Page 520 - Handbook of Battery Materials

16.3 SEI Formation on Carbonaceous Electrodes 493

16.3.2
The First Intercalation Step in Carbonaceous Anodes
The first 1.5 charge–discharge cycles of lithium/carbon cells are presented in
Figure 16.4 for both graphite (b) and petroleum coke (a) [69]. In both cases, the first
intercalation capacity is larger than the first deintercalation capacity.
This difference is the irreversible capacity loss (Q IR ). Dahn and co-workers [69]
were the first to correlate Q IR with the capacity required for the formation of
the SEI. They found that Q IR is proportional to the specific surface area of the
carbon electrode and, assuming the formation of an Li 2 CO 3 film, calculated an SEI
thickness of 45 ± 5 ˚ A on the carbon particles, consistent with the barrier thickness
needed to prevent electron tunneling [1, 2]. They concluded [69] that when all the
available surface area is coated with a film of the decomposition products, further
decomposition ceases.

1.6
∆x=0.5
F in Li X C 6
1.2
VOLTAGE (volts) 0.8

0.4 I
discharge charge
0
(a) 0 10 20 30 40
1.6
F ∆x=1 in
Li X C 6
1.2
VOLTAGE (volts) 0.8 E

0.4 I

discharge charge
0
0 20 40 60 80 100 120 140 160
(b) TIME (hours)
Figure 16.4 (a) The first 1.5 cycles of a lithium/petroleum
coke cell and (b) the first 1.5 cycles of a lithium/graphite
cell [74].