Abstract:This paper deeply discusses the key factor of "fineness" in the lithium battery manufacturing process, including the concept of particle size and particle size distribution, its impact on battery performance such as energy density, cycle life and safety, describes the detection and control methods of fineness in detail, and analyzes the key role of fineness in different scenarios in combination with the actual situation. Through the comprehensive study of these aspects, the importance of fineness in ensuring the quality and performance of lithium batteries is revealed.
I. Introduction
In order to obtain high-performance, safe and reliable lithium batteries in the production process of lithium batteries, every link in the manufacturing process is crucial. Among them, "fineness", the particle size and particle size distribution of battery materials, has gradually become the focus of research and industrial production. Fineness has a profound impact on the performance and safety of lithium batteries, and accurate control and detection of fineness is a key step to improve the quality of lithium batteries.
2. The basic concept of particle size and particle size distribution
(1) Granularity
Particle size refers to the size of the particles of the material. In lithium batteries, different materials such as positive electrode, negative electrode and separator, etc., the particle size of the particles will affect the performance of the battery. Taking cathode materials as an example, the uniformity and specific size of the particle size of commonly used lithium cobalt oxide and ternary materials will affect the charging and discharging characteristics and capacity of the battery.
(2) Particle size distribution
Particle size distribution describes the proportion of particles of different particle sizes in a material. An ideal particle size distribution should have the appropriate width and peak values to ensure optimal packing density, ion transport, and electron conduction of the battery material in the electrodes.
3. The influence of particle size and particle size distribution on the performance of lithium batteries
(1) Energy density
1. Influence of the particle size of the cathode material
Larger cathode material particle size may lead to a longer diffusion path and an increase in internal resistance during the embedding and ejection of lithium ions, thereby reducing the energy density of the battery.
2. Effect of the particle size of the anode material
A too small anode material particle size may cause an excessive increase in specific surface area, resulting in irreversible lithium-ion loss and reducing the actual usable capacity of the battery.
(2) Cycle life
1. Particle agglomeration and crushing: The uneven particle size and particle size distribution can easily lead to the agglomeration or fragmentation of particles during charging and discharging, destroying the electrode structure and affecting the cycle life.
2. Uneven stress distribution: Large particle size differences may lead to uneven stress distribution inside the electrode, accelerating the aging and failure of the electrode material.
(3) Security
1. Excessive separator size: Excessive separator size increases the possibility of microscopic defects, which may lead to internal short circuits and potential safety hazards.
2. The influence of cathode particle size on thermal runaway: Larger cathode particles may be more prone to thermal runaway at high temperatures, affecting the safety performance of the battery.
Fourth, the fineness of the detection method
(1) Laser diffraction method
Principle: The particle size distribution is calculated by irradiating the sample particles with a laser to measure the angle and intensity of the scattered light.
Advantages: wide measuring range, fast speed, high accuracy.
Scope of application: It is suitable for particle size analysis of most lithium battery materials.
(2) Dynamic light scattering method
Principle: Measure the particle size of a particle based on the fact that the intensity of the scattered light varies with the motion of the particle.
Advantages: Accurate measurement of nanoscale particles.
Scope of application: It is often used to study nanoscale particles such as conductive agents in lithium batteries.
(3) Electron microscopy
1. Scanning Electron Microscopy (SEM)
Principle: Scan the surface of the sample with an electron beam to generate a secondary electron image, which can visually observe the shape and size of the particles.
Advantages: High resolution and detailed particle topography information.
2. 透射电子显微镜(TEM)
Principle: The electron beam passes through the sample to form a projected image that can accurately measure the particle size.
Advantages: Extremely high resolution for the analysis of small particles.
Fifth, the fineness control method
(1) Synthesis process optimization
1. Co-precipitation method
By controlling the reaction conditions such as temperature, stirring speed, feeding speed, etc., the precise control of the particle size and particle size distribution of the material can be realized.
2. Sol-gel method
The preparation process and gelation conditions of the sol were adjusted to prepare a material with uniform particle size.
(2) Crushing and grading technology
For raw materials with larger particle sizes, mechanical grinding such as ball milling, jet grinding and other methods, combined with grading equipment, are used to screen out the particles in the required particle size range.
(3) Surface decoration and coating
The surface of the particles is modified or coated to improve the agglomeration between the particles and optimize the particle size distribution.
(4) Monitoring in the production process
In multiple production processes, such as raw material preparation, slurry mixing, and electrode coating, the fineness is detected in real time, and the process parameters are adjusted in time to ensure the consistency of mass production.
6. Conclusions and prospects
As a key parameter in the lithium battery manufacturing process, fineness has a significant impact on the performance and safety of the battery. Through advanced detection technology and precise control methods, the particle size and particle size distribution can be optimized to improve the quality and competitiveness of lithium batteries. Careful control of fineness will become an indispensable and important part of the lithium battery manufacturing process. Therefore, scientific researchers, manufacturers and related practitioners in the industry should attach great importance to the research and control of fineness, so as to create high-quality, high-performance lithium battery products.
Article source: lithium battery technology knowledge platform
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