들은 반응기 코어부의 상하부분의 혼합을 균일하게 하기 위하여 원통을 설치하였다. 역날개식 설계도 상하 균일 혼합을 위한 것이고, 반응기의 내면에 설치된 배플(baffle)을 내벽과 이격시키는 것은 물결의 세기와 방향를 조절하며, 터블런트(turbulent) 효과를 증대시켜 반응액의 지역적 불균일성을 해결하기 위한 것이다. 따라서 상기 반응기를 이용한 경우, 기존의 반응기를 사용한 경우 보다 얻어진 수산화물의 탭 밀도는 약 10% 이상 향상된다. 수산화물의 탭 밀도는 1.95g/㎤, 바람직하게는 2.1g/㎤이상, 보다 바람직하게는 2.4g/㎤이다.The reactor has a rotor blade designed in reverse wing type, 1 to 4 baffles are separated from the inner wall by 2 to 3 cm, and these baffles are formed in a cylinder to uniformly mix the upper and lower parts of the reactor core. Installed. The reverse wing design is also designed for uniform mixing up and down, and the separation of the baffles installed on the inner surface of the reactor from the inner wall controls the intensity and direction of the waves and increases the turbulent effect to solve the local nonuniformity of the reaction solution. It is to. Therefore, when using the reactor, the tap density of the obtained hydroxide than the conventional reactor is improved by about 10% or more. The tap density of the hydroxide is 1.95 g / cm 3, preferably 2.1 g / cm 3 or more, and more preferably 2.4 g / cm 3.

이하, 본 발명의 실시예를 첨부된 도1내지 도4에 의거하여 상세히 설명하지만, 이들 실시예로 본 발명이 한정되는 것은 아니다. Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 1 to 4, but the present invention is not limited to these embodiments.

[실시예 1]Example 1

공침 반응기(용량 4L, 회전모터의 출력 80W이상)에 증류수 4리터를 넣은 뒤 질소가스를 반응기에 0.5리터/분의 속도로 버블링하여 공급함으로써, 용존산소를 제거하였다. 반응기의 온도를 50℃로 유지시키면서 1000rpm으로 교반하였다. 4 liters of distilled water was put into the coprecipitation reactor (capacity 4L, the output of the rotary motor more than 80W), and nitrogen gas was bubbled into the reactor at a rate of 0.5 liters / minute to remove dissolved oxygen. Stirring at 1000 rpm while maintaining the temperature of the reactor at 50 ℃.

황산니켈, 황산망간 및 황산코발트 몰비가 1 : 1 : 1 비율로 혼합된 2.4M 농도의 금속 수용액을 0.3리터/시간으로, 4.8M 농도의 암모니아 용액을 0.03리터/시간으로 반응기에 연속적으로 투입하였다. 또한 pH 조정을 위해 4.8M 농도의 수산화나트륨 용액을 공급하여 pH가 11로 유지되도록 하였다. A nickel aqueous solution of 2.4 M concentration mixed with nickel sulfate, manganese sulfate, and cobalt sulfate in a ratio of 1: 1 is continuously added to the reactor at 0.3 liters per hour and 4.8 M of ammonia solution at 0.03 liters per hour in the reactor. . In addition, a pH of 4.8 M sodium hydroxide solution was supplied to adjust the pH to maintain a pH of 11.

임펠러 속도는 1000rpm으로 조절하였다. 유량을 조절하여 용액의 반응기 내의 평균체류시간은 6시간 정도가 되도록 하였으며, 반응이 정상상태에 도달 한 후에 상기 반응물에 대해 정상상태 지속시간을 주어 좀더 밀도 높은 복합금속수산화물을 얻도록 하였다. Impeller speed was adjusted to 1000 rpm. By adjusting the flow rate, the average residence time of the solution in the reactor was about 6 hours, and after the reaction reached a steady state, a steady state duration was given to the reactant to obtain a more dense composite metal hydroxide.

정상상태에 도달한 상기 복합금속수산화물에 1 : 1 : 1의 몰비로 공급되던 황산니켈, 황산망간 및 황산코발트 금속 수용액을 황산니켈, 황산망간의 몰비 1 : 1 로 교체한 뒤 1~6시간 상기와 같은 조건으로 반응 시켰다. Nickel sulfate, manganese sulfate, and cobalt sulfate aqueous solutions supplied to the composite metal hydroxide in a molar ratio of 1: 1: 1 were replaced with a molar ratio 1: 1 of nickel sulfate, manganese sulfate, and then 1 to 6 hours. The reaction was carried out under the same conditions.

다음으로 오버플로파이프(overflow pipe)를 통하여 구형의 니켈망간코발트 복합수산화물을 연속적으로 얻었다. 상기 복합금속수산화물을 여과하고, 물 세척한 후에 110℃ 온풍건조기에서 15시간 건조시켜 금속복합산화물 형태의 전구체를 얻었다.Next, a spherical nickel manganese cobalt composite hydroxide was continuously obtained through an overflow pipe. The composite metal hydroxide was filtered, washed with water, and then dried in a 110 ° C. hot air dryer for 15 hours to obtain a precursor of a metal composite oxide form.

상기 전구체와 수산화리튬(LiOH)을 1 : 1.05 몰비로 혼합한 후에 2℃/min의 승온 속도로 가열한 후 500℃에서 5시간 유지시켜 예비 소성을 수행하였으며, 뒤이어 900℃에서 15시간 소성시켜 코어부는 Li[Ni1/3Co1/3Mn1/3]O2로 쉘부는 Li[Ni1/2Mn1/2]O2 로 구성된 코어쉘을 형성하는 양극 활물질 분말을 얻었다. After mixing the precursor and lithium hydroxide (LiOH) in a 1: 1.05 molar ratio, and heated at a temperature increase rate of 2 ℃ / min and maintained at 500 ℃ for 5 hours, followed by preliminary firing at 900 ℃ 15 hours followed by firing core The part obtained Li [Ni 1/3 Co 1/3 Mn 1/3 ] O 2 and the shell part obtained a positive electrode active material powder forming a core shell composed of Li [Ni 1/2 Mn 1/2 ] O 2 .

상기의 방법으로 제조된 코어쉘 구조를 가지는 리튬이차전지용 양극 활물질과 도전재로 아세틸렌블랙, 결합제로는 폴리비닐리덴 플루오라이드(PVdF)를 80:10:10의 중량비로 혼합하여 슬러리를 제조하였다. 상기 슬러리를 20㎛ 두께의 알루미늄박에 균일하게 도포하고, 120℃에서 진공 건조하여 리튬이차전지용 양극을 제조하였다.A slurry was prepared by mixing a positive electrode active material for a lithium secondary battery having a core shell structure prepared by the above method, acetylene black as a conductive material, and polyvinylidene fluoride (PVdF) as a binder in a weight ratio of 80:10:10. The slurry was uniformly applied to an aluminum foil having a thickness of 20 μm, and vacuum dried at 120 ° C. to prepare a cathode for a lithium secondary battery.

상기 양극과 리튬 호일을 상대 전극으로 하며, 다공성 폴리에틸렌막(셀가르드 엘엘씨 제, Celgard 2300, 두께: 25㎛)을 세퍼레이터로 하고, 에틸렌 카보네이트와 디에틸 카보네이트가 부피비로 1:1로 혼합된 용매에 LiPF6가 1M 농도로 녹아 있는 액체 전해액을 사용하여 통상적으로 알려져 있는 제조공정에 따라 코인 전지를 제조하였다. 제조된 코인 전지를 전기화학 분석장치(Toyo System, Toscat 3100U)를 사용하여 3.0~4.3 볼트 영역에서 양극 활물질 특성을 평가하였다.A solvent in which the positive electrode and the lithium foil are used as counter electrodes, a porous polyethylene membrane (Celgard ELC, Celgard 2300, thickness: 25 μm) is used as a separator, and ethylene carbonate and diethyl carbonate are mixed at a volume ratio of 1: 1. A coin battery was prepared according to a commonly known manufacturing process using a liquid electrolyte in which LiPF 6 was dissolved at a concentration of 1 M. The manufactured coin battery was evaluated for the positive electrode active material in the 3.0 ~ 4.3 volt region using an electrochemical analyzer (Toyo System, Toscat 3100U).

[비교예 1]Comparative Example 1

양극 활물질 제조시 쉘부층을 가지지 않는 Li[Ni1/3Co1/3Mn1/3]O2을 제조한 것을 제외하고는 실시예1과 동일한 방법으로 분말을 합성하고 코인형의 반쪽전지를 제조하였다. Powder was synthesized in the same manner as in Example 1 except that Li [Ni 1/3 Co 1/3 Mn 1/3 ] O 2 having no shell layer was prepared in the preparation of the positive electrode active material, and a coin-type half cell was prepared. Prepared.

[비교예 2]Comparative Example 2

양극 활물질 제조시 쉘부층을 가지지 않는 Li[Ni1/2Mn1/2]O2 조성을 제조한 것을 제외하고는 실시예1과 동일한 방법으로 분말을 합성하고 코인형의 반쪽전지를 제조하였다.When manufacturing a positive electrode active material does not have a shell layer Powders were synthesized in the same manner as in Example 1 except that a Li [Ni 1/2 Mn 1/2 ] O 2 composition was prepared, and a coin-type half cell was prepared.

도1은 (Ni1/3Co1/3Mn1/3)(OH)2를 110℃ 온풍건조기에서 15시간 건조시킨 복합산화물 분말, 도2는 (Ni1/3Co1/3Mn1/3)(OH)2에 (Ni1/2Mn1/2)(OH)2를 3시간 반응시킨 [(Ni1/3Co1/3Mn1/3)x(Ni1/2Mn1/2)1-x](OH)2 복합산화물 분말, 도3은 (Ni1/3Co1/3Mn1/3)(OH)2에 (Ni1/2Mn1/2)(OH)2를 3시간 반응시킨 후 리튬염으로 소성한 Li[(Ni1/3Co1/3Mn1/3)x(Ni1/2Mn1/2)1-x]O2 소결체 분말의 표면을 깍아내어 그 절단면을 관찰한 FE-SEM 사진이다. 코어쉘 구조의 [(Ni1/3Co1/3Mn1/3)x(Ni1/2Mn1/2)1-x](OH)2 전구체와 Li[(Ni1/3Co1/3Mn1/3)x(Ni1/2Mn1/2)1-x]O2 소결체 분말의 FE-SEM을 보면 (Ni1/3Co1/3Mn1/3)(OH)2 전구체와 동일한 입자형상을 가지나 표면에 코어부와 다른 쉘부의 층이 생긴 것을 확인 할 수 있다. 특히 Li[(Ni1/3Co1/3Mn1/3)x(Ni1/2Mn1/2)1-x]O2 소결체 분말의 경우는 코어부와는 다른 형태로 쉘부에 1㎛ 두께로 일정하게 쌓여있다. 따라서 코어부와 쉘부에 합성된 것이 각각 다른 조성이라는 것을 알 수 있다.1 is a composite oxide powder obtained by drying (Ni 1/3 Co 1/3 Mn 1/3 ) (OH) 2 in a 110 ° C. hot air dryer for 15 hours, and FIG. 2 (Ni 1/3 Co 1/3 Mn 1 / 3) (OH) to 2 (Ni 1/2 Mn 1/2) ( OH) 2 in which the reaction for 3 hours [(Ni 1/3 Co 1/3 Mn 1/3 ) x (Ni 1/2 Mn 1 / 2 ) 1-x ] (OH) 2 composite oxide powder, FIG. 3 shows (Ni 1/3 Co 1/3 Mn 1/3 ) (OH) 2 to (Ni 1/2 Mn 1/2 ) (OH) 2 After reacting for 3 hours, the surface of the Li [(Ni 1/3 Co 1/3 Mn 1/3 ) x (Ni 1/2 Mn 1/2 ) 1-x ] O 2 sintered powder calcined with lithium salt It is FE-SEM photograph which cut out and observed the cut surface. [(Ni 1/3 Co 1/3 Mn 1/3 ) x (Ni 1/2 Mn 1/2 ) 1-x ] (OH) 2 precursor with core shell structure and Li [(Ni 1/3 Co 1 / The FE-SEM of 3 Mn 1/3 ) x (Ni 1/2 Mn 1/2 ) 1-x ] O 2 sintered powder shows (Ni 1/3 Co 1/3 Mn 1/3 ) (OH) 2 precursor It has the same particle shape as, but it can be seen that a layer of the shell part and the core part is formed on the surface. Particularly, in the case of Li [(Ni 1/3 Co 1/3 Mn 1/3 ) x (Ni 1/2 Mn 1/2 ) 1-x ] O 2 sintered powder, it is different from the core part. Constantly stacked in thickness. Therefore, it can be seen that the composites of the core portion and the shell portion have different compositions.

도 4는 Li[Ni1/3Co1/3Mn1/3]O2 소결체 분말, Li[(Ni1/3Co1/3Mn1/3)x(Ni1/2Mn1/2)1-x]O2 소결체 분말, Li[Ni1/2Mn1/2]O2 소결체 분말의 엑스선 회절패턴(XRD)을 나타내었다. 모든 분말들의 회절피크에서 (006)과 (102) 피크 분리, (018)과 (110) 피크 분리가 잘 나타나 있고, (003)과 (104) 피크비가 1이상 인 것으로부터 상기 리튬복합산화물은 공간군 R-3m을 가지는 헥사고날(hexagonal)-NaFeO2 구조를 가지며, 특히 Li[(Ni1/3Co1/3Mn1/3)x(Ni1/2Mn1/2)1-x]O2와 같이 코어쉘 형성 된 후에도 결정성이 우수한 층상 화합물임을 알 수 있다. 또한 표면에 Li[Ni1/2Mn1/2]O2 소결체가 존재하는 코어쉘 구조의 Li[(Ni1/3Co1/3Mn1/3)x(Ni1/2Mn1/2)1-x]O2는 (006)과 (102) 피크와 (018)과 (110) 피크에서 Li[Ni1/2Mn1/2]O2와 Li[Ni1/3Co1/3Mn1/3]O2이 혼합되어 있는 형태로 피크가 나타나 있는 것을 알 수 있다.4 is a Li [Ni 1/3 Co 1/3 Mn 1/3 ] O 2 sintered powder, Li [(Ni 1/3 Co 1/3 Mn 1/3 ) x (Ni 1/2 Mn 1/2 ) The X-ray diffraction pattern (XRD) of the 1-x ] O 2 sintered powder and Li [Ni 1/2 Mn 1/2 ] O 2 sintered powder was shown. In the diffraction peaks of all the powders, the (006) and (102) peak separations, the (018) and (110) peak separations are well represented, and the lithium composite oxide has a space ratio of 1 or more. Hexagonal-NaFeO 2 structure with group R-3m, in particular Li [(Ni 1/3 Co 1/3 Mn 1/3 ) x (Ni 1/2 Mn 1/2 ) 1-x ] It can be seen that it is a layered compound having excellent crystallinity even after core shell formation such as O 2 . In addition, Li [(Ni 1/3 Co 1/3 Mn 1/3 ) x (Ni 1/2 Mn 1/2 ) of core-shell structure with Li [Ni 1/2 Mn 1/2 ] O 2 sintered body on the surface ) 1-x ] O 2 with Li [Ni 1/2 Mn 1/2 ] O 2 and at (006) and (102) peaks and (018) and (110) peaks. It can be seen that the peak appears in a form in which Li [Ni 1/3 Co 1/3 Mn 1/3 ] O 2 is mixed.

도 5에 실시예1, 비교예1, 비교예2의 방법으로 합성한 각각의 물질을 3.0∼4.3 V 범위에서 인가 전류 0.4㎃로 실험한 싸이클에 따른 방전용량을 나타내었다. Li[Ni1/3Co1/3Mn1/3]O2은 168mAh/g의 초기용량으로 싸이클이 진행되면서 50 싸이클시 157mAh/g으로 7%의 용량감소를 보이고, Li[Ni1/2Mn1/2]O2 전극은 18mAh/g의 용량이 감소한 150mAh/g의 용량을 보이고 50 싸이클시 146mAh/g으로 3%의 용량감소를 보인다. 반면 코어쉘 구조인 Li[(Ni1/3Co1/3Mn1/3)x(Ni1/2Mn1/2)1-x]O2은 계획대로 초기용량은 Li[Ni1/3Co1/3Mn1/3]O2과 비슷한 164mAh/g의 고용량을 나타내면서 50 싸이클시 159mAh/g으로 3%의 용량감소를 나타내었다. 이는 전해액과 반응하는 쉘부를 안정성이 높은 Li[Ni1/2Mn1/2]O2로 쌓아 용량감소를 막으면서 고용량의 양극 활물질을 제조한 것이다. 5 shows discharge capacities according to cycles in which each material synthesized by the method of Example 1, Comparative Example 1, and Comparative Example 2 was tested with an applied current of 0.4 mA in the range of 3.0 to 4.3 V. FIG. Li [Ni 1/3 Co 1/3 Mn 1/3 ] O 2 showed a capacity reduction of 7% to 157mAh / g at 50 cycles as the cycle proceeded to an initial capacity of 168mAh / g, and Li [Ni 1/2 The Mn 1/2 ] O 2 electrode has a capacity of 150mAh / g with a reduced capacity of 18mAh / g and a capacity reduction of 3% with 146mAh / g at 50 cycles. On the other hand, Li [(Ni 1/3 Co 1/3 Mn 1/3 ) x (Ni 1/2 Mn 1/2 ) 1-x ] O 2, which is the core shell structure, has an initial capacity of Li [Ni 1/3 The high capacity of 164mAh / g, which is similar to Co 1/3 Mn 1/3 ] O 2 , was reduced by 3% to 159mAh / g at 50 cycles. This is to prepare a high capacity positive electrode active material while preventing the capacity decrease by stacking the shell portion reacting with the electrolyte with high stability Li [Ni 1/2 Mn 1/2 ] O 2 .

도 6은 Li[Ni1/3Co1/3Mn1/3]O2, Li[(Ni1/3Co1/3Mn1/3)x(Ni1/2Mn1/2)1-x]O2 그리고 Li[Ni1/2Mn1/2]O2의 충전 후 각각의 시차중량열분석에 관한 데이터이다. Li[Ni1/3Co1/3Mn1/3]O2는 225℃에서 발열이 시작되어 235℃에서 주 발열피크가 나타나고 Li[Ni1/2Mn1/2]O2는 275℃에서의 발열이 시작하고 285℃에서 주 발열피크가 보인다. 또한 Li[(Ni1/3Co1/3Mn1/3)x(Ni1/2Mn1/2)1-x]O2는 예상대로 Li[Ni1/3Co1/3Mn1/3]O2보다 25℃가 증가한 250℃에서 발열이 시작되어 260℃에서 주 발열피크가 나타난다. 이것은 코어쉘 구조인 Li[(Ni1/3Co1/3Mn1/3)x(Ni1/2Mn1/2)1-x]O2가 Li[Ni1/3Co1/3Mn1/3]O2에 쉘부를 Li[Ni1/2Mn1/2]O2로 쌓아 Li[Ni1/3Co1/3Mn1/3]O2보다 열적 안정성이 크게 향상되었다는 것을 알 수 있다.6 is Li [Ni 1/3 Co 1/3 Mn 1/3 ] O 2 , Li [(Ni 1/3 Co 1/3 Mn 1/3 ) x (Ni 1/2 Mn 1/2 ) 1-x ] O 2 and Data on the differential weight thermal analysis after charging Li [Ni 1/2 Mn 1/2 ] O 2 . Li [Ni 1/3 Co 1/3 Mn 1/3 ] O 2 starts to generate heat at 225 ℃ and the main exothermic peak appears at 235 ℃ and Li [Ni 1/2 Mn 1/2 ] O 2 at 275 ℃. Fever starts and the main fever peak is seen at 285 ° C. In addition, Li [(Ni 1/3 Co 1/3 Mn 1/3 ) x (Ni 1/2 Mn 1/2 ) 1-x ] O 2 As expected, heat generation began at 250 ° C, 25 ° C higher than Li [Ni 1/3 Co 1/3 Mn 1/3 ] O 2 , and the main exothermic peak appears at 260 ° C. This is because Li [(Ni 1/3 Co 1/3 Mn 1/3 ) x (Ni 1/2 Mn 1/2 ) 1-x ] O 2 is Li [Ni 1/3 Co 1/3 Mn 1/3] to build up portions Li [Ni 1/2 Mn 1/2] O 2 in the shell O 2 Li [Ni 1/3 Co 1/3 Mn 1/3] O 2 than was seen that the thermal stability significantly improved Can be.

이상의 설명에서와 같이 본 발명은 하나의 바람직한 구체예에 대해서만 기술하였으나, 상기의 구체예를 바탕으로 한 본 발명의 기술사상 범위 내에서의 다양한 변형 및 수정이 가능함은 당업자에게 있어서 명백한 것이며, 또한, 이러한 변형 및 수정이 첨부된 특허청구범위에 속함은 당연한 것이다.As described above, the present invention has been described for only one preferred embodiment, but it is apparent to those skilled in the art that various changes and modifications can be made within the technical spirit of the present invention based on the above embodiments. It is natural that such variations and modifications fall within the scope of the appended claims.

이와 같이 본 발명에 의한 수산화염 공침법을 사용하여 제조된 층상 암염 구조와 코어쉘 구조를 갖는 양극 활물질은 코어부는 고용량의 삼성분계 양극 활물질로 전해질과 접하는 쉘부는 안정성이 높은 이성분계 층상계 양극 활물질로 구성되어 용량과 충전밀도가 높고 수명특성이 개선되며 열적 안전성이 우수하다. As described above, the cathode active material having the layered rock salt structure and the core shell structure manufactured by using the hydroxide co-precipitation method according to the present invention has a core component having a high capacity ternary cathode active material, and the shell portion contacting the electrolyte has a high stability two-component layered cathode active material. It is composed of high capacity, high packing density, improved life characteristics, and excellent thermal safety.

Claims (10)

코어쉘 구조를 가지는 리튬이차전지용 양극 활물질에 있어서, In a cathode active material for a lithium secondary battery having a core shell structure, 코어부는 조성식 Liδ[NixCo1-2xMnx]O2(1.0≤δ<1.2, 0.3<x<0.45), 쉘부는 Liδ[Nix'Mn1-x']O2 (1.0≤δ<1.2, 0.49<x'<0.55)로 이루어진 것을 특징으로 하는 코어쉘 구조를 가지는 리튬이차전지용 양극 활물질. Core portion composition formula Li δ [Ni x Co 1-2x Mn x] O 2 (1.0≤δ <1.2, 0.3 <x <0.45), the shell portion Li δ [Ni x 'Mn 1 -x'] O 2 (1.0≤ A cathode active material for a lithium secondary battery having a core shell structure, characterized by consisting of δ <1.2, 0.49 <x '<0.55). 제 1항에 있어서, 상기 쉘부의 두께는 전체 양극 활물질 두께의 7~80%인 것을 특징으로 하는 코어쉘 구조를 가지는 리튬이차전지용 양극 활물질. The cathode active material of claim 1, wherein the shell portion has a thickness of 7 to 80% of the total thickness of the cathode active material. 제 1항에 있어서, 상기 코어부 평균입경은 5 내지 15㎛이고, 상기 양극 활물질의 전체입자의 평균입경은 16 내지 25㎛인 것을 특징으로 하는 코어쉘 구조를 가지는 리튬이차전지용 양극 활물질. The cathode active material of claim 1, wherein an average particle diameter of the core part is 5 to 15 μm, and an average particle diameter of all the particles of the cathode active material is 16 to 25 μm. 제1항 내지 제3항 중 어느 한 항 기재의 코어쉘 구조를 가지는 리튬이차전지용 양극 활물질을 이용한 것을 특징으로 하는 리튬이차전지.The lithium secondary battery using the positive electrode active material for lithium secondary batteries which has the core-shell structure of any one of Claims 1-3. 니켈, 망간, 코발트계 전이금속 수용액, 암모니아 수용액 및 염기성 수용액을 반응기에 동시에 혼합하여 구형의 침전물을 얻는 제1단계;  A first step of simultaneously mixing nickel, manganese, cobalt-based transition metal aqueous solution, ammonia aqueous solution and basic aqueous solution in a reactor to obtain a spherical precipitate; 상기 침전물 위에 전이금속혼합계 수용액, 암모니아 수용액 및 염기성 수용액을 반응기에 동시에 혼합하여 전이금속수산화물이 덮여진 코어쉘 복합금속수산화물의 침전물을 얻는 제2단계;  A second step of obtaining a precipitate of the core-shell composite metal hydroxide covered with the transition metal hydroxide by simultaneously mixing the transition metal mixed solution, the ammonia solution and the basic aqueous solution on the precipitate on the precipitate; 상기 침전물을 건조 또는 열처리하여 코어쉘 복합금속수산화물 또는 코어쉘 복합금속산화물을 얻는 제3단계;  Drying or heat treating the precipitate to obtain a core-shell composite metal hydroxide or a core-shell composite metal oxide; 상기 코어쉘 복합금속수산화물 또는 코어쉘 복합금속산화물에 리튬염을 혼합하여 코어쉘 리튬복합금속산화물을 얻는 제4단계를 포함하는 것을 특징으로 하는 코어쉘 구조를 가지는 리튬이차전지용 양극 활물질의 제조방법. And a fourth step of obtaining a core-shell lithium composite metal oxide by mixing lithium salt with the core-shell composite metal hydroxide or core-shell composite metal oxide. 제 5항에 있어서, 상기 제1단계에서 전구체로서 2종 이상의 금속염을 포함하는 수용액을 혼합하여 사용하고, 암모니아와 금속염의 몰 비는 0.2 내지 0.4, 반응 용액의 pH는 10.5 내지 12로 조절하여 10 내지 20 시간 반응시키는 것을 특징으로 하는 코어쉘 구조를 가지는 리튬이차전지용 양극 활물질의 제조방법.The method of claim 5, wherein the first step is used by mixing an aqueous solution containing two or more metal salts as a precursor, the molar ratio of ammonia and metal salt is 0.2 to 0.4, the pH of the reaction solution is adjusted to 10.5 to 12 to 10 Method for producing a cathode active material for a lithium secondary battery having a core shell structure characterized in that for 20 hours to react. 제 5항에 있어서, 상기 제2단계는 반응시간을 1 내지 10시간으로 조절하여 쉘층의 두께를 조절하는 것을 특징으로 하는 코어쉘 구조를 가지는 리튬이차전지용 양극 활물질의 제조방법.The method of claim 5, wherein the second step of controlling the thickness of the shell layer by adjusting the reaction time to 1 to 10 hours. 제 5항에 있어서, 상기 제3단계는 110℃에서 15시간 건조시키거나, 400~550 ℃에서 5 내지 10시간 가열하는 것을 특징으로 하는 코어쉘 구조를 가지는 리튬이차전지용 양극 활물질 제조방법.6. The method of claim 5, wherein the third step is dried at 110 ° C. for 15 hours or heated at 400 to 550 ° C. for 5 to 10 hours. 7. 제 6항에 있어서, 상기 제4단계는 300~550℃에서 5시간 유지시켜 예비 소성하는 단계, 700℃ 내지 1100℃에서 공기나 산소의 산화성 분위기에서 10 내지 20시간 소성하는 단계, 600~750℃에서 10시간 어닐링하는 것을 특징으로 하는 코어쉘 구조를 가지는 리튬이차전지용 양극 활물질의 제조방법.The method of claim 6, wherein the fourth step is a step of pre-firing by maintaining for 5 hours at 300 ~ 550 ℃, 10 to 20 hours firing in an oxidizing atmosphere of air or oxygen at 700 ℃ to 1100 ℃, 600 ~ 750 ℃ Method for producing a cathode active material for a lithium secondary battery having a core shell structure, characterized in that the annealing for 10 hours. 제 5항에 있어서, 상기 코발트계 전이금속수용액의 반응 분위기는 질소 흐름하, pH는 10.5내지 12.5이내, 반응온도는 30 내지 80℃이며, 반응교반기 rpm은 500내지 2000이내인 것을 특징으로 하는 코어쉘 구조를 가지는 리튬이차전지용 양극 활물질의 제조방법.The core according to claim 5, wherein the reaction atmosphere of the cobalt-based transition metal aqueous solution is nitrogen flow, pH is 10.5 to 12.5, reaction temperature is 30 to 80 ° C, and the reaction stirrer rpm is 500 to 2000. A method for producing a cathode active material for a lithium secondary battery having a shell structure.
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