Lithium layered oxides

Surprisingly the layered oxides with the same structures as the layered dichalcogenides were not studied in that time period. The thought was presumably that oxides toward the right of the periodic table would be of little interest, and it was not considered that lithium could be readily removed... 

Finally, Al (/= 5/2) and Co NMR spectroscopy have been used to probe AP+ in Al-doped lithium cobalt oxides and lithium nickel oxides. A Al chemical shift of 62.5 ppm was observed for the environment Al(OCo)e for an AP+ ion in the transition-metal layers, surrounded by six Co + ions. Somewhat surprisingly, this is in the typical chemical shift range expected for tetrahedral environments (ca. 60—80 ppm), but no evidence for occupancy of the tetrahedral site was obtained from X-ray diffraction and IR studies on the same materials. Substitution of the Co + by AF+ in the first cation coordination shell leads to an additive chemical shift decrease of ca. 7 ppm, and the shift of the environment A1(0A1)6 (20 ppm) seen in spectra of materials with higher A1 content is closer to that expected for octahedral Al. The spectra are consistent with a continuous solid solution involving octahedral sites randomly occupied by Al and Co. It is possible that the unusual Al shifts seen for this compound are related to the Van-Vleck susceptibility of this compound. 

Fig. 7.16 Schematic structure of layered lithium metal oxides. (By permission of Dr A.R. Armstrong, University of St Andrews.)...

The layered oxide ion conductors Srj Bi9 0(27-.t)/2 and BaBigOis show similar intercalation reactions with iodine. The iodine atoms intercalate into the van der Waals gap between adjacent Bi sheets to form stage 1 compounds. The spacing between adjacent Bi layers increases by 3 A corresponding to the intercalation of a monolayer of iodine atoms. Micro-Raman spectroscopy shows that the intercalated iodine species is predominantly I3. Ag-1 intercalated Sri,5Bi7,50i2.75, was synthesized by reaction with iodine and then in a second step with silver metal. Intercalation of lithium iodide into the ferroelectric layered compound Bi4Ti30i2 j has also been reported. ... 

Reversible electrochemical lithium deintercalation from 2D and 3D materials is important for applications in lithium-ion batteries. New developments have been realized in two classes of materials that show exceptionally promising properties as cathode materials. The first includes mixed layered oxides exemplified by LijMn Nij, Co ]02, where the Mn remains inert to oxidation/reduction and acts as a framework stabilizer while the other elements carry the redox load. Another class that shows much potential is metal phosphates, which includes olivine-type LiFeP04, and the NASICON-related frameworks Li3M2(P04)3. 

Quasi-layered oxides of the type AMO2 (A = Li, Na M = bivalent Ti, V, Cr, Mn, Fe, Co, Ni) prepared by high-temperature solid-state reactions have also been studied as possible cathodes since these materials undergo loss of alkali metal upon treatment with I2 or Br2 in acetonitrile. Of these, LiCo02 is the material of choice in the current generation of lithium batteries. A practical problem here is the expense of Co. However, LiNi02 doped with 10-30 mole% LiCoCh shows promise as a replacement. ... 

The corrosion resistance of stainless steels and nickel-based alloys in aqueous solutions can often be increased by addition of chromium or aluminum. " Chromium protects the base metal from corrosion by forming an oxide layer at the surface. Chromium is also considered to be an important alloying metal for steels in MCFC applications. Chromium containing stainless steel, however, leads to the induced loss of electrolyte. Previous studies done to characterize the corrosion behavior of chromium in MCFC conditions have shown the formation of several lithium chromium oxides by reaction with the electrolyte. This corrosion process also results in increased ohmic loss because of the formation of scales on the steel. Aluminum additions similarly have a positive effect on corrosion resistance. " However, corrosion scales formed in aluminum containing alloys show low conductivity leading to a significant ohmic polarization loss. 

Various materials are used for production of the three main components of a lithium ion battery. Research and development of these materials is where the automotive chemist is severely needed. The main components of the battery are the electrolyte, cathode, and anode. For the cost imperative, graphite is used most often in the anode. The cathode is typically a layered lithium cobalt oxide, lithium iron phosphate, or lithium manganese oxide. Other materials, such as TiS2, have been used [18]. Of course, properties vary depending on the choice of anode, cathode, electrolyte, etc. 

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