LiF/Li3N-Rich Electrode-Electrolyte Interfaces Enabled by Multi-Functional Electrolyte Additive to Achieve High-Performance Li/LiNi0.8Co0.1Mn0.1O2 Batteries.

LiPF6-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/H2O in the electrolyte, and preferentially be decomposed on the Ni-rich cathode (LiNi0.8Co0.1Mn0.1O2, NCM811) to generate LiF/Li3N-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/LiNi0.8Co0.1Mn0.1O2 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.

LiF-Rich Electrode-Electrolyte Interfaces Enabled by Bifunctional Electrolyte Additive to Achieve High-Performance Li/LiNi0.8Co0.1Mn0.1O2 Batteries.

Commercial Li-ion batteries use LiPF6-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 (-CF3) 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 LiNi0.8Co0.1Mn0.1O2 particles' inner microcrack evolution and the growth of dendritic Li are adequately addressed. Consequently, the HFM additive enables a Li/LiNi0.8Co0.1Mn0.1O2 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.

Poly-1,3-dioxolane anchoring graphitic carbon nitride to achieve high-energy-density solid-state Li metal batteries.

Solid-state Li metal batteries (SSLMBs) are promising solutions for the next-generation energy storage devices with high energy densities and safety. Accordingly, the advanced solid-state electrolytes are further needed to address the challenges-low ionic conductivity, poor interfacial compatibility and uncontrollably Li dendrites, boosting the electrochemical and safety performances of SSLMBs. Herein, a "flexible and rigid" strategy is proposed to enhance the electrochemical and mechanical properties of polyethylene oxide (PEO)-based electrolytes. Specifically, the flexible poly-1,3-dioxolane (poly-DOL) and rigid graphitic carbon nitride (g-C3N4) are coordinated by a coupling reaction to prepare g-C3N4-poly-DOL, which is further employed as the filler for the PEO matrix to fabricate a composite polymer electrolyte g-C3N4-pDOL-PEO. The flexible poly-DOL and rigid g-C3N4 together endow the PEO-based electrolyte with good interfacial stability, high ion-conductivity and strong mechanical strength. Consequently, the Li/g-C3N4-pDOL-PEO/LiFePO4 cell delivers high cyclability with a capacity retention ratio of 89.7 % after 150 cycles and an average Coulombic efficiency over 99.9 %, and, the Li/g-C3N4-pDOL-PEO/Li cell can stably cycle beyond 300 h at 0.2 mAh cm-2 with small polarization (13 mV). The "flexible and rigid" strategy coupling the polymer with the filler provides an effective electrolyte design for high-performance SSLMBs.

High-performance Li/LiNi0.8Co0.1Mn0.1O2 batteries enabled by optimizing carbonate-based electrolyte and electrode interphases via triallylamine additive.

Lithium (Li) metal batteries (LMBs), paired with high-energy-density cathode materials, are promising to meet the ever-increasing demand for electric energy storage. Unfortunately, the inferior electrode-electrolyte interfaces and hydrogen fluoride (HF) corrosion in the state-of-art carbonate-based electrolytes lead to dendritic Li growth and unsatisfactory cyclability of LMBs. Herein, a multifunctional electrolyte additive triallylamine (TAA) is proposed to circumvent those issues. The TAA molecule exhibits strong nucleophilicity and contains three unsaturated carbon-carbon double bonds, the former for HF elimination, the later for in-situ passivation of aggressive electrodes. As evidenced theoretically and experimentally, the preferential oxidation and reduction of carbon-carbon double bonds enable the successful regulation of components and morphologies of electrode interfaces, as well as the binding affinity to HF effectively blocks HF corrosion. In particular, the TAA-derived electrode interfaces are packed with abundant lithium-containing inorganics and oligomers, which diminishes undesired parasitic reactions of electrolyte and detrimental degradation of electrode materials. When using the TAA-containing electrolyte, the cell configuration with Li anode and nickel-rich layered oxide cathode and symmetrical Li cell deliver remarkably enhanced electrochemical performance with regard to the additive-free cell. The TAA additive shows great potential in advancing the development of carbonate-based electrolytes in LMBs.

Halloysite nanotubes modified poly(vinylidenefluoride-co-hexafluoropropylene)-based polymer-in-salt electrolyte to achieve high-performance Li metal batteries.

Solid-state Li metal batteries (SSLMBs) are one of the most promising energy storage devices, as they offer high energy density and improved safety compared to conventional Li-ion batteries. However, the large-scale application of SSLMBs at room temperature is restricted by the main challenges such as low ionic conductivity and poor cyclic performance. Herein, a composed polymer-in-salt electrolyte (CPISE) is fabricated, which is composed of polyvinylidene vinylidene hexafluoropropene (PVDF-HFP) and high-concentration Li bis(trifluoromethanesulphonyl)imide (LiTFSI), reinforced with natural halloysite nanotubes (HNTs). The High concentration of LiTFSI and introduced HNTs synergized with PVDF-HFP to provide more various Li+ transport pathways. Additionally, the backbones of the uniform dispersion of HNTs in the CPISE effectively boosts the physicochemical nature of the CPISE. As a result, the prepared CPISE achieves excellent mechanical strength, high ionic conductivity (1.23*10-3 S cm-1) and high Li+ transference number (0.57) at room temperature. Consequently, in existence of the CPISE, the Li symmetric cell cycles stably beyond 800 h at 0.15 mA cm-2 and the LiFePO4/Li cell displays impressive cyclic performance with capacity retention of 79% after 1000 cycles at 30 °C. Furthermore, the superiority and the functional mechanism of the CPISE are discovered in detail. This work provides a promising strategy for the development of high-performance SSMLBs at room temperature.

LiF-Rich Interfaces and HF Elimination Achieved by a Multifunctional Additive Enable High-Performance Li/LiNi0.8Co0.1Mn0.1O2 Batteries.

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.

Zeolitic imidazolate framework upgrading polyethylene oxide composite electrolyte for high-energy solid-state lithium batteries.

The energy density of solid-state lithium batteries (SSLBs) has been primarily limited by the low ionic conductivity of solid electrolyte and poor interface compatibility between electrolyte and electrodes. Herein, a multifunctional composite solid polymer electrolyte (CSPE) based on polyethylene oxide (PEO) embedded with zeolitic imidazolate framework-8 deposited on carboxymethyl cellulose (ZIF@CMC) is reported. The ZIF@CMC interpenetrated in PEO matrix creates a continuous Li+ conductive network by combining Zn2+ in ZIF with the unsaturated group in PEO to boost the Li+ transport through the PEO chain segment. On the other hand, Zn2+ can bond with bis(trifluoromethane)sulfonimide (TFSI-) anion, thus promoting the dissolution of lithium salt and releasing more lithium ions. This CSPE demonstrates brilliant electrochemical properties, including a high ionic conductivity of 1.8 × 10-4 S cm-1 at room temperature and a wide electrochemical window of 5 V. The integrated LiFePO4/CSPE/Li batteries using 20 wt.% ZIF-8@CMC show excellent reversible capacity of 145.6 mAh g-1 with a capacity retention of 88.95 % after 200 cycles at a high current density of 0.5C. Our study proposed a novel and effective strategy to construct high-performance solid-state lithium batteries.

Multifunctional Electrolyte Additive for Bi-electrode Interphase Regulation and Electrolyte Stabilization in Li/LiNi0.8Co0.1Mn0.1O2 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.

Benzoic Anhydride as a Bifunctional Electrolyte Additive for Hydrogen Fluoride Capture and Robust Film Construction over High-Voltage Li-Ion Batteries.

High-voltage LiNi0.8 Co0.1 Mn0.1 O2 (NCM811)-based Li-ion batteries (LIBs) with enhanced performance can be achieved by properly tailoring the electrolyte systems. Benzoic anhydride (BA) was proposed here as a promising bifunctional electrolyte additive that can not only construct a robust cathode-electrolyte interface (CEI) film on the electrode surface but also capture HF/H2 O in the electrolyte effectively. Compared to the cell without the BA additive, the capacity of Li/NCM811 half-cell with 1.0 wt % BA was increased from 128.5 to 149.6 mAh g-1 after 200 cycles at 1 C between 3.0 and 4.3 V. Even at a higher cut-off voltage of 4.5 V, the BA-containing Li/NCM811 half-cell delivered a capacity retention of 69 % after 200 cycles, much higher than that of the half-cell without the additive (56 %). Both theoretical calculation and experimental results verified that the BA additive could be preferentially oxidized to form a stable interface film with high conductivity that protected the NCM811 cathode and suppressed the decomposition of the electrolyte.