A bifunctional fluorinated ether co-solvent for dendrite-free and long-term lithium metal batteries

Zhang, Guangzhao; Deng, Xiaojun; Li, Jiawei; Wang, Jun; Shi, Guoli; Yang, Yu; Chang, Jian; Yu, Kai; Chi, Shang‐Sen; Wang, Hui; Wang, Peng; Liu, Zhongbo; Gao, Yuan; Zheng, Zijian; Deng, Yonghong; Wang, Chaoyang

doi:10.1016/j.nanoen.2022.107014

Cited by 49 publications

(35 citation statements)

References 31 publications

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“…We interpret these in the same manner as FSI – shielding/deshielding (Figure S7), i.e., with deshielding indicating stronger Li + coordination . Consistently, upfield shifts have been attributed elsewhere to fluorine-shielding self-interactions, such as hydrogen bonding, among bulk (uncoordinated) molecules that are enhanced when the indicated molecules are driven out of the coordination environment . The results suggest that sulfamoylfluorides coordinate weakly to Li + , while sulfonylfluorides do not.…”

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confidence: 56%

“…15 Consistently, upfield shifts have been attributed elsewhere to fluorineshielding self-interactions, such as hydrogen bonding, among bulk (uncoordinated) molecules that are enhanced when the indicated molecules are driven out of the coordination environment. 38 The results suggest that sulfamoylfluorides coordinate weakly to Li + , while sulfonylfluorides do not. Regardless, even the species that do coordinate to Li + have a curiously negligible effect on CE.…”

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confidence: 99%

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Probing the Functionality of LiFSI Structural Derivatives as Additives for Li Metal Anodes

et al. 2022

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Lithium (Li) metal is a compelling replacement for graphite anodes in Li-ion batteries to increase gravimetric energy if the cyclability can be improved. Motivated by high Li Coulombic efficiency (CE) achieved with electrolytes featuring the bis(fluorosulfonyl)imide (FSI − ) anion, this work examined chemically related sulfonyl/sulfamoyl fluoride additives to correlate FSI − -relevant structural features with CE. Across three exemplary carbonate-and glyme-based electrolytes, extended solid, liquid, and gas phase characterizations reveal that Li + coordination is necessary yet insufficient for FSI − derivatives to affect cycling. Beyond coordination, the reactivity of the baseline solvent and the key structural features of the additives are shown to strongly regulate CE, with possession of an N center�common to sulfamoylfluorides and FSI − �consistently leading to higher CE. Some derivatives outperform FSI − in short-term cycling; however, they have difficulty competing with the longevity of FSI − . These results provide insights for developing improved additives in the future through careful consideration of reactant structure and solvent codesign.

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confidence: 99%

Probing the Functionality of LiFSI Structural Derivatives as Additives for Li Metal Anodes

et al. 2022

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“…[29,30] In recent years, nonsolvating hydrofluoroethers (HFEs) have been proposed as a new class of cosolvents for ILEs, [29][30][31][32] which is inspired by a similar approach applied to organic-solvent-based concentrated electrolytes. [33][34][35][36][37][38][39] Due to the poor solvation capability of HFEs toward Li + , the ILEs, needing a high Li + concentration to unlock non-vehicular Li + transport, [40,41] are diluted, but with the local Li + coordination preserved. This, and HFEs' high compatibility toward LMAs, promote Li + transport in ILEs without compromising the CE of Li stripping/plating.…”

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confidence: 99%

Difluorobenzene‐Based Locally Concentrated Ionic Liquid Electrolyte Enabling Stable Cycling of Lithium Metal Batteries with Nickel‐Rich Cathode

Liu

Mariani

Diemant

et al. 2022

Advanced Energy Materials

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the high reactivity of both the lithium metal anode (LMA) and Ni-rich NMC usually leads to poor interfacial compatibility with the conventional electrolytes and consequently limited cyclability. [4][5][6][7] Without a sufficiently protective solidelectrolyte interphase (SEI) on LMAs, side reactions between lithium and electrolytes cause lithium dendritic growth and low stripping/plating coulombic efficiency (CE). [8][9][10] At the cathode/electrolyte interface, parasitic electrolyte degradation occurs due to the highly reactive Ni 4+ species generated upon delithiation. This is accelerated by increasing Ni content in the cathode, resulting in limited reversibility of the Ni-rich NMC cathode and thickening of the cathode/electrolyte interphase (CEI) upon cycling. [11,12] Among the strategies proposed to enhance the cyclability of LMBs, electrolyte engineering appears to be one of the most effective and feasible approaches, as the electrolyte plays a keyrole in the CEI and SEI formation. [13][14][15][16][17][18][19] Ionic liquid electrolytes (ILEs), with high electrochemical stability, are valuable options for Li/Ni-rich NMC cells in this context. [20][21][22][23] For instance, Wu et al. [24] have recently reported highly stable cycling of Li/LiNi 0.88 Co 0.09 Mn 0.03 O 2 cells up to 300 cycles with a capacity retention of 88% in [LiTFSI] 0.2 [Pyr 14 FSI] 0.8 (LiTFSI = lithium bis(trifluoromethanesulfonyl)imide, Pyr 14 FSI = N-butyl-Nmethyl pyrrolidinium bis(fluorosulfonyl)imide). Unfortunately, the excellent performance has been only achieved with low cathode mass loading (<5 mg cm −2 ), or/and low current density Lithium metal batteries (LMBs) with nickel-rich cathodes are promising candidates for next-generation, high-energy batteries. However, the highly reactive electrodes usually exhibit poor interfacial compatibility with conventional electrolytes, leading to limited cyclability. Herein, a locally concentrated ionic liquid electrolyte (LCILE) consisting of lithium bis(fluorosulfonyl)imide (LiFSI), 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EmimFSI), and 1,2-difluorobenzene (dFBn) is designed to overcome this challenge. As a cosolvent, dFBn not only promotes the Li + transport with respect to the electrolyte based on the ionic liquid only, but also has beneficial effects on the electrode/electrolyte interphases (EEIs) on lithium metal anodes (LMAs) and LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811) cathodes. As a result, the developed LCILE enables dendritefree cycling of LMAs with a coulombic efficiency (CE) up to 99.57% at 0.5 mA cm −2 and highly stable cycling of Li/NMC811 cells (4.4 V) at C/3 charge and 1 C discharge (1 C = 2 mA cm −2 ) for 500 cycles with a capacity retention of 93%. In contrast, the dFBn-free electrolyte achieves lithium stripping/plating CE, and the Li/NMC811 cells' capacity retention of only 98.22% and 16%, respectively under the same conditions. The insight into the coordination structure, promoted Li + transport, and EEI characteristics gives fundamental information essential for fu...

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“…[22] Recently, diluting ILEs with non-solvating co-solvents, e.g., hydrofluoroethers or fluorinated aromatic compounds, has been proven to be an effective approach in mitigating the aforementioned deficiencies without compromising the high compatibility toward LMAs, [12,[23][24][25] inspired by organic-solvent-based concentrated electrolytes. [26][27][28][29][30] The co-solvents usually contain highly fluorinated (e.g., trifluoro-, or difluoro-substituted)…”

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Locally Concentrated Ionic Liquid Electrolyte with Partially Solvating Diluent for Lithium/Sulfurized Polyacrylonitrile Batteries

et al. 2022

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The development of Li/sulfurized polyacrylonitrile (SPAN) batteries requires electrolytes that can form stable electrolyte/electrode interphases simultaneously on lithium‐metal anodes (LMAs) and SPAN cathodes. Herein, a low‐flammability locally concentrated ionic liquid electrolyte (LCILE) employing monofluorobenzene (mFBn) as the diluent is proposed for Li/SPAN cells. Unlike non‐solvating diluents in other LCILEs, mFBn partially solvates Li+, decreasing the coordination between Li+ and bis(fluorosulfonyl)imide (FSI−). In turn, this triggers a more substantial decomposition of FSI− and consequently results in the formation of a solid electrolyte interphase (SEI) rich in inorganic compounds, which enables a remarkable Coulombic efficiency (99.72%) of LMAs. Meanwhile, a protective cathode electrolyte interphase (CEI), derived mainly from FSI− and organic cations, is generated on the SPAN cathodes, preventing the dissolution of polysulfides. Benefiting from the robust interphases simultaneously formed on both the electrodes, a highly stable cycling of Li/SPAN cells for 250 cycles with a capacity retention of 71% is achieved employing the LCILE and only 80% lithium‐metal excess.

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A bifunctional fluorinated ether co-solvent for dendrite-free and long-term lithium metal batteries

Cited by 49 publications

References 31 publications

Probing the Functionality of LiFSI Structural Derivatives as Additives for Li Metal Anodes

Probing the Functionality of LiFSI Structural Derivatives as Additives for Li Metal Anodes

Difluorobenzene‐Based Locally Concentrated Ionic Liquid Electrolyte Enabling Stable Cycling of Lithium Metal Batteries with Nickel‐Rich Cathode

Locally Concentrated Ionic Liquid Electrolyte with Partially Solvating Diluent for Lithium/Sulfurized Polyacrylonitrile Batteries

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