lithium with cheaper alternatives might make future batteries less susceptible to price fluctuations when the market expands. [5] This concern has in turn spawned a flurry of research activity to look beyond LIB technology. In view of the various rechargeable batteries, sodiumion batteries (SIBs) that consist of a main element of seawater made their presence felt in the battery industry due to their chemical similarity (e.g., only 0.3 V more positive than lithium) but higher abundance compared to lithium, [6] as illustrated in Table 1. SIBs work in the same way as LIBs in that they involve the reversible migration of cations/anions across a separator toward the electrodes to realize voltage-driven electrochemical reactions. [7] The upward trend for sodium-ion battery research is driven by the concern over the scarcity and price rise of lithium. Hence, these major merits, as well as the suitable redox potential (E = 0.3 V vs Li) make the SIB an appropriate choice as a rechargeable battery system.In fact, SIBs started almost in parallel with LIBs in the 1980s but the development of LIBs eventually eclipsed SIBs due to the electrochemical performances of SIBs. [8,9] A major obstacle is that it is difficult to get a sodium host material with comparable operating voltage and capacity as the LIB analogs. Firstly, the larger Na + radius (0.98 Å) than that of Li + (0.69 Å) leads to the kinetically sluggish Na + insertion/extraction and transport cross the host-material framework, which will always make the specific capacity and rate capacity largely degraded. [10] Secondly, the larger volume expansion caused by Na + insertion will also bring a change in the phase and lattice of the host materials, making it difficult to achieve a favorable electrochemical stability compared with the LIB counterparts. [11] In addition, they also suffer from a lower specific energy than LIBs, due to the lower potential and larger atomic weight of sodium. It is still a challenge to build an affordable Na-host materials endowed with a high specific energy (e.g., 500 W h kg −1 in LIBs). [12] Recently, the topic of SIBs was revisited in the hope of exploring possible ways to overcome the concerns about the low energy density and poor cycling life of SIBs.In spite of the above distinct drawbacks, SIBs can actually behave slightly differently in some chemical aspects. For instance, sodium does not react with aluminum, which is contrary to the alloying tendency of lithium. In the commercial market, manufacturers could appreciate this "inertness" to reduce the production cost of batteries by substituting the Among the various energy solutions, lithium-ion batteries (LIBs) play an important role in the process of the transition from fossil fuels to renewables. However, the necessity to replace lithium with cheaper alternatives due to its scarcity has recently attracted great interest to developing sodium-ion batteries (SIBs). Hence, the discovery and development of suitable cathode materials that exhibit high specific capacity, good cycling stabil...