Rechargeable Lithium Metal Batteries Research Articles

Deciphering the effect of nucleation/growth kinetics on the morphology of Li plating/stripping on vertically aligned carbon nanofibers - A low-tortuosity 3-D nanostructured carbon host

Reversible lithium metal anodes (LMAs) are the holy grail for future rechargeable lithium metal batteries. Three-dimensional (3-D) conductive hosts have been extensively explored as an effective approach to suppressing dendrite formation and enabling reversible Li plating/stripping. However, the microscopic morphologies of Li plating and their correlation with the cell performance are not clear. Herein we unravel these issues using the vertically aligned carbon nanofiber (VACNF) array as a model 3-D conductive carbon host which has a well-defined vertical low-tortuosity structure allowing observation of the intrinsic Li morphologies infiltrated into the 3-D host. The VACNF array indeed provides much higher stability and reversibility for Li plating/stripping due to its high surface area and lithiophilic properties. We found that Li plating on both VACNF array and planar Cu electrodes follows the classical nucleation and growth model. Though the low plating current density (≤0.10 mA/cm2) provides better cycling stability consistent with the Sand’s equation, it forms sparse irregular grains stacked with dendrite-like long Li fibers. In contrast, the moderate to high plating current densities (1.0 − 5.0 mA/cm2) produce more uniform Li morphologies consisting of smaller micro-columns or micro-spheres. By decoupling the plating and stripping current densities, we unravel that the more uniform micro-columnar Li infiltrated in the VACNF array obtained at the moderate plating current density (∼1.0 mA/cm2) indeed exhibits the highest cycling performance. This provides new insights into the relationship between macroscopic electrochemical tests and microscopic Li morphologies, aiding in optimizing the performance of LMAs based on 3-D conductive hosts.

Advanced Electrolytes for Rechargeable Lithium Metal Batteries with High Safety and Cycling Stability

Advanced Electrolytes for Rechargeable Lithium Metal Batteries with High Safety and Cycling Stability

Interfacial solvation-structure regulation for stable Li metal anode by a desolvation coating technique

Rechargeable lithium (Li) metal batteries face challenges in achieving stable cycling due to the instability of the solid electrolyte interphase (SEI). The Li-ion solvation structure and its desolvation process are crucial for the formation of a stable SEI on Li metal anodes and improving Li plating/stripping kinetics. This research introduces an interfacial desolvation coating technique to actively modulate the Li-ion solvation structure at the Li metal interface and regulate the participation of the electrolyte solvent in SEI formation. Through experimental investigations conducted using a carbonate electrolyte with limited compatibility to Li metal, the optimized desolvation coating layer, composed of 12-crown-4 ether-modified silica materials, selectively displaces strongly coordinating solvents while simultaneously enriching weakly coordinating fluorinated solvents at the Li metal/electrolyte interface. This selective desolvation and enrichment effect reduce solvent participation to SEI and thus facilitate the formation of a LiF-dominant SEI with greatly reduced organic species on the Li metal surface, as conclusively verified through various characterization techniques including XPS, quantitative NMR, operando NMR, cryo-TEM, EELS, and EDS. The interfacial desolvation coating technique enables excellent rate cycling stability (i.e., 1C) of the Li metal anode and prolonged cycling life of the Li||LiCoO2 pouch cell in the conventional carbonate electrolyte (E/C 2.6 g/Ah), with 80% capacity retention after 333 cycles.

Three-dimensional copper current collector as an anode for rechargeable anode-less lithium-ion batteries

The formation of dendrites presents a significant challenge that hampers the performance of lithium metal batteries, leading to rapid capacity degradation, low coulombic efficiency, and potential short circuits. In this regard we have engineered a rechargeable lithium metal battery without a conventional anode – lithium, employing commercially available LiNi1/3Co1/3Mn1/3O2 as a cathode and enhanced three-dimensional copper foam current collector as an anode. The modification of the three-dimensional copper foam current collector with gold effectively reduced the local current density while providing a substantial surface area for lithium deposition. Moreover, our approach incorporates a blend of salts, namely lithium bis(trifluoromethanesulfonyl)imide and lithium difluoro(oxalato)borat, resulting in an impressive reversible capacity of 100 mAh g−1 with an outstanding coulombic efficiency of 99.9% after 50 cycles. These discoveries hold particular significance in the advancement of next-generation energy storage systems characterized by high energy density and immunity to dendrite formation.

Trilithium salt of tetrahydroxyanthraquinone: A high-voltage and stable organic cathode material for rechargeable lithium metal and lithium-ion batteries

Organic cathode materials (OCMs) have drawn considerable attention for lithium batteries but suffer from unfavorable dissolution problem and thus inferior cycling performance. Salification is a simple approach to restrain the dissolution but most reported lithium-salt-type OCMs are still unable to achieve good cycling stability due to poorly conjugated and/or asymmetric structure. Herein, we report a novel air-stable, largely conjugated, and symmetric organic lithium salt synthesized from 1,4,5,8-tetrahydroxyanthraquinone (THAQ), namely Li3THAQ. It possesses a layered crystalline structure with large interlayer spacings, which is relatively stable in the reversible conversion between Li4THAQ and Li2THAQ. Benefiting from this, Li3THAQ exhibits exceptional electrochemical performance within 2.0–3.6 V, including high reversible capacity (192 mAh g−1), high discharge potential (2.93 V vs. Li+/Li), high rate capability (75 % capacity retention at 5000 mAh g−1 vs. 50 mAh g−1), and high cycling stability (95 % capacity retention after 500 cycles). Additionally, it can be also matched with natural graphite anode to construct a Li-ion full-cell, which was rarely reported for OCMs. In brief, Li3THAQ shows great advantages in structure stability, electrochemical performance, and practicability compared to its counterparts, and the in-depth mechanism understanding provides important insights into the development of lithium-salt-type OCMs.

Solvation and Interfacial Chemistry in Ionic Liquid Based Electrolytes toward Rechargeable Lithium-metal Batteries

Rechargeable lithium metal batteries (LMBs) are highly promising technologies for high-energy-density storage systems due to the low electrochemical potential and high theoretical capacity of lithium metal anode. The electrolyte plays...

Design of sulfonimide anions for rechargeable lithium batteries.

Sulfonimide salts are considered as promising electrolyte materials in the construction of high-performant rechargeable lithium-ion batteries (LIBs) and lithium metal batteries (LMBs), owing to their delocalized negative charges, superior structural flexibility, and decent thermal/chemical stability. In this work, a historical overview of the development of sulfonimide anions in the field of electrolyte materials is presented, and the unique features of sulfonimide anions are discussed, in comparison with some popular anions [e.g., hexafluorophosphate anion (PF6-)] being employed for batteries. The key advances in the design of sulfonimide salts as electrolyte materials are scrutinized, encompassing their use in nonaqueous liquid electrolytes, ionic liquid electrolytes, and solid polymer electrolytes. Based on the existing reports and our experiences in this domain, possible research directions related to further improvement of sulfonimide-based electrolytes are highlighted. Besides demonstrating the status quo and research progress, this work also expands the structural design toolkit of sulfonimide-based electrolytes, which may accelerate the development and realization of sulfonimide anion-based electrolytes in practical LIBs/LMBs and simultaneously give new impetus to other kinds of rechargeable battery technologies (e.g., sodium and potassium batteries).

Performance evaluation of lithium metal rechargeable batteries with a lithium excess cation-disordered rocksalt based positive electrode under high mass loading and lean electrolyte conditions

Operation of 500 W h kg−1 class rechargeable batteries was demonstrated. Non-destructive XCT analysis revealed volume expansion of the lithium metal electrode as the primary reason for the capacity fading.

Lithium Silicates as an Artificial SEI for Rechargeable Lithium Metal Batteries

The major motivation of replacing lithium-ion batteries with lithium metal batteries is to obtain higher energy density by adopting the metallic lithium anode (3860 mAh g-1, theoretically), which means they can store more energy in the same volume or weight. One of the main challenges of rechargeable lithium metal batteries is the formation of lithium dendrites during the charging process.1 Lithium dendrites are tiny needle-like structures that can grow from the surface of the lithium metal electrode and penetrate the separator, causing battery short-circuiting. This can lead to safety issues, including the potential for fire or explosion. Another challenge is the formation of solid-electrolyte interface (SEI) on the surface of the lithium metal electrode, which can reduce the battery's efficiency and cycle life.2 The SEI layer can also lead to the formation of inactive lithium and increase the risk of dendrite growth.In the present work, various lithium silicates have been synthesized to be implemented as the artificial SEI layer via a facile dry coating method.3,4 The lithium silicate coating acts as a protective barrier that prevents direct contact between the lithium metal and the electrolyte, which may cause undesirable side reactions and reduce the efficiency and lifespan of the battery.4 The lithium silicate-based artificial SEI layer improves the stability and efficiency of lithium metal batteries by reducing unwanted surface reactions, improving ion transport kinetics, and protecting the lithium metal anode from mechanical deformation and unstable SEI formation during extended cycling. This laminated lithium anode structure could be an effective design for the future development of long-cycle-life lithium metal batteries. F. Wu et al., Energy Storage Materials, 15, 148–170 (2018).X.-B. Cheng et al., Adv. Sci., 3, 1500213 (2016).A. Bhat, P. Sireesha, Y. Chen, and Y. Su, ChemElectroChem, 9 (2022) https://onlinelibrary.wiley.com/doi/10.1002/celc.202200772.Y.-S. Su, K.-C. Hsiao, P. Sireesha, and J.-Y. Huang, Batteries, 8, 2 (2022). Figure 1

Enhancing Performance of Anode-Free Li-Metal Batteries

Because of their higher energy density, compared to lithium-ion batteries, rechargeable lithium-metalbatteries (LMB) have been considered one of the most attractive next-generation energy-storagesystems (ESS). A promising approach to improving LMB performance, that has gained interest inrecent years, is the use of anode-free lithium-metal batteries (AFLMB). Such battery configurationenables elimination of the problem of using excessive amounts of lithium in LMBs, hence increasingthe specific energy of the battery. This work explores the beneficial effects of integrating metal-oxidenanoparticles (MONPs) into the liquid electrolyte of AFLMB. It was found that the addition of lowconcentrations of MONPs significantly improves coulombic efficiency (CE), capacity retention (CR)and the Solid-Electrolyte-Interphase (SEI) properties. SEM images revealed a smoother lithiummorphology for MONPs cells and XPS analysis showed great differences in the SEI composition. Theresistance of the cell components, extracted via electrochemical impedance spectroscopy (EIS), hasbeen significantly lowered due to the addition of MONPs. The performance of the AFLMB, withoutMONPs, was 97.1% CE and CR of 70% within 12 cycles, while cells with 0.5% SnO2 , 1% Al2O3 and1% TiO2 was 99.1%, 98.8% and 99.4% CE, and CR of 70% within 39, 38 and 36 cycles, respectively.Combinations of two MONPs resulted in 99.9% CE, which is among the highest found in the literaturefor AFLMB.

(Electrodeposition Division Research Award) Electrodeposition as an Enabling Technology in Future Semiconductors, Energy Storage, and Sustainable Metal Production

Electrodeposition is a truly fascinating process. On the one hand, it is highly complex as it entails a myriad of intricately intertwined physiochemical events (transport, kinetics, nucleation, growth, to name a few). Despite this, to a practitioner, electrodeposition can be remarkably simple, easy to control, and safe to operate. Electrodeposition is also extremely versatile, enabling fabrication of various materials (metals, alloys, semiconductors), fabrication onto conductive or resistive substrates, facilitating intricate pattern formation, and providing selectivity in growth. These advantages make electrodeposition a process of choice in a broad range of technologically-important applications: batteries, semiconductor devices, electrometallurgy, and others.1-3 Morphology control is crucial in the industrial practice of electrodeposition. During metallization of nano-scale interconnects in advanced semiconductor devices, metal deposition with near atomic precision is required.1 Similarly, during operation of lithium metal rechargeable batteries, electrodeposition must be controlled to avoid dendritic growth during battery charging.2 Electrodeposition processes in high temperature molten salts, such as those used for electrowinning rare-earth metals, favor spongy deposits which can manifest in entrapment of impurities – here too, controlling morphology is central to overall electrowinning efficacy.3 In this talk, I will discuss and demonstrate how unprecedented morphology control can be achieved in electrodeposition. Such control leverages fundamental understanding of the electrochemical processes at the electrode-electrolyte interface. Specifically, by regulating the electrolyte properties, applied current or potential waveforms, and by employing ‘additives’, the diffusion-reaction processes can be controlled yielding desirable electrodeposit morphologies. Such design of electrodeposition processes is considerably aided by mathematical modeling. I will provide a few examples of how quantitative modeling enables improved process designs in aforementioned applications.During my odyssey in electrodeposition since 2001, I have been fortunate to have exceptional colleagues, collaborators, sponsors, mentors, students and friends, who have made this journey enjoyable and enriching. I am also very thankful for my affiliation to the Electrochemical Society and its electrodeposition division. In my talk, I will provide a few perspectives and anecdotes on how the ECS community has positively impacted me personally and professionally.

Operando Ultrasonic Characterization of Lithium Metal Batteries

Significant progress has been made in understanding and engineering rechargeable lithium metal batteries. Here, I discuss ultrasound as a technique to probe cell-level dynamics for lithium metal batteries in liquid and solid electrolytes. Multiple imaging modalities provide information on physical properties of lithium metal cells, including electrode wetting and consumption, lithium microstructural change and gas evolution. In a first case study, I discuss correlations between ultrasonic transmission signals and lithium microstructure size in liquid electrolytes, as a function of stack pressure and temperature. Anode and cathode effects can be decoupled. In a second case, acoustic amplitude is used to detect void formation in solid-state electrolytes. Third, ultrasound is used to characterize the formation process for various anode-free cells, where the improved chemical and electrochemical stability of localized ether electrolytes is correlated with decreased rates of cell swelling and minimal gas formation. Ultrasonic characterization and imaging is a portable and non-invasive means of probing commercial lithium metal cells after manufacturing, during use, or at the end-of-service.

Polymer/ceramic gel electrolyte with in-situ interface forming enhances the performance of lithium metal batteries

With the introduction of solid-state electrolytes, solid-state lithium-metal batteries face enormous challenges of low electrolyte ion conductivity and high electrode electrolyte interface impedance. Here, we adopt a strategy of combining rigidity and flexibility to design a polymer/ceramic composite gel electrolyte films (CSEs) with a fiber like structure and local defect channels for rechargeable lithium metal batteries. The CSEs synthesized in situ on LiFePO4 electrode by ultraviolet (UV) curing method, which combines the high ionic conductivity of Li6.5La3Zr1.5Ta0.5O12 (LLZTO) ceramic particles and the flexibility of poly(vinylidene fluoride-co -hexafluoropropylene) (PVDF-HFP) polymer electrolyte. In order to investigate the effect of crosslinker on the performance of electrolytes, 1,6-hexanediol diacrylate (HDDA) and ethoxylated trimethylolpropane triacrylate (ETPTA) were used in the preparation process of ultraviolet (UV) curing method. A comparison was made between gel electrolytes using HDDA and ETPTA crosslinkers, electrolytes containing ETPTA exhibited good overall performance in terms of ion conductivity (7.89 × 10−4 S cm−1), Li+ transference number (0.63), glass transition temperature (−26.2 °C), good flexibility, thermal stability. As a result, the assembled LiFePO4||electrolytes containing ETPTA||Li batteries exhibit excellent the first discharge capacity (151.9 mAh g−1 with 0.1C), good rate performance and its capacity retention rate is 93.1 % after 300 cycles. This study provides a new strategy for the rational design and process method of high-performance CSEs for rechargeable solid lithium metal batteries.

A review of low-temperature lithium metal battery research

Rechargeable lithium metal batteries (LMBs) are one of the promising energy storage systems, which have the advantage of a high theoretical specific capacity of 3860 mAh/g and a low reduction potential of −3.04 V vs. SHE. With the development of society, the large use of batteries in low-temperature areas is inevitable. Typically, batteries fail at low temperatures, especially with temperatures below −20 °C, but the research on low-temperature behavior is limited. According to previous research on low-temperature lithium metal batteries, the main challenge is to suppress serious dendrite growth at low temperatures. Here, we reviewed the state-of-art progress of low-temperature LMBs, including protect layer, three-dimensional collector, and electrolyte. We found that most of the research works relate to electrolytes because a novel electrolyte can easily solvate, contribute to ion transportation, and be conducive to solid electrolyte interfacial (SEI) film formation, which can accelerate the kinetics at low temperatures, thus suppressing the serious dendrite growth at low temperatures. We propose that solid electrolytes can suppress the dendrite growth of LMBs at low temperatures effectively because solid electrolytes are not easy to be pierced.

Construction and performance of PVDF-HFP-matrix comb-like gel copolymer electrolyte for high-performance quasi-solid-state lithium-metal batteries

Rechargeable lithium metal batteries (LMBs) have encountered bottlenecks in energy density, durability, and safety issues. Designing functional polymer electrolytes has been considered as an effective way to develop high-performance of LMBs. In this study, PVDF-HFP-matrix polymeric electrolytes blended with copolymer P(MMA-co-PEGMEMA) (PPxPy) via a simple one-pot free-radical polymerization are successfully designed and prepared. It has been found that the PPxPy electrolytes can construct different comb-like networks via systematically tuning monomer ratios. The tailored PP5P5 gel electrolyte exhibited high ionic conductivity of 0.74 × 10−3 S cm−1 at room temperature (RT), an enlarged electrochemical window up to 4.77 V, high lithium-ion transference number tLi+ of 0.65, and good mechanical property with Yang's modulus up to 131 MPa. Benefited from these good properties, the Li||LiFePO4 batteries assembled with PP5P5 gel electrolyte achieved an exceptional discharge capacity of 152 mAh g−1 with nearly 100 % Coulombic efficiency after 150 cycles at 1C. Furthermore, the Li|PP5P5|NCM811 cell exhibits excellent reversible specific capacity of 188 mAh g−1 at 0.1C. Consequently, it can be anticipated the as-prepared functional polymer structure to provide a reliable method for the preparation of polymer electrolytes in quasi-solid-state batteries with high-energy-density.

Carbonate-Based Localized High Concentrated Electrolyte for Long-Cycle-Life Lithium Metal Batteries

Rechargeable Lithium Metal Batteries (LMBs) using high-voltage cathodes can deliver the highest possible energy densities among all electro-chemistries. However, the notorious reactivity of metallic lithium as well as the catalytic nature of the cathode materials largely prevent their practical application. Here, we demonstrate a formulated carbonate-based high concentrated electrolyte with LiPF6 that supports the most commercial aggressive and high-voltage cathode to realize a highly stable Li metal full-cell with limited metallic Li. The formation of stable Li2O/LiF-rich solid electrolyte interface (SEI) layers afforded stable operations of resultant LMBs under practical working conditions. Our electrolyte contributes to both high efficiency of 99.5% for Li||Cu half cell and ~100% for lithium full cells based on 4.3 V Ni-rich LiNi0.8Mn0.1Co0.1O2 (NMC811) cathodes. Notably, at a loading of 4.0 mAh.cm−2, our full cells showed a capacity retention of ~80% over 280 cycles at lean electrolyte condition of 5 μL.mAh-1. The effective stabilization that inhibited the aggressive chemistries at extreme potentials in LMBs upon practical conditions by our electrolyte was determined to be the formation of the dense, inorganic-rich interphase.

Nanospinbar-Assisted Convective Ionic Transfer Toward Dendrite-Free Li Metal Batteries

Building high-energy-density batteries with Li-metal anodes (LMAs) featuring ultrahigh specific capacity (3860 mAh g−1) and low working voltage (−3.04 V vs. SHE) have been revisited to surpass the energy density limit of current Li-ion batteries. For instance, a successful transition from conventional graphite (372 mAh g–1) to ultrathin LMAs can deliver higher cell energies (over 500 Wh kg–1). Nonetheless, Li electrodeposition is challenging due to the dendrite formation and random growth. Extensive Li dendrite growth can enlarge the active surface area where side reactions occur, thereby severely deteriorating the Li surface and depleting the electrolyte, leading to poor cycling stability. Eventually, the Li dendrite tips can pierce the separator, causing cell short-circuiting, thereby increasing the safety risk. This is a major hurdle that must be overcome prior to commercialization. Therefore, inhibiting uneven dendritic Li plating is essential for safe and stable cycling of rechargeable lithium metal batteries (LMBs).Inhibiting uneven, dendritic Li electroplating is crucial for the safe and stable cycling of LMBs. Homogeneous, fast Li+ transport toward the Li surface is required for uniform, dendrite-free deposition. Electrodeposition strongly depends on the mass transfer of the ionic species. In a diffusion-limited regime, such as higher currents and lack of convection, inherently limited Li+ diffusion causes a strong concentration gradient or even total Li+ depletion. Moreover, traditional ionic transport of static liquid electrolytes involving electromigration and molecular diffusion can trigger a greater disparity in Li concentration over the Li surface, leading to irregular dendrite growth.This study presents a microturbulence-assisted convective Li+ transfer for suppressing dendrite growth using a magnetic nanospinbar (NSB)-dispersed colloidal electrolyte. We synthesized an ultrahigh-aspect-ratio NSB consisting of a paramagnetic Fe3O4 nanoparticle array and a silica outer coating. Manipulating the external electromagnetic force can remotely control the rotation of individual NSBs without dispersion failure, thereby generating a microturbulence flow inside the cell. Regardless of the electrolyte composition, rotating the NSB can reduce the Li+ diffusion layer thickness from the bulk and evenly redistribute Li+ flux over the Li surface, thereby suppressing Li dendrite growth. The NSB-dispersed electrolyte with advanced salt/solvent compositions demonstrated stable cycling of LMBs over 600 cycles at 70% capacity retention, thereby outperforming the NSB-free cell.Figure. 1. Concept of convective Li+ transfer assisted by remote NSB stirring. Apart from stagnant electrolytes, magnetic-field-responsive NSB dispersed in the liquid electrolyte can redistribute Li+ flux near LMA through remote stirring, enabling facile, homogenous Li+ transfer and thereby leading to uniform, dendrite-free Li electroplating Figure 1

Flash Point of Gel-Polymer Electrolytes: Effect of the Molecular Interaction between Nitrile (HNBR) and Carbonyl (PC)

Gel-polymer electrolytes are receiving increasing attention as they compromise between a good ionic conductivity (10-3S/cm) [1, 2] and good safety features. The solvent trapped into the polymeric matrix increases the ionic conductivity while the polymeric matrix enhances safety due to its mechanical strength repressing dendrite growth [3, 4]. Gel polymer electrolytes are almost universally presumed to be less flammable than current commercialize battery (organic liquid electrolyte) [5, 6]. However, there is no universal test to compare the flammability of a liquid and the flammability of a gel.Our work focuses on the flash point measurement of gel-polymer electrolytes. The flash point temperature is a standardized test and is one of the top experiments to measure flammability [7]. The Flash point temperature is well studied for liquid electrolytes [7, 8] but had never been conducted for gel-polymers. We developed a method to analyze the flash point of gel-polymer electrolytes by pairing the closed-cup flash point tester with a thermal imaging camera. This new apparatus was used it to analyze a promising system: HNBR with different grade of nitrile doped with PC. The goal is to find the relation between the flash point and the nitrile contains in the polymeric matrices.Our research sheds light on the effect of molecular interactions between the nitrile of HNBR and the carbonyl of PC on the flammability of the overall gel-polymer electrolyte with FT-IR. The study has also been conducted adding a lithium salt (LiTFSI) to be representative of real battery application. Agrawal, R.C. and G.P. Pandey, Solid polymer electrolytes: materials designing and all-solid-state battery applications: an overview. J. Phys. D: Appl. Phys., 2008. 41(22): p. 223001-223019.Cheng, X., et al., Gel Polymer Electrolytes for Electrochemical Energy Storage. Advanced Energy Materials, 2018. 8(7).Hassouna, J. and B. Scrosati, Review—Advances in Anode and Electrolyte Materials for the Progress of Lithium-Ion and beyond Lithium-Ion Batteries. Journal of The Electrochemical Society, 2015. 162 p. A2582-A2588.Ren, W., et al., Advanced gel polymer electrolytes for safe and durable lithium metal batteries: Challenges, strategies, and perspectives. Energy Storage Materials, 2021. 34: p. 515-535.Castillo, J., et al., Safe, Flexible, and High-Performing Gel-Polymer Electrolyte for Rechargeable Lithium Metal Batteries. Chemistry of Materials, 2021. 33(22): p. 8812-8821.Li, Q., et al., Progress in electrolytes for rechargeable Li-based batteries and beyond. Green Energy & Environment, 2016. 1(1): p. 18-42.Liu, X.S. and Z.Y. Liu, Research Progress on Flash Point Prediction. Journal of Chemical and Engineering Data, 2010. 55(9): p. 2943-2950.Catoire, L., S. Paulmier, and V. Naudet, Experimental determination and estimation of closed cup flash points of mixtures of flammable solvents. Process Safety Progress, 2006. 25(1): p. 33-39.

Lithium Metal Anode Using Fluorination on Iron Powder for Lithium Metal Batteries

High-energy-density batteries have been gaining considerable attentions in renewable energy, and Li metal anodes are potential candidates for developing such batteries. Therefore, many attempts were carried out to find alternative ways to use Li by mixing it with tiny metal powders or impregnating the porous media. However, most materials used in battery fabrication are lithiophobic to molten Li; hence, infusion of Li into porous structures or powders with an intrinsically lithiophobic surface presents challenges in developing Li metal batteries. Optimizing and improving molten Li's wettability is one approach to address this. Herein, we propose an efficient and straightforward direct fluorination method for achieving an ultra-lithiophilic fluoride layer on the surface of the Fe powder. Fluorination of Fe powders resulted in a remarkable increase in the wettability of molten Li by a growth of Fe-F layer on the surface of Fe powder. This layer was lithiophilic and showed high wettability. Moreover, an anode prepared using fluorinated Fe-Li metal showed no evidence of short circuits or dendrite formation after the cycle test at 0.1 and 0.2 mA cm-2. In contrast, a pure Li anode and pristine Fe powder showed unstable charge-discharge characteristics in cycle tests. The proposed fluorination is the most practical and straightforward method among those reported. Thus, the proposed method will further develop rechargeable lithium-metal battery technology.

Fluorinated Nonflammable In Situ Gel Polymer Electrolyte for High-Voltage Lithium Metal Batteries.

Rechargeable lithium metal batteries (LMBs) offer excellent opportunities for applications requiring high-energy-density battery systems. So far, it has received a lot of interest in pairing higher-energy-density high-voltage nickel-rich cathodes. Here, fluorinated solvents were used instead of the usual carbonate solvents to prepare gel polymer electrolytes (FGPE) by in situ polymerization of polymers introducing the fluorine-containing groups. Theoretically and experimentally, FGPE has proven to be ultra-compatible with the lithium metal anode and LiNi0.8Co0.1Mn0.1O2 cathode. A stable plating/stripping process of over 2000 h can be achieved for symmetrical lithium cells using FGPE. The Li||FGPE||NCM811 cell has a longer cycle life at a high voltage (4.5 V). In addition, the zero self-extinguishing time indicates that the FGPE has sufficient safety. In summary, the design of this electrolyte provides ideas to improve the safety and energy density of LMBs.