Peter Raimann

Silicon/Graphite Composite Electrodes for High-Capacity Anodes: Influence of Binder Chemistry on Cycling Stability

The binders influence on the cycling stability of high-energy anodes for lithium-ion batteries is demonstrated. Varying the binders nature strongly influences the composite electrodes performance on deep charging/discharging. If sodium-carboxymethylcellulose is used as binding agent, then a chemical bond between binder and silicon particles can be detected (attenuated total reflection-Fourier transform infrared spectroscopy). Consequently, a reaction mechanism that describes a condensation reaction between the binder and the silicon particles is verbalized. It is shown that, not necessarily the binders physical flexibility, but its chemical interaction with the active masses is the major claim leading to long-lasting reversible lithium uptake/release.

Electrolyte Decomposition Reactions on Tin- and Graphite-Based Anodes are Different

In ethylene carbonate- and propylene carbonate-based electrolytes, ethylene and propylene gas evolution have been monitored by on line mass spectrometry. The gases evolve on graphite but not on the lithium storage alloy. The results point to a difference in the electrolyte decomposition mechanism and thus in the solid electrolyte interphase (SEI) formation mechanism. This is discussed in view of solvent co-intercalation reactions, which only arise when graphite anodes are used. The ultimate conclusion is that, due to the different side reactions occurring on graphite and lithium storage alloys, the SEI compositions and the requirements on the SEI performance are different.