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The work function difference (WFD) between the two electrode materials has a positive effect on the potential window for the asymmetric supercapacitors (ASCs) theoretically, but there is no relevant investigation. Here, we use the kelvin probe force microscope to detect contact potential difference (CPD) which can well represent the WFD between carbon@K 0·5 Mn 2 O 4 positive material and four metal oxides anode materials, namely MoO 3 , V 2 O 5 , Fe 2 O 3 and WO 3 respectively. What's more, the relationship between WFD and the potential window is studied by combining contact potential difference with electrochemical testing. We find that the as-fabricated carbon@K 0·5 Mn 2 O 4 //MoO 3 device exhibits the widest potential window of 2.42 V with the maximum WFD. As a result, the carbon@K 0·5 Mn 2 O 4 //MoO 3 have a high energy density of 66.7 Wh kg−1 at the power density of 5.95 kW kg−1. Our study provides a new experimental reference for constructing supercapacitor devices with wide potential window and high energy density. • Reveal the effect of work function difference on the supercapacitors potential window. • Assembled Carbon@K 0·5 Mn 2 O 4 //MoO 3 device exhibits voltage window of 2.42 V. • The device shows energy density of 66.7 Wh kg−1 at the power density of 5.95 kW kg−1. [ABSTRACT FROM AUTHOR]

The gradient temperature was manipulated to construct hollow irregular carbon spheres with regulated intrinsic defects and surface area targeting favorable potassium storage. An enlarged surface area, increased intrinsic defects, and superior conductivity induced more surface-active interfaces. These actions facilitated a high reversible capacity as well as excellent cycling stability. [ABSTRACT FROM AUTHOR]

Si‐based anode electrodes stand out for its excellent capacity among the numerous anode electrodes for lithium‐ion batteries. However, there is still a problem that the volume expansion from the alloying reaction of Li and Si often leads to structural collapse and rapidly capacity degradation. Here, Si nanoparticles (Si NPs) are coated via metal‐organic frameworks (MOFs) derived skeleton to buffer its volume expansion, thereby improving electrochemical properties. Scanning electron microscopy was applied to revealed morphology and structure of the composite material. The results demonstrate that the structure of the prepared composite is Si NPs encapsulated in the unique carbon skeleton. The as‐prepared Si@MIL‐125‐500 exhibits excellent electrochemical performances with an excellent reversible capacity of 304.3 mAh g−1 at 5 A g−1 even after 400 cycles. In addition, the initial coulombic efficiency (ICE) reached up to 86 %. The improved electrochemical performance could be attributed to the distinctive structure of the carbon coated Si NPs and stable titanium(IV) center site, which has improved the electrical conductivity and cycling stability of Si NPs. Moreover, the empty space inside the MOF's carbon skeleton can release the volume strain of Si during electrochemical process. There is an improvement of electrochemical properties for LIBs due to Si NPs restricted in MIL‐125. [ABSTRACT FROM AUTHOR]

Pseudocapacitors are promising energy storage devices combining the merit of fast charging ability and high energy density. Constructing electrode materials for pseudocapacitors with two-dimensional (2D) materials has become a trending topic. However, it is still a challenge to address the restacking propensity of the 2D materials and to broaden the operational potential window of pseudocapacitors. We herein demonstrate a facile hydrothermal reaction of synthesizing a three-dimensional V 2 O 3 tubes (assembled with ultrathin nanosheets) coated with MoS 2 nanosheets and explore their electrochemical properties for pseudocapacitors. The V 2 O 3 tubes prevent the restacking of MoS 2 nanosheets and serve as conductive scaffold for fast electron transport. Owing to the multi-valence of both Mo and V, the potential window of composite is able to straddle between negative and positive potentials. Therefore, the V 2 O 3 @MoS 2 composite electrode exhibits a broad operational potential range between −1.0 V and +1.0 V, and a high reversible capacitance of 655 F g −1  at 20 mV s −1 . Moreover, an asymmetric pseudocapacitor with our composite as a positive electrode achieves a high specific capacitance (108.7 F g −1  at 0.5 A g −1 ), high energy density (31.8 W h kg -1 ) and excellent cycling stability (no capacitance decay after 35000 cycles). [ABSTRACT FROM AUTHOR]

[Display omitted] • Cu 39 S 28 , CoS 2 and ZnS are uniformly embedded in the porous N-rich carbon. • Multi-shell structure buffers volumetric stress and increases anode utilization. • Carbon coating and N doping enhance stability and reaction kinetics of anode. Transition metal sulfides (TMSs) have been considered as one type of promising anode materials for sodium-ion batteries (SIBs) due to their high theoretical capacity and outstanding redox reversibility. However, the application of TMSs for SIB anode still faces the fatal challenge mainly pertaining to rapid capacity decay and slow reaction kinetics. Herein, we employ Cu/Zn co-doped ZIF-67 (Cu/Zn-ZIF-67) as the precursor to prepare multi-shell hollow carbon-coated Cu 39 S 28 -CoS 2 -ZnS@nitrogen doped carbon cubes (CCZS@NC@C-15), where the outer shell is a carbon coating layer, and the interior is the double shells formed by Cu 39 S 28 , CoS 2 and ZnS in a porous nitrogen-rich carbon matrix. The as-prepared CCZS@NC@C-15 with unique multi-shell structure can not only effectively buffer the volumetric stress during the sodium insertion/extraction processes, but also increase the volume utilization rate of anode materials. Additionally, the porous carbon cube structure not only increases the contact area between the anode materials and the electrolyte but also prevent the agglomeration of active particles effectively. Furthermore, the carbon coating layer combine with the internal N-rich carbon matrix increases the conductivity of anode and improve the electrochemical stability. As a result, the as-prepared CCZS@NC@C-15 anode shows the remarkable electrochemical stability and rate capability. Our research provides a new strategy for the rational design of TMSs with unique structure for high-performance SIBs. [ABSTRACT FROM AUTHOR]