High temperature metal oxide thermochemical energy storage materials: Thermodynamic and kinetic investigations

Cobalt (Co-) and copper (Cu-) based metal oxides are promising materials for high-temperature thermochemical energy storage (HT-TCES) due to their rapid redox kinetics, low thermal hysteresis, substantial energy density, and unlimited storage duration. However, their commercial application is hindered by challenges involving multi-physics and cross-scale coupling phenomenon. A comprehensive investigation is essential for material optimization and scale up. Therefore, this study experimentally explores Co- and Cu-based metal oxides mixed with Al 2 O 3 and MgO respectively through comprehensive micro/macro-structure, thermodynamic and kinetics characterization. The results reveal that Co 3 O 4 /CoO with 10 wt% Al 2 O 3 (CoAl10) shows redox-enthalpy of 378 J g -1 and 359 J g -1 after 150 cycles, corresponding to reductions of 1.6 % and 8.8 %. While for CuO/Cu 2 O with 15 wt% MgO (CuMg15), maintains redox-reaction enthalpy of 448 J g -1 and 446 J g -1 with reductions of 24 % and 21 %. During cycling, spinel CoAl 2 O 4 and spinel-like Cu 2 MgO 3 structures formed enhance oxygen vacancy formation and mechanical strength. Notably, CoAl10 can withstand maximum compressive stress of 8 MPa for after 60 cycles. Kinetic models for CoAl10 and CuMg15 were developed using experimental data, providing insights to improve thermochemical energy storage models and advance material development for HT-TCES applications. This work aims to elucidate the multi-scale mechanisms governing performance and durability, paving the way for optimized Co- and Cu-based metal oxides in high-temperature energy storage systems.