Nonaqueous electrolyte rechargeable battery and method for manufacturing nonaqueous electrolyte rechargeable battery
A lithium-ion rechargeable battery includes an electrode body rolled about a roll axis to be low-profile. In a cross section orthogonal to the roll axis, the electrode body includes a planar flat portion pressed to have a low profile and two semicircular rod-shaped bent portions bent and formed on opposite ends of the flat portion. Combined resistance of reaction resistance caused by an inter-electrode distance with solution resistance caused by air permeance of the separator in site, longitudinally extending from center to a peripheral surface of each bent portion, equals combined resistance of the reaction resistance with the solution resistance in site, extending from straight line to a peripheral surface of the flat portion in a thickness-wise direction, to obtain uniform resistance of the electrode body, thereby limiting deposition of lithium metal caused by non-uniform current density.
1 . A method for manufacturing a nonaqueous electrolyte rechargeable battery that includes an electrode body, a nonaqueous electrolyte, and a rectangular box-shaped battery case accommodating the electrode body and the nonaqueous electrolyte, the method comprising:
laminating a positive electrode including a positive base and a positive composite material layer and a negative electrode including a negative base and a negative composite material layer with a porous resin separator disposed between the positive electrode and the negative electrode to form the electrode body, wherein the separator includes a framework and a three-dimensional mesh portion formed on the framework;
rolling the laminated electrode body about a roll axis;
low-profile pressing the electrode body, which was rolled in the rolling, from a direction orthogonal to the roll axis to form a planar flat portion F and two semicircular rod-shaped bent portions R on opposite ends of the flat portion F; and
restoring the electrode body from elastic deformation occurred in the low-profile pressing; wherein
when
a direction parallel to the roll axis of the electrode body is referred to as a width-wise direction,
a direction orthogonal to the roll axis of the electrode body and a surface of the flat portion F is referred to as a thickness-wise direction,
a direction orthogonal to the width-wise direction and the thickness-wise direction is referred to as a longitudinal direction,
a point located on a center axis of the semicircular rod-shaped bent portions R is referred to as a center C of the bent portions R,
a site extending from the center C of each bent portion R to a peripheral surface of the bent portion R in the longitudinal direction upon completion of the restoring is referred to as a site D,
the centers C of the two bent portion R are connected by a straight line, and a site extending from the straight line to a peripheral surface of the flat portion F in the thickness-wise direction upon completion of the restoring is referred to as a site B,
a distance from one peripheral surface of the flat portion F to the other peripheral surface in the thickness-wise direction of the electrode body upon completion of the restoring is referred to as a thickness-wise dimension B′,
a lamination thickness of the electrode body upon completion of the rolling is referred to as an electrode body lamination thickness E, and
a distance from one peripheral surface of the flat portion F to the other peripheral surface in the thickness-wise direction of the electrode body upon completion of the low-profile pressing is referred to as a thickness-wise dimension B″,
the three-dimensional mesh portion of the separator in the site B is plastically deformed by compressing the three-dimensional mesh portion of the separator in the site B beyond a yield point of the three-dimensional mesh portion through the low-profile pressing, and
a pressing force of the low-profile pressing is adjusted such that:
a thickness of the site D/a thickness of the site B is greater than or equal to 1.01 and less than or equal to 1.10;
an air permeance of the site B/an air permeance of the site D is greater than or equal to 0.90 and less than or equal to 0.99;
the thickness-wise dimension B′/(2×the electrode body lamination thickness E) is greater than or equal to 0.98 and less than or equal to 1.00; and
the thickness-wise dimension B″/the thickness-wise dimension B′ is greater than or equal to 0.88 and less than or equal to 0.98.
2 . The method according to claim 1 , wherein the ranges of the thickness of the site D/the thickness of the site B, the air permeance of the site B/the air permeance of the site D, the thickness-wise dimension B′/(2×the electrode body lamination thickness E), and the thickness-wise dimension B″/the thickness-wise dimension B′ are set so that a combined resistance Rdc of a reaction resistance Rd 1 caused by an inter-electrode distance with a solution resistance Rd 2 caused by the air permeance of the separator in the site D equals a combined resistance Rbc of a reaction resistance Rb 1 caused by an inter-electrode distance with a solution resistance Rb 2 caused by the air permeance of the separator in the site B.
3 . The method according to claim 1 , wherein the nonaqueous electrolyte rechargeable battery is a lithium-ion rechargeable battery.