Switching Electrolyte Interfacial Model to Engineer Solid Electrolyte Interface for Fast Charging and Wide‐Temperature Lithium‐Ion Batteries

Abstract

Engineering the solid electrolyte interphase (SEI) that forms on the electrode is crucial for achieving high performance in metal-ion batteries. However, the mechanism of SEI formation resulting from electrolyte decomposition is not fully understood at the molecular scale. Herein, a new strategy of switching electrolyte to tune SEI properties is presented, by which a unique and thinner SEI can be pre-formed on the graphite electrode first in an ether-based electrolyte, and then the as-designed graphite electrode can demonstrate extremely high-rate capabilities in a carbonate-based electrolyte, enabling the design of fast-charging and wide-temperature lithium-ion batteries (e.g., graphite | LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622)). A molecular interfacial model involving the conformations and electrochemical stabilities of the Li + -solvent-anion complex is presented to elucidate the differences in SEI formation between ether-based and carbonate-based electrolytes, then interpreting the reason for the obtained higher rate performances. This innovative concept combines the advantages of different electrolytes into one battery system. It is believed that the switching strategy and understanding of the SEI formation mechanism opens a new avenue to design SEI, which is universal for pursuing more versatile battery systems with greater stability.

Dipole–Dipole Interaction Induced Electrolyte Interfacial Model To Stabilize Antimony Anode for High-Safety Lithium-Ion Batteries

“…One may consider the SEI effect on the Sb electrode stability, besides the electrolyte stability (i.e., compatibility). Here, we adopt an exchange experiment to show the SEI effect, where the reliability of such exchange experiment has been verified in our previously reported works, such as the graphite ,,, and alloying anode , studied in lithium, sodium, and potassium-ion batteries, respectively. − First, we used a bulk Sb electrode to assemble an Sb|Li half-cell using the compatible electrolyte (e.g., 1.2 M LiFSI in TEP/HFE) and then cycled the cell for 20 cycles to form an SEI (i.e., Sb@SEI) (Figure a 1 ,a 2 ). Then, we disassembled the cell and used the Sb@SEI electrode to reassemble a new battery using an incompatible electrolyte (e.g., 4.4 M LiFSI in EC/EMC, 4.4 M LiFSI in TEP, or 1.2 M LiTFSI in TEP-HFE) (Figure a 3 ).…”

Weak Solvent–Solvent Interaction Enables High Stability of Battery Electrolyte

“…In this way, the redox properties of the electrolyte components, including solvent, additive, and anion during the polarization, − as well as the recently proposed M + –solvent–anion complex formed during the desolvation process on the electrode surface, − have been widely studied to evaluate the electrolyte, since they can be highly influenced by the widely existing electrostatic interactions between M + , anions, and solvent molecules with uneven charge distribution. Then, varying the interactions of M + –solvent, M + –anion pair, and anion–solvent by changing the type and quantity of solvents, anions, additives, etc., have received significant attention recently to tune the electrolyte properties. − It is worth noting that solvent–solvent interaction has rarely been mentioned before, as such interaction is considered to be very weak, 1–2 orders of magnitude weaker than the ion–ion interaction between M + –anion and the ion-dipole interaction between M + –solvent .…”

Quantitative Chemistry in Electrolyte Solvation Design for Aqueous Batteries

“…Identifying the different molecular behaviors of different solvents, additives, and anions in the metal-ion solvation structure in aqueous electrolyte will facilitate optimizing the amounts and the kinds of solvents, additives, and metal salts used quantitatively and accurately. In particular, the amount of H-bonds in the electrolyte needs to be quantified to a certain degree at least, as it can significantly influence the solvation structure and interfacial behaviors (i.e., the metal-ion desolvation process , ), in turn determining the electrolyte stability and electrode performance. This is a challenging but interesting type of research in solution chemistry, particularly when the kinds of organic additives and/or the electrolyte concentration is changed.…”