Silicon Anode Material Grain Control for Volume Expansion
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Solution Overview
Problem
Silicon-based active materials for negative electrodes in lithium secondary batteries experience significant volume expansion during charging and discharging, leading to damage of the conductive path and reduced battery performance.
Innovation Solution
A silicon-based active material with a crystal grain size of 300 nm or less and a uniform particle size distribution is produced by increasing the cooling rate using a low-temperature sonicated substrate, forming standing waves during atomization to ensure even lithium ion incorporation and reduce crystal grain growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If silicon-based active material is used to increase capacity, then energy density is improved, but volume expansion during charge/discharge causes conductive path damage and reduced reliability
Solution Approach 1:
The silicon-based active material is divided into fine particles with a diameter of 10 μm or less, and further into crystal grains with a size of 300 nm or less. This segmentation reduces volume expansion stress on individual particles, preventing conductive path damage while maintaining high capacity.
Solution Approach 2:
The patent applies different properties to different levels of the material structure: the overall particle size is controlled at 10 μm or less for electrode integration, while the internal crystal grain size is controlled at 300 nm or less for stress management. This multi-scale quality control simultaneously addresses energy density and reliability requirements.
2Manufacturing precision
If cooling rate is increased to reduce crystal grain size, then particle size uniformity is improved, but manufacturing process complexity increases
Solution Approach 1:
Ultrasonic vibration is applied during the cooling process to promote uniform nucleation and inhibit crystal grain growth. This mechanical vibration method achieves fine and uniform crystal grain sizes (300 nm or less) without requiring excessively complex cooling systems, as the vibration field naturally distributes nuclei uniformly throughout the molten material.
Solution Approach 2:
The patent changes the cooling rate parameter to a specific range (10³-10⁶ K/s) and combines it with ultrasonic vibration frequency parameters to achieve the desired crystal grain size. By optimizing these physical parameters within specific ranges, the patent achieves particle size uniformity without overly complicating the manufacturing process.
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 solution suppresses crack formation and uneven charge/discharge issues, improving the life performance and capacity retention of lithium secondary batteries by ensuring uniform lithium ion distribution and controlling volume expansion.
Implementation Method 1
spraying the melted silicon raw material onto an ultra-vibration low-temperature substrate
Implementation Method 2
forming standing waves during atomization to ensure even lithium ion incorporation and reduce crystal grain growth
Implementation Method 3
when the cooling rate is increased through a low-temperature sonicated substrate, the growth of crystal grains may be reduced
Data Source
AI summary
A negative electrode active material includes a silicon-based active material having a crystal grain size of about 300 nm or less. The silicon-based active material has a value of about 2.00 or less as defined by Equation 1 below. The silicon-based active material includes SiOx (x=0) and at least one selected from SiOx (0<x<2), and includes about 70 parts by weight or more of the SiOx (x=0) based on 100 parts by weight of the silicon-based active material.(D90−D10)/D50 [Equation 1]In Equation 1, D90, D10, and D50 represent diameters of particles corresponding to 90%, 10%, and 50% by volume in a size distribution, respectively.