Patent ID: 6936379

Claim:
An implantable medical device, which comprises: a) a housing; b) a control circuitry contained inside the housing to control functioning of the medical device; c) an electrochemical cell contained inside the housing for powering the control circuitry, the cell comprising: i) an anode; ii) a cathode of a first cathode active material different than a second cathode active material, the first cathode active material being of a first energy density and a first rate capability and the second cathode active material being of a second energy density and a second rate capability, wherein the first cathode active material is contacted to one side of a current collector and facing the anode with the second cathode active material positioned on the opposite side of the current collector, and wherein the first energy density of the first cathode active material is less than the second energy density of the second cathode active material while the first rate capability of the first cathode active material is greater than the second rate capability of the second cathode active material; and iii) an electrolyte activating the anode and the cathode; and d) a conductor for connecting the medical device to a body intended to be assisted by the medical device; e) wherein the cell's discharge capacity (A) from an Elective Replacement Indicator voltage to an end-of-life (End of Life) voltage and a theoretical capacity (B) of the cell are determinable; f) wherein the efficiencies of the first and second cathode active materials as (C) and (D), respectively, in terms of deliverable capacity from the A Elective Replacement Indicator voltage to the End of Life voltage are determinable; and g) wherein the cell's deliverable capacity from the Elective Replacement Indicator voltage to the End of Life voltage is determinable by the control circuitry using the equation: A/B=[C×a ratio of a first theoretical capacity of the first cathode active material:a second theoretical capacity of the second cathode active material+D]/(the ratio of the first theoretical capacity:the second theoretical capacity+1).