Development of advanced materials and Sri Lankan minerals

for rechargeable batteries

NATIONAL INSTITUTE OF FUNDAMENTAL STUDIES (NIFS)

Nanotechnology/Physics of Materials Project

Project Description

Project (A): Development of advanced materials for rechargeable batteries

Study of effect of dopents in advanced transition metal oxide semiconductorsDevelopment of low-cost and nano technological methods for battery material synthesis

Project (B): Development of Sri Lankan minerals for rechargeable batteriesDevelopment of Sri Lankan vein graphite for the direct use in rechargeable Li-ion batteriesStructural modification / Conversion into nano materials of Sri Lankan graphite for future Na-ion, Mg-ion and hybrid batteriesProject (C): Investigations on devising rechargeable batteries in Sri Lanka

Using locally developed materials

Our strategy :Development of low-cost and performance enhanced transition metal oxide electrode materials, with cheaper additives and using novel but low-cost nano-material synthesis techniques

Li(Ni1/3)Mn1/3Co(1/3-xMx)O2, [M = Al, Fe, Mg, Ba, Na, Cu, Zn ..] for Li-ion battery cathodes

NaNi0.4Mn0.4Co0.2MxOδ [M = Li, Mg, Ba, Ag, Al, Cu, Fe, Ti ..] for Na-ion battery cathodes

Mg1-xMxO2, [M = Mn, Co ..] for Mg-ion battery cathodes MTiO3 [M = Mg, Na ..] for Na and Mg ion battery anodes

Considering the cost and efficiency, semi-conducting oxides such as transition metal

oxides, are thebest practical electrode materials for rechargeable

batteries

Project (A): Development of advanced materials for rechargeable batteries

- transition metal oxides

Compounds containing multivalent ions have the potential for electronic conductivity;

Due to intrinsic non-stoichiometry OR through doping

Developement of Glycine Nitrate Combustion (GNC) technique

as a low-cost nano-material synthesis process

G:N = 1.5

G:N = 0.2

G:N = 0.5

G:N = 0.3

G:N = 0.6

G:N = 0.8

G:N = 0.4

G:N = 1.0

Optimization of Glycine:Nitrate (G:N) ratio in GNC process

G:N = 1.2

Li(Ni1/3Mn1/3Co1/3)O2

Successful synthesis of the solid solution phase of the required R3m layered structure of Li(Ni1/3Mn1/3Co1/3)O2 electrode materials used in Li-ion batteries

A low-cost wet-chemical method

Self sustaining rapid process with high yield

Can produce homogeneous fine (nano size) particles with dual particle morphology appropriate for LIB

G:N Ratio 0.2 0.4 0.6 0.8 1.0

Particle Size (nm)

78 68 64 62 58

Performance of the developed Li(Ni1/3Co1/3Mn1/3)O2 based cathodes in Li-ion rechargeable cells

Very high discharge capacity of 180 mAhg-1 at room temperature, considerably higher than that reported for LiCoO2 (128 mAhg-1)

-20 0 20 40 60 80 100 120 140 160 180 200 220

2.5

3.0

3.5

4.0

4.5

Pot

entia

l Vs

Li/L

i+

Capacity mAhg-1

C rate = C/5 , Cycle Between 2.4 – 4.6 V

In CR2032 coin cells using lithium metal foil as the counter and reference electrodes with 1M LiPF6 electrolyte.

M x

1st cycle charge

capacitymAhg-1

1st cycle dischargeCapacitymAhg-1

1st cycle irreversible

capacity mAhg-1

333 0 212 180 42

Mg 0.08205 143 62

Na 0.04

248 175 73

LiCoO2 147 128 12

Project (B): Development of Sri Lankan minerals for rechargeable batteries

- natural vein graphite

STEP I: UPGRADING GRAPHITE - Development of low-cost but efficient purification techniques

- Surface modification of purified graphite STEP II: BATTEY GRADE GRAPHITE Development of upgraded graphite for rechargeable batteries

- Direct use in Li-ion batteries- Through interlayer expansion / Conversion to nano

materials

DEVELOPMENT OF SRI LANKAN NATURAL VEIN GRAPHITE

Sri Lanka is the only commercial producer of vein graphite, which is the rarest and most valuable form of graphite. Limitations: Impurities and inferior surface structure

Shiny-slippery-fibrous

Coarse flakes of radial

Needle-platy

Coarse striated-flaky

Many specialized markets such as rechargeable batteries command premium prices for natural graphite but require upgrading through purification and further modification

STEP I: Upgrading of Sri Lankan vein graphite

Purification

Acid Leachi

ng

with5 vol.% HCl

at 60 0C

Roasting with

5 wt.% NaOH

Acid treatment

with5 vol.% H2SO4

Alkali Roasting

Acid Digestion

HF digestionWith a

mixture of HF, HNO3

and H2SO4

Vacuum drying

Surface modification

Mild Oxidati

on

Thermal OxidationAt 550 0C

Chemical Oxidation01) with HNO3 02) with H2O2,03) With (NH4)2S2O8

Chemical decomposition

Mixing with AgNO3 in water/ethanol

Adding formaldehy

de and depositing ultrafine

Ag particles

on graphite surface

Alkali Coating

Mixing with 0.5% Li2CO3)aq

Drying at 100 0C

Simultaneous

purification &

modification

Upgraded Sri Lankan vein graphite

Purifying by acid leaching Purifying by alkali roasting

Low cost and easy process with low energy consumingAll these techniques use low concentrations of mineral acids/alkali at low temperaturesMore environmental friendly than other purification techniques Our recent

study with HF acid

digestion resulted over 99.9 % purity

& modified surface in all

four structural varieties

Raw Graphite Purified Graphite Modified Graphite

STEP II: Developed Sri Lankan graphite for the anode of Li-ion batteries

LIB anode requires a porous carbon and graphite is the optimum suitor Graphite is the second largest component by weight in LIB

High cost of synthetic graphite has increased the use of natural graphite

Raw Sri Lankan natural graphite

Electrode from developed graphite

Developed battery grade graphite

Li-ion battery with our electrodes

Discharge capacityTheoretically expected value: 375 mAhg-1

Raw vein graphite : 286 mAhg-1

Our developed local vein graphite: 378 mAhg-1

SUMMARY: Discharge Capacity & Cycle Performance of graphite anodes

250

300

350

400

450

0 5 10 15 20 25 30 35 40 45 50 55

CC

_Dis

char

ge(m

A h

g-1

)

Number of Cycles

Charge - discharge rate = 0.2C

Project (C): Investigations on Devising rechargeable batteries in Sri Lanka

Performance of a full Li-ion rechargeable battery

with both anode and cathode materials developed at NIFS

Method:- CCCV (3 -4.2 V), Charge Discharge 0.2 C rate 3-4.2 V vs Li/Li+Anode: Developed Sri Lankan GraphiteCathode: Developed Li(Ni1/3Co1/3Mn1/3)O2

0 2 4 6 8 10

0

50

100

1500 2 4 6 8 10

0

20

40

60

80

100

Col

umbi

c E

ffici

ency

%

Cap

acity

(mA

hg-1)

Cycle Number

Charge Discharge Irreversibl

1st cycle discharge capacity: 98.7 mAhg-1

Structural modification / Conversion of Sri Lankan graphite into nano materials for future Na-ion, Mg-ion and hybrid batteries - through converting to extended graphite (by improved Hummers’s method)

ν C=O stretching :- 1720-1680 cm-1, ν O-H stretching :- 1360 - 1400 cm-1 and ν C-O stretching :- 1260-1000 cm-1

ν c=c stretching :- 1637 cm-1

Aliphatic C-H :- doublet at 2921 and 2850 cm-1

FTIR spectrum of Graphite (Green) and Extended Graphite (Blue)

X-ray diffractograms of Graphite (Blue) and Extended Graphite (brown) The main peak in graphite at

26.7 degrees corresponds to an interlayer spacing of ~ 0.3 nm.The newly formed broad peak at 9.6 degrees (corresponding to an interlayer spacing of ~ 0.9 nm) indicate formation of EG.This results in an interlayer expansion and indicate the possibility of intercalating bigger ions such as Na, Mg … ???

5.00 15.00 25.00 35.00 45.00 55.00 65 .00 75.00 85 .00

Inte

nsit

y/a.

u

2 theta/degrees

SSF vein graphite

5.00 15 .00 25 .00 35.00 45.00 55 .00 65.00 75 .00 85 .00

Inte

nsit

y/a.

u

2 theta/degrees

Expanded graphite by SSF

(002)

EG

(004)

a

b

Our recent studies showed a very strong dependence of the expansion of interlayer spacing on the vein graphite variety and the oxidant used

Investigations on ion intercalation to EG is currently going on

Thank you