PEDOT:PSS Electroactive Binder for Silicon Nanoparticles in Li-Ion Battery Applications

International audienceSilicon is for many years a coveted Li-ion battery material by the scientific community. This material exhibits a high theoretical specific capacity of 3579 mAh/g (10 times higher than graphite material) making it very promising for Li-ion negative electrodes. However, two main problems appear with silicon electrode during cycling, its structural degradation (leading to a loss of contact between silicon particles) and the instability of the Solid Electrolyte Interphase (SEI), mainly due to the huge volume expansion of Silicon particles during cycling (around 300 %). Different ways have been studied to tackle these problems, including the nanostructuration of Si particles to reduce the stress undergone during charge/discharge cycles. More recently, the use of conducting polymers as binders inside the electrode formulation was studied in place of classical binders like PVDF or CMC. The use of a conducting polymer as an alternative to traditional insulating binder in combination with conductive additive (carbon black, graphene…) allows to play the role of both binder and electronical conductor. Consequently, it leads to reduce space and interfacial parameters by the elimination of these inorganic (and non-active) conductive materials in the electrode formulation. The conducting polymer used in this work is the PEDOT:PSS. This polymer is well known for its good chemical and mechanical stability and its potential high electrical conductivity (10-2 to 103 S/cm). It is mainly studied in the domain of photovoltaic and its use in the battery domain for electrode formulations begins to appear. The results of this study will be devoted to the evaluation of Li-ion negative electrode containing Silicon (or Silicon@carbon composite) nanoparticles with PEDOT:PSS binder. Si and Si@C nanoparticles are synthesized by laser pyrolysis. This process offers the possibility to decrease the size of the particles and to coat the silicon by a carbon shell, all in one step of synthesis. Electrode formulations containing the active material (Si or Si@C) and the PEDOT: PSS binder (without other additives) are coated on a Cu current collector to perform electrochemical tests. Cyclic voltammetry, Electrochemical Impedance Spectroscopy (EIS) and galvanostatic cycling were performed in half-cells containing the Si (or Si@C)/PEDOT:PSS electrode versus a lithium foil. Specific capacities up to 1000-1500 mAh/g and stable over more than a hundred cycles of charge/discharge were achieved. These very encouraging results highlight the potential of PEDOT:PSS as electroactive binder for silicon electrodes in Li-ion batteries