It remains a great challenge to design and manufacture battery‐type supercapacitors with satisfactory flexibility, appropriate mechanical property, and high energy density under high power density. ...Herein, a concept of porous engineering is proposed to simply prepare two‐layered bimetallic heterojunction with porous structures. This concept is successfully applied in fabrication of flexible electrode based on CuO‐Co(OH)2 lamella on Cu‐plated carbon cloth (named as CPCC@CuO@Co(OH)2). The unique structure brings the electrode a high specific capacity of 3620 mF cm−2 at 2 mA cm−2 and appropriate mechanical properties with Young's modulus of 302.0 MPa. Density functional theory calculations show that porous heterojunction provides a higher intensity of electron state density near the Fermi level (E–Ef = 0 eV), leading to a highly conductive CPCC@CuO@Co(OH)2 electrode with both efficient charge transport and rapid ion diffusion. Notably, the supercapacitor assembled from CPCC@CuO@Co(OH)2//CC@AC shows high energy density of 127.7 W h kg−1 at 750.0 W kg−1, remarkable cycling performance (95.53% capacity maintaining after 10 000 cycles), and desired mechanical flexibility. The methodology and results in this work will accelerate the transformative developments of flexible energy storage devices in practical applications.
A universal strategy for constructing lamellar porous heterojunctions is developed to fabricate flexible electrodes for high‐performance energy storage devices. The resulted electrodes have a unique energy band structure with higher electronic density of states near the Fermi level and high conductivity, which achieve efficient charge transport and shortened the ion diffusion distance.
Due to the ultrahigh theoretical specific capacity (3860 mAh g−1) and low redox potential (−3.04 V vs. standard hydrogen electrode), Lithium (Li) metal anode (LMA) received increasing attentions. ...However, notorious dendrite and volume expansion during the cycling process seriously hinder the development of high energy density Li metal batteries. Constructing three‐dimensional (3D) current collectors for Li can fundamentally solve the intrinsic drawback of hostless for Li. Therefore, this review systematically introduces the design and synthesis engineering and the current development status of different 3D collectors in recent years (the current collectors are divided into two major parts: metal‐based current collectors and carbon‐based current collectors). In the end, some perspectives of the future promotion for LMA application are also presented.
Constructing three‐dimensional (3D) current collector can solve the nature problem of hostless for Li, suppress the growth of Li dendrites and alleviate the volume expansion during repeated cycles. This review summarizes the recent development that facilitates the use of current collectors for Li metal anodes.
Electrolyte additive is an effective strategy to inhibit the uncontrolled growth of Li dendrites for lithium metal batteries (LMBs). However, most of the additives are complex synthesis and prone to ...decompose in cycling. Herein, in order to guide the homogeneous deposition of Li+, carbonized polymer dots (CPDs) as electrolyte additives are successfully designed and synthesized by microwave (M‐CPDs) and hydrothermal (H‐CPDs) approaches. The controllable functional groups containing N or O (especially pyridinic‐N, pyrrolic‐N, and carboxyl group) enable CPDs to keep stable in electrolytes for at least 3 months. Meanwhile, the clusters formed between CPDs and Li+ through electrostatic interaction effectively guide the uniform Li dispersion and limit the “tip effect” and dendrite formation. Moreover, as lithiophilic groups increase, the strong electrostatic interference for the solvation effect of Li+ in the electrolyte is formed, which induces faster Li+ diffusion/transfer. As expected, H‐CPDs achieve the ultra‐even Li+ transfer. The corresponding Li//LiFePO4 full cell delivers a high capacity retention rate of 93.8% after 200 cycles, which is much higher than that of the cells without additives (61.2%) and with M‐CPDs (83.7%) as additives. The strategy in this work provides a theoretical direction for CPDs as electrolyte additives used in energy storage devices.
Two kinds of carbonized polymer dots (CPDs) (M‐CPDs and H‐CPDs) as electrolyte additives are successfully designed and synthesized. H‐CPDs with more pyridinic‐N, pyrrolic‐N, and COOH deliver more even Li+ flux through abundant H‐CPDs‐Li clusters bound by strong electrostatic interaction. The symmetrical cell exhibits enhanced cycling stability of 3700 h.
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.
The controlling of carbonized polymer dots amount on MoS2 realizes flower‐like nanospheres structure with achieved high‐performance Li/Na storage.
The slot waveguide has attracted considerable attention because of its ability to confine and guide electromagnetic energy at the subwavelength scale beyond the diffraction limit. We propose a novel ...terahertz slot waveguide structure to achieve a better tradeoff between propagation length and field confinement capacity, the novel waveguide consisting of a two slot structure. The performances of terahertz waveguides were investigated using the finite-element method. The results demonstrated that the hybrid slot waveguide (HSW) provides significantly enhanced field confinement in low index slot regions: more than five times that of traditional low index slot waveguides (LISWs). An optimized HSW structure was achieved by tuning the tradeoff between mode confinement and propagation length. We also showed that its integration in conventional planar waveguide circuits was greatly improved compared with the LISWs, by comparing their crosstalk. The proposed new HSW structure has great potential to enable THz production of compact integration and could lead to true semiconductor-basedTHz applications with high performance.
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•A novel hollow sphere structure donates the TiO2/MoO2@N-doped carbon composite a large surface area, a shorter diffusion way, alleviating the volume variation.•N-doped carbon layer ...enhances the durability, reaction kinetics and conductivity of the electrode.•The synergistic effect of components and hollow structure demonstrates in the electrochemical properties.•TiO2/MoO2@NC HS anode exhibits superior electrochemical performance in LIBs/SIBs.
Constructing nanostructured hollow materials is one of the most effective approaches to improve the cycling stability in batteries by accommodating the volume variation. Combined with the synergy of hybrid composition, high-performance energy storage materials are expected to be achieved. Herein, the anatase TiO2 is coated into a MoO2@N-doped carbon hollow sphere structure (denoted as TiO2/MoO2@NC HS) through a simple two-step method. The unique TiO2/MoO2@NC HS composite overcomes the poor cyclic stability of MoO2 and the low specific capacity of TiO2. Moreover, its hollow sphere structure facilitates electrolyte access and simultaneously provides shorter charge transportation paths, which assures rapid Li+/Na+ reaction kinetics. When utilized as an anode in LIBs /SIBs, TiO2/MoO2@NC HS composite exhibits a satisfactory electrochemical performance with high reversible capacities of 1423.9 mAh g−1 at 100 mA g−1 after 200 cycles in LIBs and reaches 572.7 mAh g−1 after 1000 cycles at 200 mAg−1 in SIBs. Furthermore, the full cell TiO2/MoO2@NC HS anode coupled with NCM111 cathode shows decent capacity with long cycling stability. This study offers a novel strategy to obtain anode composite that will find applications in energy storage devices.
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•An all-carbon-based substrate loaded with N-enriched CDs is developed.•CDs significantly induce the uniform nucleation of Li in the initial plating stage.•The CDs with ordered ...structure provide fast Li+ transport channels.•CD@RGCCF exhibits decent electrochemical cycling stability and long cycle-life over 5000 h with a small voltage fluctuation of 10.5 mV.
Three dimensional (3D) carbon-based current collectors have attracted much attentions as host for Li metal anodes (LMAs) owing to their lightweight, flexible, and wide sources etc. However, the lithiophobic nature of carbon makes it difficult to achieve low nucleation overpotential and dendrite-free Li deposition. Herein, carbon dots (CDs) with nitrogen (N)-rich were introduced to modify carbonized cotton fiber (CCF) coated by reduced graphene oxide (CD@RGCCF). Coating graphene oxide (GO) increases the active site of cotton fiber (CF), which facilitates the growth of CDs on the surface of CF fiber. The introduction of ordered structure CDs drives fast migration of Li+ in the “highway-like” channels and induces the uniform nucleation of Li in the initial stage. As a result, the obtained CD@RGCCF decreases the nucleation overpotential of Li, and achieves dendrite-free Li deposition. the CD@RGCCF|Li half cells exhibit extending cycling life over 5000 h with a voltage hysteresis of 10.5 mV at 2 mA cm−2. As coupled with the LiFePO4 (LFP), the Li@CD@RGCCF||LFP composite anode enables a high reversible specific capacity and improved cycle stability. This work provides a low-cost modification method for carbon substrate to realize dendritic-free LMAs.
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•GO anchored with CPDs (CPD@GO) flexible substrate is developed.•CPDs successfully regulate the dispersion and interlayer spacing of GO.•The deposition of Li is achieved between the ...interlayers and on surfaces.•The composition (LiF and Li3N) of SEI can be tuned.•The Li@CPD@RGO-3 exhibits lower voltage hysteresis (10.5 mV at 1 mA cm−2).
Flexible lithium metal anode with ultrahigh theoretical specific capacity suffers from uncontrollable growth of lithium dendrite and severe volume changes during Li plating/stripping process. To address these issues, a novel kind of flexible graphene oxide (GO) film anchored with carbonized polymer dots (CPDs) (CPD@GO) composite substrate was fabricated via a one-step microwave approach in which CPDs successfully regulate the dispersion and interlayer spacing of GO. Nanoscale CPDs act as lithiophilic nucleation sites to promote Li uniform deposition between the interlayers rather than on the surface of GO. The abundant surface functional groups of CPDs result in the generation of more stable components for solid electrolyte interphase (SEI) with high ionic conductivity of LiF and Li3N through accelerating the degradation dynamics of lithium salt. As a result, the obtained lithium anode presents small fluctuant profiles with lower voltage hysteresis (10.5 mV after 2600 h of operation at 1.0 mA cm−2). The coin and pouch full cells constructed with LiFePO4 remain decent cycling performance. This work paves a new sight for the application of carbon materials in energy storage devices.
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•The nanocubes offer uniform lithiophilicity sites.•The anode possesses excellent mechanical properties.•The anode can accommodate substantial amounts of Li deposition.•The anode can ...maintain stable cycling for 5660 h at 40 mA cm−2.•The full cell shows good capacity retention after 2890 cycles at 1C.
The incorporation of a conductive three-dimensional (3D) scaffold in lithium metal anodes (LMAs) represents one of the most effective strategies for mitigating the uncontrolled formation of lithium dendrites. In this study, a promising substrate is fabricated by one-step co-deposition of NiCo nanocubes on carbon fiber composite (CFC). The bimetallic nanocubes offer an abundance of lithiophilicity sites and exhibit exceptional mechanical properties, thereby enhancing the stability of the electrode. By incorporating pyridine and pyrrole nitrogen, along with the synergistic effect of bimetal ions, the stability of solid electrolyte interphase (SEI) film is also enhanced, interface resistance is reduced, and uniform lithium metal deposition is achieved, effectively inhibiting dendrite growth especially at high current densities, with a lifespan up to 5660 h at ultra-high current density up to 40 mA cm−2. When paired with LiFePO4, the full battery exhibits satisfied dynamic stability and ultra-long cycle stability during repeated shelving, maintaining good capacity retention after 2890 cycles at 1C. This work provides a new idea for the practical application of lithium metal battery.
Lithium metal anode with high theoretical capacity has attracted lots of attention, but dendrite growth results in poor cyclic stability during the process of repeated plating/stripping. Herein, a ...scaffold constructed by surface growth of hierarchical lithiophilic acicular CoNiO2 on the porous Ni foam (NF@CoNiO2) is synthesized and used to construct three-dimensional (3D) host for lithium metal anode. The experimental results show that the lithium dendrite growth is effectively inhibited and satisfactory cycling performance is achieved. Benefiting from the stable lithiophilic sites, good conductivity from the NF, large porosity, and high strength 3D structure, the host enable Li||NF@CoNiO2@Li cells to deliver low hysteresis voltage (7.7 mV) and ultra-long cycling stability (more than 2800 h, 1400 cycles) at 1 mA cm−2 with a capacity of 1 mAh cm−2. The full cells configured the NF@CoNiO2@Li anode with LiFePO4 still display a reversible discharge capacity of 126.2 mAh g−1 after 140 cycles with a Coulombic efficiency of 92.5% at 1C. This work paves a feasible way to construct the lithiophilic skeleton for dendrite-free lithium metal anode.
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