• 자원환경지질
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• 제55권6호
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• pp.661-669
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• 2022

다양한 전자기기의 발전을 통하여 에너지 저장소자의 소형화, 고효율 및 그린에너지화가 요구되며, 이를 위한 유망한 물질로서 그래핀 및 그래핀 하이브리드와 같은 뛰어난 전기화학적 특성을 지니고 있는 나노재료가 각광받고 있다. 특히 전기차산업에서 이차전지의 원가 절감은 관련 산업의 확산을 결정할 수 있는 핵심요소이며, 따라서 배터리 소재 기술에 대한 연구개발 동향을 분석하고 향후 기술발전방향에 대해 대응하는 것이 무엇보다 중요하다. 따라서 본 연구에서는 이차전지용 그래핀 음극소재 기술의 국가/기업별 특허 동향 분석을 수행하고 분석결과에 대한 시사점을 도출하여 향후 음극재 소재 관련 연구개발 활동에 방향성을 제시하고자 하였다. 분석결과, 실제 특허시장 별 특허동향분석에서 보여진 것처럼 음극재 소재 기술의 경우 미국, 유럽 특허시장의 외국인 비중은 대한민국, 일본 특허시장에 비해 높게 나타났으며, 이는 미국, 유럽 시장성이 높음을 의미한다. 또한 일본의 경우, 음극재 소재 기술 분야에서 선도적인 기술로 독과점하고 있기 때문에 일본 국적의 출원인이 일본 특허시장뿐만 아니라 다른 국가에서도 높은 수준의 출원을 보인다. 마지막으로 대한민국, 미국 특허시장에서 연구기관의 비중은 일본, 유럽 특허시장에 비해 높은 수준을 유지하고 있으며 이는 해당국가에서 아직까지 기술의 상업화가 더디게 진행되고 있음을 알 수 있다. 따라서 이차전지 소재의 높은 수입률로 인한 가격경쟁력 하락이라는 단점을 극복하기 위해서라도 국내 연구기관과 기업들은 본 연구에서 분석한 주요국 및 주요 기업의 특허 동향 결과를 자체 소재 개발 및 확보 전략을 수립하는데 사용해야 할 것이다.

• Bulletin of the Korean Chemical Society
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• 제34권4호
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• pp.1199-1204
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• 2013

Nanocomposites consisting of Sn nanoparticles and graphene oxide (GO) were electrophoretically deposited onto Cu current collectors that was used for anodes in Li ion batteries (LIBs). In order to optimize the electrochemical performance of nanocomposites as an anode material by controlling the oxygen functionality, the GO was subjected to $O_3$ treatment prior to electrophoretic deposition (EPD). During thermal reduction of the GO in the nanocomposites, the Sn nanoparticles were reduced in size, along with the formation of SnO and/or $SnO_2$ at a small fraction, relying on the oxygen functionalities of the GO. The variation in the duration of time for the $O_3$ irradiation resulted in a small change in total oxygen content, but in a significantly different fraction of each functional group in the GO, which influenced the Sn nanoparticle size and the amount of SnO (and/or $SnO_2$). As a result, the EPD films prepared with the GO that possessed the least amount of carboxylic groups (made by treating GO in an $O_3$ environment for 3 h) showed the best performance, when compared with the nanocomposites composed of untreated GO or GO that was $O_3$-treated for a duration of less than 3 h.

• Korean Chemical Engineering Research
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• 제55권3호
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• pp.430-435
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• 2017

$Li_4Ti_5O_{12}$ (LTO)는 리튬이차전지용 음극활물질로써 충방전에 따른 체적변화가 매우 적고, 삽입과 탈리 반응에 따른 높은 가역성 때문에 수명 특성이 좋다는 장점을 가지고 있다. 본 연구에서는 LTO의 단점인 낮은 전기전도도를 보완하고자 전도성이 좋은 탄소계열 소재인 그래핀과 CNT를 첨가 하였다. LTO입자가 나노 크기이므로, 그래핀이 LTO표면에 위치하여 전도성 향상을 시키기 어렵다고 생각했다. 따라서 추가로 CNT를 첨가시켜 LTO입자와 그래핀 사이에 전도성 네트워크를 형성하여, 그래핀만 첨가하였을 때 보다 전도성이 향상되었다. 또한 탄소물질의 첨가 시점을 LTO합성 전후로 나누어, 각각의 용량 및 수명특성의 효율을 비교해 보았다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.288-288
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• 2013

Lithium-ion battery (LIB) is one of the most important rechargeable battery and portable energy storage for the electric digital devices. In particular, study about the higher energy capacity and longer cycle life is intensively studied because of applications in mobile electronics and electric vehicles. Generally, the LIB's capacity can be improved by replacing anode materials with high capacitance. The graphite, common anode materials, has a good cyclability but shows limitations of capacity (~374 mAh/g). On the contrary, silicon (Si) and germanium(Ge), which is same group elements, are promising candidate for high-performance LIB electrodes because it has a higher theoretical specific capacity. (Si:4200 mAh/g, Ge:1600 mAh/g) However, it is well known that Si volume change by 400% upon full lithiation (lithium insertion into Si), which result in a mechanical pulverization and poor capacity retention during cycling. Therefore, variety of nanostructure group IV elements, including nanoparticles, nanowires, and hollow nanospheres, can be promising solution about the critical issues associated with the large volume change. However, the fundamental research about correlation between the composition and structure for LIB anode is not studied yet. Herein, we successfully synthesized various structure of nanowire such as Si-Ge, Ge-Carbon and Si-graphene core-shell types and analyzed the properties of LIB. Nanowires (NWs) were grown on stainless steel substrates using Au catalyst via VLS (Vapor Liquid Solid) mechanism. And, core-shell NWs were grown by VS (Vapor-Solid) process on the surface of NWs. In order to characterize it, we used FE-SEM, HR-TEM, and Raman spectroscopy. We measured battery property of various nanostructures for checking the capacity and cyclability by cell-tester.

• 한국결정성장학회지
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• 제33권6호
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• pp.203-209
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• 2023

차세대 나트륨이온전지용 음극 소재로 유망한 코발트 황화물 나노복합체를 간단한 수열법을 통해 합성하였다. 본 연구에서는 배터리의 전기화학적 에너지 저장 성능 향상을 위해 코발트 황화물 나노입자와 환원된 산화그래핀과 복합화 된 코발트 황화물 나노복합체를 제조하여 비교해주었다. 제조된 나노복합체 전극은 가역적이고 안정적인 사이클 성능(전류밀도 200 mA g^-1에서 30 사이클 후 62 %)을 보였다. 개선된 전기화학적 특성은 수열합성 과정에서 코발트 황화물의 입자 크기가 작고 균일하게 분포되어 나트륨 이온의 확산 경로를 극대화함에서 기인하였다. 뿐만 아니라 전환 반응 중 음극재의 박리 및 부피 팽창을 효과적으로 억제함으로써 차세대 나트륨이온전지용 유망한 음극 소재로써의 가능성을 보여주었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.198.2-198.2
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• 2014

We investigated change of the electronic structure, chemical states and elements ratio in graphene film by using photoelectron spectroscopy (PES). The graphene electrode has attracted considerable interest due to its possible applications in flexible organic light emitting diodes (F-OLEDs). However, to use the graphene for OLEDs, sufficient increase of work function is required, that is related with hole injection barrier. Plasma treatment is one of the most widely used method in OLEDs to increase the work function of the anode such as indium tin oxide (ITO). In this work, we used the plasma treatment, which is generated by various gas types such as O2, and Ar to increase the work function of the graphene film. From these results, we discuss the relation among the change of work function, plasma power, plasma treatment time and gas types.

• 한국분말재료학회지
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• 제24권4호
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• pp.308-314
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• 2017

$Fe_3O_4$/Fe/graphene nanocomposite powder is synthesized by electrical wire explosion of Fe wire and dispersed graphene in deionized water at room temperature. The structural and electrochemical characteristics of the powder are characterized by the field-emission scanning electron microscopy, X-ray diffraction, Raman spectroscopy, field-emission transmission electron microscopy, cyclic voltammetry, and galvanometric discharge-charge method. For comparison, $Fe_3O_4$/Fe nanocomposites are fabricated under the same conditions. The $Fe_3O_4$/Fe nanocomposite particles, around 15-30 nm in size, are highly encapsulated in a graphene matrix. The $Fe_3O_4$/Fe/graphene nanocomposite powder exhibits a high initial charge specific capacity of 878 mA/g and a high capacity retention of 91% (798 mA/g) after 50 cycles. The good electrochemical performance of the $Fe_3O_4$/Fe/graphene nanocomposite powder is clearly established by comparison of the results with those obtained for $Fe_3O_4$/Fe nanocomposite powder and is attributed to alleviation of volume change, good distribution of electrode active materials, and improved electrical conductivity upon the addition of graphene.

• Journal of Electrochemical Science and Technology
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• 제13권1호
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• pp.159-166
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• 2022

The assembly of the micron-sized Si/CNT/carbon composite wrapped with graphene (SCG composite) is designed and synthesized via a spray drying process. The spherical SCG composite exhibits a high discharge capacity of 1789 mAh g^-1 with an initial coulombic efficiency of 84 %. Moreover, the porous architecture of SCG composite is beneficial for enhancing cycling stability and rate capability. In practice, a blended electrode consisting of spherical SCG composite and natural graphite with a reversible capacity of ~500 mAh g^-1, shows a stable cycle performance with high cycling efficiencies (> 99.5%) during 100 cycles. These superior electrochemical performance are mainly attributed to the robust design and structural stability of the SCG composite during charge and discharge process. It appears that despite the fracture of micro-sized Si particles during repeated cycling, the electrical contact of Si particles can be maintained within the SCG composite by suppressing the direct contact of Si particles with electrolytes.

• 한국재료학회지
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• 제32권11호
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• pp.474-480
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• 2022

Lithium-ion batteries (LIBs) are powerful energy storage devices with several advantages, including high energy density, large voltage window, high cycling stability, and eco-friendliness. However, demand for ultrafast charge/discharge performance is increasing, and many improvements are needed in the electrode which contains the carbon-based active material. Among LIB electrode components, the conductive additive plays an important role, connecting the active materials and enhancing charge transfer within the electrode. This impacts electrical and ionic conductivity, electrical resistance, and the density of the electrode. Therefore, to increase ultrafast cycling performance by enhancing the electrical conductivity and density of the electrode, we complexed Ketjen black and graphene and applied conductive agents. This electrode, with the composite conductive additives, exhibited high electrical conductivity (12.11 S/cm), excellent high-rate performance (28.6 mAh/g at current density of 3,000 mA/g), and great long-term cycling stability at high current density (88.7 % after 500 cycles at current density of 3,000 mA/g). This excellent high-rate performance with cycling stability is attributed to the increased electrical conductivity, due to the increased amount of graphene, which has high intrinsic electrical conductivity, and the high density of the electrode.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
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• pp.111.2-111.2
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• 2015

Typical electrodes (metal or indium tin oxide (ITO)), which were used in conventional organic light emitting devices (OLEDs) structure, have transparency and conductivity, but, it is not suitable as the electrode of the flexible OLEDs (f-OLEDs) due to its brittle property. Although Graphene is the most well-known alternative material for conventional electrode because of present electrode properties as well as flexibility, its carrier injection barrier is comparatively high to use as electrode. In this work, we performed plasma treatment on the graphene surface and alkali metal doping in the organic materials to study for its possibility as anode and cathode, respectively. By using Ultraviolet Photoemission Spectroscopy (UPS), we investigated the interfaces of modified graphene. The plasma treatment is generated by various gas types such as O2 and Ar, to increase the work function of the graphene film. Also, for co-deposition of organic film to do alkali metal doping, we used three different organic materials which are BMPYPB (1,3-Bis(3,5-di-pyrid-3-yl-phenyl)benzene), TMPYPB (1,3,5-Tri[(3-pyridyl)-phen-3-yl]benzene), and 3TPYMB (Tris(2,4,6-trimethyl-3-(pyridin-3-yl)phenyl)borane)). They are well known for ETL materials in OLEDs. From these results, we found that graphene work function can be tuned to overcome the weakness of graphene induced carrier injection barrier, when the interface was treated with plasma (alkali metal) through the value of hole (electron) injection barrier is reduced about 1 eV.