A Non‐Expendable Leveler as Electrolyte Additive Enabling Homogenous Lithium Deposition

Abstract

Li metal anodes have been extensively studied owing to their unparalleled advantages in achieving high energy density. However, safety issues originating from dendritic Li growth are always a huge hindrance for applications in Li metal batteries (LMBs). In this study, a functional additive, 4,6‐dimethyl‐2‐mercaptopyrimidine (DMP), which is a typical leveler in the copper electroplating industry, was selected to suppress Li dendrite formation. Various Li‐metal‐based batteries were systematically investigated and they showed stable performances, such as excellent cycling stability above 800 h at 3 mA cm−2 in Li||Li cells and 400 cycles with high coulombic efficiencies (CEs >98%) at 1 mA cm−2 in Li||Cu cells. Furthermore, a comprehensive verification of the protective mechanism induced by the DMP leveling agent showed that the leveler updated the Li+ solvation structure and occupied the inner Helmholtz plane of the Li anode. The planar DMP molecular layer absorbed on the surface of the Li metal could suppress side reactions and modified the Li deposition behavior via steric hindrance, inducing homogeneous Li deposition. Interestingly, the DMP leveler did not participate in the formation of the solid electrolyte interphase. This study can stimulate further ideas on non‐depleting but effective levelers as electrolyte additives for high‐performance LMBs.This article is protected by copyright. All rights reserved

Rational Molecular Engineering via Electron Reconfiguration toward Robust Dual-Electrode/Electrolyte Interphases for High-Performance Lithium Metal Batteries

“…The improved performances of Li metal with the SN additive were also realized under high capacity and current density (Figure b). The symmetrical cell cycled in BCE-SN maintains stable cycling for 432 h under harsh conditions of 3 mA/cm 2 and 3 mA h/cm 2 , while the control cell quickly fails within 150 h. As shown in Figure c and Table S1, the electrochemical performances of Li metal are significantly improved by the SN additive, superior to many recently reported works. − …”

Recent Progress on Multifunctional Electrolyte Additives for High‐Energy‐Density Li Batteries – A Review

“…One particular case is the so‐called leveler functional additive (4,6‐dimethyl‐2‐mercaptopyrimidine, DMP) that updated the Li + solvation structure and occupied the inner Helmholtz plane of the Li anode. The planar DMP molecular layer absorbed on the surface of the Li metal can suppress side reactions and modify the Li deposition behavior via steric hindrance, inducing homogeneous Li deposition, and the DMP leveler does not participate in the formation of the solid electrolyte interphase [111] . Therefore, in the future, novel additives that change the Li+ solvation structure will be different from traditional sacrificial additives, paving the way for exploring the direct structure‐performance relationship between additives and electrolyte.…”

Weak Solvation Chemistry in Fluorinated Nonflammable Electrolytes Achieves Stable Cycling in High-Voltage Lithium Metal Batteries

“…However, the conventional electrolyte is not well-suited for stable cycling in Li||NCM811. On the one hand, the performance and safety of cells are seriously affected by the decomposition and gas generation of ethylene carbonate (EC), − the deterioration of the cathode electrolyte interface (CEI) caused by the catalytic oxidizability of NCM811. − On the other hand, the incompatibility of conventional carbonate electrolytes with metallic lithium generates an unstable solid electrolyte interface (SEI), leading to dendrite growth and dead lithium generation, − which may result in internal short circuits, thermal runaway, or explosion …”

“…On the one hand, the performance and safety of cells are seriously affected by the decomposition and gas generation of ethylene carbonate (EC), 3−6 the deterioration of the cathode electrolyte interface (CEI) caused by the catalytic oxidizability of NCM811. 7−10 On the other hand, the incompatibility of conventional carbonate electrolytes with metallic lithium generates an unstable solid electrolyte interface (SEI), 11 leading to dendrite growth and dead lithium generation, 12−15 which may result in internal short circuits, thermal runaway, or explosion. 16 Much effort has been devoted to enhancing the tolerance of solvent 17,18 and regulating the solvation structure 15,19,20 to stabilize the electrode interface, in which one of the important strategy is to engage anions in Li + coordination to form an anion-derived robust and ion-transport-friendly interface.…”