Battery Electrodes Research Articles

Lithium Plating Characteristics in High Areal Capacity Li-Ion Battery Electrodes.

Li-ion battery degradation and safety events are often attributed to undesirable metallic lithium plating. Since their release, Li-ion battery electrodes have been made progressively thicker to provide a higher energy density. However, the propensity for plating in these thicker pairings is not well understood. Herein, we combine an experimental plating-prone condition with robust mesoscale modeling to examine electrode pairings with capacities ranging from 2.5 to 6 mAh/cm2 and negative to positive (N/P) electrode areal capacity ratio from 0.9 to 1.8 without the need for extensive aging tests. Using both experimentation and a mesoscale model, we identify a shift from conventional high state-of-charge (SOC) type plating to high overpotential (OP) type plating as electrode thickness increases. These two plating modes have distinct morphologies, identified by optical microscopy and electrochemical signatures. We demonstrate that under operating conditions where these plating modes converge, a high propensity of plating exists, revealing the importance of predicting and avoiding this overlap for a given electrode pairing. Further, we identify that thicker electrodes, beyond a capacity of 3 mAh/cm2 or thickness >75 μm, are prone to high OP, limiting negative electrode (NE) utilization and preventing cross-sectional oversizing the NE from mitigating plating. Here, it simply contributes to added mass and volume. The experimental thermal gradient and mesoscale model either combined or independently provide techniques capable of probing performance and safety implications of mild changes to electrode design features.

Rational Design of Flexible, Self-Supporting, and Binder-Free Prussian White/KetjenBlack/MXene Composite Electrode for Sodium-Ion Batteries with Boosted Electrochemical Performance.

Due to their cost-effectiveness, abundant resources, and suitable working potential, sodium-ion batteries are anticipated to establish themselves as a leading technology in the realm of grid energy storage. However, sodium-ion batteries still encounter challenges, including issues related to low energy density and constrained cycling performance. In this study, a self-supported electrode composed of Prussian white/KetjenBlack/MXene (TK-PW) is proposed. In the TK-PW electrode, the MXene layer is coated with Prussian white nanoparticles and KetjenBlack with high conductivity, which is conducive to rapid Na+ dynamics and effectively alleviates the expansion of the electrode. Notably, the electrode preparation method is uncomplicated and economically efficient, enabling large-scale production. Electrochemical testing demonstrates that the TK-PW electrode retains 74.9% of capacity after 200 cycles, with a discharge capacity of 69.7 mAh·g-1 at 1000 mA·g-1. Furthermore, a full cell is constructed, employing a hard carbon anode and TK-PW cathode to validate the practical application potential of the TK-PW electrode.

Nafion-protected Na3V2 (PO4)3 electrodes for aqueous zinc-ion batteries: A breakthrough in dissolution resistance and electrochemical enhancement

The field of zinc-ion batteries requires advancements in electrode materials and configurations for improved performance and longevity. This research focuses on Na3V2 (PO4)3 (NVP) as a cathode material for aqueous zinc-ion batteries, addressing its dissolution in Zn(CF3SO3)2 electrolytes. A protective Nafion coating was applied using a dip coating technique, with the optimal 20% Nafion solution yielding a 32-µm thick coating. EDS analysis confirmed 16.75% Zn insertion, and EIS analysis showed charge-transfer resistances of 10 O (bare) and 30 O (coated). The Nafion-coated NVP demonstrated enhanced electrochemical performance, achieving nearly 90 mAh/g over 55 cycles with 98% capacity retention. This performance surpasses existing benchmarks, highlighting the potential of Nafion-coated NVP in zinc-ion batteries. This work underscores the transformative potential of Nafion-coated NVP in zinc-ion battery technology, providing a pathway for more durable and efficient energy storage solutions.

Purification of Spherical Graphite as Anode for Li-Ion Battery: A Comparative Study on the Purifying Approaches.

Graphite is a versatile material used in various fields, particularly in the power source manufacturing industry. Nowadays, graphite holds a unique position in materials for anode electrodes in lithium-ion batteries. With a carbon content of over 99% being a requirement for graphite to serve as an electrode material, the graphite refinement process plays a pivotal role in the research and development of anode materials for lithium-ion batteries. This study used three different processes to purify spherical graphite through wet chemical methods. The spherical graphite after the purification processes was analysed for carbon content by using energy-dispersive X-ray (EDX) spectroscopy and was evaluated for structural and morphological characteristics through X-ray diffraction (XRD), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) analyses. The analyses results indicate that the three-step process via H2SO4-NaOH-HCl cleaning can elevate the carbon content from 90% to above 99.9% while still maintaining the graphite structure and spherical morphology, thus enhancing the surface area of the material for anode application. Furthermore, the spherical graphite was studied for electrochemical properties when used as an anode for Li-ion batteries using cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) measurements. The results demonstrated that the purification process significantly improves the material's capacity with a specific capacity of 350 mAh/g compared to the 280 mAh/g capacity of the anode made of spherical graphite without purification.

An Efficient FEniCS implementation for coupling lithium-ion battery charge/discharge processes with fatigue phase-field fracture

Accurately predicting the fatigue failure of lithium-ion battery electrode particles during charge–discharge cycles is essential for enhancing their structural reliability and lifespan. The fatigue failure of lithium-ion battery electrode particles during charge–discharge cycles poses a significant challenge in maintaining structural reliability and lifespan. To address this critical issue, this study presents a mathematical formulation for fatigue failure in lithium-ion batteries, utilizing the phase-field approach to fracture modeling. This approach, widely employed for fracture failure analysis, offers a comprehensive framework for capturing the complex interplay between mechanical deformation, chemical lithium concentration, and crack formation. Specifically, an additive decomposition of the strain tensor is employed to account for the swelling and shrinkage effects induced by lithium diffusion. Moreover, open-source code (https://github.com/noiiG) is provided, constituting a convenient platform for future developments, e.g., multi-field coupled problems. The developed chemo-mechanical model undergoes fatigue failure package is written in FEniCS as a popular free open-source computing platform for solving partial differential equations in which simplifies the implementation of parallel FEM simulations. Several numerical simulations with two different case studies corresponding to monotonic charge process and fatigue charge/discharge process are performed to demonstrate the correctness of our algorithmic developments.

Construction of High-Performance Anode of Potassium-Ion Batteries by Stripping Covalent Triazine Frameworks with Molten Salt.

Covalent triazine frameworks (CTFs) are promising battery electrodes owing to their designable functional groups, tunable pore sizes, and exceptional stability. However, their practical use is limited because of the difficulty in establishing stable ion adsorption/desorption sites. In this study, a melt-salt-stripping process utilizing molten trichloro iron (FeCl3) is used to delaminate the layer-stacked structure of fluorinated covalent triazine framework (FCTF) and generate iron-based ion storage active sites. This process increases the interlayer spacing and uniformly deposits iron-containing materials, enhancing electron and ion transport. The resultant melt-FeCl3-stripped FCTF (Fe@FCTF) shows excellent performance as a potassium ion battery with a high capacity of 447 mAh g-1 at 0.1 A g-1 and 257 mAh g-1 at 1.6 A g-1 and good cycling stability. Notably, molten-salt stripping is also effective in improving the CTF's Na+ and Li+ storage properties. A stepwise reaction mechanism of K/Na/Li chelation with C═N functional groups is proposed and verified by in situ X-ray diffraction testing (XRD), ex-situ X-ray photoelectron spectroscopy (XPS), and theoretical calculations, illustrating that pyrazines and iron coordination groups play the main roles in reacting with K+/Na+/Li+ cations. These results conclude that the Fe@FCTF is a suitable anode material for potassium-ion batteries (PIBs), sodium-ion batteries (SIBs), and lithium-ion batteries (LIBs).

Establishing Li-acetylide (Li2C2) as functional element in solid-electrolyte interphases in lithium-ion batteries

Previously, lithium-acetylide (Li2C2) had been identified as electrolyte degradation product on lithium-metal based electrodes using Raman spectroscopy. This raised the question, if Li2C2 is also be formed on graphitic electrodes in lithium-ion batteries without lithium metal present. In order to shed light on this research question, we performed a series of in situ Raman experiments with graphitic electrodes in half- and full-cell configuration. The recorded cell potential dependent spectra clearly prove the presence of Li2C2 in the lithiated state of the electrodes, but the according peak vanishes when delithiating. This observation indicates a somewhat reversible process involving Li2C2. Several chemical/electrochemical reactions are in question to contribute to this effect. With respect to its properties and potential role in the solid-electrolyte interphase (SEI) DFT calculations of Li2C2-nanoclusters were performed, which revealed an exceptionally low energy band gap, hence a remarkable electric conductivity. In conjunction with a relatively high ionic conductivity, Li2C2 appears to play a key role in the degradation of lithium-ion batteries, which had not yet been revealed nor taken into account in simulations of the interphase.

Determination traction-separation parameters and its sensitivity analysis of bilinear cohesive zone model through experimental and numerical peeling analysis of electrodes

The optimization of traction-separation parameters within the cohesive zone model (CZM) is crucial for accurately simulating electrode peeling failure in lithium-ion batteries. This study performed 180° peeling tests on NCM electrodes and used Abaqus software alongside the sim-flow optimization tool for simulation analysis, aiming to accurately replicate the failure behavior at the lithium-ion battery electrode interface. Experimental results were used to determine the fracture energy of the electrode interface, while numerical simulations analyzed the peeling performance of the electrode. By fitting the force-displacement curves from both simulation and experiment, the traction-separation parameters within the bilinear CZM were optimized. Additionally, the study analyzed the effects of traction-separation parameters, as well as the modulus and thickness of the current collector, on peeling behavior. The results showed that a significant increase in the interface stiffness and strength increased the steady-state peeling force. Among these, the fracture energy had the most significant influence on the steady-state peeling force. Furthermore, while the modulus and thickness of the current collector affected the maximum peeling force, their effect on the steady-state peeling force was negligible. These findings enhance the accuracy of simulating the failure behavior of the electrode interface.

4D Tomography for neutron depth profiling applications

High-rate Neutron Depth Profiling (NDP) is a very efficient and precise probe for studying the evolution of lithium concentration in thin-layer structures, e.g., battery electrodes. NDP is typically limited to a one-dimensional depth analysis summed over the profile area covered by the neutron beam. We developed a detector system based on double-sided silicon strip detectors (DSSSD) with extremely thin and homogeneous entrance windows to provide a new quality of NDP measurements in 3+1 dimensions for the N4DP instrument at the FRM II in Garching, Germany. Using the 6Li(n, α)3H reaction in an experiment conducted at the research reactor in Delft, we achieved a lateral position resolution down to ∼100μm and an energy resolution with FWHM≈10keV for the triton particles at energies of 2.7MeV. High-resolution 3D pictures with a contrast uncertainty <10% per pixel can be achieved faster than 1 picture per minute. This rate can be adjusted individually for each experiment by sacrificing granularity in the position measurement.

DANOISE; A 3D Printable Battery Cell for Laboratory Operando X‐Ray Diffraction and Absorption Spectroscopy**

AbstractStudying structural and electronic processes in the materials inside a battery as they occur during battery operation is key for developing novel improved materials for future generations of batteries. Such studies often entail X‐ray diffraction and absorption spectroscopy, which have so far primarily been conducted at synchrotron facilities despite the widespread use of laboratory‐based X‐ray diffraction and absorption spectroscopy for day‐to‐day characterisation. With the “Developed in Aarhus: New Operando In‐house Scattering Electrochemical” (DANOISE) cell, these experiments are brought into the laboratories making in‐house operando X‐ray diffraction and absorption spectroscopy on‐demand additions to the existing facilities. The chic and facile design of the DANOISE cell provides high quality scattering and absorption data besides providing reliable electrochemical performance. In this work, we describe the design of the DANOISE cell and demonstrate the capabilities of the cell using different commercial technologies for Li‐ion batteries and from a new Na‐ion battery electrode material.

A Flexible Na‐Ion Supercapacitor/Battery Hybrid Device

AbstractA hybrid supercapacitor/battery device is proposed by integrating Na3V2(PO4)2F3 and multi‐walled carbon nanotubes as the battery electrode and carbon nanofiber as a supercapacitor electrode. The device made via the slurry casting of electrode material on foldable thin nickel foils leads to a robust, mechanically flexible sodium‐ion capacitor/battery (supercapattery) as a hybrid energy storage system. The device exhibits a specific capacitance of 136 F g−1 with a corresponding specific capacity of 95 C g−1 at a potential scan rate of 1 mV s−1, a maximum working voltage of 0.70 V, and a power density of 15 kW kg−1 at 2.50 Wh kg−1. Mechanical flexibility tests show practically unperturbed electrochemical properties at significant bending angles of up to 160°, indicating excellent robustness during large‐scale device deformation. The current study offers new avenues to develop energy storage systems for next‐generation portable and wearable energy storage devices that can be integrated into a variety of platforms.

Iodine- and nitrogen-CO-doped carbon flower materials for the anode electrode of lithium-ion batteries

As green anode materials with wide distribution, controllable cost, and diversified structure, carbon materials have received more attention. In this paper, iodine- and nitrogen-co-doped carbon flower materials were prepared. The flower-like structure of the material ensures the rapid diffusion of lithium ions, and the synergistic effect of iodine and nitrogen atoms improves the pore size distribution, the conductivity and the active sites of carbon materials realizing the high ion storage and the fast charge diffusion. As the anode material of lithium-ion batteries, the iodine- and nitrogen-co-doped carbon flower could have the capacitance of 410 mAh g[Formula: see text] at the current density of 0.1 A g[Formula: see text] after 150 cycles and 181 mAh g[Formula: see text] at the high current density of 2.0 A g[Formula: see text] after 1000 cycles. The results of electrochemical impedance spectroscopy, kinetics, and GITT show this material has fast charge transport kinetics and excellent rate performance.

Recent Progress in our Understanding of the Degradation of Carbon‐Based Electrodes in Vanadium Redox Flow Batteries – Current Status and Next Steps

AbstractThis mini‐review summarises and discusses recent findings form the literature on the degradation of carbon‐based electrodes for vanadium redox flow batteries (VRFBs). It becomes evident that the focus of current investigations is on carbon paper, carbon felt and graphite felt electrodes, which is understandable from a practical point of view. However, the structural complexity of these materials often prohibits doubtless attribution of observed performance reduction (or increase) to changes in the electrode materials. Among the discussed major causes for degradation are formation or change of surface functional groups, changes in the carbon sp2/sp3 ratio, intercalation of ions as well as formation of inhibiting adsorbates. In order to gain deeper insight into the changes of carbon electrodes in VRFBs under relevant operation conditions, the authors suggest reducing complexity of the investigated materials and applying in situ‐studies under well‐defined and controllable conditions on model electrodes. These studies then should be extended towards more practical systems and may finally help to reduce degradation phenomena including enhanced overvoltages and thus could improve cycling and energy efficiency as well as long‐term stability of vanadium redox flow batteries.

Influence of Carbonisation Temperatures on Multifunctional Properties of Carbon Fibres for Structural Battery Applications

AbstractCarbon fibres are multifunctional materials considered for the realisation of structural battery electrodes. Processing conditions affect the carbonaceous microstructure of carbon fibres. The microstructure dictates the fibre‘s mechanical properties, i. e. modulus and strength, as well as its electrochemical capacity. Here, carbon fibre processing conditions are investigated to identify the effect of carbonisation temperature on carbon fibre multifunctionality. Different thermal conditions during carbonisation are considered, while keeping the precursor material, applied tension, and oxidation temperature constant. The carbonaceous microstructure of fibres is investigated via wide‐angle x‐ray scattering (WAXS) and transmission electron microscopy (TEM) analyses to determine the effect of the carbonisation temperature. Mechanical and electrochemical tests are performed to characterise carbon fibre multifunctionality with respect to mechanical and electrochemical performance. A moderate trade‐off between mechanical and electrochemical performance is demonstrated, where the elastic modulus and strength decrease and the electrochemical capacity increase with reduced carbonisation temperature. Here, for the studied temperature interval, the elastic modulus and strength is found to drop up to 7 % with a 15 % increase in capacity. Thus, fibres customised for targeted multifunctionality within a limited design space can be realised by careful selection of the processing conditions in conventional carbon fibre manufacture.

Online detection and identification of cathode cracking in Lithium-ion battery cells

Cyclic charging and discharging of Lithium-ion (Li-ion) battery cells lead to the contraction and expansion of the battery electrodes. These contractions and expansions result in the development of internal stresses within the electrodes, further culminating in the growth of cracks. Typically, the cracks in anodes lead to an increase in the surface area hence facilitating a faster SEI layer growth, and a lot of research to model such faults has already been conducted in this area. However, when it comes to cracks in the cathode, the research is still a little under-explored. Not detecting the potential cathode crack growth may lead to quick degradation of battery cells which results in capacity fade or resistance growth. If these kinds of faulty batteries are not detected, it may result in hazardous scenarios like battery fires even during nominal usage. Therefore, the real-time monitoring of these cathode cracks is essential for health-conscious battery operation. This paper is an attempt to design such real-time monitoring algorithm that can detect and identify crack growths in the cathode. The algorithm is developed by fusing a variation of the Single Particle Model (SPM) capturing Lithium concentration dynamics in the cathode and an empirical model capturing crack growth — in conjunction with real-time feedback-based coupled filters. The coupled filter consists of two filters working in cascade where the first filter generates a primary residual based on cathode SPM and terminal voltage feedback. Subsequently, the second filter utilizes this primary residual as feedback in conjunction with the empirical crack growth model — ultimately producing an estimate of the crack growth. This estimated crack growth is used to detect and identify the cathode cracking mechanism. Proposed approach is tested with experimental as well as simulation studies, illustrating its effectiveness.

Radical Polymer-based Positive Electrodes for Dual-Ion Batteries: Enhancing Performance with γ-Butyrolactone-based Electrolytes.

Dual-ion batteries (DIBs) represent a promising alternative for lithium ion batteries (LIBs) for various niche applications. DIBs with polymer-based active materials, here poly(2,2,6,6-tetramethylpiperidinyl-N-oxyl methacrylate) (PTMA), are of particular interest for high power applications, though they require appropriate electrolyte formulations. As the anion mobility plays a crucial role in transport kinetics, Li salts are varied using the well-dissociating solvent γ-butyrolactone (GBL). Lithium difluoro(oxalate)borate (LiDFOB) and lithium bis(oxalate)borate (LiBOB) improve cycle life in PTMA||Li metal cells compared to other Li salts and a LiPF6- and carbonate-based reference electrolyte, even at specific currents of 1.0 A g-1 (≈10C), whereas LiDFOB reveals a superior rate performance, i. e., ≈90 % capacity even at 5.0 A g-1 (≈50C). This is attributed to faster charge-transfer/mass transport, enhanced pseudo-capacitive contributions during the de-/insertion of the anions into the PTMA electrode and to lower overpotentials at the Li metal electrode.

Acetone as an agent for PVDF recovery and delamination of lithium-ion battery electrodes

An acetone-based process to recover polyvinylidene fluoride (PVDF) from Li-ion battery electrodes has been developed. The PVDF binder was first dissolved away using acetone and the electrode material was subsequently subject to stirring in acetone for delamination from the current collector. The electrode became separated into electrode materials, PVDF binder, and current collector. The solubility of PVDF in acetone was measured as a function of temperature and was found to increase with temperature, reaching a maximum value at around 150 °C. The dissolution rate of PVDF both in its pure state and in electrodes was measured against temperature. The former was much faster than the latter. The diffusion of PVDF out of the electrodes was modelled mathematically for predicting the time for material recovery. The research demonstrates the potential of establishing a direct recycling process by enabling the recovery of PVDF, electrode materials and current collectors from Li-ion batteries.

Quantifying Interfacial Ion Transfer at Operating Potassium-Insertion Battery Electrodes within Highly Concentrated Aqueous Solutions.

Electrode/electrolyte interfacial ion transfer is a fundamental process occurring during insertion-type redox reactions at battery electrodes. The rate at which ions move into and out of the electrode, as well as at interphase structures, directly impacts the power performance of the battery. However, measuring and quantifying these ion transfer phenomena can be difficult, especially at high electrolyte concentrations as found in batteries. Herein, we report a scanning electrochemical microscope method using a common ferri/ferrocyanide (FeCN) redox mediator dissolved in an aqueous electrolyte to track changes in alkali ions at high electrolyte concentrations (up to 3 mol dm-3). Using voltammetry at a platinum microelectrode, we observed a reversible E1/2 shift of ∼60 mV per decade change in K+ concentrations. The response showed high stability in sequential measurements and similar behavior in other aqueous electrolytes. From there, we used the same FeCN mediator to position the microelectrode at the surface of a potassium-insertion electrode. We demonstrate tracking of local changes in the K+ concentration during insertion and deinsertion processes. Using a 2D axisymmetric, finite element model, we further estimate the effective insertion rates. These developments enable characterization of a key parameter for improving batteries, the interfacial ion transfer kinetics, and future work may show mediators appropriate for molar concentrations in nonaqueous electrolytes and beyond.

Cobalt- and copper-doped NASICON-type LATP polymer composite electrolytes enabling lithium titania electrode for solid-state lithium batteries with high-rate capability and excellent cyclic performance

This study reports cobalt- and copper-doped NASICON-type Li1.5Al0.5Ti1.7(PO4)3 (LATP) polymer composite solid-state electrolytes (CSEs) enabling Li4Ti5O12 (LTO) electrode with high-rate capability and excellent cyclic performance for solid-state lithium batteries. The fast Li+ conductor of Co- and Cu-doped LATP powders was successfully synthesized through a modified sol-gel method followed by thermal calcination. The equivalent series resistance as the linear decreasing function of the dopant concentration can be viewed, whereas the ionic conductivity showed an increasing function of the dopant amount. This reveals that the dopant concentration plays a positive role in facilitating the ionic conduction, and the ionic conductivity achieves as high as 3.18 × 10−4 S cm−1 (Co-doping) and 2.99 × 10−4 S cm−1 (Cu-doping) at ambient temperature. The changes in lattice characteristics and microstructure that the Co and Cu doping rely on are responsible for the elevated conductivity. The solid-state cell equipped with LTO-supported CSEs demonstrated not only high-rate capability at 5C (with a capacity retention of 84.6 % compared to the original capacity at 0.2C), but also superior cyclic stability with excellent Coulombic efficiency (> 99.2 %) over 425 cycles using Co- and Cu-doped LATP ceramics. With the aid of fast Li+ NASICON-type ceramics, the CSEs establish a conductive ionic pathway that facilitates Li+ ionic transport within the electrolyte while reducing the interfacial electrolyte/electrode resistance in solid-state cells (Li||CSE||LTO).

Advanced-design cross-linked binder enables high-performance silicon-based anodes through in-situ crosslinking based on sodium carboxymethyl cellulose and poly-lysine

Practical employment of silicon (Si) electrodes in lithium-ion batteries (LIBs) is limited due to the severe volume changes suffered during charging-discharging process, causing serious capacity fading. Here, a composite polymer (CP-10) containing sodium carboxymethyl cellulose (CMC-Na) and poly-lysine (PL) is proposed for the binder of Si-based anodes, and a multifunctional strategy of “in-situ crosslinking” is achieved to alleviate the severe capacity degradation effectively. A cross-linked three-dimensional (3D) network is established through the strong hydrogen bonding interaction and reversible electrostatic interactions within CP-10, offering favorable mechanical tolerance for the extreme volume expansion of Si. Moreover, hydrogen bonding interaction along with ion-dipole interaction formed between CP-10 and Si surface enhance the bonding capability of Si-based anodes, promoting the maintenance of anodes' integrity. Consequently, over 800 cycles are achieved for the Si@CP-10 at 0.5C while maintaining a fixed discharge specific capacity of 1000 mAh g−1. Moreover, the Si/C@CP-10 can stably operate over 500 cycles with a capacity retention of 77.12 % at 1C. The prolonged cycling lifetime of Si/C and Si anodes suggests great potential for this strategy in promoting the implementation of high-capacity LIBs.