Sustainable and efficient energy storage devices are crucial to meet the soaring global energy demand. In this context, Na‐ion batteries (NIBs) have emerged as one of the excellent alternatives to the Li‐ion batteries, due to the uniform geographical distribution, abundance, cost‐effectiveness, comparable operating voltage as well as similar intercalation chemistry. However, due to larger size of Na and other related issues, a subtle strategy of research is required for the development of electrode materials for NIBs to enhance overall electrochemical performance. Here, we provide a comprehensive review on recent advances of polyanionic cathode materials for NIBs for cost effective and large scale energy storage applications. Owing to their great thermal and chemical stability, high redox potential (inductive effect), and rich structural diversity, polyanionic cathodes have been considered potential candidates in recent years. We cover a large number of polyanionic materials and conclude with the strategies to improve the energy and power density of NIB. This article is categorized under: Energy Research & Innovation > Science and Materials Energy and Development > Science and Materials Energy and Transport > Science and Materials

We report the detailed analysis of electrochemical investigation of honeycomb structured Na$_{2}$Ni$_{2}$TeO$_{6}$ material as a cathode for sodium-ion batteries using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), galvanostatic charge-discharge (GCD)...

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In recent years, the mixed phosphate-based polyanionic electrode materials have attracted great attention in sodium-ion batteries (SIBs) due to their structural stability during cycling and open framework for ion diffusion. Here, we report the electrochemical performance of a Na 4 Co 3 (PO 4 ) 2 P 2 O 7 /nitrogen-doped carbon (NCPP/NC) composite as a negative electrode (anode) for SIBs in the working potential range of 0.01−3.0 V. It delivers a reversible discharge capacity of 250 mA h g −1 at 0.5 C current rate, which corresponds to the insertion/extraction of four sodium ions. The rate capability study indicates the reversible mechanism and highly stable capacity (61 mA h g −1 ) even at a high rate of up to 5 C as compared to pristine NCPP. The incorporation of the N-doped carbon spheres in the composite is expected to enhance the electronic/ionic conductivity, which plays an important role in improving the performance and stability up to 400 cycles at 1 C rate. Intriguingly, the analysis of cyclic voltammetry data measured at different scan rates confirms the capacitive/diffusive-controlled mechanism, and the extracted diffusion coefficient is found to be around 10 −10 cm 2 s −1 . Our results demonstrate that the NCPP/NC composite is also a potential candidate as an anode in SIBs due to its three-dimensional framework, cost effectiveness, enhanced specific capacity, and further possibility of improving the stability.

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Sodium ion batteries (SIBs) are considered as an efficient alternative for lithium-ion batteries (LIBs) owing to the natural abundance and low cost of sodium than lithium. In this context, the anode materials play a vital role in rechargeable batteries to acquire high energy and power density.In order to demonstrate transition metal dichalcogenide (TMD) as potential anode materials, we have synthesized MoSeTe sample by conventional flux method, and the structure and morphology are characterized using x-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and Raman spectroscopy. These characterisations confirm the hexagonal crystal symmetry with p63/mmc space group and layered morphology of MoSeTe. We investigate the electrochemical performance of a MoSeTe as a negative electrode (anode) for SIBs in the working potential range of 0.01 to 3.0 V. In a half-cell configuration, the MoSeTe as an anode and Na metal as counter/reference electrode exhibits significant initial specific discharge capacities of around 475 and 355 mAhg −1 at current densities of 50 and 100 mAg −1 , respectively. However, the capacity degraded significantly like ≈200 mAhg −1 in 2nd cycle, but having ≈100% Coulombic efficiency, which suggest for further modification in this material to improve its stability. The cyclic voltammetry (CV) study reveals the reversibility of the material after 1st cycle, resulting no change in the initial peak positions. The electrochemical impedance spectroscopy (EIS) measurements affirms the smaller charge transfer resistance of fresh cells than the cells after 10th cycle. Moreover, the extracted diffusion coefficient is found to be of the order of 10 −14 cm 2 s −1 .

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Sodium-ion batteries (SIBs) have received significant attention as promising alternative for energy storage applications owing to the large availability and low cost of sodium. In this paper we study the electrochemical behavior of Na 0.7 Co 1-x Nb x O 2 (x = 0 and 0.05 samples), synthesized via solid-state reaction. The Rietveld refinement of x-ray diffraction pattern reveals the hexagonal crystal symmetry with P63/mmc space group. The Na 0.7 Co 0.95 Nb 0.05 O 2 cathode exhibits a specific capacity of about 91 mAhg -1 at a current density of 6mAg -1 , whereas Na 0.7 CoO 2 exhibits comparatively low specific capacity (70 mAhg -1 at a current density of 6mAg -1 ). The cyclic voltammetry (CV) and electron impedance spectroscopy (EIS) were performed to determine the diffusion coefficient of Na, which found to be in the range of 10 !! − 10 !!" cm 2 s -1 .