KR20200089474A - Positive electrode active material for lithium secondary battery, method for preparing the same and lithium secondary battery including the positive electrode active material - Google Patents
Positive electrode active material for lithium secondary battery, method for preparing the same and lithium secondary battery including the positive electrode active material Download PDFInfo
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- KR20200089474A KR20200089474A KR1020190006238A KR20190006238A KR20200089474A KR 20200089474 A KR20200089474 A KR 20200089474A KR 1020190006238 A KR1020190006238 A KR 1020190006238A KR 20190006238 A KR20190006238 A KR 20190006238A KR 20200089474 A KR20200089474 A KR 20200089474A
- Authority
- KR
- South Korea
- Prior art keywords
- active material
- positive electrode
- sulfur
- carbon
- secondary battery
- Prior art date
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- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 66
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 62
- 239000007774 positive electrode material Substances 0.000 title claims abstract description 61
- 238000000034 method Methods 0.000 title claims description 15
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- Y02E60/10—Energy storage using batteries
Abstract
Description
본 발명은 리튬 이차전지용 양극 활물질, 그 제조방법 및 이를 포함하는 리튬 이차전지에 관한 것으로서, 더욱 상세하게는, 황과 탄소의 혼합 비율이 상이한 다종의 탄소-황 복합체를 양극 활물질로 혼합 적용하여 전지의 성능을 개선시킬 수 있는, 리튬 이차전지용 양극 활물질, 그 제조방법 및 이를 포함하는 리튬 이차전지에 관한 것이다.The present invention relates to a positive electrode active material for a lithium secondary battery, a method of manufacturing the same, and a lithium secondary battery including the same, and more specifically, a mixture of a variety of carbon-sulfur composites having different mixing ratios of sulfur and carbon as a positive electrode active material, The present invention relates to a lithium secondary battery including a cathode active material for a lithium secondary battery, a method of manufacturing the same, and a method for improving the performance of the lithium secondary battery.
에너지 저장 기술에 대한 관심이 갈수록 높아짐에 따라, 휴대폰, 태블릿(tablet), 랩탑(laptop) 및 캠코더, 나아가서는 전기 자동차(EV) 및 하이브리드 전기 자동차(HEV)의 에너지까지 적용분야가 확대되면서, 전기화학소자에 대한 연구 및 개발이 점차 증대되고 있다. 전기화학소자는 이러한 측면에서 가장 주목을 받고 있는 분야이고, 그 중에서도 충방전이 가능한 리튬-황 전지와 같은 리튬계 이차전지의 개발은 관심의 초점이 되고 있으며, 최근에는 이러한 전지를 개발함에 있어서 용량 밀도 및 비 에너지를 향상시키기 위하여, 새로운 전극과 전지의 설계에 대한 연구개발로 이어지고 있다.As the interest in energy storage technology increases, the fields of application extend to the energy of mobile phones, tablets, laptops and camcorders, and even electric vehicles (EVs) and hybrid electric vehicles (HEVs). Research and development of chemical devices is gradually increasing. The electrochemical device is the field that is receiving the most attention in this aspect, and among them, the development of a lithium-based secondary battery such as a lithium-sulfur battery capable of charging and discharging has become a focus of interest, and recently, in developing such a battery, capacity In order to improve the density and specific energy, it has led to research and development of new electrode and cell designs.
이와 같은 전기화학소자, 그 중에서도 리튬 이차전지 가운데 리튬-황(Li-S) 전지는 높은 에너지 밀도를 가져, 리튬이온전지를 대체할 수 있는 차세대 이차전지로 각광 받고 있다. 이러한 리튬-황 전지 내에서는, 방전 시 황의 환원반응과 리튬 메탈의 산화반응이 일어나며, 이 때, 황은 고리 구조의 S8로부터 선형 구조의 리튬 폴리설파이드(Li2S2, Li2S4, Li2S6, Li2S8)를 형성하게 되는데, 리튬-황 전지는 폴리설파이드(Polysulfide, PS)가 완전히 Li2S로 환원되기까지 단계적 방전 전압을 나타내는 것이 특징이다.Among these electrochemical devices, especially lithium secondary batteries, lithium-sulfur (Li-S) batteries have high energy density and are in the spotlight as next-generation secondary batteries that can replace lithium-ion batteries. In such a lithium-sulfur battery, a reduction reaction of sulfur and an oxidation reaction of lithium metal occur during discharging, where sulfur is a lithium polysulfide having a linear structure from S 8 (Li 2 S 2 , Li 2 S 4 , Li 2 S 6 , Li 2 S 8 ), which is characterized in that the lithium-sulfur battery exhibits a stepwise discharge voltage until polysulfide (PS) is completely reduced to Li 2 S.
이와 같은 리튬-황 전지의 황 양극은 비전도성으로서, 양극재의 대부분은 전기화학 반응에 기여하는 황(sulfur)과 이의 담지체인 전도성의 탄소계 물질을 혼합하여 사용하고 있으며, 이 때 사용되는 탄소계 물질에 따라 황의 반응성, 고율 특성 및 수명 특성 등에 영향을 미치게 된다(즉, 전지의 성능에 영향을 미치는 형태, 크기 및 전도도 등의 인자가 탄소마다 차이가 있음). 하지만, 리튬-황 전지는 최종 반응 생성물인 Li2S가 S에 비해 부피가 증가하면서 전극 구조를 변화시키고, 중간 생성물인 폴리설파이드는 전해질에 쉽게 용해되기 때문에 방전 반응 중에 지속적으로 녹아 나와 양극 활물질의 양이 감소한다. 결국, 전지의 퇴화가 가속되어 전지의 반응성 및 수명특성이 저하될 수밖에 없다. 이를 해결하기 위하여, 탄소의 표면을 개질시키는 기술들이 개발되고 있으나, 열처리 등 길고 복잡한 공정이 수반되어야 하는 어려움이 있거나 폴리설파이드의 용출 감소 정도가 미약하여, 아직까지 구체적인 해결 방안을 찾지 못하고 있는 실정이다. 따라서, 전지의 성능을 향상시킬 수 있는 양극 활물질의 개발이 요구된다.The sulfur anode of the lithium-sulfur battery is non-conductive, and most of the cathode material is a mixture of sulfur contributing to the electrochemical reaction and a conductive carbon-based material, which is a carrier, and is used in this case. Depending on the material, it affects the reactivity of the sulfur, high rate characteristics, and life characteristics (ie, factors such as shape, size, and conductivity that affect the performance of the battery differ for each carbon). However, in the lithium-sulfur battery, the electrode structure changes as the final reaction product Li 2 S increases in volume compared to S, and the polysulfide, an intermediate product, dissolves easily in the electrolyte and continuously melts during the discharge reaction, resulting in the positive electrode active material. The amount decreases. As a result, degeneration of the battery is accelerated, and the reactivity and life characteristics of the battery are inevitably reduced. In order to solve this, technologies for modifying the surface of carbon have been developed, but there are difficulties that require long and complicated processes such as heat treatment, or the degree of polysulfide elution reduction is weak, so no specific solution has been found. . Therefore, development of a positive electrode active material capable of improving the performance of the battery is required.
따라서, 본 발명의 목적은, 황과 탄소의 혼합 비율이 상이한 다종의 탄소-황 복합체를 양극 활물질로 혼합 적용하여 전지의 성능을 개선시킬 수 있는, 리튬 이차전지용 양극 활물질, 그 제조방법 및 이를 포함하는 리튬 이차전지를 제공하는 것이다.Therefore, the object of the present invention is a lithium secondary battery positive electrode active material capable of improving the performance of a battery by mixing and applying various types of carbon-sulfur composites having different mixing ratios of sulfur as a positive electrode active material, a method of manufacturing the same, and the same That is to provide a lithium secondary battery.
상기 목적을 달성하기 위하여, 본 발명은, 황이 탄소재에 담지된 2종 이상의 활물질 복합체를 포함하며, 상기 2종 이상의 활물질 복합체 중 어느 한 종의 활물질 복합체에 포함된 황과 탄소재의 함량비는 다른 종에 포함된 황과 탄소재의 함량비와 상이한 것을 특징으로 하는 리튬 이차전지용 양극 활물질을 제공한다.In order to achieve the above object, the present invention includes two or more active material complexes in which sulfur is supported on a carbon material, and the content ratio of sulfur and carbon materials included in any one of the active material complexes of the two or more active material complexes is It provides a positive electrode active material for a lithium secondary battery, characterized in that different from the content ratio of sulfur and carbon contained in other species.
또한, 본 발명은, (a) 2종 이상의 탄소재 각각을 황과 혼합 및 반응시켜 상기 탄소재 각각에 황이 담지된 2종 이상의 활물질 복합체를 제조하는 단계; 및 (b) 상기 제조된 2종 이상의 활물질 복합체를 혼합하는 단계;를 포함하며, 상기 2종 이상의 활물질 복합체 중 어느 한 종의 활물질 복합체에 포함된 황과 탄소재의 함량비는 다른 종에 포함된 황과 탄소재의 함량비와 상이한 것을 특징으로 하는 리튬 이차전지용 양극 활물질의 제조방법을 제공한다.In addition, the present invention, (a) by mixing and reacting each of the two or more carbon materials with sulfur to prepare a composite of two or more active materials in which sulfur is supported on each of the carbon materials; And (b) mixing the two or more active material complexes prepared above; wherein the content ratio of sulfur and carbon material contained in one of the two or more active material complexes is included in the other species. It provides a method for producing a positive electrode active material for a lithium secondary battery, characterized in that different from the content ratio of sulfur and carbon materials.
또한, 본 발명은, 상기 리튬 이차전지용 양극 활물질을 포함하는 양극; 리튬계 음극; 상기 양극과 음극의 사이에 개재되는 전해질; 및 분리막;을 포함하는 리튬 이차전지를 제공한다.In addition, the present invention, the positive electrode containing the positive electrode active material for the lithium secondary battery; Lithium-based negative electrode; An electrolyte interposed between the positive electrode and the negative electrode; And a separator; provides a lithium secondary battery comprising a.
본 발명에 따른 리튬 이차전지용 양극 활물질, 그 제조방법 및 이를 포함하는 리튬 이차전지에 의하면, 황과 탄소의 혼합 비율이 상이한 다종의 탄소-황 복합체를 양극 활물질로 혼합 적용함으로써 전지의 성능을 개선시킬 수 있는 장점이 있다.According to the positive electrode active material for a lithium secondary battery according to the present invention, a manufacturing method thereof, and a lithium secondary battery comprising the same, it is possible to improve the performance of the battery by mixing and applying various types of carbon-sulfur composites having different mixing ratios of sulfur and carbon as the positive electrode active material There is an advantage.
도 1은 본 발명의 일 실시예에 따른 리튬-황 전지와 비교예에 따른 리튬-황 전지의 수명 특성을 비교 대조한 그래프이다.
도 2는 본 발명의 일 실시예에 따른 리튬-황 전지와 비교예에 따른 리튬-황 전지의 충전 프로파일을 비교 대조한 그래프이다.1 is a graph comparing and comparing the life characteristics of a lithium-sulfur battery according to an embodiment of the present invention and a lithium-sulfur battery according to a comparative example.
2 is a graph comparing and comparing the charging profile of a lithium-sulfur battery according to an embodiment of the present invention and a lithium-sulfur battery according to a comparative example.
이하, 본 발명을 상세히 설명한다.Hereinafter, the present invention will be described in detail.
본 발명에 따른 리튬 이차전지용 양극 활물질은, 황이 탄소재에 담지된 2종 이상의 활물질 복합체를 포함하며, 상기 2종 이상의 활물질 복합체 중 어느 한 종의 활물질 복합체에 포함된 황과 탄소재의 함량비는 다른 종에 포함된 황과 탄소재의 함량비와 상이한 것을 특징으로 한다.The positive electrode active material for a lithium secondary battery according to the present invention includes two or more active material complexes in which sulfur is supported on a carbon material, and the content ratio of sulfur and carbon materials contained in any one of the two or more active material complexes is an active material complex. It is characterized by being different from the content ratio of sulfur and carbon materials contained in other species.
본 출원인은, 리튬 이차전지, 그 중에서도 리튬-황 전지의 양극 활물질로 적용되는 황-탄소 복합체를 다종으로 하되, 종 간 황과 탄소재의 혼합 비율을 서로 다르게 적용하고, 또한 추가적으로, 2종 이상의 활물질 복합체(또는, 황-탄소 복합체)에서 황 담지체로 적용되는 탄소재를 입도와 형상이 서로 다른 2종 이상 사용함으로써, 리튬 이차전지의 수명특성을 개선시켰다.Applicants, the lithium secondary battery, in particular, the sulfur-carbon composite applied as a positive electrode active material of a lithium-sulfur battery is used as a plurality of species, but the mixing ratio of sulfur and carbon materials between species is applied differently, and additionally, two or more kinds By using two or more types of carbon materials having different particle sizes and shapes in the active material composite (or sulfur-carbon composite) as a sulfur carrier, life characteristics of the lithium secondary battery are improved.
상기 활물질 복합체는 황이 탄소재에 담지된, 즉 다시 말해, 황과 탄소재를 포함하는 것으로서, 2종 이상 제한 없이 사용될 수 있다. 예를 들어, 상기 활물질 복합체가 2종인 경우, 황이 제1 탄소재에 담지된 제1 활물질 복합체 및 황이 제2 탄소재에 담지된 제2 활물질 복합체를 포함하게 되며, 상기 활물질 복합체가 3종 이상인 경우에는, 제1 및 제2 활물질 복합체 이외에, 제3 활물질 복합체 등이 추가로 포함될 수 있다. 즉, 본 발명에 있어서, 상기 활물질 복합체의 개수는, 활물질 복합체 간 황과 탄소재의 함량비를 다르게 적용할 수 있고, 추가적으로, 각 활물질 복합체에 포함된 탄소재의 평균입도와 형상이 서로 다르기만 하다면 특별한 제한이 없다.The active material composite is sulfur is supported on a carbon material, that is, as containing sulfur and carbon material, it can be used without limitation of two or more. For example, when the active material complex is two types, the first active material complex in which sulfur is supported on the first carbon material and the second active material complex in which sulfur is supported on the second carbon material are included, and the active material complex is three or more types In addition to the first and second active material complex, a third active material complex and the like may be further included. That is, in the present invention, the number of the active material composite, the content ratio of sulfur and carbon material between the active material composite can be applied differently, additionally, only the average particle size and shape of the carbon material included in each active material composite is different from each other There are no special restrictions.
이와 같은 활물질 복합체들은 리튬 이차전지의 양극 활물질로서 다양한 비율로 혼합될 수 있다. 예를 들어, 2종의 활물질 복합체가 사용되면, 그 함량비는 중량비로서 1 : 9 내지 9 : 1일 수 있고, 바람직하게는 2 : 8 내지 8 : 2일 수 있다. 그밖에, 3종 이상의 활물질 복합체가 사용되는 경우에는, 본 발명의 취지에 벗어나지 않는 범위 내에서 적절한 함량비로 적용될 수 있다.These active material composites may be mixed in various proportions as a positive electrode active material of a lithium secondary battery. For example, when two types of active material complexes are used, the content ratio may be 1:9 to 9:1 as a weight ratio, and preferably 2:8 to 8:2. In addition, when three or more types of active material complexes are used, they may be applied at an appropriate content ratio within a range not departing from the spirit of the present invention.
상기 활물질 복합체 각각에 포함되는 탄소재는 전도성을 향상시키기 위한 것으로서, 탄소나노튜브(carbon nanotube, CNT), 그래핀(graphene) 및 그래핀 옥사이드(graphene oxide, GO) 등, 황의 담지가 가능하도록 기공이 형성되어 있고 전도성을 가지는 탄소 소재라면 특별한 제한 없이 사용될 수 있다.The carbon material included in each of the active material composites is for improving conductivity, and pores are provided to support sulfur, such as carbon nanotube (CNT), graphene and graphene oxide (GO). If it is formed and has a conductive carbon material, it can be used without particular limitation.
상기 2종 이상의 각 활물질 복합체에 포함된 황과 탄소재의 혼합 비율은 중량비로서 1 내지 9 : 1, 바람직하게는 1.5 내지 6 : 1, 더욱 바람직하게는 1.5 내지 4 : 1일 수 있다. 만일, 상기 황 및 탄소재의 함량비가 상기 범위를 벗어나거나, 상기 2종 이상의 활물질 복합체 중 어느 한 종의 활물질 복합체에 포함된 황과 탄소재의 함량비가, 다른 종에 포함된 황과 탄소재의 함량비와 동일한 경우에는, 리튬 이차전지의 성능 향상을 극대화시키는데 어려움이 있을 수 있다.The mixing ratio of the sulfur and the carbon material contained in each of the two or more active material composites may be 1 to 9:1, preferably 1.5 to 6:1, more preferably 1.5 to 4:1 as a weight ratio. If the content ratio of the sulfur and carbon material is out of the above range, or the content ratio of sulfur and carbon material contained in any one of the active material composites of the two or more active material complexes, the sulfur and carbon material contained in the other species When the content ratio is the same, it may be difficult to maximize the performance improvement of the lithium secondary battery.
따라서, 상기 2종 이상의 활물질 복합체가 2종의 활물질 복합체인 경우, 예를 들어, 상기 양극 활물질은 황과 탄소재의 함량비가 중량비로서 7 : 3 내지 9 : 1 인 활물질 복합체 1종과, 4 : 6 내지 7 : 3인 활물질 복합체 1종을 포함할 수 있다. 보다 구체적인 예를 들면, 어느 한 종의 활물질 복합체에 포함된 황과 탄소재의 함량비는 중량비로서 8 : 2, 다른 한 종의 활물질 복합체에 포함된 황과 탄소재의 함량비는 중량비로서 6 : 4일 수 있고, 또 다른 예로 각 함량비는 중량비로서 8.5 : 1.5과 6 : 4일 수 있는 등, 상기 2종 이상의 각 활물질 복합체를 구성하는 황과 탄소재의 함량비가 모두 상기 범위에 포함되고, 상기 예시와 같이 각 활물질 복합체에 포함된 황과 탄소재의 함량비가 서로 다르기만 하면, 상기 활물질 복합체 각각의 함량비에는 특별한 제한이 없다.Thus, when the two or more active material complexes are two active material complexes, for example, the positive electrode active material has a content ratio of sulfur and carbon materials of 7 to 3 to 9: 1 as a weight ratio, and one active material complex, and 4: 6 to 7: 3 may include one active material complex. For a more specific example, the content ratio of sulfur and carbon material contained in one type of active material composite is 8: 2 as the weight ratio, and the content ratio of sulfur and carbon material contained in the other type of active material composite is 6: as a weight ratio. It may be 4, and as another example, each content ratio may be 8.5:1.5 and 6:4 as a weight ratio, and the content ratios of sulfur and carbon materials constituting each of the two or more active material complexes are all included in the above range. As long as the content ratios of the sulfur and carbon materials contained in each active material composite are different from each other, there is no particular limitation on the content ratio of each of the active material composites.
한편, 상기 2종 이상의 활물질 복합체 중 어느 한 종의 활물질 복합체에 포함된 탄소재는 다른 종에 포함된 탄소재와 평균입도 및 형상 중 어느 하나 이상이 서로 다를 수 있으며, 이 경우, 리튬 이차전지의 수명특성을 보다 향상시킬 수 있다. 상기 탄소재의 평균입도는 2 내지 200 ㎛, 바람직하게는 5 내지 100 ㎛로서, 상기 탄소재의 평균입도가 상기 범위를 벗어날 경우, 전극 코팅 불량을 야기하거나 슬러리 막힘 현상이 발생할 수 있고, 상기 각 활물질 복합체에 포함되는 각각의 탄소재 입도가 서로 다르지 않은 경우에는, 전지의 수명특성 개선 효과가 매우 미미하거나 없을 수 있다.On the other hand, the carbon material contained in the active material composite of any one of the above two or more active material composite may have any one or more of the average particle size and shape and the carbon material included in the other species, in this case, the life of the lithium secondary battery Characteristics can be further improved. The average particle size of the carbon material is 2 to 200 μm, preferably 5 to 100 μm, and when the average particle size of the carbon material is outside the above range, electrode coating failure may occur or slurry clogging may occur. When the particle sizes of the carbon materials included in the active material composite are not different from each other, the effect of improving the life characteristics of the battery may be very insignificant or absent.
즉, 예를 들어, 상기 2종 이상의 활물질 복합체 중 어느 한 종의 활물질 복합체에 포함된 탄소재의 평균입도는 5 내지 40 ㎛이고, 다른 종의 활물질 복합체에 포함된 탄소재의 평균입도는 15 내지 90 ㎛일 수 있다. 즉, 탄소재의 평균입도가 큰 탄소재를 적용하는 경우 과전압이 개선되며 용량 발현이 용이한 특징이 있고, 평균입도가 작은 탄소재를 적용하는 경우에는 전하의 출입이 용이하여 출력 특성 향상에 용이하기 때문에, 이들의 장점을 모두 가지도록 각 활물질 복합체에 포함되는 각 탄소재의 평균입도를 서로 다르게 구성하는 것이 바람직하다.That is, for example, the average particle size of the carbon material included in the active material composite of any one of the two or more active material composites is 5 to 40 μm, and the average particle size of the carbon material included in the active material composite of other species is 15 to It may be 90 μm. That is, when a carbon material having a large average particle size is applied, overvoltage is improved and capacity is easily expressed. When a carbon material having a small average particle size is applied, it is easy to get in and out of charge and improve output characteristics. Therefore, it is preferable to configure the average particle size of each carbon material included in each active material composite differently so as to have all of these advantages.
상기 탄소재 형상의 경우, 예를 들어, 어느 하나는 탄소나노튜브로 적용하고, 나머지는 그래핀 옥사이드 등 다른 탄소재로 적용하게 되면 자연스럽게 각 탄소재의 형상이 상이해질 수 있다. 반면, 동종의 탄소재를 사용하고 또한 그 입도까지 동일한 경우에는, 탄소재들 간 형상이 반드시 달라야만 전지의 수명특성을 개선시킬 수가 있다. 여기서, 상기 탄소재 중 탄소나노튜브(CNT)의 형상에 대하여 설명하면, 상기 CNT의 형상으로는 대표적으로 CNT가 엉켜 구형의 형태를 이루는 entangle type과, CNT가 정렬되어 하나의 타래를 이루는 bundle type으로 분류할 수 있다. 상기 entangle type의 경우 과전압 개선이나 용량 발현 측면에서 이점을 가지며, 상기 bundle type의 경우에는 고율 특성 개선 및 반응 부산물 분해에 효과가 있다. 따라서, 이들의 장점을 모두 가지도록 각 활물질 복합체에 포함되는 각 탄소재의 형상을 서로 다르게 구성하는 것이 바람직하다.In the case of the carbon material shape, for example, if one is applied as a carbon nanotube, and the other is applied as another carbon material such as graphene oxide, the shape of each carbon material may naturally be different. On the other hand, when the same carbon materials are used and the particle size is the same, the shapes between the carbon materials must be different to improve the life characteristics of the battery. Here, when the shape of the carbon nanotube (CNT) among the carbon materials is described, the shape of the CNT is typically a entangle type in which a CNT is entangled to form a spherical shape, and a bundle type in which CNTs are arranged to form a single skein. Can be classified as The entangle type has an advantage in terms of overvoltage improvement or capacity development, and the bundle type is effective in improving high rate characteristics and decomposing reaction byproducts. Therefore, it is preferable to configure the shape of each carbon material included in each active material composite differently to have all of these advantages.
종합하면, 상기 각 활물질 복합체에 포함되는 각각의 탄소재는 서로 종류가 다르거나(이 경우 탄소재 간 평균입도와 형상은 자연스레 달라짐), 동종일 경우에는 탄소재 간에 평균입도 및 형상 중 어느 하나 이상이 달라야만 본 발명의 취지에 부합할 수 있는 것이다. 한편, 상기 탄소재의 표면에는 황이 담지되는 기공이 형성되어 있으며, 이때, 상기 탄소재의 기공 부피는 0.5 내지 5 cm3일 수 있다.In summary, each of the carbon materials included in each of the active material composites is different from each other (in this case, the average particle size and shape naturally vary), or in the case of the same type, any one or more of the average particle size and shape between the carbon materials Only if it is different can it meet the spirit of the present invention. Meanwhile, pores in which sulfur is supported are formed on the surface of the carbon material, and in this case, the pore volume of the carbon material may be 0.5 to 5 cm 3 .
다음으로, 본 발명에 따른 리튬 이차전지용 양극 활물질의 제조방법에 대하여 설명한다. 상기 리튬 이차전지용 양극 활물질의 제조방법은, (a) 2종 이상의 탄소재 각각을 황과 혼합 및 반응시켜 상기 탄소재 각각에 황이 담지된 2종 이상의 활물질 복합체를 제조하는 단계 및 (b) 상기 제조된 2종 이상의 활물질 복합체를 혼합하는 단계를 포함하며, 상기 2종 이상의 활물질 복합체 중 어느 한 종의 활물질 복합체에 포함된 황과 탄소재의 함량비는 다른 종에 포함된 황과 탄소재의 함량비와 상이한 것을 특징으로 한다.Next, a method of manufacturing a positive electrode active material for a lithium secondary battery according to the present invention will be described. The method for manufacturing the positive electrode active material for a lithium secondary battery includes: (a) mixing and reacting each of two or more carbon materials with sulfur to prepare a composite of two or more active materials in which sulfur is supported on each of the carbon materials, and (b) the production And mixing the two or more active material complexes, wherein the content ratio of sulfur and carbon materials contained in one of the two or more active material complexes is the content ratio of sulfur and carbon materials included in the other species. It is characterized by different from.
상기 2종 이상의 활물질 복합체 중 어느 한 종의 활물질 복합체에 포함된 황과 탄소재의 함량비는 중량비로서 7 : 3 내지 9 : 1이고, 다른 종에 포함된 황과 탄소재의 함량비는 중량비로서 4 : 6 내지 7 : 3일 수 있다.The content ratio of sulfur and carbon materials contained in any one of the two or more active material composites as a weight ratio is 7: 3 to 9: 1, and the content ratio of sulfur and carbon materials contained in other species is a weight ratio. It may be 4:6 to 7:3.
상기 (a) 단계에서 활물질 복합체는, 평균입도 및 형상 중 어느 하나 이상이 서로 다른 탄소재를 각각 포함할 수 있는 것으로서, 2종 이상일 수 있다. 예를 들어, 2종의 활물질 복합체가 제조되는 경우에는, 황과 제1 탄소재를 혼합 및 반응시켜 제1 활물질 복합체를 제조하고, 이어서, 황과 제2 탄소재를 혼합 및 반응시켜 제2 활물질 복합체를 제조할 수 있으며, 공정 환경 등에 따라 각각의 활물질 복합체를 동시에 제조할 수도 있는 등, 활물질 복합체의 개수나 제조 순서에는 특별한 제한이 없다(단, 제조되는 활물질 복합체의 개수는 둘 이상이어야 한다). 이때, 상기 2종 이상의 각 활물질 복합체를 구성하는 황과 탄소재의 혼합 비율은 중량비로서 1 내지 9 : 1, 바람직하게는 1.5 내지 6 : 1, 더욱 바람직하게는 1.5 내지 4 : 1일 수 있으나, 상기 2종 이상의 활물질 복합체 중 어느 한 종의 활물질 복합체에 포함된 황과 탄소재의 함량비는 다른 종에 포함된 황과 탄소재의 함량비와 서로 달라야만 본 발명의 목적을 달성할 수 있다.In the step (a), the active material composite may have two or more kinds of carbon materials having one or more of average particle size and shape, respectively. For example, when two types of active material composites are produced, the first active material composite is prepared by mixing and reacting sulfur and the first carbon material, and then, the second active material is mixed and reacted with sulfur and the second carbon material. There is no particular limitation on the number of active material complexes or the manufacturing order, such as the production of composites and the production of each active material complex at the same time depending on the process environment, etc. (however, the number of active material complexes being manufactured must be two or more) . At this time, the mixing ratio of the sulfur and the carbon material constituting each of the two or more active material composites may be 1 to 9: 1, preferably 1.5 to 6: 1, more preferably 1.5 to 4: 1 as a weight ratio, To achieve the object of the present invention, the content ratios of sulfur and carbon materials contained in one of the two or more active material composites must be different from the content ratios of sulfur and carbon materials contained in another species.
상기 (a) 단계에 있어서, 상기 반응은 120 내지 200 ℃, 바람직하게는 150 내지 180 ℃의 온도에서 5 내지 60 분, 바람직하게는 20 내지 40 분 동안 수행될 수 있다. 그밖에, 상기 탄소재에 대한 정의나, 그 평균입도 및 형상 등에 관한 설명은 전술한 바로 대체한다.In the step (a), the reaction may be performed at a temperature of 120 to 200°C, preferably 150 to 180°C for 5 to 60 minutes, preferably 20 to 40 minutes. In addition, the definition of the carbon material, the description of the average particle size and shape, etc., is replaced by the above-described bar.
상기 (b) 단계에 있어서, 상기 제조된 활물질 복합체들은 리튬 이차전지의 양극 활물질로서 다양한 비율로 혼합될 수 있다. 예를 들어, 2종의 활물질 복합체가 사용되면, 그 함량비는 중량비로서 1 : 9 내지 9 : 1일 수 있고, 바람직하게는 2 : 8 내지 8 : 2일 수 있다. 그밖에, 3종 이상의 활물질 복합체가 사용되는 경우에는, 본 발명의 취지에 벗어나지 않는 범위 내에서 적절한 함량비로 적용될 수 있다. 한편, 상기 (b) 단계에서 혼합되는 활물질 복합체들은 슬러리의 형태가 바람직하나, 본 발명의 범주를 벗어나지만 않는다면 그 혼합 형태에는 특별한 제한이 없고, 또한, 당업계에서 통용되는 그것을 준용할 수 있다.In step (b), the prepared active material composites may be mixed in various ratios as a positive electrode active material of a lithium secondary battery. For example, when two types of active material complexes are used, the content ratio may be 1:9 to 9:1 as a weight ratio, and preferably 2:8 to 8:2. In addition, when three or more types of active material complexes are used, they may be applied at an appropriate content ratio within a range not departing from the spirit of the present invention. On the other hand, the active material complexes mixed in the step (b) are preferably in the form of a slurry, but there is no particular limitation on the mixed form unless it is outside the scope of the present invention, and it can be applied to those commonly used in the art.
마지막으로, 상기 리튬 이차전지용 양극 활물질을 포함하는 리튬 이차전지에 대하여 설명하면, 상기 리튬 이차전지는, 상기 리튬 이차전지용 양극 활물질을 포함하는 양극; 리튬계 음극; 상기 양극과 음극의 사이에 개재되는 전해질; 및 분리막;을 포함한다.Finally, when describing a lithium secondary battery including the positive electrode active material for a lithium secondary battery, the lithium secondary battery includes: a positive electrode comprising a positive electrode active material for a lithium secondary battery; Lithium-based negative electrode; An electrolyte interposed between the positive electrode and the negative electrode; And a separation membrane.
여기서, 상기 양극 활물질의 함량은 상기 양극 100 중량부에 대하여 50 내지 95 중량부, 바람직하게는 60 내지 90 중량부일 수 있다. 상기 양극 활물질의 함량이 양극 전체 중량 100 중량부에 대하여 50 중량부 미만이면 양극 활물질에 의한 전지의 전기화학적 특성이 저하될 수 있고, 95 중량부를 초과하면 바인더 및 도전재와 같은 추가적인 구성 성분이 소량으로 포함될 수 있어 효율적인 전지의 제조가 어려울 수 있다. 그밖에, 본 발명에 따른 리튬 이차전지는, 리튬-황 전지, 리튬 메탈 전지 및 리튬 공기 전지 등의 리튬계 이차전지일 수 있으나, 리튬-황 전지가 본 발명의 취지에 가장 부합할 수 있다.Here, the content of the positive electrode active material may be 50 to 95 parts by weight, preferably 60 to 90 parts by weight based on 100 parts by weight of the positive electrode. When the content of the positive electrode active material is less than 50 parts by weight based on 100 parts by weight of the positive electrode, the electrochemical properties of the battery due to the positive electrode active material may be lowered, and when it exceeds 95 parts by weight, a small amount of additional components such as a binder and a conductive material As it may be included, it may be difficult to manufacture an efficient battery. In addition, the lithium secondary battery according to the present invention may be a lithium-based secondary battery such as a lithium-sulfur battery, a lithium metal battery and a lithium air battery, but the lithium-sulfur battery may best meet the spirit of the present invention.
한편, 상기 양극 활물질을 제외한 양극의 제반 구성, 음극, 전해질 및 분리막은 당업계에서 사용하는 통상의 것일 수 있으며, 이하, 이들에 대한 구체적인 설명을 하도록 한다.On the other hand, the overall configuration of the positive electrode, except for the positive electrode active material, the negative electrode, the electrolyte, and the separator may be a common one used in the art, and will be described below in detail.
본 발명의 리튬 이차전지에 포함되는 양극은, 전술한 양극 활물질 이외에 바인더 및 도전재 등을 더 포함한다. 상기 바인더는 양극 활물질과 도전재 등의 결합 및 집전체에 대한 결합에 조력하는 성분으로서, 예컨대, 폴리비닐리덴플루오라이드(PVdF), 폴리비닐리덴플루오라이드-폴리헥사플루오로프로필렌 공중합체(PVdF/HFP), 폴리비닐아세테이트, 폴리비닐알코올, 폴리비닐에테르, 폴리에틸렌, 폴리에틸렌옥사이드, 알킬화 폴리에틸렌옥사이드, 폴리프로필렌, 폴리메틸(메트)아크릴레이트, 폴리에틸(메트)아크릴레이트, 폴리테트라플루오로에틸렌(PTFE), 폴리비닐클로라이드, 폴리아크릴로니트릴, 폴리비닐피리딘, 폴리비닐피롤리돈, 스티렌-부타디엔 고무, 아크릴로니트릴-부타디엔 고무, 에틸렌-프로필렌-디엔 모노머(EPDM) 고무, 술폰화 EPDM 고무, 스틸렌-부틸렌 고무, 불소 고무, 카르복시메틸셀룰로우즈(CMC), 전분, 히드록시프로필셀룰로우즈, 재생 셀룰로우즈, 및 이들의 혼합물로 이루어진 군에서 선택되는 1종 이상을 사용할 수 있으나, 반드시 이에 한정되는 것은 아니다.The positive electrode included in the lithium secondary battery of the present invention further includes a binder and a conductive material in addition to the positive electrode active material described above. The binder is a component that assists in the binding of the positive electrode active material and the conductive material and the like to the current collector, for example, polyvinylidene fluoride (PVdF), polyvinylidene fluoride-polyhexafluoropropylene copolymer (PVdF/ HFP), polyvinyl acetate, polyvinyl alcohol, polyvinyl ether, polyethylene, polyethylene oxide, alkylated polyethylene oxide, polypropylene, polymethyl (meth)acrylate, polyethyl (meth)acrylate, polytetrafluoroethylene (PTFE) ), polyvinylchloride, polyacrylonitrile, polyvinylpyridine, polyvinylpyrrolidone, styrene-butadiene rubber, acrylonitrile-butadiene rubber, ethylene-propylene-diene monomer (EPDM) rubber, sulfonated EPDM rubber, styrene -Butylene rubber, fluorine rubber, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, and mixtures thereof, and one or more selected from the group consisting of these can be used, but must be It is not limited to this.
상기 바인더는 통상적으로 양극 총 중량 100 중량부를 기준으로 1 내지 50 중량부, 바람직하게는 3 내지 15 중량부 첨가된다. 상기 바인더의 함량이 1 중량부 미만이면 양극 활물질과 집전체와의 접착력이 불충분해질 수 있고, 50 중량부를 초과하면 접착력은 향상되지만 그만큼 양극 활물질의 함량이 감소하여 전지 용량이 낮아질 수 있다.The binder is usually 1 to 50 parts by weight, preferably 3 to 15 parts by weight based on 100 parts by weight of the total positive electrode. If the content of the binder is less than 1 part by weight, the adhesive force between the positive electrode active material and the current collector may be insufficient, and if it exceeds 50 parts by weight, the adhesive strength is improved, but the content of the positive electrode active material decreases, so that the battery capacity may be lowered.
상기 양극에 포함되는 도전재는 리튬 이차전지의 내부 환경에서 부반응을 유발하지 않고 당해 전지에 화학적 변화를 유발하지 않으면서 우수한 전기전도성을 가지는 것이라면 특별히 제한되지 않으며, 대표적으로는 흑연 또는 도전성 탄소를 사용할 수 있으며, 예컨대, 천연 흑연, 인조 흑연 등의 흑연; 카본 블랙, 아세틸렌 블랙, 케첸 블랙, 뎅카 블랙, 써멀 블랙, 채널 블랙, 퍼네이스 블랙, 램프 블랙, 서머 블랙 등의 카본블랙; 결정구조가 그라펜이나 그라파이트인 탄소계 물질; 탄소 섬유, 금속 섬유 등의 도전성 섬유; 불화 카본; 알루미늄, 니켈 분말 등의 금속 분말; 산화 아연, 티탄산 칼륨 등의 도전성 위스키; 산화 티탄 등의 도전성 산화물; 및 폴리페닐렌 유도체 등의 도전성 고분자;를 단독으로 또는 2종 이상 혼합하여 사용할 수 있으나, 반드시 이에 한정되는 것은 아니다.The conductive material included in the positive electrode is not particularly limited as long as it has excellent electrical conductivity without causing a side reaction in the internal environment of the lithium secondary battery and does not cause a chemical change in the battery, and typically graphite or conductive carbon can be used. Graphite, such as natural graphite and artificial graphite; Carbon blacks such as carbon black, acetylene black, ketjen black, denka black, thermal black, channel black, furnace black, lamp black, and summer black; A carbon-based material having a crystal structure of graphene or graphite; Conductive fibers such as carbon fibers and metal fibers; Carbon fluoride; Metal powders such as aluminum and nickel powders; Conductive whiskey such as zinc oxide and potassium titanate; Conductive oxides such as titanium oxide; And conductive polymers, such as polyphenylene derivatives; may be used alone or in combination of two or more, but is not limited thereto.
상기 도전재는 통상적으로 양극 전체 중량 100 중량부를 기준으로 0.5 내지 50 중량부, 바람직하게는 1 내지 30 중량부로 첨가된다. 도전재의 함량이 0.5 중량부 미만으로 너무 적으면 전기전도성 향상 효과를 기대하기 어렵거나 전지의 전기화학적 특성이 저하될 수 있으며, 도전재의 함량이 50 중량부를 초과하여 너무 많으면 상대적으로 양극 활물질의 양이 적어져 용량 및 에너지 밀도가 저하될 수 있다. 양극에 도전재를 포함시키는 방법은 크게 제한되지 않으며, 양극 활물질에의 코팅 등 당분야에 공지된 통상적인 방법을 사용할 수 있다. 또한, 필요에 따라, 양극 활물질에 도전성의 제2 피복층이 부가됨으로 인해 상기와 같은 도전재의 첨가를 대신할 수도 있다.The conductive material is usually added in an amount of 0.5 to 50 parts by weight, preferably 1 to 30 parts by weight based on 100 parts by weight of the total positive electrode. If the content of the conductive material is less than 0.5 part by weight, it is difficult to expect an effect of improving the electrical conductivity or the electrochemical properties of the battery may be deteriorated. If the content of the conductive material exceeds 50 parts by weight, the amount of the positive electrode active material is relatively high. Less capacity and energy density can be reduced. The method of including the conductive material in the positive electrode is not particularly limited, and a conventional method known in the art, such as coating on a positive electrode active material, can be used. In addition, if necessary, the addition of a conductive material as described above may be substituted because a conductive second coating layer is added to the positive electrode active material.
또한, 본 발명의 양극에는 그 팽창을 억제하는 성분으로서 충진제가 선택적으로 첨가될 수 있다. 이러한 충진제는 당해 전지에 화학적 변화를 유발하지 않으면서 전극의 팽창을 억제할 수 있는 것이라면 특별히 제한되는 것은 아니며, 예컨대, 폴리에틸렌, 폴리프로필렌 등의 올리핀계 중합체; 유리섬유, 탄소 섬유 등의 섬유상 물질; 등을 사용할 수 있다.Further, a filler may be selectively added to the positive electrode of the present invention as a component that inhibits its expansion. The filler is not particularly limited as long as it can suppress the expansion of the electrode without causing a chemical change in the battery, and includes, for example, olefinic polymers such as polyethylene and polypropylene; Fibrous materials such as glass fiber and carbon fiber; Etc. can be used.
상기 양극 활물질, 바인더 및 도전재 등을 분산매(용매)에 분산, 혼합시켜 슬러리를 만들고, 이를 양극 집전체 상에 도포한 후 건조 및 압연함으로써, 본 발명의 양극을 제조할 수 있다. 상기 분산매로는 NMP(N-methyl-2-pyrrolidone), DMF(Dimethyl formamide), DMSO(Dimethyl sulfoxide), 에탄올, 이소프로판올, 물 및 이들의 혼합물을 사용할 수 있으나, 반드시 이에 한정되는 것은 아니다.The positive electrode of the present invention can be prepared by dispersing and mixing the positive electrode active material, binder, and conductive material in a dispersion medium (solvent) to form a slurry, and then applying it on a positive electrode current collector, followed by drying and rolling. As the dispersion medium, NMP (N-methyl-2-pyrrolidone), DMF (Dimethyl formamide), DMSO (Dimethyl sulfoxide), ethanol, isopropanol, water, and mixtures thereof may be used, but are not limited thereto.
상기 양극 집전체로는 백금(Pt), 금(Au), 팔라듐(Pd), 이리듐(Ir), 은(Ag), 루테늄(Ru), 니켈(Ni), 스테인리스스틸(STS), 알루미늄(Al), 몰리브데늄(Mo), 크롬(Cr), 카본(C), 티타늄(Ti), 텅스텐(W), ITO(In doped SnO2), FTO(F doped SnO2), 및 이들의 합금과, 알루미늄(Al) 또는 스테인리스스틸의 표면에 카본(C), 니켈(Ni), 티타늄(Ti) 또는 은(Ag)을 표면 처리한 것 등을 사용할 수 있으나, 반드시 이에 한정되는 것은 아니다. 양극 집전체의 형태는 호일, 필름, 시트, 펀칭된 것, 다공질체, 발포체 등의 형태일 수 있다.The positive electrode current collector includes platinum (Pt), gold (Au), palladium (Pd), iridium (Ir), silver (Ag), ruthenium (Ru), nickel (Ni), stainless steel (STS), aluminum (Al ), molybdenum (Mo), chromium (Cr), carbon (C), titanium (Ti), tungsten (W), ITO (In doped SnO 2 ), FTO (F doped SnO 2 ), and alloys thereof , Surface treatment of aluminum (Al) or stainless steel with carbon (C), nickel (Ni), titanium (Ti) or silver (Ag) may be used, but is not limited thereto. The positive electrode current collector may be in the form of foil, film, sheet, punched, porous body, foam, or the like.
상기 음극은 해당 기술 분야에 알려진 통상적인 방법에 따라 제조할 수 있다. 예를 들어, 음극 활물질, 도전재, 바인더, 필요에 따라 충진제 등을 분산매(용매)에 분산, 혼합시켜 슬러리를 만들고, 이를 음극 집전체 상에 도포한 후 건조 및 압연하여 음극을 제조할 수 있다. 상기 음극 활물질로는 리튬 금속이나 리튬 합금(예컨대, 리튬과 알루미늄, 아연, 비스무스, 카드뮴, 안티몬, 실리콘, 납, 주석, 갈륨 또는 인듐 등과 같은 금속과의 합금)를 사용할 수 있다. 상기 음극 집전체로는 백금(Pt), 금(Au), 팔라듐(Pd), 이리듐(Ir), 은(Ag), 루테늄(Ru), 니켈(Ni), 스테인리스스틸(STS), 구리(Cu), 몰리브데늄(Mo), 크롬(Cr), 카본(C), 티타늄(Ti), 텅스텐(W), ITO(In doped SnO2), FTO(F doped SnO2), 및 이들의 합금과, 구리(Cu) 또는 스테인리스 스틸의 표면에 카본(C), 니켈(Ni), 티타늄(Ti) 또는 은(Ag)을 표면 처리한 것 등을 사용할 수 있으나, 반드시 이에 한정되는 것은 아니다. 음극 집전체의 형태는 호일, 필름, 시트, 펀칭된 것, 다공질체, 발포체 등의 형태일 수 있다.The cathode may be prepared according to a conventional method known in the art. For example, a negative electrode active material, a conductive material, a binder, and a filler, if necessary, can be dispersed and mixed in a dispersion medium (solvent) to make a slurry, and then coated on a negative electrode current collector, followed by drying and rolling to produce a negative electrode. . As the negative electrode active material, a lithium metal or a lithium alloy (for example, an alloy of lithium and aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin, gallium, or indium, etc.) may be used. Examples of the negative electrode current collector include platinum (Pt), gold (Au), palladium (Pd), iridium (Ir), silver (Ag), ruthenium (Ru), nickel (Ni), stainless steel (STS), and copper (Cu) ), molybdenum (Mo), chromium (Cr), carbon (C), titanium (Ti), tungsten (W), ITO (In doped SnO 2 ), FTO (F doped SnO 2 ), and alloys thereof , Surface treatment of copper (Cu) or stainless steel with carbon (C), nickel (Ni), titanium (Ti), or silver (Ag) may be used, but is not limited thereto. The shape of the negative electrode current collector may be in the form of foil, film, sheet, punched, porous body, foam, or the like.
상기 분리막은 양극과 음극 사이에 개재되어 이들 사이의 단락을 방지하고 리튬이온의 이동 통로를 제공하는 역할을 한다. 상기 분리막으로는 폴리에틸렌, 폴리프로필렌과 같은 올레핀계 폴리머, 유리섬유 등을 시트, 다중막, 미세다공성 필름, 직포 및 부직포 등의 형태로 사용할 수 있으나, 반드시 이에 한정되는 것은 아니다. 한편 전해질로서 폴리머 등의 고체 전해질(예컨대, 유기 고체 전해질, 무기 고체 전해질 등)이 사용되는 경우에는 상기 고체 전해질이 분리막을 겸할 수도 있다. 구체적으로는, 높은 이온 투과도와 기계적 강도를 가지는 절연성의 얇은 박막을 사용한다. 분리막의 기공 직경은 일반적으로 0.01 내지 10 ㎛, 두께는 일반적으로 5 내지 300 ㎛ 범위일 수 있다.The separator is interposed between the positive electrode and the negative electrode to prevent a short circuit between them and serves to provide a passage for lithium ions. As the separator, olefin-based polymers such as polyethylene and polypropylene, glass fibers, and the like can be used in the form of sheets, multi-layer membranes, microporous films, woven fabrics, and non-woven fabrics, but are not limited thereto. On the other hand, when a solid electrolyte such as a polymer (eg, an organic solid electrolyte, an inorganic solid electrolyte, etc.) is used as the electrolyte, the solid electrolyte may also serve as a separator. Specifically, an insulating thin film having high ion permeability and mechanical strength is used. The pore diameter of the separator may generally range from 0.01 to 10 μm, and the thickness may generally range from 5 to 300 μm.
상기 전해질 또는 전해액으로는 비수계 전해액(비수계 유기 용매)으로서 카보네이트, 에스테르, 에테르 또는 케톤을 단독으로 또는 2종 이상 혼합하여 사용할 수 있으나, 반드시 이에 한정되는 것은 아니다. 예를 들어, 디메틸 카보네이트, 디에틸 카보네이트, 디프로필 카보네이트, 메틸프로필 카보네이트, 에틸프로필 카보네이트, 메틸에틸 카보네이트, 에틸렌 카보네이트, 프로필렌 카보네이트, 부틸렌 카보네이트, γ-부틸로락톤, n-메틸 아세테이트, n-에틸 아세테이트, n-프로필 아세테이트, 인산 트리에스테르, 디부틸 에테르, N-메틸-2-피롤리디논, 1,2-디메톡시 에탄, 테트라히드록시 프랑(Franc), 2-메틸 테트라하이드로푸란과 같은 테트라하이드로푸란 유도체, 디메틸설폭시드, 포름아미드, 디메틸포름아미드, 디옥소런 및 그 유도체, 아세토니트릴, 니트로메탄, 포름산 메틸, 초산 메틸, 트리메톡시 메탄, 설포란, 메틸 설포란, 1,3-디메틸-2-이미다졸리디논, 프로피온산 메틸, 프로피온산 에틸 등의 비양자성 유기 용매가 사용될 수 있으나, 반드시 이에 한정되는 것은 아니다.As the electrolyte or electrolyte, a carbonate, ester, ether, or ketone may be used alone or in combination of two or more as a non-aqueous electrolyte (non-aqueous organic solvent), but is not limited thereto. For example, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, methylethyl carbonate, ethylene carbonate, propylene carbonate, butylene carbonate, γ-butylolactone, n-methyl acetate, n- Such as ethyl acetate, n-propyl acetate, phosphoric acid triester, dibutyl ether, N-methyl-2-pyrrolidinone, 1,2-dimethoxy ethane, tetrahydroxy franc, 2-methyl tetrahydrofuran Tetrahydrofuran derivatives, dimethylsulfoxide, formamide, dimethylformamide, dioxron and its derivatives, acetonitrile, nitromethane, methyl formate, methyl acetate, trimethoxymethane, sulfolane, methyl sulfolane, 1,3 -Aprotic organic solvents such as dimethyl-2-imidazolidinone, methyl propionate, and ethyl propionate may be used, but are not limited thereto.
상기 전해액에는 리튬염을 더 첨가하여 사용할 수 있으며(이른바, 리튬염 함유 비수계 전해액), 상기 리튬염으로는 비수계 전해액에 용해되기 좋은 공지의 것, 예를 들어 LiCl, LiBr, LiI, LiClO4, LiBF4, LiB10Cl10, LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiPF3(CF2CF3)3, LiAlCl4, CH3SO3Li, CF3SO3Li, (CF3SO2)2NLi, 클로로 보란 리튬, 저급 지방족 카르본산 리튬, 4 페닐 붕산 리튬, 이미드 등을 들 수 있으나, 반드시 이에 한정되는 것은 아니다. 상기 (비수계) 전해액에는 충방전 특성, 난연성 등의 개선을 목적으로, 예를 들어 피리딘, 트리에틸포스파이트, 트리에탄올아민, 환상 에테르, 에틸렌 디아민, n-글라임(glyme), 헥사 인산 트리 아미드, 니트로벤젠 유도체, 유황, 퀴논 이민 염료, N-치환 옥사졸리디논, N,N-치환 이미다졸리딘, 에틸렌글리콜 디알킬 에테르, 암모늄염, 피롤, 2-메톡시 에탄올, 삼염화 알루미늄 등이 첨가될 수도 있다. 필요에 따라서는, 불연성을 부여하기 위해 사염화탄소, 삼불화에틸렌 등의 할로겐 함유 용매를 더 포함시킬 수도 있고, 고온보존 특성을 향상시키기 위해 이산화탄산 가스를 더 포함시킬 수도 있다.A lithium salt may be further added to the electrolyte solution (so-called non-aqueous electrolyte solution containing lithium salt), and the lithium salt is a well-known one that is soluble in a non-aqueous electrolyte solution, for example, LiCl, LiBr, LiI, LiClO 4 , LiBF 4 , LiB 10 Cl 10 , LiPF 6 , LiCF 3 SO 3 , LiCF 3 CO 2 , LiAsF 6 , LiSbF 6 , LiPF 3 (CF 2 CF 3 ) 3 , LiAlCl 4 , CH 3 SO 3 Li, CF 3 SO 3 Li, (CF 3 SO 2 ) 2 NLi, lithium chloroborane, lower aliphatic lithium carboxylate, lithium 4-phenyl borate, imide, and the like, but are not limited thereto. The (non-aqueous) electrolytic solution is for the purpose of improving charge/discharge characteristics, flame retardancy, etc., for example, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme (glyme), hexaphosphate triamide , Nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxy ethanol, aluminum trichloride, etc. can be added It might be. If necessary, a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride may be further included to impart non-flammability, or carbon dioxide gas may be further included to improve high temperature storage properties.
한편, 본 발명의 리튬 이차전지는 당 분야의 통상적인 방법에 따라 제조될 수 있다. 예를 들어, 양극과 음극 사이에 다공성의 분리막을 넣고, 비수 전해액을 투입함으로써 제조할 수 있다. 본 발명에 따른 리튬 이차전지는 소형 디바이스의 전원으로 사용되는 전지 셀에 적용됨은 물론, 중대형 디바이스의 전원인 전지모듈의 단위전지로 특히 적합하게 사용될 수 있다. 이러한 측면에서, 본 발명은 또한 2개 이상이 리튬 이차전지가 전기적으로 연결(직렬 또는 병렬)되어 포함된 전지모듈을 제공한다. 상기 전지모듈에 포함되는 리튬 이차전지의 수량은, 전지모듈의 용도 및 용량 등을 고려하여 다양하게 조절될 수 있음은 물론이다.On the other hand, the lithium secondary battery of the present invention can be manufactured according to a conventional method in the art. For example, it can be produced by placing a porous separator between the positive electrode and the negative electrode, and adding a non-aqueous electrolyte. The lithium secondary battery according to the present invention is applied not only to a battery cell used as a power source for a small device, but also as a unit cell of a battery module that is a power source for a medium-sized device. In this aspect, the present invention also provides a battery module including two or more lithium secondary batteries are electrically connected (serial or parallel). Of course, the number of lithium secondary batteries included in the battery module may be variously adjusted in consideration of the use and capacity of the battery module.
나아가, 본 발명은 당 분야의 통상적인 기술에 따라 상기 전지모듈을 전기적으로 연결한 전지팩을 제공한다. 상기 전지모듈 및 전지팩은 파워 툴(Power Tool); 전기차(Electric Vehicle, EV), 하이브리드 전기차(Hybrid Electric Vehicle, HEV), 및 플러그인 하이브리드 전기차(Plug-in Hybrid Electric Vehicle, PHEV)를 포함하는 전기차; 전기 트럭; 전기 상용차; 또는 전력 저장용 시스템 중 어느 하나 이상의 중대형 디바이스 전원으로 이용 가능하나, 반드시 이에 한정되는 것은 아니다.Furthermore, the present invention provides a battery pack electrically connecting the battery modules according to conventional techniques in the art. The battery module and the battery pack are a power tool (Power Tool); An electric vehicle including an electric vehicle (EV), a hybrid electric vehicle (HEV), and a plug-in hybrid electric vehicle (PHEV); Electric truck; Electric commercial vehicles; Alternatively, the power storage system may be used as a power supply for any one or more medium and large devices, but is not limited thereto.
이하 본 발명의 이해를 돕기 위하여 바람직한 실시예를 제시하나, 이는 본 발명을 예시하는 것일 뿐, 본 발명의 범주 및 기술사상 범위 내에서 다양한 변경 및 수정이 가능함은 당업자에게 있어서 명백한 것이며, 이러한 변경 및 수정이 첨부된 특허청구범위에 속하는 것도 당연한 것이다.Hereinafter, preferred embodiments are provided to help the understanding of the present invention, but these are merely illustrative of the present invention, and it is apparent to those skilled in the art that various changes and modifications are possible within the scope and technical scope of the present invention. It is natural that the modifications fall within the scope of the appended claims.
[실시예 1] 양극 활물질의 제조 [Example 1] Preparation of positive electrode active material
먼저, 황(sulfur)과 평균입도가 57.27 ㎛이고 entangled 형상을 가지는 탄소나노튜브를 8 : 2의 중량비로 혼합한 후 155 ℃에서 30 분간 반응시켜 제1 활물질 복합체를 제조하였고, 또한, 황과 평균입도가 28.09 ㎛이고 bundle 형상을 가지는 탄소나노튜브를 6 : 4의 중량비로 혼합한 후 155 ℃에서 30 분간 반응시켜 제2 활물질 복합체를 제조하였다. 이어서, 상기 제조된 제1 활물질 복합체와 제2 활물질 복합체를 7.5 : 2.5의 중량비로 슬러리 제조 시 1,500 rpm의 속도로 교반 혼합하여, 전체 황/탄소 비율이 중량비로서 7.5 : 2.5인 양극 활물질을 제조하였다.First, a first active material composite was prepared by mixing sulfur with carbon nanotubes having an average particle size of 57.27 μm and an entangled shape in a weight ratio of 8:2, and reacting at 155° C. for 30 minutes. Carbon nanotubes having a particle size of 28.09 μm and a bundle shape were mixed at a weight ratio of 6:4, and then reacted at 155° C. for 30 minutes to prepare a second active material composite. Subsequently, the prepared first active material composite and the second active material composite were stirred and mixed at a speed of 1,500 rpm when preparing a slurry at a weight ratio of 7.5:2.5, thereby preparing a positive electrode active material having a total sulfur/carbon ratio of 7.5:2.5 as a weight ratio. .
[실시예 2] 양극 활물질의 제조 [Example 2] Preparation of positive electrode active material
평균입도가 57.27 ㎛이고 entangled 형상을 가지는 탄소나노튜브 대신 평균입도가 40.33 ㎛이고 entangled 형상을 가지는 탄소나노튜브를 사용한 것을 제외하고는, 상기 실시예 1과 동일하게 수행하여 양극 활물질을 제조하였다.A cathode active material was prepared in the same manner as in Example 1, except that a carbon nanotube having an average particle size of 40.33 μm and an entangled shape was used instead of a carbon nanotube having an average particle size of 57.27 μm and an entangled shape.
[실시예 3] 양극 활물질의 제조 [Example 3] Preparation of positive electrode active material
제1 활물질 복합체에 포함된 황과 탄소나노튜브의 함량비를 8 : 2의 중량비에서 8.5 : 1.5의 중량비로 변경하고, 제1 활물질 복합체와 제2 활물질 복합체를 7.5 : 2.5의 중량비 대신 6 : 4의 중량비로 변경하여 혼합한 것을 제외하고는, 상기 실시예 1과 동일하게 수행하여 전체 황/탄소 비율이 중량비로서 7.5 : 2.5인 양극 활물질을 제조하였다.The content ratio of sulfur and carbon nanotubes contained in the first active material composite is changed from a weight ratio of 8:2 to a weight ratio of 8.5:1.5, and the first active material composite and the second active material composite are replaced by a weight ratio of 7.5:2.5 instead of 6:4. A positive electrode active material having a total sulfur/carbon ratio of 7.5:2.5 as a weight ratio was prepared in the same manner as in Example 1, except that the mixture was changed to a weight ratio of.
[비교예 1] 양극 활물질의 제조 [Comparative Example 1] Preparation of positive electrode active material
황과 평균입도가 57.27 ㎛이고 entangled 형상을 가지는 탄소나노튜브를 7.5 : 2.5의 중량비로 혼합한 후 155 ℃에서 30 분간 반응시켜 양극 활물질을 제조하였다(즉, 상기 실시예 1의 제1 활물질 복합체).A positive electrode active material was prepared by mixing sulfur and carbon nanotubes having an average particle size of 57.27 µm and having an entangled shape in a weight ratio of 7.5: 2.5 and reacting at 155° C. for 30 minutes (ie, the first active material composite of Example 1). .
[비교예 2] 양극 활물질의 제조 [Comparative Example 2] Preparation of positive electrode active material
제1 활물질 복합체에 포함된 황과 탄소나노튜브의 함량비와 제2 활물질 복합체에 포함된 황과 탄소나노튜브의 함량비를 모두 7.5 : 2.5의 중량비로 변경한 것을 제외하고는, 상기 실시예 1과 동일하게 수행하여 전체 황/탄소 비율이 중량비로서 7.5 : 2.5인 양극 활물질을 제조하였다.Example 1, except that the content ratio of sulfur and carbon nanotubes contained in the first active material composite and the content ratio of sulfur and carbon nanotubes contained in the second active material composite were both changed to a weight ratio of 7.5:2.5. A positive electrode active material having a total sulfur/carbon ratio of 7.5:2.5 as a weight ratio was prepared in the same manner as described above.
[실시예 4~6, 비교예 3~4] 리튬-황 전지의 제조 [Examples 4 to 6 and Comparative Examples 3 to 4] Preparation of lithium-sulfur batteries
리튬-황 전지용 양극의 제조Preparation of anode for lithium-sulfur batteries
상기 실시예 1 내지 3, 비교예 1 및 2에서 각각 제조된 양극 활물질, 도전재로서 super-P 및 바인더로서 폴리비닐리덴플루오라이드(PVdF)를 88 : 5 : 7의 중량비로 혼합하고, NMP 용매에 분산시켜 슬러리를 제조한 후, 이를 알루미늄 집전체(Al foil)에 500 ㎛의 두께로 코팅한 후, 120 ℃의 진공 오븐에서 13 시간 동안 건조하여 리튬-황 전지용 양극을 제조하였다.The positive electrode active materials prepared in Examples 1 to 3 and Comparative Examples 1 and 2, super-P as a conductive material, and polyvinylidene fluoride (PVdF) as a binder were mixed in a weight ratio of 88:5:7, and NMP solvent After dispersing in a slurry to prepare it, the aluminum current collector (Al foil) was coated with a thickness of 500 μm, and then dried in a vacuum oven at 120° C. for 13 hours to prepare a positive electrode for a lithium-sulfur battery.
리튬-황 전지의 제조Preparation of lithium-sulfur batteries
상기 제조된 양극을 음극(Li metal foil)과 대면하도록 위치시킨 후, 그 사이에 폴리에틸렌 분리막을 개재시켰고, 이어서, 디메틸에테르 용매에 4 M 농도로 LiFSI가 용해된 전해액을 주입하여 리튬-황 전지를 제조하였다.After placing the prepared positive electrode to face the negative electrode (Li metal foil), a polyethylene separator was interposed therebetween, and then, a lithium-sulfur battery was injected by injecting an electrolyte solution in which LiFSI was dissolved at a concentration of 4 M in a dimethyl ether solvent. It was prepared.
[실험예 1] 전지의 수명특성 평가 [Experimental Example 1] Evaluation of battery life characteristics
상기 실시예 4 내지 6, 비교예 3 및 4에서 제조된 리튬-황 전지의 충방전 반복에 따른 잔여 용량을 확인하여, 각 리튬-황 전지의 수명특성을 평가하였다. 도 1은 본 발명의 일 실시예에 따른 리튬-황 전지와 비교예에 따른 리튬-황 전지의 수명 특성을 비교 대조한 그래프이고, 도 2는 본 발명의 일 실시예에 따른 리튬-황 전지와 비교예에 따른 리튬-황 전지의 충전 프로파일을 비교 대조한 그래프이다.The remaining capacity of the lithium-sulfur batteries prepared in Examples 4 to 6 and Comparative Examples 3 and 4 was repeated according to charging and discharging, and the life characteristics of each lithium-sulfur battery were evaluated. 1 is a graph comparing the life characteristics of a lithium-sulfur battery according to an embodiment of the present invention and a lithium-sulfur battery according to a comparative example, and FIG. 2 is a lithium-sulfur battery according to an embodiment of the present invention It is a graph comparing and comparing the charging profile of the lithium-sulfur battery according to the comparative example.
도 1 및 2에 도시된 바와 같이, 본 발명에 따라 황과 탄소재의 함량비가 상이한 2종 이상의 활물질 복합체를 양극 활물질로 적용한 리튬-황 전지(실시예 4 내지 6)는, 1종의 단일 활물질 복합체를 양극 활물질로 적용한 통상의 리튬-황 전지(비교예 3)에 비하여, 수명특성이 향상된 것을 확인할 수 있었다. 특히, 실시예에서 제조된 대부분의 전지의 경우, 도 2를 통하여 확인할 수 있듯이, 비교예 3에서 제조된 전지에 비하여 초기 방전 용량 또한 증가한 것을 알 수 있었다.1 and 2, a lithium-sulfur battery (Examples 4 to 6) in which two or more active material composites having different sulfur and carbon content ratios as a positive electrode active material according to the present invention are used as a single active material. Compared to a conventional lithium-sulfur battery (Comparative Example 3) in which the composite was used as a positive electrode active material, it was confirmed that the life characteristics were improved. In particular, it can be seen that, in the case of most of the batteries manufactured in Examples, the initial discharge capacity also increased compared to the batteries prepared in Comparative Example 3, as can be seen through FIG. 2.
한편, 두 활물질 복합체의 황-CNT 함량비를 다르게 적용한 실시예 4의 전지와, 두 활물질 복합체의 황-CNT 함량비를 동일하게 적용한 비교예 4의 전지를 비교 대조하여 본 결과, 실시예 1의 전지 성능이 실시예 2의 전지 성능 대비 우수함을 확인할 수 있었으며, 이상을 통하여, 본 발명에서와 같이 황과 탄소의 혼합 비율이 상이한 다종의 탄소-황 복합체를 적정 비율로 혼합하여 양극으로 적용하게 되면, 수명특성 등 전지의 성능이 우수해지는 것을 알 수 있다.On the other hand, compared to the battery of Example 4 to which the sulfur-CNT content ratios of the two active material composites were applied differently, and the battery of Comparative Example 4 to which the sulfur-CNT content ratios of the two active material composites were equally compared, as a result of comparison, the Example 1 It was confirmed that the battery performance was superior to the battery performance of Example 2, and through the above, when mixed with a suitable ratio of various carbon-sulfur composites having different sulfur and carbon mixing ratios as in the present invention and applied as an anode, , It can be seen that the performance of the battery, such as life characteristics, is excellent.
Claims (13)
상기 2종 이상의 활물질 복합체 중 어느 한 종의 활물질 복합체에 포함된 황과 탄소재의 함량비는 다른 종에 포함된 황과 탄소재의 함량비와 상이한 것을 특징으로 하는 리튬 이차전지용 양극 활물질.Sulfur contains a composite of two or more active materials supported on a carbon material,
A positive electrode active material for a lithium secondary battery, characterized in that the content ratio of sulfur and carbon materials contained in one of the two or more active material composites is different from the content ratio of sulfur and carbon materials contained in the other species.
(b) 상기 제조된 2종 이상의 활물질 복합체를 혼합하는 단계;를 포함하며,
상기 2종 이상의 활물질 복합체 중 어느 한 종의 활물질 복합체에 포함된 황과 탄소재의 함량비는 다른 종에 포함된 황과 탄소재의 함량비와 상이한 것을 특징으로 하는 리튬 이차전지용 양극 활물질의 제조방법.(a) mixing and reacting each of two or more carbon materials with sulfur to prepare two or more active material composites in which sulfur is supported on each of the carbon materials; And
(b) mixing the two or more active material complexes prepared above; including,
Method for producing a positive electrode active material for a lithium secondary battery, characterized in that the content ratio of sulfur and carbon materials contained in one of the two or more active material composites is different from the content ratio of sulfur and carbon materials contained in the other species. .
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