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Massive efforts have been devoted to enhancing performances of Li–S batteries to meet the requirements of practical applications. However, problems remain in enhancing the energy density and improving the cycle life. We present a free-standing structure of walnut-shaped VS4 nanosites combine with carbon nanotubes (NTs) as cathodes. In this framework, NT arrays provide high surface area and conductivity for high sulfur loadings, and VS4 nanosites facilitate trapping and catalytic conversions of lithium polysulfides. The synergistic effects of free-standing NT arrays and VS4 nanosites have enabled high rate capability up to 6 C and long-term cycling with a low decay rate of 0.037% up to 1200 cycles at 2 C. Moreover, the designed cathode can achieve high areal capacities up to ∼13 mAh·cm–2 and estimated gravimetric energy density of 243.4 Wh·kg–1 at a system level, demonstrating great potential in practical applications of Li–S batteries.

Room-temperature sodium-ion batteries have attracted great attentions for large-scale energy storage applications in renewable energy. However, exploring suitable anode materials with high reversible capacity and cyclic stability is still a challenge. The VS 4 , with parallel quasi-1D chains structure of V 4+ (S 2 2− ) 2 , which provides large interchain distance of 5.83 Å and high capacity, has showed great potential for sodium storage. Here, the uniform cuboid-shaped VS 4 nanoparticles are prepared as anode for sodium-ion batteries by the controllable of graphene oxide (GO)-template contents. It exhibits superb electrochemical performances of high-specific charge capacity (≈580 mAh·g −1 at 0.1 A·g −1 ), long-cycle-life (≈98% retain at 0.5 A·g −1 after 300 cycles), and high rates (up to 20 A·g −1 ). In addition, electrolytes are optimized to understand the sodium storage mechanism. It is thus demonstrated that the findings have great potentials for the applications in high-performance sodium-ion batteries.

Nanoporous composite films of multi-walled carbon nanotubes (MWNTs) and polyaniline (PAn) were grown electrochemically from acidic aqueous solutions, such that the constituents were deposited simultaneously onto graphite electrodes. Scanning electron microscopy (SEM) revealed that the composite films consisted of nanoporous networks of MWNTs coated with PAn. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) demonstrated that these composite films had similar electrochemical response rates to pure PAn films, but a lower resistance and much improved mechanical integrity. The specific electrochemical capacitance of the composite films, per unit area of the original electrode, reached as high as 3.5 F cm 22 , a significantly greater value than that of 2.3 F cm 22 for pure PAn films prepared similarly.

A hybrid ion capacitor (HIC) based on potassium ions (K + ) is a new high‐power intermediate energy device that may occupy a unique position on the Ragone chart space. Here, a direct performance comparison of a potassium ion capacitor (KIC) versus the better‐known sodium ion capacitor is provided. Tests are performed with an asymmetric architecture based on bulk ion insertion, partially ordered, dense carbon anode (hard carbon, HC) opposing N‐ and O‐rich ion adsorption, high surface area, cathode (activated carbon, AC). A classical symmetric “supercapacitor‐like” configuration AC–AC is analyzed in parallel. For asymmetric K‐based HC–AC devices, there are significant high‐rate limitations associated with ion insertion into the anode, making it much inferior to Na‐based HC–AC devices. A much larger charge–discharge hysteresis (overpotential), more than an order of magnitude higher impedance R SEI , and much worse cyclability are observed. However, K‐based AC–AC devices obtained on‐par energy, power, and cyclability with their Na counterpart. Therefore, while KICs are extremely scientifically interesting, more work is needed to tailor the structure of  “Na‐inherited” dense carbon anodes and electrolytes for satisfactory K ion insertion. Conversely, it should be possible to utilize many existing high surface area adsorption carbons for fast rate K application.

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Using first-principles calculation based on density functional theory, diffusion of Mg atom into α- and β-Sn was investigated. The diffusion barriers are 0.395 and 0.435 eV for an isolated Mg atom in the α- and β-Sn, respectively. However, the diffusion barriers of the Mg atom decrease in the α-Sn, whereas they increase in the β-Sn, when an additional Mg atom was inserted near the original diffusing Mg atom, which is mainly due to strong binding of Mg-Mg atoms in the β-Sn. Therefore, it is better to use the α-Sn, rather than the β-Sn, as an anode material for Mg ion batteries.