Foil Current Collector Research Articles

Physical and Electrochemical Properties of Transition Metal Oxides with Hollow Structure As Sulfur Host Material for Lithium-Sulfur Batteries

INTRODUCTION Because of its high theoretical energy density, possibly low cost, and environmental friendliness, lithium-sulfur (Li-S) batteries have received a lot of interest. However, the principal disadvantage impeding the success of Li–S batteries lies in the severe leakage and migration of soluble lithium polysulfide intermediates out of cathodes upon cycling caused “shuttle effect”. The loss of active sulfur species incurs significant capacity decay and poor battery lifespans which has prevented it from commercial realization.Several researches have been conducted with an attempt to improve capacity of batteries while maintaining life of the Li-S cellใ including an introduction of nanostructured cathode host materials. Two main approaches have currently been explored a. chemical confinement and b. physical confinement to anchor the lithium poly-sulfide (LiPSs) reaction products durin the charging process. Transition metal oxides such as TiO2 and SnO2 has been studied with a potential material to anchor polysulfides via Lewis acid–base interactions and thus maybe able to chemically confine LiPSs within or on the transition metal oxide. Physical confinement may also be possible by trapping LiPSs within a transition metal oxide host structure e.g. hollow structure and thus help impedes polysulfide dissolution into the electrolyte. In this study, TiO2 and SnO2 are focused to understand the physical and electrochemical properties of sulfur host material with hollow structures. The in situ XAS is also conducted to understand the behavior of the dissolution and migration of long-chain LiPSs intermediates (Li2S x , 4 ≤ x ≤ 8) in the sulfur cathode upon discharge. EXPERIMENTAL The transition metal oxide, TiO2 and SnO2, were successfully synthesized by a templated method. The synthesis process involved four steps, preparation of SiO2 spheres, synthesis of SiO2@transition metal oxide core-shell structure by coating transition metal oxide shell on SiO2 and crystallization by calcination and etching the SiO2@transition metal oxide to form hollow transition metal oxide spheres. Structural properties of the synthesized samples were studied by X-ray diffraction (XRD) using Cu-Kα (λ=1.5418 Å) radiation. Particle morphologies and size of the resulting compounds were observed using a field emission scanning electron microscope. Composite electrodes for electrochemical studies were prepared by doctor blade coating of a slurry compound onto carbon-coated aluminium foil current-collectors. The transition metal oxide and sulfur composite, conductive carbon and PVDF binder were mixed in the ratio of 80:10:10 by weight. Electrochemical characterizations were performed by in 2032 coin cells and Galvanostatic charge-discharge cycling was done between 1.8-3.0 V at 0.1C using a MACCOR Series 4000 at room temperature. RESULTS AND DISCUSSIONS Based on the XRD results, single phase anatase TiO2 and tetragonal SnO2 were both successfully synthesized by the templated method. SEM images (Fig. 1a and 1b) demonstrate that TiO2 and SnO2 are generally spherical structures with nanometer scale dimensions ranging from 250-350 nm and 450-500 nm, respectively. The interior hollow region can be seen clearly in the images of broken spheres. The shelled surface of the synthesized powders is hierarchically made up of interconnected nanocrystals providing a possibly porous structure. Hence, the hierarchically porous and hollow structure has a large surface area for adsorbing the LiPSs distributed in the electrolyte.Fig. 1c shows the charge and discharge voltage profiles of SnO2 and sulfur composite electrode cathode in the first five cycles. Two discharge plateaus were clearly observed, which might be attributed to the two-step sulfur-lithium reaction process. The initial plateau, centered about 2.30 V, was commonly attributed to the reduction of the S8 ring and the formation of S8 2−. The second discharge plateau at 2.10 V was attributed to further reduction of the higher polysulfides (Li2S n , 4 ≤ n ≤ 8) to the lower polysulfides (Li2S n , n ≤ 3). There exhibited two plateaus in the charge process at about 2.25 and 2.35 V, respectively. Electrochemical performance in relations to capacity retention and the in situ XAS to understand the behavior of the dissolution and migration of LiPSs will be discussed in the meeting. Figure 1

Thermoexpandable Microsphere-Coated Al Foil Current Collector for Lithium-Ion Batteries with Improved Safety

Thermoexpandable Microsphere-Coated Al Foil Current Collector for Lithium-Ion Batteries with Improved Safety

Sequential separation of battery electrode materials and metal foils in aqueous media

To recycle high-value lithium-ion battery components, it is imperative to efficiently separate electrode materials from current collector foils and to separate cathodes from anodes. This study investigates the delamination behaviors of cathodes and anodes from their respective current collectors in aqueous media. Whereas anode films can easily detach from copper foils in water, the delamination of cathode films does not exhibit the same behavior in water; instead, the cation exchange reaction results in lithium leaching and aluminum corrosion in the presence of water. A buffer solution with surfactant additives has been designed to prevent aluminum corrosion and to improve solution wetting behavior, thereby facilitating cathode delamination. The delamination difference enables the sequential recovery of electrode materials and metal foils at different separation stages, simplifying the traditionally intricate processes within a one-pot recovery system. The recovered materials retain their crystal structure and morphology, and there are no signs of aluminum corrosion or residues on the metal foils. The sequential separation technique achieves nearly 100% separation efficiency for electrode materials from metal foils and over 98% separation efficiency for cathode and anode materials.

Quantifying the influence of temperature on Al current collector dissolution in LiTFSI-based lithium-ion battery electrolytes via coupled on-line mass analysis

This work portrays the dissolution behavior of aluminum foil current collectors in nonaqueous lithium bis(trifluoromethanesulfonyl)imide (LiTFSI)-based battery electrolytes in greater detail. This is achieved via a setup utilizing an electroanalytical flow cell (EFC) coupled to inductively coupled plasma mass spectrometry (ICP-MS), allowing unprecedented real-time analysis as well as quantification of dissolution. We show that the preparation of Aluminum foil samples drastically influences the reproducibility of measurements. Already gentle cleaning procedures will lead to tiny scratches on the oxide surface, which heavily affect the dissolution behavior of the sample. We also investigate the influence of temperature on dissolution by comparing measurements at 25, 40, and 60 °C. We show that the dissolution at 40 °C is increased by a factor of 1.5 compared to 25 °C and a factor of 3 for 60 °C, respectively. The faradaic efficiency of the Al dissolution process during cyclic voltammetric (CV) measurements is identified to be ∼ 65 – 75%.

Polymer@Cu composite foils with through-hole arrays as lightweight and flexible current collectors for lithium-ion batteries

The current collector is a critical component of lithium-ion batteries (LIBs). Herein, copper-coated polymer films (P@Cu) with through-hole arrays are developed lightweight and flexible current collectors. The through-hole arrays are created by laser drilling the polyimide film substrate. P@Cu composite current collectors are fabricated by electroless Cu deposition on polyimide films with through-hole arrays, which form three-dimensional conductive paths. As the anode current collector for LIBs, P@Cu exhibit a total electrode mass-specific capacity that is 54.58 % higher than that of the commercial Cu foil. Due to the polyimide substrate, the tensile deformation of P@Cu is 6.69 % higher than that of the commercial Cu foil. After 30,000 bending cycles, the conductivity of P@Cu is only reduced by 3.39 %, while the commercial Cu foil current collectors have broken by this point. The P@Cu composite foils with through-hole arrays are high-performance lightweight and flexible current collectors for LIBs.

Influence of the Crusher Settings and a Thermal Pre-Treatment on the Properties of the Fine Fraction (Black Mass) from Mechanical Lithium-Ion Battery Recycling

With the increasing number of electric vehicles (EVs) rises the need to recycle their used lithium-ion batteries (LIBs). During the mechanical process of the recycling of the LIB cells, a fine fraction, the so-called black mass, is created. This black mass consists mostly of the coatings originating from the cells’ electrodes and residues from the electrolyte, together with a low amount of Al and Cu from the crushed current collector foils. The amount of black mass as well as its composition is influenced by the chosen grid size at the crusher discharge. To reduce solvent emissions during the recycling process, a thermal pre-treatment can be added before crushing, which also influences the black mass and its properties due to changes in the adhesion between electrode foils and coating. This study investigates the influence of the crusher settings as well as the pre-treatment temperatures to find an optimum between the recovery of the coating and conductive salt, while limiting the amount of Al and Cu in the black mass.

Overcoming Challenges: Extending Cycle Life of Aqueous Zinc-Ion Batteries at High Zinc Utilization through a Synergistic Strategy.

Aqueous zinc-ion batteries (AZIBs) face challenges in achieving high energy density compared to conventional lithium-ion batteries (LIBs). The lower operating voltage and excessive Zn metal as anode pose constraints on the overall energy storage capacity of these batteries. An effective approach is to reduce the thickness of the Zn metal anode and control its mass appropriately. However, under the condition of using a thin Zn anode, the performance of AZIBs is often unsatisfactory. Through experiments and computational simulations, the electrode structural change and the formation of dead Zn as the primary reasons for the failure of batteries under a high Zn utilization rate are identified. Based on this understanding, a universal synergistic strategy that combines Cu foil current collectors and electrolyte additives to maintain the structural and thermodynamic stability of the Zn anode under a high Zn utilization rate (ZUR) is proposed. Specifically, the Cu current collectors can ensure that the Zn anode structure remains intact based on the spontaneous filling effect, while the additives can suppress parasitic side reactions at the interface. Ultimately, the symmetric cell demonstrates a cycling duration of 900 h at a 70% ZU, confirming the effectiveness of this strategy.

Effect of Laser-Textured Cu Foil with Deep Ablation on Si Anode Performance in Li-Ion Batteries.

Si is a highly promising anode material due to its superior theoretical capacity of up to 3579 mAh/g. However, it is worth noting that Si anodes experience significant volume expansion (>300%) during charging and discharging. Due to the weak adhesion between the anode coating and the smooth Cu foil current collector, the volume-expanded Si anode easily peels off, thus damaging anode cycling performance. In the present study, a femtosecond laser with a wavelength of 515 nm is used to texture Cu foils with a hierarchical microstructure and nanostructure. The peeling and cracking phenomenon in the Si anode are successfully reduced, demonstrating that volume expansion is effectively mitigated, which is attributed to the high specific surface area of the nanostructure and the protection of the deep-ablated microgrooves. Moreover, the hierarchical structure reduces interfacial resistance to promote electron transfer. The Si anode achieves improved cycling stability and rate capability, and the influence of structural features on the aforementioned performance is studied. The Si anode on the 20 μm-thick Cu current collector with a groove density of 75% and a depth of 15 μm exhibits a capacity of 1182 mAh/g after 300 cycles at 1 C and shows a high-rate capacity of 684 mAh/g at 3 C.

Electrochemical Performances of Powder-Impregnated Carbon Fiber-Based Positive Structural Electrodes

Carbon fibers have been in focus within the last decades in designing and constructing lightweight structures. They can be used in a large range of applications such as clothing, transportation gadget, sports materials, as well as in more unusual applications such as batteries. Their mechanical functionality in addition to good electrochemical and electrical features suggest that they can replace battery components such as the graphite anode and the current collector foils. A battery fully based on carbon fibers, often referred to as the structural battery introduced in 2004 by Wetzel et.al. [1], is a multifunctional battery that can carry the load and store the energy simultaneously. An advantage of this battery design is the less overall weight of the device due to eliminating dead mass by removing current collectors and additives from the total structure. Instead, introducing carbon fibers into lithium-ion batteries decreases the non-active mass as well as provides mechanical stability to the system. Carbon fibers show similar electrochemical behavior to graphite, and can therefore be used as negative active material thanks to their capability of reversible lithium intake capacity up to 350 mAh g-1. Furthermore, the fibers have an electrical conductivity of about 1000 S cm-1 and are therefore very suitableas current collectors [2]. Ultimately in structural batteries, also called laminated composite batteries, the carbon fiber-containing electrodes are separated by a structural battery electrolyte (SBE) consisting of a bulk phase (polymer/matrix) that encases the reinforcing between the laminas. The polymer matrix holds the carbon fibers together and transfers the loads to fibers, while carbon fibers carry the load. Figure 1a shows a cross-sectional schematic illustration of a structural battery. The lower lamina corresponds to the negative electrode where the SBE is reinforced with carbon fibers. In the upper lamina, SBE is reinforced with carbon fibers that are coated with a positive electrode material (e.g. LiFePO4 /LFP). A structural battery electrolyte (SBE) has been developed at KTH as a load-carrying polymer matrix that simultaneously conducts ions [3] and that can be combined with the carbon fiber negative electrode material. However, manufacturing the positive structural electrodes is a challenge, as the continuous carbon fibers need to be in close proximity with active materials that should also adhere well to the carbon fibers. In this context, achieving an even distribution of the positive electrode particles is expected to affect many of the structural battery performance metrics, and in particular the electrical, electrochemical and mechanical functionality [2].In this work, we produced positive structural electrodes based on PAN-based carbon fibers with powder impregnation technique in a water-based slurry composition. This technique is not only environmentally friendly but also allows good control of impregnation uniformity and active material/fiber ratio. By this method, continuous carbon fibers were impregnated (i.e., tightly mixed) with active material (LiFePO4) along with electrode components to obtain self-standing positive electrodes. The as-prepared samples show a good and uniform mixing with the active material through interlayers of carbon fibers in tow, leading to a lower internal resistance (SEM images in Figure1c.). The carbon fiber-based positive electrodes have been tested with different electrochemical methods to obtain their performances in half-cells (Figure1b.). The results show promising capacity retention and rate capability.

(Invited) Stable Anode-Free All-Solid-State Lithium Battery through Tuned Metal Wetting on the Copper Current Collector

It is demonstrated that a standard copper foil current collector with appropriately modified surface chemistry will allow for stable lithium cycling in an anode-free all-solid-state lithium battery (AF-ASSB). An argyrodite solid electrolyte Li6PS5Cl (LPSCl) is employed without any modifications or secondary interlayers. The tuned lithophilic copper surface allows for stable plating and stripping, reducing the overpotentials and significantly improving the Coulombic efficiency (CE). During continuous plating experiments using half-cells (1 mA cm-2), the accumulated thickness of electrodeposited Li on Li2Te-Cu is more than 70 μm, which is the thickness of Li foil counter-electrode. Full AF-ASSB with NMC811 cathode delivers an initial CE of 83% at 0.2C, with a cycling CE above 99%. Post-mortem cryo-FIB-SEM analysis demonstrates uniform electrodeposited metal microstructure, with no signs of voids or dendrites at the collector-SE interface. The same copper current collector but unmodified leads to inhomogeneous Li plating, with “dead metal” formation and an irregular honeycomb-like solid electrolyte interphase (SEI) interspersed with pores. Density functional theory and mesoscale calculations provide complementary insight regarding nucleation-growth behavior. Unlike for conventional liquid-electrolyte metal batteries, the role of current collector/support lithiophilicity has not been explored for emerging AF-ASSBs. Figure 1

(Invited) Experimental and Data Analysis Platforms to Better Understand the Corrosion and Discharge of Powdered Zn

Zinc anodes have been a cornerstone of many commercial and pre-commercial battery technologies including primary and secondary alkaline cells, Zn-air batteries and Zn-ion batteries. To maximize the performance of devices at both the lab and commercial scales, moderate surface area (mm-sized) Zn powder is used – either immobilized onto a diffusion electrode or incorporated into a slurry. Unlike nano-sized materials, micron-sized materials are poorly characterized by traditional electrochemical techniques like thin-film rotating disk electrodes, because the roughness introduced by the relatively large particles disrupts the ideal fluid flow near the surface, negating the mathematical description of the electrode behavior. This leads many researchers to try and characterize the Zn behavior in more application-like cells. The downside of doing this is that there is a strong influence of the counter electrode, electrolyte solution and the efficacy of the specific individual in assembling the cells. Therefore, there is a need to develop new platforms that have the ability to determine the electrochemical properties of powdered Zn – most notably achievable capacity and corrosion current – and to develop analytical models to describe their behavior.Over the past several years, our group has been developing new platforms to understand how Zn behaves during discharge and charge, including 1-D cells and cells that mimic the geometry of a primary alkaline battery [1]. However, those platforms have their limitations. In this talk, another new cell, coined the “gravity cell” will be discussed. The gravity cell has a small well where Zn (either as raw powder or in slurry form) is gravity deposited onto an indium foil current collector. Typically, a gel electrolyte is placed on top of the Zn bed, followed by liquid electrolyte, which also contains the counter and reference electrodes. The gravity cell is used to both discharge the Zn powder and to measure its corrosion characteristics. This can be done as a function of mass loading, which introduces limitations into the behavior as the Zn discharges from the Zn/gel interface towards the current collector. This type of discharge, limited by Ohmic resistance, requires new mathematical frameworks to extract the desired parameters. This talk will focus on the design of the cell as well as the derivation of the mathematical framework. Then, data will be shown using several types of Zn powder both in the presence and absence of surfactants that aim to reduce the corrosion rate.

Dry Battery Electrode Manufacturing Enabled By Continuous Powder Mixing

Lithium-Ion Battery electrode manufacturing is a cost- and energy-intensive process that usually relies on the use of a hazardous and expensive solvent, N-methyl-2-pyrrolidone (NMP), for cathodes. After coating the battery-slurry to a current collector, the solvent needs to be evaporated to obtain a porous electrode suitable for the use in a Lithium-Ion Battery. The solvent is a processing material and unwanted in the final product. In fact, solvent residues can fuel parasitic side-reactions within the battery cell and hence deteriorate battery lifetime and safety. The utilization of NMP in battery production plants demands costly labor protection and explosion safety measurements during mixing and coating and necessitates a highly energy and floor-space demanding drying step using thermic drying ovens of up to 100 meters.[1] For ecological and economic reasons, NMP is not emitted in large-scale production facilities, but condensed and recycled by distillation. The NMP-recovery system adds additional floor space and energy demand to the production site. The drying and solvent recovery can account for up to 39% of the total energy demand of a Lithium-Ion Battery Cell production and therefore produce significant CO2 emissions.[2] A solvent-free, dry electrode manufacturing that eliminates the use of solvents hence reduces the floor space, energy demand and cost of a production plant and eases safety and environmental concerns. Different approaches have been reported in the literature to put dry coating into practice,[3],[4] yet most strategies, for example spray coating or brush coating, lack of a feasible implementation into large scale production. In contrast, a dry coating approach that is sometimes referred to as the Maxwell-Process is, according to media reports, currently installed at Tesla’s Gigafactories in Berlin and Austin.[5] In fact, a publicly available teardown of a Tesla 4680 battery cell hints that a dry coated anode could already be used in commercial vehicles.[6] Compared to the state-of-the-art electrode manufacturing process, dry coating requires different polymeric binder systems that form spiderweb-like structures of fine fibrils connecting the electrochemical active particles and the conductive additive particles. PTFE is highly suitable since it is stable towards typical electrolytes and cathode materials and is known to easily form fibrils. These properties are also utilized to produce expanded PTFE membranes like Gore-Tex. The fibril-network in the battery context is primarily formed by a high-shear dry mixing process. The powder mixture is then compressed to a free-standing electrode film (powder-to-film) by a heated rolling mill (calender) and the resulting film is ultimately laminated to a current collector foil (film-to-foil). We demonstrate that a twin screw-extruder can be used to tune the degree of binder-fibrillation during dry-mixing of NMC-based cathode mixtures. Extrusion based mixing allows to use powder mixtures with little amounts of PTFE binder (1 wt%) to produce self-supporting, free-standing cathode films and, ultimately, battery electrodes with high flexibility and sufficient mechanical stability. We show a superior rate-performance and cycling-stability of single-layer pouch cells with dry-coated cathodes compared to cells with wet coated reference electrodes of likewise composition and electrode design. Possible causes for the improved performance focusing on microstructural electrode properties are discussed.[1] Westphal, Bastian G.; Kwade, Arno (2018): Critical electrode properties and drying conditions causing component segregation in graphitic anodes for lithium-ion batteries. In: Journal of Energy Storage 18, S. 509–517.[2] Erik Emilsson, Lisbeth Dahllöf (2019): Lithium-Ion Vehicle Battery Production. IVL Swedish Environmental Research Institute.[3] Duffner, Fabian; Kronemeyer, Niklas; Tübke, Jens; Leker, Jens; Winter, Martin; Schmuch, Richard (2021): Post-lithium-ion battery cell production and its compatibility with lithium-ion cell production infrastructure. In: Nat Energy 6 (2), S. 123–134.[4] Verdier, Nina; Foran, Gabrielle; Lepage, David; Prébé, Arnaud; Aymé-Perrot, David; Dollé, Mickaël (2021): Challenges in Solvent-Free Methods for Manufacturing Electrodes and Electrolytes for Lithium-Based Batteries. In: Polymers 13 (3).[5] https://www.tagesspiegel.de/berlin/tesla-coup-mit-giga-berlin-neue-technologie-soll-wasserverbrauch-minimieren/27244032.html[6] https://www.youtube.com/watch?v=8WPPBhqeekw Figure 1

Electroforming as a Novel One-Step Manufacturing Method of Structured Aluminum Foil Current Collectors for Lithium-Ion Batteries

Conventionally, cathode current collectors for lithium-ion batteries (LIB) consist of an aluminum foil generally manufactured by a rolling process. In the present work, a novel one-step manufacturing method of structured aluminum foil current collectors for lithium-ion batteries by electroforming is introduced. For this, a low-temperature chloride-based ionic liquid was used as an electrolyte and a rotating cylinder out of stainless steel as a temporary substrate. It was shown that the structure of the aluminum foils can be adjusted from dense and flat to three-dimensional by choosing an appropriate substrate rotation speed and current density. Scanning electron microscopy (SEM) and white light interferometry (WLI) were utilized to analyze the foils’ surface morphology, structure and topography. The SEM analysis of the aluminum foils showed that the rolling process produced a foil with small grains, while electrodeposition resulted in foils with different degrees of grain growth and seed formation. This was in total agreement with WLI results that revealed significant differences in terms of roughness parameters, including the peak-to-valley difference Rpv, the root-mean-square roughness Rq and the arithmetic mean roughness Ra. These were, respectively, equal to 6.8 µm, 0.35 µm and 0.279 µm for the state-of-the-art foil and up to 96.6 µm, 10.92 µm and 8.783 µm for the structured electroformed foil. Additionally, cyclic voltammetry (CV) of the aluminum foils was used to investigate their passivation behavior within the typical LIB cathode potential operation window. The strong decrease in the current density during the second cycle compared to the first cycle, where an anodic peak appeared between 4.0 and 4.4 V vs. Li/Li+, demonstrated that passivation occurs in the same manner as observed for commercial Al current collectors.

A method for the reproducible and accurate determination of electrical resistances based on multi-layer joints in lithium-ion batteries

The transition from fossil fuels to renewable energy sources is significantly influenced by the development of energy storage systems such as batteries. One of the crucial steps in the production of lithium-ion batteries is the electrical connection of the individual electrodes by weld seams. Various joining processes, such as laser beam welding or ultrasonic metal welding, are used for this purpose. An important quality feature of the connections is a low electrical joint resistance, which is essential for reducing cell-internal energy losses and avoiding thermal inhomogeneities in the cells.The aim of this work was to determine the electrical resistance of the joint between a stack of foils and an arrester tab. For this purpose, a measuring method was developed and applied to different sample configurations. The influence of different probe tips on the measurement results was compared using single current collector foils and arrester tabs. The measurement of the electrical resistance was possible in the considered range with a maximum relative uncertainty of 2.38%. Using the presented approach made it possible to evaluate the influence of the seam trajectory on the electrical resistance for cell-internal contacting. In addition, the measuring method is suitable for comparing different welding strategies and, thus, for designing the cell-internal joining processes regarding the resulting electrical joint resistances.

Enhancing electrochemical properties of commercial lithium titanate using cuprous chloride nanoparticle-modified copper foil current collectors

For the first time, CuCl nanoparticles were fabricated at ambient temperature onto the surface of a copper (Cu) foil current collector through using an immersing approach, in which the immersing solution only contained 0.6 M CuSO4 and a very small amount of hexadecyl trimethyl ammonium chloride (HTAC). For simplicity, all as-prepared CuCl nanoparticles modified copper foils were labeled as CuCl/Cu. The specimens of CuCl/Cu prepared in the presence of 4 mM, 8 mM and 12 mM HTAC were designated as specimen a, b and c, respectively. The lithium titanate (Li4Ti5O12, LTO) electrodes assembled using the as-prepared CuCl/Cu exhibited an outstanding electrochemical performance as compared to the conventional LTO electrode manufactured using the commercial bare copper foil. Such as, the initial discharge capacity (DC) value of the LTO electrode assembled using specimen b at 0.2 C was measured to be 216 mAh g−1, which was about 1.3 times that of the conventional LTO electrode (165 mAh g−1). More importantly, at 10 C after 100 cycles, the DC value of the LTO electrode assembled using specimen b was retained to be as high as 143 mAh g−1, being about 3.1 times higher than that of the conventional LTO electrode (46 mAh g−1). A room temperature immersing approach for preparing CuCl nanoparticles and a novel method to significantly improve the electrochemical behavior of the conventional LTO electrode are developed in this work, which is very meaningful not only to the development of CuCl related material science but also to the further progress of LTO based lithium ion batteries (LIBs).

Targeting new ways for large-scale, high-speed surface functionalization using direct laser interference patterning in a roll-to-roll process

Direct Laser Interference Patterning (DLIP) is used to texture current collector foils in a roll-to-roll process using a high-power picosecond pulsed laser system operating at either fundamental wavelength of 1064 nm or 2nd harmonic of 532 nm. The raw beam having a diameter of 3 mm @ 1/e 2 is shaped into an elongated top-hat intensity profile using a diffractive so-called FBS®-L element and cylindrical telescopes. The shaped beam is split into its diffraction orders, where the two first orders are parallelized and guided into a galvanometer scanner. The deflected beams inside the scan head are recombined with an F-theta objective on the working position generating the interference pattern. The DLIP spot has a line-like interference pattern with about 15 μm spatial period. Laser fluences of up to 8 J cm−2 were achieved using a maximum pulse energy of 0.6 mJ. Furthermore, an in-house built roll-to-roll machine was developed. Using this setup, aluminum and copper foil of 20 μm and 9 μm thickness, respectively, could be processed. Subsequently to current collector structuring coating of composite electrode material took place. In case of lithium nickel manganese cobalt oxide (NMC 622) cathode deposited onto textured aluminum current collector, an increased specific discharge capacity could be achieved at a C-rate of 1 °C. For the silicon/graphite anode material deposited onto textured copper current collector, an improved rate capability at all C-rates between C/10 and 5 °C was achieved. The rate capability was increased up to 100% compared to reference material. At C-rates between C/2 and 2 °C, the specific discharge capacity was increased to 200 mAh g−1, while the reference electrodes with untextured current collector foils provided a specific discharge capacity of 100 mAh g−1, showing the potential of the DLIP technology for cost-effective production of battery cells with increased cycle lifetime.

Stable High-Capacity Elemental Sulfur Cathodes with Simple Process for Lithium Sulfur Batteries.

Lithium sulfur batteries are suitable for drones due to their high gravimetric energy density (2600 Wh/kg of sulfur). However, on the cathode side, high specific capacity with high sulfur loading (high areal capacity) is challenging due to the poor conductivity of sulfur. Shuttling of Li-sulfide species between the sulfur cathode and lithium anode also limits specific capacity. Sulfur-carbon composite active materials with encapsulated sulfur address both issues but require expensive processing and have low sulfur content with limited areal capacity. Proper encapsulation of sulfur in carbonaceous structures along with active additives in solution may largely mitigate shuttling, resulting in cells with improved energy density at relatively low cost. Here, composite current collectors, selected binders, and carbonaceous matrices impregnated with an active mass were used to award stable sulfur cathodes with high areal specific capacity. All three components are necessary to reach a high sulfur loading of 3.8 mg/cm2 with a specific/areal capacity of 805 mAh/g/2.2 mAh/cm2. Good adhesion between the carbon-coated Al foil current collectors and the composite sulfur impregnated carbon matrices is mandatory for stable electrodes. Swelling of the binders influenced cycling retention as electroconductivity dominated the cycling performance of the Li-S cells comprising cathodes with high sulfur loading. Composite electrodes based on carbonaceous matrices in which sulfur is impregnated at high specific loading and non-swelling binders that maintain the integrated structure of the composite electrodes are important for strong performance. This basic design can be mass produced and optimized to yield practical devices.

Impact of Electrode Architecture on Electrochemical Performance of Aqueous Processed, High‐Loaded Lithium‐Ion Battery Cathodes

AbstractThis study compares two electrode architectures, one with a porous carbon current collector (PC) and the other with a state‐of‐the‐art aluminum foil current collector (AF). The results show that the porous carbon outperforms the aluminum foil at high loadings (∼8 mAh/cm2) during cycling, likely due to better adhesion. The characterization methods used in the study include electrochemical cycling, electrochemical impedance spectroscopy (EIS), galvanostatic intermittent titration technique (GITT), and scanning electron microscopy (SEM). These methods provide insight into the performance of the two electrode architectures and allow for a comprehensive comparison between them. The findings of this study indicate that the use of porous carbon as a current collector can lead to improved performance in high‐loading electrode applications, making it a promising alternative to traditional aluminum foil current collectors.

Directing High-Efficiency Na Plating with Carbon–Aluminum Junction Interfaces for Anode-Free Na Metal Batteries

Anode-free sodium metal batteries are highly promising for future energy storage but suffer from much faster cycling degradation as they are sensitive to even trace levels of irreversible side reactions. This work focuses on the most practical Al foil current collectors and systematically examined the effect of nanosized carbon coating on improving the Na plating and stripping stability. We identified that the carbon–Al junction interface generated by carbon coating enabled more uniform Na deposition with lower overpotentials, delivering higher than 99.8% Faradaic efficiencies for a wide range of cycling currents between 0.5 and 3.0 mA cm–2. This performance is much better than the 96.4% efficiency observed on uncoated Al foils under the same conditions and is also confirmed under lean electrolyte and freezing electrolyte conditions and can be attributed to the stronger interfacial binding and enhanced sodiophilic properties of the carbon–aluminum junction sites. These sites not only ensure uniform Na plating but also eliminates side reactions that would otherwise cause electrolyte depletion. As a result, Na-metal free full cells assembled with a high capacity Na3V2(PO4)3 cathode delivered ∼93% capacity retention for 100 cycles, higher than the ∼42% of retention of uncoated Al foil.

Automated geometry characterization of laser-structured battery electrodes

Micro structuring of battery electrodes with pulsed laser radiation substantially increases the performance of lithium-ion batteries. For process design and monitoring, determining the resulting hole diameters and depths is essential. This study presents an automated, model-based approach for the geometry characterization of laser-drilled structures in battery electrodes. An iteratively re-weighted least squares algorithm is used for fitting of a reference plane to confocal laser scanning microscopy images of laser-structured electrodes. Using a threshold-based segregation of the generated weights, the holes are segmented from the pristine electrode surfaces. The results from the automated geometry determination were found to coincide well with manual measurements. By reducing the image resolution, the runtime of the code could be decreased, which yet lowered the accuracy of the hole depth prediction. In a sensitivity analysis, the algorithm performed stably under changes in the recording conditions, such as altered image brightness, frame rate, or vertical resolution. In conclusion, the presented method reduces the effort and increases the reproducibility for analyzing large experimental data sets in laser electrode structuring. Furthermore, the approach can be successfully transferred to other applications, which is demonstrated by indentations in battery current collector foils stemming from electrode calendering.