K. Prasanna

Environment-Friendly Cathodes Using Biopolymer Chitosan with Enhanced Electrochemical Behavior for Use in Lithium Ion Batteries

The biopolymer chitosan has been investigated as a potential binder for the fabrication of LiFePO4 cathode electrodes in lithium ion batteries. Chitosan is compared to the conventional binder, polyvinylidene fluoride (PVDF). Dispersion of the active material, LiFePO4, and conductive agent, Super P carbon black, is tested using a viscosity analysis. The enhanced structural and morphological properties of chitosan are compared to the PVDF binder using X-ray diffraction analysis (XRD) and field emission scanning electron microscopy (FE-SEM). Using an electrochemical impedance spectroscopy (EIS) analysis, the LiFePO4 electrode with the chitosan binder is observed to have a high ionic conductivity and a smaller increase in charge transfer resistance based on time compared to the LiFePO4 electrode with the PVDF binder. The electrode with the chitosan binder also attains a higher discharge capacity of 159.4 mAh g(-1) with an excellent capacity retention ratio of 98.38% compared to the electrode with the PVDF binder, which had a discharge capacity of 127.9 mAh g(-1) and a capacity retention ratio of 85.13%. Further, the cycling behavior of the chitosan-based electrode is supported by scrutinizing its charge-discharge behavior at specified intervals and by a plot of dQ/dV.

An enhanced electrochemical and cycling properties of novel boronic Ionic liquid based ternary gel polymer electrolytes for rechargeable Li/LiCoO 2 cells

A new generation of boronic ionic liquid namely 1-ethyl-3-methylimidazolium difluoro(oxalate)borate (EMImDFOB) was synthesized by metathesis reaction between 1-ethyl-3-methylimiazolium bromide and lithium difluoro(oxalate)borate (LiDFOB). Ternary gel polymer electrolyte membranes were prepared using electrolyte mixture EMImDFOB/LiDFOB with poly vinylidenefluoride-co-hexafluoropropylene (PVdF-co-HFP) as a host matrix by facile solvent-casting method and plausibly demonstrated its feasibility to use in lithium ion batteries. Amongst ternary gel electrolyte membrane, DFOB-GPE3, which contained 80 wt% of EMImDFOB/LiDFOB and 20 wt% PVdF-co-HFP, showed excellent electrochemical and cycling behaviors. The highest ionic conductivity was found to be 10−3 Scm−1 at 378 K. Charge-discharge profile of Li/DFOB-GPE3/LiCoO2 coin cell displayed a maximum discharge capacity of 148.4 mAhg−1 at C/10 rate with impressive capacity retention capability and columbic efficiency at 298 K.

Eco-friendly nitrogen-containing carbon encapsulated LiMn2O4 cathodes to enhance the electrochemical properties in rechargeable Li-ion batteries.

This study describes the synthesis of nitrogen-containing carbon (N-C) and an approach to apply the N-C material as a surface encapsulant of LiMn2O4 (LMO) cathode material. The N heteroatoms in the N-C material improve the electrochemical performance of LMO. A low-cost wet coating method was used to prepare N-C@LMO particles. The N-C@LMO was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), high-resolution Raman spectroscopy (HR-Raman), field emission scanning electron microscopy (FE-SEM), and field emission scanning transmission electron microscopy (FE-TEM) with elemental mapping. Furthermore, the prepared samples were electrochemically studied using the AC electrochemical impedance spectroscopy (EIS) and the electrochemical cycler. XPS suggested that the N-C coating greatly reduced the dissolution of Mn and EIS showed that the coating greatly suppressed the charge transfer resistance, even after long-term cycling. The control of Mn dissolution and inner resistance allowed faster Li-ion transport between the two electrodes resulting in improved discharge capacity and cycling stability.

Headway in rhodanide anion based ternary gel polymer electrolytes (TILGPEs) for applications in rechargeable lithium ion batteries: an efficient route to achieve high electrochemical and cycling performances

In this present investigation, we developed a new category of rhodanide anion based ternary gel polymer electrolytes (TILGPEs) with high electrochemical and thermal stability, which advantageously use the harmonizing properties of a temperature-responsive polymer poly vinylidene fluoride-co-hexafluoropropylene (PVdF-co-HFP) and room temperature ionic liquid (1-ethyl-3-methylimiazolium rhodanide (thiocyanate), (EMImSCN)). TILGPEs were fabricated using a facile solution cast method by incorporating EMImSCN and lithium rhodanide (LiSCN) into PVdF-co-HFP based membranes. Among the series of electrochemical tests including electrochemical impedance spectroscopy, cyclic voltammetry, linear sweep voltammetry and chronoamperometry, the membrane with 80 wt% electrolyte mixtures (EMImSCN/LiSCN) showed better performance in all aspects. The maximum ionic conductivity was found to be in the order of 2.8 × 10−4 S cm−1 at 298 K. The LiFePO4/TILGPE3/Li cell offered a maximum discharge capacity of 149.8 mA h g−1 at C/10 rate. The inimitable properties allowed the effective use of the rhodanide TILGPEs as active separators for the development of advanced lithium ion batteries.

A facile and highly efficient short-time homogenization hydrothermal approach for the smart production of high-quality α-Fe2O3 for rechargeable lithium batteries

In the present work, we have synthesized zero-dimensional (0D) and three-dimensional (3D) iron oxide (α-Fe2O3) sub-micron particles using a one-pot hydrothermal approach. Morphological studies reveal that the as-synthesized spherical α-Fe2O3 (SFO) material consists of nanospheres with void spaces. The prepared SFO delivers a high specific surface area of 100.80 m2 g−1 and significantly increases the contact area between the electrode and the electrolyte. The initial galvanostatic specific capacity of the SFO materials was 1306 mA h g−1 at a current density of 100 mA g−1, which is superior to that of bare cubic α-Fe2O3 (CFO). Moreover, the mesoporous SFO shows a good cycling stability with a capacity retention rate of 91.4% after 100 cycles. These attractive results suggest that the mesoporous SFO shows a good electrochemical performance as a negative electrode material for high-performance Li-ion batteries.

Preparation and Characterization of the LiNi0.8Co0.1Mn0.1O2 Cathode Active Material by Electrophoretic Deposition

The electrophoretic deposition (EPD) process enables more uniform coating layers and saves time over the traditional laminating (LN) process. LiNi0.8Co0.1Mn0.1O2 (NCM811) is prepared by EPD and LN processes in this study. The electrode materials, which are composed of active materials, conductive agents, and binders, are more uniformly dispersed on the substrate by the EPD process when compared with the LN process. Since the weight ratio of NCM811 can be changed through the EPD process, the specific capacity is calculated by weighing the deposited active materials after the process. The crystal structure and particle morphology of the prepared cathode electrode are investigated by X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM), respectively. The electrode prepared by EPD delivers a specific discharge capacity of 189.3 mAh g-1 at a current rate of 0.2 C at the first cycle and exhibits capacity retention of 88.6% after the 40th cycle. Compared with LN, EPD shows a good rate capability at various current rates from 0.2 to 2.5 C. These results provide the evidence of the superior electrochemical properties and process efficiency of the electrodes prepared by EPD.

A Rapid One-Pot Synthesis of Novel High-Purity Methacrylic Phosphonic Acid (PA)-Based Polyhedral Oligomeric Silsesquioxane (POSS) Frameworks via Thiol-Ene Click Reaction

Herein, we demonstrate a facile methodology to synthesis a novel methacrylic phosphonic acid (PA)-functionalized polyhedral oligomeric silsesquioxanes (POSSs) via thiol-ene click reaction using octamercapto thiol-POSS and ethylene glycol methacrylate phosphate (EGMP) monomer. The presence of phosphonic acid moieties and POSS-cage structure in POSS-S-PA was confirmed by Fourier transform infrared (FT-IR) and nuclear magnetic resonance (1H, 29Si and 31P-NMR) analyses. Matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrum of POSS-S-PA acquired in a dithranol matrix, which has specifically designed for intractable polymeric materials. The observed characterization results signposted that novel organo-inorganic hybrid POSS-S-PA would be an efficacious material for fuel cells as a proton exchange membrane and high-temperature applications due to its thermal stability of 380 °C.