A Novel Cathode Material with a Concentration‐Gradient for High‐Energy and Safe Lithium‐Ion Batteries

A high‐energy functional cathode material with an average composition of Li[Ni_0.72Co_0.18Mn_0.10]O₂, mainly comprising a core material Li[Ni_0.8Co_0.2]O₂ encapsulated completely within a stable manganese‐rich concentration‐gradient shell is successfully synthesized by a co‐precipitation process. The Li[Ni_0.72Co_0.18Mn_0.10]O₂ with a concentration‐gradient shell has a shell thickness of about 1 µm and an outer shell composition rich in manganese, Li[Ni_0.55Co_0.15Mn_0.30]O₂. The core material can deliver a very high capacity of over 200 mA h g^?1, while the manganese‐rich concentration‐gradient shell improves the cycling and thermal stability of the material. These improvements are caused by a gradual and continuous increase of the stable tetravalent Mn in the concentration‐gradient shell layer. The electrochemical and thermal properties of this cathode material are found to be far superior to those of the core Li[Ni_0.8Co_0.2]O₂ material alone. Electron microscopy also reveals that the original crystal structure of this material remains intact after cycling.     

Manipulating the Electronic Structure of Li‐Rich Manganese‐Based Oxide Using Polyanions: Towards Better Electrochemical Performance

Lithium‐rich manganese‐based layered oxides show great potential as high‐capacity cathode materials for lithium ion batteries, but usually exhibit a poor cycle life, gradual voltage drop during cycling, and low thermal stability in the highly delithiated state. Herein, a strategy to promote the electrochemical performance of this material by manipulating the electronic structure through incorporation of boracic polyanions is developed. As‐prepared Li[Li_0.2Ni_0.13Co_0.13Mn_0.54](BO₄)_0.015(BO₃)_0.005O_1.925 shows a decreased M‐O covalency and a lowered O 2p band top compared with pristine Li[Li_0.2Ni_0.13Co_0.13Mn_0.54]O₂. As a result, the modified cathode exhibits a superior reversible capacity of 300 mA h g^?1 after 80 cycles, excellent cycling stability with a capacity retention of 89% within 300 cycles, higher thermal stability, and enhanced redox couple potentials. The improvements are correlated to the enhanced oxygen stability that originates from the tuned electronic structure. This facile strategy may further be extended to other high capacity electrode systems.     

A High‐Energy Li‐Ion Battery Using a Silicon‐Based Anode and a Nano‐Structured Layered Composite Cathode

High capacity electrodes based on a Si composite anode and a layered composite oxide cathode, Ni‐rich Li[Ni_0.75Co_0.1Mn_0.15]O₂, are evaluated and combined to fabricate a high energy lithium ion battery. The Si composite anode, Si/C‐IWGS (internally wired with graphene sheets), is prepared by a scalable sol–gel process. The Si/C‐IWGS anode delivers a high capacity of >800 mAh g^?1 with an excellent cycling stability of up to 200 cycles, mainly due to the small amount of graphene (～6 wt%). The cathode (Li[Ni_0.75Co_0.1Mn_0.15]O₂) is structurally optimized (Ni‐rich core and a Ni‐depleted shell with a continuous concentration gradient between the core and shell, i.e., a full concentration gradient, FCG, cathode) so as to deliver a high capacity (>200 mAh g^?1) with excellent stability at high voltage (～4.3 V). A novel lithium ion battery system based on the Si/C‐IWGS anode and FCG cathode successfully demonstrates a high energy density (240 Wh kg^?1 at least) as well as an unprecedented excellent cycling stability of up to 750 cycles between 2.7 and 4.2 V at 1C. As a result, the novel battery system is an attractive candidate for energy storage applications demanding a high energy density and long cycle life.     

Microstructure Evolution of Concentration Gradient Li[Ni0.75Co0.10Mn0.15]O2 Cathode for Lithium‐Ion Batteries

Detailed analysis of the microstructural changes during lithiation of a full‐concentration‐gradient (FCG) cathode with an average composition of Li[Ni_0.75Co_0.10Mn_0.15]O₂ is performed starting from its hydroxide precursor, FCG [Ni_0.75Co_0.10Mn_0.15](OH)₂ prior to lithiation. Transmission electron microscopy (TEM) reveals that a unique rod‐shaped primary particle morphology and radial crystallographic texture are present in the prelithiation stage. In addition, TEM detected a two‐phase structure consisting of MnOOH and Ni(OH)₂, and crystallographic twins of MnOOH on the Mn‐rich precursor surface. The formation of numerous twins is driven by the lattice mismatch between MnOOH and Ni(OH)₂. Furthermore, the twins persist in the lithiated cathode; however, their density decrease with increasing lithiation temperature. Cation disordering, which influences cathode performance, is observed to continuously decrease with increasing lithiation temperature with a minimum observed at 790 °C. Consequently, lithiation at 790 °C (for 10 h) produced optimal discharge capacity and cycling stability. Above 790 °C, an increase in cation disordering and excessive coarsening of the primary particles lead to the deterioration of electrochemical properties. The twins in the FCG cathode precursor may promote the optimal primary particle morphology by retarding the random coalescence of primary particles during lithiation, effectively preserving both the morphology and crystallographic texture of the precursor.     

Adiponitrile (C6H8N2): A New Bi‐Functional Additive for High‐Performance Li‐Metal Batteries

Rechargeable batteries with a Li metal anode and Ni‐rich Li[Ni_xCo_yMn_1?x?y]O₂ cathode (Li/Ni‐rich NCM battery) have been emerging as promising energy storage devices because of their high‐energy density. However, Li/Ni‐rich NCM batteries have been plagued by the issue of the thermodynamic instability of the Li metal anode and aggressive surface chemistry of the Ni‐rich cathode against electrolyte solution. In this study, a bi‐functional additive, adiponitrile (C₆H₈N₂), is proposed which can effectively stabilize both the Li metal anode and Ni‐rich NCM cathode interfaces. In the Li/Ni‐rich NCM battery, the addition of 1 wt% adiponitrile in 0.8 m LiTFSI + 0.2 M LiDFOB + 0.05 M LiPF₆ dissolved in EMC/FEC = 3:1 electrolyte helps to produce a conductive and robust Li anode/electrolyte interface, while strong coordination between Ni⁴⁺ on the delithiated Ni‐rich cathode and nitrile group in adiponitrile reduces parasitic reactions between the electrolyte and Ni‐rich cathode surface. Therefore, upon using 1 wt% adiponitrile, the Li/full concentration gradient Li[Ni_0.73Co_0.10Mn_0.15Al_0.02]O₂ battery achieves an unprecedented cycle retention of 75% over 830 cycles under high‐capacity loading of 1.8 mAh cm^?2 and fast charge–discharge time of 2 h. This work marks an important step in the development of high‐performance Li/Ni‐rich NCM batteries with efficient electrolyte additives.     

Fluorinated Polyimide as a Novel High‐Voltage Binder for High‐Capacity Cathode of Lithium‐Ion Batteries

An increase in the energy density of lithium‐ion batteries has long been a competitive advantage for advanced wireless devices and long‐driving electric vehicles. Li‐rich layered oxide, xLi₂MnO₃?(1?x)LiMn_1?y?zNi_yCo_zO₂, is a promising high‐capacity cathode material for high‐energy batteries, whose capacity increases by increasing charge voltage to above 4.6 V versus Li. Li‐rich layered oxide cathode however suffers from a rapid capacity fade during the high‐voltage cycling because of instable cathode–electrolyte interface, and the occurrence of metal dissolution, particle cracking, and structural degradation, particularly, at elevated temperatures. Herein, this study reports the development of fluorinated polyimide as a novel high‐voltage binder, which mitigates the cathode degradation problems through superior binding ability to conventional polyvinylidenefluoride binder and the formation of robust surface structure at the cathode. A full‐cell consisting of fluorinated polyimide binder‐assisted Li‐rich layered oxide cathode and conventional electrolyte without any electrolyte additive exhibits significantly improved capacity retention to 89% at the 100th cycle and discharge capacity to 223–198 mA h g^?1 even under the harsh condition of 55 °C and high charge voltage of 4.7 V, in contrast to a rapid performance fade of the cathode coated with polyvinylidenefluoride binder.     

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.     

Faster Activation and Slower Capacity/Voltage Fading: A Bifunctional Urea Treatment on Lithium‐Rich Cathode Materials

Li‐rich layered oxides are promising cathode materials for next‐generation Li‐ion batteries because of their extraordinary specific capacity. However, the activation process of the key active component Li₂MnO₃ in Li‐rich materials is kinetically slow, and the complex phase transformation with electrode/electrolyte side reactions causes fast capacity/voltage fading. Herein, a simple thermal treatment strategy is reported to simultaneously tackle these challenges. The introduction of a urea thermal treatment on Li‐rich material Li_1.87Mn_0.94Ni_0.19O₃ leads to oxygen deficiencies and partially reduced Mn ions on the oxide surface for activating the Li‐rich phase. In situ synchrotron study confirms that the urea‐treated cathode shows much faster Li extraction from both Li and transition metal layers with less oxygen evolution upon charging than that of untreated counterparts. Moreover, the decomposition products of urea during thermal treatment subsequently deposit on the surface of cathode material, leading to a unique passivation layer against side reactions between electrode and electrolyte. Soft X‐ray absorption spectroscopy reveals the structural evolution mechanism with a significantly suppressed dissolution of Mn species over cycling measurement. The urea‐treated Li_1.87Mn_0.94Ni_0.19O₃ shows accelerated activation kinetics to reach high capacity of 270 mA h g^–1 and demonstrates excellent capacity retention of 98.49% over 300 cycles with slower voltage decay.     

Layered P2‐Type K0.44Ni0.22Mn0.78O2 as a High‐Performance Cathode for Potassium‐Ion Batteries

Potassium‐ion batteries (KIBs) are emerging as one of the most promising candidates for large‐scale energy storage owing to the natural abundance of the materials required for their fabrication and the fact that their intercalation mechanism is identical to that of lithium‐ion batteries. However, the larger ionic radius of K⁺ is likely to induce larger volume expansion and sluggish kinetics, resulting in low specific capacity and unsatisfactory cycle stability. A new Ni/Mn‐based layered oxide, P2‐type K_0.44Ni_0.22Mn_0.78O₂, is designed and synthesized. A cathode designed using this material delivers a high specific capacity of 125.5 mAh g^?1 at 10 mA g^?1, good cycle stability with capacity retention of 67% over 500 cycles and fast kinetic properties. In situ X‐ray diffraction recorded for the initial two cycles reveals single solid‐solution processes under P2‐type framework with small volume change of 1.5%. Moreover, a cathode electrolyte interphase layer is observed on the surface of the electrode after cycling with possible components of K₂CO₃, RCO₂K, KOR, KF, etc. A full cell using K_0.44Ni_0.22Mn_0.78O₂ as the cathode and soft carbon as the anode also exhibits exceptional performance, with capacity retention of 90% over 500 cycles as well as superior rate performance. These findings suggest P2‐K_0.44Ni_0.22Mn_0.78O₂ is a promising candidate as a high‐performance cathode for KIBs.     

Novel Cathode Materials for Na‐Ion Batteries Composed of Spoke‐Like Nanorods of Na[Ni0.61Co0.12Mn0.27]O2 Assembled in Spherical Secondary Particles

The development of high‐energy and high‐power density sodium‐ion batteries is a great challenge for modern electrochemistry. The main hurdle to wide acceptance of sodium‐ion batteries lies in identifying and developing suitable new electrode materials. This study presents a composition‐graded cathode with average composition Na[Ni_0.61Co_0.12Mn_0.27]O₂, which exhibits excellent performance and stability. In addition to the concentration gradients of the transition metal ions, the cathode is composed of spoke‐like nanorods assembled into a spherical superstructure. Individual nanorod particles also possess strong crystallographic texture with respect to the center of the spherical particle. Such morphology allows the spoke‐like nanorods to assemble into a compact structure that minimizes its porosity and maximizes its mechanical strength while facilitating Na⁺‐ion transport into the particle interior. Microcompression tests have explicitly verified the mechanical robustness of the composition‐graded cathode and single particle electrochemical measurements have demonstrated the electrochemical stability during Na⁺‐ion insertion and extraction at high rates. These structural and morphological features contribute to the delivery of high discharge capacities of 160 mAh (g oxide)^?1 at 15 mA g^?1 (0.1 C rate) and 130 mAh g^?1 at 1500 mA g^?1 (10 C rate). The work is a pronounced step forward in the development of new Na ion insertion cathodes with a concentration gradient.     

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.     

Armoring LiNi1/3Co1/3Mn1/3O2 Cathode with Reliable Fluorinated Organic–Inorganic Hybrid Interphase Layer toward Durable High Rate Battery

Ternary layered oxide materials have attracted extensive attention as a promising cathode candidate for high‐energy‐density lithium‐ion batteries. However, the undesirable electrochemical degradation at the electrode–electrolyte interface definitively shortens the battery service life. An effective and viable approach is proposed for improving the cycling stability of the LiNi_1/3Co_1/3Mn_1/3O₂ cathode using lithium difluorophosphate (LiPO₂F₂) paired with fuoroethylene carbonate (FEC) as co‐additives into conventional electrolytes. It is found that the co‐additives can greatly reduce the interface charge transfer impedance and significantly extend the life span of LiNi_1/3Co_1/3Mn_1/3O₂//Li (NMC//Li) batteries. The developed cathode demonstrates exceptional capacity retention of 88.7% and remains structural integrity at a high current of 5C after 500 cycles. Fundamental mechanism study indicates a dense, stable fluorinated organic–inorganic hybrid cathode‐electrolyte interphase (CEI) film derived from LiPO₂F₂ in conjunction with FEC additives on the surface of NMC cathode material, which significantly suppresses the decomposition of electrolyte and mitigates the dissolution of transition metal ions. The interfacial engineering of the electrode materials stabilized by the additives manipulation provides valuable guidance for the development of advanced cathode materials.     

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.     

Tuning Anionic Redox Activity and Reversibility for a High‐Capacity Li‐Rich Mn‐Based Oxide Cathode via an Integrated Strategy

When fabricating Li‐rich layered oxide cathode materials, anionic redox chemistry plays a critical role in achieving a large specific capacity. Unfortunately, the release of lattice oxygen at the surface impedes the reversibility of the anionic redox reaction, which induces a large irreversible capacity loss, inferior thermal stability, and voltage decay. Therefore, methods for improving the anionic redox constitute a major challenge for the application of high‐energy‐density Li‐rich Mn‐based cathode materials. Herein, to enhance the oxygen redox activity and reversibility in Co‐free Li‐rich Mn‐based Li_1.2Mn_0.6Ni_0.2O₂ cathode materials by using an integrated strategy of Li₂SnO₃ coating‐induced Sn doping and spinel phase formation during synchronous lithiation is proposed. As an Li⁺ conductor, a Li₂SnO₃ nanocoating layer protects the lattice oxygen from exposure at the surface, thereby avoiding irreversible oxidation. The synergy of the formed spinel phase and Sn dopant not only improves the anionic redox activity, reversibility, and Li⁺ migration rate but also decreases Li/Ni mixing. The 1% Li₂SnO₃‐coated Li_1.2Mn_0.6Ni_0.2O₂ delivers a capacity of more than 300 mAh g^?1 with 92% Coulombic efficiency. Moreover, improved thermal stability and voltage retention are also observed. This synergic strategy may provide insights for understanding and designing new high‐performance materials with enhanced reversible anionic redox and stabilized surface lattice oxygen.     

Enhanced Cycling Stability of Rechargeable Li–O2 Batteries Using High‐Concentration Electrolytes

The stability of electrolytes against highly reactive, reduced oxygen species is crucial for the development of rechargeable Li–O₂ batteries. In this work, the effect of lithium salt concentration in 1,2‐dimethoxyethane (DME)‐based electrolytes on the cycling stability of Li–O₂ batteries is investigated systematically. Cells with highly concentrated electrolyte demonstrate greatly enhanced cycling stability under both full discharge/charge (2.0–4.5 V vs Li/Li⁺) and the capacity‐limited (at 1000 mAh g^?1) conditions. These cells also exhibit much less reaction residue on the charged air‐electrode surface and much less corrosion of the Li‐metal anode. Density functional theory calculations are used to calculate molecular orbital energies of the electrolyte components and Gibbs activation energy barriers for the superoxide radical anion in the DME solvent and Li⁺–(DME) _n solvates. In a highly concentrated electrolyte, all DME molecules are coordinated with salt cations, and the C–H bond scission of the DME molecule becomes more difficult. Therefore, the decomposition of the highly concentrated electrolyte can be mitigated, and both air cathodes and Li‐metal anodes exhibit much better reversibility, resulting in improved cyclability of Li–O₂ batteries.     

Local State‐of‐Charge Mapping of Lithium‐Ion Battery Electrodes

Current lithium‐ion battery technology is gearing towards meeting the robust demand of power and energy requirements for all‐electric transportation without compromising on the safety, performance, and cycle life. The state‐of‐charge (SOC) of a Li‐ion cell can be a macroscopic indicator of the state‐of‐health of the battery. The microscopic origin of the SOC relates to the local lithium content in individual electrode particles and the effective ability of Li‐ions to transport or shuttle between the redox couples through the cell geometric boundaries. Herein, micrometer‐resolved Raman mapping of a transition‐metal‐based oxide positive electrode, Li_1‐x(Ni_yCo_zAl_1‐y‐z)O₂, maintained at different SOCs, is shown. An attempt has been made to link the underlying changes to the composition and structural integrity at the individual particle level. Furthermore, an SOC distribution at macroscopic length scale of the electrodes is presented.     

Electrical Conductivity Gradient Based on Heterofibrous Scaffolds for Stable Lithium‐Metal Batteries

The inability to guide the nucleation locations of electrochemically deposited Li has long been considered the main factor limiting the utilization of high‐energy‐density Li‐metal batteries. In this study, an electrical conductivity gradient interfacial host comprising 1D high conductivity copper nanowires and nanocellulose insulating layers is used in stable Li‐metal anodes. The conductivity gradient system guides the nucleation sites of Li‐metal to be directed during electrochemical plating. Additionally, the controlled parameter of the intermediate layer affects the highly stable Li‐metal plating. The electrochemical behavior is confirmed through experiments associated with the COMSOL Multiphysics simulation data. The distributed Li‐ion reaction flux resulting from the controlled electrical conductivity enables stable cycling for more than 250 cycles at 1 mA cm^?2. The gradient system effectively suppresses dendrite growth even at a high current density of 5 mA cm^?2 and ensures Li plating and stripping with ultra‐long‐term stability. To demonstrate the high‐energy‐density full‐cell application of the developed anode, it is paired with the LiNi_0.8Co_0.1Mn_0.1O₂ cathode. The cells demonstrate a high capacity retention of 90% with an extremely high Coulombic efficiency of 99.8% over 100 cycles. These results shed light on the formidable challenges involved in exploiting the engineering aspects of high‐energy‐density Li‐metal batteries.     

Emerging Dual‐Channel Transition‐Metal‐Oxide Quasiaerogels by Self‐Embedded Templating

The lack of precise control of particle sizes is the critical challenge in the assembly of 3D interconnected transition‐metal oxide (TMO) for newly‐emerging energy conversion devices. A self‐embedded templating strategy for preparing the TMO@carbon quasiaerogels (TMO@C‐QAs) is proposed. By mimicking an aerogel structure at a microscale, the TMO@C‐QA successfully assembles size‐controllable TMO nanoparticles into 3D interconnected structure with surface‐enriched carbon species. The morphological evolutions of intermediates verify that the self‐embedded Ostwald ripening templating approach is responsible for the dual‐channel TMO@C‐QA formation. The general self‐embedded templating strategy is easily extended to prepare various TMO@C‐QAs, including the Co₃O₄@C‐QA, Mn₃O₄@C‐QA, Fe₂O₃@C‐QA, and NiO@C‐QA. Benefiting from the unparalleled 3D interconnected network of aerogels, the Co₃O₄@C‐QA displays superior bifunctional catalytic activities for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), as well as high specific capacity and excellent long‐term stability for lithium‐ion battery (LIB) anode. A proof‐of‐concept battery‐powered electrolyzer with Co₃O₄@C‐QA cathode and anode powered by a full LIB with Co₃O₄@C‐QA anode is presented. The battery‐powered electrolyzer made of the state‐of‐the‐art TMOs can exhibit great competitive advantages due to its supreme multifunctional energy conversion performance for future water electrolysis.     

Facile Preparation of High‐Content N‐Doped CNT Microspheres for High‐Performance Lithium Storage

Herein, high‐content N‐doped carbon nanotube (CNT) microspheres (HNCMs) are successfully synthesized through simple spray drying and one‐step pyrolysis. HNCM possesses a hierarchically porous architecture and high‐content N‐doping. In particular, HNCM800 (HNCM pyrolyzed at 800 °C) shows high nitrogen content of 12.43 at%. The porous structure derived from well‐interconnected CNTs not only offers a highly conductive network and blocks diffusion of soluble lithium polysulfides (LiPSs) in physical adsorption, but also allows sufficient sulfur infiltration. The incorporation of N‐rich CNTs provides strong chemical immobilization for LiPSs. As a sulfur host for lithium–sulfur batteries, good rate capability and high cycling stability is achieved for HNCM/S cathodes. Particularly, the HNCM800/S cathode delivers a high capacity of 804 mA h g^?1 at 0.5 C after 1000 cycles corresponding to low fading rate (FR) of only 0.011% per cycle. Remarkably, the cathode with high sulfur loading of 6 mg cm^?2 still maintains high cyclic stability (capacity of 555 mA h g^?1 after 1000 cycles, FR 0.038%). Additionally, CNT/Co₃O₄ microspheres are obtained by the oxidation of CNTs/Co in the air. The as‐prepared CNT/Co₃O₄ microspheres are employed as an anode for lithium‐ion batteries and present excellent cycling performance.     

In‐Plane Assembled Orthorhombic Nb2O5 Nanorod Films with High‐Rate Li+ Intercalation for High‐Performance Flexible Li‐Ion Capacitors

Organic hybrid supercapacitors that consist of a battery electrode and a capacitive electrode show greatly improved energy density, but their power density is generally limited by the poor rate capability of battery‐type electrodes. In addition, flexible organic hybrid supercapacitors are rarely reported. To address the above issues, herein an in‐plane assembled orthorhombic Nb₂O₅ nanorod film anode with high‐rate Li⁺ intercalation to develop a flexible Li‐ion hybrid capacitor (LIC) is reported. The binder‐/additive‐free film exhibits excellent rate capability (≈73% capacity retention with the rate increased from 0.5 to 20 C) and good cycling stability (>2500 times). Kinetic analyses reveal that the high rate performance is mainly attributed to the excellent in‐plane assembly of interconnected single‐crystalline Nb₂O₅ nanorods on the current collector, ensuring fast electron transport, facile Li‐ion migration in the porous film, and greatly reduced ion‐diffusion length. Using such a Nb₂O₅ film as anode and commercial activated carbon as cathode, a flexible LIC is designed. It delivers both high gravimetric and high volumetric energy/power densities (≈95.55 Wh kg^?1/5350.9 W kg^?1; 6.7 mW h cm^?3/374.63 mW cm^?3), surpassing previous typical Li‐intercalation electrode‐based LICs. Furthermore, this LIC device still keeps good electrochemical attributes even under serious bending states (30°–180°).