[Expectant_Philosopher (OP)]

Energy storage in a capacitor depends on storing positive and negative charges separately.  Breakdown of the electric field occurs with sufficient energy to create a circuit in the storage medium.  In a vacuum the breakdown occurs at the Schwinger limit, a point at which electron-positron pairing occurs by subatomic impurities present in the vacuum.  Could we create the vacuum in a sub-atomically shielded magnetic bottle for the positive side and another for the negative side, then load each bottle with appropriate charges using a laser pumped through a multistage filter for negative charges and a parallel laser pump with multistage filter for positive charges.  All this to create an energy storage device substantially better than any battery.