Jong-Tae Son

Fabrication of LiCoO2 thin films by sol-gel method and characterisation as positive electrodes for Li/LiCoO2 cells

Abstract LiCoO 2 thin films are receiving attention as positive electrodes (cathodes) for thin-film microbatteries. In this study, LiCoO 2 thin films are fabricated by a sol–gel spin-coating method and a post-annealing process. The thermal decomposition behaviour of the precursor is investigated by thermogravimetry/differential thermal analysis TG/DTA and mass spectroscopy. The crystallinity, microstructure and electrochemical properties of the final films are also studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and galvanostatic charge-discharge cycling tests. Films heat-treated under appropriate conditions exhibit high capacity and good crystallinity and are therefore considered to be candidates as cathodes for thin-film microbatteries.

Characteristics of tin nitride thin-film negative electrode for thin-film microbattery

Abstract Tin nitride is a relatively unknown compound. In this study, the tin nitride thin film is examined as a negative electrode for a thin-film microbattery. Reactive rf magnetron sputtering is used for deposition of films with varying deposition temperature. The charge–discharge properties of thin films deposited at room temperature, 100 and 200°C are found to be satisfactory. As the irreversible capacity fraction increases, rechargeability is improved. Finally, it is suggested that the electrochemical characteristics of tin nitride are similar to those of the tin oxide system. The charge–discharge characteristics are investigated in several ways.

Lattice parameter as a measure of electrochemical properties of LiMn2O4

Abstract Many factors affect the electrochemical properties of LiMn 2 O 4 . Among these factors the amount of Mn 3+ is an important factor which largely influences the capacity and capacity fading. However, it is difficult to detect the amount of Mn 3+ by chemical titration method. In this research we try to relate the amount of Mn 3+ with the lattice parameter. Lattice parameter is easy to measure. Therefore, if the amount of Mn 3+ can be deduced by the lattice parameter, it will be very helpful to control and design the electrochemical properties of LiMn 2 O 4 . The results show a good relationship among the lattice parameter, the amount of Mn 3+ and the capacity. Thus, lattice parameter could be used to deduce the electrochemical properties of LiMn 2 O 4 , although many works are still needed to construct a firm relationship.

The electrochemical properties of thin-film LiCoO2 cathode prepared by sol–gel process

LiCoO2 thin films have received attention as cathodes of thin-film microbatteries in these days. In this study, LiCoO2 thin films were fabricated by a sol–gel spin coating method and an annealing process. They were deposited on Pt(111) and Pt(200) substrates to investigate the effect of orientation of current collector. The crystallinity, microstructure and electrochemical properties of final films are also studied by XRD, SEM and galvanostatic charge/discharge cycling test. Films heat-treated under appropriate conditions exhibit high capacity and good crystallinity so those films are considered to be candidates as cathodes for thin-film microbatteries.

Effect of target properties on deposition of lithium nickel cobalt oxide thin-films using RF magnetron sputtering

Abstract Electrochemically active lithium nickel cobalt oxide thin-film has not been fabricated until now. To fabricate stoichiometric lithium nickel cobaltate films, a sputtering target of proper composition has been synthesized via a solid-state reaction. The films are deposited by RF magnetron sputtering at room temperature. As-deposited films show an amorphous structure. By varying the deposition conditions—such as the working pressures and deposition times—thin-films with different characteristics are produced. The relationship between physical characteristics and electrochemical properties is investigated. A crystallized thin-film prepared by an annealing method displays a good discharge capacity and cycle life.

Effects of Calcinations Temperature on the Electrochemical Properties of Li(Ni0.6Co0.2Mn0.2)O2 Lithium-ion Cathode Materials

Using Na2CO3 and MeSO4 (Me = Ni, Co and Mn) as starting materials, the pre- cursor of (Ni0.6Co0.2Mn0.2)CO3 has been synthesized by carbonate co-precipitation. The precur- sor was mixed with Li2CO3, and calcined at 750, 850, and 950 o C in air. Effect of calcinations temperature on characteristics of Li(Ni0.6Co0.2Mn0.2)O2 cathode materials was investigated. The structure and characteristics of Li(Ni0.6Co0.2Mn0.2)O2 were determined by X-ray diffraction (XRD), Scanning electron microscopy (SEM) and electrochemical measurements. The X-ray diffraction (XRD) results show that the intensity ratio of I(003)/I(104) increased and the R-factor ratio decreased with the increase of calcinations temperature. And Scanning electron microscopy (SEM) result show that the primary particle size increased. Especially, the Li(Ni0.6Co0.2Mn0.2)O2 calcined at 950 o C for 24 H shows excellent electrochemical performances with reversible spe- cific capacity of 165.3 mAhg �1 (cut-off voltage 2.5~4.3 V, 0.1 C(17 mAhg �1 )) and good capacity retention of 95.4% after 50 th charge/discharge cycles(cut-off voltage 2.5~4.3 V, 1 C(170 mAhg �1 )).

Synthesis and Electrochemical Properties of Li[Fe 0.9 Mn 0.1 ]PO 4 Nanofibers as Cathode Material for Lithium Ion Battery by Electrospinning Method

양극활물질은 낮은 가격과 안정성으로 인해 리튬 이차전지 시장에서 큰 관심을 받고 있다. 그러나 낮은 이온 전도도와 작동전압 때문에 상업적으로 이용되기엔사용분야의 응용에 제한이 있다. 이러한 문제를 해결하기 위해서 철 양이온을 망간 양이온과같은 전이금속으로 치환함으로써 작동전압을 높이는 연구가 시행되고 있다. 또한 미세구조의 나노화를 통해 리튬 이온의 확산거리를 짧게 만들어 줌으로써 이온 전도도를 높여주는 연구도 진행 중이다. 그래서 이번 연구에서는 이온의 확산거리를 짧게 만들어 주기 위해 표면적을 넓힐수 있는 전기방사를 이용해 물질을 합성하였고, 이를 확인하기 위하여 시차주사현미경 관측을 통해 균일한 나노 섬유의 형성을 확인하였다. 또한 결정구조를 관찰하기 위해 X-선 회절 분석을하였는데, 다른 상의 관찰 없이 단일상의 결정구조를 얻음을 확인하였다. 전기화학적 성능 확인방법으로는 충방전 테스트기를 이용하여 초기 충방전 곡선을 분석하였고, 계면저항 및 리튬 양이온의 확산을 알아보기 위해 임피던스 측정을 실행하였다. Abstract : LiFePO

Improvement of Electrochemical Properties and Thermal Stability of a Ni-rich Cathode Material by Polypropylene Coating

The interface between the surface of a cathode material and the electrolyte gives rise to surface reactions such as solid electrolyte interface (SEI) and chemical side reactions. These reactions lead to increased surface resistance and charge transfer resistance. It is consequently necessary to improve the electrochemical characteristics by suppressing these reactions. In order to suppress unnecessary surface reactions, we coated cathode material using polypropylene (PP). The PP coating layer effectively reduced the SEI film that is generated after a 4.3 V initial charging process. By mitigating the formation of the SEI film, the PP-coated Li[(Ni0.6Co0.1Mn0.3)0.36(Ni0.80Co0.15Al0.05)0.64)]O2(NCS) electrode provided enhanced transport of Li ions due to reduced SEI resistance (RSEI) and charge transfer resistance (Rct). The initial charge and discharge efficiency of the PP-coated NCS electrode was 96.2 % at a current density of 17 mA/g in a voltage range of 3.0 ~ 4.3 V, whereas the efficiency of the NCS electrode was only 94.7 %. The presence of the protective PP layer on the cathode improved the thermal stability by reducing the generated heat, and this was confirmed via DSC analysis by an increased exothermic peak.

The Structural and Electrochemical Properties of Li[Ni 0.6-x Ba x Co 0.1 Mn 0.3 ]O 2 (x = 0, 0.01) by Barium Doping

리튬 이차전지 양극소재인 Ni-rich계의

The Structural Stability and Electrochemical Properties of Fe Doped Li(Ni0.575Co0.1Mn0.325)O2

Li[Ni_{1-x-y}Co_xMn_y]O_2