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Rehman et al. Energy Mater 2024;4:400068 https://dx.doi.org/10.20517/energymater.2024.06 Page 45 of 64

longevity of the anode in half and full-cell operations.

An intermetallic Sn-Bi SIB anode has been recently proposed, showing stable and sustaining capacity as an
-1
SIB anode. The optimized SnBi composition showed a capacity of 508 mAh g in the first cycle and a
[269]
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capacity of 420 mAh g at 1 C after cycling 200 times . The synchrotron operando XRD showed the origin
of different Sn and Bi intermetallic alloyed compositions during (dis)charging phases. At different
electrochemical potentials, Sn and Bi particles in the intermetallic get sodiated to various levels. When one
phase is active (sodiated), the other is dormant. In this way, the system is buffered to manage volumetric
stresses. An anode-less configuration has recently been opted to utilize the Bi array deposited onto a copper
foil to form Cu@Bi alloy . The fabricated material was tested in both half-cell and full-cell configurations
[270]
after initial activation. The full cell comprising the Cu@Bi anode and NVP as cathode delivered a capacity of
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95.6 mAh g over 80 cycles. A binary melt-spun alloy Fe-As has recently been tested as an SIB anode by
[271]
Patel et al. . This anode delivered an ultrahigh and stable capacity of 965 mAh g at 50 mA g over 400
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cycles Additionally, it demonstrated an excellent sodiation rate performance of 668 mAh g at 2 A g ,
surpassing most of the common SIB anodes. Beyond that, melt-spun fibers showed 770 mAh g of sodiation
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capacity after 200 cycles at 50 mA g (with over 97% CE). Detailed ex-situ XRD highlighted the
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compositional and phase transformations, confirming the formation of Na As during sodiation and the
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appearance of an iron-rich phase. This study highlighted the excellent potential of intermetallic alloy
materials for being opted as commercial anodes for SIBs. Similarly, Sb-Zn electrodeposited intermetallic
alloy showed superior Na storage capacity as a binder-free anode in SIBs, whereby different Sb and Zn
+
[120]
alloying with sodium was traced during the charge/discharge process .
Recently, a hybrid SIB anode composed of FeSb S /Sb/rGO that offers a highly stable capacity of
2 4
366.1 mAh g over 100 cycles at 0.1 A g has been reported . The material showed quite durable
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[115]
performance at higher current densities and offered a capacity of 252.7 mAh g at 10 A g over 100 cycles.
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The reaction mechanism involved dual alloying/dealloying followed by a conversion reaction with good
reversibility, which could mitigate challenges faced by SIB anodes. Shen et al. have newly proposed a
Sb-Co-P alloying anode showing superior SIB anode performance . Among those with the best
[164]
compositions, Sb Co P delivered a capacity of 586.3 mAh g after 100 cycles at a current density of 100
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46.9 32.1
21.0
mA g (CE: 77.6%). In-situ XRD demonstrated changes in peak intensities and the formation of Na P and
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Na Sb with Co nanoparticles. A nanoalloy of Sn-Ni doped with N-doped C presented an efficient 3D
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structure with a pomegranate-like morphology. It has been tested for an SIB anode both in half-cell and
full-cell configuration . The SIB had a half-cell capacity of 332.1 mAh g over 100 cycles at 0.2 A g and a
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-1
[272]
full-cell capacity of 112.5 mAh g at 0.1 A g over 60 cycles. The intact morphology with N-doped C
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improved the electronic conductivity with multiple ion transport pathways for effective ion shuttling.
In fact, a unique strategy has recently been employed by Li et al. to fabricate a modified anode material .
[273]
They incorporated Sn into copper sulfide and then partially substituted Sn with Zn, which garnered a
sodium uptake capability of the electrode with stable performance and fast charging behavior. The Sn-Zn-
based copper sulfide maintained a capacity of 560 mAh g at 0.2 A g with a retention capacity of 100% for
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80 K cycles. The material furnished a highly fast charging of 4 s per charge with an input of 190 mAh g . A
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freshly developed mesoporous Sn/SnO -Ni@C composited alloy has shown marked performance as an SIB
2
-1
anode. The composite furnished a stable capacity of 342.6 mAh g at 0.2 A g after 200 cycles while the
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anode delivered a capacity of 219.3 mAh g at 1.0 A g when cycled 1,000 times . The excellent interplay
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[274]
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between the Sn/SnO and Ni has mitigated effects of volume expansion and capacity degradation. Another
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fascinating study has highlighted a 3D core-shell heterostructured SnO coated with barium titanate (acting
2
[206]
as core) and covered with phosphorous-doped C (BTO@SnO @P-C) [Figure 20A] . The unique selection
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