Creating Lithium‐Ion Electrolytes with Biomimetic Ionic Channels in Metal–Organic Frameworks

Solid‐state electrolytes are the key to the development of lithium‐based batteries with dramatically improved energy density and safety. Inspired by ionic channels in biological systems, a novel class of pseudo solid‐state electrolytes with biomimetic ionic channels is reported herein. This is achieved by complexing the anions of an electrolyte to the open metal sites of metal–organic frameworks (MOFs), which transforms the MOF scaffolds into ionic‐channel analogs with lithium‐ion conduction and low activation energy. This work suggests the emergence of a new class of pseudo solid‐state lithium‐ion conducting electrolytes.     

2D Frameworks of C2N and C3N as New Anode Materials for Lithium‐Ion Batteries

Novel layered 2D frameworks (C₃N and C₂N‐450) with well‐defined crystal structures are explored for use as anode materials in lithium‐ion batteries (LIBs) for the first time. As anode materials for LIBs, C₃N and C₂N‐450 exhibit unusual electrochemical characteristics. For example, C₂N‐450 (and C₃N) display high reversible capacities of 933.2 (383.3) and 40.1 (179.5) mAh g^?1 at 0.1 and 10 C, respectively. Furthermore, C₃N shows a low hypothetical voltage (≈0.15 V), efficient operating voltage window with ≈85% of full discharge capacity secured at >0.45 V, and excellent cycling stability for more than 500 cycles. The excellent electrochemical performance (especially of C₃N) can be attributed to their inherent 2D polyaniline frameworks, which provide large net positive charge densities, excellent structural stability, and enhanced electronic/ionic conductivity. Stable solid state interface films also form on the surfaces of the 2D materials during the charge/discharge process. These 2D materials with promising electrochemical performance should provide insights to guide the design and development of their analogues for future energy applications.     

Multishelled NixCo3–xO4 Hollow Microspheres Derived from Bimetal–Organic Frameworks as Anode Materials for High‐Performance Lithium‐Ion Batteries

Metal–organic frameworks (MOFs) featuring versatile topological architectures are considered to be efficient self‐sacrificial templates to achieve mesoporous nanostructured materials. A facile and cost‐efficient strategy is developed to scalably fabricate binary metal oxides with complex hollow interior structures and tunable compositions. Bimetal–organic frameworks of Ni‐Co‐BTC solid microspheres with diverse Ni/Co ratios are readily prepared by solvothermal method to induce the Ni _x Co_{3? x} O₄ multishelled hollow microspheres through a morphology‐inherited annealing treatment. The obtained mixed metal oxides are demonstrated to be composed of nanometer‐sized subunits in the shells and large void spaces left between adjacent shells. When evaluated as anode materials for lithium‐ion batteries, Ni _x Co_{3? x} O₄‐0.1 multishelled hollow microspheres deliver a high reversible capacity of 1109.8 mAh g^?1 after 100 cycles at a current density of 100 mA g^?1 with an excellent high‐rate capability. Appropriate capacities of 832 and 673 mAh g^?1 could also be retained after 300 cycles at large currents of 1 and 2 A g^?1, respectively. These prominent electrochemical properties raise a concept of synthesizing MOFs‐derived mixed metal oxides with multishelled hollow structures for progressive lithium‐ion batteries.     

SnO2‐Based Nanomaterials: Synthesis and Application in Lithium‐Ion Batteries

The development of new electrode materials for lithium‐ion batteries (LIBs) has always been a focal area of materials science, as the current technology may not be able to meet the high energy demands for electronic devices with better performance. Among all the metal oxides, tin dioxide (SnO₂) is regarded as a promising candidate to serve as the anode material for LIBs due to its high theoretical capacity. Here, a thorough survey is provided of the synthesis of SnO₂‐based nanomaterials with various structures and chemical compositions, and their application as negative electrodes for LIBs. It covers SnO₂ with different morphologies ranging from 1D nanorods/nanowires/nanotubes, to 2D nanosheets, to 3D hollow nanostructures. Nanocomposites consisting of SnO₂ and different carbonaceous supports, e.g., amorphous carbon, carbon nanotubes, graphene, are also investigated. The use of Sn‐based nanomaterials as the anode material for LIBs will be briefly discussed as well. The aim of this review is to provide an in‐depth and rational understanding such that the electrochemical properties of SnO₂‐based anodes can be effectively enhanced by making proper nanostructures with optimized chemical composition. By focusing on SnO₂, the hope is that such concepts and strategies can be extended to other potential metal oxides, such as titanium dioxide or iron oxides, thus shedding some light on the future development of high‐performance metal‐oxide based negative electrodes for LIBs.     

Nanoscale Engineering of Heterostructured Anode Materials for Boosting Lithium‐Ion Storage

Rechargeable lithium‐ion batteries (LIBs), as one of the most important electrochemical energy‐storage devices, currently provide the dominant power source for a range of devices, including portable electronic devices and electric vehicles, due to their high energy and power densities. The interest in exploring new electrode materials for LIBs has been drastically increasing due to the surging demands for clean energy. However, the challenging issues essential to the development of electrode materials are their low lithium capacity, poor rate ability, and low cycling stability, which strongly limit their practical applications. Recent remarkable advances in material science and nanotechnology enable rational design of heterostructured nanomaterials with optimized composition and fine nanostructure, providing new opportunities for enhancing electrochemical performance. Here, the progress as to how to design new types of heterostructured anode materials for enhancing LIBs is reviewed, in the terms of capacity, rate ability, and cycling stability: i) carbon‐nanomaterials‐supported heterostructured anode materials; ii) conducting‐polymer‐coated electrode materials; iii) inorganic transition‐metal compounds with core@shell structures; and iv) combined strategies to novel heterostructures. By applying different strategies, nanoscale heterostructured anode materials with reduced size, large surfaces area, enhanced electronic conductivity, structural stability, and fast electron and ion transport, are explored for boosting LIBs in terms of high capacity, long cycling lifespan, and high rate durability. Finally, the challenges and perspectives of future materials design for high‐performance LIB anodes are considered. The strategies discussed here not only provide promising electrode materials for energy storage, but also offer opportunities in being extended for making a variety of novel heterostructured nanomaterials for practical renewable energy applications.     

A Novel High‐Capacity Anode Material Derived from Aromatic Imides for Lithium‐Ion Batteries

A novel anode material for lithium‐ion batteries derived from aromatic imides with multicarbonyl group conjugated with aromatic core structure is reported, benzophenolne‐3,3′,4,4′‐tetracarboxylimide oligomer (BTO). It could deliver a reversible capacity of 829 mA h g^?1 at 42 mA g^?1 for 50 cycles with a stable discharge plateaus ranging from 0.05–0.19 V versus Li⁺/Li. At higher rates of 420 and 840 mA g^?1, it can still exhibit excellent cycling stability with a capacity retention of 88% and 72% after 1000 cycles, delivering capacity of 559 and 224 mA h g^?1. In addition, a rational prediction of the maximum amount of lithium intercalation is proposed and explored its possible lithium storage mechanism.     

Nanospace‐Confinement Synthesis: Designing High‐Energy Anode Materials toward Ultrastable Lithium‐Ion Batteries

Exploiting high‐capacity and durable electrode materials is pivotal to developing lithium‐ion batteries (LIBs) and their applications. Multiscaled nanomaterials have been demonstrated to efficiently couple the advantages of each component on different scales in energy storage fields. However, the precise control of the microstructure remains a great challenge for maximizing their contributions. Nanospace‐confined synthesis provides a proactive strategy to build novel multiscaled nanomaterials with controllable internal void space for circumventing the intrinsic volume effects in the charge/discharge process. Herein, the rational design and synthesis of multiscaled high‐capacity anode materials are mainly summarized according to their electrochemical mechanisms by choosing 1D channel, 2D interlayer, and 3D space as representative confinement reaction environments. The structure–performance relationships are clarified with the assistance of quantitative calculations, molecular simulations, and so forth. Finally, future potentials and challenges of such a synthesis tactic in designing high‐performance electrode materials for next‐generation secondary batteries are outlooked.     

One‐Pot Hydrothermal Synthesis of FeMoO4 Nanocubes as an Anode Material for Lithium‐Ion Batteries with Excellent Electrochemical Performance

Metal molybdates nanostructures hold great promise as high‐performance electrode materials for next‐generation lithium‐ion batteries. In this work, the facial design and synthesis of monodisperse FeMoO₄ nanocubes with the edge lengths of about 100 nm have been successfully prepared and present as a novel anode material for highly efficient and reversible lithium storage. Well‐defined single‐crystalline FeMoO₄ with high uniformity are first obtained as nanosheets and then self‐aggregated into nanocubes. The morphology of the product is largely controlled by the experimental parameters, such as the reaction temperature and time, the ratio of reactant, the solution viscosity, etc. The molybdate nanostructure would effectively promote the insertion of lithium ions and withstand volume variation upon prolonged charge/discharge cycling. As a result, the FeMoO₄ nanocubes exhibit high reversible capacities of 926 mAh g⁻¹ after 80 cycles at a current density of 100 mA g⁻¹ and remarkable rate performance, which indicate that the FeMoO₄ nanocubes are promising materials for high‐power lithium‐ion battery applications.     

30 Years of Lithium‐Ion Batteries

Over the past 30 years, significant commercial and academic progress has been made on Li‐based battery technologies. From the early Li‐metal anode iterations to the current commercial Li‐ion batteries (LIBs), the story of the Li‐based battery is full of breakthroughs and back tracing steps. This review will discuss the main roles of material science in the development of LIBs. As LIB research progresses and the materials of interest change, different emphases on the different subdisciplines of material science are placed. Early works on LIBs focus more on solid state physics whereas near the end of the 20th century, researchers began to focus more on the morphological aspects (surface coating, porosity, size, and shape) of electrode materials. While it is easy to point out which specific cathode and anode materials are currently good candidates for the next‐generation of batteries, it is difficult to explain exactly why those are chosen. In this review, for the reader a complete developmental story of LIB should be clearly drawn, along with an explanation of the reasons responsible for the various technological shifts. The review will end with a statement of caution for the current modern battery research along with a brief discussion on beyond lithium‐ion battery chemistries.     

Nanoarchitectured Design of Porous Materials and Nanocomposites from Metal‐Organic Frameworks

The emergence of metal‐organic frameworks (MOFs) as a new class of crystalline porous materials is attracting considerable attention in many fields such as catalysis, energy storage and conversion, sensors, and environmental remediation due to their controllable composition, structure and pore size. MOFs are versatile precursors for the preparation of various forms of nanomaterials as well as new multifunctional nanocomposites/hybrids, which exhibit superior functional properties compared to the individual components assembling the composites. This review provides an overview of recent developments achieved in the fabrication of porous MOF‐derived nanostructures including carbons, metal oxides, metal chalcogenides (metal sulfides and selenides), metal carbides, metal phosphides and their composites. Finally, the challenges and future trends and prospects associated with the development of MOF‐derived nanomaterials are also examined.     

Novel Carbon‐Encapsulated Porous SnO2 Anode for Lithium‐Ion Batteries with Much Improved Cyclic Stability

Porous SnO₂ submicrocubes (SMCs) are synthesized by annealing and HNO₃ etching of CoSn(OH)₆ SMCs. Bare SnO₂ SMCs, as well as bare commercial SnO₂ nanoparticles (NPs), show very high initial discharge capacity when used as anode material for lithium‐ion batteries. However, during the following cycles most of the Li ions previously inserted cannot be extracted, resulting in considerable irreversibility. Porous SnO₂ cubes have been proven to possess better electrochemical performance than the dense nanoparticles. After being encapsulated by carbon shell, the obtained yolk–shell SnO₂ SMCs@C exhibits significantly enhanced reversibility for lithium‐ions storage. The reversibility of the conversion between SnO₂ and Sn, which is largely responsible for the enhanced capacity, has been discussed. The porous SnO₂ SMCs@C shows much increased capacity and cycling stability, demonstrating that the porous SnO₂ core is essential for better lithium‐ion storage performance. The strategy introduced in this paper can be used as a versatile way to fabrication of various metal‐oxide‐based composites.