P. Ramesh Kumar

Enhanced properties of porous CoFe2O4–reduced graphene oxide composites with alginate binders for Li-ion battery applications

Porous CoFe2O4 nanoclusters with different concentrations of graphene based composites were synthesized by a simple solvothermal process. The electrochemical properties of prepared CoFe2O4–reduced graphene oxide (rGO) composites were evaluated using polyvinylidene fluoride and Na-alginate as binder materials. The CoFe2O4 + 20% rGO composite with alginate exhibited a high stable capacity of 1040 mA h g−1 at 0.1 C (91 mA g−1) rate with excellent rate capability. The observed enhancement in electrochemical properties of the CoFe2O4 + 20% rGO composite with alginate is due to the high stability and good transportation network while charging–discharging.

Na3V2O2x(PO4)2F3−2x: a stable and high-voltage cathode material for aqueous sodium-ion batteries with high energy density

The reversible electrochemical activity of the Na3V2O2x(PO4)2F3−2x compound in an aqueous solution is reported for the first time. Na3V2O2x(PO4)2F3−2x with multi-walled carbon nanotubes (MWCNTs) exhibits a long-term stability for up to 1100 cycles in aqueous electrolytes. Two different types of Na-ion full-cells demonstrate the feasibility of the Na3V2O2x(PO4)2F3−2x/MWCNT composite as a cathode for aqueous sodium-ion batteries. A high full-cell voltage of 1.7 V and a high energy density of 84 W h kg−1 were achieved using Zn metal as an anode.

High performance of MoS2 microflowers with a water-based binder as an anode for Na-ion batteries

Na-ion batteries have risen as an alternative system to current Li-ion batteries due to the wide range of availability and low price of sodium resources. Here we report the binder effect on sodium storage properties of MoS2 microflowers with nano-sized petals which are prepared by a combination of a hydrothermal reaction and solid-state reaction. The electrochemical performance of MoS2 microflowers with different binders is evaluated against pure Na metal in a half-cell configuration through a conversion reaction. Especially, the electrode of MoS2 microflowers with a Na-alginate binder shows an excellent cycling stability, delivering a high discharge capacity of 595 mA h g−1 after 50 cycles. The MoS2 microflowers with the Na-alginate binder also exhibit high rate capability, retaining a capacity of 236 mA h g−1 at 10C without any carbonaceous materials. The improved electrochemical performance was mainly attributed to the synergetic effect of the morphology of the MoS2 microflowers and good adhesive capabilities of the alginate binder. Furthermore, we report a Na-ion fuel cell using the MoS2 microflower anode with Na3V2O2x(PO4)2F3−2x/C as a cathode material.

A high capacity MnFe2O4/rGO nanocomposite for Li and Na-ion battery applications

A porous MnFe2O4/reduced graphene oxide (rGO) nanocomposite with high storage capacity was prepared by a hydrothermal method. The MnFe2O4/rGO nanocomposite sample was characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy and high resolution transmission electron microscopy. The electrochemical characteristics with lithium as well as sodium were studied using cyclic voltammetry and a battery cycle tester. In this work, apart from the lithium storage, the sodium storage ability of the spinel type MnFe2O4 as an anode is demonstrated for the first time. The prepared MnFe2O4/rGO composite with sodium alginate binder shows a highly stable capacity of 905 mA h g−1 versus Li/Li+ and 258 mA h g−1 versus Na/Na+ at 0.1C rate. The enhancement in capacity and excellent cycleability of the MnFe2O4/reduce graphene oxide nanocomposite is due to constrained volume expansion during conversion reactions and enhancement of electrical conductivity.

A high rate and stable electrode consisting of a Na3V2O2X(PO4)2F3−2X–rGO composite with a cellulose binder for sodium-ion batteries

Sodium ion batteries are a promising alternative to conventional lithium-ion batteries, mostly for large scale energy storage applications. In this paper, we report sodium vanadium oxy-fluorophosphate as a cathode material for sodium-ion batteries with 8.0 wt% reduced graphene oxide (rGO), synthesized via solid state reaction followed by a hydrothermal method. The newly reported Na3V2O2X(PO4)2F3−2X–rGO (NVOPF–rGO) composite with a hydrophilic carboxymethyl cellulose sodium (CMC-Na) binder shows enhanced rate performance and highly stable cyclability; it delivers a stable reversible capacity of 108 mA h g−1 in a sodium half-cell, and it exhibits 98% capacity retention at a 0.1C rate over 250 cycles. Furthermore, the as-prepared NVOPF–rGO composite exhibits discharge capacities of 98 mA h g−1 and 64 mA h g−1 at 0.2C and 2C rates, respectively, in a full-cell configuration with a NaTi2(PO4)3–MWCNT (NTP–M) anode for 1000 cycles.