Rechargeable lithium‐metal batteries (LMBs) are regarded as the “holy grail” of energy‐storage systems, but the electrolytes that are highly stable with both a lithium‐metal anode and high‐voltage ...cathodes still remain a great challenge. Here a novel “localized high‐concentration electrolyte” (HCE; 1.2 m lithium bis(fluorosulfonyl)imide in a mixture of dimethyl carbonate/bis(2,2,2‐trifluoroethyl) ether (1:2 by mol)) is reported that enables dendrite‐free cycling of lithium‐metal anodes with high Coulombic efficiency (99.5%) and excellent capacity retention (>80% after 700 cycles) of Li||LiNi1/3Mn1/3Co1/3O2 batteries. Unlike the HCEs reported before, the electrolyte reported in this work exhibits low concentration, low cost, low viscosity, improved conductivity, and good wettability that make LMBs closer to practical applications. The fundamental concept of “localized HCEs” developed in this work can also be applied to other battery systems, sensors, supercapacitors, and other electrochemical systems.
A novel “localized high‐concentration electrolyte,” which consists of 1.2 m lithium bis(fluorosulfonyl)imide in a mixture of dimethyl carbonate/bis(2,2,2‐trifluoroethyl) ether (1:2 by mol), enables dendrite‐free cycling of lithium‐metal anodes with high Coulombic efficiency of 99.3% and excellent capacity retention (>80% after 700 cycles) of Li||LiNi1/3Mn1/3Co1/3O2 batteries.
Rechargeable Li–S batteries are regarded as one of the most promising next‐generation energy‐storage systems. However, the inevitable formation of Li dendrites and the shuttle effect of lithium ...polysulfides significantly weakens electrochemical performance, preventing its practical application. Herein, a new class of localized high‐concentration electrolyte (LHCE) enabled by adding inert fluoroalkyl ether of 1H,1H,5H‐octafluoropentyl‐1,1,2,2‐tetrafluoroethyl ether into highly‐concentrated electrolytes (HCE) lithium bis(fluorosulfonyl) imide/dimethoxyether (DME) system is reported to suppress Li dendrite formation and minimize the solubility of the high‐order polysulfides in electrolytes, thus reducing the amount of electrolyte in cells. Such a unique LHCE can achieve a high coulombic efficiency of Li plating/stripping up to 99.3% and completely suppressing the shuttling effect, thus maintaining a S cathode capacity of 775 mAh g−1 for 150 cycles with a lean electrolyte of 4.56 g A−1 h−1. The LHCE reduces the solubility of lithium polysulfides, allowing the Li/S cell to achieve super performance in a lean electrolyte. This conception of using inert diluents in a highly concentrated electrolyte can accelerate commercialization of Li–S battery technology.
A new class of nonflammable localized high‐concentration electrolyte (HCE) with similar superior solvation structures and unique functions but lower cost, smaller viscosity, and better wettability than traditional HCEs is designed to simultaneously suppress the shuttle effect of lithium polysulfide and growth of lithium dendrites with minimized electrolyte usage of 4.56 g A−1 h−1 in Li–S batteries.
LiNixMnyCo1−x−yO2 (NMC) cathode materials with Ni ≥ 0.8 have attracted great interest for high energy‐density lithium‐ion batteries (LIBs) but their practical applications under high charge voltages ...(e.g., 4.4 V and above) still face significant challenges due to severe capacity fading by the unstable cathode/electrolyte interface. Here, an advanced electrolyte is developed that has a high oxidation potential over 4.9 V and enables NMC811‐based LIBs to achieve excellent cycling stability in 2.5–4.4 V at room temperature and 60 °C, good rate capabilities under fast charging and discharging up to 3C rate (1C = 2.8 mA cm−2), and superior low‐temperature discharge performance down to −30 °C with a capacity retention of 85.6% at C/5 rate. It is also demonstrated that the electrode/electrolyte interfaces, not the electrolyte conductivity and viscosity, govern the LIB performance. This work sheds light on a very promising strategy to develop new electrolytes for fast‐charging high‐energy LIBs in a wide‐temperature range.
Advanced localized high‐concentration electrolytes are developed to inhibit Ni dissolution and particle cracking in high‐Ni (≥0.8) LiNixMnyCo1−x−yO2 cathode materials when cycling under 4.4 V through formation of uniform, robust, and conductive electrode/electrolyte interfaces, thus enabling excellent long‐term cycling stability in a wide‐temperature range, superior fast‐charging and fast‐discharging capabilities, and superior low‐temperture performance when compared to conventional electrolytes.
In this work, an ether‐based electrolyte is adopted instead of conventional ester‐based electrolyte for an Sb2O3‐based anode and its enhancement mechanism is unveiled for K‐ion storage. The anode is ...fabricated by anchoring Sb2O3 onto reduced graphene oxide (Sb2O3‐RGO) and it exhibits better electrochemical performance using an ether‐based electrolyte than that using a conventional ester‐based electrolyte. By optimizing the concentration of the electrolyte, the Sb2O3‐RGO composite delivers a reversible specific capacity of 309 mAh g−1 after 100 cycles at 100 mA g−1. A high specific capacity of 201 mAh g−1 still remains after 3300 cycles (111 days) at 500 mA g−1 with almost no decay, exhibiting a longer cycle life compared with other metallic oxides. In order to further reveal the intrinsic mechanism, the energy changes for K atom migrating from surface into the sublayer of Sb2O3 are explored by density functional theory calculations. According to the result, the battery using the ether‐based electrolyte exhibits a lower energy change and migration barrier than those using other electrolytes for K‐ion, which is helpful to improve the K‐ion storage performance. It is believed that the work can provide deep understanding and new insight to enhance electrochemical performance using ether‐based electrolytes for KIBs.
By the optimization of solution and solute in electrolyte, Sb2O3‐RGO combined with a high‐concentration ether‐based electrolyte exhibits superior cycle life, stemming the suppression of by‐products in a battery. Furthermore, according to the density functional theory calculation, it is also found that the ether‐based electrolyte can accelerate the insertion of K‐ions, which is helpful to improve the K‐ion storage performance.
The stability of electrolytes against highly reactive, reduced oxygen species is crucial for the development of rechargeable Li–O2 batteries. In this work, the effect of lithium salt concentration in ...1,2‐dimethoxyethane (DME)‐based electrolytes on the cycling stability of Li–O2 batteries is investigated systematically. Cells with highly concentrated electrolyte demonstrate greatly enhanced cycling stability under both full discharge/charge (2.0–4.5 V vs Li/Li+) and the capacity‐limited (at 1000 mAh g−1) conditions. These cells also exhibit much less reaction residue on the charged air‐electrode surface and much less corrosion of the Li‐metal anode. Density functional theory calculations are used to calculate molecular orbital energies of the electrolyte components and Gibbs activation energy barriers for the superoxide radical anion in the DME solvent and Li+–(DME)
n solvates. In a highly concentrated electrolyte, all DME molecules are coordinated with salt cations, and the C–H bond scission of the DME molecule becomes more difficult. Therefore, the decomposition of the highly concentrated electrolyte can be mitigated, and both air cathodes and Li‐metal anodes exhibit much better reversibility, resulting in improved cyclability of Li–O2 batteries.
Superior performance of rechargeable Li–O2 batteries based on high‐concentration Li bis(trifluoromethanesulfonyl)imide (LiTFSI)–1,2‐dimethoxyethane (DME) electrolyte is related to enhanced stability of the Li‐metal anode and air electrode in this electrolyte. This finding provides a significant insight into the fundamental mechanism of high‐concentration electrolytes in enhancing the stability of air cathodes and Li‐metal anodes in rechargeable Li–O2 batteries.
Aqueous electrolyte‐based batteries have attracted increasing attention because of nonflammability, low cost, high power density, and environmental friendliness. However, the low energy density of ...aqueous lithium‐ion batteries caused by the narrow stable electrochemical window of water and electrode materials with low capacity severely limits their further development. In this regard, the development of metal anodes with high specific capacity shows excellent prospects. For example, metal zinc and aluminum anodes have high theoretical specific capacity, rich resources, and environmental friendliness, and can be used as promising anodes for high‐energy‐density aqueous rechargeable metal batteries. Unfortunately, metal anodes usually face balance issues with regard to stability and activity associated with dendrite growth and undesired side reactions in water‐based electrolytes, which is still a great challenge for aqueous metal batteries. In this review, various aqueous metal batteries including aqueous rechargeable metal batteries and aqueous metal–air batteries are summarized and highlighted. Recent advances in the design of high‐safety aqueous electrolytes and the strategies for metal anode protection are comprehensively reviewed. In addition, emerging challenges and some perspectives on the development of high‐energy‐density aqueous metal batteries are included.
In this review, various aqueous metal batteries including aqueous rechargeable metal batteries and aqueous metal–air batteries are summarized, especially including recent advances in the design of high‐safety aqueous electrolytes and the strategies for metal anode protection. Moreover, emerging challenges and some perspectives on the development of high‐energy‐density aqueous metal batteries are presented.
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 concentrated potassium bis(fluorosulfonyl)imide/dimethoxyethane, which forms a durable SEI on the graphite surface and enables highly reversible K+ intercalation/deintercalation without solvent cointercalation. Furthermore, this LHCE shows a high ionic conductivity (13.6 mS cm−1) and excellent oxidation stability up to 5.3 V (vs K+/K), which enables compatibility with high‐voltage cathodes. The kinetics study reveals that K+ intercalation/deintercalation does not follow the same pathway. The potassiated graphite exhibits excellent depotassiation rate capability, while the formation of a low stage intercalation compound is the rate‐limiting step during potassiation.
A localized high‐concentration electrolyte is designed by adding a highly fluorinated ether into the concentrated potassium bis(fluorosulfonyl)imide/dimethoxyethane, which forms a durable potassium fluoride (KF)‐rich passivation layer on the graphite surface and enables highly reversible K+ intercalation/deintercalation without solvent cointercalation. The potassium‐ion batteries with the high‐loading graphite (≈8 mg cm−2) anode can operate over 300 cycles with negligible capacity decay.
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•Recent advances in electrolytes for AZIB are reviewed.•Inorganic, organic and hybrid zinc salt electrolytes are clarified.•The function of electrolyte concentration is ...analyzed.•Hydrogel-based electrolytes are discussed by different cross-linking type.
Energy crisis caused by traditional energy utilization technology intensifies the demand for high energy density and environmentally friendly secondary batteries. As prospective alternative energy source with high capacity, rechargeable aqueous zinc ion batteries (AZIBs) have raised great concern. In AZIBs, electrolyte plays an important role in determining operating window, electrochemical performance, security, flexibility and cost. This review describes the insight into the electrolyte strategies for AZIBs. Firstly, diverse electrolytes consisting of organic, inorganic and hybrid zinc salts are classified and evaluated by chemical composition and property. Secondly, the choice of electrolyte concentration containing moderate and ultra-high concentration is discussed. Thirdly, flexible hydrogel electrolytes are introduced by different cross-linking types, including chemical cross-linking, physical cross-linking and uncross-linking. Fourthly, aqueous bio-electrolytes are prospected as good biocompatible or biodegradable candidate. Finally, the bottleneck and possible future development direction are put forward for the electrolytes of AZIBs.
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Optimizing the pore structure and its interaction with the electrolytes was vital for enhancing the performance of supercapacitors based on the electrical double layer mechanism. In ...this study, graded porous carbon material (STP) with outstanding properties was prepared by adjusting the activation temperature and KOH dosage in the microwave pyrolysis process of sargassum thunbergii. The results demonstrated that better electrochemical performance was obtained when 1 M NaNO3 was used as electrolyte and STP-800-3 was employed as electrode material, attributed to its excellent specific surface area (SSA) of 2011.8 m2 g-1, high micropore ratio, and the optimal matching degree between micropore size and electrolyte ion diameter. Moreover, the operating voltage window was expanded to 2.0 V in supercapacitors assembled with 6 M NaNO3 high-concentration electrolyte. Simultaneously, the symmetric supercapacitors exhibited a remarkable specific capacitance of 290.0 F g-1, a high energy density of 39.0 W h kg-1, and outstanding capacity retention at 70.9% after 10,000 charge/discharge cycles based on 6 M NaNO3 electrolyte. Consequently, the results provided valuable technical support and theoretical basis to foster progress of novel and high-performance supercapacitors.
Carbonate‐based electrolytes are incompatible with lithium (Li) metal anode because the generated solid electrolyte interphase (SEI) undergoes repeated breakage‐repair, resulting in the accumulation ...of inactive Li including Li+ compounds and electrically isolated dead Li0 in the SEI. Therefore, exploiting a suitable strategy to construct a stable SEI while efficiently rejuvenating the inactive Li capacity is urgent and more thoughtful than just building a stereotyped SEI layer. Herein, an innovative strategy is proposed of high‐concentration additive (HCA) of LiNO3 inspired by (localized) high‐concentration electrolyte and inactive Li restoration methodology via triiodide/iodide (I3−/I−) redox couple to improve the compatibility of carbonate‐based electrolytes. The HCA of LiNO3 can maintain the cation–anion aggregates solvation structures in the carbonate‐based bulk electrolyte and induce the in situ formation of superior‐ionic‐conductivity NO3−‐derived SEI. Moreover, the reversible I3−/I− redox couple can further optimize the SEI and constantly rejuvenate the inactive Li including solvent/LiNO3‐derived Li2O, a derivative has almost been acquiescent in LiNO3‐additive electrolytes, and dead Li0 into delithiated cathode. Consequently, epitaxy‐like planar Li deposition, better reversibility, and higher capacity retention can be realized and are systematically verified by Li||Cu half cells, full cells with excess/limited Li (N/P ratio = 1.5) and anode‐free lithium metal batteries.
The high‐concentration additive (HCA) of LiNO3 and triiodide/iodide (I3−/I−) redox couple are synergistically introduced into carbonate‐based electrolyte. The HCA of LiNO3 can maintain the cation–anion aggregate structure in carbonate‐based bulk electrolyte, leading to the NO3−‐derived solid electrolyte interphase (SEI). The I3−/I− redox couple can further optimize the SEI and constantly rejuvenate the inactive Li capacity contained in solvent/LiNO3‐derived Li2O and dead Li0 into delithiated cathode.
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