Quantification of Pseudocapacitive Contribution in Nanocage‐Shaped Silicon–Carbon Composite Anode

Pseudocapacitive materials have been highlighted as promising electrode materials to overcome slow diffusion‐limited redox mechanism in active materials, which impedes fast charging/discharging in energy storage devices. However, previously reported pseudocapacitive properties have been rarely used in lithium‐ion batteries (LIBs) and evaluation methods have been limited to those focused on thin‐film‐type electrodes. Hence, a nanocage‐shaped silicon–carbon composite anode is proposed with excellent pseudocapacitive qualities for LIB applications. This composite anode exhibits a superior rate capability compared to other Si‐based anodes, including commercial silicon nanoparticles, because of the higher pseudocapacitive contribution coming from ultrathin Si layer. Furthermore, unprecedent 3D pore design in cage shape, which prevents the particle scale expansion even after full lithiation demonstrates the high cycling stability. This concept can potentially be used to realize high‐power and high‐energy LIB anode materials.     

Iron‐Oxide‐Based Advanced Anode Materials for Lithium‐Ion Batteries

Iron oxides, such as Fe₂O₃ and Fe₃O₄, have recently received increased attention as very promising anode materials for rechargeable lithium‐ion batteries (LIBs) because of their high theoretical capacity, non‐toxicity, low cost, and improved safety. Nanostructure engineering has been demonstrated as an effective approach to improve the electrochemical performance of electrode materials. Here, recent research progress in the rational design and synthesis of diverse iron oxide‐based nanomaterials and their lithium storage performance for LIBs, including 1D nanowires/rods, 2D nanosheets/flakes, 3D porous/hierarchical architectures, various hollow structures, and hybrid nanostructures of iron oxides and carbon (including amorphous carbon, carbon nanotubes, and graphene). By focusing on synthesis strategies for various iron‐oxide‐based nanostructures and the impacts of nanostructuring on their electrochemical performance, novel approaches to the construction of iron‐oxide‐based nanostructures are highlighted and the importance of proper structural and compositional engineering that leads to improved physical/chemical properties of iron oxides for efficient electrochemical energy storage is stressed. Iron‐oxide‐based nanomaterials stand a good chance as negative electrodes for next generation LIBs.     

High‐Performance Silicon Anodes Enabled By Nonflammable Localized High‐Concentration Electrolytes

Silicon anodes are regarded as one of the most promising alternatives to graphite for high energy‐density lithium‐ion batteries (LIBs), but their practical applications have been hindered by high volume change, limited cycle life, and safety concerns. In this work, nonflammable localized high‐concentration electrolytes (LHCEs) are developed for Si‐based anodes. The LHCEs enable the Si anodes with significantly enhanced electrochemical performances comparing to conventional carbonate electrolytes with a high content of fluoroethylene carbonate (FEC). The LHCE with only 1.2 wt% FEC can further improve the long‐term cycling stability of Si‐based anodes. When coupled with a LiNi_0.3Mn_0.3Co_0.3O₂ cathode, the full cells using this nonflammable LHCE can maintain >90% capacity after 600 cycles at C/2 rate, demonstrating excellent rate capability and cycling stability at elevated temperatures and high loadings. This work casts new insights in electrolyte development from the perspective of in situ Si/electrolyte interphase protection for high energy‐density LIBs with Si anodes.     

One‐to‐One Comparison of Graphite‐Blended Negative Electrodes Using Silicon Nanolayer‐Embedded Graphite versus Commercial Benchmarking Materials for High‐Energy Lithium‐Ion Batteries

While existing carbonaceous anodes for lithium–ion batteries (LIBs) are approaching a practical capacitive limit, Si has been extensively examined as a potential alternative because it shows exceptional gravimetric capacity (3579 mA h g^?1) and abundance. However, the actual implementation of Si anodes is impeded by difficulties in electrode calendering processes and requirements for excessive binding and conductive agents, arising from the brittleness, large volume expansion (>300%), and low electrical conductivity (1.56 × 10^?3 S m^?1) of Si. In one rational approach to using Si in high‐energy LIBs, mixing Si‐based materials with graphite has attracted attention as a feasible alternative for next‐generation anodes. In this study, graphite‐blended electrodes with Si nanolayer‐embedded graphite/carbon (G/SGC) are demonstrated and detailed one‐to‐one comparisons of these electrodes with industrially developed benchmarking samples are performed under the industrial electrode density (>1.6 g cc^?1), areal capacity (>3 mA h cm^?2), and a small amount of binder (3 wt%) in a slurry. Because of the favorable compatibility between SGC and conventional graphite, and the well‐established structural features of SGC, great potential is envisioned. Since this feasible study utilizes realistic test methods and criteria, the rigorous benchmarking comparison presents a comprehensive understanding for developing and characterizing Si‐based anodes for practicable high‐energy LIBs.     

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.     

Graphene‐Containing Nanomaterials for Lithium‐Ion Batteries

Graphene‐containing nanomaterials have emerged as important candidates for electrode materials in lithium‐ion batteries (LIBs) due to their unique physical properties. In this review, a brief introduction to recent developments in graphene‐containing nanocomposite electrodes and their derivatives is provided. Subsequently, synthetic routes to nanoparticle/graphene composites and their electrochemical performance in LIBs are highlighted, and the current state‐of‐the‐art and most recent advances in the area of graphene‐containing nanocomposite electrode materials are summarized. The limitations of graphene‐containing materials for energy storage applications are also discussed, with an emphasis on anode and cathode materials. Potential research directions for the future development of graphene‐containing nanocomposites are also presented, with an emphasis placed on practicality and scale‐up considerations for taking such materials from benchtop curiosities to commercial products.     

Interweaving 3D Network Binder for High‐Areal‐Capacity Si Anode through Combined Hard and Soft Polymers

Si anodes suffer an inherent volume expansion problem. The consensus is that hydrogen bonds in these anodes are preferentially constructed between the binder and Si powder for enhanced adhesion and thus can improve cycling performance. There has been little research done in the field of understanding the contribution of the binder's mechanical properties to performance. Herein, a simple but effective strategy is proposed, combining hard/soft polymer systems, to exploit a robust binder with a 3D interpenetrating binding network (3D‐IBN) via an in situ polymerization. The 3D‐IBN structure is constructed by interweaving a hard poly(furfuryl alcohol) as the skeleton with a soft polyvinyl alcohol (PVA) as the filler, buffering the dramatic volume change of the Si anode. The resulting Si anode delivers an areal capacity of >10 mAh cm^?2 and enables an energy density of >300 Wh kg^?1 in a full lithium‐ion battery (LIB) cell. The component of the interweaving binder can be switched to other polymers, such as replacing PVA by thermoplastic polyurethane and styrene butadiene styrene. Such a strategy is also effective for other high‐capacity electroactive materials, e.g., Fe₂O₃ and Sn. This finding offers an alternative approach in designing high‐areal‐capacity electrodes through combined hard and soft polymer binders for high‐energy‐density LIBs.     

Structure Design and Composition Engineering of Carbon‐Based Nanomaterials for Lithium Energy Storage

Carbon‐based nanomaterials have significantly pushed the boundary of electrochemical performance of lithium‐based batteries (LBs) thanks to their excellent conductivity, high specific surface area, controllable morphology, and intrinsic stability. Complementary to these inherent properties, various synthetic techniques have been adopted to prepare carbon‐based nanomaterials with diverse structures and different dimensionalities including 1D nanotubes and nanorods, 2D nanosheets and films, and 3D hierarchical architectures, which have been extensively applied as high‐performance electrode materials for energy storage and conversion. The present review aims to outline the structural design and composition engineering of carbon‐based nanomaterials as high‐performance electrodes of LBs including lithium‐ion batteries, lithium–sulfur batteries, and lithium–oxygen batteries. This review mainly focuses on the boosting of electrochemical performance of LBs by rational dimensional design and porous tailoring of advanced carbon‐based nanomaterials. Particular attention is also paid to integrating active materials into the carbon‐based nanomaterials, and the structure–performance relationship is also systematically discussed. The developmental trends and critical challenges in related fields are summarized, which may inspire more ideas for the design of advanced carbon‐based nanostructures with superior properties.     

Recent Advances in Rechargeable Magnesium‐Based Batteries for High‐Efficiency Energy Storage

Benefiting from higher volumetric capacity, environmental friendliness and metallic dendrite‐free magnesium (Mg) anodes, rechargeable magnesium batteries (RMBs) are of great importance to the development of energy storage technology beyond lithium‐ion batteries (LIBs). However, their practical applications are still limited by the absence of suitable electrode materials, the sluggish kinetics of Mg²⁺ insertion/extraction and incompatibilities between electrodes and electrolytes. Herein, a systematic and insightful review of recent advances in RMBs, including intercalation‐based cathode materials and conversion reaction‐based compounds is presented. The relationship between microstructures with their electrochemical performances is comprehensively elucidated. In particular, anode materials are discussed beyond metallic Mg for RMBs. Furthermore, other Mg‐based battery systems are also summarized, including Mg–air batteries, Mg–sulfur batteries, and Mg–iodine batteries. This review provides a comprehensive understanding of Mg‐based energy storage technology and could offer new strategies for designing high‐performance rechargeable magnesium batteries.     

Transition Metal Oxide Anodes for Electrochemical Energy Storage in Lithium‐ and Sodium‐Ion Batteries

Lithium‐ion batteries (LIBs) with outstanding energy and power density have been extensively investigated in recent years, rendering them the most suitable energy storage technology for application in emerging markets such as electric vehicles and stationary storage. More recently, sodium, one of the most abundant elements on earth, exhibiting similar physicochemical properties as lithium, has been gaining increasing attention for the development of sodium‐ion batteries (SIBs) in order to address the concern about Li availability and cost—especially with regard to stationary applications for which size and volume of the battery are of less importance. Compared with traditional intercalation reactions, conversion reaction‐based transition metal oxides (TMOs) are prospective anode materials for rechargeable batteries thanks to their low cost and high gravimetric specific capacities. In this review, the recent progress and remaining challenges of conversion reactions for LIBs and SIBs are discussed, covering an overview about the different synthesis methods, morphological characteristics, as well as their electrochemical performance. Potential future research directions and a perspective toward the practical application of TMOs for electrochemical energy storage are also provided.     

All‐Nanomat Lithium‐Ion Batteries: A New Cell Architecture Platform for Ultrahigh Energy Density and Mechanical Flexibility

The ongoing surge in demand for high‐energy/flexible rechargeable batteries relentlessly drives technological innovations in cell architecture as well as electrochemically active materials. Here, a new class of all‐nanomat lithium‐ion batteries (LIBs) based on 1D building element‐interweaved heteronanomat skeletons is demonstrated. Among various electrode materials, silicon (Si, for anode) and overlithiated layered oxide (OLO, for cathode) materials are chosen as model systems to explore feasibility of this new cell architecture and achieve unprecedented cell capacity. Nanomat electrodes, which are completely different from conventional slurry‐cast electrodes, are fabricated through concurrent electrospinning (for polymeric nanofibers) and electrospraying (for electrode materials/carbon nanotubes (CNTs)). Si (or rambutan‐shaped OLO/CNT composite) powders are compactly embedded in the spatially interweaved polymeric nanofiber/CNT heteromat skeletons that play a crucial role in constructing 3D‐bicontinuous ion/electron transport pathways and allow for removal of metallic foil current collectors. The nanomat Si anodes and nanomat OLO cathodes are assembled with nanomat Al₂O₃ separators, leading to the fabrication of all‐nanomat LIB full cells. Driven by the aforementioned structural/chemical uniqueness, the all‐nanomat full cell shows exceptional improvement in electrochemical performance (notably, cell‐based gravimetric energy density = 479 W h kg_Cell^?1) and also mechanical deformability, which lie far beyond those achievable with conventional LIB technologies.     

Hierarchical Structures Based on Two‐Dimensional Nanomaterials for Rechargeable Lithium Batteries

Two‐dimensional (2D) nanomaterials (i.e., graphene and its derivatives, transition metal oxides and transition metal dichalcogenides) are receiving a lot attention in energy storage application because of their unprecedented properties and great diversities. However, their re‐stacking or aggregation during the electrode fabrication process has greatly hindered their further developments and applications in rechargeable lithium batteries. Recently, rationally designed hierarchical structures based on 2D nanomaterials have emerged as promising candidates in rechargeable lithium battery applications. Numerous synthetic strategies have been developed to obtain hierarchical structures and high‐performance energy storage devices based on these hierarchical structure have been realized. This review summarizes the synthesis and characteristics of three styles of hierarchical architecture, namely three‐dimensional (3D) porous network nanostructures, hollow nanostructures and self‐supported nanoarrays, presents the representative applications of hierarchical structured nanomaterials as functional materials for lithium ion batteries, lithium‐sulfur batteries and lithium‐oxygen batteries, meanwhile sheds light particularly on the relationship between structure engineering and improved electrochemical performance; and provides the existing challenges and the perspectives for this fast emerging field.     

Sodium‐Ion Battery Materials and Electrochemical Properties Reviewed

The demand for electrochemical energy storage technologies is rapidly increasing due to the proliferation of renewable energy sources and the emerging markets of grid‐scale battery applications. The properties of batteries are ideal for most electrical energy storage (EES) needs, yet, faced with resource constraints, the ability of current lithium‐ion batteries (LIBs) to match this overwhelming demand is uncertain. Sodium‐ion batteries (SIBs) are a novel class of batteries with similar performance characteristics to LIBs. Since they are composed of earth‐abundant elements, cheaper and utility scale battery modules can be assembled. As a result of the learning curve in the LIB technology, a phenomenal progression in material development has been realized in the SIB technology. In this review, innovative strategies used in SIB material development, and the electrochemical properties of anode, cathode, and electrolyte combinations are elucidated. Attractive performance characteristics are herein evidenced, based on comparative gravimetric and volumetric energy densities to state‐of‐the‐art LIBs. In addition, opportunities and challenges toward commercialization are herein discussed based on patent data trend analysis. With extensive industrial adaptations expected, the commercial prospects of SIBs look promising and this once discarded technology is set to play a major role in EES applications.     

An Antiaging Electrolyte Additive for High‐Energy‐Density Lithium‐Ion Batteries

High‐capacity Li‐rich layered oxide cathodes along with Si‐incorporated graphite anodes have high reversible capacity, outperforming the electrode materials used in existing commercial products. Hence, they are potential candidates for the development of high‐energy‐density lithium‐ion batteries (LIBs). However, structural degradation induced by loss of interfacial stability is a roadblock to their practical use. Here, the use of malonic acid‐decorated fullerene (MA‐C₆₀) with superoxide dismutase activity and water scavenging capability as an electrolyte additive to overcome the structural instability of high‐capacity electrodes that hampers the battery quality is reported. Deactivation of PF₅ by water scavenging leads to the long‐term stability of the interfacial structures of electrodes. Moreover, an MA‐C₆₀‐added electrolyte deactivates the reactive oxygen species and constructs an electrochemically robust cathode‐electrolyte interface for Li‐rich cathodes. This work paves the way for new possibilities in the design of electrolyte additives by eliminating undesirable reactive substances and tuning the interfacial structures of high‐capacity electrodes in LIBs.     

Ultrahigh‐Energy‐Density Lithium‐Ion Batteries Based on a High‐Capacity Anode and a High‐Voltage Cathode with an Electroconductive Nanoparticle Shell

The combination of high‐capacity anodes and high‐voltage cathodes has garnered a great deal of attention in the pursuit of high‐energy‐density lithium‐ion batteries. As a facile and scalable electrode‐architecture strategy to achieve this goal, a direct one‐pot decoration of high‐capacity silicon (Si) anode materials and of high‐voltage LiCoO₂ (LCO) cathode materials is demonstrated with colloidal nanoparticles composed of electroconductive antimony‐doped tin oxide (ATO). The unusual ATO nanoparticle shells enhance electronic conduction in the LCO and Si electrode materials and mitigate unwanted interfacial side reactions between the electrode materials and liquid electrolytes. The ATO‐coated LCO materials (ATO‐LCO) enable the construction of a high‐mass‐loading cathode and suppress the dissolution of cobalt and the generation of by‐products during high‐voltage cycling. In addition, the ATO‐coated Si (ATO‐Si) anodes exhibit highly stable capacity retention upon cycling. Integration of the high‐voltage ATO‐LCO cathode and high‐capacity ATO‐Si anode into a full cell configuration brings unprecedented improvements in the volumetric energy density and in the cycling performance compared to a commercialized cell system composed of LCO/graphite.     

Biomaterials for High‐Energy Lithium‐Based Batteries: Strategies,Challenges, and Perspectives

Developing high‐performance batteries through applying renewable resources is of great significance for meeting ever‐growing energy demands and sustainability requirements. Biomaterials have overwhelming advantages in material abundance, environmental benignity, low cost, and more importantly, multifunctionalities from structural and compositional diversity. Therefore, significant and fruitful research on exploiting various natural biomaterials (e.g., soy protein, chitosan, cellulose, fungus, etc.) for boosting high‐energy lithium‐based batteries by means of making or modifying critical battery components (e.g., electrode, electrolyte, and separator) are reported. In this review, the recent advances and main strategies for adopting biomaterials in electrode, electrolyte, and separator engineering for high‐energy lithium‐based batteries are comprehensively summarized. The contributions of biomaterials to stabilizing electrodes, capturing electrochemical intermediates, and protecting lithium metal anodes/enhancing battery safety are specifically emphasized. Furthermore, advantages and challenges of various strategies for fabricating battery materials via biomaterials are described. Finally, future perspectives and possible solutions for further development of biomaterials for high‐energy lithium‐based batteries are proposed.     

All‐Solid‐State Lithium‐Ion Microbatteries Using Silicon Nanofilm Anodes: High Performance and Memory Effect

All‐solid‐state thin film lithium batteries are promising devices to power the next generations of autonomous microsystems. Nevertheless, some industrial constraints such as the resistance to reflow soldering (260 °C) and to short‐circuiting necessitate the replacement of the lithium anode. In this study, a 2 V lithium‐ion system based on amorphous silicon nanofilm anodes (50–200 nm thick), a LiPON electrolyte, and a new lithiated titanium oxysulfide cathode Li_1.2TiO_0.5S_2.1 is prepared by sputtering. The determination of the electrochemical behavior of each active material and of whole systems with different configurations allows the highlighting of the particular behavior of the Li_xSi electrode and the understanding of its consequences on the performance of Li‐ion cells. Lithium‐ion microbatteries processed with industrial tools and embedded in microelectronic packages exhibit particularly high cycle life (?0.006% cycle^?1), ultrafast charge (80% capacity in 1 min), and tolerate both short‐circuiting and reflow soldering. Moreover, the perfect stability of the system allows the assignment of some modifications of the voltage curve and a slow and reversible capacity fade occurring in specific conditions, to the formation of Li₁₅Si₄ and to the expression of a “memory effect.” These new findings will help to optimize the design of future Li‐ion systems using nanosized silicon anodes.     

Ultrahigh‐Capacity and Fire‐Resistant LiFePO4‐Based Composite Cathodes for Advanced Lithium‐Ion Batteries

The growing demand for advanced energy storage devices with high energy density and high safety has continuously driven the technical upgrades of cell architectures as well as electroactive materials. Designing thick electrodes with more electroactive materials is a promising strategy to improve the energy density of lithium‐ion batteries (LIBs) without alternating the underlying chemistry. However, the progress toward thick, high areal capacity electrodes is severely limited by the sluggish electronic/ionic transport and easy deformability of conventional electrodes. A self‐supported ultrahigh‐capacity and fire‐resistant LiFePO₄ (UCFR‐LFP)‐based nanocomposite cathode is demonstrated here. Benefiting from the structural and chemical uniqueness, the UCFR‐LFP electrodes demonstrate exceptional improvements in electrochemical performance and mass loading of active materials, and thermal stability. Notably, an ultrathick UCFR‐LFP electrode (1.35 mm) with remarkably high mass loading of active materials (108 mg cm^?2) and areal capacity (16.4 mAh cm^?2) is successfully achieved. Moreover, the 1D inorganic binder‐like ultralong hydroxyapatite nanowires (HAP NWs) enable the UCFR‐LFP electrode with excellent thermal stability (structural integrity up to 1000 °C and electrochemical activity up to 750 °C), fire‐resistance, and wide‐temperature operability. Such a unique UCFR‐LFP electrode offers a promising solution for next‐generation LIBs with high energy density, high safety, and wide operating‐temperature window.     

Nanoflake‐Assembled Hierarchical Na3V2(PO4)3/C Microflowers: Superior Li Storage Performance and Insertion/Extraction Mechanism

Na₃V₂(PO₄)₃ (NVP) has excellent electrochemical stability and fast ion diffusion coefficient due to the 3D Na⁺ ion superionic conductor framework, which make it an attractive cathode material for lithium ion batteries (LIBs). However, the electrochemical performance of NVP needs to be further improved for applications in electric vehicles and hybrid electric vehicles. Here, nanoflake‐assembled hierarchical NVP/C microflowers are synthesized using a facile method. The structure of as‐synthesized materials enhances the electrochemical performance by improving the electron conductivity, increasing electrode–electrolyte contact area, and shortening the diffusion distance. The as‐synthesized material exhibits a high capacity (230 mAh g^?1), excellent cycling stability (83.6% of the initial capacity is retained after 5000 cycles), and remarkable rate performance (91 C) in hybrid LIBs. Meanwhile, the hybrid LIBs with the structure of NVP || 1 m LiPF₆/EC (ethylene carbonate) + DMC (dimethyl carbonate) || NVP and Li₄Ti₅O₁₂ || 1 m LiPF₆/EC + DMC || NVP are assembled and display capacities of 79 and 73 mAh g^?1, respectively. The insertion/extraction mechanism of NVP is systematically investigated, based on in situ X‐ray diffraction. The superior electrochemical performance, the design of hybrid LIBs, and the insertion/extraction mechanism investigation will have profound implications for developing safe and stable, high‐energy, and high‐power LIBs.     

Advanced Electrolytes for Fast‐Charging High‐Voltage Lithium‐Ion Batteries in Wide‐Temperature Range

LiNi_xMn_yCo_1?x?yO₂ (NMC) cathode materials with Ni ≥ 0.8 have attracted great interest for high energy‐density lithium‐ion batteries (LIBs) but their practical applications under high charge voltages (e.g., 4.4 V and above) still face significant challenges due to severe capacity fading by the unstable cathode/electrolyte interface. Here, an advanced electrolyte is developed that has a high oxidation potential over 4.9 V and enables NMC811‐based LIBs to achieve excellent cycling stability in 2.5–4.4 V at room temperature and 60 °C, good rate capabilities under fast charging and discharging up to 3C rate (1C = 2.8 mA cm^?2), and superior low‐temperature discharge performance down to ?30 °C with a capacity retention of 85.6% at C/5 rate. It is also demonstrated that the electrode/electrolyte interfaces, not the electrolyte conductivity and viscosity, govern the LIB performance. This work sheds light on a very promising strategy to develop new electrolytes for fast‐charging high‐energy LIBs in a wide‐temperature range.