An Asymmetric Sodium Extraction/Insertion Mechanism for the Fe/V-Mixed NASICON Na₄FeV(PO₄)₃

Reversible Activation of V4+/V5+ Redox Couples in NASICON Phosphate Cathodes

“…The slight Fe oxidation could be ascribed to exposure to air during transfer or measurements, which is similar to other Fe-based phosphate cathodes reported. [13,32] Moreover, the element concentration of samples determined by inductively coupled plasma-optical emission spectroscopy (ICP) also presents an acceptable consistency with their designed chemical composition (Table S8, Supporting Information), verifying high purities of these cathodes.…”

“…Several prominent peaks between 0-4 Å could be assigned to the first TM-O (TM = V or Fe) coordination shell and TM-P/Na outer shells. [32,43] At the first TMO coordination shell, the lowered EXAFS signal intensity and shorted interatomic distance could be observed along with the extraction of Na + from lattice crystal. While the EXAFS signals collected at the pristine and discharged (to 2.0 V) states are almost overlapping, indicating complete reversibility of the redox processes.…”

Na+-Activation Engineering in the Na3V2(PO4)3 Cathode with Boosting Kinetics for Fast-Charging Na-Ion Batteries

“…27−31 Beyond this, the rational design of the crystal lattice via element doping and substitution promotes the functional regulation of the inherent structure to achieve the desired performance. 32−34 Based on this, 3d transition metals such as Ti, Fe, Mn, Ni, Al, and Cr have been introduced as promising alternatives for vanadium to design specific NASICON compounds, such as Na 3 VTi(PO 4 ) 3 , 35 Na 4 VFe(PO 4 ) 3 , 36 N a 4 M n V ( P O 4 ) 3 , 3 7 N a 3 + x V x N i 1 − x ( P O 4 ) 3 , 3 8 Na 3 V 1.5 Al 0.5 (PO 4 ) 3 , 39 Na 3 Cr 0.5 V 1.5 (PO 4 ) 3 , 40 and so forth. Compared with the pure NVP cathode, the discovery of these components has effectively reduced the raw material cost and obtained superior Na-storage performance owing to the strengthened bonding interaction and structural stability.…”

“…So far, considerable efforts have been made on the modification of electronic/ionic transmission paths to ameliorate the intrinsic conductivity, including conductive network construction, size/morphology regulation, and lattice-oriented regulation. ,− The carbon coating strategy with the 1D carbon nanotube, 2D reduced graphene oxide, , or 3D porous graphene aerogel could accelerate the efficient electronic transport to varying degrees relying on the highly conductive carbon network distributed in the active materials. As for the microstructure, the small particle size in cathode materials could reduce the diffusion length of ions and electrons, while special morphology induces the benign evolution of the interface contact and reaction strain, jointly contributing to the facilitation of electrochemical reaction. − Beyond this, the rational design of the crystal lattice via element doping and substitution promotes the functional regulation of the inherent structure to achieve the desired performance. − Based on this, 3d transition metals such as Ti, Fe, Mn, Ni, Al, and Cr have been introduced as promising alternatives for vanadium to design specific NASICON compounds, such as Na 3 VTi­(PO 4 ) 3 , Na 4 VFe­(PO 4 ) 3 , Na 4 MnV­(PO 4 ) 3 , Na 3+ x V x Ni 1– x (PO 4 ) 3 , Na 3 V 1.5 Al 0.5 (PO 4 ) 3 , Na 3 Cr 0.5 V 1.5 (PO 4 ) 3 , and so forth. Compared with the pure NVP cathode, the discovery of these components has effectively reduced the raw material cost and obtained superior Na-storage performance owing to the strengthened bonding interaction and structural stability.…”

Constructing p-type substitution induced by Ca2+ in defective Na3V2−xCax(PO4)3/C wrapped with conductive CNTs for high-performance sodium-ion batteries

“…[23][24][25] Carbon nanotubes (CNTs), as a type of carbon material with a special structure and high electrical conductivity, have been widely used in electrode materials and matrix loading. [26][27][28] After adding CNTs, a network between the particles is established, which affords fast diffusion channels for Na + and improves the electronic conductivity. Besides changing the surface of NVP, another option is changing its bulk phase.…”