Cathode materials polyanionic

The third member of orthosilicate family of cathode materials, Li2CoSi04, has not attracted a lot of attention - probably due to several reasons. The first could be due to expected much higher voltages of cobalt-containing polyanions, the second might be due to even worse intrinsic conductivity expected for Li2CoSi04 and, last but not the least, cobalt-based orthosilicates cannot be justified as a cheap or environment-friendly material. 

Ong, S.P., and Ceder, G. (2011) Novel mixed polyanions lithium-ion battery cathode materials predicted by high-throughput ah initio computations. 

In the last two decades, compounds with different polyanion groups such as phosphates (P04 ), pyrophosphates (P2O7" ), silicates(Si04" ), sulfates(S04 ), borates (B03 ) as well as their lluorinated compounds have been widely investigated in the literature. In this chapter, some recent studies of polyanion compounds for use in Li-ion batteries are introduced and summarized. Some review papers in this field can also be found in the literature [5, 6]. Here, we mainly focus on the different polyanion compounds in use as cathode materials, except for olivine-type LiFeP04 and its analogues. 

Multiple bimetallic sulfates with the formula Li2M(S04)2 (M = Fe, Mn, Co) have been proposed as new polyanionic Li-ion battery cathode compounds since the discovery of LiFePOa as a promising positive electrode material [5, 95, 96]. The Fe-based Li2Fe(S04)2 exhibits an open circuit voltage of 3.83 V versus Li /Li°, which is the highest potential ever obtained for the Fe /Fe redox couple in an iron-based, fluorine-free compound, and is only matched by the triplite phase of LiFe(S04)F [97, 98]. This finding has not only paved the way for the development of a totally new class of fluorine-free compounds but could also reveal fundamental structure-property relationships in Li-ion cathode materials. 

Gong ZL, Yang Y (2011) Recent advances in the research of polyanion-type cathode materials for Li-ion batteries. Energ Environ Sci 4 3223-3242... 

The discussion of materials reactivity is followed by chapters on carbon (Ogumi 6- Inaba) and manganese vanadate and molybdate anode materials for hthium-ion batteries. A brief chapter on oxide cathode materials by Goodenough gives a brief overview of current work on "traditional" lithium metal oxide materials and polyanionic compounds. 

Zhang HZ, Qiao QQ, Li GR, Gao XP (2014) P04 polyanion-doping for stabilizing li-iich layered oxides as cathode materials for advanced lithium-ion batteries. J Mater Chem A 2 7454-7460... 

---