KR102690253B1 - Thermally expanded-reduced graphene oxide, manufacturing method, sulfur-carbon complex and lithium secondary battery comprising thereof - Google Patents
Thermally expanded-reduced graphene oxide, manufacturing method, sulfur-carbon complex and lithium secondary battery comprising thereof Download PDFInfo
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- KR102690253B1 KR102690253B1 KR1020180139657A KR20180139657A KR102690253B1 KR 102690253 B1 KR102690253 B1 KR 102690253B1 KR 1020180139657 A KR1020180139657 A KR 1020180139657A KR 20180139657 A KR20180139657 A KR 20180139657A KR 102690253 B1 KR102690253 B1 KR 102690253B1
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- sulfur
- graphene oxide
- thermally expanded
- reduced graphene
- positive electrode
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Abstract
본 발명은 400 내지 1200m2/g의 비표면적을 가지는 열팽창된 환원 그래핀 옥사이드, 이의 제조방법, 이를 포함하는 황-탄소 복합체 및 리튬 이차전지에 관한 것이다.The present invention relates to thermally expanded reduced graphene oxide having a specific surface area of 400 to 1200 m 2 /g, a method for producing the same, a sulfur-carbon composite containing the same, and a lithium secondary battery.
Description
본 발명은 열팽창된 환원 그래핀 옥사이드, 이의 제조방법, 이를 포함하는 황-탄소 복합체 및 리튬 이차전지에 관한 것이다.The present invention relates to thermally expanded reduced graphene oxide, a method for producing the same, a sulfur-carbon composite containing the same, and a lithium secondary battery.
탄소 원자들로만 구성된 나노 물질로 풀러렌, 탄소나노튜브, 그래핀을 포함한 흑연질 탄소 소재는 우수한 전기적 특성, 물리적 및 화학적 안정성을 가지고 있으므로 학계와 산업분야의 관심을 받고 있다.Graphite carbon materials, including fullerenes, carbon nanotubes, and graphene, which are nanomaterials composed only of carbon atoms, have excellent electrical properties, physical and chemical stability, and are attracting attention from academia and industry.
특히, 그래핀은 체적 대비 매우 높은 비표면적, 우수한 전기전도도 및 물리적 화학적 안정성으로 인해 획기적인 신소재로 각광받고 있는 물질이다. 탄소 소재 중 그래핀은 풍부하고 값이 싼 천연 혹은 합성 흑연(graphite)을 원료로 하여 화학적 산화, 박리(exfoliation) 과정 그리고 화학적 또는 열적 환원처리를 거쳐 대량생산이 가능하며 그 제조방법이 개시되어 있다.In particular, graphene is a material that is attracting attention as a groundbreaking new material due to its very high specific surface area compared to volume, excellent electrical conductivity, and physical and chemical stability. Among carbon materials, graphene can be mass-produced using abundant and inexpensive natural or synthetic graphite through chemical oxidation, exfoliation, and chemical or thermal reduction, and its manufacturing method is disclosed. .
한편, 최근 몇 년 동안 이차 전지용 전극 및 슈퍼커패시터 또는 환경 흡착제에 적용되는 탄소체의 부족한 특성 등을 보완하거나 성능 향상 효과를 유도하기 위해서 표면 활성화 및 도핑을 통한 표면 기능화가 이루어지고 있다.Meanwhile, in recent years, surface functionalization through surface activation and doping has been carried out to compensate for the insufficient properties of carbon materials applied to secondary battery electrodes, supercapacitors, or environmental adsorbents, or to induce performance improvement effects.
다만, 종래의 탄소소재를 이용하여 마이크로 입자 구조를 합성하며 조건 제어를 통한 균일한 밀도, 크기, 형태 및 조성을 제어가 어려우며 복잡한 합성 과정을 가지게 된다. 그래서, 이러한 문제점을 극복하고 간단한 합성 과정을 통한 기능화된 탄소 구조체의 개발이 필요한 시점이다.However, while synthesizing micro particle structures using conventional carbon materials, it is difficult to control uniform density, size, shape, and composition through condition control, and it requires a complicated synthesis process. Therefore, it is time to overcome these problems and develop functionalized carbon structures through a simple synthesis process.
한편, 이차전지 중에서도, 리튬-황 전지는 이론 에너지 밀도가 약 2600Wh/kg으로서, 에너지 밀도가 약 570Wh/kg인 리튬 이온 전지의 약 7배에 해당하는 높은 값을 갖는다. 또한, 리튬-황 전지의 양극 소재로 사용되고 있는 황은 자원이 풍부하여 가격이 저렴하므로 전지의 제조단가를 낮출 수 있다는 장점을 갖고 있다. 이러한 장점들로 인해, 리튬-황 전지는 높은 관심을 받고 있다.Meanwhile, among secondary batteries, lithium-sulfur batteries have a theoretical energy density of about 2600 Wh/kg, which is about 7 times higher than that of lithium-ion batteries with an energy density of about 570 Wh/kg. In addition, sulfur, which is used as a cathode material for lithium-sulfur batteries, has abundant resources and is inexpensive, so it has the advantage of lowering the manufacturing cost of the battery. Because of these advantages, lithium-sulfur batteries are receiving great attention.
상기와 같은 장점에도 불구하고, 리튬-황 전지의 전기화학 반응 중에 리튬 폴리설파이드가 중간 생성물로서 생성되어 리튬-황 전지의 수명에는 한계가 있다. 리튬-황 전지의 전기화학 반응 중에 생성되는 리튬 폴리설파이드는 유기 전해액에 대한 용해도가 높아, 방전 반응 중에 지속적으로 유기 전해액에 용해된다. 이에 따라, 황을 포함하는 양극 소재의 양이 감소하여 전지 자체의 수명이 저하되는 문제가 있다. 또한, 황 자체가 전기전도도가 매우 낮기 때문에, 양극 재료로 황만을 사용할 수가 없어 전도성 카본 및 고분자 등의 전도성 소재를 함께 이용하여 복합체를 만들거나, 이들에 황을 코팅하는 기술이 필수적으로 요구된다. 이와 같이 양극 활물질로서 황만을 사용할 수 없고 황 이외의 다른 전도성 소재가 함께 포함되기 때문에, 셀 전체의 에너지 밀도가 저하되는 문제가 있다. 이를 해결하기 위해서, 양극 재료 내의 황의 함량을 최대화시키는 반면, 전도성 소재의 함량을 최소화시키며, 전도성 소재에 황을 고르게 담지시켜야 한다.Despite the above advantages, there is a limit to the lifespan of the lithium-sulfur battery because lithium polysulfide is generated as an intermediate product during the electrochemical reaction of the lithium-sulfur battery. Lithium polysulfide produced during the electrochemical reaction of a lithium-sulfur battery has high solubility in the organic electrolyte solution, and is continuously dissolved in the organic electrolyte solution during the discharge reaction. Accordingly, there is a problem that the amount of cathode material containing sulfur decreases and the lifespan of the battery itself decreases. In addition, since sulfur itself has very low electrical conductivity, sulfur alone cannot be used as an anode material, so a technology for making a composite using conductive materials such as conductive carbon and polymer, or coating them with sulfur, is essential. As such, since only sulfur cannot be used as the positive electrode active material and other conductive materials other than sulfur are also included, there is a problem that the energy density of the entire cell is lowered. To solve this problem, the sulfur content in the positive electrode material must be maximized, while the content of the conductive material must be minimized, and the sulfur must be evenly supported on the conductive material.
상기의 문제를 해결하기 위하여 많은 연구가 지속적으로 요구되고 있다. Much research is continuously required to solve the above problems.
그래핀 옥사이드를 열처리하여 팽창 및 환원시키면 비표면적 및 기공 부피가 증가하여 그래핀 옥사이드에 담지되는 황의 함량을 증가시키며, 황의 담지를 고르게 할 수 있다는 것을 확인하여 본 발명을 완성하게 되었다.The present invention was completed by confirming that when graphene oxide is expanded and reduced by heat treatment, the specific surface area and pore volume increase, thereby increasing the content of sulfur supported in graphene oxide, and evenly supporting sulfur.
따라서, 본 발명은 높은 비표면적 및 기공 부피를 가지는 열팽창된 환원 그래핀 옥사이드(Thermally expanded-reduced graphene oxide, TE-rGO) 및 이의 제조방법을 제공하는 것을 목적으로 한다.Therefore, the purpose of the present invention is to provide thermally expanded-reduced graphene oxide (TE-rGO) with high specific surface area and pore volume and a method for manufacturing the same.
또한, 본 발명은 상기 열팽창된 환원 그래핀 옥사이드 및 황을 포함하는 황-탄소 복합체 및 이를 양극 활물질로 포함하는 리튬 이차전지를 제공하는 것을 목적으로 한다.Additionally, the present invention aims to provide a sulfur-carbon composite containing the thermally expanded reduced graphene oxide and sulfur and a lithium secondary battery containing the same as a positive electrode active material.
상기 목적을 달성하기 위하여,In order to achieve the above purpose,
본 발명은 비표면적이 400 내지 1200m2/g인 열팽창된 환원 그래핀 옥사이드(Thermally expanded-reduced graphene oxide, TE-rGO)를 제공한다.The present invention provides thermally expanded-reduced graphene oxide (TE-rGO) having a specific surface area of 400 to 1200 m 2 /g.
또한, 본 발명은 (a)그래핀 옥사이드를 300 내지 500℃의 온도로 열처리하여 열팽창시키는 단계; 및In addition, the present invention includes the steps of (a) thermally expanding graphene oxide by heat treatment at a temperature of 300 to 500°C; and
(b)상기 열팽창된 그래핀 옥사이드를 700 내지 1200℃의 온도로 열처리하여 환원시키는 단계;를 포함하는 열팽창된 환원 그래핀 옥사이드 제조방법을 제공한다.(b) reducing the thermally expanded graphene oxide by heat treatment at a temperature of 700 to 1200°C; providing a method for producing thermally expanded reduced graphene oxide comprising a.
또한, 본 발명은 상기 본 발명의 열팽창된 환원 그래핀 옥사이드; 및In addition, the present invention relates to the thermally expanded reduced graphene oxide of the present invention; and
상기 열팽창된 환원 그래핀 옥사이드의 내부 및 표면 중 적어도 일부에 황;을 포함하는 황-탄소 복합체를 제공한다.Provided is a sulfur-carbon composite containing sulfur on at least a portion of the interior and surface of the thermally expanded reduced graphene oxide.
또한, 본 발명은 양극; 음극; 상기 양극과 음극 사이에 개재되는 분리막; 및 전해액을 포함하는 리튬 이차전지로,In addition, the present invention is an anode; cathode; A separator interposed between the anode and the cathode; and a lithium secondary battery containing an electrolyte,
상기 양극은 상기 본 발명의 황-탄소 복합체를 포함하는 리튬 이차전지를 제공한다.The positive electrode provides a lithium secondary battery containing the sulfur-carbon composite of the present invention.
본 발명의 열팽창된 환원 그래핀 옥사이드(Thermally expanded-reduced graphene oxide, TE-rGO)는 높은 비표면적 및 기공 부피를 가짐에 따라, 많은 양의 황을 담지할 수 있고, 황의 담지를 고르게 할 수 있다.The thermally expanded-reduced graphene oxide (TE-rGO) of the present invention has a high specific surface area and pore volume, so it can support a large amount of sulfur and evenly support sulfur. .
따라서, 상기 열팽창된 환원 그래핀 옥사이드의 내부 및 표면 중 적어도 일부에 황을 포함하는 황-탄소 복합체를 양극 활물질로 포함하는 리튬 이차전지는 황의 반응성을 향상시킬 수 있어 우수한 초기 방전용량 및 수명특성을 나타낼 수 있다.Therefore, a lithium secondary battery containing a sulfur-carbon complex containing sulfur on at least a portion of the interior and surface of the thermally expanded reduced graphene oxide as a positive electrode active material can improve the reactivity of sulfur, resulting in excellent initial discharge capacity and lifespan characteristics. It can be expressed.
도 1은 본 발명의 열팽창된 환원 그래핀 옥사이드의 SEM 사진이다.
도 2는 환원 그래핀 옥사이드의 SEM 사진이다.
도 3은 실시예 1의 열팽창된 환원 그래핀 옥사이드(Thermally expanded-reduced graphene oxide, TE-rGO) 및 비교예 1(reduced graphene oxide, rGO)의 환원 그래핀 옥사이드의 평균 기공 크기에 따른 기공 부피를 측정한 그래프이다.
도 4는 실험예 2의 초기 방전용량을 측정한 그래프이다.
도 5는 실험예 2의 전지의 수명 특성을 측정한 그래프이다.Figure 1 is an SEM photograph of thermally expanded reduced graphene oxide of the present invention.
Figure 2 is an SEM photo of reduced graphene oxide.
Figure 3 shows the pore volume according to the average pore size of the thermally expanded-reduced graphene oxide (TE-rGO) of Example 1 and the reduced graphene oxide of Comparative Example 1 (reduced graphene oxide (rGO)). This is a measured graph.
Figure 4 is a graph measuring the initial discharge capacity of Experimental Example 2.
Figure 5 is a graph measuring the lifespan characteristics of the battery of Experimental Example 2.
이하, 본 발명을 보다 자세히 설명한다.Hereinafter, the present invention will be described in more detail.
열팽창된 환원 그래핀 옥사이드Thermally expanded reduced graphene oxide
본 발명은 비표면적이 400 내지 1200m2/g인 열팽창된 환원 그래핀 옥사이드(Thermally expanded-reduced graphene oxide, TE-rGO)에 관한 것이다.The present invention relates to thermally expanded-reduced graphene oxide (TE-rGO) with a specific surface area of 400 to 1200 m 2 /g.
상기 열팽창된 환원 그래핀 옥사이드는 그래핀 옥사이드(graphene oxide)를 열처리하여 열팽창된 그래핀 옥사이드를 제조한 후, 상기 열팽창된 그래핀 옥사이드를 다시 열처리하여 환원시킴으로써 제조된 것일 수 있다.The thermally expanded reduced graphene oxide may be manufactured by heat treating graphene oxide to produce thermally expanded graphene oxide, and then heat treating the thermally expanded graphene oxide again to reduce it.
본 발명에서는 상기와 같이 열팽창 및 환원 단계를 거쳐 제조된 그래핀 옥사이드를 열팽창된 환원 그래핀 옥사이드(Thermally expanded-reduced graphene oxide, TE-rGO)로 정의한다.In the present invention, graphene oxide prepared through the thermal expansion and reduction steps as described above is defined as thermally expanded-reduced graphene oxide (TE-rGO).
본 발명에서 상기 열팽창된 환원 그래핀 옥사이드는 황을 담지할 수 있는 담지체로 사용될 수 있으며, 상기의 비표면적 및 기공부피를 가짐으로써 보다 많은 양의 황을 담지할 수 있을 뿐만 아니라, 내부 기공 및 표면에 황을 고르게 담지할 수 있다. In the present invention, the thermally expanded reduced graphene oxide can be used as a carrier capable of supporting sulfur, and by having the above specific surface area and pore volume, not only can a larger amount of sulfur be supported, but also internal pores and surface Sulfur can be evenly supported.
만약, 탄소재의 내부 및 표면 중 적어도 일부에 황이 담지된 황-탄소 복합체에서 황의 담지량이 너무 적을 경우, 황-탄소 복합체의 탄소재 비율이 늘어나 전지의 에너지 밀도가 저하될 수 있다. 또한, 황이 고르게 담지되지 못하면 탄소재의 표면을 황이 덮고 있어 황-탄소 복합체의 전기 전도도가 감소하는 문제가 발생할 수 있다.If the amount of sulfur supported in a sulfur-carbon composite in which sulfur is supported on at least part of the interior and surface of the carbon material is too small, the proportion of carbon material in the sulfur-carbon composite may increase and the energy density of the battery may decrease. In addition, if sulfur is not evenly contained, the surface of the carbon material may be covered with sulfur, which may cause a problem in which the electrical conductivity of the sulfur-carbon composite is reduced.
그러나, 상기 열팽창된 환원 그래핀 옥사이드의 내부 및 표면 중 적어도 일부에 황이 담지된 황-탄소 복합체는 많은 양의 황을 고르게 담지시킬 수 있으며, 그에 따라 이를 양극 활물질로 사용하는 리튬 이차전지의 반응성을 향상시켜 우수한 초기 방전용량 및 수명특성을 구현할 수 있다.However, the sulfur-carbon composite in which sulfur is supported on at least a portion of the interior and surface of the thermally expanded reduced graphene oxide can evenly support a large amount of sulfur, thereby improving the reactivity of a lithium secondary battery using it as a positive electrode active material. By improving it, excellent initial discharge capacity and lifespan characteristics can be realized.
구체적으로, 상기 열팽창된 환원 그래핀 옥사이드의 비표면적은 400 내지 1200m2/g이고, 바람직하게는 600 내지 1200m2/g, 보다 바람직하게는 800 내지 1200m2/g일 수 있다.Specifically, the specific surface area of the thermally expanded reduced graphene oxide may be 400 to 1200 m 2 /g, preferably 600 to 1200 m 2 /g, and more preferably 800 to 1200 m 2 /g.
상기 비표면적이 400 내지 1200m2/g이면 열팽창된 환원 그래핀 옥사이드에 많은 양의 황을 고르게 담지시킬 수 있다.If the specific surface area is 400 to 1200 m 2 /g, a large amount of sulfur can be evenly supported on the thermally expanded reduced graphene oxide.
또한, 상기 열팽창된 환원 그래핀 옥사이드의 기공 부피는 3 내지 7cm3/g이고, 바람직하게는 4 내지 6cm3/g일 수 있다.Additionally, the pore volume of the thermally expanded reduced graphene oxide may be 3 to 7 cm 3 /g, and preferably 4 to 6 cm 3 /g.
상기 기공부피가 3 내지 7cm2/g이면 열팽창된 환원 그래핀 옥사이드에 많은 양의 황을 고르게 담지시킬 수 있다.If the pore volume is 3 to 7 cm 2 /g, a large amount of sulfur can be evenly supported on the thermally expanded reduced graphene oxide.
상기 본 발명의 열팽창된 환원 그래핀 옥사이드는 열팽창 및 환원 단계를 거쳐 제조됨으로써 뒤틀린(crumpled) 페이퍼 구조를 가질 수 있다.The thermally expanded reduced graphene oxide of the present invention may have a crumpled paper structure by being manufactured through thermal expansion and reduction steps.
상기 뒤틀린 페이퍼 구조를 가짐에 따라 상기와 같이 높은 비표면적 및 기공 부피를 가질 수 있으며, 그에 따라 상술한 효과를 나타낼 수 있다.By having the twisted paper structure, it is possible to have a high specific surface area and pore volume as described above, thereby exhibiting the above-mentioned effects.
열팽창된 환원 그래핀 옥사이드 제조방법Method for manufacturing thermally expanded reduced graphene oxide
또한, 본 발명은 열팽창된 환원 그래핀 옥사이드(Thermally expanded-reduced graphene oxide, TE-rGO)의 제조방법에 관한 것으로, In addition, the present invention relates to a method for producing thermally expanded-reduced graphene oxide (TE-rGO),
(a)그래핀 옥사이드를 300 내지 500℃의 온도로 열처리하여 열팽창시키는 단계; 및(a) thermally expanding graphene oxide by heat treatment at a temperature of 300 to 500°C; and
(b)상기 열팽창된 그래핀 옥사이드를 700 내지 1200℃의 온도로 열처리하여 환원시키는 단계;를 포함한다.(b) reducing the thermally expanded graphene oxide by heat treatment at a temperature of 700 to 1200°C.
상기 (a)단계는 그래핀 옥사이드(graphene oxide)를 열처리하여 열팽창시키는 단계이다.Step (a) is a step of thermally expanding graphene oxide by heat treatment.
상기 열처리를 수행함에 따라 그래핀 옥사이드의 산소 작용기(oxygen functional group)가 용이하게 제거되어 그래핀 옥사이드의 열팽창이 용이하게 일어날 수 있다. 그래핀 옥사이드의 열팽창이 일어나면 그래핀 옥사이드의 산소 작용기(oxygen functional group)가 열(thermal shock)에 의해 제거되어 팽창된 뒤틀린(crumpled) 페이퍼 구조를 가질 수 있다. As the heat treatment is performed, the oxygen functional group of the graphene oxide is easily removed, so that thermal expansion of the graphene oxide can easily occur. When thermal expansion of graphene oxide occurs, the oxygen functional group of the graphene oxide is removed by thermal shock, resulting in an expanded, crumpled paper structure.
상기 (a)단계의 그래핀 옥사이드는 파우더 형태일 수 있다.The graphene oxide in step (a) may be in powder form.
필름 형태의 그래핀 옥사이드는 적층 구조(stacked structure)를 가지므로 목적하고자 하는 비표면적을 가지는 열팽창된 환원 그래핀 옥사이드를 얻을 수 없다. 따라서, 본 발명에서는 파우더 형태의 그래핀 옥사이드를 사용하는 것이 바람직하다.Since graphene oxide in the form of a film has a stacked structure, thermally expanded reduced graphene oxide having the desired specific surface area cannot be obtained. Therefore, in the present invention, it is preferable to use graphene oxide in powder form.
또한, 상기 열처리는 300 내지 500℃의 온도로 5 내지 30분 동안 수행될 수 있으며, 바람직하게는 350 내지 450℃의 온도로 5 내지 15분 동안 수행될 수 있다.Additionally, the heat treatment may be performed at a temperature of 300 to 500°C for 5 to 30 minutes, and preferably may be performed at a temperature of 350 to 450°C for 5 to 15 minutes.
상기 열처리 온도 및 시간이 상기 범위 미만이면 그래핀 옥사이드의 열팽창이 충분히 일어나지 않아 높은 비표면적을 얻을 수 없고, 상기 범위를 초과하면 수득율(yield)이 저하될 수 있다.If the heat treatment temperature and time are less than the above range, thermal expansion of graphene oxide does not occur sufficiently and a high specific surface area cannot be obtained, and if it exceeds the above range, the yield may be reduced.
상기 (b)단계는 상기 (a)단계에서 제조된 열팽창된 그래핀 옥사이드를 열처리하여 환원시키는 단계이다.Step (b) is a step of reducing the thermally expanded graphene oxide prepared in step (a) by heat treatment.
상기 (b)단계에서 추가적인 열처리를 수행함에 따라 열팽창된 그래핀 옥사이드의 환원 과정이 일어나며, 그에 따라 최종적으로 뒤틀린(crumpled) 페이퍼 구조의 열팽창된 환원 그래핀 옥사이드를 얻을 수 있다.As additional heat treatment is performed in step (b), a reduction process of the thermally expanded graphene oxide occurs, and thus the thermally expanded reduced graphene oxide with a final crumpled paper structure can be obtained.
또한, 상기 열처리는 700 내지 1200℃의 온도로 1 내지 5시간 동안 수행될 수 있으며, 바람직하게는 800 내지 1000℃의 온도로 2 내지 4시간 동안 수행될 수 있다.Additionally, the heat treatment may be performed at a temperature of 700 to 1200°C for 1 to 5 hours, and preferably may be performed at a temperature of 800 to 1000°C for 2 to 4 hours.
상기 열처리 온도 및 시간이 상기 범위 미만이면 열팽창된 그래핀 옥사이드의 열팽창이 충분히 일어나지 않아 높은 비표면적을 얻을 수 없고, 상기 범위를 초과하면 수득율(yield)이 저하될 수 있다.If the heat treatment temperature and time are less than the above range, thermal expansion of the thermally expanded graphene oxide does not occur sufficiently and a high specific surface area cannot be obtained, and if it exceeds the above range, the yield may be reduced.
상기 열팽창된 환원 그래핀 옥사이드는 열팽창 및 환원 단계를 거쳐 뒤틀린 페이퍼 구조를 가지게 되며, 그에 따라 높은 비표면적 및 기공 부피를 나타낼 수 있다.The thermally expanded reduced graphene oxide undergoes thermal expansion and reduction steps to have a twisted paper structure, and thus can exhibit high specific surface area and pore volume.
본 발명의 제조방법으로 제조된 열팽창된 환원 그래핀 옥사이드는 황을 담지할 수 있는 담지체로 사용될 수 있으며, 높은 비표면적 및 기공 부피를 가짐에 따라 많은 양의 황을 고르게 담지할 수 있다. 따라서, 상기 열팽창된 환원 그래핀 옥사이드의 내부 및 표면 중 적어도 일부에 황이 담지된 황-탄소 복합체는 많은 양의 황을 고르게 담지시킬 수 있으며, 그에 따라 이를 양극 활물질로 사용하는 리튬 이차전지의 반응성을 향상시켜 우수한 초기 방전용량 및 수명특성을 구현할 수 있다.The thermally expanded reduced graphene oxide produced by the production method of the present invention can be used as a carrier capable of supporting sulfur, and can evenly support a large amount of sulfur as it has a high specific surface area and pore volume. Therefore, the sulfur-carbon composite in which sulfur is supported on at least a portion of the interior and surface of the thermally expanded reduced graphene oxide can evenly support a large amount of sulfur, thereby improving the reactivity of a lithium secondary battery using it as a positive electrode active material. By improving it, excellent initial discharge capacity and lifespan characteristics can be realized.
보다 자세하게는, 상기 열팽창된 환원 그래핀 옥사이드의 비표면적은 400 내지 1200m2/g이고, 바람직하게는 600 내지 1200m2/g, 보다 바람직하게는 800 내지 1200m2/g일 수 있다.More specifically, the specific surface area of the thermally expanded reduced graphene oxide may be 400 to 1200 m 2 /g, preferably 600 to 1200 m 2 /g, and more preferably 800 to 1200 m 2 /g.
상기 비표면적이 400 내지 1200m2/g이면 열팽창된 환원 그래핀 옥사이드에 많은 양의 황을 고르게 담지시킬 수 있다.If the specific surface area is 400 to 1200 m 2 /g, a large amount of sulfur can be evenly supported on the thermally expanded reduced graphene oxide.
또한, 상기 열팽창된 환원 그래핀 옥사이드의 기공 부피는 3 내지 7cm3/g이고, 바람직하게는 4 내지 6cm3/g일 수 있다.Additionally, the pore volume of the thermally expanded reduced graphene oxide may be 3 to 7 cm 3 /g, and preferably 4 to 6 cm 3 /g.
상기 기공부피가 3 내지 7cm2/g이면 열팽창된 환원 그래핀 옥사이드에 많은 양의 황을 고르게 담지시킬 수 있다.If the pore volume is 3 to 7 cm 2 /g, a large amount of sulfur can be evenly supported on the thermally expanded reduced graphene oxide.
황-탄소 복합체sulfur-carbon complex
본 발명은 열팽창된 환원 그래핀 옥사이드; 및 상기 열팽창된 환원 그래핀 옥사이드의 내부 및 표면 중 적어도 일부에 황;을 포함하는 황-탄소 복합체에 관한 것이다.The present invention relates to thermally expanded reduced graphene oxide; and sulfur on at least a portion of the interior and surface of the thermally expanded reduced graphene oxide.
상기 열팽창된 환원 그래핀 옥사이드는 상술한 바와 동일하며, 상술한 제조방법으로 제조된 것일 수 있다.The thermally expanded reduced graphene oxide is the same as described above, and may be manufactured using the manufacturing method described above.
상기 황은 황 원소(Elemental sulfur, S8), 유기황 화합물 Li2Sn(n≥1) 및 탄소-황 폴리머((C2Sx)n: x=2.5 ~ 50, n≥2) 이루어진 군으로부터 선택된 1종 이상일 수 있다. 바람직하게는 무기 황(S8)을 사용할 수 있다.The sulfur is a group consisting of elemental sulfur (S 8 ), organic sulfur compound Li 2 S n (n≥1), and carbon-sulfur polymer ((C 2 S x ) n : x=2.5 to 50, n≥2) It may be one or more types selected from. Preferably, inorganic sulfur (S 8 ) can be used.
본 발명에 따른 황-탄소 복합체에서 열팽창된 환원 그래핀 옥사이드와 황은 1:1 내지 1:9의 중량비로 혼합되는 것이 바람직하다. 열팽창된 환원 그래핀 옥사이드의 함량이 상기 범위를 초과하면 활물질인 황의 함량이 낮아져 전지 용량 확보에 있어서 문제가 발생하고, 상기 범위 미만이면 열팽창된 환원 그래핀 옥사이드의 함량이 전기 전도도를 부여하기에 부족하게 되므로, 상기 범위 내에서 적절히 조절한다.In the sulfur-carbon composite according to the present invention, the thermally expanded reduced graphene oxide and sulfur are preferably mixed at a weight ratio of 1:1 to 1:9. If the content of thermally expanded reduced graphene oxide exceeds the above range, the content of sulfur, which is an active material, decreases, causing problems in securing battery capacity. If it is less than the above range, the content of thermally expanded reduced graphene oxide is insufficient to provide electrical conductivity. Therefore, adjust appropriately within the above range.
본 발명의 황-탄소 복합체의 복합화 방법은 본 발명에서 특별히 한정하지 않으며 당 업계에서 통상적으로 사용되는 방법이 사용될 수 있다. 일례로, 상기 본 발명의 열팽창된 환원 그래핀 옥사이드와 황을 단순 혼합한 다음 열처리하여 복합화 하는 방법이 사용될 수 있다.The method of complexing the sulfur-carbon complex of the present invention is not particularly limited in the present invention, and methods commonly used in the art may be used. For example, a method of simply mixing the thermally expanded reduced graphene oxide and sulfur of the present invention and then heat treating them to form a composite may be used.
상기 황은 열팽창된 환원 그래핀 옥사이드의 내부 및 표면 중 적어도 일부에 담지되어 있으며, 표면 보다는 내부에 보다 많은 양의 황이 담지되어 있다.The sulfur is supported on at least part of the interior and surface of the thermally expanded reduced graphene oxide, and a larger amount of sulfur is supported on the inside than on the surface.
본 발명에서 열팽창된 환원 그래핀 옥사이드의 내부는 열팽창된 환원 그래핀 옥사이드의 기공을 의미한다.In the present invention, the interior of the thermally expanded reduced graphene oxide refers to the pores of the thermally expanded reduced graphene oxide.
본 발명의 황-탄소 복합체의 직경은 본 발명에서 특별히 한정하지 않으며, 다양할 수 있으나, 바람직하게는 0.1 내지 20μm, 보다 바람직하게는 1 내지 10 μm 일 수 있다. 상기 범위를 만족할 때, 고로딩의 전극을 제조할 수 있다.The diameter of the sulfur-carbon composite of the present invention is not particularly limited in the present invention and may vary, but is preferably 0.1 to 20 μm, more preferably 1 to 10 μm. When the above range is satisfied, a high loading electrode can be manufactured.
상기 황-탄소 복합체는 탄소재로 상술한 본 발명의 열팽창된 환원 그래핀 옥사이드를 사용하므로, 종래의 환원 그래핀 옥사이드 대비 많은 양의 황을 고르게 담지시킬 수 있다. 따라서, 본 발명의 황-탄소 복합체를 포함하는 리튬 이차전지는 초기 방전용량 및 수명특성 향상 효과를 가질 수 있다.Since the sulfur-carbon composite uses the thermally expanded reduced graphene oxide of the present invention described above as a carbon material, a large amount of sulfur can be evenly supported compared to the conventional reduced graphene oxide. Therefore, the lithium secondary battery containing the sulfur-carbon composite of the present invention may have the effect of improving initial discharge capacity and lifespan characteristics.
리튬 이차전지Lithium secondary battery
본 발명은 양극; 음극; 상기 양극과 음극 사이에 개재되는 분리막; 및 전해액을 포함하는 리튬 이차전지로,The present invention is an anode; cathode; A separator interposed between the anode and the cathode; and a lithium secondary battery containing an electrolyte,
상기 양극은 상기 본 발명의 황-탄소 복합체를 양극 활물질로 포함한다.The positive electrode includes the sulfur-carbon composite of the present invention as a positive electrode active material.
상기 황-탄소 복합체를 양극 활물질로 포함함에 따라, 본 발명의 리튬 이차전지는 리튬-황 전지일 수 있다.By including the sulfur-carbon composite as the positive electrode active material, the lithium secondary battery of the present invention may be a lithium-sulfur battery.
상기 양극은 양극 집전체와 상기 양극 집전체의 일면 또는 양면에 도포된 양극 활물질층을 포함할 수 있다.The positive electrode may include a positive electrode current collector and a positive electrode active material layer applied to one or both sides of the positive electrode current collector.
상기 양극 집전체는 양극 활물질을 지지하며, 당해 전지에 화학적 변화를 유발하지 않으면서 높은 도전성을 가지는 것이라면 특별히 제한되는 것은 아니다. 예를 들어, 구리, 스테인리스 스틸, 알루미늄, 니켈, 티타늄, 팔라듐, 소성 탄소, 구리나 스테인리스 스틸 표면에 카본, 니켈, 은 등으로 표면 처리한 것, 알루미늄-카드뮴 합금 등이 사용될 수 있다.The positive electrode current collector supports the positive electrode active material and is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, palladium, calcined carbon, surface treatment of copper or stainless steel with carbon, nickel, silver, etc., aluminum-cadmium alloy, etc. can be used.
상기 양극 집전체는 그것의 표면에 미세한 요철을 형성하여 양극 활물질과의 결합력을 강화시킬 수 있으며, 필름, 시트, 호일, 메쉬, 네트, 다공질체, 발포체, 부직포체 등 다양한 형태를 사용할 수 있다.The positive electrode current collector can strengthen the bonding force with the positive electrode active material by forming fine irregularities on its surface, and can be used in various forms such as film, sheet, foil, mesh, net, porous material, foam, and non-woven fabric.
상기 양극 활물질층은 양극 활물질, 바인더 및 도전재를 포함할 수 있다.The positive electrode active material layer may include a positive electrode active material, a binder, and a conductive material.
상기 양극 활물질은 상술한 본 발명의 황-탄소 복합체를 포함한다.The positive electrode active material includes the sulfur-carbon composite of the present invention described above.
상술한 바와 같이, 황-탄소 복합체의 탄소재는 본 발명의 열팽창된 환원 그래핀 옥사이드이고, 높은 비표면적 및 기공 부피를 가짐에 따라 보다 많은 양의 황을 고르게 담지할 수 있다. 따라서, 본 발명에서 양극의 황의 로딩량은 2 내지 15mg/cm2일 수 있으며, 바람직하게는 6 내지 10mg/cm2일 수 있다. 이와 같이 높은 로딩량을 가짐에 따라 상기 양극을 포함하는 리튬 이차전지는 초기 방전용량 및 수명 특성 효과를 나타낼 수 있다.As described above, the carbon material of the sulfur-carbon composite is the thermally expanded reduced graphene oxide of the present invention, and has a high specific surface area and pore volume, so it can evenly support a larger amount of sulfur. Therefore, in the present invention, the sulfur loading amount of the anode may be 2 to 15 mg/cm 2 , and preferably 6 to 10 mg/cm 2 . With such a high loading amount, the lithium secondary battery including the positive electrode can exhibit effects on initial discharge capacity and lifespan characteristics.
상기 양극은 상기 양극 활물질 이외에 전이금속 원소, ⅢA족 원소, ⅣA족 원소, 이들 원소들의 황 화합물, 및 이들 원소들과 황의 합금 중에서 선택되는 하나 이상의 첨가제를 더 포함할 수 있다.In addition to the positive electrode active material, the positive electrode may further include one or more additives selected from transition metal elements, Group IIIA elements, Group IVA elements, sulfur compounds of these elements, and alloys of these elements and sulfur.
상기 전이금속 원소로는 Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Os, Ir, Pt, Au 또는 Hg 등이 포함되고, 상기 ⅢA족 원소로는 Al, Ga, In, Ti 등이 포함되며, 상기 ⅣA족 원소로는 Ge, Sn, Pb 등이 포함될 수 있다.The transition metal elements include Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Os, Ir, Pt, Au or Hg, etc. are included, the group IIIA elements include Al, Ga, In, Ti, etc., and the group IVA elements may include Ge, Sn, Pb, etc.
상기 도전재는 전기 전도성을 향상시키기 위한 것으로, 리튬 이차전지에서 화학변화를 일으키지 않는 전자 전도성 물질이면 특별한 제한이 없다.The conductive material is intended to improve electrical conductivity, and there is no particular limitation as long as it is an electronically conductive material that does not cause chemical changes in a lithium secondary battery.
일반적으로 카본블랙(carbon black), 흑연, 탄소섬유, 카본 나노튜브, 금속 분말, 도전성 금속산화물, 유기 도전재 등을 사용할 수 있고, 현재 도전재로 시판되고 있는 상품으로는 아세틸렌 블랙계열(쉐브론 케미컬 컴퍼니(Chevron Chemical Company) 또는 걸프 오일 컴퍼니(Gulf Oil Company) 제품 등), 케트젠 블랙(Ketjen Black) EC 계열 (아르막 컴퍼니(Armak Company) 제품), 불칸(Vulcan) XC-72(캐보트 컴퍼니(Cabot Company) 제품) 및 수퍼 P(엠엠엠(MMM)사 제품) 등이 있다. 예를 들면 아세틸렌블랙, 카본블랙, 흑연 등을 들 수 있다.In general, carbon black, graphite, carbon fiber, carbon nanotubes, metal powder, conductive metal oxide, organic conductive materials, etc. can be used. Products currently sold as conductive materials include acetylene black series (Chevron Chemical) Company (Chevron Chemical Company or Gulf Oil Company products, etc.), Ketjen Black EC series (Armak Company product), Vulcan XC-72 (Cabot Company) (Cabot Company) and Super P (MMM). Examples include acetylene black, carbon black, and graphite.
또한, 상기 양극 활물질은 양극 활물질을 양극 집전체에 유지시키고, 활물질 사이를 이어주는 기능을 갖는 바인더를 포함할 수 있다. 상기 바인더로서, 예를 들면, 폴리비닐리덴 풀루오라이드-헥사풀루오로프로필렌(PVDF-co-HFP), 폴리비닐리덴 풀루오라이드(polyvinylidene fluoride, PVDF), 폴리아크릴로니트릴(polyacrylonitrile), 폴리메틸 메타크릴레이트(polymethyl methacrylate), 스티렌-부타디엔 고무(styrene butadiene rubber, SBR), 카르복실 메틸 셀룰로오스(carboxyl methyl cellulose, CMC) 등의 다양한 종류의 바인더가 사용될 수 있다.Additionally, the positive electrode active material may include a binder that has the function of maintaining the positive electrode active material in the positive electrode current collector and connecting the active materials. As the binder, for example, polyvinylidene fluoride-hexafluoropropylene (PVDF-co-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, poly Various types of binders can be used, such as methyl methacrylate, styrene-butadiene rubber (SBR), and carboxyl methyl cellulose (CMC).
상기와 같은 양극은 통상의 방법에 따라 제조될 수 있으며, 구체적으로는 양극 활물질과 도전재 및 바인더를 유기 용매 상에서 혼합하여 제조한 슬러리 상태의 양극 활물질층 형성용 조성물을 집전체 위에 도포 및 건조하고, 선택적으로 전극 밀도의 향상을 위하여 집전체에 압축 성형하여 제조할 수 있다. 이때 상기 유기 용매로는 양극 활물질, 바인더 및 도전재를 균일하게 분산시킬 수 있으며, 쉽게 증발되는 것을 사용하는 것이 바람직하다. 구체적으로는 아세토니트릴, 메탄올, 에탄올, 테트라하이드로퓨란, 물, 이소프로필알코올 등을 들 수 있다.The positive electrode as described above can be manufactured according to a conventional method. Specifically, a composition for forming a positive active material layer in a slurry state prepared by mixing a positive active material, a conductive material, and a binder in an organic solvent is applied and dried on a current collector. , Optionally, it can be manufactured by compression molding on a current collector to improve electrode density. At this time, it is preferable to use an organic solvent that can uniformly disperse the positive electrode active material, binder, and conductive material and that evaporates easily. Specifically, acetonitrile, methanol, ethanol, tetrahydrofuran, water, isopropyl alcohol, etc. are mentioned.
상기 양극 활물질층 형성용 조성물을 양극 집전체 상에 당업계에 알려진 통상의 방법을 이용하여 코팅할 수 있으며, 예를 들면 딥핑(dipping)법, 스프레이(spray)법, 롤 코트(roll court)법, 그라비아 인쇄법, 바코트(bar court)법, 다이(die) 코팅법, 콤마(comma) 코팅법 또는 이들의 혼합 방식 등 다양한 방식을 이용할 수 있다.The composition for forming the positive electrode active material layer can be coated on the positive electrode current collector using a common method known in the art, for example, dipping method, spray method, or roll court method. A variety of methods can be used, such as gravure printing, bar court, die coating, comma coating, or a combination thereof.
이와 같은 코팅 과정을 거친 양극 활물질층은 이후 건조 과정을 통해 용매나 분산매의 증발, 코팅막의 조밀성 및 코팅막과 집전체와의 밀착성 등이 이루어진다. 이때 건조는 통상적인 방법에 따라 실시되며, 이를 특별히 제한하지 않는다.The positive active material layer that has gone through this coating process undergoes a subsequent drying process to achieve evaporation of the solvent or dispersion medium, density of the coating film, and adhesion between the coating film and the current collector. At this time, drying is carried out according to a conventional method and is not particularly limited.
상기 음극은 리튬계 금속이며, 리튬계 금속의 일 측에 집전체를 더욱 포함할 수 있다. 상기 집전체는 음극 집전체가 사용될 수 있다.The negative electrode is a lithium-based metal, and may further include a current collector on one side of the lithium-based metal. The current collector may be a negative electrode current collector.
상기 음극 집전체는 전지에 화학적 변화를 유발하지 않으면서 높은 도전성을 가지는 것이라면 특히 제한하지 않으며, 구리, 알루미늄, 스테인리스 스틸, 아연, 티타늄, 은, 팔라듐, 니켈, 철, 크롬, 이들의 합금 및 이들의 조합으로 이루어진 군으로부터 선택될 수 있다. 상기 스테인리스 스틸은 카본, 니켈, 티탄 또는 은으로 표면 처리될 수 있으며, 상기 합금으로는 알루미늄-카드뮴 합금을 사용할 수 있고, 그 외에도 소성 탄소, 도전재로 표면 처리된 비전도성 고분자, 또는 전도성 고분자 등을 사용할 수도 있다. 일반적으로 음극 집전체로는 구리 박판을 적용한다.The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and may include copper, aluminum, stainless steel, zinc, titanium, silver, palladium, nickel, iron, chromium, alloys thereof, and these. It may be selected from the group consisting of a combination of. The stainless steel may be surface treated with carbon, nickel, titanium, or silver, and the alloy may be an aluminum-cadmium alloy, and in addition, calcined carbon, a non-conductive polymer surface-treated with a conductive material, or a conductive polymer, etc. You can also use . Generally, a thin copper plate is used as the negative electrode current collector.
또한, 그 형태는 표면에 미세한 요철이 형성된/미형성된 필름, 시트, 호일, 네트, 다공질체, 발포체, 부직포체 등 다양한 형태가 사용될 수 있다.In addition, various forms may be used, such as films, sheets, foils, nets, porous materials, foams, and non-woven fabrics with or without fine irregularities formed on the surface.
또한, 상기 음극 집전체는 3 내지 500 ㎛의 두께 범위인 것을 적용한다. 상기 음극 집전체의 두께가 3 ㎛ 미만이면 집전 효과가 떨어지며, 반면 두께가 500 ㎛를 초과하면 셀을 폴딩(folding)하여 조립하는 경우 가공성이 저하되는 문제점이 있다.In addition, the negative electrode current collector is used in a thickness range of 3 to 500 ㎛. If the thickness of the negative electrode current collector is less than 3 ㎛, the current collecting effect is reduced. On the other hand, if the thickness is more than 500 ㎛, there is a problem that processability is reduced when the cell is folded and assembled.
상기 리튬계 금속은 리튬 또는 리튬 합금일 수 있다. 이때 리튬 합금은 리튬과 합금화가 가능한 원소를 포함하고, 구체적으로 리튬과 Si, Sn, C, Pt, Ir, Ni, Cu, Ti, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Sb, Pb, In, Zn, Ba, Ra, Ge 및 Al로 이루어진 군으로부터 선택되는 1종 이상과의 합금일 수 있다.The lithium-based metal may be lithium or a lithium alloy. At this time, the lithium alloy includes elements that can be alloyed with lithium, specifically lithium and Si, Sn, C, Pt, Ir, Ni, Cu, Ti, Na, K, Rb, Cs, Fr, Be, Mg, Ca, It may be an alloy with one or more types selected from the group consisting of Sr, Sb, Pb, In, Zn, Ba, Ra, Ge, and Al.
상기 리튬계 금속은 시트 또는 호일의 형태일 수 있으며, 경우에 따라 집전체 상에 리튬 또는 리튬 합금이 건식 공정에 의해 증착 또는 코팅된 형태이거나, 입자 상의 금속 및 합금이 습식 공정 등에 의해 증착 또는 코팅된 형태일 수 있다.The lithium-based metal may be in the form of a sheet or foil, and in some cases, lithium or lithium alloy may be deposited or coated on a current collector by a dry process, or metals and alloys on particles may be deposited or coated by a wet process, etc. It may be in a given form.
상기 양극과 음극 사이는 통상적인 분리막이 개재될 수 있다. 상기 분리막은 전극을 물리적으로 분리하는 기능을 갖는 물리적인 분리막으로서, 통상의 분리막으로 사용되는 것이라면 특별한 제한 없이 사용 가능하며, 특히 전해액의 이온 이동에 대하여 저저항이면서 전해액 함습 능력이 우수한 것이 바람직하다.A conventional separator may be interposed between the anode and the cathode. The separator is a physical separator that has the function of physically separating electrodes, and can be used without particular limitations as long as it is used as a normal separator. In particular, it is desirable to have low resistance to ion movement in the electrolyte solution and excellent electrolyte moisturizing ability.
또한, 상기 분리막은 양극과 음극을 서로 분리 또는 절연시키면서 양극과 음극 사이에 리튬 이온의 수송을 가능하게 한다. 이러한 분리막은 다공성이고 비전도성 또는 절연성인 물질로 이루어질 수 있다. 상기 분리막은 필름과 같은 독립적인 부재이거나, 또는 양극 및/또는 음극에 부가된 코팅층일 수 있다.Additionally, the separator separates or insulates the positive and negative electrodes from each other and enables the transport of lithium ions between the positive and negative electrodes. These separators are porous and may be made of non-conductive or insulating materials. The separator may be an independent member such as a film, or may be a coating layer added to the anode and/or cathode.
상기 분리막으로 사용될 수 있는 폴리올레핀계 다공성 막의 예로는, 고밀도 폴리에틸렌, 선형 저밀도 폴리에틸렌, 저밀도 폴리에틸렌, 초고분자량 폴리에틸렌과 같은 폴리에틸렌, 폴리프로필렌, 폴리부틸렌, 폴리펜텐 등의 폴리올레핀계 고분자를 각각 단독으로 또는 이들을 혼합한 고분자로 형성한 막을 들 수 있다.Examples of polyolefin-based porous membranes that can be used as the separation membrane include polyolefin-based polymers such as high-density polyethylene, linear low-density polyethylene, low-density polyethylene, and ultra-high molecular weight polyethylene, polypropylene, polybutylene, and polypentene, respectively, individually or together. Examples include membranes formed from mixed polymers.
상기 분리막으로 사용될 수 있는 부직포의 예로는, 폴리페닐렌옥사이드(polyphenyleneoxide), 폴리이미드(polyimide), 폴리아미드(polyamide), 폴리카보네이트(polycarbonate), 폴리에틸렌테레프탈레이트(polyethyleneterephthalate), 폴리에틸렌나프탈레이트(polyethylenenaphthalate), 폴리부틸렌테레프탈레이트(polybutyleneterephthalate), 폴리페닐렌설파이드(polyphenylenesulfide), 폴리아세탈(polyacetal), 폴리에테르설폰(polyethersulfone), 폴리에테르에테르케톤(polyetheretherketone), 폴리에스테르(polyester) 등을 각각 단독으로 또는 이들을 혼합한 고분자로 형성한 부직포가 가능하며, 이러한 부직포는 다공성 웹(web)을 형성하는 섬유 형태로서, 장섬유로 구성된 스펀본드(spunbond) 또는 멜트블로운(meltblown) 형태를 포함한다.Examples of nonwoven fabrics that can be used as the separator include polyphenyleneoxide, polyimide, polyamide, polycarbonate, polyethyleneterephthalate, and polyethylenenaphthalate. , polybutyleneterephthalate, polyphenylenesulfide, polyacetal, polyethersulfone, polyetheretherketone, polyester, etc., individually or Nonwoven fabrics made of polymers mixed with these are possible, and such nonwoven fabrics are in the form of fibers that form a porous web, and include spunbond or meltblown forms made of long fibers.
상기 분리막의 두께는 특별히 제한되지는 않으나, 1 내지 100 ㎛ 범위가 바람직하며, 더욱 바람직하게는 5 내지 50 ㎛ 범위이다. 상기 분리막의 두께가 1 ㎛ 미만인 경우에는 기계적 물성을 유지할 수 없으며, 100 ㎛를 초과하는 경우에는 상기 분리막이 저항층으로 작용하게 되어 전지의 성능이 저하된다.The thickness of the separator is not particularly limited, but is preferably in the range of 1 to 100 ㎛, and more preferably in the range of 5 to 50 ㎛. If the thickness of the separator is less than 1 ㎛, the mechanical properties cannot be maintained, and if it exceeds 100 ㎛, the separator acts as a resistance layer and battery performance deteriorates.
상기 분리막의 기공 크기 및 기공도는 특별히 제한되지는 않으나, 기공 크기는 0.1 내지 50 ㎛이고, 기공도는 10 내지 95%인 것이 바람직하다. 상기 분리막의 기공 크기가 0.1 ㎛ 미만이거나 기공도가 10% 미만이면 분리막이 저항층으로 작용하게 되며, 기공 크기가 50 ㎛를 초과하거나 기공도가 95%를 초과하는 경우에는 기계적 물성을 유지할 수 없다.The pore size and porosity of the separator are not particularly limited, but it is preferable that the pore size is 0.1 to 50 ㎛ and the porosity is 10 to 95%. If the pore size of the separator is less than 0.1 ㎛ or the porosity is less than 10%, the separator acts as a resistance layer, and if the pore size is greater than 50 ㎛ or the porosity is greater than 95%, the mechanical properties cannot be maintained. .
상기 전해액은 리튬염을 함유하는 비수계 전해질로서 리튬염과 전해액으로 구성되어 있으며, 전해액으로는 비수계 유기 용매, 유기 고체 전해질 및 무기 고체 전해질 등이 사용된다.The electrolyte is a non-aqueous electrolyte containing a lithium salt and is composed of a lithium salt and an electrolyte. Non-aqueous organic solvents, organic solid electrolytes, and inorganic solid electrolytes are used as the electrolyte.
상기 리튬염은 리튬-황 전지용 전해액에 통상적으로 사용되는 것이라면 제한없이 사용될 수 있다. 예를 들어, LiSCN, LiBr, LiI, LiPF6, LiBF4, LiB10Cl10, LiSO3CF3, LiCl, LiClO4, LiSO3CH3, LiB(Ph)4, LiC(SO2CF3)3, LiN(SO2CF3)2, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, LiFSI, 클로로 보란 리튬, 저급 지방족 카르본산 리튬 등으로 이루어진 군으로부터 1종 이상이 포함될 수 있다.The lithium salt may be used without limitation as long as it is commonly used in electrolytes for lithium-sulfur batteries. For example, LiSCN, LiBr, LiI, LiPF 6 , LiBF 4 , LiB 10 Cl 10 , LiSO 3 CF 3 , LiCl, LiClO 4 , LiSO 3 CH 3 , LiB(Ph) 4 , LiC(SO 2 CF 3 ) 3 , LiN(SO 2 CF 3 ) 2 , LiCF 3 CO 2 , LiAsF 6 , LiSbF 6 , LiAlCl 4 , LiFSI, lithium chloroborane, lithium lower aliphatic carboxylate, etc. may be included.
또한, 상기 전해액에서 리튬염의 농도는 0.2 내지 2 M, 구체적으로 0.6 내지 2 M, 더욱 구체적으로 0.7 내지 1.7 M일 수 있다. 상기 리튬염의 농도가 0.2 M 미만으로 사용하면 전해액의 전도도가 낮아져서 전해액 성능이 저하될 수 있고, 2 M 을 초과하여 사용하면 전해액의 점도가 증가하여 리튬 이온의 이동성이 감소될 수 있다.Additionally, the concentration of lithium salt in the electrolyte solution may be 0.2 to 2 M, specifically 0.6 to 2 M, and more specifically 0.7 to 1.7 M. If the lithium salt is used at a concentration of less than 0.2 M, the conductivity of the electrolyte may decrease and electrolyte performance may deteriorate, and if it is used at a concentration exceeding 2 M, the viscosity of the electrolyte may increase and the mobility of lithium ions may decrease.
상기 비수계 유기용매는 리튬염을 잘 용해시켜야 하며, 본 발명의 비수계 유기용매로는, 예컨대, N-메틸-2-피롤리디논, 프로필렌 카보네이트, 에틸렌 카보네이트, 부틸렌 카보네이트, 디메틸 카보네이트, 디에틸 카보네이트, 에틸메틸 카보네이트, 감마-부티로락톤, 1,2-디메톡시 에탄, 1,2-디에톡시 에탄, 테트라히드록시프랑(franc), 2-메틸 테트라하이드로푸란, 디메틸술폭시드, 1,3-디옥소란, 4-메틸-1,3-디옥센, 디에틸에테르, 포름아미드, 디메틸포름아미드, 디옥소란, 아세토니트릴, 니트로메탄, 포름산 메틸, 초산메틸, 인산 트리에스테르, 트리메톡시 메탄, 디옥소란 유도체, 설포란, 메틸 설포란, 1,3-디메틸-2-이미다졸리디논, 프로필렌 카보네이트 유도체, 테트라하이드로푸란 유도체, 에테르, 피로피온산 메틸, 프로피온산 에틸 등의 비양자성 유기용매가 사용될 수 있으며, 상기 유기 용매는 하나 또는 둘 이상의 유기용매들의 혼합물일 수 있다.The non-aqueous organic solvent must dissolve the lithium salt well, and non-aqueous organic solvents of the present invention include, for example, N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, Ethyl carbonate, ethylmethyl carbonate, gamma-butyrolactone, 1,2-dimethoxy ethane, 1,2-diethoxy ethane, tetrahydroxy franc (franc), 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1, 3-dioxolane, 4-methyl-1,3-dioxene, diethyl ether, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid triester, trime Aprotic substances such as toxin methane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl pyropionate, ethyl propionate, etc. An organic solvent may be used, and the organic solvent may be one or a mixture of two or more organic solvents.
상기 유기 고체 전해질로는, 예컨대, 폴리에틸렌 유도체, 폴리에틸렌 옥사이드 유도체, 폴리프로필렌 옥사이드 유도체, 인산 에스테르 폴리머, 폴리 에지테이션 리신(Agitation lysine), 폴리에스테르 설파이드, 폴리비닐 알코올, 폴리 불화비닐리덴, 이온성 해리기를 포함하는 중합체 등이 사용될 수 있다.The organic solid electrolyte includes, for example, polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphoric acid ester polymers, poly agitation lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, ionic dissociation. A polymer containing a group, etc. may be used.
상기 무기 고체 전해질로는, 예컨대, Li3N, LiI, Li5NI2, Li3N-LiI-LiOH, LiSiO4, LiSiO4-LiI-LiOH, Li2SiS3, Li4SiO4, Li4SiO4-LiI-LiOH, Li3PO4-Li2S-SiS2 등의 Li의 질화물, 할로겐화물, 황산염 등이 사용될 수 있다.Examples of the inorganic solid electrolyte include Li 3 N, LiI, Li 5 NI 2 , Li 3 N-LiI-LiOH, LiSiO 4 , LiSiO 4 -LiI-LiOH, Li 2 SiS 3 , Li 4 SiO 4 , Li 4 Nitride, halide, sulfate, etc. of Li such as SiO 4 -LiI-LiOH, Li 3 PO 4 -Li2 S -SiS 2 may be used.
본 발명의 전해질에는 충·방전 특성, 난연성 등의 개선을 목적으로, 예컨대, 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, 에틸렌 글리콜 디알킬 에테르, 암모늄염, 피롤, 2-메톡시 에탄올, 삼염화 알루미늄 등이 첨가될 수도 있다. 경우에 따라서는, 불연성을 부여하기 위하여, 사염화탄소, 삼불화에틸렌 등의 할로겐 함유 용매를 더 포함시킬 수도 있고, 고온 보존 특성을 향상시키기 위하여 이산화탄산 가스를 더 포함시킬 수도 있으며, FEC(Fluoro-ethylene carbonate), PRS(Propene sultone), FPC(Fluoro-propylene carbonate) 등을 더 포함시킬 수 있다.The electrolyte of the present invention includes, for example, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexaphosphoric acid triamide, and nitroamine for the purpose of improving charge/discharge characteristics, flame retardancy, etc. Benzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxy ethanol, aluminum trichloride, etc. may be added. . In some cases, halogen-containing solvents such as carbon tetrachloride and trifluoroethylene may be further included to provide incombustibility, and carbon dioxide gas may be further included to improve high-temperature preservation characteristics, and FEC (Fluoro-ethylene carbonate), PRS (Propene sultone), FPC (Fluoro-propylene carbonate), etc. may be further included.
상기 전해질은 액상 전해질로 사용할 수도 있고, 고체 상태의 전해질 세퍼레이터 형태로도 사용할 수 있다. 액상 전해질로 사용할 경우에는 전극을 물리적으로 분리하는 기능을 갖는 물리적인 분리막으로서 다공성 유리, 플라스틱, 세라믹 또는 고분자 등으로 이루어진 분리막을 더 포함한다.The electrolyte can be used as a liquid electrolyte or in the form of a solid electrolyte separator. When used as a liquid electrolyte, it further includes a physical separator that has the function of physically separating electrodes and is made of porous glass, plastic, ceramic, or polymer.
이하, 본 발명의 이해를 돕기 위하여 바람직한 실시예를 제시하나, 하기 실시예는 본 발명을 예시하는 것일 뿐 본 발명의 범주 및 기술사상 범위 내에서 다양한 변경 및 수정이 가능함은 당업자에게 있어서 명백한 것이며, 이러한 변형 및 수정이 첨부된 특허청구범위에 속하는 것도 당연한 것이다.Hereinafter, preferred embodiments are presented to aid understanding of the present invention. However, the following examples are merely illustrative of the present invention, and it is clear to those skilled in the art that various changes and modifications are possible within the scope and spirit of the present invention. It is natural that such variations and modifications fall within the scope of the attached patent claims.
실시예 1. 열팽창된 환원 그래핀 옥사이드 제조Example 1. Preparation of thermally expanded reduced graphene oxide
그래핀 옥사이드(graphene oxide, GO, 제품명 SE2430, sixth element 사)를 비활성 분위기에서 400℃의 온도로 10분 동안 열처리하여 열팽창된 그래핀 옥사이드를 제조하였다.Graphene oxide (GO, product name SE2430, Sixth Element) was heat-treated at 400°C for 10 minutes in an inert atmosphere to prepare thermally expanded graphene oxide.
상기 열팽창된 그래핀 옥사이드를 비활성 분위기에서 900℃의 온도로 3시간 동안 열처리하여 열팽창된 환원 그래핀 옥사이드(Thermally expanded-reduced graphene oxide, TE-rGO)를 제조하였다.The thermally expanded graphene oxide was heat-treated at a temperature of 900° C. for 3 hours in an inert atmosphere to prepare thermally expanded-reduced graphene oxide (TE-rGO).
상기 TE-rGO를 SEM을 이용하여 관찰한 결과, 뒤틀린(crumple) 페이퍼 구조를 가지고 있음을 확인하였다(도 1).As a result of observing the TE-rGO using an SEM, it was confirmed that it had a crumple paper structure (Figure 1).
실험예 1. 열팽창된 환원 그래핀 옥사이드의 비표면적, 기공 부피 및 평균 기공 크기 측정Experimental Example 1. Measurement of specific surface area, pore volume and average pore size of thermally expanded reduced graphene oxide
상기 실시예 1에서 제조한 TE-rGO와 함께, 환원 그래핀 옥사이드(reduced graphene oxide, SE1231, sixth element 사, 도 2)를 비교예 1로 하여 TE-rGO 및 rGO의 비표면적, 기공 부피 및 평균 기공 크기를 측정하였다.In addition to the TE-rGO prepared in Example 1, reduced graphene oxide (SE1231, Sixth Element, FIG. 2) was used as Comparative Example 1 to determine the specific surface area, pore volume, and average of TE-rGO and rGO. Pore size was measured.
상기 실시예 1의 TE-rGO 및 비교예 1의 rGO의 비표면적, 기공 부피 및 평균 기공 크기를 기공분포 측정기(Porosimetry analyzer; Bell Japan Inc, Belsorp-II mini)를 사용하여 질소 가스 흡착 유통법에 의해 BET(Brunauer-Emmett-Teller; BET) 6 점법으로 측정하였으며, 결과를 하기 표 1에 나타내었다.The specific surface area, pore volume, and average pore size of TE-rGO of Example 1 and rGO of Comparative Example 1 were measured using a pore distribution analyzer (Bell Japan Inc, Belsorp-II mini) using a nitrogen gas adsorption distribution method. It was measured using the BET (Brunauer-Emmett-Teller; BET) 6-point method, and the results are shown in Table 1 below.
본 발명의 실시예 1의 TE-rGO는 비교예 1의 rGO 대비 높은 비표면적, 기공 부피 및 평균 기공 크기를 보였다.TE-rGO of Example 1 of the present invention showed higher specific surface area, pore volume, and average pore size compared to rGO of Comparative Example 1.
이는 본 발명의 TE-rGO는 열팽창 및 환원 단계를 수행함에 따라 뒤틀린 페이퍼 구조를 가지며, 그로 인하여 rGO 대비 높은 비표면적, 기공 부피 및 평균 기공 크기를 갖는 것임을 알 수 있다.This shows that the TE-rGO of the present invention has a distorted paper structure as thermal expansion and reduction steps are performed, and as a result, it has a higher specific surface area, pore volume, and average pore size than rGO.
또한, 상기의 비표면적 및 기공 부피를 나타냄으로써, TE-rGO는 rGO 대비 많은 양의 황을 고르게 담지할 수 있음을 알 수 있다.In addition, by showing the above specific surface area and pore volume, it can be seen that TE-rGO can evenly support a larger amount of sulfur than rGO.
<리튬-황 전지 제조><Lithium-sulfur battery manufacturing>
실시예 2.Example 2.
상기 실시예 1에서 제조한 TE-rGO 및 황을 3:7의 중량비로 혼합한 후, 155℃의 온도에서 35분 동안 반응시켜 TE-rGO의 내부(기공) 및 표면에 황이 담지된 황-탄소 복합체를 제조하였다.TE-rGO and sulfur prepared in Example 1 were mixed at a weight ratio of 3:7 and then reacted at a temperature of 155°C for 35 minutes to produce sulfur-carbon with sulfur supported on the interior (pores) and surface of TE-rGO. A composite was prepared.
아세토니트릴 중에서 상기 황-탄소 복합체, 도전재 및 바인더를 볼밀을 사용하여 믹싱하여 양극 활물질 슬러리를 제조하였다. 이때 황-탄소 복합체는 양극 활물질로 사용되었으며, 도전재로는 카본블랙을, 바인더로는 폴리에틸렌옥사이드(분자량 5,000,000g/mol)을 각각 사용하였으며, 혼합 비율은 중량비로 황-탄소 복합체:도전재:바인더가 90:5:5가 되도록 하였다. 상기 양극 활물질 슬러리를 알루미늄 집전체에 도포한 후 건조하여 양극을 제조하였다.A positive electrode active material slurry was prepared by mixing the sulfur-carbon composite, conductive material, and binder in acetonitrile using a ball mill. At this time, the sulfur-carbon composite was used as the positive electrode active material, carbon black was used as the conductive material, and polyethylene oxide (molecular weight 5,000,000 g/mol) was used as the binder, and the mixing ratio was sulfur-carbon composite: conductive material: The binder was made to be 90:5:5. The positive electrode active material slurry was applied to an aluminum current collector and dried to prepare a positive electrode.
이 때 양극 활물질의 로딩량은 5 mAh/cm2 이하였으며, 황의 로딩량은 6.7mg/cm2 이었다.At this time, the loading amount of the positive electrode active material was 5 mAh/cm 2 or less, and the loading amount of sulfur was 6.7 mg/cm 2 .
두께가 40 ㎛인 리튬 금속 박막을 음극으로 사용하였다.A lithium metal thin film with a thickness of 40 μm was used as the cathode.
상기 제조된 양극과 음극을 대면하도록 위치시키고 그 사이에 폴리에틸렌 분리막을 게재한 후, 전해액을 주입하여 코인형의 리튬-황 전지를 제조하였다.A coin-type lithium-sulfur battery was manufactured by placing the prepared positive electrode and the negative electrode face to face, placing a polyethylene separator between them, and then injecting an electrolyte solution.
상기 전해액은 1M LiFSI 1wt%의 LiNO3가 용해된 DOL(1,3-dioxolane):DEGDME(diethylene glycol dimethyl ether)=4:6 (v/v) 혼합액을 사용하였다.The electrolyte was a mixture of 1 M LiFSI and 1 wt% of LiNO 3 dissolved in DOL (1,3-dioxolane):DEGDME (diethylene glycol dimethyl ether)=4:6 (v/v).
비교예 2.Comparative Example 2.
상기 실시예 1의 TE-rGO 대신에 비교예 1의 rGO를 사용한 것을 제외하고는 상기 실시예 2와 동일하게 실시하여 비교예 2의 리튬-황 전지를 제조하였다.A lithium-sulfur battery of Comparative Example 2 was manufactured in the same manner as Example 2, except that rGO of Comparative Example 1 was used instead of TE-rGO of Example 1.
실험예 2. 리튬-황 전지의 초기 방전용량 및 수명 특성 측정Experimental Example 2. Measurement of initial discharge capacity and life characteristics of lithium-sulfur battery
2-1. 초기 방전용량 측정2-1. Initial discharge capacity measurement
상기 실시예 2 및 비교예 2에서 제조한 리튬-황 전지에 대해, 충·방전 측정장치를 사용하여 충·방전 특성 변화를 시험하였다. 얻어진 전지는 0.1C/0.1C 충전/방전 조건에서 초기 용량을 살펴보았으며, 그 결과를 도 4에 나타내었다.For the lithium-sulfur batteries manufactured in Example 2 and Comparative Example 2, changes in charge and discharge characteristics were tested using a charge and discharge measuring device. The initial capacity of the obtained battery was examined under 0.1C/0.1C charge/discharge conditions, and the results are shown in Figure 4.
실시예 2의 리튬-황 전지의 초기 방전 용량은 1200 mAh/g을 초과하였으며, 비교예 2의 리튬-황 전지의 초기 방전 용량은 1100 mAh/g 미만이었다.The initial discharge capacity of the lithium-sulfur battery of Example 2 exceeded 1200 mAh/g, and the initial discharge capacity of the lithium-sulfur battery of Comparative Example 2 was less than 1100 mAh/g.
실시예 2의 리튬-황 전지는 양극 활물질인 황-탄소 복합체의 탄소재가 실시예 1의 TE-rGO이며, 상기 TE-rGO는 실험예 1에서 측정한 바와 같이 높은 비표면적 및 기공 부피를 가짐에 따라 많은 양의 황을 고르게 담지할 수 있어 황의 반응성 향상에 기여를 하여 초기 방전용량이 매우 높은 것을 알 수 있다.In the lithium-sulfur battery of Example 2, the carbon material of the sulfur-carbon composite, which is the positive electrode active material, is TE-rGO of Example 1, and the TE-rGO has a high specific surface area and pore volume as measured in Experimental Example 1. Accordingly, a large amount of sulfur can be evenly supported, contributing to improving the reactivity of sulfur, resulting in a very high initial discharge capacity.
반면, 비교예 2의 리튬-황 전지는 양극 활물질인 황-탄소 복합체의 탄소재가 비교예 1의 rGO이며, 상기 rGO는 실험예 1에서 측정한 바와 같이 실시예 1의 TE-rGO 보다 매우 작은 비표면적 및 기공 부피를 가짐에 따라, TE-rGO 만큼의 황을 고르게 담지할 수 없어 실시예 2 보다 낮은 초기 방전 용량을 보였다.On the other hand, in the lithium-sulfur battery of Comparative Example 2, the carbon material of the sulfur-carbon composite, which is the positive electrode active material, is rGO of Comparative Example 1, and the rGO has a much smaller ratio than the TE-rGO of Example 1 as measured in Experimental Example 1. Due to its surface area and pore volume, it was unable to evenly support as much sulfur as TE-rGO, resulting in a lower initial discharge capacity than Example 2.
따라서, 본 발명의 리튬-황 전지는 양극 활물질인 황-탄소 복합체의 탄소재로 비표면적 및 기공 부피가 매우 높은 TE-rGO를 사용함에 보다 많은 양의 황을 고르게 담지할 수 있어 황의 반응성을 증대시킴에 따라 높은 초기 방전 용량을 나타낼 수 있다.Therefore, the lithium-sulfur battery of the present invention uses TE-rGO, which has a very high specific surface area and pore volume, as the carbon material of the sulfur-carbon composite, which is the positive electrode active material, and can evenly support a larger amount of sulfur, thereby increasing the reactivity of sulfur. Depending on the condition, a high initial discharge capacity can be achieved.
2-2. 수명 특성 측정2-2. Measurement of lifetime characteristics
상기 실시예 2 및 비교예 2에서 제조한 리튬-황 전지에 대해, 충·방전 측정장치를 사용하여 초기 3 cycle 동안 0.1C/0.1C 충전/방전, 그 이후 3 cycle 동안 0.2C/0.2C 충전/방전하고, 이후 0.3C/0.5C로 충전/방전하여 50 cycle의 충·방전을 반복하여 수명특성을 측정하였고, 그 결과를 도 5에 나타내었다.For the lithium-sulfur battery prepared in Example 2 and Comparative Example 2, charge/discharge was performed at 0.1C/0.1C for the first 3 cycles and at 0.2C/0.2C for the next 3 cycles using a charge/discharge measuring device. /discharged, and then charged/discharged at 0.3C/0.5C and repeated 50 cycles of charge/discharge to measure the lifespan characteristics, and the results are shown in Figure 5.
실시예 2의 리튬-황 전지는 0.5C의 고율 구간에서 방전 용량이 약 800mAh/g로 측정되었으며, 50사이클 동안 용량을 유지하였다.The lithium-sulfur battery of Example 2 had a discharge capacity of about 800 mAh/g at a high rate of 0.5 C, and maintained the capacity for 50 cycles.
반면, 비교예 2의 리튬-황 전지는 0.5C의 고율 구간에서 방전 용량은 600mAh/g 미만이었으며, 약 40사이클 이후 전지가 퇴화되어 용량을 유지하지 못하였다.On the other hand, the lithium-sulfur battery of Comparative Example 2 had a discharge capacity of less than 600 mAh/g at a high rate of 0.5 C, and the battery deteriorated after about 40 cycles and failed to maintain capacity.
따라서, 본 발명의 리튬-황 전지는 양극 활물질인 황-탄소 복합체의 탄소재로 비표면적 및 기공 부피가 매우 높은 TE-rGO를 사용함에 따라 보다 많은 양의 황을 고르게 담지하여 황의 반응성을 증가시킴으로써 향상된 수명 특성을 나타낼 수 있다.Therefore, the lithium-sulfur battery of the present invention uses TE-rGO, which has a very high specific surface area and pore volume, as the carbon material of the sulfur-carbon composite, which is the positive electrode active material, and thereby increases the reactivity of sulfur by evenly supporting a larger amount of sulfur. It can exhibit improved lifespan characteristics.
Claims (13)
상기 황-탄소 복합체는 열팽창된 환원 그래핀 옥사이드; 및 상기 열팽창된 환원 그래핀 옥사이드의 내부 및 표면 중 적어도 일부에 황;을 포함하며,
상기 열팽창된 환원 그래핀 옥사이드는 비표면적이 400 내지 1200m2/g이며, 기공 부피는 3 내지 7cm3/g인, 양극 활물질.A positive electrode active material containing a sulfur-carbon complex,
The sulfur-carbon composite is thermally expanded reduced graphene oxide; And sulfur on at least a portion of the interior and surface of the thermally expanded reduced graphene oxide,
The thermally expanded reduced graphene oxide is a positive electrode active material having a specific surface area of 400 to 1200 m 2 /g and a pore volume of 3 to 7 cm 3 /g.
(b)상기 열팽창된 그래핀 옥사이드를 700 내지 1200℃의 온도로 열처리하여 환원시키는 단계; 및
(c)상기 열팽창된 환원 그래핀 옥사이드와 황을 혼합하여 황-탄소 복합체를 제조하는 단계;를 포함하는 제1항 및 제3항 중 어느 한 항의 양극 활물질 제조방법.(a) thermally expanding graphene oxide by heat treatment at a temperature of 300 to 500°C;
(b) reducing the thermally expanded graphene oxide by heat treatment at a temperature of 700 to 1200°C; and
(c) mixing the thermally expanded reduced graphene oxide with sulfur to produce a sulfur-carbon composite;
상기 양극은 제1항 및 제3항 중 어느 한 항의 양극 활물질을 포함하는 리튬 이차전지.anode; cathode; A separator interposed between the anode and the cathode; and a lithium secondary battery containing an electrolyte,
The positive electrode is a lithium secondary battery comprising the positive electrode active material of any one of claims 1 and 3.
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