New Insights into the Performance Degradation of Fe-Based Layered Oxides in Sodium-Ion Batteries: Instability of Fe3+/Fe4+ Redox in α-NaFeO2

sources into large-scale grids, inexpensive, efficient, and fast-responding electrical energy storage (EES) systems are essential to store the off-peak energy and releasing the stored energy during the onpeak period. Among various EES systems, rechargeable batteries represent one of the most competitive technologies because of their high conversion efficiency and environmental friendliness. [1][2][3][4] For stationary EES systems, batteries with low cost, high safety, high rate capability, and long cycle stability are highly desired.Lithium (Li)-ion batteries (LIBs) have achieved great success in the market of portable electronics and electric vehicles since their commercialization by Sony Company in 1991. However, the shortage of Li resources in nature gives rise to a concern about its sustainable development in grid scale. Compared with Li, sodium resource has rich natural abundance in the earth crust and a worldwide distribution, consequently leading to a low price of sodium-based raw materials (e.g., the cost of Na 2 CO 3 is about 25-30 times lower than that of Li 2 CO 3 ). Besides, sodium has a suitable redox potential (E 0 (Na + /Na) = −2.71 V versus standard hydrogen electrode (SHE), 0.3 V above that of Li + /Li) and similar physical and chemical properties with lithium. [5,6] Therefore, rechargeable sodium-ion batteries (SIBs), which have a similar "rockingchair" working principle of LIBs, are emerging as an appealing choice as alternatives for LIBs. Note that it is difficult for SIBs to bypass LIBs in terms of energy densities because of the much higher weight of Na and lower standard electrochemical potential. [7][8][9][10] Nevertheless, the use of low-cost materials, including inexpensive Na-based raw materials and Al current collectors for both cathodes and anodes in SIBs, could significantly reduce the cost. In this case, SIBs could be applied where cost-effectiveness rather than energy density is the most critical issue, e.g., in the field of large-scale EES. As a result, sodiumbased electroactive materials are enjoying renewed interest especially for very low cost systems for grid storage. [11,12] Given that cathode materials are the key component that determines energy density and cost, tremendous efforts have been devoted to exploring suitable positive electrode materials with high reversible capacity, rapid Na ions insertion/extraction, and good cycling stability in the past few years. [13,14] A broad range of compounds, including layered oxides, polyanionic frameworks, hexacyanoferrates, and organics, haveThe increasing demand for replacing conventional fossil fuels with clean energy or economical and sustainable energy storage drives better battery research today. Sodium-ion batteries (SIBs) are considered as a promising alternative for grid-scale storage applications due to their similar "rockingchair" sodium storage mechanism to lithium-ion batteries, the natural abundance, and the low cost of Na resources. Searching for appropriate electrode materials with acceptable electrochemical perfor...

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Section: Mostly Studied Single-metal-based Oxidesmentioning

confidence: 99%

Layered Oxide Cathodes for Sodium‐Ion Batteries: Phase Transition, Air Stability, and Performance

Wang

You

Yin

et al. 2017

Advanced Energy Materials

661

464

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“…The decomposition process can be initiated by many factors, such as moisture, elevated temperature, and strongly oxidizing environments. For example, Lee et al [19] reported that in a charged state of α-NaFeO 2 , more than 20% of the formed Fe 4+ species would spontaneously react with electrolyte during open-circuit storage due to its strong oxidization capability (Figure 2a). This oxidation slabs upon exposure to high voltages because of its anomalously large interlayer distances (7.0 Å), which could significantly deteriorate the sodium storage reversibility.…”

Section: Issues Related To High-voltage Electrochemical Operationmentioning

confidence: 99%

Section: Issues Related To High-voltage Electrochemical Operationmentioning

confidence: 99%

Progress in High‐Voltage Cathode Materials for Rechargeable Sodium‐Ion Batteries

You

Manthiram

2017

Advanced Energy Materials

448

268

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potential (E° = −2.71 V vs standard hydrogen electrode (SHE) for Na + /Na, 0.3 V higher than that of Li + /Li).[5] Thus, rechargeable batteries based on sodium electrochemistry are considered as promising alternatives for grid-scale EES applications, which put specific requirements on the cost and sustainable resource supply of the battery. The component parts and the working principle for sodium-ion batteries (SIBs) are quite similar to those of LIBs, as shown in Figure 1. [6] Na + ions migrate between a positive electrode (cathode) and a negative electrode (anode) through an Na + electrolyte in between. Both electrodes are composed of intercalation compounds that allow reversible insertion and extraction of Na + ions. [7] Studies on Na + ions intercalation chemistry can be traced back to 1980s, [8] yet they did not attract much attention due to the LIBs, which held significant advantages in energy output and electrochemical stability over other rechargeable batteries and dominated the research/market for the next two decades. With the concern of potential shortage of Li resources, some concerted effort began to revisit the SIB technology and its key materials, especially after the year 2010. Al foil can be used as current collectors for the anode rather than Cu in SIBs because Na does not alloy with Al, which may help to further reduce the cost and increase the energy density. [9] Besides the cost advantages, SIBs also offer opportunities to obtain a faster kinetics with the electrochemical reaction; for example, it may enable a high Na + conductivity in bulk solid within a wide temperature range [10] and an easier charge transfer owing to less pronounced solvation. Such merits, according to the recent work, have led to surprisingly low polarization and high-rate capability (e.g., in Na 3 V 2 (PO 4 ) cathode materials), [11] making SIBs quite appealing for high-power applications. [12] Although SIBs present a less expensive raw materials compared with LIBs, it is worth noting that the higher energynormalized cost of prototype SIBs [13] demonstrates the importance to improve its energy density, which can be realized by increasing the output voltage or capacity. Given that the output voltage of an SIB is determined by the electrode potential difference between the positive and the negative electrodes and the positive electrode is the bottleneck for boosting the energy output of SIBs, major efforts have been devoted to develop advanced cathode materials with high output voltage and high capacity. [14] Prominent potential cathode candidates including Room-temperature rechargeable sodium-ion batteries are considered as a promising alternative technology for grid and other storage applications due to their competitive cost benefit and sustainable resource supply, triumphing other battery systems on the market. To facilitate the practical realization of the sodium-ion technology, the energy density of sodium-ion batteries needs to be boosted to the level of current commercial Li-ion batteries. An effective approach...

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“…When applying a higher charging voltage above 3.5 V, the irreversible structural degradation caused by Jahn-Teller distortion and polarization results in a significantly deteriorated rate reversibility and a big loss of sodium transition pathway. [54] Nonetheless, a-NaFeO 2 can present a high thermal stability which is a concern more in largescale application such as EVs to avoid serious security issues. The fully charged Na 0.58 FeO 2 powder decomposed thermally at a temperature higher than 300 °C, showing a better thermal stability in the electrolyte than its counterparts in LIBs.…”

Section: Single Transition-metal Oxidesmentioning

confidence: 99%

Advanced Cathode Materials for Sodium‐Ion Batteries: What Determines Our Choices?

et al. 2017

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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...

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New Insights into the Performance Degradation of Fe-Based Layered Oxides in Sodium-Ion Batteries: Instability of Fe³⁺/Fe⁴⁺ Redox in α-NaFeO₂

Cited by 190 publications

References 27 publications

Layered Oxide Cathodes for Sodium‐Ion Batteries: Phase Transition, Air Stability, and Performance

Layered Oxide Cathodes for Sodium‐Ion Batteries: Phase Transition, Air Stability, and Performance

Progress in High‐Voltage Cathode Materials for Rechargeable Sodium‐Ion Batteries

Advanced Cathode Materials for Sodium‐Ion Batteries: What Determines Our Choices?

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