Performance enhancement of carbon-coated Si nanoparticles for lithium-ion batteries through the generation of lithophilic sites by a simple oxidation process.

A simple surface modification strategy to generate lithophilic sites in carbon-coated Si nanoparticles significantly enhances the capacity as well as cycling stability. [Display omitted] • A simple surface treatment process generates lithophilic surface groups on carbon-coated Si nanoparticles. • The surface-functionalized electrode of Si-C-AT shows a higher diffusion coefficient than Si-C. • The Si-C-AT shows a reversible capacity of 1575 mA h g−1 after 200 cycles at a current rate of 0.5C. • Functional groups on the Si-C-AT assist in accumulating the lithium-ions in excess on the carbon surface. Silicon nanoparticles (Si NPs) are potential anode materials for next-generation lithium-ion batteries due to their natural abundance, low discharge potential, and high theoretical capacity. Carbon coating improves the capacity of the Si NPs, protects them from disintegration during the lithiation/delithiation process, and provides an additional conductive matrix. Surface modification as a tool leading to capacity enhancement in carbon-coated Si NPs has rarely been explored. It is a straightforward process that involves the surface functionalization of carbon-coated Si NPs (Si-C) with the oxidizing acidic mixture. The surface-treated Si-C functionalized with carboxyl and hydroxyl groups in excess on the carbon surface of Si-C NPs. As a result of surface modification, the acid-treated Si-C (Si-C-AT) displayed a higher reversible capacity of 1575 mA h g−1 after 200 cycles compared to the Si-C (1261 mA h g−1) and bare Si (961 mA h g−1). This high capacity of Si-C-AT is a cumulative outcome of the functional groups and the disordered structure of the carbon shell. The functional groups act as lithophilic sites, and the disordered carbon shell facilitates the insertion-desertion of lithium ions. The simple surface modification strategy proposed in the present study significantly enhances the cyclability of the Si-C-AT NPs and has great potential for application in carbon-coated materials for lithium-ion batteries. [ABSTRACT FROM AUTHOR]