Monolayer,Bilayer, and Bulk BSi as Potential Anode Materials of Li-Ion Batteries

Monolayer, bilayer, and bulk BSi are studied to explore their application potential as anode materials of Li-ion batteries. Structural stability and metallicity are obtained in each case. The Li storage capacities of monolayer and bilayer BSi are 1378 and 689 mAh g⁻¹, respectively, with average open circuit voltages of 1.30 and 0.47 V as well as Li diffusion barriers of 0.48 and 0.27 eV. Bulk BSi realizes a layered structure in the presence of a small amount of Li and its Li diffusion barrier of 0.48 eV is identical to that of graphite and lower than that of bulk Si (0.58 eV). The Li storage capacity of bulk BSi is found to be 689 mAh g⁻¹, i. e., much higher than that of graphite (372 mAh g⁻¹). The volume expansion turns out to be 33 % and the chemical bonds remain intact at full lithiation, outperforming the 72 % volume expansion of bulk Si at the same capacity and thus pointing to excellent cyclability.     

Electrolyte Regulation towards Stable Lithium‐Metal Anodes in Lithium–Sulfur Batteries with Sulfurized Polyacrylonitrile Cathodes

Lithium–sulfur (Li–S) batteries are highly regarded as the next‐generation energy‐storage devices because of their ultrahigh theoretical energy density of 2600 Wh kg^?1. Sulfurized polyacrylonitrile (SPAN) is considered a promising sulfur cathode to substitute carbon/sulfur (C/S) composites to afford higher Coulombic efficiency, improved cycling stability, and potential high‐energy‐density Li–SPAN batteries. However, the instability of the Li‐metal anode threatens the performances of Li–SPAN batteries bringing limited lifespan and safety hazards. Li‐metal can react with most kinds of electrolyte to generate a protective solid electrolyte interphase (SEI), electrolyte regulation is a widely accepted strategy to protect Li‐metal anodes in rechargeable batteries. Herein, the basic principles and current challenges of Li–SPAN batteries are addressed. Recent advances on electrolyte regulation towards stable Li‐metal anodes in Li–SPAN batteries are summarized to suggest design strategies of solvents, lithium salts, additives, and gel electrolyte. Finally, prospects for future electrolyte design and Li anode protection in Li–SPAN batteries are discussed.     

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.     

Revisiting Surface Modification of Graphite: Dual‐Layer Coating for High‐Performance Lithium Battery Anode Materials

Surface modification of electrode active materials has garnered considerable attention as a facile way to meet stringent requirements of advanced lithium‐ion batteries. Here, we demonstrated a new coating strategy based on dual layers comprising antimony‐doped tin oxide (ATO) nanoparticles and carbon. The ATO nanoparticles are synthesized via a hydrothermal method and act as electronically conductive/electrochemically active materials. The as‐synthesized ATO nanoparticles are introduced on natural graphite along with citric acid used as a carbon precursor. After carbonization, the carbon/ATO‐decorated natural graphite (c/ATO‐NG) is produced. In the (carbon/ATO) dual‐layer coating, the ATO nanoparticles coupled with the carbon layer exhibit unprecedented synergistic effects. The resultant c/ATO‐NG anode materials display significant improvements in capacity (530 mA h g^?1), cycling retention (capacity retention of 98.1 % after 50 cycles at a rate of C/5), and low electrode swelling (volume expansion of 38 % after 100 cycles) which outperform that of typical graphite materials. Furthermore, a full‐cell consisting of a c/ATO‐NG anode and an LiNi_0.5Mn_1.5O₄ cathode presents excellent cycle retention (capacity retention of >80 % after 100 cycles). We envision that the dual‐layer coating concept proposed herein opens a new route toward high‐performance anode materials for lithium‐ion batteries.     

Nafion/Titanium Dioxide‐Coated Lithium Anode for Stable Lithium–Sulfur Batteries

Lithium–sulfur (Li–S) batteries have shown great potential as high energy‐storage devices. However, the stability of the Li metal anode is still a major concern. This is due to the formation of lithium dendrites and severe side reactions with polysulfide intermediates. We herein develop an anode protection method by coating a Nafion/TiO₂ composite layer on the Li anode to solve these problems. In this architecture, Nafion suppresses the growth of Li dendrites, protects the Li anode, and prevents side reactions between polysulfides and the Li anode. Moreover, doped TiO₂ further improves the ionic conductivity and mechanical properties of the Nafion membrane. Li–S batteries with a Nafion/TiO₂‐coated Li anode exhibit better cycling stability (776 mA h g^?1 after 100 cycles at 0.2 C, 1 C=1672 mA g^?1) and higher rate performance (787 mA h g^?1 at 2 C) than those with a pristine Li anode. This work provides an alternative way to construct stable Li anodes for high‐performance Li–S batteries.     

Air‐Stable Lithium Spheres Produced by Electrochemical Plating

Lithium metal is an ideal anode for next‐generation lithium batteries owing to its very high theoretical specific capacity of 3860 mAh g^?1 but very reactive upon exposure to ambient air, rendering it difficult to handle and transport. Air‐stable lithium spheres (ASLSs) were produced by electrochemical plating under CO₂ atmosphere inside an advanced aberration‐corrected environmental transmission electron microscope. The ASLSs exhibit a core–shell structure with a Li core and a Li₂CO₃ shell. In ambient air, the ASLSs do not react with moisture and maintain their core–shell structures. Furthermore, the ASLSs can be used as anodes in lithium‐ion batteries, and they exhibit similar electrochemical behavior to metallic Li, indicating that the surface Li₂CO₃ layer is a good Li⁺ ion conductor. The air stability of the ASLSs is attributed to the surface Li₂CO₃ layer, which is barely soluble in water and does not react with oxygen and nitrogen in air at room temperature, thus passivating the Li core.     

Cobalt–Manganese Mixed‐Sulfide Nanocages Encapsulated by Reduced Graphene Oxide: In Situ Sacrificial Template Synthesis and Superior Lithium Storage Properties

This work demonstrates a facile in situ synthesis of cobalt–manganese mixed sulfide (CoMn‐S) nanocages on reduced graphene oxide (RGO) sheets by using a crystalline Co–Mn precursor as the sacrificial template. The CoMn‐S/RGO hybrid was applied as the anode for Li‐ion storage and exhibited superior specific capacity, excellent cycling performance, and great rate capability. In particular, lithium storage testing revealed that the hybrid delivered high discharge–charge capacities of 670 mA h g⁻¹ at 1.0 A g⁻¹ after 400 cycles and 925 mA h g⁻¹ at 0.1 A g⁻¹ after 300 cycles. The outstanding electrochemical performance of CoMn‐S/RGO is attributed to the close entanglement of nanocages with RGO nanosheets achieved by the synthetic method, which greatly improves ion/electron transport along the interfaces and efficiently mitigates volume dilation during lithium reactions. This rational design of both the composition and architecture of mixed metal sulfides can be expanded to other composite systems for high‐capacity Li‐ion batteries and provides a unique insight into the development of advanced hybrid electrode materials.     

High capacity silicon/carbon composite anode materials for lithium ion batteries

Silicon/carbon composite materials are prepared by pyrolysis of pitch embedded with graphite and silicon powders. As anode for lithium ion batteries, its initial reversible capacity is 800–900 mAh/g at 0.25 mA/cm² in a voltage range of 0.02/1.5 V vs. Li. The material modification by adding a small amount of CaCO₃ into precursor improves the initial reversibility (η₁=84%) and suppresses the capacity fade upon cycling. A little higher insertion voltage of the composites than commercial CMS anode material improves the cell safety in the high rate charging process.     

Integration of Graphite and Silicon Anodes for the Commercialization of High‐Energy Lithium‐Ion Batteries

Silicon is considered a most promising anode material for overcoming the theoretical capacity limit of carbonaceous anodes. The use of nanomethods has led to significant progress being made with Si anodes to address the severe volume change during (de)lithiation. However, less progress has been made in the practical application of Si anodes in commercial lithium‐ion batteries (LIBs). The drastic increase in the energy demands of diverse industries has led to the co‐utilization of Si and graphite resurfacing as a commercially viable method for realizing high energy. Herein, we highlight the necessity for the co‐utilization of graphite and Si for commercialization and discuss the development of graphite/Si anodes. Representative Si anodes used in graphite‐blended electrodes are covered and a variety of strategies for building graphite/Si composites are organized according to their synthetic methods. The criteria for the co‐utilization of graphite and Si are systematically presented. Finally, we provide suggestions for the commercialization of graphite/Si combinations.     

Understanding High‐Rate K+‐Solvent Co‐Intercalation in Natural Graphite for Potassium‐Ion Batteries

Graphite shows great potential as an anode material for rechargeable metal‐ion batteries because of its high abundance and low cost. However, the electrochemical performance of graphite anode materials for rechargeable potassium‐ion batteries needs to be further improved. Reported herein is a natural graphite with superior rate performance and cycling stability obtained through a unique K⁺‐solvent co‐intercalation mechanism in a 1 m KCF₃SO₃ diethylene glycol dimethyl ether electrolyte. The co‐intercalation mechanism was demonstrated by ex situ Fourier transform infrared spectroscopy and in situ X‐ray diffraction. Moreover, the structure of the [K‐solvent]⁺ complexes intercalated with the graphite and the conditions for reversible K⁺‐solvent co‐intercalation into graphite are proposed based on the experimental results and first‐principles calculations. This work provides important insights into the design of natural graphite for high‐performance rechargeable potassium‐ion batteries.     

Electrolyte Regulation towards Stable Lithium-Metal Anodes in Lithium–Sulfur Batteries with Sulfurized Polyacrylonitrile Cathodes

Lithium–sulfur (Li–S) batteries are highly regarded as the next-generation energy-storage devices because of their ultrahigh theoretical energy density of 2600 Wh kg⁻¹. Sulfurized polyacrylonitrile (SPAN) is considered a promising sulfur cathode to substitute carbon/sulfur (C/S) composites to afford higher Coulombic efficiency, improved cycling stability, and potential high-energy-density Li–SPAN batteries. However, the instability of the Li-metal anode threatens the performances of Li–SPAN batteries bringing limited lifespan and safety hazards. Li-metal can react with most kinds of electrolyte to generate a protective solid electrolyte interphase (SEI), electrolyte regulation is a widely accepted strategy to protect Li-metal anodes in rechargeable batteries. Herein, the basic principles and current challenges of Li–SPAN batteries are addressed. Recent advances on electrolyte regulation towards stable Li-metal anodes in Li–SPAN batteries are summarized to suggest design strategies of solvents, lithium salts, additives, and gel electrolyte. Finally, prospects for future electrolyte design and Li anode protection in Li–SPAN batteries are discussed.     

Using Simple Spray Pyrolysis to Prepare Yolk–Shell‐Structured ZnO–Mn3O4 Systems with the Optimum Composition for Superior Electrochemical Properties

A spray‐pyrolysis process is introduced as an effective tool for the preparation of yolk–shell‐structured materials with electrochemical properties suitable for anode materials in Li‐ion batteries (LIBs). Yolk–shell‐structured ZnO–Mn₃O₄ systems with various molar ratios of the Zn and Mn components are prepared. The yolk–shell‐structured ZnO–Mn₃O₄ powders with a molar ratio of 1:1 of the Zn and Mn components are shown to have high capacities and good cycling performances.     

A Bio‐Inspired,Heavy‐Metal‐Free,Dual‐Electrolyte Liquid Battery towards Sustainable Energy Storage

Wide‐scale exploitation of renewable energy requires low‐cost efficient energy storage devices. The use of metal‐free, inexpensive redox‐active organic materials represents a promising direction for environmental‐friendly, cost‐effective sustainable energy storage. To this end, a liquid battery is designed using hydroquinone (H₂BQ) aqueous solution as catholyte and graphite in aprotic electrolyte as anode. The working potential can reach 3.4 V, with specific capacity of 395 mA h g⁻¹ and stable capacity retention about 99.7 % per cycle. Such high potential and capacity is achieved using only C, H and O atoms as building blocks for redox species, and the replacement of Li metal with graphite anode can circumvent potential safety issues. As H₂BQ can be extracted from biomass directly and its redox reaction mimics the bio‐electrochemical process of quinones in nature, using such a bio‐inspired organic compound in batteries enables access to greener and more sustainable energy‐storage technology.     

Unlocking Reversible Silicon Redox for High-Performing Chlorine Batteries

Chlorine (Cl)-based batteries such as Li/Cl₂ batteries are recognized as promising candidates for energy storage with low cost and high performance. However, the current use of Li metal anodes in Cl-based batteries has raised serious concerns regarding safety, cost, and production complexity. More importantly, the well-documented parasitic reactions between Li metal and Cl-based electrolytes require a large excess of Li metal, which inevitably sacrifices the electrochemical performance of the full cell. Therefore, it is crucial but challenging to establish new anode chemistry, particularly with electrochemical reversibility, for Cl-based batteries. Here we show, for the first time, reversible Si redox in Cl-based batteries through efficient electrolyte dilution and anode/electrolyte interface passivation using 1,2-dichloroethane and cyclized polyacrylonitrile as key mediators. Our Si anode chemistry enables significantly increased cycling stability and shelf lives compared with conventional Li metal anodes. It also avoids the use of a large excess of anode materials, thus enabling the first rechargeable Cl₂ full battery with remarkable energy and power densities of 809 Wh kg⁻¹ and 4,277 W kg⁻¹, respectively. The Si anode chemistry affords fast kinetics with remarkable rate capability and low-temperature electrochemical performance, indicating its great potential in practical applications.     

Hexagonal‐Shaped Tin Glycolate Particles: A Preliminary Study of Their Suitability as Li‐Ion Insertion Electrodes

Tin glycolate particles were prepared by a simple, one‐step, polyol‐mediated synthesis in air in which tin oxalate precursor was added to ethylene glycol and heated at reflux. Hexagonal‐shaped, micron‐sized tin glycolate particles were formed when the solution had cooled. A series of tin oxides was produced by calcination of the synthesized tin glycolate at 600–800 °C. It was revealed that the micron‐sized, hexagonal‐shaped tin glycolate now consisted of nanosized tin‐based particles (80–120 nm), encapsulated within a tin glycolate shell. XRD, TGA, and FT‐IR measurements were conducted to account for the three‐dimensional growth of the tin glycolate particles. When applied as an anode material for Li‐ion batteries, the synthesized tin glycolate particles showed good electrochemical reactivity in Li‐ion insertion/deinsertion, retaining a specific capacity of 416 mAh g^?1 beyond 50 cycles. This performance was significantly better than those of all the other tin oxides nanoparticles (<160 mAh g^?1) obtained after heat treatment in air. We strongly believe that the buffering of the volume expansion by the glycolate upon Li–Sn alloying is the main factor for the improved cycling of the electrode.     

Formation of Nanostructured MnO/Co/Solid–Electrolyte Interphase Ternary Composites as a Durable Anode Material for Lithium‐Ion Batteries

Nanoporous MnO frameworks with highly dispersed Co nanoparticles were produced from MnCO₃ precursors prepared in a gel matrix. The MnO frameworks that contain 20 mol % Co exhibited excellent cycle performance as an anode material for Li‐ion batteries. The solid–electrolyte interphase (SEI) formed in the frameworks through the electrochemical reaction mediates the active materials, such as MnO, Mn, and Li₂O, during the conversion reaction in the charge–discharge cycle. The Co nanoparticles and SEI provide the electron and Li‐ion conductive networks, respectively. The ternary nanocomposites of the MnO framework, metallic Co nanoparticles, and embedded SEI are categorized as durable anode materials for Li‐ion batteries.     

Lithium Azide as an Electrolyte Additive for All‐Solid‐State Lithium–Sulfur Batteries

Of the various beyond‐lithium‐ion battery technologies, lithium–sulfur (Li–S) batteries have an appealing theoretical energy density and are being intensely investigated as next‐generation rechargeable lithium‐metal batteries. However, the stability of the lithium‐metal (Li°) anode is among the most urgent challenges that need to be addressed to ensure the long‐term stability of Li–S batteries. Herein, we report lithium azide (LiN₃) as a novel electrolyte additive for all‐solid‐state Li–S batteries (ASSLSBs). It results in the formation of a thin, compact and highly conductive passivation layer on the Li° anode, thereby avoiding dendrite formation, and polysulfide shuttling. It greatly enhances the cycling performance, Coulombic and energy efficiencies of ASSLSBs, outperforming the state‐of‐the‐art additive lithium nitrate (LiNO₃).     

Porous Core–Shell CuCo2S4 Nanospheres as Anode Material for Enhanced Lithium-Ion Batteries

Porous core–shell CuCo₂S₄ nanospheres that exhibit a large specific surface area, sufficient inner space, and a nanoporous shell were synthesized through a facile solvothermal method. The diameter of the core–shell CuCo₂S₄ nanospheres is approximately 800 nm„ the radius of the core is about 265 nm and the thickness of the shell are approximately 45 nm, respectively. On the basis of the experimental results, the formation mechanism of the core–shell structure is also discussed. These CuCo₂S₄ nanospheres show excellent Li storage performance when used as anode material for lithium-ion batteries. This material delivers high reversible capacity of 773.7 mA h g⁻¹ after 1000 cycles at a current density of 1 A g⁻¹ and displays a stable capacity of 358.4 mA h g⁻¹ after 1000 cycles even at a higher current density of 10 A g⁻¹. The excellent Li storage performance, in terms of high reversible capacity, cycling performance, and rate capability, can be attributed to the synergistic effects of both the core and shell during Li⁺ ion insertion/extraction processes.     

A Porphyrin Complex as a Self‐Conditioned Electrode Material for High‐Performance Energy Storage

The novel functionalized porphyrin [5,15‐bis(ethynyl)‐10,20‐diphenylporphinato]copper(II) (CuDEPP) was used as electrodes for rechargeable energy‐storage systems with an extraordinary combination of storage capacity, rate capability, and cycling stability. The ability of CuDEPP to serve as an electron donor or acceptor supports various energy‐storage applications. Combined with a lithium negative electrode, the CuDEPP electrode exhibited a long cycle life of several thousand cycles and fast charge–discharge rates up to 53 C and a specific energy density of 345 Wh kg⁻¹ at a specific power density of 29 kW kg⁻¹. Coupled with a graphite cathode, the CuDEPP anode delivered a specific power density of 14 kW kg⁻¹. Whereas the capacity is in the range of that of ordinary lithium‐ion batteries, the CuDEPP electrode has a power density in the range of that of supercapacitors, thus opening a pathway toward new organic electrodes with excellent rate capability and cyclic stability.     

Double‐Shelled Nanocages with Cobalt Hydroxide Inner Shell and Layered Double Hydroxides Outer Shell as High‐Efficiency Polysulfide Mediator for Lithium–Sulfur Batteries

Lithium–sulfur (Li‐S) batteries have been considered as a promising candidate for next‐generation electrochemical energy‐storage technologies because of their overwhelming advantages in energy density. Suppression of the polysulfide dissolution while maintaining a high sulfur utilization is the main challenge for Li–S batteries. Here, we have designed and synthesized double‐shelled nanocages with two shells of cobalt hydroxide and layered double hydroxides (CH@LDH) as a conceptually new sulfur host for Li–S batteries. Specifically, the hollow CH@LDH polyhedra with complex shell structures not only maximize the advantages of hollow nanostructures for encapsulating a high content of sulfur (75 wt %), but also provide sufficient self‐functionalized surfaces for chemically bonding with polysulfides to suppress their outward dissolution. When evaluated as cathode material for Li–S batteries, the CH@LDH/S composite shows a significantly improved electrochemical performance.