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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]

With the widespread applications of electric vehicles, power grid stabilization, and high‐pulsed power loads, high‐power lithium‐ion batteries (LIBs) are in urgent demand. However, the existing experimental‐based design of high‐power batteries is usually costly and inefficient, and provides limited information on the complex physicochemical processes inside the batteries. Digital twin concept is promising for capturing the batteries' electrochemical performance, and optimizing the power capability of LIBs. Here, an electrochemical‐thermal coupled model is developed as a digital twin model for rational design of ultrahigh‐power LiFePO4/graphite LIBs. The model can accurately predict the batteries' performance and help to predetermine the optimal parameters to achieve an ultrahigh power capability. After model‐guided optimization, the battery shows a high energy density of 92.38 Wh kg−1 at an ultrafast discharging current of 50 C and can withstand 150 C pulse discharging tests. Notably, the digital twin model can reveal experimentally inaccessible time‐ and space‐resolved information and identify the rate‐determining steps inside the battery. Hence, model‐driven optimization of ultrahigh‐power LiFePO4/graphite batteries is successfully realized aiming at the critical factors in the rate‐determining steps. The work provides an instructive design of ultrahigh‐power LiFePO4/graphite batteries, which might guide the future direction to boost the power capability of LIBs. [ABSTRACT FROM AUTHOR]

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]

Ni-rich layered oxide, one of the most promising cathode materials for lithium-ion batteries (LIBs) with high energy density, is suffering from the intrinsic hypersensitivity to moisture and acid gas (CO 2 , SO 2 , etc.) in the environment, leading to the generation and growth of residual lithium compounds (e.g. Li 2 CO 3), accompanied by surficial phase transition, high alkalinity and electrochemical deterioration. Eliminating these negative effects would require considerable energy and manpower, which hinders the promotion of Ni-rich cathode materials. Herein, we introduced crosslinked poly-methylhydrosiloxane (PMHS) and hydroxy‑terminated poly-dimethylsiloxane (denoted as PDMS-OH) hydrophobic film to in situ coat single-crystal LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811), isolating its Ni-rich electrode surface from moisture and acid gas to prevent side reactions. Specifically, the desired crosslinking layer, which is optimized by increasing the relative content of PMHS and decreasing the absolute content of PDMS-OH, endows the coated NCM811 with an appreciable improvement in hydrophobicity and storage performances and effectively suppresses the formation and growth of residual lithium compounds on the surface of NCM811 particles in a simulated damp-heat storage environment. Simultaneously, the crosslinked coating diminished the extraction of Li and Ni during exposure and maintained the high electrochemical performance of NCM811. This proposed strategy to crosslink polysiloxane film on the surface of Ni-rich cathode materials greatly alleviates the problem of storage failure, which will promote the practical popularization of Ni-rich cathode materials in LIBs. In situ crosslinked polysiloxanes coating layer endows surface of Ni-rich oxide cathode material with appreciable and durable hydrophobicity, successfully improving the ability of Ni-rich oxide cathode to resist severe environments and preventing electrochemical deterioration from side reactions induced by H 2 O or other acid gasses. [Display omitted] [ABSTRACT FROM AUTHOR]

Graphene is considered as a promising electrode material for supercapacitors due to its large specific surface area, excellent electrical conductivity and so on. In this paper, few-layer graphene is prepared by self-propagating combustion reaction between CO and metal magnesium, using powder MgO as deposition template. Graphene with a high specific surface area of up to 928 m2 g−1 replicates the morphological feature of powder MgO. Raman spectroscopy analysis demonstrates that the graphene layer decreases when the dosage of MgO template is increased. The specific capacitance of as-prepared sample exhibits the highest specific capacitance of 222 F g−1 at the current density of 1 A g−1 in EMI [TFSI] electrolyte. The sample demonstrates a "double high" performance with high specific energy density and high specific power density. A high energy density of 76.3 Wh kg−1 can be achieved at a specific power density of 1.75 kW kg−1, and it can still remain 48.6 Wh kg−1 when the specific power density reaches a high level of 35 kW kg−1. • Self-propagating combustion reaction synthesis graphene. • Synthesis graphene from CO and Mg. • Synthesized graphene has good structural properties. • Excellent capacitive performances in the electrolyte of EMI [TFSI]. [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]

Abstract: This paper demonstrates an asymmetric micro supercapacitor with superior overall performance that combines the advantages of both MnO2 positive electrode and carbon negative electrode for energy storage on a chip. Nano-structured MnO2 with rough surface is synthesized as active material for micro electrode. A self-supporting composite containing MnO2 and another containing nanoporous activated carbon (AC) are separated in an interdigital structure by using micro-electro-mechanical systems (MEMS) fabrication technologies. Measurements of the prototype show that the asymmetric micro supercapacitor has well-performed capacitive behavior, and its working voltage range is extended from 1 V to 1.5 V in aqueous electrolyte due to the MnO2–AC configuration. Calculations prove that it stores much higher energy densities than symmetric ones using either MnO2 or AC. Moreover, this work provides an attractive approach to achieve various asymmetric micro energy storage systems on chips. [Copyright &y& Elsevier]