Nickel-metal hydride storage battery and assembly of the same

A nickel-metal hydride storage battery comprising

• (i) an electrode plate assembly comprising:
• a positive electrode plate comprising spherical nickel hydroxide particles having cobalt oxide on the surface thereof, yttrium oxide particles and a porous nickel substrate retaining both of said particles;
• a negative electrode plate containing a hydrogen storage alloy;
• a separator interposed between said positive and negative electrode plates, said electrode plates and said separator being spirally wound;
• and current collectors of one polarity and the other polarity being located respectively on the top and bottom of said spirally wound electrode plates and separator,
• (ii) an alkaline electrolyte and
• (iii) a battery case having a substantially rectangular parallelepiped part for accommodating said electrode plate assembly and said alkaline electrolyte,
• the amount of said alkaline electrolyte being 70 to 90% of the volume V of the residual space in said battery given by the equation (1):
• V=S·h−(V1+V2+V3+V4) (1)
• where S is the cross sectional area of the inner space of said substantially rectangular parallelepiped part, h is the height of said electrode plate assembly, V1 is the true volume of said positive electrode plate, V2 is the true volume of said negative electrode plate, V3 is the true volume of said separator, and V4 is the volume of said two current collectors;
• wherein the cross section of said substantially rectangular parallelepiped part has a substantially square outer shape with four curved or chamfered corners, and r/a ratio is 0.40 or less when the distance between opposite sides of said substantial square is represented by a and the length of a straight segment of said side is represented by a−2r.

An assembly comprising a plurality of nickel-metal hydride storage batteries,

• each of said batteries comprising
• (i) an electrode plate assembly comprising:
• a positive electrode plate comprising spherical nickel hydroxide particles having cobalt oxide on the surface thereof, yttrium oxide particles and a porous nickel substrate retaining both of said particles;
• a negative electrode plate containing a hydrogen storage alloy;
• a separator interposed between said positive and negative electrode plates, said electrode plates and said separator being spirally wound;
• and current collectors of one polarity and the other polarity being located respectively on the top and bottom of said spirally wound electrode plates and separator,
• (ii) an alkaline electrolyte and
• (iii) a battery case having a substantially rectangular parallelepiped part for accommodating said electrode plate assembly and said alkaline electrolyte,
• the amount of said alkaline electrolyte being 70 to 90% of the volume V of the residual space in said battery given by the equation (1):
• V=S·h−(V1+V2+V3+V4) (1)
• where S is the cross sectional area of the inner space of said substantially rectangular parallelepiped part, h is the height of said electrode plate assembly, V1 is the true volume of said positive electrode plate, V2 is the true volume of said negative electrode plate, V3 is the true volume of said separator, and V4 is the volume of said two current collectors,
• said batteries arranged such that at least one side face of each of said batteries faces a side face of another one of said batteries;
• and
• wherein said battery case comprises a bottomed case having a circular opening, and said opening is sealed with a disc-shaped seal plate, the edge of said opening crimping onto the periphery of said seal plate.