Performance Of Lithium Metal Batteries Research Articles

LiF Artifacts in XPS Analysis of the SEI for Lithium Metal Batteries.

The solid electrolyte interphase (SEI) is considered to be the key to the performance of lithium metal batteries (LMBs). The analysis of the SEI and cathode electrolyte interphase (CEI) composition (especially F 1s spectra) by X-ray photoelectron spectroscopy (XPS) has become a consensus among researchers. However, the surface-sensitive XPS characterization is susceptible to LiF artifacts due to several factors, leading to the overexaggerated role of LiF in the analysis of the SEI and CEI. In this paper, we conduct a systematic study on the reasons for the LiF artifacts in the XPS characterization of LMBs. The decomposition of the SEI and CEI components under argon ion sputtering, the reaction between Li2CO3 and LiPF6 in the electrolyte, influence of different sample pretreatments, the selection of the XPS measurement region, and the measurement time on the resulting spectra are investigated. The results indicate that the high content of LiF in the SEI and CEI may be attributed to the LiF artifacts, and the role of LiF in the SEI may be overexaggerated as a consequence. This work sounds an alarm about the potential misuse of argon ion sputtering and the lack of rigorous XPS characterization in SEI studies. This work also helps to set up standardized XPS characterization to provide a more accurate understanding of the role of SEI components.

In Situ Electrochemically Deposited Mg Seeds Stabilizing the Lithium Metal Anode

AbstractLithium metal, recognized for its extremely low reaction potential and ultrahigh theoretical specific capacity, is regarded as the “Holy Grail” of anode materials. However, the formation of lithium dendrites result in rapid cell capacity degradation and considerable safety issues, hindering its further advancement. In this study, in situ Mg seeds are generated on the lithium metal surface during cycling by incorporating MgCl2 into the electrolyte. These Mg seeds function as thiophilic sites, which lower the Li nucleation barrier and promote uniform Li nucleation and growth. Consequently, symmetric cells constructed with the carbonate electrolyte can cycle stably for over 400 h at a current density of 1 mA cm−2 and a capacity of 1 mAh cm−2. Notably, full cells using Li4Ti5O12 as the cathode can maintain stable cycling for 300 cycles, achieving a capacity retention rate of 71.9 %. This method has demonstrated its effectiveness in mitigating lithium dendrites formation and enhancing the performance of lithium metal batteries.

Enhancing performance of lithium metal batteries through acoustic field application

The graphic illustrates how an external acoustic field stabilizes the SEI layer by enhancing lithium-ion mass transfer at slip lines and kinks, reducing pit formation and promoting a more uniform SEI, ultimately improving battery performance.

Probing Electrochemical Reactions at the Electrode-Electrolyte Interface in Lithium Metal Battery, Combining Experimental Approach and Computational Calculation

Lithium-ion batteries have attracted significant attention for applications such as energy supply for electric vehicles, large-scale stationary power sources, and energy storage for renewable energy. Research and development of various electrode materials continue for further increasing charge / discharge capacity, expanding operation lifetime. Theoretical capacity of lithium metal is 3860 mAh/g, which is approximately 10 times larger than that of graphite negative electrode (372 mAh/g), which is commonly used in conventional lithium-ion batteries. Therefore, lithium metal batteries, which combine lithium metal negative electrode with a commonly used Lithium nickel manganese cobalt oxides (NCM) positive electrode, are expected to significantly increase energy density and considered to be one of the promising next-generation batteries. Improving the performance of the electrolyte solution is essential to fully utilize the newly developed electrode materials for both positive and negative electrodes. As lithium metal exhibits the most negative potential (-3.04 V v.s. SHE), the electrolyte solution must possess high reduction stability. At the same time, passivation film, solid electrolyte interface (SEI), formed on lithium metal also plays an important role to prevent further decomposition of electrolyte solution. Meanwhile, positive electrodes have oxidation potentials of 4.2 V or higher, and the reactivity at the positive electrode (cathode) and the electrolyte interface (CEI) is also a crucial factor influencing the performance of lithium metal batteries. Thus, controlling the reactions of the electrolyte solution at the electrode interface is a critical factor for operating lithium metal batteries stably and reliably over the long term.In recent years, research and development of electrolyte solutions have focused on enhancing reduction and oxidation stability by exploring various types of solvents, electrolyte salts, and controlling their concentrations. Ether-based electrolyte solutions are known for their higher reduction stability comparing commercially available carbonate-based electrolyte solutions. However, the oxidative stability of conventional concentration ether-based electrolyte solution is quite low, leading the decomposition at oxidation potentials over 4 V. Strategies to improve the oxidative stability of ether-based electrolyte solutions have been extensively studied, and one of the candidates is increasing electrolyte salt concentration.In this study, we have conducted electrochemical performance tests on lithium metal batteries using a concentrated electrolyte solution of ether-based solvents and LiFSI (Lithium bis(trifluoromethanesulfonyl)imide), with lithium metal and NCM positive electrode. As the solvation structures in the electrolyte solution directly affect the formation mechanism of SEI and CEI, the solvation structures are estimated by Raman spectroscopy, and their chemical stability and decomposition mechanisms are estimated by DFT calculations. We have conducted detailed analyses of reduction and oxidative decomposition reactions occurring at the electrode surface, and confirmed the applicability of the prediction combining Raman spectroscopy and DFT calculation. Figure 1

Dielectric additive induced weak Li solvation towards stabilized solid electrolyte interface for 4.6V lithium metal batteries

Developing stable electrode-electrolyte interphases on Li metal anode (LMA) and high voltage cathode is crucial for producing durable Li metal batteries. Electrolyte engineering has been regarded as an efficient way to in-situ construct stable and robust interphase. Herein, a dielectric electrolyte system is proposed by introducing LiNbO3 nanoparticles to liquid carbonate-based electrolyte for regulating Li+ solvation structure, and thus inducing stable inorganic-rich solid electrolyte interphase. Moreover, these dielectric nano LiNbO3 additives can regulate the Li+ flux through their build-in electric field to guide dendrite free Li deposition. These multi-functional features of LiNbO3 allow for exceptional cyclic performance in both symmetric cell configuration (3300 h at 0.5 mA cm−2 and 1 mA h cm−2) and Li||LiNi0.8Co0.1Mn0.1O2 half-cell charged at 4.6 V with capacity retention of 80% over 200 cycles. These results demonstrate great potential of dielectric electrolyte on improving the performance of lithium metal batteries.

Ternary-salt localized high-concentration electrolyte: An ideal companion facilitating stable high-voltage cycling of lithium metal batteries

The strategic design of novel electrolytes to further enhance the overall performance of lithium metal batteries (LMBs) is highly desirable. Herein, combining the synergistic effect of multiple functional lithium (Li) salts and the solvation structure advantage of localized high-concentration electrolyte (LHCE), we propose a novel ternary-salt localized high-concentration electrolyte (TSLHCE) termed CETHER3-TDE that achieves broad electrochemical stability window, dendrite-free Li deposition, effective electrode interface protection, flame retardancy, and significantly enhances the cycling performance of LMBs. CETHER3-TDE enables Li (50 μm thickness) ||NMC622 (13.8 mg cm−2, 2.50 mAh cm−2) cell to achieve an impressive capacity retention of 83 % after 300 cycles with a cut-off voltage of 4.4 V. Additionally, it enables the Li (50 μm thickness) ||NMC811 (19.8 mg cm−2, 3.96 mAh cm−2) cell to achieve a capacity retention of 83.6 % after 170 cycles, under an ultrahigh cut-off voltage of 4.6 V. Furthermore, the Li metal pouch cell employing CETHER3-TDE, featuring a low negative/positive (N/P) capacity ratio of 1.33 and lean electrolytes of 2.3gAh−1, attains an energy density of 413 Wh kg−1 and maintains stable cycling at 4.6 V. Moreover, analysis conducted by Accelerating Rate Calorimeter has verified that CETHER3-TDE enhances both the thermal stability as well as the thermal runaway trigger temperature of LMBs, thereby substantially improving their safety. This work provides valuable insights for future research on multi-salt complex electrolyte system for practical application in high-energy-density and high safety LMBs.

A covalently bonded, LiF-rich solid electrolyte interphase for Li metal batteries with superior low-temperature performance

The solid electrolyte interphase (SEI) layer plays a critical role in determining the performance of lithium metal batteries (LMBs). Here, we show that treating Li foils with 4,4,5,5,5-pentafluoropentanol (PFPO) results in the formation of a novel LiF-rich organic/inorganic SEI layer (designated as LiF-PO) that enhances the performance of LMBs. Compared to the native SEI layer that is electrochemically formed in LMBs, the LiF-PO SEI layer is mechanically robust, adopts a compact structure, and exhibits high Li+ conductivity. These features enable Li//Li symmetric cells to exhibit superior performance metrics, even at low temperatures, including inhibited Li dendrite growth, reduced polarization voltage, and elongated cycling lifetime. Moreover, compared to lithium–sulfur cells prepared using bare Li foils, the cells prepared using PFPO-treated Li foils also exhibit markedly improved performance at low temperatures in terms of specific capacity (796 mA h g−1 vs. 559 mA h g−1 at 0.1 C and −20 °C), rate capability (519 mA h g−1 vs. 222 mA h g−1 at 3 C and 0 °C), and cycling stability (504 mA h g−1 vs. 253 mA h g−1 at 0.1 C after 100 cycles at −20 °C). The lessons learned from our study establish new principles for designing high-performance SEI layers and may be extended to other types of metal batteries.

A novel strategy to improve the electrochemical properties of in-situ polymerized 1,3-dioxolane electrolyte in lithium metal batteries

The application of solid-state electrolytes (SSEs) is anticipated to enhance the safety performance of lithium metal batteries (LMBs). However, the progress of SSEs has been hindered by the unstable electrode–electrolyte interfaces (EEIs). In this study, in-situ polymerization of 1,3-dioxolane (DOL) is employed for the preparation of SSEs, with the addition of tributyl borate (TBB) to establish stable EEIs, particularly under high-voltage conditions. On one hand, the addition of TBB promotes the dissociation of lithium salts and increases the concentration of free Li+, resulting in an increase in room temperature ionic conductivity to 1.13 × 10−4 S cm−1 and an improvement in the Li+ transference number to 0.69 for the prepared poly-DOL electrolytes (PDE-TBB). Benefiting from the enhanced Li+ transport, the Li/PDE-TBB/Li symmetric cell exhibits a cycle life exceeding 1,000 h with a low polarization voltage as low as 12 mV, and the Li/PDE-TBB/LiFePO4 cell demonstrates exceptional cyclic stability over 800 cycles at 1C, with a coulombic efficiency exceeding 99.8 % and a capacity retention of 89.6 %. On the other hand, PDE-TBB exhibits improved stability under high-voltage conditions and the capacity to establish robust boron-rich cathode electrolyte interphase (CEI) on the LiNi0.8Co0.1Mn0.1O2 (NCM811) surface, thereby enhancing the structural stability of cathode materials and ensuring exceptional cycling performance of Li/PDE-TBB/NCM811cell. This work presents a promising strategy for developing novel ether-based SSEs suitable for high-voltage lithium metal batteries.

Fast Li+ De‐Solvation Kinetics with PDDA Intercalated‐Montmorillonite Hybrid Artificial Interface Layer on Cu Substrate for Lithium Metal Batteries in a Wide Climate Temperature

AbstractThe tolerance requirement of lithium metal batteries in harsh environments presents great challenges to electrode materials and electrolytes because temperature plays a significant effect in electrochemical processes. In this study, a new artificial layer on a copper current collector that boosts the de‐solvation kinetics and provides electrostatic shielding effects is presented to enhance the electrochemical performance of lithium metal batteries. This new artificial layer is constructed with poly(diallyl dimethyl ammonium chloride) (PDDA) and exfoliated montmorillonite (MMT) nanosheets, which combine the advantages of both inorganic clay and organic polymer. Within this protective hybrid layer, the PDDA cations increase the interlayer spacing of MMT, broadening the diffusion pathways of Li+ and accelerating their fast diffusion. Moreover, the PDDA‐MMT protective layer facilitates Li+ de‐solvation at the interface of the Li anode and electrolyte, enabling the rapid and reversible plating/stripping of lithium metal. As a result, the as‐prepared PDDA‐MMT@Cu anode exhibits excellent stability, and good rate performance is achieved in a commercial electrolyte in the temperature range of −20–60 °C. By combining enhanced diffusion kinetics and electrostatic shielding as an artificial protective layer, this clay‐polymer composite provides a synergistic interaction and offers new inspiration for the development of lithium metal batteries.

In-situ construction of high-performance artificial solid electrolyte interface layer on anode surfaces for anode-free lithium metal batteries

The electrochemical performance of lithium metal batteries (LMBs) was hampered by the uncontrolled growth of lithium (Li) dendrites. To address this issue, the extensive application of artificial solid electrolyte interphase (SEI) coatings on anode surfaces emerged as an effective solution. Electrospinning, as an innovative technique for fabricating artificial SEI layers on the surface of copper (Cu) foil, effectively mitigated Li volume strain during cycling. In this study, an electrospun organic–inorganic composite nanofiber membrane was in-situ fabricated on Cu foil, serving as an artificial SEI layer (CuWs) for anode-free LMBs (AF-LMBs) to enhance battery performance. Lithiophilic polyvinylpyrrolidone was used as the polymer matrix, and Cu nitrate served as the inorganic functional particles capable of in-situ redox reactions. The CuWs with their three-dimensional (3D) network structure accommodated electrode volume changes and suppressed Li dendrite growth during Li deposition and stripping. Additionally, CuWs facilitated the in-situ generation of Li nitrate (LiNO3), which helped stabilize SEI layer and enhance Li utilization. The release sites of LiNO3 on the nanofibers enabled the in-situ reduction of metallic Cu, providing nucleation sites for Li deposition and forming the 3D ion–electron hybrid conductive networks. This CuWs layer reduced interfacial resistance and nucleation barriers, promoting uniform Li+ distribution on the anode surface. Li-Cu cells incorporating CuWs exhibited remarkable cycling stability, enduring over 460 cycles at 1.0 mA cm−2 and 1.0 mAh cm−2 with an average Coulombic efficiency of over 98.6 %. In Li-poor cells, the LFP|PE|CuWs achieved stable cycling for more than 30 cycles at 1.0 C, with a capacity retention rate of 92.0 %. These findings demonstrated that the CuWs membrane significantly enhanced the electrochemical performance of Li-poor cells and provided a novel artificial SEI protective strategy for advanced AF-LMBs with high energy density.

SEI Formation and Lithium-Ion Electrodeposition Dynamics in Lithium Metal Batteries via First-Principles Kinetic Monte Carlo Modeling.

The stabilization and enhanced performance of lithium metal batteries (LMBs) depend on the formation and evolution of the Solid Electrolyte Interphase (SEI) layer as a critical component for regulating the Li metal electrodeposition processes. This study employs a first-principles kinetic Monte Carlo (kMC) model to simulate the SEI formation and Li+ electrodeposition processes on a lithium metal anode, integrating both the electrochemical electrolyte reduction reactions and the diffusion events giving place to the SEI aggregation processes during battery charge and discharge processes. The model replicates the competitive interactions between organic and inorganic SEI components, emphasizing the influence of the cycling regime. Results indicate that grain boundaries within the SEI facilitate faster lithium-ion transport compared to crystalline regions, crucial for improving the performance and stability of LMBs. The findings underscore the importance of dynamic SEI modeling for further development of next-generation high-energy-density batteries.

The long-lasting maintenance of the pore structure achieves the stability of lithium metal batteries

The separator is considered critical to the safety and performance of lithium metal batteries (LMBs), however, the separator structure fails under high temperature conditions due to damage resulting in decreased mechanical strength, which causes short-circuiting of the battery. This paper describes a novel process to prepare stable and uniform dispersions of aramid nanofibers (ANFs) by bottom-up low-temperature polymerization, and then crosslink the ANFs with N2 plasma-treated polypropylene (PP) separator through capping isocyanate crosslinkers. The composite separator not only has excellent mechanical properties with hardness and modulus of elasticity up to 0.35 and 2.26 GPa, which is three times higher than the PP separator, but also has high-temperature thermal stability, the size maintenance rate reaches 99.8 % at 200 °C. Meanwhile, real-time monitoring of the pore size at different temperatures by synchrotron radiation small-angle X-ray scattering (SR-SAXS) showed that the pore radius of gyration was kept at 8.81 nm and the size change rate was only 22.8 % at 200 °C, which demonstrated that the composite separator had an outstanding ability to maintain the pore structure to ensure the stability of the ionic transport channel. Therefore, the crosslinked composite separator has greater potential for improving the performance and safety of LMBs in extreme high-temperature environments.

A Short Review and Future Prospects of Biomass-Based Solid Polymer Electrolytes for Improving the Performance of Lithium Metal Batteries

A Short Review and Future Prospects of Biomass-Based Solid Polymer Electrolytes for Improving the Performance of Lithium Metal Batteries

Advances in Functional Organosulfur-Based Mediators for Regulating Performance of Lithium Metal Batteries.

Rechargeable lithium metal batteries (LMBs) are promising next-generation energy storage systems due to their high theoretical energy density. However, their practical applications are hindered by lithium dendrite growth and various intricate issues associated with the cathodes. These challenges can be mitigated by using organosulfur-based mediators (OSMs), which offer the advantages of abundance, tailorable structures, and unique functional adaptability. These features enable the rational design of targeted functionalities, enhance the interfacial stability of the lithium anode and cathode, and accelerate the redox kinetics of electrodes via alternative reaction pathways, thereby effectively improving the performance of LMBs. Unlike the extensively explored field of organosulfur cathode materials, OSMs have garnered little attention. This review systematically summarizes recent advancements in OSMs for various LMB systems, including lithium-sulfur, lithium-selenium, lithium-oxygen, lithium-intercalation cathode batteries, and other LMB systems. It briefly elucidates the operating principles of these LMB systems, the regulatory mechanisms of the corresponding OSMs, and the fundamentals of OSMs activity. Ultimately, strategic optimizations are proposed for designing novel OSMs, advanced mechanism investigation, expanded applications, and the development of safe battery systems, thereby providing directions to narrow the gap between rational modulation of organosulfur compounds and their practical implementation in batteries.

Deciphering the Decomposition Mechanisms of Ether and Fluorinated Ether Electrolytes on Lithium Metal Surfaces: Insights from CMD and AIMD Simulations.

The performance of lithium metal batteries can be significantly enhanced by incorporating fluorinated ether-based electrolytes, yet the solid electrolyte interphase (SEI) formation mechanism on lithium metal surfaces remains elusive. This study employs classical and ab initio molecular dynamics simulations to investigate the decomposition mechanisms of lithium bis(fluoromethanesulfonyl)imide (LiFSI) in 1,2-diethoxyethane (DEE) and its fluorinated analogues, F5DEE and F2DEE, when in contact with lithium metal. Our findings indicate that F5DEE-based electrolytes favor the formation of a FSI-rich primary solvation shell around Li+, while F2DEE-based electrolytes yield a solvent-rich environment. The normalized number density at the Li/electrolyte/Li interface shows a depletion of FSI anions in the electrochemical double layer (EDL) structure near the Li anode upon charging, with the distance between the first main peak of the FSI anion and Li anode following the order F5DEE < DEE < F2DEE. Analysis of the electronic projected density of states and charge transfer dynamics unveils the reductive dissociation pathways of FSI anions and fluorinated DEE solvents on the lithium metal surface, taking into account the influence of the EDL structure. DEE is identified as the most reduction-stable solvent, leading to the selective dissociation of FSI anions and the formation of an entirely inorganic SEI. In contrast, F2DEE displays a pronounced reduction tendency, forming an organic-rich SEI due to the solvent-dominated lowest unoccupied molecular orbital at the interface. F5DEE, competing with FSI anions for reduction, results in the formation of an inorganic-rich hybrid SEI with the highest LiF content. The simulation results correlate well with experimental observations and underscore the pivotal role of various fluorinated functional groups in the formation of EDL and SEI near the lithium metal surface.

Modified Liquid Electrolyte with Porous Liquid Type-II for Lithium-Metal Batteries

Liquid electrolytes modified by adding type-II porous liquid (PL) were designed and prepared to study its effect on the performance of lithium-metal batteries. Porous liquids provide internal, permanent, and empty porosity which are capable of coordinating and transporting Li+. The potential of the porous liquid to capture and transport ions with high mobility leads to enhancement in battery performance. In this study, the physicochemical properties of electrolytes, mechanism of solvation, transport, and electrical conductivity of lithium ions through the new electrolytes will be presented, and the potential of the liquid electrolyte based on the type-II porous liquid to develop the battery performance was investigated. This modification effectively improved the Li ionic conductivity of the electrolyte because of the Li+ ion solvation by type-II PL. The dissociation of Li+-TFSI− ion pairs and the formation of complexes with Li+ ions (Li-PL) were improved by using the type-II PL, resulting in an increase in the ionic conductivity of the electrolyte. Our findings suggest that the use of PL electrolytes can be a good candidate for improvement in physicochemical properties of electrolytes leading to an enhancement in Lithium-Metal Batteries.

Application of artificial SEI layers for lithium metal battery anodes

Unpredictable lithium dendrite growth on the metal anode and repeated destruction and creation of the solid electrolyte interphase (SEI) layer result in hidden risks and low Coulombic efficiencies (CEs). Researchers have found that designing a high-quality SEI layer can prevent the growth of dendrite. However, designing and forming a high-quality SEI layer is still a problem. Making trade-off between capacity reduction caused by the SEI layer and better cycle stability significantly limits the general performance of lithium metal batteries. In this research, characteristics of SEI layers and some significant advancements made in SEI formation are outlined. Some designs for the SEI layers on the lithium metal anodes include designing hybrid polymer SEI layers, producing synthetic SEI layers. By controlling the behaviours of Li ions throughout the stripping and depositing processes, the capacity and stability of Li metal anodes may be improved. Finally, some case studies of the applying of SEI in lithium metal battery systems are introduced.

Stability and performance of lithium metal batteries using silicon and silver alloyed separator surfaces

Lithium metal is renowned for its exceptional theoretical capacity and the lowest electrochemical potential, making it a cornerstone for batteries that can push the boundaries of energy and power density. However, its widespread adoption has been hindered by significant drawbacks, such as an unstable solid electrolyte interface (SEI) layer, substantial volume changes during charge-discharge cycles, and the formation of lithium dendrites. In our study, we have addressed these challenges by employing an innovative alloying technique to modify the surface of the separator with silicon (Si) and silver (Ag). This approach facilitates the formation of LiSi and LiAg alloys on the separator surface, leading to the creation of a novel lithium metal-lithium alloy composite anode. Our electrochemical tests have demonstrated that batteries equipped with this surface-modified lithium alloy composite anode exhibit superior coulombic efficiency and an impressively extended cycle life. Furthermore, when utilizing an ether-based electrolyte, the LiAg and LiSi alloy composite anodes have shown remarkable capacity retention rates of 89.1 % and 86.3 %, respectively, after 200 cycles in full cell tests. These results are notably superior to those of anodes made with bare lithium metal. In conclusion, the development of the face-to-face lithium alloy composite anode holds great promise for the practical application of lithium batteries with enhanced stability and performance. This advancement is a significant step towards realizing the full potential of lithium metal batteries in a variety of applications.

Highly Conductive Single-Ion Polymeric Electrolyte for Long-Cycle-Life Lithium Metal Batteries

Considerable research has been conducted on single-ion conductive polymeric electrolytes with high lithium ion transference numbers. However, low ionic conductivity is a long-standing challenge for lithium metal batteries, hindering the development of extending their cycle life. In this study, we synthesized a novel fluorine-containing single-ion polymeric electrolyte, LiP(VDF-co-MAF)BB (Polyvinylidene fluoride trifluoromethyl acrylate lithium borate polymer; subsequently referred to as PPMBB), exhibiting a room temperature conductivity of 1.03 × 10−3 S/cm. This electrolyte demonstrates a high lithium ion transference number of 0.7901 and an extended electrochemical stability window of 5.5 V. Under a 2 C discharge rate, it manifests a remarkable discharge specific capacity of 146.8 mAh/g. Moreover, even after 364 cycles, the capacity retention remains at 76%. The single-ion polymeric gel electrolyte designed in this work provides a promising strategy for the prolonged cycling performance of lithium metal batteries.

Influence of the PET-PTFE Separator Pore Structure on the Performance of Lithium Metal Batteries.

The separator is a crucial component in lithium batteries, as it physically separates the cathode and the anode while allowing ion transfer through the internal channel. The pore structure of the separator significantly influences the performance of lithium batteries, particularly lithium metal batteries. In this study, we investigate the use of a Janus separator composed of poly(ethylene terephthalate) (PET)-polytetrafluoroethylene (PTFE) fibers in lithium metal batteries. This paper presents a comprehensive analysis of the impact of this asymmetric material on the cycling performance of the battery alongside an investigation into the influence of two different substrates on lithium-ion deposition behavior. The research findings indicate that when the rigid PET side faces the lithium metal anode and the soft PTFE side faces the cathode, it significantly extends the cycling lifespan of lithium metal batteries, with an impressive 82.6% capacity retention over 2000 cycles. Furthermore, this study demonstrates the versatility of this separator type in lithium metal batteries by assembling the lithium metal electrode with high cathode-loading capacities (4 mA h/cm2). In conclusion, the results suggest that the design of asymmetric separators can serve as an effective engineering strategy with substantial potential for enhancing the lifespan of lithium metal batteries.