Large-scale Lithium-ion Batteries Research Articles

Strategies and Perspectives on Enhancing Energy Density in Lithium-Ion Batteries

The rapidly growing demand for clean energy transportation and storage systems emphasizes the need for the development of large-scale lithium-ion batteries. Achieving this goal requires a comprehensive approach that considers not only technical aspects but also social, environmental, and economic perspectives. Specifically, the next-generation batteries should exhibit high energy and power densities, long-term cycle stability, and the efficient utilization of low-cost, abundant raw materials. The cathode material is the key determinant of these requirements. This presentation will introduce progress and strategies for enhancing cathode materials and their corresponding cell performances. These strategies include goals to enable reversible redox reaction processes through elemental and compositional choices, as well as crystal structural variations ranging from order to disorder. Furthermore, we combine these with advanced characterization techniques to understand the correlation between material properties and electrochemical behavior at multiple length and depth scales. The discussion also delves into a deeper understanding of the fundamental mechanisms of performance, coupled with advancements in new materials. Overall, the presentation aims to provide valuable insights into the strategy for developing the next generation of lithium-ion batteries.

Propagation dynamics of the thermal runaway front in large-scale lithium-ion batteries: Theoretical and experiment validation

Large-scale lithium-ion batteries are favored in electric vehicles and energy storage stations; for instance, BYD blade batteries and CATL Kirin batteries are popular. A tiny defect will trigger thermal runaway from a local point towards the other parts of the battery, and the boundary between the failure region and the intact region is called the “thermal runaway front,” of which the dynamics are still unclear. Herein, this paper deduces two formulas for the moving speed (vTR) of the thermal runaway front by applying the principles of energy conservation (Formula I) and flame front (Formula II); formulas for the thermal runaway front velocity (vTR) are derived. The velocity vTR conforms to the 1/2 power of the heat conductivity and reaction rate in both formulas. Data regression for the experimental data demonstrated that the overall estimation error was 10 % using Formula I and 25 % using Formula II. As the zero velocity value indicates the termination of thermal runaway propagation, further derivations reveal that forced cooling can suppress thermal runaway as long as the heat dissipation power is higher than the heat generation power. Sufficient heat dissipation time is achieved by the time delay of heat transfer in the long run of thermal runaway propagation. The formula for the dynamics of thermal runaway propagation universally applies to various large-scale lithium-ion batteries, assisting the safe design of high-energy batteries and providing new insights into suppressing battery thermal runaway by the heat transfer delay effect.

Investigating the Structure and Performance of Electrodes Made by Dry and Wet Slurry Processes

Performance, cost, and safety are vital factors in producing and handling lithium-ion batteries. Using a dry process reduces the cost and environmental impact of producing large-scale lithium-ion battery electrodes significantly as solvents are eliminated. Thus, in this study, solvent-free dry electrostatic spray deposition (ESD) and conventional slurry processes were compared to uncover the influence of the manufacturing process on thick LiNi0.8Mn0.1Co0.1O2 (NMC 811) positive electrodes. More pressure during calendering was found necessary for the dry-made (dry) electrodes to have the same porosity, leading to more cracks within the NMC particles and better adhesion. At slower discharge rates, below 2 C, the dry electrodes exhibited a higher specific capacity or about the same capability than that of the slurry-made ones. At higher discharge rates, greater than 2 C, both types of electrodes have poor rate performance, though the slurry-made (slurry) electrodes had a slightly higher capacity. Despite more calendering-induced cracks in the dry electrodes, both electrodes had comparable long-term cycling behavior when tested in full cells with graphite-negative electrodes. This study shows the viability of using the dry-powder ESD process for manufacturing thick electrodes with high active material content, meeting the need for high energy demand.

Thermal behaviour of large scale lithium-ion battery for electric vehicle and hybrid electric vehicle application: a review

Thermal behaviour of large scale lithium-ion battery for electric vehicle and hybrid electric vehicle application: a review

Thermal behaviours of large scale lithium-ion battery for electric vehicle and hybrid electric vehicle application: a review

Thermal behaviours of large scale lithium-ion battery for electric vehicle and hybrid electric vehicle application: a review

A Physics-Informed Composite Network for Modeling of Electrochemical Process of Large-Scale Lithium-Ion Batteries

A Physics-Informed Composite Network for Modeling of Electrochemical Process of Large-Scale Lithium-Ion Batteries

Open access dataset, code library and benchmarking deep learning approaches for state-of-health estimation of lithium-ion batteries

Great progress has been made in deep learning (DL) based state-of-health (SOH) estimation of lithium-ion batteries, which helps to provide recommendations for predictive maintenance and replacement of lithium-ion batteries. However, despite the abundance of articles, few open-source codes are publicly available. While there are several public datasets, they tend to be more oriented toward simulating laboratory environments rather than real-world usage scenarios. Moreover, they solely provide raw data without any corresponding preprocessing codes, resulting in inconsistencies in preprocessing methods across different papers. These reasons lead to unfair comparisons and ineffective improvements. In response to these problems, this paper publishes a large-scale lithium-ion battery run-to-failure dataset, consisting of 55 batteries, and provides a unified data preprocessing method. Besides, we comprehensively evaluate 5 well-known DL-based models to provide benchmark research. To be specific, first, the existing DL-based SOH estimation methods are reviewed in detail. Second, we provide a comprehensive evaluation of DL-based models on 2 large-scale datasets, including 100 batteries, with 3 input types and 3 normalization methods. Third, we make the complete evaluation codes and dataset publicly available for better comparison and model improvement. Fourth, we discuss future DL-based SOH estimation, including unsupervised learning, transfer learning, interpretability, and physics-informed machine learning. We emphasize the importance of open-source code, provide baseline estimation errors (error upper bounds), and discuss existing issues in this field. The code library is available at: https://github.com/wang-fujin/SOHbenchmark.

Understanding the influence of the confined cabinet on thermal runaway of large format batteries with different chemistries: A comparison and safety assessment study

With the increasing development of large format lithium-ion batteries (LIBs) in automotive sectors, thermal runaway (TR) and fire hazards have become crucial challenges. A series of overheating experiments were performed on four large format LIBs with various chemistries under two conditions. To simulate the electric vehicle applications, the cabinet was employed in the confined space tests. The results showed that under the condition of stopping heating at safety venting (SV), all LiNixCoyMnzO2 (NCM) cells caught fire and TR, while no TR occurred for LiFePO4 (LFP) cells. The LFP cells cannot ignite spontaneously but only spray the electrolyte during TR. The triggering temperatures of TR for NCM cells are similar and close to the temperature of SV for LFP cells. For NCM LIBs, with the ratio of nickel increasing, the TR hazards increase, including the thermal and toxic hazards, larger than that of LFP cells. From the aspects of the TR risks and TR hazards, a safety assessment method was established to grade the fire hazards. Compared with open space tests, the LIBs with different chemistries in confined space tests have the same TR risks but lower TR hazards. The fire-induced toxicity was quantitatively evaluated by determining the fractional effective concentration and fractional effective dose. Moreover, the fire of LIBs is compared to the gas jet flame and pool fire of several typical fuels. Such a comparison analysis on large-scale LIBs with different chemistries can contribute to the selection of cells and safety design for automotive sectors.

Introduction to grid‐scale battery energy storage system concepts and fire hazards

AbstractAs the world continues to enact progressive climate change targets, renewable energy solutions are needed to achieve these goals. One such solution is large‐scale lithium‐ion battery (LIB) energy storage systems which are at the forefront in ensuring that solar‐ and wind‐generated power is delivered when the grids need it most. However, the perceived hazards of LIBs due to recent events in the United States and Australia pose a risk to their future success. When a battery energy storage system (BESS) has a multilayered approach to safety, the thermal runaway, fire, and explosion hazards can be mitigated. Successful implementation of this approach requires cooperation, collaboration, and education across all stakeholder groups to break down these preconceived notions. Much can be learned from the recent BESS fire and explosion events to inform safer design and operation. These events and their contributing factors share many commonalities with historic losses in the hydrocarbon industry. Fire and process safety engineers who have traditionally worked in the hydrocarbon industry can be of immense value to the BESS industry.

Thermally Conductive Nitride-Based Ceramic-Coated-Separator for Lithium-Ion Batteries

As the demand for electric vehicles (EVs) increases, a lot of research to achieve high-energy-density lithium-ion batteries (LIBs) is being actively conducted. However, charging an EV, which takes longer than refueling an internal combustion engine vehicle (ICEVs), is still a common concern. As a way to address this problem, high-rate charging can lead to heat accumulation inside LIBs. In particular, in the case of polyolefin-based separators such as polyethylene and polypropylene, which are currently widely used in LIBs, their low melting temperature threatens the safety of cells during fast charging. To compensate for the low thermal stability of these polyolefin-based separators, ceramic-coated separators (CCS), in which a ceramic coating layer is introduced on the surface of the separator, have now become an essential component for securing the safety of LIBs. Nevertheless, conventional oxide- or hydroxide-based ceramic materials such as Al2O3, Mg(OH)2, AlOOH, etc. still have low thermal conductivity to suppress the heat accumulation especially in large-scale LIBs. Thus, CCSs were fabricated using a nitride-based ceramic material having excellent thermal conductivity. After the CCS was prepared, air permeability, ionic conductivity, thermal stability, and adhesion properties of the ceramic coating layer were measured to be compared with those of Al2O3-based CCSs. In addition, the thermal conductivity of nitride- and oxide-based CCSs are compared to confirm the possibility to improve the heat dissipation characteristics of the LIBs.

Voltage Differential Analysis during Power Discharge Operation in Energy Storage Systems

Constant Power Discharge (CPD) is a lucrative operating mode for grid-tied ESS in many energy markets. The CPD mode corresponds to an increasing current drawn as the ESS discharges. The operation can be modeled with an aged anode and cathode open circuit potentials (OCPn/p+RRC) model that can let us identify electrode-level (eSOH) parameters and resistance growth even though we do not have slow discharge with Constant Current. This identification process from realistic ESS field data, namely constant power discharge, will enable continuous eSOH diagnostics and lead to real-time and operando quantification of loss of active material and loss of lithium inventory (LAM and LLI, respectively).In addition, the timing of when the cell groups' differential voltage peaks occur when the battery system is under constant power operations inform us about the imbalance among cell groups in a module of a battery system, as shown in the figure. Using the time separation among cell differential voltage peaks as a metric of cell imbalance can improve cell balancing algorithms that measure cell imbalance using maximum or minimum voltage, which can be directly affected by the power limits of the battery system.The efficacy of the proposed algorithms is evaluated for multi-cell modules consisting of NMC/graphite cells, operating as part of a large-scale grid-connected energy storage system. Ultimately, by enabling improved diagnostics of the state of health of individual cells in a battery system and improved cell balancing algorithms, this work will enhance the performance and safety of large-scale lithium-ion battery systems. Figure 1

Experimental Investigation of Thermal Runaway Behavior and Hazards of a 1440 Ah LiFePO4 Battery Pack

The thermal runaway (TR) behavior and combustion hazards of lithium-ion battery (LIB) packs directly determine the implementation of firefighting and flame-retardants in energy storage systems. This work studied the TR propagation process and dangers of large-scale LIB packs by experimental methods. The LIB pack consisted of twenty-four 60 Ah (192 Wh) LIBs with LiFePO4 (LFP) as the cathode material. Flame performance, temperature, smoke production, heat release rate (HRR), and mass loss were analyzed during the experiment. The results indicated that TR propagation of the LIB pack developed from the outside to the inside and from the middle to both sides. The development process could be divided into five stages corresponding to the combustion HRR peaks. In the initial stages, the main factor causing LFP battery TR under heating conditions was the external heat source. With the propagation of TR, heat conduction between batteries became the main factor. Hazard analysis found that the HRRmax of the LIB pack was 314 KW, more than eight times that of a single 60 Ah battery under heating conditions. The LIB pack had higher normalized mass loss and normalized THR (6.94 g/Ah and 187 KJ/Ah, respectively) than a single LFP battery. This study provides a reference for developing strategies to address TR propagation or firefighting in energy storage systems.

A multi‐objective parallel layered equalizer for large‐scale lithium ion battery system

The equalisers available are difficult to give consideration to both high balance efficiency and fast balance speed, and their performances are unstable as the number of the series-connected batteries increases, so they are unsuitable for a large-scale battery system. A multi-objective parallel layered equaliser based on battery working states for the large-scale lithium-ion battery system is presented. The equaliser has two types of balance objects and two corresponding layers, and the first layer and the second layer take the single battery and the battery unit as the balance object, respectively. The multi-objective parallel layered balance means that multiple balance objects are selected as the balance objectives simultaneously at each layer. The balance speed is fast due to the multi-objective parallel balance. The balance efficiency is high due to the short energy path and the complementary pulse width modulation (PWM) control in the first layer, and the double voltage value of the balance object in the second layer. Moreover, the performance of the equaliser is stable, even when the number of series-connected batteries is large. In short, the proposed equaliser features high efficiency, fast speed, and strong scalability. Further, the experimental platform for a battery system with twelve series-connected lithium-ion phosphate batteries is built, and then the balance experiments have been completed. Finally, the effectiveness of the equaliser is verified by the corresponding experimental results.

Study of Improving the Thermal Stability of Ceramic Coated Separator Via Chemical Crosslinking between Ceramic Particles and Polymeric Binders

Lithium-ion batteries (LIBs) are used in everyday applications such as portable electronics and electric vehicles (EVs) in our daily life. In large-scale batteries such as EVs, high energy density has been developed to secure longer mileage with one charge. Securing battery safety becomes extremely challenging as densifying the cell energy and increasing the battery. The safety of batteries must be guaranteed from the cell to the module, the pack, and the system, and it must not be ignored at every step. The separator is highlighted at the cell level as it plays an essential part in safety. To guarantee the safety of large-scale LIBs, it is essential to employ a ceramic-coated separator (CCS). To secure thermal stability using CCSs, the certain thickness of ceramic coating layer (CCL) is required. In contrast, the thicker CCL can act as a resistive layer in the cell, and in the worst case, the ceramic that has fallen off the CCS surface can act as a side reactant in the cell. However, if the CCL is thin, the desired thermal stability may not be obtained. The key technology is to improve adhesion while reducing the thickness of the CCL.For this purpose, polydopamine nano layer is preliminary introduced on the surface of ceramic particles via simple solution polymerization. Then, poly(acrylic acid) binder, which can react with amine groups in polydopamine, is chosen for aqueous ceramic coating slurry. Thus, this combination can make several crosslinking points within CCL, which lead to higher adhesion within the CCL after electrolyte impregnation. As a result, the adhesion within the CCL of cross-linked CCS is increased by 70% compared to the non-crosslinked CCS. Furthermore, the adhesion does not decrease when impregnated with the electrolyte. Also, cross-linked CCS showed better shrinkage property than commercialized CCS with the same composition because the cross-linked CCS did not shrink even when exposed for 1 hour at a high temperature of 160 °C. From this study, with crosslinking reaction within coating layer, it is possible to improving heat resistance and physical properties of separator without increasing thickness of CCL.

State of health monitoring by gas generation patterns in commercial 18,650 lithium-ion batteries

• Non-disruptive lab made Raman spectroscopic system is applied for gas analysis. • Four distinct phases of gas expulsion were found until commercial LIB’s end of life (EOL). • Mathematical model related to SOH is proposed based on the 4 gas expulsion phases. Because large-scale lithium-ion battery (LIB) packs are compactly constructed using many LIB cells, one battery can cause fire of the other LIB cells when a few cells of them are damaged by accident owing to the latent risk of thermal decomposition reactions. To alleviate this problem, research seeks to provide an understanding of the gas generating mechanisms during cycling, electrolyte decomposition, and electrode material reactions. Understanding gas behaviors can prevent propagation of a battery fire and other hazardous situations. Therefore, in this study, we investigate commercial 18,650 cylindrical cells with long-term cycling. A lab-made in-situ Raman spectroscopic system and comprehensive transient electrochemical analyses are utilized to explore four gas expulsion phases. In addition, gas generation data are assessed for various overcharging voltage cutoffs (4.2–4.6 V). For the first time, furthermore, a simple empircal mathematical model is proposed, based on the distinct gas evolution phases, that can provide the insight into the state of health (SOH) of commercial 18,650 cells.

Experimental study on the thermal runaway and fire behavior of LiNi0.8Co0.1Mn0.1O2 battery in open and confined spaces

With the increasing deployment of large-scale lithium ion batteries (LIBs), thermal runaway (TR) and fire behavior are significant potential risks, especially for high energy density cells. A series of thermal abuse tests and hazard analysis on 117 Ah LiNi0.8Co0.1Mn0.1O2/graphite LIBs were performed under two conditions, “open space” and “confined space”. In open space tests, the fire behavior of LIBs was characterized with respect to the TR process, temperature characteristics, mass variation, voltage, heat release rate and gas release. To simulate the application scenarios in electric vehicles, a confined cabinet was introduced. The effects of state of charge and confined cabinet on the fire behavior of individual cell were analyzed. Furthermore, a real-scale scenario was considered for the evaluation of fire-induced toxicity using Fractional Effective Dose (FED) and Fractional Effective Concentration (FEC) models. The obtained results show that the effects of asphyxiant gases are more significant than those of irritant gases. The maximum FEC and FED values are greater than the critical threshold of 1, indicating the catastrophic toxicity in such fire scenarios. The minimum fresh air renewal rate required is computed to provide quantitative guides for ventilation management, firefighting and rescue.

Techno-Economic Analysis of Utility-Scale Solar Photovoltaic Plus Battery Power Plant

Decarbonizing the global power sector is a key requirement to fight climate change. Consequently, the deployment of renewable energy (RE) technologies, notably solar photovoltaic (PV), is proceeding rapidly in many regions. However, in many of these regions, the evening peak is predominantly being served by fossil-fired generators. Furthermore, as the evening peak is projected to increase in the coming years, there are plans to install more fossil-fired peaking generators. A cleaner alternative is to enable solar PV plants to provide clean power after sunset by pairing them with large-scale lithium-ion batteries to provide evening peak generation. In this work, we performed a techno-economic analysis of a solar PV plus battery (PVB) power plant using the island of Mauritius as a case study. We assessed the impacts of the battery size, inverter loading ratio (ILR), tracking type, and curtailment on the levelized cost of electricity (LCOE). The main results show that the LCOE of utility-scale PVB systems are comparable to that of fossil-fired peaking generators for this case study. Tracking was shown to exacerbate the clipping loss problem and its benefits on LCOE reduction decrease as the ILR increases. The availability of the PVB system to serve the evening peak was found to be high. The curtailment analysis also showed that planners must not rely solely on storage, but rather should also improve grid flexibility to keep PVB integration affordable. Overall, the practical insights generated will be useful to utility planners in charting their generation expansion strategy.

Mitigating overcharge induced thermal runaway of large format lithium ion battery with water mist

• Overcharge induced thermal runaway can be efficiently prevented with water mist. • Over 80% of the total heat generation is released after the thermal runaway. • The battery flame can be suppressed within several seconds with water mist. • The maximum cooling power of water mist can reach 9.0 kW in the tests. Thermal runaway (TR) is one of the ringleaders of lithium ion battery (LIB) hazard, which has become a major safety concern. Especially to the large-scale LIBs, the TR has been intensified owing to the expanded capacity. Hence, effective countermeasures are urgently needed. In this study, the cooling control capacity of water mist (WM) on mitigating the overcharge induced TR for large-scale LIB is experimentally studied. The thermal hazard processes with and without WM have been comprehensively investigated. Results show that the battery flame experiences rapid increasing process from 0.02 m to 0.9 m, which intensifies the inhomogeneity of temperature distribution. The total heat accumulation of the LIB reaches 1971.0 kJ, over 80% of which is generated after TR. A critical inflection point during TR development has been identified, where the WM has been introduced to successfully suppress the TR. For cases with continuous overcharge current, the occurrence of TR is unstoppable, but the hazard has been significantly mitigated with the maximum temperature decreases to 122.1 °C, and over 1000 kJ heat has been dissipated during WM release. This work confirms the excellent cooling capacity of WM on the large-scale LIB, and the overcharge induced TR can be effectively mitigated.

Thermal runaway characteristics and failure criticality of massive ternary Li-ion battery piles in low-pressure storage and transport

Thermal runaway is a major safety concern for Lithium-ion batteries in manufacture, storage, and transport. Facing the frequent incidents in the air transport of massive batteries, more reliable fire prediction and protection strategies under low-pressures conditions are urgently needed. Herein, thermal runaway criticality of the open-circuit cylindrical battery piles (up to 9 cells with 30% SOC) under a hot boundary is investigated inside a novel low-pressure chamber (20–100 kPa). Characteristics battery temperatures for the safety venting and thermal runaway are measured to analyze the influences of pressure and cell number on battery failures. Results indicate that lowering the pressure could promote an earlier and stronger safety venting and weaken the intensity of the exothermic reactions inside cells, which is verified by the surface morphology of the electrodes. The overall fire risk is higher with higher pressure and larger battery-pile size, as indicated by the lower minimum boundary temperature for thermal runaway (255 °C~385 °C). Moreover, a simplified heat transfer model is established to explain the trend of thermal-runaway criteria and the influence of the low-pressure environment. This work delivers new insights into the effects of pressure and pile size on battery thermal runaway, which can help to improve the safe storage and transport of large-scale lithium-ion battery piles under varied pressure conditions.

Experimental comparison of Oxygen Consumption Calorimetry and Sensible Enthalpy Rise Approach for determining the heat release rate of large-scale lithium-ion battery fires

From a fire safety point of view, the burning behavior of lithium-ion batteries is of high interest. The heat release rate (HRR) is the most important fire parameter to analyze the fire hazards of burning objects, so that an accurate determination of it is crucial. In this paper, two different measurement techniques, the Oxygen Consumption Calorimetry (OCC) and the Sensible Enthalpy Rise Approach (SERA) are simultaneously performed in the same calorimeter to measure the HRR of two different types of lithium-ion batteries. HRR values as well as total energies determined by SERA are higher than measured with OCC: The total energy released is about 10–12 times (SERA) and 6–9.5 times (OCC) the electrical stored energy for both battery types, whereas the timescales of the release differ strongly between the types, resulting in maximum HRRs of 3.4 MW (SERA) and 1.5 MW (OCC) for one module of type A and 0.8 MW (SERA) and 0.6 (OCC) of type B respectively. Furthermore, a sensitive dependency of the HRR measurement with SERA on the position of the wall temperature measurement is observed.