Alkali-Activated Metakaolin Geopolymers as Structural Electrolytes: Insights into Structure–Function Relationships and Energy Storage Potential

The integration of mechanical robustness and ionic conductivity within cementitious materials represents a promising strategy toward multifunctional structural electrolytes for energy‐storage‐integrated construction systems. In this study, alkali‐activated metakaolin (MK) geopolymers were modified with different sodium salts (Na 2 SO 4 , NaCl, and NaOH) to elucidate the correlation between gel structure evolution, ion transport behavior, and electrochemical performance. Results showed that the incorporation of sodium salts significantly enhanced the ionic conductivity and capacitive performance of the geopolymer electrolytes. The Na 2 SO 4 ‐modified sample (MK‐S) exhibited the highest ionic conductivity of 33.22 mS cm -1 and an areal capacitance of 603.93 mF cm -2 , corresponding to a 4.5‐fold increase over unmodified MK. This improvement is attributed to the synergistic effect of increased mobile Na + concentration and optimized pore connectivity induced by SO 4 2- coordination. These findings demonstrate a viable route toward durable structural solid electrolytes for next‐generation energy‐storage‐integrated building materials.