Robust Solid Electrolyte Interphase Research Articles

Enhanced salt content and stabilized bilayer passivation interphase toward long-life and high-safety anode-free lithium battery

Anode-free lithium batteries (AFBs) offer optimal energy density, low cost, and simple manufacturing, making them desirable for next-generation high-energy-density batteries. However, the continuous consumption of electrolyte and Li metal through the undesirably constructed solid electrolyte interphase (SEI) significantly limits the cycling and thermal stability of AFBs. To address this challenge, dual-solvent localized high-LiFSI salt concentration electrolytes (DS-LHCEs) are designed by the addition of sulfolane (SF) due to its higher LiFSI solubility and highly consistent Li+-solvent binding energy with DME. High LiFSI content increases the salt-to-solvent concentration, decreases the amount of free solvent molecules, and restricts the side reaction between the free solvent and Li metal. As a result, a flat and dense Li metal with a robust LiF-rich SEI is deposited on Cu foil. Moreover, the introduction of trioxane (TO) constructs a high-strength outer organic SEI layer, which protects the weak grain boundaries of the inner inorganic SEI layer, further enhancing the stability of the Li metal anode. This results in assembled AFB pouch cells with a superior lifetime (206 cycles with 80 % capacity retention) and a much higher onset self-heating temperature (119 °C vs. 58 °C in the DME-based baseline electrolyte).

The Regulation of Solid Electrolyte Interphase on Composite Lithium Anodes in Solid-State Batteries.

Solid-state lithium metal batteries (SSLMBs) with solid polymer electrolyte (SPE) are highly promising for next-generation energy storage due to their enhanced safety and energy density. However, the stability of the solid electrolyte interphase (SEI) on the lithium metal/SPE interface is a major challenge, as continuous SEI degradation and regeneration during cycling lead to capacity fading. This article investigates the SEI formation on lithium anodes (l-SEI) and composite lithium anodes (c-SEI) in solid-state lithium metal batteries. The composite anodes form a uniform Li2S-rich inorganic SEI layer and a thinner organic SEI layer, effectively passivating the interface for enhanced cycling stability. Specifically, the full cells with c-SEI anodes sustain over 400 cycles at 0.5 C under a high areal capacity of 2.0 mAh cm-2. Moreover, the reversible high-loading solid-state pouch cells exhibit exceptional safety even after curling and cutting. These findings offer valuable insights into developing composite electrodes with robust SEI for solid-state polymer-based lithium metal batteries.

Li2MoO4 Tailored Anion‐enhanced Solvation Sheath Layer Promotes Solution‐phase Mediated Li‐O2 Batteries

AbstractThe high overpotential of Li‐O2 batteries (LOBs) is primarily triggered by sluggish charge transfer kinetics at the reaction interfaces. A typical LiBr redox mediator (RM) catalyst can effectively reduce the battery's overpotential. However, it is prone to shuttling and corroding the Li anode, leading to RM loss and reduced energy efficiency. To address these challenges, we introduced Li2MoO4 into the LiBr‐containing electrolyte to promote the solution‐phase mediated LOBs. This addition tailors the anion‐enhanced Li+ solvation sheath layer and forms a robust anion‐derived solid electrolyte interphases (SEI) on the Li anode. The robust SEI effectively mitigates the corrosion of soluble Br3−/Br2 and attacks by highly reactive oxygen species. Additionally, the dispersed and high‐density Li2MoO4 exhibits strong adsorption capabilities for O2/LiO2 and Br‐related species during the discharge/charge process, thereby promoting the growth and decomposition of Li2O2 in the solution phase and inhibiting the shuttle effect of Br‐related species in LOBs. Consequently, the LOBs demonstrate exceptional cycling stability (415 cycles) and high energy efficiency (86.2 %), paving the way for the sustainable development and practical application of these battery systems.

The Regulation of Solid Electrolyte Interphase on Composite Lithium Anodes in Solid‐State Batteries

AbstractSolid‐state lithium metal batteries (SSLMBs) with solid polymer electrolyte (SPE) are highly promising for next‐generation energy storage due to their enhanced safety and energy density. However, the stability of the solid electrolyte interphase (SEI) on the lithium metal/SPE interface is a major challenge, as continuous SEI degradation and regeneration during cycling lead to capacity fading. This article investigates the SEI formation on lithium anodes (l‐SEI) and composite lithium anodes (c‐SEI) in solid‐state lithium metal batteries. The composite anodes form a uniform Li2S‐rich inorganic SEI layer and a thinner organic SEI layer, effectively passivating the interface for enhanced cycling stability. Specifically, the full cells with c‐SEI anodes sustain over 400 cycles at 0.5 C under a high areal capacity of 2.0 mAh cm−2. Moreover, the reversible high‐loading solid‐state pouch cells exhibit exceptional safety even after curling and cutting. These findings offer valuable insights into developing composite electrodes with robust SEI for solid‐state polymer‐based lithium metal batteries.

Li2MoO4 Tailored Anion-enhanced Solvation Sheath Layer Promotes Solution-phase Mediated Li-O2 Batteries.

The high overpotential of Li-O2 batteries (LOBs) is primarily triggered by sluggish charge transfer kinetics at the reaction interfaces. A typical LiBr redox mediator (RM) catalyst can effectively reduce the battery's overpotential. However, it is prone to shuttling and corroding the Li anode, leading to RM loss and reduced energy efficiency. To address these challenges, we introduced Li2MoO4 into the LiBr-containing electrolyte to promote the solution-phase mediated LOBs. This addition tailors the anion-enhanced Li+ solvation sheath layer and forms a robust anion-derived solid electrolyte interphases (SEI) on the Li anode. The robust SEI effectively mitigates the corrosion of soluble Br3 -/Br2 and attacks by highly reactive oxygen species. Additionally, the dispersed and high-density Li2MoO4 exhibits strong adsorption capabilities for O2/LiO2 and Br-related species during the discharge/charge process, thereby promoting the growth and decomposition of Li2O2 in the solution phase and inhibiting the shuttle effect of Br-related species in LOBs. Consequently, the LOBs demonstrate exceptional cycling stability (415 cycles) and high energy efficiency (86.2 %), paving the way for the sustainable development and practical application of these battery systems.

Monofluorinated Phosphate with Unique P-F Bond for Nonflammable and Long-Life Lithium-Ion Batteries.

Lithium-ion batteries (LIBs) with conventional carbonate-based electrolytes suffer from safety concerns in large-scale applications. Phosphates feature high flame retardancy but are incompatible with graphite anode due to their inability to form a passivated solid electrolyte interphase (SEI). Herein, we report a monofluorinated co-solvent, diethyl fluoridophosphate (DEFP), featuring a unique P-F bond that allows a trade-off between safety and electrochemical performance in LIBs. The P-F bond in DEFP weakens ion-dipole interactions with Li+ ions, lowering the desolvation barrier, and simultaneously reduces the lowest unoccupied molecular orbital (LUMO) of DEFP, promoting the formation of a robust and inorganic-rich SEI. Additionally, DEFP exhibits improved thermal stability due to both robust SEI and the inherent flame-retardant properties of the P-F bond. Consequently, the optimized DEFP-based electrolyte exhibits improved cyclability and rate capacity in LiNi0.8Co0.1Mn0.1O2||graphite full cells compared with triethyl phosphate-based electrolytes and commercial carbonate electrolytes. Even at a low E/C ratio of 3.45 g Ah-1, the 1.16 Ah NCM811||Gr pouch cells achieve a high capacity retention of 94.2 % after 200 cycles. This work provides a promising approach to decouple phosphate safety and graphite compatibility, paving the way for safer and high-performance lithium-ion batteries.

Constructing a Functional Fast‐Ion Conductor Interface for Vertically Aligned Titanium Boride Nanosheets to Achieve Superior Sodium‐Ion Storage Performances

AbstractDesigning excellent anode materials to enhance the sluggish interfacial kinetics of Na+ is a key challenge in improving the electrochemical performance of sodium‐ion batteries (SIBs). Herein, an ultra‐thin fast‐ionic conductor NaB5C coating TiB2 nanoflowers with vertically aligned nanosheet arrays to form yolk–shell TiB2@NaB5C (TBNBC) nanospheres as an anode material for SIBs. The unique structure creates direct and short ion/electron transfer pathways and reserves enough space to prevent the uneven electrochemical reactions from TiB2 nanosheets aggregation and stacking, thus ensuring the long‐term cycling stability of SIBs. Additionally, the NaB5C coating with fast‐ionic conductor functional interphase provides rapid Na+ transport channels and effectively reduces the Na+ de‐solvation barrier, accelerating Na+ reaction kinetics. Furthermore, a homogeneous and robust solid electrolyte interphase (SEI) film including inorganic boron species and fluorine‐rich inner layer is constructed on the TBNBC electrode to delocalize stress and induce a uniform Na+ flux, further promoting fast Na+ interphase reaction kinetics. Consequently, the optimized composites achieve ultrastable cycling performances of 173 mAh g−1 over 5000 cycles at 10 A g−1. More importantly, they also exhibit an outstanding capacity of 182.2 mAh g−1 at −20 °C. This work offers opportunities for the energy storage use of transition metal borides under extreme conditions.

Monofluorinated Phosphate with Unique P−F Bond for Nonflammable and Long‐Life Lithium‐Ion Batteries

AbstractLithium‐ion batteries (LIBs) with conventional carbonate‐based electrolytes suffer from safety concerns in large‐scale applications. Phosphates feature high flame retardancy but are incompatible with graphite anode due to their inability to form a passivated solid electrolyte interphase (SEI). Herein, we report a monofluorinated co‐solvent, diethyl fluoridophosphate (DEFP), featuring a unique P−F bond that allows a trade‐off between safety and electrochemical performance in LIBs. The P−F bond in DEFP weakens ion‐dipole interactions with Li+ ions, lowering the desolvation barrier, and simultaneously reduces the lowest unoccupied molecular orbital (LUMO) of DEFP, promoting the formation of a robust and inorganic‐rich SEI. Additionally, DEFP exhibits improved thermal stability due to both robust SEI and the inherent flame‐retardant properties of the P−F bond. Consequently, the optimized DEFP‐based electrolyte exhibits improved cyclability and rate capacity in LiNi0.8Co0.1Mn0.1O2||graphite full cells compared with triethyl phosphate‐based electrolytes and commercial carbonate electrolytes. Even at a low E/C ratio of 3.45 g Ah−1, the 1.16 Ah NCM811||Gr pouch cells achieve a high capacity retention of 94.2 % after 200 cycles. This work provides a promising approach to decouple phosphate safety and graphite compatibility, paving the way for safer and high‐performance lithium‐ion batteries.

Machine Learning-Assisted Bayesian Optimization for the Discovery of Effective Additives for Dendrite Suppression in Lithium Metal Batteries.

In the pursuit of enhancing the performance and safety of lithium (Li)-metal batteries, the discovery of effective electrolyte additives to suppress Li dendrites has emerged as a paramount objective. In this study, we employ an inverse design strategy to identify potential additives for dendrite mitigation. Two key mechanisms, namely, the formation of robust solid electrolyte interphase layers and the leveling mechanism, serve as the foundation for our investigation. Our inverse design strategy is guided by molecular properties such as the lowest unoccupied molecular orbital energy and interaction energy upon Li surface adsorption. An active learning process utilizing Bayesian optimization (BO) was utilized to identify potential molecules with ideal properties. Through this screening process, we uncover a collection of 62 molecules with the potential to act as SEI-forming additives, along with 106 molecules for leveling additives, both surpassing the performance of established additives reported in the literature. This work highlights the potential of BO methods in computationally based inverse design of materials for many applications, and the discovered additives could potentially boost the commercialization of Li-metal batteries.

Tuning Reaction Kinetics of Fluorinated Molecules to Construct Robust Solid Electrolyte Interphases on SiOx Anode.

Introducing fluorinated electrolyte additives to construct LiF-rich solid-electrolyte interphase (SEI) on Si-based anodes is proven an effective strategy for coping with its massive volume changes during cycling. However, most current research on fluorine-containing additives focuses on their thermodynamics of decomposition, lacking studies on the correlation between the molecular structure of additives and their decomposition kinetics. Herein, two fluorinated ester additives, diethyl fluoromalonate (F1DEM) and diethyl 2,2-difluoromalonate (F2DEM) were designed and synthesized. Through combining a wealth of characterizations and simulations, it is revealed that despite the similar reduction thermodynamics, the favorable reduction kinetics of single-fluorinated F1DEM facilitate a LiF-rich layer during the early stage of SEI formation, contributing to the formation of a more robust SEI on SiOx anode compared to the difluorinated F2DEM. Consequently, the proposed additive achieves excellent cycling stability (84 % capacity retention after 1000 cycles) for 5 Ah 21700 cylindrical batteries under practical testing conditions. By unveiling the role of reaction kinetics, a long-overlooked aspect for the study of electrolyte additives, this work sheds light on how to construct a stable SEI on Si-based anodes.

Tuning Reaction Kinetics of Fluorinated Molecules to Construct Robust Solid Electrolyte Interphases on SiOx Anode

AbstractIntroducing fluorinated electrolyte additives to construct LiF‐rich solid‐electrolyte interphase (SEI) on Si‐based anodes is proven an effective strategy for coping with its massive volume changes during cycling. However, most current research on fluorine‐containing additives focuses on their thermodynamics of decomposition, lacking studies on the correlation between the molecular structure of additives and their decomposition kinetics. Herein, two fluorinated ester additives, diethyl fluoromalonate (F1DEM) and diethyl 2,2‐difluoromalonate (F2DEM) were designed and synthesized. Through combining a wealth of characterizations and simulations, it is revealed that despite the similar reduction thermodynamics, the favorable reduction kinetics of single‐fluorinated F1DEM facilitate a LiF‐rich layer during the early stage of SEI formation, contributing to the formation of a more robust SEI on SiOx anode compared to the difluorinated F2DEM. Consequently, the proposed additive achieves excellent cycling stability (84 % capacity retention after 1000 cycles) for 5 Ah 21700 cylindrical batteries under practical testing conditions. By unveiling the role of reaction kinetics, a long‐overlooked aspect for the study of electrolyte additives, this work sheds light on how to construct a stable SEI on Si‐based anodes.

LiF-enriched interphase promotes Li+ desolvation and transportation enabling high-performance carbon anode under wide-range temperature

Li-ion batteries (LIBs) have made inroads into the electric vehicle area with high energy densities, but they still suffer from slow kinetics of Li+ limited by the graphite anode especially at high current density and low-temperature conditions. Sluggish de-solvation of Li+ at the electrode surface and slow Li+ transfer in solid electrolyte interphase (SEI) are main determining factors that restrict the fast-charging and low-temperature performance of graphite-based LIBs. Here, we construct the sodium lignosulfonate layer with abundant polar functional groups on the lithium-montmorillonite surface, which can make it simple for electrons transfer to promote in-situ formation of LiF-based SEI with high ionic conductivity. The thin and robust LiF-based SEI promotes the de-solvation of Li salts and Li+ transfer as proved by the comprehensive electrochemical studies and density functional theory (DFT) calculations. Consequently, a combination of excellent stability and fast-charging ability for LIBs at room and low temperatures is achieved. The designed anode shows the remarkable capacity of 1500 mAh/g at 0.1 A/g, which was 3–4 times better than the commercial graphite. At the high current density of 5 A/g, it can still keep stable with the capacity retention of 70 % after 7000 cycles. Besides, an impressive 70 % of their room-temperature capacity is attained at −10 °C and 150 mAh/g is achieved under the extremely low temperature of −40 °C. This study establishes the effective strategy to construct the LiF-rich interface on the surface of anode to improve the Li+ kinetics and stability of the battery.

UV‐Triggered In Situ Formation of a Robust SEI on Black Phosphorus for Advanced Energy Storage: Boosting Efficiency and Safety via Rapid Charge Integration Plasticity

AbstractBlack phosphorus (BP) emerges as a highly promising electrode material for next generation of energy‐storage systems. Yet, its full potential is hindered by the instability of the solid‐electrolyte interphase (SEI) and the inflammability of its liquid systems. Here a pioneering UV‐induced in situ strategy is introduced for SEI construction, which leverages rapid electron supply to fracture sulfur‐dihalide bonds. This technique yields internal dihalide inorganic components and an external polymer segment, with any excess organic material being purged through pores. The (E)‐2‐chloro‐4‐((3′‐chloro‐4′‐hydroxyphenyl)diazinyl)phenyl acrylate (CA), with chlorine‐terminated groups, is initially in situ transformed into a flame‐retardant phenyl carboxylic acid (PCA), and then encapsulated within an ultrathin BP nanostructure, further nested in nitrogen (N), boron (B) co‐doped carbon (C) sheets that accommodate cobalt (Co) single atoms/nanoclusters (Co‐NBC). The Co‐NBC@BP@PCA construct demonstrates an impressive initial Coulombic efficiency (ICE) of 99.1% and maintains exceptional stabilities in terms of mechanical, chemical, and electrochemical performancecritical for prolonged cycle and calendar life. This research sheds light on the interplay between the rapid charge supply integrated in situ plasticity (RSIP) approach and the proactive establishment of an artificial SEI layer, offering profound insights into enhancing the durability and providing a solid foundation for advancements in energy storage technology.

High‐Performance Na‐Storage and Sodiation Behavior Identification in Cellulose‐Derived Hard Carbon by High‐Resolution Element Mapping Microscopy

Nowadays, hard carbon is one of the most promising anode materials for sodium‐ion batteries. However, the Na‐storage performance of hard carbon varies for different precursors and synthetic processes due to disparities in the dopant content, dimensions, and categories of defects, graphitic domains, which lead to controversial explanations for the energy storage mechanism. Herein, self‐freestanding membrane of cellulose‐derived carbon fibers is presented, delivering a reversible Na‐storage capacity of 330 mAh g−1 at 50 mA g−1 due to abundant ordered graphitic zones with enlarged interlayer spacings around 0.39 ± 0.03 nm. Benefiting from a robust solid electrolyte interphase layer rich in NaF nanocrystals, the membrane also holds a superior rate capability of 100 mAh g−1 at 2 A g−1 and long‐term cycling stability with capacity retention of 82.6% at 1.5 A g−1 for 4000 cycles. A clear sodiation behavior of Na+ intercalation into enlarged carbon graphitic layers at the slope step above 0.10 V and Na cluster evolution in the micropores at the plateau step around 0.01–0.10 V is disclosed by high‐resolution element mapping microscopy, different from the accepted mechanism of Na+ intercalation into graphitic layers at the plateau step.

Regulating Anode-Electrolyte Interphasial Reactions by Zwitterionic Binder Chemistry in Lithium-Ion Batteries with High-Nickel Layered Oxide Cathodes and Silicon-Graphite Anodes.

The practical application of silicon (Si)-based anodes faces challenges due to severe structural and interphasial degradations. These challenges are exacerbated in lithium-ion batteries (LIBs) employing Si-based anodes with high-nickel layered oxide cathodes, as significant transition-metal crossover catalyzes serious parasitic side reactions, leading to faster cell failure. While enhancing the mechanical properties of polymer binders has been acknowledged as an effective means of improving solid-electrolyte interphase (SEI) stability on Si-based anodes, an in-depth understanding of how the binder chemistry influences the SEI is lacking. Herein, a zwitterionic binder with an ability to manipulate the chemical composition and spatial distribution of the SEI layer is designed for Si-based anodes. It is evidenced that the electrically charged microenvironment created by the zwitterionic species alters the solvation environment on the Si-based anode, featuring rich anions and weakened Li+-solvent interactions. Such a binder-regulated solvation environment induces a thin, uniform, robust SEI on Si-based anodes, which is found to be the key to withstanding transition-metal deposition and minimizing their detrimental impact on catalyzing electrolyte decomposition and devitalizing bulk Si. As a result, albeit possessing comparable mechanical properties to those of commercial binders, the zwitterionic binder enables superior cycling performances in high-energy-density LIBs under demanding operating conditions.

Triple salts electrolyte for high cyclability and high capability in practical safe nickel-rich batteries

The pursuit of extended driving ranges of electric vehicles has spurred the use of nickel-rich layered cathodes, yet raised safety concerns. Existing ethylene carbonate-free electrolytes improve safety but compromise electrochemical performances due to the delicate balance between anode interphases. We introduce a novel electrolyte composed of propylene carbonate (PC) and triple lithium salts, which synergistically reinforces both cathode and anode interfaces. PC's low kinetic reactivity with LiNi0.8Mn0.1Co0.1O2 (NCM811) at the cathode minimizes heat generation and oxygen evolution. To stabilize the anode, bis(fluorosulfonyl)imide (FSI-) anions are integrated to construct an anion-driven interface, while difluoro(oxalato)borate (DFOB-) is added to lower PC's de-solvation energy and prevent co-intercalation. NCM811/Graphite pouch cells utilizing this electrolyte show enhanced safety, cyclability, and rate capability, surviving 60 min at 180℃ without incident. Post-mortem analysis reveals suppressed parasitic reactions and the formation of a robust solid electrolyte interphase (SEI). This research offers a critical framework for the design of electrolytes tailored for high-energy lithium-ion batteries.

Ferroelectric Dipoles Tailoring Solid-Electrolyte-Interphase Chemistry to Enable Reversible Lithium Metal Batteries.

Solid-electrolyte interphase (SEI) plays a decisive role in building reliable Li metal batteries. However, the scarcity of anions in Helmholtz layer (HL) caused by electrostatic repulsion usually leads to the inferior SEI derived from solvents, resulting in dendrites and 'dead' Li. Therefore, regulating the distribution of anions in electric double layer (EDL) and continuously introducing more anions into HL to tailor anions-derived SEI is crucial for achieving stable Li plating/stripping. Herein, by jointly utilizing the controlled defects of reduced graphene oxide (rGO) and the oriented dipoles of ferroelectric BaTiO3 (BTO), the rGO-BTO composite layer sustainedly brings more TFSI- and NO3 - into anion-defecient HL, promoting favorable decomposition of anions and guiding the generation of robust and fast-Li+-transport SEI containing more inorganics LiF and Li3N species. Thus, the resulting Li deposit shows smooth and dense morphologies without dendrites, leading to high average Coulombic efficiency. The Li//Cu@rGO-BTO (10 mAh cm-2 plated Li) cell exhibits an enhanced Li plating/stripping stability (2700 h) and a higher rate capability. The LiFePO4 full cell (N/P≈6.3) using rGO-BTO displays an enhanced capacity retention (82.0 % @ 430 cycles). This work provides a new insight on the construction of robust SEI by regulating the distribution of anions within EDL.

Robust bilayer solid electrolyte interphase for Zn electrode with high utilization and efficiency

Construction of a solid electrolyte interphase (SEI) of zinc (Zn) electrode is an effective strategy to stabilize Zn electrode/electrolyte interface. However, single-layer SEIs of Zn electrodes undergo rupture and consequent failure during repeated Zn plating/stripping. Here, we propose the construction of a robust bilayer SEI that simultaneously achieves homogeneous Zn2+ transport and durable mechanical stability for high Zn utilization rate (ZUR) and Coulombic efficiency (CE) of Zn electrode by adding 1,3-Dimethyl-2-imidazolidinone as a representative electrolyte additive. This bilayer SEI on Zn surface consists of a crystalline ZnCO3-rich outer layer and an amorphous ZnS-rich inner layer. The ordered outer layer improves the mechanical stability during cycling, and the amorphous inner layer homogenizes Zn2+ transport for homogeneous, dense Zn deposition. As a result, the bilayer SEI enables reversible Zn plating/stripping for 4800 cycles with an average CE of 99.95% (± 0.06%). Meanwhile, Zn | |Zn symmetric cells show durable lifetime for over 550 h with a high ZUR of 98% under an areal capacity of 28.4 mAh cm−2. Furthermore, the Zn full cells based on the bilayer SEI functionalized Zn negative electrodes coupled with different positive electrodes all exhibit stable cycling performance under high ZUR.

Modification of polypropylene separator with multifunctional layers to achieve highly stable sodium metal anode

Separator modification is an effective approach to suppress dendrite growth to realize high-energy sodium metal batteries (SMBs) in practical applications, however, its success is mainly subject to surface modification. Herein, a separator with multifunctional layers composed of N-doped mesoporous hollow carbon spheres (HCS) as the inner layer and sodium fluoride (NaF) as the outer layer on commercial polypropylene separator (PP) is proposed (PP@HCS-NaF) to achieve stable cycling in SMB. At the molecular level, the inner HCS layer with a high content of pyrrolic-N induces the uniform Na+ flux as a potential Na+ redistributor for homogenous deposition, whereas its hollow mesoporous structure offers nano-porous buffers and ion channels to regulate Na+ ion distribution and uniform deposition. The outer layer (NaF) constructs the NaF-enriched robust solid electrolyte interphase layer, significantly lowering the Na+ ions diffusion barrier. Benefiting from these merits, higher electrochemical performances are achieved with multifunctional double-layered PP@HCS-NaF separators compared with single-layered separators (i.e. PP@HCS or PP@NaF) in SMBs. The Na||Cu half-cell with PP@HCS-NaF offers stable cycling (280 cycles) with a high CE (99.6%), and Na||Na symmetric cells demonstrate extended lifespans for over 6000 h at 1 mA cm−2 with a progressively stable overpotential of 9 mV. Remarkably, in Na||NVP full-cells, the PP@HCS-NaF separator grants a stable capacity of ∼81 mA h g−1 after 3500 cycles at 1 C and an impressive rate capability performance (∼70 mA h g−1 at 15 C).

Regulating Anode‐Electrolyte Interphasial Reactions by Zwitterionic Binder Chemistry in Lithium‐Ion Batteries with High‐Nickel Layered Oxide Cathodes and Silicon‐Graphite Anodes

AbstractThe practical application of silicon (Si)‐based anodes faces challenges due to severe structural and interphasial degradations. These challenges are exacerbated in lithium‐ion batteries (LIBs) employing Si‐based anodes with high‐nickel layered oxide cathodes, as significant transition‐metal crossover catalyzes serious parasitic side reactions, leading to faster cell failure. While enhancing the mechanical properties of polymer binders has been acknowledged as an effective means of improving solid‐electrolyte interphase (SEI) stability on Si‐based anodes, an in‐depth understanding of how the binder chemistry influences the SEI is lacking. Herein, a zwitterionic binder with an ability to manipulate the chemical composition and spatial distribution of the SEI layer is designed for Si‐based anodes. It is evidenced that the electrically charged microenvironment created by the zwitterionic species alters the solvation environment on the Si‐based anode, featuring rich anions and weakened Li+‐solvent interactions. Such a binder‐regulated solvation environment induces a thin, uniform, robust SEI on Si‐based anodes, which is found to be the key to withstanding transition‐metal deposition and minimizing their detrimental impact on catalyzing electrolyte decomposition and devitalizing bulk Si. As a result, albeit possessing comparable mechanical properties to those of commercial binders, the zwitterionic binder enables superior cycling performances in high‐energy‐density LIBs under demanding operating conditions.