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Graphite Intercalation with Large Fluoroanions Dept. of Chemistry and Center for Advanced Materials, Oregon State University.

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Presentation on theme: "Graphite Intercalation with Large Fluoroanions Dept. of Chemistry and Center for Advanced Materials, Oregon State University."— Presentation transcript:

1 Graphite Intercalation with Large Fluoroanions Dept. of Chemistry and Center for Advanced Materials, Oregon State University

2 Oregon State University2 Intercalation

3 Oregon State University3 Intercalation Hosts Ion exchange: (fixed charge density) smectite clayNa x+y [Al 2-y Mg y Si 4-x Al x O 10 (OH) 2 ] layered double hydroxide[Mg 3 Al(OH) 8 ]Cl metal phosphorous sulfideK 0.4 [Mn 0.8  0.2 PS 3 ] Redox reaction: (variable charge density) metal dichalocogenideLi x [MoS 2 ] layered oxidesLi x [CoO 2 ], Na x [MoO 3 ] graphiteK[C 8 ], [C 24 ]HF 2

4 Oregon State University4 Energetics For clays – reaction is ion-exchange: Na + Mont - + N(R) 4 + Cl - (aqu) -> N(R) 4 + Mont - + NaCl (aqu) For graphite – reaction is redox: C x + A -> C x + A - ΔH rxn = I (C x ) - E a (A) - ΔH L

5 Oregon State University5 Graphite structure C-C in-plane = 1.42 Å Usually (AB) n hexgonal stacking Interlayer distance = Å Source: A B A Graphite is a semi-metal, chemically stable, light, strong

6 Oregon State University6 Graphite Intercalation oxidant This is an acceptor-type GIC Donor-type reduces layers and intercalates cations

7 Oregon State University7 GIC types Reduction M + C x - Group 1 except Na Oxidation C x + An - F, Br 3 -, O (OH) BF 4 -, P  BiF 6 -, GeF 6 2- to PbF 6 2-, MoF 6 -, NiF 6 2-, TaF 6 -, Re  PtF 6 - SO 4 -, NO 3 -, ClO 4 -, IO 3 -, VO 4 3-, CrO 4 2- AlCl 4 -, GaCl 4 -,FeCl 4 -, ZrCl 6 -,TaCl 6 -

8 Oregon State University8 Staging and dimensions I c = d i + (n - 1) (3.354 Å) For fluoro, oxometallates d i ≈ 8 A, for chlorometallates d i ≈ 9-10 A

9 Oregon State University9 Graphite oxidation potentials H 2 O oxidation potential vs Hammett acidity Colored regions show the electrochemical potential for GIC stages. 49% hydrofluoric acid All GICs are unstable in ambient atmosphere, they oxidize H 2 O

10 Oregon State University10 GIC special issues Anions must be oxidatively stable Larger anions could give larger galleries, wider range of chemistry GICs that rapidly decompose in air or aqueous acid are hard to process further

11 Oregon State University11 C x PFOS - preparation C x + K 2 Mn(IV)F 6 + KSO 3 C 8 F 17  C x SO 3 C 8 F 17 + K 3 Mn(III)F 6 (C x PFOS) Solvent = aqueous HF 3.35 A

12 Oregon State University12 C x PFOS intercalate structure Anions self- assemble as bilayers within graphite galleries

13 Oregon State University13 PFOS twist angle Chain twist defined by FC-CF tortion angle

14 Oregon State University14 C x PFOS thermal stability KPFOS C x PFOS

15 New syntheses: chemical method N S O O CF 3 S O O F3CF3C.. C x + K 2 MnF 6 + LiN(SO 2 CF 3 ) 2 C x N(SO 2 CF 3 ) 2 + K 2 LiMnF 6 oxidant anion source GIC 1, % hydrofluoric acid, ambient conditions 2. hexane, air dry Oxidant and anion source are separate and changeable. Surprising stability in 50% aqueous acid.

16 Oregon State University16 C x N(SO 2 CF 3 ) 2 chem prepn

17 New syntheses: N(SO 2 CF 3 ) 2 orientation FFFF

18 Oregon State University18 C x N(SO 2 CF 3 ) 2 echem prepn 2  1 3  2

19 Oregon State University19 C x N(SO 2 CF 3 ) 2 - echem prepn C x PFOS C x N(SO 2 CF 3 ) 2

20 Oregon State University20 C x N(SO 2 CF 3 ) 2 anion orientation

21 Oregon State University21 C x N(SO 2 CF 3 ) 2 thermal stability LiN(SO 2 CF 3 ) 2

22 Oregon State University22 Imide (NR 2 - ) intercalates Anion MW d i / Å N(SO 2 CF 3 ) N(SO 2 C 2 F 5 ) N(SO 2 CF 3 ) (SO 2 C 4 F 9 )

23 Oregon State University23 Other intercalated anions Anion MW d i / Å C(SO 2 CF 3 ) SO 3 C 8 F SO 3 C 10 F SO 3 C 6 F 10 (C 2 F 5 )

24 nm C x B(O 2 C 2 O(CF 3 ) 2 ) 2 Stage nm Stage 1 C x B(O 2 C 2 (CF 3 ) 4 ) 2 Borate chelate GIC’s Blue: obs Pink: calc Unexpected anion orientation - long axis to sheets T

25 Oregon State University25 Intercalation rates Intercalate Temp / °CReaction Anion half-life / h SO 3 C 8 F N(SO 2 CF 3 ) N(SO 2 CF 3 )(SO 2 C 4 F 9 ) N(SO 2 CF 2 CF 3 ) C(SO 2 CF 3 ) 3 70> 1000 SO 3 C 6 F 5 20, 70no reaction

26 Oregon State University26 GIC ambient stabilities

27 Oregon State University27 Application - IRP strategy 1. Intercalation 2. Removal 3. Optional cycle Targets 1.increase internal volume and disorder not surface area 2.low residual content Parameters: intercalate anion, reduction method (thermolysis, hydrolysis, hydrogenation)

28 Oregon State University28 IRP charge-discharge GIC is CxPFOS stage 2 removal is by heating under N 2 for 3 h rate = C / 20 irrevreversible

29 Oregon State University29 IRP for Li ion battery anodes e - + C x + Li + = C x Li


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