Hierarchical Na₃V₂(PO₄)₂F₃ Microsphere Cathodes for High-Temperature Li-Ion Battery Application

Abstract

Sodium superionic conductor (NASICON)-structured Na 3 V 2 (PO 4 ) 2 F 3 cathode materials have received vast attention in the high-temperature storage performance due to their structural and thermal stability. Herein, hierarchical Na 3 V 2 (PO 4 ) 2 F 3 microspheres (NVPF-HMSs) consisting of nanocubes were designed by a one-pot facial solvothermal method. The hierarchical Na 3 V 2 (PO 4 ) 2 F 3 microsphere size is 2–3 μm, which is corroborated by FE-SEM and HR-TEM analyses. The NVPF-HMSs have been demonstrated as a cathode in Li-ion batteries at both low and elevated temperatures (25 and 55 °C, respectively). The NVPF-HMS cathode in a Li-ion cell exhibits reversible capacities of 119 mA h g –1 at 0.1 C and 85 mA h g –1 at 1 C with an 82% retention after 250 cycles at 25 °C. At elevated temperatures, the NVPF-HMS cathode exhibits a superior capacity of 110 mA h g –1 at 1 C along with a retention of 90% after 150 cycles at 55 °C. Excellent capacity and cyclability were achieved at 55 °C due to its hierarchical morphology with a robust crystal structure, low charge-transfer resistance, and improved ionic diffusivity. The Li-ion storage performance of the NVPF-HMS cathode material at elevated temperatures was analyzed for the first time to understand the high-temperature storage property of the material, and it was found to be a promising candidate for elevated-temperature energy storage applications.

Polyaniline-Coated Na3V2(PO4)2F3 Cathode Enables Fast Sodium Ion Diffusion and Structural Stability in Rechargeable Batteries

“…The capacity for 2%PANI@NVPF at 5C is similar to that reported for NVPOF@CNT/PANI at 5C but we do not use CNT which can simplify the synthesis route . Also, the hierarchical Na 3 V 2 (PO 4 ) 2 F 3 microspheres (NVPF-HMSs) cycled versus Li at 5C is much poorer than our results . Therefore, the proposed PANI coating seems to be a rational concept for developing coated cathodes for Na-ion battery applications.…”

An Efficient Methodology Combining K-Means Machine Learning and Electrochemical Modelling for the Determination of Ionic Diffusivity and Kinetic Properties in Battery Electrodes

“…This equation was proposed by Weppner et al and can be applied as long as the assumption for its use is satisfied [ 43 , 44 ]. In Equation (3), L represents the characteristic diffusion length equal to for spherical-like active material particles as the ones of NVPF [ 45 , 46 ], is the duration of the discharge current pulse, and and represent the changes in the steady-state potential and in the transient potential of the electrode.…”

Increasing Tap Density of Carbon-Coated Na3V2(PO4)2F3 via Mechanical Grinding: Good or Bad Idea?

“…For Na 3 V 2 (PO 4 ) 2 F 3 or its derivatives Na 3 V 2 (PO 4 ) 2 F 3– y O y , the few data available in the literature report tap density between 0.8 and 1.2 g/cm 3 , which is comparable to the value estimated for other polyanionic electrode materials such as Na 3 V 2 (PO 4 ) 3 or Na 2 FePO 4 F (see Table ). − Direct synthesis of nanoparticles, and growing particles with a platelet morphology or in a porous template, results in an active material with a low tap density (0.8 to 1 g/cm 3 ). The highest tap density values (1.2 g/cm 3 ) are reported for microsphere particles obtained by annealing at high temperature after a first low-temperature shaping chemical process such as spray drying .…”