Exceptional Energy Density Research Articles

Constructing stable solid electrolyte interphases to enhance the calendar life of anode-free lithium metal batteries

Advancement of anode-free lithium metal batteries (AFLMBs) has been appreciated due to their exceptional volumetric energy density and manufacturing simplicity. However, AFLMBs suffer from poor cycle performance due to the absence of excess lithium and current research lacks an understanding of lithium corrosion and calendar aging in AFLMBs. Here, we investigate the practical effects of chemical and galvanic corrosion on battery performance (calendar life) through a modified full-cell cycling experiment. The impact of galvanic corrosion is negligible, whereas chemical corrosion during a rest period reduces the capacity retention (CR) from 47% to 32% over 100 cycles. Consequently, a corrosion control strategy is implemented, substituting 1,2-dimethoxyethane with 1,2-dimethoxypropane (DMP), which has weaker lithium ion solvation properties due to its inductive effect. This approach results in the formation of a Li2O-rich solid-electrolyte interphase (SEI) layer, which effectively prevents direct contact of lithium with the electrolyte and the formation of additional SEI layers. Consequently, the decrease in CR due to chemical corrosion is considerably mitigated in DMP-based electrolyte, with only a slight decrease from 51% to 49%. This study provides insights into lithium corrosion in practical AFLMBs and offers guidelines for designing less-corrosive electrolytes to improve AFLMB performance for diverse industrial applications as energy-storage devices.

Scalable Production of Thin and Durable Practical Li Metal Anode for High‐Energy‐Density Batteries

AbstractUtilization of thin Li metal is the ultimate pathway to achieving practical high‐energy‐density Li metal batteries (LMBs), but its practical implementation has been significantly impeded by formidable challenges of poor thinning processability, severe interphase instability and notorious dendritic Li growth. Here we report a practical thin (10–40 μm) Li/Mo/Li2Se with concurrently modulated interphase and mechanical properties, achieved via a scalable mechanical rolling process. The in situ generated Li2Se and Mo not only enhance the mechanical strength enabling the scalable fabrication of thin Li metal, but also promote homogeneous Li electrodeposition. Significantly, the Li/Mo/Li2Se demonstrates ultrahigh‐rate performance (15 mA cm−2) and ultralong‐lifespan cycling sustainability (2700 cycles) with exceptional anti‐pulverization capability. The Li|LiFePO4 cells show substantially prolonged cyclability over 1200 cycles with an ultralow decay rate of ~0.01 % per cycle. Moreover, the Li|LiNi0.8Co0.1Mn0.1O2 pouch cells deliver enhanced cycling stability even under the extremely harsh conditions of low negative‐to‐positive‐capacity (N/P) ratio of ~1.2 and lean electrolyte of ~0.95 g Ah−1, showing an exceptional energy density of 329.2 Wh kg−1. This work sheds light on facile pathway for scalable production of durable thin Li metal anode toward reliable practicability.

A Supramolecular Deep Eutectic Electrolyte Enhancing Interfacial Stability and Solution Phase Discharge in Li−O2 Batteries

AbstractLi−O2 batteries (LOBs) have gained widespread recognition for their exceptional energy densities. However, a major challenge faced by LOBs is the lack of appropriate electrolytes that can effectively balance reactant transport, interfacial compatibility, and non‐volatility. To address this issue, a novel supramolecular deep eutectic electrolyte (DEE) has been developed, based on synergistic interaction between Li‐bonds and H‐bonds through a combination of lithium salt (LiTFSI), acetamide (Ace) and boric acid (BA). The incorporation of BA serves as an interface modification additive, acting as both Li‐bonds acceptor and H‐bonds donor/acceptor, thereby enhancing the redox stability of the electrolyte, facilitating a solution phase discharge process and improving compatibility with the Li anode. Our proposed DEE demonstrates a high oxidation voltage of 4.5 V, an ultrahigh discharge capacity of 15225 mAh g−1 and stable cycling performance of 196 cycles in LOBs. Additionally, the intrinsic non‐flammability and successful operation of a Li−O2 pouch cell indicate promising practical applications of this electrolyte. This research broadens the design possibilities for LOBs electrolytes and provides theoretical insights for future studies.

Magnetic Field Enable Lithium Ions to Penetrate Lithophilic 3D Collectors and Enhance Electrochemical Performance

Abstract Lithium metal batteries, celebrated for their exceptional energy density, are promising for advanced energy storage. Nevertheless, the dynamic deformation of lithium metal during cycling often leads to the unchecked proliferation of lithium dendrites, compromising the solid electrolyte interface. This not only deteriorates cycle stability but also poses significant safety risks. In our approach, we develop a three-dimensional lithium-affinitive composite current collector, utilizing an external magnetic field. The lithiophilic nature of V2O5, coupled with the deformability support provided by nickel foam and the depth-enhancing influence of the magnetic field on lithium metal deposition, collectively contribute to a more controlled and stable lithium environment. Our findings indicate that this novel setup allows for a lithium metal deposition depth of up to 310 μm, markedly curtailing the growth of dendrites in successive cycles. Remarkably, batteries reassembled with this magnetically-enhanced, lithium pre-deposited current collector exhibits a coulombic efficiency of 98.3% after 320 cycles at 1 mA cm-2. Moreover, a full cell, equipped with LiFePO4, delivers an initial capacity of 158.4 mAh g-1 at 1 C.

Ta-ions doping impact on structural modifications and bandgap tuning of NiCo2O4 hexagonal nanosheets for high rated pseudocapacitor electrodes

Getting higher activity, lower cost and especially better stability at the same time is still one of the biggest problems in the supercapacitors research. Morphology tailoring and crystal imperfections induce d due to doping based defects in ternary transition metal oxides at the nano-scale level is crucial for enhancing the performance of supercapacitors. This research investigates of the utilization of Ta-doped NiCo2O4 (Ta-NCO) hexagonal nano-sheets for supercapacitor electrodes. The structural and morphological study of pristine and Ta-doped samples has been determined using XRD, SEM, TEM and HRTEM. The enhanced inherent conductivity and diffusion at the interface are also confirmed using electrochemical measurements study. The NCO-5 material exhibits a notable enhancement in capacitance and cycling retention. The NCO-5 electrode demonstrates a high specific capacitance (Cs) of 2445.7 F/g at 1 A/g. The pseudocapacitive behavior by power law (b = 0.67) and an increase in capacitive contribution with the scan rate reaching a value of 47.2 % at 100 mV/s by Dunn method exhibits it suitability of pseudocapacitors. The low Rct value signifies it improved capacitive performance as deduced from EIS measurements. Crucially, it maintains around 95.3 % of its capacitance after undergoing 10,000 GCD cycles. The high specific capacitance, remarkable capacitive characteristics and high stability of NCO-5 make it an excellent contestant for supercapacitor applications. The fabricated asymmetric supercapacitor (NCO-5//AC) shows exceptional energy density (ED) of 96.35 Wh/kg with power density (PD) of 825.03 W/kg.

Enhancing the electrochemical performance of a nickel molybdenum nitride for an energy storage device using cobalt nitride and phosphorus doping

Compared to traditional energy storage devices, hybrid solid-state supercapacitors have gained a lot of attention because of their exceptional power, energy density and outstanding cyclic stability. Transition metal nitrides are eminent candidates with high-performance electrochemical properties for energy storage devices. In this work, a high-performance CoN/NiMoN interface with P-doping was prepared by a simple feasible strategy for the positive electrode of a supercapacitor. The electrochemical performance in a 2 M KOH electrolyte revealed a specific capacity of 2070C·g−1 at a 5 A·g−1, which is exceptional compared to recently reported literature. Encapsulating NiMoN with CoN and its P-doping, resulting in a three-dimensional structure with desirable textural properties and easy permeation of electrolyte, enhances the electrochemical performances prepared electrode. Further, a hybrid solid-state supercapacitor was prepared with P-CoN/NiMoN (positive) and activated carbon (negative) as a electrodes. The prepared P-CoN/NiMoN//activated carbon supercapacitor showed an operating potential window of 1.7 V with an admirable specific capacity of 573.99C·g−1, for 135.5 Wh·kg−1 energy and 850 W·kg−1 power density at a 1 A·g−1. The results provide a feasible strategy to prepare and modify the electrochemical properties of NiMoN by CoN encapsulation and P-doping. The method gives insights for the preparation of other transition metal nitrides for high-density energy storage without much change in the power density.

Fabrication of ZnCr2O4/MnO2 composite electrodes by sonication procedure for advanced symmetric supercapacitors

In order to develop advanced energy storage devices, it is necessary to manufacture supercapacitor electrode that have both long electrochemical cycle lifetimes and high energy densities. These properties can only be obtained by developing heterostructure pseudo-capacitive materials. The combination of MnO2 nanorods and ZnCr2O4 nanoparticles resulted in a synergistic effect, which increased the electroactive surface area for charge storage. This effect was not observed when each component utilized individually. The material ZnCr2O4 nanoparticles facilitated the MnO2 nanorods. In present study, ZnCr2O4, MnO2 and their composite was fabricated by simple sonication process. These fabricated samples were tested by using different techniques which includes X-ray diffraction (XRD), Raman analysis, Brunauer Emmett Teller (BET) and scanning electron microscopy (SEM). Electrochemical analysis of fabricated materials exhibited an exceptional specific capacitance (Csp = 1175.35 F g−1), energy density (Ed = 15.95 Wh Kg−1) and power density (Pd = 869.4 W kg−1). These materials are anticipated to act as the support for electrochemical energy storage devices that utilize an ideal electrode structure, meticulously select the appropriate transition metal oxide (TMO) and analyse electrochemical characteristics for supercapacitive performance. This study exhibits the remarkable efficiency of the nanostructured ZnCr2O4/MnO2 electrode in supercapacitors with high energy density (Ed).

A Supramolecular Deep Eutectic Electrolyte Enhancing Interfacial Stability and Solution Phase Discharge in Li-O2 Batteries.

Li-O2 batteries (LOBs) have gained widespread recognition for their exceptional energy densities. However, a major challenge faced by LOBs is the lack of appropriate electrolytes that can effectively balance reactant transport, interfacial compatibility, and non-volatility. To address this issue, a novel supramolecular deep eutectic electrolyte (DEE) has been developed, based on synergistic interaction between Li-bonds and H-bonds through a combination of lithium salt (LiTFSI), acetamide (Ace) and boric acid (BA). The incorporation of BA serves as an interface modification additive, acting as both Li-bonds acceptor and H-bonds donor/acceptor, thereby enhancing the redox stability of the electrolyte, facilitating a solution phase discharge process and improving compatibility with the Li anode. Our proposed DEE demonstrates a high oxidation voltage of 4.5 V, an ultrahigh discharge capacity of 15225 mAh g-1 and stable cycling performance of 196 cycles in LOBs. Additionally, the intrinsic non-flammability and successful operation of a Li-O2 pouch cell indicate promising practical applications of this electrolyte. This research broadens the design possibilities for LOBs electrolytes and provides theoretical insights for future studies.

Engineering Mn Vacancies to Enhance Ion Kinetics in Layered Manganese Silicate for High-Energy and Durable Intercalation Pseudocapacitance.

Transition metal silicates (TMSs) are potential electrodes for aqueous metal-ion intercalation pseudocapacitors owing to their superior theoretical capacity and high structural stability. However, the narrow interlayer spacing and intrinsic inert basal plane of TMSs lead to sluggish ions and charge transfer, causing an undesirable energy storage performance. Herein, rich Mn vacancies are introduced in layered manganous silicates (M2-xS@FA) to expedite K+ diffusion, while enhancing charge storage capacity and prolonging lifespan. In situ characterizations validate the K+ intercalation pseudocapacitance mechanism with evident crystal structure and valence state variations in M2-xS@FA. Both theoretical calculations and electrochemical experimental evaluations elucidate the imperative role of Mn vacancies in enhancing K+ diffusion kinetics and electron transfer through increased interlayer spacing and activated basal plane. Mn vacancies further boost the charge storage capacity by providing additional K+ storage sites, while simultaneously reinforcing local atomic bonding within M2-xS@FA, thereby augmenting structural stability. The assembled aqueous asymmetric solid-state cell, featuring a M2-xS@FA cathode, demonstrates exceptional power and energy densities (144.08 W h kg-1 at 375.80 W kg-1) and ultralong lifespan (100% capacity retention after 10,000 cycles). This work heralds a paradigm whereby modulating cation vacancies in layered TMSs significantly enhances K+ storage and stability for high-energy intercalation pseudocapacitance.

Scalable Production of Thin and Durable Practical Li Metal Anode for High-Energy-Density Batteries.

Utilization of thin Li metal is the ultimate pathway to achieving practical high-energy-density Li metal batteries (LMBs), but its practical implementation has been significantly impeded by formidable challenges of poor thinning processability, severe interphase instability and notorious dendritic Li growth. Here we report a practical thin (10-40 μm) Li/Mo/Li2Se with concurrently modulated interphase and mechanical properties, achieved via a scalable mechanical rolling process. The in-situ generated Li2Se and Mo not only enhance the mechanical strength enabling the scalable fabrication of thin Li metal, but also promote homogenous Li electrodeposition. Significantly, the Li/Mo/Li2Se demonstrates ultrahigh-rate performance (15 mA cm-2) and ultralong-lifespan cycling sustainability (2700 cycles) with exceptional anti-pulverization capability. The Li|LiFePO4 cells show substantially prolonged cyclability over 1200 cycles with an ultralow decay rate of ~0.01% per cycle. Moreover, the Li|LiNi0.8Co0.1Mn0.1O2 pouch cells deliver enhanced cycling stability even under the extremely harsh conditions of low negative-to-positive-capacity (N/P) ratio of ~1.2 and lean electrolyte of ~0.95 g Ah-1, showing an exceptional energy density of 329.2 Wh kg-1. This work sheds light on facile pathway for scalable production of durable thin Li metal anode toward reliable practicability.

ALD with Enhanced Nucleation on Polymeric Separator for Improved Li-S Batteries

Lithium-sulfur (Li-S) batteries, known for their exceptional energy densities, are at the forefront of the next generation of energy storage systems. However, their practical application is hindered by the polysulfide shuttle effect, which significantly impairs discharge capacity and cycling stability. This research introduces a novel solution to these challenges through the use of atomic layer deposition (ALD) of Al₂O₃ on commercial polypropylene/polyethylene/polypropylene (PP/PE/PP) separators.ALD is a thin-film deposition technique that allows for precise control of layer thickness and composition at the atomic scale. ALD is characterized by its ability to produce extremely uniform and conformal layers, making it an ideal method for applications where surface chemistry plays a critical role, such as in battery separators. The technique is particularly advantageous in applications requiring high precision and control, like in our approach to enhancing Li-S batteries.In our study, the inert separator was treated with UV ozone to enhance the nucleation of ALD precursors, with the goal of reducing polysulfide shuttling. The use of ALD-modified separators in batteries demonstrated a marked increase in specific capacity, reaching approximately 1150 mAh/g, and reduced overpotential, indicative of improved kinetic efficiency. Further, we explored the structural and chemical modifications of the separator, employing X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Our findings indicate that ALD of Al₂O₃ on the separators significantly improved the adsorption of polysulfides, thereby mitigating the shuttle effect.In addition to improved polysulfide interaction, we also examined the impact on polysulfide adsorption on the formation of the solid-electrolyte interphase (SEI). Our results showed that modified batteries exhibited no polysulfide presence on the anode, suggesting a stable and effective SEI. This observation is significant, as it indicates that our approach enhances specific capacity and cycling stability by controlling the formation of a more effective SEI.Overall, our research demonstrates how strategic modifications at the separator level, particularly through the application of ALD and UV ozone, can significantly enhance the overall performance of Li-S batteries. By leveraging the unique advantages of ALD, especially through Al₂O₃ deposition, we provide a viable pathway to enhance the efficiency and stability of Li-S batteries.

Architectural design and optimization of internal structures in 3D printed electrodes for superior supercapacitor performance

The architecture of electrodes plays a pivotal role in the transfer and transportation of charges during electrochemical reactions. Selecting optimal electrode materials and devising well-conceived electrode structures can substantially enhance the electrochemical performance of devices. This manuscript leverages 3D printing technology to fabricate asymmetric supercapacitor devices featuring regular layered configurations. By investigating the impact of various materials on the internal architecture of printed electrodes, we establish a stratified electrode structure with an orderly arrangement, thereby significantly improving asymmetric charge transfer between electrodes. The application of 3D printing technology to construct electrode structures effectively mitigates the agglomeration of electrode materials. The 3D-printed VCG//MXene devices demonstrate exceptional areal capacitance (205.57 mF cm−2) and energy density (60.03 μWh cm−2), with a power density of 0.174 W cm−2. Consequently, selecting appropriate materials for fabricating printable electrode structures and achieving efficient 3D printing is anticipated to offer novel insights into the construction and enhancement of miniature asymmetric micro-supercapacitor (MSCs) devices.

High Energy Density Asymmetric Tetrathiafulvalene Derivative as a Catholyte for Non-Aqueous Redox Flow Batteries

The inherent intermittency challenge associated with renewable energy sources prompts the rapid development of cost-effective, grid-scale energy storage technologies. Redox flow batteries (RFBs) represent a promising solution to this problem owing to their remarkable potential for scalability and the tunability offered by a wide range of available solution-based chemistries. However, to-date, RFB commercialization has been challenged by a lack of long-lived, energy-dense, and earth abundant charge storage materials. Many of these challenges can be addressed with the development of non-aqueous organic redox flow batteries (NAORFBs). Such batteries leverage the wide potential window (> 5.5 V) offered by organic solvents with the synthetic tunability of organic redox cores to create highly energy dense battery systems with electrolytes based on earth abundant materials (i.e., carbon, nitrogen, sulfur, oxygen, etc.). The energy density of NAORFBs can be optimized with strategies such as increasing the solubility of redoxmers, increasing the number of electrons transferred by redoxmers, and increasing the magnitude of the potential of employed redox materials [1]. Of these, solubility can be enhanced through the grafting of polar side groups to a redoxmer, while redox potential can be increased through the attachment of either electron-withdrawing or donating substituents, in the case of catholyte and anolytes, respectively, near or in conjugation with the redox core [2]. Recently, our group has demonstrated tetrathiafulvalene (TTF) as a robust, two-electron active catholyte material in NAORFBs [3]. Namely, TTF exhibits reversible oxidation events at 0.03 and 0.43 V vs. Ag/Ag+ (Figure 1A). Underivatized TTF, which is highly insoluble in many polar organic solvents, can be made miscible in MeCN, carbonates, and ethereal solvents, with the attachment of four PEG3 chains to the TTF core ((PEG3)2-TTF) (Figure 1B). When paired with a low potential Li metal anode, an RFB incorporating 0.5 M (PEG3)2-TTF (1.0 M e- concentration) in 1.0 M LiPF6-EC/EMC supporting electrolyte exhibits overall operating cell potentials of 3.44 and 3.64 V vs. Ag/Ag+. Here we describe our most recent efforts to develop a further optimized, rationally designed asymmetric TTF derivative – (PEG3/PerF)-TTF – incorporating both a perfluorophenyl ring fused directly to the TTF core and two PEG3 side chains (Figure 1B). The electron-withdrawing perfluorophenyl group functions to substantially raise the potential of both redox events to 0.43 V and 0.65 V vs. Ag/Ag+, while the two PEG3 chains allow the material to retain miscibility in polar solvents. The performance of (PEG3/PerF)-TTF has been successfully demonstrated in a battery at an even higher concentration of 0.75 M (1.5 M e- concentration) (Figure 1C). When also paired with a Li metal anode in 1.0 M LiPF6-EC/EMC supporting electrolyte, the battery exhibits exceptional operational energy density of 96 Wh/L at 6 mA/cm2 current density and capacity retention of 83.1% over 16.8 d of continuous operation (99.0% per d). These results further demonstrate TTF as a highly versatile catholyte with remarkable potential for application in NAORFBs.

Mechanistic Understanding of the Role of Bis(4-nitrophenyl) Carbonate (BNC) As Additive on the Solvation Structure and Polysulfides Shuttling Effect Towards Capacity Improvement in Lithium-Sulfur Batteries

The lithium-sulfur (Li-S) batteries are considered as one of the most promising devices for next-generation energy storage applications, owing to its exceptional theoretical capacity and energy density. However, persistent challenges have hampered its performance, notably the sluggish polysulfides conversion kinetics and the polysulfides shuttling phenomenon. These issues lead to irreversible active material loss, rapid capacity decay, low coulombic efficiency, and a limited cycle life. This study demonstrates that bis(4-nitrophenyl) carbonate (BNC) can serve as an effective agent in anchoring dissolved polysulfides, thereby preventing their migration to the anode. Furthermore, this investigation indicates that BNC has the capability to modify the solvation structure of polysulfides in the electrolyte. The presence of 0.01M BNC induces a downfield shift in the 7Li NMR spectrum, signifying a strengthened solvation structure on Li-ion. This solvation modification results in altered kinetics, specifically a reduced Li2S2/Li2S conversion without sacrificing capacity, as confirmed by operando X-ray absorption spectroscopy (XAS). Operando Raman spectroscopy reveals the suppression of long-chain polysulfides (at 400 cm-1) and intermediate polysulfides (at 453 cm-1) with 0.01M BNC, mitigating sulfur shuttling to the anode. This observation is corroborated by X-ray fluorescence (XRF) mapping. Analysis of the corresponding X-ray absorption near-edge structure (XANES) demonstrates that both anodes and cathodes with 0.01M BNC exhibit lower levels of unconverted polysulfides over extended cycles. This improvement is attributed to the kinetic consequences resulting from solvation structure alteration. However, this investigation cautions against an indiscriminate increase in BNC concentration, as higher concentrations may lead to the over-conversion of soluble polysulfides. This nuanced understanding of the solvation structure's intrinsic mechanism, coupled with chemical reactions, provides valuable insights for practical design of Li-S batteries Figure 1

Synthesis and electrochemical performance of low cost nitrogen-doped carbon cryogel composites as supercapacitor electrodes

Developing cost-effective methods for synthesizing Nitrogen-doped carbon cryogels is crucial for advancing supercapacitor technology due to their enhanced electrochemical properties. Nitrogen-doped porous carbon cryogels are synthesized through the freeze-drying method by substituting resorcinol with phenol and using urea/melamine as nitrogen sources. The effect of nitrogen sources on the structure and electrochemical performance is investigated. In the case of carbon cryogel composites samples, using melamine as the nitrogen source (PMF) is more favorable than using urea (PUF), while both nitrogen-doped samples significantly outperform the undoped samples (PF). The PMF sample displays a specific surface area of 1119.00 m2 g−1, and a nitrogen content of 2.19 wt%. In the three-electrode system, the specific capacitance of the PMF sample reaches up to 247.9 F g−1 at a current density of 0.5 A g−1, and its rate performance is 85.52 %. By comparison, the PF sample exhibits specific capacitance and rate performance of 85.4 F g−1 and 33.44 % under the same parameters. The assembled symmetric supercapacitor in a buckle type system also demonstrates exceptional energy density (14.41 Wh kg−1), long-term cycle stability, and a favorable capacitance retention rate (72.2 %). These excellent electrochemical performances can be attributed to the synergistic effects of the hierarchical pore structures and heteroatoms doping.

Sulfur-Functionalized Carbon Nanotubes with Inlaid Nanographene for 3D-Printing Micro-Supercapacitors and a Flexible Self-Powered Sensing System.

Digital fabrication of miniaturized micro-supercapacitors (MSCs) holds immense promise for advancing customized, integrated microelectronic systems. As potential electrode materials, carbonaceous nanomaterials, such as carbon nanotubes (CNTs), stand out due to their excellent conductivity and mechanical robustness yet suffer from low ionic storage sites, which restrict further applications. Herein, we introduce a sulfur-assisted in situ activating strategy for obtaining sulfur-functionalized carbon nanotube frameworks integrated with inlaid graphene nanosheets (S-CNT/GNS). Specifically, sulfur functionality enriches the surface charge density with improved interfacial hydrophilicity, while the inlaid nanographene sheets provide abundant ionic adsorption sites. By direct 3D printing of the S-CNT/GNS ink, planar MSCs were fabricated with desirable functionality and outstanding electrochemical performance. Notably, the developed MSCs exhibit a high areal capacitance of 0.47 F cm-2, an exceptional energy density of 64.6 μWh cm-2, and a high-power density of 34.2 mW cm-2. Furthermore, an all-flexible self-powered sensing system with photovoltaic cells and a stretchable sensor was built upon the customized S-CNT/GNS MSCs, demonstrating a highly effective capability for real-time monitoring of human physiological signals and body movements. This work not only presents a promising approach for the development of high-performance MSCs but also lays the groundwork for the creation of advanced wearable/flexible microelectronics systems.

Approaching Theoretical Capacity: 0D/2D Amorphous/Crystalline Bi‐Based Heterostructures Anode for Aqueous Alkaline Rechargeable Batteries

AbstractAlthough various bismuth (Bi) electrode materials are reported to assemble aqueous alkaline rechargeable batteries (AARBs) owing to desirable potential window and high theoretical capacity, the Bi‐based electrode materials are still confronted with by their “death space” and poor stability. Herein, a zero‐dimensional/two‐dimensional (0D/2D) amorphous/crystalline BiOx‐Bi heterostructure is successfully synthesized by a one‐step reduction method for achieving nearly theoretical capacity. Under proper NaBHNaBH4 content, the Bi33+ is reduced to form ultra‐thin 2D metallic bismuth nanoflakes (Bi‐nf), and incompletely reduced amorphous 0D BiOx nanodots are embedded in Bi‐nf to form the target BiOx/Bi‐nf heterostructure. The embedded 0D nanodots inhibit the aggregation of 2D Bi‐nf, accelerate the mass transport rate with more oxygen vacancies and pores at heterogeneous interface, and the active centers of amorphous nanodots and ultrathin nanoflakes are recognized as completely accessible which is benefit for up to theoretical capacity. Accordingly, the optimized 0D/2D amorphous/crystalline BiOx‐Bi‐nf heterostructure electrode presents an admirable capacity of 350 mAh g−1 at 1 A g−1 and outstanding capacity retention of 79.9% at 20 A g‐1. Moreover, the assembled BCNP (basic cobalt/nickel phosphate)//BiOx/Bi‐nf battery exhibits exceptional energy density of 191.64 Wh kg‐1 at 1.28 kW kg‐1 power density and durable stability (80% after 14000 cycles).

Electrocatalytic tungsten boride quantum dots anchored reduced graphene oxide as the desolvation promotor for efficient sulfur redox kinetics

Lithium-sulfur (Li-S) batteries boast a multitude of compelling attributes, chief among them being their exceptional energy density and relatively low raw material costs. However, the sluggish redox kinetics of sulfur stemming from the considerable desolvation energy barrier and the notorious shuttle effect of lithium polysulfides, pose significant challenges in the commercialization of Li-S batteries. In this work, ultra-fine WB quantum dots were in-situ and uniformly dispersed on reduced graphene oxide nanosheets (WB-rGO) by mild melting-salt method, in which the abundant oxygen-containing functional groups in graphene oxide effectively prevent the agglomeration of WB. Such ultra-fine WB quantum dot as well as dual-active sites stemming from W and electronics-deficient B, confer the WB-rGO composite with improved electrochemical active surface area for dissociating Li+-solvents molecules and catalyzing polysulfides transformations, thus improving cycling and rate performance of Li-S battery. Hence, the cells with WB-rGO@PP maintained a stable long-term cycling (650 mAh g−1 after 900 cycles at 1 C with an average decay rate of 0.038 % per cycle) and an impressive rate capability (740 mAh g−1 at 4 C). Even at a sulfur loading of 4.7 mg cm−2, the cell performed a high areal capacity of 3.6 mAh cm−2 after 200 cycles.

Prussian Blue Analogues Derived Bimetallic CoNi@NC as Efficient Oxygen Reduction Reaction Catalyst for Mg‐Air Batteries

The magnesium‐air (Mg‐air) batteries are regarded as a highly promising system for electrochemical energy conversion and storage, owing to exceptional energy density, notable safety and eco‐friendliness. The development of high‐performance and durable non‐noble metal catalysts for the cathodic oxygen reduction reaction (ORR) is crucial for advancing the practical use of Mg‐air batteries. The synergistic interaction between different metals in bimetallic catalysts is an effective strategy for enhancing the activity and stability of the catalysts. Herein, various prussian blue analogues (PBA) were selected as precursors to synthesis the bimetallic CoNi@NC, monometallic Co@NC and Ni@NC catalysts due to tunable chemical compositions. Compared with Co@NC and Ni@NC, the bimetallic CoNi@NC pyrolyzed at 600°C (CoNi@NC‐600) exhibits outstanding ORR performances and stability in alkaline (0.1 M KOH) and neutral (3.5 wt% NaCl) electrolytes. Following 5000 CV cycles, the half‐wave potentials for CoNi@NC‐600 show only minor negative shifts of 8 and 7 mV, respectively. Meanwhile, the CoNi@NC‐600 possesses the similar ORR reaction mechanism and activity with Pt/C. The primary Mg‐air battery assembled with CoNi@NC‐600 displays better discharge performances than that of Co@NC and Ni@NC. This study lays the foundation for future investigations into the advancement of non‐precious bimetallic catalysts for ORR in Mg‐air batteries.

Carbon-modified NiCo2O4 as an electrode material for supercapacitors

Transition metal oxides are a promising class of electrode materials for pseudocapacitors due to their high electrochemical activity and eco-friendly nature. However, they possess poor intrinsic conductivity which results in the low energy density of the assembled supercapacitors. In this study, electrodes composed of amorphous C-modified NiCo2O4 (C/NiCo2O4/NF) on nickel foam substrate were prepared by electrochemical deposition and thermostatic heating method. The incorporation of amorphous C compensates for the low electrical conductivity of NiCo2O4 materials, thereby significantly enhancing the electrochemical performance. The galvanostatic charge-discharge (GCD) test results reveal an impressive specific capacitance of 379.4 mF/cm2 at a current density of 1.5 mA/cm2, and with a capacitance retention rate of 87.1 %. In addition, the symmetric supercapacitor assembled using C/NiCo2O4 electrode materials exhibits exceptional energy density and power density, reaching maximum values of 522.3 μWh/cm2 and 900 μW/cm2 respectively. The device is capable of illuminating LED for up to 8 min, further demonstrating its practical applicability. These results underscore the feasibility and promise of C/NiCo2O4 as an electrode material for the advancement of high-performance supercapacitors.