A\nCommercial Conducting Polymer as Both Binder and\nConductive Additive for Silicon Nanoparticle-Based Lithium-Ion Battery\nNegative Electrodes

Abstract

This work describes silicon nanoparticle-based\nlithium-ion battery\nnegative electrodes where multiple nonactive electrode additives (usually\ncarbon black and an inert polymer binder) are replaced with a single\nconductive binder, in this case, the conducting polymer PEDOT:PSS.\nWhile enabling the production of well-mixed slurry-cast electrodes\nwith high silicon content (up to 95 wt %), this combination eliminates\nthe well-known occurrence of capacity losses due to physical separation\nof the silicon and traditional inorganic conductive additives during\nrepeated lithiation/delithiation processes. Using an <i>in situ</i> secondary doping treatment of the PEDOT:PSS with small quantities\nof formic acid, electrodes containing 80 wt % SiNPs can be prepared\nwith electrical conductivity as high as 4.2 S/cm. Even at the relatively\nhigh areal loading of 1 mg/cm², this system demonstrated\na first cycle lithiation capacity of 3685 mA·h/g (based on the\nSiNP mass) and a first cycle efficiency of ∼78%. After 100\nrepeated cycles at 1 A/g this electrode was still able to store an\nimpressive 1950 mA·h/g normalized to Si mass (∼75% capacity\nretention), corresponding to 1542 mA·h/g when the capacity is\nnormalized by the total electrode mass. At the maximum electrode thickness\nstudied (∼1.5 mg/cm²), a high areal capacity of\n3 mA·h/cm² was achieved. Importantly, these electrodes\nare based on commercially available components and are produced by\nthe standard slurry coating methods required for large-scale electrode\nproduction. Hence, the results presented here are highly relevant\nfor the realization of commercial LiB negative electrodes that surpass\nthe performance of current graphite-based negative electrode systems.