A Carbonyl Compound‐Based Flexible Cathode with Superior Rate Performance and Cyclic Stability for Flexible Lithium‐Ion Batteries

A sulfur‐linked carbonyl‐based poly(2,5‐dihydroxyl‐1,4‐benzoquinonyl sulfide) (PDHBQS) compound is synthesized and used as cathode material for lithium‐ion batteries (LIBs). Flexible binder‐free composite cathode with single‐wall carbon nanotubes (PDHBQS–SWCNTs) is then fabricated through vacuum filtration method with SWCNTs. Electrochemical measurements show that PDHBQS–SWCNTs cathode can deliver a discharge capacity of 182 mA h g⁻¹ (0.9 mA h cm⁻²) at a current rate of 50 mA g⁻¹ and a potential window of 1.5 V–3.5 V. The cathode delivers a capacity of 75 mA h g⁻¹ (0.47 mA h cm⁻²) at 5000 mA g⁻¹, which confirms its good rate performance at high current density. PDHBQS–SWCNTs flexible cathode retains 89% of its initial capacity at 250 mA g⁻¹ after 500 charge–discharge cycles. Furthermore, large‐area (28 cm²) flexible batteries based on PDHBQS–SWCNTs cathode and lithium foils anode are also assembled. The flexible battery shows good electrochemical activities with continuous bending, which retains 88% of its initial discharge capacity after 2000 bending cycles. The significant capacity, high rate performance, superior cyclic performance, and good flexibility make this material a promising candidate for a future application of flexible LIBs.     

A Novel Graphite–Graphite Dual Ion Battery Using an AlCl3–[EMIm]Cl Liquid Electrolyte

Herein, a novel graphite–graphite dual ion battery (GGDIB) based on a AlCl₃/1‐ethyl‐3‐methylimidazole Cl ([EMIm]Cl) room temperature ionic liquid electrolyte, using conductive graphite paper as cathode and anode material is developed. The working principle of the GGDIB is investigated, that is, metallic aluminum is deposited/dissolved on the surface of the anode, and chloroaluminate ions are intercalated/deintercalated in the cathode material. The self‐discharge phenomenon and pseudocapacitive behavior of the GGDIB are also analyzed. The GGDIB shows excellent rate performance and cycle performance due to the high ionic conductivity of ionic liquids. The initial discharge capacity is 76.5 mA h g⁻¹ at a current density of 200 mA g⁻¹ over a voltage window of 0.1–2.3 V, and the capacity remains at 62.3 mA h g⁻¹ after 1000 cycles with a corresponding capacity retention of 98.42% at a current density of 500 mA g⁻¹. With the merits of environmental friendliness and low cost, the GGDIB has a great advantage in the future of energy storage application.     

Hierarchically 3D structured milled lamellar MoS2/nano-silicon@carbon hybrid with medium capacity and long cycling sustainability as anodes for lithium-ion batteries

A hierarchically 3D structured milled lamellar MoS₂/nano-silicon@carbon hybrid with medium capacity and long-term lifespan is designed by a green and scalable approach using ball milling process and spray-drying/pyrolysis routes. The microspheres consist of low-content nano-silicon (20 wt%), milled lamellar MoS₂ sheets and porous carbon skeletons. A mixture of silicon nanoparticles and MoS₂ flakes serves as an inner core, while porous carbon pyrolyzed from petroleum pitch acts as a protective shell. The particular architecture affords robust mechanical support, abundant buffering space and enhanced electrical conductivity, thus effectively accommodating drastic volume variation during repetitive Li⁺ intercalation/extraction. The Si/MoS₂@C hybrid delivers a high initial discharge specific capacity of 1257.8 mA h g⁻¹ and exhibits a reversible capacity of 767.52 mA h g⁻¹ at a current density 100 mA g^-1 after 250 cycles. Most impressively, the electrode depicts a superior long-cycling durability with a discharge capacity of 537.6 mA h g⁻¹ even after 1200 cycles at a current density of 500 mA g^-1. Meanwhile, the hybrid also shows excellent rate performance such as 388.1 mA h g⁻¹ even at a large current density of 3000 mA g^-1.     

A Binder‐Free and Free‐Standing Cobalt Sulfide@Carbon Nanotube Cathode Material for Aluminum‐Ion Batteries

Rechargeable aluminum‐ion batteries (AIBs) are considered as a new generation of large‐scale energy‐storage devices due to their attractive features of abundant aluminum source, high specific capacity, and high energy density. However, AIBs suffer from a lack of suitable cathode materials with desirable capacity and long‐term stability, which severely restricts the practical application of AIBs. Herein, a binder‐free and self‐standing cobalt sulfide encapsulated in carbon nanotubes is reported as a novel cathode material for AIBs. The resultant new electrode material exhibits not only high discharge capacity (315 mA h g⁻¹ at 100 mA g⁻¹) and enhanced rate performance (154 mA h g⁻¹ at 1 A g⁻¹), but also extraordinary cycling stability (maintains 87 mA h g⁻¹ after 6000 cycles at 1 A g⁻¹). The free‐standing feature of the electrode also effectively suppresses the side reactions and material disintegrations in AIBs. The new findings reported here highlight the possibility for designing high‐performance cathode materials for scalable and flexible AIBs.     

In Situ Carbon‐Doped Mo(Se0.85S0.15)2 Hierarchical Nanotubes as Stable Anodes for High‐Performance Sodium‐Ion Batteries

Sodium‐ion batteries (SIBs) are promising energy storage devices, but suffer from poor cycling stability and low rate capability. In this work, carbon doped Mo(Se_0.85S_0.15)₂ (i.e., Mo(Se_0.85S_0.15)₂:C) hierarchical nanotubes have been synthesized for the first time and serve as a robust and high‐performance anode material. The hierarchical nanotubes with diameters of 300 nm and wall thicknesses of 50 nm consist of numerous 2D layered nanosheets, and can act as a robust host for sodiation/desodiation cycling. The Mo(Se_0.85S_0.15)₂:C hierarchical nanotubes deliver a discharge capacity of 360 mAh g⁻¹ at a high current density of 2000 mA g⁻¹ and keep a 81.8% capacity retention compared to that at a current density of 50 mA g⁻¹, showing superior rate capability. Comparing with the second cycle discharge capacities, the nanotube anode can maintain capacities of 102.2%, 101.9%, and 97.8% after 100 cycles at current densities of 200, 500, and 1000 mA g⁻¹, respectively. This work demonstrates the best cycling performance and high‐rate sodium storage capabilities of MoSe₂ for SIBs to date. The hollow interior, hierarchical organization, layered structure, and carbon doping are beneficial for fast Na⁺‐ion and electron kinetics and are responsible for the stable cycling performance and high rate capabilities.     

Homologous Heterostructured NiS/NiS2@C Hollow Ultrathin Microspheres with Interfacial Electron Redistribution for High-Performance Sodium Storage

Nickel sulfides with high theoretical capacity are considered as promising anode materials for sodium-ion batteries (SIBs); however, their intrinsic poor electric conductivity, large volume change during charging/discharging, and easy sulfur dissolution result in inferior electrochemical performance for sodium storage. Herein, a hierarchical hollow microsphere is assembled from heterostructured NiS/NiS₂ nanoparticles confined by in situ carbon layer (H-NiS/NiS₂@C) via regulating the sulfidation temperature of the precursor Ni-MOFs. The morphology of ultrathin hollow spherical shells and confinement of in situ carbon layer to active materials provide rich channels for ion/electron transfer and alleviate the effects of volume change and agglomeration of the material. Consequently, the as-prepared H-NiS/NiS₂@C exhibit superb electrochemical properties, satisfactory initial specific capacity of 953.0 mA h g⁻¹ at 0.1 A g⁻¹, excellent rate capability of 509.9 mA h g⁻¹ at 2 A g⁻¹, and superior longtime cycling life with 433.4 mA h g⁻¹ after 4500 cycles at 10 A g⁻¹. Density functional theory calculation shows that heterogenous interfaces with electron redistribution lead to charge transfer from NiS to NiS₂, and thus favor interfacial electron transport and reduce ion-diffusion barrier. This work provides an innovative idea for the synthesis of homologous heterostructures for high-efficiency SIB electrode materials.     

Fe2VO4 Hierarchical Porous Microparticles Prepared via a Facile Surface Solvation Treatment for High‐Performance Lithium and Sodium Storage

Preventing the aggregation of nanosized electrode materials is a key point to fully utilize the advantage of the high capacity. In this work, a facile and low‐cost surface solvation treatment is developed to synthesize Fe₂VO₄ hierarchical porous microparticles, which efficiently prevents the aggregation of the Fe₂VO₄ primary nanoparticles. The reaction between alcohol molecules and surface hydroxy groups is confirmed by density functional theory calculations and Fourier transform infrared spectroscopy. The electrochemical mechanism of Fe₂VO₄ as lithium‐ion battery anode is characterized by in situ X‐ray diffraction for the first time. This electrode material is capable of delivering a high reversible discharge capacity of 799 mA h g^?1 at 0.5 A g^?1 with a high initial coulombic efficiency of 79%, and the capacity retention is 78% after 500 cycles. Moreover, a remarkable reversible discharge capacity of 679 mA h g^?1 is achieved at 5 A g^?1. Furthermore, when tested as sodium‐ion battery anode, a high reversible capacity of 382 mA h g^?1 can be delivered at the current density of 1 A g^?1, which still retains at 229 mA h g^?1 after 1000 cycles. The superior electrochemical performance makes it a potential anode material for high‐rate and long‐life lithium/sodium‐ion batteries.     

Capacity stabilization of layered Li0.9Mn0.9Ni0.1O2 cathode material by employing ZnO coating

Li_0.9Mn_0.9Ni_0.1O₂ has been prepared by an ion-exchange process and evaluated as the positive electrode material for lithium-ion battery application. The particles of the oxide have been subjected to surface modification by coating a thin layer of ZnO. Both the ZnO coated and bare samples have been characterized by chemical analysis, powder X-ray diffraction, scanning electron microscopy, EDAX, EDS-dot mapping, cyclic voltammetry, charge–discharge cycling and AC impedance spectroscopy. The physicochemical studies suggest the formation of a layered structure in the oxide with a uniformly dispersed ZnO coating on fine particles. The electrochemical studies suggest a stable discharge capacity of 210 mA h g⁻¹ for ZnO coated oxide over about 50 cycles tested in the studies. By contrast, the capacity of bare oxide decreases rapidly on cycling. The enhanced performance of these electrodes is also reflected in AC impedance studies.     

Double-Walled NiTeSe–NiSe2 Nanotubes Anode for Stable and High-Rate Sodium-Ion Batteries

Electrodes made of composites with heterogeneous structure hold great potential for boosting ionic and charge transfer and accelerating electrochemical reaction kinetics. Herein, hierarchical and porous double-walled NiTeSe–NiSe₂ nanotubes are synthesized by a hydrothermal process assisted in situ selenization. Impressively, the nanotubes have abundant pores and multiple active sites, which shorten the ion diffusion length, decrease Na⁺ diffusion barriers, and increase the capacitance contribution ratio of the material at a high rate. Consequently, the anode shows a satisfactory initial capacity (582.5 mA h g⁻¹ at 0.5 A g⁻¹), a high-rate capability, and long cycling stability (1400 cycles, 398.6 mAh g⁻¹ at 10 A g⁻¹, 90.5% capacity retention). Moreover, the sodiation process of NiTeSe–NiSe₂ double-walled nanotubes and underlying mechanism of the enhanced performance are revealed by in situ and ex situ transmission electron microscopy and theoretical calculations.     

Surface modification with oxygen vacancy in Li-rich layered oxide Li1.2Mn0.54Ni0.13Co0.13O2 for lithium-ion batteries

A couple of layered Li-rich cathode materials Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ without any carbon modification are successfully synthesized by solvothermal and hydrothermal methods followed by a calcination process. The sample synthesized by the solvothermal method (S-NCM) possesses more homogenous microstructure, lower cation mixing degree and more oxygen vacancies on the surface, compared to the sample prepared by the hydrothermal method (H-NCM). The S-NCM sample exhibits much better cycling performance, higher discharge capacity and more excellent rate performance than H-NCM. At 0.2 C rate, the S-NCM sample delivers a much higher initial discharge capacity of 292.3 mAh g⁻¹ and the capacity maintains 235 mAh g⁻¹ after 150 cycles (80.4% retention), whereas the corresponding capacity values are only 269.2 and 108.5 mAh g⁻¹ (40.3% retention) for the H-NCM sample. The S-NCM sample also shows the higher rate performance with discharge capacity of 118.3 mAh g⁻¹ even at a high rate of 10 C, superior to that (46.5 mAh g⁻¹) of the H-NCM sample. The superior electrochemical performance of the S-NCM sample can be ascribed to its well-ordered structure, much larger specific surface area and much more oxygen vacancies located on the surface.     

Sandwich‐like MoS2@SnO2@C with High Capacity and Stability for Sodium/Potassium Ion Batteries

Sandwich‐like MoS₂@SnO₂@C nanosheets are prepared by facile hydrothermal reactions. SnO₂ nanosheets can attach to exfoliated MoS₂ nanosheets to prevent restacking of adjacent MoS₂ nanosheets, and carbon transformed from polyvinylpyrrolidone is coated on MoS₂@SnO₂, forming a sandwich structure to maintain cycling stability. As an anode for sodium‐ion batteries, the electrode greatly deliverers a high initial discharge specific capacity of 530 mA h g^?1 and maintains at 396 mA h g^?1 after 150 cycles at 0.1 A g^?1. Even at a large current density of 1 A g^?1, it can hold 230 mA h g^?1 after 450 cycles. Besides, as an anode for K⁺ storage, the electrode also shows a discharge capacity of 312 mA h g^?1 after 25 cycles at 0.05 A g^?1. This work may provide a new strategy to prepare other composites which can be applied to new kind of rechargeable batteries.     

Li-ion storage performance and electrochemically induced phase evolution of layer-structured Li[Li<Subscript>0.2</Subscript>Mn<Subscript>0.54</Subscript>Ni<Subscript>0.13</Subscript>Co<Subscript>0.13</Subscript>]O<Subscript>2</Subscript> cathode material

Li-rich Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂ (LMNC) powders were synthesized by a gel-combustion method. The related microstructure, electrochemical performance and electrochemically induced phase evolution were characterized. The 900°C calcined powders have a hexagonal layered structure with high ordered degree and low cationic mixing level. The calcined materials as cathode electrode for Li-ion battery deliver the high electrochemical properties with an initial discharge capacity of 243.5 mA?h?g^–1 at 25 mA?g^–1 and 249.2 mA?h?g^–1 even after 50 cycles. The electrochemically induced phase evolution investigated by a transmission electron microscopy indicates that Li⁺ ions deintercalated first from the LiMO₂ (M = Mn, Co, Ni) component and then from Li₂MnO₃ component in the LMNC during the charge process, while Li⁺ ions intercalated into Li_1–xMO₂ component followed by into MnO₂ component during the discharge process.     

Low-temperature synthesis of CeB6 nanowires and nanoparticles as feasible lithium-ion anode materials

Metallic CeB₆ nanomaterials were prepared via the low-temperature solution combustion method (nanoparticles) and high-pressure solid state reaction (nanowires). X-ray diffraction patterns and High-resolution transmission electron microscopy images reveal that CeB₆ nanoparticles are highly crystalline and CeB₆ nanowires are single crystals. The X-ray photoelectron spectroscopy analysis indicates that the cerium is present in the +3 and +4 mixed-valence state in CeB₆. As lithium-ion anodes, CeB₆ nanowires (nanoparticles) electrode achieves a capacity of ~531 (338) mA h g⁻¹ in the initial cycle and keeps a reversible capacity of ~225 (185) mA h g⁻¹ after 60 cycles. CeB₆ nanowires are tested for 6000 cycles at 1000 mA g⁻¹, which shows a specific capacity approaching to the capacity at 100 mA g⁻¹ in spite of fluctuation within a narrow range, and keep ~168 mA h g⁻¹ after 6000 cycles, indicating a stable cycling performance owing to the excellent metal-like conductivity of (~5.67 × 10³ S m⁻¹). The reason of capacity rising is that the reduction and oxidation levels of CeB₆ electrodes are improved after the 2nd cycle with Li⁺ insertion/extraction. Meanwhile, kinetic analysis reveals that the Li⁺ storage mechanism is mainly controlled by a surface capacitive behavior.     

Synthesis of MoS2@C Nanotubes Via the Kirkendall Effect with Enhanced Electrochemical Performance for Lithium Ion and Sodium Ion Batteries

A MoS₂@C nanotube composite is prepared through a facile hydrothermal method, in which the MoS₂ nanotube and amorphous carbon are generated synchronically. When evaluated as an anode material for lithium ion batteries (LIB), the MoS₂@C nanotube manifests an enhanced capacity of 1327 mA h g^?1 at 0.1 C with high initial Coulombic efficiency (ICE) of 92% and with capacity retention of 1058.4 mA h g^?1 (90% initial capacity retention) after 300 cycles at a rate of 0.5 C. A superior rate capacity of 850 mA h g^?1 at 5 C is also obtained. As for sodium ion batteries, a specific capacity of 480 mA h g^?1 at 0.5 C is achieved after 200 cycles. The synchronically formed carbon and stable hollow structure lead to the long cycle stability, high ICE, and superior rate capability. The good electrochemical behavior of MoS₂@C nanotube composite suggests its potential application in high‐energy LIB.     

Amine–Aldehyde Condensation-Derived N-Doped Hard Carbon Microspheres for High-Capacity and Robust Sodium Storage

Hard carbon is generally accepted as the choice of anode material for sodium-ion batteries. However, integrating high capacity, high initial Coulombic efficiency (ICE), and good durability in hard carbon materials remains challenging. Herein, N-doped hard carbon microspheres (NHCMs) with abundant Na⁺ adsorption sites and tunable interlayer distance are constructed based on the amine–aldehyde condensation reaction using m-phenylenediamine and formaldehyde as the precursors. The optimized NHCM-1400 with a considerable N content (4.64%) demonstrates a high ICE (87%), high reversible capacity with ideal durability (399 mAh g⁻¹ at 30 mA g⁻¹ and 98.5% retention over 120 cycles), and decent rate capability (297 mAh g⁻¹ at 2000 mA g⁻¹). In situ characterizations elucidate the adsorption–intercalation-filling sodium storage mechanism of NHCMs. Theoretical calculation reveals that the N-doping decreases the Na⁺ adsorption energy on hard carbon.     

Graphene‐Protected 3D Sb‐based Anodes Fabricated via Electrostatic Assembly and Confinement Replacement for Enhanced Lithium and Sodium Storage

Alloy anodes have shown great potential for next‐generation lithium‐ion batteries (LIBs) and sodium‐ion batteries (SIBs). However, these applications are still limited by inherent huge volume changes and sluggish kinetics. To overcome such limitations, graphene‐protected 3D Sb‐based anodes grown on conductive substrate are designed and fabricated by a facile electrostatic‐assembling and subsequent confinement replacement strategy. As binder‐free anodes for LIBs, the obtained electrode exhibits reversible capacities of 442 mAh g⁻¹ at 100 mA g⁻¹ and 295 mAh g⁻¹ at 1000 mA g⁻¹, and a capacity retention of above 90% (based on the 10th cycle) after 200 cycles at 500 mA g⁻¹. As for sodium storage properties, the reversible capacities of 517 mAh g⁻¹ at 50 mA g⁻¹ and 315 mAh g⁻¹ at 1000 mA g⁻¹, the capacity retention of 305 mAh g⁻¹ after 100 cycles at 300 mA g⁻¹ are obtained, respectively. Furthermore, the 3D architecture retains good structural integrity after cycling, confirming that the introduction of high‐stretchy and robust graphene layers can effectively buffer alloying anodes, and simultaneously provide sustainable contact and protection of the active materials. Such findings show its great potential as superior binder‐free anodes for LIBs and SIBs.     

A Gradient Doping Strategy toward Superior Electrochemical Performance for Li-Rich Mn-Based Cathode Materials

Lithium-rich layered oxides (LLOs) are concerned as promising cathode materials for next-generation lithium-ion batteries due to their high reversible capacities (larger than 250 mA h g⁻¹). However, LLOs suffer from critical drawbacks, such as irreversible oxygen release, structural degradation, and poor reaction kinetics, which hinder their commercialization. Herein, the local electronic structure is tuned to improve the capacity energy density retention and rate performance of LLOs via gradient Ta⁵⁺ doping. As a result, the capacity retention elevates from 73% to above 93%, and the energy density rises from 65% to above 87% for LLO with modification at 1 C after 200 cycles. Besides, the discharge capacity for the Ta⁵⁺ doped LLO at 5 C is 155 mA h g⁻¹, while it is only 122 mA h g⁻¹ for bare LLO. Theoretical calculations reveal that Ta⁵⁺ doping can effectively increase oxygen vacancy formation energy, thus guaranteeing the structure stability during the electrochemical process, and the density of states results indicate that the electronic conductivity of the LLOs can be boosted significantly at the same time. This strategy of gradient doping provides a new avenue to improve the electrochemical performance of the LLOs by modulating the local structure at the surface.     

Dispersed distribution derived integrated anode for lithium ion battery

With the development of portable communication devices and electric vehicles, there is a great need for energy storage devices with lighter weight and higher energy density. In this paper, a new method by combining waster-paper-synthesized conductive paper (CP) and active material MnO₂ together is developed to obtain a new type of anode without any binder for lithium ion batteries. By this way, we can obtain low density anode with active material in CP, instead of the commonly-used heavy metal current collector. Also, binder has been abandoned, which are usually used to combine active material into anode, to further decrease weight. The multi walled carbon nanotube (MWCNT) was added in serves as a component of CP and the conductive agent for active material. Compared to traditional anode coated on Cu current collector, the CP-combined anode can greatly improve the electrochemical performance of active material MnO₂. It can let more particles to fully participate in the reaction and therefore boost the specific capacity to a great extent (about 3 times higher). It delivered an initial specific capacity of 1629.9 mA h g⁻¹ at a current density of 100 mA g⁻¹ and maintained about 67% even after 100 cycles. What’s more, it shows reversible capacity of about 260 mA h g⁻¹ at high current density of 1000 mA h g⁻¹. Our original synthesis method of anode, which shows far-reaching referential value and environmental significance, can be generalized to other electrodes and other battery systems.     

Porous Carbon Nanofibers Encapsulated with Peapod‐Like Hematite Nanoparticles for High‐Rate and Long‐Life Battery Anodes

Fe₂O₃ is regarded as a promising anode material for lithium‐ion batteries (LIBs) and sodium‐ion batteries (SIBs) due to its high specific capacity. The large volume change during discharge and charge processes, however, induces significant cracking of the Fe₂O₃ anodes, leading to rapid fading of the capacity. Herein, a novel peapod‐like nanostructured material, consisting of Fe₂O₃ nanoparticles homogeneously encapsulated in the hollow interior of N‐doped porous carbon nanofibers, as a high‐performance anode material is reported. The distinctive structure not only provides enough voids to accommodate the volume expansion of the pea‐like Fe₂O₃ nanoparticles but also offers a continuous conducting framework for electron transport and accessible nanoporous channels for fast diffusion and transport of Li/Na‐ions. As a consequence, this peapod‐like structure exhibits a stable discharge capacity of 1434 mAh g^?1 (at 100 mA g^?1) and 806 mAh g^?1 (at 200 mA g^?1) over 100 cycles as anode materials for LIBs and SIBs, respectively. More importantly, a stable capacity of 958 mAh g^?1 after 1000 cycles and 396 mAh g^?1 after 1500 cycles can be achieved for LIBs and SIBs, respectively, at a large current density of 2000 mA g^?1. This study provides a promising strategy for developing long‐cycle‐life LIBs and SIBs.     

A Novel High‐Capacity Anode Material Derived from Aromatic Imides for Lithium‐Ion Batteries

A novel anode material for lithium‐ion batteries derived from aromatic imides with multicarbonyl group conjugated with aromatic core structure is reported, benzophenolne‐3,3′,4,4′‐tetracarboxylimide oligomer (BTO). It could deliver a reversible capacity of 829 mA h g^?1 at 42 mA g^?1 for 50 cycles with a stable discharge plateaus ranging from 0.05–0.19 V versus Li⁺/Li. At higher rates of 420 and 840 mA g^?1, it can still exhibit excellent cycling stability with a capacity retention of 88% and 72% after 1000 cycles, delivering capacity of 559 and 224 mA h g^?1. In addition, a rational prediction of the maximum amount of lithium intercalation is proposed and explored its possible lithium storage mechanism.