NOVELTY - A lithium-ion battery (200) comprises a positive electrode (210) comprising a current collector and first active material; negative electrode (220) comprising a current collector and second active material; and auxiliary electrode (260) comprising a current collector and third active material. The three active materials are configured to allow doping and undoping of lithium ions. The third active material exhibits charging and discharging capacity below a corrosion potential of current collector of negative electrode and above a decomposition potential of first active material.    USE - A lithium-ion battery for an implantable medical device implanted within a body or torso of a patient, or implantable neurological stimulation device. The battery may be provided as a button cell battery, thin film solid state battery or another lithium-ion battery configuration. Can also be used in other types of implantable medical devices such as pacemakers, cardiac contractility modulators, cardioverters, drug administering devices, diagnostic recorders or cochlear implants for alleviating adverse effects of health ailments; non-implantable medical devices; and other applications including computers (e.g. laptop computers), phones (e.g. cellular, mobile or cordless phones), and automobiles.    ADVANTAGE - The lithium-ion battery is relatively tolerant to over-discharge conditions; may be repeatedly cycled (i.e. charged and discharged) to near-zero-voltage conditions without significant decline in battery performance; and may be fully discharged while the materials for both electrodes, including their corresponding current collectors, are stable (e.g. corrosion of current collectors and/or decomposition of active material may be avoided). The occurrence of reduced device functionality (i.e. the need to recharge more frequently) and corrosion of current collectors and battery case (202) (with incumbent possibility of leaking potentially corrosive and toxic battery contents) may be reduced or avoided.    DETAILED DESCRIPTION - A lithium-ion battery (200) comprises a positive electrode (210) comprising a current collector and first active material; negative electrode (220) comprising a current collector and second active material; and auxiliary electrode (260) comprising a current collector and third active material. The auxiliary electrode is configured for selective electrical connection to negative electrode. The three active materials are configured to allow doping and undoping of lithium ions. The third active material exhibits charging and discharging capacity below a corrosion potential of current collector of negative electrode and above a decomposition potential of first active material.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of a portion of lithium-ion battery having an auxiliary negative electrode.    Battery (200)    Case (202)    Positive electrode (210)    Negative electrode (220)    Auxiliary electrode (260)