Xiaoyu Jiang,Ziqi Zeng,Lifen Xiao,Xinping Ai,Hanxi Yang,Yuliang Cao
Development of intrinsically safe and long lifespan sodium-ion batteries (SIBs) is urgently needed for large-scale energy storage applications. However, most of the currently developed SIBs suffer from insufficient cycle life and potential unsafety. Herein, we construct an all-phosphate sodium-ion battery (AP-SIB) using a Na3V2(PO4)3 cathode, NaTi2(PO4)3 anode, and nonflammable trimethyl phosphate (TMP) electrolyte. The AP-SIB exhibits not only high safety, high rate performance, and ultralong cycle life but also zero-strain characteristics due to the inverse volume change of the phosphate cathode and anode during charge and discharge cycles, offering a safer and cycle-stable Na-ion technology for electric storage applications.
For Na 3 V 2 (PO 4 ) 3 (NVP) cathode, the activity and utilization rate of Na and V is the key to affecting its electrochemical properties. However, few studies can simultaneously optimize both. Currently, a facile hydrothermal route is proposed to successfully synthesize the honeycomb-like porous NVP@CHSLS cathodes possessing anchoring effects to enhance the immobilization of active Na/V through in situ carbonation with chitosan and sodium lignosulfonate. DFT calculations demonstrate the N/S co-doped carbon skeleton gains more electrons and behaves with superior charge transfer capability. Accordingly, XAFS verifies the existence of hypervalent V 4+ for the charge balance, as well as a newly generated C-N-V bond inside the bulk, which significantly inhibits the dissolution of V in the electrolyte. Moreover, ex-situ and after-cycled XRD verifies beneficial electrochemical intermediums such as Na 2 S manifest extra sodium fixation characteristics, which not only enter into the CEI membrane to reduce the loss of Na + , but also participate in the de-intercalation of Na + . Furthermore, honeycomb-like porous morphology enriches the active sites for Na + migration and improves the wettability of electrolytes, demonstrated by contact Angle and AFM tests. Consequently, the optimized NVP@CHSLS-2 reveals a high postactivated capacity of 104.5 mAh g −1 at 60 C, and it remains at 98.8% after 10 000 cycles at 60 C.
Sodium-ion batteries (SIBs) are regarded as promising candidates for large-scale stationary energy storage systems because of the high abundance of Na resources. Na superionic conductor polyanionic cathode (NASICON), such as Na 3 (VO 1-x PO 4 ) 2 F 1+2x (0 ≤ x ≤ 1, NVPF 1+2x ) and Na 3 V 2 (PO 4 ) 3 (NVP), shows intriguing electrochemical performances due to their robust open structure and superior cycle stability. Inspired by phase manipulation and conductive reduced graphene oxide (rGO) incorporation, a hierarchical NVPF 1+2x @NVP core-shell structure is elaborately synthesized and conformally wrapped by rGO via a facial microwave-assisted hydrothermal approach. F-free surface of NVPF 1+2x @NVP particle possesses intimate contact with rGO framework without strong mutual repulsive force while conductive rGO endows NVPF 1+2x @NVP with high electronic conductivity to ensure fast electron transport . Combining the synergistic effect between delicate design of core-shell structure and conductive rGO framework, the NVPF 1+2x @NVP/rGO-600 °C electrode achieves a high discharge capacity of 105.9 mAh g −1 at 0.5 C with an impressive capacity retention of 99.1% after 200 cycles, delivering an excellent rate capability of 90.6 mAh g −1 at 10 C. Moreover, the NVPF 1+2x @NVP/rGO-600 °C electrode possesses an alleviated polarization, small impedance and fast electron/Na + diffusion properties due to this synergistic effect. The full cell using NVPF 1+2x @NVP/rGO-600 °C cathode and hard carbon (HC) anode shows an initial discharge capacity of 80.0 mAh g −1 at 0.2 C and rate capability of 45.2 mAh g −1 at 10 C, which could light an LED lamp and manifest its prospective application. Our findings provide new insights into a broadly applicable material design combining morphological phase manipulation with conductive rGO framework incorporation, which synergistically boosts the electrochemical performance of NASICON cathode towards advanced SIBs with a higher energy density , faster charging rate and more practical applications.
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