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Page 2 of 64 Rehman et al. Energy Mater 2024;4:400068 https://dx.doi.org/10.20517/energymater.2024.06

INTRODUCTION
Sodium-ion batteries (SIBs) have recently drawn attention as current lithium reservoirs are depleting which
poses severe supply issues. This situation is further complicated due to polarization of the world's primary
energy economies . Although energy density supplied by current generation lithium-ion batteries (LIBs) is
[1,2]
fascinating, many other competitors have joined this race and gained subtle success at lower costs and
[3]
[6]
[8]
[5]
higher safety, including SIBs , lithium-sulfur , Zinc-ion , alkaline metal , solid-state , metal air , redox
[4]
[7]
flow batteries , and supercapacitors . Each of these systems offers some advantages in terms of capacity,
[10]
[9]
energy and power density, benignity, safety, and longevity. At the same time, each has certain limitations
that need to be fixed soon to delimit their potential [11,12] . Although battery systems with metallic anodes and
sulfur cathodes offer ideal performances, they suffer from serious issues presently [13-15] . SIBs share the same
components and design assembly as LIBs but with different materials and kinetics. However, the larger
ionic radius and molar mass of Na than Li pose more restrictions whereby the higher redox potential of
+
+
Na results in lower energy density and theoretical capacity (1,166 mA g for Na and 3,861 mAh g for
-1
-1
Li) [16,17] . From a cost perspective, lithium mineral ore price is highly fluctuating, with a 2023 price of around
7,000 Euro/Ton. Its price is expected to increase, although the energy per ton price is speculated to remain
stagnant. However, it remains difficult to predict its price due to highly fluctuating geopolitical situations in
the world [18-20] . Nevertheless, the high abundance of sodium with uniform distribution across the globe
presents much cheaper alternatives to LIBs. In addition, cell assembly for SIBs uses cheaper current
collectors, i.e., Al foil, which is not compatible with LIBs anode due to Li-Al alloy formation [21,22] . The
compatibility of highly ionic conductive and safe electrolyte additives in SIBs has also opened future
gateways for high-rate and wide temperature-sustaining batteries, particularly for grid-scale applications.
SIB anodes have potential to be explored for high capacity with several advantages along with a diverse
selection of materials offering multiple mechanisms and optimization possibilities. Therefore, they have
opened a wide research window for optimized SIB performance. Notably, graphite, a recognized
commercial LIB anode, has a mismatched size for Na shutting. The low capacity and unstable performance
+
behavior of current SIB anodes have impeded their commercialization [3,23] . SIB anodes can be categorized
into three basic types based on the prevailing Na storage mechanism: intercalation, alloying, and
+
[24]
conversion-type .
Although research on SIBs was initially started with LIBs in the 1990s, the much higher performance of LIBs
[25]
than SIBs has left little admiration for the advancement of SIBs . Recent improvements in SIB capacity
have been bestowed by nanoengineering and adopting advanced tools for material performance with in-situ
and postmortem analysis of SIB cells. These adaptabilities have let a paradigm focus on SIB advancements
for next-generation batteries. Appreciably, many emerging cathodes, such as NaCoO , NaMnO ,
2
2
P2-Na [Ni Mn ]O , NaV O , Na V (PO ) (NVP), and others, have shown promise for coupling with
4 3
0.66
0.33
0.66
2
8
6
2
3
SIB anodes to provide a working potential in the range of 3-4 V and a capacity of 100-200 mAh g -1[26] .
However, metallic sodium, as an anode in SIBs, is currently not plausible due to immense dendrite
formation, highly unstable solid electrolyte interphase (SEI), and other side reactions [7,27] . Meanwhile,
alloying anodes promise higher capacity provision than conversion and intercalating anodes. Still,
significant volumetric changes can lead to pulverization, electrical contact loss, and huge capacity fading
while also parting to slow down the kinetics. Thus, one of the front-line challenges in commercializing next-
generation SIBs is finding a suitable alloying material as an SIB anode that can overcome these challenges
[28]
without compromising capacity or efficiency in the long run . Targeting these limitations, many
approaches, including nano-structural modifications, carbon coating, and introducing binary/ternary alloys
and hybrids, have been adopted [29,30] .