WO2021091507A1

WO2021091507A1 - A battery with dendritic shaped tabs

Info

Publication number: WO2021091507A1
Application number: PCT/TR2020/050981
Authority: WO
Inventors: Erdal ÇETKİN; Şahin GÜNGÖR; Sinan GÖÇMEN
Original assignee: İzmi̇r Yüksek Teknoloji̇ Ensti̇tüsü
Priority date: 2019-11-06
Filing date: 2020-10-22
Publication date: 2021-05-14
Also published as: TR201917239A1

Abstract

The invention is a battery (10) that decreases thermal resistance and current density by improving the tab designs which would be a thin rectangular prism as a standard and that can be used in any vehicle which requires energy especially in electric/hybrid vehicles, its features; It includes a positive tab (13) with a dendritic design similar to the tree root structure, integrated into the cathode layer (16) in order to cool the battery (10) more effectively and create a more relieved current flow path; it includes a negative tab (14) with a dendritic design similar to the tree root structure, integrated into the anode layer (15) in order to cool the battery (10) more effectively and create a more relieved current flow path which are how it is characterized.

Description

A BATTERY HAVING TABS WITH DENDRITIC STRUCTURE

DESCRIPTION Field of the Invention:

The invention subject is based on the improvement of the very thin rectangular prism shaped tab designs in batteries which are primarily used in electric/hybrid vehicles in addition to be used in automotive, software, defense industries with dendritic structures to reduce thermal resistance and current density.

State of the Art:

Experimental studies which focus on the heat generation mechanisms of electric vehicle batteries documented that the maximum heat generation and maximum temperature values occur around the negative tab during charging process and near the positive tab while discharging occur. The reason for this physical phenomenon is that the electric current lines are concentrated on the tabs during the charging/discharging process. Currently, there are many numerical and experimental studies on battery cooling techniques.

However, currently there is no study which rely on the fact of heat generation due to electrochemical reactions yielding the maximum temperature to occur near the tabs and which consider an integrated cooling system is designed that also includes tab regions. Nowadays, it is aimed to develop environmentally-friendly and silent electric vehicle systems by reducing the transportation systems based on fossil fuels. The most important and critical issue to be improved in this field is that the pouch, prismatic or cylindrical type batteries in the battery packs are cooled homogeneously below the maximum allowable temperature limit. In the literature, there are many numerical and experimental studies on battery thermal management systems. These systems are divided into two main categories: passive and active systems. In addition, there are many possible heat transfer approach under these two main category such as air-cooled, direct-cooled, phase-change materials, and heat pipes, etc. (Kim et al. 2019). In the literature, researchers working on energy and heat transfer concentrated only on cooling, while researchers working in basic sciences such as chemistry and physics focus on chemical reactions and heat generation in batteries. However, most of the studies which design or analyze a battery thermal management system have ignored the time-dependent chemical reactions in the battery and non-uniform heat generation related with chemical reactions. The study of Ghalkhani et al., 2017 which experimentally investigated current density and temperature distribution in a battery shows that regions where current density and temperature distribution during charge and discharge processes were determined to be maximum at negative and positive tabs, respectively.

Hunt et al. (2016) showed experimentally that cooling from the battery cell surface could not provide sufficient end results and demonstrated the importance of cooling from the battery tabs to minimize battery capacity loss. The change of battery capacity was evaluated according to the experimental investigations having 1000 charge/discharge cycles. This study shows that the integrated cooling from the tab and battery surface significantly reduced the capacity loss compared to cooling only from the battery surface, especially at charge rates greater than 2C. However, the study does not include any improvement or optimization regarding thermal management system design or tab design.

The main problem in the studies of aiming homogeneous cooling of various battery types (pouch, cylindrical, prismatic) in electric vehicle battery packs is to rely on cooling only from the battery surface. In the literature, cooling from the tabs is considered for a battery cell and only capacity loss was documented by Hunt et al. (2016) where neither thermal management system design nor application was considered. In addition to that many recent studies which experimentally examines current density and heat generation in the battery model revealed that the maximum current density and the maximum temperature values were obtained around the negative or positive tabs according to the charge/discharge processes. These show the importance of cooling from the tabs and the need for integrated cooling which includes heat transfer from the tabs was revealed. Proposed dendritic structures will enable effective cooling from tab surfaces, decreased resistance for current paths of electric current lines, more uniform current density in the battery, and faster charging opportunities for electric vehicle batteries.

A lithium-ion battery cell is mentioned in the US patent document (US2019027795(A1)) encountered in the literature search. The mentioned battery cell contains a lot of cell layers that reject heat placed on tabs. Cooling can be performed on positive and negative tabs with these cell layers. These cell layers prevent heat transfer and keep the battery cool. However, there is not any dendritic tab design in the document.

A battery cell is described in the US patent document (US2018254467(A1)) encountered in the literature search. The described battery cell has advantages such as shorter charging times and reduction of capacity loss. However, there is not any dendritic tab design in the document.

The battery capacity mentioned in Chinese patent document (CN107069099 (A)) was increased by shaping the cell tabs into spiral form. At the same time, the battery has also features of fast charging and discharging. However, there is not any dendritic tab design in the document.

Consequently, there is a need for a battery in which the state of the art is progressed, and its disadvantages are eliminated.

Brief Description of the Invention:

The invention is related with an electric/hybrid vehicle battery in which the state of the art is progressed, its disadvantages are eliminated, and extra advantages are included. The aim of the invention is to document a new battery in which the charging time is reduced with relieving the current paths by reducing the high current density and heating problem that occurs around the tabs and which provides uniform temperature distribution in the battery cell. Another aim of the invention is to document a new battery in which more efficient cooling is provided with the dendritic structure of the tab design, and thus safety risks are also reduced.

Another aim of the invention is to document a new battery in which more effective thermal management is provided even without cooling by reducing the current density and increasing the current uniformity.

Another aim of the invention is to document a new battery in which the capacity loss is reduced with the tab design that provides decrease in resistance on the current density to decrease heat generation near concentrated heating zones. Another aim of the invention is to document a new battery in which the lifecycle is increased with more efficient and more uniform thermal management.

The mentioned invention is a battery that can be used in all kinds of vehicles that require electrical energy, especially electric/hybrid vehicles as well as electricity storage applications in which the thermal resistance and current density are reduced by embedded dendritic heat sink structure. It includes a positive tab with a dendritic design similar to the tree root structure, integrated into the cathode layer in order to cool the battery more effectively and create a more relieved current flow path. Besides, it includes a negative tab with a dendritic design similar to the tree root structure, integrated into the anode layer in order to cool the battery more effectively and create a more relieved current flow path.

Description of the Drawings:

The invention will be described with reference to the accompanying figures, so that the features of the invention will be clearly understood. However, it is not intended to limit the invention to these particular embodiments. On the contrary, it is intended to cover all alternatives, modifications and equivalents that may be included within the scope of the invention as defined by the appended claims. The details shown are only for the purpose of illustrating preferred embodiments of the invention. It should be understood that they are presented to provide the most useful and easy to understand description of the embodiment of the methods, and the rules and conceptual features of the invention. In these drawings;

Figure - 1 Perspective view of battery subject to invention.

Figure - 2 Exploded assembly view of battery subject to invention.

The figures that will help to understand the invention are numbered as shown in the attached illustration and are given below with their titles. Description of the References:

10. Battery

11. Positive current collector

12. Negative current collector 13. Positive tab

14. Negative tab

15. Anode layer

16. Cathode layer

17. Separator-electrolyte layer

Description of the Invention:

In this detailed description, the battery (10) that is the subject of the invention is explained with examples that will not have any limiting effect for better understanding of the subject. In the description, the developed battery (10) with dendritic designs attached to the tabs is described that would have very thin rectangular prism shaped tab designs which are being used in automotive, software, defense industries and especially in electric/hybrid vehicles where dendritic structures will reduce thermal resistance and current density.

The perspective view of the battery (10) subject to invention is given in Figure 1. The mentioned battery (10) is in the form of a rectangular prism and its dimensions may vary depending on the area, device or vehicle that is used in. The battery (10) that is subject of the invention is primarily intended for use in electric/hybrid vehicles. Charging time and range of electric vehicle are major disadvantages of current technology. Research are being conducted to charge batteries at high charging rates (C-rate> 2) to reduce the battery charging times, but in parallel to this, the amount of heat generated in the batteries (10) increases as charging rates increases. The regions in which the current density and temperature values are maximum in the batteries (10) are located near the tabs. The invention that is the subject to the description focuses on the development of the tabs mentioned. Figure 2 shows the exploded view of the battery (10) which is the subject of the invention. Accordingly, the battery (10) has a positive current collector (11) and a negative current collector (12) that collect current in battery outer layers. The positive current collector (11) and the negative current collector (12) are made of aluminium and copper, respectively, which are highly conductive materials. Between the positive current collector (11) and the negative current collector (12), there are cathode layer (16), separator-electrolyte layer (17) and anode layer (15), respectively. The separator-electrolyte layer (17) provides the transfer of ionic molecules between the anode and cathode layers (15, 16) according to charge and discharge processes. The battery (10) is integrated into the cathode layer (16) with the positive tab (13) and the anode layer (15) with the negative tab (14).

Although the tabs (13, 14) of conventional batteries (10) are in the form of a rectangular prism, the battery (10) that is the subject of the invention is designed in the form of dendritic structure. Thus, a more efficient cooling of the battery and a more comfortable flow path is provided. In this case, the charging times are also reduced. The dendritic tab (13, 14) design was inspired by tree root geometry. Similar to how branches of a tree root system decreases the resistance for how tree collects water from ground, the tabs (13, 14) in the invention ease the transfer of electrical current and heat with a dendritic structure which is the basis of the invention. Thus, the dendritic tabs (13, 14) can transfer the current more easily and provide a more effective cooling. The tab (13, 14) design with dendritic structure should be produced from high thermoelectrically conductive material even that material may vary depending on the battery (10) type and capacity. The designed tab (13, 14) with dendritic structure allows the electric current line to be relieved and the current density to be become uniform. In addition, the battery is being cooled from tab (13, 14) would increase effectiveness of cooling which yield, and thus decrease the required time for charging by reducing the resistance which is another contribution of the invention.

Claims

1 The invention is a battery (10) that decreases thermal resistance and current density by improving the tab designs which would be a thin rectangular prism as a standard and that can be used in any vehicle which requires energy especially in electric/hybrid vehicles, its features;

- It includes a positive tab (13) with a dendritic design similar to the tree root structure, integrated into the cathode layer (16) in order to cool the battery (10) more effectively and create a more relieved current flow path,

- It includes a negative tab (14) with a dendritic design similar to the tree root structure, integrated into the anode layer (15) in order to cool the battery (10) more effectively and create a more relieved current flow path. These are how the invention is characterized.