Morphology Control of LiMnPO 4 Cathodes by a Careful Choice of Additives
- PDF / 6,631,132 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 11 Downloads / 146 Views
Morphology Control of LiMnPO4 Cathodes by a Careful Choice of Additives
Hung-Cuong Dinh1, Sun-il Mho1, Yongku Kang2, and In-Hyeong Yeo3 1
Division of Energy Systems Research, Ajou University, Suwon 443-749, Korea Division of Advanced Materials, Korea Research Institute of Chemical Technology, Daejeon 305-600, Korea 3 Department of Chemistry, Dongguk University, Seoul 100-715, Korea 2
ABSTRACT LiMnPO4 cathode materials of various sizes and shapes are synthesized by a hydrothermal method. In order to control the morphology of the LiMnPO4 particles, a nonionic surfactant or a cationic surfactant has employed as a key additive to the reactant solution. LiMnPO4 nanoparticles of grain-shape and rod-shape can be made with sizes between about 100 and 300 nm by adding a nonionic large polymer surfactant. Micrometer-sized LiMnPO4 particles of cuboid shape result from the reaction with a cationic surfactant. LiMnPO4 spheres of about 20 μm diameter are produced when no surfactant is added. The cathode composed of nanocrystalline (about 100 nm size) LiMnPO4 exhibited the best performance with the specific capacity of 153 mAhg-1 for the first battery cycle. INTRODUCTION There is a growing interest in the LiMnPO4 cathode due to the moderate theoretical capacity, low cost, reversibility, thermal stability rendering high safety, and environmental friendliness. Olivine structured LiMnPO4 is considered as the most promising cathode of Li-ion batteries for applications in electric vehicles and in large scale energy storages [1-11]. LiMnPO4 can offer a higher energy density than LiFePO4 due to a higher redox potential of Mn2+/Mn3+ couple (4.1V vs. Li/Li+) than that of Fe2+/Fe3+ couple (3.45V vs. Li/Li+) in the phosphate framework. However, the very low conductivity of LiMnPO4 limits the practical usage in high power applications. To improve electrochemical performance, multi-prong efforts have been made such as reducing the crystalline particle size, doping cations, coating conductive carbon, and forming composite LiMPO4 electrode by adding carbon or polymers [4-11]. In order to control the morphology and the crystallinity of the LiMPO4 particles, various synthetic routes for LiMPO4 have been developed such as the solid-state reaction, the sol-gel synthesis, the polyol process, and hydrothermal method. The hydrothermal approach has the advantage of prepareing nanosized materials with well-defined morphology under relatively low temperatures and high pressures [10-13]. The particle size and shape can be effectively controlled by a careful choice of surfactants, solvents, and reaction parameters in the hydrothermal synthesis [14-16]. The surfactant added to the reactant solution plays a critical role in determining the morphology of the LiMnPO4, by effectively controlling the nucleation and the growth of particles .
In this work, we employed a block copolymer of poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (P123) and a cationic surfactant of hexadecyltrimethyl ammonium bromide (CTAB) in a mixture sol
Data Loading...
