Constructing Low‐Solvation Electrolytes for Next‐Generation Lithium‐Ion Batteries

Abstract

The realization of high‐concentration electrolytes (HCEs) is a benchmark breakthrough attributed to the modification of cation aggregation, which owns technical advantages over the widely used conventional electrolytes. Due to the high cost brought by the large amount of lithium (Li) salts, high viscosity, low Li+ conductivity, and wettability of the HCE system, the concept of localized HCEs (LHCEs) is proposed to improve the aforementioned shortcomings without affecting the performances of high‐energy‐density batteries. Nevertheless, the effect factors of the weakly solvated structure of LHCEs have not been summarized, so it is urgent to conclude this direction to further survey the low‐solvation structure and properties. Hence, for the first time we offer a comprehensive and distinct overview on the electrolyte development, strategies for constructing low‐solvation structure, and scientific perspectives for lithium‐ion batteries, especially by focusing on the binding energies between cation and solvents, solvation and de‐solvation process, structure of novel solvents, and selection of Li salts. Emphasis is placed on the relevance of constructing low‐solvation structure and forming electrode/electrolyte interphases, and new insights into weakly solvated electrolytes associated with efficient solid electrolyte interphase and cathode electrolyte interphase layers are presented for developing next‐generation lithium‐ion batteries.

Exploiting the Steric Effect and Low Dielectric Constant of 1,2-Dimethoxypropane for 4.3 V Lithium Metal Batteries

“…Our findings highlight the importance of the fine structural manipulation of electrolyte solvents to adjust the solvation structure toward advancing LMBs to practically viable options. Moreover, the structurally fine-tuned solvents could be applied beyond LMBs such as LIBs operating under extreme fast charging conditions or at low temperatures. − …”

Atomic Insights into Advances and Issues in Low‐Temperature Electrolytes

“…Nowadays, weakly solvating electrolyte has become a new research trend of high‐voltage and low‐temperature electrolyte, because of its excellent derivative ability of inorganic‐rich SEI film. [ 97 ] A series of solvents with weak solvation were screened and applied in the development of electrolyte, including tris(2,2,2‐trifluoroethyl) phosphate (TEP), [ 98 ] diethyl ether (DEE), [ 99 ] dimethoxymethane (DMM), [ 100 ] 1,3‐dioxane (1,3‐DX), [ 25c ] and dimethyl dimethoxy silicane (DMSi). [ 101 ] In fact, weakly solvating electrolyte is the coordination effect between ion–solvent and cation–anion interactions.…”

Theory of Cation Solvation and Ionic Association in Non-Aqueous Solvent Mixtures

“…In fact, next-generation electrolytes are engineered to tune the solvation shell of cations, and therefore physicochemical and interfacial properties of the electrolytes [4-8, 13, 24]. For example, localized high-concentration electrolytes (LHCE) [14][15][16][25][26][27][28] use typical salts, such as fluoro-sulfonamides, in high ratios with ether solvents which historically showed promising compatibility with lithium metal anodes, such as 1,2-dimethoxyethane, but which are notoriously limited in terms of oxidative stability [29][30][31][32]. The singular aspect of LHCE's is their use of diluents, generally in the form of fluorinated ethers, which are non-solvating, but highly oxidatively stable [14][15][16][25][26][27][28].…”

“…For example, localized high-concentration electrolytes (LHCE) [14][15][16][25][26][27][28] use typical salts, such as fluoro-sulfonamides, in high ratios with ether solvents which historically showed promising compatibility with lithium metal anodes, such as 1,2-dimethoxyethane, but which are notoriously limited in terms of oxidative stability [29][30][31][32]. The singular aspect of LHCE's is their use of diluents, generally in the form of fluorinated ethers, which are non-solvating, but highly oxidatively stable [14][15][16][25][26][27][28]. Thus, the non-fluorinated solvent and anion is mostly retained in the lithium coordination shell, where it has enhanced oxidative stability, while the fluorinated ether diluent strictly appears outside of the lithium coordination shell, serving to lubricate the electrolyte (decrease viscosity) while remaining stable against both electrodes [14][15][16][25][26][27][28].…”

“…The singular aspect of LHCE's is their use of diluents, generally in the form of fluorinated ethers, which are non-solvating, but highly oxidatively stable [14][15][16][25][26][27][28]. Thus, the non-fluorinated solvent and anion is mostly retained in the lithium coordination shell, where it has enhanced oxidative stability, while the fluorinated ether diluent strictly appears outside of the lithium coordination shell, serving to lubricate the electrolyte (decrease viscosity) while remaining stable against both electrodes [14][15][16][25][26][27][28]. However, a major issue in engineering such next-generation electrolytes is knowing exactly how the solvation shell of the cations will be effected by the mixtures which are created to balance the physicochemical and interfacial properties, as they are often not just an average of their neat properties.…”