A Self‐Standing and Flexible Electrode of Yolk–Shell CoS2 Spheres Encapsulated with Nitrogen‐Doped Graphene for High‐Performance Lithium‐Ion Batteries

Flexible lithium‐ion batteries (LIBs) have recently attracted increasing attention with the fast development of bendable electronic systems. Herein, a facile and template‐free solvothermal method is presented for the fabrication of hybrid yolk–shell CoS₂ and nitrogen‐doped graphene (NG) sheets. The yolk–shell architecture of CoS₂ encapsulated with NG coating is designed for the dual protection of CoS₂ to address the structural and interfacial stability concerns facing the CoS₂ anode. The as‐prepared composite can be assembled into a film, which can be used as a binder‐free and flexible electrode for LIBs that does not require any carbon black conducting additives or current collectors. When evaluating lithium‐storage properties, such a flexible electrode exhibits a high specific capacity of 992 mAh g^?1 in the first reversible discharge capacity at a current rate of 100 mA g^?1 and high reversible capacity of 882 mAh g^?1 after 150 cycles with excellent capacity retention of 89.91 %. Furthermore, a reversible capacity as high as 655 mAh g^?1 is still achieved after 50 cycles even at a high rate of 5 C due to the yolk–shell structure and NG coating, which not only provide short Li‐ion and electron pathways, but also accommodate large volume variation.     

Lithium Germanate (Li2GeO3): A High‐Performance Anode Material for Lithium‐Ion Batteries

A simple, cost‐effective, and easily scalable molten salt method for the preparation of Li₂GeO₃ as a new type of high‐performance anode for lithium‐ion batteries is reported. The Li₂GeO₃ exhibits a unique porous architecture consisting of micrometer‐sized clusters (secondary particles) composed of numerous nanoparticles (primary particles) and can be used directly without further carbon coating which is a common exercise for most electrode materials. The new anode displays superior cycling stability with a retained charge capacity of 725 mAh g^?1 after 300 cycles at 50 mA g^?1. The electrode also offers excellent rate capability with a capacity recovery of 810 mAh g^?1 (94 % retention) after 35 cycles of ascending steps of current in the range of 25–800 mA g^?1 and finally back to 25 mA g^?1. This work emphasizes the importance of exploring new electrode materials without carbon coating as carbon‐coated materials demonstrate several drawbacks in full devices. Therefore, this study provides a method and a new type of anode with high reversibility and long cycle stability.     

A New Anode for Lithium‐Ion Batteries Based on Single‐Walled Carbon Nanotubes and Graphene: Improved Performance through a Binary Network Design

Carbon nanomaterials, especially graphene and carbon nanotubes, are considered to be favorable alternatives to graphite‐based anodes in lithium‐ion batteries, owing to their high specific surface area, electrical conductivity, and excellent mechanical flexibility. However, the limited number of storage sites for lithium ions within the sp²‐carbon hexahedrons leads to the low storage capacity. Thus, rational structure design is essential for the preparation of high‐performance carbon‐based anode materials. Herein, we employed flexible single‐walled carbon nanotubes (SWCNTs) with ultrahigh electrical conductivity as a wrapper for 3D graphene foam (GF) by using a facile dip‐coating process to form a binary network structure. This structure, which offered high electrical conductivity, enlarged the electrode/electrolyte contact area, shortened the electron‐/ion‐transport pathways, and allowed for efficient utilization of the active material, which led to improved electrochemical performance. When used as an anode in lithium‐ion batteries, the SWCNT‐GF electrode delivered a specific capacity of 953 mA h g^?1 at a current density of 0.1 A g^?1 and a high reversible capacity of 606 mA h g^?1 after 1000 cycles, with a capacity retention of 90 % over 1000 cycles at 1 A g^?1 and 189 mA h g^?1 after 2200 cycles at 5 A g^?1.     

Transition‐Metal Carbodiimides as Molecular Negative Electrode Materials for Lithium‐ and Sodium‐Ion Batteries with Excellent Cycling Properties

We report evidence for the electrochemical activity of transition‐metal carbodiimides versus lithium and sodium. In particular, iron carbodiimide, FeNCN, can be efficiently used as negative electrode material for alkali‐metal‐ion batteries, similar to its oxide analogue FeO. Based on ⁵⁷Fe Mössbauer and infrared spectroscopy (IR) data, the electrochemical reaction mechanism can be explained by the reversible transformation of the Fe?NCN into Li/Na?NCN bonds during discharge and charge. These new electrode materials exhibit higher capacity compared to well‐established negative electrode references such as graphite or hard carbon. Contrary to its oxide analogue, iron carbodiimide does not require heavy treatments (such as nanoscale tailoring, sophisticated textures, or coating) to obtain long cycle life with current density as high as 9 A g^?1 for hundreds of charge–discharge cycles. Similar to the iron compound, several other transition‐metal carbodiimides M_x(NCN)_y with M=Mn, Cr, Zn can cycle successfully versus lithium and sodium. Their electrochemical activity and performance open the way to the design of a novel family of anode materials.     

Nitrogen‐Doped Carbon Embedded MoS2 Microspheres as Advanced Anodes for Lithium‐ and Sodium‐Ion Batteries

Rational design and synthesis of advanced anode materials are extremely important for high‐performance lithium‐ion and sodium‐ion batteries. Herein, a simple one‐step hydrothermal method is developed for fabrication of N‐C@MoS₂ microspheres with the help of polyurethane as carbon and nitrogen sources. The MoS₂ microspheres are composed of MoS₂ nanoflakes, which are wrapped by an N‐doped carbon layer. Owing to its unique structural features, the N‐C@MoS₂ microspheres exhibit greatly enhanced lithium‐ and sodium‐storage performances including a high specific capacity, high rate capability, and excellent capacity retention. Additionally, the developed polyurethane‐assisted hydrothermal method could be useful for the construction of many other high‐capacity metal oxide/sulfide composite electrode materials for energy storage.     

Fabrication of Fe‐Doped LiCoO2 Sandwich‐Like Nanocomposites as Excellent Performance Cathode Materials for Lithium‐Ion Batteries

In this article, the two‐layer sandwiched graphene@LiFe_0.2Co_0.8O₂ nanoparticles (SG@LFCO) have been prepared and investigated as high‐rate and long‐life cathode materials for rechargeable lithium‐ion batteries. The materials possess a high‐surface area (267.1 m² g^?1) and lots of void spaces. By combining various favorable conditions, such as Fe doping, coating graphene, and designing novel morphology, the as‐prepared materials deliver a specific capacity of 115 mAh g^?1 at 10 C. At the 0.1 C cycling rate, the capacity retention of 97.2 % is sustained after 250 cycles and a coulombic efficiency of around 97.6 % is obtained.     

Amorphous cobalt silicate nanobelts@carbon composites as a stable anode material for lithium ion batteries

During the past decade, tremendous attention has been given to the development of new electrode materials with high capacity to meet the requirements of electrode materials with high energy density in lithium ion batteries. Very recently, cobalt silicate has been proposed as a new type of high capacity anode material for lithium ion batteries. However, the bulky cobalt silicate demonstrates limited electrochemical performance. Nanostructure engineering and carbon coating represent two promising strategies to improve the electrochemical performance of electrode materials. Herein, we developed a template method for the synthesis of amorphous cobalt silicate nanobelts which can be coated with carbon through the deposition and thermal decomposition of phenol formaldehyde resin. Tested as an anode material, the amorphous cobalt silicate nanobelts@carbon composites exhibit a reversible high capacity of 745 mA h g^–1 at a current density of 100 mA g^–1, and a long life span of up to 1000 cycles with a stable capacity retention of 480 mA h g^–1 at a current density of 500 mA g^–1. The outstanding electrochemical performance of the composites indicates their high potential as an anode material for lithium ion batteries. The results here are expected to stimulate further research into transition metal silicate nanostructures for lithium ion battery applications.     

An Ultrastable Anode for Long‐Life Room‐Temperature Sodium‐Ion Batteries

Sodium‐ion batteries are important alternative energy storage devices that have recently come again into focus for the development of large‐scale energy storage devices because sodium is an abundant and low‐cost material. However, the development of electrode materials with long‐term stability has remained a great challenge. A novel negative‐electrode material, a P2‐type layered oxide with the chemical composition Na_2/3Co_1/3Ti_2/3O₂, exhibits outstanding cycle stability (ca. 84.84 % capacity retention for 3000 cycles, very small decrease in the volume (0.046 %) after 500 cycles), good rate capability (ca. 41 % capacity retention at a discharge/charge rate of 10 C), and a usable reversible capacity of about 90 mAh g^?1 with a safe average storage voltage of approximately 0.7 V in the sodium half‐cell. This P2‐type layered oxide is a promising anode material for sodium‐ion batteries with a long cycle life and should greatly promote the development of room‐temperature sodium‐ion batteries.     

A Bipolar and Self‐Polymerized Phthalocyanine Complex for Fast and Tunable Energy Storage in Dual‐Ion Batteries

Bipolar redox organics have attracted interest as electrode materials for energy storage owing to their flexibility, sustainability and environmental friendliness. However, an understanding of their application in all‐organic batteries, let alone dual‐ion batteries (DIBs), is in its infancy. Herein, we propose a strategy to screen a variety of phthalocyanine‐based bipolar organics. The self‐polymerizable bipolar Cu tetraaminephthalocyanine (CuTAPc) shows multifunctional applications in various energy storage systems, including lithium‐based DIBs using CuTAPc as the cathode material, graphite‐based DIBs using CuTAPc as the anode material and symmetric DIBs using CuTAPc as both the cathode and anode materials. Notably, in lithium‐based DIBs, the use of CuTAPc as the cathode material results in a high discharge capacity of 236 mAh g^?1 at 50 mA g^?1 and a high reversible capacity of 74.3 mAh g^?1 after 4000 cycles at 4 A g^?1. Most importantly, a high energy density of 239 Wh kg^?1 and power density of 11.5 kW kg^?1 can be obtained in all‐organic symmetric DIBs.     

Controllable Synthesis of Mesoporous Peapod‐like Co3O4@Carbon Nanotube Arrays for High‐Performance Lithium‐Ion Batteries

Transition metal oxides are regarded as promising anode materials for lithium‐ion batteries because of their high theoretical capacities compared with commercial graphite. Unfortunately, the implementation of such novel anodes is hampered by their large volume changes during the Li⁺ insertion and extraction process and their low electric conductivities. Herein, we report a specifically designed anode architecture to overcome such problems, that is, mesoporous peapod‐like Co₃O₄@carbon nanotube arrays, which are constructed through a controllable nanocasting process. Co₃O₄ nanoparticles are confined exclusively in the intratubular pores of the nanotube arrays. The pores between the nanotubes are open, and thus render the Co₃O₄ nanoparticles accessible for effective electrolyte diffusion. Moreover, the carbon nanotubes act as a conductive network. As a result, the peapod‐like Co₃O₄@carbon nanotube electrode shows a high specific capacity, excellent rate capacity, and very good cycling performance.     

Hierarchical SnO2/Carbon Nanofibrous Composite Derived from Cellulose Substance as Anode Material for Lithium‐Ion Batteries

A hierarchical fibrous SnO₂/carbon nanocomposite composed of fine SnO₂ nanocrystallites immobilized as a thin layer on a carbon nanofiber surface was synthesized employing natural cellulose substance as both scaffold and carbon source. It was achieved by calcination/carbonization of the as‐deposited SnO₂‐gel/cellulose hybrid in an argon atmosphere. As being employed as an anode material for lithium‐ion batteries, the porous structures, small SnO₂ crystallite sizes, and the carbon buffering matrix possessed by the nanocomposite facilitate the electrode–electrolyte contact, promote the electron transfer and Li⁺ diffusion, and relieve the severe volume change and aggregation of the active particles during the charge/discharge cycles. Hence, the nanocomposite showed high reversible capacity, significant cycling stability, and rate capability that are superior to the nanotubular SnO₂ and SnO₂ sol–gel powder counter materials. For such a composite with 27.8 wt % SnO₂ content and 346.4 m² g^?1 specific surface area, a capacity of 623 mAh g^?1 was delivered after 120 cycles at 0.2 C. Further coating of the SnO₂/carbon nanofibers with an additional carbon layer resulted in an improved cycling stability and rate performance.     

An Insoluble Benzoquinone‐Based Organic Cathode for Use in Rechargeable Lithium‐Ion Batteries

Application of organic electrode materials in rechargeable batteries has attracted great interest because such materials contain abundant carbon, hydrogen, and oxygen elements. However, organic electrodes are highly soluble in organic electrolytes. An organic electrode of 2,3,5,6‐tetraphthalimido‐1,4‐benzoquinone (TPB) is reported in which rigid groups coordinate to a molecular benzoquinone skeleton. The material is insoluble in aprotic electrolyte, and demonstrates a high capacity retention of 91.4 % (204 mA h g⁻¹) over 100 cycles at 0.2 C. The extended π‐conjugation of the material contributes to enhancement of the electrochemical performance (155 mA h g⁻¹ at 10 C). Moreover, density functional theory calculations suggest that favorable synergistic reactions between multiple carbonyl groups and lithium ions can enhance the initial lithium ion intercalation potential. The described approach may provide a novel entry to next‐generation organic electrode materials with relevance to lithium‐ion batteries.     

Wintersweet‐Flower‐Like CoFe2O4/MWCNTs Hybrid Material for High‐Capacity Reversible Lithium Storage

CoFe₂O₄/multiwalled carbon nanotubes (MWCNTs) hybrid materials were synthesized by a hydrothermal method. Field emission scanning electron microscopy and transmission electron microscopy analysis confirmed the morphology of the as‐prepared hybrid material resembling wintersweet flower “buds on branches”, in which CoFe₂O₄ nanoclusters, consisting of nanocrystals with a size of 5–10 nm, are anchored along carbon nanotubes. When applied as an anode material in lithium ion batteries, the CoFe₂O₄/MWCNTs hybrid material exhibited a high performance for reversible lithium storage. In particular, the hybrid anode material delivered reversible lithium storage capacities of 809, 765, 539, and 359 mA h g^?1 at current densities of 180, 450, 900, and 1800 mA g^?1, respectively. The superior performance of CoFe₂O₄/MWCNTs hybrid materials could be ascribed to the synergistic pinning effect of the wintersweet‐flower‐like nanoarchitecture. This strategy could also be applied to synthesize other metal oxide/CNTs hybrid materials as high‐capacity anode materials for lithium ion batteries.     

Scalable Dry Production Process of a Superior 3D Net‐Like Carbon‐Based Iron Oxide Anode Material for Lithium‐Ion Batteries

Carbon‐based transition‐metal oxides are considered as an appropriate anode material candidate for lithium‐ion batteries. Herein, a simple and scalable dry production process is developed to produce carbon‐encapsulated 3D net‐like FeO_x /C materials. The process is simply associated with the pyrolysis of a solid carbon source, such as filter paper, adsorbed with ferrite nitrate. The carbon derived from filter paper induces a carbothermal reduction to form metallic Fe, the addition of carbon and iron increase the conductivity of this material. As expected, this 3D net‐like FeO_x /C composite delivers an excellent charge capacity of 851.3 mAh g⁻¹ after 50 cycles at 0.2 A g⁻¹ as well as high stability and rate performance of 714.7 mAh g⁻¹ after 300 cycles at 1 A g⁻¹. Superior performance, harmlessness, low costs, and high yield may greatly stimulate the practical application of the products as anode materials in lithium‐ion batteries.     

Carbon‐Coated Hierarchical SnO2 Hollow Spheres for Lithium Ion Batteries

Hierarchical SnO₂ hollow spheres self‐assembled from nanosheets were prepared with and without carbon coating. The combination of nanosized architecture, hollow structure, and a conductive carbon layer endows the SnO₂‐based anode with improved specific capacity and cycling stability, making it more promising for use in lithium ion batteries.     

Core–Shell Carbon‐Coated CuO Nanocomposites: A Highly Stable Electrode Material for Supercapacitors and Lithium‐Ion Batteries

Herein we present a simple method for fabricating core–shell mesostructured CuO@C nanocomposites by utilizing humic acid (HA) as a biomass carbon source. The electrochemical performances of CuO@C nanocomposites were evaluated as an electrode material for supercapacitors and lithium‐ion batteries. CuO@C exhibits an excellent capacitance of 207.2 F g^?1 at a current density of 1 A g^?1 within a potential window of 0–0.46 V in 6 M KOH solution. Significantly, CuO electrode materials achieve remarkable capacitance retentions of approximately 205.8 F g^?1 after 1000 cycles of charge/discharge testing. The CuO@C was further applied as an anode material for lithium‐ion batteries, and a high initial capacity of 1143.7 mA h g^?1 was achieved at a current density of 0.1 C. This work provides a facile and general approach to synthesize carbon‐based materials for application in large‐scale energy‐storage systems.     

A Long‐Life Lithium Ion Battery with Enhanced Electrode/Electrolyte Interface by Using an Ionic Liquid Solution

In this paper, we report an advanced long‐life lithium ion battery, employing a Pyr₁₄TFSI‐LiTFSI non‐flammable ionic liquid (IL) electrolyte, a nanostructured tin carbon (Sn‐C) nanocomposite anode, and a layered LiNi_1/3Co_1/3Mn_1/3O₂ (NMC) cathode. The IL‐based electrolyte is characterized in terms of conductivity and viscosity at various temperatures, revealing a Vogel–Tammann–Fulcher (VTF) trend. Lithium half‐cells employing the Sn‐C anode and NMC cathode in the Pyr₁₄TFSI‐LiTFSI electrolyte are investigated by galvanostatic cycling at various temperatures, demonstrating the full compatibility of the electrolyte with the selected electrode materials. The NMC and Sn‐C electrodes are combined into a cathode‐limited full cell, which is subjected to prolonged cycling at 40 °C, revealing a very stable capacity of about 140 mAh g^?1 and retention above 99 % over 400 cycles. The electrode/electrolyte interface is further characterized through a combination of electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) investigations upon cell cycling. The remarkable performances reported here definitively indicate that IL‐based lithium ion cells are suitable batteries for application in electric vehicles.     

Conformal Surface Coatings to Enable High Volume Expansion Li‐Ion Anode Materials

An alumina surface coating is demonstrated to improve electrochemical performance of MoO₃ nanoparticles as high capacity/high‐volume expansion anodes for Li‐ion batteries. Thin, conformal surface coatings were grown using atomic layer deposition (ALD) that relies on self‐limiting surface reactions. ALD coatings were tested on both individual nanoparticles and prefabricated electrodes containing conductive additive and binder. The coated and non‐coated materials were characterized using transmission electron microscopy, energy‐dispersive X‐ray spectroscopy, electrochemical impedance spectroscopy, and galvanostatic charge/discharge cycling. Importantly, increased stability and capacity retention was only observed when the fully fabricated electrode was coated. The alumina layer both improves the adhesion of the entire electrode, during volume expansion/contraction and protects the nanoparticle surfaces. Coating the entire electrode also allows for an important carbothermal reduction process that occurs during electrode pre‐heat treatment. ALD is thus demonstrated as a novel and necessary method that may be employed to coat the tortuous network of a battery electrode.     

Continuous supercritical hydrothermal synthesis: lithium secondary ion battery applications

Nanosized lithium iron phosphate (LiFePO₄) and transition metal oxide (MO, where M is Cu, Ni, Mn, Co, and Fe) particles are synthesized continuously in supercritical water at 25?C30?MPa and 400??C under various conditions for active material application in lithium secondary ion batteries. The properties of the nanoparticles, including crystallinity, particle size, surface area, and electrochemical performance, are characterized in detail. The discharge capacity of LiFePO₄ was enhanced up to 140?mAh/g using a simple carbon coating method. The LiFePO₄ particles prepared using supercritical hydrothermal synthesis (SHS) deliver the reversible and stable capacity at a current density of 0.1?C rate during ten cycles. The initial discharge capacity of the MO is in the range of 800?C1,100?mAh/g, values much higher than that of graphite. However, rapid capacity fading is observed after the first few cycles. The continuous SHS can be a promising method to produce nanosized cathode and anode materials.     

Graphite Anode for a Potassium‐Ion Battery with Unprecedented Performance

Graphite as an anode for the potassium ion battery (PIBs) has the merits of low cost and potentially high energy density, while suffering from limited cycle time and inferior stability. Herein we, using a concentrated electrolyte, demonstrate that formation of a robust inorganic‐rich passivation layer on the graphite anode could resolve these problems. Consequently, the PIBs with graphite anode could operate for over 2000 cycles (running time of over 17 months) with negligible capacity decay, and had a high area capacity over 7.36 mAh cm^?2 with a high mass loading of 28.56 mg cm^?2. These unprecedented performances of graphite are comparable to that of traditional lithium‐ion batteries, and may promote the rapidly development of high performance PIBs.