Formation Of Solid Electrolyte Interphase Layer Research Articles

Constructing stable solid electrolyte interphases to enhance the calendar life of anode-free lithium metal batteries

Advancement of anode-free lithium metal batteries (AFLMBs) has been appreciated due to their exceptional volumetric energy density and manufacturing simplicity. However, AFLMBs suffer from poor cycle performance due to the absence of excess lithium and current research lacks an understanding of lithium corrosion and calendar aging in AFLMBs. Here, we investigate the practical effects of chemical and galvanic corrosion on battery performance (calendar life) through a modified full-cell cycling experiment. The impact of galvanic corrosion is negligible, whereas chemical corrosion during a rest period reduces the capacity retention (CR) from 47% to 32% over 100 cycles. Consequently, a corrosion control strategy is implemented, substituting 1,2-dimethoxyethane with 1,2-dimethoxypropane (DMP), which has weaker lithium ion solvation properties due to its inductive effect. This approach results in the formation of a Li2O-rich solid-electrolyte interphase (SEI) layer, which effectively prevents direct contact of lithium with the electrolyte and the formation of additional SEI layers. Consequently, the decrease in CR due to chemical corrosion is considerably mitigated in DMP-based electrolyte, with only a slight decrease from 51% to 49%. This study provides insights into lithium corrosion in practical AFLMBs and offers guidelines for designing less-corrosive electrolytes to improve AFLMB performance for diverse industrial applications as energy-storage devices.

Balancing Potassiophilicity and Catalytic Activity of Artificial Interface Layer for Dendrite-Free Sodium/Potassium Metal Batteries.

Potassium metal batteries (PMBs), with high energy density and low cost, are considered a promising option for grid-scale energy storage systems. However, challenges such as the uneven nucleation of K and instability of the solid electrolyte interphase (SEI) layer result in dendrite growth and poor cyclic performance, limiting practical application. To address them, constructing an artificial interface layer with rich defects can enhance the potassium affinity and promote the uniform nucleation of potassium, yet this can also catalyze electrolyte to decompose, leading to unstable SEI formation and poor cycle stability. Herein, a carbon layer with a locally ordered structure (SC-1600) is constructed as the artificial interface to achieve a balance between K affinity and catalytic activity. This optimized design allows for the uniform nucleation of potassium metal and the formation of a dense SEI layer. SC-1600@K symmetric cell can operate for 2000h at 0.5mAcm-2 with a capacity of 0.5 mAhcm-2, and the developed full cell shows a high capacity retention of 78% after 1500 cycles at 1 Ag-1. Besides, SC-1600@Na effectively extend the life of sodium metal batteries. This work provides a new insight for the construction of efficient K metal artificial interface layer.

Enhanced electrochemical cyclability of composite sodium metal anode with inorganic-rich solid electrolyte interphase

The practical application of sodium (Na) metal anode in rechargeable batteries is impeded by inferior electrochemical properties and safety hazards arising from uneven Na plating/stripping behaviors. The Na-ion diffusion within the solid electrolyte interphase (SEI) plays a pivotal role in influencing these behaviors and the electrochemical performance of the Na metal anode. In this study, we leveraged the spontaneous reaction between red phosphorus (P) and metallic Na to fabricate a Na/Na3P (NNP) composite foil using a straightforward folding and mechanical rolling method at room temperature. The in-situ formed Na3P phase fosters the formation of an inorganic-rich SEI layer with high ionic conductivity, effectively enhancing the Na-ion diffusion kinetics and curbing the formation of Na dendrites. Moreover, the Na3P present in the NNP composite can continually replenish the functional component and promptly repair the fracture of the SEI layer, thereby ensuring the stability of its structure and properties. Consequently, the NNP composite electrode significantly extends the Na plating/stripping cyclic lifespan compared to a bare Na anode. As a demonstration, the Na3V2(PO4)3||NNP full cell exhibits stable performance over 400 cycles with 96.7 % capacity retention at 5C. This work paves the way for designing stable SEI layers with fast ion diffusion capability for alkali metal anodes, and the findings are anticipated to propel the development of alkali metal batteries.

LiF modified hard carbon from date seeds as an anode material for enhanced low-temperature lithium-ion batteries

The performance of traditional Li-ion batteries deteriorates when operating at sub-zero temperatures mainly due to the slow diffusion of Li-ions in commercial negative electrode materials. Various alternative anodes have been explored, but complex fabrication methods hinder practical implementation. This work proposes a cost-effective anode material, a porous structured nitrogen-doped hard carbon synthesized from date seeds with further LiF modification to achieve an artificial LiF-rich solid electrolyte interphase (SEI) layer. The resulting anode material showcases promising characteristics, achieving a specific capacity of 525 mAh g−1 after 50 cycles at room temperature. Furthermore, it maintains a substantial capacity of 280 mAh g−1 after 100 cycles at −20 °C. Notably, even when subjected to a high current of 2C at −20 °C, the electrode still provides a remarkable capacity of 72 mAh g−1 after 500 cycles. The outstanding charge storage performance at low temperatures is attributed to the predominance of capacitance-controlled charge storage mechanisms in the prepared anode. Post-mortem analysis confirms structural stability and formation of a uniform LiF-rich SEI layer. This novel approach presents a practical solution to the difficulties encountered by LIBs in cold environments, paving the way for improved battery performance and longevity.

Ultra‐Long and Rapid Operating Sodium Metal Batteries Enabled by Multifunctional Polarizable Interface Stabilizer

AbstractAbundant and economical sodium (Na) metal batteries promise superior energy densities compared to lithium‐ion batteries; however, they face commercialization challenges owing to problematic interfacial reactions leading to dendrite formation during cycling. This paper reports the ultra‐long and rapid operation of Na metal batteries enabled by the introduction of a vinylpyrrolidone (VP)‐based multifunctional interface stabilizer in the electrolyte. The VP electrolyte additive provides benefits such as surface flattening, durable solid electrolyte interphase layer formation, preservation of fresh Na, and acceleration of horizontal crystal growth along the (110) plane. Symmetric Na–Na cells with the stabilizer exhibit notably stable operation for over 5 000 cycles at a high current density of 5 mA cm−2, surpassing previous research. Performance improvement is also demonstrated in a full‐cell configuration with an Na3V2(PO4)2O2F cathode. This approach offers a promising solution for achieving performance levels comparable to lithium‐ion batteries in Na metal battery technology.

Effects of Electrolyte Solvent Composition on Solid Electrolyte Interphase Properties in Lithium Metal Batteries: Focusing on Ethylene Carbonate to Ethyl Methyl Carbonate Ratios

This study investigated the influence of variations in the mixing ratio of ethylene carbonate (EC) to ethyl methyl carbonate (EMC) on the composition and effectiveness of the solid electrolyte interphase (SEI) in lithium-metal batteries. The SEI is crucial for battery performance, as it prevents continuous electrolyte decomposition and inhibits the growth of lithium dendrites, which can cause internal short circuits leading to battery failure. Although the properties of the SEI largely depend on the electrolyte solvent, the influence of the EC:EMC ratio on SEI properties has not yet been elucidated. Through electrochemical testing, ionic conductivity measurements, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy, the formation of Li2CO3, LiF, and organolithium compounds on lithium surfaces was systematically analyzed. This study demonstrated that the EC:EMC ratio significantly affected the SEI structure, primarily owing to the promotion of the formation of a denser SEI layer. Specifically, the ratios of 1:1 and 1:3 facilitated a uniform distribution and prevalence of Li2CO3 and LiF throughout the SEI, thereby affecting cell performance. Thus, precise control of the EC:EMC ratio is essential for enhancing the mechanical robustness and electrochemical stability of the SEI, thereby providing valuable insights into the factors that either enhance or impede effective SEI formation.

In Situ Ions Induced Formation of KxF-Rich SEI Layers toward Ultrastable Life of Potassium-Ion Batteries.

Engineering F-rich solid electrolyte interphase (SEI) layers is regarded as an effective strategy to enable the long-term cycling stability of potassium-ion batteries (KIBs). However, in the conventional KPF6 carbonate electrolytes, it is challenging to form F-containing SEI layers due to the inability of KPF6 to decompose into KxF. Herein, AlCl3 is employed as a novel additive to change the chemical environment of the KPF6 carbonate electrolyte. First, due to the large charge-to-radius ratio of Al3+, the Al-containing groups in the electrolyte can easily capture F from PF6 - and accelerate the formation of KxF in SEI layer. In addition, AlCl3 also reacts with trace H2O or solvents in the electrolytes to form Al2O3, which can further act as a HF scavenger. Upon incorporating AlCl3 into conventional KPF6 carbonate electrolyte, the hard carbon (HC) anode exhibits an ultra-long lifespan of 10000 cycles with a high coulombic efficiency of ≈100%. When coupled with perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA), the full cell exhibits a high capacity retention of 81% after 360 cycles-significantly outperforming cells using conventional electrolytes. This research paves new avenues for advancing electrolyte engineering towards developing durable batteries tailored for large-scale energy storage applications.

Enhancing Charging Efficiency with Lithium Silicate in Silicon Composite Anode Materials Through Lithiothermic Reduction Reaction Synthesis

AbstractThis study synthesizes silicon (Si) powders with lithium silicates including lithium orthosilicate (Li4SiO4), lithium metasilicate (Li2SiO3), and lithium disilicate (Li2Si2O5), creating a composite structure of crystalline Si within a LixSiyOz matrix through the lithiothermic reduction reaction (LTRR) process. The reduction of Li‐ion consumption of the anode is investigated by 1) initial solid electrolyte interphase (SEI) layer formation, 2) SEI layer formation in response to Si expansion‐induced damage, 3) trapping of Li ions at Si defects, and 4) side reactions during initial charge and discharge cycles. Si/LixSiyOz electrode exhibits a specific capacity of 1522.2 mAh g−1 and an initial coulombic efficiency of 83.5%. The effect of the calendering process is observed, and a pressurization condition of 5000 kgf cm−2 or less is set, and the ICE is improved to 93.4%–96%. Si/LixSiyOz electrodes outperform pure crystalline Si electrodes in specific capacity (7.3%), ICE (42%), and retention characteristics (17%). The integration of the LixSiyOz matrix into Si anodes enhances Li‐ion transport and partially suppresses Si expansion. Additionally, the Si/LixSiyOz electrode exhibits superior rate capability in the 0.2–1.6 A g−1 range.

Electrolyte solvent composition regulating endows CoSe2 hollow nanocage anode with stable potassium ion storage

Metal selenides are ideal anode materials for potassium-ion batteries (PIBs) due to their significant merits of favorable conductivity and ion transport property. However, the inevitable volume changes of metal selenides electrode during potassiation/depotassiation processes result in the fracture and reconstruction of the solid electrolyte interphase (SEI) layer, causing capacity decay and significantly limiting their practical applications. Reasonable morphology control accompanied by uniform and rigid SEI layer formation are key factors in improving the electrochemical cycling stability of metal selenides. In this paper, nano-hollow CoSe2 (CoSe2@CNC) anode materials are prepared using ZIF-67 as the precursor. The differences of electrochemical performances for CoSe2@CNC anode material in ester-based and ether-based electrolytes have been investigated in detail. Results demonstrate that the SEI layer formed in the ester-based electrolyte is loose and thick, leading to electrode pulverization and material detachment after several cycles, resulting in rapid degradation of cycle performance. In contrast, a thin and inorganic-rich SEI layer containing more inorganic components is formed in the ether-based electrolyte, effectively protecting the electrode from damage, facilitating electronic transfer at the electrode electrolyte interphase, and optimizing potassium ions storage performance.

Simultaneous Realization of Multilayer Interphases on a Ni-Rich NCM Cathode and a SiOx Anode by the Combination of Vinylene Carbonate with Lithium Difluoro(oxalato)borate.

Ni-rich NCM and SiOx electrode materials have garnered the most attention for advanced lithium-ion batteries (LIBs); however, severe parasitic reactions occurring at their interfaces are critical bottlenecks in their widespread application. In this study, an effective additive combination (VL) composed of vinylene carbonate (VC) and lithium difluoro(oxalato)borate (LiDFOB) is proposed for both Ni-rich NCM and SiOx electrode materials. The LiDFOB additive individually delivers inorganic-rich cathode-electrolyte interphase (CEI) and solid-electrolyte interphase (SEI) layers in anodic and cathodic polarizations before the VC additive. Subsequently, the VC additive is capable of the formation of additional CEI and SEI layers composed of relatively organic-rich components through an electrochemical reaction; thus, inorganic-organic hybridized CEI and SEI layers are simultaneously formed at the Ni-rich NCM and SiOx electrodes. Accordingly, the VL-assisted electrolyte exhibits remarkably prolonged cycling retention for the Ni-rich NCM cathode (86.5%) and SiOx anode (72.7%), whereas the standard electrolyte shows a substantial decrease in cycling retention for the Ni-rich NCM cathode (59.2%) and SiOx anode (18.1%). Further systematic analyses prove that VL-assisted electrolytes form effective interphases for Ni-rich NCM and SiOx electrodes simultaneously, thereby leading to stable and prolonged cycling behaviors of LIBs that offer high energy densities.

Utilizing High-Capacity Spinel-Structured High-Entropy Oxide (CrMnFeCoCu)3O4 as a Graphite Alternative in Lithium-Ion Batteries

In the realm of advanced anode materials for lithium-ion batteries, this study explores the electrochemical performance of a high-entropy oxide (HEO) with a unique spinel structure. The equiatomic composition of CrMnFeCoCu was synthesized and subjected to a comprehensive materials characterization process, including X-ray diffraction and microscopy techniques. The multicomponent alloy exhibited a multiphase structure, comprising two face-centered cubic (FCC) phases and an oxide phase. Upon oxidation, the material transformed into a spinel oxide with a minor presence of CuO. The resulting high-entropy oxide demonstrated excellent electrochemical behavior when utilized as an anode material. Cyclic voltammetry revealed distinctive reduction peaks attributed to cation reduction and solid electrolyte interphase (SEI) layer formation, while subsequent cycles showcased high reversibility. Electrochemical impedance spectroscopy indicated a decrease in charge transfer resistance during cycling, emphasizing the remarkable electrochemical performance. Galvanostatic charge/discharge tests displayed characteristic voltage profiles, with an initial irreversible capacity attributed to SEI layer formation. The HEO exhibited promising rate capability, surpassing commercial graphite at higher current densities. The battery achieved 80% (275 mAh g−1) of its initial stable capacity at a current density of 500 mA g−1 by the 312th cycle. Post-mortem analysis revealed structural amorphization during cycling, contributing to the observed electrochemical behavior. This research highlights the potential of HEOs as advanced anode materials for lithium-ion batteries, combining unique structural features with favorable electrochemical properties.

Low-Temperature and Fast-Charge Sodium Metal Batteries.

Low-temperature operation of sodium metal batteries (SMBs) at the high rate faces challenges of unstable solid electrolyte interphase (SEI), Na dendrite growth, and sluggish Na+ transfer kinetics, causing a largely capacity curtailment. Herein, low-temperature and fast-charge SMBs are successfully constructed by synergetic design of the electrolyte and electrode. The optimized weak-solvation dual-salt electrolyte enables high Na plating/stripping reversibility and the formation of NaF-rich SEI layer to stabilize sodium metal. Moreover, an integrated copper sulfide electrode is in situ fabricated by directly chemical sulfuration of copper current collector with micro-sized sulfur particles, which significantly improves the electronic conductivity and Na+ diffusion, knocking down the kinetic barriers. Consequently, this SMB achieves the reversible capacity of 202.8mAhg-1 at -20°C and 1C (1C = 558mAg-1). Even at -40°C, a high capacity of 230.0mAhg-1 can still be delivered at 0.2C. This study is encouraging for further exploration of cryogenic alkali metal batteries, and enriches the electrode material for low-temperature energy storage.

Elastic MXene conductive layers and electrolyte engineering enable robust potassium storage.

The precisely engineered structures of materials greatly influence the manifestation of their properties. For example, in the process of alkali metal ion storage, a carefully designed structure capable of accommodating inserted and extracted ions will improve the stability of material cycling. The present study explores the uniform distribution of self-grown carbon nanotubes to provide structural support for the conductive and elastic MXene layers of Ti3C2Tx-Co@NCNTs. Furthermore, a compatible electrolyte system has been optimized by analyzing the solvation structure and carefully regulating the component in the solid electrolyte interphase (SEI) layer. Mechanistic studies demonstrate that the decomposition predominantly controlled by FSI- leads to the formation of a robust inorganic SEI layer enriched with KF, thus effectively inhibiting irreversible side reactions and major structural deterioration. Confirming our expectations, Ti3C2Tx-Co@NCNTs exhibits an impressive reversible capacity of 260 mA h g-1, even after 2000 cycles at 500 mA g-1 in 1 M KFSI (DME), surpassing most MXene-based anodes reported for PIBs. Additionally, density functional theory (DFT) calculations verify the superior electronic conductivity and lower K+ diffusion energy barriers of the novel superstructure of Ti3C2Tx-Co@NCNTs, thereby affirming the improved electrochemical kinetics. This study presents systematic evaluation methodologies for future research on MXene-based anodes in PIBs.

In Situ Raman Spectroelectrochemical Investigation of Composite Si Nanoparticle-Based Anode for Li-Ion Batteries during (de)Lithiation Process

The key degradation processes in the composite anode for the Li-ion batteries (LIBs) prepared using Si nanoparticles (SiNPs) with two types of a conductive carbon-based matrix [carbon black (CB) and carbonized polypyrrole (CPPy)] were studied by in situ Raman spectroelectrochemistry (SEC). This combined technique provides non-destructive and real-time monitoring of the chemical and structural changes that occur during battery operation. These processes, such as the crystal lattice changes (expansion/contraction) and possible degradation/amorphization of silicon, the solid electrolyte interphase (SEI) layer formation on the electrode surface during the charge/discharge reactions, and the stability of the carbon-based matrix, significantly affect the performance of Si-based LIBs in many ways. Especially, the large silicon volume expansion (more than 300%) and associated stress cause mechanical instability resulting in rapid capacity fading. To overcome this challenge, various strategies have been proposed, including the use of CPPy as a conductive matrix to prevent large volumetric changes and also provide a pathway for electron transfer.This study investigates the initial degradation mechanisms such as the formation of the SEI layer, as well as possible structural changes caused by the volume expansion of SiNPs. The shift of the first-order Raman peak of Si at 521 cm-1 which is assigned to crystalline silicon is related to the stress evolution in nanoparticles caused by the (de)lithiation-induced stress (tensile-to-compressive transition) in SiNPs and the native oxide on their surface. Additionally, the detailed in situ Raman measurement of the first lithiation cycle allowed us to detect the decomposition of the electrolyte (LiPF6 in EC/DMC) close to the Si surface which is associated with SEI layer formation. A decrease in the intensity of the Raman vibrational modes (700–1050 cm−1) of EC/DMC corresponding to the decomposition of the electrolyte was observed at reduction potentials of 0.8 V and 0.3 V vs. Li/Li+ corresponding to the same potentials determined by cyclic voltammetry. The Si-based anode containing CPPy as active carbon showed better electrochemical properties (higher charge/discharge capacity and cycling stability) in Li-ion batteries than Si/CB despite the higher conductivity of the latter. The correlation between the chemical structure of the active carbon and the electrochemical properties of the resulting Si-based anodes will be discussed.Acknowledgment: This work was supported by the Czech National Foundation, Project No. 21–09830S.

Enhancing Cycle Life of Lithium Metal Batteries By Regulating Solid-Electrolyte Interphase Using Gel Polymer Electrolyte

Lithium metal with high theoretical capacity and low redox potential is one of the promising anode materials for high energy density batteries. However, the lithium metal has safety problems and poor cycling performance, due to the growth of Li dendrite and side reactions between Li and electrolytes. One of the most effective strategies to stabilize Li metal is forming robust solid-electrolyte interphase (SEI). Recently, anion-derived and inorganic-rich SEI is known to be stable and ionic conductive, leading to good cycling stability. One of the most popular strategies to form durable SEI is to use the localized high-concentration electrolytes (LHCE) which construct an anion-derived SEI layer on Li metal. In this work, we synthesized LHCE-based gel polymer electrolytes to form a stable SEI layer and enhance cycling stability. Small amount of cross-linking agent was added into dimethoxyethane (DME)-based LHCE when synthesizing gel polymer electrolyte. The functional groups in cross-linking agents increase Li+ and anion interaction in the gel polymer electrolytes, resulting in formation of the stable SEI layer. The solvation structure and chemical composition of the SEI layer were investigated by density functional theory (DFT) calculation and spectroscopic analyses such as FT-IR, Raman, and XPS. The Li/NCM811 cells with LHCE-based gel polymer electrolyte were assembled for the cycling test, and they exhibited superior cycling performance than liquid electrolyte-based cells.

Dynamic Molecular Investigation of the Solid-Electrolyte Interphase of an Anode-Free Lithium Metal Battery Using In Situ Liquid SIMS and Cryo-TEM.

We use in situ liquid secondary ion mass spectroscopy, cryogenic transmission electron microscopy, and density functional theory calculation to delineate the molecular process in the formation of the solid-electrolyte interphase (SEI) layer under the dynamic operating conditions. We discover that the onset potential for SEI layer formation and the thickness of the SEI show dependence on the solvation shell structure. On a Cu film anode, the SEI is noticed to start to form at around 2.0 V (nominal cell voltage) with a final thickness of about 40-50 nm in the 1.0 M LiPF6/EC-DMC electrolyte, while for the case of 1.0 M LiFSI/DME, the SEI starts to form at around 1.5 V with a final thickness of about 20 nm. Our observations clearly indicate the inner and outer SEI layer formation and dissipation upon charging and discharging, implying a continued evolution of electrolyte structure with extended cycling.

Interface Controls Large-Volume Change Anodes Pulverization

Micron sized alloys have been considered as the most attractive candidates for advanced lithium or sodium ion battery anodes due to their high capacity, cost effectiveness, and ease of mass production. However, their large volume variation during (de)alloying reaction with Li or Na ions causes severe mechanical degradation of anode materials, resulting in particle pulverization and loss of electrical interparticle contact. In addition, this substantial volumetric fluctuation leads to newly exposed anode surface to electrolyte and instability of solid-electrolyte interphase (SEI), which can bring about continuously formation of SEI layers. To mitigate the large volume change issues of micron sized alloys, various approaches have been studied such as introducing various electrolytes and additives for stabilizing the SEI layers. However, these modified SEI layers are still not enough to suppress the large volume fluctuation of micron sized alloys.Here, we demonstrate that the effect of interface between electrolyte and anode surface on anode pulverization. With micron sized alloying anodes for sodium-ion batteries (Bi and Sn), we observed substantially different pulverization behavior as a choice of electrolyte solvents leading to different anode-electrolyte interface. This different interface reactivity between solvents has a big impact on not only pulverization behavior of alloying anodes but also formation and growth of SEI layers on the surface of anode. Thus, the electrochemical performances of the alloying anodes also can be influenced by its interface characteristics. We thoroughly analyzed the effect of interface of alloying anode from electrode-level to nanoscale by various characterization tools such as Scanning electron microscopy (SEM), X-ray computed tomography (X-ray CT), X-ray photoelectron spectroscopy (XPS), Atom probe tomography (APT), and cryo-transmission electron microscopy (TEM). Moreover, we clarified the mechanism of the interface reaction and pulverization pathway by theoretical simulations. We believe this study can help researchers to understand the degradation behavior of large volume change alloy anodes.

Synergistic dual electrolyte additives for fluoride rich solid-electrolyte interface on Li metal anode surface: Mechanistic understanding of electrolyte decomposition

Improving the quality of the solid-electrolyte interphase (SEI) layer is highly imperative to stabilize the Li-metal anodes for the practical application of high-energy–density batteries. However, controllably managing the formation of robust SEI layers on the anode is challenging in state-of-the-art electrolytes. Herein, we discuss the role of dual additives fluoroethylene carbonate (FEC) and lithium difluorophosphate (LiPO2F2, LiPF) within the commercial electrolyte mixture (LiPF6/EC/DEC) considering their reactivity with Li metal anodes using density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations. Synergistic effects of dual additives on SEI formation mechanisms are explored systematically by invoking different electrolyte mixtures including pure electrolyte (LP47), mono-additive (LP47/FEC and LP47/LiPF), and dual additives (LP47/FEC/LiPF). The present work suggests that the addition of dual additives accelerates the reduction of salt and additives while increasing the formation of a LiF-rich SEI layer. In addition, calculated atomic charges are applied to predict the representative F1s X-ray photoelectron (XPS) signal, and our results agree well with the experimentally identified SEI components. The nature of carbon and oxygen-containing groups resulting from the electrolyte decompositions at the anode surface is also analyzed. We find that the presence of dual additives inhibits undesirable solvent degradation in the respective mixtures, which effectively restricts the hazardous side products at the electrolyte-anode interface and improves SEI layer quality.

Ti3CNTx MXene/rGO scaffolds directing the formation of a robust, layered SEI toward high-rate and long-cycle lithium metal batteries

The practical usage of lithium (Li) metal anodes has been hindered by the inherent uncontrolled growth of Li dendrites during stripping/plating. Approaching regulation of uniform Li deposition and robust solid-electrolyte interphase (SEI) is of significance. Herein, we utilized the unique surface chemistry of two-dimensional titanium carbonitride (Ti3CNTx) and the three-dimensional reduced graphene oxide (rGO)-based conductive scaffold architecture, to regulate the Li nucleation and SEI. The lithiophilic functional groups on Ti3CNTx improve the charge-transfer-promoted decomposition of LiN(CF3SO2)2 and resulting in the formation of a uniform SEI layer decorated with evenly distributed LiF and ordered layered Li2O, as evidenced by cryogenic transmission electron microscopy. The Ti3CNTx-rGO-Li electrodes based full cells with LiFePO4 guarantee a superior cycling lifespan over 900 cycles with a capacity retention of 77.7% at 30 C. This work demonstrates that through surface engineering and multiscale architecture design, the suppression of Li dendrites and formation of robust SEI layer can be achieved simultaneously.

An Inorganic-Rich SEI Layer by the Catalyzed Reduction of LiNO3 Enabled by Surface-Abundant Hydrogen Bonding for Stable Lithium Metal Batteries.

Lithium (Li) metal anodes (LMAs) are promising anode candidates for realizing high-energy-density batteries. However, the formation of unstable solid electrolyte interphase (SEI) layers on Li metal is harmful for stable Li cycling; hence, enhancing the physical/chemical properties of SEI layers is important for stabilizing LMAs. Herein, thiourea (TU, CH4 N2 S) is introduced as a new catalyzing agent for LiNO3 reduction to form robust inorganic-rich SEI layers containing abundant Li3 N. Due to the unique molecular structure of TU, the TU molecules adsorb on the Cu electrode by forming CuS bond and simultaneously form hydrogen bonding with other hydrogen bonds accepting species such as NO3 - and TFSI- through its NH bonds, leading to their catalyzed reduction and hence the formation of inorganic-rich SEI layer with abundant Li3 N, LiF, and Li2 S/Li2 S2 . Particularly, this TU-modified SEI layer shows a lower film resistance and better uniformity compared to the electrochemically and naturally formed SEI layers, enabling planar Li growth without any other material treatments and hence improving the cyclic stability in Li/Cu half-cells and Li@Cu/LiFePO4 full-cells.