Fuel cell technology and rechargeable
batteries
Dr. Jonathan C.Y. [email protected]
http://personal.cityu.edu.hk/~appchung/Teaching.htm
Dept. of Physics and Materials Sciencehttp://www.ap.cityu.edu.hk/
City University of Hong Konghttp://www.cityu.edu.hk/
Public Interest Subject matters:
What are fuel cells, batteries and rechargeable batteries?
Why some rechargeable batteries explode?
Accidents in the past. A dream: thin Film batteries. Another dream: fuel cells that drink beer!!
PDAPDA
Mobile Mobile PhonePhone
Laptop Laptop ComputerComputer
High-Technology Electronics Equipments
MP3 MP3 PlayerPlayer
Digital CameraDigital CameraPMPPMP
Agenda
1. The construction of a battery2. The electrochemical reaction3. A fuel cell4. The rechargeable batteries5. Ni-Cd, Ni-MH6. Li-ion rechargeable batteries:7. What type of batteries will explode?8. Thin film rechargeable batteries
History of batteries1800 Voltaic pile: silver zinc1836 Daniell cell: copper zinc1859 Planté: rechargeable lead-acid cell1868 Leclanché: carbon zinc wet cell1888 Gassner: carbon zinc dry cell1898 Commercial flashlight, D cell1899 Junger: nickel cadmium cell1946 Neumann: sealed NiCd1960s Alkaline, rechargeable NiCd1970s Lithium, sealed lead acid1990 Nickel metal hydride (NiMH)1991 Lithium ion1999 Lithium ion polymer
Electrodes
Electrochemical cell Cathode is the electrode where
reduction takes place. Anode is the electrode where oxidation
takes place.Battery
Positive electrode: (+) of the cell Discharging: cathode (reduction)
Negative electrode: (-) of the cell Discharging: anode (oxidation)
Good vs. bad batteries
1. Voltage (materials, thermodynamics)2. Spontaneous Chemical reaction (unwanted side reac
tion)3. Oxidation of the electrodes (surface and bulk: affect t
he kindetics of the electro-chemical reaction)4. Degradation of the electrolyte (decompose?)5. Effects of environmental contaminants (poisoning?)6. High energy per unit weight7. Safety (to human and equipment)
Primary (Disposable) Batteries1. Zinc carbon (flashlights, toys)2. Heavy duty zinc chloride (radios,
recorders)3. Alkaline (all of the above)4. Lithium (photoflash)5. Silver, mercury oxide (hearing aid,
watches)6. Zinc air
Battery Characteristics Size
Physical: button, AAA, AA, C, D, ... Energy density (watts per kg or cm3)
Longevity Capacity (Ah, for drain of C/10 at 20°C) Number of recharge cycles
Discharge characteristics (voltage drop) Cost Behavioral factors
Temperature range (storage, operation) Self discharge Memory effect
Environmental factors Leakage, gassing, toxicity Shock resistance
Standard Zinc Carbon Batteries Chemistry
Zinc (-), manganese dioxide (+)ammonium chloride aqueous electrolyte
Features+ Inexpensive, widely available Inefficient at high current drain Poor discharge curve (sloping) Poor performance at low temperatures
Alkaline Battery Discharge
Heavy Duty Zinc Chloride Batteries
Chemistry Zinc (-), manganese dioxide (+)Zinc chloride aqueous electrolyte
Features (compared to zinc carbon)+ Better resistance to leakage+ Better at high current drain+ Better performance at low temperature
Standard Alkaline Batteries Chemistry
Zinc (-), manganese dioxide (+)Potassium hydroxide aqueous electrolyte
Features + 50-100% more energy than carbon zinc+ Low self-discharge (10 year shelf life)± Good for low current (< 400mA), long-life use Poor discharge curve
Alkaline-Manganese Batteries
Lithium Manganese Dioxide Chemistry
Lithium (-), manganese dioxide (+)Alkali metal salt in organic solvent electrolyte
Features + High energy density+ Long shelf life (20 years at 70°C)+ Capable of high rate discharge Expensive
Choice of Anode Materials
Elements (V)Melting
pointAh/g Ah/cm3
Li (-3.05) 180.5 3.86 2.08
Na (-2.7) 97.8 1.16 1.12
Mg (-2.4) 650 2.2 3.8
Al (-1.7) 659 2.98 8.1
Ca (-2.87) 851 1.34 2.06
Fe (-0.44) 1528 0.96 7.5
Zn (-0.76) 419 0.82 5.8
Cd (-0.40) 321 0.48 4.1
Pb (-0.13) 327 0.26 2.9
Battery or Pack Two or more electrochemical
cells electrically interconnected in an appropriate series/parallel arrangement to provide the required operating voltage and current levels. Under common usage, the term "battery" is often also applied to a single cell.
Projected Production Yield of battery in pack from cells
Production yield of composing cells and battery packs
Number of cells Voltage (V) 80% 90% 95% 99%
1 1.5 80% 90% 95% 99%
2 3.0 64% 81% 90% 98%
3 4.5 51% 73% 86% 97%
4 6.0 41% 66% 81% 96%
5 7.5 33% 59% 77% 95%
6 9.0 26% 53% 74% 94%
7 10.5 21% 48% 70% 93%
8 12.0 17% 43% 66% 92%
Applications Lead acid starter: vehicles Industrial lead acid: power backup
systems, traction applications Primary batteries
Agenda
1. The construction of a battery2. The electrochemical reaction3. A fuel cell4. The rechargeable batteries5. Ni-Cd, Ni-MH6. Li-ion rechargeable batteries:7. What type of batteries will explode?8. Thin film rechargeable batteries
Definition of battery1. “A battery is a device that converts the chemical energy con
tained in its active materials directly into electrical energy by means of an electrochemical oxidation- reduction (redox) reaction”
M(s) → Mn+(dis) + ne- ormM(s) + nXm-(dis) → MmXn(s) + (n·m)e-
2. The active material at the anode of a battery is the “fuel” that undergoes oxidation.
3. When this anode material or fuel is a metal, the oxidation process consists of corrosion.
4. This is sometime called “constructive corrosion”.
Constructive vs. Destructive corrosion
Electro-chemical reaction vs. chemical reaction
A typical battery
salt bridge (allows ions to migrate)
4CuSO4ZnSO
Reduction at Cathode (e.g. Cu)
Oxidation at Anode (e.g. Zn)
load
e
Half Cell I Half Cell II
Electrochemical Cell
Salt bridge only allows negative ions to migrate through. This also limits the current flow. (kinetics)
Need to find a low-resistance bridge.
.)(2
.)(22
2
IICueCu
IeZnZn
Electrochemical ActivityCathodeHigh Electron Affinity (re
duction: gain electrons) Gold Mercury Silver Copper Lead Nickel Cadmium Iron Zinc Aluminum Magnesium Sodium Potassium Lithium
AnodeLow Electron Affinity (oxidation: lose electrons)
1. What are the differences between a chemical reaction and an electrochemical reaction?
2. We want to have electrochemical reaction for battery.
3. Thermodynamics
Schematic of Battery Properties of electrode Properties of electrolyte Properties of the electrolyte-electrolyte
interface Properties of the separator Properties of
package
Reaction Energy & Activation energy
Thermodynamics: EKinetics: E1, and E2
A + BC + E1 A--B--C AB +C + E2
Thermodynamics A comparison of energy before and after a reactionEtotal= Echemical + Esurface +Edefects +Eelastic +Einterface +Ekinetic +……EAB= Etotal (B-A)
E can be determined by experimental methods We can thus determine whether a transformation is ex
othermic (favourable) or endothermic The thermodynamic analysis only let us know that the
reaction (or transformation) is favorable, it do not tell us “how” can and “when” will the reaction take place
The importance of kinetics
The “ultimate equilibrium” may be not practically achievable when EA (activation energy) required is too large slow reaction
Small EA fast reaction ( fast spontaneous discharge)
EA(AB)
A
B
E
Agenda
1. The construction of a battery2. The electrochemical reaction3. A fuel cell4. The rechargeable batteries5. Ni-Cd, Ni-MH6. Li-ion rechargeable batteries:7. What type of batteries will explode?8. Thin film rechargeable batteries
Fuel Cell Vs. Nuclear bomb Vs. Explosives A fuel cell is a device that uses hydrogen
and oxygen to create electrochemical process
Electrolyte sandwiched between a porous anode and a cathode
Fuel cell construction1. Hydrogen rich fuel2. Anode: a catalyst separates protons and electrons3. Cathode: oxygen combines with e-, protons, or water,
resulting in water or hydroxide ions4. Polymer electrolyte membrane (PEM) and phosphoric
acid fuel cells: protons move through the electrolyte to cathode producing water and heat
5. Alkaline, molten carbonate, and solid oxide fuel cells: negative ions travel through the electrolyte to the anode generating water and electrons
6. The electrons from the anode cannot pass through the membrane to the cathode: they must travel via a circuit
Fuel cell system A fuel processor An energy conversion device A current converter Heat recovery system Others: (optional)
Cell humidity control Temperature control Gas pressure control Wastewater control
Fuel Processor Pure Hydrogen fuel cell: only require a filter to
control purity H-rich fuel cell:
a reformer to convert hydrocarbons into a gas mixture of hydrogen and carbon compound (reformate)
Remove impurity from reformate (prevent poisoning of the catalysts)
What is the meaning of poisoning?
Fuel Pure Hydrogen Hydrogen-rich fuels:
Methanol Gasoline Diesel Gasified coal
Magnesium-Air Fuel Cell (http://www.magpowersystems.com/)
Fuel Cell vs. Primary battery
1. What are the differences and similarity between fuel cell and primary battery?
2. What are the differences and similarity between fuel cell and rechargeable battery?
Agenda
1. The construction of a battery2. The electrochemical reaction3. A fuel cell4. The rechargeable batteries5. Ni-Cd, Ni-MH6. Li-ion rechargeable batteries:7. What type of batteries will explode?8. Thin film rechargeable batteries
Secondary (Rechargeable) Batteries Lead acid Nickel cadmium (NiCd) Nickel metal hydride (NiMH) Alkaline Lithium ion Lithium ion polymer
Why they are rechargeable?
Reversible reaction
% reversible reaction No. of Cycle Retained Capacity99.00% 100 36.6%99.00% 500 0.7%99.00% 1000 0.0%99.00% 2000 0.0%99.90% 100 90.5%99.90% 500 60.6%99.90% 1000 36.8%99.90% 2000 13.5%99.95% 100 95.1%99.95% 500 77.9%99.95% 1000 60.6%99.95% 2000 36.8%99.99% 100 99.0%99.99% 500 95.1%99.99% 1000 90.5%99.99% 2000 81.9%
Volumetric Energy and Specific Energy
Battery Materials Importance of battery materials
Portable electronic and electric appliances, e.g. cellular telephones, video cameras, lap-top computers and hand tools
Market increase by 2 digit (%) p.a. Electric vehicles
Require higher capacities and better performances relative to Ni/Cd batteries.
Ni/MH (metal hydride) is one promising candidate Li-ion is even lighter but more expensive
Battery Capacity
Type Capacity (mAh) Density (Wh/kg)
Alkaline AA 2850 124
Rechargeable Alkaline 1600 80
NiCd AA 750 41
NiMH AA 1100 51
Lithium ion 1200 100
Lead acid 2000 30
Performance Characteristics
Discharge Rates
Type Voltage Peak Drain
Optimal Drain
Alkaline 1.5 0.5C < 0.2C
NiCd 1.25 20C 1C
Nickel MH 1.25 5C < 0.5C
Lead acid 2 5C 0.2C
Lithium ion 3.6 2C < 1C
Voltage: application dependent
Current: higher is better
Other performance indicators (2004)
NiCd NiMH Lead Acid
Li-ion Li-ion polymer
ReusableAlkaline
Gravimetric Energy Density (Wh/kg)
45-80 60-120 30-50 110-160 100-130 80 (initial)
Internal Resistance (includes peripheral circuits) in mW
100 to 2006V pack
200 to 3006V pack
<10012V pack
150 to 2507.2V pack
200 to 3007.2V pack
200 to 20006V pack
Overcharge Tolerance
moderate low high very low low moderate
Operating Temperature (discharge only)
-40 to 60°C
-20 to 60°C
-20 to 60°C
-20 to 60°C
0 to 60°C
0 to 65°C
Maintenance Requirement
30 to 60 days
60 to 90 days
3 to 6 months
not req. not req. not req.
Cost per Cycle (US$)11
$0.04 $0.12 $0.10 $0.14 $0.29 $0.10-0.50
Commercial use since
1950 1990 1970 1991 1999 1992
Lead-acid Battery
cathode: PbO2
anode: PbEelctrolyte: H2SO4
Reactions:Cathode: PbO2+4H++SO4
2-+2e- ↔ PbSO4+2H2OAnode: Pb+SO4
2- ↔ PbSO4+2e-
Overall: Pb + PbO2 + H2SO4 2 PbSO4 + 2 H2O
Degradation Oxide formation (kinetics) Precipitation (electrolyte) Contamination (electrolyte)
Agenda
1. The construction of a battery2. The electrochemical reaction3. A fuel cell4. The rechargeable batteries5. Ni-Cd, Ni-MH6. Li-ion rechargeable batteries:7. What type of batteries will explode?8. Thin film rechargeable batteries
Ni-Cd Batterycathode: Ni(OH)2
anode: CdElectrolyte: KOH(aq)
Reaction at cathode:-Ni(OH)2 + OH- -NiOOH + H2O + e-
Reaction at anode:O2 + 2H2O + 4e- 4OH-
4OH- + 2Cd 2Cd(OH)2 +4e-
Cross-section of a classic NiCd cell
While charging, the cell pressure of a NiCd can reach 1379 kilopascals (kPa) or 200 pounds per square inch (psi). A venting system is added on one end of the cylinder. Venting occurs if the cell pressure reaches between 150 and 200 psi.
The negative and positive plates are rolled together in a metal cylinder. The positive plate is sintered and filled with nickel hydroxide. The negative plate is coated with cadmium active material. A separator moistened with electrolyte isolates the two plates. [Panasonic Battery]
Pros and ConsAdvantages: High current application Mature technologyDisadvantages: Memory Poisonous Cd (Environmental problems)
Ni-MH Batterycathode: Ni(OH)2anode: MElectrolyte: KOHReaction at cathode:
Ni(OH)2 + OH- NiOOH + H2O +e-
Reaction at anode:M + H2O +e- MH +OH-
Overall Reaction:MH + NiOOH M + Ni(OH)2
Charge¯discharge mechanism of Ni¯MH battery
Capacity densities of electrodes(Ni-Cd vs. Ni-MH)
Advantages of Ni-MH batteries
Compare with Ni-Cd batteries: 1.5-2 times high energy density 400mAh/g (or 2000m
Ah/l) free from the poisonous metal Cd No concentration change of electrolyte because ther
e is no precipitation formation No memory effect and can sustain high rate charge a
nd discharge High tolerance to over-charging and over-dischargin
g Voltage characteristics similar to Ni-Cd, ready substit
ute
Development of MH battery materials
Initial focused on gas-phase hydrogen storage tanks, hydrogen purifiers and chemical heat pumps
1970: first H-storage material for rechargeable batteries electrode Corrosion, short cyclic life and poor charge retention
1984: LaNi5, substituting Ni with Co and a small amount of Si --> La-Ni-Co-Si (or Al)
Mm-Ni-Co-Si(or Al) (Mm: Ce-rich mischmetal)Ml-Ni-Co-Si(or Al (Ml: La-rich mischmetal)AB5 type alloys
AB2 type: V-Ti-Zr-Ni 1990: appear on the market and is growing fast AB/A2B type TiNi/Ti2Ni: no distinct merit AB type (MgNi): short cycle life
The demand of battery materials: Hybrid electric vehicle Toyota “Prius” and its battery pack.
Key materials and technologies for Ni¯MH batteries
The Well Accepted or Marketed MH Electrode Alloys
Metal Hydride Electrodes
Ni-metal hydride battery adopt a hydrogen storage alloy as its negative electrode
Absorb and desorb reversibly a large amount of hydrogen Ni(OH)2+MMH2+NiOOH
where M stands for the hydrogen storage alloy Equilibrium potential at 20oC, 1 atm, in 6M KOH relative to mecury
oxide electrode is related with the hydrogen dissociation pressure PH2 by the Nernst equation
Eeq(H2O/H) – Eeq(HgO/Hg) = -0.9324 – 0.0291 log PH The electrochemical capacity per unit weight is determined by the
hydrogen atom absorbed per unit mole of alloy H/MC = 2.68 x 104 (H/M) / W
where W is the average molecular weight of the alloys (in g)
Requirement of battery materials Corrosion resistance (alkaline) and long cycle life High electrochemical capacity (mAh/g) Stable equilibrium hydrogen pressure 10-4-10-1 MPa (-2
0~60oC) Good surface activity and kinetic property High charge retention (14-21 days) Low cost Light weight
Problem with M-H electrodes
Concept of material design for battery alloys:
Micro-designing the Composition Surface structure Microstructure (e.g. grain
size, grain boundaries)
Which structure (intermetallics) is the best?
AB5: most successful and well accepted capacity not the largest stable porous and corrosion resistance RE-oxide surface lay
er --> good and balanced overall properties AB2: bigger H-storage capacity
Zr, Ti produce thick dense passive surface V, Mn makes oxide porous (soluble in KOH --> poor performa
nce and unstable) AB/A2B: no specific advantages AB: fast decay, experimental stage
Cycling Capacity Decay vs. Alloying
Ways to improve Cycling Capapcity Decay by alloying: Substituting Co and small amount of Si, Al for Ni Co reduces the volume expansion on hydriding pulverization (the reduction of matter to powder) is a
lso reduced Al and Si segregate at grain boundaries and give bett
er corrosion resistance to KOH Too much Al or Si reduces the porosity and increase t
he surface resistance --> high worsen current rate performance
Ti, Zr, Ce, Nd
Cycling Capacity Decayvs. Grain Size
Ways to improve cycling capacity decay by controlling grain size:
Smaller grain size --> long cycling lives (grain boundaries can accommodate the volumetric changes during the charge-discharge cycle)
Depends on mode of solidification and heat treatment Passifying element segregated at grain boundary are
better protective layers (if the protective layers are too thick, the resistance will be too high heating effect & low kinetics)
Cycling Capacity Decay(Micro-encapsulation)
Ways to improve cycling capacity decay by micro-encapsulation:
The deposition of a thin coating of porous Cu or Ni on the surface of hydrogen storage alloy particles by electrodeless plating (chemical reaction in a bath with heat and catalyst)
better high rate capacity better low temperature performance lower capacity decay Ni or Cu forms anti-oxidation barriers and micro-curr
ent collector --> facilitate electron transfer
Electrochemical Capacityvs. composition
Ways to improve electrochemical capacity by alloying (composition):
Proper substitution for Ni --> increase electrochemical capacity
Rare-earth (RE) elements Non-stoichiometric A:B (e.g. MmBx with
B(Ni-Mn-Co-Al) (Ni:Mn:Co:Al=0.64:0.2:0.04:0.12 and 3.85x 5)
Rate Capacity vs. surface resistance
Ways to reduce surface resistance: Micro-encapsulation Control of additives: too much -->
oxide impede hydrogen and current flow
Mo, B and Ta
Cost vs. alloying
Ways to lower cost by alloying: La and Co are expensive Use mischmetal to substitute La Reduction of Co: with Ce and Nd
Energy density per volume and weight for small rechargeable batteries
Agenda
1. The construction of a battery2. The electrochemical reaction3. A fuel cell4. The rechargeable batteries5. Ni-Cd, Ni-MH6. Li-ion rechargeable batteries7. What type of batteries will explode?8. Thin film rechargeable batteries
Comparison of critical materials in batteries
Battery type cathode anode
Li-ion LiCoO2, LiMn composite
Graphite
Ni-MH Ni(OH)2 Hydrogen storage
materials (M)
Li-Ion Battery Technology
Energy Densities of Rechargeable Batteries
10 100 1000 (Wh/l)
100
10
Li-IonRechargeable Battery
Ni-MH
Ni-Cd(Cylindrical Type)
Ni-Cd(Button Type)
Lead-Acid
(Wh/kg)
Gra
vim
etric
Volumetric Energy Density
Li or Li-ion Battery cathode: Lithium or Li-ion cathode Electrolyte: liquid or solid (for thin film) anode: Graphite Current collector
The electron transfer is mediated by mobile ions released from an ion source, the anode, and neutralized in the electron exchanger, the cathode.
The positive ion is transmitted through a fast ion conductor which is a good electronic insulator, the separators.
Li-ion as conducting materials intercalates and disintercalates in batteries.
The Li-ion Battery
Li-ion Batterycathode: LiCoO2, LiMn compositeanode: GraphiteElectrolyte: Li salt organic solution
It is NOT due to the oxidation and reduction of the electrodes
Li-ion travel between the electrodes on charging and discharging
No Memory Effect Li-ion batteries have none of the memory effects seen in rechargeable Ni
Cd batteries. (“memory effect” refers to the phenomenoon where the apparent discharge capacity of a battery is reduced when it is repetitively discharged incompletely and then recharged).
Li-Ion Battery Mechanisms
Li+
ANODE
e
e
e
CATHODE
e
e
+ -
Discharge
Li+
Li+
Li1-xCoO2 Electrolyte Carbon
Delithiation (charge: Li-ion to carbon/graphite)
Lithiation (discharge)
e
e
e
e
Li1-xCoO2
for 0<x<0.5
Li1-xCoO2
for 0<x<0.5
Structure of LiCoO2
Space group: R3ma = 2.81 Å and c = 14.08 Å
-c
a
A
C
B
B
A
C
Li+
Co3+
O2-
Smaller volumetric change is better!
Solid Electrolyte Interface (SEI)
1. The reaction between the electrolyte and the electrode may lead to the formation of the SEI.
2. Insulator SEI limit the diffusion of Li ions and charge carriers (lower ionic and electron conductivity, RSEI increase) poor electrochemical performances when cycling the electrodes
3. RSEI is temperature dependent4. “Elastic passive” SEI: (a) limit the dissolution of the elect
rodes in the corrosive electrolyte improve in cycling stability of the electrodes
5. Such elastic passive films could prevent continuous decomposition of the electrolyte because the passive films prevent exposure of fresh electrode surface to electrolyte (normally occurring at the crack due to expansion and shrinkage of electrode materials/particles during lithiation and delithiation).
Necessary SEI1. The formation of a SEI film on the electrode surface is
necessary for maintaining its stability and a smooth intercalation and de-intercalation of lithium, since this film prevents the direct contact of the compounds via lithium intercalation with the electrolytes
2. This film need to be porous so that Li ions can move from the electrolyte solution into the electrode.
3. Solvated Li ions should be prohibited from passing through the SEI; otherwise solvent molecules can intercalate into electrode and cause destruction of the electrode
4. Surface structures of the electrode materials are crucial to the formation of SEI and consequently the electrochemical performance
5. Surface modification: mild oxidation, deposition of metals and metal oxides, coating with polymers and carbons
Analysis of SEI FTIR Raman spectroscopy XPS SEM EIS AC impedance
Agenda
1. The construction of a battery2. The electrochemical reaction3. A fuel cell4. The rechargeable batteries5. Ni-Cd, Ni-MH6. Li-ion rechargeable batteries:7. What type of batteries will explode?8. Thin film rechargeable batteries
Short circuiting due to Li crystal growth
Melting of Electrode(Li Anode) Li anode will melt at ~180oC It flows to the cathode and may lead to
short circuiting further overheating and
EXPLOSION!!!
Problems of Li and Li-ion batteries1. Li metal has low melting point and might explode wh
en overheated Protection circuit to prevent overheat due to overcharge or
overdischarge PP membrane to prevent short circuiting between the Cath
ode and Anode2. Pressure relief valve to release the excessive pressur
e3. Separator membrane with good mechanical strengt
h to prevent the damage due to crystal disposition4. Microporous membrane which can be melted to bloc
k the ion passage.
Heat Generation in the Li-ion Battery Chemical reaction between electrolyte and Anode Thermal decomposition of the electrolyte Chemical reaction between electrolyte and
Cathode Thermal decomposition/melting of the anode Thermal decomposition of the cathode Heat generation due to internal resistance of the
battery
Reaction between electrolyte and electrodes There is a structural separation film
between Temperature increase will reduce the
mechanical strength of the separator The heat source can be external and
internal Heating may enhance the electro-chemical
and chemical reaction and result in even high temperature
Decomposition of the Electrolyte EC-PC/LiAsF6 < 190oC
EC-(2-Me-THF)(50/50)/LiAsF6 and others < 145oC or 155oC
LiCF3SO3 <260oC Gas vapor may be generated Solid electrolyte
Melting of Electrode(Li Anode) Li anode will melt at ~180oC It flows to the cathode and may lead to
short circuiting further overheating and EXPLOSION!!!
Safety Devices1. PTC: protection circuit against overheating2. Separator with micro-pore that will close
preventing the migration of Li-ion through the electrolyte when overheated
3. Safety valve to release gas before explosion or fire
4. Smart charging and discharging control circuit
Are we safe?
AlPO4-Coated LiCoO2Bare LiCoO2
Short Circuit & Temperature Uprise
Cell Fired and Exploded
Breakthrough in the Safety Hazard of Li-Ion Battery
~500°C
Temperatureonly ~60°C
ExcellentThermal Stability
~60°C
0 20 40 60 80 100 120 140 1600
2
4
6
8
10
12
14
Voltage
Temperature
Time (min)
Cel
l Vol
tage
(V
)
0
100
200
300
400
500
Tem
pera
ture
(o C
)
0 20 40 60 80 100 120 140 1600
2
4
6
8
10
12
14
Voltage
Temperature
Cel
l Vol
tage
(V)
Time (min)
0
20
40
60
80
100
Tem
pera
ture
(o C
)
TEM Image of AlPO4-Nanoparticle-Coated LiCoO2
EDS confirms the Al and P components in the nanoscale-coating layer.
EDS confirms the Al and P components in the nanoscale-coating layer.
AlPO4 nanoparticles (~3 nm) embedded
in the coating layer (~15 nm).
AlPO4 nanoparticles (~3 nm) embedded
in the coating layer (~15 nm).
Agenda
1. The construction of a battery2. The electrochemical reaction3. A fuel cell4. The rechargeable batteries5. Ni-Cd, Ni-MH6. Li-ion rechargeable batteries:7. What type of batteries will explode?8. Thin film rechargeable batteries
MEMORYDISPLAY
BATTERY
Mobile Information Control
Smart card (average current: ~10 pA)1)
Combination ATM/debit/credit cards Portable health-care files Security card keys
RF-ID tags (average current: ~10 μA)2)
Implantable medical devices (1~4 μA)3)
Hearing loss Epilepsy, Parkinson's disease Blood pump
Semiconductors, integrated circuits Non-volatile memory backup (nvSRAM)
1 www.bits-chips.nl/showdoc.asp?pct_id=16&pub_id=1112 http://www.soc-eusai2005.org/proceedings/articles_paglnes/35_pdf_file.pdf3 Pacing Clin Electrophysiol. 1994 Jan;17(1):13-6.
Applications of Thin Film Battery
Micro-battery on chips
Schematic view of the four layers of the thin battery
3 ways for the intermetallic compound to react with Li1. x Li + MM’y ↔ Lix MM’y
2. x Li + MM’y ↔ LixM + yM’3. (x+y) Li + MM’z ↔ yLi + LixM ↔ LixM zLiy/z M’
As a result, a composite of two finely interdispersed lithiated phases is obtained.
Li-ion thin film solid state battery Electric charge transport by a single type of ions, a cat
ion A+. The anion is immobilized in the crystal lattice. The electrolyte is a solid fast ion conductor. The blocking of the anions prevents passivation, corro
sion and solvent electrolysis reaction. No gas formation totally sealed batteries.
Examples for Materials for thin film Li-ion batteriesCathode, Anode, ElectrolyteLi, MoS2, LiAsF6
Li-Al, TiS2, LiPF6/(Me-DOL+other)
Li alloy, C, LiClO4
……
All solid state thin film battery Solid Cathode Solid Anode Solid electrolyte???
+
Cathode dep. (LiMn2O4 , 0.4 µm)
Solid electrolyte (Lipon, 1 µm)
Anode evaporation (Li)
All solid state thin film battery!
Thin Film Battery System – All Solid State
Oak Ridge National Laboratory
Photographs of some of the prototype Li/Lipon/LiCoO2 thin-film batteries
fabricated at ORNL.
http://www.ornl.gov/sci/cmsd/main/Programs/BatteryWeb/index.htm
J.B. Bates founded “Oak Ridge Micro-Energy. Inc.”in 2001
VoltaFlex
Solid Polymer Electrolyte
Roll-to-Roll Technology (Sandwich)
Prof. D.Sadoway and M.Mayers at MIT
www.voltaflex.com
Contents Inorganic Thin Film Electrolyte LiTi2(PO4)3
LiPON Li4SiO4-Li3PO4
Polymer Electrolyte SOL in Porous Membrane Solid Polymer Spin Coating Polymer
New Structure & System High Power TFB Planar inter-connections of TFB Micro Battery High Efficiency TFB Systems
Inorganic Solid Electrolytes LiTi2(PO4)3
LiPON
Li4SiO4-Li3PO4
Solid Electrolytes
LiTi2(PO4)3
Deposition conditionsProcessing gas : ArProcessing pressure : 10 mTorrRF power : 100 W
Rapid thermal annealing
15 sec in O2 ambientAnnealing T ↑, ionic conductivity ↑
RF power ↑ Ion conductivity ↓
Deposition rate ↑
Pressure ↑ Ion conductivity ↓
Deposition rate ↓
Solid ElectrolytesLiPON
Solid Electrolytes
Effect of Ti and W doping on the ionic conductivity of LiPON
doping concentration ↑ ionic conductivity ↓
Doped LiPON
LiMn2O4/LiPON/Li TFB
AC impedance spectrum and equivalent circuit
Voltage : 4.05 V Amplitude : 10 mV Frequency : 1 MHz ~ 30 mHz
Rel : electrolyte resistance
Rlipon : Lipon resistance
Rg : contact resistance
Rct : charge transfer resistance
Clipon : Lipon capacitance
Cg : contact capacitance
Cdl : double layer capacitance Zw : Waburg impedance
LiMn2O4/LiPON/Li TFB Variation of resistance and capacitance upon charge-discharge cycles
Solid Electrolyte
Li4SiO4-Li3PO4
Only Ar gas ionic conductivity : ~10-5 S/cm
Solid Electrolyte Arrhenius plots
Activation Energy : 0.202 eV
Activation Energy : 0.548 eV
<Li4SiO4-Li3PO4><LiPON>
Summary of Inorganic Solid Electrolyte
Thin-film LiTi2(PO4)3 Electrolyte Ionic conductivity : 5×10-6 S/cm RTA : 600°C
Thin-film LiPON Electrolyte Ionic conductivity : 4.5×10-6 S/cm Activation Energy : 0.202 eV
Thin-film Li4SiO4-Li3PO4 Electrolyte Ionic conductivity : 9×10-5 S/cm Activation Energy : 0.548 eV
Inorganic Amorphous Solid Electrolyte
Very brittle and difficult for fuel cell fabrication Lithium phosphorus oxynitride (Lipon)
J.B. Bates et al. Oak Ridge National Lab Li2O-V2O5-SiO2 Lithium sulfur oxynitride (Lison) Li1.9Si0.28P1.0O1.1N1.0 (LISIPON)
Very slow deposition rate-not practical RF reactive magnetron sputtering Pulsed laser deposition Ion beam assisted deposition Plasma enhanced chemical vapor deposition
Crystalline Poly-Ethylene Oxide
Double PEO chain forms the transport channel of Li+
Only cation moves PEO:LiX=6:1 10-7 S/cm at 25 oC PEO Mw=1,000g
The structures of PEO6:LiAsF6. (Left) View of the structure along a showing rows of Li+ ions perpendicular to the page. (Right) View of the structure showing the relative position of the chains and their conformation (hydrogens not shown). Thin lines indicate coordination around the Li+ cation.Blue spheres, lithium; white spheres, arsenic; magenta, fluorine; green, carbon; red, oxygen
Ref.: P.G.Bruce, 2003, JACS
LiPON vs Polymer Electrolyte LiPON vs. Spin-coated SPE
LiPON (Lithium Phosphorus Oxynitride)
Spin Coated SPE
10-6S/cm 10-4~10-5S/cm
Magnetron Sputtering Spin Coating
Conductivity
Method
6~24hrs to obtain 1µm < 1 min.Dep. Rate
Very Poor GoodProductivity
Brittle FlexibleDuctility
Fab of Thin Film Cathode
1x1 inch Oxide Wafer
H2O2+H2SO4 1:1 30min 80oCWafer cleaning1
~100ÅAr+O2 10sccm, 100W, 20min at
R.TTiO
2 sputtering2
~2000ÅAr 10sccm, 100W, 30min at 350oCPt sputtering3
1000~3000ÅAr+O2 10sccm, 90W, 6hr at 300oCLiMn2O4 sputtering4
Tube furnaceO2 ambient (400oC, 550oC, 750oC)
2hrAnnealing5
until ~150oCIn furnaceSlow cooling6
Cycle testPurified
ElectrolyteLi/LiClO
4 1M in PC/Cathode7
20 30 40 50 60 70 80
LiM
nO
2 (
22
1)
PtPtPt
SiO2(4
40
)
(40
0)
(31
1)
Inte
nsi
ty (
a.u
.)
C u K2d e g re e )
(11
1)
SiO2
Crystal structure of LiMn2O4 Thin Film
SiO2/Si substrate
Pt/TiO2(~2000Å)
LiMn2O
4(~2000Å)
750ºC, 2hrs annealing
FE-SEM of LiMn2O4 Thin Film
100 nm
(a)
1 µm
(b)
100 nm 1 µm
Before heat treatment After heat treatment
•Partially crystallized during sputtering due to the substrate temperature
•Grain size: ~70nm
•750oC, 2 시간 , O2 ambient in Furnace•Grain size: ~80nm
Porous membrane
Lithium
P(VdF-HFP) + Acetone (Solvent) + Poly Ethylen Glycol
(non-solvent)at 50oC, Stirring
5hrs
Pour on flat glass and dry acetone for
1~5hrs in air
methanol
Remove PEG with methanol
Wetting with Sol Electrolyte
membrane
Lithium
LiMn2O
4 on Wafer
P(VdF-HFP) Porous Membrane
D
poly(vinylidene fluoride-co-hexafluoropropylene)
SOL: 1M LiClO4:(PEO)1 in PC Ion conductivity ~ 5 x 10-4 S/cm
Polymer Electrolyte
Add PEO andStirring 2 days
Pour on teflon mold and
dry for 3 days
Leave 5hrs on shelf without stirring to
remove pores
Solid Polymer
electrolyte
LiClO4 +
Acetonitril
Spin Coating
on Thin Film LiMn2O4
LiClO4:PEO=1:20
Li/SOL/ LiMn2O4/Pt
Similar to liquid electrolyte except the slightly higher interface resistance
No change at Li side IR after 100 cycles but 200 Ω->650 Ω at LiMn2O4
side 0 200 400 600 800 1000
0
-200
-400
-600
-800
-1000
Imag
.(Z
)
Real (Z)
after 1st cycle after 100th cycle
Sol electrolyte in Porous membrane
Li
LiMn2O4 /Pt/TiO2/SiO
2/Si
Discharge Curve AC Impedance
0 10 20 30 40 50 603.0
3.5
4.0
4.5
5.0
Vol
tage
(V
)
Capacity (Ah cm - 2 m - 1)
1st cycle 100th cycle
Current density= 100 µA cm-2
Cell size = 0.1 cm2
OCV=4.0 V
Li/polymer/ LiMn2O4/Pt (sandwich cell)
0 10 20 30 40 50 603.0
3.5
4.0
4.5
5.0
Vol
tage
(V
)
Capac ity ( Ah cm -2 m -1)
1st cycle 100th cycle
Solid Electrolyte+
+
Sol
Sol
LiMn2O
4/Pt/TiO
2/SiO
2/Si
Li/glass
고체전해질 두께 =70 µmi= 100 µA/cm2
0 1 0 0 2 0 0 3 0 0 4 0 0 5 0 00
-1 0 0
-2 0 0
-3 0 0
-4 0 0
-5 0 0
0 5 10 15 20 25 300
-5-10-15-20-25-30
Imag
.(Z
)
Real (Z)
1st cycle 50th cycle 100th cycle
OCV=4.0 V
1.5Hz
Pt/LiMn2O4/Sol-polymer-Sol/Li
0 10 20 30 40 50 603.0
3.5
4.0
4.5
5.0
1st 100th
Volta
ge (
V)
Capacity (Ah/cm2-m)
Charge
Discharge
Cell geometry : 0.1cm2 X 280nm
J=100A/cm2
Li/polymer/ LiMn2O4/Pt (spin coating)
Solid Polymer Electrolyte Cell:
LiMn2O
4: 280 nm
Electrolyte: Solid PEO:LiClO4 18:1
Anode: Evaporated Li filmMaintain 85% of initial capacity at
100th cycleCoulombic efficiency=93%
Li/spin coated polymer (25 μm)/LiMn2O4/Pt
Li
Spin coating of polymer electrolyte LiMn
2O
4/Pt/TiO
2/SiO
2/Si
0 5 10 15 20 250
-5
-10
-15
-20
-25
-0.1 0.0 0.1 0.2 0.3 0.40.0
-0.1
-0.2
-0.3
-0.4
Imag
.(Z
) k
Real(Z) k
1st cycle 100th cycle
OCV : 4.0V
Spin Coating for All Solid State Li Battery
CTR at Li side increases by two times after 100 cycles
CTR at LiMn2O4side increases by three times after 100 cycles
18 Ω
3.2 kΩ
9.4 nF
6.9 kΩ
9.4 µF
1st
23 Ω
6.2 kΩ
7.7 nF
22 kΩ
5.0 µF
100th
RE
RLi
CLi
RMn
CMn
Cycle
Li
Spin coated electrolyte/ LiMn
2O
4/Pt/TiO
2/SiO
2/Si
Li/polymer(25 μm)/LiMn2O
4/Pt
El Li LiMn2O
4
Zw
RE
electrolyte Li/electrolyteinterface
electrolyte/LiMn2O
4interface
CLi
CMn
RLi
RMn
CG
1.6x10-5 S cm-1
1.3x10-5 S cm-1σ
Summary All solid state rechargeable lithium battery
was fabricated and under the cycling test at current density of 100 μA/cm2 (~ 6C rate), initial capacity turned out to be 53 μAh/cm2 μm, 85% of which could be maintained after 100 cycles.
This cell might be good enough for RF-ID tag which consumes average current of 10 μA and for Muti-media Smart Card of 10pA.
For further improvement, research on the unidentified material (30 nm) at the interface between cathode and solid electrolyte formed during the cycling seems to be important.
Some Properties of solid state thin film batteries Up to 300 Wh/kg >70000 recharge cycles (200 year?) Up to 50C rates at 80% efficiency Charge Retention: less than 1% charge loss pe
r year. 3.6 volts Capacity: upto 1 mA hour per cm2.
New TFB for High Efficiency Cell structure
Cathode
Electrolyte
Anode
LiMn2O
4Mesh
PEO based polymerLi
Cu foil
Normal
2 Anode
2 Cathode