Lithiated cobalt oxide

M.S. Yazici, J.R. Sehnan, Oxidation-lithiation of nickel, iron and cobalt in contact with molten carbonate, SoHd State Ion. 124 (1999) 149-160. 

The principal fault of lithiated cobalt oxide as the positive electrode material consists of the impossibility of full delithiation as a rule, the material with the formula... 

Other common members of the anodic ECM family are niobium and cobalt oxides. The lithiated versions of these oxides appear as convenient counterelectrodes in WO3 windows. Thin films of these lithiated oxides, prepared by sputtering on ITO-glasses, show reversible removal of lithium ions accompanied by electrochromic colour changes [44-46]. For instance, films of Lio.sCo02 can be cycled with good reversibility between a pale transparent bronze to a deep brown colour, this allowing the realization of windows of the type ... 

Note that in order to limit the extraction of lithium to jc=0.5 in the lithiated cobalt oxide positive electrode, this electrode needs to be oversized in terms of mass. 

Lithium/lithiated cobalt oxide (Li/Li CoO ) Li Li jCoOj LiAsE(j/LiBE4, ME/MA Polypropylene xLi + Lii, Co02 LiCo02... 

The charge and discharge reactions of the Li/Li4Ni02 battery are similar to those of the lithiated cobalt oxide system ... 

Fig. 13 Schematic mechanism of a conversion reaction based on a metal oxide MO. a The first cycle, showing the lithiation step yielding metal nanoparticles embedded in a Ii20 matrix and the delithiation step leaving nanosized metal oxide particles, b The ovtaxiU reaction illustrated with cobalt oxide (CoO). Starting with large CoO particles, the first lithiation yields Co nanoparticles embedded in Li20 (horizontal), the Co nanoparticles catalyze Li20 decomposition and Li extraction when the polarization is reversed, which results in nanosized CoO. Thanks to the nanosized particles, the electrode can be cycled between CoO and Li20 + Co as lithium is added or removed (vertical). Note however that the electrolyte decomposition (gel-like layer) is favored by the nanosized metal particles b is reprinted with permission from [157]...

There have been a number of studies of the physical and bonding behavior of these mixed transition-metal oxides, which conclude that in the fully lithiated compounds the cobalt is trivalent, the nickel predominantly divalent, and the manganese tetra-valent. Thus, the electrochemically active species is predominantly nickel with the cobalt playing an... 

Electrodes The electrocatalytic material of an MCFC is nickel. The cathode becomes oxidized and lithiated during the first hours of the operation. Nickel oxide is soluble in molten carbonates thus in the course of the operation two undesirable effects may occur (1) metallic nickel particles are formed in the electrolyte which can lead to an electronic short circuit of the electrodes, (2) the size of the cathode diminishes. Two approaches have been proposed for solving these problems the use of less corrosive molten carbonate mixtures and more stable cathodes containing iron and cobalt. The nickel anodes usually contain chromium, which promotes the sintering process. 

While a diversity of active materials are apphed in the positive electrodes of primary lithium cells, the choice of the positive electrode in lithium ion batteries is limited. The positive electrodes of lithium ion batteries are made almost exclusively of lithiated cobalt or nickel oxides and of lithium-manganese spinels. 

Lithium ion batteries are generally manufactured (assembled) in the discharged state, that is, the negative electrode is a pure carbon material and the positive electrode is made of lithiated cobalt or nickel oxides or of lithium-manganese spinel. This is because of the fact that lithiated cobalt and nickel oxides, same as lithium-manganese spinels, are much more stable toward exposure to the atmosphere than lithiated carbon materials that interact with oxygen and water from the air vigorously. 

We speak of a direct conversion when there is an alteration of the chemical structure of the material in the wake of a reaction of decomposition of the original material, MX, in a composite electrode comprising nanoparticles of metal M° encapsulated in a LiX matrix. There is no formation of a lithiated metal alloy as before, but rather of metal particles which are inactive in comparison to lithium. The reaction leads to the formation of a metastable compound LiX (essentially Li20). In theory, this compound which is formed is not stable, but it is considered to be so because of its very slow rate of transformation. Many transition-metal oxides are involved oxides of cobalt CoO and C03O4, of copper CuO, of nickel NiO and of iron FeO and Fc203. Other compounds such as NiPs and FeS2 can also be considered. 

Julien C, Castro-Garcia S (2001) Lithiated cobaltates for Li-ion batteries. Structure, morphology and electrochemistry of oxides grown by solid-state reaction, wet chemistry and flhn deposition. J Power Sourc 97-98 290-293... 

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