A 74 wt% silicon composite electrode delivers 1000 cycles with 74% capacity retention against NMC811 cathodes and a cell stack energy density of 212 W h kg⁻¹ in a standard carbonate electrolyte with two simple chemical and process improvements.

We demonstrate that the addition of CO ₂ to a standard 1.0 M LiPF ₆ 3:7 wt% ethylene carbonate:ethyl methyl carbonate electrolyte results in the formation of a thinner insoluble solid electrolyte interphase (SEI) that is dominated by the presence of LiF. In contrast, cells without CO ₂ result in a thicker insoluble SEI layer containing more organic constituents. The CO ₂ is incorporated in the dimethyl carbonate soluble part of the SEI composed primarily of polymeric poly(ethylene oxide) (PEO) on the surface of a thin inorganic layer. This combination of properties from CO ₂ addition provides an improved cycling performance through the reduction of irreversible side reactions, leading to higher coulombic efficiency. The results indicate that CO ₂ incorporates into the SEI and plays a role similar to additives like fluorinated ethylene carbonate and vinylene carbonate with respect to polymeric components.

700 °C is the optimal heat treatment temperature for pitch-coated silicon electrodes. Both the amorphous carbon/pitch and silicon are active materials but store Li⁺ ions through different ion storage mechanisms and contribute to overall performance.

A study on polyimide binder for Li ion batteries, showing active lithiation/delithiation with first cycle capacity loss, formation of dendrite-like morphology, elastic modulus increase, and overall electronic resistivity increase during lithiation.