27 7 Vol. 27 No CHINESE JOURNAL OF APPLIED CHEMISTRY July CV SEM EIS DTD. MCMB / 0. 01% DTD MCMB /Li. 300 ma h /g 350 ma h /g

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1 27 7 Vol. 27 No CHINESE JOURNAL OF APPLIED CHEMISTRY July * 1 mol /L LiPF 6 / CV SEM EDS EIS DTD MCMB / 0. 01% DTD MCMB /Li 300 ma h /g 350 ma h /g CV DTD 1. 4 V vs Li /Li + MCMB SEI DTD LiMn 2 O 4 O646 DOI /SP. J A EV HEV SEI 1-2 SEI SO 3 2 S 2 - x 4 CS SO 2 SEI ES EC Yu 6 1 mol /L LiPF 6 /EC + DMC + DEC % ES LiCoO 2 / DTD 1 mol /L LiPF 6 /EC + DMC + EMC DTD CV SEM EDS EIS DTD / mol /L LiPF 6 /EC + DMC + EMC DTD > 98% MCMB LiMn 2 O 4 CT2001A CHI 660C LEO-1530 FE-SEM LEO EDS Oxford CB zcwang@ xmu. edu. cn

2 MCMB MCMB PVDF N- -2- NMP h 16 MPa LiMn 2 O 4 PVDF Gaussian 03 B3LYP 6-31G d 8 EC DMC EMC DTD MCMB LiMn 2 O 4 Ar < 0. 05% < 0. 01% 0 ~ 0. 5 mv /s CV SEI Celgard2400 Ar 15 h MCMB /Li V 5 mv Hz ~ 100 khz DTD MCMB frontier molecular orbital FMO HOMO LUMO HOMO LUMO 1 DTD LUMO E LUMO LUMO DTD MCMB Table 1 1 DTD Frontier orbital energies for common solvents used and DTD Reagent Structure E HOMO /ev E LUMO /ev EC DMC EMC DTD

3 MCMB /Li 0. 2C DTD DTD DTD 0. 1% DTD 0. 01% DTD 300 ma h /g 350 ma h /g MCMB 0. 01% DTD MCMB DTD C MCMB /Li DTD Fig. 1 Plot of capacity retention of MCMB /Li cell 0. 6 V 1 at 0. 2C rate and room temperature φ DTD /% a. 0 b c d SEI The cell charge and discharge cut-off voltages were 0. 6 V 3. 0 V and V respectively SEI 0. 01% DTD MCMB 1. 4 V 1 DTD MCMB SEI 0. 6 V DTD SEI 1. 4 V MCMB SEI DTD MCMB SEI Fig. 2 2 MCMB Cyclic voltammograms of MCMB electrode in different electrolytes at 0. 5 mv / s SEM EDS 3 MCMB CV 2 SEM 3 2 MCMB DTD MCMB DTD MCMB SEI DTD SEI

4 Fig. 3 3 MCMB SEM SEM images of surface morphologies of MCMB electrodes DTD SEI EDS SEI 4 MCMB DTD CV 2 EDS 2 C O F DTD S DTD MCMB SEI F P LiPF 6 SEI MCMB Fig. 4 4 MCMB EDS EDS analysis of MCMB electrode surface SEI / Warburg Li + 13 ~ 15 5 DTD MCMB /Li V Nyquist 5A 5B DTD DTD DTD / DTD MCMB SEI Li DTD LiMn 2 O 4 6 LiMn 2 O % DTD 5 DTD DTD 7 LiMn 2 O 4 /Li 1C 7 DTD LiMn 2 O 4

5 7 827 Fig. 5 5 MCMB /Li Nyquist Nyquist plots for MCMB / Li cell measured at different voltages φ DTD /% A. 0 B V /V vs Li /Li + a b c d Fig. 6 6 LiMn 2 O 4 7 Cyclic voltammograms of LiMn 2 O 4 electrode in different electrolytes at 0. 5 mv /s 1C LiMn 2 O 4 / Li Fig. 7 Plot of capacity retention of LiMn 2 O 4 /Li cell at 1C rate and room temperature φ DTD /%. a. 0 b The cell charge and discharge cut-off voltages were 3. 5 V and 4. 5 V respectively 8 LiMn 2 O 4 CV 5 SEM 8a 8b Fig. 8 8 LiMn 2 O 4 SEM SEM images of surface morphologies of LiMn 2 O 4 electrodes

6 % DTD LiMn 2 O 4 DTD LiMn 2 O 4 SEI DTD LiMn 2 O 4 1 Buqa H Wursig A Vetter J Spahr M E Krumeich F Novak P. J Power Sources J Lu M Cheng H Yang Y. Electrochim Acta J Ein-Eli Y Thomas S R Koch V R. J Electrochem Soc J Wagner M W Liebenow C Besenhard J O. J Power Sources J Ein-Eli Y. J Electroanal Chem J Yu B T Qiu W H Li F S Cheng L. J Power Sources J Xu M Q Li W S Zuo X X Liu J S Xu X. J Power Sources J Wang B Qu Q T Xia Q Wu Y P Li X Gan C L Ree T V. Electrochim Acta J Xie X H Chen L B Sun W Xie J Y. J Power Sources J Chen R J Wu F Li L Guan Y B Qiu X P Chen S Li Y J Wu S X. J Power Sources J Matsuoka O Hiwara A Omi T Toriida M Hayashi T Tanaka C Saito Y Ishida T Tan H Ono S S Yamamoto S. J Power Sources J Ota H Sakata Y Inoue A Yamaguchi S. J Electrochem Soc J A Ufheil J Baertsch M C Wursig A Novak P. Electrochim Acta J Zheng H H Fu Y B Zhang H C Abe T Ogumi Z. Electrochem Solid State Lett J A Nakahara H Yoon S Y Nutt S. J Power Sources J Effect of Ethylene Sulfate as Electrolyte Additive on Performance of Li-ion Batteries YAO Yi-Wen XU Jie YAO Wan-Hao WANG Zhou-Cheng * YANG Yong College of Chemistry and Chemical Engineering Xiamen University Xiamen Abstract Ethylene sulfate DTD was studied as an additive to 1 mol /L LiPF 6 /ethylene carbonate EC + dimethyl carbonate DMC + methyl ethyl carbonate EMC by volume electrolyte for lithium ion batteries. The effects of DTD on lithium ion battery performance and on the mesocarbon microbead MCMB electrode /electrolyte interphase were investigated by galvanostatic charge-discharge measurements cyclic voltammetry CV scanning electron microscopy SEM energy dispersive spectroscopy EDS and electrochemical impedance spectroscopy EIS. The results show that DTD with a volume ratio of 0. 01% can increase the reversible discharge capacity from 300 ma h /g to 350 ma h /g and cycleability of MCMB /Li cell. SEM observation and EIS analysis suggest that DTD facilitates the morphology of solid electrolyte interface SEI formed on the surface of the MCMB electrode and reduces the total resistance of the cell. CV measurements reveal that DTD can be electrochemically reduced at potentials around 1. 4 V vs Li /Li + during the first reduction engaged in the formation of SEI. At the same time DTD has no adverse effect on the LiMn 2 O 4 electrode. Keywords lithium ion battery ethylene sulfate additive solid electrolyte interface