Ultrahigh Specific Capacitance Research Articles

Microwave construction of the 3D porous interconnected structure of NiCoCr medium-entropy alloy with ultra-high specific capacity for supercapacitors and electrocatalysis

The effective design of bifunctional electrodes with unique morphology and remarkable electrochemical properties for energy conversion and storage devices is a promising but challenging endeavor. Herein, self-supporting NiCoCr medium-entropy alloy (MEA) with a hierarchical porous network structure was in situ synthesized on nickel foam (NiCoCr/NF) by a simple and rapid microwave route. The optimal NiCoCr/NF presented an ultra-high specific capacity of 3011.8 C g−1 (1 A g−1) and outstanding charge/discharge sustainability (83.4% retention at 10 A g−1 over 50,000 cycles) due to its multi-component synergistic effect and hierarchical porous structure. Meanwhile, subtle lattice distortions and electron density redistribution in the NiCoCr MEA tuned electronic structures, resulting in a low overpotential and Tafel slope. Aqueous and solid-state asymmetric supercapacitors were fabricated by using NiCoCr/NF as a cathode and Bi/NF as an anode. The aqueous supercapacitor displayed an exceptional energy density of 314.4 Wh kg−1 at a power density of 800 W kg−1 with 81.8% retention at 10 A g−1 over 20,000 cycles. This study provides a new strategy for the efficient synthesis of electrode materials with interconnected network structures and paves the way for the broader application based on medium-entropy and high-entropy materials as promising candidates for future energy storage devices.

Solvent-Controlled Synthesis of Zn–Co–S@Ni12P5 Arrays with Ultra-High Specific Capacitance for Hybrid Supercapacitor

Solvent-Controlled Synthesis of Zn–Co–S@Ni₁₂P₅ Arrays with Ultra-High Specific Capacitance for Hybrid Supercapacitor

One-Step Construction of Closed Pores Enabling High Plateau Capacity Hard Carbon Anodes for Sodium-Ion Batteries: Closed-Pore Formation and Energy Storage Mechanisms.

Closed pores play a crucial role in improving the low-voltage (<0.1 V) plateau capacity of hard carbon anodes for sodium-ion batteries (SIBs). However, the lack of simple and effective closed-pore construction strategies, as well as the unclear closed-pore formation mechanism, has severely hindered the development of high plateau capacity hard carbon anodes. Herein, we present an effective closed-pore construction strategy by one-step pyrolysis of zinc gluconate (ZG) and elucidate the corresponding mechanism of closed-pore formation. The closed-pore formation mechanism during the pyrolysis of ZG mainly involves (i) the precipitation of ZnO nanoparticles and the ZnO etching on carbon under 1100 °C to generate open pores of 0.45-4 nm and (ii) the development of graphitic domains and the shrinkage of the partial open pores at 1100-1500 °C to convert the open pores to closed pores. Benefiting from the considerable closed-pore content and suitable microstructure, the optimized hard carbon achieves an ultrahigh reversible specific capacity of 481.5 mA h g-1 and an extraordinary plateau capacity of 389 mA h g-1 for use as the anode of SIBs. Additionally, some in situ and ex situ characterizations demonstrate that the high-voltage slope capacity and the low-voltage plateau capacity stem from the adsorption of Na+ at the defect sites and Na-cluster formation in closed pores, respectively.

Cation-driven self-assembly of core–shell covalent organic frameworks@Ti3CN MXene nanospheres for high-performance aqueous zinc-ion hybrid supercapacitors

Rechargeable aqueous Zn-ion hybrid supercapacitors (ZISCs) with the superiorities of high theoretical capacity, low redox potential and aqueous electrolytes with superior ionic conductivity (∼1 S cm−1) are promising energy storage systems. However, a primary concern persists due to the absence of cathode materials with both high energy densities and satisfactory cycling stability for robust ZISCs. In this study, we design a spherical core–shell covalent organic frameworks@Ti3CN MXene (CM-P) cathode via a cation-driven electrostatic self-assembly strategy. The CM-P with the constructed heterostructures shows both well-organized pore channels and excellent intrinsic conductivity, facilitating fast accessibility to intrinsic redox-active sites (such as C = O and N), and promoting effective ion diffusion characterized by low energy barriers. Consequently, the CM-P cathodes demonstrate excellent electrochemical performance, featuring an ultrahigh specific capacity of 260 mAh/g at 0.1 A, a high-rate capability with 68 % retention at 1 A/g, and long-term cycling stability. First-principle calculations elucidate that the enhanced charge-storage mechanism relies on the heterostructures of CM-P, accelerating ion adsorption/diffusion and electron transfer. Furthermore, the assembled CM-P//Zn ZISCs devices show a high energy density of 217.1 Wh kg−1 along with power density of 22.3 kW kg−1. This work provides an innovative approach to design COFs-based heterostructures for advanced ZISCs.

Realization of high-capacity coulombic efficiency in sodium alginate/carbon nanotube double network coated Si-anode for lithium-ion batteries

Silicon (Si) is considered as one of the most promising anodes for the next-generation lithium-ion batteries (LIBs) owing to its ultra-high specific capacity, low redox potential and the second abundance of elements in the earth's crust. However, drastic volume change will directly cause electrode pulverization, thus leading to low initial coulombic efficiency (ICE) and terrible cycling stability. In this work, a sodium alginate (SA)‑carbon nanotube (CNT) derived double carbon-coated Si composite (SA-CNT@Si) was prepared through freeze-drying technique followed by high-temperature carbonization, where SA was utilized to encase Si nanospheres, with CNT serving as the conductive framework that interconnects Si spheres. These composites exhibit improved electrical conductivity and stability throughout the charge and discharge cycles when employed as the anodes in LIBs, demonstrating superior electrochemical properties. The SA-CNT@Si electrode with a mass ratio of Si: SA: CNT = 5: 1: 0.75, achieved a first discharge specific capacity of 2200.8 mAh g−1 at a current density of 500 mA g−1 (with the initial three cycles at 100 mA g−1), along with an ICE of 86.2%. Even after 500 cycles, it maintained a capacity of 607 mAh g−1. This study presents a novel approach to designing Si-based anode materials characterized by both high electrical conductivity and structural stability.

Analysis of Pressure Characteristics of Ultra-High Specific Energy Lithium Metal Battery for Flying Electric Vehicles

The lithium metal battery is likely to become the main power source for the future development of flying electric vehicles for its ultra-high theoretical specific capacity. In an attempt to study macroscopic battery performance and microscopic lithium deposition under different pressure conditions, we first conduct a pressure cycling test proving that amplifying the initial preload can delay the battery failure stage, and the scanning electron microscope (SEM) shows that the pressure is effective in improving the electrode’s surface structure. Secondly, we analyze how differing pressure conditions affect the topography of lithium deposits by coupling the nonlinear phase-field model with the force model. The results show that the gradual increase in the external pressure is accompanied by a drop in the length of the dendrite and the migration curvature in the diaphragm, and the deposition morphology is gradually geared towards smooth and thick development, which can significantly reduce the specific surface area of lithium dendrite. However, as cyclic charging and discharging continue, the decrease in the electrolyte diffusion coefficient results in higher internal stress inside the battery, and thus the external pressure must be increased so as to achieve marked inhibitory effects on the growth of the lithium dendrite.

Lithiophilic ZnCu alloy sites on copper current collector for high performance Li metal anode

Lithium (Li) metal has been widely regarded as the optimal anode material for the high-energy density rechargeable batteries, due to its ultrahigh theoretical specific capacity and lowest electrochemical potential. However, the formation of Li dendrites presents a significant safety concern, which limits its practical application. In this paper, to address this issue, an efficient and cost-effective strategy was proposed to prepare a zinc-copper composite collector (ZCC) with outstanding electrochemical performance, which can effectively suppress the formation of lithium dendrites. The lithophilic surface with ZnCu alloy nanoparticles was achieved through physical vapor deposition followed by annealing treatment. The ZCC collector enables dendrite-free deposition of Li due to its negligible nucleation overpotential. Even at high area capacity of 3 mAh cm−2 at 1 mA cm−2 in half-cells, the ZCC exhibits exceptional cycling performance and high coulomb efficiency. Preloaded with Li, the composite electrode (Li/ZCC) delivers an enhanced lifespan with low overpotential evidently. Matched with LiFePO4 (LFP) cathode, LFP||Li/ZCC full cells reveal a superior cycling stability with enhanced capacity retention of 85 % (after 1000 cycles at 1 C) and 87 % (after 800 cycles at 3 C) respectively.

Dual-active centers of porous triazine frameworks for efficient Li storage

Integrating n-type and p-type redox-active centers into porous frameworks is an efficient approach to simultaneously mitigate the intrinsic problems of poor utility, low output voltage, and sluggish kinetics of organic electrodes for lithium ion batteries (LIBs). However, it is challenging to achieve an optimal utilization of the well-defined ordered porous structure and the multiple active centers due to the stacking structure of conventional covalent organic frameworks. Herein, we develop a post-modification approach to synthesize a bipolar pyrene-4,5,9,10-tetraone based porous covalent triazine frameworks (CTFs) for efficient dual-ion storage. The post-modification method successfully protects the active carbonyl groups under harsh conditions and effectively exposes the redox centers. The amorphous phase dominated CTFs enables excellent Li+ diffusion and high utilization of active sites, leading to ultrahigh specific capacity of 351 mAh/g at 0.2 A/g and impressive stability for 3000 cycles at 5.0 A/g. Moreover, the efficient dual-ion storage mechanism was confirmed by the in-depth investigation with ex situ FT-IR, and XPS study. Theoretical calculations also unveil the unique energy storage pathway using both p-doped and n-doped states for the intercalation of anions and cations. This work highlights the significance of the integrating strategy which allows the combination of dual-active-center with conjugated porous structure, broadening the avenues of organic electrode materials towards high-performance LIBs.

Cobalt vacancy boosting Co3-xO4@C with superior pseudocapacitive lithium storage

The Co3O4 as anode for lithium ion batteries (LIBs) suffers the sluggish electrode kinetics and severe capacity fade during the cycles. The defective engineering of Co3O4 with oxygen/cobalt defects is an effective strategy to optimize Co3O4 with enhanced electrochemical properties. Herein, a series of 3D inter-connected Co3-xO4@C-y nanostructures with abundant Co defects are synthesized through a hydrothermal approach with subsequent heating-controlled process. Benefiting from its rich surface cobalt-defective sites and the 3D interconnected frameworks, as well as its high surface area and residual carbon layer, the Co3-xO4@C-y synthesized at y = 400 °C as anode for LIBs displays superior pseudocapacitive lithium storage properties with an ultra-high reversible specific capacity of 1900.7 mAh g−1 at 0.2 A g−1, excellent rate capability (e.g., 1415.1 mAh g−1 at 10 A g−1) and ultra-long cycling stability (e.g., 1160.5 mAh g−1 at 15 A g−1 after 2000 cycles).

H+/Cu2+ co-assisted corrosion synthesis of sustainable silicon dendrite anodes

Silicon (Si)-based materials have been identified as next-generation preferred anode materials owing to their ultra-high specific capacity, environmental friendliness and low price. However, the defects in Si-based materials (e.g., the large volume change with unstable solid electrolyte interface during repeated lithiation/delithiation processes and low intrinsic conductivity), will significantly destroy the integrity of electrode structure and get slow dynamic performance, resulting in a fast capacity fading. Herein, we prepared various silicon‑aluminum‑copper dendrites (named SCD-1/2/3) via a two-step displacement dealloying process, which was devoted to simultaneously improving structural instability, low ionic/electronic conductivity of Si crystals. Therefore, the SCD-2 anode possessed an initial Coulombic efficiency of 80 % and exhibited a superior capacity of 1851.7 mA h g−1 at 1 A g−1 after 100 cycles. This paper provides a simple method to gain the Si anodes with high initial Coulombic efficiency, relieved volume expansion and long cycling life.

Cation-Loaded Porous Mg2+-Zeolite Layer Direct Dendrite-Free Deposition toward Long-Life Lithium Metal Anodes.

Lithium metal, with ultrahigh theoretical specific capacity, is considered as an ideal anode material for the lithium-ion batteries. However, its practical application is severely plagued by the uncontrolled formation of dendritic Li. Here, a cation-loaded porous Mg2+-Zeolite layer is proposed to enable the dendrite-free deposition on the surface of Li metal anode. The skeleton channels of zeolite provide the low coordinated Li+-solvation groups, leading to the faster desolvation process at the interface. Meanwhile, anions-involved solvation sheath induces a stable, inorganic-rich SEI, contributing to the uniform Li+ flux through the interface. Furthermore, the co-deposition of sustained release Mg2+ realizes a new faster migration pathway, which proactively facilitates the uniform diffusion of Li on the lithium substrate. The synergistic modulation of these kinetic processes facilitates the homogeneous Li plating/stripping behavior. Based on this synergistic mechanism, the high-efficiency deposition with cyclic longevity exceeding 2100h is observed in the symmetric Li/Li cell with Mg2+-Zeolite modified anode at 1mA cm-2. The pouch cell matched with LiFePO4 cathode fulfills a capacity retention of 88.4% after 100 cycles at a severe current density of 1 C charge/discharge. This synergistic protective mechanism can give new guidance for realizing the safe and high-performance Li metal batteries.

First-principles prediction of one-dimensional conductive metallic organic polymers as ultrahigh energy density anode for lithium-ion batteries.

Metal-Organic Polymers (MOPs) have attracted growing attention for lithium-ion battery (LIB) applications due to their merits in orderly ionic transportation and robust structure stability in electrochemical reactions. However, they suffer from poor electronic conductivity. In this work, we apply first-principles density functional theory to explore the potential of three one-dimensional (1D) electrically conductive C6H2S4TM (TM = Fe, Co, and Ni) MOPs with the π-d conjugated coordination as anode materials for Li+ ions storage. Our theoretical results reveal that these 1D MOPs possess a superior theoretical capacity of over 748 mA h g-1. In particular, the 1D C6H2S4Ni MOP shows an exceptional theoretical specific capacity of 1110 mA h g-1 based on the three-electron transferring reaction, which significantly outperforms the traditional graphite-based anode material in LIBs. Moreover, the resonant charge transfer between Ni metal and ligand within the 1D C6H2S4Ni MOP reduces the diffusion energy barrier of the Li atoms when they migrate on the surface of the MOP. The ultrahigh theoretical specific capacity of the C6H2S4Ni MOP predicts that it can be a promising anode material for LIBs.

Nickel aerogel @ ultra-thin NiCo-LDH nanosheets integrated freestanding film as a collaborative adsorption and accelerated conversion cathode to improve the rate performance of lithium sulfur batteries

It is a great challenge to develop freestanding ultralight cathodes for lithium–sulfur battery exhibiting good electrochemical performances. Herein, ultrathin porous nickel–cobalt layered double hydroxide (NiCo-LDH) nanosheets were grown on the surface of ultra-light nickel microwire aerogels (NMWAs), and there is capillary action in the gaps formed by the ordered arrangement due to the presence of magnetic filed in the preparation process, which has the advantages of synergistic adsorption and accelerated conversion kinetics of lithium polysulfide. Because of the abundant hydrophilic hydroxyl groups on the surface of NiCo-LDH and the capillary action of NMWAs, the integrated freestanding film cathode sulfur host (NMWAs@NiCo-LDH/S) provides excellent rate performance as well as cycling stability. The film cathode has an ultra-high initial specific capacity of 1238.4 mAh g−1 at 0.1C and an excellent reversible capacity of 805.8 mAh/g at 5.0C. Even after 700 cycles at a high current density of 5.0C, it still provides a reversible capacity of 647.1 mAh g−1 with a capacity decay rate of only 0.018 % per cycle. This work provides a simple and new way for the design of high rate lithium–sulfur battery film cathodes with good cycle stability.

Engineering of lithiophilic hosts for stable lithium metal anodes

Lithium (Li0) metal has been deemed the desired anode for the future of cutting-edge rechargeable Li batteries benefiting from its lowest reduction potential and ultrahigh theoretical specific capacity. Nevertheless, the large-scale applications of Li metal batteries are restricted by scattered Li dendrite formation and uncontrollable volume expansion. To address these issues, a currently prevalent measure is to use structured lithiophilic hosts for Li metal. The enhanced lithiophilicity of hosts is significant for regulating the Li nucleation barrier. By virtue of these lithiophilic measures, the Li nucleation sites will be well controlled and the Li plating layer will be more stable. Through this article, we classified various lithiophilic hosts and described their applications for Li metal batteries, including heteroatom-doping carbon, lithiophilic-material loading hosts and gradient skeletons. We discussed the inherent advantages and lithophilic mechanisms of these hosts on optimizing the lithophilic properties and analyzed various factors that induced the formation of dendrite Li. Moreover, the review outlines the current challenges and perspectives for Li metal anodes, and some understanding of the lithiophilic chemistry is given.

Accelerating lithium-sulfur battery reaction kinetics and inducing 3D deposition of Li2S using interactions between Fe3Se4 and lithium polysulfides

Although lithium-sulfur batteries (LSBs) exhibit high theoretical energy density, their practical application is hindered by poor conductivity of the sulfur cathode, the shuttle effect, and the irreversible deposition of Li2S. To address these issues, a novel composite, using electrospinning technology, consisting of Fe3Se4 and porous nitrogen-doped carbon nanofibers was designed for the interlayer of LSBs. The porous carbon nanofiber structure facilitates the transport of ions and electrons, while the Fe3Se4 material adsorbs lithium polysulfides (LiPSs) and accelerates its catalytic conversion process. Furthermore, the Fe3Se4 material interacts with soluble LiPSs to generate a new polysulfide intermediate, LixFeSy complex, which changes the electrochemical reaction pathway and facilitates the three-dimensional deposition of Li2S, enhancing the reversibility of LSBs. The designed LSB demonstrates a high specific capacity of 1529.6 mA h g−1 in the first cycle at 0.2 C. The rate performance is also excellent, maintaining an ultra-high specific capacity of 779.7 mA h g−1 at a high rate of 8 C. This investigation explores the mechanism of the interaction between the interlayer and LiPSs, and provides a new strategy to regulate the reaction kinetics and Li2S deposition in LSBs.

Boosting the ORR/OER Activity of Cobalt-Based Nano-Catalysts by Co 3d Orbital Regulation.

The transition metal oxides/sulfides are considered promising catalysts due to their abundant resources, facile synthesis, and reasonable electrocatalytic activity. Herein, a significantly improved intrinsic catalytic activity is achieved for constructing a Co-based nanocrystal (Co-S@NC) with the coordination of Co─S, Co─S─C, and Co─Nx─C. The calculational and experimental results demonstrate that the diversified chemical environment of Co-cations induces the transition of 3d orbitals to a high spin-state that exhibits the coexistence of Co2+ with fully occupied dπ orbitals and Co3+ with unpaired electrons in dπ orbitals. The diverse dπ orbitals occupation contributes to an elevated d-band center of Co ions, which accelerates oxygen reduction reaction and oxygen evolution reaction electrocatalytic kinetics of the Co-S@NC nanocrystal. Therefore, the Li-O2 batteries with Co-S@NC as cathode catalyst exhibit 300 cycles at the current density of 500 mA g-1 with a cut-off capacity of 1000 mAh g-1. Moreover, the ultrahigh discharge specific capacity of 34 587 mAh g-1 is obtained at a current density of 1000 mA g-1, corresponding to the energy density 949 Wh kg-1 of a prototype Li-O2 battery. The study on 3d orbital regulation of nanocrystals provides an innovative strategy for bifunctional electrocatalysts toward the practical application of metal-air batteries.

Electron-repulsion effect of anti-solvent strategy for long-cycle nickel sulfide-containing potassium-ion batteries

Transition metal dichalcogenides experience severe structural degradation when used as anodes in potassium-ion batteries, resulting in undesirable electrochemical behaviors. To tackle this challenge, a novel approach involving "anti-solvent-enhanced local high-concentration electrolytes" was proposed to enhance the electrochemical stability of transition metal dichalcogenides for potassium-ion storage. This improvement is attributed to the facilitation of the aggregation of local solvation structures within the ether-based electrolyte. We demonstrate the effectiveness of this method by utilizing nickel sulfide composite materials. By diluting the ether-based high-concentration electrolyte with 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (HFE) anti-solvent, the nickel sulfide containing anode achieved an ultra-high specific capacity of 382 mAh g−1 after 1500 cycles at 1 A g−1. We found that the HFE anti-solvent, with its high concentration of negatively charged fluorine atoms, exerts a strong electron-repulsion effect on the bis(fluorosulfonyl)imide anions, promoting the aggregation of local solvation structures. It not only lowers the desolvation energy but also exhibits high stability during interactions with the interface, thereby improving and keeping the K-ion’s migration ability. This, in turn, improves the cycling stability of the electrode during the potassiation-depotassiation process. We believe that this new strategy of improving potassium-ion storage performance will drive advancements in related fields.

Designing electron/ion dual-phase conductor Ni@TiO2 for high-performance lithium-ion storage: Combining insertion and space charge mechanism

In this study, we construct an yolk-shell Ni@TiO2 nanosphere to investigate its performance in lithium-ion batteries. The composite possesses a synergistic storage mode consisting of a Li+-accepting and an electron-accepting phase. Used as an anode material, it delivers ultra-high specific capacity with excellent rate performance and cycling stability. In situ magnetic characterization and thermodynamic simulation reveal the existence of space charge storage mechanism. We propose an overall view on the Li storage mechanism of the Ni@TiO2 and demonstrate the importance of space charge storage for performance improvement in Li-ion batteries.

DFT insights into the adsorption mechanisms of lithium polysulfides on Ni2P (0001) surface for lithium–sulfur batteries

Reliable and sustainable energy storage systems are crucial for a renewable energy future. The ultrahigh theoretical specific capacity and energy density of lithium–sulfur batteries (LSBs) make them one of the most promising next-generation battery technologies. However, their large-scale applications are seriously limited by rapid capacity fading and poor Coulombic efficiency owing to the shuttling of lithium polysulfides (LiPSs). Herein, we investigate nickel phosphide (Ni2P) as an effective host material to realize high-performance LSBs based on first-principles density functional theory (DFT) calculations. Our calculated adsorption energies of the LiPSs species reveal that the Ni2P(0001) surface possesses moderate to high adsorption strength and the adsorption process is facilitated via charge transfer from the LiPSs to the interacting Ni2P(0001) surface atoms. Due to the strong interactions between Ni2P(0001) and LiPSs (Li2Sx, x = 1, 2, 4, 6 and 8), we observe elongation of the intramolecular Li–S bonds in LiPSs upon their adsorption. The stronger adsorption of Li2S coupled with its spontaneous dissociation suggests a faster charging process could occur on the on Ni2P(0001) surface. These results demonstrate that Ni2P can provide effective anchoring sites for the soluble LiPSs, potentially having implications for the design of electrodes for practical LSBs.

Enhancing air stability of LiMg alloy anode through Yb segregation at grain boundaries

Owing to the ultrahigh theoretical specific capacity and the most negative electrochemical potential, lithium metal has become the most promising lithium battery anode material. However, it is highly susceptible to oxidation during industrial production and storage processes. The polycrystal surface of the lithium metal anode serves as the site for oxidation reaction, and the reaction pathway is inevitably influenced by the microstructure of the anode surface. especially the grain boundaries, which with higher activity than a crystallographic plane, leading to intercrystalline oxidation reactions. Within the LiMg@Yb alloy system, ytterbium (Yb) segregated at the grain boundaries, leading to a reduction in intercrystalline energy as predicted by Density Functional Theory (DFT) calculations. Thus, the LiMg@Yb alloy can effectively suppress intercrystalline oxidation reactions and enhance air stability. More impressively, even exposed to ambient air for 0.5 h, the LiMg@Yb-0.5||LFP full cell exhibited a higher capacity retention rate (80.7%) than the bare Li-0.5||LFP (35.9%) after 100 cycles. This work presents a new approach for enhancing air stability by inhibiting intercrystalline oxidation reactions between anodes and air.