Introduction: The History of Lithium Ion Battery
Increased reliance on electric powered transportation, wireless devices, and electronics worldwide has caused an uprise in demand for the development of lithium-ion batteries. Electric vehicles, which use electrochemical cell batteries, have risen due to both increasing popularity and a cultural shift to reduce carbon emissions. In 2018, according to the Global Carbon Project, CO2 emission from transportation hit an all-time high of 37.15 billion tonnes (Global Carbon Budget, 2019).
With the price of fossil fuels and government subsidies increasing, it reduces the price gap between traditional combustion engines and electric-powered engines.
Figure 1 shows the increase in the usage of lithium-ion batteries coinciding with increased consumer use, showing positive development in the electric vehicle sector (Yoshino, 2012) and thus an increased need for batteries.
Figure 1 Expansion in demand for Lithium-Ion batteries, GWh – Gigawatt hours (Deng, 2015)
A complete battery pack is made up of the number of cells with low voltage and power specifications fixed in a parallel format. Different chemistry of battery cells decides compatibility for a specific application, i.e. domestic or industrial, stationary or portable, high power or high voltage. Despite the electrochemical versatility, battery pack modelling affects many parameters such as lifetime, cycle-life, efficiency, specific power and energy, and safety and cost. Overall, battery pack modelling and testing adapt to the particular requirement of the application.
Manufacturing Of The Battery Pack
Battery cells come with specific current, voltage and power capacity. To run automotive, computer or aircraft applications, they require high voltage and current. For high voltage and amp power capacity, many cells need to be connected in series or parallel format to meet the correct requirements (Ko et al., 2019).
Selection Of Cell
The capacity and weight of the battery cell differ as per its construction and type. The initial step to designing the battery pack is to select the appropriate battery cell which should meet the criteria of the application as shown in Table 1 (Rajasekhar & Gorre, 2016) (Amp & Cells, 2014). The chemical properties affect the voltage and Amp hour (Ah) capacity of the battery cell. Due to the advantages of the lithium-ion battery, it is used for the formation of the battery pack.
Table 1 Pros and cons of cylindrical and prismatic cell
| Type of cell | Pros | Cons |
| Cylindrical Cell | Standardized size | Require more space |
| Â | Easy construction, Low cost | Tolerance issue |
| Â |
Can handle high internal pressure |
Become hard to increase capacity |
| Prismatic Cell | Thin and Light in weight | More expensive |
| Â | More stable | Complicate construction |
| Â | High volumetric efficiency | Swelling issue |
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Cell Configuration
The second step is to determine the number of cells in the series or parallel configuration of the battery cell. The setup of the battery pack is based on the voltage and current rating of every cell. To make the battery pack compact, the series and parallel configuration can be optimized (Maiser, 2014). A series configuration consists of batteries connected by the positive of one cell to the negative of the next cell. As shown in Fig. 2, a series configuration connection adds the voltage capacity of each cell to deliver the total terminal voltage.
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In parallel configurations, the positive and negative of every cell are connected as shown in Fig. 3. This adds more Ah capacity to each cell.
Structural Design
Electrical Interconnection
Nickel Strip
| Size | Optimal | Acceptable | Poor |
|---|---|---|---|
|
0.1 mm × 5 mm
|
< 2.1 A
|
~3.0 A
|
> 4.2 A
|
|
0.1 mm x 7 mm
|
< 3.0 A
|
~4.5 A
|
> 6.0 A
|
|
0.15 mm x 7 mm
|
< 4.7 A
|
~ 7.0 A
|
> 9.4 A
|
|
0.2 mm x 7 mm
|
< 6.4 A
|
~ 9.6 A
|
>12.8 A
|
|
0.3 mm x 7 mm
|
< 10.0 A
|
~ 15.0 A
|
> 20.0 A
|
 Table 2 Acceptable current levels for pure nickel strip (Mike, 2017)
The division of maximum battery current to the current carrying capacity of the nickel strip gives the number of pieces needed. For example, if two parallel groups with four cells in each configuration are being used to create a total of 20 A battery current with the help of 0.15 mm × 8 mm nickel strip (5A current varying capacity), then it requires 20 A/ 5 A = 4 strips to carry the present (Figure 4). Similarly, if the battery current is 40 A, then eight nickel strips are needed because two pieces are needed for a single connection. The best battery pack design is to stay within the criteria of the nickel's optimal current capacity. If the dimension of the nickel strip is chosen from the poor current position, it could start to overheat and damage the thermal ability of the battery pack.
Spot Welder
Mechanical Structure
I. Thickness and expansion of the cell
II. Insulation
III. Ventilation to the cell
IV. Physical protection of the cell
Thermal Management
Battery Management System (BMS)
- Cell monitoring (voltage, current, and temperature)
- Supervising the battery pack behaviour (the state of charge, energy, performance)
- Cell balancing
- Charging and discharging limit of the battery pack
- BMS is a vast area to discover. It comes in the form of an integrated circuit with necessary programming and sensors. The main advantage of the BMS is that it’s programmable and the limit of the functions is manageable as per the requirement and application.
- Nuvation Engineering (U.S.)
- Valence Technology, (U.S.)
- Linear Technology Corporation (U.S.)
- Eberspaecher Vecture (CANADA)
- Nuvation Energy (USA)
- ON Semiconductor (USA)
- JTT Electronics (CANADA)
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References:
Amp, M., & Cells, H. N. (2014). Battery Pack Design , Validation , and Assembly Guide using A123 Systems. 1–71.
Deng, D. (2015). Li-ion batteries: Basics, progress, and challenges. Energy Science and Engineering, 3(5), 385–418. https://doi.org/10.1002/ese3.95
Global Carbon Budget. (2019). No Title. https://www.globalcarbonproject.org/carbonbudget/
IEA. (2019). Global EV Outlook 2019. In IEA. https://www.iea.org/reports/global-ev-outlook-2019 Jossen, A., Späth, V., Döring, H., & Garche, J. (1999). Reliable battery operation - a challenge for the battery management system. Journal of Power Sources, 84(2), 283–286. https://doi.org/10.1016/S0378-7753(99)00329-8
Lewchalermwong, N., Masomtob, M., Lailuck, V., & Charoenphonphanich, C. (2018). Material selection and assembly method of battery pack for compact electric vehicle. IOP Conference Series: Materials Science and Engineering, 297(1). https://doi.org/10.1088/1757- 899X/297/1/012019
Maiser, E. (2014). Battery packaging - Technology review. AIP Conference Proceedings, 1597(February), 204–218. https://doi.org/10.1063/1.4878489
Mike. (2017). How Much & What Size Nickel Strips Should You Use.
Rajasekhar, M. V., & Gorre, P. (2016). High voltage battery pack design for hybrid electric vehicles. 2015 IEEE International Transportation Electrification Conference, ITEC-India 2015, 1–7. https://doi.org/10.1109/ITEC-India.2015.7386876
Rothgang, S., Nordmann, H., Schaper, C., & Sauer, D. U. (2012). Challenges in battery pack design.
Thomas Industry Update. (n.d.). Top US and International Battery Suppliers and Manufacturers. https://www.thomasnet.com/articles/top-suppliers/battery-manufacturers-suppliers/
University, B. (2019). Series and Parallel Battery Configurations.
Weicker, P. (2014). A Systems Approach to Lithium-ion Battery Management. Artech House. World Energy Council. (2019). Energy Storage Monitor: Latest trends in energy storage. www.worldenergy.org
Yoshino, A. (2012). The birth of the lithium-ion battery. Angewandte Chemie - International Edition, 51(24), 5798–5800. https://doi.org/10.1002/anie.201105006
