Batteries, Volume 6, Issue 4 (December 2020) – 14 articles

The temperature and heat produced by lithium-ion (Li-ion) batteries in electric and hybrid vehicles is an important field of investigation as it determines the power, performance, and cycle life of the battery pack. This paper presented both laboratory data and simulation results at C-rates of 1C, 2C, 3C, and 4C at an ambient temperature of approximately 23 °C. During experiment thermocouples were placed on the surface of the battery. The thermal model assumed constant current discharge and was experimentally validated. It was observed that temperature increased with C-rates at both the surface and the tabs. We note that at 4C the battery temperature increased from 22 °C to 47.40 °C and the tab temperature increased from 22 °C to 52.94 °C. Overall, the simulation results showed that more heat was produced in the cathode than the anode, the primary source of heat was the electrolyte resistance, and the battery temperature was the highest near the tabs and in the internal space of the battery. Simulation of the lithium concentration within the battery showed that the lithium concentration was more uniform in the anode than in the cathode. These results can help the accurate thermal design and thermal management of Li-ion batteries. Full article

A hermetic dense polymer-carbon composite-based current collector foil (PCCF) for lithium-ion battery applications was developed and evaluated in comparison to state-of-the-art aluminum (Al) foil collector. Water-processed LiNi_0.5Mn_1.5O₄ (LMNO) cathode and Li₄Ti₅O₁₂ (LTO) anode coatings with the integration of a thin carbon primer at the interface to the collector were prepared. Despite the fact that the laboratory manufactured PCCF shows a much higher film thickness of 55 µm compared to Al foil of 19 µm, the electrode resistance was measured to be by a factor of 5 lower compared to the Al collector, which was attributed to the low contact resistance between PCCF, carbon primer and electrode microstructure. The PCCF-C-primer collector shows a sufficient voltage stability up to 5 V vs. Li/Li⁺ and a negligible Li-intercalation loss into the carbon primer. Electrochemical cell tests demonstrate the applicability of the developed PCCF for LMNO and LTO electrodes, with no disadvantage compared to state-of-the-art Al collector. Due to a 50% lower material density, the lightweight and hermetic dense PCCF polymer collector offers the possibility to significantly decrease the mass loading of the collector in battery cells, which can be of special interest for bipolar battery architectures. Full article

Three major components in a cathode of aqueous rechargeable lithium batteries are the active material, the polymer binder, and the carbon conductive additive. The stability of each component in the battery is the key to long service life. To evaluate the stability of the carbon component, we introduce here a quick and direct testing method. LiMn₂O₄ is chosen as a typical active material for the preparation of the cathode, with polyvinylidene fluoride (PVdF), and a commercial carbon, which is chosen among Acetylene black, superP, superP-Li, Ketjen black 1, Ketjen black 2, Graphite, KS-6, splintered glassy carbon, and splintered spherical carbon. This method reveals the correlation between the electrochemical stability of a carbon and its physical and structural properties. This helps researchers choose the right carbon component for a Li-ion cathode if they want the battery to be robust, especially at near full state of charge. Full article

Cobalt is a critical, high-value metal used extensively in batteries and other sustainable technologies. To secure its supply in future, it is utmost important to recover cobalt efficiently from industrial wastes and recycled End-of-Life batteries. This study aims at finding ways to improve the reduction of cobalt as well as valuable metals nickel and copper in nickel slag cleaning furnace conditions by using both traditional fossil-based coke and a more sustainable option, low-CO₂ footprint biochar, as reductants. A cobalt-rich fraction of battery scrap (25.5 wt% Co) was also used as a secondary feed. The experimental technique consisted of reduction experiments with different times at 1400 °C under inert atmosphere, quick quenching and Electron Probe X-ray Microanalysis. The use of biochar resulted in faster reaction kinetics in the reduction process, compared to coke. Moreover, the presence of battery scrap had a clear impact on the behavior and reduction kinetics of the elements and/or enhanced settling and separation of matte and slag. The addition of scrap increased notably the distribution coefficients of the valuable metals but consequently also the iron concentration in matte which is the thermodynamic constraint of the slag cleaning process. Full article

The impacts on battery cell ageing from high current operation are investigated using commercial cells. This study utilised two tests–(i) to establish the maximum current limits before cell failure and (ii) applying this maximum current until cell failure. Testing was performed to determine how far cycling parameters could progress beyond the manufacturer’s recommendations. Current fluxes were increased up to 100 C cycling conditions without the cell undergoing catastrophic failure. Charge and discharge current capabilities were possible at magnitudes of 1.38 and 4.4 times, respectively, more than that specified by the manufacturer’s claims. The increased current was used for longer term cycling tests to 500 cycles and the resulting capacity loss and resistance increase was dominated by thermal fatigue of the electrodes. This work shows that there is a discrepancy between manufacturer-stated current limits and actual current limits of the cell, before the cell undergoes catastrophic failure. This presumably is based on manufacturer-defined performance and lifetime criteria, as well as prioritised safety factors. For certain applications, e.g., where high performance is needed, this gap may not be suitable; this paper shows how this gap could be narrowed for these applications using the testing described herein. Full article

In this work, optimal siting and sizing of a battery energy storage system (BESS) in a distribution network with renewable energy sources (RESs) of distribution network operators (DNO) are presented to reduce the effect of RES fluctuations for power generation reliability and quality. The optimal siting and sizing of the BESS are found by minimizing the costs caused by the voltage deviations, power losses, and peak demands in the distribution network for improving the performance of the distribution network. The simulation results of the BESS installation were evaluated in the IEEE 33-bus distribution network. Genetic algorithm (GA) and particle swarm optimization (PSO) were adopted to solve this optimization problem, and the results obtained from these two algorithms were compared. After the BESS installation in the distribution network, the voltage deviations, power losses, and peak demands were reduced when compared to those of the case without BESS installation. Full article

The thermal behavior of a commercial lithium-ion cell with the cathode material LiNi_0.6Mn_0.2Co_0.2O₂ (NMC622) was investigated during the cycling process using a Tian-Calvet calorimeter (C80, SETARAM Instrumentation, France). Various current flows of 42.5, 85, and 170 mA corresponding to charging rates of 0.5, 1, and 2 C, respectively, were applied in the measurements. The corresponding heat flow rates were measured by the C80 calorimeter at 30 °C. The reversible heat effect due to the reversible electrochemical reaction was quantified by the entropy change measurement. The irreversible heat effect due to internal resistances was determined by the electrochemical impedance spectroscopy (EIS) and the galvanostatic intermittent titration technique (GITT). The results were compared with the direct measurement of the heat effect by calorimetry during electrochemical cycling. Full article

The capacitance of Lithium-ion Capacitors (LiCs) highly depends on their terminal voltage. Previous research found that it varies in a nonlinear manner with respect to the voltage. However, none of them modeled the capacitance evolution while considering the physicochemical phenomena that happen in a LiC cell. This paper focuses on developing a new capacitance model that is based on the Stern model of the electrochemical double layer capacitance. The model accounts for the asymmetric V-shape of the C(V) curve, which reflects the variation of the capacitance with respect to the voltage. The novelty of this study concerns the development of a model for LiCs that relies on the fundamental theory of Stern for the differential capacitance. The basic model of Stern is modified in order to account for the hybrid physicochemical structure of LiCs. Moreover, the model was applied to three aged cells to which accelerated calendar aging tests were applied at three voltage values: 2.2, 3 and 3.8 V. A drift of the voltage corresponding to the minimum capacitance was detected for the aged cells. This voltage is related to the neutral state of the positive electrode. The main cause of this phenomenon concerns the loss of lithium ions from the negative electrode of a LiC. In addition, capacitance values decreased after aging, showing an eventual blocking of the pores of the positive electrode. Therefore, the analysis of the C(V) curve was found to be an interesting tool for the interpretation of aging mechanisms. Full article

Batteries as a multi-disciplinary field have been analyzed from the electrical, material science and electrochemical engineering perspectives. The first principle-based four-dimensional degradation model (4DM) of the battery is used in the article to connect the interdisciplinary sciences that deal with batteries. The 4DM is utilized to identify the physical manifestation that electrolyte degradation has on the battery and the response observed in the terminal voltage. This paper relates the different kinds of side reactions in the electrolyte and the material properties affected due to these side reactions. It goes on to explain the impact the material property changes has on the electrochemical reactions in the battery. This paper discusses how these electrochemical reactions affect the voltage across the terminals of the battery. We determine the relationship the change in the terminal voltage has due to the change in the design properties of the electrolyte. We also determine the impact the changes in the electrolyte material property have on the terminal voltage. In this paper, the lithium ion concentration and the transference number of the electrolyte are analyzed and the impact of their degradation is studied. Full article

Automation equipment with different functions from different manufacturers is common in lithium ion battery manufacturing workshops, which is manifested as heterogeneous data distributed at different network levels at the information level. The interconnection between a workshop system and equipment is the basis for realizing manufacturing informatization and intelligence, and is a core problem of intelligent manufacturing workshop integration. The key to solve this problem is to establish a standardized and consistent information model. Aiming at the problem of information interconnection, this paper established an information model of the intelligent manufacturing workshop of lithium ion batteries based on the analysis of the architecture, functional categories, and information interaction of the intelligent manufacturing workshop. Then, by clarifying the attribute set, component set, and the information objects contained in each information model, the hierarchical architecture of the information model was constructed. Then, the rules that map the information model in to the OLE for Process Control Unified Architecture (OPC UA) address space is established. The approach for implementing data storage and interaction of the information model based on the OPC UA server/client are also discussed. Finally, taking the soft-pack battery manufacturing workshop as an example, the information model is applied to realize the interconnection and interoperability of production management data, material management data, equipment management data, and quality management data among various levels of the workshop, which verifies the feasibility of the proposed information model. Full article

TiO₂ represents one of the promising anode materials for lithium ion batteries due to its high thermal and chemical stability, relatively high theoretical specific capacity and low cost. However, the electrochemical performance, particularly for mesoporous TiO₂, is limited and must be further developed. Elemental doping is a viable route to enhance rate capability and discharge capacity of TiO₂ anodes in Li-ion batteries. Usually, elemental doping requires elevated temperatures, which represents a challenge, particularly for sulfur as a dopant. In this work, S-doped TiO₂ nanotubes were successfully synthesized in situ during the electrochemical anodization of a titanium substrate at room temperature. The electrochemical anodization bath represented an ethylene glycol-based solution containing NH₄F along with Na₂S₂O₅ as the sulfur source. The S-doped TiO₂ anodes demonstrated a higher areal discharge capacity of 95 µAh·cm⁻² at a current rate of 100 µA·cm⁻² after 100 cycles, as compared to the pure TiO₂ nanotubes (60 µAh·cm⁻²). S-TiO₂ also exhibited a significantly improved rate capability up to 2500 µA·cm⁻² as compared to undoped TiO₂. The improved electrochemical performance, as compared to pure TiO₂ nanotubes, is attributed to a lower impedance in S-doped TiO₂ nanotubes (STNTs). Thus, the direct S-doping during the anodization process is a promising and cost-effective route towards improved TiO₂ anodes for Li-ion batteries. Full article

Understanding dynamic behavior of a battery and the possibility of simulating it is necessary during design of IoT systems. This plays a critical role, especially for industrial devices with low-power demands planned for long lasting operation. While cost limitation mostly leads to use of the low-budget batteries with fast degradation, a model of these batteries supplying low-power loads is provided here. The overall model is in open-loop form because no access to the terminal measurements is available during the design phase. The identification process of the relation between the state of charge and related electromotive force as a key element of the model is discussed. Moreover, guidelines are suggested for identification of this relation. Furthermore, SoC estimation based on the Coulomb counting is modified to include a dynamic inter-cycle aging factor. This factor enables replication of the degradation within a single cycle. In spite of simplicity of this concept, it is able to reduce the model’s estimation error evaluated with two different types of loads. The overall model provides promising results with relative errors less than 0.2%. Full article

The VO²⁺/VO₂⁺ redox couple commonly employed on the positive terminal of the all-vanadium redox flow battery was investigated at various states of charge (SOC) and H₂SO₄ supporting electrolyte concentrations. Electron paramagnetic resonance was used to investigate the VO²⁺ concentration and translational and rotational diffusion coefficient (D_T, D_R) in both bulk solution and Nafion membranes. Values of D_T and D_R were relatively unaffected by SOC and on the order of 10⁻¹⁰ m²s⁻¹. Cyclic voltammetry measurements revealed that no significant changes to the redox mechanism were observed as the state of charge increased; however, the mechanism does appear to be affected by H₂SO₄ concentration. Electron transfer rate (k₀) increased by an order of magnitude (10⁻⁶ ms⁻¹ to 10⁻⁸ ms⁻¹) for each H₂SO₄ concentrations investigated (1, 3 and 5 M). Analysis of cyclic voltammetry switching currents suggests that the technique might be suitable for fast determination of state of charge if the system is well calibrated. Membrane uptake and permeability measurements show that vanadium absorption and crossover is more dependent on both acid and vanadium concentration than state of charge. Vanadium diffusion in the membrane is about an order of magnitude slower (~10⁻¹¹ m²s⁻¹) than in solution (~10⁻¹⁰ m²s⁻¹). Full article

In recent years, solid lithium-ion conductors have been widely studied because of their applications as electrodes and solid electrolytes in rechargeable lithium-ion batteries. Citric acid (CA) and ethylenediaminetetraacetic acid (EDTA) were employed to synthesize the nanostructured NASICON-type Li_1.4Al_0.4Ti_1.6(PO₄)₃ ceramic. The chelating agent, together with an ethylene glycol (EG) and the esterification agent were employed to form a network decorated with uniform dispersed metal ions under specific conditions: molar ratio [complexing agent/metal ions] = 1 and the molar ratio [EG/EDTA] = 6, whereas the solution pH was kept below 1. A well crystalline NASICON structure was formed following the heat treatment of the produced gel at 630 °C. Simultaneous thermal analysis (STA) revealed lower required temperature for pyrolysis and crystallization using EDTA. Powder X-ray diffraction (PXRD) showed the formation of larger crystallite size when citric acid was employed. The data from scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS) have confirmed the higher apparent porosity and a larger proportion of grain boundaries in the case of EDTA-assisted synthesis. Full article