Lithium Iodide Battery

Lithium Iodide. Lithium iodide [10377-51 -2/, Lil, is the most difficult lithium halide to prepare and has few appHcations. Aqueous solutions of the salt can be prepared by carehil neutralization of hydroiodic acid with lithium carbonate or lithium hydroxide. Concentration of the aqueous solution leads successively to the trihydrate [7790-22-9] dihydrate [17023-25-5] and monohydrate [17023-24 ] which melt congmendy at 75, 79, and 130°C, respectively. The anhydrous salt can be obtained by carehil removal of water under vacuum, but because of the strong tendency to oxidize and eliminate iodine which occurs on heating the salt ia air, it is often prepared from reactions of lithium metal or lithium hydride with iodine ia organic solvents. The salt is extremely soluble ia water (62.6 wt % at 25°C) (59) and the solutions have extremely low vapor pressures (60). Lithium iodide is used as an electrolyte ia selected lithium battery appHcations, where it is formed in situ from reaction of lithium metal with iodine. It can also be a component of low melting molten salts and as a catalyst ia aldol condensations. 

The demand for electrically operated tools or devices that can be handled independently of stationary power sources led to a variety of different battery systems which are chosen depending on the field of application. In the case of rare usage, e.g., for household electric torches or for long-term applications with low current consumption, such as watches or heart pacemakers, primary cells (zinc-carbon, alkaline-manganese or lithium-iodide cells) are chosen. For many applications such as starter batteries in cars, only rechargeable battery systems, e.g., lead accumulators, are reasonable with regard to costs and the environment. 

Lithium iodide is the electrolyte in a number of specialist batteries, especially in implanted cardiac pacemakers. In this battery the anode is made of lithium metal. A conducting polymer of iodine and poly-2-vinyl pyridine (P2VP) is employed as cathode because iodine itself is not a good enough electronic conductor (Fig. 2.3a). The cell is fabricated by placing the Li anode in contact with the polyvinyl pyridine-iodine polymer. The lithium, being a reactive metal, immediately combines with the iodine in the polymer to form a thin layer of lithium iodide, Lil, which acts as the electrolyte ... 

In order for the battery to function, the lithium iodide must be able to transfer ions. Lil adopts the sodium chloride structure, and there are no open channels for ions to use. In fact, the cell operation is sustained by the Schottky defect population in the... 

Lithium iodide pacemaker batteries use lithum iodide as the electrolyte, separating the lithium anode and the iodine anode. The function of the electrolyte is to transport ions but not electrons. Lithium iodide achieves this by the transport of Li+ ions from the anode to the cathode. This transport is made possible by the presence of Li vacancies that are generated by the intrinsic Schottky defect population present in the solid. Lithium ions jump from vacancy to vacancy during battery operation. 

In addition to the liquid conductors described above, two types of solid-state ionic conductois have been developed one involves inorganic compounds and the other is based on polymeric materials. Several inorganic solids have been found to have excellent conductivity resulting wholly from ionic motion in the crystal lattice. One solid electrolyte, lithium iodide, Lil, has found application in heart-pacer batteries even though it has a fairly low conductivity. 

Lithium batteries are used in many portable consumer electronic devices and are also widely used in industry. The most common type of lithium cell used in consumer applications comprises metallic lithium as the anode and manganese dioxide as the cathode, with a Li salt such as Li perchlorate or Li tetrafluoroborate dissolved in an organic solvent. Lithium batteries find application in many long-life, critical devices such as cardiac pacemakers and other implantable electronic medical devices. These devices use special lithium-iodide batteries designed to last 15 years or more. Lithium batteries can be used in place of ordinary alkaline cells in many devices such as clocks and cameras. Although they are more expensive, lithium cells provide a much longer life, and thereby minimize battery replacement. 

The development of organic or inorganic lithium-ion conductor such as lithium super-ion conducting glass (LISICON). lithium iodide (Lit), solid polymer electrolytes(SPE) were activated with progress of a lithium battery. In these electrolytes, the technology of solid electrolyte is useful to improve the performance of batteries. 

Fig. 2.1 At beginning-of-life (BOL), the lithium iodide battery exhibits an output voltage of 2.8 V, which slowly decays until it nearly depletes, whereupon the voltage decays more rapidly. At around 2.0-2.4V, the elective replacement indicator is triggered, which usually leaves 6 months before the pulse generator will begin to behave abnormally as it reaches its end of useful life (EOL).

Lithium iodide batteries are also affected by extremes of cold or heat. Although these effects are not seen when a device is implanted, be aware that ... 

Iodine adducts of nylon-6 formed a battery with Li and lithium iodide solid electrolyte The current efficiency at 500 kil load was about 50% based on the iodine added. Activated carbon fibre (ACF) can also be doped to form a battery with Li ... 

A dry cell is not truly dry, because the electrolyte is an aqueous paste. Solid-state batteries have been developed, however. One of these is a lithium-iodine battery, a voltaic cell in which the anode is lithium metal and the cathode is an I2 complex. These solid-state electrodes are separated by a thin crystalline layer of lithium iodide (Figure 20.11). Current is carried through the crystal by diffusion of Li" ions. Although the cell has high resistance and therefore low current, the battery is very reliable and is used to power heart pacemakers. The battery is implanted within the patient s chest and lasts about ten years before it has to be replaced. 

The anode is lithium metal and the cathode is a complex of iodine, I2 the electrodes are separated by a thin crystalline layer of lithium iodide.The battery consists of two cells enclosed in a titanium shell. 

One example is the lithium iodide electrolyte in a typical cardiac pacemaker battery. Another one is the mixture of lithium halides with - for immobilization -magnesium oxide in some thermal batteries, and a further one a mixture of lithium iodide with aluminium oxide or silica for some memory back-up systems. 

The first lithium/iodine cardiac pacemaker battery was implanted in 1972. This type of battery proved to be very successful in this field and for other applications, too. The special features of this solid state battery are explained with its technique, which is limited with its extremely high energy density and reliability, especially for low rate applications. This technique is based firstly on the electrode couple of lithium and iodine with its high energy content - the OCV of the lithium/iodine cell is 2.80 V -and secondly on the favorable fact that the product of the cell reaction, the lithium iodide (LiJ), forms very tight and continuous layers between the active material of the electrodes, which are acceptable ionic conductors with negligible electronic... 

The Li/FeS2 battery uses lithium for the anode, iron disulfide for the cathode, and lithium iodide in an organic solvent blend as the electrolyte. The cell reactions are... 

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