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Rehman et al. Energy Mater 2024;4:400068 https://dx.doi.org/10.20517/energymater.2024.06 Page 13 of 64

layers in the material. At the phase interface, this structure enabled lattice deformation and electron
redistribution, accelerating ion migration and charge transfer while the porous carbon increased its
electronic conductivity. As a consequence, the MoSe /SnSe @C composite showed a good cycling
2
2
-1
performance for SIBs with a reversible capacity of 591.4 mAh g over 110 cycles at 0.1 A g and a capacity of
-1
334 mAh g after 200 cycles at 0.5 A g . Ex-situ high-resolution TEM (HRTEM) elucidated the sequential
-1
-1
conversion of the material upon (de)intercalation with MoSe , showing higher reversible transformation
2
than the SnSe phase.
2
Tin-based phosphides
Sn can also form alloys with P that could reversibly intercalate Na in the assembly of anode for SIBs.
+
Among various phosphides, the most common one is Sn P with a rhombohedral crystal structure that has
4 3
garnered more interest due to its superior electrical conductance, higher gravimetric capacity
-1
(1,132 mAh g ), higher structural endurance, and ability to operate the derived anode at a lower
potential . Although other tin phosphides such as SnP and SnP are also known, Sn P has been explored
[99]
0.94
4 3
3
the most widely as an SIB anode [100,101] . Pan et al. have presented uniformly structured ultrasmall Sn P
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nanoparticles using a low-temperature phosphatization methodology and constructed a 3D framework
afterward by implanting these Sn P nanoparticle assemblies onto graphene aerogel . As an anode, it
[102]
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-1
showed an impressive initial performance with an initial discharge capacity of 1,180 mAh g at 0.1 A g that
-1
consequently reduced to about 657 mAh g over 100 cycles with a good rate capability (462 and 403 mAh g
-1
-1
at current densities of 1 and 2 A g , respectively). The same research group also proposed a rational
-1
synthetic design of Sn P microspheres fully protected by thick hollow C shell [Figure 6A]. The material has
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[103]
impressive sustained capacity as an SIB anode, as depicted in Figure 6B . In the course of (dis)charging,
this hollow protective carbon spherical shell efficiently accommodated volume variations. The enhanced
electrochemical performance of Sn P @C was attributed to its distinctive morphological design. The
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Sn P @Ccomposite has demonstrated good sodiation performance as an anode with a capacity of
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420 mAh g over 300 cycles at a current density of 0.2 A g . Also, after extensive cycling 4,000 times, stable
-1
-1
-1
capacities of 205 and 103 mAh g at large current densities of 2 and 5 A g , respectively, were attained.
-1
Similarly, the µ-sized Sn P delivered an extremely high reversible capacity of 960.3 mAh g at 100 mA g
-1
-1
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with an ICE of 89.8% after 100 cycles in a diglyme (DGM)-based electrolyte. Also, a capacity retention of
75.1% was recorded after 100 cycles. Such excellent Na storage performance was due to the flexible,
compact, and uniform SEI layer in the ether-based electrolyte, which successfully inhibited the separation
[104]
and aggregation of active components and provided favorable kinetics . A fascinating biomimetic
heterostructured Sn P grown on CNT (Sn P @CNT/C) has been developed by a hydrothermal reaction.
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This biomimetic bottle brush was designed as a structure in which CNTs served as a “stem” to provide an
electron-transferring superhighway and mechanical stability. To enhance the contact area of the CNT
surface with the electrolyte along with shortened ion diffusion channels, Sn P nanoscale assemblies
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functioned as a “fructus”. Furthermore, stresses generated during (de)sodiation were recurrently buffered.
The Sn P @CNT/C hybrid anode exhibited an outstanding electrochemical performance with a steadily high
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capacity of 742 mAh g after 150 cycles at 0.2 C, together with 449 mAh g at 2 C after 500 cycles. The
-1
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following conversion-alloying reactions occurred:
+
-
Sn P + 24Na + 24 e → Na Sn + 3Na P
3
4
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15
Na Sn ↔ 4Sn + 15Na + 15e -
+
4
15
+
Na P ↔ P + 3Na + 3e -
3