Discharge Reaction Mechanisms in Li / SOCl2 Cells

Abstract

The processes taking place during the discharge of Li/SOC12/C cells were studied. Test vehicles included wound D, bobbin configuration 2D cells, and 2000 A-hr prismatic cells. Dried cathodes taken from 2D cells, discharged at 150 mA were analyzed quantitatively for lithium-sulfur oxyaeid salts. Little or no such salt was found for cells discharged at ambient temperature. Measurements of the open-circuit voltage of this system as a function of temperature showed essentially linear dependence with positive slope between ~-72 ~ and --20~ but the voltage fell more steeply as the temperature approached --60~Appearance of a nonvolatile reducing species occurred in the cathodes of cells discharged at --20~ which were not present in cathodes from cells discharged at higher temperature. Controlled potential electrolysis of supporting electrolytes containing limited amounts of SOCI.~ were carried out between 0 ~ and 25~ The electrical equivalent of thionyl chloride was found to be between 1.5 and 2.0 F/mole. The 200,0 A-hr cells were used to measure dissolved SO2 and SO2 escaping at atmospheric pressure and ambient temperature from anode-limited and cathode-limited cells. The amount of SO2 produced was found to be only a fraction of that predicted by 4Li ~-2SOCls -+ S § SO2 + 4LiC1 until near the end of discharge. The total amount of SOs produced by the end of discharge was not more than predicted by this reaction. Vented, anode-limited cells did not release SO2 while cathode-limited cells did. Temperature cycling of electrolyte taken from cells immediately after discharge was carried out in a sealed vessel. Pressure hysteresis occurred, which could not be duplicated with simulated used electrolyte made with S, SOs, SOC12, LiA1C14, and cathode material. At --20~ and below, the discharge reaction 8Li + 3SOCls-~ 2S ~-Li2SO8 ~-6LiC1 may be significant, while at temperatures higher than this, the reaction 2nLi + nSOC12-~ 2nLiC1 + (SO), may predominate, where the (SO)n remains in solution. Slow decomposition according to (SO)h-> (n/2)S + (n/2)SOz may subsequently take place.

Pushing the Theoretical Limit of Li-CFx Batteries: A Tale of Bifunctional Electrolyte

“…The concept of a bifunctional electrolyte will be in stark contrast to the SOCl 2 catholytes utilized in the Li-SOCl 2 batteries where the electrolyte is the cathode that is active at all potentials and relies on a LiCl passive film to maintain stability with the anode . The Li-CF x battery system offers one of the best energy densities with up to 7 times the capacity of LiCoO 2 -based Li-ion system, a conventional Li-ion battery cathode, and up to 2 times the capacity of thionyl chloride, the nearest energy dense primary cathode .…”

Transforming a Primary Li-SOCl2 Battery into a High-Power Rechargeable System via Molecular Catalysis

“…Li-SOCl 2 batteries, which are the classic primary cells, are receiving renewed scientific and industrial interest , due to their low flammability and high energy densities (>700 Wh kg –1 ) over a wide operating temperature range (from −60 to 150 °C), thus outperforming state-of-the-art Li-ion batteries. − However, the poor reversibility of the cathode reaction hinders their further application. , Li-SOCl 2 batteries typically use porous carbon cathodes to store the discharge products. Upon discharging, the reduction of the catholyte SOCl 2 to S, SO 2 , and LiCl occurs in one step at the carbon cathode. − During charging, the electrochemical oxidation of LiCl proceeds via the formation of Cl 2 as an intermediate, undergoing a series of chemical reactions to partially regenerate SOCl 2 (see Section Charging Mechanism of the Li-SOCl 2 /I 2 System).…”

A Rechargeable K/Br Battery

“…It is widely used in military, aerospace, and civil equipment due to its highest specific energy (590 Wh kg −1 ) of all commercial batteries, high operating voltage (≈3.6 V), and long shelf life (>10 years). [ 1–3 ] Another unique attribute of the Li/SOCl 2 battery is its constant voltage over the entire discharge cycle. However, Li/SOCl 2 battery cannot be recharged after discharging.…”