Synthesis and Characterization of Sulfide-Solid-Electrolytes
High-Performance Sulfide-based Solid-state Electrolytes ...
Transcript of High-Performance Sulfide-based Solid-state Electrolytes ...
High-Performance Sulfide-based Solid-state
Electrolytes and Interfaces for All-solid-
state Li Batteries
Presenter: Dr. Feipeng Zhao
Advisor: Prof. Andy Xueliang Sun
Western University, Canada
October, 2021
1
240th ECS meeting
Conclusions
Advanced electrolyte and derived anode interface
Acknowledgements
Introduction: Sulfide-based ASSLMBs
Outline
• Fluorinating Li6PS5Cl (LPSI) SSEs
• Sn-substituted Li6PS5I (LPSI) and Li3PS4 (LPS)SSEs
• Solid-state batteries and sulfide SSEs
• Challenges and strategies
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S. HessJ, et al. J. Electrochm. Soc. 2015, 162, A3084 H. Li, et al. Chem. Rev. 2020, 120, 6820–6877
Introduction: why solid state?
3
Commercial Li-ion batteries
(LIBs)
fire
degassing
explosion
Flash points (FPs) and self-extinguishing
times (SETs) of electrolytes
Anode: graphite
Cathode: LCO, LFP, NMC, LMO, etc.
Electrolytes: flammable organic liquid
ASSLMBs are much safer and can improve the performance:• SSEs: non-flammable, cannot leak• Cells: Improved energy density
(packing techniques, avoiding using inactive separators)
F. Zhao, Y. Li, X. Sun. 2021, to be submitted; R. Kanno, et al. Nat. Energy 2016, 1, 16030; J. Schnell, et al. J. Power Sources 2018, 382, 160
All-solid-state Li metal batteries(ASSLMBs)
Introduction: why solid state?
4
Toyota’s battery road map
Packing of ASSLMBs
Li metal
Solid-state electrolytes (SSEs)
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Introduction: sulfide SSEs
BY News from Tokyo Institute of Technology, 2016H. Zhu, et al. Adv. Mater. 2019, 31, 1901131
Advantages of sulfide SSEs:• High σ (10-2 S cm-1, comparable to
Liquid electrolyte) • Decent mechanical properties• Low grain-boundary resistance
Upgrade trend of solid-state electrolytes (SSEs):• Improved ionic conductivity (σ)• From oxides/chlorides to sulfides• Accompanied by polymer-based
Ion
ic c
on
ductivity,
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Challenge I and stretagies: Air sensitivity
H2S derived from degradation of sulfide-based electrolytes
M. Tatsumisago, et al. Solid State Ionics 2011, 182, 116-119; A. Hayashi, et al. J. Mater. Chem. A, 2013, 1, 6320-6326Y
Inte
nsi
ty (
a.u
.)
H2S gas Chromatogram
P2S64-
Adding MxOy (M = Fe, Zn, and Bi) nanoparticles as absorbents
Replacing S with O in the Li2S-P2S5 system
1
3 Replacing P with As or Sn in the LixMSx system
2
Strategy H2Sgeneration
Ionic conductivity
Note
1 Suppressed Reduced CANNOT avoid H2S generation
fundamentally
2 Suppressed Reduced -
3 Suppressed Dramaticallyreduced
As substitution can improve σ, but NOT
practical
Improving the air stability of sulfide SSEs while keeping the ionic conductivity is very important!
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Challenge II: electrode/sulfide interface issues
Sulfide SSEs(Li-P-S
Li-P-S-M,Li-P-S-halogen,
…)
Li anode
Li3P, Li2S,
Li halides,Li-M,
…
Li dendrites propagation2
Oxide-based
cathode (LCO, NMC, NCA)
Interfacial side reactions1 Interfacial side reactions
2 Space-charge layer (SCL) effect
1
TMs: Transition metal elements of cathode active materials; LCO: LiCoO2; NMC: LiNixMnyCozO2; NCA: LiNi0.8Co0.15Al0.05O2
Y. Mo, et al. ACS Appl. Mater. Interfaces 2015, 7, 23685; H. Zhu, et al. Matter 2020, 3, 57-94;K. Takata. Acta Mater. 2013, 61, 759-770
POx,
SOx,
Reduced TMs,
…
SEI (solid-electrolyte interphase) CEI (cathode-electrolyte interphase)
High reduction potential of sulfide SSEs Low oxidation potential of sulfide SSEs
Growth and propagation of Li dendrites
SCL formation
Interface stability (anode and cathode) can determine battery performance!
Li-deficient layer
Li metal
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Strategies for Li/sulfide interface
Placing interlayer (electro)chemically1
Main requirements:
Smooth and robust surface
(Electro-)Chemically inert
Only Li-ion conductive interface
Self-terminating side reaction
Simple fabrication
Without losing energy density
√√Only Li-ion conductive
√×Li-ion & electron conductive
× ×Only electron conductive
J. Janek, et al. Solid State Ionics 2015, 278, 98-105
Constructing Li-M alloy (Ag, In, Al)2
Modifying sulfide SEs with LiI doping 3
Ideal model:
Reported strategies:
Modifying sulfide SSEs is the most straightforward and feasible method!
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Objectives and organization
Modifying SSEs
Sulfide SSEs
Li anode
SEI
High ionic conductivity
Air stability
Li anode interface
Part 1Fluorinating sulfide SSEs for improved Li/sulfide interface stability
Part 2 Sn-substituted Li6PS5I and glass-ceramic Li3PS4 to realize high ionic conductivity, Li compatibility, and air stability
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Background: Argyrodite-type Li6PS5X
The item Argyrodite is named from one natural mineral ‘Ag8GeS6‘. LGPS: Li10GeP2S12C. Yu, F. Zhao, X. Sun, et al. Nano Energy 2021, 83, 105858W. Zeier, et al. J. Am. Chem. Soc. 2017, 139, 10909-10918
• High popularity of LPSCl (synthesis, understanding, battery performance)• Ionic conductivity: σ (LGPS) > σ (LPSCl) > σ (LPS) (LPSCl, > 10-3 S cm-1 at RT)• Cheaper precursors (Li2S + P2S5 + LiCl) compared with preparing LGPS
Li6PS5X: LPSX, X = Cl or Br or I
Choosing LPSC as the base sulfide SEs:
High crystallinity (cubic)
Can fluorinated LPSCl derive LiF at the Li/sulfide interface and improve the stability?
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Motivations
LiF-rich SEI is an essential component to suppress Li dendrites and prevent interfacial reactions:
1. Low electronic conductivity 2. High bulk modulus3. High interface energy with Li metal
4. High Li-ion diffusivity derived from LiF in SEI
C. Wang, et al. Science Advances 2018, 4, 9245; F. Mashayek, et al. J. Phys. Chem. C 2019, 123, 10237−10245B. Gallant, et al. Proc. Nati. Acad. Sci. U.S.A. 2020, 117, 73-79;
Benefit of fluorinating electrolytes
Heterogeneous interface: Higher Li-ion diffusivity
Calculation on the Li+ diffusion at LiF-related GB
Synthesis and structure
Li2SP2S5
LiClLiF
Ball milling Sealing in quartz tube Annealing in muffle oven
Synthesis route (solid reaction method) towards Li6PS5Cl1-xFx (x = 0, 0.05,0.3, 0.5, 0.7, 0.8, 1)
Pelleting
XRD results
Interaction between F and PS43- molecules was confirmed by Raman.
Raman results
Fluorinating Li6PS5Cl can induce formation of a mixture of distorted Li6PS5Cl and β-Li3PS4.
Stretching P-S in PS4
12F. Zhao, et al. ACS Energy Lett. 2020, 5, 4, 1035-1043
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Improved Li/Li6PS5Cl1-xFx interface
Li-Li symmetric cell test: to evaluate the Li/electrolyte interface stabilityLi metal
Li metal
cyclerSSEs
Excellent high rate performance can be obtained for Li6PS5Cl0.3F0.7 SSEs. It was the best in solid-state cells and comparable to the liquid electrolyte system.
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Characterizations of LiF-rich interface
Li/Li6PS5Cl0.3F0.7 interface after symmetric cell cycling 0.1 mA cm-2/ 0.1 mAh cm-2 for ~200 h
SEM ToF-SIMS
XPS depth profiling
X-ray electrons
Ar etching
Interface
Smooth and sheet-like (dense) interface was formed in-situ.
High F concentration was found at the Li/SSEs interface.
Rich-LiF (sub-micro thick) containing interface was confirmed by XPS (684.8 eV).
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Objectives and organization
Modifying SSEs
High ionic conductivity
Air stability
Li anode interface
Part 1Fluorinating sulfide SSEs for improved Li/sulfide interface stability
Part 2 Sn-substituted Li6PS5I and glass-ceramic Li3PS4 to realize high ionic conductivity, Li compatibility, and air stability
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Hard base: O
Soft base: S
Hard acid: P
Soft acid: Sn
√×√
Sn-S bonding stabilize the structure (HSAB)
Chem. Mater. 2012, 24, 2211−2219
Nat. Energy 2018, 3, 310
With LiSnprotective layer
Pristine Li
In-situ triggered Li-Sn alloy regulate Li deposition
Low-valence element substitution P (V) Sn (IV) to improve the structure
J. Mater. Chem. A, 2018, 6, 645
2.4×10-3 S/cmLi6+xP1-xSixSBr
P (V) Si (IV)
0.7×10-3 S/cm
• Expansion of unit cell• Increase of Li+ number
Motivations: why Sn substitution
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Compound LPSI-20Sn LPSI
a, Å 10.218 10.145
b, Å 10.218 10.145
c, Å 10.218 10.145
V, Å3 1066.711 1,044.134
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Structure of Sn-substituted LPSI
Li6+xP1-xSnxS5I (LPSI-xSn, x= 0, 10, 20, 30, 50, 80, 100%)
Li2SP2S5
LiISnS2
Synthesis
Ball milling +
annealing in Vac.
XRD XRD refinement
Reaction equation: (5+x) Li2S + (1-x) P2S5 + (2x) SnS2 + 2 LiI = 2 Li6+xP1−xSnxS5I
The Argyrodite phase is pure when the substitution percentage is less than 20%;
The aliovalent Sn (IV) substitution leads to a expanded unit cell and increase Li+ contents.
Li6.24P0.823Sn0.177S4.58I0.9
F. Zhao, et al. Adv. Energy Mater. 2020, 10, 1903422
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Ionic conduction of Sn-substituted LPSI
Sn substitution can improve the σ significantly. 20% is the optimized value, LPSI-20Sn: 125-time increase in the RT ionic conductivity Variable-Temp 7Li-NMR indicate a ultralow activation energy (Ea).
Derived from EIS measurements
LPSI LPSI-20Sn
σ at RT (S/cm)
2.8 × 10-6 3.5 × 10-4
Ea(eV)
0.424 0.304
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Motivations
Clarifying the ‘three-in-one’ effect of Sn-substitution strategy
• Ruling out the effect of LiI formation on the stability of Li metal interface• Studying the possibility of generating Li-Sn alloys and its influence on performance• Obtaining high RT σ over 10-3 S cm-1 for sole applications (rather than as interlayer)
Crystal structure of β-Li3PS4
Sulfide prototype Most air-stable in Li2S-P2S5 system Wider electrochemical window Low cost
o Metastable at RT (need to be embedded as ceramic in glass)
o Insufficient σ: 1-3.8 ×10-4 S/cmo Zn, Si can replace P, BUT only Li
dynamic was studied.
Pros.
Cons.
Li3+xSixP1-xS4 x=0.4 σ = 0.64 mS/cm
x=0.25 σ = 1.2 mS/cm
Li1-2xZnxP1-xS4 x=0.6 σ = 0.57 mS/cm
Y. Mo, et al. ACS Appl. Mater. Interfaces 2015, 7, 23685; G. Ceder, et al. Energy Environ. Sci. 2016, 9, 3272-3278; N. Suzuki, et al. Chem. Mater. 2018, 30, 2236-2244; Linda Nazar, et al. Chem. Mater. 2019, 31, 7801-7811.
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Synthesis and structure
Li2SP2S5
SnS2
High-energy ball milling
Glassy precursors(g)
Glass-ceramicsamples (gc)
Annealing in vacuumed quartz tube
Using DSC to determine the heating temperature
Synthesis route (solid reaction)
XRD results
Compound Li3.2P0.8Sn0.2S4 Li3PS4
a, Å 13.159 13.066
b, Å 8.025 8.015
c, Å 6.135 6.101
V, Å3 647.885 638.92
At the substitution percentage of 20%, gc-Li3.2P0.8Sn0.2S4
showed only β-phase Li3PS4, but with an expanded unit cell.
F. Zhao, et al. Adv. Mater. 2021, 33, 8, 2006577
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Ionic conduction of Sn-substituted gc-Li3PS4
6.5-times increase after the 20% (optimized) Sn substitution (gc-Li3.2P0.8Sn0.2S4), reaching 1.22 × 10-3
S/cm with Ea = 0.311 eV at RT (gc-Li3PS4: 1.94 × 10-4 S/cm, Ea = 0.381 eV). Dynamic 7Li-NMR revel the improved local Li-ion transport after Sn substitution.
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Air stability of gc-Li3.2P0.8Sn0.2S4
Exposing to 5%-humidity air overnight
gc-Li3.2P0.8Sn0.2S4 gc-Li3PS4
1.21 × 10-3 S/cm 1.94 × 10-4 S/cm
1.03 × 10-3 S/cm 0.25 × 10-4 S/cm
Unobservable change of XRD and XANES (before and after 5%-humidity exposure) indicate the robust structure consisting of (P/Sn)S4 tetrahedra;
High σ over 10-3 S cm-1 can be obtained after exposing to 5%-humidity air overnight, which is important for applications.
(simulating dry-room environment)
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Li compatibility of gc-Li3.2P0.8Sn0.2S4
gc-Li3.2P0.8Sn0.2S4
gc-Li3PS4
Li symmetric cell
XPS results
Simulation (finite element method)
Uniform Li+ flux through the entire interface and towards the Li metal electrode
Li-Sn alloys were embedded in the insulating matrix (Li2S + Li3P), serving as the stabilized Li/sulfide interface (the interfacial reaction is self-terminating).
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Li/gc-Li3.2P0.8Sn0.2S4 /LCO full cells
0.05
@RTUnit: C
0.1
0.20. 5
0.1
0.81
0 5 10 15 20 25 30 350
30
60
90
120
150
180
Sp
ec
ific
Ca
pa
cit
y (
mA
h g
-1)
Cycle Number
0 20 40 60 80 100 120 1402.7
3.0
3.3
3.6
3.9
4.2
Vo
lta
ge
(V
vs
. L
i/L
i+)
Specific Capacity (mAh g-1)
Li//gc-Li3PS
4//LCO full cell
1st Charging
1st Disharging
Li//gc-Li3.2
P0.8
Sn0.2
S4//LCO full cell
1st Charging
1st Disharging 0.05C@RT
0 10 20 30 40 50 600
30
60
90
120
150
180
gc-Li3.2
P0.8
Sn0.2
S4
gc-Li3PS
4
Sp
ec
ific
Ca
pa
cit
y (
mA
h g
-1)
Cycle Number
0
20
40
60
80
100
Co
ulo
mb
ic E
ffic
ien
cy
(%
)
@RT
0.1 C
0.05 C
0.1 C
96% 1st CE
125 mAh g-1@ 0.05C91 mAh g-1@ 1C
118 mAh g-1@ 0.1C77% retention after 60 cycles
0.1 C
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Conclusions
Fluorinated sulfide SSEs could derive LiF-rich interface in-situ and improve the stability of Li metal/sulfide interface.
Sn-substituted LPSI sulfide SSEs showed significantly improved ionic conductivity and ‘three-in-one’ strategy of the Sn substitution was studied systematically in Sn-substituted Li3PS4 glass-ceramic.
Acknowledgement
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Supervisor:
Dr. Xueliang Andy Sun
Group photo 2019
Collaborators:
Prof. Yining Huang, NMR, Western University
Prof. T.K. Sham, Synchrotron, Western University
Dr. Jian Wang, Beamline Scientist, CLS
Dr. Yongfeng Hu, Beamline Scientist, CLS
Dr. Renfei Feng, Beamline Scientist, CLS
Dr. Rana Sodhi, XPS, University of Toronto
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Thanks for your attention!
Supporting information
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Full cell performance
Full cell test: to demonstrate applicable capability
Very similar electrochemical behavior to the liquid electrolyte full batteries. Excellent cycling stability and rate capability in full cells: 95% capacity
retention after 50 cycles and 85.7 mAh/g at 1 C (1.3 mA cm-2) at RT.
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Background
Argyrodite-type Li6PS5X (LPSX, X = Cl, Br, I)
Li interface stability of iodine (I)-containing sulfide SSEs
W. Zeier, et al. J. Am. Chem. Soc. 2017, 139, 10909-10918;C. Wang, et al. Nano Energy 2018, 53, 958-966; C. Wang, et al. Adv. Energy Mater. 2018, 8, 1703644.
vs.
The derived LiI-containing interface is compatible with Li metal.
Disorder of S (4d)/X (4a) correlate the σ σ (LPSCl) > σ (LPSBr) >> σ (LPSI) (10-3 vs. 10-6 S/cm)
LPS: Li3PS4
LPS30I: 70Li3PS4·30LiI
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Li metal/LPSI-20Sn interface stability
Symmetric cell testing Interface characterizations
Stable Li plating/stripping happened to the Li/LPSI-20Sn interface, even at high rate (1 mA cm-2); High ionic conductivity is also important for stable Li plating/stripping assuming LiI formed at Li/LPSI; LiI at the interface was confirmed by XPS, and distributed uniformly.
(The sample after symmetric cell cycling ~60h)
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LPSI-20Sn as interlayer for full cells
Highly reversible charge and discharge curves; 123.7 mAh/[email protected], 93.8 mAh/g@1C, the 1st coulombic efficiency is up to 91%; Negligible decay in the initial 20 cycle at 1C, 88.5% capacity retention after 50 cycles.
33
Synthesis and structure
ss-NMR results
Existence of (P/Sn)S4 tetrahedral; Deconvolution of the 31P NMR spectra indicates the amorphous content is ~12.4%.
Raman results SEM image
Nanozised primary particles
Uniform Sn doping
8 µm