리튬이차전지 양극 소재 성능 향상을 위한 최신 기술 동향 및 연구 전망

박서현 ( Seohyeon Park ),오필건 ( Pilgun Oh ) 한국화상학회 2021 한국화상학회지 Vol.27 No.2

본 논문에서 리튬이온전지용 양극 소재의 개발 동향과 함께 앞으로 필요한 양극 소재의 연구 방향을 제시한다. 현재 리튬이온 전지는 지구 환경 개선을 위한 친환경 에너지로 주목받고 있으며, 전기차와 에너지저장 시스템 등에서의 다양한 활용으로 고용량 및 고안정성 소재 개발에 초점을 맞추어 연구가 진행되고 있다. 특히, 리튬이온전지 양극 소재의 경우 전지의 가격 및 성능을 결정하기 때문에 활발한 연구가 이루어지며, 그중 높은 이론 용량을 가지는 Ni-rich 계 layered 구조의 양극 소재에 대한 연구가 집중되고 있다. 그러나, 고용량 특성을 달성하기 위한 Ni-rich 계 양극 소재는 높은 Ni 조성에 의해 비용량이 증가함에 따라 전기화학적 불안정성 또한 증가하는 문제를 가지기 때문에 활용에 한계를 가진다. 이를 해결하기 위한 방법으로 본 논문에서는 양극 소재의 표면 개질 방법과 원소치환 방법에 대해 언급하며, 이에 진일보하여 리튬이온전지의 가격 경쟁력을 확보하기 위한 양극 소재의 연구 방향을 제안한다. This study presents the development trends of cathode materials in lithium-ion batteries and the future research direction of cathode materials. Currently, lithium-ion batteries have been focused on improving the global environment, and research of lithium-ion batteries continues to concentrate on increasing the capacity and stability as lithium-ion battery application focus moves towards electric vehicles and energy storage systems. The study of cathode materials is considered important in determining the property and cost of lithium-ion batteries. Among such studies, researchers have concentrated on layered structure cathode materials with a high theoretical capacity. However, applying Ni-rich cathodes as a means to achieve high capacity has limited utilization because the high Ni composition in cathode materials causes increasing electrochemical instability during the charge process. In order to solve this problem, this study presents the ideas about the research method of surface modification and atomic substitution, suggesting a novel future research direction for cathode materials to ensure the price competitiveness of lithium-ion batteries.

Selective outer surface modification of polycrystalline Ni-rich cathode for sulfide all-solid-state lithium-ion battery

최재홍,황준혁,Tom James Embleton,고경목,조미나,이채원,윤정식,박서현,손윤국,오필건 한국화학공학회 2023 Korean Journal of Chemical Engineering Vol.40 No.3

In order to achieve a high energy density, Ni-rich polycrystalline materials have been explored as cathode materials for application in ASSLB applying sulfide solid electrolyte. However, the interaction between the electrode and the solid electrolyte comes with severe problems, such as a poor solid electrolyte interface and interfacial stress fracturing during the charge-discharge process. To alleviate the side reaction and the interfacial resistance, a coating layer between the cathode and sulfide electrolyte has since been proposed and developed. However, the inner surface of the primary particles in the polycrystalline can also be a form of coating layer, which does not meet the solid electrolyte and it is hence an inefficient coating mechanism for an ASSLB where the cathode/electrolyte interface occurs purely at the cathode outer surface. Here, we report a new coating strategy for Ni-rich polycrystalline cathode materials using a sol-gel process that focusses on improving the cathode/electrolyte interface of ASSLB. Commercial polycrystalline LiNi0.8Co0.1Mn0.1O2 was coated with 1 wt% lithium and cobalt acetate precursor with different coating coverage being achieved via control of the stirring speed (200 and 600 rpm). The coating materials, which uniformly coated on the inner and outer surfaces of the polycrystalline (I-NCM), showed effectively improved electrochemical performance with the structural stability in LIB, where the liquid electrolyte has contact with inner surface of polycrystalline materials. However, the cathode material, which was mainly coated on the outer surface of polycrystalline materials (O-NCM), exhibited improved performance in the ASSLB, which only has contact with the electrolyte at the surface of the active material polycrystalline. The physical properties of the coated cathode material were analyzed using SEM and XRD, and the electrochemical performance was investigated through initial charge/discharge capacity and cycle stability in both LIB and ASSLB simultaneously. This concept of intentionally surface coating the polycrystalline material can be applied as a new coating strategy to realize improvements in both electrochemical properties and electrode structural stability of ASSLB.

Synergetic effects of blended cathode active materials: Simulation and Experiment

( Williams Agyei Appiah ),박주남,변승우,유명현,이용민 한국공업화학회 2017 한국공업화학회 연구논문 초록집 Vol.2017 No.1

In the quest to achieve a higher capacity electrode materials for lithium ion batteries, different active materials for both cathode and anode are being studied. However, the available electrode materials which have been discovered have both good and bad sides. Hence, the electrochemical characteristics of Li-ion cells made of blended cathode material composed of LiMn2O4 and LiNi0.6Co0.2Mn0.2O2 and an artificial graphite anode are being studied via both experiments and simulation. The cycle performance of the two pure cell chemistries we modelled by considering Mn2+ dissolution in the cathode and solid electrolyte interphase information in the anode. By fitting our model predictions to the experimental data, the percentage of each contributing factor to the total capacity fade was determined. Ragone plots were used to study the correlation between the energy density and average specific power of the two pure chemistries and their blends.

Li[Ni0.3Co0.4Mn0.3]O2 양극물질의 Li-La-Ti-O코팅 효과

이혜진,박보건,유제혁,김석범,박용준,윤수현,김관수 한국전기전자재료학회 2009 전기전자재료학회논문지 Vol.22 No.10

Li(Ni, Co, Mn)O2 has been known as one of the most promising cathode materials for lithium secondary batteries. However, it has some problems to overcome for commercialization such as inferior rate capability and unstable thermal stability. In order to address these problems, surface modification of cathode materials by coating has been investigated. In the coating techniques, selection of coating material is a key factor of obtaining enhanced properties of cathode materials. In this work, we introduced solid electrolyte (Li-La-Ti-O) as a coating material on the surface of Li[Ni0.3Co0.4Mn0.3]O2 cathode. Specially, we focused on a rate performance of Li-La-Ti-O coated Li[Ni0.3Co0.4Mn0.3]O2 cathode. Both bare and Li-La-Ti-O 2 wt.% coated sample showed similar discharge capacity at 0.5C rate. However, as the increase of charge-discharge rate to 3C, the coated samples displayed better discharge capacity and cyclic performance than those of bare sample.

선박평형수 처리를 위한 전기화학 반응에서 음극의 영향

김동석 ( Dong Seog Kim ),박혜진 ( Hye Jin Park ),윤종문 ( Jong Mun Yoon ),박용석 ( Yong Seok Park ),박영식 ( Young Seek Park ) 한국환경과학회 2014 한국환경과학회지 Vol.23 No.6

In this study, we examined the effect of cathode from electrolysis reactor for treating ballast water. We are going to select a suitable cathode for seawater electrolysis after considering the effect on the generation of the oxidant of cathode and the electrode deposition materials adhering to the surface of cathode. Anode is Ru-Ti-Pd electrode and cathode are Ti, Pt, JP520 (Ni-Pt-Ce) electrodes. Using the cathode of the three types, experiments were conducted to examine the effects of TRO (total residual oxidants) generation concentration and RNO (N, N-Dimethyl-4-nitrosoaniline, indicator of the generation of OH radical) degradation concentration (in 1, 35 psu), ohmic drop, FESEM(field emission scanning electron microscope) observation of cathode surface and EDX (energy dispersive X-ray spectroscopy) measurements of attached fouling material. The results showed that TRO generation concentration and RNO degradation concentration in according to each type of cathode are not different. The attached fouling materials were observed on the surface of Ti and the JP520 electrode by the observation of SEM after electrolysis for two hours, but it was not observed on the surface of Pt electrode. When considering the surface ohmic drop of cathode and the attached fouling materials, Pt electrode was judged as the excellent cathode.

Superior Hybrid Cathode Material Containing Lithium-Excess Layered Material and Graphene for Lithium-Ion Batteries

Jiang, Ke-Cheng,Wu, Xing-Long,Yin, Ya-Xia,Lee, Jong-Sook,Kim, Jaekook,Guo, Yu-Guo American Chemical Society 2012 ACS APPLIED MATERIALS & INTERFACES Vol.4 No.9

<P>Graphene-wrapped lithium-excess layered hybrid materials (Li<SUB>2</SUB>MnO<SUB>3</SUB>·LiMO<SUB>2</SUB>, M = Mn, Ni, Co, hereafter abbreviated as LMNCO) have been synthesized and investigated as cathode materials for lithium-ion batteries. Cyclic voltammetry measurement shows a significant reduction of the reaction overpotential in benefit of the graphene conducting framework. The electrochemical impedance spectroscopy results reveal that the graphene can greatly reduce the cell resistance, especially the charge transfer resistance. Our investigation demonstrates that the graphene conducting framework can efficiently alleviate the polarization of pristine LMNCO material leading to an outstanding enhancement in cell performance and cycling stability. The superior electrochemical properties support the fine hybrid structure design by enwrapping active materials in graphene nanosheets for high-capacity and high-rate cathode materials.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2012/aamick.2012.4.issue-9/am301202a/production/images/medium/am-2012-01202a_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am301202a'>ACS Electronic Supporting Info</A></P>

전기자동차용 리튬이온전지를 위한 양극전극 분말 재료의 연구 동향

신동요,안효진,Shin, Dong-Yo,Ahn, Hyo-Jin 한국분말재료학회 (*구 분말야금학회) 2019 한국분말재료학회지 (KPMI) Vol.26 No.1

High performance lithium-ion batteries (LIBs) have attracted considerable attention as essential energy sources for high-technology electrical devices such as electrical vehicles, unmanned drones, uninterruptible power supply, and artificial intelligence robots because of their high energy density (150-250 Wh/kg), long lifetime (> 500 cycles), low toxicity, and low memory effects. Of the high-performance LIB components, cathode materials have a significant effect on the capacity, lifetime, energy density, power density, and operating conditions of high-performance LIBs. This is because cathode materials have limitations with respect to a lower specific capacity and cycling stability as compared to anode materials. In addition, cathode materials present difficulties when used with LIBs in electric vehicles because of their poor rate performance. Therefore, this study summarizes the structural and electrochemical properties of cathode materials for LIBs used in electric vehicles. In addition, we consider unique strategies to improve their structural and electrochemical properties.

Controversy on necessity of cobalt in nickel-rich cathode materials for lithium-ion batteries

Rui Wang,Lifan Wang,Yujie Fan,Woochul Yang,Chun Zhan,Liu Guicheng 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.110 No.-

Since the layered oxide LiCoO2 as the cathode material for commercial Li ion batteries, especially, nickelrichlayered oxide cathode materials are consolidating their status as the cathode material of choice andenabling a significant success of the passenger electric vehicle industry. Generally, cobalt in cathodes hasbeen considered necessary in enhancing electrochemical performance. However, they are still facing criticalchallenges in further commercialization. For instance, cobalt caused more severe structural degradationand capacity degradation at high potential. Additionally, it triggered O2 and heat release, whicheventually cause the interfacial instability and thermal instability of the cathode materials. Prior studiesalso confirmed that cobalt plays double-edged roles in cathodes, and questioned its necessity. Meanwhile, not only is it facing a roadblock caused by high-cost restrictions, but more importantly,50% of world mine production originates from copper-cobalt ore in the Democratic Republic of theCongo (DRC), where geopolitical instability and harsh working conditions could halt cobalt exports. Therefore, many studies have explored the possibility of cobalt-free materials. This review shed newlights on understanding the role of cobalt and reveals the perspectives of technical challenges in currentstate by the practical aspect for cobalt-free cathode materials, thereby helping to advance the futuredevelopment of next-generation low-cost and long-calendar-life batteries.

Zn와 Al을 첨가한 LiNi_0.85Co_0.15O₂ 양극활물질의 제조 및 전기화학적 특성평가

김수진 ( Su-jin Kim ),서진성 ( Jin-seong Seo ),나병기 ( Byung-ki Na ) 한국화학공학회 2021 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.59 No.1

본 연구에서는 LiNi_0.85Co_0.15O₂의 전기화학적 특성과 열적 안정성을 향상시키기 위하여 LiNi_0.85Co_0.15O₂에 이종원소인 Zn와 Al을 함께 첨가하여 고상법으로 합성하였다. 물질의 결정 구조, 크기 및 표면 상태는 XRD, SEM을 이용하여 분석하였고 전기화학적 특성은 충방전기를 이용하여 CV(cyclic voltammetry), 초기 충·방전 프로파일, 출력 특성, 수명특성 등을 측정하였다. Al-O의 강한 결합에너지는 양극활물질의 구조적 안정성을 향상시켰으며, Li⁺와 Ni²⁺의 양이온 혼합을 막아 전기화학적 특성 또한 향상되었다. Zn의 큰 이온반경은 양극활물질의 격자상수를 증가시켜 단위 셀의 부피가 확장되었다. Zn와 Al을 0.025몰씩 첨가한 물질의 경우, 0.5 C-rate의 전류밀도에서 100 사이클 동안 80%의 용량유지율을 보여주었으며 이 결과는 NC 양극활물질보다 12% 높은 수치이다. 또한, 5 C-rate에서의 방전용량은 104 mAh/g으로 기존의 NC 양극활물질보다 36 mAh/g 높은 수치를 보였다. Zn과 Al이 0.025몰씩 첨가된 NC 양극활물질은 출력특성, 수명 특성에서 우수한 특성을 보여주었다. Zn and Al added LiNi_0.85Co_0.15O₂ cathode materials were synthesized to improve electrochemical properties and thermal stability using a solid-state route. Crystal structure, particle size and surface shape of the synthesized cathode materials was measured using XRD (X-ray diffraction) and SEM (scanning electron microscopy). CV (cyclic voltammetry), first charge-discharge profiles, rate capability, and cycle life were measured using battery cycler (Maccor, series 4000). Strong binding energy of Al-O bond enhanced structure stability of cathode material. Electrochemical properties were improved by preventing cation mixing between Li+ and Ni²⁺. Large ion radius of Zn⁺ increased lattice parameter of NC cathode material, which meant unit-cell volume was expanded. NCZA25 showed 80% of capacity retention at 0.5 C-rate during 100 cycles, which was 12% higher than that of NC cathode. The discharge capacity of NCZA25 showed 104 mAh/g at 5 C-rate. NCZA25 achieved 36 mAh/g more capacity than that of NC cathod. NCZA25 cathode material showed excellent rate capability and cycling performance.

Deciphering the thermal behavior of lithium rich cathode material by <i>in situ</i> X-ray diffraction technique

Muhammad, Shoaib,Lee, Sangwoo,Kim, Hyunchul,Yoon, Jeongbae,Jang, Donghyuk,Yoon, Jaegu,Park, Jin-Hwan,Yoon, Won-Sub Elsevier 2015 Journal of Power Sources Vol.285 No.-

<P><B>Abstract</B></P> <P>Thermal stability is one of the critical requirements for commercial operation of high energy lithium-ion batteries. In this study, we use <I>in situ</I> X-ray diffraction technique to elucidate the thermal degradation mechanism of 0.5Li<SUB>2</SUB>MnO<SUB>3</SUB>-0.5LiNi<SUB>0.33</SUB>Co<SUB>0.33</SUB>Mn<SUB>0.33</SUB>O<SUB>2</SUB> lithium rich cathode material in the absence and presence of electrolyte to simulate the real life battery conditions and compare its thermal behavior with the commercial LiNi<SUB>0.33</SUB>Co<SUB>0.33</SUB>Mn<SUB>0.33</SUB>O<SUB>2</SUB> cathode material. We show that the thermal induced phase transformations in delithiated lithium rich cathode material are much more intense compared to similar single phase layered cathode material in the presence of electrolyte. The structural changes in both cathode materials with the temperature rise follow different trends in the absence and presence of electrolyte between 25 and 600 °C. Phase transitions are comparatively simple in the absence of electrolyte, the fully charged lithium rich cathode material demonstrates better thermal stability by maintaining its phase till 379 °C, and afterwards spinel structure is formed. In the presence of electrolyte, however, the spinel structure appears at 207 °C, subsequently it transforms to rock salt type cubic phase at 425 °C with additional metallic, metal fluoride, and metal carbonate phases.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Thermal degradation mechanism of lithium rich electrode material is investigated. </LI> <LI> In the absence of electrolyte, LMC shows better thermal stability compared to NMC. </LI> <LI> In the presence of electrolyte, thermal decomposition of LMC is accelerated. </LI> <LI> Catalytic activity of electrolyte in thermal decomposition is electrode dependent. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>