Li Metal Anode Research Articles

Lithium Metal Recovery from Sea Water by a Flexible and Scalable Membrane with Lithium-Ion Exclusive Channels.

Sea water is abundant in lithium reserves, and extracting lithium metal from it holds the potential to not only mitigate the shortage of lithium in light of the fast-growing electric vehicle industry, but also serve as an anode electrode to provide electricity. The task, however, is challenging due to the harsh reactions and low lithium concentration in sea water. Here, we present a single-channel strategy based on a flexible and scalable lithium ion-sieve membrane for efficient lithium extraction. Our composite membrane exhibits high separation factor βLi/Na of more than 2.87 × 107 with an ionic conductivity of 6.2×10-5 S cm-1. Lithium metal was electrolytically extracted from sea water through a hybrid-electrolyte system, which yielded a high Coulombic efficiency of 98.04% and a low energy consumption of 17.4 kWh kgLi-1 at an optimized extracting current of 200 μA cm-2. The extracted lithium metal can be directly integrated into a lithium-sulfur battery, delivering an energy output of 395 Wh kg-1. To demonstrate its industrial viability, we also fabricate a pouch cell with Li metal anode extracted by an amplified extraction prototype. This study has the potential to dispel concerns of lithium depletion and facilitate the sustainable development of lithium-based energy storage systems.

PVDF Binder in All-Solid-State Lithium Batteries with NCM/Sulfide/PVDF Cathode, Oxide/PEO SE Layer, and Li-metal Anode

Sulfide-based solid electrolyte such as Li6PS5Cl (LPSCl) is unstable in contact with Li metal electrode due to decomposing to by-product resulting in poor performance. Therefore, the introduction of an interlayer to suppress reactivity is essential. In this study, instead of an interlayer, an oxide/polymer composite electrolyte was applied to suppress side reactions, while a sulfide-based electrolyte was used at the cathode to improve interfacial control between the cathode and the electrolyte. All-solid-state lithium batteries (ASLBs) were prepared by applying sulfide-based solid electrolyte (argyrodite, Li6PS5Cl) including NCM424, polyvinylidene fluoride (PVDF), and Super-P in a composite cathode layer, and a composite solid electrolyte (CSE) layer by mixing an oxide-based solid electrolyte (garnet, Al-doped Li7La3Zr2O12 (LLZO)), polymer (PEO, polyethylene oxide) and lithium metal as the anode. In this study, NCM424 powder was coated with LiNbO3 to prevent chemical reaction with the sulfide electrolyte. As the PVDF binder was applied to the cathode of the ASLB, the discharge capacity of the cell was approximately 163 mAh g−1 at 70 °C, 0.1 C, and 4.2 V cut-off and its capacity retention was 83% after 50 cycles. The effects of the PVDF were evaluated using both pouch-type cells. The capacity and cycle retention are greatly dependent on the PVDF content of the cathode materials and the drying temperature during the fabrication of the cathode. When the cathode with PVDF binder was dried at 130 °C, initial cycling was required for activation of the pouch cell, and it was possible to overcome this by adding a plasticizer.

Atomic Ni-catalyzed cathode and stabilized Li metal anode for high-performance Li–O2 batteries

The Li–O2 battery (LOB) has attracted growing interest, including for its great potential in next-generation energy storage systems due to its extremely high theoretical specific capacity. However, a series of challenges have seriously hindered LOB development, such as sluggish kinetics during the oxygen reduction and oxygen evolution reactions (ORR/OER) at the cathode, the formation of lithium dendrites, and undesirable corrosion at the lithium metal anode. Herein, we propose a strategy based on the ultra-low loading of atomic Ni catalysts to simultaneously boost the ORR/OER at the cathode while stabilizing the Li metal anode. The resultant LOB delivers a superior discharge capacity (>16000 mA h g−1), excellent long-term cycling stability (>200 cycles), and enhanced high rate capability (>300 cycles @ 500 mA g−1). The working mechanisms of these atomic Ni catalysts are revealed through carefully designed in situ experiments and theoretical calculations. This work provides a novel research paradigm for designing high-performance LOBs that are usable in practical applications.

Bipolar Textile Composite Electrodes Enabling Flexible Tandem Solid-State Lithium Metal Batteries.

A majority of flexible and wearable electronics require high operational voltage that is conventionally achieved by serial connection of battery unit cells using external wires. However, this inevitably decreases the energy density of the battery module and may cause additional safety hazards. Herein, a bipolar textile composite electrode (BTCE) that enables internal tandem-stacking configuration to yield high-voltage (6 to 12V class) solid-state lithium metal batteries (SSLMBs) is reported. BTCE is comprised of a nickel-coated poly(ethylene terephthalate) fabric (NiPET) core layer, a cathode coated on one side of the NiPET, and a Li metal anode coated on the other side of the NiPET. Stacking BTCEs with solid-state electrolytes alternatively leads to the extension of output voltage and decreased usage of inert package materials, which in turn significantly boosts the energy density of the battery. More importantly, the BTCE-based SSLMB possesses remarkable capacity retention per cycle of over 99.98% over cycling. The composite structure of BTCE also enables outstanding flexibility; the battery keeps stable charge/discharge characteristics over thousands of bending and folding. BTCE shows great promise for future safe, high-energy-density, and flexible SSLMBs for a wide range of flexible and wearable electronics.

Eliminating Hydrogen Fluoride through Piperidine-Doped Separators for Stable Li Metal Batteries with Nickel-Rich Cathodes.

Hydrofluoric acid (HF)-induced electrode and interfacial structure degeneration poses a significant challenge for high-voltage lithium metal batteries (LMBs). To address this issue, we propose a separator strategy that involves decorating a regular polyethylene (PE) separator with molecular sieves (TW) impregnated with piperidine (PI). The porous structure of the TW serves as a reaction chamber for PI and HF. As a result, the HF content in the controlled electrolyte with 500 ppm H2O (ELE-500) is notably reduced when using TW@PI-PE separators, thereby shielding nickel-rich cathodes from HF etching. Simultaneously, due to the hydrolysis of Li salts, and the inertness of PI towards H2O, a uniform lithium fluoride (LiF)-rich solid electrolyte interphase can form on the Li metal anode, further mitigating dendrite formation. The lifespan of the symmetric Li cell using the TW@PI-PE separator is doubled in ELE-500, exhibiting stable 500-hour cycles at 3 mA cm-2 and 3 mAh cm-2. Additionally, with the effective limitation of transition metal (TM) dissolution, the 4.6-V LMBs employing a LiNi0.8Co0.1Mn0.1O2 cathode maintain an 81% capacity retention over 100 cycles, even in ELE-1000. The innovative TW@PI system presented here offers a fresh perspective for future research aimed at eliminating HF in LMBs.

Lithiophilic Reduced Graphene Oxide/Carbonized Zeolite Imidazolate Framework-8 Composite Host for Stable Li Metal Anodes.

Lithium (Li) metal is regarded as a next-generation anode material owing to its high energy density. However, issues such as dendritic growth and volume changes during charging and discharging pose significant challenges for commercialization. We propose using lithiophilic reduced graphene oxide (rGO) and carbonized zeolite imidazolate framework-8 (C-ZIF-8) composites as host materials for Li to address these problems. The rGO/C-ZIF-8 composites are synthesized through a simple redox reaction followed by carbonization and are characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The roles of chemical composition, characteristics, and morphology are demonstrated. As a result of these favorable structural and functional properties, the Li symmetric cell with rGO/C-ZIF-8 exhibits a stable voltage profile for more than 100 h at 1 mA cm-2 without short-circuiting. A relatively low Li plating/stripping overpotential of ~101.5 mV at a high current density of 10 mA cm-2 is confirmed. Moreover, a rGO/C-ZIF-8-Li full cell paired with a LiFePO4 cathode demonstrates good cyclability and rate capability.

Scalable Production of Thin and Durable Practical Li Metal Anode for High-Energy-Density Batteries.

Utilization of thin Li metal is the ultimate pathway to achieving practical high-energy-density Li metal batteries (LMBs), but its practical implementation has been significantly impeded by formidable challenges of poor thinning processability, severe interphase instability and notorious dendritic Li growth. Here we report a practical thin (10-40 μm) Li/Mo/Li2Se with concurrently modulated interphase and mechanical properties, achieved via a scalable mechanical rolling process. The in-situ generated Li2Se and Mo not only enhance the mechanical strength enabling the scalable fabrication of thin Li metal, but also promote homogenous Li electrodeposition. Significantly, the Li/Mo/Li2Se demonstrates ultrahigh-rate performance (15 mA cm-2) and ultralong-lifespan cycling sustainability (2700 cycles) with exceptional anti-pulverization capability. The Li|LiFePO4 cells show substantially prolonged cyclability over 1200 cycles with an ultralow decay rate of ~0.01% per cycle. Moreover, the Li|LiNi0.8Co0.1Mn0.1O2 pouch cells deliver enhanced cycling stability even under the extremely harsh conditions of low negative-to-positive-capacity (N/P) ratio of ~1.2 and lean electrolyte of ~0.95 g Ah-1, showing an exceptional energy density of 329.2 Wh kg-1. This work sheds light on facile pathway for scalable production of durable thin Li metal anode toward reliable practicability.

Reveal the capacity loss of lithium metal batteries through analytical techniques

AbstractHigh energy density and stable long cycle are the basic requirements for an ideal battery. At present, lithium (Li) metal anode is regarded as one of the most promising anode materials, but it still faces major problems in terms of capacity fading and safe and stable long‐term cycle. The reason for the continuous fading of Li anode capacity is mainly due to the loss of active Li source, and the loss of Li source is mainly due to the continuous generation of dead Li. At the same time, the unstable interface and dendrite growth of Li anodes during the Li plating/delithiation process eventually lead to battery safety issues. In fact, recent studies have shown that the disordered expansion of dendrites is the main reason for the infinite generation of dead Li. Therefore, here we take different detection techniques as clues, review the exploration process of qualitative and quantitative research on the source and mechanism of Li capacity loss, and summarize the strategies to reduce dead Li generation and capacity fading by inhibiting dendrite formation. In particular, we give suggestions on the development of advanced testing methods on how to further study the problem of dead Li, and also give relevant strategy suggestions on how to completely solve the problem of capacity loss in the future, with the main goal of suppressing dendrites.

A Homogeneous Janus Membrane Based on Functionalized MOFs Crosslinked by Aramid Nanofibers for Quasi-Solid-State Lithium Sulfur Batteries.

Lithium-sulfur batteries (LSBs) are considered as promising candidates in the next generation of high energy density devices. However, the serious shuttle effect, irreversible dendrite growth of Li metal anode, and the potential safety hazard impede the practical application of LSBs. Herein, a novel homogeneous Janus membrane based on functionalized MOFs crosslinked by aramid nanofibers is designed and synthesized to simultaneously solve the above challenges in quasi-solid-state LSBs. The aramid nanofibers with good mechanical properties and thermal stability act as a homogeneous scaffold to crosslink the MOF particles with different ligands on both sides and this Janus membrane upgrades the stability and safety on both the cathode and anode. Specifically, the amino ligand-decorated MOFs contribute to homogenize Li-ion flux and stabilize the lithium anode, and the sulfonic ligand-decorated MOFs effectively suppress the shuttle effect by the dual effects of chemical adsorption and electrostatic repulsion. The quasi-solid-state LSBs assembled with this homogeneous Janus membrane deliver excellent rate performance and cycling stability. Moreover, it exhibits a high initial capacity of 923.4 mAh g-1 at 1C at 70°C, and 697.3 mAh g-1 is retained after 100 cycles, indicating great potential for its application in high-safety LSBs.

Pulse Charge Suppressing Dendrite Growth at Low Temperature by Rapidly Replenishing Lithium Ion on Anode Surface.

Dendrite growth of lithium (Li) metal anodes is considered as one of the most tough issues for Li metal batteries with a theoretically high energy density. This is attributed to the rapid exhaustion of Li ions at the electrode/electrolyte interface, which is even worse at low temperatures with poor diffusion kinetics of Li ions. Here, pulse charge with intermittent rest time during battery charging is proposed to handle the dendrite growth issue of Li metal anodes at low temperatures. The depleted Li ions near the interfaces can be rapidly replenished during the rest time, thus effectively suppressing the dendrites growth. Further investigation found that the large dendrites can be suppressed at the Li ion nucleation stage. The equivalent lifespan considering the rest time is proposed. At -10 °C, the lifespan of Li||Li batteries cycled under 3 mA cm-2 and 1 mAh cm-2 is increased from 24 h to equivalent 64 h. Li||LiNi0.5Co0.2Mn0.3O2 batteries with 80% capacity retention can be stably operated from 39 cycles to 56 cycles. This design presents an efficient and convenient strategy to regulate the deposition behaviors of Li metal anodes with a dendrite-free morphology.

Quasi-solid-state sulfur cathode with ultralean electrolyte via in situ polymerization

Lean electrolytes (< 5 μL mgsulfur−1) play a critical role in the realization of Li-S battery devices with high energy density for practical applications. However, lean-electrolyte Li-S batteries suffer from rapid cycling deterioration caused by the worsened shuttle effect under low electrolyte/sulfur ratio (E/S). Herein, via in situ polymerization, we realize a quasi-solid-state polymer Li-S battery with lean electrolytes. In this system, the polymer electrolyte with flexible polymer chains can block the diffusion of polysulfides and protect the Li-metal anode from being corroded by polysulfides. Furthermore, in the in situ polymerization route, the liquid precursor can wet the porous cathode, the separator and the Li anode abundantly, so that the consequent solidification not only promises a highly integrated structure of the whole cell, but also freezes the electrolyte in the best distribution condition for the electrochemical reaction, especially under lean electrolyte condition. Notably, the quasi-solid-state Li-S battery can discharge normally with ultralean electrolyte of even 1 μL mgsulfur−1. Moreover, the pouch cell with low E/S (3 μL mg−1) delivers a high energy density of 369.8 Wh kg−1. This work demonstrates the feasibility of quasi-solid-state Li-S batteries under lean-electrolyte condition, accelerating the application of high-energy-density Li-S batteries in the future.

Concentrated precipitation electrolyte for reviving ultrathin lithium metal anode

Realizing high-performance lithium metal batteries requires the presence of a robust solid-electrolyte interphase (SEI) on the Li metal surface that forms before or during operation. Herein, high concentrations of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and lithium nitrite (LiNO3) are employed to create a novel concentrated precipitation electrolyte (CPE) and form an inorganic-rich SEI. It is found that an ultrathin Li metal anode (thickness of 25 μ m) in the CPE remains highly reversible over 300 cycles with an average Coulombic efficiency (CE) of 97.21 % in an asymmetric Cu|Li cell. The CPE enables superior stability to the LiFePO4 (LFP) cathode at a high mass loading of ∼15 mg cm−2 and reaches a capacity retention of 82.8 % after 100 cycles with an average CE of 99.94 %. This study elucidates the mechanism of LiTFSI and LiNO3 in enhancing the physiochemical properties of the SEI surface layer. It is believed that this design concept and the findings can be broadened to optimize SEIs via electrolyte engineering for practical Li metal batteries.

Construction of flexible asymmetric composite polymer electrolytes for high-voltage lithium metal batteries with superior performance

The primary obstacle hindering the application of composite solid electrolytes lies in the varying demands posed by the Li metal anode and the cathode, which needs to be capable of suppressing dendrite growth and resisting high voltage simultaneously. In this work, a new asymmetric composite solid-state electrolyte prepared via electrospinning and in-situ polymerization is proposed to address these shortcomings. In this bilayer architecture, polyacrylonitrile (PAN) layer of high-voltage tolerance, polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) layer of robust mechanical strength and good compatibility towards Li-anode are constructed, and metal-organic-frameworks (MOFs) are pre-embedded within both layers. The unique design provides a wide electrochemical stability window meanwhile ensures uniform lithium deposition. Remarkably, it exhibits a superior lithium utilization of 41 mAh cm−2 using a lean polymer electrolyte precursor and a high critical current density of 2.2 mA cm−2 with a thickness of 40 μm. Beneficial from the formation of a self-adjustable gradient solid electrolyte interphase in the Li/PVDF-HFP interface, the asymmetric electrolyte endows Li||Li and Li||NCM811 cells with excellent cycling stability. Moreover, the solid-state pouch cell exhibits reliable operation under extreme conditions. This work provides inspiration for the design and fabrication of composite solid electrolytes for next-generation high-voltage Li metal batteries.

Horizontal Lithium Electrodeposition on Atomically Polarized Monolayer Hexagonal Boron Nitride.

Both uncontrolled Li dendrite growth and corrosion are major obstacles to the practical application of Li-metal batteries. Despite numerous attempts to address these challenges, effective solutions for dendrite-free reversible Li electrodeposition have remained elusive. Here, we demonstrate the horizontal Li electrodeposition on top of atomically polarized monolayer hexagonal boron nitride (hBN). Theoretical investigations revealed that the hexagonal lattice configuration and polarity of the monolayer hBN, devoid of dangling bonds, reduced the energy barrier for the surface diffusion of Li, thus facilitating reversible in-plane Li growth. Moreover, the single-atom-thick hBN deposited on a Cu current collector (monolayer hBN/Cu) facilitated the formation of an inorganic-rich, homogeneous solid electrolyte interphase layer, which enabled the uniform Li+ flux and suppressed Li corrosion. Consequently, Li-metal and anode-free full cells containing the monolayer hBN/Cu exhibited improved rate performance and cycle life. This study suggests that the monolayer hBN is a promising class of underlying seed layers to enable dendrite- and corrosion-free, horizontal Li electrodeposition for sustainable Li-metal anodes in next-generation batteries.

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.

The MOFs derived Co, Zn co-doping porous carbon framework as the collector for stable Li metal anodes

The Li metal anode is regarded as the most potential electrode material in the next-generation energy storage system, because of the high energy density and specific capacity. However, the advancement of Li metal anode is restricted by the volume changing and dendrite growth. In this paper, the Co and Zn co-doped porous carbon framework (CF-CZ) derived from MOF structure was designed and produced to realize the dendrite-free Li metal anode. The porous structure could accommodate the deposited Li metal, which relaxes the pressure of electrode structure and relieves the volume changes. Meanwhile, the Co, Zn co-doping effectively improves the lithiophilicity of framework, which attracts Li+ and decreases the nucleation barrier. Besides, numerous micropores of MOF structure could divide the Li+ flux to reduce the local current density for dense sedimentation. With the synergies of co-doping and porous structure, the symmetric cell of CF-CZ shows better electrochemical performance (the overvoltage can be stable at 14 mV after 1200 cycles) than pure Cu foil, and the LFP cells deliver 116.4 mAh g−1 at 1 C after 200 cycles. As a consequence, the CF-CZ possesses the potential to be applied in Li metal anodes.

Correlating Homogeneity and Microstructure of in Situ plated Li in “Anode-Free” Solid-State Batteries

Solid-state batteries utilizing Li metal anodes have the potential to offer increased safety and higher energy density compared to state-of-the-art Li-ion batteries. To achieve these energy density gains, the Li metal anode must be thin (<25 µm). Manufacturing of thin Li metal anodes is complicated by the reactivity of Li metal, which forms a thin passivation layer even in controlled environments. The “anode-free” cell manufacturing approach provides an alternative to these challenges. These cells are manufactured with a bare anode current collector (CC) and the Li metal anode is plated in situ at the CC/solid-state electrolyte interface during the first charging step using the Li stored in the cathode active material. While manufacturing cells with in situ formed Li anodes may offer benefits, removing all excess Li in the cell also poses many challenges. The Coulombic efficiency of these cells must be >99.99% to retain 90% capacity over 1,000 cycles [1]. Therefore, when the Li anode is formed in situ during the first charge, the temperature, pressure, and current density must be carefully tuned to optimize the reversibility of the plated Li. To achieve high reversibility of Li metal anodes, the plated Li should be dense, conformal to the current collector and solid-state electrolyte, homogeneous in thickness, and ideally have a small grain size. These objectives can be achieved by tuning the plating parameters during in situ Li deposition, including pressure, temperature, and current density. It has been previously shown that applying 5 MPa of pressure could improve the homogeneity of in situ formed Li anodes in solid-state cells [2].However, applying pressures >1 MPa is undesirable for practical applications [3]. Therefore, it is necessary to alter the in situ plated Li using other parameters, including the temperature and current density used during plating. Here, we show the effect of plating current density and temperature on the homogeneity and microstructure of in situ formed Li anodes in solid-state cells. It is demonstrated that optimized plating current protocols can improve the homogeneity of plated Li without the need for elevated temperatures. Finally, the relationship between the homogeneity of the in situ plated Li and the reversibility upon stripping is studied using unidirectional stripping experiments. These results illustrate the importance of carefully controlling the parameters for Li plating to enable high Coulombic efficiency in situ formed Li anodes in solid-state cells.

(Invited) A Facile Three-Dimensional Lightweight Current Collector Strategy for High Energy Density Lithium Metal Batteries

Despite the great achievement in the development of rechargeable lithium (Li) metal batteries (LMBs) with high energy densities, their practical application is still facing difficulties due to the intrinsic issues of Li metal anode (LMA) including high reactivity and dendritic Li formation which cause low Coulombic efficiency, constant loss of Li and electrolyte, and unstable solid electrolyte interphase (SEI) layer, etc. Additionally, from the structural point of view, LMA which consists of Li foil on the two-dimensional copper (Cu) current collector brings the formidable loss of the areal capacity that leads to less specific energy density since Cu is non-faradaic and one of the heavy metals. Further, the “hostless” feature of LMA induces more issues like volume expansion and limited utilization of Li. To address such issues, a metal-coated polymeric three-dimensional (3D) scaffold is designed here. In this study, Cu is selected as an electronic conductivity provider, and electrospun polyimide (PI) is chosen as a 3D scaffold because of its high thermal stability and good mechanical properties. Cu-coated PI (Cu@PI) was produced via a facile electroless process. Driven by the structural/material uniqueness, the developed 3D Cu@PI current collector enables a uniform/continuous Li-ion conduction pathway thus leading to dense Li deposition and enhancing the electrochemical performance of LMBs containing the electrochemically deposited Li on Cu@PI and the specific energy density due to the great reduction in substrate weight. We anticipate the suggested new strategy of 3D structured LMAs would lead to a facile route toward the high energy density LMBs beyond the conventional technologies.

Solvation-Property Relationship of Lithium-Sulfur Battery Electrolytes Probed via Potentiometric Measurements

The Li-S battery is a promising next-generation battery chemistry that offers high energy density and low cost. Li-S battery has a unique chemistry with intermediate sulfur species readily solvated in electrolytes, and understanding their implications is important from both practical and fundamental perspectives. However, the nature of the solvated sulfur species, their interactions and their impact on the battery remains elusive, in part due to the paucity of techniques. Recently, our group developed a potentiometric technique to probe the solvation free energy of electrolytes. In this study, we utilize the technique to formulate solvation-property relationships in various electrolytes and investigate its impact on the solvated lithium polysulides (LiPS). We find that solvation free energy impacts Li-S battery voltage profile, LiPS solubility, Li-S battery cyclability and the Li metal anode, which are all critical to the battery's performance. Weaker solvation leads to a lower 1st plateau voltage, higher 2nd plateau voltage, lower LiPS solubility, and superior cyclability of Li-S full cell and Li metal anode. We explore the mechanisms behind these observed phenomena and discuss the implications for the design of high-performance electrolytes for Li-S batteries.

Molecular Understanding of Li Metal Anode

Developing new liquid electrolyte is a promising approach to enable the next-generation high-energy Li metal battery for wide-ranging application such as electric vehicles (EV). However, the high reactivity of Li metal interface renders it crucial to form favorable solid-electrolyte interphase (SEI), via active electrolyte decomposition, for highly reversible operation of Li-metal anode (LMA). Therefore, deeply understanding how the molecular structures of electrolyte species precisely control both the interfacial reactivity and the operational reversibility of LMA, can further guide and inspire new electrolyte systems with progressively improved battery performance.Herein, we systematically investigated the impact of Li salts with different imide anions dissolved in ether-based solvent, on the resulting Coulombic efficiencies (CE) of LMA, whereas beneficial and detrimental molecular motifs were first identified. By leveraging the non-washing XPS protocol newly developed at Stanford, we managed to uncover the distinct molecular reactivity leading to reductive bond cleavage as well as new bond formation at Li-metal potential. Such nanoscale reactivity of SEI-forming reactions was discovered to profoundly govern the macroscopic performance of LMA, which simultaneously emphasized the significance of electric double layer (EDL). Importantly, aided by gas-titration experiments to quantify the by-products in SEI, we revealed the critical molecular origins of irreversible capacity loss of LMA during continuous Li-metal plating and stripping. These new insights allow us to formulate rational strategies of molecular engineering to design LMA interface with high reversibility and minimal side reactivity.