RUTILE CRYSTAL STRUCTURE

z

x

y

SEEING THE 1-D CHANELS IN RUTILE

NEW METASTABLE POLYMORPH OF TiO2 BASED ON K2Ti4O9 SLAB STRUCTURE - (010) PROJECTION SHOWN

K+ at y = 3/4

K+ at y = 1/4

Different to rutile, anatase or brookite forms of TiO2

Finding the number of crystallographically inequivalent oxygen sites in the K2Ti4O9 slab and the number of each

Oxygen count 1/3 + 3/4

Oxygen count 4 + 1/2 +2 +1/3

Oxygen count 1/3 + 3/4 1/3

1/3

1/3 1/41/41/4

1/41/41/4

1/2 1/21/21/2

1 1 1 1

Topotactic loss of H2O from H2Ti4O9 to give “Ti4O8” (TiO2 slabs) plus H2O, where two bridging oxygens in slab are protonated (TiOHTiOTiOH)

[Ti(IV)4O9]2-

CHIMIE DOUCE: SOFT CHEMISTRY

• Figlarz synthesis of new WO3

• WO3 (cubic form) + 2NaOH Na2WO4 + H2O

• Na2WO4 + HCl (aq) gel

• Gel (hydrothermal) 3WO3.H2O

• 3WO3.H2O (air, 420oC) WO3 (hexagonal tunnel structural form of tungsten trioxide)

• More open tunnel form than cubic ReO3 form of WO3

Slightly tilted cubic polymorph of WO3 with corner sharing Oh WO6 building blocks, only protons and smaller alkali cations can be injected into cubic shaped voids in structure to form bronzes like NaxWO3 and HxWO3

1-D hexagonal tunnel polymorph of WO3 with corner sharing Oh WO6 building blocks, can inject larger alkali and alkaline earth cations into structure to form bronzes like RbxWO3 and BaxWO3

Hexagonal tunnels

Injection of larger M+ cations like K+ and Ba2+ than maximum of Li+ and H+ in c-WO3

Apex sharing WO6 Oh building blocks

Structure of h-WO3 showing large 1-D tunnels

MOLTEN SALT ELECTROCHEMICAL REDUCTIONS OF OXYANIONS: GROWTH OF CRYSTALS

• Molten mixtures of precursors - product crystallizes from melt - inert crucibles and electrodes like Pt, graphite CATHODE

• Reduction of TM oxides to lower oxidation state materials

• CaTi(IV)O3 (perovskite)/CaCl2 (850oC) CaTi(III)2O4 (spinel)

• Na2Mo(VI)O4/Mo(VI)O3 (675oC) Mo(IV)O2 (large crystals)

• Li2B4O7/LiF/Ta(V)2O5 (950oC) Ta(II)B2

• Na2B4O7/NaF/V(V)2O5/Fe(III)2O3 (850oC) Fe(II)V(III)2O4 (spinel)

SYNTHETIC FORM: SHAPE IS EVERYTHING IN THE MATERIALS WORLD

• When thinking about a solid state synthesis of a particular composition it is also important to plan the form of the material that will ultimately be required for a specific application

• Shape is everything when it comes to designing structure-property-function-utility relations

• Form counts - polycrystalline, nanocrystalline, film, superlattice, wire, single crystal and so forth

BASICS LSSB: INJECTION-INTERCALATION CATHODES TiO2, NbSe3, WO3, MoS2, V6O13, LixCoO2

• Li+/e- charge equivalents of anode

• Voc, EF(anode-cathode)

• Electrode-electrolyte interfacial kinetics• Polymer segment dynamics

• Polymer Tg controls crystalline vs glassy

• Li+/PEO cooperative motion effects• Goal Li+ RT conductivity• Needs liquid (low MW PEO) plastisizers• Electrode-electrolyte mechanical stability• Electrode-electrolyte chemical stability• Rocking chair architecture• Secondary battery can be cycled• Operational lifetime• Safety, environmentally correct

LiLi3NLixCLixCFLiAlLiSnLixMnO2

PEO

Li+

Li+

Li+ Li+

Li+

Li+

anode electrolyte cathode

SPE

LiCoO2

LiCoO2

LixC6

Li

ROCKING CHAIR LSSB

HOW TO SYNTHESIZE A BETTER LSSB?

Improved Performance Cathode, Anode and Electrolyte

TEMPLATE SYNTHESIS OF NANOSCALE BATTERY CATHODE MATERIALS

A BETTER BATTERY CATHODE USING NANOSCALE MATERIALS - NANODIFFUSION LENGTHS FOR Li+

DIFFUSIVE INTERCALATION

• Template synthesis is a versatile nanomaterial fabrication method used to make monodisperse nanoparticles of a variety of materials including metals, semiconductors, carbons, and polymers.

• The template method has been used to prepare nanostructured lithium-ion battery electrodes in which nanofibers or nanotubes of the electrode material protrude from an underlying current-collector surface like the bristles of a brush.

• Nano-structured electrodes of this type composed of carbon, LiMn2O4, V2O5, Sn, TiO2 and TiS2 have been prepared.

A BETTER BATTERY CATHODE USING NANOSCALE MATERIALS - NANODIFFUSION LENGTHS FOR Li+

DIFFUSIVE INTERCALATION

• In all cases, the nanostructured electrode showed dramatically improved rate capabilities relative to thin-film control electrodes composed of the same material.

• The rate capabilities are improved because the distance that Li must diffuse in the solid state (the current- and power-limiting step in Li-ion battery electrodes) is significantly smaller in the nanostructured electrode.

• For example, in a nanofiber-based electrode, the distance that Li must diffuse is restricted to the radius of the fiber, which may be as small as 50 nm.

A BETTER BATTERY CATHODE USING NANOSCALE MATERIALS - NANODIFFUSION LENGTHS FOR Li+

DIFFUSIVE INTERCALATION

• Beating mechanical stability problem of repeated intercalation-deintercalation expansion-contraction cycles

• In addition to improved rate capabilities, the nanostructured electrodes do not suffer from poor cyclability observed for conventional electrodes.

• This is because the absolute volume changes in the nanofibers are small, and because of the brush-like configuration, there is room to accommodate the volume expansion around each nanofiber.

• Improved cycle life results show nanostructured electrode can be driven through 1400 charge/discharge cycles without loss of capacity.

nc-TiO2

Nanocrystal-PEO electrolytes solid plasticisers for LSSB

Ti(IV)-X- surface coordinated anion

Li+ cation

Ti(IV)-O surface coordinated oxygen of PEO polymer chain

PEO polymer chain coordinated to Li+ cation and surface Ti(IV)

LiClO4-PEO-nc-TiO2

• LiClO4-PEO-nc-TiO2 -high surface area nanocrystalline ceramic

• Brnsted and Lewis acid-base sites - surface Ti(IV) coordination to O(CH2CH2)-

• Surface Ti(IV) binding to counteranion X-

• Polymer-particle crosslinking - no 60oC glass transition

• nc-TiO2 stabilizes glassy polymer state at RT

• Domains of local polymer disorder at PEO-nc-TiO2 interface

• Optimal anchoring promotes local structural and dynamical modifications• High RT Li+ conductivity• Excellent mechanical stability, improved stress-strain curves• Reduced reactivity with solid compared to liquid plasticizer• Less cooperative PEO segmental motion with enhanced interfacial mobility of

Li+

• Transport number t(Li+), 0.3 pristine LiClO4-PEO, 0.6 in LiClO4-PEO-nc-TiO2

nc-TiO2

nc-CERAMIC OXIDES: SOLID PLASTICISERS IN POLYMER-ELECTROLYTE LITHIUM BATERIES

• LiClO4 : PEO = 1 : 8, 10 wt% nc-TiO2 or Al2O3,

• anchoring PEO oxygens and counteranions to Brnsted/Lewis acid surface sites,

• enhanced corrosion resistance of electrodes,

• better mechanical stability PEO,

• higher Li+ conductivity & transport number,

• local disorder of polymer, loss of Tg, stabilizes RT glassy state,

• discards need for PEO-Li+ cooperative segmental motion

METHODS FOR SYNTHESIZING NANOCLUSTERS AND NANOCRYSTALS

• Vaporization of metals (thermal, laser ablation) in inert gas - condensation of mixture - Pt, Au

• Supersonic molecular beams - Knudsen cell vaporization with inert gas expansion - condensation into vacuum and mass selection and mass spectroscopy detection - Si, GaAs

• Plasma-arc vaporization - condensation - WC, SiC

• Aerosol spray pyrolysis of salt, sol-gel precursor solution - Y3Fe5O12, Mn0.8Zn0.2FeO4, PbZr0.52Ti0.48O3, YBa2Cu3O7, ZrO2, TiO2

• Microemulsions, micelles, zeolites - precursors - confined nucleation and arrested nanocluster growth - capped CdSe, FePt, TiO2, YBa2Cu3O7

LENGTH SCALES IN CHEMISTRY, PHYSICS

AND BIOLOGY

Peter Day, Chemistry in Britain

Spatial and quantum confinement and dimensionality

WHEN IS SMALL GOOD?

Sub-dividing or perforating mattermono- or polydispersed particles, crystalline or amorphous, micro (<10 Å),

meso (10-1000 Å) or macro (>1000 Å) length scale, organized or random arrangements, channels or pores, structure-composition-defects, surface

area, sites, charge, hydrophobicity, functionality

Property-function

QSEs, of e, h, or hrelative to materials size, dimensionality, interaction strength of components, interconnection and integration of parts, hierarchy

and system architecture, function

WHEN IS SMALL GOOD?

Properties that are size and shape tunablemechanical, thermal, acoustical, dielectric, surface vs bulk,

electrical, optical, electro-optical, magnetic, photonic, catalytic, photochemical, photophysical, electrochemical, separation, recognition,

composite

CAPPED MONODISPERSED SEMICONDUCTOR NANOCLUSTERS

nMe2Cd + nnBu3PSe + mnOct3PO (nOct3PO)m(CdSe)n + n/2C2H6 + nnBu3P

EgC = Eg

B + (h2/8R2)(1/me* + 1/mh*) - 1.8e2/R

Coulomb interaction between e-h

Quantum localization term

ARRESTED GROWTH OF MONODISPERSED

NANOCLUSTERS

CRYSTALS, FILMS ANDLITHOGRAPHIC

PATTERNS

nMe2Cd + nnBu3PSe + mnOct3PO (nOct3PO)m(CdSe)n + n/2C2H6 + nnBu3P

MONODISPERSED CAPPED CLUSTER SINGLE CRYSTALS

methanol

2-propanol

toluene

Rogach AFM 2002

THINK SMALL DO BIG THINGS!!!

EgC = Eg

B + (h2/8R2)(1/me* + 1/mh*) - 1.8e2/R

SELF-ASSEMBLING AUROTHIOL CLUSTERS

HAuCl4(aq) + Oct4NBr (Et2O) Oct4NAuCl4 (Et2O)

nOct4NAuCl4(Et2O) + mRSH + 3nNaBH4 Aun(SR)m

CAPPED METAL CLUSTER CRYSTAL

CLUSTER SELF-ASSEMBLY DRIVEN BY HYDROPHOBIC INTERACTIONS BETWEEN ALKANE TAILS OF

ALKANETHIOLATE CAPPING GROUPS ON GOLD NANOCRYSTALLITES

CAPPED FePt NANOCLUSTER SUPERLATTICE HIGH-DENSITY DATA STORAGE MATERIALS

ZEOLATE CAPPED SEMICONDUCTOR CLUSTERS

ZEOLATE LIGAND

Crown ether - zeolate ligand analogy - metal coordination

chemistry of zeolites

TOPOTACTIC MOCVD

Intrazeolite reaction of acid zeolite Y (HY) with known amounts of Me2Cd or Me4Sn vapors

Gives anchored MeCdY and Me3SnY, which react with H2S or H2Se to create encapsulated and zeolate capped nanoclusters Cd4S4Y and Sn4S6Y

Defined by Reitveld PXRD structure refinement

MOCVD TOPOTAXY OF INTRAZEOLITE TIN SULFIDE, CADMIUM SELENIDE AND SILICON AND GERMANIUM NANOCLUSTERS

INTRAZEOLITE CVD OF SILICON

NANOCLUSTERS

• Si2H6 + H56Y (Si2H5)8-Y

• (Si2H5)8-Y (Si8)8-Y

• Superlattice of Si8 clusters in ZY

QUANTUM CONFINED SILICON - < 5 nm -MAKING SILICON GLOW THROUGH NANOCHEMISTRY

INTRAZEOLITE TUNGTEN OXIDE NANOCLUSTERS

NANOWIRES - FABRICATION OR SYNTHESIS

• Top down advanced nanolithography fabrication methods - expensive and time consuming

• Bottom up chemical synthesis methods - economical and fast

• Creation of 1D nanowires - used as functional components and interconnects in building nanodevices and nanocircuitry through self assembly strategies

• Most successful purely synthesis methods involve vapor-solid VS, vapor-liquid-solid VLS, solution-liquid solid SLS and solution-solid SS processes

• These chemical approaches have led to carbon nanotubes, metal and semiconductor nanowires and a range of inorganic materials

• Other approaches involve structure directing templates like channels in porous alumina, hexagonal lyotropic liquid crystals and block copolymers