Page 95 - Read Online

Page 26 of 64 Rehman et al. Energy Mater 2024;4:400068 https://dx.doi.org/10.20517/energymater.2024.06

-1
-1
100 mA g while sustaining 65.6% of the capacity over 5,000 cycles at an ampere density of 2 A g . During
(dis)charging, the strong interaction between rGO and NRP/Na P inhibited volume variations.
3
To better protect the RP-C composites from air exposure and the resultant capacity engulfing process, a
protective coating of polypyrrole (PPy) has been proposed, which could enhance the conductivity and
impart electrolyte and air stabilization . This strategy resulted in stable electrode material at ambient
[155]
-1
conditions having a high RP content with a stable reversible capacity of 800 mAh g at a current density of
50 mA g . Jin et al. have adopted an assisted double annealing strategy to ensure highly porous conductive
-1
-
networks interconnected inside the P host . The extra-short Na /e diffusion pathways in the conductive
[156]
+
matrix supported the structure from volume variations and exhibited an astonishing longevity over 2,000
cycles with 1,027 mAh g of steady capacity at 4 A g and an equally competitive rate behavior.
-1
-1
An SIB anode with a distinguished performance and real-time performance-mechanistic evaluation has
been reported by Liu et al. . In-situ TEM and simulations detected “liquid-like” properties, metallic
[157]
character, and structural endurance in the RP CNF composite. The highly encapsulated RP inside the C
matrix, akin to a core-shell structure, mitigated side reactions. This observation of liquidity of RP on
sodiation was dually verified using time-lapse scanning TEM (STEM) images. The optimized capacity of
1,019 mAh g over 5,000 cycles at 1 A g was a benchmark. Details are shown in Figure 12.
-1
-1
MXene-supported uniform-sized RP nanoparticles were additionally integrated with multi-walled CNTs
(MWCNTs), leading to outstanding stability and improved mobility of Na /e transportation . The hybrid
-
+
[158]
showed a capacity of 371.6 mAh g at 0.2 A g over 100 cycles. A facile methodology for high-capacity SIB
-1
-1
anodes with high mass loadings has been reported by Zhu et al. . A composite of wood-derived carbon
[159]
and CNTs was coupled to RP. Multi-channeled ion and electronic pathways with a compact but porous
framework synchronously improved the capacity retention ability at high mass loadings. Although optimal
redox kinetics at a lower mass loading (8.2 mg cm ) was achieved even at a high mass loading of
-2
-1
~14 mg cm , capacity preservation of 53.9% was attained. A superior gravimetric capability of 468.8 mAh g
-2
and real rate capacity of 1.63 mAh g at 106.6 mAcm were captured. A liquid exfoliation strategy for
-1
-2
amorphous RP nanoplates synthesis and their composite with CNTs has been proposed recently by
Kaur et al. . A superior air stability was achieved with low oxidative degradation that enabled the
[160]
composite to attain higher capacities above 2,000 mAh g over 1,000 cycles. Other composite hybrids and
-1
phosphorous alloys have been extensively explored as SIB alloying anodes with many recent detailed
reviews [161-164] . Zhang et al. have reported a composite SIB anode (Sb/P@C) that could deliver a capacity of
[165]
-1
350 mAh g at 500 mA g . At 50 mA g , a capacity of above 400 mAh g was sustained over 100 cycles .
-1
-1
-1
Germanium-based anodes for SIBs
Germanium (Ge) has been highlighted for its strong alloying potential with Na and less volume expansion
+
than Sn and Sb conversion-alloying anodes. However, its theoretical capacity (369 mAh g ) is limited for
-1
SIBs because 1 mol of Na in the resulting NaGe formulation showed unfavored kinetics in the crystalline
+
Ge, which rendered it below the limelight of energy storage community. Although it has 1,000 times
superior electrical conduction than Si, the crystalline Ge has a very minor affinity for Na that can only
+
-1
provide a capacity of 20 mAh g . Thus, many derivatives, especially those with amorphous Ge, have been
proposed both theoretically and experimentally, whereby a theoretical capacity of 576 mAh g
-1
(corresponding to Na Ge) has been achieved in the amorphous phase [45,166,167] . Lu et al. have presented
1.56
detailed in-situ TEM-supported evidence of (de)sodiation changes in amorphous Ge nanowires . The
[45]
unique appearance of pores in the desodiated state and their reappearance upon sodiation in the Ge
nanowires were due to sodiation-induced defects during in-situ HRTEM. The large volume expansion of