Copper Current Collector Research Articles

Porous Copper Current Collectors for Advanced Anode Architectures

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High Capacity and Excellent Stability of Lithium Ion Battery Anode Using Interface-Controlled Binder-Free Multiwall Carbon Nanotubes Grown on Copper

We present a novel binder-free multiwall carbon nanotube (MWCNT) structure as an anode in Li ion batteries. The interface-controlled MWCNT structure, synthesized through a two-step process of catalyst deposition and chemical vapor deposition (CVD) and directly grown on a copper current collector, showed very high specific capacity, almost three times as that of graphite, excellent rate capability even at a charging/discharging rate of 3 C, and no capacity degradation up to 50 cycles. Significantly enhanced properties of this anode could be related to high Li ion intercalation on the carbon nanotube walls, strong bonding with the substrate, and excellent conductivity.

Electrochemical Lithium Deposition-dissolution Reaction of a Ti Modified Multi-layered Solid Electrolyte Sheet

Multi-layered solid electrolyte sheets (OHARA sheet (Ohara Inc., Kanagawa, Japan)/lithium phosphorus oxynitride (LiPON)) with a copper current collector film on the LiPON side were prepared, and the effects of Ti modification at the OHARA sheet/LiPON interface on the electrochemical lithium deposition-dissolution reaction were investigated. Lithium plating-stripping current in cyclic voltammograms increased with an appropriate amount of Ti modification, indicating that Li+ transfer resistance at the OHARA sheet/LiPON interface decreased due to the modification. In addition, the Ti modification stabilized the electrochemical lithium deposition-dissolution reaction. This suggested that Ti modification increase the number of Li+ transfer sites at the interface, resulting in a good distribution of nucleation reaction sites on the copper film as well as the stabilization of the current collector film.

Electrochemical behavior of copper current collector in imidazolium-based ionic liquid electrolytes

The electrochemical behaviors of copper current collector in 1-alkyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl] imide ionic liquid electrolytes were investigated and compared with that in ethylene carbonate/dimethyl carbonate solutions. Cyclic voltammetry results showed that large oxidation–reduction current of the copper foil appeared in ethylene carbonate/dimethyl carbonate solutions, while a much smaller current in the room temperature ionic liquid electrolytes decreased gradually, indicating that the copper foil was anodically stable. Further study by X-ray photoelectron spectroscopy analysis showed that an unstable product was composed mainly of the carbonate and carbonyl species on the surface of the copper foil after the electrochemical measurement in ethylene carbonate/dimethyl carbonate solutions, leading to the dissolution of the copper foil. While a better passivating film from the reduction of the anions in the room temperature ionic liquid electrolytes covered the surface of copper foil and protected the copper foil from being oxidized even in a higher potential. These results indicate that the use of room temperature ionic liquid electrolytes can improve the stability of copper current collector in the advanced lithium ion batteries.

Fabrication and electrochemical properties of novel ternary Sb–Co–P alloy electrodes for lithium-ion batteries

A novel ternary Sb–Co–P alloy electrode was prepared by electroplating on copper current collector as a promising negative electrode material for lithium-ion batteries. The structural and morphological features of the Sb–Co–P alloy were characterized by powder X-ray diffraction (XRD) and scanning electron microscope (SEM). The as-prepared alloy electrode exhibits a high specific capacity and an excellent cycleability. The initial discharge and charge capacities of the Sb–Co–P alloy anode were measured 700 and 539 mA h g −1, respectively. The results suggest that the Sb–Co–P alloy material obtained by the electrodeposition shows a good candidate anode material for lithium-ion batteries.

Carbon nanotubes for lithium ion batteries

Lithium ion batteries are receiving considerable attention in applications, ranging from portable electronics to electric vehicles, due to their superior energy density over other rechargeable battery technologies. However, the societal demands for lighter, thinner, and higher capacity lithium ion batteries necessitate ongoing research for novel materials with improved properties over that of state-of-the-art. Such an effort requires a concerted development of both electrodes and electrolyte to improve battery capacity, cycle life, and charge–discharge rates while maintaining the highest degree of safety available. Carbon nanotubes (CNTs) are a candidate material for use in lithium ion batteries due to their unique set of electrochemical and mechanical properties. The incorporation of CNTs as a conductive additive at a lower weight loading than conventional carbons, like carbon black and graphite, presents a more effective strategy to establish an electrical percolation network. In addition, CNTs have the capability to be assembled into free-standing electrodes (absent of any binder or current collector) as an active lithium ion storage material or as a physical support for ultra high capacity anode materials like silicon or germanium. The measured reversible lithium ion capacities for CNT-based anodes can exceed 1000 mAh g−1 depending on experimental factors, which is a 3× improvement over conventional graphite anodes. The major advantage from utilizing free-standing CNT anodes is the removal of the copper current collectors which can translate into an increase in specific energy density by more than 50% for the overall battery design. However, a developmental effort needs to overcome current research challenges including the first cycle charge loss and paper crystallinity for free-standing CNT electrodes. Efforts to utilize pre-lithiation methods and modification of the single wall carbon nanotube bundling are expected to increase the energy density of future CNT batteries. Other progress may be achieved using open-ended structures and enriched chiral fractions of semiconducting or metallic chiralities that are potentially able to improve capacity and electrical transport in CNT-based lithium ion batteries.

Electrodeposition and lithium storage performance of novel three-dimensional porous Fe–Sb–P amorphous alloy electrode

The three-dimensional porous Fe–Sb–P amorphous alloy electrodes were prepared by electroplating on porous copper current collector. The structure and electrochemical performance of the electroplated Fe–Sb–P amorphous alloy electrodes have been investigated in detail. XRD results showed that the as-deposited Fe–Sb–P alloy electrode exhibits an amorphous nature. Electrochemical tests indicated that at the 50th cycle, the Fe–Sb–P amorphous alloy electrodes can deliver a discharge capacity of 448 mAh g −1. The porous and amorphous structure of electrode of Fe–Sb–P alloy was beneficial in relaxing the volume expansion during cycling, which improved the cycle ability of Fe–Sb–P alloy electrode.

Alloying of electrodeposited silicon with lithium—a principal study of applicability as anode material for lithium ion batteries

The possibility to electrodeposit silicon directly on a copper current collector out of organic electrolyte and ionic liquid was investigated with the aim to alloy the deposited silicon with lithium to prove the possible use as negative electrode in lithium ion batteries. Cyclovoltammetric analyses have shown in comparison to electrodes containing high crystalline silicon similar behaviour during the electrochemical alloying and dealloying process. SEM analyses have shown a particle size of the deposited silicon in submicron range.

High rate capability pure Sn-based nano-architectured electrode assembly for rechargeable lithium batteries

New high surface area nano-architectured copper current collectors have been designed based on simple electrodeposition method. The nano-architectured electrode design not only increases the effective surface area of the electrode but it is also very suitable for sustaining the mechanical and structural strain during electrochemical reaction. In this work, a nano-architectured Sn anode for Li-ion battery, based on Li–Sn alloying reaction, delivers very high cycle life and good power performance compared to planar tin films. This electrode could be successfully used in the field of 3D microbatteries.

Synthesis and electrochemical properties of Sn 87Co 13 alloys by NaBH 4 and sodium naphthalenide reduction methods

Sn 87Co 13 alloys are prepared by two different reduction methods and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and electrochemical cycling. One method, using NaBH 4 as a reducing agent, obtains aggregated particles with particle sizes from 20 to 200 nm. The second method, using sodium naphthalenide as a reducing agent, shows a well-dispersed nanoalloy coated with amorphous carbon, with a particle size of 15 nm. Although electrochemical results shows that the charge capacity of the two alloys is quite similar, 662 mAh/g, the capacity retention of the nanoalloy prepared using sodium naphthalenide was 427 mAh/g, which is two times higher after 30 cycles than the bulk analogue obtained using NaBH 4. This is due to the uniform particle size and amorphous carbon layer that effectively reduces anisotropic volume expansion and also minimizes particle aggregation and pulverization that causes a direct electrical disconnection with the copper current collector.

Study on Sn-Co alloy Electrodes for Lithium Secondary Batteries: II. Nanocomposite System

In our previous work, an amorphous alloy film prepared by electrocodeposition on Cu foil with rough surface was found to transform to a new phase structure during charge-discharge cycle to show more stable reaction with lithium. In this work, we prepared film on copper current collector which originally included the new phase structure, and examined its electrochemical and structural properties by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, extended X-ray absorption fine structure, and magnetic susceptibility measurement. Influence of the phase transformation on the cyclability is discussed in terms of adhesion between the film and current collector.

Nano-structured Copper Current Collector Covered by Fe3O4 Thin Film, a High Rate Capabilities Electrode for Lithium Battery Applications

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All-solid-state lithium polymer secondary battery with LiNi 0.5Mn 1.5O 4 by mixing of Li 3PO 4

5 V-class all-solid-state lithium polymer secondary batteries were prepared by the mixing of solid inorganic electrolyte (SIE, Li 3PO 4) with LiNi 0.5Mn 1.5O 4 powder. The discharge capacity exhibited >120 and >550 mWh g −1 at the operation temperature of 333 K. We also prepared a lithium-metal-free battery by using copper current collector at the anode, and exhibit the similar discharge capacity. Our demonstration indicates the marked improvement in the energy density of lithium polymer batteries through a simple preparation, which leads to the manufacture of large-scaled batteries.

Flexible graphite as battery anode and current collector

In making graphite-based electrodes and current collectors, there is significant simplification if a flexible graphite process is used. The lithium intercalation capacity of Grafoil ® 1 1 ®GRAFOIL is a registered trademark of Advanced Energy Technology Inc. flexible graphite sheet and its powder was evaluated using electrochemical charge–discharge cycling in half-cell configuration (coin cell with Li anode and graphite cathode). The sheet form was used with and without a copper current collector. Excellent electrical conductivity of the monolithic material with very low interface resistance helps as current collector and electrode. The comparatively low capacity of Grafoil ® sheet is thought to be due to diffusion limitation of the structure, especially in the light of the very high capacity of its powder form. The highly irreversible capacity of the powdered material may be due to unfunctionalized graphitic structures or impurities present in the powder. Impedance response for the first intercalation–deintercalation was different than responses taken after several cycles. The presence of a second impedance arc suggests structural modification is taking place in the graphite anode, possibly through formation of a porous structure as a result of graphite expansion.

Tin Alloy-Graphite Composite Anode for Lithium-Ion Batteries

A composite anode material was prepared that contains nanosize (<100 nm) particles of tin alloy and The alloys were electroplated at high current densities (above from aqueous solutions, directly onto the copper current collector, and were coated by a polyvinylidene fluoride-graphite matrix at a ratio of alloy:graphite matrix 70:30 and 80:20 w/w, respectively. The processes involved in electrode production by this method are inexpensive, simple, and fast. Over 40 (100% depth of discharge) cycles were demonstrated, in half-cell, and over 30 were demonstrated with a battery containing 1 M ethylene carbonate-diethyl carbonate electrolyte. The faradaic efficiency is less than 100%. Lithium is fully deinserted from the host matrix only when the anode is cycled at low current densities. The kinetics of lithium insertion to and deinsertion from the composite anode material, slow gradually as the cycle number increases. X-ray diffraction patterns of the anode material show that the alloy becomes amorphous during cycling, while the graphite does not. X-ray photoelectron-spectroscopy measurements reveal that the solid electrolyte interphase consists of mainly LiF, small amounts of and possibly, polymeric substances. The electrochemical behavior of the alloy changes with cycle number, while that of the graphite does not. The fall of the deinsertion capacity of the graphite from the first cycle to the 34th by more than 50% proves that the active material in the anode suffers from particle-to-particle break off. © 2002 The Electrochemical Society. All rights reserved.

Study on the anode behavior of Sn and Sn–Cu alloy thin-film electrodes

Anodes based on tin metal powder offer large specific capacity, but also exhibit large irreversible capacity and poor cycle performance. In order to use them as a negative electrode for lithium secondary batteries, we focused on the electrodepositing process and investigated an electrodeposited tin layer on copper foil. In the full charge–discharge condition, charging and discharging between 0 and 2.0 V versus Li/Li +, the first discharge capacity was 940 mAh g −1, which was 2.5 times as large as that of graphite, and the coulomb efficiency in the first cycle was 93%, but its cycle performance was not improved. In order to enhance the interface strength between the active material and the copper foil, we investigated an anode which was fabricated by annealing an as-deposited anode. In the full charge–discharge condition, the first charge–discharge characteristics were almost equivalent to the as-deposited anode, and the retention capacity ratio after 10 cycles was improved from 20 to 94%. It is considered that this improvement resulted from the formation of two different tin–copper intermetallic compound layers between the tin layer and the copper current collector due to the heat treatment. A small cell using this annealed anode as a negative electrode was also investigated. This cell offered good cycle performance for the first 20 cycles.

The study of lithium insertion–deinsertion processes into composite graphite electrodes by in situ atomic force microscopy (AFM)

Li insertion–deinsertion into composite graphite electrodes, comprising synthetic graphite flakes (6 μm average size), polyvinylidene difluoride binder (PVdF), and copper current collectors, in commonly used alkyl carbonate solutions were studied by in situ atomic force microscopy (AFM). In this study, we were able to probe by in situ AFM the behavior of practical, composite graphite electrodes in ethylene carbonate–dimethyl carbonate (EC–DMC) solutions containing salts such as LiAsF 6 and LiPF 6 during entire lithiation–delithiation cycles. These in situ micro/nanomorphological studies could probe surface film formation on the graphite particles, as well as periodic volume changes in the graphite flakes during Li insertion–deinsertion cycles. These cyclic volume changes can explain the capacity fading of graphite electrodes upon prolonged cycling, in Li-ion batteries. While the overall morphology of these electrodes remains steady upon cycling in the appropriate solutions (in which the Li–C electrodes are efficiently passivated), there is a continuous problem in the extent of accommodation of the small volume changes in the graphite particles upon lithiation–delithiation, by the surface films. It is suggested that graphite electrodes fail during prolonged cycling due to small scale, continuous reactions of the active mass with solution species, which gradually increase their impedance and decrease the content of the lithium stored in the electrodes.

Effect of mild oxidation of natural graphite (NG7) on anode-electrolyte thermal reactions

The effect of mild oxidation of natural graphite (NG7) and some other parameters on the reaction between a fully lithiated graphite anode (Li x C6, x=1.0–1.1) and 1 M lithium hexafluoroarsenate in ethylene carbonate and diethyl carbonate electrolyte (1:2, v/v) were studied by differential scanning calorimetry (DSC). It was found that mild oxidation of the graphite suppressed the exothermic reaction of the fully lithiated anode with the electrolyte, most probably as a result of the formation of a more stable and chemically bonded solid electrolyte interphase. Separation and removal of the small graphite particles from the anode mixture suppressed this reaction further. It was also found that the copper current collector, the amount of electrolyte and binder as well as other parameters have a significant influence on the heat evolution as measured by DSC.

Development of polymer-based lithium secondary battery

Novel polymer composites based on polydisulfide compounds are developed as a high energy density cathode material for lithium rechargeable batteries. A polymer composite composed of 2,5-dimercapto-1,3,4-thiadiazole (DMcT) and conducting polymer polyaniline (PAn) on a copper current collector provides high charge density exceeding 225Ah/kg-cathode with average discharge voltage at 3.4V. The composite cathode showed excellent rate capability and cyclability (>500 cycles). Surface analysis and electrochemical studies indicate that a DMcT-Cu complex plays an important role in the observed improvement of the battery performances with a copper current collector. Large increase in the charge density to 550Ah/kg-cathode is achieved by adding elemental sulfur (S8) to the DMcT/PAn composite cathode.

New Composite Cathodes for Lithium Rechargeable Batteries

New organic composites based on thiol-compounds are developed as a cathode material for lithium batteries. A conducting polymer polyaniline (PAn) accelerates slow redox reactions of the organic sulfur compounds with multiple thiol groups, such as 2,5-dimercapto-1,3,4-thiadiazole (DMcT). A composite cathode composed of DMcT and PAn on a copper current collector provides high charge density exceeding 225Ah/kg-cathode and is capable of being charged and discharged at high rates with excellent cyclability (>500 cycles). Surface analysis and electrochemical studies indicate that a DMcT-Cu complex plays an important role in the observed battery performances of the composite on a copper current collector. Large increase in the charge density to 550Ah/kg-cathode is achieved by adding elemental sulfur (S8) to the composite cathode.