Reactions at the interface between multi-component glasses and metallic lithium films
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C. H. F. Peden Inorganic Materials Chemistry Division, Sandia National Laboratories, Albuquerque, New Mexico 87185-5800 (Received 24 October 1988; accepted 15 February 1989)
The reactions of vacuum deposited thin films of lithium with various complex glasses have been explored using x-ray photoelectron spectroscopy (XPS). In contrast to lithium reactions with simple glasses such as silica or boron oxides, the reactions are predominantly those of the network modifiers such as sodium, potassium, and magnesium. XPS and x-ray induced Auger lineshapes indicate the migration of the network modifier to the near surface region followed by its reduction. In the case of magnesium, there is evidence for stable alloy formation with unreacted lithium following these migration and reduction steps.
I. INTRODUCTION
GLASS INSULATOR:
Tailored composition silicate and boro-aluminate glasses have found widespread application as insulators and separators in high energy density battery systems.1"2 Glass composition can be adjusted to optimize specific physical and chemical properties by varying the types and amounts of network forming and modifying components. The most critical and least understood property of these glasses for electrochemical application is their corrosion resistance when in the presence of an active metal like lithium, a strong reductant (Fig. 1). Induced corrosion of glasses is observed when the glass is held at a potential which corresponds to that of Li + /Li° or an equivalent alkali metal,2 and lithium buildup can occur at the interfacial region between a given glass and the metal.3 Two models exist which attempt to explain these observations of accelerated corrosion and lithium buildup: (a) a direct reduction/ spontaneous electrochemical alloying model4 and (b) an underpotential deposition (UPD) model.5 Little information has been published pertaining to the reaction products formed when pure lithium comes into contact with a glass surface with a complex composition. However, corrosion studies indicate that overall corrosion resistance scales with decreases in silica content within a series of multicomponent glasses.6 We have chosen to model this corrosion process by deposition of lithium overlayers on fresh fractured substrate glasses (Table I). The glasses of interest as insulators or separators include TA-23 (a boro-alumino-silicate), and members of the CABAL family (calcium boro-aluminates). The response of a complex multi-component glass can be better understood by evaluating that of simpler compositional analogs. As a result, a variety of silicates and aluminosilicates have been included in this study. The properties of a)
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J. Mater. Res., Vol. 4, No. 4, Jul/Aug 1989
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Passivation Layer
Corrosion product SO2/CH3CN/Li +
GLASS SEPARATOR:
Li Anode
Glass mat -*W///////M7MA
Electrolyte
Cathode FIG. 1. Schematic of applications where lithium/glass interfaces are formed.
a glass are also determined by the
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