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Li-Mn-O Thin Film Cathode prepared at Room Temperature. 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
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Li-Mn-O Thin Film Cathode prepared at Room Temperature Jeong-Kyu Lima, Hyeon-Young Leea, Serk-Won Janga, Seung -Joo Leeb and Sung-Man Leea 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 Kangwon Nat’l Univ. Thin Film & Battery Materials Lab. National Research Lab.
Introduction LiMn2O4 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 LiMn2O4 and LiMnO2 targets at room temperature. In this work Kangwon Nat’l Univ. Thin Film & Battery Materials Lab. National Research Lab.
Experimental procedure Target preparation - 2 inch disk type - Pressing : cold pressing or hot pressing - Sintering : 950℃ for 12hr in air Thin film fabrication - RF power : 30~75 W - Substrate : SUS (0.3t, Φ12) - film thickness : 0.5 to 2 ㎛ - Ar/O2 mixture : from 10/1 to 20/1 (5 mTorr) Structural & Mechanical analysis Electrochemical analysis - XRD (X-ray diffractometer) - α-step (Thickness profiler) - FE-SEM ( Field Emission – Scanning Electron Microscope ) - CR2016 Coin Cells - Anode : Li foil - Electrolyte : 1M LiPF6 dissolved in EC/DEC 1M LiClO4 dissolved in PC - cut-off voltage : 2.0 - 4.5V (5~50 ㎂/㎠) 2.3 - 4.3V Kangwon Nat’l Univ. Thin Film & Battery Materials Lab. National Research Lab.
Structure Analysis X-Ray Diffraction a. LiMn2O4 b. LiMnO2 Deposited thin film amorphous or nanao-crystalline Kangwon Nat’l Univ. Thin Film & Battery Materials Lab. National Research Lab.
Charge/Discharge curve : LiMn2O4 Cell test condition a. cutoff Voltage : 2.0-4.5V b. current density : 20㎂ c. Electrolyte : 1M LiPF6 +EC/DEC(1/1, v/v) Kangwon Nat’l Univ. Thin Film & Battery Materials Lab. National Research Lab.
Charge/Discharge curve : LiMnO2 a. as-deposited b. post-annealing (200℃) Cell test condition a. cutoff Voltage : 2.5-4.3V b. current density : 30㎂ c. Electrolyte : 1M LiPF6 +EC/DEC(1/1, v/v) Kangwon Nat’l Univ. Thin Film & Battery Materials Lab. National Research Lab.
Capacity vs cycle number : LiMn2O4 Cell test condition a. cutoff Voltage : 2.0-4.5V b. current density : 10, 20, 50㎂ c. Electrolyte : 1M LiPF6 +EC/DEC(1/1, v/v) 10 ㎂ 20 ㎂ 50 ㎂ Kangwon Nat’l Univ. Thin Film & Battery Materials Lab. National Research Lab.
Capacity vs cycle number : LiMnO2 Cell test condition a. cutoff Voltage : 2.5-4.3V b. current density : 30㎂ c. Electrolyte : 1M LiPF6 +EC/DEC(1/1, v/v) Kangwon Nat’l Univ. Thin Film & Battery Materials Lab. National Research Lab.
Rate-capability : LiMn2O4 Q i Normalized capacity = at 2nd cycle Q i = 5㎂ Kangwon Nat’l Univ. Thin Film & Battery Materials Lab. National Research Lab.
Conclusion Thin film electrodes produced by r.f. sputtering from an LiMn2O4 target showed reasonable electrochemical properties as a cathode for thin film rechargeable lithium batteries. Thin films deposited from a LiMnO2 target exhibits a poor cyclability, which is significantly improved by post-annealing at 200℃ Kangwon Nat’l Univ. Thin Film & Battery Materials Lab. National Research Lab.