Quasi-solid sodium ions electrolyte of ${\hbox {Na}}_{2} \hbox {O}{-} {\hbox {B}}_{2} {\hbox {O}}_{3}{-} {\hbox {SiO}}_{2} {-} {\hbox {H}}_{2} \hbox {O}$ system hydrated glass

Abstract

${\hbox {Na}}_{2}\hbox {O} {-} {\hbox {B}}_{2} {\hbox {O}}_{3}{-} {\hbox {SiO}}_{2}{-} {\hbox {H}}_{2} {\hbox {O}}$ system hydrated glass with $T_{\mathrm {g}}$ ranges from $-10 \hbox { to } 150^{\circ }$C is synthesized by aqueous chemical methods and is applied to symmetrical cells as quasi-solid electrolyte. At the temperature around $T_{\mathrm {g}}$, the solid state transforms to quasi-solid state, whose mechanical property keeps like gel electrolyte, but the conductivity leaps from $5.31 \times 10^{-6} \, {\hbox {S cm}}^{-1}$ to $5.43 \times 10^{-3} \, {\hbox {S cm}}^{-1}$, much higher than most of the glass–ceramic electrolytes. As most of the solvated water is evaporated, ${\hbox {H}}_{2}{\hbox {O}}$ left in the system distributes in the intervals as hydroxyl, which is much benefit to the ions transportation, and more important is to increase the voltage window to 2.24 V and even higher. The cycle performance is also researched. After 1000 circulations, there is still 65% capacity retention and no obvious damage is discovered in the electrolyte, which means much better cycle property of the electrolyte than gel electrolyte. Other compositions in the quasi-solid system including different contents of ${\hbox {B}}_{2}{\hbox {O}}_{3}$, ${\hbox {Na}}_{2} {\hbox {SO}}_{4}$ and m in sodium silicate ${\hbox {NaO}}_{2}{\cdot }{\hbox {mSiO}}_{2}$ are also studied. In general, quasi-solid ${\hbox {Na}}_{2}\hbox {O} {-} {\hbox {B}}_{2}{\hbox {O}}_{3}{-} {\hbox {SiO}}_{2}{-} {\hbox {H}}_{2}{\hbox {O}}$ system owns better conductivity and cycle performance than most glass–ceramic solid electrolyte, and it is environment-friendly, inexpensive and practical to be used as sodium ions quasi-solid electrolyte.