Electrochemical cell having minimized cell swelling and method for powering an implantable medical device

The minimization or elimination of swelling in lithium cells containing CF as part of the cathode electrode and discharged under high rate applications is described. When CF materials are synthesized from fibrous carbonaceous materials, in comparison to petroleum coke, cell swelling is greatly reduced, and in some cases eliminated. Preferred precursors are carbon fibers and MCMB.