Intercalation of graphite with antimony tetrachloride fluoride

Flexible,transparent and self-standing Sb doped SnO2(ATO) nanofiber films were successfully fabricated by means of a low-cost and scalable electrospinning process,with tin tetrachloride and antimony trichloride as precursors. The as-prepared ATO nanofiber films are typical interconnected nanofiber networks and show a single SnO2 rutile crystal structures. With increasing the calcination temperature from 520 ℃ to 700℃,the average diameter of ATO nanofibers decrease from 200 nm to 150 nm,but accompanied by an increase in the average diameter of ATO nanoparticles. Meanwhile,the transmittance of the ATO nanofiber film increases from 72% to 80%,while their resistance decreases from 5. 23 Ω·cm to 2. 20 Ω·cm. Importantly,after500 cycles of bending,the self-standing ATO nanofibers show no obvious electrical degradation. The ATO nanofiber films show promise for application in many fields,such as flexible liquid crystal displays,solar cells and flexible and transparent functional electronics.

The feasibility of modifying graphite, by intercalation, to reduce galvanic reactions in carbon fiber reinforced metal matrix composites is investigated. A nickel chloride intercalation compound and a reduced nickel chloride intercalation compound were prepared, and their electrochemical properties studied in deaerated 0.1 N . The open‐circuit potential of is about 0.500 V more positive than that of natural graphite while that of is about 700 V more negative than that of natural graphite. In the latter case, the potential difference relative to aluminum is reduced by about 50%. Distinct changes in the cathodic behavior of graphite upon intercalation and reduction are also observed. Results are discussed in terms of the effects of these changes on galvanic interactions with aluminum alloy Al 6061‐T6.

The intercalation of graphite by the third-transition-series metal hexafluorides has yielded the graphite salts, C/sub 8//sup +/OsF/sub 6//sup -/, C/sub 8//sup +/IrF/sub 6//sup -/ and C/sub 12//sup 2 +/PtF/sub 6//sup 2 -/. The fluoroplatinate salt represents the highest electron withdrawal from the graphite network yet achieved. Analogues to the Os and Ir salts have been obtained both by fluorination of Group V pentaflouride intercalates, C/sub 8/MF/sub 5/ (M = As, Sb), and by the interaction of the dioxygenyl salts with graphite (8C + O/sub 2/MF/sub 6/ ..-->.. C/sub 8/MF/sub 6/ + O/sub 2/+). Non-intercalating binary fluorides have been observed to intercalate in the presence of a fluorine-rich environment (e.g., 8C + PF/sub 5/ + 1/2 F/sub 2/ ..-->.. C/sub 8/PF/sub 6/). GeF/sub 4/, which also does not spontaneously intercalate graphite, has been observed to interact with graphite in the presence of 2 atmospheres of fluorine overpressure to give the fluoroplatinate salt analogue, C/sub 12//sup 2 +/GeF/sub 6//sup 2 -/. This material is in equilibrium with the pentafluorogermanate at ordinary pressures and temperatures. C/sub 12//sup 2 +/GeF/sub 6//sup 2 -/ ..-->.. C/sub 12//sup +/GeF/sub 5//sup -/ + 1/2 F/sub 2/. C/sub 12/GeF/sub 6/ must have an oxidizing potential close to that of fluorine itself. The graphite fluorometallate salts are both electronic and ionic (F/sup -/) conductors. For the C/sub 8//sup +/MF/sub 6//sup -/ salts, a maximum electronic conductivity an order of magnitude greater than the parent graphite has been observed for stage two. The high oxidizing potential, coupled with the fluoride ion transport capability of the graphite salts, has been exploited in the construction of solid-state galvanic cells. These cells use the graphite fluorometallate salts as electrode materials in combination with a superionic fluoride-ion-conducting solid electrolyte.

Introduction With the accelerated development of next-generation rechargeable batteries, graphite fluoride with high energy density and excellent discharge potential flatness into rechargeable batteries has recently become to attract attention as an active material. In particular, lithium-graphite fluoride rechargeable battery using graphite fluoride derived from natural graphite has been reported in a previous study, which has increased the feasibility of this system.1 The charge and discharge reactions of this system can be considered as follows.2 (CxF)n + nLi+ + ne- ⇆ xnC + nLiF (1)In charging process, carbon is fluorinated and graphite fluoride is formed. However, it has problems such as extremely fast degradation and increased potential hysteresis compared to lithium-ion batteries. These problems may be caused by the low conductivity and high dissociation energy of lithium fluoride. Another possible cause is the amorphous carbon formed when graphite fluoride is discharged, which is unfavorable for graphite fluoride compounds (F-GICs) formation. However, no detailed studies about F-GIC forming mechanism have been carried out, and further research is required.In this study, experiments were carried out using graphite fluoride composite electrodes. Furthermore, we used the composite electrode mixed with carbon and lithium fluoride as a model of discharge product of graphite fluoride. From these experiments, the aim is to clarify the electrochemical reaction mechanism of this system by investigating the influence of the size of lithium fluoride and the crystallinity of carbon on the electrochemical properties. Experimental methods First, in order to investigate the influence of lithium fluoride crystal size, graphite fluoride (CF) obtained by fluorinated scary graphite composite electrodes were prepared. The electrodes were first discharged to 1.5 V at a current density of 50 mA g- 1. Then, the electrodes were left at OCV for 1 hour or 1 week to prepare electrodes with different crystallinity of lithium fluoride.Second, in order to investigate the influence of the crystallinity of carbon, ball-milled and non-ball-milled natural graphite (SNO-15) were prepared and mixed with lithium fluoride, respectively, to produce carbon and lithium fluoride composite electrodes named WBMCL and WNBMCL electrodes, respectively.Two-electrode type coin cell was used for the electrochemical measurements. The composite electrodes were used as the working electrode and lithium metal was used as the counter electrode. The electrolyte was 5.8 mol dm- 3 LiBF4/sulfolane (C4H8O2S). Charge-discharge measurements were carried out at a current density of 50 mA g- 1 and in a voltage range of 1.5-5.3 V. Results and discussion (Effect of LiF size)XRD measurements were performed on cells left at OCV for 1 hour and 1 week after the first discharge of the CF composite electrode, showing that lithium fluoride crystal growth was more advanced on the electrode left for 1 week after discharge. To investigate the effect of lithium fluoride crystal size, charge-discharge experiments were carried out using these electrodes with different lithium fluoride crystal sizes. Charge-discharge curves are shown in Figure 1 (a). It was confirmed that there was not significant difference in reversible capacity between these two electrodes, and that the size of the lithium fluoride had no adverse effect on the charging of the lithium-graphite fluoride rechargeable battery. This result indicated the fact that partially dissolved fluoride ions from lithium fluoride react with carbon, rather than directly dissociating and reacting with lithium fluoride, which has a high dissociation energy.(Effect of crystallinity on the system)XRD measurements confirmed that ball-milled carbon was amorphous. To investigate the effect of carbon crystallinity, charge-discharge measurements of WBMCL and WNBMCL electrodes were carried out. Results are shown in Figure 1(b), (c). It was confirmed that the WBMCL composite electrode had a larger capacity. From these results, it can be inferred that graphite with high crystallinity is not suitable for charging lithium-graphite fluoride rechargeable batteries, and that amorphous carbon is more advantageous.In summary, on the charge-discharge reaction of lithium-graphite fluoride rechargeable batteries, the effect of carbon crystallinity was found to be more significant than the crystallite size of lithium fluoride. References 1) Ito, C. Lee, Y. Miyahara, S. Yamazaki, T. Yamada, K. Hiraga, T, Abe, and K. Miyazaki, Chem. Mater., 34, 8711-8718, (2022).2) Zhan, S. Yang, Y. Wang, Y. Wang, L. Ling, K, and X. Feng, Adv. Mater. Interfaces., 1, 4, (2014). Figure 1