Nickel-hydrogen secondary cell

A nickel-hydrogen secondary battery comprising:

• a positive electrode including a positive electrode mixture which contains a nickel compound as a major component and which is supported on a first collector sheet;
• a negative electrode including a negative electrode mixture which contains a hydrogen absorbing alloy as a major component, a binder and an electrically conductive material which is supported on a second collector sheet, said positive electrode and said negative electrode being stacked up alternately or rolled up with a separator interposed therebetween to form an electrode group;
• and
• a battery case containing the electrode group together with an electrolyte, said battery case having an opening closed with a sealing plate which is provided with a positive electrode terminal,
• wherein the binder contains at least carboxylated styrene-butadiene copolymer latex, and the electrically conductive material contains metal flakes or short metal fibers, and
• wherein the metal flakes or the short metal fibers overlap with each other to surround the hydrogen absorbing alloy powder and to have an orientation such that the metal flakes or the short metal fibers connect with each other along their lengths.

A nickel-hydrogen secondary battery comprising:

• a positive electrode including a positive electrode mixture which contains a nickel compound as a major component and which is supported on a first collector sheet;
• a negative electrode including a negative electrode mixture which contains a hydrogen absorbing alloy as a major component, a binder and an electrically conductive material which is supported on a second collector sheet, said positive electrode and said negative electrode being stacked up alternately or rolled up with a separator interposed therebetween to form an electrode group;
• and
• a battery case containing the electrode group together with an electrolyte, said battery case having an opening closed with a sealing plate which is provided with a positive electrode terminal,
• wherein at least an edge portion of the second collector sheet of said negative electrode is electrically connected to said battery case via a collector plate welded to the edge portion of the second collector sheet,
• wherein the binder contains at least carboxylated styrene-butadiene copolymer latex, and the electrically conductive material contains metal flakes or short metal fibers, and
• wherein a portion of said positive electrode forming the electrode group on which the positive electrode mixture is supported has an area of 30 cm2 or more per theoretical capacity (unit:
• Ah) of the battery.

A nickel-hydrogen secondary battery comprising:

• a positive electrode including a positive electrode mixture which contains a nickel compound as a major component and which is supported on a first collector sheet;
• a negative electrode including a negative electrode mixture which contains a hydrogen absorbing alloy as a major component, a binder and an electrically conductive material which is supported on a second collector sheet, said positive electrode and said negative electrode being stacked up alternately or rolled up with a separator interposed therebetween to form an electrode group;
• and
• a battery case containing the electrode group together with an electrolyte, said battery case having an opening closed with a sealing plate which is provided with a positive electrode terminal,
• wherein at least an edge portion of the second collector sheet is electrically connected to said battery case via a collector plate welded to the edge portion of the second collector sheet,
• wherein the binder contains at least carboxylated styrene-butadiene copolymer latex, and the electrically conductive material contains metal flakes or short metal fibers,
• wherein the hydrogen absorbing alloy is surface-treated with acid or alkali, and
• wherein a compound of rare-earth element adheres to at least part of a surface of the hydrogen absorbing alloy.

A nickel-hydrogen secondary battery comprising:

• a positive electrode including a positive electrode mixture which contains a nickel compound as a major component and which is supported on a first collector sheet;
• a negative electrode including a negative electrode mixture which contains a hydrogen absorbing alloy as a major component, a binder and an electrically conductive material which is supported on a second collector sheet, said positive electrode and said negative electrode being stacked up alternately or rolled up with a separator interposed therebetween to form an electrode group;
• and
• a battery case containing the electrode group together with an electrolyte, said battery case having an opening closed with a sealing plate which is provided with a positive electrode terminal,
• wherein at least an edge portion of the second collector sheet of said negative electrode is electrically connected to said battery case via a collector plate welded to the edge portion of the second collector sheet,
• wherein the binder contains at least carboxylated styrene-butadiene copolymer latex, and the electrically conductive material contains metal flakes or short metal fibers, and
• wherein the negative electrode mixture is a dried mixture containing 0.1 to 5.0 parts by weight of carboxylated styrene-butadiene copolymer latex containing 30 to 50 wt % bound butadiene and 60 wt % or more insoluble toluene, 0.05 to 5.0 parts by weight of nickel flakes or short nickel fibers, and 0.05 to 5.0 parts by weight of carbon black, with respect to 100 parts by weight of the hydrogen absorbing alloy.