Variable layer thickness in curved battery cell

A portable electronic device, comprising:

• a display;
• a processor and memory;
• and
• a battery configured to power the portable electronic device, the battery comprising:
• a first cell comprising a set of layers including an anode, a cathode, and a separator configured to electrically isolate the anode and the cathode of the first cell, a layer of the set of layers of the first cell having a first curvature;
• and
• a second cell comprising a set of layers including an anode, a cathode, and a separator configured to electrically isolate the anode and the cathode of the second cell, a layer of the set of layers of the second cell having a second curvature, the second curvature differing from the first curvature in a cross-sectional plane defined by a radial direction and a circumferential direction, the first curvature and the second curvature being separated from a common center of curvature in the cross-sectional plane by respective radial distances along the radial direction.