Lityum İyon Bataryalar

Sunuş

Lityum iyon piller sundukları performans özellikleri ile elektrikli araçlarda en çok tercih edilen şarj edilebilir pil teknolojisi konumundadır. Ağırlıklarına ve büyüklüklerine oranla verebildikleri yüksek enerji sayesinde sadece otomotiv endüstrisinde değil hemen hemen tüm sahalarda sıklıkla kullanılan bir türdür.  Bu konumu nedeniyle Lityum İyon bataryalar üzerine birçok Ar-Ge faaliyeti yürütülmektedir ve teknoloji dünyasında popülerliğini koruyan bir araştırma konusudur. Bu yazımızda da Lityum İyon Batarya Teknolojisisi hakkındaki temel bilgileri bulabileceğiniz bir derleme çalışmasını sizlerle paylaşıyorum. Bataryalarda kullanılan kimyasalların performans, ömür ve maliyet gibi parametreler üzerindeki etkileri hakkında değerli bilgiler bulabilirsiniz. Kıymetli dostum Halil Zınar Düzgün’nün hazırlamış olduğu bu yazının özellikle Lityum İyon Batarya Teknolojileri hakkında araştırma yapan öğrencilerin ve işin detayına girmeyi seven teknoloji meraklılarının hoşuna gideceğini düşünüyorum. Kendisine bu vesile ile teşekkür ederim.

Lityum İyon Batarya Teknolojileri

Lityum İyon batarya teknolojileri hakkında bu yazı helebioku.com’daki ilk İngilizce yazı olma özelliğini de taşıyor. Dünya’da üretilen bilimin/bilginin ve internette paylaşılan içeriklerin çok büyük bir kısmının İngilizce olduğu günümüz dünyasında bu kaynaklardan faydalanabilmenin büyük bir avantaj olduğu gerçeğini göz ardı edemeyiz. Ağırlıklı olarak Türkçe içerikleri sizlerle buluşturmaya devam edecek olsak da özellikle genç okurlarımızın İngilizce kaynaklara erişim açısından kendilerini mutlaka yetiştirmeleri gerektiğini de belirtmeden geçemiyorum. Lityum iyon bataryalar hakkında bu yazı bunun başlangıcı olsun 🙂

Elektrikli Yerli Otomobil Projesi ve TOGG

LITHIUM ION BATTERY FOR FULLY ELECTRIC VEHICLES

Introduction

With the industrial revolution and the maturation of the serial production lines, a significant growth has been realized in the automotive sector. With the increasing love of human beings in cars, today millions of vehicles are produced every year. 

Most of the produced vehicles are using fossil fuels. This used fuel has caused a serious increase in carbon and nitrogen emissions lately. Along with the increase in the number of vehicles and used fossil fuels, serious changes have been observed in the world’s climate nowadays. In the recent period, there have been important developments in the use of renewable energy sources in order to reduce the effects of this global warming, reduce emission values ​​and protect our world. In the automotive industry, new type of fuel researches has been carried out for many years. Apart from petroleum products, vehicles using alcohol, solar energy, electricity and hydrogen fuels have been produced.

Electrıc Vehıcles

Recently, the biggest trend in the automotive industry is the concept of electric vehicles. As a result of environmentalist initiatives, the automotive world is making new developments to protect the nature. Especially the hybrid and electric vehicle works have made great progress in the last 20 years. It shows that the entrepreneurial companies such as Tesla will take remarkable place in the formation of the electrical vehicle market. Today, when we look at the reasons why this market is very small compared to fossil fuel vehicles, high costs of vehicles, low ranges and charging times compared to fossil fuel vehicles come to the fore. The most important ingredient affecting these factors is the batteries of these vehicles.

The history of electric vehicles goes back to the 19th century. It has found itself a place because internal combustion engines were not sufficiently developed at the time electrical vehicles first appeared. However, internal combustion engine vehicles have developed rapidly, especially the insufficient battery capacity of electric vehicles has left them in the background. Although small-scale improvements were made in electrical vehicles in the 20th century, the fact that these vehicles took their place in the market and showed a rapid development especially in the 21st century.

Cell -> Module -> Pack

In fact, electrical vehicle batteries are not different from the batteries we currently use in our phones or computers. We can think that EV batteries are created as parallel or sequentially packaged batteries from which we use in our phones. The smallest elements of the batteries are called ‘Cell’ which meet the energy needs of vehicles. By combining the cells, we achieve components named ‘Module’ and modules are come together to form named ‘Pack’.

The development of batteries has gained great momentum especially with the acceleration of technology at the beginning of the 21th century. Lithium batteries have significantly improved their life cycle, particularly with the replacement of lead acid batteries used at the end of the 20th century. There were important milestones that the batteries had to overcome during the development process. The most important problems are the rapidly falling performances of the batteries. At the same time, the expectation of an increase in the capacity of the batteries was another factor.

In recent studies, important developments have been achieved in these issues. Of course, on the other hand performance improvements are made and improvements caused heating and combustion problems in the batteries. Increasing technology and performance requirements brought new and complex solutions according to the usage area of ​​the batteries. For example, a passenger car battery provides the required voltage to electric motor to meet the motion need of a vehicle of approximately 2.5 tons and this influence high voltage changes in the battery cells.

Heatıng Problem

Rapidly changing voltage of the battery causes a significant heating problem. To ensure that the battery operates in an efficient temperature range and most importantly to eliminate safety risks on the vehicle, manufacturers have developed thermal management systems to protect the battery. The sizes of battery cells and modules differ among manufacturers. However, manufacturers use a thermal management system to cool the battery. This system is realized in the simplest way by providing cold liquid flow between the battery cells.

Cells are the smallest building blocks which meet the energy needs of the batteries. It is the part where the energy transfer is made in line with the electro chemical potential of the material used. In this project, the path to be followed regarding the selection criteria of this item, as well as which material should be chosen will be explained. Parameters such as function, objective, constraint will be determined for the selection criteria and then the results will be shared through the investigation of Ashby charts with the help of Merit indices and material properties.

Material Selection Strategy

To be able to choose the material, first, it is necessary to define the general work and draw the general frame. In order to select the material for the battery, objectives, constraints, function and free variables will be defined. Basically, the fundamental energy requirement is the basic need for battery development. After determining our function as the maximum energy density, it is essential to determine our objective correctly to meet the requirements. Depending on this, our objective;

Minimize mass: Providing maximum efficiency from the battery is very important aspect in vehicles. Providing minimum energy will be possible with lower weight conditions so minimizing mass is important to increase vehicle range. At the same time, reducing the mass of the vehicle will also contribute to the durability characteristics of the vehicle by reducing the loads coming from the road.

Maximize standard reduction potential: It is the reduction tendency value of the material and it is measured in voltage. It is required to ensure that the battery operates at maximum efficiency and to regulate its sequences during charge and discharge.

Our constraints indicate the characteristics that we will need minimally when choosing materials. Constraints;

Reversible chemical behavior: All substances in nature can’t chemically react reversely. The battery is also exposed to bidirectional chemical reactions while charge and discharge occurs.

Free variable is going to be material.

Material Selection Parameters

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Battery is a component with a high level of voltage. High voltages cause high current flow in the battery. Highly resistant materials will cause overheat in the battery. Even though there are thermal management systems, the high thermal conductivity of the material will help cooling process to happen faster. It is important not to harm the nature in terms of the chemical reactions taking place in the batteries which means recycle fraction is crucial. Our Merit indexes show that metals are more suitable choices for battery materials.

Energy Densıty

The standard reduction potential is the tendency of reduction of the chemical species. This parameter is one of the most important parameters for battery performance. The high reduction value is one of the features to be considered. Higher reduction causes the material ease to be ionized and help electron to separate easily. Chemical reaction in the battery is basically electron flow of the material. Considering this situation, it is understood why different materials such as Ni, Zn, Pb, Li are used in batteries.

Weight is one of the most important features of a vehicle. Many vehicle manufacturers include weight reduction studies in product development processes. The produced vehicles are primarily subjected to a weight reduction project after their release. Battery is one of the heaviest components in an electrical vehicle. Depending on the size and energy capacity of the battery, it can reach 400 kg in a passenger car. From this point of view, lightening of the battery is essential. Considering the table, the fact that lithium has small dimensions and low density in ion form makes lithium ion one of the most important candidates.

Lıfe expeCtancy

Evaluation based on life expectancy says that materials such as zinc, nickel and lithium come to the fore. In terms of peak power values, which means energy capacities, Nickel and lithium ion show a similar attitude. However, although lithium ion is not at the lowest level in terms of cost, specific energy and especially energy efficiency values show that it is the best candidate for battery performance.

Material intensity is the weight value required to store 1 kWh of energy in the material. Lowest material intensity values show that the material is most efficient. Considering of energy efficiencies, it is seen that Lithium is more efficient than Nickel.

PrIce / Performance RatIo

The most important issue when developing a component is the price/performance ratio of the supplied product. It is important to get the most suitable product at the lowest price. In electrical vehicles, the price of an expensive component such as batteries is vital importance. Battery constitutes the largest budget item in the bill of material of a vehicle development process.  Lithium is the most affordable material, outperforming other competitors.

Results

Lithium ion batteries were found to be the most suitable option for the battery as a result of the evaluations. In the market of electric vehicles, customers are waiting to have longer range in their vehicles. Therefore, vehicle manufacturers must improve battery performance. Battery life expectancies constitute another leg of this performance matrix. Of course, the main issue is cleaning the air which is polluted with fossil fuels. However, the battery itself must be nature friendly. All these parameters show that lithium ion batteries are the most accurate battery material in today’s technology and knowledge.

Conclusion

The material selection process is made to find the cheapest material that will meet the minimum requirements to fulfill the requirements of the work performed. The main purpose of the designs is to take place in the market. Customer centricity plays an important role in product development processes. Battery performance is the biggest reason for electric vehicles not getting enough space in the market yet. While the ranges of internal combustion vehicles have been up to 1400-1500 kilometers, 500 kilometers are spoken in the electric vehicle market.

Of course, battery performance is determined not only by the chemical nature of the battery, but also by how these chemical structures are managed. Therefore, manufacturers have developed new solutions such as thermal management and battery management systems to get maximum performance from the battery. The correct management of the battery plays an important role for the range and life needs. As a result, despite all these studies, the performance of the batteries is not enough in today’s conditions. With the recent research and development activities, serious improvements are inevitable in the coming period.

Kapanış & Teşekkür

Lityum iyon bataryalar hakkındaki bu paylaşımın faydalı olmasını umuyorum. Elektrikli araçlar ve Lityum iyon (Li-ion) bataryalar hakkındaki çalışmalarını bizimle paylaşan Halil Zınar Düzgün’e bir kez daha teşekkür ederim.

References

1. Özyeğin University ME535 Course Material
2. Achim Kampker, Heiner H. Heimes, Mathias Ordung, Christoph Lienemann, Ansgar Hollah, Nemanja Sarovic- Evaluation of a Remanufacturing for Lithium Ion Batteries from Electric Cars 
3. Yu Miao , Patrick Hynan , Annette von Jouanne  and Alexandre Yokochi- Current Li-Ion Battery Technologies in Electric Vehicles and Opportunities for Advancements
4. Mehrdad Ehsani, Yimin Gao, Sebastien E. Gay, Ali Emadi- Modern Electric, Hybrid Electric and Fuel Cell Vehicles Fundamentals, Theory And Design 
5. Arghya Sardar, Sajid Mubashır -Evaluation of EV Battery: Role of Material Availability
6. EU Commission Staff Working Document – Report on Raw Materials for Battery Applications (Brussels, 22.11.2018)
7. McGraw-Hill, Handbook of Batteries third edition
8. Asian Development Bank, Handbook on Battery Energy Storage System (December 2018)
9. C. Monroy Aceves, A.A. Skordos, M.P.F. Sutcliffe – Design selection methodology for composite structures
10. M. Ferrante, S.F. Santos, J.F.R. de Castro – Materials Selection as an Interdisciplinary Technical Activity: Basic Methodology and Case Studies
11. Andrew F. Burke – Batteries and Ultracapacitors for Electric, Hybrid, and Fuel Cell Vehicles
12. https://socratic.org/questions/how-do-you-rank-oxidizing-agents