The four major product characteristics of large cylindrical lithium batteries

This article will introduce in detail the four major characteristics of large cylindrical steel shell lithium batteries（4680 battery）: large volume and high capacity, electrodeless lug design, high energy density, and dry electrode technology.

1. Large Volume High Capacity

A large volume means the ability to encapsulate more active materials (such as positive and negative electrode materials), thereby achieving a significant increase in the capacity of individual batteries. The capacity of 46800 batteries can be about five times that of 21700 batteries.

The current priority scheme is a 46mm size.

Continuously increasing the size will raise safety concerns and risks to the battery's cycle life. In terms of diameter, the vehicle's range begins to decrease starting from 46mm, and the marginal benefits of cost reduction diminish. Therefore, considering both the performance and cost of battery packs, a 46mm diameter is the preferred option in terms of performance and economy at the current technological level.

2. No-pole ear (all-pole ear) design

Traditional cylindrical batteries have tabs on the top and bottom for connecting to external circuits for power transmission. The large cylindrical battery adopts an all-lug design.

Design advantages of non-pole ear (all-pole ear)

Monopole ear structure: electrons flow in the current collector through the entire spanwise length of the wound pole piece;

Full lug design: the path of electrons in the current collector is only the axial length;

Comparison: the circulation path is shortened, the internal resistance of the battery is reduced, the conduction area is increased, and the heat dissipation area is increased;

Advantages: Improved rate performance, fast charging and larger current discharge. Theoretically, the charging speed can be increased by about 6 times and the internal resistance can be reduced to one-fifth of the original.

3. High Energy Density

Utilizing high-nickel cathodes and silicon anodes increases energy density, with high-nickel cathodes and silicon anodes being employed in the 4680 battery.

Regarding cathode materials, increasing the nickel content not only enhances the battery's energy density but also reduces the relatively expensive cobalt content, thereby lowering the cost of cathode materials.

Concerning anode materials, silicon offers a higher gravimetric capacity than existing graphite systems. An anode with high gravimetric capacity can enhance the battery's energy density.

4. Dry Electrode Process

Traditional electrode coating employs a wet process, where electrode powder is mixed with solvents to form a slurry, which is then evenly coated onto the current collector foil. The solvent is later dried and recovered.

In the dry electrode process, electrode powder is directly mixed with the binder PTFE and coated onto the current collector via roll pressing. This method eliminates the energy-intensive drying step, thus reducing the production cost of battery cells.

Advantages of Dry Electrode Process:

Simplified Process: Eliminates the drying step after coating the slurry of electrode powder mixed with binder solvent onto the current collector foil in the traditional wet process.

Cost Reduction: Saves on raw material costs for solvents and equipment costs for solvent use, evaporation, and recovery.

Improved Electrode Performance: The binder exists in a fibrous form, allowing for closer contact between the electrode's active materials and conductive agent particles. This results in improved conductivity, higher capacity, and faster charge-discharge rates.

Compatible with Lithium Replenishment Process for Negative Electrodes: Dry electrode technology eliminates the need for organic solvents, allowing direct use of lithium powder during negative electrode replenishment, thereby optimizing the issue of low initial efficiency.

The emergence of 4680 redefines cylindrical batteries, which will drive comprehensive breakthroughs in the fields of positive electrode materials, negative electrode materials, packaging technology and structural parts, and drive technological innovation in the whole industrial chain.