Polycarbon monofluoride

Lithium CFj. The Li/CF rbattery consists of a lithium anode, polycarbon monofluoride cathode, and microporous polypropylene separator saturated with organic electrolyte. These batteries are used as power sources for watches, portable calculators, memory applications, and so on. 

Carbon fluoride [also known as carbon monofluoride, polycarbon monofluoride, graphite fluoride, or (CFx)n] is a solid, layered, non-stoichiometric fluorocarbon of empirical formula CFX, where 0 < x < 1.25, obtained by the action of elemental fluorine on carbon. Fluorine combines with carbon and yields three solid compounds CFX, C2FX, and C4FX as well as varying amounts of volatile fluorocarbons as byproducts. With appropriate selection of fluorination conditions nearly 100% conversion of carbon to carbon tetrafluoride can occur. 

An ideal kinetic study would be made under conditions where the product is only graphite fluoride or polycarbon monofluoride with no byproducts formed. In terms of reaction kinetics, one method to follow the reaction is to measure the weight change as a function of the reaction time. Using this method the reaction rate of fluorine with carbon can be evaluated. Various carbon structures have been employed with sufficient fluorination contact time provided at a particular temperature for the carbon to reach fluorine saturation. The weight increase vs the temperature can be monitored at atmospheric pressure. Figure 515 shows the carbon structure and the temperature dependency of the fluorination reaction of various graphites. 

Fully fluorinated carbons with the empirical formula CFX (where x > 1) arc hydrophobic, snow-white in color, and inert towards strong acids (aqua regia, hydroiodic acid), strong alkalis and nascent hydrogen. They are also insoluble in organic solvents. Polycarbon monofluoride or CF, u is a crcam-colored material, a very poor conductor, and has properties close to CFX where x > 1. 

Polycarbon monofluoride is also known as carbon fluoride or graphite fluoride. This material is of strategic importance for the industrialized nations. It plays a very important role due to its unique properties which have been responsible for its large industrial demand. The chemists have not settled their scores to confirm whether it is inorganic or organic compound but one thing is sure that the industry is exploring this compound continuously. 

Lithium-polycarbonate-monofluoride batteries are widely used in consumer electronics that require low to moderate power, military communications, RFID, transportation, automated meter readings, and medical defibrillators. 

The active components of the cell are lithium for the anode and polycarbon monofluoride (CF) for the cathode. The value of is typically 0.9 to 1.2. Carbon monofluoride is an interstitial compound, formed by the reaction between carbon powder and fluorine gas. While electrochemically active, the material is chemically stable in the organic electrolyte and does not thermally decompose up to 400" C, resulting in a long storage life. Different electrolytes have been used typical electrolytes are lithium hexafluorarsenate (LiAsFg) in S-butyrolactone (GBL) or lithium tetrafluoroborate (LiBFJ in propylene carbonate (PC) and dimethoxyethane (DME). 

Figure 14.61 shows the constraction of a coin-type battery. The Li/(CF) cells are typically constracted with an anode of lithium foil roUed onto a collector and a cathode of Teflon-bonded polycarbon monofluoride and acetylene black on a nickel collector. Nickel-plated steel or stainless steel is used for the case material. The coin cells are crimped-sealed using a polypropylene gasket. 

Fluorination of graphite leads to a polycarbon monofluoride of ideal composition CF. Incompletely fluorinated samples with compositions CFq. . .. o.s are nearly black while those of compositions CFo.g 0.95 and CF0.95... 1.13 are grey and white, respectively. Carbon monofluoride was found to be a superior lubricant especially at high temperatures and in oxidizing atmospheres [404]. CF is used... 

There is good reason to assume that fluoro-Grignards form as part of the PIR in the condensed phase with Mg/PTFE and Mg/PMF (polycarbon monofluoride) [9, 29]. Samples of both Mg/PTFE and Mg/PME heated just above their observed PIR-onset temperature (500 and 520°C) show signals in the FTIR spectrum (Figures 6.2 and 6.3), which can be assigned to a C-Mg-F units. After further exposure of the samples at T > 700 °C, these stmctures disappear and characteristic vibrations for MgF2 are seen in both samples. 

Figure 56.19 Capacity retention of Eagle Richer lithium-polycarbon monofluoride (LDFS) and lithium-thionyl chloride (LTC) batteries (Courtesy of Eagle Richer)...

These researches opened the door to the fabrication and commercialization of varieties of primary hthium batteries since the late l%0s nonaqueous hthium cells, especially the 3-V primary systems, have been developed. These systems include lithium-sulfur dioxide (Li//S02) cehs, lithium-polycarbon monofluoride (Li//(CF t) ) cells introduced by Matsuschita in 1973, lithium-manganese oxide (Li//Mn02) cells commercialized by Sanyo in 1975, lithium-copper oxide (Li//CuO) cells, lithium-iodine (Li//(P2VP)1J cells. During the same period, molten salt systems (LiCl-KCl eutecticum) using a Li-Al alloy anode and a FeS cathode were introduced [1]. The lithium-iodine battery has been used to power more than four million cardiac pacemakers since its introduction in 1972. During this time the lithium-iodine system has established a record of reliability and performance unsurpassed by any other electrochemical power source [18]. 

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