Facile Synthesis of a Common Na‐Ion Battery Cathode Material Na₃V₂(PO₄)₂F₃ by Spark Plasma Sintering

Abstract

ln the pursuit of facile, fast, and efficient methods for the synthesis of various compounds for a variety of applications, spark plasma sintering (SPS) technique is considered to be a powerful and simple tool. Using this technique, a po pular cathode material for Na-ion batteries Na 3 V 2 (P0 4) 2 F 3 is synthesized and char acterized with X-ray diffraction and scanning electron microscopy (SEM), and is electrochemically tested in Swagelok-type cells in a galvanostatic mode. The matter, a lot of research eff ort has already been put into developing new, safe, high performance electrode materials for SIBs. Na 3 V 2 (PO 4) i F 3 (NVPF) has been consid ered as one of the very prornising cathode materials for SIB due to its high electro chemical stability, good electrochernical per formance (theoretical capacity: 128 mAh g-1 for 2Na + intercalation), and fast ion trans port propertiesP1 Since the discovery of its crystal structure in 1999 by Le Meins etaJ.,121 many synthetic routes of ptrre NVPF and its composites have been proposed and realized,13-81 including carbothermal redue tion, solid state, hydrothermal, and sol gel (followed by heat treatrnent) syntheses. Although these methods seem to be rather facile, their dtrration varies from 8 to 65 h obtained material is compared with the conventionally synthesized (via a solid state route) sample. SEM analysis shows 2 times smaller particles in the case of SPS-synthesized material compared with the solid-state-synthesized material which is to be expected from the fast (40 min in totaQ SPS synthesis tha t practically excludes grain/particle growth and promotes much faster diffusion, thereby drastically enhancing the reaction kinetics. Electrochemical perfor mance of the SPS-obtained material shows an improvement in decreasing the overpotential and reducing the capacity loss at high Crates (SC).

Ionothermal Synthesis of Polyanionic Electrode Material Na3V2(PO4)2FO2 through a Topotactic Reaction

“…6,9 In the first charge-discharge cycle, the discharge capacity is slightly greater than the charge one (Figure 7a S1). 20,21,[53][54][55][56][57][58][59] Two phenomena could promote this good capacity retention. First, the platelet morphology, corresponding to the (ab) crystallographic plane of Na 3 V 2 (PO 4 ) 2 FO 2 , is probably favoring fast Na + diffusion in the channels localized in the same plane.…”

“…9 Furthermore, oxygen substitution also enhances the Na + diffusivity within the diffusion channels and stabilizes the structure, especially at the overcharged states, [9][10][11] making these oxygen-substituted compositions interesting for practical applications. 4,8 In recent years, several synthetic approaches such as sol-gel, 12,13 solvothermal, [14][15][16][17][18] ball-milling, 19,20 spark plasma sintering, 21 and spray drying 22 have been developed to optimize the carbon-coating layer, the morphology, and the particle size of Na 3 V 3+ 2-y V 4+ y (PO 4 ) 2 F 3-y O y . The as-obtained materials crystallize in the form of hollow microspheres, nano or microcubes, spherical nanoparticles, 3D array, or nano-flower morphologies, which often exhibit outstanding performance at high cycling rates due to an enhanced electrode-electrolyte interface allowing a better ionic diffusion process.…”

Layer Shape LiFePO4 Obtained by Powder Extrusion Molding as Solid Boosters for Ferro/Ferricyanide Catholyte in Semisolid Redox Flow Battery: Effect of Porosity and Shape

“…Several synthetic routes and molding techniques have been proposed in the case of LFP, especially with the research effort to fabricate ultrathick ceramic (additive-free) electrodes for maximizing the capacity of Li-ion and Na-ion batteries. [36][37][38][39][40] Among them, powder extrusion molding (PEM) presents several advantages for industrial applications such as: being a continuous process, rapidness, easiness, low cost and easy scalability. [37,41] Furthermore, the shape and the thickness of the extruded materials can be controlled by the die located at the exit of the extruder, allowing to obtain for instance films, cylindrical filaments or prismatic ones.…”

Dually Decorated Na3V2(PO4)2F3 by Carbon and 3D Graphene as Cathode Material for Sodium‐Ion Batteries with High Energy and Power Densities

“…As for cathode materials, the polyanionic compounds have recently been intensively attractive for SIBs because of their advantages such as high working voltage, excellent thermal stability and large channel for Na + transport, which result from stable frame structure of polyanionic compounds and inductive effects of polyanionic groups. [8] Recently the investigated polyanion cathode materials mainly include NaVPO 4 F, [9] NaFePO 4 , [10,11] Na 3 V 2 (PO 4 ) 3 , [12][13][14][15][16][17] Na 2 FePO 4 F, [18] Na 3 Cr 2 (PO 4 ) 3 [19] Na 3.5 Mn 0.5 V 1.5 (PO 4 ) 3 , [20] Na 2 MnPO 4 F, [21] Na 3 V 2 O 2 (PO 4 ) 2 F, [22][23][24][25][26][27] Na 4 MnV(PO 4 ) 3 , [28] Na 3 V 2 (PO 4 ) 2 F 3 , [29][30][31][32][33][34][35][36][37][38][39][40][41][42] Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 , [43,44] and Na 2 Fe 2 (SO 4 ) 3 , [45,46] which all display higher working voltage than their oxide counterparts. Among the above-mentioned polyanion compounds for SIBs, Na 3 V 2 (PO 4 ) 2 F 3 with NASICON (sodium superionic conductor) structure has been considered as one of the most promising candidates because of its higher working voltage, higher mobility of Na + , better cyclability, larger capacity, and hence larger energy density.…”