Design of Non‐Incendive High‐Voltage Liquid Electrolyte Formulation for Safe Lithium‐Ion Batteries

Rechargeable lithium metal batteries (LMBs) with high energy densities can be achieved by coupling a lithium metal anode (LMA) and a LiNi0.8Co0.1Mn0.1O2 (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 (Li2CO3 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 LiPF6 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.

Section: Resultsmentioning

confidence: 85%

Multifunctional Electrolyte Additive for Bi-electrode Interphase Regulation and Electrolyte Stabilization in Li/LiNi_0.8Co_0.1Mn_0.1O₂ Batteries

Jiang

Yin

et al. 2022

“…Clearly, three redox peak pairs at 3.9, 4.0, and 4.2 V are detected, respectively, representing the phase inversion of H1+M, M +H2, and H2+H3 (H and M are hexagonal and monoclinic phases, respectively) of the NCM811 material. 40 With the PFTF additive, the potential difference (ΔV) of the H1+M phase is 0.18 V in the initial cycle (Figure 2d), which is lower than 0.24 V in the blank electrolyte. It is suggested that the PFTF-derived CEI film possesses a rapid Li + transport rate.…”

Section: Resultsmentioning

confidence: 92%

“…In addition, the impact of PFTF on the procedure of Li + intercalation/deintercalation is investigated by analyzing the CV curves of Li/NCM811 batteries (Figure d,e). Clearly, three redox peak pairs at 3.9, 4.0, and 4.2 V are detected, respectively, representing the phase inversion of H1+M, M+H2, and H2+H3 (H and M are hexagonal and monoclinic phases, respectively) of the NCM811 material . With the PFTF additive, the potential difference (Δ V ) of the H1+M phase is 0.18 V in the initial cycle (Figure d), which is lower than 0.24 V in the blank electrolyte.…”

Section: Resultsmentioning

confidence: 96%

LiF-Rich Interfaces and HF Elimination Achieved by a Multifunctional Additive Enable High-Performance Li/LiNi_0.8Co_0.1Mn_0.1O₂ Batteries

Lei

Yin

et al. 2023

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 LiPF6 salt. Herein, the carbonate electrolyte based on LiPF6 is formulated by a multifunctional electrolyte additive pentafluorophenyl trifluoroacetate (PFTF) to adapt the Li/LiNi0.8Co0.1Mn0.1O2 (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.

“…In both the first (first) and second (second) cycles, three sets of redox couples at 3.9, 4.0, and 4.2 V, respectively, which reflect phase inversion between H1+M, M+H2, and H2+H3, are present in cells with various electrolytes (hexagonal and monoclinic phases are H and M, respectively). 44 Notedly, when the H1+M phase inversion occurs in the first cycle, the potential difference (ΔV) is 0.305 V in the HFM-added electrolyte lower than 0.528 V in the baseline, indicating that HFM additive helps to improve Li + reaction reversibility during the initial Li + de/intercalation process. At the second cycle, a significantly decreased ΔV of 0.041 V in the HFM-containing electrolyte can be observed and it is also much lower than that in the reference (0.144 V).…”

Section: Resultsmentioning

confidence: 99%

“…Examining how HFM affects the kinetic behaviors during the Li + delithiation/intercalation process, the CV measurements are conducted on Li/NCM811 batteries with and without HFM (Figure d,e). In both the first (first) and second (second) cycles, three sets of redox couples at 3.9, 4.0, and 4.2 V, respectively, which reflect phase inversion between H1+M, M+H2, and H2+H3, are present in cells with various electrolytes (hexagonal and monoclinic phases are H and M, respectively) . Notedly, when the H1+M phase inversion occurs in the first cycle, the potential difference (Δ V ) is 0.305 V in the HFM-added electrolyte lower than 0.528 V in the baseline, indicating that HFM additive helps to improve Li + reaction reversibility during the initial Li + de/intercalation process.…”

Section: Resultsmentioning

confidence: 99%

LiF-Rich Electrode–Electrolyte Interfaces Enabled by Bifunctional Electrolyte Additive to Achieve High-Performance Li/LiNi_0.8Co_0.1Mn_0.1O₂ Batteries

Lei,

Xu,

Yin

et al. 2023

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.