An electrochemical cell comprising, a cell housing formed of a flexible sheet, the cell housing having a first housing portion , and a second housing portion that is joined to the first housing portion along a sealed joint to form a pouch, an electrode assembly disposed in the cell housing , the electrode assembly including positive electrode portions alternating with negative electrode portions, the positive electrode portions and the negative electrode portions being separated by at least one separator and stacked along a stack axis , and a lead tab that extends through the sealed joint , the lead tab including a first end that is disposed inside the cell housing and is electrically connected to one of the positive electrode portions and the negative electrode portions, a second end that is opposed to the first end and disposed outside the cell housing , a longitudinal axis that extends between the first end and the second end , and a first cross section that is transverse to the longitudinal axis , the first cross section including a width dimension that is transverse to the longitudinal axis and a thickness dimension that is transverse to both the longitudinal axis and the width dimension, wherein the first cross section has a first thickness (t1) in a center of the width dimension, and a second thickness (t2) at opposed ends of the width dimension, where the first thickness (t1) is larger than the second thickness (t2), and the transition between the first thickness (t1) and the second thickness (t2) is a concavity having a first radius (R1). a cell housing formed of a flexible sheet, the cell housing having a first housing portion , and a second housing portion that is joined to the first housing portion along a sealed joint to form a pouch, an electrode assembly disposed in the cell housing , the electrode assembly including positive electrode portions alternating with negative electrode portions, the positive electrode portions and the negative electrode portions being separated by at least one separator and stacked along a stack axis , and a lead tab that extends through the sealed joint , the lead tab including a first end that is disposed inside the cell housing and is electrically connected to one of the positive electrode portions and the negative electrode portions, a second end that is opposed to the first end and disposed outside the cell housing , a longitudinal axis that extends between the first end and the second end , and a first cross section that is transverse to the longitudinal axis , the first cross section including a width dimension that is transverse to the longitudinal axis and a thickness dimension that is transverse to both the longitudinal axis and the width dimension, wherein a first end that is disposed inside the cell housing and is electrically connected to one of the positive electrode portions and the negative electrode portions, a second end that is opposed to the first end and disposed outside the cell housing , a longitudinal axis that extends between the first end and the second end , and a first cross section that is transverse to the longitudinal axis , the first cross section including a width dimension that is transverse to the longitudinal axis and a thickness dimension that is transverse to both the longitudinal axis and the width dimension, wherein the first cross section has a first thickness (t1) in a center of the width dimension, and a second thickness (t2) at opposed ends of the width dimension, where the first thickness (t1) is larger than the second thickness (t2), and the transition between the first thickness (t1) and the second thickness (t2) is a concavity having a first radius (R1). <EOS>