Non-Flammable Phosphate Electrolyte with High Salt-to-Solvent Ratios for Safe Potassium-Ion Battery

Zeng, Guifang; Xiong, Shenglin; Qian, Yitai; Ci, Lijie; Feng, Jinkui

doi:10.1149/2.1171906jes

Cited by 51 publications

(59 citation statements)

References 39 publications

(71 reference statements)

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“…[97][98][99][100][101] Specifically, the intercalation behavior of naked K + ions into graphite with concentrated and localized highconcentration KFSI electro lytes is associated with the formation of compact and dense inorganic SEI layers that originated from FSI -, which effec tively suppress the K + solvent cointercalation in dilute electro lytes. [32,94,107,101] This is in accordance with the electrochemical behavior of graphite anodes in the 4.2 m LiTFSI/acetonitrile (AN) electrolyte. [172]…”

Section: Concentration Dependency Of Sei Layersupporting

confidence: 77%

“…Nev ertheless, as a result of the continuous decomposition of the solvents and formation of an instable SEI layer, diluted phos phate electrolytes do not work well. [33] Moderately concentrated electrolytes were developed by using 3.3 m KFSI/trimethyl phosphate (TMP) ( Figure 6be) and 2 m KFSI/triethyl phos phate (TEP), [32,107] where stable FSIderived passivation films were induced. Therefore, good electrochemical performance of K metal, graphite anodes, and PTCDA||potassiated graphite full cells was demonstrated.…”

Section: Organic Liquid Electrolytesmentioning

confidence: 99%

“…In comparison, for the concentrated electrolyte systems, the decrease of the LUMO energy levels of anions caused by its interaction with K + ions leads to a preferen tial anion reduction reaction. [32,104,107,171] For example, a thinner anionderived SEI layer was formed in the electrolyte of 2.5 m KPF 6 /DEGDME compared with that in 1 m KPF 6 /DEGDME, thus enhanced performance was achieved on KVOPO 4 and K 1.69 Mn[Fe(CN) 6 ] 0.85 •4H 2 O cathodes. [171] Also the KTFSIbased concentrated electrolytes, such as 5 m KTFSI/DEGDME, 5 m KTFSI/DME and 4 m KTFSI/EC:DEC, allow more TFSIions to reach the interface and can introduce a more compact and thinner SEI layer with a larger amount of inorganic spe cies.…”

Section: Concentration Dependency Of Sei Layermentioning

confidence: 99%

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Electrolytes and Interphases in Potassium Ion Batteries

et al. 2021

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Potassium ion batteries (PIBs) are recognized as one promising candidate for future energy storage devices due to their merits of cost‐effectiveness, high‐voltage, and high‐power operation. Many efforts have been devoted to the development of electrode materials and the progress has been well summarized in recent review papers. However, in addition to electrode materials, electrolytes also play a key role in determining the cell performance. Here, the research progress of electrolytes in PIBs is summarized, including organic liquid electrolytes, ionic liquid electrolytes, solid‐state electrolytes and aqueous electrolytes, and the engineering of the electrode/electrolyte interfaces is also thoroughly discussed. This Progress Report provides a comprehensive guidance on the design of electrolyte systems for development of high performance PIBs.

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Section: Concentration Dependency Of Sei Layersupporting

confidence: 77%

Section: Organic Liquid Electrolytesmentioning

confidence: 99%

Section: Concentration Dependency Of Sei Layermentioning

confidence: 99%

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Electrolytes and Interphases in Potassium Ion Batteries

et al. 2021

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“…[47] It can be clearly seen that the intensity of the characteristic peak in the low-concentration system is weaker than the high-concentration system, indicating that the higher electrolyte can induce more solvation, thereby reducing the amount of free solvent in the electrolyte, and thus inhibiting the dissolution of PAQS in the electrolyte. [48,49] Besides, a similar phenomenon was observed in FTIR spectra of the electrolytes ( Figure S11, Supporting Information). It is worth mentioning that the electrolyte of 5 m NaTFSI in DOL:DME has reached saturation, leading to high viscosity and low ionic electron conductivity, [50] which might be the reason why the capacity of PAQS in SIBs with high-concentration electrolyte decays rapidly.…”

supporting

confidence: 76%

Electrochemical Study of Poly(2,6‐Anthraquinonyl Sulfide) as Cathode for Alkali‐Metal‐Ion Batteries

Gao

Fan

et al. 2020

Advanced Energy Materials

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Organic electrode materials are extensively applied for alkali metal (lithium, sodium, and potassium)‐ion batteries (LIBs, SIBs, and PIBs) due to their sustainability and low cost. As a typical organic cathode, poly(2,6‐anthraquinonyl sulfide) (PAQS) shows high theoretical capacity, yet its electrochemical behavior and mechanisms in alkali‐metal‐ion batteries still require clarification. Herein, PAQS microspheres are synthesized and applied as cathodes for LIBs, SIBs, and PIBs. When using traditional low‐concentration electrolytes, the reduction voltage and the initial discharge capacity of PAQS electrode in LIB, SIBs, PIBs are 2.11 V/103 mAh g−1, 1.76/1.30 V/134 mAh g−1, 1.94/1.54 V/198 mAh g−1 at 100 mA g−1, respectively, while the cycling stability of PAQS is in the order of LIBs > SIBs > PIBs. To further promote the practical application of PIBs, a facile method is demonstrated to improve the cycle stability of PAQS for PIBs by using a novel high‐concentration electrolyte. The cycling stability of PIBs with PAQS can be improved significantly to 1200 cycles with a capacity decay of 0.031% per cycle. This work may provide guidelines for developing innovative organic materials used in applicable metal‐ion batteries demonstrates the impact of electrolyte optimization on improving the cycling stability.

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“…The trimethyl phosphate (TMP) has many advantages to be employed as electrolyte solvent, due to its fire-retardant property, wide liquid-phase temperature ranges from −46 to 197 °C, low viscosity (2.3 mPa s), and high dielectric constant (21.6). [17,21,22] In this work, a nonflammable TMPbased electrolyte with high compatibility and the ability to form a stable F-rich SEI was designed in response to the challenges for PIBs of high safety and long-term calendar life. This compatible electrolyte was optimized with KFSI (salt) and TMP (solvent) at a molar ratio of 3:8.…”

mentioning

confidence: 99%

Manipulating the Solvation Structure of Nonflammable Electrolyte and Interface to Enable Unprecedented Stability of Graphite Anodes beyond 2 Years for Safe Potassium‐Ion Batteries

et al. 2020

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redox potential of K + is close to that of Li + but lower than for Na +. [1-4] Another important motivation for PIB research is that K + cations can be reversibly intercalated into the commercial graphite anode used for LIBs with a high theoretical capacity of 279 mAh g −1 based, on the generated compound KC 8 , which offers the encouraging prospect of PIBs suitable for high manufacturability, by using the commercial production lines for LIBs. [5-7] For the large-scale applications of PIBs, long-term calendar life and high safety are the most two critical factors. The graphite anode in PIBs, however, suffers from poor stability due to the continual decomposition of the electrolyte and insufficient solid electrolyte interphase (SEI) protection. [8] The electrolyte plays a vital role in determining the performance of electrode materials and regulating the SEI to eliminate interfacial side reactions and ensure long-term cyclability and high safety. Tremendous efforts have been made to regulate electrolytes by altering the salts, solvents, additives, and/ or concentrations. [9,10] In the case of the salt for PIBs, the most attractive one is potassium bis(fluorosulfonyl)imide (KFSI), as it could lead to a more stable SEI than is possible with other salts, such as KPF 6 and potassium bis(trifluoromethanesulfonyl) imide. [11-14] Also, it has been demonstrated that the stability of graphite can be enhanced by simply increasing the salt concentration in conventional carbonate or ether-based electrolytes. An electrolyte consisting of KFSI and ethyl methyl carbonate (EMC) at the high molar ratio of 1:2.5 made the graphite anode work for 17 months. Benefiting from the robust inorganic-rich SEI layer generated by the concentrated KFSI with EMC, this long cycle-life performance of graphite is the best that has ever been achieved in reported electrolytes. [15] The carbonate or ether-based electrolytes are highly combustible and volatile, however, which poses a great potential hazard for accidents involving explosion and fire. Although the volatility and flammability can be reduced in highly concentrated electrolytes, safety still remains an issue, especially for large-scale implementation. [16,17] It is well known that the flammability of the electrolyte is mainly determined by the property of solvents, and thus, there are also efforts toward developing nonflammable electrolytes Potassium-ion batteries (PIBs) are attractive for low-cost and large-scale energy storage applications, in which graphite is one of the most promising anodes. However, the large size and the high activity of K + ions and the highly catalytic surface of graphite largely prevent the development of safe and compatible electrolytes. Here, a nonflammable, moderate-concentration electrolyte is reported that is highly compatible with graphite anodes and that consists of fire-retardant trimethyl phosphate (TMP) and potassium bis(fluorosulfonyl)imide (KFSI) in a salt/solvent molar ratio of 3:8. It shows unprecedented stability, as evidenced by its 74% capacity r...

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Non-Flammable Phosphate Electrolyte with High Salt-to-Solvent Ratios for Safe Potassium-Ion Battery

Cited by 51 publications

References 39 publications

Electrolytes and Interphases in Potassium Ion Batteries

Electrolytes and Interphases in Potassium Ion Batteries

Electrochemical Study of Poly(2,6‐Anthraquinonyl Sulfide) as Cathode for Alkali‐Metal‐Ion Batteries

Manipulating the Solvation Structure of Nonflammable Electrolyte and Interface to Enable Unprecedented Stability of Graphite Anodes beyond 2 Years for Safe Potassium‐Ion Batteries

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