Metal oxides (MOs) have been widely investigated as promising high-capacity anode material for lithium ion batteries, but they usually exhibit poor cycling stability and rate performance due to the huge volume change induced by the alloying reaction with lithium. In this article, we present a double protection strategy by fabricating a two-dimensional (2D) core-shell nanostructure to improve the electrochemical performance of metal oxides in lithium storage. The 2D core-shell architecture is constructed by confining the well-defined graphene based metal oxides nanosheets (G@MO) within carbon layers. The resulting 2D carbon-coated graphene/metal oxides nanosheets (G@MO@C) inherit the advantages of graphene, which possesses high electrical conductivity, large aspect ratio, and thin feature. Furthermore, the carbon shells can tackle the deformation of MO nanoparticles while keeping the overall electrode highly conductive and active in lithium storage. As the result, the produced G@MO@C hybrids exhibit outstanding reversible capacity and excellent rate performance for lithium storage (G@SnO(2)@C, 800 mAh g(-1) at the rate of 200 mA g(-1) after 100 cycles; G@Fe(3)O(4)@C, 920 mAh g(-1) at the rate of 200 mA g(-1) after 100 cycles).

Because of advantages such as excellent electronic conductivity, high theoretical specific surface area, and good mechanical flexibility, graphene is receiving increasing attention as an additive to improve the conductivity of sulfur cathodes in lithium-sulfur (Li-S) batteries. However, graphene is not an effective substrate material to confine the polysulfides in cathodes and stable the cycling. Here, we designed and synthesized a graphene-based layered porous carbon material for the impregnation of sulfur as cathode for Li-S battery. In this composite, a thin layer of porous carbon uniformly covers both surfaces of the graphene and sulfur is highly dispersed in its pores. The high specific surface area and pore volume of the porous carbon layers not only can achieve a high sulfur loading in highly dispersed amorphous state, but also can act as polysulfide reservoirs to alleviate the shuttle effect. When used as the cathode material in Li-S batteries, with the help of the thin porous carbon layers, the as-prepared materials demonstrate a better electrochemical performance and cycle stability compared with those of graphene/sulfur composites.

No abstract

with SIBs, potassium-ion batteries (KIBs) deliver a higher working voltage due to the lower redox potential of K + /K (−2.92 V vs SHE) than that of Na + /Na (−2.71 V vs SHE). [14] In addition, K + has been demonstrated to be reversibly intercalated/ deintercalated into graphite anode, while very limited amounts of Na + could. [14] However, as the research on KIBs is still at the infancy stage, the mechanisms at an atomic scale and interfaces are unclear. In addition, owing to the large size of K + that would cause sluggish kinetics, only a few of cathode materials (Prussian blue and its analogues) [16] and anode materials (graphite, [14] Sn 4 P 3 /C) [13] were investigated. Therefore, developing suitable electrode materials with good performance as well as comprehensively investigating the mechanism are of great importance.On the other hand, another new type of battery called dual-ion battery (DIB) [5][6][7][8][9][10][11] also arouses scientists' concern, which generally consists of dual graphitic carbon electrodes. Owing to the intrinsic redox amphotericity of graphitic carbon materials, both cations (Li + ) and anions (PF 6 − , BF 4 − , TFSI − , etc.) are intercalated/deintercalated into graphite anode and graphite cathode, respectively, during the charging/discharging process in the dual-graphite DIB. Apparently, the dual-graphite DIBs show advantages in terms of low cost, good safety, and environmental friendliness. In addition, the high working voltage (mainly above 4.5 V) [5] of the DIB caused by high anion intercalation potential is also beneficial for high energy density. Extensive researches on DIBs have been focused on exploiting high-capacity cathode materials, [6c] alternative anode materials, [6a,7-11] as well as suitable electrolyte compositions, [5] and great progresses on their development have been made.In this work, on the purpose of combining both advantages of KIBs and DIBs, we first report a dual-carbon battery (DCB) based on a potassium-ion electrolyte (1 m KPF 6 in carbonate solvent), using expanded graphite (EG) as cathode material and mesocarbon microbead (MCMB) as anode. The working mechanism of the as-prepared K-ion-based dual-carbon battery (named as K-DCB) was investigated, which was further demonstrated to deliver a reversible discharge capacity of 61 mA h g −1 at 1 C (1 C corresponding to 100 mA g −1 ) current rate and also show good cycling performance for 100 cycles with negligible capacity decay. Moreover, the battery works reversibly and stably over a wide voltage window of 3.0-5.2 V with medium discharge voltage of 4.5 V, the highest value among the reported KIBs. [12][13][14][15][16] Figure 1a schematically shows the working mechanism of the K-DCB configuration utilizing an EG cathode and MCMB Although potassium-ion batteries (KIBs) have been considered to be promising alternatives to conventional lithium-ion batteries due to large abundance and low cost of potassium resources, their development still stays at the infancy stage due to the lack of appropriate cathode and anod...

No abstract

Dual‐ion batteries (DIBs) have attracted increasing attention owing to their merits of high working voltage, low cost, and especially environmental friendliness. However, the cycling stability of most DIBs is still unsatisfying due to the decomposition of conventional liquid carbonate electrolytes under high working voltages. Exploration of gel polymer electrolytes (GPEs) with good electrochemical stability at high voltage is a possible strategy to optimize their cycling stability. A high‐performance flexible DIB based on a poly(vinylidene fluoride‐hexafluoro propylene) GPE codoped with poly(ethylene oxide) and graphene oxide via weak bond interactions is herein reported for the first time. The prepared polymer electrolyte shows a 3D porous network with significantly improved ionic conductivity up to 2.1 × 10−3 S cm−1, which is favorable for fast ionic transportation of both cations and anions. As a result, this DIB exhibits excellent cycling stability with a capacity retention of 92% after 2000 cycles at a high current rate of 5C (1C is corresponding to 100 mA g−1), which is among the best performances of DIBs. Moreover, good flexibility and thermal stability (up to 90 °C) are also achieved for this battery, indicating its potential applications for high‐performance flexible energy storage devices.

The lowC oulombic efficiency and serious safety issues resulting from uncontrollable dendrite growth have severely impeded the practical applications of lithium (Li) metal anodes.H erein we report as table quasi-solid-state Li metal battery by employingah ierarchical multifunctional polymer electrolyte (HMPE). This hybrid electrolyte was fabricated via in situ copolymerizing lithium 1-[3-(methacryloyloxy)propylsulfonyl]-1-(trifluoromethanesulfonyl)imide (LiMTFSI) and pentaerythritol tetraacrylate (PETEA) monomers in traditional liquid electrolyte,w hichi sa bsorbed in ap oly(3,3-dimethylacrylic acid lithium) (PDAALi)-coated glass fiber membrane.T he well-designed HMPE simultaneously exhibits high ionic conductivity (2.24 10 À3 Scm À1 at 25 8 8C), near-single ion conducting behavior (Li ion transference number of 0.75), good mechanical strength and remarkable suppression for Li dendrite growth. More intriguingly,t he cation permselective HMPE efficiently prevents the migration of negatively charged iodine (I) species,w hich provides the as-developed Li-I batteries with high capacity and long cycling stability.

as hybridization of MoS 2 with quantum dots and heterostructures with other 2D materials to suppress the dark current and enhance the broad spectral range in the NIR region were attempted. While convenient, these approaches are not scalable for large-scale implementation due to the complicated procedures as well as expensive material and instrument-related costs. [17][18][19] To overcome the aforementioned issues, a promising approach is to create multifunctional hybrid photodetectors by simple solution mixing of MoS 2 with other 2D materials. The different band gaps and dark currents of 2D materials and the low-cost solution process offers a convenient route to engineering and controlling the photodetection properties. [20][21][22] In addition, the arrays of hybrid photodetectors fabricated on flexible substrates, such as plastic and paper, would be beneficial for future wearable applications. [23,24] Recently, 2D organic semiconductors, such as graphitic carbon nitride (g-C 3 N 4 ), have emerged as promising UV-and visible-light-active photocatalysts in the arena of solar energy conversion and environmental applications. [25][26][27][28] Their unique electrical and optical properties, wide band gap (≈2.7 eV), stability in ambient conditions, and low dark current make them attractive for UV light photodetection, but very little work has been carried out so far. Compared to other 2D materials, by considering its merits, g-C 3 N 4 is a promising candidate for hybridizing with MoS 2 because not only does it suppress the dark current of MoS 2 , but also allows hybrid broadband photodetection from UV to visible region. In addition, the crystal lattice matching [29,30] and the ultrafast charge transfer between MoS 2 and g-C 3 N 4 at the interface may lead to efficient separation of photogenerated carriers, as predicted by a recent computational study. [31] Herein we report, to the best of our knowledge for the first time, mechanically flexible 2D organic-inorganic hybrid thin film photodetectors consisting of inorganic MoS 2 and organic g-C 3 N 4 nanosheets for broadband photodetection. Simple but robust solution mixing of MoS 2 and g-C 3 N 4 offers an extremely convenient route to controlling their composition in the hybrid films and thus allows for tuning the optoelectronic properties. Hybrid thin films with 5:5 ratio of MoS 2 and g-C 3 N 4 (henceforth denoted as 5:5 hybrid films) exhibited excellent photodetection performance in terms of ON/OFF photocurrent ratio, specific detectivity, responsivity, and response time upon both Flexible 2D inorganic MoS 2 and organic g-C 3 N 4 hybrid thin film photodetectors with tunable composition and photodetection properties are developed using simple solution processing. The hybrid films fabricated on paper substrate show broadband photodetection suitable for both UV and visible light with good responsivity, detectivity, and reliable and rapid photoswitching characteristics comparable to monolayer devices. This excellent performance is retained even after the films are severely...