Bi nanoparticles with different oxidation states embedded in porous carbon nanosheets as high-performance anode for lithium-ion battery

Bi-based material is a new candidate anode for LIBs. Herein, we fabricate Bi nanoparticles (NPs) with different oxidation states embedded in mesoporous carbon matrix based on bismuth citrate-engaged etching-pyrolysis strategies. For Bi@MCNSs-500, the oxidation state of Bi is Bi3+. Nevertheless, for Bi@MCNSs-700 and Bi@MCNSs-900, Bi appears as a metallic phase (Bi0 and Bi3+). Bi@MCNSs-700 shows excellent electrochemical properties as anode material for LIBs. Bi@MCNSs-700 has an initial discharge capacity of 1422.65 mAh g−1 at 0.05 A g−1 and it exhibits high capacity of 312 mAh g−1 at 5 A g−1, and exhibits excellent cycling performance (1 A g−1, 393.2 mAh g−1 after 1000 cycles). Such extraordinary performances are attributed to (1) ultra-small Bi NPs and suitable oxidation states can provide massive active sites and facilitate Li+ storage. (2) the porous carbon nanosheets can improve the conductivity, and effectively offer sufficient space to adapt to volume changes during cycling, thus improving cycling stability for Li+ storage. This work provides perspective into the design of excellent Bi-based materials for LIBs.