Background: Bismuth (Bi) has been studied due to its high theoretical gravimetric capacity of
385 mAh g−1, which is as important as gravimetric capacity for the practical application of battery systems
in electronic mobile devices. However, there have been limited fundamental explorations on the electrochemical
performances of Bi. Furthermore, the mechanism differences for the Bi anodes in lithium-ion
batteries (LIBs) and sodium-ion batteries (NIBs) should be further investigated.
Methods: The Bi nanowires were fabricated by vacuum melting and pressure injection method. Briefly, a
Bi bulk was placed into an injection apparatus and heated up above 275 °C (melt point of Bi: 271.3 °C),
and then the melt was injected into the AAO pores by a hydraulic force. After the injection process, the
chamber was kept in vacuum to cool down slowly. Subsequently, the AAO template was dissolved away
slowly in the etching solution (0.4 M H3PO4+ 0.2 M CrO3) at 60 °C for 72 h to expose Bi nanowires. Finally,
after sonication dispersion, centrifugal sedimentation and rinsing with deionized water several times
to remove the excess H3PO4-CrO3 mixture, the free-standing Bi nanowires were collected.
Results: The morphologies of AAO, AAO/Bi and Bi nanowires were tested and presented in detail. It
found that the Bi nanowires can be obtained by pressure injection method followed with dissolve the AAO
template. After boll milling with C to form Bi/C nanocomposites, the nanocomposites were assembled as
an electrode of LIBs or NIBs. It exhibited high capacities in LIBs, while for NIBs, the capacity retention
was relatively low.
Conclusion: Bi nanowires have been prepared by mechanical pressure injection method and thoroughly
dissolution of the AAO template. After successive milling of Bi nanowires with carbon black, Bi/C nanocomposites
are obtained. The Bi/C nanocomposites used as electrode in LIBs exhibit high capacities and
the initial discharge/charge capacities of Bi/C anode are around 1223.4/571.9, 905.9/412.3, 829.2/ 362.6
mAh g-1 at current densities of 20, 200 and 500 mA g-1, respectively. The enhanced electrical performances
are attributed to the smaller size of Bi nanowires and the introduced carbon black to buffer the volume
changes during discharge/charge process. In NIBs, the capacity retention after 50 cycles reaches 284.7,
196.2 and 168.3 mAh g-1 at current densities of 20, 200 and 500 mA g-1, respectively. Furthermore, in
LIBs, Bi and Li+ ions combine together through an alloying process, while in NIBs, only an intercalation
process occurs for Bi and Na+ without indication of alloying.