Multi-phase integration and structural hydration are effective material design strategies for advanced electrode materials with high capacity and fast lithiation. Herein, a novel layered-spinel lithium manganite hydrate is successfully synthesized through a one-step hydrothermal lithiation process. Structure characterizations, electrochemical properties, reaction mechanisms and kinetic analysis are investigated in detail. The layered-spinel coexistence, stable intercalated water, abundant interfaces/defects and mesoporous architectures comprising 2D nanosheets help to shorten the Li-ion transport pathway, promote electronic/ion conductivity, increase Li storage sites and maintain structural stability. With combined diffusion-controlled and pseudocapacitive reaction mechanisms, the layered-spinel lithium manganite hydrate exhibits superior electrochemical behaviors, showing great potentials for high-capability and ultrafast lithium storage. The comprehensive utilization of multi-phase integration and structural hydration promotes the diversity of material and structure systems, and further paves new way for the design of other high-performance electrode materials.