Inorganic–Organic Hybrid Electrolytes Based on Al-Doped Li7La3Zr2O12 and Ionic Liquids (original) (raw)
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Solid State Ionics A multiple electrolyte concept for lithium-metal batteries
A cross-linked polymer membrane formed by poly(ethylene oxide) (PEO), N-methoxyethyl-N-methylpyrrolidium (fluorosulfonyl)(trifluoromethanesulfonyl)imide (Pyr 12O1 FTFSI) ionic liquid and LiFTFSI salt is proposed as the electrolyte for lithium-metal batteries. The ternary membrane has a PEO:Pyr 12O1 FTFSI:LiFTFSI composition of 20:6:4 by mole, which ensures thermal stability up to 220 °C, overall ionic conductivity of 10 − 3 S cm − 1 at 40 °C and suitable Li + transport properties. Combined with the LiFePO 4 composite electrode, whose pores are filled with the Pyr 12O1 FTFSI:LiFTFSI electrolyte, and Li-metal anode, it yields Li/LiFePO 4 cells delivering at 40 °C stable capacity (150 mAh g − 1 or 0.7 mAh cm − 2) with coulombic efficiency higher than 99.5%. Impedance spectroscopy measurements reveal low resistance of the electrode/electrolyte interface at both the anode and the cathode. Preliminary results at 20 °C indicates a capacity of 130 mAh g − 1 at C/10 rate (17 mA g − 1) with coulombic efficiency higher than 99.5%, thereby suggesting PEO:Pyr 12O1 FTFSI:LiFTFSI as suitable electrolyte for lithium-metal polymer batteries for stationary storage applications, coupled for example with PV and wind generation.
Electrochimica Acta, 2010
Several 1-alkyl-2,3-dimethylimidazolium bis(trifluoromethanesulfonyl)imide ionic liquids (alkyl-DMimTFSI) were prepared by changing carbon chain lengths and configuration of the alkyl group, and their electrochemical properties and compatibility with Li/LiFePO 4 battery electrodes were investigated in detail. Experiments indicated the type of ionic liquid has a wide electrochemical window (−0.16 to 5.2 V vs. Li + /Li) and are theoretically feasible as an electrolyte for batteries with metallic lithium as anode. Addition of vinylene carbonate (VC) improves the compatibility of alkyl-DMimTFSI-based electrolytes towards lithium anode and LiFePO 4 cathode, and enhanced the formation of solid electrolyte interface to protect lithium anodes from corrosion. The electrochemical properties of the ionic liquids obviously depend on carbon chain length and configuration of the alkyl, including ionic conductivity, viscosity, and charge/discharge capacity etc. Among five alkyl-DMimTFSI-LiTFSI-VC electrolytes, Li/LiFePO 4 battery with the electrolyte-based on amyl-DMimTFSI shows best charge/discharge capacity and reversibility due to relatively high conductivity and low viscosity, its initial discharge capacity is about 152.6 mAh g −1 , which the value is near to theoretical specific capacity (170 mAh g −1 ). Although the battery with electrolyte-based isooctyl-DMimTFSI has lowest initial discharge capacity (8.1 mAh g −1 ) due to relatively poor conductivity and high viscosity, the value will be dramatically added to 129.6 mAh g −1 when 10% propylene carbonate was introduced into the ternary electrolyte as diluent. These results clearly indicates this type of ionic liquids have fine application prospect for lithium batteries as highly safety electrolytes in the future.
LiZnSO4F Made in an Ionic Liquid: A Ceramic Electrolyte Composite for Solid-State Lithium Batteries
Angewandte Chemie International Edition, 2011
The search for good solid electrolytes constitutes a major goal towards the development of safer lithium batteries. A few candidates do exist, but they suffer either from narrow electrochemical window stability or too low ionic conductivity. Herein we report the ionic-liquid-assisted synthesis of a novel LiZnSO 4 F fluorosulfate phase having a sillimanite LiTiOPO 4 -type structure, which on simply pressed samples shows a room-temperature ionic conductivity of 10 À5 -10 À7 S cm À1 together with a 0-5 V electrochemical stability window range, while ionic-liquid-free LiZnSO 4 F shows an ionic conductivity four orders of magnitude lower (10 À11 S cm À1 ). While robustly reproducible but not yet fully understood, this finding offers new opportunities to tailor inorganic composites with higher ionic conductivity. The origin of such results is demonstrated to be rooted in a surface effect associated with the grafting of a lithium-containing ionic liquid layer. This finding opens up new opportunities for the design of ceramic composites with higher ionic conductivity and should serve as an impetus for further exploiting the chemistry of ionic liquid grafting on oxides.
Advanced Materials Technologies, 2017
Solid‐state electrolytes have been identified as one of the most attractive materials for the fabrication of reliable and safe lithium batteries. This work demonstrates a facile strategy to prepare highly conductive organic ionic plastic crystal (OIPC) composites by combination of a low weight fraction of Li+ doped OIPC (N‐ethyl‐N‐methylpyrrolidinium bis(fluorosulfonyl)amide, [C2mpyr][FSI]) with commercial poly(vinylidene difluoride) (PVDF) powder. Benefiting from the enhancement of lithium ion dynamics, as evidenced by the solid‐state NMR measurements, the composite electrolyte shows an order of magnitude higher conductivity than that of the bulk material. Lithium metal/LiFePO4 cells incorporating the prepared composite electrolytes show impressively high specific capacity and good cycling stability (99.8% coulombic efficiency after 1200 cycles at 2 C, room temperature), which is the first demonstration of long‐term cycling performance at such high rate for an OIPC‐based electrolyt...
Industrial & Engineering Chemistry Research, 2019
A mixture of n-methyl-n-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide, [PYR13][TFSI] and npropyl-n-methylpyrrolidinium bis(fluorosulfonyl)imide, [PYR13][FSI] ionic liquids (ILs) is investigated for lithium−metal batteries. Specifically, the relation among conductivity, solvation structure, and Li + mobility is investigated in a Li/IL/IL type ternary mixture. Li + anion coordination numbers with both [TFSI] and [FSI] in the ternary mixtures are derived from Raman analysis. The Li + transference number was measured by a combination of potentiostatic polarization and electrochemical impedance spectroscopy (EIS) techniques. The electrochemical stability and transport property of the developed ternary mixture were confirmed with Li−Li symmetrical and Li−LiFePO 4 cells. The ternary system exhibited improved rate capability compared to binary parent electrolytes as well as the state-of-the art carbonate-based electrolyte at −20°C, and slightly better cycling stability at 25°C. This study demonstrates the flexibility in tailoring physical properties and the Li + solvation environment by ternary Li/ IL/IL mixtures for enhanced battery performance.
New functionalized quaternary ammonium ILs with two ether groups are reported. They have low viscosity and good electrochemical stability. Li/LiFePO 4 cells using these IL electrolytes have good electrochemical performance. a b s t r a c t New functionalized ILs based on quaternary ammonium cations with two ether groups and bis(trifluoromethanesulfonyl)imide (TFSA À ) anion are synthesized and characterized. Physical and electrochemical properties, including melting point, thermal stability, viscosity, conductivity and electrochemical stability are investigated for these ILs. All these ILs are liquids at room temperature except N,N-diethyl-N,N-bis(2-ethoxyethyl)ammonium TFSA (N22(2o2)(2o2)-TFSA, T m ¼ 29.7 C), and the viscosities of N-methyl-N-ethyl-N-(2-methoxyethyl)-N-(2-ethoxyethyl)ammonium TFSA (N12(2o1)(2o2)-TFSA) and N-methyl-N-ethyl-N,N-bis(2-ethoxyethyl)ammonium TFSA (N12(2o2)(2o2)-TFSA) are 68.0 cP and 63.0 cP at 25 C, respectively. N-Methyl-N,N-diethyl-N-(2-methoxyethyl)ammonium TFSA (DEMEeTFSA) and five ILs with lower viscosity are chosen to dissolve 0.6 mol kg À1 of LiTFSA as IL electrolytes without additive for lithium battery. Lithium plating and striping on Ni electrode can be observed in these IL electrolytes, and cycle performances of lithium symmetrical cells are also investigated for these IL electrolytes. Li/LiFePO 4 cells using these IL electrolytes without additives have good cycle property at the current rate of 0.1 C, and the N-methyl-N-ethyl-N,N-bis(2-methoxyethyl)ammonium TFSA (N12(2o1)(2o1)-TFSA) and N12(2o2)(2o2)-TFSA electrolytes own better rate property than DEMEeTFSA electrolyte.
Enhanced ionic conductivity in PEO-LiClO4 hybrid electrolytes by structural modification
Journal of Electroceramics, 2006
Poly(ethylene oxide)-LiClO 4-TiO 2 organicinorganic hybrids were synthesized for Li-polymer battery electrolytes using sol-gel processing. The hybrids containing TiO 2 component showed the uniform film formation and also increased ionic conductivity. The hybrid films containing 10 wt% TiO 2 showed the smooth surface morphologies and also the highest ionic conductivity. The molecular-level hybrid formation between PEO and TiO 2 components was identified using FTIR analyses. The hybrids containing TiO 2-Al 2 O 3 mixtures showed the enhanced ionic conductivity compared to those containing only TiO 2 most probably due to the Lewis acidic group formation at the surface of Al 2 O 3 components. The PEO-LiClO 4-TiO 2-Al 2 O 3 hybrids showed high stability both in ionic conductivity and crystallinity. By the sol-gel processing two inorganic components were successfully introduced in the PEO matrix and high-performance solid electrolytes were achieved.
Li Ion Conducting Polymer Gel Electrolytes Based on Ionic Liquid/PVDF-HFP Blends
Journal of The Electrochemical Society, 2007
Ionic liquids thermodynamically compatible with Li metal are very promising for applications to rechargeable lithium batteries. 1-methyl-3-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide (P 13 TFSI) is screened out as a particularly promising ionic liquid in this study. Dimensionally stable, elastic, flexible, nonvolatile polymer gel electrolytes (PGEs) with high electrochemical stabilities, high ionic conductivities and other desirable properties have been synthesized by dissolving Li imide salt (LiTFSI) in P 13 TFSI ionic liquid and then mixing the electrolyte solution with poly(vinylideneco-hexafluoropropylene) (PVDF-HFP) copolymer. Adding small amounts of ethylene carbonate to the polymer gel electrolytes dramatically improves the ionic conductivity, net Li ion transport concentration, and Li ion transport kinetics of these electrolytes. They are thus favorable and offer good prospects in the application to rechargeable Li batteries including open systems like Li/air batteries, as well as more "conventional" rechargeable lithium and lithium ion batteries. As is well known, Li is the most electropositive and lightest metal, and thus has the greatest theoretical specific capacity of 3860 Ah/kg.1 , 2 This has attracted worldwide efforts of researchers and manufacturers to develop advanced battery technologies based on lithium. To date, the rechargeable lithium ion battery has already been one of the best choices in view of specific capacity and cycle stability. 1 However, rechargeable lithium metal batteries with even higher specific capacities are still unavailable in the market, especially lithium/air batteries which possess the highest theoretical specific energy (as high as 13,000 Wh/g, excluding the oxygen from the air). Conventional Li/air batteries based on aqueous electrolytes suffer from fast capacity loss due to corrosion of lithium by water and are also nonrechargeable. Abraham and Jiang first reported a rechargeable lithium/oxygen cell using organic polymer gel electrolytes and demonstrated its advantages such as an all solid state design, rechargeablity and a high capacity. 3 Read studied the effect of electrolyte and air cathode formulation on the electrochemical properties of an Li/O 2 organic electrolyte cell and found that electrolyte composition has the largest effect on discharge capacity and rate capability. 4 Both groups incorporated common organic solvents in the electrolyte, i.e., ethylene carbonate (EC), propylene carbonate (PC), 1,2-dimethoxyethane, diethyl carbonate (DEC), dimethyl carbonate, γ-butyrolactone, tetrahydrofuran, or tetrahydropyran. 3, 4 The highly reactive lithium metal cannot, however, be thermodynamically compatible with common organic solvents. The fact that the air cathode of Li/air cells must be open to the ambient environment poses
Polymer/ceramic composite solid electrolyte is an appealing solution for the exploitation of flexible solid-state lithium-metal batteries. Here we report a solid-state Li-ion electrolyte composing of poly(vinylidene fluoride-cohexafluoro propylene) (PVDF-HFP) polymer, ceramic powder Li 6.5 La 3 Zr 1.5 Ta 0.5 O 12 (LLZTO) and lithium salt LiTFSI. The composite electrolyte exhibits a high ionic conductivity of 8.80 × 10 −5 S·cm −1 at room temperature. A coin battery with LiFePO 4 cathode is cycled under 0.5 C at room temperature for long cycles, achieving a Coulombic efficiency of 99.6% without virtually capacity loss (1st: 101.4 mAh·g −1 and 500th: 110.9 mAh·g −1 ). Such excellent performance can be ascribed to the formation of high ionic conductivity by LLZTO active garnet reducing polymer crystallinity. These results show that the developed polymer/ceramic composite has potential to be a high-performance electrolyte for solid-state lithium-metal batteries.