Preparation of a Reduced Graphene Oxide Wrapped Lithium‐Rich Cathode Material by Self‐Assembly

A lithium‐rich cathode material wrapped in sheets of reduced graphene oxide (RGO) and functionalized with polydiallyldimethylammonium chloride (PDDA) was prepared by self‐assembly induced from the electrostatic interaction between PDDA–RGO and the Li‐rich cathode material. At current densities of 1000 and 2000 mA g^?1, the PDDA–RGO sheet wrapped samples demonstrated increased discharge capacities, increasing from 125 to 155 mA h g^?1 and from 82 to 124 mA h g^?1, respectively. The decreased resistance implied by this result was confirmed from electrochemical impedance spectroscopy results, wherein the charge‐transfer resistance of the pristine sample decreased after wrapping with the PDDA–RGO sheets. The PDDA–RGO sheets served as a protective layer sand as a conductive material, which resulted in an improvement in the retention capacity from 56 to 81 % after 90 cycles.     

Solvated Graphene Frameworks as High‐Performance Anodes for Lithium‐Ion Batteries

A solvent‐exchange approach for the preparation of solvated graphene frameworks as high‐performance anode materials for lithium‐ion batteries is reported. The mechanically strong graphene frameworks exhibit unique hierarchical solvated porous networks and can be directly used as electrodes with a significantly improved electrochemical performance compared to unsolvated graphene frameworks, including very high reversible capacities, excellent rate capabilities, and superior cycling stabilities.     

Elastic and Wearable Wire‐Shaped Lithium‐Ion Battery with High Electrochemical Performance

A stretchable wire‐shaped lithium‐ion battery is produced from two aligned multi‐walled carbon nanotube/lithium oxide composite yarns as the anode and cathode without extra current collectors and binders. The two composite yarns can be well paired to obtain a safe battery with superior electrochemical properties, such as energy densities of 27 Wh kg^?1 or 17.7 mWh cm^?3 and power densities of 880 W kg^?1 or 0.56 W cm^?3, which are an order of magnitude higher than the densities reported for lithium thin‐film batteries. These wire‐shaped batteries are flexible and light, and 97 % of their capacity was maintained after 1000 bending cycles. They are also very elastic as they are based on a modified spring structure, and 84 % of the capacity was maintained after stretching for 200 cycles at a strain of 100 %. Furthermore, these novel wire‐shaped batteries have been woven into lightweight, flexible, and stretchable battery textiles, which reveals possible large‐scale applications.     

2 D Manganese Vanadate Nanoflakes as High‐Performance Anode for Lithium‐Ion Batteries

Nanometer‐sized flakes of MnV₂O₆ were synthesized by a hydrothermal method. No surfactant, expensive metal salt, or alkali reagent was used. These MnV₂O₆ nanoflakes present a high discharge capacity of 768 mA h g^?1 at 200 mA g^?1, good rate capacity, and excellent cycling stability. Further investigation demonstrates that the nanoflake structure and the specific crystal structure make the prepared MnV₂O₆ a suitable material for lithium‐ion batteries.     

A Deep‐Cycle Aqueous Zinc‐Ion Battery Containing an Oxygen‐Deficient Vanadium Oxide Cathode

Rechargeable aqueous zinc‐ion batteries are attractive because of their inherent safety, low cost, and high energy density. However, viable cathode materials (such as vanadium oxides) suffer from strong Coulombic ion–lattice interactions with divalent Zn²⁺, thereby limiting stability when cycled at a high charge/discharge depth with high capacity. A synthetic strategy is reported for an oxygen‐deficient vanadium oxide cathode in which facilitated Zn²⁺ reaction kinetic enhance capacity and Zn²⁺ pathways for high reversibility. The benefits for the robust cathode are evident in its performance metrics; the aqueous Zn battery shows an unprecedented stability over 200 cycles with a high specific capacity of approximately 400 mAh g^?1, achieving 95 % utilization of its theoretical capacity, and a long cycle life up to 2 000 cycles at a high cathode utilization efficiency of 67 %. This work opens up a new avenue for synthesis of novel cathode materials with an oxygen‐deficient structure for use in advanced batteries.     

One‐Pot Synthesis of Carbon‐Coated Nanostructured Iron Oxide on Few‐Layer Graphene for Lithium‐Ion Batteries

Nanostructure engineering has been demonstrated to improve the electrochemical performance of iron oxide based electrodes in Li‐ion batteries (LIBs). However, the synthesis of advanced functional materials often requires multiple steps. Herein, we present a facile one‐pot synthesis of carbon‐coated nanostructured iron oxide on few‐layer graphene through high‐pressure pyrolysis of ferrocene in the presence of pristine graphene. The ferrocene precursor supplies both iron and carbon to form the carbon‐coated iron oxide, while the graphene acts as a high‐surface‐area anchor to achieve small metal oxide nanoparticles. When evaluated as a negative‐electrode material for LIBs, our composite showed improved electrochemical performance compared to commercial iron oxide nanopowders, especially at fast charge/discharge rates.     

Facile Mechanochemical Synthesis of Nano SnO2/Graphene Composite from Coarse Metallic Sn and Graphite Oxide: An Outstanding Anode Material for Lithium‐Ion Batteries

A facile method for the large‐scale synthesis of SnO₂ nanocrystal/graphene composites by using coarse metallic Sn particles and cheap graphite oxide (GO) as raw materials is demonstrated. This method uses simple ball milling to realize a mechanochemical reaction between Sn particles and GO. After the reaction, the initial coarse Sn particles with sizes of 3–30 μm are converted to SnO₂ nanocrystals (approximately 4 nm) while GO is reduced to graphene. Composite with different grinding times (1 h 20 min, 2 h 20 min or 8 h 20 min, abbreviated to 1, 2 or 8 h below) and raw material ratios (Sn:GO, 1:2, 1:1, 2:1, w/w) are investigated by X‐ray diffraction, X‐ray photoelectron spectroscopy, field‐emission scanning electron microscopy and transmission electron microscopy. The as‐prepared SnO₂/graphene composite with a grinding time of 8 h and raw material ratio of 1:1 forms micrometer‐sized architected chips composed of composite sheets, and demonstrates a high tap density of 1.53 g cm^?3. By using such composites as anode material for LIBs, a high specific capacity of 891 mA h g^?1 is achieved even after 50 cycles at 100 mA g^?1.     

Multiple Ambient Hydrolysis Deposition of Tin Oxide into Nanoporous Carbon To Give a Stable Anode for Lithium‐Ion Batteries

A novel ambient hydrolysis deposition (AHD) methodology that employs sequential water adsorption followed by a hydrolysis reaction to infiltrate SnO₂ nanoparticles into the nanopores of mesoporous carbon in a conformal and controllable manner is introduced. The empty space in the SnO₂/C composites can be adjusted by varying the number of AHD cycles. An SnO₂/C composite with an intermediate SnO₂ loading exhibited an initial specific delithiation capacity of 1054 mAh g^?1 as an anode for Li‐ion batteries. The capacity contribution from SnO₂ in the composite electrode approaches the theoretical capacity of SnO₂ (1494 mAh g^?1) if both Sn alloying and SnO₂ conversion reactions are considered to be reversible. The composite shows a specific capacity of 573 mAh g^?1 after 300 cycles, that is, one of the most stable cycling performances for SnO₂/mesoporous carbon composites. The results demonstrated the importance of well‐tuned empty space in nanostructured composites to accommodate expansion of the electrode active mass during alloying/dealloying and conversion reactions.     

Three‐Dimensional Fe2N@C Microspheres Grown on Reduced Graphite Oxide for Lithium‐Ion Batteries and the Li Storage Mechanism

Nanostructured iron compounds as lithium‐ion‐battery anode material have attracted considerable attention with respect to improved electrochemical energy storage and excellent specific capacity, so lots of iron‐based composites have been developed. Herein, a novel composite composed of three‐dimensional Fe₂N@C microspheres grown on reduced graphite oxide (denoted as Fe₂N@C‐RGO) has been synthesized through a simple and effective technique assisted by a hydrothermal and subsequent heating treatment process. As the anode material for lithium‐ion batteries, the synthetic Fe₂N@C‐RGO displayed excellent Li⁺‐ion storage performance with a considerable initial capacity of 847 mAh g^?1, a superior cycle stability (a specific discharge capacity of 760 mAh g^?1 remained after the 100th cycle), and an improved rate‐capability performance compared with those of the pure Fe₂N and Fe₂N‐RGO nanostructures. The good performance should be attributed to the existence of RGO layers that can facilitate to enhance the conductivity and shorten the lithium‐ion diffusion path; in addition, the carbon layer on the surface of Fe₂N can avert the structure decay caused by the volume change during the lithiation/delithiation process. Moreover, in situ X‐ray absorption fine‐structure analysis demonstrated that the excellent performance can be attributed to the lack of any obvious change in the coordination geometry of Fe₂N@C‐RGO during the charge/discharge processes.     

Synthesis of Mesoporous Wall‐Structured TiO2 on Reduced Graphene Oxide Nanosheets with High Rate Performance for Lithium‐Ion Batteries

Mesoporous wall‐structured TiO₂ on reduced graphene oxide (RGO) nanosheets were successfully fabricated through a simple hydrothermal process without any surfactants and annealed at 400 °C for 2 h under argon. The obtained mesoporous structured TiO₂–RGO composites had a high surface area (99 0307 m² g^?1) and exhibited excellent electrochemical cycling (a reversible capacity of 260 mAh g^?1 at 1.2 C and 180 mAh g^?1 at 5 C after 400 cycles), demonstrating it to be a promising method for the development of high‐performance Li‐ion batteries.     

Hierarchical Surface Atomic Structure of a Manganese‐Based Spinel Cathode for Lithium‐Ion Batteries

The increasing use of lithium‐ion batteries (LIBs) in high‐power applications requires improvement of their high‐temperature electrochemical performance, including their cyclability and rate capability. Spinel lithium manganese oxide (LiMn₂O₄) is a promising cathode material because of its high stability and abundance. However, it exhibits poor cycling performance at high temperatures owing to Mn dissolution. Herein we show that when stoichiometric lithium manganese oxide is coated with highly doped spinels, the resulting epitaxial coating has a hierarchical atomic structure consisting of cubic‐spinel, tetragonal‐spinel, and layered structures, and no interfacial phase is formed. In a practical application of the coating to doped spinel, the material retained 90 % of its capacity after 800 cycles at 60 °C. Thus, the formation of an epitaxial coating with a hierarchical atomic structure could enhance the electrochemical performance of LIB cathode materials while preventing large losses in capacity.     

Cu3V2O8 Nanoparticles as Intercalation‐Type Anode Material for Lithium‐Ion Batteries

Cu₃V₂O₈ nanoparticles with particle sizes of 40–50 nm have been prepared by the co‐precipitation method. The Cu₃V₂O₈ electrode delivers a discharge capacity of 462 mA h g^?1 for the first 10 cycles and then the specific capacity, surprisingly, increases to 773 mA h g^?1 after 50 cycles, possibly as a result of extra lithium interfacial storage through the reversible formation/decomposition of a solid electrolyte interface (SEI) film. In addition, the electrode shows good rate capability with discharge capacities of 218 mA h g^?1 under current densities of 1000 mA g^?1. Moreover, the lithium storage mechanism for Cu₃V₂O₈ nanoparticles is explained on the basis of ex situ X‐ray diffraction data and high‐resolution transmission electron microscopy analyses at different charge/discharge depths. It was evidenced that Cu₃V₂O₈ decomposes into copper metal and Li₃VO₄ on being initially discharged to 0.01 V, and the Li₃VO₄ is then likely to act as the host for lithium ions in subsequent cycles by means of the intercalation mechanism. Such an “in situ” compositing phenomenon during the electrochemical processes is novel and provides a very useful insight into the design of new anode materials for application in lithium‐ion batteries.     

Electrophoretic Deposition of Binder‐Free MnO2/Graphene Films for Lithium‐Ion Batteries

Binder‐free, nano‐sized needlelike MnO₂ ‐submillimeter‐sized reduced graphene oxide (nMnO₂‐srGO ) hybrid films with abundant porous structures were fabricated through electrophoretic deposition and subsequent thermal annealing at 500 °C for 2 h. The as‐prepared hybrid films exhibit a unique hierarchical morphology, in which nMnO₂ with a diameter of 20—50 nm and a length of 300—500 nm is randomly anchored on both sides of srGO . When evaluated as binder‐free anodes for lithium‐ion half‐cell, the nMnO₂‐srGO composites with a content of 76.9 wt% MnO₂ deliver a high capacity of approximately 1652.2 mA •h•g⁻¹ at a current density of 0.1 A•g⁻¹ after 200 cycles. The high capacity remains at 616.8 mA •h•g⁻¹ (ca. 65.1% capacity retention) at a current density as high as 4 A•g⁻¹. The excellent electrochemical performance indicates that the nMnO₂‐srGO hybrid films could be a promising anode material for lithium ion batteries (LIBs ).     

Excellent Performance of Few‐Layer Borocarbonitrides as Anode Materials in Lithium‐Ion Batteries

Borocarbonitrides (B_xC_yN_z) with a graphene‐like structure exhibit a remarkable high lithium cyclability and current rate capability. The electrochemical performance of the B_xC_yN_z materials, synthesized by using a simple solid‐state synthesis route based on urea, was strongly dependent on the composition and surface area. Among the three compositions studied, the carbon‐rich compound B_0.15C_0.73N_0.12 with the highest surface area showed an exceptional stability (over 100 cycles) and rate capability over widely varying current density values (0.05–1 A g^?1). B_0.15C_0.73N_0.12 has a very high specific capacity of 710 mA h g^?1 at 0.05 A g^?1. With the inclusion of a suitable additive in the electrolyte, the specific capacity improved drastically, recording an impressive value of nearly 900 mA h g^?1 at 0.05 A g^?1. It is believed that the solid–electrolyte interphase (SEI) layer at the interface of B_xC_yN_z and electrolyte also plays a crucial role in the performance of the B_xC_yN_z .     

Towards a Safe Lithium–Sulfur Battery with a Flame‐Inhibiting Electrolyte and a Sulfur‐Based Composite Cathode

Of the various beyond‐lithium‐ion batteries, lithium–sulfur (Li‐S) batteries were recently reported as possibly being the closest to market. However, its theoretically high energy density makes it potentially hazardous under conditions of abuse. Therefore, addressing the safety issues of Li‐S cells is necessary before they can be used in practical applications. Here, we report a concept to build a safe and highly efficient Li‐S battery with a flame‐inhibiting electrolyte and a sulfur‐based composite cathode. The flame retardant not only makes the carbonates nonflammable but also dramatically enhances the electrochemical performance of the sulfur‐based composite cathode, without an apparent capacity decline over 750 cycles, and with a capacity greater than 800 mA h^?1 g^?1(sulfur) at a rate of 10 C.