Artificial Graphite Void Structure for Low-Expansion Battery Anodes
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Solution Overview
Problem
Conventional techniques fail to effectively suppress the volume expansion of negative electrodes in lithium ion secondary batteries, leading to inefficiencies in charge and discharge processes.
Innovation Solution
The use of artificial graphite particles with specific porosity and internal void characteristics, including a porosity of 0.7 to 15% and average circularity of 0.1 to 0.6, oriented in parallel with the graphite layer, which absorb and manage the expansion of the interplanar distance of the graphite crystal, thereby reducing the volume change of the negative electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If graphite particles are used as negative electrode active material, then high capacity is achieved, but volume expansion of the negative electrode occurs during charging
Solution Approach 1:
The patent applies porous materials by introducing internal voids within graphite particles with controlled porosity (5-20%). These internal voids act as buffer spaces that accommodate the expansion of graphite interlayer distance during lithium ion insertion, thereby suppressing overall volume expansion of the negative electrode while maintaining high capacity
Solution Approach 2:
The patent changes physical parameters of graphite particles by controlling the size, distribution, and porosity of internal voids. Specifically, the void radius is controlled at 0.5-2.0 μm and porosity at 5-20%, which optimizes the balance between capacity and volume expansion suppression. The interlayer distance is also controlled at 3.35-3.40 Å to accommodate expansion
2Volume of moving object
If graphite particles are oriented perpendicular to current collector, then thickness direction expansion is suppressed, but fundamental volume change of negative electrode cannot be suppressed
Solution Approach 1:
The patent applies segmentation by dividing the graphite particle structure into solid graphitic regions and internal void regions. This segmentation allows the voids to independently accommodate volume changes without affecting the overall electrode structure, providing fundamental volume change suppression that orientation alone cannot achieve
Solution Approach 2:
The patent applies beforehand cushioning by pre-introducing internal voids into graphite particles before electrode assembly. These voids serve as pre-prepared buffer spaces that cushion the expansion stress during lithium ion insertion, preventing both thickness direction expansion and fundamental volume change
3Volume of moving object
If internal voids are introduced in graphite particles, then volume expansion is suppressed, but manufacturing complexity increases
Solution Approach 1:
The patent simplifies manufacturing by controlling void parameters within specific ranges (void radius 0.5-2.0 μm, porosity 5-20%) rather than requiring precise complex structures. This parameter control approach allows standard manufacturing processes to produce the desired void structures without excessive complexity
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
This configuration significantly reduces the expansion of the negative electrode, enhancing the battery's performance by maintaining electrode stability and increasing capacity.
Implementation Method 1
The artificial graphite particles have a porosity of 0.7 to 15%
Implementation Method 2
heating a graphite precursor from 1000°C to 2600°C or more within five hours to graphitize the graphite precursor
Data Source
Figure 1
Figure 2A~2C
Figure 3
AI summary
A negative electrode active material capable of suppressing expansion of a negative electrode is provided. The negative electrode active material disclosed herein includes artificial graphite particles having a plurality of internal voids. The artificial graphite particles have an internal porosity of 0.7 to 15%. When binarization is performed on a cross-sectional electron microscopic image of 10 or more of the artificial graphite particles arbitrarily selected, circular approximation is then performed on internal voids having cross-sectional areas of 1000 nm2 or more, and circularities of 20 or more of the internal voids arbitrarily selected in each particle are determined, the internal voids have an average circularity of 0.1 to 0.6.