MIT Energy Initiative Cambridge MA
New Vistas in Electrochemical Energy Storage
Sept 7, 2016
Prof. Linda Nazar, FRSC Senior Canada Research Chair
Electrochemical Energy Materials Laboratory
Amiens BASF International Scientific Network for Electrochemistry and Batteries Joint Center for Energy Storage Research DOE, USA Thanks to:
C. Xia, R. Black, R. Fernandes, D. Kundu, X. Liang, X. Sun, P. Bonnick, V. Duffort, B. Adams
Waterloo Institute for Nanotechnology and the Quantum-Nano Centre University of Waterloo, Waterloo ON Canada Agenda :
Waterloo Institute for Nanotechnology and the Introduction: Li-ion Quantum-Nano Centre
Storing electrons and ions: - Chemical transformation Li-Sulfur and metal-oxygen batteries-
Storing electrons and ions: - Multivalent intercalation batteries: Mg and Zn -ion
Conclusions
3 Global Energy Assessment: Cambridge Univ Press, 2012
GEA – the first global and interdisciplinary assessment of energy challenges and solutions – identifies 41 pathways to provide sustainable energy for the world by 2050
“Integrated energy storage is an area where technology lags and needs intense development if systems with optimum overall efficiency gains are to be attained”
4 Energy Storage: A Challenge of the 21st Century
New electrochemical energy storage chemistry needed
Exploit renewable energy Power the world: big Enable low cost, high resources computing, small devices range electric vehicles Different materials Different energy needs Different cost point Wind Solar Smart energy delivery Electric (+ solar): Kiira Motors MWh Wh - MWh kWh Chemical energy to electrical energy and work (downhill, discharge)
Chemicals Batteries Electricity Electrical energy back to chemical energy (uphill, charge) Progress in Li-ion technology: driven by portable devices
Capacity: 2014 Electrons stored per mass (mAh/g) or volume (mAh/L)
Light weight/dense
Source: Sony (Japan) Capacity * Voltage = Energy density Wh/kg or Wh/L
Increase in energy density by year for 18650 cells Limit ~ 280 Wh/kg based on “intercalation” chemistry Problems: cost, safety
6 Energy storage perspective: 2x in ED, -2x in cost
2 MW
Li-ion battery
Li - miEV / C0 / Lion air
density 250 Wh/kg,
800Wh/l Li
oxides
-
Li
S
Zn
-
M
-
LiFeO
Sony
air
-
O O metal
Sony
Zn
Energy
-
4
ion LiMnO
1990 2004 2005 2007 2015 Future Development Li-Ion Cell Operation
(+) I (-)
Li+ - Li+ A Li+ Li+ Li+ A- A- Li+ Li+ Li+ Li+ Li+ + A- Li Li+ A- (V) Voltage Li+ Li+ Li+ Li+ A- Li+ Li+ Li+ Li+ Li+ A- A- Li+ Capacity (mAh/g) LiCoO graphite
2
8/75 Li-Ion Cell Operation
(Charge) (+) I (-)
Li+ - Li+ A Li+ Li+ Li+ Li+ A- A- e- Li+ Li+ Li+ Li+ Li+ cell voltage + A- - Li Li+ Li+ e A- (V) Voltage Li+ Li+ Li+ Li+ A- Li+ Li+ + + + + Li Li Li -Li A- e A- Li+ Capacity (mAh/g) + - + - LiCoO2 Li1-xCoO2 + xLi + xe xLi + xe + C LixC
9/75 Li-Ion Cell Operation
(Discharge) (+) (-)
Li+ - Li+ A Li+ Li+ Li+ Li+ A- A- e- Li+ + + + + Li Li Li Li cell voltage + A- - Li Li+ Li+ e A- (V) Voltage Li+ Li+ Li+ Li+ A- Li+ Li+ + + + + Li Li Li -Li A- e A- Li+ Capacity (mAh/g) + - + - Li1-xCoO2 + xLi + xe LiCoO2 LixC xLi + xe + C
10/75 Vehicular energy storage: looking to the far future
(Toyota, MRS Bull 2015)
All-solid-state batteries (Li, Na, Li-S, etc) have in common with Lithium-air the requirement of strict control of electrochemical interfaces
11 Ion intercalation vs chemical transformations
Transition metal oxides: good e- transport
21 22 23 24 25 26 27 28 29 30 Chalcogens Sc Ti V Cr Mn Fe Co Ni Cu Zn 16 O Intercalation cell Chemical Transformation cell
- - 32 e e : light S - + Li+ 3 weight charge Se 52
Li+ discharge Te
Graphite + 84 Li conducting LiCoO2 S ↔ Li S electrolyte 2 Po Step change Dissolution-precipitation
12 Lithium-chalcogenide (O2, Sulfur) batteries: similar
Li-Sulfur Li-Oxygen
Earth abundant inexpensive
+ - + - 2Li + 2e + S Li2S (E°= 2.27 V ) 2Li + 2e + O2 Li2O2 (E°= 2.96V) Energy density = 2500 Wh/kg Energy density = 3500 Wh/kg
+ - Factor of 7 0,7Li + 0.7e + Li07MO2 LiMO2 Factor of 3.5 Energy density = 220 Wh/kg ≈ 350 Wh/kg ≈ 1000 Wh/kg x 3 ..but limited cycling ≈ 200 Wh/kg 650 Wh/kg possible? Redox transform electrochemical systems
+ - + - + - Li + e + 2 Li0.5CoO2→ 2 LiCoO2 S2 + 2 Li /e ↔ Li2S O2 + 2 Li /e ↔ Li2O2 - MW/e- = 196 MW/e- = 23 MW/e = 23 • Dissolution-crystallization and disproportionation chemistry e- e- e-
2- 2- 2- S8 (solid) S8 Sn (n: 3 to 6) S2 Li2S (soluble) (insoluble) 2- - S8 + S6 2S 3 solids) reactive
- 2- O2 (gas) O2 O2 (Li2O2) 2LiO 2 ” + O2)
1. 14 Redox transform electrochemical systems
• Dissolution-crystallization and disproportionation chemistry e- e- e-
2- (-0.25) S8 S (soluble) (insoluble) 2- - S8 + S6 2S3
reactive
- O2 (gas) O2
2LiO2 (Li2O2) + O2) Prone to disproportionation reactions Intermediates in the electrochemical reactions very problematic
1. 15 Reactive radicals
Aging
1. 16 Li-O2 batteries: a lot of hype, a lot of challenges
+ - O2 + 2 Li /e ↔ 2 LiO2 → Li2O2 + O2 Positive Electrode ● minimal overpotential for oxygen reduction
● reactivity of host electrode with Li2O2 nanoporous, stable conductive host ● Overcome large overpotential on charge
Organic Electrolyte
.- ● O2 solubility, diffusivity ● electrolyte reacts with superoxide O2 ● Li salt solubility
Review of Li-O2: D. Aurbach, B. McCloskey, L.F. Nazar, P. Bruce* Nature Energy (in press, 2016) A long term prospect
17 But….steps forward in understanding
+ - + - Discharge: Li /e + O2 → LiO2 → Charge: Li2O2 → Li2-xO2 + x Li /e
Superoxide formed on surface: dissolution competes with 2nd reduction : dependent on current density and solvation
Micron-sized Li2O2 L. Nazar et al., JACS 2013; EES (2013); Y. Shao- Horn, JPCL, 2013
+ - -• Li2-xO2 → O2 + x Li + x e Favour large aggregates via O2 transport M. Wagemaker, Nazar et al., JACS (2015), JPCL 2016
18 Inherent solution mediation in Na-oxygen cells
Theor: 1600 Wh/kg + - O2 + Na /e ↔ NaO2
19 Na-O2 Battery: phase transfer catalysis, high capacity
] )
-2 2 10 ppm H O 10 ppm benzoic acid 2.4 - 2 4
2.4 cm
) +
mAh cm
1111111111
[
mAh 2 (
2.2 dis
2.2 C
[V] 0
Capacity cell 0 5 10 15
E Water content [ppm]
2.0 E (V vs. Na/Na (V E vs. Crystalline NaO2 cubes 1.8 0 1 2 3 4 5 High capacity Sol’n Mechanism -2-2 CapacityCapacity ( mAh[ mAh cmcm] )
- 0 ppm H2O HA + O2•- ⇆ HO2 + A + + Quasi-amorphous NaO films HO2 + Na → NaO2 + H 2 reverse on charge Negligible capacity Xia, Nazar et al. Nature Chemistry 2015, 7, 496–501 Surface Mechanism Phase transfer catalysis not possible for Li-O2
2.6 b) 4.5 Li-O2 echem superoxide Na-O2 echem
) 2.5
not stable +
)
+ 4.0 2.4 3.5 Charge 2.3 E° = 2.27 V
E° = 2.96 V V vs. Na/Na
V vs. Li/Li 3.0 (
( 2.2 E
E 2.5 2.1 0.0 0.1 0.2 0.3 0.4 0.5 0.0 0.1 0.2 0.3 0.4 0.5 2 2 Capacity (mAh/cm ) Capacity (mAh/cm )
+ H+ + O HO 2H + O2 H2O2 2 2
O2 O2 + + + H2O2 Li2-xO2 + H HO2 + Na NaO2 + H
+ NaO Na+ + O Li2O2 2Li + O2 2 2
21 Redox Mediators – THE solution on charge (& discharge)
Soluble molecules in the electrolyte oxidized at a potential
slightly above the equilibrium potential of Li2O2.
- Br /Br2 D. Aurbach et al, TTF- TTF+/3.5-3.7V Angew Chemie, 2016 P.G. Bruce et al, Nature Chemistry, 2014
+ 2+ TDPA - TDPA - TDPA TEMPO- TEMPO+ 3.1/3.5 V 3.8V L. Nazar et al, J. Janek et al, JACS, 2015 ACS Central Sci, 2015
22 A Dual Step Redox Mediator for Li-O2 Cell
RM/RM+ RM/RM2+
TTF 3.5 V 3.7 V quantitative TEMPO 3.8 V
TDPA 3.1 V 3.5 V
Kundu, Nazar et al., ACS Central Science, 2015
Requires that the negative Li electrode be passivated
23 Detrimental reactivity of HO2 with glyme electrolyte Charge
“Operando” ESR studies show HO2 generates glyme radicals electrolyte decomposition products
10 ppm 120 min Charge
= 6.4 G N = 19.5 G H
= 6.4 G N = 19.7 G H 500 ppm 15 min Charge 3300 3320 3340 3360 3380
Find electrolytes stable to radical (HO2) hydrogen abstraction
C. Xia, L. Nazar, J. Baugh et al., J. Am Chem. Soc (2016)
24 Down the Periodic Table
25 The Li 2Li + Li cheese 2 — S S ( maintain - Li S Battery and the Redox Shuttle b(Li + a(Li Li e 2 S) 2 Li - 2 Discharge S 2 2 8 S S + 6 4 ) ) Li milk 2 active Separator S x e cheese - Li Li Li mass? mass? + + 2 S Lithium theoretical capacity 1675 500 - 1000 - > 350 mAh Charge /g Wh internal today /kg Li 2 S Polysulfide shuttle x “short circuit” 2500 mAh Wh Li /kg (full cell) /g @ 2V 2 S x/2 1. Lithium 26 Desirable shuttles
1. 27 The Crossroads
All solid state sulfur batteries The Problem with Carbon
Porous carbons Low sulfur loading, low sulfur fractions decreased funding no large scale commercialization High electrolyte ratios “catholyte” – like cells 150 Wh/L
solve the problems with multipronged approaches - find ways for dissolution/precipitation to function in low electrolyte and high sulfur loading
LiPS very soluble LiPS poorly soluble High donor number solvents, “Pb-acid battery” Protected negative electrode – like Li-O2
28 Li-S for transportation applications: critical metrics
Challenges: high current densities (∼7 mA/cm2) high sulfur loading ~ 7 mg/cm2 electrolyte ~1.3 – 1.9 μl/mg
---- Kevin G. Gallagher et al
Calculated cell-level energy density and specific
energy for a 100 kWhuse, 80 kW and 360 V Li-S battery as a function of the electrolyte vol% in the cathode (50–90%) and excess Li amount in the anode (50–400%).
Gallagher et al., J. Electrochem. Soc., 162 (6) A982-A990 (2015) Are these goals achievable - how?
29 The Problem with Porous Carbon
The Good Problem interaction with withCarbon sulfur
No interaction with intermediate lithium polysulfides OR Li2S
In situ cell: synchrotron (APS)
Cuisinier, Balasubramanian, Nazar, J. Phys. Chem Lett (2014)
30 Operando XANES: Ti4O7/S cathode shows strong interaction
Solid: Ti4O7/S Dash: C/S
During discharge: Much lower fraction of polysulfides at all stages (efficient trapping)
Li2S precipitates earlier and more progressively
. Ti4O7-polysulfide interaction promotes charge transfer
31 Ti4O7 - surface enhanced electrochemistry
disproportionation Carbon Upon electrochemical reduction Solvated Li+ (receiving e- and Li+): Li S 2- 2 x “disconnected” Sulfur reduced and dissolves to form Li2S solvated lithium polysulfides S8 → Li2S isolated from electron wiring Carbon e- e- e- e-
Ti4O7 Sulfur reduces and adsorbs on metallic oxide surface → “adsorbed” Li S e- e- 2 Solvated Li+ • Uniform deposition of Li S e- 2 • Suppress polysulfide diffusion/shuttle S 2- • Improved capacity retention 8 Li2Sx Ti-O e- e- e- e- Q. Pang, D. Kundu, M. Cuisinier, L. F. Nazar, x Nature Comm, 5 : 4759 (2014) “adsorbed” Li2S
32 Surface interactions of LiPS with polar hosts are key
The Problem with Carbon
33 First-principle calculations – quantitative study of interactions
DFT (VASP code)
Simulated the adsorption of various numbers (1,2,4) of Li2S2 molecules The substrates span the same basal area . Example optimized geometries of 2 Li2S2 adsorbed on the substrates a Pristine carbon b N-doped c g-C3N4
No specific bonding Interaction via a Li-N bond
. Binding energy average per Li2S2 14.9 mg/cm2 sulfur loading electrolyte/sulfur ratio = 3.5: 1 µl/mg
Pang, Nazar et al ACS Nano, (2016); Adv. Energ. Mater. (2016)
34 Polysulfide chemical trapping: surface-active mediators
MnO2 nanosheets – 10 nm thick 75 wt % sulfur/ “inorganic graphene” Capacity fade rate = 0.04% per cycle over 2000 cycles
A. Formation of thiosulfate via oxidation of LiPS/ reduction of Mn4+: S/KB cell
0 0.5 4 8 12 hr hr hr hr hr
S/MnO2 nanosheet B. Catenation of sulfur to form cell polythionate complex
Liang, Nazar et al., Nat. Commun. 6, 5682 (2015) The “Goldilocks” Principle
Redox to Redox to No redox thiosulfate thiosulfate & sulfate
Co3O4 NiO Cu O TiO MnO Ti4O7 2 2 2 V2O5
0 1 2 3 4 V Fe O * 2 3 V2O3 CoO VO2 NiOOH CuO * Fe3O4
Electrochemical reactivity of different metal oxides with LiPSs as a function of redox potential vs Li/Li+ Same process occurs for graphene oxide (reduced by LiPS – thiosulfate/ polythionate)
Nazar, Sommers et al., Adv. Energy Mater. 6, 1501636 (2015)
36 Interaction between polysulfide and MnO2 or graphene oxide
ST (-1) Li-S/MnO2 cell cathode SB (0) Li2S4
Li2S4/MnO2
Li2S4/Graphene At 2.3 V: partial reduction or oxidation oxide
Li2S4/ Graphene Core-shell micron-sized sulfur with an inorganic coating
− ퟐ− ퟑ− − ퟔ 푴풏푶ퟒ + ퟑ푺 + 푯ퟐ푶 → ퟔ 푴풏푶ퟐ + 푺푶ퟒ + [푯(푺푶ퟒ)ퟐ] + 푶푯
Liang, Nazar et al., ACS Nano (2015)
Sustain high sulfur areal loadings X. Liang, L. F. Nazar et al, Angewandte Chemie 2015; Adv. Mater., 2016 on-line Concept of “sparingly soluble-solvents” for polysulfides
Utilize a “non-solvent” electrolyte Solid-solid transformation? Highly limited solution process?
Cuisinier, Nazar et al., EES 2015. S8 ? Li2S
Utilize a sparingly soluble electrolyte Optimum properties for solution-based reactivity? tn Controlling precip of Li2S – needs a polar metallic host, RMs
39 Critical Factors for Liquid Electrolyte Cell design
Q. Pang, X. Liang, L.F. Nazar, Nature Energy (in press, 2016)
40 Divalent batteries: intercalation of Mg2+, Zn2+ ions
Electron transfer/ion mass not higher than Li+/e- The Problem with Carbon but… Advantage: metal anode (no dendrite formation, i.e., Mg) - greatly increases energy density compared to carbon in Li-ion cell
Chevrel phases (Mo6S8) first to be studied as cathode* Mg insertion examined in oxides**
Disadvantage: multivalent cations exhibit (?) low mobility in most high voltage host materials (ie, oxides) - desolvation penalty for multivalent cations high - nascent understanding of factors at play
*D. Aurbach et al., Nature 2000 ** P. Novak et al, 1997
41 “Soft” anions: Mg (de)intercalation in the thiospinel Ti2S4
Mg full cell with thiospinel cathode shows 190 mAh g-1 capacity, twice that of benchmark (2000), and relatively stable capacity retention.
X. Sun, Z. Rong, G. Ceder, L.F. Nazar et al., Energy Environ Sci (2016); ACS Energy Lett 2016 Diffusion energy barriers in Ti2S4 agree with computation
In collaboration with Berkeley Theory Team: M. Liu, Z. Rong, K. Persson, G. Ceder
Mg self-diffusion coefficients (60° C) and corresponding energy barriers for Mg
diffusion in cubic Ti2S4 calculated in dilute and concentrated limits
DMg (at 333K) expt: 530 meV; theory: 550 meV DMg (at 333K) ≈ 0.1X DLi at 298 K Nanomaterials required A.C. James and J.B. Goodenough, Solid State Ionics, 27, 37 (1988). Multivalent Intercalation (Aqueous) Advantages
. Divalent cation does not require desolvation from solvent shell . Screening of divalent cation charge in lattice by solvent – enhanced mobility
44 2016 to be a breakout year for stationary energy storage
01/05/2016 - Philippe Bourchard Aqueous Zn-ion batteries
Why Zn metal ? . Stable in water: high corrosion resistance . High abundance, production; non toxic . Suitable redox potential (0.76 V vs. SHE) High volumetric energy density (d: 7.14 g cm-3) . Small exchange current for HER on Zn: large kinetic voltage window ~2.4 V for Zn based aqueous rechargeable batteries.
Aqueous Batteries ? . Low-cost, safe, easy to manufacture and dispose
Aqueous Zn-ion Batteries >> Safe and environmentally benign alternatives to their aprotic counterparts, can have ultra-high rate capabilities.
3 Efficient Zn stripping and plating
Highly reversible Zn stripping and deposition
WE: SS rod CE: Zn disk/metal
Electrolyte: 1M ZnSO4-H2O
HER - - 2H2O + 2e → H2 + 2OH
. Zn2+ + 2e- ↔ Zn with ~100 % coulombic efficiency (Qox/Qred) . Rechargeable aqueous Zn-ion batteries: ~2.4 V window . No dendritic growth at pH < 7
4 Layered Host: Water Assisted Facile Zn2+ Intercalation
Zn2+ Zn2+
c a b
2+ Host Structure Expanded host structure Zn intercalated in electrolyte host
5
Nanofiber morphology - short diffusion path, easy fab
SEM/TEM images of nanofibers Free-standing electrodes
H2O-slurry H2O-based binder Sustainable & High-Rate Zn2+ ion Storage
. Highly reversible Zn intercalation & stable cycling . 1000 cycles: ≥ 80 % capacity retention . Energy density (pouch cell): 450 Wh/L . Coulombic efficiency: ≥ 99% . High rate capability: discharge/charge in 8 min < $70/kWh
D. Kundu, B. Adams, V. Duffort, L.F. Nazar, Nature Energy (2016)
6 Integrated electrochemical energy storage
More important today than at any time in history: new small & large-scale demands
Off-peak capture essential
Storage ↔ Grid Home ↔ EV Na/Zn- ion Redox flow Li-ion EV ↔ Grid Na/Li sulfur Li sulfur/air metal/air Grid ↔ Devices
52 Research team and collaborators
Prof. M. Saiful Islam, Univ Bath Prof. M. Wagemaker, TU Delft Prof. Gerd Ceder, Berkeley Dr. Mali Balasubramanian, Argonne, USA Prof. J. Baugh, UW Prof. Jurgen Janek, Giessen/KIT
BASF International Scientific Network for Electrochemistry and Batteries NRCan
1. 53 Thank you – we welcome visitors
Waterloo Institute for Nanotechnology and the Quantum-Nano Centre