Classification of tabs/Pros and Cons

The tab is a metal conductor that leads out from the cathod and anode electrodes of the battery cell. It is connected to the battery shell or external module structure. The current must flow through the tab to connect to the outside of the battery. According to the number and area of the tabs, the tab design can be divided into monopolar tabs, bipolar tabs/multi-polar tabs, and full tabs.

1. Monopolar tabs: A small battery has a cathode tab and a anode tab, and each tab has a tab that extends out to conduct current.

2. Bipolar tabs/multi-polar tabs: If only one tab is used, the charging and discharging of the current will cause excessive internal resistance, which is easy to cause various safety problems, so the current battery gradually adopts Bipolar tabs or even multi-polar tabs. For example, during the lamination process, each layer of tabs has a tab.

3. Full tabs: At present, Chinese cylindrical batteries have formed two mainstream full tab forms: soft connection and hard connection.

Soft connection refers to a section of the tab on the collector plate connected to the shell, while hard connection refers to "no tab". Tesla's 4680 battery adopts a "tab-less" structure, but the "tab-less" battery does not really have no tabs. Instead, it directly uses the entire collector tail as the tab through a clever structural design, and increases the conduction area and connection area of the tab through the structural design of the cover plate (ie, the collector plate), thereby shortening the conduction distance of the tab.

The traditional monopolar tabs design can only transmit charges along the length of the current collector, and the long conduction distance leads to a large internal resistance. The maximum current transmission distance of the full tabs design is the height of the electrode rather than the length. The electrode height is usually 5%-20% of the electrode length. Therefore, the resistance is reduced by 5-20 times compared to the monopolar tabs, thereby improving the transmission efficiency and greatly improving the battery's rate performance.

As can be seen from the schematic diagram, the full tabs battery cell can withstand large charge and discharge currents and has excellent high-rate charge and discharge capabilities. It can meet the requirements for high-rate performance of batteries, such as rapid acceleration of electric vehicles and instantaneous high-power output. It is also suitable for some special application scenarios with high power requirements, such as high-power power banks, power tools, drones, etc.

In addition, the full tabs design is conducive to the uniform distribution and rapid dissipation of heat. Since the ear is distributed on the entire electrode surface, heat can be conducted away more quickly, reducing the heat accumulation of the battery during the charge and discharge process, effectively avoiding local overheating, improving the safety and stability of the battery, and also helping to extend the battery life. For example, in high temperature environments or when charging and discharging at high rates, the battery temperature can be better controlled.

1. Monopolar Tab

Advantages:

• Simple structure: A monopolar tab connects to one polarity (Cathode or Anode), and its connection method is relatively simple.
• Lower cost: Due to its simple manufacturing process, the cost of monopolar tabs is generally lower.
• Suitable for small batteries: Especially used for smaller capacity batteries or in applications where cost is a higher concern.

Disadvantages:

• Lower efficiency: The current flow in monopolar tabs is less efficient than in bipolar or full tabs, leading to more heat generation in high-load conditions.
• Limited current carrying capacity: The design of monopolar tabs means they are less efficient at carrying high currents, which can lead to issues with overheating under high power demands.

2. Bipolar Tab

Advantages:

• Improved efficiency: Bipolar tabs are typically connected to both cathode and anode electrodes, shortening the current path and reducing resistance, thus improving efficiency.
• Lower heat generation: With a shorter current path, bipolar tabs generate less heat compared to monopolar tabs, maintaining a lower operating temperature.
• Higher current carrying capacity: The design allows bipolar tabs to carry higher currents, making them suitable for applications with high power demands.

Disadvantages:

• More complex manufacturing process: Bipolar tabs require more complex manufacturing processes with higher precision and more steps.
• Higher cost: Due to the complexity of the manufacturing process, bipolar tabs generally cost more than monopolar tabs.
• Size limitations: Bipolar tabs may face size and shape limitations, especially in compact battery designs.

3. Full Tab

Advantages:

• Maximum current carrying capacity: Full tabs cover the entire polarity of the battery, providing a larger contact area and better current carrying capacity. They are ideal for high-power applications like electric vehicles and energy storage systems.
• Higher efficiency: Full tabs offer the best current paths and contact areas, resulting in the highest efficiency among the three tab types and minimizing internal resistance and heat loss.
• Improved battery stability: A larger contact area provides more stable electrical connections, reducing the risk of battery performance degradation.

Disadvantages:

• Most complex manufacturing process: Full tabs require the most precise design and manufacturing, involving more steps in the production process.
• Highest cost: Due to the complexity and more materials required for manufacturing, full tabs are typically the most expensive of the three types.
• Size constraints: In some small battery designs, it may be difficult to implement full tabs due to space limitations, making them less suitable for compact battery applications.