How Crystallite Size Controls the Reaction Path in Nonaqueous Metal Ion Batteries: The Example of Sodium Bismuth Alloying

Abstract

Crystallite size effects can influence the performance of battery materials by making the structural chemistry deviate from what is predicted by the equilibrium phase diagram. The implications of this are profound: the properties of many battery materials should be reassessed. Sodium ion battery anodes made from nanocrystalline bismuth form different phases during electrochemical cycling compared to anodes with larger crystallites. This is due to the formation of a metastable cubic polymorph of Na 3 Bi on the crystallite surfaces. The structural differences (weaker Na−Bi bonds, different coordination of Na to Bi) between the metastable cubic Na 3 Bi phase found in the nanocrystals and the hexagonal equilibrium polymorph which dominates the larger crystallites offer an explanation for the improvements in cycling behavior observed for the nanostructured anode.

A Venture Synthesis and Fabrication of BiVO4 as a Highly Stable Anode Material for Na‐Ion Batteries

“…reported difficult to identify the signal of any Mo containing phase in Na−Bi phases and similar situation also was observed in the present investigation. This result was good agreement of CV and earlier report of Bi electrodes ,…”

“…The coulombic efficiency in the first cycle was 70.68%. The initial capacity was larger than the theoretical capacity became of the SEI formation on the surface of the electrode, reaction of Na with conducting agent (super P) present in the BiVO 4 electrode and some side reactions ,. Thereby, the initial sodiation capacity is higher than theoretical capacity at lower current density.…”

“…During the first sodiation process, the peak at 1.25 V may be ascribed to the BiVO 4 conversion reaction ( ) . The two peaks at 0.57 and 0.34 V during sodiation and 0.72 and 0.82 V during desodiation can rather be assigned to the two stage alloying reaction Bi to NaBi to Na 3 Bi ,. Below 0.25 V of sodiation peak, it may be associated with electrolyte decomposition and Na counter electrode polarization .…”

“…This higher density means that the Bismuth delivers a relatively higher volumetric energy density . In addition, Bismuth is much stable electrode due to lower volume expansion compared to Sn and Sb . For the reason in past decades, it has been widely investigated as various applications such as photocatalysts and solar cell applications, etc.…”

Alloy‐Based Anode Materials toward Advanced Sodium‐Ion Batteries

“…In addition to the commonly studied alloy-type anodes discussed above, Si-, [32,33,[184][185][186][187][188] Ge-, [187,[189][190][191][192][193] and Bi-based alloys [194][195][196][197][198][199][200] are also investigated as promising anode materials for SIBs. Typical examples of Si-, Ge-, and Bi-based anode materials and their electrochemical performance are summarized in Table 4.…”