Graphite intercalation compounds containing fluoroanions

New chemical synthesis strategies have been investigated for the preparation of acceptor-type graphite intercalation compounds (GIC's) with fluoroanions in order to obtain new materials and to develop a better understanding of the synthetic approaches and properties of the products. New GIC's containing borate chelate anion such as bis(oxalato)borate, CxB[OC(O)C(O)O]₂•δF, are prepared by the chemical oxidation of graphite with fluorine gas in the presence of a solution containing the intercalate anion in anhydrous hydrofluoric acid. Due to the chemical method employed (F₂/AHF as the oxidizing agent), fluoride co-intercalates are present in the galleries. The GIC's compositions are determined using a newly-developed digestion method with an ion-selective electrode and potentiometer. The composition parameters x and δ are obtained using both elemental and thermogravimetric analyses (TGA). Elemental analyses of B and F for a stage 1 GIC indicate x [approximately equal to] 41 and δ [approximately equal to] 4. Powder XRD data and the structural refinement of these GIC's show that the intercalate anions "stand up" in the galleries, with the longer anion dimension oriented perpendicular to the graphene sheets, leading to the relatively large gallery height of di [approximately equal to] 1.42 nm. The same chemical synthesis strategy is also used for chemical preparations of other two borate chelate GIC's; bis(perfluoropinacolato)borate, CxB[OC(CF₃)₂C(CF3)₂O]₂•δF, and bis(hexafluorohydroxyisobutyrato)borate, CxB[OC(CF₃)₂C(O)O]₂•δF. Stage 1 GIC's of these anions are obtained with the gallery height, di, of 1.43-1.45 nm. The fluoride co-intercalate contents in these GIC samples are also determined. The composition parameters x and δ are obtained using elemental analyses for stage 1 CxB[OC(CF₃)₂C(CF₃)₂O]2•δF and for stage 1 CxB[OC(CF₃)₂C(O)O]₂•δF. TGA cannot be used to confirm these compositions due to the incomplete degradation of intercalates. Most likely, anions and their degradation products are trapped in the bulk of the large flaky graphite particles. The detailed compositions of GIC's containing bis(trifluoromethanesulfonyl) imide, CxN(SO₂CF₃)₂•δF, and perfluorooctanesulfonate, CxC₈F₁₇SO₃•δF and fluoride co-intercalates are determined for the first time. These GIC's are prepared in aqueous HF, using K₂MnF₆ as the oxidizing agent. The fluoride co-intercalate content is approximately equimolar to anion content in both GIC's. For CxN(SO₂CF₃)₂•δF, the fluoride content increases steadily with reaction time while the anion content is relatively constant. In contrast, CxC₈F₁₇SO₃•δF shows little change in the fluoride content over time

Analysis of bis(trifluoromethylsulfonyl)imide-doped paramagnetic graphite intercalation compound using F-19 very fast magic angle spinning nuclear magnetic resonance

F atoms bonding to paramagnetic/conductive graphene layers in accepter-type graphite intercalation compounds (GICs) are analyzed using very fast magic angle spinning nuclear magnetic resonance, which is applied for the first time on F-19 nuclei to investigate paramagnetic materials. In the bis(trifluoromethylsulfonyl)imide(TFSI)-doped GIC, C-F bonds between fluorine atoms and graphene layers conform to a weak bonding of F to the graphene sheets. TFSI anions intercalated in the GIC do not show overall molecular motion; even at room temperature only the CF3 groups rotate