A holistic approach is required where the performance of the electrodes and electrolyte needs to be improved simultaneously. On the anode side, Si has been considered as the best candidate to give much higher capacities reaching, in theory, 10 times those of graphite. [1,2] However, in practice Si alone cannot deliver this high capacity reversibly due to many problems associated with volume expansion/shrinking during lithiation/de-lithiation. Also, current cathode materials have limited specific capacity to 150-200 mAh/g and can only be coated up to certain thickness before fracture or polarization takes place. A composite of silicon and graphite with capacities between 500 and 1000 mAh/g has been considered as a transient and practical alternative. In this work we have conducted theoretical and experimental study of silicon, graphite, and binder composite electrodes. We have calculated the percentage of improvement in capacity of composites and in energy density of full cells. We have tested more than 50 compositions in half cells with different ratios, binder type and silicon (shape, size and surface chemistry). Also, we have tested full cells using NMC cathode, a carbonate solvent mixture and various additives.

We will show the result of our theoretical and experimental findings and demonstrate the actual parameters that need to be optimized in order to reach real improvements in practical energy density of Li-ion full cells.

[1] Chae-Ho Yim, Fabrice M Courtel, Yaser Abu-Lebdeh, Journal of Materials Chemistry, 1(28), 2013 8234.

[2] Nuha Salem, Matt Lavrisa and Yaser Abu-Lebdeh, 2015,  Energy Technology, DOI 10.1002/ente.201500250.