• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.37 no.2
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• pp.215-222
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• 2024

Ni-rich cathode materials have been developed as the most promising candidates for next-generation cathode materials for lithium-ion batteries because of their high capacity and energy density. In particular, the electrochemical performance of lithium-ion batteries could be enhanced by increasing the contents of nickel ion. However, there are still limitations, such as low structural stability, cation mixing, low capacity retention and poor rate capability. Herein, we have successfully developed the nanorod-type Ni-rich cathode materials by using co-precipitation method. Particularly, the nanorod-type primary particles of LiNi_0.7Co_0.15Mn_0.15O₂ could facilitate the electron transfer because of their longitudinal morphology. Moreover, there were holes at the center of secondary particles, resulting in high permeability of the electrolyte. Lithium-ion batteries using the prepared nanorod-type LiNi_0.7Co_0.15Mn_0.15O₂ achieved highly improved electrochemical performance with a superior rate capability during battery cycling.

• Journal of the Korean Electrochemical Society
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• v.9 no.4
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• pp.158-169
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• 2006

The present article is concerned with the overview of the chemically/surface modified cubic spinel $LiMn_2O_4$ as a cathode electrode far lithium ion secondary batteries. Firstly, this article presented a comprehensive survey of the cubic spinel structure and its correlated electrochemical behaviour of $LiMn_2O_4$. Subsequently, the various kinds of the chemically/surface modified $LiMn_2O_4$ and their electrochemical characteristics were discussed in detail. Finally, this article reviewed our recent research works published on the mechanism of lithium transport through the chemically/surface modified $Li_{1-\delta}Mn_2O_4$ electrode from the kinetic view point by the analyses of the experimental potentiostatic current transients and ac-impedance spectra.

• Corrosion Science and Technology
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• v.21 no.4
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• pp.250-257
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• 2022

Transition metal sulfide materials have emerged as a new anode material for Li secondary batteries owing to their high capacity and rate capability facilitated by fast Li-ion transport through the layered structure. Among these materials, niobium disulfide (NbS₂) has attracted much attention with its high electrical conductivity and high theoretical capacity (683 mAh g^-1). In this study, we propose a facile synthesis of Fe_xNbS₂/C composite via simple ball milling and heat treatment. The starting materials of FeS and Nb were reacted in the first milling step and transformed into an Fe-Nb-S composite. In the second milling step, activated carbon was incorporated and the sulfide was crystallized into Fe_xNbS₂ by heat treatment. The prepared materials were characterized by X-ray diffraction, electron spectroscopies, and X-ray photoelectron spectroscopy. The electrochemical test results reveal that the synthesized Fe_xNbS₂/C composite electrode demonstrates a high reversible capacity of more than 600 mAh g^-1, stable cycling stability, and excellent rate performance for Li-ion battery anodes.

• Journal of the Korean Ceramic Society
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• v.47 no.6
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• pp.638-642
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• 2010

The spinel material $Li_4Ti_5O_{12}$ has attracted considerable attention as an anode electrode material for many battery applications owing to its light weight and high energy density. However, the real capacity of $Li_4Ti_5O_{12}$ powder as determined by the solid-state method is lower than the ideal capacity. In this study, we investigated the effect of the dopants in M-doped spinel $Ba_xLi_{4-2x}Ti_5O_{12}$(x=0.005, 0.05, 0.1) powders prepared by the solid-state reaction method and used as the anode material in lithiumion batteries. The results confirmed the effect of the Ba and Sr dopants on the powder properties of the spinel $Li_4Ti_5O_{12}$, which exhibited a pure spinel structure without any secondary phase in its XRD pattern. Moreover, the electrochemical properties of the spinel M-LTO materials were investigated using a half cell. The electrochemical data show that cells with anodes made of undoped $Li_4Ti_5O_{12}$ and Ba- and Sr-doped $Li_4Ti_5O_{12}$ have discharge capacities of 97, 130, and 112 mAh/g, respectively, at the first cycle. Moreover, the Ba- and Sr-doped spinel $Li_4Ti_5O_{12}$ demonstrated good properties in the mid-voltage range at 1.55 V, showing stable cyclic voltammogram properties which surpassed those of the same material without Ba or Sr at 1 C after 100 cycles.

• Corrosion Science and Technology
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• v.22 no.4
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• pp.287-296
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• 2023

Li-ion batteries have been gaining increasing importance, driven by the growing utilization of renewable energy and the expansion of electric vehicles. To meet market demands, it is essential to ensure high energy density and battery safety. All-solid-state batteries (ASSBs) have attracted significant attention as a potential solution. Among the advantages, they operate with an ion-conductive solid electrolyte instead of a liquid electrolyte therefore significantly reducing the risk of fire. In addition, by using high-capacity alternative electrode materials, ASSBs offer a promising opportunity to enhance energy density, making them highly desirable in the automotive and secondary battery industries. In ASSBs, Li metal can be used as the anode, providing a high theoretical capacity (3860 mAh/g). However, challenges related to the high interfacial resistance between Li metal and solid electrolytes and those concerning material degradation during charge-discharge cycles need to be addressed for the successful commercialization of ASSBs. This review introduces and discusses the interfacial reactions between Li metal and solid electrolytes, along with research cases aiming to improve these interactions. Additionally, future development directions in this field are explored.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.602-606
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• 2003

Silicon has been developed as an alternate anode material for lithium secondary batteries. A simple approach to improve the electrical contact of silicon powder has described. Carbon-coated and silver-coated silicon have been prepared by chemical vapor deposition and electroless plating respectively. Assembled cells, which consisted of surface modified silicon, lithium foil and $Li^+$ contained organic electrolyte, have been studied using electrochemical methods. Carbon-coated silicon was improved in the electrochemical performance such as reversibility and resistance compared to surface-unmodified silicon.

• Carbon letters
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• v.11 no.4
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• pp.343-346
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• 2010

The various expanded graphites (EGs) was prepared and applied as anode material for high power Li-ion secondary battery (LIB). By changing the processing conditions of EG, a series of EG with different structure were produced, showing the changed electrochemical properties. The charge-discharge test showed that the initial reversible capacity of EG anodes prepared at the suitable conditions was over 400 mAh/g and the charge capacity at 5 C-rate was 83.2 mAh/g. These values demonstrated the much improved electrochemical properties as compared with those for the graphite anode of 360 mAh/g and 19.4 mAh/g, respectively, showing the possibility of EG anode materials for high power LIB.

• Journal of the Korean Ceramic Society
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• v.43 no.2 s.285
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• pp.121-125
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• 2006

[ $LiFePO_4$ ] is one of the promising materials for cathode material of secondary lithium batteries due to its high energy density, low cost, environmental friendliness and safety. $LiFePO_4$ was synthesized by the solid-state reaction method at 500 - 800°C. The crystal structure of $LiFePO_4$ was analyzed by X-ray powder diffraction. The samples synthesized at 600 and $700^{\circ}C$ showed a single phase of a olivine structure. The particle sizes were increased and the specific surface areas were decreased with heating temperatures. The electrochemical performance was investigated by coin cell test. The discharge capacities at 0.1 C-rate were 118 mAh/g and 112 mAh/g at $600^{\circ}C,\;700^{\circ}C$, respectively. In an attempt to improve the electrical conductivity of cathode materials, $LiFePO_4/graphite$ composite was prepared with various graphite contents. The electrical conductivity and discharge capacity were increased with increasing the graphite contents in composite samples. The rate capabilities at high current densities were also improved.

• 한국전기화학회:학술대회논문집
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• 1998.12a
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• pp.153-166
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• 1998

Lithium ion Batteries commercially available since the early nineties in Japan are going to be more and more important for portable electronic devices and even EV applications. Today several companies around the world are working hard to join to market for Lithium secondary batteries. Based on the growing interest for commercial use of batteries also the materials have to be reviewed in order to meet large scale production needs. The requirements especially for electrolytes for lithium batteries are extremely high. The solvents and the lithium salts should be of highest purity. So the supply of these chemicals including packaging, transportation and storage but also the handling in production are critical items in this field. Frolic impurities are very critical for LiPF6 based electrolytes. The influence of water is tremendous. But also the other protic impurities like alcoholes are playing an Important role for the electrolyte quality. The reaction of these species with LiPF6 leads to formation of HF which further reacts with cathode materials (spinel) and anode. To understand the role of the protic impurities more clearly the electrolyte was doped with such compounds and was analyzed for protic impurities and HF. These results which directly show the relation between impurities and quality will be presented and discussed. In addition several investigations on different packaging materials as well as methods to analyze and handle the sensititive material will be addressed. These questions which are only partly discussed in literature so far and never been investigated systematically cover some of the key parameters for understanding of the battery chemicals. This investigation and understanding however is of major importance for scientist and engineers in the field of Lithium ion and Lithium polymer batteries.

• Journal of the Korean Ceramic Society
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• v.38 no.5
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• pp.424-430
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• 2001

Cut-off 전압 변화에 따른 충방전 특성을 알아보기 위하여 Mn을 다른 전이 금속이 Co와 Ni로 소량 치환시킨 Li(M $n_{1-{\delta}}$ $n_{\delta}$)$_2$ $O_4$(M=Ni, Co, $\delta$=0, 0.05, 0.1, 0.2)를 고상 반응법으로 80$0^{\circ}C$에서 48시간 동안 유지하여 합성하였다. 충방전의 cut-off 전압은 2.5~4.4V, 3.0~4.5V, 3.5~4.5V, 3.5V~4.7V의 네 가지 전압범위고 하였다. 충방전 실험결과, Li(M $n_{1-{\delta}}$ $n_{\delta}$)$_2$ $O_4$의 용량은 각각 Co와 Ni의 $\delta$=0.1에서 최대를 보였다. Co 치환 조성 재료와 순물질 모두에서 최대의 용량을 보인 cut-off 전압대는 3.5~4.5V 이었는데 이때의 Li(M $n_{0.9}$ $Co_{0.1}$)$_2$ $O_4$와 LiM $n_2$ $O_4$의 초기 충전용량과 초기 방전용량은 각각 118, 119mAh/g과 114, 104mAh/g 이었다. 또한 모든 cut-off 전압대에서 Li(M $n_{0.9}$ $Co_{0.1}$)$_2$ $O_4$는 순수한 LiM $n_2$ $O_4$보다 더 높은 용량과 우수한 싸이클 성능을 보였으며 그 결과는 밀착형 전지구성에서도 일치하였다.하였다.