Carbonyl-rich Poly(pyrene-4,5,9,10-tetraone Sulfide) as Anode Materials for High-Performance Li and Na-Ion Batteries

Organic carbonyl electrode materials are widely employed for alkali metal-ion secondary batteries in terms of their sustainability, structure designability and abundant resources. As a typical redox-active organic electrode materials, pyrene-4, 5, 9, 10-tetraone (PT) shows high theoretical capacity due to the rich carbonyl active sites. But its electrochemical behavior in secondary batteries still needs further exploration. Herein, PT-based linear polymers (PPTS) is synthesized with thioether bond as bridging group and then employed as an anode material for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). As expected, PPTS shows improved conductivity and insolubility in the non-aqueous electrolyte. When used as an anode material for LIBs, PPTS delivers a high reversible specific capacity of 697.1 mAh g⁻¹ at 0.1 A g⁻¹ and good rate performance (335.4 mAh g⁻¹ at 1 A g⁻¹). Moreover, a reversible specific capacity of 205.2 mAh g⁻¹ at 0.05 A g⁻¹ could be obtained as an anode material for SIBs.     

Advanced Li-Ion Batteries with High Rate,Stability, and Mass Loading Based on Graphene Ribbon Hybrid Networks

To optimize the cycle life and rate performance of lithium-ion batteries (LIBs), ultra-fine Fe₂O₃ nanowires with a diameter of approximately 2 nm uniformly anchored on a cross-linked graphene ribbon network are fabricated. The unique three-dimensional structure can effectively improve the electrical conductivity and facilitate ion diffusion, especially cross-plane diffusion. Moreover, Fe₂O₃ nanowires on graphene ribbons (Fe₂O₃/GR) are easily accessible for lithium ions compared with the traditional graphene sheets (Fe₂O₃/GS). In addition, the well-developed elastic network can not only undergo the drastic volume expansion during repetitive cycling, but also protect the bulk electrode from further pulverization. As a result, the Fe₂O₃/GR hybrid exhibits high rate and long cycle life Li storage performance (632 mAh g⁻¹ at 5 A g⁻¹, and 471 mAh g⁻¹ capacity maintained even after 3000 cycles). Especially at high mass loading (≈4 mg cm⁻²), the Fe₂O₃/GR can still deliver higher reversible capacity (223 mAh g⁻¹ even at 2 A g⁻¹) compared with the Fe₂O₃/GS (37 mAh g⁻¹) for LIBs.     

Isomer Effect on Energy Storage of π-Extended S-Shaped Double[6]Heterohelicene

Recently, chiral and nonplanar cutouts of graphene have been the favorites due to their unique optical, electronic, and redox properties and high solubility compared with their planar counterparts. Despite the remarkable progress in helicenes, π-extended heterohelicenes have not been widely explored. As an anode in a lithium-ion battery, the racemic mixture of π-extended double heterohelical nanographene containing thienothiophene core exhibited a high lithium storage capability, attaining a specific capacity of 424 mAh g⁻¹ at 0.1 A g⁻¹ with excellent rate capability and superior long-term cycling performance over 6000 cycles with negligible fade. As a first report, the π-extended helicene isomer (PP and MM), with the more interlayer distance that helps faster diffusion of ions, has exhibited a high capacity of 300 mAh g⁻¹ at 2 A g⁻¹ with long-term cycling performance over 1500 cycles compared to the less performing MP and PM isomer and racemic mixture (150 mAh g⁻¹ at 2 A g⁻¹). As supported by single-crystal X-ray analysis, a unique molecular design of nanographenes with a fixed (helical) molecular geometry, avoiding restacking of the layers, renders better performance as an anode in lithium-ion batteries. Interestingly, the recycled nanographene anode material displayed comparable performance.     

Nine-Electron Transfer of Binder Synergistic π-d Conjugated Coordination Polymers as High-Performance Lithium Storage Materials

To solve the problems such as the dissolution and the poor conductivity of organic small molecule electrode materials, we construct π-d conjugated coordination polymer Ni-DHBQ with multiple redox-active centers as lithium storage materials. It exhibits an ultra-high capacity of 9-electron transfers, while the π-d conjugation and the laminar structure inside the crystal ensure fast electron transport and lithium ion diffusion, resulting in excellent rate performance (505.6 mAh g⁻¹ at 1 A g⁻¹ after 300 cycles). The interaction of Ni-DHBQ with the binder CMC synergistically inhibits its dissolution and anchors the Ni atoms, thus exhibiting excellent cycling stability (650.7 mAh g⁻¹ at 0.1 A g⁻¹ after 100 cycles). This work provides insight into the mechanism of lithium storage in π-d conjugated coordination polymers and the synergistic effect of CMC, which will contribute to the molecular design and commercial application of organic electrode materials.     

Importing Tin Nanoparticles into Biomass-Derived Silicon Oxycarbides with High-Rate Cycling Capability Based on Supercritical Fluid Technology

Silicon oxycarbides (SiOC) are regarded as potential anode materials for lithium-ion batteries, although inferior cycling stability and rate performance greatly limit their practical applications. Herein, amorphous SiOC is synthesized from Chlorella by means of a biotemplate method based on supercritical fluid technology. On this basis, tin particles with sizes of several nanometers are introduced into the SiOC matrix through the biosorption feature of Chlorella. As lithium-ion battery anodes, SiOC and Sn@SiOC can deliver reversible capacities of 440 and 502 mAh g⁻¹ after 300 cycles at 100 mA g⁻¹ with great cycling stability. Furthermore, as-synthesized Sn@SiOC presents an excellent high-rate cycling capability, which exhibits a reversible capacity of 209 mAh g⁻¹ after 800 cycles at 5000 mA g⁻¹; this is 1.6 times higher than that of SiOC. Such a novel approach has significance for the preparation of high-performance SiOC-based anodes.     

Scalable Synthesis of One-Dimensional Mesoporous ZnMnO3 Nanorods with Ultra-Stable and High Rate Capability for Efficient Lithium Storage

The cost-efficient ZnMnO₃ has attracted increasing attention as a prospective anode candidate for advanced lithium-ion batteries (LIBs) owing to its resourceful abundance, large lithium storage capacity and low operating voltage. However, its practical application is still seriously limited by the modest cycling and rate performances. Herein, a facile design to scalable synthesize unique one-dimensional (1D) mesoporous ZnMnO₃ nanorods (ZMO-NRs) composed of nanoscale particles (≈11 nm) is reported. The 1D mesoporous structure and nanoscale building blocks of the ZMO-NRs effectively promote the transport of ions/electrons, accommodate severe volume changes, and expose more active sites for lithium storage. Benefiting from these appealing structural merits, the obtained ZMO-NRs anode exhibits excellent rate behavior (≈454 mAh g⁻¹ at 2 A g⁻¹) and ultra-long term cyclic performance (≈949.7 mAh g⁻¹ even over 500 cycles at 0.5 A g⁻¹) for efficient lithium storage. Additionally, the LiNi_0.8Co_0.1Mn_0.1O₂//ZMO-NRs full cell presents a practical energy density (≈192.2 Wh kg⁻¹) and impressive cyclability with approximately 91 % capacity retention over 110 cycles. This highlights that the ZMO-NRs product is a highly promising high-rate and stable electrode candidate towards advanced LIBs in electronic devices and sustainable energy storage applications.     

Study of the Lithium Storage Mechanism of N-Doped Carbon-Modified Cu2S Electrodes for Lithium-Ion Batteries

Owing to their high specific capacity and abundant reserve, Cu_xS compounds are promising electrode materials for lithium-ion batteries (LIBs). Carbon compositing could stabilize the Cu_xS structure and repress capacity fading during the electrochemical cycling, but the corresponding Li⁺ storage mechanism and stabilization effect should be further clarified. In this study, nanoscale Cu₂S was synthesized by CuS co-precipitation and thermal reduction with polyelectrolytes. High-temperature synchrotron radiation diffraction was used to monitor the thermal reduction process. During the first cycle, the conversion mechanism upon lithium storage in the Cu₂S/carbon was elucidated by operando synchrotron radiation diffraction and in situ X-ray absorption spectroscopy. The N-doped carbon-composited Cu₂S (Cu₂S/C) exhibits an initial discharge capacity of 425 mAh g⁻¹ at 0.1 A g⁻¹, with a higher, long-term capacity of 523 mAh g⁻¹ at 0.1 A g⁻¹ after 200 cycles; in contrast, the bare CuS electrode exhibits 123 mAh g⁻¹ after 200 cycles. Multiple-scan cyclic voltammetry proves that extra Li⁺ storage can mainly be ascribed to the contribution of the capacitive storage.     

Structure Engineering of BiSbSx Nanocrystals Embedded within Sulfurized Polyacrylonitrile Fibers for High Performance of Potassium-Ion Batteries

Potassium-ion batteries (PIBs) are regarded as promising candidates in next-generation energy storage technology; however, the electrode materials in PIBs are usually restricted by the shortcomings of large volume expansion and poor cycling stability stemming from a high resistance towards diffusion and insertion of large-sized K ions. In this study, BiSbS_x nanocrystals are rationally integrated with sulfurized polyacrylonitrile (SPAN) fibres through electrospinning technology with an annealing process. Such a unique structure, in which BiSbS_x nanocrystals are embedded inside the SPAN fibre, affords multiple binding sites and a short diffusion length for K⁺ to realize fast kinetics. In addition, the molecular structure of SPAN features robust chemical interactions for stationary diffluent discharge products. Thus, the electrode demonstrates a superior potassium storage performance with an excellent reversible capacity of 790 mAh g⁻¹ (at 0.1 A g⁻¹ after 50 cycles) and 472 mAh g⁻¹ (at 1 A g⁻¹ after 2000 cycles). It's one of the best performances for metal dichalcogenides anodes for PIBs to date. The unusual performance of the BiSbS_x@SPAN composite is attributed to the synergistic effects of the judicious nanostructure engineering of BiSbS_x nanocrystals as well as the chemical interaction and confinement of SPAN fibers.     

Scalable Synthesis of Porous SiFe@C Composite with Excellent Lithium Storage

Utilizing cost-effective raw materials to prepare high-performance silicon-based anode materials for lithium-ion batteries (LIBs) is both challenging and attractive. Herein, a porous SiFe@C (pSiFe@C) composite derived from low-cost ferrosilicon is prepared via a scalable three-step procedure, including ball milling, partial etching, and carbon layer coating. The pSiFe@C material integrates the advantages of the mesoporous structure, the partially retained FeSi₂ conductive phase, and a uniform carbon layer (12–16 nm), which can substantially alleviate the huge volume expansion effect in the repeated lithium-ion insertion/extraction processes, effectively stabilizing the solid–electrolyte interphase (SEI) film and markedly enhancing the overall electronic conductivity of the material. Benefiting from the rational structure, the obtained pSiFe@C hybrid material delivers a reversible capacity of 1162.1 mAh g⁻¹ after 200 cycles at 500 mA g⁻¹, with a higher initial coulombic efficiency of 82.30 %. In addition, it shows large discharge capacities of 803.1 and 600.0 mAh g⁻¹ after 500 cycles at 2 and 4 A g⁻¹, respectively, manifesting an excellent electrochemical lithium storage. This work provides a good prospect for the commercial production of silicon-based anode materials for LIBs with a high lithium-storage capacity.     

Hierarchical Hollow-Nanocube Ni−Co Skeleton@MoO3/MoS2 Hybrids for Improved-Performance Lithium-Ion Batteries

Improving the performance of anode materials for lithium-ion batteries (LIBs) is a hotly debated topic. Herein, hollow Ni−Co skeleton@MoS₂/MoO₃ nanocubes (NCM-NCs), with an average size of about 193 nm, have been synthesized through a facile hydrothermal reaction. Specifically, MoO₃/MoS₂ composites are grown on Ni−Co skeletons derived from nickel–cobalt Prussian blue analogue nanocubes (Ni−Co PBAs). The Ni−Co PBAs were synthesized through a precipitation method and utilized as self-templates that provided a larger specific surface area for the adhesion of MoO₃/MoS₂ composites. According to Raman spectroscopy results, as-obtained defect-rich MoS₂ is confirmed to be a metallic 1T-phase MoS₂. Furthermore, the average particle size of Ni−Co PBAs (≈43 nm) is only about one-tenth of the previously reported particle size (≈400 nm). If assessed as anodes of LIBs, the hollow NCM-NC hybrids deliver an excellent rate performance and superior cycling performance (with an initial discharge capacity of 1526.3 mAh g⁻¹ and up to 1720.6 mAh g⁻¹ after 317 cycles under a current density of 0.2 A g⁻¹). Meanwhile, ultralong cycling life is retained, even at high current densities (776.6 mAh g⁻¹ at 2 A g⁻¹ after 700 cycles and 584.8 mAh g⁻¹ at 5 A g⁻¹ after 800 cycles). Moreover, at a rate of 1 A g⁻¹, the average specific capacity is maintained at 661 mAh g⁻¹. Thus, the hierarchical hollow NCM-NC hybrids with excellent electrochemical performance are a promising anode material for LIBs.     

Pseudocapacitive Lithium Storage of Cauliflower-Like CoFe2O4 for Low-Temperature Battery Operation

Binary transition-metal oxides (BTMOs) with hierarchical micro–nano-structures have attracted great interest as potential anode materials for lithium-ion batteries (LIBs). Herein, we report the fabrication of hierarchical cauliflower-like CoFe₂O₄ (cl-CoFe₂O₄) via a facile room-temperature co-precipitation method followed by post-synthetic annealing. The obtained cauliflower structure is constructed by the assembly of microrods, which themselves are composed of small nanoparticles. Such hierarchical micro–nano-structure can promote fast ion transport and stable electrode–electrolyte interfaces. As a result, the cl-CoFe₂O₄ can deliver a high specific capacity (1019.9 mAh g⁻¹ at 0.1 A g⁻¹), excellent rate capability (626.0 mAh g⁻¹ at 5 A g⁻¹), and good cyclability (675.4 mAh g⁻¹ at 4 A g⁻¹ for over 400 cycles) as an anode material for LIBs. Even at low temperatures of 0 °C and −25 °C, the cl-CoFe₂O₄ anode can deliver high capacities of 907.5 and 664.5 mAh g⁻¹ at 100 mA g⁻¹, respectively, indicating its wide operating temperature. More importantly, the full-cell assembled with a commercial LiFePO₄ cathode exhibits a high rate performance (214.2 mAh g⁻¹ at 5000 mA g⁻¹) and an impressive cycling performance (612.7 mAh g⁻¹ over 140 cycles at 300 mA g⁻¹) in the voltage range of 0.5–3.6 V. Kinetic analysis reveals that the electrochemical performance of cl-CoFe₂O₄ is dominated by pseudocapacitive behavior, leading to fast Li⁺ insertion/extraction and good cycling life.     

MOF-derived Core-Shell CoP@NC@TiO2 Composite as a High-Performance Anode Material for Li-ion Batteries

Transition-metal phosphides have been regarded as promising anode materials for high-energy lithium-ion batteries (LIBs) due to their high capacity and low cost. However, the mechanical pulverization and resultant capacity fade critically limit their further development. Here, we have designed an innovative core-shell CoP@NC@TiO₂ composite with an exotic rhombic dodecahedral morphology derived from ZIF-67 precursor, which combines both advantages from TiO₂ with excellent cycling stability and CoP with high capacity. The additional MOF-derived N-doped carbon framework is considered to improve the electrical conductivity and accommodate the volume expansion of CoP particles. Moreover, the outer TiO₂ shell can also buffer the mechanical stress and maintain the integrity of composite. With the unique structure, the core-shell CoP@NC@TiO₂ composite material exhibits excellent electrochemical performance with a considerable discharge specific capacity of 706.3 mAh g⁻¹ at a current density of 100 mA g⁻¹ after 200 cycles and outstanding rate capacity. Hence, our work demonstrates that this core-shell structure strategy combined with MOF-derived carbon framework could provide a practical pathway towards enhanced electrode materials for energy storage and conversion.     

Phosphorus-Doping-Induced Surface Vacancies of 3D Na2Ti3O7 Nanowire Arrays Enabling High-Rate and Long-Life Sodium Storage

Sodium-ion batteries have attracted interest as an alternative to lithium-ion batteries because of the abundance and cost effectiveness of sodium. However, suitable anode materials with high-rate and stable cycling performance are still needed to promote their practical application. Herein, three-dimensional Na₂Ti₃O₇ nanowire arrays with enriched surface vacancies endowed by phosphorus doping are reported. As anodes for sodium-ion batteries, they deliver a high specific capacity of 290 mA h g⁻¹at 0.2 C, good rate capability (50 mA h g⁻¹at 20 C), and stable cycling capability (98 % capacity retention over 3100 cycles at 20 C). The superior electrochemical performance is attributed to the synergistic effects of the nanowire arrays and phosphorus doping. The rational structure can provide convenient channels to facilitate ion/electron transport and improve the capacitive contributions. Moreover, the phosphorus-doping-induced surface vacancies not only provide more active sites but also improve the intrinsic electrical conductivity of Na₂Ti₃O₇, which will enable electrode materials with excellent sodium storage performance. This work may provide an effective strategy for the synthesis of other anode materials with fast electrochemical reaction kinetics and good sodium storage performance.     

Oxygen Vacancies-rich Manganese Oxide with Flower-like Nanosheets for High Performance Supercapacitors

Here, flower-like manganese oxide with enriched oxygen vacancies were reported for high performance supercapacitors. The moderate oxygen-vacancy were achieved by controlling annealing atmosphere. Benefiting from improving the conductivity and the density of active sites, MnO_x−Ar sample as an electrode material has remarkable specific capacity (339 mAh g⁻¹ at 0.5 A g⁻¹), extraordinary rate capability (90 % capacity retention at 1 A g⁻¹), and good cycling property (90 % capacity retention at 1 A g⁻¹ after 5000 cycles). Additionally, the asymmetric supercapacitor (ASC) was assembled which used the MnO_x−Ar sample as cathode and Kochen Black (KB) as anode, which displayed a remarkable energy density (16 Wh kg⁻¹) at a large power density (7593 W kg⁻¹). These results, on the one hand, further expand the application of MnO₂-based materials, and on the other hand, offer a new perspective for the oxygen non-stoichiometry in material electrochemistry.     

A Multi-Wall Sn/SnO2@Carbon Hollow Nanofiber Anode Material for High-Rate and Long-Life Lithium-Ion Batteries

Multi-wall Sn/SnO₂@carbon hollow nanofibers evolved from SnO₂ nanofibers are designed and programable synthesized by electrospinning, polypyrrole coating, and annealing reduction. The synthesized hollow nanofibers have a special wire-in-double-wall-tube structure with larger specific surface area and abundant inner spaces, which can provide effective contacting area of electrolyte with electrode materials and more active sites for redox reaction. It shows excellent cycling stability by virtue of effectively alleviating pulverization of tin-based electrode materials caused by volume expansion. Even after 2000 cycles, the wire-in-double-wall-tube Sn/SnO₂@carbon nanofibers exhibit a high specific capacity of 986.3 mAh g⁻¹ (1 A g⁻¹) and still maintains 508.2 mAh g⁻¹ at high current density of 5 A g⁻¹. This outstanding electrochemical performance suggests the multi-wall Sn/SnO₂@ carbon hollow nanofibers are great promising for high performance energy storage systems.     

Alkynyl Boosted High-Performance Lithium Storage and Mechanism in Covalent Phenanthroline Framework

The poor conductivity of the pristine bulk covalent organic material is the main challenge for its application in energy storage. The mechanism of symmetric alkynyl bonds (C≡C) in covalent organic materials for lithium storage is still rarely reported. Herein, a nanosized (≈80 nm) alkynyl-linked covalent phenanthroline framework (Alkynyl-CPF) is synthesized for the first time to improve the intrinsic charge conductivity and the insolubility of the covalent organic material in lithium-ion batteries. Because of the high degree of electron conjugation along alkynyl units and N atoms from phenanthroline groups, the Alkynyl-CPF electrodes with the lowest HOMO–LUMO energy gap (ΔE=2.629 eV) show improved intrinsic conductivity by density functional theory (DFT) calculations. As a result, the pristine Alkynyl-CPF electrode delivers superior cycling performance with a large reversible capacity and outstanding rate properties (1068.0 mAh g⁻¹ after 300 cycles at 100 mA g⁻¹ and 410.5 mAh g⁻¹ after 700 cycles at 1000 mA g⁻¹). Moreover, by Raman, FT-IR, XPS, EIS, and theoretical simulations, the energy-storage mechanism of C≡C units and phenanthroline groups in the Alkynyl-CPF electrode has been investigated. This work provides new strategies and insights for the design and mechanism investigation of covalent organic materials in electrochemical energy storage.     

A novel conjugated porous polymer based on triazine and imide as cathodes for sodium storage

Organic electrode materials have attracted more and more attention for sodium-ion batteries (SIBs) that are regarded as one of the most promising alternatives of lithium-ion batteries, because they can endure the storage of large sodium ions (with a larger radius than that of lithium ions) without obvious volume change. Herein, we report a novel conjugated porous polymer (TPIP) based on triazine and imide as cathodes material for SIBs. TPIP has abundant redox-active sites, good thermal stability (400°C) and large specific surface area (306 m² g⁻¹). As a result, TPIP electrode delivered a specific capacity of 120 mAh g⁻¹ after 50 cycles at a current density of 0.1 A g⁻¹ and 85 mAh g⁻¹ after 150 cycles at a current density of 1.0 A g⁻¹. Ex-situ X-ray photoelectron spectra and Fourier transform infrared spectra showed that the TPIP electrodes reversibly stored three sodium ions per unit through the triazine rings and half of the carbonyl groups. These results deepen our understanding of charge storage mechanisms of polymers with triazine and imide units and will provide guidance for the future design of electrode materials for high-performance SIBs.     

Pitch-Based Laminated Carbon Formed by Pressure Driving at Low Temperature as High-Capacity Anodes for Lithium Energy Storage Systems

Pitch has been used to prepare electrodes by high-temperature heat treatments for supercapacitors, lithium-ion batteries, on account of its rich aromatic ring structure. Here, the toluene-soluble component of pitch is used to prepare a kind of laminated carbon. This was realized by a template-free synthesis at low temperature with the addition of pressure. The toluene-soluble component has a small molecular weight, which makes the thermal deformation ability stronger and then enhances the orientation of the carbon layer with the help of pressure. The prepared anode exhibits a splendid electrochemical performance compared with the traditional graphite anode. A high stable capacity of approximately 550 mAh g⁻¹ at 50 mA g⁻¹, which is much higher than graphite (372 mAh g⁻¹), is obtained. Also, when the current density is up to 2 A g⁻¹, the capacity is about 150 mAh g⁻¹. Surprisingly, it also delivers a superior cycling performance. And when used as the anode/cathode electrode for lithium-ion capacitors, a high energy density can be obtained. The present work offers an opportunity to utilize the pitch source in lithium energy storage with promising cycle life, high energy/power density, and low cost.     

Rechargeable Sodium-Ion Battery Based on Polyazaacene Analogue Anode

The high theoretical specific capacity, strong structural designability and relatively inexpensive manufacturing cost make the exploration of organic electrode materials more attractive in recent years. In this article, owing to the large π-conjugated structure, plenty of nitrogen heteroatoms and multiring aromatic system, polyazaacene analogue poly(1,6-dihydropyrazino[2,3 g]quinoxaline-2,3,8-triyl-7-(2H)-ylidene-7,8-dimethylidene) (PQL) was applied as the anode in sodium-ion batteries (SIBs). PQL was almost insoluble in conventional liquid organic electrolyte (1 M NaClO₄ in ethylene carbonate (EC)/dimethyl carbonate (DMC) (v:v=1 : 1) with 5 % fluoroethylene carbonate (FEC)), which strongly improved its cycle stability. The initial discharge capacity was obtained to be 1825 mAh g⁻¹ at the current density of 100 mA g⁻¹ and stabilized at 317 mAh g⁻¹ after 400 cycles with the coulombic efficiency as high as 97 %. It not only showed good rate capability at high current densities (202, 183 mAh g⁻¹ at 1 A g⁻¹ and 1.5 A g⁻¹) but also had a superior energy density around 290 Wh kg⁻¹.