Affiliation:
1. Department of Electrical Energy Storage Fraunhofer Institute for Solar Energy Systems ISE Heidenhofstraße 2 79110 Freiburg Germany
2. Institute for Inorganic and Analytical Chemistry (IAAC) University of Freiburg Albertstraße 21 79104 Freiburg Germany
3. Freiburger Materialforschungszentrum (FMF) University of Freiburg Stefan-Meier-Straße 21 79104 Freiburg Germany
4. Chair for Electrical Energy Storage Systems Institute for Photovoltaics (ipv) University of Stuttgart Pfaffenwaldring 47 70569 Stuttgart Germany
Abstract
AbstractThe aim of manufacturing silicon‐carbon (Si/C) composites for lithium‐ion batteries is to embed silicon particles into a carbon matrix or shell, which results in improved electrical conductivities and cycling stability by avoiding the direct solid electrolyte interphase (SEI) formation on the silicon surfaces. In this study, we explore the production of Si/C composites containing one (single) and two (multiple) carbon shells, achieved through the carbonization of polyacrylonitrile. We thoroughly analyze the carbonization process of polyacrylonitrile and investigate the structural, physical, and electrochemical properties of the resulting Si/C composites. Our findings indicate that the increase of the carbon fraction and the second thermal treatment during the manufacturing of multiple carbon shells (MCS) have a significant impact on the conductivity of the powders, increasing it by one order of magnitude. We also discover that the MCS cover the silicon surface more effectively, as revealed through etching in a NaOH solution and subsequent elemental analysis. The MCS composite, containing 30 wt.% silicon, exhibits the best cycling performance in half‐cells at 0.5 C, with an initial capacity of 776 mAh g−1 and a capacity retention of 83.0 % after 100 cycles.