Due to climate change, the energy system needs to change from traditional fossil fuels to be dominated by renewable energy sources. Not only the energy system, but the increasing number of vehicles and emissions from the transport sector are a problem for climate change and that need to be solved. Both can be solved with batteries, to handle climate change issue. The lithium-ion batteries (LIBs) have a high energy density which is important due to the less needed materials for the batteries. LIBs can be used in a battery energy storage system (BESS) to store the excess energy for later usage, and as an electric vehicle (EV) battery. For these high energy density batteries, there comes drawbacks such as safety issues by deviating temperatures which have effects on the capacity, lifetime, performance, and in worst case a thermal runaway can occur which may lead to fire and explosions. These temperature issues can be solved with a battery thermal management system (BTMS), which can manage temperature deviation. Cylindrical battery cells with the dimension 18650 with the cell chemistry Lithium-Nickel-Cobalt-Aluminum-Oxide (NCA) will be investigated with different discharge rates, how the heat generation increases, and how it can be handled by cooling systems. A battery pack will be built up in computational fluid dynamics (CFD) software called Ansys Fluent, to be simulated and see how the influence of cooling methods affect the energy density of the 18650 batteries. Air-cooling and liquid-cooling with fan as air-cooling and plate cooling as liquid cooling will be used in this work. 20 cells were investigated with air and liquid cooling, with two different cases with air-cooling. 100 cells with just liquid cooling during 0,5C was investigated on how the number of cells impacted on the energy density. It was seen that the different discharge rates (C-rate) had an impact on the amount of cooling, with air cooling being not as good as liquid cooling for cooling the battery pack and more flow was needed. The energy density in relation to weight showed that 20 cells with less spacing using air-cooling had the best energy density at 196,68 Wh/kg. It was also seen that the number of cells had an impact on the energy density in relation to volume. With the best energy density with 100 cells using liquid cooling at 279,96 Wh/L.

Over the last ten years the Li-ion battery cells plays a significant role in the world’s decarbonization and reduction of CO2 emission. They are widely applied in many industries, such as consumer electronics, transportation and energy storage industries. The number of batteries cells varies from a few to thousands in a battery application, they are connected in series and/or parallel according to their designed voltage and capacity. It is a great advantage to be able to electrically connect the positive and negative sides of the battery from one side when designing and manufacturing battery modules and battery packs, because the whole built height of module could be a little lower and the rest of space below the cell body is free for cooling or thermal management. In this thesis project, different bonding technologies were compared, and ultrasonic wire bonding was selected to connect the negative electrode (shoulder) of battery and busbar. However, bonding on the shoulder of battery was still a challenge. The mechanism of ultrasonic wire bonding and the surface condition of the shoulder were studied in the project in order to develop the bonding process. Besides, the DoE experiment was used to further optimize the parameters of the wire bonding process. The 4 most influential factors were obtained from 7 factors from the screening factor experiment. Then a full factorial experiment was carried out for evaluation. Finally, a series of optimized parameters could be summarized. / Under de senaste tio åren har litiumjonbattericellerna spelat en betydande roll för världens koldioxidutsläpp och minskning av CO2-utsläpp. De används i stor utsträckning inom många industrier, såsom hemelektronik, transport och energilagringsindustrier. Antalet battericeller varierar från några få till tusentals i en batteriapplikation, de är seriekopplade och/eller parallellt beroende på den spänning och kapacitet de är avseddaför. Det är en stor fördel att kunna koppla ihop batteriets positiva och negativa sidorelektriskt på samma sida när man designar och tillverkar batterimoduler ochbatteripaket, eftersom hela bygghöjden på modulen kan vara lite lägre och resten av utrymmet under cellkroppen är fri för kylning eller termisk hantering. I detta examensarbete jämfördes olika bindningsteknologier och ultraljudstrådsbindning valdes för att ansluta den negativa elektroden (axeln) på batteriet och samlingsskenan. Att fästa på axeln av batteriet var dock fortfarande en utmaning. Mekanismen för ultraljudstrådbindning och axelns yttillstånd studerades i projektet för att utveckla bindningsprocessen. Dessutom användes DoE-experimentet för att ytterligare optimera parametrarna för trådbindningsprocessen. De 4 mest inflytelserika faktorerna erhölls från 7 faktorer från screeningfaktorexperimentet. Därefter utfördes ett fullständigt faktorexperiment för utvärdering. Slutligen kunde en serie optimerade parametrar sammanställas.