Air-Stable Porous Fe2N Encapsulated in Carbon Microboxes with High Volumetric Lithium Storage Capacity and a Long Cycle Life

Regulating Electron Filling and Orbital Occupancy of Anti-Bonding States of Transition Metal Nitride Heterojunction for High Areal Capacity Lithium-Sulfur Full Batteries

The commercialization of lithium-sulfur (Li-S) battery is seriously hindered by the shuttle behavior of lithium (Li) polysulfide, slow conversion kinetics, and Li dendrite growth. Herein, a novel hierarchical p-type iron nitride and n-type vanadium nitride (p-Fe2N/n-VN) heterostructure with optimal electronic structure, confined in vesicle-like N-doped nanofibers (p-Fe2N/n-VN⊂PNCF), is meticulously constructed to work as "one stone two birds" dual-functional hosts for both the sulfur cathode and Li anode. As demonstrated, the d-band center of high-spin Fe atom captures more electrons from V atom to realize more π* and moderate σ* bond electron filling and orbital occupation; thus, allowing moderate adsorption intensity for polysulfides and more effective d-p orbital hybridization to improve reaction kinetics. Meanwhile, this unique structure can dynamically balance the deposition and transport of Li on the anode; thereby, more effectively inhibiting Li dendrite growth and promoting the formation of a uniform solid electrolyte interface. The as-assembled Li-S full batteries exhibit the conspicuous capacities and ultralong cycling lifespan over 2000 cycles at 5.0 C. Even at a higher S loading (20 mg cm-2) and lean electrolyte (2.5 µL mg-1), the full cells can still achieve an ultrahigh areal capacity of 16.1 mAh cm-2 after 500 cycles at 0.1 C.

Tailoring 2D carbides and nitrides based photo-catalytic nanomaterials for energy production and storage: a review

2D carbides and nitrides-based nanomaterials because of their unusual physical and chemical properties and a vast range of energy-storage applications have attracted tremendous attention. However, 2D carbides and nitrides-based nanomaterials and their corresponding composites have many intrinsic constraints in terms of energy-storage applications. The nano-engineering of these 2D materials is widely investigated, to improve their performance for practical application. In this Review article, the current progress and research on 2D carbides and nitrides-based nanostructures are presented and debated, concentrating on their methods of preparation, and energy conservation applications for example Lithium-ion-battery, supercapacitors, and Sodium-ion-battery. In conclusion, the problems, and recommendations essential to be discussed for the progress of these 2D nanomaterials for energy-storage applications based on carbides and nitrides are displayed.

Rational Design of Silicon Nanodots/Carbon Anodes by Partial Oxidization Strategy with High-Performance Lithium-Ion Storage

Silicon (Si) is considered a promising anode material for rechargeable lithium-ion batteries (LIBs) due to its high theoretical capacity, low working potential, and safety features. However, the practical use of Si-based anodes is hampered by their huge volume expansion during the process of lithiation/delithiation, and they have relatively low intrinsic electronic conductivity, therefore seriously restricting their application in energy storage. Here, we propose a facile approach to directly transform siliceous biomass (bamboo leaves) into a porous carbon skeleton-wrapped Si nanodot architecture through a partial oxidization strategy and magnesium thermal reaction to obtain a high Si nanodot component composite (denoted as Si/C-O). With the synergistic effect of the porous carbon skeleton structure and uniformly dispersed Si nanodots, the Si/C-O composite anode with a stable structure that can avoid pulverization and accommodate volume expansion during cycling is fabricated. As expected, the biomass-converted Si/C-O anode not only presents a high Si component (59.7 wt %) by TGA but also exhibits an excellent capacity of 1013 mAh g^-1 at 0.5 A g^-1 and robust cycling stability with a capacity retention of 526 mAh g^-1 after 650 cycles. Moreover, the Si/C-O anode demonstrates considerable performance in practical LIBs when assembled with a commercial LiNi_0.8Co_0.1Mn_0.1O₂ cathode. This work provides an effective strategy and long-term insights into the utilization of porous Si-based materials converted by biomass to design and synthesize high-performance LIB materials.

Unveiling the Activity Origin of Iron Nitride as Catalytic Material for Efficient Hydrogenation of CO2 to C2+ Hydrocarbons

Developing efficient catalytic materials and unveiling the active species are significant for selective hydrogenation of CO₂ to C₂₊ hydrocarbons. Fe₂ N@C nanoparticles were reported to exhibit outstanding performance toward selective CO₂ hydrogenation to C₂₊ hydrocarbons (C₂₊ selectivity: 53.96 %; C₂ -C₄ ⁼ selectivity, 31.03 %), outperforming corresponding Fe@C. In situ X-ray diffraction, ex situ Mössbauer and X-ray photoelectron spectra revealed that iron nitrides were in situ converted to highly active iron carbides, which acted as the real active species. Moreover, the combined results of in situ diffuse reflectance infrared Fourier transform spectroscopy and control experiments suggested an in situ formed carbonyl iron-mediated conversion mechanism from iron nitrides to iron carbides.

Iron Nitride@C Nanocubes Inside Core-Shell Fibers to Realize High Air-Stability, Ultralong Life, and Superior Lithium/Sodium Storages

Poor air stability and severe structure pulverization are crucial issues for metal nitrides in metal-ion batteries. Herein, core-shell hybrid fibers (CSHN fiber) filled with metal nitride@C hollow nanocubes are introduced to be a new self-supporting anode for sodium-ion and lithium-ion batteries. The hierarchical carbon network provides fast electronic pathways and gives high protection for iron nitrides. Meanwhile, the self-supporting electrode avoids the complicated electrode fabrication process and decreases the opportunity to air exposure. Moreover, its porous nature ensures high buffer to volumetric expansion and improves the cycling stability. Therefore, it is a good platform to realize fast kinetics and high durability. For the first time, Fe₂N@N-doped carbon CSHN hybrid fibers are constructed. Their influences on air stability and electrochemical behaviors are studied. Impressively, they achieve high stabilities in both lithium-ion (92.8%, at 5 A g^-1, 1000 cycles) and sodium-ion (95.6%, at 2 A g^-1, 2000 cycles) batteries. Therefore, this work introduces a new method to construct superior performance nitride anodes. Moreover, it also provides a new insight on the fabrication of highly efficient structures for diverse functional materials.

The fluorination-assisted dealloying synthesis of porous reduced graphene oxide-FeF2@carbon for high-performance lithium-ion battery and the exploration of its electrochemical mechanism

Based on the dealloying conception, a porous rGO-FeF₂@C is attained and shows a great electrochemical performance. An intriguing phenomenon has been that the decrease in charge cut-off voltage contributes to the higher discharge plateau.

Transition metal nitrides for electrochemical energy applications

This review comprehensively summarizes the progress on the structural and electronic modulation of transition metal nitrides for electrochemical energy applications.

Ultrafast and durable Li/Na storage by an iron selenide anode using an elastic hierarchical structure

An exquisite composite consisting of polycystic FeSe/C microspheres encapsulated within a three-dimensional graphene framework was designed and fabricated for fast and durable Li-/Na-storage applications.

Energy storing bricks for stationary PEDOT supercapacitors

Fired brick is a universal building material, produced by thousand-year-old technology, that throughout history has seldom served any other purpose. Here, we develop a scalable, cost-effective and versatile chemical synthesis using a fired brick to control oxidative radical polymerization and deposition of a nanofibrillar coating of the conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT). A fired brick’s open microstructure, mechanical robustness and ~8 wt% α-Fe₂O₃ content afford an ideal substrate for developing electrochemical PEDOT electrodes and stationary supercapacitors that readily stack into modules. Five-minute epoxy serves as a waterproof case enabling the operation of our supercapacitors while submerged underwater and a gel electrolyte extends cycling stability to 10,000 cycles with ~90% capacitance retention.

Fired brick is a universal building material, produced by thousand-year-old technology, which throughout history has seldom served any other purpose. Here, the authors show that bricks can store energy after chemical treatment to convert their iron oxide content into conducting polymer nanofibers.

Dynamic electrocatalyst with current-driven oxyhydroxide shell for rechargeable zinc-air battery

Recent fruitful studies on rechargeable zinc-air battery have led to emergence of various bifunctional oxygen electrocatalysts, especially metal-based materials. However, their electrocatalytic configuration and evolution pathway during battery operation are rarely spotlighted. Herein, to depict the underlying behaviors, a concept named dynamic electrocatalyst is proposed. By selecting a bimetal nitride as representation, a current-driven “shell-bulk” configuration is visualized via time-resolved X-ray and electron spectroscopy analyses. A dynamic picture sketching the generation and maturation of nanoscale oxyhydroxide shell is presented, and periodic valence swings of performance-dominant element are observed. Upon maturation, zinc-air battery experiences a near two-fold enlargement in power density to 234 mW cm⁻², a gradual narrowing of voltage gap to 0.85 V at 30 mA cm⁻², followed by stable cycling for hundreds of hours. The revealed configuration can serve as the basis to construct future blueprints for metal-based electrocatalysts, and push zinc-air battery toward practical application.

Interest in rechargeable Zn-air batteries has been renewed in recent years, however, their oxygen electrocatalysts remain not fully understood. Here the authors reveal the presence of a current-driven oxyhydroxide shell in a so-called dynamic eletrocatalyst that enables optimized battery performance.

Gallium Nitride Nanoparticles Embedded in a Carbon Nanofiber Anode for Ultralong-Cycle-Life Lithium-Ion Batteries

Recently, gallium (Ga), one of the liquid metals (LMs), has been explored with special attention because of its liquid phase nature as a self-healing agent and Li storage characteristics. The current challenge that restricts the practical use of Ga is handling Ga easily without loss and understanding its reaction behavior in Li-ion batteries. One solution that helps to address the problem associated with liquid phases is to make solid phases such as gallium oxides and nitrides as starting materials for a stable conversion reaction. Here, we have successfully incorporated GaN nanoparticles into carbon confiners [1D carbon nanofibers (CNFs) with the outermost carbon coating layer] as an anode for the Li-ion battery. By preserving liquid Ga derived from GaN after the conversion reaction in conductive walls, long-term cycling performance (over 5000 cycles) is achievable. This work provides an insight into the LM-relevant materials/carbon composite in the area of the rechargeable battery.

Phase Transition Triggers Explosion-like Puffing Process to Make Popcorn-Inspired All-Conductive Anodes for Superb Aqueous Rechargeable Batteries

The major accomplishment of electrochemical energy-storage devices is closely linked to the advent of state-of-the-art techniques to make optimal electrode systems. Herein, we demonstrate a unique popcorn-inspired strategy to develop all-conductive and highly puffed Fe⊂carbon nanopopcorns as superb anodes for rechargeable Ni/Fe batteries. Temperature-dependent systematic studies show that the nanopopcorn evolution mechanism is governed by typical phase variation from Fe₂O₃ nanospheres to dispersed Fe⁰ nanodebris, whose formation induces catalytic reconstruction/conversion from hydrocarbons to graphitic nanolayers while triggering the explosion-like instant puffing process beyond 700 °C. The as-built Fe⊂carbon hybrids with favorable loosened structures, open-up/enlarged surface areas, and intrinsically conducting nature enable great electrochemical reactivity and cyclic stability (reversible capacity higher than ∼420 mA h g^-1 in all cycles without obvious capacity decay), as well as outstanding rate behaviors (∼300 mA h g^-1 is still retained at ∼20 A g^-1). Full-cell devices of NiO@carbon (+)//Fe⊂carbon (-) can exhibit Max. energy/power densities of up to ∼140.8 W h kg^-1 and ∼15.6 kW kg^-1, respectively. This work sheds a fundamental light on arts to configure puffed electrodes for advanced electrodes in various important applications while holding great promise for high-rate/capacity aqueous rechargeable batteries.

Bio-Derived Hierarchical Multicore-Shell Fe2N-Nanoparticle-Impregnated N-Doped Carbon Nanofiber Bundles: A Host Material for Lithium-/Potassium-Ion Storage

Despite the significant progress in the fabrication of advanced electrode materials, complex control strategies and tedious processing are often involved for most targeted materials to tailor their compositions, morphologies, and chemistries. Inspired by the unique geometric structures of natural biomacromolecules together with their high affinities for metal species, we propose the use of skin collagen fibers for the template crafting of a novel multicore-shell Fe2N-carbon framework anode configuration, composed of hierarchical N-doped carbon nanofiber bundles firmly embedded with Fe2N nanoparticles (Fe2N@N-CFBs). In the resultant heterostructure, the Fe2N nanoparticles firmly confined inside the carbon shells are spatially isolated but electronically well connected by the long-range carbon nanofiber framework. This not only provides direct and continuous conductive pathways to facilitate electron/ion transport, but also helps cushion the volume expansion of the encapsulated Fe2N to preserve the electrode microstructure. Considering its unique structural characteristics, Fe2N@N-CFBs as an advanced anode material exhibits remarkable electrochemical performances for lithium- and potassium-ion batteries. Moreover, this bio-derived structural strategy can pave the way for novel low-cost and high-efficiency syntheses of metal-nitride/carbon nanofiber heterostructures for potential applications in energy-related fields and beyond.

3D pomegranate-like TiN@graphene composites with electrochemical reaction chambers as sulfur hosts for ultralong-life lithium-sulfur batteries

The low loading and poor cycling performance of sulfur cathodes are among the critical barriers restricting the practical application of lithium-sulfur (Li-S) batteries. The rational design of composites consisting of transition metals and conductive nanocarbon is considered an effective strategy to construct cathode materials for Li-S batteries with excellent cycling stability and rate capability. Herein, we propose a spray drying method to fabricate 3D pomegranate-like titanium nitride (TiN)@graphene composites as hosts for sulfur cathodes. The hollow spheres are coated with graphene layers to form a shell, serving as a highly efficient electrochemical reaction chamber and a reservoir for polysulfides. The TiN@graphene/S electrode exhibits an excellent capacity of 810 mA h g^-1 after 200 cycles at 0.5C. The cathodes with high areal sulfur loadings of 2.8 and 3.6 mg cm^-2 maintained remarkable capacities of 568 and 515 mA h g^-1, respectively, after 500 cycles. The TiN hollow spheres not only accommodate the large volume expansion of sulfur but also improve the conversion of polysulfides during the discharge/charge process. The excellent electrical conductivity of the few-layered graphene shell facilitates electron transport and maintains structural stability. This work offers a strategy to combine inorganic compounds and nanocarbon as sulfur hosts to improve the electrochemical properties of Li-S batteries.

Micrometer-Sized Porous Fe2 N/C Bulk for High-Areal-Capacity and Stable Lithium Storage

High-capacity anodes of lithium-ion batteries generally suffer from poor electrical conductivity, large volume variation, and low tap density caused by prepared nanostructures, which make it an obstacle to achieve both high-areal capacity and stable cycling performance for practical applications. Herein, micrometer-sized porous Fe₂ N/C bulk is prepared to tackle the aforementioned issues, and thus realize both high-areal capacity and stable cycling performance at high mass loading. The porous structure in Fe₂ N/C bulk is beneficial to alleviate the volumetric change. In addition, the N-doped carbon conducting networks with high electrical conductivity provide a fast charge transfer pathway. Meanwhile, the micrometer-sized Fe₂ N/C bulk exhibits a higher tap density than that of commercial graphite powder (1.03 g cm^-3 ), which facilitates the preparation of thinner electrode at high mass loadings. As a result, a high-areal capacity of above 4.2 mA h cm^-2 at 0.45 mA cm^-2 is obtained at a high mass loading of 7.0 mg cm^-2 for LIBs, which still maintains at 2.59 mA h cm^-2 after 200 cycles with a capacity retention of 98.8% at 0.89 mA cm^-2 .

Facile fabrication of a jarosite ultrathin KFe3(SO4)2(OH)6@rGO nanosheet hybrid composite with pseudocapacitive contribution as a robust anode for lithium-ion batteries

Earth-abundant and acid-resistant KFe₃(SO₄)₂(OH)₆@rGO nanosheets deliver stable lithium storage properties, owing to the induced pseudocapacitive contribution.

Surface Gradient Ti-Doped MnO2 Nanowires for High-Rate and Long-Life Lithium Battery

Cryptomelane-type α-MnO₂ has been demonstrated as a promising anode material for high-energy Li-ion batteries because of its high capacity and intriguing [2 × 2] tunnel structure. However, applications of MnO₂ electrode, especially at high current rates and mass active material loading, are limited by the poor mechanical stability, unstable solid electrolyte interphase layer, and low reversibility of conversion reactions. Here, we report a design of homogeneous core-shell MnO₂ nanowires (NWs) created by near-surface gradient Ti doping (Ti-MnO₂ NWs). Such a structurally coherent core-shell configuration endowed gradient volume expansion from the inner core to the outer shell, which could effectively release the stress of the NW lattice during cycling and avoid pulverization of the electrode. Moreover, the gradiently doped Ti is able to avoid the Mn metal coarsening, reducing the metal particle size and improving the reversibility of the conversion reaction. In this way, the Ti-MnO₂ NWs achieved both high reversible areal and volumetrical capacities (2.3 mA h cm^-2 and 991.3 mA h cm^-3 at 200 mA g^-1, respectively), a superior round-trip efficiency (Coulombic efficiency achieved above 99.5% after only 30 cycles), and a long lifetime (a high capacity of 742 mA h g^-1 retained after 3000 cycle at 10 A g^-1) at a high mass loading level of 3 mg cm^-2. In addition, the detailed conversion reaction mechanism was investigated through in situ transmission electron microscopy, which further evidenced that the unique homogeneous core-shell structure could largely suppress the separation of core and shell upon charging and discharging. This new NW configuration could benefit the design of other large-volume-change lithium battery anode materials.

Bottom-Up Construction of Reduced-Graphene-Oxide-Anchored MnO with an Nitrogen-Doped Carbon Coating for Synergistically Improving Lithium-Ion Storage

Designing an advanced architecture to overcome the innate issue of MnO-based anode materials in terms of low electrical conductivity and severe volume change during cycling is still a challenge toward which more effort needs devoted. Here, an intriguing hybrid involving the architecture of reduced graphene oxide (RGO)-anchored MnO within an nitrogen-codoped carbon coating (RGO-MnO@NC) is reported via a simple and facile approach and regarded as a promising lithium-ion (Li⁺) anode material with high rate capacity, large specific capacity, and a long cycle lifespan simultaneously. The resulting porous conductive carbon layer could not only promote the electron/ion transfer but also alleviate the volume variation for retaining a relatively stable solid electrolyte interphase and prevent MnO from direct contact with the electrolyte to reduce unexpected lithium consumption. The existing internal voids offer the space to accommodate volume expansion in the lithiation/delithiation processes, and RGO could build a large conductive network for better electron transfer. Consequently, the RGO-MnO@NC electrode presents high Li⁺ storage capacity (699 mAh g^-1 at 0.1 A g^-1), excellent cycling performance (607 mAh g^-1 at 1 A g^-1 over 550 cycles), and a remarkable rate performance. Through kinetic analysis, it is revealed that RGO-MnO@NC exhibits an enhanced capacitive contribution for Li⁺ storage, showing a typical faradaic surface pseudocapacitive mechanism. This work proposes a new strategy to ameliorate the deficiency of the electrode material toward the conductivity and volume change for enhanced Li⁺ storage.

Dual-template engineering of triple-layered nanoarray electrode of metal chalcogenides sandwiched with hydrogen-substituted graphdiyne

Hybrid nanostructures integrating electroactive materials with functional species, such as metal-organic frameworks, covalent organic frameworks, graphdiyne etc., are of significance for both fundamental research and energy conversion/storage applications. Here, hierarchical triple-layered nanotube arrays, which consist of hydrogen-substituted graphdiyne frameworks seamlessly sandwiched between an outer layer of nickel–cobalt co-doped molybdenum disulfide nanosheets and an inner layer of mixed cobalt sulfide and nickel sulfide (Co₉S₈/Ni₃S₂), are directly fabricated on conductive carbon paper. The elaborate triple-layered structure emerges as a useful hybrid electrode for energy conversion and storage, in which the organic hydrogen-substituted graphdiyne middle layer, with an extended π-conjugated system between the electroactive nanomaterials, provides built-in electron and ion channels that are crucial for performance enhancement. This dual-template synthetic method, which makes use of microporous organic networks to confine a self-template, is shown to be versatile and thus provides a promising platform for advanced nanostructure-engineering of hierarchical multi-layered nanostructures towards a wide range of electrochemical applications.

Multi-shelled nanomaterials offer interesting electrochemical properties, but have been limited in composition. Here the authors use dual templating to integrate electroactive metal chalcogenide layers with hydrogen-substituted graphdiyne, achieving electrocatalytic activity for hydrogen evolution.

Necklace-Like Structures Composed of Fe3 N@C Yolk-Shell Particles as an Advanced Anode for Sodium-Ion Batteries

It is of great importance to develop cost-effective electrode materials for large-scale use of Na-ion batteries. Here, a binder-free electrode based on necklace-like structures composed of Fe₃ N@C yolk-shell particles as an advanced anode for Na-ion batteries is reported. In this electrode, every Fe₃ N@C unit has a novel yolk-shell structure, which can accommodate the volumetric changes of Fe₃ N during the (de)sodiation processes for superior structural integrity. Moreover, all reaction units are threaded along the carbon fibers, guaranteeing excellent kinetics for the electrochemical reactions. As a result, when evaluated as an anode material for Na-ion batteries, the Fe₃ N@C nano-necklace electrode delivers a prolonged cycle life over 300 cycles, and achieves a high C-rate capacity of 248 mAh g^-1 at 2 A g^-1 .

N-Doped Dual Carbon-Confined 3D Architecture rGO/Fe3O4/AC Nanocomposite for High-Performance Lithium-Ion Batteries

To address the issues of low electrical conductivity, sluggish lithiation kinetics and dramatic volume variation in Fe₃O₄ anodes of lithium ion battery, herein, a double carbon-confined three-dimensional (3D) nanocomposite architecture was synthesized by an electrostatically assisted self-assembly strategy. In the constructed architecture, the ultrafine Fe₃O₄ subunits (∼10 nm) self-organize to form nanospheres (NSs) that are fully coated by amorphous carbon (AC), formatting core-shell structural Fe₃O₄/AC NSs. By further encapsulation by reduced graphene oxide (rGO) layers, a constructed 3D architecture was built as dual carbon-confined rGO/Fe₃O₄/AC. Such structure restrains the adverse reaction of the electrolyte, improves the electronic conductivity and buffers the mechanical stress of the entire electrode, thus performing excellent long-term cycling stability (99.4% capacity retention after 465 cycles relevant to the second cycle at 5 A g^-1). Kinetic analysis reveals that a dual lithium storage mechanism including a diffusion reaction mechanism and a surface capacitive behavior mechanism coexists in the composites. Consequently, the resulting rGO/Fe₃O₄/AC nanocomposite delivers a high reversible capacity (835.8 mA h g^-1 for 300 cycles at 1 A g^-1), as well as remarkable rate capability (436.7 mA h g^-1 at 10 A g^-1).

MXene-Based Electrode with Enhanced Pseudocapacitance and Volumetric Capacity for Power-Type and Ultra-Long Life Lithium Storage

Powerful yet thinner lithium-ion batteries (LIBs) are eagerly desired to meet the practical demands of electric vehicles and portable electronic devices. However, the use of soft carbon materials in current electrode design to improve the electrode conductivity and stability does not afford high volumetric capacity due to their low density and capacity for lithium storage. Herein, we report a strategy leveraging the MXene with superior conductivity and density to soft carbon as matrix and additive material for comprehensively enhancing the power capability, lifespan, and volumetric capacity of conversion-type anode. A kinetics favorable 2D nanohybrid with high conductivity, compact density, accumulated pseudocapacitance, and diffusion-controlled behavior is fabricated by coupling Ti3C2 MXene with high-density molybdenum carbide for fast lithium storage over 300 cycles with high capacities. By replacing the carbonaceous conductive agent with Ti3C2 MXene, the electrodes with better conductivity and dramatically reduced thickens could be further manufactured to achieve 37-40% improvement in capacity retention and ultra-long life of 5500 cycles with extremely slow capacity loss of 0.002% per cycle at high current rates. Ultrahigh volumetric capacity of 2460 mAh cm-3 could be attained by such MXene-based electrodes, highlighting the great promise of MXene in the development of high-performance LIBs.

Compact-Nanobox Engineering of Transition Metal Oxides with Enhanced Initial Coulombic Efficiency for Lithium-Ion Battery Anodes

A novel strategy is proposed to construct a compact-nanobox (CNB) structure composed of irregular nanograins (average diameter ≈ 10 nm), aiming to confine the electrode-electrolyte contact area and enhance initial Coulombic efficiency (ICE) of transition metal oxide (TMO) anodes. To demonstrate the validity of this attempt, CoO-CNB is taken as an example which is synthesized via a carbothermic reduction method. Benefiting from the compact configuration, electrolyte can only contact the outer surface of the nanobox, keeping the inner CoO nanograins untouched. Therefore, the solid electrolyte interphase (SEI) formation is reduced. Furthermore, the internal cavity leaves enough room for volume variation upon lithiation and delithiation, resulting in superior mechanical stability of the CNB structure and less generation of fresh SEI. Consequently, the SEI remains stable and spatially confined without degradation, and hence, the CoO-CNB electrode delivers an enhanced ICE of 82.2%, which is among the highest values reported for TMO-based anodes in lithium-ion batteries. In addition, the CoO-CNB electrode also demonstrates excellent cyclability with a reversible capacity of 811.6 mA h g^-1 (90.4% capacity retention after 100 cycles). These findings open up a new way to design high-ICE electrodes and boost the practical application of TMO anodes.

Tailoring yolk–shell FeP@carbon nanoboxes with engineered void space for pseudocapacitance-boosted lithium storage

A unique yolk–shell FeP@C nanobox is synthesized by an etching-in-box combined with a phosphidation-in-box approach, manifesting remarkable pseudocapacitance-boosted lithium ion storage properties.