Spherical Graphite Processing for Higher Yield and Fine Particle Control
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Solution Overview
Problem
Current methods for producing spherical graphite for lithium-ion batteries result in low yield and high waste, as they can only produce graphite with a median diameter of 14-25 μm, limiting their use to capacity-type batteries and wasting 60-70% of graphite powder as cheap metallurgical recarburizers or refractory materials.
Innovation Solution
A multi-stage process involving primary and secondary pulverization, shaping, and ultrafine pulverization and shaping steps to produce spherical graphite with a median diameter of 3-12 μm, increasing the utilization rate of graphite raw materials and meeting the needs of both capacity-type and rate-type lithium-ion batteries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If natural graphite is pulverized and processed into spherical particles through multiple low-speed and high-speed pulverization and grinding, then the tap density is increased, but the particle size is limited to 14-25 μm and yield is only 30-40%
Solution Approach 1:
The patent divides the pulverization process into multiple stages with different speed configurations. Low-speed pulverization (500-1500 rpm) is performed first to avoid excessive fine powder generation, followed by high-speed pulverization (1500-3000 rpm) to achieve the target particle size of 3-25 μm. This segmented approach allows both high yield (60-70% increase) and precise particle size control simultaneously.
Solution Approach 2:
The patent dynamically adjusts the pulverization speed during the process. The ball mill operates at variable speeds, transitioning from low-speed initial pulverization to high-speed final sizing. This dynamic speed adjustment enables the system to optimize both yield and particle size distribution, producing spherical graphite with D50 of 3-25 μm while maintaining high yield.
2Shape
If multiple jet mills and spheroidizing units are connected in series to prepare spherical graphite, then the spherical shape is improved, but the device complexity and production cost increase significantly
Solution Approach 1:
The patent makes the ball mill perform multiple functions: initial pulverization, shaping, and final sizing, all in one device. By adjusting operational parameters (speed, time, ball-to-powder ratio), the same ball mill can produce spherical graphite of different particle sizes (D50 3-25 μm). This eliminates the need for multiple specialized units, reducing device complexity while maintaining good sphericity.
Solution Approach 2:
The patent achieves different particle sizes and sphericity by changing operational parameters rather than using different equipment. By adjusting ball mill speed (500-3000 rpm), pulverization time (1-24 hours), and ball-to-powder ratio (2:1 to 10:1), the system can produce spherical graphite with D50 of 3-25 μm. This parameter-based flexibility replaces complex multi-unit equipment configurations.
3Adaptability or versatility
If natural graphite is pulverized to produce spherical graphite with D50 of 14-25 μm, then the capacity-type battery requirements are met, but rate-type battery applications are not supported and 60-70% graphite powder is wasted
Solution Approach 1:
The patent produces spherical graphite with a broad particle size range (D50 3-25 μm) that can serve both capacity-type and rate-type lithium-ion batteries. The smaller particles (3-12 μm) suit rate-type batteries requiring fast ion transport, while larger particles (14-25 μm) suit capacity-type batteries. This universal product range eliminates the need for separate production lines and prevents waste of graphite powder.
Solution Approach 2:
The patent uses parameter adjustment (pulverization speed, time, and ball-to-powder ratio) to produce spherical graphite with variable particle sizes (D50 3-25 μm) from the same raw material. This allows flexible adaptation to different battery type requirements without changing equipment or discarding material, thereby increasing adaptability and reducing substance loss.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The process increases the utilization rate of graphite by 25-35%, producing spherical graphite with good sphericity, uniform particle size distribution, and high tap density, meeting the requirements of various lithium battery applications.
Implementation Method 1
natural graphite was subjected to primary pulverization in a mechanical pulverizer, and then to circular grinding in multiple shaping classifiers connected in series
Implementation Method 2
natural graphite is made into spherical particles through multiple low-speed and high-speed pulverization and grinding
Implementation Method 3
the pulverized graphite was classified by a cyclone separator
Data Source
AI summary
A preparation method for a spherical graphite for lithium batteries firstly adopts a combination of primary pulverization, secondary pulverization and shaping to produce spherical graphite with D50 of 13-25 μm, and then adopts a combination of ultrafine primary pulverization, ultrafine secondary pulverization and shaping to produce spherical graphite of small particle size with D50 of 3-12 μm from tailings produced during the production of spherical graphite with D50 of 13-25 μm for the first time. The method increases the utilization rate of graphite raw materials by 25-35%, and can prepare spherical graphite with D50 of 13-25 μm and spherical graphite with D50 of 3-12 μm at the same time. An alternative method adopts a combination of primary pulverization, secondary pulverization, ultrafine primary pulverization, ultrafine secondary pulverization and shaping to produce spherical graphite of small particle size with D50 of 13-25 μm directly from raw materials for the first time.