Aqueous Chloride-Ion Battery within a Neutral Electrolyte Based on a CoFe-Cl Layered Double Hydroxide Anode

Aqueous chloride-ion batteries (ACIBs) with environmental friendliness and high safety hold great potential to fulfill the green energy demand for ocean desalination. Herein, for the first time, a composite consisting of Cl--intercalated CoFe layered double hydroxides (CoFe-Cl-LDH) cross-linked with CNTs (CoFe-Cl-LDH/CNT) is synthesized and demonstrated to be a novel high-performance anode for ACIBs in a neutral NaCl aqueous solution. While exhibiting a high initial capacity of ∼190 mAh g-1 at 200 mA g-1, CoFe-Cl-LDH/CNT is capable of delivering a reversible capacity of ∼125 mAh g-1 after 200 cycles. At a high current density of 400 mA g-1, it still holds a capacity of ∼120 mAh g-1. The excellent Cl- storage performance can be contributed to the unique topochemical transformation feature that reverses intercalation/deintercalation of Cl- along with valence changes of Co2+/Co3+ and Fe2+/Fe3+ during charge/discharge and the improved electronic conductivity by hybridizing with CNTs. It is interesting that the invertible insertion/extraction of interlayer H2O was discovered, which could be beneficial to the capacity after cycles to a certain extent. The Cl--intercalated LDH material declared in this work shows its feasibility on Cl- capture/release in aqueous anion-type batteries and provides a new opportunity for future development of ACIBs or aqueous desalination technology.

A Potential Polycarbonyl Polyimide as Anode Material for Lithium-Ion Batteries

Organic polymers have been considered reliable candidates for lithium storage due to their high capacity and lack of volume expansion. Compared with other organic polymers, polyimide has become a very promising electrode material for lithium-ion batteries (LIBs) because of its easy synthesis, customizable structure and structural stability. A large number of studies have confirmed that the benzene ring structure of polyimide has strong lithium storage capacity as an anode material. Hence, we designed and synthesized polyimide organic polymer (PBPAQ) for the first time. The unique spherical flower structure of this material enhances the interaction between the electrode material and the electrolyte by increasing the contact area. The PBPAQ anode has a specific discharge capacity of 738 mAh g-1 after 100 cycles at 0.1 A g-1 . The excellent lithium storage performance of this material laid a foundation for the research of the anode of LIBs in the future.

Bio-Based Binder Development for Lithium-Ion Batteries

The development of rechargeable lithium-ion battery (LIB) technology has facilitated the shift toward electric vehicles and grid storage solutions. This technology is currently undergoing significant development to meet industrial applications for portable electronics and provide our society with "greener" electricity. The large increase in LIB production following the growing demand from the automotive sector has led to the establishment of gigafactories worldwide, thus increasing the substantial consumption of fossil-based and non-sustainable materials, such as polyvinylidene fluoride and/or styrene-butadiene rubber as binders in cathode and anode formulations. Furthermore, the use of raw resources, such as Li, Ni, and Mn in cathode active materials and graphite and nanosilicon in anodes, necessitates further efforts to enhance battery efficiency. To foster a global sustainable transition in LIB manufacturing and reduce reliance on non-sustainable materials, the implementation of bio-based binder solutions for electrodes in LIBs is crucial. Bio-based binders such as cellulose, lignin, alginate, gums, starch, and others can address environmental concerns and can enhance LIBs' performance. This review aims to provide an overview of the current progress in the development and application of bio-based binders for LIB electrode manufacturing, highlighting their significance toward sustainable development.

Body Armor-Inspired Double-Wrapped Binder with High Energy Dispersion for a Stable SiOx Anode

The high specific capacity and relatively low volume expansion of silicon suboxide (SiO_x) highlight its potential as one of the most promising anode materials for lithium-ion batteries. Nevertheless, the traditional binder of polyacrylic acid (PAA) still cannot adapt to enormous stress during the repeated volume expansion/contraction owing to its intrinsic rigid backbone. Inspired by the "soft and hard composite body armor", we herein design a double-wrapped binder consisting of PAA with a high internal Young's modulus (hard part) and polyurethane (DOU) with a low external Young's modulus (soft part). When the SiO_x particle expands during lithiation, the rigid PAA firstly accommodates the volume change to dissipate most of the inner stress, and the elastic DOU with triple dynamic bonds serves as a buffer layer to absorb the residual stress via the breakage/formation of dynamic bonds. By optimizing the PAA/DOU ratio, the SiO_x anode can maintain the integrity during long-term cycling and deliver a relatively high reversible capacity of 1064.1 mAh g^-1 with a preeminent capacity retention of 83.7% at 0.5C after 300 cycles. Such a double-wrapped binder can provide a novel design strategy for multicomponent functional polymer binders toward high-performance SiO_x anodes.

High-Performance Alkali Metal Ion Storage in Bi2Se3 Enabled by Suppression of Polyselenide Shuttling Through Intrinsic Sb-Substitution Engineering

Bismuth selenide holds great promise as a kind of conversion-alloying-type anode material for alkali metal ion storage because of its layered structure with large interlayer spacing and high theoretical specific capacity. Nonetheless, its commercial development has been significantly hammered by the poor kinetics, severe pulverization, and polyselenide shuttle during the charge/discharge process. Herein, Sb-substitution and carbon encapsulation strategies are simultaneously employed to synthesize Sb_xBi_2-xSe₃ nanoparticles decorated on Ti₃C₂T_x MXene with encapsulation of N-doped carbon (Sb_xBi_2-xSe₃/MX⊂NC) as anodes for alkali metal ion storage. The superb electrochemical performances could be assigned to the cationic displacement of Sb³⁺ that effectively inhibits the shuttling effect of soluble polyselenides and the confinement engineering that alleviates the volume change during the sodiation/desodiation process. When used as anodes for sodium- and lithium-ion batteries, the Sb_0.4Bi_1.6Se₃/MX⊂NC composite exhibits superior electrochemical performances. This work offers valuable guidance to suppress the shuttling of polyselenides/polysulfides in high-performance alkali metal ion batteries with conversion/alloying-type transition metal sulfide/selenide anode materials.

The Recent Progress of Pitch Nanoengineering to Obtain the Carbon Anode for High-Performance Sodium Ion Batteries

As an anode material for sodium ion batteries (SIBs), carbon materials have attracted people's interest because of their abundant resources, good structural stability and low cost. Among most carbon precursors, pitch is viewed as a promising one because of a higher carbon content, good oxidation reversibility and low cost. However, the pitch-based carbon obtained with direct pyrolysis of pitch displays a high degree of graphitization and small layer spacing, which is unfavorable for the storage of sodium ions. In recent years, with the aid of the development of the nanoengineering process, the storage of sodium ions with pitch-based carbon has been drastically improved. This review article summarizes the recent progress of pitch nanoengineering to obtain the carbon anode for high-performance SIBs, including porous structure adjustment, heteroatom doping, co-carbonization and pre-oxidation. In addition, the merits and demerits of a variety of nanoengineering processes are discussed, and future research directions of pitch-based carbon are prospected.

Uniformly Dispersed Sb-Nanodot Constructed by In Situ Confined Polymerization of Ionic Liquids for High-Performance Potassium-Ion Batteries

Antimony (Sb) is a potential candidate anode for potassium-ion batteries (PIBs) owing to its high theoretical capacity. However; in the process of potassium alloying reaction; the huge volume expansion (about 407%) leads to pulverization of active substance as well as loss of electrical contact resulting in rapidly declining capacity. Herein; uniformly dispersed Sb-Nanodot in carbon frameworks (Sb-ND@C) were constructed by in situ confined polymerization of ionic liquids. Attributed to the uniformly dispersed Sb-ND and confinement effect of carbon frameworks; as anode for PIBs; Sb-ND@C delivered a superior rate capability (320.1 mA h g^-1 at 5 A g^-1) and an outstanding cycling stability (486 mA h g^-1 after 1000 cycles; achieving 89.8% capacity retention). This work offers a facile route to prepare highly dispersed metal-Nanodot via the in situ polymerization of ionic liquid for high-performance metal-ion batteries.

Multifunctional Hollow Porous Fe3O4@N-C Nanocomposites as Anodes of Lithium-Ion Battery, Adsorbents and Surface-Enhanced Raman Scattering Substrates

At present, it is still a challenge to prepare multifunctional composite nanomaterials with simple composition and favorable structure. Here, multifunctional Fe₃O₄@nitrogen-doped carbon (N-C) nanocomposites with hollow porous core-shell structure and significant electrochemical, adsorption and sensing performances were successfully synthesized through the hydrothermal method, polymer coating, then thermal annealing process in nitrogen (N₂) and lastly etching in hydrochloric acid (HCl). The morphologies and properties of the as-obtained Fe₃O₄@N-C nanocomposites were markedly affected by the etching time of HCl. When the Fe₃O₄@N-C nanocomposites after etching for 30 min (Fe₃O₄@N-C-3) were applied as the anodes for lithium-ion batteries (LIBs), the invertible capacity could reach 1772 mA h g^-1 after 100 cycles at the current density of 0.2 A g^-1, which is much better than that of Fe₃O₄@N-C nanocomposites etched, respectively, for 15 min and 45 min (948 mA h g^-1 and 1127 mA h g^-1). Additionally, the hollow porous Fe₃O₄@N-C-3 nanocomposites also exhibited superior rate capacity (950 mA h g^-1 at 0.6 A g^-1). The excellent electrochemical properties of Fe₃O₄@N-C nanocomposites are attributed to their distinctive hollow porous core-shell structure and appropriate N-doped carbon coating, which could provide high-efficiency transmission channels for ions/electrons, improve the structural stability and accommodate the volume variation in the repeated Li insertion/extraction procedure. In addition, the Fe₃O₄@N-C nanocomposites etched by HCl for different lengths of time, especially Fe₃O₄@N-C-3 nanocomposites, also show good performance as adsorbents for the removal of the organic dye (methyl orange, MO) and surface-enhanced Raman scattering (SERS) substrates for the determination of a pesticide (thiram). This work provides reference for the design and preparation of multifunctional materials with peculiar pore structure and uncomplicated composition.

Co-activation for enhanced K-ion storage in battery anodes

The relative natural abundance of potassium and potentially high energy density has established potassium-ion batteries as a promising technology for future large-scale global energy storage. However, the anodes' low capacity and high discharge platform lead to low energy density, which impedes their rapid development. Herein, we present a possible co-activation mechanism between bismuth (Bi) and tin (Sn) that enhances K-ion storage in battery anodes. The co-activated Bi-Sn anode delivered a high capacity of 634 mAh g-1, with a discharge plateau as low as 0.35 V, and operated continuously for 500 cycles at a current density of 50 mA g-1, with a high Coulombic efficiency of 99.2%. This possible co-activation strategy for high potassium storage may be extended to other Na/Zn/Ca/Mg/Al ion battery technologies, thus providing insights into how to improve their energy storage ability.

Dissolution Mechanism of Eutectic and Hypereutectic Mg-Sn Alloy Anodes for Magnesium Rechargeable Batteries

Magnesium rechargeable batteries (MRBs) are presently attracting much attention due to their low cost, high safety, and high theoretical volumetric capacity. Traditionally, pure magnesium metal has been used as an anode for MRBs, but its poor cycle performance, modest compatibility with conventional electrolytes, and sluggish kinetics limit the further development of MRBs. In this work, eutectic and hypereutectic Mg-Sn alloys were designed and studied as anodes for MRBs. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results confirmed that these alloys contained unique microstructures consisting of α-Mg, Mg₂Sn, and eutectic phases. The dissolution processes of the Mg-Sn alloys were studied in an all-phenyl-complex (APC) electrolyte. A multiple-step electrochemical dissolution process and a special adsorption interface layer were established for the Mg-Sn alloy anodes with an eutectic phase. Hypereutectic alloys with mixed phases showed better battery performance than the eutectic alloy owing to their superior mechanical properties. In addition, the morphology and Mg dissolution mechanism of the Mg-Sn alloys during the 1^st dissolution process were characterized and discussed.

Construction of Microporous Zincophilic Interface for Stable Zn Anode

Aqueous zinc ion batteries (AZIBs) are promising electrochemical energy storage devices due to their high theoretical specific capacity, low cost, and environmental friendliness. However, uncontrolled dendrite growth poses a serious threat to the reversibility of Zn plating/stripping, which impacts the stability of batteries. Therefore, controlling the disordered dendrite growth remains a considerable challenge in the development of AZIBs. Herein, a ZIF-8-derived ZnO/C/N composite (ZOCC) interface layer was constructed on the surface of the Zn anode. The homogeneous distribution of zincophilic ZnO and the N element in the ZOCC facilitates directional Zn deposition on the (002) crystal plane. Moreover, the conductive skeleton with a microporous structure accelerates Zn²⁺ transport kinetics, resulting in a reduction in polarization. As a result, the stability and electrochemical properties of AZIBs are improved. Specifically, the ZOCC@Zn symmetric cell sustains over 1150 h at 0.5 mA cm^-2 with 0.25 mA h cm^-2, while the ZOCC@Zn half-cell achieves an outstanding Coulombic efficiency of 99.79% over 2000 cycles. This work provides a simple and effective strategy for improving the lifespan of AZIBs.

Challenges and Solutions for Low-Temperature Lithium-Sulfur Batteries: A Review

The lithium-sulfur (Li-S) battery is considered to be one of the attractive candidates for breaking the limit of specific energy of lithium-ion batteries and has the potential to conquer the related energy storage market due to its advantages of low-cost, high-energy density, high theoretical specific energy, and environmental friendliness issues. However, the substantial decrease in the performance of Li-S batteries at low temperatures has presented a major barrier to extensive application. To this end, we have introduced the underlying mechanism of Li-S batteries in detail, and further concentrated on the challenges and progress of Li-S batteries working at low temperatures in this review. Additionally, the strategies to improve the low-temperature performance of Li-S batteries have also been summarized from the four perspectives, such as electrolyte, cathode, anode, and diaphragm. This review will provide a critical insight into enhancing the feasibility of Li-S batteries in low-temperature environments and facilitating their commercialization.

Cobalt-Iron Oxyhydroxide Obtained from the Metal Phosphide: A Highly Effective Electrocatalyst for the Oxygen Evolution Reaction at High Current Densities

The development of high current density anodes for the oxygen evolution reaction (OER) is fundamental to manufacturing practical and reliable electrochemical cells. In this work, we have developed a bimetallic electrocatalyst based on cobalt-iron oxyhydroxide that shows outstanding performance for water oxidation. Such a catalyst is obtained from cobalt-iron phosphide nanorods that serve as sacrificial structures for the formation of a bimetallic oxyhydroxide through phosphorous loss concomitantly to oxygen/hydroxide incorporation. CoFeP nanorods are synthesized using a scalable method using triphenyl phosphite as a phosphorous precursor. They are deposited without the use of binders on nickel foam to enable fast electron transport, a highly effective surface area, and a high density of active sites. The morphological and chemical transformation of the CoFeP nanoparticles is analyzed and compared with the monometallic cobalt phosphide in alkaline media and under anodic potentials. The resulting bimetallic electrode presents a Tafel slope as low as 42 mV dec-1 and low overpotentials for OER. For the first time, an anion exchange membrane electrolysis device with an integrated CoFeP-based anode was tested at a high current density of 1 A cm-2, demonstrating excellent stability and Faradaic efficiency near 100%. This work opens up a way for using metal phosphide-based anodes for practical fuel electrosynthesis devices.

Spatially Confined Fe7S8 Nanoparticles Anchored on a Porous Nitrogen-Doped Carbon Nanosheet Skeleton for High-Rate and Durable Sodium Storage

Iron sulfides are widely explored as anodes of sodium-ion batteries (SIBs) owing to high theoretical capacities and low cost, but their practical application is still impeded by poor rate capability and fast capacity decay. Herein, for the first time, we construct highly dispersed Fe₇S₈ nanoparticles anchored on a porous N-doped carbon nanosheet (CN) skeleton (denoted as Fe₇S₈/NC) with high conductivity and numerous active sites via facile ion adsorption and thermal evaporation combined procedures coupled with a gas sulfurization treatment. Nanoscale design coupled with a conductive carbon skeleton can simultaneously mitigate the above obstacles to obtain enhanced structural stability and faster electrode reaction kinetics. With the aid of density functional theory (DFT) calculations, the synergistic interaction between CNs and Fe₇S₈ can not only ensure enhanced Na⁺ adsorption ability but also promote the charge transfer kinetics of the Fe₇S₈/NC electrode. Accordingly, the designed Fe₇S₈/NC electrode exhibits remarkable electrochemical performance with superior high-rate capability (451.4 mAh g^-1 at 6 A g^-1) and excellent long-term cycling stability (508.5 mAh g^-1 over 1000 cycles at 4 A g^-1) due to effectively alleviated volumetric variation, accelerated charge transfer kinetics, and strengthened structural integrity. Our work provides a feasible and effective design strategy toward the low-cost and scalable production of high-performance metal sulfide anode materials for SIBs.

Conductive MOF on ZIF-Derived Carbon Fibers as Superior Anode in Sodium-Ion Battery

Superior specific capacity, high-rate capability, and long-term cycling stability are essential to anode materials in sodium-ion batteries, and conductive metal-organic frameworks (cMOF) with good electronic and ionic conductivity may satisfy these requirements. Herein, conductive neodymium cMOF (Nd-cMOF) produced in situ on the zeolitic imidazolate framework (ZIF)-derived carbon fiber (ZIF-CFs) platform is used to synthesize the Nd-cMOF/ZIF-CFs hierarchical structure. Four types of ZIFs with different pore diameters are prepared by electrospinning. In this novel structure, ZIF-CFs provide the electroconductivity, flexible porous structure, and mechanical stability, while Nd-cMOF provides the interfacial kinetic activity, electroconductivity, ample space, and volume buffer, consequently giving rise to robust structural integrity and excellent conductivity. The sodium-ion battery composed of the Nd-cMOF/ZIF-10-CFs anode has outstanding stability and electrochemical properties, such as a specific capacity of 480.5 mAh g^-1 at 0.05 A g^-1 as well as capacity retention of 84% after 500 cycles.

Toward Highly Selective Heteroatom Dopants in Hard Carbon with Superior Lithium Storage Performance

Hard carbons (HCs) have gained much attention for next-generation high energy density lithium-ion battery (LIB) anode candidates. However, voltage hysteresis, low rate capability, and large initial irreversible capacity severely affect their booming application. Herein, a general strategy is reported to fabricate heterogeneous atom (N/S/P/Se)-doped HC anodes with superb rate capability and cyclic stability based on a three-dimensional (3D) framework and a hierarchical porous structure. The obtained N-doped hard carbon (NHC) exhibits an excellent rate capability of 315 mA h g^-1 at 10.0 A g^-1 and a long-term cyclic stability of 90.3% capacity retention after 1000 cycles at 3 A g^-1. Moreover, the as-constructed pouch cell delivers a high energy density of 483.8 W h kg^-1 and fast charging capability. The underlying mechanisms of lithium storage are illustrated by electrochemical kinetic analysis and theoretical calculations. It is demonstrated that heteroatom doping imposes significant effects on adsorption and diffusion for Li⁺. The versatile strategy in this work opens an avenue for rational design of advanced carbonaceous materials with high performance for LIB applications.

A Novel and Sustainable Approach to Enhance the Li-Ion Storage Capability of Recycled Graphite Anode from Spent Lithium-Ion Batteries

The ubiquitous manufacturing of lithium-ion batteries (LIBs) due to high consumer demand produces inevitable e-waste that imposes severe environmental and resource sustainability challenges. In this work, the charge storage capability and Li-ion kinetics of the recovered water-leached graphite (WG) anode from spent LIBs are enhanced by using an optimized amount of recycled graphene nanoflakes (GNFs) as an additive. The WG@GNF anode exhibits an initial discharge capacity of 400 mAh g^-1 at 0.5C with 88.5% capacity retention over 300 cycles. Besides, it delivers an average discharge capacity of 320 mAh g^-1 at 500 mA g^-1 over 1000 cycles, which is 1.5-2 times higher than that of WG. The sharp increase in electrochemical performance is due to the synergistic effects of Li-ion intercalation into the graphite layers and Li-ion adsorption into the surface functionalities of GNF. Density functional theory calculations reveal the role of functionalization behind the superior voltage profile of WG@GNF. Besides, the unique morphology of spherical graphite particles trapping into graphene nanoflakes provides mechanical stability over long-term cycling. This work explains an efficient strategy to upgrade the electrochemical compatibility of recovered graphite anode from spent LIBs toward next-generation high-energy-density LIBs.

Hexagonal Sb Nanocrystals as High-Capacity and Long-Cycle Anode Materials for Sodium-Ion Batteries

Antimony (Sb) is regarded as a promising anode material for sodium ion batteries (SIBs) on account of its high theoretical specific capacity (∼660 mAh g^-1) and low cost. However, the large volume expansion (∼390%) during charging has inhibited its practical application. Herein, hexagonal Sb nanocrystals encapsulated by P/N-co-doped carbon nanofibers (Sb@P-N/C) were prepared using a low-cost but mass-produced electrospinning method. The as-prepared Sb@P-N/C, used as anode material for SIBs, exhibits unexpected cycling stability and rate capability, with 500.1 mAh g^-1 at 50 mA g^-1 after 200 cycles and 295.6 mAh g^-1 at 500 mA g^-1 after 400 cycles. Especially, the full battery fabricated by Na (Ni_1/3Fe_1/3Mn_1/3) O₂ || Sb@P-N/C possesses a reversible specific capacity of 66.8 mAh g^-1 at 50 mA g^-1 over 60 cycles. This simple and low-cost fabrication technology combined with unique crystal morphology offers new strategies for the advancement of sodium ion batteries (SIBs) in energy storage and electrical transportation.

A Novel Two-Dimensional TiClO as a High-Performance Anode Material for Mg-Ion Batteries: A First-Principles Study

Searching for efficient electrode materials with excellent electrochemical performance is of great significance to the development of magnesium-ion batteries (MIBs). Two-dimensional Ti-based materials are appealing for use in MIBs due to their high cycling capability. On the basis of density functional theory (DFT) calculations, we comprehensively investigate a novel two-dimensional Ti-based material, namely, TiClO monolayer, as a promising anode for MIBs. Monolayer TiClO can be exfoliated from its experimentally known bulk crystal with a moderate cleavage energy of 1.13 J/m². It exhibits intrinsically metallic properties with good energetical, dynamical, mechanical, and thermal stabilities. Remarkably, TiClO monolayer possesses an ultra-high storage capacity (1079 mA h g^-1), a low energy barrier (0.41-0.68 eV), and a suitable average open-circuit voltage (0.96 V). The lattice expansion for the TiClO monolayer is slight (<4.3%) during the Mg-ion intercalation. Moreover, bilayer and trilayer TiClO can considerably enhance the Mg binding strength and maintain the quasi-one-dimensional diffusion feature compared with monolayer TiClO. All these properties indicate that TiClO monolayers can be utilized as high-performance anodes for MIBs.

Effect of High-Energy Ball Milling, Capping Agents and Alkalizer on Capacitance of Nanostructured FeOOH Anodes

This investigation is motivated by interest in nanostructured FeOOH anodes for aqueous asymmetric supercapacitors operating in Na₂SO₄ electrolyte. The research goal is the fabrication of anodes with high active mass loading of 40 mg cm^-2, high capacitance and low resistance. The influence of high-energy ball milling (HEBM), capping agents and alkalizer on the nanostructure and capacitive properties is investigated. HEBM promotes the crystallization of FeOOH, which results in capacitance reduction. Capping agents from the catechol family, such as tetrahydroxy-1,4-benzoquinone (THB) and gallocyanine (GC), facilitate the fabrication of FeOOH nanoparticles, eliminate the formation of micron size particles and allow the fabrication of anodes with enhanced capacitance. The analysis of testing results provided insight into the influence of the chemical structure of the capping agents on nanoparticle synthesis and dispersion. The feasibility of a conceptually new strategy for the synthesis of FeOOH nanoparticles is demonstrated, which is based on the use of polyethylenimine as an organic alkalizer-dispersant. The capacitances of materials prepared using different nanotechnology strategies are compared. The highest capacitance of 6.54 F cm^-2 is obtained using GC as a capping agent. The obtained electrodes are promising for applications as anodes for asymmetric supercapacitors.

Regenerated Graphite-Derived Cellular-Inspired Polydopamine@NiO@Graphite toward Robust Lithium Storage

Although transition metal-based anodes for batteries are preferred owing to their higher energy density, the potential for structural collapse due to volume expansion has hindered their development. Herein, a simulated cellular structured anode composed of uniform nanoparticles and wrapped polydopamine is designed to direct the electronic/ionic diffusion channel and effectively address the volume expansion problem. The controlled-release effects of the polymer between the nano-interface protect the three-dimensional (3D) structures from collapsing during the electrochemical process. The constructed conductive networks along the NiO nanoparticle configurations effectively induce the transfer path and further accelerate the diffusion rate. Furthermore, interstitial filling unlocks the inactive component and triggers the deep delivery of electrons, which boosts battery performance. Therefore, the 3D structured PDA@NiO@G anode prepared from a recycled graphite conductive substrate exhibits excellent specific capacity (500 mAh g^-1 at 0.1 A g^-1) and significantly improved long-cycle performance (402 mAh g^-1 after 500 cycles at 0.5 A g^-1). The structure modulation strategy provides meaningful insight into transition metal anodes for the fabrication of high kinetics and prolonged life lithium-ion batteries, as well as the reuse of the spent graphite anode.

Fluorine- and Acid-Free Strategy toward Scalable Fabrication of Two-Dimensional MXenes for Sodium-Ion Batteries

MXenes are emerging 2D materials that have gained great attention because of their unique physical-chemical properties. However, the wide application of MXenes is prohibited by their high cost and environmentally harmful synthesis process. Here a fluoride- and acid-free physical vacuum distillation strategy is proposed to directly synthesize a series of MXenes. Specifically, by introducing a low-boiling-point element into MAX and subsequently evaporating A elements via physical vacuum distillation, fluoride-free MXenes (Ti₃C₂T_x, Nb₂CT_x, Nb₄C₃T_x, Ta₂CT_x, Ti₂NT_x, Ti₃CNT_x, etc.) are fabricated. This is a green and one-step process without any acid/alkaline involved and with all reactions inside a vacuum tube furnace, avoiding any contamination to external environments. Besides, the synthetic temperature is controlled to regulate the layered structures and specific surface areas of MXenes. Accordingly, the synthesized Ti₃C₂T_x MXene exhibits improved sodium storage performance. This method may provide an alternative for the scalable production of MXenes and other 2D materials.

Polycrystal Li2ZnTi3O8/C anode with lotus seedpod structure for high-performance lithium storage

Lotus-seedpod structured Li₂ZnTi₃O₈/C (P-LZTO) microspheres obtained by the molten salt method are reported for the first time. The received phase-pure Li₂ZnTi₃O₈ nanoparticles are inserted into the carbon matrix homogeneously to form a Lotus-seedpod structure, as confirmed by the morphological and structural measurements. As the anode for lithium-ion batteries, the P-LZTO material demonstrates excellent electrochemical performance with a high rate capacity of 193.2 mAh g^-1 at 5 A g^-1 and long-term cyclic stability up to 300 cycles at 1 A g^-1. After even 300 cyclings, the P-LZTO particles can maintain their morphological and structural integrity. The superior electrochemical performances have arisen from the unique structure where the polycrystalline structure is beneficial for shorting the lithium-ion diffusion path, while the well-encapsulated carbon matrix can not only enhance the electronic conductivity of the composite but also alleviate the stress anisotropy during lithiation/delithiation process, leading to well-preserved particles.

Ultra-fine SnO2 nanocrystals anchored on reduced graphene oxide as a high-performance anode material for sodium-ion batteries

SnO2 has attracted extensive research attentions as a promising anode material for sodium-ion batteries (SIBs) due to its high theoretical capacity. However, its application is largely hindered by sluggish sodium ion diffusion and drastic volume change during the conversion reaction and alloying process. Herein, ultra-fine SnO2 nanocrystals (3-5 nm) anchored on reduced graphene oxide (rGO) is demonstrated as a promising anode material for SIBs. Ultra-fine SnO2 nanocrystals are uniformly grown on rGO sheets by a facile one-step hydrothermal process. Nano-scaled SnO2 grains tolerate volume expansion and provide shortened diffusion pathway for sodium ions, and meanwhile rGO acts as an excellent conductive matrix, thus endowing the composite electrode with excellent electrochemical performance. More importantly, the ratio of SnO2 to rGO in the composite is optimized. The optimized sample delivers an initial charge capacity of 518 mAh g-1 at a current density of 50 mA g-1, and 504 mAh g-1 after 300 cycles at a current density of 100 mA g-1. Furthermore, a capacity of 287 mAh g-1 can be maintained after 1000 cycles at a current density of 1000 mA g-1.

In Situ Synthesis of Amorphous GeSe/CNT Composite via Defective-carbon-mediated Chemical Bonding for Ultrastable Na Ion Storage

Herein, we report the in situ synthesis of amorphous GeSe/CNT composite via defective-carbon-mediated chemical bonding for ultrastable Na-ion storage. Structural defects in CNTs play a crucial role in the chemical bonding and bonding strength in GeSe/CNTs composites. Specifically, the bonding strength tends to increase with increasing defect concentrations of CNTs. Remarkably, the strong chemical bonding between GeSe and CNTs significantly weakens Ge-Se bonds and promotes amorphization of GeSe, thus facilitating a reversible conversion reaction and enhancing Na-ion diffusion. Consequently, GeSe/CNTs composite exhibits outstanding cyclability of 87.9% even after 1000 cycles at 1 A g-1 and a high-rate capability of 288.3 mA h g-1 at 10 A g-1. Our work presents a promising approach for the amorphization of electrode materials enabled by the defective-carbon-mediated strong chemical bonding for Li-, Na-, and K-ion batteries.