Lithium battery requires highly strict and complex manufacturing techniques and technologies that mainly comprise the following steps.
1. Paste Mixing:
This process involves mix of battery paste additives to produce active positive and negative electrode materials under high-speed stirring in a mixing machine.
2. Electrode Coating:
The active electrode materials are evenly applied to both sides of metallic foils. The coated foils are then dried and baked before proceeding to the cutting machine. The battery cell may suffer internal short circuit from any bur on the edge of cut foil strips. The cutting machine requires absolute precision and maintenance to ensure the quality of cells. In addition, though anode and cathode cells in a battery have similar form and are produced on similar if not identical equipment, in order to avoid destroying the battery, the contamination between anode and cathode materials is particularly crucial to battery production. Anode and cathode materials are usually processed in separate rooms as a result.
The assembly process mainly consists of casting anode and cathode plates and placing a separator between the anode and the cathode. There are two different electrode structures used depending on the types of casing, a stacked structure for prismatic cells and a spiral wound structure for cylindrical cells.
- Prismatic Cells
If a slim pack is desired, prismatic cells are often used to optimize the use of space for high capacity battery applications. The manufacturing process uses a stacked electrode structure where cutting of anode and cathode foils is required to stack electrode plates with a separator sandwiched between the anode and cathode. While optimization of the use of space is achieved, the design is disadvantaged by more complexity and subsequently higher manufacturing costs due to the fact that stacked electrode plates require a clamping mechanism to connect all anodes/cathodes together to the main terminal post.
- Cylindrical Cells
Anode and cathode foils are cut into two long strips that are rolled together with a separator in between. A two-strip structure simplifies the construction of battery requiring a single tab connection to corresponding terminals.
Once the assembly is completed, each cell has to be put through at least one precisely controlled charge/discharge cycle to activate the materials, transforming them into their useable form. During formation, data of cell performance are gathered for quality analysis and traceability. A strict process and rigid tolerance particularly ensure sorting of cells into different performance groups which allows early detection of performance failure.
Lithium batteries are widely used in our daily lives. The safety standards are met through a series of test procedures in the laboratory to ensure absolute reliability and zero tolerance to flames/explosion in the events of internal short circuit, overcharge, overheating (constant 150℃ for 10 minutes), puncture (by a 3mm pin), and collision (10 kg object free fall from 1 meter high).