▎ 摘　　要

Finding suitable electrode materials for energy storage devices with large ions like Na+ and K+ is notoriously difficult. Herein, MnO2@graphene with hierarchical lamellar structure has be synthesized. The flower-like lamellar-structured MnO2 and nanosheets of graphene combine together to form the composite with vast space for large ions to transport and store, as well as huge surface area for reactions. Sandwiched between graphene nanosheets, electrical conductivity and mechanical properties of MnO2 are highly enhanced, enabling it to withstand large current shock and long time cycling. In Li, Na and K ion batteries, MnO2@graphene all shows excellent electrochemical performance. Also, when coupled with liquid K-Na anode, MnO2@graphene displays better performance than with solid K anode, indicating its great potential at dendrite-free K ion battery. MnO2@graphene promotes the exploitation of more suitable electrode materials for alkali ion batteries, deepens understanding of their inner mechanisms, and boosts their commercialization.