Stress‐Relieved Nanowires by Silicon Substitution for High‐Capacity and Stable Lithium Storage

Silicon is promising as a high energy anode for next‐generation lithium‐ion batteries. However, severe capacity fading upon cycling associated with huge volume change is still an obstacle for silicon toward practical applications. Herein, the authors report that Si‐substituted Zn₂(GeO₄)_0.8(SiO₄)_0.2 nanowires can effectively suppress volume expansion effect, exhibiting high specific capacity (1274 mA h g^?1 at 0.2 A g^?1 after 700 cycles) and ultralong cycling stability (2000 cycles at 5 A g^?1 with a capacity decay rate of 0.008% per cycle), which represents outstanding comprehensive performance. The superior performance is ascribed to the substitution of Si atom that imparts to the nanowires not only high reactivity and reversibility, but also the unique stress‐relieved property upon lithiation which is further confirmed by detailed density‐functional theory computation. This work provides a new guideline for designing high‐performance Si‐based materials toward practical energy storage applications.     

Fast‐Charging and Ultrahigh‐Capacity Lithium Metal Anode Enabled by Surface Alloying

Li metal anodes are going through a great revival but they still encounter grand challenges. One often neglected issue is that most reported Li metal anodes are only cyclable under relatively low current density (<5 mA cm^?2) and small areal capacity (<5 mAh cm^?2), which essentially limits their high‐power applications and results in ineffective Li utilization (<1%). Herein, it is reported that surface alloyed Li metal anodes can enable reversible cycling with ultrafast rate and ultralarge areal capacity. Low‐cost Si wafers are used and are chemically etched down to 20–30 µm membranes. Simply laminating a Si membrane onto Li foil results in the formation of Li_xSi alloy film fused onto Li metal with mechanical robustness and high Li‐ion conductivity. Symmetric cell measurements show that the surface alloyed Li anode has excellent cycling stability, even under high current density up to 25 mA cm^?2 and unprecedented areal capacity up to 100 mAh cm^?2. Furthermore, the surface alloyed Li anode is paired with amorphous MoS₃ cathode and achieves remarkable full‐cell performance.     

Densification by Compaction as an Effective Low‐Cost Method to Attain a High Areal Lithium Storage Capacity in a CNT@Co3O4 Sponge

Achieving a high areal capacity is essential for the transfer of outstanding laboratory electrode results to commercial applications and also to ensure there exists a capacity matched cathode and anode for a properly tuned battery. Despite intensive efforts, most electrode materials exhibit areal capacities lower than that of the graphite anodes (4 mA h cm^?2). An effective and low‐cost approach is reported to attain a high areal capacity via an intense densification by compacting a porous carbon nanotube sponge grafted with Co₃O₄ nanoparticles. The hybrid sponge can be compacted to a large degree (up to a tenfold densification) while still keeping its structural integrity and the 3D porous network. This method allows achieving a mass loading of up ?to 14.3 mg cm^?2 and an areal capacity of 12 mA h cm^?2 (at a current density of 200 mA g^?1) together with a gravimetric capacity of >800 mA h g^?1. This densification by compaction approach offers an effective and low‐cost strategy to develop high mass loading and areal capacity electrodes for practical energy storage systems.     

H2V3O8 Nanowire/Graphene Electrodes for Aqueous Rechargeable Zinc Ion Batteries with High Rate Capability and Large Capacity

Aqueous rechargeable zinc ion batteries are considered a promising candidate for large‐scale energy storage owing to their low cost and high safety nature. A composite material comprised of H₂V₃O₈ nanowires (NWs) wrapped by graphene sheets and used as the cathode material for aqueous rechargeable zinc ion batteries is developed. Owing to the synergistic merits of desirable structural features of H₂V₃O₈ NWs and high conductivity of the graphene network, the H₂V₃O₈ NW/graphene composite exhibits superior zinc ion storage performance including high capacity of 394 mA h g^?1 at 1/3 C, high rate capability of 270 mA h g^?1 at 20 C and excellent cycling stability of up to 2000 cycles with a capacity retention of 87%. The battery offers a high energy density of 168 W h kg^?1 at 1/3 C and a high power density of 2215 W kg^?1 at 20 C (calculated based on the total weight of H₂V₃O₈ NW/graphene composite and the theoretically required amount of Zn). Systematic structural and elemental characterization confirm the reversible Zn²⁺ and water cointercalation electrochemical reaction mechanism. This work brings a new prospect of designing high‐performance aqueous rechargeable zinc ion batteries for grid‐scale energy storage.     

Hierarchical Zn–Co–S Nanowires as Advanced Electrodes for All Solid State Asymmetric Supercapacitors

A facile two‐step strategy is developed to design the large‐scale synthesis of hierarchical, unique porous architecture of ternary metal hydroxide nanowires grown on porous 3D Ni foam and subsequent effective sulfurization. The hierarchical Zn–Co–S nanowires (NWs) arrays are directly employed as an electrode for supercapacitors application. The as‐synthesized Zn–Co–S NWs deliver an ultrahigh areal capacity of 0.9 mA h cm^?2 (specific capacity of 366.7 mA h g^?1) at a current density of 3 mA cm^?2, with an exceptional rate capability (≈227.6 mA h g^?1 at a very high current density of 40 mA cm^?2) and outstanding cycling stability (≈93.2% of capacity retention after 10 000 cycles). Most significantly, the assembled Zn–Co–S NWs//Fe₂O₃@reduced graphene oxide asymmetric supercapacitors with a wide operating potential window of ≈1.6 V yield an ultrahigh volumetric capacity of ≈1.98 mA h cm^?3 at a current density of 3 mA cm^?2, excellent energy density of ≈81.6 W h kg^?1 at a power density of ≈559.2 W kg^?1, and exceptional cycling performance (≈92.1% of capacity retention after 10 000 cycles). This general strategy provides an alternative to design the other ternary metal sulfides, making it facile, free‐standing, binder‐free, and cost‐effective ternary metal sulfide‐based electrodes for large‐scale applications in modern electronics.     

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.     

Novel K3V2(PO4)3/C Bundled Nanowires as Superior Sodium‐Ion Battery Electrode with Ultrahigh Cycling Stability

Sodium‐ion battery has captured much attention due to the abundant sodium resources and potentially low cost. However, it suffers from poor cycling stability and low diffusion coefficient, which seriously limit its widespread application. Here, K₃V₂(PO₄)₃/C bundled nanowires are fabricated usinga facile organic acid‐assisted method. With a highly stable framework, nanoporous structure, and conductive carbon coating, the K₃V₂(PO₄)₃/C bundled nanowires manifest excellent electrochemical performances in sodium‐ion battery. A stable capacity of 119 mAh g^?1 can be achieved at 100 mA g^?1. Even at a high current density of 2000 mA g^?1, 96.0% of the capacity can be retained after 2000 charge–discharge cycles. Comparing with K₃V₂(PO₄)₃/C blocks, the K₃V₂(PO₄)₃/C bundled nanowires show significantly improved cycling stability. This work provides a facile and effective approach to enhance the electrochemical performance of sodium‐ion batteries.     

3D Nanowire Arrayed Cu Current Collector toward Homogeneous Alloying Anode Deposition for Enhanced Sodium Storage

Alloying electrodes are regarded as promising anodes for lithium/sodium storage thanks to their multielectron reaction capacity, moderate voltage plateau, and high electrical conductivity. However, huge volume change upon cycling, especially for sodium storage, usually causes the loss of electrical connection between active components and their delaminations from traditional current collectors, thus leading to rapid capacity decay. Herein, a unique 3D current collector is assembled from 1D nanowire arrays anchored on 3D porous Cu foams for constructing core‐shelled Cu@Sb nanowires as advanced sodium‐ion battery (SIB) anodes. The so‐formed hierarchical 3D anode with interconnected 3D micrometer sized pores and abundant voids between nanowires not only effectively accommodates the structural strains during repeated cycling but also ensures the structural integrity and contributes to a uniform ion/electron scattered distribution throughout the whole surface. When employed as anodes for SIBs, the obtained electrode shows a high capacity of 605.3 mAh g^?1 at 330 mA g^?1, and demonstrates a high capacity retention of 84.8% even at a high current density of 3300 mA g^?1. The 3D nanowire arrayed Cu current collector in this work can offer a promising strategy for designing and building advanced alloy anodes for lithium/sodium storage.     

Rationally Designed Hierarchical TiO2@Fe2O3 Hollow Nanostructures for Improved Lithium Ion Storage

Hollow and hierarchical nanostructures have received wide attention in new‐generation, high‐performance, lithium ion battery (LIB) applications. Both TiO₂ and Fe₂O₃ are under current investigation because of their high structural stability (TiO₂) and high capacity (Fe₂O₃), and their low cost. Here, we demonstrate a simple strategy for the fabrication of hierarchical hollow TiO₂@Fe₂O₃ nanostructures for the application as LIB anodes. Using atomic layer deposition (ALD) and sacrificial template‐assisted hydrolysis, the resulting nanostructure combines a large surface area with a hollow interior and robust structure. As a result, such rationally designed LIB anodes exhibit a high reversible capacity (initial value 840 mAh g^?1), improved cycle stability (530 mAh g^?1 after 200 cycles at the current density of 200 mA g^?1), as well as outstanding rate capability. This ALD‐assisted fabrication strategy can be extended to other hierarchical hollow metal oxide nanostructures for favorable applications in electrochemical and optoelectronic devices.     

Black Phosphorus Quantum Dot/Ti3C2 MXene Nanosheet Composites for Efficient Electrochemical Lithium/Sodium‐Ion Storage

The exploration of new and efficient energy storage mechanisms through nanostructured electrode design is crucial for the development of high‐performance rechargeable batteries. Herein, black phosphorus quantum dots (BPQDs) and Ti₃C₂ nanosheets (TNSs) are employed as battery and pseudocapacitive components, respectively, to construct BPQD/TNS composite anodes with a novel battery‐capacitive dual‐model energy storage (DMES) mechanism for lithium‐ion and sodium‐ion batteries. Specifically, as a battery‐type component, BPQDs anchored on the TNSs are endowed with improved conductivity and relieved stress upon cycling, enabling a high‐capacity and stable energy storage. Meanwhile, the pseudocapacitive TNS component with further atomic charge polarization induced by P? O? Ti interfacial bonds between the two components allows enhanced charge adsorption and efficient interfacial electron transfer, contributing a higher pseudocapacitive value and fast energy storage. The DMES mechanism is evidenced by substantial characterizations of X‐ray photoelectron spectroscopy and X‐ray absorption fine structure spectroscopy, density functional theory calculations, and kinetics analyses. Consequently, the composite electrode exhibits superior battery performance, especially for lithium storage, such as high capacity (910 mAh g^?1 at 100 mA g^?1), long cycling stability (2400 cycles with a capacity retention over 100%), and high rate capability, representing the best comprehensive battery performance in BP‐based anodes to date.     

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.     

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.     

Plating/Stripping Behavior of Actual Lithium Metal Anode

Lithium (Li) metal anodes exhibits the potential to enable rechargeable Li batteries with a high energy density. However, the irreversible plating and stripping behaviors of Li metal anodes with high reactivity and dendrite growth when matching different cathodes in working cells are not fully understood yet. Herein the working manner of very thin Li metal anodes (50 µm, 10 mAh cm^?2) is probed with different sequences of Li plating and stripping at 3.0 mA cm^?2 and 3.0 mAh cm^?2. Dendrite growth and dead Li forms on the surface of the initially plated Li electrode (P‐Li), while Li dendrites form in the pit of the initially stripped Li electrode (S‐Li). This induces the differences in reactive sites, distribution of dead Li, and voltage polarization of Li metal anodes. There is a gap of 15–20 and 13–16 mV for the end voltages between S‐Li and P‐Li during stripping and plating, respectively. When matching LiFePO₄ and FePO₄ cathodes, P‐Li | LiFePO₄ cells exhibit a 30‐cycle longer lifespan with smaller end polarization due to differences in the sequences of Li plating and stripping. This contribution affords emerging working principles for actual Li metal anodes when matching lithium‐containing and lithium‐free cathodes.     

High Polarity Poly(vinylidene difluoride) Thin Coating for Dendrite‐Free and High‐Performance Lithium Metal Anodes

The high‐polarity β‐phase poly(vinylidene difluoride) (β‐PVDF), which has all trans conformation with F and H atoms located on the opposite sides of the polymer backbone, is demonstrated to be a promising artificial solid‐electrolyte interphase coating on both Cu and Li metal anodes for dendrite‐free Li deposition/stripping and enhanced cycling performance. A thin (≈4 µm) β‐PVDF coating on Cu enables uniform Li deposition/stripping at high current densities up to 5 mA cm^?2, Li‐plating capacity loadings of up to 4 mAh cm^?2, and excellent cycling stability over hundreds of cycles under practical conditions (1 mA cm^?2 with 2 mAh cm^?2). Full cells containing an LiFePO₄ cathode and an anode of either β‐PVDF coated Cu or Li also exhibit excellent cycling stability. The profound effects of the high‐polarity PVDF coating on dendrite suppression are attributed to the electronegative F‐rich interface that favors layer‐by‐layer Li deposition. This study offers a new strategy for the development of dendrite‐free metal anode technology.     

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.     

Confined Fe2VO4⊂Nitrogen‐Doped Carbon Nanowires with Internal Void Space for High‐Rate and Ultrastable Potassium‐Ion Storage

Developing low‐cost, high‐capacity, high‐rate, and robust earth‐abundant electrode materials for energy storage is critical for the practical and scalable application of advanced battery technologies. Herein, the first example of synthesizing 1D peapod‐like bimetallic Fe₂VO₄ nanorods confined in N‐doped carbon porous nanowires with internal void space (Fe₂VO₄?NC nanopeapods) as a high‐capacity and stable anode material for potassium‐ion batteries (KIBs) is reported. The peapod‐like Fe₂VO₄?NC nanopeapod heterostructures with interior void space and external carbon shell efficiently prevent the aggregation of the active materials, facilitate fast transportation of electrons and ions, and accommodate volume variation during the cycling process, which substantially boosts the rate and cycling performance of Fe₂VO₄. The Fe₂VO₄?NC electrode exhibits high reversible specific depotassiation capacity of 380 mAh g^?1 at 100 mA g^?1 after 60 cycles and remarkable rate capability as well as long cycling stability with a high capacity of 196 mAh g^?1 at 4 A g^?1 after 2300 cycles. The first‐principles calculations reveal that Fe₂VO₄?NC nanopeapods have high ionic/electronic conductivity characteristics and low diffusion barriers for K⁺‐intercalation. This study opens up new way for investigating high‐capacity metal oxide as high‐rate and robust electrode materials for KIBs.     

Enhanced Cyclability of Lithium–Oxygen Batteries with Electrodes Protected by Surface Films Induced via In Situ Electrochemical Process

Although the rechargeable lithium–oxygen (Li–O₂) batteries have extremely high theoretical specific energy, the practical application of these batteries is still limited by the instability of their carbon‐based air‐electrode, Li metal anode, and electrodes, toward reduced oxygen species. Here a simple one‐step in situ electrochemical precharging strategy is demonstrated to generate thin protective films on both carbon nanotubes (CNTs), air‐electrodes and Li metal anodes simultaneously under an inert atmosphere. Li–O₂ cells after such pretreatment demonstrate significantly extended cycle life of 110 and 180 cycles under the capacity‐limited protocol of 1000 mA h g^?1 and 500 mA h g^?1, respectively, which is far more than those without pretreatment. The thin‐films formed from decomposition of electrolyte during in situ electrochemical precharging processes in an inert environment, can protect both CNTs air‐electrode and Li metal anode prior to conventional Li–O₂ discharge/charge cycling, where reactive reduced oxygen species are formed. This work provides a new approach for protection of carbon‐based air‐electrodes and Li metal anodes in practical Li–O₂ batteries, and may also be applied to other battery systems.     

High and Reversible Lithium Ion Storage in Self‐Exfoliated Triazole‐Triformyl Phloroglucinol‐Based Covalent Organic Nanosheets

Covalent organic framework (COF) can grow into self‐exfoliated nanosheets. Their graphene/graphite resembling microtexture and nanostructure suits electrochemical applications. Here, covalent organic nanosheets (CON) with nanopores lined with triazole and phloroglucinol units, neither of which binds lithium strongly, and its potential as an anode in Li‐ion battery are presented. Their fibrous texture enables facile amalgamation as a coin‐cell anode, which exhibits exceptionally high specific capacity of ≈720 mA h g^?1 (@100 mA g^?1). Its capacity is retained even after 1000 cycles. Increasing the current density from 100 mA g^?1 to 1 A g^?1 causes the specific capacity to drop only by 20%, which is the lowest among all high‐performing anodic COFs. The majority of the lithium insertion follows an ultrafast diffusion‐controlled intercalation (diffusion coefficient, D_Li⁺ = 5.48 × 10^?11 cm² s^?1). The absence of strong Li‐framework bonds in the density functional theory (DFT) optimized structure supports this reversible intercalation. The discrete monomer of the CON shows a specific capacity of only 140 mA h g^?1 @50 mA g^?1 and no sign of lithium intercalation reveals the crucial role played by the polymeric structure of the CON in this intercalation‐assisted conductivity. The potentials mapped using DFT suggest a substantial electronic driving‐force for the lithium intercalation. The findings underscore the potential of the designer CON as anode material for Li‐ion batteries.     

A Novel Aluminum‐Ion Battery: Al/AlCl3‐[EMIm]Cl/Ni3S2@Graphene

Due to an ever‐increasing demand for electronic devices, rechargeable batteries are attractive for energy storage systems. A novel rechargeable aluminum‐ion battery based on Al³⁺ intercalation and deintercalation is fabricated with Ni₃S₂/graphene microflakes composite as cathode material and high‐purity Al foil as anode. This kind of aluminum‐ion battery comprises of an electrolyte containing AlCl₃ in an ionic liquid of 1‐ethyl‐3‐methylimidazolium chloride ([EMIm]Cl). Galvanostatic charge/discharge measurements have been performed in a voltage range of 0.1–2.0 V versus Al/AlCl₄ ^?. An initial discharge specific capacity of 350 mA h g^?1 at a current density of 100 mA g^?1 is achieved, and the discharge capacity remains over 60 mA h g^?1 and coulombic efficiency of 99% after 100 cycles. Typically, for the current density at 200 mA g^?1, the initial charge and discharge capacities are 300 and 235 mA h g^?1, respectively. More importantly, it should be emphasized that the battery has a high discharge voltage plateau (≈1.0 V vs Al/AlCl₄ ^?). These meaningful results represent a significant step forward in the development of aluminum‐ion batteries.     

Highly Interconnected Si Nanowires for Improved Stability Li‐Ion Battery Anodes

Silicon exhibits the largest known capacity for Li insertion in anodes of Li‐ion batteries. However, because of large volume expansion/phase changes upon alloying, Si becomes powder‐like after a few charge‐discharge cycles. Various approaches have been explored in the past to circumvent this problem, including the use of nanomaterials, particularly Si nanowires. However, even though nanowires resist cracking very well, anodes based on Si nanowires still see their original capacity fade away upon cycling, because of wire detachment from the substrate, due to the stress generated at their roots upon alloying with Li. Here, we present a silicon nanowire growth strategy yielding highly interconnected specimens, which prevents them from being individually detached from the substrate. We report a ～100% charge retention after 40 cycles at C/2 rate, without charging voltage limitation. We also show that our anodes can be cycled at 8C rates without damage and we grow nanowires with a density of 1.2 mg/cm², yielding anodes delivering a 4.2 mAh/cm² charge density. Finally, we point out that a better understanding of the interactions of silicon with electrolytes is needed if the field is to progress in the future.