Potassium Metal as Reliable Reference Electrodes of Nonaqueous Potassium Cells

Hosaka, Tomooki; Muratsubaki, Shotaro; Kubota, Kei; Onuma, Hiroo; Komaba, Shinichi

doi:10.1021/acs.jpclett.9b00711

Cited by 105 publications

(176 citation statements)

References 14 publications

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“…There have been several notable successes for stable plating/stripping of K metal, which were based on clever electrolyte design. Authors found that high‐concentrated potassium bis(fluoroslufonyl)imide (KFSI)–dimethoxyethane (DME) electrolyte forms a uniform SEI on the surface of potassium, enabling reversible plating/stripping electrochemistry at ambient temperature . By comparison, electrolytes of 1 m potassium hexafluorophosphate (KPF 6 )‐DME, 1 m KTFSI‐DME, and 0.8 m KPF 6 in EC/DEC all led to cell failure within 10–20 cycles .…”

Section: Methodsmentioning

confidence: 99%

“…Authors found that high-concentrated potassium bis(fluoroslufonyl)imide (KFSI)dimethoxyethane (DME) electrolyte forms a uniform SEI on the surface of potassium, enabling reversible plating/stripping electrochemistry at ambient temperature. [14,16,24] By comparison, electrolytes of 1 m potassium hexafluorophosphate (KPF 6 )-DME, 1 m KTFSI-DME, and 0.8 m KPF 6 in EC/DEC all led to cell failure within 10-20 cycles. [14] The superconcentrated KFSI-DME electrolyte (mole ratio = 0.1 of KFSI/DME = 0.1 and 0.5) can efficiently passivate the K surface and enable reversible K plating and stripping electrochemistry with a high CE (≈99%) and relatively long life (100 cycles).…”

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Dendrite‐Free Potassium Metal Anodes in a Carbonate Electrolyte

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Potassium (K) metal anodes suffer from a challenging problem of dendrite growth. Here, it is demonstrated that a tailored current collector will stabilize the metal plating–stripping behavior even with a conventional KPF6‐carbonate electrolyte. A 3D copper current collector is functionalized with partially reduced graphene oxide to create a potassiophilic surface, the electrode being denoted as rGO@3D‐Cu. Potassiophilic versus potassiophobic experiments demonstrate that molten K fully wets rGO@3D‐Cu after 6 s, but does not wet unfunctionalized 3D‐Cu. Electrochemically, a unique synergy is achieved that is driven by interfacial tension and geometry: the adherent rGO underlayer promotes 2D layer‐by‐layer (Frank–van der Merwe) metal film growth at early stages of plating, while the tortuous 3D‐Cu electrode reduces the current density and geometrically frustrates dendrites. The rGO@3D‐Cu symmetric cells and half‐cells achieve state‐of‐the‐art plating and stripping performance. The symmetric rGO@3D‐Cu cells exhibit stable cycling at 0.1–2 mA cm−2, while baseline Cu prematurely fails when the current reaches 0.5 mA cm−2. The half‐cells cells of rGO@3D‐Cu (no K reservoir) are stable at 0.5 mA cm−2 for 10 000 min (100 cycles), and at 1 mA cm−2 for 5000 min. The baseline 3D‐Cu, planar rGO@Cu, and planar Cu foil fails after 5110, 3012, and 1410 min, respectively.

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Section: Methodsmentioning

confidence: 99%

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Dendrite‐Free Potassium Metal Anodes in a Carbonate Electrolyte

et al. 2019

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“…As suggested by the authors, special care should be taken in the evaluation of electrode materials for sodium‐ion batteries in half cells because of the pronounced effects related to the sodium metal electrode; similar issue has been also recently reported by Komaba and co‐workers for potassium metal. [ 21 ] Hatchard et al [ 22 ] studied the NaCrO 2 cathode material using NaPF 6 and NaTFSI in PC and EC:DEC (1/2 vol) electrolytes in sodium half‐cells and symmetric cells, confirming that half‐cell tests were not useful for evaluating the cycling performance due to a high impedance increase at the Na metal electrode. Using symmetric cells, the authors achieved a columbic efficiency of 99.97% for the cell employing 1 m NaTFSI in EC:DEC electrolyte, suggesting this as a more reliable method for the characterization of a given cathode material, i.e., excluding the influence of the counter Na metal electrode.…”

Section: Electrolytes For Na‐based Rechargeable Batteriesmentioning

confidence: 99%

Electrolytes and Interphases in Sodium‐Based Rechargeable Batteries: Recent Advances and Perspectives

Eshetu

Elia

Armand

et al. 2020

Advanced Energy Materials

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technologies. Unlike lithium, whose market is already very tight, sodium mineral deposits are almost infinite, evenly distributed worldwide, much easier to extract and thereby attainable at low cost. [1][2][3][4] If the realization of Na-rechargeable batteries could be practically possible, there will be nearly three orders of magnitude relaxation in the constraints on lithium-based resources, accompanied by sustainability, improved environmental benevolence, and cost reduction ( Table 1). Even more appealing is the possible use of the widely available and lighter aluminum, rather than copper, as negative current collector and hard carbon from renewable sources instead of graphite for the negative electrode. Finally, the stability of sodium-ion batteries (SIBs) in the fully discharged state would significantly enhance the safety associated with the shipment of large-format SIBs worldwide.These beneficial features of sodiumbased cells revived the research work on Na-based rechargeable batteries and accordingly captured the attention of both the academic research and industry sectors. However, similar to LIB, most of the research work in Na-based batteries have focused on the development and elaboration of negative and positive For sodium (Na)-rechargeable batteries to compete, and go beyond the currently prevailing Li-ion technologies, mastering the chemistry and accompanying phenomena is of supreme importance. Among the crucial components of the battery system, the electrolyte, which bridges the highly polarized positive and negative electrode materials, is arguably the most critical and indispensable of all. The electrolyte dictates the interfacial chemistry of the battery and the overall performance, having an influence over the practical capacity, rate capability (power), chemical/thermal stress (safety), and lifetime. In-depth knowledge of electrolyte properties provides invaluable information to improve the design, assembly, and operation of the battery. Thus, the full-scale appraisal of both tailored electrolytes and the concomitant interphases generated at the electrodes need to be prioritized. The deployment of large-format Na-based rechargeable batteries also necessitates systematic evaluation and detailed appraisal of the safety-related hazards of Na-based batteries. Hence, this review presents a comprehensive account of the progress, status, and prospect of various Na + -ion electrolytes, including solvents, salts and additives, their interphases and potential hazards.

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“…c) Capacity retention at the same potassiation/depotassiation rates (red) and at the potassiation rates of 0.025 C with different depotassiation rates (blue). [13,33] Such a large impedance from the K metal may conceal the electrochemical performance of graphite in PIBs, thus a highly stable reference electrode with the three-electrode setup is preferred to evaluate the actual K ion storage capabilities of graphite. e) GITT curves of K-graphite cells with 2.76 m KFSI/DME-HFE electrolyte at 11.1 mA g −1 .…”

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confidence: 99%

Localized High‐Concentration Electrolytes Boost Potassium Storage in High‐Loading Graphite

Qin

Xiao

Zheng

et al. 2019

Advanced Energy Materials

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155

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graphite has a theoretical capacity of 279 mAh g −1 . [3,17] In 2015, Ji and Hu have separately demonstrated the electrochemical intercalation of K ions into graphite in potassium hexafluorophosphate (KPF 6 )/ ethylene carbonate (EC)-diethyl carbonate (DEC) electrolytes. [4,18] However, their works did not achieve a highly reversible K + insertion/extraction process in KPF 6 /EC-DEC electrolyte because the formed solid electrolyte interphase (SEI) becomes fragile and unstable due to the large volume variation (≈60%) during K + insertion/extraction. [19,20] Compared to the conventional lowconcentration electrolyte (LCE), adopting a high-concentration electrolyte (HCE, e.g., >3 m) is a promising strategy to solve the above problem because it possesses some unusual physicochemical and electrochemical properties due to the unique solvation structure of ions, which make it different from an LCE. [21][22][23][24] In 2007, Jeong adopted the concentrated lithium bisperfluoroethylsulfonyl imide LiN(SO 2 C 2 F 5 ) 2 / propylene carbonate (PC) to realize a reversible graphite anode for lithium-ion batteries. [24] Recently, Komaba and Lu have reported the highly reversible graphite anode for PIBs at concentrated potassium bis(fluorosulfonyl)imide (KFSI)/ dimethoxyethane (DME) and KFSI/ethyl methyl carbonate electrolytes, respectively. [25,26] Despite these progresses, the issues of high viscosity, low ionic conductivity, and the increased cost of the HCE still hinder its practical applications. To overcome these disadvantages in using HCE, several groups have added a low-polarity cosolvent to dilute an HCE by forming a localized high-concentration electrolyte (LHCE). It is believed that the introduced cosolvent does not participate in the solvation process. Zhang's group used the bis(2,2,2,-tri-fluoroethyl) ether to dilute the concentrated lithium bis(fluorosulfonyl) imide (LiFSI)/dimethyl carbonate and improve the coulombic efficiency (CE) of lithium metal anodes without dendrite formation. [27] They also diluted concentrated LiFSI in sulfone with a fluorinated ether for high-voltage (4.9 V) lithium metal batteries. [28] Wang's group used the same cosolvent in the concentrated LiFSI/DME to increase both coulombic efficiencies of S cathode and Li anode for Li-S batteries. [29] However, none of the LHCE reported to date has been applied in PIBs, its stability and compatibility with PIBs remain in question.Herein, our work reports for the first time that a highly reversible K + insertion/extraction into graphite interlayer can Reversible intercalation of potassium-ion (K + ) into graphite makes it a promising anode material for rechargeable potassium-ion batteries (PIBs). However, the current graphite anodes in PIBs often suffer from poor cyclic stability with low coulombic efficiency. A stable solid electrolyte interphase (SEI) is necessary for stabilizing the large interlayer expansion during K + insertion. Herein, a localized high-concentration electrolyte (LHCE) is designed by adding a highly fluorinated ether into the con...

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Potassium Metal as Reliable Reference Electrodes of Nonaqueous Potassium Cells

Cited by 105 publications

References 14 publications

Dendrite‐Free Potassium Metal Anodes in a Carbonate Electrolyte

Dendrite‐Free Potassium Metal Anodes in a Carbonate Electrolyte

Electrolytes and Interphases in Sodium‐Based Rechargeable Batteries: Recent Advances and Perspectives

Localized High‐Concentration Electrolytes Boost Potassium Storage in High‐Loading Graphite

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