why there are no standard potentials more negative than -3v?

Reduction potential(also known asredox potential,oxidation / reduction potential,is a measure of the tendency of achemical speciesto acquireelectronsand thereby bereduced. Reduction potential is measured involts(V), or millivolts (mV). Each species has its own intrinsic reduction potential; the more positive the potential, the greater the species' affinity for electrons and tendency to be reduced
because in the method for calculating standard electrode potential lithium has the highest negative value which is -3.05.moreover with the loss of electron it acquires fully filled electronic configuration