Manab Kundu

Hierarchically Designed SiOx/SiOy Bilayer Nanomembranes as Stable Anodes for Lithium Ion Batteries

Hierarchically designed SiOx /SiOy rolled-up bilayer nanomembranes are used as anodes for lithium-ion batteries. The functionalities of the SiO(x,y) layers can be engineered by simply controlling the oxygen content, resulting in anodes that exhibit a reversible capacity of about 1300 mA h g(-1) with an excellent stability of over 100 cycles, as well as a good rate capability.

Poly(vinylidene fluoride-co-chlorotrifluoroethylene) (PVDF-CTFE) lithium-ion battery separator membranes prepared by phase inversion

Separator membranes based on poly(vinylidene fluoride-co-chlorotrifluoroethylene) (PVDF-CTFE) were prepared by a solvent casting technique based on its phase diagram in N,N-dimethylformamide (DMF) solvent. The microstructure of the PVDF-CTFE separator membranes depends on the initial position (temperature and concentration) of the solution in the phase diagram of the PVDF-CTFE/DMF system. A porous microstructure is achieved for PVDF-CTFE membranes with solvent evaporation temperatures up to 50 °C for a polymer/solvent relative concentration of 20 wt%. The ionic conductivity of the separator depends on the degree of porosity and electrolyte uptake, the highest room temperature value being 1.5 mS cm−1 for the sample with 20 wt% of polymer concentration and solvent evaporation temperature at 25 °C saturated with 1 mol L−1 lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) in propylene carbonate (PC). This PVDF-CTFE separator membrane in Li/C–LiFePO4 half-cell shows good cyclability and rate capability, showing a discharge value after 50 cycles of 92 mA h g−1 at 2C, which is still 55% of the theoretical value. PVDF-CTFE separators are thus excellent candidates for high-power and safe lithium-ion battery applications.

Polyaniline-Containing composites based on highly porous carbon cloth for flexible supercapacitor electrodes

Composites based on commercially available carbon cloth Busofit T-040 and conductive polymer polyaniline are fabricated using the electrochemical polymerization of aniline on the surface of carbon-cloth fibers. The sequence of technological operations for obtaining the composite is optimized; the procedure of preliminary modification of the carbon-cloth surface by electrochemical etching is worked out; and the capacitive characteristics of the obtained composites for use as flexible supercapacitor electrodes are studied. It is found that the introduction of polyaniline into the composition of composite electrode structures leads to an increase in the capacitance by 2–2.5 times compared to the initial carbon cloth due to the pseudocapacitance of polyaniline while maintaining a high electrical conductivity and efficiency. For a composite based on etched carbon cloth, the specific capacitance is 267 F/g (8.9 F/cm2 per unit of the geometric surface of the electrode) with a charge efficiency of 97–99%. The specific surface area of the composite, determined by the BET method, is 548 m2/g.