Silicon Anode Powder Size Control for Stable Battery Cycling
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Solution Overview
Problem
The use of silicon-based materials in anodes for lithium-ion batteries is limited by large volume expansion during charging, leading to mechanical degradation, poor cycle performance due to thick SEI formation, and reduced coulombic efficiency, which affects the battery's life and charging/discharging rates.
Innovation Solution
A silicon-based powder with a narrow particle size distribution, where less than 8% of the particles are larger than twice the average size (d50), and a controlled oxygen content, is used to minimize mechanical stress and SEI formation, enhancing coulombic efficiency and charge/discharge rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based materials are used in anodes to increase theoretical capacity, then energy density is improved, but volume expansion during charging causes mechanical degradation
Solution Approach 1:
The silicon-based material is divided into particles with a controlled narrow size distribution (d50 between 5-50 μm, with less than 8% of particles larger than twice the d50). This segmentation reduces the overall volume expansion stress and prevents mechanical degradation while maintaining high theoretical capacity.
2Reliability
If silicon particles are reduced to submicron or nanosized to accommodate volume change, then mechanical degradation is reduced, but particle size control becomes more difficult
Solution Approach 1:
The patent specifies precise particle size parameters (d50 between 5-50 μm, with less than 8% of particles larger than twice the d50) to optimize the balance between mechanical stability and manufacturability. This parameter control enables reliable performance while maintaining feasible manufacturing processes.
3Reliability
If thick SEI forms on the anode surface, then passivation layer is created, but lithium availability is reduced and electrical resistance increases
Solution Approach 1:
The controlled particle size distribution (d50 between 5-50 μm with narrow distribution) modifies the surface area to volume ratio, which influences SEI formation kinetics. This parameter optimization allows for adequate passivation while minimizing excessive lithium consumption and electrical resistance, thereby maintaining good charging and discharging rates.
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 results in higher coulombic efficiency and improved cycle life by reducing mechanical stress and SEI formation, allowing for better dispersion and utilization of silicon particles, thus enhancing the battery's performance.
Implementation Method 1
by alloying or insertion, in this material
Implementation Method 2
by alloying or insertion, in this material
Implementation Method 3
a thick SEI, a Solid-Electrolyte Interface, may be formed on the anode. An SEI is a complex reaction product of the electrolyte and lithium
Data Source
AI summary
A silicon-based powder for use in the negative electrode of a battery comprises silicon-based particles. The silicon-based particles have a number-based particle size distribution having a d50, and less than 8.0% of the particles have a size which is larger than twice the d50. The silicon-based powder may be embedded in a matrix to form an active material powder. Preferably d50<150 nm and d10>10 nm. The cycle efficiency of a negative electrode of a battery, made using such a powder, is much improved.