Na<sub>2</sub>FePO<sub>4</sub>F Fluorophosphate as Positive Insertion Material for Aqueous Sodium‐Ion Batteries

Sharma, Lalit; Nakamoto, Kosuke; Sakamoto, Ryo; Okada, Shigeto; Barpanda, Prabeer

doi:10.1002/celc.201801314

Cited by 33 publications

(25 citation statements)

References 42 publications

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“…[ 4 ] This lack of electrochemical stability is often not immediately apparent in cells reported in literature due to the choice of low‐voltage anode–cathode couples, [ 29–33 ] the use of high C‐rates, [ 24–27,29,32–36 ] excess electrolyte that compensates low efficiencies, [ 26 ] overly optimistic electrochemical stability windows determined by high‐scan‐rate linear sweep voltammetry experiments, [ 25–27,33–38 ] and/or by reporting only few cycles. [ 23,24,27,30,31,35,37–40 ] These studies strongly indicate that the anion plays a crucial role in solution structure as well as SEI‐forming ability of highly concentrated electrolytes, with large consequences for electrochemical stability and battery performance. Molecular dynamics studies revealed that in concentrated solutions water–cation, water–water, and cation–anion interactions, i.e., ion‐pairing and agglomeration, are highly sensitive to the nature of the anion.…”

Section: Introductionmentioning

confidence: 99%

Anion Selection Criteria for Water‐in‐Salt Electrolytes

Reber

Grissa

Becker

et al. 2020

Advanced Energy Materials

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Water‐in‐salt electrolytes have enabled the development of novel high‐voltage aqueous lithium‐ion batteries. This study explores the reasons why analogous sodium electrolytes have struggled to reach the same level of electrochemical stability. Solution structure and electrochemical stability are compared for 11 sodium salts, selected among the major classes of salts proposed for highly concentrated electrolytes. The water environment established for each anion is related to its position in the Hofmeister series and a surprisingly strong correlation between the chaotropicity of the anion and the resulting electrochemical stability of the electrolyte is found. The search for suitable sodium salts is complicated by the fact that higher salt concentrations are needed than for their lithium equivalents. Reaching such a high concentration of >25 mol kg−1 with one or a combination of multiple sodium salts that have the desired properties remains a major challenge. Hence, alternative approaches such as multisolvent systems should be explored. The water solubility of NaTFSI can be increased from 8 to 30 mol kg−1 in the presence of ionic liquids. Such a ternary electrolyte enables stable cycling of a 2 V class sodium‐ion battery based on the NaTi2(PO4)3/Na2Mn[Fe(CN)6] electrode couple for 300 cycles at 1C with a Coulombic efficiency of >99.5%.

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Section: Introductionmentioning

confidence: 99%

Anion Selection Criteria for Water‐in‐Salt Electrolytes

Reber

Grissa

Becker

et al. 2020

Advanced Energy Materials

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“…Full cell with NaTi 2 (PO 4 ) 3 as anode delivered a capacity of 85 mAh g −1 at 1 mA cm −2 in a potential window of 0–1.8 V. The stability of NFPF was confirmed by the retention of (dis)charge profile obtained during cycling. It demonstrates the excellent stability of NFPF against aqueous media in spite of having hygroscopic F‐ion in the system …”

Section: Other 3d Metal‐based Fluorophosphatesmentioning

confidence: 86%

An Overview of Mixed Polyanionic Cathode Materials for Sodium‐Ion Batteries

Senthilkumar¹,

Murugesan²,

Sharma³

et al. 2018

Small Methods

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104

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to battery driven (electric) mobility. While a multibillion-dollar industry has come up catering various needs, the manifold consumption of Li-based resources has led to steep price rise and concerns over future geo-political tension due to its nonuniform geographic distribution. To combat this imminent issue, various alternative battery chemistries (termed as "Beyond Li-ion batteries") are widely pursued, particularly to replace Li-ion batteries in applications unrestricted by gravimetric and/or volumetric energy density. In this case, sodium-ion batteries (NIBs) are touted as the emerging futuristic battery chemistry owing to the widespread availability of sodium-based resources and well-understood electrochemical operation involving the Na + charge carriers. [1][2][3][4][5] In the quest to build robust sodiumion batteries, various 2D layered transition metal oxides and 3D polyanionic framework materials have been unraveled. While the oxide cathodes can deliver high theoretical (and reversible) capacity, they suffer from lower redox potential owing to strong covalence nature. [6] It is more so acute in case of Na-ion batteries considering the higher potential of Na/Na + (−2.71 V vs normal hydrogen electrode (NHE)) vis-à-vis Li/Li + (−3.03 V vs NHE). This issue can be circumvented by implementing polyanionic cathode materials with tunable crystal structure, robust framework providing safe operation and higher redox potential due to inductive effect. [7,8] Following the inductive effect principle, plethora of cathodes with polyanionic units [(XO 4 ) m n− : X = B, P, Si, S, W, Mo, As, Ti, V, etc.] have been discovered both for Li-ion and Na-ion batteries. [9,10] Moving a step further with polyanionic chemistry, off late, materials discovery has been realized by using different types of polyanion units. These subclass of materials are known as "mixed polyanionic" cathode materials, which can be designed by simultaneously having i) polyanionic units [(XO 4 ) m n− , X = P, S, V, etc.] along with other single anions [Y − = F − /OH − /O 2− /N 3− ], ii) different structural units of same polyanion units [(XO m ) (X 2 O m ), e.g., PO 4 -P 2 O 7 , BO 3 -B 2 O 5 , SO 4 -S 2 O 3 , etc.], and iii) two different oxyanionic [(XO 4 ) m n− ] units (e.g., PO 4 -SO 4 , PO 4 -NO 3 , PO 4 -CO 3 , etc.) as illustrated in Figure 1. These polyanionic combinations can lead to rich structural diversity and multi ple electron redox activity leading to robust electrochemical "Building better batteries" remains an ongoing process to cater diverse energy demands starting from small-scale consumer electronics to large-scale automobiles and grid storage. While Li-ion batteries have carried this burden over the last three decades, the ever-growing and highly diverse applications (based on size, energy-density, and stationary vs mobile usages) have led to an era of "beyond lithium-ion batteries." In this postlithium-battery era, sodium-ion batteries (NIBs) have emerged as a pragmatic option particularly for large-scale applications. They attract...

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“…Recently, Sharma et al tested Na 2 FePO 4 F (NFPF) by employing 17 m NaClO 4 aqueous electrolyte. [210] Using this supersaturated electrolyte, the operating voltage window can be enlarged to 2.8 V in 17 m NaClO 4 visa-vis 1.23 V in conventional water-based electrolytes. [211] The NFPF half-cell delivered a reversible discharge capacity of 84 mAh g −1 when cycled in an optimized voltage range of −0.9 to 0.9 V versus Ag/AgCl reference electrode at 1 mA cm −2 current density as shown in Figure 11a.…”

Section: Fluorophosphates In Aqueous Batteriesmentioning

confidence: 99%

“…With this idea, Na 2 FePO 4 F was tested in aqueous electrolytes as well. [ 210 ] It exhibited excellent electrochemical activity. The excellent electrochemical performance of Na 2 FePO 4 F in aqueous electrolytes coupled with energy‐savvy and economical synthesis and elemental abundance of Na (with respect to Li) makes it a strong candidate among fluorophosphates for possible commercialization targeting stationary storage applications.…”

Section: Perspectivesmentioning

confidence: 99%

Fluorophosphates: Next Generation Cathode Materials for Rechargeable Batteries

Sharma

Adiga

Alshareef

et al. 2020

Advanced Energy Materials

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steadily depleting. These realities have triggered significant efforts to harness renewable energy sources like hydro, solar, geothermal, or tidal energy that are intermittent in nature. Economic and sustainable energy storage devices can be coupled with renewable energy generators to realize uninterrupted energy supply. In this sector, rechargeable batteries form the most viable energy storage devices. Today, lithium-ion batteries dominate the electronics market due to their high volumetric and specific energy density. [1-5] The manifold consumption of lithium resources due to the booming multibillion-dollar industry and limited global lithium reserves have raised concerns over the future supply of Li-based precursors to cater to the large scale production of lithium-ion batteries. To alleviate this issue, various alternatives using earth-abundant elements (e.g., monovalent Na + /K + and multivalent Mg 2+ /Ca 2+ /Al 3+) have been proposed to replace LIBs. [6-10] The energy density of batteries is limited by the performance of cathodes. Thus, over the last five decades, three major types of insertion materials have been examined as cathodes for secondary batteries: layered transition metal oxides, Mn-based spinels, and polyanion type materials (Figure 1a). 2D layered transition metal oxides have been extensively studied, but issues like oxygen loss at high potentials raise safety concerns and hence oxides like LiCoO 2 or LiNi 1−x−y Co x Mn y O 2 (x < 1, y < 1) are mainly limited to small portable electronics. Though oxides deliver high energy density, they have lower redox potentials due to highly covalent MO bonding character. [11] This issue can be evaded by implementing 3D polyanionic cathode materials with tuneable (high) redox potential along with structural/thermal stability leading to safe battery operation. [12,13] Plethora of insertion materials have been reported with different polyanionic subunits [(XO 4

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Na₂FePO₄F Fluorophosphate as Positive Insertion Material for Aqueous Sodium‐Ion Batteries

Cited by 33 publications

References 42 publications

Anion Selection Criteria for Water‐in‐Salt Electrolytes

Anion Selection Criteria for Water‐in‐Salt Electrolytes

An Overview of Mixed Polyanionic Cathode Materials for Sodium‐Ion Batteries

Fluorophosphates: Next Generation Cathode Materials for Rechargeable Batteries

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Na2FePO4F Fluorophosphate as Positive Insertion Material for Aqueous Sodium‐Ion Batteries

Cited by 33 publications

References 42 publications

Anion Selection Criteria for Water‐in‐Salt Electrolytes

Anion Selection Criteria for Water‐in‐Salt Electrolytes

An Overview of Mixed Polyanionic Cathode Materials for Sodium‐Ion Batteries

Fluorophosphates: Next Generation Cathode Materials for Rechargeable Batteries

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Product

Resources

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Na₂FePO₄F Fluorophosphate as Positive Insertion Material for Aqueous Sodium‐Ion Batteries