Graphite-Silicon Anode Composition for Contact-Stable Battery Cycling
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Solution Overview
Problem
Lithium secondary batteries face challenges with the high volume change of silicon-based materials during charging and discharging, leading to reduced initial lifetime characteristics due to physical contact breakdown and decreased conductivity.
Innovation Solution
An anode material layer comprising large-particle graphite, small-particle silicon-based material, and fine-particle graphite, with specific particle size conditions (D50 ratios) to improve electron conductivity and stability, ensuring effective contact and capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based material is used as anode active material to increase capacity, then theoretical capacity increases significantly, but volume change during charging and discharging causes physical contact breakdown and spalling
Solution Approach 1:
The patent applies the nesting principle by placing small-particle silicon-based material inside large-particle graphite. The silicon particles are embedded within the graphite particles, creating a nested structure where the graphite shell accommodates the volume expansion of silicon during lithiation while maintaining structural integrity and preventing spalling.
Solution Approach 2:
The patent uses composite materials by combining graphite and silicon-based materials in a specific particle size configuration. The composite structure leverages the high capacity of silicon while using graphite as a stable matrix to constrain volume changes, achieving both high capacity and improved reliability.
2Quantity of substance
If silicon-based material is used to achieve high capacity, then energy density increases, but conductivity decreases due to spalling and physical contact breakdown
Solution Approach 1:
The nested structure places conductive graphite particles surrounding silicon particles, creating continuous conductive pathways. Even when silicon expands during charging, the graphite shell maintains electrical contact, preventing the conductivity loss that would occur with spalling in conventional silicon structures.
Solution Approach 2:
The patent changes the particle size parameters of both graphite and silicon materials, with graphite particles being larger than silicon particles. This parameter optimization ensures that the graphite matrix provides sufficient mechanical support and conductive pathways while accommodating silicon volume changes, thereby maintaining electrical conductivity.
3Reliability
If graphite particle size is reduced to improve conductivity, then electron conductivity increases, but capacity per unit mass decreases
Solution Approach 1:
The patent segments the anode material into two distinct particle size groups: large-particle graphite and small-particle silicon-based material. This segmentation allows each component to fulfill its specific function - graphite provides conductivity and structural stability while silicon provides high capacity, overcoming the trade-off between particle size and performance.
Solution Approach 2:
The patent applies local quality by assigning different functions to different particle sizes and materials. Large graphite particles provide structural support and conductivity, while small silicon particles embedded within provide high capacity. Each location in the composite has optimized properties for its specific function.
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 anode configuration significantly enhances the initial lifetime characteristics of lithium secondary batteries by maintaining stable conductivity and capacity through proper particle sizing and distribution.
Implementation Method 1
improve electron conductivity and stability, ensuring effective contact and capacity
Data Source
AI summary
The present disclosure relates to an anode for a lithium secondary battery, wherein an anode material layer is formed on at least one surface of an anode current collector, andthe anode material layer includes large-particle graphite, a small-particle silicon-based material, and fine-particle graphite, and satisfies the following conditions 1 to 3:[Condition 1] Average diameter D50 of the large-particle graphite (D1): 1 to 50 μm[Condition 2] Average diameter D50 of the small-particle silicon-based material (D2): 0.155D1 to 0.414D1 [Condition 3] Average diameter D50 of the fine-particle graphite (D3): 0.155D1 to 0.414D1, or 0.155D2 to 0.414D2.