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

Ultrafast-Loaded Nickel Sulfide on Vertical Graphene Enabled by Joule Heating for Enhanced Lithium Metal Batteries

The design and fabrication of a lithiophilic skeleton are highly important for constructing advanced Li metal anodes. In this work, a new lithiophilic skeleton is reported by planting metal sulfides (e.g., Ni3S2) on vertical graphene (VG) via a facile ultrafast Joule heating (UJH) method, which facilitates the homogeneous distribution of lithiophilic sites on carbon cloth (CC) supported VG substrate with firm bonding. Ni3S2 nanoparticles are homogeneously anchored on the optimized skeleton as CC/VG@Ni3S2, which ensures high conductivity and uniform deposition of Li metal with non-dendrites. By means of systematic electrochemical characterizations, the symmetric cells coupled with CC/VG@Ni3S2 deliver a steady long-term cycle within 14 mV overpotential for 1800 h (900 cycles) at 1 mA cm-2 and 1 mAh cm-2. Meanwhile, the designed CC/VG@Ni3S2-Li||LFP full cell shows notable electrochemical performance with a capacity retention of 92.44% at 0.5 C after 500 cycles and exceptional rate performance. This novel synthesis strategy for metal sulfides on hierarchical carbon-based materials sheds new light on the development of high-performance lithium metal batteries (LMBs).

3D Porous Fibers with Spatial Traps and Excellent Zn2+ Transport Kinetics Enable Stable Zn-Based Aqueous Battery

Adverse side reactions and uncontrolled Zn dendrites growth are the dominant factors that have restricted the application of Zn ion batteries. Herein, a 3D self-supporting porous carbon fibers (denoted as PCFs) host is developed with "trap" effect to adjust the Zn deposition. The unique open structural design of N-doped carbon can act as the zincophilic sites to induce uniform deposition and inhibit adverse side reactions. More importantly, the porous hollow PCFs host with "trap" effect can induce Zn deposition in the fiber by adjusting the local electric field and current density, thereby increasing the specific energy density of the battery and inhibiting dendrite growth. In addition, the 3D open frameworks can regulate Zn2+ flux to enable outstanding cycling performance at ultra-high current densities. As expected, the PCFs framework guarantees the uniform Zn plating and stripping with an outstanding stability over 6000 cycles at the current density of 40 mA cm-2. And the Zn@PCFs||MnO2 full battery shows an excellent lifespan over 1300 cycles at 2000 mA g-1.

A 3D Hierarchical Host with Gradient-Distributed Dielectric Properties toward Dendrite-free Lithium Metal Anode

The conventional conductive three-dimensional (3D) host fails to effectively stabilize lithium metal anodes (LMAs) due to the internal incongruity arising from nonuniform lithium-ion gradient and uniform electric fields. This results in undesirable Li "top-growth" behavior and dendritic Li growth, significantly impeding the practical application of LMAs. Herein, we construct a 3D hierarchical host with gradient-distributed dielectric properties (GDD-CH) that effectively regulate Li-ion diffusion and deposition behavior. It comprises a 3D carbon fiber host modified by layer-by-layer bottom-up attenuating Sb particles, which could promote Li-ion homogeneously distribution and reduce ion concentration gradient via unique gradient dielectric polarization. Sb transforms into superionic conductive Li3Sb alloy during cycling, facilitating Li-ion dredging and pumps towards the bottom, dominating a bottom-up deposition regime confirmed by COMSOL Multiphysics simulations and physicochemical characterizations. Consequently, a stable cycling performance of symmetrical cells over 2000 h under a high current density of 10 mA cm-2 is achieved. The GDD-CH-based lithium metal battery shows remarkable cycling stability and ultra-high energy density of 378 Wh kg-1 with a low N/P ratio (1.51). This strategy of dielectric gradient design broadens the perspective for regulating the Li deposition mechanism and paves the way for developing high-energy-density lithium metal anodes with long durability.

Modification of carbon nanofibers for boosting oxygen electrocatalysis

Oxygen electrocatalysis is a key process for many effective energy conversion techniques, which requires the development of high-performance electrocatalysts. Carbon nanofibers featuring good electronic conductivity, large specific surface area, high axial strength and modulus, and good resistance toward harsh environments have thus been recognized as reinforcements in oxygen electrocatalysis. This review summarizes the recent progress on carbon nanofibers as electrocatalysts for oxygen electrocatalysis, with special focus on the modulation of carbon nanofibers for further elevating their electrocatalytic performance, which includes morphological and structural engineering, surface and pore size distribution, defect engineering, and coupling with other electroactive materials. Additionally, the correlation between the geometrical/electronic structure of their active centers and electrocatalytic activity is systematically discussed. Finally, conclusions and perspectives of this interesting research field are presented, which we hope will provide guidance for the future fabrication of more advanced carbon-fiber-based electrocatalysts.

Structural Design of 3D Current Collectors for Lithium Metal Anodes: A Review

Due to the ultrahigh theoretical specific capacity (3860 mAh g-1) and low redox potential (-3.04 V vs. standard hydrogen electrode), Lithium (Li) metal anode (LMA) received increasing attentions. However, notorious dendrite and volume expansion during the cycling process seriously hinder the development of high energy density Li metal batteries. Constructing three-dimensional (3D) current collectors for Li can fundamentally solve the intrinsic drawback of hostless for Li. Therefore, this review systematically introduces the design and synthesis engineering and the current development status of different 3D collectors in recent years (the current collectors are divided into two major parts: metal-based current collectors and carbon-based current collectors). In the end, some perspectives of the future promotion for LMA application are also presented.

Recent Advances in Flexible Wearable Technology: From Textile Fibers to Devices

Smart textile fabrics have been widely investigated and used in flexible wearable electronics because of their unique structure, flexibility and breathability, which are highly desirable with integrated multifunctionality. Recent years have witnessed the rapid development of textile fiber-based flexible wearable devices. However, the pristine textile fibers still can't meet the high standards for practical flexible wearable devices, which calls for the development of some effective modification strategies. In this review, we summarize the recent advances in the flexible wearable devices based on the textile fibers, putting special emphasis on the design and modifications of textile fibers. In addition, the applications of textile fibers in various fields and the critical role of textile fibers are also systematically discussed, which include the supercapacitors, sensors, triboelectric nanogenerators, thermoelectrics, and other self-powered electronic devices. Finally, the main challenges that should be overcome and some effective solutions are also manifested, which will guide the future development of more effective textile fiber-based flexible wearable devices.

A 3D Lithiophilic Host for Dendrite-Free Lithium Metal Anode via One-Step Carbonization of an Energetic Metal-Organic Framework

Low Coulombic efficiency (CE) and safety issues are huge problems that hinder the practical application of Li metal anodes. Constructing Li host structures decorated with functional species can restrain the growth of Li dendrites and alleviate the great volume change. Here, a 3D porous carbonaceous skeleton modified with rich lithiophilic groups (Zn, ZnO, and Zn(CN)2 ) is synthesized as a Li host via one-step carbonization of a triazole-containing metal-organic framework. The nano lithiophilic groups serve as preferred sites for Li nucleation and growth, regulating a uniform Li+ flux and uniform current density distribution. In addition, the 3D porous network functions as a Li reservoir that provides rich internal space to store Li, thus alleviating the volumetric expansion during Li plating/stripping process. Thanks to these component and structural merits, an ultra-low overpotential for Li deposition is achieved, together with high CE of over 99.5% for more than 500 cycles at 1 mA cm-2 and 1 mAh cm-2 in half cells. The symmetric cells exhibit a prolonged cycling of 900 h at 1 mA cm-2 . The full cells by coupling Zn/ZnO/Zn(CN)2 @C-Li anode with LiFePO4 cathode deliver a high capacity retention of 94.3% after 200 cycles at 1 C.

Excellent Polymerized Ionic-Liquid-Based Gel Polymer Electrolytes Enabled by Molecular Structure Design and Anion-Derived Interfacial Layer

Polymerized ionic liquid (PIL)-based gel polymer electrolytes (GPEs) are well known as highly safe and stable electrolytes but with low ambient ionic conductivity. Herein, we first designed and synthesized an IL monomer with a long and flexible side chain and then mixed it with LiTFSI and MEMPTFSI to construct a PIL-based GPE (denoted as GM-GPE). The special molecular structure of the monomer greatly improves the ionic transport through the PIL chain, and the introduction of MEMPTFSI plasticizer further improves the ionic conductivity, promoting a TFSI--anion-derived SEI formation to suppress Li dendrite growth and forming an electrostatic shielding effect of MEMP+ cations to promote the uniform deposition of Li+. Consequently, the as-prepared GM-GPE exhibits high ambient ionic conductivity (4.3 × 10-4 S cm-1, 30 °C), robust electrochemical stability, excellent thermal stability, nonflammability, and superior ability to inhibit Li dendrite growth. The resultant LiFePO4|GM-GPE|Li cell exhibits a high discharge capacity of 150 mA h g-1 at 0.2 C along with a good cycling stability and rate capability. This work brings about new guidance for the development of high-quality GPEs with high ionic conductivity, high stability, and safety for long cycling and dendrite-free lithium metal batteries.

Influence of Brönsted Acid Sites on Activated Carbon-Based Catalyst for Acetylene Dimerization

Activated carbon (AC) has been widely used as a support material with both tunable acidity and abundant functional groups for solid acid catalysts in various chemical processes such as acetylene dimerization. A facile, mild acid modification method that directly activates AC to generate rich defects and oxygen functional group surface structures with Brönsted acid sites and an enhanced conductivity is presented here. Impressively, the catalyst with optimized Brönsted acid sites and an enhanced dispersion of active components exhibited a superior acetylene dimerization catalytic activity. Moreover, theoretical calculations indicated that an increase in hydrogen concentration could inhibit the formation of coke. This research offered a feasible potential way to devise and construct a carbon-based solid acid catalyst with an excellent catalytic performance.

Using a cyclocarbon additive as a cyclone separator to achieve fast lithiation and delithiation without dendrite growth in lithium-ion batteries

Carbon materials are widely used for reversible lithium uptake in the anode of lithium-ion batteries. Nevertheless, the challenge of uncontrollable dendrite deposition during fast charge-discharge cycles remains a grand hurdle. Various strategies have been explored to prevent detrimental heterogeneous dendrite metal deposits, such as interface engineering and electrolyte modification, but they often compromise the reverse diffusion freedom of Li+ ions during discharging and are incompatible with the most mainstream use of graphite as an anode material. Here, we propose the incorporation of a novel carbon allotrope of cyclocarbon as a potential additive in the anode. In contrast to conventional carbon materials, density functional theory calculations reveal that cyclocarbon has a much higher affinity for Li atoms than Li+ ions, even surpassing the inherent cohesion of Li atoms, due to the charge transfer from the 2s orbital of Li atoms to the unique in-plane π orbital of cyclocarbon. Furthermore, ab initio molecular dynamics simulations show that Li+ ions can shuttle freely back and forth across cyclocarbon, whereas the lithiation process for Li atoms occurs rapidly within picoseconds. The delithiation of Li atoms within cyclocarbon follows a voltage-gated mechanism that is effectively controlled by an external electric field of 3 V nm-1. Remarkably, cyclocarbon exhibits potential compatibility with commercialized graphite electrodes via the π-π interaction and also can be extended to sodium-ion and potassium-ion batteries. These distinct compatibility, scalability and electrochemical properties of cyclocarbon provide a new avenue to realize both safety and ultrafast rechargeable performance of ion batteries.

Difluoroethylene Carbonate as an Electrolyte Additive for Engineering the Electrolyte-Electrode Interphase of Lithium Metal Batteries

Difluoroethylene carbonate (DFEC) featuring abundant fluorine atoms has been proposed as a multifunctional electrolyte additive to boost the stability of the electrolyte-electrode interphase of lithium metal batteries. Thus, introducing the DFEC additive enables a high capacity retention rate of the Li||NCM811 full cell (up to 75% after 200 cycles) at 4.5 V high voltage.

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.

High Rate and Low-Temperature Stable Lithium Metal Batteries Enabled by Lithiophilic 3D Cu-CuSn Porous Framework

Lithium (Li) metal is regarded as the "Holy Grail" of anodes for high-energy rechargeable lithium batteries by virtue of its ultrahigh theoretical specific capacity and the lowest redox potential. However, the Li dendrite impedes the practical application of Li metal anodes. Herein, lithiophilic three-dimensional Cu-CuSn porous framework (3D Cu-CuSn) was fabricated by a vapor phase dealloying strategy via the difference in saturated vapor pressure between different metals and the Kirkendall effect. CuSn alloy sites were converted into LiSn alloy sites through the molten Li infusion method, and composite Li metal anodes (3D Cu-LiSn-Li) are achieved. Alloyed tin, as the bridge between the porous copper substrate and metallic Li, plays a critical role in optimizing Li nucleation and enhancing the fast lithium migration kinetics. This work demonstrates that lithiophilic binary copper alloys are an effective way to achieve room-temperature high rate performance and satisfied low-temperature cycling stability for Li metal batteries.

Superstable potassium metal batteries with a controllable internal electric field

Stable potassium metal batteries (PMBs) are promising candidates for electrical energy storage due to their ability to reversibly store electrical energy at a low cost. However, dendritic growth and large volume changes hinder their practical application. Here, referring to the morphology and structure of a virus, a bionic virus-like-carbon microsphere (BVC) was designed as the anode host for a PMB. A BVC with a three-dimensional structure can not only control the electric field, which can suppress dendrite formation, but can also provide a larger space to accommodate the volume change during the cycle progress. The designed potassium (K) metal anode exhibits excellent cycle life and stability (during 1800 h of repeated plating/stripping of K at a current density of 0.1 mA cm-2, K-BVC can realize a very stable K metal anode with low voltage hysteresis). Stable cyclability and improved rate capability can be realized in a full cell using Prussian blue over 400 cycles. This research provides a new idea for the development of stable K metal anodes and may pave the way for the practical application of next-generation metal batteries.

A Highly-Lithiophilic Mn3O4/ZnO-Modified Carbon Nanotube Film for Dendrite-Free Lithium Metal Anodes

Lithium metal anode is deemed as a potential candidate for high energy density batteries, which has attracted increasing attention. Unfortunately, Li metal anode suffers from issues such as dendrite grown and volume expansion during cycling, which hinders its commercialization. Herein, we designed a porous and flexible self-supporting film comprising of single-walled carbon nanotube (SWCNT) modified with a highly-lithiophilic heterostructure (Mn₃O₄/ZnO@SWCNT) as the host material for Li metal anodes. The p-n-type heterojunction constructed by Mn₃O₄ and ZnO generates a built-in electric field that facilitates electron transfer and Li⁺ migration. Additionally, the lithiophilic Mn₃O₄/ZnO particles serve as the pre-implanted nucleation sites, dramatically reducing the lithium nucleation barrier due to their strong binding energy with lithium atoms. Moreover, the interwoven SWCNT conductive network effectively lowers the local current density and alleviates the tremendous volume expansion during cycling. Thanks to the aforementioned synergy, the symmetric cell composed of Mn₃O₄/ZnO@SWCNT-Li can stably maintain a low potential for more than 2500 h at 1 mA cm^-2 and 1 mAh cm^-2. Furthermore, the Li-S full battery composed of Mn₃O₄/ZnO@SWCNT-Li also shows excellent cycle stability. These results demonstrate that Mn₃O₄/ZnO@SWCNT has great potential as a dendrite-free Li metal host material.

Molten salt synthesis of NiCo-NiCo2O4@C nanotubes as anode materials for Li-ion batteries

The construction of carbon-encapsulated transition metal nanotube structures is a preferred method that can effectively slow down volume expansion, improve cycling stability and enhance the electrical conductivity of the reactive sites of lithium-ion batteries. In this study, nanotubes of carbon-coated NiCo-NiCo₂O₄ nanoparticles (NC-NCO@C) were prepared by a one-step molten salt method at high temperature using Ni and Co as catalytic centers and sodium acetate as carbon source. We used NC-NCO@C-2 nanotubes as anode materials for lithium-ion batteries(LIBs), which exhibited excellent lithium storage performance and good stability, with a specific capacity of 616.26 mAh g^-1 after 1000 cycles at a high current density of 1 A g^-1. In addition, NC-NCO@C-2 were used as anodes in lithium-ion full cells and LiFePO₄ (LFP) was used as the cathode. The NC-NCO@C-2//LFP full-cell exhibits high capacity and good cycling stability, with a capacity of 100.7 mAh g^-1 after 100 cycles and a capacity retention rate of 92%. The construction of NC, NCO, and carbon ternary complexes was found to activate and promote the reversible conversion of certain inorganic components at the solid electrolyte interfaces (SEI), which effectively reduced the volume change during cycling, increased the electrical conductivity, and improved the cycling stability of the electrode. The proposed one-step molten salt synthesis of Carbon-coated metals complexes with excellent compatibility characteristics, is expected to solve the problem of volume change in transition metals, which is encountered in LIBs applications.

Nanoarray Architecture of Ultra-Lithiophilic Metal Nitrides for Stable Lithium Metal Anodes

Lithium metal anode (LMA) is puzzled by the serious issues corresponding to infinite volume change and notorious lithium dendrite during long-term stripping/plating process. Herein, the transition metal nitrides array with outstanding lithiophilicity, including CoN, VN, and Ni₃ N, are decorated onto carbon framework as "nests" to uniform Li nucleation and guide Li metal deposition. These transition metal nitrides with excellent conductivity can guarantee the fast electron transport, therefore maintain a stable interface for Li reduction. In addition, the designed multi-dimensional structure of metal nitride array decorated carbon framework can effectively regulate the growth of Li metal during the stripping/plating process. Of note, attributing to the lattice-matching between CoN and Li metal, the composite Li/CoN@CF anode exhibits ultra-stable cycling performance in symmetrical cells (over 4000 h@1 mA cm^-2 with 1 mAh cm^-2 and 1000h@20 mA cm^-2 with 20 mAh cm^-2 ). The assembled full cells based on Li/CoN@CF composite anode, LiFePO₄ or S as cathodes, deliver excellent cycling stability and rate capability. This strategy provides an effective approach to develop a stable lithium metal anode for lithium metal batteries.

Thermal-Stable Separators: Design Principles and Strategies Towards Safe Lithium-Ion Battery Operations

Lithium-ion batteries (LIBs) are momentous energy storage devices, which have been rapidly developed due to their high energy density, long lifetime, and low self-discharge rate. However, the frequent occurrence of fire accidents in laptops, electric vehicles, and mobile phones caused by thermal runaway of the inside batteries constantly reminds us of the urgency in pursuing high-safety LIBs with high performance. To this end, this Review surveyed the state-of-the-art developments of high-temperature-resistant separators for highly safe LIBs with excellent electrochemical performance. Firstly, the basic properties of separators (e. g., thickness, porosity, pore size, wettability, mechanical strength, and thermal stability) in constructing commercialized LIBs were introduced. Secondly, the working mechanisms of advanced separators with different melting points acting in the thermal runaway stage were discussed in terms of improving battery safety. Thirdly, rational design strategies for constructing high-temperature-resistant separators for LIBs with high safety were summarized and discussed, including graft modification, blend modification, and multilayer composite modification strategies. Finally, the current obstacles and future research directions in the field of high-temperature-resistant separators were highlighted. These design ideas are expected to be applied to other types of high-temperature-resistant energy storage systems working under extreme conditions.

Advances in Nanofibrous Materials for Stable Lithium-Metal Anodes

Lithium metal is regarded as the most potential anode material for improving the energy density of batteries due to its high specific capacity and low electrode potential. However, the practical application of lithium-metal anodes (LMAs) still faces severe challenges such as uncontrollable dendrites growth and large volume expansion. The development of functional nanomaterials has brought opportunities for the revival of LMAs. Among them, nanofibrous materials show great application potential for LMAs protection due to their distinct functional and structural features. Here, the latest research progress in nanofibrous materials for LMAs is systematically outlined. First, the problems existing in the practical application of LMAs are analyzed. Then, prospective strategies and recent research progress toward stable LMAs based on nanofibrous materials are summarized from the aspects of artificial protective layers, three-dimensional frameworks, separators, and solid-state electrolytes. Finally, the future development of nanofibrous materials for the protection of lithium-metal batteries is summarized and prospected. This review establishes a close connection between nanofibrous materials and LMA modification and provides insight for the development of high-safety lithium-metal batteries.

Spatially Confined Li Growth on Honeycomb-like Lithiophilic Layered Double Hydroxide Nanosheet Arrays toward a Stable Li Metal Anode

A lithium metal anode (LMA) is appealing due to its high theoretical capacity and low electrochemical potential. Unfortunately, the practical application of LMAs is restricted by the uncontrollable Li dendrite growth and tremendous volume change. Herein, lithiophilic honeycomb-like layered double hydroxide (LDH) nanosheet arrays supported on a flexible carbon cloth (NiMn-LDHs NAs@CC) are synthesized as the Li host to spatially confine the Li deposition, guiding Li growth via a conformal and uniform manner. First, the lithiophilic NiMn-LDHs NAs as nucleation seeds render the CC substance outstanding lithiophilicity and reduce the nucleation barrier. The hierarchical honeycomb-like structure then directs the oriented Li deposition and provides an open channel for fast ion transport. Finally, the CC skeleton offers a high specific surface for decreasing the inhomogeneous distribution of the current density and enough space for alleviating the volume variations, synergistically inhibiting the dendritic Li growth. As a consequence, the NiMn-LDHs NAs@CC symmetric cell exhibits a low overpotential of less than 17 mV at 2 mA cm^-2 and a long lifespan of 2100 h at 3 mA cm^-2. In addition, when paired with the LiNiCoMnO₂ (NCM111) cathode, the NiMn-LDHs NAs@CC@Li full cell presents enhanced cycling stability and rate capability in comparison to the CC@Li full cell, implying the great potential of the NiMn-LDHs NAs@CC in stabilizing the LMA.

N,S-Doped Porous Carbon Nanobelts Embedded with MoS2 Nanosheets as a Self-Standing Host for Dendrite-Free Li Metal Anodes

Metallic Li is one of the most promising anodes for high-energy secondary batteries. However, the enormous volume changes and severe dendrite formation during the Li plating/stripping process hinder the practical application of Li metal anodes (LMAs). We have developed a sulfate-assisted strategy to synthesize a self-standing host composed of N,S-doped porous carbon nanobelts embedded with MoS2 nanosheets (MoS2 @NSPCB) for use in LMAs. In situ measurements and theoretical calculations reveal that the uniformly distributed MoS2 derivatives within the carbon nanobelts serve as stable lithiophilic sites which effectively homogenize Li nucleation and suppress dendrite formation. In addition, the hierarchical porosity and 3D nanobelt networks ensure fast Li-ion diffusion and accommodate the volume change of Li deposits during the plating/stripping process. As a result, a Li-Li symmetric cell using the MoS2 @NSPCB host operates steadily over 1500 h with an ultralow voltage hysteresis (≈24.2 mV) at 3 mA cm-2 /3 mAh cm-2 . When paired with a LiFePO4 cathode, the current collector-free LMA endows the full cell with a high energy density of 460 Wh kg-1 and good cycling performance (with a capacity retention of ≈70% even after 1600 cycles at 10 C).

Pomegranate-Inspired Graphene Parcel Enables High-Performance Dendrite-Free Lithium Metal Anodes

Uncontrolled lithium dendrites seriously hinder the commercialization of lithium metal batteries in comparison to the durable lithium-ion batteries. Herein, inspired by squashy pomegranate structure, a novel loading strategy of metallic lithium (Li) is introduced to construct dendrite-free Li metal anodes through porous reduced graphene oxide/Au (PRGO/Au) composite microrods (MRs) as unique storage parcels. The abundant internal voids and robust host structure are capable of achieving high mass loading of Li metal and effectively alleviating the conceivable volume change during cycling, accompanied by the preferential selective plating/stripping of Li inside the graphene-based MRs with the embedded Au nanonuclei. As a result, the obtained PRGO/Au-Li anodes deliver a long-lifespan stable cycling up to 600 h with a high specific capacity of ≈2140 mA h g^-1 and voltage hysteresis as low as 20 mV in the absence of dendrites. The assembled full cells exhibit excellent rate capability and cycling stability. This work provides an alternative strategy to construct advanced high-energy-density lithium batteries via the unique 1D bioinspired graphene-based packaging strategy.

Modulating SEI formation via tuning the solvation sheath for lithium metal batteries

The solvation sheath of Li⁺-glyme was modulated to enhance Li⁺-TFSI^- association by adopting a highly polar solvent, especially water molecules, which affects the solid electrolyte interface (SEI) layer composition. By the Li⁺-TFSI^- association, a TFSI^- anion-derived SEI layer is formed on the Li metal anode, resulting in higher Li metal anode efficiency.

Achieving Electronic Engineering of Vanadium Oxide-Based 3D Lithiophilic Sandwiched-Aerogel Framework for Ultrastable Lithium Metal Batteries

Lithium (Li) metal is one of the most promising anode materials for the next-generation batteries, which owns superior specific capacity and energy density. Unfortunately, lithium dendrites that is formed during the charging/discharging process tends to induce capacity degradation and thus short lifespan. In this study, the vanadium oxide (V2O5) and nitrogen-doped vanadium oxide (N-V2O3, N-VO0.9)-modified three-dimensional (3D) reduced graphene oxide ((N)-VOx@rGO) with tunable electronic properties are demonstrated to enable the dendrite-free Li deposition. The soft lithiophilic rGO as the scaffold can provide sufficient void space for Li storage. Meanwhile, the rigid (N)-VOx uniformly anchored on rGO can perfectly maintain the 3D structure, which is crucial for Li to enter the inner space of the 3D framework. Consequently, the (N)-VOx@rGO electrodes achieve dendrite-free electrodeposition under the multifarious deposition capacity and current densities. Compared with the bare lithium electrodes, the asymmetrical cells of (N)-VOx@rGO anode can cycle stably up to 400 h at 2 mA cm-2 current density, together with a low nucleation overpotential of ∼20 mV.

Built-In Stable Lithiophilic Sites in 3D Current Collectors for Dendrite Free Li Metal Electrode

Stable lithiophilic sites in 3D current collectors are the key to guiding the uniform Li deposition and thus suppressing the Li dendrite growth, but such sites created by the conventional surface decoration method are easy to be consumed along with cycling. In this work, carbon fiber (CF)-based 3D porous networks with built-in lithiophilic sites that are stable upon cycling are demonstrated. Such heterostructured architecture is constructed by the introduction of zeolitic imidazolate framework-8-based nanoparticles during the formation of the 3D fibrous carbonaceous network and the following annealing. The introduced Zn species are found to be re-distributed along the entire individual CF in the 3D network, and function as lithiophilic sites that favor the homogenous lithium nucleation and growth. The 3D network also presents a multi-scale porous structure that improves the space utilization of the host. The corresponding symmetric cells adopting such 3D anode demonstrate excellent cycling performance, especially at a high rate (300 cycles at 10 mA cm^-2 with a capacity of 5 mA h cm^-2 ). A full cell with LiFePO₄ cathode shows a capacity retention of 98% after cycling at 1C for 300 cycles. This method provides an effective design strategy for 3D hosting electrodes in dendrite-free alkali metal anode applications.

Atomically Dispersed Cu in Zeolitic Imidazolate Framework Nanoflake Array for Dendrite-Free Zn Metal Anode

Aqueous Zn metal batteries (AZMBs) have been considered as a promising alternative to the existing Li-ion batteries. Nevertheless, the large-scale application of the AZMBs is restricted by the dendrite formation and side reactions within the Zn metal anodes (ZMAs) during cycling. Herein, an atomically dispersed Cu in leaf-like Zn-coordinated zeolitic imidazolate framework (ZIF-L) nanoflakes on Ti mesh (CuZIF-L@TM) as ZMA host is developed. The 3D conductive network formed by the interconnected ZIF-L nanoflakes can reduce the local current density and homogenize the electric field distribution. Moreover, experimental data and theoretical calculations reveal the Cu single atoms within the ZIF-L can serve as the zincophilic sites to facilitate the Zn deposition. As expected, the CuZIF-L@TM host enables a homogeneous Zn deposition on the surface without dendrites. The resultant CuZIF-L@TM/Zn electrode shows stable Zn plating/stripping over 1100 h at 1 mA cm^-2 with a low voltage hysteresis of about 50 mV. As a proof of concept, a full cell based on the designed CuZIF-L@TM/Zn anode shows a stable cycling performance over 1000 cycles.

Electrospun Nanofibers for Integrated Sensing, Storage, and Computing Applications

Electrospun nanofibers have become the most promising building blocks for future high-performance electronic devices because of the advantages of larger specific surface area, higher porosity, more flexibility, and stronger mechanical strength over conventional film-based materials. Moreover, along with the properties of ease of fabrication and cost-effectiveness, a broad range of applications based on nanomaterials by electrospinning have sprung up. In this review, we aim to summarize basic principles, influence factors, and advanced methods of electrospinning to produce hundreds of nanofibers with different structures and arrangements. In addition, electrospun nanofiber based electronics composed of both two-terminal and three-terminal devices and their practical applications are discussed in the fields of sensing, storage, and computing, which give rise to the further integration to realize a comprehensive and brain-like system. Last but not least, the emulation of biological synapses through artificial synaptic transistors and additionally optoelectronics in recent years are included as an important step toward the construction of large-scale, multifunctional systems.

Confined Co9S8 nanocrystals into N/S-Co-doped carbon nanofibers as a chainmail-like electrocatalyst for high-performance lithium-sulfur batteries with high sulfur loading

Accelerating phase transposition efficiency of lithium polysulfides (LiPSs) to L₂S and hampering the solution of LiPSs are the keys to stabilizing lithium-sulfur (Li-S) batteries. Hence, the sulfiphilic ultrafine Co₉S₈ nanoparticles embedded lithiophilic N, S co-doping carbon nanofibers (Co₉S₈/NSCNF) are prepared via the dual-template method, which are then used as sulfur host in Li-S batteries. Particularly, the double active sites (Co₉S₈ and N, S) in Co₉S₈/NSCNF are prone to form "Co-S", "Li-O" or "Li-N" bonds, and then simultaneously improving the chemisorption and interface transposition capability of LiPSs. In case of the S@ Co₉S₈/NSCNF composites with high sulfur loading of 89% are employed as cathode, the cell possesses optimized "sulfiphilicity" and "lithiophilicity", which achieves remarkable sulfur electrochemistry, including outstanding reversibility of 816.8mAhg^-1 over 500 cycles at 1.0C, excellent rate property of 742.2mAhg^-1at 5.0C, and long-term cycling with a low attenuation of 0.011% per cycle over 1800 cycles at 3.0C. Impressively, a remarkable areal capacity of 11.51mAhcm^-2 is retained under the sulfur loading of 15.3 mg cm^-2 for 50 cycles. This research will deepen the understanding of the complex LiPSs interface transposition procedure and provide new ideas for the design of new host materials.

Using Metal Cation to Control the Microstructure of Cobalt Oxide in Energy Conversion and Storage Applications

Herein, a facile and efficient synthesis of microstructured Co₃ O₄ for both supercapacitor and water-splitting applications is reported. Metal cations (Fe³⁺ , Cu²⁺ ) serve as structure-directing agents regulating the structure of Co compounds, which are subsequently annealed to yield Co₃ O₄ . Detailed characterizations and density functional theory (DFT) calculations reveal that the in situ Cl-doping introduces oxygen defects and provides abundant electroactive sites, and narrows the bandgap, which enhances the electron excitation of the as-formed Co₃ O₄ . The as-prepared Cl-doped Co₃ O₄ hierarchical nanospheres (Cl-Co₃ O₄ -h) display a high specific capacitance of 1629 F g^-1 at 1 A g^-1 as an electrode for supercapacitors, with excellent rate capability and cyclability. The Cl-Co₃ O₄ -h//activated carbon (AC) asymmetric supercapacitor (ASC) electrode achieves a specific capacitance of 237 F g^-1 at 1 A g^-1 , with an energy density of 74 Wh kg^-1 at a power density of 807 W kg^-1 and even maintains 47 Wh kg^-1 at the higher-power density of 24.2 kW kg^-1 . An integrated electrolyzer for water-splitting with Cl-Co₃ O₄ -h as both cathode and anode can be driven by Cl-Co₃ O₄ -h//AC ASC. The electrolyzer provides a high current density of 35 mA cm^-2 at a cell voltage of 1.6 V, with good current density retention over 50 h.

Lithium-Sulfur Batteries Meet Electrospinning: Recent Advances and the Key Parameters for High Gravimetric and Volume Energy Density

Lithium-sulfur (Li-S) batteries have been regarded as a promising next-generation energy storage technology for their ultrahigh theoretical energy density compared with those of the traditional lithium-ion batteries. However, the practical applications of Li-S batteries are still blocked by notorious problems such as the shuttle effect and the uncontrollable growth of lithium dendrites. Recently, the rapid development of electrospinning technology provides reliable methods in preparing flexible nanofibers materials and is widely applied to Li-S batteries serving as hosts, interlayers, and separators, which are considered as a promising strategy to achieve high energy density flexible Li-S batteries. In this review, a fundamental introduction of electrospinning technology and multifarious electrospinning-based nanofibers used in flexible Li-S batteries are presented. More importantly, crucial parameters of specific capacity, electrolyte/sulfur (E/S) ratio, sulfur loading, and cathode tap density are emphasized based on the proposed mathematic model, in which the electrospinning-based nanofibers are used as important components in Li-S batteries to achieve high gravimetric (WG ) and volume (WV ) energy density of 500 Wh kg-1 and 700 Wh L-1 , respectively. These systematic summaries not only provide the principles in nanofiber-based electrode design but also propose enlightening directions for the commercialized Li-S batteries with high WG and WV .

A Designed Lithiophilic Carbon Channel on Separator to Regulate Lithium Deposition Behavior

Issues with unstable SEI formation and uncontrollable lithium dendrite growth impede the practical use of lithium anode in high-energy batteries. Herein, a lithiophilic carbon channel on separator is designed to regulate lithium deposition behavior. The designed channel is formed by carbon nanosheet with cubic cavity (CNCC) prepared by hard template method. The CNCC with a large specific surface area and good electrolyte wettability can effectively reduce the local current density. Besides, the CNCC coated separator with high Young's modulus can mechanically inhibit the growth of lithium dendrites. Notably, CNCC coating can become lithiophilic during lithium plating/striping process, which is beneficial for homogeneous lithium deposition and low lithium nucleation overpotential. As a result, based on the CNCC coated separator, the symmetric Li|Li cell cycle over 2600h at 6 mA cm^-2 for 2 mAh cm^-2 , while the Li|Cu cell reaches average Coulombic efficiency of 98.5% at 2 mA cm^-2 for 2 mAh cm^-2 .

Formation of Super-Assembled TiOx /Zn/N-Doped Carbon Inverse Opal Towards Dendrite-Free Zn Anodes

Uncontrolled growth of Zn dendrites and side reactions are the major restrictions for the commercialization of Zn metal anodes. Herein, we develop a TiO_x /Zn/N-doped carbon inverse opal (denoted as TZNC IO) host to regulate the Zn deposition. Amorphous TiO_x and Zn/N-doped carbon can serve as the zincophilic nucleation sites to prevent the parasitic reactions. More importantly, the highly ordered IO host homogenizes the local current density and electric field to stabilize Zn deposition. Furthermore, the three-dimensional open networks could regulate Zn ion flux to enable stable cycling performance at large current densities. Owing to the abundant zincophilic sites and the open structure, granular Zn deposits could be realized. As expected, the TZNC IO host guarantees the steady Zn plating/stripping with a long-term stability over 450 h at the current density of 1 mA cm^-2 . As a proof-of-concept demonstration, a TZNC@Zn||V₂ O₅ full cell shows long lifespan over 2000 cycles at 5.0 A g^-1 .

Facile fabrication of Fe/Fe3C embedded in N-doped carbon nanofiber for efficient degradation of tetracycline via peroxymonosulfate activation: Role of superoxide radical and singlet oxygen

The toxic metal ions leaching and metal nanoparticles agglomeration were the critical issues for metal-based carbon materials during the peroxymonosulfate (PMS) activation processes. Herein, a facile strategy was first proposed that zero-dimensional Fe/Fe₃C nanoparticles were embedded in one-dimensional N-doped carbon nanofiber (Fe/Fe₃C@NCNF) to solve the above challenges. The as-obtained Fe/Fe₃C@NCNF-800 possessed a low E_a value (11.7 kJ/mol) and exhibited high activity for activating PMS to degrade tetracycline (TC) in a wide range of pH 3-11. As expected, the iron ions leaching concentration of Fe/Fe₃C@NCNF-800 was very low (0.082 mg/L). Meanwhile, the Fe/Fe₃C@NCNF-800 was easily recovered from the reaction solution due to its magnetic properties. Both superoxide radicals (O₂^∙-) and non-radical of singlet oxygen (¹O₂) were the primary reactive oxygen species (ROS) in the Fe/Fe₃C@NCNF-800/PMS system via quenching tests and electron spin resonance spectroscopy (ESR). The catalytic mechanism suggested that the Fe/Fe₃C and graphitic N were the main active sites in the Fe/Fe₃C@NCNF-800 for PMS activation. This work provided a facile method for the preparation of Fe-based carbon materials with high catalytic ability, low metal leaching and easy recycling, showing a broad prospect for environmental applications.

Polymer Zwitterion-Based Artificial Interphase Layers for Stable Lithium Metal Anodes

Lithium (Li) metal batteries are promising future rechargeable batteries with high-energy density as the Li metal anode (LMA) possesses a high specific capacity and the lowest potential. However, the commercial application of the LMA has been hindered by a low Coulombic efficiency and dendrite growth, which are related to the unstable interphase with poor Li⁺ ion transport. Herein, we report novel polymer zwitterion-based artificial interphase layers (AILs) with improved Li⁺ ion transport and high stability for long-life LMAs. Benefitting from the unique zwitterion effect within the polymer zwitterion-based AILs, a high Li⁺ ion transference number (0.81) and a good ionic conductivity (0.75 × 10^-4 S cm^-1) can be realized simultaneously at the interface. By regulating the weight ratio of the sulfonate group and the phosphate group in polymer zwitterion-based AILs, the modified LMA enables long-term Li plating/stripping for 1400 h at 1 mA cm^-2 and stable cycling in a full cell. This interfacial engineering concept could shed light on the development of safe LMAs.

Boosting the K+-adsorption capacity in edge-nitrogen doped hierarchically porous carbon spheres for ultrastable potassium ion battery anodes

Although carbon materials have great potential for potassium ion battery (KIB) anodes due to their structural stability and abundant carbon-containing resources, the limited K⁺-intercalated capacity impedes their extensive applications in energy storage devices. Current research studies focus on improving the surface-induced capacitive behavior to boost the potassium storage capacity of carbon materials. Herein, we designed edge-nitrogen (pyridinic-N and pyrrolic-N) doped carbon spheres with a hierarchically porous structure to achieve high potassium storage properties. The electrochemical tests confirmed that the edge-nitrogen induced active sites were conducive for the adsorption of K⁺, and the hierarchical porous structure promoted the generation of stable solid electrolyte interphase (SEI) films, both of which endow the resulting materials with a high reversible capacity of 381.7 mA h g^-1 at 0.1 A g^-1 over 200 cycles and an excellent rate capability of 178.2 mA h g^-1 at 5 A g^-1. Even at 5 A g^-1, the long-term cycling stability of 5000 cycles was achieved with a reversible capacity of 190.1 mA h g^-1. This work contributes to deeply understand the role of the synergistic effect of edge-nitrogen induced active sites and the hierarchical porous structure in the potassium storage performances of carbon materials.

Fiber Surface/Interfacial Engineering on Wearable Electronics

Surface/interfacial engineering is an essential technique to explore the fiber materials properties and fulfil new functionalities. An extensive scope of current physical and chemical treating methods is reviewed here together with a variety of real-world applications. Moreover, a new surface/interface engineering approach is also introduced: self-assembly via π-π stacking, which has great potential for the surface modification of fiber materials due to its nondestructive working principle. A new fiber family member, metal-oxide framework (MOF) fiber shows promising candidacy for fiber based wearable electronics. The understanding of surface/interfacial engineering techniques on fiber materials is advanced here and it is expected to guide the rational design of future fiber based wearable electronics.

Rational Design of the Lotus-Like N-Co2 VO4 -Co Heterostructures with Well-Defined Interfaces in Suppressing the Shuttle Effect and Dendrite Growth in Lithium-Sulfur Batteries

The shuttle effect caused by soluble lithium polysulfides (LiPSs) and intrinsic slow electrochemical transformation from LiPSs to Li₂ S/Li₂ S₂ will induce undesirable cycling performance, which is the primary obstruct limiting the practical applications of lithium-sulfur (Li-S) batteries. Here a convenient method is designed to fabricate the 2D louts-like N-Co₂ VO₄ -Co heterostructures with well-abundant interfaces and oxygen vacancies (V_o ), endowing the materials with both "sulfiphilic" and "lithiophilic" features. When employed as the modification layer coated on commercial Celgard 2400 separator, the as-prepared N-Co₂ VO₄ -Co/PP with synergistic adsorption-electrocatalysis effects achieves desirable sulfur electrochemistry, thus showing a high initial discharge capacity of 1466.4 mAh g^-1 at 0.1 C and stable cycle life with a fade rate of 0.03% per cycle over 1000 cycle at 3.0 C. Moreover, a superior areal capacity of 12.84 mAh cm^-2 is preserved under high sulfur loading of 14.3 mg cm^-2 .

Flexible electrodes with high areal capacity based on electrospun fiber mats

The ever-growing portable, flexible, and wearable devices impose new requirements from power sources. In contrast to gravitational metrics, areal metrics are more reliable performance indicators of energy storage systems for portable and wearable devices. For energy storage devices with high areal metrics, a high mass loading of the active species is generally required, which imposes formidable challenges on the current electrode fabrication technology. In this regard, integrated electrodes made by electrospinning technology have attracted increasing attention due to their high controllability, excellent mechanical strength, and flexibility. In addition, electrospun electrodes avoid the use of current collectors, conductive additives, and polymer binders, which can essentially increase the content of the active species in the electrodes as well as reduce the unnecessary physically contacted interfaces. In this review, the electrospinning technology for fabricating flexible and high areal capacity electrodes is first highlighted by comparing with the typical methods for this purpose. Then, the principles of electrospinning technology and the recent progress of electrospun electrodes with high areal capacity and flexibility are elaborately discussed. Finally, we address the future perspectives for the construction of high areal capacity electrodes using electrospinning technology to meet the increasing demands of flexible energy storage systems.

Uniform Deposition and Effective Confinement of Lithium in Three-Dimensional Interconnected Microchannels for Stable Lithium Metal Anodes

Lithium dendrite formation has hindered the practical implementation of lithium metal batteries with higher energy densities compared with those of conventional lithium-ion batteries. Herein, a nanoconfinement strategy to access dendrite-free lithium metal anodes comprising three-dimensional (3D) hollow porous multi-nanochannel carbon fiber embedded with TiO₂ nanocrystals (HTCNF) is reported. The transport of the lithium ions is facilitated by the 3D architecture. Functioning as nanoseeds, the TiO₂ nanocrystals guide the lithium ions toward forming uniform deposits, which are further confined inside the hollow carbon fibers and the 3D HTCNF layer. Site-selective deposition coupled with the nanoconfinement of lithium metal modifies the Li plating/stripping behavior and effectively suppresses the dendrite growth. The HTCNF-Li cell delivers a stable cycling performance of 1300 h with a voltage hysteresis as low as 6 mV. The assembled HTCNF-Li//LiFePO₄ full cell displays a compelling rate performance and enhanced cycling stability with high capacity retention (90% after 400 cycles at 0.5 C). Our results demonstrate a new and potentially scalable route to resolve the lithium dendrite growth issue for enhanced electrochemical performances, which can be further extended to other metal battery systems.

Confining Nano-GeP in Nitrogenous Hollow Carbon Fibers toward Flexible and High-Performance Lithium-Ion Batteries

Although graphite has been used as anodes of lithium-ion batteries (LiBs) for 30 years, its unsatisfactory energy density makes it insufficient toward some new electronic products such as unmanned aerial vehicles. Herein, in situ synthesis of nano-GeP confined in nitrogen-doped carbon (GeP@NC) fibers was designed and performed via coaxial electrospinning followed by a phosphating process. This way ensured the paper-like GeP@NC-x electrode with high conductivity, high flexibility, and lightweight properties, which simultaneously solved the key scientific problems of difficulty in structural design and severe volume expansion of GeP. The inner diameter and wall thickness of the nanofibers can be effectively controlled by adjusting the size of electrospinning needles. It was suggested that the fibers not only effectively inhibited the growth of GeP, resulting in the synthesis of nano-GeP with size less than 50 nm, but also alleviated the volume expansion/agglomeration and improved the diffusion kinetics of Li⁺ in nano-GeP during cycling. The Li⁺ diffusion coefficient can be improved by reducing the inner diameter and wall thickness of the fibers. As a model system, the paper-like electrode (GeP@NC-2) with a fiber diameter of 280 nm and a wall thickness of 110 nm exhibited the best electrochemical performance. When applied as anodes in LiBs, it displayed a reversible capacity of 612 mAh g^-1 at the 600th cycle at 1 A g^-1, while GeP@NC-0 with a solid structure only delivered 239 mAh g^-1. Furthermore, the GeP@NC-2 also exhibited good long-term cycling stability at 5 A g^-1, and the capacity displayed a slight difference of 221.2 and 209.0 mAh g^-1 in a voltage range of 0∼3 V and 0∼1.5 V, respectively. The well-defined synthetic approach combined with unique nanostructural design provided a meaningful reference for the rational design and development of next-generation flexible and high-performance LiB anodes.

Rational Design and Engineering of One-Dimensional Hollow Nanostructures for Efficient Electrochemical Energy Storage

The unique structural characteristics of one-dimensional (1D) hollow nanostructures result in intriguing physicochemical properties and wide applications, especially for electrochemical energy storage applications. In this Minireview, we give an overview of recent developments in the rational design and engineering of various kinds of 1D hollow nanostructures with well-designed architectures, structural/compositional complexity, controllable morphologies, and enhanced electrochemical properties for different kinds of electrochemical energy storage applications (i.e. lithium-ion batteries, sodium-ion batteries, lithium-sulfur batteries, lithium-selenium sulfur batteries, lithium metal anodes, metal-air batteries, supercapacitors). We conclude with prospects on some critical challenges and possible future research directions in this field. It is anticipated that further innovative studies on the structural and compositional design of functional 1D nanostructured electrodes for energy storage applications will be stimulated.

Stabilizing Na metal anode with NaF interface on spent cathode carbon from aluminum electrolysis

We report the synthesis of spent cathode carbon (SCC) with a NaF interface from aluminum electrolysis, and its application as a Na metal anode host. The SCC anode exhibits superior ion conductivity and a high shear modulus. The natural NaF interface on the SCC anode can regulate Na+ transmission and inhibit dendrite growth. Furthermore, the anode can be used to turn waste into treasure through directly using spent cathodic carbon without any chemical processing. The green SCC electrode exhibits a higher flat voltage and better reversibility compared with purified cathode carbon without NaF.