Boron-Modified Silicon Carbonitride as a Sulfur Host for Stable Lithium–Sulfur Batteries

Abstract

Failure in lithium–sulfur batteries (LSBs) is largely attributed to the uncontrolled transport of soluble polysulfides. Therefore, an electrically conducting matrix that hosts elemental sulfur and prevents polysulfide dissolution into the electrolyte is highly desirable. Covalent ceramics prepared through a polymer pyrolysis route contain polar bonds and a 3D network of conducting carbon phase that could enable chemical and physical adsorption of soluble lithium polysulfides (LiPSs) and electrical transport, respectively. Herein, we report the preparation of boron-integrated silicon carbonitride (Si–B–C–N) from thermochemical conversion of a single-source precursor and its use as a sulfur host for LSBs. The SiBCN host provided superior electrochemical performance compared to the neat SiCN host, delivering an initial capacity of 1039.3 mAh g_s⁻¹ and retaining 858.8 mAh g_s⁻¹ after 100 cycles at 0.1 C with nearly 100% coulombic efficiency, exhibiting a 25.8% improvement over SiCN, possibly associated with the presence of B─N bonds, which enhanced the adsorption of intermediate LiPSs. These findings highlight the advantages of compositional tuning in PDCs, which can enhance the reversibility of sulfur's electrochemical reactions, inhibit active material loss, and improve cycling stability in LSBs.