Abstract
A novel bismuth–carbon composite, in which bismuth nanoparticles were anchored in a nitrogen-doped carbon matrix (Bi@NC), is proposed as anode for high volumetric energy density lithium ion batteries (LIBs). Bi@NC composite was synthesized via carbonization of Zn-containing zeolitic imidazolate (ZIF-8) and replacement of Zn with Bi, resulting in the N-doped carbon that was hierarchically porous and anchored with Bi nanoparticles. The matrix provides a highly electronic conductive network that facilitates the lithiation/delithiation of Bi. Additionally, it restrains aggregation of Bi nanoparticles and serves as a buffer layer to alleviate the mechanical strain of Bi nanoparticles upon Li insertion/extraction. With these contributions, Bi@NC exhibits excellent cycling stability and rate capacity compared to bare Bi nanoparticles or their simple composites with carbon. This study provides a new approach for fabricating high volumetric energy density LIBs.
Highlights
Power sources with high volumetric and gravimetric energy densities are urgently needed to meet the small size and long service life requirements of various applications from information technology to transportation [1,2,3,4,5,6]
ZIF-8 was used as precursor and zinc nanoparticles (Zn@NC) was obtained via carbonization of ZIF-8 under H2/Ar
A galvanic replacement reaction took place, when Bi3? ions were introduced. This enabled the Bi nanoparticles to replace Zn nanoparticles in situ, resulting in a special configuration of Bi nanoparticles anchored in the skeleton of nitrogen-doped porous carbon
Summary
Power sources with high volumetric and gravimetric energy densities are urgently needed to meet the small size and long service life requirements of various applications from information technology to transportation [1,2,3,4,5,6]. Bismuth gives a volumetric capacity of 3430 mAh cm-3, which is far higher than those of other metal anodes and about five-bold than that of graphite [17] It yields potential hysteresis the same as graphite [18]. The improved cycling stability of bismuth in these efforts can be attributed to the controlled coating of carbon layer on bismuth, which enhances electronic conductivity and alleviates the mechanical strain of bismuth during lithiation/delithiation [23, 24]. The pores in the carbon matrix provided space to alleviate the mechanical strain of bismuth during lithiation/delithiation With these features, the resultant carbon/bismuth composite exhibited excellent performance as anode for LIBs when compared to other bismuth anodes that have been reported in other literatures. The product Bi@C was obtained by heating the precipitate at 550 °C for 3 h under N2 at the rate 2 °C min-1
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