Dual carbon enables highly reversible alloying/dealloying behavior of ultra-small Bi nanoparticles for ultra-stable Li storage

Abstract

Bismuth (Bi) have attracted attentions as promising anode material for lithium-ion batteries (LIBs) due to its high capacity and suitable working potential. Nevertheless, poor ion diffusion kinetics and huge volume expansion, lead to irreparable particle pulverization and re-agglomeration in the discharge/charge process, which is not conducive to the rapid and ultra-long-period storage of Li+. Herein, ultra-small Bi nanoparticles encapsulated in double carbon microrods (Bi/C@C MRs) are synthesized via using Bi-based MOFs precursor coupled with polymerization coating process and followed calcination. The MOF-derived inner cross-linked carbon encapsulated ultra-small Bi nanoparticles, and the polymeric layer of resorcinol- formaldehyde transformed into outer carbon shell was coated on the outer surface of Bi/C microrods. The inner cross-linked carbon can suppress the severe volume change and re-agglomeration of Bi nanoparticles during the repeated alloying/de-alloying process, as well as accelerate the Li+ and electron transition. Furthermore, outer carbon layer can not only further buffer the volume change, but also avoid directly contact between Bi nanoparticles and electrolyte during the cycling process. As a result, the Bi/C@C MRs exhibits excellent structural stability and highly reversible alloying/dealloying behavior during the long-term cycling process. Bi/C@C MRs sustain a ultra-long cycle life of ∼ 506 mA h g−1 at 1000 mA g−1 up to 3000 loops, and an excellent rate performance of 279 mA h g−1 at an ultrahigh rate of 10000 mA g−1. Above results provided new insight to achieve ultra-long cycle life and excellent rate performance anodes for practical LIBs.