Prepn. of a polymer matrix for a rechargeable zinc halide electrolyte electrochemical cell comprises polymerising a soln. consisting of an acrylic monomer in the presence of a redox initiator and a zinc halide electrolyte.    Also claimed are: (1) a rechargeable zinc halide electrolyte electrochemical cell comprising a laminate of (a) an electrically conducting chemically inert material, (b) a membrane matrix formed from a hydrophilic polymer matrix in which is immobilised a zinc halide electrolyte including a bromine complexing agent, and (c) an electrically conducting layer adapted to adsorb and absorb halogen; (2) a battery contg. above cells connected in series to form a rechargeable zinc halide electrolyte electrochemical battery; and (3) a bipolar non-flow zinc halide storage battery.     The acrylic monomer is (meth)acrylamide, acrylic acid, vinylpyrrolidone or polyethylene-glyco-acrylate. The oxidative part of the redox initiator is selected from persulphates of Na, K or Al, t-butyl peroxide, H2 O2, benzoyl peroxide, and methyl ethyl ketone peroxide. The reductive part of the redox initiator is selected from bisulphate, meta-bisulphate (pyrosulphite), dithionate, ascorbic acid, sodium thiosulphate and sodium formaldehyde sulphoxylate. The soln. comprises 1-10 molar acrylamide, 0.0001-1 molar redox initiator, 0.1-6 molar zinc halide, 0.1-6 molar complexing agent and pref. an additional halide salt, esp. potassium chloride or ammonium chloride. Pref. the soln. further includes a bromine complexing agent in amt. of 0.01-4 molar. It is selected from N-ethyl-N-methylmorpholine bromide, N-ethyl-N-methyl pyrrolidium bromide, N-methoxymethyl-N-methyl piperidinium bromide, N-chloromethyl-N-methyl-pyrrolidinium bromide, all belonging to the gp. of unsymmetrically substd. quaternary ammonium salts.    ADVANTAGE -   The addition of the Br complexing agent decreases corrosion after prolonged cycling and decreases cell self discharge. The prepn. does not require coupling agents. The cell has good conductivity. The polymer matrix can be prepd. in situ in the cell.