Insights into the Electrochemical Performance of 1.8 Ah Pouch and 18650 Cylindrical NMC:LFP|Si:C Blend Li-ion Cells
Résumé
Silicon has become an integral negative electrode component for lithium-ion batteries
in numerous applications including electric vehicles and renewable energy sources. However, its
high capacity and low cycling stability represent a significant trade-off that limits its widespread
implementation in high fractions in the negative electrode. Herein, we assembled high-capacity
(1.8 Ah) cells using a nanoparticulate silicon graphite (1:7.1) blend as the negative electrode material
and a LiFePO4 LiNi0.5Mn0.3Co0.2O2 (1:1) blend as the positive electrode. Two types of cells were
constructed: cylindrical 18650 and pouch cells. These cells were subjected both to calendar and
cycling aging, the latter exploring different working voltage windows (2.5 3.6 V, 3.6 4.5 V, and
2.5 4.5 V). In addition, one cell was opened and characterised at its end of life by means of X-ray
diffraction, scanning electron microscopy, and further electrochemical tests of the aged electrodes. Si
degradation was identified as the primary cause of capacity fade of the cells. This work highlights
the need to develop novel strategies to mitigate the issues associated with the excessive volumetric
changes of Si.
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