리튬이차전지용 SnO2/Li4Ti5O12의 합성 및 전기화학적 특성

양아름,나병기 한국청정기술학회 2015 청정기술 Vol.21 No.4

In order to increase the capacity of the lithium ion battery, the capacity of the anode should be increased. SnO2 and Li4Ti5O12 were studied to replace the graphite as the anode materials. In this study, SnO2/Li4Ti5O12 composite materials were synthesized by solid-state method. The study reported here attempts to enhance the electrochemical capacity of Li4Ti5O12 through the incorporation of SnO2. Sn-based Li ion storage materials are loaded on Li4Ti5O12 surface. The SnO2/Li4Ti5O12 composite material has higher capacity than Li4Ti5O12, but the cycling capacity was decreased due to SnO2. 리튬이차전지에서 전지의 용량을 증가시키기 위하여 음극의 전기화학적 용량을 증가시키는 것이 중요하다. 음극활물질 중에서 SnO2와 Li4Ti5O12는 흑연을 대체하기 위한 물질로 많은 연구가 진행되고 있다. 본 연구에서는 SnO2/Li4Ti5O12 혼합물을고상법으로 합성하였으며, SnO2를 Li4Ti5O12에 혼합하여 전기화학적인 용량을 증가시키는 실험을 수행하였다. SnO2가 혼합될 경우에 Li4Ti5O12의 용량보다 큰 전기화학적 용량을 갖는 물질을 합성할 수 있었다. 하지만 SnO2의 특성으로 인하여 사이클이 진행됨에 따라서 용량이 감소하는 현상이 관찰되었다.

Synthesis and Electrochemical Characteristics of Spherical Li₄Ti₅O₁₂/CNT Composite Materials for Hybrid Capacitors

Yang, Joeng-Jin,Kim, Yu-Ri,Jeong, Moon-Gook,Yuk, Yong-Jae,Kim, Han-Joo,Park, Soo-Gil The Korean Electrochemical Society 2015 Journal of electrochemical science and technology Vol.6 No.2

Spherical Li₄Ti₅O₁₂ and Li₄Ti₅O₁₂ carbon nanotube (CNT) composites were synthesized using a colloid system. The electrochemical properties of the composites were thoroughly examined to determine their applicability as hybrid capacitor anodes. The electrical conductivity of the spherical Li₄Ti₅O₁₂-CNT composite was improved over that of the spherical Li₄Ti₅O₁₂ composite. The synthesized composites were utilized as the anode of a hybrid capacitor, which was assembled with an activated carbon (AC) positive electrode. The CNTs attached on the spherical Li₄Ti₅O₁₂ particles contributed to a 51% reduction of the equivalent series of resistance of the Li₄Ti₅O₁₂-CNTs/AC hybrid capacitor compared to the Li₄Ti₅O₁₂/AC hybrid capacitor. Moreover, the Li₄Ti₅O₁₂-CNTs/AC hybrid capacitor showed a larger capacitance than the Li₄Ti₅O₁₂/AC hybrid capacitor; specifically, the Li₄Ti₅O₁₂-CNT/AC hybrid capacitor showed 1.6 times greater capacitance at 40 cycles with a 10 mA cm⁻² loading current density.

졸-겔법으로 합성한 Cr 첨가 Li₄Ti₅O₁₂의 전기화학적 특성

김선아,조우람,정구현,조병원,나병기,Kim, Sun-Ah,Cho, Woo-Ram,Jeong, Koo-Hyun,Cho, Byung-Won,Na, Byung-Ki 한국전기화학회 2011 한국전기화학회지 Vol.14 No.1

Cr을 첨가한 $Li_4Ti_5O_{12}$의 전기화학적 특성을 고찰하였다. 산화물에 금속원자가 치환될 경우에 결정구조가 변화되며, $Li_4Ti_5O_{12}$의 전기화학적 특성이 변화하게 된다. 졸-겔법을 이용하여 $Li_4Ti_{5-x}Cr_xO_{12}$ (x = 0~0.2)를 제조하였으며, 전기로에서 $800{\sim}850^{\circ}C$로 공기중에서 12시간 동안 열처리하였다. 시료의 물리적인 특성은 TG-DTA, XRD, SEM, FT-IR을 사용하여 측정하였으며, 전기화학적인 특성은 0.01~2.0V의 범위에서 배터리충방전기를 사용하여 측정하였다. $Li_4Ti_5O_{12}$는 1C에서 169.9 mAh/g의 용량을 나타내었으며, 0.1C로 변화되었을 경우에 초기용량의 97.5%를 나타내었다. $Li_4Ti_{4.9}Cr_{0.1}O_{12}$ 시료는 1C에서 193.8 mAh/g의 용량을 보였으며, 0.1C에서는 초기용량의 98.8%를 나타내었다. The electorchemical properties of $Li_4Ti_5O_{12}$ added with Cr was tested. The addition or substitution of atoms to $Li_4Ti_5O_{12}$ are expected to modify the crystal structure, and therefore to change the electrochemical performances of $Li_4Ti_5O_{12}$. After the spinel structure $Li_4Ti_{5-x}Cr_xO_{12}$ (x = 0~0.2) were obtained via sol-gel method, the gel was heated in a muffle furnace at $800{\sim}850^{\circ}C$ for 12 h in air. The physical properties of the samples were characterized by TG-DTA, XRD, SEM, FT-IR, and the electrochemical properties were tested with battery cycler at 0.01~2.0 V range. The $Li_4Ti_5O_{12}$ exhibited 169.9 mAh/g at 1C and capacity recovery was 97.5% of the initial capacity at 0.1C. $Li_4Ti_{4.9}Cr_{0.1}O_{12}$ (Cr 1% added) showed best performance of 193.8 mAh/g at 1C and the capacity recovery was increased to 98.8% of the initial capacity at 0.1C.

Effect of Zn2+ and F- Co-Modification on the Structure and Electrochemical Performance of Li4Ti5O12 Anode Material

Aijia Wei,Wen Li,Lihui Zhang,Xiaohui Li,Xue Bai,Zhenfa Liu 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2017 NANO Vol.12 No.5

Zn2+ and F- ions are successfully used to modify pure Li4Ti5O12 via a co-precipitation method followed by calcination at 400℃ for 5 h in an Ar atmosphere in order to further investigate the reaction mechanism of the fluoride modification process. Zn2+ and F- co-modified Li4Ti5O12 samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and electrochemical measurements. After the modification process, no ZnF2 coating layer is formed on the surface of Li4Ti5O12, instead, F- ions react with Li4Ti5O12 to generate a new phase, composed of a small amount of anatase TiO2, rutile TiO2, LiF, and Zn2+ ions are suspected to form a ZnO coating layer on Li4Ti5O12 particles. The electrolyte reduction decomposition is suppressed in Zn2+ and F- co-modified Li4Ti5O12 due to the ZnO coating layer. 1 wt.% Zn2+ and F- co-modified Li4Ti5O12 exhibits the best rate capability, which leads to a charge capacity of 236.7, 227.8, 222.1, 202.7, 188.9 and 150.7 mAh g -1 at 0.2C, 0.5C, 1C, 3C, 5C and 10C, respectively, between 0 V and 3 V. Furthermore, 1 wt.% Zn2+ and F- comodified Li4Ti5O12 exhibits 96.0% charge capacity retention at 3C rate after 200 cycles, which is significantly higher than that of pure Li4Ti5O12 (78.4%).

PVC를 원료로 탄소코팅한 Li4Ti5O12의 합성 및 전기화학적 특성

현시철,나병기 한국청정기술학회 2018 청정기술 Vol.24 No.1

In this study, Li4Ti5O12 anode materials for lithium ion battery were synthesized by dry ball-mill method. Polyvinyl chloride (PVC) as a carbon source was added to improve electrochemical properties. When the PVC was added after Li4Ti5O12 formation, the spinel structure was well synthesized and it was confirmed by X-ray diffraction (XRD) experiments. When the carbon material was added before the synthesis and the heat treatment was performed, it was confirmed that a material having a different crystal structure was synthesized even when a small amount of carbon material was added. In the case of Li4Ti5O12 without the carbon material, the electrical conductivity value was about 10 μS m-1, which was very small and similar to that of the nonconductor. As the carbon was added, the electrical conductivity was greatly improved and increased up to 10,000 times. Electrochemical impedance spectroscopy (EIS) analysis showed that the size of semicircle corresponding to the resistance decreased with the carbon addition. This indicates that the resistance inside the electrode is reduced. According to the Cyclic voltammetry (CV) analysis, the potential difference between the oxidation peak and the reduction peak was reduced with carbon addition. This means that the rate of lithium ion insertion and deinsertion was increased. Li4Ti5O12 with 9.5 wt% PVC added sample showed the best properties in rate capabilities of 180 mA h g-1 at 0.2 C-rate, 165 mA h g-1 at 0.5 C-rate, and 95.8 mA h g-1 at 5 C-rate. 리튬이온전지의 음극활물질로 사용되는 Li4Ti5O12를 건식 볼밀법으로 합성하였고, Li4Ti5O12의 전기화학적 특성을 향상시키기 위하여 탄소소재인 polyvinyl chloride (PVC)를 첨가하였다. PVC는 Li4Ti5O12를 합성하고 난 후에 첨가하였을 때 스피넬구조를 갖는 물질이 잘 합성되었음을 X-ray diffraction (XRD) 실험으로 확인하였다. 합성하기 전에 탄소재를 첨가하여 열처리를 한 경우에는 탄소재가 미량 첨가되더라도 다른 결정구조의 물질이 합성되는 것을 확인할 수 있었다. 탄소재를 첨가하지 않은 Li4Ti5O12의 경우 전기전도도 값이 약 10 μS m-1으로 부도체에 가까운 매우 작은 값을 보였다. 탄소를 첨가함에 따라서 전기전도도가 크게 향상되었으며, 압력을 증가시킬 경우에 최대 10,000배 이상 증가되었다. Electrochemical impedance spectroscopy (EIS) 분석결과 탄소를 첨가할 경우 저항에 해당하는 반원의 크기가 감소하였으며, 이는 전극내의 저항이 감소하였음을 보여준다. Cyclic voltammetry (CV) 분석에 의하면 탄소를 첨가할 경우에 산화피크와 환원피크의 전위차가 줄어들었으며, 이는 리튬이온의 삽입과 탈리의 속도가 증가하였음을 의미한다. PVC를 9.5 wt% 첨가한 물질의 경우, 0.2 C-rate에서 180 mA h g-1, 0.5 C-rate에서 165 mA h g-1, 5C-rate에서 95.8 mA h g-1의 용량을 나타냄으로써 우수한 출력 특성을 보여주었다.

The Electric Properties of Surface Coating with CePO₄ and M₃(PO₄)₂ (M=Mg, Zn) on Li₄Ti₅O₁₂ for Energy Storage Capacitor

Lee, Jong-Kyu,Yoon, Jung-Rag The Korean Institute of Electrical Engineers 2018 Journal of Electrical Engineering & Technology Vol.13 No.1

The $Li_4Ti_5O_{12}$ of anode material for the hybrid capacitor was coated using $CePO_4$, $M_3(PO_4)_2$ (M=Mg, Zn). The capacitance of phosphate coated $Li_4Ti_5O_{12}$ was found to be lower than that of $Li_4Ti_5O_{12}$, whereas the equivalent series resistance was higher than that of $Li_4Ti_5O_{12}$. With an increase in cycle number, the base of cylindrical cell exhibited swelling due to gas generated from the reaction between $Li_4Ti_5O_{12}$ and electrolyte. The swelling cycle number of phosphate coated $Li_4Ti_5O_{12}$ was higher than that of $Li_4Ti_5O_{12}$ due to improvement in electrochemical stability. Based on the results, it is proposed that phosphate coating can be employed as a barrier layer to control the gassing reaction by isolating the $Li_4Ti_5O_{12}$ particle from electrolyte solution.

The Electric Properties of Surface Coating with CePO4 and M3(PO4)2 (M=Mg, Zn) on Li4Ti5O12 for Energy Storage Capacitor

이종규,윤정락 대한전기학회 2018 Journal of Electrical Engineering & Technology Vol.13 No.1

The Li 4 Ti 5 O 12 of anode material for the hybrid capacitor was coated using CePO 4 , M 3 (PO 4 ) 2 (M=Mg, Zn). The capacitance of phosphate coated Li 4 Ti 5 O 12 was found to be lower than that of Li 4 Ti 5 O 12 , whereas the equivalent series resistance was higher than that of Li 4 Ti 5 O 12 . With an increase in cycle number, the base of cylindrical cell exhibited swelling due to gas generated from the reaction between Li 4 Ti 5 O 12 and electrolyte. The swelling cycle number of phosphate coated Li 4 Ti 5 O 12 was higher than that of Li 4 Ti 5 O 12 due to improvement in electrochemical stability. Based on the results, it is proposed that phosphate coating can be employed as a barrier layer to control the gassing reaction by isolating the Li 4 Ti 5 O 12 particle from electrolyte solution.

Ru를 첨가한 음극활물질 Li4Ti5O12의 전기화학적 특성

조우람,나병기 한국청정기술학회 2014 청정기술 Vol.20 No.4

There is an increasing interest in the development of rechargeable batteries suitable for use in both hybrid electricvehicles and energy storage systems that require higher charge & discharge rates, bigger battery sizes and increased safety of thebatteries. Spinel-type lithium titanium oxide (Li4Ti5O12) as a potential anode for lithium ion batteries has many advantages. It is azero-strain materials and it experiences no structural change during the charge/discharge precess. Thus, it has long cycle life dueto its structural integrity. It also offers a stable operation voltage of approximately 1.55 V versus Li+/Li, above the reductionpotential of most organic electrolyte. In this study, Ru added Li4Ti5O12 composites were synthesized by solid state process. Thecharacteristics of active material were investigated with TGA-DTA, XRD, SEM and charge/discharge test. The capacity wasreduced when Ru was added, however, the polarization decreased. The capacity rate of Li4Ti5O12 with Ru (3%, 4%) addition wasreduced during the charge/discharge precess with 10 C-rate as a high current density. 전기자동차와 하이브리드 전기자동차에 요구되는 높은 충․방전 속도, 안전성, 대형화에 적합한 충․방전 전지의 개발은많은 관심을 받고 있다. 스피넬 구조의 Li4Ti5O12는 리튬이온이차전지의 음극활물질로 충․방전 시 부피변화가 거의 없기 때문에 수명특성이 뛰어나고, 전해액이 분해되는 전위보다 높은 작동 전압을 갖기 때문에 안정한 장점이 있다. 본 실험에서는Li4Ti5O12의 단점인 전기전도성을 향상시키고자 소량의 Ru를 첨가하여 Li4Ti5O12를 고상법으로 제조하여 테스트하였다. TGA-DTA, XRD, SEM, 충․방전 테스트를 통해 분석을 실시하였다. Ru를 첨가하였을 때 용량은 약간 감소하였지만, 분극현상이 감소하는 것을 확인하였다. 그리고 Ru를 3%와 4% 첨가하였을 때 높은 전류밀도인 10 C-rate 충․방전에서 용량감소율이 줄었다.

Li_4Ti_5O_12 Nanofiber의 전기화학적 특성에 미치는 Oleic Acid 코팅 효과

김은경 ( Eun Kyung Kim ),최병현 ( Byung Hyun Choi ),지미정 ( Mi Jung Ji ),정성헌 ( Sung Hun Jung ),김광범 ( Kwang Bum Kim ) 대한금속재료학회(구 대한금속학회) 2013 대한금속·재료학회지 Vol.51 No.3

For preparing spinel Li_4Ti_5O_12 nanofiber, a hydrogen titanate nanofiber precursor was mixed with LiOH·H2O and then the mixture was treated at 130℃ in an autoclave for 24 hrs. The hydrogen titanate nanofiber precursor was made using a TiO2 and NaOH solution as the starting material. As a result, the diameter of the Li4Ti5O12 nanofiber was 5-10nm and the length was over 100 nm longer fiber. The oleic acid (C17H33COOH) coated Li4Ti5O12 nanofiber with different oleic acid contents (5, 7.5, and 10 wt%) was obtained by a simple mixing method and heat treatment at 450℃ in a N_2 atmosphere. The results clearly revealed that the surface of the Li4Ti5O12 nanofiber was coated with an amorphous carbon layer (1 nm). The crystallinity of the samples was also enhanced. The oleic acid coated Li_4Ti_5O_12 nanofiber (5 wt% and 7.5 wt%) displayed a much lower impedance than the Li_4Ti_5O_12 nanofiber because of the decreased charge transfer resistance, therefore, it had an improved discharging/charging capacity, c-rate and cycle performance.

The formation mechanism of solid solution Li4Ti5O12-y prepared by carbon thermal reduction and the effect of Ti3+ on electrochemical performance

양귀균,박수진 한국공업화학회 2018 한국공업화학회 연구논문 초록집 Vol.2018 No.0

Solid solution Li4Ti5O12-y samples were synthesized by one step solid state carbon thermal reduction reaction using Li2CO3, anatase and carbon black under nitrogen atmosphere. An underlying formation mechanism is proposed which directs us well to prepare solid solution Li4Ti5O12-y. The formation mechanism of solid solution Li4Ti5O12-y was investigated by in situ variable temperature X-Ray diffraction (VT-XRD) and thermal gravimetric analysis/differential scanning calorimetry system (TGA-DSC). Firstly, partial Ti4+ turn to Ti3+ (TiO2-TiO2-x) due to the existence of carbon black. Secondly, Li2CO3 reacts with TiO2-x (anatase) to form Li2TiO3. Thirdly, Li2TiO3 reacts with TiO2-x to form solid solution Li4Ti5O12-y, anatase starts to transform into rutile at the same time. Rutile reacts with Li2TiO3 to form Li4Ti5O12-y at higher temperature. As a result, the as-prepared material exhibits good rate capability and cycling stability with 99.3% capacity retention after 200 cycles.