context: Electrides are a unique class of materials, where the electron density is neither localised at an atomic orbital nor fully delocalised like in metals. Instead, their electrons occupy interstitial regions formed by cavities in the crystal structure, where they act as anions. Materials with anionic electrons offer versatile functionalities, such as high electrical conductivity, ultra-low work function, and non-linear optical responses, ranging their applications as electron emitters, battery anodes, and agent catalysts.