Fuel cell technology and rechargeable batteries Dr. Jonathan C.Y. Chung Jonathan.chung@cityu.edu.hk...

Fuel cell technology and rechargeable

batteries

Dr. Jonathan C.Y. ChungJonathan.chung@cityu.edu.hk

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

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)

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.

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)

Agenda

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

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

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

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

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)

Li-IonRechargeable Battery

Ni-Cd(Cylindrical Type)

Ni-Cd(Button Type)

Lead-Acid

(Wh/kg)

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

CATHODE

Discharge

Li1-xCoO2 Electrolyte Carbon

Delithiation (charge: Li-ion to carbon/graphite)

Lithiation (discharge)

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

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

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

Voltage

Temperature

Time (min)

0 20 40 60 80 100 120 140 1600

Voltage

Temperature

Time (min)

TEM Image of AlPO4-Nanoparticle-Coated LiCoO2

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

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

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

PtPtPt

SiO2(4

C u K2d e g re e )

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

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

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

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

Real (Z)

after 1st cycle after 100th cycle

Sol electrolyte in Porous membrane

LiMn2O4 /Pt/TiO2/SiO

Discharge Curve AC Impedance

0 10 20 30 40 50 603.0

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

Capac ity ( Ah cm -2 m -1)

Solid Electrolyte+

LiMn2O

4/Pt/TiO

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

Real (Z)

1st cycle 50th cycle 100th cycle

OCV=4.0 V

Pt/LiMn2O4/Sol-polymer-Sol/Li

0 10 20 30 40 50 603.0

1st 100th

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

Spin coating of polymer electrolyte LiMn

4/Pt/TiO

0 5 10 15 20 250

-0.1 0.0 0.1 0.2 0.3 0.40.0

Real(Z) k

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

3.2 kΩ

9.4 nF

6.9 kΩ

9.4 µF

6.2 kΩ

7.7 nF

22 kΩ

5.0 µF

Spin coated electrolyte/ LiMn

4/Pt/TiO

Li/polymer(25 μm)/LiMn2O

El Li LiMn2O

electrolyte Li/electrolyteinterface

electrolyte/LiMn2O

4interface

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

LiMn2O

PEO based polymerLi

Cu foil

Normal

2 Anode

2 Cathode

Fuel cell technology and rechargeable batteries Dr. Jonathan C.Y. Chung Jonathan.chung@cityu.edu.hk...

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