Autogenous Silicon Milling for Battery Anodes
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Solution Overview
Problem
Current methods for producing nanosize silicon particles for lithium ion battery anodes face challenges such as high contamination from milling media, mechanical stress leading to particle rupture, and inefficient energy use due to agglomeration of small particles during dry milling, which results in low production yields and poor mechanical stability of electrodes.
Innovation Solution
A process involving autogenous wet milling using silicon granules as both the material to be milled and milling media, with specific size distributions and properties to minimize contamination and maximize the production of silicon particles with 50 nm<d50<1000 nm, achieving low metallic impurity levels and improved mechanical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If ceramic or steel milling media are used for wet milling of silicon particles, then nanosize silicon particles can be produced, but the milled material becomes contaminated with foreign atoms from the milling media
Solution Approach 1:
The patent applies homogeneity by using silicon granules as milling media that are compositionally identical to the silicon particles being milled. This eliminates foreign atom contamination from ceramic or steel media while maintaining effective size reduction through mechanical action. The milling media and processed material share the same material composition, ensuring product purity.
Solution Approach 2:
The patent uses an organic solvent as an intermediary medium in which both the silicon particles to be milled and the silicon granule milling media are suspended. This liquid intermediary enables effective mechanical milling while preventing direct contact between the silicon material and potentially contaminating mill walls or fixtures, isolating the milling action to the silicon-on-silicon granule interactions.
2Ease of manufacture
If dry milling is used to produce microsize silicon particles, then the process is simple, but small particles agglomerate leading to inefficient energy use and low production yields
Solution Approach 1:
The patent transitions from dry milling to wet milling by introducing an organic solvent as a liquid medium. This hydraulic approach prevents particle agglomeration by maintaining particles in a dispersed suspended state during milling, allowing continuous effective size reduction without the energy waste associated with breaking up agglomerates that occurs in dry milling processes.
Solution Approach 2:
The patent changes the physical state parameter of the milling environment from dry to wet conditions by introducing an organic solvent. This parameter change fundamentally alters the milling dynamics, preventing particle aggregation and enabling sustained size reduction efficiency that directly improves production yield while maintaining process simplicity.
3Quantity of substance
If silicon is used as anode material in lithium ion batteries, then very high theoretical specific capacity is achieved, but severe mechanical stressing occurs due to large volume change during lithium intercalation and deintercalation
Solution Approach 1:
The patent applies segmentation by reducing silicon to nanosize particles with a volume-weighted mean diameter of 50-1000 nm. This divides the bulk silicon material into numerous small particles, which reduces the absolute volume change experienced by each individual particle during lithium intercalation. The nanoscale segmentation prevents the severe mechanical stress and particle rupture that occurs in bulk silicon, maintaining structural integrity while preserving high lithium 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 process effectively produces silicon particles with low metallic impurities and high mechanical stability, leading to improved cyclic behavior and reduced irreversible capacity loss in lithium ion battery electrodes, with enhanced energy storage capabilities and prolonged cycling stability.
Implementation Method 1
a mixture containing a suspension comprising a silicon to be comminuted and milling media composed of silicon is set into motion in the milling space of a milling medium mill; the silicon is comminuted by the movements of the mixture in the milling space
Implementation Method 2
A process involving autogenous wet milling using silicon granules as both the material to be milled and milling media
Data Source
AI summary
The invention relates to a method for size-reducing silicon, wherein a mixture containing a suspension containing silicon to be size-reduced and silicon grinding media is set in motion in the grinding space of a grinding media mill. The size-reduced silicon is used as the active material in the anode of a lithium-ion battery.