| abstract |
It is an object of the present invention to reduce instability of an electrode of a hybrid energy storage device in a deep discharge or overcharge state. Means for Solving the Problem It has at least one lead-based positive electrode, at least one carbon-based negative electrode, a separator between the electrodes, and a case for holding the electrode, the separator, and the acidic electrolyte. The above objects and advantages are achieved by a hybrid energy storage device having at least one cell. The separator is gas permeable. The amount of acidic electrolyte in the at least one cell is less than the allowable limit of acidic electrolyte absorption by the gas permeable separator, at least one positive electrode, and at least one negative electrode. As the cell is assembled, the case is closed and there is no acidic electrolyte in the assembled cell. |