The effect of SiO₂ additives on solid hydroxide ion-conducting polymer electrolytes: a Raman microscopy study

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Science

Background:

• Alkaline polymer electrolytes are crucial for electrochemical devices.
• Optimizing conductivity and longevity of these electrolytes is an ongoing challenge.
• The influence of filler additives on electrolyte performance requires detailed investigation.

Purpose of the Study:

• To investigate the effect of micro- (mSiO2) and nano-sized (nSiO2) silicon dioxide additives on the conductivity and longevity of tetraethylammonium hydroxide (TEAOH)-poly(acrylamide) (PAM) polymer electrolytes.
• To understand the role of relative humidity (RH) on the performance of these modified electrolytes.
• To correlate structural changes with observed electrochemical properties.

Main Methods:

• Electrochemical impedance spectroscopy (EIS) was used to measure ionic conductivity.
• Raman microscopy was employed to analyze structural changes and crystallization.
• Studies were conducted under varying relative humidity conditions (75% RH and 45% RH).

Main Results:

• At 75% RH, nano-sized SiO2 (nSiO2) significantly boosted OH- ionic conductivity to 25 mS cm-1, whereas micro-sized SiO2 (mSiO2) resulted in lower conductivity (10 mS cm-1).
• At 45% RH, dehydration led to crystallization and reduced conductivity in all electrolytes.
• mSiO2 accelerated TEAOH crystallization, while nSiO2 delayed it, impacting electrolyte longevity.

Conclusions:

• Nano-sized SiO2 additives are effective in enhancing ionic conductivity and improving the hydration stability of TEAOH-PAM polymer electrolytes.
• The size of SiO2 particles critically influences the crystallization behavior and ionic transport properties of the polymer electrolyte.
• Raman microscopy provides valuable insights into the structural mechanisms governing the performance of SiO2-modified polymer electrolytes.