Highly promoted solvent-co-intercalation process in pencil graphite anode and Na3V2(PO4)3 cathode in full-cell Na-ion battery.

The electrochemical performance of graphite recovered from 6H-pencil with the highest content of SiO2 is evaluated in both Na-ion half and full-cell assemblies. The concept of sodium co-intercalation into graphite is exploited by fabricating cells with electrolytes based on tetraethylene glycol dimethyl ether (G4) and diethylene glycol dimethyl ether (G2). The capacity at high current rates is maximum when the G2-based electrolyte is used, both in half and full cells, while the capacity retention after high current rates is better in a G4-based system. Upon calculating the capacity contribution, the G2-based system shows prominent capacitance-based charge storage, whereas the G4-based system has a higher contribution from the Faradaic mechanism. The former also shows a faster diffusion mechanism. While G2 based system has higher capacity retention in half-cell, G4 based system has higher capacity retention in full-cell. When G2 is used as the electrolyte solvent, the irreversibility during cycling is high, affecting cell performance. The full cells with G4 and G2 electrolytes show maximum energy/power densities of 33 Wh kg-1/2.7 kW kg-1 and 23 Wh kg-1/1.4 kW kg-1, respectively. Our study shows that the charge storage mechanism can be varied by tuning the electrolyte solvent. This study is the first to explore pencil graphite for sodium-ion storage.

Fabrication of Na-Ion Full-Cells using Carbon-Coated Na3 V2 (PO4 )2 O2 F Cathode with Conversion Type CuO Nanoparticles from Spent Li-Ion Batteries.

Spent lithium-ion batteries (LIBs) offer immense potential in the form of resources such as Li, transition metals (Co, Ni, and Mn), graphite, and Cu, which can be recovered through suitable recycling procedures. The Cu-current collector is recovered from spent LIBs and converted as a copper oxide (CuO) anode for Na-ion batteries. The performance of CuO is evaluated with carboxymethyl cellulose (CMC) (CuO-C), and polyvinylidene fluoride (PVdF) (CuO-P) binders in CuO half-cell and CuO/carbon-coated Na3 V2 (PO4 )2 O2 F (CuO/NVPOF) full-cell assemblies. The CuO-C half-cell displays superior electrochemical performance than CuO-P in terms of cycling and rate performance showing 88% more capacity. To study the stabilization and solid electrolyte interphase growth in CuO-C, an in situ impedance study is conducted. However, the full-cell, CuO-P/NVPOF displays better capacity retention during cycling with Coulombic efficiency >95% from the second cycle, whereas CuO-C/NVPOF could hardly maintain only >90%. For conversion type CuO, it is apparent that, though the CMC binder supports half-cell performance, the PVdF binder is suitable for the practical cell/full-cell configuration.

Impact of carbonate-based electrolytes on the electrochemical activity of carbon-coated Na3V2(PO4)2F3 cathode in full-cell assembly with hard carbon anode.

An immense effort has been put into developing high-performance electrodes to commercialize sodium-ion batteries, but research on developing an efficient electrolyte is lacking. This study aims to find the best carbonate-based electrolyte systems by incorporating the existing ideas reported in this field. The sodium superionic conductor (NASICON) type Na3V2(PO4)2F3-C (NVPF-C) was chosen as a cathode, and its compatibility with four different carbonate-based electrolyte solutions was studied in the half-cell assembly. Additionally, full-cell assembly with hard carbon as an anode is also explored. Binary and ternary combinations of the solvents ethylene carbonate, propylene carbonate, and dimethyl carbonate were employed with and without fluoroethylene carbonate as an additive. A systematic study was performed, including the in-situ impedance technique, and to determine the compatibility. Detailed galvanostatic studies for NVPF-C based half-cells, as well as hard carbon/NVPF-C full-cells, are performed, which shows that 1 M NaClO4 in propylene carbonate:dimethyl carbonate + fluoroethylene carbonate is a better electrolyte composition for this assembly. Subsequently, a temperature study was carried out on this electrolyte to test its performance.

Focus on Spinel Li4 Ti5 O12 as Insertion Type Anode for High-Performance Na-Ion Batteries.

Sodium-ion batteries (SIBs) toward large-scale energy storage applications has fascinated researchers in recent years owing to the low cost, environmental friendliness, and inestimable abundance. The similar chemical and electrochemical properties of sodium and lithium make sodium an easy substitute for lithium in lithium-ion batteries. However, the main issues of limited cycle life, low energy density, and poor power density hamper the commercialization process. In the last few years, the development of electrode materials for SIBs has been dedicated to improving sodium storage capacities, high energy density, and long cycle life. The insertion type spinel Li4 Ti5 O12 (LTO) possesses "zero-strain" behavior that offers the best cycle life performance among all reported oxide-based anodes, displaying a capacity of 155 mAh g-1 via a three-phase separation mechanism, and competing for future topmost high energy anode for SIBs. Recent reports offer improvement of overall electrode performance through carbon coating, doping, composites with metal oxides, and surface modification techniques, etc. Further, LTO anode with its structure and properties for SIBs is described and effective methods to improve the LTO performance are discussed in both half-cell and practical configuration, i.e., full-cell, along with future perspectives and solutions to promote its use.