In lithium-ion batteries, the anodes are typically made from graphite. There is potential for the use of silicon as an alternative to graphite, however bare silicon particles exhibit poor chemical stability with the most common electrolyte formulations. This causes the formation of an unstable solid electrolyte interphase, leading to a fast capacity fade and poor cycling stability of the electrodes. Although a wide range of lab-scale methods employing different silicon morphologies and their composites have been successfully demonstrated, the lack of a facile and scalable process is preventing an immediate introduction into large-scale manufacturing.
Prof. Mangolini and his colleagues from the University of California, Riverside have developed a novel process for coating silicon nanoparticles with a conformal shell of carbon specifically optimized for electrochemical energy storage applications. This process allows for simple control of the thickness and degree of graphitization of the nanoparticles. The introduction of a highly-graphitic carbon coating on the surface of the silicon particles serves as a buffer layer, promoting a more robust cycling, and improves the overall electrical conductivity of the silicon-carbon composite. Replacement of 10% by weight of graphite in the electrode composition results in an increase of 60% in the storage capacity silicon-carbon core-shell nanocomposites represent a promising high storage capacity alternative to the current graphite-based lithium-ion battery anodes, while also overcoming the obstacles that prevent the use of silicon particles in energy storage applications.
Fig 1: High-resolution TEM images showing the high uniformity of the carbon coating wrapping a single silicon nanoparticle.