Patent ID: 7846571

Claim:
A method to adjust a lithium supply of a battery cell including a first working electrode in a first layer, a second working electrode in a second layer, 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, one of: (a) transferring lithium from the auxiliary electrode to at least one of the two working electrodes and (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 are electronically connected within the cell; and a second separator region extending between the first and second layers and 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: include a negative electrode and a positive electrode; and 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.