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Novel Carbon Materials for Electrochemical Applications. Giselle Sandí. Chemistry Division. In 1785 Luigi Galvani observed, while dissecting a frog, that the frog’s legs would twitch whenever touched by a steel rod. Topics of Discussion. The Rocking Chair Model: Lithium Ion Batteries

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In 1785 Luigi Galvani observed, while dissecting a frog, that

the frog’s legs would twitch whenever touched by a steel rod


Topics of discussion
Topics of Discussion that

  • The Rocking Chair Model: Lithium Ion Batteries

  • Types of Electrodes

    • Anodes of Choice

  • Synthesis and Characterization of Novel Carbon Materials

  • Electrochemical Performance

  • New Directions

  • Acknowledgments



Comparison of the energy density of the that

most common rechargeable batteries

Lithium-Ion (High Energy)

Lithium-Ion (Long Life)

Silver-Cadmium

Nickel-Hydrogen

Lead -Acid (Automotive)

Nickel Cadmium (High Energy)

Lead -Acid (High Energy)

Nickel-Cadmium (Sealed)

Alkaline Manganese


Problems with metallic Li that

Cathode

Li = Anode

e-

e-


The rocking chair model
The Rocking Chair Model that

Charge

Li+

Li+

Cathode

Electrolyte

Anode

Li+

Li+

Discharge


Types of electrodes
Types of Electrodes that

Anode materials

Cathode materials

  • Pitches

  • Cokes

  • Natural graphite

  • Fullerenes

  • Synthetic carbons

  • Transition metal oxides

  • and chalcogenides

  • Uni-dimensional structures: TiS3, NbSe3

  • Bi-dimensional structures

  • Metal sulfides of Ti, Nb, Ta, Mo, and W

  • Metal oxides of V, Cr, Fe, Co, Ni and Mn

  • Three-dimensional structure

  • Manganese oxides: -MnO2 (Mn2O4)

  • Organic molecules

  • Polymers


Practical Considerations that

  • Selection of a suitable electrolyte

    • To minimize the decomposition that occurs during

      the lithiation of the carbon  formation of a

      passivating layer

    • Liquid electrolytes: LiPF6/EC/DEC

    • Polymer electrolytes

  • Low surface area carbons

    • Amount of lithium consumed in the formation of the

      passivating layer is proportional to the surface area

      of the carbon


The novel approach
The Novel Approach that

At the beginning….

Intercalation

+

+

Silicate layer

Pore

+

+

-nH2O

+

+

+

+

Hydroxyl cation

Pillared clay (PILC)


Carbon precursors
Carbon Precursors that

Linear

polymer

Condensation

polymer similar

to phenoplasts

O

O

O

Mechanism similar to Schll

reaction: 2 ArH Ar-Ar + H2

Incorporation of liquid monomer

followed by low temperature

polymerization reaction

AlCl3

H+

H

H

H

C

C

C

H

H

H

Gaseous hydrocarbon is deposited in the PILC

layers and pyrolized


Loading methods

Pyrene that

Loading Methods

pyrolize at 700 °C

under N2, dissolve

in HF, and reflux in

HCl

overnight

dry

Styrene

N2

Wash out excess and dry

To vacuum

C2H4 or C3H6

PILC

Styrene

C2H4 or

C3H6

N2


Characterization techniques
Characterization Techniques that

  • X-ray powder diffraction

  • Thermal gravimetric analysis

  • Scanning electron microscopy

  • Transmission electron microscopy

  • Scanning tunneling microscopy

  • Near-edge X-ray absorption fine structure

  • Small angle neutron scattering

  • Small angle X-ray scattering

  • NMR techniques

  • Electrochemical techniques


XRD of carbon samples derived that from the “templating” method


High resolution TEM of a carbon sample that synthesized using PILC/pyrene





SANS Analysis that

Theory of Freltoft, Kjems, and Sinha (Phys. Rev. B. 1986)

q-df

Log S (Q)

1/

1/r

Log Q ()

Where:

df = fractal dimension

r = hole radius

 = cutoff length



Schematic representation of the mechanism of formation of porous carbon using PILC/pyrene

Al2O3

15 Å

r0

N2, 700 °C

r0

3.7 Å

11.4 Å

HF, HCl

Al2O3


Coin cell used to test the porous carbon using PILC/pyreneelectrochemical performance

Electrodes were prepared using:

90% m/m carbon

5% m/m carbon black

5% m/m binder (PVDF in NMP)


Electrochemical parameters porous carbon using PILC/pyrene

Where:

charge is the charge capacity

t0 is the starting time

t is the current time

I is the current value measured

for this data point

Applied current for 20 hrs (C/20):

I20h = 18.6 (mA) x Wact (g)


Voltage profiles of the second porous carbon using PILC/pyrenecycle of various C/Li cells




Role of curved vs. planar carbon Li/C coin cellslattices in the lithium uptake

Influence of a curved lattice (C60) on the nature of lithium

bonding and spacing in endohedral lithium complexes

The curved ring

structure of the

C60 facilitated the

close approach of

the lithiums (2.96 Å),

even in the trilithiated

species

Interior of the C60 is large enough to easily

accommodate two or three lithium atoms


Role of curved vs. planar carbon Li/C coin cellslattices in the lithium uptake…..

  • Implications:

  • 2.96 Å is closer than the interlithium distance in the stage-one

    LiC6 complex

  • Lithium anode capacities may be improved over graphitic

    carbon by synthesizing carbons with curved lattices such

    as corannulene

  • Concept was experimentally tested using corannulene as a

    model electrode material



Electrochemical NMR Li/C coin cells

  • Uses:

  • Near electrode chemistry

    • Electrode-electrolyte interface

    • Electrolyte depletion zone

  • Transport properties of battery materials

    • Electrolyte penetration

    • Redox chemistry at the SEI

    • Li “location” and chemical nature

Potentiostat

Working Electrode

Counter Electrode

NMR Spectrometer


Electrochemical NMR…New approach Li/C coin cells

The “old” cell

The “new” toroid

cavity coin cell

Working electrode (current collector) and NMR detector (central conductor)

Carbon sample

Celgard separator

Lithium

Copper mesh

 Standard 2032 size

 In situ NMR detector

 Imaging capability


Electrochemical NMR…Spectra obtained using the new cell Li/C coin cells

A) Li intercalated into graphite, Li:C 0.8:6

B) Li-corannulene complex, Li:C  1.8:6


An advanced synthetic route to produce Li/C coin cells

high performance carbons…..sepiolite clay

A= Two tetrahedral sheets and a central magnesium octahedral sheet

N= neutral sites

B= cross section of an ideal fiber

P= charged adsorption sites


XRD of sepiolite, sepiolite/propylene composite, Li/C coin cells

and carbon obtained after removal of the template


TEM of sepiolite, sepiolite/propylene composite, Li/C coin cells

and carbon obtained after removal of the template


Voltage profile and efficiency of carbon Li/C coin cells

electrodes derived from sepiolite/propylene


Electrochemical NMR…Spectra Li/C coin cells

obtained using the new cell


Cu mesh Li/C coin cells

Cu mesh

Polypropylene bag

Electrolyte

Separator

Carbon

Li

Pouch electrochemical cell for in situ SAXS experiments


In situ Li/C coin cells SAXS results of a carbon electrodes a) derived

from sepiolite and b) commercial graphite

a

Lattice expansion upon

Li incorporation

b

There are no changes in the

structure upon Li incorporation


Changes in the power law slope Li/C coin cells

with discharge from 2.6 to 0 V


Summary Li/C coin cells

  • The novel approach for synthesizing carbon produced good

  • candidates for electrochemical applications

  • Understanding the performance of these carbons as a

    function of structure has been a main goal of this

    research

  • More efforts will be dedicated to conducting in situ SAXS

    and NMR experiments to elucidate the Li “location”

    upon charging and discharging electrochemical

    cells


ACKNOWLEDGMENTS Li/C coin cells

This work was performed under the auspices of the

U.S. Department of Energy, Office of Basic Energy

Sciences, Division of Chemical Sciences, under

contract number W-31-109-ENG-38.

Randy Winans (CHM)

Kathleen Carrado (CHM)

Christopher Johnson (CMT)

Rex Gerald and Robert Klingler (CMT)

P. Thiyagarajan (IPNS)

Sönke Seifert (CHM, APS)

Roseann Csencsits (MSD)

Lawrence Scanlon (Wright Patterson AFB)

Lawrence Scott (Boston College)


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