Analysis of Main Factors Limiting the Improvement of Electrochemical Performances of Low‐Concentration Electrolyte

Abstract

The low‐concentration electrolyte possesses the benefits of desirable wettability, low viscosity, and low cost. However, the mechanism of its poor electrochemical performance is not clear. Herein, the properties of interfacial films on the surface of LiFePO4 (LFP) cathode material formed by electrolytes with different concentrations are compared by interfacial component analysis. It is shown that moderate content of lithium fluoride increases the length of Li+–ethylene carbonate bond from 1.676 to 1.824 Å through lithium bond and then decreases the desolvation activity energy of Li+ ion, which effectively promotes the desolvation process of Li+ ion at the interface of LFP/electrolyte, and finally ensures the perfect performance of the battery. That is, the fundamental cause for the undesirable electrochemical performances of the low‐concentration electrolyte is the low content of LiF components in the interface film rather than the low ionic conductivity of the electrolyte itself. This indicates the direction of optimizing the electrochemical performance of low‐concentration electrolytes.

An Ultralow‐concentration and Moisture‐resistant Electrolyte of Lithium Difluoro(oxalato)borate in Carbonate Solvents for Stable Cycling in Practical Lithium‐ion Batteries

“…The excellent cathode, anode, and full cell performances unambiguously verify the efficacy of low‐concentration LiDFOB electrolytes for practical applications. We further highlight that this electrolyte exhibits the record‐low salt/solvent mass ratio (2 : 98) and molar concentration (0.16 M) in the context of ULCEs, [19c,f,j,20e–h] as shown in Figure 4h. Detailed information and some comments on the low‐concentration electrolytes are further provided in Table S2.…”

Improving performances of the electrode/electrolyte interfaceviathe regulation of solvation complexes: a review and prospect

“…A large number of solvated complexes of SSIP are formed, making the composition of the EEI film completely dependent on the competitive reaction among the free anions, free solvent molecules, and solvent molecules coordinated with Li + at the EEI. 20 The anion is the most efficient species for producing inorganic-rich EEI films. However, it is generally required that anions are reduced before the solvent reaction in the electrolyte, so some salt anions with lower the lowest unoccupied molecular orbital (LUMO) are often selected.…”

Anion-Induced Uniform and Robust Cathode–Electrolyte Interphase for Layered Metal Oxide Cathodes of Sodium Ion Batteries

“…LCEs have weak ion–solvent interactions, showing good development potential under fast charge and low-temperature conditions. However, due to the large amount of organic components in the CEI film, the electrochemical performance is still unsatisfactory . At present, some works are devoted to constructing anion-rich solvated structures via introducing a large number of anions in the solvated sheath of the cation to enhance the performance of the battery.…”

“…However, due to the large amount of organic components in the CEI film, the electrochemical performance is still unsatisfactory. 24 At present, some works are devoted to constructing anion-rich solvated structures via introducing a large number of anions in the solvated sheath of the cation to enhance the performance of the battery. For example, weakly solvated electrolytes (WSE) that use low-polarity solvents were proposed to weaken the interaction between cations and solvents, promoting the formation of more AGGs.…”