NOVELTY - A power supply device consists of battery cells (12) provided with a wound electrode component wound in a state in which a positive electrode and a negative electrode are mutually insulated through a separator, a battery exterior component, and a protection mechanism which ensures safety during increase in internal pressure. The positive mix layer contains lithium carbonate. Each battery cell is arranged in parallel such that the winding axis of the wound electrode component is in vertical direction.    USE - Power supply device. Uses include but are not limited to electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, backup power supply apparatus mounted in computer server racks, backup power supply apparatus used for wireless base stations, mobile telephone, household power supply devices, and electrical storage apparatus combined with solar cell.    ADVANTAGE - The power supply device prevents drop in fluidity of gas inside a battery cell and causes the protection mechanism which operates in a case where the internal pressure of a battery cell rises to operate promptly.    DETAILED DESCRIPTION - A power supply device consists of battery cells provided with a wound electrode component wound in a state in which the positive electrode and negative electrode are mutually insulated through a separator, a battery exterior component, and a protection mechanism which ensures safety during increase in internal pressure. The positive electrode has a positive mix layer, and the negative electrode has a negative mix layer. The positive mix layer contains lithium carbonate. Each battery cell is arranged in parallel such that the winding axis of the wound electrode component is in vertical direction.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic isometric view of battery block, battery control apparatus, and peripheral structure. (Drawing includes non-English language text)    Battery block (4)    Battery control apparatus (6)    Battery cell (12)    Spacer (14)    End plate (18)