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Rehman et al. Energy Mater 2024;4:400068 https://dx.doi.org/10.20517/energymater.2024.06 Page 19 of 64

Current potentials of Sb alloys are inhibited by the formation of powdery material that is not compatible
with binders, thus hampering ion penetration and electron transport. Recent endeavors to overcome these
issues are much more focused. Shen et al. have fabricated a self-supported intermetallic Sb-Zn alloy anode
[120]
via pulse electrodeposition . When this anode was employed as a binder-free anode for SIB, it achieved
an initial capacity of 377 mAh g at 300 m A g . After cycling over 320 cycles, it still maintained a
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capacity of 261 mAh g . The rate performance of the electrode was found to be 308 mAh g at
1,600 mA g . In comparison, the fabricated anode using constant potential electrodeposition
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methodology showed much lower performance. Operando XRD studies showed active participation of
Zn and Sb to originate NaZn and Na Sb phases that could transform during the charge/discharge
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13
process. The optimum performance of the electrode was ascribed to alloying, structural, and cooperative
effects of Zn.
Antimony-based oxides
+
Oxides of antimony have good alloying potential with Na . In particular, Sb O and Sb O have high
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theoretical capacities of 1,103 and 1,120 mAh g , respectively. The Sb O with a cubic structure subsequently
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3
underwent a conversion-alloying process to yield Sb and Na O reversibly. However, the low conductivity of
2
Na O limited its capacity. Akin to tin oxides, low conductivity, huge volume variations, and pulverization
2
problems also persist in Sb O and Sb O anodes [24,121,122] . The conversion-alloying reaction is illustrated as
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2
4
follows:
Sb O + 6Na + 6e → 2Sb + 3Na O (Conversion, Sb O )
+
-
2
3
3
2
2
2Sb + 6Na + 6e → 2Na Sb (Alloying, Sb O )
+
-
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2
3
Sb O + 8Na + 8e ↔ 2Sb + 4Na O (Conversion, Sb O )
-
+
2
2
4
4
2
-
+
2Sb + 6Na + 6e ↔ 2Na Sb (Alloying, Sb O )
4
3
2
[123]
Octahedral Sb O has been prepared by a low-cost and facile alkaline aqueous synthesis method . As an
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3
SIB anode, the material exhibited superior performance (435.6 mAh g , 0.1 A g current density, and
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50 cycles) to commercial Sb O powder. Its electrochemical performance was attributed to the unique
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3
structure that provided active surfaces for effective electrolyte wetting and fast kinetics that provided many
active sites and improved interactions on interfaces between electrodes and electrolytes. A nickel-supported
Sb O SIB anode with a good performance (445 mAh g ) and a CE of 89% over 200 cycles has been
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2
3
previously reported . The template-assisted synthesized 3D scaffold excellently buffered volume variation
[124]
in this electrode. Volume deformation during (de)sodiation cycles was also minimized with the designed
nano-scaffold structure.
[125]
A porous Sb O @Sb hybrid reported previously by Ma et al. showed a low ICE of 67.9% . However, this
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hybrid delivered highly regaining capacity in subsequent (de)sodiation cycles with a refined capacity of
658 mAh g over 200 cycles (CE 99.8%) and an outstanding rate performance (200 mAh g ) at a very high
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ampere density of 29.7 A g . Furthermore, a full cell demonstration (using NVP cathode) showed a
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competing cyclability with 473 mAh g over 100 cycles (CE 92.7), along with a rate performance of
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432 mAh g at 5 A g . Operando XRD and in-situ Raman excellently traced intermediate phases that
provided a mechanistic understanding of capacity retention in the Sb O conversion-alloying anode. An
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electrospun Sb O @NC freestanding membrane fabricated for SIB anode utilization retained good
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reversibility in capacity (527.3 mAh g over 100 cycles at 0.1 A g ) . The sodium storage behavior
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-1 [126]
involved a capacitive mechanism that demonstrated a high potential. The anode showed a high sustaining
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capacity of 400 mAh g at 1 A g over extended cycling of 700 times.