Thermal energy storage technology is crucial for building heating and domestic hot water supply

playing an essential role in optimizing energy utilization. Hydrated salts have emerged as prominent materials for thermochemical energy storage (TCES)

with their sorption kinetics directly impacting thermal energy conversion efficiency. This study experimentally analyzes the microstructure and sorption performance of the EV/K

2

CO

3

composite sorbent. Numerical analysis methods are employed to evaluate the validity of various sorption kinetics models and to elucidate the sorption mechanism and potential limitations of the composite sorbent. The findings indicate that EV can disperse K

2

CO

3

salt particles while preserving a porous structure

thereby improving the sorption kinetics efficiency and stability of the EV/K

2

CO

3

composite sorbent. At low relative pressure

EV/K

2

CO

3

demonstrates a chemical adsorption mechanism

with nucleation models accurately predicting its sorption behavior

primarily limited by the nucleation and growth of hydrated salt crystals. At moderate relative pressure

EV/K

2

CO

3

exhibits a mechanism involving both chemical adsorption and solution absorption

with diffusion models and the first-order model showing higher prediction accuracy

primarily l

imited by diffusion within or outside the product layer. At high relative pressure

EV/K

2

CO

3

primarily undergoes solution absorption

with geometric contraction models and the first-order model displaying good predictive performance

primarily limited by the reaction phase interface. This study enhances comprehension of the sorption mechanism of the EV/K

2

CO

3

composite

providing a scientific foundation for the development of high-performance TCES materials suitable for building and environmental applications.