SEI Layer Research Articles

Boosting the Interfacial Stability of the Li6PS5Cl Electrolyte with a Li Anode via In Situ Formation of a LiF-Rich SEI Layer and a Ductile Sulfide Composite Solid Electrolyte.

Due to its good mechanical properties and high ionic conductivity, the sulfide-type solid electrolyte (SE) can potentially realize all-solid-state batteries (ASSBs). Nevertheless, challenges, including limited electrochemical stability, insufficient solid-solid contact with the electrode, and reactivity with lithium, must be addressed. These challenges contribute to dendrite growth and electrolyte reduction. Herein, a straightforward and solvent-free method was devised to generate a robust artificial interphase between lithium metal and a SE. It is achieved through the incorporation of a composite electrolyte composed of Li6PS5Cl (LPSC), polyethylene glycol (PEG), and lithium bis(fluorosulfonyl)imide (LiFSI), resulting in the in situ creation of a LiF-rich interfacial layer. This interphase effectively mitigates electrolyte reduction and promotes lithium-ion diffusion. Interestingly, including PEG as an additive increases mechanical strength by enhancing adhesion between sulfide particles and improves the physical contact between the LPSC SE and the lithium anode by enhancing the ductility of the LPSC SE. Moreover, it acts as a protective barrier, preventing direct contact between the SE and the Li anode, thereby inhibiting electrolyte decomposition and reducing the electronic conductivity of the composite SE, thus mitigating the dendrite growth. The Li|Li symmetric cells demonstrated remarkable cycling stability, maintaining consistent performance for over 3000 h at a current density of 0.1 mA cm-2, and the critical current density of the composite solid electrolyte (CSE) reaches 4.75 mA cm-2. Moreover, the all-solid-state lithium metal battery (ASSLMB) cell with the CSEs exhibits remarkable cycling stability and rate performance. This study highlights the synergistic combination of the in-situ-generated artificial SE interphase layer and CSEs, enabling high-performance ASSLMBs.

SEI-Coated Carbon Particles: Electrochemomechanical Fracture Mechanisms

By starting from fundamental physical principles, a generalized theoretical framework was developed to engineer the intercalation-induced mechanical degradation in SEI-coated carbon particles from the surrounding electrolyte in rechargeable lithium-ion batteries (LIBs). Six elemental regimes of fracture formation in spherical electrochemically active carbon particles of radius, r p , coated with an SEI layer of thickness, δ ≪ r p , have been identified: The pristine regime, the SEI debonding regime, the SEI surface flaw regime, the surface carbon flaw regime (delithiation), the internal circular carbon flaw regime (lithiation), and the carbon exfoliation regime (lithiation); as well as four combined regimes during delithiation and four combined regimes during lithiation. Results are summarized in terms of C-Rate versus particle size, degradation maps, to identify LIB operation conditions where the performance can be optimized, while suppressing the decrepitation of the SEI-coated carbon particle system. Improved porous electrode layers that deliver longer battery life are possible by selecting electrolytes that considering the design of SEI-coated carbon particles of tailored elastic stiffness and critical stress intensity factor, so that they are safe from developing a chemomechanically induced flaw, exfoliation, or carbon re-forming, during both lithiation or delithiation in the 1 to 10 μm size particle, and C-Rates < 1 C.

Stabilizing Lithium-Oxygen Batteries through In Situ Generated Phenyl/LiF-Rich Hybrid SEI Layer with Sulfonyl Fluoride Electrolyte Additive

Lithium-oxygen batteries have a wide application due to their ultra-high theoretical energy density. However, uncontrollable lithium dendrites and highly reactive oxygen species greatly cause the corrosion of lithium anodes and the degradation of the electrolytes. In our work, we introduce 4-Methylbenzenesulfonyl Fluoride (4-MBSF) as a highly efficient film-forming additive. It can form a stable inorganic-organic composite solid electrolyte interfacial layer and inhibit the growth of lithium dendrites to stabilize the lithium anode, thus dramatically enhancing the lives of lithium-oxygen batteries. The sulfonyl fluoride group of 4-MBSF can react with LiOH to form a LiF-rich protective layer on the lithium metal surface, which can improve stripping/deposition stability and ionic conductivity. Besides, the π-conjugation of the benzene ring can improve the flexibility of the SEI layer to accommodate volume changes of the lithium anode during cycling and inhibit the attacks of the reactive oxygen species. The cycle life of lithium-oxygen batteries with 4-MBSF is prolonged to 400 cycles.

Suppressing the Growth of Dendrites On Ultrathin Lithium Metal Anodes by an Amide Electrolyte Additive

The practical applications of high energy density lithium (Li) metal rechargeable batteries are hindered by the formation of lithium dendrites. Besides, using the thick Li anodes (typically 50 μm to 750 μm) provide more Li inventory than is needed in the cell as well as disappears the advantage of high energy density of Li metal over Li-ion batteries.Therefore, in this study, N-N-diallyl-2,2,2-trifluoroacetamide (NDT) is proposed as an electrolyte additive to inhibit the growth of dendrites on the ultrathin Li anode (20 μm). By virtue of its preferential reduction as well as its participation in the primary Li+ solvation shell, NDT contributes to the formation of a Li3N-contained uniform SEI layer on the Li metal, leading to a low polarization in LillLi cells. Be benefited, the LillLFP cell, utilizing a carbonate-based electrolyte containing 2 wt% NDT, exhibits a prolonged life-span, an enhanced reversibility, along with a retention capacity of 72% after 75 cycles, while the cell using baseline electrolyte shows a retention capacity of 68% after 50 cycles at 0.3 C. Additionally, NDT improves the ionic conductivity, and wettability of the electrolyte to the separator. These significant findings provide valuable insights for designing electrolyte additives to stabilize ultrathin Li metal anodes.

Reduction of Irreversible Capacity in Lithium-ion Batteries

This article is focused on a research of negative materials for Lithium-ion batteries. In the research are considered methods, which can lead to enhance capacity of Lithium-ion batteries. The increase of the battery capacity is based on reduction of irreversible capacity. The majority of Li-ion batteries which are used in this time has negative electrode make from graphite. On interface between electrolyte and graphite electrode originates the SEI layer (Solid-Electrolyte Interphase), this layer is the cause of irreversible capacity of graphite. This layer is indispensable for appropriate battery function but for creating this layer is consumed almost one-third potential capacity of Li-ion cell. In our research we attempted to prepare the material which would reduce these capacity losses. Was designed a concept where n-butyllithium (C4H9Li) reagent behaves as the source of lithium atoms and graphite acts like acceptor of lithium atoms. This process is called „lithiation“, our conception presents n-butyllithium like oxidative reagent which is able to reduce graphite material by Li atoms. Lithium atoms are intercalated between graphite sheets (as at charging process), resulting of this process is new lithiated electrode material which can be used for prepare of negative electrode for Li-ion cells.

Sustained Release-Driven Interface Engineering Enables Fast Charging Lithium Metal Batteries.

LiNO3 has attracted intensive attention as a promising electrolyte additive to regulate Li deposition behavior as it can form favorable Li3N, LiNxOy species to improve the interfacial stability. However, the inferior solubility in carbonate-based electrolyte restricts its application in high-voltage Li metal batteries. Herein, an artificial composite layer (referred to as PML) composed of LiNO3 and PMMA is rationally designed on Li surface. The PML layer serves as a reservoir for LiNO3 release gradually to the electrolyte during cycling, guaranteeing the stability of SEI layer for uniform Li deposition. The PMMA matrix not only links the nitrogen-containing species for uniform ionic conductivity but also can be coordinated with Li for rapid Li ions migration, resulting in homogenous Li-ion flux and dendrite-free morphology. As a result, stable and dendrite-free plating/stripping behaviors of Li metal anodes are achieved even at an ultrahigh current density of 20mA cm-2 (>570h) and large areal capacity of 10 mAh cm-2 (>1200h). Moreover, the Li||LiFePO4 full cell using PML-Li anode undergoes stable cycling for 2000 cycles with high-capacity retention of 94.8%. This facile strategy will widen the potential application of LiNO3 in carbonate-based electrolyte for practical LMBs.

One-stone, two birds: Three-dimensional structure and rich-inorganic solid electrolyte interface derived from Bi nanoparticles modified Ti3C2/CNT/rGO aerogel for anode-free potassium metal batteries

Potassium (K) metal batteries are very promising next generation electrochemical energy storage system due to the usage of K metal with low cost and high energy density. However, the practical application of K metal batteries and even anode-free K metal batteries are still confronting huge challenges owing to the formation of “dead K” resulting from the uncontrollable growth of K dendrite and the infinite volume variation, as well as the continuous consumption of electrolyte component during charge/discharge processes. Herein, a novel “one-stone, two birds” strategy was proposed for the first time by designing a three-dimensional (3D) potassiophilic current collector composed of“Bi nanoparticles modified Ti3C2/CNT/rGO cross-linked 3D porous aerogel hosts (marked as Bi/CTG)”and spontaneously in-situ forming a rich-inorganic SEI layer simultaneously. The modification of Bi nanoparticles could improve potassiophilicity of hosts and guide uniform K metal deposition. The 3D porous structure of Bi/CTG hosts could accommodate the deposited K metal to restrain serious volume variation during K plating/stripping process. Simultaneously, the spontaneous generation of KF and K3Bi between the deposited K metal and Bi/CTG could contribute SEI layer and improve the stability of SEI layer. The integrated merits are conductive to realize stable and reversible cycling of anode-free K metal battery. As a result, Bi/CTG@Cu//PB anode-free K metal battery delivers extraordinary energy density of 152.8 Wh kg−1 at a power density of 6110 W kg−1. This study paves the way to realize high energy density anode-free K metal battery through a simple “one-stone, two birds” strategy.

Achieving highly stable sodium metal batteries with self-adapting and high-ionic-mobility ceramic fiber membranes

Tough issues like sodium (Na) dendrite growth and poor anode reversibility hinder the practical application of sodium metal batteries (SMBs) with moderate liquid electrolytes. To settle these problems, using a smart self-adapting Al2SiO5 ceramic fiber (CF) membrane is demonstrated to enable homogeneous Na depositions and inhibit the dendritic growth. This inorganic membrane itself has superb thermal stability, high ionic mobility (Na+ transference number: 0.65) and electrolyte wettability over traditional glass fiber (GF) or polymeric ones, guaranteeing the low voltage polarization (14 mV) and long-cyclic lifetime (over 600 h) in symmetric cells testing. Notably, aluminous components in CF membranes would interact with F-based molecules in the electrolyte phase, thereby releasing some Al3+ species that can be electrochemically deposited onto the anodic interface. The packed (+)Na3V2(PO4)3|CF|Na(−) full SMBs exhibit far superior cyclic stability (capacity retention over 78.7 % after 600 cycles at 1C) than other counterparts. The in-situ detection/postmortem analysis reveal that Al/F-based inorganics formed in as-built SEI layers play a vital role in Na metal anode protection. This work may provide a viable strategy to overcome the constraints of high-energy SMBs in practical applications.

Composition Analysis of the Solid Electrolyte Interface of NaK Anodes in Na-Ion Batteries.

Sodium-ion batteries have emerged as a promising alternative to Li-ion batteries due to the abundance of sodium. However, anodes in Na-ion batteries face challenges such as dendrite formation and an unstable solid electrolyte interface layer. To address these challenges, NaK liquid metal alloy anodes have been proposed as an alternative because they do not form dendrites. In our study, we demonstrate that the NaK alloy anode interacts with the commonly used ethylene carbonate and dimethyl carbonate electrolyte, leading to a continuously growing unstable SEI layer, evidenced by cycling failures under 100 cycles and an increasing charge transfer resistance in electrochemical impedance spectroscopy studies. In situ surface-enhanced Raman spectroscopy and X-ray photoelectron spectroscopy reveal that over the course of cycling the surface of the NaK anode becomes increasingly sodium-rich. After 30 cycles, XPS analysis detects only trace amounts of potassium on the NaK anode surface. When the electrolyte is analyzed postcycling using inductively coupled plasma optical emission spectroscopy, there is a noticeable increase in potassium levels, suggesting that potassium metal dissolves into the electrolyte. The introduction of a 10 wt % fluoroethylene carbonate additive can mitigate this problem to some extent, enabling an enhanced cycling performance of up to 800 cycles at 1C. Nevertheless, the dissolution of K metal is still evident in the XPS results, albeit to a lesser degree. These discoveries provide valuable insights for designing a more robust SEI layer for the NaK anode.

A Green Asymmetric Bicyclic Co-Solvent Molecule for High-Voltage Aqueous Lithium-Ion Batteries.

Hybridizing aqueous electrolytes with organic co-solvents can effectively expand the voltage window of aqueous electrolytes while reducing salt usage, but most reported co-solvents are usually flammable and toxic, hardly achieving compatibility between safety and electrochemical performance. Here, a new non-flammable and non-toxic low-salt-concentration (1.85 m) aqueous electrolyte is reported using the green co-solvent isosorbide dimethyl ether (IDE). Owing to its unique 3D molecular structure, IDE can form a five-membered ring structure by binding the Li ion. The steric hindrance effect from IDE weakens its solvation ability, generating anion-participated solvation structures that produce a robust and uniform LiF-rich solid electrolyte interphase layer while containing elastic IDE-derived organics. Moreover, the multiple O atoms in IDE can effectively regulate the intermolecular hydrogen bonding networks, reducing H2O molecule activity and expanding the electrochemical window. Such unique solvation structures and optimized hydrogen bonding networks enabled by IDE effectively suppress electrode/electrolyte interfacial side reactions, achieving a 4.3 V voltage window. The as-developed Li4Ti5O12(LTO)||LiMn2O4(LMO) full cell delivers outstanding cycling performance over 450 cycles at 2 C. The proposed green hybrid aqueous electrolyte provides a new pathway for developing high-voltage aqueous lithium batteries.

Bianionic coordination solvation structure electrolyte for high-voltage lithium metal batteries

High-voltage lithium metal batteries (HV-LMBs) comprising Ni-rich cathodes (such as LiNi0.8Mn0.1Co0.1O2) and a lithium metal anode (LMA) are highly promising with an energy density of 500 Wh kg−1. However, the stability of the electrode/electrolyte interface of HV-LMBs presents significant challenges. In addition, LMAs have several limitations, such as dendrite growth, production of dead-Li0, and repeated collapse and reconstruction of the SEI layer. Ni-rich cathode materials suffer from rapid capacity decline and structural collapse. Herein, we report an electrolyte with a bianionic coordination solvation structure (CF1) with a high voltage window and significantly enhanced stability at the electrode/electrolyte interface. Raman spectra and molecular dynamics (MD) simulations confirmed the unique solvation structure of CF1. XPS and cryo-TEM indicate that a unique heterogeneous phase SEI of LiF-rich crystals is formed in the CF1 electrolyte, which facilitates the uniform and dense deposition of Li while inhibiting the growth of lithium dendrites. Moreover, the CF1 electrolyte has a high ionic conductivity (7.84 mS cm−1), which is favorable for rapid Li+migration. An Li||Cu cell using the CF1 electrolyte achieved an average coulombic efficiency (CE) of 99.6%. Meanwhile, the Li||Li symmetric cell exhibits stable cycling for 1200 h (1.0 mA cm−2, 0.5 mAh cm−2). Furthermore, the Li||NCM811 full cell with the CF1 electrolyte was stable for 270 cycles, with 81% capacity retention at a cut-off voltage of 4.5 V (N/P = 2.5, 0.5 C). Our study presents a new approach for designing electrolytes for HV-LMBs, aimed at streamlining their practical implementation.

Crosslinked Gel Polymer Electrolyte from Trimethylolpropane Triglycidyl Ether by In Situ Polymerization for Lithium-Ion Batteries.

Electrolytes play a critical role in battery performance. They are associated with an increased risk of safety issues. The main challenge faced by many researchers is how to balance the physical and electrical properties of electrolytes. Gel polymer electrolytes (GPEs) have received increasing attention due to their satisfactory properties of ionic conductivity, mechanical stability, and safety. Herein, we develop a gel network polymer electrolyte (GNPE) to address the challenge mentioned earlier. This GNPE was formed by tri-epoxide monomer and bis(fluorosulfonyl)imide lithium salt (LiFSI) via an in situ cationic polymerization under mild thermal conditions. The obtained GNPE exhibited a relatively high ionic conductivity (σ) of 2.63 × 10-4 S cm-1, lithium transference number (tLi+, 0.58) at room temperature (RT), and intimate electrode compatibility with LiFePO4 and graphite. The LiFePO4/GNPE/graphite battery also showed a promising cyclic performance at RT, e.g., a suitable discharge specific capacity of 127 mAh g-1 and a high Coulombic efficiency (>97%) after 100 cycles at 0.2 C. Moreover, electrolyte films showed good mechanical stability and formed the SEI layer on the graphite anode. This study provides a facile method for preparing epoxy-based electrolytes for high-performance lithium-ion batteries (LIBs).

Improved electrochemical performance of solid-state lithium metal batteries with stable SEI and CEI layers via in situ formation technique

Lithium-metal batteries (LMBs) using sandwich-type hybrid solid electrolytes (SHSEs) have been increasingly popular because of their high safety and improved electrochemical performance.

Bottom-up deposition of lithium on 3D lithiophobic–lithiophilic host for long-life lithium metal anodes

The features of 3D carbon skeletons can regulate the composition of the SEI layer to achieve bottom-up Li deposition behavior.

Operando investigations of the solid electrolyte interphase in the lithium mediated nitrogen reduction reaction

Operando GI-WAXS showed that the SEI layer formed by LiBF4 enhances Li-NRR performance by limiting proton transport to the electrode. Intermediate LiNxHy species give insight into the mechanism of Li-NRR.

Dual role of hBN as an artificial solid–electrolyte interface layer for safe zinc metal anodes

Monolayer and large area hBN as an artificial SEI layer shows dual role in preventing the undesired side reaction of HER and inducing the heteroepitaxial grown of Zn, successfully resolving the dendrite issue for safe Zn metal anode.

A “three in one” strategy realized using a fluorinated gold-doped titanium silicalite layer on a copper current collector for stable lithium metal batteries

Long cycle life was realized on a fluorinated, Au doped titanium silicalite modified Cu (ATSF-5/Cu) current collector by Li affinity of Au nanoparticles, microporous properties of titanium silicalite and the formation of the LiF-rich SEI layer.

Computational Screening of Ca‐Containing Coating Materials for Electrodes of Ca‐Ion Batteries

The energy storage system utilizing calcium as a charge carrier is gaining prominence due to its abundance in the Earth’s crust, reduction potential that is comparable to lithium (Li/Li+ = −3.04 V, Ca/Ca2+ = −2.84 V), and its nontoxic nature. Enabling practical Ca‐ion batteries demands overcoming challenges in forming both electrically nonconductive and ionically conductive SEI layers. We propose a coating strategy and thermodynamic screening via the Materials Project database to pinpoint suitable coating materials. Our selection criteria encompass phase stability, electronic properties, and electrochemical stability. Among 787 compounds, we identified 46 candidates (29 anodic, 24 cathodic, and 7 of them are on both sides) based on reduction/oxidation potential and width of the stability window. Optimal compounds such as Ca4Cl6O and CaCN2 for anodes, and Ca(AlCl4)2, CaCO3, CaSO4, KCaF3, and CaAlF5 for cathodes exhibit superior interfacial stability for electrode coating, holding promise for Ca‐ion batteries. This study can provide foundational insights into coating materials for Ca‐ion batteries, offering guidance for electrode interface stabilization and practical battery design.

In situ interface engineering of highly nitrogen-rich triazine-based covalent organic frameworks for an ultra-stable, dendrite-free lithium-metal anode

Highly N-rich triazine-based COFs as a multiple lithiophilic SEI layer is designed via in situ interface engineering, which induces uniform Li+ flux and plating/stripping, decreases the Li+ migration barrier, and suppresses Li-dendrite growth.

In situ construction of a static-dynamic hybrid interface toward stable Zn anodes for aqueous Zn-ion batteries.

Aqueous Zn-ion batteries are promising candidates for next-generation energy storage devices due to the advantages of high safety, low cost and good environmental friendliness. However, the uncontrollable dendrite growth and undesirable side reactions occurring on the Zn anode result in poor cycling stability. Herein, a Lewis base, triethanolamine, is used as the electrolyte additive to construct a hybrid solid-electrolyte interphase layer composed of a static ZnSO4·3Zn(OH)2·4H2O layer and dynamic quaternary ammonium ion adsorption layer. The static SEI layer acts as a physical barrier between the Zn anode and electrolyte, thus effectively suppressing chemical corrosion and the hydrogen evolution reaction. The dynamic layer can not only regulate the ion flux at the interface, but also promote the de-solvation of solvated Zn2+, thus leading to homogenous Zn deposition along the (002) electro-crystallization orientation. As a result, the Zn anode demonstrates an extended cycle life of 2500 h at a current density of 1.0 mA cm-2, with an areal capacity of 1.0 mA h cm-2 and a high coulombic efficiency (CE) of 98.94%. The Zn‖V2O5 cells exhibit a specific capacity of 178.4 mA h g-1 after 500 cycles, indicating both high capacity and robust cycling stability, which are essential for practical applications.