An electrode assembly includes a first electrode plate including a first electrode current collector and a first electrode active material layer thereon, a second electrode plate including a second electrode current collector and a second electrode active material layer thereon, a separator between the first electrode plate and the second electrode plate, a first electrode tab coupled to the first electrode current collector, and a second electrode tab coupled to the second electrode current collector, wherein a region of the first electrode current collector including the first electrode tab faces a wound first electrode plate, wherein a region of the second electrode current collector including the second electrode tab faces a wound second electrode plate, and wherein the second electrode active material layer is only on one surface of the second electrode current collector in a region preceding a first winding turn of the second electrode plate.

Provided is a hydrogen storage alloy which is characterized in that two or more crystal phases having different crystal structures are layered in a c-axis direction of the crystal structures. The hydrogen storage alloy is further characterized in that a difference between a maximum value and a minimum value of a lattice constant a in the crystal structures of the laminated two or more crystal phases is 0.03 or less.

A positive electrode active material includes a plurality of groups of particles. The plurality of groups of particles has a particle diameter of more than or equal to 300 nm and less than or equal to 3 m. Each of the groups includes two or more particles. The two or more particles are each a lithium-containing complex phosphate including one or more of iron, nickel, manganese, and cobalt. The group of particles includes a first particle and a second particle each having a major diameter and a minor diameter in the upper surface when seen from a predetermined direction. The major diameters of the first and second particles are substantially parallel to each other. The major diameter of the first particle is two to six times larger than the minor diameter of the first particle and the minor diameter of the first particle is more than or equal to 20 nm and less than or equal to 130 nm.

A positive electrode active material includes a plurality of groups of particles. The plurality of groups of particles has a particle diameter of more than or equal to 300 nm and less than or equal to 3 m. Each of the groups includes two or more particles. The two or more particles are each a lithium-containing complex phosphate including one or more of iron, nickel, manganese, and cobalt. The group of particles includes a first particle and a second particle each having a major diameter and a minor diameter in the upper surface when seen from a predetermined direction. The major diameters of the first and second particles are substantially parallel to each other. The major diameter of the first particle is two to six times larger than the minor diameter of the first particle and the minor diameter of the first particle is more than or equal to 20 nm and less than or equal to 130 nm.

A separator winding core is configured such that at least one of side surfaces has a large frictional force between the side surface and one side surface of another separator winding core of the same type. Such a separator winding core is less likely to fall down when it is stacked on another separator winding core of the same type. Provided is a separator winding core having side surfaces around which no separator is to be wound and at least one of which has an arithmetic mean roughness of not less than 0.16 m. The separator winding core is stackable with one or more other separator winding cores of the same type in such a position that one of the side surfaces of the separator winding core faces upward while the other one of the side surfaces of the separator winding core faces downward.

A separator winding core is configured such that at least one of side surfaces has a large frictional force between the side surface and one side surface of another separator winding core of the same type. Such a separator winding core is less likely to fall down when it is stacked on another separator winding core of the same type. Provided is a separator winding core having side surfaces around which no separator is to be wound and at least one of which has an arithmetic mean roughness of not less than 0.16 m. The separator winding core is stackable with one or more other separator winding cores of the same type in such a position that one of the side surfaces of the separator winding core faces upward while the other one of the side surfaces of the separator winding core faces downward.

A button cell includes a housing having a cell cup with a flat bottom area and having a cell top with a flat top area. The button cell also includes an electrode-separator assembly winding disposed within the housing. The electrode-separator assembly winding includes a multi-layer assembly that is wound in a spiral shape about an axis. The multi-layer assembly includes a positive electrode formed from a first current collector coated with a first electrode material, a negative electrode formed from a second current collector coated with a second electrode material, and a separator disposed between the positive electrode and the negative electrode. The button cell further includes a winding core around which the multi-layer assembly is wound. The winding core provides a contact pressure on a first metal foil output conductor in an axial direction to facilitate electrical contact between the first metal foil output conductor and the housing.

A button cell includes a housing having a cell cup with a flat bottom area and having a cell top with a flat top area. The button cell also includes an electrode-separator assembly winding disposed within the housing. The electrode-separator assembly winding includes a multi-layer assembly that is wound in a spiral shape about an axis. The multi-layer assembly includes a positive electrode formed from a first current collector coated with a first electrode material, a negative electrode formed from a second current collector coated with a second electrode material, and a separator disposed between the positive electrode and the negative electrode. The button cell further includes a winding core around which the multi-layer assembly is wound. The winding core provides a contact pressure on a first metal foil output conductor in an axial direction to facilitate electrical contact between the first metal foil output conductor and the housing.

A rechargeable button cell including a housing half-parts comprising a housing cup and a housing top separated from one another by an electrically insulating seal or film seal is disclosed. The button cell includes an electrode-separator assembly within the housing having a positive and a negative electrode in the form of flat layers connected to one another by a porous plastic film separator. The electrodes each include a metallic film or mesh embedded in a respective electrode material as a current collector, which acts as an output conductor that connects the electrodes to one of the flat bottom or flat top areas of the housing.

A rechargeable button cell including a housing half-parts comprising a housing cup and a housing top separated from one another by an electrically insulating seal or film seal is disclosed. The button cell includes an electrode-separator assembly within the housing having a positive and a negative electrode in the form of flat layers connected to one another by a porous plastic film separator. The electrodes each include a metallic film or mesh embedded in a respective electrode material as a current collector, which acts as an output conductor that connects the electrodes to one of the flat bottom or flat top areas of the housing.