Nitrogen-doped carbon nanotubes as an anode for a highly robust potassium-ion hybrid capacitor

Progress and obstacles in electrode materials for lithium-ion batteries: a journey towards enhanced energy storage efficiency

This review critically examines various electrode materials employed in lithium-ion batteries (LIBs) and their impact on battery performance. It highlights the transition from traditional lead-acid and nickel-cadmium batteries to modern LIBs, emphasizing their energy density, efficiency, and longevity. It primarily focuses on cathode materials, including LiMn2O4, LiCoO2, and LiFePO4, while also exploring emerging materials such as organosulfides, nanomaterials, and transition metal oxides & sulfides. It also presents an overview of the anode materials based on their mechanism, e.g., intercalation-deintercalation, alloying, and conversion-type anode materials. The strengths, limitations, and synthesis techniques associated with each material are discussed. This review also delves into cathode materials, such as soft and hard carbon and high-nickel systems, assessing their influence on storage performance. Additionally, the article addresses safety concerns, recycling strategies, environmental impact evaluations, and disposal practices. It highlights emerging trends in the development of electrode materials, focusing on potential solutions and innovations. This comprehensive review provides an overview of current lithium-ion battery technology, identifying technical challenges and opportunities for advancement to promote efficient, sustainable, and environmentally responsible energy storage solutions. This review also examines the issues confronting lithium-ion batteries, including high production costs, scarcity of materials, and safety risks, with suggestions to address them through doping, coatings, and incorporation of nanomaterials.

Self-hybridization structures of BiOBr0.5Cl0.5: An ultra-high capacity anode material for half/full potassium-ion batteries

Potassium-ion batteries (PIBs) are gaining attention among emerging technologies for their cost-effectiveness and the abundance of resources they utilize. Within this context, bismuth oxyhalides (BiOX) have emerged as exceptional candidates for anode materials in PIBs due to their unique structural and superior electrochemical properties. However, challenges such as structural instability and low electronic conductivity remain to be addressed. In this study, a flower-like BiOBr0.5Cl0.5/rGO composite anode material was synthesized, demonstrating outstanding K+ storage performance. The self-hybridized structure enhances ion adsorption and diffusion, which in turn improves charge and discharge efficiency as well as long-term stability. In situ X-ray diffraction (XRD) tests confirmed the gradual release and alloying potassium storage mechanism of Bi metal, which occurs through the intermediate KxBiOBr0.5Cl0.5 phase within the BiOBr0.5Cl0.5 anode. This composite exhibited a high specific capacity of 246.4 mAh/g at 50 A/g and maintained excellent capacity retention after 2400 cycles at 5 A/g. Additionally, in full battery tests, it showed good rate performance and long cycle life, maintaining a discharge specific capacity of 119.6 mAh/g at a high current density of 10 A/g. Comprehensive characterizations revealed insights into the structural, electrochemical, and kinetic properties, advancing high-performance PIBs.

Biomass-Derived Materials for Advanced Rechargeable Batteries

Biomass-derived materials generally exhibit uniform and highly-stable hierarchical porous structures that can hardly be achieved by conventional chemical synthesis and artificial design. When used as electrodes for rechargeable batteries, these structural and compositional advantages often endow the batteries with superior electrochemical performances. This review systematically introduces the innate merits of biomass-derived materials and their applications as the electrode for advanced rechargeable batteries, including lithium-ion batteries, sodium-ion batteries, potassium-ion batteries, and metal-sulfur batteries. In addition, biomass-derived materials as catalyst supports for metal-air batteries, fuel cells, and redox-flow batteries are also included. The major challenges for specific batteries and the strategies for utilizing biomass-derived materials are detailly introduced. Finally, the future development of biomass-derived materials for advanced rechargeable batteries is prospected. This review aims to promote the development of biomass-derived materials in the field of energy storage and provides effective suggestions for building advanced rechargeable batteries.

Recent Advances in Functionalized Biomass-Derived Porous Carbons and their Composites for Hybrid Ion Capacitors

Hybrid ion capacitors (HICs) have aroused extreme interest due to their combined characteristics of energy and power densities. The performance of HICs lies hidden in the electrode materials used for the construction of battery and supercapacitor components. The hunt is always on to locate the best material in terms of cost-effectiveness and overall optimized performance characteristics. Functionalized biomass-derived porous carbons (FBPCs) possess exquisite features including easy synthesis, wide availability, high surface area, large pore volume, tunable pore size, surface functional groups, a wide range of morphologies, and high thermal and chemical stability. FBPCs have found immense use as cathode, anode and dual electrode materials for HICs in the recent literature. The current review is designed around two main concepts which include the synthesis and properties of FBPCs followed by their utilization in various types of HICs. Among monovalent HICs, lithium, sodium, and potassium, are given comprehensive attention, whereas zinc is the only multivalent HIC that is focused upon due to corresponding literature availability. Special attention is also provided to the critical factors that govern the performance of HICs. The review concludes by providing feasible directions for future research in various aspects of FBPCs and their utilization in HICs.

Revealing the Effect of the Microstructure on Potassium Storage Behavior in a Two-Dimensional Mesoporous Carbon Anode

Hard carbon is considered as the most promising anode material for potassium-ion energy storage devices. Substantial progress has been made in exploring advanced hard carbons to solve the issues of sluggish kinetics and large volume changes caused by the large radius of K+. However, the relationship between their complicated microstructures and the K+ charge storage behavior is still not fully explored. Herein, a series of two-dimensional mesoporous carbon microcoins (2D-MCMs) with tunable microstructures in heteroatom content and graphitization degree are synthesized by a facile hard-template method and follow a temperature-controllable annealing process. It is found that high heteroatom content makes for surface-driven K+ storage behavior, which increases the capacity-contribution ratio from a high potential region, while a high graphitization degree makes for K+ intercalation behavior, which increases the capacity-contribution ratio from a low potential region. Electrochemical results from a three-electrode Swagelok cell demonstrate that a 2D-MCM anode with more capacity contribution from a low working region allows the porous carbon cathode to be operated in a much wider electrochemical window, thus storing more charge. As a result, potassium-ion capacitors based on the optimized 2D-MCM anode deliver a high energy density of 113 Wh kg-1 and an exhilarating power density of 51,000 W kg-1.

Electrochemical Performance of Chemically Activated Carbons from Sawdust as Supercapacitor Electrodes

Activated carbons (ACs) have been the most widespread carbon materials used in supercapacitors (SCs) due to their easy processing methods, good electrical conductivity, and abundant porosity. For the manufacture of electrodes, the obtained activated carbon based on sawdust (karagash and pine) was mixed with conductive carbon and polyvinylidene fluoride as a binder, in ratios of 75% activated carbon, 10% conductive carbon black, and 15% polyvinylidene fluoride (PVDF) in an N-methyl pyrrolidinone solution, to form a slurry and applied to a titanium foil. The total mass of each electrode was limited to vary from 2.0 to 4.0 mg. After that, the electrodes fitted with the separator and electrolyte solution were symmetrically assembled into sandwich-type cell construction. The carbon's electrochemical properties were evaluated using cyclic voltammetry (CV) and galvanostatic charge-discharge (CGD) studies in a two-electrode cell in 6M KOH. The CV and CGD measurements were realized at different scan rates (5-160 mV s^-1) and current densities (0.1-2.0 A g^-1) in the potential window of 1 V. ACs from KOH activation showed a high specific capacitance of 202 F g^-1 for karagash sawdust and 161 F g^-1 for pine sawdust at low mass loading of 1.15 mg cm^-2 and scan rate of 5 mV s^-1 in cyclic voltammetry test and 193 and 159 F g^-1 at a gravimetric current density of 0.1 A g^-1 in the galvanostatic charge-discharge test. The specific discharge capacitance is 177 and 131 F g^-1 at a current density of 2 A g^-1. Even at a relatively high scan rate of 160 mV s^-1, a decent specific capacitance of 147 F g^-1 and 114 F g^-1 was obtained, leading to high energy densities of 26.0 and 22.1 W h kg^-1 based on averaged electrode mass. Surface properties and the porous structure of the ACs were studied by scanning electron microscopy, energy-dispersive X-ray analysis, Raman spectroscopy, and the Brunauer-Emmett-Teller method.

One-step and room-temperature fabrication of carbon nanocomposites including Ni nanoparticles for supercapacitor electrodes

With the increasing importance of power storage devices, demand for the development of supercapacitors possessing both rapid reversible chargeability and high energy density is accelerating. Here we propose a simple process for the room temperature fabrication of pseudocapacitor electrodes consisting of a faradaic redox reaction layer on a metallic electrode with an enhanced surface area. As a model metallic electrode, an Au foil was irradiated with Ar+ ions with a simultaneous supply of C and Ni at room temperature, resulting in fine metallic Ni nanoparticles dispersed in the carbon matrix with local graphitization on the ion-induced roughened Au surface. A carbon layer including fine Ni nanoparticles acted as an excellent faradaic redox reaction layer and the roughened surface contributed to an increase in surface area. The fabricated electrode, which included only 14 μg cm-2 of Ni, showed a stored charge ability three times as large as that of the bulky Ni foil. Thus, it is believed that a carbon layer including Ni nanoparticles fabricated on the charge collective electrode with an ion-irradiation method is promising for the development of supercapacitors from the viewpoints of the reduced use of rare metal and excellent supercapacitor performance.

Construction of three-dimensional nitrogen doped porous carbon flake electrodes for advanced potassium-ion hybrid capacitors

It is of great significance to develop a new kind of green and environmentally friendly potassium ion energy storage device, with stable structures and large specific capacity. In this manuscript, a facile and robust way is reported to construct nitrogen doped porous carbon flake (NPCF) through NaCl template and pyrolysis method. 3D porous structures can be formed and interconnected NPCF are used as potassium ion batteries (PIBs) anode. High content of pyridinic N/pyrrolic N and enlarged interlayer distance of NPCF are obtained. Specifically, the anode delivers a high reversible capacity of 326.3 mAh g^-1 at the current density of 50 mA g^-1, and shows up outstanding cycle stability and represents long cycle life of 10,000 cycles at a current density of 5000 mA g^-1. Moreover, the cyclic voltammetry kinetic analysis shows that the main capacitive process plays a leading role in the potassium storage mechanism. Consequently, equipped with activate carbon (AC) as cathode and NPCF as anode, the assembled potassium ion hybrid capacitors (PIHCs) achieve an energy density of 65.8 Wh kg^-1 at 100 mA g^-1, and maintains 30 Wh kg^-1 even at a high current density of 5000 mA g^-1.

Prospects of Electrode Materials and Electrolytes for Practical Potassium-Based Batteries

Potassium-ion batteries (PIBs) have attracted tremendous attention because of their high energy density and low-cost. As such, much effort has focused on developing electrode materials and electrolytes for PIBs at the material levels. This review begins with an overview of the high-performance electrode materials and electrolytes, and then evaluates their prospects and challenges for practical PIBs to penetrate the market. The current status of PIBs for safe operation, energy density, power density, cyclability, and sustainability is discussed and future studies for electrode materials, electrolytes, and electrode-electrolyte interfaces are identified. It is anticipated that this review will motivate research and development to fill existing gaps for practical potassium-based full batteries so that they may be commercialized in the near future.

Ultra-High Sulfur-Doped Hierarchical Porous Hollow Carbon Sphere Anodes Enabling Unprecedented Durable Potassium-Ion Hybrid Capacitors

Sulfur doping is a promising path to ameliorate the kinetics of carbon-based anodes. However, the similar electronegativity of sulfur and carbon and the poor thermal stability of sulfur severely restrict the development of high-sulfur-content carbon-based anodes. In this work, ultra-high sulfur-doped hierarchical porous hollow carbon spheres (SHCS) with a sulfur content of 6.8 at % are synthesized via a direct high-temperature sulfur-doping strategy. An SHCS has sulfur bonded to the carbon framework including C-S-C and C-SO_x-C, which enlarges its interlayer distance (0.411 nm). In the K half-cell, benefiting from the considerable content and the reasonable architecture of sulfur, the SHCS exhibits significantly improved reversible specific capacity, initial Coulombic efficiency, and cyclability than hierarchical porous hollow carbon spheres without sulfur. Remarkably, the potassium ion hybrid capacitor device fabricated with the SHCS anode achieves excellent energy/power density (135.6 W h kg^-1/17.7 kW kg^-1) and unprecedented durability over 26,000 cycles at 2 A g^-1. This research provides a superior strategy to design high-sulfur-content carbon-based anodes with excellent potassium storage performance.

Covalent Fixing of MoS2 Nanosheets with SnS Nanoparticles Anchored on g-C3N4/Graphene Boosting Fast Charge/Ion Transport for Sodium-Ion Hybrid Capacitors

The sluggish layered structural sodium reaction kinetics and the easy restacking property are major obstacles hindering the practical application of MoS₂-based electrodes for sodium storage. Herein, covalently assembled two-phase MoS₂-SnS supported by a hierarchical graphitic carbon nitride/graphene (MoS₂-SnS@g-C₃N₄/G) composite is constructed to improve cycling cyclability and rate performances for Na storage. The multiphase MoS₂-SnS@g-C₃N₄/G is featured with a covalent assembly strategy and an interconnected network architecture. This unique structural design can not only enhance the conductivity and facilitate fast interfacial electron transport, which is confirmed by experiments and density functional theory, but also buffer the volumetric changes of MoS₂-SnS. As a result, the as-obtained MoS₂-SnS@g-C₃N₄/G anode delivers a high reversible capacity of 834 mA h g^-1 at 0.1 A g^-1, a high rate capability of 452 mA h g^-1 at 5 A g^-1, and a long-term cycling stability (320 mA h g^-1 at 2 A g^-1 with 54.7% retention after 500 cycles) for the Na half-cell. Coupling with activated carbon (AC), our MoS₂-SnS@g-C₃N₄/G||AC sodium-ion hybrid capacitor delivers high energy/power densities (193.1 W h kg^-1/90 W kg^-1 and 41.5 W h kg^-1/18,000 W kg^-1) and a stable cycle life in the potential range of 0-4.0 V.

Rational Design and Engineering of One-Dimensional Hollow Nanostructures for Efficient Electrochemical Energy Storage

The unique structural characteristics of one-dimensional (1D) hollow nanostructures result in intriguing physicochemical properties and wide applications, especially for electrochemical energy storage applications. In this Minireview, we give an overview of recent developments in the rational design and engineering of various kinds of 1D hollow nanostructures with well-designed architectures, structural/compositional complexity, controllable morphologies, and enhanced electrochemical properties for different kinds of electrochemical energy storage applications (i.e. lithium-ion batteries, sodium-ion batteries, lithium-sulfur batteries, lithium-selenium sulfur batteries, lithium metal anodes, metal-air batteries, supercapacitors). We conclude with prospects on some critical challenges and possible future research directions in this field. It is anticipated that further innovative studies on the structural and compositional design of functional 1D nanostructured electrodes for energy storage applications will be stimulated.