Lithiation-delithiation process

Particles surface chemistry also plays a role in aging processes. Beyond the lithiation/delithiation mechanisms within the bulk of the particles leading to the phases described above, the particles surfaces undergo liieir own... 

M is electrochemically inactive transition metal (M = Fe, Ni, Cu, and Co). M also provides a matrix that buffers volume changes occurring with the lithiation-delithiation processes, therefore the mechanical integrity between Sn nanoparticles and with current collector can be maintained. Both preparation of alloy nanopowders and thin films are popular strategies. 

Li2FeSi04 can offer a high operating voltage and capacity based on the Fe / Fe and Fe /Fe redox couples during the lithiation/delithiation processes. However, its slow Li+-ion diffusion rate (approximately cm /s) and low electronic conductivity lead to poor rate capability, which becomes a major obstacle to its commercial application. Carbon coating and decreasing particle size to nanoscale are two effective approaches to overcome these obstacles. 

In fact metal-oxygen bonds play a double role in the Li electrochemical storage processes (1) they contribute to the irreversible capacity losses during the first lithiation/delithiation cycle due to the formation of Li oxides or peroxide and (2) they stabilize Li-M system especially for those metals that do not alloy with Li. 

The analysis of magnetic properties is also useful to study the local structure of the lamellar materials at different stages of the lithiation/delithiation process [76]. It has also been used successfully to characterize electrode materials of different families. In spinel compounds, for instance, we can mention the detection of... 

Fig. 15 Voltage composition curve for a CoO/Li cell cycled between 0.01 and 3 V. The inset shows a TEM micrograph of the nanostructured composite electrode at the end of the lithiation process. Note the large voltage hysteresis ( 1 V) between lithiation and delithiation. Reprinted with permission from Ref. [157]...

The theoretical value of the stress generated at the contact interface between the electrodeposited active material and substrate was calculated to obtain the order of magnitude of the stress generated by lithiation. As it has been reported from previous studies,the actual electrode is not a uniform material and is expected to contain and/or form voids and cracks with lithiation. It has also been shown by in situ atomic force microscopy (AFM) observations that the electrode experiences plastic deformation, and the thickness of the electrode changes irreversibly to some extent with the lithiation and delithiation process. Because of such indeterminate nature of the assumptions, the absolute value of the calculated stress is not the subject of discussion. 

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