Lithium/cobalt sulfide pulse power battery

Abstract

PurposeMolten salt batteries are suitable for pulse power applications because of the low effective internal impedance. This paper deals with a bipolar battery having a Li alloy anode, COS, cathode material, and electrolyte of mixed Li halides. The system is semi-dry because the amount of electrolyte is limited.Fundamental investigations to determine operating voltage limits, active material utilizations, capacity ratios, states of charge, and capacity reserves need to be determined in semi-dry conditions to be unequivocal. This requirement precludes a reference electrode and, instead, the function of a counter-electrode and reference electrodes were combined. This paper describes methods and shows comparisons with literature voltammetry data and use of galvanostatic procedures. The results obtained with several Li alloys and with COS, electrodes are discussed along with application of these electrochemical design of pulse batteries. IntroductionMolten salt electrolyte batteries have become candidates for pulse power because they have low effective internal impedances l . These attributes are due in part to the electrochemical reaction rates at the elevated temperatures and enhanced further by the selection of the couples and the electrolyte.The system of interest to us includes an anode of a lithium alloy, a COS, cathode (that is reduced with the concurrent production of Li ,S) and an electrolyte of mixed binary halides having a single cation which is the Lit ion. The laws of conservation of matter and charge precludes concentration gradients in the electrolyte2.Deploying this electrochemical system in a bipolar arrangement minimizes both ohmic drops in the intercell connections and weight because the cell wall serves the dual function of wall and intercell connector. As an intercell connector the bipolar wall has a large cross sectional area and a short length resulting in minimization of the ohmic drop3.The bipolar arrangement requires that a common electrolyte pathway between cells in aseries stack be avoided; such afault gives rise to intercell leakage currents causing non-uniformities between cells. Making the cells semi-dry, and treating the bipolar wall edge minimizes electrolyte creep thereby preventing the establishment of common electrolyte pathways. The semi-dry concepr was originally used to stabilize the nonbonded separator. In the experimental work here the separator consists of a pressed pellet of MgO and electrolyte. The anode and cathode were similarly made of active material and electrolyte which were pelletized.Molten salt batteries have been modeled for pulse power applications5 with inductive loads and for capacitative charging. In order to study discharge of the several plateaus and the subsequent charging to increase energy and power outputs, some additional information is needed.Voltage limits on charge are necessary to avoid electrolysis. Similarly, voltage limits on discharge set the electrochemical processes of each electrode within the cell.Modified constant potential charges are envi...

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