Self-Repairable Silicon Anodes Using a Multifunctional Binder for High-Performance Lithium-Ion Batteries

Despite of extremely high theoretical capacity of Si (3579 mAh g⁻¹), Si anodes suffer from pulverization and delamination of the electrodes induced by large volume change during charge/discharge cycles. To address those issues, herein, self-healable and highly stretchable multifunctional binders, polydioxythiophene:polyacrylic acid:phytic acid (PEDOT:PAA: PA, PDPP) that provide Si anodes with self-healability and excellent structural integrity is designed. By utilizing the self-healing binder, Si anodes self-repair cracks and damages of Si anodes generated during cycling. For the first time, it is demonstrated that Si anodes autonomously self-heal artificially created cracks in electrolytes under practical battery operating conditions. Consequently, this self-healable Si anode can still deliver a reversible capacity of 2312 mAh g⁻¹ after 100 cycles with remarkable initial Coulombic efficiency of 94%, which is superior to other reported Si anodes. Moreover, the self-healing binder possesses enhanced Li-ion diffusivity with additional electronic conductivity, providing excellent rate capability with a capacity of 2084 mAh g⁻¹ at a very high C-rate of 5 C.     

Dendrimer Based Binders Enable Stable Operation of Silicon Microparticle Anodes in Lithium-Ion Batteries

High-capacity anode materials (e.g., Si) are highly needed for high energy density battery systems, but they usually suffer from low initial coulombic efficiency (CE), short cycle life, and low-rate capability caused by large volume changes during the charge and discharge process. Here, a novel dendrimer-based binder for boosting the electrochemical performance of Si anodes is developed. The polyamidoamine (PMM) dendrimer not only can be used as binder, but also can be utilized as a crosslinker to construct 3D polyacrylic acid (PAA)-PMM composite binder for high-performance Si microparticles anodes. Benefiting from maximum interface interaction, strong average peeling force, and high elastic recovery rate of PAA-PMM composite, the Si electrode based on PAA-PMM achieves a high specific capacity of 3590 mAh g⁻¹ with an initial CE of 91.12%, long-term cycle stability with 69.80% retention over 200 cycles, and outstanding rate capability (1534.8 mAh g⁻¹ at 3000 mA g⁻¹). This work opens a new avenue to use dendrimer chemistry for the development of high-performance binders for high-capacity anode materials.     

Carbon Nanotube-Reinforced Dual Carbon Stress-Buffering for Highly Stable Silicon Anode Material in Lithium-Ion Battery

Silicon (Si) anode suffers from huge volume expansion which causes poor structural stability in terms of electrode material, solid electrolyte interface, and electrode, limiting its practical application in high-energy-density lithium-ion batteries. Rationally designing architectures to optimize the stress distribution of Si/carbon (Si/C) composites has been proven to be effective in enhancing their structural stability and cycling stability, but this remains a big challenge. Here, metal-organic frameworks (ZIF-67)-derived carbon nanotube-reinforced carbon framework is employed as an outer protective layer to encapsulate the inner carbon-coated Si nanoparticles (Si@C@CNTs), which features dual carbon stress-buffering to enhance the structural stability of Si/C composite and prolong their cycling lifetime. Finite element simulation proves the structural advantage of dual carbon stress-buffering through significantly relieving stress concentration when Si lithiation. The outer carbon framework also accelerates the charge transfer efficiency during charging/discharging by the improvement of lithium-ion diffusion and electron transport. As a result, the Si@C@CNTs electrode exhibits excellent long-term lifetime and good rate capability, showing a specific capacity of 680 mAh g⁻¹ even at a high rate of 1 A g⁻¹ after 1000 cycles. This work provides insight into the design of robust architectures for Si/C composites by stress optimization.     

Ultrahigh coulombic efficiency electrolyte enables Li||SPAN batteries with superior cycling performance

Raising the coulombic efficiency of lithium metal anode cycling is the deciding step in realizing long-life rechargeable lithium batteries. Here, we designed a highly concentrated salt/ether electrolyte diluted in a fluorinated ether: 1.8 M LiFSI in DEE/BTFE (diethyl ether/bis(2,2,2-trifluoroethyl)ether), which realized an average coulombic efficiency of 99.37% at 0.5 mA cm⁻² and 1 mAh cm⁻² for more than 900 cycles. This electrolyte also maintained a record coulombic efficiency of 98.7% at 10 mA cm⁻², indicative of its ability to provide fast-charging with high cathode loadings. Morphological studies reveal dense, dendrite free Li depositions after prolonged cycling, while surface analyses confirmed the formation of a robust LiF-rich SEI layer on the cycled Li surface. Moreover, we discovered that this ether-based electrolyte is highly compatible with the low-cost, high-capacity SPAN (Sulfurized polyacrylonitrile) cathode, where the constructed Li||SPAN cell exhibited reversible cathode capacity of 579 mAh g⁻¹ and no capacity decay after 1200 cycles. A cell where a high areal loading SPAN electrode (>3.5 mAh cm⁻²) is paired with only onefold excess Li was constructed and cycled at 1.75 mA cm⁻², maintaining a coulombic efficiency of 99.30% for the lithium metal. Computational simulations revealed that at saturation, the Li-FSI complex forms contact ion pairs, with a first solvation shell comprising DEE molecules, and a second solvation shell with a mix of DEE/BTFE. This study provides a path to enable high energy density Li||SPAN batteries with stable cycling.     

The Structural and Electronic Engineering of Molybdenum Disulfide Nanosheets as Carbon-Free Sulfur Hosts for Boosting Energy Density and Cycling Life of Lithium–Sulfur Batteries

The compact sulfur cathodes with high sulfur content and high sulfur loading are crucial to promise high energy density of lithium–sulfur (Li–S) batteries. However, some daunting problems, such as low sulfur utilization efficiency, serious polysulfides shuttling, and poor rate performance, are usually accompanied during practical deployment. The sulfur hosts play key roles. Herein, the carbon-free sulfur host composed of vanadium-doped molybdenum disulfide (VMS) nanosheets is reported. Benefiting from the basal plane activation of molybdenum disulfide and structural advantage of VMS, high stacking density of sulfur cathode is allowed for high areal and volumetric capacities of the electrodes together with the effective suppression of polysulfides shuttling and the expedited redox kinetics of sulfur species during cycling. The resultant electrode with high sulfur content of 89 wt.% and high sulfur loading of 7.2 mg cm⁻² achieves high gravimetric capacity of 900.9 mAh g⁻¹, the areal capacity of 6.48 mAh cm⁻², and volumetric capacity of 940 mAh cm⁻³ at 0.5 C. The electrochemical performance can rival with the state-of-the-art those in the reported Li–S batteries. This work provides methodology guidance for the development of the cathode materials to achieve high-energy-density and long-life Li–S batteries.     

Tellurium: A High-Volumetric-Capacity Potassium-Ion Battery Electrode Material

Currently, exploring high-volumetric-capacity electrode materials that allow for reversible (de-)insertion of large-size K⁺ ions remains challenging. Tellurium (Te) is a promising alternative electrode for storage of K⁺ ions due to its high volumetric capacity, confirmed in lithium-/sodium-ion batteries, and the intrinsic good electronic conductivity. However, the charge storage capability and mechanism of Te in potassium-ion batteries (KIBs) have not been unveiled until now. Here, a novel K–Te battery is constructed, and the K⁺-ion storage mechanism of Te is revealed to be a two-electron conversion-type reaction of 2K + Te ↔ K₂Te, resulting in a high theoretical volumetric capacity of 2619 mAh cm⁻³. Consequently, the rationally fabricated tellurium/porous carbon electrodes deliver an ultrahigh reversible volumetric capacity of 2493.13 mAh cm⁻³ at 0.5 C (based on Te), a high-rate capacity of 783.13 mAh cm⁻³ at 15 C, and superior long-term cycling stability for 1000 cycles at 5 C. This excellent electrochemical performance proves the feasibility of utilizing Te as a high-volumetric-capacity active material for storage of K⁺ ions and will advance the practical application of KIBs.     

Electrochemical investigation of silicon/carbon composite as anode material for lithium ion batteries

Silicon-graphite composites were prepared by mechanical ball milling for 20 h under argon protection. The microstructure and electrochemical performance of the composites were characterized by X-ray diffraction (XRD), scanning electron microscopy, and electrochemical experiments. XRD showed that the materials prepared by ball milling were composites consisting of Si and graphite powders. The composite electrode showed the best performance, especially when annealed at 200 °C for 2 h, which had a reversible capacity of 595 mAh g⁻¹ and an initial coulombic efficiency of 66%, and still retained 469 mAh g⁻¹ after 40 cycles with about 0.6% capacity loss per cycle.     

A Novel Approach to Realize Si‐Based Porous Wire‐In‐Tube Nanostructures for High‐Performance Lithium‐Ion Batteries

Hollow inorganic nanostructures have drawn great attention due to their fascinating features, such as large surface area, high loading capacity, and high permeability. The formation, characterization, and application of partially and entirely hollow structure by applying a Si‐based reactive ion deposition and etching method on silicon nanowire as a template are reported. This fabrication technique is extended to a stainless steel substrate to be used as the binder‐free anode for high capacity and high rate lithium‐ion batteries. The electrochemical analyses exhibit that in addition to the high initial discharge capacity of 4125 mAh g^?1 at a rate of C/16, the best performing electrode shows discharge/charge capacity of as high as 3302.14/2832.1 mAh g^?1, respectively, with an excellent charge capacity retention of 96.7% over 100 cycles at a rate density of 1 C. Even at a rate of 12 C, the as‐designed structure is still able to deliver an impressive 1553 mAh g^?1, which probably is attributed to fast lithium diffusion in its hollow part and high porosity of Si and alumina layer. It is proved that the change in hollowness ratio significantly affects capacity retention and average coulombic efficiency of the lithium‐ion cells.     

Stacking‐Controlled Assembly of Cabbage‐Like Graphene Microsphere for Charge Storage Applications

Nanostructured graphene electrodes generally have a low density, which can limit the volumetric performance for energy storage devices. The liquid‐phase mild reduction process of graphene oxide sheets is combined with the continuous aerosol densification process to produce high‐density graphene agglomerates in the form of microspheres. The produced graphene assembly shows the cabbage‐like morphology with a high density of 0.75 g cm^?3. In spite of such high density, the cabbage‐like graphene microspheres have narrow‐ranged mesopores and a high surface area. The cabbage‐like graphene microsphere exhibits both high gravimetric and volumetric energy densities due to the optimized microstructure, which shows a high gravimetric capacitance of 177 F g^?1 and volumetric capacitance of 117 F cm^?3 in supercapacitors. As a cathode for lithium‐ion capacitors, the cabbage‐like graphene delivers a reversible capacity of ≈176 mAh g^?1. The stacking‐control approach provides a new pathway to control the microstructure of the graphene assembly and corresponding charge storage characteristics for energy storage applications.     

High-Energy Interlayer-Expanded Copper Sulfide Cathode Material in Non-Corrosive Electrolyte for Rechargeable Magnesium Batteries

Rechargeable magnesium batteries (RMB) have been regarded as an alternative to lithium-based batteries because of their abundant elemental resource, high theoretical volumetric capacity, and multi-electron redox reaction without the dendrite formation of magnesium metal anode. However, their development is impeded by their poor electrode/electrolyte compatibility and the strong Coulombic effect of the multivalent Mg²⁺ ions in cathode materials. Herein, copper sulfide material is developed as a high-energy cathode for RMBs with a non-corrosive Mg-ion electrolyte. Given the benefit of its optimized interlayer structure, good compatibility with the electrolyte, and enhanced surface area, the as-prepared copper sulfide cathode exhibits unprecedented electrochemical Mg-ion storage properties, with the highest specific capacity of 477 mAh g⁻¹ and gravimetric energy density of 415 Wh kg⁻¹ at 50 mA g⁻¹, among the reported cathode materials of metal oxides, metal chalcogenides, and polyanion-type compounds for RMBs. Notably, an impressive long-term cycling performance with a stable capacity of 111 mAh g⁻¹ at 1 C (560 mA g⁻¹) is achieved over 1000 cycles. The results of the present study offer an avenue for designing high-performance cathode materials for RMBs and other multivalent batteries.     

Nanoscale Borate Coating Network Stabilized Iron Oxide Anode for High-Energy-Density Bipolar Lithium-Ion Batteries

High-capacity metal oxides based on non-toxic earth-abundant elements offer unique opportunities as advanced anodes for lithium-ion batteries (LIBs). But they often suffer from large volumetric expansion, particle pulverization, extensive side reactions, and fast degradations during cycling. Here, an easy synthesis method is reported to construct amorphous borate coating network, which stabilizes conversion-type iron oxide anode for the high-energy-density semi-solid-state bipolar LIBs. The nano-borate coated iron oxide anode has high tap density (1.6 g cm⁻³), high capacity (710 mAh g⁻¹ between 0.5 – 3.0 V, vs Li/Li⁺), good rate performance (200 mAh g⁻¹ at 50 C), and excellent cycling stability (≈100% capacity resention over 1,000 cycles at 5 A g⁻¹). When paired with high-voltage cathode LiCoO₂, it enables Cu current collector-free pouch-type classic and bipolar full cells with high voltage (7.6 V with two stack layers), achieving high energy density (≈350 Wh kg⁻¹), outstanding power density (≈6,700 W kg⁻¹), and extended cycle life (75% capacity retention after 2,000 cycles at 2 C), superior to the state-of-the-art high-power LIBs using Li₄Ti₅O₁₂ anode. The design and methodology of the nanoscale polyanion-like coating can be applied to other metal oxides electrode materials, as well as other electrochemical materials and devices.     

Silicon Decorated Cone Shaped Carbon Nanotube Clusters for Lithium Ion Battery Anodes

In this work, we report the synthesis of an three‐dimensional (3D) cone‐shape CNT clusters (CCC) via chemical vapor deposition (CVD) with subsequent inductively coupled plasma (ICP) treatment. An innovative silicon decorated cone‐shape CNT clusters (SCCC) is prepared by simply depositing amorphous silicon onto CCC via magnetron sputtering. The seamless connection between silicon decorated CNT cones and graphene facilitates the charge transfer in the system and suggests a binder‐free technique of preparing lithium ion battery (LIB) anodes. Lithium ion batteries based on this novel 3D SCCC architecture demonstrates high reversible capacity of 1954 mAh g^?1 and excellent cycling stability (>1200 mAh g^?1 capacity with ≈100% coulombic efficiency after 230 cycles).     

Coordinating Interface Polymerization with Micelle Mediated Assembly Towards Two-Dimensional Mesoporous Carbon/CoNi for Advanced Lithium–Sulfur Battery

Lithium-sulfur battery has attracted significant attention by virtues of their high theoretical energy density, natural abundance, and environmental friendliness. However, the notorious shuttle effect of polysulfides intermediates severely hinders its practical application. Herein, a novel 2D mesoporous N-doped carbon nanosheet with confined bimetallic CoNi nanoparticles sandwiched graphene (mNC-CoNi@rGO) is successfully fabricated through a coordinating interface polymerization and micelle mediated co-assembly strategy. mNC-CoNi@rGO serves as a robust host material that endows lithium-sulfur batteries with a high reversible capacity of 1115 mAh g⁻¹ at 0.2 C after 100 cycles, superior rate capability, and excellent cycling stability with 679.2 mAh g⁻¹ capacity retention over 700 cycles at 1 C. With sulfur contents of up to 5.0 mg cm⁻², the area capacity remains to be 5.1 mAh cm⁻² after 100 cycles at 0.2 C. The remarkable performance is further resolved via a series of experimental characterizations combined with density functional theory calculations. These results reveal that the ordered mesoporous N-doped carbon-encapsulated graphene framework acts as the ion/electron transport highway with excellent electrical conductivity, while bimetallic CoNi nanoparticles enhance the polysulfides adsorption and catalytic conversion that simultaneously accelerate the multiphase sulfur/polysulfides/sulfides conversion and inhibit the polysulfides shuttle.     

Graphene Caging Silicon Particles for High‐Performance Lithium‐Ion Batteries

Silicon holds great promise as an anode material for lithium‐ion batteries with higher energy density; its implication, however, is limited by rapid capacity fading. A catalytic growth of graphene cages on composite particles of magnesium oxide and silicon, which are made by magnesiothermic reduction reaction of silica particles, is reported herein. Catalyzed by the magnesium oxide, graphene cages can be conformally grown onto the composite particles, leading to the formation of hollow graphene‐encapsulated Si particles. Such materials exhibit excellent lithium storage properties in terms of high specific capacity, remarkable rate capability (890 mAh g^?1 at 5 A g^?1), and good cycling retention over 200 cycles with consistently high coulombic efficiency at a current density of 1 A g^?1. A full battery test using LiCoO₂ as the cathode demonstrates a high energy density of 329 Wh kg^?1.     

A Quadruple‐Hydrogen‐Bonded Supramolecular Binder for High‐Performance Silicon Anodes in Lithium‐Ion Batteries

With extremely high specific capacity, silicon has attracted enormous interest as a promising anode material for next‐generation lithium‐ion batteries. However, silicon suffers from a large volume variation during charge/discharge cycles, which leads to the pulverization of the silicon and subsequent separation from the conductive additives, eventually resulting in rapid capacity fading and poor cycle life. Here, it is shown that the utilization of a self‐healable supramolecular polymer, which is facilely synthesized by copolymerization of tert‐butyl acrylate and an ureido‐pyrimidinone monomer followed by hydrolysis, can greatly reduce the side effects caused by the volume variation of silicon particles. The obtained polymer is demonstrated to have an excellent self‐healing ability due to its quadruple‐hydrogen‐bonding dynamic interaction. An electrode using this self‐healing supramolecular polymer as binder exhibits an initial discharge capacity as high as 4194 mAh g⁻¹ and a Coulombic efficiency of 86.4%, and maintains a high capacity of 2638 mAh g⁻¹ after 110 cycles, revealing significant improvement of the electrochemical performance in comparison with that of Si anodes using conventional binders. The supramolecular binder can be further applicable for silicon/carbon anodes and therefore this supramolecular strategy may increase the choice of amendable binders to improve the cycle life and energy density of high‐capacity Li‐ion batteries.     

Surface Coating Constraint Induced Anisotropic Swelling of Silicon in Si–Void@SiO x Nanowire Anode for Lithium‐Ion Batteries

Here a simple and an environmentally friendly approach is developed for the fabrication of Si–void@SiO_x nanowires of a high‐capacity Li‐ion anode material. The outer surface of the robust SiO_x backbone and the inside void structure in Si–void@SiO_x nanowires appropriately suppress the volume expansion and lead to anisotropic swelling morphologies of Si nanowires during lithiation/delithiation, which is first demonstrated by the in situ lithiation process. Remarkably, the Si–void@SiO_x nanowire electrode exhibits excellent overall lithium‐storage performance, including high specific capacity, high rate property, and excellent cycling stability. A reversible capacity of 1981 mAh g^?1 is obtained in the fourth cycle, and the capacity is maintained at 2197 mAh g^?1 after 200 cycles at a current density of 0.5 C. The outstanding overall properties of the Si–void@SiO_x nanowire composite make it a promising anode material of lithium‐ion batteries for the power‐intensive energy storage applications.     

Exploiting High-Voltage Stability of Dual-Ion Aqueous Electrolyte Reinforced by Incorporation of Fiberglass into Zwitterionic Hydrogel Electrolyte

Rechargeable zinc aqueous batteries are key alternatives for replacing toxic, flammable, and expensive lithium-ion batteries in grid energy storage systems. However, these systems possess critical weaknesses, including the short electrochemical stability window of water and intrinsic fast zinc dendrite growth. Hydrogel electrolytes provide a possible solution, especially cross-linked zwitterionic polymers that possess strong water retention ability and high ionic conductivity. Herein, an in situ prepared fiberglass-incorporated dual-ion zwitterionic hydrogel electrolyte with an ionic conductivity of 24.32 mS cm⁻¹, electrochemical stability window up to 2.56 V, and high thermal stability is presented. By incorporating this hydrogel electrolyte of zinc and lithium triflate salts, a zinc//LiMn_0.6Fe_0.4PO₄ pouch cell delivers a reversible capacity of 130 mAh g⁻¹ in the range of 1.0–2.2 V at 0.1C, and the test at 2C provides an initial capacity of 82.4 mAh g⁻¹ with 71.8% capacity retention after 1000 cycles with a coulombic efficiency of 97%. Additionally, the pouch cell is fire resistant and remains safe after cutting and piercing.     

Dual‐Functionalized Double Carbon Shells Coated Silicon Nanoparticles for High Performance Lithium‐Ion Batteries

To address the challenge of huge volume change and unstable solid electrolyte interface (SEI) of silicon in cycles, causing severe pulverization, this paper proposes a “double‐shell” concept. This concept is designed to perform dual functions on encapsulating volume change of silicon and stabilizing SEI layer in cycles using double carbon shells. Double carbon shells coated Si nanoparticles (DCS‐Si) are prepared. Inner carbon shell provides finite inner voids to allow large volume changes of Si nanoparticles inside of inner carbon shell, while static outer shell facilitates the formation of stable SEI. Most importantly, intershell spaces are preserved to buffer volume changes and alleviate mechanical stress from inner carbon shell. DCS‐Si electrodes display a high rechargeable specific capacity of 1802 mAh g⁻¹ at a current rate of 0.2 C, superior rate capability and good cycling performance up to 1000 cycles. A full cell of DCS‐Si//LiNi_0.45Co_0.1Mn_1.45O₄ exhibits an average discharge voltage of 4.2 V, a high energy density of 473.6 Wh kg⁻¹, and good cycling performance. Such double‐shell concept can be applied to synthesize other electrode materials with large volume changes in cycles by simultaneously enhancing electronic conductivity and controlling SEI growth.     

Ultra‐light Hierarchical Graphene Electrode for Binder‐Free Supercapacitors and Lithium‐Ion Battery Anodes

A mild and environmental‐friendly method is developed for fabricating a 3D interconnected graphene electrode with large‐scale continuity. Such material has interlayer pores between reduced graphene oxide nanosheets and in‐plane pores. Hence, a specific surface area up to 835 m² g⁻¹ and a high powder conductivity up to 400 S m⁻¹ are achieved. For electrochemical applications, the interlayer pores can serve as “ion‐buffering reservoirs” while in‐plane ones act as “channels” for shortening the mass cross‐plane diffusion length, reducing the ion response time, and prevent the interlayer restacking. As binder‐free supercapacitor electrode, it delivers a specific capacitance up to 169 F g⁻¹ with surface‐normalized capacitance close to 21 μF cm⁻² (intrinsic capacitance) and power density up to 7.5 kW kg⁻¹, in 6 m KOH aqueous electrolyte. In the case of lithium‐ion battery anode, it shows remarkable advantages in terms of the initiate reversible Coulombic efficiency (61.3%), high specific capacity (932 mAh g⁻¹ at 100 mA g⁻¹), and robust long‐term retention (93.5% after 600 cycles at 2000 mAh g⁻¹).     

Establishing Transition Metal Phosphides as Effective Sulfur Hosts in Lithium–Sulfur Batteries through the Triple Effect of “Confinement–Adsorption–Catalysis”

Structurally optimized transition metal phosphides are identified as a promising avenue for the commercialization of lithium–sulfur (Li–S) batteries. In this study, a CoP nanoparticle-doped hollow ordered mesoporous carbon sphere (CoP-OMCS) is developed as a S host with a “Confinement–Adsorption–Catalysis” triple effect for Li–S batteries. The Li-S batteries with CoP-OMCS/S cathode demonstrate excellent performance, delivering a discharge capacity of 1148 mAh g⁻¹ at 0.5 C and good cycling stability with a low long-cycle capacity decay rate of 0.059% per cycle. Even at a high current density of 2 C after 200 cycles, a high specific discharge capacity of 524 mAh g⁻¹ is maintained. Moreover, a reversible areal capacity of 6.56 mAh cm⁻² is achieved after 100 cycles at 0.2 C, despite a high S loading of 6.8 mg cm⁻². Density functional theory (DFT) calculations show that CoP exhibits enhanced adsorption capacity for sulfur-containing substances. Additionally, the optimized electronic structure of CoP significantly reduces the energy barrier during the conversion of Li₂S₄ (L) to Li₂S₂ (S). In summary, this work provides a promising approach to optimize transition metal phosphide materials structurally and design cathodes for Li–S batteries.