Artificial Graphite Void Structure for Low-Expansion Battery Anodes
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional techniques fail to effectively suppress the expansion of negative electrodes in lithium ion secondary batteries, leading to volume changes during charging and discharging, which affects the battery's performance.
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 helps absorb 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 conventional graphite particles are used in the negative electrode, then the electrode can provide sufficient capacity, but the electrode expands significantly during charging and discharging
Solution Approach 1:
The patent applies porous materials by introducing internal voids within graphite particles. These voids act as buffer spaces that accommodate the expansion of graphite layers during lithium insertion, preventing external volume increase while maintaining capacity. The porosity allows the graphite structure to expand internally rather than externally.
Solution Approach 2:
The patent changes physical parameters by controlling the porosity (0.7-15%) and void characteristics (circularity 0.1-0.6) of graphite particles. By adjusting these parameters, the graphite structure can accommodate expansion internally. The patent also changes the interplanar distance parameter through controlled expansion to optimize lithium insertion while managing volume changes.
2Volume of moving object
If graphite layers are oriented perpendicular to the current collector to suppress expansion, then thickness direction expansion is reduced, but fundamental volume change of the negative electrode is not suppressed
Solution Approach 1:
The patent shifts the expansion management from external dimensional control (orientation) to internal dimensional control (voids within particles). Instead of relying on layer orientation to suppress expansion, the patent introduces internal voids that absorb expansion in three dimensions, providing more comprehensive volume change suppression regardless of orientation.
Solution Approach 2:
The patent applies beforehand cushioning by pre-introducing voids into the graphite particle structure before electrode assembly. These voids serve as pre-prepared buffer spaces that cushion the expansion stress during subsequent charging cycles, preventing both thickness and lateral expansion.
3Volume of moving object
If internal voids are introduced into graphite particles to suppress expansion, then volume change is reduced, but the structural integrity and capacity may be compromised
Solution Approach 1:
The patent optimizes parameters by controlling porosity within 0.7-15% and void circularity within 0.1-0.6. These parameter ranges balance expansion suppression with capacity maintenance. The interplanar distance is also controlled at 3.36-3.38 Å to ensure proper lithium insertion while accommodating void structure.
Solution Approach 2:
The patent applies local quality by creating non-uniform void distribution within graphite particles. The voids are strategically positioned and sized (with specific circularity characteristics) to provide expansion buffer in critical regions while preserving lithium insertion sites. This localized void placement maintains capacity while suppressing expansion.
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 capacity and stability by effectively managing the interplanar distance expansion, thus improving the overall performance of the secondary battery.
Implementation Method 1
the internal voids are oriented in parallel with the graphite layer, and expansion of the negative electrode is further suppressed
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
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 a 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.