1

Department of PhysicsDepartment of PhysicsNational University of SingaporeNational University of Singapore

Singapore Singapore

www.physics.nus.edu.sg/solidstateionics

Bulk- and Nano- Materials as Electrodes for Li Ion Batteries

B.V.R. Chowdari

2

Outline

Introduction: Importance, Principle & Status

Need for R&D on LIB Alternative electrode materialsNano-particles as electrodesSelect examples Conclusions

Lithium ion Batteries (LIB)

Lithium Ion Batteries - Portable Power Source.

Used in: Mobile phones, Cameras, Laptops, Electric Vehicles (EV and HEV), Load-leveling, Space program, MEMS (All-solid state Li-ion micro-batteries), Medical Implants (hearing aids, pace makers), Credit cards, ….

Demand: ~ 300 Million cells per year, ~ US$2 Billion, ~ Annual growth rate 40%.

Characteristics: High energy density, light weight, design- flexibility, long life span, 3.6 V working voltage (3 times that of Ni-MH cells).

Components of LIBCathode (positive electrode): LiCoO2 (oxide with a layer structure; layers of [O-Li-O-Co-]).Anode (negative electrode): Graphite (layer structure; layers of hexagonally packed C atoms).Electrolyte:Li-salt solution in a solvent (Ex.: LiPF6 – dissolved in organic solvents, EC+DEC) or Li-salt immobilized in a gel or solid inorganic Li-ion conductor (Ex.: amorphous Li-P-O-N).Misc. others: battery case, current collectors, etc.

Lithium ions shuttle between electrodes during operation -- hence the name, Li-ion Battery.

5

Principle of operation of LIBThe Cell(battery) uses layered compounds as electrodes

(intercalation/de-intercalation of Li ions)

Cell is assembled in the discharged-state and hence has to be ‘charged’before use.

Charging reaction :

Cathode: LiCoO2 →Li1-x CoO2 +xLi+ +xe-

Anode: xLi++xe-+C→Lix C Graphite; x=0.5

Electrolyte: LiPF6 in non-aq. Solvent. (Due to high voltage, water can not be used as solvent.)

Overall reaction:LiCoO2 + C→Li1-x CoO2 + Lix C (charge)

Li1-x CoO2 +Lix C→LiCoO2 + C (discharge)

Cell voltage: 3.6V; Cell capacity (product of current and time of discharge) depends on x and weight of cathode and anode.

6

Disadvantages of LiCoO2 cathode

High cost & toxicity due to cobalt. Only 50% of the theoretical capacity (274 mA.h/g) is utilized.Large irreversibility when charged to > 4.2V.Thermal stability is low in the charged-state(decomposes at T >

230°C).

Charged-electrode can oxidize (decompose) the electrolyte - battery capacitydegradation.

7

Research needed on LIBTo reduce the cost, in comparison to Ni- MH batteries. To improve safety-in-operation.To extend the temp.- range of operation:from (-5°C to +50°C) to (-30°C to +80°C).

Research on the Electrode and Electrolyte Materials is the Key.

Future Generation Cathodes for LIBAlternatives to LiCoOAlternatives to LiCoO2 2 ::

Mixed oxides with Ni, Mn replacing Copartly or fully: Li(Nix Mnx Co1-2x )O2 , x≤1/2Li(Ni1-xCox)O2 , x≤1/2Li(Ni1/3Mn1/3Co1/3)O2 (x=1/3)Li(Ni1/2Mn1/2)O2 (x=1/2)Lix(Ni1/3Mn2/3)O2

Improved LiMn2O4 (spinel network- structure, 4.0V).Capacity fading is not completely suppressed even bydoping or surface coating or morphological changes.

LiFePO4 --- layer- structure (3.6V, without cobalt or nickel)Irreversible capacity loss, two-phase reaction, lowelectronic conductivity.

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Strategies for Cathode improvementSuppress/eliminate the phase transitions during Li-cycling -will lead to an increased reversible capacity.

Metal ion substitution at Co/Ni/Mn sites in LiCoO2,Li(Ni0.33Co0.33Mn0.33)O2, LiMn2O4 (First & Second generation cathodes).

Surface-coating of cathode particles with TiO2/ZrO2/Al2O3-- will lead to suppression of electrolyte-decomposition.

Improve the electronic conductivity in LiFePO4 (2nd Generation cathode) by carbon-coating -- will lead to better current-pick-up (rate capability)

Search for new Li-Metal-P-Si-O compounds with layer structure -will lead to new/novel Cathodes.

Disadvantages of Graphite AnodeCapacity is 372 mA.h/g (theor.);Practical: 310-330 mA.h/g. Low density (~2 g/cc); hence, low Volumetric Capacity.Charged anode (LixC) is a highly reducing agent; can reduce the liq. electrolyte to other compounds.

Charged anode has a low potential (V=0.1V vs. Li). Hence, at high-rate charge, Li-metal can deposit on the surface of graphite. This can lead to dendrite formation of Li making it unsafe.

Future Generation Anodes for LIBAlternatives to Graphite have come-upModified Graphite: Sn-coated C; C-nano-tubes,..Li4Ti5O12 (spinel structure; V=1.5V vs. Li).

Tin (Sn)- pure and mixed oxides(ATCO; SnO; SnO2 , SnP2 O7 , CaSnO3 ) --- ICoO, NiO, and other mixed 3d-, 4d-metalOxides ---- II

Mechanism of operation differs in I and III: SnO →Sn-metal↔ Li4.4Sn(alloy) (V=0.5V vs Li)II: nano-CoO +2Li ↔ Li2O+Co(nano)(V~2V vs.

Li (Conversion).

Nano-materials as Electrodes

••

Large surface areaLarge surface area (cm(cm22/g) /g) ---- higher higher electrode/electrolyte contact area electrode/electrolyte contact area ---- higher higher charge/discharge current rates charge/discharge current rates ---- improved capacity improved capacity utilization of both cathode and anode. utilization of both cathode and anode.

••

Short path lengthsShort path lengths for electronic and ionic transport for electronic and ionic transport ---- higher charge/discharge current rates. higher charge/discharge current rates.

••

Better accommodationBetter accommodation of lattice strain of Li of lattice strain of Li insertion/removal insertion/removal ---- improved cycleimproved cycle--life.life.

••

New types of reactionsNew types of reactions which are not possible with which are not possible with bulk take place:bulk take place:

nano-FeFe22OO33 + 0.5Li ↔ Li0.5FeFe22OO33 (bulk Fe(bulk Fe22OO3 3 gives Fegives Fe--metal and Limetal and Li22O).O).nano-CoO+ 2Li ↔ Li2O+Co (Conversion)

(reverse reaction does not occur with bulk Co).

AdvantagesAdvantages

Nano-materials as Electrodes

••

An increase in the undesirable electrode/electrolyte An increase in the undesirable electrode/electrolyte side reactionsside reactions, especially in the charged, especially in the charged--state state ---- solvent drysolvent dry--up; selfup; self--discharge; poor cycledischarge; poor cycle-- and and calendarcalendar--life.life.

••

Inferior packing of particles Inferior packing of particles ---- smaller volumetric smaller volumetric density; lower capacitydensity; lower capacity--utilization.utilization.

••

Complex synthesis procedures, especially for Complex synthesis procedures, especially for mixedmixed--oxides.oxides.

••

Difficult to make large quantities with uniform Difficult to make large quantities with uniform NanoNano-- size.size.Thus, it is worth investigating electrode materials in Thus, it is worth investigating electrode materials in nanonano--form for LIB.form for LIB.

DisadvantagesDisadvantages

Nano-size Tin and 3d-metal Oxide Anodes for LIB

Beneficial Effects are more clearly seen with nano-particles.

I: SnO or SnO2→Sn-metal↔ Li4.4Sn(alloy) (V=0.5V vs. Li)II: CoO +2Li ↔ Li2O+Co (V~2V vs. Li)

Co3O4, NiO, FeO, CuO are also studied; best results are with CoO for Li-cyclability.Capacity of 600-700 mA.h/g stable till 100

cycles.

LIB (Cells) with CoO anode was fabricated & tested (Cathode: LiCoO2; LiMn2O4).

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Strategies for Anode improvementTin (Sn) containing compounds and Metal-O compounds are the 2nd Generation Anodes.

Tin (Sn) containing compounds -- work by Li-alloying-de-alloying Reactions (Sn+ 4.4 Li ↔Li4.4Sn) … (1)

Metal-O compounds work by ‘Conversion’ Reaction. (CoO+ 2 Li ↔Co+Li2O) … (2)

Suppress /reduce the unit cell volume changes in (1)

by using nano-size particles -- will lead to stable and increased capacity during long-term cycling (applicable for (1) and (2)).

by using a matrix element (M) which will help in absorbing the unit cell volume changes in (1). M can be a electrochemically active/inactive element.

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Strategies for Anode improvement

Surface-coating of anode particles with TiO2/ZrO2-- will reduce the effect of unit cell volume changesin (1).

Improve the electronic conductivity in (2) by carbon-coating -- will lead to better current-pick-up (Rate capability).

Search for new Metal-N-P-Si-O compounds, containing two or more metals which can work by Eqns. (1) and (2)

-- will lead to new/novel high-capacity Anodes.(e.g., Our work on (V,Sb,Sn)O4 and ZnCo2O4)

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Our studies on LIB Electrode Materials Our studies on LIB Electrode Materials

LiCoO2, LiNiO2 [ Chem. Mater. 2006, J. Power Sources 2005]

Li (Ni1-x Mnx)O2 (Electrochim. Acta 2002; 2005)

Li (Co1-x Mx )O2, M = Ni, Mn, Al, Mg, Rh etc. {J Phys. Chem. 2007; J . Electrochem. Soc. 2004; Electrochim. Acta 2003}

O2-type Li((2/3)+x)(Ni1/3Mn2/3)O2 [ J. Electrochem. Soc .2003]

Surface-coating of Li(Ni0.8Co0.2)O2 by CoO; NiO ; AlPO4 [J. Power Sources 2004; 2005]

Li[M1/6Mn11/6]O4, M=Co, Ni, Al. [J. Mater. Chem. 2003, Solid State Ionics 2003]

LiMn2O4- Ru-doping [to be published]

OXIDE CATHODES: Aim: Improve the capacity & Li-cyclability

Studies by our Group

Oxide AnodesOxide AnodesMethodology: •

Synthesis of new and known Sn- and transition metal- compounds;•

In-situ carbon coating and novel synthesis of Mo and W- compounds;• Physical characterization, electrochemical studies.

• Tin- based Oxides: Perovskites: Nano- and bulk-CaSnO3 ; SrSnO3 ; BaSnO3Sn-Pyrochlores: Y2 Sn2 O7 , Nd2 Sn2 O7 ; HollanditeHollandite--type structure: Ktype structure: K2 ((MSnMSn))2 OO16 , M= Fe, Li, Mg ; In, Co., M= Fe, Li, Mg ; In, Co.

• Tin- & Fe-based Oxides: CaFe2 O4 ; {(Li,Ca)(Fe,Sn)2 }O4

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Studies by our Group

Oxide Anodes (Contd.)Oxide Anodes (Contd.)

•

3d- Trans. Metal based Oxides: NanoNano flakeflake--FeFe22 OO3 3 , , nanowallsnanowalls--NiONiO; ; Ca2 Fe2 O5 ; Ca2 Co2 O5 (Brownmillerite & related structure); •

Oxide SpinelsSpinels: MCo: MCo2 OO4 , M= Co, Zn, Ni, , M= Co, Zn, Ni, MnMn, Cu, Fe, Mg ; , Cu, Fe, Mg ;

TiOF2 and NbO2 F.•

4d/5d- Trans. Metal Oxides: Carbon-coated nano-

phase CaMoO4 and CaWO4 . •

Metal Cluster Compounds: LiMMoMetal Cluster Compounds: LiMMo33 OO88 , M= Ho, Y; , M= Ho, Y;

MnMn2 MoMo33 OO88 ..

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Materials Preparation

Preparation of Nano/submicron sized materials:

Molten salt method, Urea combustion method, Sol-gel, Co-precipitation, Freeze drying, Ion-exchange method ( Na by Li exchange), Solid state method, Carbothermal reduction (Metal oxides+carbon), Solvothermal method and Ball-milling technique.

Thin films : Physical vapor deposition technique(Rf-magnetron sputtering)

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Materials Characterization Techniques

Physical characterization:Structure: X-Ray Diffraction (XRD), Rietveld refinement,Valence states : X-Ray Photo Electron Spect.,Electronic structure : X-ray Abs. Fine Structure (XAFS)Morphology: Scanning Electron Microscopy (SEM)/EDAX, Transmission Electron Microscopy (TEM).Physical properties : IR, Raman and Magnetic studies.Chemical Analysis : ICP, TGA/DTA, DSC

BET(Bruneauer Emeinmet & Teller) Surface Area, DensityThin films: Rutherford Back Scattering (RBS), Auger Electron Spectr. (AES), Atomic Force Microscopy (AFM).

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Materials Characterization Techniques

Electrochemical studies:Cyclic voltammetry (CV) : Redox couple / Structural phase transitionsGalvanostatic cycling : Performance of batteriesElectrochemical Impedance Spectroscopy (EIS) : -Electrode kinetics; Li-diffusion coefficientsResistance (Re , Rsf , Rct , Rb ) and Capacitance (Csf , Cdl and Cb ) and Cint

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• (Cathode)

// (Electrolyte)

// (Anode){Active material : Carbon : PVDF} // Separator, LiPF6

(EC: DMC) // Li-

metal (70:15:15) wt.%

• Cathode prepared by doctor-blade method; typical mass ~3 mg of active material.

Coin type Cell (2016) [20 mm dia; 1.6 mm thick]

Current collector: Cu-foil for anodes and Al-foil for cathodesCells were fabricated in Ar-filled Glove box.

Test cell Fabrication

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Examples of our work on AnodesExamples of our work on Anodes(I) (V1/2 Sb1/2 Sn)O4 -

Possibility for Li-Sn

and Li-Sb

alloy

formation. Alloying and de-alloying reaction. M.V. Reddy, G.V. Subba

Rao, B.V.R. Chowdari [To be

published]

(II)

CoN –

Conversion reaction similar to CrN

and hence high capacity is a possibility.B.K. Das, M.V. Reddy, Subba

Rao, B.V.R. Chowdari

[submitted]

(III)

(Cd1/3 Co1/3 Zn1/3 )CO3 –

Possible to see whether both conversion of carbonate and alloying reaction takes place. Y. Sharma, N. Sharma, G.V. Subba

Rao, B.V.R. Chowdari

[submitted ]

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(V1/2 Sb1/2 Sn)O4

Earlier, we studied the Li-cyclability of cation-deficient oxide, VSbO4,

Presently we prepared tin-containing compound, (V1/2Sb1/2Sn)O4. Here, alloying-de-alloying reactions of Li3Sb and Li4.4Sn occur at low potentials (<1.0V vs. Li).

It has a theoretical reversible capacity of 598 mAh/g.

Preparation :Bulk (V1/2Sb1/2Sn)O4 was prepared by solid state reaction at 800ºC, 8 h in air from NH4 VO3 , Sb2 O3 and SnO2 .

For particle size reduction, 2.5g bulk sample (10g of SS-balls) was ball-milled for 18 h using Spex Ball miller (D8000)

Powder was characterized by various techniques.

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XRD patterns of bulk and ball-milled (V1/2 Sb1/2 Sn)O4

Tetragonal crystal structure (space group, P42/mnm). The lattice parameters :

(a) Bulk : a= 4.707(5)Å; c= 3.165(6) Å; (b) Ball-milled: a= 4.690 (1)Å; c= 3.150(8) ÅFWHM in (b) shows that the particle has reduced to nano-size.

Miller indices are shown.

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TEM and other studies

TEM shows ball-milled (V1/2Sb1/2Sn)O4 (I) has nano-sized particles, ~30 nm.

The expt. density of ball-milled (I) is 6.461g/cm3 and compares well with calculated X-ray density 6.474 g/cm3.

BET surface areas of bulk and ball milled (V1/2Sb1/2Sn)O4 are 2.5 and 10.2 (±0.2) m2/g.

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Cyclic voltammetry

Plot of Current vs. Voltage as a continuous scan. Gives Voltage (potential) at which the reactions occur.Smoothly varying curve :- single-phase reaction.Sharp peak :- two-phase reaction.

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Cyclic Voltammetry (CV): (V1/2 Sb1/2 Sn)O4

0.0 0.5 1.0 1.5 2.0 2.5

-0.0025

-0.0020

-0.0015

-0.0010

-0.0005

0.0000

0.0005

0.0010

0.0015

Cur

rent

(A)

Cell potential ( V vs. Li)

6

1

2

(b)ball-milled

The cathodic peak at ~ 0.2 V is attributed to the alloy (Li4.4Sn or Li3Sb) formation. In the 1st cycle oxide reduces to metal. V will form VO.

Further cycling is limited to alloying region 1.0 V. Going beyond that will cause oxidation; Sn to SnO and Sb to SbO.

The anodic peak at (~ 0.5V) is attributed to de-alloying reaction.

(a) bulk and (b) ball milled. V= 0.005-3.0V vs. Li; Scan rate : 0.058mV/s. Number indicates cycle number.

0.0 0.5 1.0 1.5 2.0

-0.004

-0.003

-0.002

-0.001

0.000

0.001

0.002

0.003

Cur

rent

(A)

Cell potential (V vs. Li)

(a) bare-(V1/2Sb1/2Sn)O4

1

15

5

30

Galvanostatic cycling

Capacity vs. voltage cycling plots of (V1/2Sb1/2Sn)O4 ; current density : 250mA/g ( ~0.5C). Number indicates the cycle

number. At room temperature. (First charge capacity 500 mA/g is taken as 1C.)

0 200 400 600 800 100012001400160018000.0

0.5

1.0

1.5

2.0

2.5

3.0(a) bare and ball milled (V1/2Sb1/2Sn)O4

Cel

l vol

tage

( V

vs.

Li)

Capacity (mAhg-1)

Ball milled (red)

Bare

0.005-1.0V; 0.5C rate

1001

1,100

100

100 50

50

Bare

1

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(V1/2 Sb1/2 Sn)O4 : Capacity vs. Cycle number

Capacity vs. cycle number profiles of bulk and ball-milled V1/2Sb1/2SnO4 at the current density 250mA/g (~0.5C).

Ball-milled compound performs better. At 0.5C, 450 mA.h/g up to 100 cycles. At 1.2C, 435 mA.h/g up to 50 cycles.

0.005-1.0:1.2C rate

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Conclusions

New rutile-type V1/2Sb1/2SnO4 is studied.Characterized by XRD, TEM, density and BET surface area methods. Galvanostatic cycling results indicate ball-milled V1/2Sb1/2 SnO4 shows excellent capacity retention during cycling, up to 100 cycles.At 0.5C, 450 mA.h/g after 100 cycles. At 1.2C, 435 mA.h/g after 50 cycles.Here, alloying-de-alloying reactions of Li3Sb and Li4.4Sn occur at low potentials (<1.0V vs. Li). Thus, V1/2Sb1/2SnO4 is a viable candidate for LIB.

33

Studies on thin-film Cobalt nitride(CoN)

34

Preparation of CoN thin films

The deposition conditions:

RF magnetron sputtering unit : Denton Vacuum Discovery 18, USA.RF power : 150 WReactive gas : N2N2 partial pressure: 10 mTorrDeposition Time : 120 minTarget : Co-metal (99.9% purity)Substrates : Cu-foil (16mm dia. 20μm thick) for electrochemical and SEM studies and Si(100) for chemical composition study using Rutherford Backscattering spectrometry (RBS).

35

10 20 30 40 50 60 70 80

(311

)

(220

)

(200

)

Int.

(arb

. uni

ts)

2 θ (degree)

Si

(a) XRD pattern of CoN

(111

)

200 300 400 500 600 700 800Channel

0

10

20

30

40

Nor

mal

ized

Yie

ld

0.5 1.0 1.5Energy (MeV)

N

Si

CoO

(b) RBS spectra of CoN film

XRD and RBS studies on CoN Thin films

XRD studies shows single phase of CoN.Lattice parameter a = 4.291 ± 0.005 Ǻ matches with the reported a = 4.297 Ǻ.Rutherford back scattering (RBS) analysis gave information about composition and thickness of the films. Film composition is CoN (1:1, stoichiometric) and thickness ~ 200nm.

Symbols : experimental spectraContinuous line : Fitted spectra

36

(a) (b)

(c)2.51 Ǻ

(111)

2.12 Ǻ

CoN (111)

CoN (200)

CoN (220)(d)

CoN morphology : SEM and HRTEM studies

SEM (a&b) shows CoN nano-whisker morphology (90nm length, 20nm width). HRTEM (c) and SAED (d) show characteristic lattice planes of CoN.

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Galvanostatic cycling of CoN

0 200 400 600 800 1000 12000.0

0.5

1.0

1.5

2.0

2.5

3.0

806040202

1

21

20 6040 80(a) CoN; 250 mAg-1

0.005 - 3.0 V

Vol

tage

(V v

s. L

i)

Capacity (mAhg-1)

Measured first-charge capacity: 760 mA.h/g at 0.33C rate (2.06 moles of Li); 700 mA.h/g at 0.59C rate (1.90 moles of Li); 640 mA.h/g at 6.6C rate (1.74 moles of L

Theor. Rev. capacity: 1102 mA.h/g (3 moles of Li per mole of CoN).

Capacity at 80th cycle: 990 (±20) mA.h/g at 0.33C rate; 950 (±20) mA.h/g (0.59C ratand 690 mA.h/g (at 6.6C rate).

(a) Voltage-capacity profiles at a current of 250 mA/g.(b) Capacity vs. cycle number plots at 0.33C, 0.59C and 6.6C rate (1C=760 mA/g).

20 40 60 800

200

400

600

800

1000

1200

1400 (b) CoN; 0.005- 3.0 V

0.33C

0.59C

6.6C

Cap

acity

(mA

hg-1)

Cycle number

Closed symbol: Disch.Open symbol: Charge

38

0.0 0.5 1.0 1.5 2.0 2.5 3.0-0.5-0.4-0.3-0.2-0.10.00.10.20.3

1st

Cur

rent

(mA)

Voltage (V vs. Li)

(a) CoN; 58μV/sec

1st

1.680.84

0.58

0.20

0.70

1.37 2.32

0.0 0.5 1.0 1.5 2.0 2.5 3.0-0.3

-0.2

-0.1

0.0

0.1

0.2 (b) CoN; 58μV/sec2, 6, 10, 15, 200.7

1.05 1.45

0.18

0.75

2.0

(a) 1st cycle and (b) 2 to 20 cycles. Scan rate : 58µV/sec. Numbers in Figs. refer to voltage values. Integer numbers refer to cycle number.

From these curves, discharge-charge mechanism can be proposed.

Cyclic Voltammetry studies of CoN

39

CoN + 0.5 Li+ + 0.5 e- → Li0.5CoN (intercalation) --- (1)

Li0.5CoN + 2.5 Li+ + 2.5 e- → Co + Li3N (conversion reaction) ---(1a) discharge cycle

Co + Li3N ↔ CoN + 3 Li+ + 3 e- ---(2) (charge-disch. cycle)

The reversible reaction (Eqn.2) gives the theoretical capacity.

Reaction mechanism

40

ConclusionsCoN thin films are prepared by reactive sputtering

technique and Characterized by RBS, XRD and HRTEM.

Galvanostatic cycling results showed a Capacity at 80th cycle: 990 (±20) mA.h/g at 0.33C rate; 950 (±20) mA.h/g at 0.59C rate, and 690 mA.h/g at 6.6C rate.

Reversible capacity arises by the conversion reaction

Co + Li3N ↔ CoN + 3 Li+ + 3 e- (charge-disch. cycle)(Theor. rev. capacity: 1102 mA.h/g (3 moles of Li per mole of CoN).

41

Studies on mixed carbonate, Cd1/3 Co1/3 Zn1/3 CO3

42

Preparation of (Cd1/3 Co1/3 Zn1/3 )CO3

1/3 (CdCl2 , CoCl2 and ZnCl2 )

Distilled water (100 mL each)

Kept on hot plate, stirring for about 2 h at 50oCNa2 CO3 .H2 O solution

Precipitate of mixed carbonates

Filter, wash and dry at 100oC for 12 h

Solution Precipitation method:

• Characterized by XRD, SEM, EDX, TEM.

• Electrochemical studies: Galvanostatic and CV.

43

•

XRD pattern of Cd1/3 Co1/3 Zn1/3 CO3 and SEM photographs

10 20 30 40 50 60 70

CCZC(a)

Cou

nts

(arb

. uni

t)

214

300

012

006

110

113

202

024

116

122

104

*

2θ, degree (Cu-Kαradn.)

* -

Impurity

• Pink color powder

The rhombohedral-hexagonal lattice parameters:

a = 4.886(5) Å ; c = 16.088(5) Å

CdCO3 : a = 4.9298 Å; c = 16.306 Å JCPDS no. # 72-1939

Average ri of cations in CCZC = 0.845 Å, less than that of Cdri of Cd2+ is 0.95 Å.

44

Morphology : SEM/EDX and TEMSEM

Flower-like agglomerated particles

0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00

keV

0

100

200

300

400

500

600

700

800

900

1000

Cou

nts

C

O

Co

Co

Co

Co

Zn

Zn

ZnZn

Cd

Cd

Cd

Atomic percentage of cations in CCZC

Cd --- 15 %; Co --- 14 %; Zn --- 13 %

Nano- needles

45

0 300 600 900 1200 1500 1800

0123

0 200 400 600 800 1000

0123 (b)

(a) CCZCRange: 0.005-3.0 VCurrent: 60mAg-1

First discharge

First charge

25,15,10

5

5

25,15,10

2

2

Volta

ge, V

Capacity, mAhg-1

Galvanostatic cycling

1st Disch. Cap. : 1790 mA.hg-1 (~ 9.3 Li)

1st Ch. Cap.: 920 mA.hg-1 (~4.8 Li)

2nd Disch. Cap. : 995 mA.hg-1 (~5.2 Li)

2nd ch. Cap. : 810 mA.hg-1 (~4.2 Li)

10th rev. cap. : ~ 680(±10) mA.hg-1 (~3.5 Li)

46

25 50 75 100 125 150 1750

300600900

1200 10 20 30 40 50 60300

600

900

1200

0.3 C0.6 C

1 C

0.6 C

1 C = 680 mAg-1

Discharge Charge

(d) 0.3 C

0.09 C

Cycle number

CCZC

CCZC Range: 0.005-3.0VCurrent: 0.09 C

(c)

Cap

acity

, mAh

g-1

Capacity vs. cycle number plots

Rate capability

At 0.3 C - 520 mA.hg-1 (2.7 Li)

At

0.6 C - 365 mA.hg-1 (1.9 Li)

At

1 C - 220 mA.hg-1 (1.14 Li)

In the range of 8-60 cycles

Capacity: 680 (±10) mA.hg-1 (3.5 Li)

Coulombic efficiency (difference

of disch. and chrg. cap. : 98%

(a)

(b)

47

0.0 0.5 1.0 1.5 2.0 2.5 3.0

-5

-4

-3

-2

-1

0

1 CCZC

Cur

rent

, mA

E vs. Li, V

CV of Cd1/3 Co1/3 Zn1/3 CO3

Structure destruction

Li-Cd, Li-Zn

de-alloy Zn, Cd MCO3 (M = Cd, Zn, Co)

Scan rate: 58 µVs-1

-4

-2

0

2

0.0 0.5 1.0 1.5 2.0 2.5 3.0-1.5

-1.0

-0.5

0.0

0.5

(a )

2-6

236

1

1

S can ra te : 58 μVs-1

R ange: 0 .005-3.0V

C C ZC

Cur

rent

, mA

(b )

61-66

Potentia l (vs. L i), V

48

0 300 600 900 1200 1500 18000.00.51.01.52.02.53.0

Volta

ge, V

Capacity, mAhg-1

Ex-situ Studies

Voltage vs. Capacity Ex-situ XRD

20 30 40 50 60 70 80

Cou

nts

(arb

. uni

t)

11001

2 104

# -Cu

# #

3V: 1st charge 0.005 V0.5 V

Bare

2θ, degrees (Cu Kα-radn.)

First disch.

First Chrg.

substrate

Flat plateau: ~ 1.0 V

Slopping region: 0.5V-0.005 V

At 0.5 V, 0.005 V : X-ray amorphous

Charging to 3.0 V: X-ray amorphous

49

Ex-situ TEM studies charged to (3.0 V after 30 cycles)

Lattice image SAED Pattern

CoCO3 (104)

CdCO3 (110)

ZnCO3 (012)

X-ray amorphous phase contains mixture of nano-size carbonates.

50

• (Cd1/3 Co1/3 Zn1/3 )CO3 +2Li++2e-→1/3(Cd+Co+Zn)+ Li2 CO3…(1)

• 1/3 Cd + Li+ + e- ↔ 1/3 (Li3 Cd) ... (2)

• 1/3 Zn + 1/3 Li+ + 1/3 e- ↔ 1/3 (LiZn) ... (3)

• 1/3 M’ + Li2 CO3 ↔ 1/3 (M’CO3 ) + 2 Li+ + 2 e- ... (4) (M’=Cd, Co, Zn)

Reaction Mechanism

Theoretical: (3.33 moles of cyclable Li) ( 645 mAhg-1)

Experimental: (3.5 moles of Li) (~ 680 mAhg-1)

51

1. For the first time, we have shown, Carbonate ion (CO32-)

acts as good as O2-, S2-, F- ion in enabling reversible ‘conversion reactions’ for Li-cyclability.

2. Both ‘alloying-de-alloying’ and ‘conversion reaction’ contribute to give large and reversible capacity, in the carbonates. (Earlier, we showed this to be applicable to oxides, like, ZnCo2 O4 )

3. Achieved theoretical capacity in the range of 8-60 cycles at 0.09 C-rate with coulombic efficiency ~98%. (~ theoretical, 3.33 moles ; exp., 3.5 Li).

4. Good rate capability: At 0.6 C, the observed capacity of 360 (±10) mA.hg-1..

5. Easy synthesis of nano-CCZC at ambient temperature and pressure. (CoCO3 and ZnCO3 can not be made at ambient temperature and pressure.)

Conclusions

52

Conclusion•

In this presentation, I have tried to give a brief account of the progresses made over the past 20 years on the electrode materials of the lithium ion batteries.

•

It is important to see that unlike lead-acid, nickel- cadmium, nickel-metal hydride and the high- temperature sodium-sulfur and sodium-nickel chloride systems which operate essentially off fixed cell chemistries, the cell voltage of lithium batteries may be tailored by varying the electrochemical potential of anode and cathode host structures to the uptake and release of lithium during charge and discharge.

Thank YouThank You******************

Research Group: Dr. G.V. Subba Rao, Dr. M.V. Reddy, Dr. N. Sharma, Mr. Y. Sharma, Mr. B. Das, Mr. Christy Cherian

Acknowledgement

Part of the work is sponsored by Defence

Advanced Research Projects Agency (DARPA), USA, Grant no. R-144-000-226-597.

54

These can give capacities in the range 300-4200 mA.h/g.Higher capacity means -- less amount of anode material in LIBs.

Metal Range, x in Alloy Theoret. Cap., mA.h/g Voltage, V vs Li

Li-C 0.0-0.17 372 0.07-0.2Li-Si 0.0-4.4 4,200 0.2Li-Sn 0.0-4.4 980 0.5

Li-Al 0.0-1.0 993 0.4Li-In 0.0-3.0 700 0.5Li-Zn 0.0-1.0 410 0.5Li-Cd 1.0-3.0 715 0.7Li-Pb 0.0-4.4 570 0.6

Li-Sb 0.0-3.0 660 1.0Li-Bi 0.0-3.0 389 0.8

LiLi--Alloy forming elementsAlloy forming elements

55

Anodes : Reaction mechanism

I: 3Li+ Li4Ti5O12 ↔ Li7Ti5O12 (Intercalation)I: SnO → Sn-metal ↔ Li4.4Sn(alloy) (V~0.5V vs. Li)

II: nano-CoO +Li ↔ Li2O+Co (‘conversion’)(V~2V vs. Li)

56

Crystal Structures of LIB cathodes

LiCoOLiCoO22 LiMnLiMn22 OO44 LiFePOLiFePO44

Ref.: Ohzuku and Brodd, J. Power Sources, 2007.

57

Ex-situ XRD patterns of cycled (V1/2Sb1/2Sn)O4 electrodes

Ex-situ XRD patterns of bare electrodes, discharged to 0.5V and 0.005V and charged to 3.0V, during the first cycle. Lines due to Cu (substrate) and Al (sample holder) are indicated.

Ex-situ XRD patterns shows amorphisation of the lattice.

58

Cyclic Voltammetry of Li(Ni1/2 Mn1/2 )O2

3.0 3.2 3.4 3.6 3.8 4.0 4.2 4.4 4.6

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.03

2 1

:RT

:50oC

ΔQ, m

A.h

Cell voltage, V

Indication of Ni2+/3+ couple in the 3.8-3.9 V region; pronounced at 50°C

Charge-discharge reaction:Li(Ni1/2 Mn1/2 )O2 ↔ Li1-x (Ni1/2 Mn1/2 )O2 +xLi+ xe (e=electron)

Smaller voltage- hysteresis of main peak at 50°C: Better reversibility of the reactionSmoothly varying curve --single-phase reaction

Scan rate: 0.058 mV/s

Ref:Shaju, Subba Rao, Chowdari, Electrochim. Acta, 2003.

59

Cyclic Voltammetry of LiCoO2

Indication of Co3+/4+ couple in the 3.8-4.0 V region; Single-phase

reaction Charge-discharge reaction:LiCoO2 ↔ Li 1-x CoO2 +xLi+ xe(e=electron)

Minor peaks at 4.1, 4.2 and 4.5 V indicate phase transitions in the compound, Li1-x CoO2. (Two--phase reaction)

These phase transitions lead to capacity-fading on cycling.

In practice, LIBs are restricted to 4.1 V, to avoid them.

Ref:Tay, Reddy, Subba Rao, Chowdari, Vittal, Chem. Mater., 2006.

60

Cyclic Cyclic VoltammetryVoltammetry of LiCoOof LiCoO22

Synthesis by molten salt Synthesis by molten salt (LiNO3+LiCl) at(LiNO3+LiCl) at

(a)(a) 650650°°CC--KOH; (b) 750KOH; (b) 750°°C;C;

(c) 850(c) 850°°C; 2.5C; 2.5--4.4V;4.4V;

(d) 850(d) 850°°C; 2.5C; 2.5--4.7 V. 4.7 V.

Main peak at 4V: SingleMain peak at 4V: Single--phase Liphase Li--interc.interc.--dede--intercinterc..Minor peaks at 4.1, 4.2 and 4.5 V

indicate phase transitions in Li1-xCoO2.

For 850850ooCC synthesis:The H1↔Monocl. ↔H1 structure transitions aresuppressed, due to excess Li.But not the H1↔(H1-3) beyond 4.4 V. Scan rate is 0.058 mVsScan rate is 0.058 mVs--1, 1, vsvs Li. Li.

Numbers are the cycle numbers.Numbers are the cycle numbers.Ref:Tan, Reddy, Subba Rao, Chowdari, J.Power Sources, 2005.

61

Cyclic Voltammetry (CV): nano-CaO·SnO2

The peaks in the first-discharge show two-phase reactions; Structure destruction, followed by alloy formation.The cathodic peak at ~0.2 V is attributed to the alloy (Li4.4Sn)

formation. The anodic peak at (~0.5V) is attributed to de-alloying reaction.

(Ref: Y.Sharma, N. Sharma, Subba Rao, Chowdari, Chem. Mater.,2008)

CV of nano-composite CaO ·SnO2.Voltage window:(a) 0.005-1.0 V and (b) 0.005-1.3 V vs Li at the scan rate of 58 V/s.

Numbers indicate the cycle number.

62

Charge-discharge cycling of Li(Ni1/2 Mn1/2 )O2 : 4 V cathode

(Shaju, Subba Rao and Chowdari, Electrochim. Acta 48(2002) 1505-1514.)

0 40 80 120 1602.53.03.54.0

Capacity, mAh/g

(b) 2,5,10,201

5,10,2021

RT; 30 mA/g; 2.5-4.2 V (CC mode)

0 10 20 30 40100

120

140

160

180

Cel

l vol

tage

, V

(c) 30 mA/g : (4.4 V); RT : (4.2 V); RT

: (4.2V); 50OC

: (4.3V); 50OC

Dis

char

ge c

apac

ity, m

Ah/

g

Cycle number

0 40 80 120 1602.53.03.54.04.5 (a)

RT; 30 mA/g; 2.5-4.4 (CC mode)11

2,10520

301

Smooth voltage profile:single phase Li-extractionICL of ~20-25 mAh/g in first cycle (Irreversible Capacity Loss)Rev. capacity: ~150 mAh/g

(4.4 V-cut-off)~130 mAh/g (4.2 Vcut-off)From the attainable cap., Ni2+ Ni4+ redox couple confirmed (4 V-region)Good cycling stability (2.5-4.2 V) at Room Temp., and 50°C.

Cycling performance at RT and 50°C

63

Galvanostatic cycling of anode, CaSnO31st Discharge process (structure

destruction and alloy formation)

CaSnO3 + 4Li+ + 4e-→ CaO + 2Li2 O + Sn

Reversible alloying of Sn with Li on cycling: Sn + xLi+ + x e-

↔ LixSn (0<x<4.4)

Smooth and identical profiles

From 4th-50th cycle: Stable capacity values of ~440 mA.h/g (range, 0.005-1.0 V; 60 mA/g).

0 200 400 600 800 1000 1200

0.00.51.01.52.0

10 mA/g : 0.005-2.0 V : 0.005-1.0 V

(a)

Cel

l Vol

tage

, V

0 100 200 300 400 500

0.0

0.4

0.8

1.20.005-1.0 V; 60 mA/g

4,5,10,20,30,40,50

4,5,10,20,30,40,50(b)

Capacity, mAh/g

0 2 4 6 8 10

Number of Li per CaSnO3

64

Cycling performance of Sol-gel CaSnO3

Increasing the voltage window (0.005-2.0V) leads to:Higher initial capacity

values (~660-690 mA.h/g).Drastic capacity fading upon cycling: 380 mA.h/gon 50th cycle.Possible cause: destruction of Li2O matrix and/ or Sn-particle agglomeration.

0.005-1.0 V: lower capacity; But, no capacity-fading (cap.values uncorrected for carbon)

0 10 20 30 40 50300

400

500

600

700

60mA/g10mA/g

(0.005-2V)

(0.005-1V)

Cap

acity

, mAh

/g

Cycle Number

65

Galvanostatic cycling of nano- composite, CaO.SnO2 Anode

Capacity vs. Cycle number

300400500600700

10 20 30 40 50 60 70 80300

450

600

10 20 30 40400

500

600

(a)

Filled symb.: DischargeOpen symb.: Charge

0.005-1.0 V

0.005-1.3 VCurrent: 60 mAg-1 Nano-'CaO.SnO2'

0.005-1.0 V

0.005-1.3 V

Nano-CaSnO3(b)

Cap

acity

, mA

hg-1

(c)Nano-'CaO.SnO2' ; 0.005-1.0 V

0.4 C0.2 C

0.12 C0.06 C

Cycle number

CaO.SnO2: 550(±10) mA.h/g(4.2 Li) stable up to 50 cycles.(0.005-1.3V)Range:0.005-1.0 V: 490 mA.h/g(3.8 Li) stable up to 50 cycles.

Good rate capability[60 mA/g=0.12C-rate]

66

Hollandites, K2 (Mx Sn8-x )O16 , M= Li, Fe, Mg, Mn*

Capacity vs. cycle number

Cycling stability is of the order : K-Co >K-Fe> K-Li>K-In>K-Mg>K-Mn

*Our previous study : Chem. Mater., 17(2005)4700.

Current rate : 60mA/g ; Voltage range : 0.005-1.0V

67

(c) Rsf Rb Rct

CPE1(Csf )

CPE2(Cb )

CPE3(Cdl )

O

i ii iii ivRe

0 50 100 150 2000

-20

-40

-60

-80

-100

3 mHz

0.35

MH

z

44.1 Hz

350 Hz 0.11 Hz

3 m

Hz

1.11 Hz

11.1 Hz

(a)

Z', ohms

: 2.86 V (fresh cell) : 3.79 V; : 3.84 V; : 3.89 V : 4.26 V (Charged to 4.4 V)

Z'' , ohm

s

0 20 40 60 80 100 120 1400

-10-20-30-40-50

55.5 Hz

0.22 Hz

22 mHz 3 m

Hz

iv

iiiiii

(b)

Li(NiLi(Ni1/21/2 MnMn1/21/2 )O)O22 : 4 V cathode: 4 V cathodeImpedance Spectra (Real vs. Impedance Spectra (Real vs. ImaginImagin. resistance under . resistance under an acan ac--bias)bias)a)a) Cell charged to various Cell charged to various

voltages (voltages (vsvs LiLi--metal);OCV metal);OCV after 3 h stand.after 3 h stand.

b)b) Expanded version at 3.84V.Expanded version at 3.84V.c)c) Equivalent circuit to evaluate Equivalent circuit to evaluate

the Impedance parameters.the Impedance parameters.

Equivalent circuitEquivalent circuit

68

Impedance ParametersSurface film-, charge transfer and bulk

ResistancesAssociated capacitances (constant phase

elements, CPEs)Warburg and intercalation capacitancesApparent Li-ion diffusion coefficient (DLi+)The above are extracted as a function of voltage.Can yield valuable information about the

stability and Li-cyclability of the compound.

69

Impedance studies on Nano- composite, CaO.SnO2

0 100 200 300 400 500 6000

100

200

300

400

0 20 40 60 80 100 120 140 160 1800

20

40

60

80

0 20 40 60 80 100 120 1400

20

40

60

80

100

31 mHz

15 mHz

70 mHz

Z'(ohm)

10 k

Hz

2 Hz100 Hz

First Discharge(a)

-Z''(

ohm

)

OCV (~2.6V) 0.2V 1.5V 0.1V 1.0V 0.05V 0.75V 0.005V 0.5V

68o

56o

19 mHz

2.5

kHz

200 Hz

First Charge(b) 0.1V 0.2V 0.5V 0.75V 1.0V

61o

25 mHz

6 Hz

10 k

Hz

11th Discharge(c) 1.0V 0.1V

0.75V 0.05V 0.50V 0.005V

Impedance spectra measured during the first discharge-charge cycle, and also during the 11th

discharge-cycle.

The spectra fitted to an equivalent circuit, and impedance parameters evaluated: Surface-film and charge-transfer resistance, bulk resistance, associated CPEs, n-values and diffusion coefficients.

The above were correlated with the observed cycling behaviour.

Nyquist plots, z’ vs. z” (ohm)

Equivalent electrical circuit

70

Ex-situ XRD studies on K2(Co2Sn6)O16

10 20 30 40 50 60 70 80

AlCuAlCu

AlCuLi2O

(a) 1stdisch.;1.0 V

(b) 1stdisch.;0.5V

(c) 1stdisch.;0.005V

(620

)

(411

)

(420

)(3

30)

(211

)

(310

)

(200

)(1

10)

2θ (deg.)

(220

)

(541

)

(K-Co)

I (a.

u.)

The patterns at 0.5V and 0.005V show the amorphization of (K-Co) due to the complete disappearance of the compound peaks.

Gives information on the state of electrode, crystalline or amorphous.

Starting (K-Co) is crystalline.

Reaction with Li reduces toCo and Sn metal.Sn further reacts with Li to form alloy, Li4.4Sn.These are nano-size, not seen in XRD.But, clearly seen in TEM and SAED.

71

Experimental Methods for study of LIB materials

Synthesis and physical characterizationX-ray diffraction to establish crystal structureSEM and TEM to establish crystal morphology, particle sizeSurface area, density

72

Experimental Methods (contd.)

Electrochemical testingCell (battery) fabricationCyclic voltammetryCharge-discharge cycling: at

various voltage ranges & current rates; at room temp., and at 55°C

Impedance spectra

73

Portable Energy Sources (Contd.)

Ref. M.S. Whittingham, MRS Bulletin, 33,411(2008).

74

Portable Energy SourcesChemical Energy → Electrical EnergyBatteries (Primary & Rechargeable)SupercapacitorsFuel Cells

Solar cells (Solar Energy → Elect. Energy)Thermoelectric(Heat Energy→ Elect. Energy) Petrol/Diesel (Chem. Energy → Mech. Energy)

75

Portable Energy Sources (Contd.)

Ref. M.S. Whittingham, MRS Bulletin, 33,411(2008).

76

Portable Energy Sources

Fig. Comparison of the driving ranges for a vehiclepowered by various battery systems or a gasoline- powered combustion engine. (Winter & Brodd, 104, 4247(2004))

77

Applications of Li-ion Batteries

Electric Vehiclehttp://en.wikipedia.org

Mars Exploration rover ”spirit”www.nasa.gov

Cellular Phone Note BookDigital camera

78

Strategies for ElectrolytesLiquid Electrolytes

Presently used in LIBs: LiPF6 dissolved in EC+DEC: σ

(ionic) at 300K: Liq. ≈

100 S/cm; Gel: ≈

10-50 S/cm).(Ethylene Carbonate+ Diethyl Carbonate) -- as liquid or immobilized in a gel, with PVDF or ‘patented binder’.

Disadvantages of LiPF6 : Expensive and toxic.

Alternatives being tried: Salt: Li-bis-oxalato borate (LiBOB)

Li-Polymer Electrolytes: Li-PEO, Li-PPY: Semi-solids/Gels, with impregnated solvent (plasticizer). σ (ionic) at 300K ≈ 10-4 - 10-5 S/cm -- Not satisfactory for use in LIBs.

(PEO: polyethylene oxide; PPY: polypyrrole)

79

Strategies for Electrolytes (contd.)Solid Electrolytes for All Solid-State Lithium ion batteries (AS-LIBs)

LIPON (Li-P-O-N) amorphous Film : σ (ionic) at 300K ≈ 10-3 -10-4 S/cm.

Viability as Solid electrolyte demonstrated in Thin-film LIBs.Disadvantages: Can not be made as bulk powder or dense ceramic.

All solid Li-polymer Electrolyte: Li2O-PEO, other Salts/Polymers. But, σ

(ionic) at 300K ≈

10-5 -10-6 S/cm)--not useful at present for LIBs.

Li-analogues of NASICON: σ (ionic) at 300K ≈ 10-4 -10-5 S/cm.

May be useful at T~80 °C, but difficult to obtain dense sintered disc.(The latter is a necessary condition for AS-LIBs)

A useful Solid-State Li-ion conductor for AS-LIBs is yet to be developed.

80

Parameters for Battery EvaluationMaximum capacity in mAh -- calculated from weights of electrodes, electrolyte, packing etc. --Total battery weight.LIBs are sold in the discharged-state

-- Need to be charged before operation.Parameters to be tested:State-of-charge (Depth of discharge)-- can be obtained from the OCV (open circuit voltage).

No dimensional change in LIB on long-term cycling (≥800 cycles)

Stability under temperature (heating to 80°C).Nail penetration test (Short-circuiting)--LIB should not explode/fire-- smoke evolution is allowed. Large-scale LIBs-- heat management under discharge.(part of electrical energy →Heat)

81

Capacity The battery capacity printed on a battery is the product of 20 hours multiplied by the maximum constant current that a new battery can supply for 20 hours at 20 C°, down to a predetermined terminal voltage per cell.

A battery rated at 100 A·h will deliver 5 A over a 20 hour period at room temperature.

Q = I.t where Q is the battery capacity (typically given in mA.h or A.h), I is the current drawn from battery (mA or A) and t is the amount of time (in hours) that a battery can sustain.

82

Capacity calculation

Theoretical capacity of an electrode is calculated from:

Faraday (96,500 coulombs per gm. equivalent) constant, molecular weight of the oxide under investigation & number of Li+ (and electrons) involved in the discharge-charge reactions.

1 Faraday (F) = 96,500 coulombs/gm. equivalent= 96500 A. sec = 96500/(60×60) A. h = 26,800 mA.h

83

Graphite (C) : Atomic wt. =12 gm Graphite (C) : Atomic wt. =12 gm 1 mole of C takes (1/6) Li to form LiC1 mole of C takes (1/6) Li to form LiC66 ..Hence, theoretical cap. = (26800/12) Hence, theoretical cap. = (26800/12) ××

(1/6)= 372 (1/6)= 372 mA.h/gmA.h/g(Practical value (Practical value ~~

310310--320 320 mA.h/gmA.h/g))

LiCoO2 : This can give one mole of Li per formula LiCoO2 : This can give one mole of Li per formula mass (LiCoO2 mass (LiCoO2 →→Li + Li + CoO2, where CoO2, where is the vacancy is the vacancy created by Licreated by Li--removal).removal).Molar mass LiCoO2 = (6.9+58.9+32) = 97.8 gmMolar mass LiCoO2 = (6.9+58.9+32) = 97.8 gmHence, Hence, theortheor. cap. = (26800/97.8) . cap. = (26800/97.8) ××

(1) = 274 (1) = 274 mA.h/gmA.h/g..In practice, only 0.5 Li are removed from the lattice In practice, only 0.5 Li are removed from the lattice giving a capacity of 137 giving a capacity of 137 mA.h/gmA.h/g

SnO2 : Mol. mass SnO2 : Mol. mass = 119+32 = 151g = 119+32 = 151g TheorTheor. capacity = (26800/151) . capacity = (26800/151) ××

(4.4) = 781 (4.4) = 781 mA.h/gmA.h/g(Since (Since 4.4 Li per 4.4 Li per SnSn are consumed in the Lithe Li4.44.4 Sn alloy Sn alloy formation.)formation.)

Capacity calculation (Contd.)

84

Experimental capacityExperimental capacity is calculated from the is calculated from the

Active mass in the electrode (excluding the weight of Active mass in the electrode (excluding the weight of binder, carbon additive etc) ~ 3binder, carbon additive etc) ~ 3--5 mg.5 mg.

Quantity of electricity passed (LiQuantity of electricity passed (Li--ions and electrons) ions and electrons) in coulombs (in coulombs (mA.hmA.h) to give the capacity in ) to give the capacity in mA.h/gmA.h/g in in the voltage range of interest.the voltage range of interest.

For cathodes, the capacities are in the range, For cathodes, the capacities are in the range, ~ 150~ 150--200 200 mA.h/gmA.h/g..

For anodes, the capacities are in the range, For anodes, the capacities are in the range, ~ 300~ 300--1000 1000 mA.h/gmA.h/g, depending on the compound., depending on the compound.

Capacity calculation (Contd.)

85

Preparation lab

Tube furnace

Box furnace

Ball miller

BET surface area analyzer

Density analyzer

Freeze drying

High temp. Box furnace

Advanced battery lab

86

Li-Battery fabrication

Glove box

Coin cell

Doctor blade

Punching Machine

Twin roller

Oven

87

Impedance analyzer

Bitrode

Battery tester 1(Model ScN

:32 channels)

Electrochemical and physical studies

Cyclic voltammetry

Bitrode

Battery tester 2(Model MCV-0.5/0.01-5 :16 channels)

Advanced battery lab facilities