Identification of Multiple Failure Mechanisms in Si-Based Electrodes for Li-Ion Batteries

Wednesday, October 14, 2015: 11:40
Russell B (Hyatt Regency)
S. D. Beattie (Warwick University), M. Loveridge, B. J. Polzin (Argonne National Laboratory), M. J. Lain (Warwick University), and I. Rubio (WMG)
Identification of multiple failure mechanisms in Si-based electrodes for Li-ion batteries

Silicon (Si) electrodes are often studied as an alternative to graphite for negative electrodes in Lithium-ion (Li-ion) battery technology due to their high theoretical specific and volumetric capacity (3579 mAh/g and 2190 mAh/cm3respectively).  Although encouraging theoretically, practical silicon electrodes exhibit relatively low cycle efficiency, causing capacity to drop quickly as a function of cycle number. There are numerous factors which conspire to reduce cycle life in silicon electrodes.  Eight of the most important factors to consider are:

1)                  Evolution of the voltage profile to higher charge voltages as a function of capacity/cycle number and the effect on cycle efficiency  (Figure 1)

2)                  Large expansion during lithiation (up to 280%)

3)                  Delamination from the current collector as a function of cycle number (Figure 2)

4)                  Instability of the Solid Electrode Interphase (SEI) due to large volume expansion

5)                  Instability of the electrolyte with lithiated silicon (Figure 3)

6)                  Excessive gassing due to electrolyte decomposition

7)                  Continued growth of electrode thickness as a function of cycle number

8)                  High porosity and therefore low volumetric energy density

This communication will present data exemplifying each of the failure mechanisms above.

In addition, the use of a Raspberry Pi to collect data for some of the experiments above will be discussed (Figure 3).