Electrolyte

High-Entropy (He) Electrolytes Improve Stability And Performance

Electrolyte

High-Entropy (He) Electrolytes Improve Stability And Performance

Increasing entropy of electrolytes improves ionic conductivity and rate capability Increasing the entropy of liquid electrolytes by introducing multiple salts was shown to alter the solvation structure, enhance the solubility and improve the ion mobility and electrochemical stability at the electrolyte-electrode interface. In this case, increasing the entropy results in a more negative Gibbs free energy of mixing, allowing for stably homogeneous electrolytes at previously inaccessible compositions (Fig. 1). Wang et. al. used LiNO3 (lithium oxonitrate), a common additive insoluble in the commercial EC/DMC electrolyte, to showcase that introducing a mixture of LiTFSI, LiFSI, and LiDFOB result in HE electrolytes with higher ionic conductivity, diffusivity, lithium ion transference number, and higher LiNO3 solubility. More stable cycling was also observed due to the denser and more uniform stripping/depositing on lithium metal (Fig. 2). Kim et. al. showed a similarly weakened solvation and ion clustering by increasing the electrolyte entropy (although here by introducing more co-solvents), and demonstrated improved ionic conductivity and cycling stability of lithium metal at high current densities for both ether and carbonate-based electrolytes (Fig. 3), where EL2, EL4, and EL5 correspond to electrolytes with 2, 4, and 5 solvents, respectively.

Figure 1.

Figure 2.

High-entropy electrolytes alter solvation structure, enhancing solubility, ion mobility, ionic conductivity, diffusivity, and electrochemical stability.

Academia | P. 219 Source: Q. Wang, C. Zhao, Z. Yao, J. Wang, F. Wu, S. G. H. Kumar, S. Ganapathy, S. Eustace, X. Bai, B. Li, J. Lu, M. Wagemaker. and Kim, S.C., Wang, J., Xu, R. et al.

Figure 3.

Extracted from the PDF; charts and images may read imperfectly.