3­D Nano­Structured Carbon/Tin Composite Anodes

Robert KosteckRobert KosteckiRobert KosteckiRobert Kostecki

Lawrence Berkeley National LaboratoryLawrence Berkeley National Laboratory

DOE Vehicle Technologies Annual Merit Review Meeting

February 27, 2008February 27, 2008

This presentation does not contain any proprietary or confidential information

TASK 5.1 Diagnostics ­ Electrode Surface Layers I. Microwave Plasma­Assisted Chemical Vapor Deposition (MPACVD) of 3­D Nano­Structured Carbon/Tin Composite Anodes Purpose of Work: Design and manufacture nano­composite C/Sn composite electrodes with improved power and energy density, and extended cycleability

Barriers Addressed: Low energy (related to cost), poor Li­ion battery cycle lifetime

Approach: Use MPACVD to produce 3­D nano­structured C/Sn thin film electrodes 

Accomplishments: 3­D nano­structured thin­film C/Sn electrodes exhibit superior electrochemical performanceelectrochemical performance

II. Interfacial Studies of Li­ion Electrodes Purpose of Work: Establish direct correlations between Li­ion electrodes surface chemistry, morphology, interfacial phenomena and electrochemical performance

Barriers Addressed: Low power, poor Li­ion battery cycle/calendar lifetime

Approach: In situ Raman and FTIR microscopy, ex situ SPM, SEM, HRTEM, and standard electrochemical methods were used to detect and characterize detrimental surface phenomena in high voltage cathodes and intermetallic anodes

Accomplishments: Evaluation of carbon additives in high­voltage (>4.3 V) cathodes; single particle Raman imaging; preliminary evaluation of surface processes on Sn

Collaborations: V. Battaglia, M. Doeff, T. Richardson, V. Srinivasan, S. Whittingham K. Zaghib,

Responses to 2006 BATT ProgramMerit Review

2006 Reviewers’ Recommendations:

1. Should continue, creative

2. Always compare benefit of MPACVD to industry SOA

3. Industrial coater investment should be addressed

4. An increased emphasis on collaborations with other PIs and battery industry partnersindustry partners

FY2007 Research Directions:

�Collaborations on fundamental problems of material science as well as engineering issues of composite electrodes manufacturing

�Further optimization of the structure, morphology ad topology of composite electrodes produced by vacuum deposition techniques

� Innovative diagnostic methodologies to determine basic thermodynamic and kinetic parameters of Li­ion materials and electrodes

um, w ea s  o par e ecrep a on

C/Sn Anodes for Li­ion Batteries

• Purpose of Work: • Intermetallic Li­ion anodes offer high capacity, improved

safety and low cost

• Barrier • Sn exhibits large volumetric expansion during alloying with lithi hich l d t ticl d it ti lithium, which leads to particle decrepitation

• Loss of mechanical and electronic integrity of the active material leads to severe degradation of anode upon cycling

• Approach • Fine dispersion of active material within 3­D architectureconstitutes an effective strategy to prevent degradation

• Carbon­Me nano­composites combine the cyclability of graphite and high charge capacity of Li­Me alloy.

Microwave Plasma­Assisted ChemicalVapor Deposition of Nanomaterials

�MPCVD offers a fast, inexpensive, and convenient method of material synthesis at relatively low temperatures

�Carbon­metal composites can be produced from organo­metallic precursors without stabilizers or reducing agents

�Large­scale thin­film vacuum deposition process in a reel­to­reel configuration has become the industry standard

Three principal microwave heating mechanisms

I. Dipolar polarization ­ molecules with permanent or inducible dipoles follow oscillating electric field

II. Conduction mechanism ­ charge carriers move in the electric field, inducing currents

III. Interfacial polarization ­ conducting inclusions in non­conducting material

3 3 4b)

a)

MMPCVDPCVD of C/Sn Thinof C/Sn Thin­­FiF lml si msExperimental MethodologyExperimental Methodology

2.45 GHz Generator Magnetron

Ar Vacuum

Precursor

Sn(OC(CH ) )

C/Me layerSubstratePrecursor

is pyrolized for 10 sSn(OC(CH3)3)4 is pyrolized for 10 s at 1200 W in microwave Ar­plasma

• We developed a fast, one­step MPCVD method for co­synthesis of nano­structured C/Sn thin­film electrodes for Li­ion applications

• Thin C/Sn composite thin­films show ~2.5:1 of C/Sn wt.% ratio

• The thickness and composition of the film were reproducible and independent of the type of substrate.

The Structure and ConductivityThe Structure and Conductivityof Pyrolyzedof Pyrolyzed CaC rbr ono sa b ns

Graphite

Aggregation>1800oC

Carbon Black

Dehydrogenation >600oC

Organic precursors

Raman Spectraof Pyrolitic Carbons

T

1000 1200 1400 1600 1800

RamanShift, (cm­1)

Electronic Resistanceof Pyrolitic Carbons

• The structure and electronic conductivity of carbon change dramatically at 600­800oC.

• Conductive graphite­like carbons can not be obtained by simple pyrolysis at T<1800oC

sp3

Raman Spectroscopy ofC/Sn Thin­Films

Raman Spectra Deconvoluted Raman Raman Spectrum of Carbons Spectrum of Carbon of C/Sn Thin­Film

Acetylene G­band G­band Black D­band

D­band

488 nm

sp3

SFG­6 sp3

Graphite

632.8 nm

1000 1200 1400 1600 1800 2000 1200 1400 1600 1000 1200 1400 1600 1800

Raman Shift (cm­1) Raman Shift (cm­1) Raman shift (cm­1)

• Strong G and D Raman bands suggest the presence of sp2­coordinated nano­crystalline graphitic carbon

• Graphitic carbon matrix is expected to display better electronic conductivity and lower Qirr than standard carbon black additive

XRD Analysis of C/Sn Thin­Films

(200)

(101)

(211)

(220)

XRD pattern of the 5 µm think C/Sn film displays broad peaks characteristic • for Sn (I41/amd) tetragonal structure (a0 = 5.86 Å, c0 = 3.19 Å)

• Average Sn crystallite size calculated using the Scherrer formula ∼15 nm

Sn

SEM/EDX of C/Sn Thin Films

10µm 100 nm

Sn C O Cu 1µm

10µm

0 2 4 6 8 E ne rg y (k eV )

• Porous 5­7 µm thick C/Sn films were grown directly on Cu­foil

• The film consists of ~300­600 nm, agglomerates, which are fused together into a micro­ and nano­porous “lava rock”­like structure

• The EDX spectrum shows strong signals characteristics for Sn, C and Cu

• Small contribution from oxygen suggests the presence of SnO impurities

HRTEM of C/Sn Composites

5 nm

100nm

50

• HRTEM images reveal 1­5 nm Sn particles 40

30 • TEM bright­field images show a uniform dispersion of Sn in the carbon matrix

20

10

• Carbon matrix displays 10–15 nm graphene 0 1 2 3 4 >4 domains and regions typical of carbon blacks Particle Size (nm)

Distribution

(%)

CurretDensity(m

A/cm

Electrochemical Behaviorof C/Sn Thin­Film Electrode

Cyclic Voltammogram ­1st scan

Currennt Density

(mA/cm

2) 0.1

0.0

­0.1

­0.2

LiSn Li4.4Sn Li0.4Sn

Li2.33Sn

SnO (?)

1.2 M LiPF6 EC/DMC (1:1 w/w) Scan rate 0.1 mVs­1

0.0 0.2 0.4 0.6 0.8 1.0

Potential (V vs. Li/Li+)

• The reversible capacity of ca. 440 mAhg­1 originates exclusively from Sn

• The irreversible capacity (~400 mAhg­1) is mainly associated with the SEI layer formation on the carbon matrix

• The cathodic peak at 0.98 V is attributed to SnO impurities

Disc

Pot 1.2 M LiPF EC/DMC (1:1 w/w)

argeCapacity(%

)

ntial(Vvs.Li/Li

Galvanostatic Cycling of C/SnThin­Film Electrodes

Pote

ential (V

vs.

Li/Li+)

Galvanostatic Cycling at 1C Rate100

1.2

1.0

0.8

0.6

0.4

0.2

Disch

harge

Capacity

(%)

80 1C rate

60

40

20 1.2 M LiPF6 EC/DMC (1:1 w/w) Scan rate 0.1 mVs­1

0.0 0 0 2 4 6 8 0 100 200 300 400 500

Time (hrs) Cycle #

• The C/Sn thin­film electrodes exhibits very good cycling performance (~40% capacity fade after 500 cycles at 1C rate)

• The electronic integrity of the C/Sn electrode is retained during cycling

• The decrease of the reversible capacity is likely associated with large Sn particles weakly bounded to the carbon matrix

Poten . 1.2 M LiPF EC/DMC (1:1 w/w) 

ial (V vs. Li/Li

Rate Capability of C/Sn Thin­Film Electrodes

1.2 5C 1C C/5 C/10

1.0 C/25

0.8

0.6

0.4 0 4 1.2 M LiPF6 EC/DMC (1:1 w/w) Scan rate 0.1 mVs­1

0.2

The electrode was charged at C/100.0

0 100 200 300 400

Discharge Capacty (mAh/g)

• The C/Sn thin­film anode shows significantly improved rate capability

• Fine dispersion of Sn particles within the carbon matrix, high porosity and network­like 3D architecture contribute to faster response of the electrode

Potenttial (V vs. Li/Li+)

electrochemical behaviorelectrochemical behavior

Conclusions

•• We demonstrated a novelWe demonstrated a novel syntsyn heh sissi tet chnch iqi ueu fof r tr heht e s  e n q e o t eproduction ofproduction of nanonano­­composite anodes foco rmposite anodes for LiLi­­ioi non bab ttt ere iei sa t r es

•• C/C/SnSn binderlessbinderless thinthin­­filmsfilms canca beb mam nun faf ctuct rer d id nn e a u a u e in a fa asta ,f st,inexpensive, singleinexpensive, single­­stepstep prop cessce ono ana y ty  ypeyp oforo ss  n n t e f subsu strst ata eb r te

•• ThinThin­­filmfilm C/C/SnSn anodes display signia fif canca tlt y iy  mpm ror vedvenodes display signi i n l i p o delectrochemical behaviorelectrochemical behavior

•• NNanoano­­structuredstructured C/C/SnSn anodes amelia oro ata e te heh did mem nsin ono alanodes ameli r t t e i e si n lchanges andchanges and retain good electronic contact betwer ene tht e ae ctict veetain good electronic contact betwe n h a ivematerial and the currentmaterial and the current colco lel ctoct rl e or

•• The significant improvement inThe significant improvement in cyclecycl aba ili iti ye b l ty isis ata trt ibi utu ede tott r b t d o tht ehehigh porosity and fine dispersion ofhigh porosity and fine dispersion of SnSn ini 3n 3­­D caD rbr ono mam trt ixica b n a r x

• A roach

Summary

• Fundamental research for improved batteries

� Nanomaterials for new generation Li­ion batteries

� Diagnostic studies of detrimental processes in Li­ion cells

� Interfacial processes – fundamental studies of processes at the electrode surface

• Approachpp

� Use MPACVD to produce 3­D nano­structured C/Me thin film electrodes

� Innovative use of in situ and ex situ spectroscopic, microscopic, X­ray, and related techniques to charcaterize Li­ion electrodes

• Accomplishments

� New synthesis routes for better materials and new electrode designs

� Demonstrated important electrochemical behavior of carbonadditives in high voltage cathodes

•

Future Work

• Study mass and charge transfer mechanisms through the electrolyte/HOPG interface and lithium diffusion in graphite � Design, construct and apply and electrochemical cell of the Devanathan­

Stachurski type to study kinetics of Li intercalation and diffusion

� Study possible correlations between formation and physico­chemical properties of the SEI layer

• Apply in situ and ex situ instrumental methods to detect and Apply in situ and ex situ instrumental methods to detect and characterize surface processes in Li­ion electrodes � Cooperate with the BATT Interfacial Studies Group to investigate the

structure and morphology of carbons and the corresponding SEI layer

� In situ studies of surface processes at model electrodes (collaboration with S. Whittingham)

• Develop plasma deposition techniques to synthesize nano­composite C/Sn­Me and C­Si thin­film anodes � Evaluate vacuum deposition techniques to produce new electrodes

architectures and compositions

4. Marie Kerlau Marek Marcinek Venkat Srinivasan Robert M. Kostecki "Studies of Local

­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­

Publications and Patents

1. Marca M. Doeff, James D. Wilcox, Rong Yu, Albert Aumentado, Marek Marcinek and Robert Kostecki, “Impact of Carbon Structure and Morphology on the Electrochemical Performance of LiFePO4/C Composites”, J. Solid State Electrochem., accepted

2. M. Marcinek, L. J. Hardwick, T. J. Richardson, X. Song and R. Kostecki, “Microwave Plasma Chemical Vapor Deposition of Nano­Structured Sn/C Composite Thin­Film Anodes for Li­ion Batteries”, J. Power Sources, 173, 965 (2007)

3. Marek Marcinek , Xiangyun Song, and Robert Kostecki, “Microwave Plasma Chemical Vapor Deposition of Nano­Composite C/Pt Thin­Films”, Electrochem. Commun., 9, 1739 (2007)

4. Marie Kerlau,, Marek Marcinek,, Venkat Srinivasan,, Robert M. Kostecki, "Studies of Local , Degradation Phenomena in Composite Cathodes for Lithium­Ion Batteries”, Electrochimica Acta, 52, 5422 (2007)

5. James D. Wilcox, Marca M. Doeff, Marek Marcinek, Robert Kostecki, “Factors Influencing the Quality of Carbon Coatings on LiFePO4”, J. Electrochem. Soc. 154, A389­A395, (2007)

6. Marie Kerlau, Marek Marcinek, Robert Kostecki, “Diagnostic Evaluation of Detrimental Phenomena in 13C­labeled Composite Cathodes for Li­ion Batteries”, J. Power Sources, accepted, 174, 1046 (2007)

1. Robert Kostecki, Marek Marcinek, “Graphitized Carbon Coatings for Composite Electrodes”, US Patent Application, IB­2176PCT

Acknowledgements

Laurence Hardwick Marek Marcinek Tom Richardson Xiangyun Song

DOE/EERE Office of Vehicle Technologies

National Center for Electron Microscopy at LBNL