A partially fluorinated polymer network enhances the Li-ion transference number of sulfolane-based highly concentrated electrolytes.

Gelation of sulfolane-based highly concentrated electrolytes using a partially fluorinated polymer enhances the Li-ion transference number of the electrolytes because acidic protons surrounded by fluorine atoms in the polymer network trap anions, and the high Li transference number is effective in suppressing the concentration polarization in Li batteries.

Linear ether-based highly concentrated electrolytes for Li-sulfur batteries.

Li-S batteries have attracted attention as next-generation rechargeable batteries owing to their high theoretical capacity and cost-effectiveness. Sparingly solvating electrolytes hold promise because they suppress the dissolution and shuttling of polysulfide intermediates to increase the coulombic efficiency and extend the cycle life. This study investigated the solubility of polysulfide (LiS) in a range of liquid electrolytes, including organic electrolytes, highly concentrated electrolytes, and ionic liquids.

Evolving better solvate electrolytes for lithium secondary batteries.

The overall performance of lithium batteries remains unmatched to this date. Decades of optimisation have resulted in long-lasting batteries with high energy density suitable for mobile applications. However, the electrolytes used at present suffer from low lithium transference numbers, which induces concentration polarisation and reduces efficiency of charging and discharging.

Enhancing Li-S Battery Performance with Limiting Li[N(SOF)] Content in a Sulfolane-Based Sparingly Solvating Electrolyte.

By enhancing the stability of the lithium metal anode and mitigating the formation of lithium dendrites through electrolyte design, it becomes feasible to extend the lifespan of lithium-sulfur (Li-S) batteries. One widely accepted approach involves the utilization of Li[N(SOF)] (Li[FSA]), which holds promise in stabilizing the lithium anode by facilitating the formation of an inorganic-dominant solid electrolyte interface (SEI) film. However, the use of Li[FSA] encounters limitations due to inevitable side reactions between lithium polysulfides (LiPSs) and [FSA] anions.

Molecular Level Origin of Ion Dynamics in Highly Concentrated Electrolytes.

Single-ion conducting liquid electrolytes are key to achieving rapid charge/discharge in Li secondary batteries. The Li transference (or transport) numbers are the defining properties of such electrolytes and have been discussed in the framework of concentrated solution theories. However, the connection between macroscopic transference and microscopic ion dynamics remains unclear.

High-concentration LiPF/sulfone electrolytes: structure, transport properties, and battery application.

Non-flammable and oxidatively stable sulfones are promising electrolyte solvents for thermally stable high-voltage Li batteries. In addition, sulfolane-based high-concentration electrolytes (HCEs) show high Li ion transference numbers. However, LiPF has not yet been investigated as the main salt in sulfone-based HCEs for Li batteries.

Molecular Dynamics Simulations of High-Concentration Li[TFSA] Sulfone Solution: Effect of Easy Conformation Change of Sulfolane on Fast Diffusion of Li Ion.

The parameters of the polarizable force field used for molecular dynamics simulations of Li diffusion in high-concentration lithium bis(trifluoromethanesulfonyl)amide (Li[TFSA]) sulfone (sulfolane, dimethylsulfone, ethylmethylsulfone, and ethyl--propylsulfone) solutions were refined. The densities of the solutions obtained by molecular dynamics simulations reproduced well the experimental values. The calculated concentration, temperature, and solvent dependencies of self-diffusion coefficients of ions and solvents in the mixtures well reproduce the experimentally observed dependencies.

Tetra-arm poly(ethylene glycol) gels with highly concentrated sulfolane-based electrolytes exhibiting high Li-ion transference numbers.

We demonstrate that tetra-arm poly(ethylene glycol) gels containing highly concentrated sulfolane-based electrolytes exhibit high Li transference numbers. The low polymer concentration and homogeneous polymer network in the gel electrolyte are useful in achieving both mechanical reliability and high Li transport ability.

Lithium Aluminate Nanoflakes as an Additive to Sulfur Cathodes for Enhanced Mass Transport in High-Energy-Density Lithium-Sulfur Pouch Cells Utilizing Sparingly Solvating Electrolytes.

The utilization of sparingly solvating electrolytes has been reckoned as a promising approach to realizing high-energy-density lithium-sulfur batteries under lean electrolyte conditions through decoupling the electrolyte amount from sulfur utilization. However, the inferior wettability of high-concentration sparingly solvating electrolytes compromises mass transport, thereby impeding the maximum utilization of active material in sulfur cathodes. To address this issue, in this study, we incorporate lithium aluminate (LiAlO) nanoflakes as an additive to sulfur cathodes to enhance the mass transport by improving the percolation and accessibility of sparingly solvating electrolytes to the bulk of the electrodes.

Concentrated Nonaqueous Polyelectrolyte Solutions: High Na-Ion Transference Number and Surface-Tethered Polyanion Layer for Sodium-Metal Batteries.

Na metal is a promising anode material for the preparation of next-generation high-energy-density sodium-ion batteries; however, the high reactivity of Na metal severely limits the choice of electrolyte. In addition, rapid charge-discharge battery systems require electrolytes with high Na-ion transport properties. Herein, we demonstrate a stable and high-rate sodium-metal battery enabled by a nonaqueous polyelectrolyte solution composed of a weakly coordinating polyanion-type Na salt, poly[(4-styrenesulfonyl)-(trifluoromethanesulfonyl)imide] (poly(NaSTFSI)) copolymerized with butyl acrylate, in a propylene carbonate solution.

On the concentration polarisation in molten Li salts and borate-based Li ionic liquids.

Electrolytes that transport only Li ions play a crucial role in improving rapid charge and discharge properties in Li secondary batteries. Single Li-ion conduction can be achieved liquid materials such as Li ionic liquids containing Li as the only cations because solvent-free fused Li salts do not polarise in electrochemical cells, owing to the absence of neutral solvents that allow polarisation in the salt concentration and the inevitably homogeneous density in the cells under anion-blocking conditions. However, we found that borate-based Li ionic liquids induce concentration polarisation in a Li/Li symmetric cell, which results in their transference (transport) numbers under anion-blocking conditions (abcLi) being well below unity.

Ion Transport in Glyme- and Sulfolane-Based Highly Concentrated Electrolytes.

Highly concentrated electrolytes (HCEs) have a similarity to ionic liquids (ILs) in high ionic nature, and indeed some of HECs are found to behave like an IL. HCEs have attracted considerable attention as prospective candidates for electrolyte materials in future lithium secondary batteries owing to their favorable properties both in the bulk and at the electrochemical interface. In this study, we highlight the effects of the solvent, counter anion, and diluent of HCEs on the Li ion coordination structure and transport properties (e.

Does Li-ion transport occur rapidly in localized high-concentration electrolytes?

The ionic conductivity and lithium-ion transference number of electrolytes significantly influence the rate capability of Li-ion batteries. Highly concentrated Li-salt/sulfolane (SL) electrolytes exhibit elevated Li transference numbers due to lithium-ion hopping a ligand exchange mechanism within their -Li-SL-Li- network. However, highly concentrated electrolytes (HCEs) are extremely viscous and have an ionic conductivity that is one order of magnitude less than that of conventional electrolytes.

Carbonaceous-Material-Induced Gelation of Concentrated Electrolyte Solutions for Application in Lithium-Sulfur Battery Cathodes.

Lithium-sulfur (Li-S) batteries can theoretically deliver high energy densities exceeding 2500 Wh kg. However, high sulfur loading and lean electrolyte conditions are two major requirements to enhance the actual energy density of the Li-S batteries. Herein, the use of carbon-dispersed highly concentrated electrolyte (HCE) gels with sparingly solvating characteristics as sulfur hosts in Li-S batteries is proposed as a unique approach to construct continuous electron-transport and ion-conduction paths in sulfur cathodes as well as achieve high energy density under lean-electrolyte conditions.

Li transference number and dynamic ion correlations in glyme-Li salt solvate ionic liquids diluted with molecular solvents.

Highly concentrated electrolytes (HCEs) have attracted significant interest as promising liquid electrolytes for next-generation Li secondary batteries, owing to various beneficial properties both in the bulk and at the electrode/electrolyte interface. One particular class of HCEs consists of binary mixtures of lithium bis(trifluoromethanesulfonyl)amide (LiTFSA) and oligoethers that behave like ionic liquids. [Li(G4)][TFSA], which comprises an equimolar mixture of LiTFSA and tetraglyme (G4), is an example.

LiNiMnO-Hybridized Gel Polymer Cathode and Gel Polymer Electrolyte Containing a Sulfolane-Based Highly Concentrated Electrolyte for the Fabrication of a 5 V Class of Flexible Lithium Batteries.

The design and fabrication of lithium secondary batteries with a high energy density and shape flexibility are essential for flexible and wearable electronics. In this study, we fabricated a high-voltage (5 V class) flexible lithium polymer battery using a lithium nickel manganese oxide (LiNiMnO) cathode. A LiNiMnO-hybridized gel polymer cathode (GPC) and a gel polymer electrolyte (GPE) membrane, both containing a sulfolane (SL)-based highly concentrated electrolyte (HCE), enabled the fabrication of a polymer battery by simple lamination with a metallic lithium anode, where the injection of the electrolyte solution was not required.

Li-Ion Transport and Solvation of a Li Salt of Weakly Coordinating Polyanions in Ethylene Carbonate/Dimethyl Carbonate Mixtures.

Electrolytes with a high Li-ion transference number () have attracted significant attention for the improvement of the rapid charge-discharge performance of Li-ion batteries (LIBs). Nonaqueous polyelectrolyte solutions exhibit high upon immobilization of the anion on a polymer backbone. However, the transport properties and Li-ion solvation in these media are not fully understood.

Solvate electrolytes for Li and Na batteries: structures, transport properties, and electrochemistry.

Polar solvents dissolve Li and Na salts at high concentrations and are used as electrolyte solutions for batteries. The solvents interact strongly with the alkali metal cations to form complexes in the solution. The activity (concentration) of the uncoordinated solvent decreases as the salt concentration is increased.

Local Structure of Li in Superconcentrated Aqueous LiTFSA Solutions.

It has been reported that aqueous lithium ion batteries (ALIBs) can operate beyond the electrochemical window of water by using a superconcentrated electrolyte aqueous solution. The liquid structure, particularly the local structure of the Li, which is rather different from conventional dilute solution, plays a crucial role in realizing the ALIB. To reveal the local structure around Li, the superconcentrated LiTFSA (TFSA: bis(trifluoromethylsulfonil)amide) aqueous solutions were investigated by means of Raman spectroscopic experiments, high-energy X-ray total scattering measurements, and the neutron diffraction technique with different isotopic composition ratios of Li/Li and H/D.

Transport Properties of Flexible Composite Electrolytes Composed of LiAlTi(PO) and a Poly(vinylidene fluoride--hexafluoropropylene) Gel Containing a Highly Concentrated Li[N(SOCF)]/Sulfolane Electrolyte.

Flexible solid-state electrolyte membranes are beneficial for feasible construction of solid-state batteries. In this study, a flexible composite electrolyte was prepared by combining a Li-ion-conducting solid electrolyte LiAlTi(PO) (LATP) and a poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) gel containing a highly concentrated electrolyte of Li[N(SOCF)] (LiTFSA)/sulfolane using a solution casting method. We successfully demonstrated the operation of Li/LiCoO cells with the composite electrolyte; however, the rate capability of the cell degraded with increasing LATP content.

Structural Effects of Solvents on Li-Ion-Hopping Conduction in Highly Concentrated LiBF/Sulfone Solutions.

Li-ion-hopping conduction is known to occur in certain highly concentrated electrolytes, and this conduction mode is effective for achieving lithium batteries with high rate capabilities. Herein, we investigated the effects of the solvent structure on the hopping conduction of Li ions in highly concentrated LiBF/sulfone electrolytes. Raman spectroscopy revealed that a Li ion forms complexes with sulfone and anions, and contact ion pairs and ionic aggregates are formed in the highly concentrated electrolytes.

Thermodynamic aspect of sulfur, polysulfide anion and lithium polysulfide: plausible reaction path during discharge of lithium-sulfur battery.

The elucidation of elemental redox reactions of sulfur is important for improving the performance of lithium-sulfur batteries. The energies of stable structures of S, S˙, S, [LiS] and LiS (n = 1-8) were calculated at the CCSD(T)/cc-pVTZ//MP3/cc-pVDZ level. The heats of reduction reactions of S and LiS with Li in the solid phase were estimated from the calculated energies and sublimation energies.

Anion effects on Li ion transference number and dynamic ion correlations in glyme-Li salt equimolar mixtures.

To achieve single-ion conducting liquid electrolytes for the rapid charge and discharge of Li secondary batteries, improvement in the Li+ transference number of the electrolytes is integral. Few studies have established a feasible design for achieving Li+ transference numbers approaching unity in liquid electrolytes consisting of low-molecular-weight salts and solvents. Previously, we studied the effects of Li+-solvent interactions on the Li+ transference number in glyme- and sulfolane-based molten Li salt solvates and clarified the relationship between this transference number and correlated ion motions.

Solvent effects on Li ion transference number and dynamic ion correlations in glyme- and sulfolane-based molten Li salt solvates.

The Li transference number of electrolytes is one of the key factors contributing to the enhancement in the charge-discharge performance of Li secondary batteries. However, a design principle to achieve a high Li transference number has not been established for liquid electrolytes. To understand the factors governing the Li transference number t, we investigated the influence of the ion-solvent interactions, Li ion coordination, and correlations of ion motions on the Li transference number in glyme (Gn, n = 1-4)- and sulfolane (SL)-based molten Li salt solvate electrolytes with lithium bis(trifluoromethansulfonyl)amide (LiTFSA).

Speciation Analysis and Thermodynamic Criteria of Solvated Ionic Liquids: Ionic Liquids or Superconcentrated Solutions?

Lithium-glyme solvated ionic liquids (Li-G SILs) and superconcentrated electrolyte solutions (SCESs) are expected to be promising electrolytes for next-generation lithium secondary batteries. The former consists of only the oligoether glyme solvated lithium ion and its counteranion, and the latter contains no full solvated Li ion by the solvents due to the extremely high Li salt concentration. Although both of them are similar to each other, it is still unclear that both should be room-temperature ionic liquids.