Li-ion diffusion

The LiMn204 spinel structure, shown in Figure 19, can be described as a cubic close-packed oxygen array with the manganese cations occupying one-half of the octahedral interstitial sites and the lithium cations one-eighth of the tetrahedral sites. The interstitial tetrahedral and octahedral spaces in the [Mn2]04 framework are interconnected to form three-dimensional pathways for Li+ ion diffusion (lO -lO " m s ). 

Other methods of chemically strengthening glass include Li ions diffused into a sodium-containing glass to create a composition profile in which the resulting surface has a lower expansion than the core region, and thus develops a compressive layer on... 

Additional experiments were also performed for a large number of cycles, which showed different capacity tendency as compared to the rate. An unusual behavior was the best capacity retention over 160 cycles is observed at high rates. For instance, the full cell cycled at C/2,1 C and 2 C exhibited 20, 30 and 56 mA h g", while the capacity was 82 mA h g" when cycled at 5 C. A lithium-ion cell based on titanium oxide nanotubes and bare LiFePO exhibited only 70 mA h g" at C/10 at the first reversible cycle [167]. The increased capacity in batteries using coated Ti02 can be ascribed to an improvement of the Li ion diffusion when Li3P04 layer is applied. Moreover, a reduced contact area between the electrodes and the electrol5fre can be achieved. 

Fig. 5.9 Schematic description of a solvated lithium ion s journey from solution bulk to graphene interior, and the impedance components associated with these steps, (a) Assignment by convention where the process occurring at low AC frequencies was assigned to charge transfer after Li-ion diffusion across the interface film, (b) Rationale by Abe and Ogumi et al., where the desolvation process of Li-(solvent)j complex is identified as responsible for the above impedance components (reproduced with the permission by Electrochemical Society from [42])...

Iddir, H. Curtiss, L.A. Li ion diffusion mechanisms in bulk monoclinic LijCOs crystals from density functional studies, J. Phys. Chem. C 2010,114, 20903-20906. 

Carbonate-containing liquid electrolytes are primarily chosen for their ability to dissolve lithium salts and their relatively low viscosity (which facilitates Li-ion diffusion between electrodes). Their flammability has in part led to interest in the use of room-temperature ionic liquids (ILs) as replacements. ILs can potentially operate in a higher voltage window relative to carbonates and also have the added benefit of being more thermally stable and having low vapor pressure. The main drawback of this class of compounds is a high viscosity. Additionally, carbonates may have to be introduced at certain voltages to form a suitable SEI for operation. 

In the nanosized Li4Ti50i2 particles, it is expected that Li" ions diffuse and electrons migrate in distances reduced by a factor of 1/1,000 or less as compared with the distances in normal micron-order LLjTi50i2 particles. Further, in the composite, electron paths are effectively formed in the electrode of nanosized LLjTi50i2 particles On the basis of these expectations, the authors synthesized a composite (nc-Li4Ti50i2/CNF) by means of a new method referred to as ultracentrifugal force (UC) method [20]. Specifically, the composite... 

Ionic diffusivity of active materials is another factor dominating electrode reaction kinetics. Li4Ti50i2 has a low Li ion diffusion coefficient on the order of 10 -10 cm s [27-31]. The huge difference in the reported Li ion diffusivities of Li4TisOi2 is attributable to the different testing methods and the different lithiation depths of the employed electrode. The low electronic conductivity and poor... 

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