Effect of Fluoroethylene Carbonate Additive on the Performance of Lithium Ion Battery

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1 February (Wuli Huaxue Xuebao) Acta Phys -Chim Sin (2) [Article] wwwwhxbpkueducn * ( ) 1 mol L -1 LiPF 6 / (EC)+ (DMC)+ (EMC)(EC DMC EMC 1 1 1) 2% (FEC) (CV) (SEM) (EDS) (EIS) FEC (MCMB) / 2% FEC MCMB (SEI) ; ; ; ; ; O646 Effect of Fluoroethylene Carbonate Additive on the Performance of Lithium Ion Battery XU Jie YAO Wan-Hao YAO Yi-Wen WANG Zhou-Cheng * YANG Yong (College of Chemistry and Chemical Engineering Xiamen University Xiamen Fujian Provine P R China) Abstract Fluoroethylene carbonate (FEC) with a volume ratio of 2% was added to the electrolyte containing 1 mol L -1 LiPF 6 in ethylene carbonate (EC) dimethyl carbonate (DMC) and methyl ethyl carbonate (EMC) (1 1 1 by volume) The effects of FEC on lithium ion battery performance and on the mesocarbon microbead (MCMB) electrode/electrolyte interphase were studied by cyclic voltammetry (CV) scanning electron microscopy (SEM) energy dispersive spectroscopy (EDS) and electrochemical impedance spectroscopy (EIS) The results indicated that the application of a 2% (volume ratio) of FEC suppressed electrolyte decomposition and caused the formation of an excellent solid electrolyte interphase (SEI) film on the MCMB electrode The battery resistance decreased while the specific capacity and cyclic stability of the battery increased Key Words Additive; Fluoroethylene carbonate; Lithium ion battery; Cyclic voltammetry; Energy dispersive spectroscopy; Electrochemical impedance spectroscopy 1991 LiPF 6 (EC) (DMC) : (1) (2) (3) (DEC) (EMC) ( ) Received: September ; Revised: October ; Published on Web: December * Corresponding author zcwang@xmueducn; Tel: (2007CB209702) 鬁 Editorial office of Acta Physico-Chimica Sinica

2 202 Acta Phys -Chim Sin 2009 Vol25 : ( Celgard mol L -1 LiPF 6 /EC+ 5%) DMC+EMC(EC DMC EMC 1 1 1) [1] ( ) FEC( 996%) 2%( ) CR2025 (solid electrolyte interphase film SEI ) SEI CT2001A [2-5] 12 MCMB / 05 mv s -1 ; MCMB/Li [67] EIS Hz 5 mv CHI 660C / EIS [8-10] ZSimpWin SEI EDS SEI LEO-1530 (FE- SEM LEO ) (EDS Oxford ) SEI (VC) [1112] SEI VC SEI (LiF 2 Li x PF y ) VC C MCMB/Li (VEC) [1314] FEC (ES) [415] (FEC) FEC EC 2% FEC (MCMB) FEC (CV) (SEM) (EDS) (EIS) FEC MCMB / 1 11 : (MCMB)/ (LiMn 2 O 4 ) (PVDF) N- (NMP) 05C rate at room temperature h 16 MPa respectively 1 Fig1 05C MCMB/Li Plot of capacity retention of MCMB/Li cell at The cell charge and discharge cut-off voltages were 30 and 0005 V

3 No Fig2 05C LiMn 2 O 4 / Li Plot of capacity retention of LiMn 2 O 4 /Li cell at 05C rate at room temperature The cell charge and discharge cut-off voltages were 35 and 45 V respectively 3 MCMB 1 mol L -1 LiPF 6 /EC+ DMC+EMC (EC DMC EMC 1:1:1) 4(c1 c2) FEC 3(a) 06 V (SEI) [1617] ; 3(b) FEC MCMB SEI 06 V FEC 06 V SEI 0 V 025 V MCMB 23 SEI EDS 2 CV MCMB (DMC ) SEM EDS 2 05C LiMn 2 O 4 / 4(a1 a2) MCMB Li 2% FEC ; 2 FEC LiMn 2 O 4 FEC EC 4(b1 b2) 2 MCMB 22 MCMB CV ; FEC 2 MCMB 5 MCMB EDS 2% FEC MCMB C 10 V 5(a) MCMB Fig3 3 MCMB Cyclic voltammograms at 05 mv s -1 of MCMB electrode in the electrolyte (a) without additive ; (b) with 2% FEC

4 204 Acta Phys -Chim Sin 2009 Vol25 Fig4 4 MCMB SEM SEM images of surface morphology of MCMB electrodes (a1 a2) before cycling; (b1 b2) after 2 cycles without additive; (c1 c2) after 2 cycles with 2% FEC 2% FEC 5(b) SEI Nyquist [18-21] 7 2% FEC 5(c) F R s CV FEC ; SEI MCMB SEI FEC R film CPE film SEI FEC ; SEI / MCMB SEI (CPE dl ) (R ct ) W 24 EIS ( V) 6 FEC ( MCMB/Li 005 V) MCMB SEI FEC Ω 2% FEC SEI 6 FEC MCMB Fig5 5 MCMB EDS EDS analysis of the MCMB electrode surface (a) before cycled in the electrolyte; (b) cycled in the electrolyte without additive; (c) cycled in the electrolyte with 2% FEC

5 No2 205 Fig8 8 EC FEC Chemical structures of EC and FEC 6 Fig6 MCMB/Li Nyquist Nyquist plots for MCMB/Li cell measured at different valtages (a) without additive; (b) with 2% FEC Fig9 9 FEC The reaction mechanism of FEC Ω M M 005 V 50 FEC MCMB SEI MCMB/Li 25 FEC 3 FEC EC 2% FEC MCMB/ ( 8 ) Li FEC LiMn 2 O 4 FEC CV FEC EDS FEC MCMB SEI C O F F MCMB FEC 9 FEC FEC C 襒 O Fig7 7 MCMB/Li Equivalent circuit for MCMB/Li cell SEI ; SEM EDS O Li + EIS 2% FEC MCMB SEI FEC MCMB SEI MCMB SEI FEC

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