Patent ID: 8617744

Claim:
An energy storage device comprising: a positive electrode comprising a nitroxyl compound having a nitroxyl cation partial structure represented by the following formula (I) in an oxidized state and having a nitroxyl radical partial structure represented by the following formula (II) in a reduced state; a negative electrode comprising a carbon material, wherein lithium ions can be reversibly intercalated into and deintercalated from said carbon material; and an electrolytic solution comprising a lithium salt and an aprotic organic solvent, wherein the negative electrode is a negative electrode comprising the carbon material wherein lithium ions are previously intercalated into said carbon material, apart from lithium ions associated with a capacity A of lithium capable of being intercalated and deintercalated in charge and discharge, and wherein a ratio of the capacity A of lithium capable of being intercalated into and deintercalated from the negative electrode in charge and discharge to a capacity C of lithium capable of being intercalated into and deintercalated from the positive electrode in charge and discharge, A/C, is in the range of 1.1â‰¦A/Câ‰¦10