In this work, hydroxyl‐functionalized Mo2C‐based MXene nanosheets are synthesized by facilely removing the Sn layer of Mo2SnC. The hydroxyl‐functionalized surface of Mo2C suppresses the shuttle effect of lithium polysulfides (LiPSs) through strong interaction between Mo atoms on the MXenes surface and LiPSs. Carbon nanotubes (CNTs) are further introduced into Mo2C phase to enlarge the specific surface area of the composite, improve its electronic conductivity, and alleviate the volume change during discharging/charging. The strong surface‐bound sulfur in the hierarchical Mo2C‐CNTs host can lead to a superior electrochemical performance in lithium–sulfur batteries. A large reversible capacity of ≈925 mAh g−1 is observed after 250 cycles at a current density of 0.1 C (1 C = 1675 mAh g−1) with good rate capability. Notably, the electrodes with high loading amounts of sulfur can also deliver good electrochemical performances, i.e., initial reversible capacities of ≈1314 mAh g−1 (2.4 mAh cm−2), ≈1068 mAh g−1 (3.7 mAh cm−2), and ≈959 mAh g−1 (5.3 mAh cm−2) at various areal loading amounts of sulfur (1.8, 3.5, and 5.6 mg cm−2) are also observed, respectively.

The high solubility of the small organic molecule materials in organic electrolytes hinders their development in rechargeable batteries. Hence, this work designs an ultrarobust hydrogen-bonded organic–inorganic hybrid material: the small organic unit of the 1,3,6,8-tetrakis (p-benzoic acid) pyrene (TBAP) molecule connected with the hydroxylated Ti3C2T x MXene through hydrogen bonds between the terminal groups of −COOH and −OH. The robust and elastic hydrogen bonds can empower the TBAP, despite being a low-molecule organic chemical, with unusually low solubility in organic electrolytes and thermal stability. The alkali-treated Ti3C2T x MXene provides a hydroxyl-rich conductive network, and the small organic molecule of TBAP reduces the restacking of MXene layers. Therefore, the combination of these two materials complements each other well, and this organic–inorganic TBAP@D-Ti3C2T x electrode delivers large reversible capacities and long cyclic life. Notably, with the assistance of the in situ FT–IR characterization of the electrode within the fully lithiated (0.005 V) and the delithiated (3.0 V) states, it is revealed that a powerful π-Li cation effect mainly governs the lithium-storage mechanism with the highly activated benzene ring and each C6 aromatic ring, which can reversibly accept six Li-ions to form a 1:1 Li/C complex.

Covalent organic polymers are attracting more and more attention for energy storage devices due to their lightweight, molecular viable design, stable structure, and environmental benignity. However, low charge-carrier mobility of pristine covalent organic materials is the main drawback for their application in lithium-ion batteries. Herein, a yolk−shell bimetal-modified quinonyl-rich covalent organic material, Co@2AQ-MnO 2 , has been designed and synthesized by in situ loading of petal-like nanosized MnO 2 and coordinating with Co centers, with the aim to improve the charge conductivity of the covalent organic polymer and activate its Li-storage sites. As investigated by in situ FT-IR, ex situ XPS, and electrochemical probing, the quinonyl-rich structure provides abundant redox sites (carbonyl groups and π electrons from the benzene ring) for lithium reaction, and the introduction of two types of metallic species promotes the charge transfer and facilitates more efficient usage of active energy-storage sites in Co@2AQ-MnO 2 . Thus, the Co@2AQ-MnO 2 electrode exhibits good cycling performance with large reversible capacity and excellent rate performance (1534.4 mA h g −1 after 200 cycles at 100 mA g −1 and 596.0 mA h g −1 after 1000 cycles at 1000 mA g −1 ).

The rechargeable lithium/sodium-iodine battery (Li/Na-I 2 ) is a promising candidate for meeting the growing energy demand. Herein, a flexible hydrogenbonded organic framework (HOF) linked to the Ti 3 C 2 T x MXene complex (HOF@Ti 3 C 2 T x ) has been presented for iodine loading. HOF is self-assembled by organic monomers through hydrogen bonding interactions between each monomer. It leads to numerous cavities in HOF structure, which can encapsulate iodine through various adsorptive sites and intermolecular interactions. The unique structure of complex can accelerate the nucleation of iodine, achieve fast reaction kinetics, stabilize iodide and retard the shuttle effect, thus improving the cycling stability of I 2 -based batteries. The I 2 /HOF@Ti 3 C 2 T x exhibits large reversible capacities of 260.2 and 207.6 mAh g À 1 at 0.2 C after repeated cycling for Li-I 2 and Na-I 2 batteries, respectively. This work can gain insights into the HOF-related energy storage application with reversible iodine encapsulation and its related redox reaction mechanisms with Li and Na metal ions.

The porous structural backbone and redox-active of covalent organic frameworks can facilitate the evolution of energy storage equipment with high electrochemical performances. However, the application of covalent organic frameworks as supercapacitor electrode materials in advanced energy storage equipment has been hindered on account of the insufficient conductivity and consecutive impoverished electrochemical performances. Here we give an account of an efficacious method for improving the electrical conductivity of anthraquinonecontaining covalent organic frameworks (COFs) by incorporating reduced graphene oxide (rGO) sheets into the COF. Benefiting from the in situ synthesis of the COF along the surface of the twodimensional rGO nanosheets, the obtained COF@rGO hybrid films possess important intermolecular π−π interaction between rGO nanosheets and the COF. Meanwhile, the presence of the COF can avoid accumulation of rGO nanosheets, thereby achieving effective electrolyte ion transportation. Therefore, the optimal COF@rGO film possesses a good specific capacitance of 451.96 F g −1 , showing breakthrough within COF-based electrodes. In addition, the assembled planar COF@rGO microsupercapacitor (COF@ rGO-MSC) delivers a large stable electrochemical window (2.5 V), a good energy density (44.22 W h kg −1 ), and an excellent structural stability.