NOVELTY - Collection of particles comprises zinc and at least one non-zinc metal having a reduction potential equal to or more positive than the reduction potential of zinc. The particles have an average diameter of 0.1-1 mm.    USE - The collection of particles is used in fuel cell fuel (claimed), useful in zinc/air (oxygen) fuel cell systems (100).    ADVANTAGE - The fuel composition has improved flow properties. The collection of particles has improved physical properties, e.g. narrower particle size distributions, improved morphology, and lower corrosion rates.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for:    (a) a fuel cell fuel comprising a collection of particles dispersed in an aqueous alkaline electrolyte;    (b) an electrochemical cell (114) comprising an anode comprising a collection of metal particles and an electrolyte in a flowable dispersion, a gas diffusion electrode comprising a catalyst for catalyzing the reduction of a gaseous oxidizing agent, and a separator between the anode and the gas diffusion electrode;    (c) a regeneration solution for use in an electrochemical cell, which comprises an alkaline aqueous electrolyte, zincate ions, and at least one non-zinc metal oxide or metal hydroxide;    (d) a regeneration unit comprising the regeneration solution, an anode, and a cathode for regenerating metal particles;    (e) a method of replenishing the fuel for a metal-based fuel cell, which comprises providing a collection of particles dispersed in an electrolyte to the anode of the fuel cell; and    (f) a method for electrolytically generating zinc particles from a solution comprising oxidized zinc, which comprises generating zinc particles from a regeneration solution by applying voltage to the regeneration solution such that oxidized zinc is reduced to zinc particles.    DESCRIPTION OF DRAWING(S) - The figure is a schematic diagram of a metal-air fuel cell designed for the continuous replenishment of metal fuel, in which a sectional side view of an anode is shown in phantom lines.    Zinc/air fuel cell system (100)    Zinc fuel tank (102)    Power source (104)    Pump (110)    Cell (114)