HIGH ENERGY BATTERIES FOR
ELECTRIC VEHICLE APPLICATIONS
Jason Zhang
Pacific Northwest National Laboratory
Richland, WA
1
Presentation in METS 2012
Taipei, Taiwan
Nov. 11-14, 2012
Outline
1. Nano-structured Materials for Li-ion batteries
1.1 High capacity anode
1.2 High voltage cathode
2. Energy Storage beyond Li-ions
2.1 Highly Stable Li-S batteries
2.2 High Capacity Li-air batteries
2.3 Li-Metal Batteries
3. Summary
2
1. Nano-structured Electrodes for Li-Ion Batteries
LiNi0.5Mn1.5O4
LiMnPO4
TiO2
Si
Tarascon & Armand, Nature 2001 414, 359-367
3
1.1 High Capacity Anodes
Self Assembly of Nano-transition Metal
Oxide/Graphene Composite
Nanosynthesis: TiO2, SnO2, and
other cathode materials
Self-assembly with
graphene
• The self-assembled structure composed of ordered “super-lattice”
nanocomposite with alternating layers of graphene nanosheets and metal oxides
• Direct manufacturing of electrodes and batteries without binders and
other additives.
4
High Performance Nano-TiO2/Graphene Composite
C/5
• Best rate capability reported on anatase TiO2 with only 2.5wt% graphene.
• Excellent cycling stability: ~ 170 mAh/g at 1C (PHEV constant output).
5
1C
Conductive Rigid Skeleton Supported Silicon as
High-Performance Li-ion Battery Anodes
a)
c)
b)
High energy
ball milling
+ Graphite
Planetary
ball milling
Si
Graphite
B4C
B 4C
Si
• Use conductive B4C as nano-/micro- millers to synthesize nano Si (< 10 nm ).
• Use rigid skeleton to support in-situ generated nano-Si.
• Use conductive carbon to coat the rigid skeleton supported silicon to form
Si/Core/graphite (SCG) which can improve the structural integrity and
conductivity of silicon anode.
6
Discharge capacity (mAh•
Discharge capacity (mAh•
·
Effects of Composition and Synthesis Condition on
the Electrochemical Performances of Si Anodes
800
600
SBG415
SBG433
SBG451
400
Both HEBM and PBM time
fixed at 8 hours
200
800
600
HEBM time
4 hours
8 hours
12 hours
400
200
PBM time fixed at 8 hours
0
0
0
25
50
0
75
10
Cycle index
1200
a)
800
600
SCG415
SCG433
SCG451
400
Both HEBM and PBM time
fixed at 8 hours
200
1200
b)
1000
Discharge capacity (mAh•g-1)
1000
Discharge capacity (mAh•g-1)
Discharge capacity (mAh•g-1)
1200
·
800
600
HEBM time
4 hours
8 hours
12 hours
400
200
PBM time fixed at 8 hours
0
25
50
0
75
10
20
30
c)
1000
800
600
PBM time
4 hours
8 hours
12 hours
400
200
HEBM time fixed at 8 hours
0
10
20
Cycle Index
Cycle Index
Cycle index
1200
c)
Discharge capacity (mAh•g-1)
1000
• The ratio of Si, Core material
and graphite are important to the electrochemical
800
performance. Si:Core:graphite
= 4:3:3 is the optimized ratio.
600
PBM time
• Ball milling time is also important to the
electrochemical performance. 8 hr milling
4 hours
400
8 hours
is good for HEBM and PBM.
12 hours
200
HEBM time fixed at 8 hours
0
0
7
30
0
0
0
20
Cycle Index
10
20
Cycle Index
30
30
1.2 High Voltage Cathodes
LiMnPO4 Synthesized in Molten Hydrocarbon Has
Preferred Growth Orientation
 Oleic
acid was used as a surfactant and paraffin acts as a
non-polar solvent that facilitate thermodynamically preferred
crystal growth without agglomeration.
• Pure phase of LiMnPO4 was obtained after 550ºC calcination.
• As-prepared LiMnPO4 nanoplates are well dispersed without stacking.
• LiMnPO4 nanoplates consists of a porous structure formed by self-assembled nanorods aligned in a
preferred orientation with high specific surface area of 37.3m2/g.
8
High Performance LiMnPO4
Synthesized in Molten Hydrocarbon
4
10
Power Density (W/Kg)
constant charge
constant charge
rate at C/25
rate at C/25
3
10
2
10
LiFePO4
LiMnPO4
1
10
(Charge C/25)
8
200
400 600
Energy Density (Wh/Kg)
• Specific capacity of 168mAh/g was achieved which is close to the theoretical capacity of LiMnPO 4.
• Flat voltage plateau at ~ 4.1 V indicates the phase transition between LiMnPO4 and MnPO4.
• At 1C and 2C rate (PHEV constant output) capacity retention is 120 mAh/g and 100 mAh/g,
respectively.
• Ragone plot indicates that the discharge power density is close in LiMnPO4 and LiFePO4
when fully charged at C/25; At low power (< 30 W/kg), energy density of
LiMnPO4 becomes comparable or higher than LiFePO4.
9
1.2 High Voltage Cathode: LiNi0.45Cr0.05Mn1.5O4
Doping significantly improve the performance of high voltage spinel
LiNi0.5Mn1.5
O4
Cr-substituted spinel
b
c
e
f
h
i
Annealed
LiNi0.5Mn1.5
O4
a
Annealed
LiNi0.45Mn1.5Cr0.0
5O4
d
g
•The relative content between ordered and
disordered phase can be tuned by changing
synthesis condition.
10
Cr-substituted spinel
•Cr-substituted spinel
LiNi0.45Cr0.05Mn1.5O4 exhibit stable
cycling and excellent rate
performance.
160
160
140
140
140
120
100
80
60
4.9 V
5.0 V
5.1 V
5.2 V
5.3 V
40
20
(a) EC-DMC
Discharge capacity (mAh/g)
160
Discharge capacity (mAh/g)
120
100
80
60
4.9 V
5.0 V
40
5.1 V
5.2 V
20
0
(b) EC-EMC
5.3 V
0
0
100
200
300
400
500
100
200
100
80
60
4.9 V
40
5.0 V
5.1 V
20
5.2 V
5.3 V
300
400
500
0
180
180
160
160
160
C/10 1C
120
C/2
1C
5C
2C
100
10C
80
60
EC-DMC
EC-EMC
40
4.9 V
20
EC-DEC
C/10
1C
1C
5C
120
C/2
2C
100
10C
80
60
EC-DMC
EC-EMC
EC-DEC
40
5.1 V
20
30
40
200
50
60
70
140 C/10 1C
300
400
500
1C
5C
C/2
120
2C
100
80
10C
60
40
EC-DMC
EC-EMC
20
0
10
Cycle number
•
•
•
140
20
0
0
100
Cycle number
180
140
(c) EC-DEC
Cycle number
Discharge capacity (mAh/g)
Discharge capacity (mAh/g)
Cycle number
11
120
0
0
Discharge capacity (mAh/g)
Discharge capacity (mAh/g)
Conventional Electrolytes are Stable up to 5.2 V
5.3 V
EC-DEC
0
0
10
20
30
40
Cycle number
50
60
70
0
10
20
30
40
50
Cycle number
Cutoff voltage ≤ 5.2 V: Very similar long cycling performance for the three carbonate mixtures.
Cutoff voltage = 5.3 V: EC-DMC is still stable but EC-DEC degrades fast.
Rate capability: EC-DMC and EC-EMC is similarly but EC-DEC is poorer.
60
70
2. Energy Storage beyond Li-ions
Comparison of Specific Energy of Various Batteries
4000
Practical specific energy based on state of the art cells
Specific Energy (Wh/kg)
3500
Theoreticall specific energy based on active components
3000
2500
2000
1500
1000
500
0
12
Li-Metal
Batteries
2.1 Highly Stable Li-S Batteries
Potential: 3-4x improvement over Li-ion
Barrier: Li2S deposition on Li metal
13
Optimization of mesoporous carbon structures
(a) MC.
(b) MC with pores completely filled
with sulfur.
(c)MC with pores partially filled
with sulfur.
14
Self-breathing Conductive Polymer to
Encapsulate Sulfur
H
N
H
SS
N
S S
S
H
S
H
S y
S
S
S
S
1-y
Discharge
800
600
(b) 3.0
400
+
S
N
H
Voltage / V vs. Li/Li
S
S S
S
S S
S
N
H
N
S S
-1
N
H
S
(c) 1000
S
Capacity / mAh g
S S
S S
S
S S
H
N
S
N
(c)
S
200
2.5
0.1 C
0.5 C
1C
2.0
1.5
1st
1.0
Polymer
In-situ
vulcanization
Charge
Polymer + Sulfur
0
200
400
600
800
-1
Polymer + Li Sulfide
0
Capacity / mAh g
0
20
40
60
80
Cycle number / n
polymer hollow nanowire
S/polymer composite
Composite discharged to 1V
Composite recharged to 3V
At C/10, initial discharge capacity is 755 mAh/g with an activation
process in the following cycles.
Even after 500 cycles at 1C the capacity retention reaches 76%.
15
100
2.2. High Capacity Li-Air Batteries
Aqueous Li-air Batteries
Alkaline: O2 + 2H2O + 4e−↔ 4OH− (3.43 V)
Acid:
O2+ 4e− + 4H+ ↔ 2H2O (4.26 V)
16
Non-Aqueous Li-air Batteries
2Li++ 2e− + O2 ↔ Li2O2
(2.96 V)
High Capacity Primary Li-air Batteries
Footprint: 4.6 cm x 4.6 cm; thickness = 3.8 mm
0.8 mil polymer membrane
Metal mesh
0.7 mm KB carbon electrode
1 mil separator with binding layer
0.5 mm Li foil
Cu mesh
+
-
3.6
3.2
2340 mAh/g carbon
2.8
Voltage (V)
2.4
2
1.6
Operated in ambient air (~20% RH) for 33 days
1.2
Total weight of the complete battery: 8.387 g
0.8
Specific energy: 362 Wh/kg
0.4
0
0
0.2
0.4
0.6
0.8
1
Cell capacity (Ah)
17
Zhang et al, J. Power Sources 195:4332–4337 (2010).
1.2
1.4
Hierarchically Porous Graphene as a Lithium-Air
Battery Electrode
a and b, SEM images of asprepared graphene-based
air electrodes
c and d, Discharged air
electrode using FGS with
C/O = 14 and C/O = 100,
respectively.
e, TEM image of discharged
air electrode.
f, Selected area electron
diffraction pattern (SAED) of
the particles: Li2O2.
18
Xiao et al. Nano Lett., 2011, 11 (11), pp 5071–5078.
Graphene as a Lithium-Air Battery Electrode
 Record Capacity of 15,000 mAh/g
19
2.3 Li-Metal Batteries
• Rechargeable Li-metal batteries are
considered the “holy grail” of energy
storage systems due to the high energy
density.
GM estimate on
HE NMC/Li metal
system: 540
Wh/kg, 1050 Wh/L
in cell level (2012)
• However, Li dendrite growth in these
batteries has prevented their practical
applications inspect of intensive works in
this field during the last 40 years.
 Dendrite-free Li metal deposition is needed
for rechargeable Li-metal batteries, Li-S
batteries, Li-air batteries.
20
Classical Li
dendrite growth
(Chianelli,
Exxon, 1976)
Effect of CsPF6 Additive on
The Morphology of Li Deposition
a
b
c
20 µm
20 µm
d
20 µm
e
20 µm
20 µm
• Control electrolyte: 1 M LiPF6 in PC.
• CsPF6 concentration in the electrolyte: (a) 0 M, (b) 0.001 M, (c) 0.005 M,
(d) 0.01 M, and (e) 0.05 M.
 Cs+ additive can effectively suppress Li dendrite growth.
21
Effect of Current Density on Li Deposition
a
b
20 µm
20 µm
d
c
20 µm
20 µm
• Electrolyte: 1 M LiPF6 in PC with 0.05 M CsPF6 as additive.
• Current density (mA cm-2): (a) 0.1, (b) 0.2, (c) 0.5, and (d) 1.0.
 SHES mechanism is effective at different current densities.
22
Morphology Changes During Long Term
Cycling of Li Electrode in Li/LTO Cells
b
a
20 µm
20 µm
Surface morphologies of Li electrodes after 100 cycles in coin cells of
Li|Li4Ti5O12 system containing electrolytes without (a) and with (b) Cs+-additive.
 SHES mechanism is effective during long term cycling.
23
Excellent Long Term Stability of Li-Metal Batteries
Using Cs+ Additive
300
250
200
90
150
80
100
Cell: Li/Li4Ti5O12
50
70
1 M LiPF6 in PC with 0.05 M CsPF6
0
0
100
200
300
400
500
600
Coulombic Efficiency (%)
Discharge Capacity (mAh/g)
100
60
700
Cycle index
 Columbic efficiency: 99.97%
 Cycling stability: Only 3.3% capacity fade in 660 cycles
24
Summary
1. Si electrode prepared by a cost effective method (ball
milling)
 822 mAh/g and a capacity retention of ~ 94% in 100 cycles.
2. High voltage, highly stable cathode
 Retain more than 80% capacity after 500 cycles.
3. Highly stable Li-S batteries
 650-800 mAh/g after 400 cycles.
4. High capacity Li-air batteries
 Li-air batteries operate in ambient air for 33 days with a specific energy of
~362 Wh/kg for the complete battery.
 Graphene based air electrode (~ 15,000 mAh/g).
5. Dendrite-Free Li-Metal Batteries
 Novel additives (Cs, Rb, etc.) based on the SHES mechanism can effectively
suppress Li dendrite growth on Li metal batteries.
 ~99.97% Coulombic efficiency and ~4.2% capacity fade in 610 cycles
for Li-metal batteries.
25
Acknowledgments
Technical Team:
Wu Xu, Jie Xiao, Xiaolin Li, Yuyan Shao, V. Viswanathan, Jianzhi Hu,
Vijayakumar Murugesan, Silas A. Towne, Phillip Koech, Donghai Mei,
Fei Ding, Zimin Nie, Yuliang Cao, Yufan Xiao, Eduard Nasybulin, Jian
Zhang, Dehong Hu, Gordon L. Graff, and Jun Liu
Financial support:
• DOE/EERE/Office of Vehicle Technology
• Laboratory Directed R&D Program of PNNL