Aiming　to　improve　the　decay　in　thermochemical　energy　storage　(TCES)　performance　of　CaO-based　looping　materials　with　the　number　of　carbonation/calcination　cycles,　a　series　of　Y/Mg-codoped　CaO-based　materials　were　prepared　by　using　the　classical　sol−gel　method　and　citric　acid　as　a　carbon　template　to　enhance　the　porosity　and　specific　surface　area.　The　structural　characterizations　showed　that　Y　and　Mg　were　presented　in　two　forms.　Part　of　Y/　Mg　was　presented　in　the　form　of　Y2O3　and　MgO　nanoparticles　with　an　average　size　of　15　and　40　nm,　respectively.　These　Y2O3　and　MgO　nanoparticles　with　high　Tammann　temperature　and　thermal　conductivity　were　highly　dispersed　to　retard　the　sintering　and　growth　of　CaO　grains.　The　rest　of　Y　and　Mg　were　doped　into　the　framework　of　the　CaO　lattice　in　atomic　form　by　substituting　Ca　atoms.　These　Y　and　Mg　created　a　large　amount　of　the　oxygen　vacancies　surrounding　Ca　atoms　to　facilitate　the　electron　transfer　from　Ca2+　ions　to　dopants,　which　enhanced　the　CO2　capture　capacity　of　CaO-based　materials　by　improving　the　kinetics　of　the　carbonation　reaction.　As　a　result,　the　optimal　CaO-based　composite　denoted　as　Ca/Y5/Mg10　exhibited　a　high　initial　energy　storage　density　of　up　to　＞2300　kJ/kg　and　held　an　excellent　looping　reaction　stability　after　25　carbonation/calcination　cycles　owing　to　the　cooperation　of　Y　with　Mg　additives.　This　work　provided　effective　and　economical　CaO-based　looping　materials　for　application　in　thermochemical　energy　storage.　©　2024　American　Chemical　Society.