| abstract |
The present invention relates to one kind to support at least 500 μ A/cm at negative electrode 2 Current density sodium electro-chemical cell, the sodium electro-chemical cell includes (i) negative electrode and (ii) sodium ion ionic liquid electrolyte, the Na ion concentration of the sodium ion ionic liquid electrolyte is not less than the 75% of the saturation limit value of sodium ion in the electrolyte, and wherein negative electrode has solid-electrolyte interphace (SEI) layer for having already passed through the result of a polarization cycle as electro-chemical cell and being formed. |