Lithium-ion Full Cell Manufacturing Process Training--Soft-Pack Battery Formation - Part 2

1. Key Factors Influencing Formation: Mechanism

Generation Process of SEI Membrane:

l Electrons are transferred from the current collector, through the conductive agent, to point A inside the graphite particles where the SEI membrane is to be formed.

l Solvated lithium ions, wrapped in the solvent, diffuse from the cathode to point B on the surface of the SEI membrane that is currently being formed.

l The electrons at point A diffuse to point B through the electron tunneling effect.

l The electrons that jump to point B react with lithium salt, solvated lithium ions, film-forming agents, etc., to continue generating the SEI membrane on the surface of the existing SEI membrane. This process results in the continuous increase of the SEI membrane thickness on the surface of the graphite particles, ultimately leading to the formation of a complete SEI membrane.

1. Basic Concepts of Formation

1.1. What is Formation?

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.

Lithium-ion Full Battery Manufacturing Process Training--Coating

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.

Lithium-ion Full Battery Manufacturing Process Training--Coating 2

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

Lithium-ion Full Battery Manufacturing Process Training--Coating 3

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.

Lithium-ion Full Cell Manufacturing Process

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

Lithium-ion Full Cell Manufacturing Process Training--Soft-Pack Battery Cell Encapsulation

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.

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