Silicon oxycarbide-encapsuled bismuth for superior lithium storage

Abstract

Bi is a promising anode for Li-ion batteries (LIBs) because of its suitable working voltage and high volumetric capacity. Nonetheless, the inevitable volume expansion during Bi alloying reactions results in severe capacity loss and cell failure. Herein, to achieve reliable alloying with high reversibility, a polymer-derived ceramic silicon oxycarbide (SiOC) coating was formed on Bi nanoparticles (NPs) by the facile dispersion of bismuth hydroxide in silicone oil and subsequent calcination. The embedment of Bi NPs in the sturdy SiOC domain relieved the local mechanical strain developed by Bi alloying upon Li+-ion insertion/extraction, achieving a highly stable capacity (507 mAh g−1 after 150 cycles at 50 mA g−1), outstanding long-term cyclability (380 mAh g−1 at 0.5 A g−1 after 500 cycles), and good cell integrity. When this composite anode was coupled with a LiNi0.5Co0.2Mn0.3O2 cathode, the full cell exhibited high gravimetric and volumetric energy densities of 343 Wh kg−1 and 607 Wh L−1, respectively. Further, kinetic and postmortem analyses confirmed the superiority of amorphous SiOC as a protective layer that hinders undesirable solid electrolyte interface generation, active material conductivity loss, and particle isolation.