Al Foil Research Articles

Optimal design and simulation investigation for high-density hydrogen storage tanks filled with rare earth-based (RE-Ca)(Ni-Co)5 optimized alloy

The slow kinetic rate due to strong thermal effect limits the practical application of metal hydride tanks in high-density hydrogen storage. In this work, we concentrate on a comprehensive experimental and numerical investigation of metal hydride beds with rare earth-based (RE-Ca)(Ni-Co)5 optimized alloy to explore faster reaction rates. Two different cylindrical tanks were manufactured to reflect de-/hydrogenation characteristics. A study on the temperature evolution in the loose powder bed was performed first, followed by five other different bed configurations: alternated powder layers with Al fiber layers, powder mixed with Al fibers, compacted discs (mixture of powder, resin and graphite), alternated compacts with Al fins and alternated Al foil-wrapped compacts with Al fins. Among them, the compacts provide good heat transfer capacity, with additional Al foils and fins for optimum thermal diffusion, reducing the reaction time by almost 50 %. Stress concentrations caused by powder accumulation can also be avoided thanks to the stable structure. Finally, the numerical model was adapted to simulate the de-/hydrogenation processes of the optimized bed and the experimental data matched well with the computational results, confirming the reliability of the model. It lays the foundation for the design and operation optimization of high-density hydrogen storage in the future.

Measurements of the neutron and gamma dose via TL/OSL in LiF:Mg,Ti and activation methods analysis of aluminum foils

The measurement of beta/gamma and neutron dose components in mixed radiation fields is described involving combined OSL and TL measurements. The accuracy of the technique is investigated by irradiation of LiF:Mg,Ti samples with 14.1 MeV neutrons and a comparison of the OSL/TL results with the neutron fluence determined by Al activation. The precision of the measurements is 6.1 to 6.7 % (1 SD) for the OSL/TL technique compared to 7.3 % for the Al foils. The advantage of the technique is the simultaneous determination of the two dose components on the same samples of 7LiF:Mg,Ti in a single dedicated TL/OSL reader.

Efficient recovery of Al foil and regeneration of cathode materials from spent lithium-ion batteries with methanol-citric acid

Efficient separation of cathode materials from current collectors is an important step to simplify the recycling process of spent lithium-ion batteries (LIBs). However, traditional methods have the shortcomings of incomplete separation, release of toxic substances and high cost. Here, the methanol-citric acid solvent (MeOH-CA), prepared from green and low-cost reagents methanol (MeOH) and citric acid (CA), can separate above 99.5 wt% of spent nickel-manganese-cobalt (NCM) cathode materials in 15 min with negligible metal loss at an ultralow temperature of 45 °C. The separated NCM has high purity and no structure changes, and the recovered Al foil is intact and non-corrosive. The mechanism analysis indicates that the reaction between MeOH-CA and Al foil and the inactivation of PVDF by the abundant hydrogen bonds in the MeOH-CA solvent cause the separation. Meanwhile, the formation of AlF3 passivation layer and the ester film on the surface of Al foil prevent further corrosion of Al foil. Through hydrothermal treatment combined with a short thermal annealing, the regenerated NCM delivers a reversible capacity of 151 mAh g−1 at 1C and 117 mAh g−1 after 100 cycles. The facile separation strategy provides a sustainable and economic solution for the recovery of spent LIBs.

Examining Performance Loss Mechanisms in Lithium-Ion Batteries with the High-Voltage Mn-Rich Spinel Positive Electrodes

The high-voltage spinel, with the nominal composition of LiNi0.5-xMn1.5+xO4 (LNMO), could be a sustainable alternative to the layered-oxide positive electrodes used in lithium-ion batteries. However, commercial acceptance has been limited as LNMO cells display rapid performance loss during cycling. To examine reasons for this loss we prepared cells with LNMO-based positive and either graphite or lithium titanate (LTO) based negative electrodes. Our initial cells displayed high impedance and rapid impedance rise during cycling. Adding single walled carbon nanotubes in the positive lowered initial cell impedance but impedance increased during cycling because of coating delamination from the Al foil. Using a primed Al current collector solved the delamination problem: cells with this current collector showed only a small impedance rise. Regarding capacity, cells with the LTO negative showed higher initial capacities and smaller fade. Our data indicate that cell capacity retention is determined by reduction reactions at the negative electrode that lower capacity and oxidation reactions at the positive electrode that increase capacity: both types of reactions deplete the cell electrolyte during extended cycling. All things considered, species generated at high voltages, either in the electrolyte or at the LNMO electrode, drive cell capacity fade.

Impact of LiAl Nucleation Kinetics on the Microstructural Evolution of Aluminum Foil Anodes in Lithium-ion Batteries

Aluminum foil anodes have the potential to significantly improve the energy density, safety, cost, and sustainability of Li-ion batteries (LIB). However, their adoption is limited by their notoriously poor cycle life, and the dramatic structural transformations of Al foil anodes during formation and cycling remain poorly understood. In this work, we investigate how the nucleation and growth kinetics of LiAl control the microstructural evolution and cycle life of Al foil anodes. First, we demonstrate the unique sensitivity of Al foil anodes to the cell design and cycling conditions and emphasize the necessity of electrochemical testing in practical full cells. Operando electrochemical impedance spectroscopy (EIS) is combined with scanning electron microscope (SEM) imaging of the lithiated foils to elucidate the relationships between LiAl nucleation kinetics and the resulting LiAl microstructure. Particularly, we investigate the effects of annealing the pristine foils, and controlling the overpotential and temperature during formation, showing that as-rolled foils lithiated at high overpotentials give a columnar LiAl microstructure. Finally, we show that uncontrolled LiAl nucleation during cycling quickly destroys this favorable columnar structure, and a significant improvement in cycle life of LiFePO4 || Al full cells is achieved by limiting the depth-of-discharge to <75%.

Multi-layer solid-state ultrasonic additive manufacturing of aluminum/copper: local properties and texture

Ultrasonic additive manufacturing (UAM) is an advanced joining technique that utilizes ultrasonic vibrations to bond layers of metal foil together. UAM offers several benefits over traditional manufacturing methods, including enhanced design flexibility and reduced material waste, and its potential applications in various industries such as aerospace, automotive, and biomedical engineering are being actively explored. The study employs a nanoindentation apparatus to investigate the effect of the UAM process on the local mechanical properties of the bonded interface, along with changes in microstructure, which were investigated using scanning electron microscopy and electron back-scattered diffraction. The results revealed a significant correlation between material hardness and local plasticity. EBSD has revealed that the grain size distribution of Al far from the interface contains 57% of the grains less than 3 µm in size, while at the interface this number rises to approximately 78%, indicating that the average grain size decreases as it approaches the interface. This result is consistent with nanoindentation results that demonstrated a gradual change in the hardness of Al foil far from the interface to close to the interface (the maximum penetration depth near the interface was 500 nm less than far from the interface). Both EBSD and nanoindentation disclose the effect of work hardening close to the interface, which is related to dislocation accumulation with a density of 8.6×10-10cm-2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$8.6\ imes {10}^{-10} {{\ ext{cm}}}^{-2}$$\\end{document} beneath the interface. The consistency of hardness and Young’s modulus with the pole figures and microscopic images demonstrated that plasticity flow and fine grain distribution would only occur in the vicinity of the interface in the softer metal region. Although the harder metal did not exhibit plasticity or recrystallization, the hardness, and Young’s modulus map indicated the formation of a layer of small grains close to the interface on the aluminum side owing to strain hardening and dynamic recrystallization.

Enabling High-Performance Battery Electrodes by Surface-Structuring of Current Collectors and Crack Formation in Electrodes: A Proof-of-Concept

Today's society and economy demand high-performance energy storage systems with large battery capacities and super-fast charging. However, a common problematic consequence is the delamination of the mass loading (including, active materials, binder and conductive carbon) from the current collector at high C-rates and also after certain cycle tests. In this work, surface structuring of aluminum (Al) foils (as a current collector) is developed to overcome the aforementioned delamination process for sulfur (S)/carbon composite cathodes of Li-S batteries (LSBs). The structuring process allows a mechanical interlocking of the loaded mass with the structured current collector, thus increasing its electrode adhesion and its general stability. Through directed crack formation within the mass loading, this also allows an enhanced electrolyte wetting in deeper layers, which in turn improves ion transport at increased areal loadings. Moreover, the interfacial resistance of this composite is reduced leading to an improved battery performance. In addition, surface structuring improves the wettability of water-based pastes, eliminating the need for additional primer coatings and simplifying the electrode fabrication process. Compared to the cells made with untreated current collectors, the cells made with structured current collectors significantly improved rate capability and cycling stability with a capacity of over 1000mAhg−1. At the same time, the concept of mechanical interlocking offers the potential of transfer to other battery and supercapacitor electrodes.

A facile route for the efficient leaching, recovery, and regeneration of lithium and iron from waste lithium iron phosphate cathode materials

The recycling of lithium iron phosphate power batteries that have exploded in retirement is urgent, but the focus and difficulty of the recycling is the effective recovery of lithium and iron elements in the cathode active material. In this study, the cathode sheets and other components of the lithium-ion batteries were obtained by pretreatment, and the cathode active material and the Al foil of the collector were recovered by stirring with dilute alkali solution (optimized conditions of alkali solution concentration 0.075 mol L-1, liquid–solid ratio 20 mL g−1, and stirring time 40 min). The H2SO4-H2O2 system was used to leach used lithium iron phosphate cathode powder, the leaching process conditions were optimized and the leaching mechanism was revealed. The leaching rates of Li and Fe elements reached 98.79 % and 94.97 %, respectively, at a H2SO4 concentration of 2.5 mol L-1, a H2O2 dosage of 6 mL, a liquid–solid ratio of 25 mL g−1, a leaching temperature of 60 °C and a leaching time of 60 min. The pH value was precisely adjusted in the chemical precipitation method to recover lithium and iron elements from cathode active material. The recovered products FePO4 and Li2CO3 were used as the precursors for the regeneration of LiFePO4 cathode material. The electrochemical performance of LiFePO4/C materials regenerated at 700 °C from the raw material with a lithium to iron molar ratio of 1.03:1 was relatively good, with a first discharge specific capacity of 160.1 mAh g-1 at 0.1 C, and a charge/discharge efficiency of 96.70 % for the first cycle. The good electrochemical performance was still maintained at a higher rate, with a capacity retention of 99.7 % after 100 cycles at 1 C.

Enhancing Durability and Capacity Retention of Ultrafine-Grained Aluminum Foil Anodes in Lithium-Ion Batteries.

In this study, we present our successful fabrication of commercial-grade pure aluminum anode foil (99.5%, 2NAl) with an ultrafine-grained (UFG) microstructure and high hardness, achieved through cold rolling. Under identical rolling conditions, a coarse-grained microstructure with a low hardness was attained from the high-purity Al foil (99.99%, 4NAl). The UFG 2NAl foil exhibited enhanced lithium-ion diffusivity and reduced nucleation and activation overpotentials for forming the β-LiAl phase compared to the 4NAl foil. The high-density grain boundaries in the UFG 2NAl foil facilitated the rapid formation of a uniform β-LiAl phase layer on its surface, thereby mitigating mechanical damage within the β-LiAl phase layer caused by volume changes during the lithiation and delithiation processes. The high hardness of the UFG 2NAl sample effectively prevented macroscopic plastic deformation during cycling, thus preserving the integrity of the β-LiAl phase layer and inhibiting the formation of cracks within the unreacted Al matrix. The collective advantages of reduced overpotential, enhanced Li-ion diffusivity, and high resistance to mechanical damage and plastic deformation in UFG 2NAl contribute to its superior durability and capacity retention compared to the high-purity Al in electrochemical cycling.

Highly Fluorinated Interphase Enables the Exceptional Stability of Monolithic Al Foil Anode for Li‐Ion Batteries

AbstractDirectly using aluminum (Al) foil as anode material offers a streamlined manufacturing process by eliminating the need for conductive additives, binders, and casting procedures. Nonetheless, monolithic Al foil anodes often suffer from mechanical failure and poor cyclability, posing challenges for practical adoption. In this study, a high‐concentration ether‐based electrolyte is employed to boost the durability of the Al foil anode. In contrast to traditional low‐concentration electrolytes, the use of 5 m lithium bis(fluorosulfonyl)imide in 1,2‐dimethoxyethane promotes the priority decomposition of anions, leading to the creation of a fluoride‐rich solid electrolyte interphase (SEI) layer with exceptional structural modulus and high ion conductivity. These outcomes, coupled with Al's superior compatibility in the chosen electrolyte, enable a record‐breaking cycle life of up to 400 cycles for Li//Al half‐cells, when operated at a high areal capacity of 1 mAh cm−2. In full‐cell configurations, an outstanding capacity retention is also observed, with 96.9% after 150 cycles even under practical conditions involving a 40 µm thin Al foil and a 7.4 mg cm−2 LiFePO4 cathode. These results not only mark the pioneering use of high‐concentration ether‐based electrolyte systems in Al foil anodes but also showcase the high potential for developing low‐cost and high‐energy Al foil‐based LIBs.

Solution-Processable Route for Large-Area Uniform 2D Semiconductor Nanofilms.

The semiconductor thin film engineering technique plays a key role in the development of advanced electronics. Printing uniform nanofilms on freeform surfaces with high efficiency and low cost is significant for actual industrialization in electronics. Herein, a high-throughput colloidal printing (HTCP) strategy is reported for fabricating large-area and uniform semiconductor nanofilms on freeform surfaces. High-throughput and uniform printing rely on the balance of atomization and evaporation, as well as the introduced thermal Marangoni flows of colloidal dispersion, that suppresses outward capillary flows. Colloidal printing with in situ heating enables the fast fabrication of large-area semiconductor nanofilms on freeform surfaces, such as SiO2/Si, Al2O3, quartz glass, poly(ethylene terephthalate) (PET), Al foil, plastic tube, and Ni foam, expanding their technological applications where substrates are essential. The printed SnS2 nanofilms are integrated into thin-film semiconductor gas sensors with one of the fastest responses (8 s) while maintaining the highest sensitivity (Rg/Ra = 21) (toward 10ppm NO2), as well as an ultralow limit of detection (LOD) of 46 ppt. The ability to print uniform semiconductor nanofilms on freeform surfaces with high-throughput promises the development of next-generation electronics with low cost and high efficiency.

Electromagnetic shielding Janus membrane for direct current‐type pressure and sliding sensing

AbstractFacing increasing electromagnetic radiation pollution, soft sensors with electromagnetic interference (EMI) shielding is highly desirable. Here, flexible electromagnetic shielding [polyacrylonitrile/Fe3O4/polyaniline]//[multiwalled carbon nanotube/polyvinyl pyrrolidone] (denoted [PAN/Fe3O4/PANI]//[MWCNT/PVP]) Janus membrane is reported for pressure and sliding sensing. The [PAN/Fe3O4/PANI] layer of Janus membrane as the force and sliding sensing unit can generate direct current‐type (DC‐type) voltage signals by conducting polymer/metal Schottky junction, whereas [MWCNT/PVP] layer serves as main electromagnetic shielding unit. Under the vertical force and horizontal sliding of aluminum (Al) foil, it can output DC‐type voltage signals based on the Schottky contact. The performance of [PAN/Fe3O4/PANI]//[MWCNT/PVP] Janus membrane for pressure and sliding sensing is appropriately explored and assessed. Moreover, the Janus membrane exhibits excellent shielding effects with average EMI shielding effectiveness (SE) of 37.54 dB in 8.2–12.4 GHz (X‐Band) frequency ranges. Thus, based on the asymmetrical double‐layer structure, soft DC‐type sensor with EMI shielding is achieved, showing utilization potential in wearable electronics and intelligent robots.

Achieving high thermal conductivity in CNTs@GF/Al laminates via a rapid and simple strategy

The present work developed a rapid and simple fabrication strategy to achieve the high thermal conductivity (TC) in graphite film (GF)/Al laminates. CNTs@GF prepared by spray flash technique was selected as reinforcement in Al matrix, then consolidated with Al foils by vaccum hot-pressing sintering. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction and Raman spectroscopy were used to evaluate the GF and interface structure. The results revealed that no interfacial reaction products were generated in the highly dense composites. Specially, due to the heat conduction channel and interlocking effects of CNTs on GF/Al interface, the laminated composite containing 56.5 vol% CNTs@GF showed an in-plane TC of 897 W (m k)−1 without bending strength sacrifice. The present work paves an efficient new way to design and fabricate GF/Al laminates for potential thermal management application.

Protective Al2O3 Thin Film Coating by ALD to Enhance the Anodic Stability of Metallic Current Collectors in Ethereal Mg Electrolyte Solutions

Rechargeable magnesium batteries (RMBs) have the potential to contribute towards alternative energy storage due to their low cost, high abundance, dendrites free deposition of Mg and high volumetric energy density. Organometallic complex-based electrolytes in ethereal solutions have been extensively studied in the context of RMBs due to their ability to facilitate highly reversible magnesium deposition in rechargeable magnesium batteries, while demonstrating wide enough electrochemical stability windows. However, these solutions containing unique mixture of organo-halo aluminate complexes have detrimental effect on the anodic stability of metallic current collectors for cathodes, like Ni and Al foils. In this work, we were able to synthesize and isolate Mg2Cl3(THF)6Ph2AlCl2/THF electrolyte as the sole electroactive species using simple precursors: Ph2AlCl and MgCl2 in THF, via atom efficient mono-chloro abstraction Schlenk technique. We characterized the anodic stability of Ni, Ni@C, Al, and Al@C current collectors by monitoring their electrochemical behavior. In addition, we investigated the anodic stability enhancement of various current collectors by Al2O3 thin films coating using Atomic Layer Deposition (ALD). Linear sweep voltametric studies showed that coating current collectors enhanced the oxidative stability of Al and Ni foils by 0.1–0.3 V vs Mg/Mg2+ compared to the uncoated foils. In particular, Al2O3 coated Al@C showed an improved oxidative stability of 2.8 V vs Mg/Mg2+. Our findings show that current collectors protection by ALD coating can help in long-term stability and improving RMBs’ energy density by using high voltage cathode materials, a crucial step in developing practical rechargeable Mg batteries.

Field‐representative evaluation of PID‐polarization in TOPCon PV modules by accelerated stress testing

AbstractPotential‐induced degradation‐polarization (PID‐p) can reduce module power, but how to project the extent to which PID‐p may occur in field conditions considering the factors of system voltage, condensed moisture, temperature, and illumination has not been clarified. Using tunnel oxide passivated contact (TOPCon) modules, this work demonstrates a method to test full‐size crystalline silicon PV modules for PID‐p to provide field‐representative results. In initial screening tests with positive or negative 1000 V electrical bias applied at 60°C for 96 h using Al foil electrodes on the glass surfaces, the module type exhibited reversible PID‐p only on the front face when the cell circuit was in negative voltage potential. No PID was detected on the rear after testing in either polarity. We then evaluated the PID‐p sensitivity on the front side under different UV irradiances while maintaining the glass surface wet to estimate real‐world susceptibility to PID‐p. The magnitude of the observed behavior was fit using a previously developed charge transfer and depletion by light model. Whereas power loss with −1000 V applied to the cell circuit at 60°C for 96 h in the dark was about 30%, testing the module front under 0.051 W·m−2 nm−1 at 340 nm UVA irradiation using fluorescent tubes, the mean degradation was only 3%. When the modules were tested in the dark for PID‐p with in situ dark current–voltage (I‐V) characterization, the thermal activation energy for degradation was 0.71 eV; for recovery in the dark, it was 0.58 eV. Whereas recovery from the degraded state at 60°C in the dark without voltage bias was 5% absolute in 38 h, rapid recovery of about 5% absolute was observed with 1000 W·s/m2 exposure at 25°C using a flash tester.

Research on human gait sensing based on triboelectric nanogenerator

To address the problem of frequent battery replacement for wearable sensors applied to fall detection among the elderly, a portable and low-cost triboelectric nanogenerator (TENG)-based self-powered sensor for human gait monitoring is proposed. The main fabrication materials of the TENG are polytetrafluoroethylene (PTFE) film, aluminum (Al) foil, and polyimide (PI) film, where PTFE and Al are the friction layer materials and the PI film is used to improve the output performance. Exploiting the ability of TENGs to monitor changes in environmental conditions, a self-powered sensor based on the TENG is placed in an insole to collect gait information. Since a TENG does not require a power source to convert physical and mechanical signals into electrical signals, the electrical signals can be used as sensing signals to be analyzed by a computer to recognize daily human activities and fall status. Experimental results show that the accuracy of the TENG-based sensor for recognizing human gait is 97.2%, demonstrating superior sensing performance and providing valuable insights for future monitoring of fall events in the elderly population.

Stability and Reliability of Dye‐Sensitized Solar‐Cell Mini‐Module for Photocharging Li‐Ion‐Battery‐Connected Internet of Things

Dye‐sensitized solar cells (DSSCs)‐integrated Li‐ion batteries (LIBs) are considered a promising solution as a wireless power source for the increasing number of miniaturized portable devices and the internet of things (IoTs). However, DSSCs suffer from stability issues because of the using volatile electrolyte solvents that leak through the seal. To solve this problem, in this study, a polymer gel electrolyte based on the high‐boiling solvent 3‐methoxypropionitrile (bp = 164–165 °C) is used, and the backside of the cells are sealed by hot press using surlyn and Al foil. A highly stable and efficient counter electrode, Pt/porous carbon (Pt/PC), is also used to fabricate the devices, which show a high PCE of 25.7%–29.4% under the illumination of 500–2000 lux. The fabricated DSSC shows outstanding stability in the room condition and under the operating condition at 50 °C. A mini‐module of 13.3 cm2, PCE of 22.9–23.3%, and Pmax of 166.4–643.0 μW can recharge a LIB while powering an IoT device by producing an output greater than the IoT device consumes. The store charge can be used when the light source is cut off, indicating the reliability of the DSSC for photocharging the LIB as a wireless power source for IoT devices.

Effect of external magnetic field on electric current-induced fracture of notched thin metallic conductors: Part 2- High magnetic fields

In the companion report (Telpande et al., n.d.), we discussed the impact of a weak external magnetic field (up to 0.4 T) on the electric current-induced fracture of pre-notched thin metallic conductors, revealing a linear decrease in critical current density, jc, necessary for crack propagation. This study extends the investigation to explore the effects of stronger external magnetic fields (0.6–1 T) on the fracture of pre-notched, current-carrying metallic foils. The experimental analysis reveals a substantial, albeit linear, drop (up to 40 %) in jc under stronger magnetic fields. Interestingly, calculations of the dynamic stress intensity factor, KIE,t, which assesses the interplay between applied current density and external magnetic field, indicate crack growth under a strong magnetic field even when KIE,t is below the plane stress critical stress intensity factor, KIC. A remarkable phenomenon emerges: the application of electric current pulses combined with strong external magnetic fields induces observable surface undulations near the notch tip. A comprehensive 3D finite element model, integrating linear and nonlinear buckling analyses under multiphysics stimuli, attributes these undulations to localized buckling near the notch tip. This buckling-induced stress redistribution near the crack tip contributes to an overall reduction in fracture toughness due to mode mixity, leading to the fracture of the Al foil below KIC. This investigation, along with the companion report (Telpande et al., n.d.), significantly advances our understanding of the effects of magnetic fields on the fracture of current-carrying conductors.

3D Radial Junctions for Robust and Flexible Optoelectronics

AbstractMarrying nanostructures with thin films is a recent trend in flexible optoelectronics to improve light trapping and mechanical stability. Radial junction (RJ) a‐Si:H thin film optoelectronics, directly deposited upon the vapor‐liquid‐solid (VLS) grown silicon nanowires (SiNWs), can pave the way to achieving excellent flexibility and a high power‐to‐weight ratio (PTWR). Thanks to their vertical‐standing geometry, SiNWs framework can enhance the mechanical stability of RJ units, by keeping the working region far away from the stress‐rich substrate surface. Using low‐melting‐point metals as catalysts, the SiNW array can be fabricated at a low temperature down to 350 °C in a PECVD system, making it possible to directly construct robust RJ units on flexible, low‐cost substrates, such as Al foil. In this review, the recent progress of the flexible RJ a‐Si:H thin film solar cells/photodetectors that are directly fabricated on the surface of low‐cost flexible substrates is reviewed. Moreover, these RJ flexible optoelectronics are demonstrated for use in wearable and real‐time health monitoring, and as cardiac pacemakers for heart stimulation. This RJ technology highlights a promising potential to establish high‐performance, low‐cost, mechanically stable flexible optoelectronic for wearable, portable applications.

Direct-spun carbon nanotube sheet: A flexible, ultralight, stackable three-dimensional current collector for high-performance lithium-ion batteries

Among the key components of a battery electrode, current collectors hold significant importance for the energy density of lithium ion batteries (LIBs) as metal foils account for a significant proportion of the total mass. Carbon nanotube sheet (CNTS) has garnered considerable attention because of its fascinating material features such as high electrical conductivity, low density, and excellent flexibility. In this study, we demonstrate the utilization of a direct-spun CNTS as a current collector in order to enhance the electrochemical performance and replace the conventional current collector, that is, aluminum (Al) foil, in LIBs. When the CNTS coated with NCM811 (NCM811/CNTS) is evaluated in LIBs, it delivers superior rate capability and cycle stability compared with Al foil-based and buckypaper-based NCM811 electrodes. It is because the CNTS with a large surface area and high electrical conductivity establishes a number of electronic pathways to the cathode electrode. In addition, the porous structure of the CNTS efficiently enhances the adhesive properties of the electrodes. Due to the synergistic benefits of CNTS, cells with stacked NCM811/CNTS electrodes are successfully fabricated. Electrode stacking with multiple NCM811/CNTS electrodes exhibits improved areal capacity and stable cycle stability, suggesting a new strategy to replace the concept of conventional thick electrodes. Moreover, pouch cells with LTO/CNTS as an anode and NCM811/CNTS as a cathode display stable electrochemical performance even under mechanical deformation (e.g., folding/unfolding)