NOVELTY - A leak-proof fuel cell comprises at least one liquid within a casing (1) that comprises at least one opening (4a-4d) which is sealed by a first structure (5a-5d) that is gas-pervious and impervious to the liquid, where at least that portion of the casing which comprises opening(s) is enclosed by a second structure (6) which allows gas to pass, and a space defined by casing and second structure comprises at least one material (10) that is capable of binding (e.g. absorbing) the liquid. The material is capable of preventing liquid that has leaked from the casing to escape from the space.    USE - As a fuel cell e.g. a portable fuel cell, a direct liquid fuel cell (such as hydride-based fuel cell e.g. borohydride fuel cell) (claimed). The portable fuel cells are useful in portable electric and electronic devices such as laptops and cell phones.    ADVANTAGE - The fuel cell has liquid binding material in space between the casing and sealing structure, that prevents liquid leaking from casing even if the first sealing structure fails to prevent liquids inside the casing from getting to the outside of casing. The liquid binding material is capable of preventing liquid that has leaked from the casing to escape from the space.    DETAILED DESCRIPTION - A leak-proof fuel cell comprises at least one liquid within a casing (1) that comprises at least one opening (4a-4d) which is sealed by a first structure (5a-5d) that is gas-pervious and impervious to the liquid, where at least that portion of the casing which comprises at least one opening is enclosed by a second structure (6) which allows gas to pass through, and a space defined by the casing and the second structure comprises at least one material (10) that is capable of binding (e.g. absorbing) the liquid. The material is capable of preventing liquid that has leaked from the casing to escape from the space. The liquid comprises a liquid fuel (such as hydride compound and/or borohydride compound), and/or a liquid electrolyte (such as an aqueous solution e.g. an alkali metal hydroxide). The first structure comprises a porous material. The material that is capable of binding the liquid comprises a material (such as superabsorbent, spongy or polymeric material) that is capable of absorbing the liquid, preferably liquids having a pH of greater than or equal to 7. The material that is capable of absorbing the liquid is present in a particulate form. The polymeric material comprises a polymer that comprises at least one monomeric unit having an acidic functionality such as a carboxylic acid group and/or a sulfonic acid group (preferably monomeric unit of unsaturated carboxylic acid). An INDEPENDENT CLAIM is included for a method of leak-proofing a fuel cell involving enclosing at least that part of the casing which comprises the gas-pervious material with a gas-pervious structure to create an enclosed space between an outer surface of the casing and an inner surface of the structure; and disposing within the space at least one material that is capable of preventing liquid that has leaked from the casing to escape from the space.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic cross sectional view of a fuel cell.    casing (1)    anode (2)    cathode (3)    openings (4a-4d)    first structure (5a-5d)    second structure (6)    liquid binding material. (10)