Establishing a pioneering laboratory for second-life battery applications Enhancing energy storage a

Abstract

Keywords: Aging; Battery; End-of-life; Laboratory; Second-life.

Introduction

Due to technological advances and the increasing reliance on intermittent renewable sources like solar and wind, energy storage has become a crucial component of grid systems. Energy storage systems (ESS) are important technologies that enable the storage and conversion of electrical energy in different forms. Although various ESS such as supercapacitors and hydroelectric storage exist, batteries have

become the most prevalent, particularly in electric vehicles (EVs), portable devices, and power grids. This widespread adoption is due to their ability to provide an environmentally friendly option for energy storage [1]. To reduce the negative effects caused by long-term use of traditional energy sources, clean energy sources have come to the fore in the fields of energy production and consumption. By encouraging the use of clean energy, elec-

*Corresponding author *E-mail adress: ibrahim.eski@yildiz.edu.tr Published by Yıldız Technical University, İstanbul, Türkiye This is an open access article under the CC BY-NC license (http://creativecommons.org/licenses/by-nc/4.0/).

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trification has become widespread in every field. However, the inability to store energy on a large scale has been a significant obstacle in this field. To overcome this obstacle, batteries have become critical for industrial and consumer applications, and their technology is constantly evolving. Next-generation batteries offer higher energy density and performance than traditional batteries [2]. In the battery industry, battery types such as Lead Acid (Pb-Acid), Lithium Ion (Li-ion), Nickel-Cadmium (NiCd) and Nickel-Metal Hydride (NiMH) are generally used [3]. In Lead Acid batteries, Pb is used as the cathode, Lead Dioxide (PbO2) as the anode and sulfuric acid (H2SO4) as the electrolyte. PbSO4 is formed in the reaction between lead dioxide and lead during charging. During discharge, this reaction occurs in reverse. This type of battery has low energy density but is suitable for high current applications. Besides, it is safe and low cost [4]. Lithium-ion batteries use lithium as the cathode, graphite (C) as the anode, and solid polymer electrolytes or liquid electrolytes as the electrolyte. During charging, lithium ions pass from the cathode to the anode. During discharge, this reaction occurs in reverse. These types of batteries have a high energy density, long life cycle, and are lightweight, but they have some disadvantages in terms of thermal stability, safety, and cost [5,6]. In Nickel-Cadmium batteries, nickel oxide-hydroxide is used as the cathode, cadmium is used as the anode, and aqueous alkaline solutions are used as the electrolyte. During charging, electrons flow from the nickel oxide-hydroxide cathode to the cadmium anode. During discharge, this reaction occurs in reverse. These types of batteries have high energy density and long cycle life, but they have disadvantages such as memory effect, environmental effects of cadmium and not being suitable for low current discharge [7,8]. Nickel-Metal Hydride batteries use nickel oxide-hydroxide as the cathode, metal hydride as the anode, and potassium hydroxide as the electrolyte. During charging, electrons flow from the nickel oxide-hydroxide cathode to the metal hydride anode. During discharge, this reaction occurs in reverse. While these types of batteries have advantages such as high energy density, high-rate capability, no memory effect and high tolerance against overdischarge, they have disadvantages such as self-discharge, charging efficiency and low life cycle [3,7]. Table 1 shows the compari-

Second-life battery applications extend the usability of end-of-life (EOL) batteries in energy storage systems, reducing waste and supporting sustainability.

Challenges in battery recycling include high costs and inadequate facilities, emphasizing the need for efficient second-life usage over traditional recycling methods.

The proposed laboratory aims to optimize battery designs for first and second use, focusing on extending lifespan and enhancing performance.

son of the mentioned batteries in terms of nominal voltage, power density, energy density, charging efficiency, life cycle, self-discharge rate, charging temperature, discharging temperature [3, 9]. Among these commonly used battery types, the most used battery type is lithium-ion batteries. These batteries are preferred in many portable devices and vehicles because they have high energy density, longer cycle life, low mass, and low self-discharge rate [5,6]. Lithium-ion batteries can be classified according to the use of different cathode materials. The use of different cathodes brings different features, advantages and disadvantages, and leads to significant variations in key performance metrics such as cycle life. This is why, as seen in Table 1, Li-ion batteries show a wide distribution in cycle life, ranging from 600 to 3000. According to different cathode types, lithium-ion batteries can be classified as follows: Lithium Nickel Manganese Cobalt Oxide (LiNiMnCoO2 or NMC), Lithium Iron Phosphate (LFP), Lithium Nickel Cobalt Aluminum Oxide (LiNiCoAlO2 or NCA), Lithium Manganese Spinel (LMO), Lithium Titanate (LTO), Lithium Nickel Alloys (Li-Ni). NMC cathode used in Lithium Nickel Manganese Cobalt Oxide (LiNiMnCoO2) batteries uses a mixture containing the elements nickel, manganese, and cobalt. By adjusting the proportions of the elements in the NMC cathode composition, it is possible to produce materials with varying characteristics. [10]. Lithium Iron Phosphate (LFP) is generally preferred for high safety and low cost, but its energy density is slightly lower than other lithium-ion battery types [11]. Lithium Nickel Cobalt Aluminum Oxide (NCA)

Table 1. Comparison of some battery technologies. Nominal voltage (V)

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uses a mixture containing the elements nickel, cobalt, and aluminum. These cathodes are generally preferred for high energy density and long life cycle [12]. Lithium Manganese Spinel (LMO) contains lithium manganate (LiMn2O4). These batteries are generally preferred for low cost and high safety. However, they are also noted for their capacity fade during cycles, particularly at high temperatures​[13]. Lithium Titanium Oxide (LTO) contains lithium titanat (Li4Ti5O12). These batteries are generally preferred for their high safety, long cycle life and fast charge/discharge features [14]. Lithium Nickel Alloys (Li-Ni) contain alloys of lithium and nickel in various proportions. These batteries are generally preferred for their high energy density and low cost [15]. Table 2 shows the comparison of the lithium-based battery types mentioned above in terms of cathode material, anode material, nominal voltage, cycle life, energy density, cost and safety. In addition, comparisons of the relevant battery types in terms of energy density and specific energy are given in Figure 1 [3,16]. The growing adoption of EVs and the development of higher-capacity batteries are key drivers behind the increasing prevalence of battery usage. However, currently the lifespan of the batteries is not at the desired levels. This situation prevents the full potential of developments in battery technology from being used. The short lifespan of batteries causes increased costs and difficulties in achieving sustainability goals. In addition, batteries that have been retired from use pose a major waste problem because they contain environmental risks due to their chemical structure. Especially with the widespread use of EVs, it is expected that a significant amount of used EV batteries will emerge in the coming years. This situation further increases the importance of waste battery management and second-life battery (SLB) applications. The increasing cumulative capacity of used EV batteries shows that the importance of second-use batteries is increas-

Figure 1. Energy density and specific energy comparison of different batteries [3]. ing and that they have a supporting role in ESS. Figure 2 shows how the supply of second-life lithium-ion batteries is today and where it is expected to reach by 2030 [17]. Although recycling of batteries is very important in terms of providing the raw materials required for battery production, it has remained far from being a solution to the waste battery problem because of the reasons like the lack of advanced recycling techniques for each battery chemistry, lack of global or regional waste battery collection networks, high recycling costs, and the inadequacy of recycling facilities. Instead, reusing batteries after their first use (i.e. second-life usage) makes a great contribution to solving the waste battery problem [18]. In addition, batteries, which still have the potential to provide high energy after their first use, only separate the valuable metals and similar materials they contain through recycling, meaning that their potential is mostly lost.

Table 2. Comparison of the lithium-based battery types. Battery type

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Figure 2. Second-life lithium-ion battery supply: Present and future. Second-life applications include evaluating used batteries in ESS, power backup systems, renewable energy integration, and other areas. In addition to extending battery life, these applications help utilize resources more effectively and reduce environmental impacts. Additionally, second-life applications are economically advantageous because the value and performance of used batteries can still be maintained. Therefore, considering and encouraging second-life applications during battery design and usage stages is an important strategy to create a sustainable battery ecosystem. This approach should be considered an important step towards a more sustainable future, both environmentally and economically. In this context, various studies have explored how second-life batteries can be effectively reused in different sectors. These studies examine the technical feasibility, economic viability, and environmental benefits of second-life scenarios in real-world applications. Table 3 provides an overview of literature studies that explore how second-life EV batteries are used in various scenarios [19]. Laboratories investigating the optimal design of batteries in the first and second use stages, aging tests and second use possibilities, and studies conducted in this field, increase awareness about the efficient use of batteries and enable an important step to be taken for an environmentally friendly energy future. In this process, critical parameters such as battery chemistry, size, cover, and cooling system must be optimized by considering the relevant constraints and requirements [42]. Thanks to these optimized parameters, the batteries will exhibit the desired performance and minimize the materials used while providing maximum performance and life. This approach will support sustainability and efficiency goals by making significant contributions to the world ecosystem. Additionally, it will facilitate the integration of renewable energy sources and increase energy efficiency by increasing the ESS’ efficiency.

Many companies operate in the field of battery design and optimization. However, services for the optimal design of batteries used in second-life applications are not yet widely available. Batteries with secondary use potential play an important role in ESS and other applications. Therefore, specially designed services are needed to increase the performance, efficiency and durability of end-of-life (EOL) batteries [43]. These services must consider factors such as battery chemistry, capacity management, storage conditions and safety to ensure that batteries use their second life in the most efficient way. Encouraging R&D studies in this field will make significant contributions to an economy that adopts an environmentally sustainable approach. Infrastracture, Technological Capacity of the Laboratory and Research & Development Activities Battery technologies are becoming increasingly crucial worldwide, especially in EVs, renewable energy integration, and energy storage. This rapid advancement has created a strong demand for qualified personnel skilled in battery design, production, testing, and second-life applications, as well as R&D. Collaboration between academia and industry plays a vital role in training these experts. Organizing specialized training programs, workshops, and knowledge-sharing platforms will help develop young talent and foster innovation. Strengthening human resources in battery technologies is essential for building a sustainable future. Battery testing laboratories and a limited number of battery aging laboratories are established in many areas, including the private sector. However, many of these laboratories were established for the purpose of producing battery cells, producing battery stacks from cells, or testing batteries for specific usage needs. The lack of an impartial and non-profit central battery design laboratory is felt. These laboratories are generally designed to suit the specific needs of the organizations. However, there is no laboratory that can record

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Table 3. Overview of application scenarios and cases of second-life EVBs. Category

Renewable energy integration, smoothing control, reducing curtailed electricity

Wind-Hamidi et al. [20], Alhadri et al. [21], BYD [22], PV-Koch-Ciobotaru et al. [23], Saez-de-Ibarra et al. [24], Leung [25], Fitzpatrick [26]

Alleviate grid congestion, offer ancillary Neubauer et al. [27], Lacey et al. [28], support to the network, and delay the Eyer and Corey [29] expansion of power transmission and distribution capacity

battery data for all types of battery cells and environmental conditions, match and make sense of these data using artificial intelligence, test next-generation battery technologies at the cell level and report their performance according to environmental conditions. Moreover, a laboratory that details the optimal application selection, sizing and pricing for the reuse of batteries by considering second-life applications will have a unique position internationally. As a result, increasing battery usage and their short lifespan leads to serious economic problem due to the use of rare-earth elements. To solve this problem, it is important to use resources in the most efficient way. The second use offers the potential to be used in other applications for up to 8-10 years after the batteries have reached their EOL [44]. However, the second use issue is not yet widespread and faces various obstacles including concerns about planning, security, financial management, and market acceptance. These factors are important challenges that need to be overcome for second use applications to become widespread and potential opportunities to be utilized [45]. The battery laboratory to be established will address the interests of a wide range of sectors that use batteries including important areas such as white goods, EVs, micromobility, telecommunications, defense industry, space industry, and electricity distribution, production, and transmission. These sectors will both play a role as customers for battery design and development and become battery providers for second-life use. In this way, batteries that have reached the end of their first life in one sector can be used as cheap energy storage units in other sectors. This will create an eco-

system and enable the recycling and reuse of batteries with reduced capacity. This approach aims to use resources more efficiently and ensure environmental sustainability. Moreover, in some cases, the needs of battery firms are based solely on data. Rather than each company setting up separate laboratories, a centralized facility offering data and testing services can more effectively meet sector requirements. Furthermore, inefficiencies and flawed designs stemming from the lack of competent personnel increase costs and reduce the battery performance. Especially in products that go directly to the end-user, high battery costs cause decision changes and raise questions in terms of reliability. Batteries that have completed their first life in applications that require high C ratio, power and energy density, such as EV and defense and space industries, can be used for another 8-10 years in applications that do not have volume and weight problems, such as UPS and grid level storage systems. However, this opportunity cannot be utilized due to lack of testing, analysis and experts. The laboratory to be established will enable next-generation battery materials to be tested in real application conditions in cell form. This step will accelerate the transformation of materials into commercial products and enable processes such as valuation and sale of patents. Moreover, academic and R&D studies on second-life applications are limited and there is not enough data for realistic aging processes of batteries. There is a lack of data, especially regarding the performance of aged batteries in applications and the parameters required for design. With the establishment

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of the laboratory, aging data will be collected and analyzed in this regard. These data will constitute an important resource for second-life applications of batteries and will support the industry’s efforts in this field.

Subunits of the Laboratory The aim of this project includes the establishment of various subunits to promote developments in battery technologies and support specialization in this field. In line with this objective, a total of nine interconnected subunits have been designed to cover the entire lifecycle of batteries—from performance evaluation and second-life optimization to economic assessment, user awareness, and training. These subunits collectively form a comprehensive and multidisciplinary research and development infrastructure that can support both industrial and academic needs in the battery sector. The overall system architecture is given in Figure 4.

In universities and R&D centers, a lack of scientists and employment in the relevant field is observed. These institutions have difficulties in recruiting qualified personnel. It is aimed for universities and R&D centers to meet this need with activities such as establishing laboratories, in-house internships, trainings and personnel exchange. In this way, competent personnel will be provided to the sector and research and development studies will be carried out more efficiently. In addition, training and information sharing through laboratories will contribute to the strengthening of universities and R&D centers in their areas of expertise. In Figure 3, the important stages in the battery laboratory to be established is given. The process begins at the cell and stack levels, where monitoring of internal resistance, thermal and mechanical design, and appropriate storage conditions are critical to ensure baseline performance. During storage and operation, the battery is exposed to temperature variations, state-of-charge changes, and aging, which affect overall capacity and reliability. Electrical and thermal protections must be implemented to ensure safe operation over a prolonged period, ideally up to ten years. As batteries retire from their first life, proper evaluation during vehicle parking duration allows early identification of degradation patterns. In the second-life stage, economically viable reuse applications are explored in consumer electronics, small-scale e-mobility, or ESS. Finally, environmentally responsible recycling is essential to recover valuable materials like nickel, manganese, and lithium while minimizing waste. Each phase in this cycle forms a critical part of the second-life battery workflow.

Each subunit has been structured to fulfill a specific role within this ecosystem. These include the Cell Aging Subunit, Stack Analysis and Aging Subunit, Battery Design and Optimization BMS Design Subunit, Data and Visualization Center, Next-Generation Battery Test Subunit, Economic Battery Management System Subunit, Training Center, and Awareness Center. Additionally, the infrastructure is supported by a mobile application interface designed to make battery monitoring accessible to all user profiles. The Cell Aging Subunit aims to conduct research to increase batteries’ performance and lifespan by examining the aging processes of battery cells. The obtained here will be held in the database and used in the Battery Design Center of the laboratory, and designs for the second use will be based on these data. This subunit will also play an important role in testing the durability of battery materials and structures for long-term use and monitoring their performance. The Stack Analysis and Aging Subunit of the laboratory is dedicated to evaluating the performance and aging behavior of battery stacks composed of multiple cells. By subjecting these stacks to various charge/discharge cycles, thermal conditions,

Figure 3. Important stages in the battery laboratory to be established.

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Figure 4. The subunits of the laboratory. and usage profiles, this unit aims to identify degradation patterns and performance losses over time. The test results will help determine the suitability of these stacks for continued use or second-life applications. Moreover, the findings from this subunit will support the development of standardized testing protocols and contribute to the design of safer and more durable battery systems suited for daily-use scenarios. The Battery Design and Optimization Subunit aims to increase the energy density, efficiency, and reliability of battery systems by employing advanced design and optimization techniques. This subunit will not only support internal R&D activities but also offer external battery design services for industrial and institutional partners. Initially, its primary focus will be on the design and optimization of newly developed battery systems, where various parameters such as cell configuration, thermal control, and electrical layout will be fine-tuned to meet application-specific requirements. In addition to new battery designs, the subunit will also play a key role in the reuse of aged batteries by utilizing performance and aging data collected from other laboratory units. By incorporating this data into the design process, the subunit will develop second-life battery systems that are both cost-effective and operationally safe. This dual-function approach—addressing both first-life and second-life battery design needs—positions the subunit as a critical component in achieving a circular battery economy and promoting sustainable energy storage practices. Figure 5 illustrates the conceptual structure of the smart Battery Management System (BMS) developed within the BMS Design Subunit. This unit is dedicated to enhancing battery safety, performance, and lifespan by focusing on the design and optimization of advanced BMS architectures. A key approach involves leveraging large-scale data acquired from battery testing processes, which is then analyzed using artificial intelligence and deep learning algorithms. Through

this data-driven strategy, the system can predict battery health status and remaining useful life with improved accuracy. In addition to its AI-driven capabilities, the smart BMS incorporates a modular hardware and software design, enabling flexible integration and rapid prototyping. As seen in the figure, the platform utilizes next-generation, high-efficiency hardware components that contribute to power savings and increased reliability. Furthermore, an integrated approach underpins the entire system, ensuring cohesive operation among sensing, control, and communication layers. The Data and Visualization Center is a subunit that aims to facilitate the monitoring and control of battery systems

Figure 5. The block diagram of smart Battery Management System (BMS).

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by collecting and analyzing data on battery performance and presenting them in a way that is understandable to users. In addition, the data in this center will be processed with artificial intelligence and form the infrastructure of the software to be used in BMSs. The Next-Generation Battery Test Subunit is designed to establish a comprehensive and advanced testing infrastructure for evaluating the performance, durability, and safety of innovative battery technologies. Within this unit, developed battery materials are first assembled into test cells, which are then subjected to controlled testing conditions using a climate control chamber to simulate various environmental parameters such as temperature and humidity. The electronic load/source unit applies dynamic charge/discharge profiles to the battery cells, while a main computer provides real-time signal control and data acquisition. All measurement results—such as voltage, current, temperature, and capacity— are recorded and analyzed through integrated software tools. After testing, the center delivers detailed technical reports and performance evaluations, enabling standardization and benchmarking of next-generation battery cells under aging and operational stress conditions. The block diagram of the battery cycle aging test setup is given in Figure 6. The Economic Battery Management System Subunit aims to conduct cost analyzes to ensure that battery systems are economically sustainable and to develop strategies to increase the economic value of energy storage projects. In addition, it is a system that will analyze the market values and price projections of second-life batteries as they transition from the first life to the second life within the optimum time. The Training Center is a subunit that aims to organize training programs on battery technologies and train qualified human resources in accordance with the needs of the

Figure 7. Conceptual mobile application interface. sector. By creating modular, classified training contents and plans, a training center will be established to meet the employment needs for the private sector and the public, including technical personnel at all levels, as well as manager and planner levels. The Awareness Center is a subunit that aims to increase the society’s knowledge about the benefits, use, recycling and sustainability of battery technologies. By informing the society about the mentioned issues, this center will extend the average battery life in the country and will also raise awareness in the relevant sectors about sustainability-supporting practices such as recycling and second use. In the final stage, all data regarding the SoH and optimum sizing of the battery will be presented as output by developing a software. The mobile application, which can run on both Android and iOS platforms, will create a user interface in this context. The interface will be designed by creating a user experience in which even people who are unfamiliar with technology can easily use the application. On the first page of the application, the user will be asked for login information to enter the system. On the other screen, the user will be able to examine technical values such as SoC and SoH values of the storage device, charge and discharge status, current, voltage, cell temperature, total number of cycles, whether the storage device is usable or not, and the status of its maximum capacity. A conceptual mobile application interface is given in Figure 7. By establishing these subunits, it is aimed to achieve goals such as developing battery technologies, increasing performance, determining safety standards, ensuring economic sustainability, training qualified human resources and raising public awareness. These subunits will contribute to the country’s leading position by supporting innovations in battery technologies and will enable an important step towards the sustainable energy future.

Conclusion

As global demand for energy storage continues to rise alongside the proliferation of EVs and renewable energy sources, the challenges of battery lifecycle management have

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become increasingly critical. Conventional battery recycling methods, while essential, remain limited in scale and efficiency, often failing to fully address the economic and environmental consequences of EOL batteries. In this context, second-life applications emerge as a highly viable and sustainable alternative that not only extends battery lifespan but also significantly reduces waste and resource consumption.

This paper presents an overview of major battery technologies and emphasizes the growing need for second-life battery usage. The proposed laboratory, with its advanced technological infrastructure and specialized subunits, aims to establish a unique ecosystem that facilitates the reuse of EOL batteries in various applications, from ESS to small-scale mobility solutions. The laboratory’s holistic design—including its focus on aging analysis, battery design optimization, smart BMS integration, economic evaluation, and data management—ensures that batteries can be repurposed safely and efficiently. Moreover, by bridging academic research and industrial needs, the lab supports the development of standards and practical solutions suited to real-world challenges.

Data Availability Statement

The authors confirm that the data that support the findings of this study are available within the article. Raw data that support the finding of this study are available from the corresponding author, upon reasonable request.

Conflict Of Interest

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Ethics

There are no ethical issues with the publication of this manuscript.

Statement On The Use Of Artificial Intelligence

Artificial intelligence was not used in the preparation of the article. [15]

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