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Fuel cell technology and rechargeable batteries. Dr. Jonathan C.Y. Chung [email protected] http://personal.cityu.edu.hk/~appchung/Teaching.htm Dept. of Physics and Materials Science http://www.ap.cityu.edu.hk/ City University of Hong Kong http://www.cityu.edu.hk/.

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Fuel cell technology and rechargeable batteries

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Fuel cell technology and rechargeable batteries l.jpg

Fuel cell technology and rechargeable batteries

Dr. Jonathan C.Y. Chung

[email protected]


Dept. of Physics and Materials Science


City University of Hong Kong


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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!!

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High-Technology Electronics Equipments

Mobile Phone

Laptop Computer


MP3 Player

Digital Camera


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  • The construction of a battery

  • The electrochemical reaction

  • A fuel cell

  • The rechargeable batteries

  • Ni-Cd, Ni-MH

  • Li-ion rechargeable batteries:

  • What type of batteries will explode?

  • Thin film rechargeable batteries

History of batteries l.jpg

History of batteries

1800Voltaic pile: silver zinc

1836Daniell cell: copper zinc

1859Planté: rechargeable lead-acid cell

1868Leclanché: carbon zinc wet cell

1888Gassner: carbon zinc dry cell

1898Commercial flashlight, D cell

1899Junger: nickel cadmium cell

1946Neumann: sealed NiCd

1960sAlkaline, rechargeable NiCd

1970sLithium, sealed lead acid

1990Nickel metal hydride (NiMH)

1991Lithium ion

1999Lithium ion polymer

Electrodes l.jpg


Electrochemical cell

  • Cathode is the electrode where reduction takes place.

  • Anode is the electrode where oxidation takes place.


  • Positive electrode: (+) of the cell

    • Discharging:cathode (reduction)

  • Negative electrode: (-) of the cell

    • Discharging: anode (oxidation)

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Good vs. bad batteries

  • Voltage (materials, thermodynamics)

  • Spontaneous Chemical reaction (unwanted side reaction)

  • Oxidation of the electrodes (surface and bulk: affect the kindetics of the electro-chemical reaction)

  • Degradation of the electrolyte (decompose?)

  • Effects of environmental contaminants (poisoning?)

  • High energy per unit weight

  • Safety (to human and equipment)

Primary disposable batteries l.jpg

Primary (Disposable) Batteries

  • Zinc carbon (flashlights, toys)

  • Heavy duty zinc chloride (radios, recorders)

  • Alkaline (all of the above)

  • Lithium (photoflash)

  • Silver, mercury oxide (hearing aid, watches)

  • Zinc air

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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

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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 l.jpg

Alkaline Battery Discharge

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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 l.jpg

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 l.jpg

Alkaline-Manganese Batteries

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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

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Choice of Anode Materials

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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.

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Projected Production Yield of battery in pack from cells

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  • Lead acid starter: vehicles

  • Industrial lead acid: power backup systems, traction applications

  • Primary batteries

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  • The construction of a battery

  • The electrochemical reaction

  • A fuel cell

  • The rechargeable batteries

  • Ni-Cd, Ni-MH

  • Li-ion rechargeable batteries:

  • What type of batteries will explode?

  • Thin film rechargeable batteries

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Definition of battery

  • “A battery is a device that converts the chemical energy contained in its active materials directly into electrical energy by means of an electrochemical oxidation- reduction (redox) reaction”

    M(s) → Mn+(dis) + ne-or

    mM(s) + nXm-(dis) → MmXn(s) + (n·m)e-

  • The active material at the anode of a battery is the “fuel” that undergoes oxidation.

  • When this anode material or fuel is a metal, the oxidation process consists of corrosion.

  • This is sometime called “constructive corrosion”.

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Constructive vs. Destructive corrosion

Electro-chemical reaction vs. chemical reaction

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A typical battery




salt bridge (allows ions to migrate)

Reduction at Cathode (e.g. Cu)

Oxidation at Anode (e.g. Zn)





Half Cell I

Half Cell II

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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.

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CathodeHigh Electron Affinity (reduction: gain electrons)















AnodeLow Electron Affinity (oxidation: lose electrons)

Electrochemical Activity

  • What are the differences between a chemical reaction and an electrochemical reaction?

  • We want to have electrochemical reaction for battery.

  • Thermodynamics

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Schematic of Battery

  • Properties of electrode

  • Properties of electrolyte

  • Properties of the electrolyte-electrolyte interface

  • Properties of the separator

  • Properties of package

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Reaction Energy & Activation energy


Kinetics:E1, and E2

A + BC + E1 A--B--C  AB +C + E2

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  • A comparison of energy before and after a reaction

    Etotal= Echemical + Esurface +Edefects +Eelastic +Einterface +Ekinetic +……

    EAB= Etotal (B-A)

  • E can be determined by experimental methods

  • We can thus determine whether a transformation is exothermic (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

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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)





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  • The construction of a battery

  • The electrochemical reaction

  • A fuel cell

  • The rechargeable batteries

  • Ni-Cd, Ni-MH

  • Li-ion rechargeable batteries:

  • What type of batteries will explode?

  • Thin film rechargeable batteries

Fuel cell l.jpg

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

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Fuel cell construction

  • Hydrogen rich fuel

  • Anode: a catalyst separates protons and electrons

  • Cathode: oxygen combines with e-, protons, or water, resulting in water or hydroxide ions

  • Polymer electrolyte membrane (PEM) and phosphoric acid fuel cells: protons move through the electrolyte to cathode producing water and heat

  • Alkaline, molten carbonate, and solid oxide fuel cells: negative ions travel through the electrolyte to the anode generating water and electrons

  • The electrons from the anode cannot pass through the membrane to the cathode: they must travel via a circuit

Fuel cell system l.jpg

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 l.jpg

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?

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  • Pure Hydrogen

  • Hydrogen-rich fuels:

    • Methanol

    • Gasoline

    • Diesel

    • Gasified coal

  • Magnesium-Air Fuel Cell (http://www.magpowersystems.com/)

Fuel cell vs primary battery l.jpg

Fuel Cell vs. Primary battery

  • What are the differences and similarity between fuel cell and primary battery?

  • What are the differences and similarity between fuel cell and rechargeable battery?

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  • The construction of a battery

  • The electrochemical reaction

  • A fuel cell

  • The rechargeable batteries

  • Ni-Cd, Ni-MH

  • Li-ion rechargeable batteries:

  • What type of batteries will explode?

  • Thin film rechargeable batteries

Secondary rechargeable batteries l.jpg

Secondary (Rechargeable) Batteries

  • Lead acid

  • Nickel cadmium (NiCd)

  • Nickel metal hydride (NiMH)

  • Alkaline

  • Lithium ion

  • Lithium ion polymer

    Why they are rechargeable?

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Reversible reaction

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Volumetric Energy and Specific Energy

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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

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Battery Capacity

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Performance Characteristics

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Discharge Rates

Voltage:application dependent

Current: higher is better

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Other performance indicators (2004)

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Lead-acid Battery





Cathode:PbO2+4H++SO42-+2e- ↔ PbSO4+2H2O

Anode:Pb+SO42- ↔ PbSO4+2e-

Overall:Pb + PbO2 + H2SO4 2 PbSO4 + 2 H2O

Degradation l.jpg


  • Oxide formation (kinetics)

  • Precipitation (electrolyte)

  • Contamination (electrolyte)

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  • The construction of a battery

  • The electrochemical reaction

  • A fuel cell

  • The rechargeable batteries

  • Ni-Cd, Ni-MH

  • Li-ion rechargeable batteries:

  • What type of batteries will explode?

  • Thin film rechargeable batteries

Ni cd battery l.jpg

Ni-Cd Battery




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 l.jpg

Cross-section of a classic NiCd cell

While charging, the cell pressure of a NiCd can reach 1379kilopascals (kPa) or 200pounds 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 200psi.

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]

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Pros and Cons


  • High current application

  • Mature technology


  • Memory

  • Poisonous Cd (Environmental problems)

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Ni-MH Battery




Reaction 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

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Charge¯discharge mechanism of Ni¯MH battery

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Capacity densities of electrodes(Ni-Cd vs. Ni-MH)

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Advantages of Ni-MH batteries

Compare with Ni-Cd batteries:

  • 1.5-2 times high energy density 400mAh/g (or 2000mAh/l)

  • free from the poisonous metal Cd

  • No concentration change of electrolyte because there is no precipitation formation

  • No memory effect and can sustain high rate charge and discharge

  • High tolerance to over-charging and over-discharging

  • Voltage characteristics similar to Ni-Cd, ready substitute

Development of mh battery materials l.jpg

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 l.jpg

The demand of battery materials: Hybrid electric vehicle Toyota “Prius” and its battery pack.

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Key materials and technologies for Ni¯MH batteries

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The Well Accepted or Marketed MH Electrode Alloys

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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+MMH2+NiOOHwhere 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/M

    C = 2.68 x 104 (H/M) / W

    where W is the average molecular weight of the alloys (in g)

Requirement of battery materials l.jpg

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 (-20~60oC)

  • Good surface activity and kinetic property

  • High charge retention (14-21 days)

  • Low cost

  • Light weight

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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)

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Which structure (intermetallics) is the best?

  • AB5: most successful and well accepted

    • capacity not the largest

    • stable porous and corrosion resistance RE-oxide surface layer --> 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 performance and unstable)

  • AB/A2B: no specific advantages

  • AB: fast decay, experimental stage

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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 also reduced

  • Al and Si segregate at grain boundaries and give better corrosion resistance to KOH

  • Too much Al or Si reduces the porosity and increase the surface resistance --> high worsen current rate performance

  • Ti, Zr, Ce, Nd

Cycling capacity decay vs grain size l.jpg

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 l.jpg

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-current collector --> facilitate electron transfer

Electrochemical capacity vs composition l.jpg

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 3.85x 5)

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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

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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

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Energy density per volume and weight for small rechargeable batteries

Agenda71 l.jpg


  • The construction of a battery

  • The electrochemical reaction

  • A fuel cell

  • The rechargeable batteries

  • Ni-Cd, Ni-MH

  • Li-ion rechargeable batteries

  • What type of batteries will explode?

  • Thin film rechargeable batteries

Comparison of critical materials in batteries l.jpg

Comparison of critical materials in batteries

Slide73 l.jpg






Rechargeable Battery






(Cylindrical Type)






(Button Type)




1000 (



Volumetric Energy Density

Li-Ion Battery Technology

Energy Densities of Rechargeable Batteries

Li or li ion battery l.jpg

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 l.jpg

The Li-ion Battery

Li ion battery l.jpg

Li-ion Battery

cathode:LiCoO2, LiMn composite


Electrolyte: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 l.jpg

No Memory Effect

  • Li-ion batteries have none of the memory effects seen in rechargeable NiCd 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).

Slide79 l.jpg




Li-Ion Battery Mechanisms


















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

Lithiation (discharge)

Slide80 l.jpg









Space group: R3m

a = 2.81 Å and c = 14.08 Å





Structure of LiCoO2


for 0<x<0.5

Smaller volumetric change is better!

Solid electrolyte interface sei l.jpg

Solid Electrolyte Interface (SEI)

  • The reaction between the electrolyte and the electrode may lead to the formation of the SEI.

  • 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

  • RSEI is temperature dependent

  • “Elastic passive” SEI: (a) limit the dissolution of the electrodes in the corrosive electrolyte  improve in cycling stability of the electrodes

  • 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 sei l.jpg

Necessary SEI

  • 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

  • This film need to be porous so that Li ions can move from the electrolyte solution into the electrode.

  • Solvated Li ions should be prohibited from passing through the SEI; otherwise solvent molecules can intercalate into electrode and cause destruction of the electrode

  • Surface structures of the electrode materials are crucial to the formation of SEI and consequently the electrochemical performance

  • Surface modification: mild oxidation, deposition of metals and metal oxides, coating with polymers and carbons

Analysis of sei l.jpg

Analysis of SEI

  • FTIR

  • Raman spectroscopy

  • XPS

  • SEM

  • EIS

  • AC impedance

Agenda84 l.jpg


  • The construction of a battery

  • The electrochemical reaction

  • A fuel cell

  • The rechargeable batteries

  • Ni-Cd, Ni-MH

  • Li-ion rechargeable batteries:

  • What type of batteries will explode?

  • Thin film rechargeable batteries

Short circuiting due to li crystal growth l.jpg

Short circuiting due to Li crystal growth

Melting of electrode li anode l.jpg

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


Problems of li and li ion batteries l.jpg

Problems of Li and Li-ion batteries

  • Li metal has low melting point and might explode when overheated

    • Protection circuit to prevent overheat due to overcharge or overdischarge

    • PP membrane to prevent short circuiting between the Cathode and Anode

  • Pressure relief valve to release the excessive pressure

  • Separator membrane with good mechanical strength to prevent the damage due to crystal disposition

  • Microporous membrane which can be melted to block the ion passage.

Heat generation in the li ion battery l.jpg

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 l.jpg

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 l.jpg

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 anode91 l.jpg

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!!!

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Safety Devices

  • PTC: protection circuit against overheating

  • Separator with micro-pore that will close preventing the migration of Li-ion through the electrolyte when overheated

  • Safety valve to release gas before explosion or fire

  • Smart charging and discharging control circuit

    Are we safe?

Slide93 l.jpg

Breakthrough in the Safety Hazard of Li-Ion Battery

Bare LiCoO2

AlPO4-Coated LiCoO2



Short Circuit & Temperature Uprise

Temperatureonly ~60°C

Cell Fired and Exploded

ExcellentThermal Stability

Slide94 l.jpg

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).

Agenda95 l.jpg


  • The construction of a battery

  • The electrochemical reaction

  • A fuel cell

  • The rechargeable batteries

  • Ni-Cd, Ni-MH

  • Li-ion rechargeable batteries:

  • What type of batteries will explode?

  • Thin film rechargeable batteries

Mobile information control l.jpg

Mobile Information Control




Applications of thin film battery l.jpg

Applications of Thin Film Battery

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=111

    2 http://www.soc-eusai2005.org/proceedings/articles_paglnes/35_pdf_file.pdf

    3 Pacing Clin Electrophysiol. 1994 Jan;17(1):13-6.

    Micro battery on chips l.jpg

    Micro-battery on chips

    Schematic view of the four layers of the thin battery

    3 ways for the intermetallic compound to react with li l.jpg

    3 ways for the intermetallic compound to react with Li

    • x Li + MM’y↔ Lix MM’y

    • x Li + MM’y ↔ LixM+ yM’

    • (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 l.jpg

    Li-ion thin film solid state battery

    • Electric charge transport by a single type of ions, a cation A+.

    • The anion is immobilized in the crystal lattice.

    • The electrolyte is a solid fast ion conductor.

    • The blocking of the anions prevents passivation, corrosion and solvent electrolysis reaction.

    • No gas formation  totally sealed batteries.

    Examples for materials for thin film li ion batteries l.jpg

    Examples for Materials for thin film Li-ion batteries

    Cathode, Anode, Electrolyte

    Li, MoS2, LiAsF6

    Li-Al, TiS2, LiPF6/(Me-DOL+other)

    Li alloy, C, LiClO4


    All solid state thin film battery l.jpg

    All solid state thin film battery

    • Solid Cathode

    • Solid Anode

    • Solid electrolyte???

    Thin film battery system all solid state l.jpg

    Thin Film Battery System – All Solid State

    Cathode dep. (LiMn2O4 , 0.4 µm)

    Solid electrolyte (Lipon, 1 µm)

    Anode evaporation (Li)

    All solid state thin film battery!


    Oak ridge national laboratory l.jpg

    Oak Ridge National Laboratory

    • Photographs of some of the prototype Li/Lipon/LiCoO2 thin-film batteries

      fabricated at ORNL.

    • J.B. Bates founded “Oak Ridge Micro-Energy. Inc.”in 2001


    Voltaflex l.jpg


    • Solid Polymer Electrolyte

    • Roll-to-Roll Technology (Sandwich)

    • Prof. D.Sadoway and M.Mayers at MIT


    Contents l.jpg


    • 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 l.jpg

    Inorganic Solid Electrolytes

    • LiTi2(PO4)3

    • LiPON

    • Li4SiO4-Li3PO4

    Solid electrolytes l.jpg

    Solid Electrolytes

    • LiTi2(PO4)3

    • Deposition conditions

      • Processing gas : Ar

      • Processing pressure : 10 mTorr

      • RF power : 100 W

    • Rapid thermal annealing

      • 15 sec in O2 ambient

      • Annealing T ↑, ionic conductivity ↑

    Solid electrolytes109 l.jpg

    Solid Electrolytes

    • LiPON

    Pressure ↑  Ion conductivity ↓

    Deposition rate ↓

    RF power ↑  Ion conductivity ↓

    Deposition rate ↑

    Solid electrolytes110 l.jpg

    Solid Electrolytes

    • Doped LiPON

    • Effect of Ti and W doping on the ionic conductivity of LiPON

      • doping concentration ↑

         ionic conductivity ↓

    Limn 2 o 4 lipon li tfb l.jpg

    LiMn2O4/LiPON/Li TFB

    • AC impedance spectrum and equivalent circuit

    • 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

    • Voltage : 4.05 V

    • Amplitude : 10 mV

    • Frequency : 1 MHz ~ 30 mHz

    Limn 2 o 4 lipon li tfb112 l.jpg

    LiMn2O4/LiPON/Li TFB

    • Variation of resistance and capacitance upon charge-discharge cycles

    Solid electrolyte l.jpg

    Solid Electrolyte

    • Li4SiO4-Li3PO4

      • Only Ar gas

         ionic conductivity :

        ~10-5 S/cm

    Solid electrolyte114 l.jpg

    Solid Electrolyte

    • Arrhenius plots



    Activation Energy : 0.202 eV

    Activation Energy : 0.548 eV

    Summary of inorganic solid electrolyte l.jpg

    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 l.jpg

    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 l.jpg

    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

    Ref.: P.G.Bruce, 2003, JACS

    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

    Lipon vs polymer electrolyte l.jpg

    LiPON vs Polymer Electrolyte

    • LiPON vs. Spin-coated SPE


    (Lithium Phosphorus Oxynitride)

    Spin Coated SPE





    Magnetron Sputtering

    Spin Coating

    Dep. Rate

    6~24hrs to obtain 1µm

    < 1 min.


    Very Poor





    Fab of thin film cathode l.jpg


    Wafer cleaning

    H2O2+H2SO4 1:1 30min 80oC

    1x1 inch Oxide Wafer

    Ar+O2 10sccm, 100W, 20min at R.T


    TiO2 sputtering



    Pt sputtering

    Ar 10sccm, 100W, 30min at 350oC


    LiMn2O4 sputtering


    Ar+O2 10sccm, 90W, 6hr at 300oC


    O2 ambient (400oC, 550oC, 750oC) 2hr



    Tube furnace


    Slow cooling

    In furnace

    until ~150oC


    Cycle test

    Li/LiClO4 1M in PC/Cathode

    Purified Electrolyte

    Fab of Thin Film Cathode

    Crystal structure of limn 2 o 4 thin film l.jpg

    750ºC, 2hrs annealing



    SiO2/Si substrate

    Crystal structure of LiMn2O4Thin Film

    Fe sem of limn 2 o 4 thin film l.jpg

    FE-SEM of LiMn2O4Thin Film

    Before heat treatment

    After heat treatment

    • Partially crystallized during sputtering due to the substrate temperature

    • Grain size: ~70nm

    • 750oC, 2시간, O2ambient in Furnace

    • Grain size: ~80nm

    P vdf hfp porous m embrane l.jpg


    Porous membrane

    P(VdF-HFP) PorousMembrane

    poly(vinylidene fluoride-co-hexafluoropropylene)


    Pour on flat glass and dry acetone for 1~5hrs in air

    P(VdF-HFP) +

    Acetone (Solvent) + Poly Ethylen Glycol (non-solvent)

    at 50oC, Stirring 5hrs

    Remove PEG with methanol


    Wetting with Sol Electrolyte



    LiMn2O4 on Wafer

    SOL: 1M LiClO4:(PEO)1 in PC

    Ion conductivity ~ 5 x 10-4 S/cm

    Polymer electrolyte l.jpg

    Polymer Electrolyte

    LiClO4 +



    Solid Polymer electrolyte

    Pour on teflon mold and

    dry for 3 days

    Spin Coating

    on Thin Film LiMn2O4

    Add PEO and

    Stirring 2 days

    Leave 5hrs on shelf without stirring to remove pores

    Li sol limn 2 o 4 pt l.jpg


    Sol electrolyte in

    Porous membrane


    LiMn2O4 /Pt/TiO2/SiO2/Si

    • 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

    OCV=4.0 V

    Current density= 100 µA cm-2

    Cell size = 0.1 cm2

    Discharge Curve

    AC Impedance

    Li polymer limn 2 o 4 pt sandwich cell l.jpg




    Solid Electrolyte




    OCV=4.0 V

    Li/polymer/ LiMn2O4/Pt (sandwich cell)


    고체전해질 두께=70 µm

    i= 100 µA/cm2


    Li polymer limn 2 o 4 pt spin coating l.jpg


    Spin coating of polymer electrolyte


    Li/polymer/ LiMn2O4/Pt (spin coating)

    Li/spin coated polymer (25 μm)/LiMn2O4/Pt

    Solid Polymer Electrolyte Cell:

    LiMn2O4: 280 nm

    Electrolyte: Solid PEO:LiClO4 18:1

    Anode: Evaporated Li film

    Maintain 85% of initial capacity at 100th cycle

    Coulombic efficiency=93%

    Spin coating for all solid state li battery l.jpg


    Spin coated electrolyte/

















    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

    Li/polymer(25 μm)/LiMn2O4/Pt





    18 Ω

    23 Ω


    3.2 kΩ

    6.2 kΩ


    9.4 nF

    7.7 nF


    6.9 kΩ

    22 kΩ


    9.4 µF

    5.0 µF


    1.6x10-5 S cm-1

    1.3x10-5 S cm-1

    Summary l.jpg


    • 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 l.jpg

    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 per year.

    • 3.6 volts

    • Capacity: upto 1 mA hour per cm2.

    New tfb for high efficiency l.jpg





    PEO based polymer



    Cu foil

    New TFB for High Efficiency

    • Cell structure


    2 Anode

    2 Cathode

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