Anode-free Lithium Metal Batteries Research Articles

Unveiling the effect of alloy-type coating for lithium metal plating and stripping on anode-free lithium metal batteries

Li dendrite formation is the root cause of capacity fading in anode-free lithium metal batteries (AFLMBs). Previous studies have shown that Au coating on Cu can seed Li nucleation by forming Li3Au for smooth Li plating and improves the cycle life of Li||Cu cells. However, unlike Li||Cu cells with excessive Li supply, in practical AFLMBs (i.e., full-cell), the active lithium is limited from the lithium intercalation cathode. The introduction of alloy-type coatings may adversely affect the cycling stability due to the pulverization effect during alloying with Li (e.g., the volume expansion rate from Au to Li3Au is 337%). Here, we evaluate the full-cell performance of AFLMBs focusing on different thicknesses of Au coating (20, 50, and 100nm) and four coating layers (alloy-type: Au, Ag; non-alloy-type: Ni, Ti). Our results show that although the alloy-type coatings (i.e., Au and Ag) lower the lithiation overpotential, the full-cells equipped with these coatings experience faster capacity fading than those with pristine and non-alloy-type coatings. When the Au-coated Cu is paired with high-mass loading NMC622 cathode, the full-cells AFLMBs exhibit inferior performance with a low initial Coulombic efficiency (89.97% and 79.75% for 20 and 100nm thick Au coating) and accelerated capacity fading, producing plated Li with porous structure and carbonyl-rich solid electrolyte interphase. This study underscores the necessity of employing a full-cell configuration for evaluating Li plating-stripping efficacy in AFLMBs, emphasizing a transition from laboratory research to practical applications.

Interrelation Between External Pressure, SEI Structure, and Electrodeposit Morphology in an Anode‐Free Lithium Metal Battery

AbstractThe interrelation is explored between external pressure (0.1, 1, and 10 MPa), solid electrolyte interphase (SEI) structure/morphology, and lithium metal plating/stripping behavior. To simulate anode‐free lithium metal batteries (AF‐LMBs) analysis is performed on “empty” Cu current collectors in standard carbonate electrolyte. Lower pressure promotes organic‐rich SEI and macroscopically heterogeneous, filament‐like Li electrodeposits interspersed with pores. Higher pressure promotes inorganic F‐rich SEI with more uniform and denser Li film. A “seeding layer” of lithiated pristine graphene (pG@Cu) favors an anion‐derived F‐rich SEI and promotes uniform metal electrodeposition, enabling extended electrochemical stability at a lower pressure. State‐of‐the‐art electrochemical performance is achieved at 1MPa: pG‐enabled half‐cell is stable after 300 h (50 cycles) at 1 mA cm−2 rate −3 mAh cm−2 capacity (17.5 µm plated/stripped), with cycling Coulombic efficiency (CE) of 99.8%. AF‐LMB cells with high mass loading NMC622 cathode (21 mg cm−2) undergo 200 cycles with a CE of 99.4% at C/5‐charge and C/2‐discharge (1C = 178 mAh g−1). Density functional theory (DFT) highlights the differences in the adsorption energy of solvated‐Li+ onto various crystal planes of Cu (100), (110), and (111), versus lithiated/delithiated (0001) graphene, giving insight regarding the role of support surface energetics in promoting SEI heterogeneity.

Re-evaluating the nano-sized inorganic protective layer on Cu current collector for anode free lithium metal batteries

Anode free lithium metal batteries (AF-LMBs) have conspicuous advantages both in energy density and the compatibility of battery manufacturing process. However, the limited cycle life of AF-LMBs is a crucial factor hindering its practical application. Fluorinated or nitride artificial inorganic solid electrolyte interphase (SEI) has been found as an effective method to prolong the lifespan of AF-LMBs. Herein, by investigating the impact of nano-sized inorganic gradient layers (LiF or Li3N) on initial Li deposition behavior, we notice that the Li+ diffusion barrier and the deposition morphology are highly depended on the thickness of inorganic layers. Thicker protective layers cause larger overpotential as well as more aggregated Li+ distribution. This study reveals that the ideal SEI should be synthesized thin and uniformly enough and uncontrollable artificial SEI can cause damage to the lifespan of AF-LMBs.

Suppressing Chemical and Galvanic Corrosion in Anode‐Free Lithium Metal Batteries Through Electrolyte Design

AbstractThe advancement of anode‐free lithium metal batteries (AFLMBs) is greatly appreciated due to their exceptional energy density. Despite considerable efforts to enhance the cycling performance of AFLMBs, the understanding of lithium corrosion, which leads to substantial capacity loss during the open circuit voltage (OCV), regardless of electrolyte chemistry, remains limited. In particular, the connection between electrolytes and lithium corrosion performance lacks clear understanding, and the impact of solid‐electrolyte interface (SEI) composition on resistance against lithium corrosion remains elusive. This study explores, for the first time, the effects of salt concentration and solvents on the lithium corrosion behavior in AFLMBs, utilizing the lithium bis(fluorosulfonyl)imide (LiFSI)‐1,2 dimethoxyethane (DME)‐1,3 dioxolane (DOL) electrolyte system. The findings reveal that increasing salt concentration leads to the suppression of chemical corrosion but exacerbation of galvanic corrosion. The key to effectively suppressing both chemical and galvanic corrosion lies in promoting the coordination of less‐soluble particles and polymers within the SEI. This conclusion is further validated by a two‐step electrolyte modification measurement. As a result, a new electrolyte formula, 0.5 M LiFSI‐0.5 M LiBF2(C2O4)‐0.5 M LiNO3(DME/fluoroethylene carbonate or FEC), is prepared and shown to have improved resistance to both chemical and galvanic corrosion, and the Coulombic efficiency loss from chemical corrosion is reduced to 0.13%.

Fabricating lithiophilic Sn nanolayer via vacuum evaporation coating for anode-free lithium metal battery

Lithium metal batteries (LMBs) have great advantages such like high energy density and capacity and low cost, which are widely studied by many researchers. As a type of LMBs, anode-free LMBs have zero Li excess, i.e., the entire Li is stripped from the cathode or current collector, obviously reducing the waste of excessive Li metal and improving the energy density of battery. However, the uneven deposition of Li will lead to the growth of Li dendrites, which reduces the columbic efficiency and cycling life of anode-free LMBs. In this work, the vacuum evaporation coating is used to synthesize a lithiophilic Sn nanolayer on Cu substrate, providing uniform deposition sites for Li. The polarization of Li deposition is reduced and the cyclability of anode-free LMBs is improved. As a result, a stable cycling performance for over 200 h at 3 mA cm−2 under 1 mAh cm−2 is achieved, demonstrating the superior Li-deposition regulation effect of Sn nanolayer.

Effect of Electrochemical Pre-Lithiation on Layered Oxide Cathodes for Anode-Free Lithium-metal Batteries.

Due to high energy density and lower manufacturing cost, anode-free lithium-metal batteries (AFLMBs) are attracting increasing attention. The challenges for developing them lie in inferior Coulombic efficiency and short cycle life due to the highly reactive lithium metal. Herein, an electrochemical pre-lithiation strategy is applied to layered oxide cathodes, specifically LiNiO2 and LiCoO2 , aiming to provide an additional lithium source and understand the effect on the cathode structure for AFLMBs. The mechanism for accommodating the excess Li depends on the structural stability of the cathodes where LiNiO2 forms lithiated Li2 NiO2 with the excess lithium in the crystalline lattice while the excess lithium in LiCoO2 forms a Li2 O phase. More importantly, an optimal amount of Li excess is necessary to maintain decent cycle stability and specific capacity in AFLMB, with 40% excess Li for LiNiO2 and 150% for LiCoO2 . While the pre-lithiation process causes particle pulverization depending on the amount of Li excess, LiCoO2 offers a much better cycle performance than LiNiO2 with a promising capacity retention of 80% after 300 cycles in AFLMB (vs 76% after 100 cycles for 40% Li excess in LiNiO2 ). This study provides a promising avenue for developing tailor-made layered oxide cathodes for AFLMBs.

Role of copper as current collectors in the reductive reactivity of polymers for anode-free lithium metal batteries - Insights from DFT and AIMD studies

Understanding the role of current collectors (CCs) in the reductive reactivity of polymers on Li metal and the resultant solid electrolyte interphase (SEI) formation is essential for improving the performance of anode-free lithium metal batteries (AFLMBs). In this study, we have examined the reactivity of three polymeric hosts: poly(ethylene oxide) (PEO), poly(ε-caprolactone) (PCL), and poly(trimethylene carbonate) (PTMC) at Li metal supported on Cu surfaces (Li/Cu) using density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations. In particular, the effect of copper (Cu) CCs on polymer stability, electronic structure, and their reduction reactions is investigated and compared to that of pure Li (100) surface. Through time-dependent Bader charge transfer analysis, electron transfer is identified as the triggering factor for polymer reduction. Based on the simulations, we find that the Cu CCs have a significant influence on the charge distribution of the Li metals, which increases electron transfer to the polymers and thereby accelerates polymers reduction. This thereby leads to different reaction mechanisms as compared to on Li-metal. The findings suggest that utilization of Cu CCs avoids the production of CO molecules and improves the quality of the formed SEI layer.

Laser-induced glassy carbon nanofiber trees

Here we report the synthesis of laser-induced glassy carbon nanofiber trees (CNFT). Unlike the previously reported laser-induced graphene (LIG) and laser-induced graphene fibers (LIGF), the CNFT do not have a highly graphenized nanostructure, as demonstrated by Raman spectroscopy, transmission electron microscopy, and X-ray diffraction. Since the CNFT are formed under conditions that usually ablate the carbon precursors, they have until recently escaped notice as a laser-induced carbon nanomaterial. We were able to both collect the CNFT in bulk using a vacuum attachment near the laser head, or we could retain the CNFT as an aerogel carpet on surfaces through the addition of water underneath our carbon precursor. We demonstrated the applicability of the CNFT as a promising energy storage material through testing a CNFT carpet on copper foil as an electrode material for anode-free lithium metal batteries. The cell exhibits low overpotential, a small nucleation energy barrier, and good cycling stability.

Overcoming Copper Substrate Thermodynamic Limitations in Anode-Free Lithium Pouch Cells via In Situ Seed Implantation.

Anode-free lithium metal batteries (AFLMBs) exhibit enhanced energy density and cost-effective manufacturing, albeit constrained by short lifespans due to inhomogeneous lithium nucleation and growth on the inherently lithiophobic Cu current collector. Although numerous attempts at Cu surface modifications aim to mitigate this thermodynamic limitation, they often result in substantial irreversible capacity loss and/or lack the stability required for practical applications. Here, we present an in situ seed implantation (ISI) strategy to address the aforementioned challenge. A 36 s ISI treatment created an ultrathin lithium metal layer, composed of uniform lithium nuclei with ∼100 nm in diameter, equating to 0.05 mAh cm-2, on the Cu substrate. This approach facilitates dense lithium deposition during cycles, effectively doubling the lifespan of an Ah-level 437 Wh kg-1 AFLMB. Our ISI strategy offers a straightforward and efficient solution that maintains battery energy density and manufacturing cost effectiveness, and its application extends beyond lithium metal.

Toward maximum energy density enabled by anode‐free lithium metal batteries: Recent progress and perspective

AbstractOwing to the emergenceof energy storage and electric vehicles, the desire for safe high‐energy‐density energy storage devices has increased research interest in anode‐free lithium metal batteries (AFLMBs). Unlike general lithium metal batteries (LMBs), in which excess Li exists to compensate for the irreversible loss of Li, only the current collector is employed as an anode and paired with a lithiated cathode in the fabrication of AFLMBs. Owing to their unique cell configuration, AFLMBs have attractive characteristics, including the highest energy density, safety, and cost‐effectiveness. However, developing AFLMBs with extended cyclability remains an issue for practical applications because the high reactivity of Li with limited inventory causes severely low Coulombic efficiency (CE), poor cyclability, and dendrite growth. To address these issues, tremendous effort has been devoted to stabilizing Li metal anodes for AFLMBs. In this review, the importance and challenges of AFLMBs are highlighted. Then, diverse strategies, such as current collectors modification, advanced electrolytes, cathode engineering, and operation protocols are thoroughly reviewed. Finally, a future perspective on the strategy is provided for insight into the basis of future research. It is hoped that this review provides a comprehensive understanding by reviewing previous research and arousing more interest in this field.

Ultralight lithiophilic three-dimensional lithium host for stable high-energy-density anode-free lithium metal batteries

Anode-free Li metal batteries (AF–LMBs) can exhibit substantially higher energy densities than that of Li-ion batteries (LIBs) and conventional LMBs; however, irreversible Li losses during Li plating/stripping, high density and low mechanical strength of state-of-the-art anode current collectors significantly undermine the energy benefits of AF configuration. Herein, we report Au-decorated insulating polyimide (PI@Au) nanofibers used as three-dimensional (3D) hosts promoting dendrite-free Li deposition. Their lithiophilic surfaces with low Li nucleation energy barrier and insulating 3D network with low local current density can synergistically regulate the uniform Li nucleation/growth following an “on fiber – in plane – on top” plating behavior. The superb Li reversibility ensures robust cycling stability of an NCM811||PI@Au AF–LMB cell with a high areal capacity of 6.4 mAh cm−2 (mass loading of 32.0 mg cm−2) for 100 cycles and high capacity retention of 86.0%. Owing to the ultrathin (10 μm) and ultralight (0.54 mg cm−2) characteristics of PI@Au nanofibers, unprecedented energy densities of 475 Wh kg−1 and 1199 Wh L−1 were achieved at the practical cell level, exceeding those of LIBs (263 Wh kg−1 and 634 Wh L−1) and LMBs (414 Wh kg−1 and 994 Wh L−1), respectively. The combination of a 3D insulating scaffold with lithiophilic decoration represents an effective strategy for designing AF–LMBs with ultrahigh energy densities.

Lithiophilic Zn3N2-Modified Cu Current Collectors by a Novel FCVA Technology for Stable Anode-Free Lithium Metal Batteries.

Anode-free lithium metal batteries (AFLMBs) offer high-energy-density battery systems, but their commercial viability is hindered by irregular lithium dendrite growth and "dead Li" formation caused by current collector defects. This study employed filtered cathode vacuum arc (FCVA) technology to fabricate Cu current collectors (CCs) with a lithiophilic Zn3N2 film. This advanced preparation process ensures an evenly distributed film that reduces the nucleation overpotential, homogenizes the interfacial electric field during plating/stripping processes, inhibits lithium dendrite growth, and forms a stable solid-electrolyte interphase (SEI). Our results show that the advanced Zn3N2@Cu CCs exhibit superior performance with a high CE of above 99.3% after 230 cycles at a current density of 0.5 mA cm-2 and an area capacity of 1 mAh cm-2. Additionally, Li-Zn3N2@Cu||Li-Zn3N2@Cu symmetrical cells had a longer stable cycle time of over 1000 h than that of Li||Li and Li-Cu||Li-Cu symmetrical cells at a current density of 1 mA cm-2 and an area capacity of 2 mAh cm-2. Compared with bare Cu CCs, the capacity retention rate is increased from 14.9 to 63.1% after 100 cycles with a 0.5C rate in the AFLMBs with LFP as the cathode. This work provides a pioneering, eco-friendly, and effective solution for the fabrication of anode CCs in AFLMBs, addressing a significant challenge in their commercial application.

High Performance Anode-Free Lithium Pouch Cells Employing Lithiophilic Gel Polymer Electrolyte with Ion Conductive Network

Anode-free lithium metal batteries have recently emerged as a next generation battery due to increased energy density by adopting bare current collector as an anode without excess lithium source. However, lithium tends to grow in uncontrolled dendritic form when depositied on a heterogeneous current collector, which eventually leads to low coloumbic efficiency and poor life span of the battery. Recent studies have attempted to apply artificial solid electrolyte interphase (SEI) on the current collector to solve theses problems. PEO-based polymeric artificial SEI is commonly used due to high lithium ion conductivity and flexiblility, but its weak physical properties limit its practical application. Herein, we report a chemically cross-linked poly (ethylene glycol) diacrylate (PEGDA)-based gel polymer electrolyte containing AgNO3 as Li nucleation seed for uniform Li deposition. It guides uniform Li-ion flux at the electrode/electrolyte interface and provides mechanical strength to suppress lithium dendrite growth. The gel polymer electrolyte was applied to anode free pouch cell and its cycling performance was investigated in the voltage range of 3.6 - 4.3 V at 0.5 C rate. Our results demonstrate that the proper combination of electrolyte and current collector can increase the conversion of polymerization and achieve stable interfacial properties with electrodes, resulting in improvement of the cycle life of anode free lithium pouch cell.

Does an LaCl3-based lithium superionic conductor work well for anode-free lithium metal batteries?

Does an LaCl3-based lithium superionic conductor work well for anode-free lithium metal batteries?

Spatially Confined Silver Nanoparticles in Mercapto Metal-Organic Frameworks to Compartmentalize Li Deposition Towards Anode-Free Lithium Metal Batteries.

As the promising next-generation energy storage solution lithium metal battery (LMB) has gained great attention but still suffers from troubles associated with the highly active metallic lithium. Herein, weaim to develop anode-free LMB engaging no Li disk or foil by modifying the Cu current collector with mercapto metal organic frameworks (MOFs) impregnating Ag nanoparticles (NPs). While the polar mercapto groups facilitate and guide Li+ transport, the highly lithiophilic Ag NPs help to enhance the electric conductivity and lower the energy barrier of Li nucleation. Furthermore, the MOF pores allow compartmentalizing bulk Li into a 3D matric Li storage so that not only the local current density is reduced, but also is the plating/stripping reversibility greatly enhanced. As a result, full cells pairing the prelithiated Ag@Zr-DMBD/Cu anodes with LiFePO4 cathodes demonstrate a high initial specific capacity of 159.8 mAh g-1 , first-cycle Coulombic efficiency of 96.6%, and long-term cycling stability over 1000 cycles with 99.3% capacity retention at 1C. This study underlines the multi-aspect functionalization of MOFs to impart lithiophilicity, polarity, and porosity to achieve reversible Li plating/stripping, and paves the way for realizing high-performance anode-free LMBs through exquisite modification of the Cu current collector. This article is protected by copyright. All rights reserved.

Effect of 3D lithiophilic current collector for anode-free Li ion batteries

The realization of anode-free lithium metal batteries (AFMBs) is limited owing to low Coulombic efficiency derived from the formation of uneven lithium plating at the anode side. Here, we induce the uniform deposition of lithium by an Au predeposited three-dimensional (3D) anodic current collector with an ether-based electrolyte. At the modified anodic current collector, the over-potential generated during the initial deposition of lithium converged to 6 mV, and stable cycling was achieved with an extremely high Coulombic efficiency of 99 % over 100 cycles. Furthermore, when compared to two-dimensional (2D) bare copper foil (LiFePO4/2D Cu), AFMBs using LiFePO4 cathode with Au predeposited 3D anodic current collector (LiFePO4/Au-3D Cu) show better rate performance and longer cycle life. This improvement in electrochemical performance is derived from the regulation of lithium deposition and inhibition of electrolyte decomposition due to the local current density through the predeposition of Au and 3D structure. This study provides a new path to realizing AFMBs.

Enhancing the Cycle Life of Lithium‐Anode‐Free Batteries through Polydopamine‐Coated Substrates

Anode‐free lithium metal batteries (AFLMBs) show promise as a means of further enhancing the energy density of current lithium‐ion batteries, as they do not require conventional graphite anodes. The anode‐free configuration, however, suffers from inferior chemical stability of the solid electrolyte interphase (SEI) layer and experiences inhomogeneous lithium deposition during charge/discharge processes, resulting in rapid capacity fading. To address these issues, a carbonized polydopamine (CPD) coating is applied to the copper current collector. The CPD‐coated copper current collector promotes highly efficient and reversible lithium plating and stripping processes, resulting in a densely packed lithium deposition that significantly improves cycling stability. The anode‐free full cell, consisting of CPD‐coated copper current collector and a LiFePO4 cathode, demonstrates significantly improved electrochemical performance, with a capacity retention of more than 63% after 100 cycles at a current rate of 0.3C. The stability of the SEI layer and the presence of lithiophilic sites are verified through a range of techniques, including optical microscopy, Raman spectroscopy, X‐ray photoelectron spectroscopy, chronoamperometry, and electrochemical impedance spectroscopy. Based on these collective findings, it can be inferred that the use of CPD coating provides a simple way to enhance the electrochemical performance of AFLMBs.

Reactivating the Dead Lithium by Redox Shuttle to Promote the Efficient Utilization of Lithium for Anode Free Lithium Metal Batteries

AbstractAnode free lithium metal batteries (AFLMBs), as a kind of novel battery configuration with zero excess lithium, can improve the energy density to the limit compared with lithium metal batteries and effectively ensure the safety. However, the lifespan of AFLMBs is a tricky problem because there is no extra lithium source to compensate for the irreversible loss of active lithium, which is mainly caused by the continuous decomposition of electrolyte and the formation of dead lithium. Herein, a redox shuttle additive, which can be oxidized in the cathode and reduced in the electrolyte reversibly, is introduced to improve the lithium utilization and lifespan of AFLMBs by reactivating the dead lithium. During the charging process, the redox shuttle additive can be oxidized on the cathode surface and serve as electron acceptor toward dead lithium. The electrically isolated dead lithium in the electrolyte can be re‐activated into active lithium ions when captured by oxidized redox shuttle additive.As a result, electrolyte with redox shuttle achieves average higher coulombic efficiency of 99.13% than electrolyte without redox shuttle (97.71%). In addition, the AFLMB with redox shuttle exhibits improved cycling performance with extended lifespan.

Single-atomic Zn-(C/N/O) lithiophilic sites induced stable lithium plating/stripping in anode-free lithium metal battery

Single-atomic Zn-(C/N/O) lithiophilic sites induced stable lithium plating/stripping in anode-free lithium metal battery

Super-three-dimensional lithiophilic Cu-based current collector for anode-free lithium metal battery

The formation of Li dendrites and dead Li, which causes short circuits, continuous side reactions, low Coulombic efficiency (CE) and thermal runaway, severely hinders the development of anode-free lithium metal batteries. Here, Cu-based current collector with super-three-dimensional lithiophilic modification layer is developed by the pyrolysis of resorcinol formaldehyde on 3D engineered copper mesh (a-RF@3D CM). The modification layer, consisting of highly dispersed CuOx sites in the O-containing defective carbon, together with the super-three-dimensional microstructure exhibits excellent lithiophilicity and capability to effectively reduce the nucleation overpotential, accommodate the uniform dendrite-free lithium deposition, promote stable and inorganic-rich solid electrolyte interphase formation, and improve the cycle stability. As a result, the a-RF@3D CM current collector exhibits reduced nucleation overpotential of 14.2 mV and prolonged cycling life over 400 cycles with average CE >98.5%. In the LiFePO4||a-RF@3D CM anode-free cell, average CE of 99.50% and capacity retention of 60.66% are successfully achieved after 100 cycles. Meanwhile, average CE 99.78% and capacity retention of 64.43% are successfully achieved in LiFePO4||Li@a-RF@3D CM cell (N/P = 1.6) after 200 cycles. The work provides feasible way to realize the fabrication of anode-free lithium metal batteries and also enhance the understanding of solid electrolyte interface evolution and regulation strategy of Li plating–stripping in advanced Li metal-based batteries.