NOVELTY - An electrochemical cell comprises an alkali metal anode; a cathode including a first portion facing the anode and comprising a cathode active material having a basis wt. of 214-340 mg/in2 such that the cell is dischargeable to deliver at least one pulse of electrical current of 15-50 mA/cm2 for a time period to deliver 20-85 joules; and an electrolyte activating the anode and the cathode.    USE - For conversion of chemical energy to electrical energy.    ADVANTAGE - By using a cathode of a relatively low basis weight active material, the present cell eliminates or reduces undesirable irreversible stable internal resistance (Rdc) growth and voltage delay in the cell and extends its useful life in an implantable medical device.    DETAILED DESCRIPTION - An electrochemical cell comprises an alkali metal anode; a cathode including a first portion facing the anode and comprising a cathode active material having a basis wt. of 214-340 mg/in2 such that the cell is dischargeable to deliver at least one pulse of electrical current of 15-50 mA/cm2 for a time period to deliver 20-85 joules; and an electrolyte activating the anode and the cathode. The cathode further comprises a conductive additive; fluoro-polymer binder material; and current collector. The electrolyte has a first solvent selected from ester, linear ether, cyclic ether and/or dialkyl carbonate, and a second solvent selected from cyclic carbonate, cyclic ester and/or cyclic amide. The electrolyte is 0.8-1.5M LiAsF6 or LiPF6 dissolved in a mixture of propylene carbonate and 1,2-dimethoxyethane (50:50 vol.). An INDEPENDENT CLAIM is included for powering an implantable medical device with electrochemical cell comprising alkali metal anode coupled to a cathode of a cathode active material activated with an electrolyte, involving positioning the anode and the cathode inside a casing with an intermediate separator prevent direct physical contact between them; activating the anode and cathode with an electrolyte; connecting a negative terminal and a positive terminal of the cell to the implantable medical device; powering the implantable medical device with the cell; and subjecting the cell to a reform protocol of discharging the cell to deliver repeated pulses of electrical current of significantly greater amplitude than that of a pre-pulse current or open circuit voltage immediately prior to the first pulse discharge of the repeated pulses.