Poly(vinylidene fluoride-hexafluoropropylene)-based membranes for lithium batteries

Poly(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) copolymer membranes were prepared by a phase inversion technique with poly(ethylene glycol) as an additive and tetrahydrofuran or acetone or dimethylformamide as solvent. The morphology, ionic conductivity and uptake of electrolyte solution by the polymer membranes were studied. The amount of intake of electrolyte solution by the polymer membranes increases with the increase of PEG content. The morphology and ionic conductivity of the polymer membranes (PM) are correlated with the physical properties of the solvents used in the phase inversion process. The cycling behavior of the membrane was examined with Li/LiCoO2 cells

Carbon nanotubes (CNTs) as a buffer layer in silicon/CNTs composite electrodes for lithium secondary batteries

A core/shell type silicon/carbon nanotubes (Si/CNTs) composite is prepared and its anodic performance in lithium secondary batteries is examined. For the growth of CNTs, a Ni catalyst is loaded on a Si surface by electroless deposition. The growth is performed by chemical vapour deposition at 600 °C using C2H2/H2 but is successful only on smaller and thinner Ni deposits. This is probably due to an easier transformation to small droplets that initiate the growth reaction. The anodic performance of a Si/CNTs composite electrode is superior to that observed with bare Si and Si/CNTs mixed electrodes. This beneficial feature is ascribed to the conductive buffering role of the CNTs layer. It is likely that the void space and the flexible characteristics in the CNTs buffer layer on the Si surface allow volume expansion of the Si core without severe electrode swelling. Because of this, the electric conductive network made among Si particles, carbon network and current-collector is well maintained, which reduces the charge-transfer resistance.This work was supported by KOSEF via the Research Center for Energy Conversion and Storage, and by the Division of Advanced Batteries in NGE Program (Project no. 10016439)

Electrochemical studies on nanofiller incorporated poly(vinylidene fluoride– hexafluoropropylene) (PVdF–HFP) composite electrolytes for lithium batteries

Composite polymer electrolytes (CPE), comprising poly(vinylidene fluoride–hexafluoropropylene) (PVdF–HFP), aluminum oxyhydroxide, (AlO[OH]n – of 40 nm and 7 lm) as filler and LiN(C2F5SO2)2 or LiClO4 as lithium salt were prepared using a solution casting technique. The membranes were subjected to XRD, impedance spectroscopy, compatibility and transport number studies. The incorporation of nanofiller greatly enhanced the ionic conductivity and the compatibility of the composite polymer electrolyte. The electrochemical properties of CPE with nano sized fillers are better than those of micron size. Charge- discharge studies of Li Cr0.01Mn1.99O4/CPE/Li cells were made at 70 C and are discussed

Poly(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) based composite electrolytes for lithium batteries

The composite polymer electrolyte (CPE) membranes, comprising of poly(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP), aluminum oxyhydroxide, (AlO[OH]n) of two different particle sizes 7 lm/14 nm and LiN(CF3SO2)2 as lithium salt were prepared using solution casting technique. The prepared membranes were subjected to XRD, impedance spectroscopy, compatibility and transport number studies. The incorporation of nanofiller greatly enhanced the ionic conductivity and the compatibility of the composite polymer electrolyte. Also LiCr0.01Mn1.99O4/CPE/Li cells were assembled and their charge–discharge profiles have been made at 70 C. The film which possesses nanosized filler offered better electrochemical properties than those with micron sized filler. The results are discussed based on Lewis acid–base theory

Electrochemical studies on cathode blends of LiMn2O4 and Li[Li1/15Ni1/5Co2/5Mn1/3O2]

Composite cathodes were prepared by blending LiMn2O4 spinel and Li[Li1/15Ni1/5Co2/5Mn1/3O2] layer by simple mixing/ball milling followed by calcination at 800 ◦C. The prepared blend materials were subjected to XRD and charge–discharge studies. The cycling results revealed that the discharge capacity and cycleability of LiMn2O4 can be considerably increased upon blending the material with layered Li[Li1/15Ni1/5Co2/5Mn1/3O2]

MgAl2SiO6-incorporated poly(ethylene oxide)-based electrolytes for all-solid-state lithium batteries

Poly(ethylene oxide) (PEO)-based composite polymer electrolytes (CPEs), comprising various concentrations of lithium hexafluorophosphate and magnesium aluminium silicate, were prepared by hot-press technique. The membranes were characterised by scanning electron microscopy, tensile and thermal analyses. It has been demonstrated that the incorporation of the ceramic filler in the polymeric matrix has significantly enhanced the ionic conductivity, thermal stability and mechanical integrity of the membrane. It also improved the interfacial properties with lithiumelectrode. Finally, an all solid-state lithium cell composed of Li/CPE/LiFePO4 has been assembled and its cycling performance was analysed at 70 °C. The cell delivered a discharge capacity of 115 mAh g−1 at 1 °C rate and is found to be higher than previous reports

Influence of Solvents on the Structural and Electrochemical Properties of Li†Li0.2Ni0.1Co0.2Mn0.5‡O2 Prepared by a Solvothermal Reaction Method

Solid solutions of LiLi0.2Ni0.1Co0.2Mn0.5O2 were prepared by solvothermal reaction with three different solvents, namely, methanol, ethanol, and 1-propanol. The prepared compounds were subjected to X-ray diffraction XRD, Raman, Fourier transform infrared, and charge–discharge studies. XRD studies revealed that the prepared compounds are of layered structure with space group R3¯m. The sample which was prepared using 1-propanol as solvent delivered the highest discharge capacity of 205 mAh/g. The electrochemical and structural properties of the prepared compounds are influenced by the physical properties of the solvents

Nanofiller incorporated poly(vinylidene fluoride–hexafluoropropylene) (PVdF–HFP) composite electrolytes for lithium batteries

Composite polymer electrolyte (CPE) membranes, comprising poly(vinylidene fluoride–hexafluoropropylene) (PVdF–HFP), aluminum oxyhydroxide (AlO[OH]n) of two different sizes 7 m/14 nm and LiN(C2F5SO2)2 as the lithium salt were prepared using a solution casting technique. The prepared membranes were subjected to XRD, impedance spectroscopy, compatibility and transport number studies. Also Li Cr0.01Mn1.99O4/CPE/Li cells were assembled and their charge–discharge profiles made at 70 ◦C. The incorporation of nanofiller greatly enhanced the ionic conductivity and the compatibility of the composite polymer electrolyte. The film which possesses a nanosized filler offered better electrochemical properties than a film with micron sized fillers. The results are discussed based on Lewis acid–base theory

Pyrolitic carbon from biomass precursors as anode materials for lithium batteries

Disordered carbonaceous materials were synthesized by the pyrolysis of banana fibers treated with pore-forming substances such as ZnCl2 and KOH. X-ray diffraction studies indicated a carbon structure with a large number of disorganized single layer carbon sheets. Addition of porogenic agent led to remarkable changes in the structure and morphology of the carbonaceous products. The product obtained with ZnCl2 treatment gave first-cycle lithium insertion and de-insertion capacities of 3325 and 400 mAh g−1, respectively. Lower capacities only could be realized in the subsequent cycles, although the coulombic efficiency increased upon cycling, which in the 10th cycle was 95%