Prediction of Novel Trigonal Chloride Superionic Conductors as Promising Solid Electrolytes for All-Solid-State Lithium Batteries.

Recently emerging lithium ternary chlorides have attracted increasing attention for solid-state electrolytes (SSEs) due to their favorable combination between ionic conductivity and electrochemical stability. However, a noticeable discrepancy in Li-ion conductivity persists between chloride SSEs and organic liquid electrolytes, underscoring the need for designing novel chloride SSEs with enhanced Li-ion conductivity. Herein, an intriguing trigonal structure (i.e., Li3SmCl6 with space group P3112) is identified using the global structure searching method in conjunction with first-principles calculations, and its potential for SSEs is systematically evaluated. Importantly, the structure of Li3SmCl6 exhibits a high ionic conductivity of 15.46 mS cm-1 at room temperature due to the 3D lithium percolation framework distinct from previous proposals, associated with the unique in-plane cation ordering and stacking sequences. Furthermore, it is unveiled that Li3SmCl6 possesses a wide electrochemical window of 0.73-4.30 V vs Li+/Li and excellent chemical interface stability with high-voltage cathodes. Several other Li3MCl6 (M = Er, and In) materials with isomorphic structures to Li3SmCl6 are also found to be potential chloride SSEs, suggesting the broader applicability of this structure. This work reveals a new class of ternary chloride SSEs and sheds light on strategy for structure searching in the design of high-performance SSEs.

First-Principles Study on Polymer Electrolyte Interface Engineering for Lithium Metal Anodes.

Modifying the interface between the lithium metal anode (LMA) and the electrolyte is crucial for achieving high-performance lithium metal batteries (LMBs). Recent research indicates that altering Li-metal interfaces with polymer coatings is an effective approach to extend LMBs' cycling lifespan. However, the physical properties of these polymer-Li interfaces have not yet been fully investigated. Therefore, the structural stability, electronic conductivity, and ionic conductivity of polymer-Li interfaces were examined based on first-principles calculations in this study. Several representative polymer compounds utilized in LMBs were assessed, including polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and polyethylene oxide (PEO). Our research revealed that lithium fluoride is formed upon fluoropolymer degradation, explaining previously observed experimental results. Polymers containing nitrile groups exhibit strong adhesion to lithium metal, facilitating the formation of the stable interface layer. Regarding electronic conductivity, the fluoropolymers preserve a good insulating property, which diminished marginally in the presence of lithium, but that of PAN and PEO significantly reduces. Additionally, lithium diffusion on PTFE and PEO demonstrates low diffusion barriers and high coefficients, enabling easy transportation. Overall, our investigation reveals that the interfaces formed between various polymers and LMA have distinct characteristics, providing new fundamental insights for designing composites with tailored interface properties.

π-π Stacked Nigrosine@Carbon Nanotube Nanocomposite as an All-in-One Additive for High Energy Flexible Batteries.

The pursuit of high energy density in lithium batteries has driven the development of efficient electrodes with low levels of inactive components. Herein, a facile approach involving the use of π-π stacked nigrosine@carbon nanotube nanocomposites as an all-in-one additive for a LiFePO4 cathode has been developed. This design significantly reduces the proportion of inactive substances within the cathode, resulting in a battery that exhibits a high specific capacity of 143 mAh g-1 at a 1 C rate and shows commendable cyclic performance. Furthermore, the elimination of rigid current collectors endows the electrode with flexibility, offering avenues for future wearable energy storage devices.

Formation of 2D Amorphous Lithium Sulfide Enabled by Mo2C Clusters Loaded Carbon Scaffold for High-Performance Lithium Sulfur Batteries.

Lithium-sulfur (Li-S) batteries, operated through the interconversion between sulfur and solid-state lithium sulfide, are regarded as next-generation energy storage systems. However, the sluggish kinetics of lithium sulfide deposition/dissolution, caused by its insoluble and insulated nature, hampers the practical use of Li-S batteries. Herein, leaf-like carbon scaffold (LCS) with the modification of Mo2C clusters (Mo2C@LCS) is reported as host material of sulfur powder. During cycles, the dissociative Mo ions at the Mo2C@LCS/electrolyte interface are detected to exhibit competitive binding energy with Li ions for lithium sulfide anions, which disrupts the deposition behavior of crystalline lithium sulfide and trends a shift in the configuration of lithium sulfide toward an amorphous structure. Combining the related electrochemical study and first-principle calculation, it is revealed that the formation of amorphous lithium sulfides shows significantly improved kinetics for lithium sulfide deposition and decomposition. As a result, the obtained Mo2C@LCS/S cathode shows an ultralow capacity decay rate of 0.015% per cycle at a high mass loading of 9.5 mg cm-2 after 700 cycles. More strikingly, an ultrahigh sulfur loading of 61.2 mg cm-2 can also be achieved. This work defines an efficacious strategy to advance the commercialization of Mo2C@LCS host for Li-S batteries.

Mediating Zn Ions Migration Behavior via ß-Cyclodextrin Modified Carbon Nanotube Film for High-Performance Zn Anodes.

Metallic Zn is considered as a promising anode material because of its abundance, eco-friendliness, and high theoretical capacity. However, the uncontrolled dendrite growth and side reactions restrict its further practical application. Herein, we proposed a ß-cyclodextrin-modified multiwalled carbon nanotube (CD-MWCNT) layer for Zn metal anodes. The obtained CD-MWCNT layer with high affinity to Zn can significantly reduce the transfer barrier of Zn2+ at the electrode/electrolyte interface, facilitating the uniform deposition of Zn2+ and suppressing water-caused side reactions. Consequently, the Zn||Zn symmetric cell assembled with CD-MWCNT shows a significantly enhanced cycling durability, maintaining a cycling life exceeding 1000 h even under a high current density of 5 mA cm-2. Furthermore, the full battery equipped with a V2O5 cathode displays an unparalleled long life. This work unveils a promising avenue toward the achievement of high-performance Zn metal anodes.

A Triply-Periodic-Minimal-Surface Structured Interphase based on Fluorinated Polymers Strengthening High-energy Lithium Metal Batteries.

The challenge of constructing a mechanically robust yet lightweight artificial solid-electrolyte interphase layer on lithium (Li) anodes highlights a trade-off between high battery safety and high energy density. Inspired by the intricate microstructure of the white sea urchin, we first develop a polyvinyl fluoride-hexafluoropropylene (PVDF-HFP) interfacial layer with a triple periodic minimal surface structure (TPMS) that could offer maximal modulus with minimal weight. This design endows high mechanical strength to an ordered porous structure, effectively reduces local current density, polarization, and internal resistance, and stabilizes the anode interface. At a low N/P ratio of ~3, using LiFePO4 as the cathode, Li anodes protected by TPMS-structured PVDF-HFP achieve an extremely low capacity-fading-rate of approximately 0.002 % per cycle over 200 cycles at 1 C, with an average discharge capacity of 142 mAh g-1. Meanwhile, the TPMS porous structure saves 50 wt % of the interfacial layer mass, thereby enhancing the energy density of the battery. The TPMS structure is conducive to large-scale additive manufacturing, which will provide a reference for the future development of lightweight, high-energy-density secondary batteries.

Amino-Functionalized Interfacial Layer Enables an Ultra-Uniform Amorphous Solid Electrolyte Interphase for High-Performance Aqueous Zinc-Based Batteries.

Aqueous rechargeable zinc-based batteries (ZBBs) are emerging as desirable energy storage systems because of their high capacity, low cost, and inherent safety. However, the further application of ZBBs still faces many challenges, such as the issues of uncontrolled dendrite growth and severe parasitic reactions occurring at the Zn anode. Herein, an amino-grafted bacterial cellulose (NBC) film is prepared as artificial solid electrolyte interphase (SEI) for the Zn metal anodes, which can significantly reduce zinc nucleation overpotential and lead to the dendrite-free deposition of Zn metal along the (002) crystal plane more easily without any external stimulus. More importantly, the chelation between the modified amino groups and zinc ions can promote the formation of an ultra-even amorphous SEI upon cycling, reducing the activity of hydrate ions, and inhibiting the water-induced side reactions. As a result, the Zn||Zn symmetric cell with NBC film exhibits lower overpotential and higher cyclic stability. When coupled with the V2 O5 cathode, the practical pouch cell achieves superior electrochemical performance over 1000 cycles.

Surface engineering toward stable lithium metal anodes.

The lithium (Li) metal anode (LMA) is susceptible to failure due to the growth of Li dendrites caused by an unsatisfied solid electrolyte interface (SEI). With this regard, the design of artificial SEIs with improved physicochemical and mechanical properties has been demonstrated to be important to stabilize the LMAs. This review comprehensively summarizes current efficient strategies and key progresses in surface engineering for constructing protective layers to serve as the artificial SEIs, including pretreating the LMAs with the reagents situated in different primary states of matter (solid, liquid, and gas) or using some peculiar pathways (plasma, for example). The fundamental characterization tools for studying the protective layers on the LMAs are also briefly introduced. Last, strategic guidance for the deliberate design of surface engineering is provided, and the current challenges, opportunities, and possible future directions of these strategies for the development of LMAs in practical applications are discussed.

Improving the intrinsic activity of ultrathin 2D-2D heterostructures by bridge-bonded Ni-O-Ti ligands for efficient oxygen evolution.

The integration of ultrathin two-dimensional (2D) semiconductors with other conductive 2D materials to form hybrid electrocatalysts with abundant heterointerfaces can enhance the electrocatalytic activity by facilitating interfacial charge transfer. However, the hybrid electrocatalysts with weak interfacial bonding have limited effect on the electrocatalytic performance because the intrinsic activity of interfacial sites cannot be altered by weak interfacial interactions. As a proof-of-concept, we design ultrathin 2D-2D heterostructures with bridge-bonded Ni-O-Ti ligands based on single-layered Ti3C2TxMXene and metal hydroxides, and further reveal the structure-activity correlation between interfacial bonding and electrocatalytic oxygen evolution reaction by combining theoretical and experimental studies. Density functional theory calculations reveal the modulation of the electronic structure of interfacial metal sites after the formation of bridged interfacial Ni-O-Ti bonding. Compared with the hydrogen-bond-linked heterostructure, the ultrathin 2D-2D heterostructure with bridge-bonded Ni-O-Ti ligands shows enhanced intrinsic activity and stability towards electrocatalytic oxygen evolution with a very low overpotential of 205 mV at 10 mA cm-2and the long-term durability. This work provides a new understanding and approach for the design and development of 2D hybrid catalysts with highly efficient electrocatalytic activity.

Rapidly Constructing Sodium Fluoride-Rich Interface by Pressure and Diglyme-Induced Defluorination Reaction for Stable Sodium Metal Anode.

Sodium (Na) metal is able to directly use as a battery anode but have a highly reductive ability of unavoidably occurring side reactions with organic electrolytes, resulting in interfacial instability as a primary factor in performance decay. Therefore, building stable Na metal anode is of utmost significance for both identifying the electrochemical performance of laboratory half-cells employed for quantifying samples and securing the success of room-temperature Na metal batteries. In this work, we propose an NaF-rich interface rapidly prepared by pressure and diglyme-induced defluorination reaction for stable Na metal anode. Once the electrolyte is dropped into the coin-type cells followed by a slight squeeze, the Na metal surface immediately forms a protective layer consisting of amorphous carbon and NaF, effectively inhibiting the dendrite growth and dead Na. The resultant Na metal anode exhibits a long-term cycling lifespan over 1800 h even under the area capacity of 3.0 mAh cm-2 . Furthermore, such a universal and facile method is readily applied in daily battery assembly regarding Na metal anode.

Highly Thermostable Interphase Enables Boosting High-Temperature Lifespan for Metallic Lithium Batteries.

In consideration of high specific capacity and low redox potential, lithium metal anodes have attracted extensive attention. However, the cycling performance of lithium metal batteries generally deteriorates significantly under the stringent conditions of high temperature due to inferior heat tolerance of the solid electrolyte interphase (SEI). Herein, controllable SEI nanostructures with excellent thermal stability are established by the (trifluoromethyl)trimethylsilane (TMSCF3 )-induced interface engineering. First, the TMSCF3 regulates the electrolyte decomposition, thus generating an SEI with a large amount of LiF, Li3 N, and Li2 S nanocrystals incorporated. More importantly, the uniform distributed nanocrystals have endowed the SEI with enhanced thermostability according to the density functional theory simulations. Particularly, the sub-angstrom visualization on SEI through a conventional transmission electron microscope (TEM) is realized for the first time and the enhanced tolerance to the heat damage originating from TEM imaging demonstrates the ultrahigh thermostability of SEI. As a result, the highly thermostable interphase facilitates a substantially prolonged lifespan of full cells at a high temperature of 70 °C. As such, this work might inspire the universal interphase design for high-energy alkali-metal-based batteries applicated in a high-temperature environment.

Stabilizing Li4SnS4 Electrolyte from Interface to Bulk Phase with a Gradient Lithium Iodide/Polymer Layer in Lithium Metal Batteries.

Sulfide electrolytes promise superior ion conduction in all-solid-state lithium (Li) metal batteries, while suffering harsh hurdles including interior dendrite growth and instability against Li and moist air. A prerequisite for solving such issues is to uncover the nature of the Li/sulfide interface. Herein, air-stable Li4SnS4 (LSS) as a prototypical sulfide electrolyte is selected to visualize the dynamic evolution and failure of the Li/sulfide interface by cryo-electron microscopy. The interfacial parasitic reaction (2Li + 2Li4SnS4 = 5Li2S + Sn2S3) is validated by direct detection of randomly distributed Li2S and Sn2S3 crystals. A bifunctional buffering layer is consequently introduced by self-diffusion of halide into LSS. Both the interface and the grain boundaries in LSS have been stabilized, eliminating the growing path of Li dendrites. The buffering layer enables the durability of Li symmetric cell (1500 h) and high-capacity retention of the LiFePO4 full-cell (95%). This work provides new insights into the hierarchical design of sulfide electrolytes.

Toward Understanding the Effect of Fluoride Ions on the Solvation Structure in Lithium Metal Batteries: Insights from First-Principles Simulations.

Regulating the structure and composition of the lithium-ion (Li+) solvation shell is crucial to the performance of lithium metal batteries. The introduction of fluorine anions (F-) into the electrolyte significantly enhances the cycle efficiency and the interfacial stability of lithium metal anodes. However, the effect of dissolved F- on the solvation shell is rarely touched in the literature. Herein, we investigate the evolution processing of the fluorine-containing solvation structure to explore the underlying mechanisms via first-principles calculations. The additive F- is found to invade the first solvation shell and strongly coordinate with Li+, liberating the bis(trifluoromethanesulfonyl) imide anion (TFSI-) from the Li+ local environment, which enhances the Li+ diffusivity by altering the transport mode. Moreover, the fluorine-containing Li+ solvation shell exhibits a higher lowest unoccupied molecular orbital energy level than that of the solvation sheath without F- additives, suggesting the reduction stability of the electrolyte. Furthermore, the Gibbs free energy calculations for Li+ desolvation reveal that the energy barrier of the Li+ desolvation process will be reduced because of the presence of F-. Our work provides new insights into the mechanisms of electrolyte fluorinated strategies and leads to the rational design of high-performance lithium metal batteries.

Synthesis of NiSe2 /Fe3 O4 Nanotubes with Heteroepitaxy Configuration as a High-Efficient Oxygen Evolution Electrocatalyst.

The rational design of high-efficient non-noble metal electrocatalysts for oxygen evolution reactions (OER) is of significance in electrochemical energy conversion. However, such low-cost but highly active electrocatalysts remain poorly developed because of the daunting synthetic challenge. Here, the synthesis of NiSe2 /Fe3 O4 nanotubes via a facile self-templating strategy, which manifests unique tetragonal morphology, asymmetric hollow interior, and unusual but adaptable heteroepitaxy structure, is reported. Benefiting from sufficient active sites and their improved activity around the heterointerface, accompanied by the good conductivity, the NiSe2 /Fe3 O4 nanotubes exhibit as a superior OER electrocatalyst, which affords the current density of 10 mA cm-2 at a very small overpotential of 199 mV, high attainable current density beyond 200 mA cm-2 , and mass activity of 984.5 A g-1 , as well as excellent stability for 100 h in the alkaline media. This work provides a unique synthetic pathway to fabricate superior OER electrocatalysts by optimizing their composition and architecture.

In-Situ Electrodeposition of Nanostructured Carbon Strengthened Interface for Stabilizing Lithium Metal Anode.

The lithium metal anode (LMA) is regarded as one of the most promising candidates for high-energy Li-ion batteries. However, the naturally formed solid electrolyte interface (SEI) is unsatisfied, which would cause continuous dendrite growth and thus prevent the practical application of the LMA. Herein, a stable electrolytic carbon-based hybrid (ECH) artificial SEI is constructed on the LMA via the in-situ electrodeposition of an electrolyte sovlent at ultrahigh voltage. This nanostructured carbon strengthened SEI exhibits much improved ionic conductivity and mechanical strength, which enables uniform Li+ diffusion, stabilizes the interface between the electrolyte and lithium metal, and inhibits Li dendrite breeding and Li pulverization. With the protection of this ECH layer, the symmetrical cells show stable long-term cycling performance over 500 h with an ultrahigh plating capacity of 5 mAh cm-2 at the current density of 5 mA cm-2. A full cell assembled with a Li[Ni0.8Co0.1Mn0.1]O2 or LiFePO4 cathode exhibits a long-term cycling life and excellent capacity retention.

Soybean Protein Fiber Enabled Controllable Li Deposition and a LiF-Nanocrystal-Enriched Interface for Stable Li Metal Batteries.

The proliferation of lithium (Li) dendrites stemming from uncontrollable Li deposition seriously limits the practical application of Li metal batteries. The regulation of uniform Li deposition is thus a prerequisite for promoting a stable Li metal anode. Herein, a commercial lithiophilic skeleton of soybean protein fiber (SPF) is introduced to homogenize the Li-ion flux and induce the biomimetic Li growth behavior. Especially, the SPF can promote the formation of a LiF-nanocrystal-enriched interface upon cycling, resulting in low interfacial impedance and rapid charge transfer kinetics. Finally, the SPF-mediated Li metal anode can achieve high Coulombic efficiency of 98.7% more than 550 cycles and a long-term lifespan over 3400 h (∼8500 cycles) in symmetric tests. Furthermore, the practical pouch cell modified with SPF can maintain superior electrochemical performance over 170 cycles under a low N/P ratio and high mass loading of the cathode.

Construction of Ni(CN)2 /NiSe2 Heterostructures by Stepwise Topochemical Pathways for Efficient Electrocatalytic Oxygen Evolution.

Exploiting effective electrocatalysts based on elaborate heterostructures for the oxygen evolution reaction (OER) has been considered as a promising strategy for boosting water splitting efficiency to produce the clean energy-hydrogen. However, constructing catalytically active heterostructures with novel composition and architecture remains poorly developed due to the synthetic challenge. In this work, it is demonstrated that unique Ni(CN)2 /NiSe2 heterostructures, composed of single-crystalline Ni(CN)2 nanoplates surrounded by crystallographically aligned NiSe2 nanosatellites, can be created from nickel-based Hofmann-type coordination polymers through stepwise topochemical pathways. When employed as the OER electrocatalyst, the Ni(CN)2 /NiSe2 heterostructures show enhanced performance, which could be attributed to optimized geometric and electronic structures of the catalytic sites endowed by the synergy between the two components. This work demonstrates a rational synthetic route for creating a novel Ni-based OER electrocatalyst that possesses nanoscale heterostructure, whose composition, spatial organization, and interface configuration can be finely manipulated.

Undervalued Roles of Binder in Modulating Solid Electrolyte Interphase Formation of Silicon-Based Anode Materials.

The use of silicon (Si) for lithium (Li) storage has the significant merits of an ultrahigh theoretical specific capacity and a low working platform, potentially enabling a high-energy-density Li-ion battery (LIB). However, the Si itself undergoes a huge volume variation (>300%) upon the lithiation/delithiation process, which inevitably causes material pulverization and electrode cracking as well as ceaselessly repairs the solid electrolyte interphase (SEI), eventually resulting in a rapid capacity decay of the Si anode. Presently, using a robust binder has been well-recognized as an effective solution, which is generally explained by its robust mechanical properties that enable the electrode integrity of the Si anode during the repeated cycling process. Comparatively, the roles of the binder in modulating the chemical composition and the spatial distribution of the Si-based SEI layer are overlooked. This review will specifically provide an overview of the correlation between the binder species and SEI properties. The binder species have a critical role of inducing a robust SEI layer by selectively allowing the electrolyte salt and the solvent to connect the Si surface in the initial discharging process. Finally, we conclude by providing the perspective of the binder design based on interfacial chemistries and new characterization techniques.

Visualizing the Sensitive Lithium with Atomic Precision: Cryogenic Electron Microscopy for Batteries.

Lithium (Li)-metal batteries are one of the most promising candidates for the next-generation energy storage devices due to their ultrahigh theoretical capacity. The realistic development of a Li metal battery is greatly impeded by the uncontrollable dendrite proliferation upon the chemically active metallic Li. To visualize the micromorphology or even the atomic structure of Li deposits is undoubtedly crucial, while imaging the sensitive Li still faces a huge challenge technically.Cryogenic electron microscopy (cryo-EM), an emerging imagery technology renowned for structural elucidation of biomaterials, is offering increased possibilities for analyzing sensitive battery materials reaching subangstrom resolution. Particularly for revealing metallic Li, cryo-EM exhibits remarkable superiority compared with the conventional electron imaging technique. On the one hand, cryo-EM could prevent the low melting-point Li metal from being damaged by the high electron dose induced thermal effect. On the other hand, the extremely low temperature immensely retards the rate of the side reaction where the Li reacts with the atmosphere or water vapor before the vacuum state. Consequently, the cryo-EM could acquire a high-resolution image of electron-beam sensitive Li in its native state at the nano- or even atomic scale, thus benefiting the fundamental perception and rational design of Li metal anodes.Thus, in this Account, we aim to highlight the significance of cryo-EM in analyzing metallic Li and developing a high-performance Li metal battery. We focus on how highly resolved cryo-EM realizes the breakthrough in detecting the crucial evolution during battery cycling, e.g., lattice ordering of Li, nanostructures of the solid electrolyte interphase (SEI), nucleation sites, and interface between the solid electrolyte and the Li anode. First, we briefly summarize the progress of Li metal imaging by cryo-EM in a timed sequence. In particular, the recent studies from our group are classified in order to systematically delineate the advantages that cryo-transmission electron microscopy (cryo-TEM) addressed on understanding and developing the Li metal battery. Second, the efforts of exhibiting the long-range ordering Li lattice are described to cognize the crystal orientation of both Li dendrites and uniform spheres. Subsequently, the nanostructures of SEI detected by cryo-TEM, maybe the most key information during Li plating/stripping, are systematically summarized. Benefitting from the subangstrom visualization on the newly formed and the particular inactive SEI after long-term cycling, we emphasize cryo-TEM's guidance in designing a robust, highly Li+ conductive, and Li-restoration facilitated SEI. We then propose the strategy of introducing a nucleation-site to enable uniform Li deposition by showing the evidence of Li nucleation atomically monitored through cryo-TEM. Moreover, the series of the work of atomic imagery and corresponding optimization of the interfaces between the polymer-based solid electrolyte and the Li anode are concluded. Finally, critical perspectives about the further step of cryo-TEM in the realistic development of high-energy density battery systems are also succinctly reviewed.

Enhanced stability of silver nanowire transparent conductive films against ultraviolet light illumination.

Silver nanowires are susceptible to degradation under ultraviolet (UV) light illumination. Encapsulating silver nanowire transparent conductive films (AgNW TCFs) with UV shielding materials usually result in the increasing of the sheet resistance or the decrease of the visible light transparency. Herein, we combine a reducing species (FeSO4) and a thin layer (overcoating) of UV shielding material to solve the stability and the optical performance issues simultaneously. The AgNW TCFs show excellent stability under continuous UV light illumination for 14 h, and their sheet resistance varies only 6%. The dramatic enhancement of the stability against UV light illumination for as-obtained TCFs will make them viable for real-world applications in touch panels and displays.