In　this　research,　the　properties　of　GaN　monolayer,　defective　GaN　monolayer　with　N　vacancies　(GaN-VN),　and　van　der　Waals　(vdW)　heterostructures　composed　of　them　and　graphene　(GaN/graphene,　GaN-VN/graphene)　are　systematically　investigated　using　density　functional　theory　(DFT),　which　includes　assessment　of　the　structure＇s　stability,　mechanical　property,　electronic　structure　analysis,　lithium　adsorption　and　diffusion　properties,　maximum　theoretical　capacity,　and　average　open-circuit　voltage.　The　calculations　show　that　two-dimensional　GaN　transforms　from　semiconductor　to　metal　by　forming　nitrogen-vacancy　defects.　This　increases　lithium　adsorption　performance　while　ensuring　rapid　electron　motion　in　the　electrode　during　lithium　adsorption　and　removal　processes.　The　synergistic　effect　between　the　heterostructure　layers　and　the　presence　of　the　built-in　electric　field　improves　the　electron　and　ion　conductivity　and　lowers　the　migration　energy　barriers.　In　addition,　the　maximum　theoretical　capacities　of　defective　GaN-VN,　GaN/graphene,　and　GaN-VN/graphene　can　reach　970　mAh/g,　884　mAh/g,　and　890　mAh/g,　respectively,　far　exceeding　those　of　the　conventional　graphite　anode　material　(372　mAh/g).　The　above　advantages　indicate　that　defective　GaN-VN,　GaN/graphene,　and　GaN-VN/　graphene　are　potential　replacements　for　lithium-ion　battery　anodes.