Page 451 - Handbook of Battery Materials

14.10 The Mixed-Conductor Matrix Concept 423

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Table 14.5 Chemical diffusion data for lithium–tin phases at 25 C.
2
–1
Phase Volts vs. Li D chem (cm s )
Li 0.7 Sn 0.560 (6–8) × 10 −8
Li 2.33 Sn 0.520 (3–5) × 10 −7
Li 4.4 Sn 0.0–0.380 (1.8–5.9) × 10 −7

1000

Sb/Li 2 sb
900 Li 2 Sb/Li 3 sb

Bi<s>/LiBi
E (mV vs. Li)
800 Bi<l>/LiBi
LiBi/Li 3 Bi

700 Bi<l>/Li 3 Bi

600
0 200 400 600
Figure 14.11 Temperature dependence of the potential of
the two-phase plateaus in the Li–Sb and Li–Bi systems [45].

14.10
The Mixed-Conductor Matrix Concept

In order to achieve appreciable macroscopic current densities while maintaining
low local microscopic charge and particle flux densities, many battery elec-
trodes that are used in conjunction with liquid electrolytes are produced with
porous micro-structures containing very fine particles of the solid reactant mate-
rials. This porous structure of high reactant surface area is permeated with the
electrolyte.
This porous fine-particle approach has several characteristic disadvantages,
among which are difficulties in producing uniform and reproducible microstruc-
tures and limited mechanical strength when the structure is highly porous.
In addition, these systems often suffer Ostwald ripening, sintering, or other
time-dependent changes in both microstructure and properties during cyclic
operation.