In recent years, metal-boron-hydrogen compounds have received attention as solid electrolytes (SE) for battery applications. These compounds have a rich chemistry allowing an organic-like array of modifications to tune their electrochemical properties.[1] Much work has been performed on closo-dodecaborates such as Li2B12H12, which can have high enough solid-state ion conductivities to act as electrolytes for battery applications for lithium, sodium, etc. The highest room temperature ionic conductivities for sodium-based solid-state electrolytes were recently published for Na-salts of the polymeric anions B24H233- and B36H344- derived from closo-B12H122-. [2, 3] Most impressively these compounds also display extreme oxidative stabilities > 6 V. The currently published synthetic method is not selective and it is difficult to achieve high yield of the desired compounds. We report an electrochemical synthesis method that is more reliable and also report the properties for Li3B24H23 for the first time.