Conjugated polymeric molecules have been heralded as promising electrode materials for the next-generation energy-storage technologies owing to their chemical flexibility at the molecular level, environmental benefit, and cost advantage. However, before any practical implementation takes place, the low capacity, poor structural stability, and sluggish ion/electron diffusion kinetics remain the obstacles that have to be overcome. Here, we report the synthesis of a few-layered two-dimensional covalent organic framework trapped by carbon nanotubes as the anode of lithium-ion batteries. Remarkably, upon activation, this organic electrode delivers a large reversible capacity of 1536 mAh g −1 and can sustain 500 cycles at 100 mA g −1 . Aided by theoretical calculations and electrochemical probing of the electrochemical behavior at different stages of cycling, the storage mechanism is revealed to be governed by 14-electron redox chemistry for a covalent organic framework monomer with one lithium ion per C=N group and six lithium ions per benzene ring. This work may pave the way to the development of high-capacity electrodes for organic rechargeable batteries.

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Covalent organic frameworks (COFs) with reversible redox behaviors are potential electrode materials for lithium‐ion batteries (LIBs). However, the sluggish lithium diffusion kinetics, poor electronic conductivity, low reversible capacities, and poor rate performance for most reported COF materials limit their further application. Herein, a new 2D COF (TFPB‐COF) with six unsaturated benzene rings per repeating unit and ordered mesoporous pores (≈2.1 nm) is designed. A chemical stripping strategy is developed to obtain exfoliated few‐layered COF nanosheets (E‐TFPB‐COF), whose restacking is prevented by the in situ formed MnO2 nanoparticles. Compared with the bulk TFPB‐COF, the exfoliated TFPB‐COF exhibits new active Li‐storage sites associated with conjugated aromatic π electrons by facilitating faster ion/electron kinetics. The E‐TFPB‐COF/MnO2 and E‐TFPB‐COF electrodes exhibit large reversible capacities of 1359 and 968 mAh g−1 after 300 cycles with good high‐rate capability.

SnS2 materials have attracted broad attention in the field of electrochemical energy storage due to their layered structure with high specific capacity. However, the easy restacking property during charge/discharge cycling leads to electrode structure instability and a severe capacity decrease. In this paper, we report a simple one-step hydrothermal synthesis of SnS2/graphene/SnS2 (SnS2/rGO/SnS2) composite with ultrathin SnS2 nanosheets covalently decorated on both sides of reduced graphene oxide sheets via C–S bonds. Owing to the graphene sandwiched between two SnS2 sheets, the composite presents an enlarged interlayer spacing of ∼8.03 Å for SnS2, which could facilitate the insertion/extraction of Li+/Na+ ions with rapid transport kinetics as well as inhibit the restacking of SnS2 nanosheets during the charge/discharge cycling. The density functional theory calculation reveals the most stable state of the moderate interlayer spacing for the sandwich-like composite. The diffusion coefficients of Li/Na ions from both molecular simulation and experimental observation also demonstrate that this state is the most suitable for fast ion transport. In addition, numerous ultratiny SnS2 nanoparticles anchored on the graphene sheets can generate dominant pseudocapacitive contribution to the composite especially at large current density, guaranteeing its excellent high-rate performance with 844 and 765 mAh g–1 for Li/Na-ion batteries even at 10 A g–1. No distinct morphology changes occur after 200 cycles, and the SnS2 nanoparticles still recover to a pristine phase without distinct agglomeration, demonstrating that this composite with high-rate capabilities and excellent cycle stability are promising candidates for lithium/sodium storage.

Graphene-wrapped CoS nanoparticles are synthesized by a solvothermal approach. The product is significantly different from porous CoS microspheres prepared in the absence of graphene under similar preparation conditions. The CoS microspheres and CoS/graphene composite are fabricated as anode materials for lithium-ion batteries. The CoS/graphene composite is found to be better suitable as an anode in terms of higher capacity and better cycling performances. The nanocomposite exhibits an unprecedented high reversible capacity of 1056 mA h/g among all cobalt sulfide-based anode materials. Good cycling performances are also observed at both small and high current rates.

units, SBUs) and coordinated organic ligands via the more flexible coordination bonds, which results in the controllable morphology and pore characteristic. [1f,g] Induced by these structural merits, COF and MOF have been widely applied in gas storage/separation, catalysis, and photoelectric conversion, and even the field of energy storage including Li-ion batteries, supercapacitors, and hydrogen storage. [2] In order to effectively combine the merits of COF and MOF and acquire the maximized performances, there are few recent reports regarding the hybridization of COF and MOF. [3] By introducing the as-prepared MOF into the synthetic process of COF, MOF@COF core-shell [3a,b] or MOF-coated COF [3c] hybrids were obtained. All these hybrids have been demonstrated with excellent photocatalytic performances as the effective photocatalysts/photocatalysis platforms for degradation of rhodamine B, [3a] dehydrogenation of ammonia borane, [3b] and H 2 evolution, [3c] respectively. This kind of approach (introducing the as-prepared MOF into the synthetic process of COF) would result in the comparatively simple combination of COF and MOF with core-shell or coating composite mode (no principal morphology change), and the molecular-level interlinked hybridization between COF and MOF remains unexplored.For the purpose of property optimization, intimate hybridization between two components is highly desirable, which may lead to further morphology adjustment, and consequent performance improvement. Considering the fact that organic groups from COF may also coordinate with metal ions of MOF, we design a COF/Mn-MOF hybrid structure with flower-like morphology, which is different from pristine COF or Mn-MOF. A strong synergistic effect relative to new active sites from MOF and COF for lithium storage is observed in the composite. Hollow or coreshell microspheres of MnS@N/S codoped carbon can also be derived with superior electrochemical properties.The COF/Mn-MOF composite with benchmarked pristine COF or Mn-MOF ( Figure S1a,b, Supporting Information) was characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR), Raman and 13 C nuclear magnetism measurements in Figure S2a-d (Supporting Information). All characteristic diffraction peaks for Mn-MOF [4] can be detected for COF/ Mn-MOF with clear shift to small angle for its two main peaks (2θ ≈ 10.5° and ≈21.7°), which is probably originated from the Covalent organic frameworks (COF) or metal-organic frameworks have attracted significant attention for various applications due to their intriguing tunable micro/mesopores and composition/functionality control. Herein, a coordination-induced interlinked hybrid of imine-based covalent organic frameworks and Mn-based metal-organic frameworks (COF/Mn-MOF) based on the MnN bond is reported. The effective molecular-level coordinationinduced compositing of COF and MOF endows the hybrid with unique flower-like microsphere morphology and superior lithium-storage performances that originate from activated Mn centers an...

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