High C-rate Research Articles

Spray-drying Al onto hydroxide precursors to prepare LiNi0.855Co0.095Al0.05O2 as a highly stable cathode for lithium-ion batteries

The very high specific discharge capacities of Ni> 90% cathodes are often undone by their extremely poor cycle life and thermal stability. Herein, Ni-poor, and Al-rich particle with double concentration gradients is fabricated by synthesizing particles of the Ni-rich hydroxide Ni0.9Co0.1(OH)2 in a highly efficient Taylor flow (TF) reactor and then depositing Al onto their surfaces using three methods: spray-drying and conventional wet and dry chemical coating. The uniformity of the surface distribution of Al on the Ni-rich transition metal oxide cathode materials affected the overall structural and electrochemical stability. Among our three systems, the cathode material prepared with the spray-dried Al exhibited the best performance, with an initial discharge capacity of 196.9 mA h g–1 and capacity retention of 93% after 100 cycles at a rate of 1 C. It also demonstrated superior electrochemical performance at higher C-rates. For example, at 10 C, it delivered an initial discharge capacity of 134.4 mA h g–1, compared with 56.8 mA h g–1 for the Al-free LiNi0.9Co0.1O2. We attribute this enhanced electrochemical performance to the presence of Al and its uniform distribution (through spray-drying processing) on the outer layer of the active material, with the Ni and Co elements remaining mainly within the core.

Structure and interface modification via Gd boosting excellent high-temperature electrochemical performance of LiMn2O4

Spinel LiMn2O4 has become one of the most attractive cathode materials for electric vehicles due to its low cost, non-toxicity, and good electrochemical performance of high C-rates. While the rapid decay of capacity at high temperature limits its further development. In this article, it is demonstrated that Gd modification can achieve the dual-modification of bulk structure and surface to effectively improve the electrochemical performance of LiMn2O4 at high temperature. It is found that Gd modification can decrease the lattice parameters and strengthens the stability of Mn–O bonds, which can efficiently improve the capacity stability by inhibiting the dissolution of Mn3+ from the electrode to the electrolyte. Besides, the Gd modification also enables the formation of the Gd2O3 coating layer on the material surface, which can significantly reduce the interfacial impedance and lower the diffusion activation energy of lithium-ion. Therefore, Gd-modified samples show a better rate capability and longer cycle life, especially at high temperature. Among them, the sample with Gd of 6000 ppm exhibited the most excellent capacity retention ratio of 82.6% after 300 cycles at 55 °C, 1C (1C = 148 mA·g-1) in the voltage range of 3.0–4.3 V, with an initial discharge capacity of 124.9 mAh·g−1.

Reduced Graphene Oxide/Glucose Co‐Assisted Micro Titanium Niobium Oxide Hybrid Anodes for Lithium‐Ion Batteries

AbstractTitanium niobium oxide (TiNb2O7) has shown great potential to replace carbon‐based anode materials for lithium‐ion batteries because of its high theoretical specific capacity and high rate performance. However, the low intrinsic Li+/e− conductivity of TiNb2O7 restricts its extensive application. To overcome this disadvantage, a novel reduced graphene oxide/glucose co‐assisted micro titanium niobium oxide hybrid anodes (G/C/TNO) was designed by a bottom‐up one‐pot method. rGO mainly acted as the carrier to reach the goal of ameliorating electronic conductivity. Glucose, as the fixative and carbon source, chiefly played a protective role in the structural integrity during cycling and synergized with rGO to improve Li+/e− transport kinetics. Therefore, the novel G/C/TNO composite displayed a high specific capacity of 208.8 mAh g−1 at 2C after 500 cycles and a good cycling stability of 161.1 mAh g−1 at a high rate of 10C in the best case.

Solvent-free dry cyclized polyacrylonitrile-coated LiNi0.87Co0.13O2 cathode for improving the electrochemical performance of Li-ion batteries

A Ni-rich LiNi0.87Co0.13O2 cathode was modified through dry surface-coating with cyclized-polyacrylonitrile (c-PAN). The c-PAN coating was obtained by heat treatment of polyacrylonitrile (PAN), used as a coating material for improving the electrochemical performance of the cathode. The cyclized PAN structure was confirmed by Raman spectroscopy, with the appearance of two carbon sp2 peaks in the range of 1200–1800 cm−1. Electrochemical tests showed that over 80% of the first discharge capacity was retained for the 2 wt% c-PAN coated electrode, whereas the capacity retention of the uncoated electrode was only about 77% after 100 cycles at a rate of 0.5C. At a high rate of 5C, the coated sample delivered a discharge capacity of 180.7 mAh g−1 in the 5th cycle and retained a discharge capacity of 212.6 mAh g−1 at 0.1C in the rate performance test, which is higher than the values of 165.2 and 198.6 mAh g−1 for the uncoated sample at 5C and 0.1C, respectively. These improvements could be attributed to the c-PAN coating layer, which limited the side reaction between the electrode and electrolyte, resulting in a higher Li-ion diffusion coefficient and a slower increase in the charge transfer resistance.

Numerical Simulation of Cooling Plate Using K-Epsilon Turbulence Model to Cool Down Large-Sized Graphite/LiFePO4 Battery at High C-Rates

In this paper, an analogous study of the velocity and temperature profiles inside microchannel cooling plates (with hydraulic diameter of 6 mm), placed on a large pouch-type LiFePO4 battery, is presented using both the laboratory and simulation techniques. For this, we used reverse engineering (RE), computed tomography (CT) scanning, Detroit Engineering Products (DEP) MeshWorks 8.0 for surface meshing of the cold plate, and STAR CCM+ for steady-state simulation. The numerical study was conducted for 20 A (1C) and 40 A (2C) and different operating temperatures. For experimental work, three heat flux sensors were used and were intentionally pasted at distributed locations, out of which one was situated near the negative tab (anode) and the other was near the positive tab (cathode), because the heat production is high near electrodes and the one near the mid body. Moreover, the realizable k-ε turbulence model in STAR CCM+ is used for simulation of the stream in a microchannel cooling plate, and the computational fluid dynamics (CFD) simulations under constant current (CC) discharge load cases are studied. Later, the validation is conducted with the lab data to ensure sufficient cooling occurs for the required range of temperature. The outcome of this research work shows that as C-rates and ambient temperature increase, the temperature contours of the cooling plates also increase.

Vibrational and electrochemical studies of pectin-a candidate towards environmental friendly lithium-ion battery development.

Pectin polymers are considered for lithium-ion battery electrodes. To understand the performance of pectin as an applied buffer layer, the electrical, magnetic, and optical properties of pectin films are investigated. This work describes a methodology for creating pectin films, including both pristine pectin and Fe-doped pectin, which are optically translucent, and explores their potential for lithium-ion battery application. The transmission response is found extended in optimally Fe-doped pectin, and prominent modes for cation bonding are identified. Fe doping enhances the conductivity observed in electrochemical impedance spectroscopy, and from the magnetic response of pectin evidence for Fe3+ is identified. The Li-ion half-cell prepared with pectin as binder for anode materials such as graphite shows stable charge capacity over long cycle life, and with slightly higher specific capacity compare with the cell prepared using polyvinylidene fluoride (PVDF) as binder. A novel enhanced charging specific capacity at a high C-rate is observed in cells with pectin binder, suggesting that within a certain rate (∼5 C), pectin has higher capacity at faster charge rates. The pectin system is found as a viable base material for organic-inorganic synthesis studies.

Enhanced electrochemical performance of O3-type NaNi0.5Mn0.3Co0.2O2 cathodes for sodium-ion batteries via Al-doping

O3-type NaNi0.5Mn0.3Co0.2O2 based positive electrode materials are very promising for sodium-ion batteries. However, the irreversible phase transition due to structural deformation leads to sluggish kinetics, rapid capacity fade, and low C-rate performance, limiting its wide practical applications. The partial substitution of Co3+ (0.545 Å) by Al3+ (0.535 Å) ions in the transition-metal layer in NaNi0.5Mn0.3Co0.2-xAlxO2 (0.01 ≤ x ≤ 0.02) is an effective strategy to address the issue of structural deformation and thus to improve the electrochemical performance of NaNi0.5Mn0.3Co0.2O2 cathode. Solution combustion synthesis of NaNi0.5Mn0.3Co0.2-xAlxO2 (x = 0.01, 0.02) shows O3-type structure of NaNi0.5Mn0.3Co0.2−xAlxO2 material with the space group of R3¯m. The composition with an overall x = 0.02 Al doping delivers an initial 120 mAh g−1 capacity at a 0.1 C rate. It retains 90 % capacity even after 200 cycles than the other stoichiometric aluminum substitution, x = 0.01 (77 %). Moreover, the NaNi0.5Mn0.3Co0.18Al0.02O2 shows a good capacity of ~ 83 mAh g−1 even at a high C-rate of 5 C, almost 70 % of the initial capacity at the 0.1 C rate. The Al-substitute NaNi0.5Mn0.3Co0.2−xAlxO2 cathode's electrochemical performance is attributed to the enhancement in the structural stability of the sodium layered transition metal oxide after the partial substitution of Co3+ by Al3+ ion. Finally, the practical sodium-ion full cells are realized using a hard carbon-based anode and NaNi0.5Mn0.3Co0.18Al0.02O2 cathode, showing 91 % capacity retention at the end of 100th cycles with an OCV of 3.5 V.

Artificial three-dimensional inverse opal cathode host materials for lithium sulfur batteries

Lithium-sulfur batteries (LSBs) are regarded as promising energy storage devices due to their high theoretical capacity. However, LSBs face great challenge in commercial uses due to their “shuttle effect”. In this work, a composite material consisting of N and O heteroatoms dispersed on three-dimensional macroporous glycine anhydride (3DMPGA) inverse opal structure is designed and synthesized by the one-step method. Compared with high temperature graphitization, low temperature pyrolysis of 3DMPGA consumes less energy. And precursor glycine is renewable, which is significant for reducing carbon emissions. The results show that 3DMPGA has an ordered porous inverse opal structure and uniform heteroatoms distribution. Lithium polysulfides are not only stored in the pores with spatial confinement but also anchored on the surface of pores via chemical adsorption, confirmed by adsorption tests and density functional theory calculation, respectively. The initial capacity of the 3DMPGA cathode at 0.5C is 848 mAh g−1, and the average attenuation rate for 300 cycles is only 0.14%. At a higher C-rate, the enhanced electrochemical performance of 3DMPGA is more obvious due to the dual-effect on mitigating the “shuttle effect”.

High-Rate Electrochemical Lithium Cycling and Structure Evolution in Mo4O11

Shear-phase early transition metal oxides, mostly of Nb, and comprising edge- and corner-shared metal–oxygen octahedra have seen a resurgence in recent years as fast-charging low-voltage electrodes for Li–ion batteries. Mo oxides, broadly, have been less well studied. Here we examine the reduced Mo oxide Mo4O11 that has a structure comprising only corner-connected MoO4 tetrahedra and MoO6 octahedra. Here we show that an electrode formed using micron sized particles of Mo4O11 as the active material can function as a high-rate Li–ion electrode against Li metal, with a stable capacity of over 200 mAh g-1 at the high rate of 5C. Operando X-ray diffraction (XRD), Raman spectroscopy, and entropic potential measurements are employed to understand the nature of charge storage. It is found that the structure dramatically changes upon the first lithiation, and subsequent cycling is completely reversible with low capacity fade. It is the newly formed, and potentially more layered structure that demonstrates high-rate cycling and small voltage polarization. This finding expands the scope of candidate high-rate electrode materials to those beyond the expected Nb-containing shear-phase oxide materials. Figure 1

(Digital Presentation) The Effect of Dominant Operational Conditions on Capacity Deterioration of Commercial Li-Ion Cells Under Accelerated Testing

Li-ion batteries (LIBs) have been used in a variety of applications including consumer electronics, electric vehicles, space exploration, the defense sector, etc. As a result, the performance and reliability of the commercial LIBs have become extremely crucial which can be monitored by the deterioration in the charge storage over continuous charge-discharge cycling [1]. However, cycling LIBs at the nominal current rate involves excessive time and resource consumption resulting in a slow battery qualification process. Accelerated testing has been proposed to examine the reliability test and for the efficient qualification process of batteries [2]. It is conducted by increasing the operational (stress factors) conditions of the LIBs that have direct implications on the performance and cycle life of a battery. During accelerated testing, capacity deterioration and increase in impedance are recorded periodically, which serve as indicators of degradation of the batteries [3]. Batteries under consideration for the degradation process are closely monitored and the above degradation indicators are recorded at elevated levels of the operational conditions than normal. This process is known as the accelerated degradation test. In literature, there are several operational conditions that have been reported to affect the capacity fade and cycle life of a battery [1-4]. However, the C-rate and ambient temperature are the widely believed dominant factors that have a significant effect on the performance of a battery [2, 4].In this work, we will present a systematic study on the performance degradation of commercial LIBs under accelerated testing using dominant operational conditions viz. C-rate and testing ambient temperature. Capacity fading of commercial cylindrical 18650-type LIBs is monitored at 1 and 2 C-rate while maintaining the ambient temperature during testing at 25 and 35 ℃ in a thermal chamber. Capacity degradation is highly sensitive to C-rate and causes faster fading at higher current rates due to mechanical degradation of electrodes, formation of SEI layer and side reactions. Discharging at high C-rates also causes ohmic heating in the cells increasing their internal temperature which further influences the chemical reaction kinetics [4]. The ambient temperature also has a strong influence on the capacity loss due to the degeneration of the positive electrode and SEI layer formation at the negative electrode [1, 4]. Accelerated testing including the synergistic effect of the ambient temperature and C-rate on the capacity fading and performance evaluation of the commercial LIBs till the end of life or 20% capacity reduction would be presented. Post cycling analysis of the Li-ion cells, in particular, electrode materials and periodic impedance measurements would enable a better understanding of battery failure under such accelerated testing. We believe that the results of this study would pave the way to shorten the duration in the detection of a battery failure and enable an efficient battery qualification process.

Hybridization of Mesoporous Carbon and Iron Oxide for Better Mitigation of Polysulfide Shuttling in Li-S Batteries

With a higher theoretical capacity, lithium-sulfur (Li-S) batteries have been considered as promising candidates for next-generation batteries. Due to the non-conducting nature of sulfur, however, lithium-sulfur batteries tend to exhibit poor performance at a high current rate (C-rate).Here we demonstrate that Fe3O4, synthesized from precursor iron (III) acetylacetonate (AAI), and mesoporous carbon material, Ketjen Black (KB), can be synergistically combined to enhance the electrochemical performance of lithium-sulfur batteries substantially. Instead of adding commercial magnetite particles into Li-S cathodes, iron oxides are synthesized and imbedded into KB from a precursor, AAI, through thermal treatments in air and Ar. The sulfur, then, is incorporated into iron oxides/KB hybrids by melting at an elevated temperature. With air-controlled electrospray as the processing method, sulfur embedded iron oxides/KB, poly(acrylic acid), and rGO sheets are mixed and directly deposited onto the carbon-coated aluminum collector, to employ as the Li-S battery cathode. X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrochemical impedance spectroscopy (EIS) studies confirm that Fe3O4 and iron carbide (Fe3C) are synthesized from the precursor, AAI, embedded in mesoporous carbon materials, and reducing the charge transfer resistance of batteries. The rate-capability tests show that systems with KB/Fe3O4 can achieve enhanced performance compared to batteries without iron oxides, especially at high C-rates. With 14 wt % of solid materials as iron oxides and iron carbide, batteries exhibit 750 mAh/g at 2C discharge/charge rates, which is 83% higher compared to systems without iron oxides. However, incorporated via 250 °C for 0.5 hr in air and 850 °C for 2 hr in Ar, the composite of KB/Fe3O4/Fe3C induces irreversible side reactions during the initial charging process, which causes a huge difference in capacity between the first and the second cycle. To achieve an optimal status with improved rate capability and acceptable initial charging time, we modify the thermal treatments and thus increase the proportion of Fe3O4 in the mixture. According to the postmortem analysis, cathodes with iron oxides can interact with soluble polysulfides strongly and alleviate the polysulfide shuttle effect significantly, compared with those without Fe3O4. Such enhanced rate capability by KB/Fe3O4 (synthesized) over KB only or KB/Fe3O4 (commercial) systems suggests that the incorporation of iron oxides can play an important role in improving the electrical conductivity of cathode and mitigating polysulfide shuttle effect. Figure 1

Optimization of Catholyte in Composite Cathodes for Garnet-Structured Llzo Electrolyte in Solid-State Batteries

The application of Li-ion batteries have been expanding at a rapid rate in recent decades due to the tremendous demands in the market for portable electronics, smart grid, and electric vehicles (EVs). All-solid-state lithium metal battery (ASSLB) is the most promising next-generation energy storage device as they can solve the safety issue resulted from liquid electrolytes.Among different types of solid-state electrolytes (SSE), garnet-type structure materials have been shown to be very promising for the development of ASSLBs owing to their high Li-ion conductivity (∼10–3 S cm–1 at RT), wide electrochemical stability window (∼6 V vs Li+/Li), and good chemical stability against Li metal. The high interfacial resistance generated by inadequate contact and interfacial reactions is a substantial impediment to the adaptation of ASSLBs. To address this challenge, a catholyte (a small amount of ionic conductors which are mostly derived from the solid electrolyte formulation) is introduced into the cathode formulation. This necessities a re-design of the cathode into a composite cathode with possibly new components such as carbon additives with high aspect ratio and conductive binders. Understanding their individual and combined impacts on performance is essential in the pursuit of optimized systems.In this work, we designed a series of composite cathode formulations defined with three cathode active materials (LFP, NMC 622 and NMC 811), three carbonaceous additives (carbon black, carbon nanofibers and carbon nanotubes), and a series of organic and inorganic molecular, and polymeric conductors along with LLZO to create a composite cathode with high capacity and stability at high C-rates. A systematic DOE approach has been utilized to evaluate the impact of each component on the electrode and cell performance and the results will be presented.

Modelling and Validation of High-Energy Density 30µm Thin-Film Solid-State LiCoO2 Cell: 1D Cahn-Hilliard Phase Separation Model

LiCoO2 (LCO) dominates the industry of high energy density Li-batteries cathodes, with almost 20% of market share. Since its introduction in 1980, scientific community produced a rich literature; in particular, several studies suggest maximizing the loaded weight of active material as an interesting route for energy density increase: over the whole weight of the cell, the impact of electrolyte, current collectors, and anode decreases, determining an increase in volumetric and gravimetric energy density. Notwithstanding, unclear correlation between electrode thickness and delivered capacity, altogether with an extremely short cycle-life and poor rate-capability, reported for cathode thicker than 10µm [1], are now halting the development of cells with thick electrodes for both solid-state deposited (PVD, pulse laser, electroplating) and tape-casted cathode.We focused our work on unveiling the causal link between thickness and available capacity in LCO cathode, providing a simple formula to relate the latter with cathode dimension, discharge current, and temperature. We propose solid-state thin-film configuration in a lithium-free battery as a test vehicle to study pure LCO cathode. This configuration introduces no additional dynamic limitation like grain-to-grain diffusion.We exploited both model and experimental results to delve into the understanding of interfacial lithium accumulation during discharge and we linked the related capacity loss to phase separation occurring around 75% of intercalated lithium [2-3]. In order to interpret both dynamic and static results we have implemented a 1D model based on Cahn-Hilliard equation [4] and solved it using COMSOL. We will provide results to foster a division of LCO cathode into two domain: from 50% to 75% of lithium intercalation, a high-rate zone, which capacity can be delivered at high C-rate without any limitation for any considered LCO thickness; from 75% to 100%, a low-rate zone, which can provide capacity only at very low C-rate.We validated the model realizing 5, 10, 20 and 30µm thick LCO cathode in a thin-film all-solid-state configuration, with LIPON as solid electrolyte, tested for discharge current density from 0.2 to 2 mAcm-2. We also present the 30µm thick LCO cathode with the highest capacity reported for thin-film configuration so far (>1mAhcm-2) and provide strong evidences of linear correlation between delivered capacity and cathode thickness. The results obtained for all-solid-state thin-film cells, can be extended to all LCO cathode, whatever the deposition technique used, as long as the particle size is the same order of the present work and the main limiting factor from the dynamic point of view is the solid diffusion in the cathode.

Introducing a Bio-Degradable Binder for Aqueous Production of NMC111 Cathodes

The LiNixMn1-x-yCoyO2 (NMC) is a widely used cathode material in lithium-ion batteries (LIBs) due to its high capacity. By enabling water-based cathode processing, the cost and environmental impact of LIBs will be reduced substantially. However, the water compatibility of Ni-containing materials has been problematic due to lithium (Li)-leaching, corrosion of the aluminium (Al) current collector, and lack of aqueous dissoluble binders. For the first time, we demonstrated that NMC111 cathodes with comparable specific capacities to the standard polyvinylidene fluoride/N-methyl-2-pyrrolidone (PVDF/NMP)-processed cathodes can be formulated in water using lignin as binder material. Rheology measurements revealed that less solvent is needed to obtain the same slurry viscosity when replacing the NMP solvent with water. Cycling voltammetry and differential scanning calorimetry revealed that lignin is electrochemically inactive between 2.5-4.5 V and thermally stable up to 152 oC, respectively. Drying the cathode coatings at 50 oC allowed for a controlled evaporation rate as surface cracks and binder migration detected using scanning electron microscopy diminished. The lignin binder provided strong cohesion forces to the carbon black (CB) and the NMC111 particles, and the use of carbon(C)-coated Al-foil (C-Al) further increased the coating's mechanical strength. Scratch tests revealed that calendaring magnified the nature of the initial mechanical strength, intensifying a poor adhesion of the coating to the Al-foil and strong cohesion between the particles. While calendering and pore removal improved the rate performance for PVDF-cathodes (85:10:5 wt % NMC:CB:binder), the rate capability of lignin-cathodes (80:11:9 wt %) decreased with lower porosity (from 53 to 0 %) and higher mass loading (9.7 mg/cm2). Particle deformation and extensive pore-blocking at high carbon contents created a Li+-transfer barrier across the cathode/electrolyte surface, decreasing the rate performance. Cathodes using a CMC/lignin-binder mix (2:7 wt% ratio) and C-Al foil (75 % capacity retention) electrochemically outperformed those with the commercial CMC/SBR mix and plain Al-foil (35 % capacity retention) at a high C-rate (5 C). Of all the aqueous produced cathodes, the uncalendered with pure lignin-binder, C-Al foil, dried at 50 oC, and a mass loading of 7.4 mg/cm2 showed the highest capacity retention at 5 C (60 %). Additionally, the lignin-cathodes have poor electrolyte wetting abilities and need longer exposure time before cycling and additional formation cycles compared to the PVDF-cathodes. Lignin-cathodes with the smallest lignin/CB matrix (90:5:5 wt% NMC:CB:binder) wetted for 35 days with 5 formation cycles at C/10 showed similar initial discharge capacity and capacity retention (154 mAh/g and 89 %) as 85:10:5 PVDF-based cathodes (153 mAh/g and 93 %) after 100 cycles at C/2.

The Influence of Calendering on the Moisture Sorption Behavior of Electrodes for Lithium-Ion Batteries

Moisture is considered to be one of the most critical contaminants in Lithium-ion batteries (LIBs), as it impairs the electrochemical performance and poses high safety risks. To reduce the moisture in the cells below a critical level, electrodes and separators for LIBs need to be post-dried before cell assembly. However, the moisture adsorption, desorption and re-adsorption behavior of electrodes is defined by the chosen material system, the manufacturing route and the microstructure of the coatings. The microstructure, in turn, is significantly determined by the calendering step, which predominantly aims at increasing the specific density and consequently, the volumetric energy density of the electrode coatings. As the calendering step decisively changes the microstructure of the electrode coatings, it can be assumed that it accordingly must have an impact on the moisture sorption behavior of the electrodes during further processing. The sorption equilibrium of electrode coatings mainly depends on the surface of the particles, the sorption in the binder system and, to a certain extent, on the capillary condensation. LIB cathodes are most commonly manufactured with polyvinylidene fluoride (PVDF) as a binder. PVDF is very hydrophobic, which is why we can assume that the moisture sorption of these cathodes is fundamentally determined by sorption on the surface and, to a lesser degree, on capillary condensation. In contrast, the moisture sorption of LIB anodes produced with a carboxymethyl cellulose/styrene-butadiene (CMC/SBR) binder system is assumed to be mainly defined by moisture sorption of the very hygroscopic binder system. Changes to the surface should only have a small influence.Hence, it is expected that the impact of the calendering step on the moisture sorption is far more pronounced for the cathodes than for the anodes. To prove this theory and analyze the impact of the calendering step in detail, the influence of different densities on the moisture sorption behavior, microstructural properties and electrochemical performance of NCM622 cathodes with PVDF binder and graphite anodes with CMC/SBR binder system is investigated. Therefore, the electrodes are calendered to three different densities in dry room atmosphere, post-dried in vacuum and assembled into coin cells.Focusing on the cathode, after calendering an increasing moisture content is observed for increasing density, measured by Karl Fischer Titration and proved by sorption measurements. Although post-drying significantly reduces the moisture content of the cathodes, the course trend is still the same with the lowest moisture at a low density and the highest moisture at high density. Via SEM analysis, a rising amount of active material particle cracks is detected with increasing density. BET measurements show that this phenomenon is accompanied by an increasing specific surface area. Hence, the increased moisture uptake of cathodes with higher density can be mainly traced back to their higher specific surface area, caused by particle cracking during calendering. Further analytics display that the chosen post-drying parameters lead to an increase of cohesion strength for all cathodes, whereas the influence on the electrical resistance depends on the density of the cathode. The electrochemical testing shows that the increased electrochemically active surface area of the cathodes with higher density results in a good performance during formation and at lower C-rates. However, the reduced porosity lowers the ionic conductivity and leads to capacity losses at higher C-rates. [1]Concerning the anode, as expected, the influence of the calendering step on the moisture sorption is much smaller. Although the specific surface area of the anodes also increases with rising density, a significant increase of moisture is not observed. Hence, the influence of the changes in microstructure is overlapped by the hygroscopic binder system of the anodes. Post-drying increases the adhesion strength of all anodes, whereas the electrical resistance seems to decrease to a small degree. The electrochemical analysis of the anodes shows a deterioration of performance with increasing density, due to limitations of the ionic conductivity at lower porosities.Altogether, we will show that for NCM622 cathodes with PVDF binder, the moisture uptake increases with increasing density after calendering, whereas there is no change in moisture content at graphite anodes with CMC/SBR binder system. These findings make an important contribution to a better process understanding and consequently, improved moisture management along the entire process chain of Lithium-ion batteries.[1] F. Huttner, A. Diener, T. Heckmann, J. C. Eser, T. Abali, J. K. Mayer, P. Scharfer, W. Schabel, A. Kwade, Increased Moisture Uptake of NCM622 Cathodes after Calendering due to Particle Breakage, J. Electrochem. Soc. 168 090539 (2021), doi.org/10.1149/1945-7111/ac24bb, CC BY 4.0

Origins of the Fast-Charging Abilities of Niobium Containing Wadsley-Roth Phases

Lithium-ion batteries (LIBs) featuring high energy density have received particular attention in recent years due to their promise as electrical energy storage devices for electric vehicles and portable electronic devices. However, most of the commercial LIBs use graphite anode which suffer from the formation of solid-electrolyte interface (SEI) layer. Moreover, the poor performance of graphite anodes at high C-rates limits their application for fast-charging LIBs. To address the challenges associated with graphite anodes, niobium-containing Wadsley-Roth shear phase materials have been suggested. Thanks to the redox potential of Nb4+ (above 1 V versus Li/Li+), the niobium containing Wadsley-Roth shear phase materials avoid SEI formation. Furthermore, a combination of edge-shared and corner-shared octahedra in this type of shear phase materials forms many tunnel-like regions where Li-ions can rapidly diffuse during lithiation and delithiation. In fact, niobium-containing Wadsley-Roth shear phase materials show impressive cycling performance as fast-charging battery materials and maintain more than 50 % of their theoretical capacity at C-rate of 10 C.This study aims to understand the fast-charging capability of niobium containing Wadsley-Roth shear phase materials accompanied by ion ordering in the application of LIBs. In addition, it aims to provide experimental evidence to elucidate the occurrence of Li-ion ordering in this type of shear phase materials. To do so, galvanostatic cycling and cyclic voltammetry were performed on selected niobium-containing Wadsley-Roth shear phase materials including TiNb2O7, PNb9O25, VNb9O25, and NaNb13O33. In addition, open circuit voltage and entropic potential of those materials were measured. The results show that ion ordering characterized by a tilde-shaped fluctuation in entropic potential was observed in all tested niobium containing Wadsley-Roth shear phase materials. Furthermore, the results indicate that the b-value approaching 0.5 corresponded to the first order transition accompanied by a two-phase coexistence while the b-value approaching 1 corresponded to the ordering of Li-ions. This analysis implies that the ion ordering phenomena can enhance the fast-charging capability of the material. This study provides valuable insights for fast-charging battery materials.

(Digital Presentation) Thermal Behaviour Prediction of Commercial Lithium-Ion Cells Under Different C-Rate and Ambient Conditions Using Surrogate Modelling

Lithium-ion batteries (LIBs) have found widespread application in energy storage due to their high energy density, low self-discharge and low maintenance characteristics. However, the stability and longevity of the batteries under extreme operating conditions is yet to be fully understood. Numerous experimental and simulation studies have been performed to elucidate the effect of temperature, current, depth of discharge, and the number of cycles [1,2,3] on the performance of LIBs. These studies show that the solid-electrolyte interface (SEI) layer and gas formation accelerate at high C-rates due to increased electrolyte decomposition [4,5]. Consequently, the cell's internal resistance increases, resulting in ever-increasing irreversible heat generation inside the cell [6]. This heat generation leads to high internal temperature and a corresponding reduction in cell capacity. The data of cell temperature for a wide range of ambient temperatures and cycling rates is limited because cell performance is typically reported at room temperature. The design of battery packs for electric vehicles(EVs) is also based on test data taken at room conditions. Given that the cell's capacity, specific energy, maximum power output is bound to depend on C-rate and ambient temperature, it is necessary to test and design battery packs based on these parameters.The thermal characteristics of a lithium-ion cell can be predicted using a physics-based thermal model or data-driven methods (DDM) relying on empirical data. Experimental determination of internal cell parameters required in physics-based thermal models is challenging and time-consuming for commercial cells. On the other hand, DDM requires only cell cycling data at specific operating conditions, thereby eliminating the need for internal parameter estimation. This model predicts the experimental input and output data pattern and fits the response surface to estimate the unknown output. In this study, surrogate modelling has been employed to estimate the surface temperature, capacity, energy, and average power of commercial lithium-ion cells for different discharge currents and ambient temperatures. Surrogate modelling, a popular data analysis and reduced-order modelling technique, aims to find a global minimum of a particular objective function using a few objective function evaluations [7]. The surrogate-based model divides experimental data into training and test data sets. The training data set is employed to train the algorithm. After that, the testing data set is used to validate the model's accuracy. Experiments were performed to develop a surrogate model, with the number of experiments decided using the design of experiments[8] for a current range of 0.5C to 3C-rate and ambient temperature range of 0°C to 45°C . The cycling of cells was performed using a high current battery cycler (Arbin), and the ambient temperature was maintained using a thermal chamber (Cincinnati). The surface temperature of commercial 18650 (NMC811) lithium-ion cells was recorded using T-type thermocouples and a National Instruments DAQ module. A polynomial response surface was fitted using surrogate modelling on experimentally obtained data. The response surface shown in figure 1. contains nine data points for the preliminary study, sub-divided into a set of seven training and two testing data. The prediction error sum of squares (PRESS) is currently bounded within 10% due to the limited training data set availability and is expected to be within a band of 1% after adding data from ongoing experiments. The estimation of temperature, capacity, and specific energy can be used to optimize and develop an improved thermal management system for electric vehicles that works under various operating conditions. References Waldmann, T., Wilka, M., Kasper, M., Fleischhammer, M., & Wohlfahrt-Mehrens, M. (2014). Journal of Power Sources, 262, 129-135.Guan, T., Sun, S., Yu, F., Gao, Y., Fan, P., Zuo, P., Du,C., & Yin, G. (2018). Electrochimica Acta, 279, 204-212.Simolka, M., Heger, J. F., Traub, N., Kaess, H., & Friedrich, K. A. (2020). Journal of The Electrochemical Society, 167(11), 110502.Xu, B., Diao, W., Wen, G., Choe, S. Y., Kim, J., & Pecht, M. (2021). Journal of Power Sources, 510, 230390.Rashid, M., & Gupta, A. (2017). Electrochimica Acta, 231, 171-184.Leng, F., Tan, C. M., & Pecht, M. (2015). Scientific reports, 5(1), 1-12.Queipo, N. V., Haftka, R. T., Shyy, W., Goel, T., Vaidyanathan, R., & Tucker, P. K. (2005). Progress in aerospace sciences, 41(1), 1-28.Li, W., Xiao, M., Peng, X., Garg, A., & Gao, L. (2019). Applied Thermal Engineering, 147, 90-100. Figure 1

A parametric study on encapsulation of elemental sulfur inside CNTs by sonically assisted capillary method: Cathodic material for rechargeable Li–S batteries

Encapsulation of elemental sulfur inside of carbon nanotubes is one of the best solutions to face the Lithium–Sulfur batteries challenges to get successful commercialization. In this work, the first parametric study of the capillary drawing-in dissolved materials in low surface tension solvents accompanying ultrasonic method is reported which has low heat consumption and convenient process. The optimized parameters are composite concentration (ratio of total composite material to solvent), ultrasonic irradiation power, ultrasonic irradiation time and initial sulfur concentration on the filling yield. A complete characterization were executed to investigate various characteristics of synthesized [email protected] composites. The results indicate that the elemental sulfur were successfully physically (no chemical bond) confined inside of the carbon nanotubes. The maximum amount of sulfur that confined inside the cavity of carbon nanotubes is 36.21 %wt. This synthesized composite as cathodic material for Li–S battery offers a stable cycling profile (81.68% capacity retention after 100 cycles at 2C) and sufficient capacity (725 mAh g−1 at 2C) at high C-rate. These results indicate that carbon nanotubes provide a high electronic conductivity shell with a cavity that balances the volume expansion of the sulfur during charge and discharge of cycles in Li–S batteries and also supplies an excellent trap for the polysulfides, prevents the dissolution of them, and controls the shuttle effect. These excellent results are believed to contribute to improvements in this technology.

Rapid and reversible Na deposition onto Al nanosheet arrays

Sodium metal battery (SMB) is regarded as a promising candidate for next-generation high-energy battery due to high theoretical capacity and abundant natural resources. However, the growth of sodium dendrites and large volume expansion during the processes of sodium plating and stripping seriously restrict the practical application of SMBs. Here, a three-dimensional skeleton of aluminum nanosheet arrays (Al NSARs) is constructed by a facile etching approach to achieve rapid and reversible Na plating/stripping. The Al NSARs with large geometric specific surface and plentiful cavities can provide rich active nucleation sites, reduce local current density and accommodate Na volume change, which lead to uniform deposition of sodium with dendrite-free morphology. As a result, Na plating/stripping on Al NSARs can stably operate over 650 cycles at 2 mA cm−2/2 mAh cm−2 with average Coulombic efficiency (CE) of 100.0% and low potential polarization of 27 mV. Moreover, the full cell of Na3V2(PO4)3‖Al NSARs@Na can run for over 1800 cycles at a high rate of 20C. These superior properties, combined with relatively low cost and weight of Al, enable our Al NSARs to be great prospect for practical applications.

Accurate determination of optimal sulfur content in mesoporous carbon hosts for high-capacity stable lithium-sulfur batteries

Mesoporous carbon materials have been widely used as hosts for sulfur encapsulation to mitigate the low electrical conductivity of sulfur, lithium polysulfide shuttle, and drastic volume changes of sulfur species associated with lithium-sulfur batteries (LSBs). The ideal sulfur-host composite should have an optimal content of sulfur that partially fills the pores of the host and produces the exact amount of final discharged product Li2S that can be completely accommodated by the pores of the host. However, accurately determining this optimal content of sulfur is a challenge and no effective method has been established. In this work, we successfully determined the optimal sulfur content for the Ketjenblack EC-600 JD (KB) sulfur host by simply characterizing sulfur-KB (SKB) composites with different sulfur contents using X-ray diffraction (XRD) spectroscopy coupled with thermogravimetric analysis (TGA). The LSB using the SKB with the optimal sulfur content of 52.9% showed a high specific capacity of 1535 mAh g−1 at 0.1C and a capacity of 680 mAh g−1 even at the high rate of 5C. Furthermore, it also showed stable cycling stability with low capacity decay rates of 0.05% and 0.09% per cycle over 500 cycles at 2C and 5C, respectively.