Artificial Graphite Density Control for Low-Expansion Battery Anodes
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Solution Overview
Problem
Secondary batteries experience volume expansion during the cycle process, leading to increased internal stress and affecting their service life and safety performance, which is a concern for new energy vehicles requiring improved electrical properties and safety.
Innovation Solution
The development of artificial graphite with a specific density ratio (PD5t/PD0.5t ≤ 1.35) that enhances deformation resistance, ensuring stable structure and improved cycle performance by controlling expansion and contraction during lithium intercalation and de-intercalation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional graphite materials are used as negative electrode, then the battery can achieve basic energy storage function, but the battery experiences significant volume expansion during cycle process leading to increased internal stress and reduced service life
Solution Approach 1:
The invention changes the physical and chemical parameters of the graphite material by controlling the graphitization temperature (2400-3000°C), carbon source composition (petroleum coke, coal tar pitch, mesophase carbon), and processing conditions to achieve a specific density ratio (PD5t/PD0.5t ≤ 1.35) that reduces volume expansion during cycling
Solution Approach 2:
The invention uses composite carbon materials including petroleum coke, coal tar pitch, and mesophase carbon as carbon sources, and combines graphite with small amounts of silicon oxide (0.1-5 wt%) or other modifiers to create a composite structure that maintains structural stability during lithium insertion/extraction cycles
2Strength
If the graphite density is increased to improve structural stability, then the deformation resistance improves, but the manufacturing complexity and process control difficulty increase
Solution Approach 1:
The invention establishes clear parameter ranges for controlling graphite density and deformation resistance, including graphitization temperature (2400-3000°C), carbon source ratios, and density ratio (PD5t/PD0.5t ≤ 1.35), which simplifies process control by providing specific target values rather than requiring complex real-time adjustments
Solution Approach 2:
The invention performs preliminary carbonization and graphitization treatments during manufacturing to pre-establish the desired density and structural properties before battery assembly, ensuring the graphite material achieves the required deformation resistance before being subjected to cycle stress
3Quantity of substance
If the graphite particle size is reduced to improve filling density, then the energy density increases, but the internal stress and expansion during cycling are exacerbated
Solution Approach 1:
The invention uses a composite approach combining different carbon sources (petroleum coke, coal tar pitch, mesophase carbon) with complementary properties to create graphite particles that achieve both high filling density and low internal stress during cycling
Solution Approach 2:
The invention applies local quality modification by incorporating small amounts of silicon oxide (0.1-5 wt%) or other additives at specific locations within the graphite structure to locally reinforce the material and reduce internal stress without compromising overall filling density
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 artificial graphite reduces volume expansion, resulting in better cycle performance, energy density, and safety characteristics in secondary batteries.
Implementation Method 1
repeated intercalation and de-intercalation of lithium
Implementation Method 2
the volume expansion of a secondary battery will occur during the cycle process
Data Source
Figure 1(a)~1(b)
Figure 2
Figure 3~4
AI summary
Embodiments of the present application provides an artificial graphite, a secondary battery, a preparation method and a device. The artificial graphite of the present application satisfies: PD5t/PD0.5t ≤ 1.35, wherein PDst is a compacted density of the artificial graphite measured under a pressure of 5 t, and PD0.5t is a compacted density of the artificial graphite measured under a pressure of 0.5 t.