Lithium-sulphur battery with high specific energy

Abstract

A battery or chemical source of electric energy may include a positive electrode including sulphur or sulphur-based organic compounds, sulphur-based polymeric compounds or sulphur-based inorganic compounds as a depolarizer, a negative electrode made of metallic lithium or lithium-containing alloys, and an electrolyte including a solution of at least one salt in at least one aprotic solvent. In order to increase the specific energy, the chemical source of electric energy may be configured to generate soluble polysulphides in the electrolyte during discharge, and the quantities of sulphur in the depolariser and the volume of electrolyte may be selected such that, after discharge of the cathode in a first stage (to a potential of 2.1-1.9V), the concentration of soluble lithium polysulphides in the electrolyte is at least 70% of a saturation concentration of the lithium polysulphides in the electrolyte.

1 . A chemical source of electric energy comprising: 
 a positive electrode comprising sulphur or sulphur-based organic compounds, sulphur-based polymeric compounds or sulphur-based inorganic compounds as a depolarizer;    a negative electrode comprising metallic lithium or lithium-containing alloys;    an electrolyte comprising a solution of at least one salt in at least one aprotic solvent, the chemical source of electric energy being configured to generate soluble polysulphides in the electrolyte during a first stage of a two stage discharge process, wherein the quantity of sulphur in the depolariser and the volume of electrolyte are selected such that, after first stage discharge of the cathode, the concentration of the soluble polysulphides in the electrolyte is at least 70% of a saturation concentration of the polysulphides in the electrolyte at operating temperature and pressure.    
   
   
       2 . A chemical source of electric energy as claimed in  claim 1 , wherein the quantity of sulphur in the depolariser and the volume of electrolyte are selected such that, after complete discharge of the cathode, the concentration of the soluble lithium polysulphides in the electrolyte is from 70 to 90% of a saturation concentration of the polysulphides in the electrolyte at operating temperature and pressure.  
   
   
       3 . A chemical source of electric energy as claimed in  claim 1 , wherein the depolarizer comprises sulphur, carbon black and polyethylene oxide.  
   
   
       4 . A chemical source of electric energy as claimed in  claim 1 , wherein the electrolyte comprises a solution of one or several lithium salts selected from the group consisting of: lithium trifluoromethanesulphonate, lithium perchlorate, lithium trifluoromethanesulfonimide, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium tetrachloroaluminate, tetraalkylammonium salt, lithium chloride, lithium bromide and lithium iodide; in one or several solvents selected from the group consisting of: dioxolane, tetrahydrofuran, dimethoxyethane, diglyme, triglyme, tetraglyme, dialkyl carbonates, sulfolane and butyrolactone.