Lithium-ion Cells Research Articles

Analysis of cell balancing of Li-ion batteries with dissipative and non-dissipative systems for electric vehicle applications

This article describes the essential components of contemporary battery management systems (BMS), such as power electronics bidirectional charging and discharging, reverse protection against constant current and voltage, and Li-ion battery cell balancing, which is the process of introducing Li-ion The majority of domestic electrical applications, including e-cars, are powered by batteries. These qualities are crucial for ensuring the safety, longevity, and effectiveness of batteries when it comes to renewable energy sources and electric vehicles (EVs). Two other crucial BMS characteristics that protect against reverse current and overcharging destroying batteries are constant current and voltage reverse protection. Ensuring that every single cell in a battery is in balance is known as evenly charging and discharging every single cell. In-depth discussions of these characteristics' advantages and operation, as well as their uses in EVs, renewable energy systems, and other contexts, are provided in this article. It is seen from the analysis that the non-dissipative lithium-ion battery cell balancing strategy, which significantly enhances safety and efficiency, provides greater benefits than the dissipative balancing approach. The modelling of an SoC charge-controlled Li-Ion battery with an optimum battery voltage of 3.6 V. Its rated capacity of 4 Ah is considered a test cell that has contrasted dissipative and non-dissipative balancing in MATLAB/Simulink with five cells in the battery bulk. It is seen from the analysis that the non-dissipative lithium-ion battery cell balancing strategy provides greater benefits than the dissipative balancing approach.

External Short-Circuit Scenarios under Different Mechanical Pressures Applied to Lithium-Ion Cells with Silicon-Dominant Anodes

Abstract The safety behavior of lithium-ion cells using high contents of silicon as new anode active material was barely investigated. This work investigates the short-circuit behavior of self-manufactured single-layered pouch cells using 70%wt microscale silicon and NCA cathodes in a novel dual reference cell setup consisting of a gold wire and a lithium metal reference electrode. Six cells were externally shortened at three different compression levels using a novel developed quasi-isothermal calorimetric shortcircuit test bench. The same current plateaus and transition zones were observed for all pressure settings, as reported in the literature for graphite-containing anodes. In addition, a direct dependency of the short-circuit intensity and the heat generation is measured for the differently compressed cells. This higher short-circuit intensity was quantitatively explained by the decreasing impedance at increased pressure levels. The built-in reference electrodes allow for monitoring of the negative terminal voltage, revealing potentials of up to 3:508 V versus Li+/Li and thus explaining the measured over-discharge in the range of ≈25% SoC. The post-mortem analysis reveals copper deposition on both electrodes and the separator, confirming the electrochemically measured over-discharge. Linear scans and potential trajectories reveal 3.379 V versus Li+/Li as oxidation potential for copper dissolution using copper||lithium-metal coin cells.

Novel SoC-Based FBG Calibration Method for Decoupled Temperature and Strain Analysis within LIB Cells

Abstract Internal temperature monitoring of battery cells can be very useful, as the core temperature can deviate significantly from that of the housing, especially in case of cells with a thick electrode stack. Conventional resistance temperature detectors can accurately measure temperature, but are limited to the outer surface of the cell due to induction effects. They are therefore not suitable for internal in situ measurements. Fiber Bragg grating (FBG) sensors are unaffected by the electric field as they operate by reflecting light. However, a specific difficulty is the distinction of temperature vs. strain effects as the grating is sensitive to both. In this work a calibration routine to separate the influences of temperature and strain in a lithium-ion battery cell is presented and examined for two multi-layer stack pouch cells (10 and 20 Ah). The obtained in situ temperature data reveal a difference of up to 2°C between center and cell housing at elevated discharge rate (4C) and a delay in detection of temperature peaks by the external sensor by 12 s. Strain data correlate with numbers of electrode layers in the stack and yield a stress of up to 27.3 MPa in the center of the 20 Ah cell.

Correction to “Evaluating Fire and Smoke Risks with Lithium-Ion Cells, Modules, and Batteries”

Correction to “Evaluating Fire and Smoke Risks with Lithium-Ion Cells, Modules, and Batteries”

Nanofillers modified with aluminum carboxylate for application in Polymer composite electrolytes for lithium-ion batteries

AbstractOne of the additives that positively influence the parameters of the electrolyte for lithium-ion cells are ceramic nanoparticles, such as SiO2 and α-Al2O3. However, they tend to agglomerate and sediment, which is an unfavorable phenomenon. An effective strategy to prevent this is to modify the surface of the particles with polymeric compounds, which can increase compatibility and stability in the electrolyte system. To reduce agglomeration and sedimentation, a method was developed to modify aluminum oxide and silica particles using aluminum carboxylate, which chemically combines with inorganic particles that have hydroxyl groups on their surface through an alkoxide bond. This method allows the introduction of oligooxyethylene groups to the ceramic surface, thus obtaining more stable systems. The effectiveness of this modification was confirmed through dynamic light scattering (DLS) measurements of particle size in liquid organic solvents, which are potential solvents for liquid electrolytes in lithium-ion cells. The modified nanosilica and aluminum oxide particles were then used as additives to solid polymer electrolytes made of poly(ethylene oxide) (PEO). This led to higher conductivity values compared to the use of unmodified fillers. The obtained values of lithium transference number for solid polymer electrolyte with PEO/CF3SO3Li and nanosilica or aluminum oxide modified with aluminum carboxylate are equal to 0.32–0.40.

Advanced Monitoring and Real-Time State of Temperature Prediction in Lithium-Ion Cells Under Abusive Discharge Conditions Using Data-Driven Modelling

Advanced Monitoring and Real-Time State of Temperature Prediction in Lithium-Ion Cells Under Abusive Discharge Conditions Using Data-Driven Modelling

Modeling and Simulation of Thermal Effects on Electrical Behavior in Lithium-Ion Cells

Thermal effects exert a crucial influence on the electrical behavior of lithium-ion batteries, significantly impacting key parameters such as the open circuit voltage curve, internal impedance, and cell degradation rate. Furthermore, these effects may give rise to electrolyte loss, resulting in a reduction in capacity. The cycling of batteries inherently generates internal heat, establishing a direct relationship between cell temperature and power demand. This article aims to provide a methodology to model electrothermal relations and temperature influence on electrical behavior in lithium-ion cells, as well as a simulation of extended cell operation under arbitrary power loads, presenting a novel approach not previously explored. It does this by considering three models: the Bernardi model for heat generation within the cell, a thermal lumped model for the cell’s temperature, and the Vogel-Fulcher-Tammann model for the capacity change as a function of temperature. These models are then connected to a state-of-the-art open circuit voltage model of a cell, providing a connection from the thermal world back into the electrical world. Experiments with different power demands occur on the simulation, including estimation of thermal parameters with relative errors under 1%, visualizing the effects of the integrated models and potential for real-cell applications.

Purification of Li2CO3 obtained through pyrometallurgical treatment of NMC black mass from electric vehicle batteries.

The recycling of lithium batteries is essential for a sustainable energy transition. However, impurities in the products obtained from the black mass can lower their market value. In this work, lithium carbonate, which has the highest market share among lithium-based products, is purified using distilled water at controlled temperature, time and stirring speed. The purification process involves dissolving lithium carbonate in distilled water at low temperatures (between 0 and 10°C), followed by crystallization through water evaporation. Optimal conditions yielded lithium carbonate with a purity of 99.66% after two stages of purification. The dependence of the variables on the final purity was deeply analyzed and the thermodynamics of the reaction was studied, confirming the exothermic nature the dissolution reaction.

Polymeric Lithium Battery using Membrane Electrode Assembly

Alternative configuration lithium cell exploits electrode and polymer electrolyte cast all‐in‐one to form a membrane electrode assembly (MEA), in analogy to fuel cell technology. The electrolyte is based on polyethylene oxide (PEO), lithium bis‐trifluoro sulfonyl imide (LiTFSI) conducting salt, LiNO3 sacrificial film‐forming agent to stabilize the lithium metal, and fumed silica (SiO2) to increase the polymer amorphous degree. The membrane has conductivity ranging from ~5×10−4 S cm‐1 at 90 °C to 1×10−4 S cm‐1 at 50 °C, lithium transference number of ~0.4, and relevant interphase stability. The MEA including LiFePO4 (LFP) cathode is cycled in polymer lithium cells operating at 3.4 V and 70 °C, with specific capacity of ~155 mAh g‐1 (1C = 170 mA gLFP‐1) for over 100 cycles, without signs of decay or dendrite formation. The cell exploiting the MEA shows enhanced electrochemical performance as compared with the one using simple polymeric membrane stacked between cathode and anode. Furthermore, the MEA reveals the key advantage of possible scalability and applicability in roll‐to‐roll systems for achieving high‐energy lithium metal battery, as demonstrated by pouch‐cell application. These data may trigger new interest on this challenging battery exploiting the polymer configuration for achieving environmentally/economically sustainable, and safe energy storage.

Tetraphenylethene-Containing Nanofilm via Interfacial Confinement Self-Assembly for Fluorescent Monitoring of SOCl2 Leakage in a Li-SOCl2 Battery Electrolyte.

Lithium thionyl chloride (Li-SOCl2) batteries are widely used due to their high energy density and long shelf life. However, the corrosive nature of SOCl2 poses a safety hazard, necessitating effective leak detection methods. We report an approach for real-time fluorescent detection of SOCl2 leakage in Li-SOCl2 batteries using a tetraphenylethene-based nanofilm. The nanofilms were prepared through the interfacial confined self-assembly method and exhibit excellent flexibility, homogeneity, tunable size and thickness, and adaptability to various substrates, enabling easy integration into sensor devices. They possess high photochemical stability and a photoluminescence quantum yield exceeding 25%, demonstrating their potential as high-performance fluorescent sensing material. The nanofilms also exhibit high sensitivity, good reproducibility, and selectivity toward SOCl2 detection. Upon exposure to SOCl2 vapor, the nanofilm shows a red-shifted and fluorescence quenching response, attributed to the protonation of the acylhydrazone bond in the nanofilm by the hydrolysis product of SOCl2, which disrupts the electronic structure of the nanofilm and leads to a decrease in the fluorescence intensity and a shift in the emission wavelength. A detection limit of ∼1.31 ppt and excellent repeatability over 300 cycles are demonstrated, highlighting their high sensitivity and reliability. This work paves the way for a highly sensitive and reliable leak detection system for Li-SOCl2 batteries, enhancing their safety and reliability in various applications.

Cost modeling for the GWh-scale production of modern lithium-ion battery cells

Battery production cost models are critical for evaluating the cost competitiveness of different cell geometries, chemistries, and production processes. To address this need, we present a detailed bottom-up approach for calculating the full cost, marginal cost, and levelized cost of various battery production methods. Our approach ensures comparability across research fields and industries, reflecting capital and imputed interest costs. We showcase the model with case studies of a prismatic PHEV2 hardcase cell and a cylindrical 4680 cell in four different chemistries. Our publicly available browser-based modular tool incorporates up-to-date parameters derived from literature and expert interviews. This work enables researchers to quickly assess the production cost implications of new battery production processes and technologies, ultimately advancing the goal of reducing the cost of electrified mobility.

Quantifying the Effect of Degradation Modes on Li-ion Battery Thermal Instability and Safety

Understanding the thermal stability of lithium-ion (Li-ion) cells is critical to ensuring optimal safety and reliability for various applications such as portable electronics and electric vehicles. In this work, we demonstrate a combined modeling and experimental framework to interrogate and quantify the role of different degradation modes on the thermal stability and safety of Li-ion cells. A physics-based Li-ion cell aging model is developed to describe the underpinning role of degradation mechanisms such as Li plating, solid electrolyte interphase growth, and the loss of electrode active material on the resulting capacity fade during cycling. By incorporating mechanistic degradation descriptors from the aging model, we develop a degradation-aware cell-level thermal stability framework that captures key safety characteristics such as thermal runaway (TR) onset temperature, self-heating rate, and peak TR temperature for different cycling conditions. Additionally, we perform electrochemical and accelerating rate calorimetry (ARC) experiments to evaluate the thermo-kinetic parameters associated with the various exothermic reactions during TR of pristine and aged Li-ion cells. Through a synergistic integration of thermo-electrochemical characteristics from the ARC experiments and degradation insights from the cell aging model, the proposed aging-coupled safety framework provides a baseline to quantify the thermal stability of Li-ion cells subject to a wide range of operating conditions and degradation scenarios.

Multi-Step Ageing Prediction of NMC Lithium-Ion Batteries Based on Temperature Characteristics

The performance of lithium-ion batteries depends strongly on their ageing state; therefore, the monitoring and the prediction of the battery state of health (SoH) is necessary for an optimized and secured functioning of battery systems. This paper evaluates and compares three artificial neural network architectures for multi-step ageing prediction of lithium-ion cells: Recurrent Neural Network (RNN), Gated Recurrent Unit (GRU) and Long short-term memory (LSTM). These models use the features extracted from the cell’s temperature to predict the cell’s capacity. The features are extracted from experimental measurements of the cell’s surface temperature and selected based on Spearman correlation analysis. The prediction results were evaluated and compared considering three different percentages of the training dataset: 60%, 70%, and 80%. Training and testing data were generated experimentally based on accelerated ageing cycling tests. During these experiments, four Nickel Manganese Cobalt/Graphite (NMC) cells were cycled under a controlled temperature environment based on a dynamic current profile extracted from the Worldwide Harmonized Light Vehicles Test Cycles.

Impact of Electrolyte Additives on the Lifetime of High Voltage NMC Lithium-Ion Pouch Cells

Abstract This work involves improving the lifetime of lithium-ion cells during high voltage cycling using electrolyte additives. Three generations of electrolyte additives were investigated and screened in NMC442/graphite pouch cells using a 24 h voltage-hold protocol at 40°C to accelerate oxidative reactions occurring at 4.4 V. Once promising additives and combinations were identified, they were then tested in cobalt-free NMC640/graphite cells for long-term cycling to upper cutoff voltages of 4.3, 4.4, and 4.5 V at temperatures of 20, 40, and 55°C. Degradation mechanisms were probed using dV/dQ analysis, micro-X-ray fluorescence spectroscopy, and electrochemical impedance spectroscopy. The primary failure mode of cells held at high voltages is due to increase in cell impedance, which is correlated to the dissolution of transition metals, specifically manganese, originating from the positive electrode. We believe this dissolution is presumably due to the formation of a high impedance rock salt surface layer on the NMC positive electrode particles. Such deleterious outcomes can be limited by selecting an appropriate electrolyte additive package. It is hoped that this paper can provide a starting point for developing NMC Li-ion cells that can operate to voltages as high as 4.4 V and still display long lifetimes.

Properties of Wedge Wire Bonded Connection Between a Composite Copper Core Aluminum Shell Wire and an 18650 Cylindrical Lithium-Ion Battery Cell.

Wedge wire bonding is a solid-state joining process that uses ultrasonic vibrations in combination with compression of the materials to establish an electrical connection. In the battery industry, this process is used to interconnect cylindrical battery cells due to its ease of implementation, high flexibility and ease of automation. Wire materials typically used in battery pack manufacturing are pure or alloyed aluminum and copper. While copper wires possess better electrical properties, the force used in the bonding process can lead to cell isolator damage and cell thermal runaway. This is an unacceptable result of the bonding process and has led to the development of new types of composite wires containing a copper core embedded in an aluminum shell. This material has the advantage of high copper electrical and thermal conductivity combined with less aggressive bonding parameters of the aluminum wire. The aim of this study was to establish a process window for the wedge wire bonding of 400 µm composite copper-aluminum Heraeus CucorAl Plus wire on the surface of a BAK 18650 battery cell. This study was conducted using a Hesse Bondjet BJ985 CNC wire bonder fitted with an RBK03 bond head designed for the bonding of copper wires. The methods used in this study included light and scanning electron microscopy of bond and battery cell cross-sections, shear testing on the XYZtec Sigma bond tester system, and energy dispersive spectroscopy. The results were compared with a previous study conducted using a wire of the same diameter and made out of high-purity aluminum.

Unveiling the Role of Filler Characteristics in Enhancing the High-Voltage Performance of Succinonitrile-Based Solid-State Lithium-Metal Batteries.

For exploiting high-energy lithium-metal batteries, it is of utmost importance to develop electrolytes that possess exceptional ionic conductivity and an extensive electrochemical stability range. In this study, 3D PAN nanofibers and polymer electrolytes incorporating various inorganic fillers with different Lewis acid-base properties were fabricated. PAN@Al-SSE exhibits exceptional ionic conductivity (0.48 mS·cm-2 at room temperature), a high Li+ transference number (0.41), and a wide electrochemical window (5.26 V). The device is able to operate stably in Li symmetric cells for more than 1000 h under a potential of 0.03 V under a current density of 0.2 mA·cm-2. Besides, the groundbreaking technology equips high-voltage Li-LiCoO2 solid-state batteries with exceptional cycling performance (91.3% and 82.1% retention after 100 cycles at 0.2 and 1 C, respectively) at room temperature. Mechanistic studies indicate that the Lewis acid-base properties of surface fillers are instrumental and crucial to form a stable solid-electrolyte interphase layer. γ-Al2O3, in particular, with more Lewis acid sites, ensures the dissociation of LiTFSI and induces the excessive decomposition and polymerization of succinonitrile. There exists an equilibrium effect between dissociation and polymerization in a succinonitrile-based solid electrolyte, which plays a critical role in improving the manifestation of succinonitrile-based solid-state lithium cells, especially under high-voltage conditions.

Numerical Research on Electrochemical Behavior, Thermal Characteristics, and Aging Formation of Lithium-Ion Cell at Different Ambient Temperatures and Charge/Discharge Rates

Numerical Research on Electrochemical Behavior, Thermal Characteristics, and Aging Formation of Lithium-Ion Cell at Different Ambient Temperatures and Charge/Discharge Rates

Experimental measurement and modeling of the internal pressure in cylindrical lithium-ion battery cells under abuse conditions

The internal pressure evolution of cylindrical lithium-ion battery cells under abuse tests is evaluated in this work. The pressure evolution is recorded through a cavity at the center of the inner structure of the cylindrical cell. Understanding pressure buildup due to exothermic reactions aids in designing safety features, such as improved venting mechanisms. The pressure activation for the safety mechanism depends on both the venting cap design and the different abuse test conditions. This study focuses on two important parameters: the state of charge (SOC) and the overheating ramp. The SOC significantly influences the venting pressure activation at the overheating abuse tests. The 18650 cell exhibits a similar venting behavior as the 21700 cell, with pressure safety mechanisms activating sooner for the 18650 cell. The geometric structure of the battery and safety mechanisms significantly influence vent-activation thresholds. After the Current Interruptor Device (CID) breakdown, pressure rises exponentially until venting occurs, due to gas generation from the decomposition of internal components and electrolyte vaporization. With the experimental data for the overheating abuse test, a model that predicts the evolution of the pressure has been developed. For the overcharging abuse test, the pressure evolution has been measured with different current rates (C-rates) to simulate overcharge with standard charging current and fast charging current. However, the internal pressure inside the cell activates the current interrupt device, which avoids overcharging the cell, thus preventing the thermal runaway (TR) from occurring.

A Novel Method for Obtaining the Electrical Model of Lithium Batteries in a Fully Electric Ultralight Aircraft

This article introduces a novel approach for developing an electrical model of the lithium batteries used in an electric ultralight aircraft. Currently, no method exists in the technical literature for accurately modeling the electrical characteristics of batteries in an electric aircraft, making this study a valuable contribution to the field. The proposed method was validated with an all-electric ultralight aircraft designed and constructed at the Pascual Bravo University Institution. To build the detailed model, a kinematic analysis was first conducted through takeoff tests, where data on the speed, acceleration, time, and distance required for takeoff were collected, along with measurements of the current and power consumed by the batteries. The maximum speed and acceleration of the aircraft were also recorded. These kinematic results were obtained using two batteries made from Samsung INR-18650-35E lithium-ion cells, and different wing configurations of the aircraft were analyzed to assess their impacts on the battery energy consumption. Additionally, the discharge cycles of the batteries were evaluated. In the second phase, laboratory tests were performed on the individual battery cells, and the Peukert coefficient was estimated based on the experimental data. Finally, using the Peukert coefficient and the kinematic results from the takeoff tests, the electrical model of the battery was fine tuned. This model allows for the creation of charging and discharging equations for ultralight lithium batteries. With the final electrical model and energy consumption data during takeoff, it becomes possible to determine the energy usage and flight range of an electric aircraft. The model indicated that the aircraft did not require a long distance to takeoff, as it reached the necessary takeoff speed in a very short time. The equations used to simulate the discharge cycles of the batteries and lithium cells accurately described their energy capacities.

Safety Aspects of Sodium-Ion Batteries: Prospective Analysis from First Generation Towards More Advanced Systems

After an introductory reminder of safety concerns pertaining to early rechargeable battery technologies, this review discusses current understandings and challenges of advanced sodium-ion batteries. Sodium-ion technology is now being marketed by industrial promoters who are advocating its workable capacity, as well as its use of readily accessible and cheaper key cell components. Often claimed to be safer than lithium-ion cells, currently only limited scientifically sound safety assessments of sodium-ion cells have been performed. However, the predicted sodium-ion development roadmap reveals that significant variants of sodium-ion batteries have entered or will potentially enter the market soon. With recent experiences of lithium-ion battery failures, sodium-ion battery safety management will constitute a key aspect of successful market penetration. As such, this review discusses the safety issues of sodium-ion batteries, presenting a twofold innovative perspective: (i) in terms of comparison with the parent lithium-ion technology making use of the same working principle and similar flammable non-aqueous solvent basis, and (ii) anticipating the arrival of innovative sub-chemistries at least partially inspired from successive generations of lithium-ion cells. The authors hope that the analysis provided will assist concerned stakeholders in the quest for safe marketing of sodium-ion batteries.