V. Focused Fundamental Research - EERE - U.S. Department of ...

V.B.8 Characterization of New Cathode Materials and Studies of Li-Air Batteries (BNL, U. Mass)
Nam – U. Mass, Yang – BNL
rigid shift of Mn K-edge was observed, indication that the
Mn ions remain at the oxidation state closer to the Mn 4+
state.
Normalized intensity (a.u.)
1.5
1.0
0.5
0.0
Before CH
After CH1
After DH1
After CH2
After DH2
After CH3
After DH3
6540 6550 6560 6570
Energy ( eV )
Figure V - 46: Ex situ XAS spectra at Mn K-edge of high energy
Li1.2Ni0.2Mn0.6O2 cathode before cycling and after 1 st , 2 nd , and 3 rd charge and
discharge
In collaboration with Prof. Qu at the University of
Massachusetts (UMASS) at Boston, a new electrolyte with
higher ionic conductivity and oxygen solubility has been
developed and studied. Up to now, the discharge rate of
Li-air cell is too low (about 0.1 mA/cm 2 ). As shown in
Figure V - 47, using our new electrolyte with increased O 2
solubility and mobility by the FTBA additives and new
solvents, almost 100 times higher discharge rate has been
achieved, making it closer to the Li-ion battery level.
Figure V - 47: Constant-current (1 mAcm -2 ) discharge of Li-O2 cells using
electrolyte with and without perfluorotributylamine (FTBA) additives
Conclusions and Future Directions
1. In collaboration with ANL, and GM R&D Center,
Li 2 MnO 3 -LiMO 2 (M=Ni, Co, Mn) high energy
density cathode materials have been studied using
combined in situ hard XAS and ex situ soft XAS. The
results of these studies provide useful information for
improving the energy density and cycleability of high
energy density Li-ion batteries.
2. In collaboration with Institute of Physics, CAS, the
mesoporous LiFe 0.6 Mn 0.4 PO 4 cathode material are
being studied by in situ XRD and XAS in comparison
with the same composition without mesoporous
structure. The results of these studies provide
important information about the effects of meso-pores
on the phase transition behavior and performance of
these new cathode materials with low cost potential.
3. Developed new in situ XRD to study cathode
materials for Li-ion batteries during chemical
delithiation.
4. Developed a novel new electrolyte with dramatically
increased O 2 solubility. The discharge rate of the Liair
cell using this electrolyte is almost 100 times
greater than the conventional electrolytes.
5. Collaborations with US industrial partners such as
Dow Chem. and GM, as well as with US and
international research institutions (ANL and UMASS
in US, IOP in China, KIST in Korea) have been
established. The results of these collaborations have
been published or presented at invited talks at
international conferences.
Future Directions
1. Complete soft and in situ hard XAS study of high
energy Li 2 MnO 3 -LiMO 2 (M=Ni, Co, Mn, Fe)
cathode materials during activation charge and
multiple cycling.
2. Complete comparative in situ XRD and XAS studies
of LiFe 1-x Mn x PO 4 (x=0 to 1) cathode materials with
different particle size and morphology during
chemical and electrochemical delithiations.
3. Develop and test the atomic layer deposition (ALD)
surface coating on new cathode materials.
4. Use time resolved XRD to study the thermal stability
of ALD surface coated Li 2 MnO 3 -LiMO 2 (M=Ni, Co,
Mn, Fe) cathode materials during heating.
5. Further develop surface and interface sensitive
techniques, such as soft x-ray absorption, TEM,
SAED, and electron energy loss spectroscopy
(EELS) for diagnostic studies on surface-bulk
differences and phase transition kinetics of electrode
materials.
6. In collaboration with UMASS Boston, continue the
effort to develop GDEs with 2 catalysts for Li-air
batteries. Start the preliminary studies of the
rechargeable Li-air cells and in situ XRD and XAS
on the GDE.
7. Develop new electrolyte systems to increase the
solubility and mobility of O 2 in the electrolyte in
order to increase the discharge rate of Li air cells.
Energy Storage R &D 506 FY 2011 Annual Progress Report