THE USE OF POLYDISULFIDES AND COPOLYMERIC DISULFIDES IN THE LI/PEO/SRPE BATTERY SYSTEM

Solid redox polymerization electrodes (SRPEs) have recently been used successfully as cathodes in lithium solid polymer electrolyte batteries. SRPEs contain organopolydisulfides, (SRS)n, as the electroactive material; upon cell discharge these materials are reductively depolymerized via scission of the disulfide linkages to di- or trithiolate salts. The thiolate salts are reoxidized to the polymeric disulfides when the cell is recharged. Organopolydisulfides are easily synthesized via a one-step process, are inexpensive, and exhibit high performance levels in batteries. A characteristic unique to the SRPE is the facile modification of physical and electrochemical properties simply by changing the organic group R, or the ability to combine the desirable features of several compounds by copolymerization. The discharge characteristics of several different polymeric and copolymeric disulfides are presented in this paper. In general aliphatic organopolydisulfides exhibit a flat discharge potential of about 2 V vs. Li, while others have higher cell voltages. The low equivalent weight and the high utilization of thick cathodes of -(SCH2CH2S)n (X8) translate into high energy densities for lithium polymer electrolyte cells.