NOVELTY - The electrolyte layer (20) for holding nonaqueous electrolyte at separator, has positive electrode (11p) containing positive electrode active material layer (15p) and positive-electrode collector (13p) and negative electrode (11n) containing negative electrode active material layer (15n) and negative-electrode collector (13n), at both surfaces. The end face portions of electrodes are rectangular in surface direction of cell layer. The battery element has reference pole (11r) which is arranged adjacent to end face portion of positive or negative electrode.    USE - For battery pack used in motor vehicle (all claimed).    ADVANTAGE - The electrical potential difference between positive and negative electrodes can be monitored correctly by arranging reference pole in battery pack. The generation of dendrite precipitation of lithium metal in negative electrode is suppressed reliably.    DETAILED DESCRIPTION - The width of the end face portions of positive and negative electrodes is 0.01-25% with respect to perimeter length of the electrodes. The shape of the electrodes becomes polygon from direction vertical to surface direction of cell layer. The distance of the end face portion and reference pole is below half of the width of the end face portion. The electrical potential of the negative electrode active material is +1.0V or less than the reduction potential of electrolyte cation such as lithium cation. The negative electrode active material is selected from carbon, graphite, boron, acetylene black, vapor-phase-epitaxy carbon fiber, tin, silicon, lead, zinc, indium, aluminum or lithium. The reference pole material is selected from lithium metal, graphite, lithium manganate, olivine-type phosphoric acid iron lithium or lithium titanate. An INDEPENDENT CLAIM is also included for method of using nonaqueous-electrolyte secondary battery that involves performing charging processing or electrodischarge treatment with respect to reference pole in order to make two-phase coexistence state to recover the composition of reference pole active material when composition of reference pole active material deviates from a two-phase coexistence state.    DESCRIPTION OF DRAWING(S) - The figure shows a sectional view of the battery element in nonaqueous-electrolyte secondary battery.    Negative electrode (11n)    Positive electrode (11p)    Reference pole (11r)    Negative electrode collector (13n)    Positive electrode collector (13p)    Negative electrode active material layer (15n)    Positive electrode active material layer (15p)