Zn　metal　is　considered　as　one　of　the　most　promising　anodes　for　aqueous　high-energy　batteries　owing　to　its　high　theoretical　capacity,　low　redox　potential,　abundant　resource,　and　low　toxicity.　However,　Zn　metal　anodes　(ZMAs)　still　suffer　from　a　few　challenging　problems　such　as　low　irreversibility　and　dendrite　growth　during　plating/stripping.　In　this　study,　we　identify　and　quantify　the　composition　of　inactive　Zn　responsible　for　capacity　loss,　which　shows　that　it　contains　57　mol%　of　unreacted　Zn-0　and　43　mol%　Zn-containing　byproducts.　Based　on　this　quantitative　result,　we　developed　an　environmentally　friendly　water/glycerol　hybrid　electrolyte,　which　enable　the　dendrite-free　plating/stripping　of　Zn　with　a　high　coulombic　efficiency　of　97.6%　over　500　cycles.　A　symmetric　Zn||Zn　cell　can　be　repeatedly　plated/stripped　for　more　than　1500　h　at　1　mA　cm(-2).　Glycerol　can　suppress　the　side　reactions　caused　by　water　in　the　hybrid　electrolyte　because　of　the　strong　binding　interactions　between　glycerol　and　the　Zn　metal.　The　molecular-scale　modeling　simulations　and　electrochemical　analysis　reveal　that　the　dense　and　uniform　Zn　electro-deposition　is　related　to　the　Zn2+-solvation-sheath　structure.　The　fundamental　understanding　of　ZMAs　in　aqueous　and　hybrid　electrolytes　opens　a　viable　route　for　the　highly　efficient　utilization　of　Zn　with　high　efficiency　and　safety.