A method for monitoring a lithium-ion battery cell includes monitoring a battery cell voltage and a corresponding charge capacity of the battery cell during an electric power event which may include either an electric power charge event or an electric power discharge event. A measured charge-capacity-derivative is determined by differentiating the charge capacity in relation to the corresponding battery cell voltage during the electric power event. The measured charge-capacity-derivative is compared with a preferred anode charge-capacity-derivative of an anode charge curve (for electric power discharge events) or an anode discharge curve (for electric power charge events), and with a preferred cathode charge-capacity-derivative of a cathode charge curve (for electric power charge events) or a cathode discharge charge curve (for electric power discharge events). A first state of health parameter of the battery cell corresponding to the comparison of the measured charge-capacity-derivative with the preferred anode charge-capacity-derivative of the anode curve is determined. And, a second state of health parameter of the battery cell corresponding to the comparison of the measured charge-capacity-derivative with the preferred cathode charge-capacity-derivative of the cathode curve is determined.