NOVELTY - Electrochemical cell (300) (I) comprises: a negative electrode assembly (310) comprising negative electrode active material and a negative electrode electrolyte (II), which is reductively stable against the negative electrode active material; and a positive electrode assembly (320) comprising positive electrode active material and a positive electrode electrolyte (III), which is oxidatively stable against the positive electrode active material, where the (II) and (III) are not the same.    USE - (I) is useful in electrochemical devices such as capacitors, electrochemical/capacitive memory, electrochemical (e.g. dye sensitized) solar cells and elctrochromic devices.    ADVANTAGE - (I) has a lithium (Li) cycling efficiency of greater than 99.7 (preferably 99.9)% over 500 cycles. (I), at the negative electrode assembly and/or the positive electrode assembly, there is an impedance value after 10 cycles and the value increases by no more than 40 (preferably no more than 10)% after 500 cycles. (I) has a capacity value after 10 cycles and the value decreases by no more than 40 (preferably no more than 10)% after 500 cycles. (I) has optimal function. (I) is electrochemically stable and robust.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for an electrochemical cell comprising: a negative electrode comprising a film of lithium metal and a film of a negative electrode electrolyte that is reductively stable against the lithium metal; and a positive electrode comprising nickel cobalt aluminum oxide and a positive electrode electrolyte that is oxidatively stable against the nickel cobalt aluminum oxide, where the negative electrode electrolyte and the positive electrode electrolyte are not the same.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic illustration of an electrochemical cell.    Electrochemical cell (300)    Negative electrode assembly (310)    Negative electrode active material particles (314)    Positive electrode assembly (320)    Intervening separator. (330)