A secondary zinc battery comprising: a unit cell comprising; a positive-electrode plate comprising a positive-electrode active material layer and a positive-electrode collector; a negative-electrode plate comprising a negative-electrode active material layer and a negative-electrode collector, the negative-electrode active material layer comprising at least one selected from the group consisting of elemental zinc, zinc oxide, zinc alloys, and zinc compounds; a layered double hydroxide separator covering or wrapping around the entire negative-electrode active material layer; and an electrolytic solution, wherein the positive-electrode active material layer, the negative-electrode active material layer, and the LDH separator each have a quadrilateral planar shape, wherein the positive-electrode collector has a positive-electrode collector tab extending from a first edge of the positive-electrode active material layer, and the negative-electrode collector has a negative-electrode collector tab extending from a second edge of the negative-electrode active material layer and beyond a vertical edge of the LDH separator, the first edge being opposite to the second edge, the unit cell being capable of collecting electricity from the positive-electrode collector tab and the negative-electrode collector tab, the positive-electrode collector tab and the negative-electrode collector tab being disposed at opposite edges of the unit cell, and wherein the LDH separator has at least two continuous closed edges, provided that an edge, adjacent to the negative-electrode collector tab, of the LDH separator is open. a unit cell comprising; a positive-electrode plate comprising a positive-electrode active material layer and a positive-electrode collector; a negative-electrode plate comprising a negative-electrode active material layer and a negative-electrode collector, the negative-electrode active material layer comprising at least one selected from the group consisting of elemental zinc, zinc oxide, zinc alloys, and zinc compounds; a layered double hydroxide separator covering or wrapping around the entire negative-electrode active material layer; and an electrolytic solution, a positive-electrode plate comprising a positive-electrode active material layer and a positive-electrode collector; a negative-electrode plate comprising a negative-electrode active material layer and a negative-electrode collector, the negative-electrode active material layer comprising at least one selected from the group consisting of elemental zinc, zinc oxide, zinc alloys, and zinc compounds; a layered double hydroxide separator covering or wrapping around the entire negative-electrode active material layer; and an electrolytic solution, wherein the positive-electrode active material layer, the negative-electrode active material layer, and the LDH separator each have a quadrilateral planar shape, wherein the positive-electrode collector has a positive-electrode collector tab extending from a first edge of the positive-electrode active material layer, and the negative-electrode collector has a negative-electrode collector tab extending from a second edge of the negative-electrode active material layer and beyond a vertical edge of the LDH separator, the first edge being opposite to the second edge, the unit cell being capable of collecting electricity from the positive-electrode collector tab and the negative-electrode collector tab, the positive-electrode collector tab and the negative-electrode collector tab being disposed at opposite edges of the unit cell, and wherein the LDH separator has at least two continuous closed edges, provided that an edge, adjacent to the negative-electrode collector tab, of the LDH separator is open.