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LiPF 6 -based carbonate electrolytes have been extensively employed in commercial Li-ion batteries, but they face numerous interfacial stability challenges while applicating in high-energy-density lithium-metal batteries (LMBs). Herein, this work proposes N-succinimidyl trifluoroacetate (NST) as a multifunctional electrolyte additive to address these challenges. NST additive could optimize Li + solvation structure and eliminate HF/H 2 O in the electrolyte, and preferentially be decomposed on the Ni-rich cathode (LiNi 0.8 Co 0.1 Mn 0.1 O 2 , NCM811) to generate LiF/Li 3 N-rich cathode-electrolyte interphase (CEI) with high conductivity. The synergistic effect reduces the electrolyte decomposition and inhibits the transition metal (TM) dissolution. Meanwhile, NST promotes the creation of solid electrolyte interphase (SEI) rich in inorganics on the Li metal anode (LMA), which restrains the growth of Li dendrites, minimizes parasitic reactions, and fosters rapid Li + transport. As a result, compared with the reference, the Li/LiNi 0.8 Co 0.1 Mn 0.1 O 2 cell with 1.0 wt.% NST exhibits higher capacity retention after 200 cycles at 1C (86.4% vs. 64.8%) and better rate performance, even at 9C. In the presence of NST, the Li/Li symmetrical cell shows a super-stable cyclic performance beyond 500 h at 0.5 mA cm -2 /0.5 mAh cm -2 . These unique features of NST are a promising solution for addressing the interfacial deterioration issue of high-capacity Ni-rich cathodes paired with LMA., (© 2024 Wiley‐VCH GmbH.)

Commercial Li-ion batteries use LiPF 6 -based carbonate electrolytes extensively, but there are many challenges associated with them, like dendritic Li growth and electrolyte decomposition, while supporting the aggressive chemical and electrochemical reactivity of lithium metal batteries (LMBs). This work proposes 1,1,1,3,3,3-hexafluoroisopropyl methacrylate (HFM) as a multifunctional electrolyte additive, constructing protective solid-/cathode-electrolyte interphases (SEI/CEI) on the surfaces for both lithium metal anode (LMA) and Ni-rich cathode to solve these challenges simultaneously. The highly fluorinated group (-CF 3 ) of the HFM molecule contributes to the construction of SEI/CEI films rich in LiF that offer excellent electronic insulation, high mechanical strength, and surface energy. Accordingly, the HFM-derived LiF-rich interphases can minimize the electrolyte-electrode parasitic reactions and promote uniform Li deposition. Also, the problems of LiNi 0.8 Co 0.1 Mn 0.1 O 2 particles' inner microcrack evolution and the growth of dendritic Li are adequately addressed. Consequently, the HFM additive enables a Li/LiNi 0.8 Co 0.1 Mn 0.1 O 2 cell with higher capacity retention after 200 cycles at 1 C than the cell with no additive (74.7 vs 52.8%), as well as a better rate performance, especially at 9 C. Furthermore, at 0.5/0.5 mAh cm -2 , the Li/Li symmetrical battery displays supersteadfast cyclic performance beyond 500 h when HFM is present. For high-performance LMBs, the HFM additive offers a straightforward, cost-effective route.

Li-metal batteries (LMBs), especially in combination with high-energy-density Ni-rich materials, exhibit great potential for next-generation rechargeable Li batteries. Nevertheless, poor cathode-/anode-electrolyte interfaces (CEI/SEI) and hydrofluoric acid (HF) attack pose a threat to the electrochemical and safety performances of LMBs due to aggressive chemical and electrochemical reactivities of high-Ni materials, metallic Li, and carbonate-based electrolytes with the LiPF 6 salt. Herein, the carbonate electrolyte based on LiPF 6 is formulated by a multifunctional electrolyte additive pentafluorophenyl trifluoroacetate (PFTF) to adapt the Li/LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) battery. It is theoretically illustrated and experimentally revealed that HF elimination and the LiF-rich CEI/SEI films are successfully achieved via the chemical and electrochemical reactions of the PFTF additive. Significantly, the LiF-rich SEI film with high electrochemical kinetics facilitates Li homogeneous deposition and prevents dendritic Li from forming and growing. Benefiting from the collaborative protection of PFTF on the interfacial modification and HF capture, the capacity ratio of the Li/NCM811 battery is boosted by 22.4%, and the cycling stability of the symmetrical Li cell is expanded over 500 h. This provided strategy is conducive to the achievement of high-performance LMBs with Ni-rich materials by optimizing the electrolyte formula.

Rechargeable lithium metal batteries (LMBs) with high energy densities can be achieved by coupling a lithium metal anode (LMA) and a LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) cathode. Nevertheless, Li dendrite growth on the LMA surface and structural collapse of the NCM811 material, closely tied with the fragile cathode-/solid-electrolyte interphases (CEI/SEI) and corrosive hydrogen fluoride (HF), seriously deteriorate their performances. Herein, trimethylsilyl trifluoroacetate (TMSTFA) as a multifunctional electrolyte additive is proposed for regulation of the CEI/SEI films and elimination of HF. For one thing, the TMSTFA-derived CEI film rich in C-O species is conductive to Li + transport and structural stability of NCM811 materials, and the TMSTFA-derived SEI film mainly consisting of inorganics (Li 2 CO 3 and LiF) and organics (C-O and O-C═O species) can significantly promote Li + homogeneous deposition and impede the Li dendrite growth. For another thing, the undesired reactions of the solvents and LiPF 6 salt are effectively retarded by the TMSTFA additive. Consequently, in the presence of TMSTFA, the capacity retention of Li/NCM811 cell is increased by 17% after 200 cycles at 1C, and the lifespan of symmetrical Li/Li cells is prolonged beyond 600 h at 0.5 mA cm -2 .