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In this study, a facile pyrolysis process is utilized to convert a mantis shrimp shell into a 3D bicontinuous porous, highly wrinkled, nitrogen-doped, graphene-like ultrathin carbon sheet (3D BWGC). The 3D BWGC achieves a high surface area of 2300 m2 g−1 and a pore volume of up to 1.63 cm3 g−1. The specific capacitance of the 3D BWGC in 0.5 M H2SO4 electrolyte is 370.9 F g−1 at a current density of 1 A g−1 and an operating voltage window of 1.1 V. By introducing Fe2+, the operating voltage window of 3D BWGC symmetric supercapacitors can reach 1.8 V in a neutral electrolyte, and a specific capacitance of 317.2 F g−1 can be obtained at a current density of 0.5 A g−1. Remarkably, the fabricated symmetric supercapacitors using 2 M MgSO4 + 0.05 M FeSO4 electrolyte demonstrated an energy density as high as 17.7 W h kg−1 at a power density of 180 W kg−1. The assembled supercapacitors exhibit good cycling performance, maintaining an initial capacitance of 87.2% over 30 000 cycles. These excellent performances indicate the promising prospects of 3D BWGC in high-performance electrochemical energy storage. [ABSTRACT FROM AUTHOR]

Polymer hydrogels are a promising electrolyte for flexible superconductors (FSCs) due to their excellent flexibility, ions transportations and interfacial compatibility. However, the large internal resistance will decrease the power density (PD) and energy density (ED) of FSCs. In this work, Ti 3 C 2 T x was introduced to polyacrylamide/calcium alginate (PC) hydrogel electrolyte to decrease the internal resistance (IR) and improve the interfacial adhesion. The polyacrylamide/calcium alginate@Ti 3 C 2 T x (PCT) composite hydrogels were successfully prepared by in-situ polymerization. Their mechanical property and adhesive property to various substrates were investigated, respectively, and a flexible supercapacitor was assembled with composite hydrogels as electrolyte and two self-made Ti 3 C 2 T x sheets as electrode. It was found composite hydrogels can adhere to various substrates, which make the voltage drop of FSCs from 163 mV to 78.9 mV. The FSCs show a good performance, whose specific capacitance is 1051.9 mF cm−2 with a current density of 1.07 mA cm−2, and the ED reaches 32.3 Wh kg−1 and the capacitance retention rate is as high as 96% at a high current density of 18.7 mA cm−2. Meanwhile, it can sensitively monitor human movements such as finger bending, frowning, swallowing, etc. This work is expected to be applied in the field of energy storage and sensing. [Display omitted] • Ti 3 C 2 T x was introduced to the PC hydrogel to decrease the internal resistance and improve the interfacial adhesion. • The FSC with PCT as electrolyte has high specific capacitance (1051.9 mF cm−2) and large energy density (32.3 Wh kg−1). • The PCT hydrogel shows a good performance in the field of sensing, it can sensitively monitor many human movements. [ABSTRACT FROM AUTHOR]

Recently, spinel high-entropy oxide (HEO) anode materials have garnered extensive attention for high-energy lithium-ion batteries due to their high specific capacity. Many studies have explored its energy storage mechanism, but few have paid attention to its characteristics in long cycle life. In this work, the whole life cycling performance of (FeCoNiCrMn)-HEO is presented and investigated for the first time. Distinct capacity trends are studied to divide the cycling life into three stages: activation, upgradation, and degradation. Ex situ morphological characterizations are conducted to reveal that the driving force of stage change is continuous particle fragmentation. As a result, refined particles promote conversion reaction reversibility and induce extra interfacial capacity, achieving 2831 mAh g−1 at 825 cycles. Density functional theory (DFT) calculations provide a deeper insight into the high entropy effect on the ultra-high extra interfacial capacity. However, continuous refinement brings about huge electrolyte interface-derived layers, which are also responsible for pre-decay and post-collapse. The view of the evolution of the lithium storage mechanism is explicitly presented and experimentally verified by high-energy ball milling and fluorinated vinyl carbonate (FEC). These above results can give practical solutions to design high specific capacity and long-life cycle stability HEO anode in the future. [Display omitted] • The whole life performance of (FeCoNiCrMn)-HEO was studied for the first time. • The driving force of capacity change is continuous particle fragmentation. • Particle refinement enhances reaction reversibility and interfacial capacity. • The high entropy effect led to the ultra-high extra capacity. [ABSTRACT FROM AUTHOR]

Capacitive lithium-ion batteries with a dual-energy storage mechanism can provide a high energy and power density, which are constructed by the addition of slightly porous carbon. Here, the effect from porous carbon, such as the proportion, specific surface area, pore size and electrical conductivity, on the rate performance is systematically studied using hybrid electrodes with LiNi 0.6 Co 0.2 Mn 0.2 O 2 and activated carbon or carbon aerogel. Compared with LiNi 0.6 Co 0.2 Mn 0.2 O 2 electrodes, the hybrid electrodes demonstrate a lower resistivity, smaller electrochemical polarization, stronger rate capability and stable capacity retention. Furthermore, Adding carbon aerogel into LiNi 0.6 Co 0.2 Mn 0.2 O 2 material is more conducive to enhancing the rate performance when compared with activated carbon. The lithium-ion full capacitor battery configured of a hard carbon anode and LiNi 0.6 Co 0.2 Mn 0.2 O 2 -carbon aerogel delivers a capacity of 97.3 mAhg−1 at 10C with an energy density reaching 323.8 Wh∙kg−1 (vs. the cathode), showing bright prospects in energy storage system with both high specific energy and power densities. [ABSTRACT FROM AUTHOR]