Lithium storage mechanism

Besides, using nanomaterials will enable some lithium-storage mechanisms available for mass storage. One such new mechanism is the so-called "conversion" mechanism [32], which is first found in transition metal oxides, then in fluorides, suliides, and nitrides [33, 57, 58], and the mechanisms can described by Eq. 6.4 ... 

Studies have also revealed that the implementation of nanostmctured electrode materials can result in the initiation of new lithium storage mechanisms. These effects typically manifest either via a pseudocapacitive storage mechanism that accommodates lithium ions on the surface/interface of the particles below a critical particle size or through a conversion mechanism that involves the formation and decomposition of at least two separate phases [28-31]. The pseudocapacitive mechanism is more pronounced because of the more prominent role of surfaces and grain interfaces in nanomaterials. Reversible conversion reactions based on the reduction and oxidation of metal nanoparticles can ensue between binary compounds comprised of some second or third period element, a transition metal oxide, and metaUic lithium [32-37]. Nanoparticles are extremely effective toward this means because of their large specific surface area that is very active toward the decomposition of the lithium binary compound. Furthermore, reduction of some micrometer sized materials to the nanoscale has been shown to activate or enable reversible electrode reactions that would otherwise not take place, typically materials with low Li-ion diflEiision coefficients. 

Various lithium storage mechanisms have been proposed for amorphous carbons, such as Li2 molecules, multilayer lithium, crystal lattice, elastic balls-elastic nets model, layer-edge-surface, nanometer graphite, C-Li-H, single graphene molecule, and storage in micropores [1]. 

Schematic illustration of the lithium storage mechanism in micropores. (Adapted from Wu, Y.P. et al, Carbon 37 1901-1908,1999.)...

The lithium storage mechanism for Ge alloys is similar to that of Si and Sn, as shown by the following ... 

Figure 11. Schematic drawing of some mechanisms for reversible lithium storage in "high-specific-charge" lithiated carbons as proposed in Refs, (a) [216], (b) [218, (c) [224], (d) [230], (e) [41], and (f) [238]. The latter figure has been reproduced with kind permission of Kureha Chemical Industry Co., Ltd.

Figure 12. Top Schematic model showing the mechanism of lithium storage in hydrogen containing carbons as proposed in Ref. [2471. Below Schematic charge/discharge curve of a hydrogen containing carbon.

Sato K, Noguchi M, Demachi A, Oki N, Endo M. A mechanism of lithium storage in disordered carbons. Science 1994 264 556-558. 

As shown in Figure 3.5.7, the capacities for most cathode materials do not differ drastically. From the 1980s when LiCoOi (125 mA h g ) was produced to recently, with the development of LiNCM (180 mA h g-1), capacities were increased by less than 50%. From chemical and structural considerations, there is a clear reason not to expect drastic increases in electrode capacities within these classes of materials (and storage mechanisms). For example, the lithium insertion and extraction reaction in LiFeP04 reads... 

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