Current Collectors For Li-ion Batteries Research Articles

Reduced graphene oxide-modified aluminum foils as highly conductive and corrosion-resistant cathode current collectors for Li-ion batteries

Aluminum (Al) foil current collector is easily corroded by the electrolyte during long-term cycling and damages the electrochemical performance of the lithium-ion batteries (LIBs), especially at high operating voltages, this limits the development of next-generation high operating voltage (5 V) LIBs. Here, we successfully fabricated reduced graphene oxide (RGO) modified Al foils with high electrical conductivity and corrosion resistance as current collectors, which significantly enhanced the corrosion resistance of current collectors in LiPF6-based electrolytes and improved the long-term cycling stability and safety of LiMn2O4 batteries at high voltages. The LiMn2O4(LMO) cells with RGO modified Al foils as the current collector (LMO/GA) exhibit a discharge capacity retention rate of 88.7 % after 200 cycles at a current density of 100 mA g−1, which is much higher than that of the cells with pristine Al foils as the current collector (LMO/PA). The reversible capacity, rate capability, and thermal stability of the LMO/GA cells have also been significantly improved with RGO mediations. This work provides a new idea for the development of long-life corrosion-resistant current collector materials for high-performance LIBs at high operating voltages.

Directly Grown Germanium Nanowires from Stainless Steel: High-performing Anodes for Li-Ion Batteries

Germanium (Ge) nanowires were fabricated directly on stainless steel current collectors for Li-ion batteries without any additional catalytic seeds. Substrates of stainless steel are unconventional...

Carbon Nanotubes Coated Paper as Current Collectors for Secondary Li-ion Batteries

AbstractWe developed a surfactant-free spray coating process to coat commercial cellulose-based paper with carbon nanotubes (CNTs) and prepared paper-CNTs current collectors for Li-ion batteries (LIBs). The paper-CNTs were used as current collectors for replacing conventional aluminum foil. Li-ion batteries assembled using paper-CNTs were coated with LiFePO4as the active material and used as cathodes with Li as the anode, and the assembled LIBs showed a high energy density of 460 Wh kg−1at a power density of 250 W kg−1. These electrodes were stable even at a current density as high as 600 mA g−1, and showed cycling stability for ~450 cycles at 150 mAh g−1. Furthermore, paper-CNTs based electrodes showed ~17% improvement in areal capacity compared to commercial aluminum-based electrodes suggesting that paper-CNTs can readily displace Al foils as current collectors.Summary: Paper based current collectors have been proposed as a cost-effective and simple replacement for aluminum current collectors. This has been achieved by a scalable spray coating of CNTs on printing papers without any surfactants or binders and subsequently testing them as current collectors for Li-ion batteries.

Carbon nanotube tissue as anode current collector for flexible Li-ion batteries—Understanding the controlling parameters influencing the electrochemical performance

In an attempt to upgrade the performance of lithium (Li)-ion batteries, carbon nanotubes (CNTs) have been suggested as a high-energy anode material. However, CNTs induce high irreversible capacity loss during the first cycle of the battery, which still poses a scientific challenge. This study explores CNT tissue as a flexible light-weight alternative to the copper (Cu) foil as an anode current collector in Li-ion batteries, employing graphite active material. The study demonstrates the impact of the graphite mass loaded on the anode performance and suggests that with the increase in the graphite mass, the irreversible capacity loss is considerably decreased. At sufficiently high graphite loadings, the performance during the first cycle becomes comparable to that of an anode utilizing the Cu current collector. This research also presents several distinct chemical pretreatments to the tissue, aiming to further decrease the irreversible capacity loss. It is suggested that this goal may be accomplished by washing the CNT with sulfuric acid prior to anode preparation, prompting better performance.

Three-dimensional carbon based current collectors for lithium-based batteries

Three-dimensional carbon materials combining excellent mechanical, electrical and thermal properties with very good electrochemical resistance have shown great potential for electrochemical energy storage. Building up a three-dimensional current collector can simultaneously optimize the conductive network in the electrochemically active layers and mitigate the volume change at the electrode level during cycling, which leads to enhanced energy density, power density and cycle stability. This review aims to provide an overview of the recent key progress on 3D carbon current collector for Li-ion batteries. According to the type of the connections at the junctions between the nano/micro-scale constituents, we categorize 3D carbon materials into two aspects: 3D carbon networks based on covalent connection and 3D carbon networks based on non-covalent connection. The requirements and the challenges of the 3D carbon based current collector’s design are discussed, which provide inspiration for further exploitation of the current collectors for Li-ion batteries and shed light on batteries based on other electrochemistry.

Li4Ti5O12 flexible, lightweight electrodes based on cellulose nanofibrils as binder and carbon fibers as current collectors for Li-ion batteries

TEMPO oxidized cellulose nanofibrils (TOCNF) were used as binder material to prepare bendable Li4Ti5O12 (LTO) electrodes. Carbon fiber (CF) layers were integrated as current collectors to enhance the mechanical properties and to increase the specific energy of the electrodes. These electrodes combined with CF current collectors (LTO/CF) show good electrochemical properties and are flexible, sustainable, mechanical and chemical stable, lightweight and produced by a water-based easy filtration process. An increase of the active material weight (LTO) from around 19% to 71% of the electrode and current collector combined weight is demonstrated with CF compared with a copper current collector. Additionally, preparation of the current collector material is non-expensive, quick and easy compared to that of carbon nanotube or graphene. To test the flexible battery application, 4000 times repeated bending was carried out on both the LTO electrodes and the LTO/CF electrodes. This had no significant effect on the morphology, mechanical and electrochemical properties of neither the LTO nor the LTO/CF electrodes. Addition of the CF layer improves the mechanical properties and specific capacity of the LTO-electrode. A thicker LTO electrode with only 2wt% TOCNF is demonstrated which is promising for thicker electrodes with high energy density. A full cell was assembled with the LTO/CF as negative electrode and LiFePO4 (LFP)/CF as positive, which exhibited a stable cycling performance and good energy density.

Crater-like architectural aluminum current collectors with superior electrochemical performance for Li-ion batteries

Crater-like architectural aluminum current collectors is prepared by a simple chemical etching method with NaOH-based solutions, and investigate the effect of aluminum surface morphology on its electrochemical performance as cathode current collector in Li-ion batteries. Characterization data reveal an acceptable tensile strength and surface hydrophilicity in the etched aluminum current collector, together with the creation of a rough surface with many reticular crater-like pits. In Li-ion cells using LiCoO2 as the active material, the crater-like architectural aluminum foil is electrochemically stable as the current collector, when in contact with other cell components during the charge–discharge processes. The improved electrochemical performance is attributed to the good electrical contact between cathode material particles and the current collector, and the resulting efficient electron transfer.

Better cycle stability and rate capability of high-voltage LiNi0.5Mn1.5O4 cathode using water soluble binder

5V LiNi0.5Mn1.5O4 (LNMO) cathodes are prepared using carboxymethyl chitosan (CCTS) as a water soluble binder and carbon coated aluminum foils (CAl) as current collector in Li-ion batteries (LIBs). CCTS exhibits an electrochemical oxidation potential as high as 5.0V. The electrochemical performance of LNMO cathode with CCTS binder is investigated and compared with the commercial non-aqueous polyvinylidene difluoride (PVDF). CCTS-CAl-LNMO electrode shows higher capacity retention (95.8%) than that of PVDF-CAl-LNMO (92.9%) and PVDF-Al-LNMO (88.52%) after 100 cycles. And, CCTS-CAl-LNMO electrode exhibits better rate capability than PVDF-CAl-LNMO, and PVDF-Al-LNMO, retaining specific capacity of 95.8mAhg−1 at 10C rate, only 87.6mAhg−1 and 1mAhg−1 for PVDF-CAl-LNMO, and PVDF-Al-LNMO, respectively. This approach can also be extended its use to other cathode materials such as LiNi1/3Co1/3Mn1/3O2 (NCM).

Processing of Al-doped ZnO protective thin films on aluminum current collectors for lithium ion batteries

In this work, aluminum current collectors for Li-ion batteries were coated with protection layers made of Al-doped ZnO (ZnO:Al) to prevent the corrosion of aluminum caused by bis(trifluoromethylsulfonyl)imide (TFSI−) at 5V. These thin films of ~100nm thickness were prepared with a facile and scalable sol-gel coating process with subsequent heat treatment by rapid thermal processing (RTP) at 500°C. The ZnO:Al films exhibited the usual hexagonal phase, a homogeneous morphology and a sufficient electronic conductivity. In electrochemical testing, chronoamperometry demonstrated that the protection layer reduces the corrosion of the aluminum current collector 120 times compared with conventional unprotected aluminum.

Reduced Graphene Oxide Films with Ultrahigh Conductivity as Li-Ion Battery Current Collectors.

Solution processed, highly conductive films are extremely attractive for a range of electronic devices, especially for printed macroelectronics. For example, replacing heavy, metal-based current collectors with thin, light, flexible, and highly conductive films will further improve the energy density of such devices. Films with two-dimensional building blocks, such as graphene or reduced graphene oxide (RGO) nanosheets, are particularly promising due to their low percolation threshold with a high aspect ratio, excellent flexibility, and low cost. However, the electrical conductivity of these films is low, typically less than 1000 S/cm. In this work, we for the first time report a RGO film with an electrical conductivity of up to 3112 S/cm. We achieve high conductivity in RGO films through an electrical current-induced annealing process at high temperature of up to 2750 K in less than 1 min of anneal time. We studied in detail the unique Joule heating process at ultrahigh temperature. Through a combination of experimental and computational studies, we investigated the fundamental mechanism behind the formation of a highly conductive three-dimensional structure composed of well-connected RGO layers. The highly conductive RGO film with high direct current conductivity, low thickness (∼4 μm) and low sheet resistance (0.8 Ω/sq.) was used as a lightweight current collector in Li-ion batteries.

Bundled and densified carbon nanotubes (CNT) fabrics as flexible ultra-light weight Li-ion battery anode current collectors

Carbon nanotubes (CNT) fabrics were studied and evaluated as anode current collectors, replacing the traditional copper foil current collector in Li-ion batteries. Glavanostatic measurements reveal high values of irreversible capacities (as high as 28%), resulted mainly from the formation of the solid electrolyte interphase (SEI) layer at the CNT fabric surface. Various pre-treatments to the CNT fabric prior to active anode material loading have shown that the lowest irreversible capacity is achieved by immersing and washing the CNT fabric with iso-propanol (IPA), which dramatically modified the fabric surface. Additionally, the use of very thin CNT fabrics (5 μm) results in a substantial irreversible capacity minimization. A combination of IPA rinse action and utilization of the thinnest CNT fabric provides the lowest irreversible capacity of 13%. The paper describes innovative and rather simple techniques towards a complete implementation of CNT fabric as an anode current collector in Li-ion batteries, instead of the relatively heavy and expensive copper foil, enabling an improvement in the gravimetric and volumetric energy densities of such advanced batteries.

Demonstrating the Feasibility of Al as Anode Current Collector in Li-Ion Batteries via In Situ Neutron Depth Profiling

The viability of using aluminum (Al) foil as the anode current collector in Li-ion batteries was demonstrated using in situ neutron depth profiling (NDP). A 500 nm thin Sn film, physical vapor deposited onto an Al foil, was monitored using NDP during lithiation and subsequent delithiation. Results indicate exclusive lithiation of the Sn electrode throughout the 0.05 to 1.00 V vs Li/Li+ range, leaving the Al foil current collector unlithiated even at the low potentials sufficient to lithiate Al. Additionally, 60–80 nm Sn nanoparticles suspended in a polyvinylidine fluoride (PVDF) matrix were cast onto an Al foil current collector and lithiated under constant current (C/6 rate). Results indicate the preferential lithiation of Sn nanoparticles. At lithiation potentials >0.3 V, Al lithiation is avoided even when the current collector is in direct contact with the electrolyte solution.

Assessing Charge Contribution from Thermally Treated Ni Foam as Current Collectors for Li-Ion Batteries

In this report we have investigated the use of Ni foam substrates as anode current collectors for Li-ion batteries. As the majority of reports in the literature focus on hydrothermal formation of materials on Ni foam followed by a high temperature anneal/oxidation step, we probed the fundamental electrochemical responses of as received Ni foam substrates and those subjected to heating at 100°C, 300°C and 450°C. Through cyclic voltammetry and galvanostatic testing, it is shown that the as received and 100°C annealed Ni foam show negligible electrochemical activity. However, Ni foams heated to higher temperature showed substantial electrochemical contributions which may lead to inflated capacities and incorrect interpretations of CV responses for samples subjected to high temperature anneals. XRD, XPS and SEM analyses clearly illustrate that the formation of electrochemically active NiO nanoparticles on the surface of the foam is responsible for this behavior. To further investigate the contribution of the oxidized Ni foam to the overall electrochemical response, we formed Co3O4 nanoflowers directly on Ni foam at 450°C and showed that the resulting electrochemical response was dominated by NiO after the first 10 charge/discharge cycles. This report highlights the importance of assessing current collector activity for active materials grown on transition metal foam current collectors for Li-ion applications.

Embroidered 3D Porous Structures As Current Collectors for Li-Ion Batteries

There is a need to improve battery designs to maximise energy and power densities. Standard planar current collectors present some limitations in electronic conductivity due to a thickness of the active mass, problems with the uniformity of thermal conductivity at high current densities, as well as difficulties with the handling of the batteries. Here, we present embroidered 3D porous structures fabricated by technical embroidery as an alternative to be used as current collectors for LiFePO4 batteries. X-ray computed micro tomography was used to provide the appropriate morphological characterisation of the 3D structures. The electrochemical behaviour of the electrodes was also investigated using charge and discharge cycles. Specific capacities as a function of the mass loading and the increase of the current densities are presented. Figure 1

Aluminium Rods As Current Collectors and Electrodes for 3D Li-Ion Micro-Batteries

The microelectronics industry has advanced at a rapid pace in the last decade. Further advancements are hampered by the lack of suitable on-board power devices. Although Li-ion batteries are the primary choice for energy storage, they cannot store enough energy per foot-print area without compromising power capability. Three-dimensional Li-ion batteries could offer the solution by using all three dimensions for efficient energy storage on a relatively small foot-print area. Aluminium rods were obtained by template assisted galvanostatic deposition of aluminium into the pores of a commercial membrane. By the subsequent chemical dissolution of the membrane, free standing arrays of aluminium rods deposited on an aluminium substrate were obtained. It was shown that the use of a nucleation pulse prior to deposition led to a homogeneous deposition of aluminium rods, while the use of pulsed current rather than constant current resulted in a narrower distribution of the rods heights [1]. Aluminium is used as a current collector in Li-ion batteries. The deposition of TiO2 onto the aluminium rods was done by means of electrophoresis and a sol-gel derived impregnation method. While the electrophoretic deposition resulted in non-conformal coated rods, the impregnation method gave a thin amorphous deposit which could be cycled against lithium [2]. Finally, aluminium can be used as a negative active material, as it alloys with lithium. A study of the alloying and dealloying of lithium and aluminium was done on the 3D aluminium rods and a model for the lithiation and delithiation of aluminium has been proposed [3]. The aluminium rods were used as a negative electrode in a Li-ion battery against LiFePO4 coated on carbon foam positive electrode in a 3D cell with different geometries of the two electrodes [4].

Integration of Si in a metal foam current collector for stable electrochemical cycling in Li-ion batteries

We improve the electrochemical performance of Li-ion batteries by trapping micron-sized silicon particles inside a metal foam current collector in Li-ion batteries.

3D morphological analysis of copper foams as current collectors for Li-ion batteries by means of X-ray tomography

Abstract As-received and chemically treated copper foams were characterized by means of laboratory X-ray tomography with a resolution of 0.5 μm. 3D image processing and analysis allowed the morphological parameters (size, sphericity, tortuosity etc.) of the pores and copper skeleton to be determined. The chemical dissolution of the Cu foam in an acid hydrogen peroxide solution results in an increase of the open pore size (from 54 to 93 μm) and a decrease of the foam thickness (from 140 to 115 μm). With an open porosity of 81.8% and a specific surface area as high as 280,000 (49,000) m2/m3 of Cu (foam), the chemically-treated Cu foam appears very attractive for use as a 3D current collector for metal (e.g. Si) based anodes for Li-ion batteries.

Genetically Programming Interfaces between Active Materials, Conductive Pathway and Current Collector in Li-Ion Batteries

In this work we genetically programmed the M13 virus, so that the new clone expressed multifunctional coat protein sequences that selectively bind to designated surfaces and species. Using these new clones, composite network consisting of ironphosphate nanowire (a-FePO4) and single wall carbon nanotubes were self-assembled onto aluminum surfaces. Spectroscopic and electrochemical characterizations confirmed the 3D-structure as well as the electrochemical activity of such composite nanowires.

Genetically Programming the Interfaces between Bio-Templated Cathode Nano-Particles and Current Collector in Li-Ion Batteries

not Available.

Al Current Collectors for Li-Ion Batteries Made via an Oxidation Process in Ionic Liquids

Efficient electrical wiring of electrodes is a key issue in the design of Li-ion batteries using insulating compounds. Approaches acting at the material level are being pursued by combining techniques to decrease the particles size and to coat them with carbon. Here, we report the texturation of the Al current collector as an additional mean to improve electrode kinetics. Bulk aluminum substrates were oxidized from EMIm TFSI/AlCl3 electrolytic baths using cyclic voltammetry techniques. A needlelike morphology was obtained after oxidation. Electrodes using this substrate and LiFePO4 powders as the active material were shown to display excellent capacity retention and high rate capability. © 2010 The Electrochemical Society. DOI: 10.1149/1.3511717 All rights reserved.