Reinforced concrete-like Na3.5V1.5Mn0.5(PO4)3@graphene hybrids with hierarchical porosity as durable and high-rate sodium-ion battery cathode

Realizing high-rate capability and high-efficiency utilization of polyanionic cathode materials is of great importance for practical sodium-ion batteries (SIBs) since they usually suffer from extremely low electronic conductivity and limited ionic diffusion kinetics. Herein, taking Na3.5V1.5Mn0.5(PO4)3 (NVMP) as an example, a reinforced concrete-like hierarchical and porous hybrid (NVMP@C@3DPG) built from 3D graphene ("rebar") frameworks and in situ generated carbon coated NVMP ("concrete") has been developed by a facile polymer assisted self-assembly and subsequent solid-state method. Such hybrids deliver superior rate capability (73.9 mAh/g up to 20 C) and excellent cycling stability in a wide temperature range with a high specific capacity of 88.4 mAh/g after 5000 cycles at 15 C at room temperature, and a high capacity retention of 97.1% after 500 cycles at 1 C (−20 °C), and maintaining a high reversible capacity of 110.3 mAh/g in full cell. This work offers a facile and efficient strategy to develop advanced polyanionic cathodes with high-efficiency utilization and 3D electron/ion transport systems.