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.     

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.     

Construction of Rich Conductive Pathways from Bottom to Top: A Highly Efficient Charge-Transfer System Used in Durable Li/Na-Ion Batteries at −20 °C

The construction of potential electrode materials with wide temperature property for high-energy-density secondary batteries has attracted great interest in recent years. Herein, a hybrid electrode, consisting of a nitrogen-doped carbon/α-MnS/flake graphite composite (α-MnS@N-C/FG), is prepared through a post-sulfurization route. In the α-MnS@N-C/FG composite, α-MnS nanoparticles wrapped by the N−C layer are uniformly embedded onto FG, forming a novel nanofoam structure. The as-obtained α-MnS@N-C/FG shows excellent lithium/sodium storage performance, with a specific capacity of 712 mA h g⁻¹ in the 700th cycle at 1.0 A g⁻¹ or 186.4 mA h g⁻¹ in the 100th cycle at 100 mA g⁻¹ using lithium or sodium foil as the counter electrode, respectively. Moreover, even operated at −20 °C, the α-MnS@N-C/FG can still attain a high specific capacity of 350 mA h g⁻¹ after 50 cycles at 100mA g⁻¹ for LIBs. This exceptional electrochemical response is attributed to the synergetic effect of the smart design of a hybrid nanofoam structure, in which the FG skeleton and N-C coating layer can significantly enhance the conductivity of the whole electrode from bottom to top. Accordingly, the enhanced redox kinetics endow the electrode with pseudocapacitive-dominated electrochemical behavior, leading to fast electrode reactions and robust structural stability in the whole electrode.     

Self-Assembled FeSe2 Microspheres with High-Rate Capability and Long-Term Stability as Anode Material for Sodium- and Potassium-Ion Batteries

Sodium- and potassium-ion batteries have attracted intensive attention recently as low-cost alternatives to lithium-ion batteries with naturally abundant resources. However, the large ionic radii of Na⁺ and K⁺ render their slow mobility, leading to sluggish diffusion in host materials. Herein, hierarchical FeSe₂ microspheres assembled by closely packed nano/microrods are rationally designed and synthesized through a facile solvothermal method. Without carbonaceous material incorporation, the electrode delivers a reversible Na⁺ storage capacity of 559 mA h g⁻¹ at a current rate of 0.1 A g⁻¹ and a remarkable rate performance with a capacity of 525 mA h g⁻¹ at 20 A g⁻¹. As for K⁺ storage, the FeSe₂ anode delivers a high reversible capacity of 393 mA h g⁻¹ at 0.4 A g⁻¹. Even at a high current rate of 5 A g⁻¹, a discharge capacity of 322 mA h g⁻¹ can be achieved, which is among the best high-rate anodes for K⁺ storage. The excellent electrochemical performance can be attributed to the favorable morphological structure and the use of an ether-based electrolyte during cycling. Moreover, quantitative study suggests a strong pseudocapacitive contribution, which boosts fast kinetics and interfacial storage.     

Proton Intercalation/De-intercalation Chemistry in Phenazine-based Anode for Hydronium-ion Batteries

Hydronium-ion batteries have received significant attention owing to the merits of extraordinary sustainability and excellent rate abilities. However, achieving high-performance hydronium-ion batteries remains a challenge due to the inferior properties of anode materials in strong acid electrolyte. Herein, a hydronium-ion battery is constructed which is based on a diquinoxalino [2,3-a:2’,3’-c] phenazine (HATN) anode and a MnO₂@graphite felt cathode in a hybrid acidic electrolyte. The fast kinetics of hydronium-ion insertion/extraction into HATN electrode endows the HATN//MnO₂@GF battery with enhanced electrochemical performance. This battery exhibits an excellent rate performance (266 mAh g⁻¹ at 0.5 A g⁻¹, 97 mAh g⁻¹ at 50 A g⁻¹), attractive energy density (182.1 Wh kg⁻¹) and power density (31.2 kW kg⁻¹), along with long-term cycle stability. These results shed light on the development of advanced hydronium-ion batteries.     

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.     

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.     

Flower-like Spherical α-Ni(OH)2 Derived NiP2 as Superior Anode Material of Sodium-Ion Batteries

Transition metal phosphides (TMPs) are promising anode candidates for sodium-ion batteries, due to their high theoretical specific capacity and working potential. However, the low conductivity and excessive volume variation of TMPs during insertion/extraction of sodium ions result in a poor rate performance and long-term cycling stability, largely limiting their practical application. In this paper, NiP₂ nanoparticles encapsulated in three-dimensional graphene (NiP₂@rGO) were obtained from the flower-like spherical α-Ni(OH)₂ by phosphating and carbon encapsulation processes. When used as a sodium-ion batteries anode material, the NiP₂@rGO composite shows an excellent cycling performance (117 mA h g⁻¹ at 10 A g⁻¹ after 8000 cycles). The outstanding electrochemical performance of NiP₂@rGO is ascribed to the synergistic effect of the rGO and NiP₂. The rGO wrapped on the NiP₂ nanoparticles build a conductive way, improving ionic and electronic conductivity. The effective combination of NiP₂ nanoparticles with graphene greatly reduces the aggregation and pulverization of NiP₂ nanoparticles during the discharge/charge process. This study may shed light on the construction of high-performance anode materials for sodium-ion batteries and to other electrode materials.     

Highly Dispersible Hexagonal Carbon–MoS2–Carbon Nanoplates with Hollow Sandwich Structures for Supercapacitors

MoS₂, a typical layered transition-metal dichalcogenide, is promising as an electrode material in supercapacitors. However, its low electrical conductivity could lead to limited capacitance if applied in electrochemical devices. Herein, a new nanostructure composed of hollow carbon–MoS₂–carbon was successfully synthesized through an l -cysteine-assisted hydrothermal method by using gibbsite as a template and polydopamine as a carbon precursor. After calcination and etching of the gibbsite template, uniform hollow platelets, which were made of a sandwich-like assembly of partial graphitic carbon and two-dimensional layered MoS₂ flakes, were obtained. The platelets showed excellent dispersibility and stability in water, and good electrical conductivity due to carbon provided by the calcination of polydopamine coatings. The hollow nanoplate morphology of the material provided a high specific surface area of 543 m² g⁻¹, a total pore volume of 0.677 cm³ g⁻¹, and fairly small mesopores (≈5.3 nm). The material was applied in a symmetric supercapacitor and exhibited a specific capacitance of 248 F g⁻¹ (0.12 F cm⁻²) at a constant current density of 0.1 A g⁻¹; thus suggesting that hollow carbon–MoS₂–carbon nanoplates are promising candidate materials for supercapacitors.     

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.     

Few-Layer MoS2 Nanosheets Encapsulated in N-Doped Carbon Hollow Spheres as Long-Life Anode Materials for Lithium-Ion Batteries

Two-dimensional molybdenum disulfide (MoS₂) has been recognized as a promising anode material for lithium-ion batteries (LIBs) due to its high theoretical capacity, but its rapid capacity decay owing to poor conductivity, structure pulverization, and polysulfide dissolution presents significant challenges in practical applications. Herein, triple-layered hollow spheres in which MoS₂ nanosheets are fully encapsulated between inner carbon and outer nitrogen-doped carbon (NC) were fabricated. Such an architecture provides high conductivity and efficient lithium-ion transfer. Moreover, the NC shell prevents aggregation and exfoliation of MoS₂ nanosheets and thus maintains the integrity of the nanostructure during the charge/discharge process. As anode materials for LIBs, the C@MoS₂@NC hollow spheres deliver a high reversible capacity (747 mA h g⁻¹ after 100 cycles at 100 mA g⁻¹) and excellent long-cycle performance (650 mA h g⁻¹ after 1000 cycles at 1.0 A g⁻¹), which confirm its potential for high-performance LIBs.     

A New Anode for Lithium‐Ion Batteries Based on Single‐Walled Carbon Nanotubes and Graphene: Improved Performance through a Binary Network Design

Carbon nanomaterials, especially graphene and carbon nanotubes, are considered to be favorable alternatives to graphite‐based anodes in lithium‐ion batteries, owing to their high specific surface area, electrical conductivity, and excellent mechanical flexibility. However, the limited number of storage sites for lithium ions within the sp²‐carbon hexahedrons leads to the low storage capacity. Thus, rational structure design is essential for the preparation of high‐performance carbon‐based anode materials. Herein, we employed flexible single‐walled carbon nanotubes (SWCNTs) with ultrahigh electrical conductivity as a wrapper for 3D graphene foam (GF) by using a facile dip‐coating process to form a binary network structure. This structure, which offered high electrical conductivity, enlarged the electrode/electrolyte contact area, shortened the electron‐/ion‐transport pathways, and allowed for efficient utilization of the active material, which led to improved electrochemical performance. When used as an anode in lithium‐ion batteries, the SWCNT‐GF electrode delivered a specific capacity of 953 mA h g^?1 at a current density of 0.1 A g^?1 and a high reversible capacity of 606 mA h g^?1 after 1000 cycles, with a capacity retention of 90 % over 1000 cycles at 1 A g^?1 and 189 mA h g^?1 after 2200 cycles at 5 A g^?1.     

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.     

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.     

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.     

Nanowire of WP as a High-Performance Anode Material for Sodium-Ion Batteries

The design and development of electrode materials with high specific capacity and long cycling life for sodium-ion batteries (SIBs) is still a critical challenge. In this communication, we report the development of tungsten phosphide (WP) nanowire on carbon cloth (WP/CC) as an anode for SIBs. The WP/CC exhibits superior sodium storage capability with 502 mA h g⁻¹ at 0.1 A g⁻¹. Moreover, this anode is capable of delivering a long lifespan at 2 A g⁻¹ with an excellent capacity retention of 99 % after 1000 cycles.     

Scalable Dry Production Process of a Superior 3D Net‐Like Carbon‐Based Iron Oxide Anode Material for Lithium‐Ion Batteries

Carbon‐based transition‐metal oxides are considered as an appropriate anode material candidate for lithium‐ion batteries. Herein, a simple and scalable dry production process is developed to produce carbon‐encapsulated 3D net‐like FeO_x /C materials. The process is simply associated with the pyrolysis of a solid carbon source, such as filter paper, adsorbed with ferrite nitrate. The carbon derived from filter paper induces a carbothermal reduction to form metallic Fe, the addition of carbon and iron increase the conductivity of this material. As expected, this 3D net‐like FeO_x /C composite delivers an excellent charge capacity of 851.3 mAh g⁻¹ after 50 cycles at 0.2 A g⁻¹ as well as high stability and rate performance of 714.7 mAh g⁻¹ after 300 cycles at 1 A g⁻¹. Superior performance, harmlessness, low costs, and high yield may greatly stimulate the practical application of the products as anode materials in lithium‐ion batteries.     

In-situ Grown SnO2 Nanospheres on Reduced GO Nanosheets as Advanced Anodes for Lithium-ion Batteries

Nanostructured tin dioxide (SnO₂) has emerged as a promising anode material for lithium-ion batteries (LIBs) due to its high theoretical capacity (1494 mA h g⁻¹) and excellent stability. Unfortunately, the rapid capacity fading and poor electrical conductivity of bulk SnO₂ material restrict its practical application. Here, SnO₂ nanospheres/reduced graphene oxide nanosheets (SRG) are fabricated through in-situ growth of carbon-coated SnO₂ using template-based approach. The nanosheet structure with the external layer of about several nanometers thickness can not only accommodate the volume change of Sn lattice during cycling but also enhance the electrical conductivity effectively. Benefited from such design, the SRG composites could deliver an initial discharge capacity of 1212.3 mA h g⁻¹ at 0.1 A g⁻¹, outstanding cycling performance of 1335.6 mA h g⁻¹ after 500 cycles at 1 A g⁻¹, and superior rate capability of 502.1 mA h g⁻¹ at 5 A g⁻¹ after 10 cycles. Finally, it is believed that this method could provide a versatile and effective process to prepare other metal-oxide/reduced graphene oxide (rGO) 2D nanocomposites.     

Synthesis of Porous Ni-Doped CoSe2/C Nanospheres towards High-Rate and Long-Term Sodium-Ion Half/Full Batteries

Carbon-layer-coated porous Ni-doped CoSe₂ (Ni-CoSe₂/C) nanospheres have been fabricated by a facile hydrothermal method followed by a new selenization strategy. The porous structure of Ni-CoSe₂/C is formed by the aggregation of many small particles (20–40 nm), which are not tightly packed together, but are interspersed with gaps. Moreover, the surfaces of these small particles are covered with a thin carbon layer. Ni-CoSe₂/C delivers superior rate performance (314.0 mA h g⁻¹ at 20 A g⁻¹), ultra-long cycle life (316.1 mA h g⁻¹ at 10 A g⁻¹ after 8000 cycles), and excellent full-cell performance (208.3 mA h g⁻¹ at 0.5 A g⁻¹ after 70 cycles) when used as an anode material for half/full sodium-ion batteries. The Na storage mechanism and kinetics have been confirmed by ex situ X-ray diffraction analysis, assessment of capacitance performance, and a galvanostatic intermittent titration technique (GITT). GITT shows that Na⁺ diffusion in the electrode material is a dynamic change process, which is associated with a phase transition during charge and discharge. The excellent electrochemical performance suggests that the porous Ni-CoSe₂/C nanospheres have great potential to serve as an electrode material for sodium-ion batteries.