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As a high-performance energy storage device consisting of a battery-type anode and a capacitor-type cathode, hybrid lithium-ion capacitors (HLICs) combine the advantages of high energy density of batteries and high power density of capacitors. However, the imbalance in electrochemical kinetics between the battery-type anode and the capacitor-type cathode hinders the further development of HLICs. Fully conjugated covalent organic frameworks have great potential as electrode materials for HLICs due to the designability of their structure. Herein, a fully conjugated covalent triazine framework (PT-CTF) integrating the hexaazatrinaphthylene unit was constructed, which provides abundant active sites (C═N and C═C groups) as the pseudocapacitive anode material for HLICs. And the connection of the triazine unit of PT-CTF improves the molecular conjugate degree, facilitating the transport of electrons. The fabricated PT-CTF||AC HLICs exhibit a high energy density (164.9 Wh kg -1 at 100 mA g -1 ), large power density (13.1 kW kg -1 at 4 A g -1 ), and excellent cycling capability (72% after 10 000 cycles at 2 A g -1 ).

Thick electrodes with high mass loading and increased content of active materials are critical for achieving higher energy density in contemporary lithium-ion batteries (LIBs). Nonetheless, producing thick electrodes through the commonly used slurry coating technology remains a formidable challenge. In this study, we have addressed this challenge by developing a dry electrode technology by using ultralong multiwalled carbon nanotubes (MWCNT) as a conductive additive and secondary binder. The mixing process of electrode compositions and the fibrillation process of the polytetrafluoroethylene (PTFE) binder were optimized. The resulting LiCoO 2 (LCO) electrode exhibited a remarkable mass loading of 48 mg cm -2 and an active material content of 95 wt %. Notably, the thick LCO electrode demonstrated a superior mechanical strength and electrochemical performance. After 100 cycles at a current density of 1/3 C, the electrode still exhibited a capacity retention of 91% of its initial capacity. This dry electrode technology provides a practicable and scalable approach to the powder-to-film LIB electrode manufacturing process.

The low ionic conductivity of LiCoO 2 limits the rate performance of the overall electrode. Here, a polymeric composite binder composed of poly(vinylidene fluoride) (PVDF) and poly(ethylene oxide) (PEO) is reported to efficiently improve the ion transport in the LiCoO 2 electrode. This is where the lithium-ion transport channel constructed by oxygen atoms of PEO can afford the electrode a lithium-ion transport number ( t Li + ) as high as 0.70 with the optimized composite binder in a mass ratio of 1:1 (O5F5), significantly higher than that of traditional PVDF (0.44). As a result, the O5F5 binder endows the LiCoO 2 electrode with an impressive capacity of 90 mAh g -1 even at 15 C, which is twice as high as the PVDF electrode. In addition, the initial Coulombic efficiency of the LiCoO 2 electrode with the O5F5 binder is close to 100% and the capacity retention is 91% after 100 cycles at 1 C. This study overcomes the problem of slow ion conductivity of the LiCoO 2 electrode, providing an easy method for developing high-rate cathode binders.

As a new class of crystalline materials, covalent organic frameworks (COFs) have long-range ordered channels and feasibility to functionalize. The well-arranged pores make it possible to contain and transport ions. Here, we designed a novel functionalized anionic COF-SS-Li by a post-synthetic method utilizing the Povarov reaction of BDTA-COF, anchoring -SO 3 - groups to the COF backbone and converting the imine linkage to a more stable quinoline unit. The grafted -SO 3 - groups and directional channels can promote the lithium-ion transport through a hopping mechanism. As a solid-state lithium-ion electrolyte, COF-SS-Li exhibits the conductivities of 9.63 × 10 -5 S cm -1 at 20 °C and 1.28 × 10 -4 S cm -1 at 40 °C and a wide electrochemical window of 4.85 V. The assembled Li|COF-SS-Li|Li symmetric cell can cycle stably for 600 h at 0.1 mA cm -2 . Also, the Li|COF-SS-Li|LiFePO 4 cell delivers an initial capacity of 117 mAh g -1 at 0.1 A g -1 and retains a capacity rate of 56.7% after 500 cycles. The research enriches the solid-state electrolytes for lithium-ion batteries.

Polymer binders play an important role in enhancing the electrochemical performance of silicon-based anodes to alleviate the volume expansion for lithium-ion batteries. It is difficult for common one-dimensional (1D) linear binders to limit the volume expansion of a silicon-based electrode when combined with silicon-based particles with scant binding points. Therefore, it is necessary to design a three-dimensional (3D) network structure, which has multiple binding points with the silicon particles to dissipate the mechanical stress in the continuous charge and discharge circulation. Here, a covalent and hydrogen bond synergist 3D network green binder (poly(acrylic acid) (PAA)-dextrin 9 (Dex 9 )) was prepared by the simple in situ thermal condensation of a one-dimensional liner binder PAA and Dex in the electrode fabrication process. The optimized SiO x @PAA-Dex 9 electrode exhibits an initial Coulombic efficiency (ICE) of 82.4% at a current density of 0.2 A g -1 . At a high current density of 1 A g -1 , it retains a capacity of 607 mAh g -1 after 300 cycles, which is approximately twice as high as that of the SiO x @PAA electrode. Furthermore, the results of in situ electrochemical dilatometry (ECD) and characterization of electrode structures demonstrate that the PAA-Dex 9 binder can effectively buffer the huge volume change and maintain the integrity of the SiO x electrodes. The research overcomes the low electrochemical stability difficulty of the 3D binder and sheds light on developing the simple fabrication procedure of an electrode.

As a promising candidate for large-scale energy storage, aqueous zinc-ion batteries (ZIBs) still lack cathode materials with large capacity and high rate capability. Herein, a spherical carbon-confined nanovanadium oxynitride with a polycrystalline feature (VN x O y /C) was synthesized by the solvothermal reaction and following nitridation treatment. As a cathode material for ZIBs, it is interesting that the electrochemical performance of the VN x O y /C cathode is greatly improved after the first charging process via in situ electrochemically oxidative activation. The oxidized VN x O y /C delivers a greatly enhanced reversible capacity of 556 mAh g -1 at 0.2 A g -1 compared to the first discharge capacity of 130 mAh g -1 and a high capacity of 168 mAh g -1 even at 80 A g -1 . The ex situ characterizations verify that the insertion/extraction of Zn 2+ does not affect the crystal structure of oxidized VN x O y /C to promise a stable cycle life (retain 420 mAh g -1 after 1000 cycles at 10 A g -1 ). The experimental analysis further elucidates that charging voltage and H 2 O in the electrolyte are curial factors to activate VN x O y /C in that the oxygen replaces the partial nitrogen and creates abundant vacancies, inducing a conversion from VN x O y /C to VN x - m O y +2 m /C and then resulting in considerably strengthened rate performance and improved Zn 2+ storage capability. The study broadens the horizons of fast ion transport and is exceptionally desirable to expedite the application of high-rate ZIBs.

The introduction of groups with high enthalpies of formation can effectively improve the detonation performance of the compounds. A series of novel energetic compounds ( 10 - 13 ) with high enthalpies of formation, high density, and high nitrogen-oxygen content were designed and synthesized by combining gem -polynitromethyl, 1,2,4-oxadiazole, furoxan, and azo groups. All the new compounds were thoroughly characterized by IR, NMR, elemental analysis, and differential scanning calorimetry. Compounds 10 and 11 were also further characterized with single-crystal X-ray diffraction. Compound 11 has high density (1.93 g cm -3 ), high enthalpy of formation (993.5 kJ mol -1 ), high detonation velocity (9411 m s -1 ), and high heat of detonation (6889 kJ kg -1 ) and is a potentially excellent secondary explosive.

Metal single-atom materials have attracted tremendous attention in the research field of lithium-sulfur (Li-S) batteries because they can effectively improve the reaction kinetics of sulfur cathodes. However, it is still difficult to determine the best metal single-atom catalyst for Li-S batteries, due to the lack of a unified measurement and evaluation method. Herein, a series of metal single-atom- and nitrogen-doped graphene materials (M-NG, M = Fe, Co, Ni, Ir, Ru) have been prepared as the catalysts for promoting the reaction kinetics of the sulfur reduction reaction process. Using rotating disk electrode measurements and density functional theory-based theoretical calculations, Ni-NG was screened out to be the best catalyst. It is found that Ni-NG materials can provide a kinetically favorable pathway for the reversible conversion of polysulfide conversion, thus increasing the utilization of sulfur. By coating the Ni-NG materials on the separator as a multifunctional interlayer, a commercially available sulfur cathode presents a stable specific capacity of 701.8 mAh g -1 at a current rate of 0.5C over 400 cycles. Even with a high sulfur loading of 3.8 mg cm -2 , a high areal capacity of 4.58 mAh cm -2 can be achieved. This work will provide a fundamental understanding of efficient single-atom catalyst materials for Li-S batteries.

Silicon oxide (SiO x , 0 < x < 2) is considered one of the most promising anode materials for next-generation lithium-ion batteries due to its high theoretical capacity. However, its commercial application is limited by the non-negligible volume change during cycling. Herein, a three-dimensional (3D) structure of carboxymethyl cellulose (CMC) cross-linked with iminodiacetic ( c -CMC-IDA 150 ) was facilely formed through in situ thermal cross-linking of CMC and iminodiacetic acid (IDA) in the fabrication process of the electrode, which could construct a robust network to restrain the volume change of the SiO x anode and maintain the integrity of the electrode. In addition, the 3D cross-linked c -CMC-IDA 150 provides sufficient contact sites to improve the adhesive strength. Thus, SiO x @ c -CMC-IDA 150 shows a prolonged cycle life, achieving a capacity of 1020 mAh g -1 after 100 cycles at a current density of 0.2 A g -1 . With the increase in the current density to 1.0 A g -1 , SiO x @ c -CMC-IDA 150 exhibits a reversible capacity of 899 mAh g -1 after 200 cycles with a capacity retention of 70.2%. This work provides a potential perspective to fabricate high-performance SiO x anodes and promote the stability of high-capacity Si-based anodes.

Lithium metal is considered to be one of the most potential anode materials on account of its high theoretical specific capacity and lowermost electrochemical potential. Nevertheless, the critical challenges of dendrite growth and low Coulombic efficiency (CE) of the lithium metal anode during cycling prevent the commercial application of the lithium metal battery. Herein, rubidium fluoride (RbF) as additives is utilized to inhibit the lithium dendrite growth. Benefiting from the stronger electropositive property of Rb + , it can adsorb on the surface of protuberances during the lithium deposition process, form an electrostatic shielding field of the surface, and guide the uniform deposition of Li + . The CE can maintain above 90% with the additives of RbF in the carbonate electrolyte. Besides that, RbF improves the cycle life and decreases the polarization, a stable cycling performance of more than 1000 h is obtained, and the overvoltage is controlled below 100 mV in the cycling test of Li∥Li symmetrical cells at 0.5 mA cm -2 . The addition of RbF offers a feasible way for the development of lithium metal batteries (LMBs) in the future.

Organic electrode materials, with low-cost synthesis and environmental friendliness, have gained significant research interest in lithium-ion batteries (LIBs). Polydopamine (PDA), as a bioderived organic electrode material, exhibits a low capacity of ∼100 mAh g -1 , greatly limiting the practical application in LIBs. In this work, we find that a simple heat treatment at 300 °C can endow PDA-derived material (PDA300) with superior electrochemical performance. The obtained PDA300 electrode exhibits an ultrahigh capacity of 977 mAh g -1 at 50 mA g -1 . Further combining the PDA300 with highly conductive Ti 3 C 2 T x MXene, the obtained PDA300/Ti 3 C 2 T x composite is demonstrated by high capacity (1190 mAh g -1 , 50 mA g -1 ), excellent rate capability (remaining 552 mAh g -1 at 5 A g -1 ), and good cycling stability (82% retaining after 1000 cycles). The outstanding lithium storage performance is highly associated with the superlithiation process of the unsaturated carbon-carbon bonds in the PDA derivative and the introduction of the highly conductive Ti 3 C 2 T x substrate with a unique two-dimensional nanostructure. This work will provide new opportunities for the expansion of high-performance organic anodes for LIBs.

The global availability of sodium makes the exploration of superior sodium-ion batteries attractive for energy storage application. MXenes, as one of the most promising anodes for sodium-ion batteries, have been reported to have many advantages, such as high electronic conductivity and a hydrophilic surface. However, the compact multilayer structure and deficient delamination significantly inhibits their application, requiring high energy and showing decreased storage capacity and poor rate capabilities. Few-layer MXene has been proved to benefit superior electrochemical properties with a better ionic conductivity and two-dimensional layer structure. Herein, we report scale delamination of few-layer MXene nanosheets as anodes for sodium-ion batteries, which are prepared via an organic solvent assist high-energy mechanical-milling method. This approach efficiently prevents the oxidation of MXene and produces few-layer nanosheets structure, facilitating fast electron transport and Na + diffusion. Electrochemical tests demonstrate that the few-layer MXenes show high specific capacity, excellent cycle stability, and good rate performance. Specifically, few-layer MXene nanosheets deliver a high reversible capacity of 267 mA h g -1 at a current density of 0.1 A g -1 . After cycling 1500 cycles at a high rate of 1 A g -1 , a reversible capacity of 76 mA h g -1 could be maintained.

Alternative battery systems based on the chemistry of sodium are being considered to offer sustainability and cost-effectiveness. Herein, a simple and new method is demonstrated to enable nickel hexacyanoferrate (NiHCF) Prussian blue analogues (PBA) nanocrystals to be an excellent host for sodium ion storage by functionalization with redox guest molecule. The method is achieved by using NiHCF PBA powders infiltrated with the 7,7,8,8-tetracyanoquinododimethane (TCNQ) solution. Experimental and ab initio calculations results suggest that TCNQ molecule bridging with Fe atoms in NiHCF Prussian blue analogue leads to electronic coupling between TCNQ molecules and NiHCF open-framework, which functions as an electrical highway for electron motion and conductivity enhancement. Combining the merits including high electronic conductivity, open framework structure, nanocrystal, and interconnected mesopores, the NiHCF/TCNQ shows high specific capacity, fast kinetics and good cycling stability, delivering a high specific capacity of 35 mAh g -1 after 2000 cycles, corresponding a capacity loss of 0.035% decay per cycle.

Interface design between current collector and electroactive materials plays a key role in the electrochemical process for lithium-ion batteries. Here, a thin graphene film has been successfully synthesized on the surface of Cu current collector by a large-scale low-pressure chemical vapor deposition (LPCVD) process. The modified Cu foil was used as a current collector to support spinel Li 4 Ti 5 O 12 anode directly. Electrochemical test results demonstrated that graphene coating Cu foil could effectively improve overall Li storage performance of Li 4 Ti 5 O 12 anode. Especially under high current rate (e.g., 10 C), the Li 4 Ti 5 O 12 electrode using modified current collector maintained a favorable capacity, which is 32% higher than that electrode using bare current collector. In addition, cycling performance has been improved using the new type current collector. The enhanced performance can be attributed to the reduced internal resistance and improved charge transfer kinetics of graphene film by increasing electron collection and decreasing lithium ion interfacial diffusion. Furthermore, the graphene film adhered on the Cu foil surface could act as an effective protective film to avoid oxidization, which can effectively improve chemical stability of Cu current collector.

Graphene is considered a promising electrochemical capacitors electrode material due to its high surface area and high electrical conductivity. However, restacking interactions between graphene nanosheets significantly decrease the ion-accessible surface area and impede electronic and ionic transfer. This would, in turn, severely hinder the realization of high energy density. Herein, we report a strategy for preparation of few-layer graphene material with abundant crumples and high-level nitrogen doping. The two-dimensional graphene nanosheets (CNG) feature high ion-available surface area, excellent electronic and ion transfer properties, and high packing density, permitting the CNG electrode to exhibit excellent electrochemical performance. In ionic liquid electrolyte, the CNG electrode exhibits gravimetric and volumetric capacitances of 128 F g(-1) and 98 F cm(-3), respectively, achieving gravimetric and volumetric energy densities of 56 Wh kg(-1) and 43 Wh L(-1). The preparation strategy described here provides a new approach for developing a graphene-based supercapacitor with high gravimetric and volumetric energy densities.

Given their high theoretical energy density, lithium-sulfur (Li-S) batteries have recently attracted ever-increasing research interest. However, the dissolution of polysulfides and uncontrolled deposition of insoluble discharge product significantly hinder the cycling stability. Herein, a nanospace-confinement copolymerization strategy for encapsulating polymeric sulfur into porous carbon matrix is presented. The morphologies and sulfur contents of carbon/polymeric sulfur (C/PS) composites could be readily tailored by controlling the copolymerization time. Confining polymeric sulfur in the porous carbon with abundant interparticle pores facilitates rapid electronic/ionic transport and mitigates dissolution of polysulfides intermediates. More importantly, the organic sulfur units dispersed in the insoluble/insulating Li2S2/Li2S phase could prevent its irreversible deposition. Such nanostructure with tailored chemistry property permits the C/PS electrodes to exhibit enhanced cycling stability and high rate capability. The nanospace-confinement copolymerization strategy features general and facial advantages, which may provide new opportunities for the future development of advanced sulfur cathodes.

A unique core-shell structure of silicon@titania (Si@TiO2) composite with silicon nanoparticles encapsulated in TiO2 hollow spheres is synthesized by a simple hydrolysis method combined with magnesiothermic reduction method. It is found that the TiO2 shell is effective for improving the electrical conductivity and structural stability. More importantly, the well-designed nanostructure with enough empty space would accommodate the volume change of silicon during the cycling. Reversible capacities of 1911.1 and 795 mAh g(-1) can be obtained at 0.05 C and a high current rate of 1 C, respectively. After 100 cycles at 0.1 C, the composite electrode still maintains a high capacity of 804 mAh g(-1). This excellent cycling stability and high-rate capability can be ascribed to the unique core-shell nanostructure and the synergistic effect between Si and TiO2.

Lithium-sulfur (Li-S) batteries are deemed to be a promising energy storage device for next-generation high energy power system. However, insulation of S and dissolution of lithium polysulfides in the electrolyte lead to low utilization of sulfur and poor cycling performance, which seriously hamper the rapid development of Li-S batteries. Herein, we reported that encapsulating sulfur into hierarchically porous carbon (HPC) derived from the soluble starch with a template of needle-like nanosized Mg(OH)2. HPC has a relatively high specific surface area of 902.5 m(2) g(-1) and large total pore volume of 2.60 cm(3) g(-1), resulting that a weight percent of sulfur in S/HPC is up to 84 wt %. When evaluated as cathodes for Li-S batteries, the S/HPC composite has a high discharge capacity of 1249 mAh g(-1) in the first cycle and a Coulombic efficiency as high as 94% with stable cycling over prolonged 100 charge/discharge cycles at a high current density of 1675 mA g(-1). The superior electrochemical performance of S/HPC is closely related to its unique structure, exhibiting the graphitic structure with a high developed porosity framework of macropores in combination with mesopores and micropores. Such nanostructure could shorten the transport pathway for both ions and electrons during prolonged cycling.