Large-size　MXene　flakes　have　drawn　growing　attention　due　to　their　fascinating　properties,　which　inevitably　suffer　from　the　low　yield　and　weak　oxidation　resistance.　Herein,　an　electrochemical　exfoliation　approach　is　proposed　to　achieve　a　high　recording　yield　of　87%　for　preparing　large　antioxidative　MXene　flakes　with　an　average　lateral　size　of　8.3 µm,　which　combines　the　etching,　electrolyte　intercalation,　interlay　expansion,　and　short-time　sonication.　Moreover,　the　MXene　flakes　can　keep　stable　for　over　three　months　in　the　presence　of　water　and　oxygen,　and　even　have　good　stability　over　500 °C　under　an　air　atmosphere,　ascribed　to　the　protection　of　the　surface　electrolyte　layer.　Combined　with　bacterial　cellulose,　the　MXene　can　serve　as　an　intelligent　resistance-type　sensor　for　contact/non-contact　fire　alarm,　and　further　integrate　with　IoT　for　remote　fire　detection　and　warning　within　1 s.　In　addition,　the　MXene　significantly　improves　the　flame-retardant　properties　of　indoor　textiles　and　household　materials,　owing　to　the　large　thermostable　2D　barriers　to　restrain　heat　and　mass　transfer.　This　work　establishes　an　innovative　and　efficient　method　to　prepare　the　large　antioxidative　MXene　flakes　in　high　yield　for　practical　usage　and　extends　its　application　to　polymeric　fire　safety.　©　2024　Wiley-VCH　GmbH.