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Click to edit Master title stylePaul Scherrer Institut, Electrochemistry Laboratory, CH-5232 Villigen PSI, Switzerland
ELECTROCHEMISTRY LABORATORY
BA
TT
ER
IES
0
75150225300375
020406080100
0 50 100 150 200 250 3000
75150225300375
020406080100
/ Charge/Discharge RT Efficiency RT
Spe
cific
cha
rge
[mA
h/g]
Cycle
Cou
lom
bic
effic
ienc
y [%
]
Mario El Kazzi, Erik J. Berg, Claire Villevieille, Pe tr NovákPaul Scherrer Institut, Electrochemical Storage Energy Section, CH-5232 Villigen PSI, Switzerland
ELECTROCHEMISTRY LABORATORY
BA
TT
ER
IES
Electrochemical performance and XPS surface analyses of HE-NCM¦LTO cells in (LP30 vs. IL) electrolytes
Scan me!
Objective Post mortem XPS – Process flow
Cycled with LP30* Cycled with BMIMBF 4**
Standard PSI CellGlove box assembling/disassembling
(I) (II)
Washed with DMC
Unwashed
Electrode
LP30
1M LiBF 4/BMIMBF 4
1 11
22
4
3 3
BF4
BMIM
LiPF6DMC EC
Sample holder
PSI XPS spectrometer
Transfer chamber
Under Aratmosphere
Al K α monochromatic source (500µm, 150W)
Flood Gun for charge compensation
Al K α and Mg K α non-monochromatic sources
Ar sputtering gun for depth profile analysis
UV lamp for band structure
HE-NCM LTO HE-NCM LTOWashed Unwashed Washed Unwashed Washed Unwashed Washed Unwashed
Conclusions
IntroductionThe instability of (electrode/electrolyte interface) at h igh temperatures (> 50 °C) and potentials (> 4.5 V) of the most common carbonate-base d electrolytes is limiting thedevelopment of the next generation of high specific energy L i-ion batteries.[1] However, these problems can mainly be o vercome by the use of ionic liquids (ILs) as alternativeelectrolyte solution. Their physical properties such as th ermal (> 120°C)/electrochemical (> 5.5 V) stability and low vapor pressu re make them a promising electrolytes.[2]
References
Negative Li4Ti5O12 (LTO)
Spinel structure
PositiveLi(Ni, Co, Mn)O 2 (HE-NCM)
Electrodes
�HE-NCM cycled versus the LTO plateau within thecutoff limits [2.4 V – 5.1 V vs. Li/Li+ ].
�LP30* and IL-based (1M LiBF4 in BMIMBF4)**used as electrolytes.
* 1M LiPF 6 with ethylene carbonate and dimethyl carbonate(EC:DMC 1:1)
** C8H15BF4N2, Cation: 1-Butyl-3-methylimidazolium, Anion: Tetrafluoroborate
80% Active material10% Super P
(Carbon)10% PVDF
[CF2-CH2]n
~20nm
Post mortem XPS and SEM
Electrochemical performance
�SEI & SPI surface composition and morphologyafter cycling.
�The origin and mechanism of the surface layerformation and its impact on the cell performance.
469 462 455
198 195 192
Binding Energy (eV)405 402 399
294 288 282
C=O
Super P
CF3
Ti4+
Ti3+
Ti2+
Unwashed
WashedDMC
� Formation of thick surface layer on LTO however is lesspronounced on HE-NCM.
� Detection of TiFx species on both electrodes related to the Ticorrosion of the cell.
� Detection of Mn and Co on LTO due to the transition metaldissolution in the electrolyte.
� After washing agglomeration of the IL on the active particles.
� Detection of IL decomposition product on both electrodes
� No detection of Ti on positive or Mn on negative electrodes
C1s Ti2p
Inte
nsity
(ar
b. u
nits
)
294 288 282
469 462 455
656 648 640
Mn2p
Pristine
C1s Ti2p Mn2p
294 288 282
469 462 455
656 648 640
Binding Energy (eV) Binding Energy (eV)
296 292 288 284
Binding Energy (eV)
Inte
nsity
(ar
b. u
nits
)
405 402 399
695 690 685
198 195 192
C1s N1s F1s B1s
Unwashed
WashedDMC
469 462 455
198 195 192
Binding Energy (eV)405 402 399
Inte
nsity
(ar
b. u
nits
)
294 288 282
C1s N1sTi2p Ti2p N1sC1s B1sB1s
Neat dropletBMIMBF 4
Financial support from BASF SE is gratefully acknowledged
� Good electrochemical cycling was demonstrated with LP30, however with the IL 36% less specificcharge was obtained with continuous fading up to 30 mAh/g after 130 cycles
� Important impact of the washing was observed on the surface composition mainly on LTO surface
With LP30 With BMIMBF 4
Super P
1
4
3
2CF3
BF4BF4
CF3
BMIM
C=OO-C=O
CO3
TiF4 TiF4
TiF4 Ti4+
Ti4+
Ti3+
C-OC=O
O-C=O
CFx
X≥2
CFx
X≥2
Super P
HydrocarbonCF2 CH2
PVdF
Super PC-C
Li2CO3
O-C=OC=O
C-O
Hydrocarbon
CF3
[1] John B. Goodenough , Rechargeable batteries: challenges old and new,J. Solid State Electrochem, 2012 16 2019-2029.
[2] M. Armand, F. Endres, D. R. MacFarlane, H. Ohno, B.Scrosati , Ionic-liquid materials for the electrochemicalchallenges of the future, Nature Materials, 2009 8 621-629.
2µm 2µm 2µm 2µm 2µm 2µm 2µm 2µm
Mn4+