The electrochemical and optical properties of lithium phosphorous oxynitride (Lipon) thin films have been studied with an emphasis on the stability window vs. lithium metal and the behavior of the Li/Lipon interface. Impedance measurements made between -26 and 140°C show that Lipon exhibits a single, Lit-ion conducting phase with an average conductivity of 2.3 (±07) X 10' S/cm at 25°C and an average activation energy of E, = 0.55 0.02 eV. No detectable reaction or degradation was evident at the Li/Lipon interface, and linear sweep voltammetry measurements on three-electrode cells indicated that Lipon is stable from 0 to about 5.5 V with respect to a Li7Li reference. The complex refractive index of Lipon was measured by spectroscopic ellipsometry. Optical bandgaps of 3.45 and 3.75 eV were obtained from the ellipsometry data and from optical absorption measurements, respectively.

Research over the last decade at Oak Ridge National Laboratory has led to the development of solid-state thin-film lithium and lithium-ion batteries. The batteries, which are less than 15 mm thick, have important applications in a variety of consumer and medical products, and they are useful research tools in characterizing the properties of lithium intercalation compounds in thin-film form. The batteries consist of cathodes that are crystalline or nanocrystalline oxide-based lithium intercalation compounds such as LiCoO and LiMn O , and anodes of lithium metal, inorganic compounds such as can deliver up to 30% of their maximum capacity between 4.2 and 3 V at discharge currents of 10 mA / cm , and at more moderate discharge-charge rates, the capacity decreases by negligible amounts over thousands of cycles. Thin films of crystalline lithium manganese oxide with the general composition Li Mn O exhibit on the initial charge significant 11x 22y 4 capacity at 5 V and, depending on the deposition process, at 4.6 V as well, as a consequence of the manganese deficiency-lithium excess. The 5-V plateau is believed to be due to oxidation Mn of ions to valence states higher than 1 4 accompanied by a rearrangement of the lattice. The gap between the discharge-charge curves of cells with as-deposited nanocrystalline Li Mn O cathodes is due to a true hysteresis as opposed to a kinetically hindered relaxation observed 11x 22y 4with the highly crystalline films. This behavior was confirmed by observing classic scanning curves on charge and discharge 1 at intermediate stages of insertion and extraction of Li ions. Extended cycling of lithium cells with these cathodes at 25 and 1008C leads to grain growth and evolution of the charge-discharge profiles toward those characteristic of well crystallized films.

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It is an old concept to fabricate lithium batteries in the discharged state with only an appropriate current collector as the negative electrode (anode). On the initial charge, metallic Li is electroplated at this anode current collector, and so, during electrochemical cycling, the battery operates as a Li battery which contains only the amount of lithium that is supplied by the positive electrode (cathode).Despite some improvements, 1 the manufacture of a practical, rechargeable Li battery that operates exclusively with an in situ plated Li anode has been prevented by the formation of mossy, dendritic, and granular metallic lithium deposits on metal foils. 2 In this paper, we report on the feasibility and electrochemical properties of a Cu/solid lithium electrolyte/LiCoO 2 thin-film battery, where Cu represents an anode current collector that does not form intermetallic compounds with lithium. Prior to the initial charge, all of the battery components are stable in air for several hours, which facilitates handling and processing of this "Li-free" lithium battery.During operation, this Li-free battery shows the maximum potential and high rate capability inherent in a Li battery but avoids the major drawbacks of a battery fabricated with a Li metal anode. The vapor deposition of a metallic lithium film is more complicated than the deposition of other metal films that are less air sensitive, and due to the low melting point of lithium (181ЊC) a Li battery does not survive the 250ЊC solder reflow process commonly used to assemble electronic circuit boards. 3 In this paper, we demonstrate that the Li free battery with an in situ plated Li anode shows no signs of degradation after being heated at 250ЊC in air for 10 min in the Li-free state. Furthermore, complete stripping of the electroplated Li anode is reversible, and since no excess Li is present, the Li-free battery cannot be destroyed by overdischarging the LiCoO 2 cathode, in contrast to a conventional Li-LiCoO 2 battery.The Li-free battery prior to operation resembles a Li-ion battery, which is also assembled in its fully discharged state. However, the Li-free battery avoids the capacity problem inherent to tin oxide-and oxynitride-based insertion materials 3-7 which have recently been proposed as anodes for Li-ion cells. These anodes are known to consume, irreversibly, between 40 and 60% of the lithium inserted during their electrochemical activation in the initial cycle due to the formation of an amorphous matrix containing Li 2 O or Li 3 N. [3][4][5]8 Despite the technically high capacity of these anodes, between 600 and 700 mAh/g, the unsatisfactory ratio of reversible to irreversible capacity severely limits the utilization of the cathode, which serves as the Li-ion cell's initial lithium source. Recently, we showed that the cathode utilization could be improved by fabricating cathodeheavy cells in which a good deal of the total reversible cell capacity was obtained by electrochemical plating and stripping of metallic lithium from the overlithiated anode ...

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