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Na3V2(PO4)3 (NVP), as a great potential cathode candidate for Na-ion batteries (NIBs), has attracted enormous interest due to its three-dimensional (3D) large open framework for convenient Na+ transport, yet its practical application is still limited by its inferior electron conductivity and sluggish Na+ diffusion kinetics. Herein, the tiny Cr doped hierarchical NVP micro-flower cathodes (i.e., Na3V2−xCrx(PO4)3@C, x ≤ 0.1), which are self-assembled with single-crystal nanoflake subunits in-situ coated with carbon nano-shell, are designed and fabricated via a scalable avenue. The optimized cathode, i.e., Na3V1.94Cr0.06(PO4)3@C (NVCP-6), was endowed with more electro-active Na(2) sites and higher electronic/ionic conductivity for efficient sodium storage. Benefiting from these competitive merits, the NVCP-6, when evaluated as a cathode towards NIBs, exhibits an ultrahigh-rate capability of 99.8 mAh·g−1 at 200 C and superior stability of 82.2% over 7300 cycles at 50 C. Furthermore, the NVCP-6 based full NIBs display remarkable electrochemical properties in terms of both high-rate capacities and long-duration cycling properties at different temperatures (−20–50 °C). The contribution, i.e., the design of “four ounces can move a thousand pounds”, here will promote the practical industrial application of NVP towards advanced NIBs.
This work was supported by the National Natural Science Foundation of China (Nos. 51904115, 52072151, 52171211, 52271218, and U22A20145), Taishan Scholars (No. ts201712050), Jinan Independent Innovative Team (No. 2020GXRC015), and Major Program of Shandong Province Natural Science Foundation (No. ZR2021ZD05).