Electrolytic degradation of sodium beta'' alumina

Thesis/Dissertation · Fri Jan 01 04:00:00 EST 1982

OSTI ID:6311465

Feldman, L A

Electrolytic degradation of sodium beta'' alumina solid electrolytes is of great importance in determining the ultimate lifetime of sodium-sulfur batteries. Experimental observations have been made on the material in short term tests. Various aspects point out the nature of breakdown, confirming the mechanism of dendritic penetration of sodium, including observation of sodium relics in cracks, sodium extrusion from cracks, measurement of a breakdown threshold at the melting point of sodium, temperature dependence of the critical current density below 100/sup 0/C, resistance drop at the critical current density, and observation of dendrites in degraded material using a silver nitrate decoration technique. A similar decoration technique also has been found useful for observing the current inhomogeneity at a beta'' alumina/aqueous electrolyte interface. Further development of some aspects of current focusing models for dendritic (Mode I) degradation is presented, showing the relation between current density, crack length, and stress intensity factor. Use of the degradation decoration applied to commercial beta alumina tubes from sodium-sulfur test cells shows unusual features indicative of sodium crack penetration into the tube walls. In these samples, observations are also made of fine scale sodium distribution which is evidence for a new mode (Mode II) of slow degradation involving electron conduction and formation of metal aheand of the dendrite.

• OSTI ID: 6311465
• Country of Publication: United States
• Language: English

Related Subjects

25 ENERGY STORAGE
250903* -- Energy Storage-- Batteries-- Materials
Components
& Auxiliaries
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
BREAKDOWN
CHALCOGENIDES
CRACK PROPAGATION
CRYSTALS
CURRENT DENSITY
DENDRITES
ELECTRIC BATTERIES
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELECTROCHEMICAL CELLS
ELECTROLYTES
LIFETIME
METAL-NONMETAL BATTERIES
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
SODIUM-SULFUR BATTERIES
SOLID ELECTROLYTES
TEMPERATURE DEPENDENCE