The intercalation of potassium ions into graphite is demonstrated to be feasible, while the electrochemical performance of potassium-ion batteries (KIBs) remains unsatisfying. More effort is needed to improve the specific capacity while maintaining a superior rate capability. As an attempt, nitrogen/oxygen dual-doped hierarchical porous hard carbon (NOHPHC) is introduced as the anode in KIBs by carbonizing and acidizing the NH -MIL-101(Al) precursor. Specifically, the NOHPHC electrode delivers high reversible capacities of 365 and 118 mA h g at 25 and 3000 mA g , respectively. The capacity retention reaches 69.5% at 1050 mA g for 1100 cycles. The reasons for the enhanced electrochemical performance, such as the high capacity, good cycling stability, and superior rate capability, are analyzed qualitatively and quantitatively. Quantitative analysis reveals that mixed mechanisms, including capacitance and diffusion, account for the K-ion storage, in which the capacitance plays a more important role. Specifically, the enhanced interlayer spacing (0.39 nm) enables the intercalation of large K ions, while the high specific surface area of ≈1030 m g and the dual-heteroatom doping (N and O) are conducive to the reversible adsorption of K ions.

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An integrated composite tin sulfide bonded on an amino-functionalized graphene as a novel anode material for NIBs is reported. Tight contact with SnS2nanocrystals and discharge products on the amino-functionalized graphene interface results in excellent electrochemical performance.

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.

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The exploration of inexpensive, facile, and large‐scale methods to prepare carbon scaffolds for high sulfur loadings is crucial for the advancement of Li–S batteries (LSBs). Herein, the authors report a new nitrogen and oxygen in situ dual‐doped nonporous carbonaceous material (NONPCM) that is composed of a myriad of graphene‐analogous particles. Importantly, NONPCM could be fabricated on a kilogram scale via inexpensive and green hydrothermal‐carbonization‐combined methods. Many active sites on the NONPCM surface are accessible for the efficient surface‐chemistry confinement of guest sulfur and its discharge product; this confinement is exclusive of physical entrapment, considering the low surface area. Electrochemical examination demonstrates excellent cycle stability and rate performance of the NONPCM (K)/S composite, even with a sulfur loading of 80 or 90 wt%. Hence, the scaffolds for LSBs exhibit potential for industrialization through further optimization and expansion of the present synthesis.

Well-distributed graphene sheets doped with nitrogen (NGS) were prepared via a thermal annealing strategy with the existence of cyanamide. The cyanamide can efficiently restrain the conglomeration of the resultant graphene sheets and synchronously make sure the doping of nitrogen. Followed by the next-step of low-temperature solvothermal route, uniform ultrasmall tin sulfide (SnS 2 ) nanocrystals were readily grown on the preformed NGS (denoted as SnS 2 -NGS).Benefiting from the synergistic function between NGS and SnS 2 , the resultant composites exhibit excellent electrochemical performance. In case of estimation as anode materials for lithium-ion batteries (LIBs), SnS 2 -NGS with moderate weight ratio of SnS 2 deliver outstanding electrochemical outcomes giving the high reversible capacity of 1407 mA h g -1 at 200 mA g -1 after 120 cycles. The composites can also maintain a reversible capacity of about 200 mA h g -1 at a high current density of 10 A g -1 . The lithium-ion storage ability of prepared SnS 2 -NGS electrode is at the top rank in comparison with the other works. The obtained composites also achieve good sodium storage ability.

In this paper, a leaf-like porous CuO-graphene nanostructure is synthesized by a hydrothermal method.The as-prepared composite is characterized using XRD, Raman, SEM, TEM and nitrogen adsorptiondesorption. The growth mechanism is discussed by monitoring the early growth stages. It is shown that the CuO nanoleaves are formed through oriented attachment of tiny Cu(OH) 2 nanowires.Electrochemical characterization demonstrates that the leaf-like CuO-graphene are capable of delivering specific capacitances of 331.9 and 305 F g À1 at current densities of 0.6 and 2 A g À1 , respectively. A capacity retention of 95.1% can be maintained after 1000 continuous charge-discharge cycles, which may be attributed to the improvement of electrical contact by graphene and mechanical stability by the layer-by-layer structure. The method provides a facile and straightforward approach to synthesize CuO nanosheets on graphene and may be readily extended to the preparation of other classes of hybrids based on graphene sheets for technological applications. Recently, graphene nanosheets (GNS) based on transition metal oxides 2,3,22 have been studied and are expected to show improved capacitance owing their enhanced electronic conductivity, due to graphene materials possessing rapid electron transfer, high mechanical strength, high elasticity, and