Silicon-Graphite Anode Composition for Stable Battery Cycle Life
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Solution Overview
Problem
Silicon-based materials used in lithium secondary batteries experience significant volume changes during charging and discharging, leading to reduced ionic and electrical conductivity, and poor initial lifetime characteristics due to physical contact breakdown and spalling.
Innovation Solution
An anode material layer comprising large-particle graphite, small-particle silicon-based material, fine-particle graphite, and carbon nanotubes, with specific diameter ratios, is used to enhance electron conductivity and stability, improving initial lifetime characteristics.
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 silicon-based material particles are embedded within graphite particles, forming a core-shell structure where silicon is nested inside graphite. This nesting approach allows the high-capacity silicon to be protected by the stable graphite shell, which accommodates volume changes and prevents direct contact breakdown of silicon during charging-discharging cycles.
Solution Approach 2:
The invention creates a composite anode material consisting of silicon-based material and graphite in specific weight ratios (0.1-10 wt% silicon). This composite structure combines the high capacity of silicon with the structural stability and conductivity of graphite, resolving the contradiction between capacity enhancement and reliability maintenance.
2Quantity of substance
If silicon-based material is used to achieve high capacity, then energy storage increases, but ionic conductivity and electrical conductivity drastically decrease
Solution Approach 1:
The composite structure of silicon-based material embedded in graphite maintains electrical conductivity through the conductive graphite matrix, while the porous structure preserves ionic conductivity by providing pathways for lithium ion transport. This composite approach allows simultaneous achievement of high capacity and maintained conductivity.
Solution Approach 2:
The anode active material layer is designed with a porous structure having specific pore volume (0.2-0.8 mL/g) and pore diameter (0.01-1 μm). This porosity facilitates lithium ion diffusion and maintains ionic conductivity while accommodating the volume expansion of silicon during lithiation, preventing conductivity loss.
3Quantity of substance
If conventional top-down Si/carbon composite method is used to improve silicon-based material characteristics, then capacity can be enhanced, but manufacturing process becomes complicated and yield decreases
Solution Approach 1:
Instead of the conventional top-down approach of coating carbon on silicon particles, this invention uses a bottom-up approach where silicon-based material is embedded within graphite particles during the formation process. This inversion of the manufacturing approach simplifies the process and improves yield while achieving the desired composite structure.
Solution Approach 2:
The silicon-based material is pre-dispersed in a solvent to form a uniform slurry before being combined with graphite particles. This preliminary dispersion action ensures homogeneous distribution of silicon within the graphite matrix, simplifying subsequent processing steps and improving manufacturing efficiency and yield.
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 material layer significantly enhances the initial lifetime characteristics of lithium secondary batteries by maintaining stable conductivity and capacity through proper distribution and connectivity of silicon-based materials with graphite particles.
Implementation Method 1
maintaining stable conductivity and capacity through proper distribution and connectivity of silicon-based materials with graphite particles
Implementation Method 2
lithium secondary batteries having high energy density and operating electric potential, long lifespan and low self-discharge
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, fine-particle graphite, and carbon nanotube, 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.