primary particle level diagnostics by transmission ... · primary particle level diagnostics by...
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Primary Particle Level Diagnostics by Transmission Electron
Microscopy
Huolin L. Xin
Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, NY
TEM Grid in a coin
cell: quasi in-situ
method
“Dry-cell” in-situ
approach
Electrochemical liquid
cell approach
Scanning Transmission Electron Microscopy
1 atom wide (1 Å) beam is scanned
across the sample to form a 2-D image100 keV
Electron beam
Lenses
ADF
Detector
Electron
Spectrometer
Sample
Elastic Scattering ~
Z1.7
NdGaO3 La0.7Sr0.3MnO3
200 pixels
68 p
ixels
Inelastic Scattering
EELS: Chemical Imaging
Nd
O
Mn
LaO K edge
Mn L2,3 edge
La M4,5 edge
Nd M4,5 edge
What are the remaining challenges in lithium ion battery?
Limited by cathode/electrolyte
interface stability
Capacity fading and thermal
stability of cathode
Surface reconstruction and chemical evolution of stoichiometric layered cathode materials for lithium-ion batteries, Feng Lin,
Isaac Markus, Dennis Nordlund, Tsu-Chien Weng, Mark Asta, H. L. Xin*, M. M. Doeff, Nature Communications, 5, 3529
LiNi0.4Mn0.4Co0.2O2
LUMO
HOMOAnode/SEI/electrolyte
Self-passivation by reducing
the electrolyte
(Li2CO3, LiF, etc…)
Cathode
Materials and voltage
dependent
Still under debate
Degraded Surface Layers of NMC442 = LiNi0.4Mn0.4Co0.2O2
• Surface structures were altered after exposing to electrolyte and
the surface layer was thickened after 1cycle of discharge-charge
Electrolyte Immersed Sample After 1 cycle
Feng Lin et al Xin*, and Doeff, Nat. Comm. 5, 3529 (2014)
20 Cycles (NMC 442)
NMC442 = LiNi0.4Mn0.4Co0.2O2
4
“4+”
“2+”
3.7 nm
Feng Lin et al Xin*, and Doeff, Nat. Comm. 5, 3529 (2014)
The Degradation is Facet DependentFeng Lin et al Xin*, and Doeff, Nat. Comm. 5, 3529 (2014)
Radiation Damage of Layer-Layer Compound
• LiNixMnxCo(1-2x)O2
300 keV
~36 pA
1024x1024 pixels,
pixel size 0.153
angstrom
pixel dwell time 6 us
frame time 7.55
sec/frame
Feng Lin et al, H. L. Xin*, Scientific Reports, 4, 5694 (2014)
Faster scanning spreads dose
• 4x faster scanning
• 300 keV
• ~36 pA, 512x512 pixels
• pixel size 0.306
angstrom
• pixel dwell time 6 us,
frame rate 1.89
sec/frame
Feng Lin et al, H. L. Xin*, Scientific Reports, 4, 5694 (2014)
High-energy Electron vs. X-ray
Henderson, Quarterly Reviews of Biophysics 28, 171 (1995)
It’s not the cross-section, but
How many damaging events
per useful imaging event.
Least DamageElastic Imaging – Electrons win
Inelastic imaging – Soft X-rays win
Electron Elastic
X-ray Elas.
Spectroscopy: What’s the True Carbon K edge?
X-ray Absorption
Ade and Stoll, Nature Mats, 8 (2009) 281Ade and Hitchcock, Polymer 49 (2008) 643
EELS of Li2CO3
500 electrons/Å2/spectrum
F Lin et al Xin*, Nat. Comm. 5, 3356 (2014)
Imaging of Pristine NMC
• No Damaging in EELS and Imaging to the Pristine Surface5
nm
5 n
m
Sp
ectru
m Im
age
1 n m1 n m
Subplixel Scanning Collage
Feng Lin et al Xin*, and Doeff, Nat. Comm. 5, 3529 (2014)
1. Gold index grid (working electrode)
2. Reversible Hydrogen Electrode (reference electrode)
3. Platinum foil (counter electrode)
4. Argon gas inlet
5. Argon gas outlet
1
2
3
45
3-D imaging for the first time the
same region before and after
electrochemical cycling
50 nm
Before After
Ex-Situ: Coarsening During Voltage CyclingY. Yu*, H. L. Xin* et al, Nano Lett.,12 (9),4417-4423 (2012)
TEM Grid-in-a Coin Cell Experiment
• Grids need be dissembled (only quasi-in situ)
• Need to wash the grids with EC; i.e. dissolvable components in the SEI are gone.
• Not in situ and needs protected transfer
• Materials are 3-D submerged in a
commercial organic electrolyte
• Provides a uniform and conductive
support
• The grid can be used in
synchrotrons and TEMs
Pros Cons
F Lin et al Xin*, Nat. Comm. 5, 3356 (2014)
Use NiO Pallets as a Model System
Anodic Conversion Reaction 2Li + NiO Ni + Li2O
• Metallic Ni (green) is nanoporous.
Before cycling 0.25 cycle
Ni
NiO
F Lin et al Xin*, Nat. Comm. 5, 3356 (2014)
Heterogeneous Nucleation/Phase Transition in Battery Anodic
Reactions
• Multiple nucleation sites– Difference in electric/ionic contact
– Difference in phase transition kinetics
0.25 cycle (being lithiated) 0.75 cycle (being delithiated)
F Lin et al Xin*, Nat. Comm. 5, 3356 (2014)
What are the Preferential Sites for Lithiation
Speculation: grain boundaries could have lower activation energy for lithiation.
Needs in-situ experiments
【111】
Channeling Contrast (brighter if on zone aixs) F Lin et al Xin*, Nat. Comm. 5, 3356 (2014)
A Dry Cell Experiment
• dKai et al, Nano Lett., 2015, 15, 1437
Real-time in situ nano-indentation
In-Situ Lithiation of NiO
Kai et al, Nano Lett., 2015, 15, 1437
Kai et al, Nano Lett., 2015, 15, 1437
An incubation period limits your battery charging speed
revealed by real-time observations
finger
shrinking core
T = ~100 sec
Take home:
cannot charge
faster than
this time
scale.
Transitions from Near-Surface to Interior Redox upon Lithiation in NiOConversion Electrode Materials
There exist and incubation time for passivity break down. Which places
an intrinsic limit on how fast you can charge your conversion materials.
Kai et al, Nano Lett., 2015, 15, 1437
Lithiation Pathways on NiO
100 Sec
Passivation
Passivity break down
Tincubation
Critical Thinking
?
Tomography Experiment
Slab Geometry:
• One image every 1-2° from ±70°
• 70 - 140 images
Acquisition
e-
Reconstruction
Requirement:
• Image intensities vary
monotonically with thickness
(STEM is superior to TEM for tomography because TEM
suffers from phase contrast and diffraction contrast
which breaks the monotony of the signal )
200 nm
Pristine c
Cycled d
Voids Formation in LMR-NMC
Grain boundaries are both migration channels and sinks for
vacancies
• Voids form along grain boundaries.
Mass-contrast
Fe
Co
Fe2/3+ vs. Fe0
• Inelastic scattering artifacts removed.
• Many more channels of signals are under processing.
5D Microscopy (x, y, z, vs. Eloss vs. t)
Live Recorded Tomography Tilt Series
• Sub-10 min electron tomography achieved in 2014
115 kx (field of view 673 nm)
1 frame/sec, a total of 600 frames
-70-70 degrees, 2 degree tilt interval
2 days
Acquiring multiple tilt series within a minutes
500 nm
Comparison between single-series reconstruct and the merged
reconstruction
• Merging multiple reconstructions reduces noise and artifacts
A cross section of
Single-series Reconstruction
A cross section of
Merged Reconstruction (4 series)
Electrochemical liquid in S/TEM
• Battery applications underdevelopment
Electrochemical liquid
cell approach
500 nm
Acknowledgement
Feng LinEric Stach
Jing Li
Xiqian Yu
Dong Su
Xiaoqing Yang
Kai He
Marca Doeff
Huolin Xin
Dennis Nordlund
Yijin LiuDeli Wang
U.S. DOE Office of
Science Facility, at
Brookhaven National
Laboratory under
Contract No. DE-
SC0012704
Students: Lili Han*,
Ruoqian Lin, Wei-Yu Pan,
Sai Vishnubhotla*,
Guangzhong Huang*, Jing
Li*, Yujing Liu*
Center for Functional Nanomaterials• Located on Long Island• Fully operational since April 2008• Two-fold mission:
– Enable nanoscience researchby external users
– Discover and understand energy-related nanomaterials
• Concentration of world-class tools and scientific expertise under one roof
• Integration with BNL’s other world-class facilities and research programs
• Huolin Xin ([email protected])