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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 35, Number 5
BKCSDE 35(5)
May 20, 2014 

 
Title
The Coating Effects of Al2O3 on a Li[Li0.2Mn0.54Co0.13Ni0.13]O2 Surface Modified with (NH4)2SO4
Author
Ji-Woo Oh, Rye-Gyeong Oh, Jung-Eui Hong, Won-Geun Yang, Kwang-Sun Ryu*
Keywords
Lithium-ion battery, Cathode, Over lithiation oxide, Surface treatments
Abstract
A series of 20 wt % (NH4)2SO4 and 3 wt % Al2O3 surface treatments were applied to Li[Li0.2Mn0.54Co0.13Ni0.13]O2 substrates. The Li[Li0.2Mn0.54Co0.13Ni0.13]O2 substrates were synthesized using a co-precipitation method. Sample (a) was left pristine and variations of the 20 wt % (NH4)2SO4 and 3 wt % Al2O3 were applied to samples (b), (c) and (d). XRD was used to verify the space group of the samples as R3m. Additional morphology and particle size data were obtained using SEM imagery. The Al2O3 coating layers of sample (b) and (d) were confirmed by TEM images and EDS mapping of the SEM images. 2032-type coin cells were fabricated in a glove box in order to investigate their electrochemical properties. The cells were charged and discharged at room temperature (25 oC) between 2.0V and 4.8V during the first cycle. The cells were then charged and discharged between 2.0V and 4.6V in subsequent cycles. Sample (d) exhibited lower irreversible capacity loss (ICL) in the first charge-discharge cycle as compared to sample (c). Sample (d) also had a higher discharge capacity of ~250 mAh/g during the first and second charge-discharge cycles when compared with sample (c). The rate capability of the Al2O3-coated sample (b) and (d) was lower when compared with sample (a) and (c). Sample (d), coated with Al2O3 after the surface treatment with (NH4)2SO4, showed an improvement in cycle performance as well as an enhancement of discharge capacity. The thermal stability of sample (d) was higher than that of the sample (c) as the result of DSC.
Page
1516 - 1522
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