Active Material-Exfoliated Graphite Composite for Li-Ion Batteries
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional lithium ion secondary batteries using silicon as negative electrodes face challenges with complex production processes and significant decreases in charge and discharge performance due to volume changes during lithium ion intercalation and deintercalation.
Innovation Solution
An active material-exfoliated graphite composite is developed, comprising partially exfoliated graphite with an average particle diameter of 1 μm to 100 μm, incorporating active materials like Si, which are capable of intercalating and deintercalating lithium ions, thereby enhancing initial capacity and reducing deterioration in charge and discharge cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Si is used as negative electrode active material to achieve higher theoretical capacity, then initial capacity is improved, but volume changes during lithium ion intercalation and deintercalation cause deterioration in charge and discharge cycle characteristics
Solution Approach 1:
Si particles are embedded within the interlayer spaces of partially exfoliated graphite, creating a nested structure where the high-capacity Si is protected by the graphite matrix. This allows Si to expand and contract during lithium ion intercalation/deintercalation without suffering the full mechanical stress, thereby maintaining cycle stability while achieving high initial capacity.
Solution Approach 2:
The invention creates a composite material combining Si particles with partially exfoliated graphite. The composite leverages the high theoretical capacity of Si (3579 mAh/g) while the graphite component provides structural stability and conductivity. The synergistic combination resolves the contradiction between high capacity and cycle stability.
2Reliability
If spherical assembly of plate-like Si materials is formed to reduce volume change, then charge and discharge cycle characteristics are improved, but the structure becomes complex and production process is complicated
Solution Approach 1:
The invention extracts Si from its conventional bulk form and processes it into fine particles, then embeds these particles within the graphite structure. This simplifies the overall structure by eliminating the need for complex spherical assemblies while still achieving volume change mitigation through the graphite matrix.
Solution Approach 2:
Instead of creating a complex overall structure, the invention applies local modification by embedding Si particles specifically within the interlayer spaces of graphite. This localized approach maintains structural simplicity while achieving the desired performance improvement.
3Quantity of substance
If Si particles are used to achieve higher capacity, then initial capacity is improved, but significant volume changes occur during lithium ion intercalation and deintercalation
Solution Approach 1:
The partially exfoliated graphite acts as a flexible confining matrix around Si particles. The graphite layers can accommodate the volume expansion of Si during lithium ion intercalation while maintaining structural integrity, effectively managing volume changes without compromising capacity.
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 active material-exfoliated graphite composite improves the initial capacity and cycle stability of lithium ion secondary batteries by incorporating Si particles within the partially exfoliated graphite, reducing volume changes and maintaining conductivity, thus providing better charge and discharge characteristics.
Implementation Method 1
materials capable of intercalating and deintercalating Li are used
Implementation Method 2
particles capable of adsorbing and desorbing lithium ions by composite formation with the partially exfoliated graphite
Data Source
AI summary
There is provided an active material-exfoliated graphite composite that allows a lithium ion secondary battery to be obtained in which the initial capacity is large and deterioration in charge and discharge cycle characteristics is less likely to occur, when used for a negative electrode material for lithium ion secondary batteries. An active material-exfoliated graphite composite comprising: partially exfoliated graphite having a structure in which graphite is partially exfoliated; and an active material that is in the form of particles capable of intercalating and deintercalating lithium ions by composite formation with the partially exfoliated graphite, or particles capable of adsorbing and desorbing lithium ions by composite formation with the partially exfoliated graphite, wherein the active material has an average particle diameter of 1 μm or more and 100 μm or less.