Patent ID: 8859120

Claim:
A method to adjust a lithium supply of a battery cell including a negative working electrode, a positive working electrode, and an auxiliary electrode, the method comprising: measuring an open circuit potential of each of the two working electrodes using the auxiliary electrode as a reference electrode during an equilibrium state of the working electrodes at open circuit; determining a state of charge of each of the two working electrodes based on the measured open circuit potential of each of the two working electrodes; and based on the determined state of charge: (a) transferring lithium from the auxiliary electrode to the positive working electrode over a path to which the negative working electrode is external; or (b) transferring lithium to the auxiliary electrode from at least one of the two working electrodes; wherein: the battery cell includes: a first separator region arranged between the two working electrodes to separate the two working electrodes so that none of the two working electrodes is electronically connected within the cell; and a second separator region arranged between the auxiliary electrode and the two working electrodes to separate the auxiliary electrode from the two working electrodes so that none of the two working electrodes is electronically connected to the auxiliary electrode within the cell; the two working electrodes are arranged to produce electrical energy output by the battery cell as a power source; each of the two working electrodes includes an active material, an inert material, an electrolyte, and a current collector; and the auxiliary electrode includes a lithium reservoir.