Mg‐Doped Na₄Fe₃(PO₄)₂(P₂O₇)/C Composite with Enhanced Intercalation Pseudocapacitance for Ultra‐Stable and High‐Rate Sodium‐Ion Storage

Abstract

Na 4 Fe 3 (PO 4 ) 2 (P 2 O 7 ) (NFPP) is considered as a promising cathode material for sodium-ion batteries (SIBs) due to its low cost, non-toxicity, and high structural stability, but its electrochemical performance is limited by the poor electronic conductivity. In this study, Mg-doped NFPP/C composites are presented as cathode materials for SIBs. Benefiting from the enhanced electrochemical kinetics and intercalation pseudocapacitance resulted from the Mg doping, the optimal Mg-doped NFPP/C composite (NFPP-Mg5%) delivers high rate performance (capacity of ≈40 mAh g −1 at 20 A g −1 ) and ultra-long cycling life (14 000 cycles at 5 A g −1 with capacity retention of 80.8%). Moreover, the in situ X-ray diffraction and other characterizations reveal that the sodium storage process of NFPP-Mg5% is dominated by the intercalation pseudocapacitive mechanism. In addition, the full SIB based on NFPP-Mg5% cathode and hard carbon anode exhibits the discharge capacity of ≈50 mAh g −1 after 200 cycles at 500 mA g −1 . This study demonstrates the feasibility of improving the electrochemical performance of NFPP by doping strategy and presents a low-cost, ultra-stable, and high-rate cathode material for SIBs.

Large Scalable Preparation of Ti-Doped Na4Fe3(PO4)2P2O7 as Cathode Material for High Rate and Long-Life Sodium-Ion Batteries

“…Its full XPS spectrum (Figure a) shows a clear presence of Na, Fe, Ti, P, O, and C elements, which is in good agreement with the EDS mapping (Figure S4). The typical Fe 2p3/2 and Fe 2p1/2 of Fe 2+ are, respectively, demonstrated as two symmetric bands with binding energies of 711.23 and 725.44 eV in Figure b . This also proves once again that Fe 3+ in the raw material is successfully reduced to Fe 2+ by carbon.…”

High‐Entropy Doping Boosts Ion/Electronic Transport of Na4Fe3(PO4)2(P2O7)/C Cathode for Superior Performance Sodium‐Ion Batteries

“…Lately, Mg‐doped Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 /C composites displays enhanced electrochemical kinetics to obtain high rate and ultralong cycling life. [ 13 ] Unfortunately, the interaction mechanism and structure evolution by metal‐ion doping are not clear. Recently, high‐entropy has been applied to materials and stimulated interest of researchers through the combination of multiple cation elements, which increases the configurational entropy and enhances robust properties of materials.…”

Atomic Manufacturing in Electrode Materials for High-Performance Batteries

“…This approach increases the number of active sites, thereby improving conductivity and promoting the interface interaction, which facilitates electrolyte infiltration and enhances current carrier diffusion. Meanwhile, metal doping, including Co, Mg, Cr, and Ti, has the potential to generate localized highly reactive regions and enhance conductivity, thus enhancing the superior rate performance of metal oxide electrodes. , Consequently, the electron transport pathway of the electrode material can be optimized by atomic manufacturing, and the rate performance of the battery can be effectively improved.…”

“…Meanwhile, metal doping, including Co, Mg, Cr, and Ti, has the potential to generate localized highly reactive regions and enhance conductivity, thus enhancing the superior rate performance of metal oxide electrodes. 91,92 Consequently, the electron transport pathway of the electrode material can be optimized by atomic manufacturing, and the rate performance of the battery can be effectively improved. The ion migration dynamics, which have a crucial impact on the rate performance of batteries, is determined by the diffusion of ions within the electroactive material.…”