Self‐Standing Porous LiCoO2 Nanosheet Arrays as 3D Cathodes for Flexible Li‐Ion Batteries

Self‐standing electrodes are the key to realize flexible Li‐ion batteries. However, fabrication of self‐standing cathodes is still a major challenge. In this work, porous LiCoO₂ nanosheet arrays are grown on Au‐coated stainless steel (Au/SS) substrates via a facile “hydrothermal lithiation” method using Co₃O₄ nanosheet arrays as the template followed by quick annealing in air. The binder‐free and self‐standing LiCoO₂ nanosheet arrays represent the 3D cathode and exhibit superior rate capability and cycling stability. In specific, the LiCoO₂ nanosheet array electrode can deliver a high reversible capacity of 104.6 mA h g^?1 at 10 C rate and achieve a capacity retention of 81.8% at 0.1 C rate after 1000 cycles. By coupling with Li₄Ti₅O₁₂ nanosheet arrays as anode, an all‐nanosheet array based LiCoO₂//Li₄Ti₅O₁₂ flexible Li‐ion battery is constructed. Benefiting from the 3D nanoarchitectures for both cathode and anode, the flexible LiCoO₂//Li₄Ti₅O₁₂ battery can deliver large specific reversible capacities of 130.7 mA h g^?1 at 0.1 C rate and 85.3 mA h g^?1 at 10 C rate (based on the weight of cathode material). The full cell device also exhibits good cycling stability with 80.5% capacity retention after 1000 cycles at 0.1 C rate, making it promising for the application in flexible Li‐ion batteries.     

3D Porous N‐Doped Graphene Frameworks Made of Interconnected Nanocages for Ultrahigh‐Rate and Long‐Life Li–O2 Batteries

The inferior rate capability and poor cycle stability of the present Li–O₂ batteries are still critical obstacles for practice applications. Configuring novel and integrated air electrode materials with unique structure and tunable chemical compositions is one of the efficient strategies to solve these bottleneck problems. Herein, a novel strategy for synthesis of 3D porous N‐doped graphene aerogels (NPGAs) with frameworks constructed by interconnected nanocages with the aid of polystyrene sphere@polydopamine is reported. The interconnected nanocages as the basic building unit of graphene sheets are assembled inside the skeletons of 3D graphene aerogels, leading to the 3D NPGA with well‐developed interconnected channels and the full exposure of electrochemically active sites. Benefiting from such an unique structure, the as‐made NPGA delivers a high specific capacity, an excellent rate capacity of 5978 mA h g^?1 at 3.2 A g^?1, and long cycle stability, especially at a large current density (54 cycles at 1 A g^?1), indicative of boosted rate capability and cycle life as air electrodes for Li–O₂ batteries. More importantly, based on the total mass of C+Li₂O₂, a gravimetric energy density of 2400 W h kg^?1 for the NPGA–O₂//Li cell is delivered at a power density of 1300 W kg^?1.     

Graphene Oxide Gel‐Derived,Free‐Standing,Hierarchically Porous Carbon for High‐Capacity and High‐Rate Rechargeable Li‐O2 Batteries

Lithium‐oxygen (Li‐O₂) batteries are one of the most promising candidates for high‐energy‐density storage systems. However, the low utilization of porous carbon and the inefficient transport of reactants in the cathode limit terribly the practical capacity and, in particular, the rate capability of state‐of‐the‐art Li‐O₂ batteries. Here, free‐standing, hierarchically porous carbon (FHPC) derived from graphene oxide (GO) gel in nickel foam without any additional binder is synthesized by a facile and effective in situ sol‐gel method, wherein the GO not only acts as a special carbon source, but also provides the framework of a 3D gel; more importantly, the proper acidity via its intrinsic COOH groups guarantees the formation of the whole structure. Interestingly, when employed as a cathode for Li‐O₂ batteries, the capacity reaches 11 060 mA h g^?1 at a current density of 0.2 mA cm^?2 (280 mA g^?1); and, unexpectedly, a high capacity of 2020 mA h g^?1 can be obtained even the current density increases ten times, up to 2 mA cm^?2 (2.8 A g^?1), which is the best rate performance for Li‐O₂ batteries reported to date. This excellent performance is attributed to the synergistic effect of the loose packing of the carbon, the hierarchical porous structure, and the high electronic conductivity of the Ni foam.     

Mesoporous Carbon Nanocube Architecture for High‐Performance Lithium–Oxygen Batteries

One of the major challenges to develop high‐performance lithium–oxygen (Li–O₂) battery is to find effective cathode catalysts and design porous architecture for the promotion of both oxygen reduction reactions and oxygen evolution reactions. Herein, the synthesis of mesoporous carbon nanocubes as a new cathode nanoarchitecture for Li–O₂ batteries is reported. The oxygen electrodes made of mesoporous carbon nanocubes contain numerously hierarchical mesopores and macropores, which can facilitate oxygen diffusion and electrolyte impregnation throughout the electrode, and provide sufficient spaces to accommodate insoluble discharge products. When they are applied as cathode catalysts, the Li–O₂ cells deliver discharge capacities of 26 100 mA h g^?1 at 200 mA g^?1, which is much higher than that of commercial carbon black catalysts. Furthermore, the mesoporous nanocube architecture can also serve as a conductive host structure for other highly efficient catalysts. For instance, the Ru functionalized mesoporous carbon nanocubes show excellent catalytic activities toward oxygen evolution reactions. Li–O₂ batteries with Ru functionalized mesoporous carbon nanocube catalysts demonstrate a high charge/discharge electrical energy efficiency of 86.2% at 200 mA g^?1 under voltage limitation and a good cycling performance up to 120 cycles at 400 mA g^?1 with the curtaining capacity of 1000 mA h g^?1.     

Enhanced Performance of P2‐Na0.66(Mn0.54Co0.13Ni0.13)O2 Cathode for Sodium‐Ion Batteries by Ultrathin Metal Oxide Coatings via Atomic Layer Deposition

Sodium‐ion batteries are widely considered as promising energy storage systems for large‐scale applications, but their relatively low energy density hinders further practical applications. Developing high‐voltage cathode materials is an effective approach to increase the overall energy density of sodium‐ion batteries. When cut‐off voltage is elevated over 4.3 V, however, the cathode becomes extremely unstable due to structural transformations as well as metal dissolution into the electrolytes. In this work, the cyclic stability of P2‐Na_0.66(Mn_0.54Co_0.13Ni_0.13)O₂ (MCN) electrode at a cut‐off voltage of 4.5 V is successfully improved by using ultrathin metal oxide surface coatings (Al₂O₃, ZrO₂, and TiO₂) deposited by an atomic layer deposition technique. The MCN electrode coated with the Al₂O₃ layer exhibits higher capacity retention among the MCN electrodes. Moreover, the rate performance of the MCN electrode is greatly improved by the metal oxide coatings in the order of TiO₂ < Al₂O₃ < ZrO₂, due to increased fracture toughness and electrical conductivity of the metal oxide coating layers. A ZrO₂‐coated MCN electrode shows a discharge capacity of 83 mAh g^?1 at 2.4 A g^?1, in comparison to 61 mAh g^?1 for a pristine MCN electrode. Cyclic voltammetry and electrochemical impedance analysis disclose the reduced charge transfer resistance from 1421 to 760.2 Ω after cycles, suggesting that the metal oxide coating layer can effectively minimize the undesirable phase transition, buffer inherent stress and strain between the binder, cathode, and current collector, and avoid volumetric changes, thus increasing the cyclic stability of the MCN electrode.     

Novel Core–Shell FeOF/Ni(OH)2 Hierarchical Nanostructure for All‐Solid‐State Flexible Supercapacitors with Enhanced Performance

Well‐controlled core–shell hierarchical nanostructures based on oxyfluoride and hydroxide are for the first time rationally designed and synthesized via a simple solvothermal and chemical precipitation route, in which FeOF nanorod acts as core and porous Ni(OH)₂ nanosheets as shell. When evaluated as electrodes for supercapacitors, a high specific capacitance of 1452 F g^?1 can be obtained at a current density of 1 A g^?1. Even as the current density increases to 10 A g^?1, the core–shell hybrid still reserves a noticeable capacitance of 1060 F g^?1, showing an excellent rate capacity. Furthermore, all‐solid‐state flexible asymmetric supercapacitor based on the FeOF/Ni(OH)₂ hybrid as a positive electrode and activated carbon as a negative electrode shows high power density, high energy density, and long cycling lifespan. The excellent electrochemical performance of the FeOF/Ni(OH)₂ core–shell hybrid is ascribed to the unique microstructure and synergistic effects. FeOF nanorod from FeF₃ by partial substitution of fluorine with oxygen behaves as a low intrinsic resistance, thus facilitating charge transfer processes. While the hierarchical Ni(OH)₂ nanosheets with large surface area provide enough active sites for redox chemical reactions, leading to greatly enhanced electrochemical activity. The well‐controllable oxyfluoride/hydroxide hybrid is inspiring, opening up a new way to design new electrodes for next‐generation all‐solid‐state supercapacitors.     

A Composite of Carbon‐Wrapped Mo2C Nanoparticle and Carbon Nanotube Formed Directly on Ni Foam as a High‐Performance Binder‐Free Cathode for Li‐O2 Batteries

Cathode design is indispensable for building Li‐O₂ batteries with long cycle life. A composite of carbon‐wrapped Mo₂C nanoparticles and carbon nanotubes is prepared on Ni foam by direct hydrolysis and carbonization of a gel composed of ammonium heptamolybdate tetrahydrate and hydroquinone resin. The Mo₂C nanoparticles with well‐controlled particle size act as a highly active oxygen reduction reactions/oxygen evolution reactions (ORR/OER) catalyst. The carbon coating can prevent the aggregation of the Mo₂C nanoparticles. The even distribution of Mo₂C nanoparticles results in the homogenous formation of discharge products. The skeleton of porous carbon with carbon nanotubes protrudes from the composite, resulting in extra voids when applied as a cathode for Li‐O₂ batteries. The batteries deliver a high discharge capacity of ≈10 400 mAh g^?1 and a low average charge voltage of ≈4.0 V at 200 mA g^?1. With a cutoff capacity of 1000 mAh g^?1, the Li‐O₂ batteries exhibit excellent charge–discharge cycling stability for over 300 cycles. The average potential polarization of discharge/charge gaps is only ≈0.9 V, demonstrating the high ORR and OER activities of these Mo₂C nanoparticles. The excellent cycling stability and low potential polarization provide new insights into the design of highly reversible and efficient cathode materials for Li‐O₂ batteries.     

Hierarchical Engineering of Porous P2‐Na2/3Ni1/3Mn2/3O2 Nanofibers Assembled by Nanoparticles Enables Superior Sodium‐Ion Storage Cathodes

Layered transition metal oxides (TMOs) are appealing cathode candidates for sodium‐ion batteries (SIBs) by virtue of their facile 2D Na⁺ diffusion paths and high theoretical capacities but suffer from poor cycling stability. Herein, taking P2‐type Na_2/3Ni_1/3Mn_2/3O₂ as an example, it is demonstrated that the hierarchical engineering of porous nanofibers assembled by nanoparticles can effectively boost the reaction kinetics and stabilize the structure. The P2‐Na_2/3Ni_1/3Mn_2/3O₂ nanofibers exhibit exceptional rate capability (166.7 mA h g^?1 at 0.1 C with 73.4 mA h g^?1 at 20 C) and significantly improved cycle life (≈81% capacity retention after 500 cycles) as cathode materials for SIBs. The highly reversible structure evolution and Ni/Mn valence change during sodium insertion/extraction are verified by in operando X‐ray diffraction and ex situ X‐ray photoelectron spectroscopy, respectively. The facilitated electrode process kinetics are demonstrated by an additional study using the electrochemical measurements and density functional theory computations. More impressively, the prototype Na‐ion full battery built with a Na_2/3Ni_1/3Mn_2/3O₂ nanofibers cathode and hard carbon anode delivers a promising energy density of 212.5 Wh kg^?1. The concept of designing a fibrous framework composed of small nanograins offers a new and generally applicable strategy for enhancing the Na‐storage performance of layered TMO cathode materials.     

Quasi‐Stable Electroless Ni–P Deposition: A Pivotal Strategy to Create Flexible Li–S Pouch Batteries with Bench Mark Cycle Stability and Specific Capacity

Development of flexible Li–S batteries brings along the flourishing prospective for energy‐hungry wearable devices. However, it is still seriously restricted due to lack of facile methods to solve its inherent problems and flexible device‐related current collection issues. Herein, quasi‐stable electroless deposition method is firstly proposed to solve these problems by fabricating 3D tunable Ni–P networks in the C/S free‐standing electrode. The ultrathin Ni–P layers which are highly conductive and strongly adhesive with electrode substrates improve the electronic conductivity by two orders of magnitude and rise initial specific capacity from 1200 to 1600 mAh g^?1. The harmful shuttle effect of polysulfide is also effectively alleviated due to the chemical adsorption and physical sieving properties of the 3D networks. The flexible pouch Li–S batteries assembled with commercially applicable structure also show high flexibility and as high as 1420 mAh g^?1 output capacity at 0.1C in cycling test. This method can definitely be extended to other flexible devices such as Li‐ion batteries, Li–O₂ batteries, and supercapacitors.     

Au‐Decorated Cracked Carbon Tube Arrays as Binder‐Free Catalytic Cathode Enabling Guided Li2O2 Inner Growth for High‐Performance Li‐O2 Batteries

Owing to their extremely high energy density, Li‐O₂ batteries have attained increasing attention in recent studies. However, deposition of the discharge product, insulating Li₂O₂, is known to seriously limit the electrochemical performance of Li‐O₂ batteries. While extensive studies have focused on relieving electrode deactivation by controlling Li₂O₂ growth, no permanent or effective mechanism is delivered. Here, a unique design comprising a catalytic cathode constructed by cracked carbon submicron tube (CST) arrays decorated with Au nanoparticles on inner walls is proposed. The introduction of Au nanoparticles not only improves electrode conductivity but also provides catalytic sites, guiding conformal growth of thin‐layered Li₂O₂ inside the cracked CST. Density functional theory calculations support that Au decoration on CST favors the conformal growth of Li₂O₂ on inner tubular walls. This growth behavior of Li₂O₂ renders easy decomposition of Li₂O₂, prevents carbon tube electrode from full, rapid deactivation, and preserves the free space for reactants transport. Li‐O₂ cells with Au@CST exhibit good rate capability (1208 mAh g^–1 at a high current density of 1000 mA g^–1) and long cycle life (112 cycles at a current density of 400 mA g^–1 with a limited capacity of 500 mAh g^–1).     

Lithium Ion Breathable Electrodes with 3D Hierarchical Architecture for Ultrastable and High‐Capacity Lithium Storage

Transition‐metal oxides show genuine potential in replacing state‐of‐the‐art carbonaceous anode materials in lithium‐ or sodium‐ion batteries because of their much higher theoretical capacity. However, they usually undergo massive volume change, which leads to numerous problems in both material and electrode levels, such as material pulverization, instable solid‐electrolyte interphase, and electrode failure. Here, it is demonstrated that lithium‐ion breathable hybrid electrodes with 3D architecture tackle all these problems, using a typical conversion‐type transition‐metal oxide, Fe₃O₄, of which nanoparticles are anchored onto 3D current collectors of Ni nanotube arrays (NTAs) and encapsulated by δ‐MnO₂ layers (Ni/Fe₃O₄@MnO₂). The δ‐MnO₂ layers reversibly switch lithium insertion/extraction of internal Fe₃O₄ nanoparticles and protect them against pulverizing and detaching from NTA current collectors, securing exceptional integrity retention and efficient ion/electron transport. The Ni/Fe₃O₄@MnO₂ electrodes exhibit superior cyclability and high‐capacity lithium storage (retaining ≈1450 mAh g^?1, ≈96% of initial value at 1 C rate after 1000 cycles).     

A Low‐Cost,Self‐Standing NiCo2O4@CNT/CNT Multilayer Electrode for Flexible Asymmetric Solid‐State Supercapacitors

The demand for a new generation of flexible, portable, and high‐capacity power sources increases rapidly with the development of advanced wearable electronic devices. Here we report a simple process for large‐scale fabrication of self‐standing composite film electrodes composed of NiCo₂O₄@carbon nanotube (CNT) for supercapacitors. Among all composite electrodes prepared, the one fired in air displays the best electrochemical behavior, achieving a specific capacitance of 1,590 F g^?1 at 0.5 A g^?1 while maintaining excellent stability. The NiCo₂O₄@CNT/CNT film electrodes are fabricated via stacking NiCo₂O₄@CNT and CNT alternately through vacuum filtration. Lightweight, flexible, and self‐standing film electrodes (≈24.3 µm thick) exhibit high volumetric capacitance of 873 F cm^?3 (with an areal mass of 2.5 mg cm^?2) at 0.5 A g^?1. An all‐solid‐state asymmetric supercapacitor consists of a composite film electrode and a treated carbon cloth electrode has not only high energy density (≈27.6 Wh kg^?1) at 0.55 kW kg^?1 (including the weight of the two electrodes) but also excellent cycling stability (retaining ≈95% of the initial capacitance after 5000 cycles), demonstrating the potential for practical application in wearable devices.     

Advanced Concentration Gradient Cathode Material with Two‐Slope for High‐Energy and Safe Lithium Batteries

Li[Ni_0.65Co_0.13Mn_0.22]O₂ cathode with two‐sloped full concentration gradient (TSFCG), maximizing the Ni content in the inner part of the particle and the Mn content near the particle surface, is synthesized via a specially designed batch‐type reactor. The cathode delivers a discharge capacity of 200 mAh g^?1 (4.3 V cutoff) with excellent capacity retention of 88% after 1500 cycles in a full‐cell configuration. Overall electrochemical performance of the TSFCG cathode is benchmarked against conventional cathode (CC) with same composition and commercially available Li[Ni_0.8Co_0.15Al_0.05]O₂ (NCA). The TSFCG cathode exhibits the best cycling stability, rate capability, and thermal stability of the three electrodes. Transmission electron microscopy analysis of the cycled TSFCG, CC, and NCA cathodes shows that the TSFCG electrode maintains both its mechanical and structural integrity whereas the NCA electrode nearly pulverizes due to the strain during cycling.     

Highly Stable Cycling of Amorphous Li2CO3‐Coated α‐Fe2O3 Nanocrystallines Prepared via a New Mechanochemical Strategy for Li‐Ion Batteries

In this study, an amorphous Li₂CO₃‐coated nanocrystalline α‐Fe₂O₃ hierarchical structure is synthesized for the first time using a facile one‐step mechanochemical process at room temperature, taking advantage of the concurrence of repeated fracture‐cold welding of material's particles and a gas‐solid redox reaction. The conformal coating and hierarchical structure significantly increase the cycling durability and rate capability. Typically, a 1–3 nm thick amorphous Li₂CO₃ layer is conformally coated on Fe₂O₃ nanocrystallines (≈10 nm in size) that form hierarchically aggregated particles 400–800 nm in size by ball milling α‐Fe₂O₃ with LiH in CO₂. The prepared Li₂CO₃‐coated nanocrystalline α‐Fe₂O₃ exhibits highly stable long‐term cyclability as it delivers a reversible capacity of 975 mAh g^?1 with 99% of retention after 400 cycles at 100 mA g^?1. At a high rate of 3000 mA g^?1, its reversible capacity still remains at 537 mAh g^?1, superior to the uncoated counterpart (311 mAh g^?1). Moreover, amorphous Li₂O and Li₂CO₃ coatings are also similarly produced on Fe₂O₃ and NiO nanocrystallines, respectively, representing the general applicability of this mechanochemical approach.     

A General One‐Pot Synthesis Strategy of 3D Porous Hierarchical Networks Crosslinked by Monolayered Nanoparticles Interconnected Nanoplates for Lithium Ion Batteries

A structure of 3D porous hierarchical networks is highly desired for mass production of electrode materials for lithium‐ion batteries due to its unique role in promoting battery performance. Herein, a general strategy using expanded graphites as both a structure‐directed template and a solution container is proposed for the synthesis of various cathode materials with 3D porous hierarchical networks formed by the crosslinkage of monolayered primary nanoparticles interconnected nanoplates, which all show high capacity, superior cyclic performance, and rate capability. The LiNi_0.8Co_0.15Al_0.05O₂/Li half cell delivers a capacity of 118 mAh g^?1 at 20 C (5.6 A g^?1) and capacity retention of 71.6% after 1000 cycles at 1 C, while the LiNi_0.8Co_0.15Al_0.05O₂/graphite full cell shows 79.9% and 80.0% capacity retentions after 1400 cycles at 1 C and 3000 cycles at 5 C, respectively. The superior performance is attributed to the unique 3D porous hierarchical networks with a stable surface and structure, which is related to the sufficient oxidization of Ni²⁺ and the formation of little residual lithium at surface intrinsic to this strategy. The study opens a generalized new avenue for facile, cheap, green, and mass production of various oxide materials with 3D porous hierarchical networks.     

Fe2O3 Nanoneedles on Ultrafine Nickel Nanotube Arrays as Efficient Anode for High‐Performance Asymmetric Supercapacitors

High performance of electrochemical energy storage devices depends on the smart structure engineering of electrodes, including the tailored nanoarchitectures of current collectors and subtle hybridization of active materials. To improve the anode supercapacitive performance of Fe₂O₃ for high‐voltage asymmetric supercapacitors, here, a hybrid core‐branch nanoarchitecture is proposed by integrating Fe₂O₃ nanoneedles on ultrafine Ni nanotube arrays (NiNTAs@Fe₂O₃ nanoneedles). The fabrication process employs a bottom‐up strategy via a modified template‐assisted method starting from ultrafine ZnO nanorod arrays, ensuring the formation of ultrafine Ni nanotube arrays with ultrathin tube walls. The novel developed NiNTAs@Fe₂O₃ nanoneedle electrode is demonstrated to be a highly capacitive anode (418.7 F g^?1 at 10 mV s^?1), matching well with the similarly built NiNTAs@MnO₂ nanosheet cathode. Contributed by the efficient electron collection paths and short ion diffusion paths in the uniquely designed anode and cathode, the asymmetric supercapacitors exhibit an excellent maximum energy density of 34.1 Wh kg^?1 at the power density of 3197.7 W kg^?1 in aqueous electrolyte and 32.2 Wh kg^?1 at the power density of 3199.5 W kg^?1 in quasi‐solid‐state gel electrolyte.     

Three‐Dimensional Co3O4@MnO2 Hierarchical Nanoneedle Arrays: Morphology Control and Electrochemical Energy Storage

In this paper, a highly ordered three‐dimensional Co₃O₄@MnO₂ hierarchical porous nanoneedle array on nickel foam is fabricated by a facile, stepwise hydrothermal approach. The morphologies evolution of Co₃O₄ and Co₃O₄@MnO₂ nanostructures upon reaction times and growth temperature are investigated in detail. Moreover, the as‐prepared Co₃O₄@MnO₂ hierarchical structures are investigated as anodes for both supercapacitors and Li‐ion batteries. When used for supercapacitors, excellent electrochemical performances such as high specific capacitances of 932.8 F g^?1 at a scan rate of 10 mV s^?1 and 1693.2 F g^?1 at a current density of 1 A g^?1 as well as long‐term cycling stability and high energy density (66.2 W h kg^?1 at a power density of 0.25 kW kg^?1), which are better than that of the individual component of Co₃O₄ nanoneedles and MnO₂ nanosheets, are obtained. The Co₃O₄@MnO₂ NAs are also tested as anode material for LIBs for the first time, which presents an improved performance with high reversible capacity of 1060 mA h g^?1 at a rate of 120 mA g^?1, good cycling stability, and rate capability.     

Ultrathin MoS2 Nanosheets@Metal Organic Framework‐Derived N‐Doped Carbon Nanowall Arrays as Sodium Ion Battery Anode with Superior Cycling Life and Rate Capability

This study reports the design and fabrication of ultrathin MoS₂ nanosheets@metal organic framework‐derived N‐doped carbon nanowall array hybrids on flexible carbon cloth (CC@CN@MoS₂) as a free‐standing anode for high‐performance sodium ion batteries. When evaluated as an anode for sodium ion battery, the as‐fabricated CC@CN@MoS₂ electrode exhibits a high capacity (653.9 mA h g^?1 of the second cycle and 619.2 mA h g^?1 after 100 cycles at 200 mA g^?1), excellent rate capability, and long cycling life stability (265 mA h g^?1 at 1 A g^?1 after 1000 cycles). The excellent electrochemical performance can be attributed to the unique 2D hybrid structures, in which the ultrathin MoS₂ nanosheets with expanded interlayers can provide shortened ion diffusion paths and favorable Na⁺ insertion/extraction space, and the porous N‐doped carbon nanowall arrays on flexible carbon cloth are able to improve the conductivity and maintain the structural integrity. Moreover, the N‐doping‐induced defects also make them favorable for the effective storage of sodium ions, which enables the enhanced capacity and rate performance of MoS₂.     

Local Built‐In Electric Field Enabled in Carbon‐Doped Co3O4 Nanocrystals for Superior Lithium‐Ion Storage

In this work, a novel concept of introducing a local built‐in electric field to facilitate lithium‐ion transport and storage within interstitial carbon (C‐) doped nanoarchitectured Co₃O₄ electrodes for greatly improved lithium‐ion storage properties is demonstrated. The imbalanced charge distribution emerging from the C‐dopant can induce a local electric field, to greatly facilitate charge transfer. Via the mechanism of “surface locking” effect and in situ topotactic conversion, unique sub‐10 nm nanocrystal‐assembled Co₃O₄ hollow nanotubes (HNTs) are formed, exhibiting excellent structural stability. The resulting C‐doped Co₃O₄ HNT‐based electrodes demonstrate an excellent reversible capacity ≈950 mA h g^?1 after 300 cycles at 0.5 A g^?1 and superior rate performance with ≈853 mA h g^?1 at 10 A g^?1.     

A Soft Lithiophilic Graphene Aerogel for Stable Lithium Metal Anode

The lithium metal anode is one of the most promising anodes for next‐generation high‐energy‐density batteries. However, the severe growth of Li dendrites and large volume expansion leads to rapid capacity decay and shortened lifetime, especially in high current density and high capacity. Herein, a soft 3D Au nanoparticles@graphene hybrid aerogel (Au? GA) as a lithiophilic host for lithium metal anode is proposed. The large surface area and interconnected conductive pathways of the Au? GA significantly decrease the local current density of the electrode, enabling uniform Li deposition. Furthermore, the 3D porous structure effectively accommodates the large volume expansion during Li plating/stripping, and the Li_xAu alloy serves as a solid solution buffer layer to completely eliminate the Li nucleation over‐potential. Symmetric cells can stably cycle at 8 mA cm^?2 for 8 mAh cm^?2 and exhibit ultra‐long cycling: 1800 h at 2 mA cm^?2 for 2 mAh cm^?2, and 1200 h at 4 mA cm^?2 for 4 mAh cm^?2, with low over‐potential. Full cells assemble with a Cu@Au? GA? Li anode and LiFePO₄ cathode, can sustain a high rate of 8 C, and retain a high capacity of 59.6 mAh g^?1 after 1100 cycles at 2 C.