Li-Mn-O Spinels

Strobel P, Le Cras F, Seguin L, Arme M, Taraseon JM (1998) Oxygen nonstoichiometry in Li-Mn-O spinel oxides a powdta- neutron diffraetion study. J Solid State Chem 135 132-139... 

Paulsen JM, Dahn JR (1999) Phase diagram of Li-Mn-O spinel in air. Chem Mater 11 3065-3079... 

Figure 3. Charge and discharge curves of an Li/Li[Li0jMn, 9]04 cell cycled at voltages between 3.0 and 4.4V at a rate of 0.1 mAcnT2 at 30 °C. To describe the composition of an Li-Mn-O ternary phase a defect-spinel formulation was assumed.

Xia, Y, and Yoshio, M. 1996. An investigation of lithium ion insertion into spinel structure Li-Mn-O compounds. Journal ofthe Electrochemical Society 143, 825-833. 

Table 2.3 Classification, spinel formula, and capacities of spinel Li-Mn-O compound ...

Thackeray MM, de Kock A, Rossouw MH, Liles D, Bittihn R, Hoge D (1992) Spinel electrodes from the Li-Mn-O system for rechargeable lithium battery applications. J Electrochem Soc 139 363-366... 

Aurbach el al. used FTIR spectroscopy to follow the surface chemical changes of cathodes including Li CoO, Li iO and LijMn204 spinel. They observed ROCO Li species in cycled Li NiOj, Li CoGj and Li Mn O cathode in EC/DMC LiAsF or LiPF electrolyte and concluded that the cathode materials are probably also covered with surface films (initially Li COj). In addition, it has been reported that cathode material has a pristine surface film of Li COj as a residue from the synthesis precursors or a product of reactions between CO in the atmosphere and the active cathode powder. The vibrational bands of Li COj are usually observed around 1505, 1435 and 868 Nevertheless no... 

Figure 3 Ex situ XRD profiles of spinel-based electrodes after cycling or storage at ambient temperature. Dots Li Mn O reflections diamonds A1 current collector. (A) Discharged to 2.4 V (B) pristine LiMrr,0 (C) charged to 4.3 V (D) cycled 50 times at C/3 (E) stored for 300 h at OCV. Reproduced Irom [32] with permission of The Electrochemical Society Inc.

Spinel electrode from the Li-Mn-O system for rechargeable lithium battery applications. 139 363-366. 

Fig. 6.17 Expanded region of the Li-Mn-O phase diagram. The Mn02-LiMn02-Li2Mn03 tie triangle includes the region of defect spinel compositions...

Although several compositions of Li -Mn O are possible with spinel structures, the AB2O4 spinel is the most desired spinel phase in the Li-Mn-O system due to its neat and flat de-intercalation to form a fully delithiated phase of X-Mn02. Gummow et al. used ternary phase diagrams shown in Figure 7.23 to review the utilisation of various Li-Mn-O phases in LIBs [37]. Improved capacity retention is demonstrated when a small amount of Mn in the spinel structure is replaced with Li, Mg or Zn. The improved cyclability... 

Triangular phase diagram for Li-Mn-O system with expanded emphasis on LiJVlnOj subsystem. (Reprinted with permission from Solid State Ionics, 69, R.J. Gummow et al.. Improved capacity retention in rechargeable 4 V lithium/Hthium manganese oxide (spinel) cells, 59-67, Copyright 1994, Elsevier.)... 

For o-Li ,Mn02, 50% of the Mn ions need to change position in order to form spinel. The characteristics of the orthorhombic, a-NaFe02-type layered, and spinel structures as well as many other ordered rock-salt structures have been covered in detail by Thackeray. ... 

The example serves to show an interesting feature the relative amounts of the various elements in the two surface films formed (under electrochemical cycling and chemical storage) are essentially identical. A small increase in the amount of Li and F is observed just below the surface, while the C content is seen to decrease. This gives us the first indication of the existence of a layered structure in the surface film. As we move into the sample, the F, O, P and Li concentrations decrease, while the relative amounts of Mn and C increase, as more of the bulk spinel electrode is exposed. The amount of surface material present is also found to increase with cycle number and storage time, suggesting that the layer formed on the LiMUjO., cathode is not sufficiently dense to serve as a barrier between the electrolyte and the oxidising environment close to the cathode surface. Fresh electrolyte can be transported to the electrode surface. 

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