An implantable medical device comprising a battery cell including: an anode； a cathode including fluorinated carbon particles； a separator between the anode and the cathode； and an electrolyte contacting the anode, the cathode, and the separator； wherein greater than 50 vol-% of the fluorinated carbon particles have a particle size within a range of 2 microns to 10 microns, and greater than 50% by number have an aspect ratio within a range of 1:1.2 to 1:8.
