Mesoporous TiO2‐Sn/C Core‐Shell Nanowire Arrays as High‐Performance 3D Anodes for Li‐Ion Batteries

Three‐dimensional mesoporous TiO₂‐Sn/C core‐shell nanowire arrays are prepared on Ti foil as anodes for lithium‐ion batteries. Sn formed by a reduction of SnO₂ is encapsulated into TiO₂ nanowires and the carbon layer is coated onto it. For additive‐free, self‐supported anodes in Li‐ion batteries, this unique core‐shell composite structure can effectively buffer the volume change, suppress cracking, and improve the conductivity of the electrode during the discharge‐charge process, thus resulting in superior rate capability and excellent long‐term cycling stability. Specifically, the TiO₂‐Sn/C nanowire arrays display rechargeable discharge capacities of 769, 663, 365, 193, and 90 mA h g^?1 at 0.1C, 0.5C, 2C 10C, and 30C, respectively (1C = 335 mA g^?1). Furthermore, the TiO₂‐Sn/C nanowire arrays exhibit a capacity retention rate of 84.8% with a discharge capacity of over 160 mA h g^?1, even after 100 cycles at a high current rate of 10C.     

Graphitic Carbon Nanocage as a Stable and High Power Anode for Potassium‐Ion Batteries

As an emerging electrochemical energy storage device, potassium‐ion batteries (PIBs) have drawn growing interest due to the resource‐abundance and low cost of potassium. Graphite‐based materials, as the most common anodes for commercial Li‐ion batteries, have a very low capacity when used an anode for Na‐ion batteries, but they show reasonable capacities as anodes for PIBs. The practical application of graphitic materials in PIBs suffers from poor cyclability, however, due to the large interlayer expansion/shrinkage caused by the intercalation/deintercalation of potassium ions. Here, a highly graphitic carbon nanocage (CNC) is reported as a PIBs anode, which exhibits excellent cyclability and superior depotassiation capacity of 175 mAh g^?1 at 35 C. The potassium storage mechanism in CNC is revealed by cyclic voltammetry as due to redox reactions (intercalation/deintercalation) and double‐layer capacitance (surface adsorption/desorption). The present results give new insights into structural design for graphitic anode materials in PIBs and understanding the double‐layer capacitance effect in alkali metal ion batteries.     

Autonomic Shutdown of Lithium‐Ion Batteries Using Thermoresponsive Microspheres

Autonomic, thermally‐induced shutdown of Lithium‐ion (Li‐ion) batteries is demonstrated by incorporating thermoresponsive polymer microspheres (ca. 4 μm) onto battery anodes or separators. When the internal battery environment reaches a critical temperature, the microspheres melt and coat the anode/separator with a nonconductive barrier, halting Li‐ion transport and shutting down the cell permanently. Three functionalization schemes are shown to perform cell shutdown: 1) poly(ethylene) (PE) microspheres coated on the anode, 2) paraffin wax microspheres coated on the anode, and 3) PE microspheres coated on the separator. Charge and discharge capacity is measured for Li‐ion coin cells containing microsphere‐coated anodes or separators as a function of capsule coverage. For PE coated on the anode, the initial capacity of the battery is unaffected by the presence of the PE microspheres up to a coverage of 12 mg cm^?2 (when cycled at 1C), and full shutdown (>98% loss of initial capacity) is achieved in cells containing greater than 3.5 mg cm^?2. For paraffin microspheres coated on the anode and PE microspheres coated on the separator, shutdown is achieved in cells containing coverages greater than 2.9 and 13.7 mg cm^?2, respectively. Scanning electron microscopy images of electrode surfaces from cells that have undergone autonomic shutdown provides evidence of melting, wetting, and resolidification of PE into the anode and polymer film formation at the anode/separator interface.     

High‐Rate and Long Cycle‐Life Alloy‐Type Magnesium‐Ion Battery Anode Enabled Through (De)magnesiation‐Induced Near‐Room‐Temperature Solid–Liquid Phase Transformation

Resources used in lithium‐ion batteries are becoming more expensive due to their high demand, and the global cobalt market heavily depends on supplies from countries with high geopolitical risks. Alternative battery technologies including magnesium‐ion batteries are therefore desirable. Progress toward practical magnesium‐ion batteries are impeded by an absence of suitable anodes that can operate with conventional electrolyte solvents. Although alloy‐type magnesium‐ion battery anodes are compatible with common electrolyte solvents, they suffer from severe failure associated with huge volume changes during cycling. Consequently, achieving more than 200 cycles in alloy‐type magnesium‐ion battery anodes remains a challenge. Here an unprecedented long‐cycle life of 1000 cycles, achieved at a relatively high (dis)charge rate of 3 C (current density: 922.5 mA g^?1) in Mg₂Ga₅ alloy‐type anode, taking advantage of near‐room‐temperatures solid–liquid phase transformation between Mg₂Ga₅ (solid) and Ga (liquid), is demonstrated. This concept should open the way to the development of practical anodes for next‐generation magnesium‐ion batteries.     

Short‐Range Order in Mesoporous Carbon Boosts Potassium‐Ion Battery Performance

The adequate potassium resource on the earth has driven the researchers to explore new‐concept potassium‐ion batteries (KIBs) with high energy density. Graphite is a common anode for KIBs; however, the main challenge faced by KIBs is that K ions have the larger size than Li and Na ions, hindering the intercalation of K ions into electrodes and thus leading to poor rate performance, low capacity, and cycle stability during the potassiation and depotassiation process. Herein, an amorphous ordered mesoporous carbon (OMC) is reported as a new anode material for high‐performance KIBs. Unlike the well‐crystallized graphite, in which the K ions are squeezed into the restricted interlayer spacing, it is found that the amorphous OMC possesses larger interlayer spacing in short range and fewer carbon atoms in one carbon‐layers cluster, making it more flexible to the deformation of carbon layers. The larger interlayer spacing and the unique layered structure in short range can intercalate more K ions into the carbon layer, accommodate the increase of the interlayer spacing, and tolerate the volume expansion, resulting in a battery behavior with high capacity, high rate capability, and long cycle life.     

Research Progress on Negative Electrodes for Practical Li‐Ion Batteries: Beyond Carbonaceous Anodes

Research activities related to the development of negative electrodes for construction of high‐performance Li‐ion batteries (LIBs) with conventional cathodes such as LiCoO₂, LiFePO₄, and LiMn₂O₄ are described. The anode materials are classified in to three main categories, insertion, conversion, and alloying type, based on their reactivity with Li. Although numerous materials have been proposed (i.e., for half‐cell assembly), few of them have reached commercial applications, apart from graphite, Li₄Ti₅O₁₂, Si, and Sn‐Co‐C. This clearly demonstrates that full‐cell studies are desperately needed rather than just characterizing materials in half‐cell assemblies. Additionally, the performance of such anodes in practical Li‐ion configurations (full‐cell) is much more important than merely proposing materials for LIBs. Irreversible capacity loss, huge volume variation, unstable solid electrolyte interface layer formation, and poor cycleability are the main issues for conversion and alloy type anodes. This review addresses how best to circumvent the mentioned issues during the construction of Li‐ion cells and the future prospects of such anodes are described in detail.     

An Upgraded Lithium Ion Battery Based on a Polymeric Separator Incorporated with Anode Active Materials

Structural/compositional characteristics at the anode/electrolyte interface are of paramount importance for the practical performance of lithium ion batteries, including cyclic stability, rate capacity, and operational safety. The anode‐electrolyte interface with traditional separator technology is featured with inevitable phase discontinuity and fails to support the stable operation of lithium ion batteries based on large‐capacity anodes with structural change in charges/discharges, such as transition metal oxide anodes. In this work, an anode/electrolyte framework based on an oxide anode and an active‐oxide‐incorporated separator is proposed for the first time and investigated for lithium ion batteries. The architecture builds a robust anode‐separator interface in LIBs, shortens Li⁺ diffusion path, accelerates electron transport, and mitigates the volume change of the oxide anode in electrochemical reactions. Remarkably, 4 wt% CuO addition in the separator leads to a 17% enhancement in the overall capacity of a battery with a CuO anode. The battery delivers an unparalleled record reversible capacity of 637.2 mAh g^?1 with a 99% capacity retention after 100 charge/discharge cycles at 0.5 C. The high performance are attributed to the robust anode‐separator interface, which gives rise to enhanced interaction between the oxide anode and the same‐oxide‐incorporated composite in the separator.     

Highly Doped 3D Graphene Na‐Ion Battery Anode by Laser Scribing Polyimide Films in Nitrogen Ambient

Conventional graphite anodes can hardly intercalate sodium (Na) ions, which poses a serious challenge for developing Na‐ion batteries. This study details a novel method that involves single‐step laser‐based transformation of urea‐containing polyimide into an expanded 3D graphene anode, with simultaneous doping of high concentrations of nitrogen (≈13 at%). The versatile nature of this laser‐scribing approach enables direct bonding of the 3D graphene anode to the current collectors without the need for binders or conductive additives, which presents a clear advantage over chemical or hydrothermal methods. It is shown that these conductive and expanded 3D graphene structures perform exceptionally well as anodes for Na‐ion batteries. Specifically, an initial coulombic efficiency (CE) up to 74% is achieved, which exceeds that of most reported carbonaceous anodes, such as hard carbon and soft carbon. In addition, Na‐ion capacity up to 425 mAh g^?1 at 0.1 A g^?1 has been achieved with excellent rate capabilities. Further, a capacity of 148 mAh g^?1 at a current density of 10 A g^?1 is obtained with excellent cycling stability, opening a new direction for the fabrication of 3D graphene anodes directly on current collectors for metal ion battery anodes as well as other potential applications.     

A Practicable Li/Na‐Ion Hybrid Full Battery Assembled by a High‐Voltage Cathode and Commercial Graphite Anode: Superior Energy Storage Performance and Working Mechanism

With the rapidly growing demand for low‐cost and safe energy storage, the advanced battery concepts have triggered strong interests beyond the state‐of‐the‐art Li‐ion batteries (LIBs). Herein, a novel hybrid Li/Na‐ion full battery (HLNIB) composed of the high‐energy and lithium‐free Na₃V₂(PO₄)₂O₂F (NVPOF) cathode and commercial graphite anode mesophase carbon micro beads is for the first time designed. The assembled HLNIBs exhibit two high working voltage at about 4.05 and 3.69 V with a specific capacity of 112.7 mA h g^?1. Its energy density can reach up to 328 W h kg^?1 calculated from the total mass of both cathode and anode materials. Moreover, the HLNIBs show outstanding high‐rate capability, long‐term cycle life, and excellent low‐temperature performance. In addition, the reaction kinetics and Li/Na‐insertion/extraction mechanism into/out NVPOF is preliminarily investigated by the galvanostatic intermittent titration technique and ex situ X‐ray diffraction. This work provides a new and profound direction to develop advanced hybrid batteries.     

Carbon Anodes for Nonaqueous Alkali Metal‐Ion Batteries and Their Thermal Safety Aspects

Since their commercialization by Sony in 1991, graphite anodes in combination with various cathodes have enabled the widespread success of lithium‐ion batteries (LIBs), providing over 10 billion rechargeable batteries to the global population. Next‐generation nonaqueous alkali metal‐ion batteries, namely sodium‐ion batteries (SIBs) and potassium‐ion batteries (PIBs), are projected to utilize intercalation‐based carbon anodes as well, due to their favorable electrochemical properties. While traditionally graphite anodes have dominated the market share of LIBs, other carbon materials have been investigated, including graphene, carbon nanotubes, and disordered carbons. The relationship between carbon material properties, electrochemical performance, and charge storage mechanisms is clarified for these alkali metal‐ion batteries, elucidating possible strategies for obtaining enhanced cycling stability, specific capacity, rate capability, and safety aspects. As a key component in determining cell performance, the solid electrolyte interphase layer is described in detail, particularly for its dependence on the carbon anode. Finally, battery safety at extreme temperatures is discussed, where carbon anodes are susceptible to dendrite formation, accelerated aging, and eventual thermal runaway. As society pushes toward higher energy density LIBs, this review aims to provide guidance toward the development of sustainable next‐generation SIBs and PIBs.     

New Binder‐Free Metal Phosphide–Carbon Felt Composite Anodes for Sodium‐Ion Battery

Metal phosphides are promising anode candidates for sodium‐ion batteries (SIBs) due to their high specific capacity and low operating potential but suffer from poor cycling stability caused by huge volume expansion and poor solid‐state ion transfer rate. Herein, a new strategy to grow a new class of mesoporous metal phosphide nanoarrays on carbon felt (CF) as binder‐free anodes for SIBs is reported. The resultant integrated electrodes demonstrate excellent cycling life up to 1000 times (>90% retention rate) and high rate capability of 535 mAh g^?1 at a current density of 4 A g^?1. Detailed characterization reveals that the synergistic effect of unique mesoporous structure for accommodating huge volume expansion during sodiation/desodiation process, ultrasmall primary particle size (≈10 nm) for providing larger electrode/electrolyte contact area and shorter ion diffusion distance, and 3D conductive networks for facilitating the electrochemical reaction, leads to the extraordinary battery performance. Remarkably, a full SIB using the new CoP₄/CF anode and a Na₃V₂(PO₄)₂F₃ cathode delivers an average operating voltage of ≈3.0 V, a reversible capacity of 553 mAh g^?1, and very high energy density of ≈280 Wh kg^?1 for SIBs. A flexible SIB with outstanding mechanical strength based on this binder‐free new anode is also demonstrated.     

Electrokinetic Phenomena Enhanced Lithium‐Ion Transport in Leaky Film for Stable Lithium Metal Anodes

The application of lithium (Li) metal anodes in Li metal batteries has been hindered by growth of Li dendrites, which lead to short cycling life. Here a Li‐ion‐affinity leaky film as a protection layer is reported to promote a dendrite‐free Li metal anode. The leaky film induces electrokinetic phenomena to enhance Li‐ion transport, leading to a reduced Li‐ion concentration polarization and homogeneous Li‐ion distribution. As a result, the dendrite‐free Li metal anode during Li plating/stripping is demonstrated even at an extremely high deposition capacity (6 mAh cm^?2) and current density (40 mA cm^?2) with improved Coulombic efficiencies. A full cell battery with the leaky‐film protected Li metal as the anode and high‐areal‐capacity LiNi_0.8Co_0.1Mn_0.1O₂ (NCM‐811) (≈4.2 mAh cm^?2) or LiFePO₄ (≈3.8 mAh cm^?2) as the cathode shows improved cycling stability and capacity retention, even at lean electrolyte conditions.     

A Safe Organic Oxygen Battery Built with Li‐Based Liquid Anode and MOFs Separator

Safe rechargeable batteries of improved energy density and high power performance are urgently needed for the development of large electric devices. Herein, an Li‐based organic liquid anode is proposed, and an organic oxygen battery with a metal organic framework membrane separator is realized, which is able to conduct Li ions and separate other large species in the system. Equipped with the dual redox mediator strategy, the organic oxygen battery exhibits superior rate performance with long cycling life and low overpotential. A “solid electrolyte interface”‐like layer is observed between the organic liquid anode and the ion conducting separator. This work not only introduces a new type of anode for Li‐based batteries, but also provides fundamental insights for the better application of biphenyl‐based liquid anodes.     

Na‐Ion Batteries for Large Scale Applications: A Review on Anode Materials and Solid Electrolyte Interphase Formation

The urgent need for optimizing the available energy through smart grids and efficient large‐scale energy storage systems is pushing the construction and deployment of Li‐ion batteries in the MW range which, in the long term, are expected to hit the GW dimension while demanding over 1000 ton of positive active material per system. This amount of Li‐based material is equivalent to almost 1% of current Li consumption and can strongly influence the evolution of the lithium supply and cost. Given this uncertainty, it becomes mandatory to develop an energy storage technology that depends on almost infinite and widespread resources: Na‐ion batteries are the best technology for large‐scale applications. With small working cells in the market that cannot compete in cost ($/W h) with commercial Li‐ion batteries, the consolidation of Na‐ion batteries mainly depends on increasing their energy density and stability, the negative electrodes being at the heart of these two requirements. Promising Na‐based negative electrodes for large‐scale battery applications are reviewed, along with the study of the solid electrolyte interphase formed in the anode surface, which is at the origin of most of the stability problems.     

Three‐Dimensional Porous Core‐Shell Sn@Carbon Composite Anodes for High‐Performance Lithium‐Ion Battery Applications

A three‐dimensional porous core‐shell Sn@carbon anode on nickel foam substrate was fabricated by electrostatic spray deposition (ESD) technique followed by high temperature treatment. The carbon shell with a thickness of about 3.2 nm was formed on porous Sn structure at high temperature. 3D porous structure and carbon shell were designed to buffer volume expansion/shrinkage of Sn lattice upon cycling and increase the electrical conductivity. After 315 charge/discharge cycles Sn@carbon anode exhibited high specific capacity of 638 mAh g^?1 with the low capacity fade of average 0.11 mAh g^?1 per cycle. Sn@carbon based anodes was demonstrated to have promising potential for high performance lithium ion batteries application.     

Influence of Silicon Nanoscale Building Blocks Size and Carbon Coating on the Performance of Micro‐Sized Si–C Composite Li‐Ion Anodes

Silicon has been intensively pursued as the most promising anode material for Li‐ion batteries due to its high theoretical capacity of 3579 mAh/g. Micro‐sized Si–C composites composed of nanoscale primary building blocks are attractive Si‐based anodes for practical application because they not only achieve excellent cycling stability, but also offer both gravimetric and volumetric capacity. However, the effects of key parameters in designing such materials on their electrochemical performance are unknown and how to optimize them thus remains to be explored. Herein, the influence of Si nanoscale building block size and carbon coating on the electrochemical performance of the micro‐sized Si–C composites is investigated. It is found that the critical Si building block size is 15 nm, which enables a high capacity without compromising the cycling stability, and that carbon coating at higher temperature improves the first cycle coulombic efficiency (CE) and the rate capability. Corresponding reasons underlying electrochemical performance are revealed by various characterizations. Combining both optimized Si building block size and carbon coating temperature, the resultant composite can sustain 600 cycles at 1.2 A/g with a fixed lithiation capacity of 1200 mAh/g, the best cycling performance with such a high capacity for micro‐sized Si‐based anodes.     

Fast Sodium Storage in TiO2@CNT@C Nanorods for High‐Performance Na‐Ion Capacitors

Na‐ion capacitors have attracted extensive interest due to the combination of the merits of high energy density of batteries and high power density as well as long cycle life of capacitors. Here, a novel Na‐ion capacitor, utilizing TiO₂@CNT@C nanorods as an intercalation‐type anode and biomass‐derived carbon with high surface area as an ion adsorption cathode in an organic electrolyte, is reported. The advanced architecture of TiO₂@CNT@C nanorods, prepared by electrospinning method, demonstrates excellent cyclic stability and outstanding rate capability in half cells. The contribution of extrinsic pseudocapacitance affects the rate capability to a large extent, which is identified by kinetics analysis. A key finding is that ion/electron transfer dynamics of TiO₂@CNT@C could be effectively enhanced due to the addition of multiwalled carbon nanotubes. Also, the biomass‐derived carbon with high surface area displays high specific capacity and excellent rate capability. Owing to the merits of structures and excellent performances of both anode and cathode materials, the assembled Na‐ion capacitors provide an exceptionally high energy density (81.2 W h kg^?1) and high power density (12 400 W kg^?1) within 1.0–4.0 V. Meanwhile, the Na‐ion capacitors achieve 85.3% capacity retention after 5000 cycles tested at 1 A g^?1.     

A Review on Design Strategies for Carbon Based Metal Oxides and Sulfides Nanocomposites for High Performance Li and Na Ion Battery Anodes

Carbon‐oxide and carbon‐sulfide nanocomposites have attracted tremendous interest as the anode materials for Li and Na ion batteries. Such composites are fascinating as they often show synergistic effect compared to their singular components. Carbon nanomaterials are often used as the matrix due to their high conductivity, tensile strength, and chemical stability under the battery condition. Metal oxides and sulfides are often used as active material fillers because of their large capacity. Numerous works have shown that by taking one step further into fabricating nanocomposites with rational structure design, much better performance can be achieved. The present review aims to present and discuss the development of carbon‐based nanocomposite anodes in both Li ion batteries and Na ion batteries. The authors introduce the individual components in the composites, i.e., carbon matrices (e.g., carbon nanotube, graphene) and metal oxides/sulfides; followed by evaluating how advanced nanostructures benefit from the synergistic effect when put together. Particular attention is placed on strategies employed in fabricating such composites, with examples such as yolk–shell structure, layered‐by‐layered structure, and composite comprising one or more carbon matrices. Lastly, the authors conclude by highlighting challenges that still persist and their perspective on how to further develop the technologies.     

Ionically Conductive Self‐Healing Binder for Low Cost Si Microparticles Anodes in Li‐Ion Batteries

A self‐healing polymer (SHP) with abundant hydrogen bonds, appropriate viscoelasticity, and stretchability is a promising binder to improve cycle performance of Si microparticle anodes in lithium (Li) ion batteries. Besides high capacity and long cycle life, efficient rate performance is strongly desirable for practical Si anode implementation. Here, polyethylene glycol (PEG) groups are incorporated into the SHP, facilitating Li ionic conduction within the binder. The concept of the SHP‐PEG binder involves improving the interface between Si microparticles and electrolytes after cycling based on the combination of self‐healing ability and fast Li ionic conduction. Through the systematic study of mixing PEG Mw and ratio, the polymeric binder combining SHP and PEG with M_w 750 in an optimal ratio of 60:40 (mol%) achieves a high discharging capacity of ≈2600 mA h g^?1, reasonable rate performance especially when >1C and maintains 80% of their initial capacity even after ≈150 cycles at 0.5C. The described concept for the polymeric binder, embedding both self‐healing ability and high Li ionic conductivity, should be equally useful for next generation batteries utilizing high capacity materials which suffer from huge volume change during cycling.     

“Water‐in‐Salt” Electrolyte Makes Aqueous Sodium‐Ion Battery Safe,Green, and Long‐Lasting

Narrow electrochemical stability window (1.23 V) of aqueous electrolytes is always considered the key obstacle preventing aqueous sodium‐ion chemistry of practical energy density and cycle life. The sodium‐ion water‐in‐salt electrolyte (NaWiSE) eliminates this barrier by offering a 2.5 V window through suppressing hydrogen evolution on anode with the formation of a Na⁺‐conducting solid‐electrolyte interphase (SEI) and reducing the overall electrochemical activity of water on cathode. A full aqueous Na‐ion battery constructed on Na_0.66[Mn_0.66Ti_0.34]O₂ as cathode and NaTi₂(PO₄)₃ as anode exhibits superior performance at both low and high rates, as exemplified by extraordinarily high Coulombic efficiency (>99.2%) at a low rate (0.2 C) for >350 cycles, and excellent cycling stability with negligible capacity losses (0.006% per cycle) at a high rate (1 C) for >1200 cycles. Molecular modeling reveals some key differences between Li‐ion and Na‐ion WiSE, and identifies a more pronounced ion aggregation with frequent contacts between the sodium cation and fluorine of anion in the latter as one main factor responsible for the formation of a dense SEI at lower salt concentration than its Li cousin.