Abstract Estimating the life of lithium ion batteries is a longstanding issue for electric vehicles as well as energy storage applications. For grid scale storage applications, this is particularly pertinent given that the commercial viability of projects is closely correlated with the accuracy of battery degradation estimations. A large volume of literature therefore is devoted to understanding various degradation mechanisms in lithium ion batteries and developing both diagnostic and prognostic degradation models. In this context, estimating calendar aging resulting from the chemical decomposition of electrolyte solution is relatively well established. Developing a cycle life counterpart however has been more challenging. The convoluted nature of interactions between various degradation mechanisms during cycling results in complex physics-based life models; coupled with a lack of detailed battery life testing data, these models are often difficult to adopt in application, both in academic and industrial settings. To this end, empirical relations such as analogues of the Wohler curve are used to estimate the ‘cycles to failure’ for battery cycling with various ‘Depth of discharges (DODs)’. In a previous publication, Deshpande et al. [1] proposed that at lower discharge/charge rates of battery operation, SEI cracking and reforming is a dominant mechanism of cell capacity loss for continuous cycling. These ideas are further exploited in this article to develop a pragmatic physics-based model for estimating Li-ion battery cycle life combining the effects of SEI growth and SEI cracking-reforming mechanisms. Such a model is of particular interest to grid scale energy storage applications where the operating C-rates are relatively mild and operational life is long. Beyond proposing a physics-based model to estimate ‘cycles to failure’ for various DODs, we also validate the model against long duration cycling datasets from the battery energy storage literature. The simplicity of the model and its adaptability for batteries with sparsely available datasets makes it highly useful.

ABSTRACT A cell’s ability to store energy, and produce power is limited by its capacity fading with age. This paper presents the findings on the performance characteristics of prismatic Lithium-iron phosphate (LiFePO4) cells under different ambient temperature conditions, discharge rates, and depth of discharge. The accelerated life cycle testing results depicted a linear degradation pattern of up to 300 cycles. Linear extrapolation reveals that at 25°C temperature, an increase in the discharge rate from 0.5 C to 0.8 C reduces the cycle life significantly by 52.9%. On the other hand, at a constant discharge rate, an increase in temperature reduced predicted cycle life in the range of 23.2–41.36%. Lithium-ion cells’ reliability modeling and analysis was carried out using an exponential distribution showing the increasing failure rate with age, with the temperature significantly reducing the expected life of the cells.

The performance of lithium-ion batteries (LIBs) is influenced by the coupled effects of environmental conditions and operational scenarios, which can impact their electrochemical performance, reliability, and safety. This review examines the individual and combined effects of temperature, vibrations, and charging/discharging ratio on LIB performance. Temperature primarily affects the rate of chemical reactions and the stability of physical structures. High temperatures accelerate the aging process, while low temperatures reduce charging and discharging efficiency. Vibrations cause internal structural damage, increasing the internal resistance and capacity decay. Additionally, the charging/discharging cycle rate, especially high rates, significantly impacts cycle stability and thermal management design. The combined effects of these factors can lead to nonlinear changes in battery performance, exacerbating the aging process and potentially triggering safety issues. This review discusses the mechanisms of these combined effects and proposes corresponding mitigation strategies based on experimental data. It provides a theoretical foundation and experimental evidence for reliability research on LIBs, which has implications for battery design, usage, and maintenance. Furthermore, this work contributes to the advancement of battery technology towards higher efficiency, greater stability, and enhanced safety.

Lithium-ion batteries provide the power for portable electronics and found many other interesting applications. It is desirable to design batteries with high energy density and long cycle life. Silicon is among the highest Li-storing anode materials in batteries, but the large capacity is accompanied by significant volume expansion that causes mechanical failure and capacity fading after few charging/discharging cycles. There is evidence that the mechanical behavior of lithiated amorphous silicon depends on the history of charging and discharging. The goal of this thesis is to better understand the mechanical properties and behavior of lithiated silicon, specifically the dependence of its properties on the state of charging/discharging, through atomistic simulation, constitutive modelling and finite elements method calculations. Amorphous high-storage-capacity Li-Si flows at lower stresses than crystalline materials but the plastic flow stress decreases with charging and discharging, indicating important non-equilibrium aspects to the flow behavior. In this thesis, a mechanistically-based constitutive model for rate-dependent plastic flow in amorphous materials, during charging and discharging is developed based on two physical concepts: (i) excess energy is stored in the material during electrochemical charging and discharging due to the inability of the amorphous material to fully relax during the charging/discharging process and (ii) this excess energy reduces the barriers

or reduces their range. Li-NMC batteries using lithium nickel manganese cobalt oxides are the most common in EV. The lithium iron phosphate battery (LFP) An electric vehicle battery is a rechargeable battery used to power the electric motors of a battery electric vehicle (BEV) or hybrid electric vehicle (HEV). They are typically lithium-ion batteries that are designed for high power-to-weight ratio and energy density. Compared to liquid fuels, most current battery technologies have much lower specific energy. This increases the weight of vehicles o For electric vehicles (EVs), actual end of life will be defined by many factors that will vary across vehicles, including the owner's willingness to continue driving the EV as its range declines, the health of other components in the vehicle, and whether or not the vehicle is involved in a crash. For practicality, however, end of life is commonly defined in repurposing studies as when a battery's capacity degrades to 80% of its initial capacity. This likely comes from the U.S. American Battery Consortium definition: "End-of-life is clarified to occur when either the net DST delivered capacity or peak power capability at 80% DOD is less than 80% of rated." One of the waste management methods is to reuse the pack. By repurposing the pack for stationary storage, more value can be extracted from the battery pack while reducing the per kWh lifecycle impact. Uneven and undesired battery degradation happens during EV operation depending on temperature during operation and charging/discharging patterns. Each battery cell could degrade differently during operation. Currently, the state of health (SOH) information from a battery management system (BMS) can be extracted on a pack level but not on a cell level. Engineers can mitigate the degradation by engineering the next-generation thermal management system. electrochemical impedance spectroscopy (EIS) can be used to ensure the quality of the battery pack. It is costly and time-i As of 2024, the lithium-ion battery (LIB) with the variants Li-NMC, LFP and Li-NCA dominates the BEV market. The combined global production capacity in 2023 reached almost 2000 GWh with 772 GWh used for EVs in 2023. Most production is based in China where capacities increased by 45% that year. With their high energy density and long cycle life, lithium-ion batteries have become the leading battery type for use in EVs. They were initially developed and commercialized for use in laptops and consumer electronics. Recent EVs are using new variations on lithium-ion chemistry that sacrifice specific energy and specific power to provide fire resistance, environmental friendliness, rapid charging and longer lifespans. These variants have been shown to have a much longer lifetime. For example, lithium-ion cells containing single wall carbon nanotubes (SWCNTs) show increased mechanical strength, suppressing degradation and leading to a longer battery lifetime. For electric vehicles (EVs), actual end of life will be defined by many factors that will vary across vehicles, including the owner's willingness to continue driving the EV as its range declines, the health of other components in the vehicle, and whether or not the vehicle is involved in a crash. For practicality, however, end of life is commonly defined in repurposing studies as when a battery's capacity degrades to 80% of its initial capacity. This likely comes from the U.S. American Battery Consortium definition: "End-of-life is clarified to occur when either the net DST delivered capacity or peak power capability at 80% DOD is less than 80% of rated." One of the waste management methods is to reuse the pack. By repurposing the pack for stationary storage, more value can be extracted from the battery pack while reducing the per kWh lifecycle impact. Uneven and undesired battery degradation happens during EV operation depending on temperature during operation and charging/discharging patterns. Each battery cell could degrade differently during operation. Currently, the state of health (SOH) information from a battery management system (BMS) can be extracted on a pack level but not on a cell level. Engineers can mitigate the degradation by engineering the next-generation thermal management system. electrochemical impedance spectroscopy (EIS) can be used to ensure the quality of the battery pack. It is costly and time-intensive to disassemble modules and cells. The module must be fully discharged. Then, the pack must be disassembled and reconfigured to meet the power and energy requirement of the second life application. A refurbishing company can sell or reuse the discharged energy from the module to reduce the cost of this process. Robots are being used to increase the safety of the dismantling process. Battery technology is non-transparent and lacks standards. Because battery development is the core part of EV, it is difficult for the manufacturer to label the exact chemistry of cathode, anode and electrolytes on the pack. In addition, the capacity and the design of the cells and packs changes on a yearly basis. The refurbishing company needs to closely work with the manufacture to have a timely update on this information. On the other hand, government can set up labeling standard. Lastly, battery costs have decreased faster than predicted. The refurbished unit may be less attractive than the new batteries to the market. Nonetheless, there have been several successes on the second-life application as shown in the examples of storage projects using second-life EV batteries. They are used in less demanding stationary storage application as peak shaving or additional storage for renewable-based generating sources. To develop a deeper understanding of the lifecycle of EV batteries, it is important to analyze the emission associated with different phases. Using NMC cylindrical cells as an example, Ciez and Whitacre found that around 9 kg CO2e kg battery−1 is emitted during raw