Electrolytes with low cationic mobility activation energies

An electrolyte comprising:

• a composite salt mixture comprising:
• between 0.975 and 0.05 mole fraction of a halogen-free closo-borate salt comprising a first cation selected from the group consisting of Li+, Na+, Mg2+, and Ca2+, and a closo-borate anion having a structure selected from the group consisting of:
• [ByH(y−z)Rz]2−, [CB(y−1)H(y−z)Rz]−, [C2B(y−2)H(y−t−1)Rt]−, [C2B(y−3)H(y−1)Rt]−, and [C2B(y−3)H(y−t−1)Rt]2−, and wherein:
• y is an integer within a range of 6 to 12;
• (z) is an integer within a range of 0 to y;
• (t) is an integer within a range of 0 to (y−1);
• and
• R is a linear, branched-chain, or cyclic C1-C18 alkyl group;
• between 0.025 and 0.95 mole fraction of a halogenated closo-borate salt comprising a second cation selected from the group consisting of Li+, Na+, and Mg2+, Ca2+ and a halogenated closo-borate anion having the structure selected from the group consisting of:
• [ByH(y−z−i)RzXi]2−, [CB(y−1)H(y−z−i)RzXi]−, [C2B(y−z)H(y−t−j−1)RzXj]−, [C2B(y−3)H(y−t−j)RtXj]−, and [C2B(y−3)H(y−t−j−1)RtXj]2−, and wherein:
• y is an integer within a range of 6 to 12;
• (z+i) is an integer within a range of 0 to y;
• (t+j) is an integer within a range of 0 to (y−1);
• X is F, Cl, Br, I, halogenated alkyl group including CF3, or a combination thereof;
• and
• R is a linear, branched-chain, or cyclic C1-C18 alkyl or fluoroalkyl group,
• wherein the composite salt mixture comprises a cationic conductivity that is at least one order of magnitude greater than a cationic conductivity of the halogen-free closo-borate salt and a cationic conductivity of the halogenated closo-borate salt.