Biomass-Derived Carbon Paper to Sandwich Magnetite Anode for Long-Life Li-Ion Battery

Catalytically Active Carbon for Oxygen Reduction Reaction in Energy Conversion: Recent Advances and Future Perspectives

The shortage and unevenness of fossil energy sources are affecting the development and progress of human civilization. The technology of efficiently converting material resources into energy for utilization and storage is attracting the attention of researchers. Environmentally friendly biomass materials are a treasure to drive the development of new-generation energy sources. Electrochemical theory is used to efficiently convert the chemical energy of chemical substances into electrical energy. In recent years, significant progress has been made in the development of green and economical electrocatalysts for oxygen reduction reaction (ORR). Although many reviews have been reported around the application of biomass-derived catalytically active carbon (CAC) catalysts in ORR, these reviews have only selected a single/partial topic (including synthesis and preparation of catalysts from different sources, structural optimization, or performance enhancement methods based on CAC catalysts, and application of biomass-derived CACs) for discussion. There is no review that systematically addresses the latest progress in the synthesis, performance enhancement, and applications related to biomass-derived CAC-based oxygen reduction electrocatalysts synchronously. This review fills the gap by providing a timely and comprehensive review and summary from the following sections: the exposition of the basic catalytic principles of ORR, the summary of the chemical composition and structural properties of various types of biomass, the analysis of traditional and the latest popular biomass-derived CAC synthesis methods and optimization strategies, and the summary of the practical applications of biomass-derived CAC-based oxidative reduction electrocatalysts. This review provides a comprehensive summary of the latest advances to provide research directions and design ideas for the development of catalyst synthesis/optimization and contributes to the industrialization of biomass-derived CAC electrocatalysis and electric energy storage.

Biomass-derived carbon materials for vanadium redox flow battery: From structure to property

Biomass-derived carbon (BDC) materials are suitable as electrode or catalyst materials for vanadium redox flow battery (VRFB), owing to the characteristics of vast material sources, environmental friendliness, and multifarious structures. A timely and comprehensive review of the structure and property significantly facilitates the development of BDC materials. Here, the paper starts with the preparation of biomass materials, including carbonization and activation. It is designed to summarize the lastest developments in BDC materials of VRFB in four different structural dimensions from zero dimension (0D) to three dimension (3D). Every dimension begins with meticulously selected examples to introduce the structural characteristics of materials and then illustrates the improved performance of the VRFB due to the structure. Simultaneously, challenges, solutions, and prospects are indicated for the further development of BDC materials. Overall, this review will help researchers select excellent strategies for the fabrication of BDC materials, thereby facilitating the use of BDC materials in VRFB design.

Synthesis and Characterization of Zinc/Iron Composite Oxide Heterojunction Porous Anode Materials for High-Performance Lithium-Ion Batteries

Environmental pollution caused by the use of fossil fuels is becoming increasingly serious, necessitating the adoption of clean energy solutions. Lithium-ion batteries (LIBs) have attracted great attention due to their high energy density and currently occupy a dominant commercial position. Metal oxide materials have emerged as promising anode materials for the next generation of LIBs, thanks to their high theoretical capacity. However, the practical application of these materials is hindered by their substantial volume expansion during lithium storage and poor electrical conductivity. In this work, a zinc/iron bimetallic hybrid oxide composite, ZnO/ZnFe2O4/NC, is prepared using ZIF-8 as a precursor (ZIF-8, one of the metal organic frameworks). The N-doped porous carbon composite improves the volume change and optimizes the lithium-ion and electron transport. Meanwhile, the ZnFe2O4 and ZnO synergistically enhance the electrochemical activity of the anode through the built-in heterojunction to promote the reaction kinetics at the interface. As a result, the material delivers an excellent cycling performance of 604.7 mAh g-1 even after 300 cycles of 1000 mA g-1. This study may provide a rational design for the heterostructure and doping engineering of anodes for high-performance lithium-ion batteries.

Fibrous wearable and implantable bioelectronics

Fibrous wearable and implantable devices have emerged as a promising technology, offering a range of new solutions for minimally invasive monitoring of human health. Compared to traditional biomedical devices, fibers offer a possibility for a modular design compatible with large-scale manufacturing and a plethora of advantages including mechanical compliance, breathability, and biocompatibility. The new generation of fibrous biomedical devices can revolutionize easy-to-use and accessible health monitoring systems by serving as building blocks for most common wearables such as fabrics and clothes. Despite significant progress in the fabrication, materials, and application of fibrous biomedical devices, there is still a notable absence of a comprehensive and systematic review on the subject. This review paper provides an overview of recent advancements in the development of fibrous wearable and implantable electronics. We categorized these advancements into three main areas: manufacturing processes, platforms, and applications, outlining their respective merits and limitations. The paper concludes by discussing the outlook and challenges that lie ahead for fiber bioelectronics, providing a holistic view of its current stage of development.

Biomass-Derived Flexible Carbon Architectures as Self-Supporting Electrodes for Energy Storage

With the swift advancement of the wearable electronic devices industry, the energy storage components of these devices must possess the capability to maintain stable mechanical and chemical properties after undergoing multiple bending or tensile deformations. This circumstance has expedited research efforts toward novel electrode materials for flexible energy storage devices. Nonetheless, among the numerous materials investigated to date, the incorporation of metal current collectors or insulative adhesives remains requisite, which entails additional costs, unnecessary weight, and high contact resistance. At present, biomass-derived flexible architectures stand out as a promising choice in electrochemical energy device applications. Flexible self-supporting properties impart a heightened mechanical performance, obviating the need for additional binders and lowering the contact resistance. Renewable, earth-abundant biomass endows these materials with cost-effectiveness, diversity, and modulable chemical properties. To fully exploit the application potential in biomass-derived flexible carbon architectures, understanding the latest advancements and the comprehensive foundation behind their synthesis assumes significance. This review delves into the comprehensive analysis of biomass feedstocks and methods employed in the synthesis of flexible self-supporting carbon electrodes. Subsequently, the advancements in their application in energy storage devices are elucidated. Finally, an outlook on the potential of flexible carbon architectures and the challenges they face is provided.

Graphene-Based Materials for the Separator Functionalization of Lithium-Ion/Metal/Sulfur Batteries

With the escalating demand for electrochemical energy storage, commercial lithium-ion and metal battery systems have been increasingly developed. As an indispensable component of batteries, the separator plays a crucial role in determining their electrochemical performance. Conventional polymer separators have been extensively investigated over the past few decades. Nevertheless, their inadequate mechanical strength, deficient thermal stability, and constrained porosity constitute serious impediments to the development of electric vehicle power batteries and the progress of energy storage devices. Advanced graphene-based materials have emerged as an adaptable solution to these challenges, owing to their exceptional electrical conductivity, large specific surface area, and outstanding mechanical properties. Incorporating advanced graphene-based materials into the separator of lithium-ion and metal batteries has been identified as an effective strategy to overcome the aforementioned issues and enhance the specific capacity, cycle stability, and safety of batteries. This review paper provides an overview of the preparation of advanced graphene-based materials and their applications in lithium-ion, lithium-metal, and lithium-sulfur batteries. It systematically elaborates on the advantages of advanced graphene-based materials as novel separator materials and outlines future research directions in this field.

Functional Carbon from Nature: Biomass-Derived Carbon Materials and the Recent Progress of Their Applications

Biomass is considered as a promising source to fabricate functional carbon materials for its sustainability, low cost, and high carbon content. Biomass-derived-carbon materials (BCMs) have been a thriving research field. Novel structures, diverse synthesis methods, and versatile applications of BCMs have been reported. However, there has been no recent review of the numerous studies of different aspects of BCMs-related research. Therefore, this paper presents a comprehensive review that summarizes the progress of BCMs related research. Herein, typical types of biomass used to prepare BCMs are introduced. Variable structures of BCMs are summarized as the performance and properties of BCMs are closely related to their structures. Representative synthesis strategies, including both their merits and drawbacks are reviewed comprehensively. Moreover, the influence of synthetic conditions on the structure of as-prepared carbon products is discussed, providing important information for the rational design of the fabrication process of BCMs. Recent progress in versatile applications of BCMs based on their morphologies and physicochemical properties is reported. Finally, the remaining challenges of BCMs, are highlighted. Overall, this review provides a valuable overview of current knowledge and recent progress of BCMs, and it outlines directions for future research development of BCMs.

Advances in Cellulose-Based Composites for Energy Applications

The various forms of cellulose-based materials possess high mechanical and thermal stabilities, as well as three-dimensional open network structures with high aspect ratios capable of incorporating other materials to produce composites for a wide range of applications. Being the most prevalent natural biopolymer on the Earth, cellulose has been used as a renewable replacement for many plastic and metal substrates, in order to diminish pollutant residues in the environment. As a result, the design and development of green technological applications of cellulose and its derivatives has become a key principle of ecological sustainability. Recently, cellulose-based mesoporous structures, flexible thin films, fibers, and three-dimensional networks have been developed for use as substrates in which conductive materials can be loaded for a wide range of energy conversion and energy conservation applications. The present article provides an overview of the recent advancements in the preparation of cellulose-based composites synthesized by combining metal/semiconductor nanoparticles, organic polymers, and metal-organic frameworks with cellulose. To begin, a brief review of cellulosic materials is given, with emphasis on their properties and processing methods. Further sections focus on the integration of cellulose-based flexible substrates or three-dimensional structures into energy conversion devices, such as photovoltaic solar cells, triboelectric generators, piezoelectric generators, thermoelectric generators, as well as sensors. The review also highlights the uses of cellulose-based composites in the separators, electrolytes, binders, and electrodes of energy conservation devices such as lithium-ion batteries. Moreover, the use of cellulose-based electrodes in water splitting for hydrogen generation is discussed. In the final section, we propose the underlying challenges and outlook for the field of cellulose-based composite materials.

Tailored engineering of Fe3O4 and reduced graphene oxide coupled architecture to realize the full potential as electrode materials for lithium-ion batteries

Developing advanced electrode materials with appropriate compositions and exquisite configurations is crucial in fabricating lithium-ion batteries (LIBs) with high energy density and fast charging capability plateau. Herein, a Fe₃O₄@reduced graphene oxide (Fe₃O₄@rGO) coupled architecture was rationally designed and in-situ synthesized. Monodispersed mesoporous Fe₃O₄ nanospheres were homogeneously formed and strongly bound on interconnected macroporous rGO frameworks to form well-defined three-dimensional (3D) hierarchical porous morphologies. This tailored Fe₃O₄@rGO coupled architecture fully exploited the advantages of Fe₃O₄ and rGO to overcome their inherent challenges, including spontaneous aggregating/excessive restacking tendency, sluggish ions diffusion/electrons transportation, and severe volume expansion/structural collapse. Benefitting from their synergistic effects, the optimized Fe₃O₄@rGO composite electrode exhibited an improved electrochemical reactivity, electrical conductivity, electrolyte accessibility, and structural stability. The optimized composite electrode displayed a high specific capacity of 1296.8 mA h g^-1 at 0.1 A g^-1 after 100 cycles, even retaining 555.1 mA h g^-1 at 2 A g^-1 after 2000 cycles. The electrochemical kinetics analysis revealed the predominantly pseudocapacitive behaviors of the Fe₃O₄@rGO heterogeneous interfaces, accounting for the excellent electrode performance. This study proposes a viable strategy for use in engineering hybrid composites with coupled architectures to optimize their potential as high-performance electrode materials for use in LIBs.

Edge-Nitrogen Enriched Porous Carbon Nanosheets Anodes with Enlarged Interlayer Distance for Fast Charging Sodium-Ion Batteries

The application of nitrogen-doped porous carbon for sodium-ion batteries (SIBs) has attracted tremendous attention. Herein, a series of edge-nitrogen enriched porous carbon nanosheets (ENPCNs) are synthesized by annealing g-C₃ N₄ and glucose in a sealed graphite crucible at different temperatures (T = 700, 800, and 900 °C). Surprisingly, under the closed thermal treatment condition, the ENPCNs-T possess a high N-doping level (>12.62 at%) and different carbon interlayer distance ranging from 0.429 to 0.487 nm. By correlating the carbon interlayer distance with the N configurations of ENPCNs-T materials, a reasonable perception of the important influence of pyrrolic N on the increase of carbon interlayer distance is proposed. When applied as anode materials for SIBs, the ENPCNs-800 exhibits a remarkable capacity (294.1 mAh g^-1 at 0.1 A g^-1 ), excellent rate performance (132.8 mAh g^-1 at 10 A g^-1 ), and outstanding cycle life (180.6 mAh g^-1 at 1 A g^-1 after 1000 cycles with a capacity retention of 104.7%). Meanwhile, the characterizations of cyclic voltammetry, galvanostatic intermittent titration technique, and electrochemical impedance spectroscopy demonstrate that the edge-nitrogen doping and enlarged carbon interlayer distance improve the capacity and fast charging performance of ENPCNs-800. Considering the detailed investigation of the Na⁺ storage mechanism and excellent electrochemical performance of ENPCNs-800, this work can pave a new avenue for the research of SIBs.

Biopolymer-based electrospun fibers in electrochemical devices: versatile platform for energy, environment, and health monitoring

Electrochemical power tools are regarded as essential keys in a world that is becoming increasingly reliant on fossil fuels in order to meet the challenges of rapidly depleting fossil fuel supplies. Additionally, due to the industrialization of societies and the growth of diseases, the need for sensitive, reliable, inexpensive, and portable sensors and biosensors for noninvasive monitoring of human health and environmental pollution is felt more than ever before. In recent decades, electrospun fibers have emerged as promising candidates for the fabrication of highly efficient electrochemical devices, such as actuators, batteries, fuel cells, supercapacitors, and biosensors. Meanwhile, the use of synthetic polymers in the fabrication of versatile electrochemical devices has raised environmental concerns, leading to an increase in the quest for natural polymers. Natural polymers are primarily derived from microorganisms and plants. Despite the challenges of processing bio-based electrospun fibers, employing natural nanofibers in the fabrication of electrochemical devices has garnered tremendous attention in recent years. Here, various natural polymers and the strategies employed to fabricate various electrospun biopolymers are briefly covered. The recent advances and research strategies used to apply the bio-based electrospun membranes in different electrochemical devices are carefully summarized, along with the scopes in various advanced technologies. A comprehensive and critical discussion about the use of biopolymer-based electrospun fibers as the potential alternative to non-renewable ones in future technologies is briefly highlighted. This review will serve as a field opening platform for using different biopolymer-based electrospun fibers to advance the electrochemical device-based renewable and sustainable technologies, which will be of high interest to a large community. Accordingly, future studies should focus on feasible and cost-effective extraction of biopolymers from natural resources as well as fabrication of high-performance nanofibrous biopolymer-based components applicable in various electrochemical devices.

Carbon Dots Embedded in Cellulose Film: Programmable, Performance-Tunable, and Large-Scale Subtle Fluorescent Patterning by in Situ Laser Writing

Fluorescent patterns with multiple functions enable high-security anti-counterfeiting labels. Complex material synthesis and patterning processes limit the application of multifunctional fluorescent patterns, so the technology of in situ fluorescent patterning with tunable multimodal capabilities is becoming more necessary. In this work, an in situ fluorescent patterning technology was developed using laser direct writing on solid cellulose film at ambient conditions without masks. The fluorescent intensity and surface microstructure of the patterns could be adjusted by programmable varying of the laser parameters simultaneously. During laser direct writing, carbon dots are generated in situ in a cellulose ester polymer matrix, which significantly simplifies the fluorescent patterning process and reduces the manufacturing cost. Interestingly, the tunable fluorescent intensity empowers the fabrication of visual stereoscopic fluorescent patterns with excitation dependence, further improving its anti-counterfeiting performance. The obtained fluorescent patterns still show ultrahigh optical properties after being immersed in an acid/base solution (pH 5-12) over one month. In addition, the anti-UV performance of the obtained laser-patterned film with transmittance around 90% is comparable to that of commercial UV-resistant films. This work provided an advanced and feasible approach to fabricating programmable, performance-tunable, subtle fluorescent patterns in large-scale for industrial application.

Zinc-Guided 3D Graphene for Thermally Chargeable Supercapacitors to Harvest Low-Grade Heat

Low-grade heat energy recycling is the key technology of waste-heat utilization, which needs to be improved. Here, we use a zinc-assisted solid-state pyrolysis route to prepare zinc-guided 3D graphene (ZnG), a 3D porous graphene with the interconnected structure. The obtained ZnG, with a high specific surface area of 1817 m²·g⁻¹ and abundant micropores and mesopores, gives a specific capacitance of 139 F·g⁻¹ in a neutral electrolyte when used as electrode material for supercapacitors. At a high current density of 8 A·g⁻¹, the capacitance retention is 93% after 10,000 cycles. When ZnG is used for thermally chargeable supercapacitors, the thermoelectric conversion of the low-grade heat energy is successfully realized. This work thus provides a demonstration for low-grade heat energy conversion.

Rapeseed meal-derived N,S self-codoped porous carbon materials for supercapacitors

N,S self-doped porous carbon with high specific surface area and gravimetric specific capacitance from rapeseed meal was successfully synthesized.

Biomass-Derived Carbon Materials: Controllable Preparation and Versatile Applications

Biomass-derived carbon materials (BCMs) are encountering the most flourishing moment because of their versatile properties and wide potential applications. Numerous BCMs, including 0D carbon spheres and dots, 1D carbon fibers and tubes, 2D carbon sheets, 3D carbon aerogel, and hierarchical carbon materials have been prepared. At the same time, their structure-property relationship and applications have been widely studied. This paper aims to present a review on the recent advances in the controllable preparation and potential applications of BCMs, providing a reference for future work. First, the chemical compositions of typical biomass and their thermal degradation mechanisms are presented. Then, the typical preparation methods of BCMs are summarized and the relevant structural management rules are discussed. Besides, the strategies for improving the structural diversity of BCMs are also presented and discussed. Furthermore, the applications of BCMs in energy, sensing, environment, and other areas are reviewed. Finally, the remaining challenges and opportunities in the field of BCMs are discussed.

Advanced Tri-Layer Carbon Matrices with π-π Stacking Interaction for Binder-Free Lithium-Ion Storage

Enabling materials with distinct features toward achieving high-performance energy storage devices is of huge importance but highly challenging. Commercial carbon cloth (CC), because of its appealing chemical and mechanical properties, has been proven to be an excellent conductive substrate for active electrode materials. However, its performance is notably poor when directly used as an electrode in energy storage, due to its low theoretical capacity and surface area. Herein, we successfully endow the CC with enhanced storage capacity via formation of a π-π stacking interaction by integrating electrochemically activated CC (denoted CC/ACC) with biomass-derived carbon (BMDC) (denoted π-CC/ECC@BMDC). The π-CC/ECC@BMDC electrode displays excellent storage performance with a high capacity of 2.53 mAh cm^-2 under 0.2 mA cm^-2 when used as anode material for lithium ion batteries (LIBs). Due to the induction energy, the negatively charged molecules of the CC/ACC functional groups interact with the BMDC during carbonization, creating the π-π stacking interaction. Based on first-principles calculations, the structural design of the tri-layer carbon enables the movement of electrons around the π-π stacking interaction, which significantly facilitates rapid transportation of electrons, creates three-dimensional (3D) ion tunnels for fast transportation of ions, and improves the electrode's mechanical and electronic properties.

Natural Cellulose Substance Based Energy Materials

Natural cellulose substances have been proven to be ideal structural templates and scaffolds for the fabrication of artificial functional materials with designed structures, psychochemical properties and functionalities. They possess unique hierarchically porous network structures with flexible, biocompatible, and environmental characteristics, exhibiting great potentials in the preparation of energy-related materials. This minireview summarizes natural cellulose-based materials that are used in batteries, supercapacitors, photocatalytic hydrogen generation, photoelectrochemical cells, and solar cells. When natural cellulose substances are employed as the structural template or carbon sources of energy materials, the three-dimensional porous interwoven structures are perfectly replicated, leading to the enhanced performances of the resultant materials. Benefiting from the mechanical strengths of natural cellulose substances, wearable, portable, free-standing, and flexible materials for energy storage and conversion are easily obtained by using natural cellulose substances as the substrates.

Regulating the carbon distribution of anode materials in lithium-ion batteries

The exploration of electrode materials is considered to be a crucial process affecting the development of lithium-ion batteries. However, the large-scale commercial application of the great mass of anode materials has been hampered by the challenges with conductivity and volume change. These problems can be solved by the combination of a carbon-matrix with anode materials, which has proven to be an effective strategy. This review aims to outline recent advances in carbon-matrix composite anodes based on different dimensions (0D, 1D, 2D, 3D and atomic scale) and functions, with the emphasis on the regulation of carbon distribution of composite anodes. Besides, the matrix forms and carbon sources have also been summarized. This review will provide some light on the future carbon-matrix electrode design trends for LIBs.

Understanding the High-Performance Anode Material of CoC2 O4 ⋅2 H2 O Microrods Wrapped by Reduced Graphene Oxide for Lithium-Ion and Sodium-Ion Batteries

Metal oxalate has become a most promising candidate as an anode material for lithium-ion and sodium-ion batteries. However, capacity decrease owing to the volume expansion of the active material during cycling is a problem. Herein, a rod-like CoC₂ O₄ ⋅2 H₂ O/rGO hybrid is fabricated through a novel multistep solvo/hydrothermal strategy. The structural characteristics of the CoC₂ O₄ ⋅2 H₂ O microrod wrapped using rGO sheets not only inhibit the volume variation of the hybrid electrode during cycling, but also accelerate the transfer of electrons and ions in the 3 D graphene network, thereby improving the electrochemical properties of CoC₂ O₄ ⋅2 H₂ O. The CoC₂ O₄ ⋅2 H₂ O/rGO electrode delivers a specific capacity of 1011.5 mA h g^-1 at 0.2 A g^-1 after 200 cycles for lithium storage, and a high capacity of 221.1 mA h g^-1 at 0.2 A g^-1 after 100 cycles for sodium storage. Moreover, the full cell CoC₂ O₄ ⋅2 H₂ O/rGO//LiCoO₂ consisting of the CoC₂ O₄ ⋅2 H₂ O/rGO anode and LiCoO₂ cathode maintains 138.1 mA h g^-1 after 200 cycles at 0.2 A g^-1 and has superior long-cycle stability. In addition, in situ Raman spectroscopy and in situ and ex situ X-ray diffraction techniques provide a unique opportunity to understand fully the reaction mechanism of CoC₂ O₄ ⋅2 H₂ O/rGO. This work also gives a new perspective and solid research basis for the application of metal oxalate materials in high-performance lithium-ion and sodium-ion batteries.

Porous Fiber Processing and Manufacturing for Energy Storage Applications

The objective of this article is to provide an overview on the current development of micro- and nanoporous fiber processing and manufacturing technologies. Various methods for making micro- and nanoporous fibers including co-electrospinning, melt spinning, dry jet-wet quenching spinning, vapor deposition, template assisted deposition, electrochemical oxidization, and hydrothermal oxidization are presented. Comparison is made in terms of advantages and disadvantages of different routes for porous fiber processing. Characterization of the pore size, porosity, and specific area is introduced as well. Applications of porous fibers in various fields are discussed. The emphasis is put on their uses for energy storage components and devices including rechargeable batteries and supercapacitors.

Nanoporous Composites of CoO x Quantum Dots and ZIF-Derived Carbon as High-Performance Anodes for Lithium-Ion Batteries

Transition-metal oxides are attracting considerable attention as anodes for lithium-ion batteries because of their high reversible capacities. However, the drastic volume change and inferior electrical conductivity greatly retard their widespread applications in lithium-ion batteries. Herein, three-dimensional nanoporous composites of CoO _x (CoO and Co₃O₄) quantum dots and zeolitic imidazolate framework-67-derived carbon are fabricated by a precipitation method. The carbon prepared by carbonization of zeolitic imidazolate framework-67 can greatly enhance the electrical conductivity of the composite anodes. CoO _x quantum dots anchored firmly on zeolitic imidazolate framework-67-derived carbon can effectively inhibit the aggregation and volume change of CoO _x quantum dots during lithiation/delithiation processes. The nanoporous structure can shorten the ion diffusion paths and maintain the structural integrity upon cycling. Meanwhile, kinetics analysis reveals that a capacitance mechanism dominates the lithium storage capacity, which can greatly enhance the electrochemical performance. The composite anodes show a high discharge capacity of 1873 mAh g^-1 after 200 cycles at 200 mA g^-1, ultralong cycle life (1246 mAh g^-1 after 900 cycles at 1000 mA g^-1), and improved rate performance. This work may provide guidelines for preparing cobalt oxide-based anodes for LIBs.

Polypyrrole coated δ-MnO2 nanosheet arrays as a highly stable lithium-ion-storage anode

Manganese dioxide (MnO₂) with a conversion mechanism is regarded as a promising anode material for lithium-ion batteries (LIBs) owing to its high theoretical capacity (∼1223 mA h g^-1) and environmental benignity as well as low cost. However, it suffers from insufficient rate capability and poor cyclic stability. To circumvent this obstacle, semiconducting polypyrrole coated-δ-MnO₂ nanosheet arrays on nickel foam (denoted as MnO₂@PPy/NF) are prepared via hydrothermal growth of MnO₂ followed by the electrodeposition of PPy on the anode in LIBs. The electrode with ∼50 nm thick PPy coating exhibits an outstanding overall electrochemical performance. Specifically, a high rate capability is obtained with ∼430 mA h g^-1 of discharge capacity at a high current density of 2.67 A g^-1 and more than 95% capacity is retained after over 120 cycles at a current rate of 0.86 A g^-1. These high electrochemical performances are attributed to the special structure which shortens the ion diffusion pathway, accelerates charge transfer, and alleviates volume change in the charging/discharging process, suggesting a promising route for designing a conversion-type anode material for LIBs.

Electrochemical activity of Samarium on starch-derived porous carbon: rechargeable Li- and Al-ion batteries

Rechargeable metal-ion batteries are considered promising electric storage systems to meet the emerging demand from electric vehicles, electronics, and electric grids. Thus far, secondary Li-ion batteries (LIBs) have seen great advances in terms of both their energy and their power density. However, safety issues remain a challenge. Therefore, rechargeable Al-ion batteries (AIBs) with a highly reliable safety advantage and active electrochemical performances have gathered intensive attention. However, the common issue for these two metal-ion batteries is the lack of cathode materials. Many advanced electrode materials reported provide greatly enhanced electrochemical properties. However, their inherent disadvantages-such as complicated fabrication procedures, restricted manufacturing parameters, and the requirement of expensive instruments-limits their potential for further applications. In this work, we demonstrate the high electrochemical activity of the lanthanide element, Sm, towards storing charges when used in both LIBs and AIBs. Lanthanide elements are often overlooked; however, they generally have attractive electrochemical properties owing to their unpaired electrons. We employed starch as both a low-cost carbon source and as a three-dimensional support for Sm metal nanoparticles. The composite product is fabricated using a one-pot wet-chemical method, followed by a simultaneous carbonization process. As a result, highly improved electrochemical properties are obtained when it is used as a cathode material for both LIBs and AIBs when compared to bare starch-derived C. Our results may introduce a new avenue toward the design of high-performance electrode materials for LIBs and AIBs.