(300g) Localized High Concentration Electrolytes for Dual Ion Lithium Batteries

An electrolyte with high Li-metal Coulombic efficiency (CE) and high anodic stability on cathodes is crucial for enabling next-generation high-energy-density lithium (Li)-metal batteries (LMBs). The high concentration electrolyte (HCE) in the current dual-ion battery (DIB) electrolyte achieves a greater capacity than the low concentration electrolyte (LCE), and stable operation at high voltage is made possible by increased electrochemical stability. It also features a solvation structure with a lot of contact ion pairs (CIPs) or cation-anion aggregates (AGG). Nevertheless, high-concentration electrolytes have high viscosity and limited ionic conductivity, which degrades the high-output characteristic of conventional DIBs. In this study, we used an electrolyte type called localized high concentration electrolytes (LHCEs). This decreases viscosity via diluent and stabilizes the contact between the lithium metal and the graphite anode, resulting in steady functioning even at high output. The differences between the three systems, HCE, LCE, and LHCE, were examined using molecular dynamic simulations (MD) and density functional theory (DFT) calculations. Each system was composed of varying proportions of dimethyl carbonate (DMC) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), with 1,1,2,2-tetrafluoroethyl -2,2,3,3-tetrafluoropropyl ether (TTE) serving as a diluent for LHCE. To determine how diluents affect the intercalation and desorption of anions, we modelled the solvation structures of anions and cations. As a result, it was found that DMC tightly coordinated with all LiTFSI salt molecules, but not TTE. The radial distribution functions of the Li-O_DMC and Li-O_TTE pairings were also built using MD simulations over the previous 200 ps. In all three systems under examination, a distinct peak for the Li-O_DMC pair was discovered around 2.05 Å, which is consistent with all LiTFSI salts. Being surrounded by DMC solvent molecules shows that DMC is the initial shell of coordination. Moreover, compared to HCE, which has significant coordination with TFSI, LHCE demonstrated significant cooperation with DMC. Coordination of DMC and TFSI yielded similar values in the case of LCE. This demonstrates that TFSI anion mobility is greatest in LHCE. Moreover, DFT simulations of the solvation structure and intercalation behavior of anions were carried out. Comparing the experimental voltage and the calculated value revealed the presence of the same pattern. In order to observe the differences based on the type of anion and the type of solvent, lithium bisfluorosulfonylimide (LiFSI) and ethyl methyl sulfone (EMS) were also used. Hence, LHCE had the highest FSI anion mobility. Surprisingly, radial distribution functions' peak values were lower than when TFSI and DMC were used. These findings will help to improve existing DIB challenges by suggesting new forms of LHCE electrolytes.