Second Life Applications Research Articles

Second Life of Lithium-Ion Batteries: Effects of Temperature Cycling

Extending the lifespan of lithium-ion batteries (LIBs) can be achieved either by repurposing batteries under similar conditions within the same application segment, as a first-life extension, or by extending them into different segments with different operations as a second-life application. In the latter case, it is crucial to comprehend not only the remaining capacity and performance properties but also the safety aspect. To address these considerations, we cycled 30Ah NMC 433 graphite LIBs under different conditions to State of health capacities of 70-80 % and subsequently, subjected them to softer degradation environments. We then deployed Incremental capacity analysis (dQ/dV) (ICA) to understand degradation mechanisms, with a particular focus on how to detect Li plating. Cycling conditions and repeated measurements revealed rapid degradation, particularly during low-temperature cycling. Combining ICA with ex-situ post-mortem analysis methods allowed for Li indications and facilitated the comparison of capacity losses with degraded performances versus degraded safety issues [1], [2].Overall, batteries cycled at high temperatures exhibited poor performance in terms of remaining capacity as depicted in Figure 1, and high resistance without significantly lowering thermal runaway temperatures. This contrasts with low-temperature degradation, where the thermal onset temperature decreases to as low as 85 oC. Intermediate temperature degradation resulted in some loss in performance, namely resistance and capacity, but not in safety. Using ICA alongside detailed more aggressive degradation allowed for detecting safety warning mechanics during the degradation testing.

Performance Analysis of Regenerated Lithium-Ion Batteries in Their Second-Life

The electric vehicle market's rapid growth is projected to yield 3 million discarded lithium-ion (Li-ion) batteries by 2040, equating to 125 GWh of energy [1]. Transitioning to a circular economy is essential to address this environmental challenge and reduce reliance on vulnerable supply chains. While lead-acid batteries are efficiently recycled, the lithium-ion industry lags in circular practices. Conventional recycling focuses on valuable element extraction, requiring reprocessing for electrode fabrication. Direct recycling preserves the cathode but damages the microstructure, demanding additional processing and heightening environmental strain [2,3]. In this study we perform a comprehensive study of regenerated batteries using an approach more consistent with a circular economy framework where a separator is layered with benign lithium material that can be activated on-demand to rejuvenate lithium inventory in a battery without electrode material degradation [4]. In this study, a series of commercial Li-ion LFP-Graphite cells were cycled in their first-life to 80% of the nominal capacity under different stress levels, where stress is a composite measure of depth of discharge and charge and discharge rate. These used batteries are then directly rejuvenated by electrochemically activating a coating of lithium oxalate material on the separator until the lithium inventory is fully replenished. The resulting (60+) rejuvenated LFP-graphite cells were subsequently cycled through a second lifetime under different stress conditions to evaluate and understand the performance of the cells in their second-life and the overall influence of first-life cycling conditions on second-life performance outcomes. Our findings support that whereas some conditions lead to almost equivalent cycling durations for the second-life cells, the key variable that dictates the second life performance is the damage accumulation and corresponding increased cell resistance occurring during the first-life. Specifically, cells cycled under higher first-life stress conditions, such as at higher rates, gave more favourable second-life performance than cells cycled under lower first-life stress conditions. The results presented provide detailed insights into the technological approach, challenges, and opportunities for the regeneration of used Li-ion batteries for second-life applications in a manner consistent with circular economy framework. Acknowledgements This work was supported by the funding received from Iowa Energy Center [Grant No. 21-IEC-007] References Baars, T. Domenech, R. Bleischwitz, H. E. Melin, O Heidrich, Circular economy strategies for electric vehicle batteries reduce reliance on raw materials, Nat Sustain, 4 (2021) 71-79. J. Baum, R. E. Bird, X. Yu, J. Ma, Lithium-ion battery recycling─overview of techniques and trends, ACS Energy Letters, 7 (2022) 712-719. Dobó, T. Dinh, T. Kulcsár, A review on recycling of spent lithium-ion batteries, Energy Reports, 9 (2023) 6362–6395.M. Fan, Q. Meng, X. Chang, C. Gu, X. Meng, Y. Yin, H. Li, L. Wan, Y. Guo, In Situ Electrochemical Regeneration of Degraded LiFePO4 Electrode with Functionalized Prelithiation Separator, Advanced Energy Materials, 12 (2022) 2103630.

Review of Economic, Technical and Environmental Aspects of Electric Vehicles

Electric vehicles (EVs) have seen significant advancements and mainstream adoption, prompting in-depth analysis of their economic, technical, and environmental impacts. Economically, while EVs offer lower operational costs than internal combustion engine vehicles, challenges remain, particularly for urban users reliant on public charging stations and the potential implementation of new road taxes to offset declining fuel tax revenues. Technically, electric motors in EVs have fewer moving parts, but battery management and cybersecurity complexities pose new risks. Transitioning from Nickel-Manganese-Cobalt (NMC) to Lithium-Iron-Phosphate (LFP) batteries reflects efforts to enhance thermal stability and mitigate fire hazards. Environmentally, lithium extraction for batteries has profound ecological impacts, including for water consumption and pollution. Battery production and the carbon footprint of the entire lifecycle remain pressing concerns, with battery recycling and second-life applications as crucial mitigation strategies. Smart integration of EVs with the energy infrastructure introduces challenges like grid stability and opportunities, such as smart, intelligent, innovative charging solutions and vehicle-to-grid (V2G) technology. Future research should develop economic models to forecast long-term impacts, advance battery technology, enhance cybersecurity, and conduct comprehensive environmental assessments to optimise the benefits of electromobility, addressing the multidimensional challenges and opportunities presented by EVs.

Impact of State of Health (SOH) on the Thermal Safety of Lithium Ion Cells for Long 1st Life and 2nd Life Applications

Lithium ion battery (LIB) safety incidents can be a threat for people and the environment. Since today, only safety tests on fresh cells are decisive for safety level determination, the effect of long-term operation on their safety characteristics needs to be addressed. A large loss of lithium over long periods of time could, for example, result in reduced structural and thermal stability of the cathode. LIBs are normally used until they reach an end-of-life criterion of typically 70%–80% state of health (SOH). However, they can be reused in second-life applications such as stationary (“grid”) energy storage, afterwards. To ensure safety during long first life and second-life, in this study the influence of aging was investigated over a higher cycle number and a longer time period than ever before. 5 Ah LiNi0.6Co0.2Mn0.2O2(NMC622)||graphite (G) pouch cells were aged at 20 °C between 530 and 3,806 cycles (151–615 d of continuous cycling). SOHs between 91% and 63% were obtained. After aging, the thermal properties of the cells were investigated by heat-wait-search experiments under adiabatic conditions using an accelerating rate calorimeter. The cells showed almost exclusively improvements in their safety characteristics, the thermal runaway even tended to be shifted to higher temperatures.

Second Life for Lithium-Ion Traction Batteries

For the reuse of traction batteries, many different scenarios exist, for example, stationary storage farms or fast charging stations. Another second-life usage scenario is the reuse of batteries as home energy storage in combination with a photovoltaic installation in a private household. This application is the focus of the present study. Home energy storage is a reasonable possibility for storing renewable energy and conserving resources, but it also includes multiple challenges regarding reliability and safety requirements. Within this study, these challenges are investigated. A battery inspection concept was developed, and a logistic model for considering the legal requirements was created. Data from different use cases were selected, and their structure was homogenized. To assess their safety, fire tests were performed. In addition, a concept for a reliability assessment that provides the possibility to evaluate the suitability of a battery for a second-life application based on usage data in its first life was developed. Based on the results, a prototype of a second-life storage system was built from traction battery cells removed from electric vehicles. This prototype is currently used to store energy from a photovoltaic system, and its usage data were collected.

Extending an Empirical Degradation Model for Li-Ion Batteries into Second-Life Applications

Lithium-ion batteries have been used increasingly in recent years for a wide range of applications, e.g., electric vehicles and large-scale power grids. Lithium-ion batteries suffer from degradation caused by their operation and their exposure to environmental conditions and thus have a limited lifetime within their first application. These batteries might be available for re-use in a different application, commonly under more moderate usage conditions. The influence of such a change in operating conditions on battery degradation within a second life application is not very well understood. Here we present the extension of an empirical degradation model that formulates the degradation process as a function of battery operations for both, first- and second life applications.Our extended semi-empirical model for battery degradation is based on work of Xu et al. [1] and combines the degradation mechanism due to the growth of the SEI layer and the degradation depth obtained in dedicated ageing tests. Within this work we focus on a commercial 64 Ah NMC-graphite pouch cell. The model parametrization is based on a large dataset containing both calendar and cycle life data of more than 100 cells, covering a large window of temperatures (5-45 °C), C-rates (0.2-1.5 C), SoC windows, and average SoC.Figure 1(a) shows the variations of state of health (SoH) with the number of the full equivalent cycle (FEC) for four cells cycling at the same constant ageing conditions (0.75C, 25°C, and 0-100% SoC). Figure 1(b) shows the fitting results of the empirical degradation model using the data from the ageing tests. It is assumed that the SEI layer model parameters are constant for this specific cell. The degradation depth increases linearly with cycle number, where the degradation rate varies with the battery operation condition. The degradation of the battery cell depends not only on external stress factors such as temperature, SoC, DoD, C-rate, but also its previous ageing history. The formation of the SEI film contributes non-linearly to the battery degradation, while the contribution of the degradation rate of different stress factors can be accounted for linearly. The degradation rate depends on the ageing modes: calendar or cycle ageing. Calendar ageing reflects the inherent degradation over time and the rate is affected by temperature and SoC. The calendar degradation rate per time unit can be obtained as a function of temperature and SoC [2, 3]. The cycle SoC window can be interpreted using DoD and mean SoC. The cycle degradation rate per FEC can be estimated as a function of temperature, mean SoC, and DoD [3]. Data-driven models and empirical correlations are applied to obtain battery degradation rate functions. The total degradation depth can be estimated by summarizing the degradation caused by the calendar ageing and the degradation resulting from all cycles.To verify the performance of the empirical degradation model, a dynamic ageing test was designed, including both calendar and cycle ageing. The historical data of SoC and temperature are shown in Figures 2 (a) and 2(b), respectively. Through analyzing the time series data of cell SoC, all cycle information can be obtained to calculate the cycle ageing. The calendar ageing was calculated based on time duration for each cycle, and the average temperature and SoC. Using the correlations for the degradation rates, the degradation depth during for each cycle can be evaluated. The accumulated degradation depth can be used to estimate the change of remaining capacity with time. Figure 2(c) shows the comparison of the prediction of SoH with the experimental data.When moving into the 2nd life regime, degradation mechanisms and their interplay become more complex, leading to a larger statistical variation in ageing rates between individual cells (i.e., see time offset in Fig 2c). This can be accounted for by readjustment of the model’s initial 2nd life SoH to the last SoH from the first life application data, as well as including statistical variation into the model’s parameters.

Extracting Thermodynamic, Kinetic, and Transport Properties from Batteries Using a Simple Analytical Pulsing Protocol

Gaining insights into the fundamental properties of lithium-ion batteries through scalable and non-destructive methods is challenging for commercial cell formats. In this work, a simple analytical pulsing protocol (APP) is performed on a commercial cell to understand its thermodynamic, kinetic, and mass transport properties. While testing procedures that rely on electrochemical pulses are well documented, the APP is novel in the level of fundamental insight that can be gained. For thermodynamics, a static-differential capacity analysis can be performed that removes the effects of kinetic and transport overpotentials and allows for the calculation of Gibbs free energy. For kinetics, the exchange current density of the cell can be calculated according to the Butler-Volmer model. For transport, a whole-cell lithium-ion diffusion coefficient can be calculated from a derivation of Fick’s second law and the generalized flux equation. Comparing the results from these properties gives an unparalleled level of mechanistic insight into battery performance from a single non-destructive technique. This APP requires no additional equipment and provides properties that can be easily correlated to materials or processing parameters. Therefore, the APP is valuable for research and development, manufacturing, quality assurance, and second-life applications, among others.

Industrial Battery State-of-Health Estimation with Incomplete Limited Data Towards Second-Life Applications

Battery State of Health (SOH) estimation is vital across applications ranging from portable electronics to electric vehicles, particularly in second-life applications where accurate prediction becomes complex due to varying degradation levels. This paper introduces a novel SOH estimation model to address the lack of labeled data, employing Domain Adversarial Neural Networks (DANN) combined with 1-dimensional Convolutional Neural Networks (CNN). The proposed method allows for effective transfer of knowledge between diverse battery conditions, enhancing adaptability and efficiency by utilizing both source and target datasets. Experimental results demonstrate that the proposed model achieves a Mean Absolute Error (MAE) of 1.68% and a Root Mean Squared Error (RMSE) of 2.50%, with minimal data. Specifically, the model requires only one cell of unlabeled data from the second-life target domain, utilizing only the dQ/dV curve for estimation. Proposed model sets a new standard in second-life battery health monitoring and management by effectively leveraging a minimal amount of data for training, this approach offers a robust solution for accurate SOH estimation, particularly in scenarios with limited access to labeled data. Conflict of Interest Statement The authors declare no conflicts of interest.

Sizing up sustainability: Influence of battery size and cell chemistry on battery-electric trucks’ life-cycle carbon emissions

Customers and legislators will increasingly demand monitoring and reducing the carbon footprint of logistic companies in the coming years. Besides the fundamental decision for a battery-electric truck, the choice of battery size and cell chemistry should be approached with the goal of minimizing the carbon footprint of the supply chain. Therefore, this paper analyzes the impact of battery size and cell chemistry on the carbon footprint and which factors influence this the most. To quantify this footprint, emissions from production, potential replacements based on battery aging, energy generation, and reuse in second-life applications for both LFP and NMC cell chemistries are considered. The results show that use phase emissions from energy generation have the largest leverage on life-cycle emissions, whereas production emissions play a minor role. If electricity with lower emissions at the home depot compared to the public electricity is available, oversizing the battery capacity tends to be the emission optimal choice. If more than 8% additional renewable energy at the home base for NMC and more than 38% for LFP is available, the largest possible battery is emission-optimal. For smaller shares, the smallest possible battery should be selected. Significant dependence on purchase year and share of second-life usage can be observed.

The safety and environmental impacts of battery storage systems in renewable energy

The integration of battery storage systems in renewable energy infrastructure has garnered significant attention due to its potential to enhance energy reliability, efficiency, and sustainability. However, alongside these benefits, concerns persist regarding the safety and environmental impacts associated with the deployment and operation of such systems. This review explores the multifaceted aspects of safety and environmental considerations in battery storage systems within the context of renewable energy. Firstly, safety concerns encompass a range of factors, including thermal runaway, fire hazards, and chemical leakage, which pose risks to both human life and property. Mitigation strategies such as advanced battery management systems and fire suppression technologies are critical for addressing these risks effectively. Secondly, environmental impacts arise throughout the lifecycle of battery storage systems, from raw material extraction to end-of-life disposal. Key issues include resource depletion, greenhouse gas emissions, and pollution from mining activities. Sustainable practices such as responsible sourcing of materials, recycling initiatives, and the development of second-life applications are essential for minimizing environmental footprints. Furthermore, the interaction between battery storage systems and renewable energy sources introduces complexities in assessing environmental impacts. While battery storage facilitates the integration of intermittent renewables like solar and wind by providing grid stabilization and energy storage capabilities, its environmental benefits may be compromised by factors such as energy-intensive manufacturing processes and reliance on non-renewable resources. The safety and environmental impacts of battery storage systems in renewable energy demand comprehensive evaluation and management strategies to maximize benefits while minimizing risks. Collaboration among stakeholders, technological innovation, and regulatory frameworks are crucial for promoting the sustainable deployment and operation of these systems in the transition towards a cleaner and more resilient energy future.

World experience of legislative regulation for Lithium-ion electric vehicle batteries considering their second-life application in power sector

Understanding and incorporating global regulatory experiences and standards related to battery management is of greatest importance, particularly when considering the rapid evolution of the electric vehicle (EV) market and its implications for energy storage and sustainability. This is especially relevant for Ukraine, where the burgeoning secondary market for EVs and a keen interest in renewable energy sources underscore the need for proactive policy-making and standardization to address the challenges of battery second life and recycling. This article delves into the role of Electric Vehicle Lithium-Ion batteries within the ambit of the circular economy, underscoring the significance of legislative frameworks across the globe with a particular focus on European initiatives in light of Ukraine's EU integration ambitions. This encompasses extending battery life through recycling and repurposing, thereby ensuring both economic viability and minimal environmental footprint. The narrative outlines the varied legislative landscapes internationally, noting the differences in strategies from Asia's technological and safety emphasis to Europe's robust regulatory directives aimed at battery lifecycle management. In Europe, the drive towards sustainable battery utilization is marked by comprehensive policies like the EU Battery Directive and the emerging Regulation on Batteries and Waste Batteries, which set forth ambitious recycling targets and introduce innovative concepts like the battery passport. Drawing from this global overview, the article posits a set of recommendations for Ukraine, suggesting the development of extensive battery management legislation, adoption of European standards to smooth the path towards EU membership, investment in recycling infrastructures, fostering of public-private partnerships, and public awareness initiatives. These recommendations are designed to elevate Ukraine's position in the sustainability, promoting environmental stewardship and economic competitiveness. The growing importance of secondary lithium-ion batteries for electric vehicles in supporting and harmonizing renewable energy sources is emphasized, and accordingly, the need for adequate legislation and standardization to support a closed-loop economy. Keywords: Lithium-Ion Batteries, Second-Life Application, EV Battery Life Cycle, Circular Economy, Repurpose, Reuse, Recycling, Standards, Regulation, Legislation.

Battery Passports for Second-Life Batteries: An Experimental Assessment of Suitability for Mobile Applications

End-of-life electric vehicle (EV) batteries can be reused to reduce their environmental impact and economic costs. However, the growth of the second-life market is limited by the lack of information on the characteristics and performance of these batteries. As the volume of end-of-life EVs may exceed the amount of batteries needed for stationary applications, investigating the possibility of repurposing them in mobile applications is also necessary. This article presents an experimental test that can be used to collect the data necessary to fill a battery passport. The proposed procedure can facilitate the decision-making process regarding the suitability of a battery for reuse at the end of its first life. Once the battery passport has been completed, the performance and characteristics of the battery are compared with the requirements of several mobile applications. Mobile charging stations and forklift trucks were identified as relevant applications for the reuse of high-capacity prismatic cells. Finally, a definition of the state of health (SoH) is proposed to track the suitability of the battery during use in the second-life application considering not only the energy but also the power and efficiency of the battery. This SoH shows that even taking into account accelerated ageing data, a repurposed battery can have an extended life of 11 years at 25 °C. It has also been shown that energy fade is the most limiting performance factor for the lifetime and that cell-to-cell variation should be tracked as it has been shown to have a significant impact on the battery life.

Fostering second-life applications for electric vehicle batteries: A thorough exploration of barriers and solutions within the framework of sustainable energy and resource management

Electric vehicles (EVs) play a crucial role in achieving Sustainable Development Goals (SDGs), specifically focusing on Goal 7, which ensures access to Affordable and Clean Energy, and Goal 9, promoting advancements in Industry, Innovation, and Infrastructure. However, the growing stockpile of used EV Batteries (EVBs) presents challenges. These EVBs, however, hold potential for second-use applications, aligning with energy conversion, resource optimization, and sustainable energy systems. This study employs a rigorous multi-criteria approach to bridge the research-practice gap by systematically evaluates and prioritizes barriers hindering the widespread adoption of second-use EVBs. The study's overarching objectives are to overcome these barriers, aligning with broader sustainability goals, and to offer insights shaping policies addressing environmental, social, and economic impacts, in coherence with SDGs 8, 11, 12, and 13. The research unfolds through a three-phase approach involving literature reviews, field visits, and expert interviews for barrier identification, theoretical framework development through literature and Delphi studies, and prioritization using the Fuzzy Best-Worst Method (FBWM). Results indicate that addressing Cost and Technological Challenges is pivotal for successful second-use EVB adoption, with proposed solutions involving regulations, recycling, and awareness. The study underscores the circular economy perspective, connecting identified barriers to specific SDGs. The FBWM proves effective in prioritizing barriers, providing actionable insights for policymakers and stakeholders. This research contributes significantly to the existing literature by systematically evaluating second-use EVBs, addressing a crucial research gap, and offering valuable pathways for broad adoption.

Aging in First and Second Life of G/LFP 18650 Cells: Diagnosis and Evolution of the State of Health of the Cell and the Negative Electrode under Cycling

Second-life applications for lithium-ion batteries offer the industry opportunities to defer recycling costs, enhance economic value, and reduce environmental impacts. An accurate prognosis of the remaining useful life (RUL) is essential for ensuring effective second-life operation. Diagnosis is a necessary step for the establishment of a reliable prognosis, based on the aging modes involved in a cell. This paper introduces a method for characterizing specific aging phenomenon in Graphite/Lithium Iron Phosphate (G/LFP) cells. This method aims to identify aging related to the loss of active material at the negative electrode (LAMNE). The identification and tracking of the state of health (SoH) are based on Incremental Capacity Analysis (ICA) and Differential Voltage Analysis (DVA) peak-tracking techniques. The remaining capacity of the electrode is thus evaluated based on these diagnostic results, using a model derived from half-cell electrode characterization. The method is used on a G/LFP cell in the format 18650, with a nominal capacity of 1.1 Ah, aged from its pristine state to 40% of state of health.

Non-linear frequency response analysis for assessment of the ageing history of lithium ion batteries: A combined simulation and experimental approach

In this work, we present a novel approach for identifying the ageing history of lithium-ion batteries based on experimental nonlinear frequency response analysis (NFRA) measurements. A regression model, trained on simulated NFRA data, is shown to be capable of quantifying degradation modes such as solid electrolyte interphase (SEI) growth, lithium plating, and loss of active material (LAM) with no a-priori knowledge of the cell’s historical duty. Our analysis, combining experimental and simulation approaches, demonstrates NFRA’s potential as a powerful tool for ageing diagnosis by capturing various degradation modes. Changes in NFRA response through life exhibit strong correlations with ageing paths, particularly in the frequency range of 0.2 to 10 Hz. Observations highlight a strong influence of the state of charge on the resultant NFRA response, emphasizing that measurements at a single open circuit voltage (OCV) and harmonics values from a single frequency are insufficient for comprehensive characterization. This analysis underscores the need for correlating NFRA at multiple OCVs and frequencies for detailed ageing assessment. Evaluation on commercially relevant cells enhanced the models’ reliability for industrial applications. This quantitative, data-driven approach using NFRA holds potential to enhance battery management strategies, extend lifespan and improve confidence in second-life applications of batteries. Future work should focus on improving regression analysis robustness, reducing dimensionality, and broadening testing conditions.

Identification and Mitigation of Predominant Challenges in the Utilization of Aged Traction Batteries within Stationary Second-Life Scenarios

As the production of battery cells experiences exponential growth and electric vehicle fleets continue to expand, an escalating number of traction batteries are nearing the conclusion of their operational life for mobility purposes, both presently and in the foreseeable future. Concurrently, the heightened interest in sustainable energy storage solutions has spurred investigations into potential second-life applications for aging traction batteries. Nonetheless, the predominant practice remains the removal of these batteries from electric vehicles, signifying the end of their life cycle, and their subsequent incorporation into recycling processes, with limited consideration for life-extending measures. This study seeks to elucidate the reasons behind the deprioritization of battery repurposing strategies. Therefore, the research team conducted two industry studies with over 20 battery experts from Europe, revealing concerns about the economic viability of repurposing batteries for stationary storage applications. A literature review of studies published since 2016 confirmed the industry’s struggles to address this issue theoretically. In conclusion, a research question was formulated, and a solution approach was delineated to assess the economic prospects of aged traction batteries within the industry’s landscape in the future. This solution approach encompasses pertinent market analysis, the identification of representative second-life applications, as well as the formulation of a methodology for evaluating the residual value of these batteries.

Techno-Economic Analysis of the Business Potential of Second-Life Batteries in Ostrobothnia, Finland

In an effort to tackle climate change, various sectors, including the transport sector, are turning towards increased electrification. As a result, there has been a swift increase in the sales of electric vehicles (EVs) that use lithium-ion batteries (LIBs). When LIBs reach their end of life in EVs, it may still be possible to use them in other, less demanding applications, giving them a second life. This article describes a case study where the feasibility of a hypothetical business repurposing Tesla Model S/X batteries in the Ostrobothnia region, Finland, is investigated. A material-flow analysis is conducted to estimate the number of batteries becoming available for second-life applications from both the Ostrobothnia region and Finland up to 2035. The cost of repurposing batteries is evaluated for four different scenarios, with the batteries being processed either on the pack, module, or cell level. Three scenarios were found to be feasible, with repurposing costs of 27.2–38.3 EUR/kWh. The last scenario, in which all battery packs are disassembled at the cell level, was found not to be feasible due to the labor intensiveness of disassembly and testing at the cell level. This work gives indications of the potential for repurposing batteries in the Ostrobothnia region and Finland.

Assessing the Impact of First-Life Lithium-Ion Battery Degradation on Second-Life Performance

The driving and charging behaviours of Electric Vehicle (EV) users exhibit considerable variation, which substantially impacts the battery degradation rate and its root causes. EV battery packs undergo second-life application after first-life retirement, with SoH measurements taken before redeployment. However, the impact of the root cause of degradation on second-life performance remains unknown. Hence, the question remains whether it is necessary to have more than a simple measure of state of health (SoH) before redeployment. This article presents experimental data to investigate this. As part of the experiment, a group of cells at around 80% SoH, representing retired EV batteries, were cycled using a representative second-life duty cycle. Cells with a similar root cause of degradation in the first life (100–80% SoH) exhibited the same degradation rate in second life after being cycled with the same duty cycle during the second life. When the root cause of degradation in the first life is different, the degradation rate in the second life may not be the same. These findings suggest that the root cause of a cell’s first-life degradation impacts how it degrades in its second life. Postmortem analysis (photographic and SEM images) reveals the similar physical condition of negative electrodes which have similar degradation rates in their second life cycle. This demonstrates that cells with a similar first life SoH and root cause of degradation indeed experience a similar life during their second life. The experimental results, along with the subsequent postmortem analysis, suggest that relying solely on SoH assessment is insufficient. It is crucial to take into account the root causes of cell degradation before redeployment.

Evaluation of the second-life potential of the first-generation Nissan Leaf battery packs in energy storage systems

Nissan Leaf was the first mass-produced electric vehicles (EV) using lithium-ion batteries (LiB). Most of the first generation (Gen 1) battery packs have been retired after approximately 10 years of operation, and some of them are repurposed to build battery energy storage systems (BESS). However, the health condition of the battery packs at the time of retirement, the battery aging trajectory, and the service life in second-life application are unclear. To answer these questions, this paper conducts a comprehensive study on the retired Nissan Leaf Gen 1 batteries. First, over 100 retired battery packs were investigated to evaluate their state of health (SOH). Secondly, a battery aging test was conducted on two battery cells which completed 7380 aging cycles. Lastly, the battery aging trajectory was analyzed. The result shows that although most retired Nissan Leaf Gen 1 battery packs have only 60 %–67 % remaining capacity, they can operate 12–20 years in second life. Whole-battery-pack utilization is preferable due to good battery consistency. A retired battery pack with a cost of $1000 can generate a $16,200 value in its second life, suggesting a good return on investment (ROI).

History-agnostic battery degradation inference

Lithium-ion batteries (LIBs) have attracted widespread attention as an efficient energy storage device on electric vehicles (EV) to achieve emission-free mobility. However, the performance of LIBs deteriorates with time and usage, and the state of health of used batteries are difficult to quantify. Having accurate estimations of a battery’s remaining life across different life stages would benefit maintenance, safety, and serve as a means of qualifying used batteries for second-life applications. Since the full history of a battery may not always be available in downstream applications, in this study, we demonstrate a deep learning framework that enables dynamic degradation rate prediction, including both short-term and long-term forecasting, while requiring only the most recent battery usage information. Specifically, our model takes a rolling window of current and voltage time-series inputs, and predicts the near-term and long-term capacity fade via a recurrent neural network. We exhaustively benchmark our model against a naive extrapolating model by evaluating the error on reconstructing the discharge capacity profile under different settings. We show that our model’s performance in accurately inferring the battery’s degradation profile is agnostic with respect to cell cycling history and its current state of health. This approach can provide a promising path towards evaluating battery health in running vehicles, enhance edge-computing battery diagnostics, and determine the state of health for used batteries with unknown cycling histories.