Development Of Lithium Metal Batteries Research Articles

A Highly Stable and Non-Flammable Deep Eutectic Electrolyte for High-Performance Lithium Metal Batteries.

Deep eutectic electrolytes (DEEs) are regarded as one of the next-generation electrolytes to promote the development of lithium metal batteries (LMBs) due to their unparalleled advantages compared to both liquid electrolytes and solid electrolytes. However, its application in LMBs is limited by electrode interface compatibility. Here, we introduce a novel solid dimethylmalononitrile (DMMN)-based DEE induced by N coordination to dissociate LiTFSI. We confirmed that the DMMN molecule can promote the dissociation of LiTFSI by the interaction between the N atom and Li+, and form the hydrogen bond with TFSI- anion, which can promote the dissociation of LiTFSI to form DEE. More importantly, due to the absence of active α-hydrogen, DMMN exhibits greatly enhanced reduction stability with Li metal, resulting in favorable electrode/electrolyte interface compatibility. Polymer electrolytes based on this DEE exhibit high ionic conductivity (0.67 mS cm-1 at 25 °C), high oxidation voltage (5.0 V vs. Li+/Li), favorable interfacial stability, and nonflammability. Li‖LFP and Li‖NCM811 full batteries utilizing this DEE polymer electrolyte exhibit excellent long-term cycling stability and excellent rate performance at high rates. Therefore, the new DMMN-based DEE overcomes the limitations of traditional electrolytes in electrode interface compatibility and opens new possibilities for improving the performance of LMBs.

Boosting Fast Charging of Lithium-Metal Batteries via Weak Interactions Between Non-Solvating Solvents and Anions in High-Safety Eutectic Electrolytes.

Proper design of the solvation structure is crucial for the development of lithium metal batteries (LMBs). In this paper, the use of 1,2-Dimethoxyethane (DME) as a non-solvating cosolvent in amide-based eutectic electrolytes is proposed to address challenges related to high viscosity, high polarization, and low conductivity, thus enhancing the compatibility with lithium metal anodes. Through physical characterization combined with simulation calculations the existence of a weak interaction between DME and anions is confirmed, which promotes the dissociation of lithium salts and increases the Li+ transference number and diffusion coefficient, thus improving the fast charging performance of eutectic electrolytes. In addition, stable SEI layer enriched with inorganic components is formed during the cycling process, resulting in uniform and dense lithium deposition. The fast charging performance of the cell can be effectively improved by utilizing the interaction between anions and solvents. The LiFePO4 (LFP)||Li cell has a capacity retention of 97% after 1200 cycles at 5 C and also performs well at high temperature of 50°C. Overall, the use of a non-solvating cosolvent in eutectic electrolytes presents a promising and innovative approach for enhancing electrolyte performance in LMBs.

A Highly Stable and Non‐Flammable Deep Eutectic Electrolyte for High‐Performance Lithium Metal Batteries

AbstractDeep eutectic electrolytes (DEEs) are regarded as one of the next‐generation electrolytes to promote the development of lithium metal batteries (LMBs) due to their unparalleled advantages compared to both liquid electrolytes and solid electrolytes. However, its application in LMBs is limited by electrode interface compatibility. Here, we introduce a novel solid dimethylmalononitrile (DMMN)‐based DEE induced by N coordination to dissociate LiTFSI. We confirmed that the DMMN molecule can promote the dissociation of LiTFSI by the interaction between the N atom and Li+, and form the hydrogen bond with TFSI− anion, which can promote the dissociation of LiTFSI to form DEE. More importantly, due to the absence of active α‐hydrogen, DMMN exhibits greatly enhanced reduction stability with Li metal, resulting in favorable electrode/electrolyte interface compatibility. Polymer electrolytes based on this DEE exhibit high ionic conductivity (0.67 mS cm−1 at 25 °C), high oxidation voltage (5.0 V vs. Li+/Li), favorable interfacial stability, and nonflammability. Li‖LFP and Li‖NCM811 full batteries utilizing this DEE polymer electrolyte exhibit excellent long‐term cycling stability and excellent rate performance at high rates. Therefore, the new DMMN‐based DEE overcomes the limitations of traditional electrolytes in electrode interface compatibility and opens new possibilities for improving the performance of LMBs.

Guiding uniform lithium deposition via three-dimensional gradient MXene/ZIF-8 structure for high-performance and dendrite-free lithium metal anodes

The development of lithium-metal batteries has been severely hindered by dendritic lithium dendrites and volume changes. Three-dimensional gradient and two-dimensional lithophilic materials have been shown to improve the electrochemical performance of lithium metal anodes significantly. In this paper, we have exploited the chemical interaction between MXene and ZIF-8 to develop a gradient structure consisting of MXene, MXene/ZIF-8, and MXene+ZIF-8 by in situ growth. In this gradient structure, with the gradual increase of interlayer conductivity, lithium ions can be deposited preferentially and uniformly at the bottom of the conductive bottom during lithium plating, overcoming many deposition problems at the top of 3D structures. It enhanced the electrochemical performances of lithium anodes including a coulombic efficiency of 99 % over 800 cycles at 0.5 mA cm−2 and 99 % over 500 cycles at 1 mAh cm−2, a long cycling life up to 800 h at 1 mA cm−2 and 1 mAh cm−2. The MXene/pt-Li||LiFePO4 cells exhibited a stable cycling performance with a capacity retention of 94 % after 800 cycles.

Numerical Modeling of 3D Printed Structures for Lithium Metal Batteries

The development of lithium metal batteries to enable their use in commercial applications can have a significant impact on the fight against climate change due to the increase in energy density compared to state of art Li-ion batteries. However, technical challenges related to limited cyclability and non-uniformity of Li electroplating need to be addressed. This requires understanding the interplay between nucleation density, solid-electrolyte-interphase (SEI) formation, transport limitations, and unstable growth. 3D printed electrodes are of interest for electrochemical devices for their ability to tailor the electrode shape and structure to minimize system losses through enhanced ion transport and increased surface area for electrochemical reactions. 3D printed structures are constrained by the resolution of the printing method which can limit the feature size of the printed architecture. Numerical modeling of these structures can elucidate the interactions of competing physical phenomena, demonstrate tradeoffs, and estimate critical length scales and design principles that make 3D printed structures outperform traditional planar electrodes. Additionally, simulations can be used to identify failure points, complement experimental results, and deepen the understanding of fundamental questions hindering Li-metal deployment. In this presentation, we will show our recent work using continuum modeling to guide the design and evaluation of 3D printed electrodes for lithium metal batteries.This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and was supported by the LLNL-LDRD program under project numbers 22-ERD-043 and 23-SI-002.

All-Fluorinated Electrolyte Engineering Enables Practical Wide-Temperature-Range Lithium Metal Batteries.

The development of lithium metal batteries (LMBs) is severely hindered owing to the limited temperature window of the electrolyte, which renders uncontrolled side reactions, unstable electrolyte/electrode interface (EEI) formation, and sluggish desolvation kinetics for wide temperature operation condition. Herein, we developed an all-fluorinated electrolyte composed of lithium bis(trifluoromethane sulfonyl)imide, hexafluorobenzene (HFB), and fluoroethylene carbonate, which effectively regulates solvation structure toward a wide temperature of 160 °C (-50 to 110 °C). The introduction of thermostable HFB induces the generation of EEI with a high LiF ratio of 93%, which results in an inhibited side reaction and gas generation on EEI and enhanced interfacial ion transfer at extreme temperatures. Therefore, an unparalleled capacity retention of 88.3% after 400 cycles at 90 °C and an improved cycling performance at -50 °C can be achieved. Meanwhile, the practical 1.3 Ah-level pouch cell delivers high energy density of 307.13 Wh kg-1 at 60 °C and 277.99 Wh kg-1 at -30 °C after 50 cycles under lean E/C ratio of 2.7 g/Ah and low N/P ratio of 1.2. This work not only offers a viable strategy for wide-temperature-range electrolyte design but also promotes the practicalization of LMBs.

Double-Salts Super Concentrated Carbonate Electrolyte Boosting Electrochemical Performance of Ni-Rich LiNi0.90Co0.05Mn0.05O2 Lithium Metal Batteries.

Current lithium-ion batteries cannot meet the requirement of higher energy density with further large-scale application of electrical vehicles. Lithium metal batteries combined with Ni-rich layered oxides cathode are expected as the one of promising solutions, while the poor electrode and electrolyte interface impedes the commercial development of lithium metal batteries. A new double-salts super concentrated (DSSC) carbonate electrolyte is proposed to improve the electrochemical performance of LiNi0.90Co0.05Mn0.05O2 (NCM9055)||Li metal battery which exhibits stable cycling performance with the capacity retention of 93.04% and reversible capacity of 173.8 mAh g-1 after 100 cycles at 1 C, while cells with conventional 1m diluted electrolyte remains only 60.55% and capacity of 114.2 mAh g-1. The double salts synergistic effect in super concentrated electrolyte promotes the formation for more balanced stable cathode electrolyte interface (CEI) inorganic compounds of CFx, LiNOx, SOF2, Li2SO4, and less LiF by X-ray photoelectron spectroscopy (XPS)test, and the uniform 2-3nm rock-salt phase protection layer on the cathode surface by transmission electron microscope (TEM) characterization, improving the cycling performance of the Ni-rich NCM9055 layered oxide cathode. The DSSC electrolyte also can relief the Li dendrite growth on Li metal anode, as well as exhibit better flame retardance, promoting the application of more safety Ni-rich NCM9055||Li metal batteries.

Fluorinated porous covalent polymer nanofilm assembled sandwich separator: Lithiophilic sites engender uniform Li+ flux towards lithium metal battery

Lithium metal is renowned for its high theoretical specific capacity and extremely low reduction potential. Nevertheless, the repeated breaking/forming of the solid electrolyte interface and uncontrolled growth of lithium dendrites in lithium metal batteries significantly impede their commercial application. In this study, we propose a novel sandwich separator (F-BtTp@PP) composed of fluorinated porous covalent polymer nanofilms (F-BtTp-Nfilm) assembled using roll-to-roll technology. The F-BtTp@PP improves the pore distribution of PP, enhances its resistance to dendrite penetration, and promotes a uniform distribution of lithium ions flux. Furthermore, Fourier-transform infrared spectroscopy and density functional theory calculations confirm the energy affinity. Abundant lithophilic sites and strong electronegative groups effectively control the deposition behavior of lithium ions, resulting in a transfer number of 0.87. This mitigates effectively the occurrence of significant concentration gradients and localized hot-spots during cycles with high current density. The symmetrical cells of F-BtTp@PP Li|Li can maintain a stable cycling voltage of 52.2 mV for 5600 h under a current density of 20 mA cm−2 and capacity density of 10 mAh cm−2. This result robustly demonstrates the exceptional efficiency of F-BtTp@PP, which can be readily scaled up for protecting lithium metal anodes and provides valuable guidance for the design and industrial development of lithium metal batteries with modified separators.

Thermal distribution evolution model of SEI in lithium metal anodes

Lithium metal batteries are considered an advantageous choice for high energy density batteries due to their extremely high theoretical specific capacity. However, the interface instability has always been the biggest challenge for the commercial development of lithium metal batteries. The evolution mechanism of the thermal field is a key factor affecting the cyclic life during the evolution of lithium metal interfaces. Herein, the interface evolution mechanism for the impact of thermal distribution on Li dendrites is revealed and quantified by the thermal distribution evolution model of the solid electrolyte interphase (SEI). Three influencing factors are outlined as follows: 1) the ratio of the SEI to electrolyte diffusion capability. 2) The SEI diffusion coefficients for both anionic and cationic species. 3) The anisotropy in the SEI. The results indicate that under the appropriate ratio, the temperature gradient at the tip of lithium dendrites and the SEI-electrolyte interface are lower, which is favorable for a more even distribution of heat within the SEI. Additionally, the diffusion of anions can also influence the temperature gradient during the evolution process of lithium dendrites. Furthermore, introducing anisotropy to the SEI can induce lateral growth of lithium dendrites and reduce the temperature gradient at the tip of the lithium dendrites and the SEI-electrolyte interface. This work provides valuable insights for the interface design of lithium metal batteries.

Manipulating the diffusion energy barrier at the lithium metal electrolyte interface for dendrite-free long-life batteries.

Constructing an artificial solid electrolyte interphase (SEI) on lithium metal electrodes is a promising approach to address the rampant growth of dangerous lithium morphologies (dendritic and dead Li0) and low Coulombic efficiency that plague development of lithium metal batteries, but how Li+ transport behavior in the SEI is coupled with mechanical properties remains unknown. We demonstrate here a facile and scalable solution-processed approach to form a Li3N-rich SEI with a phase-pure crystalline structure that minimizes the diffusion energy barrier of Li+ across the SEI. Compared with a polycrystalline Li3N SEI obtained from conventional practice, the phase-pure/single crystalline Li3N-rich SEI constitutes an interphase of high mechanical strength and low Li+ diffusion barrier. We elucidate the correlation among Li+ transference number, diffusion behavior, concentration gradient, and the stability of the lithium metal electrode by integrating phase field simulations with experiments. We demonstrate improved reversibility and charge/discharge cycling behaviors for both symmetric cells and full lithium-metal batteries constructed with this Li3N-rich SEI. These studies may cast new insight into the design and engineering of an ideal artificial SEI for stable and high-performance lithium metal batteries.

Solid Electrolyte Interphase Recombination on Graphene Nanoribbons for Lithium Anode.

The practical application of lithium metal batteries is hindered by the lithium dendrite issue, which is seriously affected by the composition and structure of the solid electrolyte interphase (SEI). Modifying the SEI can regulate lithium dendrite formation and growth. Here, we experimentally realize a Li protective layer of LiTFSI-ether electrolyte induced a natural SEI grafted on graphene nanoribbons (SEI@GNRs) via their in situ reactions. The experimental results and theoretical calculations uncover that the 3D structure of SEI@GNRs can reduce the local current density and Li+ flux. The natural SEI in SEI@GNRs, especially the rich inorganic species of LiF, Li3N, and Li2S, decreases the Li+ nucleation overpotential, makes Li+ ion deposition and nucleation uniform, and isolates electron transport. Their synergetic effect suppresses Li dendrite formation and growth, increasing the electrochemical performance of lithium metal batteries. The design strategy is beneficial for the development of lithium metal batteries.

Single‐Step Deformation Processing of Ultrathin Lithium Foil and Strip

AbstractNext‐generation, high‐efficiency energy storage and conversion systems require development of lithium metal batteries. But the high cost of production and constraints on thickness of lithium (anode) foils continue to limit adoption for integration into battery cell architectures. Here, a novel lithium anode manufacturing solution is demonstrated – single‐step production of ultrathin gauge foil formats directly from solid ingot. Hybrid cutting‐based deformation processes, involving large plastic strains and strain rates, produce foil to sub‐10 µm thickness, with surface quality even superior to present Li anode processing routes. Energy analysis shows the single‐stage processing is ≈50% more efficient than conventional processing by extrusion‐rolling. Through in situ force measurements and high‐speed imaging of the cutting it also characterize – for the first time – the flow stress of Li to strain rates of 800 sec−1, revealing a power‐law relationship. The results present a paradigm shift in manufacturing and integration of solid lithium anodes for energy applications.

A Step Towards the Impossible – the Combination of High Ionic Conductivity and Mechanical Stability in Highly Crystalline Solid Polyketone Electrolytes

Implementation of solid polymer electrolytes (SPEs) is believed to be one pathway forward in the development of lithium-metal batteries (LMBs) that are both safe and possesses high capacities. This combination is possible since the free-standing SPE maintains its mechanical integrity during electrochemical and thermal exposure while utilizing lithium metal as the negative electrode, thus accessing the extremely high theoretical capacity of lithium metal. The main drawback for SPEs are however the poor ionic conductivity compared to the liquid electrolytes used in lithium-ion batteries today.[1] The low ionic conductivity for SPEs stems from the conduction mechanism of the ions, which is a slower process in SPEs compared to in liquid electrolytes. In general, the conductivity in SPEs are confined to the amorphous regions, where segmental motion of the polymer chains facilitates the ion transport; while the crystalline regions restrict the movements of the polymer chains and impairs the ion transport.[2] The highly crystalline polyketone poly(1-oxoheptamethylene) (POHM) is a material that has shown interesting characteristics for implementation as a SPE in batteries. In earlier studies, the polyketone revealed an extensive improvement of the ionic conductivity upon increasing the salt concentration, although the crystallinity remained with a high melting point.[3] Herein this study, the effect of the crystallinity on the characteristics and the performance was investigated further. To understand its effect, a second less hydrogenated version of POHM was synthesized, POHM-75, which is fully amorphous at high salt concentrations. The characteristics of the polyketones were in addition also compared with the more well-studied SPEs, that is polyethylene oxide (PEO) and poly(trimethylene carbonate) (PTMC). Focus of the presentation is on the interplay between the ionic conductivity and mechanical stability for the polyketones, for which something different to the normally observed tradeoff between the two properties is observed. The electrochemical performance of the polyketones are furthermore evaluated when implemented as SPEs in LMBs at extreme temperature environments, a possible application area for mechanically stable SPEs.[1] D. Zhou, D. Shanmukaraj, A. Tkacheva, M. Armand, G. Wang, Chem 2019, 5, 2326-2352.[2] M. A. Ratner, P. Johansson, D. F. Shriver, MRS Bulletin 2011, 25, 31-37.[3] T. Eriksson, H. Gudla, Y. Manabe, T. Yoneda, D. Friesen, C. Zhang, Y. Inokuma, D. Brandell, J. Mindemark, Macromolecules 2022, 55, 10940-10949. Figure 1

Understanding steric hindrance effect of solvent molecule in localized high-concentration electrolyte for lithium metal batteries

High energy density lithium metal batteries (LMBs) have garnered significant research interests in the past decades. However, the growth of lithium dendrites and the low Coulombic efficiency (CE) of Li metal anode pose significant challenges for the development of LMBs. Herein, we report a triethyl orthoformate (TEOF)-based localized high-concentration electrolyte (LHCE) that facilitates a highly reversible Li metal anode with dendrite-free deposition morphologies and an average Coulombic efficiency of 99.1% for 450 cycles. Mechanistic study reveal that the steric hindrance caused by the terminal ethyl groups in the TEOF solvent molecule results in a weak solvating ability, leading to the formation of anion-dominant solvation structures. The anion-dominant solvation sheaths play an essential role in the formation of a LiF-rich solid-electrolyte interphase (SEI), which effectively suppresses the growth of Li dendrites. Furthermore, the TEOF-based electrolyte demonstrates the stable cycling of high-voltage Li||NMC811 cells. These results provide insights into understanding of steric hindrance effect on electrolyte solvation structure and offer valuable guidance for the design of electrolyte solvents in the development of lithium metal batteries.

Rapid self-healing, highly conductive and near-single-ion conducting gel polymer electrolytes based on dynamic boronic ester bonds for high-safety lithium metal batteries

Polymer electrolytes with high ionic conductivity and good self-healing capability are crucial for the development of lithium metal batteries with enhanced rate capability and safety. However, the application of self-healable polymer electrolytes is hindered by low ionic conductivity and slow self-healing speed. Herein, boronic ester based self-healing gel polymer electrolyte (PBAD-PEG) with high ionic conductivity and fast self-healing speed is developed. PBAD-PEG is fabricated by thiol-ene click reaction of a multifunctional monomer 2,2′-(1,4-phenylene)-bis (4-allyloxy-1,3,2-dioxaborolane) (PBAD) consisting of two dynamic boronic ester bonds, pentaerythritol tetra(3-mercaptopropionate) and polyethylene glycol diacrylate. Abundant reversible boronic ester bonds endow PBAD-PEG with good flexibility and excellent self-healing ability. PBAD-PEG can self-heal within 1 h at room temperature after damaged, which effectively restores the ionic conductivities and mechanical properties. PBAD-PEG possesses high ionic conductivity of 8.67 × 10−4 S cm−1 at 25 °C. Lewis acid-base interactions between anions and boron atoms of PBAD-PEG contributes to ultrahigh lithium-ion transference number of 0.71. PBAD-PEG exhibits significant resistance to the growth of Li dendrites. The fabricated LiFePO4/Li batteries with PBAD-PEG achieve significantly boosted cycle stability (capacity retention of 92.6 % after 150 cycles). More importantly, LiFePO4/Li cells with the healed PBAD-PEG also show excellent cycle performance.

Dual-type gel polymer electrolyte for high-voltage lithium metal batteries with excellent cycle life

The most attractive approach for maximizing the energy density of rechargeable lithium batteries is to combine a lithium metal anode with a high-voltage cathode. However, the dendritic formation of lithium at the anode and the highly oxidizing conditions that cause electrolyte decomposition at the cathode have hindered the practical development of lithium metal batteries (LMBs). In this study, we report a dual-type gel polymer electrolyte (GPE) composed of an anolyte and a catholyte that can address the drawbacks of both the anode and cathode sides. The anolyte is a poly(ethylene oxide)-based composite solid polymer electrolyte that is chemically stable with lithium metal and has a high mechanical strength for suppressing lithium dendrite growth. A cross-linked gel polymer electrolyte with high lithium-ion conductivity and oxidative stability was used as the catholyte. The Li/LiCoO2 cell assembled with a dual-type GPE exhibited a high discharge capacity of 181.1 mAh g−1 (areal capacity: 3.15 mAh cm−2) in the voltage range of 3.0–4.5 V and excellent cycle life, with a capacity retention of 74 % after 700 cycles at 25 °C and 0.5 C rate. Our study proposes a promising electrolyte system for LMBs with high energy density and good cycle life.

In situ construction of fluorine-containing modified gel polymer electrolyte with high interfacial stability for high-rate lithium metal battery

Gel polymer electrolytes (GPEs) play a crucial role in promoting the development of lithium metal batteries, as they combine the high ionic conductivity of liquid electrolytes with the enhanced safety provided by solid electrolytes. However, traditional polymer electrolytes are typically poured using non-in-situ methods, which results in poor electrode-electrolyte contact and compromises their performance. In this paper, in situ thermal polymerization is utilized to incorporate di-pentaerythritol pentaacrylate (DPPA) and 3,3,4,4,5,5,6,6,7,7,8,8-tridecafluorooctyl acrylate (TFOA) into PAN spinning porous membranes. Application of TFOA reduces the crystallinity of GPEs and thus enhancing the Li+ transport capability, which enables the newly constructed GPEs to exhibit an ionic conductivity of 2.52 × 10−3 S cm−1 and a lithium-ion transport number of 0.61 at 30 °C. Simultaneously, fluoro-containing groups actively contribute to the formation of a negative solid electrolyte interphase (SEI) film full of LiF, ensuring the stable operation of Li symmetrical batteries for over 2000 h at a current density of 0.40 mA cm−2. The capacity retention rate of lithium metal batteries (LMBs) with commercial NCM811 cathodes reaches 88.2% after 300 cycles. We firmly believe that our newly designed gel polymer electrolytes (GPEs) can offer a viable solution for high-voltage and high-rate LMBs.

Tuning and Balancing the Donor Number of Lithium Salts and Solvents for High-Performance Li Metal Anode.

The low reversibility of Li deposition/stripping in conventional carbonate electrolytes hinders the development of lithium metal batteries. Herein, we proposed a combination of solvents with a moderate donor number (DN) and LiNO3 as the sole salt, which has rarely been attempted due to its low solubility or dissociation degree in common solvents. It is found that the DN value of solvents is highly correlated to the reversibility of Li deposition behavior when LiNO3 is applied as the sole salt. The combination of LiNO3 and solvents with moderate DN behaves like a quasi-concentrated electrolyte even at a common or moderate concentration, while neither the solvents with poor solubility and low dissociation for LiNO3 (which usually corresponds to a low DN) nor the solvents with high dissociation for LiNO3 (which usually corresponds to an overly high DN) can achieve a high reversibility for low conductivity or excessive solvent decomposition. As a result, a Coulombic efficiency as high as 99.6% for Li deposition/stripping is achieved with the optimized combination. We believe this work will give a better understanding of the role of anions and solvents in the regulation of the solvation structure, and DN can be utilized as an important guideline to sieve suitable solvents for LiNO3 as the main salt to exhibit intriguing properties beyond traditional cognition.

Lithiophilic Cu3Sn Modified Cu Foil as Current Collector for Stable Lithium Metal Anodes

AbstractThe development of lithium metal battery is severely restricted by its uncontrolled dendrite growth and volume change. In this work, we designed a controllable lithiophilic Cu3Sn modified commercial Cu foil as current collector via simple industrial electroplating and heat treatment. As a Li‐reservoir substrate for efficient deposition/stripping of Li metal, the introduction of Cu3Sn not only increases multiple active sites for the deposition of Li, but also provides more transfer paths for lithium ions. The Li metal anodes prepared by molten Li on the Cu current collector with dispersed Cu3Sn active sites provide a uniform lithiophilic surface, which could effectively promote a uniform Li deposition/stripping and suppress the formation of lithium dendrites. As a result, the assembled symmetric battery is stable at a low over‐point position for 1600 h without short circuit at 1 mA cm−2 with 1 mAh cm−2, the full battery paired with LiFePO4 still maintains a high‐capacity retention rate of 97.1 % and a coulombic efficiency (CE) of 99.5 % after 400 cycles at a current density of 2 C. This work provides a facile and controllable strategy for the design of current collectors with high lithium affinity for stable lithium metal anode applications.

Quasi‐Solid‐State Composite Electrolytes with Multifunctional 2D Molecular Brush Fillers for Long‐Cycling Lithium Metal Batteries†

Comprehensive SummaryThe ever‐growing demand for next‐generation high‐energy‐density devices drives the development of lithium metal batteries with enough safety and high performance, in which quasi‐solid‐state composite electrolytes (QSCEs) with high ionic conductivity and lithium ion transference number () are highly desirable. Herein, we successfully synthesize a kind of two‐dimensional (2D) molecular brush (GO‐g‐PFIL) via grafting poly(ionic liquid) side‐chain (poly(3‐(3,3,4,4,4‐pentafluorobutyl)‐1‐vinyl‐1H‐imidazol‐3‐ium bis(trifluoromethanesulfonyl)imide), denoted as PFIL) on the surface of 2D graphene oxide (GO) sheet. GO‐g‐PFIL is used as multifunctional filler to prepare novel composite membranes and corresponding QSCEs (e.g., QSCE‐PH/GPFIL3/P). The as‐obtained QSCE‐PH/GPFIL3/P integrates features of PFIL side‐chain‐enhanced lithium ion conduction, poly(vinylidene fluoride‐co‐hexafluoropropene) backbone‐induced flexibility, and GO‐strengthened mechanical property. As a result, our ultrathin (21 μm) self‐supporting QSCE‐PH/GPFIL3/P exhibits high ionic conductivity (3.24 × 10−4 S·cm−1) and excellent (0.82) at room temperature, and Li/LFP full cell with QSCE‐PH/GPFIL3/P shows superior rate performance (high specific capacities of 79 mAh·g−1 at 30 °C and 5 C) and excellent cycling performance (high capacity retention of 91% after 500 cycles at 80 °C and 1 C).