Intercalation lithium battery cathodes

The electrochemical intercalation/insertion is not a special property of graphite. It is apparent also with many other host/guest pairs, provided that the host lattice is a thermodynamically or kinetically stable system of interconnected vacant lattice sites for transport and location of guest species. Particularly useful are host lattices of inorganic oxides and sulphides with layer or chain-type structures. Figure 5.30 presents an example of the cathodic insertion of Li+ into the TiS2 host lattice, which is practically important in lithium batteries. 

Lii+ rV308 has received considerable attention as a cathode material for secondary lithium batteries over the past few years. Lii+ rV308 has a layered framework suitable for reversible lithium intercalation processes that can allow up to four Li+ ions per formula unit to be inserted (i.e., xcan vary from 0 to... 

Titanium disulfide, like the disulfides of Zr, Hf, V, Nb, and Ta, has a layer structure two adjacent close-packed layers of S atoms have Ti atoms in octahedral interstices. These sandwiches are then stacked so that there are adjacent layers of S atoms. Lewis bases such as aliphatic amines can be intercalated between these adjacent sulfur layers similar intercalation compounds can be made with M and MSe2 compounds for M = Ti, Zr, Hf, V, Nb, and Ta. Many of these have potentially useful electrical properties, including use as cathode material for lithium batteries, and superconductivity, and may be compared with the intercalation compounds of... 

Bruce, P.G., Armstrong, A.R., and Gitzendaimer, R.L., New intercalation compounds for lithium batteries layered LiMn02, J. Mater. Chem., 9, 193, 1999. Armstrong, A.R., Robertson, A.D., and Bruce, P.G., Structural transformation on cycling layered Li(Mni yCOy)02 cathode materials, Electrochim. Acta, 45, 285, 1999. 

Materials for cathodes and anodes (insertion electrodes) for rechargeable lithium batteries are called intercalation compounds and constimte a special class of electroactive material [122]. The intercalation refers to the reversible insertion of mobile guest species into a crystalline host lattice, which contains an interconnected system of empty lattice sites of appropriate size, while the structural integrity of the host lattice is formally conserved [122]. 

Fig. 3.3 Schematic of a rechargeable lithium battery in discharge/charge mode. The lithium ion is intercalated in the anode during charging and in the cathodes during discharging. The layered host lattice in the cathode and anode is also illustrated, considering a cathode composed of a lithium cobalt host and an anode composed of a crystalhne structure of hexagonal graphite...

Of interest are HSCs, in which the active anode material and material of support for the cathode is graphene and the cathode material is lithium iron phosphate LiFeP04 (or some other substance intercalating lithium) that is used as the cathodic material in lithium ion batteries (LIBs). Such HSCs contain nonaqueous electrolytes, for example, 1M LiPFg/EC-fDM. These HSCs have considerably higher power density values but lower energy density values as compared to LIBs. 

The active cathodic material is an intercalation compound, namely a compound with an open structure which allows reversible insertion-deinsertion of lithium ions from-to the electrolyte medium. This makes intercalation compounds very suitable electrodes for rechargeable lithium batteries [10] and indeed they are currently used for this purpose in liquid electrolyte sytems [11]. In the case of the LPBs of interest here, the electrochemical discharge process may be described as the dissolution of lithium at the anode, the migration of the Li" ions across the PEO-LiX electrolytic membrane and its insertion within the structure of the hosting intercalation compound IC ... 

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