Solid Solution Strengthening of Bismuth Antimonide as a Sodium Storage Material

Abstract

A relationship between the mechanical property and charge−discharge performance of bismuth antimonide (Bi−Sb) solid solution electrodes was experimentally investigated for the first time as Na-ion battery anodes. The nanoindentation measurements revealed that three kinds of electrodes of Bi−Sb solid solution (Bi 0.8 Sb 0.2 , Bi 0.5 Sb 0.5 , and Bi 0.2 Sb 0.8 ) showed 100 times higher indentation elastic modulus compared to the Bi electrode by the effect of solid solution strengthening and that Bi 0.2 Sb 0.8 has the most elastic property among the solid solutions. The charge−discharge cycling tests confirmed that the reversible capacities of a Bi electrode and Sb electrode rapidly decayed, owing to pulverization of active materials induced by their large volumetric changes during sodiation−desodiation reactions. The Bi-rich solid solution (Bi 0.8 Sb 0.2 ) also showed poor cyclability. It is suggested that the pulverization of Bi 0.8 Sb 0.2 could not be avoided because of its less elastic property. The cycling performance of Bi−Sb electrodes was remarkably improved with increasing the ratio of Sb. The Sb-rich solid solution (Bi 0.2 Sb 0.8 ) electrode exhibited the best performance with the reversible capacity of 520 mA h g −1 , even at the 200th cycle. We consider that the pulverization of Bi 0.2 Sb 0.8 was effectively suppressed because it has reasonably elastic property in addition to a high indentation elastic modulus as a result of the solid solution strengthening. This knowledge would be very meaningful in the development of the next-generation alloying-type anode materials with high capacities.

Unveiling the Electrochemical Mechanism of High-Capacity Negative Electrode Model-System BiFeO3 in Sodium-Ion Batteries: An In Operando XAS Investigation

“…A previous work carried out on the Na storage behavior of Fe 2 O 3 reported similar observations . In the subsequent charge step, oxidation peaks were observed at ∼0.75 V (denoted by “B*”) with shoulders around 0.83 V (denoted by “A*”) and 1.2 V (denoted by “C*”), respectively, which could probably be indicating the corresponding stepwise dealloying reaction followed by the oxidation of metallic species; such as Bi and Fe. ,, The appearance of these peaks is in well agreement with the observations on the Bi–Sb electrode, and it confirms the reversibility of the Bi alloying–dealloying reactions . In the subsequent discharge, a reduction peak appears at ∼1.2 V (denoted by “C”), followed by another cathodic peak close to 0.5 V (denoted by “A”), probably indicating the subsequent reduction of metal oxides formed at the end of charge to metallic species.…”

“…41,44 Another cathodic peak was observed at ∼0.3 V (denoted by "B"), which could be originated from the alloying reaction between Na and Bi to form intermetallic Na 3 Bi. 47 A similar behavior was also shown by the Bi−Sb electrode in a Na half-cell, as reported by Usui et al 53 Furthermore, this region may include electrochemical activity, resulting from the conversion of BFO to metallic Fe via a sodiated iron oxide. A previous work carried out on the Na storage behavior of Fe 2 O 3 reported similar observations.…”

“…In the first discharge, a sharp reduction peak was observed at 0.68 V versus Na + /Na (denoted by “A′”), which could be attributed to the conversion of BFO to metallic Bi and Fe similar to what was reported for BFO in Li-ion batteries. , Another cathodic peak was observed at ∼0.3 V (denoted by “B”), which could be originated from the alloying reaction between Na and Bi to form intermetallic Na 3 Bi . A similar behavior was also shown by the Bi–Sb electrode in a Na half-cell, as reported by Usui et al Furthermore, this region may include electrochemical activity, resulting from the conversion of BFO to metallic Fe via a sodiated iron oxide. A previous work carried out on the Na storage behavior of Fe 2 O 3 reported similar observations .…”

“…41,44,54 The appearance of these peaks is in well agreement with the observations on the Bi−Sb electrode, and it confirms the reversibility of the Bi alloying− dealloying reactions. 53 In the subsequent discharge, a reduction peak appears at ∼1.2 V (denoted by "C"), followed by another cathodic peak close to 0.5 V (denoted by "A"), probably indicating the subsequent reduction of metal oxides formed at the end of charge to metallic species. Note that there is a shift in the potential, where the cathodic peak "A" appears in the second discharge, in comparison with the first discharge (peak "A′"), probably due to a change in the mechanism, particularly due to the difference in the nature of metal oxides present at the initial state (electrode before electrochemical treatment) and formed at the end of first charge, which get reduced in the subsequent discharge.…”

Electrochemical Polarization Part 2: Electrochemical Devices

“…7 As another approach to improve anode performance, solid solution strengthening of anode materials was applied. 8 Antimony and bismuth have high theoretical capacities of 660 and 385 mAh g ¹1 , respectively. However, electrodes composed of elemental Sb or Bi suffer from capacity decay induced by the large volumetric changes during cycling.…”