Battery repurposing is becoming an integral part of the battery industry. In order to make the battery manufacturing industry more sustainable, various stakeholders who use batteries are finding various solutions to reduce the carbon footprint. Battery repurposing is one of the most effective and sustainable methods to reduce a battery’s overall carbon footprint. Usually, new batteries are used for electric vehicles (EVs) to ensure reliable quality, safety, and high performance. The state of health (SoH) of newly manufactured batteries will typically be 100% and will gradually decrease once used. When the battery’s SoH reaches 80% or anywhere below 80%, they are removed from the EV vehicles and utilized for other second-life applications such as energy storage systems etc.
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Because of the rapid adoption of EVs, many batteries are expected to enter the second-life market in the upcoming decade. At this rate, the second-life batteries market size is expected to increase from US $430 million in to $7,392 million by , according to P&S Intelligence. Developing countries like India, Indonesia, the Philippines, Thailand, Sri Lanka, and areas in Africa are also expected to purchase a considerable market share of used batteries for second-life applications. Many of the second-life battery application customers are not properly validating the cells, which leads to various problems which include safety issues, performance decline, etc.
In the battery industry, quality assessment of batteries represents a challenging task, with second-life battery assessments representing an even more complex task. Such batteries require a strict quality assessment to allow for their second life application and any compromise in this area would imply considerable costs for the industry. This article offers suggestions for second-life battery cell consumers, with the top 5 parameters that should be considered before purchasing a used battery for the second-life application.
This article, highlight the most standard and important parameters common to most second-life batteries and does not offer an exhaustive review of all parameters at hand.
Top 5 parameters to look into before purchasing a used battery for second life application
Battery Chemistry
State of Health (SoH)
Form factor
Battery’s history and prior use
Battery datasheet
Battery chemistry
Batteries are composed of different chemistry, with unique features for individual chemistries used for specific applications. The voltage and current of the chemistries will vary with the given form factor. These are some of the chemistries which are used for various applications: Lithium Manganese oxide (LMO), Lithium Iron Phosphate (LFP), Nickel Manganese Cobalt (NMC), Lithium Nickel Cobalt Aluminum Oxide (NCA), Lithium Cobalt Oxide (LCO), Lithium titanate (LTO), etc. The research and development of new materials are evolving to increase the performance (e.g. energy, power, etc.) of batteries
Buyers should know exactly in which application they are going to deploy these second-life batteries. Because these Li-ion cells are classified as Energy cells and Power cells based on their performance and their specific application.
Energy cells - They have a high energy density, Designed for high voltage systems. But it has slow charging and discharging time and it has a longer lifetime.
Power cells - They have a low energy density, Designed for low voltage systems. but it quickly charges and discharges and it has a shorter lifetime.
Buyers should be aware of their dimension constraints beforehand in order to identify which chemistry cell they are going to purchase. Every chemistry has unique voltage and current profiles within the given form factor that will determine the dimensions of the model of the system. Customers should have a tentative budget. The clarity in the budget will also help the customer to choose the most desirable chemistry at the given budget.
State of Health (SOH)
State of health (SoH) is a numeric metric (in percentage points) used as a key parameter to explain the health of the battery at any given point. Typically, the battery’s SoH will be 100% at the time of manufacturing and decreases over time due to usage.
SoH is one of the most important performance parameters. The End of Life (EoL) of the new battery can be set when the battery loses 20% of its initial 100% capacity. The second-life battery starts its working phase at 80% SoH and the EoL of the second-life battery is fixed at 60% and sometimes at 40% SoH, based on its second-life application and battery chemistry.
It is ideal to use batteries with SoH ranging between 80% to 60% for second-life applications. For certain chemistries, you can even use the batteries with 40% SoH but it is completely application-specific.
It is not advisable to use a battery below 40% SoH, although some chemistry cells may perform sufficiently well below 40%, there is a high risk of falling into sudden death of battery is very high below 40% SoH.
There are various parameters to determine the cost of the battery, but SoH is one of the key parameters one should look at while procuring batteries for second-life application. Depending upon the specific application other parameters can be prioritized
Battery form factor
The battery form factor (Dimension details) is another important parameter one should look at before purchasing used batteries. Each form factor has its own performance advantages and unique thermal dissipation model. So it is good to pre-model the system with your preferred form factor and simulate the thermal dissipation and then choose the form factor for bulk purchasing.
Most of the time second-life application industries are not using this process, if you build your system with a perfect form factor it will improve the life of the battery too.
Cylindrical (,,), Prismatic and Pouch are the three traditional form factors of the Li-ion battery. Nowadays, new form factors like blade batteries and cylindrical cells are coming into the market for specific applications.
Battery datasheet
A battery’s datasheet is a brief technical document that compiles important technical specifications to explain the technical parameters of the battery cell.
Important parameters you should look for in the battery datasheet:
Nominal Voltage
Operating Voltage
Internal resistance
Current
Number of cycles (Charging and discharging graph)
Operating temperature
Cell chemistry and form factor
Manufacturing date
Warranty guidelines
Note that if one’s battery belongs to a tier 1 manufacturer, then the data in the battery data sheet may be reliable, however, if your battery is from a tier 2 or tier 3 manufacturer, one may need to cross-check the data through third-party validation. Most of the time, second-life application industries do not cross-check datasheet information due to cost and time concerns, yet this is a crucial step.
Battery’s History and prior use
Many second-life sellers do not actually have information pertaining to the battery’s complete history and prior use. The history of batteries will help the assembler to understand the battery better. These are the following information one should know before making a purchase decision:
Who is the battery’s original manufacturer?
When and where was the battery manufactured?
In which application was it deployed?
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Was the battery under a cooling system in its first life?
Data acquired by the Battery Management System (BMS).
Are there any safety concerns with this batch of batteries (like fire or overheating)?
Original performance datasheet of the battery provided by the battery manufacturer
Current performance datasheet of the battery provided by the reseller validated by a third party
Such information is crucial to know whether you are buying these batteries from a legal seller because countries have their own import and export policies. With a proper history of the batteries, you will not face any issues during the time of import in your country in which you do the assembly of the second life system. Sometimes you may also get tax benefits, but it depends on the country’s policy. The previous BMS data will help you to understand the battery better and you can decide whether to directly use the modules or if you need to dismantle them into individual cells to deploy in its second life application
Conclusion
This article outlines the top five parameters a buyer should consider before purchasing used batteries for second-life applications. We all know batteries are becoming a major part of the energy industry and the demand for batteries is growing, however adequate, safe, and durable battery use requires careful scrutiny. Its complexity is further increased in the case of a battery’s second-life application.
To make a second-life application safer, industry actors should adopt high-quality standards when analyzing, sorting, and assembling systems using second-life batteries.
Source:
https://www.sciencedirect.com/science/article/pii/S#:~:text=Consequently%2C%20as%20reused%20batteries%20start,However%2C%20Fig.
https://www.sciencedirect.com/science/article/pii/S?via%3Dihub
https://www.mdpi.com/-/13/2/375
About the Author
Mr.Barath Venkatesan
Intern - Battery Associates
Barath Venkatesan is a Junior consultant at Battery Associates. He has a bachelor’s degree in Nanoscience and Technology and is doing his master's currently in Material Engineering and Nanotechnology at Politecnico di Milano university in Milan, Italy. He is passionate about the circular energy economy and he currently works with various stakeholders in the battery ecosystem to create a sustainable world through the power of batteries.
Cylindrical lithium battery is a kind of lithium ion battery, its shape is cylindrical, so it is called cylindrical lithium battery. The structure of a typical cylindrical battery includes: casing, cap, cathode, anode, separator, electrolyte, PTC element, gasket, safety valve, etc. Generally, the battery shell is the anode of the battery, the cap is the cathode of the battery, and the battery shell is made of nickel-plated steel plate.
Since Tesla's battery day in September proposed large cylindrical cells, large cylindrical cells have once again become the focus of the battery industry in the market. In addition to Tesla, China's leading cell factories have also begun to invest in the mass industrialization of large cylindrical cells.
According to the data shown by Tesla, the large cylindrical lithium battery will increase the energy by 5 times on the basis of the cylindrical cells, increase the mileage by 16%, and reduce the cost by 14%. Its technical temptation is very significant. However, during the period of rapid development of China's new energy vehicles in the past, first-line brands including CATL and BYD all focused on the technical route of square cells. At present, the industrialization of power batteries is basically based on square batteries, and even Tesla has purchased square batteries with a capacity of about 161Ah in China for use in one of its models.
From a technical perspective, both technical routes have their own value and advantages. In a complex battery system, although batteries account for the highest cost, in terms of safety and cost performance, we cannot only focus on one dimension of batteries. For example, Tesla has industrialized and applied the cylinder and to electric vehicles with energy exceeding 70KWH through advanced management system design. In fact, it is using advanced management to optimize the performance of the battery system.
● Advantages of small capacity flexibility
Due to size and process limitations of cylindrical cells, the capacity of a single cell is usually small. For example, ternary battery 3.5Ah, iron-lithium battery 6Ah, iron-lithium battery 15Ah, iron-lithium battery 20Ah, etc. Aside from electric vehicles and large-scale energy storage markets, in other fields, such as AGV, portable energy storage, and home energy storage, the capacity of single-module batteries is usually not very large. In practical applications, the large-capacity square cells positioned for automobiles and large-scale energy storage do not necessarily exactly match the market demand, including size and capacity.
The small-capacity cylindrical lithium battery can be connected in parallel to meet the battery module capacity needs of certain market demands. For example, the two types of lithium batteries 24V60Ah and 48V30Ah used in AGV cars are relatively common needs. Three types of cylinders, , and , can be combined in parallel to form the required 60Ah or 30Ah modules. At the same time, there are more flexible operation possibilities in the space structure to meet the design requirements of different models.
● Cost advantage
In the production and manufacture of all lithium-ion batteries in lithium battery companies in the world, the process standardization of cylindrical lithium battery is the highest, and it is also the earliest commercialized battery. The assembly efficiency is significantly higher than that of square batteries and pouch batteries. The winding process of cylindrical batteries has reached the level of 200PPM with the gradual improvement of automation. Even though the efficiency of large cylindrical lithium batteries is slightly lower than that of traditional / cylindrical cells, it is much higher than the efficiency of stacking or winding processes of square cells and pouch cells (usually around 10PPM).
The reason for the small capacity of the cylindrical lithium battery is that the strip-shaped continuous pole piece after coating is cut into strip-shaped small pole pieces, and the miniaturization of the pole piece can improve the utilization rate of the entire pole piece material. Usually under the same screening criteria and automation level, the material utilization rate of cylindrical cells is 3-5% higher than that of square cells.
● The heat dissipation effect is obvious
Lithium-ion battery fires are all caused by thermal runaway, and the spread of thermal runaway is also the main concern of battery system safety performance. Cylindrical structure is the most likely solution to thermal runaway, while square and pouch structures are basically unsolvable. The low capacity of a single cell causes thermal runaway to release less energy, which is different from high-energy, large-capacity square cells or pouch cells. At the same time, with the gradual improvement of material safety, the heat release caused by thermal runaway is reduced, which significantly increases the safety of the battery system.
The curved surface structure of the cylindrical lithium battery limits the heat transfer process between the cells to a certain extent, and has a certain positive effect on the spread of thermal runaway. However, square batteries and pouch batteries are basically unsolvable in this regard. Furthermore, with the promotion of the full-tab process, the heat transfer of cylindrical cells is more on the upper and lower end caps of the cells, and the heat transfer on the curved surface will also be reduced.
The above is some analysis and thinking based on different application scenarios of lithium batteries with different structures. Although the focus is on analyzing the advantages of cylindrical lithium battery, it is undeniable that cylindrical cells have shortcomings in certain application fields. At the same time, it is also necessary to objectively understand the own advantages of square cells and pouch cells.
With the development of lithium battery technology, there are more and more types of cylindrical lithium battery. Cylindrical lithium battery are divided into lithium cobalt oxide, lithium manganese oxide, and ternary materials. The three material systems have different advantages. Let's take a look at the models and specifications of cylindrical lithium battery. Cylindrical lithium battery is usually represented by five digits. Counting from the left, the first and second digits refer to the diameter of the battery, the third and fourth digits refer to the height of the battery, and the fifth digit refers to the circle. There are many types of cylindrical lithium battery, the more common ones are , , , , , , and so on.
● battery
The battery is a cylindrical lithium battery with a diameter of 10mm and a height of 44mm. It is the same size as what we often call the 7th battery. This battery capacity is generally small, only a few hundred mAh, and is mainly used in mini electronic products. Such as flashlights, mini stereos, megaphones, etc.
● battery
The battery is a cylindrical lithium battery with a diameter of 14mm and a height of 50mm. This is also the size of what we have always called the AA battery. This kind of battery is generally 3.7V or 3.2V. The nominal capacity is relatively small, a little larger than the battery, generally mAh, and the discharge performance is superior. The most important application field is consumer electronics, such as wireless audio, electric toys, digital cameras, etc.
● battery
The battery is a cylindrical lithium battery with a diameter of 16mm and a height of 34mm. Due to its shorter height and relatively small capacity, this kind of battery often appears in glare flashlights, LED flashlights, headlights, laser lights, lighting fixtures, etc.
● battery
The battery is a lithium-ion battery with a diameter of 18mm and a height of 65mm. Its biggest feature is that it has a very high energy density, almost reaching 170 Wh/kg, so this battery is a battery with better cost performance. Most of the battery store we often see are batteries, because it is a relatively mature lithium-ion battery, and the system quality is stable in all aspects. It is widely used in occasions with a battery capacity of about 10 kWh, such as mobile phones, notebook computers and other small electrical appliances.
● battery
The battery is a cylindrical lithium battery with a diameter of 21mm and a height of 70mm. Because of its larger volume and greater space utilization, the energy density of the battery cell and the system can be improved, and its volumetric energy density is much higher than that of the battery. Widely used in digital, electric vehicles, balance cars, solar energy lithium-ion battery street lights, LED lights, power tools, etc.
● battery
The battery is a cylindrical lithium battery with a diameter of 26mm and a height of 65mm, with a nominal voltage of 3.2V and a nominal capacity of mAh. This kind of cylindrical lithium battery has the characteristics of excellent capacity and high consistency, and has gradually become a trend to replace batteries. Many products in power lithium batteries will also gradually favor it.
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