NOVELTY - A lithium-ion battery (100) comprises wound cell unit. The wound cell unit comprises positive and negative electrodes (710, 720). The positive electrode comprises current collector (712, 722) and first active material (714). The negative electrode comprises current collector and second active material (724). The second active material has potential greater than 0.2 volts versus lithium reference electrode. The lithium-ion battery has wound electrode configuration.    USE - Lithium ion batteries for implantable medical devices, e.g. implantable neurological stimulation device used to treat, e.g. pain, incontinence, movement disorders such as epilepsy, Parkinson's disease, and sleep apnea.    ADVANTAGE - The battery eliminates the use of excess electrode area and active material resulting in battery having higher energy density. The battery provides enhanced flexibility in physical design of the battery. The battery uses a certain materials that allow for elimination of relatively complicated and expensive design rules that intended to prevent lithium plating at the negative electrode, thus providing inexpensive manufacturing processes, material reduction and cost savings. The battery uses lithium titanate material that allows for charging and discharging of battery at higher rates, and offers superior cycle life because they are zero-strain material that does not experience shrinkage or contraction with lithium doping/de-doping, thus making them free from strain-related degradation mechanisms.    DETAILED DESCRIPTION - A lithium-ion battery comprises wound cell unit. The wound cell unit comprises positive and negative electrodes. The positive electrode comprises current collector and first active material. The negative electrode comprises current collector and second active material. The second active material has potential greater than 0.2 volts versus lithium reference electrode. The lithium-ion battery has wound electrode configuration. The wound cell unit comprises region (726) where edge of positive electrode is provided proximate an edge of negative electrode and second active material near the edge of the negative electrode does not extend beyond the first active material near the edge of positive electrode. The second active material has potential greater than 0.3, preferably 1.5 volts versus lithium reference electrode. The second active material extends to the edge of the negative electrode and the first active material extends to the edge of the positive electrode.    DESCRIPTION OF DRAWING(S) - The figure shows a cross sectional view of the lithium ion battery with accordion style electrodes.    Lithium-ion battery (100)    Casing (702)    Positive and negative electrodes (710, 720)    Current collector (712, 722)    First active material (714)    Second active material (724)    Region (726)