Supernormal Conversion Anode Consisting of High-Density MoS2 Bubbles Wrapped in Thin Carbon Network by Self-Sulfuration of Polyoxometalate Complex

Structural Engineering of Anode Materials for Low-Temperature Lithium-Ion Batteries: Mechanisms, Strategies, and Prospects

The severe degradation of electrochemical performance for lithium-ion batteries (LIBs) at low temperatures poses a significant challenge to their practical applications. Consequently, extensive efforts have been contributed to explore novel anode materials with high electronic conductivity and rapid Li+ diffusion kinetics for achieving favorable low-temperature performance of LIBs. Herein, we try to review the recent reports on the synthesis and characterizations of low-temperature anode materials. First, we summarize the underlying mechanisms responsible for the performance degradation of anode materials at subzero temperatures. Second, detailed discussions concerning the key pathways (boosting electronic conductivity, enhancing Li+ diffusion kinetics, and inhibiting lithium dendrite) for improving the low-temperature performance of anode materials are presented. Third, several commonly used low-temperature anode materials are briefly introduced. Fourth, recent progress in the engineering of these low-temperature anode materials is summarized in terms of structural design, morphology control, surface & interface modifications, and multiphase materials. Finally, the challenges that remain to be solved in the field of low-temperature anode materials are discussed. This review was organized to offer valuable insights and guidance for next-generation LIBs with excellent low-temperature electrochemical performance.

"Fast-Charging" Anode Materials for Lithium-Ion Batteries from Perspective of Ion Diffusion in Crystal Structure

"Fast-charging" lithium-ion batteries have gained a multitude of attention in recent years since they could be applied to energy storage areas like electric vehicles, grids, and subsea operations. Unfortunately, the excellent energy density could fail to sustain optimally while lithium-ion batteries are exposed to fast-charging conditions. In actuality, the crystal structure of electrode materials represents the critical factor for influencing the electrode performance. Accordingly, employing anode materials with low diffusion barrier could improve the "fast-charging" performance of the lithium-ion battery. In this Review, first, the "fast-charging" principle of lithium-ion battery and ion diffusion path in the crystal are briefly outlined. Next, the application prospects of "fast-charging" anode materials with various crystal structures are evaluated to search "fast-charging" anode materials with stable, safe, and long lifespan, solving the remaining challenges associated with high power and high safety. Finally, summarizing recent research advances for typical "fast-charging" anode materials, including preparation methods for advanced morphologies and the latest techniques for ameliorating performance. Furthermore, an outlook is given on the ongoing breakthroughs for "fast-charging" anode materials of lithium-ion batteries. Intercalated materials (niobium-based, carbon-based, titanium-based, vanadium-based) with favorable cycling stability are predominantly limited by undesired electronic conductivity and theoretical specific capacity. Accordingly, addressing the electrical conductivity of these materials constitutes an effective trend for realizing fast-charging. The conversion-type transition metal oxide and phosphorus-based materials with high theoretical specific capacity typically undergoes significant volume variation during charging and discharging. Consequently, alleviating the volume expansion could significantly fulfill the application of these materials in fast-charging batteries.

Carbonized Polymer Dots for Controlling Construction of MoS2 Flower-Like Nanospheres to Achieve High-Performance Li/Na Storage Devices

Despite being one of the most promising materials in anode materials, molybdenum sulfide (MoS2 ) encounters certain obstacles, such as inadequate cycle stability, low conductivity, and unsatisfactory charge-discharge (CD) rate performance. In this study, a novel approach is employed to address the drawbacks of MoS2 . Carbon polymer dots (CPDs) are incorporated to prepare three-dimensional (3D) nanoflower-like spheres of MoS2 @CPDs through the self-assembly of MoS2 2D nanosheets, followed by annealing at 700 °C. The CPDs play a main role in the creation of the nanoflower-like spheres and also mitigate the MoS2 nanosheet limitations. The nanoflower-like spheres minimize volume changes during cycling and improve the rate performance, leading to exceptional rate performance and cycling stability in both Lithium-ion and Sodium-ion batteries (LIBs and SIBs). The optimized MoS2 @CPDs-2 electrode achieves a superb capacity of 583.4 mA h g-1 at high current density (5 A g-1 ) after 1000 cycles in LIBs, and the capacity remaining of 302.8 mA h g-1 after 500 cycles at 5 A g-1 in SIBs. Additionally, the full cell of LIBs/SIBs exhibits high capacity and good cycling stability, demonstrating its potential for practical application in fast-charging and high-energy storage.

Preparation and Evaluation of Co-Doped Fe7S8/C Composites for Lithium Storage

Fe₇S₈ has a high theoretical capacity (663 mAh g^-1) and can be prepared at a low cost, making it advantageous for production. However, Fe₇S₈ has two disadvantages as a lithium-ion battery anode material. The first is that the conductivity of Fe₇S₈ is not good. The second is that when the lithium ion is embedded, the volume expansion of the Fe₇S₈ electrode is serious. That is why Fe₇S₈ has not been used in real life yet. In this paper, Co-Fe₇S₈/C composites were prepared by doping Co into Fe₇S₈ through a one-pot simple hydrothermal method. In situ Co is doped into Fe₇S₈ to produce a more disordered microstructure to improve ion and electron transport performance, thereby reducing the activation barrier of the main material. The Co-Fe₇S₈/C electrode presents a high specific discharge capacity of 1586 mAh g^-1 and a Coulombic efficiency (CE) of 71.34% at an initial cycle at 0.1 A g^-1. After 1500 cycles, the specific discharge capacity remains at 436 mAh g^-1 (5 A g^-1). When the current density returns to 0.1 A g^-1, the capacity almost returns to the initial level, showing excellent rate performance.

Triple Conductive Wiring by Electron Doping, Chelation Coating and Electrochemical Conversion in Fluffy Nb2 O5 Anodes for Fast-Charging Li-Ion Batteries

High-rate anode material is the kernel of developing fast-charging lithium ion batteries (LIBs). T-Nb2 O5 , well-known for its "room and pillar" structure and bulk pseudocapacitive effect, is expected to enable the fast lithium (de)intercalation. But this property is still limited by the low electronic conductivity or insufficient wiring manner. Herein, a strategy of triple conductive wiring through electron doping, chelation coating, and electrochemical conversion inside the microsized porous spheres consisting of dendrite-like T-Nb2 O5 primary particles is proposed to achieve the fast-charging and durable anodes for LIBs. The penetrative implanting of conformal carbon coating (derivative from polydopamine chelate) and NbO domains (induced by excess discharging) reinforces the global supply of electronically conductive wires, apart from those from Co/Mn heteroatom or O vacancy doping. The polydopamine etching on T-Nb2 O5 spheres promotes their evolution into fluffy morphology with better electrolyte infiltration. The synergic electron and ion wiring at different scales endow the modified T-Nb2 O5 anode with ultralong cycling life (143 mAh g-1 at 1 A g-1 after 8500 cycles) and high-rate performance (144.1 mAh g-1 at 10.0 A g-1 ). The permeation of multiple electron wires also enables a high mass loading of T-Nb2 O5 (4.5 mg cm-2 ) with a high areal capacity of 0.668 mAh cm-2 even after 150 cycles.

Porous Amorphous Silicon Hollow Nanoboxes Coated with Reduced Graphene Oxide as Stable Anodes for Sodium-Ion Batteries

Amorphous silicon (a-Si), due to its satisfactory theoretical capacity, moderate discharge potential, and abundant reserves, is treated as one of the most prospective materials for the anode of sodium-ion batteries (SIBs). However, the slow Na⁺ diffusion kinetics, poor electrical conductivity, and rupture-prone structures of a-Si restrict its further development. In this work, a composite (a-Si@rGO) consisting of porous amorphous silicon hollow nanoboxes (a-Si HNBs) and reduced graphene oxide (rGO) is prepared. The a-Si HNBs are synthesized through "sodiothermic reduction" of silica hollow nanoboxes at a relatively low temperature, and the rGO is covered on the surface of the a-Si HNBs by electrostatic interaction. The as-synthesized composite anode applying in SIBs exhibits a high initial discharge capacity of 681.6 mAh g^-1 at 100 mA g^-1, great stability over 2000 cycles at 800 mA g^-1, and superior rate performance (261.2, 176.8, 130.3, 98.4, and 73.3 mAh g^-1 at 100, 400, 800, 1500, and 3000 mA g^-1, respectively). The excellent electrochemical properties are ascribed to synergistic action of the porous hollow nanostructure of a-Si and the rGO coating. This research not only offers an innovative synthetic means for the development of a-Si in various fields but also provides a practicable idea for the design of other alloy-type anodes.

Boosted π-Li Cation Effect in the Stabilized Small Organic Molecule Electrode via Hydrogen Bonding with MXene

The high solubility of the small organic molecule materials in organic electrolytes hinders their development in rechargeable batteries. Hence, this work designs an ultrarobust hydrogen-bonded organic-inorganic hybrid material: the small organic unit of the 1,3,6,8-tetrakis (p-benzoic acid) pyrene (TBAP) molecule connected with the hydroxylated Ti₃C₂T_x MXene through hydrogen bonds between the terminal groups of -COOH and -OH. The robust and elastic hydrogen bonds can empower the TBAP, despite being a low-molecule organic chemical, with unusually low solubility in organic electrolytes and thermal stability. The alkali-treated Ti₃C₂T_x MXene provides a hydroxyl-rich conductive network, and the small organic molecule of TBAP reduces the restacking of MXene layers. Therefore, the combination of these two materials complements each other well, and this organic-inorganic TBAP@D-Ti₃C₂T_x electrode delivers large reversible capacities and long cyclic life. Notably, with the assistance of the in situ FT-IR characterization of the electrode within the fully lithiated (0.005 V) and the delithiated (3.0 V) states, it is revealed that a powerful π-Li cation effect mainly governs the lithium-storage mechanism with the highly activated benzene ring and each C6 aromatic ring, which can reversibly accept six Li-ions to form a 1:1 Li/C complex.

Exploiting Redox-Complementary Peptide/Polyoxometalate Coacervates for Spontaneously Curing into Antimicrobial Adhesives

Recently, there has been a wave of reports on the fabrication of peptide-based underwater adhesives with the aim of understanding the adhesion mechanism of marine sessile organisms or creating new biomaterials beyond nature. However, the poor shear adhesion performance of the current peptide adhesives has largely hindered their applications. Herein, we proposed to sequentially perform the interfacial adhesion and bulk cohesion of peptide-based underwater adhesives using two redox-complementary peptide/polyoxometalate (POM) coacervates. The oxidative coacervates were prepared by mixing oxidative H₅PMo₁₀V₂O₄₀ and cationic peptides in an aqueous solution. The reductive coacervates consisted of K₅BW₁₂O₄₀ and cysteine-containing reductive peptides. Each of the individual coacervate has well-defined spreading capacity to achieve fast interfacial attachment and adhesion, but their cohesion is poor. However, after mixing the two redox-complementary coacervates at the target surface, effective adhesion and spontaneous curing were observed. We identified that the spontaneous curing resulted from the H₅PMo₁₀V₂O₄₀-regulated oxidization of cysteine-containing peptides. The formed intermolecular disulfide bonds improved the cross-linking density of the dual-peptide/POM coacervates, giving rise to the enhanced bulk cohesion and mechanical strength. More importantly, the resultant adhesives showcased excellent bioactivity to selectively suppress the growth of Gram-positive bacteria due to the presence of the polyoxometalates. This work raises further potential in the creation of biomimetic adhesives through the orchestrating of covalent and noncovalent interactions in a sequential fashion.

Ultrafine MoS2 Nanosheets Vertically Patterned on Graphene for High-Efficient Li-Ion and Na-Ion Storage

Hierarchically two-dimensional (2D) heteroarchitecture with ultrafine MoS₂ nanosheets vertically patterned on graphene is developed by using a facile solvothermal method. It is revealed that the strong interfacial interaction between acidic Mo precursors and graphene oxides allows for uniform and tight alignment of edge-oriented MoS₂ nanosheets on planar graphene. The unique sheet-on-sheet architecture is of grand advantage in synergistically utilizing the highly conductive graphene and the electroactive MoS₂, thus rendering boosted reaction kinetics and robust structural integrity for energy storage. Consequently, the heterostructured MoS₂@graphene exhibits impressive Li/Na-ion storage properties, including high-capacity delivery and superior rate/cycling capability. The present study will provide a positive impetus on rational design of 2D metal sulfide/graphene composites as advanced electrode materials for high-efficient alkali–metal ion storage.

Boosting the lithium storage performance by synergistically coupling ultrafine heazlewoodite nanoparticle with N, S co-doped carbon

Transition metal sulfides, as an important class of inorganics, have been shown to be potential high-performance electrode candidates for lithium-ion batteries (LIBs) in account of their high activity towards lithium storage, rich types and diverse structures. Despite these advantages, structure degradation related with volume variations upon electrochemical cycling restricts their further development. In this present study, a unique hybrid structure with ultrafine heazlewoodite nanoparticles (less than 10 nm) in-situ confined in nitrogen and sulfur dual-doped carbon (Ni₃S₂@NSC) was constructed though a facile pyrolysis process, using a novel Ni-based metal chelates as the precursor. Specifically, enhanced structure stability, shortened Li⁺ migration distance and improved reaction dynamics can be obtained simultaneously in the designed structure, thereby allowing to realize high lithium storage performance. Consequently, a remarkable reversible capacity of 955.9 mAh g^-1 (0.1 A g^-1 after 100 cycles) and a superior long-term cycling stability up to 1200 cycles (863.7 mAh g^-1 at 1.0 A g^-1) are obtained. Importantly, the fundamental understanding on the improved lithium storage of Ni₃S₂@NSC based on the synergistic coupling reveals that the combination between Ni₃S₂ and NSC at the hetero-interface through the doped sulfur atoms contributes to the integrity of electrode and improved kinetics.

Lithium Ion Repulsion-Enrichment Synergism Induced by Core-Shell Ionic Complexes to Enable High-Loading Lithium Metal Batteries

A core-shell additive with anionic Keggin-type polyoxometalate (POM) cluster as core and N-containing cation of ionic liquid (IL) as shell is proposed to stabilize Li-metal batteries (LMBs). The suspended POM derived complex in ether-based electrolyte is absorbed around the protuberances of anode and triggers a lithiophobic repulsion mechanism for the homogenization of Li⁺ redistribution. The gradually released POM cores with negative charge then enrich Li⁺ and co-assemble with Li. The Li⁺ repulsion-enrichment synergism can compact Li deposition and reinforce solid electrolyte interphase. This sustained-release additive enables Li∥Li symmetric cells with a long lifetime over 500 h and 300 h at high current densities of 3 and 5 mA cm^-2 respectively. The complex additive is also compatible with high-voltage Li∥LiNi_0.8 Co_0.15 Al_0.05 O₂ (NCA) cells. Even with a NCA loading as high as ca. 20 mg cm^-2 , the additive contained Li∥NCA cell can still cycle for over 100 cycles at 2.6 mA cm^-2 .

Electrochemical Performance of Orthorhombic CsPbI3 Perovskite in Li-Ion Batteries

A facile solution process was employed to prepare CsPbI₃ as an anode material for Li-ion batteries. Rietveld refinement of the X-ray data confirms the orthorhombic phase of CsPbI₃ at room temperature. As obtained from bond valence calculations, strained bonds between Pb and I are identified within PbI₆ octahedral units. Morphological study shows that the as-prepared δ-CsPbI₃ forms a nanorod-like structure. The XPS analysis confirm the presence of Cs (3d, 4d), Pb (4d, 4f, 5d) and I (3p, 3d, 4d). The lithiation process involves both intercalation and conversion reactions, as confirmed by cyclic voltammetry (CV) and first-principles calculations. Impedance spectroscopy coupled with the distribution function of relaxation times identifies charge transfer processes due to Li metal foil and anode/electrolyte interfaces. An initial discharge capacity of 151 mAhg⁻¹ is found to continuously increase to reach a maximum of ~275 mAhg⁻¹ at 65 cycles, while it drops to ~240 mAhg⁻¹ at 75 cycles and then slowly decreases to 235 mAhg⁻¹ at 100 cycles. Considering the performance and structural integrity during electrochemical performance, δ-CsPbI₃ is a promising material for future Li-ion battery (LIB) application.

Consecutive Nucleation and Confinement Modulation towards Li Plating in Seeded Capsules for Durable Li-Metal Batteries

A dual modulation strategy of consecutive nucleation and confined growth of Li metal is proposed by using the metal-organic framework (MOF) derivative hollow capsule with inbuilt lithiophilic Au or Co-O nanoparticle (NP) seeds as heterogeneous host. The seeding-induced nucleation enables the negligible overpotential and promotes the inward injection of Li mass into the abundant cavities in host, followed by the conformal plating of Li on the outer surface of host during discharging. This modulation alleviates the dendrite growth and volume expansion of Li plating. The interconnected porous host network enables enhancement of cycling and rate performances of Li metal (a lifespan over 1200 h for Au-seeding symmetric cells, and an endurance of 220 cycles under an ultrahigh current density of 10 mA cm^-2 for corresponding asymmetric cells). The hollow capsules integrated with lithiophilic seeds solve the deformation problem of Li metal for durable and long-life Li-metal batteries.

Unraveling the Beneficial Microstructure Evolution in Pyrite for Boosted Lithium Storage Performance

Pyrite FeS₂ as a high-capacity electrode material for lithium-ion batteries (LIBs) is hindered by its unstable cycling performance owing to the large volume change and irreversible phase segregation from coarsening of Fe. Here, the beneficial microstructure evolution in MoS₂ -modified FeS₂ is unraveled during the cycling process; the microstructure evolution is responsible for its significantly boosted lithium storage performance, making it suitable for use as an anode for LIBs. Specifically, the FeS₂ /MoS₂ displays a long cycle life with a capacity retention of 116 % after 600 cycles at 0.5 A g^-1 , which is the best among the reported FeS₂ -based materials so far. A series of electrochemical tests and structural characterizations substantially revealed that the introduced MoS₂ in FeS₂ experiences an irreversible electrochemical reaction and thus the in situ formed metallic Mo could act as the conductive buffer layer to accelerate the dynamics of Li⁺ diffusion and electron transport. More importantly, it can guarantee the highly reversible conversion in lithiated FeS₂ by preventing Fe coarsening. This work provides a fundamental understanding and an effective strategy towards the microstructure evolution for boosting lithium storage performances for other metal sulfide-based materials.

Mesoporous Iron-doped MoS2/CoMo2S4 Heterostructures through Organic-Metal Cooperative Interactions on Spherical Micelles for Electrochemical Water Splitting

Mesoporous metal sulfide hybrid (meso-MoS₂/CoMo₂S₄) materials via a soft-templating approach using diblock copolymer polystyrene-block-poly(acrylic acid) micelles are reported. The formation of the meso-MoS₂/CoMo₂S₄ heterostructures is based on the sophisticated coassembly of dithiooxamide and metal precursors (i.e., Co²⁺, PMo₁₂), which are subsequently annealed in nitrogen atmosphere to generate the mesoporous material. Decomposing the polymer leaves behind mesopores throughout the spherical MoS₂/CoMo₂S₄ hybrid particles, generating numerous electrochemical active sites in a network of pores that enable faster charge transfer and mass/gas diffusion that enhance the electrocatalytic performance of MoS₂/CoMo₂S₄. Doping the spherical meso-MoS₂/CoMo₂S₄ heterostructures with iron improves the electronic properties of the hybrid meso-Fe-MoS₂/CoMo₂S₄ material and consequently results in its superior electrochemical activities for both hydrogen evolution reaction and oxygen evolution reaction.

Inner-Stress-Optimized High-Density Fe3O4 Dots Embedded in Graphitic Carbon Layers with Enhanced Lithium Storage

The volume variation of electrode materials will lead to poor cyclability of lithium-ion batteries during the lithiation/delithiation process. Instead, inner-stress fragmentation is creatively used to change carbon-layer-capped Fe₃O₄ particles ∼30 nm in diameter into high-density Fe₃O₄ dots ∼4 nm in size embedded in ultrathin carbon layers. The optimized structure shows a remarkable 45.2% enhancement of lithium storage from 804.7 (the 10th cycle) to 1168.7 mA h g^-1 (the 250th cycle) at 500 mA g^-1, even retaining 1239.5 mA h g^-1 after another 550 cycles. The electrochemical measurements reveal the enhanced capacitive behavior of the high-density Fe₃O₄ dots@C layers, which have more extra active sites for the insertion/extraction of Li⁺ ions, confirmed by the differential capacity plots, leading to remarkably increased specific capacity during cycling. The restructured electrode also shows a superior rate capacity and excellent cycling stability (938.7 and 815.4 mA h g^-1 over 2000 cycles at 1000 and 2000 mA g^-1, respectively). X-ray photoelectron spectroscopy and transmission electron microscopy characterizations show that the optimized structure has stable structural and componential stability even at large rates. This work presents an MOF-guided synthesis of high-density Fe₃O₄-dots' anode material optimized by inner-stress fragmentation, showing a feasible route to design high-efficiency electrode materials.

MoS2/carbon composites prepared by ball-milling and pyrolysis for the high-rate and stable anode of lithium ion capacitors

Lithium ion capacitors (LICs), bridging the advantages of batteries and electrochemical capacitors, are regarded as one of the most promising energy storage devices. Nevertheless, it is always limited by the anodes that accompany with low capacity and poor rate performance. Here, we develop a versatile and scalable method including ball-milling and pyrolysis to synthesize exfoliated MoS₂ supported by N-doped carbon matrix derived from chitosan, which is encapsulated by pitch-derived carbon shells (MoS₂/CP). Because the carbon matrix with high nitrogen content can improve the electron conductivity, the robust carbon shells can suppress the volume expansion during cycles, and the sufficient exfoliation of lamellar MoS₂ can reduce the ions transfer paths, the MoS₂/CP electrode delivers high specific capacity (530 mA h g^-1 at 100 mA g^-1), remarkable rate capability (230 mA h g^-1 at 10 A g^-1) and superior cycle performance (73% retention after 250 cycles). Thereby, the LICs, composed of MoS₂/CP as the anode and commercial activated carbon (21 KS) as the cathode, exhibit high power density of 35.81 kW kg^-1 at 19.86 W h kg^-1 and high energy density of 87.74 W h kg^-1 at 0.253 kW kg^-1.

Conductive Holey MoO2-Mo3N2 Heterojunctions as Job-Synergistic Cathode Host with Low Surface Area for High-Loading Li-S Batteries

Li-S batteries have several advantages in terms of ultrahigh energy density and resource abundance. However, the insulating nature of S and Li₂S, solubility and shuttle effects of lithium polysulfides (LiPSs), and slow interconversion between LiPSs and S/Li₂S/Li₂S₂ are significant impediments to the commercialization of Li-S batteries. Exploration of the advanced S host skeleton simultaneously with high conductivity, adsorbability, and catalytic activity is highly desired. Herein, a heterojunction material with holey nanobelt morphology and low surface area (95 m²/g) is proposed as a compact cathode host to enable a conformal deposition of S/Li₂S with homogeneous spatial distribution. The rich heterointerfaces between MoO₂ and Mo₃N₂ nanodomains serve as job-synergistic trapping-conversion sites for polysulfides by combining the merits of conductive Mo₃N₂ and adsorptive MoO₂. This non-carbon heterojunction substrate enables a high S loading of 75 wt % even under low surface area. The initial capacity of MoO₂-Mo₃N₂@S reaches 1003 mAh/g with a small decay rate of 0.024% per cycle during 1000 cycles at 0.5 C. The long-term cyclability is preserved even under a high loading of 3.2 mg/cm² with a reversible capacity of 451 mAh/g after 1000 cycles. The Li-ion diffusion coefficient for MoO₂-Mo₃N₂@S is extremely high (up to 2.7 × 10^-7 cm²/s) benefiting from LiPS conversion acceleration at heterojunctions. The affinity between LiPSs and heterojunction allows a dendrite-free Li plating at anode even after long-term cycling. Well-defined heterointerface design with job-sharing or job-synergic function appears to be a promising solution to high-performance Li-S batteries without the requirement of loose or high-surface-area carbon network structures.

Highly Reversible Conversion Anodes Composed of Ultralarge Monolithic Grains with Seamless Intragranular Binder and Wiring Network

Conversion anodes enable a high capacity for lithium-ion batteries due to more than one electron transfer. However, the collapse of the host structure during cycling would cause huge volume expansion and phase separation, leading to the degradation and disconnection of the mixed conductive network of the electrode. The initial nanostructuring and loose spatial distribution of active species are often resorted to in order to alleviate the evolution of the electrode morphology, but at the cost of the decrease of grain packing density. The utilization of ultralarge microsized grains of high density as the conversion anode is still highly challenging. Here, a proof-of-concept grain architecture characterized by endogenetic binder matrix and wiring network is proposed to guarantee the structural integrity of monolithic grains as large as 50-100 μm during deep conversion reaction. Such big grains were fabricated by self-assembly and pyrolysis of a Keggin-type polyoxometalate-based complex with protonated tris[2-(2-methoxyethoxy)-ethyl]amine (TDA-1-H⁺). The metal-organic precursor can guarantee the firm adherence of numerous Mo-O clusters and nuclei into a highly elastic monolithic structure without evident grain boundaries and intergranular voids. The pyrolyzed TDA-1-H⁺ not only serves as in situ binder and conductive wire to glue adjacent Mo-O moieties but also acts as a Li-ion pathway to promote sufficient lithiation on surrounding Mo-O. Such a monolithic electrode design leads to an unusual high-conversion-capacity performance (1000 mAh/g) with satisfactory reversibility (reaching at least 750 cycles at 1 A/g). These cycled grains are not disassembled even after undergoing long-term cycling. The conception of the intragranular binder is further confirmed by consolidating the MoO₂ porous network after in situ stuffing of MoS₂ nanobinders.

Glucose-Induced Synthesis of 1T-MoS2 /C Hybrid for High-Rate Lithium-Ion Batteries

1T phase MoS₂ possesses higher conductivity than the 2H phase, which is a key parameter of electrochemical performance for lithium ion batteries (LIBs). Herein, a 1T-MoS₂ /C hybrid is successfully synthesized through facile hydrothermal method with a proper glucose additive. The synthesized hybrid material is composed of smaller and fewer-layer 1T-MoS₂ nanosheets covered by thin carbon layers with an enlarged interlayer spacing of 0.94 nm. When it is used as an anode material for LIBs, the enlarged interlayer spacing facilitates rapid intercalating and deintercalating of lithium ions and accommodates volume change during cycling. The high intrinsic conductivity of 1T-MoS₂ also contributes to a faster transfer of lithium ions and electrons. Moreover, much smaller and fewer-layer nanosheets can shorten the diffusion path of lithium ions and accelerate reaction kinetics, leading to an improved electrochemical performance. It delivers a high initial capacity of 920.6 mAh g^-1 at 1 A g^-1 and the capacity can maintain 870 mAh g^-1 even after 300 cycles, showing a superior cycling stability. The electrode presents a high rate performance as well with a reversible capacity of 600 mAh g^-1 at 10 A g^-1 . These results show that the 1T-MoS₂ /C hybrid shows potential for use in high-performance lithium-ion batteries.

All-Transparent Stretchable Electrochromic Supercapacitor Wearable Patch Device

Flexible and stretchable electrochromic supercapacitor systems are widely considered as promising multifunctional energy storage devices that eliminate the need for an external power source. Nevertheless, the performance of conventional designs deteriorates significantly as a result of electrode/electrolyte exposure to atmosphere as well as mechanical deformations for the case of flexible systems. In this study, we suggest an all-transparent stretchable electrochromic supercapacitor device with ultrastable performance, which consists of Au/Ag core-shell nanowire-embedded polydimethylsiloxane (PDMS), bistacked WO₃ nanotube/PEDOT:PSS, and polyacrylamide (PAAm)-based hydrogel electrolyte. Au/Ag core-shell nanowire-embedded PDMS integrated with PAAm-based hydrogel electrolyte prevents Ag oxidation and dehydration while maintaining ionic and electrical conductivity at high voltage even after 16 days of exposure to ambient conditions and under application of mechanical strains in both tensile and bending conditions. WO₃ nanotube/PEDOT:PSS bistacked active materials maintain high electrochemical-electrochromic performance even under mechanical deformations. Maximum specific capacitance of 471.0 F g^-1 was obtained with a 92.9% capacity retention even after 50 000 charge-discharge cycles. In addition, high coloration efficiency of 83.9 cm² C^-1 was shown to be due to the dual coloration and pseudocapacitor characteristics of the WO₃ nanotube and PEDOT:PSS thin layer.

In Situ Self-Formed Nanosheet MoS3/Reduced Graphene Oxide Material Showing Superior Performance as a Lithium-Ion Battery Cathode

Although lithium-sulfur (Li-S) batteries have 5-10 times higher theoretical capacity (1675 mAh g^-1) than present commercial lithium-ion batteries, Li-S batteries show a rapid and continuous capacity fading due to the polysulfide dissolution in common electrolytes. Here, we propose the use of a sulfur-based cathode material, amorphous MoS₃ and reduced graphene oxide (r-GO) composite, which can be substituted for the pure sulfur-based cathodes. In order to enhance kinetics and stability of the electrodes, we intentionally pulverize the microsized MoS₃ sheet into nanosheets and form an ultrathin nano-SEI on the surface using in situ electrochemical methods. Then, the pulverized nanosheets are securely anchored by the oxygen functional group of r-GO. As a result, the electrochemically treated MoS₃/r-GO electrode shows superior performance that surpasses pure sulfur-based electrodes; it exhibits a capacity of about 900 mAh g^-1 at a rate of 5C for 2500 cycles without capacity fading. Moreover, a full-cell battery employing the MoS₃/r-GO cathode with a silicon-carbon composite anode displays a 3-5 times higher energy density (1725 Wh kg^-1/7100 Wh L^-1) than present LIBs.

Stacking of Tailored Chalcogenide Nanosheets around MoO2-C Conductive Stakes Modulated by a Hybrid POM⊂MOF Precursor Template: Composite Conversion-Insertion Cathodes for Rechargeable Mg-Li Dual-Salt Batteries

Mg anode has pronounced advantages in terms of high volumetric capacity, resource abundance, and dendrite-free electrochemical plating, which make rechargeable Mg-based batteries stand out as a representative next-generation energy storage system utilized in the field of large-scale stationary electric grid. However, sluggish Mg²⁺ diffusion in cathode lattices and facile passivation on the Mg anode hinder the commercialization of Mg batteries. Exploring a highly electroactive cathode prototype with hierarchical nanostructure and compatible electrolyte system with the capability of activating both an anode and a cathode is still a challenge. Here, we propose a POM⊂MOF (NENU-5) core-shell architecture as a hybrid precursor template to achieve the stacking of tailored chalcogenide nanosheets around MoO₂-C conductive stakes, which can be employed as conversion-insertion cathodes (Cu_1.96S-MoS₂-MoO₂ and Cu₂Se-MoO₂) for Mg-Li dual-salt batteries. Li-salt modulation further activates the capacity and rate performance at the cathode side by preferential Li-driven displacement reaction in Cu⁺ extrusible lattices. The heterogeneous conductive network and conformal dual-doped carbon coating enable a reversible capacity as high as 200 mAh/g with a coulombic efficiency close to 100%. The composite cathode can endure a long-term cycling up to 400 cycles and a high current density up to 2 A/g. The diversity of MOF-based materials infused by functional molecules or clusters would enrich the nanoengineering of electrodes to meet the performance demand for future multivalent batteries.

Metal chelate induced in situ wrapping of Ni3S2 nanoparticles into N, S-codoped carbon networks for highly efficient sodium storage

Metal-dithiooxamide chelate derived Ni₃S₂ nanoparticles wrapped in N, S codoped carbon networks exhibit excellent sodium storage performance.

High-Rate Nanostructured Pyrite Cathodes Enabled by Fluorinated Surface and Compact Grain Stacking via Sulfuration of Ionic Liquid Coated Fluorides

Metal-polysulfide batteries are attracting broad attention as conversion reaction systems of high theoretical energy density and low cost. However, their further applications are hindered by the low loading of active species, excess conductive additive, and loose (nanostructured) electrode networkss. Herein, we propose that compact grain stacking and surface fluorination are two crucial factors for achieving high-rate and long-life pyrite (FeS₂) cathodes enabled by sulfurating ionic liquid wrapped open-framework fluorides. Both of the factors can accelerate the Li- and Na-driven transport across the pyrite-electrolyte interface and conversion propagation between adjacent grains. Such an electrode design enables a highly reversible capacity of 425 mAh/g after 1000 cycles at 1 C for Li storage and 450 mAh/g after 1200 cycles at 2 C for Na storage, even under a high loading of pyrite grains and ultrathin carbon coating (<2 nm). Its cathode energy density can reach to 800 and 350 Wh/kg for Li and Na cells, respectively, under a high power density of 10000 W/kg. The cross-linkage between ionic liquid and fluoride precursors appears to be a solution to the reinforcement of surface fluorination.

Polyoxometalates/Active Carbon Thin Separator for Improving Cycle Performance of Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries have great potential for the next generation of energy-storage devices owing to their high theoretical energy density. However, the polysulfides' shuttling effect seriously degraded the cycle stability and capacity and hindered their commercial applications. Here, we design and fabricate a bifunctional composite separator including a polypropylene (PP) matrix layer and Keggin polyoxometalate [PW₁₂O₄₀]^3-/Super P composite retarding layer by utilizing the Coulombic repulsion between polyanion and polysulfides. Such a binary composite separator shows the effects in enhancing the Coulombic efficiency and cycling stability. Compared with the polypropylene (PP) matrix separator, the capacity is improved by 41% after 120 cycles when using the PW₁₂/Super P separator. It is the first time that the polyoxometalate (POM) matrix is used as a bifunctional separator for lithium-sulfur batteries, demonstrating the promise of POM-based separators in reducing the shuttling effect of Li-S battery.

Chitosan-Induced Synthesis of Hierarchical Flower Ridge-like MoS2/N-Doped Carbon Composites with Enhanced Lithium Storage

Continuous hierarchical MoS₂/C micro/nanostructured composite with strong structural stability and efficient lithium ion and electron transport channels is an urgent need for its successful application in lithium ion battery anode materials. In this study, continuous hierarchical flower ridge-like MoS₂/N-doped carbon micro/nanocomposite (MoS₂/NC) was first synthesized through a simple chitosan-induced one-pot hydrothermal and postsintering method. The amino-containing chitosan is demonstrated to be important not only in nitrogen-doped carbon source, soft template, and surfactant but also in controlling the interlayer distance between adjacent MoS₂ layers. The detailed hierarchical structure, phase characteristics, the number of MoS₂ stacked layers, and interlayer distance were characterized using a scanning electron microscope, transmission electron microscope, X-ray diffraction, and so forth. It reveals that the interconnected nanoflowers composed of few-layer MoS₂ (≤3 layers) nanoflakes with an expanded interlayer distance vertically grow on two-dimensional N-doped carbon nanosheets in the MoS₂/NC composite. When examined as anode of lithium ion batteries, this unique hierarchical MoS₂/NC micro/nanostructure shows better electrochemical performance. The electrode delivers a reversible capacity of 904.7 mA h g^-1 at 200 mA g^-1 after 100 cycles, outstanding cycle stability at high rates (742, 686, 534 mA h g^-1 at 500, 1000, 2000 mA g^-1 after 400 cycles, respectively) and superior rate performance. The above synthesis strategy is a good choice for constructing other hierarchical transition-metal disulfides or oxides and carbon micro/nanostructures to improve their electrochemical performance.

Inverse Capacity Growth and Pocket Effect in SnS2 Semifilled Carbon Nanotube Anode

SnS₂ with high theoretical capacity has been impeded from practical applications as the anode of lithium-ion (Li-ion) batteries due to its large volume expansion and fast capacity decay. A nanostructure of the SnS₂ semifilled carbon nanotube (SnS₂@CNT) has been realized by plasma-assisted fabrication of Sn semifilled CNT (Sn@CNT) followed by post-sulfurization. When serving as the anode of a Li-ion battery, SnS₂@CNT delivers an initial discharge capacity of 1258 mAh g^-1 at 0.3 A g^-1. Instead of capacity fading, SnS₂@CNT shows inverse capacity growth to 2733 mAh g^-1 after 470 cycles. The high-resolution transmission electron microscopy images show that the void in CNTs, after cycling, is fully filled with pulverized SnS₂ grains which have a shortened Li-ion diffusion path and enhanced surface area for interfacial redox reactions. In addition, the CNTs, like a pocket, confine the pulverized SnS₂, maintain the electric contact and structural integrity, and thus allow the electrodes to work safely under long cyclic loadings and extreme temperature conditions.

High Rate Magnesium-Sulfur Battery with Improved Cyclability Based on Metal-Organic Framework Derivative Carbon Host

Mg batteries have the advantages of resource abundance, high volumetric energy density, and dendrite-free plating/stripping of Mg anodes. However the injection of highly polar Mg²⁺ cannot maintain the structural integrity of intercalation-type cathodes even for open framework prototypes. The lack of high-voltage electrolytes and sluggish Mg²⁺ diffusion in lattices or through interfaces also limit the energy density of Mg batteries. Mg-S system based on moderate-voltage conversion electrochemistry appears to be a promising solution to high-energy Mg batteries. However, it still suffers from poor capacity and cycling performances so far. Here, a ZIF-67 derivative carbon framework codoped by N and Co atoms is proposed as effective S host for highly reversible Mg-S batteries even under high rates. The discharge capacity is as high as ≈600 mA h g^-1 at 1 C during the first cycle, and it is still preserved at ≈400 mA h g^-1 after at least 200 cycles. Under a much higher rate of 5 C, a capacity of 300-400 mA h g^-1 is still achievable. Such a superior performance is unprecedented among Mg-S systems and benefits from multiple factors, including heterogeneous doping, Li-salt and Cl^- addition, charge mode, and cut-off capacity, as well as separator decoration, which enable the mitigation of electrode passivation and polysulfide loss.