PEO-LiTFSI

Fig. 7.11 (a) Diffusion in a PEO/LiTFSI electrolyte from simulation and experiment, (b) Ionic conductivity in a PEO/LiTFSI electrolyte from simulation and experiment... 

Diddens D, Heuer A, Borodin O (2010) Understanding the lithium transport within a Rouse-based model for a PEO/LITFSI polymer electrolyte. Macromolecules 43 2028... 

Gorecki W, Jeannin M, Belorizky E, Roux C, Armand M (1995) Physical properties of solid polymer electrol3de PEO(LiTFSI) complexes. J Phys Cond Matter 7(34) 6823-6832... 

MARZANTOWICZ, M., DYGAS, J.R., KROK, F., NOWII SKI, J.L., TOMASZEWSKA, A., FLORJAI CZYK, z. and ZYGADLO-MONIKOWSKA, E., 2006b. Crystalline phases, morphology and conductivity of PEO LiTFSI electrolytes in the eutectic region. Journal of Power Sources, 159(1 Spec, iss.), 420-430. 

A net decrease in PEO crystallinity was observed with the incorporation of fillers. ° In PEO/LiTFSI complexes, an amorphous structure, stable for several months, can be obtained with the incorporation of small amounts of fillers. Using Li nuclear magnetic resonance (NMR) investigation, Dai et found that the addition of nanometric AI2O3 to PEO/Lil electrolyte suppressed the formation of crystalline phases. The ceramic fillers, because of their large surface area, may prevent local PEO organisation and significantly reduce PEO crystallisation kinetics. 

The dielectric study of nanocomposite polymer electrolytes performed by Jayathilaka et al indicated that the quantity of free ions was not modified significantly with the addition of AI2O3 to PEO/LiTFSI electrolyte. However an increase in ion mobility was noted. 

Some authors " observed improved mechanical properties in polymer electrolytes with added nanofiUers. The rheological behaviour of filled and unfilled PEO-LiTFSI electrolytes was studied at 85 °C. A significant... 

SHIN, J.H., HENDERSON, W.A., TIZZANI, c., et al. Characterization of solvent-free polymer electrolytes consisting of ternary PEO-LiTFSI-PYR14TFSI,/. Electrochem. Soc., 2006,153, A1649-A1654. 

A high ambient temperature conductivity of 10 Scm was measured with LiTFSI dissolved in the P2S5-PEO matrix, i.e, in salt-in-polymer materials. The decoupling of Li+ motions from polymer segmental motions was demonstrated, suggesting that, in certain cases, the transport number for Li+ ions in the phosphorus sulfide-PEO matrix will be much higher than in a typical PEO-based salt-in-polymer system. 

MD simulations of comb-branch polyethers of the structure shown in Fig. 7.14 (PEPE5) have been performed [60]. SPEs formed from this comb-branch polymer have also been studied experimentally [70-72]. A comparison of the ionic conductivity of SPEs with LiTFSI and this comb-branch polymer from simulation and experiment, along with the conductivity of a linear PEO SPE with same salt concentration is shown in Fig. 7.14 [60]. Good agreement between experiment and simulation is apparent. Furthermore, the conductivity of the comb-branch SPE is very similar to that of the linear PEO SPE. The slightly higher conductivity in the linear PEO SPE is facilitated by the lower molecular weight (2,380 Da) of the linear polymer compared to the comb-branch (around 6,000 Da). 

In fact, conductivity due to the Li" cation transport only in [pyri3][TFSI] + 0.25 LiTFSI was found to be somewhat greater than that for a model poly(ethylene oxide)(PEO-based)/LiTFSI polymer electrolyte but 1-2 orders of magnitude lower than conductivity of ethylene carbonate/LiTFSI liquid electrolyte depending on temperature [86]. 

LiTFSI is the abbreviation for LiN(S02CF3)2 (hthium bis(trifluoromethanesulfonyl)imide). It corrodes the aluminum of the current collectors with a voltage higher than 4.2 V. However, as PEO requires the voltage to be limited to 4 V, we can use LiTFSI with no danger of degradation of the element. 

The electrolyte is a poly(ethylene oxide) (PEO) film with a dissolved hthium salt LiTFSI. In order to obtain a sufficiently good ionic conductivity, we need to operate the battery at a temperature greater than the glass transition temperature of the polymer. The operating temperature required is 60-80°C, which limits the field of application to large batteries, which notably precludes the mobile market. Under no circumstances must the thermal degradation temperature of the PEO, which is around 120 C, be surpassed. 

Pyrrolium- and piperidinium-based ILs have cations containing five- and six-membered rings. Their physicochemical properties are similar to linear quaternary ammonium ILs, and they perform similar to the linear quaternary ammonium-based ILs when they are used as an electrolyte for lithium-ion batteries. When a LiTFSI/PEO+PjjTFSI polymer electrolyte is used in a... 

The electrical properties of polymer electrolytes based on chitosan/PEO blends with LiTFSI salt were described by Idris et al. Conductivities between 10 and 10 S/cm were reported for samples based on swelling chitosan membranes and ammonium salts (NH4NO3 and NH4CF3SO3), which in water promote the protonation of chitosan amino groups, leading to protonic conductivity. ... 

PEI-b-PEO-b-PEI copolymer weighing 150 mg and different quantities of lithium bis (trifluoromethyl sulphonylimide) (LiTFSI) or Cu(TFSI)2 salts, were dissolved in 10 ml dry methanol, under agitation, in an inert atmosphere, so that the ratio between the cation and the coordinating atoms was 1/12 for both LT/O and Cu" 7N. 

After 48 h of agitation a yellow solution of LiTFSI-block copolymer, and a blue solution of Cu(TFSI)2-block-copolymer were obtained. The solvent was evaporated under inert atmosphere, at room temperature (RT). In a similar way the polymer electrolyte based on PEI-b-PEO-b-PEI copolymer and the mixture of the two salts (LiTFSI and Cu(TFSI)2) was prepared. 

Jannasch (2001) grafted a PEO side chain onto the polyethylene chain, leading to the ion conductivity increasing to 3.2 x 10 S/cm at room temperature after doping with LiTFSI. In addition, they also prepared a branch polyacrylate copolymer where the side chain is composed of poly(ethylene glycol) (PEG), and alkane or fluorinated alkane (Gavelin et al, 2002). As the resulting polymer is amorphous, the ion conductivity reached 8 x 10- S/cm. 

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