ABSTRACT
VI. CONCLUSIONS After the intensive work on the use of covalent carbon fluorides in lithium primary batteries of the 1970s and 1980s, more attention has been paid during these last years on carbon fluorides synthesized at lower temperatures. The elec trochemical behavior of the latter is governed by the semicovalent character of the C-F bonds, which allows a higher discharge voltage and partial electrode reversibility in polymer electrolyte to be achieved. At present, a large volume of work is being carried out by lithium battery manufacturers to design new positive electrode materials that work at a high discharge voltage (=4 V) and showing reversible behavior. The so-called lithium-ion battery [63] uses LiM 02 (M = Co, Ni, Mn, . . . ) as positive electrode materials because of their excellent reversible behavior. However, these materials have low specific capacity and a higher price (especially LiCo02). It would seem to be a real challenge to build
Figure 21 Structural model of intercalated layer of C48PF64PC second-stage, /c = 17.34 A. (From Ref. 29.)
stable graphite fluorides and oxide fluorides or other GICs that undergo a re versible reaction involving either lithium or anion intercalation for 4-V lithium rechargeable batteries.
