Propylene carbonate PC-based electrolytes

The structure and composition of the lithium surface layers in carbonate-based electrolytes have been studied extensively by many investigators [19-37], High reactivity of propylene carbonate (PC) to the bare lithium metal is expected, since its reduction on an ideal polarizable electrode takes place at much more positive potentials compared with THF and 2Me-THF [18]. Thevenin and Muller [29] found that the surface layer in LiC104/PC electrolyte is a mixture of solid Li2C03 and a... 

Hashmi and Upadhyaya compared the electrochemical properties of the electrochemically synthesized MnO /PPy composite electrodes, fabricated with different electrolytes, namely polymer electrolyte film (polyvinyl alcohol [PVA]-HjPO aqueous blend), aprotic liquid electrolyte (LiClO -propylene carbonate [PC]), and polymeric gel electrolyte (poly methyl methacrylate [PMMA]-ethylene carbonate [EC]-PC-NaClO ) [60]. The cell with aqueous PVA-H PO showed non-capacitive behavior owing to some reversible chemical reaction of MnO with water, while the MnO / PPy composite was found to be a suitable electrode material for redox supercapacitors with aprotic (non-aqueous) electrolytes. The solid-state supercapacitor based on the MnO /PPy composite electrodes with gel... 

Experiments were conducted on trilayer PPy actuators to validate the effectiveness of the redox level-dependent admittance model. The electrolyte used was tetrabutylammonium hexafluorophosphate (TBA+PFg) in the solvent propylene carbonate (PC). The samples were predoped with PFg during fabrication, and the nominal concentration Co in the absence of DC bias was estimated to be fOOO mol/m based on the deposition conditions. In experiments different values of Cq were achieved by applying appropriate DC biases. Sinusoidal voltages of amplitude 0.05 V and frequency 0.08 — 200 Hz were superimposed on the DC voltage, as perturbations, for the measurement of admittance (or equivalently, impedance) spectra. 

Most of the liquid electrolytes used in the commercial lithium-ion cells are the nonaqueous solutions, in which roughly 1 mol (tar (= M) of lithium hexafluoro-phosphate (LiPF ) salt is dissolved in the mixture of carbonate solvents selected from cyclic carbonates - ethylene carbonate (EC), and propylene carbonate (PC) and linear carbonates - dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) -, whose chemical structures are displayed in Fig. 4.2. Recently, another type of liquid electrolyte based on 1.5 M LiBFyy-butyrolactone (GBL) + EC came onto the market for the laminated thin Uthium-ion ceUs with an excellent safety performance. Many other solvents and Uthium salts have limited appUcations, although much effort has been made to develop new materials. Into the above baseline electrolyte solutions, a small amount of the additives are dissolved, which are so-called functional electrolytes. ... 

The standard composition of an electrolyte in LlBs is a mixture of cycUc carbonates (such as ethylene carbonate (EC) and propylene carbonate (PC)) and chain carbonates (such as dimethyl carbonate (DMC), ethyl methyl carbonate (EMC abbreviated as MEC below), and diethyl carbonate (DEC)), to which about 1 mol/L of a lithium salt (such as lithium hexafluorophosphate (LiPF )) is added. Ube Industries, Ltd. discovered that if small amounts of impurities exist in the electrolyte, decomposition current generated from the impurities begins to flow, which leads to the formation of undesirable thick SET This spurred the development of a pioneering high-grade purification process for the base electrolyte in 1997 [16]. High purity is a key feature of functional electrolytes developed by Ube Industries, Ltd. and enables production of transparent and chemically stable electrolytes, in contrast to the conventional electrolytes which were less stable and brown owing to its low purity (Fig. 3.1). 

Formation of the SEI layer plays an important role on the cycling stability of silicon-based anodes. Kulova and Skundin [109] reported a method used to preform the SEI layer on an electrode surface (prior to initial cathodic polarization) by direct contact of silicon and lithium metal in the electrolyte. The electrolyte was 1-M LiC104 in a mixture of propylene carbonate (PC) and dimethoxyethane. This method effectively reduced the irreversible capacity of the amorphous silicon electrode. Pretreatment of nanometer-sized silicon in ethanol also can form functionalized surfaces on the silicon particles that improve adhesion of silicon-based electrodes. A stable capacity of 2,500 mAh/g after 25 cycles has been reported for ethanol-treated silicon electrodes [110]. 

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