Scalable 2D Mesoporous Silicon Nanosheets for High‐Performance Lithium‐Ion Battery Anode

Constructing unique mesoporous 2D Si nanostructures to shorten the lithium‐ion diffusion pathway, facilitate interfacial charge transfer, and enlarge the electrode–electrolyte interface offers exciting opportunities in future high‐performance lithium‐ion batteries. However, simultaneous realization of 2D and mesoporous structures for Si material is quite difficult due to its non‐van der Waals structure. Here, the coexistence of both mesoporous and 2D ultrathin nanosheets in the Si anodes and considerably high surface area (381.6 m² g^?1) are successfully achieved by a scalable and cost‐efficient method. After being encapsulated with the homogeneous carbon layer, the Si/C nanocomposite anodes achieve outstanding reversible capacity, high cycle stability, and excellent rate capability. In particular, the reversible capacity reaches 1072.2 mA h g^?1 at 4 A g^?1 even after 500 cycles. The obvious enhancements can be attributed to the synergistic effect between the unique 2D mesoporous nanostructure and carbon capsulation. Furthermore, full‐cell evaluations indicate that the unique Si/C nanostructures have a great potential in the next‐generation lithium‐ion battery. These findings not only greatly improve the electrochemical performances of Si anode, but also shine some light on designing the unique nanomaterials for various energy devices.     

Strong Coupling of MoS2 Nanosheets and Nitrogen‐Doped Graphene for High‐Performance Pseudocapacitance Lithium Storage

Layered material MoS₂ is widely applied as a promising anode for lithium‐ion batteries (LIBs). Herein, a scalable and facile dopamine‐assisted hydrothermal technique for the preparation of strongly coupled MoS₂ nanosheets and nitrogen‐doped graphene (MoS₂/N‐G) composite is developed. In this composite, the interconnected MoS₂ nanosheets are well wrapped onto the surface of graphene, forming a unique veil‐like architecture. Experimental results indicate that dopamine plays multiple roles in the synthesis: a binding agent to anchor and uniformly disperse MoS₂ nanosheets, a morphology promoter, and the precursor for in situ nitrogen doping during the self‐polymerization process. Density functional theory calculations further reveal that a strong interaction exists at the interface of MoS₂ nanosheets and nitrogen‐doped graphene, which facilitates the charge transfer in the hybrid system. When used as the anode for LIBs, the resulting MoS₂/N‐G composite electrode exhibits much higher and more stable Li‐ion storage capacity (e.g., 1102 mAh g^?1 at 100 mA g^?1) than that of MoS₂/G electrode without employing the dopamine linker. Significantly, it is also identified that the thin MoS₂ nanosheets display outstanding high‐rate capability due to surface‐dominated pseudocapacitance contribution.     

S‐Doped TiSe2 Nanoplates/Fe3O4 Nanoparticles Heterostructure

2D Sulfur‐doped TiSe₂/Fe₃O₄ (named as S‐TiSe₂/Fe₃O₄) heterostructures are synthesized successfully based on a facile oil phase process. The Fe₃O₄ nanoparticles, with an average size of 8 nm, grow uniformly on the surface of S‐doped TiSe₂ (named as S‐TiSe₂) nanoplates (300 nm in diameter and 15 nm in thickness). These heterostructures combine the advantages of both S‐TiSe₂ with good electrical conductivity and Fe₃O₄ with high theoretical Li storage capacity. As demonstrated potential applications for energy storage, the S‐TiSe₂/Fe₃O₄ heterostructures possess high reversible capacities (707.4 mAh g⁻¹ at 0.1 A g⁻¹ during the 100th cycle), excellent cycling stability (432.3 mAh g⁻¹ after 200 cycles at 5 A g⁻¹), and good rate capability (e.g., 301.7 mAh g⁻¹ at 20 A g⁻¹) in lithium‐ion batteries. As for sodium‐ion batteries, the S‐TiSe₂/Fe₃O₄ heterostructures also maintain reversible capacities of 402.3 mAh g⁻¹ at 0.1 A g⁻¹ after 100 cycles, and a high rate capacity of 203.3 mAh g⁻¹ at 4 A g⁻¹.     

Rational Design of Three‐Layered TiO2@Carbon@MoS2 Hierarchical Nanotubes for Enhanced Lithium Storage

Here we demonstrate the rational design and synthesis of three‐layered TiO₂@carbon@MoS₂ hierarchical nanotubes for anode applications in lithium‐ion batteries (LIBs). Through an efficient step‐by‐step strategy, ultrathin MoS₂ nanosheets are grown on nitrogen‐doped carbon (NC) coated TiO₂ nanotubes to achieve the TiO₂@NC@MoS₂ tubular nanostructures. This smart design can effectively shorten the diffusion length of Li⁺ ions, increase electric conductivity of the electrode, relax volume variation of electrode materials upon cycling, and provide more active sites for electrochemical reactions. Owing to these structural and compositional features, the hierarchical TiO₂@NC@MoS₂ nanotubes manifest remarkable lithium storage performance with good rate capability and long cycle life.     

Elaborately Designed Hierarchical Heterostructures Consisting of Carbon‐Coated TiO2(B) Nanosheets Decorated with Fe3O4 Nanoparticles for Remarkable Synergy in High‐Rate Lithium Storage

The capacity and conductivity deficiencies of TiO₂(B) are addressed simultaneously through a smart morphological and compositional design. Elaborately designed hierarchical heterostructures are reported, consisting of carbon‐coated TiO₂(B) nanosheets decorated with Fe₃O₄ nanoparticles, based on a facile self‐assembly strategy. The novel hierarchical heterostructures exhibit a remarkable synergy by bridging the intriguing functionalities of TiO₂(B) nanosheets (high safety and durability), Fe₃O₄ nanoparticles (high theoretical capacity), and carbon coatings (high conductivity), which results in significantly improved cycle and rate performances. A startlingly high reversible capacity of 763 mA h g⁻¹ is delivered at 500 mA g⁻¹ after 200 charging−discharging cycles. Even when the current density is as high as 10 000 mA g⁻¹, the reversible capacity is still up to 498 mA h g⁻¹. This smart morphological and compositional design opens up new opportunities for developing novel, multifunctional hierarchical heterostructures as promising anode materials for next‐generation, high‐power lithium‐ion batteries.     

A Single‐Step Hydrothermal Route to 3D Hierarchical Cu2O/CuO/rGO Nanosheets as High‐Performance Anode of Lithium‐Ion Batteries

As anodes of Li‐ion batteries, copper oxides (CuO) have a high theoretical specific capacity (674 mA h g^?1) but own poor cyclic stability owing to the large volume expansion and low conductivity in charges/discharges. Incorporating reduced graphene oxide (rGO) into CuO anodes with conventional methods fails to build robust interaction between rGO and CuO to efficiently improve the overall anode performance. Here, Cu₂O/CuO/reduced graphene oxides (Cu₂O/CuO/rGO) with a 3D hierarchical nanostructure are synthesized with a facile, single‐step hydrothermal method. The Cu₂O/CuO/rGO anode exhibits remarkable cyclic and high‐rate performances, and particularly the anode with 25 wt% rGO owns the best performance among all samples, delivering a record capacity of 550 mA h g^?1 at 0.5 C after 100 cycles. The pronounced performances are attributed to the highly efficient charge transfer in CuO nanosheets encapsulated in rGO network and the mitigated volume expansion of the anode owing to its robust 3D hierarchical nanostructure.     

Novel 2D Layered Molybdenum Ditelluride Encapsulated in Few‐Layer Graphene as High‐Performance Anode for Lithium‐Ion Batteries

Molybdenum ditelluride nanosheets encapsulated in few‐layer graphene (MoTe₂/FLG) are synthesized by a simple heating method using Te and Mo powder and subsequent ball milling with graphite. The as‐prepared MoTe₂/FLG nanocomposites as anode materials for lithium‐ion batteries exhibit excellent electrochemical performance with a highly reversible capacity of 596.5 mAh g^?1 at 100 mA g^?1, a high rate capability (334.5 mAh g^?1 at 2 A g^?1), and superior cycling stability (capacity retention of 99.5% over 400 cycles at 0.5 A g^?1). Ex situ X‐ray diffraction and transmission electron microscopy are used to explore the lithium storage mechanism of MoTe₂. Moreover, the electrochemical performance of a MoTe₂/FLG//0.35Li₂MnO₃·0.65LiMn_0.5Ni_0.5O₂ full cell is investigated, which displays a reversible capacity of 499 mAh g^?1 (based on the MoTe₂/FLG mass) at 100 mA g^?1 and a capacity retention of 78% over 50 cycles, suggesting the promising application of MoTe₂/FLG for lithium‐ion storage. First‐principles calculations exhibit that the lowest diffusion barrier (0.18 eV) for lithium ions along pathway III in the MoTe₂ layered structure is beneficial for improving the Li intercalation/deintercalation property.     

Fe2VO4 Hierarchical Porous Microparticles Prepared via a Facile Surface Solvation Treatment for High‐Performance Lithium and Sodium Storage

Preventing the aggregation of nanosized electrode materials is a key point to fully utilize the advantage of the high capacity. In this work, a facile and low‐cost surface solvation treatment is developed to synthesize Fe₂VO₄ hierarchical porous microparticles, which efficiently prevents the aggregation of the Fe₂VO₄ primary nanoparticles. The reaction between alcohol molecules and surface hydroxy groups is confirmed by density functional theory calculations and Fourier transform infrared spectroscopy. The electrochemical mechanism of Fe₂VO₄ as lithium‐ion battery anode is characterized by in situ X‐ray diffraction for the first time. This electrode material is capable of delivering a high reversible discharge capacity of 799 mA h g^?1 at 0.5 A g^?1 with a high initial coulombic efficiency of 79%, and the capacity retention is 78% after 500 cycles. Moreover, a remarkable reversible discharge capacity of 679 mA h g^?1 is achieved at 5 A g^?1. Furthermore, when tested as sodium‐ion battery anode, a high reversible capacity of 382 mA h g^?1 can be delivered at the current density of 1 A g^?1, which still retains at 229 mA h g^?1 after 1000 cycles. The superior electrochemical performance makes it a potential anode material for high‐rate and long‐life lithium/sodium‐ion batteries.     

Hierarchical TiO2/SnO2 Hollow Spheres Coated with Graphitized Carbon for High‐Performance Electrochemical Li‐Ion Storage

A self‐templated strategy is developed to fabricate hierarchical TiO₂/SnO₂ hollow spheres coated with graphitized carbon (HTSO/GC‐HSs) by combined sol–gel processes with hydrothermal treatment and calcination. The as‐prepared mesoporous HTSO/GC‐HSs present an approximate yolk‐double–shell structure, with high specific area and small nanocrystals of TiO₂ and SnO₂, and thus exhibit superior electrochemical reactivity and stability when used as anode materials for Li‐ion batteries. A high reversible specific capacity of about 310 mAh g^?1 at a high current density of 5 A g^?1 can be achieved over 500 cycles indicating very good cycle stability and rate performance.     

Ultrathin Nanosheet Assembled Sn0.91Co0.19S2 Nanocages with Exposed (100) Facets for High‐Performance Lithium‐Ion Batteries

Ultrathin 2D inorganic nanomaterials are good candidates for lithium‐ion batteries, as well as the micro/nanocage structures with unique and tunable morphologies. Meanwhile, as a cost‐effective method, chemical doping plays a vital role in manipulating physical and chemical properties of metal oxides and sulfides. Thus, the design of ultrathin, hollow, and chemical doped metal sulfides shows great promise for the application of Li‐ion batteries by shortening the diffusion pathway of Li ions as well as minimizing the electrode volume change. Herein, ultrathin nanosheet assembled Sn_0.91Co_0.19S₂ nanocages with exposed (100) facets are first synthesized. The as‐prepared electrode delivers an excellent discharge capacity of 809 mA h g^?1 at a current density of 100 mA g^?1 with a 91% retention after 60 discharge–charge cycles. The electrochemical performance reveals that the Li‐ion batteries prepared by Sn_0.91Co_0.19S₂ nanocages have high capacity and great cycling stability.     

High‐Performance Photovoltaic Detector Based on MoTe2/MoS2 Van der Waals Heterostructure

Van der Waals heterostructures based on 2D layered materials have received wide attention for their multiple applications in optoelectronic devices, such as solar cells, light‐emitting devices, and photodiodes. In this work, high‐performance photovoltaic photodetectors based on MoTe₂/MoS₂ vertical heterojunctions are demonstrated by exfoliating‐restacking approach. The fundamental electric properties and band structures of the junction are revealed and analyzed. It is shown that this kind of photodetectors can operate under zero bias with high on/off ratio (>10⁵) and ultralow dark current (≈3 pA). Moreover, a fast response time of 60 µs and high photoresponsivity of 46 mA W^?1 are also attained at room temperature. The junctions based on 2D materials are expected to constitute the ultimate functional elements of nanoscale electronic and optoelectronic applications.     

Low‐Temperature Growth of All‐Carbon Graphdiyne on a Silicon Anode for High‐Performance Lithium‐Ion Batteries

In situ weaving an all‐carbon graphdiyne coat on a silicon anode is scalably realized under ultralow temperature (25 °C). This economical strategy not only constructs 3D all‐carbon mechanical and conductive networks with reasonable voids for the silicon anode at one time but also simultaneously forms a robust interfacial contact among the electrode components. The intractable problems of the disintegrations in the mechanical and conductive networks and the interfacial contact caused by repeated volume variations during cycling are effectively restrained. The as‐prepared electrode demostrates the advantages of silicon regarding capacity (4122 mA h g^?1 at 0.2 A g^?1) with robust capacity retention (1503 mA h g^?1) after 1450 cycles at 2 A g^?1, and a commercial‐level areal capacity up to 4.72 mA h cm^?2 can be readily approached. Furthermore, this method shows great promises in solving the key problems in other high‐energy‐density anodes.     

A High‐Performance Lithium‐Ion Capacitor Based on 2D Nanosheet Materials

Lithium‐ion capacitors (LICs) are promising electrical energy storage systems for mid‐to‐large‐scale applications due to the high energy and large power output without sacrificing long cycle stability. However, due to the different energy storage mechanisms between anode and cathode, the energy densities of LICs often degrade noticeably at high power density, because of the sluggish kinetics limitation at the battery‐type anode side. Herein, a high‐performance LIC by well‐defined ZnMn₂O₄‐graphene hybrid nanosheets anode and N‐doped carbon nanosheets cathode is presented. The 2D nanomaterials offer high specific surface areas in favor of a fast ion transport and storage with shortened ion diffusion length, enabling fast charge and discharge. The fabricated LIC delivers a high specific energy of 202.8 Wh kg^?1 at specific power of 180 W kg^?1, and the specific energy remains 98 Wh kg^?1 even when the specific power achieves as high as 21 kW kg^?1.     

Electrostatically Assembling 2D Nanosheets of MXene and MOF‐Derivatives into 3D Hollow Frameworks for Enhanced Lithium Storage

As an essential member of 2D materials, MXene (e.g., Ti₃C₂T_x) is highly preferred for energy storage owing to a high surface‐to‐volume ratio, shortened ion diffusion pathway, superior electronic conductivity, and neglectable volume change, which are beneficial for electrochemical kinetics. However, the low theoretical capacitance and restacking issues of MXene severely limit its practical application in lithium‐ion batteries (LIBs). Herein, a facile and controllable method is developed to engineer 2D nanosheets of negatively charged MXene and positively charged layered double hydroxides derived from ZIF‐67 polyhedrons into 3D hollow frameworks via electrostatic self‐assembling. After thermal annealing, transition metal oxides (TMOs)@MXene (CoO/Co₂Mo₃O₈@MXene) hollow frameworks are obtained and used as anode materials for LIBs. CoO/Co₂Mo₃O₈ nanosheets prevent MXene from aggregation and contribute remarkable lithium storage capacity, while MXene nanosheets provide a 3D conductive network and mechanical robustness to facilitate rapid charge transfer at the interface, and accommodate the volume expansion of the internal CoO/Co₂Mo₃O₈. Such hollow frameworks present a high reversible capacity of 947.4 mAh g^?1 at 0.1 A g^?1, an impressive rate behavior with 435.8 mAh g^?1 retained at 5 A g^?1, and good stability over 1200 cycles (545 mAh g^?1 at 2 A g^?1).