1. Thin Film & Battery Materials Lab. National Research Lab. Kangwon Nat’l Univ. Heon-Young Lee a, Seung-Joo Lee b, Sung-Man Lee a a Department of Advanced Material Science and Engineering Kangwon National University b Microsystem Research Center, Korea Institute of Science & Technology (KIST) Heon-Young Lee a, Seung-Joo Lee b, Sung-Man Lee a a Department of Advanced Material Science and Engineering Kangwon National University b Microsystem Research Center, Korea Institute of Science & Technology (KIST) Sn based anodes for lithium rechargeable microbatteries Sn based anodes for lithium rechargeable microbatteries

2. Thin Film & Battery Materials Lab. National Research Lab. Kangwon Nat’l Univ. Thin Film Microbattery as a Micro Power Source Battery composed of - Thin film electrodes (Negative & Positive) - Thin film electrolyte Incorporated into Devices Discharge Charge Li + ion - + Electrolyte Positive electrode Negative electrode Substrate Positive electrode Negative electrode Electrolyte Current collector TFB IC IC card   m

3. Thin Film & Battery Materials Lab. National Research Lab. Kangwon Nat’l Univ. Micro Battery MEMS Electronics Power Implantable Device Electronics Smart card Hazard card On-chip appl. Micro PDA MEMS Medical Military Aerospace Micro mechanics Microbattery-based technology in the 21 st century

4. Thin Film & Battery Materials Lab. National Research Lab. Kangwon Nat’l Univ. Thin Film anode electrodes IntroductionIntroduction low melting point (181 ℃ ) & high reactivity with air limit the application area low melting point (181 ℃ ) & high reactivity with air limit the application area : Large capacity active phase significant volume change during cycling drastic capacity fade : Large capacity active phase significant volume change during cycling drastic capacity fade buffering inactive elements enhanced cyclability (?) buffering inactive elements enhanced cyclability (?) Active / inactive alloys (SnM) Li-alloys ( Si, Sn, Al) Lithium metal

5. Thin Film & Battery Materials Lab. National Research Lab. Kangwon Nat’l Univ. Sn-Zr (active / inactive composites) Suppress agglomeration of Sn strong affinity between Sn and M limits the Sn alloying with Li and forms a buffering phase Suppress agglomeration of Sn strong affinity between Sn and M limits the Sn alloying with Li and forms a buffering phase  H Sn-Zr   H Sn-Li Buffering effect Fine and uniform distribution of the Sn excellent stability Buffering effect Fine and uniform distribution of the Sn excellent stability Sn-Zr-Ag (ternary system) Formation enthalpy( △ H f ) of M-Sn system Background & Approach

6. Thin Film & Battery Materials Lab. National Research Lab. Kangwon Nat’l Univ. To Investigate the possibility of Sn, Sn-Zr thin-film as anode for microbatteries Fabrication of Sn-Zr-(Ag) thin films Evaluation of Electrochemical characteristics of Sn-Zr-(Ag) thin films To Investigate the possibility of Sn, Sn-Zr thin-film as anode for microbatteries Fabrication of Sn-Zr-(Ag) thin films Evaluation of Electrochemical characteristics of Sn-Zr-(Ag) thin films Objective

7. Thin Film & Battery Materials Lab. National Research Lab. Kangwon Nat’l Univ. Thin Film Fabrication Substrate : Cu disc (12 mm dia.) Substrate cooling : Cooling or without cooling Sputtering Targets : Co-sputtering or Co-deposition by e-beam (Sn & Zr or Si & Zr & Ag) Deposition Conditions : - Base P. : 2  10 -6 Torr - Atmosphere : 5  10 -3 Torr Ar ambient - Negative DC bias : 0 – 100V was applied for some samples Film Characterization Composition - RBS Electrochemical Test : Discharge & Charge Cell construction : 2016 coin type cell Counter & Reference electrode : Li foil Electrolyte : 1M LiPF 6 in EC/DEC Thickness - Profilometer Morphology - SEM Structure - XRD Experimental Procedure : Negative Electrode

8. Thin Film & Battery Materials Lab. National Research Lab. Kangwon Nat’l Univ. First charge-discharge curves for pure Sn thin film electrode film thickness : 700 Å low irreversible capacity The plateau at 0.69, 0.53 and 0.43 V are associated with the Sn, Li 2 Sn 5 and LiSn phases

9. Thin Film & Battery Materials Lab. National Research Lab. Kangwon Nat’l Univ. (a) 300 Å (b) 700 Å (c) 1200 Å Normalised capacity vs. cycle number for Sn thin films of vatious thickness The discharge capacity is normalised against the first discharge capacity The cycling performance is little improved by a decrease in film thickness

10. Thin Film & Battery Materials Lab. National Research Lab. Kangwon Nat’l Univ. a b c (a) before cycling (b) after 6 cycles (c) after 20 cycles As a result of large volumetric change with lithium insertion the formation of large cracks and the delamination of active material from the substrate loss of electronic contact between the active materials as well as between the active material and the current collector poor cyclelability Surface morphology of Sn thin-film Anodes after cycles

11. Thin Film & Battery Materials Lab. National Research Lab. Kangwon Nat’l Univ. (a) Sn 62 Zr 38 (b) Sn 64 Zr 34 Ag 2 (c) Sn 57 Zr 33 Ag 10 The cycling performances of the Ag- containing Sn-Zr films are better than that of the Sn-Zr sample The 10 at.% Ag containing electrode (Sn 57 Zr 33 Ag 10 ) exhibits a stable capacity retention for long cycles Cycle Performance The capacity vs. cycle number for Sn-Zr-Ag thin films

12. Thin Film & Battery Materials Lab. National Research Lab. Kangwon Nat’l Univ. (a) Sn 62 Zr 38 (b) Sn 64 Zr 34 Ag 2 (c) Sn 57 Zr 33 Ag 10. XRD 2Θ Structure of Sn-Zr-Ag thin-film Anodes Ag-doped samples, even for the film containing 2 at. % Ag, the diffraction lines of Sn cannot be distinguished may be attributed to the existence of very finely dispersed Sn within the matirix

13. Thin Film & Battery Materials Lab. National Research Lab. Kangwon Nat’l Univ. (c) Sn 57 Zr 33 Ag 10 FESEM (b) Sn 64 Zr 34 Ag 2 (a) Sn 62 Zr 38 Surface morphology of Sn-Zr-Ag thin-film Anodes The Ag-doped films show a fine and uniform distribution of the Sn aggregated particles compared with that of the undoped sample

14. Thin Film & Battery Materials Lab. National Research Lab. Kangwon Nat’l Univ. Conclusion The cyclability of Sn-Zr thin films is improved with the addition of Zr although the capacity decreases The cycling stability of Sn-Zr thin film electrodes appear to be significantly increased by doping Ag into the film The cyclability of Sn-Zr thin films is improved with the addition of Zr although the capacity decreases The cycling stability of Sn-Zr thin film electrodes appear to be significantly increased by doping Ag into the film