Capacity Retention Rate Research Articles

Detecting and repairing micro defects in perfluorinated ion exchange membranes for redox flow batteries

Ion exchange membranes play a vital role in redox flow batteries. However, polymer membranes with a microscopic thickness of approximately 20–50 μm are susceptible to micro defects, which substantially reduces the battery's energy efficiency and cycling stability. Hence, there is a need for an effective strategy to identify and resolve membrane imperfections, which is currently missing in the literature. In this work, a pressure-retention setup and hot-pressing method are proposed and show that defective membranes can be effectively identified and resolved. For instance, a membrane with around 100-μm pinholes exhibits a low coulombic efficiency of 77.5 % at the current density of 100 mA cm−2. However, the coulombic efficiency can be raised to 96.3 % by removing the defects, thus attaining the level of the undamaged pristine membrane (96.4 %). The capacity retention rate of the vanadium redox flow batteries with the repaired membrane is 71.1 % over 100 cycles at the current density of 200 mA cm−2, close to that of the pristine membrane (72.2 %). In addition, the repaired membrane exhibits quite similar physicochemical properties to the pristine membrane from various characterizations. The proposed method represents a convenient, economical, and non-destructive membrane detecting and repairing strategy, demonstrating great potential for redox flow batteries.

APullulan polysaccharide-based flame-retardant polyelectrolyte hydrogel for high-safety flexible zinc ion capacitors

Potential safety hazards such as leakage, flammability and thermal runaway of liquid electrolytes in conventional energy storage devices have seriously hindered their further development. In this work, a flame-retardant polyacrylamide/pullulan/phytic acid (PAM/PUL/PA) hydrogel electrolyte is prepared by using PA as flame-retardant additive, PAM as main polymer chain by one-step radical polymerization method. The PAM/PUL/PA hydrogel shows good flame-retardant properties with limiting oxygen index of up to 58 %, high mechanical performance with stretch up to 1535 % and 92 kPa tensile stress. Zinc ion capacitor (ZIC) assembled with the PAM/PUL/PA hydrogel as electrolyte and separator exhibits high ionic conductivity of 22.54 mS cm−1, high specific capacity of 111.5 mAh g−1 at 0.1 A g−1 and energy density of 97.57 Wh kg−1 at a power density of 49.99 W kg−1, as well as good capacitance retention of 74.6 % even after 10,000 cycles. Furthermore, the ZIC has outstanding flexibility, the capacitance retention rate almost unchanged even after 1000 consecutive bending of deformations. These excellent properties are attributed to the hydrogen bonds easily formed by polar functional groups in hydrogels and the electrostatic interactions with metal ions. This work presented a simple and general pathway to prepare high-safety flexible energy storage devices with multifunctional properties.

Direct Regeneration of Industrial LiFePO4 Black Mass Through A Glycerol‐Enabled Granule Reconstruction Strategy

AbstractWith the increasing sales of electric vehicles, lots of spent lithium‐ion batteries (LIBs) assembled with LiFePO4 (LFP) cathodes will retire in the next few years, posing a significant challenge for their effective and environmentally‐friendly recycling. The main reason why spent LFP cathodes fail to re‐utilize lies in the lattice defects caused by lithium loss and structural defects resulting from stress accumulation. In this work, we propose an in situ granule reconstruction strategy to directly regenerate spent LFP black mass (S−BM) using glycerol in industry settings. The hydroxyl groups abundant in glycerol serves as electron donor that help reduce Fe (III) and repair Fe−Li antisite defects (FeLi). Additionally, the chelating properties of glycerol intervene with structurally disintegrated particles, inhibiting Oswald ripening effect and promoting bonding of grain boundaries to generate lamellar microcrystals with homogeneous grain size, recover their morphology and crystal structure after a facile annealing procedure. Furthermore, the regenerated LFP restores Fe−O bonds which further inhibits structural distortion and improve Li+ migration kinetics. As a result, the regenerated industrial LFP black mass (R−BM) exhibits superior lithium storage performance with a discharge capacity of 123.2 mA h g−1 after 500 cycles at 5.0 C (a capacity retention rate of 93.1 %).

Comparison of three different industrial lignin-based porous carbon electrodes for electrochemical applications

Abstract In order to fully utilize industrial lignin, a comparative study was conducted on the properties of porous carbon electrodes prepared by activating different industrial lignin as precursors. The results revealed that carbon electrodes prepared with sodium lignosulfonate (CM-S) exhibited superior specific surface area (SSA) (1,593.5 m2 g−1) and pore volume (PV) (1.03 cm3 g−1) due to the largest relative molecular mass (Mn = 4,539, Mw = 7,290), which is greater than that prepared with alkali lignin (CM-A) and kraft lignin (CM-K), and displayed a well-developed micro-mesoporous macropore hierarchy which was feasible for the efficiency of electron mobility. The electrochemical properties of materials were evaluated, and CM-S showed a mass-specific capacitance of 201 F g−1 at 0.2 A g−1 current density, along with an impressive capacitance retention rate of 54.7 % at 10 A g−1 current density, which is more potential than CM-A and CM-K (specific capacitances: 100 F g−1 and 75 F g−1 respectively). Additionally, maximum energy and power density of CM-S were measured to be 6.98 W h kg−1 and 2306 W kg−1 with excellent retention rate of 95.5 % after 10,000 charge–discharge cycles at a current density of 5 A g−1. Comparatively, sodium lignosulfonate, compared with alkali lignin and kraft lignin, emerges as a more ideal precursor material for porous carbon electrode.

High-Performance Flexible and Symmetric Supercapacitors Based on Micro-Flower-Like MnSe@Ti3C2Tx Heterostructure.

Flexible supercapacitors, renowned for their exceptional power density and cycling stability, are a focus in the field of energy storage. Ti3C2Tx MXene is a promising electrode material for supercapacitors owing to its excellent metallic conductivity. However, its stacking layered structure limits device performance on specific capacitance, operating voltage, and energy density. Herein, a MnSe@Ti3C2Tx heterostructure is developed to enhance the electrochemical performance of Ti3C2Tx-based electrode materials. With the solvothermal synthesis method, MnSe nanosheets are in situ grown on Ti3C2Tx surface to form micro-flower-like MnSe@Ti3C2Tx heterostructures by adjusting the ratio of ethanolamine solvent and the amount of Ti3C2Tx. The specific capacitance of the optimized heterostructure (E3/MnSe@Ti3C2Tx-45) is as high as 721.4Fg-1 at 1Ag-1, approximately ten times higher than that of pure Ti3C2Tx. The MnSe@Ti3C2Tx flexible symmetric supercapacitor (MT-FSC) based on E3/MnSe@Ti3C2Tx-45 exhibits a wide working voltage window of 1.2V and a large energy density of 28.68Whkg-1 at 308.23Wkg-1. The capacitance retention rate keeps 90.77% after 4000 charge-discharge cycles. Furthermore, MT-FSC can power LEDs even under large-angle (90°) bending. This heterostructure electrode material not only improves the electrochemical performance of Ti3C2Tx-based flexible supercapacitors but also offers a robust energy supply for flexible wearable electronic devices.

Biomass nanoarchitectonics for porous carbon materials with exceptionally high mesoporous ratio through urea-regulated co-activation strategy and their application in supercapacitors

The synthesis of porous carbon with a high mesoporous ratio is a significant challenge, particularly when utilizing heteroatom-enriched biomass precursors as feedstock. In this work, bio-based porous carbon with a 95 % mesoporous ratio was synthesized by using chitosan and lignosulfonates as biomass precursors, combined with a urea-regulated co-activation strategy. The high mesoporous formation of porous carbon can primarily be attributed to four factors: (1) the formation of a cross-linked 3D network, (2) the generation of nitrogen-containing gas resulting from urea decomposition, (3) the depolymerization of LS and (4) KOH-activated carbonization. Besides, the specific surface area and mesoporous ratio can be adjusted by varying the ratio of KOH to urea, ranging from 1793 m2 g−1 to 2876 m2 g−1 and from 22 % to 95 %, respectively. The application of density functional theory calculations reveals that the synergistic effect of N/S co-doping facilitates rapid ion adsorption reactions on carbon surfaces, further improving the electrochemical performance. As carbon electrode materials for supercapacitors in a three-electrode device, the capacitance reaches up to 263 F g−1 at 1 A g−1. The symmetric supercapacitors fabricated using CS@LS/C-800–1:0.5 achieved an impressive energy density of 17.8 Wh·kg−1 at a power density of 300.6 W kg−1, along with a remarkable capacitance retention rate of 96.6 %. This strategy provides a novel insight into enhancing the mesoporous ratio of bio-based porous carbon materials, thereby significantly broadening the application scope of biomass materials.

Oxygen Vacancy Engineering of TiNb2O7 Modified PE Separator Toward Dendrite-Free Lithium Metal Battery.

Lithium metal battery with high specific energy and high safety is crucial for the next-generation energy storage technologies. However, the poor thermal stability, lower mechanical performance, and poor electrochemical performance of the commercially available polyethylene (PE) separator hinders the development of high-specific lithium metal batteries. Herein, a functional PE separator is prepared by innovative coating the TiNb2O7 microspheres with oxygen vacancies on the surface of PE (denoted as TNO-x-PE). The porosity, contact angle, electrolyte uptake rate, thermal shrinkage rate, mechanical properties, conductivity as well as lithium ions transference number of the TNO-x modified PE separator are all improved. The favorable TNO-x is beneficial for facilitating fast Li+ migration and impeding anions transfer, guiding the uniform distribution of lithium-ion flux. Consequently, the lithium symmetric cells with TNO-x-PE separator can be stably cycled more than 1600 h at 1 mA cm-2, and the initial capacity of the LFP/Li cells with TNO-x-PE separator is as high as 139.8 mAh g-1, and after 500 cycles, the capacity retention rate is still 99.5%. This work may provide a new idea to construct a multi-functional separator with high safety and superior electrochemical performance and promote the development of LMBs.

N, P Co-Doped Hard Carbon Anodes for High-Performance Lithium-Ion Batteries with Enhanced Capacity Retention and Cycle Stability.

Compared to the traditional graphite anode, heteroatom-doped polymer carbon materials have high capacity retention due to their high porosity and porous structure. Therefore, they have great potential for application in lithium-ion battery (LIB) anodes. In this work, an N, P co-doped precursor polymer material (MBPp), synthesized via a one-pot method using bisphenol-A (C-source), melamine (N-source), and 9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (P-source). The resulting N, P-co-doped hard carbon materials (MBPs) were prepared at various pyrolysis temperatures, yielding microporous, mesoporous, and macroporous structures. MBP materials demonstrated excellent electrochemical performance as LIB anodes. Notably, MBP-900 achieved a reversible capacity of 262 mAh g-1 at 1000 mA g-1 (in 0.005-2.0 V voltage range) with a capacity retention rate of 97.1 % after 1000 cycles. These findings highlight the significance of MBP materials, which possess numerous defects, large layer gaps, and excellent cycle stability, in advancing the development of polymer anode materials for LIBs.

Activated carbon-loaded nano-transition metal Ni catalysts for enhancing hydrogen storage behavior of Mg

In this study, a three-dimensional porous activated carbon material (Ni/AC) catalyst loaded with nano-Ni particles was prepared via the impregnation method to enhance the hydrogen storage performance of Mg. The experiments showed that adding a small amount of Ni/AC makes the Mg–Ni/AC composite begin to desorb hydrogen at 519 K, which is 99 K lower than pure Mg. The composite begins to absorb hydrogen at 335 K, and at 373 K, it absorbs 5.7 wt% H₂ within 180 min. After 20 cycles, the capacity retention rate is 99.2%, demonstrating excellent hydrogen absorption/desorption kinetics and cyclic stability. Characterization and density functional theory (DFT) calculations revealed that the improvement in the hydrogen storage performance of the Mg–Ni/AC composite is due to the synergistic effect between Ni and activated carbon. The activated carbon effectively disperses Ni and enhances the diffusion of hydrogen atoms within the composite, while the addition of Ni weakens the Mg–H bond strength.

Mn-Rich Induced Alteration on Band Gap and Cycling Stability Properties of LiMnxFe1-xPO4 Cathode Materials.

Olivine-type LiMnxFe1-xPO4 (LMFP) has inherited the excellent heat-stable structure of LiFePO4 (LFP) and the high-voltage property of LiMnPO4 (LMP), which shows great promise as a high-safety, high-energy-density cathode material. In order to combine the high energy density and excellent electrochemical performance, it is essential to consider the Mn/Fe ratio. This paper presents a theoretical investigation of the lattice structure parameters, embedded lithium voltage, local electron density, migration barrier, and lithium ion delithiation and lithiation mechanism of different LiMnxFe1-xPO4 (0.5 ≤ x ≤ 0.8) compounds. In situ-coated LiMnxFe1-xPO4 (0.5 ≤ x ≤ 0.8) composite cathode materials with a size of 100-200 nm were prepared by a hydrothermal method to verify the theoretical study. LiMn0.6Fe0.4PO4/C exhibited a specific capacity of 140.2 and 97.58 mA h·g-1 at 1 and 5C, respectively, and a remarkable capacity retention rate of 88.5% after 200 cycles at 1C. When LiMn0.6Fe0.4PO4/C was assembled into a flexible pouch battery and subjected to long cycle tests at different rates and squeeze and extrusion tests, it demonstrated a capacity retention rate of 99.35% for 100 cycles at 0.2C and 93.2% for 200 cycles at 0.5C. Moreover, the structural evolution of LiMn0.6Fe0.4PO4/C were analyzed in situ XRD, indicating a high stability and the resulted as obtine electrochemical performance, paving the way for optimization of high-energy-density LMFP cathode materials.

Study on the surface modification of regenerated and repaired LiNi0.5Co0.2Mn0.3O2 single crystal

Due to the relatively small particle size of single crystals, the high specific surface area increases the side reactions between the electrode and the electrolyte. Without proper surface modification, single-crystal particles tend to interact directly with the electrolyte, leading to side reactions that impair the electrochemical performance of the material. To address this issue, constructing a coating layer on the material's surface is one effective solution. In this study, a wet-coating technique was employed to co-coat single-crystal LiNi0.5Co0.2Mn0.3O2 cathode material with vanadium (V) and samarium (Sm). SEM and TEM tests revealed the presence of a V-Sm coating layer with a thickness of approximately 1–3 nm on the surface of the coated samples. The coated material demonstrated a capacity retention rate of 86.5 % after 450 cycles at a 1 C rate (1 C = 160 mA h g−1), which represents an improvement of about 6.7 % compared to the original material. EIS results indicated that the V-Sm coating stabilized the surface SEI film of the material and inhibited the growth of charge transfer resistance (Rct). XPS analysis of the electrodes after cycling showed that the V-Sm coating effectively protected the material by isolating it from direct contact with the electrolyte, suppressing the decomposition of the electrolyte during cycling, and reducing adverse side reactions between the material and the electrolyte, thereby enhancing the overall electrochemical performance of the material.

Multistage Template-Oriented Design and Tailoring of the Hierarchical Porous Biocarbon Materials for High-Performance Supercapacitors.

Interfacial regulation is crucial for the enhancement of the specific surface area and supercapacitive performance in porous carbon materials. However, traditional porous carbon obtained through potassium hydroxide activation is confronted with a complicated preparation process. Herein, hierarchical porous biocarbons (HPBC) were facilely prepared by using the multiscale template method and wheat flour as a precursor without any activation. A spherical SiO2 template and wheat flour can be closely combined by gelatinization so as to effectively confine and spatially orient carbon materials. Benefiting from the hierarchical porous structure achieved through the use of templates at different sizes, HPBC-3 has the best electrochemical performance of 223.6 F·g-1 at 1 A·g-1. Moreover, the assembled HPBC-3//HPBC-3 symmetrical supercapacitor demonstrates a remarkable energy density of 15.6 W h·kg-1 and exhibits exceptional cycling performance with a capacitance retention rate of 106% after 5000 cycles. The results fully demonstrate the promising application of the obtained hierarchical porous carbon in supercapacitors.

Design of cellulose/polyethylene oxide/EMITFSI-based composite electrolyte with synergistic transport mechanism for high-performance solid-state lithium batteries

Despite its theoretically high energy density, polymer solid-state lithium batteries (PSSLBs) exhibit lower actual energy density. This discrepancy arises from the low ionic conductivity of the polymer solid-state electrolyte (PSSE) due to the coupling of lithium ion (Li+) transport to the relaxation of polymer chain segments. The objective of this study is to optimize the Li+ transport in PSSE. This is achieved by incorporating 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMITFSI) to plasticize both cellulose and polyethylene oxide (PEO). By leveraging the synergistic effects of cellulose and PEO, an ion-conducting network is established. This network allows Li+ to form multiple Li-O coordination simultaneously with the hydroxyl group (OH) of cellulose and the ether group (EO) of PEO, thereby enabling Li+ to transport between the two polymers in a decoupled manner. The PSSE demonstrated an ionic conductivity of 4 × 10-4 mS/cm (at room temperature) and a Li+ transference number of 0.43, significantly exceeding traditional PEO-based values of 10-5 mS/cm and 0.1–0.2. Additionally, the high voltage stability of EMITFSI extends the electrochemical stability window of PSSE, achieving a stability window of 5 V. The assembled LiFePO4/Li cell achieved a specific capacity of 138 mA h/g at 50℃ (0.5C) with a capacity retention rate of 80 % after 280 cycles. This represents an innovative method for preparing high-energy–density solid-state lithium batteries.

Electrochemical performance of YMg2Ni9 hydrogen storage electrode alloy in-situ coated with Ni3S2

The YMg2Ni9 hydrogen storage alloy in-situ coated with Ni3S2 was successfully prepared by hydrothermal sulfurization treatment and investigated as the anode material in nickel-metal hydride (Ni-MH) batteries for the first time. Owing to the high electronic conductivity and electrocatalytic activity of Ni3S2 nanoflake coating, the electrochemical performance of the YMg2Ni9 alloy electrode is significantly enhanced. The alloy electrode treated in 0.3 M Na2S solution exhibits the highest discharge capacity of 230.8 mAh/g and superior cycling stability, maintaining a capacity retention rate of 85.1 % after 100 cycles. The increase in the discharge capacity of the electrode is credited to the Ni3S2 coating on the surface of the alloy, which possesses a nanoflake structure, facilitating the surface electrochemical reaction and providing more channels for hydrogen diffusion. In addition, Ni3S2 nanoflakes wrapped around the surface of the alloy can stabilize the reaction interface between the alloy and the electrolyte and slow down the alkali erosion, thus improving the cycle life of the electrode. The present study offers beneficial information for investigating a potential anode material for Ni-MH batteries.

A highly-proton conductive poly(vinyl alcohol)/silica nanocomposite membrane for PANI@GNP symmetric supercapacitor separator

Polyaniline (PANI) has potential as an anode and cathode for proton based batteries (PBs) owing to its high energy density (295 mAh g−1) and excellent reversible redox activity. Achieving proton electrolytes with fast single-proton conduction behavior, separator-required mechanical properties and good proton transport channel is essential but extremely challenging for the practical success of PBs. Herein, this proton separator is constructed with nano-silica grid points in polyvinyl alcohol (PVA) chains cross-linked by sulfuric acid. Results show that PVA/inorganic composite proton membrane (PIC-PM) can immobilize the sulfate anions and help dissociate H+, which leads to a high ionic conductivity (8.6 × 10−2 S cm−1). Moreover, PIC-PM shows enough toughness and mechanical strength to puncture resistance. When the PIC-PM was applied to assemble a PANI@GNP symmetric supercapacitor, it delivers a high capacity of 943.1 F/g at 0.5 A/g; a rate capability of 74.9 % with the current density increasing from 0.5 to 5 A/g; and a capacity retention rate of 84.3 % after 1000 cycles in a current density of 3.5 A/g.

Synthesis of Fe₃O₄/FeS₂ composites via MOF-templated sulfurization for high-performance hybrid supercapacitors

The development of advanced anode materials for supercapacitors is crucial for driving innovation in the field of new energy technologies. Although iron-based materials exhibit significant potential, their electrical conductivity and cyclic stability remain challenges. In this study, Fe3O4/FeS2 composites were successfully synthesized using a sacrificial MOF template and a solid-state sulfurization process. The composite preserved the original morphology of Fe-MOF, while numerous nanoscale particles were generated through heterogeneous sulfurization. Notably, the SMFO-2 composite exhibited a specific capacity of 208.5 mAh g−1 at a current density of 1 A g⁻¹. When integrated into a hybrid supercapacitor (HSC) with SMFO-2 serving as the anode and super-electric activated carbon (AC) as the cathode, the device exhibited excellent electrochemical performance. Specifically, it achieved a capacity retention rate of 78.6 % after 10,000 charge-discharge cycles at 2 A g⁻¹. Furthermore, the HSC achieved an optimal energy density of 28.8 Wh kg⁻¹ at a power density of 375 W kg⁻¹, successfully powering a small bulb, highlighting its strong potential of the Fe3O4/FeS2 composite for real-world practical applications.

Hierarchical Porous Structured Si/C Anode Material for Lithium-Ion Batteries by Dual Encapsulating Layers for Enhanced Lithium-Ion and Electron Transports Rates.

Silicon (Si) is a promising anode material for next-generation lithium-ion batteries (LIBs) due to its high specific capacity and abundance. However, challenges such as significant volume expansion during cycling and poor electrical conductivity hinder its large-scale application. In this study, the multifunction of sodium polyacrylate (PAAS) utilized to develop a hierarchical porous silicon-carbon anode (Si/SiOx@C) through a simple and efficient method. The hierarchical porous structure successively consists of nano-silicon cores, SiOx encapsulating layers, surrounding space, and phenolic resin-derived carbon shells with carbon chains connecting the SiOx layers and carbon shells in the space. The SiOx nanolayers promote Li⁺ transport, while excess PAAS, removed by washing, generates space for volume expansion, improving cycling performance. Residual carbon chains of PAAS and carbon shells form a conducting carbon network, enhancing electron transport and rate performance. As an anode for LIBs, the composite delivers a high reversible capacity of 685.3 mAh g⁻¹ after 1000 cycles at 1 C with a capacity retention rate of 54.7%. Full cells with the Si/SiOx@C anode and LiNi0.8Co0.1Mn0.1O2 cathode exhibit an excellent capacity retention rate of 96.8% after 200 cycles at 1 C. This work provides a novel approach for the rational design and engineering of advanced LIBs.

A novel NASICON-typed Na3V1.96Cr0.03Mn0.01(PO4)2F3 cathode for high-performance Na-ion batteries

Na3V2(PO4)2F3 (NVPF) with a NASICON structure has attracted widespread attention as a cathode material for sodium-ion batteries due to its stable 3d open framework, high operating voltage, and high theoretical energy density. However, this material faces limitations in practical applications due to its inherently low intrinsic electronic conductivity and the high cost of vanadium. In this study, we substituted vanadium with low-cost elements and synthesized a series of NVPF cathode materials with varying levels of Cr/Mn doping using a simple sol-gel method. The optimal NVPF-Cr/Mn1 cathode exhibits discharge specific capacities of 119.7 mAh g−1 at 1C and 109.8 mAh g−1 at 10C. Additionally, the discharge specific capacity of NVPF-Cr/Mn1 is 106.9 mAh g−1, with a capacity retention rate of 80 % after 400 cycles. These performance improvements are attributed to the synergistic effect of co-doping with chromium (Cr) and manganese (Mn): they expand the channels for sodium ion transport within the lattice, reduce the material's impedance and polarization, enhance the kinetics of sodium ion diffusion reactions, effectively prevent lattice distortion, and significantly improve long-term cycling performance. By strategically designing NASICON-type cathodes and employing multi-metal ion substitutions to regulate composition, we not only enhance the battery's cycle life but also contribute to reducing the cost of electrode materials. This approach opens up new possibilities for practical applications in the field of energy storage.

Hollow transition metal chalcogenides derived from vanadium-based metal organic framework for hybrid supercapacitors with excellent energy-density and stability

In-situ synthesized hollow transition metal chalcogenides have gained significant attention on account of their excellent electrochemical properties. Here, Ni-doped V-MOF (V(Ni)-MOF) nanorod arrays as precursor are first grown on nickel foam (NF). Subsequently, the nanorod arrays are converted into V(NiCo)-OH hollow nanotube arrays with cross-linked nanosheets by Co2+ etching. Finally, V(NiCo)-OH/NF is converted into V(NiCo)-X/NF (X = O, S and Se) by annealing or ion exchange. Due to the unique morphology of hollow nanotube arrays with cross-linked nanosheets and synergistic effect of multi-metal components, the V(NiCo)-Se/NF achieves an outstanding specific capacity (1806.7 C g−1 at 1 A g−1), which is higher than that of V(NiCo)-O/NF (1208.3 C g−1) and V(NiCo)-S/NF (1558.4 C g−1). In addition, the capacity retention rate is 91.7 % (at 10 A g−1 after 10, 000 cycles). Utilizing V(NiCo)-Se/NF (positive) and activated carbon/NF (negative), the hybrid supercapacitor (HSC) achieves an impressive high energy density of 114.8 Wh kg−1 (at 679.5 W kg−1). Moreover, two HSCs in series can power the LED and stopwatch, and keep working for more than 60 min, displaying good practical application capabilities.

Surface-functionalized metal–organic framework with high specific surface area optimizing composite solid electrolyte for high-performance solid-state lithium metal batteries

Solid-state lithium metal batteries (SSLMBs) are the potential candidates of next-generation batteries for safety and remarkable energy density against lithium ion batteries with liquid electrolyte widely applied these days. Even if composite solid electrolytes (CSEs), as the core of SSLMBs, have drawn much attention and devotion for the promising application potential, they are subject to low ionic conductivity, insufficient mechanical strength, and severe interfacial stability deficiency. Herein, we prepare a composite solid electrolyte containing poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) as a polymer matrix and polydopamine-modified ZIF-8 (ZIF-8@PDA) as a filler to tackle the challenges, and named as PHZP. The existing PDA on ZIF-8 particle’s surface is helpful to the uniform dispersal of filler in the whole composite solid electrolyte. Consequently, the PHZP membrane exhibits the good properties in ionic conductivity of 0.31 mS cm−1 at 25 ℃, enhanced lithium-ion transference number of 0.41, and extended electrochemical window of 4.8 V. More importantly, the PHZP membrane demonstrates the plating/stripping performance of Li in Li||PHZP||Li symmetric cell for over 2700 h with a small overpotential. LiNi0.5Co0.2Mn0.3O2||PHZP||Li (NCM523||PHZP||Li) cell possesses the first discharge capacity of 150 mAh/g and a capacity retention rate up to 95.8 % after 400 cycles at 0.5 C, and a capacity retention rate of 89 % after 800 cycles at 1 C. In the meantime, LiFePO4||PHZP||Li (LFP||PHZP||Li) cell also provides a capacity retention rate of 94.2 % after 100 cycles at 0.1 C. This work provides a simple and promising strategy to enhance the electrochemical performance of CSEs in SSLMBs, which would also be applied to the other energy storage/conversion fields.