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Rechargeable magnesium batteries (RMBs) have emerged as one of the promising energy storage devices, and polymer electrolytes with high safety, stability, and structural flexibility are the ideal choice for RMBs. Herein, a novel in situ crosslinked gel polymer electrolyte, PDTE is reported, via facile ring‐opening polymerization in RMBs. The electrolyte exhibits a remarkable room‐temperature ionic conductivity of 2.8 × 10−4 S cm−1 and highly reversible Mg plating/stripping behavior (98.9% Coulombic efficiency, 2000 cycles) with a low overpotential (<0.1 V). Mo6S8||PDTE||Mg coin cells demonstrate exceptional cycling stability and rate capability at a wide temperature range (−20 to 50 °C), characterizing an average discharge capacity of 81.6 mAh g−1 at 10 C for 7500 cycles at room temperature, and 97.4 and 111.7 mAh g−1 at 0.2 C for 400 and 50 cycles at −20 and 50 °C, respectively. The pouch cell exhibits a high energy density of 204 Wh kg−1 with a high retention of 90.6% at 0.2 C for 350 cycles, along with significantly improved safety and remarkable flexibility. Additionally, good compatibility with conversion‐type cathode Cu3Se2 validates the application versatility of PDTE. The development of this gel polymer electrolyte provides a feasible approach for the research on semi‐solid‐state electrolytes for RMBs. [ABSTRACT FROM AUTHOR]

Aqueous zinc–manganese batteries with low cost, reliable safety, and considerable energy density, show promise for grid‐scale storage. Their durable operation is highly dependent on the reversibility and stability of both electrode interfaces, which is limited by the different requirements of the interfaces of manganese‐based cathodes and zinc anodes. Here, a quasi‐decoupled solid–liquid hybrid electrolyte is proposed, which demonstrates good compatibility and high reversibility for both interfaces with different electrolyte environments, showing quasi‐decoupling characteristics. Such a hybrid electrolyte can endow the anode interface with abundant favorable nucleation sites for achieving uniform zinc platting/stripping, as well as limit the presence of free H2O molecules, to suppress side‐reactions. This electrolyte is also adapted to a reversible and stable MnO2/Mn2+ manganese deposition/dissolution reaction at the cathode interface by restricting OH−/H+ ion diffusion, preventing formation of irreversible electrochemically inert MnOOH. As a result, the quasi‐decoupled solid–liquid hybrid electrolyte enables Zn||Zn cycling for more than 500 h, and a specific capacity of a Zn||α‐MnO2 battery up to 348 mAh g−1 at 0.2 A g−1. It also allows 87% capacity retention after 500 cycles at 0.5 A g−1. This work provides a new insight into electrolyte design that focuses on the different requirements of differing electrode interfaces. [ABSTRACT FROM AUTHOR]

In this paper, a flexible self-supported electrode based on the porous composite of NiS2 and Ti3C2Tx grown on carbon cloth (NiS2/Ti3C2Tx-CC) was designed and synthesized. Due to the introduction of highly conductive and flexible Ti3C2Tx, the NiS2/Ti3C2Tx-CC electrode achieves a 1.4-fold increase (1214 C g-1 at 2 A g-1) in the specific capacity, a 1.3-fold increase in the rate capability (63% of capacity retention with the current density increases from 2 to 20 A g-1), and a 2.0-fold increase in the cyclic stability (∼83% of capacity retention at the current density of 20 A g-1 after 2000 charge–discharge cycles) compared with the NiS2-CC electrode. Meanwhile, there is no obvious capacity attenuation at the bending angle of 180°, indicating the prominent flexibility of the NiS2/Ti3C2Tx-CC electrode. Accordingly, an all-solid asymmetric supercapacitor (ASC) is fabricated, which exhibits a high energy density of 57.55 Wh kg-1 at the power density of 800 W kg-1. Furthermore, ∼97% of initial capacity is maintained at the current density of 5 A g-1 after 1000 charge–discharge cycles, indicating the good cycling stability. These satisfactory electrochemical behaviors can be also ascribed to the introduction of Ti3C2Tx, which can facilitate the rapid electron transport at the interface of the composite and maintain the outstanding mechanical integrality of the electrode during charge–discharge processes. [ABSTRACT FROM AUTHOR]

With markedly expansive demand in energy storage devices, rechargeable batteries will concentrate on achieving the high energy density and adequate security, especially under harsh operating conditions. Considering the high capacity (3860 mA h g−1) and low electrochemical potential (−3.04 V vs the standard hydrogen electrode), lithium metal is identified as one of the most promising anode materials, which has sparked a research boom. However, the intrinsically high reactivity triggers a repeating fracture/reconstruction process of the solid electrolyte interphase, side reactions with electrolyte and lithium dendrites, detrimental to the electrochemical performance of lithium metal batteries (LMBs). Even worse, when exposed to air, lithium metal will suffer severe atmospheric corrosion, especially the reaction with moisture, leading to grievous safety hazards. To settle these troubles, constructing air‐stable protective layers (ASPLs) is an effective solution. In this review, besides the necessity of ASPLs is highlighted, the modified design criteria, focusing on enhancing chemical/mechanical stability and controlling ion flux, are proposed. Correspondingly, current research progress is comprehensively summarized and discussed. Finally, the perspectives of developing applicable lithium metal anodes (LMAs) are put forward. This review guides the direction for the practical use of LMAs, further pushing the evolution of safe and stable LMBs. [ABSTRACT FROM AUTHOR]

Layered double hydroxide (LDH) is potentially excellent supercapacitor (SC) materials, but the low conductivity and easy agglomeration limit the further improvement of their electrochemical properties. Therefore, LDHs are requisite to grow on some conductive substrates to produce high-performance SC. In this paper, the conductive two-dimensional (2D) transition metal carbides, nitrides and carbonitrides (called MXene) were explored as the substrate to directly deposit NiFe-LDH nanosheets by a one-step hydrothermal method, then a three-dimensional (3D) porous NiFe-LDH/MXene electrode was obtained. The morphology and electrochemical performance of the composite electrodes were analyzed and investigated. The results show that the NiFe-LDH/MXene electrode has larger specific capacitance (720.2 F/g) than NiFe-LDH (465 F/g), and the capacitance of the composite electrode retained 86% after 1000 cycles (only 24% for NiFe-LDH), showing excellent cycle stability. The improved electrochemical performance of the composites is caused by the stable sheet-like structure of NiFe-LDH during charge-discharge time and the conductive network formed by the MXene, which can accelerates electron transport. In addition, the asymmetric SC based on NiFe-LDH/MXene positive electrode display a power density of 758.27 W/kg at an energy density of 42.4 Wh/Kg. These results indicate the NiFe-LDH/MXene composites can be applied as the novel candidate of high-performance SC electrodes. • The LDH/MXene synergistic hybrid structure is developed with MXene nanosheets as the substrate. • Prominent electrical performance is attributed to MXene providing a fast charge transfer path for LDH. • The anchoring of LDH on MXene surface provides the material with enhanced cyclic stability. [ABSTRACT FROM AUTHOR]

In this paper, a highly deformable and conductive freestanding electrode based on the composite of MnO 2 and MXene on carbon cloth is designed. Benefiting from the synergistic coupling of MXene and MnO 2 , the novel electrode has enhanced electrochemical performance (511.2 F/g) compared with MnO 2 nanorods/carbon cloth (302.3 F/g), and when the current increases by 5 times (1 A/g to 5 A/g), 60.3% capacitance was retained, suggesting excellent rate capability. The capacitance of the composite electrode was reduced by only 17% after 10,000 cycles, showing excellent cycle stability. In addition, an asymmetric flexible supercapacitor based on MnO 2 nanorods/MXene/carbon cloth exhibited a high energy density of 29.58 Wh/kg at a power density of 749.92 W/kg. The assembled supercapacitor presented excellent mechanical properties, even if the capacitor is bent 180°, the performance is almost unchanged. The above results demonstrate that MnO 2 /MXene/CC electrode has a potential for high-performance flexible supercapacitors. • Hierarchically structured MnO 2 nanorods/MXene/CC was fabricated. • Electrode combines flexibility and high conductivity. • Unique three-layer structure provides improved electrochemical performance. • After 10,000 cycles, the degradation is less than 17%. [ABSTRACT FROM AUTHOR]

In this paper, a facile two-step method was adopted to in-situ develop a flexible electrode with NiCo-LDH nanowires@NiCo-LDH nanosheets core-shell structure on carbon fiber cloth (CFC). The electrochemical properties of the composite materials with different Ni/Co molar ratios nanosheets were systematically studied. It is found that the NiCo-LDH nanowires@Ni2Co1-LDH nanosheets (NiCo@Ni2Co1) composite material achieves a high areal capacitance of 9.67 F/cm2 at 5 mA/cm2 and a good cycling stability (75% capacitance retention after 2000 cycles). The excellent performance benefits from the distinct core-shell structure and the synergistic effect of NiCo-LDH nanosheets and NiCo-LDH nanowires. Moreover, a solid-state flexible asymmetric supercapacitor (ASC) assembled with NiCo@Ni2Co1/CFC as positive electrode and activated carbon on CFC as negative electrode can work stably at a voltage of 1.6 V. This ASC displays a high areal energy density of 298.6 uWh/cm2 at a current density of 1 mA/cm2 and with a corresponding areal power density of 0.80 mW/cm2. • A NiCo@NiCo-LDH core-shell structure was synthesized by a two-step method. • The NiCo@Ni2Co1-LDH composite shows a high areal capacitance of 9.67 F/cm2. • The assembled asymmetric supercapacitor exhibits a high areal energy density. [ABSTRACT FROM AUTHOR]

The supercapacitor (SC) based on nickel cobalt layered double hydroxide (NiCo-LDH) has aroused great interest in the field of energy storage. However, the agglomeration and low electrical conductivity are unfavorable for electrochemical performance. Herein, Ag nanowires (Ag NWs) was first dip-coated on nickel foam (NF) to form a conductive substrate, on which the NiCo-LDH nanosheet array in-situ grew to construct an efficient three-dimensional (3D) self-supported hierarchical structure NiCo-LDH/Ag NWs/NF electrode. The presence of Ag NWs inhibits aggregation of LDH nanosheets and accelerates the electron transfer. Electrochemical studies exhibit that NiCo-LDH/Ag/NF hybrid electrode possesses the higher specific capacitance of 2920.6 F g−1 at a current density of 5 A g−1 and excellent cycling stability (89.8% after 2000 cycles) compared with the electrode without Ag NWs. The asymmetric supercapacitor (ASC) with the NiCo-LDH/Ag/NF heterostructure as the positive electrode and active carbon (AC) as the negative electrode displays a high energy density of 42.9 Wh kg−1 at a power density of 800 W kg−1. When two aqueous ASCs were assembled in series and charged for only 1 min, the stored energy was capable of powering two green light-emitting-diodes (LEDs) for more than 3 min, indicating NiCo-LDH/Ag/NF electrode material shows great potential application in supercapacitor. Image 1 • Ag NWs and 3D ultrathin NiCo-LDH nanosheets are successively decorated on Ni foam. • The conductivity and active sites of electrode are enhanced by the addition of Ag NWs. • The specific capacitance of NiCo-LDH/Ag/NF electrode is 2920.6 F g−1 at 5 A g−1. • The assembled asymmetric supercapacitor exhibits high energy and power densities. [ABSTRACT FROM AUTHOR]

In this study, Ti 3 C 2 T x was directly deposited on carbon cloth (CC) to obtain a flexible substrate for NiCo-S. Then, 3D self-supported flexible NiCo-S/Ti 3 C 2 T x /CC composite electrode was prepared by a two-step hydrothermal method. Compared with the NiCo-S/CC electrode, the specific capacity of the NiCo-S/Ti 3 C 2 T x /CC electrode increases from 908 to 1690 C g−1 at 2 A g−1. The rate capability (2–20 A g−1) increases from 42% to 66%, and the cyclic performance (5000 charge-discharge cycles at a current density of 10 A g−1) increases from 50% to 82%. The enhanced electrochemical performance may be attributed to the introduction of Ti 3 C 2 T x , which reduces the resistance of composite and facilitates the electron/ion transport, while the presence of Ti2+ in Ti 3 C 2 T x provides more sites for redox reactions. The assembled flexible all-solid supercapacitor (NiCo-S/Ti 3 C 2 T x /CC//AC) manifests a high energy density of 62 Wh kg−1 at 800 W kg−1 and an excellent cyclic stability with 89% capacity retention after 5000 cycles at 10 A g−1. In addition, the device demonstrates no obvious capacity change at different states and bending angles, showing broad application prospects in high-performance wearable energy-storage devices. • NiCo-S/Ti 3 C 2 T x /CC flexible electrode was fabricated by a two-step hydrothermal method. • Introduction of high conductive Ti 3 C 2 T x improved electrochemical performance. • -The assembled ASCs supercapacitor shows well stability at different states and bending angles. [ABSTRACT FROM AUTHOR]

• Nanosheet, nanoneedle and hybrid structure of NiCo 2 O 4 nanoarrays were synthesized. • Nanoneedle-nanosheet hybrid structure improved electrochemical performance. • The hybrid structure electrode combines excellent cyclic stability and flexibility. [Display omitted] In this paper, three different morphologies of NiCo 2 O 4 nanoarrays, namely, nanosheet (S-NiCo 2 O 4), nanoneedle (N-NiCo 2 O 4) and their hybrid nanostructure (M-NiCo 2 O 4) were successfully prepared on flexible carbon cloth (CC) by a hydrothermal method. The structures, surface morphologies and compositions of the samples were respectively characterized by XRD, SEM, EDS, and XPS, and the effect of NiCo 2 O 4 morphologies on the electrochemical performances was systematically investigated. It is found that the M-NiCo 2 O 4 /CC electrode demonstrates the best supercapacitive performance among the three kinds of samples, typically its specific capacitance is 1347.4 F/g at 1 A/g (1509.1 F/cm2 at 1 mA/cm2), much higher than that of S-NiCo 2 O 4 (938.4 F/g at 1 A/g) and N-NiCo 2 O 4 (1022.4 F/g at 1 A/g). Meanwhile, the M-NiCo 2 O 4 /CC sample exhibits excellent rate capability (81.6%, from 1 A/g to 15 A/g) and cycling stability (92.4% retention after 10,000 cycles). In addition, an flexible solid-state asymmetric supercapacitor (ASC) with M-NiCo 2 O 4 /CC as positive electrode manifests great capacity retention (94% after 5000 cycles) and outstanding energy density of 41.7 Wh/kg at the power density of 750 W/kg. Moreover, the charge-discharge time shows no significant change after 2000 bends, demonstrating its application potential in the field of flexible SCs. The excellent performance is attributed to the unique hybrid porous structure of one-dimensional (1D) nanoneedles and two-dimensional (2D) nanosheets. [ABSTRACT FROM AUTHOR]

• 3D self-supporting heterostructure NiCo-LDH/ZnO NR/CC and NiCo-LDH/ZnO NF/CC flexible composites were synthesized. • NiCo-LDH nanoflakes grown on ZnO NF/CC substrate are more compact and uniform than those on ZnO NR/CC substrate. • NiCo-LDH/ZnO NF/CC shows 2.6-time higher specific capacitance and 1.5-time better cycle stability than NiCo-LDH/ZnO NR/CC. • The as-assembled NiCo-LDH/ZnO NF//AC ASC delivers a high energy density of 51.39 Wh kg−1 (800 W kg−1). ga1 Two kinds of nanostructured ZnO, namely nanorods (ZnO NR) and nanoflakes (ZnO NF) were first prepared on conductive flexible carbon cloth (CC) by a hydrothermal route. Then nickel cobalt layered double hydroxide (NiCo-LDH) nanoflakes were directly hydrothermally deposited on them to construct three-dimensional (3D) self-supporting heterostructure NiCo-LDH/ZnO NR/CC and NiCo-LDH/ZnO NF/CC flexible electrodes. The effects of different nanostructured ZnO on morphology, structure and electrochemical performance of NiCo-LDH/ZnO/CC composite materials were investigated. It is found that NiCo-LDH nanoflakes grown on ZnO NF/CC substrate are more compact and uniform than those on ZnO NR/CC substrate. Moreover, NiCo-LDH/ZnO NF/CC electrode presents better electrochemical properties than NiCo-LDH/ZnO NR/CC electrode with 2.6 times higher specific capacitance (1577.6 F g−1 at 1 A g−1), 2.2 times better rate capability, and 1.5 time greater cycle stability, which may be attributed to the larger contact area and more redox-active sites provided by the NiCo-LDH NFs grown on ZnO NFs. Furthermore, the as-assembled solid-state flexible NiCo-LDH/ZnO NF//AC (active carbon) asymmetric supercapacitor (ASC) delivers a maximal energy density of 51.39 Wh kg−1 (800 W kg−1) with a high operating window of 1.6 V, and exhibits great cyclic stability with 87.3% capacitance retaining after 1000 cycles, which is higher than many reported ASCs. Finally, two packaged ASCs in series successfully lighted a red light-emitting diode (LED, 2.2 V/20 mA), evincing the potentiality of practical application. [ABSTRACT FROM AUTHOR]