Solvent Decomposition Research Articles

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

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

In-Operando Isothermal Microcalorimetry to Accelerate Screening of New Battery Chemistries

Screening new cell chemistries using traditional electrochemical methods is a time prohibitive process that significantly slows the pace of research. These methods involve cycling the cell until signs of degradation or sufficient capacity fade are evident, and typically take months to complete. In-operando isothermal microcalorimetry is an established but underutilized technique for measuring the activity of parasitic, or non-reversible reactions during charge cycling [1,2,3,4]. A parasitic reaction is a blanket term for any side reactions that occur within a battery, including solvent breakdown, lithium plating, self-discharge reactions, and growth or decomposition of the solid electrolyte interphase. Battery formulations with high parasitic heat are strongly correlated with early cell failure. Compared to electrochemical cycling, the average parasitic heat over the full voltage range can be determined in a time frame as low as 2 weeks, allowing researchers to realize a time savings up to 75%. Additional time savings are also possible if only a narrow voltage range is of interest.In this study, we present results that demonstrate the measurement of the parasitic heat of a commercial 18650 lithium-ion battery using the TA Instruments Battery Cycler Microcalorimeter Solution. This method involves slow galvanostatic cycling at isothermal conditions with a simultaneous measurement of heat flow, voltage, and applied current. The parasitic heat is isolated from the total heat flow using the Integration-Subtraction method, with calculations performed automatically by the software [1]. The coulombic efficiency is also measured per cycle, showing an inverse relationship to the parasitic power. As a screening tool, this data could be used to select battery formulations most likely to meet performance goals in long-term cycling experiments, rather than wasting valuable time and lab space on a trial-and-error approach. The results highlight how in-operando isothermal microcalorimetry is a powerful screening tool for investigating the efficiency of new cell chemistries and electrolyte formulations in a fraction of the time compared to traditional methods.[1] L.J. Krause, L.D. Jensen, V.L. Chevrier. Measurement of Li-Ion Battery Electrolyte Stability by Electrochemical Calorimetry. J. Electrochem. Soc. 2017, 164 (4), A889-A896.[2] L.J. Krause, L.D. Jensen, J.R. Dahn. Measurement of Parasitic Reactions in Li Ion Cells by Electrochemical Calorimetry. J. Electrochem. Soc. 2012, 159 (7), A937-A943.[3] J.C. Burns, Adil Kassam, N.N. Sinha, L.E. Downie, Lucie Solnickova, B.M. Way, J.R. Dahn. Predicting and Extending the Lifetime of Li-Ion Batteries. J. Electrochem. Soc. 2013, 160, A1451.[4] E. R. Logan, A. J. Louli, Matthew Genovese, Simon Trussler,and J. R. Dahn. Investigating Parasitic Reactions in Anode-Free Li Metal Cells with Isothermal Microcalorimetry. J. Electrochem. Soc. 2021, 168, 060527.

Tris(trimethylsilyl) Phosphite and Lithium Difluoro(oxalato)borate as Electrolyte Additives for LiNi0.5Mn1.5O4‐Graphite Lithium‐Ion Batteries

AbstractRaising the energy density of lithium‐ion batteries (LIBs) through the operation of high‐voltage cathodes presents a challenge in terms of practical use due to electrolyte degradation. Consequently, it is imperative to explore new materials to circumvent this issue. In this study, a combination of tris(trimethylsilyl) phosphite (TMSPi) and lithium difluoro(oxalato)borate (LiDFOB) is presented as film‐forming additives in a conventional LiPF6‐containing carbonate‐based electrolyte solution in high‐voltage LiNi0.5Mn1.5O4‐graphite full cells. At high voltage, TMSPi oxidizes on the LiNi0.5Mn1.5O4 (LNMO) cathode surface prior to the decomposition of electrolyte solvents, promoting the formation of a stable cathode electrolyte interphase (CEI) layer. In tandem, given that LiDFOB has a lower reduction potential than ethylene carbonate (EC), it has the possibility of forming a solid electrolyte interphase (SEI) on the graphite anode surface. Combining the two additives was found to suppress the degradation of the electrolyte to a large extent. Among the investigated concentration of the additives, the combination of 1 wt. % TMSPi and 2 wt. % LiDFOB added to LP40 electrolyte exhibits improved capacity retention of 80 % after 400 cycles at 0.3 C, compared to the electrolyte with no additive with 67 % capacity retention over the same period. Thereby, the combination of TMSPi with LiDFOB provides an improvement for high voltage LIBs.

1,3,5-Trifluorobenzene endorsed EC-free electrolyte for high-voltage and wide-temperature lithium-ion batteries

Ethylene carbonate (EC) is susceptible to the aggressive chemistry of nickel-rich cathodes, making it undesirable for high-voltage lithium-ion batteries (LIBs). The arbitrary elimination of EC leads to better oxidative tolerance but always incurs interfacial degradation and electrolyte decomposition. Herein, an EC-free electrolyte is deliberately developed based on gradient solvation by pairing solvation-protection agent (1,3,5-trifluorobenzene, F3B) with propylene carbonate (PC)/methyl ethyl carbonate (EMC) formulation. F3B keeps out of inner coordination shell but decomposes preferentially to construct robust interphase, inhibiting solvent decomposition and electrode corrosion. Thereby, the optimized electrolyte (1.1 M) with wide liquid range (−70–77 °C) conveys decent interfacial compatibility and high-voltage stability (4.6 V for LiNi0.6Mn0.2Co0.2O2, NCM622), qualifying reliable operation of practical NCM/graphite pouch cell (81.1% capacity retention over 600 cycles at 0.5 C). The solvation preservation and interface protection from F3B blaze a new avenue for developing high-voltage electrolytes in next-generation LIBs.

Inert Filler Selection Strategies in Li-Ion Gel Polymer Electrolytes.

The main role of inert fillers in polymer electrolytes is to enhance ionic conductivity. However, lithium ions in gel polymer electrolytes (GPEs) conduct in liquid solvent rather than along the polymer chains. So far, the main role of inert fillers in improving the electrochemical performance of GPEs is still unclear. Here, various low-cost and common inert fillers (Al2O3, SiO2, TiO2, ZrO2) are introduced into GPEs to study their effects on Li-ion polymer batteries. It is found that the addition of inert fillers has different effects on ionic conductivity, mechanical strength, thermal stability, and, dominantly, interfacial properties. Compared with other gel electrolytes containing SiO2, TiO2, or ZrO2 fillers, those with Al2O3 fillers exhibit the most favorable performance. The high performance is ascribed to the interaction between the surface functional groups of Al2O3 and LiNi0.8Co0.1Mn0.1O2, which alleviates the decomposition of the organic solvent by the cathode, resulting in the formation of a high-quality Li+ conductor interfacial layer. This study provides an important reference for the selection of fillers in GPEs, surface modification of separators, and cathode surface coating.

A Nonflammable Electrolyte for High-Voltage Lithium Metal Batteries

The electrochemical instability of the polar solvents in electrolytes often causes reduction/oxidation at the surface of both Li anodes and nickel-rich cathodes in high-voltage lithium metal batteries (LMBs). Here, we design a bipolar molecule-regulated electrolyte with a capsule-like solvation structure and nonflammability to stabilize high-voltage LMBs. The key enabler is to design and synthesize a nonflammable bipolar molecule with a ion-dissociative polar head and a perfluorinated nonpolar tail. The bipolar solvent promotes the formation of capsule-like solvation sheaths via weak coordination and encapsulates the polar molecules inside the primary solvation shell, drastically reducing the detrimental decomposition of solvents. Finally, the assembled high-voltage cell provides high capacity retention (Li||LiNi0.8Co0.1Mn0.1O2: >90%) during 200 charge/discharge cycles under strict conditions. The capsule-like electrolyte also enables a 420 mAh pouch cell with a cell-level energy density of 440 Wh kg–1 along with long cycling stability over 150 cycles (retention: 92%).

Interfacial-Catalysis-Enabled Layered and Inorganic-Rich SEI on Hard Carbon Anodes in Ester Electrolytes for Sodium-Ion Batteries.

Constructing a homogenous and inorganic-rich solid electrolyte interface (SEI) can efficiently improve the overall sodium-storage performance of hard carbon (HC) anodes. However, the thick and heterogenous SEI derived from conventional ester electrolytes fails to meet the above requirements. Herein, an innovative interfacial catalysis mechanism is proposed to design a favorable SEI in ester electrolytes by reconstructing the surface functionality of HC, of which abundant CO (carbonyl) bonds are accurately and homogenously implanted. The CO (carbonyl) bonds act as active centers that controllably catalyze the preferential reduction of salts and directionally guide SEI growth to form a homogenous, layered, and inorganic-rich SEI. Therefore, excessive solvent decomposition is suppressed, and the interfacial Na+ transfer and structural stability of SEI on HC anodes are greatly promoted, contributing to a comprehensive enhancement in sodium-storage performance. The optimal anodes exhibit an outstanding reversible capacity (379.6 mAh g-1 ), an ultrahigh initial Coulombic efficiency (93.2%), a largely improved rate capability, and an extremely stable cycling performance with a capacity decay rate of 0.0018% for 10 000 cycles at 5 A g-1 . This work provides novel insights into smart regulation of interface chemistry to realize high-performance HC anodes for sodium storage.

Effect of Salt Concentration on the Interfacial Solvation Structure and Early Stage of Solid–Electrolyte Interphase Formation in Ca(BH4)2/THF for Ca Batteries

The Ca2+ solvation structure at the electrolyte/electrode interface is of central importance to understand electroreduction stability and solid-electrolyte interphase (SEI) formation for the novel multivalent Ca battery systems. Using an exemplar electrolyte, the concentration-dependent solvation structure of Ca(BH4)2-tetrahydrofuran on a gold model electrode has been investigated with various electrolyte concentrations via electrochemical quartz crystal microbalance with dissipation (EQCM-D) and X-ray photoelectron spectroscopy (XPS). For the first time, in situ EQCM-D results prove that the prevalent species adsorbed at the interface is CaBH4+ across all concentrations. As the salt concentration increases, the number of BH4- anions associated with Ca2+ increases, and much larger solvated complexes such as CaBH4+·4THF or Ca(BH4)3-·4THF form at the interface at high concentrations prior to Ca plating. Different interfacial chemistries lead to the formation of SEIs with different components demonstrated by XPS. High electrolyte concentrations reduce the solvent decomposition and promote the formation of thick, uniform, and inorganic-rich (i.e., CaO) SEI layers, which contribute to improved Ca plating efficiency and current density in electrochemical measurements.

Solvent‐Free Electrolyte for High‐Temperature Rechargeable Lithium Metal Batteries

AbstractThe formation of lithiophobic inorganic solid electrolyte interphase (SEI) on Li anode and cathode electrolyte interphase (CEI) on the cathode is beneficial for high‐voltage Li metal batteries. However, in most liquid electrolytes, the decomposition of organic solvents inevitably forms organic components in the SEI and CEI. In addition, organic solvents often pose substantial safety risks due to their high volatility and flammability. Herein, an organic‐solvent‐free eutectic electrolyte based on low‐melting alkali perfluorinated‐sulfonimide salts is reported. The exclusive anion reduction on Li anode surface results in an inorganic, LiF‐rich SEI with high capability to suppress Li dendrite, as evidenced by the high Li plating/stripping CE of 99.4% at 0.5 mA cm−2 and 1.0 mAh cm−2, and 200‐cycle lifespan of full LiNi0.8Co0.15Al0.05O2 (2.0 mAh cm−2) || Li (20 µm) cells at 80 °C. The proposed eutectic electrolyte is promising for ultrasafe and high‐energy Li metal batteries.

Electrostatic Covalent Organic Frameworks as On-Demand Molecular Traps for High-Energy Li Metal Battery Electrodes

Regulating electrostatic interactions between charged molecules is crucial for enabling advanced batteries with electrochemical reliability. To address this issue, herein, we present a class of electrostatic covalent organic frameworks (COFs) as on-demand molecular traps for high-energy-density Li metal batteries (LMBs). A bipyridine-based COF and its quaternized derivative are synthesized and incorporated into LiNi0.8Co0.1Mn0.1O2 (NCM811) cathodes and Li metal protective layers, respectively. These COF molecular traps are effective in chelating transition metal ions dissolved from the cathodes, enhancing Li+ desolvation, suppressing solvent decomposition, and immobilizing anions of electrolytes. The resulting LMB with the COF molecular traps fully utilizes the theoretical specific capacity of NCM811 at cathodes and allows stable Li plating/stripping at anodes. A pouch-type LMB full cell with the COF molecular traps provides high gravimetric/volumetric energy densities (466.7 Wh kgcell–1/1370.1 Wh Lcell–1) under a constrained cell configuration, exceeding those of previously reported Li metal batteries based on porous crystalline frameworks.

Pentafluoropyridine additive induced SEI film regulation and remarkable performance improvement of the lithium primary batteries

Lithium primary batteries with lithium metal anode are extensively applied in the portable appliances and electronic fields for the high specific energy and power, low self-discharge and wide operating temperature. However, the application of lithium metal anode causes the safety and stability issues. Herein, the pentafluoropyridine (C5F5N) was applied as an electrolyte additive in lithium primary battery, to construct a suitable surface layer on lithium anode to increase the stabilization and electrochemical performance. With C5F5N additive, the discharge capacity of the Li primary battery increases to 422.1 mAh/g at 0.01 C, compared to 62.2 mAh/g of the pristine battery. Meanwhile, the storage performance of the batteries was also greatly enhanced with the C5F5N additive. After stored for 60 days at room temperature, the Li primary battery with additive displays a specific discharge capacity of 180.7 mAh/g, much higher than the pristine battery without additive (43.6 mAh/g). The significant improvements in capacitive and storage performances are attributed to the additive induced inhibition of decomposition of solvents and lithium salts and tuning of SEI composition on lithium anode surface. The C5F5N is a promising electrolyte additive for the further development and application of high-performance Li primary batteries.

La2O3 Filler's Stabilization of Residual Solvent in Polymer Electrolyte for Advanced Solid‐State Lithium‐Metal Batteries

Polymer solid electrolytes (SEs) with high safety and flexibility are ideal for advanced lithium‐metal solid‐state batteries (SSBs). Among various polymer SEs, polyvinylidene fluoride‐co‐hexafluoropropylene (PVDF‐HFP) polymer SEs have gained increased attention for their high dielectric constants, high ionic conductivity, and excellent flexibility. However, severe side reactions at the interface caused by the decomposition of residual DMF solvent significantly reduce the cycle life of PVDF‐HFP‐based SSBs. Herein, La2O3 nanoparticles are used as new inorganic fillers to form a PVDF‐HFP/LiFSI/La2O3‐40% composite polymer electrolyte (PVDF‐HFP/La2O3 CPE). Benefiting from the interaction between La2O3 and N,N‐dimethylformamide (DMF) solvent molecules, the cell cycling stability is greatly improved. In addition, the PVDF‐HFP/LiFSI solid electrolyte (PVDF‐HFP SE) containing 40 wt% La2O3 has the highest ionic conductivity of 1.33 × 10−3 S cm−1 at 25 °C. It also exhibits a higher lithium‐ion transference number of 0.52 and lower polarization. The PVDF‐HFP/La2O3 CPE here ensures high ionic conductivity and stable interface chemistry in SSB, demonstrating a promising application potential.

Amide- and Urea-Based Solvents for Li–O2 Batteries. Part I: Experimental Evaluation

Nonaqueous Li–O2 batteries have the potential to aid in the electrification of our society due to their relatively high theoretical energy density. Unfortunately, the technology suffers from large degrees of irreversibility due to the aggressive chemical environment associated with the oxidation of the discharge product lithium peroxide. Herein, we present a study of a range of linear and cyclic amides and ureas as aprotic electrolyte solvents for the Li–O2 battery, some of which show slight increases in reversibility relative to the well-established pseudo-stable glymes, although we find that none provide reversibility necessary to enable a rechargeable system. Using quantitative differential electrochemical mass spectrometry, acid titrations, and isotopic labeling of O2 and carbon in the positive electrode, we provide insight into the degradation pathways for these solvents. In the companion article, we compare our experimental results presented here to solvent decomposition pathways including a Baeyer–Villiger oxidation mechanism.

Tuning of electrolyte solvation structure for low-temperature operation of lithium–sulfur batteries

Lithium–sulfur batteries (LSBs) can be good candidates for low-temperature batteries owing to the use of solvents with low freezing points. However, the clustering of lithium polysulfides (LiPSs) and inhomogeneous lithium deposition hinder the successful operation of LSBs at low temperatures. Herein, we demonstrate that changing the solvation state of solvents and polysulfides (PSs) in an electrolyte via a high-donor number (DN) salt anion (NO3−) enables operation at low temperatures; NO3− relieves LiPS clustering by strongly coordinating to lithium ions, thereby improving the kinetics and diffusion process of LiPSs at −20 °C. Furthermore, the NO3−-coordinated lithium ion solvation structure facilitates the desolvation process of lithium ions and mitigates solvent decomposition at the lithium metal electrode, which results in excellent cycling stability at −20 °C. A pouch cell with a LiNO3-rich electrolyte provides 76% of its room-temperature discharge capacity and operates stably for 100 cycles at −20 °C. The results of this study broaden our knowledge about the factors determining the low-temperature performance of LSBs. Moreover, they imply that controlling the electrolyte solvation structure can result in high-performance LSBs for operation at low temperatures.

Revealing mechanisms of activated carbon capacity fade in lithium-ion capacitors

The capacity fade mechanism of activated carbon (AC) electrode in Li-ion electrolyte was studied via electrochemical impedance spectroscopy (EIS) and post-mortem electrode characterizations at different stages of electrochemical cycling. Electrochemical cycling was conducted in half cells incorporating the AC working electrode, Li metal counter electrode, and 1 M LiPF6 in EC:DMC (1:1) electrolyte. Three phases were identified during the ageing process that corresponded with transformation of the passivation layer at the electrode surface and charge transfer impedance derived from the EIS analysis. Surface area and morphology analysis showed that the AC surface was progressively transformed by degradation products that reduced the available surface area and accessibility of electrolyte moieties into the pores. X-ray photoelectron spectroscopy suggested that the degradation products are from the LiPF6 salt decomposition and carbonate solvent decomposition, while Raman analysis demonstrated increased defects in the electrode as cycling progressed. The capacity fade was therefore caused by the synergistic effect of electrolyte degradation and active material transformation.

Having Your Cake and Eating It Too: Electrode Processing Approach Improves Safety and Electrochemical Performance of Lithium-Ion Batteries

A layered Li[NixCoyMn1-x-y]O2 (NCM)-based cathode is preferred for its high theoretical specific capacity. However, the two main issues that limit its practical application are severe safety issues and excessive capacity decay. A new electrode processing approach is proposed to synergistically enhance the electrochemical and safety performance. The polyimide's (PI) precursor is spin-coated on the LiNi0.5Co0.2Mn0.3O2 (NCM523) electrode sheet, and the homogeneous sulfonated PI layer is in situ produced by thermal imidization reaction. The PI-spin coated (PSC) layer provides improvements in capacity retention (86.47% vs 53.77% after 150 cycles at 1 C) and rate performance (99.21% enhancement at 5 C) as demonstrated by the NCM523-PSC||Li half-cell. The NCM523-PSC||graphite pouch full cell proves enhanced capacity retention (76.62% vs 58.58% after 500 cycles at 0.5 C) as well. The thermal safety of the NCM523-PSC cathode-based pouch cell is also significantly improved, with the critical temperature of thermal safety T1 (the beginning temperature of obvious self-heating temperature) and thermal runaway temperature T2 increased by 60.18 and 44.59 °C, respectively. Mechanistic studies show that the PSC layer has multiple effects as a passivation layer such as isolation of electrode-electrolyte contact, oxygen release suppression, solvation structure tuning, and the decomposition of carbonate solvents as well as LiPF6 inhibition. This work provides a new path for a cost-effective and scalable design of electrode decoration with synergistic safety-electrochemical kinetics enhancement.

Sonoluminescence intensity and ultrasonic cavitation temperature in organic solvents: Effects of generated radicals

Ultrasonic cavitation in organic solvents remains poorly understood in contrast with aqueous systems, largely because of complexities related to solvent decomposition. In this study, we sonicated different types of organic solvents (i.e. linear alkanes, aliphatic alcohols, aromatic alcohols, and acetate esters) under argon saturation. The average temperature of the cavitation bubbles was estimated using the methyl radical recombination method. We also discuss the effects of the physical properties of the solvents, such as vapor pressure and viscosity, on the cavitation temperature. The average cavitation bubble temperature and sonoluminescence intensity were higher in organic solvents with lower vapor pressure; for aromatic alcohols, these values were particularly high. It was found that the specific high sonoluminescence intensities and average cavitation temperatures exhibited in aromatic alcohols are caused by the highly resonance-stable generated radicals. The results obtained in this study are very useful for acceleration of sonochemical reaction in organic solvents, which are indispensable for organic synthesis and material synthesis.

Effect of N-doping-derived solvent adsorption on electrochemical double layer structure and performance of porous carbon

N-doped porous carbon has been extensively investigated for broad electrochemical applications. The performance is significantly impacted by the electrochemical double layer (EDL), which is material dependent and hard to characterize. Limited understanding of doping-derived EDL structure hinders insight into the structure–performance relations and the rational design of high-performance materials. Thus, we analyzed the mass and chemical composition variation of EDL within electrochemical operation by electrochemical quartz crystal microbalance, in-situ X-ray photoelectron spectroscopy, and time-of-flight secondary ion mass spectrometry. We found that N-doping triggers specifically adsorbed propylene carbonate solvent in the inner Helmholtz plane (IHP), which prevents ion rearrangement and enhances the migration of cations. However, this specific adsorption accelerated solvent decomposition, rendering rapid performance degradation in practical devices. This work reveals that the surface chemistry of electrodes can cause specific adsorption of solvents and change the EDL structure, which complements the classical EDL theory and provide guidance for practical applications.

Flavone as a novel multifunctional electrolyte additive to improve the cycle performance of high-voltage LiNi0.5Mn1.5O4 batteries

The high operating voltage of LiNi0.5Mn1.5O4 (LNMO) material poses a challenge to conventional carbonate-based electrolyte, whose continuous decomposition leads to the fast capacity fading of battery. Herein, flavone (FLA) as a novel multifunctional electrolyte additive is introduced into basic electrolyte (1.0 M LiPF6 - ethylene carbonate + dimethyl carbonate) to significantly improve the cycle performance of LNMO/Li battery. Experiments and density functional theory (DFT) calculations manifest that FLA can be preferentially oxidized and reduced to generate stable surface films to ameliorate the decomposition of other electrolyte solvent. Besides, the FLA-derived Li2CO3-rich surface films can improve interfacial stability and ensure high ionic conductivity. In addition, FLA is more inclined to react with HF compared with EC and DMC, thereby alleviating LNMO corrosion and transition metal ions dissolution by HF, and consequently enhance the stability of bulk structure. The preferential reduction of FLA contributes to the formation of a stable passivation layer with high ionic conductivity on Li anode, which is conducive to uniform lithium deposition during the cycling and prolonging battery cycle life. The cycle performances of LNMO/Li and LNMO/Graphite batteries using the electrolyte containing 1 wt% FLA are significantly improved compared with those using basic electrolyte.

Unveiling the effect and correlative mechanism of series-dilute electrolytes on lithium metal anodes

An emerging development direction for electrolytes is the utilization of low-concentration electrolytes (LCE, generally less than 0.5 M) owing to their promising properties such as better wetting ability, reduced costs, and fast electrochemical kinetics, which have been studied in several battery scenarios. However, the direct assessment of LCEs with Li metal anodes has not yet been done, which would provide new insights to high-energy-density rechargeable lithium metal batteries (LMBs). For this purpose, apparent cycling performances of Li metal anode (LMA) in series-diluted (0.1∼1.0 M) ether-based electrolytes are reported in this study with Li||Li and Li||Cu cells, showing the enhanced performances with the concentration increasing. Moreover, the concentration effect and the underlying mechanism are revealed in detail by using coordinated post-mortem analyses and theoretical simulations, demonstrating that the preferential solvent decomposition in LCEs induces the organic-dominant interfacial layer on LMAs. Such layer demonstrates low interface stability, causing poor cycling performance among various current densities in Li half cells. However, comprehensive results also indicate that LCEs are facing a good opportunity because of the fast interfacial charge transfer kinetics originating from the weak solvation nature. This work elucidates the roles of electrolyte concentration on the LMA and uncovers their correlative mechanism of series-diluted electrolytes. It is a certain breakthrough for this timely research to provide a comprehensive perspective for designing novel low-concentration electrolytes.