Current Collector For Lithium-ion Batteries Research Articles

Revisiting the Corrosion of the Aluminum Current Collector in Lithium-Ion Batteries.

The corrosion of aluminum current collectors and the oxidation of solvents at a relatively high potential have been widely investigated with an aim to stabilize the electrochemical performance of lithium-ion batteries using such components. The corrosion behavior of aluminum current collectors was revisited using a home-build high-precision electrochemical measurement system, and the impact of electrolyte components and the surface protection layer on aluminum foil was systematically studied. The electrochemical results showed that the corrosion of aluminum foil was triggered by the electrochemical oxidation of solvent molecules, like ethylene carbonate, at a relative high potential. The organic radical cations generated from the electrochemical oxidation are energetically unstable and readily undergo a deprotonation reaction that generates protons and promotes the dissolution of Al3+ from the aluminum foil. This new reaction mechanism can also shed light on the dissolution of transitional metal at high potentials.

Sigmoidal current collector for lithium-ion battery

In the current study, we investigated sigmoidal current collector in lithium-ion battery (LIB). Traditionally, the active material in an LIB electrode is coated on a flat current collector. By rendering the current collector sigmoidal-shaped, cracking and debonding of active material layer could be promoted, which would considerably increase the internal impedance, as the LIB is mechanically abused, beneficial to thermal-runaway mitigation. The energy absorption capacity is also improved, enabling multifunctional LIB cell design. This technique has important relevance to large-sized LIB systems, for which cell robustness and fire safety are prioritized.

Analytical Model on Lithiation-Induced Interfacial Debonding of an Active Layer From a Rigid Substrate

By directly solving the prescribed differential equations, an analytical method based on the cohesive model has been developed to investigate the interfacial debonding process induced by lithiation in an axisymmetric thin film electrode where an elastic active layer is bonded on a rigid substrate. The assumption of rigid substrate has been proved acceptable for high-modulus substrates such as copper and aluminum which are common materials for current collectors in lithium-ion batteries. For the case where the weak interface is assumed and the radial concentration gradient is neglected, an extremely simplified solution has been obtained. The simplified solution which has acceptable accuracy provides a good guidance for understanding and predicting the interfacial debonding.

X-ray micro tomography of three-dimensional embroidered current collectors for lithium-ion batteries

X-ray micro computed tomography (μCT) is used for the morphological characterization of three-dimensional (3D) embroidered current collectors for LiFePO4 batteries. A conventional 2D planar configuration (aluminium foil as current collector) and two types of 3D embroidered configurations were compared. The μCT images were used to identify the different components in each configuration as well as to evaluate the corresponding volume fractions, porosities, mass fractions and apparent densities. Microtomographic scans complement analysis of typical galvanostatic charge/discharge cycles and confirm the suitability of 3D embroidered current collectors for their use in lithium-ion batteries.

In Situ Carbonized Cellulose-Based Hybrid Film as Flexible Paper Anode for Lithium-Ion Batteries.

Flexible free-standing carbonized cellulose-based hybrid film is integrately designed and served both as paper anode and as lightweight current collector for lithium-ion batteries. The well-supported heterogeneous nanoarchitecture is constructed from Li4Ti5O12 (LTO), carbonized cellulose nanofiber (C-CNF) and carbon nanotubes (CNTs) using by a pressured extrusion papermaking method followed by in situ carbonization under argon atmospheres. The in situ carbonization of CNF/CNT hybrid film immobilized with uniform-dispersed LTO results in a dramatic improvement in the electrical conductivity and specific surface area, so that the carbonized paper anode exhibits extraordinary rate and cycling performance compared to the paper anode without carbonization. The flexible, lightweight, single-layer cellulose-based hybrid films after carbonization can be utilized as promising electrode materials for high-performance, low-cost, and environmentally friendly lithium-ion batteries.

Multiphysics simulations of nanoarchitectures and analysis of germanium core-shell anode nanostructure for lithium-ion energy storage applications

This paper reports multiphysics simulations (COMSOL) of relatively low conductive cathode oxide materials in nanoarchitectures that operate within the appropriate potential range (cut-off voltage 2.5 V) at 3 times the C-rate of micron scale thin film materials while still accessing 90% of material. This paper also reports a novel anode fabrication of Ge sputtered on a Cu nanotube current collector for lithium-ion batteries. Ge on Cu nanotubes is shown to alleviate the effect of volume expansion, enhancing mechanical stability at the nanoscale and improved the electronic characteristics for increased rate capabilities.

Core-shell Ti@Si coaxial nanorod arrays formed directly on current collectors for lithium-ion batteries.

Silicon is a promising candidate to replace the dominantly used carbon as the anode material for lithium ion batteries (LIBs). Si has the highest theoretical capacity (4200 mA·h/g) and is one of the most abundant elements. Unfortunately, Si has the issues of huge volume variation upon dis/charge cycling and low conductivity, leading to poor cycling and rate performances. Designing special nanostructures and improving conductivity and integration of Si electrodes could dramatically enhance their performance. Here, we introduce a novel strategy to integrate the core-shell nanorod arrays of Ti@Si on Ti foil with good conductivity as an additive-free electrode. The Ti core functions as a stable metallic support for the Si shell and dramatically reduces the diffusion length. The as-prepared core-shell nanorod arrays of Ti@Si on Ti foil, without any postsynthesis treatment, as electrodes demonstrated reversible capacity of 1125 mA·h/g over at least 30 cycles with highly improved Coulombic efficiency.

Development of a 3d current collector for the positive electrode in lithium-ion batteries

So far, expanded metals or metal foils have been used as current collectors for the positive electrode in state of the art lithium-ion batteries (LIBs). In this work, a new 3D current collector for the positive electrode of LIBs was investigated. Non-woven polymer was metallized with Al by physical vapour deposition (PVD). To prove its feasible application as a current collector in LIBs, LiCoO2 (LCO) composite electrodes were fabricated and compared to common LCO composite electrodes coated on “state of the art” aluminium foil. All cathodes were characterised by scanning electron microscopy, as well as electrochemical methods, and the results were compared. In combination with the main advantages of 3D current collectors such as improved mechanical stability and possibility of higher mass loadings, the 3D structure of the non-woven polymer increases the contact surface by five times compared to conventional current collector foils, reducing the assignment of Al significantly.

Novel Design of Silicon Electrode Based on Stainless Steel Metal Fibril As Current Collector for Lithium-Ion Batteries

Silicon (Si) has been one of the promising anode materials targeting for the next high capacity lithium-ion batteries (LIBs). Lithium ions are reversibly stored in Si based on an alloy mechanism, and thus Si can possess much higher level of theoretical capacity (4,200mAh/g), over 10 times, compared to that of commercial graphite (372mAh/g) [1]. Unfortunately, however, inherent low electric conductivity and poor cell performance has hindered commercialization of Si for a decade.In order to solve these drawbacks, nano-sized and nano-structured silicon has been introduced. In this work, we developed novel design silicon electrode based on stainless steel metal fibril. In order to achieve this goal, we introduced 3-D current collectors based on stainless steel metal fibril (SF) to increase free volume within Si anodes [2] Subsequently, Si coated by radio frequency (RF) magnetron sputtering method. Coating thickness and loading amount of Si active material on SF was controlled around 1μm and 0.2mg/cm2, respectively. Electrochemical performance of as-prepared SF based Si anode was evaluated using charge-discharge machine (PNE, Koran). Surface changes of as-prepared Si anodes were monitored by Scanning Electron Microscope (TOPCOM, japan)-Energy Dispersive X-ray Spectroscopy (AMETEK, USA).

Evaluation of decomposition products of EMImCl·1.5AlCl3 during aluminium electrodeposition with different analytical methods

Ionic liquids are of great importance for electrodeposition of metals, which can't be deposited from aqueous electrolytes due to their negative standard potentials. In this paper non-woven polymers were coated with aluminium by electrodeposition from 1-ethyl-3-methyl-imidazolium chloride and subsequently established as 3D current collectors for lithium-ion batteries. We investigated the long-term stability of the ionic liquid (IL) for electrodeposition of aluminium under process-oriented conditions. The degradation products were analysed by headspace gas chromatography-mass spectrometry, pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS) and 1H/13C nuclear magnetic resonance spectroscopy (NMR). The main decomposition products derived from thermal degradation, especially from cleavage of an alkyl chain and were identified as chloromethane, dichloromethane, methylimidazole, ethylimidazole and deprotonated 1-ethyl-3-methylimidazole.

Silicon Electrode Based On Steel Use Stainless Microfiber Current Collector for Lithium-Ion Batteries

not Available.

Flexible single-walled carbon nanotube/polycellulose papers for lithium-ion batteries

Flexible and highly conductive single-walled carbon nanotube/polycellulose papers (SWCNT/PPs) were developed as current collectors for lithium-ion batteries by a simple and scalable process. The flexible electrodes based on SWCNT/PP conductors consisted of a unique three-dimensional interwoven structure of electrode materials and cellulose fibers with CNTs and exhibited flexibility, good electrochemical performance and excellent cyclic stability. Full cells using Li4Ti5O12 and LiFePO4 electrodes based on SWCNT/PPs showed a first discharge capacity of 153.5 mA h g−1 with Coulombic efficiencies of 90.6% at 0.1 C and discharge capacity of 102.6 mA h g−1 at high rate (10 C). Full cells based SWCNT/PP conductors showed higher capacities and lower electrochemical interfacial resistance compared to metallic current collectors. Half cells using anatase TiO2 hierarchical spheres based on SWCNT/PP conductors also exhibited outstanding electrochemical performance, verifying the stability of SWCNT/PP conductors to various electrode materials. Our results demonstrated the potential versatility of composite electrodes and conductive SWCNT/PPs for flexible and portable micropower devices.

Corrosion/passivation of aluminum current collector in bis(fluorosulfonyl)imide-based ionic liquid for lithium-ion batteries

The corrosion behavior of aluminum foil that is used as the positive current collector for lithium-ion batteries is studied in N-methyl-N-propyl-pyrrolidinium bis(fluorosulfonyl)imide (PMPyr-FSI), which is considered as a highly attractive solvent due to a very low viscosity. This work reports that FSI anion is corrosive for aluminum foil upon anodic polarization (>4.0V vs. Li/Li+). The pitting corrosion is, however, greatly reduced by adding lithium hexafluorophosphate (LiPF6). The anion of the salt is known to be a corrosion inhibitor for aluminum. It likely reacts to generate hydrofluoric acid that then attacks the native aluminum oxide (Al2O3) to produce a strong passivation layer comprising aluminum fluoride (AlF3). Resultantly, the high rate capability, which is the potential merit achievable by using the FSI-containing ionic liquid solvent, can be implemented with a LiCoO2 positive electrode.

Computational and experimental studies of laser cutting of the current collectors for lithium-ion batteries

Sizing electrodes is an important step during Lithium-ion battery manufacturing processes since poor cut edge affects battery performance significantly and sometime leads to fire hazard. Mechanical cutting could result in a poor cut quality with defects. The cutting quality can be improved by using a laser, due to its high energy concentration, fast processing time, small heat-affected zone, and high precision. The cutting quality is highly influenced by operating parameters such as laser power and scanning speed. Thus, we studied a numerical simulation to provide a guideline for achieving clear edge quality. In order to simulate electrodes laser cutting for Lithium-Ion batteries, understanding the behavior of current collectors is crucial. This study focuses on current collectors, such as pure copper and aluminium. Numerical studies utilized a 3D self-consistent mathematical model for laser–material interaction. Observations of penetration time, depth, and threshold during laser cutting processes of current collectors are described. The model is validated experimentally by cutting current collectors and single side-coated electrodes with a single mode fiber laser. The copper laser cutting is laser intensity and interaction time dependent process. The aluminium laser cutting depends more on laser intensity than the interaction time. Numerical and experimental results show good agreement.

Electrochemical Stability of Carbon Fibers Compared to Aluminum as Current Collectors for Lithium-Ion Batteries

The electrochemical behaviors of highly conductive, fully-graphitic, semi-graphitic and non-graphitic carbon fibers were studied as the cathode current collectors of lithium batteries in standard electrolyte (alkyl carbonate/LiPF6) solutions and compared to bare aluminum (Al). All of these current collectors demonstrate a stable electrochemical behavior within the potential range of 2.5 to 5 V, due to passivation by surface films. Carbon fibers have comparable electrochemical stability of Al and may be used in place Al foil. While the carbon fibers do not contribute any irreversible or extra capacity when they are cycled below 4.5 V, for fully-graphitic and semi-graphitic fibers PF−6 intercalation and deintercalation into the carbon fiber may occur when they are cycled at high potentials >4.5 V.

Investigation of Thermal Treatment effect of Anode Current Collectors in Lithium-Ion Batteries

not Available.

Micro-Ploughing Process of Copper Current Collector for Lithium-Ion Battery

A three-dimensional “fin-groove” composite structure copper current collector was fabricated by micro-ploughing process. 3D and common 2D carbon anodes for lithium- ion batteries were prepared. The electrochemical properties of these electrodes were studied by linear sweep cyclic voltammetry (CV) and charge-discharge (C-D) test. 2D anode showed high contact resistance, high coulombic efficiency but poor cycle performance. In contrast, 3D anode showed the structure superiority in reinforcing bonding force between active materials and copper substrate, improving the conductive environment and alleviating volume changes. It was believed that 3D anode can keep high coulombic efficiency and improve the cycle performance of lithium- ion batteries.

Electrochemical behavior and passivation of current collectors in lithium-ion batteries

This paper examines several metals that are commonly employed as current collectors of positive and negative electrodes for rechargeable lithium batteries. Current collectors must be electrochemically stable when in contact with the cell component during the potential operation window of an electrode. Various electrochemical techniques have been used to investigate the corrosion of current collector materials. In practice, continued corrosion of current collectors leads to a gradual increase in the internal resistance of cells, which causes the capacity to fade gradually. Corrosion of the current collector may induce a short-circuit, affecting its safety. Thus, the formation of thick and compact, protective passive film on the metal surface is highly important so as to ensure battery performance and safety. Depending on the salts and additives, different types of protective films are formed. The solubility of these surface layers in the electrolyte is a determining factor in the overall stability of the current collector. In this review, we introduce the electrochemical behavior and protective film formation processes of various metallic current collectors in representative electrolytes.

An Approach to Make Macroporous Metal Sheets as Current Collectors for Lithium-Ion Batteries

A simple method and approach is described to produce macroporous metal sheets as current collectors for lithium-ion batteries. This method is based on slurry blending, tape casting, sintering, and reducing of metal oxides and produces a uniform macroporous metal sheet. As an example, a macroporous copper sheet was prepared and used as the current collector for a silicon thin-film anode material. Such a porous copper substrate allows Si to have a much better adhesion, lower electrical contact resistance, higher capacity, capacity retention, and longer cycle life than on surface-roughened Cu foil and smooth Cu foil. This methodology produces very limited wastes and is also adaptable to many other materials such as Ni porous sheets at an industrial-scale production that is easy to be achieved.

Linear-Sweep Thermammetry Study on Corrosion Behavior of Al Current Collector in Ionic Liquid Solvent

The corrosion behavior of A1 foil as the current collector for lithium-ion batteries is studied by linear-sweep thermammetry. The onset temperature for Al pitting corrosion depends on Li salt that is dissolved in an ionic liquid solvent; lithium bis(trifluo- romethanesulfonyl)imide (LiTFSI) < lithium bis(perfluoroethanesulfonyl)imide (LiBETI) < LiPF 6 < LiBF 4 , With LiBF 4 , no corrosion current is observed until 1 10°C. X-ray photoelectron spectroscopy study reveals that this Al surface is covered by Al-F compound (presumably AlF 3 ). Due to the formation of a highly passivating AlF 3 layer in this electrolyte, the high voltage LiNi 0.5 Mn 1.5 O 4 positive electrode coated on Al foil can be successfully cycled at 65°C without electrode failure.