Stable Lithium Metal Batteries Research Articles

Tuning the Nucleophilicity of Anion in Lithium Salt to Enable an Anion‐Rich Solvation Sheath for Stable Lithium Metal Batteries

AbstractTraditional lithium salts typically adhere to the designing principles of enhancing cation‐anion dissociation degree to obtain a high electrolyte conductivity. This promotes the invention of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), where the symmetric electron‐withdrawing trifluoromethanesulfonyl groups significantly delocalize the negative charge density around the nitrogen atom, thereby weakening the electrostatic interaction between Li+ and the anion. Herein, deviating from the general principle, lithium (methanesulfonyl)(trifluoromethanesulfonyl) imide (LiMTFSI) is deliberately designed by substituting a unilateral electron‐withdrawing trifluoromethyl (─CF3) group of LiTFSI with an electron‐donating methyl (─CH3) group, to tune the nucleophilicity of the anion. This modification enhances Li‐anion interaction, causing the anion to replace the solvent molecules in the Li+ solvation shell. Additionally, the MTFSI− anion exhibits an elevated donor number to facilitate the solubility of LiNO3 in carbonate‐based electrolytes. The synergistic effect of these changes suppresses the decomposition of solvent and helps construct a stable solid electrolyte interphase (SEI) enriched with multiple inorganic lithium salts (e.g., Li2S, Li3N, and LiNxOy) on the Li metal anode, which enables the 500 mAh Li||LiNi0.5Co0.2Mn0.3O2 pouch cell to operate steadily for 150 cycles. It is believed this work would provide new insights and another dimension for designing functional anions beyond their role as charge carriers.

Integration of deformable matrix and lithiophilic sites for stable and stretchable lithium metal batteries

In response to the growing interest in wearable devices, the demand for next-generation wearable devices that can endure various mechanical deformations such as folding and stretching is also increasing. As a result, the development of stretchable batteries, capable of operating under diverse conditions, is regarded as crucial for the advancement of these future wearable technologies. Many current studies on stretchable batteries suffer from limited energy density and complicated fabrication procedures. Thus, the development of batteries that meet both high stretchability and energy density remains challenging due to these factors. Herein, we propose a stretchable and lithiophilic matrix as a host for lithium (Li) metal anodes to realize stretchable Li metal batteries (LMBs), which consists of a polymer matrix embedded with silver nanoparticles (AgNPs). The lithiophilic AgNPs are incorporated both on the surface and within the elastic fiber matrix, providing facile Li nucleation kinetics and an electron-conductive network. Surface AgNPs serve as a primary electron pathway and offer numerous nucleation seeds to facilitate uniform Li electrodeposition. Meanwhile, AgNPs embedded in the matrix provide a sturdy conductive network even under mechanical deformation. Consequently, the structure-forming factors of stretchable lithiophilic Ag-incorporated matrix (SLiM) electrode contribute to enhanced electrochemical properties as a versatile Li metal host. As a proof of concept, the designed all-stretchable LMB with the SLiM electrode demonstrates minimal degradation of electrochemical performance in deformable conditions and confirms the feasibility of an LMB in stretchable application. This work provides insight into stretchable LMBs aimed at both highly deformable and high-energy-density wearable devices.

A modified separator based on ternary mixed-oxide for stable lithium metal batteries

Li metal batteries (LMBs) are among the most promising options for next-generation secondary batteries under the rapidly growing demand for high-energy–density electrochemical energy storage. However, the implementation of LMBs are hindered by major obstacles such as dentritic Li deposition and low cycling Coulombic efficiency. A practical functional separator is developed in this study, which consists of a Lewis acidic mixed oxide of ZrO2-SiO2-Al2O3 as a functional coating with anion anchoring ability to modulate ion transport in the vicinity of the Li metal anode, delivering a high Li+ transference number of 0.88 in carbonate electrolytes that suppresses dendrite formation. The strong Lewis acid sites in ZrO2-SiO2-Al2O3 originate from coordinatively unsaturated Zr4+ ions, which immobilize anions and reduce their decomposition rate. This significantly improves the chemical stability of the electrolyte and induces a more stable solid electrolyte interphase layer. The modified separator enables an anode-free cell containing a high-loading LiNi0.8Co0.1Mn0.1O2 cathode to present stable charge and discharge cycling for 150 cycles at 0.5C. By effectively suppressing Li dendrite growth and supporting the long-term operation of anode-free LMBs, this study offers a novel approach to rationally design mixed oxides with high Lewis acidity for functional separators.

Recent advances in functionalized separator for dendrites‐free and stable lithium metal batteries

AbstractLithium (Li) metal anode is considered the “Holy grail” for the most promising next‐generation rechargeable lithium metal batteries (LMBs) because of ultra‐high theoretical specific capacity, ultra‐low reduction potential and small density. However, uncontrolled lithium dendrite growth and inevitable side reaction seriously hindered the application of practical LMBs because of the deteriorating electrochemical performances and exacerbating the safety issues of LMBs. Thus, improving the electrochemical performances of LMBs by constructed of functionalized separator is promising for overcoming the above‐mentioned challenges due to its' significantly advantages, such as enhancing mechanical and thermal stability, regulating the diffusion and migration of Li ions, homogenizing Li ion flux, forming protective layer on Li anode surfaces, etc. The relational investigations have significantly increased since 2020, while the comprehensive reviews on this research direction are relatively rare, especially in the detailed mechanism aspects. In this review, an overview in functionalized separator for stable LMBs is discussed in detail. Firstly, the current issues of LMBs are in‐depth discussion and the general strategies are summarized. Subsequently, the requirements and limitations of separator, as well as the advantages of functionalized separator are summarized and reviewed. Most importantly, the protection mechanisms and research advances of advanced functionalized separator are comprehensively discussed and summarized. Furthermore, the applications of functionalized separator in rechargeable lithium metal‐based full cells are reviewed. Finally, the challenges and potential opportunities for the future development and rational design of functionalized separator are highlighted in rechargeable LMBs to obtain future research directions related to the significant strategy of constructing dendrite‐free and stable LMBs.

Designing a Refined Multi-Structural Polymer Electrolyte Framework for Highly Stable Lithium-Metal Batteries.

Rational structural designs of solid polymer electrolytes featuring rich interface-phase morphologies can improve electrolyte connection and rapid ion transport. However, these rigid interfacial structures commonly result in diminished or entirely inert ionic conductivity within their bulk phase, compromising overall electrolyte performance. Herein, a multi-component ion-conductive electrolyte was successfully designed based on a refined multi-structural polymer electrolyte (RMSPE) framework with uniform Li+ solvation chemistry and rapid Li+ transporting kinetics. The RMSPEis constructed via polymerization-induced phase separation based on a rational combination of lithiophilic components and rigid/flexible chain units with significant hydrophobic/hydrophilic contrasts. Further refined by coating a robust polymer network, this all-organic design endows a homogenous micro-nano porous structure, providing a novel framework favorable for rapid ion transport in both its soft interfacial and bulk phases. The RMSPE exhibited excellent ion conductivity of 1.91 mS cm-1 at room temperature and a high Li+ transference number of 0.7. Assembled symmetrical Li cells realized stable cycling for over 2400 h at 3.0 mA cm-2. LiFePO4 full batteries demonstrated a long lifespan of 3300 cycles with a capacity retention of 93.5% and stable cycling performance at -35 °C. This innovative design concept offers a promising perspective for achieving high-performance polymer-based Li metal batteries.

Interphase Optimum via Synergistic Effect of Poly(1,3‐dioxolane) Electrolytes and Lithium Difluorophosphate for Stable Lithium Metal Batteries

Interphase Optimum via Synergistic Effect of Poly(1,3‐dioxolane) Electrolytes and Lithium Difluorophosphate for Stable Lithium Metal Batteries

Covalent Triazine Based Frameworks with Donor‐Donor‐π‐Acceptor Structures for Dendrite‐Free Lithium Metal Batteries

AbstractThe appearance of disordered lithium dendrites and fragile solid electrolyte interfaces (SEI) significantly hinder the serviceability of lithium metal batteries. Herein, guided by theoretical predictions, a multi‐component covalent triazine framework with partially electronegative channels (4C‐TA0.5TF0.5‐CTF) is incorporated as a protective layer to modulate the interface stability of the lithium metal batteries. Notably, the 4C‐TA0.5TF0.5‐CTF with optimized electronic structure at the molecular level by fine‐tuning the local acceptor‐donor functionalities not only enhances the intermolecular interaction thereby providing larger dipole moment and improved crystallinity and mechanical stress, but also facilitates the beneficial effect of lithiophilic sites (C−F bonds, triazine cores, C=N linkages and aromatic rings) to further regulate the migration of Li+ and achieve a uniform lithium deposition behavior as determined by various in‐depth in/ex situ characterizations. Due to the synergistic effect of multi‐component organic functionalities, the 4C‐TA0.5TF0.5‐CTF modified full cells perform significantly better than the common two/three‐component 2C‐TA‐CTF and 3C‐TF‐CTF electrodes, delivering an excellent capacity of 116.3 mAh g−1 (capacity retention ratio: 86.8 %) after 1000 cycles at 5 C and improved rate capability. This work lays a platform for the prospective molecular design of improved organic framework relative artificial SEI for highly stable lithium metal batteries.

Tuning the ion-dipole interactions between fluoro and carbonyl (EC) by electrolyte design for stable lithium metal batteries

Tuning the ion-dipole interactions between fluoro and carbonyl (EC) by electrolyte design for stable lithium metal batteries

Self-Healing fluorinated polymer deep eutectic electrolytes for stable lithium metal batteries

Lithium metal batteries (LMB) have attracted great attention in the last two decades for their high theoretical capacity and ultralow redox potential. However, LMB commercial applications still face safety risks such as electrolyte leakage, short circuits and even spontaneous combustion. Fluorinated polymer electrolytes have the advantages of high thermal stability and wide electrochemical window, endowing them an ideal alternative to liquid electrolytes. This work draws inspiration from the self-healing mechanism by introducing 2-ureido-4-pyrimidinone (UPy) units and successfully demonstrates that the fluorinated polymer deep eutectic electrolytes (FPDE) show high electrochemical performances in LMB. Self-healing structural units can alleviate the volumetric expansion of lithium anode during the charging and discharging process, while the fluorinated group endow the electrolyte wide electrochemical window, high migration number and superior interface stability. The joint effect of deep eutectic electrolytes and fluoroalkane makes FPDE show excellent flame-retardant performance with 0 s self-extinguish time. Symmetric Li||Li cell using the FPDE shows stable performance up to 6000 h. The full cell with Li||FPDE||LFP provides 80.4 % capacity retention after 600 cycles. This work might show some potential for development high safety LMBs.

Lewis-basic nitrogen-rich covalent organic frameworks enable flexible and stretchable solid-state electrolytes with stable lithium-metal batteries

Designing flexible and stretchable solid-state electrolytes (SSEs) holds promise but challenge in flexible all-solid-state lithium-metal batteries (LMBs) owing to their insufficient ion conductivity and mechanical strength. Herein, we develop nitrogen-rich covalent organic frameworks (NCOF) with abundant Lewis-basic N atoms as lithiophilic sites to incorporate Lewis-acidic Li+ into its inner order structure for fabricating flexible and stretchable PEO-LI+@NCOF SSEs with the crosslinking of polyethylene oxide (PEO). The SSE film displays high mechanical strain (2.2 MPa), Young's modulus (689 MPa), stretchability (1000 %), ion conductivity (2.4 × 10–4 S cm-1), good flame resistance, and wide electrochemical window (4.8 V). Owing to the rich Lewis-basic N atoms with strong Li+ adsorption energy, orderly nanochannels, and negative charge environment within NCOFs, the SSE film endows orderly and rapid ion migration, low Li-ion diffusion barrier, and significantly enhanced ion conductivity for uniform lithium plating/stripping and suppressing Li-dendrite growth. The crosslinking of Li+@NCOF with PEO greatly enhances the mechanical stretchability, flame resistance, and electrochemical window of PEO-based SSEs. Consequently, the Li/PEO-LI+@NCOF/Li symmetrical cell exhibits stable cycling without short-circuiting for 1200 h at 0.1 mA cm-2/0.1 mAh cm-2. The LiFePO4/PEO-LI+@NCOF/Li battery exhibits a 500-cycle long lifespan at 1 C (78 % capacity retention), and its pouch cell verifies promising applications in flexible all-solid-state LMBs. Therefore, introducting Lewis-basic N-rich COFs verifies an effective strategy to design a flexible and stretchable SSE film with high mechanical strength, superior ion conductivity and flame resistance.

Solvent-derived inorganic F and N-rich solid electrolyte interface for stable lithium metal batteries

Extensive research has focused on the lithium (Li) metal anode, but progress in developing this technology has been hindered by the formation of lithium dendrites and their irreversible effects. In this study, an inorganic LiF-Li3N-rich solid electrolyte interface (SEI) is established in ether electrolyte through the direct use of 2,3-difluoro-5-(trifluoromethyl)pyridine (DP) to enable uniform Li deposition and enhance interfacial properties for a stable Li metal anode. Theoretical calculations show that DP has a higher tendency to decompose on lithium metal. An alternative approach involving the inclusion of additional anions into the solvation sheath of Li+ ions using weakly solvating solvents is proposed. During Li plating, DP is reduced to form a LiF and Li3N-rich SEI, resulting in a heterogeneous SEI layer on the Li metal anode surface. This approach allows stable cycling of Li|Li cells for over 1800 h at current densities of 5 mA cm−2 and 15 mAh cm−2. The method presented here has potential significance in the identification of suitable electrolytes for future research on lithium metal anodes.

Accelerating lithium ion transport via increasing the entropy of the electrolyte for stable lithium metal batteries

Promoting inorganic-rich solid-electrolyte interphase (SEI) formation by constructing anion-rich solvated structures is a promising strategy for improving the long-term cycling of lithium-metal batteries. However, the increase of anions within the solvated structure inevitably reduces the coordination of Li+ with the solvent, which leads to a low lithium diffusion coefficient and a decreased lithium conductivity. Here, high entropy electrolyte is achieved by increasing the molecular diversity in electrolyte. Multiple anions (TFSI−, FSI−, NO3− and PF6−) presented in entropy electrolyte individually coordinate with Li+, creating a diverse and anion-rich solvation structure. The large variety of solvation structures leads to a diversified Li+ diffusion barriers in the electrolyte, which results in the increase of channels available for Li+ diffusion. Thus, three-dimensional diffusion with high Li+ diffusion coefficient occurs in HE electrolytes. Furthermore, the anion-rich solvation structures promote the formation of the inorganic-rich SEI. As a result, over 2000 h of reversible Li plating/stripping with a low overpotential less than 27 mV is achieved in Li||Li cell using electrolyte modified by high-entropy strategy. Besides, the Li||LFP full cell with a negative capacity/positive capacity (N/P) ratio of 4.52 exhibits remarkably enhanced cycling stability, retaining 83.6% of its initial capacity after 150 cycles. This strategy offers a novel approach for accelerating Li+ transport kinetics and constructing stable SEI in lithium metal batteries.

Real-Time Monitoring of Electrochemical Reactions in All-Solid-State Lithium Batteries by Simultaneous Grazing-Incidence Small-Angle/Wide-Angle X-Ray Scattering

Polyethylene oxide (PEO)-based composite electrolytes (PCEs) are considered as the promising candidates for next generation lithium metal batteries due to its high safety, easy fabrication and good electrochemical stability. However, the material suffers from low conductivity and high crystallinity of the ethylene oxide (EO) chain, which inhibits its commercialization. Therefore, it is crucial to understand the electrochemcial process as well as Li+ transfer pathway within PEO-based batteries. Using operando grazing-incidence small-angle and wide-angle X-ray scattering (GISAXS and GIWAXS) in Li||Cu cell framework, we find that the electrochemical reaction within the PCE is highly correlated with the evolution of the buried morphology and crystalline structure evolution of the PCE. This two irreversible reactions, PEO-Li+ reduction and TFSI- decomposition, cause changes in both the crystalline structure and morphology of the PCE. In addition, the reversible Li plating/stripping process alters the inner morphology, especially the PEO-LiTFSI domain radius, rather than causing crystalline structure changes. This work provides a new path to monitor a working battery in real time, thereby enabling detailed understanding of electrochemically-induced changes of the microscopic morphology and crystalline structure of PCE, which is essential for developing high transferable and interface stable PCE-based lithium metal batteries. Figure 1

Stable Lithium Metal Batteries Enabled by Dilute Cationic Additives

Conventional Li-ion electrolytes consist of carbonate solvents and Li-ion salts that were made for carbonaceous negative electrodes. When the electrolytes are used with metallic lithium anodes, carbonate electrolytes lead to low charge-discharge cycle stability due to adverse reactive species at the anode surface.1-4 This reactive species are called the solid electrolyte interface (SEI).1 SEI instabilities/inhomogeneities result in its continuous thickening and formation of electronically non-active dead lithium.2 SEI composition and structure are affected by both solvent and electrolyte chemistry in bulk solution and, more importantly, at the electrode-electrolyte interface.4 Current research studies suggest that X-rich (where X is a halogen) SEI yields superior performance compared to halogen-free SEI.1,5 Electrolytes that have large volume fractions of halogenated species have statistically higher probability to be reduced at the electrode surface and yield X-rich SEI layers.6 Therefore, the use of halogenated solvent and/or high concentrated (> 1 M) lithium salt with halogenated anions has been actively explored for LiMBs. However, the high cost of Li salts and high viscosity of the electrolyte at high salt concentration make the concentrated electrolytes unrealistic for commercial battery applications. In search of a cost-effective solution for high performance LiMBs, halogenated electrolyte additives could serve as an ideal approach since only a small amount of the additive would be potentially required to induce similar X-rich interface that can be seen in the case of the halogenated ether electrolyte. In this meeting abstract, we present a new concept that leverages favorable electrostatic interactions with the electrolyte additive to drive the formation of robust SEI layers even at low additive content. Specifically, custom-designed additives can be electrostatically attracted to the negatively charged electrode, creating a high population of halogenated species at the anode surface even at a dilute Li salt concentration. Effective SEI formation with a low-concentration additive circumvents the challenges associated with the current state-of-the-art approach of using halogenated species at high concentration (i.e., unfavorably high solution viscosity and high cost). Reference 1 Louli, A. J. et al. Diagnosing and correcting anode-free cell failure via electrolyte and morphological analysis. Nature Energy 5, 693-702, (2020).2 Chen, K.-H. et al. Dead lithium: mass transport effects on voltage, capacity, and failure of lithium metal anodes. Journal of Materials Chemistry A 5, 11671-11681, (2017).3 Lin, D. et al. Three-dimensional stable lithium metal anode with nanoscale lithium islands embedded in ionically conductive solid matrix. Proc Natl Acad Sci U S A 114, 4613-4618, (2017).4 Lin, D., Liu, Y. & Cui, Y. Reviving the lithium metal anode for high-energy batteries. Nat Nanotechnol 12, 194-206, (2017).5 Yu, Z. et al. Molecular design for electrolyte solvents enabling energy-dense and long-cycling lithium metal batteries. Nature Energy 5, 526-533, (2020).6 Yamada, Y., Wang, J., Ko, S., Watanabe, E. & Yamada, A. Advances and issues in developing salt-concentrated battery electrolytes. Nature Energy 4, 269-280, (2019).

A high-flash-point quasi-solid polymer electrolyte for stable nickel-rich lithium metal batteries

In the exploration of next-generation high-energy–density batteries, lithium metal is regarded as an ideal candidate for anode materials. However, lithium metal batteries (LMBs) face challenges in practical applications due to the risks associated with organic liquid electrolytes, among which their low flash points are one of the major safety concerns. The adoption of high flash point quasi-solid polymer electrolytes (QSPE) that is compatible with the lithium metal anode and high-voltage cathode is therefore a promising strategy for exploring high-performance and high-safety LMBs. Herein, we employed the in-situ polymerization of poly (epoxidized soya fatty acid Bu esters-isooctyl acrylate-ditrimethylolpropane tetraacrylate) (PEID) to gel the liquid electrolyte that formed a PEID-based QSPE (PEID-QSPE). The flash point of PEID-QSPE rises from 25 to 82 °C after gelation, contributing to enhanced safety of the battery at elevated temperatures, whereas the electrochemical window increases to 4.9 V. Moreover, the three-dimensional polymer framework of PEID-QSPE is validated to facilitate the uniform growth of the solid electrolyte interphase on the anode, thereby improving the cycling stability of the battery. By employing PEID-QSPE, the Li|LiNi0.9Co0.05Mn0.05O2 cell achieved long-term cycling stability (Coulombic efficiency, 99.8%; >200 cycles at 0.1 C) even with a high cathode loading (∼5 mg cm−2) and an ultrathin Li (∼50 μm). This electrolyte is expected to afford inspiring insights for the development of safe and long-term cyclability LMBs.

Multifunctional nitrile additives for inducing pseudo-concentration gel-polymer electrolyte: Enabling stable high-voltage lithium metal batteries

High-voltage lithium metal batteries (LMBs) are promising for next-generation high-energy storage systems. Unfortunately, their implementation has been severely plagued by the interfacial instability between the high-voltage cathodes/lithium metal (LM) anodes and electrolytes. To tackle these challenges, a novel nitrile additive, 1,4-dicyanobenzene (DCB) (Synonyms: terephthalonitrile), is added to the in situ polymerized pentaerythritol tetraacrylate-based gel polymer electrolyte (GPE). The DCB additive, as demonstrated both theoretically and experimentally, plays a crucial role in altering the Li+ coordinated solvation structure within the GPE. This alteration leads to the formation of a pseudo-concentrated electrolyte with a tightly packed Li+ cluster, expanding the electrochemical stability window of the electrolyte. Moreover, the DCB-included GPE significantly improves its compatibility with both LM anode and high-voltage cathode, attributed to the modified solvation structure and the generated LiF-rich electrolyte/electrode interphases. Accordingly, the GPE enables stable cyclic performance of LMBs based on a 4.9 V LiNi0.5Mn1.5O4 cathode at a low relative negative/positive ratio of 4, achieving a high reversible capacity of 123.8 mAh g−1 with a capacity retention of 87.7 % over 500 cycles at 0.5 C. This work provides new insights into enhancing the cyclability of high-voltage LMBs via the synergistic effect of additives and GPE.

Amorphous High‐Entropy Alloy Interphase for Stable Lithium Metal Batteries

AbstractThe unstable anode/electrolyte interphase induces severe lithium dendrite growth hindering the practical application of lithium metal batteries. The lithium alloy interphase presents a promising strategy for regulating Li+ plating/stripping behavior. However, binary or ternary alloys are insufficient to address various challenges in lithium metal batteries and the high temperature required for alloy preparation hampers their direct applications on lithium metal surfaces. In this study, a high‐entropy alloy (HEA) interphase is developed on lithium metal surfaces via room‐temperature magnetron sputtering, showcasing multifunctional advantages in regulating Li+ plating/stripping behavior. The cocktail effect of the (HEA) facilitated the formation of a homogeneous amorphous interphase with abundant lithiophilic sites and magnetic properties, promoting uniform Li+ nucleation and deposition. Furthermore, the high mechanical strength and corrosion resistance of HEA provided physicochemical stability for the lithium anode interphase, consistently suppressing dendrite growth. Consequently, lithium metal anodes with HEA interphases exhibited robust cycling performance lasting over 4000 h at 2 mA cm−2. The LFP full battery demonstrated high‐capacity retention of 90% with an average Coulombic efficiency of 99.7%. Thus, the HEA interphases on lithium metal surfaces offer controllable regulation of Li+ deposition behavior through high‐entropy manipulation, opening novel strategies for stable lithium metal batteries.

Covalent Triazine Based Frameworks with Donor-Donor-π-Acceptor Structures for Dendrite-Free Lithium Metal Batteries.

The appearance of disordered lithium dendrites and fragile solid electrolyte interfaces (SEI) significantly hinder the serviceability of lithium metal batteries. Herein, guided by theoretical predictions, a multi-component covalent triazine framework with partially electronegative channels (4C-TA0.5TF0.5-CTF) is incorporated as a protective layer to modulate the interface stability of the lithium metal batteries. Notably, the 4C-TA0.5TF0.5-CTF with optimized electronic structure at the molecular level by fine-tuning the local acceptor-donor functionalities not only enhances the intermolecular interaction thereby providing larger dipole moment and improved crystallinity and mechanical stress, but also facilitates the beneficial effect of lithiophilic sites (C-F bonds, triazine cores, C=N linkages and aromatic rings) to further regulate the migration of Li+ and achieve a uniform lithium deposition behavior as determined by various in-depth in/ex situ characterizations. Due to the synergistic effect of multi-component organic functionalities, the 4C-TA0.5TF0.5-CTF modified full cells perform significantly better than the common two/three-component 2C-TA-CTF and 3C-TF-CTF electrodes, delivering an excellent capacity of 116.3 mAh g-1 (capacity retention ratio: 86.8 %) after 1000 cycles at 5 C and improved rate capability. This work lays a platform for the prospective molecular design of improved organic framework relative artificial SEI for highly stable lithium metal batteries.

Highly Tough Slide-Crosslinked Gel Polymer Electrolyte for Stable Lithium Metal Batteries.

Gel polymer electrolytes (GPEs) hold great promise for the practical application of lithium metal batteries. However, conventional GPEs hardly resists lithium dendrites growth and maintains long-term cycling stability of the battery due to its poor mechanical performance. Inspired by the slide-ring structure of polyrotaxanes (PRs), herein we developed a dynamic slide-crosslinked gel polymer electrolyte (SCGPE) with extraordinary stretchability of 970.93 % and mechanical strength of 1.15 MPa, which is helpful to buffer the volume change of electrodes and maintain mechanical integrity of the battery structure during cycling. Notably, the PRs structures can provide fast ion transport channels to obtain high ionic conductivity of 1.73×10-3 S cm-1 at 30 °C. Additionally, the strong polar groups in SCGPE restrict the free movement of anions to achieve high lithium-ion transference number of 0.71, which is favorable to enhance Li+ transport dynamics and induce uniform Li+ deposition. Benefiting from these features, the constructed Li|SCGPE-3|LFP cells exhibit ultra-long and stable cycle life over 1000 cycles and high-capacity retention (89.6 % after 1000 cycles). Even at a high rate of 16 C, the cells deliver a high capacity of 79.2 mAh g-1. The slide-crosslinking strategy in this work provides a new perspective on the design of advanced GPEs for LMBs.

Synergistic effect of LixSi/Li3N artificial interface and 3D framework for enabling Dendrite-free, long-life lithium metal anodes

Lithium metal is highly favored as an ideal anode material in future high-capacity lithium batteries due to its appealing properties. Nevertheless, the implementation of lithium metal batteries (LMBs) is severely plagued by challenges such as instable solid electrolyte interface (SEI), uncontrolled growth of dendrite, and severe volume expansion. Herein, to address the aforementioned issues, an artificial SEI layer is fabricated, which is comprised of LixSi alloy and Li3N. The in-situ generated LixSi/Li3N interface is formed on the carbon fiber (denoted as CF/LixSi/Li3N) through a spontaneous reaction between molten Li and Si3N4. Density functional theory (DFT) calculations reveal that LixSi alloy has low ion diffusion energy barrier, which facilitates the low nucleation overpotential of Li+ and enables homogeneous lithium deposition. Li3N can further promote the rapid Li+ transport due to the excellent Li+ conductivity. In addition, the reserved 3D space effectively mitigates the volume change along cycling procedure. Owing to the synergistic effect of the LixSi/Li3N protective layer and the 3D structure, the composite anode shows higher cycling stability with a lifetime of more than 3000 cycles at 1 mA cm−2. Furthermore, matched with commercial LiFePO4 (LFP) and LiNi5Co2Mn3O2 (NCM523) cathodes, the full cells also exhibit impressive electrochemical properties. This work introduces an ingenious approach for constructing stable lithium metal anodes and effective lithium metal batteries.