Electrolytes For Lithium Metal Batteries Research Articles

Low-viscosity ether-functionalized pyrazolium ionic liquids based on dicyanamide anions: properties and application as electrolytes for lithium metal batteries

Two ether-functionalized pyrazolium ionic liquids based on dicyanamide anion were used as new electrolytes in Li/LiFePO4 cells.

Novel mixtures of ether-functionalized ionic liquids and non-flammable methylperfluorobutylether as safe electrolytes for lithium metal batteries

Li/LiFePO4cells using safe electrolytes composed of ether-functionalized ILs and non-flammable methylperfluorobutylether showed good rate performance.

Composite Block Copolymer Electrolytes for Lithium Metal Batteries

Lithium metal has been widely investigated for next generation rechargeable batteries due to its extremely high theoretical specfic capacity. However, lithium dendrite formation at the lithium metal anode-electrolyte interfaces is considered to be one of major factors in deteriorating the performance of lithium metal batteries. To suppress the lithium dendrite growth, solid polymer electrolytes (SPE) with high mechanical strength and electrochemical stability have been studied to replace liquid electrolyte. In this case, using SPE in lithium metal batteries, low ionic conductivity and high interfacial resistance of SPEs are still remained critical problems. In order to achieve the high ionic conductivity and mechanical strength simultaneously in solid polymer electrolytes for lithium metal batteries, we applied block copolymer (BCP) composed of structural and ionic conducting domains in this study. In addition, we fabricated organic/inorganic hybrid block copolymer composite electrolytes with ionic liquids and nanoparticles for improving ionic conductivity and mechanical strength. The effects of composite block copolymer electrolytes were evaluated in terms of ionic conductivity as well as mechanical strength. In addition, interfacial resistance and ESW (electrochemical stability window) were also performed to understand the functions of hybrid components. In particular, these properties could be crucially affected by change of composition of block copolymer and hybrid components, which resulted in the different behavior inside polymer matrix and interface between electrode/electrolyte.

Optimization of Block Copolymers As Electrolytes for Lithium Metal Batteries

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Nanocomposites of Titanium Dioxide and Polystyrene-Poly(ethylene oxide) Block Copolymer as Solid-State Electrolytes for Lithium Metal Batteries

There is considerable interest in developing solid electrolytes for rechargeable lithium batteries as they have the potential to increase both energy density due to incorporation of a lithium metal anode and safety of batteries due to the fact that they are nonflammable. Block copolymers with a mechanically hard non-conducting block and a soft ion-conducting block provide an avenue for obtaining highly conducting rigid solids. In this study we add surface-modified TiO2 nanoparticles to a mixture of polystyrene-block-poly(ethylene oxide) and bis(trifluoromethane)sulfonimide lithium salt. The presence of BF4− moieties on the surface of the particles was essential for obtaining macroscopically homogeneous electrolytes; macrophase separation was observed with the same nanoparticles with surfaces covered with oleic acid. The stability of these composite electrolytes against lithium metal electrodes was tested in symmetric lithium-composite electrolyte-lithium cells. The surprising result was that electrolytes with 24 wt% nanoparticles exhibited optimum stability; the amount of charge passed before dendrite formation observed in the optimized composite electrolyte was a factor of 4.7 larger than that of the neat block copolymer electrolyte. Both tensile and shear moduli of the electrolytes were non-monotonic functions of particle concentration with peaks in the vicinity of 17 to 20 wt%.

Fast Charge/Discharge of Li Metal Batteries Using an Ionic Liquid Electrolyte

Because of their potentially superior safety characteristics, room temperature ionic liquids (RTILs or ILs) have been vigorously researched as a potential replacement for current commercial lithium battery electrolytes, which are based on volatile and flammable organic carbonates. However, relatively poor battery performance, which is a consequence of the higher viscosity and lower conductivity of these materials, has prevented them becoming mainstream electrolytes for commercial lithium batteries. Amongst various RTILs, those containing the bis(fluorosulfonyl)imide (FSI) anion exhibit high conductivities and diffusivities, making them interesting potential electrolytes for lithium metal batteries. Here, we evaluate the electrochemical stability, lithium electrochemistry, and Li+ transference numbers of FSI-based ionic liquid electrolytes intended for use in rechargeable Li metal batteries. We show that ILs containing high concentrations of lithium, up to 3.2 mol.kg−1 in C3mpyr FSI, have excellent rate capability (higher than that of standard battery electrolytes) with both the lithium metal electrode and LiCoO2 cathode, in spite of their significantly higher viscosities and lower conductivities. This unusual behavior is ascribed to the concomitant increase in transference number with increasing Li-salt concentration.

Polymerized ionic liquids with guanidinium cations as host for gel polymer electrolytes in lithium metal batteries

AbstractPolymerized ionic liquids (PILs) having guanidinium cations with different counter‐anions, such as PF6− and N(CF3SO2)2− (TFSI−), were synthesized by copolymerization of a guanidinium ionic liquid monomer with methyl acrylate followed by an anion exchange reaction. Furthermore, incorporating a guanidinium ionic liquid, LiTFSI salt and nano‐size SiO2, a quaternary gel polymer electrolyte based on one of the PILs as the polymer host was prepared. The quaternary gel polymer electrolyte was chemically stable even at a higher temperature of 80 °C in contact with the lithium anode. In particular, the electrolyte exhibited high lithium ion conductivity, wide electrochemical stability window and good lithium stripping/plating performance. Li/LiFePO4 batteries with the quaternary gel polymer electrolyte at 80 °C had capacities of 140 and 130 mA h g−1 respectively at 0.1 and 0.2 C current rates. Copyright © 2011 Society of Chemical Industry

Dendrite-Free Electrodeposition and Reoxidation of Lithium-Sodium Alloy for Metal-Anode Battery

Two ionic liquids, EMI-AlCl4 and N1114-TFSI, that support both lithium and sodium deposition/dissolution were studied as potential electrolytes for lithium metal batteries. In both cases, lithium’s dendritic growth was suppressed by adding a small amount of sodium to a lithium electrolyte. This results in a co-deposition or alloying process that hinders dendrite growth. SEM images show a significant difference in morphology obtained by the addition of sodium. A smooth deposit was not enough for stable cycling of the lithium anode because of lithium’s reactivity with the electrolyte. Vinylene carbonate (VC) was added to the N1114-TFSI to form a stable SEI layer. Cyclic voltammetry and chronopotentiometry was carried out on tungsten and stainless steel electrodes to obtain efficiency measurements. The combination of a small amount of sodium in the electrolyte, along with VC as an SEI former, lead to significant improvements in cycling performance and efficiency.

Ionic Liquids as Electrolytes in Lithium Metal Batteries

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Improved composite materials for rechargeable lithium metal polymer batteries

Abstract The performance of several polymer electrolytes for lithium metal batteries for electric vehicle applications are reported. The best performing electrolyte is the composite PEO 20 LiCF 3 SO 3 –γLiAlO 2 , which was prepared by a solvent-free procedure. It showed coulombic efficiency values of the lithium deposition–stripping process of 94%–96%. Electrochemical tests of lithium polymer battery (LPB) prototypes based on a 3 V LiMn 2 O 4 composite cathode material laminated together with the PEO 20 LiCF 3 SO 3 –γLiAlO 2 electrolyte gave promising results for electric vehicle applications. Even under non-optimized battery design, the prototypes delivered, at the C/3 rate and at 94°C, 40%–30% of theoretical capacity over 100 charge–discharge cycles.

Investigation on lithium/polymer electrolyte interface for high performance lithium rechargeable batteries

Performance data of several linear and cross-linked polymer electrolytes are reported and the electrochemical criteria for the selection of electrolytes to be used in electric vehicle lithium metal batteries are discussed. Further, laboratory lithium cells with LiMn 2O 4 composite cathode were tested to ascertain the effective viability of these polymer in solid-state batteries and preliminary results are reported. This study clearly demonstrates the importance of a broad-based electrochemical characterization in selecting an electrolyte for lithium metal batteries.