Corrosion Of Aluminum Current Collector Research Articles

Study of the Corrosion Behavior of Cathode Current Collector in LiFSI Electrolyte.

Cycling aging is the one of the main reasons affecting the lifetime of lithium-ion batteries and the contribution of aluminum current collector corrosion to the ageing is not fully recognized. In general, aluminum is corrosion resistant to electrolyte since a non-permeable surface film of alumina is naturally formed. However, corrosion of aluminum current collector can still occur under certain conditions such as lithium bis(fluorosulfonyl)imide (LiFSI)-based electrolyte or high voltage. Herein, we investigates the corrosion of aluminum current collector in the electrolyte of 1.2 M LiFSI in ethylene carbonate (EC) and ethyl methyl carbonate (EMC) mixed solvents. The electrochemical results shows that the corrosion current of aluminum is enhanced by cycling time and potential, which is correlated with the surface species and morphology. The formation of AlF3, which is induced by deep penetration of F- anions through surface passivation film, leads to internal volume change and the surface crack in the end. Our work will be inspiring for future development of high-energy-density and high-power-density lithium-ion batteries in which the LiFSI salt will be intensively used.

Liquid Structure and Anti-Corrosion Effect of Super-Concentrated Electrolyte Solution

For realizing sustainable world, Lithium-ion batteries are required to have higher energy density. Aluminum metal have been dominantly used as a current collector of positive electrode. A mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC) containing 1 mol dm-3 Lithium hexafluorophosphate (LiPF6) has been used as an electrolyte solution. Aluminum forms thin passivation layer on its surface, preventing the corrosion. However, aluminum corrosion may occur due to this electrolyte solution under high voltage condition. Recently, super-concentrated electrolyte solution (SCES) [1], which consists of only two or three times as much solvent as lithium salt, has been attracting attention as a new electrolyte solution of high-voltage lithium-ion battery. Motsumoto et al. proposed that aluminum corrosion was remarkably suppressed in lithium bis(trifluoromethanesulfonyl)imide (LiTFSI)-based SCES [2]. To clarify the corrosion-inhibiting factor of SCES, we investigated aluminum corrosion in the several lithium salts based SCESs [3]. And we found that lithium perchlorate (LiClO4)-based SCES could suppress corrosion of Aluminum current collector. Liquid structure of the SCES may plays an important role in corrosion suppression. In the present work, we demonstrated Raman spectroscopy and Quantum chemical calculations to reveal the liquid structure of the LiClO4-based SCES.The LiClO4 based SCES was prepared by dissolving LiClO4 into DMC as the molar ratio of 1 : 2. For comparison, DMC solution containing 1 mol dm-3 LiClO4 and neat DMC was also prepared. Raman spectroscopic experiments were conducted using Laser Raman spectrophotometer (NRS-5100, JASCO) installed a laser at 532 nm. Quantum calculations were performed using the Gaussion 9 program suite (Gaussian, USA). Geometry optimization were conducted at the B3LYP/6-311+G(d,p) level. An intensive peak is observed at approximately 915 cm-1 for neat DMC. When a small amount of LiClO4 is added to DMC (corresponding to 1 mol dm-3 LiClO4 solution), new peak is observed at approximately 932 cm-1. This peak can be assigned to ClO4 - anion. A new peak appears at approximately 950 cm-1 with increasing LiClO4 (corresponding to the SCES). According to the Quantum calculations, the new peak is assigned to aggregate in which the ClO4 - cross-links Li+. In addition, HOMO energy of a contact ion pair (CIP), in which ClO4 - coordinates to Li+, is lower than that of free ClO4 - anion. The oxidative stability of ClO4 - increases by forming CIP and aggregate. The decomposition products of ClO4 - may affect the Aluminum corrosion. The high oxidative stability of LiClO4-based SCES may prevent the Aluminum corrosion.

Important Impact of the Slurry Mixing Speed on Water-Processed Li4Ti5O12 Lithium-Ion Anodes in the Presence of H3PO4 as the Processing Additive.

The aqueous processing of lithium transition metal oxides into battery electrodes is attracting a lot of attention as it would allow for avoiding the use of harmful N-methyl-2-pyrrolidone (NMP) from the cell fabrication process and, thus, render it more sustainable. The addition of slurry additives, for instance phosphoric acid (PA), has been proven to be highly effective for overcoming the corresponding challenges such as aluminum current collector corrosion and stabilization of the active material particle. Herein, a comprehensive investigation of the effect of the ball-milling speed on the effectiveness of PA as a slurry additive is reported using Li4Ti5O12 (LTO) as an exemplary lithium transition metal oxide. Interestingly, at elevated ball-milling speeds, rod-shaped lithium phosphate particles are formed, which remain absent at lower ball-milling speeds. A detailed surface characterization by means of SEM, EDX, HRTEM, STEM-EDX, XPS, and EIS revealed that in the latter case, a thin protective phosphate layer is formed on the LTO particles, leading to an improved electrochemical performance. As a result, the corresponding lithium-ion cells comprising LTO anodes and LiNi0.5Mn0.3Co0.2O2 (NMC532) cathodes reveal greater long-term cycling stability and higher capacity retention after more than 800 cycles. This superior performance originates from the less resistive electrode-electrolyte interphase evolving upon cycling, owing to the interface-stabilizing effect of the lithium phosphate coating formed during electrode preparation. The results highlight the importance of commonly neglected─frequently not even reported─electrode preparation parameters.

Performance and ageing behavior of water-processed LiNi0.5Mn0.3Co0.2O2/Graphite lithium-ion cells

In this study, water-processed LiNi0.5Mn0.3Co0.2O2 cathodes (NMC532) are investigated. Notably, corrosion of aluminum current collector occurring in aqueous processing owing to alkalinity of NMC slurry is avoided through addition of phosphoric acid which buffers the slurry pH, or by using a carbon-coated collector. The impact of small amounts of phosphoric acid on the electrochemical performance is evaluated in half-cells, and the best formulations are selected to perform further ageing tests in pouch cells. In particular, post mortem analyses such as electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy are conducted on the cathodes after long-term cycling in Li-ion cells to fully understand the enhanced cycling stability observed with H3PO4-containing water-based cathode. These analyses allow to conclude on the influence of the binder, the current collector, and the aqueous immersion of the NMC532 powder.

Passivation Behavior of Aluminum in a Carbonate-Free Electrolyte Based on Lithium Bis(fluorosulfonyl)imide and Sulfolane

Carbonate-free electrolytes comprising lithium bis(fluorosulfonyl)imide (LiFSI) and sulfolane (SL) (LiFSI/SL) with medium concentrations show excellent cycle stabilities with high Coulombic efficiencies. The high Coulombic efficiencies indicate that there is no corrosion of aluminum current collectors despite the absence of LiPF6. X-ray photoelectron spectroscopy and electrochemical quartz crystal microbalance measurements show that the passivation layer on the aluminum current collector in LiFSI/SL consists of LiF and sulfurous species. The study findings will expand the applicability range of lithium-ion batteries, the current mainstay of sustainable energy sources.

Investigation of Li-Ion Batteries for Fast Charging at Low Temperature

Fast-charging of Li-ion batteries has become a major interest, since it is seen as the strategy of choice to enable a wider adoption of electric vehicles (EVs) by bringing a realistic solution to long-range transit. However, very little is known about how repeated fast-charging affects the battery performances in the long term, and how winter temperatures, more extreme in northern countries such as Canada, may impact the fast charging ability of the battery. Optimization of both the chemistry and the manufacturing parameters are needed to develop EV batteries capable of sustaining repeated fast-charging.The work was carried out during a four years project at the National Research Council of Canada, with the overall objective to get a better understanding of the parameters affecting the ability of a Li-ion battery to charge at high rate and sustain repeated fast-charging, especially at low temperatures.A first set of experiments investigated the comparative fast charging performance of a number of 18650 format commercial cells at various temperatures. Figure 1 shows a table summarizing the ability of 11 of these cells to charge under different regimes at room temperature or -10 °C. Interestingly, the variability in the results seemed to be related to multiple parameters. Also, the capability rating for fast-charging was not the same at ambient, sub-ambient or sub-zero temperatures. Best contenders were repeatedly fast-charged for 300 cycles at various temperatures. Here again the results showed differences in how the cells are able to sustain repeated fast-charging. The cells were then disassembled for an in-depth post-mortem study of the failure modes due to fast-charging. A number of degradation mechanisms were revealed, including macroscopic deterioration of the electrodes at the core of the jelly-roll, aluminum current collector corrosion, exfoliation of graphite and formation of thick SEI films at the anode surface. Figure 2 shows example of results from the post-mortem analysis.In a second set of experiments, the fast-charging performance of selected components was comparatively investigated in laboratory cells, including various active materials, separators and electrolyte formulations. In an example of results to be presented, Figure 3 displays the fast-charging capability of several cathode materials in full cells at 23 and 0 °C. LFP and NCA seem to be the best choices for fast-charging Li-ion cells at ambient temperature whereas LCO shows the lowest performances for rates over C/3. However, LFP showed some limitations at 0 °C, whereas LCO happened to be the best performing cathode. These results clearly show that even if the graphite anode bears the most significant challenges relative to fast-charging, cathode materials should not be overlooked in the optimization of fast-charging capabilities.The third set of experiments, currently being carried out, studies the effects of electrode manufacturing parameters (loading, porosity, N/P ratio) using a pilot-scale pouch cell prototyping line, and supported by model simulations.The presentation will highlight the results of all three sets of experiments, including results from simulation, electrochemical testing and post-mortem analysis, in an attempt to give the audience a comprehensive guidance towards the chemistries and manufacturing parameters of Li-ion cells better suited for fast-charging. Figure 1

In situ crosslinked PMMA gel electrolyte from a low viscosity precursor solution for cost-effective, long lasting and sustainable lithium-ion batteries

To address the shortcomings of current gel electrolytes such as cost, processability, safety and sustainability, we report here on the in situ preparation of a crosslinked gel polymer electrolyte by polymerization of methyl methacrylate with poly(ethylene glycol) dimethacrylate within a liquid electrolyte composed of an ethylene carbonate/propylene carbonate low volatility solvent mixture. Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) is used as main lithium salt since it is stable thermally and vs. hydrolysis, which is advantageous for gel formation and recycling. Aluminum current collector corrosion and the efficient operation of the graphite anode are addressed via the use of lithium bis(oxalato)borate (LiBOB), vinylene carbonate and 1-propene 1,3-sultone as additives. The self-standing elastomeric gel electrolyte allows reaching conductivities close to those of the liquid fraction with a conductivity of 3.9 mS cm−1 at 20 °C probably due to a high mobility as suggested by the glass transition temperature that is almost unaffected by the presence of the polymer. From a processing point of view, the use of methyl methacrylate (MMA) allows decreasing the viscosity of the precursor solution for efficient wetting of the cell components prior to thermal polymerization. The good contact allows cycling graphite/LiMn0.33Ni0.33Co0.33O2 (NMC111) cells with a 2.1 mAh cm−2 areal capacity steadily for hundreds of cycles.

Lithium metal batteries capable of stable operation at elevated temperature

Rechargeable lithium metal batteries have attracted wide attention due to high theoretical energy density. For practical applications, high-temperature performance of lithium batteries is essential due to complex application environments, in terms of safety and cycle life. However, it's difficult for normal operation of lithium metal batteries at high temperature above 55–60 °C using current lithium hexafluorophosphate (LiPF6) electrolyte systems. Herein, a kind of new electrolyte system is designed by adding two thermal-stable lithium salts together (i.e. lithium bis(trifluoromethanesulfonimide) (LiTFSI) and lithium difluoro(oxalato)borate (LiDFOB)) into carbonate solvents with high boiling/flashing point (i.e. ethylene carbonate (EC) and propylene carbonate(PC)). Small amount of LiPF6 is also added to prevent the corrosion of aluminum current collector. The results indicate that the new electrolyte possesses superior high-temperature performance, meanwhile, it effectively suppresses the formation of lithium dendrite by synergy effects of salts and solvents. Li/LiCoO2 cells with high LiCoO2 real capacity (2.4 mAh/cm2) using this kind of new electrolyte shows excellent cycling performance at elevated temperature up to 80 °C. Such performance is achieved for the first time for rechargeable Li metal battery using liquid organic electrolytes. It overcomes the operation temperature upper limit of traditional Li-ion batteries (i.e. 55–60 °C), which would effectively reduce thermal runaway risk and simplify the thermal management of Li metal batteries in reality.

Role of perfluoropolyether-based electrolytes in lithium metal batteries: Implication for suppressed Al current collector corrosion and the stability of Li metal/electrolytes interfaces

The development of safe and high performance lithium metal batteries represents a major technological challenge for this new century. Historically, intrinsic instabilities of conventional liquid organic electrolytes induced battery failures and safety issues that hinder the practical utilization of advanced rechargeable lithium metal batteries. Herein, we report a multifunctional perfluoropolyether-based liquid polymer electrolyte (PFPE-MC/LiTFSI), presenting a unique “anion-solvent” interaction. This interaction optimizes the interfacial chemistry of lithium metal batteries, which effectively inhibits the corrosion of aluminum current collectors, suppresses lithium dendrite growth, and also facilitates the formation of a thin and stable SEI layer on Li anode. Even at a high current density of 0.7 mA cm−2, the lithium dendrites do not form after 1360 h of continuous operation. The LiFePO4|PFPE-MC/LiTFSI|Li cell delivers a stable cycling performance with over 99.9% columbic efficiency either at ambient temperature or high temperature, which is significantly superior to those using traditional carbonate electrolytes. In addition, PFPE-MC/LiTFSI electrolyte also possesses eye-catching properties, such as being non-flammable, non-volatile, non-hygroscopic, and existing in the liquid state between −90 °C and 200 °C, which further ensures the high safety of the lithium metal batteries, making this electrolyte promising for the development of high energy lithium metal batteries.

The Influence of Pre-Treatment Methods of Electrode Material Onaluminum current Collector for EDLC

Background: Serious corrosion in the aluminum current collector occurs when it reacts with electrolyte above the limit voltage. The higher the energy density of an electric double layer capacitor (EDLC), the more it is necessary to understand the aluminum corrosion of the EDLC.Furthermore, in order to study the corrosion of aluminum current collector in EDLC, it is necessary to remove the coated active material from the aluminum. Methods: Physical polishing, Ultrasonic treatment and Heat Treatment are used for removing the active material of the electrode. Findings: The influence of the electrolyte on the aluminum current collector depends on the presence or absence of the active material. The ideal method to remove the active material from an electrode of an EDLC would be by performing ultrasonic treatment for less than 45 seconds after heat treatment at 300 ° C for 10 minutes on the electrode which has been sufficiently cleaned with ethanol avoiding water. Improvements/Applications: In this work, we studied the effect of various treatment methods used for removing electrode active material on Al current collector and proposed the most suitable pre-treatment method to correctly analyze the deterioration of the current collector in the EDLC.

TFSI and TDI Anions: Probes for Solvate Ionic Liquid and Disproportionation-Based Lithium Battery Electrolytes.

Highly concentrated electrolytes based on Li-salts and chelating solvents, such as glymes, are promising as electrolytes for lithium batteries. This is due to their unique properties, such as higher electrochemical stabilities, compliance with high-voltage electrodes, low volatility and flammability, and inertness toward aluminum current collector corrosion. The nature of these properties originates from the molecular-level structure created in either solvate ionic liquids (SILs) or the less common ionic aggregates by disproportionation reactions. The nature of the anion plays a crucial role, and here, we present a computational study using TFSI and TDI anions as probes, revealing increasing differences upon increased salt concentration. TFSI-based electrolytes preferably form SILs, while TDI-based electrolytes form ionic aggregates. The latter lead to an unexpected creation of "free" cationic species even at (very) high salt concentrations and thus promise of ample lithium ion transport.

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.

Chemical Stability of Lithium 2-Trifluoromethyl-4,5-dicyanoimidazolide, an Electrolyte Salt for Li-Ion Cells

Lithium hexafluorophosphate (LiPF6) is ubiquitous in commercial lithium-ion batteries, but it is hydrolytically unstable and corrosive on electrode surfaces. Using a more stable salt would confer multiple benefits for high-voltage operation, but many such electrolyte systems facilitate anodic dissolution and pitting corrosion of aluminum current collectors that negate their advantages. Lithium 2-trifluoromethyl-4,5-dicyanoimidazolide (LiTDI) is a new salt that was designed specifically for high-voltage cells. In this study we demonstrate that in carbonate electrolytes, LiTDI prevents anodic dissolution of Al current collectors, which places it into a select group of corrosion inhibitors. However, we also demonstrate that LiTDI becomes reduced on lithiated graphite, undergoing sequential defluorination and yielding a thick and resistive solid-electrolyte interphase (SEI), which increases impedance and lowers electrode capacity. The mechanistic causes for this behavior are examined using computational chemi...

Electrochemical Properties of Mo Doped High Voltage Cathode for Lithium-Ion Battery

Lithium-ion batteries play an important role in portable electronic devices and e-mobility due to their high gravimetric energy density. However they are not able to meet the growing demand for higher capacity batteries for extended range electric vehicles. Alternatively, lithium-sulfur batteries based on multi-step redox conversion reaction provide a theoretical specific capacity of 1675 mAh/g. However LiS batteries also suffer from many problems, such as severe volumetric expansion/contraction during lithiation/de-lithiation, polysulfide (PS) dissolution and shuttling dendritic lithium growth on the anode, corrosion of aluminum current collector, low sulfur utilization and low current efficiency (CE). In this manuscript, we demonstrate that specific types of sulfur allotropes react differently from standard orthorhombic sulfur used in state of art LiS batteries. Significant improvements are achieved by using sulfur allotropes as both cathode active mass and 3D structural additive. Dissolution of polysulfides is confined within the cathode by the use of a bi-functional additive capable of controlling cathode reaction and the first discharge plateau is extended to deliver a capacity of 408 mAh/g at 0.2C which is close to theoretical limit of 418 mAh/g for long chain PS (Fig.1). Instead of using various methods for controlling PS dissolution and migration which are mostly based on PS binding and interaction with host-catalyst structures, we used a bi-functional additive capable to control both reaction proceeding as well as its kinetics. This method allows PS dissolution but reactions are strictly limited into cathode compartment and cannot proceed outside the cathode. An important aspect of this approach is significantly reduced side-reaction between PS and electrolyte. Fig.1: Comparison of discharge curves of standard electrode and electrode with bi-functional additive 0.7M LiTFSI + 0.25M LiNO3 , DOL/DME 2:1 v/v, active mass S loading bi-additive 1.95 mg/cm2, standard 1.65 mg/cm2 This research has been carried by Graphene Batteries AS in close cooperation with the Centre for Research and Utilization of Renewable Energy (CVVOZE) as a part of collaboration project NPU I programme (project No. LO1210), (project No. FEKT-S-14-2293) Figure 1

Development of Sulfolane-Based Electrolytes for Li-ion batteries

The quest for higher energy density Li-ion batteries pushes toward ‘high voltage’ cathode operating above 4.5V. However, if such materials have been proposed for many years in the case of LiNi0.5 Mn1.5 O4 1 or more recently for LiCoPO4F2, the implementation of such materials is currently prevented by the lack of adapted electrolyte. Several reports deal with high voltage electrolytes such as ionic liquids, dinitrile compounds or fluorinated carbonates. Yet, another class of solvents investigated are the alkyl sulfone, linear3 or cyclic4. Among them, sulfolane, despites its high viscosity has been reported to allow low potential anode operation (such as Li metal or graphite), while other reports point out the high oxidative stability of the electrolytes made thereof4, which was explained based on fundamental studies such as QC5 and MD6. Mixtures of sulfolane seem able to allow room temperature operation of both graphite and high voltage electrodes but no report can be found of a sulfolane-based electrolyte compatible, at the same time, with graphite and a high voltage electrodes. Thus, we examine here the possibility of forming new electrolyte system, based on sulfolane/DMC mixtures for room temperature operation. In particular, the role of the Li salt has been investigated as it is known to play a role on conductivity, via viscosity and dissociation in a solvent system that has a lower dielectric constant and higher viscosity than alkyl carbonate mixtures such as EC/DMC. In addition, keeping the application in mind, SEI building on graphite and aluminum current collector corrosion are also dependent on the Li salt or mixture used. Thus several inorganic and organic Li salts have been investigated in terms of conductivity and electrochemical stability and tested versus graphite and LiNi0.5 Mn1.5 O4 electrodes in a DMC/sulfolane mixed solvent.

Effect of aqueous‐based cathode slurry pH and immersion time on corrosion of aluminum current collector in lithium‐ion batteries

Corrosion of aluminum can occur during the manufacturing of lithium‐ion batteries when using aqueous‐based cathode slurries. In exposure tests, the alkaline pH value of aqueous‐based cathode slurries and immersing time were revealed as the principle factors that control the corrosion of aluminum during the cathode manufacturing process. The nickel manganese cobalt oxide active material used in the slurry does not have a direct impact on corrosion of the aluminum current collector. The initiation and evolution of localized corrosion on aluminum are closely related to the formation of galvanic cells between aluminum matrix and intermetallic particles. X‐ray photoelectron spectroscopy results confirmed that the pH of cathode slurry was the only factor that alters aluminum surface composition, during which the oxide passive film was gradually degraded into hydroxide. Electrochemical characterizations showed that aluminum electrodes gave remarkably different response to the different pH of test solutions. The time‐pH‐variant electrochemical response was ascribed to the change of passive film and electric double layer properties.

Corrosion of Aluminum Current Collectors of Cycle-Life Tested Li-Ion Batteries

The aluminum current collectors from six ATD cells that were commercially fabricated and cycle-life (charge/discharge) tested at 25ºC were microscopically inspected for evidence of corrosion. The results clearly show that aluminum covered with porous cathodes of LiNi0.8Co0.15Al0.5O2 of cycle-life ATD cells cycled at 25{degree sign}C is susceptible to significant underdeposit corrosion in LiPF6-containing battery electrolytes. Aluminum current collectors of uncycled ATD cells contain mechanical pits formed during the attachment of the cathode, but with cycling at 25{degree sign}C there is an increase in percentage pit area, in the number of pits, in pit-size-distribution, and in pit depth, which is a strong evidence of corrosion of Al current collectors of ATD cells. The formation of corrosion pits, corrosion of mechanical pits, and the non negligible amount of aluminum that was found in the electrolytes (~2700 ppm) of cycle-life tested ATD cells explain the significant contribution of corrosion to the power fade and capacity fade and the possibility of mechanical degradation of the cathode as well.

Corrosion of Aluminum Current Collectors in High-Power Lithium-Ion Batteries for Use in Hybrid Electric Vehicles

The aluminum current collectors of 11 cycle-life tested Advance Technology Development (ATD) batteries were investigated for evidence of corrosion. The batteries were commercially fabricated and were charge/discharge cycled at temperatures of 25 and . Our findings clearly show that aluminum current collectors covered with porous cathodes of are susceptible to significant crevice corrosion in ethylene carbonate (EC) ethylmethyl carbonate (EMC) (3:7) with . Aluminum current collectors of uncycled ATD cells contain mechanical pits formed during the attachment of the cathode, but with cycling at there is an increase in percentage of pit area, in the number of pits, in the pit-size-distribution, and in pit depth, which is strong evidence of corrosion of aluminum current collectors of ATD cells. The formation of corrosion pits was confirmed by the presence of corrosion products inside pits and by the pits’ surface morphology. Because corrosion of the aluminum current collectors produces corrosion pits, corrosion of mechanical pits, cracks in the aluminum foil, significant concentrations of aluminum in the ATD electrolytes, and possible mechanical degradation of the cathode, corrosion is expected to significantly effect the battery’s power fade and capacity fade.

Effect of gel electrolytes containing silica nanoparticles on aluminum corrosion

We have investigated corrosion of aluminum current collectors in electrolytes containing LiTFSI salt by chronopotentiometry, cyclic voltammetery, chronoamperometry, electrochemical impedance spectroscopy, and optical microscopy. Open-circuit potentials for cells with gel electrolytes containing silica nanoparticles are relatively stable in comparison to the corresponding baseline liquid, which suggests that the Al/electrolyte interface is more stable in presence of silica nanoparticles. Cyclic voltammetery and chronoamperometry data show that the current density for Li/electrolyte/Al cells with gel electrolytes containing fumed silica was less than that for baseline liquid electrolyte. The Nyquist plot for liquid electrolyte after chronoamperometry is semicircular-like, that is a corrosion reaction occurred. After cell disassembly, black particulates are evident and pits are observed on the aluminum foil. In comparison, no corrosion products are observed for cells containing gel electrolytes, and the Nyquist plots indicate that corrosion does not occur appreciably. Gel electrolytes produce impedance spectra with a large phase lag over a wide frequency range, which is not observed for the baseline liquid electrolyte. These phenomena may be interpreted as a good film-coating behavior associated with gel electrolytes, which results in a lower aluminum corrosion rate.

Corrosion of Aluminum Current Collectors of Cycle-Life Tested Li-Ion Batteries

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