Lithium Metal Electrode with Increased Air Stability and Robust Solid Electrolyte Interphase Realized by Silane Coupling Agent Modification

Air Corrosion of Layered Cathode Materials for Sodium-Ion Batteries: Cation Mixing and a Practical Suppression Strategy

Layered oxide cathodes of sodium-ion batteries (SIBs) are considered promising candidates due to their fascinating high capacity, good cyclability, and environmental friendliness. However, the air sensitivity of layered SIB cathodes causes high electrode manufacturing costs and performance deterioration, hampering their practical application. Herein, a commercial O3-type layered Na(Ni1/3Fe1/3Mn1/3)O2 (NNFM) material is adopted to investigate the air corrosive problem and the suppression strategy. We reveal that once the layered material comes in contact with ambient air, cations migrate from transition metal (TM) layers to sodium layers at the near surface, although Na+ and TM ions show quite different ion radii. Experimental results and theoretical calculations show that more Ni/Na disorder occurs in the air-exposed O3-NNFM materials, owing to a lower Ni migration energy barrier. The cation mixing results in detrimental structural distortion, along with the formation of residual alkali species on the surface, leading to high impedance for Na+ diffusion during charge/discharge. To tackle this problem, an ultrathin and uniform hydrophobic molecular layer of perfluorodecyl trimethoxysilane is assembled on the O3-NNFM surface, which significantly suppresses unfavorable chemistry and structure degradation during air storage. The in-depth understanding of the structural degradation mechanism and suppression strategy presented in this work can facilitate high-energy cathode manufacturing from the perspective of future practical implementation and commercialization.

Engineering a Dynamic Solvent-Phobic Liquid Electrolyte Interphase for Long-Life Lithium Metal Batteries

The heterogeneity, species diversity, and poor mechanical stability of solid electrolyte interphases (SEIs) in conventional carbonate electrolytes result in the irreversible exhaustion of lithium (Li) and electrolytes during cycling, hindering the practical applications of Li metal batteries (LMBs). Herein, this work proposes a solvent-phobic dynamic liquid electrolyte interphase (DLEI) on a Li metal (Li-PFbTHF (perfluoro-butyltetrahydrofuran)) surface that selectively transports salt and induces salt-derived SEI formation. The solvent-phobic DLEI with C-F-rich groups dramatically reduces the side reactions between Li, carbonate solvents, and humid air, forming a LiF/Li3PO4-rich SEI. In situ electrochemical impedance spectroscopy and Ab-initio molecular dynamics demonstrate that DLEI effectively stabilizes the interface between Li metal and the carbonate electrolyte. Specifically, the LiFePO4||Li-PFbTHF cells deliver 80.4% capacity retention after 1000 cycles at 1.0 C, excellent rate capacity (108.2 mAh g-1 at 5.0 C), and 90.2% capacity retention after 550 cycles at 1.0 C in full-cells (negative/positive (N/P) ratio of 8) with high LiFePO4 loadings (15.6 mg cm-2) in carbonate electrolyte. In addition, the 0.55 Ah pouch cell of 252.0 Wh kg-1 delivers stable cycling. Hence, this study provides an effective strategy for controlling salt-derived SEI to improve the cycling performances of carbonate-based LMBs.

Preparation of highly elastic superhydrophobic CNF/Fe3O4 based materials modified in aqueous phase for oil-water separation

Magnetic superhydrophobic materials have broad application prospect in oil-water separation. In this study, a magnetic and superhydrophobic aerogel with lamellar structure was successfully prepared using cellulose nanofibrils (CNF) as the skeleton, Fe3O4 as the magnetic ion, 1H, 1H, 2H, 2H trialkylfluorooctane triethoxysilane (FS) and 3-(2-aminoethyl amino)-propyl trimethoxysilane (AS) as the combined modifier. The prepared aerogel shows lower density (38.63 mg/cm3), excellent magnetic (15.13 emu/g), high elasticity and good oil sorption properties (21 g/g). In addition, FS/AS also exhibits excellent mechanical properties and superhydrophobic ability (water contact angle (WCA) of 151.9 ± 1.4°), as it provides sufficient toughness and low surface energy for the layer-branch structure. It should be noted that the entire preparation process is carried out in the aqueous phase, without the use of any organic solvents, providing a green oil-water separation strategy.

PDOL-Based Solid Electrolyte Toward Practical Application: Opportunities and Challenges

Polymer solid-state lithium batteries (SSLB) are regarded as a promising energy storage technology to meet growing demand due to their high energy density and safety. Ion conductivity, interface stability and battery assembly process are still the main challenges to hurdle the commercialization of SSLB. As the main component of SSLB, poly(1,3-dioxolane) (PDOL)-based solid polymer electrolytes polymerized in-situ are becoming a promising candidate solid electrolyte, for their high ion conductivity at room temperature, good battery electrochemical performances, and simple assembly process. This review analyzes opportunities and challenges of PDOL electrolytes toward practical application for polymer SSLB. The focuses include exploring the polymerization mechanism of DOL, the performance of PDOL composite electrolytes, and the application of PDOL. Furthermore, we provide a perspective on future research directions that need to be emphasized for commercialization of PDOL-based electrolytes in SSLB. The exploration of these schemes facilitates a comprehensive and profound understanding of PDOL-based polymer electrolyte and provides new research ideas to boost them toward practical application in solid-state batteries.

Recent Progress on the Air-Stable Battery Materials for Solid-State Lithium Metal Batteries

Solid-state lithium metal batteries (SSLMBs) offer numerous advantages in terms of safety and theoretical specific energy density. However, their main components namely lithium metal anode, solid-state electrolyte, and cathode, show chemical instability when exposed to humid air, which results in low capacities and poor cycling stability. Recent studies have shown that bioinspired hydrophobic materials with low specific surface energies can protect battery components from corrosion caused by humid air. Air-stable inorganic materials that densely cover the surface of battery components can also provide protection, which improves the storage stability of the battery components, broadens their processing conditions, and ultimately decreases their processing costs while enhancing their safety. In this review, the mechanism behind the surface structural degradation of battery components and the resulting consequences are discussed. Subsequently, recent strategies are reviewed to address this issue from the perspectives of lithium metal anodes, solid-state electrolytes, and cathodes. Finally, a brief conclusion is provided on the current strategies and fabrication suggestions for future safe air-stable SSLMBs.

Modulation of Si-O Structure in Uniformly Ultrasmall Silicon Oxycarbide for Superior Lifespan of Lithium Metal Anodes

Utilizing nanoseeds guiding homogeneous deposition of lithium is an effective strategy to inhibit disorderly growth of lithium, where silicon oxide has been attracting attention as a transform seed. However, the research on silicon-oxide-based seeds has concentrated more on utilizing their lithiophilicity but less on their Si-O structures, which could result in different failure mechanisms. In this study, various Si-O structures of silicon oxycarbide carbon nanofibers are prepared by adjusting the content of octa(aminopropylsilsesquioxane). According to XANES and experimental observations, the C-rich SiOC has an active Si-O-C structure but generates a larger volume variation during lithiation, while in the O-rich phase, the silica-oxygen tetrahedral structure can contribute to alleviate the volume expansion but has poor electrochemical activity. SiOC, which is dominated by SiO3C, has a suitable Si-O and silica-oxygen tetrahedral-structure distribution, which balances the electrochemical activity and volume expansion. This allows the host to demonstrate an excellent lifespan over 3740 h with a tiny voltage hysteresis (22 mV) at 2 mA cm-2, and it retains a favorable capacity of 97 mA h g-1 after 630 cycles with a high Coulombic efficiency of 99.7% in full cells. This study experiences the influence of various Si-O structures on lithium metal anodes.

Interfacial Manipulation via In Situ Constructed Fast Ion Transport Channels toward an Ultrahigh Rate and Practical Li Metal Anode

The successful substitution of Li metal for the conventional intercalation anode can promote a significant increase in the cell energy density. However, the practical application of the Li metal anode has long been fettered by the unstable solid electrolyte interface (SEI) layer on the Li metal surface and notorious dendritic Li growth. Herein, a stabilized SEI layer with in situ constructed fast ion transport channels has successfully been achieved by a robust In2S3-cemented poly(vinyl alcohol) coating. The modified Li metal demonstrates significantly enhanced Coulombic efficiency, high rate performance (10 mA cm-2), and ultralong life cycling stability (∼4900 cycles). The Li|LiCoO2 (LCO) cell presents an ultralong-term stable operation over 500 cycles at 1 C with an extremely low capacity decay rate (∼0.018% per cycle). And the Li|LCO full cell with the ultrahigh loading cathode (∼25 mg cm-2) and ultrathin Li foil (∼40 μm) also reveals a prolonged cycling performance under the low negative-to-positive capacity ratio of 2.2. Furthermore, the Li|LCO pouch cell with a commercial cathode and ultrathin Li foil still manifests excellent cycling performance even under the harsh conditions of limited Li metal and lean electrolyte. This work provides a cost-effective and scalable strategy toward high performance practical Li metal batteries.

Low-temperature anode-free potassium metal batteries

In contrast to conventional batteries, anode-free configurations can extend cell-level energy densities closer to the theoretical limit. However, realizing alkali metal plating/stripping on a bare current collector with high reversibility is challenging, especially at low temperature, as an unstable solid-electrolyte interphase and uncontrolled dendrite growth occur more easily. Here, a low-temperature anode-free potassium (K) metal non-aqueous battery is reported. By introducing Si-O-based additives, namely polydimethylsiloxane, in a weak-solvation low-concentration electrolyte of 0.4 M potassium hexafluorophosphate in 1,2-dimethoxyethane, the in situ formed potassiophilic interface enables uniform K deposition, and offers K||Cu cells with an average K plating/stripping Coulombic efficiency of 99.80% at -40 °C. Consequently, anode-free Cu||prepotassiated 3,4,9,10-perylene-tetracarboxylicacid-dianhydride full batteries achieve stable cycling with a high specific energy of 152 Wh kg-1 based on the total mass of the negative and positive electrodes at 0.2 C (26 mA g-1) charge/discharge and -40 °C.

Reactivation of an air-passivated lithium metal anode through halogen regulation

A comprehensive study was conducted to investigate the failure mechanism of the lithium metal anode (LMA) in air. Simultaneously, an effective reactivation strategy was developed using halogen regulation. Specifically, iodine treatment converts the passivation layer of the exposed Li into LiI with fast Li+ transport ability, thereby improving the electrochemical performance.

Surface Modification of TiO2 by Hyper-Cross-Linked Polymers for Efficient Visible-Light-Driven Photocatalytic NO Oxidation

Solar-driven photocatalysis offers an environmentally friendly and sustainable approach for the removal of air pollutants such as nitric oxides without chemical addition. However, the low specific surface area and adsorption capacity of common photocatalysts restrict the surface reactions with NO at the ppb-level. In this study, imidazolium-based hyper-cross-linked polymer (IHP) was introduced to modify the surface of TiO₂ to construct a porous TiO₂/IHP composite photocatalyst. The as-prepared composite with hierarchical porous structure achieves a larger specific surface area as 309 m²/g than that of TiO₂ (119 m²/g). Meanwhile, the wide light absorption range of the polymer has brought about the strong visible-light absorption of the TiO₂/IHP composite. In consequence, the composite photocatalyst exhibits excellent performance toward NO oxidation at a low concentration of 600 ppb under visible-light irradiation, reaching a removal efficiency of 51.7%, while the generation of the toxic NO₂ intermediate was suppressed to less than 1 ppb. The enhanced NO adsorption and the suppressed NO₂ generation on the TiO₂/IHP surface were confirmed by in situ monitoring technology. This work demonstrates that the construction of a porous structure is an effective approach for efficient NO adsorption and photocatalytic oxidation.

Chemically bonding inorganic fillers with polymer to achieve ultra-stable solid-state sodium batteries

Inorganic/organic composite solid electrolytes (CSEs) have attracted ever-increasing attentions due to their outstanding mechanical stability and processibility. However, the inferior inorganic/organic interface compatibility limits their ionic conductivity and electrochemical stability, which hinders their application in solid-state batteries. Herein, we report a homogeneously distributed inorganic fillers in polymer by in-situ anchoring SiO₂ particles in polyethylene oxide (PEO) matrix (I-PEO-SiO₂). Compared with ex-situ CSEs (E-PEO-SiO₂), SiO₂ particles and PEO chains in I-PEO-SiO₂ CSEs are closely welded by strong chemical bonds, thus addressing the issue of interfacial compatibility and realizing excellent dendrite-suppression ability. In addition, the Lewis acid-base interactions between SiO₂ and salts facilitate the dissociation of sodium salts and increase the concentration of free Na⁺. Consequently, the I-PEO-SiO₂ electrolyte demonstrates an improved Na⁺ conductivity (2.3 × 10^-4 S cm^-1 at 60 °C) and Na⁺ transference number (0.46). The as constructed Na₃V₂(PO₄)₃ ‖ I-PEO-SiO₂ ‖ Na full-cell demonstrates a high specific capacity of 90.5 mAh g^-1 at 3C and an ultra-long cycling stability (>4000 cycles at 1C), outperforming the state-of-the-art literatures. This work provides an effective way to solve the issue of interfacial compatibility, which can enlighten other CSEs to overcome their interior compatibility.

Tuning the Covalent Coupling Degree between the Cathode and Electrolyte for Optimized Interfacial Resistance in Solid-State Lithium Batteries

The development of promising solid-state lithium batteries has been a challenging task mainly due to the poor interfacial contact and high interfacial resistance at the electrode/solid-state electrolyte (SSE) interface. Herein, we propose a strategy for introducing a class of covalent interactions with varying covalent coupling degrees at the cathode/SSE interface. This method significantly reduces interfacial impedances by strengthening the interactions between the cathode and SSE. By adjusting the covalent coupling degree from low to high, an optimal interfacial impedance of 33 Ω cm^-2 was achieved, which is even lower than the interfacial impedance using liquid electrolytes (39 Ω cm^-2). This work offers a fresh perspective on solving the interfacial contact problem in solid-state lithium batteries.

A Self-Reconfigured, Dual-Layered Artificial Interphase Toward High-Current-Density Quasi-Solid-State Lithium Metal Batteries

The uncontrollable dendrite growth and unstable solid electrolyte interphase have long plagued the practical application of Li metal batteries. Herein, a dual-layered artificial interphase LiF/LiBO-Ag is demonstrated that is simultaneously reconfigured via an electrochemical process to stabilize the lithium anode. This dual-layered interphase consists of a heterogeneous LiF/LiBO glassy top layer with ultrafast Li-ion conductivity and lithiophilic Li-Ag alloy bottom layer, which synergistically regulates the dendrite-free Li deposition, even at high current densities. As a result, Li||Li symmetric cells with LiF/LiBO-Ag interphase achieve an ultralong lifespan (4500 h) at an ultrahigh current density and area capacity (20 mA cm^-2 , 20 mAh cm^-2 ). LiF/LiBO-Ag@Li anodes are successfully applied in quasi-solid-state batteries, showing excellent cycling performances in symmetric cells (8 mA cm^-2 , 8 mAh cm^-2 , 5000 h) and full cells. Furthermore, a practical quasi-solid-state pouch cell coupling with a high-nickel cathode exhibits stable cycling with a capacity retention of over 91% after 60 cycles at 0.5 C, which is comparable or even better than that in liquid-state pouch cells. Additionally, a high-energy-density quasi-solid-state pouch cell (10.75 Ah, 448.7 Wh kg^-1 ) is successfully accomplished. This well-orchestrated interphase design provides new guidance in engineering highly stable interphase toward practical high-energy-density lithium metal batteries.

Reversible Magnesium Metal Cycling in Additive-Free Simple Salt Electrolytes Enabled by Spontaneous Chemical Activation

Rechargeable magnesium (Mg) batteries can offer higher volumetric energy densities and be safer than their conventional counterparts, lithium-ion batteries. However, their practical implementation is impeded due to the passivation of the Mg metal anode or the severe corrosion of the cell parts in conventional electrolyte systems. Here, we present a chemical activation strategy to facilitate the Mg deposition/stripping process in additive-free simple salt electrolytes. By exploiting the simple immersion-triggered spontaneous chemical reaction between reactive organic halides and Mg metal, the activated Mg anode exhibited an overpotential below 0.2 V and a Coulombic efficiency as high as 99.5% in a Mg(TFSI)₂ electrolyte. Comprehensive analyses reveal simultaneous evolution of morphology and interphasial chemistry during the activation process, through which stable Mg cycling over 990 cycles was attained. Our activation strategy enabled the efficient cycling of Mg full-cell candidates using commercially available electrolytes, thereby offering possibilities of building practical Mg batteries.

Probing the Mechanically Stable Solid Electrolyte Interphase and the Implications in Design Strategies

The inevitable volume expansion of secondary battery anodes during cycling imposes forces on the solid electrolyte interphase (SEI). The battery performance is closely related to the capability of SEI to maintain intact under the cyclic loading conditions, which basically boils down to the mechanical properties of SEI. The volatile and complex nature of SEI as well as its nanoscale thickness and environmental sensitivity make the interpretation of its mechanical behavior many roadblocks. Widely varied approaches are adopted to investigate the mechanical properties of SEI, and diverse opinions are generated. The lack of consensus at both technical and theoretical levels has hindered the development of effective design strategies to maximize the mechanical stability of SEIs. Here, the essential and desirable mechanical properties of SEI, the available mechanical characterization methods, and important issues meriting attention for higher test accuracy are outlined. Previous attempts to optimize battery performance by tuning SEI mechanical properties are also scrutinized, inconsistencies in these efforts are elucidated, and the underlying causes are explored. Finally, a set of research protocols is proposed to accelerate the achievement of superior battery cycling performance by improving the mechanical stability of SEI.

Self-Assembly Monolayer Inspired Stable Artificial Solid Electrolyte Interphase Design for Next-Generation Lithium Metal Batteries

Lithium metal is widely regarded as the "ultimate" anode for energy-dense Li batteries, but its high reactivity and delicate interface make it prone to dendrite formation, limiting its practical use. Inspired by self-assembled monolayers on metal surfaces, we propose a facile yet effective strategy to stabilize Li metal anodes by creating an artificial solid electrolyte interphase (SEI). Our method involves dip-coating Li metal in MPDMS to create an SEI layer that is rich in inorganic components, allowing uniform Li plating/stripping under a low overpotential over 500 cycles in carbonate electrolytes. In comparison, pristine Li metal shows a rapid increase in overpotential after merely 300 cycles, leading to failure soon after. Molecular dynamics simulations demonstrate that this uniform artificial SEI suppresses Li dendrite formation. We further demonstrated its enhanced stability pairing with LiFePO₄ and LiNi_1-x-yCo_xMn_yO₂ cathodes, highlighting the proposed strategy as a promising solution for practical Li metal batteries.

Recyclable TPA-Modified MIL-88-Supported Ionic Pt as a Highly Efficient Catalyst for Alkene Hydrosilylation

The hydrosilylation reaction driven by a homogeneous catalyst has been widely used in the industrial synthesis of functionalized silicone compounds. However, the homogeneous catalyst for hydrosilylation has the shortcomings of nonrecyclability, undesirable side reactions, and high cost. In this work, a highly efficient heterogeneous catalyst was prepared by loading Pt ions on MIL-88 modified with trimethoxy[3-(phenylamino)propyl]silane. In comparison with previous research studies, the resulting catalyst can exhibit high catalytic activity and excellent stability during the hydrosilylation reaction, which was attributed to the presence of a pyrrolic nitrogen structure between TPA-MIL-88 and the Pt ion. Besides them, 1.2%Pt/TPA-MIL-88 showed the highest catalytic activity and can be reused five times without significant deactivation. Importantly, 1.2%Pt/TPA-MIL-88 also achieved satisfactory results when it was used to catalyze the hydrosilylation reaction for other olefins, implying great potential for application in the silicone industry.

Lithiophilic and Anticorrosive Cu Current Collector via Dual-Bonded Porous Polymer Coating for Stable Lithium-Metal Batteries

Li metal is the ultimate anode material for next-generation high-energy-density rechargeable batteries. However, the uncontrollable growth of Li dendrites and low Coulombic efficiency (CE) prevent it from practical applications in Li metal batteries (LMBs). Here, a facile and low-cost strategy is developed to decorate a Cu current collector with a self-assembled γ-aminopropyltrimethoxysilane (γ-APS) film. The thin polymer film with nanopores promotes the formation of cobblestone-like Li deposition and suppresses Li-dendrite formation due to its low surface energy. The protecting layer not only increases the lithiophilicity of the Cu current collector but also alleviates the ambient corrosion and galvanic corrosion in practical use. Owing to these advantages, the half cell using γ-APS-Cu collectors exhibits a high average CE value of 99.2% for 100 cycles. The symmetric cell of γ-APS-Cu@Li shows an improved lifespan of 1400 h with a small voltage hysteresis of 12 mV at 0.5 mA cm-2. The full cell assembled with LiFePO4 (LFP) cathodes and γ-APS-Cu@Li anodes delivers a high capacity of 136 mAh g-1 after 600 cycles at 0.5C.

Roles of Trimethyl Borate in Constructing an Interphase on Li Anode: Angel or Demon?

Although coupling a lithium metal anode with a Ni-rich layer cathode is a promising approach for high-energy lithium metal batteries, both electrodes are plagued by their intrinsic unstable interfaces which trigger electrolyte decomposition, lithium dendritic growth, and transition metal dissolution during cycling. Making use of electrolyte additives is one of the most effective solutions to address this issue. In this paper, we explore the roles of trimethyl borate (TMB)─a common film-forming additive to protect high-nickel-ratio ternary cathodes─in suppressing lithium dendrite growth. It is found that, on the one hand, the borate-containing solid electrolyte interphase (SEI) derived from the decomposition of TMB facilitates Li⁺ transport, homogenizing the deposition of Li ions. On the other hand, TMB as an anion receptor provokes LiPF₆ decomposition, prompting the formation of SEI with superfluous LiF. As a result, it is imperative to raise awareness of this double-edge additive when using it to be immune to lithium dendrite and cathodic degradation.

Air-Stable Protective Layers for Lithium Anode Achieving Safe Lithium Metal Batteries

With markedly expansive demand in energy storage devices, rechargeable batteries will concentrate on achieving the high energy density and adequate security, especially under harsh operating conditions. Considering the high capacity (3860 mA h g^-1 ) and low electrochemical potential (-3.04 V vs the standard hydrogen electrode), lithium metal is identified as one of the most promising anode materials, which has sparked a research boom. However, the intrinsically high reactivity triggers a repeating fracture/reconstruction process of the solid electrolyte interphase, side reactions with electrolyte and lithium dendrites, detrimental to the electrochemical performance of lithium metal batteries (LMBs). Even worse, when exposed to air, lithium metal will suffer severe atmospheric corrosion, especially the reaction with moisture, leading to grievous safety hazards. To settle these troubles, constructing air-stable protective layers (ASPLs) is an effective solution. In this review, besides the necessity of ASPLs is highlighted, the modified design criteria, focusing on enhancing chemical/mechanical stability and controlling ion flux, are proposed. Correspondingly, current research progress is comprehensively summarized and discussed. Finally, the perspectives of developing applicable lithium metal anodes (LMAs) are put forward. This review guides the direction for the practical use of LMAs, further pushing the evolution of safe and stable LMBs.

Ultrathin Solid Polymer Electrolyte Design for High-Performance Li Metal Batteries: A Perspective of Synthetic Chemistry

Li metal batteries (LMBs) have attracted widespread attention in recent years because of their high energy densities. But traditional LMBs using liquid electrolyte have potential safety hazards, such as: leakage and flammability. Replacing liquid electrolyte with solid polymer electrolyte (SPE) can not only significantly improve the safety, but also improve the energy density of LMBs. However, till now, there is only limited success in improving the various physical and chemical properties of SPE, especially in thickness, posing great obstacles to further promoting its fundamental and applied studies. In this review, the authors mainly focus on evaluating the merits of ultrathin SPE and summarizing its existing challenges as well as fundamental requirements for designing and manufacturing advanced ultrathin SPE in the future. Meanwhile, the authors outline existing cases related to this field as much as possible and summarize them from the perspective of synthetic chemistry, hoping to provide a comprehensive understanding and serve as a strategic guidance for designing and fabricating high-performance ultrathin SPE. Challenges and opportunities regarding this burgeoning field are also critically evaluated at the end of this review.

Facile Electroless Plating Method to Fabricate a Nickel-Phosphorus-Modified Copper Current Collector for a Lean Lithium-Metal Anode

The compatibility of current collectors with reactive Li is key to inducing stable Li cycling and prolonged cycle life of lean Li-metal batteries. Herein, a thin and uniform layer of Ni-P complex was built on the surface of a Cu current collector (NiP@Cu) via an efficient, controllable, and cost-effective electroless plating method. The thickness, morphology, composition, and roughness of the Ni-P deposition were successfully regulated. Lithiophilicity of the current collector was greatly improved by Ni-P deposition, which effectively reduced the Li nucleation overpotential and suppressed the Li dendrite growth. In addition, NiP@Cu promoted an inorganic LiF/Li₃P-rich solid electrolyte interphase to facilitate interfacial charge transfer and eliminate excessive side reactions between Li and the electrolyte. As a result, the Coulombic efficiency of half-cells remained above 98.5% for more than 400 cycles at 0.5 mA/cm² and 98.2% for more than 250 cycles at 1 mA/cm². Full cells with NiP@Cu also showed superior performance compared to those with bare Cu. This work proposes a promising surface modification method to develop a stable, dendrite-free, and cost-effective anode current collector for high-energy-density lean Li-metal batteries.

Non-Flammable Ester Electrolyte with Boosted Stability Against Li for High-Performance Li Metal Batteries

In traditional non-flammable electrolytes a trade-off always exists between non-flammability and battery performance. Previous research focused on reducing free solvents and forming anion-derived solid-electrolyte interphase. However, the contribution of solvated anions in boosting the stability of electrolyte has been overlooked. Here, we resolve this via introducing anions into Li⁺ solvation sheaths using anions with similar Gutmann donor number (DN) to that of solvents. Taking trimethyl phosphate fire-retardant (DN=23.0 kcal mol^-1 ) and NO₃ ^- (DN=22.2 kcal mol^-1 ) as an example, NO₃ ^- is readily involved in the Li⁺ solvation sheath and reduces the polarity of solvent. This results in boosted stability of electrolyte against Li. The developed non-flammable electrolyte has low viscosity, high ionic conductivity and is low cost. The reversibility of Li-Cu cell was improved to 99.49 % and the lifespan of practical LMBs was extended by >100 %.

Recent progresses and challenges in aqueous lithium–air batteries relating to the solid electrolyte separator: A mini-review

The lithium–air (Li–air) battery utilizes infinite oxygen in the air to store or release energy through a semi-open cathode structure and bears an ultra-high theoretical energy density of more than 1,000 Wh/kg. Therefore, it has been denoted as the candidate for next-generation energy storage in versatile fields such as electric vehicles, telecommunications, and special power supply. Among all types of Li–air batteries, an aqueous Li–air battery bears the advantages of a high theoretical energy density of more than 1,700 Wh/kg and does not have the critical pure oxygen atmosphere issues in a non-aqueous lithium–air battery system, which is more promising for the actual application. To date, great achievements have been made in materials’ design and cell configurations, but critical challenges still remain in the field of the solid electrolyte separator, its related lithium stripping/plating at the lithium anode, and catholyte design. In this mini-review, we summarized recent progress related to the solid electrolyte in aqueous Li–air batteries focusing on both material and battery device development. Moreover, we proposed a discussion and unique outlook on improving solid electrolyte compatibility and battery performance, thus designing an aqueous Li–air battery with higher energy density and better cycle performance in the future.

Electrolyte Engineering Enables High Performance Zinc-Ion Batteries

Zinc-ion batteries (ZIBs) feature high safety, low cost, environmental-friendliness, and promising electrochemical performance, and are therefore regarded as a potential technology to be applied in large-scale energy storage devices. However, ZIBs still face some critical challenges and bottlenecks. The electrolyte is an essential component of batteries and its properties affect the mass transport, energy storage mechanisms, reaction kinetics, and side reactions of ZIBs. The adjustment of electrolyte formulas usually has direct and obvious impacts on the overall output and performance. In this review, advanced electrolyte strategies are overviewed for optimizing the compatibility between cathode materials and electrolytes, inhibiting anode corrosion and dendrite growth, extending electrochemical stability windows, enabling wearable applications, and enhancing temperature tolerance. The underlying scientific mechanisms, electrolyte design principles, and recent progress are presented to provide a better understanding and inspiration to readers. In addition, a comprehensive perspective about electrolyte design and engineering for ZIBs is included.

Limited Lithium Loading Promises Improved Lithium-Metal Anodes in Interface-Modified 3D Matrixes

Confining Li metal in a three-dimensional (3D) matrix has been proven effective in improving the Li-metal anodes; however, in most studies, the loading of Li in the 3D matrix is far excessive, resulting in a dense bulk Li-metal anode with a low Li-utilization rate, forfeiting the effect of the 3D matrix. Here, we show that limiting the loading of Li metal within an interface-modified 3D carbon matrix not only increases the Li-utilization rate but also improves the electrochemical performance of the Li-metal anode. We use lithiophilic Fe₂O₃ granules anchored on a 3D carbon fiber scaffold to guide molten Li dispersion onto the fibers with controlled Li loading. Limiting Li loading maximizes the interface lithiophilic effect of the Fe₂O₃ granules while preserving sufficient space for electrolyte infusion, collectively ensuring uniform Li deposition and fast Li⁺ transport kinetics. The Li anode with limited Li dosage achieves remarkably improved Li-anode performances, including long lifespan, low voltage polarization, and low electrochemical resistance in both the symmetric cells and full cells. The improved electrochemical performance of the limited Li anode substantiates the importance to reduce Li loading from a fresh perspective and provides an avenue for building practical Li-metal batteries.

Functional Polymer Materials for Advanced Lithium Metal Batteries: A Review and Perspective

Lithium metal batteries (LMBs) are promising next-generation battery technologies with high energy densities. However, lithium dendrite growth during charge/discharge results in severe safety issues and poor cycling performance, which hinders their wide applications. The rational design and application of functional polymer materials in LMBs are of crucial importance to boost their electrochemical performances, especially the cycling stability. In this review, recent advances of advanced polymer materials are examined for boosting the stability and cycle life of LMBs as different components including artificial solid electrolyte interface (SEI) and functional interlayers between the separator and lithium metal anode. Thereafter, the research progress in the design of advanced polymer electrolytes will be analyzed for LMBs. At last, the major challenges and key perspectives will be discussed for the future development of functional polymers in LMBs.

Tailoring the Solvation Sheath of Cations by Constructing Electrode Front-Faces for Rechargeable Batteries

Solvent molecules within the solvation sheath of cations (e.g., Li⁺ , Na⁺ , Zn²⁺ ) are easily to be dehydrogenated especially when coupled with high-voltage cathodes, and lead to detrimental electrolytes decompositions which finally accelerate capacity decays of rechargeable batteries. Tremendous efforts are devoted to tackle with this long-lasting issue. Among them, salt-concentrated strategies are frequently employed to tailor the solvation sheath of cations and improve the stabilities of electrolytes. However, the cost challenges caused by adding extra dose of expensive salts, additives/cosolvents in preparing highly concentrated electrolytes, hinder their further utilizations to some extent. Introducing porous materials-based electrode front-faces on the surface of electrodes even within dilute electrolytes can transfer the high-energy-state desolvated solvents from the reactive electrodes to the nonconductive porous material surfaces, thus eliminate the contact chances between desolvated solvents and electrode materials, and greatly reduce solvents-related decomposition issues. Herein, recent advances in using electrode front-faces to tailor the solvation sheath of metal ions for rechargeable batteries are discussed. Finally, perspectives to the future challenges and opportunities of constructing electrode front-faces to tailor the solvation sheath of cations by constructing electrode front-face for rechargeable batteries are provided.

Enhanced Cyclability of Lithium Metal Anodes Enabled by Anti-aggregation of Lithiophilic Seeds

Constructing 3D skeletons modified with lithiophilic seeds has proven effective in achieving dendrite-free lithium metal anodes. However, these lithiophilic seeds are mostly alloy- or conversion-type materials, and they tend to aggregate and redistribute during cycling, resulting in the failure of regulating Li deposition. Herein, we address this crucial but long-neglected issue by using intercalation-type lithiophilic seeds, which enable antiaggregation owing to their negligible volume expansion and high electrochemical stability against Li. To exemplify this, a 3D carbon-based host is built, in which ultrafine TiO₂ seeds are uniformly embedded in nitrogen-doped hollow porous carbon spheres (N-HPCSs). The TiO₂@N-HPCSs electrode exhibits superior Coulombic efficiency, high-rate capability, and long-term stability when evaluated as compertitive anodes for Li metal batteries. Furthermore, the superiority of intercalation-type seeds is comprehensively revealed through controlled experiments by various in situ/ex situ electron and optical microscopies, which highlights the excellent structural stability and lithiophilicity of TiO₂ nanoseeds upon repeated cycling.

Lithiophilic onion-like carbon spheres as lithium metal uniform deposition host

Lithium metal is considered as a promising anode material for next-generation secondary batteries, owing to its high theoretical specific capacity (3860 mA h g^-1). Nevertheless, the practical application of Li in lithium metal batteries (LMBs) is hampered by inhomogeneous Li deposition and irreversible "dead Li", which lead to low coulombic efficiency (CE) and safe hazards. Designing unique lithiophilic structure is an efficient strategy to control Li uniformly plating /stripping. Here, we report the silver (Ag) nanoparticles coated with nitrogen-doped onion-like carbon microspheres (Ag@NCS) as a host to reduce the nucleation overpotential of Li for dendrite-free LBMs. The Ag@NCS were prepared by a simple one-step injection pyrolysis. The lithiophilic Ag is demonstrated to be priority selective deposition of Li in the carbon cage. Meanwhile, the onion-like structure benefits to uniform lithium nucleation and dendrite-free lithium during cycling. Impressively, we successfully captured lithium metal on different hosts at atomic scale, further proving that Ag@NCS can effectively and uniformly deposit Li. Besides, Ag@NCS show a superiorly electrochemical performance with a low nucleation overpotential (∼1 mV), high CE and stable cycling performance (over 400 cycles at 0.5 mA cm^-2) compared to the Ag-free onion-like carbon in LMBs. Even under harsh conditions (1 mA cm^-2, 4 mA h cm^-2), Ag@NCS still present superior cycling stability for more than 150 cycles. Furthermore, a full cell composed of LiFePO₄ cathode exhibits significantly improved voltage hysteresis with low voltage polarization. This work provides a new choice and route for the design and preparation of lithiophilic host materials.

Shielding polysulfides enabled by a biomimetic artificial protective layer in lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries are widely considered to be next-generation storage technologies due to their high energy density, low cost and non-toxicity. However, the soluble lithium polysulfides (LiPS) migrating to the anode side inevitably causes side reactions with the Li anode, resulting in severe corrosion of the Li anode, loss of active materials, and rapid battery failure. Therefore, it is necessary to develop effective strategies to avoid LiPS exposure to Li anodes. Herein, a stable UiO-66-ClO₄/PDMS (PDUO-Cl) biomimetic protective layer is rationally constructed by the drip coating method. The PDUO-Cl protective layer can effectively suppress the side reaction of Li metal with LiPSs/electrolyte and homogenize the Li⁺ flux, thus avoiding corrosion of the Li metal anode. As a result, the symmetric cell with the PDUO-Cl protective layer delivers a stable cycle performance greater than 1400 h under a current density of 0.5 mA cm^-2. The Li-S batteries with a PDUO-Cl protective layer still show relatively better rate performance and cycling stability (69% after 100 cycles at 0.1 C). This work provides new insights into the design of protective strategies for Li anodes in Li-S batteries.

Crystal Plane Reconstruction and Thin Protective Coatings Formation for Superior Stable Zn Anodes Cycling 1300 h

Some new insights into traditional metal pretreatment of anticorrosion for high stable Zn metal anodes are provided. A developed pretreatment methodology is employed to prefer the crystal plane of polycrystalline Zn and create 3.26 µm protective coatings mainly consisting of organic polymers and zinc salts on Zn foils (ROZ@Zn). In this process, Zn metal exhibits a surface-preferred (001) crystal plane proved by electron backscattered diffraction. Preferred (001) crystal planes and ROZ coatings can regulate Zn²⁺ diffusion, promote flat growth of Zn, and prevent side reactions. As a result, ROZ@Zn symmetrical cells exhibit superior plating/stripping performance over 1300 h. Impressively, it is significantly prolonged over 40 times in comparison to the bare Zn symmetric cell at 5 mA cm^-2 . Moreover, Zn//MnO₂  button cells have a high capacity retention of 96.3% after 1600 cycles and pouch cells have a high capacity 122 mAh g^-1  after 200 cycle at 5 C. This work provides inspiration for high stable aqueous Zn metal batteries using the developed metal pretreatment of anticorrosion, which will be a viable, low-cost, and efficient technology. More interesting, it demonstrates the availability of reconstructing crystal planes by the largely heterogeneous reaction activation of the different crystal planes to H⁺ .

Recent Progress and Future Advances on Aqueous Monovalent-Ion Batteries towards Safe and High-Power Energy Storage

Aqueous monovalent-ion batteries have been rapidly developed recently as promising energy storage devices in large-scale energy storage systems owing to their fast charging capability and high power densities. In recent years, Prussian blue analogues, polyanion-type compounds, and layered oxides have been widely developed as cathodes for aqueous monovalent-ion batteries because of their low cost and high theoretical capacity. Furthermore, many design strategies have been proposed to expand their electrochemical stability window by reducing the amount of free water molecules and introducing an electrolyte addictive. This review highlights the advantages and drawbacks of cathode and anode materials, and summarizes the correlations between the various strategies and the electrochemical performance in terms of structural engineering, morphology control, elemental compositions, and interfacial design. Finally, this review can offer rational principles and potential future directions in the design of aqueous monovalent-ion batteries.

One Stone for Multiple Birds: A Versatile Cross-Linked Poly(dimethyl siloxane) Binder Boosts Cycling Life and Rate Capability of an NCM 523 Cathode at 4.6 V

Increasing working voltage is a promising way to increase the energy density of lithium-ion batteries. Cycling and rate performance deteriorated due to excessive electrolyte decomposition and uncontrolled formation of a cathode-electrolyte interface (CEI) layer at a high voltage. A new concept is proposed to construct a high-voltage-stable electrode-electrolyte interface. An elastomeric poly(dimethyl siloxane) (PDMS) binder is incorporated into the electrode to modify the LiNi_0.5Co_0.2Mn_0.3O₂ (NCM 523) particle surface via an in situ cross-linking reaction between hydroxy-terminated PDMS and methyl trimethoxy silane promoted by moisture at ambient conditions (MPDMS). Improved electrochemical performance is achieved with the MPDMS binder in terms of reversible capacity (201 vs 185 mAh·g^-1 at 0.2C), capacity retention (80 vs 68%, after 300 cycles at 1C), and rate performance (55.6% increase at 5C), as demonstrated by the NCM 523||Li half-cell. The NCM 523||graphite full-cell also shows improved performance at 4.6 V (147 vs 128 mAh·g^-1, 82 vs 76%, after 200 cycles at 1C). The mechanism studies indicate that MPDMS exerts multiple effects, including cathode surface passivation, solvation structure tuning, electrolyte uptake enhancement, and mechanical stress relief. This work provides an inspiring route to realize high-voltage application of lithium-ion battery technology.

Prussian Blue Analogues for Sodium-Ion Batteries: Past, Present, and Future

Prussian blue analogues (PBAs) have attracted wide attention for their application in the energy storage and conversion field due to their low cost, facile synthesis, and appreciable electrochemical performance. At the present stage, most research on PBAs is focused on their material-level optimization, whereas their properties in practical battery systems are seldom considered. This review aims to first provide an overview of the history and parameters of PBA materials and analyze the fundamental principles toward rational design of PBAs, and then evaluate the prospects and challenges for PBAs for practical sodium-ion batteries, hoping to bridge the gap between laboratory research and commercial reality.

Double-Faced Bond Coupling to Induce an Ultrastable Lithium/Li6PS5Cl Interface for High-Performance All-Solid-State Batteries

Sulfide-type solid electrolytes (SSEs) are supposed to be preferential candidates for all-solid-state Li metal batteries (ASSLMBs) due to their satisfactory Li⁺ conductivity and preferable mechanical stiffness. Nonetheless, the poor stability between the Li anode and SSEs and uncontrolled Li dendrite growth severely restrict their commercial application. Herein, an amphiphilic Li_xSiO_y-enriched solid electrolyte interphase (SEI) as a "Janus" layer was first introduced at the Li/SSEs interface, and it exhibited bond coupling reactivity with both the Li anode and SSEs by forming Li-S, Li-O-Si, and Si-S covalent bonds, which is called the pincer effect. In addition to the physical isolation of Li and SSEs to prevent side reactions between them, Li_xSiO_y with high ionic conductivity offers abundant and evenly distributed transport channels for fast Li⁺ migration. As evidenced by in situ microscopy, the high-strength anodic interface constructed by the pincer effect and in situ decomposition mentioned above is free from mechanical damage during the Li plating/stripping. As a result, the symmetric cells exert an outstanding cycling performance for over 2000 h at 0.2 mA cm^-2 and even 500 h at 0.5 mA cm^-2 without evident resistance growth. The artificial SEI layer with the pincer effect and its effective application in interfacial stabilization put forward a new perspective for the commercialization of ASSLMBs.

A surface-nitridized 3D nickel host for lithium metal anodes with long cycling life at a high rate

Three dimensional (3D) metal structures such as nickel (Ni) and copper (Cu) frames have long been regarded as a good host for lithium (Li) metal. However, Li deposition on different metals often causes obvious over-potential, affecting the electrode performance in lithium metal batteries. Here, a Ni-N-O interface was created by surface nitridation to the Ni micro-particles, which were made into 3D current collectors. The directly grown Ni₃N created a thin and lithiophilic layer containing dense Li nucleation sites. The homogeneous distribution of amorphous Ni₃N and NiO at the interface allowed for a fast transfer of both electrons and ions, and thus facilitated smooth and even plating/stripping of lithium. High cycling stability and rate capability were simultaneously achieved. The 3D Li@N-Ni anode exhibited an extremely low voltage hysteresis of ∼10 mV over 850 h in a symmetric cell. The full battery paired with LiFePO₄ achieved steady cycling at 5C for 1500 cycles, with coulombic efficiency constantly higher than 99.2% and an average capacity loss of 0.027 mA h g^-1 per cycle, demonstrating a rational strategy for the design and fabrication of efficient lithium anodes for practical applications.

Multifunctional Protection Layers via a Self-Driven Chemical Reaction To Stabilize Lithium Metal Anodes

The Li metal anode is considered one of the most potential anodes due to its highest theoretical specific capacity and the lowest redox potential. However, the scalable preparation of safe Li anodes remains a challenge. In the present study, a LiF-rich protection layer has been developed using self-driven chemical reactions between the Li_3xLa_2/3-xTiO₃/polyvinylidene fluoride/dimethylacetamide (LLTO/PVDF/DMAc) solution and the Li metal. After coating the LLTO/PVDF/DMAc solution to Li foil, PVDF reacted with Li spontaneously to form LiF, and the accompanying Ti⁴⁺ ions (in LLTO) were reduced to Ti³⁺ to form a mixed ionic and electronic conductor Li_xLLTO. The protective layer can redistribute the Li-ion transport, regulate the even Li deposition, and inhibit the Li dendrite growth. When paired with LiFePO₄, NCM811, and S cathodes, the batteries have demonstrated excellent capacity retention and cycling stability. More importantly, a volumetric energy density of 478 Wh L^-1 and 78% capacity retention after 310 cycles have been achieved by using a S/Li_xLLTO-Li pouch cell. This work provides a feasible avenue to provide large-scale preparation of safe Li anodes for the next-generation pouch-type Li-S batteries as ideal power sources for flexible electronic devices.

An Antipulverization and High-Continuity Lithium Metal Anode for High-Energy Lithium Batteries

Lithium metal is one of the most promising anode candidates for next-generation high-energy batteries. Nevertheless, lithium pulverization and associated loss of electrical contact remain significant challenges. Here, an antipulverization and high-continuity lithium metal anode comprising a small number of solid-state electrolyte (SSE) nanoparticles as conformal/sacrificial fillers and a copper (Cu) foil as the supporting current collector is reported. Guiding by the SSE, this new anode facilitates lithium nucleation, contributing to form a roundly shaped, micro-sized, and dendrite-free electrode during cycling, which effectively mitigates the lithium dendrite growth. The embedded Cu current collector in the hybrid anode not only reinforces the mechanical strength but also improves the efficient charge transfer among active lithium filaments, affording good electrode structural integrity and electrical continuity. As a result, this antipulverization and high-continuity lithium anode delivers a high average Coulombic efficiency of ≈99.6% for 300 cycles under a current density of 1 mA cm^-2 . Lithium-sulfur batteries (elemental sulfur or sulfurized polyacrylonitrile cathodes) equipped with this anode show high-capacity retentions in their corresponding ether-based or carbonate-based electrolytes, respectively. This new electrode provides important insight into the design of electrodes that may experience large volume variation during operations.

Fatigue-Resistant Interfacial Layer for Safe Lithium Metal Batteries

The plating/stripping of Li dendrites can fracture the static solid electrolyte interphase (SEI) and cause significant dynamic volume variations in the Li anode, which give rise to poor cyclability and severe safety hazards. Herein, a tough polymer with a slide-ring structure was designed as a self-adaptive interfacial layer for Li anodes. The slide-ring polymer with a dynamically crosslinked network moves freely while maintaining its toughness and fracture resistance, which allows it can to dissipate the tension induced by Li dendrites on the interphase layer. Moreover, the slide-ring polymer is highly stretchable, elastic, and displays an ultrafast self-healing ability, which allows even pulverized Li to remain coalesced without disintegrating upon consecutive cycling. The Li anodes demonstrate greatly improved suppression of Li dendrite formation, as evidenced by the high critical current density (6 mA cm^-2 ) and stable cycling for the full cells with high-areal capacity LiFePO₄ , high-voltage NCM, and S cathodes.

Nano-SiO2 and Silane Coupling Agent Co-Decorated Graphene Oxides with Enhanced Anti-Corrosion Performance of Epoxy Composite Coatings

Coatings are of great significance for irons and steels in regards to the harsh marine environment. Graphene oxides (GO) have been considered as an ideal filler material of epoxy coating. However, the undesired dispersion in the epoxy together with easy agglomeration and stacking remain great problems for practical application of GO composited epoxy coatings. A method that can effectively solve both self-aggregation and poor dispersion of GO is highly desired. Herein, we present a high dispersion strategy of graphene oxides in epoxy by co-decoration of nano-SiO₂ and silane coupling agent. The co-decorated GO filled epoxy coating exhibits high anti-corrosion performance, including high electrochemical impedance, high self-corrosive potential, low self-corrosive current, and superior electrochemical impedance stability for ten days to Q235 carbon steel. This work displays new possibilities for designing novel coating materials with high performance toward practical marine anti-corrosion applications.

Liquid Metal Composites with Enhanced Thermal Conductivity and Stability Using Molecular Thermal Linker

Gallium-based liquid metal (LM) composite with metallic fillers is an emerging class of thermal interface materials (TIMs), which are widely applied in electronics and power systems to improve their performance. In situ alloying between gallium and many metallic fillers like copper and silver, however, leads to a deteriorated composite stability. This paper presents an interfacial engineering approach using 3-chloropropyltriethoxysilane (CPTES) to serve as effective thermal linkers and diffusion barriers at the copper-gallium oxide interfaces in the LM matrix, achieving an enhancement in both thermal conductivity and stability of the composite. By mixing LM with copper particles modified by CPTES, a thermal conductivity (κ) as high as 65.9 W m^-1 K^-1 is achieved. In addition, κ can be tuned by altering the terminal groups of silane molecules, demonstrating the flexibility of this approach. The potential use of such composite as a TIM is also shown in the heat dissipation of a computer central processing unit. While most studies on LM-based composites enhance the material performance via direct mixing of various fillers, this work provides a different approach to fabricate high-performance LM-based composites and may further advance their applications in various areas including thermal management systems, flexible electronics, consumer electronics, and biomedical systems.

Growth Mechanism of Micro/Nano Metal Dendrites and Cumulative Strategies for Countering Its Impacts in Metal Ion Batteries: A Review

Metal-ion batteries are capable of delivering high energy density with a longer lifespan. However, they are subject to several issues limiting their utilization. One critical impediment is the budding and extension of solid protuberances on the anodic surface, which hinders the cell functionalities. These protuberances expand continuously during the cyclic processes, extending through the separator sheath and leading to electrical shorting. The progression of a protrusion relies on a number of in situ and ex situ factors that can be evaluated theoretically through modeling or via laboratory experimentation. However, it is essential to identify the dynamics and mechanism of protrusion outgrowth. This review article explores recent advances in alleviating metal dendrites in battery systems, specifically alkali metals. In detail, we address the challenges associated with battery breakdown, including the underlying mechanism of dendrite generation and swelling. We discuss the feasible solutions to mitigate the dendrites, as well as their pros and cons, highlighting future research directions. It is of great importance to analyze dendrite suppression within a pragmatic framework with synergy in order to discover a unique solution to ensure the viability of present (Li) and future-generation batteries (Na and K) for commercial use.

Dendrite-Suppressing Polymer Materials for Safe Rechargeable Metal Battery Applications: From the Electro-Chemo-Mechanical Viewpoint of Macromolecular Design

Metal batteries have been emerging as next-generation battery systems by virtue of ultrahigh theoretical specific capacities and low reduction potentials of metallic anodes. However, significant concerns regarding the uncontrolled metallic dendrite growth accompanied by safety hazards and short lifespan have impeded practical applications of metal batteries. Although a great deal of effort has been pursued to highlight the thermodynamic origin of dendrite growth and a variety of experimental methodologies for dendrite suppression, the roles of polymer materials in suppressing the dendrite growth have been underestimated. This review aims to give a state-of-the-art overview of contemporary dendrite-suppressing polymer materials from the electro-chemo-mechanical viewpoint of macromolecular design, including i) homogeneous distribution of metal ion flux, ii) mechanical blocking of metal dendrites, iii) tailoring polymer structures, and iv) modulating the physical configuration of polymer membranes. Judiciously tailoring electro-chemo-mechanical properties of polymer materials provides virtually unlimited opportunities to afford safe and high-performance metal battery systems by resolving problematic dendrite issues. Transforming these rational design strategies into building dendrite-suppressing polymer materials and exploiting them towards polymer electrolytes, separators, and coating materials hold the key to realizing safe, dendrite-free, and long-lasting metal battery systems.

Understanding the Effects of the Low-Concentration Electrolyte on the Performance of High-Energy-Density Li-S Batteries

High-energy-density Li-S batteries have been impeded by low power rate and low sulfur utilization of high-sulfur-loading cathode and unstable Li metal anode. Herein, a new method protocol was proposed to separately investigate the effects of low-concentration electrolytes on the cathode and the anode for Li-S batteries. It was found that 0.5 M LiTFSI showed better cycling stability than the standard concentration of 1.0 M LiTFSI under the condition of high sulfur loading due to its better wettability toward the electrode. In addition, the low-concentration electrolyte could improve the stability of the Li-electrolyte interface, which was attributable to a higher content of the organic component in the solid electrolyte interface (SEI), owing to the participation of more solvent in the buildup of the SEI. The flexible and elastic organic components could be more capable of accommodating the volume changes in the Li metal anode. Consequently, the low-concentration electrolyte could be more suitable for high-energy-density Li-S batteries. We anticipate this research could provide some inspirations for the development of high-energy-density and low-cost Li-S batteries.

Lotus-Root-Like Carbon Fibers Embedded with Ni-Co Nanoparticles for Dendrite-Free Lithium Metal Anodes

The growth of lithium (Li) dendrites and the huge volume change are the critical issues for the practical applications of Li-metal anodes. In this work, a spatial control strategy is proposed to address the above challenges using lotus-root-like Ni-Co hollow prisms@carbon fibers (NCH@CFs) as the host. The homogeneously distributed bimetallic Ni-Co particles on the N-doped carbon fibers serve as nucleation sites to effectively reduce the overpotential for Li nucleation. Furthermore, the 3D conductive network can alter the electric field. More importantly, the hierarchical lotus-root-like hollow fibers provide sufficient void space to withstand the volume expansion during Li deposition. These structural features guide the uniform Li nucleation and non-dendritic growth. As a result, the NCH@CFs host enables a very stable Li metal anode with a low voltage hysteresis during repeated Li plating/stripping for 1200 h at a current density of 1 mA cm^-2 .

Constructing nitrided interfaces for stabilizing Li metal electrodes in liquid electrolytes

Traditional Li ion batteries based on intercalation-type anodes have been approaching their theoretical limitations in energy density. Replacing the traditional anode with metallic Li has been regarded as the ultimate strategy to develop next-generation high-energy-density Li batteries. Unfortunately, the practical application of Li metal batteries has been hindered by Li dendrite growth, unstable Li/electrolyte interfaces, and Li pulverization during battery cycling. Interfacial modification can effectively solve these challenges and nitrided interfaces stand out among other functional layers because of their impressive effects on regulating Li⁺ flux distribution, facilitating Li⁺ diffusion through the solid-electrolyte interphase, and passivating the active surface of Li metal electrodes. Although various designs for nitrided interfaces have been put forward in the last few years, there is no paper that specialized in reviewing these advances and discussing prospects. In consideration of this, we make a systematic summary and give our comments based on our understanding. In addition, a comprehensive perspective on the future development of nitrided interfaces and rational Li/electrolyte interface design for Li metal electrodes is included.

In this perspective, we make a systematic summary and give out our comments on constructing nitrided interfaces for stabilizing Li metal electrodes.