Current Collector Materials Research Articles

Unlocking self-discharge: Unveiling the mysteries of electrode-free Zn-MnO2 batteries with advanced in situ techniques in mild acid aqueous electrolytes

We introduce a novel approach to Zinc-MnO2 battery architecture utilizing a 3D network of carbon nanofibers as both current collector and electrode material, promising enhanced performance and longevity for large-scale energy storage. Employing mild aqueous electrolytes, we address the challenge of managing self-discharge, crucial for short-term energy storage. Advanced coupled characterization techniques, including in-situ EQCM (Electrochemical Quartz Crystal Microbalance) and high-resolution optical microscopy, elucidate self-discharge mechanisms across over multiple length scales. Findings reveal that the self-discharge is mainly at the zinc electrode due to concomitant dissolution of Zinc (corrosion) and HER (Hydrogen Evolution Reaction) phenomena. Interestingly, the corrosion current was estimated irrespective of charging protocol and remains consistent, indicating the independence of zinc corrosion kinetics from the length scale. Finally, the morphology of the zinc layer appears to be critical, suggesting that self-discharge is primarily a chemical process. This innovative design strategy offers the potential for high-performance Zinc-MnO2 batteries with extended cycle life to meet the requirements of large-scale energy storage applications.

Corrosion of stainless steel and molybdenum used as PCC in Na//Sb-Bi liquid metal batteries under cycling conditions

Material compatibility is a major challenge in the development of liquid metal batteries. In this study, the corrosion behavior of two candidate positive current collector materials, austenitic stainless steel and molybdenum, in Na//SbBi9 liquid metal batteries is investigated. In-situ corrosion in operating cells is compared with static corrosion in SbBi9 (corresponding to the fully charged state) and Na0.30Sb0.07Bi0.63 (representing the fully discharged state) at 450 °C. Stainless steel shows a much better corrosion resistance in Na-Sb-Bi alloy (corrosion depth below 1 μm after 750 h static exposure) than in SbBi9 (7–9 μm corrosion layer) thanks to the formation of a thin oxide layer. The corrosion under cycling conditions shows similar characteristics (formation of solid Fe-Cr-Ni-Sb compounds), though accelerated, as static exposure to SbBi9. Molybdenum exhibits a very good corrosion resistance both in static and in cycling conditions, showing merely a minor dissolution into the adjacent alloy.

Electrophoretically deposited nickel titanate/CNT composite as promising anode for lithium/sodium ion batteries

In this study, we have demonstrated that electrophoretically fabricated NiTiO3 (NTO)/CNT composite is a viable negative electrode for lithium and sodium ion batteries, with favorable electrochemical performance. NTO/CNT exhibited initial discharge capacity of 1032 mAhg−1 and 751 mAhg−1 at 100 mAg−1 with a retained capacity of ∼ 412 mAhg−1 and ∼ 180 mAhg−1 even after 100 cycles against lithium and sodium ion respectively. CNT helps in buffering the volume fluctuations by giving structural stability and enables good cycle life performance. Also such good performance can be ascribed to the porous microstructure, good adherence property with the current collector and uniform active material distribution with carbon black and CNT on the deposited film.

Optimizing Electrodeposition of Polyaniline on Various Woven Steel Mesh Sizes for Enhanced Supercapacitor Performance.

The development of efficient supercapacitors hinges on the innovation of superior electrodes, which are pivotal in augmenting their energy storage capabilities. Supercapacitors, recognized for their high-power density and extended cycle life, play a crucial role as sustainable solutions in addressing energy storage challenges. A fundamental aspect of supercapacitor functionality involves the electrode material, which works in concert with other key components such as the current collector, separator, and electrolyte. This study focuses on evaluating the impact of the current collector material on the performance of symmetric supercapacitors. We investigated the electropolymerization of polyaniline on woven steel mesh current collectors of varying mesh sizes, ranging from 20 to 200 mesh per inch, using assorted deposition conditions. The electrochemically modified woven steel meshes were utilized to construct symmetric supercapacitors. The electrochemical performance of the assembled supercapacitors, configured in a two-electrode system, was investigated using a variety of electrochemical techniques to better understand the kinetics of electrolyte ion migration. Notably, the 20-mesh size, characterized by the fewest pores per inch, demonstrated superior performance with an optimum capacitance of 4730 mF/cm2, an energy density of 317.8 μWh/cm2, and a power density of 400 μW/cm2 at a current density of 1 mA/cm2.

Electrodeposition of Nanotwinned Cu Foils with Different Microstructures

In recent years, electric vehicles have been considered one of the most forward-looking industries in the world. In 2023, electric vehicles have occupied 16% of the light vehicle sales market. The expansion of the electric vehicle market is expected due to the goal of 2050 net zero emissions. This has led to increased performance requirements for automotive lithium batteries (LIBs). In general, copper foil is an important material for LIB anode current collector. Since The volumetric expansion during the charge-discharge cycles of LIBs introduces significant stress, the resulting large stress may damage the copper foil at the anode, causing the battery to eventually fail. Therefore, the mechanical properties of the copper foil need to be enhanced. In this study, different organic additives are added during electrodeposition to increase the mechanical strength of the nanotwinned copper (NT-Cu) foil while still maintaining good electrical conductivity. With organic additive B, the ultimate tensile strength (UTS) can be increase to 750 MPa, yield strength (YS) to 550 MPa, with an increase of 66% and 74 % compared to the Cu foils fabricated by additive A, and the international annealed copper standard (IACS) remains at 83.7%. Facilitated by focused ion beam (FIB), in the case of organic additive A, its microstructure is columnar nanotwin copper, and for additive B, its microstructure is a mixture of columnar nanotwin copper and fine grains. The difference of the microstructure contributes to the additional strength. Furthermore, linear sweep voltammetry (LSV) analysis is used to illustrate the relationship between type of additives, tensile strength, and reduction potential. Figure 1

Controlling Current Distribution in Slurry Electrolytes for Redox Flow Batteries

Slurry electrodes have the potential to decouple the power and storage capacities of hybrid redox flow batteries1 (RFB). In more commonly studied true RFB chemistries, such as all-vanadium, the power and storage capacities can be considered separately2; the power capacity is dependent on the flow cell design while the storage capacity is dependent on the amount of positive and negative electrolyte that can be stored. These decoupled capacities allow true RFB’s to be highly scalable. However, in hybrid RFB chemistries, such as all-iron, solid metal is deposited within the flow cell during charge, limiting the storage capacity of the battery based on the geometry of the flow cell3. This limitation can be addressed by incorporating a slurry electrode in the negative electrolyte. By depositing the reduced metal on this mobile dispersion of electrically conductive carbon particles, hybrid redox RFB’s may achieve high scalability while utilizing less expensive materials, such as iron or zinc1,4. To successfully augment the scalability of hybrid RFB’s, the current distribution of the metal deposition reaction must occur predominantly on the mobile slurry electrode, rather than on the stationary current collector. This current distribution is dependent on numerous factors, including the electrical conductivity of the slurry electrode, the ionic conductivity of the electrolyte, the kinetics of the faradaic reaction, and mass transfer to both the stationary current collector and to the slurry particles. In this work, we explore three approaches to controlling the current distribution in slurry electrodes. In the first approach, we explore the utility of slurry electrodes consisting of multiple types of carbon particles. Our earlier work has shown that slurries of varying carbon type can have significantly different electrochemical performance5. Slurries consisting of carbon black particles with high specific surface area can minimize the kinetic resistance of the faradaic reactions but struggle to distribute current away from the current collector due to their low electrical conductivity. Meanwhile, slurries consisting of more electrically conductive, but lower surface area graphitic particles can facilitate faradaic current away from the current collector but may not minimize kinetic resistance to the same degree. By using a slurry electrode consisting of mostly graphitic particles with a small portion of high surface area carbon black, the faradaic current may be kinetically facile in addition to well distributed through the slurry. In the second approach, we explore options to hinder the ionic conductivity of the electrolyte. The faradaic current distribution through the slurry electrode depends heavily on the competition between the ionically and electronically conductive routes. Typically, the ionic conductivity is heavily favored due to the desire for high per-volume energy density and the low pH required to keep the metallic reactants soluble. By hindering the ionic conductivity of the electrolyte, either by utilizing viscosity increasing additives or by lessening the ionic concentration, the faradaic current may be better spread through the slurry. In the third approach, we explore options for controlling the current distribution via varying reaction kinetics on various electrode surfaces. While considerable work6,7 has been done comparing the reaction kinetics of homogeneous redox reactions on various electrode materials (glassy carbon, basal/edge plane graphite, platinum...) relatively little work has been done regarding metal deposition reactions. By changing the current collector material to one with poor deposition kinetics relative to the slurry electrode material, the current distribution may be enhanced on the slurry.(1) Petek, T. J. Enhancing the Capacity of All-Iron Flow Batteries: Understanding Crossover and Slurry Electrodes. Ph.D. Thesis 2015, No. May.(2) Weber, A. Z.; Mench, M. M.; Meyers, J. P.; Ross, P. N.; Jeffrey, T.; Liu, Q. Redox Flow Batteries, a Review. J. Appl. Electrochem. 2011, 41 (10), 1–72. https://doi.org/https://doi.org/10.1007/s10800-011-0348-2.(3) Dinesh, A.; Olivera, S.; Venkatesh, K.; Santosh, M. S.; Priya, M. G.; Inamuddin; Asiri, A. M.; Muralidhara, H. B. Iron-Based Flow Batteries to Store Renewable Energies. Environ. Chem. Lett. 2018, 16 (3), 683–694. https://doi.org/10.1007/s10311-018-0709-8.(4) Petek, T. J.; Hoyt, N. C.; Savinell, R. F.; Wainright, J. S. Slurry Electrodes for Iron Plating in an All-Iron Flow Battery. J. Power Sources 2015, 294, 620–626. https://doi.org/10.1016/j.jpowsour.2015.06.050.(5) Tam, V.; Wainright, J. Electrochemical Behavior of Low Loading Slurry Electrodes for Redox Flow Batteries. J. Electrochem. Soc. 2023, 170 (1), 010538. https://doi.org/10.1149/1945-7111/acb10a.(6) Mccreery, R. L.; Mcdermott, M. T. Comment on Electrochemical Kinetics at Ordered Graphite Electrodes. Anal. Chem 2012, 84. https://doi.org/10.1021/ac2031578.(7) Chen, P.; McCreery, R. L. Control of Electron Transfer Kinetics at Glassy Carbon Electrodes by Specific Surface Modification. Anal. Chem. 1996, 68 (22), 3958–3965. https://doi.org/10.1021/ac960492r. Figure 1

Comparative Investigation of Large-Scale Cells of Supercapacitors Using Low-Temperature Electrolytes

The implementation of the concept of sustainable development for humanity, the advancement of alternative energy, hybrid and electric transport, and backup power supply systems, necessitate the creation of efficient energy storage devices. Such systems include lithium-ion, nickel-metal hydride, and redox flow batteries, where Faraday processes play a crucial role in energy storage mechanisms. One notable advantage of double-layer supercapacitors (SCs) as energy storage devices is the absence of Faraday processes during charge and discharge [1,2]. Moreover, the absence of Faraday processes, the rate of which sharply decreases with decreasing temperature, makes SC cells practically the only devices where power and energy features can potentially be maintained at a sufficient level at extremely low temperatures, down to minus 70-80°C [3]. The demand for developing energy storage systems capable of operating at extreme temperatures without extensive thermal control, such as space avionics systems, electric aircraft, uncrewed aerial vehicles, and electric and hybrid electric vehicles, is growing.Various methods have been adopted today to improve the performance of supercapacitors at low temperatures [4,5]. The central aspect in this direction is electrolytes, which have the most critical impact on the supercapacitor performance at these temperatures. While many investigations have been conducted on laboratory cells, a comparative analysis of the electrochemical characteristics of cells based on the developed electrolytes (non-aqueous electrolytes) was carried out to understand the correlation between laboratory and large-scale manufactured SC cells.The electrolyte mixture was prepared using organic substances: acetonitrile (AN), ethyl acetate (EA), toluene (TL), diethyl ether (DE), and vinylene carbonate (VC). A 1.2 M solution of salt TEMA TFB was used to prepare the electrolyte. Test electrolyte mixtures were prepared by adding the test additive in the amount of 5, 10, 15, and 20 vol% for DE and TL and 0.1, 1, 3, and 5 vol% for VC to the AN: EA (3:1 by volume %) mixture. These co-solvents were chosen due to their low melting point, relatively low viscosity, and moderate dielectric constant values.A comprehensive investigation of the physical-chemical and electrochemical properties demonstrates that additives to the electrolyte mixture can extend the lower boundary of the operating temperature range down to −68°C, providing good electrochemical characteristics of the cells: capacitance and stability during long-term cycling [6].To understand the behavior of developed electrolytes in large-scale SC cells, manufactured large-scale SC cells (LSC) with a standard initial capacitance of 1500F were used. Figure 1a shows the capacitance change of large-scale SC cells based on electrolyte mixture AN: EA (3:1), AN: EA (3:1) +3%VC, AN: EA (3:1) +10%DE, and AN: EA (3:1) +10%TL at +25°C. It is evident that the capacitance of LSC-based SC is nearly maintained for more than 1000 charge-discharge cycles at a temperature of +25°C, demonstrating better performance than laboratory cells. Equivalent measurements were also carried out on the self-discharge of LSC-based SC cells (Fig. 1d), showing only a slight voltage drop for just over 2 days.This behaviour indicates high resistance to various electrochemical processes, such as electrochemical decomposition of the activated electrode material and electrolyte compound,corrosion of the current-collector material,undesirable Faraday redox processes. Notably, the leakage current for large-scale cells is lower than for small (laboratory) cells, enhancing the capacitance retention ability for large-scale cells. Figure 1. Cycle-life stability (a, b, c) and self-discharge behavior (d) of the LSC cells based on electrolyte mixtures at temperatures of 25 °C (a, d), -60 (b) and -65 (c).For all samples, an increase in capacitance is observed as the number of charge-discharge cycles increases (Fig.1). This is likely due to the high current value (50A) used for large-scale cells, causing Joule heating in the cell structures, and increasing the temperature of the electrolyte mixture by several degrees.Tests of the developed electrolytes as part of laboratory SC cells and large-scale industrially produced SC cells confirmed their high resource stability during 10,000 cycles of continuous charge-discharge at a current density of 1.5 A/g, including at a temperature corresponding to the upper limit of the operating temperature range. Additionally, the resistance of SCs with these electrolytes to self-discharge was demonstrated, showcasing the possibility of a "cold start" of SC elements at a temperature of –60 °C.

Constructing Three-Dimensional Architectures to Design Advanced Copper-Based Current Collector Materials for Alkali Metal Batteries: From Nanoscale to Microscale.

Alkali metals (Li, Na, and K) are deemed as the ideal anode materials for next-generation high-energy-density batteries because of their high theoretical specific capacity and low redox potentials. However, alkali metal anodes (AMAs) still face some challenges hindering their further applications, including uncontrollable dendrite growth and unstable solid electrolyte interphase during cycling, resulting in low Coulombic efficiency and inferior cycling performance. In this regard, designing 3D current collectors as hosts for AMAs is one of the most effective ways to address the above-mentioned problems, because their sufficient space could accommodate AMAs' volume expansion, and their high specific surface area could lower the local current density, leading to the uniform deposition of alkali metals. Herein, we review recent progress on the application of 3D Cu-based current collectors in stable and dendrite-free AMAs. The most widely used modification methods of 3D Cu-based current collectors are summarized. Furthermore, the relationships among methods of modification, structure and composition, and the electrochemical properties of AMAs using Cu-based current collectors, are systematically discussed. Finally, the challenges and prospects for future study and applications of Cu-based current collectors in high-performance alkali metal batteries are proposed.

The study of electrochemical stabilization mechanism of Pt, GC, SS304, Ti and Cu as current collectors for aqueous lithium-ion batteries by electrochemical approaches

This paper employs electrochemical methods (linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS)) to investigate the electrochemical behavior of platinum, glassy carbon, 304 stainless steel, titanium, and copper in 21 and 1 M LiTFSI electrolytes. The LSV results indicate that the electrochemical stability window of the materials varies with the electrolyte concentration, and the stability window is wider in the high-concentration system. Through Tafel polarization curves and EIS analysis, the overpotential of the charge exchange process differs due to the type of material and the concentration of the electrolyte, mainly attributed to the influence of the proportion of free water, electrolyte viscosity, and SEI film formation on electrode process kinetics. After comparative analysis, glassy carbon exhibits a higher overpotential than other materials at both the cathode and anode, effectively suppressing water decomposition. These findings provide theoretical support for the development of high-performance aqueous lithium-ion battery current collector materials.

Fabrication of a Porous Copper/Graphite/Zirconium Oxide Hybrid Anode via Screen Printing for Lithium‐Ion Batteries

AbstractRedesigning anode structures in Li‐ion batteries (LIBs) has been a focus of research aimed at surpassing the energy density of conventional LIBs. Although anode‐free LIBs present a promising architecture, their low Coulombic efficiency is a major drawback. This paper introduces a novel hybrid anode that integrates the current collector (CC) and active materials into a single, cohesive porous structure, which supports both de/intercalation and de/plating reactions. The hybrid anode consists of a porous Cu matrix with embedded ZrO2 powders and graphite; the quantity of graphite is only a third of that present in a traditional graphite anode. The porous structure and additives enhance the electrochemical performance of the hybrid anode by minimizing the Li–electrolyte interactions, forming a stable solid–electrolyte interface and Li4Zr3O8 passivation layer, and reducing the nucleation overpotential. Especially, the unique surface morphology, characterized by a negative curvature between sintered Cu particles, lowers the diffusion potential, which further reduces the nucleation overpotential. Additionally, the periodic mesh‐imprinted top surface, created via screen printing, promotes uniform Li plating. The results demonstrate that the cycling performance and energy density offered by the fabricated hybrid anode are superior to those of conventional graphite anodes.

Flexible Aqueous Cr-Ion Hybrid Supercapacitors with Remarkable Electrochemical Properties in all Climates.

The integration of hostless battery-like metal anodes for hybrid supercapacitors is a realistic design method for energy storage devices with promising future applications. With significant Cr element deposits on Earth, exceptionally high theoretical capacity (1546 mAh g-1), and accessible redox potential (-0.74 V vs. reversible hydrogen electrode) of Cr metals, the design of Cr anodes has rightly come into our focus. This work presents a breakthrough design of a flexible Cr-ion hybrid supercapacitor (CHSC) based on a porous graphitized carbon fabric (PGCF) substrate prepared by K2FeO4 activation. In the CHSC device, PGCF acts as both a current collector and cathode material due to its high specific surface area and superior conductivity. The use of a highly concentrated LiCl-CrCl3 electrolyte with high Cr plating/stripping efficiency and excellent antifreeze properties enables the entire PGCF-based CHSC to achieve well-balanced performance in terms of energy density (up to 1.47 mWh cm-2), power characteristics (reaching 9.95 mW cm-2) and durability (95.4 % capacity retention after 30,000 cycles), while realizing it to work well under harsh conditions of -40 °C. This work introduces a new concept for low-temperature energy storage technology and confirms the potential application of Cr anodes in hybrid supercapacitors.

Flexible Aqueous Cr‐Ion Hybrid Supercapacitors with Remarkable Electrochemical Properties in all Climates

AbstractThe integration of hostless battery‐like metal anodes for hybrid supercapacitors is a realistic design method for energy storage devices with promising future applications. With significant Cr element deposits on Earth, exceptionally high theoretical capacity (1546 mAh g−1), and accessible redox potential (−0.74 V vs. reversible hydrogen electrode) of Cr metals, the design of Cr anodes has rightly come into our focus. This work presents a breakthrough design of a flexible Cr‐ion hybrid supercapacitor (CHSC) based on a porous graphitized carbon fabric (PGCF) substrate prepared by K2FeO4 activation. In the CHSC device, PGCF acts as both a current collector and cathode material due to its high specific surface area and superior conductivity. The use of a highly concentrated LiCl−CrCl3 electrolyte with high Cr plating/stripping efficiency and excellent antifreeze properties enables the entire PGCF‐based CHSC to achieve well‐balanced performance in terms of energy density (up to 1.47 mWh cm−2), power characteristics (reaching 9.95 mW cm−2) and durability (95.4 % capacity retention after 30,000 cycles), while realizing it to work well under harsh conditions of −40 °C. This work introduces a new concept for low‐temperature energy storage technology and confirms the potential application of Cr anodes in hybrid supercapacitors.

Freestanding Films of Reduced Graphene Oxide Fully Decorated with Prussian Blue Nanoparticles for Hydrogen Peroxide Sensing.

Developing thin, freestanding electrodes that work simultaneously as a current collector and electroactive material is pivotal to integrating portable and wearable chemical sensors. Herein, we have synthesized graphene/Prussian blue (PB) electrodes for hydrogen peroxide detection (H2O2) using a two-step method. First, an reduced graphene oxide/PAni/Fe2O3 freestanding film is prepared using a doctor blade technique, followed by the electrochemical deposition of PB nanoparticles over the films. The iron oxide nanoparticles work as the iron source for the heterogeneous electrochemical deposition of the nanoparticles in a ferricyanide solution. The size of the PB cubes electrodeposited over the graphene-based electrodes was controlled by the number of voltammetric cycles. For H2O2 sensing, the PB10 electrode achieved the lowest detection and quantification limits, 2.00 and 7.00 μM, respectively. The findings herein evidence the balance between the structure of the graphene/PB-based electrodes with the electrochemical performance for H2O2 detection and pave the path for developing new freestanding electrodes for chemical sensors.

Integrated Textile Supercapacitors Enhanced with Energy‐Absorbing Spacer Fabrics and Ti3C2Tx MXene

AbstractThe rapid development of wearable electronics requires energy storage devices capable of withstanding both static and dynamic deformations. The versatility of textile supercapacitors renders them promising candidates, but their low electrochemical performance especially under mechanical deformation, poses many limitations for practical use. In this study, MXene‐based textile supercapacitors are designed and fabricated using hierarchical spacer fabrics as the skeleton to provide robust mechanical support and stable performance. Ti3C2Tx MXene is adopted as the current collector and active material for the spacer fabric supercapacitor, resulting in an impressive areal capacitance of 415 mF cm−2 with a MXene loading of 4.2 mg cm−2. Remarkable stability and durability are achieved in the form of three‐dimensional (3D) textile supercapacitors, even under both static and dynamic deformations. The compressive behaviors of these supercapacitors can be easily adjusted (e.g., from 10 to 168 KPa at 50% compression) by altering the spacer fabric structure, demonstrating their energy‐absorption (damping of kinetic energy) capability and their potential to meet the requirements of various wearable applications.

Role of Interface Strain and Chemo-Mechanical Effects during Electroplating in Sodium Metal Battery Anodes.

In this study, we demonstrate that elastic strain applied to a current collector can influence the overall thermodynamic and kinetic picture of sodium metal electrodeposition and hence the performance of a sodium metal battery. To controllably study the role of strain in electrochemical performance, we utilize NiTi foil as a stable current collector, nucleation interface, and superelastic material. Our findings demonstrate that a locked-in elastic tensile strain near 8% results in 40 mV lower onset potential for sodium electrodeposition, 19% decrease in charge transfer resistance, and 20% lower cumulative sodium loss, among other effects. These performance improvements are correlated primarily to the control of the irreversible behavior in the first few minutes of electroplating. Given the prevalence of strain buildup in commercial battery cell configurations, our work highlights that strained current collector interfaces can result in significant long-term chemo-mechanical performance outcomes broadly relevant to sodium and other metal battery design considerations.

Insights into self-discharge processes of Al-graphite batteries

Aluminum graphite dual ion batteries (AGDIB) have been widely explored thanks to abundant electrode materials, a long cycle life and high power density. However, the shelf life of AGDIBs is so far barely understood. This work's detailed self-discharge investigations allow the quantification of capacity losses for up to 4 weeks, confirm a deintercalation mechanism by Raman spectroscopy and X-ray diffraction, and furthermore give insight to influence factors. While a cell employing typical materials such as a natural graphite cathode, Mo current collector and AlCl3/[EMIm]Cl=1.5 ionic liquid electrolyte exhibits a capacity loss of 10 % in 24 h, this value can be significantly reduced to 3 % in 24 h when using a glassy carbon current collector and AlCl3/Et3NHCl=1.5 electrolyte instead. Iron impurities within the electrolyte do not affect battery capacities or self-discharge, since it is deposited on the Al anode within the battery soon after assembly. In general, the instability of the current collector material, gas evolution due to electrolyte oxidation at high cell potentials, and cationic electrolyte species greatly influence the self-discharge independently. Electrolyte speciation changes directly related to self-discharge processes are revealed by IR spectroscopy.

Phytic-Acid-Modified Copper Foil as a Current Collector for Lithium-Ion Batteries

Electrolytic copper foil is ideal for use in the anode current collectors of lithium-ion batteries (LIBs) because of its abundant reserves, good electrical conductivity, and soft texture. However, electrolytic copper foil is prone to corrosion in electrolytes and weak bonding to the anode substance. Surface modification of copper foil is considered an effective method of improving the overall electrochemical performance of LIBs. In this study, a 5 nm thickness phytic acid (PA)-based film is constructed on electrolytic copper foil using a fast electrodeposition process (about 10 s). PA-treated copper foil (PA-Cu) displays an improved corrosion resistance in electrolytes because of a strong complexation between the PA and copper. It is found that PA-treated copper foil also bonds better with graphite particles compared with pristine copper foil. LIBs with PA-Cu foils as their current collectors exhibit enhanced cycling stability, improved capacity retention, and superior rate performance at both low and high current densities. Our study offers a novel avenue for the development of high-performance electrode current collector materials for LIBs.

Challenges and Breakthroughs Towards the Development and Optimisation of a Zero Excess Li-S Battery

There is currently a large demand to produce batteries and energy storage devices offering both improved volumetric and gravimetric energy densities to help prevent the catastrophic effects of climate change. One promising candidate is the lithium-sulfur (Li-S) chemistry due to the high theoretical capacity and abundance of sulfur. However, current designs require a 1000% excess of Li metal which impedes their commercialisation. An area gaining momentum is the development of “anode-free” or zero excess lithium (ZEL) cells which minimise inactive materials and mitigate the challenges of handling Li metal foils during fabrication. So far, most studies involving anode-free have been based on the Li-ion chemistry and there are significantly fewer systematic studies concerning ZEL Li-S cell fabrication and optimisation. However, nearly all fall short of targets required for commercialisation.Here we present the development of an Li2S ZEL cell composed of a Li2S/C65/SBR positive electrode material paired with a metallic current collector. The design allows for a Li-limited LiS battery where Li-ions are reversibly plated and stripped to a metallic current collector surface. We initially investigate the effects of electrolyte volume :Li2S mg (ES) ratio, conductive carbon loading, C-rate capacity dependency, various current collector materials and positive electrode substrates. The optimised cell achieves good capacity retention with a Coulombic efficiency of over 98% after 50 cycles, and a final capacity of 400 mAh g-1.Previous studies have shown difficulties in achieving consistent results and are often distorted by a large volume of conductive carbon present in the cathode substrate [1, 2]. Therefore, investigations into capacity losses stemming from the cathode are presented using a range of air-tight characterisation techniques. The performance is also closely correlated to the efficiency of reversible Li deposition onto the metallic current collector, as evaluated by comparison to the use of Li negative electrodes. In the ZEL set up, losses from dead Li formation and SEI instability result in permanent loss of Li inventory with no reservoir to replenish. To counter this, initial investigations attempting to apply an ionically conductive coating to the metal current collector surface are shown.[1]. S. Nanda, A. Gupta and A. Manthiram, Adv. Energy Mater., 2018, 8, 2–7.[2]. S. Nanda, A. Bhargav and A. Manthiram, Joule, 2020, 4, 1121–1135.

Development and Testing of Innovative Carbon Nanotubes/ Copper Composite Foils, Towards Lighter and Mechanically Improved Anode Current Collector for Lithium-Ion Batteries

Up to now, copper is an essential material for lithium-ion battery industry as preferential candidate for anode current collectors due to its high conductivity, low price, and electrochemical stability in the working potential range of the anodic electroactive material. However, such component, accounting for 8.1% of the battery total weight, does not participate in any energy storage processes. [1] Thus, the trend is in this industry is to decrease the weight as well as the thickness of the collector foil to optimize the gravimetric energy of the whole lithium-ion battery system. It is therefore of interest to explore the development of lighter current collectors with equal/improved mechanical and electrical properties.Nanocarbon materials such as Multi-Wall Carbon Nanotubes (MWCNTs) and Single-Wall Carbon Nanotubes (SWCNTs) display a combination of performances, namely high electrical conductivity, low density and high mechanical stability, of a high interests to be combined with copper as innovative lightweight current collectors. Such nanocarbon/copper composite represents a valid alternative to foster the rapid change the battery technology is undergoing.In 2013, Subramaniam et al. [2] reported the fabrication of a Copper /Carbon nanotubes (Cu-CNTs) composites with a similar specific conductivity than that of copper and an ampacity increased by two orders of magnitude. Moreover, Arai et al. have shown, by Electrochemical impedance analysis, that MWCNTs additive in a copper matrix can serve as preferential electron conduction pathway inside a Lithium-ion battery anode. [3]Recently, a new promising and scalable way to fabricate nanocarbon/copper composite has been demonstrated by our team. The process involved the coating of MWCNTs by a dispersing agent, namely the Polydopamine biopolymer, their spraying, and finally the electrochemical plating of metallic copper inside the porosity of the MWCNTs network.[4]Following similar approach, the present work exhibits the fabrication of a free standing MWCNTs/ Copper composite current collector foil of a thickness of 9 µm, a value reaching the industrial standards required by the Lithium-ion battery market players for the next generation cells.[5] Scanning Electron Microscopy and Transmission Microscopy have been used to investigate the interaction between the copper matrix and the carbonaceous reinforcement additive. Figure 1. displays a cross section of nanocarbon/copper composite obtain via Focused Ion Beam slicing, where homogeneous mixing of copper and carbon phases down to nanoscale is highlighted. Such experiments contribute to the understanding of the copper nucleation mode on modified MWCNTs which remains insufficiently controlled to this day.Nanoindentation technique and electromechanical tensile testing bench were combined to study the mechanical properties of such material to be used under mechanical stress as battery collector. In contrary to conventional indentation technique where the mechanical properties of micro-size area are probed, indentation at nanoscale allow the probing of the local mechanical heterogeneity of a composite material. Using such technique, the fabricated self-standing nanocarbon/copper composite was shown to display average hardness and Young modulus close to those of pure carbon (3.5 GPa and 152 GPa respectively).Electrochemical performances of the composite as anode battery collector are under test into pouch and coin-cells battery architecture. The adhesion strength between the electrode slurry and the nanocomposite substrate material is expected to be reinforced by the addition of a nanocarbon. A focus was made on the impact of the use of this new collector material on the cycling stability of typical Lithium-ion battery commercial mixture. Preliminary results indicate that the Cu/MWCNT composite is a promising current collector material to withstand the expansion/contraction imposed by the working cycles of a rechargeable Lithium-ion battery.[1] Zhu, P. Gastol, D. Marshall, J. Sommerville, R. Goodship, V. Kendrick, E. J Power Sources, 485, 229321 (2021)[2] Subramaniam, C. Yamada, T. Kobashi, K. Sekiguchi, A. Futaba, Yumura, D. N. Hata, K. Nat Commun,4, 2202 (2013).[3] Shimizu, M. Ohnuki, T. Ogasawara, T. Banno, Arai, S., RSC Advances, 9(38), 21939-21945 (2019)[4] Duhain, A. Guillot, J. Lamblin, G. Lenoble, D., RSC Advances,11(63), 40159-40172 (2020)[5] Copper Foil Market, Straits Research, 9.5.2.3.(2022)Figure 1. Scanning Electron Microscopy imaging of the cross section of MWCNTs/Copper composite with a thickness lower than 3 µm – 7kV acceleration, 45° tilt.. Figure 1

Fast Ionic Actuators with Silver–Silver Chloride Electrodes and a Mixed Ionic Liquid Electrolyte

Excellent conductivity makes silver (Ag) an attractive electrode and current collector material for a variety of devices, also promising faster soft actuators. However, high reactivity challenges the use of Ag in electrochemical systems, as dendritic growth can create undesired conduction pathways and short‐circuit the oppositely polarized electrodes. The challenge of rapid Ag electrochemical migration is addressed using a mixed mixed‐room temperature ionic liquid (RTIL) system (l‐ethyl‐3‐methylimidazolium bis‐(trifluoromethylsulfonyl)‐imide and trihexyl(tetradecyl)phosphonium chloride) that prevents short‐circuiting by engaging the produced Ag+ ions with Cl− anions. The stability of the system is demonstrated on an ionic actuator using Ag–silver chloride (AgCl) electrodes and a mixed‐RTIL electrolyte. The work demonstrates fast (in 5 s) transfer of a large (0.2 C cm−2) charge to high‐specific‐surface‐area carbon without observable dendritic growth in cycling and good electromechanical performance: 4° s−1 deflection rate at 0.8 V s−1 scan rate. Simple spray‐deposition of the Ag–AgCl electrodes promises scalable and cost‐effective fabrication. The combination of high stability and vast charge capacity encourages the engagement of Ag‐based electrodes for many electrochemical applications involving organic electrolytes also beyond robotics.