3D Hierarchical Porous α‐Fe2O3 Nanosheets for High‐Performance Lithium‐Ion Batteries

To develop a long cycle life and good rate capability electrode, 3D hierarchical porous α‐Fe₂O₃ nanosheets are fabricated on copper foil and directly used as binder‐free anode for lithium‐ion batteries. This electrode exhibits a high reversible capacity and excellent rate capability. A reversible capacity up to 877.7 mAh g^?1 is maintained at 2 C (2.01 A g^?1) after 1000 cycles, and even when the current is increased to 20 C (20.1 A g^?1), a capacity of 433 mA h g^?1 is retained. The unique porous 3D hierarchical nanostructure improves electronic–ionic transport, mitigates the internal mechanical stress induced by the volume variations of the electrode upon cycling, and forms a 3D conductive network during cycling. No addition of any electrochemically inactive conductive agents or polymer binders is required. Therefore, binder‐free electrodes further avoid the uneven distribution of conductive carbon on the current collector due to physical mixing and the addition of an insulator (binder), which has benefits leading to outstanding electrochemical performance.     

3D Amorphous Carbon with Controlled Porous and Disordered Structures as a High‐Rate Anode Material for Sodium‐Ion Batteries

Sodium‐ion batteries (SIBs) have a promising application prospect for energy storage systems due to the abundant resource. Amorphous carbon with high electronic conductivity and high surface area is likely to be the most promising anode material for SIBs. However, the rate capability of amorphous carbon in SIBs is still a big challenge because of the sluggish kinetics of Na⁺ ions. Herein, a three‐dimensional amorphous carbon (3DAC) with controlled porous and disordered structures is synthesized via a facile NaCl template‐assisted method. Combination of open porous structures of 3DAC, the increased disordered structures can not only facilitate the diffusion of Na⁺ ions but also enhance the reversible capacity of Na storage. When applied as anode materials for SIBs, 3DAC exhibits excellent rate capability (66 mA h g^?1 at 9.6 A g^?1) and high reversible capacity (280 mA h g^?1 at a low current density of 0.03 A g^?1). Moreover, the controlled porous structures by the NaCl template method provide an appropriate specific surface area, which contributes to a relatively high initial Coulombic efficiency of 75%. Additionally, the high‐rate 3DAC material is prepared via a green approach originating from low‐cost pitch and NaCl template, demonstrating an appealing development of carbon anode materials for SIBs.     

Electrochemical Performance of Porous Carbon/Tin Composite Anodes for Sodium‐Ion and Lithium‐Ion Batteries

The electrochemical performance of mesoporous carbon (C)/tin (Sn) anodes in Na‐ion and Li‐ion batteries is systematically investigated. The mesoporous C/Sn anodes in a Na‐ion battery shows similar cycling stability but lower capacity and poorer rate capability than that in a Li‐ion battery. The desodiation potentials of Sn anodes are approximately 0.21 V lower than delithiation potentials. The low capacity and poor rate capability of C/Sn anode in Na‐ion batteries is mainly due to the large Na‐ion size, resulting in slow Na‐ion diffusion and large volume change of porous C/Sn composite anode during alloy/dealloy reactions. Understanding of the reaction mechanism between Sn and Na ions will provide insight towards exploring and designing new alloy‐based anode materials for Na‐ion batteries.     

Mesoporous TiO2‐Sn/C Core‐Shell Nanowire Arrays as High‐Performance 3D Anodes for Li‐Ion Batteries

Three‐dimensional mesoporous TiO₂‐Sn/C core‐shell nanowire arrays are prepared on Ti foil as anodes for lithium‐ion batteries. Sn formed by a reduction of SnO₂ is encapsulated into TiO₂ nanowires and the carbon layer is coated onto it. For additive‐free, self‐supported anodes in Li‐ion batteries, this unique core‐shell composite structure can effectively buffer the volume change, suppress cracking, and improve the conductivity of the electrode during the discharge‐charge process, thus resulting in superior rate capability and excellent long‐term cycling stability. Specifically, the TiO₂‐Sn/C nanowire arrays display rechargeable discharge capacities of 769, 663, 365, 193, and 90 mA h g^?1 at 0.1C, 0.5C, 2C 10C, and 30C, respectively (1C = 335 mA g^?1). Furthermore, the TiO₂‐Sn/C nanowire arrays exhibit a capacity retention rate of 84.8% with a discharge capacity of over 160 mA h g^?1, even after 100 cycles at a high current rate of 10C.     

A Novel α‐MoO3/Single‐Walled Carbon Nanohorns Composite as High‐Performance Anode Material for Fast‐Charging Lithium‐Ion Battery

Orthorhombic α‐MoO₃ is a potential anode material for lithium‐ion batteries due to its high theoretical capacity of 1100 mAh g^?1 and excellent structural stability. However, its intrinsic poor electronic conductivity and high volume expansion during the charge–discharge process impede it from achieving a high practical capacity. A novel composite of α‐MoO₃ nanobelts and single‐walled carbon nanohorns (SWCNHs) is synthesized by a facile microwave hydrothermal technique and demonstrated as a high‐performance anode material for lithium‐ion batteries. The α‐MoO₃/SWCNH composite displays superior electrochemical properties (654 mAh g^?1 at 1 C), excellent rate capability (275 mAh g^?1 at 5 C), and outstanding cycle life (capacity retention of >99% after 3000 cycles at 1 C) without any cracking of the electrode. The presence of SWCNHs in the composite enhances the electrochemical properties of α‐MoO₃ by acting as a lithium storage material, electronic conductive medium, and buffer against pulverization.     

Highly Doped 3D Graphene Na‐Ion Battery Anode by Laser Scribing Polyimide Films in Nitrogen Ambient

Conventional graphite anodes can hardly intercalate sodium (Na) ions, which poses a serious challenge for developing Na‐ion batteries. This study details a novel method that involves single‐step laser‐based transformation of urea‐containing polyimide into an expanded 3D graphene anode, with simultaneous doping of high concentrations of nitrogen (≈13 at%). The versatile nature of this laser‐scribing approach enables direct bonding of the 3D graphene anode to the current collectors without the need for binders or conductive additives, which presents a clear advantage over chemical or hydrothermal methods. It is shown that these conductive and expanded 3D graphene structures perform exceptionally well as anodes for Na‐ion batteries. Specifically, an initial coulombic efficiency (CE) up to 74% is achieved, which exceeds that of most reported carbonaceous anodes, such as hard carbon and soft carbon. In addition, Na‐ion capacity up to 425 mAh g^?1 at 0.1 A g^?1 has been achieved with excellent rate capabilities. Further, a capacity of 148 mAh g^?1 at a current density of 10 A g^?1 is obtained with excellent cycling stability, opening a new direction for the fabrication of 3D graphene anodes directly on current collectors for metal ion battery anodes as well as other potential applications.     

Ultrathin MoS2 Nanosheets as Anode Materials for Sodium‐Ion Batteries with Superior Performance

Few‐layer MoS₂ nanosheets are successfully synthesized using a simple and scalable ultrasonic exfoliation technique. The thicknesses of the MoS₂ nanosheets ares about 10 nm as measured by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The unique nanosheet architecture renders the high‐rate transportation of sodium ions due to the short diffusion paths provided by ultrathin thickness and the large interlayer space within the MoS₂ crystal structure (d₍₀₀₂₎ = 6.38 Å). When applied as anode materials in sodium‐ion batteries, MoS₂ nanosheets exhibit a high, reversible sodium storage capacity and excellent cyclability. The MoS₂ nanosheets also demonstrate good electrochemical performance at high current densities.     

Hard Carbon Microtubes Made from Renewable Cotton as High‐Performance Anode Material for Sodium‐Ion Batteries

Sodium‐ion batteries (SIBs) have attracted more and more attention for scalable electrical energy storage due to the abundance and wide distribution of Na resources. However, the anode still remains a great challenge for the application of SIBs. Here the production of uniform hard carbon microtubes (HCTs) made from natural cotton through one simple carbonization process and their application as an anode are reported. The study shows that the electrochemical performance of the HCTs is seriously affected by the carbonization temperature due to the difference in their microstructure and heteroatomic content. The HCTs carbonized at 1300 °C deliver the highest reversible capacity of 315 mAh g^?1 and good rate capability due to their unique tubular structure. This contribution not only provides a new approach for the preparation of hard carbon materials with unique tubular microstructure using natural inspiration, but it also deepens the fundamental understanding of the sodium storage mechanism.     

Structural Engineering of Multishelled Hollow Carbon Nanostructures for High‐Performance Na‐Ion Battery Anode

Hard carbon has long been considered the leading candidate for anode materials of Na‐ion batteries. Intensive research efforts have been carried out in the search of suitable carbon structure for an improved storage capability. Herein, an anode based on multishelled hollow carbon nanospheres, which are able to deliver an outstanding electrochemical performance with an extraordinary reversible capacity of 360 mAh g^?1 at 30 mA g^?1, is designed. An interesting dependence of the electrochemical properties on the multishelled structural features is identified: with an increase in the shell number of the model carbon materials, the sloping capacity in the charge/discharge curve remains almost unchanged while the plateau capacity continuously increases, suggesting an adsorption‐filling Na‐storage mechanism for the multishelled hollow hard carbon materials. The findings not only provide new perspective in the structural design of high‐performance anode materials, but also shed light on the complicated mechanism behind Na‐storage by hard carbon.     

3D Porous Cu–Zn Alloys as Alternative Anode Materials for Li‐Ion Batteries with Superior Low T Performance

Zinc is recently gaining interest in the battery community as potential alternative anode material, because of its large natural abundance and potentially larger volumetric density than graphite. Nevertheless, pure Zn anodes have shown so far very poor cycling performance. Here, the electrochemical performance of Zn‐rich porous Cu–Zn alloys electrodeposited by an environmentally friendly (aqueous) dynamic hydrogen bubble template method is reported. The lithiation/delithiation mechanism is studied in detail by both in situ and ex situ X‐ray diffraction, indicating the reversible displacement of Zn from the Cu–Zn alloy upon reaction with Li. The influence of the alloy composition on the performance of carbon‐ and binder‐free electrodes is also investigated. The optimal Cu:Zn atomic ratio is found to be 18:82, which provides impressive rate capability up to 10 A g^?1 (≈30C), and promising capacity retention upon more than 500 cycles. The high electronic conductivity provided by Cu, and the porous electrode morphology also enable superior lithium storage capability at low temperature. Cu₁₈Zn₈₂ can indeed steadily deliver ≈200 mAh g^?1 at ?20 °C, whereas an analogous commercial graphite electrode rapidly fades to only 12 mAh g^?1.     

A High‐Energy NASICON‐Type Cathode Material for Na‐Ion Batteries

Over the last decade, Na‐ion batteries have been extensively studied as low‐cost alternatives to Li‐ion batteries for large‐scale grid storage applications; however, the development of high‐energy positive electrodes remains a major challenge. Materials with a polyanionic framework, such as Na superionic conductor (NASICON)‐structured cathodes with formula Na_xM₂(PO₄)₃, have attracted considerable attention because of their stable 3D crystal structure and high operating potential. Herein, a novel NASICON‐type compound, Na₄MnCr(PO₄)₃, is reported as a promising cathode material for Na‐ion batteries that deliver a high specific capacity of 130 mAh g^?1 during discharge utilizing high‐voltage Mn^2+/3+ (3.5 V), Mn^3+/4+ (4.0 V), and Cr^3+/4+ (4.35 V) transition metal redox. In addition, Na₄MnCr(PO₄)₃ exhibits a high rate capability (97 mAh g^?1 at 5 C) and excellent all‐temperature performance. In situ X‐ray diffraction and synchrotron X‐ray diffraction analyses reveal reversible structural evolution for both charge and discharge.     

1T′‐ReS2 Confined in 2D‐Honeycombed Carbon Nanosheets as New Anode Materials for High‐Performance Sodium‐Ion Batteries

ReS₂ (rhenium disulfide) is a new transition‐metal dichalcogenide that exhibits 1T′ phase and extremely weak interlayer van der Waals interactions. This makes it promising as an anode material for sodium‐ion batteries. However, achieving both a high‐rate capability and a long‐life has remained a major research challenge. Here, a new composite is reported, in which both are realized for the first time. 1T′‐ReS₂ is confined through strong interfacial interaction in a 2D‐honeycombed carbon nanosheets that comprise an rGO inter‐layer and a N‐doped carbon coating‐layer (rGO@ReS₂@N‐C). The strong interfacial interaction between carbon and ReS₂ increases overall conductivity and decreases Na⁺ diffusion resistance, whilst the intended 2D‐honeycombed carbon protective layer maintains structural morphology and electrochemical activity during long‐term cycling. These findings are confirmed by advanced characterization techniques, electrochemical measurement, and density functional theory calculation. The new rGO@ReS₂@N‐C exhibits the greatest rate performance reported so far for ReS₂ of 231 mAh g^?1 at 10 A g^?1. Significantly, this is together with ultra‐stable long‐term cycling of 192 mAh g^?1 at 2 A g^?1 after 4000 cycles.     

Soft Carbon as Anode for High‐Performance Sodium‐Based Dual Ion Full Battery

Sodium‐based dual ion full batteries (NDIBs) are reported with soft carbon as anode and graphite as cathode for the first time. The NDIBs operate at high discharge voltage plateau of 3.58 V, with superior discharge capacity of 103 mA h g^?1, excellent rate performance, and long‐term cycling stability over 800 cycles with capacity retention of 81.8%. The mechanism of Na⁺ and PF₆^? insertion/desertion during the charging/discharging processes is proposed and discussed in detail, with the support of various spectroscopies.