GB1408940A - Non-aqueous electric current-producing primary and - Google Patents

Abstract

1408940 Primary and secondary cells POWER CONVERSION Inc 27 Nov 1972 [2 Dec 1971] 54753/72 Heading H1B A substantially non-aqueous secondary or primary cell includes a negative electrode selected from the alkali metals and alkaline earth metals more electropositive than zinc in the electrochemical series, a positive electrode insulated therefrom, and a liquid electrolyte comprising liquid SO 2 under pressure mixed with an anhydrous liquid organic compound, the SO 2 comprising 60 to 90% by weight of the liquid electrolyte, and a solute in the form of a salt of the negative electrode metal dissolved in the electrolyte and wherein the water content of the cell is less than 50 parts per million. The SO 2 is maintained in the liquid state by providing an above atmospheric pressure, referred to 22‹ C. In the liquid electrolyte solution the liquid SO 2 is preferably 65-85% by weight thereof. The organic compound forming the remainder of the electrolyte may be selected from nitriles, dimethyl sulphoxide, amides, pentacyclic esters, lactones, N-methyl 1,2-pyrolidone, amines, ethers, secondary amine halides and esters such as methyl, ethyl or phenyl acetate or formate or methyl benzoate. The organic compound may be a mixture of, for example, 80-60% by volume of methyl formate, methyl acetate, ethyl formate or ethyl acetate together with 20-40% by volume of propylene or ethylene carbonate. The solute dissolved in the electrolyte has a metallic ion of the same metal which forms the anode and an anodic ion which may be a chlorate, perchlorate, thiocyanate, cyanide, rhodanide, iodide, fluoride, chloride, bromide, sulphide, sulphate, picrate, fluoborate, hydride or borohydride. A preferred example is IM LiBr. The negative electrode (anode) may be formed entirely of alkali or alkaline earth metal, e.g. Li, K, Ca, Ba or Na or this metal may be pressed into a conductive but inert screen of Ni, Cu, Ag or Fe. The positive electrode (cathode) comprises a conductive metal or non-metal inert to the electrolyte, e.g. carbon, boron, Pt, Zr, Ta and preferably a finely divided material such as C, Ni, Al, Ag, Cu, Pt mixed with paper, glass or asbestos fibres, plastics powders together with a fluorocarbon resin binder such as polytetrafluoroethylene or chlorotrifluoroethylene. A separator may be disposed between the electrodes which comprises fibrous synthetic materials such as a copolymer of vinyl chloride and acrylonitrile, polyamide polymers, copolymers of polyvinyl alcohol and polyvinylchloride, polyacrylate esters and porous polyethylene. In an example in a cell including 80% by weight SO 2 in the electrolyte a pressure of 45 p.s.i. gauge is employed to maintain the SO 2 in the liquid state and in a cell including 60% by weight SO 2 , 25 p.s.i. gauge is required. Examples are given in which respectively the anodes are K, Ca, Ba, Li and Na, the organic compound dimethylsulphoxide, ethyl formate and propylene carbonate, isopropylamine, ethylene diamine and methyl acetate and the solute is KBr, Ca(ClO 3 ) 2 , BaBr 2 , LiF, NaBr.