Highly Safe 100-Wh-class Lithium-ion Battery Using Lithium Bis(trifluoromethanesulfonyl)amide-Tetraethylene Glycol Dimethyl Ether Equimolar Complex-based Quasi-solid-state Electrolyte

Abstract

A highly safe 100 Wh-class laminated lithium ion battery (LIB) was developed. For ensuring safety of the LIB, a liquid electrolyte was quasi-solidified at silica surfaces. For the liquid electrolyte, a solvate ionic liquid (SIL), which is an equimolar complex of lithium bis(trifluoromethanesulfonyl)amide (LiTFSA) and tetraethylene glycol dimethyl ether (G4), Li(G4)TFSA, was used. For enhancing discharge-rate capability, Li(G4)TFSA was diluted by propylene carbonate (PC). Then, for enhancing cycle life, vinylene carbonate (VC) and hexafluorophosphate anion (PF 6 −)based salt were added for forming an solid-electrolyte interphase (SEI) on the graphite negative electrode and an AlF 3 at the surface of the aluminum current collector of the positive electrode, respectively. The assembled LIB exhibited initial discharge capacity of 32 Ah and coulombic efficiency of 76%. Regardless of high energy-type, the developed battery exhibited high discharge capacity of 26.2 Ah at 2 C. Its retention ratio of discharge capacity at the 118th cycle is high, i.e., 96%. The developed LIB (with energy density of 363 Wh L −1) generated neither fire nor smoke in a nail-penetration test. These results suggest that the developed LIB has high safety compared to a LIB comprised of a conventional organic liquid electrolyte.

Molten Li Salt Solvate-Silica Nanoparticle Composite Electrolytes with Tailored Rheological Properties

“…6 The high mechanical strength of the present MLS-based colloidal gel electrolytes may also contribute to the above appealing features in battery systems. The silica-based quasi-solid electrolytes containing the MLSs can indeed be employed for highly safe 100 Wh-class allsolid state Li-ion batteries, as demonstrated by Unemoto et al 31 Figure 3 displays the V silica -dependence of the shear thickening behavior for the [BF 4 ]-based MLS-silica composites. With increasing V silica , the maximum peak viscosity increased and the critical shear rate, at which the viscosity starts to increase, systematically shifted to a lower shear rate for both systems.…”

Towards a High‐Performance Lithium‐Metal Battery with Glyme Solution and an Olivine Cathode

“…Furthermore, the use of suitable additives remarkably enhanced the electrode passivation behavior, leading to promising cell performances. Indeed, literature works have shown that vinylene carbonate (VC), fluoroethylene carbonate (FEC), and lithium nitrate (LiNO 3 ) may improve the SEI between anode and electrolyte. In particular, it is widely demonstrated that LiNO 3 ‐containing electrolytes may form a uniform and stable anode passivation layer containing both organic ( e.g ., ROLi and ROCO 2 Li) and inorganic ( e.g ., Li x NO y , Li 3 N, and Li 2 O) species, which can mitigate the parasitic reactions in the cell and limit the lithium dendrite growth .…”

Analysis of Solid-Electrolyte Interphase at the Interface between a Graphite Negative Electrode and a Diluted Solvate Ionic Liquid-Based Quasi-Solid-State Electrolyte

“…However, the application of such extras compromises the volumetric energy density of the battery pack. 2 Ensuring high thermal stability and high safety of the cells by means of constituent materials enables the cooling parts and extra spaces to be eliminated, thus leading to an enhanced volumetric energy density of the battery pack.…”

“…In addition, SIL can be quasi-solidified through its interaction with the oxide surfaces. 2,6,7 A quasi-solidstate electrolyte (QSE) prepared by mixing of the SILs with oxide particles, and fixing them with a polytetrafluoroethylene (PTFE) binder enables the liquid phase to be stored at high concentration. For example, when Li(G4)TFSA is mixed with fumed silica nanoparticles with a 7 nm diameter, the QSE can contain 80% of the electrolyte while remaining in a self-standing sheet.…”

“…9 In an earlier study, we developed a QSE composed of Li(G4) TFSA and fumed silica as a highly safe electrolyte and used it in the assembly of a high energy density battery pack. 2 Rate performances of the cell using the Li(G4)TFSA-based QSE were poor owing to the high viscosity of Li(G4)TFSA, which provides pathways for Li ions in the QSE. The high viscosity and high concentration of the LiTFSA in the QSE leads to a high concentration polarization resistance.…”