1. Li-Mn-O Thin Film Cathode prepared at Room Temperature Thin Film & Battery Materials Lab. National Research Lab. Kangwon Nat’l Univ. Jeong-Kyu Lim a, Hyeon-Young Lee a, Serk-Won Jang a, Seung -Joo Lee b and Sung-Man Lee a a Department of Advanced Material Science and Engineering, Kangwon National University, Chuncheon, Kangwondo, 200-701, South Korea b Microsystem Center, Korea Institute of Science and Technology, Seoul, South Korea

2. Introduction Thin Film & Battery Materials Lab. National Research Lab. Kangwon Nat’l Univ. LiMn 2 O 4 spinel and related compounds  Of great interest for use as cathodes in rechargeable lithium batteries. Crystalline thin-film lithium manganese oxide cathodes  Fabricated by physical vapor deposition followed by a high-temperature annealing. The fabrication of the thin-film cathodes without post-annealing at high temperatures  Useful for extensive applications of thin film lithium batteries. The preparation and electrochemical characterization of thin-film lithium manganese oxide cathodes by r.f. sputtering from LiMn 2 O 4 and LiMnO 2 targets at room temperature. In this work

3. Experimental procedure - 2 inch disk type - Pressing : cold pressing or hot pressing - Sintering : 950 ℃ for 12hr in air Target preparation - RF power : 30~75 W - Substrate : SUS (0.3t, Φ12) - film thickness : 0.5 to 2 ㎛ - Ar/O 2 mixture : from 10/1 to 20/1 (5 mTorr) Thin film fabrication - XRD (X-ray diffractometer) - α-step (Thickness profiler) - FE-SEM ( Field Emission – Scanning Electron Microscope ) Structural & Mechanical analysis - CR2016 Coin Cells - Anode : Li foil - Electrolyte : 1M LiPF 6 dissolved in EC/DEC 1M LiClO 4 dissolved in PC - cut-off voltage : 2.0 - 4.5V (5~50 ㎂ / ㎠ ) 2.3 - 4.3V Electrochemical analysis Thin Film & Battery Materials Lab. National Research Lab. Kangwon Nat’l Univ.

4. Structure Analysis Thin Film & Battery Materials Lab. National Research Lab. Kangwon Nat’l Univ. Deposited thin film amorphous or nanao-crystalline X-Ray Diffraction a. LiMn 2 O 4 b. LiMnO 2

5. Charge/Discharge curve : LiMn 2 O 4 Thin Film & Battery Materials Lab. National Research Lab. Kangwon Nat’l Univ. Cell test condition a. cutoff Voltage : 2.0-4.5V b. current density : 20 ㎂ c. Electrolyte : 1M LiPF 6 +EC/DEC(1/1, v/v)

6. Charge/Discharge curve : LiMnO 2 Thin Film & Battery Materials Lab. National Research Lab. Kangwon Nat’l Univ. Cell test condition a. cutoff Voltage : 2.5-4.3V b. current density : 30 ㎂ c. Electrolyte : 1M LiPF 6 +EC/DEC(1/1, v/v) a. as-deposited b. post-annealing (200 ℃ )

7. Thin Film & Battery Materials Lab. National Research Lab. Kangwon Nat’l Univ. 20 ㎂ 50 ㎂ Capacity vs cycle number : LiMn 2 O 4 10 ㎂ Cell test condition a. cutoff Voltage : 2.0-4.5V b. current density : 10, 20, 50 ㎂ c. Electrolyte : 1M LiPF 6 +EC/DEC(1/1, v/v)

8. Thin Film & Battery Materials Lab. National Research Lab. Kangwon Nat’l Univ. Capacity vs cycle number : LiMnO 2 Cell test condition a. cutoff Voltage : 2.5-4.3V b. current density : 30 ㎂ c. Electrolyte : 1M LiPF 6 +EC/DEC(1/1, v/v)

9. Thin Film & Battery Materials Lab. National Research Lab. Kangwon Nat’l Univ. Rate-capability : LiMn 2 O 4 Normalized capacity = at 2 nd cycle Q Q i i = 5 ㎂

10. Conclusion Thin Film & Battery Materials Lab. National Research Lab. Kangwon Nat’l Univ. Thin film electrodes produced by r.f. sputtering from an LiMn 2 O 4 target showed reasonable electrochemical properties as a cathode for thin film rechargeable lithium batteries. Thin films deposited from a LiMnO 2 target exhibits a poor cyclability, which is significantly improved by post-annealing at 200 ℃