• PDF / 9,071,200 Bytes
• 5 Pages / 612 x 792 pts (letter) Page_size
• 15 Downloads / 227 Views

DOWNLOAD

REPORT

---

Electrode Characteristics of Sputtered Lithium Manganese Oxide Films with DiamondLike-Carbon Top Layer Hee-Soo Moon, Kwang-Sun Ji, Won-Il Cho* Young-Soo Yun* and Jong-Wan Park Division of Materials Science and Engineering, Hanyang University, 17 Haengdang-Dong, Seongdong-Ku, Seoul 133-791, Korea *Korea Institute of Science and Technology 39-1, Hawolkok-Dong, Sungbuk-Ku, Seoul 136-791, Korea ABSTRACT There have been increasing interests in lithium rechargeable batteries, especially microbatteries, with rapid development of portable electronic equipments and MEMS(Micro electromechanical systems) technology. In this work, lithium manganese oxide, as a strong candidate for the battery materials, which is more abundant, stable in ambient state and less toxic than the other oxides such as lithium nickel oxides and lithium cobalt oxides, was deposited by rf magnetron sputter. The effect of thermal treatment on the microstructure and electrode characteristics of lithium manganese oxide cathode was investigated. In electrochemical experiment using liquid electrolyte, half-cell failure would be caused by manganese dissolution, degradation of electrolyte materials during charging/discharging process and so on. In this research we focus on interface reaction problem that would affect the cyclability and lifetime of microbattery. In order to reduce the interface reaction during operation, we introduce DLC(Diamond-like-Carbon) film that has high electrical resistivity, mechanical hardness and chemical stability. DLC film was deposited on sputtered lithium manganese oxide electrode by ECRCVD(Electron Cyclotron Resonance Chemical Vapor Deposition). DLC-top-layer LiMn2O4 film was more stable during charging/discharging reaction and higher discharge capacity in wide voltage windows than LiMn2O4 film. INTRODUCTION With development of semiconductor technology and demand for low power, battery operated device is on the rise, particularly in portable equipment requiring longer operation with higher reliability. Advances in the miniaturization of electronic device and MEMS(Micro-ElectroMechanical Systems) technology have reduced the current and power requirements of some of these devices to extremely low levels. This has made possible the use of thin film solid-state microbatteries as power sources for these devices. Therefore, it is important to develop long lasting and high-energy efficient thin film batteries that can be as an integral part of MEMS. During several decades, many researchers are achieving the new materials and fabrication techniques of cathode thin film for microbatteries1. Among many materials, LiMn2O4 thin film is particularly interesting, since it can reversibly intercalate one Li ion per mole, without altering the λ-MnO2 framework2,3. This system has a 4V operating voltage versus Li metal negative electrode and good electrochemical behavior is expected due to the favorable kinetics for fast Li ion diffusion through the three dimensional channel of the λ-MnO2 spinel structure. In general, to investigate electrochemica