A film that contains Ni.sub.2O.sub.3H as a main component.

The composite diaphragm for a zinc secondary battery, including: a base diaphragm and a conductive film for the zinc secondary battery, the conductive film being connected to one end of the base diaphragm. The conductive film includes a porous polymer film, and pores of the porous polymer film are filled with conductive compositions, the conductive compositions including 1-10 parts by weight of a conductive agent and 0.1-1 part by weight of an additive. The conductive agent includes at least one of graphite, conductive carbon black, acetylene black, or a graphene carbon nanotube; and the additive includes at least one of a tin powder, a tin dioxide powder, a bismuth powder, a bismuth oxide powder, an indium powder, an indium oxide powder, a lead powder, a lead oxide powder, a cadmium powder, or a cadmium oxide powder.