Lithium-ion battery is a secondary battery (rechargeable battery) that mainly relies on the intercalation and deintercalation of Li+ between two electrodes. With the continuous development of downstream industries such as new energy vehicles, the production scale of lithium-ion batteries is expanding. This article takes lithium cobalt oxide as an example to comprehensively explain the principle, formula and process flow of lithium-ion batteries, the performance and testing of lithium batteries, production precautions and design principles.
1. The principle, formula and process flow of lithium-ion batteries;
1. Working Principle
1. Positive electrode structure
LiCoO2 + conductive agent + binder (PVDF) + current collector (aluminum foil)
2. Negative electrode structure
Graphite + Conductive agent + Thickener (CMC) + Binder (SBR) + Current collector (Copper foil)
l Formation refers to the process of activating the cathode and anode materials inside a battery after it has been fully rested following electrolyte injection. This activation is achieved through a specific charging and discharging cycle, which also leads to the formation of a SEI (Solid Electrolyte Interphase) film on the surface of the active materials. The SEI film helps to improve the overall performance of the battery in terms of charging and discharging, self-discharge, and storage capabilities.
1.Coating Basics
Purpose: To uniformly coat a fluid slurry onto the surface of a metal foil, dry it, and produce a battery electrode
Principle: The coating roller rotates to carry the slurry, and the amount of slurry transferred is adjusted by adjusting the gap between the doctor blade and the roller. The relative rotation of the back roller and the coating roller is used to transfer the slurry onto the substrate. Subsequently, the solvent in the slurry is evaporated through drying and heating, causing the solid matter to adhere to the substrate.
1.Electrode Shedding
Negative electrodes are prone to powder shedding
Main reason：
1.Formula issues,insufficient bonding strength leading to material loss
2.Excessive baking temperature,rapid solvent evaporation resulting in SBR
bleeding.Insufficient adhesive between the material and the current collector leading to material loss
1.Coating Basics
Purpose：To uniformly coat a fluid slurry onto the surface of a metal foil, dry it, and produce a battery electrode
Principle:The coating roller rotates to carry the slurry, and the amount of slurry transferred is adjusted by adjusting the gap between the blade and the roller. The relative rotation of the back roller and the coating roller is used to transfer the slurry onto the substrate. Subsequently, the solvent in the slurry is evaporated through drying and heating, causing the solid matter to adhere to the substrate.
1.The function of adhesives
Cathode and anode slurries：
Provide viscosity to ensure that particles in the slurry do not easily settle and maintain sslurry stability
Provide viscosity for good fluidity
Provide viscosity to facilitate effective dispersion of materials
1.Baking
1.1.The main purpose of baking is to remove moisture from the bare cell
H2O can cause the decomposition of LiPF6, leading to an increase in HF levels:
H2O can react with organic solvents in the electrolyte to produce alcohol and CO2, for example:
During the formation process, H2O can decompose, producing H2, consuming lithium ions,
reducing the initial efficiency and capacity of the battery, and damaging the battery interface.
1.Rolling Principle
Roll pressing is a process that utilizes a roll press machine (as shown in Figure 1,the roll press machine used in the industry consists of three core components: a pair of rollers, an unwinding device, and a rewinding device) to compress the thickness of the electrode (as shown in Figure 1). This compression increases the compaction density of the electrode coating, reduces the thickness of the electrode, and ultimately enhances the energy density of the battery.
1.Process Flow
The main components of a lithium battery include a positive electrode with an active material typically being lithium cobalt oxide, a separator made of PP or PE composite membrane, a negative electrode with carbon as the active material, organic electrolyte, and a battery case made of aluminum-plastic composite film. The manufacturing process involves slurry preparation, film coating, assembly, and formation. In recent years, electronic products have become increasingly thinner and lighter, with faster charging speeds and reduced space, resulting in higher demands for the energy density of lithium batteries. Lithium batteries need to be continuously updated and improved to meet these demands, further trending towards smaller, lighter, and thinner batteries. The related topics of lithium batteries have always been a hot research focus. Adopting suitable materials and cell manufacturing processes can improve battery performance. For specific materials and processes, please consult Canrd!
1.Role and Selection Criteria of Separators
1.1.Role of Separator
1) The separator is an important component of lithium-ion batteries.
2) Electronic insulation and ionic conductivity.
Introduction and Synthesis of Lithium Ion Batteries Negative Material At present, the negative materials used in lithium-ion batteries are...
